JP2003288978A - Microwave irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave irradiation device enhancing strength of an electric field by throttling a microwave beam and heating a ceramic to a joinable high temperature by increasing a density of power. <P>SOLUTION: The microwave irradiation device has a high frequency microwave source 13 for generating a high frequency microwave; a mode converter for converting an in-wave guide transmission mode from this high frequency microwave source to a beam-like transmission mode in the air and reflecting the high frequency microwave of the beam-like transmission mode to irradiate an object to be irradiated; and a low frequency microwave source 31 for generating the low frequency microwave and irradiating the objects to be heated (object to be irradiated) 20, 21 with the low frequency microwave. The irradiation to the objects 20, 21 to be heated with the microwave is carried out by the high frequency microwave source 13 and the low frequency microwave source 31. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave irradiation device for joining ceramics to each other by utilizing microwave heating.

[0002]

2. Description of the Related Art As a first conventional ceramics joining technique, for example, there is one relating to a microwave irradiator disclosed in Japanese Patent Publication No. 02-62516. In that bulletin,
The structure of the microwave irradiation device (ceramic bonding device) is shown in FIG. In FIG. 7, I is a microwave generating means, II is a cavity resonator, III is a pressurizing means for applying a compressive force to the joint surface of ceramics, IV is a temperature control means, 20 is ceramics, and 201 is ceramics. Bonding surfaces, 202 indicate both ends of the ceramic.

Next, the operation will be described. Microwaves sent from the microwave generator are cavity resonators.
Guided by II. The cavity resonator II has a high unloaded Q value and is designed to resonate with a large electric field strength. The ceramics 20 is located in a portion where the electric field strength of the electric field in the resonance state is maximum so that the joint surface 201 is parallel to the vibration direction of the electric field. Since the electric field distribution in the cavity resonator II is large at the central portion and small at both ends thereof, the temperature of the junction 201 becomes maximum, and by forming a temperature distribution in which the temperature drops sharply toward both ends 202. , The joint is heated to a high temperature to join. When the ceramic is alumina, for example, the microwave absorption coefficient of alumina increases sharply from around 1000 ° C, so positive feedback is applied to further accelerate the temperature rise and the electric field distribution causes a temperature distribution. Is further emphasized, and the difference between the temperature at the joint and the temperature at both ends is increased. Further, it is considered that the temperature control means IV cools both end portions in order to forcibly form such a temperature distribution from the outside.

Next, the second conventional ceramics joining technique will be described. FIG. 8 is a diagram of a main part of the microwave heating apparatus disclosed in Japanese Patent Laid-Open No. 4-137391. Figure 8
In the figure, 1 is a beam-shaped microwave generator, 2 is a microwave beam, 3 is a microwave focusing device, 4 is an entrance, and 5
Is a first reflector, 6 is a second reflector, and 7 is an object to be heated. Here, the operation of the apparatus will be described. The microwave beam 2 generated by the beam-shaped microwave generator 1 enters the microwave focusing device 3 through the entrance 4,
It is reflected by the first reflector 5 and the second reflector 6 and travels back and forth between the two reflectors. Since it passes through the heated body 7 during that time, the heated body 7 is heated at that time.

[0005]

As described above, the ceramics bonding apparatus according to the first conventional ceramics bonding technique is configured to always irradiate the ceramics with microwaves for heating in the cavity resonator. There is. Therefore,
There are restrictions on the size and shape of the target ceramics,
There was a problem that it was not suitable for practical use. Further, there is a problem that a portion that does not fit in the cavity resonator is not heated, so that the temperature does not rise, the temperature difference in the ceramic becomes large, and the ceramic is easily cracked.

Further, the second conventional ceramics joining apparatus using the ceramics technique heats the object to be heated while reciprocating the microwaves between the plurality of reflectors, but in reality, the object to be heated is heated. The microwaves are reflected or refracted by the heat treatment, so there is a problem that the effect of heating the microwaves by repeatedly passing through the object to be heated is not obtained as expected. However, there is a problem in that the temperature difference in the object to be heated becomes large and cracks easily because it is difficult. Further, in any of the conventional techniques, there is no method for judging whether or not the joining of the objects to be heated is completed, and there is a problem that it is not practical.

Therefore, the present invention has been made to solve such a problem, in which a microwave is propagated in the form of a beam, and the microwave beam is further narrowed to increase the electric field strength and the power density. By doing so, it is an object of the present invention to provide a novel microwave irradiation device capable of heating ceramics to a high temperature at which they can be bonded without using a cavity resonator. Further, the present invention is
While expanding the range of choices for the shape and size of the target ceramics, we aim to put it into practical use, reduce the temperature difference inside the heated object during heating, and prevent cracking and destruction of the heated object.
Another object of the present invention is to provide a novel microwave irradiating device capable of reliably joining ceramics by providing a means for detecting the completion of joining.

[0008]

A microwave irradiator according to a first aspect of the present invention includes a high frequency microwave source for generating a high frequency microwave and a propagation mode in a waveguide from the high frequency microwave source to a beam-like propagation mode in the air. A mode converter that converts and reflects the high frequency microwave of the beam-like propagation mode to irradiate the irradiation target, and a low frequency microwave that generates low frequency microwave and irradiates the irradiation target with the low frequency microwave. A microwave source, and the microwave is irradiated to the irradiation target by the high frequency microwave source and the low frequency microwave source.

The microwave irradiator according to claim 2 is
A microwave source that generates microwaves, a mode converter that converts the propagation mode in the waveguide from the microwave source into a beam-like propagation mode in the air and irradiates the irradiation target with microwaves, and heats the irradiation target And heating the irradiation target by the heating unit, and irradiating the irradiation target with the microwave from the microwave source.

A microwave radiating device according to a third aspect of the present invention is the microwave radiating device according to the first or second aspect, wherein the mode converter includes an antenna that reflects microwaves and is rotatably arranged around a central axis of the antenna. belongs to.

The microwave irradiator according to claim 4 is
4. The object according to claim 1, wherein the object to be irradiated is arranged on a rotatable pedestal.

A microwave irradiating device according to a fifth aspect of the present invention is the microwave radiating device according to any one of the first to fourth aspects, wherein the object to be irradiated is a ceramic material for bonding ceramics to each other.

A microwave irradiator according to a sixth aspect of the present invention is a high-frequency microwave source for generating high-frequency microwaves, and a waveguide propagation mode from the high-frequency microwave source is converted into a beam-like propagation mode in air, and the beam-like propagation mode is obtained. A mode converter that reflects a high-frequency microwave of a propagation mode to irradiate an irradiation target, a low-frequency microwave source that generates a low-frequency microwave and irradiates the irradiation target with a low-frequency microwave,
It is provided in the vicinity of the irradiated body, and is provided with a detection means for detecting the temperature of the irradiated body, and a control means for controlling the output of the high frequency microwave source by the detecting means.

The microwave radiating device according to a seventh aspect of the present invention is the microwave radiating device according to the sixth aspect, wherein the detecting means is a light receiving section for detecting the temperature of the object to be irradiated.

A microwave irradiating device according to an eighth aspect of the present invention is characterized in that the control means is controlled so as to reduce or stop the power supply of the high frequency microwave source.
As described in.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. Hereinafter, the first embodiment will be described with reference to FIGS. 1 and 2. Figure 1
FIG. 3 is a side view for explaining the microwave irradiation device according to the first embodiment. FIG. 2 is a front view thereof. In FIG. 1 and FIG. 2, 11 is an electron tube such as a gyrotron that oscillates microwaves, 12 is a magnetic field generating device such as an electromagnet that forms a magnetic field necessary for the operation of the electron tube 11, and 13 is the electron tube 11 and a magnetic field. Generator 12 and electron tube 1
1 is a high-frequency microwave source including a power source (not shown) for supplying electric power to the unit 1. Reference numeral 14 is a plate for attaching an antenna or curved mirror described later, 15 is an antenna with which the curved mirror is irradiated with microwaves propagating through the waveguide, 16
Is a mirror support for supporting the curved mirror, and 17 is an antenna 1.
A curved mirror that reflects the microwave radiated by 5 into a beam shape and irradiates the object to be heated. Reference numeral 18 denotes a housing for preventing the microwave from leaking to the outside of the apparatus.
Reference numeral 9 is an arrow indicating the state of microwave propagation. Reference numeral 40 is a mode converter including a plate 14, an antenna 15, a mirror support 16, and a curved mirror 17.

Further, 20 and 21 are objects to be irradiated (hereinafter also referred to as objects to be heated) such as ceramics which are heated and joined by microwave irradiation, and 22 are objects to be heated 20, 21.
Is a heating jig for maintaining an appropriate positional relationship, 23 is a pedestal on which the objects to be heated 20, 21 and the heating jig 22 are placed, 24 is a roller for allowing the pedestal 23 to move smoothly,
Reference numeral 25 is a roller shaft, and 26 is a bearing of the shaft 25. 27
Is a mount on which the electron tube 11 and the magnetic field generator 12 are placed. Reference numeral 31 is a low-frequency microwave source that efficiently outputs microwaves at a frequency lower than that of a gyrotron such as a magnetron. Reference numeral 32 is a waveguide for guiding the microwave output from the low frequency microwave source 31. Further, reference numerals 33 and 34 in FIG. 2 prevent the microwave from leaking out of the device, and the objects to be heated 20, 2 are heated.
It is a door for putting 1 in and out.

Next, the operation of the microwave irradiation apparatus according to the first embodiment will be described. The electron tube 11 receives electric power from a power supply device (not shown) and magnetic field from the magnetic field generation device 12, and outputs microwaves. The frequency of this microwave is, for example, 24.125 GHz. This frequency is a frequency assigned for use in industrial applications and has a wavelength of 12.4 mm. This microwave is emitted from the electron tube 11, reaches the antenna 15, and irradiates the curved mirror 17. The curved mirror 17 is designed to have a shape in which the microwave is reflected in a beam shape as shown by an arrow 19 and at the same time, the heated objects 20 and 21 are focused. The objects to be heated 20 and 21 are arranged so that the joining portions of the objects to be heated 20 and 21 are located at positions where they are subjected to microwave irradiation, and the parts to be heated are joined by heating.

When microwave heating is performed by the microwave irradiation apparatus according to the first embodiment, the diameter of the microwave beam at the focus of the microwave can be narrowed down as the wavelength of the microwave becomes smaller. it can. An electron tube often used in this technical field is a magnetron, but the frequency of the magnetron is often 2.45 GHz, and the frequency of the microwave used in the ceramics bonding apparatus according to the present invention is 24.125 GHz. Since it is about 10 times that, the wavelength can be reduced to about 1/10, that is, the beam diameter can be narrowed to 1/10. Therefore, it means that a microwave beam having a higher power density can be obtained.

The temperature reached by the microwave heating of the object to be heated is determined by the power density of the incident microwave and the ambient temperature. That is, even if the ambient temperature is low, the reached temperature can be easily increased to a high temperature if the microwave power density is high. For example, using alumina as the object to be heated and oscillating a microwave of about 3.6 kW with a gyrotron,
If the diameter of the microwave beam is reduced to about 50 mm, the surface temperature of alumina will reach about 1380 ° C in about 1 minute. Since microwave heating is internal heating, the internal temperature at this time is even higher than the surface temperature.
It means that the temperature is over 00 ℃.

From the low frequency microwave source 31,
For example, 2.45 GHz microwave is supplied. The electric field generated by the microwaves is widely distributed in the housing 18 and heats a microwave-absorbing object therein, as in a household microwave oven. Therefore, the objects to be heated 20 and 21 are heated almost uniformly by the microwave of the low frequency. The object to be heated 20 in this state,
By irradiating 21 with a microwave beam of a higher frequency, the temperature difference within the objects to be heated 20, 21 becomes smaller. Ceramics are cracked or broken during heating because a large temperature difference occurs in the ceramics and stress is generated due to the difference in expansion. Therefore, if the temperature difference in the ceramics is reduced, cracking or breakage is less likely to occur.

As described above, according to the first embodiment of the present invention, it is possible to bond the ceramics to be heated without using the cavity resonator used in the conventional technique of this type. Since it can be heated up to the temperature, the range of selection of the size and shape of the target heated object is greatly expanded, and if the heating jig has the function of rotating the heated object, the micro object can be rotated while rotating the heated object. Since it is also possible to perform wave irradiation, it is possible to provide a ceramics bonding apparatus that can be used for various purposes. Further, according to the first embodiment, since the heating by the microwave of the low frequency is also used, it is possible to reduce the temperature difference inside the object to be heated, and it becomes difficult for the object to be heated to crack or break. If a magnetron is used as a low-frequency microwave supply device, the magnetron is generally a highly efficient electron tube, so for example, part of the heating is handled by the magnetron compared to the case of heating to the junction temperature only with a gyrotron. As a whole, a device with high power efficiency can be obtained.

Here, in FIG. 2, the door has only one entrance and one exit, but if this door is a double door, the high-frequency and low-frequency microwave sources will be used even when the object to be heated is taken in and out of the apparatus. It is possible to obtain a microwave irradiation device that can be continuously operated without stopping.

Embodiment 2. Next, the microwave irradiation apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a configuration diagram for explaining the second embodiment. In FIG. 3, the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding portions, and thus the description thereof will be omitted. In the second embodiment, the electron tube 11 is placed vertically so that the microwave beams 19 are finally irradiated to the objects to be heated 20, 21 from the lateral direction. In this way, as shown in FIG. 3, the heated objects 2 in the stacked state are
Microwaves can be conveniently irradiated to 0 and 21. Therefore, there is an advantage that a jig for joining can be omitted. Further, by using the pedestal 23 as a rotating table, it becomes easy to heat the objects to be heated 20, 21 while rotating them, and it becomes possible to make the bonding strength uniform over the entire bonding surface. It should be noted that the fact that uniform bonding can be obtained by irradiating microwaves while rotating the objects to be heated 20, 21 is not limited to the second embodiment, and similar effects can be obtained in other embodiments. Can be obtained.

Embodiment 3. Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a configuration diagram for explaining the third embodiment. 4, the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding portions,
The description is omitted. Embodiments 1 and 2 described so far
In the above, a low frequency microwave source such as a magnetron is used to heat the whole of the objects to be heated 20, 21, but the configuration may be made as in the third embodiment. That is,
In FIG. 4, reference numeral 36 is a heater for heating the housing 18 and the space inside the housing 18, and 37 is a heater control device for controlling the current passed through the heater. The heater 36 is provided in the housing 1
Since the inside of 8 is heated to a certain temperature, the object to be heated that has entered the inside of the apparatus is heated and its temperature rises to that temperature. By doing so, even when the joining portion is locally heated by the microwave beam, the temperature difference in the heated body becomes small, and cracking or breakage hardly occurs. Although not shown in FIG. 4, if the housing 18 is covered with a heat insulating material or the like, the effect of suppressing the power consumption can be obtained.

The heater temperature may be determined in consideration of the following. That is, if the heater temperature is too low, the temperature difference inside the heated object cannot be reduced, and it becomes difficult to suppress cracking or destruction. Further, if it is too high, the heater material becomes expensive, and at the same time, the heater material needs to be replaced in a relatively short period, resulting in maintenance costs. Considering these things, the optimum heater temperature is determined. Even with such means, it is possible to provide a ceramics bonding apparatus in which cracking or breakage is unlikely to occur.

An example of the idea for properly using the heater and the low frequency microwave source described in the first embodiment will be described below. Since the housing is heated to a high temperature when a heater is used, a material that does not easily deteriorate even at high temperatures is required as a material for the housing, but such a material is generally expensive. Therefore, when it is not necessary to raise the temperature of the housing so much, that is, when ceramics is a material that can be bonded at a relatively low temperature, using a heater can reduce power consumption and cost of the entire device. There is.
The advantage of using the low-frequency microwave source is that the temperature of only the object to be heated rises, so that the housing and the like can be made of easily available materials.

Fourth Embodiment Next, a microwave irradiation apparatus according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 5 is a configuration diagram for explaining the fourth embodiment. In FIG. 5, the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding portions, and thus the description thereof will be omitted. In FIG. 5, reference numeral 41 denotes a light receiving portion of temperature measuring means such as a radiation thermometer for measuring the temperature of the object to be heated, and 42 denotes a part of temperature measuring means for propagating infrared rays received by the light receiving portion. An optical fiber, 43 is a body of temperature measuring means and a control device for calculating the temperature from infrared rays propagated by the optical fiber and controlling the output of the high frequency and low frequency microwave sources, 44 is a signal line, and 45 is a high frequency microwave source. A power source constituting the unit, 46 is a power line for sending power from the power source to the electron tube 11.

In the fourth embodiment having such a configuration,
A means for detecting and determining that the joining of the objects to be heated is completed will be described. The temperature and heating pattern required for joining various materials to be heated are preliminarily input as data to the control device 43.
During operation, the driver inputs what the material to be joined is. The controller 43 controls the high-frequency and low-frequency microwave source 1 according to the previously input data.
3 and 31 are activated. At this time, the output power of the high frequency and low frequency microwave sources is controlled while simultaneously monitoring the temperature of the object to be heated by the temperature measuring means. And
For example, when the object to be heated is alumina, the temperature is raised to 1700 ° C. and the temperature is maintained at 1700 ° C. for about 3 minutes. If the temperature of the heated object changes according to the data entered in advance,
At that time, it is detected and judged that the joining is completed, and thereafter, the microwave power is lowered to gradually lower the temperature of the object to be heated. By doing so, the first embodiment
In addition to the effect obtained in (1), it becomes possible to provide a ceramics bonding apparatus capable of reliably bonding various materials.

Embodiment 5. Next, a microwave irradiation apparatus according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 6 is a configuration diagram for explaining the fifth embodiment. 6, the same reference numerals as those in FIG. 1 and FIG. 2 indicate the same or corresponding portions, and the description thereof will be omitted. In the fifth embodiment, the mode converter 40 has a structure capable of rotating around the central axis of the antenna 15 by, for example, driving a motor. By doing this, even if the joint is long,
Since the irradiation position of the microwave beam can be moved by rotating the mode converter 40, the selection range of the shape of the target object to be heated further increases.

[0031]

As described above, according to the present invention, the electric field strength is increased by narrowing down the microwave beam,
By increasing the power density, it is possible to heat the ceramics to a high temperature at which they can be bonded without using the cavity resonator.

Further, according to the present invention, the range of selection of the shape and size of the target ceramics is expanded and the ceramics are put into practical use to reduce the temperature difference in the heated body during heating and to heat the heated body. The effect of being able to prevent cracking and destruction of

Further, according to the present invention, by providing a means for detecting / determining the completion of joining, it is possible to reliably join the ceramics.

[Brief description of drawings]

FIG. 1 is a side view of a microwave irradiation device according to a first embodiment.

FIG. 2 is a front view of the microwave irradiation device according to the first embodiment.

FIG. 3 is a configuration diagram of a microwave irradiation device according to a second embodiment.

FIG. 4 is a configuration diagram of a microwave irradiation device according to a third embodiment.

FIG. 5 is a configuration diagram of a microwave irradiation device according to a fourth embodiment.

FIG. 6 is a configuration diagram of a microwave irradiation device according to a fifth embodiment.

FIG. 7 is a configuration diagram showing a first microwave irradiation device according to a conventional technique.

FIG. 8 is a configuration diagram showing a second microwave irradiation device according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microwave generator, 2 ... Microwave beam, 3 ... Microwave focusing device, 4 ... Inlet, 5 ... 1st reflector,
6 ... 2nd reflector, 7 ... Heated object, 11 ... Electron tube, 12
... Magnetic field generator, 13 ... High frequency microwave source, 14 ...
A plate for attaching a mirror, 15 ... Antenna, 16 ...
Mirror support, 17 ... Curved mirror, 18 ... Housing, 19 ...
Arrows showing the state of microwave propagation, 20, 21 ... Object to be heated, 22 ... Heating jig, 23 ... Pedestal, 24 ... Roller,
25 ... Roller shaft, 26 ... Bearing, 27 ... Stand, 31 ...
Low frequency microwave source, 32 ... Waveguide, 33, 34 ...
Door, 36, 36 ... Heater, 37 ... Heater control device, 40
... Mode converter, 41 ... Light receiving part of temperature measuring means,
42 ... Optical fiber, 43 ... Main body and control device, 44 ...
Signal line, 45 ... Power source forming part of high-frequency microwave source, 46 ... Power line

Claims (8)

[Claims] 1. A high-frequency microwave source for generating high-frequency microwaves and a waveguide propagation mode from the high-frequency microwave source are converted into a beam-like propagation mode in the air, and the high-frequency microwaves in the beam-like propagation mode are reflected. And a low-frequency microwave source for generating a low-frequency microwave and irradiating the irradiated body with a low-frequency microwave. The high-frequency microwave source and the low-frequency microwave A microwave irradiating device, wherein a microwave source irradiates the object to be irradiated with microwaves. 2. A microwave source for generating microwaves,
The microwave source has a mode converter that converts the propagation mode in the waveguide into a beam-like propagation mode in the air to irradiate the irradiation target with microwaves, and a heating unit that heats the irradiation target. A microwave irradiating device, wherein the object to be irradiated is heated by a heating means and the microwave from the microwave source is applied to the object to be irradiated. 3. The mode converter comprises an antenna that reflects microwaves and is rotatably arranged around a central axis of the antenna.
The microwave irradiator described in. 4. The microwave irradiation apparatus according to claim 1, wherein the object to be irradiated is arranged on a rotatable pedestal. 5. The microwave irradiation apparatus according to claim 1, wherein the irradiation target is a ceramic material for bonding ceramics to each other. 6. A high-frequency microwave source for generating high-frequency microwaves and a waveguide propagation mode from the high-frequency microwave source are converted into a beam-like propagation mode in the air, and the high-frequency microwaves in the beam-like propagation mode are reflected. And a low-frequency microwave source for generating low-frequency microwaves to irradiate the irradiated body with low-frequency microwaves, and a mode converter for irradiating the irradiated body with the low-frequency microwaves, A microwave irradiating device comprising: a detection unit that detects the temperature of the irradiation body; and a control unit that controls the output of the high-frequency microwave source by the detection unit. 7. The microwave irradiation apparatus according to claim 6, wherein the detection unit is a light receiving unit that detects the temperature of the irradiation target. 8. The microwave irradiating device according to claim 6, wherein the control unit controls the power supply of the high frequency microwave source so as to reduce or stop the power supply.