JPS6021477B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety circuit for early detection of a defect in a switch that controls the generation of high frequency waves in response to the opening and closing of a door in a high frequency heating device having a digital control circuit.

Recently, with the improvement and widespread use of semiconductor integration technology, electronic control circuits including microcomputers and the like have come to be used in home appliances such as microwave ovens.

In a microwave oven equipped with such an electronic control circuit, at least one of the plurality of door switches is connected to the input section of the control circuit, and high frequency generation is performed based on door opening or closing information from this switch. It was customary to perform controls such as stopping or interrupting the countdown of an electronic timer section. In other words, the main power source is indirectly controlled via the control circuit based on the reversal of the door switch when the door is opened or closed. Therefore, even if this door switch causes welding or contact failure, it is difficult to notice the abnormality in this door switch unless you pay attention to abnormalities in the main wing power supply or timer, and the failure may be hidden behind other normal door switch operations. There is also a high possibility that it will get lost. Furthermore, it is not possible to determine whether the door switch itself is defective or the control circuit is malfunctioning. The present invention takes these points into consideration and provides a safety circuit that immediately notifies the user of a door switch failure.

The configuration of the present invention will be explained below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention.

Two door switches 1 that open and close in response to opening and closing of the door.
, 2 are provided, 1 is connected to the control circuit and 2 is connected to the main power supply. 3 is a relay controlled by a control circuit and corresponds to a conventional time switch. 4 is a magnetron, 5 is a cooling fan, and 6 is a high voltage transformer.

Next, the operation of the door switch will be explained. The door switch 1 inputs an L level to the control circuit when the door is opened, and an H level when the door is closed. Figure 2 shows the NOR
7 shows a signal input to the circuit. a, b'c are each N
Corresponds to input/output a, b, and c of OR7. Inputs a and b to NOR 7 are delayed by integration circuits 8 and 9, and output c is as shown in the figure. Here, TH shown by a broken line is the threshold level of this NOR. In NOR, output c becomes H level only when inputs a and b are both L level. In other words, the state of the door switch 1 changes to H level when the input of the discharge cycle is below the threshold level, a little later than points A and B where the state of the door switch 1 is reversed, and when the input of the charging fin cycle reaches the threshold level. Return to L level. In other words, a one-shot pulse is generated every time the door is opened or closed. This pulse passes through ORIO and AN
At DII, a logical AND is performed with a periodic signal of an oscillator 12 consisting of a multipipulator or the like. That is, the buzzer 13 sounds only while the pulse c is at H level. d is the output to this ANDI, that is, the input signal to the buzzer drive circuit 14. With this configuration, the buzzer sounds only once each time the door is opened or closed, thereby informing the user that the door switch 1 is in good condition. The buzzer 13 is configured to notify the user when the number key 15 or cooking start key 16 on the operation panel is pressed, or when cooking is finished.

Thereby, if there is an abnormality in the buzzer circuit, it will not be mistaken for an abnormality in the door switch 1. In other words, since the notification means is used for multiple purposes, a defect in the notification unit itself and an abnormality in the part to be notified are not mixed together. When I press a key, the buzzer sounds, but when I open and close the door, the buzzer doesn't go off.This can be determined to be a problem with the door switch 1 itself. Next, the procedure for pressing the keys will be explained. When any of the numeric keys 15 is pressed, the pressed key is converted into a binary code by the encoder 17. In other words, “6
If the key "011" is pressed, a signal "011" is output. At the same time, pass through OR18 and reach counter 19a.
, 19b, 19c, and 19d. This SF signal causes the output of the encoder 17, that is, the binary code of the key just pressed, to be shifted by one position to the right. In other words, "011" is preset in the counter 19a, and the data before 19a is moved to 19b.By repeating this operation, a 4-digit cooking time is preset in the counter 19.Depending on the timer configuration, There are 1G ships for a to d, and select town counters such as hexadecimal.For example, if you have a minute/second timer with 19d as the top digit, 19a is 1G Hayabusa, 19b is hexadecimal, 19c is IG Hayabusa, 1
Choose 9d as decimal or hexadecimal. 20 is 2
A display decoder converts the hexadecimal code into display data, and 21 is a display section.

On the other hand, the output of OR18 is input to the buzzer drive circuit, and the buzzer sounds q while the key is pressed. Therefore, the buzzer also alerts you to a defective input key. Next, press the cooking start key 16,
The operation of the door switch 1 and the operation of the timer when cooking is started will be explained.

When the cooking start key 16 is pressed, the flip-flop 22
is set. As a result, the output Q changes to H level,
The switching transistor 23 is turned on to start energizing the coil of the relay 3. Therefore, if the door is closed at this time, the door switch 2 is closed and the magnetron starts to be energized. On the other hand, the door switch 1 is also closed, and the reset terminal R of the flip-flop is connected to the L via OR24.
The level is entered. That is, the start signal becomes valid and the flip-flop 22 is set as described above. Furthermore, when the cooking starts, the flip-flop 22
The output ST signal is converted to the clock pulse CL by AND25.
It is logically ANDed with K, and the supply of a clock pulse to the T terminal of the counter 19a begins. When the counter 19a finishes counting down a preset predetermined value, it outputs a borrow signal B, which is successively input to the upper counters.

If you open the door during this cooking process, the buzzer 13 will sound once, and at the same time the reset terminal R of the flip-flop 22 will sound.
changes to H level.

At this time, since the cooking start key 16 has already been released, the set terminal S has returned to the L level, and the output Q is then inverted to the L level. In other words, the start signal ST changes to L level, so the relay 3 opens and interrupts the supply of electricity to the magnetron. Further, the clock pulse CLK to the counter 19 cannot be inputted because the ST signal becomes L, and the countdown is stopped. Therefore, the relay 3 plays the role of a door switch as well as a time switch, and also acts as a spokesperson for the main power circuit of the door switch 1, which is only a small capacity switch that only transmits information. To resume cooking, the door must be closed again and the cooking start key must be pressed. When the cooking time has passed, the top digit 19
Pollo signal B is output from d.

This is also input to the drive circuit of the buzzer 13 and sounds the end notification buzzer. At the same time, it is also input to the reset terminal R of the flip-flop 22 via the OR 24, and the output Q is inverted to L level. That is, the relay 3 is turned on and the magnetron 4 is turned off. The BORO signal is appropriately delayed by the integrating circuit 26 and then input to the clear terminal c of the counter 19, returning the counter to its initial state.
Of course, the borrow signal is also cleared at this time, and the buzzer stops sounding. With this configuration, the user can quickly learn of welding or contact failure in the door switch, and the failure will not be hidden behind other door switches that are operating normally.

Therefore, the user can confirm that the door switch is operating normally and start cooking with peace of mind. Furthermore, since this notification means is used for multiple purposes, it is easy to distinguish between a failure in the notification circuit itself and a failure in the door switch. In addition to the buzzer, the notification means may also be a visual means such as a light emitting diode. It goes without saying that the control circuit can also be replaced with soft logic using a microcomputer or the like.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention, and FIG. 2 is a timing diagram thereof. 1...Door switch, 3...Relay, 4...Magnetron, 1
3...Buzzer. Figure 1 Figure 2

Claims (1)

[Claims] 1. A heating chamber in which the object to be heated is placed, a high-frequency generator that irradiates high-frequency waves to the heating chamber, a door that can be opened and closed at the opening of the heating chamber, and an operating state that changes in response to the opening and closing operations of this door. a control circuit for inputting door opening/closing information from the switch element, an input means for inputting various commands to the control circuit, a notification means, and a means for controlling energization to the high frequency generator. The high-frequency heating device comprises a high-frequency heating device, wherein the notification means notifies at least an effective input by the input means and an inversion of the switch element.