JP5425577B2 - Microwave oven and magnetron for microwave oven - Google Patents

Description

  The present invention relates to a microwave oven and a magnetron used therefor.

  In general, a microwave oven includes an electrical room, a heating chamber, a magnetron for microwave oven (hereinafter referred to as “magnetron”), and a waveguide in a casing. A magnetron or the like that generates microwaves is provided in the electrical compartment. And in the heating chamber, the turntable which mounts a non-heating thing is provided. The waveguide is a tube having a rectangular cross section, and is disposed from above the electrical chamber to above the heating chamber, and plays a role of guiding the microwave generated by the magnetron to the heating chamber. The output portion of the magnetron is inserted through a through hole formed in the waveguide, and protrudes into the waveguide such that the magnetron tube axis is perpendicular to the waveguide axis (see, for example, Patent Documents 1 and 2). reference).

  In general, a magnetron has an oscillating portion composed of an anode portion and a cathode portion, and an output portion composed of an insulating cylinder, an exhaust pipe, and a cap.

  The anode part consists of an anode cylinder and a vane. The cylindrical anode cylinder extends in the axial direction of the magnetron tube. The plate-shaped vane has one side joined to the inner wall of the anode cylinder and the other side is a free end. The cathode part is a spiral filament extending in the magnetron tube axis direction, and is disposed in the anode cylinder.

  The insulating cylindrical body constituting the output portion is joined to the end portion of the output side metal sealing body fixed to the end portion of the anode cylinder. The exhaust pipe is joined to the end of the insulating cylindrical body. The cap is attached to the outer peripheral surface of the exhaust pipe and surrounds the exhaust pipe.

  The magnetron includes a pair of magnets and a yoke. The pair of magnets are respectively disposed outside the metal sealing body and are magnetized in the magnetron tube axis direction. The yoke is disposed so as to surround the anode cylinder and the magnet, and a magnetic circuit is formed by the magnet, the pole piece, and the yoke (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 9-167681 JP 2000-68044 A JP 2007-335351 A

  The load characteristics of the magnetron will be described with reference to FIGS. FIG. 8 is a Reike diagram before adjusting the load characteristics of the magnetron. FIG. 9 is a Reike diagram after adjusting the load characteristics of the magnetron.

  The load characteristics of the magnetron will be described using the Reike diagrams shown in FIGS. The Reike diagram is a constant output and a constant frequency represented by contour lines on an impedance diagram displayed in polar coordinates. The coordinates in the radial direction of the Rieke diagram indicate the standing wave ratio (VSWR) with respect to the load, and the coordinates in the circumferential direction indicate the phase (λg) of the standing wave. The phase scale of the Rieke diagram is rounded so as to rotate once at the wavelength λg / 2 in the waveguide. The change in oscillation output and oscillation frequency can be read based on the magnitude and phase of reflected power from the load and its phase.

  In the state shown in FIG. 8, the maximum efficiency phase of the magnetron is located at 0.34λg. When the oven impedance (impedance of the microwave oven) under typical operating conditions is set to the range A on the Reike diagram (VSWR is 1.5 to 4 and the standing wave phase is 0.2 to 0.32λg), the magnetron Is out of the oven impedance range A. Therefore, the heating efficiency of the microwave oven is low.

  Therefore, the load efficiency of the magnetron is adjusted to match the maximum efficiency phase of the magnetron with the oven impedance under typical operating conditions, thereby improving the output efficiency. As this method, it is known that the load characteristic of the magnetron is adjusted by increasing the height of the cap.

  In the state shown in FIG. 9, the maximum efficiency phase of the magnetron is located at 0.30 λg, and the maximum efficiency phase of the magnetron coincides with the oven impedance range A under typical operating conditions. Therefore, the heating efficiency of the microwave oven is improved as compared with the state shown in FIG.

  Here, EIA. In the J standard (TT-3006), the inner dimensions of a microwave oven waveguide having a magnetron frequency of 2.45 GHz are defined as a width of 109.2 mm and a height of 54.6 mm. The output portion of the magnetron is inserted through a through-hole formed in the waveguide, and protrudes into the waveguide so that the magnetron tube axis is perpendicular to the waveguide axis. Therefore, when the height of the cap is increased, the height of the output portion of the magnetron is also increased, the distance between the tip of the output portion of the magnetron and the inner wall of the waveguide is shortened, and discharge is likely to occur.

  Therefore, the present invention has been made to solve the above-described problems, and has an object of suppressing the discharge generated between the output portion of the magnetron and the waveguide with good output efficiency of the microwave oven. And

  In order to achieve the above object, the magnetron according to the present invention has an oven impedance set within a range of a standing wave ratio of 1.5 to 4 and a standing wave phase of 0.2 to 0.35λg. A magnetron for use in a microwave oven, and an anode extending in the magnetron tube axial direction, and a cylindrical metal sealing body in which an input side end extending in the magnetron tube axial direction is joined to an output side end of the anode And an insulating cylindrical body made of ceramic that extends in the magnetron tube axial direction and has an input-side end joined to an output-side end of the metal sealing body and has a height in the magnetron tube axial direction of 8 to 9 mm. An antenna penetrating the metal sealing body and the insulating cylindrical body and extending from the anode to the output side, and an input side end extending in the magnetron tube axial direction is an output side end of the insulating cylindrical body Joined to the part An exhaust pipe that is sealed by crushing and holding the antenna; a cylindrical cap side part that extends in the axial direction of the magnetron pipe and is attached to the exhaust pipe and surrounds the outer periphery of the exhaust pipe; And a cap having a disc-shaped cap front end portion closing an output side end portion of the cap side portion.

  In order to achieve the above object, the microwave oven according to the present invention has an oven impedance set within a range of a standing wave ratio of 1.5 to 4 and a standing wave phase of 0.2 to 0.35λg. A rectangular parallelepiped waveguide extending in a direction perpendicular to the magnetron tube axis and having a height in the magnetron tube axis direction of 54.1 to 55.1 mm, and an anode extending in the magnetron tube axis direction, A cylindrical metal seal that extends in the axial direction of the magnetron tube and has an end on the input side joined to an end on the output side of the anode, and an end on the input side that extends in the axial direction of the magnetron tube Output from the anode through the inside of the insulating cylindrical body made of ceramic, the metal sealing body, and the insulating cylindrical body. Antenna extending to the side, The exhaust pipe extending in the axial direction of the magnetron tube and joined to the output side end of the insulating cylindrical body, the output side end sealed by crushing, and holding the antenna, and A cylindrical cap side portion that extends in the axial direction of the magnetron tube and is attached to the exhaust pipe and surrounds the outer periphery of the exhaust pipe; and a disc-shaped cap front end portion that closes the output side end of the cap side portion; The insulating cylinder and the exhaust pipe protrude into the inside of the waveguide perpendicular to the axial direction of the waveguide.

  According to the present invention, the output efficiency of the microwave oven is good, and the discharge generated between the magnetron output section and the waveguide is suppressed.

It is a schematic sectional drawing of the microwave oven which concerns on embodiment of this invention. It is a schematic sectional drawing of the magnetron which concerns on embodiment of this invention. It is a schematic sectional drawing of the output part periphery of the magnetron in the microwave oven which concerns on embodiment of this invention. It is a figure for demonstrating the microwave oven and magnetron which concern on embodiment of this invention, Comprising: It is the table | surface which showed the dimension of the microwave oven and magnetron which concerns on Examples 1 thru | or 10 and Comparative Examples 1 thru | or 5. It is a figure for demonstrating the magnetron which concerns on embodiment of this invention, Comprising: It is a Reike diagram of the magnetron which concerns on the comparative example 1. FIG. It is a figure for demonstrating the magnetron which concerns on embodiment of this invention, Comprising: It is the Reike diagram of the magnetron which concerns on Example 1. FIG. It is a figure for demonstrating the magnetron which concerns on embodiment of this invention, Comprising: It is the figure which showed the relationship between the height of an output part, and a maximum efficiency phase. It is a Reike diagram before adjusting the load characteristic of a magnetron. It is a Reike diagram after adjusting the load characteristic of a magnetron.

  A microwave oven and a microwave oven for a microwave oven (hereinafter simply referred to as “magnetron”) according to an embodiment of the present invention will be described with reference to FIGS.

  First, the outline of the structure of the microwave oven 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of a microwave oven according to an embodiment of the present invention.

  The microwave oven 1 is set with an oven impedance under typical operating conditions (with a standing wave ratio of 1.5 to 4 and a standing wave phase of 0.2 to 0.35λg). The microwave oven 1 has an electrical component chamber 82, a heating chamber 83, a magnetron 10, and a waveguide 70 in the casing 81.

  In the electrical chamber 82, a magnetron 10 that generates microwaves, a high-voltage transformer 84 that applies a high voltage to the magnetron, a cooling fan (not shown), a microcomputer (not shown), and the like are provided. And in the heating chamber 83, the turntable 86 on which the non-heating thing 85 is mounted is provided, and the turntable 86 is connected with the rotor (not shown) of a motor.

  The waveguide 70 has a rectangular cross section, and is disposed from above the electrical chamber 82 to above the heating chamber 83. A through hole 72 is formed near the electrical component chamber 82 of the lower sidewall 71 of the waveguide 70 (side wall adjacent to the electrical component chamber 82 and the heating chamber 83) 71. The output portion of the magnetron 10 is inserted through the through hole 72 and protrudes into the waveguide 70. The magnetron 10 is disposed with respect to the waveguide 70 so that the magnetron tube axis 100 is perpendicular to the waveguide axis 101.

  On the other hand, an opening 73 is formed near the heating chamber 83 of the lower side wall 71 of the waveguide 70, and the inside of the waveguide 70 and the inside of the heating chamber 83 communicate with each other through the opening 73. That is, the waveguide 70 plays a role of guiding the microwave generated by the magnetron 10 to the heating chamber 83.

  Next, an outline of the structure of the magnetron 10 according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of a magnetron according to an embodiment of the present invention.

  The anode part 11 has an anode cylinder 12 and ten vanes 13. The cylindrical anode cylinder 12 extends in the direction of the magnetron tube axis 100 which is the central axis of the magnetron 10. The plate-shaped ten vanes 13 have one side joined to the inner wall of the anode cylinder 12 and the other side being a free end. The free end of the vane 13 is disposed on the same cylindrical surface extending along the magnetron tube axis 100, and this cylindrical surface is referred to as a vane inscribed cylindrical surface 14. The ten vanes 13 spread radially from the vane inscribed cylindrical surface 14 to the inner wall of the anode cylinder 12. The ten vanes 13 are connected by strap rings 15 and 16 which are paired in large and small, and are brazed to the upper and lower ends of the vanes 13 every other circumferential direction.

  The cathode portion 21 is a helical filament extending in the direction of the magnetron tube axis 100 and is disposed in the anode cylinder 12. The cathode portion 21 is disposed on the inner side of the vane inscribed cylindrical surface 14 that is an electron action space with a gap from the free ends of the ten vanes 13. The anode part 11 and the cathode part 21 function as an oscillation part that generates a high frequency. The input side end (lower end in FIG. 2) of the cathode portion 21 is fixed to a ring-shaped end hat 22, and the output end (upper end in FIG. 2) of the cathode portion 21 is fixed. The disk-shaped end hat 23 is fixed.

  The center support rod 24 passes through the center of the spiral filament of the cathode portion 21 and is connected to the cathode portion 21 via a disk-shaped end hat 23. The side support rod 25 is connected to the cathode portion 21 via a ring-shaped end hat 22. The center support rod 24 and the side support rod 25 support the cathode portion 21 and also serve as leads for supplying current to the cathode portion 21.

  The pair of funnel-shaped input side pole piece 31 and output side pole piece 32 are each formed with a through hole at the center, and the center of the through hole is located on the magnetron tube shaft 100. The pair of input side pole pieces 31 and the output side pole pieces 32 are arranged to face each other, and are respectively arranged on the input side end (lower end in FIG. 2) of the anode cylinder 12 and the input side of the anode cylinder 12. It is joined to the end (the upper end in FIG. 2).

  A cylindrical input-side metal sealing body (lower metal sealing body in FIG. 2) 33 is fixed to the input-side end of the anode cylinder 12 and the input-side pole piece 31. An insulating stem 35 is joined to an end portion (lower end portion in FIG. 2) of the input side metal sealing body 33 away from the input side pole piece 31.

  On the other hand, a cylindrical output-side metal sealing body (upper metal sealing body in FIG. 2) 34 is fixed to the output-side end of the anode cylinder 12 and the output-side pole piece 32. An insulating cylindrical body 40 made of ceramic is joined to an end portion of the output side metal sealing body 34 away from the output side pole piece 32. Further, an exhaust pipe 61 is joined to an end portion of the insulating cylindrical body 40 away from the metal sealing body 34. An antenna 62 is derived from one of the ten vanes 13. The antenna 62 penetrates the output side pole piece 32 and extends inside the metal sealing body 34 and the insulating cylindrical body 40, and the tip thereof is sandwiched by the exhaust pipe 61. The cap 50 surrounds the outer periphery of the exhaust pipe 61.

  The pair of magnets 63 and 64 are formed in the same ring shape. The magnets 63 and 64 are respectively arranged outside the metal sealing bodies 33 and 34 and above and below the anode cylinder 12 and are magnetized in the direction of the magnetron tube axis 100. The yokes 65 and 66 are disposed so as to surround the anode cylinder 12 and the magnets 63 and 64. A magnet circuit is formed by the magnets 63 and 64 and the yokes 65 and 66. Further, a radiator 67 for cooling the oscillation unit is disposed between the anode cylinder 12 and the yoke 65.

  Next, the details of the insulating cylindrical body, which is a characteristic part of the microwave oven 1 and the magnetron 10 of the present embodiment, and the surrounding structure will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view around the output part of the magnetron in the microwave oven according to the embodiment of the present invention.

  An opening 92 around the magnetron tube shaft 100 is formed at the output-side end 91 of the output-side yoke 66. The inner diameter of the opening 92 is designed to be larger than the outer diameter of the metal seal 34 on the output side. The end portion 91 of the yoke 66 is in contact with the lower wall 71 of the waveguide 70.

  An annular plate-like spacer 93 is disposed between the output-side end face of the output-side magnet 64 and the input-side end face of the end portion 91 of the output-side yoke 66. The spacer 93 is formed with an opening 94 centered on the magnetron tube axis 100. The inner diameter of the opening is designed to be substantially the same as the outer diameter of the output side metal sealing body 34. A rising portion 95 to the output side is formed at the opening 94 portion of the spacer 93.

  Between the inner edge of the opening 92 of the end 91 of the output side yoke and the rising portion 95 of the spacer 93, an annular plate-like gasket ring 96 is disposed. The gasket ring 96 is made of mesh metal (for example, copper).

  The inner diameter of the through hole 72 of the waveguide 70 is designed to be larger than the outer diameter of the metal seal 34 on the output side and smaller than the inner diameter of the opening 92 of the yoke 66. A falling portion 74 to the input side is formed in the through hole 72 portion of the waveguide 70. The gasket ring 96 is held between the falling part 74 and the spacer 93.

  The output part of the magnetron 10 (the insulating cylinder 40, the exhaust pipe 61, and the cap 50) includes an opening 94 of the spacer 93, an opening of the gasket ring 96, an opening 92 of the yoke 66, and a lower wall 71 of the waveguide 70. This through-hole 72 is inserted into the waveguide 70. The end of the insulating cylindrical body 40 on the input side is located substantially on the surface where the through hole 72 of the waveguide 70 is formed.

  The cap 50 is formed by integrally molding a metal cap side 51 and a cap tip 52. The cap side part 51 is formed in a cylindrical shape and extends in the direction of the magnetron tube axis 100. The cap side portion 51 is attached to the outer peripheral surface of the exhaust pipe 61 and surrounds the outer periphery of the exhaust pipe 61. The cap tip 52 is formed in a disc shape and closes the output side end of the cap side 51.

  The internal dimensions of the waveguide 70 are EIA. This is a design value defined in the J standard (TT-3006), and the distance between the lower side wall 71 and the upper side wall 75 facing the lower side wall 71 (hereinafter referred to as “the height of the waveguide in the axial direction of the magnetron tube”) h1 Is designed to be 54.6 mm (manufacturing error: 0.5 mm) and width is 109.2 mm (manufacturing error: 0.5 mm).

  The height h2 of the insulating cylinder 40 in the direction of the magnetron tube axis 100 is designed to be 8.5 mm (manufacturing error: 0.5 mm). Further, the height h3 of the cap side portion 51 in the direction of the magnetron tube axis 100 is designed to be 17.5 mm (manufacturing error: 0.5 mm).

  That is, the height (hereinafter referred to as “the height of the output portion”) h4 from the end 41 on the input side of the insulating cylindrical body 40 to the cap tip 52 in the direction of the magnetron tube axis 100 is 26.0 mm (manufacturing error: 0.5mm). The distance h5 between the cap tip 52 and the upper wall 75 of the waveguide 70 facing the cap tip 52 is designed to be 28.6 mm (manufacturing error: 1.0 mm).

  Operations and effects of the microwave oven 1 and the magnetron 10 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a diagram for explaining the microwave oven and magnetron according to the embodiment of the present invention, and is a table showing dimensions of the microwave oven and magnetron according to Examples 1 to 10 and Comparative Examples 1 to 5. . FIG. 5 is a diagram for explaining the magnetron according to the embodiment of the present invention, and is a Reike diagram of the magnetron according to Comparative Example 1. FIG. 6 is a diagram for explaining the magnetron according to the embodiment of the present invention, and is a Reike diagram of the magnetron according to the first example. FIG. 7 is a diagram for explaining the magnetron according to the embodiment of the present invention, and is a diagram showing the relationship between the height of the output unit and the maximum efficiency phase.

  The microwave ovens 1 according to Examples 1 to 10 and the microwave ovens according to Comparative Examples 1 to 5 are all designed in the same manner except for the dimensions shown in FIG. These microwave ovens can be said to be general as microwave ovens, and the standing wave ratio is 1.5 to 4 and the standing wave phase is in the range of 0.2 to 0.32λg under typical operating conditions. Oven impedance is set. The magnetrons according to Comparative Examples 1 to 5 are conventional magnetrons, and the height h2 of the magnetron tube shaft 100 of the insulating cylindrical body 40 is designed to be 10 mm.

  The Reike diagram of the magnetron according to comparative example 1 is as shown in FIG. The maximum efficiency phase of the magnetron 10 is 0.34λg, which is out of the oven impedance range A. Therefore, the heating efficiency of the microwave oven is low.

  On the other hand, the Reike diagram of the magnetron 10 according to the first embodiment is as shown in FIG. 6, and the maximum efficiency phase of the magnetron 10 is 0.27λg, which coincides with the oven impedance range A. Therefore, the microwave oven 1 according to Example 1 has higher heating efficiency than the microwave oven according to Comparative Example 1.

  As can be seen from FIG. 7, when the height h2 of the magnetron tube shaft 100 of the insulating cylindrical body 40 is reduced, the maximum efficiency phase is lowered and can be brought close to the oven impedance range A. As a result, the heating efficiency of the microwave oven 1 is improved. In addition, since the height h3 of the cap side portion 51 in the direction of the magnetron tube axis 100 is not increased as in the prior art (that is, the height h4 of the output portion is not increased), the cap tip portion 52 and the waveguide 70 are used. The discharge generated between the upper wall 75 and the upper wall 75 can be suppressed.

  In addition, if the height h2 of the magnetron tube shaft 100 of the insulating cylindrical body 40 is designed to be 7.5 mm or less, it is effective in reducing the maximum efficiency phase, but the dielectric strength of the insulating cylindrical body 40 decreases, and the ceramic This is not preferable because there is a high risk that a discharge will occur between the two.

  Further, if the height h4 of the output part exceeds 29 mm (that is, if h5 is smaller than 25.6 mm), there is a possibility that electric discharge occurs between the cap tip part 52 and the upper wall 75 of the waveguide 70. Therefore, the height h4 of the output part is desirably 29 mm or less. Further, in consideration of the height of the insulating cylinder 40 and the exhaust pipe 61 in the direction of the magnetron tube axis 100, the height h4 of the output part is desirably 25.0 mm or more.

  When the height h4 of the output part is 25.0 to 29 mm (that is, h5 is 25.6 to 29.6 mm), the maximum efficiency phase coincides with the range A of the oven impedance, and the heating efficiency is further improved. In addition, the discharge generated between the cap tip 52 and the upper wall 75 of the waveguide 70 can be further suppressed.

DESCRIPTION OF SYMBOLS 1 ... Microwave oven, 10 ... Magnetron for microwave ovens, 11 ... Anode part, 12 ... Anode cylinder, 13 ... Bain, 14 ... Vane inscribed cylindrical surface, 15, 16 ... Strap ring, 21 ... Cathode part, 22, 23 ... End hat, 24 ... Center support rod, 25 ... Side support rod, 31 ... Input side pole piece, 32 ... Output side pole piece, 33 ... Input side metal seal, 34 ... Output side metal seal, 35 ... Insulating stem, 40 ... insulating cylinder, 41 ... input side end of insulating cylinder, 50 ... cap, 61 ... exhaust pipe, 62 ... antenna, 63, 64 ... magnet, 65, 66 ... yoke, 67 ... radiator, DESCRIPTION OF SYMBOLS 70 ... Waveguide, 71 ... Lower side wall of waveguide, 72 ... Through-hole of waveguide, 73 ... Opening of waveguide, 74 ... Falling part of waveguide, 75 ... Upper side wall of waveguide 81 ... Case, 82 ... Loading chamber, 83 ... heating chamber, 84 ... voltage transformer, 85 ... non-heated material, 86 ... turntable, 91 ... end of yoke, 92 ... opening at end of yoke, 93 ... spacer, 94 ... opening in spacer, 95 ... Rising portion of spacer, 96 ... Gasket ring, 100 ... Magnetron tube axis, 101 ... Waveguide shaft

Claims (5)

A magnetron used in a microwave oven having a standing wave ratio of 1.5 to 4 and an oven impedance set in a range of a standing wave phase of 0.2 to 0.35λg,
An anode extending in the direction of the magnetron tube axis;
A cylindrical metal sealing body that extends in the axial direction of the magnetron tube and has an end on the input side joined to an end on the output side of the anode;
An insulating cylindrical body made of ceramic and extending in the magnetron tube axial direction and having an input side end joined to an output side end of the metal sealing body and having a height of 8 to 9 mm in the magnetron tube axial direction;
An antenna extending from the anode to the output side through the metal sealing body and the insulating cylindrical body;
An exhaust pipe extending in the axial direction of the magnetron tube and joined to the output side end of the insulating cylindrical body, and the output side end sealed by crushing to hold the antenna; and
A cylindrical cap side part that extends in the axial direction of the magnetron pipe and is attached to the exhaust pipe and surrounds the outer periphery of the exhaust pipe, and a disc-shaped cap front end part that closes the output side end of the cap side part And a cap having a magnetron.   2. The magnetron according to claim 1, wherein a height in an axial direction of the magnetron tube from an input side end portion of the insulating cylindrical body to an output side end portion of the cap is 25.0 to 29.0 mm. . A microwave oven in which the standing wave ratio is 1.5 to 4 and the standing wave phase is in the range of 0.2 to 0.35λg, and the oven impedance is set;
A rectangular parallelepiped waveguide extending in a direction perpendicular to the magnetron tube axis and having a height in the magnetron tube axis direction of 54.1 to 55.1 mm;
An anode extending in the magnetron tube axis direction, an end on the input side extending in the magnetron tube axis direction is joined to an end on the output side of the anode, and a cylindrical metal sealing body, extending in the magnetron tube axis direction on the input side Of the insulating cylinder, the height of the axial direction of the magnetron tube is 8 to 9 mm and made of ceramic, the metal sealing body, and the insulating cylinder An antenna extending through the inside from the anode to the output side, extending in the magnetron tube axial direction, an input side end is joined to an output side end of the insulating cylindrical body, and an output side end is sealed by crushing An exhaust pipe that is cut and holds the antenna, and a cylindrical cap side part that extends in the axial direction of the magnetron pipe and is attached to the exhaust pipe and surrounds the outer periphery of the exhaust pipe, and an output side of the cap side part End of ; And a magnetron having a cap having a by a disc-shaped cap tip is closed,
The microwave oven characterized in that the insulating cylindrical body and the exhaust pipe protrude into the waveguide perpendicular to the axial direction of the waveguide. 4. The electron according to claim 3 , wherein a height in the magnetron tube axial direction from an input side end portion of the insulating cylindrical body to an output side end portion of the cap is 25.0 to 29.0 mm. range. The microwave oven according to claim 3 or 4, wherein a distance between the cap tip portion and the inner surface of the waveguide facing the cap tip portion is 25.6 to 29.6 mm.

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