JP4851562B2 - Pneumatic tire manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pneumatic tire. In particular, the present invention relates to an improvement in the tire vulcanization process.

  The manufacturing method of a pneumatic tire includes a vulcanization step. A mold and a bladder are used for this vulcanization process. The mold is made of metal. The bladder is made of rubber. The bladder is accommodated in a mold.

  In the vulcanization process, the raw cover (also referred to as an uncrosslinked tire) obtained in the preforming process is put into an opened mold. When thrown, the bladder is contracted. When thrown, the bladder is positioned inside the raw cover. The bladder expands by filling with gas. Due to this expansion, the raw cover is deformed. This deformation is called shaping. The mold is tightened and the internal pressure of the bladder is increased.

  The raw cover is pressed between the cavity surface of the mold and the outer surface of the bladder. The raw cover is heated by heat conduction from the mold and the bladder. The rubber composition of the raw cover flows by pressurization and heating. The air in the mold moves due to the flow and is discharged from the mold. The rubber causes a crosslinking reaction by heating, and a tire is obtained. A tire manufacturing method using a bladder is disclosed in JP-A-6-143288.

  The shape of the inner surface of the tire depends on the shape of the bladder when inflated. Since the bladder is made of rubber, the accuracy of the shape during expansion is not sufficient. Furthermore, when the bladder is used repeatedly, the shape at the time of expansion varies due to changes in physical properties and thickness over time. It is not easy to control the shape of the inner surface of the tire.

  A metal core may be used instead of the bladder. The core is hard and has excellent dimensional accuracy. Further, the dimensional variation is suppressed in this core. With this core, a tire having excellent dimensional accuracy can be obtained.

  In the manufacturing method in which the core is used, it is necessary to prepare cores having different sizes for each tire size. The core is generally expensive. The manufacture of tires with cores is expensive.

  The core does not expand like a bladder. The distance between the cavity surface of the mold and the core is substantially constant. In the vulcanization process using a core, the pressure applied to the raw cover depends on the thermal expansion of the raw cover. For this reason, in a region where the thickness is small in the raw cover, the pressure is insufficient due to a small expansion amount. Air remains due to insufficient pressure. Due to the lack of pressure, the rubber members constituting the raw cover may not be sufficiently joined together.

  A tire may be manufactured by using a hard core that contacts only the bead portion of the low cover together with the bladder. In this manufacturing method, the bladder is inflated from the inside of the core. Since the core comes into contact with the bead portion, the shape of the bead portion matches the design shape. The portion of the inner surface of the raw cover that does not contact the core is pressurized by the bladder, so that the rubber members constituting the raw cover are reliably joined together. With this manufacturing method, a high-quality tire can be obtained. This core is less expensive than the core that contacts the entire inner surface of the raw cover. An example of such a manufacturing method is disclosed in Japanese Patent Application Laid-Open No. 2008-137258.

  The core may include a core plate that is divided into a plurality of members in the circumferential direction. The core can vary in outer diameter. This core can be used for manufacturing tires of different sizes. By using this core, a tire can be obtained at low cost.

JP-A-6-143288 JP 2008-137258 A

  The core disclosed in Japanese Patent Application Laid-Open No. 2008-137258 contacts the raw cover. For this reason, rubber may adhere to the core. This adhesion contaminates the core. By-products generated by the rubber crosslinking reaction also contaminate the core. In particular, when the core includes a core plate divided into a plurality of members, rubber and by-products enter the gaps between the members. This contamination impairs the durability of the core. Maintenance of a contaminated core takes time. With this manufacturing method, it is difficult to stably manufacture a pneumatic tire excellent in quality. Manufacturing methods that are inferior in stability affect manufacturing costs.

  The pneumatic tire has an inner liner inside thereof. This inner liner plays a role of maintaining the internal pressure of the tire.

  In this manufacturing method, the inner surface of the raw cover comes into contact with the core and the bladder located inside the core. For this reason, a part of the inner liner may be caught between the bladder and the core. This biting reduces the thickness of the inner liner. An excessively thin thickness affects air shielding properties. And from a viewpoint of air shielding, if a thick inner liner is adopted, production cost will increase.

  An object of the present invention is to provide a production method capable of obtaining a pneumatic tire excellent in quality at a low cost.

A method for manufacturing a pneumatic tire according to the present invention includes:
(1) A tread, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each positioned substantially radially inward of the sidewalls, and the tread and the sidewalls A step of forming a raw cover comprising a carcass extending between one bead and the other bead along the inside;
(2) In a vulcanizing apparatus comprising a mold, a bladder positioned inside the mold, and a core positioned further inside the bladder, the step of putting the raw cover between the mold and the bladder; ,
(3) The outer surface of the raw cover is in contact with the cavity surface of the mold, the inner surface of the raw cover is in contact with the outer surface of the bladder, and the bead portion of the raw cover is separated from the inner surface of the bladder by the core. The raw cover is heated in a pressed state.

  Preferably, in this pneumatic tire manufacturing method, the ratio of the radial height from the bead base line to the tip of the core to the maximum height from the bead base line to the carcass is 0.2 or more and 0. .7 or less.

  Preferably, in the pneumatic tire manufacturing method, in the raw cover heating step, the tip of the core is located radially inward from a position corresponding to the maximum tire width of the raw cover.

  Preferably, in this method for manufacturing a pneumatic tire, the bead includes a core and an apex located on the radially outer side of the core. In the heating process of the raw cover, the tip of the core is located radially outside the core. Preferably, the tip of the core is located radially outside the tip of the apex.

  Preferably, in the method for manufacturing a pneumatic tire, the core includes a core plate. The core plate is composed of a plurality of members divided in the circumferential direction. The core can be reduced in diameter in the raw cover charging process and can be expanded in the raw cover heating process.

  In the method for manufacturing a pneumatic tire according to the present invention, the core does not contact the raw cover. In this manufacturing method, contamination of the core is prevented. Maintenance of this core is easy. This manufacturing method can contribute to the improvement of the durability of the core. According to this core, a tire having a bead with high dimensional accuracy can be obtained. Since only the bladder comes into contact with the inner surface of the raw cover, a part of the inner liner is not caught between the core and the bladder as in the conventional manufacturing method. In this manufacturing method, it is not necessary to consider this biting when setting the thickness of the inner liner. In this manufacturing method, an inner liner having a small thickness can be employed. This manufacturing method can contribute to a reduction in production cost. By using this manufacturing method, a high-quality pneumatic tire can be obtained stably and at low cost.

FIG. 1 is a cross-sectional view illustrating an example of a tire obtained by a method for manufacturing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a part of a vulcanizing apparatus used for manufacturing the tire of FIG. FIG. 3 is a plan view showing a core provided in the vulcanizing apparatus of FIG. 2. FIG. 4 is a plan view showing a reduced diameter state of the core shown in FIG. FIG. 5 is a cross-sectional view showing another part of the vulcanizing apparatus of FIG. FIG. 6 is an enlarged cross-sectional view showing a part of FIG.

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

  The pneumatic tire 2 shown in FIG. 1 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, an inner liner 14, and a chafer 16. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car. The tire 2 has a substantially left-right symmetric shape centered on a one-dot chain line CL in FIG. This alternate long and short dash line CL represents the equator plane of the tire 2. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. In addition, the manufacturing method of the pneumatic tire of this invention can be applied also to manufacture of the tire with which various vehicles, such as a light truck, a truck, a bus | bath, are mounted | worn besides a passenger car.

  The tread 4 is made of a crosslinked rubber. The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 18. The tread surface 18 is in contact with the road surface.

  The sidewall 6 is made of a crosslinked rubber. The sidewall 6 extends substantially inward in the radial direction from the end 20 portion of the tread 4.

  The bead 8 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 22 and an apex 26 extending radially outward from the upper surface 24 of the core 22. The core 22 has a ring shape. The core 22 is formed by winding a non-stretchable wire (typically a steel wire). The apex 26 is tapered outward in the radial direction. The apex 26 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 28. The carcass ply 28 is bridged between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. The end 30 of the folded carcass ply 28 is located radially inward from the end 20 of the tread 4. This end 30 is located radially outside the tip 32 of the apex 26. Although not shown, the carcass ply 28 includes a plurality of cords arranged in parallel and a topping rubber. The carcass 10 has a radial structure.

  The belt 12 is located on the radially outer side of the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 includes an inner layer 34 and an outer layer 36. The end 38 of the inner layer 34 is located in the vicinity of the end 20 of the tread 4. Although not shown, each of the inner layer 34 and the outer layer 36 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane.

  The inner liner 14 is joined to the inner peripheral surface of the carcass 10. The inner liner 14 is made of a crosslinked rubber. The inner liner 14 is made of rubber having excellent air shielding properties. The inner liner 14 plays a role of maintaining the internal pressure of the tire 2.

  In FIG. 1, what is indicated by the symbol PA is the maximum width point. The maximum width point PA is the outermost point in the axial direction. In the tire 2, the end 30 of the carcass ply 28 is located radially outside the maximum width point PA. The tip 32 of the apex 26 is located radially inward from the maximum width point PA. This maximum width point PA is located between the end 30 of the carcass ply 28 and the tip 32 of the apex 26 in the radial direction. In addition, when a pattern, a character, etc. are attached to the side surface of the tire 2, the maximum width point PA is determined based on the side surface excluding this pattern, the character, etc.

  FIG. 2 is a cross-sectional view showing a part of a vulcanizing device 42 used for manufacturing the tire 2 of FIG. By using this vulcanizer 42, the tire 2 is obtained from the raw cover. The vulcanizing device 42 includes a bladder 44, an upper clamp 46, a lower clamp 48, a rod 50, and a core 52. In FIG. 2, the left-right direction corresponds to the radial direction of the tire 2. The vertical direction corresponds to the axial direction of the tire 2.

  The bladder 44 is cylindrical and hollow. As will be described later, the raw cover is disposed outside the bladder 44 in the radial direction. The bladder 44 is made of a crosslinked rubber. One end 54 a of the bladder 44 is attached to the upper clamp 46. The other end 54 b of the bladder 44 is attached to the lower clamp 48. When the bladder 44 is filled with gas, the bladder 44 expands. Due to this expansion, the bladder 44 contacts the inner surface of the raw cover. As the gas is discharged from the bladder 44, the bladder 44 contracts. FIG. 2 shows a state of the bladder 44 before contacting the raw cover.

  The rod 50 is located inside the bladder 44. The upper end 56 of the rod 50 is fixed to the upper clamp 46. The rod 50 passes through the lower clamp 48. The vulcanizing device 42 is configured such that the rod 50 slides up and down with respect to the lower clamp 48. When the rod 50 slides upward, the upper clamp 46 rises. When the rod 50 slides downward, the upper clamp 46 is lowered toward the lower clamp 48. The slide of the rod 50 adjusts the position of the bladder 44 relative to the raw cover.

  The core 52 is located inside the bladder 44. The core 52 is accommodated in the bladder 44. The core 52 is located between the upper clamp 46 and the lower clamp 48. The core 52 is disposed in a space formed by the bladder 44, the upper clamp 46 and the lower clamp 48.

  The core 52 includes a pair of core plates 58 and a pair of elastic members 60. Each core plate 58 is substantially ring-shaped. The core plate 58 includes a support surface 62. The support surface 62 has a shape equivalent to the inner surface 64 in the bead 8 portion of the tire 2 of FIG.

  The core plate 58 is made of a metal material. The core plate 58 is hard. Examples of the metal material include steel, stainless steel, and aluminum alloy. From the viewpoint of light weight, the metal material is preferably an aluminum alloy.

  The stretchable member 60 is configured to be stretchable in the radial direction. A core plate 58 is attached to the elastic member 60.

  FIG. 3 is a plan view showing the core 52 provided in the vulcanizer 42 of FIG. FIG. 3 shows the core plate 58 and the elastic member 60 located on the upper side. As illustrated, the core plate 58 is divided into a plurality of members 59 in the circumferential direction. More specifically, the core plate 58 includes four first members 59a and four second members 59b. The first member 59a and the second member 59b are alternately arranged in the circumferential direction.

  In this vulcanizing device 42, each elastic member 60 is composed of eight bars 61. These bars 61 extend radially outward from the rod 50. As shown, four of the eight bars 61 are attached to the first member 59a. The remaining four bars 61b are attached to the second member 59b.

  In FIG. 3, the bar 61 constituting the elastic member 60 is extended. The first member 59a and the second member 59b are in contact with each other. In the vulcanizing device 42, the state in which the first member 59 a and the second member 59 b are in contact with each other is the diameter expansion state of the core 52.

  FIG. 4 is a plan view showing a reduced diameter state of the core 52 shown in FIG. As shown in the figure, the first member 59a and the second member 59b constituting the core plate 58 slide inward in the radial direction when the bar 61 constituting the elastic member 60 contracts inward in the radial direction. To do. The core 52 is reduced in diameter by this slide. In the reduced diameter state, the first member 59a is located on the radially outer side of the second member 59b.

  In this vulcanizing device 42, the core 52 is expanded in diameter by the elastic member 60 extending radially outward. The first member 59a and the second member 59b come into contact with each other due to the diameter expansion. There is no gap between the members 59 of the core plate 58. And as above-mentioned, when this expansion-contraction member 60 shrinks radially inward, the core 52 is diameter-reduced. FIG. 2 shows the core 52 in a reduced diameter state.

  In the vulcanizing device 42, each of the elastic member 60 a located on the upper side and the elastic member 60 b located on the lower side can be slid up and down along the rod 50. The vertical position of the core plate 58a positioned on the upper side and the core plate 58b positioned on the lower side are adjusted by the sliding of the elastic member 60.

  FIG. 4 is a cross-sectional view showing another part of the vulcanizing device 42 of FIG. The vulcanizing device 42 further includes a mold 66. In FIG. 3, a part of the mold 66 is shown together with the bladder 44, the core 52 and the raw cover 68.

  The mold 66 includes a large number of tread segments 70, a pair of upper and lower side plates 72, and a pair of upper and lower bead rings 74. The segment 70, the side plate 72, and the bead ring 74 are made of a metal material. The segment 70, the side plate 72, and the bead ring 74 are hard. The planar shape of the segment 70 is substantially arcuate. The segment 70 includes a holder 76 and a plurality of pieces 78. A large number of segments 70 are connected in a ring shape. The number of segments 70 is usually 3 or more and 20 or less. The side plate 72 and the bead ring 74 are substantially ring-shaped. This mold 66 is a so-called “split mold”. A cavity surface 80 is formed by the segment 70, the side plate 72 and the bead ring 74.

  In this manufacturing method, the tire 2 is obtained as follows. Members such as the tread 4, the sidewalls 6, and the beads 8 are combined to form the raw cover 68. Although not shown in the figure, the structure of the members such as the tread 4, the sidewalls 6, and the beads 8 in the raw cover 68 is the same as that of the members in the tire 2 shown in FIG. In the raw cover 68, the sidewall 6 extends substantially inward in the radial direction from the end 20 portion of the tread 4. The bead 8 is located substantially inward of the sidewall 6 in the radial direction. The carcass 10 is bridged between one bead 8 and the other bead 8 along the inside of the tread 4 and the sidewall 6.

  The raw cover 68 is inserted between the mold 66 and the bladder 44. At the time of injection, the bladder 44 is contracted and the core 52 is contracted. By inserting, the bladder 44 and the core 52 are positioned inside the raw cover 68. By filling the gas after the introduction, the bladder 44 gradually expands. Due to this expansion, the outer surface 82 of the bladder 44 gradually contacts the inner surface 84 of the raw cover 68. The outer surface 86 of the raw cover 68 gradually contacts the cavity surface 80 of the mold 66. The state in which the bladder 44 is most expanded is shown in FIG.

  In the vulcanizing device 42 in which the raw cover 68 is accommodated, the mold 66 is tightened and the internal pressure of the bladder 44 is increased. The diameter of the core 52 is increased, and the core plate 58 is disposed at a position overlapping the portion of the bead 8 of the raw cover 68 in the axial direction. The core 52 a located on the upper side is raised along the rod 50. By this rise, the support surface 62 a of the core 52 a is pressed against the inner surface 88 of the bladder 44. The core 52 b located on the lower side is lowered along the rod 50. By this lowering, the support surface 62 b of the core 52 b is pressed against the inner surface 88 of the bladder 44. In this manufacturing method, the raw cover 68 is pressurized by the bladder 44 and the core 52.

  In this vulcanization process, the raw cover 68 is heated by heat conduction from the mold 66 and the bladder 44. The raw cover 68 is heated in the vulcanization process. The rubber composition of the raw cover 68 flows by pressurization and heating. The air in the mold 66 moves due to the flow and is discharged from the mold 66. The rubber causes a crosslinking reaction by heating, and the tire 2 is obtained.

  In this manufacturing method, the outer surface 90 of the tire 2 is formed by bringing the outer surface 86 of the raw cover 68 into contact with the cavity surface 80. The inner surface 64 of the tire 2 is formed by the outer surface 82 of the bladder 44 abutting against the inner surface 84 of the raw cover 68.

  In this manufacturing method, the portion of the bead 8 of the raw cover 68 is heated while being pressed by the core 52 from the inner surface 88 of the bladder 44. As described above, the support surface 62 of the core 52 has the same shape as the inner surface 64 of the bead 8 portion. In the tire 2 molded while maintaining this state, the dimensional accuracy of the bead 8 is high. By this manufacturing method, the tire 2 including the beads 8 having a shape that is not deviated from the design shape is obtained.

  In this vulcanization process, the portion of the bead 8 is sandwiched between the mold 66 and the core plate 58 and heated. In other words, this bead 8 portion is sandwiched between two hard members and heated. In the tire 2 obtained by this manufacturing method, the dimensional accuracy of the bead 8 is high. By this manufacturing method, the tire 2 including the beads 8 having a shape that is not deviated from the design shape is obtained.

  In this vulcanizing device 42, since the core 52 is located inside the bladder 44, the core 52 does not directly contact the raw cover 68. In this vulcanizing device 42, contamination of the core 52 with rubber and by-products is prevented. Maintenance of the core 52 is easy. The core 52 is excellent in durability. According to the core 52, the high-quality pneumatic tire 2 can be manufactured stably. By using this manufacturing method, the pneumatic tire 2 excellent in quality can be obtained at low cost.

  In this vulcanizing device 42, only the bladder 44 abuts on the inner surface 84 of the raw cover 68, so that a part of the inner liner is not caught between the core and the bladder 44 as in the conventional manufacturing method. Absent. In this manufacturing method, it is not necessary to consider this biting when setting the thickness of the inner liner. In this manufacturing method, an inner liner having a small thickness can be employed. This manufacturing method can contribute to a reduction in production cost.

  When the tire 2 is incorporated in the rim, the bead 8 is fitted to the rim. In the tire 2 obtained by the manufacturing method according to the present invention, since the shape of the bead 8 is appropriate, the bead 8 contacts the rim in an appropriate state. Therefore, the air filled in the tire 2 does not leak from between the bead 8 and the rim. The shape of the bead 8 affects the deflection of the tire 2. In the tire 2, an appropriate deflection can be obtained. When the tire 2 is assembled on the rim, an appropriate fitting pressure is generated. The bead 8 of the tire 2 does not deviate from the rim when the vehicle is rapidly accelerated and suddenly decelerated. The tire 2 maintains the wheel balance. In the tire 2, there is little variation in the dimensions of the beads 8 in the circumferential direction. The tire 2 is excellent in uniformity.

  In this manufacturing method, the raw cover 68 is sufficiently pressurized by the bladder 44 and the core 52. By this pressurization, the rubber composition flows sufficiently and air is discharged. By this pressurization, the rubber members constituting the raw cover 68 are reliably joined. By the manufacturing method in which the core 52 and the bladder 44 are used in combination, the high-quality tire 2 can be obtained.

  The core 52 is less expensive than a conventional core that contacts the entire inner surface 84 of the raw cover 68. Further, the core 52 can be used for manufacturing a plurality of tires 2 having the same bead 8 shape and different sizes. The versatility of the core 52 is high. By using the core 52, the high-quality tire 2 can be obtained at low cost.

  In this manufacturing method, by devising the shape of the core plate 58, the bead 8 having an arbitrary shape can be formed without depending on the shape of the bladder 44. The highly functional tire 2 can be obtained by the bead 8 having a special shape.

  FIG. 5 is an enlarged cross-sectional view illustrating a part of FIG. FIG. 4 shows a part of the raw cover 68, the bladder 44, and the core 52. The outer surface 86 of the raw cover 68 corresponds to the cavity surface 80 of the mold 66. What is indicated by the symbol PB is the tip of the core 52. As described above, what is indicated by the symbol PA is the maximum width point.

  In this vulcanization step, the tip PB is located radially inward from the end 20 of the tread 4. The core 52 is less expensive than the core that contacts the entire inner surface 84 of the raw cover 68. The tip PB is located in the vicinity of the maximum width point PA. The core 52 can be used for manufacturing a plurality of tires 2 having different sizes. The tip PB is located radially inward from the maximum width point PA. The core 52 can be used more effectively for manufacturing a plurality of tires 2 having different sizes. The core 52 is excellent in versatility.

  In this vulcanization step, the tip PB is located radially outside the core 22 of the bead 8. The core 52 can contribute to forming the bead 8 having an appropriate shape. The tire 2 manufactured by this manufacturing method is excellent in uniformity. The tire 2 is excellent in response characteristics. The tire 2 has high quality. The tip PB is located radially outside the tip 32 of the apex 26. The core 52 can effectively contribute to the molding of the bead 8 having an appropriate shape. The tire 2 manufactured by this manufacturing method is of high quality.

  In FIG. 4, a point PR represents a point on the cavity surface 80 corresponding to the intersection of a line defining the rim diameter (see JATMA) of the rim to which the tire 2 is mounted and the outer surface of the tire 2. The solid line BBL is a straight line that passes through this point PR and extends in the axial direction. In this specification, this solid line BBL is referred to as a bead baseline. A double arrow HC is a maximum height from the bead base line to the carcass 10 (hereinafter, carcass height). The carcass height HC is obtained by measuring the radial height from the bead base line to the inner surface 92 of the carcass 10 on the equator plane CL. A double-headed arrow HA represents the height in the radial direction from the bead base line to the maximum width point PA. This radial height HA is referred to as the maximum width height. A double-headed arrow LB represents a radial distance (height) from the bead base line to the tip PB. This radial distance LB is referred to as the core distance.

  In this manufacturing method, the ratio of the core distance LB to the case height HC is preferably 0.2 or more and 0.8 or less. By setting this ratio to 0.2 or more, the core 52 can contribute to forming the bead 8 having an appropriate shape. This manufacturing method can manufacture a high-quality tire 2. In this respect, the ratio is more preferably equal to or greater than 0.3. By setting this ratio to 0.8 or less, the core 52 can be effectively used for manufacturing a plurality of tires 2 having different sizes. The core 52 is excellent in versatility. In this respect, the ratio is more preferably equal to or less than 0.7.

  In this manufacturing method, the ratio of the core distance LB to the maximum width height HA is preferably 0.3 or more and 1.5 or less. By setting this ratio to 0.3 or more, the core 52 can contribute to the formation of the bead 8 having an appropriate shape. This manufacturing method can manufacture a high-quality tire 2. In this respect, the ratio is more preferably equal to or greater than 0.5. By setting this ratio to 1.5 or less, the core 52 can be effectively used for manufacturing a plurality of tires 2 having different sizes. The core 52 is excellent in versatility. In this respect, the ratio is more preferably equal to or less than 1.3.

  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 tire shown in FIG. 1 was manufactured using a vulcanizing apparatus including a mold, a bladder, and a core shown in FIGS. The size of this tire is 195 / 65R15. The height HC of the case is 110 mm. The maximum width height HA is 60 mm. The radial height (apex height) from the bead base line to the tip of the apex is 45 mm. The height in the radial direction (core height) from the bead baseline to the top surface of the core is 6.5 mm. In this vulcanizer, the core is located inside the bladder. The core distance LB is 55 mm. Therefore, the ratio (LB / HC) is 0.5. The ratio (LB / HA) is 0.92. In Table 1, “A” is displayed when the core is used, and “inside” is displayed when the core is placed inside the bladder.

[Example 2-7]
A tire was manufactured in the same manner as in Example 1 except that the distance (LB) of the core was changed to change the ratio (LB / HC) and the ratio (LB / HA).

[Comparative Example 2]
A tire was manufactured in the same manner as in Example 1 except that the core was disposed outside the bladder. In Table 1, the case where the core is arranged outside the bladder is displayed as “outside”.

[Comparative Example 1]
A tire was manufactured in the same manner as in Example 1 except that the core was not used. In Table 1, “B” indicates that the core is not used.

[Evaluation of Uniformity]
RFV was measured according to the conditions of the uniformity test specified in “JASO C607: 2000”. The average value of the results of measuring 20 tires is an index value with the comparative example 2 as 100, and is shown in Table 1 below. The smaller this number, the higher the evaluation.

[Running test]
A tire was incorporated into a rim, and the tire and rim were mounted on a passenger car. This passenger car is a front engine rear wheel drive type. The engine displacement of this passenger car is 3000 cc. This passenger car was run at a high speed on the racing circuit, and the driver was given a response characteristic. This result is an index value with Comparative Example 2 taken as 100, and is shown in Table 1 below. The higher the number, the higher the evaluation.

[Contamination of core]
After 100 tires were manufactured, the core was taken out from the vulcanizer and the presence or absence of contamination of the core was confirmed. Table 1 below shows “G” when no contamination is found and “NG” when contamination is found.

[Observation of inner surface of tire]
The inner surface of the manufactured tire was visually observed to check for biting. Table 1 below shows “G” when no biting is recognized and “NG” when biting is recognized.

  As shown in Table 1, the manufacturing method of the example has a 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.

DESCRIPTION OF SYMBOLS 2 ... Tire 4 ... Tread 6 ... Side wall 8 ... Bead 10 ... Carcass 12 ... Belt 42 ... Vulcanizing device 44 ... Bladder 46 ... Upper clamp 48 ... Lower clamp 50 ... Rod 52 ... Core 58, 58a, 58b ... Core plate 60, 60a, 60b ... Expandable member 66 ... Mold 68 ... Low cover 70 ..Segment 72 ... Side plate 74 ... Bead ring 80 ... Cavity surface

Claims (6)

A tread, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each positioned substantially inward of the sidewall in the radial direction, and along the inside of the tread and the sidewalls A low cover provided with a carcass bridged between one bead and the other bead;
In a vulcanizing apparatus including a mold, a bladder positioned inside the mold, and a core positioned further inside the bladder, the mold and the bladder are provided with a core plate having a ring shape. A step of inserting the raw cover between
The outer surface of the raw cover is in contact with the cavity surface of the mold, the inner surface of the raw cover is in contact with the outer surface of the bladder, and the bead portion of the raw cover is expanded from the inner surface of the bladder. A method of manufacturing a pneumatic tire including a step of heating the raw cover while being pressed by the child plate.   2. The air according to claim 1, wherein a ratio of a height in a radial direction from the bead base line to the tip of the core to a maximum height from the bead base line to the carcass is 0.2 or more and 0.7 or less. A method for manufacturing a tire.   3. The method for manufacturing a pneumatic tire according to claim 1, wherein, in the heating step of the raw cover, the tip of the core is positioned radially inward from the tire maximum width point. The bead includes a core and an apex located outside the core in the radial direction;
The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein in the heating step of the raw cover, the tip of the core is positioned radially outward from the core.   The method for manufacturing a pneumatic tire according to claim 4, wherein a tip of the core is positioned radially outward from a tip of the apex. The core plate is composed of a plurality of members divided in the circumferential direction,
The method for manufacturing a pneumatic tire according to any one of claims 1 to 5, wherein the core can be reduced in diameter in the charging process of the raw cover and can be expanded in the heating process of the raw cover.

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