CN1470804A

CN1470804A - Microwave oven

Info

Publication number: CN1470804A
Application number: CNA03122685XA
Authority: CN
Inventors: 部w澄; 岡部眞澄
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2002-07-25
Filing date: 2003-03-31
Publication date: 2004-01-28
Anticipated expiration: 2023-03-31
Also published as: TW200401872A; KR20040010082A; TWI221185B; JP2004060923A; CN1255650C; KR100488635B1

Abstract

The present invention provides a microwave oven for controling the input power with a simple structure. The magnetron is driven by a drive circuit comprising a control circuit for controlling the drive circuit to control an input power of the magnetron. The controlling circuit has a ROM for recording a control index and controls the drive circuit according to the control index such that the input power of the magnetron is controlled to be constant.

Description

Micro-wave oven

Technical field

The present invention relates to carry out the micro-wave oven (microwaveoven) of the input power control of magnetron (magnetron).

Background technology

Fig. 6 illustrates the circuit of existing micro-wave oven, particularly the drive circuit of magnetron 100.Be connected with drive circuit of magnetron 102 on AC power 101, this drive circuit 102 is made of DC power supply circuit 103, converter (inverter) circuit 104, high frequency transformer (high frequency transformer) 105 and voltage doubling rectifing circuit 106.

In said structure, converter circuit 104 comprises switch element (switching elements) 104a, 104b, this

switch element

104a, 104b by control circuit 107 controlling carry out switch (on, off).Then, by this switch motion at the last generation of elementary winding (primary winding) 105a of high frequency transformer 105 high frequency electric, on the voltage doubling rectifing circuit 106 that the primary side with this high frequency transformer 105 is connected, produce voltage multiplying rectifier power, drive magnetron 100.

And say that the output of above-mentioned magnetron 100 changes according to the temperature of this magnetron 100, the temperature of this magnetron 100 and driven by magnetron begin to rise simultaneously, and be relevant with it, and anode voltage reduces, and magnetron output reduces.As controlling a kind of mode that this magnetron is output as setting, existing following mode.

That is, because in fact be difficult to directly detect magnetron output, so, by detecting the input power relevant and controlling input power, control magnetron output with magnetron output.As shown in Figure 6, the current sensing means 108 that is made of for example current transformer is set on the power circuit of AC power 101, detection current value and known voltage (normally definite value 100V) according to this current sensing means 108 detect input power, control the opening (ON) time of switch element 104a of above-mentioned converter circuit 104, the control high frequency electric, so that it is this detection input power becomes regulation, for example certain.

But, in such existing structure, current sensing means 108 checkout gears such as grade must be arranged, therefore the shortcoming of cost height (cost overrun) is arranged.

The present invention its objective is the micro-wave oven that provides the simple structure of a kind of usefulness to realize the control of input power in view of the above problems.

Summary of the invention

The starting point of the invention of claim 1 is as follows.That is, one drives magnetron, and temperature just rises, and loss just produces, and anode voltage just reduces.Because this anode voltage reduces, magnetron output just reduces, and just shows as input power and reduces.For the regulation input power,, just can recover magnetron output if increase the input power of this difference.At this,, test in advance by the present inventor and to try to achieve as the control data of the input power that is used to compensate above-mentioned difference.That is, because from driving magnetron, along with time course, temperature rises and the loss of magnetron becomes big, so, input power is also increased.Obtain and make input power increase what control data this moment.

Therefore, the invention of claim 1 has and is characterised in that, comprising: the magnetron that is used for the eddy-current heating heating object; Drive this driving magnetron device; In order to control and control the driving control device of above-mentioned drive unit for the input power of above-mentioned magnetron,

Above-mentioned driving control device has that to have stored the input power that is used to control above-mentioned magnetron be the storage device of the control data of setting, controls above-mentioned drive unit according to this control data.

In the invention of claim 1, just produce loss even drive magnetron, but because driving control device carries out accessory drive according to control data (control data), so, do not need checkout gear such as existing current sensing means just can control input power and become setting.Its result helps cheapization of cost (cost).

The invention of claim 2 has and is characterised in that, data storage device when driving control device comprises stopping of the control data of storage driven by magnetron when stopping, when driven by magnetron begins, stopping with the driven by magnetron of distance last time is not condition through the stipulated time, and the control data in the data storage device carries out accessory drive when stopping based on being stored in.

Along with end of cooking, magnetron one stops to drive, and soon, the magnetron temperature just is in high state.For once more the cooking of beginning under this state, driving magnetron at the beginning, anode voltage just is in low state, and is in the initial value of control characteristic, probably will input power little and magnetron output is not enough, the cooking failure.

Yet, in the invention of aforesaid right requirement 2, when driven by magnetron began, stopping with the driven by magnetron of distance last time was not condition through the stipulated time, promptly, do not drop to condition with the magnetron temperature, control data in the data storage device carries out accessory drive when stopping based on being stored in, therefore, even under the situation of the cooking continuously, magnetron also can obtain enough input powers and not have the deficiency of magnetron output, does not cause the cooking failure.

The invention of claim 3 has and is characterised in that, comprises the temperature sensor that detects external air temperature, comprises the compensation arrangement that compensates control data according to the detected temperatures that is detected by this temperature sensor.

If under the control data normal temperature condition, externally under the situation that air themperature is high (situation that anode voltage is low), the input power after just reducing some and begin to drive magnetron according to this control data, in addition, externally under the situation that air themperature is low, some input powers just raise.

Yet, in the invention of claim 3, detect external air temperature because be provided with by temperature sensor, compensate the compensation arrangement of control data according to this detected temperatures, so, can prevent the change that produces because of external air temperature to the input power of magnetron input.

Description of drawings

Fig. 1 is the circuit diagram that one embodiment of the present of invention are shown.

Fig. 2 is the longitudinal sectional drawing that the schematic configuration of micro-wave oven is shown.

Fig. 3 is the figure that the variation of magnetron temperature, anode voltage, control characteristic, input power is shown.

Fig. 4 is the figure that illustrates for the variation of the input current of external air temperature.

Fig. 5 is the figure that the control content of control circuit is shown.

Fig. 6 is the circuit diagram that prior art is shown.

The specific embodiment

Below, referring to figs. 1 through Fig. 5 one embodiment of the present of invention are described.At first, in Fig. 2, the main body 1 of micro-wave oven is made of outer container 2 and interior case 3, and interior case 3 inside constitute heating clamber 4.Outer bottom at this heating clamber 4 disposes turntable motor (turntable motor) 5, and its rotating shaft is outstanding in heating clamber 4, connects rotation net 6.On this rotation net 6, disposing the rotating disc 7 that to take down.Spatial portion between the right plate of the right plate of interior case 3 and outer container 2 constitutes Machine Room 8.In Machine Room 8, magnetron 9 is installed on the right plate of interior case 3, just in heating clamber 4, supply with the microwave (microwave) that this magnetron 9 produces from an excitation mouthful 3a.In addition, the temperature sensor 10 that is used to detect external air temperature is being set on above-mentioned Machine Room 8.

In addition, it is drive circuit 12 that Fig. 1 illustrates the drive unit that is connected to commercial ac power source 11, and it is used for driving control magnetron 9.Describe about this drive circuit 12.Two ends in AC power 11, the input terminal that connects the full-wave rectifying circuit 14 that constitutes by diode bridge (diode bridge) by capacitor (capacitor) 13, in its lead-out terminal one is connected to an end of smmothing capacitor (smoothing capacitor) 16 by choke coil (choke coil) 15, and another is connected to the other end of capacitor 16.Constitute DC power supply circuit 17 by these capacitors 13, full-wave rectifying circuit 14, choke coil 15, smmothing capacitor 16.

Dc source circuit (DC power line) 17a at this DC power supply circuit 17 is connecting converter circuit 18 on the 17b.The structure of this converter circuit 18 is as follows.At dc source circuit 17a, the

switch element

19,20 that is connected in series between the 17b and constitutes by for example IGBT, be connected fly-wheel diode (freewheel diode) 21,22 with their inverse parallels ground, in addition, at dc source circuit 17a,

capacitor

23 and 24 are being connected in series on the 17b.Then, when the shared splicing ear of

switch element

19,20 is connected with the terminal of the elementary winding 25a of high frequency transformer 25, be connected with the emitter stage of capacitor 27 with the switch element 20 of underarm (lower arm) by resistance 26.In addition, the shared tie point of above-mentioned

capacitor

23,24 is connected with another terminal of the elementary winding 25a of high frequency transformer 25.

Primary side at above-mentioned high frequency transformer 25 is provided with secondary windings (secondary winding) 25b and Filament Winding (filament winding) 25c, is connecting voltage doubling rectifing circuit 28 on secondary windings 25b.This voltage doubling rectifing circuit 28 is with 29,30 and two

capacitors

31,32 of two diodes (diode) and two circuit structures that

resistance

33,34 connects into as shown in figure, plus high-pressure on magnetron 9.

The

switch element

19 and 20 of above-mentioned converter circuit 18 utilizes the control circuit 35 shown in Fig. 1, carry out switch control by the dutycycle (デユ-テイ-ratio) of the primary and secondary of high frequency, at elementary winding 25a upper reaches high frequency electric, induction of high frequency electric current on secondary windings 25b and Filament Winding 25c.The high frequency electric of sensing on secondary windings 25b becomes high pressure by voltage doubling rectifing circuit 28, is added on the magnetron 9, and then magnetron 9 oscillation actions.

Structure as the driving control device and the control circuit 35 of compensation dress transposition comprises microcomputer, and utilization changes over linearity (linear) with the ETAD expected time of arrival and departure of the switch element 19 of converter circuit 18, will stepless terrace land control input power.Under this situation, particularly switch

element

19,20, it is that " opening " and switch element 20 are the time that " pass " and switch element 20 are opened as if growth switch element 19 for "open" state for " pass " state and switch element 19 (OFF) that switch element 19 is arranged in one-period, just can make input current become big, the anode voltage of magnetron 9 can be improved, just output can be improved.

In addition, include CPU, ROM and RAM in the microcomputer in above-mentioned control circuit 35, the function of data storage device when this ROM has stopping of control data when stopping as the storage device of storage control data and storage magnetron.In addition, give the switch input to above-mentioned control circuit 35, on this switch input circuit 36, do not illustrate, but comprise time setting switch and starting switch (start switch) etc. as switch from switch secondary input circuit 36.In addition, control turntable motor 5 by drive circuit 37, have again, on this drive circuit 37, connecting AC power 11 by control circuit 35.

Below, describe about above-mentioned control data.In Fig. 3, under the temperature conditions of for example normal temperature (20 ℃), make for the type of drive (ETAD expected time of arrival and departure of switch element 19) of the converter circuit 18 of magnetron 9 from initial just under certain situation, when having driven magnetron 9, the temperature of magnetron 9 is shown in characteristic curve Tm, rise during initial 5 minutes, just be roughly certain afterwards.Thereupon, the loss of magnetron 9 increases, and anode voltage ebm also roughly reducing in initial 5 minutes, just is roughly certain afterwards.Thereby the output of magnetron 9 also reduces down to input power.Be necessary to make the input power increase of this part.Therefore, in the present embodiment, control characteristic y is set in investigation in advance, as the control data for the type of drive of converter circuit 18.

Promptly, under normal temperature condition, use specified loads, the maximum of the magnetron 9 that obtains after 5 minutes is allowed the type of drive of input power when (being maximal input under the big state of the loss of magnetron 9), when promptly the ETAD expected time of arrival and departure T of the switch element 19 of the converter circuit 18 under this situation is made as benchmark control characteristic " 100 ", after 5 minutes (state that the loss of magnetron 9 is big), the control characteristic of rated input power that is used to obtain magnetron 9 is the most desirable for " 96 ".

From at first, if drive magnetron 9 with this index " 96 " because begin the initial stage in driven by magnetron (lose little state) too much with regard to input power, therefore, can reduce the control characteristic of the input power of this part with regard to setting.That is, control characteristic shown in the characteristic curve y of Fig. 3 like that, be " 86 " driving the time started point, after 5 minutes, rise up to " 96 " with regard to straight line, just keep should " 96 " constant afterwards.

Thereby if to establish this control data be that control characteristic is y, the elapsed time is x minute, y=((96-86)/5) x+86 then, and 0＜x≤5 wherein, y=96 is x＞5 o'clock.This control characteristic is stored among the ROM of control circuit 35.In addition, this control characteristic y will compensate according to external air temperature (temperature within doors of micro-wave oven is set), and following setting of this penalty constant h is stored among the above-mentioned ROM then.That is, at the maximum input current that illustrates on the characteristic curve Ij of Fig. 4 under the situation that does not have compensation about control characteristic y for external air temperature.Under this situation, if make external air temperature be lower than roughly 15 degree, maximum input current just surpasses 14.50A, allows that to maximum input current is approaching.

Therefore, in the present embodiment, when establishing external air temperature and being t, h=0.98 when making temperature compensation coefficient h in 10 ℃＜t＜15 ℃, h=0.96 during t≤10 ℃, h=1.00 during 15 ℃≤t (not compensation) has with dashed lines H again _iMaximum current after the compensation is shown.

Below, the input power control to control circuit 35 describes with reference to the flow chart of Fig. 5.Cooked after the time set by switch input circuit 36, starting switch one leaves, and just begins the control shown in this flow chart.That is, in step (step) S1, judge apart from end of cooking last time (magnetron 9 drives and stops) and whether passed through the stipulated time, for example more than 5 minutes.If passed through, just carry out the transition to step S2, set the initial value of the time x that " 0 " uses as control characteristic.Then, carry out the transition to step S3, set " 0 " as cooking time t (resetting).

In following step S4, begin counting (count) about time x and time t.Then, in step S5, judge time x about above-mentioned control characteristic y (minute) whether be 0＜x 5, if in this scope, just carry out the transition to step S6, setting control characteristic y is y=((96-86)/5) x+86.

Then, in step S7, the detected temperatures setting compensation coefficient h according to temperature sensor 10 compensates above-mentioned control characteristic y.That is, deciding hy again is control characteristic.

Then, in step S8, according to control characteristic hy control change device circuit 18.That is, the ETAD expected time of arrival and departure of the switch element 21 of control change device circuit 18 is to equal (hy/100) T.Then, in following step S9, judged whether to arrive the cooking time that the cooking time t of process is set, do not arrived, just turned back to step S4, the circulation of touring execution in step S5, S6, S7, S8, S9, S4 if.Resemble in this wise, in elapsed time x, set control characteristic y.Under this situation, owing to reduce anode voltage ebm in turn, therefore, compensation is because of its reduction that reduces the input power of part generation, and result, input power just are controlled so as to certain.

Time x is if surpass 5 minutes, and just " NO " according to step S5 carries out the transition to step S10, and setting control characteristic y is " 96 ".According to the ETAD expected time of arrival and departure of the switch element 21 of this control characteristic y control change device circuit 18, and then the control input power becomes certain.

At this,, just store the time x on this time point if arrived the cooking time that gastronomical process time t has been set.Promptly store the control characteristic y that represents by time x.If the stored time is x '.Then, close the

switch element

21,22 of converter circuit 18, stop the driving of magnetron 9.

In above-mentioned step S1, during not through 5 minutes, just carry out the transition to step S12 at the end of cooking of distance last time, read the time x ' of last stored, the initial value of fixed time x by step S4 counting is x '.Then,, carry out the transition to step S4 and step S5, further carry out the transition to step S6 or step S10, ask control characteristic y through step S3.That is, control characteristic y is defined as since the control characteristic of time point of end of cooking last time.

Resemble in this wise, according to present embodiment, produce loss even drive magnetron 9, but owing to control the converter circuit 18 of drive circuit 12 according to control characteristic y by control circuit 35, therefore, do not need checkout gear such as existing current sensing means can control input power yet and become prescribed condition next fixed (with reference to characteristic curve Q of Fig. 3).Its result can help cheapization of cost.

Under this situation, it is certain controlling input power, but also can for example improve input power at the heating beginning initial stage, makes its reduction afterwards, can ask control characteristic with standby under this situation in advance.

In addition, according to present embodiment, data storage device ROM when control circuit 35 comprises stopping of control characteristic y during the storage driven by magnetron is when stopping, when driven by magnetron begins, stopping with the driven by magnetron of distance last time is not condition through the stipulated time, begins to drive control with the control characteristic y that is stored among the ROM, therefore, even the cooking failure does not take place in continuous cooking yet.

That is, along with end of cooking, magnetron 9 stops to drive, and soon, the magnetron temperature just is in high state.For once more the cooking of beginning under this state, the driving of magnetron 9 at the beginning, anode voltage just is in low state, and is in the initial value of control characteristic, probably will input power little and magnetron output is not enough, the cooking failure.

Yet, resemble in this wise above-mentioned, when driven by magnetron began, stopping with the driven by magnetron of distance last time was not condition through the stipulated time, promptly, do not drop to condition with the magnetron temperature, begin to drive control with the control characteristic y that is stored among the ROM, therefore, even under the situation of the cooking continuously, magnetron also can obtain enough input powers and not have the deficiency of magnetron output, does not cause the cooking failure.

In addition,,, compensate control characteristic y according to this detected temperatures because detect external air temperatures by temperature sensor 10 according to present embodiment, so, the change that produces because of external air temperature can be prevented to the input power of magnetron input.

Have again, in the above-described embodiments,, but boosting or primary cut-out of the voltage that for example changes DC power supply circuit 17 can be set also, control it by the control data of setting in addition by the ETAD expected time of arrival and departure of the switch element 21 of control characteristic y control change device circuit 18.

The effect of invention

From the above description, the present invention can realize with simple structure the control of input power, can realize Cheapization of cost.

The explanation of Reference numeral

The 9-magnetron

12-drive circuit (drive unit)

35-control circuit (driving control device, storage device, data storage device, compensation arrangement when stopping)

Claims

1. a micro-wave oven is characterized in that, comprising:

The magnetron that is used for the eddy-current heating heating object;

Drive this driving magnetron device;

In order to control and control the driving control device of above-mentioned drive unit for the input power of above-mentioned magnetron,

Above-mentioned driving control device has has stored the storage device that the input power that is used to control above-mentioned magnetron becomes the control data of setting, controls above-mentioned drive unit according to this control data.

2. micro-wave oven as claimed in claim 1, it is characterized in that, data storage device when driving control device comprises stopping of the control data of storage driven by magnetron when stopping, when driven by magnetron begins, stopping with the driven by magnetron of distance last time is not condition through the stipulated time, and the control data in the data storage device carries out accessory drive when stopping based on being stored in.

3. micro-wave oven as claimed in claim 1 is characterized in that, comprises the temperature sensor that detects external air temperature, comprises the compensation arrangement that compensates control data according to the detected temperatures that is detected by this temperature sensor.