Manufacturing method for pneumatic tires

Abstract

To provide a manufacturing method of a tire that has little adverse effect on uniformity.SOLUTION: The pneumatic tire manufacturing method comprises a step of winding a long rubber member 1 extruded from an extruder into a cylindrical winding tube 12, a step of pulling out the long rubber member 1 from the winding tube 12 to cut out into a rubber member for tread 2 that forms the tread of one tire, and a step of winding the cut-out rubber member for tread 2 around a drum 34 to form a ring-shaped tread 3. A diameter of a main body 18 that is a portion of the winding tube 12 around which the long rubber member 1 is wound, is greater than or equal to a diameter of the drum 34.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for manufacturing pneumatic tires.

Background Art

[0002] The tread of a pneumatic tire is formed by molding a rubber member for the tread in a ring shape. When manufacturing the rubber member for the tread, first, a long rubber member is extruded from an extruder. The long rubber member has a width and thickness close to those of the tread of a pneumatic tire and is a rubber member long in the extrusion direction. The extruded long rubber member is wound around a winding cylinder called a reel or a bobbin (see, for example, Patent Document 1). The winding cylinder has a small diameter. A long rubber member having a length corresponding to several tens of rubber members for the tread is wound around the winding cylinder.

[0003] The long rubber member wound around the winding cylinder is conveyed to a molding location having a drum. Then, at the molding location, the long rubber member is pulled out from the winding cylinder and cut, and a rubber member for the tread having a length corresponding to one tire is cut out. The cut rubber member for the tread is wound around the drum and molded into a ring shape.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in conventional methods, as described above, extremely long rubber members, equivalent to dozens of tread rubber members, are wound multiple times around a small-diameter winding cylinder. As a result, the longer rubber members become compressed towards the inner diameter when wound. Consequently, the thickness of the tread rubber members does not match at the front and rear ends, creating a step at the joint between the front and rear ends of the tread rubber members on the drum. Such a step negatively affects the uniformity of the pneumatic tire.

[0006] Therefore, the object of the present invention is to provide a method for manufacturing pneumatic tires that has minimal adverse effects on uniformity. [Means for solving the problem]

[0007] The present invention includes embodiments shown below.

[0008] [1] A method for manufacturing a pneumatic tire, comprising the steps of winding a long rubber member extruded from an extruder onto a winding cylinder, pulling out the long rubber member from the winding cylinder and cutting it to cut out a tread rubber member that will become the tread of a tire, and winding the cut tread rubber member onto a drum to form a ring-shaped tread, wherein the winding cylinder has a cylindrical body which is the part around which the long rubber member is wound, and the diameter of the body is equal to or greater than the diameter of the drum.

[0009] [2] The method for manufacturing a pneumatic tire according to [1], wherein the length of the long rubber member wound onto the winding cylinder is the length of 10 to 16 of the tread rubber members.

[0010] [3] A method for manufacturing a pneumatic tire according to [1] or [2], wherein the long rubber member is cut using an ultrasonic cutter.

[0011] [4] A method for manufacturing a pneumatic tire according to any one of [1] to [3], wherein when cutting the long rubber member, the angle between the bottom surface of the long rubber member and the cut surface is 25 ± 4°. [Effects of the Invention]

[0012] The above manufacturing method has minimal adverse effects on the uniformity of the finished pneumatic tire. [Brief explanation of the drawing]

[0013] [Figure 1] A perspective view of a long rubber component, seen from diagonally above. [Figure 2] (a) is a perspective view of the tread rubber component seen from diagonally above. (b) is a side view of the tread rubber component. (c) is a magnified view of the vicinity of the cross-section of (b). [Figure 3] A perspective view of the ring-shaped tread, seen from the side at an angle. [Figure 4] A side view of the winding area for long rubber components. [Figure 5] A view of the winding cylinder from the direction of arrow A in Figure 4. [Figure 6] A side view of the ring-shaped tread manufacturing equipment in the molding area. [Figure 7] Block diagram of a ring-shaped tread manufacturing machine. [Figure 8] A diagram showing the winding process of a long rubber material. [Figure 9] A side view of the ring-shaped tread manufacturing machine. A diagram showing the cutting of a long rubber component. [Figure 10] A top-down view of a part of the cutting device. The image shows the cutting of a long rubber component. [Figure 11] A side view of a part of the cutting device. The image shows the cutting of a long rubber component. [Figure 12] A side view of the ring-shaped tread manufacturing machine. A diagram showing the heating of the rubber material for the tread. [Figure 13] A side view of a ring-shaped tread manufacturing machine. The diagram shows the process of winding the tread rubber material onto the drum.

Best Mode for Carrying Out the Invention

[0014] An embodiment will be described with reference to the drawings. Note that the embodiments described below are merely examples, and those appropriately modified without departing from the gist of the present invention are included in the scope of the present invention.

[0015] This embodiment relates to a method of cutting a long rubber member 1 (see FIG. 1) at a plurality of locations in its longitudinal direction to form a plurality of tread rubber members 2 (see FIG. 2), and each tread rubber member 2 is formed into a ring-shaped ring tread 3 (see FIG. 3).

[0016] Here, the long rubber member 1 is a rubber member that is long in one direction. This "one direction" is the longitudinal direction of the long rubber member 1. The long rubber member 1 has a width and thickness close to those of the tread in the finally completed pneumatic tire (hereinafter simply referred to as "tire").

[0017] Also, the tread rubber member 2 is a rubber member that forms one tread of the tire. The longitudinal direction of the tread rubber member 2 coincides with the longitudinal direction of the long rubber member 1. The length of the tread rubber member 2 in the longitudinal direction substantially coincides with the length of the tread in the tire circumferential direction of the finally completed tire. Since the tread rubber member 2 is cut out from the long rubber member 1, it has the same width and thickness as the long rubber member 1. The bottom surface 2a of the tread rubber member 2 is the surface that was originally the bottom surface 1a of the long rubber member 1 (see FIG. 11). The front end and the rear end of the tread rubber member 2 are the cut surfaces 2b when the long rubber member 1 is cut. This cut surface 2b is inclined with respect to the bottom surface 2a.

[0018] The "width" and "thickness" of the long rubber member 1 and the tread rubber member 2 refer to the lengths measured in a cross-section perpendicular to the longitudinal direction of the long rubber member 1 and the tread rubber member 2. The "width" is the length in the lateral direction of the bottom surfaces 1a and 2a. The "thickness" is the length in the direction perpendicular to the bottom surfaces 1a and 2a. The "lateral direction" refers to the direction perpendicular to the longitudinal direction when viewed from above. Figures 1 and 2 show the "longitudinal direction" and "lateral direction".

[0019] Furthermore, the ring-shaped tread 3 is a rubber member formed by joining the front and rear ends of the tread rubber member 2 to create a ring shape. The bottom surface 2a of the tread rubber member 2 becomes the inner surface of the ring-shaped tread 3. The "front end" is the end of the longitudinal direction of the tread rubber member 2 that reaches the drum 34 first when the tread rubber member 2 is wrapped around the drum 34, as will be described later.

[0020] Figures 4 to 7 show the tire manufacturing apparatus of this embodiment. The tire manufacturing apparatus is located in two separate locations: a winding area for the long rubber member 1 (Figure 4) and a molding area for the ring-shaped tread 3 (Figure 6). The winding area for the long rubber member 1 is where the long rubber member 1 is wound onto the winding cylinder 12. The molding area for the ring-shaped tread 3 is where the ring-shaped tread 3 is manufactured from the long rubber member 1.

[0021] In the winding area for the long rubber member 1 shown in Figure 4, an extruder 11 is positioned to extrude the long rubber member 1. The extruder 11 is of a known structure that extrudes rubber with a constant cross-sectional shape from a die 11a. The long rubber member 1 is extruded from this extruder 11. The direction of extrusion from the extruder 11 is the longitudinal direction of the long rubber member 1.

[0022] When the long rubber member 1 is extruded from the extruder 11, a winding cylinder 12 is positioned in front of the extruder 11. As shown in Figure 5, the winding cylinder 12 has a cylindrical body 18 and flanges 19 provided on both sides of the body 18 in the axial direction. The body 18 is the part around which the long rubber member 1 is wound. The diameter of the body 18 is greater than or equal to the diameter of the drum 34 (see Figure 6), which will be described later. Also, the diameter of the flanges 19 is greater than the diameter of the body 18. Note that the diameter of the body 18 of the winding cylinder 12 is the diameter measured at the surface in which the long rubber member 1 actually makes contact.

[0023] As shown in Figure 4, the winding cylinder 12 is mounted on a trolley 13. The trolley 13 has a lower frame 14, an upper frame 15 that rises upward from the lower frame 14, wheels 16 attached to the bottom of the lower frame 14, and a rotating shaft 17 provided on the upper frame 15.

[0024] The winding cylinder 12 is supported by the rotation axis 17 of the trolley 13. This allows the winding cylinder 12 to rotate around the rotation axis 17 while mounted on the trolley 13. The winding cylinder 12 winds the long rubber material 1 into a roll while rotating. Furthermore, as described above, the trolley 13 has wheels 16, so the winding cylinder 12 can be moved while remaining mounted on the trolley 13.

[0025] A ring-shaped tread manufacturing apparatus 40 is located at the molding site of the ring-shaped tread 3 shown in Figure 6. The ring-shaped tread manufacturing apparatus 40 is composed of a cutting device 31, a first conveyor 32, a second conveyor 33, and a drum 34, arranged in this order. The cutting device 31 is a device that cuts a long rubber member 1 into tread rubber members 2. The first conveyor 32 and the second conveyor 33 are devices that transport the tread rubber members 2 cut by the cutting device 31 toward the drum 34. The drum 34 is a device on which the tread rubber members 2 are wound to form the ring-shaped tread 3.

[0026] In Figure 6, the cutting device 31 is on the upstream side of the material flow, and the drum 34 is on the downstream side of the material flow. The direction from upstream to downstream is the conveying direction of the long rubber member 1 and the tread rubber member 2. The conveying direction of the long rubber member 1 and the tread rubber member 2 coincides with their longitudinal direction.

[0027] The area upstream of the cutting device 31 is where the trolley 13 carrying the winding cylinder 12 is positioned. The long rubber member 1, pulled out from the winding cylinder 12, is sent to the cutting device 31.

[0028] The cutting device 31 consists of a table 30 and a structure on the table 30. Two receiving members 35 are provided on the table 30, side by side in the direction of transport. A blade 37 for cutting the long rubber member 1 is provided between the two receiving members 35. A pressing member 36 that moves up and down is also provided above the two receiving members 35. The pressing member 36 lowers and presses down on the long rubber member 1 by sandwiching it between itself and the receiving members 35.

[0029] With the two pressing members 36 pressing down on the long rubber member 1, the blade 37 moves from one side of the long rubber member 1 to the other in the lateral direction to cut the long rubber member 1 (see Figure 10). The direction of movement of the blade 37 is lateral.

[0030] The blade 37 used here is a blade for an ultrasonic cutter. An ultrasonic cutter has a known configuration consisting of a blade 37, a transducer, a piezoelectric element, an oscillator, etc. The blade 37 is attached to a transducer into which a piezoelectric element is incorporated. The oscillator applies an AC voltage to the piezoelectric element, causing the transducer and blade 37 to vibrate at a frequency in the ultrasonic range.

[0031] The blade 37 is inclined with respect to the bottom surface 1a of the long rubber member 1 (see Figure 11). Therefore, the cut surfaces 1b and 2b cut by the blade 37 are inclined surfaces with respect to the bottom surfaces 1a and 2a of the long rubber member 1 and the tread rubber member 2. The inclination angle θ of the blade 37 with respect to the bottom surface 1a of the long rubber member 1 is 25±4°. Therefore, the inclination angle θ of the cut surfaces 1b and 2b with respect to the bottom surfaces 1a and 2a of the long rubber member 1 and the tread rubber member 2 is 25±4°. Note that when the long rubber member 1 is cut, the bottom surface 1a of the long rubber member 1 coincides with the surface connecting the two receiving members 35 on which the long rubber member 1 lies.

[0032] On the table 30, multiple rollers 38 are arranged in the conveying direction in places where there are no receiving members 35. When a drive device (not shown), such as a feed roller, is driven, the long rubber member 1 is conveyed on the rollers 38 from the upstream side to the downstream side.

[0033] The first conveyor 32 and the second conveyor 33 are conveyors that transport the tread rubber member 2 downstream. A heating device, the first heater 41, is provided above the second conveyor 33. Another heating device, the second heater 42, is provided between the first conveyor 32 and the second conveyor 33. The length in the transport direction from the first heater 41 to the second heater 42 is approximately equal to the longitudinal length of the tread rubber member 2. When the tread rubber member 2 stops at the upstream position on the second conveyor 33, the first heater 41 can heat the front end of the tread rubber member 2, and the second heater 42 can heat the rear end of the tread rubber member 2.

[0034] Furthermore, a length measuring sensor 43 is provided on the first conveyor 32. The length measuring sensor 43 is a sensor that measures the length in the longitudinal direction of the tread rubber member 2 on the first conveyor 32. The control unit 44, which will be described later, controls the transport speed of the second conveyor 33 based on the measurement results from the length measuring sensor 43.

[0035] The drum 34 is a drum with a known structure for forming tread rings. Multiple belts are pre-stacked on the drum 34. The tread rubber material 2, transported from the second conveyor 33, is wrapped around these belts. The front and rear ends of the wrapped tread rubber material 2 are joined together to form a ring-shaped tread 3. As soon as the ring-shaped tread 3 is completed, the tread ring, which is made up of multiple belts and the ring-shaped tread 3 stacked together, is also completed.

[0036] The diameter of the drum 34 is less than or equal to the diameter of the main body 18 of the winding cylinder 12. The diameter of the drum 34 is the diameter measured at the surface in contact with the tire components such as the belt. In a typical drum 34, multiple segments are arranged to form a cylinder, and the tire components are attached to the surfaces of these segments. In such a configuration, the diameter of the drum 34 is the diameter measured at the surface of the segments.

[0037] The ring-shaped tread manufacturing apparatus 40 is equipped with a control unit 44. As shown in Figure 7, the control unit 44 is connected to a pressing member 36, a moving device 39 for moving the blade 37 laterally, a first conveyor 32, a second conveyor 33, a first heater 41, a second heater 42, a drum 34, and the like. The control unit 44 controls the connected equipment and the like.

[0038] In the tire manufacturing method of this embodiment, first, a carcass band, which consists of laminated carcass plies and an inner liner, and a tread ring, which consists of multiple belts with ring-shaped treads 3 laminated on their outer surfaces, are molded separately. Next, shaping and turn-up are performed on the carcass band. Then, the tread ring is attached to the outer surface of the carcass band, which has expanded due to shaping, and a sidewall is attached to the side of the carcass band to form a green tire. Finally, vulcanization molding is performed on the green tire to complete the tire.

[0039] In the manufacturing of the ring-shaped tread 3 in this tire manufacturing method, first, the long rubber member 1 is extruded from the extruder 11 at the winding location for the long rubber member 1. As shown in Figure 8, the extruded long rubber member 1 is wound onto the winding cylinder 12. The long rubber member 1 is wound with its bottom surface 1a facing radially inward.

[0040] During winding, the winding cylinder 12 is mounted on a trolley 13. The rotation of the winding cylinder 12 for winding may be performed automatically by a motor (not shown) or manually. The length (length in the longitudinal direction) of one long rubber member 1 wound onto the winding cylinder 12 is equivalent to 10 to 16 tread rubber members 2.

[0041] After the winding of the long rubber member 1 is complete, the trolley 13, with the winding cylinder 12 still on it, is transported to the molding area for the ring-shaped tread 3. Then, as shown in Figure 6, the trolley 13 is positioned upstream of the cutting device 31.

[0042] In the ring-shaped tread molding area, first, the long rubber member 1 is pulled out from the winding cylinder 12. The pulled-out long rubber member 1 is transported on the rollers 38 of the table 30. During this transport, the bottom surface 1a of the long rubber member 1 is facing downwards and in contact with the rollers 38. When the front end of the long rubber member 1 has been transported a predetermined distance downstream from the blade 37, the transport of the long rubber member 1 stops.

[0043] Next, the two pressing members 36 descend and press down on the long rubber member 1 on both sides of the blade 37. Then, as shown in Figures 9 to 11, the blade 37 cuts the long rubber member 1 between the two pressing members 36. In detail, the blade 37, having entered the long rubber member 1, vibrates and moves from one side of the long rubber member 1 to the other (i.e., in the direction of arrow B in Figure 10), thereby cutting the long rubber member 1. The vibration frequency of the blade 37 during cutting is, for example, 35 kHz to 45 kHz. The movement speed of the blade 37 during cutting is, for example, 250 to 550 mm / min.

[0044] As described above, the blade 37 is inclined, so as shown in Figure 11, the cut surfaces 1b and 2b are inclined surfaces with respect to the bottom surface 1a of the long rubber member 1 and the bottom surface 2a of the tread rubber member 2. The angle θ between the bottom surface 1a and the cut surface 1b of the long rubber member 1 is 25±4°. Also, the angle θ between the bottom surface 2a and the cut surface 2b of the tread rubber member 2 (however, the smaller of the angles formed on both sides in the longitudinal direction) is also 25±4°.

[0045] One tread rubber member 2 is cut from the long rubber member 1 in a single operation. The cut tread rubber member 2 is sent to the first conveyor 32.

[0046] When the entire tread rubber member 2 is placed on the first conveyor 32, the first conveyor 32 stops temporarily. Then, the length (length in the longitudinal direction) of the tread rubber member 2 is measured by the length measuring sensor 43. The measurement result is sent to the control unit 44. Once the measurement is complete, the first conveyor 32 resumes transporting the tread rubber member 2.

[0047] Next, the tread rubber member 2 is transported from the first conveyor 32 to the second conveyor 33. When the front end of the tread rubber member 2 reaches below the first heater 41, the transport of the tread rubber member 2 stops. As shown in Figure 12, at this point, the rear end of the tread rubber member 2 is above the second heater 42.

[0048] While the transport is stopped, the front and rear ends of the tread rubber member 2 are heated by the heaters 41 and 42, respectively. The heating causes the temperature of the cut surface 2b of the tread rubber member 2 to reach 40-60°C. At this temperature, the front and rear ends of the tread rubber member 2 soften and their adhesiveness increases.

[0049] Next, the first conveyor 32 resumes transporting the tread rubber material 2. Then, the tread rubber material 2 is transported from the first conveyor 32 to the second conveyor 33.

[0050] Next, the tread rubber material 2 is transported from the second conveyor 33 to the drum 34, as shown in Figure 13, and wound onto the drum 34. This winding is performed by the rotation of the second conveyor 33, which feeds out the tread rubber material 2, and the rotating drum 34 winding up the fed-out tread rubber material 2.

[0051] During this winding process, the drum 34 rotates at a predetermined constant rotational speed. Meanwhile, the rotational speed of the second conveyor 33 is changed depending on the measurement result of the length of the tread rubber member 2 by the length measuring sensor 43. For example, if the measurement result of the length measuring sensor 43 reveals that the length of the tread rubber member 2 is longer than the target value, the control unit 44 increases the rotational speed of the second conveyor 33 to a higher value than the reference value and increases the feed speed of the tread rubber member 2. Conversely, if the measurement result of the length measuring sensor 43 reveals that the length of the tread rubber member 2 is shorter than the target value, the control unit 44 decreases the rotational speed of the second conveyor 33 to a lower value than the reference value and decreases the feed speed of the tread rubber member 2. This control allows the front and rear ends of the tread rubber member 2 to be aligned on the drum 34 even if the length of the tread rubber member 2 differs slightly from the target value.

[0052] As described above, the front and rear ends of the tread rubber member 2 soften and become more adhesive, so when the front and rear ends of the tread rubber member 2 coincide on the drum 34, they are joined together. The joining of the front and rear ends completes the ring-shaped tread 3.

[0053] Multiple belts are pre-wrapped around the drum 34. The tread rubber material 2 is wrapped around these belts to form a ring-shaped tread 3. Simultaneously with the completion of the ring-shaped tread 3, a tread ring is also completed, with the ring-shaped tread 3 attached to the belts.

[0054] Using the method described above, between 10 and 16 tread rubber members 2 are cut from a single long rubber member 1. These tread rubber members 2 are then transported one by one to a drum 34, where they are each formed into a ring-shaped tread 3.

[0055] Tires using this type of ring-shaped tread 3 are used, for example, as radial tires for trucks and buses.

[0056] According to the tire manufacturing method of this embodiment, effects such as less adverse effects on tire uniformity are obtained.

[0057] Specifically, in this embodiment, the winding cylinder 12 used for winding the long rubber member 1 has a main body 18, the part around which the long rubber member 1 is wound, with a diameter greater than or equal to the diameter of the drum 34. Therefore, the length of the long rubber member 1 that can be wound up in one rotation of the winding cylinder 12 is long, and even when the entire long rubber member 1 is wound up, the number of turns of the long rubber member 1 on the winding cylinder 12 is small. Because the number of turns of the long rubber member 1 is small in this way, the inner part of the winding of the long rubber member 1 is less likely to be crushed.

[0058] Because the long rubber member 1 is less prone to deformation, the thickness of the front and rear ends of the tread rubber member 2 is more likely to match, and a step is less likely to occur at the joint between the front and rear ends of the tread rubber member 2 on the drum 34. Therefore, adverse effects on the uniformity of the tire caused by such a step are less likely to occur.

[0059] Furthermore, since the length of the long rubber member 1 wound onto the winding cylinder 12 is 16 or less in terms of the number of tread rubber members 2, the number of windings of the long rubber member 1 on the winding cylinder 12 is small, and the long rubber member 1 is less likely to be crushed. Also, since the length of the long rubber member 1 wound onto the winding cylinder 12 is 10 or more in terms of the number of tread rubber members 2, the number of winding cylinders 12 and trolleys 13 that need to be prepared for tire production can be reduced, and productivity does not deteriorate.

[0060] Furthermore, although the long rubber member 1 is cut using an ultrasonic cutter, the blade 37 of the ultrasonic cutter vibrates at ultrasonic frequencies while cutting the long rubber member 1, resulting in smooth cut surfaces 1b and 2b. Therefore, steps and other irregularities are less likely to occur at the joint between the front and rear ends of the tread rubber member 2 cut from the long rubber member 1, minimizing adverse effects on the uniformity of the tire.

[0061] Here, the long rubber member 1 is cut by moving the blade 37 of the ultrasonic cutter in the lateral direction of the long rubber member 1. Therefore, compared to cutting by lowering the cutter blade from top to bottom, the cut surfaces 1b and 2b are less likely to become rough.

[0062] Furthermore, when cutting the long rubber member 1, if the angle θ between the bottom surface 1a of the long rubber member 1 and the cut surface 1b is 21° (25°-4°) or greater, the blade 37 that enters the thick long rubber member 1 from above can reach the bottom surface 1a. Also, if the angle θ is 21° or greater, the resistance that the blade 37 receives from the rubber will not be excessive.

[0063] Furthermore, when cutting the long rubber member 1, the angle θ between the bottom surface 1a of the long rubber member 1 and the cut surface 1b is 29° (25° + 4°) or less, which ensures sufficient surface area of ​​the cut surface 2b of the tread rubber member 2, making it easy to join the front and rear ends of the tread rubber member 2. Also, because the angle θ is 29° or less, even if the position or angle at which the blade 37 enters is slightly off, a step is less likely to occur at the joint between the front and rear ends of the tread rubber member 2.

[0064] Furthermore, as described above, the length of the tread rubber member 2 is measured before winding it onto the drum 34, and based on the measurement result, the feed speed of the tread rubber member 2 from the second conveyor 33 is adjusted when winding the tread rubber member 2 onto the drum 34. As a result, the front and rear ends of the tread rubber member 2 can be aligned on the drum 34.

[0065] Examples and comparative examples are shown in Table 1. Example 1 is an example of a tire manufactured using the method of the above embodiment. Example 2 differs from Example 1 in that, when cutting the long rubber member, an ultrasonic cutter was not used, and the long rubber member was cut by lowering a blade from above. The comparative example differs from Example 1 in that a winding cylinder with a main body diameter smaller than the drum diameter was used, and the long rubber member was cut with a blade lowered from above, similar to Example 2. These differences are shown in the "Manufacturing Conditions" column of Table 1.

[0066] As shown in Table 1, the test items are the thickness difference by location in the tread, the thickness difference by location in the tire, and uniformity.

[0067] In the test to determine the thickness difference depending on the location of the tread, the thickness of the tread rubber material was first measured at three locations along its longitudinal direction. The thickness was measured at the shoulder of the tread. After measurement, the thickness difference depending on the location of the tread was determined by subtracting the thickness of the thinnest part (the part at the other end of the longitudinal direction of the tread rubber material, which was at the innermost end of the winding cylinder) from the thickness of the thickest part (the part at one end of the longitudinal direction of the tread rubber material, which was at the outermost diameter on the winding cylinder).

[0068] In the test to determine the thickness difference depending on the location of the tire, the thickness from the inner surface to the outer surface of the tire was first measured at three locations in the circumferential direction of the completed tire. The thickness measurement was performed at the shoulder of the tread. After measurement, the thickness difference depending on the location of the tire was determined by subtracting the thickness of the thinnest part (the part of the tread that was on the innermost side of the winding cylinder) from the thickness of the thickest part (the part of the tread that was on the outermost side of the winding cylinder).

[0069] As a measure of uniformity, RFV (Radial Force Variation) testing was performed. The test method conformed to JIS D4233 (2001).

[0070] The test results are shown in Table 1. In the comparative example, it was found that there were differences in thickness depending on the location in the tread, and that these differences in thickness remained even after the tire was made, affecting the uniformity. However, from a comparison between Example 2 and the comparative example, it was confirmed that by making the diameter of the winding cylinder body larger than the drum diameter, the differences in thickness depending on the location in the tread and tire were reduced, and the uniformity improved. Furthermore, from a comparison between Example 1 and Example 2, it was confirmed that cutting the long rubber material with an ultrasonic cutter further improved the uniformity. Regarding uniformity, it was found that Example 2 showed a 20.5% reduction compared to the comparative example, and Example 1 showed a 27.3% reduction compared to the comparative example.

[0071] [Table 1] [Explanation of Symbols]

[0072] 1…Long rubber member, 1a…Bottom surface, 1b…Cut surface, 2…Rubber member for tread, 2a…Bottom surface, 2b…Cut surface, 3…Ring-shaped tread, 11…Extruder, 11a…Die, 12…Winding cylinder, 13…Cart, 14…Lower frame, 15…Upper frame, 16…Wheel, 17…Rotating shaft, 18…Main body, 19…Flange, 30…Table, 31…Cutting device, 32…First conveyor, 33…Second conveyor, 34…Drum, 35…Receiving member, 36…Pressing member, 37…Blade, 38…Roller, 39…Moving device, 40…Ring-shaped tread manufacturing device, 41…First heater, 42…Second heater, 43…Length measuring sensor, 44…Control unit

Claims

1. The process involves winding the long rubber material extruded from the extruder onto a winding cylinder, The process of pulling out the long rubber member from the winding cylinder and cutting it to cut out the rubber member for the tire tread, A step of wrapping the cut-out tread rubber material around a drum to form a ring-shaped tread, In a method for manufacturing a pneumatic tire, A method for manufacturing a pneumatic tire, characterized in that the winding cylinder has a cylindrical body which is the portion around which the long rubber member is wound, and the diameter of the body is greater than or equal to the diameter of the drum.

2. The method for manufacturing a pneumatic tire according to claim 1, wherein the length of the long rubber member wound onto the winding cylinder is the length of 10 to 16 of the tread rubber members.

3. A method for manufacturing a pneumatic tire according to claim 1 or 2, wherein the long rubber member is cut using an ultrasonic cutter.

4. A method for manufacturing a pneumatic tire according to claim 1 or 2, wherein when cutting the long rubber member, the angle between the bottom surface of the long rubber member and the cut surface is 25 ± 4°.

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