JPS6344277B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a microwave heating device for heating an object having a large surface area relative to its volume, such as a sheet. Conventionally, microwave heating devices have been known that supply microwaves to a waveguide having a ladder section and heat an object being scanned over the waveguide using leakage radio waves from the ladder section (for example, (Opening 52-20039). Also known is a microwave heating device that uses a microstrip line as a waveguide and has a ladder section formed in its center conductor (for example, Japanese Patent Application No. 108,644/1982).

However, the plurality of slits constituting the ladder portion were all rectangular and long in the direction perpendicular to the propagation direction of the microwave. Therefore, when an object to be heated is scanned in a direction perpendicular to the direction of propagation of microwaves, it is heated in a striped manner at a portion corresponding to each slit, resulting in so-called uneven baking. Furthermore, in order to prevent uneven baking, the object to be heated is scanned at an angle of 70° to 80° with respect to the direction of propagation of the microwave. However, this required the ladder section to be longer than necessary, making the entire device larger and requiring a more powerful microwave oscillator.

First, we will explain the specific structure of a conventional example using a microstrip line.
In the figure, 2 is a dielectric substrate made of alumina ceramic or the like, and 3 is a grounding plate attached to the bottom surface of this substrate 2. This grounding plate 3 is made of a conductive material such as silver or copper, and is connected to an outer conductor 5 of a coaxial cable 4 connected to one end of the microstrip line 1 . Reference numeral 6 denotes a central conductor in which a plurality of rectangular slits 7, which are long in the direction perpendicular to the microwave propagation direction, are formed, and a ladder portion 8 is formed, which is also made of a conductive material such as silver or copper, and which is made of a conductive material such as silver or copper. It is pasted on the top surface of 2. This center conductor 6 is connected to the center conductor 9 of the coaxial cable 4. 1
0 is a dummy load connected to the other end of the microstrip line 1 , which consumes the microwaves that have not been completely consumed in the ladder section 8 without reflecting them.

In this conventional example, when microwaves are supplied from a microwave oscillator (not shown) to the microstrip line 1 via the coaxial cable 4, some radio waves leak from the ladder section 8 and A thin object to be heated 11 which is scanned over 8 in the direction of the chain arrow is heated. Specifically, it is used for vulcanizing rubber films and fixing toner in electronic copying machines. An example of fixing in a copying machine will be explained below. In this conventional example, there was a risk of uneven burning as described above.

Further, as an example of scanning the copy paper 11, which is the object to be heated, with an inclination, there is one as shown in FIG. In addition, for the parts other than the microstrip line 1 in Figure 2 and the following figures,
Since there is no difference from the embodiment shown in FIG. 1, the explanation will be omitted. In addition, microstrip line 1
Regarding the configuration of each part, the same parts are given the same figure numbers and detailed explanations will be omitted. In FIG. 2, 1 is a microstrip line, and 11 is a copying machine that scans at an angle of approximately 70° to the center line of the microstrip line 1 . In this embodiment, as mentioned above, there was a problem in that the apparatus became large in size.

In order to solve the above-mentioned problems, as shown in Fig. 3, the slits 7 are tilted at an angle of 70° to 80° with respect to the microwave propagation direction (that is, the center of the microstrip line 1 is (gives a slope to the line)
It is conceivable that the copy paper 11 be scanned in the perpendicular direction. However, if the slits 7 are formed with an inclination to the microwave propagation direction,
The amount of microwave leakage in this part is reduced,
This may lead to insufficient fixation.

The present invention solves all of the above-mentioned difficulties, and one embodiment thereof will be described below with reference to FIG. 4. 1 is a microstrip line, and slit 7
Except for the shape of..., the structure is similar to that of the conventional example. The center conductor 6 of this microstrip line 1
, a plurality of wavy slits 7 as shown in the figure are formed at regular pitches along the microwave propagation direction so as to cross the central conductor 6. The slits 7 may be formed by a series of circular arcs in different directions, or may be formed into a sine curve. When the copy paper 11 is scanned in the direction of the arrow on the ladder portion 8 formed by these slits 7, the copy paper 11 is fixed.

In the present invention, since the slits 7 are curved, even if the copy paper 11 is scanned in a direction perpendicular to the direction of propagation of microwaves, uneven burning as in the conventional example does not occur.

Furthermore, since the copy paper 11 can be scanned in a direction perpendicular to the direction of propagation of microwaves, the apparatus does not become bulky, and the drawbacks of the conventional example shown in FIG. 2 can be solved.

Furthermore, since the slits 7 are not formed at an angle with respect to the microwave propagation direction, the amount of radio waves leaked from the ladder portion 8 is sufficient. When experimenting using the same microwave oscillator and microstrip line of the same size, the embodiment of the present invention (Figure 4)
Now, the leakage radio waves (from the ladder section 8) are about 3 to 4 times the amount (electric field strength) of the embodiment shown in FIG.
was able to be observed. Therefore, sufficient fixing can be achieved simply by using a microwave oscillator with an output that is 1/3 to 1/4 that of the conventional example.

As mentioned above, according to the present invention, not only does uneven baking not occur, but the entire device can be downsized, and furthermore, sufficient microwave heating can be achieved only by using an inexpensive, low-output microwave oscillator. The device can be realized.

Although the embodiments have been described using microstrip lines as waveguides, it goes without saying that similar effects can be obtained by using general waveguides.

[Brief explanation of drawings]

1 to 3 are a perspective view and a plan view showing different conventional examples, respectively, and FIG. 4 is a plan view showing an embodiment of the present invention. 1 ... Microstrip line, 6... Center conductor,
7...Slit, 8...Ladder section, 11...Copy paper.

Claims (1)

[Scope of Claims] 1. A waveguide including a plurality of wavy slits formed on one side along the propagation direction of microwaves, and means for scanning the object to be heated over the slits, A microwave heating device characterized in that the slit is formed in a direction transverse to the waveguide. 2. The microwave heating device according to claim 1, wherein the waveguide is formed of a microstrip line, and a slit is formed in the center conductor of the waveguide.