JPS58161290A - Microwave 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 relates to improvements in microwave heating devices. Conventionally, various microwave heating devices have been proposed using microstrip lines in which a ladder pattern is formed on the center conductor or ground conductor (for example, Japanese Patent Applications No. 55-108644 and No. 56-112729).

However, in these conventional examples, the microwave is largely reflected at the rear edge of the slit at the rear end (the end facing the microwave supply side) of the slits forming the ladder pattern. However, there is a risk that standing waves will be generated, causing so-called "uneven heating" of the heated object.

The reason for this is thought to be that the impedance of the rear end C iron of the rearmost slit changes (decreases) rapidly. Therefore, when a thin object to be heated as shown in Figure 1 is scanned over the ladder pattern in the direction of the arrow, only the diagonally shaded area (where standing waves are generated) will be heated strongly (the area where standing waves are generated), and the other areas will be heated. This means that it will not be heated very much.
To explain the figure in more detail, the sine curve indicated by the solid line in this figure is a traveling wave fA) propagating in the microstrip line. Further, the sine curve indicated by the dashed line represents the reflection tI1 of the traveling wave (A) reflected at the reflecting surface (H) (the rear end edge of the rearmost slit). (B). The sine curve indicated by the dotted line is a standing wave (C) generated by combining the traveling wave (A) and the reflected wave (B). As can be seen from this figure, if there is a portion (H) that reflects the traveling wave (A), a standing wave (C) will be generated.

Therefore, if only this reflective surface (H) is removed, the standing wave (C
), but this is practically difficult.

The present invention was made in view of the drawbacks of the conventional examples, and
Without eliminating the standing waves, we can calculate the position where the standing waves occur by χ
・The object is to be reciprocated by the same dimension as n/2+χ/4 (χ is the effective wavelength of the microwave, and n is an integer) to uniformly heat the entire surface of the object to be heated.

That is, the present invention provides a microstrip line in which a plurality of slits are formed in at least one conductor to form a ladder pattern, a means for supplying microwaves to the microstrip line, and a first conductor on the ladder pattern. In this microwave heating device equipped with a means for scanning the object to be heated, at least a part of the slit at the end located near the side opposite to the microwave supply side is periodically closed. , a means is provided for the conductive member to approach and separate from the slit without contacting the slit, and have the following relationship (where χ is the effective wavelength of the microwave within the microstrip line, and n is an integer including 0). This is a characteristic feature.

In addition, as a means to shift the generation position of the standing wave by χ・n/2+χ/4, the specification and drawings of Japanese Patent Application No. 191209/1987 show that the front and rear edges of the slit at the rearmost end are periodically shorted. The means to do so are described. However, in this case, when high-power microwaves were supplied to the microstrip line, sparks were generated each time the line was repeatedly shorted and opened, making the ground conductor susceptible to damage.

Embodiments of the present invention will be described below with reference to the drawings. Third
The figure is a perspective view showing one embodiment of the present invention, and (1) is a microstrip line. This microstrip line 111 consists of a dielectric substrate (2) made of a dielectric material such as polytetrafluoroethylene, a ground conductor (3) made of copper foil (a grounding conductor) attached to the upper surface of the dielectric substrate (2), and The ground conductor (3) has a long slit (5) perpendicular to the propagation direction of the microwave. was established,
A ladder pattern 16) is formed. In this embodiment, the pitch α of the slits 51 is set to 1/4. (7) is a microstrip line (υI), which is a coaxial cable for supplying microwaves. (8
) is a closing copper plate that moves toward and away from each other without contacting it so as to close a part of the slit (5a) at the end facing the microwave supply side.This closed M@ plate (8) is The vibration means (9) provided at the rear end (right end in the figure) of the microstrip line 11) moves periodically in the direction of the arrow. Note that it is desirable that the clearance between the closed copper plate (8) and the ground conductor (3) be less than 1 mm. 11 (11 is a copy paper as an object to be heated to which unfixed toner is adhered, and is conveyed multiple times in the direction of the arrow while being held between two transfer rollers 1+11 fl old trowel. FIG. 8), and Fig. 5 is a plan view thereof.In order to prevent the ground conductor (3) of the microstrip line (1) and the closed copper plate (81) from coming into contact with each other, a thin insulating sheet is placed between them. It is also possible to intervene.

When the occluding copper plate (8) approaches and closes the slit (5a), the microwaves that are about to leak from the slit (5a) are suppressed and the impedance decreases, so that the second slit from the rear 7 ) The microwave is reflected at the rear edge of (5b). Further, when the closed copper plate (8) is separated and the slit 7) (5a) is opened, the microwave is reflected at the rear edge of the rearmost slit (5a), as in the conventional example. Therefore, when the vibration means (9) operates, the closed copper plate (8) moves through the rearmost slit (5).
a) Approaching and separating from each other is repeated, and the position where the standing wave is generated moves back and forth intermittently about 6 times between two positions separated by λ/4. Next, the state of the heating distribution that changes due to the hyperactivity of the standing wave generation position will be explained according to FIG. 6. ill moves in the direction of the arrow with the copy paper, and the shaded area indicates the heated portion of the copy paper tel. In FIG. 6, initially, the blocking copper plate (8) is in a position away from the pickpocket 71-(5a), and the copy paper f1
01 shows the heating state when the closed copper plate (8) approaches the slit 7) (5a) at the same time as the upper part of the ladder pattern (6) is applied. As can be seen from this figure, when the slit (5a) is closed,
The standing wave shifts by a dimension of λ/4. Therefore, when the closed copper plates (8) of Surin 1-(5a) are moved closer and closer to each other and this is repeated, a heating distribution as shown by the shaded area in FIG. 7 is generated. Therefore, if the approach and separation are repeated at a high frequency compared to the traveling speed of 27q[l[l], the entire surface will be heated uniformly.

In addition, in the above embodiment, the blocking copper plate (8) is moved parallel to the microwave propagation direction (horizontal direction), or
This closed copper plate +81 is used with a vibrator or cam,
It may be moved in a direction perpendicular (vertical direction) to the surface of the ladder pattern (6).

According to the present invention, as shown in FIG.
Means for alternately reflecting microwaves is provided, and α−χ・
Since the relationship is n/2+χ/4, the position where the standing wave occurs reciprocates by the same dimension as λ/4, and the object to be heated can be heated uniformly.

However, there is no risk of sparks occurring.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a heating state due to standing waves in a conventional example, Fig. 2 is a waveform diagram showing a state in which standing waves are generated, and Figs. 3 to 7 are diagrams showing an example of the present invention. 5 is a perspective view, FIG. 4 is a partially sectional side view showing the main part, FIG. 5 is a plan view showing the main part, and FIGS. 6 and 7 are schematic diagrams showing the state of heating distribution. be. Ill...Microst IJ tube line, (21 peak dielectric substrate, +31...ground conductor, +41...center conductor, 151 (5a) (5b) slit, 16)
...Ladder pattern, (7) mountain coaxial cable, (81
--Closing copper plate, (9) Vibration means, tlol Inner heated object, (111... Transfer roller. Fig. 1 ◇ Fig. 2 Fig. 5 Fig. 6 ◇

Claims (1)

[Claims] 1. A microstrip line in which a ladder pattern is formed by opening a plurality of slits at a constant pitch α along the propagation direction of microwaves. In the microwave heating apparatus, the microwave heating device is equipped with means for supplying fibro waves to the fibro strip line, and means for scanning the object to be heated on the ladder pattern. In order to periodically close at least a portion of the slit at the end, a means is provided for the conductive member to approach and separate from the slit without contacting the slit (where χ is the microstrip line of the fibrous wave). (n is an integer including 0).