JP7502935B2 - Tire building method - Google Patents

Description

The present invention relates to a tire molding method.

A green tire is formed as follows. The carcass ply is wound around a first forming drum to form a carcass band, and a pair of bead members are attached to both axial ends of the carcass band. Next, the portion of the carcass band that is axially outward of the portion where the pair of bead members are attached is folded back to encase the bead members. Meanwhile, the belt, tread rubber, etc. are wound around a second forming drum to form the tread band.

Next, the carcass band and tread band are detached from the first and second molding drums while being gripped from the outer periphery, and are transferred to the third molding drum by the respective transfer means so that the tread band is positioned on the outer diameter side of the carcass band. Then, on the third molding drum, the carcass band is bulged outward in the radial direction and joined to the inner periphery of the tread band, thereby forming a green tire.

The bead member comprises a ring-shaped bead core made of steel wire and a bead filler made of rubber material with a triangular cross section that extends from the bead core radially outward of the tire. The bead filler is attached to the bead core in advance and then assembled to the carcass band.

Patent Document 1 discloses a thin and high bead filler for ensuring the rigidity of the tire side portion while suppressing the weight increase of the pneumatic tire. The thin and high bead filler has a narrow width portion whose tire width direction thickness is narrower than the bead core (e.g., tire width direction thickness is 3.0 mm or less), and the tire radial direction height of the narrow width portion is set to a predetermined value (e.g., 30 mm) or more.

JP2004-351995

Before vulcanization, thin, high bead fillers have low rigidity and are prone to collapse and deformation in the tire axial direction during the preparation process in which they are attached to the bead core and during the bead assembly process in which they are attached to the carcass band. This collapse and deformation can cause air pockets to form in the sidewalls of pneumatic tires.

The objective of the present invention is to provide a tire molding method that prevents air pockets in the tire side sections caused by the collapse and deformation of thin and high bead fillers.

The present invention provides a pair of bead members each including a ring-shaped bead core, a bead filler extending from an outer end portion on the outer side of the tire in the radial direction of the bead core toward the radial outside while decreasing in cross section, and a reinforcing member attached to a side surface of the bead filler, wherein the bead filler is configured as a thin and high bead filler having a narrow width portion formed with a width of 3.0 mm or less that is narrower than the width of an inner end portion on the inner side of the tire in the radial direction of the bead filler, and a tire radial height of the narrow width portion is 30 mm or more, a carcass ply is wound around a cylindrical forming drum, the pair of bead members are assembled to the radially outer and both axial ends of the carcass ply, the bead filler is pressed and bent toward the inner side in the width direction of the forming drum and stitched so as to follow the outer surface of the carcass ply, and a portion of the width direction outer side of the carcass ply is folded back toward the inner side in the width direction of the carcass ply, and the bead members are assembled to the carcass ply before being assembled to the carcass ply.
The present invention provides a tire building method in which the reinforcing member in a band state is attached to the thin, high bead filler in a band state to form a reinforcing filler in a band state, and the reinforcing filler is wound around the outer periphery of the ring-shaped bead core.

The axial direction of the forming drum and the radial direction of the forming drum correspond to the tire width direction and tire radial direction, respectively.

According to this configuration, the stiffness of the thin and high bead filler is ensured by attaching a reinforcing member to the thin and high bead filler in a band state that is not wrapped around the outer circumference of the bead core to form the reinforcing filler. This makes it possible to suppress the bead filler from collapsing toward the inside of the width direction of the carcass band during bead forming, in which the reinforcing filler in a band state is wrapped around the ring-shaped bead core, and during bead assembly, in which the bead member is assembled to the carcass band. As a result, air pockets caused by the collapse of the bead filler are easily avoided.

The reinforcing member may be peeled off from the bead filler after the stitching and before the folding.

This configuration allows the thin and high bead filler to be used even in pneumatic tires that do not have a reinforcing member on the outer surface of the bead filler in the tire width direction.

The adhesive strength of the reinforcing member may be set to 3.0 N or more and 5.0 N or less.

The adhesive strength referred to here refers to the force required to peel the reinforcing member from the bead filler per unit area, and the greater this force is, the better the adhesiveness is.

According to this configuration, the reinforcing member has an adhesive strength of 3.0 N or more, so that the adhesive strength to the bead filler is ensured. In addition, the reinforcing member has an adhesive strength of 5.0 N or less, so that it is easy to peel off from the bead filler after stitching.

The amount of collapse in the tire width direction due to the weight of the tip portion of the reinforcing filler on the outer side in the tire radial direction may be set so as to satisfy the following.
0.0≦B/A≦0.3
A: Height of reinforcing filler in tire radial direction B: Fall amount of tip of reinforcing filler in tire width direction

This configuration makes it easier to align the reinforcing filler along the outer surface of the carcass ply during stitching while suppressing the collapse deformation of the bead filler in the tire width direction during bead molding and bead assembly. If B/A is smaller than 0, the bending rigidity increases excessively, making it difficult to align the reinforcing filler along the outer surface of the carcass ply during stitching. On the other hand, if B/A is greater than 0.3, the bending rigidity of the reinforcing filler is too low, making it difficult to suppress the collapse deformation in the tire width direction.

The reinforcing member may be formed with a constant tire radial dimension and a constant thickness.

This configuration allows the reinforcing members to be evenly positioned around the tire circumferential direction of the bead filler, reducing uneven application of the bead filler that can occur due to the presence or absence of reinforcing members and changes in their thickness during stitching.

The reinforcing member may be attached to an area of 50% or more in the tire radial direction of the outer side of the bead filler in the tire width direction.

This configuration reduces uneven application of the bead filler in the tire radial direction.

The tire building method of the present invention can prevent air pockets in the tire side caused by the collapse and deformation of the thin and high bead filler.

1 is a meridian cross-sectional view of a pneumatic tire equipped with a thin, high bead filler according to the present invention. FIG. 2 is a partially enlarged view of FIG. 5 is a schematic diagram showing a process of forming a reinforcing filler by attaching a reinforcing member in a strip state to a bead filler in a strip state. FIG. 1 is a diagram showing the process of attaching a strip of reinforcing filler to a ring-shaped bead to form a bead component. FIG. 4 is an explanatory diagram for explaining deformation of a reinforcing filler in the tire axial direction. Schematic diagram of the bead assembly process in the green tire molding process. Schematic diagram of the stitching process in the green tire molding process. Schematic diagram of the turn-up process in the green tire molding process. FIG. 11 is a schematic diagram showing a first modified example of the reinforcing member, illustrating a step of peeling off the peel-off auxiliary member after stitching in the green tire molding process. FIG. 11 is a schematic diagram showing a second modified example of a reinforcing member. FIG. 13 is a schematic diagram showing a modified example of a bead filler.

Embodiments of the present invention will now be described with reference to the accompanying drawings. Note that the following description is essentially merely illustrative and is not intended to limit the present invention, its applications, or its uses. The drawings are schematic, and the ratios of dimensions, etc., differ from the actual ones.

Figure 1 is a meridian half cross-section of a pneumatic tire 1 before assembly to a rim, which is molded by a tire molding method according to one embodiment of the present invention, and only one side in the tire width direction with respect to the tire equator line CL is shown. The pneumatic tire 1 comprises a tread portion 10, a pair of sidewall portions 20 extending radially inward from both ends of the tread portion 10 in the tire width direction, and a pair of bead portions 30 located at the radially inner ends of each of the pair of sidewall portions 20.

A carcass ply 4 is laid across the inner side of the tire of the tread portion 10 and the sidewall portion 20 between a pair of bead portions 30. A plurality of belt layers 7 and belt reinforcing layers 8 are wound around the tire circumferential direction between the tread portion 10 and the carcass ply 4, in order from the inner side in the tire radial direction. An inner liner 3 is arranged on the inner side of the carcass ply 4.

A chafer layer 5 is disposed around the bead portion 30. The chafer layer 5 is disposed adjacent to the outer surface side (opposite the bead portion 30) of the carcass ply 4, and is folded back from the inner side in the tire width direction to the outer side around the bead portion 30 together with the carcass ply 4 and rolled up to the outer diameter side in the tire radial direction.

The bead portion 30 includes a bead member 30A having a bead core 31 and a bead filler 32 connected to it and extending radially outward in the tire. The bead core 31 is formed into a ring shape by bundling multiple bead wires. The bead filler 32 is made of a rubber material formed into a triangular cross section, and is attached in a ring shape along the outer end surface 31a of the bead core 31 on the outer side in the tire radial direction.

As shown in FIG. 2, the thickness of the bead filler 32 in the tire width direction decreases from the base end (inner end) 32a attached to the bead core 31 toward the tip end 32b. The width W1 of the inner end 32a of the bead filler 32 is set to be equal to the width of the bead core 31. The bead filler 32 has a narrow width portion 32c formed with a width in the tire width direction of 3.0 mm or less. The narrow width portion 32c has a tire radial height H1 of 30 mm or more. In other words, the bead filler 32 is a so-called thin and high bead filler.

The bead filler 32 may have a narrow width portion 32c and may have a tire radial height H2 of 50 mm or more. The tire radial height H2 of the bead filler 32 may be set to 30% to 65% of the tire cross-sectional height H0 (see FIG. 1). Here, the tire cross-sectional height H0 is calculated by multiplying the nominal cross-sectional width of the tire by the aspect ratio.

The bead member 30A also has a reinforcing member 40 disposed on the outer surface in the tire width direction, i.e., between the wound-up carcass ply 4 and the bead filler 32. The reinforcing member 40 is a steel reinforcing cord covered with rubber.

Next, a tire molding method for a pneumatic tire 1 having a thin and high bead filler according to an embodiment will be described with reference to Figs. 3A to 5. Fig. 3A is a schematic diagram showing the process of molding a reinforcing filler 33. Fig. 3B is a schematic diagram showing the process of molding a bead member 30A. Fig. 4 is an explanatory diagram of the collapse deformation of the reinforcing filler 33 toward the inside in the tire width direction due to its own weight. Figs. 5A to 5C are half cross-sectional views of a molding drum 50 showing the process of molding a green tire.

In the process of forming the bead member 30A, as shown in FIG. 3A, a reinforcing member 40 in a band state is attached to the side surface 32d (see FIG. 2) located on the outer side in the tire width direction of the bead filler 32 in a band state to form the reinforcing filler 33. As described above, the reinforcing member 40 includes a steel reinforcing cord, and therefore has higher rigidity than the unvulcanized bead filler 32 formed of rubber material. By attaching the reinforcing member 40 to the bead filler 32, a reinforcing filler 33 in which the bead filler 32 is reinforced is obtained.

As shown in FIG. 4, the width H3 of the reinforcing member 40 extending in the tire radial direction is formed to be constant, and the thickness t in the tire width direction is also formed to be constant. The reinforcing member 40 has a width that allows it to be attached to an area of 50% or more of the tire radial direction of the side surface 32d on the outer side in the tire width direction of the bead filler 32. In this embodiment, the width H3 of the reinforcing member 40 is set to be approximately the same dimension as the side surface 32d on the outer side in the tire width direction of the bead filler 32 before vulcanization molding. In other words, the reinforcing member 40 is attached to approximately the entire surface of the side surface 32d on the outer side in the tire width direction of the bead filler 32. Since the reinforcing member 40 is attached to the bead filler 32 in a band state, it is cut to a predetermined length according to the length of the bead filler 32 in the band state.

Next, as shown in FIG. 3B, in the process of forming the bead member 30A, the tip portion 33a of the band-like reinforcing filler 33 is attached to the outer peripheral surface of the ring-shaped bead core 31 with the tip portion 33a extended radially outward in the tire direction. Since the stiffness of the reinforcing filler 33 is increased by the reinforcing member 40, it is easy to attach the reinforcing filler 33 while suppressing deformation caused by collapse in the tire width direction inward.

More specifically, as mentioned above, the bead filler 32 is made of rubber and has low rigidity in an unvulcanized state. Furthermore, since the bead filler 32 is made of a thin and high bead filler, when the bead filler 32 is stretched in the tire radial direction, as shown by the imaginary line in Figure 4, it may collapse and deform toward the inside in the tire width direction with respect to the line segment L1 extending in the tire radial direction.

In contrast, as shown in FIG. 4, the reinforcing filler 33 to which the reinforcing member 40 is attached to increase its rigidity is set so that the amount of tilt (displacement) B in the tire width direction due to its own weight with respect to the line segment L1 extending in the tire radial direction of the tip portion 33a when the reinforcing filler 33 is stretched in the tire radial direction satisfies the following:

Ａ：補強フィラー３３のタイヤ径方向高さＡ
Ｂ：補強フィラー３３の先端部３３ａのタイヤ幅方向への倒れ量

A: Height A of the reinforcing filler 33 in the tire radial direction
B: Amount of inclination of the tip portion 33 a of the reinforcing filler 33 in the tire width direction

As a result, if B/A is less than 0, it is difficult to deform the reinforcing filler 33 along the carcass ply 4 when stitching the reinforcing filler 33 in the green tire molding process described below, and an air pocket may occur between the carcass ply 4 and the reinforcing filler 33. If B/A is greater than 0.3, the reinforcing filler 33 may collapse and deform under its own weight, making it difficult to attach it along the carcass ply 4, causing wrinkles, and an air pocket may occur between the side portion 20. For example, if the radial height A of the reinforcing filler 33 is 50 mm, the displacement B may be set to 15 mm or less.

The radial height A of the reinforcing filler 33 and the amount of displacement B of the tip portion 33a of the reinforcing filler 33 toward the inside in the tire width direction relative to the line segment L1 extending in the tire radial direction are dimensions before vulcanization molding and after the reinforcing filler 33 is assembled to the bead core 31.

The bending rigidity of the reinforcing member 40 may be set to, for example, 80% to 150% of the bending rigidity of the carcass ply 4. Since the bending rigidity of the reinforcing member 40 is set to 80% or more of the bending rigidity of the carcass ply 4, it is possible to suppress the collapse deformation of the bead filler 32 toward the inside in the tire width direction when the bead member 30A is molded and when the bead member 30A is assembled. On the other hand, since the bending rigidity of the reinforcing member 40 is set to 150% or less of the bending rigidity of the carcass ply 4, it does not hinder the deformation of the bead filler 32 to fit along the outer surface of the carcass ply 4 during stitching, which will be described later.

As shown in FIG. 5A, the forming drum 50 is divided into three parts in the direction of the drum axis X (the same as the tire width direction), with the central drum 52 located in the center and the end drums 54, 54 located on both sides of it, each of which is configured to be able to expand and contract independently. The end drum 54 is provided with a turn-up bladder 56.

In the green tire molding process, first, an unvulcanized inner liner layer (not shown) is wrapped around the outer circumference of the molding drum 50, and then an unvulcanized carcass ply 4 is wrapped around that outer circumference in a cylindrical shape.

Next, a pair of bead members 30A are placed on both widthwise ends of the outer peripheral surface of the wrapped carcass ply 4. When assembling the bead members 30A, as shown in FIG. 5A, the end drum 54 is reduced in diameter relative to the central drum 52, and therefore a step is formed between the outer peripheral surface of the central drum 52 and the outer peripheral surface of the end drum 54. The bead members 30A are assembled along the outside of this step.

In this embodiment, as described above, the reinforcing member 40 is attached to the entire circumference of the bead filler 32 on both sides of the bead filler 32 in the drum axial direction at this stage, so that the bead filler 32 is prevented from collapsing and deforming in the drum axial direction X when the bead member 30A is assembled. As a result, air pockets caused by the collapsing deformation of the reinforcing filler 33 are prevented.

Next, as shown in FIG. 5B, the reinforcing filler 33 is pressed and bent inward in the drum axial direction so as to fit along the outer peripheral surface of the carcass ply 4 using a pressing member (not shown) such as a stitcher roller. In detail, the reinforcing filler 33 is pressed against the carcass ply 4 arranged along the curved surfaces at both ends of the central drum 52, and the tip 33a side of the reinforcing filler 33 is bent inward in the drum axial direction. At this time, the reinforcing filler 33 is located radially outward of the forming drum 50 than the bead filler 32. As described above, the reinforcing member 40 has a constant thickness t and is attached to the entire surface of the bead filler 32. This makes it possible to suppress uneven attachment when the reinforcing filler 33 is deformed along the carcass ply 4 due to the presence or absence of the reinforcing member 40 and the change in thickness t during stitching.

Then, as shown in FIG. 5C, the side portions 4B on both sides of the carcass ply 4 are folded back inward in the drum axial direction (i.e., turned up) so as to encase the bead members 30A, respectively. In this example, the turn-up bladder 56 provided on the end drum 54 is filled with gas, causing the turn-up bladder 56 to expand, and as a result, the side portions 4B of the carcass ply 4 are folded back inward in the drum axial direction X simultaneously over the entire circumference of the drum, and the bead members 30A are encased in the carcass ply 4. Here, the side portions 4B of the carcass ply 4 refer to the portions of the carcass ply 4 located outside the position where the bead members 30A are placed in the drum axial direction X.

The process after the turn-up is the same as in conventional manufacturing methods. For example, the unvulcanized sidewall rubber that will become the sidewall portion 20 is arranged in a predetermined position to form the carcass band. Meanwhile, the belt, tread rubber, etc. are wound around the second forming drum to form the tread band. Next, the carcass band and tread band are detached from the first and second forming drums while being gripped from the outer periphery, and are transferred to the third forming drum by the respective transfer means so that the tread band is positioned on the outer diameter side of the carcass band. Then, in the third forming drum, the carcass band is bulged outward in the radial direction and bonded to the inner circumferential surface of the tread band to form a green tire. The obtained green tire is placed in a vulcanization mold and vulcanized to obtain a pneumatic tire.

The tire building method described above provides the following advantages:

The stiffness of the thin and high bead filler 32 is ensured by attaching the reinforcing member 40 to the thin and high bead filler 32 in a band state before being wrapped around the outer circumference of the bead core 31 to form the reinforcing filler 33. This makes it possible to suppress the bead filler 32 from collapsing inward in the tire width direction (drum width direction) during bead forming when the reinforcing filler 33 in a band state is attached to the ring-shaped bead core 31, and during bead assembly when the bead member 30A is assembled to the carcass ply 4. As a result, air pockets caused by collapsing deformation of the bead filler 32 are easily avoided.

As described above, the amount of inclination in the tire width direction due to the weight of the radially outer tip portion 33a of the reinforcing filler 33 relative to the radially extending line segment L1 satisfies the following.
0.0≦B/A≦0.3
A: Height of the reinforcing filler 33 in the tire radial direction B: Fall amount of the tip portion 33a of the reinforcing filler 33 in the tire width direction

This configuration makes it easy to align the reinforcing filler 33 along the outer surface of the carcass ply 4 during stitching, while suppressing the inward collapse deformation of the bead filler 32 in the width direction during bead molding and bead assembly. If B/A is smaller than 0, it is difficult to align the reinforcing filler 33 along the outer surface of the carcass ply 4 during stitching because the bending stiffness is high at the corners. On the other hand, if B/A is larger than 0.3, it is difficult to suppress the collapse deformation in the tire width direction because the bending stiffness of the reinforcing filler 33 is too low.

In addition, since the reinforcing member 40 is formed with a constant thickness t, it is possible to suppress uneven application of the reinforcing filler 33 to the carcass ply 4 that may occur due to the presence or absence of the reinforcing member 40 and changes in thickness t during stitching.

The width W3 of the reinforcing member 40 is set to be approximately the same as the length of the side surface 32d on the outer side in the tire width direction of the bead filler 32, so uneven attachment of the reinforcing filler 33 to the carcass ply 4 can be suppressed in the tire radial direction as well. Also, there is no need to prepare a reinforcing member 40 for each length of the bead filler 32 in the tire circumferential direction.

The present invention is not limited to the configuration described in the above embodiment, and various modifications are possible.

Although the configuration in which the pneumatic tire includes the reinforcing member 40 has been described, the present invention may be applied to a pneumatic tire that uses a thin and high bead filler but does not include the reinforcing member 40. In this case, as shown in FIG. 6, the reinforcing member 40 is composed of a peelable reinforcing member 140 that is peeled off from the bead filler 32 after stitching and before turning up.

This configuration allows the thin and high bead filler to be applied even to a pneumatic tire (not shown) that does not have a reinforcing member 40 on the outer surface of the bead filler 32 in the tire width direction of the pneumatic tire 1 in Figure 1.

The adhesive strength of the separation reinforcement member 140 is set to 3.0 N or more and 5.0 N or less. In this embodiment, the adhesive strength refers to the load required to separate the separation reinforcement member 140 from the bead filler 32 per 4000 ^mm2 , and the larger this is, the better the adhesiveness is. The adhesive strength of the separation reinforcement member 140 may be set to 50% or more and 90% or less of the adhesive strength of the carcass ply 4.

With this configuration, the adhesive strength of the peeling reinforcement member 140 to the bead filler 32 is ensured by a tackiness of 3.0 N or more, and it can be peeled off from the bead filler 32 by a tackiness of 5.0 N or less.

In addition, in this embodiment, the reinforcing member 40 is attached to the entire surface of the side surface 32d on the outer side of the tire of the bead filler 32, but this is not limited to the above. As shown in FIG. 7, the reinforcing member 40 may be attached to at least the narrow portion 32c of the bead filler 32. This increases the rigidity of the narrow portion 32c, and suppresses deformation of the bead filler 32. In addition, since the reinforcing member 40 is disposed only in necessary areas, the increase in weight of the pneumatic tire 1 can also be suppressed.

In the present embodiment, the bead filler 32 has a triangular cross-sectional shape, but is not limited to this. As shown in FIG. 8, the bead filler 332 may have a triangular portion 332a connected to the bead core 31 and having a substantially triangular cross-sectional shape, and a narrow portion 332b that extends radially outward from the radial outer side of the triangular portion 332a and narrows toward the tire radial outer side. In this case, the reinforcing member 340 may be attached to the entire surface of the bead filler 332 located on the outer side in the tire width direction, or may be attached only to the narrow portion 332b.

In addition, in this embodiment, a tire molding method in which the carcass ply is folded back and then expanded is described. However, the tire can also be molded in a tire molding method in which the portions of the carcass ply located on the inner side of a pair of bead members in the tire width direction are expanded radially outward to form the case body, and then both side portions of the carcass ply located on the outer side of the pair of bead members in the tire width direction are folded back in the tire width direction around the pair of bead members and attached to the sides of the case body. In this case, the peeling reinforcement member 140 is peeled off after the carcass ply is expanded and before it is turned up.

4 Carcass ply 30A Bead member 31 Bead core 31a Outer end 32 Bead filler 32a Inner end 32c Narrow width portion 33a Tip portion 40 of reinforcing filler Reinforcing member 50 Forming drum 140 Peeling reinforcing member A Height B of reinforcing filler in tire radial direction Displacement amount H3 Width t of reinforcing member Thickness W1 of reinforcing member Width

Claims (6)

A pair of bead members is prepared, each of which includes a ring-shaped bead core, a bead filler extending from an outer end portion on the outer side of the tire in the radial direction of the bead core while decreasing in cross section toward the radially outward direction, and a reinforcing member attached to a side surface of the bead filler, wherein the bead filler is configured as a thin and high bead filler having a narrow width portion that is narrower than the width of an inner end portion on the inner side of the tire in the radial direction of the bead filler and has a width of 3.0 mm or less, and the height of the narrow width portion in the tire radial direction is 30 mm or more,
The carcass ply is wound around a cylindrical forming drum,
The pair of bead members are assembled to the radially outer side and both axially opposite ends of the carcass ply,
The bead filler is pressed and bent inward in the width direction of the forming drum, and stitched along the outer surface of the carcass ply;
A widthwise outer portion of the carcass ply is folded back to a widthwise inner portion of the carcass ply,
Before being assembled to the carcass ply, the bead member
A tire building method in which the reinforcing member in a band state is attached to the thin, high bead filler in a band state to form a reinforcing filler in a band state, and the reinforcing filler is wrapped around the outer periphery of the ring-shaped bead core. The tire building method according to claim 1, wherein the reinforcing member is peeled off from the bead filler after the stitching and before the folding back. 3. The tire building method according to claim 2, wherein the adhesive strength of the reinforcing member is set to be equal to or greater than 3.0 N and equal to or less than 5.0 N. The tire building method according to claim 1 , wherein an amount of inclination in the tire width direction due to the weight of a tip end portion on an outer side in the tire radial direction of the reinforcing filler satisfies the following:
0.0≦B/A≦0.3
A: Height of reinforcing filler in tire radial direction B: Fall amount of tip of reinforcing filler in tire width direction The tire molding method according to any one of claims 1 to 4, wherein the reinforcing member has a constant tire radial dimension and a constant thickness. The tire molding method according to any one of claims 1 to 5, wherein the reinforcing member is attached to an area of the bead filler on the outer side in the tire width direction that occupies 50% or more of the tire radial direction.

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