JP2012106423A - Tire production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high-quality tire stably.SOLUTION: The tire production method includes the steps of: obtaining a low cover by a preliminary molding (STEP1); supplying the low cover into a mold (STEP2); filling a bladder located inside the low cover with a first heating medium and adjusting the internal pressure of the bladder at a primary pressure P1 while heating the low cover (STEP3); further filling the bladder with a second heating medium and adjusting the internal pressure of the bladder at a secondary pressure P2 while heating the low cover (STEP4); and further filling the bladder with a pressure medium to pressurize the low cover (STEP5). In the tire production method, the secondary pressure P2 is higher than the primary pressure P1.

Description

  The present invention relates to a tire manufacturing method.

  The tire is obtained by pressurizing and heating a raw cover (also referred to as an uncrosslinked tire) in a cavity surrounded by a mold and a bladder.

  This tire manufacturing method includes (1) a step of filling a bladder with a heating medium and heating the raw cover, (2) a step of further filling the bladder with a pressurizing medium and pressurizing while heating the raw cover, and (3) A step of discharging the heating medium and the pressure medium from the bladder is included.

  In this manufacturing method, the expanded bladder presses the raw cover against the cavity surface of the mold. The rubber flows and the air between the cavity surface and the raw cover is discharged. The rubber sinks into the cavity surface, forming the outer surface of the tire.

  Air may remain between the raw cover and the cavity surface. In this case, a bear is formed on the surface of the tire. Bears impair tire quality.

  A split mold may be used as the mold. This mold includes an arc-shaped tread segment. In this mold, a ring-shaped cavity surface is formed by arranging a plurality of segments.

  A vent hole may be provided in the mold. The vent hole encourages air discharge. This vent hole can contribute to prevention of bear generation. However, rubber will flow into the vent hole. In this case, spew is formed on the surface of the tire. Spew detracts from the appearance of the tire. Spew can be removed by cutting, but this cutting takes time. The rubber composition that has undergone a crosslinking reaction may remain in the vent hole. The remaining air hinders air discharge and causes a bear. The vent hole is cleaned for the purpose of restraining the bear. This cleaning takes time.

  In order to prevent the generation of bears and spews, various studies have been made on tire manufacturing methods. Examples of this study are disclosed in Japanese Patent Application Laid-Open Nos. 9-300356 and 2002-36245.

JP-A-9-300356 JP 2002-36245 A

  FIG. 10 shows the change over time in the internal pressure of the bladder from the start of the heating process to the completion of the discharge process in the conventional manufacturing method. The horizontal axis represents time, and the vertical axis represents pressure. In FIG. 10, the start time of the heating process is shown as t0, and the internal pressure of the bladder at that time t0 is shown as a reference pressure P0 (usually 0 kPa). In FIG. 10, a double arrow S1 represents a heating process, a double arrow S2 represents a pressurization process, and a double arrow S3 represents a discharge process.

  In the heating step S1, the internal pressure of the bladder reaches the primary pressure P1 at time t1 due to filling of the heating medium. In this heating step S1, the internal pressure of the bladder is held at this primary pressure P1 until time t2.

  At time t2, the pressurizing step S2 is started. In the pressurizing step S2, the bladder is filled with a pressurizing medium. By this filling, the internal pressure of the bladder reaches the secondary pressure P2 at time t3. In the pressurizing step S2, the internal pressure of the bladder is held at the secondary pressure P2 until time t4.

  At time t4, the discharging process S3 is started. In this discharge step S3, the heating medium and the pressure medium are discharged from the bladder. Due to this discharge, the internal pressure of the bladder decreases. This discharge is completed at time t5. Thereafter, the tire is removed from the mold.

  In this manufacturing method, the time (t1-t0) from the start of the heating step S1 to the arrival at the primary pressure P1 is about 10 seconds. In the heating step S1, the internal pressure of the bladder is increased to the primary pressure P1 all at once.

  In this manufacturing method, the air between the raw cover and the cavity surface may not be sufficiently discharged. In this case, there is a problem that air remains and bears are generated on the surface of the tire. In particular, this problem becomes significant when a raw cover having a profile that does not match the profile of the cavity surface is put into the mold.

  The shape and thickness of the raw cover may be adjusted. This adjustment prevents the occurrence of bears. However, in this case, the rubber flows into a minute gap at the dividing position of the mold, resulting in excessive spew. With this manufacturing method, it is difficult to stably produce high-quality tires.

  An object of the present invention is to provide a production method capable of stably producing a high-quality tire.

The tire manufacturing method according to the present invention includes:
(1) obtaining a raw cover by preforming;
(2) a step of putting the raw cover into a mold;
(3) filling the bladder located inside the raw cover with the first heating medium and heating the raw cover while causing the internal pressure of the bladder to reach the primary pressure P1;
(4) filling the bladder with a second heating medium and further heating the raw cover while causing the internal pressure of the bladder to reach the secondary pressure P2,
(5) a step of further filling the bladder with a pressurizing medium and pressurizing the raw cover. In this manufacturing method, the secondary pressure P2 is higher than the primary pressure P1.

  In this tire manufacturing method, it is preferable that the first pressurization speed until the primary pressure P1 is reached in the first heating step is the second pressure until the secondary pressure P2 is reached in the second heating step. Less than the pressure speed. The mold is preferably a spuleless mold. The first filling time Ta is preferably 30 seconds or longer and 100 seconds or shorter. The primary pressure P1 is preferably 3 kPa or more and 10 kPa or less. The second filling time Tb is preferably 30 seconds or less. The heating time Tc from the time when the internal pressure of the bladder reaches the secondary pressure P2 to the start of filling with the pressurized medium is preferably 120 seconds or more and 180 seconds or less.

  In the manufacturing method according to the present invention, since the internal pressure of the bladder is precisely controlled, the generation of bears is effectively prevented. According to this manufacturing method, a high-quality tire can be produced stably.

FIG. 1 is a plan view showing a part of a vulcanizing apparatus used in a tire manufacturing method according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a perspective view showing a mold segment constituting the vulcanizing apparatus of FIG. 1. FIG. 4 is a flowchart showing a tire manufacturing method. FIG. 5 is a graph showing the change over time in the internal pressure of the bladder. FIG. 6 is a perspective view showing a part of a mold used in a tire manufacturing method according to another embodiment of the present invention. FIG. 7 is a cross-sectional view along the circumferential direction of the core constituting the segment of FIG. FIG. 8 is a perspective view showing a shim used in the core of FIG. FIG. 9 is an enlarged cross-sectional view showing a part of the block of FIG. FIG. 10 is a graph showing the change over time in the internal pressure of the bladder in the conventional tire manufacturing method.

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

  FIG. 1 and FIG. 2 show a vulcanizing device 2 used in a tire manufacturing method according to an embodiment of the present invention. The vulcanizing apparatus 2 includes a bladder 4 and a mold 6. In FIG. 2, what is indicated by a symbol R is a raw cover (also referred to as an uncrosslinked tire). In the vulcanizing apparatus 2, the raw cover R is pressurized and heated in a cavity 8 surrounded by the bladder 4 and the mold 6. A tire is obtained by this pressurization and heating. In addition, the direction shown by the double arrow A in FIG. 1 is a circumferential direction, and the direction perpendicular | vertical to this paper surface is an axial direction. In FIG. 2, the horizontal direction is the radial direction, and the vertical direction is the axial direction.

  The bladder 4 is made of a crosslinked rubber. As shown in FIG. 2, the bladder 4 is located inside the raw cover R in the radial direction. The bladder 4 has a substantially cylindrical shape.

  In the vulcanizer 2, the bladder 4 is filled with gas. This filling causes the bladder 4 to expand. When gas is discharged from the inside, the bladder 4 contracts.

  The mold 6 includes a large number of tread segments 10, a pair of upper and lower side plates 12, and a pair of upper and lower bead rings 14. The planar shape of the segment 10 is substantially arcuate. In this mold 6, a large number of segments 10 are arranged in a ring shape. The number of segments 10 is usually 3 or more and 20 or less. In this mold 6, the side plate 12 and the bead ring 14 are substantially ring-shaped. This mold 6 is a so-called “split mold”. In the mold 6, the cavity surface 16 is configured by combining the segment 10, the side plate 12, and the bead ring 14. This cavity surface 16 forms the outer surface of the tire. Although not shown, the mold 6 is provided with a vent hole.

  In FIG. 3, a segment 10 is shown. In FIG. 3, the direction indicated by the arrow X is the radial direction, and the direction indicated by the arrow Y is the axial direction.

  In the mold 6, the segment 10 includes a holder 18 and a block 20. The holder 18 is made of steel or aluminum alloy. The block 20 is attached to the holder 18. Although not shown, the block 20 is fixed to the holder 18 by inserting bolts into screw bushes provided on the back surface thereof.

  The block 20 includes a molding surface 22. The molding surface 22 forms a part of the cavity surface 16. The molding surface 22 includes a convex portion 24 and a concave portion 26. This convex part 24 respond | corresponds to the groove | channel of the tread of a tire. A tread pattern is formed on the tire by the convex portions 24 and the concave portions 26. 2, illustration of the convex part 24 and the recessed part 26 is abbreviate | omitted.

  The block 20 is made of a metal material. A typical metallic material is an aluminum alloy. The block 20 is obtained by cutting a plate material. This block 20 is comprised from the single member.

  In the mold 6, the surface 28 of the segment 10 that abuts the adjacent segment 10 is referred to as a divided surface. A minute gap is generated between the dividing surface 28 and another dividing surface 28 adjacent to the dividing surface 28. In the mold 6, air is discharged through this gap.

  FIG. 4 is a flowchart showing a tire manufacturing method. This manufacturing method includes a preforming step (STEP 1), a charging step (STEP 2), a first heating step (STEP 3), a second heating step (STEP 4), a pressurizing step (STEP 5), and a discharging step (STEP 6). .

  In the preforming step (STEP 1), members such as a tread, a sidewall, and a bead are prepared. These members are combined in a former (not shown). By this combination, the raw cover R is obtained.

  In the charging step (STEP 2), the raw cover R is charged into the opened mold 6. At the time of charging, the bladder 4 is contracted inside the mold 6. After the charging, the mold 6 is closed and the first heating step (STEP 3) is started.

  In the first heating step (STEP 3), the bladder 4 is filled with the first heating medium. This filling causes the bladder 4 to expand. The bladder 4 contacts the raw cover R.

  In this manufacturing method, the first heating medium is steam whose temperature is adjusted from 180 ° C. to 200 ° C. This first heating medium is at a high temperature. Moreover, the heat capacity of the first heating medium is large. For this reason, a sufficient amount of heat is supplied to the raw cover R by the first heating medium. In the first heating step, the raw cover R is heated by the first heating medium. As the first heating medium, nitrogen gas whose temperature is adjusted from 180 ° C. to 200 ° C. may be used.

  FIG. 5 shows the change over time in the internal pressure of the bladder 4 from the start of the first heating step (STEP 3) to the completion of the discharge step (STEP 6). In FIG. 5, the horizontal axis represents time and the vertical axis represents pressure. The start time of the first heating step is t0, and the internal pressure of the bladder 4 at the time t0 is indicated as the reference pressure P0. In this manufacturing method, the reference pressure P0 is 0 kPa.

  As shown in the drawing, in the first heating step (STEP 3), the internal pressure of the bladder 4 gradually increases due to the filling of the first heating medium. The internal pressure of the bladder 4 reaches the primary pressure P1 at time t1. In this first heating step, the bladder 4 is filled with the first heating medium, and the raw cover R is heated. The internal pressure of the bladder 4 is allowed to reach the primary pressure P1 over time.

  In the second heating step (STEP 4), the bladder 4 is further filled with a second heating medium. This filling further expands the bladder 4. The bladder 4 sufficiently contacts the raw cover R. The bladder 4 spreads the raw cover R. The bladder 4 adjusts the shape of the raw cover R.

  In this production method, the second heating medium is the same steam as that of the first heating medium described above, the temperature of which is adjusted from 180 ° C. to 200 ° C. Therefore, this second heating medium is also high temperature and has a large heat capacity. For this reason, a sufficient amount of heat is supplied to the raw cover R by the second heating medium. The raw cover R is further heated by the second heating medium. As the second heating medium, nitrogen gas whose temperature is adjusted from 180 ° C. to 200 ° C. may be used. In this manufacturing method, a series of steps from the first heating step to the second heating step is also referred to as a heating step.

  As shown in FIG. 5, the second heating step (STEP 4) is started at time t1. In this manufacturing method, the second heating step is started immediately after the internal pressure of the bladder 4 reaches the primary pressure P1. In the second heating step, the internal pressure of the bladder 4 is increased at a stroke by filling the second heating medium. The internal pressure of the bladder 4 reaches the secondary pressure P2 at time t2. The internal pressure of the bladder 4 is held at the secondary pressure P2 until time t3. This secondary pressure P2 is the highest pressure reached in the heating process. This secondary pressure P2 is higher than the primary pressure P1. In this manufacturing method, the secondary pressure P2 is adjusted to 15 kPa.

  In the pressurizing step (STEP 5), the bladder 4 is further filled with a pressurizing medium. By this filling, the bladder 4 further expands. The bladder 4 presses the raw cover R against the cavity surface 16 of the mold 6. By this pressing, the raw cover R is pressurized.

  As shown in FIG. 5, the pressurizing step (STEP 5) is started at time t3. In this pressurizing step, the internal pressure of the bladder 4 further increases due to the filling of the pressurizing medium. The internal pressure of the bladder 4 reaches the tertiary pressure P3 at time t4. The internal pressure of the bladder 4 is held at the tertiary pressure P3 until time t5. This tertiary pressure P3 is the highest ultimate pressure in the pressurizing step. In this manufacturing method, the tertiary pressure P3 is adjusted to 21 kPa.

  In this manufacturing method, the time from when filling of the pressurized medium is started until the internal pressure of the bladder 4 reaches the tertiary pressure P3 (hereinafter, pressurization time) is set to 30 seconds or less. The time from when the internal pressure of the bladder 4 reaches the tertiary pressure P3 until the discharge of the heating medium and the pressure medium is started (hereinafter referred to as pressure holding time) is set to 180 seconds or more and 600 seconds or less.

  In this pressurizing step (STEP 5), the bladder 4 is filled with the first heating medium and the second heating medium in addition to the pressurizing medium. For this reason, in this pressurization process, the raw cover R is pressurized and heated. The rubber flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained.

  In this manufacturing method, room temperature nitrogen gas is used as the pressurizing medium. The pressure medium is at a lower temperature than the first heating medium and the second heating medium. The heat capacity of the pressure medium is smaller than that of the first heating medium and the second heating medium. For this reason, this pressurization medium can prevent the temperature rise by adiabatic compression. In this pressurizing step (STEP 5), the temperature at which the raw cover R is heated is appropriately maintained, so that a properly vulcanized tire can be obtained. This pressure medium can contribute to the production of high-quality tires. Moreover, as described above, the pressurizing medium is nitrogen gas. For this reason, this pressurizing medium can also contribute to the improvement of the durability of the bladder 4.

  As shown in FIG. 5, the discharging process (STEP 6) is started at time t5. In the discharging step, the heating medium and the pressure medium are discharged from the bladder 4. Due to the discharge of the heating medium and the pressure medium, the internal pressure of the bladder 4 decreases. This discharge is completed at time t6. Thereafter, the tire is taken out from the mold 6.

  In this manufacturing method, the primary pressure P1 as the highest ultimate pressure in the first heating step (STEP 3) is lower than the secondary pressure P2. Moreover, the internal pressure of the bladder 4 is allowed to reach the primary pressure P1 over time. In the first heating step, the heating of the raw cover R is prioritized over the discharge of air. From the viewpoint that air is effectively discharged in the subsequent steps, the primary pressure P1 is preferably 3 kPa or more, and more preferably 4 kPa or more. The primary pressure P1 is preferably 10 kPa or less, and more preferably 6 kPa or less.

  As described above, in the second heating step (STEP 4), the internal pressure of the bladder 4 is made to reach the secondary pressure P2 at once. Since the raw cover R is sufficiently heated in the first heating step (STEP 3), the rubber as a whole has an appropriate fluidity when the second heating step is started. Since the internal pressure of the bladder 4 is increased to the secondary pressure P2 at a stretch while the rubber has an appropriate fluidity, the rubber flows along the cavity surface 16 of the mold 6. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. With this manufacturing method, high-quality tires can be produced stably.

  In FIG. 5, the double-headed arrow Ta represents the time from the start of filling the first heating medium until the internal pressure of the bladder 4 reaches the primary pressure P1. This time Ta is referred to as a first heating time. A double-headed arrow Tb represents a time from when filling of the second heating medium is started until the internal pressure of the bladder 4 reaches the secondary pressure P2. This time Tb is referred to as a second heating time. A double-headed arrow Tc represents a time from when the internal pressure of the bladder 4 reaches the secondary pressure P2 to when filling of the pressurized medium is started. This time Tc is referred to as a heating and holding time. Note that the double arrow Td is the pressurization time described above, and the double arrow Te is the pressurization holding time described above.

  In this manufacturing method, the first heating time Ta is preferably 30 seconds or more and 100 seconds or less. By setting the time Ta to 30 seconds or more, the raw cover R is sufficiently heated in the first heating step. For this reason, when the second heating step is started, the rubber as a whole has adequate fluidity. Since the internal pressure of the bladder 4 is increased to the secondary pressure P2 at a stretch while the rubber has an appropriate fluidity as a whole, the rubber flows along the cavity surface 16 of the mold 6. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. By setting the time Ta to 100 seconds or less, the fluidity inhibition associated with the rubber crosslinking reaction is prevented. Since the rubber has an appropriate fluidity, the discharge of air is promoted. Even in this case, the formation of the bear is prevented.

  In this manufacturing method, the second heating time Tb is preferably 30 seconds or less. Since the internal pressure of the bladder 4 is increased from the primary pressure P1 to the secondary pressure P2 at once, air is effectively discharged. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. From this viewpoint, the time Tb is more preferably 20 seconds or less, and further preferably 15 seconds or less.

  In this manufacturing method, the first heating time Ta is preferably longer than the second heating time Tb. In this manufacturing method, since the raw cover R is sufficiently heated in the first heating step, the rubber has an appropriate fluidity as a whole when the second heating step is started. Since the internal pressure of the bladder 4 is increased to the secondary pressure P2 at a stretch while the rubber has an appropriate fluidity as a whole, the rubber flows along the cavity surface 16 of the mold 6. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented.

  In this manufacturing method, the time until the internal pressure of the bladder 4 reaches the secondary pressure P2 in the heating process (hereinafter referred to as pressure increase time) is indicated by the sum of the first heating time Ta and the second heating time Tb. From the viewpoint that the raw cover R is sufficiently heated, the pressure increase time is preferably 60 seconds or more. From the viewpoint of preventing the rubber from being excessively vulcanized, the pressure increase time is preferably 110 seconds or less.

  The ratio of the difference (P1−P0) between the primary pressure P1 and the reference pressure P0 to the first heating time Ta is the first pressurization speed R1 until the primary pressure P1 in the first heating step is reached. The ratio of the difference (P2−P1) between the secondary pressure P2 and the primary pressure P1 to the second heating time Tb is the second pressurization speed R2 until the secondary pressure P2 in the second heating step is reached. In this manufacturing method, the first pressurization speed R1 is smaller than the second pressurization speed R2. In this manufacturing method, in the first heating step, the internal pressure of the bladder 4 is increased to the primary pressure P1 over time. For this reason, since the raw cover R is sufficiently heated, the rubber as a whole has an appropriate fluidity when the second heating step is started. Since the internal pressure of the bladder 4 is increased to the secondary pressure P2 at a stretch while the rubber has an appropriate fluidity as a whole, the rubber flows along the cavity surface 16 of the mold 6. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented.

  In this manufacturing method, from the viewpoint that sufficient heating of the raw cover R is promoted, the first pressurization rate R1 is preferably 0.05 kPa / second or more, and preferably 0.17 kPa / second or less. From the viewpoint of contributing to air discharge, the second pressurization rate R2 is preferably 0.5 kPa / second or more, and preferably 1.2 kPa / second or less. The ratio of the second pressurization speed R2 to the first pressurization speed R1 is preferably 2.9 or more and preferably 50 or less from the viewpoint that heating of the raw cover R is promoted and air is effectively discharged.

  In this manufacturing method, from the viewpoint that the raw cover R is sufficiently heated, the heating and holding time Tc is preferably 120 seconds or more. From the viewpoint of preventing the rubber from being overvulcanized, the heating holding time Tc is preferably 180 seconds or less.

  In this manufacturing method, the total time required for the heating step is indicated by the sum of the first heating time Ta, the second heating time Tb, and the heating holding time Tc. From the viewpoint of sufficiently heating the raw cover R, the total time is preferably 190 seconds or more. From the viewpoint of preventing the rubber from being excessively vulcanized, the total time is preferably 260 seconds or less.

  In this manufacturing method, since the internal pressure of the bladder 4 is precisely controlled, generation of bears is effectively prevented. According to this manufacturing method, a high-quality tire can be produced stably.

  In this manufacturing method, even if the raw cover R having a profile that does not match the profile of the cavity surface 16 is put into the mold 6, the residual air is effectively suppressed. Since the formation of the bear is prevented, the shape and thickness of the raw cover R need not be adjusted. From the viewpoint of preventing bears, it is not necessary to provide a portion having an excessive thickness on the raw cover R, so that inflow of rubber into a minute gap at the division position of the mold 6 can be suppressed. According to this manufacturing method, excessive spew formation is suppressed.

  FIG. 6 is a perspective view showing a part of a mold 30 used in a tire manufacturing method according to another embodiment of the present invention. FIG. 6 shows a tread segment 32 as a constituent member of the mold 30. Although not shown, the configuration of the mold 30 other than the segment 32 is the same as that of the mold 6 shown in FIG. This mold 30 is a “split mold”. In FIG. 6, the direction indicated by the arrow X is the radial direction, and the direction indicated by the arrow Y is the axial direction.

  In the mold 30, the segment 32 includes a holder 34 and a block 36. The holder 34 is made of steel or aluminum alloy. The block 36 is attached to the holder 34.

  The block 36 has a molding surface 38. The molding surface 38 forms part of the cavity surface 40 that forms the outer surface of the tire. The molding surface 38 includes a convex portion 42 and a concave portion 44. The convex portion 42 corresponds to a tread groove of the tire. The convex portion 42 and the concave portion 44 form a tread pattern on the tire.

  FIG. 7 is a cross-sectional view of the block 36 constituting the segment 32 of FIG. 6 along the circumferential direction. In FIG. 7, the direction perpendicular to the paper surface is the axial direction. The direction indicated by the double arrow A is the circumferential direction.

  The block 36 includes a base 46 and a core 48. The base 46 surrounds the core 48. The upper surface 50, the lower surface 52, and the back surface 54 of the core 48 are in contact with the base 46. The base 46 is made of a metal material. A typical metallic material is an aluminum alloy.

  The core 48 includes a piece 56 and a shim 58. In this embodiment, the core 48 includes ten pieces 56 arranged in parallel. The number of pieces 56 is appropriately determined in consideration of the shape of the raw cover and the like. Although not shown, these pieces 56 are bound together using bolts and nuts on the back side thereof.

  Each piece 56 is plate-shaped. The piece 56 is made of a metal material. A typical metallic material is an aluminum alloy. The front surface of the piece 56 forms a molding surface 38.

  Shown in FIG. 8 is a shim 58. The shim 58 is made of a metal material. A typical metallic material is stainless steel. The shim 58 has a thin plate shape. The planar shape of the shim 58 is substantially rectangular.

  As shown in FIG. 7, the shim 58 is sandwiched between two adjacent pieces 56. A slit 60 is formed between two adjacent pieces 56 by the shim 58. In the mold 30, the slit 60 extends in the axial direction. The slit 60 reaches the molding surface 38.

  In the mold 30, the core 48 is obtained by stacking a large number of pieces 56. When stacking, a shim 58 is disposed between the pieces 56 and 56. These pieces 56 and shims 58 are integrated by bolts and nuts not shown. The core 48 thus configured is inserted into a mold, and molten metal is poured around the core 48. By devising the molten metal runner, melting of the piece 56 by the molten metal can be prevented. This molten metal solidifies in the mold. The base 46 is formed by solidification. In this way, a block 36 having a base 46 and a core 48 is obtained. In this block 36, the core 48 is firmly fixed to the base 46 by casting.

  Block 36 is cut to an appropriate size and shape. The cut block 36 is cut to form a molding surface 38 having an uneven pattern. After such processing, the block 36 is mounted on the holder 34, and the segment 32 shown in FIG. 6 is obtained.

  In this mold 30, as in the mold 30 described above, a large number of segments 32 are arranged in a ring shape. A minute gap is generated between the dividing surface 62 of one segment 32 and the dividing surface 62 of the segment 32 adjacent thereto. In the mold 30, air is discharged through this gap.

  The core 48 of the mold 30 includes a large number of slits 60 extending in the axial direction. Each slit 60 is exposed to the molding surface 38 as the cavity surface 40. When the raw cover is vulcanized using the mold 30, the air between the raw cover and the cavity surface 40 moves through the slit 60. The air reaches the dividing surface 62 and is discharged. In the mold 30, even air in a region away from the dividing surface 62 can move to the dividing surface 62 through the slit 60. In this mold 30, air is effectively discharged. This mold 30 can contribute to prevention of bear generation. In the mold 30, air can be sufficiently discharged even if a vent hole is not provided. A tire without spew is obtained by the mold 30 having no vent hole. Such a mold 30 is called a spuleless mold.

  FIG. 9 is an enlarged cross-sectional view showing a part of the block 36 of FIG. In FIG. 9, the distance indicated by the arrow L1 is the distance from the inner end 64 of the shim 58 to the back face 54 of the piece 56, and the arrow L2 is the distance from the cavity face 40 to the back face 54. is there. The distance L1 is sufficiently smaller than the distance L2. In other words, the shim 58 is located in the vicinity of the back surface 54, and the cavity surface 40 and the inner end 64 of the shim 58 are separated. The shim 58 does not hinder the movement of air through the slit 60. In light of air movement, the ratio (L1 / L2) is preferably equal to or less than 0.5 and more preferably equal to or less than 0.3. The ratio (L1 / L2) is preferably 0.1 or more.

  The number of slits 60 in one core 48 is preferably 5 or more. In the core 48 provided with five or more slits 60, air can be sufficiently discharged. In this respect, the number of slits 60 is more preferably 10 or more. From the viewpoint of easy manufacture of the core 48, the number of slits 60 is preferably 100 or less, and more preferably 30 or less. In this mold 30, the number of slits 60 in one core 48 is nine.

  In FIG. 9, what is indicated by an arrow P <b> 1 is the width of the slit 60 in the cavity surface 40. The width P1 is preferably 0.001 mm or more. The air is sufficiently discharged by the slit 60 having the width P1 of 0.001 mm or more. In this respect, the width P1 is more preferably 0.02 mm or more. The width P1 is preferably 0.1 mm or less. The rubber composition hardly flows into the slit 60 having the width P1 of 0.1 mm or less. Since formation of spew is prevented, a tire having an excellent appearance can be obtained. In this respect, the width P1 is more preferably 0.09 mm or less.

  In the mold 30, the piece 56 or the shim 58 is slightly deformed by tightening a nut (not shown). Due to this deformation, the width P1 tends to be smaller than the thickness T1 of the shim 58 (see FIG. 8). Further, even if the shim 58 is located in the vicinity of the back surface 54, the width P1 tends to be smaller than the thickness T1. In order to achieve an appropriate width P1, the thickness T1 is preferably 0.01 mm or more, and more preferably 0.03 mm or more. The thickness T1 is preferably 1.0 mm or less, and more preferably 0.15 mm or less. This thickness T1 is measured in a state where no load is applied. The width W1 (see FIG. 9) of the piece 56 is preferably 3 mm or more, and preferably 100 mm or less.

  In this manufacturing method, a tire is manufactured in the same manner as the above-described manufacturing method except that the configuration of the mold 30 is different. This manufacturing method includes the same steps as the manufacturing method shown in the flowchart of FIG. That is, in this manufacturing method, a step of obtaining a raw cover by preforming (STEP 1), a step of putting the raw cover into the mold 30 (STEP 2), a bladder located inside the raw cover is filled with the first heating medium, and the raw cover is formed. A step of allowing the internal pressure of the bladder to reach the primary pressure P1 over time while heating (STEP 3), and further filling the bladder with a second heating medium to further heat the raw cover while reducing the internal pressure of the bladder. A step of reaching the next pressure P2 at a stretch (STEP 4), a step of further filling the bladder with a pressurized medium and pressurizing the raw cover (STEP 5), and a step of discharging the heating medium and the pressurized medium from the bladder (STEP 6). It is out.

  In this manufacturing method, in the first heating step (STEP 3), the internal pressure of the bladder is allowed to reach the primary pressure P1 lower than the secondary pressure P2 over time. In the first heating step, the heating of the raw cover is prioritized over the discharge of air. From the viewpoint that air is effectively discharged in the subsequent steps, the primary pressure P1 is preferably 3 kPa or more, and more preferably 4 kPa or more. The primary pressure P1 is preferably 10 kPa or less, and more preferably 6 kPa or less. In this manufacturing method, the internal pressure of the bladder when the filling of the first heating medium is started is set as the reference pressure P0. In this manufacturing method, the reference pressure P0 is 0 kPa.

  As described above, in the second heating step (STEP 4), the internal pressure of the bladder is made to reach the secondary pressure P2 at once. Since the raw cover is sufficiently heated in the first heating step (STEP 3), the rubber as a whole has adequate fluidity when the second heating step is started. Since the internal pressure of the bladder is increased to the secondary pressure P2 at a stretch while the rubber has an appropriate fluidity, the rubber flows along the cavity surface 40 of the mold 30. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. Moreover, the mold 30 is a spuleless mold. In this manufacturing method, spew formation is suppressed. This manufacturing method can effectively prevent generation of bears and spews. According to this manufacturing method, a high-quality tire can be produced stably.

  In this manufacturing method, the time from the start of filling of the first heating medium until the internal pressure of the bladder reaches the primary pressure P1 (hereinafter referred to as the first heating time Ta) is preferably 30 seconds to 100 seconds. By setting the time Ta to 30 seconds or more, the raw cover is sufficiently heated in the first heating step. For this reason, when the second heating step is started, the rubber as a whole has adequate fluidity. Since the internal pressure of the bladder is increased to the secondary pressure P2 in a state where the rubber has an appropriate fluidity as a whole, the rubber flows along the cavity surface 40 of the mold 30. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. By setting the time Ta to 100 seconds or less, the fluidity inhibition associated with the rubber crosslinking reaction is prevented. Since the rubber has an appropriate fluidity, the discharge of air is promoted. Even in this case, the formation of the bear is prevented.

  In this manufacturing method, the time from the start of filling of the second heating medium until the internal pressure of the bladder reaches the secondary pressure P2 (hereinafter referred to as the second heating time Tb) is preferably 30 seconds or less. Since the internal pressure of the bladder is increased from the primary pressure P1 to the secondary pressure P2, air is effectively discharged. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. From this viewpoint, the time Tb is more preferably 20 seconds or less, and further preferably 15 seconds or less. In addition, since a spuleless mold is used as the mold 30, the formation of spew is suppressed. In this manufacturing method, since generation | occurrence | production of a bear and a spew is prevented effectively, a high quality tire can be produced stably.

  In this manufacturing method, the first heating time Ta is preferably longer than the second heating time Tb. In this manufacturing method, since the raw cover is sufficiently heated in the first heating step, the rubber as a whole has an appropriate fluidity when the second heating step is started. Since the internal pressure of the bladder is increased to the secondary pressure P2 in a state where the rubber has an appropriate fluidity as a whole, the rubber flows along the cavity surface 40 of the mold 30. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. In addition, since a spuleless mold is used as the mold 30, the formation of spew is suppressed. In this manufacturing method, since generation | occurrence | production of a bear and a spew is prevented effectively, a high quality tire can be produced stably.

  In this manufacturing method, the pressure increase time of the internal pressure of the bladder in the heating process is indicated by the sum of the first heating time Ta and the second heating time Tb. From the viewpoint that sufficient heating of the raw cover is promoted, the pressure increase time is preferably 60 seconds or more. From the viewpoint of preventing the rubber from being excessively vulcanized, the pressurization time is preferably 110 seconds or less.

  The ratio of the difference (P1−P0) between the primary pressure P1 and the reference pressure P0 to the first heating time Ta is the first pressurization speed R1 until the primary pressure P1 in the first heating step is reached. The ratio of the difference (P2−P1) between the secondary pressure P2 and the primary pressure P1 to the second heating time Tb is the second pressurization speed R2 until the secondary pressure P2 in the second heating step is reached. In this manufacturing method, the first pressurization speed R1 is smaller than the second pressurization speed R2. In this manufacturing method, in the first heating step, the internal pressure of the bladder is increased to the primary pressure P1 over time. In the first heating step, the raw cover is sufficiently heated. For this reason, when the second heating step is started, the rubber as a whole has adequate fluidity. Since the internal pressure of the bladder is increased to the secondary pressure P2 in a state where the rubber has an appropriate fluidity as a whole, the rubber flows along the cavity surface 40 of the mold 30. This rubber flow facilitates the discharge of air. In this manufacturing method, since the remaining of air is suppressed, formation of a bear is prevented. In addition, since a spuleless mold is used as the mold 30, the formation of spew is suppressed. In this manufacturing method, since generation | occurrence | production of a bear and a spew is prevented effectively, a high quality tire can be produced stably.

  In this manufacturing method, from the viewpoint that sufficient heating of the raw cover is promoted, the first pressurization rate R1 is preferably 0.05 kPa / second or more, and preferably 0.17 kPa / second or less. From the viewpoint of contributing to air discharge, the second pressurization rate R2 is preferably 0.5 kPa / second or more, and preferably 1.2 kPa / second or less. The ratio of the second pressurization speed R2 to the first pressurization speed R1 is preferably 2.9 or more and more preferably 50 or less from the viewpoint that heating of the low cover is promoted and air is effectively discharged.

  In this manufacturing method, the heating and holding time Tc is preferably 120 seconds or longer from the viewpoint that the raw cover is sufficiently heated. From the viewpoint of preventing the rubber from being overvulcanized, the heating holding time Tc is preferably 180 seconds or less.

  In this manufacturing method, the total time required for the heating step is indicated by the sum of the first heating time Ta, the second heating time Tb, and the heating holding time Tc. From the viewpoint of sufficiently heating the raw cover, the total time is preferably 190 seconds or more. From the viewpoint of preventing the rubber from being excessively vulcanized, the total time is preferably 260 seconds or less.

  In this manufacturing method, since the internal pressure of the bladder is precisely controlled, generation of bears is effectively prevented. In addition, since a spuleless mold is used as the mold 30, the formation of spew is suppressed. In this manufacturing method, generation of bears and spews is effectively prevented. According to this manufacturing method, a high-quality tire can be produced stably.

  In this manufacturing method, even if a raw cover having a profile that does not match the profile of the cavity surface 40 is put into the mold 30, residual air is effectively suppressed. Since formation of the bear is prevented, adjustment of the shape and thickness of the raw cover is unnecessary. From the viewpoint of preventing bears, it is not necessary to provide a portion having an excessive thickness on the raw cover. In addition, a spuleless mold is used as the mold 30. According to this manufacturing method, the generation of bears and spews is effectively prevented. This manufacturing method can contribute to stable production of high-quality tires.

  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]
The raw cover obtained by the preforming was put into a mold having the segments shown in FIGS. 6 and 7 to manufacture a tire. This segment is provided with a large number of slits exposed on the molding surface. This segment is a multi-segment. In the table, the type of mold (supure mold) having this segment is indicated by “S”. In the first heating step, steam whose temperature was adjusted to 180 ° C. was filled in a bladder having an internal pressure of 0 kPa (reference pressure P0). While filling the raw cover by this filling, the internal pressure of the bladder was allowed to reach 5 kPa (primary pressure P1) over time. The first heating time Ta was 60 seconds. In the second heating step, the steam was further filled in the bladder to further heat the raw cover, and the internal pressure of the bladder was reached to 15 kPa at a stretch. The second heating time Tb was 10 seconds. The internal pressure of the bladder was maintained at 15 kPa. The heating and holding time Tc was 150 seconds. In the pressurization step, the bladder was further filled with nitrogen gas at room temperature. By this filling, the internal pressure of the bladder reached 21 kPa at a stretch. The pressurization time Td was 10 seconds. The internal pressure of the bladder was maintained at 21 kPa. The pressure holding time Te was 360 seconds. In this pressing step, the raw cover was pressed and heated to obtain a tire. In the discharging process, steam and nitrogen gas were discharged, and the tire was removed from the mold. The internal pressure of the bladder in Example 1 was controlled by the profile shown in FIG. In Example 1, this cycle was repeated, and 1000 tires were manufactured.

[Example 3-8]
A tire was manufactured in the same manner as in Example 1 except that the first heating time Ta was as shown in Tables 1 and 2 below.

[Examples 9-12]
A tire was manufactured in the same manner as in Example 1 except that the primary pressure P1 was as shown in Table 3 below.

[Examples 13-14]
A tire was manufactured in the same manner as in Example 1 except that the second heating time Tb was as shown in Tables 3 and 4 below.

[Examples 15-16]
A tire was manufactured in the same manner as in Example 1 except that the heat holding time Tc was as shown in Table 4 below.

[Examples 17-18]
A tire was manufactured in the same manner as in Example 1 except that the primary pressure P1, the first heating time Ta, and the second heating time Tb were as shown in Table 1 below.

[Example 2]
A tire was manufactured in the same manner as in Example 1 except that the mold was changed to the mold shown in FIG. This mold comprises the segments shown in FIG. This segment is not provided with a slit exposed on the molding surface. This segment is conventional. In the table, the type of a mold having a conventional segment (normal mold) is indicated by “N”.

[Comparative Example 1]
The raw cover obtained by the preforming was put into a mold having the segments shown in FIGS. 6 and 7 to manufacture a tire. As described above, this segment is provided with a number of slits exposed on the molding surface. This segment is a multi-segment. In the table, the type of mold (supure mold) having this segment is indicated by “S”. In the heating step, steam whose internal pressure was adjusted to 180 ° C. was filled in a bladder having an internal pressure of 0 kPa (reference pressure P0). While the raw cover was heated by this filling, the internal pressure of the bladder was made to reach 15 kPa (primary pressure P1) at once. The time from filling the steam until the internal pressure reached 15 kPa was 10 seconds. The internal pressure of the bladder was maintained at 15 kPa for 180 seconds. In the pressurization step, the bladder was further filled with nitrogen gas at room temperature. By this filling, the internal pressure of the bladder reached 21 kPa at a stretch. The pressurization time Td was 10 seconds. The internal pressure of the bladder was maintained at 21 kPa. The pressure holding time Te was 360 seconds. In this pressing step, the raw cover was pressed and heated to obtain a tire. In the discharging process, steam and nitrogen gas were discharged, and the tire was removed from the mold. The internal pressure of the bladder in Comparative Example 1 was controlled by the profile shown in FIG. In this comparative example 1, this cycle was repeated, and 1000 tires were manufactured.

[Comparative Example 2]
A tire was manufactured in the same manner as in Comparative Example 1 except that the mold was changed to the mold shown in FIG. As described above, this mold includes the segments shown in FIG. This segment is not provided with a slit exposed on the molding surface. This segment is conventional. In the table, the type of a mold having a conventional segment (normal mold) is indicated by “N”.

[Evaluation of bear incidence]
The appearance of the manufactured tire was observed to confirm the occurrence of bears. The ratio of the number of tires in which generation of bears is confirmed to 1000 manufactured tires is shown in Tables 1, 2, 3, and 4 below as the generation rate of bears. The smaller this value, the better (the occurrence of bears is suppressed).

[Evaluation of spew generation index]
The appearance of the manufactured tire was observed to confirm the occurrence of spew. The state of occurrence of this spew is an index value and is shown in Table 1, Table 2, Table 3, and Table 4 below. The smaller this value is, the better (the occurrence of spew is suppressed).

  As shown in Table 1, Table 2, Table 3, and Table 4, the manufacturing method of the example has higher evaluation than the manufacturing method of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The method described above can be applied to the manufacture of various tires.

2 ... Vulcanizing device 4 ... Bladder 6, 30 ... Mold 8 ... Cavity 10, 32 ... Segment 12 ... Side plate 14 ... Bead ring 16, 40 ... Cavity Surface 18, 34 ... Holder 20, 36 ... Block 28, 62 ... Split surface 46 ... Base 48 ... Core 56 ... Piece 58 ... Shim 60 ... Slit

Claims (7)

Obtaining a raw cover by preforming; and
The process of putting this raw cover into the mold,
Filling the bladder located inside the raw cover with the first heating medium and heating the raw cover while causing the internal pressure of the bladder to reach the primary pressure P1,
Filling the bladder with a second heating medium and further heating the raw cover while causing the internal pressure of the bladder to reach the secondary pressure P2,
And further filling the bladder with a pressurizing medium and pressurizing the raw cover.
The method for manufacturing a tire, wherein the secondary pressure P2 is higher than the primary pressure P1.   The first pressurization speed until the primary pressure P1 is reached in the first heating step is smaller than the second pressurization speed until the secondary pressure P2 is reached in the second heating step. The manufacturing method of the tire as described in any one of.   The tire manufacturing method according to claim 1, wherein the mold is a spuleless mold.   The tire manufacturing method according to any one of claims 1 to 3, wherein the first filling time Ta is not less than 30 seconds and not more than 100 seconds.   The tire manufacturing method according to any one of claims 1 to 4, wherein the primary pressure P1 is 3 kPa or more and 10 kPa or less.   The tire manufacturing method according to any one of claims 1 to 5, wherein the second filling time Tb is 30 seconds or less.   7. The heating time Tc from when the internal pressure of the bladder reaches the secondary pressure P <b> 2 to when charging of the pressurized medium is started is 120 seconds or more and 180 seconds or less. 7. Tire manufacturing method.

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