Method for detecting punctures in tire curing bladders

Abstract

To provide a method for detecting a puncture in a tire vulcanization bladder, which can detect bladder puncture early in a vulcanization process.SOLUTION: There is provided a method for detecting a puncture of a bladder during a vulcanization process in which an unvulcanized tire set in a vulcanization mold is heated and pressurized from an inside with the bladder. The vulcanization process has the steps of: heating the tire with the bladder having a first internal pressure applied by feed of a first vulcanization medium; and pressurizing the tire with the bladder having a second internal pressure higher than the first internal pressure applied by feed of a second vulcanization medium after the heating step. In the pressurizing step, the bladder having the second internal pressure is de-pressurized at least temporarily, and a sensor detects leakage of the first vulcanization medium to detect a puncture.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for detecting a puncture that has occurred in a tire vulcanization bladder used in the vulcanization molding of a tire. [Background technology]

[0002] Conventionally, a rubber tire vulcanization bladder (hereinafter simply referred to as "bladder") has been used for vulcanization molding of tires. The bladder is placed inside an unvulcanized tire (raw tire) set in a vulcanization mold, and expands and deforms in response to the supply of a vulcanization medium with adjusted pressure and temperature. During the vulcanization process, the expanded and deformed bladder presses the tire against the tire molding surface of the vulcanization mold. The tire is heated and pressurized from the outside by the vulcanization mold, and is also heated and pressurized from the inside by the bladder.

[0003] Bladders can become punctured due to deterioration over time. If a tire is vulcanized using a punctured bladder, there is a risk of molding defects due to leakage of the vulcanization medium. Therefore, after the tire has been vulcanized and is removed from the vulcanization mold, a puncture can be detected through molding defects that occur in the tire. However, if bladder replacement work is started at this point, the vulcanizer must be stopped, including the time required for pre-setup (preparation for replacement), which inevitably results in a significant drop in operating rate.

[0004] Patent Documents 1 and 2 each describe a method for detecting a bladder puncture before the tire is removed from the vulcanization mold. However, these methods detect a puncture at the final stage of the vulcanization process, when the vulcanization medium filled inside the bladder is discharged to the outside. Therefore, even if the bladder replacement work is started immediately after detecting a puncture, there is a high possibility that the vulcanizer will have to be stopped, including the time it takes to perform pre-setup, which will inevitably result in a significant decrease in operating rate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-39288 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-191332 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure has been made in consideration of the above-described circumstances, and its purpose is to provide a method for detecting a puncture in a tire vulcanization bladder that can detect a bladder puncture early during the vulcanization process. [Means for solving the problem]

[0007] The disclosed method is a method for detecting a puncture in a bladder during a vulcanization process in which an unvulcanized tire set in a vulcanization mold is heated and pressurized from the inside by a bladder, the vulcanization process including a heating step in which the tire is heated in the bladder at a first internal pressure by supplying a first vulcanization medium, and a pressurization step in which, after the heating step, the tire is pressurized in the bladder at a second internal pressure higher than the first internal pressure by supplying a second vulcanization medium, and in the pressurization step, the bladder at the second internal pressure is at least temporarily depressurized, and a puncture is detected by detecting the leaked first vulcanization medium with a sensor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of a vulcanizer. [Figure 2] Graph showing an example of the change in the internal pressure of the bladder [Figure 3] Image showing steam trapped between the bladder and tire [Figure 4] Table showing specific examples of the time breakdown of the vulcanization process DETAILED DESCRIPTION OF THE INVENTION

[0009] First, an example of the configuration of a vulcanizer will be described. FIG. 1 shows a schematic cross section of a vulcanizer 100 taken along a tire meridian cross section. The vulcanizer 100 of this embodiment comprises a vulcanization mold 1 (hereinafter, sometimes simply referred to as the "mold 1"), a container 2 that holds the mold 1, a tire vulcanization bladder 3 (hereinafter, sometimes simply referred to as the "bladder 3") that is a rubber bag, and a central mechanism 4 provided in the center of the mold 1. In FIG. 1, the mold 1 is in a closed state, and a tire T is set with its axial direction facing up and down. The left side in FIG. 1 is the outer side in the tire radial direction, and the right side is the inner side in the tire radial direction.

[0010] The mold 1 includes a tread mold 11 for molding the tread of the tire T, side molds 12 and 13 for molding the sidewalls of the tire T, and bead rings 14 and 15 into which the bead portions of the tire T are fitted. The tread mold 11 is composed of multiple sectors divided in the tire circumferential direction, which are gathered together to form a ring when the mold is closed. The mold 1 is a segmented mold equipped with such a divided type tread mold 11, but is not limited to this and may be, for example, a two-piece mold divided into upper and lower halves at the center of the tread mold.

[0011] The mold 1 has a tire molding surface 16 that contacts the outer surface of the set tire T. The tire molding surface 16 includes the inner surface of the tread mold 11 and the inner surfaces of the side molds 12 and 13. Although not shown, the inner surface of the tread mold 11 has projections and depressions for forming the tread pattern of the tire. The ventilation hole 17, also called a vent hole, is formed and opens into the tire molding surface 16 of the mold 1. Although FIG. 1 shows only one ventilation hole 17 opening into the inner surface of the tread mold 11, in reality, a large number of ventilation holes opening into the inner surfaces of the tread mold 11 and the side molds 12 and 13 are formed.

[0012] The container 2 includes a plurality of segments 21 provided corresponding to each sector, and an outer ring 22 arranged radially outward of the segments 21. The tread mold 11 is held by the segments 21. The outer peripheral surface of the segment 21 and the inner peripheral surface of the outer ring 22 that engages with it are formed by tapered surfaces having the same inclination. These tapered surfaces are each inclined downward and outward in the radial direction of the tire. The tread mold 11 is configured to be movable radially in the tire as the outer ring 22 moves up and down.

[0013] The container 2 further includes an upper platen 23 that supports the side molds 12, a lower platen 24 that supports the side molds 13, and an arm 25 that supports the outer ring 22. The upper platen 23 is configured to be able to move up and down. The segments 21 are supported on the lower surface of the upper platen 23 so as to be able to slide along the tire radial direction. The arm 25 is attached to a guide 26 that is erected on the upper surface of the upper platen 23 so as to be able to move up and down. As the arm 25 moves up and down relative to the guide 26, the outer ring 22 moves up and down relative to the segments 21, and each sector held by the segment 21 moves in the tire radial direction.

[0014] Tire vulcanization is performed in the mold closed state shown in Figure 1. The container 2 has a heat source such as an electric heater or a steam jacket, which causes the mold 1, maintained at a high temperature, to heat the tire T from the outside. Once vulcanization is complete, the tread mold 11 is expanded (each sector is moved radially outward) by the mechanism of the container 2 described above, and the tread mold 11 and side mold 12 are raised, transitioning to the mold open state. In the mold open state, it is possible to remove the tire after vulcanization or to set an unvulcanized tire.

[0015] The bladder 3 is disposed inside the tire T set in the mold 1. The bladder 3 expands and deforms when a vulcanization medium, which will be described later, is supplied, and contracts and deforms when the vulcanization medium filled therein is discharged. In the vulcanization process, the tire T is pressed against the tire molding surface 16 by the expanded and deformed bladder 3. The bladder 3 is supported by the central mechanism 4. More specifically, the upper end of the bladder 3 is supported by an upper clamp 42 of the central mechanism 4, and the lower end of the bladder 3 is supported by a lower clamp 43 of the central mechanism 4.

[0016] The center mechanism 4 includes a center post 41 extending in the vertical direction at the center of the mold 1. The center post 41 is disposed at a distance from the mold 1 on the inner side in the tire radial direction. An upper clamp 42 and a lower clamp 43 are attached to the center post 41. At least a portion of each of the upper clamp 42 and the lower clamp 43, together with the bladder 3, is configured to be detachable from the center post 41. Although not shown, the center post 41 is provided with supply ports for a first supply line 51s and a second supply line 51n for supplying a vulcanization medium to the inside of the bladder 3, and a discharge port for a discharge line 52 for discharging the vulcanization medium filled inside the bladder 3 to the outside.

[0017] The vulcanizer 100 is provided with a first supply line 51s and a second supply line 51n that communicate with the interior of the bladder 3 via supply ports, and a discharge line 52 that communicates with the interior of the bladder 3 via a discharge port. A supply source 53s for a first vulcanization medium is connected to the first supply line 51s, and a supply source 53n for a second vulcanization medium is connected to the second supply line 51n. Supply valves 54 and 55 are provided on the first supply line 51s and the second supply line 51n, respectively. A discharge valve 56 is provided on the discharge line 52. The opening and closing operations of each valve can be controlled by a control device (not shown).

[0018] The vulcanizer 100 is provided with an exhaust line 61 that communicates with an air vent 17 that is formed by opening into the tire molding surface 16 of the mold 1. During vulcanization, excess air between the outer surface of the tire T and the tire molding surface 16 is discharged from the air vent 17 through the exhaust line 61 to the outside. The path from the air vent 17 to the exhaust line 61 is provided via gaps in the container 2 (for example, gaps between the tread mold 11 and the segments 21, gaps between the side mold 12 and the upper platen 23, gaps between the side mold 13 and the lower platen 24, etc.), but is not limited to this. Sealing materials (not shown) are attached to required locations in the gaps in the container 2, and the excess air is configured to be sent to the exhaust line 61 appropriately.

[0019] The exhaust line 61 branches midway, and one of the branches 61a is connected to a suction device 62, and the other branch 61b is connected to an atmosphere release valve 63. The opening and closing operations of a valve 64 of the suction device 62 and the atmosphere release valve 63 provided in the branch 61a are controlled by a control device (not shown). The sensor 65 is installed upstream of the atmosphere release valve 63 connected to the exhaust line 61. The sensor 65, together with a pressure gauge 66, is installed between a branch point 61c of the exhaust line 61 and the atmosphere release valve 63. The sensor 65 is installed upstream of the pressure gauge 66, but the positions may be reversed. In this embodiment, an example is shown in which the sensor 65 is a temperature sensor.

[0020] Next, a method for vulcanizing and molding a tire T using the vulcanizer 100 and detecting a puncture in the bladder 3 during this process will be described. The vulcanization and molding of a tire is carried out through a vulcanization process in which an unvulcanized tire T set in a mold 1 is heated and pressurized. In the vulcanization process, the unvulcanized tire T is heated and pressurized from the outside by the mold 1, and the tire T is heated and pressurized from the inside by the bladder 3. As will be described later, according to this embodiment, it is possible to detect a puncture in the bladder 3 during the vulcanization process, or more specifically, at a relatively early stage in the vulcanization process.

[0021] The vulcanization process includes a heating step in which the tire T is heated in a bladder 3 whose internal pressure is P1 (corresponding to the first internal pressure) by supplying a first vulcanization medium, and a pressurizing step in which, after the heating step, the tire T is pressurized in a bladder 3 whose internal pressure is P2 (corresponding to the second internal pressure) higher than the internal pressure P1 by supplying a second vulcanization medium. As an example, the internal pressure P1 is 1.6 MPa, and the internal pressure P2 is 2.4 MPa. A fluid that serves as a heating medium, preferably steam, is used as the first vulcanization medium. A fluid that serves as a pressurizing medium, preferably an inert gas, is used as the pressurizing gas. In this embodiment, an example is shown in which steam is used as the first vulcanization medium and nitrogen gas (N2 gas) is used as the second vulcanization medium.

[0022] FIG. 2 is a graph showing the transition of the internal pressure of the bladder 3. The horizontal axis represents time, and the vertical axis represents the internal pressure of the bladder 3. The range from T1 to T2 on the horizontal axis corresponds to the heating stage, and the range from T2 to T6 corresponds to the pressurizing stage. After the mold 1 containing the unvulcanized tire T is closed, steam with adjusted pressure and temperature is supplied into the bladder 3. The bladder 3 is maintained at a constant internal pressure P1 for a predetermined time (until time T2). During this time, the supply valve 54 is open, and the supply valve 55 and the discharge valve 56 are closed. The tire T is heated from the inside by the bladder 3, which is inflated and deformed by the supply of steam, and is also heated from the outside by being pressed against the tire molding surface 16.

[0023] When closing the mold 1 (for example, from immediately before the completion of mold closing until 30 seconds after the start of steam supply), it is preferable to operate the suction device 62 with the atmosphere release valve 63 closed to suck out excess air between the outer surface of the tire T and the tire molding surface 16. This makes it possible to prevent molding defects caused by residual air. The sucked air is sent to the tank of the suction device 62 through the exhaust line 61. At this time, the status of exhaust by the suction device 62 can be confirmed by the gauge pressure (negative pressure) detected by the pressure gauge 66. As described above, installing a sealant in the gap of the container 2 is effective in enhancing the suction effect. After suction is completed, the valve 64 of the branch path 61a is closed, and then the atmosphere release valve 63 is opened.

[0024] If the bladder 3 is punctured, steam leaks from the bladder 3 during the heating stage. However, as shown in the image diagram in FIG. 3, the steam S that leaks to the outside of the bladder 3 is likely to be trapped between the outer surface of the bladder 3 and the inner surface of the tire T. This is thought to be due to the fact that the leak progresses gradually through small tears R in the bladder 3 and that the bladder 3 is maintained at a constant internal pressure P1 during the heating stage. For convenience, in the following description, the steam S trapped in this way may be referred to as "steam TS." It is thought that the trapped steam TS loses heat to the tire T, causing some or all of it to condense and become drainage.

[0025] At the time T2 in FIG. 2, the heating stage is switched to the pressurizing stage. When switching, the supply valve 54 is closed and the supply valve 55 is opened, so that nitrogen gas with adjusted pressure and temperature is supplied into the bladder 3. This causes the bladder 3 to be pressurized to a higher internal pressure P2, further pressurizing the tire T and promoting vulcanization. Also, during the pressurizing stage, the bladder 3, which has been set to the internal pressure P2, is at least temporarily depressurized. The depressurization of the bladder 3 is achieved by closing the supply valve 55 while keeping the exhaust valve 56 closed to stop the supply of nitrogen gas, thereby reducing the internal pressure of the bladder 3 as heat is absorbed by the tire T. The initial depressurization occurs in the range from T2 to T3 in FIG. 2.

[0026] In this embodiment, the bladder 3, whose internal pressure is set to P2 as described above, is depressurized, and the leaked steam is detected by the sensor 65, thereby detecting a puncture. By depressurizing the bladder 3, the pressure of the trapped steam TS becomes relatively high, allowing it to leak out from between the bladder 3 and the tire T. For example, the steam TS shown in FIG. 3 moves to the right in accordance with the depressurization of the bladder 3, and can leak out from between the bladder 3 and the tire T. Note that if the trapped steam TS has drained, the drain will re-evaporate due to the depressurization of the bladder 3, and together with the volume expansion associated with evaporation, the pressure of the steam TS will become relatively high, causing it to leak out from between the bladder 3 and the tire T.

[0027] The sensor 65 detects the temperature of the air sent to the sensor 65. When trapped steam TS leaks during the pressurization stage, air hotter than normal is sent to the sensor 65, allowing the steam to be detected accurately. The sensor 65 is not particularly limited as long as it can detect steam, and may be, for example, a humidity sensor. The determiner 67 shown in FIG. 1 compares the detection result of the sensor 65 with a preset threshold value, and if the threshold value is exceeded, determines that a puncture has occurred in the bladder 3. The determination result is transmitted to an alarm 68 capable of outputting sound, light, or an image, and notifies the operator when a puncture is detected. These devices are controlled by a control device (not shown).

[0028] Steam leaking from between the bladder 3 and the tire T enters the gap in the container 2 described above. In this embodiment, the sensor 65 detects the steam sent through the gap in the container 2 and the exhaust line 61. The installation of a sealant in the gap in the container 2 is beneficial in supplying the leaked steam to the sensor 65 through the exhaust line 61. The branch path 61b is located sufficiently far from the mold 1 and the container 2, and is configured so that air cooled to near the atmospheric temperature (ambient temperature) is released into the atmosphere. Therefore, if high-temperature steam (for example, near 100°C) is contained, a sudden temperature difference occurs, and therefore the sensor 65 can accurately detect the steam.

[0029] 2, in the pressurization stage of this embodiment, when the internal pressure of the bladder 3 reaches P2, the supply of nitrogen gas is immediately stopped to depressurize the bladder 3. In other words, when the internal pressure of the bladder 3 reaches P2, the supply valve 55 is closed. This method accelerates the timing at which the trapped steam TS leaks, allowing for earlier detection of a puncture in the bladder 3.

[0030] Furthermore, in the pressurization stage of this embodiment, depressurization of the bladder 3 by stopping the supply of nitrogen gas (i.e., closing the supply valve 55) and pressurization of the bladder 3 by restarting the supply of nitrogen gas (i.e., opening the supply valve 55) are alternately repeated. Specifically, the initial depressurization is performed in the range from T2 to T3 in FIG. 2, and at time T3, the supply of nitrogen gas is restarted to repressurize the bladder 3, and depressurization and pressurization are similarly alternately repeated thereafter. As a result, steam TS that did not leak during the initial depressurization may leak during the second or subsequent depressurizations, increasing the likelihood of puncture detection. Furthermore, the intermittent supply of nitrogen gas has the effect of stirring the inside of the bladder 3, thereby achieving a uniform temperature.

[0031] In the pressurization stage of this embodiment, when the depressurized bladder 3 reaches a predetermined internal pressure P3 (corresponding to a third internal pressure) that is higher than the internal pressure P1 and lower than the internal pressure P2 (times T3, T4, and T5 in FIG. 2), the supply of nitrogen gas is resumed to pressurize the bladder 3. As an example, the internal pressure P3 is 2.1 MPa. In FIG. 2, depressurization is performed four times, but the number of times is not particularly limited as long as the bladder 3 is depressurized at least temporarily. As shown in FIG. 2, the time it takes for the depressurized bladder 3 to reach the internal pressure P3 from the internal pressure P2 gradually becomes longer. This is because the temperature of the tire T increases over time, and as a result, the gradient of the decrease in the internal pressure of the bladder 3 due to heat absorption by the tire T gradually becomes smaller.

[0032] 2, in order to finish heating and pressurizing the tire T, the discharge valve 56 is opened to discharge the vulcanization medium filled inside the bladder 3. This causes the bladder 3 to shrink and deform, and the mold 1 is opened so that the vulcanized tire can be removed from the mold 1. The methods described in the above-mentioned Patent Documents 1 and 2 detect a puncture in the bladder 3 at the timing when the vulcanization medium is discharged.

[0033] According to this embodiment, a puncture in the bladder 3 can be detected early in the vulcanization process (for example, in the first half of the vulcanization process, between T2 and T3 in FIG. 2). For example, if a puncture is detected at time T7, the time thereafter can be used for preparatory work (preparation for replacement). Therefore, the replacement work for the bladder 3 can be started immediately after the vulcanized tire is removed from the mold 1, or after a short preparatory work has been performed, thereby reducing the downtime of the vulcanizer 100. Examples of preparatory work include attaching a spare bladder to the jig (upper and lower clamps) and transporting this assembly to the vicinity of the mold 1 using a transport device such as a lifter.

[0034] Figure 4 is a table showing a specific example of the breakdown of the time for the vulcanization process. Common to Examples 1 to 4 is that the steam pressure supplied to the bladder during the heating stage is 1.6 MPa and the temperature is 203°C. Furthermore, the nitrogen gas pressure supplied to the bladder during the pressurization stage is 2.3 MPa and the temperature is room temperature. During the pressurization stage, the bladder is alternately depressurized and pressurized, as shown in Figure 2, and nitrogen gas is supplied intermittently.

[0035] Example 1 is an example in which there is no function to detect bladder punctures. Therefore, the occurrence of a puncture is detected through the condition of the tire after it has been removed from the mold and vulcanized. As a result, there is no time available for replacement preparation (time that can be used for setup during the vulcanization process). When replacing the bladder, the vulcanizer must be stopped, including the time for setup, which inevitably results in a significant drop in operating rate.

[0036] In Example 2, a puncture is detected when the vulcanization medium in the bladder is being discharged at the end of the vulcanization process. Therefore, even if there is a time available for preparation for replacement, it is less than 0.5 minutes, and there is no practical time available for setup during the vulcanization process. Therefore, when replacing the bladder, the vulcanizer must be stopped, including the time for setup, which inevitably results in a significant drop in operating rate.

[0037] In Example 3, as in the above-described embodiment, a puncture is detected when the bladder is decompressed during the pressurization stage. Therefore, even though the vulcanization time is the same as in Examples 1 and 2, a replacement preparation time of 6.5 to 7.5 minutes is obtained. If pre-setup is performed during this time, the bladder replacement work can be started immediately after the vulcanization process, which contributes to shortening the downtime of the vulcanizer. Furthermore, even if pre-setup cannot be completed during the vulcanization process, the pre-setup time is shortened by the amount that has already been performed, which also contributes to shortening the downtime of the vulcanizer.

[0038] Like Example 3, Example 4 is an example in which a puncture is detected when the bladder is depressurized during the pressurization stage. In Example 4, the pressurization stage takes longer than in Example 3, so 9.5 to 10.5 minutes of preparation time for replacement is obtained. This ensures more time for pre-setup during the vulcanization process, effectively shortening the downtime of the vulcanizer and preventing a significant drop in operating rate.

[0039] [1] As described above, the method disclosed herein is a method for detecting a puncture in a bladder 3 during a vulcanization process in which an unvulcanized tire T set in a vulcanization mold 1 is heated and pressurized from the inside by a bladder 3, and the vulcanization process includes a heating stage in which the tire T is heated in the bladder 3 whose internal pressure is P1 by supplying steam as a first vulcanization medium, and a pressurization stage in which, after the heating stage, the tire T is pressurized in the bladder 3 whose internal pressure is P2 higher than the internal pressure P1 by supplying nitrogen gas as a second vulcanization medium.In the pressurization stage, the bladder 3 whose internal pressure is P2 is at least temporarily reduced, and the leaked steam TS is detected by a sensor 65 to detect a puncture.

[0040] According to this method, the first vulcanization medium (steam TS) trapped in the heating stage is leaked by depressurizing the bladder 3 in the pressurizing stage, and this leakage is detected by the sensor 65, thereby making it possible to detect a puncture of the bladder 3 early in the vulcanization process. As a result, the downtime of the vulcanizer 100 can be shortened, and a significant drop in the operating rate due to replacement of the bladder 3 can be suppressed.

[0041] [2] In the method [1] above, it is preferable that the sensor 65 is a temperature sensor, which makes it possible to accurately detect the high temperature of the first vulcanizing medium (steam TS).

[0042] [3] In the above method [1] or [2], it is preferable to use a sensor 65 to detect steam sent through an exhaust line 61 communicating with an air hole 17 formed in the tire molding surface 16 of the vulcanization mold 1. This method is convenient for detecting the first vulcanization medium (steam TS) leaking due to the decompression of the bladder 3.

[0043] [4] In the method [3] above, it is preferable that the exhaust line 61 branches midway, one branch 61a is connected to a suction machine 62, the other branch 61b is connected to an air release valve 63, and the sensor 65 is installed between a branch point 61c of the exhaust line 61 and the air release valve 63. This method is convenient for detecting the first vulcanization medium (steam TS) leaking due to the pressure reduction in the bladder 3.

[0044] [5] In any one of the above methods [1] to [4], in the pressurizing step, it is preferable to immediately stop the supply of nitrogen gas when the internal pressure of the bladder 3 reaches P2, thereby depressurizing the bladder 3. According to this method, the timing at which the first vulcanization medium (steam TS) leaks can be advanced, and a puncture of the bladder 3 can be detected earlier.

[0045] [6] In any one of the above methods [1] to [5], it is preferable that in the pressurizing step, the supply of nitrogen gas is stopped to depressurize the bladder 3, and the supply of nitrogen gas is resumed to pressurize the bladder 3. According to this method, the first vulcanization medium (steam TS) that did not leak out during the first depressurization of the bladder 3 may leak out during the second or subsequent depressurization, thereby increasing the possibility of detecting a puncture.

[0046] The puncture detection method of the present disclosure detects a bladder puncture during the vulcanization process, which includes the heating and pressurizing stages described above, and any of the conventionally known vulcanizers, mold structures, vulcanization conditions, etc. can be used in the vulcanization process.

[0047] Although the embodiments of the present disclosure have been described above, it should be understood that the specific configuration is not limited to these embodiments. The scope of the present disclosure is not limited to the above-described embodiments, but is indicated by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0048] Therefore, for example, in the above-described embodiment, an example was shown in which the suction machine 62 connected to the exhaust line 61 was operated at the start of the vulcanization process to suck out excess air between the outer surface of the tire T and the tire molding surface 16, but this is not limiting. In the puncture detection method of the present disclosure, such suction is not essential and may be omitted.

[0049] In the above embodiment, the supply valve 55 is closed while the exhaust valve 56 is kept closed to stop the supply of nitrogen gas in order to at least temporarily reduce the pressure of the bladder 3, which has an internal pressure of P2. However, this is not limiting. For example, instead of or in addition to closing the supply valve 55, the internal pressure of the bladder 3 may be reduced by opening the exhaust valve 56.

[0050] In the above-described embodiment, the steam TS is detected by the sensor 65 installed between the branch point 61c of the exhaust line 61 and the atmosphere release valve 63, but this is not limiting. The sensor 65 may be installed at another location in the exhaust line 61 or at a location other than the exhaust line 61, as long as it can detect the leaked steam TS (first vulcanization medium).

[0051] The method for detecting a puncture in a tire vulcanization bladder of the present disclosure is not limited to the above-described embodiment, and various improvements and modifications are possible within the scope of the invention. [Explanation of symbols]

[0052] 1 Vulcanization mold 2. Container 3. Tire curing bladder 4 Central mechanism 16 Tire molding surface 17 Ventilation holes 61 Exhaust line 61a Fork 61b Fork 61c Junction 62 Suction machine 63 Atmospheric release valve 65 sensors 100 Vulcanizer

Claims

1. A method for detecting a puncture in a bladder during a vulcanization process in which an unvulcanized tire set in a vulcanization mold is heated and pressurized from the inside by the bladder, comprising: the vulcanization process includes a heating step of heating the tire in the bladder, the bladder having a first internal pressure set by supplying a first vulcanization medium, and a pressurizing step of pressurizing the tire in the bladder, the second internal pressure being higher than the first internal pressure, by supplying a second vulcanization medium after the heating step, A method for detecting a puncture in a tire vulcanization bladder, characterized in that, in the pressurizing step, the bladder, which has been set to the second internal pressure, is at least temporarily depressurized, and the puncture is detected by detecting the leaked first vulcanization medium with a sensor.

2. The method of claim 1 , wherein the sensor is a temperature sensor.

3. 2. The method according to claim 1, wherein the sensor detects the first vulcanization medium sent through an exhaust line communicating with an air hole formed in the tire molding surface of the vulcanization mold.

4. The exhaust line branches off midway, one branch is connected to a suction machine, and the other branch is connected to an air release valve; The method of claim 3 , wherein the sensor is installed between a branch point of the exhaust line and the atmosphere relief valve.

5. 2. The method according to claim 1, wherein in the pressurizing step, the supply of the second vulcanization medium is stopped immediately when the bladder is brought to the second internal pressure, thereby depressurizing the bladder.

6. The method according to any one of claims 1 to 5, wherein the pressurizing step alternately repeats decompression of the bladder by stopping the supply of the second vulcanization medium and pressurization of the bladder by restarting the supply of the second vulcanization medium.

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