JPS58194288A - High frequency heater - 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 The present invention consists of 1. S, M, (industrial, scientific, medical) This relates to a high frequency heating device that has an oscillation frequency in the 916 MHz band, which is one of the frequency bands. The present invention provides a high-frequency heating device having an elaborate heating chamber (for heating).

Microwave oven 2, which is a typical example of conventional high-frequency heating equipment
As is well known, this system is equipped with a magnetron having an oscillation frequency in the 2460 MH2 band as a high-frequency heating heat source. Therefore, the dimensions of the width, depth, and height of the heating chamber, which has a volume that functions usefully as a consumer device, are about 2 to 3 times larger than the excitation wavelength (z12ctn) that excites the heating chamber. Therefore, several types of electromagnetic field modes can occur in the heating chamber, and it is impossible to select the most suitable electromagnetic field mode for the object to be heated stored in the heating chamber. High-frequency heating was performed effectively by disturbing the electromagnetic field distribution in the room or by rotating the object to be heated.

However, a complicated additional mechanism was required.The present invention was made in consideration of these points, and the present invention has been made in view of the above-mentioned problems. The excitation wavelength that excites the heating chamber of the lever is comparable9 1
The 5 MHz band (wavelength: 33 m) was selected as the oscillation frequency of the high-frequency heating heat source to limit the electromagnetic field mode generated within the heating chamber, and TE2o1 was selected as the electromagnetic field mode that could occur, and the heating chamber was configured for this electromagnetic field mode. do37
The present invention provides a high-frequency heating device whose main purpose is to heat an object to be heated with high frequency with high efficiency by devising each dimension.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a partially cutaway external view of a high-frequency heating device showing an embodiment of the present invention, and FIG. 2 is a diagram showing the electric field distribution generated in the heating chamber of FIG. 1.

The device includes: 1. S, M1 frequency band 9
High frequency heating heat source 1 whose oscillation frequency is 15 MHz band
is constituted by a solid-state high-frequency generator constructed using solid-state elements, and the high-frequency power generated by the solid-state high-frequency generator is transmitted through a transmission line 2 and guided into a heating chamber 3. This heating chamber is configured so that the electric field distribution generated inside the chamber is such that a TE2°1 mode having two standing waves in the width direction and one standing wave in the depth direction is generated in the e1a MHz band, as shown in Figure 2. ing.

That is, the electric field strength is uniform in the height direction. Heating chamber 3
The power supply unit 4 that supplies high frequency power to this TE2゜1
It is provided at a predetermined position on the upper wall of the heating chamber to generate a mode. 6 is applied to the heating chamber JP-A-58-19428
8 (2) Door for putting in and taking out hot materials, 6 is the handle of the door.

7 is an operation panel, and 8 is a leg rubber.

The TE2o1 mode selection will be described using FIG.

FIG. 3 is a water load characteristic diagram of the heating chamber resonance frequency.

The horizontal axis is the resonance frequency (unit: MHz), and the vertical axis is the water load (unit: CC). Width dimension a1 height dimension b1 depth dimension C of the heating chamber and subscripts m, n of electromagnetic field mode TEmns,
As is well known in microwave engineering, s has the following relationship.

Here, vo is the speed of light in free space (3 x 10" mm).

fo is the resonant frequency, λ. is the resonance wavelength (heating chamber excitation wavelength at no load).

By the way, λ shown in the above formula. In other words, when there is no load to be heated in the heating chamber, 51 is in free space. effect, resulting in wavelength compression. Now, if this compression ratio is a(a(1)) and the excitation wavelength of the heating chamber under load is λ9, then the relationship λq=λ0/α holds true, that is, λ9>λ.

Therefore, by accommodating the water load, the resonant frequency of the heating chamber will be shifted lower. FIG. 3 shows this characteristic.

The heating chamber used as a sample has a width dimension of 317sua and a height dimension of 2
40111. Depth dimension is 3171EII and s when no load is applied.
A heating chamber producing a TE111 mode at lsMHz and a width dimension of 36511. A heating chamber was used that had a height of 240 m and a depth of 365 m and produced a TE2o1 mode at 918.3 MHz under no load. In addition, the water storage container is a commercially available 10
A 00CG beaker and a SOCC crack were used.

The following can be understood from the characteristics shown in FIG.

The heating chamber without standing waves in the height direction of the heating chamber is 6 bays,
- When the load changes, the amount of change in the resonant frequency is smaller than in a heating chamber that has standing waves in the height direction.

The change in load amount at this time refers not only to the absolute amount, but also to the change in the base area of the load and the change in the height direction.

The resonance frequency of the characteristic shown in Figure 3 is the frequency at which the electric field strength in the heating chamber is measured and the strength is maximum. This suggests that high frequency power is accumulated.

By the way, 1. The S, M, and frequency bands are limited, and 1. In order to perform high-frequency heating efficiently within the S, M, frequency band, it is best to select the electromagnetic field mode generated in the heating chamber so as to generate as much resonance frequency as possible within this band. For the invention, we selected the TE2°1 mode, which allows us to create a practical shape for consumer equipment.

FIG. 4 is a characteristic diagram of a heating chamber that produces the TE2°1 mode.

Dimension in the direction in which the horizontal axis has two standing waves (this invention 71, -
- In the light, the width dimension) (unit: m) is shown, and the vertical axis indicates the dimension in the direction in which one standing wave is present (in the present invention, the depth dimension) (unit: m). Note that the increment was 11 m.

The broken lines in the figure are equal resonant frequency lines, and the straight line E is a straight line whose width and depth are equal. By the way, one of the parameters for measuring the characteristics of a heating chamber is the Q characteristic. The Q value is the energy W stored in the heating chamber, the power P lost over time in the heating chamber, and the excitation frequency f of the heating chamber at no-load. , there is a relationship Q=2πfOr.

In addition, there is a well-known relational expression in microwave engineering regarding the excitation mode generated in the heating chamber and each dimension of the heating chamber, and T
In the E2o1 mode, there is a relationship.

JP-A-58-194288 (3) Here, δ is the depth of the skin of the material constituting the heating chamber (the length at which the amplitude of the high frequency wave incident on the surface of the material is attenuated to -).

When the height of the heating chamber is 24013 and 8 is a constant, a=372111. When c=374111, Q takes the maximum value QM. For this 0M value, the equal Q value line when the no-load resonance frequency is 900 MHz to 930 MHz is shown by a dotted line in the figure.

It is suggested that the larger the Q value, the less high frequency power is wasted on the wall surface constituting the heating chamber.

By the way, according to the load characteristics of the 01 heating chamber resonance frequency in the TE mode shown in FIG. 3, p, 1. In order to have as many resonant frequencies of the heating chamber under load as possible within the S, M frequency bands, the resonant frequency of the heating chamber under no load must be 1. S,
M, preferably near the upper limit of the frequency band.

However, as shown in Figure 4, the relationship between the resonant frequency of the heating chamber under no load and the Q value of the heating chamber shows that as the frequency increases, the Q value tends to decrease. The feature is that the dimensions of the heating chamber are limited in consideration of the phenomena shown in 0. The first phenomenon is the stability of the entire device.

Since the door to the heating chamber includes a radio wave leakage prevention mechanism and is quite heavy, by reducing the width of the heating chamber, the shape of the door can be made smaller and the weight can be reduced. Furthermore, if the width direction is narrowed, the depth direction will inevitably become longer in order to produce TE2°1, so the center of gravity of the entire device will move rearward, which will improve stability.

The second is improved usability.

Basically, the size of the object to be heated may be any size as long as it can be accommodated in the heating chamber, and the object to be heated is generally placed approximately at the center of the bottom wall of the heating chamber. By the way, in the TE2o1 mode, as the electric field distribution is shown in FIG. 2, there are two places where the electric field is very strong, and the interval between them is about i of the heating chamber dimension in the direction having two standing waves. For this reason, if the dimensions of the heating chamber in the direction of the two standing waves are made as small as possible, the electric field near the center of the heating chamber will be higher than that of 10, -1. High-frequency heating can also be performed with sufficiently high efficiency.

As described above, the present invention provides a heating chamber shape that combines the inherent physical characteristics of the heating chamber that produces the TE2゜1 mode and a means for improving usability, with two heating chambers in the width direction and one in the depth direction. It has a standing wave of 1, and has a dimension configuration in which the dimension in the depth direction is equal to or longer than the dimension in the width direction.

Using Fig. 4, the dimension in the direction with 21 standing waves is the width direction dimension of the heating chamber shown in Fig. 1, and the dimension in the direction with 1m+ standing waves is the depth direction dimension. The shaded area in the figure is the area where the features and effects of the present invention are beneficial.

In addition, in Figure 4, the width direction dimension and depth direction dimension are each 3.
Although the case where the chair is changed from 60IaIl to 3801111 is shown, it is clear that even in an area where the width direction dimension is 3501EIB or less or the depth direction dimension is 380cm or more, it is possible to use the chair + ramie if it meets the spirit of the present invention. It is.

As described above, the present invention has 1. S, M, 91 which is one of the frequency bands
In a high-frequency heating device equipped with a high-frequency heating heat source having an oscillation frequency in the 5 MHz band and a heating chamber that generates an excitation 2φ1 oscillation mode, which is the TE mode, in this frequency band, there are two The present invention provides a high-frequency heating device that has a wave mode and has a dimension in the depth direction that is equal to or longer than the dimension in the width direction. (2) Use the TE2φ1 mode that does not have standing waves in the height direction of the heating chamber. As a result, the dimensional accuracy in the height direction of the heating chamber is low, and manufacturing control is easy.

(3) By increasing the depth dimension, the stability of the main body of the device is increased and it is easy to use.

(4) By reducing the width dimension with two standing waves, the strong electric field approaches the center of the heating chamber, allowing efficient high-frequency heating even for small objects. .

(5) When equipped with a turntable, the dimension in the width direction is less than the dimension in the execution direction, making it easy for the user to specify the size of the object to be heated that can be housed in the heating chamber and heated by rotation.

It has the following effects.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway external view of a high-frequency heating device showing an embodiment of the present invention, Fig. 2 is an electric field distribution diagram generated in the heating chamber of Fig. 1, and Fig. 3 is a diagram of the resonant frequency of the heating chamber versus water. Load amount characteristic diagram,
FIG. 4 is a characteristic diagram of a heating chamber that produces the TE2°1 mode of the present invention. 1...91 High frequency heating device having an oscillation frequency in the f5MHz band, 3...Heating chamber that produces TE2φ1. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3y! A 0

Claims (1)

[Claims] 1, S, M, 915MH, one of the frequency bands! The heating chamber includes a high-frequency heating heat source having an oscillation frequency of TE2φ1 in the frequency band, and the heating chamber has two standing wave modes in the width direction and one standing wave mode in the depth direction. and wherein the dimension in the depth direction is greater than or equal to the dimension in the width direction.