JPH05115364A - Bowl detector of induction heat rice cooker - Google Patents

Abstract

PURPOSE:To securely judge whether a bowl is existing or not even if the electric source voltage varies by detecting the inverted value of the DC level rectified from AC and the zero-cross point of AC and inputting the lag pulses to a judging means. CONSTITUTION:DC rectified from a DC source 6 is made flat and smooth by a filter 8. The high-frequency waves generated by putting on and off of the flat DC by the use of a switching element 11 is actuated on a resonance circuit 10 composed of a heating coil 3 and a resonance condenser 9 to induction-heat the bottom of bowl 2. The zero-cross point of AC is detected by a ZVP generator 14 and inputted in a judging means 15 after a lag time 17 of a specified interval. Also, the output level of DC voltage is inverted 13 to input into the judging means 15. The bowl is judged from both inputs by the judging means 15 as to whether the bowl is existing or not. If a bowl is existing, the switching element 11 is put on and off through a controller 12 and if it is not existing, it is kept to be put off. In this way, the judgement as to whether a bowl is existing or not can be securely done, even if the electric source voltage varies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pan detecting device for detecting the presence or absence of a pan in an induction heating rice cooker using induction heating.

[0002]

2. Description of the Related Art A conventional pan detecting device for an induction heating rice cooker will be described with reference to FIGS.

The structure of the conventional induction heating rice cooker will be described with reference to FIG. The induction heating rice cooker 1 includes a pan 2 made of a magnetic material such as iron, a heating coil 3 for heating the pan 2 during rice cooking, a body heater 4 for heating the pan 2 from the side during rice cooking and heat retention, and its heat. It is composed of a protective frame body 5 made of iron that spreads over the entire side surface of the pot 2.

FIG. 7 shows the configuration of a pan detecting circuit of the induction heating rice cooker 1. A rectifier circuit 7 converts the AC voltage of the AC power supply 6 into a DC voltage. A filter 8 is connected to the DC output terminal of the rectifier circuit 7 to shape the output waveform. Further, 10 is a resonance circuit, which is a heating coil 3
And a resonance capacitor 9. This resonance circuit 1
0 is a switching element 1 for generating a resonance current.
1 is connected. The switching element 11 is on / off controlled by the control means 12. Reference numeral 13 is a level conversion means for converting the voltage across the filter 3 into a voltage of 5 V or less. Reference numeral 14 is a ZVP generating means for detecting 0 V of the AC power supply 6 and outputting a detection pulse. Reference numeral 15 indicates that if the voltage at the valley portion of the voltage of the level converting means 13 when the detection pulse of the ZVP generating means is output becomes a certain voltage or less, it is determined that the pot is present It is a judging means for outputting the result to 12. The determination means 15 and the control means 12 are configured in the microprocessor means 16, and the determination and control are configured by program determination and program control.

The operation of the pan detecting device of the induction heating rice cooker configured as described above will be described below.
AC 100 V supplied by the AC power supply 6 is converted into DC by the rectifier circuit 7 and the filter 8 and supplied to the heating coil 3. The presence / absence of the pan 2 is usually detected before heat retention or rice cooking and when a timer for cooking rice is set. That is, this is to inform the user that the user has inadvertently forgot to set the pan 2 when instructing to keep heat, cook rice, or the like. In addition, the pot is always detected even during operations such as rice cooking and heat retention. This is to stop the circuit of the induction heating rice cooker immediately so that if the user removes the pan from the induction heating rice cooker for some reason during operation, the circuit of the induction heating rice cooker will not be broken. ..

In this case, the presence / absence of the pan is detected as follows. The control means 12 uses the switching element 11
When the pan 2 is set, the impedance of the resonance circuit 10 becomes small, and the resonance current flows through the heating coil 3 when the pan is controlled. However, when the temperature is being maintained, the power is small, so that the current flowing through the heating coil 3 is small, and the output voltage of the rectifier circuit 7 and the filter 8 changes as if the voltage was slightly raised near 0 V as shown by the solid line in FIG. To do. In particular, the minimum voltage becomes the highest when the temperature is kept at 115 VAC. When pan 2 is not set,
The impedance of the resonance circuit 12 increases, the resonance current is a small current, and the output voltages of the rectifier circuit 7 and the filter 8 change as shown by the broken line in FIG. 8 when the voltage of the AC power supply is near 0V. Especially, the minimum voltage becomes the lowest when there is no AC85V pan. As can be seen from FIG. 8, the output voltage waveform greatly differs depending on the presence / absence of the AC100V pan 2, but when the power supply voltage fluctuates, the difference between the AC115V pan and the AC85V panless voltage level decreases, and the output voltage waveform is constant. It is difficult to judge by voltage level.

When this portion is converted by the level converting means 13, the output voltage waveform of the level converting means 13 is shown in FIG.
The voltage is converted to a maximum DC 5V voltage, which is easy to handle as shown in FIG. As shown in FIG. 9, the timing at which the output of the level converting means 13 becomes the minimum is a little behind the timing at which the ZVP generating means 14 outputs the detection pulse. The output voltage of the level conversion means 13 is output to the determination means 15.

At this time, the output voltage of the level converting means is measured, and if it is a certain level or higher, it is determined that there is no pot, and if not, there is a pot. On the other hand, when the ZVP generation circuit 14 detects 0 V of the AC power supply 8, it outputs detection pulses to the determination means 15 at the timing shown in FIG.

The presence or absence of a pan in the microprocessor means 16 is constantly monitored for the presence of a zero volt pulse in the ZVP generating means 14 as shown in FIG. 10, and when the zero volt pulse is input to the microprocessor means 16, the presence or absence of a pan is immediately detected. Check. To check the presence or absence of this pot, as shown in FIG. 11, the voltage at the valley portion of the output of the level converting means 13 is measured 15 times each time a zero volt pulse is input, and the voltage is below a certain voltage (for example, below 3V). ) Is 8 times or more, it is determined that there is a pan. Otherwise, it is determined that there is no pot. When it is determined that there is no pan, the operation mode is released, the standby mode is entered, and predetermined work (JOB1 to JOBN) is performed as shown in FIG. These tasks are repeated every time a zero volt pulse is input.

As described above, the conventional induction heating rice cooker is activated in response to a key input, and is in a standby mode, which is a state before starting a predetermined operation, and during rice cooking, heat retention, and reserved operation. Even in the mode, the same method is used to detect the presence or absence of a pan. In the operation mode, the presence or absence of the pan is always detected, and if the pan is present, the operation is continued and the predetermined work (JO
(B1 to JOBN) is continued, and the pan presence / absence detection and predetermined work are repeatedly performed throughout the operation mode. If it is determined that there is no pan during the operation mode, cancel the operation mode,
The control output of the switching element 11 is stopped and a predetermined work (JOB1 to JOBN) is continued.

[0011]

However, in the above configuration, when the voltage of the AC power supply fluctuates to AC115V or AC85V, the voltage across the filter 8 also changes and the AC voltage fluctuates.
There was a problem that it was difficult to determine the presence / absence of a pot at a certain constant voltage level, because the voltage was about the same when the pot was kept warm at 115V and when the pot was not at AC85V.

Further, in this type of pan detection, if the power supply voltage changes due to a momentary power failure or the like during the operation mode, it is easy to erroneously determine that there is no pan even if there is a pan. In this case, the operation mode is released to the standby mode, and the operation is stopped during the rice cooking.

Further, in the induction heating rice cooker, the pan is surrounded by a protective frame cylinder made of iron in order to heat or keep the pan from the side. Therefore, the heating coil and the protective frame body are close to each other, and even when there is no pot, the impedance of the resonance circuit 10 is lowered by the magnetic coupling between the heating coil 3 and the protective frame body, and a large current flows through the switching element 11.
As for the voltage across the filter 8, the difference between the minimum voltages with and without the pan is small, and it is difficult to determine the presence or absence of the pan 2.

The present invention solves the above-mentioned problems of the conventional structure, and provides a pan detection device for an induction heating rice cooker capable of reliably determining the presence or absence of a pan even when the power supply voltage changes. Is the primary purpose. A second object is to provide a pan detection device for an induction heating rice cooker that does not cause misjudgment. A third object of the present invention is to provide a pan detection device for an induction heating rice cooker having a configuration capable of facilitating pan detection. A fourth object is to provide a pan detection device for an induction heating rice cooker that can easily determine the presence or absence of a pan.

[0015]

A first means of the present invention for achieving the first object is a rectifier circuit for rectifying an AC power source and converting it into a direct current, and an AC component connected to the rectifier circuit to remove an AC component. A filter, a resonance circuit that is connected to the filter and that includes a heating coil and a resonance capacitor, a switching element that is connected to the resonance circuit and that generates a resonance current, and a control unit that controls on / off of the switching element; ZVP generating means connected to an AC power source for detecting zero voltage and generating a pulse; level converting means connected to the output side of the rectifying circuit or filter for converting the voltage level at the connection point into a desired voltage; The presence or absence of a pot from the output of the level conversion means upon receiving the output of the delay means and the output of the delay means It is an induction heating cooker pan detection apparatus comprising a determining means.

The second means of the present invention for attaining the second object is, in addition to the configuration of the first means of the present invention, the control means when the induction heating rice cooker is in a standby mode. This is a pan detection device for an induction heating rice cooker in which the conditions for determining the presence or absence of a pan are changed in the operation mode state.

A third means of the present invention for achieving the third object is a pan detecting device for an induction heating rice cooker in which a protective frame body for keeping the side surface of the pan warm is made of a non-magnetic material.

The fourth means of the present invention for achieving the fourth object is an induction heating in which a metal ring made of a non-magnetic material is arranged between a heating coil and a protective frame body which keeps the side surface of the pot warm. It is used as a pan detection device for a rice cooker.

[0019]

The first means of the present invention operates as follows.
When a resonance current flows through the resonance circuit due to the on / off operation of the switching element, the voltage waveform near the minimum voltage of the output of the rectifier circuit or the filter changes depending on the presence or absence of the pan. The inventor has discovered that the timing of the minimum voltage without the pan is slightly behind the timing of the minimum voltage with the pan, and this phenomenon is used to detect the presence or absence of the pan. That is, this change is taken out by the level conversion means, and the delay means for delaying the ZVP pulse by an appropriate time reads the output voltage of the level conversion means at the timing when the pulse is generated to judge the presence or absence of the pot. There is something. This judgment is made by comparing the output of the level conversion means with a preset threshold value, and if it is low, it means that the pot is present, and if not, it means that the pot is not present.

The second means of the present invention has the following operation in addition to the operation of the first means of the present invention. That is, the determination means continues to determine the presence or absence of a pan during operation modes such as rice cooking, heat retention, and reservation. At this time, even if it is determined that there is no pan, the control means does not immediately release the operation mode, and immediately or after a predetermined time, again,
Operates to detect the presence / absence of a pot for a predetermined time or number of times. Therefore, even if it is determined that there is no pot due to an erroneous determination due to fluctuations in the power supply voltage or the like, the next determination will be normal and the rice cooking operation can be continued.

Further, according to the third means of the present invention, since the protective frame barrel for keeping the pot warm is made of a non-magnetic material, the protective frame barrel and the heating coil are not magnetically coupled without the pot. Therefore, the impedance of the resonance circuit does not decrease, and the decrease in the voltage across the filter is reduced. For this reason, the difference between the case with the pan and the case without the pan becomes large, and it is easy to determine whether or not the pan is present.

In the fourth means of the present invention, a non-magnetic material is arranged between the protective frame body for heating the pot and the heating coil. The bond is weakened as compared with the configuration of the third means of the present invention. Therefore, the presence / absence of the pot can be more surely and easily determined.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the first means of the present invention will be described with reference to FIGS. The body configuration of the induction heating rice cooker is the same as that of the conventional induction heating rice cooker shown in FIG. 6, and the description thereof will be omitted. The electric circuit of the induction heating rice cooker 1 has the following connection configuration. A rectifying circuit 7 composed of a diode or the like for rectifying the AC voltage supplied from the AC power supply 6, a filter 8 for removing an AC component from the rectified waveform, and a resonance circuit 10 including the heating coil 3 and the resonance capacitor 9 connected to the filter 8. A switching element 11 connected to the resonance circuit 10, and the resonance circuit 1 by controlling the switching element 11.
The main control circuit is constituted by the control means 12 which produces an oscillating current at zero. The above is the same as the conventional configuration. Reference numeral 14 is a ZVP generating means which is connected to the AC power source 6 and detects 0V to generate a pulse. ZVP generation means 1
The output of 4 is connected to the delay means 17 which delays this output pulse by several hundred microseconds. Reference numeral 13 is a level conversion means that is connected to the output terminal of the rectifier circuit 7 and converts the level of the voltage at the connection point into a desired voltage. The determination means 15 receives the output of the level conversion means 13 and the output pulse of the ZVP generation means 14 delayed by an appropriate time by the delay means 17, determines the presence or absence of the pan 2, and outputs this output to the control means 12. It is outputting.

In this embodiment, the judgment means 15, the control means 12 and the delay means 17 are the microprocessor means 16
The delay / judgment and control consist of program delay, program judgment and program control. Further, although the level conversion means 13 is connected to the output point of the rectifier circuit 7 in this embodiment, it may be connected to the filter 8 of the next stage.

Induction heating rice cooker 1 configured as described above
The operation of will be described below. AC100 supplied by AC power supply 6
V is converted into direct current by the rectifier circuit 7 and the filter 8 and supplied to the heating coil 3. The detection of the pot is performed as follows. First, when a user inputs a rice cooking key or the like (not shown), the control means 12 causes the switching element 1 to operate.
The on / off control of 1 is started. When the pan 2 is set, the impedance of the resonance circuit 10 becomes small and the resonance current flows through the heating coil 3. Since this resonance current is large, the output voltages of the rectifier circuit 7 and the filter 8 change as shown by the solid line in FIG. 8 described in the operation of the conventional example. When the pot 2 is not set, only the magnetic coupling between the heating coil 3 and the protective frame body 5 increases the impedance of the resonance circuit 10 as compared to when the pot 2 is set, and the rectifier circuit 7 and the filter are connected. The output voltage of No. 8 changes as shown by the broken line in FIG. In this way, the output voltage waveform of the AC power supply 6 near 0 V differs depending on the presence or absence of the pot 2.
The voltage near 0V is converted by the level conversion means 13 into a voltage of maximum DC 5V which is easy to handle and is easy to detect the presence or absence of the pot 2, as shown in FIG. 9 used in the description of the conventional example.
It outputs to the determination circuit 15. On the other hand, ZVP generation means 14
Outputs a detection pulse when 0V of the AC power supply 6 is detected, and when the microprocessor means 16 receives the detection pulse, the microprocessor means 16 delays it by several hundred microseconds by the delay means 17 composed of a program, and then outputs it to the determination means 15. Outputs detection pulse.

In this case, in this embodiment, when the microprocessor means 16 receives the detection pulse, it is delayed by several hundred microseconds by the delay means 17 composed of a program, for the following reason. The presence / absence of the pan 2 needs to be reliably detected even during heat retention at low power. Since the delay means 17 is used in this embodiment, as shown in FIG.
Difference D with and without pan 2 at the time of the detection pulse
_{When 0} is compared with the voltage difference D ₁ at the time point when several hundreds of microseconds have elapsed after the generation of this detection pulse, it is clear that D ₁ > D ₀ . As a result, in this embodiment, the presence or absence of the pan 2 can be detected more reliably. The determination means 15 measures the output voltage of the level conversion means 13 when receiving the detection pulse. This measurement is ZV
Each time the detection pulse of the P generation means 14 is generated, the measurement is performed 15 times, and a predetermined threshold value (eg DC3) is measured 8 times or more.
If it is larger than V), it is determined that there is no pot, otherwise it is determined that there is a pot. The control means 12 receives the result and continues or stops the control of the switching element 11.
The judging means 15 normally measures 15 times or more to make a majority judgment. This is to prevent malfunction due to noise or the like.

The output voltage of the level conversion means 13 changes when the power supply voltage changes, but the power supply voltage changes during the time when the minimum voltage of the level conversion means 13 appears after the ZVP generation means 14 outputs the detection pulse. But it doesn't change much. That is, the delay time is a threshold value of the time with and without the pot.

In this case, the judging means 15 for measuring the output voltage of the level converting means 13 may be constituted by using an AD converter or a comparator. Further, the level conversion means 13 is the simplest method by resistance division, but in the present embodiment, a limiter circuit with a zener diode added is used in order to easily detect the presence or absence of a pot. Of course, other circuits may be used as the level converting means.

Further, the delay / determination / control means is constructed by using the program of the microprocessor means 16 in the present embodiment, but it may be constructed by hardware. In addition, it is easier to make a determination if the delay time is changed depending on the difference in power supply frequency (50 and 60 Hz).

As described above, according to this embodiment, it is possible to reliably determine the presence or absence of the pot even if the power supply voltage fluctuates.

Next, an embodiment of the second means of the present invention will be described with reference to FIG. The difference from the embodiment of the first means of the present invention is the configuration of the program control of the control means 12. In other words, in this embodiment, even if it is determined that there is no pan, the processing program for pan no detection is changed depending on whether the state is the operation mode or the standby mode.

The detection of the presence or absence of the pot 2 is as shown in FIG. 11 described in the conventional example. In the present embodiment, as shown in FIG. 3, even if it is determined that the pot 2 does not exist once during operation, the operation mode is not immediately stopped and switched to the standby mode, but a predetermined detection timer time or The check is repeated as many times as the number of pans detected. Even if it is determined that there is no pot 2, the operation mode is switched to the standby mode. Therefore, according to the present embodiment,
Even if it is mistakenly detected that the pan 2 is not present due to fluctuations in the power supply voltage or the like, the detection will return to normal by the next detection.

In this embodiment, the mode is changed from the operation mode to the standby mode after repeating the check for a predetermined detection timer time or the number of times of pan detection, but if the heating is continued without the pan, Since the circuit will be destroyed, there is a conventional method of immediately changing from the operation mode to the standby mode once the state where the pot 2 is not present is detected. Further, in this embodiment, the operation mode is checked after detecting the presence or absence of the pot 2, but the order may be changed.

Next, an embodiment of the third means of the present invention will be described. The configuration of this embodiment is as shown in FIG.
The configuration is the same as that of FIG. 6 described in the conventional example. However, in this embodiment, the protective frame body 18 that constitutes the rice cooker is made of a non-magnetic material such as aluminum. This protective frame body 18
It is for dissipating the heat of the body heater 4, and may be made of resin as long as it has good heat conduction.

The operation of this embodiment will be described below. In this embodiment, the protective frame body 18 is made of a non-magnetic material such as aluminum. For this reason, the magnetic coupling between the heating coil 3 and the protective frame cylinder 18 is reduced, the voltage across the filter is increased when there is no pot, and the presence or absence of the pot 2 is easily determined.

Next, an embodiment of the fourth means of the present invention will be described with reference to FIG. In this embodiment, a metal ring 1 made of a non-magnetic material such as copper is provided between the protective frame body 5 and the heating coil 3.
9 are arranged.

With this structure, the magnetic coupling between the heating coil 3 and the protective frame body 5 is further reduced, the voltage across the filter is increased when there is no pot, and the presence or absence of the pot 2 is easier to determine. It will be.

[0038]

As described above, according to the first means of the present invention, a rectifying circuit for rectifying an AC power supply and converting it into a DC, a filter connected to this rectifying circuit for removing an AC component, and a filter for this filter are provided. A resonance circuit, which is connected to the resonance circuit and includes a heating coil and a resonance capacitor, a switching element that is connected to the resonance circuit to generate a resonance current, a control unit that controls on / off of the switching element, and a zero volt that is connected to the AC power supply. Of the output pulse of the rectifying circuit or the filter, the level converting means for converting the level of the voltage at the connection point into a desired voltage, and the output pulse of the ZVP generating means. The delay means that delays for a fixed time after the occurrence, and the judgment means that receives the output of the delay means and judges the presence or absence of the pan from the output of the level conversion means As pan detection for an induction heating cooker comprising a, even if the supply voltage fluctuates, certainly, is capable of performing the determination of the presence or absence of pan.

According to the second means of the present invention, in addition to the configuration of the first means of the present invention, the control means is provided when the induction heating rice cooker is in the standby mode state and in the operation mode state. In addition, in addition to the effect of the first means of the present invention, as a pan detection device of an induction heating rice cooker in which the judgment condition of the presence or absence of a pan is changed, even when it is determined that there is no pan due to a change in the power supply voltage, etc. In the next determination, the device becomes normal and the rice cooking operation can be continued.

According to the third means of the present invention, the pot detecting device of the induction heating rice cooker in which the protective frame body for keeping the side surface of the pot warm is made of a non-magnetic material can easily detect the pot. Is.

Furthermore, according to the fourth means of the present invention, as a pan detecting device for an induction heating rice cooker, a metal ring made of a non-magnetic material is added between a heating frame and a protective frame body for keeping the side surface of the pan warm. The pot can be detected more easily.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a pan detection device of an induction heating rice cooker showing an embodiment of the first means of the present invention.

FIG. 2 is an output waveform diagram of the level converting means with and without a pot in the embodiment.

FIG. 3 is a flowchart of a control program in the embodiment of the second means of the present invention.

FIG. 4 is a configuration diagram of a main body of an induction heating rice cooker according to an embodiment of a third means of the present invention.

FIG. 5 is a configuration diagram of the main body of the induction heating rice cooker according to the embodiment of the fourth means of the present invention.

FIG. 6 is a body configuration diagram showing a conventional induction heating rice cooker.

[Fig. 7] Circuit configuration diagram of the pan detection device of the induction heating rice cooker

[Figure 8] Output waveform diagram of the rectifier circuit with and without the pot

FIG. 9 is an output waveform diagram of the level conversion means.

FIG. 10 is a flowchart of the control program.

[Fig. 11] Flow chart of the same pot presence detection program

[Explanation of symbols]

 2 pan 3 heating coil 7 rectifier circuit 8 filter 9 resonance capacitor 10 resonance circuit 11 switching element 12 control means 13 level conversion means 14 ZVP generation means 15 judgment means 17 delay means 18 protective frame body 19 metal ring

Claims (4)

[Claims] 1. A rectifying circuit for rectifying an AC power source and converting it into a direct current, a filter connected to this rectifying circuit for removing an AC component, a resonance circuit connected to this filter and comprising a heating coil and a resonance capacitor, A switching element connected to the resonance circuit for generating a resonance current, a control means for turning on / off the switching element, a ZVP generation means connected to the AC power source for detecting zero volt and generating a pulse, and the rectification circuit. Alternatively, level conversion means connected to the output side of the filter for converting the level of the voltage at the connection point into a desired voltage, and delay means for delaying the output pulse of the ZVP generation means for a fixed time.
A pan detecting device for an induction heating rice cooker, comprising: a judging means for judging the presence or absence of a pan from the output of the level converting means in response to the output of the delay means. 2. The pot detecting device for an induction heating rice cooker according to claim 1, wherein the control means changes a condition for determining whether or not the induction heating rice cooker is in a standby mode state and an operating mode state. .. 3. The pot detecting device for an induction heating rice cooker according to claim 1, wherein a protective frame body for keeping the side surface of the pot warm is made of a non-magnetic material. 4. The pan detecting device for an induction heating rice cooker according to claim 1, wherein a metal ring made of a non-magnetic material is arranged between a heating frame and a protective frame body for keeping the side surface of the pan warm.