JPH05129073A - High frequency heating device - Google Patents

Abstract

PURPOSE:To output an output larger than the rated output of a device for a determined time in a high frequency heating device, and shorten heating time. CONSTITUTION:A high frequency heating device is formed of a magnetron 32, a high voltage power converting part 33, a control part 34, and a large output control part 41, and the large output control part 41 has a stop state detecting means for detecting the operation stop state of the high voltage power converting part 33. According to the signal of the stop state detecting means, the clocking time of a large output timer means is regulated, and an output larger than a rated output is outputted for the regulated clocking time. According to this constitution, the enlargement of a cooling structure accompanying an output increase can be prevented, and cooking time can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating device for heating foods, fluids and the like, and more particularly to a high frequency heating device using a semiconductor power converter for generating high frequency power in its power supply device. is there.

[0002]

2. Description of the Related Art A power supply circuit of a high-frequency heating device such as a microwave oven for home use has a structure as shown in FIG. In FIG. 6, when the operation switch 1 is turned on, the commercial power supply 2 is connected to the high voltage transformer 3. The output of the secondary winding 4 of the high voltage transformer 3 is rectified by the capacitor 5 and the diode 6 and supplied to the magnetron 7. The heater winding 8 of the high voltage transformer 3 is connected to the cathode of the magnetron 7 to heat the cathode. Therefore, the magnetron 7 oscillates and outputs high frequency electromagnetic waves (radio waves),
Dielectric heating is possible.

FIG. 6 (a) is a diagram showing the passage of time of the radio wave output P ₀ of the magnetron 7 after turning on the switch 1 at time t = 0.

When the switch 1 is turned on at t = 0, the cathode heater power and the high voltage power are simultaneously applied to the magnetron 7. At t = t ₁ after about 1 to 2 seconds, the temperature of the cathode rises sufficiently and the radio wave output P ₀ rises, and thereafter, it is kept substantially constant as shown in the figure. Of course, due to the temperature characteristics of the magnetron 7 and the high-voltage transformer 3, there may be a slight decrease in radio wave output over time,
Basically, it is configured to maintain the radio wave output P ₀ (for example, 500 W) defined as the rated output of the device.

FIG. 7B is a diagram showing a temperature rise of components inside the apparatus when the high-frequency heating apparatus is operated as described above. For example, the temperature T _{M of the} magnetron 7 and the temperature T _a of the air around the high-voltage transformer 3 rise as shown in FIG.

FIG. 8 is a sectional view of the high frequency heating apparatus. An oven 10, a magnetron 7, a high-voltage transformer 3 and the like are arranged inside the housing 9 as shown in the figure, and are forcedly cooled by a cooling fan 11. Since the efficiency of the magnetron 7 is about 60% and the efficiency of the high voltage transformer 3 is about 90%, in the case of a device having an actual radio wave output rating of 500 W, the magnetron 7 is about 300 W and the high voltage transformer 7 is
A loss of about 100 W occurs. Therefore, the temperature of these parts gradually increases during operation as shown in FIG. 7B, and the time t = t ₂ (for example, 15 minutes) determined by the thermal time constant of each part.
Up at a relatively fast rate until t = t
_{In 3} (for example, 60 to 120 minutes), the temperature of the entire apparatus reaches the maximum temperature and becomes saturated.

As described above, the high-frequency heating device has many components with relatively low conversion efficiency such as the magnetron 7 and the high-voltage transformer 3, and accordingly, the heat loss is large, so that the temperature rise during operation is relatively large and it takes a long time. It reaches a stable temperature.

The guarantee of the rated output P ₀ of the device must be made of an insulating material or a constituent material capable of maintaining sufficient safety even if such a heat loss occurs. Therefore, the structure of the cooling condition and the specifications of each part are specified. It is designed to meet such guarantee conditions.

That is, at t = t ₃ in FIG. 7 (b), the constituent materials, the parts specifications, and the cooling structure are determined in due consideration of the temperature rise that has occurred.

Therefore, when the rated output is 500 W and 6
In the case of 00 W, the cooling conditions and the parts specifications are largely different. For example, in the magnetron 7, since the generated loss is different, the cooling structure becomes large and the size and cost are increased, and the high voltage transformer 3 is inevitably increased in size and price.

[0011]

As described above, the conventional high-frequency heating device is a component that can ensure the safety and reliability of the device under temperature conditions when the temperature rise due to heat loss of the device is stable. It was configured by using the specifications of.

However, since the high-frequency heating device is a unique heating method called dielectric heating, the heating time is relatively short, and reheating, which is often used in ordinary households, usually requires 5 hours.
It is extremely often used with a heating time of about a minute or less. That is, in FIG. 7 (b), there are very many usages such as ending the usage at a time of t = t ₀ ,
Usually, cooking that reaches t ₃ is rarely performed. Therefore, in most cases, the high-frequency heating device that guarantees the temperature rise at t = t ₃ , which does not need to be guaranteed under many usage conditions, is used for the usage time of t = t _{0 in} most cases. In this respect, the quality is excessive. However, in rare cases, there may be a use condition up to t = t ₃ , so that such a substantial excess quality is unavoidable.

[0013]

The present invention has been made in order to solve the problems of the conventional high-frequency heating apparatus, and has the structure described below.

That is, a power supply unit supplied with electric power from the outside, a high-voltage power conversion unit having a boosting means for converting the power from the power supply unit into high-voltage power, and a control for controlling the operation of the high-voltage power conversion unit. Section, an electromagnetic wave radiation section that radiates electromagnetic wave energy from the output of the high-voltage power conversion section, and the control section so that the electromagnetic wave energy that is larger than the rated output in the steady state is output during the time measured by the high-power time measuring means. And a large output control unit, and the large output control unit is provided with a stop state detection unit for detecting a state when the high-voltage power conversion unit or the electromagnetic wave emission unit is stopped, the signal of this stop state detection unit The configuration is such that the time counting time of the high output time measuring means is adjusted.

Further, the stop state detecting means includes the high voltage power converting section, the electromagnetic wave radiating section, or the temperature detecting means of their atmosphere.

Furthermore, the stop state detecting means includes stop time measuring means for measuring the time during which the operation of the high-voltage power converter is stopped.

Further, the high-voltage power conversion unit includes an inverter having a semiconductor element.

[0018]

With the above construction, the high-frequency heating device according to the present invention has the following actions.

Since the time-measurement time of the high-power time-measurement means of the high-power control unit is adjusted by the signal of the stopped state detection means, and the radio wave output larger than the rated output is output only for the time-measurement time, the steady maximum value is obtained. Greater power output can be obtained and heating time can be shortened significantly, and the cooling configuration, heat resistance specifications or quality performance of each component can be made appropriate without excessiveness, and sufficient safety and reliability can be achieved. Is guaranteed.

Further, by configuring the stop state including the temperature detecting means, it is possible to reliably detect the state of the heat generating portion at the time of stop and set a large output time, and to ensure safety and reliability. While maintaining this, a large electric wave output is realized and speed heating is realized.

Furthermore, the stop state is detected by measuring the operation stop time of the high-voltage power converter, and the state of the heat-generating part at the time of stop is simple and inexpensive without providing any special temperature detecting means. Is set to set a large output time, and a large electric wave output is easily and quickly maintained while maintaining safe and high reliability.

Further, by configuring the high-voltage power converter by using the inverter, the control section controls the operating state of the semiconductor element by the instruction of the large output control section based on the signal of the stop state detecting means, and the large radio wave output is obtained. Is easily realized.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a high frequency heating apparatus showing an embodiment of the present invention. In the figure, a filter circuit including a commercial power source 20, a diode bridge 21, an inductor 22 and a capacitor 23 constitutes a power source section 24, and includes a capacitor 26, a step-up transformer 27, a transistor 28, a diode 29, a capacitor 30, and a diode 3.
1, and power is supplied to a power converter (high-voltage power converter) 33 including the magnetron 32. Power converter 33
Is composed of an inverter including a capacitor 26, a step-up transformer 27, a transistor 28, and a diode 29, a high-voltage rectifying circuit including a capacitor 30 and a diode 31 that rectifies the output of the step-up transformer 27, and a magnetron 32 that generates high-frequency power. , This magnetron 32
Also functions as a radio wave radiating unit that radiates this high frequency power as electromagnetic wave energy. Of course, the power converter 33 may be composed of a semiconductor oscillator that oscillates at 900 MHz or 2450 MHz, and an antenna or the like may be provided as a radio wave radiating section.

The transistor 28 receives a switching control signal of, for example, 20 KHz to 200 KHz from the control unit 34 and performs a switching operation. Therefore, a high frequency voltage is generated in the primary winding 35 of the step-up transformer 27, the high frequency voltage is boosted, rectified and supplied to the magnetron 32, and the magnetron 32 oscillates. A signal proportional to the input current is sent from the input current detector 36 to the control unit 34. This input current detection signal is sent to the operational amplifier 37 in the control unit 34 as shown in FIG. 2, compared with the signal of the reference signal generator 38, and its error signal is sent to the pulse width control circuit 39. Has been done. Therefore, the conduction time of the transistor 28 is controlled, and the input current is controlled to a predetermined value by so-called pulse width control.
As a result, the electromagnetic wave (radio wave) output P ₀ of the magnetron 32 is constantly controlled to a predetermined value (for example, 500 W).

In such a structure, when operating the high-frequency heating device, a heating start command is sent from the heating start circuit 40 to the start control section (large output control section) 41. Upon receiving the heating start command, the activation control unit 41 sends a rising signal to the control unit 34 to operate at an output (eg, 600 W) larger than the rated output (eg, 500 W) in the steady state for a predetermined time at the start of operation. give.

FIG. 3A shows the radio wave output P ₀ indicating this state.
FIG. When the transistor 28 starts to operate at t = 0, the magnetron 32 starts to oscillate at t = t ₁ after 1 to 2 seconds, and the radio wave output P ₀ is controlled to be 600 W, which is higher than the steady state (that is, the rated value). And t _S
At the subsequent time t ₄ , its output P ₀ is controlled to be 500 W in the steady state (that is, rated). Such control of the radio wave output P ₀ can be realized by various methods. For example, as shown in FIG. 2, the activation controller 41 controls the signal generated by the reference signal generator 38 of the input current. This can be easily achieved. That is, FIG.
This can be realized by changing the reference signal of the input current after the time t _S so that the output P ₀ of (a) changes.

The time t _S in FIG. 3 (a) is a time for generating a higher output than in a steady state while the temperature of the device and each component is sufficiently low. Therefore, FIG.
As is clear from (b), the time when the internal temperature of the device or the temperature of each component is lower than a predetermined temperature may be set as t _S.
From such a concept, as shown in FIG. 4, for example, t _S represents the anode temperature of the magnetron 7 or its ambient temperature or the temperature of the radiation fin of the transistor 28 by the thermistor 42 before starting the device. The signal of the reference signal generator 43 and the comparator 4 are detected as a signal.
The activation control unit 41 configured to compare in 4 can be configured to determine the temperature control center. Further, as shown in FIG. 5, a stop time counter 45 that counts the operation stop time of the equipment (that is, the time during which the device and the parts are cooled) is provided, and the time counted by the stop time counter 45 before the start of the device is set. A start-up modulation counter 46 is provided, which detects the signal representing the state, determines the time t _{S based} on this signal, counts t _S , and changes the reference signal 38 of the input current after t _S. The operating state may be detected to determine this t _S.

Further, of course, the start control section 41 may be constituted by a simple timer device by fixing and fixing t _S for a short time of, for example, about 5 minutes.

[0030] In order to inform that it is thus controlled greater than the steady state the radio wave output P ₀ to the user, as shown in FIG. 2, the display unit 47 is provided, the activation control unit 41 of this
By making it operate with the signal of, the user can recognize the power-up state (that is, 600W) or the steady state (500W) to perform cooking, which is extremely convenient and high-speed cooking. It can be performed.

Further, as shown in FIG. 3B, the radio wave output P₀To
t_SGradually decrease over time, t _SSteady output after time
Similar effect even if it is configured to reduce the power (500 W)
Is obtained.

[0032]

As described above, according to the present invention, since the high output heating time is adjusted by the signal of the stopped state detecting means, it is possible to output the radio wave output larger than the rated output in the steady state, and the heating time is greatly increased. It is possible to shorten the time, and since the large output time is adjusted according to the state at the time of stoppage, the cooling configuration of each component, the heat resistance specification or the quality performance should be made appropriate without being excessive, and sufficient safety It is possible to provide a high-frequency heating device that can guarantee the reliability and reliability. Therefore, it is possible to realize a high-frequency heating device which can be heated at a great speed and which is inexpensive and highly reliable.

Further, the temperature of the heat generating portion is detected by using the temperature detecting means, and the state at the time of stop is detected by this signal, so that a large output is obtained based on the signal surely detecting the state at the time of stop. It is possible to provide a high-frequency heating device capable of adjusting heating time and realizing speed heating by high-power heating while ensuring more reliable safety and reliability.

Furthermore, by providing a means for measuring the operation stop time, the state at the time of stop can be discriminated by a simple time measurement without using a sensor such as a special temperature detector, and based on this signal, a large output time can be obtained. You can adjust
It is possible to perform high-power heating extremely easily and at low cost according to the state at the time of stop. Therefore, it is possible to provide a high-frequency heating device that can realize a large speed heating and is low in cost and highly reliable.

With the configuration in which the magnetron is driven by the inverter, the control of the large output time based on the signal of the stopped state detecting means by the control unit can be easily performed only by controlling the control signal of the inverter. Therefore, it is possible to realize a low-frequency high-frequency heating device in which the control configuration and circuit configuration of the control unit by the high output control unit are extremely simple.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high-frequency heating device showing an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a control unit of the circuit.

FIG. 3 is a waveform diagram showing a temporal change in radio wave output of the high-frequency heating device.

FIG. 4 is a circuit diagram of a main part of a large output control unit of the high-frequency heating device.

FIG. 5 is a block diagram showing another embodiment of the same circuit.

FIG. 6 is a circuit diagram of a conventional high frequency heating device.

FIG. 7 (a) is a diagram showing a time change of a radio wave output of the high-frequency heating apparatus, and (b) is a waveform diagram showing a temperature rise of parts and the like in the high-frequency heating apparatus.

FIG. 8 is a cross-sectional view showing the configuration of a high-frequency heating device.

[Explanation of symbols]

 24 Power Supply Unit 27 Boosting Unit (Boosting Transformer) 28 Semiconductor Element 32 Radio Wave Radiating Unit 33 High Voltage Power Converter (Power Converter) 34 Controller 41 Large Output Controller (Startup Controller)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Niwa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Takahiro Matsumoto 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Villa Daisuke 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Koji Yoshino, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A power supply unit to which electric power is externally supplied, a high-voltage power conversion unit that includes a booster unit and converts the power from the power supply unit into high-voltage power, and a control unit that controls the operation of the high-voltage power conversion unit. And a control unit for controlling the control unit so as to output an electromagnetic wave energy larger than the rated output in the steady state during the time measured by the high-power time measuring unit and the radio wave emitting unit that receives the output of the high-voltage power conversion unit and radiates the electromagnetic wave energy. A large output control section, and the high output control section is provided with a stop state detection means for detecting a state when the high voltage power conversion section or the electromagnetic wave emission section stops operating, and a signal of the stop state detection means is provided. The high-frequency heating device configured to adjust the timed time of the high output timekeeping means. 2. The high-frequency heating apparatus according to claim 1, wherein the stop state detecting means includes a high-voltage power converter, an electromagnetic wave emitter, or a temperature detector for detecting the temperature of the atmosphere thereof. 3. The high-frequency heating apparatus according to claim 1, wherein the stop state detecting means includes stop time measuring means for measuring the time during which the high voltage power converter is not operating. 4. The high-frequency heating apparatus according to claim 1, wherein the high-voltage power converter is composed of an inverter including one or more semiconductor elements and drives the magnetron.