JP2699351B2 - High frequency heating equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for a high-frequency heating device having a plurality of high-frequency generators, and to control an apparatus by detecting an abnormal current generated when a high-frequency generator fails. Is what you do. 2. Description of the Related Art Generally, when a failure occurs in a high-frequency generator in a high-frequency heater, for example, as shown in Japanese Utility Model Application Laid-Open No. 58-24996, a secondary circuit of a power transformer for driving the high-frequency generator is provided. A method of detecting and controlling a change in current is employed. FIGS. 5 and 6 show a conventional example, in which an abnormal current of the secondary coil 3 of the high-voltage transformer 2 which is generated when a magnetron 1 or the like as a high-frequency generator fails, is provided in the magnetic circuit 4. Detected by the magnetic sensor 5,
The input current is controlled. When at least one of the high-frequency generators, that is, the magnetron 1, the high-voltage rectifier 6, and the high-voltage capacitor 7 is opened, the primary current of the high-voltage transformer 2 becomes a very small value of only the exciting current. In this case, only the stop of the high frequency oscillation does not result in an extremely unsafe state, but the generation of the high frequency is stopped and the heating operation is interrupted. Next, the anode of the high-voltage rectifier 6 and the magnetron 1
When a short circuit occurs between the cathodes, if a current 1.5 to 2 times the normal current flows through the secondary coil 3 of the high-voltage transformer, the coil of the high-voltage transformer is burned, which is extremely unsafe. At this time, the primary current of the high-voltage transformer 2 has only a secondary resonance current near the resonance voltage, and has no load. As described above, only the excitation current of the high-voltage transformer has an extremely small value. Next, when the high-voltage capacitor 7 is short-circuited, the secondary coil 3 of the high-voltage transformer is half-wave short-circuited by the high-voltage rectifier, and a very large current is generated in the secondary coil 3 to be in a very dangerous state. The primary current is also very large and often breaks the power supply breaker. Therefore, in the related art, as shown in the conventional example, an increase in the current of the secondary coil 3 of the transformer that is in a dangerous state is detected by a magnetic sensor in the magnetic circuit, and the primary input current of the high-voltage transformer is controlled. I was Problems to be Solved by the Invention According to the conventional example, the driving voltage of the high-frequency generator is usually as high as 3 to 5 KV, and it is very difficult to detect the circuit current to which this voltage is applied. In order to secure the insulation distance, it is necessary to make the detection means very large,
Even if a situation where the voltage of the secondary circuit is temporarily applied to the detection means occurs, a means for preventing an electric shock accident due to a high voltage is required, and as a result, it becomes very expensive. Had been lost. This type of heating device is often used as a microwave oven for business use in kitchens such as restaurants and hotels. However, it is desired to heat an object to be heated in a short time. A high frequency output was obtained by operation, and this was used for this purpose. In this case, in particular, it was necessary to provide the same number of the high frequency generators as the abnormality detection device, which made the device extremely large and expensive. . SUMMARY OF THE INVENTION The present invention solves the above-described problems and provides a method and a configuration for detecting an abnormality of a high-frequency heating device and controlling a power supply circuit thereof with a simple configuration. Means for Solving the Problems According to the present invention, a plurality of high frequency generators are provided in a primary circuit of a high voltage transformer for driving each of the high frequency generators. The current flowing in the circuit is detected, the values between the two are compared on the electronic circuit, and the primary circuit of the high-voltage transformer showing a value deviated by a preset current range or more is turned off by a relay connected in series. When a failure occurs in a certain high-frequency generator, a value different from the primary input current of another normal high-frequency generator is shown. The present invention pays attention to the difference from the normal current, and performs control based on the difference. Generally, a high-frequency generator shows various input currents depending on an operation state.
The absolute value of the current value of the secondary coil of the high-voltage transformer also changes after long-term use, the state of the object to be heated, or the fluctuation of the power supply voltage. Although the current of the primary circuit also changes, the primary circuit currents of the high-voltage transformers of a plurality of high-frequency generators operating in parallel have the same operating conditions, and the absolute values of the respective current values change, but the current values of each other change. The relative difference between is hardly changed. Therefore, under any operating conditions, if a difference occurs in the relative current value, it can be determined that the fault has occurred. Compared with the conventional art, the effect of the current malfunction due to the operating conditions can be ignored and the probability of malfunction is reduced as much as possible. Embodiment An embodiment of the present invention will be described with reference to FIGS. The same components as those in the conventional example are denoted by the same reference numerals. In order to increase the high-frequency output, the magnetron 1 as a high-frequency generator is provided with the same specifications in two microwave power supply devices 9 and 9 ′ provided above and below the heating chamber 8, respectively. The upper magnetron is 1 and the magnetron provided in the lower power supply device 9 'is 1'. The magnetrons 1 and 1 'each have a power supply circuit composed of two high-voltage transformers 2 and 2' of the same specification, high-voltage capacitors 7 and 7 ', and high-voltage rectifiers 6 and 6'. Is provided.
The primary coils 10, 10 'of the high-voltage transformers 2 and 2' are provided with current detecting devices 11, 11 'as shown in FIG. 1, respectively, in series. The current detectors 11 and 11 'are high-voltage transformers 2.
And an iron core 1 connected in series to the primary coils 10, 10 'of 2'
Coil A13, 13 'wound on coils 2, 12' and coils A13, 13 'provided coaxially and coils B14, 14' insulated, coil A13 and coil B14, and coil A13 ' B
14 'are configured to be magnetically coupled. The current detectors 11 and 11 'are provided with a control circuit 15 for controlling the entire body.
Are provided together with other electronic circuit components on the printed circuit board 16 that constitutes the component. The current flowing through the high-voltage transformer primary coils 10, 10 'also flows through the coils A13, 13', and the iron cores 12, 1 'respectively.
Excite 2 '. This magnetic flux generates a voltage corresponding to the primary current in the coils B14 and 14 '. The voltage generated in the coils B14, 14 'is connected to the rectifying / smoothing circuits 17, 17', and is converted to DC. The DC-converted output voltage is proportional to the current flowing through the primary coil of the high-voltage transformer. Similarly, the number of turns of each coil, the size of the iron core, and the constants of the capacitors and resistors of the rectifier circuit are set. In the embodiment, the primary coil 1
When the current flowing through 0 and 10 'is 10A, the output voltage is 5V and the current is 1
It is configured to be 0.5V at A. Rectification, smoothing circuit 1
Outputs of 7, 17 'are input terminals of microcomputer circuit 18.
19,19 '. Microcomputer circuit 18
Is an operation key input means 20 for controlling the main body, a display means 21 for indicating an operation state, and a high-voltage transformer 2 for driving the respective high-frequency generators for controlling the main body.
The current detecting devices 11 and 11 'described above are connected to the primary coils 10 and 10' of 2 '.
A control relay 22 having contacts connected in series with
22 ', which is configured to control the operation of the main body according to a pre-programmed procedure. The microcomputer circuit is operated by converting the power supply voltage into a voltage necessary for the operation by the power transformer 23 and converting the voltage into a direct current.
Further, the microcomputer circuit 18 is provided with a secondary coil 24 of a power transformer 23 and a voltage input terminal 25 for taking in a part of the output voltage. Further, the main body has a door 27 provided on the front surface of the heating chamber 8 for taking in and out the object to be heated 26, and opens and closes in response to opening and closing of the door 27,
A door switch 28 having a contact for connecting and disconnecting the inputs of the high voltage transformers 2 and 2 ', a fuse 29 which operates when an excessive current is generated in the primary power supply circuit, and the like are provided. In this configuration, the operator normally sets the heating time on the RAM of the microcomputer circuit 18 by operating the operation key 20, and the contact of the power relays 22 and 22 'is closed by operating the heating start for the set time. , High voltage transformer
A voltage is applied to the magnetrons 2 and 2 ', and power is supplied to the magnetrons 1 and 1'. Is programmed so that heating is performed by applying pressure to Further, the microcomputer circuit 18 has a third
The program shown in the flowchart of FIG.
That is, the main body takes in the input voltage from the voltage input terminal 25 at a constant period during operation. It is determined whether this voltage value is within a preset voltage range. In the embodiment, when the voltage is shifted by 15% or more with respect to the rated voltage, the power relay 2
Turn off both 22 and 22 'to stop high frequency generation. As another embodiment, the voltage may be detected even in a state where the main body does not operate, and if the voltage is abnormal, the operation may not be performed from the beginning. In another embodiment, the outputs of the current detectors 11 and 11 'may be corrected according to the ratio of the detected voltage to the rated voltage. If the voltage is within the normal range, the operation is continued and the DC voltage obtained by rectifying and smoothing the voltage generated in the coil B14 of the current detection device 11 is taken in.
Store it temporarily on AM. This is A. Similarly, the DC output detected by the current detector 11 'is taken.
This is B. Next, the value of B is subtracted from A, and the magnitudes are compared. The sign of this value is determined, and if it is positive, that is, A>
If B, A / B operation is performed. If negative, that is, if A <B, the operation of-(B / A) is performed. It is determined whether the result is larger or smaller than 1.2 in the embodiment. That is, it is determined whether or not the difference between A and B is 20% or more. If the value is smaller than 1.2, that is, there is no abnormality in the two high-frequency generators, it is determined that there is an error caused by a variation in the constants of the components, and the process returns to the original routine to take in the input voltage again. If A is larger than B and the difference between A and B is 20% or more, the value of A which has been set beforehand and which is normal when A is 20%
A value that is higher by% is subtracted, and it is determined whether the value is positive or negative. If it is positive, the current of A is abnormally large, that is, 1.2 times or more larger than the value of B, and is larger than the rated current of A. Therefore, in the secondary circuit of the high-voltage transformer 2, the high-voltage capacitor 7 There were measured the number of times N ₁ for determining a short-circuited, if more than 5 times the state has continued continued, turn output to the relay 22, the contact is opened the relay 22, the only abnormal current flowing through the high-voltage transformer 2 Cut. The display means 21 displays FO3 indicating an abnormality. Conversely, if the value is negative, the value of B is abnormally low compared to the normal state.
High pressure rectifier 6 'and the magnetron 1' short circuit, etc., or determines that a part has become an open state of the secondary circuit, 'cut, high-voltage transformer 2' relay 22 when the number N ₂ was followed over five times Turn off the flowing current. The display means displays FO4. In either case, once the relay 22 or 22 'is turned off, the relay is programmed to hold until the power is turned off. Conversely, if B is larger than A and the difference is 20% or more, a value that is 20% higher than the preset value of B that has been set before B is subtracted from B, and whether this value is positive or negative Make a decision. If it is positive then the current of B is abnormally large, it is determined that the short circuit condition, such as a high voltage condenser 7 in the second order path of the high-voltage transformer 2 ', counts the number of times N _3, if this state continues continuously five or more times The relay 22 'is turned off, and only the input to the high voltage transformer 2' is turned off. The display means 21 displays FO2 and notifies an abnormality. Similarly to the above, if the value becomes negative, the value of A is abnormally lower than normal, and it is determined that the high-voltage rectifier 6 and the magnetron 1 in the secondary circuit of the high-voltage transformer 2 are short-circuited or open. counting the number of times N _4, if this state continues continued five times or more, cutting only the input to the high voltage transformer 2 off the relay 22. The display means displays FO1. The measurement is performed every 0.1 sec. The above is the case of two high-frequency generators, but in the case of a larger number, the same number of current detectors are provided as described above, and AB, B, C are detected for detected signals A, B, C,. B−
C, C... Calculate the difference between the two by calculating XA,
It is determined whether or not the difference is equal to or larger than the difference set in consideration of the current deviation due to the variation, and if there is a difference, as in the above-described embodiment, the difference is larger or smaller than the value at the preset rated current. Based on the determination, it is determined which circuit has failed, and the control relay contact of only the failed circuit is opened. Effects of the Invention In the present invention having the above configuration and the program, as described at the outset, by detecting a plurality of abnormality detection devices in the primary circuit element, there is no need for protection against high voltage as compared with the related art. Only the insulation distance and the like can be reduced, and the size can be extremely reduced. In the present embodiment, in particular, the current detection devices 11 and 11 'are provided on the printed circuit board 16 constituting the microcomputer circuit 18 for controlling the main body, so that the production cost can be reduced. By implementing the present invention, the following effects were obtained. Abnormality can be more accurately detected and controlled in the current that fluctuates depending on the operation state of the device. In other words, according to the conventional method, the magnitude of each current value and the absolute value of the signal are detected and controlled. Therefore, each time the operating condition changes, the value changes, which value is normal and which value is normal. Sometimes it was difficult to judge whether something was abnormal. According to the present invention, the change in the current difference between the two high-frequency generators that always operates under the same operating conditions is detected, so that the current change due to the operating conditions can be ignored. As an embodiment, by detecting the primary input voltage together, the main body is operated at a voltage deviating from the resonance voltage, and the high voltage transformer 2 which is generated when the magnetrons 1, 1 'and the high voltage rectifiers 6, 6' are short-circuited. Abnormality can be detected very accurately, such as preventing malfunction due to an increase in the primary and primary currents, and instantaneous and accurate detection of failures in the high-voltage transformer secondary circuit, which may cause ignition or electric shock. , Safety can be ensured. Further, according to the embodiment of the present invention, when one of the plurality of high-frequency generators fails, only the failed circuit stops operating, and the other circuits continue operating, so that the heating output decreases, but the heating operation continues. By doing so, the heating work is not interrupted in the busy kitchen room and the usability is greatly improved, compared to the conventional method in which the entire apparatus stops due to a partial failure. Also, when repairs are to be performed after a failure occurs, by checking the contents displayed on the display means, the failure location can be specified in more detail, the repair time can be greatly reduced, the efficiency is improved and the equipment can not be used Can also be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part of a high-frequency heating apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the embodiment, FIG. FIG. 4 is a side sectional view of the same, FIG. 5 is a circuit diagram showing a conventional example, and FIG. 6 is a perspective view of the main part. 1,1 '… magnetron, 2,2'… high voltage transformer, 6,
6 '… High voltage condenser, 7,7'… High voltage condenser, 8
…… Heating room, 10,10 ′ …… High voltage transformer primary coil, 11,
11 '... current detection device, 15 ... control circuit, 16 ... printed circuit board, 18 ... microcomputer circuit, 21 ... display means, 22, 22' ... control relay, 23 ... power transformer, 25 ... ... Voltage input terminal.

Claims (1)

(57) [Claims] A plurality of high-frequency generators for heating the object to be heated in the body and a power supply circuit for driving each of the high-frequency generators; and the same number of current detection means for individually detecting the primary input current of the power supply circuit, A control circuit for comparing the value of the primary input current detected by the current detection means with each other, and controlling a primary current of a power supply circuit for driving each of the high-frequency generators based on the compared data; If the output of the difference between the primary currents of the power supply circuit detected by the current detection means is positive and the current value on the reduced side is larger than the current value of the ratio set to the normal value, at least the value is reduced. The primary circuit of the power supply circuit on the other side is cut off and the excess current on the reduced side is displayed, and the current value on the reduced side is set at a ratio of a current value set to a normal value. Also at least if at least One or both of a configuration for interrupting the primary circuit of the power supply circuit on the other side and displaying an undercurrent of the reduced side is provided, and the primary circuit of the power supply circuit detected by the current detection means is provided. When the output of the difference is negative and the current value on the reduced side is larger than the current value of the set ratio with respect to the normal value, at least the primary circuit of the power supply circuit on the reduced side is shut off, and A configuration for displaying an excessive current on the reduced side, and a primary circuit of the power supply circuit on the reduced side at least when the current value on the reduced side is smaller than a current value of a set ratio with respect to a normal value. One or both of the configurations for shutting off the current and displaying an undercurrent on the reduced side is provided. Further, a power supply voltage detecting means is provided in the main body, and the heating operation of the main body is performed outside of a predetermined voltage range. Characterized by the provision of means for disabling Wave heating device. 2. A current transformer is connected in series to the primary circuit of the power supply circuit as current detection means, and means for rectifying and smoothing the output of the current transformer is provided. The DC voltage is proportional to the current flowing through the primary circuit of the power supply circuit. The high-frequency heating device according to claim 1, wherein the high-frequency heating device has a configuration for performing comparison by: