Heat generating unit, heat treatment device, and heater design method for heat treatment device

Abstract

To provide a heating section capable of absorbing microwave energy by an arrangement pattern and to provide a heat treatment apparatus capable of suppressing heating variations of an object to be heated and improving heating efficiency.SOLUTION: A heat treatment apparatus 1 includes a heater 9 installed on an inner wall of a chamber 4 and a microwave irradiation device 6 for irradiating an object to be heated 5 placed in the chamber 4 with microwave to execute hybrid heating by the heater and microwave. The heater 9 has a meander pattern in which an arrangement pattern periodically turns and a turn length L is set to such a length that energy absorption amount of microwave becomes at most a fixed range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat generating unit and a heat treatment apparatus for heating a heated portion, and more particularly to a heat treatment apparatus that performs hybrid heating of an object to be heated housed in a chamber using two heating means, namely, microwaves and a heater, and a heater design method for the heat treatment apparatus. [Background technology]

[0002] A typical heat generating part that heats a heated part is, for example, a heater provided in a chamber, which directly heats the heated part in the chamber from the outside.

[0003] In addition, in a device that uses microwaves to heat an object placed in a chamber instead of a heater, the microwaves penetrate into the inside of the object, making it possible to shorten the heating process time and save energy.

[0004] However, when an object is heated using only microwaves, a large amount of heat is dissipated from the object, causing a temperature difference between the inside and outside of the object, which may result in a deterioration in the quality of the object.

[0005] In view of this, a heat treatment apparatus has been proposed which performs hybrid heating using microwaves and other heating sources (Patent Document 1).

[0006] For example, in the hybrid heating heat treatment apparatus shown in Patent Document 1, a susceptor heated by microwaves as another heating source is provided in a chamber, and the object to be heated is heated from the inside by microwaves while the object to be heated is heated from the outside by the susceptor heated by microwaves, thereby achieving uniform heating of the object to be heated.

[0007] In addition, in the hybrid heating heat treatment device shown in Patent Document 2, a microwave absorber heated by microwaves as another heating source is provided on the side wall inside the chamber, and the object to be heated is heated from the inside by microwaves, while the microwave absorber heated by microwaves heats the object from the outside, thereby achieving uniform heating of the object to be heated. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2015-536434 [Patent Document 2] JP 2004-352595 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the devices shown in Patent Documents 1 and 2, microwave heating and indirect heating (heating the object to be heated indirectly by heating a microwave absorber placed in the chamber with microwaves) are performed, so the capacity of the microwave irradiation device becomes large and high costs are unavoidable.

[0010] The present invention aims to improve the heating efficiency by improving the configuration of the heating unit, and also aims to provide a heat treatment apparatus that suppresses unevenness in temperature rise of an object to be heated and improves the heating efficiency. [Means for solving the problem]

[0011] The heat generating portion of the present invention is characterized in that the arrangement pattern is a meandering pattern that turns periodically, and absorbs energy when irradiated with microwaves.

[0012] The arrangement pattern of the heat generating parts is a meandering pattern that turns periodically, and when microwaves are irradiated, the meandering pattern allows the heat generating parts to absorb microwave energy. Because the heat generating parts can absorb microwave energy and generate heat due to the meandering pattern, there is no need to provide a separate structure such as a susceptor for absorbing energy. In addition, the heat generating parts can easily be configured with an electric heater, etc., and in such a configuration, the heat generating parts can be heated by both the heater and microwaves. In addition, the meandering pattern allows the absorption of microwave energy to be suppressed, and thus microwaves can be used efficiently to heat the object to be heated.

[0013] In this way, the heating efficiency can be improved by adjusting the amount of microwave absorption.

[0014] By performing hybrid heating on the object to be heated, it is possible to suppress variations in temperature rise in the heated portion.

[0015] For the following reasons, by devising the shape of the meandering pattern, it is possible to solve the problem of microwave heating of the heater, that is, to suppress the loss of microwaves due to dielectric heating of the heater, thereby further improving the heating efficiency.

[0016] That is, as described later, various simulations were performed and it was found that there is a correlation between the wavelength (frequency) of the radiated microwaves and the heat generated by the heater. It was also found that there is a correlation between the shape of the heater and the heat generated by the heater for microwaves of the same wavelength. In other words, it is presumed that the heater behaves as an antenna for microwaves. If the performance as an antenna for the radiated microwaves is high, the microwave energy will be consumed as heat generated by the heater, and if the performance as an antenna is low, this consumption will be small.

[0017] In this invention, since the heater arrangement pattern is a meandering pattern, it is considered that the heater behaves as a meandering antenna. Therefore, by devising the shape of the meandering pattern, it is possible to reduce the performance as an antenna, prevent microwave energy from being consumed as heat generation by the heater, and increase the irradiation efficiency of microwave energy to the heated object, i.e., increase the heating efficiency of microwave energy to the heated object.

[0018] The heat treatment apparatus of the present invention includes a microwave irradiation unit that irradiates microwaves to an object to be heated in a chamber, and a heater including the heat generating unit, and performs hybrid heating of the object to be heated by microwaves and the heater. The heat generating unit of the heater is disposed in the chamber.

[0019] Furthermore, since the heat generating portion of the heater is disposed inside the chamber, the heat generating portion of the heater can heat the object to be heated more efficiently.

[0020] In addition, by making the arrangement pattern of the heat generating part of the heater a meandering pattern, the heater wiring becomes the pattern with the highest density. The heater output is determined by the length of the heater, so the desired output density can be easily obtained. The meandering pattern can be adjusted and arranged according to the dimensions and shape of the wall surface inside the chamber. This makes it possible to avoid making the structure inside the chamber complicated. And, by making the heater wiring dense, a heater with a desired heater output can be provided in a small space. Furthermore, when performing hybrid heating using microwaves and a heater, it is an issue to prevent the heater from being heated by the microwaves. In this invention, since the arrangement pattern of the heat generating part of the heater is a meandering pattern, it is possible to solve the issue that the amount of microwave energy absorption by the microwaves cannot be adjusted by devising the shape of the meandering pattern for the following reason, that is, it is possible to suppress the loss due to dielectric heating of the microwaves in the heater. This further improves the heating efficiency.

[0021] As described above, in this invention, the temperature rise variation of the heated part can be suppressed by hybrid heating. In addition, by disposing the heat generating part of the heater inside the chamber, the heating efficiency of the heated object by the heat generating part of the heater is improved. In addition, by making the heater arrangement pattern a meandering pattern, the shape can be devised to prevent microwave energy from being consumed as heat generated by the heater, and the heating efficiency can be further improved. In addition, there is an advantage that a mechanism for isolating the heater from microwaves is not required, the desired output density can be easily obtained, and the structure of the heat treatment device can be simplified.

[0022] In this invention, the length L of one turn, which is the sum of the length of one turn portion of the heater and the length of one straight portion, is set to a length such that the amount of microwave energy absorption by the heater is within a certain range.

[0023] When the heater is arranged in a meandering pattern, the challenge is to determine which part of the shape should be devised to reduce the amount of microwave energy absorbed by the heater without reducing the total length (area) of the heater wire. According to the results of a simulation analysis, it was found that the amount of energy absorbed can be varied by adjusting the length of one turn L, which is the sum of the length of one straight section and the length of one turn of the heater. Therefore, the length of one turn L is set to a length that keeps the amount of microwave energy absorbed by the heater within a certain range.

[0024] In the present invention, it is preferable that the length L of one turn is set to a length such that L / λ falls within a certain range with 0.5 as the center, where λ is the wavelength of the microwave.

[0025] More specifically, it is desirable to set the length L of one turn to a length such that L / λ falls within a range of 0.35 to 0.7, preferably 0.4 to 0.6, and more preferably 0.4 to 0.55. Effect of the Invention

[0026] According to this invention, the arrangement pattern of the heat generating parts is a meandering pattern that periodically turns, so that when microwaves are irradiated, the energy can be absorbed. Because the heat generating parts are capable of absorbing microwave energy and generating heat due to their meandering pattern shape, there is no need to provide a separate structure such as a susceptor for absorbing energy, and the device can be made smaller and the heat generation efficiency is improved. In addition, since the heat generating parts can easily be configured with electric heaters, etc., in such a configuration, the heat generating parts can be heated by both the heater and microwaves.

[0027] Hybrid heating can suppress variations in temperature rise in the heated area. In addition, by locating the heat generating part of the heater inside, the heating efficiency of the heat generating part of the heater for the heated object is improved.

[0028] In addition, the arrangement is a meandering pattern, and by devising the shape, it is possible to prevent microwave energy from being consumed as heat generation by the heater, further improving the heating efficiency. [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic structural diagram of a heat treatment apparatus according to an embodiment of the present invention; [Diagram 2] 1 shows a part of the arrangement pattern of meander-shaped heaters. [Diagram 3] Simulation results over a wide frequency range are shown. [Figure 4] Simulation results for four types of heater shapes are shown. [Diagram 5] Simulation results for three different heater geometries are shown. [Figure 6] Simulation results for four additional heater geometries are presented. [Figure 7] The simulation results for the degree of microwave absorption and the amount of heat generated are shown below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] 1 is a schematic structural diagram of a heat treatment apparatus according to an embodiment of the present invention, in which (A) is a front cross-sectional view of the heat treatment apparatus, and (B) is a diagram showing an arrangement pattern of heaters.

[0031] The heat treatment device 1 is provided with a chamber 4 composed of a heat insulating material 2 made of a material such as ceramic, and a metal cover 3 surrounding the heat insulating material 2, the cross section of which is formed into a hollow box shape. An object 5 to be heated is disposed within the chamber 4. The object 5 to be heated is a processing item that is heated by absorbing microwaves, and the material of the object 5 is not limited. In addition, a microwave irradiation device 6 that irradiates microwaves to the object 5 to be heated within the chamber 4 is disposed outside the chamber 4, and the microwave irradiation device 6 and the chamber 4 are connected by a waveguide 7.

[0032] In the illustrated example, the chamber 4 is provided with transport rollers 8 on which the object 5 to be heated is placed and transported in the forward and backward directions toward the paper surface. The transport rollers 8 are used as a means for transporting the object 5 to be heated to another chamber provided in the front or rear of the paper surface when the object 5 to be heated is continuously processed. It is also possible to process the object 5 to be heated alone in the chamber 4 without providing the transport rollers 8.

[0033] An electric heater (hereinafter, heater) 9 is provided on the inner wall of the chamber 4 of the heat treatment device 1. The heater wire, which is the heat generating part of the heater 9, is made of a metal such as Kanthal or Nichrome. In this example, the heater 9 is configured by arranging the heater wire on the upper inner wall and the left and right inner walls of the chamber 4 in FIG. 1, and generates heat by being supplied with power from an external power source (not shown). Hereinafter, this heater wire will be simply referred to as the heater 9. Also, as shown in FIG. 1(B), the heater 9 is a single heater wire arranged in multiple rows as a whole, and each row is made to meander. By making the arrangement pattern of the heater 9 into a multiple row meandering pattern in this way, the density is increased.

[0034] The heater 9 may be made of ceramics such as SiC, MoSi2, etc., in addition to Kanthal, Nichrome, etc. as its material.

[0035] It is also possible to use other heaters, such as a sheathed heater or a regenerative radiant tube burner, instead of heater 9, which generate heat when connected to an external heat source (electricity, gas, etc.) and whose exposed parts inside the chamber are made of metal or ceramic. In this case as well, the heat generating parts are disposed on the upper inner wall and the left and right inner walls of chamber 4.

[0036] In the above configuration, the heater 9 heats the object 5 from the outside by setting the atmospheric temperature in the chamber to a predetermined temperature, and the microwave irradiated from the microwave irradiator 6 heats the object 5 from the inside. This eliminates the temperature difference between the inside and outside of the object 5, uniformly heats the object, and suppresses the temperature rise variation of the heated part. In addition, by configuring the heater 9 as a metal-based electric heater made of nichrome or the like, the output is determined by the resistance value of the heater 9, that is, the length of the heater 9, so that the desired output density can be easily obtained. In addition, by making the arrangement pattern of the heater 9 a meandering pattern of multiple rows, the heater wiring becomes high density and the heating efficiency of the object to be heated is improved. And, by arranging the heater 9, which is a heat generating part, on the upper inner wall and the left and right inner walls of the chamber 4, it is not necessary to isolate the heat generating part of the heater from the microwave, and the heater 9 is arranged in the space irradiated with the microwave. Therefore, the heating efficiency of the object to be heated is improved from the viewpoint of this structure as well.

[0037] In this embodiment, the shape of the heater 9 is optimized so as not to absorb microwaves. As described above, the heater 9, which is arranged in a meandering pattern, is presumed to behave as a meander-shaped antenna for the irradiated microwaves. If the heater 9 has high performance as an antenna for the irradiated microwaves, the microwave energy is consumed as heat generation by the heater 9, and if the heater 9 has low performance as an antenna, the consumption is reduced.

[0038] The shape of the heater 9 is optimized on the premise that the heater 9 behaves as a meander-shaped antenna for microwaves, as described above. That is, as a result of the following consideration, it was found that the amount of microwave energy absorption by the heater varies by adjusting the length L of one turn (hereinafter sometimes simply referred to as the turn length L). Therefore, the turn length L is set to a length that keeps the amount of microwave energy absorption by the heater within a certain range.

[0039] Figure 2 shows a part of the arrangement pattern of meander-shaped heaters. In the figure, the turn length L is equal to the length L1 of one turn portion plus the lengths L2 and L3 of two straight portions on the top and bottom that connect to length L1. L2 and L3 are each half the length of one straight portion L4 that connects to length L1 of the turn portion. For convenience, hereinafter, the turn length L is defined as the length L1 of the turn portion plus the length of one straight portion L4.

[0040] The following is a specific example of a simulation in which the turn length L is the sum of the length of the turn portion L1 and the length of one straight portion L4. The simulation was performed in the configuration shown in Figure 1 without applying current to the heater.

[0041] First, a broad frequency simulation was performed as shown in FIG.

[0042] In Fig. 3(A), microwaves were irradiated onto a test heater wire (turn length L = 174 mm) with a meandering pattern, and the microwave frequency was swept to investigate the position where the VSWR peak appears. This investigation revealed that the first peak was the maximum. Note that the larger the VSWR value, the worse the heater's microwave absorption, i.e., the worse the antenna performance. From Fig. 3(A), the position of the first peak is approximately 0.8 GHz (λ = 375 mm). At this time, L / λ = 174 / 375 = 0.5. Fig. 3(B) shows the position where the VSWR peak appears when the frequency is swept with L / λ on the horizontal axis. From the same figure, the position where the first peak is the maximum is L / λ = 0.5.

[0043] In FIG. 3(A), L=174 mm, but even when L was changed, the peak was largest when L / λ=0.5.

[0044] From the above, the VSWR value can be maximized by determining the turn length L such that L / λ=0.5.

[0045] Next, to determine the shape of the turn length L, a simulation was performed using L1 and L4 (=L2+L3) as parameters as shown in Figures 4 and 5. For the sake of convenience, the turn portion L1 is referred to as the interval L5, and the straight portion L4 is referred to as the row width L4.

[0046] Figures 4 and 5 show the VSWR values ​​when the microwave frequency is swept for four types of shapes (1), (26), (79), and (13) (numbers indicate the shape number and have no particular meaning). Figure 4(B) shows the VSWR values ​​when the frequency is swept with L / λ on the horizontal axis for the four types of shapes (1), (26), (79), and (13).

[0047] In FIG. 4(A), from the VSWR values ​​of shapes (1), (26), (79), and (13), it can be seen that as the turn length L increases, the VSWR peak position moves toward lower frequencies.

[0048] In Figures 4(A) and (B), the VSWR values ​​of the shapes (26) and (79) show that for the same turn length L, the smaller spacing L5 results in a higher VSWR value.

[0049] 4A and 4B, the VSWR values ​​for shapes (1), (79), and (13) show that for the same spacing L5, the VSWR peak value is larger when the row width L4 is larger. Also, the VSWR peak value shifts to lower frequencies when the row width L4 is larger.

[0050] In addition, simulations were performed for three other shapes (5), (9), and (12) with the same turn length, as shown in Figures 5(A) and (B). In this example, too, the VSWR value was higher for the smaller spacing L5 with the same turn length.

[0051] Furthermore, simulations were performed for four other shapes (23), (17), (24), and (25) with the same spacing L4, as shown in Figures 6(A) and 6(B). In this example, as in Figures 4(A) and 4(B), with the same spacing, the VSWR peak value is larger for the larger row width L4, and the VSWR peak value for the larger row width L4 shifts to lower frequencies.

[0052] From the above simulation results, when the microwave frequency is 2.45 GHz, it can be seen that the shape (79) is preferable among the four types in Fig. 4 in terms of preventing microwave absorption. Moreover, among the three types in Fig. 5, shape (5) is preferable, and among the four types in Fig. 6, shapes (24) or (25) are preferable.

[0053] Also, from Fig. 4(B), Fig. 5(B) and Fig. 6(B), the absorption of microwaves can be prevented by setting the length L per turn so that L / λ is in the range of 0.35 to 0.7 with 0.5 as the center, preferably 0.4 to 0.6, and more preferably 0.4 to 0.55. That is, when the microwave frequency is 2.45 GHz, λ=122 mm, so that the length L per turn is 42.7 mm to 85.4 mm, preferably 48.8 mm to 73.2 mm, and more preferably 48.8 mm to 67.1 mm. Also, from Fig. 4 and Fig. 5, the interval L5 is preferably small. In practice, from the viewpoint of bending workability of the heater wire, the radius of the turn portion is preferably about 10 mm.

[0054] The reason why it is better for the interval L5 or the radius of the turn portion to be small is that, since the directions of the magnetic fields generated in the upper and lower straight portions L2 and L3 connected to the turn portion are opposite to each other, it is thought that the smaller the interval L5 or the radius of the turn portion, the smaller the distance between the straight portions of L2 and L3 becomes, and the easier it is to cancel these magnetic fields, i.e., the antenna efficiency decreases. In practice, from the viewpoint of bending workability of the heater wire, the radius of the turn portion is about 10 mm, preferably about 9 mm to 12 mm.

[0055] Since the length L of one turn is selected within the range of 42.7 mm to 85.4 mm as described above, once the radius of the turn portion, that is, the length L1 of the turn portion, is determined, the interval L4 is determined from L=L4+L1.

[0056] Figure 7 shows the results of a simulation showing the degree of microwave absorption (Figure 7(A)) and the amount of heat generated (Figure 7(B)) for the shapes (1) and (79) shown in Figure 4. The microwave frequency is 2.45 GHz.

[0057] As can be seen from the figure, when the frequency is 2.45 GHz, the VSWR value of shape (1) is 5, while the VSWR value of shape (79) is 80. As a result, the amount of heat generated by shape (79) is minimal compared to the amount of heat generated by shape (1).

[0058] In this way, in the present invention, by optimizing the shape of the heater 9 so as to reduce microwave absorption, it is possible to prevent the heater 9 from consuming the energy output from the microwave irradiation device 6, making it possible to configure a heat treatment device with good heating efficiency. Also, there is no need to provide a structure that isolates the heater 9 from microwaves. [Explanation of symbols]

[0059] 1-Heat Treatment Equipment 2- Insulation 3-Metal cover 4-Chamber 5-Heated object 6-Microwave irradiation device 9-Heater

Claims

1. A meandering pattern that is connected to a power source or heat source to generate heat and has a periodically turning arrangement pattern, The meandering pattern is A heat generating portion characterized in that a length L of one turn, which is the sum of the length of one turn portion of the meandering pattern and the length of one straight portion connected to this turn portion, is set in a shape such that L / λ is within a range of 0.35 to 0.7, when the wavelength of the microwave during microwave irradiation is λ.

2. 2. The heat generating portion according to claim 1, wherein the length L of one turn is set to a length such that L / .lambda. falls within a range of 0.4 to 0.

6.

3. 2. The heat generating portion according to claim 1, wherein the length L of one turn is set to a length such that L / λ falls within a range of 0.4 to 0.

55.

4. The heat generating portion according to any one of claims 1 to 3, wherein the heat generating portion is an electric heater.

5. A chamber that accommodates an object to be heated; A microwave irradiation unit that irradiates microwaves onto the object to be heated in the chamber; A heater including the heat generating portion according to any one of claims 1 to 4, A heat treatment apparatus, characterized in that a heat generating portion of the heater is disposed within the chamber.

6. A chamber that accommodates an object to be heated; A microwave irradiation unit that irradiates microwaves onto the object to be heated in the chamber; A heater. In a heat treatment apparatus, the heating parts of the heaters are arranged in the chamber in a meandering pattern that periodically turns, a length of one turn of the heat generating part plus a length of one straight section connected to the turn part, the length of the turn part being used as a parameter to determine an amount of energy absorption by the heater for the frequency of the microwave through a simulation, and to determine a length of the turn part at which the amount of energy absorption is reduced to within a predetermined range.

Images