JPH0471188A - High frequency heating device - Google Patents

Abstract

PURPOSE:To eliminate dispersion resulting from through hole, enhance the accuracy in matching, and have thawing stably at all times by forming an antenna detection circuit on the same plane of a printed circuit board. CONSTITUTION:An antenna 9 is formed on the oversurface of a printed circuit board 8 as extension of a wiring pattern 10c, and the reflex electric waves reflected by food 1 and having penetrated the exposed part 21a of the base board 8 are sensed. Because the exposed part 21a on the rear side of the base board 8 and the antenna 9 on its front side can be formed precisely both through etching process, the sensing accuracy is enhanced to a great extent to enable precision control.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a high-frequency heating device for heating frozen foods or room-temperature foods, and particularly relates to a high-frequency heating device that automatically detects the presence or absence of food and the thawing state (conventional). (Technology) A conventional thawing detection method for this type of high-frequency heating device will be explained.

The manual high-frequency heating device is called Time Auto.
A heating time is set in advance for each food weight, and the food is heated for a time corresponding to the weight by inputting the food weight by operating a key.

Further, the fully automatic high-frequency heating device is equipped with a weight sensor, automatically detects the weight of food, and heats the food for a preset time depending on the weight. Therefore, compared to time auto, manual operation of heavy keys is not required.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 56-159087, there is a high-frequency heating device that detects a change in the state of food based on the amount of reflected power from a heating chamber and automatically heats the food optimally.

This type of conventional high frequency heating device will be explained with reference to FIGS. 3 to 9.

FIG. 3 is a schematic cross-sectional view showing the configuration of a conventional high-frequency heating device. , between a high-frequency radiation device 5 placed on the side wall of the heating chamber 4 and metal shield boxes 6 and 7 placed above the slit 4a formed in the ceiling of the heating chamber 4 and divided into upper and lower parts. Antenna 9 and its detection circuit 1 formed on the lower and upper surfaces of the housed printed circuit board 8
0, the above-mentioned detection circuit 10, and lead wire I.
] and a controller 13 that drives the electric motor 2 of the turntable 3, the high-frequency radiator 5, and the cooling fan 12 according to the detected data. The above slit 4a is provided with a resin slit cover 1 in order to prevent the antenna 9 housed in the lower shield box 7 from being contaminated by food particles, steam, etc. in the heating chamber 4.
4. Close the lid.

FIG. 4 is an exploded perspective view of the above-mentioned wave detection section, FIG. 5 is a plan view of the printed circuit board 8, and FIG. 6 is a circuit diagram thereof.

In FIG. 4, the ceiling surface of the heating chamber 4 is provided with round holes 4b for positioning and square holes 4c for mounting on both sides and near both ends of a slit 4a formed therein. The lower shield box 7 has the above-mentioned slit 4 on the bottom.
A square hole 7a whose width and length are both larger than a, a positioning round hole 7b corresponding to the positioning round hole 4b on both sides thereof,
In the above installation, a notch 7C is formed that coincides with the inner end of the square hole 4c, and the four rising walls 7 of the bottom surface are formed.
d is provided with a ventilation window 7e continuous to the above-mentioned notch 7C, and at its upper end is formed a mounting shelf 7f with a guide edge on the outside, and furthermore, a screw hole 7 is formed approximately in the center thereof.
g is provided. The upper shield box 6 has a plurality of ventilation windows 6a punched out on the ceiling surface and side wall surface, respectively.
Screw holes 6C corresponding to the above-mentioned screw holes 7g are provided in the projecting portions 6b on the four sides. The printed circuit board 8 will be described in detail later, so to briefly describe it, an antenna 9 is formed on the bottom surface, and a detection circuit 10 is formed on the top surface. The board 15, which has 14 boards, is made by punching and forming a metal plate, and has a pentagonal hole 15a in the center with two parallel sides along the antenna 9, and two holes on each side for soldering. Four screw holes 15c are provided corresponding to the hole 15b and the screw hole 6c described above. The upper surface of the slit cover 14 has the above-mentioned positioning round holes 4b and 7b.
A guide protrusion +4a that is inserted into the lower shield box 7, and an engagement protrusion 14c that is inserted into the square hole 4C and that engages and fixes the engagement claw 14b in the notch 7C of the lower shield box 7. 4
The screws 16 are used to attach the board 15 to which the printed circuit board 8 is soldered into the upper and lower shield boxes 6 and 7. The ventilation windows 6a and 7e provided in the upper and lower shield boxes 6 and 7, respectively, have the length of each side set to 174 wavelengths or less of the heating high frequency to prevent wave leakage and at the same time prevent cooling air from the cooling fan 12. It is now possible to incorporate some of the

The lower shield box 7 also serves to reduce the amount of heat conducted from the heating chamber 4 and prevent the printed circuit board 8 from overheating.

Moving on to FIG. 6, the power obtained from the antenna 9 is detected by the detection diode 17, integrated by the capacitance component 18, passed through the low-pass filter I9, and then passed through the output terminal 1.
Detector circuit output V from 0a to lead wire 11. El? is output as Note that the antenna 9 is connected to the ground terminal 10b to the lead wire It via a low-pass filter 20 connected in parallel with the detection diode 17.

Turning to FIG. 5, the printed circuit board 8 is coated with copper foil over its entire back surface, and then etched to form an antenna 9 and a pentagonal exposed board portion 21a surrounding the antenna 9 with long sides parallel to the antenna 9. A wiring pattern 10c including a microstrip line forming an integral capacitance component 18 and two low-pass filters 19 and 20 together with the copper foil 21 is formed on the surface thereof, and a wiring pattern 10c is formed on the surface thereof. Mount the detection diode 17 and other resistors and capacitors.

Further, the wiring pattern 10c on the front surface, the copper foil 21 and the antenna 9 on the back surface are connected through through holes 22, 23 and 24, respectively.

Note that the printed circuit board 8 has an insulating film over the entire surface, except for four exposed copper foil portions 21b on the back surface indicated by circles with dashed lines and multiple exposed wiring pattern portions 10d on the front surface indicated as rectangles with solid lines. It is formed.

Returning to FIG. 4, in order to assemble one or more components, first, solder the printed circuit board 8 to the copper foil exposed portion 21b and the board 15 using the holes 15b to attach the board. . Next, install the lower shield box 7 on the shelf 7.
To attach the above board to f, place the plate 15 and upper shield box 6 one on top of the other, and fix with screws 16. Next, when the guide protrusion 14a and the engagement protrusion +4c of the slit cover 14 are pushed in from inside the heating chamber 4, aligning them with the positioning round hole 4b and the mounting square hole 4C, they are fixed by the action of the engagement claw 14b. be done.

Next, the positioning round hole 7b and notch 7C of the assembled lower shield box 7 are aligned with the guide protrusion 14a and the engagement protrusion 14c of the slit cover 14, and the slit cover 14 is removed from the inside of the heating chamber 4. When pushed in while supporting, the engaging claw 14b engages with the notch 7C and is fixed.

The operation of the high frequency heating device configured as above will be explained.

When radio waves are emitted from the high-frequency radiator 5 to the food 1 placed on the turntable 3 in the heating chamber 4, some of the high-frequency waves, including reflected waves, pass through the resin slit cover 14 depending on the condition of the food 1. It passes through a slit 4a made in the ceiling of the heating chamber 4, is captured by an antenna 9 formed on the bottom surface of a printed circuit board 8, is detected and integrated by a detection circuit IO, and is then sent from a lead wire 11 to a controller 13 as a detection output. Sent.

The controller 13 learns the condition of the food from the detection output, determines the optimal thawing time, and controls the high-frequency radiation device 5 and the cooling fan 12.
．． The electric motor 2 of the turntable 3 is controlled.

Next, a heating control method will be explained with reference to FIGS. 7 to 9.

FIG. 7 is a characteristic diagram showing the time change of the detection circuit output v0°. How long does it take for the turntable 3 of the high frequency heating device to rotate once? , 1 is divided into several sections tt2..., and the maximum value v, 1°■02, etc. in each section is determined.

At this time, vt1 is the weight m of food I, as shown in FIG.
Since it changes in accordance with , the weight m can be calculated from (1) and (1). Also, as shown in FIG. 9, V, , -V roughly corresponds to the initial temperature of the food, so V.

The initial temperature T can be estimated from V. In the above method.

The initial state of the food 1 can be known and the optimal thawing time can be determined.

(Problems to be Solved by the Invention) However, the above-mentioned methods using time autos and weight sensors are difficult to solve due to the temperature, shape, and placement of the food 1.

Because the food is thawed by heating for a certain amount of time, regardless of the ingredients, the finished product will vary widely. For example, frozen food brought home from shopping will have a high initial temperature, so if you decide the thawing time based on weight, it may end up boiling. In addition, there is a problem in that food that has been stored for a long time in a freezer with a strong cooling capacity and whose initial temperature is low may not be thawed at all, making it difficult to use.

In addition, if the reflected voltage is used, theoretically the initial reflected voltage V
Not only can the weight m be detected at t1, but it should also be possible to estimate the initial temperature of the food and how it has been placed by using changes in the reflected voltage over time, etc. However, in reality, the configuration of the antenna 9 that captures the reflected voltage and the detection circuit 1 There is a problem in that the detection output varies depending on the configuration of .degree. or the matching state of both.

In particular, the detection circuit 10 is configured on the top surface of the printed circuit board 8, which is not exposed to radio waves to avoid noise, and the bottom surface is configured so that the antenna 9 is directly exposed to radio waves. connected via. Therefore, the hole diameter 1 position of the through hole 24,
There was a problem of large variations due to unstable factors such as plating thickness. The present invention solves the above problems and provides a high-frequency heating device that accurately extracts reflected voltage and defrosts foods with high precision.

(Means for Solving the Problems) In order to solve the above problems, the present invention forms an antenna and a detection circuit on the upper surface of a printed circuit board.

(Function) With the above configuration, the detection level by the antenna 9 is determined by the length of the antenna 9 and the size of the copper foil exposed portion 21a, and if the etching accuracy is achieved, extremely stable detection can be achieved, so accurate thawing detection is possible. Realized.

(Example) An example of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a schematic cross-sectional view of a high-frequency heating device showing an embodiment of the present invention, and FIG. 2 is a plan view of a printed circuit board according to the present invention.

In FIG. 2, the printed circuit board 8 of this embodiment is different from the conventional example shown in FIG.
As an extension of oc, there are two points: a point formed on the top surface of the printed circuit board 8, and a point at which reflected radio waves reflected from the food 1 and transmitted through the substrate exposed portion 21a of the printed circuit board 8 are detected, as shown in FIG.

Since the rest is the same as the conventional example, the same components are given the same reference numerals and their explanations will be omitted. Also, the food 1
Since the weight detection and processing time control methods are also the same, their explanations will be omitted. However, since both the board exposed portion 21a on the back side of the printed circuit board 8 and the antenna 9 on the front side can be formed with high precision by etching processing, the detection accuracy can be improved. This greatly improves control and enables highly accurate control.

(Effects of the Invention) As explained above, according to the present invention, since the antenna and the detection circuit are configured on the same surface of the printed circuit board, variations caused by through holes are eliminated, matching precision is increased, and accurate It is possible to obtain a high-frequency heating device that can detect waves and constantly perform stable defrosting. Furthermore, since the antenna is not contaminated, a highly reliable high-frequency heating device with stable performance and little change over time can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a high-frequency heating device according to the present invention, FIG. 2 is a plan view of its printed circuit board, FIG. 3 is a schematic cross-sectional view of a conventional high-frequency heating device, and FIG. 4 is a detection section of the same. 5 is a plan view of the printed circuit board, FIG. 6 is a diagram of the detection circuit, and FIG. 7 is the output V of the detection circuit. 0. 8 is a characteristic diagram showing the time change of the detection circuit output v, 1 and the food weight m, and FIG. 9 is a characteristic diagram showing the detection circuit output V tt
It is a characteristic diagram of the initial temperature T of food. ...Round hole for positioning, 4c...Square hole for mounting, 5...High frequency radiator, 6...
・Upper shield box, 6a, 7e...ventilation window,
6b... overhang, 6c. +5c...screw hole, 7...lower shield box, 7
a... Square hole, 7c... Notch, 7d... Standing wall, 7f... Mounting on shelf, 7g... Screw hole, 8... Printed circuit board, 9... Antenna ,1
0...Detection circuit, loa...Output terminal, 10b...
・Ground terminal, lOc...wiring pattern, lod...
Wiring pattern exposed part, 11...Lead wire, 12...
... Cooling fan, 13 ... Controller, 14 ... Slit cover 14a ... Guide projection, 14b ... Engagement claw, +4c ... Engagement projection, 15 ... Board mounting plate ,
15a... pentagonal hole, 15b... hole for soldering,
j6... screw, I7... detection diode,
18... Integral capacitance component, 19.20.
...Low pass filter, 21...Copper foil, 21a...
Substrate exposed part, 21b... Silver foil exposed part, 22.23.2
4...Through hole.

Claims (2)

[Claims] (1) A heating chamber equipped with a turntable on which food is placed;
A high-frequency radiator that radiates electromagnetic waves to heat the food, an antenna formed on a printed circuit board that detects some of the waves reflected from the food, and its detection circuit, and controls various equipment operations using the output of the detection circuit. 1. A high-frequency heating device comprising a controller and a controller, characterized in that the antenna is formed on the same surface as the detection circuit. (2) The high-frequency heating device according to claim (1), wherein the antenna and detection circuit forming surface of the printed circuit board is disposed on a surface opposite to the heating chamber.