JPH03252083A - High frequency heating device - Google Patents

Abstract

PURPOSE:To precisely take out a reflective power with a simple structure to allow highly precise thawing of food by forming an antenna and a wave detecting circuit on the same base plate. CONSTITUTION:Electric waves 4 from a wave radiating part 3 are reflected by a food 2 placed in a heating chamber 1. At that time, depending on the state of the food 2, a part 5 of the waves containing reflective waves are passed through a slit 6 opened on the heating chamber 1 wall surface and detected by an antenna 8 fixed by a mounting metal fitting 7. The antenna 8 is formed on a double face base plate 10 same as a wave detecting circuit 9, and the waves detected by the antenna 8 are detected by the wave detecting circuit 9 and sent to a controller 11. In the controller 11, the state of the food is known according to the detected wave quantity, and the optimum thawing time is judged to control the operation of the wave radiating part 3. Hence, the reflective power can be precisely taken out with a simple structure to highly precisely thaw the food.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-frequency heating device that automatically detects the presence or absence of food, thawing state, etc.

BACKGROUND OF THE INVENTION A conventional thawing detection method for a high-frequency heating device will be described.

With Time Auto, the heating time is set in advance for each weight of food, and by manually inputting the weight of the food, the food will be heated for a time corresponding to that weight.

In addition, the weight sensor automatically detects the weight of the food, so there is no need to manually operate the weight key compared to Time Auto, but after the weight is detected, it heats up until the preset time like Time Auto. It becomes.

Furthermore, the concept of detecting changes in the state of food based on the amount of reflected power from the heating chamber has been considered for some time, as shown in Japanese Patent Application Laid-Open No. 159087/1987, but it has not been realized. .

Problems to be Solved by the Invention When thawing is detected using methods such as time auto or weight sensors, thawing is completed by heating for a certain amount of time regardless of the initial part, shape, placement, ingredients, etc. of the food, so it is possible to If you perform thawing detection on items whose condition varies greatly and whose initial temperature is high (for example, a frozen item that is 1 m long after being brought home from shopping), it may become hot, or items whose initial temperature is low (for example, if you store it in a freezer with strong cooling capacity for a long time). When thawing was detected on stored food (food), it was found that it had not been thawed at all, making it very inconvenient for the user.

Next, by using the amount of reflected power, it is theoretically possible not only to determine the weight based on the amount of initial reflected power, but also to estimate the initial temperature of the food and how it is placed by using changes in the amount of reflected power over time. However, in reality, the configuration of the antenna that captures the reflected power, the configuration of the detection circuit, or the matching between the two was poor, resulting in only data with a large amount of variation in the detected output, so it was not possible to put it into practical use.

The present invention solves these conventional problems,
The purpose is to accurately extract reflected power with a simple configuration and provide accurate defrosting of food.

Means for Solving the Problems In order to solve the above problems, the high frequency heating device of the present invention has the following features:
a heating chamber that stores food; a radio wave radiation section that radiates electromagnetic waves to the food to heat the food; an antenna that detects part of the electromagnetic waves within the heating chamber; and a detection circuit that detects the power detected by the antenna. The antenna and the detection circuit are formed on the same substrate.

The high-frequency heating device of the present invention is placed in the heating chamber and detects the reflected power, which varies depending on the condition of the food, using an antenna, and then detects and controls the reflected power using a detection circuit formed on the same substrate as the antenna. Good thawing detection is achieved.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 is a cross-sectional view of the configuration of a high-frequency heating device showing this embodiment. A radio wave emitter 3 is placed on the food 2 placed in the heating chamber 1.
Radio waves 4 are emitted. At this time, a portion 5 of the radio waves including reflected waves depending on the state of the food 2 passes through a slit 6 made in the wall of the heating chamber 1 and is detected by an antenna 8 fixed with a metal fitting 7.

The antenna 8 is configured and connected to the detection circuit 9 on the same screen substrate 10 , and the radio waves detected by the antenna 8 are detected by the detection circuit 9 and sent to the controller 11 . The controller 11 knows the state of the food according to the detected amount, determines the optimum thawing time, and controls the operation of the radio wave emitting section 3 (that is, stops oscillation when the optimum thawing time comes).

Figures 2 and 3 are views rotated by 180'' around the A-A' axis, showing the front and back configurations of the screen board 10, where the antenna 8 and the detection circuit 9 are arranged. The antenna 8 is surrounded by a ground plane 12 made of copper foil.
It is also made of copper foil.

The antenna 8 and the detection circuit 9 are connected by a through hole 13, and the back surface of the antenna 8 has no body foil except for the connecting portion of the through hole 13. The detection circuit 9 is arranged on the back side of the ground plane 12 so as not to overlap the back side of the antenna 8 . Here, the antenna 8 is a copper foil antenna, which is different from a slip antenna with a rear surface grounded on a boat, and whose detection amount is thought to be determined approximately by the length of the long side l.

FIG. 4 is a sectional view of the main part of the installation. The fitting 7 is fixed so as to cover the slit 6 in the wall of the heating chamber 1, and is connected to the ground plane 12 of the screen substrate 10. The antenna 8 is surrounded by a ground plane 12 and has a through hole 13.
It is connected to the detection circuit 9 on the back side.

Here, the effect of this example is that the antenna is surrounded by a ground plane and fixed to the wall of the heating chamber with metal fittings, which suppresses leakage to the outside and makes it difficult to detect noise from the outside world.Furthermore, the antenna is made of copper foil. However, unlike a slip antenna, there is no back ground, so the antenna has good dimensional accuracy and can be constructed in a small space.

FIG. 5 is a sectional view of a main part showing another embodiment around the antenna 8, in which the antenna 8 made of a conductor penetrates the substrate 10 and is directly attached to the detection circuit 9.

FIG. 6 is a circuit configuration diagram showing an example of the detection circuit 9. As shown in FIG.

The power P obtained from the antenna is detected by a surface-mounted detection diode 14, and then passed through an LPF (low pass filter) 16.
After being filtered by , it is sent to the controller as a detection output V611. When a detection circuit is configured on a screen substrate as described above, the inductance and capacitance components of the LPFs 15 and 16 are often configured with microstrip lines.

Figure 7 shows the detection output■. FIG. 3 is a characteristic diagram showing changes in at over time. An example of a control method within the controller will be explained. The time tvyt required for the turntable of the high-frequency heating device to rotate once is divided into several sections, 1°0. Divide into...
Maximum values Vt, VB, etc. in each section are determined. At this time, since the VLI changes in accordance with the weight of the food, the weight m can be calculated from the Vtt as shown in FIG. In addition, since V□-Vti roughly corresponds to the initial temperature of the food, the initial state of the food can be determined by a method of 0 or more that can conversely estimate the initial temperature T from V% + Vti as shown in Figure 9. It is possible to determine the optimal defrosting time.

Effects of the Invention As described above, the high frequency heating device of the present invention provides the following effects.

Since the antenna and the detection circuit are constructed on the same board, the matching accuracy between the antenna and the circuit is good.

Furthermore, the antenna is mounted near the oven wall, which is easier to install than when the antenna and detection circuit are on separate boards, and it is easier to achieve matching accuracy between the coupling hole on the oven and the antenna.

Furthermore, since the transmission line connecting the antenna and the detection circuit can be short, transmission loss peculiar to high frequencies can be suppressed as much as possible.

Further, since a dedicated antenna board is not required, cost reduction and miniaturization are possible.

Furthermore, when the antenna and detection circuit are configured with opposing screens on the same board, the ground plane of the detection circuit also serves to suppress radio waves that attempt to leak outside from around the antenna, reducing noise to the operation of external equipment. It can be prevented.

Similarly, since the antenna can be configured using a part of the space on the back side (ground side) of the detection circuit, it is possible to significantly downsize the antenna.

Similarly, when fixing the board to the oven wall, the antenna surface faces the coupling hole on the oven, so the detection surface faces the opposite direction from the oven wall across the board, and the detection circuit Elements such as diodes are not easily affected by radiant heat, so they can provide stable detection output.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a high-frequency heating device according to an embodiment of the present invention, Figs. 2 and 3 are block diagrams showing an example of the structure of an antenna and a detection circuit, and Fig. 4 is an example of a main body mounting structure. 5 is a sectional view showing an example of another configuration around the antenna, FIG. 6 is a circuit configuration diagram showing an example of a detection circuit, and FIG.
The figure is a characteristic diagram showing the time change of the detection circuit output VOEIT,
FIG. 8 is a characteristic diagram showing the relationship between the detection circuit output Vt+ and food weight m, and FIG. 9 is a characteristic diagram showing the relationship between the detection circuit output V, -V, ., and the initial temperature T of the food. 1... Heating chamber, 2... Food, 3...
...Radio wave emitting part, 7...Mounting metal fittings, 8...
...Antenna, 9...Detection circuit, 10...
...Screen board, 11...Controller. Figure 1 ~ Voice av! , t 2- Food S---Electrical equipment i-Weight scale 7--1 Take it directly (Setting tool 8-Antea Q-Experiment 5* 2 Fig. τrrt 0 HarH Fig. 3 Fig. Fig. 〃also Fig. θ S t6 1&ri (#C)

Claims (2)

[Claims] (1) A heating chamber that stores food, a radio wave radiator that radiates electromagnetic waves to heat the food, an antenna that detects a part of the electromagnetic waves in the heating chamber, and a detector that detects the electric power detected by the antenna. A high-frequency heating device comprising a circuit and a controller for controlling various equipment operations, and in which the antenna and the detection circuit are formed on the same substrate. (2) The high-frequency heating device according to claim (1), wherein the antenna and the detection circuit are respectively arranged on opposing screens of the board.