JP4832315B2 - High frequency heating device - Google Patents

Description

  The present invention relates to a high-frequency heating apparatus that radiates high-frequency energy into a heating chamber using a rotating antenna to heat food or the like at high frequency.

  As shown in FIG. 6, the conventional high-frequency heating apparatus of this type includes a heating chamber 21 and a high-frequency supply chamber 23 for supplying high-frequency energy into the heating chamber 21 at a lower portion thereof. 7 is provided with a rotating antenna 26 shown in FIG.

  A coupling hole 25 is provided in the bottom surface of the high frequency supply chamber 23, a waveguide 24 is connected to the coupling hole 25, and a magnetron 28 that generates high frequency energy is connected to the other end of the waveguide 24. The high frequency energy is transmitted through the waveguide 24 and supplied into the high frequency supply chamber 23 through the coupling hole 25.

  The rotating antenna 26 is connected to a driving device 29 provided outside the high-frequency supply chamber 23 through the coupling hole 25 and is rotated.

  The food that is the object to be heated is placed on the object to be heated placing plate 22 made of a dielectric provided above the high frequency supply chamber 23, and scattered in each direction in the heating chamber 21 by the rotation of the rotating antenna 26. High frequency heating is performed by the generated high frequency energy.

  As shown in FIG. 7, the rotating antenna 26 includes a slit 27 formed by cutting a metal disk into a circular shape, a rectangular shape, a fan shape, or the like (see, for example, Patent Document 1).

JP 2002-286229 A

  However, in the above-described prior art, the high frequency energy radiated from the rotating antenna 26 into the heating chamber 21 is the center of a heated object such as food placed on the heated object mounting plate 22 due to the shape of the heating chamber 21. There is a problem that uneven heating occurs such that the portion is weak and the outer peripheral portion is strong, or conversely the central portion is strong and the outer peripheral portion is weak.

  Further, depending on the shape of the rotating antenna 26, particularly the shape of the slit 27, the installation position, etc., high frequency energy is not efficiently generated from the magnetron 28, or due to mismatching such as an increase in reflected power in the transmission path through which the high frequency energy is transmitted. There was a problem that the heated product was not heated efficiently.

The present invention has been made in order to solve the above-described problems. A heating chamber for storing a heated object, a heated object mounting plate made of a dielectric provided on the bottom surface of the heated chamber, and the covered object. A high-frequency supply chamber provided below the heated object mounting plate, a coupling hole provided in the bottom surface of the high-frequency supply chamber for supplying high-frequency energy to the high-frequency supply chamber, a magnetron for generating high-frequency energy, A magnetron is attached and connected to the coupling hole to supply high-frequency energy; an inner conductor provided through the coupling hole and facing substantially vertically into the high-frequency supply chamber; and A metal flat plate rotating antenna connected to the one end of the high-frequency supply chamber substantially horizontally, a dielectric shaft connected in the waveguide of the inner conductor, and a drive unit that rotationally drives the dielectric shaft. Prepared, Serial toward the outer peripheral side starting from the central portion to the rotating antenna provided a spiral slit in two symmetrical, the width of the slit is wider radially outward of the central portion, each of the start point and the start point of the spiral slit , And the interval between the end points are set to ½ wavelength and 1 wavelength of the oscillation frequency of the magnetron, respectively .

  Further, the width of the spiral slit is continuously increased toward the outer peripheral side.

  Since the high-frequency heating device of the present invention is configured as described above, the high-frequency energy radiated from the rotating antenna is uniformly radiated. A device can be provided.

  In addition, since the degree of coupling of high-frequency energy to the rotating antenna increases, the high-frequency energy that is reflected decreases and the high-frequency energy is efficiently radiated into the heating chamber, whereby the object to be heated is heated in a short time.

  An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a longitudinal sectional view of an essential part of a high-frequency heating apparatus showing an embodiment of the present invention. A heating chamber 1 for storing an object to be heated is provided with an object mounting plate 2 made of, for example, crystallized glass made of a dielectric on the bottom, and a high frequency supply is provided below the object to be heated mounting plate 2. A chamber 3 is provided, and a rotating antenna 8 is provided in the high-frequency supply chamber 3.

  A coupling hole 6 for supplying high-frequency energy to the high-frequency supply chamber 3 is provided at the center of the bottom surface of the high-frequency supply chamber 3, and the waveguide 5 connected to the coupling hole 6, The high frequency energy is supplied into the high frequency supply chamber 3 by the magnetron 4 that supplies the high frequency energy connected to the end.

  The coupling hole 6 has an inner conductor 7 that penetrates the coupling hole 6 and faces the vertical direction in the high-frequency supply chamber 3. A rotating antenna 8 in the high-frequency supply chamber 3 is connected to one end of the inner conductor 7. They are connected approximately horizontally.

  One end of a dielectric shaft 9 made of a dielectric is connected to the other end of the inner conductor 7 facing the waveguide 5, and the other end of the dielectric shaft 9 is connected to a hole 10 formed in the waveguide 5. The rotating antenna 8 is rotated by the driving unit 11 through the dielectric shaft 9 and the inner conductor 7.

  The food 12 as the object to be heated is placed on the object to be heated placing plate 2, supplied to the high frequency supply chamber 3, and scattered in each direction in the heating chamber 1 by the rotation of the rotating antenna 8. High frequency heating is performed by energy.

  FIG. 2 is a plan view of the rotating antenna 8. The rotating antenna 8 is a flat plate made of a highly conductive metal such as aluminum, and is provided with two spiral-shaped slits 8a that are left-handed from the central portion to the outer peripheral side of a circular plate having a thickness of 1 mm and a diameter of 190 mm. The slit width of the part is W1, the slit width of the outer peripheral side is W2, and the width of the slit 8a is continuously increased from the central part to the outer peripheral side, and the central part is narrow and the outer peripheral side is widened. Yes. The width of the slit 8a may be increased stepwise instead of continuously increasing from the center to the outer peripheral side.

  The rotating antenna 8 provided with the spiral slit 8a as described above is generally called a spiral antenna, and the radiation characteristic of such a spiral antenna has no change in the slit width. When radiation is strong and this is used for heating, the object to be heated such as food on the object-to-be-heated object mounting plate 2 just above the antenna is heated at the center part of the antenna and the outer peripheral part is weak. It tends to be.

  Therefore, in the present invention, the width of the slit 8a provided in the rotating antenna 8 is narrow at the center, widened at the outer periphery, and continuously widened from the center toward the outer periphery. The energy is controlled to be uniformly emitted from the entire slit 8a.

  That is, in this embodiment, the slit width W1 at the center of the rotating antenna 8 shown in FIG. 2 is 12 mm, and the slit width W2 at the outer periphery is 24 mm.

In addition, the spacing P1, P2 between the start point and the start point, and the end point and the end point of each of the two spiral slits 8a provided symmetrically is set to approximately one half wavelength and one wavelength of the oscillation frequency of the magnetron 4, The coupling of the high frequency energy is increased by providing the slit 8a so that the start point and the end point are positioned at the position where the electric field maximum point of the high frequency energy supplied to the rotating antenna 8 is located. In this embodiment, the oscillation frequency of the magnetron 4 is set to 2450 MHz, and the intervals P1 and P2 between the start point and the start point and the end point and the end point of the spiral slit 8a of the rotating antenna 8 shown in FIG. ing.

  Next, the effect | action by the above structure is demonstrated.

  The high frequency energy generated from the magnetron 4 propagates through the waveguide 5 and propagates to the high frequency supply chamber 3 by the coaxial coupling between the coupling hole 6 provided in the center of the bottom surface of the high frequency supply chamber 3 and the inner conductor 7.

  In the high-frequency supply chamber 3, when the rotating antenna 8 having the slit 8a formed in the left turn is rotated to the right by the drive unit 11, the spiral slit 8a gradually moves to the outer peripheral portion as it rotates. Then, the high frequency energy radiated from the slit 8a moves to the outer peripheral portion and diffuses and is scattered, thereby improving the uneven heating of the article 12 to be heated.

  In order to investigate the effect of improving the heating unevenness, the following test was conducted.

First, the slit width of the spiral slit 13a provided symmetrically with the two rotating antennas 13 as shown in FIG. 3 is set to the spiral slit provided in the rotating antenna 8 of the embodiment of the present invention shown in FIG. Using the rotating antenna 8 of the embodiment of the present invention shown in FIG. 2 with a slit width of 18 mm which is an intermediate value between the widths W1 and W2, and the slit width being constant from the start point of the central part to the end point of the outer peripheral part. The temperature distribution of the object to be heated 12 placed on the object-to-be-heated object mounting plate 2 was calculated by calculating with a computer using an electromagnetic field analysis method using the TLM method. In addition, the space | interval between each starting point of slit 13a, and the space | interval between end points were made the same with the rotating antenna 8 of the Example shown in FIG.

The analysis conditions at this time are assumed to be a frozen visa pie with a heated object 12 having a diameter of 330 mm and a thickness of 10 mm. The physical constant at the time of analysis is a relative permittivity of 4.4, conductivity of 0.0722 s / m, density of 794 kg / It was m ^3.

  Further, the analysis method is to decompose this heated object into 174,000 cells and calculate the temperature rise value of each cell by analysis, and as shown in FIG. As shown in FIG. 4, the temperature distribution on the xz plane viewed along AA 'in FIG. The bright part shows a high temperature rise, and the dark part shows a low temperature rise. In addition, the coefficient of variation was obtained from the temperature rise value of each cell, and the heating unevenness was evaluated.

  As a result, the heating temperature distribution of the object to be heated 12 in the case of the rotating antenna 13 having the constant width of the slit 13a shown in FIG. It is bright and has a high temperature distribution in the center. On the other hand, the heating temperature distribution of the object to be heated 12 in the case of the rotating antenna 8 of this embodiment provided with the slit width shown in FIG. The brightness of h4 in the peripheral portion is similar, and the temperature of the object to be heated 12 is rising as a whole.

Further, the coefficient of variation obtained from the temperature rise value of each cell based on the result of FIG. 4B at this time was 0.39, and the coefficient of variation of FIG. 4A was 0.51. As the coefficient of variation is smaller, the unevenness of heating is smaller, so the slit width is continuously increased from the central part to the outer peripheral side, and the rotation of this embodiment is provided so that the central part is narrow and the outer peripheral side is widened. By using the antenna 8, a significant improvement in heating unevenness was confirmed.

  Thus, since the high frequency energy radiated | emitted from the rotating antenna 8 comes to be radiated | emitted uniformly, the high frequency energy is irradiated to the to-be-heated material 12 whole, and the high frequency heating apparatus with few uneven heating can be provided.

  Next, as shown in FIG. 5, in the case where the rotating antenna 8 of the embodiment of the present invention is used, what kind of power density distribution the heated object 12 placed on the heated object placing plate 2 has It was calculated by a computer using an electromagnetic field analysis method using the TLM method. The bright part indicates that the power density is high, and the dark part indicates that the power density is low. FIG. 5 shows the power density distribution obtained by analysis corresponding to the rotating antenna 8 of this embodiment. As a result, it can be seen that the start point and the end point of each of the spiral slits 8a provided symmetrically with respect to the half wavelength and the one wavelength are bright and the power density is high. This indicates that the starting point and the ending point of the slit 8a are located at the position that is the electric field maximum point of the high-frequency energy supplied to the rotating antenna 8.

  Therefore, by selecting the start point and start point, and the interval between the end point and end point of the spiral slits 8a provided symmetrically to be ½ wavelength and 1 wavelength, respectively, the coupling of high frequency energy is increased, and the rotating antenna 8 The high-frequency heating apparatus that reduces the reflected high-frequency energy and efficiently introduces the high-frequency energy into the heating chamber 1 and can heat the article to be heated 12 in a short time can be provided.

  Thus, since the high frequency energy radiated | emitted from the rotating antenna 8 comes to radiate | emit uniformly, high frequency energy is irradiated to the to-be-heated material 12 whole, and the high frequency heating apparatus with few unevenness of a heating can be provided.

  In addition, since the degree of coupling of the high frequency energy with respect to the rotating antenna 8 increases, the reflected high frequency energy is reduced and the high frequency energy is efficiently radiated into the heating chamber 1, so that the object to be heated 12 can be shortened in a short time. Heated.

  Note that the diameter of the rotating antenna 8 and the dimensions of the slit widths W1 and W2 described in the above embodiment are not limited to the above values, and may be set within a range in which equivalent effects can be obtained.

  Further, the shape of the rotary antenna 8 does not have to be a disc flat plate, and the slit 8a may be wound clockwise.

It is a principal part longitudinal cross-sectional view of the high frequency heating apparatus which shows one Example of this invention. Similarly, it is a top view of a rotating antenna. It is a top view of a rotating antenna with a constant slit width. (A) It is a figure which shows the result of having analyzed the temperature distribution of the to-be-heated object at the time of using a rotating antenna with constant slit width. (B) It is a figure which shows the result of having analyzed the temperature distribution of the to-be-heated object at the time of using the rotating antenna in a present Example. It is a figure which shows the power density distribution analysis result of the to-be-heated object 12 mounted on the to-be-heated object mounting board 2 about the case where the rotating antenna 8 of a present Example is used. It is a principal part longitudinal cross-sectional view of the conventional high frequency heating apparatus. It is a top view of the rotation antenna of the conventional high frequency heating apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating chamber 3 High frequency supply chamber 4 Magnetron 5 Waveguide 6 Coupling hole 7 Inner conductor 8 Rotating antenna 8a Slit 9 Dielectric shaft 11 Drive part

Claims (2)

A heating chamber for storing the object to be heated, a heated object mounting plate made of a dielectric material provided on the bottom surface of the heating chamber, a high frequency supply chamber provided below the heated object mounting plate, A coupling hole provided on the bottom surface of the high-frequency supply chamber for supplying high-frequency energy to the high-frequency supply chamber, a magnetron for generating high-frequency energy, and the magnetron are attached and connected to the coupling hole to supply high-frequency energy. A waveguide, an inner conductor provided substantially vertically through the coupling hole and facing the high-frequency supply chamber, and a metal flat plate connected to one end of the inner conductor substantially horizontally in the high-frequency supply chamber. A rotating antenna; a dielectric shaft connected within the waveguide of the inner conductor; and a drive unit that rotationally drives the dielectric shaft. Provided slit into two symmetrical, the width of the slit is wider radially outward of the central portion,
A high-frequency heating apparatus, wherein the spiral slit has a start point and a start point, and an interval between the end point and the end point set to ½ wavelength and one wavelength of the oscillation frequency of the magnetron, respectively .   2. The high frequency heating apparatus according to claim 1, wherein the width of the spiral slit is continuously increased toward the outer peripheral side.

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