JP2011054416A - High frequency heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of an unsafe situation that a user feels a sense of uneasiness strongly when a bobbin is brought into thermal fatigue by an abnormal use, an abnormal installation state, a use for an extremely long period of time or the like, a crack is generated and a spark is generated between a winding and a core, finally the winding brings about insulation breakdown to be in a layer short state, and heat generation is further increased at that part, thus resulting in smoke generation and a fire or the like. <P>SOLUTION: By forming a structure which divides the structure of the bobbin of a boosting transformer into a primary winding side having a primary winding and a high-voltage winding side having a high-voltage winding, since there can be formed a double-insulation structure in a gap between a core and the bobbin, the spark between the winding and the core can surely be prevented even if the bobbin has the thermal fatigue and the crack is generated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high-voltage switching transformer used for an inverter power supply type high-frequency heating device, and more particularly to a technique for protecting the device and improving safety.

  As an inverter type high frequency heating apparatus, there is one provided with a transformer unit in which a transformer is mounted on a printed circuit board (for example, see Patent Document 1).

  FIG. 5 is a block diagram showing a circuit configuration of a transformer unit in the inverter type high frequency heating apparatus.

  In FIG. 5, the alternating current from the commercial power supply 11 is rectified to direct current by the rectifier circuit 13. The rectified voltage is smoothed by the choke coil 14 and the smoothing capacitor 15 on the output side of the rectifier circuit 13 and is given to the input side of the inverter circuit 102.

  By controlling the semiconductor switching element (IGBT) 17 in the inverter circuit 102 to be turned on / off by the control circuit 29, a desired high frequency (20 to 50 kHz) bidirectional current is generated on the primary side of the step-up transformer 18. Flowing.

  The high-frequency power generated on the primary side of the step-up transformer 18 is boosted by the step-up transformer 18 and high-voltage high-frequency power is generated on the secondary side. The secondary side of the step-up transformer 18 is connected to a voltage doubler full-wave rectification type high voltage circuit 19 composed of high voltage diodes 191 and 192 and high voltage capacitors 193 and 194, and a high voltage DC voltage ( For example, −4 KV) is applied.

  Further, power is supplied from the other secondary winding (heater winding) 5 of the step-up transformer 18 to the cathode (filament) 121 of the magnetron 10, and electrons are generated from the heated cathode 121 and reach the anode. As a result, microwave energy is irradiated to the object to be heated in the heating chamber (not shown).

  The control circuit 29 controls the inverter 102 based on a command from the control unit of the high-frequency heating device through the connector 26. Thus, the control circuit 29 controls the power supply to the secondary side by the on / off control of the IGBT 17 and controls the intensity of the output microwave from the magnetron 10.

  FIG. 6 is a schematic cross-sectional view showing the structure of a step-up transformer mounted on a conventional transformer unit. As shown in FIG. 6, the step-up transformer 18 used in the above-described transformer unit has a bobbin 2 in which a primary winding 3, a secondary winding 4, and a heater winding 5 are wound concentrically. The core 1 is inserted into the center of the bobbin 2 from both sides.

JP 2004-304142 A

In FIG. 5, the temperature of the step-up transformer 18 rises due to heat generated by the heater winding 5 that warms the primary winding 3, the high-voltage winding 4, and the cathode 121 of the magnetron 10 during high-frequency heating.

  Since the heat generation stops after the high-frequency heating is finished, the temperature of the step-up transformer 18 decreases. As the temperature rises and falls repeatedly, the material constituting the step-up transformer 18 gradually deteriorates due to thermal fatigue.

  In the case of use under bad conditions that cannot be assumed or failure of cooling parts, for example, the high-frequency heating device is installed vertically, left and right, When the rear five surfaces are placed in contact with the surroundings and the air supply / exhaust port is blocked, or when the motor fan of the cooling fan is disconnected and the cooling fan becomes inoperable, The bobbin 2 may crack.

  In FIG. 6, a high voltage of about 3000 V is applied between the high voltage winding 4 and the core 1 connected to the ground, but the distance is not so large, so that if the crack 7 occurs in the bobbin 2, the high voltage winding A spark may occur between the core 4 and the core 1 (see an enlarged view in FIG. 6).

  When a spark occurs, the inverter circuit portion 102 also fluctuates greatly due to the large fluctuation of the high-voltage circuit 19 in FIG. 5. When this fluctuation is detected, it is designed to stop high-frequency heating for safety. Yes. Accordingly, the generation of sparks is also stopped.

  However, when high-frequency heating is started again, a spark is generated again, and this is detected again and the operation of stopping high-frequency heating is repeated.

  Furthermore, if this repeated operation is continued, the insulation of the high-voltage winding 4 is destroyed by heat generation, the high-voltage winding 4 becomes in a rare short state, further heat is generated in the rare short portion, and in the worst case, smoke and ignition are caused. It can be a situation.

  In order to prevent the occurrence of sparks, that is, to prevent the deterioration of the bobbin 2, the distance between the high voltage winding 4 and the core 1 is further increased, or the insulation thickness of the exterior of the high voltage winding 4 is increased to increase the withstand voltage. Although there is a method, the shape of the step-up transformer 18 is increased, the cost is increased, and it is contrary to the convenience of the user.

  In view of this, the present invention solves this problem, and the bobbin is thermally fatigued due to abnormal use, abnormal installation conditions, or use for an extremely long period of time, cracks are generated, and sparks are generated between the winding and the core. The wire will break down and become a short-circuited state, which will generate more heat and generate smoke and fire, resulting in a very uneasy or unsafe situation for the user. It is an object of the present invention to provide an apparatus for preventing the above-described problem.

  The present invention has been made in order to solve the above-described problems, and rectifies an AC power supply and increases the frequency of the inverter, a boosting transformer that boosts high-frequency power output by the inverter, and the boosting transformer. A high-voltage circuit including a high-voltage diode that converts an output into a high-voltage DC voltage; and a magnetron that receives the high-voltage DC voltage and emits microwaves, and the step-up transformer has a core connected to a ground potential, Since the step-up transformer is divided into a primary winding side having a primary winding and a high-voltage winding side having a high-voltage winding, a double insulation structure can be formed in the gap between the core and the bobbin. Even if the bobbin is thermally fatigued and cracks are generated, the spark between the winding and the core can be reliably prevented.

  According to the present invention, the structure of the bobbin of the step-up transformer is divided into a primary winding side having a primary winding and a high-voltage winding side having a high-voltage winding, so that the gap between the core and the bobbin is 2 Since a heavy insulation structure can be made, even if the bobbin is thermally fatigued and cracks are generated, sparks between the winding and the core can be reliably prevented.

Sectional drawing which shows the structure of the step-up transformer which concerns on Embodiment 1 of this invention Sectional drawing which shows generation | occurrence | production of a crack in the pressure | voltage rise transformer which concerns on Embodiment 1 Sectional drawing which shows the structure of the step-up transformer concerning Embodiment 2 of this invention Sectional drawing which shows generation | occurrence | production of a crack in the pressure | voltage rise transformer which concerns on Embodiment 2 Block configuration diagram showing the circuit configuration of a conventional high-frequency heating device Sectional drawing showing the structure of a step-up transformer mounted on a conventional high-frequency heating device

  A first invention rectifies an AC power supply and increases the frequency of the inverter unit, a step-up transformer that boosts high-frequency power output from the inverter unit, and a high-voltage diode that converts the output of the step-up transformer into a high-voltage DC voltage A high voltage circuit including a magnetron that receives the high voltage DC voltage and radiates microwaves, the step-up transformer has a core connected to a ground potential, and the step-up transformer has a primary winding having a primary winding. The structure is divided into a wire side and a high voltage winding side having a high voltage winding.

  Thereby, since a double insulation structure can be made in the gap between the core and the bobbin, even if the bobbin is thermally fatigued and cracks are generated, the spark between the winding and the core can be reliably prevented. .

  According to a second aspect of the present invention, in particular, in the first aspect, the bobbin structure of the step-up transformer is configured such that the diameter for inserting the core is larger on the high-voltage winding side than on the primary winding side. In this structure, a double insulation structure can be formed in the gap between the core and the bobbin.

  According to a third aspect of the present invention, in particular, in the first aspect, the bobbin structure of the step-up transformer is configured such that the diameter for inserting the core is larger on the primary winding side than on the high-voltage winding side. In this structure, a double insulation structure can be formed in the gap between the core and the bobbin.

  In a fourth aspect of the present invention, in particular, in any one of the first to third aspects, the bobbin material on the primary winding side and the high voltage winding side of the step-up transformer uses the same material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that this embodiment is merely an exemplification that embodies the present invention, and the present invention includes various modes in which changes are made within the scope of the configurations described in the claims.

(Embodiment 1)
FIG. 1 shows the structure of a step-up transformer 18 of a high-frequency heating device according to Embodiment 1 of the present invention. FIG. 1 (a) shows a state where a bobbin 2 is divided, and FIG. Each state is shown. FIG. 2 is a cross-sectional view of the step-up transformer 18 particularly when a crack is generated.

1 and 2, the primary winding 3 on the inverter unit 102 side and the high-voltage winding 4 on the boosting side are concentrically centered around the core 1 and are separated from each other by a predetermined step-up ratio (winding). The core 1 is grounded to stabilize the operation of the step-up transformer 18 and to ensure safety (reference numeral 195 in FIG. 2).

Since the step-up transformer 18 is energized during high-frequency heating, the heater winding 5 that warms the cathode portion (filament) of the primary winding 3 and the high-voltage winding 4 magnetron 10 (FIG. 2) generates heat. The temperature rises.

  Since heat generation stops after the high-frequency heating is finished, the temperature of the step-up transformer 18 decreases. Therefore, the step-up transformer 18 repeats a so-called temperature cycle in which the temperature rises and falls repeatedly. The material to be gradually deteriorated.

  Although it is a deterioration that does not become a problem under normal use conditions, if it is used abnormally under bad conditions that cannot be assumed by the installation conditions or use conditions of the high-frequency heating device, or if other parts for cooling parts fail, for example, furniture When the air supply / exhaust port of the high-frequency heating device is blocked by being attached to the top, bottom, left, or right back of the inside, or the motor coil part of the cooling fan of the high-frequency heating device is disconnected, When a trouble occurs such that the cooling fan becomes inoperable, there is a concern that a crack 7 may occur in the bobbin 2 as shown in FIG.

  However, as shown in FIG. 1, the structure of the bobbin 2 is divided into a primary winding side having the primary winding 3 and a high-voltage winding side having the high-voltage winding 4, and further, the primary winding 3 side The bobbin 2 is stretched to the high voltage winding 4 side, and the diameter of the core 1 inserted is made larger on the high voltage winding 4 side than the primary winding 3 side. A double insulation structure can be formed in the gap between the two.

  With this double insulation structure, as shown in FIG. 2, even if a high voltage of about 3000 V is applied between the high voltage winding 4 and the core 1 portion connected to the ground, a crack 7 occurs in the bobbin 2 portion of the step-up transformer 18. Since the double bobbins 36 and 37 are present, no spark is generated between the core 1 and the high voltage winding 4 (enlarged structure portion).

  In other words, conventionally, sparks are generated many times through the crack 7 part, the high-voltage winding 4 part is abnormally heated and a dielectric breakdown occurs, resulting in a rare-short state. Although ignition has occurred, such a situation can be avoided by adopting a double structure insulating structure between the core 1 of the bobbin 2 and the high voltage winding 4.

(Embodiment 2)
3 and 4 show the structure of the step-up transformer 18 of the high-frequency heating device according to the second embodiment of the present invention, and are sectional views of the step-up transformer 18 at the normal time and when a crack occurs, respectively.

  As shown in FIG. 3, the structure of the bobbin 2 is divided into a primary winding side having the primary winding 3 and a high voltage winding side having the high voltage winding 4.

  Further, the bobbin 2 on the high-voltage winding 4 side extends the resin of the bobbin 2 to the primary winding 3 side, and the diameter for inserting the core 1 is larger on the primary winding 3 side than the high-voltage winding 4 side. 4, a double insulation structure can be formed in the gap between the core 1 and the bobbin 2 on the primary winding 3 side.

  With such a structure, even if a crack 7 occurs in the bobbin 2 portion of the step-up transformer 18 and a high voltage of about 600 V is applied between the primary winding 3 and the core 1 portion connected to the ground, the double-structure bobbin Since 36 and 37 are present, no spark is generated (enlarged structure portion).

  In other words, conventionally, sparks are generated many times through the crack 7 portion, the high-voltage winding 4 portion abnormally heats up and a dielectric breakdown occurs, resulting in a rare-short state. The rare-short portion further generates heat and generates smoke or ignition. However, such a situation can be avoided by adopting a double structure insulation structure between the core 1 of the bobbin 2 and the high voltage winding 4.

  The present invention is applied to a high-frequency heating apparatus that heats food, such as a microwave oven.

DESCRIPTION OF SYMBOLS 1 Core 2 Bobbin 3 Primary winding 4 High voltage winding 5 Heater winding 7 Bobbin crack part 8 High frequency heating device 9 Inverter unit board 10 Magnetron 11 Commercial power supply 13 Diode bridge 14 Choke coil 15 Smoothing capacitor 16 Resonance capacitor 17 Power transistor (IGBT) )
18 Step-up transformer 19 Double voltage full-wave rectifier circuit 27 Control board (High-frequency heating device controller board)
29 Inverter control circuit 33 Heating chamber 36, 37 Double insulation structure part of bobbin 101 Rectification filter part 102 Inverter part
121 Cathode 191, 192 High voltage diode 193, 194 High voltage capacitor

Claims (4)

An inverter unit that rectifies an AC power supply and increases the frequency, a step-up transformer that boosts high-frequency power output from the inverter unit, and a high-voltage circuit that includes a high-voltage diode that converts the output of the step-up transformer into a high-voltage DC voltage; A magnetron that radiates microwaves upon receiving the high-voltage DC voltage, the step-up transformer has a core connected to a ground potential, and the bobbin of the step-up transformer includes a primary winding side having a primary winding; A high frequency heating apparatus having a structure in which a double insulation structure can be formed in a gap between the core and the bobbin by dividing the structure into a high voltage winding side having a high voltage winding. The bobbin structure of the step-up transformer has a structure in which the diameter for inserting the core is larger on the high-voltage winding side than on the primary winding side, thereby providing a double insulation structure in the gap between the core on the high-voltage winding side and the bobbin. The high-frequency heating device according to claim 1, wherein the high-frequency heating device can be made. The bobbin structure of the step-up transformer has a structure in which the diameter for inserting the core is larger on the primary winding side than on the high-voltage winding side, thereby providing a double insulation structure in the gap between the core and bobbin on the primary winding side. The high-frequency heating device according to claim 1, wherein the high-frequency heating device can be made. The high-frequency heating device according to any one of claims 1 to 3, wherein the bobbin material on the primary winding side and the high-voltage winding side of the step-up transformer uses the same material.

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