JPS641918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency heater having a power relay and a temperature sensitive switch.

Most high-frequency heaters are equipped with a temperature-sensitive switch, which disconnects the power when the temperature at the top of the heating chamber or the outlet temperature rises, or when the temperature of the high-frequency oscillator rises abnormally.
Prevents fire and electric shock. However, since the input current of a high-frequency heater is generally as large as ten amperes, the temperature-sensitive switch must have a large capacity, is expensive, and has the risk of welding of the contacts. The failure mode is a dangerous failure.

In the present invention, a temperature-sensitive switch is inserted into the power coil of the control circuit, and by opening and closing a minute current,
The purpose is to improve the reliability of temperature-sensitive switches, eliminate dangerous failures such as welding, and make safe failures such as poor contact due to oxidation and sulfidation, thereby increasing the safety of high-frequency heaters. .

An embodiment of the present invention will be explained below.
FIG. 1 is an external view of a high-frequency heater according to an embodiment of the present invention, and FIG. 2 shows its circuit.

1 is the main body that also serves as the exterior, and there is a heating chamber 2 inside.
It is equipped with a high-frequency oscillator that oscillates high-frequency energy, and other power supply components. 2 is a heating chamber in which food is placed and cooked by high frequency heating; 3 is a timer for setting the cooking time; this contact 31
is designed to open and close the main power supply. 4 is a start switch that starts cooking;
The knob 5 serves as an output setting means for the high frequency oscillator, and also has the function of displaying its output level. Reference numeral 8 is linked to a knob 5 serving as an output setting means, and controls the intermittent cycle of a first electromagnetic switch 6 that intermittents the high frequency output irradiated into the heating chamber 2.
This is a control unit that drives the second electromagnetic switch 11 that changes the high frequency output irradiated into the main power source 13 and opens and closes the connection between the main power source 13 and the transformer 9. The first electromagnetic switch 6 has a first switch 6a connected between the secondary winding 9b of the transformer 9 and the high frequency oscillator 14.
A first coil 6b is provided to open and close the first switch 6a, and the first coil 6b is connected to the control section 8. Also, the second electromagnetic switch 1
1 is provided in series with the main power supply 13 and the primary winding 9a of the transformer 9, and is connected to a start switch 4.
A second switch 11a provided in parallel with the second switch 11a, and a second coil 1 that opens and closes the second switch 11a.
1b is provided, and the second coil 11b is connected to the control unit 8.
It is connected to the. The control unit 8 is a transformer 9
By receiving power supply from the quaternary winding 10 of the second electromagnetic switch 11, the second switch 11a of the second electromagnetic switch 11 connecting the main power source 13 and the transformer 9 is kept closed. Reference numeral 12 denotes a temperature-sensitive switch that is installed in series between the quaternary winding 10 and the control unit 8 and senses the temperature of the wall surface and exhaust port of the heating chamber 2, as well as the high-frequency oscillator 14. When high temperature is detected, the temperature-sensitive switch 12 becomes open, and the control unit 8
Power will not be supplied to. Note that 7 is an indicator lamp indicating that the device is operating.

Now, the timer 3 is set, the high frequency output level is also set, and when the switch 4 is turned on, a voltage is applied to the primary winding of the transformer 9, and a predetermined voltage is generated in the 4th winding 10 of the transformer 9. Using this as a power source, the control unit 8 operates, and the second electromagnetic switch 1
1 is driven, this contact is closed to form a self-holding circuit, and the high-frequency heater operates. timer 3
When the set time has passed, the contact 31 opens the main power supply and the voltage of the quaternary winding 10 is also stopped.
The control unit 8 whose power has been stopped opens the second electromagnetic switch 11, and the high-frequency heater stops operating. The above is normal operation.

If you forget to put food in the heating chamber 2 and operate it for a long time, or if the control unit 8 malfunctions or the timer 3 coil breaks, the temperature inside the heating chamber 2 becomes abnormally high, and the food may become carbonized. It may catch fire, creating a dangerous situation. At this time, temperature sensitive switch 1
2 senses this, opens the circuit, stops the power supply of the control unit 8, opens the second electromagnetic switch 11 and SW 6 that cuts off the high frequency output, and stops the high frequency heater.

In addition, if the cooling fan motor is locked or the intake port is blocked, the temperature of the high-frequency oscillator will rise rapidly, which may melt the electric wires inside the main unit and cause a ground fault. Similarly, a temperature sensitive switch senses this and opens the circuit, also stopping the high frequency heater.

As shown in FIG. 2, since the temperature-sensitive switch 12 is inserted between the quaternary winding 10, which is the power supply section of the control section 8, and the control section 8, when the temperature-sensitive switch 12 is opened, the control section Power is no longer supplied to 8. Then, the first switch 6a of the first electromagnetic switch 6 becomes open, the high frequency irradiation of the high frequency oscillator 14 stops, and the second switch 11a of the second electromagnetic switch 11 becomes open, and the blower is turned on.
Power is not supplied to M _F , and blower M _F stops. Furthermore, even if the temperature of the heating chamber wall or the like falls and the temperature-sensitive switch 12 returns to the closed state, the closed holding function of the second electromagnetic switch 11 of the control unit 8 is released, i.e. second switch 11
Since a is in the open state, power is not supplied to the control unit 8, and the high frequency oscillator 14 and the blower _MF do not start operating naturally, thereby further ensuring safety.

Furthermore, the temperature-sensitive switch 12 is inexpensive because it opens and closes a minute current, and the failure mode is limited to safe failures such as poor contact, thereby increasing the safety of the high-frequency heater.

As explained above, according to the present invention, a temperature-sensitive switch is used as a detector, but a temperature-sensitive fuse, which is structurally impossible with large currents, can also be used because the switching current becomes a minute current. Compared to temperature-sensitive switches, higher accuracy and reliability can be obtained, and even higher safety can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an external view of a high-frequency heater showing an embodiment of the present invention, and FIG. 2 is an electric circuit diagram thereof. 8... Control unit, 9... Transformer, 10... Quaternary winding, 11... Second electromagnetic switch, 12... Temperature sensitive switch, 13... Low voltage transformer.

Claims (1)

[Claims] 1 A heating chamber 2 that accommodates the object to be heated, and a high frequency oscillator 14 that supplies high frequency output into the heating chamber 2
, a transformer 9 connected to the main power supply 13, a secondary winding 9b of the transformer 9, and the high frequency oscillator 1.
a first electromagnetic switch 6, which is composed of a first switch 6a connected between 4 and a first coil 6b, which opens and closes the first switch 6a, and which cuts off the high frequency output of the high frequency oscillator 14; A second switch is provided in series with the main power supply 13 and the primary winding 9a of the transformer 9, and in parallel with the start switch 4.
switch 11a and its second switch 11
The second coil 11b, which opens and closes the
The control section 8 is connected to the electromagnetic switch 11, the first coil 6b and the second coil 11b, and is supplied with power from the quaternary winding 10 of the transformer 9, and the quaternary winding 10. and a temperature-sensitive switch 12 that is installed in series between the heating chamber 2 wall surface, the exhaust port, and the high-frequency oscillator 14, and the temperature-sensitive switch 12 is provided in series between the heating chamber 2 wall surface, the exhaust port, and the high-frequency oscillator 14. The second electromagnetic switch 11 receives power from the quaternary winding 10 generated by the current flowing through the transformer 9.
The main power supply 1 is turned on by keeping the switch 11a closed.
3 and the transformer 9, the control section 8 receives power supply from the quaternary winding 10, and receives a signal from the knob 5 serving as the output setting means of the high frequency oscillator 14, and controls the first The first switch 6a of the electromagnetic switch 6 is closed/opened, and the temperature-sensitive switch 12 is opened, thereby stopping the power supply to the control section 8. A high-frequency heater that releases the closing/holding function of the second electromagnetic switch 11 and the closing/opening function of the first electromagnetic switch 6.