JPS5811035Y2 - High frequency heating device - Google Patents

Description

[Detailed description of the invention] This invention detects the temperature of food by touching or inserting it into the food storage, and sends this signal to a control circuit without going through a transmission line to control the oscillation of a high-frequency oscillator. This invention relates to a high frequency heating device.

Recently, high-frequency heating devices that control high-frequency heating by detecting food temperature have been gaining popularity due to reasons such as being able to be used with turntables, being convenient to handle, and being easy to clean. , so-called wireless coupling of a temperature sensor and a control circuit has been proposed.

However, in order to avoid using a transmission line, a transmitter is required for the temperature sensor, and the frequency used is free from interference from heating microwaves, and the length of the antenna that can be installed on the temperature sensor is also limited. Due to this limitation, it is common to use the vHF band.

When such a frequency band is used in a heating cabinet, both the transmitting antenna and the receiving antenna have directivity, and reception may vary depending on the position and direction of the temperature detector, especially when food is placed on a turntable and rotated. There were times when it became extremely difficult.

The present invention has been made in view of the above-mentioned problems, and an embodiment of the present invention will be described below with reference to the attached drawings. In FIG. 3 is a turntable rotatably installed at the inner bottom of the heating chamber 2; 4 is a temperature detector for detecting the temperature of the food 5 placed on the turntable 3; 6 is a temperature setting dial; 7 is a Time setting dial, 8 is a cooking switch.

In the above configuration, the operation is based on the temperature setting dial 6.
When only the time setting dial 7 is set, cooking ends when the temperature of the food 5 reaches the set temperature, and when only the time setting dial 7 is set, the food 5 is heated for the set time and cooking ends. In addition, when the temperature setting dial 6 and time setting dial 7 are set at the same time, from the time when the temperature of the food 5 reaches the set temperature, the food temperature is kept at the same temperature for the set time and cooking ends. do.

The effect of this heat retention is that it is suitable for promoting the fermentation of yeast and saccharification of sweet potatoes, etc., or for stew dishes, and expands the range of cooking.

FIG. 2 is a block diagram showing the circuit configuration of the high-frequency heating device shown in FIG. A carrier wave is oscillated, mixed with the above-mentioned modulated signal in a modulation circuit 12, and transmitted from a transmission antenna 13.

On the other hand, the signal received by the receiving antenna 14 is sent via a tuning circuit 15 and a demodulation circuit 16 to a control device 18 provided between a power supply circuit 17 and a heating high-frequency oscillator 19.

In addition, the modulation method is to convert the carrier wave oscillated by the local oscillator 11 into an FM pulse by changing the resistance value of the heat-sensitive element 9 into a pulse whose density cycle changes.
It's changing.

FIG. 3 shows a specific circuit configuration of the control device 18. First, the signal received by the receiving antenna 14 is transmitted via the FM front end 20 (including the tuning circuit 15, demodulation circuit 16, etc.) to a The demodulated pulse signal is extracted from b, and the received signal level is extracted from b.

The pulse signal is differentiated by a differentiating circuit made up of a capacitor 21 and a resistor 22, and converted into a DC signal voltage via a diode 23 by an integrating circuit made of a capacitor 24 and a resistor 25.

On the other hand, the variable resistor 27 is connected to the temperature setting dial 6, and an arbitrary set voltage is obtained and compared with the aforementioned DC signal voltage by the comparator 29.

. Note that the resistors 26 and 28 are used to determine the upper and lower limits of the set voltage.

Here, when the temperature of the food 5 is low and the DC signal voltage is lower than the set voltage, the output of the comparator 29 becomes I, the transistor 30 turns off, the transistor 31 turns on, and the S input of the flip-flop 32 goes high. , R input goes low.

At this time, when a trigger pulse is input to the T input, the Q output becomes high, the transistors 33 and 34 are turned on, the electromagnetic coil 35 is energized, the reed switch 36 is closed, and the heating high frequency oscillator 19 is activated.

Next, when the DC signal voltage becomes higher than the set voltage, the output of the comparator 29 is high and the transistor 30 is turned on.
31 is turned off, the S input of the flip-flop 32 is low, and the R input is high.

At this time, when the I/Riga pulse is input to the T input, the Q output becomes I, the transistors 33 and 34 are turned off, the contact of the reed switch 36 is opened, and the heating high frequency oscillator 19 stops its oscillation operation.

On the other hand, when the received signal level taken out from b of the FM front end 20 is higher than the reference level set by the resistors 37 and 38, that is, when it is normally received, the output of the comparator 39 becomes high, and the PUT (Prog
rable Uni-JunctionTransi
stor), 40, resistors 41, 42, 43, 44, and capacitor 45 operate to provide the above-mentioned flip-flop, allowing the Q output to transition from on to off or from fo to on. becomes.

Further, when the received signal level becomes lower than the reference level, that is, when the reception condition deteriorates, the comparator 39
The output becomes low and the above-described relaxation oscillation circuit stops oscillating, so that the flip-flop 32 cannot make a transition, so the heating high-frequency oscillator 19 maintains its current state.

On the other hand, when the relaxation oscillation circuit is operating, the transistor 46 is turned on periodically, so the capacitor 47 is not charged. However, if the relaxation oscillation circuit stops operating and this state continues for a long time, the When an abnormality occurs in the device, the transistor 46 remains off, and when the charging voltage of the capacitor 47 becomes higher than the voltage given by the variable resistor 48, the output of the comparator 49 becomes high, and the transistors 50 and 51 turns on, current flows through the relay coil 52, and the normally closed contact 53 opens.

This normally closed contact 53 opens the self-holding of the main relay (not shown) of the high frequency heating device, and the high frequency heating device stops operating.

The delay time of the delay circuit formed by the resistors 54, 55, 48 and the capacitor 47 can be selected by adjusting the variable resistor 48, and if this delay time is made longer than the cycle of the turntable 3, You can easily determine whether reception is difficult due to location or due to an abnormality in the transmitter/receiver.

As described above, in this invention, the directivity of the transmitter/receiver antenna can prevent unstable operation or malfunction due to fluctuations in the reception level, and if an abnormal condition occurs in the transmitter/receiver, it can be detected early. Therefore, it is possible to provide a highly safe high-frequency heating device that prevents overheating.

[Brief Description of the Drawings] Fig. 1 is an external perspective view of a high-frequency heating device showing an embodiment of the present invention, Fig. 2 is a block diagram showing the circuit configuration thereof, and Fig. 3 is a circuit diagram of the control device. be. 2... Heating storage, 4... Temperature detector, 5
... Food, 13 ... Transmission antenna, 1
4... Receiving antenna, 18... Control device, 19... High frequency oscillator for heating.

Claims (3)

[Scope of utility model registration request] (1) A temperature detection means that detects the temperature of the food by contacting or inserting it into the food in the heating chamber; a transmitter that modulates and transmits a carrier wave using the detection signal of the temperature detection means as a modulation signal;
It includes a receiver that receives a signal from the transmitter, and a control device that controls oscillation of a high-frequency oscillator using the signal received from the receiver, and the control device controls the level of the signal received from the receiver and the reference level. The high-frequency heating device is configured to compare the received signal level, make the received signal valid only when the received signal level is higher than the reference level, and control the oscillation of the high-frequency oscillator. (2) The high-frequency heating device according to claim 1, wherein the control device is configured to maintain the operation of the high-frequency oscillator in its current state for a certain period of time when the received signal level becomes lower than the reference level. (3) The high-frequency heating device according to claim 2, wherein the control device is configured to stop the operation of the high-frequency oscillator when the received signal level is lower than the reference level for a certain period of time.