JP2010244786A - Sheathed heater, and heating method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheathed heater providing two or more sites each having different heating temperature with the use of a single coil-shaped sheathed heater, and to provide a heating method using the same. <P>SOLUTION: An electrode pole 15 is welded to either end of a heating wire 13 with a given resistance value, and the heating wire 13 is inserted into a metal pipe 12. The metal pipe 12 is formed by sealing electrode poles 15 at either terminal part by filling electric insulation powder 14 around the heating wire 13 in the metal pipe 12. The metal pipe 12 is molded into a coil shape. Upon molding it into a coil shape, a coil inner diameter 16 of the metal pipe 12 is set so as a distance between a surface of the metal pipe 12 and a heated object is to be small at a site making a heating temperature of the heated object high, and the distance is to be long at a site lowering the heating temperature. By changing the coil inner diameter 16 or a coil pitch of the coil molded in a coil shape, two sites or more of different heating temperature areas can be given to the heated object with a single coil-shaped sheath heater 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheathed heater, and more particularly to a sheathed heater having different heating temperature regions on the surface of an object to be heated and a heating method using the same.

  As shown in FIG. 9A, the sheathed heater of Conventional Example 1 disclosed in Patent Document 1 inserts a heating wire 13 into the metal pipe 12 and is filled with an electrically insulating powder 14 around the heating wire 13. And two or more different heat generation regions are provided. In this sheathed heater, the heating wire 13 is divided in the middle of the metal pipe 12, and the electrode rod 15 connected to the end of the heating wire 13 in the middle of the metal pipe 12 passes through the center of the remaining heating wire 13. The configuration is provided.

  In addition to Conventional Example 1 described above, as Conventional Example 2 disclosed in Patent Document 2, as shown in FIG. 9B, a plurality of heating wires 13 and 13 having different wire diameters in the metal pipe 12 are provided. There is a configuration using '. According to this method, two or more different heat generation regions can be provided by using the heating wires 13 and 13 ′ having different wire diameters. However, the number of parts increases as in the conventional example 1, and the heater Having complex processing during construction remains the same.

JP-A-2-148683 JP 2001-185335 A

  The sheathed heater of Conventional Example 1 shown in FIG. 9 (a) has a problem that the number of parts is increased because there are two heating wires and four electrode bars for one sheathed heater. Moreover, since the structure is complicated, it must be assembled while ensuring an insulation distance so as not to approach other parts, and therefore there is a problem that the assembling work is difficult. In addition, since the internal structure and surface shape of the sheathed heater are uniform, the radiated heat flow rate is only uniform. It is difficult to realize not only uniform heating but also different temperature distributions on the object to be heated.

  On the other hand, in Conventional Example 2, as shown in FIG. 9B, a plurality of heating wires having different wire diameters are arranged inside the sheathed heater and connected to each other. In this method, since the amount of heat generated by the heating wire can be changed according to the wire diameter, local heating is also possible in addition to uniform heating. The means of changing the internal configuration of the sheathed heater itself and providing a plurality of wire diameters of the heating wires in the metal pipe, which is a constituent material, requires a heating wire corresponding to that when many temperature changes are desired. In addition, the number of connection points will also increase. The problem of complicated assembly has not been solved.

  Depending on the object to be heated, machining may not be realized unless a temperature is applied to each region. An example is heat processing of glass or resin material. These materials are heated to the softening point and then processed by applying an external force. However, in the heat bending process, it is desirable that the temperature decrease starts immediately after the completion of annealing after obtaining the desired processed shape. In this case, a heating method in which the amount of heat is not applied after the completion of processing is necessary so that unintended deformation does not occur in a portion where a bent shape has already been obtained. However, as described above, in the two conventional examples, there is a problem that the shape of the sheathed heater that cannot give different temperature distributions, or the problem that the assembly of the sheathed heater can be complicated although different temperature distributions can be given. A heater and a heating method using the heater are necessary.

  The present invention solves the above-described problems of the prior art, and provides a sheathed heater that provides two or more regions having different heating temperatures using a single coiled sheathed heater and a heating method using the sheathed heater. With the goal.

  The present invention has been made in order to achieve the above-mentioned object, and after arranging a heating wire inside a metal pipe and enclosing an electrically insulating powder, the metal pipe is formed into a coil shape, and the formed coil shape By changing the coil inner diameter and the coil pitch, the heating temperature region of the object to be heated is provided in two or more different regions.

  By adopting such a configuration, a sheathed heater can be provided that has a smaller number of parts than the conventional technology and can easily secure an insulation distance, and can provide a heating object with a region having a different heating temperature. It is to provide.

  According to the sheathed heater of the present invention, it is not necessary to perform pre-processing such as shape processing of a heating wire in a conventional metal pipe or connection of heating wires having different wire diameters, and furthermore, heating wires having different wire diameters are used. Therefore, without increasing the number of connecting parts, it is possible to easily assemble the insulation distance and to form a metal pipe with a heating wire in a simple configuration into a coil shape. By changing the coil inner diameter and / or the coil pitch, there is an effect that two or more regions having different heating temperatures can be given to the surface of the object to be heated.

The figure which shows the coiled sheathed heater which varied the coil internal diameter of Embodiment 1 in this invention, and its partial cross section In the manufacturing process of the sheathed heater according to the first embodiment, (a) is a flowchart showing a case where the coil inner diameter is changed, and (b) is a case where the coil pitch is changed. (A) is a relative positional relationship with the heating target of the sheathed heater molded in a coil shape, and (b) is a diagram showing the sheathed heater before being molded into a coil shape. Obtaining the form factor of radiant heat transfer (a) is the parameter of the heated object and the object to be heated, (b) is a graph showing an example The figure which shows the coiled sheathed heater which varied the coil pitch of this Embodiment 2, and its partial cross section The figure which shows the coil-shaped sheathed heater which made the coil internal diameter and coil pitch of this Embodiment 3 variable, and its partial cross section. The figure which shows the example of application to the heating bending process of the glass tube of this Embodiment 4. Temperature profile of glass tube by numerical analysis of heat bending process In the conventional sheathed heater, (a) is a sectional view of Conventional Example 1, (b) is a sectional view of Conventional Example 2.

  The present invention is a sheathed heater in which a metal pipe is formed in a coil shape in a sheathed heater in which a heating wire is inserted into a metal pipe and an electric insulating powder is filled around the heating wire. In addition, a sheathed heater is provided that can give two or more regions with different heating temperatures to the object to be heated by forming the metal pipe of the sheathed heater into a coil shape and changing the inner diameter and pitch of the coil shape. To do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a coiled sheathed heater and a partial cross section thereof according to Embodiment 1 of the present invention. FIG. 2A is a flowchart showing a manufacturing process when the sheathed heater of FIG. 1 is manufactured. Here, components having the same functions corresponding to the components described in FIG. 9 showing the conventional example are given the same reference numerals, and the same applies to the following drawings.

  As shown in FIG. 1, the metal pipe 12 has a heating wire 13. In addition, an electric insulating powder 14 is filled around the heating wire 13. There are electrode rods 15 welded to both ends of the heating wire 13.

  Then, as shown in FIG. 3A, the metal pipe 12 of the sheathed heater is formed in a coil shape, and it is assumed that a heating object 31 having a straight pipe shape is inserted into the coil shape and heated. To do. Hereinafter, the manufacturing process of the sheathed heater of FIG. 1 will be described with reference to FIG.

  First, the electrode rod 15 is welded to both ends of the heating wire 13 having a predetermined resistance value (step S1). The heating wire 13 with the electrode rod 15 welded is inserted into the metal pipe 12 (step S2). An electric insulating powder 14 is filled around the heating wire 13 inserted into the metal pipe 12 (step S3), and both ends are sealed as shown in FIG. 3B (step S4).

  In this state, the metal pipe 12 is formed in a coil shape (step S5). Assuming that the straight pipe-shaped heating object 31 shown in FIG. 3 (a) is heated, the surface of the metal pipe 12 and the heating object in the coiled sheathed heater 11 with respect to a location where the heating temperature is desired to be set higher. The coil inner diameter 16 of the metal pipe 12 is set so that the distance to the coil 31 is small and the distance is large for a portion where the heating temperature is desired to be set low (step S6).

  By forming the coiled sheathed heater 11 as described above, the predetermined area of the heating object 31 can be heated more than the other areas. This is because the form of heating the heating object of the sheathed heater uses radiant heat transfer.

  The heat flow rate applied to the heating object 31 is determined by the distance between the surface of the metal pipe 12 and the heating object 31 (see (Equation 1) and (Equation 2)). According to (Equation 1) and (Equation 2), it is clear that even if the initial temperature relationship between the surface of the metal pipe 12 and the heating object 31 is the same, the amount of heat received by the heating object 31 varies depending on the distance. It is. That is, by forming the sheathed heater in a coil shape and changing the coil inner diameter 16 of the coiled sheathed heater 11 for each part, the heat flow rate q received by the heating object 31 changes depending on the part, and thereby the heating temperature Can be changed locally.

In equation (1), q is the amount of heat heating object 31 in the straight pipe shape is subjected, epsilon is emissivity, sigma is the Stefan-Boltzmann constant, T _h is the surface temperature of the metal pipe 13, T ₀ is heated in straight shape This is the initial temperature of the object 31. F is a form factor and is a numerical value mainly determined by the distance and arrangement between the heated object and the object to be heated.

  Here, as an example, the form factor F with the parameters shown in FIG.

L ₁ and L ₂ are the dimensions of the heated object and the object to be heated, and h is the distance between them.

FIG. 4B shows the shape factor F obtained when L ₁ = L ₂ = 10 mm and h = 10 mm. It can be seen that as the distance h between the heated object and the object to be heated increases, the form factor F decreases rapidly. Although this can be predicted to some extent by using mathematical formulas, it is effective to tabulate the form factors of the sheathed heater and the heating object that are actually used.

  In the first embodiment, the heat flow rate q applied to the object to be heated can be changed by changing the coil inner diameter 16 (distance h) of the coiled sheathed heater 11. By this effect, the area | region used as a different heating temperature can be given to the surface of a heating target object. Furthermore, this Embodiment 1 is an effective means when the width dimension of the coiled sheathed heater 11 has restrictions so that it may not contact with the heating target 31 during heat processing.

(Embodiment 2)
Embodiment 2 of the present invention will be described with reference to a flowchart showing manufacturing steps when manufacturing the sheathed heater shown in FIG. As shown in the procedure shown in FIG. 2B, the processes S1 to S5 are the same as in the first embodiment. After the metal pipe 12 is formed in a coil shape, the coil pitch 17 of the coiled sheathed heater 11 is set. Change (step S7). Thus, forming the sheathed heater also exhibits the same effect as that of the first embodiment (see FIG. 5).

  That is, from the above-described (Equation 2), in the portion where the coil pitch 17 of the coiled sheathed heater 11 is dense, the heating object 31 receives a large amount of heat from the surface of the metal pipe 12 in which a plurality are closely arranged. become. Moreover, in the part where the coil pitch 17 of the coiled sheathed heater 11 is sparse, the distance between the metal pipes 12 is increased, and the amount of heat received by the heating object 31 from the surface is reduced.

  In the second embodiment, since the heat flow rate radiated from the sheathed heater 11 to the heating object 31 is changed by changing the coil pitch 17, the heat input per unit area of the surface of the heating object changes. Due to this effect, different heating temperature regions can be given to the surface of the object to be heated. Furthermore, this Embodiment 2 is an effective means when the diameter dimension of the coiled sheathed heater 11 has restrictions so that it may not contact with the heating target object 31 during heat processing.

(Embodiment 3)
FIG. 6 is a diagram showing a coiled sheathed heater and a partial cross-sectional view thereof according to Embodiment 3 of the present invention. In the third embodiment, the dimensions (width, diameter) of the sheathed heater 11 are not particularly limited because they do not come into contact with the heating object 31 during the heat processing described in the first and second embodiments. Embodiments 1 and 2 are combined. The coil inner diameter 16 and the coil pitch 17 of the coiled sheathed heater 11 are changed simultaneously. Thereby, the area | region which can obtain a bigger heating temperature difference can be given to the heating target object 31.

(Embodiment 4)
FIG. 7 is a view showing an example applied to the glass tube heating bending process in Embodiment 4 of the present invention. The coiled sheathed heater 11 of each of the embodiments described above can be applied to a process of heating and bending a pipe-shaped glass tube 71 as shown in FIG.

  The glass tube heat bending process mainly consists of a heating process and a moment application process, but the part where the glass tube is heated and bent must be cooled to the softening point or lower in the next stage. .

  In the case where the inner diameter of the coiled sheathed heater 11 is constant, the portion where the bending process has already been performed is also heated, and a problem that the intended portion of the glass tube does not bend occurs. If the shape proposed in the present invention is used, it is possible to sufficiently carry out the preheating before heating, and it is possible to prevent excessive heating from being performed on the location after the end of bending.

  As shown in FIG. 7, a pipe-shaped glass tube 71 is disposed inside the coiled sheathed heater 11 (in this example, the shape of the first embodiment). When the coiled sheathed heater 11 is energized, it moves in the negative x-axis direction (arrow m), performs a circular motion of bending R at the bending R forming portion 72 of the glass tube 71, and simultaneously a bending moment 73 is applied to the glass tube 71. Is granted. Then, it moves in the y-axis positive direction.

At this time, the following three conditions are necessary.
(Condition 1) The glass tube 71 is sufficiently heated immediately before the coiled sheathed heater 11 passes through the bent R-formed portion 72.
(Condition 2) Bending deformation occurs due to the bending moment 73 that reaches and is applied to the softening point at the bending R forming portion 72.
(Condition 3) After the passage through the coiled sheathed heater 11, the bent R-formed portion 72 bent in advance is immediately cooled so as not to be deformed by heating.

  In order to satisfy these conditions, a coil shape is provided such that the inner diameter decreases in the direction of movement of the coiled sheathed heater 11. Accordingly, since the distance 18 between the coiled sheathed heater 11 and the glass tube 71 is small at the stage before bending, a larger amount of heat is given to the glass tube 71, and the distance 18 ′ becomes large at the stage after bending. Do not give a large amount of heat.

  Specifically, the diameter of the metal pipe 12 of the coiled sheathed heater 11 is 2.0 mm, and the coil pitch of the coiled sheathed heater 11 is uniform at 2.2 mm. Further, the number of turns of the coiled sheathed heater 11 is 4 so as not to contact the glass tube 71 during the bending process. The coiled sheathed heater 11 has an average inner diameter of 6.5 mm, a maximum inner diameter of 8.0 mm, and a minimum inner diameter of 5.0 mm. The movement speed of the coiled sheathed heater 11 was set to 1.0 mm / sec at the straight line portion and 0.05 rad / sec at the bending R forming portion. That is, the inner diameter of the coiled sheathed heater 11 has a relationship of maximum inner diameter: average inner diameter: minimum inner diameter = 16: 13: 10.

  The object to be heated is a glass tube 71 (borosilicate glass) having an outer diameter of 4.0 mm and an inner diameter of 3.0 mm. The bending R after the heat bending process is 10.0 mm. A solid line (A) in FIG. 8 is obtained by numerical analysis of the temperature profile of the bent R-formed portion 72. A broken line (B) in FIG. 8 is a temperature profile of the bending R forming portion 72 when the inner diameter of the coiled sheathed heater 11 is made uniform by 6.5 mm.

  In the coiled sheathed heater 11 of the present invention, it can be seen that the glass softening point is reached when the bending moment is applied, and the temperature rapidly decreases thereafter.

  As described above, the coiled sheathed heater 11 of the present invention receives the object to be heated by forming the sheathed heater in a coil shape without complicating the internal structure of the heater and changing the coiled inner diameter and pitch. The amount of heat is changed.

  The coiled sheathed heater 11 of the present invention has a particularly remarkable effect when a cold cathode tube for a liquid crystal backlight is bent. This is because a cold cathode tube used for a liquid crystal backlight is greatly affected by variations in brightness, and the processing accuracy of the bent portion of the bent cold cathode tube is important. By bending the cold cathode tube for the backlight of the liquid crystal using the coiled sheathed heater 11 of the present invention, it is possible to bend by controlling the amount of heat received by the cold cathode tube, and bending cooling with little variation in brightness. It becomes possible to make a cathode tube.

  The coiled sheathed heater in the present invention is formed by forming a metal pipe into a coil shape without complicating the internal configuration of the metal pipe into which the heating wire is inserted, and changing the formed coiled coil inner diameter and coil pitch. The amount of heat received by the object to be heated can be changed, local heating of the object to be heated can be realized, and it can be used for heat bending processing of glass or thermoplastic resin.

DESCRIPTION OF SYMBOLS 11 Coiled sheath heater 12 Metal pipe 13 Heating wire 14 Electrical insulation powder 15 Electrode rod 16 Coil inner diameter 17 Coil pitch 18, 18 'Distance 31 Heating object 71 Glass tube 72 Bending R molding location 73 Bending moment

Claims (6)

In a sheathed heater comprising a heating wire therein and an electrically insulating powder filled around the heating wire,
A sheathed heater, characterized in that the coil inner diameter of the coiled metal pipe is partially different. In a sheathed heater comprising a heating wire therein and an electrically insulating powder filled around the heating wire,
A sheathed heater, wherein the coil pitch of the coiled metal pipe is partially different. In a sheathed heater comprising a heating wire therein and an electrically insulating powder filled around the heating wire,
A sheathed heater, wherein the coiled metal pipe has a partially different coil inner diameter and coil pitch.   The sheathed heater according to claim 1, wherein a coil inner diameter of the coiled metal pipe satisfies a relationship of maximum inner diameter: average inner diameter: minimum inner diameter = 16: 13: 10.   A heating method using a sheathed heater, wherein the sheathed heater according to any one of claims 1 to 4 is used to form two or more different heating temperature regions on an object to be heated.   The heating method using a sheathed heater according to claim 5, wherein the object to be heated is a cold cathode tube for a backlight of liquid crystal.

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