JPS594475Y2 - High frequency heating device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high frequency heating device equipped with a food temperature detection device.

Conventionally, high-frequency heating devices have been equipped with a thermostat as a measure against damage to elements such as transistors in the temperature control circuit due to induced lightning or the like.

However, with this configuration, the high-frequency heating device senses overheating and stops high-frequency oscillation, so even if a fire is prevented, it is still dangerous to some extent, and the risk of burns cannot be avoided. I got angry.

Therefore, the present invention improves safety by simultaneously opening means for stopping high-frequency oscillation other than the main switch, such as a high-pressure switch for variable high-frequency output, using the output of the temperature control circuit, and prevents overheating of the high-frequency heating device. It is something to do.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In Fig. 1, 1 is a latch switch that is linked to the opening and closing of the door covering the front opening of the heating cabinet, 2 is a cooking switch, and 3
4a is a contact of a relay 4 provided in a control circuit 11 which will be described later; 5 is a high-voltage transformer whose primary winding is connected to a power source via a latch switch 1 and a contact 3a; 6 is a capacitor that constitutes a voltage doubler rectifier circuit together with diode 7; 8 is a magnetron used as a high-frequency oscillation means connected to the secondary side of the high voltage transformer 5 via the voltage doubler rectifier circuit; and 9a is connected to the tertiary side of the high voltage transformer. The high voltage switch 9 provided in the control circuit 11
10 is a probe of the temperature detector, and 11 is a control circuit that varies the output by changing the ON/OFF duty cycle of the contact 9a of the high voltage switch 9.

Next, the operation will be explained.

First, when the door is closed, the latch switch 1 is closed, and then when the cooking switch 2 is pressed, the coil of the relay 3 is energized, the contact 3a is closed, and this state is self-maintained, and the high voltage transformer 5 is energized.

As a result, a high voltage doubled and rectified by the capacitor 6 and the diode 7 is applied to the magnetron 8, and the magnetron 8 operates in oscillation to dielectrically heat the food stored in the heating chamber.

At this time, when making the high frequency output variable, the contact 9a of the high voltage switch 9 is turned on and off by the control circuit 11,
By changing this duty cycle, the output can be made variable.

Then, when the food reaches the preset temperature, the probe 1
0, the control circuit 11 operates to open contacts 4 a and 9 a, and the cooking ends.

Next, the configuration and operation of the control circuit 11 will be explained with reference to FIG. 2.

First, a diode 12 and a capacitor 13 are used to rectify and smooth the DC voltage.
Uni-junction Transistor)2
3.24, the multivibrator formed by the resistors 14 to 21 and the capacitor 22 is supplied, the duty cycle of oscillation is made variable by the variable resistor 21, and the high voltage switch 9 is driven by the transistor 27.

Switch 21 a and resistor 25 associated with variable resistor 21
is for keeping the transistor 27 in an on state.

On the other hand, the thermistor 10a that senses the temperature of the food is built in near the tip of the probe 10 of the temperature detector.
This resistance value decreases as the food temperature increases.

Then, the voltage divided by the thermistor 10a, the temperature setting resistor 29, and the resistor 30 is applied to the anode of the PUT 34, and the voltage is applied to the anode of the PUT 34 by the resistors 31 and 32.
Voltage is supplied to the gate of 4.

Now, as the temperature of the food increases, the resistance value of the thermistor 10a decreases, and when the anode voltage of PUT34 exceeds the gate voltage, PUT34 is turned on, transistor 39 is turned on through resistor 35, and transistor 39 is turned on through resistor 37. The transistor 40 is turned on and the relay 4 is operated.

At the same time, the transistor 26 is turned on via the resistor 36, the base voltage of the transistor 27 is bypassed, the transistor 27 is turned off, and the contact 9a of the high voltage switch 9 is opened.

In a circuit configured in this way, if the transistor 40 is destroyed by induced lightning and becomes an open side failure, the relay 4 cannot be driven, that is, the relay contact 3a remains closed and power is supplied to the high voltage transformer. continues to be.

At this time, in the conventional system, the high pressure switch 9 is continuously turned on or intermittently just to output a predetermined output regardless of the food temperature, so it is extremely dangerous to continue heating even after the food temperature reaches the predetermined temperature. state.

However, according to the present invention, the high-pressure switch 9 is turned off at the same time when the food temperature is reached, and this state is maintained, so that overheating of the high-frequency heating device can be prevented.

As described above, the present invention has a third relay contact installed in parallel on the power supply side from the normally open first relay contact installed on the primary side of the high voltage transformer.
A control circuit, which is provided on the tertiary side of the high-voltage transformer and includes a temperature sensor, controls the food temperature to a predetermined value by connecting the relay contact of the Therefore, even if one relay contact becomes closed due to induced lightning during cooking, the other relay contact will open when the food temperature reaches a predetermined value, and the food will not overheat. , it will be safe.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a high-frequency heating device showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a specific configuration of the control circuit. 1... Latch switch, 3, 4... Relay, 3 a, 4 a... Relay contact, 9...
...High pressure switch, 9a...Contact of high pressure switch, 10...Probe, 10a...
...Thermistor, 11... Control circuit.

Claims (1)

[Scope of utility model registration request] A primary side of a high voltage transformer is connected to the power supply via a normally open first relay contact, and a high frequency oscillation means is connected to the secondary side of the high voltage transformer via a normally open second relay contact,
On the primary side of the high voltage transformer, a cooking switch for closing the first relay contact and a normally closed third relay contact are connected in series on the power supply side in parallel with the same primary side from the first relay contact. A temperature sensor is connected to the tertiary side of the high voltage transformer via a control circuit, and the second relay contact has an intermittent function for controlling the high frequency output by the control circuit. When the temperature of the food detected by the temperature detector reaches a preset temperature, the control circuit simultaneously opens the second relay contact and the third relay contact to finish cooking. High frequency heating device.