JP2007260962A - Tire molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire molding method capable of shortening the time required in a molding process and capable of still more uniformly vulcanizing a tire constituent member large in thickness. <P>SOLUTION: In the tire molding method for molding a green tire by winding strip rubber S molded by a strip rubber molding machine 20 around a molding drum 10, the strip rubber S is molded by the strip rubber molding machine 20 in a state that a vulcanization degree is made different corresponding to the depth position of the tread part 6, around which the strip rubber S is wound, from the surface of the tire. Preferably, a plurality of strip rubber molding machines 20a, 20b and 20c are provided corresponding to the depth position of a layer and the vulcanization degree is set so as to be different at every strip rubber molding machine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tire molding method for molding a green tire by winding a strip rubber molded by a strip rubber molding machine around a molding drum.

  Generally, when manufacturing a pneumatic tire, each tire component such as an inner liner, sidewall, and tread is bonded together in an unvulcanized state to form a green tire, which is then placed in a mold. It is manufactured by vulcanization molding. However, since tires have different shapes and thicknesses for each component member, it is difficult to uniformly vulcanize each member in the vulcanization process. That is, a thick member such as a tread portion needs to have a long vulcanization time in order to vulcanize the inside. Therefore, if the vulcanization time is determined in accordance with a portion that takes time for vulcanization, a member having a small thickness may be overvulcanized. Then, the following patent documents 1 and 2 are known as a well-known technique for homogenizing vulcanization.

  In the tire manufacturing method disclosed in Patent Document 1, a carcass layer is mounted between a pair of left and right bead portions, and an unvulcanized tire casing in which a belt layer is disposed on the outer periphery of the carcass layer is molded. Separately from the tire casing, a strip-shaped unvulcanized rubber is wound around the cylindrical body multiple times to form an endless annular laminated rubber, and a tread pattern is molded from the laminated rubber to the outer periphery, or vulcanized or semi-vulcanized The endless annular precure tread is molded, the annular precure tread is fitted to the outer peripheral surface of the tire casing to form a green tire, and the green tire is vulcanized.

  In the method for manufacturing a tire disclosed in Patent Document 2, a vulcanized or semi-vulcanized tire casing in which a carcass layer is mounted between a pair of left and right bead portions and a belt layer is disposed on the outer periphery of the carcass layer is provided in advance. While molding, a vulcanized or semi-cured endless annular tread with a tread pattern formed on the outer peripheral surface is pre-formed, and a plurality of strip-shaped unvulcanized rubber is wound around the outer peripheral surface of the tire casing to form an adhesive layer In addition, an endless annular tread is fitted thereon to form a fitting body, and then the unvulcanized portion of the fitting body is vulcanized.

JP-A-10-193471 Japanese Patent Laid-Open No. 10-193472

  However, the tire manufacturing methods disclosed in Patent Documents 1 and 2 have the following problems. In Patent Document 1, it is necessary to prepare a pre-cured tread with a tread pattern formed in advance in a process different from the tire casing, and there is a problem that the process becomes complicated. In addition, the tire casing is unvulcanized, which is insufficient in terms of uniformly vulcanizing the entire tire. Similarly in Patent Document 2, it is necessary to prepare a pre-cured tread with a tread pattern formed in advance in a separate process, and there is a problem that the process becomes complicated. The tire casing is vulcanized or semi-vulcanized, but the entire tire casing is vulcanized and molded, which is insufficient in that the entire tire is uniformly vulcanized. In particular, for tire components having a large thickness such as the tread portion, a large difference in thermal history tends to occur between a position close to the tire surface and a deep position. is there.

  The present invention has been made in view of the above circumstances, and the problem is that the time required for the molding process can be shortened and the vulcanization can be made even more uniform even with thick tire components. Is to provide a simple tire molding method.

In order to solve the above problems, a tire molding method according to the present invention is as follows.
A tire molding method for molding a green tire by winding a strip rubber molded by a strip rubber molding machine around a molding drum,
It is characterized in that it is molded by a strip rubber molding machine with the degree of vulcanization varied depending on the depth position of the layer around which the strip rubber is wound from the tire surface.

  The operation and effect of the tire molding method having such a configuration will be described. In forming the green tire in the present invention, a method called a strip build method is used. In this method, strip rubber having a predetermined cross-sectional shape having a relatively small cross-sectional area is repeatedly wound around a molding drum to form a rubber component having a desired shape. By sequentially winding the strip rubber from the lower layer, the layers can be stacked to form a tire having a desired cross-sectional shape. Here, when the strip rubber is wound around the molding drum, the strip rubber is molded in a state where the degree of vulcanization is varied according to the depth position of the layer from the tire surface. That is, the deeper the position, the higher the degree of vulcanization, and on the tire surface, the strip rubber is wound with the degree of vulcanization being small or unvulcanized. Thereby, when a molded green tire is vulcanized, a tire vulcanized in a uniform state can be manufactured. Further, according to the molding method of the present invention, the vulcanization degree is adjusted and wound around the molding drum, so it is not necessary to prepare a semi-vulcanized tire component member in a separate process. Can be shortened. As a result, it is possible to provide a tire molding method capable of shortening the time required for the molding process and making the vulcanization even more uniform even with a thick tire component.

  In the present invention, it is preferable that a plurality of strip rubber molding machines are provided corresponding to the depth positions of the layers, and the vulcanization degree is set to be different for each strip rubber molding machine.

  According to this configuration, a plurality of strip rubber molding machines are prepared in advance, and the vulcanization degree is set to be different for each molding machine. Therefore, it is not necessary to change the degree of vulcanization during the molding in each molding machine, and each layer can be molded efficiently.

  In the present invention, the layer is preferably a layer constituting a tread portion. Since the tread portion has a particularly large thickness among the tire constituent members, it is particularly effective to use the molding method according to the present invention.

  In the present invention, it is preferable to vary the degree of vulcanization by varying the set temperature in each strip rubber molding machine.

  By changing the set temperature in each molding machine, the degree of vulcanization of the molded strip rubber can be changed. Only by changing the setting of the temperature adjusting mechanism, the degree of vulcanization of the strip rubber molded by each molding machine can be set. That is, before the vulcanization step, a certain degree of thermal history is added to the internal rubber (deep position from the surface) in advance to make a semi-vulcanized state to cover the vulcanization delay.

  In the present invention, it is preferable to vary the degree of vulcanization by changing the amount of the vulcanization accelerator used in each strip rubber molding machine.

  When molding strip rubber, a vulcanization accelerator is used. By changing the amount of this vulcanization accelerator for each molding machine, the degree of vulcanization of the strip rubber discharged from the molding machine can be changed. Can do. Also by such a method, a certain degree of heat history can be added to the internal rubber to make it a semi-vulcanized state.

  In the present invention, it is preferable to change the vulcanization speed by changing the amount of the vulcanization accelerator used in each strip rubber molding machine.

  Further, by changing the amount of the vulcanization accelerator for each molding machine, unvulcanized strip rubber having a different vulcanization speed can be discharged from each molding machine. According to this method, it is possible to recover the delay of the vulcanization start by using a compound having a high vulcanization speed by the internal rubber, and a uniform vulcanization state can be achieved in the entire tire.

  A preferred embodiment of a tire forming method according to the present invention will be described with reference to the drawings. First, a basic configuration of a pneumatic tire will be described with reference to FIG.

<Tire configuration>
FIG. 1 is a cross-sectional view showing a typical configuration of a pneumatic tire. The tire is formed of tire constituent members such as an inner liner 1, a bead wire 2, a bead filler 3, a sidewall portion 4, a shoulder portion 5, and a tread portion 6. The inner liner 1 is a thin rubber layer formed inside the tire. The bead wire 2 has a function of fixing the tire to the rim. The bead filler 3 increases the rigidity of the bead portion. The sidewall portion 4 occupies most of the side surface portion of the tire and also has a function of protecting the carcass 7. The shoulder portion 5 is located between the tread portion 6 and the sidewall portion 4 and forms a relatively thick rubber layer. The tread portion 6 is located outside the belt layer 8 and protects the carcass, and various tread patterns are formed on the surface.

<Tire molding method>
Next, a method for forming a green tire will be described with reference to the schematic view of FIG. FIG. 2 shows three strip rubber molding machines 20 (hereinafter simply referred to as molding machines), and the case of molding the tread portion 6 among tire constituent members will be described. Each molding machine 20 uses the same structure, but is adjusted in advance so that the degree of vulcanization of the extruded strip rubber S is different. The strip rubber S has a cross-sectional shape having a relatively small cross-sectional area, and the tread portion 6 having a desired cross-sectional shape can be formed by sequentially laminating these. Examples of the cross-sectional shape of the strip rubber S include a triangular shape and a rectangular shape.

  Although the tread portion 6 is illustrated in FIG. 2, since the tread portion 6 is thick, when the strip rubber S is laminated, the three-layer structure of the first layer 6 a, the second layer 6 b, and the third layer 6 c is illustrated. Consists of. The third layer 6c is closest to the tire surface, and the first layer 6a is at the deepest position. In such a case, when the finally produced green tire is vulcanized in the vulcanization step, the degree of vulcanization differs between a layer close to the surface and a layer deep from the surface. In such a case, since there is a problem in the raw burn state, if the vulcanization time is adjusted to the first layer 6a that takes the longest time for vulcanization, the third layer 6c located on the tire surface is in the overvulcanized state. there is a possibility.

  Therefore, in the present invention, the strip rubber S is extruded and molded in a state where the degree of vulcanization is changed in advance according to the position of each layer 6a to 6c. Therefore, a molding machine responsible for molding each layer is determined in advance. The first molding machine 20a is responsible for the first layer 6a, the second molding machine 20b is responsible for the second layer 6b, and the third molding machine 20c is responsible for the third layer 6c. . As for the strip rubber S discharged from each molding machine 20, the first molding machine 20a has the most advanced vulcanization degree, the second molding machine 20b has a medium degree of vulcanization, and the third molding machine 20c has The vulcanization degree is set to be low or unvulcanized. As described above, since the green tire is formed with the degree of vulcanization advanced toward the inside of the tire, the entire tire is vulcanized in a uniform state after the final vulcanization step.

<Configuration of molding machine>
Next, the structure of the equipment including the strip rubber molding machine 20 used for molding the green tire will be described. All three molding machines 20 shown in FIG. 2 can have the same structure. In FIG. 3, the forming drum 10 is driven by a servo motor 11 around a drum shaft 10a. Further, the molding machine 20 is provided and is driven in three directions by a driving device 26. Specifically, a first direction orthogonal to the drum shaft 10a, a second direction parallel to the drum shaft 10a, and a third direction that is a turning direction around a predetermined axis. These three directions can be driven independently, and can be driven by combining appropriate directions. Thereby, the molding machine 20 can be caused to perform a complicated movement operation.

  In order to wind the strip rubber S around the outer peripheral surface of the molding drum 10, the molding die 21 (a mold for extruding the strip rubber S with a predetermined cross-sectional shape) is made into a cross-sectional shape (profile) of the rubber layer. Must be moved accordingly. Therefore, by allowing the molding machine 20 to move in three directions as described above, the molding die 21 of the molding machine 20 can be moved with a high degree of freedom.

  In FIG. 3, the molding machine 20 includes a molding die 21, a gear pump 22, and an extruder 23. The molding die 21 has a mold part for extruding the strip rubber S having a predetermined cross-sectional shape. The extruder 23 includes a screw 23a for kneading rubber and a hopper 23b for charging a rubber material. A drive motor 24 for driving the screw 23a is provided. The rubber material kneaded by the extruder 23 is supplied to the gear pump 22, and the gear pump 22 has a function of supplying a fixed amount of rubber material to the molding die 21. Therefore, the gear pump 22 includes a pair of gears 22a. The rotational axis of the gear 22a is in the horizontal direction in FIG. 3 for convenience of illustration, but there is no problem even if it is installed in the vertical direction.

  The rubber material is not particularly limited as the present invention. For example, general-purpose rubbers such as natural rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR) can be used. . In addition, a vulcanization accelerator and the like are added together with the rubber material.

  The strip rubber S extruded from the molding die 21 is wound around the outer periphery of the molding drum 10. The forming drum 10 is rotationally driven by the servomotor 11 in the illustrated R direction. The gear 22 a of the gear pump 22 is rotationally driven by a servo motor 25. The driving device 26 is a mechanism for moving the entire molding machine 20 in the three directions described above.

  A temperature control mechanism is provided inside the molding machine 20. These temperature control mechanisms include a pipe for circulating water or warm water (oil may be used instead of water), and the temperature of the molding machine 20 is controlled by the temperature of the liquid to be circulated. The first temperature adjustment mechanism 30 has a function of adjusting the temperature inside the gear pump 22. The second temperature adjustment mechanism 31 is provided inside the cylinder 23 c of the extruder 23. The third temperature adjustment mechanism 32 is provided inside the screw 23 a of the extruder 23. Each of these temperature control mechanisms 30 to 32 can control the temperature independently. The temperature control mechanisms 30 to 32 are controlled by the temperature control unit 33. The control device 34 performs overall control of operations on the molding drum 10 and the molding machine 20.

  In the present invention, the temperature control setting is changed for each molding machine 20 under the control of the temperature control unit 33. As a result, the strip rubber S having a different vulcanization degree can be molded for each molding machine 20. For example, the temperature control of the molding machine 20a is set to 100 ° C., the molding machine 20b is set to 90 ° C., and the molding machine 20c is set to 80 ° C.

The state of previously vulcanized strip rubber S in the present invention is a semi-vulcanized state, the degree of this semi-vulcanization, a thermal history received until the rubber is completely vulcanized with X ₁₀₀ , extruded rubber of the received thermal history (residual heat including) when the X _alpha, can be defined by _{(X α / X 100) ×} 100 (%). In the above, for example, the molding machine 20a is set to 20% vulcanization, the molding machine 20b is set to 10% vulcanization, and the molding machine 20c is set to be unvulcanized. However, the definition of semi-vulcanization is not limited to this, and other definitions can also be used.

<Another embodiment>
In the present embodiment, unvulcanized and semi-vulcanized control is performed by the temperature control mechanism, but the amount of the vulcanization accelerator that is added together with the rubber material may be varied in each molding machine 20. Moreover, you may make it adjust a vulcanization degree by changing the setting of the rotation speed of a screw or a gear pump with each molding machine 20. FIG.

  In the present embodiment, the tread portion 6 has been described as an example. However, for example, the configuration of the present invention can also be adopted when a sidewall portion is formed. Moreover, if the number of layers is two or more, the configuration of the present invention can be applied.

  In the present invention, in the case of winding around the molding drum 10, not only when winding directly around the molding drum 2, but when rubber has already been wound around the circumference of the molding drum 2, it is wound over the rubber. Embodiments are also included.

  In the present embodiment, the molding machine 20 is an extrusion molding machine and can continuously extrude the strip rubber S. However, an injection molding machine may be used instead of the extrusion molding machine. In the case of an injection molding machine, the amount of strip rubber formed by one molding is limited, but by repeatedly molding this, tire molding by strip build can be performed.

  In the present embodiment, it has been explained that the strip rubber is discharged and molded from each molding machine 20 with different vulcanization degrees. However, the amount of the vulcanization accelerator is made different in each molding machine 20, and the vulcanization speed is increased. Different unvulcanized strip rubbers may be discharged from each molding machine 20. By varying the vulcanization speed, it is possible to obtain a uniform vulcanized state throughout the tire as a result.

Sectional view showing a typical configuration of a pneumatic tire The figure explaining the molding method of the tread part of a tire The figure which shows the structure of a molding drum and a strip rubber molding machine

Explanation of symbols

6 Tread part 6a First layer 6b Second layer 6c Third layer 10 Molding drum 20 Molding machines 20a, 20b, 20c Molding machine 21 Molding base 22 Gear pump 23 Extruder 33 Temperature control section 34 Control device S Strip rubber

Claims (6)

A tire molding method for molding a green tire by winding a strip rubber molded by a strip rubber molding machine around a molding drum,
A strip rubber molding machine that can extrude the strip rubber in a semi-vulcanized state, and varies the degree of vulcanization according to the depth position from the tire surface of the layer around which the strip rubber is wound. The tire molding method characterized by molding by the method.   The tire molding method according to claim 1, wherein a plurality of strip rubber molding machines are provided corresponding to the depth positions of the layers, and the vulcanization degree is set to be different for each strip rubber molding machine. .   The tire forming method according to claim 1, wherein the layer is a layer constituting a tread portion.   The tire molding method according to any one of claims 1 to 3, wherein the vulcanization degree is varied by varying the set temperature in each strip rubber molding machine.   The tire molding method according to any one of claims 1 to 3, wherein the degree of vulcanization is varied by changing the amount of a vulcanization accelerator used in each strip rubber molding machine. The tire molding method according to any one of claims 1 to 3, wherein the vulcanization speed is varied by changing the amount of a vulcanization accelerator used in each strip rubber molding machine.

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