JP2723285B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention drives a magnetron with a high-frequency inverter, and heats and cooks an object to be cooked by microwaves output from the magnetron. About.

(Prior Art) There is a conventional cooking device using a magnetron that directly boosts an input voltage from a commercial AC power supply by a boosting transformer and rectifies the boosted output voltage to drive the magnetron. In such a heating cooker, a method of turning on / off an input voltage to a step-up transformer in order to change a microwave output from the magnetron is adopted,
By varying the on / off ratio, the average microwave output from the magnetron is varied.

Also, other conventional cooking devices include Japanese Patent Publication No. 59-14236.
There is a configuration in which a magnetron is driven by using a frequency converter as disclosed in Japanese Patent Application Laid-Open Publication No. H11-209,878. In this cooking device, the microwave output from the magnetron is changed by changing the frequency of the frequency converter.

The change in the microwave output from the magnetron in the heating cooker using the above-described step-up transformer is a change as an average value, whereas the microwave output from the magnetron in the heating cooker using the frequency converter is almost the same. It can be changed as instantaneous power, and is superior to a cooking device using a step-up transformer. In addition, both heating cookers can continuously heat the object to be cooked at the maximum output, and can also heat the object to be cooked with an output smaller than the maximum output.

Specifically, in a cooking device using the above-mentioned step-up transformer, the maximum output can be set by setting the off time of the input voltage to the step-up transformer to 0, but the output cannot exceed this maximum output. In addition, in a cooking device using a frequency converter, it is possible in principle to produce a maximum output larger than the maximum output by varying the frequency of the frequency converter. When a large amount of stress is applied to each element such as a switching element, a transformer or a magnetron, and the maximum output is continuously generated, each element will be destroyed. It is difficult to happen.

(Problems to be Solved by the Invention) Each of the conventional cooking devices described above can freely change the microwave output below the maximum output that can be continuously heated. There is a problem that a large microwave output cannot be generated.

The present invention has been made in view of the above circumstances, and its purpose is to generate a microwave output larger than a normal continuous maximum output, to shorten the heating and cooking time, and to stop the operation after the operation is stopped. An object of the present invention is to provide a high-frequency heating cooker that cools a heat generating part and generates a microwave output larger than a continuous maximum output for as long as possible.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, a high-frequency heating cooker of the present invention drives a magnetron via a drive circuit including an inverter, and outputs a microwave output from the magnetron. A high-frequency heating cooker for heating and cooking an object to be cooked, wherein the magnetron generates a maximum output greater than a normal continuous maximum output within a range in which a heating section including the drive circuit and the magnetron is not damaged. And cooling means for cooling the heat generating portion even after the driving of the magnetron by the driving circuit is stopped.

(Operation) In the high-frequency heating cooker of the present invention, the drive circuit is controlled so that the magnetron generates a maximum output larger than the normal continuous maximum output within a range where the heat generating portion is not damaged, and the heat generating portion is operated even after the operation is stopped. Cooling.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration of a high-frequency heating cooker according to one embodiment of the present invention. The high frequency heating cooker shown in FIG. 1 operates using an AC voltage from a commercial power supply 1, and the AC voltage from the commercial power supply 1 is closed by closing a door of the high frequency heating cooker. , 2b and the relay contact 3 to the fan motor 4 and the rectifying bridge 5 of the rectifying circuit 8 for rectification.

A fan (not shown) is attached to the fan motor 4, and the fan cools the switching transistor 9, the high-frequency transformer 12, the magnetron 17, and the like of the inverter circuit 13 described later.

The rectifier bridge 5 of the rectifier circuit 8 rectifies an AC voltage from the commercial power supply 1 and converts it into a DC voltage. The DC voltage is smoothed by the choke coil 6 and the smoothing capacitor 7 and supplied to the inverter circuit 13. The inverter circuit 13 includes a primary coil 12a of the high-frequency transformer 12, a switching transistor 9 connected in series to the primary coil 12a, a regenerative current diode 10 connected in parallel to the switching transistor 9, and a resonance capacitor 11. it is intended to generate a high output voltage in the secondary coil 12b of the high-frequency transformer 12 by intermittently rectifier circuit 8 primary current I ₂ flowing through the primary coil 12a of the high-frequency transformer 12 from the switching transistor 9.

The intermittent operation of the switching transistor 9 in the inverter circuit 13 causes the secondary coil 12 of the high-frequency
The high output voltage generated at b is supplied to the half-wave voltage doubler rectifier circuit 16 and is boosted to a double voltage.

The half-wave voltage doubler rectifier circuit 16 is composed of a secondary coil 12b of the high-frequency transformer 12, a voltage doubler capacitor 11, and a voltage doubler diode 15. While being applied between the anode and the cathode, the voltage generated in the tertiary coil 12c of the high-frequency transformer 12 is also applied to the filament of the magnetron 17, whereby the magnetron 17 is driven,
Outputs microwave.

The AC voltage from the commercial power supply 1 is converted to a predetermined voltage via a transformer 18 and supplied to a control circuit 19,
It is rectified to a predetermined DC voltage by a rectifier circuit (not shown) or the like, and is supplied to each part of the control circuit 19 as an operating voltage of the control circuit 19. The control circuit 19 includes a microcomputer 22, a clock oscillator 23 that generates a reference clock for operation supplied to the microcomputer 22, and a microcomputer.
A relay driving unit 21 for controlling the opening and closing of the relay contact 3 in response to a command signal from the microcomputer 22; and an output setting unit for setting a microwave output value in accordance with a command signal from the microcomputer 22
24, and a PWM unit 25 supplied with the microwave set value set in the output setting unit 24 and controlling the switching of the switching transistor 9 in accordance with the set value. An input signal is supplied from the operation unit 20 to the microcomputer 22, and the microcomputer 22 performs an operation according to the input signal.

Further, a temperature detecting element 27 is provided near the switching transistor 9 of the inverter circuit 13, and the resistance value of the temperature detecting element 27 changes in accordance with the temperature of the heat generated from the switching transistor 9, This change in resistance is detected by the temperature detecting section 26 and converted into temperature information, and the detected temperature from the temperature detecting section 26 is supplied to the microcomputer 22.

In the high-frequency heating cooker configured as described above,
First, the operation of the inverter circuit 13 will be described with reference to FIGS.
This will be described with reference to the drawings. FIG. 2 is a diagram showing the waveform of each part when the high-frequency cooking device of FIG. 1 is operated at a normal continuous maximum output, and FIG. 3 is a diagram showing a maximum maximum output larger than the continuous maximum output of FIG. It is a figure which shows the waveform of each part at the time of operating a high frequency heating cooker so that an output may be generated.

The PWM unit 25 of the control circuit 19 supplies an ON signal corresponding to a time corresponding to the set value set in the output setting unit 24 by the microcomputer 22 to the switching transistor 9 of the inverter circuit 13. The ON signal supplied from the PWM unit 25 to the switching transistor 9 is shown in FIG.
Has a duration ton from time to to t1, as shown in ( ₁ ), and when this ON signal is supplied to the switching transistor 9, the switching transistor 9 is turned on during this ON signal. When the switching transistor 9 is turned on, a time so that the current I ₁ as shown in FIG. 2 (a) to the switching transistor 9 gradually increases as the inductance of the high-frequency transformer 12 via a primary coil 12a of the high-frequency transformer 12 with flowing from to to t _1, Similarly flows as second view current I ₂ as shown in (c) is increased gradually to the primary coil 12a of the high-frequency transformer 12. Thus, the collector-emitter voltage Vce of the switching transistor 9 when the switching transistor 9 is on is a very small voltage as shown in FIG. 2 (b).

Further, in this case, the secondary coil 12b of the high-frequency transformer 12
FIG. 2 (d) and (e)
The secondary current I ₃ and the magnetron current I ₄ flows indicated, respectively, the magnetron 17 by the magnetron current I ₄
Are driven to generate microwaves. Among the high-frequency transformer 12 of the secondary coil 12b to flow the secondary current I _3, in the positive direction of current magnetron 17 flows as the anode current, the other negative direction current times voltage half-wave voltage doubler rectifier circuit 16 The voltage charged in the capacitor for voltage doubler 14 is added to the voltage in the positive direction in the next cycle, and the doubled voltage is applied to the magnetron 17 via the diode 15 for charging. It has become so.

During the on-time ton from time to to t ₁ , the switching transistor 9 includes the primary coil 12 of the high-frequency transformer 12.
flowing the same current as the current flowing in a while, become time t _1, when the ON signal is lost, the switching transistor 9 is turned off, the current I ₁ and the second view which has been flowing to the switching transistor 9 (a 0) as shown in FIG. After switching transistor 9 is turned off, the resonance state flows into the resonant capacitor 11 as shown at time t ₁ after the second view current I ₂ flowing in the primary coil 12a of high-frequency transformer 12 (c) And the resonance capacitor 11
Is charged, the voltage of the resonance capacitor 11, that is, the collector-emitter voltage Vc of the switching transistor 9
e rises as shown in FIG. 2 (b). In this resonant state, the collector when the direction of the current I ₂ flowing in the primary coil 12a of high-frequency transformer 12 are reversed - emitter voltage Vce becomes the highest voltage, then the voltage Vce
Decreases, the voltage Vce at time t ₂ becomes zero. With such voltage Vce becomes a time instant t ₂ becomes 0, the current I ₂ flowing through the primary coil 12a of high-frequency transformer 12 rather than flowing to the resonance capacitor 11, flows through the regenerative current diode 10 as a current I ₁ And I ₁ = I ₂ .

At time t ₃ when the predetermined time delay from the time t _2, PWM unit 25
, An ON signal is generated again and supplied to the switching transistor 9, and the switching transistor 9 is turned ON again. When the switching transistor 9 is turned on, the current I flowing through the primary coil 12a of the high-frequency transformer 12
₂ instead of the current I ₁ from the time t ₄ when a positive direction again through the regenerative current diode 10, to flow the switching transistor 9. Similarly, during the on-time ton when the switching transistor 9 is turned on, the currents I ₁ and I ₂ are supplied to the switching transistor 9 and the primary coil 12a of the high-frequency transformer 12 so as to gradually increase with a gradient according to the inductance of the high-frequency transformer 12. respectively flow, repeating the operation that becomes the resonant state again after the on-time ton, whereby the second view magnetron current I ₄ as shown in (e) flows through the magnetron 17, thereby the magnetron 17 is driven, micro Generates waves.

Here, the output setting unit is controlled by the microcomputer 22.
When the initial value corresponding to the ON time smaller than the ON time ton shown in FIG. 2 is set to 24, the current I ₁ flowing through the switching transistor 9 and the primary coil 12a flowing through the high frequency transformer 12 as described above. The primary current I ₂ , the secondary current I ₃ flowing through the secondary coil 12b of the high-frequency transformer 12, and the magnetron current I ₄ flowing through the magnetron 17 all have small current values in proportion to this set value. That is, the microwave output from the magnetron 17 can be changed to an arbitrary value by changing the on-time ton for driving the switching transistor 9.

FIG. 3 is a diagram showing operation waveforms of respective parts corresponding to FIG. 2 at the time of overdrive in which an instantaneous maximum output larger than the maximum output at the time of continuous operation shown in FIG. 2 is output. In FIG.
In order to output an instantaneous maximum output from the magnetron 17 larger than the continuous maximum output in FIG. 2 by forming an overdrive state, the on-time ton longer than the on-time ton shown in FIG.
Is set. As a result, the current waveforms I ₁ ,
As can be seen from the comparison with the corresponding current waveforms of the respective parts in FIG. ₂ , I ₂ , I ₃ , and I ₄ all become large at the time when the on-time ton ends and the switching transistor 9 is turned off. It has become. Therefore, the magnetron 17 outputs a microwave having the highest output larger than the continuous maximum output shown in FIG. Incidentally, in the overdrive state, the current I ₁ flowing through the switching transistor 9 increases, the collector of the switching transistor 9 - The process also increased emitter voltage Vce, heat generated from the switching transistor 9 increases correspondingly, If the overdrive state is continued, the switching transistor 9 will be destroyed. Also,
Similarly, since the current flowing in the high-frequency transformer 12 and the magnetron 17 is also large, the heat generated from the high-frequency transformer 12 and the magnetron 17 is correspondingly large, and if the overdrive state continues as it is, the high-frequency transformer 12 and the magnetron 17 It will be damaged.

By the way, such a switching transistor 9,
The destruction and breakage of each element such as the high-frequency transformer 12 and the magnetron 17 due to the overdrive state is caused by a temperature rise due to heat generated by current and voltage in each element, and this temperature rise does not occur instantaneously, Starting operation in the overdrive state, the temperature of each element gradually rises,
The temperature reaches the breakdown temperature, and it takes a certain time from the start of the operation until the temperature reaches the breakdown temperature.

More specifically, this will be described with reference to FIG. FIG. 4 (a) is a graph showing the operation time of the high-frequency cooking device of FIG. 1 on the horizontal axis, and the temperature of the switching transistor 9 detected by the temperature detecting element 27 on the vertical axis. 4 (b) to (d), the horizontal axis indicates the time taken corresponding to the time on the horizontal axis in FIG. 4 (a), and the vertical axis indicates the output level from the magnetron 17.

When the high frequency heating cooker of Figure 1 when operating in a continuous maximum output shown in FIG. 2, as shown by curve A in 4 (a), which starts operating at time t _10, temperature of the switching transistor 9 in operation starting time t ₁₀ was the initial phase temperatures T ₁ gradually increases, at time t ₁₂ becomes the saturated temperature T _3, the temperature of the switching transistor 9 be further continued operation saturation The temperature does not rise above the temperature, and the switching transistor 9 can continue the continuous operation without being broken. In this normal continuous state, as shown in FIG. 4 (c), the high-frequency heating cooker does not break even if it continuously outputs a continuous maximum output of, for example, 500 watts.

On the other hand, when the high-frequency heating cooker is operated in the overdrive state shown in FIG. 3 by generating the maximum output larger than the continuous maximum output in the normal continuous state, the curve B in FIG. as shown, the temperature of the switching transistor 9 rises from rapidly the curve a, the switching transistor 9 should saturate raised to a temperature T ₆ to be destroyed, lower than the saturation temperature T ₆ It indicates that destroyed at t ₁₂ became failure temperature T _5. The over-drive state, as shown in FIG. 4 (d), the high-frequency cooking device generates a maximum output of greater than the maximum continuous output for example, 700 watts, will be destroyed at the time t _12.

A curve C shown in FIG. 4A indicates that the temperature of the switching transistor 9 is the saturation temperature T ₃ at the continuous maximum output.
Until time t ₁₁ becomes slightly lower predetermined safety temperature T ₂ than the time at which the high frequency heating cooker is operated at the over-drive state so as to generate the maximum output, becomes the predetermined overdrive safety temperature T ₂ t ₁₁ and subsequent are those operated by reducing the output to maximum continuous output. Temperature of the switching transistor 9 By thus operate eventually saturate at a saturation temperature T ₃ during continuous maximum output is the switching transistor 9 will not be destroyed. FIG. 4 (b)
, While indicating the output state of the high-frequency heating cooker in this case, the period from time t ₁₀ to t ₁₁ generates the maximum output of the overdrive state of for example, 700 watts, time t ₁₁ after the example 5
It produces a continuous maximum output of 00 watts.

By the way, in the actual use state, the high-frequency heating cooker may be operated continuously plural times, or the operating environment temperature may be low or high, and in these cases, the initial operation at the start of operation of the apparatus may be performed. the temperature T ₁ becomes different that will that this initial temperature T the duration of the over-drive state also differ capable of generating an instantaneous maximum output by _one. For example, when generating an instantaneous maximum output in the over-drive state when a low initial temperatures T ₁ at the start of device operation, the time until the temperature of the switching transistor 9 reaches the overdrive safe temperature T _2, i.e. the instantaneous maximum output the duration of the over-drive state becomes longer, which may occur, also the initial temperature T when ₁ is high, overdrive temperature of the switching transistor 9 is capable of generation time, namely the instantaneous maximum output to reach the over-driving safety temperature T ₂ The duration of the state will be shorter.

This will be specifically described with reference to FIG. Fig. 5 (a)
5A to 5F show the time on the horizontal axis, the vertical axis shows the temperature of the switching transistor 9 in FIGS. 5A to 5C, and FIGS. 5D to 5F show the temperature from the magnetron 17 in FIG. Indicates the output level. Further, (a) and (d) in FIG. 5 correspond, (b) and (e) correspond, and (c) and (f) correspond.

Figure 5 (a), (d) is a diagram when the initial temperature of the switching transistor 9 at the start of device operation occurs the instantaneous maximum output by the device from the start device operating in an over drive condition in the case of T ₁ is there. As shown in FIG. 6 (a), the temperature of the switching transistor 9 is gradually increased from an initial temperature T _1, the over-drive state when t ₂₅ the temperature of the switching transistor 9 becomes overdriven safety temperature T ₂ stop the case with a reduced normal maximum continuous output is the duration of the over-drive state for generating an instantaneous maximum output to reach the over-driving safety temperature T ₂ from the time to to t _25.

Further, FIG. 5 (b), (e) is a case where the initial temperature is a temperature T ₁ a than the initial temperature T _1, the temperature of the transistor 9 in this case is overdriven safety at time t ₂₃ Temperature T ₂
Reached, the duration of the over-drive state for generating an instantaneous maximum output is shorter as compared with the case in from time to to t23 of the initial temperature T _1.

Further, FIGS. 5 (c) and 5 (f) show that the initial temperature is higher T.
_1b is a case, t ₂₁ from the case reached overdrive safety temperature T ₂ at time t ₂₁ temperature of the switching transistor 9, the duration of the over-drive state to the instantaneous maximum output time to
And even shorter.

In any case shown in FIG. 5, the temperature of the switching transistor 9 at the time of switching to the normal continuous maximum output after operating in the overdrive state from each initial temperature and generating the instantaneous maximum output becomes almost the same. Without breaking each element, it is possible to generate an instantaneous maximum output in each case and operate in an overdrive state,
It can be seen that the duration of the overdrive state that can generate the instantaneous maximum output depends on the initial temperature, and the duration of the overdrive state that can generate the instantaneous maximum output depends on the initial temperature.

This will be described more specifically with reference to FIG. 6 (a) to 6 (d) show time on the horizontal axis, FIG. 6 (a) shows the temperature of the switching transistor 9 on the vertical axis, and FIGS. 6 (b) to 6 (d) show the temperature from the magnetron 17. Indicates the output level. 6 (b) to 6 (d) correspond to the curves B to D in FIG. 6 (a), respectively.

In Figure 6, the high frequency heating cooker at time t ₁₀ it is assumed to have stopped previous operation, the temperature of the switching transistor 9 when this stop is saturation temperature T _3. Then, the temperature of the switching transistor 9 in this time t ₁₀ is what was in the saturation temperature T _3, as shown by the curve A shown by a dotted line in FIG. 6 (a), is gradually reduced by stopping the final Specifically, the temperature will drop to the ambient temperature.

Here, as indicated by the curve B and the sixth view of FIG. 6 (a) (b), begins to stop at time t _10, from the time t ₁₁ where the saturation temperature T ₃ after stopping decreased to a temperature T ₁₁ re-driven by the over-drive state for generating an instantaneous maximum output, the temperature of the switching transistor 9 is again raised from the temperature T ₁₁ at time t _11, it reaches the overdrive safety temperature T ₂ at time t _11a. Therefore, after this time actuates by lowering the normal maximum continuous output, to stabilize the saturated temperature T ₃ during continuous maximum output temperature of the switching transistor 9. Incidentally, the duration of the over-drive state of the instantaneous maximum output in this case is until t _11a consisting of time t ₁₁ of the temperature T ₁₁ to overdrive safe temperature T _2.

Further, as indicated by the curve C and the sixth view of FIG. 6 (a) (c), beginning to stop from time t _10, the instantaneous from time t ₂₁ to the saturation temperature T ₃ at stop was lowered to a temperature T ₂₁ re-driven by the over-drive state of maximum output, the temperature of the transistor 9 is increased again from time t _21, it reaches the overdrive safety temperature T ₂ at time t _21a. The duration of the over-drive state of the instantaneous maximum output in this case is until t _21a consisting of time t ₂₁ of the temperature T ₂₁ to overdrive safe temperature T _2.

That is, comparing the duration of the overdrive state of the instantaneous maximum output in the two examples described above, the longer the stop time, the lower the initial temperature when the device is cooled and the restart is started, the lower the instantaneous maximum output is. It can be seen that the duration of the overdrive state is long.

Similarly, as indicated by the curve D and the sixth view of FIG. 6 (d) (d), the stop time is longer, if further initial temperature at the time of re-operation start is a T ₃₁ low, i.e. the time re-driven by the over-drive state of the instantaneous maximum output from the time t ₃₁ by lengthening the further stop time what has been stopped from t _10, the over-drive state of the instantaneous maximum output longer time t _31a
Continue until.

As described above, it can be seen that the duration of the overdrive state in which the instantaneous maximum output can be generated becomes longer as the stop time is longer, but the longer the stop time, the lower the initial temperature due to the cooling action during that time. That's why.

The dotted curve A shown in FIG. 6 (a) is the saturation temperature.
Gradually naturally decreases during the stop time from an initial temperature of T _3, and finally shows the temperature drop curve drops to ambient temperature, other curves B, C, D each between the natural decrease respectively FIG. 7 shows a temperature change in the case where the fan motor 4 is restarted from the time point. In this case, in order to make the temperature drop naturally within the stop time indicated by the curve A more rapidly, the fan motor When the switching transistor 9 is forcibly cooled by this operation, the initial temperatures at the start of the re-driving indicated by the curves B, C and D become the initial temperatures T ₁₁ and T ₂₁ shown in FIG. 6, respectively. , lower than the T _31, that amount would be lengthened the duration of the over-drive state capable of generating instantaneous maximum output.

FIG. 7 is the same as FIG. 6 when the fan is operated by the fan motor 4 to forcibly cool the switching transistor 9 even after the apparatus stops. Thus, in Figure 7, curve A dotted line shows the temperature to decrease from an initial temperature of the saturation temperature T ₃ in the forced cooling by fan, than the temperature drop curve for natural cooling shown by FIG. 6 of the dotted curve A It turns out that it has fallen sharply.

Accordingly, the curves B, C, D in FIG. 6 (a) and the curves in FIG. 7 (a) corresponding to FIGS. 6 (b), (c), (d)
B, C, D, and each initial period determined by the forced cooling of the curve A after the same stop periods t10 to t11, t10 to t21, and t10 to t31 shown in FIGS. 7 (b), (c), and (d), respectively. Temperature T _11a , T _21a , T _31a
Are all lower than the corresponding initial temperatures T ₁₁ , T ₂₁ and T ₃₁ in FIG. 6, respectively. As a result, this is driven during each from a low initial temperature to over-drive condition, each duration tb occurring instantaneous maximum output, tc, td is the duration t ₁₁ for generating a corresponding instantaneous maximum output of Figure 6, respectively −t _11a , t _21a , t
It is clear that they are all longer than ₃₁ −t _31a .

As described above, according to the present invention, the heating unit including the inverter circuit 13 and the magnetron 17 of the high-frequency heating cooker is forcibly cooled by the operation of the fan by the fan motor 4 during the stop time. The purpose of the present invention is to reduce the temperature and extend the duration of an overdrive state in which an instantaneous maximum output can be generated as much as possible.

FIG. 8 is a flowchart showing the operation of the high-frequency heating cooker of FIG. 1 based on such a principle. In this figure, when it is detected that the heating has stopped, that is, that the device has stopped (step 110), the fan motor 4 is further driven to continue the rotation of the cooling fan without stopping the fan motor 4 (step 120). When it is confirmed that the temperature of the switching transistor 9 has dropped to a predetermined value (step 130). The operation of the fan motor 4 is stopped to stop the rotation of the cooling fan (step 140).

FIG. 9 is a flowchart showing the operation of another embodiment of the present invention. The operation shown in the figure is the same as the operation shown in FIG. 8 except that the cooling fan is operated for a predetermined time in step 135 instead of step 130 in the operation shown in FIG.

8 and 9, the cooling fan is forcibly cooled by the cooling fan until the temperature of the switching transistor 9 decreases to a predetermined value or for a predetermined time, whereby the temperature of the switching transistor 9 is reduced. The temperature is rapidly reduced to a predetermined value close to the ambient temperature, and even if the device is restarted during the rapid reduction, the initial temperature at that time is reduced as much as possible.

In the present embodiment, the control operation for generating the instantaneous maximum output in the overdrive state is performed.
Suppose there was a cooking that required a minute heating, in this case 700
Assuming that the instantaneous maximum output time of watts can be 3 minutes, a cooking time of 2.86 minutes, that is, 4.times.500 / 700 = 2.86 minutes is sufficient by using the instantaneous maximum output of 700 watts.

Similarly, in the case of cooking that requires heating at 500 watts for 6 minutes, a heat treatment of 4.8 minutes, that is, 6-3 × 700/500 + 3 = 4.8 minutes may be performed by using the instantaneous maximum output of 700 watts. In other words, the cooking time can be shortened.

In the above embodiment, the case where the control is performed by detecting the temperature of the switching transistor 9 is performed. However, the present invention is not limited to this, and the temperature of the high-frequency transistor 12 or the magnetron 17 may be detected.

[Effects of the Invention] As described above, according to the present invention, the drive circuit is controlled such that the magnetron generates the maximum output larger than the normal continuous maximum output within a range where the heat generating portion is not damaged, and the operation is stopped. Since the heat-generating part is cooled afterwards, it is possible to perform heating cooking by generating a maximum output larger than the normal continuous maximum output, thereby shortening the heating cooking time and also at the start of operation of the device. Since the initial temperature is rapidly lowered, the duration during which the instantaneous maximum output can be generated at the start of the restart of the apparatus can be made as long as possible, and the cooking time can be shortened.

[Brief description of the drawings]

1 is a circuit diagram of a high-frequency heating cooker according to one embodiment of the present invention, FIG. 2 is an operation waveform diagram of each unit when the high-frequency heating cooker of FIG. 1 generates a maximum output during continuous operation, Third
FIGS. 4A to 4C are diagrams showing operation waveforms of respective parts when the high-frequency heating cooker of FIG. 1 generates an instantaneous maximum output, and FIGS. 4 to 7 are diagrams for explaining the principle of the high-frequency heating cooker of FIG. FIG. 8, FIG. 8 and FIG. 9 are flow charts showing the operation of the high frequency heating cooker of FIG. 9 switching transistor, 12 high-frequency transformer, 13 inverter circuit, 17 magnetron, 19 control circuit, 24 output setting section, 25 PWM section, 26 temperature detection section, 27 …… Temperature detection element.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tatsuya Nakagawa 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref. Toshiba Audio-Video Engineering Co., Ltd. (56) References Japanese Utility Model Showa 49-48548 (JP, U) Japanese Utility Model Showa 63-108004 (JP, U)

Claims (3)

(57) [Claims] 1. A high-frequency heating cooker for driving a magnetron via a drive circuit comprising an inverter and heating and cooking an object to be cooked by microwaves output from the magnetron, wherein the heating circuit includes the drive circuit and a magnetron. Control means for controlling the drive circuit so that the magnetron generates a maximum output greater than a normal continuous maximum output within a range where the magnetron is not damaged; and even after stopping the drive of the magnetron by the drive circuit, cooling the heating section. A high-frequency heating cooker comprising: 2. The method according to claim 1, wherein the cooling means is provided for a predetermined time after the stop.
The high frequency heating cooker according to claim 1, further comprising a time limit means for cooling the heat generating portion. 3. The high-frequency heating apparatus according to claim 1, wherein said cooling means includes means for cooling said heat generating portion until at least one temperature of said drive circuit or magnetron becomes lower than a predetermined value. Cooking device.