JPS6131516Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cooking device using a high frequency transformer.

Conventionally, in cooking appliances using high-frequency transformers, such as microwave ovens and induction cooking appliances, heating control has been performed by changing the duty cycle. Therefore, there is a drawback that the temperature of the heated object hunts upward and downward around a predetermined temperature, and the predetermined temperature cannot be maintained accurately.

The present invention relates to a cooking device devised to maintain a constant temperature of the object to be heated in the above-mentioned cooking device.

A composite cooking device which is an embodiment of the present invention is constructed as shown in FIG. According to this, 1 connects a commercial frequency power supply (AC100V60/50Hz) to a high frequency (20~
30KHz), and its output terminal is connected to the primary winding of the high frequency transformer 2. The secondary winding of the high-frequency transformer 2 is provided with a high-voltage terminal 21 and a low-voltage terminal 22 with different numbers of turns, and the high-voltage terminal 21 is connected to a magnetron drive circuit 5 composed of a capacitor 3 and a diode 4. By closing 6, a high voltage power source is applied to drive the magnetron 7 that supplies microwaves into the oven. On the other hand, an induction heating coil drive circuit 10 formed by a capacitor 8 and an induction heating coil 9 is connected to the low voltage terminal 22, and when a switch 11 linked to the switch 6 is closed, the switch 6 is opened and the magnetron 7 is driven. The beam is cut off, and an alternating magnetic flux is emitted from the induction heating coil 9 to heat the pot 12.

In this way, when the switches 6 and 11 are selectively closed, when the high frequency transformer 2 is connected to the magnetron drive circuit 5, the magnetron 7 outputs 2450 MHz.
Microwaves are output and the food inside the oven is microwave-cooked. On the other hand, when the high frequency transformer 2 is connected to the induction heating coil drive circuit 10, the pot 12 is heated by the alternating magnetic flux output from the induction heating coil 9, and the food in the pot 12 is heated and cooked by the conductive heat.

The high-frequency transformer 2 is a transformer having an AC magnetic pole around which a primary winding and a secondary winding are wound, as well as a DC magnetic pole around which a control winding 23 is wound. When such a high-frequency transformer is used, by changing the direct current flowing through the control winding 23, the amount of magnetic flux on the secondary side is changed, and the secondary current can be changed. That is, the magnetic flux generated when current flows through the primary winding passes through the secondary magnetic pole and the DC magnetic pole around the control winding 23. By changing the direct current flowing through the control winding 23, the magnetic resistance of the magnetic flux path on the control winding side changes, so the amount of magnetic flux on the control winding side and the secondary winding side can be changed.

Reference numeral 13 denotes a DC constant current circuit, which is connected to the control winding 23 of the high frequency transformer 2 and allows DC current to flow therethrough. Since a current flows through the secondary winding of the high frequency transformer 2 in proportion to this DC current, both the output of the magnetron 7 and the output of the induction heating coil 9 are controlled by the DC constant current circuit 13. Moreover, since the output can be adjusted by simply changing the value of the DC current, the output level can be set arbitrarily without changing the duty cycle as in the conventional method, which is very advantageous for cooking.

Conventionally, in this type of cooker, a temperature-dependent resistor such as a thermistor is provided to maintain the temperature of the heated object at a constant level, and the temperature of the heated object is detected directly or indirectly. When the temperature at the detection point becomes higher than the set value, the heating source stops operating,
When the temperature drops below the set value, the operation of the heating source is restarted, and thereafter, such intermittent operation of the heating source is repeated to maintain a constant value. However, with such intermittent operation of the heating source, the temperature of the heated object fluctuates up and down within a certain temperature range based on the set temperature, so accurate temperature characteristics have not been obtained.

The present invention was developed in view of these points, and it controls the current flowing through the control winding 23 of the high-frequency transformer 2 shown in FIG. Alternatively, the present invention provides a composite cooker in which the output of the induction heating coil is adjusted.

The cooking device of the present invention has a DC constant current circuit 13 shown in FIG.
The feature is that it is configured as shown in Figure 3, and the second
The circuit shown in the figure is an example of a general conventional circuit.

According to FIG. 3, 101 is a step-down rectifier and smoothing circuit connected to a commercial high-frequency power source (AC100V) via input terminals X and X', and has the function of converting into low-voltage direct current. A capacitor 111 is connected to the output terminal of the step-down rectifying and smoothing circuit 101 through a Zener diode 108 and a resistor 109 which are connected in series, and a transistor 107 whose collector and emitter are connected in series with a resistor 110. Note that the control winding 23 is connected via the output terminals Y and Y'. The Zener diode 108 includes a variable resistor 102 and a resistor 1.
A thermistor 103 in series with 12 is connected in parallel,
The output terminal of the variable resistor 102 is connected to the B contact (reference voltage terminal), and the connection point between the thermistor 103 and the resistor 112 is connected to the A contact (automatic adjustment terminal).The movable contact of the switch 105 is connected to the base of the transistor 106. is connected. This transistor 106 has an emitter and collector connected to the transistor 10.
7 collector/base connected in parallel. 104
is a temperature detection circuit connected to the thermistor 103, which energizes the relay 113 and switches the switch 105 to the a contact when the set temperature of the heated object is detected. The thermistor 103 is inserted into the object to be heated and directly detects the temperature of the object to be heated, but it is installed at the exhaust port of the oven and is discharged from the oven chamber to indirectly detect the temperature of the object to be heated based on the exhaust temperature. to be detected.
Here, the variable resistor 102 works to change the constant current value of the DC constant current circuit 13 by moving the output terminal.

According to the composite cooker constructed as described above, the operation of rapidly raising the temperature of the object to be heated to a desired set temperature and maintaining it at that set temperature will now be explained. At the start of cooking, the switch 105 is on the b contact side. The temperature detection circuit 104 operates to sequentially detect the temperature of the heated object as it is heated. Thereafter, when the temperature of the object to be heated reaches the set value, the temperature detection circuit 104 energizes the relay 113 and switches the switch 105 to the a contact. When the switch 105 is switched to this state, the thermistor 103 is connected to the base of the transistor 106, and the temperature change of the object to be heated acts on the transistor 107.
That is, the output of switch 105 is supplied to transistor 106 as a current control signal. Therefore, when the temperature of the object to be heated tries to rise further after reaching the set value, the resistance value of the thermistor 103 decreases, and the base voltage of the transistor 106 decreases.
Accordingly, the emitter current of transistor 107 is reduced. Therefore, the secondary current of the high frequency transformer 2 is controlled, and the output of the magnetron 7 or induction heating coil 9 is reduced. Conversely, if the temperature of the heated object falls below the set value, thermistor 1
The resistance value of transistor 03 increases, raising the base voltage of transistor 106. Accordingly, transistor 1
Since the emitter current of 07 is increased, the secondary current of the high frequency transformer 2 is promoted, and the output of the magnetron 7 or induction heating coil 9 is lowered.

In this way, the output current of the DC constant current circuit 13, in other words, the control winding 23 is adjusted based on the temperature of the heated object.
Due to the feedback effect that controls the secondary current of the high-frequency transformer 2 by changing the control current flowing through the high-frequency transformer 2, the object to be heated is efficiently maintained at the set temperature.

As mentioned above, according to the present invention, when the heating source is turned on,
Since the heated object can be maintained at a constant temperature without turning off, accurate temperature characteristics can be obtained.

In addition, rapid heating is performed with a constant heating source until the heated object reaches a predetermined temperature, and after the heated object reaches the predetermined temperature, heating is performed while increasing or decreasing the output of the heating source based on the temperature of the heated source. You can cook efficiently.

In addition, since the temperature-dependent resistor for detecting that the heated object has reached a predetermined temperature and the temperature-dependent resistor for maintaining the heated object at a constant temperature are used, the circuit configuration can be simplified. It becomes easy.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of a composite cooker according to an embodiment of the present invention. FIG. 2 shows an example of a conventional DC constant current circuit 13. FIG. 3 shows an example of the present invention of the DC constant current circuit 13. DESCRIPTION OF SYMBOLS 1... High frequency converter, 2... High frequency transformer, 5... Magnetron drive circuit, 7... Magnetron, 9... Induction heating coil, 10... Induction heating coil drive circuit, 13... DC constant current circuit, 2
3... Control winding, 101... Step-down rectifier smoothing circuit,
103...Thermistor, 104...Temperature detection circuit, 105...Switch, a, b...Terminal, 10
6,107...Transistor.

Claims (1)

[Claims for Utility Model Registration] A high-frequency transformer with a high-frequency conversion output connected to the primary side and a heating source drive circuit connected to the secondary side,
A cooking device configured to supply current through a constant current circuit to a control winding wound around the DC magnetic pole of this high-frequency transformer, and adjust the output of the heating source by controlling the current flowing through the control winding. In this case, the constant current circuit has a first terminal that supplies a reference voltage, a second terminal that supplies the output of a temperature-dependent resistor that detects the temperature of the heated object, and a voltage of the second terminal. a temperature detection circuit that detects that the temperature of the heated object has reached a predetermined temperature based on the temperature detection circuit; and an output of the temperature detection circuit that selectively switches the first terminal to the second terminal; 1. A cooking appliance comprising: switch means for using the voltage at the second terminal as a current control signal.