EP3429314A1

EP3429314A1 - High frequency heating device

Info

Publication number: EP3429314A1
Application number: EP17763052.2A
Authority: EP
Inventors: Keijirou Kunimoto; Daisuke Hosokawa; Yoshiharu Oomori
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2016-03-10
Filing date: 2017-03-02
Publication date: 2019-01-16
Also published as: JPWO2017154712A1; JP6893302B2; CN108781488B; EP3429314A4; WO2017154712A1; CN108781488A

Abstract

A high frequency heating device according to the present disclosure includes: a heating chamber having an opening on a front surface and accommodating an object to be heated; a high frequency wave generation unit that supplies high frequency waves to the heating chamber to heat the object to be heated; and a door that covers the opening in an openable manner and has a radio wave sealing portion at a position facing a peripheral edge surface of the opening. The radio wave sealing portion is provided with an open hole formed at a position facing the peripheral edge surface of the opening, and a choke groove curving toward the heating chamber with respect to the open hole. The choke groove is formed by bonding a plurality of conductors. The plurality of conductors includes a first conductor provided with a protrusion protruding to an inner side of the heating chamber near a bonding portion where the plurality of conductors is bonded. A backside space of the protrusion constitutes a part of the choke groove.

Description

TECHNICAL FIELD

The present disclosure relates to a high frequency heating device such as a microwave, and more particularly to a high frequency heating device provided with a radio wave sealing portion that shields radio waves (particularly, microwaves which are high frequency waves) that are going to leak to an outside from between a heating chamber and a door.

BACKGROUND ART

Conventionally, as a most basic concept regarding a radio wave sealing portion used for a high frequency heating device, a quarter-wave impedance inversion method in which a choke groove is formed in a door of the high frequency heating device has been proposed. FIG. 14 is a perspective view showing an external appearance of a microwave which is a conventional high frequency heating device. FIG. 15 is a sectional view, along line 15-15, of a radio wave sealing portion provided between heating chamber 103 and door 102 of the microwave shown in FIG. 14.
High frequency waves generated inside heating chamber 103 provided in microwave main body 101 are going to propagate from right to left (z direction) in FIG. 15 through gap 106 between door 102 and opening peripheral edge surface 105 which is located on an outer periphery of opening 104 of heating chamber 103 so as to face door 102. In the conventional microwave, choke groove 108 formed by bending conductor 107 is provided in door 102, and length L of choke groove 108 is set to be a quarter (about 30 mm) of wavelength λ of a frequency to be used. With this, impedance Zin seen from an opening side of choke groove 108 becomes infinite, so that the high frequency waves in the z direction attenuate (for example, see PTL 1).
In the conventional configuration described above, open hole 109 at an inlet of choke groove 108 and gap 106 are disposed to face opening peripheral edge surface 105, and this configuration generally provides an advantage to reduce the width dimension (z direction) of opening peripheral edge surface 105. However, due to choke groove 108 having large length L, it is difficult to reduce the width (y direction) of door 102.
PTL 1 also discloses a radio wave sealing portion shown in FIGS. 16 and 17 for reducing the depth of choke groove 108. Reducing length L of choke groove 108, that is, making choke groove 108 compact, with radio wave shielding performance being maintained by curving choke groove 108 as described above has been proposed.
In the configuration shown in FIG. 16, a single conductor is bent five times to obtain dead end choke groove 108. In this configuration, conductor 110 for forming the choke groove can be made only by bending a single conductor. Therefore, this configuration is well suited to mass production, and thus, widely applied.
In the configuration shown in FIG. 17, conductor 111 having a recessed shape and conductor 112 having an L shape are joined to each other to form choke groove 108 curving toward heating chamber 103. Similar to the configuration shown in FIG. 15, this configuration has open hole 109 at an inlet of choke groove 108 and gap 106 which are disposed to face opening peripheral edge surface 105, thereby being capable of reducing the width dimension (z direction) of opening peripheral edge surface 105.
Further, a microwave has been proposed in which high frequency wave propagation path 118 defined by a gap between opening peripheral edge surface 105 and door 102 is formed on an inner wall surface 117 side of heating chamber 103 to improve radio wave shielding performance (see PTL 2, for example).
PTL 2 proposes a microwave having door 102 which is provided with, inside of an outer periphery, choke groove 114 formed by bending a single conductor four times as shown in FIG. 18. Protrusion 116 protruding toward heating chamber 103 is formed on outer periphery inner wall 115 on a heating chamber 103 side of door 102. High frequency wave propagation path 118 is formed which attenuates high frequency waves by protrusion 116 and inner wall surface 117 of heating chamber 103 before the high frequency waves enter choke groove 114, with door 102 being closed.
With this configuration, high frequency waves sufficiently attenuate in high frequency wave propagation path 118 before reaching choke groove 114, whereby it is unnecessary to rely only on choke groove 114 for radio wave shielding performance.
In addition, PTL 3 and PTL 4 propose a microwave in which high frequency wave propagation path 118 is formed in inner wall surface 117 of the heating chamber to reduce the width of opening peripheral edge surface 105 as shown in FIG. 18. With this configuration, a wall thickness of microwave main body 101 can be reduced. Thus, it is possible to downsize the main body with the capacity of the heating chamber being unchanged, or to increase the capacity of the heating chamber with the size of the main body being unchanged.
In the conventional choke structure shown in FIG. 17, for example, choke groove 108 curves toward heating chamber 103, and therefore, not only dimension L (y direction) but also the dimension of opening peripheral edge surface 105 in the z direction can be reduced. However, L-shaped conductor 112 constitutes an inner surface of heating chamber 103 and becomes nearly flat when door 102 is closed. Therefore, the strength is likely to be low. In addition, the thickness of L-shaped conductor 112 cannot be increased in the light of weight and cost. Therefore, during bonding between L-shaped conductor 112 and conductor 111, L-shaped conductor 112 is likely to warp or undulate due to stress caused by welding, crimping, or the like. Therefore, there arises a problem of an increase in variation during assembly and degradation in appearance.
On the other hand, in the configuration shown in FIG. 18, the gap between opening peripheral edge surface 105 and conductor 113 can be narrowed, whereby the width dimension of opening peripheral edge surface 105 can be accordingly reduced. However, choke groove 114 curves outward, and thus, opening peripheral edge surface 105 needs to face choke groove 114 across the entire width of choke groove 114. Accordingly, the width dimension of opening peripheral edge surface 105 cannot be decreased at a location facing choke groove 114.
Notably, Unexamined Japanese Patent Publication No. S58-066285 (PTL 5), Unexamined Japanese Patent Publication No. S58-066287 (PTL 6), Unexamined Japanese Patent Publication No. S58-066288 (PTL 7), Unexamined Japanese Patent Publication No. S58-150292 (PTL 8), Unexamined Japanese Patent Publication No. S58-194290 (PTL 9), Unexamined Japanese Patent Publication No. S58-201289 (PTL 10), and Unexamined Japanese Patent Publication No. S58-201290 (PTL 11) are given as documents relating to the prior arts described above.

Citation List

Patent Literatures

PTL 1: Unexamined Japanese Patent Publication No. H06-132078
PTL 2: Japanese Patent No. 4647548
PTL 3: Unexamined Japanese Patent Publication No. S62-5595
PTL 4: Examined Japanese Utility Model Publication No. S51-9083
PTL 5: Unexamined Japanese Patent Publication No. S58-066285
PTL 6: Unexamined Japanese Patent Publication No. S58-066287
PTL 7: Unexamined Japanese Patent Publication No. S58-066288
PTL 8: Unexamined Japanese Patent Publication No. S58-150292
PTL 9: Unexamined Japanese Patent Publication No. S58-194290
PTL 10: Unexamined Japanese Patent Publication No. S58-201289
PTL 11: Unexamined Japanese Patent Publication No. S58-201290

SUMMARY OF THE INVENTION

The present disclosure addresses the foregoing problems, and aims to provide a high frequency heating device having a rigid and stable radio wave sealing structure and enabling reduction in a wall thickness between an outer box of a main body and an inner wall surface of a heating chamber.
In order to address the above-mentioned conventional problems, a high frequency heating device according to the present disclosure includes: a heating chamber having an opening on a front surface and accommodating an object to be heated; a high frequency wave generation unit that supplies high frequency waves to the heating chamber to heat the object to be heated; and a door that covers the opening in an openable manner and has a radio wave sealing portion at a position facing a peripheral edge surface of the opening. The radio wave sealing portion is provided with an open hole formed at a position facing the peripheral edge surface of the opening, and a choke groove curving toward the heating chamber with respect to the open hole. The choke groove is formed by bonding a plurality of conductors. The plurality of conductors includes a first conductor provided with a protrusion protruding to an inside of the heating chamber near a bonding portion of the plurality of conductors. A backside space of the protrusion constitutes a part of the choke groove.
The protrusion is provided near the bonding portion where the conductors are bonded, whereby the conductors constituting the choke groove are three-dimensionally reinforced to have increased strength. Thus, distortion of the bonding portion or variation during assembly can be reduced.
In addition, due to the choke groove curving toward the heating chamber, a resonance space can be formed on a heating chamber side. Therefore, an area of the choke groove facing the peripheral edge surface of the opening can be decreased.
Furthermore, due to protrusion protruding toward the inside of the heating chamber, a gap is formed between a side surface of the heating chamber and the protrusion. The gap functions as a high frequency wave propagation path for attenuating high frequency waves, and accordingly, a gap between the peripheral edge surface of the opening and the conductors can be decreased.
As described above, the width of the peripheral edge surface of the opening can be greatly reduced, whereby a wall thickness between an outer shell of the main body and the inner wall surface of the heating chamber can be greatly reduced.
The present disclosure can provide a high frequency heating device having a rigid and stable radio wave sealing structure and enabling reduction in a wall thickness between an outer box of the main body and the inner wall surface of the heating chamber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a high frequency heating device with a door being opened according to a first exemplary embodiment of the present disclosure.
FIG. 2 is a longitudinal sectional view of the high frequency heating device with the door being closed according to the first exemplary embodiment of the present disclosure.
FIG. 3 is a partial sectional view of a radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present invention.
FIG. 4 is a partial sectional perspective view of the radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure.
FIG. 5 is a diagram showing radio wave leakage characteristics of the high frequency heating device according to the first exemplary embodiment of the present disclosure.
FIG. 6 is a partial sectional view of another radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure.
FIG. 7 is a partial sectional view of still another radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure.
FIG. 8 is a partial sectional view of still another radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure.
FIG. 9 is a partial sectional view of still another radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure.
FIG. 10 is a partial sectional view of a radio wave sealing portion in a high frequency heating device according to a second exemplary embodiment of the present disclosure.
FIG. 11 is a conceptual diagram of high frequency waves propagating to the radio wave sealing portion in the high frequency heating device according to the second exemplary embodiment of the present disclosure.
FIG. 12 is a partial sectional view of a radio wave sealing portion in a high frequency heating device according to a third exemplary embodiment of the present disclosure.
FIG. 13 is a conceptual diagram showing a shape of an inner wall surface of a heating chamber relative to a shape of a protrusion in the third exemplary embodiment of the present disclosure.
FIG. 14 is a perspective view showing an external appearance of a conventional high frequency heating device.
FIG. 15 is a sectional view of a radio wave sealing portion, along line 15-15, in the high frequency heating device shown in FIG. 14.
FIG. 16 is a partial sectional view of a radio wave sealing portion in a conventional high frequency heating device disclosed in PTL 1.
FIG. 17 is a partial sectional view of the radio wave sealing portion in the high frequency heating device.
FIG. 18 is a partial sectional view of a radio wave sealing portion in a conventional high frequency heating device disclosed in PTL 2.

DESCRIPTION OF EMBODIMENTS

A high frequency heating device according to the present disclosure includes: a heating chamber having an opening on a front surface and accommodating an object to be heated; a high frequency wave generation unit that supplies high frequency waves to the heating chamber to heat the object to be heated; and a door that covers the opening in an openable manner and has a radio wave sealing portion at a position facing a peripheral edge surface of the opening. The radio wave sealing portion is provided with an open hole formed at a position facing the peripheral edge surface of the opening, and a choke groove curving toward the heating chamber with respect to the open hole. The choke groove is formed by bonding a plurality of conductors. The plurality of conductors includes a first conductor provided with a protrusion protruding to an inner side of the heating chamber near a bonding portion of the plurality of conductors. A backside space of the protrusion constitutes a part of the choke groove.
With this configuration, the conductors constituting the choke groove are three-dimensionally reinforced, whereby strength is increased. Accordingly, distortion of the bonding portion which receives stress due to bonding such as welding is prevented, whereby variation can be reduced.
In addition, due to the choke groove curving toward the heating chamber, a resonance space can be formed on a heating chamber side. Therefore, an area of the choke groove facing the peripheral edge surface of the opening can be decreased. Furthermore, due to protrusion protruding toward the inside of the heating chamber, a gap is formed between a side surface of the heating chamber and the protrusion. The gap functions as a high frequency wave propagation path for attenuating high frequency waves, and accordingly, a gap between the peripheral edge surface of the opening and the conductors can be decreased.
In this way, the width of the peripheral edge surface of the opening can be greatly reduced, whereby a wall thickness between an outer shell of a main body and an inner wall surface of the heating chamber can be greatly reduced.
In addition, the back surface of the protrusion is used as the resonance space, whereby a wasteful space can be reduced, and the radio wave sealing portion can be made compact.
A height of the protrusion may be from 2 mm to 10 mm inclusive.
When the height of protrusion is 2 mm or more, stable radio wave shielding performance can be maintained. When the height of protrusion is 10 mm or less, the protrusion does not interfere with an object to be heated which is to be accommodated in the heating chamber, and further, degradation in appearance can be prevented.
A surface of the protrusion facing the inner wall surface of the heating chamber has an inclined surface inclined to the heating chamber.
With this configuration, the gap formed between the protrusion and the inner wall of the heating chamber forms an inclined path which is gradually narrowed. High frequency waves entering the inclined path are repeatedly reflected at different angles on a wall surface of the inclined path, and turn back toward an inlet. Accordingly, the amount of high frequency waves entering the choke groove can be reduced, whereby the radio wave shielding performance can be improved.
A proportion of high frequency waves turning back to the inlet is determined based on an angle of inclination, a height of the protrusion, a width of the inclined path, the gap between the peripheral edge surface of the opening and the conductors, and other factors. In addition, in the configuration where the door is rotated, interference between the protrusion and the inner wall surface of the heating chamber upon opening and closing the door can be prevented.
The inner wall surface of the heating chamber facing the inclined surface of the protrusion may be inclined to form a constant gap with the inclined surface. "Being constant" herein means "being substantially constant".
With the configuration described above, when the door is rotated, the gap and angle between the protrusion and the inner wall surface of the heating chamber upon opening and closing the door can be stably maintained, whereby the radio wave shielding performance upon opening and closing the door can be stabilized.
Exemplary embodiments of the present disclosure will be described below with reference to the drawings. Note that the exemplary embodiments should not be construed as limiting the present disclosure.

(First exemplary embodiment)

FIG. 1 is a perspective view of a high frequency heating device with a door being opened according to a first exemplary embodiment of the present disclosure. FIG. 2 is a longitudinal sectional view of the high frequency heating device with the door being closed according to the first exemplary embodiment of the present disclosure. FIG. 3 is a partial sectional view of a radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure. FIG. 4 is a partial sectional perspective view of the radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure. FIG. 5 is a diagram showing radio wave leakage characteristics of the high frequency heating device according to the first exemplary embodiment of the present disclosure. FIG. 6 is a partial sectional view of another radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure. FIG. 7 is a partial sectional view of still another radio wave sealing portion in the high frequency heating device according to the first exemplary embodiment of the present disclosure.
In the following description, a side where opening 4 of heating chamber 3 is formed is defined as a front side of high frequency heating device 1, and an inner side of heating chamber 3 is defined as a rear side (inner side) of high frequency heating device 1. Further, a right side of high frequency heating device 1 when high frequency heating device 1 is viewed from front is simply defined as a right side, and a left side of high frequency heating device 1 when high frequency heating device 1 is viewed from front is simply defined as a left side.
As shown in FIG. 1, microwave 1 which is a representative example of the high frequency heating device has heating chamber 3 inside box-shaped outer box 2 which is open at a front surface. Food which is a representative example of an object to be heated is accommodated in heating chamber 3. Door 5 which opens and closes opening 4 is mounted to the front surface of outer box 2. Opening peripheral edge surface 6 (hereinafter referred to as front plate 6) is provided between opening 4 and outer box 2 so as to face door 5 when door 5 is closed.
As shown in FIG. 2, a space is formed between an outer periphery of heating chamber 3 and outer box 2. Components for heating control such as high frequency wave generation unit 11 are housed in space 10 below heating chamber 3. High frequency wave generation unit 11 that is one of heating units for heating food includes components such as magnetron 12, wave guide 13, and rotating antenna 14.
High frequency waves generated by magnetron 12 are transmitted through wave guide 13 and radiated to the inside of heating chamber 3. Rotating antenna 14 which is rotated for diffusing radio waves diffuses the high frequency waves radiated to heating chamber 3 throughout heating chamber 3. This configuration prevents standing waves of the high frequency waves from being fixed, thereby reducing uneven heating of food. Fan 15 for cooling magnetron 12 mainly during high frequency heating is provided near magnetron 12. Fan 15 supplies cooling air to magnetron 12.
Upper heater 17 which is one of the components for heating food is provided in space 16 above heating chamber 3. Inner heater 19 which is one of the components for heating food is provided in space 18 behind heating chamber 3.
Door 5 is configured to be opened and closed vertically. However, a manner of opening and closing door 5 is not limited to this configuration. The door may be supported on either a left end or a right end so as to be opened and closed laterally, or the door may be drawable.
Next, a configuration of radio wave sealing portion 30 provided at a position facing front plate 6 will be described with reference to FIG. 3. FIG. 3 is a partial transverse sectional view of a front left part of microwave 1 with door 5 being closed.
In FIG. 3, radio wave sealing portion 30 is provided with open hole 31 formed on a surface facing front plate 6, and choke groove 32 curving toward heating chamber 3 with respect to open hole 31. Choke groove 32 is formed by bonding recessed plate 33 (conductor) and projecting plate 34 (conductor) to each other. Projecting plate 34 has protrusion 36 which is formed near bonding portion 35 of both plates so as to protrude to the inside of heating chamber 3 (to the inner side of heating chamber 3). A state of being near bonding portion 35 means herein that protrusion 36 is located within 30 mm from bonding portion 35, for example. It is more preferable that protrusion 36 is formed within 20 mm from bonding portion 35.
Bonding portion 35 of both plates is disposed on a heating-chamber 3 center side of protrusion 36 such that backside space 74 of protrusion 36 on projecting plate 34 constitutes a part of choke groove 32.
Protrusion 36 is provided to form constant gap 37 with inner wall surface 7 of heating chamber 3 when door 5 is closed. An effective depth of choke groove 32 is set to be approximately a quarter of the wavelength of high frequency waves radiated to heating chamber 3.
High frequency waves radiated to the inside of heating chamber 3 enter choke groove 32 through open hole 31 while attenuating and being adjusted through gap 37 and gap 38 between front plate 6 and projecting plate 34. A phase of high frequency waves reflected in choke groove 32 is inverted at open hole 31 of choke groove 32, and therefore, impedance becomes infinite. Accordingly, a leakage of high frequency waves can be prevented.
In addition, high frequency waves attenuate while propagating through gap 37 between protrusion 36 and inner wall surface 7 of heating chamber 3, and therefore, a propagation length of gap 38 between front plate 6 and projecting plate 34 can be decreased. Further, due to choke groove 32 curving toward heating chamber 3, an area of radio wave sealing portion 30 facing front plate 6 can be accordingly decreased, and thus, a wall thickness between inner wall surface 7 of heating chamber 3 and outer box 2 can be greatly reduced.
Plastic choke cover 42 is provided between recessed plate 33 and front plate 6. Choke cover 42 prevents entry of foreign matters into choke groove 32 and improves appearance.
Inner glass 45 is disposed on a heating chamber 3 side of protrusion 36 for preventing entry of hot air, foreign matters, or steam through a punched hole (not shown) formed in the center of projecting plate 34.
Recessed plate 33 is formed by bending a plate four times. Protrusion 36 of projecting plate 34 is molded by drawing press. Recessed plate 33 and projecting plate 34 are bonded at bonding portion 35 by projection welding.
Bonding portion 35 is disposed on the heating-chamber 3 center side of protrusion 36 and near protrusion 36, whereby the strength is improved. Due to protrusion 36 being formed into a box shape, the strength of projecting plate 34 can be dramatically improved as compared to a flat plate. Therefore, even if strain and stress are generated on bonding portion 35 due to welding, the deformation of projecting plate 34 such as warpage or waving can be significantly reduced. Accordingly, variation during assembly is prevented and appearance can be improved.
Slits 43 and slits 44 are formed at regular intervals in end 40 of recessed plate 33 and end 41 of projecting plate 34, respectively, to form a periodic structure as shown in FIG. 4. With this, the propagation of high frequency waves along choke groove 32 is suppressed, whereby a leakage of high frequency waves can further be reduced.
Next, a relation between the height of protrusion 36 and radio wave shielding performance will be described with reference to FIG. 5. FIG. 5 shows radio wave leakage characteristics for each gap of door 5 with the horizontal axis indicating the height of protrusion 36 and the vertical axis indicating leakage of radio waves. The leakage of radio waves is represented by a power density of leaked radio waves at a position 5 cm away from the gap between door 5 and the main body of microwave 1 when the magnetron of the microwave is driven. The technical standard of Electrical Appliances and Materials Safety Act specifies that the leakage of radio waves is 1 mW/cm² or less during operation with door 5 being closed, and that the leakage of radio waves is 5 mW/cm² or less in a state where door 5 is opened to a position just before the position where an oscillation stop device for the magnetron is operated.
The characteristics with a 1 mm gap of door 5 in FIG. 5 indicate radio wave leakage performance with door 5 being closed, and the prescribed value of 1 mW/cm² or less in this state is satisfied, regardless of the height of the protrusion. However, if the protrusion is lower, a margin from the prescribed value is small, and therefore, the height of the protrusion is preferably 2 mm or more in consideration of a margin.
The characteristics with a 3 mm gap of door 5 indicate a state where door 5 is opened to the maximum position where the magnetron is operable, and the height of the protrusion for satisfying the prescribed value of 5 mW/cm² or less is 2 mm or more. In this case, a preferable height of the protrusion is 5 mm or more in consideration of a margin.
As described above, it is preferable that, as a minimum necessary condition for satisfying the regulation, the height of the protrusion is set to be 2 mm or more. Considering a margin, the height of the protrusion is set to be 5 mm or more.
Meanwhile, the higher the protrusion is, the less radio waves leaks. However, if the height exceeds 10 mm, it is highly likely that protrusion 36 interferes with an object to be heated or a container accommodated in heating chamber 3 upon closing door 5. In addition, when door 5 is opened, a step is conspicuous, which may deteriorate appearance. Accordingly, the height of the protrusion is preferably 10 mm or less.
From the above, when the height of the protrusion is set to be from 2 mm to 10 mm inclusive, the radio wave shielding performance that satisfies the prescribed values can be obtained. Further, the interference between protrusion 36 and the object to be heated which is to be accommodated in heating chamber 3 can be prevented, and the deterioration in appearance can be prevented.
The present exemplary embodiment shows the configuration in which two plates, recessed plate 33 and projecting plate 34, are bonded to each other at bonding portion 35. However, the present exemplary embodiment does not limit the number and shape of plates, the bonding method, and the like. For example, bonding portion 53 between projecting plate 50 and recessed plate 55 may be provided at the back of protrusion 36 as shown in FIG. 6.
Further, the present disclosure is not limited to the configuration shown in FIG. 3. For example, recessed plate 60 is bent six times to form choke groove 76 having a complex shape with a plurality of curves as shown in FIG. 7.
Further, end 61 of recessed plate 60 may be bent in the opposite direction or end 61 may not be bent. With this configuration, the high frequency wave propagation path required for radio wave shielding can be achieved with narrower space, whereby radio wave sealing portion 30 can be made more compact.
In the configuration in the first exemplary embodiment, protrusion 36 serves as a resonance space of choke groove 32. Therefore, a wasteful space can be reduced, whereby the radio wave sealing portion can be made compact.
Further, choke groove 32 curves only toward heating chamber 3 with respect to open hole 31, whereby the dimension from open hole 31 to an outside (to the left in FIG. 6) can be minimized. Accordingly, an area of choke groove 32 facing front plate 6 can be significantly reduced.
In addition, bonding portion 35 is provided on the heating-chamber 3 center side of protrusion 36. Therefore, bonding portion 35 can be disposed at the back of inner glass 45, whereby a weld mark can be made invisible. Thus, the appearance can further be improved.
Moreover, recessed plate 33 has a shape in which choke groove 32 is open, and therefore, can be formed by a single bending process by means of a press. Thus, recessed plate 33 is easy to be formed, and low-cost production can be achieved.
In the present exemplary embodiment, end 40 of recessed plate 33 is directed outward (directed to an opposite side to heating chamber 3). However, it is not limited to have such a shape. For example, the end may be directed inward (toward heating chamber 3) like end 81 of recessed plate 80 shown in FIG. 8, or the end may not be bent.
In the present exemplary embodiment, projecting plate 34 constitutes one surface of door 5, and when door 5 is closed, projecting plate 34 constitutes a part of the inner wall of heating chamber 3. However, the configuration is not limited thereto. As shown in FIG. 9, recessed plate 83 may constitute one surface of door 5, and serve as the inner wall of heating chamber 3. Projecting plate 84 is bonded to recessed plate 83 at bonding portion 85 to form choke groove 72.

(Second exemplary embodiment)

Next, a configuration around a radio wave sealing portion in a high frequency heating device according to a second exemplary embodiment of the present disclosure will be described in detail with reference to the drawings. FIG. 10 is a partial sectional view of the radio wave sealing portion in the high frequency heating device according to the second exemplary embodiment of the present disclosure. FIG. 11 is a conceptual diagram of high frequency waves propagating to the radio wave sealing portion in the high frequency heating device according to the second exemplary embodiment of the present disclosure. It should be noted that, in the present exemplary embodiment, configurations and functions similar to those in the first exemplary embodiment are given identical reference signs, and are not described in detail below. The overall configuration of the high frequency heating device in the present exemplary embodiment is similar to the configuration of microwave 1 shown in FIGS. 1 to 7.
The second exemplary embodiment is different from the first exemplary embodiment in that, in radio wave sealing portion 90, protrusion facing surface 92 of protrusion 91 facing inner wall surface 7 of heating chamber 3 is inclined to heating chamber 3, as shown in FIG. 10. Specifically, gap 93 between inner wall surface 7 of heating chamber 3 and protrusion facing surface 92 is formed into a wedge shape.
When high frequency waves enter into wedge-shaped gap 93 at angle θ larger than a predetermined angle, the high frequency waves are repeatedly reflected on inner wall surface 7 of heating chamber 3 and protrusion facing surface 92. During the repeated reflection, the high frequency waves are deflected and returned back to heating chamber 3 as indicated by arrows in FIG. 11. Therefore, this configuration can reduce a proportion of high frequency waves propagating through gap 93 and gap 38 between front plate 6 and projecting plate 34 and reaching choke groove 32. Thus, a leakage of high frequency waves can further be reduced.
When an axis of rotation of door 5 for closing and opening door 5 is provided inside door 5, the tip of protrusion 91 located on a rotating end (upper side if door 5 is a front open door) upon opening and closing door 5 follows a trajectory to get close to the bonding portion between inner wall surface 7 of heating chamber 3 and front plate 6. To avoid interference between protrusion 91 and inner wall surface 7 of heating chamber 3 due to variation during assembly, a gap between inner wall surface 7 of heating chamber 3 and protrusion facing surface 92 is generally set to be large. In the present exemplary embodiment, protrusion facing surface 92 is inclined to heating chamber 3. Therefore, interference between protrusion 91 and inner wall surface 7 of heating chamber 3 can be avoided without increasing the volume of gap 93.

(Third exemplary embodiment)

Next, a configuration around a radio wave sealing portion in a high frequency heating device according to a third exemplary embodiment of the present disclosure will be described in detail with reference to the drawings. FIG. 12 is a partial sectional view of the radio wave sealing portion in the high frequency heating device according to the third exemplary embodiment of the present disclosure. FIG. 13 is a conceptual diagram showing a shape of an inner wall surface of a heating chamber relative to a shape of a protrusion in the third exemplary embodiment of the present disclosure. It should be noted that, in the present exemplary embodiment, configurations and functions similar to those in the first and second exemplary embodiments are given identical reference signs, and are not described in detail below. The overall configuration of the high frequency heating device in the present exemplary embodiment is similar to the configuration of microwave 1 shown in FIGS. 1 to 9.
The third exemplary embodiment is different from the first and second exemplary embodiments in that, in radio wave sealing portion 90, end face 94 of inner wall surface 7 of heating chamber 3 facing inclined protrusion facing surface 92 is inclined so as to form substantially constant gap 95 with protrusion facing surface 92, as shown in FIGS. 12 and 13.
As shown in FIG. 13, predetermined space X is formed so that protrusion 91 and inner wall surface 7 of heating chamber 3 do not interfere with each other even if the relative position between protrusion 91 and inner wall surface 7 of heating chamber 3 varies in a direction parallel to the surface of front plate 6 due to variation in size or mounting variation. Protrusion facing surface 92 and end face 94 are inclined substantially parallel to each other, and therefore, width H of gap 95 is smaller than space X according to inclination angle θ. As described above, width H of gap 95 can be decreased, whereby attenuation of propagating high frequency waves can be increased.

INDUSTRIAL APPLICABILITY

As described above, the high frequency heating device according to the present disclosure is applicable not only to single-function microwaves having only a high frequency heating function but also microwaves having an oven function or grilling function and microwaves having a steam function. Thus, the high frequency heating device according to the present disclosure is widely applicable to domestic and industrial microwaves.

REFERENCE MARKS IN THE DRAWINGS

1: microwave (high frequency heating device)
2: outer box
3: heating chamber
4: opening
5: door
6: opening peripheral edge surface (front plate)
7: inner wall surface
11: high frequency wave generation unit
30, 90: radio wave sealing portion
32, 72, 76: choke groove
33, 55, 60, 80, 83: recessed plate (conductor)
34, 50, 84: projecting plate (conductor)
35, 53, 85: bonding portion
36, 91: protrusion
74: backside space
92: protrusion facing surface

Claims

A high frequency heating device comprising:
a heating chamber having an opening on a front surface and accommodating an object to be heated;

a high frequency wave generation unit that supplies high frequency waves to the heating chamber to heat the object to be heated; and

a door that covers the opening in an openable manner and has a radio wave sealing portion at a position facing a peripheral edge surface of the opening,
wherein the radio wave sealing portion is provided with an open hole formed to face the peripheral edge surface of the opening, and a choke groove that curves toward the heating chamber with respect to the open hole,
the choke groove is formed by bonding a plurality of conductors,
the plurality of conductors includes a first conductor provided with a protrusion protruding toward an inner side of the heating chamber near a bonding portion of the plurality of conductors, and
a backside space of the protrusion constitutes a part of the choke groove.
The high frequency heating device according to claim 1, wherein a height of the protrusion is from 2 mm to 10 mm inclusive.
The high frequency heating device according to claim 1, wherein the protrusion has a surface facing an inner wall surface of the heating chamber, the surface having an inclined surface inclined to the heating chamber.
The high frequency heating device according to claim 3, wherein the inner wall surface of the heating chamber facing the inclined surface of the protrusion is inclined to form a constant gap with the inclined surface.