Tire manufacturing methods

Abstract

To provide a manufacturing method by which high-quality tires can be efficiently obtained.SOLUTION: A tire manufacturing method includes: step A of charging a low cover 2 to a mold 6; step B of supplying gas to a bladder 12 located inside the low cover 2 and increasing internal pressure of the bladder 12 to pressure P1; step C of discharging the gas from the bladder 12 through a discharge pipe 36 and reducing the internal pressure of the bladder 12 to pressure P3; step D of supplying the gas to the bladder 12 to increase the internal pressure of the bladder; and step E of discharging the gas from the bladder 12 through the discharge pipe 36 and lowering the internal pressure of the bladder 12 to a pressure lower than the pressure P3. During at least a part of a period of step C, a flow path area of the discharge pipe 36 is smaller than a flow path area of the discharge pipe 36 in step E.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a tire. Specifically, this specification discloses an improved tire vulcanization process.

Background Art

[0002] A tire is obtained through a vulcanization process. In this vulcanization process, a green tire (uncured tire) is pressurized and heated within a mold. This pressurization is achieved by the expansion of a bladder located inside the green tire. This expansion is achieved by filling the bladder with gas. After the pressurization is completed, this gas is discharged through a discharge pipe.

[0003] Japanese Unexamined Patent Application Publication No. 2020-152031 discloses a vulcanization process involving a short-time gas purge. Due to the gas purge, the internal pressure of the bladder temporarily decreases. Due to the gas purge, the gas in the bladder flows. This flow eliminates the temperature distribution within the bladder. A tire with a suppressed crosslink density distribution can be obtained with a bladder having a suppressed temperature distribution. A tire with a suppressed crosslink density distribution is excellent in the uniformity of various performances.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In typical vulcanizing equipment, the discharge pipe for purging also serves as the discharge pipe for releasing gas after pressurization is complete. A discharge pipe with a large inner diameter is selected to ensure that the gas is released quickly after pressurization is complete. When this discharge pipe is used for purging, the internal pressure of the bladder reaches the predetermined value in a short time. In other words, the purging time is short. If the purging time is too short, the temperature distribution inside the bladder will not be sufficiently eliminated. Furthermore, if the purging time is too short, the decrease in internal pressure is difficult to detect with instruments. If detection is not performed, it becomes impossible to control whether or not the purging was performed properly.

[0006] If the exhaust pipe is left open for an extended period, a prolonged purge can occur. However, this opening significantly reduces the temperature inside the bladder. Prolonged opening is undesirable from an energy efficiency standpoint.

[0007] The applicant's intention is to provide a manufacturing method that can efficiently produce high-quality tires. [Means for solving the problem]

[0008] The tire manufacturing method disclosed herein is A: The process of inserting the low cover into the mold. B: A process of supplying gas to the bladder located inside the above low cover and raising the internal pressure of this bladder to pressure P1. C: A process of discharging the gas from the bladder through the discharge pipe and reducing the internal pressure of the bladder to pressure P3. D: A step of supplying the above gas to the above bladder and increasing the internal pressure of the above bladder. and E: A process of discharging the gas from the bladder through the discharge pipe and reducing the internal pressure of the bladder to a pressure lower than the pressure P3. It has the following characteristics. During at least a portion of this step C, the flow area of ​​the discharge pipe is smaller than the flow area of ​​the discharge pipe in step E. [Effects of the Invention]

[0009] This manufacturing method allows for prolonged purging without a significant drop in temperature within the bladder. This method also allows for the efficient production of high-quality tires. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a conceptual diagram showing a vulcanizing apparatus used in a tire manufacturing method according to one embodiment. [Figure 2] Figure 2 is a schematic diagram showing the second discharge valve of the apparatus in Figure 1, along with a portion of the second discharge pipe. [Figure 3] Figure 3 is a cross-sectional view showing a portion of the second discharge valve in Figure 2. [Figure 4] Figure 4 is a cross-sectional view showing a portion of the second discharge valve in Figure 2. [Figure 5] Figure 5 is a cross-sectional view showing a portion of the second discharge valve in Figure 2. [Figure 6] Figure 6 is a flowchart showing an example of a tire manufacturing method using the apparatus shown in Figure 1. [Figure 7] Figure 7 is a graph showing the bladder pressure in the manufacturing method shown in Figure 6. [Modes for carrying out the invention]

[0011] Preferred embodiments of the tire mold will be described in detail below, with reference to drawings as appropriate.

[0012] Figure 1 schematically shows the vulcanizing apparatus 4 together with the low cover 2. This vulcanizing apparatus 4 includes a mold 6, an upper plate 8, a lower plate 10, a bladder 12, a pressure gauge 14, a main supply pipe 16, a main discharge pipe 18, a first supply pipe 20, a first supply valve 22, a second supply pipe 24, a second supply valve 26, a third supply pipe 28, a third supply valve 30, a first discharge pipe 32, a first discharge valve 34, a second discharge pipe 36, a second discharge valve 38, a third discharge pipe 40, and a third discharge valve 42.

[0013] The mold 6 is ring-shaped. The mold 6 has an upper mold 44 and a lower mold 46. Each of the upper mold 44 and the lower mold 46 has a cavity surface 48. The upper mold 44 is movable relative to the lower mold 46 in the vertical direction. When the upper mold 44 descends and mates with the lower mold 46, the mold 6 is closed. In FIG. 1, the closed mold 6 is shown. By closing the mold 6, a cavity is formed. In this cavity, the local cover 2 is accommodated coaxially with the mold 6. This mold 6 is a so-called two-piece mold. The vulcanizing device 4 may have a mold including a plurality of segments movable in the radial direction.

[0014] The upper plate 8 has a disc shape. The upper plate 8 is hard. The material of the upper plate 8 is metal (typically steel).

[0015] The lower plate 10 has a disc shape. The lower plate 10 is hard. The material of the lower plate 10 is metal (typically steel).

[0016] The bladder 12 is flexible. In this embodiment, the bladder 12 has a toroidal shape. This bladder 12 has an upper opening 50 and a lower opening 52. The upper opening 50 is blocked by the upper plate 8. The lower opening 52 is blocked by the lower plate 10. The upper plate 8, the lower plate 10, and the bladder 12 form a space S. This space S is closed except for communication with the main supply pipe 16 and the main discharge pipe 18 to be described in detail later.

[0017] The main supply pipe 16 passes through the lower mold 46 and reaches the lower plate 10. This main supply pipe 16 communicates with the space S of the bladder 12. The main discharge pipe 18 passes through the lower mold 46 and reaches the lower plate 10. This main discharge pipe 18 communicates with the space S of the bladder 12.

[0018] The first supply pipe 20 communicates with the main supply pipe 16. In other words, the first supply pipe 20 communicates with the space S via the main supply pipe 16. The first supply pipe 20 may communicate directly with the space S without passing through the main supply pipe 16. The first supply valve 22 is attached to the first supply pipe 20. In the present embodiment, the first supply valve 22 is a so-called piston valve.

[0019] The second supply pipe 24 communicates with the main supply pipe 16. In other words, the second supply pipe 24 communicates with the space S via the main supply pipe 16. The second supply pipe 24 may communicate directly with the space S without passing through the main supply pipe 16. The second supply valve 26 is attached to the second supply pipe 24. In the present embodiment, the second supply valve 26 is a so-called piston valve.

[0020] The third supply pipe 28 communicates with the main supply pipe 16. In other words, the third supply pipe 28 communicates with the space S via the main supply pipe 16. The third supply pipe 28 may communicate directly with the space S without passing through the main supply pipe 16. The third supply valve 30 is attached to the third supply pipe 28. In the present embodiment, the third supply valve 30 is a so-called piston valve.

[0021] The first discharge pipe 32 communicates with the main discharge pipe 18. In other words, the first discharge pipe 32 communicates with the space S via the main discharge pipe 18. The first discharge pipe 32 may communicate directly with the space S without passing through the main discharge pipe 18. The first discharge valve 34 is attached to the first discharge pipe 32. In the present embodiment, the first discharge valve 34 is a so-called piston valve.

[0022] The second discharge pipe 36 communicates with the main discharge pipe 18. In other words, the second discharge pipe 36 communicates with the space S via the main discharge pipe 18. The second discharge pipe 36 may communicate directly with the space S without passing through the main discharge pipe 18. The second discharge valve 38 is attached to the second discharge pipe 36. The structure of the second discharge valve 38 will be described in detail later.

[0023] The third discharge pipe 40 is in communication with the main discharge pipe 18. In other words, the third discharge pipe 40 is in communication with space S via the main discharge pipe 18. The third discharge pipe 40 may also be in direct communication with space S without going through the main discharge pipe 18. The third discharge valve 42 is attached to the third discharge pipe 40. In this embodiment, the third discharge valve 42 is a so-called piston valve.

[0024] Figure 2 is a schematic diagram showing the second discharge valve 38 of the apparatus 2 in Figure 1, along with a portion of the second discharge pipe 36. The second discharge valve 38 has multiple valve elements. Specifically, the second discharge valve 38 has a piston valve 54, a quick valve 56, an inlet solenoid valve 58, and an outlet solenoid valve 60. The second discharge valve 38 further has an operating pipe 62, a retraction space S1, and a spring 63. Nitrogen gas (N2), which will be described in detail later, flows through the second discharge pipe 36. Operating air (OA) flows through the operating pipe 62. The spring 63 is housed in the retraction space S1. In this embodiment, the spring 63 is a so-called compression spring.

[0025] The piston valve 54 has a piston 64 and a rod 65. The lower end 66 of the piston 64 is in contact with a spring 63. The piston 64 is biased upward by the spring 63. The piston 64 can move in the vertical direction in Figure 2. The movement of the piston 64 causes a variation in the degree to which the piston 64 penetrates the second discharge pipe 36. This variation causes a variation in the flow path area in the second discharge pipe 36. The quick valve 56 is connected to the piston valve 54. The inlet solenoid valve 58 is connected to the quick valve 56 via an operating pipe 62. The outlet solenoid valve 60 is connected to the quick valve 56 via an operating pipe 62.

[0026] Figure 3 shows a portion of the second discharge valve 38 in Figure 2. In Figure 3, the second discharge pipe 36 is blocked by the piston 64. The flow area of ​​the second discharge pipe 36 is zero. The ratio of the flow area of ​​the second discharge pipe 36 to the cross-sectional area of ​​the inner surface of the second discharge pipe 36 (flow area ratio) is 0%.

[0027] When the inlet solenoid valve 58 (see Figure 2) is opened, operating air presses the piston valve 54 via the quick valve 56. This pressure causes the piston 64 to descend against the biasing force of the spring 63. The piston 64 after it has descended is shown in Figure 4. In Figure 4, the entire piston 64 is housed in the retraction space S1. The piston 64 is not located inside the second discharge pipe 36. The flow area of ​​the second discharge pipe 36 is equal to the cross-sectional area of ​​the inner surface of the second discharge pipe 36 (excluding the area of ​​the rod 65). In other words, the flow area ratio is substantially 100%.

[0028] When the inlet solenoid valve 58 (see Figure 2) is closed and the outlet solenoid valve 60 is opened, operating air is released and the piston valve 54 is depressurized. This depressurization causes the piston 64, pushed by the spring 63, to rise. During this rise, the outlet solenoid valve 60 is closed, and the piston 64 stops midway up. The piston 64 after stopping is shown in Figure 5. In Figure 5, a portion of the second discharge pipe 36 is blocked by the piston 64. The flow area of ​​the second discharge pipe 36 is greater than zero and smaller than the cross-sectional area of ​​the inner surface of the second discharge pipe 36. In other words, the flow area ratio is greater than 0% and less than 100%. The state of the second discharge valve 38 shown in Figure 5 is called "half-open".

[0029] Figure 6 shows a flowchart of the tire manufacturing method. At the start of this manufacturing method, all valves are closed. In this manufacturing method, the low cover 2 is prepared (STEP 1). The low cover 2 is obtained by assembling several rubber parts. This low cover 2 is loaded into the open mold 6 (STEP 2). The low cover 2 is placed on the lower mold 46. At this time, the bladder 12 is in a contracted state. The bladder 12 is located inside the low cover 2.

[0030] Next, the first supply valve 22 is opened, and air is supplied to the bladder 12 via the first supply pipe 20 and the main supply pipe 16. This supply causes the bladder 12 to expand (STEP 3). After a predetermined amount of air has been supplied to the bladder 12, the first supply valve 22 is closed. The expanded bladder 12 contributes to the positioning of the low cover 2.

[0031] Next, the upper mold 44 descends, and the mold 6 closes (STEP 4). At the same time, the first discharge valve 34 opens, and the air inside the bladder 12 is discharged through the main discharge pipe 18 and the first discharge pipe 32. This discharge causes the bladder 12 to contract (STEP 5). After contraction, the first discharge valve 34 is closed.

[0032] Next, the second supply valve 26 is opened, and steam is supplied to the bladder 12 via the second supply pipe 24 and the main supply pipe 16. The steam is hot. The supply of steam causes the bladder 12 to expand and its temperature to rise (STEP 6). After a predetermined amount of steam has been supplied to the bladder 12, the second supply valve 26 is closed.

[0033] Next, the third supply valve 30 is opened, and nitrogen gas is supplied to the bladder 12 via the third supply pipe 28 and the main supply pipe 16. The nitrogen gas is under high pressure. The supply of nitrogen gas increases the internal pressure of the bladder 12 (STEP 7). This increase is called the "first internal pressure increase." The bladder 12, with its high internal pressure, presses the low cover 2 against the cavity surface 48. Furthermore, heat is conducted from the bladder 12 to the low cover 2.

[0034] Next, with the third supply valve 30 still open, the second discharge valve 38 is opened. The second discharge valve 38 is in the state shown in Figure 4. At this time, the flow area ratio of the second discharge pipe 36 is 100%. When the second discharge valve 38 is opened, the gas (a mixed gas mainly consisting of nitrogen gas) inside the bladder 12 is discharged through the main discharge pipe 18 and the second discharge pipe 36. This discharge causes the internal pressure of the bladder 12 to decrease (STEP 8). This decrease is called the "first internal pressure decrease".

[0035] When the pressure gauge 14 detects that the internal pressure of the bladder 12 has reached a predetermined value of Pa, the third supply valve 30 remains open and the second discharge valve 38 is partially open. The second discharge valve 38 is in the state shown in Figure 5. At this time, the flow area ratio of the second discharge pipe 36 is greater than 0% and less than 100%. With the second discharge valve 38 partially open, the gas inside the bladder 12 is further discharged through the main discharge pipe 18 and the second discharge pipe 36. This discharge further reduces the internal pressure of the bladder 12 (STEP 9). This reduction is called the "second internal pressure drop".

[0036] When the pressure gauge 14 detects that the internal pressure of the bladder 12 has reached a predetermined value Pb, the second discharge valve 38 is closed. Since the third supply valve 30 remains open, nitrogen gas is additionally supplied to the bladder 12 via the third supply pipe 28 and the main supply pipe 16. The supply of nitrogen gas causes the internal pressure of the bladder 12 to rise again (STEP 10). This rise is referred to as the "second internal pressure rise." The bladder 12 presses the low cover 2 against the cavity surface 48. Furthermore, heat is conducted from the bladder 12 to the low cover 2. Heat is also conducted to the low cover 2 from heat sources not shown. The low cover 2 is pressurized and heated. Due to the pressurization and heating, the rubber composition of the low cover 2 flows within the cavity. This rubber composition undergoes a crosslinking reaction.

[0037] After sufficient time has elapsed for the cross-linking reaction of the rubber in the low cover 2 to proceed, the third supply valve 30 is closed. Furthermore, the second discharge valve 38 is opened. The second discharge valve 38 is in the state shown in Figure 4. At this time, the flow area ratio of the second discharge pipe 36 is 100%. When the second discharge valve 38 is opened, the gas in the bladder 12 is discharged through the main discharge pipe 18 and the second discharge pipe 36. This discharge reduces the internal pressure of the bladder 12 (STEP 11).

[0038] Next, the second discharge valve 38 is closed and the third discharge valve 42 is opened. The inside of the bladder 12 is sucked through the third discharge pipe 40 and the main discharge pipe 18. This suction causes the bladder 12 to contract (STEP 12). After the suction is complete, the mold 6 is opened (STEP 13). The finished tire is removed from the mold 6.

[0039] Figure 7 shows the progression of the internal pressure of the bladder 12. As mentioned above, in the "first internal pressure increase" step, the internal pressure of the bladder 12 increases due to the supply of nitrogen gas (STEP 7). This increase brings the internal pressure to pressure P1.

[0040] As mentioned above, in the "first internal pressure reduction" step, the internal pressure of the bladder 12 decreases due to the discharge of gas (STEP 8). Due to this decrease, the internal pressure reaches pressure P2. As mentioned above, the second discharge valve 38 is half-open when the internal pressure reaches Pa, but since there is a time lag in the change in internal pressure, the internal pressure continues to decrease and reaches pressure P2 thereafter.

[0041] As mentioned above, in the "second internal pressure reduction" step, the internal pressure of the bladder 12 decreases further due to the discharge of gas (STEP 9). Due to this decrease, the internal pressure reaches pressure P3. As mentioned above, the second discharge valve 38 is closed when the internal pressure reaches Pb, but there is a time lag in the change in internal pressure, so the internal pressure continues to decrease and reaches pressure P3 afterward.

[0042] As mentioned above, in the "second internal pressure increase" process, the internal pressure of the bladder 12 increases again due to the supply of nitrogen gas (STEP 10). This increase brings the internal pressure to pressure P1. In other words, the pressure achieved by the "second internal pressure increase" is the same as the pressure achieved by the "first internal pressure increase". The pressure achieved by the "second internal pressure increase" may be slightly different from the pressure achieved by the "first internal pressure increase".

[0043] In Figure 7, arrow T1 represents the time from the start of the decrease in internal pressure (STEP 8) to the completion of the increase in internal pressure (STEP 10). Time T1 is a few seconds. During tire vulcanization, the internal pressure of the bladder 12 is maintained at approximately pressure P1 for several tens of minutes. In other words, the tire vulcanization time is several tens of minutes. For just a few seconds during this vulcanization time, there is a state in which the internal pressure is lower than pressure P1.

[0044] The reduction in internal pressure from pressure P1 to pressure P3 is achieved by the discharge of gas. This discharge is called purging. The purging and the subsequent pressure increase cause gas to flow inside the bladder 12. This flow agitates the gas inside the bladder 12. This agitation suppresses the temperature distribution of the bladder 12. In a manufacturing method that includes purging, the heat conduction from the bladder 12 to the low cover 2 is uniform. This manufacturing method can produce a tire with a suppressed crosslink density distribution. This tire exhibits excellent uniformity in various performance aspects such as handling stability, ride comfort, and cornering characteristics.

[0045] By stirring, localized high temperatures inside the bladder 12 can be prevented. Consequently, localized overcuring of the low cover 2 can be suppressed. In this manufacturing method, the heating of the part of the bladder 12 that is not easily heated in conventional manufacturing methods (the part housed in the lower mold 46) is promoted. Consequently, a shorter vulcanization time can be achieved.

[0046] The flow path area S2 during the second internal pressure drop (STEP 9) is smaller than the flow path area S1 during the first internal pressure drop (STEP 8). Therefore, as shown in Figure 7, the rate of decompression during the second internal pressure drop (STEP 9) is smaller than the rate of decompression during the first internal pressure drop (STEP 8). The arrow T2 in Figure 7 represents the time required for the internal pressure to decrease from pressure P1 to pressure P3.

[0047] The dashed line L in Figure 7 represents the change in internal pressure when it is assumed that the decrease in internal pressure from pressure P1 to pressure P3 is achieved solely by the flow path area S1. In this case, arrow T3 represents the time required for the internal pressure to decrease from pressure P1 to pressure P3.

[0048] In the manufacturing method according to this embodiment, time T2 is greater than time T3. In other words, purging is performed over a long period of time. The small flow path area S2 enables this long purging period. This purging thoroughly agitates the gas inside the bladder 12. This purging can contribute to the uniformity of the tire. Furthermore, the decrease in internal pressure due to prolonged purging is easily detected by instruments. Even if the vulcanizing apparatus 4 does not have particularly high-performance instruments, fluctuations in internal pressure can be accurately controlled.

[0049] In Figure 7, arrow T4 represents the time from when the internal pressure of the bladder 12 reaches 1950 kPa during the first internal pressure decrease (STEP 8) or the second internal pressure decrease (STEP 9) until this internal pressure reaches 1950 kPa during the second internal pressure increase (STEP 10). In other words, time T4 is the time during which the internal pressure of the bladder 12 is maintained at 1950 kPa or less. From the viewpoint of making the decrease in internal pressure easily detectable by instruments, time T4 is preferably 0.8 seconds or more, more preferably 1.0 second or more, and particularly preferably 1.2 seconds or more.

[0050] As mentioned above, the gas discharged after the crosslinking reaction (STEP 11) is performed by the second discharge pipe 36. From the viewpoint of exhaust efficiency, a pipe with a large inner diameter is used as the second discharge pipe 36. By using a valve that allows adjustment of the flow path area as the second exhaust valve, a sufficiently large time T2 can be achieved despite the large inner diameter of the second discharge pipe 36. In this manufacturing method, a purge pipe with a small inner diameter is unnecessary. Because the flow path area is adjusted, the internal pressure of the bladder 12 does not decrease significantly even when time T2 is large. This manufacturing method is energy efficient.

[0051] In this embodiment, the flow path area S1 during the first internal pressure reduction (STEP 8) is the same as the flow path area S3 during the gas discharge after the crosslinking reaction (STEP 11). The flow path area S2 during the second internal pressure reduction (STEP 9) is smaller than the flow path area S3. In this embodiment, the following equation is satisfied. S2 < S1 = S3 In other words, a small flow path area S2 is achieved during a portion of the period when the internal pressure of the bladder 12 decreases from pressure P1 to pressure P3, and a large flow path area S1 is achieved in the remaining portion. The ratio of the flow path area S2 to the flow path area S1 (S2 / S1) is preferably 0.20 or more and 0.80 or less. This ratio (S2 / S1) is more preferably 0.30 or more, and particularly preferably 0.35 or more. This ratio (S2 / S1) is more preferably 0.70 or less, and particularly preferably 0.65 or less.

[0052] A small flow path area may be achieved over the entire period during which the internal pressure decreases from pressure P1 to pressure P3. In other words, the following two equations may be satisfied. S1 < S3 S2 < S3

[0053] The flow path area may remain constant throughout the entire period during which the internal pressure decreases from pressure P1 to pressure P3. In other words, the following equation may be satisfied. S1 = S2 < S3

[0054] The reduction in internal pressure from pressure P1 to pressure P3 may be achieved by three or more stages of flow path area. Alternatively, the reduction in internal pressure from pressure P1 to pressure P3 may be achieved by a gradual change in flow path area.

[0055] From the viewpoint of tire uniformity and accuracy of internal pressure control, the time T2 from when gas begins to be discharged through the second discharge pipe 36 until the internal pressure of the bladder 12 reaches the minimum pressure P3 is preferably 1.5 seconds or more, more preferably 1.8 seconds or more, and particularly preferably 2.0 seconds or more. This time T2 is preferably 4.0 seconds or less.

[0056] From the viewpoint of tire uniformity and accuracy of internal pressure management, the difference between pressure P1 and pressure P3 (P1-P3) is preferably 250 kPa or more, more preferably 275 kPa or more, and particularly preferably 300 kPa or more. From the viewpoint of energy efficiency, this difference (P1-P3) is preferably 450 kPa or less, more preferably 425 kPa or less, and particularly preferably 400 kPa or less. [Examples]

[0057] The effects of the tire manufacturing method described in the following examples will be clarified, but the scope disclosed herein should not be interpreted as limiting based on the description of these examples.

[0058] [Example 1] A tire was manufactured using the apparatus shown in Figure 1 and the method shown in Figure 6. The size of this tire was 135 / 50R12.

[0059] [Examples 2-5] The tires were manufactured in the same manner as in Example 1, except that the tire size was as follows.

[0060] [Comparative Example 1] Using the apparatus shown in Figure 1, a tire with size 205 / 60R14 was manufactured in the same manner as in Example 1, except that the flow path area of ​​the second discharge pipe was reduced to 100%.

[0061] [Rating 1] During the vulcanization process, the time T2 required to reach the minimum pressure was measured. The results are shown in the table below.

[0062] [Rating 2] Pressure measurements were taken every 1.0 second during the vulcanization process, and it was determined whether or not the minimum pressure of 1950 kPa or below was detected. The results are shown in the table below.

[0063] Tire size T2 (Capture possible) Example 1: 135 / 50R12, 2.0 seconds, OK Example 2: 175 / 55R15, 2.1 seconds, OK Example 3: 195 / 80R15, 2.2 seconds, OK Example 4: 265 / 65R18, 2.3 seconds, OK Example 5: 265 / 40R22, 2.5 seconds, achievable. Comparative example 1 205 / 60R14 1.4 seconds Not possible

[0064] Based on these evaluation results, the superiority of the manufacturing method described in the example is clear.

[0065] [Disclosure items] The following items constitute a disclosure of preferred embodiments.

[0066] [Item 1] A: The process of inserting the low cover into the mold. B: A process of supplying gas to the bladder located inside the above low cover and raising the internal pressure of this bladder to pressure P1. C: A process of discharging the gas from the bladder through the discharge pipe and reducing the internal pressure of the bladder to pressure P3. D: A step of supplying the above gas to the above bladder and increasing the internal pressure of the above bladder. and E: A process of discharging the gas from the bladder through the discharge pipe and reducing the internal pressure of the bladder to a pressure lower than the pressure P3. It is equipped with, A tire manufacturing method wherein, for at least a portion of the duration of step C, the flow area of ​​the discharge pipe is smaller than the flow area of ​​the discharge pipe in step E.

[0067] [Item 2] The above step C is, C1: A step of discharging the gas from the bladder through the discharge pipe while the flow path area S1 of the discharge pipe has been achieved. and C2: A process in which the gas is discharged from the bladder through the discharge pipe, with the valve achieving a flow path area S2 smaller than the flow path area S1. The manufacturing method described in item 1, including the method described in item 1.

[0068] [Item 3] The manufacturing method according to item 2, wherein the ratio (S2 / S1) of the above-mentioned flow channel area S2 to the above-mentioned flow channel area S1 is 0.20 or more and 0.80 or less.

[0069] [Item 4] The manufacturing method according to any one of items 1 to 3, wherein in step C above, the time from when the gas is discharged from the bladder through the discharge pipe until the internal pressure of the bladder reaches the pressure P3 is 1.5 seconds or more.

[0070] [Item 5] The manufacturing method according to any one of items 1 to 4, wherein the difference (P1-P3) between the pressure P1 in step B and the pressure P3 in step C is 250 kPa or more and 450 kPa or less. [Industrial applicability]

[0071] Various types of pneumatic tires can be manufactured using this manufacturing method. [Explanation of Symbols]

[0072] 2. Low cover 4. Vulcanizing equipment 6. Mold 12. Bladder 16...Main supply pipe 18...Main discharge pipe 20...First supply pipe 22. First supply valve 24...Second supply pipe 26...Second supply valve 28...Third supply pipe 30. Third supply valve 32...First discharge pipe 34. First exhaust valve 36...Second discharge pipe 38...Second exhaust valve 40...Third discharge pipe 42...Third exhaust valve 54. Piston valve 56...Quick Valve 58...Inlet Solenoid Valve 60... Outlet Solenoid Valve 62...operation tube 64...piston

Claims

1. A: The process of inserting the low cover into the mold. B: A process of supplying gas to the bladder located inside the above-mentioned low cover and raising the internal pressure of this bladder to pressure P1. C: A step of discharging the gas from the bladder through the discharge pipe and reducing the internal pressure of the bladder to pressure P3. D: A step of supplying the above gas to the above bladder and increasing the internal pressure of the above bladder. and E: A process of discharging the gas from the bladder through the discharge pipe and reducing the internal pressure of the bladder to a pressure lower than the pressure P3. It is equipped with, A tire manufacturing method wherein, for at least a portion of the duration of step C, the flow area of ​​the discharge pipe is smaller than the flow area of ​​the discharge pipe in step E, The above step C is, C1: A step of discharging the gas from the bladder through the discharge pipe while the flow path area S1 of the discharge pipe has been achieved. and C2: A step of discharging the gas from the bladder through the discharge pipe while a flow path area S2 smaller than the flow path area S1 is achieved by the valve. A tire manufacturing method, including the manufacturing process itself.

2. The manufacturing method according to claim 1, wherein the ratio of the flow channel area S2 to the flow channel area S1 (S2 / S1) is 0.20 or more and 0.80 or less.

3. The manufacturing method according to claim 1 or 2, wherein in step C above, the time from when the gas is discharged from the bladder through the discharge pipe until the internal pressure of the bladder reaches the pressure P3 is 1.5 seconds or more.

4. The manufacturing method according to claim 1 or 2, wherein the difference (P1-P3) between the pressure P1 in step B and the pressure P3 in step C is 250 kPa or more and 450 kPa or less.

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