JP2016182801A - Manufacturing method of cushion tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a cushion tire which prevents air from remaining in a space between a rubber and a bead core.SOLUTION: The invention relates to a manufacturing method of a cushion tire 2 including a bead core 8 therein. The manufacturing method includes the steps of: molding a low cover 32; and vulcanizing the low cover 32. A step for molding the lower cover 32 includes the steps of: forming a layer of unvulcanized rubber which includes the bead core 8 therein; and pre-heating the layer of the unvulcanized rubber to discharge air existing between the bead core 8 and the unvulcanized rubber. Preferably, a temperature of the pre-heating ranges 50°C to 90°C.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for manufacturing a cushion tire. Specifically, the present invention relates to a method for manufacturing a cushion tire incorporating a bead core.

  The cushion tire is a solid tire having no air inside. As a cushion tire, a “pneumatic type” that can be used by being directly incorporated into a rim for a pneumatic tire is frequently used. Cushion tires are mainly used for industrial vehicles such as forklift trucks to which a large load is applied.

  When a vehicle loaded with a large load starts or stops, a large force is applied in the circumferential direction between the cushion tire and the rim. By repeatedly starting and stopping, the tire may slip relative to the rim. The sliding of the tire with respect to the rim is called rim slip. There is a need for a cushion tire in which rim slip is prevented.

  In order to prevent the rim slip of the cushion tire, a method of embedding a bead core in the base layer of the tire is used. A study on this method is reported in Japanese Patent Application Laid-Open No. 8-21661. The bead core described in this publication is composed of an outer bead core near the flange of the rim and an inner bead core positioned on the inner side in the axial direction. These bead cores extend in the circumferential direction of the tire. This bead core improves the force with which the tire tightens the rim. This tightening force prevents rim slip.

JP-A-8-21661

  In manufacturing a cushion tire, a sheet of unvulcanized rubber is first wound around a molding drum. A sheet of unvulcanized rubber is laminated to the molding drum. In a cushion tire in which a bead core is buried inside the tire, the bead core is disposed on the sheet while the rubber sheet is laminated on the drum. After placing the bead core, the unvulcanized rubber sheet is laminated again. As a result, the raw cover is formed. This raw cover is put into a mold. The raw cover is pressurized and heated by a mold. Thereby, the rubber composition of a raw cover raise | generates a crosslinking reaction. A cushion tire is obtained by this cross-linking reaction.

  In a tire incorporating a bead core, air tends to remain between the unvulcanized rubber and the bead core in the process of forming the raw cover. When the raw cover is put into the mold, a process of repeating opening and closing of the mold (called bumping) is performed in order to discharge air remaining between the raw cover and the mold. Since the raw cover is put in the mold at room temperature, the fluidity of the rubber constituting the raw cover is low at this time. The air remaining between the rubber and the bead core is not sufficiently discharged even during bumping because the bead core and the rubber having low fluidity become an obstacle. The remaining air that is not discharged can cause a decrease in the adhesion between the rubber and the bead core. This can be a cause of separation between the rubber and the bead core. In the tire described in JP-A-8-21661, separation between rubber and a bead core may occur.

  In order to discharge the air remaining between the rubber and the bead core, a molding drum whose outer diameter can be expanded and contracted may be used. When molding the raw cover, after the bead core is disposed, the outer diameter of the drum is increased to bring the rubber and the bead core into close contact. However, this method may not sufficiently discharge air.

  In order to prevent air from remaining between the rubber and the bead core, there is a method in which a recess is formed on the sheet in advance and the bead core is disposed in the recess. However, this method requires a step of forming a recess in the sheet. Furthermore, this method may not sufficiently discharge air.

  An object of the present invention is to provide a method for manufacturing a cushion tire in which air is prevented from remaining between a rubber and a bead core.

  The present invention relates to a method of manufacturing a cushion tire including a bead core therein. This manufacturing method includes a step of forming a raw cover and a step of vulcanizing the raw cover. The step of forming the raw cover includes the step of forming an unvulcanized rubber layer including the bead core therein, and discharging the air existing between the bead core and the unvulcanized rubber. Preheating the layer of vulcanized rubber.

  Preferably, the preheating temperature is 50 ° C. or higher and 90 ° C. or lower.

  In the case where the cushion tire includes a base layer including the bead core and a tread located radially outside the base layer, preferably, the step of forming the unvulcanized rubber layer includes the base Forming a first unvulcanized rubber layer for the layer, and forming the raw cover includes a second unvulcanized second tread for the tread on a radially outer side of the first unvulcanized rubber layer. The method further includes the step of forming a rubber layer, wherein the step of preheating the unvulcanized rubber layer preheats the first unvulcanized rubber layer after the formation of the second unvulcanized rubber layer. It is a process to do.

  In the case where the cushion tire includes a base layer including the bead core and a tread located on the radially outer side of the base layer, a process for forming the unvulcanized rubber layer is performed for the base layer. A step of forming a first unvulcanized rubber layer, the step of preheating the unvulcanized rubber layer is a step of preheating the first unvulcanized rubber layer, and a step of molding the raw cover May further include a step of forming a second unvulcanized rubber layer for the tread on the radially outer side of the first unvulcanized rubber layer after preheating.

  The method for manufacturing a cushion tire according to the present invention includes a step of preheating an unvulcanized rubber layer including a bead core therein in the step of forming a raw cover. This preheating increases the fluidity of the unvulcanized rubber layer. This rubber does not interfere with air discharge. Thereby, the air remaining between the bead core and the rubber is easily discharged outside in the vulcanization process. In this tire manufacturing method, air is prevented from remaining between the rubber and the bead core.

FIG. 1 is a cross-sectional view illustrating a part of a cushion tire manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 2 is a schematic view showing a process of winding a sheet of unvulcanized rubber. FIG. 3 is a cross-sectional view showing the middle of the process of forming the low cover of the cushion tire of FIG. FIG. 4 is a cross-sectional view showing the middle of the process of forming the low cover of the cushion tire of FIG. FIG. 5 is a schematic view showing a state where the raw cover of the cushion tire of FIG. 1 is preheated. FIG. 6 is a cross-sectional view showing a process of vulcanizing the raw cover of the cushion tire of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view of the cushion tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. What is indicated by the symbol R is a rim. This rim R is a regular rim. The regular rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In FIG. 1, the tire 2 is incorporated in a rim R. The cushion tire 2 is a pneumatic type.

  The tire 2 includes a tread 4, a base layer 6, a bead core 8, and a skin layer 10.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 12 that contacts the road surface. A groove 14 is carved in the tread surface 12. The groove 14 forms a tread pattern. The tread 4 is made of a crosslinked rubber having excellent wear resistance and grip properties. In the present embodiment, the tread 4 is formed from a single rubber. The tread 4 may be formed from two or more rubbers.

  The base layer 6 is located inside the tread 4 in the radial direction. The base layer 6 is made of a crosslinked rubber. Although not shown, in the present embodiment, the base layer 6 includes short fibers. The short fiber is obtained by cutting a cord made of an organic fiber into a short piece. Examples of preferable organic fibers include polyester fibers, nylon fibers, polyethylene naphthalate fibers, and aramid fibers. A mixture of a plurality of types of short fibers may be used. The base layer 6 may not contain short fibers. The base layer 6 may be formed of two or more rubbers.

  The bead core 8 is located inside the base layer 6. The bead core 8 is buried in the base layer 6. The bead core 8 extends in the circumferential direction. The bead core 8 has a ring shape. Although not shown, the bead core 8 includes a wound non-stretchable wire. A typical material for the wire is steel. The bead core 8 improves the force with which the tire 2 tightens the rim R. The bead core 8 contributes to prevention of rim slip. In the tire 2 of FIG. 1, three bead cores 8 are located in the base layer 6. The number of bead cores 8 is not limited to three. The number of bead cores 8 may be two or less. The number of bead cores 8 may be four or more.

  The skin layer 10 forms the side surface of the tire 2. The skin layer 10 is located on the outer side in the axial direction of the tread 4 and the base layer 6. The skin layer 10 protects the tread 4 and the base layer 6.

  Below, one Embodiment of the manufacturing method of the cushion tire 2 which concerns on this invention is shown. The manufacturing method of the tire 2 includes a step of forming a raw cover and a step of vulcanizing the raw cover.

The step of forming the raw cover further includes (1) a step of forming a first unvulcanized rubber layer for the base layer 6 including the bead core 8 therein,
(2) forming a second unvulcanized rubber layer for the tread 4 on the radially outer side of the first unvulcanized rubber layer;
(3) forming a third unvulcanized rubber layer for the skin layer 10 on the side surfaces of the first unvulcanized rubber layer and the second unvulcanized rubber layer; and (4) the bead core 8 and the first unvulcanized rubber layer. Including preheating the formed first unvulcanized rubber layer, the second unvulcanized rubber layer, and the third unvulcanized rubber layer to discharge air existing between the rubber and the rubber. Yes.

  In the step of forming the raw cover, in the step (1), as shown in FIG. 2, first, a first unvulcanized rubber sheet 16 is prepared. This first unvulcanized rubber sheet 16 is wound on a molding drum. In FIG. 2, what is indicated by a symbol D is a molding drum. The drum D is cylindrical. The drum D is configured to rotate around a central axis indicated by a symbol O. The direction indicated by the arrow P is the rotation direction of the drum D. This rotational direction P corresponds to the circumferential direction of the tire 2.

  As shown in FIG. 2, the starting end of the sheet 16 is placed on the drum D. The drum D is rotated in the direction indicated by the arrow P. Thereby, the sheet | seat 16 is wound by the circumferential direction. Thereafter, the bead core 8 is disposed on the layer of the wound sheet 16. In the tire 2, four bead cores 8 are arranged. After the bead core 8 is arranged, the first unvulcanized rubber sheet 16 is further wound. As a result, the bead core 8 is buried in the first unvulcanized rubber layer. FIG. 3 shows a state in which the first unvulcanized rubber layer 18 is formed on the drum D.

  In the step (2), a second unvulcanized rubber sheet for the tread 4 is prepared. This sheet is wound on the outer side in the radial direction of the first unvulcanized rubber layer 18 using the drum D. As shown in FIG. 4, a second unvulcanized rubber layer 20 is formed on the radially outer side of the first unvulcanized rubber layer 18.

  In the step (3), a third unvulcanized rubber is prepared for the skin layer 10. This is bonded to the side surfaces of the first unvulcanized rubber layer 18 and the second unvulcanized rubber layer 20. FIG. 4 shows a state after the third unvulcanized rubber layer 22 is laminated. In FIG. 4, a third unvulcanized rubber layer 22 is laminated on the drum D. After removing the first unvulcanized rubber layer 18 and the second unvulcanized rubber layer 20 from the drum D, the third unvulcanized rubber layer 22 may be bonded together.

  In the step (4), the first unvulcanized rubber layer 18, the second unvulcanized rubber layer 20, and the third unvulcanized rubber layer 22 are removed from the drum D. As shown in FIG. 5, they are put in a heating tank 24 and preheated. This preheating is performed in order to discharge air remaining between the first unvulcanized rubber and the bead core 8 in a later vulcanization step. This preheating enhances the fluidity of the first unvulcanized rubber. The inside of the heating tank 24 is set to a temperature at which the crosslinking reaction of the first unvulcanized rubber, the second unvulcanized rubber, and the third unvulcanized rubber does not proceed. With this preheating, the process of forming the raw cover is completed. Thereby, a raw cover is obtained.

  In the process of vulcanizing the raw cover, a mold is used. FIG. 6 is a cross-sectional view showing the mold 26. The left-right direction in FIG. 6 is the radial direction. This mold 26 is a two-piece mold. The mold 26 includes an upper mold 28 and a lower mold 30. FIG. 6 also shows the raw cover 32. In the raw cover 32, the third unvulcanized rubber layer 22 is omitted.

  In this step, the mold 26 is first opened. That is, the upper mold 28 is separated from the lower mold 30. In this state, the raw cover 32 is set inside the lower mold 30. Thereafter, the mold 26 is closed. That is, the upper mold 28 is overlaid on the lower mold 30. At this time, air may remain between the mold 26 and the raw cover 32. In order to discharge air, the mold 26 is normally opened and closed repeatedly with the raw cover 32 set. This process is called bumping. As described above, in the raw cover 32, the fluidity of the first unvulcanized rubber is enhanced by the above-described preheating. For this reason, the air remaining between the first unvulcanized rubber of the raw cover 32 and the bead core 8 is also discharged by bumping.

  The raw cover 32 set in the mold 26 is heated. This heating causes the unvulcanized rubber to undergo a crosslinking reaction. The base layer 6 is obtained from the first layer unvulcanized rubber layer 18. The tread 4 is obtained from the layer 20 of the second layer unvulcanized rubber. The skin layer 10 is obtained from the layer 22 of the third layer unvulcanized rubber. By this crosslinking reaction, the cushion tire 2 is obtained.

  The effects of the present invention will be described below.

  In a tire incorporating a bead core, air tends to remain between the rubber and the bead core in the process of forming the raw cover. When the raw cover is put into the mold, bumping is performed in order to discharge air remaining between the raw cover and the mold. Since the raw cover is put in the mold at room temperature, the fluidity of the rubber constituting the raw cover is low at this time. The air remaining between the rubber and the bead core is not sufficiently discharged even during bumping because the bead core and the rubber having low fluidity become an obstacle. The remaining air that is not discharged can cause a decrease in the adhesion between the rubber and the bead core. This can be a cause of separation between the rubber and the bead core.

  The method for manufacturing the cushion tire 2 according to the present invention includes a step of preheating a layer of unvulcanized rubber including the bead core 8 therein in the step of forming the raw cover 32. This preheating increases the fluidity of the unvulcanized rubber layer. This rubber does not interfere with air discharge. Thereby, the air remaining between the bead core 8 and the rubber is discharged to the outside by bumping in the vulcanization process. The air remaining between the bead core 8 and the rubber is easily discharged outside in the vulcanization process. In the method for manufacturing the tire 2, air is prevented from remaining between the rubber and the bead core 8.

  As for the temperature in the heating tank 24 in the case of preheating, 50 degreeC or more is preferable. By setting the temperature in the heating tank 24 to 50 ° C. or higher, the fluidity of the unvulcanized rubber is effectively enhanced. Thereby, the air remaining between the bead core 8 and the rubber can be effectively discharged. From this viewpoint, the temperature in the heating tank 24 is more preferably 60 ° C. or higher, and further preferably 80 ° C. or higher.

  The temperature in the heating tank 24 during preheating is preferably 90 ° C. or lower. By setting the temperature in the heating tank 24 during preheating to 90 ° C. or less, it is possible to prevent the unvulcanized rubber from causing a crosslinking reaction.

  The preheating time is preferably 3 hours or more. By setting the preheating time to 3 hours or more, the fluidity of the unvulcanized rubber is effectively enhanced. From this viewpoint, this time is more preferably 4 hours or more.

  Below, other embodiment of the manufacturing method of the cushion tire 2 which concerns on this invention is shown. The manufacturing method of the tire 2 includes a step of forming a raw cover and a step of vulcanizing the raw cover.

The step of forming the raw cover further includes (1) a step of forming a first unvulcanized rubber layer for the base layer 6 including the bead core 8 therein,
(2) a step of preheating the formed first unvulcanized rubber layer in order to discharge air existing between the bead core 8 and the first unvulcanized rubber;
(3) a step of forming a second unvulcanized rubber layer for the tread 4 on the radially outer side of the first unvulcanized rubber layer after preheating; and (4) a first unvulcanized rubber layer and a second layer. A step of forming a third unvulcanized rubber for the skin layer 10 on the side surface of the unvulcanized rubber layer is included.

  In the step of molding the raw cover, in the step (1), first, a first unvulcanized rubber sheet is prepared. The sheet of the first unvulcanized rubber is wound on the molding drum D.

  The leading edge of the sheet is placed on the drum D, and the drum D is rotated. Thereby, the sheet is wound in the circumferential direction. Thereafter, the bead core 8 is placed on the layer of the wound sheet. After disposing the bead core 8, a sheet of first unvulcanized rubber is further wound. As a result, the bead core 8 is buried in the first unvulcanized rubber layer.

  In the step (2), the first unvulcanized rubber layer is removed from the drum D. The first unvulcanized rubber layer is put in a heating tank and preheated. This preheating is performed in order to discharge air remaining between the first unvulcanized rubber and the bead core 8 in a later vulcanization step. This preheating enhances the fluidity of the first unvulcanized rubber. The inside of the heating tank is set to a temperature at which the crosslinking reaction of the first unvulcanized rubber does not proceed.

  In the step (3), the preheated first unvulcanized rubber layer is mounted on a drum different from the drum D. A second unvulcanized rubber sheet for the tread 4 is prepared. This sheet is wound on the outer side in the radial direction of the pre-heated first unvulcanized rubber layer using this drum. At this time, it is preferable that the second unvulcanized rubber sheet has a high temperature immediately after being discharged from a roll or an extruder. A second unvulcanized rubber layer is formed on the radially outer side of the first unvulcanized rubber layer.

  In the step (4), a third unvulcanized rubber is prepared for the skin layer 10. This is bonded to the side surfaces of the first unvulcanized rubber layer and the second unvulcanized rubber layer. Thereby, a raw cover is obtained.

  In the process of vulcanizing the raw cover, a mold 26 is used. This mold 26 is a two-piece mold 26. The mold 26 includes an upper mold 28 and a lower mold 30.

  In this step, the mold 26 is first opened. That is, the upper mold 28 is separated from the lower mold 30. In this state, the raw cover is set inside the mold 26. Thereafter, the mold 26 is closed. That is, the upper mold 28 is overlaid on the lower mold 30. At this time, air may remain between the mold 26 and the raw cover. In order to discharge air, the mold 26 is normally opened and closed repeatedly with the raw cover set. This process is called bumping. As described above, in the raw cover, the fluidity of the first unvulcanized rubber is enhanced by the preheating described above. This rubber does not interfere with air discharge. For this reason, the air remaining between the first unvulcanized rubber of the low cover and the bead core 8 is also discharged by bumping.

  The raw cover set in the mold 26 is heated. This heating causes the unvulcanized rubber to undergo a crosslinking reaction. The base layer 6 is obtained from the first layer unvulcanized rubber layer. A tread 4 is obtained from the second unvulcanized rubber layer. The skin layer 10 is obtained from the third unvulcanized rubber layer. By this crosslinking reaction, the cushion tire 2 is obtained.

  The manufacturing method of the cushion tire 2 according to the present invention includes a step of preheating a layer of unvulcanized rubber including the bead core 8 therein in the step of molding the raw cover. This preheating increases the fluidity of the unvulcanized rubber layer. Thereby, the air which remained between the bead core 8 and rubber | gum is discharged | emitted outside by the bumping process in a vulcanization process. The air remaining between the bead core 8 and the rubber is easily discharged outside in the vulcanization process. In the method for manufacturing the tire 2, air is prevented from remaining between the rubber and the bead core 8.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A cushion tire having the configuration shown in FIG. 1 was manufactured using the manufacturing method according to the present invention. The size of this tire is 600-9. The manufacturing conditions of this tire are shown in Example 1 in Table 1 below. In this manufacturing method, after the first unvulcanized rubber layer, the second unvulcanized rubber layer, and the third unvulcanized rubber layer are formed, the whole is preheated. This is shown as “all layers” in the “preheated layer” column of Table 1. The preheating conditions are as shown in Table 1.

[Comparative Example 1]
The manufacturing method of Comparative Example 1 is the same as that of Example 1 except that preheating is not performed. This is a conventional manufacturing method.

[Example 2]
In the production method of Example 2, preheating was performed after the formation of the first unvulcanized rubber layer, and layers of the second unvulcanized rubber and the third unvulcanized rubber were formed after the preheating. This is shown as “first layer” in the “preheated layer” column of Table 1. The preheating conditions are as shown in Table 1.

[Evaluation of residual air]
The prototype tire was disassembled, and it was confirmed by visual observation whether air remained between the bead core and the rubber. Ten tires were observed for each example and comparative example. This result is shown in Table 1 as “None” when no air residue is observed, and “Yes” when even one air residue is confirmed.

  As shown in Table 1, according to the present invention, a cushion tire in which residual air is suppressed is obtained. From this evaluation result, the superiority of the present invention is clear.

  The tire manufacturing method according to the present invention can be applied to tires for industrial vehicles.

2 ... Tire 4 ... Tread 6 ... Base layer 8 ... Bead core 10 ... Skin layer 12 ... Tread surface 14 ... Groove 16 ... Sheet 18 ... First not yet Vulcanized rubber layer 20 ... Second unvulcanized rubber layer 22 ... Third unvulcanized rubber layer 24 ... Heating tank 26 ... Mold 28 ... Upper mold 30 ...・ Lower mold 32 ... Raw cover

Claims (4)

A method of manufacturing a cushion tire including a bead core therein,
Including a step of forming a raw cover and a step of vulcanizing the raw cover,
The step of forming the raw cover includes
Forming a layer of unvulcanized rubber containing the bead core therein;
A method of manufacturing a cushion tire, including a step of preheating the unvulcanized rubber layer in order to discharge air existing between the bead core and the unvulcanized rubber.   The method for manufacturing a cushion tire according to claim 1, wherein the preheating temperature is 50 ° C or higher and 90 ° C or lower. The cushion tire includes a base layer including the bead core, and a tread located on the radially outer side of the base layer,
The step of forming the unvulcanized rubber layer is a step of forming a first unvulcanized rubber layer for the base layer,
Forming the raw cover further includes forming a second unvulcanized rubber layer for the tread on the radially outer side of the first unvulcanized rubber layer;
The cushion according to claim 1 or 2, wherein the step of preheating the unvulcanized rubber layer is a step of preheating the first unvulcanized rubber layer after the formation of the second unvulcanized rubber layer. Tire manufacturing method. The cushion tire includes a base layer including the bead core, and a tread located on the radially outer side of the base layer,
The step of forming the unvulcanized rubber layer is a step of forming a first unvulcanized rubber layer for the base layer,
The step of preheating the unvulcanized rubber layer is a step of preheating the first unvulcanized rubber layer;
The step of forming the raw cover further includes a step of forming a second unvulcanized rubber layer for the tread on the radially outer side of the first unvulcanized rubber layer after preheating. The manufacturing method of the cushion tire as described in.

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