JP2012117753A - Microwave heating apparatus - Google Patents

Abstract

A microwave heating apparatus capable of effectively reducing the loss of microwaves in a visible light transmitting member provided in a heating chamber and maintaining high heating efficiency of an object to be heated.
A heating chamber having a plurality of wall surfaces including a metal member, an opening for taking in and out the object to be heated, and a door for opening and closing the opening, and containing the object to be heated and cooking by heating. A visible light transmitting member provided on a part of the wall surface including the door 110 constituting the heating chamber 50 so as to face the heating chamber, and a magnetron 30 for generating a microwave for heating the object to be heated. The visible light transmitting member is longer than the dimension ratio of the vertical and horizontal sides of the wall surface provided, and further optically toward the heating chamber. By adopting a configuration in which the viewing angle is widened in a substantially horizontal direction, the area can be reduced, so that the loss of microwaves is suppressed and the object is supplied with high efficiency.
[Selection] Figure 1

Description

  The present invention relates to a microwave heating apparatus that heats an object to be heated with microwaves.

  Conventional microwave heating apparatuses generally include a heating chamber that accommodates an object to be heated, as represented by a microwave oven, and microwaves generated by microwave generating means such as a magnetron are supplied to the heating chamber. To subject the object to be heated to dielectric heating.

  As a technique for feeding microwaves into the heating chamber, a microwave transmission waveguide is provided, an antenna is provided in an opening that penetrates from the waveguide to the heating chamber, and the microwave is led into the heating chamber. It radiates | emits (for example, refer patent document 1).

  FIG. 11 shows a conventional microwave heating apparatus described in Patent Document 1. In FIG. As shown in FIG. 11, an antenna 15 and a horizontal rotation component 17 are provided at substantially the center of the coupling hole 20 between the waveguide 14 and the heating chamber 2. 2 to radiate. A heater 10 is provided around the antenna.

JP 58-181289 A

  However, the power feeding unit is provided on any wall surface of the heating chamber so that microwaves are efficiently supplied to the object to be heated placed in the heating chamber. In addition, there may be a need to arrange other members.

  For example, a member such as a radiant heating element (heater) for heating an object to be heated by radiant heat, a temperature detecting means for detecting the temperature of the heating chamber, or a metal fitting for supporting and fixing these is provided around the antenna in the heating chamber. By being present, the microwave radiation from the antenna is affected by the shape and arrangement of those members, and the electric field distribution is biased or absorbed, resulting in heat loss and deterioration of the heating efficiency of the object to be heated. .

  In addition, in order to improve the user's convenience, a window is provided on the front surface with a door for taking in and out the object to be heated so that the presence of the object to be heated in the heating chamber and the heating state can be confirmed. There is. In addition, there is an illumination light source that illuminates the inside of the heating chamber and an illumination window that transmits the illumination light, so that the visibility of the inside of the heating chamber is improved.

  Conventionally, those in which a plurality of holes are arranged in a metal plate (punching plate) are widely used so that visible light can be transmitted while shielding microwaves from the heating chamber.

  However, if the punching plate surface is exposed to the heating chamber as it is, the use of a microwave heating device (oil or the like scatters from the object to be heated such as food) is not cleanable when dirt is attached, and is left as it is. However, it was difficult to use because the heating chamber was difficult to see and the lighting effect was reduced. For this reason, a glass plate is provided so as to face the heating chamber together with a punching plate for shielding radio waves to improve the cleaning property.

  On the other hand, when the dielectric glass is exposed to the heating chamber, the microwave is absorbed and the heating efficiency of the object to be heated is lowered. This has a larger influence on the heating efficiency as the glass surface area and the volume of the glass exposed to the heating chamber are larger, that is, in the heating chamber illumination glass and the heating chamber viewing window.

  In recent years, microwave ovens for cooking food tend to increase the volume of the heating chamber by providing shelves on which food can be placed in multiple stages, and with this trend, door windows and lighting windows tend to increase in size. is there. As described above, there is room for improvement in improving the heating efficiency in configuring the visible light transmitting member.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a microwave heating apparatus that increases the heating efficiency of an object to be heated by reducing the loss of microwave radiation.

  A heating chamber that has a plurality of wall surfaces including a metal member, an opening for taking in and out the object to be heated, and a door that opens and closes the opening, accommodates the object to be heated and cooks therein, and constitutes the heating chamber A visible light transmitting member provided on a part of the wall surface including the door facing the heating chamber, microwave generating means for generating microwaves for heating the object to be heated, and microwaves in the heating chamber The visible light transmitting member is vertically longer than the dimensional ratio of the vertical and horizontal sides of the wall surface provided, and further optically extends the viewing angle in a substantially horizontal direction toward the heating chamber. It is a configuration.

  As a result, the width (horizontal) dimension of the visible light transmitting member can be reduced, so that the exposure of the visible light transmitting member in the heating chamber is reduced, and the microwave radiation is absorbed by the visible light transmitting member. Since the rate of loss is reduced, it is supplied to the object to be heated with high efficiency.

  The microwave heating apparatus of the present invention can effectively radiate microwaves into a heating chamber and maintain the heating efficiency of an object to be heated high.

Front sectional drawing of the microwave heating device in Embodiment 1 of this invention Side surface sectional drawing of the microwave heating apparatus in Embodiment 1 of this invention Front view of microwave heating apparatus in Embodiment 1 of the present invention WW sectional drawing of the visual recognition window in the microwave heating device in Embodiment 1 of the present invention. Sectional drawing of the electric power feeding part in Embodiment 1 of this invention Schematic configuration diagram of a power feeding unit in Embodiment 1 of the present invention The figure which shows the other antenna shape in Embodiment 1 of this invention Sectional drawing which shows the shape of the antenna board in Embodiment 1 of this invention Sectional drawing which shows the structure of the reflective wall in Embodiment 1 of this invention Detailed sectional view of the power feeding section in the first embodiment of the present invention Front sectional view of a conventional microwave heating device

1st invention has the several wall surface containing a metal member, the opening which puts in / out a to-be-heated object, and the door which opens and closes this opening, The heating chamber which accommodates a to-be-heated object inside and heat-cooks it And a visible light transmitting member provided on a part of the wall surface including the door constituting the heating chamber so as to face the heating chamber, and a microwave generating means for generating a microwave for heating the object to be heated And a feeding section that feeds microwaves to the heating chamber, wherein the visible light transmitting member is longer than the dimension ratio of the vertical and horizontal sides of the wall surface provided, and further optically approximately toward the heating chamber. The viewing angle is widened in the horizontal direction.

  Thereby, since the same effect can be obtained even if the width (horizontal direction) dimension of the visible light transmitting member is reduced, the exposed area of the visible light transmitting member in the heating chamber can be reduced. The ratio of loss due to absorption by the visible light transmitting member is reduced, and the material is supplied to the object to be heated with high efficiency.

  According to a second aspect of the present invention, the visible light transmitting member according to the first aspect of the present invention is configured to widen the viewing angle by changing the thickness of the glass in a substantially horizontal direction, and the surface facing the heating chamber of the glass is a conductive metal. The conductive film layer made of an oxide is provided.

  Thereby, since the electric field generated by the microwave can be eliminated by the conductive coating layer, the absorption of the microwave by the visible light transmitting member can be reduced. Further, even if the glass volume is increased by changing the thickness of the glass in order to widen the horizontal viewing angle, an increase in the loss of microwaves associated therewith can be suppressed, so that the object is heated with high efficiency.

  In a third invention, the visible light transmitting member in the first or second invention is an illumination window that transmits illumination light of a heating chamber from a light source. Illumination from the light source passes through the visible light transmitting member and optically spreads in a substantially horizontal direction, so that a wide range of the heating chamber can be irradiated even if the width of the illumination window is reduced.

  Thereby, since absorption of a microwave can be suppressed, it supplies to a to-be-heated material with high efficiency. Furthermore, even in the case where a shelf capable of placing an object to be heated in a plurality of stages is provided in the heating chamber, the visible light transmitting member is configured to be vertically longer than the dimension ratio of the vertical and horizontal sides of the wall surface, thereby placing the object to be heated. Even when the heating chamber is partitioned by, for example, any height can be illuminated.

  In a fourth invention, the visible light transmitting member in the first or second invention is a viewing window provided on a heating chamber door for visually recognizing the inside of the heating chamber.

  As a result, the horizontal width of the viewing window can be reduced with respect to the opening surface of the heating chamber provided with the door, and accordingly, absorption of microwaves can be suppressed, so that the object can be supplied with high efficiency. The Furthermore, even when the heating chamber is provided with shelves on which the object to be heated can be placed in a plurality of stages, the viewing window is configured to be vertically long with respect to the opening surface, so that any object to be heated can be visually recognized. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 to FIG. 2 are main part cross-sectional views showing a schematic configuration of a microwave oven that is a microwave heating apparatus according to an embodiment of the present invention, and FIG. 1 is viewed from the front (door side into which an object to be heated is placed). FIG. 2 is a sectional configuration view as seen from the side.

  1 and 2, a heating chamber 50 for storing an object to be heated such as food has a wall surface made of a metal material, and a power feeding unit 40 for feeding microwaves is formed at a substantially upper center of the heating chamber 50. A microwave lead-out hole 41, an antenna shaft 42, and an antenna plate 43 are arranged to radiate microwaves into the heating chamber 50.

  The waveguide 35 is a transmission means for transmitting the microwave radiated from the magnetron 30 which is a microwave generation means to the power feeding unit 40.

  The food 200 that is the object to be heated is placed on a table 80 placed on a shelf 58 provided in the heating chamber 50. The shelves 58 are provided in a plurality of stages on the side surfaces on both sides so that the user can select the height on which the food is placed according to the form of the food and cooking.

  A heater 55 is provided in the upper part of the heating chamber 50, and the food can be directly heated by the radiant heat of the heater 55 in addition to the heating by the microwave, corresponding to a plurality of cooking menus.

  The heater 55 has a configuration in which a heating wire is sealed together with a filler in a copper pipe. One end (terminal side) is fixed to the rear wall surface of the heating chamber, and the tip (heat generating portion exposed to the heating chamber) side is held by the heater support member 56.

  The heater support member 56 is made of a thermosetting resin material and is configured to support with a degree of freedom corresponding to the thermal expansion of the heater. Note that the material of the heater support member 56 may not be a resin but may be made of ceramic such as an insulator according to the required heat resistance temperature, and the influence on the microwave can be made smaller than that of the metal fitting.

  The structure of the heater support member 56 is provided to prevent deformation and misalignment due to impact during use and thermal expansion and softening during heater energization when the heater 55 is transported, but is suitable for these purposes. The configuration is not limited as long as it is provided, and for example, a concave or convex portion may be provided on the wall surface to directly or indirectly support or sandwich the heater. As a result, simplification of the configuration and loss of microwaves can be expected.

  In addition, a lower heater 62 is provided below the bottom surface of the heating chamber 50. A convection heater 61 for cooking hot air and a fan 60 are provided on the rear side, and hot air is sent to the heating chamber 50. Further, the temperature of the heating chamber 50 is detected by the thermistor 75 during heating.

  The food is put into the heating chamber by opening the door 110. An operation / display unit 100 is arranged above the door 110, and an operation switch (not shown) and an operation setting button (not shown) are provided. Also, the heating time (heating temperature) can be arbitrarily set by the user with the operation knob 101 and is instructed to the control means 90.

  The illumination 70 is provided, and the heating condition of the food can be visually observed by the user by illuminating the inside of the heating chamber 50 during the heating operation. An illumination window 71 that is a visible light transmissive member is provided in front of the illumination 70.

  The illumination window 71 is made of heat resistant glass. The illumination window 71 is vertically long so that the light is not obstructed regardless of the shelf 80 on which the food 200 is placed on either of the two upper and lower shelves. Thus, the irradiation range can be widened even if the lateral width is reduced.

  Accordingly, the shape is longer than the dimensional ratio of the vertical and horizontal sides of the wall surface 52. In the present embodiment, the dimensions of the illumination window are 150 mm long and 50 mm wide.

  A conductive film 72 is provided on the side of the illumination window 71 facing the heating chamber 50. As a result, the electric field generated by the microwave can be eliminated by the conductive coating layer, so that the absorption of the microwave in the illumination window 71 can be reduced.

  The material for the conductive coating layer is preferably highly conductive, but conductive metal oxides such as tin oxide and indium oxide are preferable in terms of conductivity and durability. In addition, you may comprise the metal plate which provided the opening between the illumination 70 and the illumination window 71 so that light may pass.

  In this case, it is possible to prevent the loss of radio waves by setting the aperture to a hole diameter or interval that does not allow microwaves to pass. The illumination 70 is not limited to a light bulb but may include LED illumination. In this case, similar illuminance can be obtained and power consumption can be reduced. In addition, even when there are restrictions on the arrangement of the light source and the illumination window, it can be avoided by optical consideration, and as a result, the degree of freedom in device design increases.

  The door 110 is provided with an open / close door detection switch (not shown), and is not operated unless the door 110 is completely closed. Also, it functions as a safety device so that if the door is opened during operation, the operation is immediately stopped.

  A viewing window 111, which is a visible light transmissive member made of heat-resistant glass, is provided at the center of the door 110 facing the heating chamber.

  The viewing window 111 is vertically long so that the state of the heating chamber can be seen without being blocked even if the table 80 on which the food 200 is placed is placed on either of the two upper and lower shelves, but the light is refracted in the lateral direction. This provides a wide-angle lens effect, so that the field of view can be widened even if the lateral width is reduced. Accordingly, the shape is longer than the size ratio of the vertical and horizontal sides of the opening 51 of the heating chamber 50.

  As shown in FIG. 3, specifically, in the present embodiment, the heating chamber 50 is a rectangular parallelepiped having a width of 450 mm, a height of 300 mm, and a depth of 400 mm, and has an effective volume of 54 liters.

  The size of the opening 51 of the heating chamber is 450 mm in width and 300 mm in height, and the size of the viewing window is 220 mm in width and 240 mm in height, which is longer than the vertical / horizontal dimension ratio of the opening of the heating chamber 50 and less than half the area. It has become. By reducing the area, microwave absorption can be reduced.

  4 is a cross-sectional view of the viewing window in FIG. 3 in the horizontal direction (W-W). As shown in FIG. 4, a conductive coating layer 112 is provided on the side of the viewing window 111 facing the heating chamber 50. As a result, the electric field generated by the microwave can be eliminated by the conductive coating layer, so that the absorption of the microwave in the viewing window 111 can be reduced.

  The material for the conductive coating layer is preferably highly conductive, but conductive metal oxides such as tin oxide and indium oxide are preferable in terms of conductivity and durability. In addition, you may comprise the metal plate 115 which provided the opening so that light could permeate | transmit the visual recognition window 111 outside.

  In this case, the aperture is 40% to 50% and the conductive coating layer 112 is not provided on the viewing window 111 so that the aperture can be set to a hole diameter or interval that does not allow microwaves to be lost. Even if the conductive coating layer 112 is provided, the microwave shielding can be doubled, so that the reliability is high.

  As an effect of reducing the area of the viewing window, in addition to reducing the loss of microwaves, restrictions on the design of the device are reduced, so a characteristic design that has been difficult in the past has been adopted, It is also conceivable to arrange the operation unit on a door other than the window surface.

On the upper surface of the heating chamber 50, an exhaust fan 65 for exhausting odors and smoke generated by heating food is provided. In addition, you may make it the structure which can provide a deodorizing agent before and behind the exhaust fan 65, and can reduce | release an odor. A ventilation fan 66 is provided to ventilate around the heating chamber 50 inside the microwave heating apparatus.

  The ventilation fan 66 is configured with a ventilation passage 67 so as to simultaneously cool the magnetron 30, the waveguide 35, and a power source (not shown). 35a is an opening provided on the side surface of the waveguide, and the cooling effect of the magnetron 30 and the waveguide 35 is improved by passing a part of the ventilation fan 66 through the opening 35a.

  The motor (antenna driving means) 45 is provided on the upper portion of the antenna shaft 42, and the antenna plate 43 rotates integrally with the antenna shaft 42 by the rotation of the driving shaft 45 a of the motor 45.

  The antenna plate is formed in a shape that is biased with respect to the center of rotation, so that the microwave is radiated uniformly toward the lower heating chamber. A reflection wall 44 is provided around the antenna plate 43 in the power feeding unit 40. In the present embodiment, the antenna shaft rotates at a speed of one rotation per 2 seconds, but may be intermittent operation such as step driving, and is not limited to this.

  In the microwave heating apparatus configured as described above, the control means 90 controls the energization of the magnetron and each heater, supplies the microwave and at least one of the radiant heat and convection heat of the heater, and heats the food. Can be done. Hereinafter, the operation and action will be described focusing on the heating (operation) by the microwave.

  First, the microwave generated by the magnetron 30 is transmitted through the waveguide 35 and led out from the waveguide 35 to the heating chamber 50 side in a coaxial configuration with the microwave lead-out hole (coupling hole) 41 and the antenna shaft 42. Further, the microwave is radiated from the antenna shaft 42 to the heating chamber 50 through the antenna plate 43.

  Microwaves are also radiated from the surface of the antenna plate 43, the outer end surface, and the outer peripheral surface of the antenna shaft 42. Since the reflection wall 44 is provided here, even if the heater 55 and the thermistor 75 are arranged around the antenna plate, the microwave is not directly radiated there, but the electric field is concentrated and heat is generated, resulting in loss. This can be prevented.

  As described above, in the present embodiment, the reflection wall 44 that reflects the horizontal radiation of the microwave is configured around the power supply unit 40, so that the microwave radiation in the heating chamber 50 is transmitted to the power supply unit. It becomes difficult to be affected by the presence or absence of the members around 40, the shape and arrangement of the members, and the emitted microwaves are supplied to the object to be heated with little loss and high efficiency.

  Further, in the present embodiment, the reflection wall 44 is configured to have a downwardly inclined surface, so that the microwave reflected by the reflection wall surface can be supplied with high efficiency to the food that is to be heated.

In the present embodiment, the conical reflecting wall surface is formed at an angle of about 45 degrees with respect to the axis of the antenna shaft 42, and this angle is the height from the power feeding unit to the object to be heated (the position of the shelf 58). To determine the optimal emission of microwaves. If the angle is increased, the spread of microwave radiation can be expected, and the reflecting wall does not need to be provided separately, and can be easily formed integrally with the wall surface of the heating chamber (such as drawing).

Conversely, by reducing the angle, the directivity can be strengthened, and radiation can be concentrated on the object to be heated. Even when the amount of the object to be heated is small, it is possible to reduce the rate at which the microwave reflected by the wall surface of the heating chamber returns from the power feeding unit to the magnetron 30 again.

  Further, the reflection wall 44 may be configured as shown in FIG. In FIG. 5, the reflecting wall 44 is configured to be substantially vertical (substantially parallel to the axis of the antenna axis). As a result, the heating chamber 50 is faced with a small area close to the movable range of the antenna plate 43.

  Thus, even when a small amount of the object to be heated is heated, the ratio of the microwaves reflected back from the wall surface of the heating chamber 50 and returning from the antenna plate 43 to the magnetron 30 can be reduced, so that the object to be heated is efficiently heated. be able to.

  6 is an arrow view from the L (down) direction in FIG. 5 and 6, the opening of the reflection wall 44 is provided with a power supply cover 46 that is a sealing member of the power supply unit. By configuring the power supply cover 46 with a low-loss dielectric, there is no loss of microwave radiation, and the power supply portion can be protected and contamination can be prevented.

  In this embodiment, the mica plate is used. However, the present invention is not limited to this, and glass or ceramic may be used. The power supply cover 46 is configured to be detachable by a fixture 47, and can be removed for cleaning or replacement when it becomes dirty.

  Further, as shown in FIG. 6, the heater 55 is formed in a ring shape with two pipes so as to surround the power supply cover 46, and a terminal portion protrudes from the heating chamber 50 to the wall surface of the heating chamber 50 by the heater fixing plate 57. Attached.

  The heating chamber 50 is supported by the heater support member 56 with a degree of freedom (without being completely restrained). Further, as shown in FIG. 5, a part of the wall surface (50r in the figure) of the heating chamber 50 may be configured to have an angle that reflects the radiant heat of the heater 55 toward the food.

  The planar shape of the reflecting wall 44 is not limited to a circle or a square as long as it does not interfere with the rotation of the antenna plate 43, and may be an ellipse, a polygon, or a combination thereof.

  The antenna plate 43 may be configured as shown in FIGS. 7 (a) and 7 (b). FIG. 7B is a cross-sectional view of FIG. 7A viewed from the arrow M (lower side). In FIG. 7A, the antenna plate 43 has a curved surface.

  Thereby, combined with the rotation of the antenna plate 43, the microwave radiated to the heating chamber 50 has an effect of being stirred also in the height direction of the heating chamber 50, the distribution in the height direction is improved, and the object to be heated is uniform. Effective for effective heating.

  In FIG. 7B, the outer shape of the antenna plate 43 is a combination of a straight line and a (curved) arc, and a deformed hole 43h is further provided to further increase the stirring effect. Thereby, even if the capacity of the heating chamber 50 is increased, the heating distribution can be made uniform.

  Further, the antenna plate 43 may be attached so as to be inclined with respect to the axis of the antenna shaft 42 as shown in FIG. The microwave radiated from the antenna plate 43 is radiated to the heating chamber 50 by the rotation of the antenna plate 43, and the microwave is stirred also in the height direction, so that the height of the heating chamber 50 is greatly enlarged to increase the capacity. Even in this case, the heating distribution can be made uniform.

  The height of the reflection wall 44 is increased by inclining the antenna plate 43. In this case, the shape of the waveguide 35 may be configured (upside down) as shown in FIG. Parts can be used effectively in space.

  As shown in FIG. 9, the reflection wall 44 may be configured separately from the heating chamber 50. Further, the reflecting wall 44 may be integrally formed of a material different from that of the power supply cover 46. The reflection wall 44 is made of a metal material, and the power supply cover is combined with a low-loss dielectric so that microwaves can be transmitted without loss, so that the power supply cover 46 is reinforced with the reflection wall 44 as a frame, so that the thickness is thin. Is possible.

  Since the reflection wall 44 is screwed onto the wall surface of the heating chamber 50, it can be easily removed and cleaned or replaced. In FIG. 9, the wall surface constituting the waveguide 35 may also be configured to serve as the wall surface of the heating chamber.

  FIG. 10 is a detailed cross-sectional view of the power feeding unit 40. In FIG. 10, the antenna shaft 42 is integrally fixed to the rotating shaft 48 rotated by the motor 45 by the antenna plate fixing member 49.

  The antenna shaft 42 and the antenna plate 43 are arranged on the outer peripheral side of the antenna shaft 42 by the antenna plate fixing member because the antenna joint 42 is provided at the center of the contact portion of the joint portion of the antenna shaft 42 with the antenna plate 43. By making a stronger contact, the microwave derived from the microwave deriving hole 41 through the surface of the antenna shaft 42 is transmitted to the antenna plate without loss.

  The antenna shaft height (coupling length) is set so that the waveguide side T1 and the heating chamber side T2 are substantially the same in FIG.

  The rotary shaft 48 is made of a fluororesin material in terms of heat resistance and slidability. The antenna plate fixing member is fastened using screws, but the present invention is not limited to this, and a rivet may be used, or a pin press fit or caulking may be used.

  As described above, in the microwave heating apparatus according to the present invention, the exposed area of the visible light transmitting member provided in the heating chamber is reduced by the lens effect, or the conductive coating layer is formed on the surface of the visible light transmitting member. It is to be provided.

  As a result, energy loss due to absorption of microwaves can be reduced, and since the emitted microwaves are supplied to the object to be heated with low loss and high efficiency, dielectric heating as represented by microwave ovens is used. The present invention can also be applied to uses such as a heating device, a thawing device, a drying device, or a garbage disposal machine.

DESCRIPTION OF SYMBOLS 30 Magnetron 35 Waveguide 40 Feed part 41 Microwave extraction hole 42 Antenna shaft 43 Antenna plate 44 Reflecting wall 45 Motor 50 Heating chamber 55 Heater

Claims (4)

A heating chamber having a plurality of wall surfaces including a metal member, an opening for taking in and out the object to be heated, and a door for opening and closing the opening; A visible light transmitting member provided on a part of a wall surface including the door to be configured facing the heating chamber, a microwave generating means for generating a microwave for heating the object to be heated, and a microwave in the heating chamber The visible light transmitting member is vertically longer than the dimensional ratio of the vertical and horizontal sides of the wall surface provided, and further has a viewing angle optically in a substantially horizontal direction toward the heating chamber. A microwave heating device with a widened configuration. The visible light transmitting member is configured to widen the viewing angle by changing the thickness of the glass in a substantially horizontal direction, and a surface of the glass facing the heating chamber is provided with a conductive coating layer made of a conductive metal oxide. Item 2. The microwave heating apparatus according to Item 1. The microwave heating device according to any one of claims 1 to 2, wherein the visible light transmitting member is an illumination window that transmits illumination light of the heating chamber from a light source. The microwave heating device according to any one of claims 1 to 2, wherein the visible light transmitting member is a viewing window provided in an open / close door that visually recognizes the inside of the heating chamber.