JP4950484B2 - Tire manufacturing method - Google Patents

Description

  The present invention relates to a tire manufacturing method. Specifically, the present invention relates to an improvement in a tire preforming process.

  In manufacturing a tire, a green tire is first preformed by a molding machine. The green tire is put into a mold and is pressurized and heated. The rubber composition of the green tire flows by this pressurization and heating. The rubber causes a crosslinking reaction by heating. In this way, a tire is obtained.

  A first molding machine and a second molding machine are used for preforming an ATV (all-terrain vehicle) tire having a radial carcass. In this preliminary molding, a carcass ply including a cord is first wound around the drum of the first molding machine. At this time, the carcass ply has a cylindrical shape. A pair of bead portions are set on the carcass ply. The bead portion has a ring shape. The carcass ply is wound around the bead portion and folded. In this way, a 1st molded object is obtained.

The first molded body is removed from the first molding machine and set in the second molding machine. In the second molding machine, the first molded body is expanded. This process is called shaping. After shaping, tread rubber or the like is bonded to the carcass ply to obtain a second molded body (that is, a green tire). A general method for forming a green tire is disclosed in Japanese Patent Laid-Open No. 2000-351164.
JP 2000-351164 A

  In the expand type first molding machine, the drum opens when the bead portion is set. The carcass ply is stretched by the operation of the drum. After the first molded body is removed from the first molding machine, the carcass ply attempts to recover. Due to this restoring force, the diameter of the central portion of the first molded body in the axial direction is reduced. Since there is a hard bead portion on the outer side in the axial direction, the diameter of the vicinity of this bead portion is not reduced.

  In the first compact having a reduced diameter, the carcass cord density is uneven. When this first molded body is subjected to shaping in the second molding machine, non-uniform expansion occurs. Non-uniform expansion hinders static balance.

  When set in the second molding machine, the first molded body is passed through the clamp ring of the second molding machine. In the first compact having a reduced diameter, the center portion is caught by the clamp ring, and therefore a long time is required for the setting operation.

  An object of the present invention is to provide a production method in which a high-quality tire can be easily obtained.

The manufacturing method according to the present invention includes:
On the drum of the first molding machine, a step of obtaining a cylindrical first molded body including a pair of bead portions and a carcass ply bridged over these bead portions;
A step in which the diameter of the center in the axial direction of the first molded body is increased;
A step of setting the first molded body in a second molding machine;
A step in which a tread rubber is bonded to the first molded body to obtain a second molded body.

  Preferably, the diameter expansion is achieved by expansion of a bladder set inside the first molded body.

  Preferably, the ratio of the maximum inner diameter of the expanded first molded body to the diameter of the drum of the first molding machine is 110% or more and 160% or less.

  In the manufacturing method according to the present invention, since the first molded body after the diameter expansion is set in the second molding machine, the first molded body and the clamp ring are hardly caught. This manufacturing method is excellent in productivity. Since the density of the carcass cord is made uniform by the diameter expansion, the tire obtained by this manufacturing method is excellent in static balance.

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

  FIG. 1 is a flowchart showing a manufacturing method according to an embodiment of the present invention. In this manufacturing method, first, the carcass ply 6 is wound around the drum 4 (or former) of the first molding machine 2 shown in FIG. 2 (STEP 1). The carcass ply 6 has a cylindrical shape. Next, the drum 4 is opened, and a pair of bead portions (not shown) are set on the carcass ply 6 (STEP 2). Next, both ends of the carcass ply 6 are folded back inward in the axial direction (STEP 3). The carcass ply 6 is wound around the bead portion by folding. In this way, a 1st molded object is obtained. The first molded body is removed from the drum 4 (STEP 4). FIG. 3 shows the first molded body 8. The vertical direction in FIG. 3 is the axial direction of the first molded body 8. The first molded body 8 includes a folded portion 10. The folded portion 10 is a part of the carcass ply 6. The first molded body 8 may include other members together with the bead portion 12 and the carcass ply 6. Examples of other members include an inner liner and a chafer.

  The carcass ply 6 is stretched by the operation of opening the drum 4. Residual stress is generated in the carcass ply 6. Due to this residual stress, the carcass ply 6 tries to recover after the first molded body 8 is removed from the first molding machine 2. With this restoring force, as shown in FIG. 3, the central portion of the first molded body 8 is reduced in diameter. Since the hard bead portion 12 is present on the outer side in the axial direction, the vicinity of the bead portion 12 is not reduced in diameter. The cross-sectional shape of the outer peripheral surface of the first molded body 8 has an arc shape that is concave in the radial direction.

  Next, the 1st molded object 8 is conveyed to the pre-shaping apparatus. This pre-shaping device 13 is shown in FIG. The pre-shaping device 13 includes a bladder 14. The bladder 14 is set with the first molded body 8 (STEP 5). The bladder 14 is accommodated inside the first molded body 8. Next, the bladder 14 is filled with gas, and the bladder 14 expands (STEP 6). In FIG. 4, the inflated bladder 14 is shown. As is clear from FIG. 4, the diameter of the first molded body 8 is increased with the expansion of the bladder 14. The diameter expansion is remarkable at the central portion in the axial direction. Due to the diameter expansion, the cross-sectional shape of the outer peripheral surface of the first molded body 8 exhibits an arc shape that is convex in the radial direction.

  FIG. 5 is a cross-sectional view taken along line VV in FIG. This VV line is a straight line orthogonal to the axial direction at the axial center. As is apparent from FIG. 4, the inner diameter of the first molded body 8 at the time of diameter expansion is maximum on the VV line. In FIG. 5, the maximum inner diameter is indicated by a double-headed arrow Df.

  Next, gas is discharged from the bladder 14 and the bladder 14 contracts (STEP 7). As the bladder 14 contracts, the first molded body 8 also contracts. The first molded body 8 is removed from the pre-shaping device 13. The first molded body 8 after being removed is shown in FIG. The first molded body 8 is pre-shaped by the bladder 14. The inner diameter of the axially central portion of the first molded body 8 shown in FIG. 6 is larger than the inner diameter of the axially central portion of the first molded body 8 shown in FIG. In FIG. 6, the cross-sectional shape of the outer peripheral surface of the first molded body 8 is substantially a straight line. The cross-sectional shape in the radial direction may be slightly convex or slightly concave.

  Next, the first molded body 8 is conveyed to the second molding machine 16. This second molding machine 16 is shown in FIG. The first molded body 8 is set on the second molding machine 16 (STEP 8). In FIG. 7, an arrow A indicates the moving direction of the first molded body 8. At the time of setting, the clamp ring 18 of the second molding machine 16 is passed through the first molded body 8. Since the inner diameter of the first molded body 8 is sufficiently large, the first molded body 8 is not caught by the clamp ring 18. Therefore, it is not necessary to apply a lubricant to the clamp ring 18. The first molded body 8 is smoothly set on the second molding machine 16.

  In the second molding machine 16, the first molded body 8 is expanded by expansion of a bladder (not shown). Due to this expansion, the first molded body 8 is shaped (STEP 9). Due to the shaping, the first molded body 8 has a toroidal shape.

  A tread rubber is bonded to the first molded body 8 (STEP 10). Another member may be bonded to the first molded body 8 before and after the tread rubber is bonded. Examples of other members include belt ply, sidewall rubber, clinch rubber, and the like. A rubber sheet in which tread rubber and sidewall rubber are integrated may be attached. In this way, a 2nd molded object (green tire) is obtained.

  Next, the second molded body is removed from the second molding machine 16 (STEP 11). The second compact is put into a mold and subjected to vulcanization (STEP 12). In vulcanization, the second compact is pressed and heated in the mold. By this pressurization and heating, the rubber composition of the second molded body flows. The rubber causes a crosslinking reaction by heating. In this way, a tire is obtained.

  In this manufacturing method, the unevenness of the density of the carcass cord is corrected by pre-shaping (that is, diameter expansion) of the first molded body 8. When the first molded body 8 having a uniform density is shaped by the second molding machine 16, the first molded body 8 expands uniformly. The tire obtained from the first molded body 8 is excellent in static balance.

  In FIG. 2, what is indicated by a double arrow Dd is the diameter of the drum 4 of the first molding machine 2. The ratio of the diameter Df to the diameter Dd is preferably 110% or more and 160% or less. By setting this ratio to 110% or more, a tire having excellent static balance can be obtained. Moreover, the first molded body 8 can be easily set on the second molding machine 16 by setting this ratio to 110% or more. From these viewpoints, the ratio is more preferably 120% or more, and particularly preferably 130% or more. If this ratio is excessive, the density of the cord is also uneven. In this respect, the ratio is more preferably equal to or less than 150%, and particularly preferably equal to or less than 140%. The internal pressure of the bladder 14 is preferably controlled so that an appropriate maximum inner diameter Df is obtained. It is preferable that the dimension of the first molded body 8 or the bladder 14 at the time of pre-shaping is detected by a sensor, and this dimension is fed back to control the internal pressure.

  It is preferable that the state shown in FIG. 4 where the bladder 14 is expanded and the first molded body 8 is expanded in diameter is maintained for a predetermined time. The holding time is preferably 20 seconds or more and 90 seconds or less. By setting the holding time to 20 seconds or more, the pre-shaping is sufficiently performed and the uniformity of the carcass code is achieved. In this respect, the holding time is more preferably 30 seconds or longer. By setting the holding time to 90 seconds or less, productivity is not hindered and the carcass cord is prevented from being scattered. In this respect, the holding time is more preferably 60 seconds or less.

  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]
In the first molding machine, the inner liner, carcass ply, bead portion and chafer were assembled to obtain a first molded body. The cross-sectional shape of the outer peripheral surface of the first molded body was concave with respect to the radial direction. This first molded body was mounted on a pre-shaping device including the bladder shown in FIG. 4, and the bladder was expanded. Due to the expansion, the diameter of the first molded body was expanded. The ratio of the diameter Df to the diameter Dd was 110%. This first molded body was set in a second molding machine. After shaping, a belt ply and tread rubber were bonded to the first molded body to obtain a second molded body. This second molded body was put into a mold and vulcanized to obtain a tire.

[Examples 2 to 6]
A tire was obtained in the same manner as in Example 1 except that the ratio of the diameter Df to the diameter Dd was as shown in Table 1 below.

[Comparative example]
A tire was obtained in the same manner as in Example 1 except that the diameter was not expanded.

[Measurement of static balance]
The static balance of the obtained tire was measured. The results are shown in Table 1 below.

[Measurement of set time]
The set time of the first molded body to the second molding machine was measured. The results are shown in Table 1 below.

  As shown in Table 1, the tire obtained by the manufacturing method of the example is excellent in static balance. Moreover, in the manufacturing method of the embodiment, the set time is short. From this evaluation result, the superiority of the present invention is clear.

  Various tires can be manufactured by the manufacturing method according to the present invention.

FIG. 1 is a flowchart showing a manufacturing method according to an embodiment of the present invention. FIG. 2 is a front view showing the first molding machine used in the manufacturing method of FIG. 1 together with the carcass ply. FIG. 3 is a sectional view showing the first molded body removed from the first molding machine. FIG. 4 is a cross-sectional view showing the first molded body having an enlarged diameter together with the pre-shaping device. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a cross-sectional view showing the first molded body after being removed from the pre-shaping device. FIG. 7 is a cross-sectional view showing the first molded body of FIG. 6 together with the second molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... 1st molding machine 4 ... Drum 6 ... Carcass ply 8 ... 1st molded object 10 ... Folding part 12 ... Bead part 13 ... Pre-shaping apparatus 14 ... Bladder 16 ... Second molding machine 18 ... Clamp ring

Claims (3)

On the drum of the first molding machine, a step of obtaining a cylindrical first molded body including a pair of bead portions and a carcass ply bridged over these bead portions;
A step in which the diameter of the center in the axial direction of the first molded body is increased;
A step of setting the first molded body in a second molding machine;
Tread rubber is bonded to the first molded body, and Nde including a step of the second molded body is obtained,
A method for manufacturing a tire, wherein a ratio of a maximum inner diameter of the expanded first molded body to a diameter of a drum of the first molding machine is 110% or more and 160% or less .   The manufacturing method according to claim 1, wherein the diameter expansion is achieved by expansion of a bladder set inside the first molded body. The method according to claim 1 or 2, wherein the ratio of the maximum inner diameter of the expanded first molded body to the diameter of the drum of the first molding machine is 120% or more and 140% or less .

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