JP3331279B2 - High frequency heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating apparatus for adjusting impedance matching between a magnetron and a heating chamber based on a detection signal of a directional coupler mounted on a rectangular waveguide wall. .

[0002]

2. Description of the Related Art As a conventional high-frequency heating apparatus of this type,
For example, as in the invention of JP-A-57-23494,
Three impedance adjusting rods are installed at a part of the inner wall of the rectangular waveguide connecting the magnetron and the heating chamber, at intervals of 1/4 of the guide wavelength of the transmitted microwave and along the traveling direction of the microwave. Then, using a driving device, the amount of protrusion of the impedance adjustment rods in the tube is controlled using a driving device so that the operating point of the magnetron approaches the maximum power region on the Rieke diagram for each food item installed in the heating chamber, and each food item is ejected. There has been proposed a method in which a heating operation is performed with the highest efficiency by storing an amount and recalling and using the stored content according to the type of food.

[0003]

In the above-mentioned prior art, three impedance adjusting rods as matching elements must be arranged in a rectangular waveguide at an interval of 1/4 of the guide wavelength. Since a driving device is required for each impedance adjusting rod, there is a problem that the structure becomes complicated. In addition, since it is necessary to take measures against leaked radio waves at the part where the adjustment rod penetrates the rectangular waveguide wall, the structure becomes larger and larger, and high-frequency heating, which is required to be smaller, such as a microwave oven, is required. There is a problem that it is difficult to apply to an apparatus. In addition, there is a problem that a reduction in reliability and a significant increase in cost cannot be avoided.

[0004] In addition, in the above-described conventional example, it takes too much time to drive and control the individual impedance adjusting rods to achieve matching as a high-frequency heating device.
There is a problem in that it is not practical for a consumer appliance that requires heating to be completed within a short time, such as a microwave oven.

In addition, since the impedance adjusting rod does not move other than the operation stored in advance, it is difficult not only to constantly obtain the optimum impedance matching for various foods having different shapes and different dielectric properties. It has a fatal disadvantage that it cannot cope with deviation of the impedance operating point that changes during heating.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a heating chamber for storing foods, a magnetron for oscillating microwaves outside the heating chamber, and one side. A rectangular waveguide connected to the magnetron and connected to the heating chamber on the other side to connect the magnetron and the heating chamber, a high-frequency power supply for driving the magnetron, and one wall of the rectangular waveguide. Direction between the connection to the magnetron and the connection to the heating chamber to detect the incident and reflected directional components of microwave power transmitted in the rectangular waveguide and output their detection signals And a fixed matching element made of a conductive material, which is mounted on the heating chamber side of the position where the directional coupler is mounted inside one wall of the rectangular waveguide and on the center line in the radio wave traveling direction. And a low-dielectric material rotatably penetratingly mounted at a position closer to the heating chamber than the position where the fixed matching element is mounted inside one wall of the rectangular waveguide and offset from the center line in the radio wave traveling direction. A variable matching element supporting shaft made of a lossy material, a variable matching element made of a conductive material attached to the variable matching element supporting shaft in a rectangular waveguide and driven to rotate, and the variable matching outside the rectangular waveguide; A rotation driving device that rotationally drives the element support shaft for a predetermined stroke and outputs information on a plurality of predetermined rotation driving positions during the driving stroke, and starts a magnetron oscillation by operating a high-frequency power supply device When the rotational driving device is operated, the variable matching element support shaft is rotationally driven, and the detection signal of the directional coupler for each of a plurality of predetermined rotational driving positions during the driving process. In addition to capturing and storing, in order to determine the optimum matching position of the rotary drive from the stored detection signal group, a specific detection signal in the detection signal group is found, and the detected rotary drive position of the detection signal High-frequency heating with a controller that controls the rotation drive device to rotate and drive the variable matching element support shaft within a predetermined rotation angle before and after the optimum matching position after rotating the variable matching element support shaft The device was configured.

Further, the order of mounting the variable matching element and the fixed matching element as viewed from the directional coupler is changed from the above-described order.

In addition, in each case, the distance from the center of the fixed matching element to the center of the variable matching element is set to be approximately １ ／ of the guide wavelength.

[0009]

When the high-frequency power supply device is operated to start the oscillation of the magnetron, the control device controls the rotary driving device to rotate the variable matching element support shaft for a predetermined stroke, and to perform a predetermined rotation during the driving stroke. The output signals of the directional coupler at the plurality of drive positions are captured and stored. The control device finds one detection signal from the stored signal group that determines that the magnetron and the heating chamber are in the best coupling state, that is, a detection signal that is determined to have impedance matching. After confirming the detected drive position, the drive device is driven to that position. Then, the variable matching element support shaft is rotationally driven within the range of a predetermined rotation angle before and after the optimum position.

In the present invention, since the variable matching element is mounted at a position deviated from the center line of the rectangular waveguide wall in the radio wave traveling direction, the stub when rotating the variable matching element support shaft is formed. Since the stub moves over a relatively large rotation angle, that is, over a relatively long distance, in a relatively large electric field strength region in the central portion of the rectangular waveguide, the magnetron and the heating based on the movement of the stub are used. This will have a significant effect on changes in chamber coupling. Furthermore, since the fixed matching element is provided on the center line in the direction of radio wave propagation between the directional coupler and the variable matching element support axis of the rectangular waveguide wall provided with the variable matching element support axis, Acts as a double stub tuner and contributes to achieving better matching over a wider range, ie, a wider range of foods.

In addition, both the variable matching element and the fixed matching element are provided on the load side as viewed from the magnetron, and the directional coupler includes an incident and reflected power component between the magnetron and the variable matching element or the fixed matching element. Is detected, efficient measurement of incident and reflected powers and impedance matching are performed.

When the order of mounting the variable matching element and the fixed matching element when the heating chamber is viewed from the position of the directional coupler is changed, the functions of the variable matching element and the fixed matching element are almost the same.

[0013] Further, since the distance between the variable matching element and the fixed matching element is apart from each other by about 1/4 of the guide wavelength, they both influence the coupling between the magnetron and the heating chamber in a mutually complementary manner. It contributes to the realization of a matched state.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. Reference numeral 1 denotes a metal heating chamber, and reference numeral 2 denotes a high-frequency power supply port provided on a side wall of the heating chamber 1. Numeral 3 is a magnetron, 4 is a high-frequency power supply for driving the magnetron 3, 5 is connected to the magnetron 3 on one side and connected to the heating chamber 1 on the other side.
Is a rectangular waveguide that connects the magnetron 3 and the heating chamber 1 by transmitting the high-frequency power generated in the above to the high-frequency power supply port 2 of the heating chamber 1.

Reference numeral 6 denotes a directional coupler, which is formed of a double-sided printed circuit board. The directional coupler is provided at substantially the center of the long side of the rectangular waveguide 5, that is, at the intermediate portion between the connection portion of the magnetron 3 and the connection portion of the heating chamber 1. It is mounted so as to be exposed to both high-frequency power oscillated from the magnetron toward the heating chamber 1 and high-frequency power reflected from the heating chamber and returned. Reference numeral 7 denotes a conductor loop for detecting microwaves in the rectangular waveguide 5 by a loop coupling method, and reference numeral 8 denotes a microstrip line for transmitting a signal related to microwave power coupled by the conductor loop 7, and 8a of these lines. Is a microstrip line for transmitting a signal relating to incident power in microwave power transmitted through the rectangular waveguide 5, and 8b is a microstrip line for transmitting a signal relating to reflected power. 9 is the microstrip line 8 (8
a, 8b) is a processing circuit for receiving, detecting, and smoothing the microwave transmitted to 8b).

Reference numeral 10 denotes a fixed matching element mounted on the center line of the ceiling wall in the rectangular waveguide 5 in the direction of radio wave propagation.

Numeral 11 denotes a variable matching element support shaft made of a low dielectric loss material (ceramic) which is rotatably penetrated and mounted at a position deviated from the center line of the ceiling wall of the rectangular waveguide 5 in the radio wave propagation direction. , 12 are the variable matching element support shafts 11
Is a variable matching element attached to the lower end. Numeral 13 denotes a disk base made of a conductive material constituting the variable matching element 12, and the variable matching element 13 has an outer diameter W which is set to approximately １ ／ of the guide wavelength of the microwave transmitted into the rectangular waveguide 5. It is attached to the support shaft 11 concentrically. Reference numeral 14 denotes a stub made of a conductive material, which is provided to protrude at a position deviated from the center of rotation of the disk base 13.

Reference numeral 15 denotes a rotation driving device such as a stepping motor for controlling the rotation angle by driving the variable matching element support shaft 11, and 16 denotes the directional coupler 6 and the rotation driving device 1.
5 and a control device connected to the high-frequency power supply device 4, which is constituted by a microcomputer. And 1
7 is a food and 18 is its saucer.

Note that the stub 14 is
And the variable matching element support shaft 11,
There is an advantage that units such as the disc base 13 and the rotary drive device 15 can be easily applied to high-frequency heating devices having different specifications.

When the food 17 is placed in the heating chamber 1 and the oscillation of the magnetron 3 is started, high-frequency power is supplied to the heating chamber 1 through the rectangular waveguide 5. Then, the dielectric heating of the food 17 is started.

Then, the control device 16 first controls the rotation driving device 15 to move the variable matching element support shaft 11 to, for example, 18.
It is driven to rotate at a predetermined angle of 0 degrees, that is, 1/2 rotation. In fact, the driving is such that the stub 14 attached at a position deviated from the rotation center of the disk base 13 moves more in the region where the electric field strength runs along the center line of the wall of the rectangular waveguide 5 in the direction of radio wave propagation. Thus, the drive stroke is determined.

The control device 16 fetches output signals relating to the incident and reflected powers of the directional coupler 6 at a plurality of predetermined rotational drive positions (rotation angle positions) during the rotational drive process, and They are stored as voltage standing wave ratio (VSWR) values for each position. Control device 16
Finds one detection signal (minimum value of the voltage standing wave ratio) that determines that the magnetron 3 and the heating chamber 1 are in the best coupling state from among those stored signal groups, and that is detected. The rotational drive position of the variable matching element support shaft 11, that is, the drive position of the rotary drive device 15 is confirmed, and the rotary drive device 15 is controlled so that the variable matching element support shaft 11 moves to the drive position.

Further, at an appropriate time thereafter, within a predetermined range (for example, a relatively small angle range of 5 degrees each before and after) around the rotational angle position determined to be the optimum coupling state, The variable matching element support shaft 11 is reciprocated and rotated so that the position of the optimum coupling state can be found again therein, so that fine impedance adjustment during cooking can be performed.

The optimum coupling state is a rotational angle position at which the reflection coefficient obtained from the input and reflected power values detected by the directional coupler 6 when the variable matching element 12 is rotationally driven is minimum and the incident power is maximum. The setting is performed by rotating the variable matching element support shaft.

The reason is that, as can be seen from the Rieke diagram of the operating impedance of the magnetron, the high-frequency output may differ depending on the phase even with the same reflection coefficient value. Is designed to operate the magnetron 3 with the highest efficiency by finding a point (position) where the incident power is maximum at the minimum reflection coefficient and at the maximum. This ensures that the food 17 stored in the heating chamber 1 is heated with the highest efficiency.

In addition, as compared with the case where the variable matching element support shaft 11 is provided without being deviated from the center line of the rectangular waveguide, the moving distance of the stub 14 is set at the center of the wall of the rectangular waveguide 5 in the radio wave traveling direction. Since it can be positioned in the region where the electric field strength is large in the region where the line runs, it is possible to exert a greater influence on the matching adjustment, that is, the adjustment of the coupling degree.

In addition, since the variable matching element and the fixed matching element are set apart from each other by about 1/4 of the guide wavelength, the two can be used as a double stub tuner to complement each other in matching the coupling between the magnetron and the heating chamber. Contributed and made it possible to match a wider range of foods.

Further, the food 17 is viewed from the magnetron 3.
Since the directional coupler 6, the fixed matching element 10, and the variable matching element 12 are mounted in this order on the side, it is possible to extremely efficiently measure the incident and reflected powers and adjust the matching.

In the above description, the variable matching element support shaft 11
Has been described only in the case of rotationally driving. However, if the amount of protrusion into the rectangular waveguide 5 is further controlled,
It is possible to perform finer control.

In the above-mentioned embodiment, the case where the quality of the matching is judged based on the voltage low wave ratio has been described. However, the present invention is not limited to this, and the judgment may be made based on the reflection coefficient obtained based on both the incident and reflected signals. Is possible. Furthermore, it is possible to make a determination by focusing only on the reflected signal.

Even if the order of mounting the variable matching element and the fixed matching element as viewed from the directional coupler is interchanged, the same excellent matching action is exerted on the coupling between the magnetron and the heating chamber.

[0032]

As described above, according to the present invention, the stub of the variable matching element can be moved within a region having a relatively large electric field strength in the rectangular waveguide. Then, the detection signals of the directional coupler for each of a plurality of predetermined drive positions in the process are stored, and then the best matching of the impedance of the heating chamber and the magnetron is obtained from the stored detection signal group. The drive position was found, the variable matching element was immediately moved to the drive position, and further fine-tuning was performed, so that the oscillation operating point of the magnetron moved to the matched high-efficiency operating point within a short time, and the efficiency was improved. Good high-frequency heating can be performed. Also,
The directional coupler, fixed matching element, and variable matching element are mounted in order on the load (food) side as viewed from the magnetron, so that extremely efficient measurement of the incident and reflected power by the directional coupler and the magnetron by the variable matching element And an extremely efficient coupling of the heating chamber. Furthermore, a double stub tuner is formed by the combination of the variable matching element and the fixed matching element, so that a wide matching region can be obtained, and excellent matching can be obtained over a wide range of loads. Above all, the present invention can greatly contribute to reducing the adverse effect on the life of the magnetron.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of an embodiment of the present invention.

FIG. 2 is a plan view of one surface side of a directional coupler used in the present invention.

FIG. 3 is a perspective view of a variable matching element used in the present invention.

FIG. 4 is a partially cutaway perspective view of a rectangular waveguide to which a variable matching element is attached.

FIG. 5 is a top view of a rectangular waveguide ceiling to which a variable matching element is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating room 3 Magnetron 4 High frequency power supply device 5 Rectangular waveguide 6 Directional coupler 7 Conductor loop 8 Microstrip line 9 Processing circuit unit 10 Fixed matching element 11 Variable matching element support shaft 12 Variable matching element 13 Disk base 14 Stub 15 Rotation drive device 16 Control device

Continuation of the front page (56) References JP-A-7-78681 (JP, A) JP-A-6-215871 (JP, A) JP-A-55-128293 (JP, A) JP-A-5-21526 (JP) , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H05B 6/70 F24C 7/02 511

Claims (3)

(57) [Claims] 1. A heating chamber (1) for storing a food (17).
And a magnetron (3) that oscillates microwaves outside the heating chamber, and connects the magnetron and the heating chamber by connecting the magnetron on one side and the heating chamber on the other side. A rectangular waveguide (5);
A high-frequency power supply (4) for driving the magnetron;
Each direction of incidence and reflection of microwave power transmitted into the rectangular waveguide, which is one wall of the rectangular waveguide and is attached between a connection with the magnetron and a connection with the heating chamber. A directional coupler (6) for detecting components and outputting their detection signals, and a position closer to the heating chamber than a position where the directional coupler is mounted inside one wall of the rectangular waveguide; A fixed matching element (10) made of a conductive material mounted on the center line in the radio wave traveling direction, and a position closer to the heating chamber than a position where the fixed matching element is mounted inside one wall of the rectangular waveguide; A variable matching element support shaft (11) made of a low dielectric loss material and rotatably penetrated at a position deviated from the center line in the radio wave traveling direction; and the variable matching element support shaft in the rectangular waveguide. Attached to A variable matching element (12) made of a conductive material which is driven to rotate, and a plurality of predetermined matching means for rotating the variable matching element support shaft for a predetermined stroke outside the rectangular waveguide and for the driving stroke. A rotary drive unit (15) for outputting information about a rotary drive position; and operating the rotary drive unit when the high-frequency power supply device is activated to start oscillating the magnetron, thereby turning the variable matching element support shaft. In addition to taking in and storing the detection signals of the directional coupler for each of a plurality of predetermined rotation driving positions during the driving process, the rotation driving device is optimized from among the stored detection signal groups. In order to determine a matching position, a specific detection signal in the detection signal group is found, and the variable matching element support shaft is turned to the rotational drive position where the detection signal is detected. And a control device (16) configured to control the rotary driving device to rotate the variable matching element support shaft within a predetermined rotation angle before and after the optimum matching position after driving. Heating equipment. 2. In one wall of the rectangular waveguide provided with the directional coupler, the fixed matching element, and the variable matching element, the rectangular waveguide extends from a position of the directional coupler toward the heating chamber side. The high-frequency heating device according to claim 1, wherein the variable matching element and the fixed matching element are mounted in this order. 3. The high-frequency heating apparatus according to claim 1, wherein a distance from a center of the fixed matching element to a center of the variable matching element is set to about １ ／ of a guide wavelength.