JPH0456091A - High frequency heating device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device having a function of detecting the presence or absence of food, the thawing state, etc.

BACKGROUND OF THE INVENTION In recent years, high-frequency heating devices that detect the presence or absence of food, the state of defrosting, etc., and control a radio wave emitting section based on the detected output have become mainstream.

Conventionally, this type of high-frequency heating apparatus detects a portion of the electromagnetic waves within the heating chamber using an antenna as shown in FIG. 8 to detect the presence or absence of food, the thawing state, etc.

The configuration will be explained below.

As shown in the figure, the antenna 1 is provided on the back side of the printed circuit board Fi2, and a part of the electromagnetic waves in the heating chamber (not shown) is detected by the detection circuit section 4 through the through hole 3.
The lead wire 5 was connected to a controller (none of which is shown) that controls the operation of the radio wave emitting section, and the operation of the radio wave emitting section was controlled depending on the presence or absence of food in the heating chamber, the thawing state, etc.

Problems to be Solved by the Invention In such a conventional high frequency heating device, the printed circuit board 2
If the opposite side of the antenna 10 is not blocked by a metal plate or the like, electromagnetic waves will leak to the outside through the portion 6 of the printed circuit board 2 where there is no copper foil. At this time, leak/! i-Radio waves not only become a noise factor to the outside, but the impedance seen from the electromagnetic waves inside the heating chamber changes depending on the proximity of a metal plate or other object near the detection circuit section 4 or the position and placement of the lead wire 5. The amount of electromagnetic waves leaking from the heating chamber changes.

Therefore, there was a problem in that the electromagnetic waves detected by the antenna 1 were greatly affected, and the detection state became extremely unstable. Furthermore, it is easy to receive external noise, and there is a risk that the antenna l will detect the noise.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to accurately detect a portion of the electromagnetic waves within the heating chamber with a simple configuration, thereby accurately detecting the thawed state of food within the heating chamber.

! Means for Solving IN In order to achieve the above object, the present invention solves the problem by providing a copper foil on the opposite side facing the antenna of the printed circuit board to which the detection circuit section is attached and the antenna is connected. It is used as a means.

Effect of the present invention By using the above-mentioned problem solving means, the impedance seen from the heating chamber becomes constant, the detection state of a part of the electromagnetic waves inside the heating chamber is stabilized, and the heating chamber is not affected by external noise. The thawing state of food can be detected with high accuracy.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4.

As shown in the figure, the heating chamber 7 stores food 8.
The radio wave emitter 9 radiates electromagnetic waves 10 to the food 8 to heat it. At this time, depending on the state of the food 8, a portion 11 of the electromagnetic waves including the reflected waves is transferred to the resin slit cover 12 and the heating chamber 7.
It is detected by an antenna 14 through a slit 13 provided on the wall of the . The antenna 14 is formed of a copper foil on a printed circuit board 15, and is connected to a detection circuit section 16 mounted on the printed circuit board 15.

The output of the detection circuit section 16 is sent to the control section 1 through a lead wire 17.
Enter 8. The controller 1 grasps the state of the food 8 according to the output of the detection circuit section 16, determines the optimum thawing time, and controls the operation of the radio wave emitting section 9 and the cooling fan 19 of the radio wave emitting section 9.

The printed circuit board 15 is a double-sided printed circuit board, and the antenna 14 is formed of copper foil on the back surface as shown in FIG.

This antenna 14 is connected via a through hole 20 to a detection circuit section 16 attached to the surface. Printed circuit board 1
The area around the antenna 14 on the back side of 5 forms a part 21 without copper foil, and the remaining part has copper foil 22 left. In addition, other than the pattern constituting the detection circuit section 16 on the surface of the printed circuit board 15, a copper foil 2 is provided on the surface facing the antenna 14.
There are 3. Here, the portion where there is no copper foil on both the front and back surfaces of the printed circuit board 15 (the portion surrounded by the two-dot chain line in FIG. 1) 2
The maximum length A of 4 is made shorter than 1/4 wavelength of the electromagnetic waves emitted from the radio wave emitting section 9 to prevent electromagnetic waves from leaking from the surface of the printed circuit board 15. Further, the copper foil 22 is connected to the ground through a metal fitting or the like at a portion 25 not coated with the resist (the portion surrounded by the dashed line in FIG. 1), and the copper foil 23 is similarly connected to the ground.

As shown in FIG. 3, the detection circuit section 16 detects and integrates the output obtained from the antenna 14 with a surface-mounted detection diode 26, and then filters it with a low-pass filter and sends the detected output VouT to the controller 18. Output.

In this case, the inductors 27, 28 and the integrating capacitance component 29, which constitute the low-pass communication filter, are constituted by microstrip lines.

As shown in FIG. 4, a slot 3 is provided on the top surface of the heating chamber 7, a matching hole 30 is provided for positioning, and the printed circuit board 15 is held in alignment with the matching hole 30 so as to suppress unnecessary leakage of electromagnetic waves. A metal sensor mount 31 is spot welded. The printed circuit board 15 is a metal sensor bed 3
2, the above-mentioned resist-free portion 25 is soldered to the use hole 33, and the sensor bed 32 is fixed to the sensor mount 31 with four screws 34 to eliminate mounting variations. The metal sensor cover 35 has screws 34
It is fastened to the sensor mount 31 together with the sensor bed 32, thereby eliminating the influence of external noise. The resin-made slit cover 12 allows the printed circuit board 15 to pass through the slit 131 alignment hole 30, etc., to prevent food waste in the heating chamber 7,
Prevents exposure to steam, etc.

To explain the operation in the above configuration, the detection output Vout of the detection circuit section 16 changes with time as shown in FIG. The interval tI+'! +
Divide into... and calculate the maximum value Vt in each section.
1. Find vw... At this time, the maximum value v,
Since 1 changes as shown in FIG. 6 in response to the weight m of the food 8, the weight m of the food 8 can be determined from the maximum value . Further, Vtl VLZ roughly corresponds to the initial temperature T of the food 8 as shown in FIG.
The initial temperature can be estimated from VLZ. Therefore, the initial state of the food 8, ie, the weight and initial temperature, can be known from the detection output, and the optimal thawing time can be determined.

At this time, since the copper foil 23 is provided on the opposite surface of the printed circuit board 15 facing the antenna 14, the 1i magnetic waves in the heating chamber 7 do not leak, and the apparent impedance of the heating chamber 7 is stabilized. Detection by antenna 14 and detection circuit section 1
The detection output detected in step 6 can accurately detect the state of food 8.

Further, the printed circuit board 15 is configured with a double-sided printed circuit board,
Since the antenna 14 is formed of copper foil on one side, the structure is simple and the impedance seen from the heating chamber 7 can be further stabilized.

Effects of the Invention As is clear from the above embodiments, according to the present invention, the tR foil is provided on the opposite side facing the antenna of the printed circuit board to which the detection circuit section is attached and the antenna is connected. electromagnetic waves do not pass through the printed circuit board,
There is no change in the impedance seen from the electromagnetic waves inside the heating chamber due to the external environment such as the distance to other metal parts or how the lead wires are fixed, and the antenna can accurately detect a part of the electromagnetic waves in the heating chamber, resulting in accurate defrosting. In addition, external noise is not detected by the antenna, improving layer detection accuracy.Furthermore, electromagnetic waves do not leak to the outside through the printed circuit board and do not become a source of noise. has.

[Brief explanation of the drawing]

Fig. 1 is a top view of a printed circuit board equipped with an antenna and a detection circuit section of a high-frequency heating device according to an embodiment of the present invention, Fig. 2 is a block diagram of the same high-frequency heating device, and Fig. 3 is a diagram of the same high-frequency heating device. A circuit diagram of the detection circuit section, Fig. 4 is an exploded perspective view of the main parts of the high-frequency heating device, Fig. 5 is a time change characteristic diagram of the detection output of the detection circuit section of the high-frequency heating device, and Fig. 6 is the detection output of the same high-frequency heating device. Fig. 7 is a characteristic diagram of the relationship between the detection output and the initial temperature of the food, and Fig. 8 is a top view of a printed circuit board equipped with the antenna and detection circuit of a conventional high-frequency heating device. It is. 7... Heating chamber, 8... Food, 9...
... Radio wave emitting section, 14 ... Antenna, 15.
... Printed circuit board, 16 ... Detection circuit section, 18 ... Controller, 23 ... Copper foil. Name of agent Patent attorney Shigetaka Awano Haka1 person Antenna print Maku Tsunekomon l1 Ifl Naka DI + Foil jTTl tTT2 no meeting 1 μ i Shinden W Radiation Immediately Figure 6 CゝC7

Claims (2)

[Claims] (1) 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 the electromagnetic waves in the heating chamber; a detection circuit that detects the detection output of the antenna; a controller for controlling the operation of the radio wave radiating section based on the output of the detection circuit section; and a printed circuit board to which the detection circuit section is attached, the antenna being connected to the printed circuit board, and facing the antenna of the printed circuit board. A high-frequency heating device with copper foil on the opposite side. (2) The high frequency heating device according to claim 1, wherein the printed circuit board is a double-sided printed circuit board, and the antenna is formed of copper foil on one side.