CN105684550A - Induction heating cooker - Google Patents

Abstract

Provided is an induction heating cooker that is capable of detecting a temperature change of a subject to be heated. This induction heating cooker selects an input current or a coil current corresponding to a change of the input current and the coil current, obtains a change quantity of the thus selected current per predetermined time, and on the basis of the change quantity per predetermined time, detects a temperature change of the subject to be heated.

Description

Induction heating cooking instrument

Technical field

The present invention relates to induction heating cooking instrument.

Background technology

In existing induction heating cooking instrument, existence judges the induction heating cooking instrument of the temperature of heating object according to the received current of invertor or manipulated variable.

Such as, propose there is following induction heating cooking instrument: have and controlled by invertor so that the constant control unit of the received current of invertor, when there is the change of the above manipulated variable of regulation within the specified time, it is judged as that the temperature variation of heating object is big thus suppresses the output (such as with reference to patent documentation 1) of invertor.

In addition, such as, also proposing to have the temperature-detecting device of the induction heating cooking instrument possessing temperature determination processing unit, said temperature determination processing unit judges the temperature (such as with reference to patent documentation 2) corresponding with the variable quantity of the received current detected out by the received current change amount detection of the intensity of variation only detecting received current.

Patent documentation 1: Japanese Unexamined Patent Publication 2008-181892 publication (page 3～page 5, Fig. 1)

Patent documentation 2: Japanese Unexamined Patent Publication 5-62773 publication (page 2～page 3, Fig. 1)

In the induction heating cooking instrument described in patent documentation 1, the driving frequency of invertor is controlled so that input electric power is constant, and change, according to this manipulated variable, the temperature variation that (Δ f) judges heating object. But, according to the material of heating object, there is manipulated variable change (Δ f) driving frequency small and the problem of the temperature variation of heating object cannot be detected out.

In the temperature-detecting device of the induction heating cooking instrument described in patent documentation 2, when the material of heating object changes, there is following problem: according to the driving frequency of invertor, there is the possibility that received current becomes excessive, invertor becomes high temperature and destroys.

Summary of the invention

The present invention completes to solve above-mentioned problem just, it is provided that a kind of material regardless of heating object, can both detect the induction heating cooking instrument of the temperature variation of heating object. And, it is provided that a kind of increase inhibiting received current, induction heating cooking instrument that reliability is high.

Induction heating cooking instrument involved in the present invention possesses: the heater coil that heating object carries out induction heating; To the driving circuit of above-mentioned heater coil supply high frequency electric power; Control the driving of above-mentioned driving circuit and control the control portion to the High frequency power that above-mentioned heater coil supplies; Detect the input electric cur-rent measure unit of the received current to above-mentioned driving circuit; And detect the coil current detecting unit of the coil current flowed at above-mentioned heater coil, above-mentioned control portion is according to the variation of above-mentioned received current and above-mentioned coil current, select the electric current of either one in above-mentioned received current and above-mentioned coil current, obtain the variable quantity of per specified time of selected electric current, and the variable quantity based on above-mentioned per specified time, detect the temperature variation of above-mentioned heating object.

According to the present invention, regardless of the material of heating object, the temperature variation of heating object can both be detected.Moreover, it is possible to suppress the increase of received current, it is possible to improve reliability.

Accompanying drawing explanation

Fig. 1 is the exploded perspective view illustrating the induction heating cooking instrument involved by enforcement mode 1.

Fig. 2 is the figure of the driving circuit illustrating the induction heating cooking instrument involved by enforcement mode 1.

Fig. 3 is the function block diagram of an example in the control portion illustrating the induction heating cooking instrument involved by enforcement mode 1.

Fig. 4 distinguishes performance chart based on the load of heating coil current and the heating object of the relation of received current in the induction heating cooking instrument involved by enforcement mode 1.

The correlogram relative to the electric current driving frequency when Fig. 5 is the temperature variation of the heating object of the induction heating cooking instrument involved by enforcement mode 1.

Fig. 6 is the figure after the part shown by dashed lines of Fig. 5 being amplified.

Fig. 7 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time.

Fig. 8 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time.

Fig. 9 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time.

Figure 10 is the figure after the part shown by dashed lines of Fig. 5 being amplified.

Figure 11 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time.

Figure 12 is the figure of other driving circuits illustrating the induction heating cooking instrument involved by enforcement mode 1.

Figure 13 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 2, temperature, electric current and the relation between the time.

Figure 14 is the figure of a part for the driving circuit illustrating the induction heating cooking instrument involved by enforcement mode 3.

Figure 15 is the figure of an example of the actuate signal illustrating the half-bridge circuit involved by enforcement mode 3.

Figure 16 is the figure of a part for the driving circuit illustrating the induction heating cooking instrument involved by enforcement mode 4.

Figure 17 is the figure of an example of the actuate signal illustrating the full-bridge circuit involved by enforcement mode 4.

Embodiment

Enforcement mode 1.

(structure)

Fig. 1 is the exploded perspective view illustrating the induction heating cooking instrument involved by enforcement mode 1.

As shown in Figure 1, have on the top of induction heating cooking instrument 100 for the top board 4 that the heating objects 5 such as pot load. At top board 4, as the heating mouth for heating object 5 being carried out induction heating, possess the first heating mouth 1, the 2nd heating mouth 2, the 3rd heating mouth 3, the first heating unit 11, the 2nd heating unit 12, the 3rd heating unit 13 is possessed accordingly, it is possible to carry out induction heating for each heating mouth mounting heating object 5 with each heating mouth.

In present embodiment 1, being provided with the first heating unit 11 and the 2nd heating unit 12 about the nearby side of main body side by side, the substantial middle in the depth side of main body is provided with the 3rd heating unit 13.

In addition, the configuration of each heating mouth is not limited to this. Such as, it is also possible to 3 are heated mouth substantially linearly in transversely arranged configuration. In addition, it is also possible to be arranged so that the position of the center of the center of the first heating unit 11 and the 2nd heating unit 12 on depth direction is different.

Top board 4 entirety can the material of transmission be made up of infrared rays such as resistance to thermal reinforced glass or sintered glass ceramicss, and and the upper surface open periphery of induction heating cooking instrument 100 main body between fix with watertight state via rubber packing ring or sealing material.At top board 4, it is formed with the pot position display of the circle of the mounting position roughly representing pot accordingly by the heated perimeter (heating mouth) of the coating of coating or printing etc. with the first heating unit 11, the 2nd heating unit 12 and the 3rd heating unit 13.

In the nearby side of top board 4, as the input unit for setting firepower when utilizing the first heating unit 11, the 2nd heating unit 12 and the 3rd heating unit 13 to be heated by heating object 5 and cooking menu (boil mode, fried pattern etc.), it is provided with operating portion 40a, operating portion 40b and operating portion 40c (following, to be sometimes referred to as operating portion 40). In addition, near operating portion 40, as reporting unit 42, be provided with display induction heating cooking instrument 100 action state and from display portion 41a, the display portion 41b of input/content of operation etc. of operating portion 40 and display portion 41c (following, to be sometimes referred to as display portion 41). In addition, it is possible to for for the situation of each heating mouth setting operation portion 40a～40c and display portion 41a～41c or the situation etc. unifying setting operation portion 40 and display portion 41 for all heating mouths, there is no special restriction.

In the lower section of top board 4 and be the inside in main body, possessing the first heating unit 11, the 2nd heating unit 12 and the 3rd heating unit 13, each heating unit is made up of heater coil (not shown).

It is provided with in the inside of the main body of induction heating cooking instrument 100: to the driving circuit 50 of the heater coil supply high frequency electric power of the first heating unit 11, the 2nd heating unit 12 and the 3rd heating unit 13; For the control portion 45 that the action of induction heating cooking instrument 100 entirety comprising driving circuit 50 is controlled.

Heater coil has the planeform of circular, by forming at circumferential direction winding with the conduction line being made up of any metal (such as copper, aluminium etc.) of insulating coating, by utilizing driving circuit 50 to each heater coil supply high frequency electric power, carry out induction heating action.

Fig. 2 is the figure of the driving circuit illustrating the induction heating cooking instrument involved by enforcement mode 1. In addition, driving circuit 50 is arranged for each heating unit, and its circuit structure can be identical, it is also possible to changes according to each heating unit. In fig. 2, a driving circuit 50 is only illustrated. As shown in Figure 2, driving circuit 50 possesses DC power supply circuit 22, invertor circuit 23, resonant capacitor 24a.

Input electric cur-rent measure unit 25a detects the electric current of the input from AC power (industrial power) 21 to DC power supply circuit 22, and is exported to control portion 45 by the voltage signal suitable with input current value.

DC power supply circuit 22 possesses diode electric bridge 22a, reactor 22b, smoothing capacitor 22c, the voltage of alternating current inputted from AC power 21 is converted to volts DS and exports to invertor circuit 23.

Invertor circuit 23 is invertor that the output of IGBT23a, 23b as switching element and DC power supply circuit 22 is connected in series, so-called semi-bridge type, and diode 23c, 23d as afterflow diode are connected in parallel with IGBT23a, 23b respectively. The direct current electric power exported from DC power supply circuit 22 is converted to the exchange electric power of the high frequency of the degree of 20kHz～50kHz by invertor circuit 23, and to the tank circuit supply being made up of heater coil 11a and resonant capacitor 24a. Resonant capacitor 24a and heater coil 11a is connected in series, and this tank circuit is formed and the corresponding resonant frequency such as the inductance of heater coil 11a and the electrical capacity of resonant capacitor 24a.In addition, the inductance of heater coil 11a characteristic variations according to metal load when heating object 5 (metal load) magnetic coupling, the resonant frequency of tank circuit changes according to the change of this inductance.

By forming by this way, the high-frequency current of the degree having tens of peace (A) that flows at heater coil 11a, utilizes the high frequency magnetic flux produced by the high-frequency current flow through that the heating object 5 on the top board 4 being placed in directly over heater coil 11a is carried out induction heating. IGBT23a, 23b as switching element are such as consisted of the semi-conductor being made up of silicon system, but can also be formed as using the structure of the charing wide band gap semiconducter such as silicon or gallium nitride based material.

By using wide band gap semiconducter in switching element, the energising loss of switching element can be reduced, and, even if making switching frequency (driving frequency) for high frequency (at a high speed), the heat radiation of driving circuit is also good, therefore, it is possible to make the radiator element miniaturization of driving circuit, it is possible to realize miniaturization and the cost degradation of driving circuit.

Coil current detecting unit 25b is connected between heater coil 11a and resonant capacitor 24a. Coil current detecting unit 25b such as detects the electric current flowed at heater coil 11a, and is exported in control portion 45 by the voltage signal suitable with heating coil current value.

Temperature detecting unit 30 is such as made up of thermistor, carrys out detected temperatures according to from heating object 5 to the heat of top board 4 heat conduction. In addition, it is not limited to thermistor, it is possible to use the arbitrary sensor such as infrared sensor.

Fig. 3 is the function block diagram of an example in the control portion illustrating the induction heating cooking instrument involved by enforcement mode 1. With reference to Fig. 3, control portion 45 is described.

The action of the induction heating cooking instrument 100 being made up of microcomputer or DSP (digital signal processor) etc. is controlled by control portion 45, possesses driving control unit 31, load identifying unit 32, drives frequency setting unit 33, curent change detecting unit 34, current selecting unit 35, input and output control unit 36, a/d converter 37.

IGBT23a, 23b output drive signal DS of invertor circuit 23 is made it to carry out switch action by driving control unit 31, thus drives invertor circuit 23. In addition, driving control unit 31 controls the High frequency power that heater coil 11a supplies thus is controlled the heating to heating object 5. This actuate signal DS is the signal that the driving frequency of the regulation of the degree of 20～50kHz by the dutycycle (such as 0.5) such as specified is formed.

Load identifying unit 32 is the unit of the load determination processing carrying out heating object 5, is the unit of the material judging heating object 5 as load. In addition, the material becoming the heating object 5 (pot) of load is distinguished and is judged to by load identifying unit 32 substantially: the such as magneticsubstance such as iron, SUS430; The non magnetic material of the high resistance such as SUS304; The non magnetic material of the low resistance such as aluminium, copper.

Drive frequency setting unit 33 to be when supplying electric power from invertor circuit 23 to heater coil 11a, set the unit of the driving frequency f of the actuate signal DS to invertor circuit 23 output. Particularly, frequency setting unit 33 is driven to have the result of determination according to load identifying unit 32 and automatically set the function driving frequency f. Specifically, frequency setting unit 33 is being driven such as to store the form determining to drive frequency f for the material according to heating object 5 and setting firepower.In addition, drive frequency setting unit 33 when being transfused to load result of determination and setting firepower, determine to drive the value fd of frequency f by referring to this form. In addition, frequency setting unit 33 is driven to set the frequency higher than the resonant frequency of tank circuit, in order to avoid received current is excessive.

Like this, frequency setting unit 33 is driven to utilize the driving frequency f corresponding to the material of heating object 5 to drive invertor circuit 23 based on load result of determination, thus can suppress the increase of received current, therefore, it is possible to suppress the high temperature of invertor circuit 23 and make reliability improve.

A/d converter 37 is the unit that the analogue value of the received current detected out by input electric cur-rent measure unit 25a and the analogue value of coil current that detects out by coil current detecting unit 25b are converted to numeral value. Such as, if the resolving power of 8, be then converted to numeral value (counting value) of 256 grades of 0～255.

Current selecting unit 35 selects the electric current of either one in received current and coil current according to the variation of received current and coil current. The detailed situation of the selection action of electric current will describe below.

Curent change detecting unit 34 be utilize drive invertor circuit 23 by the driving frequency f=fd driving frequency setting unit 33 to set time detection received current and coil current in, the unit of the variation delta I (time variations) of per specified time of electric current that current selecting unit 35 is selected. In addition, the specified time can be set in advance during, it is also possible to be can be changed by the operation of operating portion 40 during.

Driving control unit 31 releases when the variation delta I detected out from curent change detecting unit 34 turns into below threshold value and drives fixing of frequency f=fd, make driving frequency f increase increasing amount Δ f (f=fd+ Δ f), and drive invertor circuit 23.

(action)

Secondly, the action of the induction heating cooking instrument 100 involved by enforcement mode 1 is described.

First, to utilizing the firepower set by operating portion 40 to be described by action when being placed in heating object 5 induction heating of the heating mouth of top board 4.

If heating object 5 is placed in heating mouth by user, and operating portion 40 made the instruction that heating starts (firepower input) by user, then control portion 45 (load identifying unit) carries out load determination processing.

Fig. 4 distinguishes performance chart based on the load of heating coil current and the heating object of the relation of received current in the induction heating cooking instrument involved by enforcement mode 1.

The material of the heating object 5 (pot), becoming load herein is roughly divided into: the magneticsubstance such as iron, SUS430; The non magnetic material of the high resistance such as SUS304; The non magnetic material of the low resistance such as aluminium, copper.

As shown in Figure 4, according to being placed in the material of the pot load of top board 4, coil current is different from the relation of received current. Control portion 45 has the load coil current shown in Fig. 4 and the relation table between received current formatted and obtain to judge form in advance in storage inside. By judging form in internal reservoir load, it is possible to the Structure composing load identifying unit of cheapness.

In load determination processing, the specific actuate signal that control portion 45 utilizes load to judge drives invertor circuit 23, according to the output signal of input electric cur-rent measure unit 25a detection received current. , meanwhile, further control portion 45 is according to the output signal detection coil current of coil current detecting unit 25b.Control portion 45 judges form according to the load of detected coil current and received current and the relation representing Fig. 4, judge the material of heating object (pot) 5 that loaded. Like this, control portion 45 (load identifying unit), based on the dependency between received current and coil current, judges the material of the heating object 5 being placed in the top of heater coil 11a.

After load determination processing more than having carried out, control portion 45 carries out the control action based on load result of determination.

When load result of determination is non-loaded, this situation report cannot heat to reporting unit 42 in control portion 45, and prompting user carries out the mounting of pot. Now, not from driving circuit 50 to heater coil 11a supply high frequency electric power.

When load result of determination is any one in magneticsubstance, the non magnetic material of high resistance and the non magnetic material of low resistance, owing to this type of pot is the material that the induction heating cooking instrument 100 of present embodiment 1 can be utilized to heat, therefore control portion 45 determines the driving frequency corresponding to the material determined. This driving frequency is set to the frequency higher than resonant frequency, in order to avoid received current is excessive. The decision of this driving frequency such as can determine by referring to the form etc. of the frequency corresponding with setting firepower to the material of heating object 5.

Control portion 45 is formed as driving invertor circuit 23 when after the driving determined frequency being fixed, starts induction heating action. In addition, when after driving frequency being fixed, the dutycycle (break make ratio) of the switching element of invertor circuit 23 is also formed as fixing state.

The correlogram relative to the electric current driving frequency when Fig. 5 is the temperature variation of the heating object of the induction heating cooking instrument involved by enforcement mode 1. In Figure 5, fine rule is the characteristic of heating object 5 (pot) when being in low temperature, and thick line is the characteristic of heating object 5 when being in high temperature.

As shown in Figure 5, characteristic change according to the temperature of heating object 5 be because: by rise in temperature, the resistivity of heating object 5 rises, and magnetic rate reduces thoroughly, and thus, the magnetic coupling of heater coil 11a and heating object 5 changes.

In the control portion 45 of the induction heating cooking instrument 100 involved by present embodiment 1, frequency also high for the frequency more maximum than the electric current (received current or coil current) shown in Fig. 5 is determined as driving frequency, and this driving frequency is fixed and controlled by invertor circuit 23.

Fig. 6 is the figure after the part shown by dashed lines of Fig. 5 being amplified.

If the driving frequency corresponding to the pot material determined by aforesaid load determination processing is fixed and controlled by invertor circuit 23, then along with heating object 5 turns into high temperature from low temperature, the current value (action point) of this driving frequency is changed towards a B by an A, with the rise in temperature of heating object 5, electric current reduces gradually.

Now, control portion 45 is when after fixing the driving frequency of invertor circuit 23, obtain the variation delta I of per specified time of electric current (received current or coil current), and the variable quantity based on this per specified time, the temperature variation of detection heating object 5.

Therefore, regardless of the material of heating object 5, the temperature variation of heating object 5 can both be detected. In addition, owing to can be detected the temperature variation of heating object 5 by the change of electric current, therefore can detected temperatures change fast compared with temperature sensor etc.

In addition, judge the material of the heating object 5 being placed in the top of heater coil 11a, determine the driving frequency of invertor circuit 23 according to the material of heating object 5, and utilize this driving frequency drives invertor circuit 23.Accordingly, it may be possible to utilize the driving frequency corresponding to the material of heating object 5 to drive invertor circuit 23 fixingly, it is possible to suppress the increase of received current. Accordingly, it may be possible to suppress the high temperature of invertor circuit 23, it is possible to improve reliability.

(the selection action of electric current)

With the rise in temperature of heating object 5, the received current utilizing input electric cur-rent measure unit 25a to detect out all declines with the coil current utilizing coil current detecting unit 25b to detect out. But, according to the material of heating object 5, coil current is different from the variation of the electric current of received current. That is, there is the material that the variable quantity (reducing amount) of the big material of the variable quantity (reducing amount) of coil current and received current is big.

Therefore, the control portion 45 of present embodiment 1 is conceived to the variation of electric current, according to the variation of received current and coil current, selects the electric current of either one in received current and coil current. Then, curent change detecting unit 34 obtains the variation delta I of the electric current that utilizes current selecting unit 35 to select, per specified time.

Like this, electric current by selecting the variable quantity of the electric current in received current and coil current big, it is possible to grasp the temperature variation of heating object 5 larger, it is possible to detect the temperature variation of heating object 5 accurately. Moreover, it is possible to improve the precision of Boiling detection, it is possible to obtain the induction heating cooking instrument that ease of use is good.

In addition, by the actual received current that measures and coil current are compared, it is possible to improve reliability further.

(boil mode 1)

Secondly, action when be have selected the boil mode boiling action of the water being fed into heating object 5 as cooking menu (pattern) by operating portion 40 is described.

Control portion 45 is identical with above-mentioned action, carries out load determination processing, it is resolved that the driving frequency corresponding to the pot material determined, and the driving frequency being determined is fixed and drive invertor circuit 23, thus implements induction heating action. Then, according to the time variations of electric current, control portion 45 judges that boiling is complete. Herein, Fig. 7 is utilized the change in elapsed time when boiling and each characteristic that carry out water to be described.

Fig. 7 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time. In the figure 7, illustrate and in heating object 5, drop into water and the change of elapsed time when boiling and each characteristic, (a) of Fig. 7 illustrates driving frequency, (b) of Fig. 7 illustrates temperature (water temperature), and (c) of Fig. 7 illustrates electric current (received current and coil current).

As shown in (a) of Fig. 7, carry out the control of invertor circuit 23 by driving frequency to fix. As shown in (b) of Fig. 7, the temperature (water temperature) of heating object 5 rises until seethe with excitement gradually, and after boiling, temperature becomes constant.

As shown in (c) of Fig. 7, with the rise in temperature of heating object 5, the received current utilizing input electric cur-rent measure unit 25a to detect out all reduces with the coil current utilizing coil current detecting unit 25b to detect out.

Current selecting unit 35 obtain to heater coil 11a supply electric power (heating starts) to td1 through the 1st heating period, the variation I1 of coil current and the variation I2 of received current. Then, variation I1 and variation I2 is compared, the electric current selecting the variation in received current and coil current big.

In addition, between the 1st heating period, td1 can be the time set in advance, it is also possible to determine according to the firepower set by operating portion 40 or cooking mode etc.

In addition, as shown in (c) of Fig. 7, with the rising of the temperature of heating object 5 correspondingly, electric current (received current and coil current) declines gradually, water boiling and after homo(io)thermism, electric current is also constant. If that is, current constant, then water boiling, boil complete.

Accordingly, the electric current that the control portion 45 of present embodiment selects the variation in received current and coil current big, the variable quantity (time variations) of per specified time of the electric current gone out selected by obtaining, variable quantity in this per specified time turns into below prescribed value, it is judged as boiling complete.

In addition, the information of prescribed value can set in control portion 45 in advance, it is also possible to inputs from operating portion 40 grade.

Then, this situation complete is boiled in operation report unit 42 report in control portion 45. Herein, as reporting unit 42, it is possible to the display of the complete grade that carries out in display portion 41 seething with excitement or use loud speaker (not shown) by acoustic notifications to user, its mode there is no special restriction.

As above, in the boil mode boiling action of setting water, when after the driving frequency of invertor circuit 23 is fixed, obtain the variable quantity of per specified time of electric current, when variable quantity when this per specified time turns into below prescribed value, boil this situation complete by reporting unit 42 report.

Accordingly, it may be possible to report that rapidly boiling of water is complete, it is possible to obtain the induction heating cooking instrument that ease of use is good.

In addition, electric current by selecting the variation of the electric current in received current and coil current big, it is possible to grasp the temperature variation of heating object 5 larger, it is possible to detect the temperature variation of heating object 5 accurately. Moreover, it is possible to improve the precision of Boiling detection, it is possible to obtain the induction heating cooking instrument that ease of use is good. In addition, by the actual received current that measures and coil current are compared, it is possible to improve reliability further.

In addition, about the control portion 45 of present embodiment 1, current selecting unit 35 obtains the variation I1 of coil current to td1 through the 1st heating period and the variation I2 of received current from heating, variation I1 and variation I2 is compared, the electric current selecting the variation in received current and coil current big.

Therefore, compared with such as selecting the situation of either one in received current and coil current when heating beginning according to the magnitude relationship of received current and coil current, current value when starting with heating is unrelated, the electric current that the variation of electric current can be selected big, it is possible to detect the temperature variation of heating object 5 accurately.

Such as shown in (c) of Fig. 8, although being the relation of coil current > received current when heating and start, but when playing through between the 1st heating period the relation of variation I2 of variation I1 < received current that the electrorheological momentum till td1 is coil current from heating, current value when starting with heating is unrelated, the received current selecting the variation of electric current big. Accordingly, it may be possible to the electric current that the variation selecting the electric current in received current and coil current is big, it is possible to grasp the temperature variation of heating object 5 larger, it is possible to detect the temperature variation of heating object 5 accurately.

(variation)

Next, the variation of the selection action of electric current is described.

(selection based on the rate of change of electric current carries out)

The analogue value of the analogue value utilizing the received current that input electric cur-rent measure unit 25a detects out and the coil current utilizing coil current detecting unit 25b to detect out is converted to numeral value by a/d converter 37.Be converted to maximum value and the resolving power of the electric current of numeral value according to a/d converter 37, the accuracy of detection of electric current is different.

Such as, be 100A if a/d converter 37 is converted to the maximum value of electric current of numeral value and is the resolving power (256 grades) of 8, then the electric current of every 1 counting value is about 0.39A. In this case, if the analogue value of electric current such as changes 3A, then numeral value variation 7 numbers (≈ 3/0.39). That is, the current value after changing by a/d converter 37 is about 2.74A (≈ 100/256 × 7).

On the other hand, such as, be 50A if a/d converter 37 is converted to the maximum value of electric current of numeral value and is the resolving power (256 grades) of 8, then the electric current of every 1 counting value is about 0.20A. In this case, if the analogue value of electric current such as changes 3A, then numeral value variation 15 numbers (≈ 3/0.20). That is, the current value after changing by a/d converter 37 is about 2.93A (≈ 50/256 × 15).

Like this, even if the variation of electric current is identical, being converted to maximum value and the resolving power of the electric current of numeral value according to a/d converter 37, the precision of the current value that control portion 45 is obtained by a/d converter 37 also can produce difference.

Accordingly, current selecting unit 35 obtains the rate of change that the numeral value playing through between the 1st heating period till td1, received current and coil current from heating is used as electric current relative to the variation (counting value) of the maximum current value being converted to digital value by a/d converter 37. Then, the rate of change of received current and the rate of change of coil current are compared, the electric current selecting the rate of change in received current and coil current big.

Consequently, it is possible to grasp the temperature variation of heating object 5 larger, it is possible to detect the temperature variation of heating object 5 accurately. Moreover, it is possible to improve the precision of Boiling detection, it is possible to obtain the induction heating cooking instrument that ease of use is good.

(between the 1st heating period the setting of td1)

In the load determination processing of above-mentioned boil mode, before heating starts and detects out boiling, carry out load judgement. Namely, it is preferable that before between the 1st heating period, td1 is the time of boiling.

Accordingly, in the selection action of electric current, current selecting unit 35 sets td1 between the 1st heating period according to playing between the 2nd short heating period of td1 between than the 1st heating period till td2, the variation I1 of coil current and the variation I2 of received current from heating.

Fig. 9 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time.

In fig .9, illustrate compared with the example with above-mentioned Fig. 7, elapsed time when reducing the amount of the water in heating object 5 and the change of each characteristic. (a) of Fig. 9 illustrates driving frequency, and (b) of Fig. 9 illustrates temperature (water temperature), and (c) of Fig. 9 illustrates electric current (received current and coil current).

As shown in (b) of Fig. 9, when the amount of the water in heating object 5 is few, it is heated to become short heat-up time till seething with excitement. In addition, as shown in (c) of Fig. 9, received current and coil current all sharply decline.

Therefore, td1 between the 1st heating period, when the variation I2 playing through between the 2nd heating period the electric current till td2 from heating is big, is set short by current selecting unit 35.

On the contrary, when variation I1, the I2 of the electric currents such as the situation that the amount of the water in heating object 5 is many or the little situation of High frequency power is little, td1 between the 1st heating period is set long.

Such as, data etc. by experiment in advance, variation I1, the I2 of storaging current and relation between td1 between the 1st heating period. Then, current selecting unit 35, based on variation I1, the I2 of the electric current of t2 between the 2nd heating period, sets td1 between the 1st heating period by referring to the information prestored.

Consequently, it is possible to improve the precision of Boiling detection further, it is possible to obtain the induction heating cooking instrument that ease of use is good.

In addition, between the 1st heating period, the set action of t1 can also regularly carry out repeatedly.

(boil mode 2)

Secondly, other control actions when have selected boil mode by operating portion 40 are described.

Control portion 45 is identical with above-mentioned action, carries out load determination processing, it is resolved that the driving frequency corresponding to the pot material determined, and the driving frequency being determined is fixed and drives invertor circuit 23 and implement induction heating action. In addition, carry out the selection action of above-mentioned electric current, select either one in received current and coil current. Then, control portion 45 according to the electric current (being only called below " electric current ") selected by received current or coil current, the variable quantity of per specified time judge that boiling is complete.

And then, when the variable quantity of the per specified time tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into below prescribed value, control portion 45 releases and drives the fixing of frequency, make the drive frequency variations of invertor circuit 23, thus the High frequency power supplied by heater coil 11a is changed. Figure 10, Figure 11 is utilized the detailed situation of such action to be described.

Figure 10 is the figure after the part shown by dashed lines of Fig. 5 being amplified.

Figure 11 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 1, temperature, electric current and the relation between the time. In fig. 11, illustrate and in heating object 5, drop into water and the change of elapsed time when boiling and each characteristic, (a) of Figure 11 illustrates driving frequency, (b) of Figure 11 illustrates temperature (water temperature), and (c) of Figure 11 illustrates electric current (electric current that current selecting unit 35 is selected).

Identical with the action of above-mentioned boil mode 1, by driving frequency fix and start heating after ((a) of Figure 11), the temperature (water temperature) of heating object 5 rises gradually until seething with excitement ((b) of Figure 11). In the control that this driving frequency is fixing, as shown in Figure 10, the current value (action point) of this driving frequency is from an E to a B variation, and with the rise in temperature of heating object 5, electric current declines gradually.

In water boiling after homo(io)thermism, electric current is also constant ((c) of Figure 11). Thus, at time t1, the variable quantity of per specified time of control portion 45 Cutoff current turns into below prescribed value, is judged as boiling complete.

Secondly, control portion 45 releases and drives the fixing of frequency, by making the driving frequency of invertor circuit 23 rise and make current reduction, the High frequency power (firepower) supplied by heater coil 11a is reduced. Now, driving frequency even if improving and firepower is reduced, temperature does not also almost decline, and therefore, as shown in Figure 10, action point moves (variation) from a B to a C.

Then, the driving frequency of invertor circuit 23 is fixed by control portion 45 again, utilizes the firepower after reducing to proceed heating.

When boiling (water boiling), desirably improving firepower even if exceeding, water temperature also can not turn into more than 100 DEG C, therefore, drives frequency even if improving and firepower is reduced and also can keep water temperature.

Like this, the variable quantity in per specified time of electric current turns into below prescribed value, the driving of control invertor circuit 23, makes the High frequency power supplied by heater coil 11a reduce, therefore, it is possible to suppress input electric power and realize energy-saving.

In addition, at time t1, the driving frequency for invertor circuit 23 is improved in control portion 45, and utilizes reporting unit 42 that user boils complete report. In addition, the report of user can be carried out before improving driving frequency, it is also possible to carry out after improving driving frequency.

Boil complete by report, it may also be useful to person drops into food material sometimes in heating object 5 (pot). Herein, it is described to have dropped into, in time t2, the situation eating material in heating object 5.

As shown in (c) of Figure 11, if dropping into food material in heating object 5 in time t2, then as shown in (b) of Figure 11, the decrease in temperature of heating object 5. This decrease in temperature reduces when input food material is such as low temperature as frozen product particularly evidently. In addition, with this decrease in temperature, as shown in (c) of Figure 11, electric current sharply increases.

Now, as shown in Figure 10, action point moves (variation) from a C to a D.

When the variable quantity of the per specified time tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into more than 2nd prescribed value, control portion 45 is judged as the interpolation action because having carried out eating material input action or water etc. and causes decrease in temperature (time t3).

In addition, the information of the 2nd prescribed value can set in control portion 45 in advance, it is also possible to inputs from operating portion 40 grade.

Then, at time t3, control portion 45 releases and drives the fixing of frequency, by making the driving frequency of invertor circuit 23 reduce and make electric current increase, the High frequency power (firepower) supplied by heater coil 11a is increased. Thus, as shown in Figure 10, action point moves (variation) from a D to an E.

Then, the driving frequency of invertor circuit 23 is fixed by control portion 45 again, utilizes the firepower after increasing to proceed heating.

At time t3, making driving frequency reduce when low temperature, therefore electric current rises further, but with the rising of temperature, electric current reduces ((b), (c) of Figure 11) gradually. Now, as shown in Figure 10, action point moves (variation) from an E to a B.

Thus, at time t4, the variable quantity of per specified time of control portion 45 Cutoff current turns into below prescribed value, is again judged as boiling complete.

Secondly, control portion 45 releases and drives the fixing of frequency, by making the driving frequency of invertor circuit 23 again rise and make current reduction, the High frequency power (firepower) supplied by heater coil 11a is reduced. After, till carry out heating the operation stopping (boil mode terminates) from operating portion 40, repeatedly carry out above-mentioned action.

By such action, the action point of Figure 10 moves (variation) according to the order of an an an E → B → C.

As above, when the variable quantity of the per specified time tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into more than 2nd prescribed value, release and drive the fixing of frequency, the driving of control invertor circuit 23, the High frequency power supplied by heater coil 11a is increased, thus can detect out rapidly the decrease in temperature of heating object 5 and firepower is increased, it is possible to realize the short period of time cooking. In addition, by realizing the short period of time cooking, it is possible to make ease of use excellent, it is possible to realize energy-saving.

In addition, such as, if keep state driving frequency fixed to control when dropping into when eating material after boiling or carry out the interpolation of water constantly, then cannot fully obtain eat material (water) the firepower needed for heating, exist cooking length of time extend, ease of use worsen and the power consumption of entirety increase problem.

In addition, in the above description, the mode driving frequency to be controlled by firepower by changing is described, but the mode that firepower is controlled by the dutycycle (break-make ratio) that can also use the switching element by changing invertor circuit 23.

(fried pattern)

Secondly, action when carrying out the fried cooking that the oil in heating object 5 is heated to specified temperature is described.

When being heated by oil, different from the boiling of water, even if driving frequency being fixed and continue to control, the change of electric current also can not be constant, and the constant temperature of oil rises, and when the most dangerous, there is the possibility that oil is on fire.

In the present embodiment, as shown in Figure 2, use thermistor, the infrared sensor equitemperature detecting unit 30 of the temperature of detection heating object 5, carry out the detection of the variable quantity of electric current and the temperature detection utilizing temperature detecting unit 30 to carry out simultaneously, thus realize the induction heating cooking instrument suppressing the overheated reliability of oil high.

If selecting fried pattern by operating portion 40 as cooking menu (pattern), then control portion 45 carries out load determination processing as hereinbefore, determine to be suitable for the driving frequency of the material of heating object 5, and the driving frequency determined is fixed and carry out induction heating action.

In addition, by the value adding the electric current hankered being exported to control portion 45 with the temperature utilizing temperature detecting unit 30 to detect out, control portion 45 can the relation of storage-temp and electric current.

Reach the temperature (specified temperature) being suitable for the fried cooking in the temperature utilizing temperature detecting unit 30 to detect out after, control portion 45 releases and drives the fixing of frequency, makes driving frequency rise gradually and firepower is reduced, to keep this temperature. Now, namely when making driving frequency rise gradually, with the driving frequency after change simultaneously, the value of the received current utilizing input electric cur-rent measure unit 25a to detect out and the temperature that utilizes temperature detecting unit 30 to detect out are stored in control portion 45.

Control portion 45 utilizes reporting unit 42 to carry out the complete report of the preheating of the fried cooking to user, and the driving frequency of invertor circuit 23 is again fixed, and utilizes the firepower after reducing to proceed heating. In addition, the report of user can be carried out before improving driving frequency, it is also possible to carry out after improving driving frequency.

After obtaining the complete report of preheating, if user drops into food material to heating object 5, then the decrease in temperature of oil. When input food material is frozen product, owing to the temperature head between food material and oil is big, if the amount of therefore input food material is many, then oil temperature sharply reduces.

When the variable quantity of per specified time of that try to achieve when after the driving frequency of invertor circuit 23 is fixing, received current or coil current turns into more than 3rd prescribed value, control portion 45 controls the driving of invertor circuit 23, and the High frequency power supplied by heater coil 11a is increased.

In addition, the information of the 3rd prescribed value can set in advance in control portion 45, it is also possible to inputs from operating portion 40 grade.

As above, when the detected temperatures of temperature detecting unit 30 has exceeded specified temperature, the High frequency power supplied by heater coil 11a is reduced, when the variable quantity of per specified time of the electric current tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into more than 3rd prescribed value, the driving of control invertor circuit 23, makes the High frequency power supplied by heater coil 11a increase.Accordingly, it may be possible to suppress the decrease in temperature of oil, ensure to be suitable for the temperature of the fried cooking, it is possible to obtain induction heating cooking instrument that shorten the time of the fried cooking, that ease of use is good.

In addition, when such as only utilizing thermistor, infrared sensor equitemperature detecting unit 30 detected temperatures, there is the problem that the context of detection of the temperature variation of the oil when dropping into food material is delayed. In the present embodiment, owing to the electric current driving frequency to fix under controlling sharply changes, therefore, by detecting the variable quantity of electric current, it is possible to detect fuel-displaced decrease in temperature.

(structure example of other driving circuits)

Then, the example employing other driving circuits is described.

Figure 12 is the figure of other driving circuits illustrating the induction heating cooking instrument involved by enforcement mode 1.

Driving circuit 50 shown in Figure 12 addition of resonant capacitor 24b for the structure shown in Fig. 2. In addition, other structures are identical with Fig. 2, mark identical label for identical part.

As mentioned above, it is necessary, utilize heater coil 11a and resonant capacitor to form tank circuit, therefore, the electrical capacity of resonant capacitor is determined by the maximum fire (maximum input electric power) needed for induction heating cooking instrument. In the driving circuit 50 shown in Figure 12, by resonant capacitor 24a and 24b is connected in parallel, it is possible to make respective electrical capacity reduce by half, even if when using 2 resonant capacitors, it is also possible to obtain cheap pilot circuit.

In addition, by the resonant capacitor 24a side that coil current detecting unit 25b is configured in the resonant capacitor being connected in parallel, electric current in coil current detecting unit 25b flowing becomes the half of the electric current flowed at heater coil 11a, therefore, it is possible to use the coil current detecting unit 25b of small-sized/small capacitances amount, small-sized and cheap pilot circuit can be obtained, it is possible to obtain cheap induction heating cooking instrument.

Enforcement mode 2.

Figure 13 is the figure illustrating the driving frequency of the induction heating cooking instrument involved by enforcement mode 2, temperature, electric current and the relation between the time. In fig. 13, illustrate dropping into water in heating object 5 and the change of elapsed time when boiling and each characteristic, (a) of Figure 13 illustrates driving frequency, (b) of Figure 13 illustrates temperature (end temperature of heating object 5), and (c) of Figure 13 illustrates electric current.

(boil mode 3)

Other control actions when have selected boil mode to utilizing operating portion 40 are described.

Control portion 45 is identical with the action described in enforcement mode 1, carries out load determination processing, it is resolved that the driving frequency corresponding to the pot material determined, and the driving frequency being determined is fixed and drives invertor circuit 23 thus implement induction heating action. Then, according to the time variations of electric current, control portion 45 judges that boiling is complete.

And then, when the variable quantity of the per specified time tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into below prescribed value, control portion 45 releases and drives the fixing of frequency, make the drive frequency variations of invertor circuit 23, thus the High frequency power supplied by heater coil 11a is changed. By Figure 13, the detailed situation of such action is described.

Identical with the action of above-mentioned boil mode 1,2, driving frequency being fixed and start heating rear ((a) of Figure 13), the end gradual temperature of heating object 5 rises until the water in heating object 5 seethes with excitement ((b) of Figure 13).In the control that this driving frequency is fixing, with the rise in temperature of heating object 5, electric current reduces gradually.

If water seethes with excitement and homo(io)thermism, then electric current is also constant ((c) of Figure 13). Thus, at time t1, the variable quantity of per specified time of control portion 45 Cutoff current turns into below prescribed value, is judged as boiling complete.

Secondly, control portion 45 releases and drives the fixing of frequency, by making the driving frequency of invertor circuit 23 rise and make current reduction, the High frequency power (firepower) supplied by heater coil 11a is reduced. Now, driving frequency even if improving and firepower is reduced, temperature does not also almost reduce. Then, the driving frequency of invertor circuit 23 is fixed by control portion 45 again, utilizes the firepower after reducing to proceed heating.

When boiling (water boiling), even if more than 100 DEG C also can not be turned into owing to exceeding desirably raising firepower water temperature, drive frequency so even improve and firepower is reduced, it is also possible to keep water temperature.

Like this, when the variable quantity when per specified time of electric current turns into below prescribed value, the driving of control invertor circuit 23, makes the High frequency power supplied by heater coil 11a reduce, therefore, it is possible to suppress input electric power and realize energy-saving.

In addition, at time t1, the driving frequency to invertor circuit 23 is improved in control portion 45, and utilizes reporting unit 42 that user boils complete report. In addition, the report of user can be carried out before improving driving frequency, it is also possible to carry out after improving driving frequency.

When obtaining boiling after complete report, it may also be useful to person sometimes keeps intact and lets go unchecked, water constantly boiling. Herein, situation about evaporating for the water in time t2 heating object 5 is described.

When at heating object 5 internal memory in the case of water, the temperature (temperature in the bottom of a pan) of heating object 5 is almost equal with water temperature, or with the temperature transition slightly higher than water temperature. That is, in the boiling of water, the homo(io)thermism of heating object 5 is about 100 DEG C.

If the water in time t2 heating object 5 evaporates, then the temperature of heating object 5 rises rapidly, and with the rising of the temperature of heating object 5, as shown in (c) of Figure 13, electric current sharply reduces.

When the variable quantity (reducing amount) of the per specified time tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into more than 4th prescribed value (when reducing more than 4th prescribed value), control portion 45 is judged as that water evaporates (time t3).

In addition, the information of the 4th prescribed value can set in advance in control portion 45, it is also possible to inputs from operating portion 40 grade.

Then, at time t3, control portion 45 stops the supply of the High frequency power to heater coil 11a (firepower). Now, control portion 45 utilizes the report that user is carried out water and evaporates by reporting unit 42.

As above, when the reducing amount (variable quantity) of the per specified time tried to achieve when after the driving frequency of invertor circuit 23 is fixing turns into more than 4th prescribed value (when reducing more than 4th prescribed value), carry out controlling to release the driving fixing, stopping invertor circuit 23 driving frequency, by stopping the supply of the High frequency power to heater coil 11a, the rising rapidly of the temperature of heating object 5 can be suppressed, it is possible to obtain the induction heating cooking instrument that security is high. In addition, by reporting that water evaporates to user, it is possible to improve security further, it is possible to obtain the induction heating cooking instrument that ease of use is good.

In addition, such as, when applying the infrared sensor of the thermistor of contact, noncontact formula as temperature detecting unit 30, also can detect water to evaporate, but it is difficult to temperature variation sharply that detection instantaneously evaporates with water, heating object 5, there is the danger (problem) that the temperature of heating object 5 rises rapidly.

In addition, in the above description, the mode driving frequency to control firepower by changing is described, but the dutycycle (break-make ratio) that can also use the switching element by changing invertor circuit 23 controls the mode of firepower.

In addition, it is possible to be combined in above-mentioned enforcement mode 1 and 2 each pattern described. Such as, it is possible to be formed as the action of composition boil pattern 2 and the action of boil mode 3 and the pattern that obtains.

In addition, in above-mentioned enforcement mode 1 and 2, the invertor circuit 23 of semi-bridge type is illustrated, it may also be use the structure of the invertor etc. of bridge-type, Single switch voltage resonance type.

And then, although the mode using the relation of coil current and primary current in the load in pot material being judged is illustrated, but the resonance voltage at two ends by detecting resonant capacitor can also be used to carry out the mode of load judgement, the mode that load judges indefinite.

Enforcement mode 3.

In present embodiment 3, the detailed situation of the driving circuit 50 of above-mentioned enforcement mode 1 and 2 is described.

Figure 14 is the figure of a part for the driving circuit illustrating the induction heating cooking instrument involved by enforcement mode 3. , in fig. 14, in addition the structure of a part for the driving circuit 50 of above-mentioned enforcement mode 1 and 2 is only illustrated.

As shown in figure 14, invertor circuit 23 possesses 1 group of arm, and this 1 group of arm is made up of 2 switching elements (IGBT23a, 23b) being connected in series between positive and negative busbar and diode 23c, 23d of being connected in antiparallel respectively with this switching element.

IGBT23a and IGBT23b carries out break-make driving by the actuate signal exported from control portion 45.

IGBT23b is formed as disconnection state by control portion 45 during making IGBT23a conducting, IGBT23b is formed as conducting state during making IGBT23a disconnect, exports the actuate signal of alternately break-make.

Thus, IGBT23a and IGBT23b is utilized to form the half-bridge inverter driving heater coil 11a.

Furthermore, it may be desirable to utilize IGBT23a and IGBT23b is formed " the half-bridge inverter circuit " of the present invention.

IGBT23a and IGBT23b, according to input electric power (firepower), is inputted the actuate signal of high frequency by control portion 45, and adjustment adds thermal output. The actuate signal exported by IGBT23a and IGBT23b, in the range of the driving frequency higher than the resonant frequency of the load circuit being made up of heater coil 11a and resonant capacitor 24a, carries out controlling so that at the electric current of load circuit flowing with than the phase place flowing applying the voltage delay in load circuit.

Secondly, the control action of the input electric power (firepower) driving frequency and dutycycle based on invertor circuit 23 carried out is described.

Figure 15 is the figure of an example of the actuate signal illustrating the half-bridge circuit involved by enforcement mode 3. (a) of Figure 15 is the example of the actuate signal of each switch under high firepower state. (b) of Figure 15 is the example of the actuate signal of each switch under low firepower state.

IGBT23a and IGBT23b of invertor circuit 23 is exported the actuate signal of the high frequency higher than the resonant frequency of load circuit by control portion 45.

By making the change of frequency of this actuate signal, the output increase and decrease of invertor circuit 23.

Such as, as shown in (a) of Figure 15, if making driving frequency reduce, then the input electric power of heater coil 11a, close to the resonant frequency of load circuit, is increased by the frequency of high-frequency current supplied by heater coil 11a.

In addition, as shown in (b) of Figure 15, if making driving frequency rise, then the frequency of the high-frequency current that heater coil 11a supplies is deviateed from the resonant frequency of load circuit, the input electric power of heater coil 11a is reduced.

And then, control portion 45 is while the control of the input electric power carrying out the change based on above-mentioned driving frequency and carry out, make the change in duty cycle of IGBT23a and IGBT23b of invertor circuit 23, thus can control the application time of the output voltage of invertor circuit 23, it is possible to control the input electric power to heater coil 11a.

When making firepower increase, increase the ratio (dutycycle) of the ON time (turn-off time of IGBT23b) of the IGBT23a in 1 cycle of actuate signal, the voltage application time width in 1 cycle is increased.

In addition, when making firepower reduce, reduce the ratio (dutycycle) of the ON time (turn-off time of IGBT23b) of the IGBT23a in 1 cycle of actuate signal, the voltage application time width in 1 cycle is reduced.

In the example of (a) of Figure 15, illustrate the situation under the identical situation of the ratio between the ON time T11a (turn-off time of IGBT23b) of the IGBT23a of 1 cycle T 11 of actuate signal and T11b turn-off time (ON time of IGBT23b) of IGBT23a (dutycycle is 50%).

In addition, in the example of (b) of Figure 15, illustrate the situation under the identical situation of the ratio between the ON time T12a (turn-off time of IGBT23b) of the IGBT23a of 1 cycle T 12 of actuate signal and T12b turn-off time (ON time of IGBT23b) of IGBT23a (dutycycle is 50%).

Control portion 45 is when obtaining in above-mentioned enforcement mode 1 and 2 variable quantity of per specified time of the electric current described, when after the driving frequency of invertor circuit 23 being fixed, be formed as the state that the dutycycle of IGBT23a and IGBT23b by invertor circuit 23 is fixing.

Consequently, it is possible to when to the input electric power of heater coil 11a constant obtain the variable quantity of per specified time of electric current.

Enforcement mode 4.

In present embodiment 4, the invertor circuit 23 using full-bridge circuit is described.

Figure 16 is the figure of a part for the driving circuit illustrating the induction heating cooking instrument involved by enforcement mode 4. , in figure 16, in addition the difference of the driving circuit 50 with above-mentioned enforcement mode 1 and 2 is only illustrated.

In present embodiment 4, heat mouth for one and it is provided with 2 heater coils. The diameter difference that 2 heater coils are such as respective, and the ground configuration in concentric circles. , heater coil little for diameter is called interior loop 11b herein, heater coil big for diameter is called exterior loop 11c.

In addition, the quantity of heater coil and configuration are not limited thereto. Such as, it is possible to be the structure configuring multiple heater coil around the heater coil of central authorities being configured at heating mouth.

Invertor circuit 23 possesses 3 groups of arms, and these 3 groups of arms are made up of 2 switching elements (IGBT) being connected in series between positive and negative busbar and the diode being connected in antiparallel respectively with this switching element. In addition, after, 1 group in 3 groups of arms is called common arm, other 2 groups are called interior loop arm and exterior loop arm.

Common arm is the arm being connected with interior loop 11b and exterior loop 11c, is made up of IGBT232a, IGBT232b, diode 232c and diode 232d.

Interior loop is the arm connected for interior loop 11b with arm, is made up of IGBT231a, IGBT231b, diode 231c and diode 231d.

Exterior loop is the arm connected for exterior loop 11c with arm, is made up of IGBT233a, IGBT233b, diode 233c and diode 233d.

IGBT233a and IGBT233b of IGBT232a and IGBT232b of common arm, IGBT231a and IGBT231b of interior loop arm, exterior loop arm drives by the actuate signal break-make exported from control portion 45.

IGBT232b is formed as disconnection state by control portion 45 during the IGBT232a conducting making common arm, IGBT232b is formed as conducting state during making IGBT232a disconnect, and exports the actuate signal of alternately break-make.

Equally, control portion 45 exports the actuate signal of IGBT233a and IGBT233b alternately the break-make making IGBT231a and IGBT231b of interior loop arm, exterior loop arm.

Thus, common arm and interior loop arm is utilized to form the full-bridge inverter driving interior loop 11b. In addition, common arm and exterior loop arm is utilized to form the full-bridge inverter driving exterior loop 11c.

Furthermore, it may be desirable to utilize common arm and interior loop arm are formed " full-bridge inverter circuit " of the present invention. In addition, common arm and exterior loop arm is utilized to form " full-bridge inverter circuit " of the present invention.

The load circuit being made up of interior loop 11b and resonant capacitor 24c is connected between the output point (tie point of IGBT232a and IGBT232b) of common arm and the output point (tie point of IGBT231a and IGBT231b) of interior loop arm.

The load circuit being made up of exterior loop 11c and resonant capacitor 24d is connected between the output point of common arm and the output point (tie point of IGBT233a and IGBT233b) of exterior loop arm.

Interior loop 11b is wound into the little heater coil of the profile of circular, is configured with exterior loop 11c in its periphery.

Coil current in interior loop 11b flowing is detected by coil current detecting unit 25c. Coil current detecting unit 25c such as detects the peak value of the electric current in interior loop 11b flowing, and is exported in control portion 45 by the voltage signal suitable with the peak value of heating coil current.

Coil current in exterior loop 11c flowing is detected by coil current detecting unit 25d. Coil current detecting unit 25d such as detects the peak value of the electric current in exterior loop 11c flowing, and is exported in control portion 45 by the voltage signal suitable with the peak value of heating coil current.

The switching element (IGBT) of each arm, according to input electric power (firepower), is inputted the actuate signal of high frequency by control portion 45, and adjustment adds thermal output.

The actuate signal exported by the switching element of common arm and interior loop arm, in the range of the driving frequency higher than the resonant frequency of the load circuit being made up of interior loop 11b and resonant capacitor 24c, carries out controlling so that at the electric current of load circuit flowing with than the phase place flowing applying the voltage delay in load circuit.

In addition, the actuate signal exported by the switching element of common arm and exterior loop arm, in the range of the driving frequency higher than the resonant frequency of the load circuit being made up of exterior loop 11c and resonant capacitor 24d, carries out controlling so that at the electric current of load circuit flowing with than the phase place flowing applying the voltage delay in load circuit.

Secondly, the phase differential mutual to the arm based on invertor circuit 23 and the control action of input electric power (firepower) that carries out is described.

Figure 17 is the figure of an example of the actuate signal illustrating the full-bridge circuit involved by enforcement mode 4.

(a) of Figure 17 is the example of the actuate signal of each switch under high firepower state and the energising moment of each heater coil.

(b) of Figure 17 is the example of the actuate signal of each switch under low firepower state and the energising moment of each heater coil.

In addition, the energising moment shown in (a) and (b) of Figure 17 is relevant to the potential difference of the output point (tie point of IGBT and IGBT) of each arm, is represented with " conducting " than the interior loop state that the current potential of the output point of arm and the output point of exterior loop arm is low by the current potential of the output of common arm point. In addition, the current potential of the output point of common arm is represented by "off" than the state of interior loop by the high state of the output point current potential of the output point of arm and exterior loop arm and for same potential.

As shown in figure 17, IGBT232a and IGBT232b of common arm is exported the actuate signal of the high frequency higher than the resonant frequency of load circuit by control portion 45.

In addition, IGBT233a and the IGBT233b of IGBT231a and the IGBT231b of more internal than the actuate signal that the actuate signal of common arm shifts to an earlier date for phase place coil arm, exterior loop arm is exported by control portion 45. In addition, the frequency of the actuate signal of each arm is same frequency, and dutycycle is also identical.

At the output point (tie point of IGBT and IGBT) of each arm, according to the on off state of IGBT and IGBT, the positive bus current potential of output or negative busbar current potential as DC power supply circuit are exported with high frequency switching. Thus, potential difference interior loop 11b being applied with between the output point of common arm and the output point of interior loop arm. In addition, potential difference exterior loop 11c being applied with between the output point of common arm and the output point of exterior loop arm.

Thus, by making the actuate signal for common arm and for the phase differential increase and decrease between the actuate signal of interior loop arm and exterior loop arm, can adjust and apply in the high-frequency voltage of interior loop 11b and exterior loop 11c, it is possible to high frequency output electric current and the received current in interior loop 11b and exterior loop 11c flowing is controlled.

When making firepower increase, the phase place α between arms, thus increase the voltage application time width in 1 cycle. In addition, the upper limit of the phase place α between arm is the situation of paraphase (phase differential 180 °), and output voltage waveforms now is roughly square wave.

In the example of (a) of Figure 17, illustrate the situation that the phase place α between arm is 180 °. In addition, the dutycycle illustrating the actuate signal of each arm is the identical situation of ratio of the situation of 50%, the ON time T13a in other words illustrating 1 cycle T 13 and T13b turn-off time.

In this case, the energising ON time width T14a of the interior loop 11b in 1 cycle T 14 of actuate signal, exterior loop 11c is identical ratio with energising width T14b turn-off time.

When making firepower reduce, compared with high firepower state, reduce the phase place α between arm, thus the voltage application time width in 1 cycle is reduced. In addition, be such as set to can not in the level connecting the relation of phase place etc. of the electric current that (turnon) Shi Yinyu flow at load circuit and flow have super-high-current thus destroy at switching element for the lower limit of phase place α between arm.

In the example of (b) of Figure 17, illustrate the situation that the phase place α between arm is less than (a) of Figure 17. In addition, the frequency of the actuate signal of each arm and (a) of dutycycle and Figure 17 are identical.

In this case, the energising ON time width T14a of the interior loop 11b in 1 cycle T 14 of actuate signal, exterior loop 11c is the time corresponding to the phase place α between arm.

Like this, it is possible to the phase-difference control utilizing arm mutual is for the input electric power (firepower) of interior loop 11b, exterior loop 11c.

In addition, in the above description, the situation making interior loop 11b and exterior loop 11c all carry out heating action is illustrated, but interior loop arm or the driving of exterior loop arm can also be stopped, only making either one in interior loop 11b or exterior loop 11c carry out heating action.

During the variable quantity of control portion 45 within the per specified time obtaining in above-mentioned enforcement mode 1 and 2 electric current described, after the driving frequency of invertor circuit 23 is fixing, the state that the dutycycle of the phase place α between being formed as arm and the switching element of each arm is fixed. In addition, other action is identical with above-mentioned enforcement mode 1 and 2.

Consequently, it is possible to when for the input electric power of interior loop 11b, exterior loop 11c constant, obtain the variable quantity of per specified time of electric current.

In addition, in present embodiment 4, coil current detecting unit 25c and coil current detecting unit 25d is utilized to detect respectively at the coil current of interior loop 11b flowing and the coil current in exterior loop 11c flowing.

Therefore, when making interior loop 11b and exterior loop 11c all carry out heating action, even if either one in coil current detecting unit 25c or coil current detecting unit 25d cannot detect coil current value because of fault etc., it is also possible to detected the variable quantity of per specified time of coil current by the detected value of the opposing party.

In addition, control portion 45 can also obtain the variable quantity of per specified time of the coil current detected out by coil current detecting unit 25c and the variable quantity of per specified time of the coil current detected out by coil current detecting unit 25d respectively, and uses the bigger side in each variable quantity to carry out each judgement action described in above-mentioned enforcement mode 1 and 2. In addition, it is possible to use the mean value of each variable quantity carries out each judgement action described in above-mentioned enforcement mode 1 and 2.

By carrying out such control, even if when the one party accuracy of detection of coil current detecting unit 25c or coil current detecting unit 25d is low, it is also possible to more precisely obtain the variable quantity of per specified time of coil current.

In addition, in above-mentioned enforcement mode 1～4, as an example of the induction heating cooking instrument of the present invention, it is illustrated for IH cooking heater (cookingheater), but the present invention is not limited thereto. The present invention can be applied to the arbitrary induction heating cooking instrument that the electric cooker etc. being carried out cooking by induction heating adopts induction heating mode.

Label explanation

1: the first heating mouth; 2: the two heating mouths; 3: the three heating mouths; 4: top board; 5: heating object; 11: the first heating units; 11a: heater coil; 12: the two heating units; 13: the three heating units; 21: AC power; 22: DC power supply circuit; 22a: diode electric bridge; 22b: reactor; 22c: smoothing capacitor; 23: invertor circuit; 23a, 23b:IGBT; 23c, 23d: diode; 24a, 24b: resonant capacitor; 25a: input electric cur-rent measure unit; 25b: coil current detecting unit;30: temperature detecting unit; 31: driving control unit; 32: load identifying unit; 33: drive frequency setting unit; 34: curent change detecting unit; 35: current selecting unit; 36: input and output control unit; 37:AD transmodulator; 40a～40c: operating portion; 41a～41c: display portion; 42: reporting unit; 45: control portion; 50: driving circuit; 100: induction heating cooking instrument; 11b: interior loop; 11c: exterior loop; 24c, 24d: resonant capacitor; 25c, 25d: coil current detecting unit; 231a, 231b, 232a, 232b, 233a, 233b:IGBT; 231c, 231d, 232c, 232d, 233c, 233d: diode.

Claims (18)

1. an induction heating cooking instrument, it is characterised in that, possess:

Heater coil, heating object is carried out induction heating by described heater coil;

Driving circuit, described driving circuit is to described heater coil supply high frequency electric power;

Control portion, described control portion controls the driving of described driving circuit, and the High frequency power that described heater coil is supplied by control;

Input electric cur-rent measure unit, described input electric cur-rent measure unit inspection is to the received current of described driving circuit; And

Coil current detecting unit, described coil current detecting unit detects the coil current flowed at described heater coil,

The electric current of either one in described received current and described coil current, according to the variation of described received current and described coil current, is selected by described control portion,

The variable quantity of per specified time of the electric current having obtained selected, and the variable quantity based on described per specified time, detect the temperature variation of described heating object.

2. induction heating cooking instrument according to claim 1, it is characterised in that,

Described control portion obtain from described heater coil supplied variation till electric power plays through between the 1st heating period, described received current and described coil current or the rate of change,

Select in described received current and described coil current, described variation or the big electric current of the described rate of change.

3. induction heating cooking instrument according to claim 2, it is characterised in that,

Described control portion according to from described heater coil supplied variation or the rate of change of at least one party in till electric power plays between the 2nd heating period short between than described 1st heating period, described received current and described coil current, set between described 1st heating period.

4. induction heating cooking instrument according to Claims 2 or 3, it is characterised in that,

Described control portion possesses the a/d converter that the analogue value that described input electric cur-rent measure unit and described coil current detecting unit detect out is converted to numeral value,

The numeral value obtaining described received current and described coil current is used as the described rate of change relative to the variation of the maximum current value being converted to numeral value by described a/d converter.

5. induction heating cooking instrument according to any one of Claims 1 to 4, it is characterised in that, possess:

Load identifying unit, described load identifying unit carries out the load determination processing of described heating object,

Described control portion drives described driving circuit according to the result of determination of described load identifying unit,

When after the driving frequency of described driving circuit being fixed, obtain the variable quantity of described per specified time,

The temperature variation of described heating object is detected based on the variable quantity of described per specified time.

6. induction heating cooking instrument according to any one of Claims 1 to 5, it is characterised in that,

When the variable quantity of described per specified time that described control portion tries to achieve when after the driving frequency of described driving circuit is fixing turns into below prescribed value,

The driving of described driving circuit is controlled, makes the High frequency power change supplied by described heater coil.

7. induction heating cooking instrument according to any one of claim 1～6, it is characterised in that,

When the variable quantity of described per specified time that described control portion tries to achieve when after the driving frequency of described driving circuit is fixing turns into below prescribed value, release the fixing of described driving frequency,

Improve the driving frequency of described driving circuit, the High frequency power supplied by described heater coil is reduced.

8. induction heating cooking instrument according to any one of claim 1～7, it is characterised in that,

When the variable quantity of described per specified time that described control portion tries to achieve when after the driving frequency of described driving circuit is fixing adds more than 2nd prescribed value,

The driving of described driving circuit is controlled, the High frequency power supplied by described heater coil is increased.

9. induction heating cooking instrument according to any one of claim 1～8, it is characterised in that,

When the variable quantity of described per specified time that described control portion tries to achieve when after the driving frequency of described driving circuit is fixing reduces more than 4th prescribed value,

Control in the way of stopping the driving of described driving circuit, thus the supply making the High frequency power to described heater coil stops.

10. induction heating cooking instrument according to claim 7 or 8, it is characterised in that,

Described control portion makes the High frequency power change supplied by described heater coil by the change in duty cycle of the driving frequency or switching element that make described driving circuit.

11. induction heating cooking instruments according to any one of claim 1～10, it is characterised in that,

When the variable quantity of described per specified time that described control portion tries to achieve when after the driving frequency of described driving circuit is fixing turns into below prescribed value, release the fixing of described driving frequency,

Make the driving frequency of described driving circuit increase, the High frequency power supplied by described heater coil reduced, and the driving frequency of described driving circuit is fixed,

When the variable quantity of the described per specified time tried to achieve when after the driving frequency of described driving circuit is fixing adds more than 2nd prescribed value, release the fixing of described driving frequency,

The driving frequency of described driving circuit is reduced, the High frequency power supplied by described heater coil is increased, and the driving frequency of described driving circuit is fixed,

When the variable quantity of the described per specified time tried to achieve when after the driving frequency of described driving circuit is fixing turns into below described prescribed value, release the fixing of described driving frequency,

Make the driving frequency of described driving circuit increase, the High frequency power supplied by described heater coil is reduced, and the driving frequency of described driving circuit is fixed.

12. induction heating cooking instruments according to any one of claim 1～10, it is characterised in that,

When the variable quantity of described per specified time that described control portion tries to achieve when after the driving frequency of described driving circuit is fixing turns into below prescribed value, release the fixing of described driving frequency,

Make the driving frequency of described driving circuit increase, the High frequency power supplied by described heater coil reduced, and the driving frequency of described driving circuit is fixed,

When the variable quantity of the described per specified time tried to achieve when after the driving frequency of described driving circuit is fixing adds more than 2nd prescribed value, release the fixing of described driving frequency,

The driving frequency of described driving circuit is reduced, the High frequency power supplied by described heater coil is increased, and the driving frequency of described driving circuit is fixed,

When the variable quantity of the described per specified time tried to achieve when after the driving frequency of described driving circuit is fixing turns into below described prescribed value, release the fixing of described driving frequency,

Make the driving frequency of described driving circuit increase, the High frequency power supplied by described heater coil reduced, and the driving frequency of described driving circuit is fixed,

When the variable quantity of the described per specified time tried to achieve when after the driving frequency of described driving circuit is fixing reduces more than 4th prescribed value,

Control in the way of stopping the driving of described driving circuit, thus the supply making the High frequency power to described heater coil stops.

13. induction heating cooking instruments according to any one of claim 1～12, it is characterised in that, possess:

Carry out the operating portion of the selection operation of pattern; And

Reporting unit,

When have selected the boil mode boiling action of setting water as described pattern, described control portion drives described driving circuit,

After the driving frequency of described driving circuit is fixing, obtain the variable quantity of per specified time of described selected electric current,

When the variable quantity of the described per specified time tried to achieve when after the driving frequency of described driving circuit is fixing turns into below prescribed value, the report of described reporting unit is utilized to boil this situation complete.

14. induction heating cooking instruments according to any one of claim 1～12, it is characterised in that, possess:

Carry out the operating portion of the selection operation of pattern; And

Detect the temperature detecting unit of the temperature of described heating object,

When have selected, as described pattern, the fried pattern that oil is heated to specified temperature, described control portion drives described driving circuit,

When the detected temperatures of described temperature detecting unit is beyond described specified temperature, control the driving of described driving circuit, the High frequency power supplied by described heater coil reduced, and the driving frequency of described driving circuit is fixed,

When the variable quantity of per specified time of selected electric current that try to achieve when after the driving frequency of described driving circuit is fixing, described adds more than 3rd prescribed value,

Control the driving of described driving circuit, the High frequency power supplied by described heater coil is increased.

15. induction heating cooking instruments according to any one of claim 5～14, it is characterised in that,

Described load identifying unit, based on the dependency between described received current and described coil current, carries out the load determination processing of described heating object.

16. induction heating cooking instruments according to any one of claim 1～15, it is characterised in that,

Described control portion, when after the driving frequency of described driving circuit being fixed, is formed as the state that the dutycycle of the switching element by described driving circuit is fixing.

17. induction heating cooking instruments according to any one of claim 1～15, it is characterised in that,

Described driving circuit is made up of the full-bridge inverter circuit with the arm that 2 switching elements are connected in series by least 2,

Described control portion, when after the driving frequency of switching element described full-bridge inverter circuit, described being fixed, is formed as state fixing for the dutycycle of the driving phase differential of the mutual described switching element of described 2 arms and described switching element.

18. induction heating cooking instruments according to any one of claim 1～15, it is characterised in that,

Described driving circuit is made up of the half-bridge inverter circuit with the arm being connected in series by 2 switching elements,

Described control portion when by described half-bridge inverter circuit, the driving frequency of described switching element fixing after, be formed as state fixing for the dutycycle of described switching element.