JPH05129076A - Microwave heating device - Google Patents

Abstract

PURPOSE:To eliminate an output error by controlling the drive of a switch means on the basis of the transmission of a magnetron and to ensure the safety of a microwave oven by judging an abnormality when the time up to oscillation is improper and too long. CONSTITUTION:When a relay coil 9 is driven to turn on a relay switch 5, the current carrying to a power source circuit 2 is conducted, and a determined frequency counter 6c, an on-period counter 6d, and a non-oscillation counter 6a are initialized, respectively. A desired time for cooking is then determined to make the counter 6c conduct a count operation, and whether a magnetron 1 is under oscillation or not is judged from the presence of an oscillation detection signal C. However, as the magnetron is not oscillated during a delay time even if the current is carried to the circuit 2, the presence of the current carrying to the circuit 2 is judged. When it is under current carrying, the counter 6a is made to conduct a count operation, and when this time exceeds a predetermined time, an abnormality is judged. Thus, a desired cooking time is counted, and when it reaches a determined value, the switch 5 is turned off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave heating device such as a microwave oven.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 63-24316 discloses a microwave oven in which a switching means for on / off control is provided on the input side of a magnetron power supply circuit including a high voltage transformer. In this case, if the on / off ratio when turning on / off the switching means is adjusted,
Output control is possible. That is, a desired output can be obtained by adjusting the ON period t in the predetermined cycle T as shown in FIG.

However, the oscillation of the magnetron does not actually start at the same time when the switching means is turned on, but starts after a delay time d of several seconds. This is because the cathode of the magnetron does not instantly rise to a sufficient temperature even when power is supplied from the magnetron power supply circuit to the magnetron by turning on the switching means. This delay time d
Is also affected by ambient temperature and magnetron conditions.

Therefore, although it is ideal that the oscillation is originally performed during the on period t, the oscillation is performed only during the period obtained by subtracting the delay time d from the on period t, which causes an output error. This error has a great influence on the finished state of cooking when cooking with low output such as thawing.

[0005]

DISCLOSURE OF THE INVENTION The present invention suppresses the occurrence of an output error and the deterioration of the finished state of cooking in a structure for controlling the energization of a magnetron power supply circuit by driving and controlling a switching means. Is what you are trying to do.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a magnetron for generating microwaves, a magnetron power supply circuit for supplying a high voltage between the anode and cathode of the magnetron and a low voltage across the cathode, and The magnetron power supply circuit comprises switching means for controlling energization, oscillation start detecting means for detecting the start of oscillation of the magnetron, and control means for driving and controlling the switching means based on the detection of oscillation start by the detecting means.

Further, the control means performs counting operation from the start of energization of the magnetron power supply circuit by the switching means to the start of oscillation by the detection means, and abnormality determination based on the count value by the count means. And an abnormality determining means for performing.

[0008]

By controlling the driving of the switching means based on the presence / absence of oscillation of the magnetron, no output error occurs.

Further, if the time until the magnetron oscillates is unsuitable and is too long, an abnormality determination is made and the safety of the microwave oven can be achieved.

[0010]

1 shows a circuit of a microwave oven according to an embodiment of the present invention. A magnetron power supply circuit 2 is provided for a magnetron 1 that generates microwaves. This power circuit 2
Is composed of a high-voltage transformer 3 and a half-wave voltage doubler rectifier circuit 4.
The high voltage transformer 3 has a primary winding 3a, a secondary winding 3b, and a heater winding 3c. The half-wave voltage doubler rectifier circuit 4 has a high voltage capacitor 4a and high voltage diodes 4b and 4c. In this case, the magnetron 1 is
A high voltage is supplied between the anode and the cathode, and a low voltage is supplied across the cathode. A switching means, that is, a relay switch 5 for controlling energization to the power supply circuit 2 is inserted on the input side of the power supply circuit 2.

On the other hand, there is provided a control unit 6 which is composed of a microcomputer and controls the microwave oven. The control unit 6 drives and controls the relay coil 9 based on the operation information from the operation unit 7 and the information from the oscillation start detection circuit 8. Based on this, the relay switch 5 is turned on and off, and the power supply to the power supply circuit 2 is controlled.

The oscillation start detection circuit 8 compares a current sensor 10 for detecting a magnetron anode current flowing when the magnetron 1 oscillates with a level based on the output of the sensor 10 and a reference level by resistors 11 and 12. And the container 13. In such a configuration, the oscillation start detection circuit 8 outputs an oscillation detection signal C to the control unit 6 when the magnetron 1 starts oscillation.

FIG. 2 shows ON / OFF timing of the relay switch 5 when a desired output is obtained. Predetermined period T
When the relay switch 5 is turned on at the starting point a1 in (25 seconds), the power supply circuit 2 is energized and the magnetron 1
The high voltage supply between the anode and the cathode and the low pressure supply between both ends of the cathode are performed. In this case, magnetron 1
Does not oscillate for a delay time d of several seconds until the cathode temperature rises sufficiently. When the delay time d elapses and the cathode temperature rises sufficiently, oscillation starts at this time point a2. At the same time, the oscillation start detection circuit 8 detects the start of oscillation and outputs the oscillation detection signal C, so that the ON period t (10 seconds or less in the case of thawing cooking) is defined.

Therefore, in the ON period of the relay switch 5, the ON period t does not include the delay time d,
Oscillation is performed during the ON period t, and an output based on the predetermined cycle T and the ON period t is obtained without error. As a result, a stable finished state of cooking can be obtained.

Further, the control section 6 performs a counting operation until the oscillation detection signal C is input, and the non-oscillation counter 6a.
And an abnormality discriminating means 6b for discriminating an abnormality when the count value of the counter 6a exceeds a certain value. Specifically, it is checked whether or not the count value exceeds 6 seconds. If the count value exceeds 6 seconds, a failure such as opening of the secondary winding 3b of the high-voltage transformer 3 occurs, which causes an oscillation detection signal. An abnormality determination is made assuming that C does not occur. When the abnormality determination is made in this way, the ON / OFF control of the relay switch 5 is stopped, and the safety of the microwave oven is ensured.

FIG. 3 shows the flow of a control program incorporated in the control unit 6, and the operation of the microwave oven will be described in detail below with reference to FIG. When cooking is performed for a desired time with a desired output, the relay coil 9 is first driven to turn on the relay switch 5. Then, the power supply circuit 2
Is energized (S1 step). At the same time, the predetermined cycle counter 6c, the ON period counter 6d, and the non-oscillation counter 6a are initialized (S2, S3, S4 steps).

Then, the desired time for cooking is counted (step S5), and the predetermined cycle counter 6
The counting operation at c is performed (S7 step), and it is determined whether or not the magnetron 1 is oscillating based on the presence or absence of the oscillation detection signal C (S9 step). Even if the power supply circuit 2 is energized, it does not oscillate during the delay time d, and then it is determined whether or not the power supply circuit 2 is energized (S1).
0 steps). Since power is being supplied now, the non-oscillation counter 6a then performs a counting operation (step S11), and it is determined whether or not the count value of the non-oscillation counter 6a exceeds 6 seconds and is abnormal (S12). Step: abnormality determining means 6b).

In this case, this count value is 6 seconds or less, and thereafter, steps S5 to S12 are repeatedly executed. Then, the magnetron 1 normally starts oscillating and the oscillation detection signal C is input before the count value exceeds 6 seconds, whereby the above repetition is ended in step S9. By the end of this repetition, the step S11 is not passed, and the counting operation of the non-oscillation counter 6a ends. Then, the counting operation of the on period counter 6d is performed (S13 step), and it is determined whether or not the count value of the on period counter 6d reaches the on period t (S14 step).

In this case, this count value has not reached the ON period t, and then S5 to S9, S13, S1.
Repeat 4 steps. When the ON period t is reached, the relay switch 5 is turned off and the power supply to the power supply circuit 2 is released (step S15).

After executing steps S3 to S10, steps S5 to S10 are repeatedly executed. This repetitive execution continues until the predetermined cycle counter counts the predetermined cycle T, and when the count of the predetermined cycle T is judged (S8 step), the operation so far is repeated.
After that, when the count of the desired cooking time is judged (S
(6 steps), if the relay switch 5 is turned on, the relay switch 5 is turned off to finish cooking.

If the oscillation detection signal C is not generated forever due to a failure such as the secondary winding 3b of the high voltage transformer 3 being opened, the count value of the non-oscillation counter 6a is repeated in steps S5 to S12. Exceeds 6 seconds, and abnormal processing is performed. That is, the drive control of the relay switch 5 is interrupted to notify the abnormality (step S16).

After the power supply circuit 2 is energized, if the oscillation detecting signal C is input within the count value of the non-oscillation counter 6a within less than 1 second, if the abnormal processing is performed, the anode of the magnetron 1 will be processed.・ Can handle failures such as short-circuiting between cathodes.

[0023]

According to the present invention, a magnetron for generating microwaves, a magnetron power supply circuit for supplying a high voltage between the anode and the cathode of the magnetron and a low voltage for both ends of the cathode, and the magnetron power supply are provided. Switching means for controlling the energization of the circuit, oscillation start detection means for detecting the start of oscillation of the magnetron,
The control means drives and controls the switching means based on the detection of the oscillation start by the detection means, and the drive control of the switching means is performed based on the presence or absence of the oscillation of the magnetron. It is possible to suppress the occurrence of the occurrence, and it is possible to significantly suppress the deterioration of the finished state of cooking.

Further, the control means performs counting operation from the start of energization of the magnetron power supply circuit by the switching means to the start of oscillation by the detection means, and abnormality determination based on the count value by the count means. And an abnormality determining means for performing
If the time until the magnetron oscillates is inappropriate and is too long, it is possible to make an abnormality determination and to secure the safety of the microwave heating device of the microwave oven.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a microwave oven according to an embodiment of the present invention.

FIG. 2 is an on / off timing diagram of a relay switch of the microwave oven.

FIG. 3 is a flow chart of a control program incorporated in a control unit of the microwave oven.

FIG. 4 is a diagram showing an example of turning on a relay switch of a conventional microwave oven,
It is an off-timing diagram.

[Explanation of symbols]

 1 magnetron 2 magnetron power supply circuit 5 relay switch 6 control unit 6a non-oscillation counter 6b abnormality determination means 8 oscillation start detection circuit

Claims (2)

[Claims] 1. A magnetron for generating microwaves,
A magnetron power supply circuit that supplies a high voltage between the anode and cathode of the magnetron and a low voltage between both ends of the cathode, a switching means that controls energization to the magnetron power supply circuit, and detects the start of oscillation of the magnetron. A microwave heating device comprising oscillation start detection means and control means for driving and controlling the switching means based on the detection of oscillation start by the detection means. 2. The counting means according to claim 1, wherein the control means performs counting operation from the start of energization of the magnetron power supply circuit by the switching means to the start of oscillation by the detection means, and a count value by the count means. A microwave heating device having an abnormality determination means for performing abnormality determination based on the above.