JP2015199236A - Method for vulcanizing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for vulcanizing a pneumatic tire that can avoid a prolonged vulcanization time and suppress energy consumption by effectively reducing a vertical temperature difference in a vulcanization bladder without using a complicated apparatus when a green tire is vulcanized by injecting steam and nitrogen gas into the vulcanization bladder.SOLUTION: By valve operation of on/off valves 8a, 8b, and 8c installed in a steam injection line 6a, a nitrogen gas injection line 6b, and a discharge line 7a, respectively, the internal pressure P of a vulcanization bladder 2 expanded by steam S injected through a steam injection line 6a is maintained in a first internal pressure range A1 by intermittently injecting the steam S into the vulcanization bladder 2 in a sealed state, and a part of the steam S is discharged from the vulcanization bladder 2 to reduce the internal pressure into a second internal pressure range A2, and then nitrogen gas N is intermittently injected into the vulcanization bladder 2 in a sealed state to maintain the internal pressure in a third internal pressure range A3 higher than the first internal pressure range A1.

Description

  The present invention relates to a method for vulcanizing a pneumatic tire, and more specifically, when a green tire is vulcanized by injecting steam and nitrogen gas into a vulcanizing bladder, the vulcanizing bladder can be used without using a complicated device. The present invention relates to a method for vulcanizing a pneumatic tire that can effectively reduce the temperature difference between the upper and lower sides, can avoid prolonged vulcanization time, and can suppress energy consumption.

  A method of vulcanizing a green tire by inserting a vulcanization bladder into a green tire installed inside a mold and injecting steam (heating medium) and nitrogen gas (pressure medium) into the vulcanization bladder is known. . In this way, in the vulcanization method using steam and nitrogen gas, the specific gravity of nitrogen gas is larger than that of steam. Therefore, in the expanded vulcanization bladder, steam is present in a compressed state, and its Nitrogen gas is present below. For this reason, in the vulcanization bladder during vulcanization, the upper temperature becomes higher than the lower temperature, resulting in an upper and lower temperature difference. Due to this, the vulcanized tire has a problem that the degree of vulcanization varies greatly in the vertical direction when vulcanized.

  In order to solve such problems, various vulcanization methods and vulcanizers have been proposed (see, for example, Patent Documents 1 and 2). Patent Document 1 proposes a vulcanizer in which a stirring blade is installed inside a vulcanization bladder. In this vulcanizer, by rotating the stirring blade, steam inside the vulcanization bladder and nitrogen gas are stirred and mixed, and the difference in the upper and lower temperatures of the vulcanization bladder can be reduced. However, in this proposal, a stirring blade must be newly installed inside the vulcanization bladder. Along with this, there is a problem that the vulcanization equipment becomes complicated. If the vulcanization equipment becomes complicated, equipment failure is likely to occur. Therefore, it is preferable to use a simple equipment. The vulcanization method and apparatus proposed in Patent Document 2 also requires additional equipment.

  On the other hand, in order to reduce the temperature difference of the vulcanization bladder, in the process of injecting steam into the vulcanization bladder, so-called steam-through operation is performed in which steam is discharged from the vulcanization bladder while injecting steam into the vulcanization bladder. Sometimes. By this steam-through operation, the newly injected steam can be condensed in the vulcanization bladder to increase the temperature of the drain, and the temperature difference between the vulcanization bladders can be reduced. However, the effect of reducing the temperature difference between the top and bottom by the steam-through operation is instantaneous and not sustainable. In addition, since a large amount of steam is injected and discharged, a large amount of energy is consumed.

JP 2009-29035 A JP 2012-96437 A

  The object of the present invention is to effectively reduce the vertical temperature difference of the vulcanization bladder without using a complicated device when vulcanizing the green tire by injecting steam and nitrogen gas into the vulcanization bladder, An object of the present invention is to provide a method for vulcanizing a pneumatic tire that can avoid prolonged vulcanization time and suppress energy consumption.

  In order to achieve the above object, the method for vulcanizing a pneumatic tire according to the present invention includes inserting a vulcanization bladder, to which a steam injection line, a nitrogen gas injection line and a discharge line are connected, into a green tire arranged inside a mold, In the vulcanization method for a pneumatic tire, the vulcanization bladder is vulcanized by steam injected through the steam injection line and nitrogen gas injected through the nitrogen gas injection line to vulcanize a green tire. Performing a first step of increasing the internal pressure of the vulcanization bladder to an initial internal pressure by injecting steam through the steam injection line, and then closing the steam injection line, the nitrogen gas injection line, and the discharge line, The second step of lowering the pressure, and only the steam injection line is open Then, by repeating the third step of increasing the internal pressure by injecting steam into the vulcanizing bladder, the internal pressure is maintained in the first internal pressure range, and then only the exhaust line is opened to perform the addition. A fourth step of lowering the internal pressure to a second internal pressure range lower than the first internal pressure range by discharging a part of the steam from the sulfur bladder is performed, and then only the nitrogen gas injection line is opened. A fifth step of increasing the internal pressure by injecting nitrogen gas into the vulcanization bladder and a sixth step of decreasing the internal pressure by closing the steam injection line, nitrogen gas injection line and discharge line are repeated. The internal pressure is raised to a pressure higher than the first internal pressure range, and then only the nitrogen gas injection line is opened. A seventh step of increasing the internal pressure by injecting nitrogen gas into the vulcanizing bladder in a state; and an eighth step of decreasing the internal pressure by closing the steam injection line, nitrogen gas injection line and discharge line. The internal pressure is maintained in a third internal pressure range that is higher than the first internal pressure range.

  According to the present invention, the internal pressure of the expanding vulcanization bladder during vulcanization is only controlled by opening / closing operations of the steam injection line, nitrogen gas injection line, and discharge line (valve operation of the on-off valve). No equipment is required. There is no steam-through operation for the purpose of raising the temperature of the drain inside the vulcanizing bladder, which is generated by condensing steam as in the past, so there is no injection or discharge of a large amount of steam, greatly reducing energy consumption. Can be suppressed.

  Then, steam is intermittently injected into the sealed vulcanization bladder, and the internal pressure of the vulcanization bladder is maintained within the first internal pressure range, so that the vulcanization bladder is generated from the initial stage where a drain is generated inside the vulcanization bladder. The upper and lower temperature difference of the vulcanization bladder can be effectively reduced by maintaining the internal drain at a high temperature. After maintaining the internal pressure of the vulcanization bladder within the first internal pressure range, the steam inside the vulcanization bladder is drastically lowered by discharging a portion of the steam from the vulcanization bladder and lowering it to the second internal pressure range. Thus, the difference in temperature between the upper and lower sides of the vulcanization bladder can be effectively reduced.

  Next, by intermittently injecting nitrogen gas into the sealed vulcanization bladder, maintaining the internal pressure of the vulcanization bladder in the second internal pressure range in a third internal pressure range that is higher than the first internal pressure range, The temperature rise above the inside of the expanding vulcanizing bladder during vulcanization can be suppressed, and the difference between the upper and lower temperatures can be effectively reduced. At this time, since the temperature rise above the inside of the vulcanization bladder is mainly suppressed, the adverse effect of increasing the vulcanization time can be avoided.

It is explanatory drawing which illustrates the whole system outline which enforces the vulcanization method of the pneumatic tire of the present invention. It is a graph which illustrates typically the relation between internal pressure P of a vulcanization bladder, and vulcanization lapse time T.

  Hereinafter, a method for vulcanizing a pneumatic tire according to the present invention will be described based on an embodiment shown in the drawings.

  The vulcanizing method for a pneumatic tire according to the present invention uses a vulcanizing system 1 illustrated in FIG. This vulcanization system 1 has a rubber-like cylindrical vulcanization bladder 2. The upper clamp part 3a and the lower clamp part 3b of the vulcanization bladder 2 are held by disk-shaped upper clamp holding parts 5a and lower clamp holding parts 5b attached to the central mechanism 4, respectively. In the center post of the center mechanism 4, there are an inlet 6 for injecting steam S as a heating medium and nitrogen gas N as a pressure medium into the vulcanizing bladder 2, and steam S and nitrogen inside the vulcanizing bladder 2. A discharge port 7 for discharging the gas N to the outside of the vulcanization bladder 2 is provided.

  This vulcanization system 1 further connects a steam injection line 6 a that connects the inlet 6 and the steam supply source 11 so as to communicate with the vulcanization bladder 2, and connects the inlet 6 and the nitrogen gas supply source 12. Thus, a nitrogen gas injection line 6b connected to the vulcanization bladder 2 so as to be able to communicate therewith and a discharge line 7a connected to the exhaust port 7 so as to be able to communicate with the vulcanization bladder 2 are provided. The steam injection line 6a, the nitrogen gas injection line 6b, and the discharge line 7a are provided with on-off valves 8a, 8b, and 8c, respectively. Furthermore, the control apparatus 10 which controls valve operation which opens and closes each on-off valve 8a, 8b, 8c is provided.

  In order to carry out the method for vulcanizing a pneumatic tire according to the present invention, first, the green tire G is placed in the mold 9 in a horizontally placed state. In this embodiment, the mold 9 includes an annular sector 9a divided into a plurality in the circumferential direction, an annular side plate 9b disposed on the upper side, and an annular side plate 9c disposed on the lower side. The vulcanization bladder 2 is inserted inside the green tire G, and the mold 9 is closed.

  In this state, the following steps 1 to 8 (S1 to S8) are performed, and the internal pressure P of the vulcanizing bladder 2 during vulcanization is controlled as schematically illustrated by the solid line in FIG. In the steps 1 to 8, the inner peripheral surface of the green tire G is pressed by the expanding vulcanizing bladder 2, and the green tire G is heated while being pressed by the mold 9.

  First, only the on-off valve 8a is opened, and the steam S supplied from the steam supply source 11 is injected into the vulcanization bladder 2 through the steam injection line 6a. The temperature of the steam S to be injected is, for example, about 150 ° C to 250 ° C.

  The injected steam S raises the internal pressure P of the vulcanizing bladder 2 to a predetermined initial internal pressure Ps and inflates it into a donut shape along the inner wall surface of the green tire G (first step). The inner peripheral surface of the green tire G is pressed by the vulcanization bladder 2 having the initial internal pressure Ps, and the green tire G is heated against the mold 9 while being heated.

  Next, the on-off valve 8a is closed, and the steam injection line 6a, the nitrogen gas injection line 6b, and the discharge line 7a are all closed to reduce the internal pressure P of the vulcanization bladder 2. (Second step). Thereafter, only the on-off valve 8a is opened, and the steam S supplied from the steam supply source 11 through the steam injection line 6a is injected into the vulcanization bladder 2 to increase the internal pressure P (third step). A part of the steam S supplied to the inside of the vulcanizing bladder 2 is condensed inside the vulcanizing bladder 2 and flows downward to form the drain D. Therefore, the internal pressure P is repeated by repeating the second step and the third step. Is maintained in the first internal pressure range A1 which is substantially equal to the initial internal pressure Ps. The pressure difference between the upper limit and the lower limit of the first internal pressure range A1 is, for example, 0.2 MPa to 0.5 MPa.

  Next, only the on-off valve 8c is opened to open only the discharge line 7a, and a part of the steam S is discharged from the inside of the expanded vulcanization bladder 2 to the outside through the discharge line 7a. Is reduced to a second internal pressure range A2 having a pressure lower than the first internal pressure range A1 (fourth step). As a result, the temperature of the steam S inside the vulcanizing bladder 2 is drastically reduced, and the difference in the upper and lower temperature inside the vulcanizing bladder 2 is reduced.

  Next, only the on-off valve 8b is opened, and only the nitrogen gas injection line 6b is opened, and the nitrogen gas N supplied from the nitrogen gas supply source 12 is injected into the vulcanization bladder 2 through the nitrogen gas injection line 6b. Then, the internal pressure P is increased (fifth step). The temperature of the nitrogen gas N to be injected is room temperature. Thereafter, the on-off valve 8b is closed, and all of the steam injection line 6a, the nitrogen gas injection line 6b, and the discharge line 7a are closed to lower the internal pressure P (sixth step). By repeating the fifth step and the sixth step, the internal pressure P in the second internal pressure range A2 is gradually increased to a pressure higher than the first internal pressure range A1.

  Next, only the on-off valve 8b is opened, and only the nitrogen gas injection line 6b is opened, and the nitrogen gas N supplied from the nitrogen gas supply source 12 is injected into the vulcanization bladder 2 through the nitrogen gas injection line 6b. Then, the internal pressure P is increased (seventh step). Alternatively, the on-off valve 8b is closed, and the steam injection line 6a, the nitrogen gas injection line 6b, and the discharge line 7a are all closed to lower the internal pressure P (eighth step). By performing the seventh step and the eighth step in random order, the internal pressure P is maintained in the third internal pressure range A3 that is higher than the first internal pressure range A1. The pressure difference between the upper limit and the lower limit of the third internal pressure range A3 is, for example, 0.1 MPa to 0.4 MPa. Thereafter, step 7 and step 8 are repeated as necessary until a preset vulcanization time Te elapses. For example, step 7 and step 8 are repeated 1 to 5 times, depending on the tire specifications.

  For example, the cycle in which the seventh step and the eighth step are repeated is longer than the cycle in which the fifth step and the sixth step are repeated. Further, for example, the difference between the average pressure in the third internal pressure range A3 and the average pressure in the first pressure range A1 is made larger than the difference between the average pressure in the first internal pressure range A1 and the average pressure in the second internal pressure range A2.

  After a predetermined vulcanization time Te has elapsed, the upper side plate 9b is moved upward, the respective sectors 9a are moved in the diameter increasing direction, and the mold 9 is opened. Next, the vulcanized tire is moved upward and extracted from the vulcanization bladder 2.

  In the present invention, as described above, the vulcanizing bladder 2 expanding during vulcanization by opening / closing the steam injection line 6a, the nitrogen gas injection line 6b, and the discharge line 7a (valve operation of the on-off valves 8a, 8b, 8c). It only controls the internal pressure P. Therefore, a complicated apparatus is unnecessary and a simple apparatus can be obtained. Thereby, even if it is an existing vulcanization equipment, it is possible to apply this invention easily, without making a big modification.

  In the present invention, the steam-through operation is not performed for the purpose of increasing the temperature of the drain D inside the vulcanizing bladder 2 generated by condensing the steam S as in the prior art. Therefore, the amount of steam S used in the present invention is small compared to the conventional method in which the steam-through operation is performed, and energy consumption can be greatly suppressed.

  In addition, by repeating the second step and the third step and controlling the internal pressure P of the vulcanization bladder 2, the inside of the vulcanization bladder 2 from the initial stage where the drain D is generated inside the vulcanization bladder 2 is obtained. The drain D can be maintained at a high temperature, and the temperature difference between the upper and lower sides of the vulcanizing bladder 2 can be effectively reduced.

  By the fourth step, a part of the steam S is discharged from the inside of the vulcanization bladder 2 expanded by the steam S, and the internal pressure P is lowered from the first internal pressure range A1 to the second internal pressure range A2, thereby vulcanizing. The temperature of the steam S inside the bladder 2 can be rapidly lowered. Thereby, the upper-lower temperature difference of the vulcanization bladder 2 can be reduced effectively.

  Thereafter, in the fifth step to the eighth step, nitrogen gas N is intermittently injected into the vulcanization bladder 2 to control the internal pressure P of the vulcanization bladder 2 during vulcanization, thereby expanding during vulcanization. The temperature rise above the inside of the vulcanizing bladder 2 is suppressed. Therefore, it is possible to effectively reduce the vertical temperature difference of the vulcanizing bladder 2, and as a result, variation in the degree of vulcanization in the vertical direction of the tire when vulcanized can be reduced. Moreover, since the temperature rise above the inside of the vulcanization bladder 2 is mainly suppressed, the adverse effect that the vulcanization time is extended can be avoided.

  Each of the predetermined initial internal pressure Ps, the first internal pressure range A1, the second internal pressure range A2, and the third internal pressure range A3 and the time for maintaining the pressure value are determined by the specifications (size, shape) of the green tire G to be vulcanized. , Rubber type, etc.). Therefore, test vulcanization is performed in advance using a green tire G having the same specifications as the green tire G to be vulcanized, and these optimum values are grasped and input to the control device 10. Based on these optimum values inputted to the control device 10, the steam injection line 6a, the nitrogen gas injection line 6b, and the discharge line 7a are opened / closed (valve operations of the on-off valves 8a, 8b, 8c).

  The type of tire vulcanized using the present invention is not particularly limited. When a run-flat tire with a thicker side than a normal tire is vulcanized by a conventional method using steam S and nitrogen gas N, the side rubber and lower The variation in the degree of vulcanization tends to increase with the side rubber on the side. Therefore, by vulcanizing using the present invention, variation in the degree of vulcanization of rubber on both side portions of the run-flat tire is reduced, and a remarkable effect can be obtained.

  When a green tire sample of a run-flat type pneumatic tire (235 / 40RF18) is horizontally vulcanized using steam and nitrogen gas, the same vulcanizing apparatus illustrated in FIG. 1 is used. Vulcanization was performed by three types of methods (Example, Conventional example, Comparative example) with different opening / closing operations (valve operation of the opening / closing valve) of the steam injection line, the nitrogen gas injection line, and the discharge line. In the example, the internal pressure P of the vulcanization bladder was controlled in the same manner as the solid line in FIG. In the conventional example, steam is injected into the vulcanization bladder to set the internal pressure P to the initial internal pressure Ps, and after a predetermined time has elapsed, the steam-through operation is performed to slightly lower the internal pressure P, and then nitrogen gas is injected into the vulcanization bladder once. Then, the internal pressure P was raised to the third internal pressure range, and the vulcanization bladder was kept in the sealed state to maintain the third internal pressure range. The comparative example is different from the conventional example only in that the steam-through operation is not performed, and after injecting steam into the vulcanization bladder to the initial internal pressure Ps for a predetermined time, nitrogen gas is injected once into the vulcanization bladder. The internal pressure P was raised to the third internal pressure range, and the vulcanization bladder was kept in the sealed state to maintain the third internal pressure range.

  As a result, the embodiment was able to reduce the amount of steam used by about 50% or more compared to the conventional example. Further, the difference in temperature between the upper and lower sides of the vulcanization bladder at the end of vulcanization can be reduced by about 80% to 90% in the embodiment compared to the comparative example, and about 20% smaller than that in the conventional example. It was.

DESCRIPTION OF SYMBOLS 1 Vulcanization system 2 Vulcanization bladder 3a Upper clamp part 3b Lower clamp part 4 Center mechanism 5a Upper clamp holding part 5b Lower clamp holding part 6 Inlet 6a Steam injection line 6b Nitrogen gas injection line 7 Outlet 7a Exhaust line 8a , 8b, 8c On-off valve 9 (9a, 9b, 9c) Mold 10 Controller 11 Steam supply source 12 Nitrogen gas supply source G Green tire

Claims (3)

A vulcanization bladder connected to a steam injection line, a nitrogen gas injection line, and a discharge line is inserted into a green tire disposed inside the mold, and the vulcanization bladder is injected through the steam injection line and the nitrogen. In a vulcanizing method for a pneumatic tire in which a green tire is vulcanized by inflating with nitrogen gas injected through a gas injection line,
The first step of raising the internal pressure of the vulcanization bladder to the initial internal pressure by injecting steam into the vulcanization bladder through the steam injection line, and then closing the steam injection line, the nitrogen gas injection line and the discharge line The internal pressure is reduced by repeatedly performing the second step of reducing the internal pressure and the third step of increasing the internal pressure by injecting steam into the vulcanization bladder with only the steam injection line open. Maintaining the first internal pressure range, and then leaving only the exhaust line open to discharge a part of the steam from the vulcanization bladder, thereby reducing the internal pressure to a second internal pressure range lower than the first internal pressure range. Performing the fourth step, and then opening only the nitrogen gas injection line, By repeatedly performing a fifth step of increasing the internal pressure by injecting nitrogen gas into the gas generator and a sixth step of decreasing the internal pressure by closing the steam injection line, the nitrogen gas injection line and the discharge line. Increasing the internal pressure to a pressure higher than the first internal pressure range, and then increasing the internal pressure by injecting nitrogen gas into the vulcanization bladder with only the nitrogen gas injection line open; and Maintaining the internal pressure in a third internal pressure range higher than the first internal pressure range by performing the eighth step of lowering the internal pressure with the steam injection line, nitrogen gas injection line, and discharge line closed. A method for vulcanizing a pneumatic tire.   The method for vulcanizing a pneumatic tire according to claim 1, wherein the seventh step and the eighth step are repeatedly performed after the sixth step.   The difference between the average pressure in the third internal pressure range and the average pressure in the first pressure range is greater than the difference between the average pressure in the first internal pressure range and the average pressure in the second internal pressure range. A method for vulcanizing a pneumatic tire as described in 1.

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