JPS61109293A - 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 Field of the Invention The present invention relates to a high-frequency heating device, and more particularly to a radio wave leakage prevention structure for an openable and closable door provided at the entrance of a heating chamber of a high-frequency heating device.

A conventional high-frequency heating device heats or cooks food, which is an object to be heated, placed in a heating chamber using high-frequency energy supplied from a magnetron, which is a source of high-frequency radio waves.

This high-frequency heating device is equipped with a door that can be opened and closed, but there is a small gap between the main body of the heating chamber and the door. Since radio waves leak to the outside through this gap, it is necessary to keep the amount of leakage below the legally permissible value, taking into account the adverse effects on the human body. For this purpose, a leakage prevention mechanism is mainly provided on the door surface.

A typical mechanism for preventing radio wave leakage in doors is the choke method, in which a choke structure with radio wave attenuation grooves is placed around the door periphery, and the dimension from the entrance of the radio wave passage formed by the heating chamber and the door to the groove is There is a method in which the length of each groove is set to 1/4 of the radio wave length used. According to this method, the population of the radio wave path becomes equivalent to being short-circuited in terms of impedance, and has the advantage that leakage of radio waves can be prevented.

In addition, as another radio wave leakage prevention mechanism, there is a method of preventing radio wave leakage by arranging periodic structures in radio wave paths and choke structures to regulate the direction of radio wave propagation. The method shown in the publication is to arrange triangular metal claws with rounded tips so as to protrude in a direction parallel to the radio wave leakage path, and to give a specific relationship to their shape and dimensions. Methods have been proposed to suppress leakage. Furthermore, in Japanese Patent Application Laid-Open No. 58-213588, which aims to make the door more compact, a parallel line transmission line having a T-branch provided on either the main body of the high-frequency heating device or the door is connected through a gap. A method has been proposed in which leakage radio waves are sealed by arranging them in the direction around the door and making the bottom gap wider than the entrance gap of this branching path.

The problem that the invention seeks to solve The point is that the door shape is large.

A means for solving the problem, that is, the present invention provides the above-mentioned device, and is a metal groove (hereinafter referred to as a groove) having a substantially U-shaped cross section at the peripheral edge.
Along with forming the door body.

The opening of the aforementioned groove is opened facing the opening peripheral overhanging wall of the heating chamber (the opening 7 run part or the satush plate part), and a cross section made from a strip-shaped metal thin plate is placed inside the groove. A bent piece (hereinafter referred to as a bent piece) having a substantially T-shaped side surface is arranged so that its opening side coincides with the opening side of the groove, and the short-circuited part of the bent piece does not come into contact with the groove, These bent pieces are provided periodically in the longitudinal direction of the groove, and the horizontal length (hereinafter referred to as width) of the approximately T-shaped portion on the side surface of the bent piece and the width of the leg portion and the short-circuit portion are selected under specific conditions. By doing so, a simple and small door with little radio wave leakage is constructed, and the high frequency heating device is made smaller.

The width W of the approximately T-shaped working bent piece and the width t1 of the leg portion increase the i/reductance component in the characteristic impedance of the radio wave transmission line, thereby suppressing radio wave leakage.

EXAMPLE An example of the present invention will be described below with reference to the drawings. 1. FIG. 1 is a perspective view showing the appearance of a high-frequency heating device according to the present invention. In the figure, 1 is a heating chamber in which food, which is an object to be heated, is stored, and 2 is a cabinet surrounding the heating chamber 1. The front peripheral edge of the cabinet 2 is an extension of the metal plate constituting the cabinet 2 and surrounds the door 3, forming a sash plate 4 which is a part of the peripheral projecting wall of the heating chamber 1.

5 is a flange portion that surrounds the entire circumference of the opening of the heating chamber 1.

It forms part of the heating chamber opening peripheral overhanging wall. 6 is an operation unit and display unit for operating the high-frequency heating device; 7
is the door handle, and 8 is the viewing window.

FIG. 2 is a sectional view of essential parts showing an embodiment of the high frequency heating device of the present invention. The same parts as in Figure 1 are indicated by the same numbers. In FIG. 2, a part of the side wall surface 9 of the heating chamber 1 has a folded part 1o, and the folded part 10 and the lower surface 11 of the open flange part 5 are joined. 12 is a part of the cabinet, and 4 is a sash 1 plate formed by extending the cabinet 12.

In front of the flange portion 5 is a metal groove 13 having a substantially U-shaped cross section, and an opening 14 of the metal groove 13 faces the flange portion 5. The outer bottom surface 15 of the groove 13 is flat and is joined to the door rear plate 13 to form the door.The bent piece 17 is made of a band-shaped metal plate, and its opening 14a is on the opening side of the groove 13. In addition, the grooves 13 are arranged periodically in the longitudinal direction of the groove 13. The depth of the space 18 of the bent piece 17 may be smaller than /4 of the radio wave length used, and is about 15 to
The power should be around 20W.

19 is a gap formed by the groove 13 and the bent piece 17.

The end 20 of the bent piece 17 is parallel to the flange portion 5.

Its final end 21 joins the opening side end of the groove 13 .

22 is a door cover made of plastic.

A plastic cover 26 covers the opening 14a of the bent piece 17. There is a viewing window (not shown) made up of a large number of small holes in the extension of the door rear plate 13, and the entire door is made up of the viewing window (not shown).

6 is a partially enlarged perspective view showing the arrangement of the grooves and bent pieces in FIG. 2, and FIG. 4 is a partially enlarged perspective view showing the shape of the bent pieces.

In FIG. 6, the plastic cover covering the outer wall of the groove 13 and the opening of the bent piece 17 has been removed.

In Figures 3 and 4, when the depth of the groove 13 is 20 to 25 mm and the width WO is 18 to 20 mm, the bent piece 17
The depth d of the space 18 is between 18 and 26. The bent surfaces 24, 25, 26, 27 of the bent piece 17 are arranged so as to be parallel to the flange portion of the heating chamber, and the width to of the space 18 of the bent piece 17 is 25 to 10 scales. The inner wall 28 of groove 17 and the inner wall surface 29 of groove 1 are parallel to each other. Folded piece 1
The cutting depths Mt and M2 of No. 7 are 5 to 10 mm.

When measuring the amount of radio wave leakage under these setting conditions,
The amount of leakage is determined by the width W of the bent piece 17 and the arrangement pitch P (P=W
+ Length of notch outlet) Width of one leg ti.

It varies depending on the width t2 of the short circuit part '51. In particular, when viewed from the side of the bent piece 17, the influence of the width W forming the horizontal plane of the approximately T-shaped bent piece and the width AI of the leg portion of the inner wall 28 (width t2 of the short-circuit portion is assumed to be the same as tl) is large.

In Figure 5, the width W is 25 mm and the pitch P is
This is a characteristic diagram showing the amount of radio wave leakage when tl is varied by 62 at t with a constant value of 50, and 32 is a characteristic curve. As tl becomes smaller, that is, as the width of the leg of the bent piece forming the leakage radio wave transmission line becomes narrower, the amount of leakage gradually decreases, and the amount of leakage can be suppressed to an extremely small amount when jl = 1 to 5++1+++.

FIG. 6 is a characteristic diagram showing the relationship between t1/W and the amount of leakage when the width W is varied in various ways, under the condition of t1=12. In the figure, W-10~40 darkness, t1=1~25II
I! 11 tends to depend on the width W, as surrounded by characteristics 33a and 53b, so the leakage amount also has a certain range. However, t i ,/W=0.2
Below, the amount of leakage decreases rapidly. The optimum value of t1/W is in the range of 0.04 to α2.

The reason why the amount of leakage decreases as the width of the legs of the bent piece is narrowed is that when the width of the transmission line for the leakage radio waves formed by one leg is narrowed, the characteristic impedance of the line changes. This is thought to be because radio wave leakage is suppressed by the increase in the inductance component.

The amount of leakage can also be reduced by changing only the width t2 of the short-circuit portion of the bent piece, but in this case, the bent piece is likely to deform during processing and attachment, so some kind of reinforcement is required.

According to the present invention, as a door component in a high-frequency heating device, a metal groove with a U-shaped cross section is provided, and a strip metal thin plate is placed in this groove with a U-shaped cross section. By arranging periodic structures in the longitudinal direction of the groove, the side surfaces of which are T-shaped and whose horizontal portion length and leg (or short-circuit portion) dimensions are in a predetermined ratio, the opening of the heating chamber is This has the advantage of providing a safe high-frequency heating device because radio waves leaking from the flange portion of the peripheral overhanging wall, the sun sea plate portion, or the gap between the sash plate and the door can be suppressed to an extremely low level. In addition, in the radio wave 71 means, the depth of the U-shaped part of the bent piece can be smaller than 1/ of the radio wave length used, and the leakage prevention effect can be exhibited, so that the door can be made smaller and the high-frequency heating device can be used. It has the advantage that it can be made more compact.

9. As another embodiment of the present invention, the opening of the U-shaped groove and the bent piece may be rotated by 90 degrees to face the Sanon-plate side, and the side wall of the U-shaped groove may be in contact with the flange. 9 The same effects as the present invention are obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the external appearance of a high-frequency heating device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of the same high-frequency heating device according to the present invention, and FIG. 6 is a U-shaped groove according to the present invention. FIG. 4 is a partially enlarged schematic view showing the arrangement of the bent pieces; FIG. 4 is a partially enlarged view of the bent pieces; FIGS. 5 and 6 are characteristic diagrams for explaining the present invention. 1...Heating chamber, 6...Door. 4...Opening peripheral overhanging wall (satush plate). 5...Flange part, 13...Metal groove. 17...Bent piece.

Claims (1)

[Claims] In a heating chamber for storing an object to be heated, and a door that can be opened and closed at the opening of the heating chamber, a metal groove (13) having a U-shaped cross section is provided at the periphery of the door (3), and the groove (13
) to the opening peripheral overhanging wall (4) of the heating chamber (1).
In the groove (13) is a bent piece (17) made of a thin metal plate having a U-shaped cross section and a T-shaped side surface, with the opening side facing the groove (13). A high-frequency heating device characterized in that the grooves (13) are provided on the opening side and periodically in the longitudinal direction of the grooves (13).