Rubber member molding method

Abstract

To provide a rubber member molding method capable of stabilizing a shape of a long rubber member.SOLUTION: In a rubber member molding method according to the embodiment, a long rubber member is extruded from an extruder 11 having a predetermined capacity and attached to a molding drum 15 to mold a cylindrical rubber member for a tire. The extruder 11 makes an extrusion speed in a latter period of an extrusion of one long rubber member slower than the extrusion speed in an earlier period of the extrusion of one long rubber member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for molding a rubber member. [Background technology]

[0002] As described in Patent Document 1, cylindrical rubber members for tires (such as treads, inner liners, and squeegees) are molded by winding a long rubber member extruded from an extruder around a former (molding drum).

[0003] The extruder is composed of a barrel into which the rubber material is put, a screw provided in the barrel, a die having an extrusion port for extruding the long rubber member from the barrel, etc. In the extruder, raw rubber material is fed into the barrel, and the fed raw rubber material is kneaded by the screw while being heated in the barrel, and is extruded from the die as a long rubber member.

[0004] When the long rubber material extruded from the extruder is wrapped around the former to form one cylindrical rubber material, extrusion from the extruder's nozzle is temporarily stopped. While extrusion is stopped, the rubber that has accumulated in the barrel is heated. When the molding of the next cylindrical rubber material begins, the rubber that was heated in the barrel is extruded from the nozzle, and new, low-temperature rubber is added to the barrel to make up for the amount of rubber that has been removed from the barrel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-192795 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is an upper limit to the amount of rubber that can be put into a barrel, and the barrel capacity may be smaller than the amount of rubber required to mold one cylindrical rubber member. In this case, when the leading portion of the long rubber member is extruded, rubber that is sufficiently heated in the barrel before extrusion begins is extruded, but when the trailing portion of the long rubber member is extruded, insufficiently heated rubber that was put into the barrel after extrusion began is extruded.

[0007] Also, even if the barrel is large and its capacity is greater than the amount of rubber required to mold one cylindrical rubber component, the rubber farther from the nozzle of the extruder tends to be cooler than the rubber closer to the nozzle. In this case, when molding one cylindrical rubber component, hot rubber is extruded from the nozzle immediately after molding begins, but after all the hot rubber has been extruded, a relatively cooler rubber is extruded.

[0008] As a result of the inventor's investigation, it was discovered that when insufficiently heated, low-temperature rubber is extruded, the pressure of the rubber near the nozzle pulsates, which causes the shape of the extruded long rubber material to become unstable.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber member molding method capable of stabilizing the shape of a long rubber member. [Means for solving the problem]

[0010] The present invention includes the embodiments set forth below.

[0011] [1] A method for molding a rubber component in which a long rubber component is extruded from a rubber extruder and attached to a molding drum to mold a cylindrical rubber component for a tire, the method being characterized in that, in the extrusion of one long rubber component, the extrusion speed in a later period of extrusion is slower than the extrusion speed in an early period of extrusion.

[0012] [2] The method for molding a rubber member according to [1], wherein one of the long rubber members is made of more rubber than the rubber capacity of the extruder.

[0013] [3] The method for molding a rubber member according to [2], wherein the extrusion speed of the long rubber member slows down before the extrusion of an amount of rubber equal to the rubber volume is completed.

[0014] [4] A method for molding a rubber member according to any one of [1] to [3], wherein a plurality of the long rubber members are extruded at predetermined time intervals, and in the extrusion of each long rubber member, the extrusion speed in a later period of the extrusion is slower than the extrusion speed in an early period of the extrusion. Effect of the Invention

[0015] According to the above method, the shape of the long rubber member can be stabilized. [Brief description of the drawings]

[0016] [Figure 1] FIG. 4 is a left-right view of the rubber member molding device. [Diagram 2] Rear view of the upper and lower forming rollers. [Diagram 3] Top view of the area from the gear pump to the molding drum. [Figure 4] FIG. 13 is a left-right view of the area from the gear pump to the forming drum when the forming roller is in the attachment position. [Diagram 5] 1 is a left-right view of the portion from the gear pump to the building drum when the pressure roller is in the pressing position. FIG. [Figure 6] FIG. [Figure 7] FIG. 4 is a graph showing time series changes in rubber pressure at the outlet of a gear pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] First, the configuration of the rubber member molding apparatus 10 of this embodiment will be described.

[0018] As shown in Figure 1, the rubber member molding apparatus 10 of this embodiment comprises an extruder 11 that extrudes extruded rubber 2, a let-off device 12 that is in the process of supplying raw rubber sheet 1, which is the raw material for the extruded rubber 2, to the extruder 11, upper and lower forming rollers 13 and 14 that sandwich the extruded rubber 2 extruded from the extruder 11 from above and below to form a rubber strip 3, a molding drum 15 to which the rubber strip 3 that has passed through the forming rollers 13 and 14 is attached, a pressing roller 16 that presses the rubber strip 3 attached to the molding drum 15, and a control unit 32 (see Figure 6) that controls the rubber member molding apparatus 10.

[0019] The raw rubber sheet 1, the extruded rubber 2, and the rubber strip 3 are all unvulcanized long rubber members. In the following description, the cross section of the long rubber member refers to a cross section perpendicular to the extension direction of the long rubber member.

[0020] In the following description, the side where the molding drum 15 is located is referred to as the front, and the side where the let-off device 12 is located is referred to as the rear. The raw rubber sheet 1, extruded rubber 2, and rubber strip 3 move forward in the rubber member molding apparatus 10. Furthermore, the left-right direction is expressed when the rubber member molding apparatus 10 is viewed from the front. The left-right direction coincides with the axial direction of the molding drum 15 and molding rollers 13, 14.

[0021] The let-off device 12 is of a known structure and has a function of adjusting the tension applied to the raw rubber sheet 1 and a function of detecting when the raw rubber sheet 1 breaks. A bobbin 17 around which the raw rubber sheet 1 is wound is disposed behind the let-off device 12. The raw rubber sheet 1 unwound from the bobbin 17 is sent to the extruder 11 via the let-off device 12.

[0022] The extruder 11 is a supply device that supplies the extruded rubber 2 toward the molding drum 15, and has a general structure as a rubber extruder. The extruder 11 includes a cylindrical hollow barrel 20, a hopper 25 connected to an upper opening 20a of the barrel 20, a screw 21 provided inside the barrel 20, a heating device 26 (see FIG. 6) attached to the outer surface of the barrel 20, a gear pump 22 connected to the front end of the barrel 20, and a nozzle 23 connected to the front end of the gear pump 22.

[0023] The hopper 25 is a portion for feeding the raw rubber sheet 1 into the barrel 20. The screw 21 is connected to a screw motor 27 (see FIG. 6) and rotates when the screw motor 27 is operated. The heating device 26 is a heater. The rubber is kneaded in the barrel 20 when the screw 21 rotates while the barrel 20 is heated by the heating device 26.

[0024] As shown in FIG. 3, two meshed gears 28 are provided inside the gear pump 22. A gear motor 29 (see FIGS. 4 to 6) is connected to these gears 28. The gear motor 29 operates to rotate the two gears 28, thereby extruding rubber forward. An opening end 24 (see FIGS. 4 and 5) is formed in the nozzle 23 connected to the gear pump 22. The opening end 24 is the front end of the flow path of the rubber passing through the inside of the nozzle 23, and is also the extrusion port of the rubber from the extruder 11. As shown in FIG. 2, the opening end 24 is circular when viewed from the front-rear direction. The opening end 24 is also the front end of the entire extruder 11.

[0025] In the extruder 11 having such a structure, the raw rubber sheet 1 fed from the hopper 25 is kneaded inside the heated barrel 20, passes through the gear pump 22, and is extruded as the extruded rubber 2 from the open end 24 of the nozzle 23.

[0026] The extrusion speed of the extruded rubber 2 extruded from the open end 24 can be determined by adjusting the number of rotations per unit time of the gear 28. The extrusion speed of the extruded rubber 2 refers to the length of the extruded rubber 2 extruded per unit time, and is proportional to the volume of the extruded rubber 2 extruded per unit time.

[0027] The rubber capacity of the extruder 11 is smaller than the amount (volume) of rubber used in one rubber strip 3. Here, the rubber capacity of the extruder 11 refers to the maximum volume of rubber that can be filled in the space from the opening 20a of the barrel 20 to the opening end 24 of the nozzle 23 without impeding the function of the extruder 11.

[0028] The upper and lower forming rollers 13, 14 are each a substantially cylindrical roller. The upper and lower forming rollers 13, 14 have the same radius. As shown in Figures 4 and 5, the upper forming roller 13 is disposed forward of the lower forming roller 14. In addition, an open end 24 of a die 23 is disposed between the upper and lower forming rollers 13, 14.

[0029] The rotation shafts 13a, 14a of the upper and lower forming rollers 13, 14 are parallel to the rotation shaft 15a of the forming drum 15. The upper and lower forming rollers 13, 14 are each connected to a forming roller motor 19 (see FIG. 6) and can be rotated by operating the forming roller motor 19. The upper forming roller 13 and the lower forming roller 14 rotate in opposite directions, and are in the directions that send the long rubber member sandwiched therebetween forward.

[0030] As shown in Fig. 2, the upper and lower forming rollers 13, 14 are in contact with each other on both the left and right sides. Meanwhile, in the center in the left and right direction, a gap 18 is formed between the upper and lower forming rollers 13, 14. The gap 18 is formed between a recess 13b formed around the entire circumference of the outer circumferential surface of the upper forming roller 13 and the outer circumferential surface of the cylindrical lower forming roller 14. This gap 18 is where the extruded rubber 2 enters and is crushed from above and below to be formed into the rubber strip 3. Therefore, the shape of the gap 18 is the target cross-sectional shape of the rubber strip 3.

[0031] The outer circumferential surfaces of the upper and lower forming rollers 13, 14 are made of metal. By adjusting the surface roughness or temperature of these metal outer circumferential surfaces, the outer circumferential surface of the upper forming roller 13 has higher adhesiveness to the long rubber material than the outer circumferential surface of the lower forming roller 14. Therefore, the rubber strip 3 that passes through the gap 18 between the upper and lower forming rollers 13, 14 adheres to the upper forming roller 13.

[0032] The extruder 11 and the forming rollers 13, 14 can move together in the forward and backward directions by operating a moving device 30 (see FIG. 6). When the extruder 11 and the forming rollers 13, 14 are at the attachment position at the frontmost part of their movement range, the upper forming roller 13 can sandwich the rubber strip 3 between itself and the forming drum 15, as shown in FIG. 4. When the extruder 11 and the forming rollers 13, 14 are at the rear part of their movement range, the forming rollers 13, 14 are far apart from the forming drum 15, as shown in FIG. 5.

[0033] The outer peripheral surface of the molding drum 15 is cylindrical. The rubber strip 3 is spirally wound around the outer peripheral surface of the molding drum 15 to mold a cylindrical rubber member for a tire. Examples of cylindrical rubber members include an inner liner and a squeegee. The molding drum 15 is connected to a drum motor 31 (see FIG. 6), and rotates in the opposite direction to the upper molding roller 13 when the drum motor 31 is operated. The rubber strip 3 is more likely to adhere to the outer peripheral surface of the molding drum 15 than to the outer peripheral surface of the upper molding roller 13. To make it easier for the rubber strip 3 to adhere to the outer peripheral surface of the molding drum 15, for example, the surface roughness of the outer peripheral surface of the molding drum 15 is smaller than that of the upper molding roller 13.

[0034] The pressing roller 16 is a pressing device for pressing the rubber strip 3 on the forming drum 15. The pressing roller 16 is attached to the advancing / retracting device 33 and can advance and retreat with respect to the forming drum 15 based on the operation of the advancing / retracting device 33. When the forming rollers 13 and 14 are in the pasting position as shown in FIG. 4, the pressing roller 16 is separated from the forming drum 15. When the forming rollers 13 and 14 retreat and the gap between the forming rollers 13 and 14 and the forming drum 15 becomes wider as shown in FIG. 5, the pressing roller 16 advances between the forming rollers 13 and 14 and the forming drum 15 and reaches the pressing position. When in the pressing position, the pressing roller 16 can press the rubber strip 3 on the forming drum 15.

[0035] 6, devices such as the forming roller motor 19, the screw motor 27, the gear motor 29, the drum motor 31, the let-off device 12, the heating device 26, the moving device 30, and the advancing / retreating device 33 are connected to the control unit 32. The control unit 32 controls these connected devices and carries out the rubber member molding method described below.

[0036] Next, a flow of molding a rubber member in the rubber member molding apparatus 10 having the above configuration will be described.

[0037] In the method of molding a member using the rubber member molding apparatus 10, the raw rubber sheet 1 drawn from the bobbin 17 is fed into the hopper 25 of the extruder 11 via the let-off device 12. The raw rubber sheet 1 passed through the hopper 25 and fed into the inside of the barrel 20 is kneaded by the rotating screw 21. The kneaded rubber reaches the open end 24 of the die 23. Before the extruder 11 starts to extrude the extruded rubber 2, the extruder 11 is on standby with the rubber filled up to the open end 24 of the die 23. During standby, the rubber inside the extruder 11 is heated.

[0038] When extrusion of the extruded rubber 2 from the extruder 11 begins, the rubber inside the barrel 20 becomes the extruded rubber 2 and is extruded forward from the open end 24 of the nozzle 23. The extrusion speed of the extruded rubber 2 from the open end 24 is adjusted by the gear pump 22. The cross-sectional shape of the extruded extruded rubber 2 is circular.

[0039] The extruded rubber 2 extruded from the open end 24 of the die 23 enters the gap 18 between the upper and lower forming rollers 13, 14, which are already rotating. By passing through the gap 18 between the upper and lower forming rollers 13, 14, the extruded rubber 2 changes shape into a rubber strip 3 having the same cross-sectional shape as the gap 18 between the upper and lower forming rollers 13, 14.

[0040] The rubber strip 3 that has passed through the gap 18 adheres to the upper forming roller 13 and rises with the rotation of the upper forming roller 13. Then, as shown in Fig. 4, the leading end 3a of the rubber strip 3 is sandwiched between the upper forming roller 13 and the forming drum 15 which is already rotating.

[0041] As described above, the rubber strip 3 is more likely to stick to the outer circumferential surface of the molding drum 15 than to the outer circumferential surface of the forming roller 13. Therefore, after being sandwiched between the forming roller 13 and the forming drum 15, the leading end portion 3a of the rubber strip 3 leaves the forming roller 13 and sticks to the forming drum 15.

[0042] After the leading portion 3a of the rubber strip 3 has been attached to the forming drum 15, while the succeeding portion of the leading portion 3a is being attached, the extruder 11 and the forming rollers 13, 14 move backward together, and the upper and lower forming rollers 13, 14 move away from the forming drum 15. At the same time that the extruder 11 and the forming rollers 13, 14 start to move backward, or before or after that, the pressing roller 16 starts to advance toward the forming drum 15. Then, when the pressing roller 16 reaches the pressing position, it presses the rubber strip 3 attached to the forming drum 15, as shown in FIG. 5.

[0043] Even after the leading end 3a of the rubber strip 3 has been attached to the molding drum 15, the extrusion of the extruded rubber 2 from the extruder 11 and the rotation of the forming rollers 13 and 14 continue, thereby continuing to supply the rubber strip 3 to the molding drum 15. During this period, the molding drum 15 rotates in the drum circumferential direction while moving at a constant speed in the drum axial direction, so that the rubber strip 3 is wound spirally around the molding drum 15. During the winding, the pressure roller 16 continues to press the rubber strip 3 attached to the molding drum 15.

[0044] When the winding of the rubber strip 3 around the molding drum 15 is nearing completion, the screw 21 of the extruder 11, the gear pump 22, and the molding rollers 13 and 14 are stopped in this order. The gear pump 22 rotates in the reverse direction for a short period of time after the screw 21 has stopped, and then stops.

[0045] Even after the screw 21 and gear pump 22 have stopped and extrusion of the extruded rubber 2 from the open end 24 of the die 23 has stopped, the forming rollers 13, 14 continue to rotate and pull the extruded rubber 2 forward, causing the extruded rubber 2 to be torn off and cut at the open end 24 of the die 23. After the cut portion passes through the gap 18 between the forming rollers 13, 14 to become the rear portion of the rubber strip 3, the forming rollers 13, 14 stop. As a result, a long rubber member of the length to be wound around the forming drum 15 (which is the extruded rubber 2 before passing through the gap 18 between the forming rollers 13, 14 and the rubber strip 3 after passing through) is cut out.

[0046] Thereafter, attachment of the rear portion of the rubber strip 3 is completed, thereby completing a cylindrical rubber member for a tire.

[0047] As described above, the extruded rubber 2 is cut at the open end 24 of the die 23. Therefore, after one long rubber material has been extruded, the extruder 11 waits in a state where the rubber is filled up to the open end 24 of the die 23 until the extrusion of the next long rubber material is started. During this wait, the rubber inside the extruder 11 is heated.

[0048] By repeating the above operation, a plurality of long rubber members are extruded at predetermined time intervals, and cylindrical rubber members are molded from each of the long rubber members.

[0049] Next, the extrusion speed of the long rubber member (extruded rubber 2 at the time of extrusion) from the extruder 11 in the flow of molding the rubber member described above will be described.

[0050] First, Fig. 7 shows the measurement results of the pressure of the rubber (rubber pressure) at the outlet of the gear pump 22 while the long rubber member was being extruded from the extruder 11. In Fig. 7, the solid line shows the time series change in the rubber pressure when the rotation speed of the gear 28 was 45 rpm, and the dashed line shows the time series change in the rubber pressure when the rotation speed of the gear 28 was 20 rpm. Since the rotation speed of the gear 28 when the dashed line data was measured was about 30% of that when the solid line data was measured, the extrusion speed when the dashed line data was measured was also about 30% of that when the solid line data was measured.

[0051] From Fig. 7, it can be seen that when the extrusion speed is fast, pulsation of the rubber pressure begins a certain time after the start of extrusion. This pulsation occurs because insufficiently heated rubber is forcibly extruded at high speed. On the other hand, when the extrusion speed is slow, the rubber pressure hardly pulsates even after a long time has passed since the start of extrusion, and although slight pulsation does occur, it starts late. This embodiment makes use of this difference.

[0052] In this embodiment, in the above-mentioned flow of molding the rubber member, the control unit 32 controls the extrusion speed of the long rubber member extruded from the extruder 11. Specifically, the control unit 32 slows down the extrusion speed while the extruder 11 is extruding one long rubber member. Therefore, the extrusion speed in the early stage of the extrusion of one long rubber member is a constant speed V1, and the extrusion speed in the later stage of the extrusion of the same long rubber member is another constant speed V2, and the speed V2 is slower than the speed V1. Here, the speed V2 is preferably half or less of the speed V1.

[0053] The timing at which the control unit 32 changes the extrusion speed from speed V1 to speed V2 (in other words, the boundary between the early and late periods in the extrusion of one long rubber member) is preferably before the completion of extrusion of an amount of rubber equal to the rubber capacity of the extruder 11. If the extrusion speed changes gradually from speed V1 to speed V2 over time, it is preferable that the change to speed V2 is completed before the completion of extrusion of an amount of rubber equal to the rubber capacity of the extruder 11.

[0054] The timing at which the extrusion of an amount of rubber equal to the rubber capacity of the extruder 11 is completed can be calculated from the rubber capacity of the extruder 11, the volume per unit length of the long rubber member, and the extrusion speed of the long rubber member. Here, the rubber capacity and volume may be converted to weight for calculation.

[0055] The timing at which the control unit 32 changes the extrusion speed from speed V1 to speed V2 depends on the rubber capacity of the extruder 11, but is, for example, when the rubber strip 3 has been wound around about halfway in the axial direction of the building drum 15.

[0056] By controlling the extrusion speed in this way, in the early stage of extrusion of one long rubber material, the long rubber material is extruded at a relatively high speed. However, since the rubber extruded at this time is sufficiently heated rubber that has been present inside the extruder 11 since before the start of extrusion, no pulsation of rubber pressure occurs, and the long rubber material is extruded smoothly.

[0057] Meanwhile, in the latter stage of extrusion of one long rubber material, insufficiently heated rubber that was put into barrel 20 after extrusion of the long rubber material started is extruded. However, since the rubber extruded at this time is extruded at a relatively low speed, no pulsation of rubber pressure occurs and the long rubber material is extruded smoothly. In this way, one long rubber material is extruded smoothly from the leading portion 3a to the trailing portion.

[0058] As described above, multiple long rubber members are extruded at a predetermined time interval, but there is a waiting time from the completion of extrusion of the n-th long rubber member to the start of extrusion of the n+1-th long rubber member. During that waiting time, the rubber used for the n+1-th long rubber member is heated inside the extruder 11, and the heating condition of the rubber inside the extruder 11 becomes close to the condition immediately before the start of extrusion of the n-th long rubber member. Therefore, in the extrusion of the n+1-th long rubber member, the control unit 32 controls the extrusion speed in the same way as in the extrusion of the n-th long rubber member. In this way, in the extrusion of all long rubber members extruded at a predetermined time interval, the control unit 32 changes the extrusion speed from speed V1 to speed V2.

[0059] When the control unit 32 changes the extrusion speed of the long rubber material extruded from the extruder 11, it also changes the rotation speeds of the forming rollers 13, 14 and the forming drum 15 accordingly. For example, when the control unit 32 slows down the extrusion speed of the long rubber material, it also slows down the rotation speeds of the forming rollers 13, 14 and the forming drum 15. It is preferable that the rate of change of the rotation speeds of the forming rollers 13, 14 and the forming drum 15 is the same as the rate of change of the extrusion speed of the long rubber material.

[0060] Next, the effects of this embodiment will be described.

[0061] As described above, in this embodiment, the control unit 32 makes the extrusion speed in the latter period of extrusion slower than the extrusion speed in the early period of extrusion when extruding one long rubber member. Here, the rubber extruded in the later period of extrusion is insufficiently heated, and if the long rubber member is extruded at the same speed as in the early period of extrusion, there is a risk of pulsation of the rubber pressure occurring near the nozzle 23. However, by slowing the extrusion speed in the later period of extrusion as described above, it is possible to prevent pulsation of the rubber pressure. Since pulsation of the rubber pressure can be prevented in this way, the shape of the long rubber member can be stabilized.

[0062] Furthermore, in this embodiment, since one long rubber member is made of more rubber than the rubber capacity of the extruder 11, in the latter stage of extrusion of one long rubber member, insufficiently heated rubber that was fed into the barrel 20 after extrusion of the long rubber member began is extruded. However, since the control unit 32 makes the extrusion speed in the latter stage of extrusion slower than the extrusion speed in the early stage of extrusion, pulsation of rubber pressure is unlikely to occur even with insufficiently heated rubber.

[0063] Conversely, since pulsation of the rubber pressure can be prevented by controlling the extrusion speed by the control unit 32, the rubber capacity of the extruder 11 may be small. Therefore, there is no need to increase the size of the rubber member molding apparatus 10.

[0064] Furthermore, in this embodiment, the control unit 32 slows down the extrusion speed of the long rubber material before the extrusion of an amount of rubber equal to the rubber capacity of the extruder 11 is completed. Therefore, insufficiently heated rubber that is put into the barrel 20 after the start of extrusion of the long rubber material can be reliably extruded from the open end 24 of the nozzle 23 at a slow speed.

[0065] In this embodiment, a plurality of long rubber members are extruded from the extruder 11 at a predetermined time interval, and the control unit 32 controls the extrusion speed of each long rubber member to be slower in the latter period than in the early period, thereby stabilizing the shapes of all the long rubber members.

[0066] Here, if the "predetermined time interval" is short, there is a risk that in the extrusion of the second or subsequent long rubber member, rubber that was located far from the nozzle 23 in the extruder 11 at the start of extrusion may be extruded in the later stage of extrusion while being insufficiently heated. However, because the control unit 32 slows down the extrusion speed in the later stage of extrusion, pulsation of the rubber pressure is unlikely to occur even if the rubber extruded in the later stage of extrusion is insufficiently heated.

[0067] Next, modified examples will be described. Various modifications can be made to the above embodiment, and some of these modifications will be described below.

[0068] <Change Example 1> The configuration of the rubber member molding device is not limited to that of the above embodiment.

[0069] For example, the forming rollers 13, 14 may not be provided between the extruder 11 and the forming drum 15 in the above embodiment. In that case, the extruded rubber 2 extruded from the extruder 11 is wound around the forming drum 15.

[0070] Furthermore, a holding device for holding the leading portion 3a of the rubber strip 3 may be disposed between the forming rollers 13, 14 and the forming drum 15 in the above embodiment. In this case, the leading portion 3a of the rubber strip 3 that has passed through the gap 18 between the forming rollers 13, 14 is held by the holding device and attached to the forming drum 15.

[0071] <Change Example 2> There are cases where the rubber capacity of the extruder 11 is sufficiently large, and the rubber capacity of the extruder 11 is equal to or larger than the amount of rubber used for one long rubber member. Specifically, there are cases where the rubber capacity of the extruder 11 is equal to the amount of rubber for one or more but less than two long rubber members, or the amount of rubber used for multiple long rubber members.

[0072] Even in this modified example, inside the extruder 11, the rubber closer to the nozzle 23 is hotter and the rubber further from the nozzle 23 is colder. Therefore, even in this modified example, the control unit 32 makes the extrusion speed in the latter period of extrusion slower than the extrusion speed in the early period of extrusion when extruding one long rubber member. This makes it difficult for pulsation of the rubber pressure to occur even if the rubber extruded in the later period of extrusion is relatively cold, and the shape of the long rubber member is stabilized.

[0073] In the case of such a modified example, the timing for changing the extrusion speed is preferably before the relatively low-temperature rubber in the extruder 11 reaches the open end 24 of the die 23. Moreover, the extrusion speed in the latter stage of extrusion is preferably half or less of the extrusion speed in the early stage of extrusion.

[0074] Also in such a modified example, multiple long rubber members are extruded at a predetermined time interval, but in extruding each long rubber member, it is preferable that the control unit 32 sets the extrusion speed in the later stage of extrusion to be slower than the extrusion speed in the early stage of extrusion. [Explanation of symbols]

[0075] 1...raw rubber sheet, 2...extruded rubber, 3...rubber strip, 3a...leading portion, 10...rubber member molding device, 11...extruder, 12...let-off device, 13...molding roller, 13a...rotating shaft, 13b...dent, 14...molding roller, 14a...rotating shaft, 15...molding drum, 15a...rotating shaft, 16...pressure roller, 17...bobbin, 18...gap, 19...molding roller motor, 20...barrel, 20a...opening, 21...screw, 22...gear pump, 23...mouthpiece, 24...opening end, 25...hopper, 26...heating device, 27...screw motor, 28...gear, 29...gear motor, 30...moving device, 31...drum motor, 32...control unit, 33...advance / retract device

Claims

1. A rubber member molding method in which a long rubber member is extruded from a rubber extruder and attached to a molding drum to mold a cylindrical rubber member for a tire, comprising: The method for molding a rubber member, wherein in extruding one long rubber member, the extrusion speed in a later stage of extrusion is slower than the extrusion speed in an early stage of extrusion.

2. 2. The method for molding a rubber member according to claim 1, wherein one long rubber member is made of more rubber than the rubber capacity of the extruder.

3. 3. The method for molding a rubber member according to claim 2, wherein the extrusion speed of the long rubber member is slowed down before the extrusion of an amount of rubber equal to the rubber volume is completed.

4. The rubber member molding method according to any one of claims 1 to 3, wherein a plurality of the long rubber members are extruded at a predetermined time interval, and an extrusion speed in a later stage of extrusion of each of the long rubber members is slower than an extrusion speed in an early stage of extrusion.

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