JP6690187B2 - Pneumatic tire vulcanization method - Google Patents

Description

  The present invention relates to a method for vulcanizing a pneumatic tire, and more particularly, to a method for vulcanizing a pneumatic tire that can effectively reduce the temperature difference between the upper and lower sides of a vulcanizing bladder while suppressing waste of energy used. It is a thing.

  A method is known in which a vulcanizing bladder is inserted into a green tire installed inside a tire mold, and steam (heating medium) and nitrogen gas (pressurizing medium) are injected into the vulcanizing bladder to vulcanize the green tire. There is. In this way, in the vulcanization method using steam and nitrogen gas, since the specific gravity of nitrogen gas is larger than that of steam, in the expanded vulcanization bladder, steam is present in a state of being compressed upward, The nitrogen gas is present below. Therefore, in the vulcanization bladder during vulcanization, the temperature on the upper side is higher than that on the lower side, and a difference in temperature between the upper and lower sides occurs. 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 have been proposed (see, for example, Patent Documents 1 and 2). In the vulcanization method proposed in Patent Document 1, after injecting steam (198 ° C.) into the vulcanization bladder, nitrogen gas heated to, for example, 160 ° C. is used as a pressurizing medium in order to reduce the temperature difference from the steam. Inject. In the vulcanization method proposed in Patent Document 2, after injecting steam into the vulcanization bladder, nitrogen gas heated to, for example, 300 to 500 ° C. is injected as a pressurizing medium in order to reduce the density difference with steam. To do.

  According to the vulcanization methods proposed in Patent Documents 1 and 2, the nitrogen gas that has been heated to a temperature considerably higher than 100 ° C. is required, so that the energy used increases. On the other hand, in reality, the vulcanization bladder is excessively heated, resulting in a waste of energy.

Japanese Patent Laid-Open No. 9-19931 JP-A-5-104540

  An object of the present invention is to provide a method of vulcanizing a pneumatic tire that can effectively reduce the difference in temperature between the vulcanization bladder while suppressing the waste of energy used.

  To achieve the above object, the pneumatic tire vulcanizing method of the present invention is a tubular vulcanizing bladder is inserted into a green tire, a heating medium is injected into the vulcanizing bladder, and then in a standard state. A method of vulcanizing a pneumatic tire, in which a green medium is vulcanized in a tire mold in a state where the vulcanization bladder is expanded to a predetermined internal pressure by injecting a pressurized medium having a larger specific gravity than a heating medium. In, the injection temperature of the pressurizing medium at the time of injecting into the vulcanization bladder is 100 ° C. or less, and the pressurization inside the vulcanization bladder in a state of being expanded to the predetermined internal pressure. The density of the pressurizing medium in the partial pressure of the medium is set to a temperature at which the density of the heating medium is equal to or less than the density of the heating medium in the partial pressure of the heating medium.

  According to the present invention, the injection temperature of the pressurizing medium at the time of injecting into the vulcanization bladder is set to 100 ° C. or lower, so that the energy required for heating the pressurizing medium can be suppressed. Furthermore, the density of the pressurizing medium in the partial pressure of the pressurizing medium inside the vulcanized bladder in the state of being expanded to the predetermined internal pressure is equal to or less than the density of the heating medium in the partial pressure of the heating medium. By setting the temperature so that the heating medium is not unevenly distributed upward in the vulcanization bladder that is vulcanizing the green tire, the pressurizing medium and the heating medium are appropriately mixed. As a result, it is possible to effectively reduce the temperature difference between the upper and lower sides of the vulcanization bladder while suppressing the waste of the energy used. Along with this, variation in the degree of vulcanization of the vulcanized tire is reduced in the vertical direction, which leads to improvement in tire quality.

  Here, for example, before the pressure medium having a temperature lower than the injection temperature is injected into the vulcanization bladder, the pressure medium is directly heated by a heater to be heated. Alternatively, the pressurized medium having a temperature lower than the injection temperature is adiabatically compressed and heated by an adiabatic volume adjuster before being injected into the vulcanization bladder.

It is an explanatory view which illustrates the whole outline of the vulcanization apparatus which performs the vulcanization method of the pneumatic tire of the present invention. It is a graph which illustrates the temperature dependence of the density of nitrogen gas in pressure 0.7MPa. When the injection temperature of nitrogen gas is set to 100 ° C., a graph illustrating a pressure condition for making the density of nitrogen gas equal to or lower than the density of steam under the partial pressure conditions of steam inside the vulcanization bladder and nitrogen gas. Is. It is explanatory drawing which illustrates the whole general outline of another vulcanization apparatus which performs the vulcanization method of the pneumatic tire of this invention. It is a graph which illustrates the temperature change of the inner surface of the upper side tire side and the inner surface of the lower side tire side in a prior art example. It is a graph which illustrates the temperature change of the inner side surface of the upper tire side and the inner side surface of the lower tire side in an Example.

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

  A pneumatic tire vulcanizing apparatus 1 (hereinafter referred to as vulcanizing apparatus 1) illustrated in FIG. 1 has a rubber-made tubular vulcanizing bladder 2. A center post 4a that constitutes the center mechanism 4 is vertically inserted through the vulcanization bladder 2. The upper clamp portion 3a and the lower clamp portion 3b of the vulcanization bladder 2 are held by a disc-shaped upper clamp holding portion 5a and a lower clamp holding portion 5b attached to the center post 4a, respectively.

  An injection port 6 is provided at a position on the outer peripheral side of the center post 4a. A heating medium M1 such as steam is injected into the vulcanization bladder 2 through the inlet 6. Further, in the standard state (temperature 0 ° C., pressure 1 atm), the pressurizing medium M2 having a larger specific gravity than the heating medium M1 is injected into the vulcanization bladder 2 through the injection port 6. As the pressurizing medium M2, for example, an inert gas such as nitrogen gas is used.

  The inlet 6 is connected to a downwardly extending injection line 7. A heater 8 is connected to the injection line 7. The central mechanism 4 is also provided with a discharge port and a discharge line for discharging the fluid inside the vulcanization bladder 2 to the outside.

  The injection direction of the heating medium M1 and the pressurizing medium M2 from the inlet 6 is set to an appropriate direction with respect to the horizontal direction. For example, the inclination direction is 0 ° or more and 30 ° or less. Is set. It is preferable to provide a plurality of inlets 6 at equal intervals in the circumferential direction, for example.

  In order to vulcanize the green tire G using the vulcanizing method of the present invention, the green tire G is placed inside the tire mold 10 in a horizontal position as illustrated in FIG. In this embodiment, the tire mold 10 includes an annular sector 10a divided into a plurality of pieces in the circumferential direction, an annular upper side plate 10b, and an annular lower side plate 10c. The vulcanization bladder 2 is inserted inside the green tire G, and the tire mold 10 is closed.

Next, steam is supplied as the heating medium M1 through the injection line 7 and injected into the vulcanization bladder 2 through the injection port 6 to heat the vulcanization bladder 2 while expanding it. The injection temperature of the heating medium M1 when injected into the vulcanization bladder 2 is, for example, about 200 ° C., and the injection pressure is about 1.4 MPa. The steam density at 200 ° C. and 1.4 MPa is 7.602 kg / m ³ .

  Next, the pressurizing medium M2 is supplied through the injection line 7 and injected into the vulcanization bladder 2 through the injection port 6 to further expand the vulcanization bladder 2. In the present invention, the injection temperature Te of the pressurized medium M2 when injecting into the vulcanization bladder 2 is specially devised. The injection temperature Te will be described later.

  The heating medium M1 and the pressurizing medium M2 injected in this manner bring the vulcanization bladder 2 to a predetermined internal pressure P and expand it. The inner peripheral surface of the green tire G is pressed by the vulcanization bladder 2, and accordingly, the green tire G is heated while being pressed by the tire mold 10 to be vulcanized.

  After the preset vulcanization time has elapsed, the heating medium M1 and the pressurizing medium M2 existing inside the vulcanization bladder 2 are discharged from the exhaust port through the exhaust line. The upper side plate 10b is moved upward, and the respective sectors 10a are moved in the radial expansion direction to open the tire mold 10. Then, the vulcanized tire is moved upward and extracted from the vulcanized bladder 2 which has contracted, and taken out from the vulcanizing apparatus 1.

  In the present invention, the injection temperature Te of the pressurized medium M2 is set to 100 ° C. or lower. In this embodiment, the pressurized medium M2 having a temperature lower than the injection temperature Te is directly heated by the heater 8 to be heated to the injection temperature Te before being injected into the vulcanization bladder 2.

  Further, the density D2 of the pressurizing medium M2 at the partial pressure P2 of the pressurizing medium M2 inside the vulcanization bladder 2 in the state where the injection temperature Te is expanded to the predetermined internal pressure P is equal to that of the heating medium M1. The temperature is set to a temperature at which the density D1 of the heating medium M1 at the pressure P1 is less than or equal to the density D1.

For example, the pressure medium M2 of 2.1 MPa is injected into the vulcanization bladder 2 into which the heating medium M1 of 1.4 MPa and 200 ° C. has been injected, so that the vulcanization bladder 2 has a predetermined internal pressure P (= 2.1 MPa). ) And expand it. The partial pressure P1 of the heating medium M1 is 1.4 MPa, and the partial pressure P2 of the pressurizing medium M2 is 0.7 MPa (= 2.1 MPa-1.4 MPa). The density D2 of the pressurized medium M2 at the partial pressure P2 is as illustrated by the line segment C1 in FIG. The density D1 of the heating medium M1 at the partial pressure P1 of the heating medium M1 is 7.602 kg / m ³ . Therefore, when the temperature of the pressurizing medium M2 at which the density D2 becomes equal to or lower than the density D1 (= 7.602 kg / m ³ ) is calculated from the line segment C1 in FIG. Therefore, the injection temperature Te is set to 80 ° C. or higher.

  Therefore, according to the present invention, the injection temperature Te of the pressurized medium M2 is set to 80 ° C or higher and 100 ° C or lower. Accordingly, since it is not necessary to heat the pressurizing medium M2 to more than 100 ° C. before injecting it into the vulcanization bladder 2, the energy required for heating the pressurizing medium M2 can be suppressed. Further, a large-scale device for heating the pressurizing medium M2 to more than 100 ° C. is unnecessary. Therefore, a person having ordinary skill in the art can obtain a great energy saving merit.

  In addition, by setting the density D2 of the pressurizing medium M2 to be equal to or lower than the density D1 of the heating medium M1, inside the vulcanization bladder 2 that is vulcanizing the green tire G, relatively light heating as in the conventional case is performed. The medium M1 is not unevenly distributed upward, and the pressurizing medium M2 and the heating medium M1 are appropriately mixed. Further, the pressurizing medium M2 heated more than necessary is not injected into the vulcanization bladder 2 and the vulcanization bladder 2 is not excessively heated. Therefore, the waste of energy used for vulcanization of the green tire G can be significantly suppressed, and the difference between the upper and lower temperatures of the vulcanization bladder 2 can be effectively reduced. Along with this, variation in the degree of vulcanization of the vulcanized tire is reduced in the vertical direction, which leads to improvement in tire quality.

  After injecting steam as the heating medium M1 into the vulcanization bladder 2 and then injecting nitrogen gas as the pressurizing medium M2, the density D2 of the nitrogen gas under the respective partial pressures P1 and P2 is changed to the density D1 of the steam. The line segment C2 illustrated in FIG. 3 and the region below the line segment C2 (the shaded region) satisfy the following requirements. By adjusting the pressures of steam and nitrogen gas in this way, the injection temperature Te of nitrogen gas that satisfies the above requirements can be made relatively low.

  As in the vulcanizing apparatus 1 illustrated in FIG. 4, a heat insulating volume adjuster 9 may be connected to the injection line 7 instead of the heater 8 illustrated in FIG. 1. The heat insulation volume adjuster 9 is composed of a heat insulation container and a piston that changes the accommodation volume of the heat insulation container. In this vulcanizing apparatus 1, the pressurized medium M2 having a temperature lower than the injection temperature Te is adiabatically compressed by the adiabatic volume adjuster 9 and heated to the injection temperature Te before being injected into the vulcanization bladder 2.

  The vulcanizer 1 may be provided with the heater 8 illustrated in FIG. 1 and the heat insulation volume adjuster 9 illustrated in FIG. 4 connected in series to the injection line 7. Then, the pressurizing medium M2 heated in order by the heater 8 and the heat insulation volume adjuster 9 and heated to the injection temperature Te can be injected into the vulcanization bladder 2. Alternatively, it is also possible to inject into the vulcanization bladder 2 the pressurizing medium M2 which is heated by the adiabatic volume adjuster 9 and the heater 8 in order and heated to the injection temperature Te.

  Using a device similar to the vulcanizing device illustrated in FIG. 1, steam of 1.4 MPa and 200 ° C. was injected into the inside of the vulcanizing bladder, and then only the injection temperature of the nitrogen gas of 2.1 MPa was different in two ways. Then, the green tire was vulcanized by setting the internal pressure of the vulcanization bladder to 2.1 MPa. The temperature changes of the inner surface of the upper tire side and the inner surface of the lower tire side of the green tire during vulcanization were measured, and the results are shown in FIGS. In the conventional example shown in FIG. 5, the nitrogen gas injection temperature was 40 ° C., and in the embodiment shown in FIG. 6, the nitrogen gas injection temperature was 90 ° C.

  In the conventional example and the example, the temperature difference between the inner surface of the upper tire side and the inner surface of the lower tire side at the end of vulcanization was 15.0 ° C and 1.5 ° C, respectively. From this result, it can be seen that the embodiment can effectively reduce the difference in the vertical temperature of the vulcanization bladder, as compared with the conventional example.

1 Vulcanizing Device 2 Vulcanizing Bladder 3a Upper Clamping Part 3b Lower Clamping Part 4 Center Mechanism 4a Center Post 5a Upper Clamp Holding Part 5b Lower Clamp Holding Part 6 Injection Port 7 Injection Line 8 Heater 9 Adiabatic Volume Adjuster 10 Tire Mold 10a Sector 10b Upper side plate 10c Lower side plate G Green tire M1 Heating medium M2 Pressurizing medium

Claims (3)

By inserting a tubular vulcanization bladder into a green tire, injecting a heating medium into the vulcanization bladder, and then injecting a pressure medium having a specific gravity larger than that of the heating medium in a standard state, In a method of vulcanizing a pneumatic tire for vulcanizing the green tire in a tire mold in a state where a sulfur bladder is expanded to a predetermined internal pressure,
The injection temperature of the pressurizing medium when injecting into the vulcanizing bladder is 100 ° C. or less, and the pressurizing medium inside the vulcanizing bladder is in an expanded state under the predetermined internal pressure. A method of vulcanizing a pneumatic tire, characterized in that the density of the pressurized medium in the partial pressure is set to a temperature at which the density of the heating medium in the partial pressure of the heating medium becomes equal to or lower.   The method for vulcanizing a pneumatic tire according to claim 1, wherein the pressurized medium having a temperature lower than the injection temperature is directly heated and heated by a heater before being injected into the vulcanization bladder. The method for vulcanizing a pneumatic tire according to claim 1 , wherein the pressurized medium having a temperature lower than the injection temperature is adiabatically compressed and heated by an adiabatic volume adjuster before being injected into the vulcanization bladder. .

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