JP4152397B2 - Method and apparatus for heating cylindrical mold - Google Patents

Description

  The present invention is, for example, a method for heating a cylindrical mold that is used for molding a fixing member such as a roller or a belt that requires high-precision dimensional stability and that is suitable for heating a cylindrical mold having a large heat capacity. And to the device.

  For example, when manufacturing the fixing roller, a manufacturing apparatus having a cylindrical mold 12 as shown in FIG. 2 is used. First, a fluororesin tube is disposed along the inner peripheral wall of the cylindrical mold 12, and the core shaft 14 is disposed at the axial center in the cylindrical mold 12, and then both ends of the cylindrical mold 12 are connected to the upper plug 15 </ b> A and the lower plug body 15 </ b> A. Cover with plug 15B. Liquid rubber is injected from the rubber injection hole 20 provided in the lower plug body 15B, and injected until the liquid rubber comes out from the air escape hole 22 of the upper plug body 15A, and the fluororesin tube and the liquid rubber are heated and cured. Perform molding.

  In order to integrally mold the rubber layer 16 and the fluororesin layer 18 on the circumference of the core shaft 14, these constituent members are arranged coaxially in the cylindrical mold 12, and then housed in a hot blast furnace and heated, although not shown. It is going to harden. However, conventionally, the thickness of the rubber layer 16 is often 1 mm or more, and the dimensional accuracy required for the cylindrical mold 12 is not strict. Therefore, the thickness of the cylindrical mold 12 is thin and the heat capacity of the mold is small. It was. For this reason, even if a hot stove was used, sufficient temperature rise could be performed.

In recent years, the development of copiers and printers that take energy saving into account has progressed, and it has been required to reduce the energy required to heat the rollers. For this reason, it is desirable to make the thickness of the rubber layer 16 laminated on the fixing member such as a roller thinner in order to reduce the heat capacity, and the required value is 0.1 to 0.00 as the thickness of the rubber layer. It is about 3 mm.
JP 2000-326329 A

By the way, the conventional technique has the following problems to be solved.
In a fixing member in which a thin rubber layer is molded on the core shaft and the fluororesin layer is formed thereon, in order to obtain the rubber layer and the fluororesin layer by integral molding, the core shaft and the cylindrical mold are accurately coaxial. Must be placed. At this time, in order to improve the accuracy of the cylindrical mold, the thickness of the mold increases and the overall heat capacity increases. Further, the bias of the heat capacity distribution due to the upper plug body 15A, the lower plug body 15B, and the like serving as the lid of the cylindrical mold 12 becomes larger than the conventional one. When this is heated by a normal hot stove, the heating time becomes enormous. In addition, if the time is to be shortened, the ambient temperature must be increased, which consumes a large amount of energy, and the equipment becomes large.

  Moreover, in order to make the thickness of the rubber layer 16 a required value, it is substantially impossible to mold with the conventional mold accuracy, and a cylindrical mold with higher dimensional accuracy is required. Moreover, in order to increase the dimensional accuracy of the cylindrical mold, it is necessary to suppress distortion after processing, and the thickness of the cylindrical mold must be increased. Specifically, it is necessary to increase the thickness of the cylindrical mold up to about 7 to 10 mm, where 3 to 4 mm is conventionally sufficient. For this reason, the heat capacity of the entire mold is increased by 2 to 3 times, and a large amount of energy and time are required to heat the mold to a temperature necessary for curing the rubber layer.

  When a cylindrical mold having a large wall thickness is heated only by a hot stove, a lot of time is required. In order to improve production efficiency, a lot of molds had to be put into the hot stove. That is, since the heating time divided by the number of molds is the heating time per mold, if the heating time per mold is reduced, the production efficiency is improved. However, in order to prepare a large number of molds, there was a problem that the corresponding funds were required and the economic efficiency was poor.

  On the other hand, a method is known in which spacers made of a magnetic material having a high relative permeability are arranged at both ends of a cylindrical mold, and an induction coil is arranged around the cylindrical mold to perform induction heating (for example, Patent Documents). 1). However, when the distribution of the magnetic field is made uniform by the spacer, the amount of heat generation becomes uniform, so that there is a problem that the temperature rise of the entire mold does not become uniform if there is a deviation of the heat capacity in the axial direction of the mold.

  When induction heating is performed, when a single induction coil having a uniform winding is used, the maximum value of the magnetic field is the central portion in the axial direction of the coil, and the maximum induced current flows at the position of the maximum value of the magnetic field. Since the amount of heat generation is proportional to the magnitude of the induced current, the maximum generation position of the magnetic field is the maximum amount of heat generation. If the mold is heated as it is, the temperature at the center of the mold in the axial direction is high and the temperature is low at both ends, which adversely affects the dimensional system of the molded product. That is, the higher the temperature, the smaller the thickness of the rubber layer after molding, and the lower the temperature, the greater the thickness of the rubber layer. Although a method of adjusting the generation distribution of the magnetic field and controlling the amount of heat generation by reducing the winding interval can be considered, the method of holding the winding becomes complicated and adjustment is difficult.

  Further, as shown in FIG. 2, in the case where the fluororesin tube or the liquid rubber disposed in the cylindrical mold 12 is heated and subjected to curing molding, the upper plug serving as a lid on the upper and lower ends of the cylindrical mold 12 The body 15A and the lower plug body 15B are required. In the cylindrical mold 12 to which the upper plug body 15A and the lower plug body 15B are attached, since the heat capacity at both ends is increased by the amount of the plug body, it is difficult to uniformly heat the entire mold including the plug body. There was a problem.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a cylindrical mold heating method and apparatus capable of heating in a short time with high energy efficiency.

The present invention solves the above problems by the following configurations.
<Configuration 1>
The cylindrical mold, around a large portion of heat capacity than the other portions, the induction coil is arranged, by energizing the alternating current to the induction coil, the portion having a large thermal capacity than other portions of the cylindrical mold A method for heating a cylindrical mold, characterized in that a magnetic flux induced in an axial direction is intensively generated to inductively heat the cylindrical mold to make the temperature rise of the entire cylindrical mold uniform .

A magnetic field distribution corresponding to the heat capacity distribution of the cylindrical mold is generated, an induced current is preferentially generated in a part having a larger heat capacity than other parts , causing Joule heat to directly heat the cylindrical mold, and the cylindrical mold By making the temperature rise of the entire mold uniform , heat treatment can be performed in a short time with good energy efficiency. The heating time can be reduced to about 1/20.

<Configuration 2>
In the heating method of the cylindrical mold according to Structure 1, the cylindrical mold a large portion of the heat capacity than the other portions are dispersed in plural positions in the axial direction, a plurality of induction coils, the other A method for heating a cylindrical mold, comprising the steps of: inductively heating the cylindrical mold in a distributed manner around each of the portions having a larger heat capacity than the portion.

It is possible to adjust the generation distribution of the magnetic field by distributing a plurality of induction coils in the axial direction and adjusting the coil interval (fixing at a free position in the axial direction). For this reason, even when there is a deviation of the heat capacity in the axial direction of the cylindrical mold, the entire mold can be heated evenly by arranging the coils so that the magnetic field is concentrated on the portion having a larger heat capacity than the other portions. become. However, since the energy efficiency is worse than that of the uniform winding single induction coil, it is necessary to design the coil in consideration of the heating time and the uniformity of the temperature distribution.

<Configuration 3>
The method for heating a cylindrical mold according to Configuration 1 or 2, wherein the induction coil is energized with an alternating current in a low frequency region of 50 to 800 Hz.

  By using an alternating current of 50 to 800 Hz, the penetration depth of the magnetic flux into the cylindrical mold can be increased. For this reason, not only the surface of the cylindrical mold but also the inside of the mold is heated, and even a mold having a large heat capacity can be heated rapidly. Moreover, since it becomes possible to heat rapidly, when manufacturing the same number, it becomes possible to reduce the number of metal mold | die by the part for shortening of heating time. Therefore, the initial investment can be greatly reduced, and the economic effect is great.

<Configuration 4>
In the heating method of the cylindrical mold according to any one of the first to third aspects, a metal member that is likely to generate heat by an induced current rather than iron in the vicinity of a portion having a larger heat capacity than the other portion of the cylindrical mold. A heating method for a cylindrical mold, wherein the heating is performed by induction.

The heat generated in the adjacent metal member is arranged by placing a metal member that is more likely to generate heat due to the induced current than iron such as aluminum or copper in the vicinity of the portion of the cylindrical mold having a larger heat capacity than other portions. Can be supplied to the portion having a large heat capacity by heat conduction, and the heating temperature for the cylindrical mold can be made uniform.

<Configuration 5>
Inductive heating of a cylindrical mold in which a portion having a larger heat capacity than the above-mentioned other portions is dispersed in a plurality of locations in the axial direction to equalize the temperature rise of the entire cylindrical mold , and a plurality of induction coils The cylindrical mold heating device is characterized by being dispersedly arranged around each of the portions having a larger heat capacity than the other portions .

Efficient heating can be performed by disposing a predetermined induction coil in advance corresponding to the cylindrical mold having a plurality of portions having a larger heat capacity than the other portions in the axial direction.

  In the present invention, a magnetic field distribution corresponding to the heat capacity distribution of the cylindrical mold is generated by a plurality of induction coils arranged substantially coaxially with the cylindrical mold, and the cap is covered with a portion having a large heat capacity, for example, an upper plug body and a lower plug body. An induced current is preferentially generated at both end portions of the cylindrical mold, and Joule heat is generated to directly heat the cylindrical mold.

In this invention, it is preferable that the alternating current supplied to an induction coil is a low frequency area | region of 50-800 Hz. In normal high frequency induction heating, only the surface of the metal is heated by energizing an alternating current having a frequency of 1 kHz or more. This utilizes the fact that the penetration depth of the magnetic field represented by the following general expression of the penetration depth of the magnetic field becomes smaller as the frequency becomes higher.
Formula for penetration depth of magnetic field; δ = 5.03 (ρ / μf) ^1/2
Where δ: penetration depth of magnetic field (cm)
ρ: Specific resistivity of heated object (μΩ · cm)
μ: Relative permeability of heated object
f: Frequency

However, in the present invention, the penetration depth of the magnetic flux into the cylindrical mold can be increased by using an alternating current of 50 to 800 Hz. For this reason, not only the surface of the cylindrical mold but also the inside of the mold is heated, and even a mold having a large heat capacity can be heated rapidly. In addition, since it becomes possible to perform heating rapidly, in the conventional method, it was necessary to put a large number of molds into a hot stove in the conventional method. Therefore, the initial investment can be greatly reduced, and the economic effect is great.
Embodiments of the present invention will be described below.

FIG. 1 is an explanatory view showing a method of heating a cylindrical mold according to the first embodiment, and the same parts as those in FIG.
Inside the cylindrical mold 12 with an inner diameter of 60.7 mm, an outer diameter of 74 mm, and a thickness of 7 mm, a 30 μm thick, etched inner PFA tube is set coaxially, and the space between the cylindrical mold 12 and the PFA tube is evacuated. Then, the PFA tube was brought into close contact with the inner surface of the cylindrical mold, and a primer was applied to the etched surface and dried.

  Next, the surface of the aluminum core shaft 14 having an outer diameter of 60 mm was roughened with a belter to remove the cutting, and then a primer was applied and dried. A cylindrical mold 12 in which a core shaft 14 and a PFA tube are set is coaxially arranged, and both ends are covered with an upper plug body 15A and a lower plug body 15B, respectively. At this time, the total weight of the mold was 8 kg.

  Liquid silicone rubber was injected from the rubber injection hole 22 provided in the lower plug body 15B of the cylindrical mold 12, and injection was performed until the liquid silicone rubber emerged from the air escape hole 22 of the upper plug body 15A.

  Next, two induction coils 24 having an inner diameter of 150 mm, a height of 200 mm, and a number of turns of 70 turns are provided around portions of the cylindrical mold 12 having a large heat capacity, that is, around the upper plug body 15A and the lower plug body 15B. Each was arranged coaxially. At this time, each induction coil 24 was disposed at a distance of 50 mm from the axial center of the cylindrical mold 12 so that the vicinity of the upper plug body 15A and the lower plug body 15B was the central position of heat generation.

  Then, an inverter having a capacity of 40 kVA and the induction coil 24 were electrically connected, and the induction coil 24 was supplied with an alternating current having a frequency of 100 Hz and a current of 280 A to perform induction heating. The surface temperature of the cylindrical mold 12 took 120 seconds to reach from 20 ° C to 120 ° C. After carrying out induction heating, it was left in a room temperature space for 10 minutes, and then poured into a cooling water bath for cooling.

  After cooling, the plugs 15A and 15B were removed from the cylindrical mold 12, and the core shaft 14 was taken out of the cylindrical mold 12. Thus, a roller having a rubber layer thickness of 0.3 mm could be obtained. The amount of power input was 566wh.

<Comparative Example 1>
When a cylindrical mold having the same configuration as that of Example 1 was put into a hot air furnace having an atmospheric temperature of 180 ° C., it took 40 minutes for the mold surface temperature to reach 120 ° C. This was immediately cooled with water and decomposed in the same manner as in Example 1 to obtain a roller having a rubber layer thickness of 0.3 mm. The input power amount at this time was 2.4 kwh.

  As is apparent from the above, Example 1 can obtain the same roller with about 1/4 of the electric energy compared to Comparative Example 1 of the conventional system, and the use of the present invention greatly improves energy efficiency. Can be improved. Further, in Example 1, compared to Comparative Example 1, the treatment could be performed in 1/4 time from heating to cooling.

  In the present invention, a cylindrical mold in which a portion having a large heat capacity is dispersed in a plurality of locations in the axial direction is induction-heated, and a plurality of induction coils are dispersedly arranged around each of the portions having a large heat capacity. A cylindrical mold heating device is included. By preparing a heating device provided with a predetermined induction coil in advance, an efficient mold heat treatment can be performed immediately.

  In the present invention, there are a system in which a plurality of induction coils are connected in series and one power source is connected to both ends thereof, and a system in which one power source is connected to each of the plurality of induction coils. Can be adopted. Since the former uses only one expensive power source, the equipment cost can be reduced. In the latter case, when there are several portions having different heat capacities in the axial direction of the cylindrical mold, alternating currents having different frequencies can be applied to the respective portions, so that an appropriate heating operation according to the heat capacity is possible.

3 is an explanatory view showing a heating method of the cylindrical mold of Example 1. FIG. It is a longitudinal cross-sectional view which shows an example of the manufacturing apparatus of a fixing roller.

Explanation of symbols

12 cylindrical mold 14 core shaft 15A upper plug body 15B lower plug body 16 rubber layer 18 fluororesin layer 20 rubber injection hole 22 air escape hole 24 induction coil

Claims (5)

Place an induction coil around the part of the cylindrical mold that has a larger heat capacity than the other parts ,
Wherein by energizing the alternating current to the induction coil, the other part the heat capacity is larger than the portion of the cylindrical mold, and induction heating the cylindrical mold by the magnetic flux induced in the axial direction centrally generate, A method for heating a cylindrical mold, characterized in that the temperature rise of the entire cylindrical mold is made uniform . In the heating method of the cylindrical metal mold according to claim 1,
For a cylindrical mold in which portions having a larger heat capacity than the other portions are dispersed in a plurality of locations in the axial direction, a plurality of induction coils are provided around each of the portions having a larger heat capacity than the other portions. A method for heating a cylindrical mold, comprising the step of inductively heating the cylindrical mold in a distributed manner. In the heating method of the cylindrical metal mold according to claim 1 or 2,
A method for heating a cylindrical mold, wherein the induction coil is energized with an alternating current in a low frequency region of 50 to 800 Hz. In the heating method of the cylindrical metal mold according to any one of claims 1 to 3,
A method for heating a cylindrical mold, characterized in that a metal member that is more likely to generate heat due to an induced current than iron is placed near a portion having a larger heat capacity than the other portion of the cylindrical mold and induction heating is performed. . Inductively heating a cylindrical mold in which portions having a larger heat capacity than the other parts are dispersed in a plurality of axial directions, and uniformizing the temperature rise of the entire cylindrical mold ,
A cylindrical mold heating apparatus, wherein a plurality of induction coils are dispersedly arranged around each of the portions having a larger heat capacity than the other portions .

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