JPH0239077B2 - JUDOKANET SUCHORIKI - Google Patents

Description

[Detailed description of the invention] The present invention relates to an induction heating cooker.

Induction heating cookers have the advantage of being safe and clean because they do not emit flames, but conversely, because they do not emit flames, it is difficult to tell at a glance whether or not they are in operation, making it difficult to turn off the power or forget to turn the power off. has the disadvantage of inadvertently heating up small loads such as knives. Therefore, conventionally, this type of cooker is equipped with a load detection circuit that detects unsuitable loads such as no load or small object load, and an alarm sounds when no load heating operation or small object load heating operation is performed. Alternatively, a method is adopted in which the user is notified of this by lighting an alarm lamp. However, in some cooking operations, for example, when cooking stir-fried foods using a frying pan, the frying pan is lifted several times during heating to stir the contents. The duration of such behavior is typically several seconds (approximately 10 seconds or less)
It is normal for the number of occurrences to be small and frequent. Each time the cooking pot is raised and lowered frequently in such a short period of time, the load detection circuit is activated and sounds an alarm or lights up (or flashes) an alarm lamp.
Doing so may cause discomfort to the user.

The present invention was made in view of the above circumstances, and when a load state of no load or a load of small objects occurs due to the user's carelessness, a load detection circuit detects an inappropriate load and generates an alarm. In this configuration, for example, when a frying pan is used to cook stir-fried food, if a short-term no-load state occurs when the frying pan is raised and lowered within a short period of time, the load detection circuit detects an inappropriate load. The purpose is also to prevent the alarm from being generated and to prevent the user from feeling uncomfortable when cooking such stir-fried food.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, 1 is an AC power supply, 2 is a power switch, 3 is a rectifier circuit consisting of a diode bridge, and 4 is an inverter, which is driven by the pulsating voltage output from the rectifier circuit 3. Incidentally, between the rectifier circuit 3 and the inverter 4, a filter circuit consisting of a choke coil and a filter capacitor is usually inserted. Reference numeral 5 denotes an induction heating coil to which a high frequency alternating current of about 20 KHz or more generated by the inverter 4 is supplied, and is wound in a flat spiral shape. induction heating coil 5
is connected in series between the power supplies together with a switching element such as a transistor in the inverter 4, and a reverse diode and a resonant capacitor are each connected in parallel to the transistor. As the switching element, in addition to a transistor, an SCR, a GTO (gate turn-off thyristor), etc. can be used. The oscillation frequency of the inverter 4 is determined by the switching element ON/OFF.
Controlled by off frequency. Reference numeral 6 denotes a cooking pot serving as a load disposed close to the induction heating coil 5, and is made of iron-based metal material. Reference numeral 7 denotes a drive circuit that controls oscillation of the inverter 4, and turns on/off switching elements within the inverter 4 at a high frequency. As this drive circuit 7, an oscillator can be used. 8 is a current transformer that detects the load current flowing through the induction heating coil 5;
is a load detection circuit which detects unsuitable loads such as no load or small loads using the detection signal from the current transformer 8, and opens and closes the AND gate 10 with its output. That is, when the load is appropriate, the output becomes "H" level, and the AND gate 10 is opened.
The high frequency pulses emitted from the drive circuit 7 are input to the inverter 4, causing the inverter 4 to oscillate. On the other hand, if the load is inappropriate, the output becomes "L" level, and the AND gate 10 is closed.
Transmission of high frequency pulses from drive circuit 7 to inverter 4 is blocked. Reference numeral 11 denotes an alarm drive circuit, ie, a timer circuit, which receives the output from the load detection circuit 9 and delays it for a certain period of time.
As mentioned above, this is the temporary removal period of the pot necessary for the cooking operation, and is appropriately set in the range from a minimum of approximately 0.5 seconds to a maximum of several seconds (approximately 10 seconds or less). Reference numeral 12 denotes an alarm sound generation circuit to which the signal delayed by the timer circuit 11 is input. Of course, an alarm lamp lighting circuit can be used instead of this alarm sound generating circuit.

FIG. 2 specifically shows the timer circuit 11 and the alarm sound generation circuit 12. In the timer circuit 11, 13 is a terminal into which a signal from the load detection circuit 9 is input, 14 is an inverting circuit, 15 is a diode, and 16
is a resistor, 17 is a capacitor, and this resistor 16
A time constant circuit 18 is constituted by the capacitor 17, and a delay time is set by this time constant. 1
Reference numerals 9 and 20 denote a diode and a resistor connected in series, which are connected in opposite directions between the diode 15 and the resistor 16, and operate as a timer reset circuit. The output of the time constant circuit 18 is input as the output of the timer circuit 11 to the alarm sound generation circuit 12 at the next stage. In the alarm sound generation circuit 12, 21
is a converter that outputs an "H" level signal when the voltage level of the input signal reaches a threshold voltage. 22
is an unstable multivibrator with NAND gate 2
3. It consists of two inverting circuits 24 and 25, a resistor 26, and a capacitor 27. 28 is a current control resistor. 29 is a piezoelectric vibrator that receives an oscillation signal from the unstable multivibrator 22 and generates an alarm sound. To explain the operation of the unstable multivibrator 22, in a normal heating state, one input signal a of the NAND gate 23 is at "L" level, and therefore the output b of the NAND gate 23 is:
The outputs c and d of the "H" inversion circuits 24 and 25 are at "L" and "H", respectively, so the other input e of the NAND gate 23 is stopped at "H". Next, if a certain period of time has passed after the inappropriate load was detected and the input signal a changes to "H", the output b of the NAND gate 23 is "L", and the inverting circuit 2
The outputs c and d of 4 and 25 become "L" and "H", respectively. Therefore, the voltage of the signal e decreases with the time constant of the resistor 26 and capacitor 27. When the voltage value of this decreased signal e becomes below the threshold voltage of the NAND gate 23, the NAND gate 23 output signal b changes to "H", and the signals c and d change to "L" and "H", respectively. Then, the voltage level of the signal e gradually increases with the time constant of the resistor 26 and capacitor 27, and when this voltage level reaches the threshold voltage of the NAND gate 23, the output of the NAND gate 23 becomes
Inverted to “L” level. By repeating this operation, the output signal d of the inverting circuit 25 becomes "H"
"L" is repeated, and in response to this signal, the vibrator 29 is driven and an alarm sound is emitted.

To explain the operation of the timer circuit 11 and the alarm sound generation circuit 12, when the cooking pot 6 is removed from the induction heating coil 5, the output of the load detection circuit 9 changes from the "H" level to the "L" level. As a result, the AND gate 10 is cut off and the inverter 4
oscillation stops. At the same time, this "L" level signal is input to the terminal 13 of the timer circuit 11, so
The signal goes to "H" level through the inversion circuit 14, and goes through the CR time constant circuit 1 through the diode 15.
8, and charging of the capacitor 17 is started. Assuming that this time constant, that is, the time required to reach the threshold voltage of the converter 21, is set to 2 seconds,
Two seconds after the inappropriate load is detected, the output of the converter 21 changes to "H" level, the unstable multivibrator 22 starts oscillating, and the piezoelectric vibrator 29 emits an alarm sound. On the other hand, if the cooking pot 6 is placed on the induction heating coil 5 again after the above set time has elapsed, for example 1 second, after the inappropriate load is detected, the "L" level signal at the terminal 13 changes to "H" level. The output of the inverting circuit 14 becomes "L" level. The charge on capacitor 17 is therefore discharged through resistor 20 and diode 19 and does not reach the threshold voltage of converter 21. Therefore no alarm action is taken.

According to the induction heating cooker of the present invention, when a load state of no load or a load of small objects occurs due to the user's carelessness, the load detection circuit continues to detect an inappropriate load for a certain period of time or more, and the alarm drive circuit issues an alarm. An alarm is appropriately generated by driving the generation circuit, and furthermore,
For example, when cooking stir-fried food using a frying pan, if a short-term no-load state occurs when the frying pan is raised and lowered within a short period of time, the load detection circuit will detect an inappropriate load. By not continuing the detection for a certain period of time and thereby causing the above alarm drive circuit to not drive the above alarm generation circuit,
Undesired alarms are not generated, and it is possible to significantly prevent the user from feeling uncomfortable when cooking such stir-fried food.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a detailed circuit diagram of the main part. 4... Inverter, 5... Induction heating coil, 7
... Drive circuit, 9 ... Load detection circuit, 11 ... Timer circuit, 12 ... Alarm sound generation circuit.

Claims (1)

[Claims] 1. An induction heating coil that is placed close to a load consisting of a cooking pot, an inverter that supplies high-frequency alternating current to the induction heating coil, and when it is detected that the load is an unsuitable load such as no load or a load of small objects, the inverter An induction heating cooker comprising a load detection circuit that stops oscillation, an alarm generation circuit, and an alarm drive circuit that drives the alarm generation circuit when the inappropriate load detection by the load detection circuit continues for a certain period of time or more.