JPH061717B2 - High frequency heating device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a so-called interlock monitor circuit for preventing high-frequency leakage when a door of a high-frequency heating device is opened and closed.

2. Description of the Related Art Generally, a high-frequency heating device uses a high-frequency oscillating circuit mainly composed of a magnetron, but in a large-sized commercial high-frequency heating device used in, for example, a restaurant, in order to obtain a large output. A plurality of high frequency oscillator circuits are used.

For example, as disclosed in Japanese Utility Model Publication No. 60-20318,
3 and 4 are views showing a conventional high-frequency heating device of this type. That is, electric power is supplied from the power source through the fuses 2a and 2b and the door switches 3a and 3b for each of the high frequency oscillation circuits 1a and 1b.
The door switches 3a and 3b are opened when the door 5 of the heating chamber 4 is opened to cut off the energization to the high frequency oscillation circuits 1a and 1b and stop the oscillation operation of the high frequency oscillation circuits 1a and 1b. Even if the door 5 is opened, if the door switch 3a is closed by welding or the like (abnormal closing), the short circuit (short circuit) is connected to the circuit on the abnormal side through the short switch 6a. A so-called interlock monitor circuit) is formed. Therefore, the applied current from the power source almost flows through this short circuit, and the high frequency oscillation circuit 1a is not supplied with sufficient power for oscillation. Further, due to the large current (about 200 A) flowing in the short circuit, the fuse 2a is blown and the high frequency oscillation circuit 1 on the abnormal side is generated.
a cannot be oscillated. The same operation is performed as when the door switch 3b is closed abnormally. Further, the short-circuit circuit is provided with a resistor 7 for limiting a short-circuit current and preventing welding and destruction of a short switch or the like.

Problems to be Solved by the Invention However, in the above-described conventional configuration, the short switches are required for the number of high-frequency oscillation circuits, and in order to mount the short switches, the shape of the entire device must be increased. It has been a factor that hinders miniaturization, which has been raised as a problem of some high-frequency heating devices.
Moreover, since the shape is increased and a plurality of short switches are required, the cost is high.

Furthermore, when the door switch 3a is closed abnormally, in addition to the short circuit (short switch 6a → resistor 7 → power supply), the short switch 6a to the short switch 6b,
Even if power is supplied to the high-frequency oscillator circuit 1b and the high-frequency oscillator circuit 1a cannot oscillate, the high-frequency oscillator circuit 1b may oscillate until the fuse 2a is blown. Even when the door switch 3b is abnormally closed, the high frequency oscillation circuit 1a oscillates in the same manner until the fuse 2b is blown.

The present invention solves the above problems, and an object of the present invention is to provide a high-frequency heating device having a simple structure and capable of realizing both miniaturization of the entire device and improvement of quality such as safety.

Means for Solving the Problems In order to achieve the above-mentioned object, a high-frequency heating device of the present invention provides a power supply including a plurality of high-frequency oscillation circuits and fuses and door switches respectively connected to these high-frequency oscillation circuits. It has a circuit and a short switch connected to the power supply circuit via a semiconductor rectifier.

Operation With the above configuration, the short circuit of the short circuit formed when the door switch is abnormally closed can be set to one for a plurality of high frequency oscillation circuits, and the door switch is abnormally opened and shorted. Apply the current from the short circuit (interlock monitor circuit) that is formed when the switch is closed to the circuit system other than the circuit system that includes this short circuit, and oscillate the current in the reverse direction of the semiconductor rectifier. This can be prevented by the characteristics of the current element.

EXAMPLES Examples of the high-frequency heating apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment, in which 8 is a control circuit, a power switch (not shown).
Connected to the power supply via the contact point 9a,
The contact point 9a is used for controlling the energization of the high frequency oscillator circuit 10a, and the contact point 9b is used for controlling the energization of the high frequency oscillator circuit 10b.
The high-frequency oscillation circuits 10a and 10b include magnetrons 11a and 11b and a drive circuit for their operation, respectively, and power source side voltages (1
The next voltage) is converted and the power required for oscillation is applied.

A series circuit including a fuse 13a, a door switch 14a and a contact point 9a is formed between the first terminal L of the power source and the primary winding of the power transformer 12a.
The first terminal L of the power source and the power transformer 12b
A fuse 13b and a door switch 14 are provided between the second winding and the next winding.
A series circuit consisting of b and the contact contact 9b is formed. The door switches 14a and 14b are both doors 1
When the door 5 is opened, it is turned off, and when the door 15 is closed, it is turned on.

The anode side of the diode 16a is connected between the door switch 14a and the contact contact 9a, and the anode side of the diode 16b is connected between the door switch 14b and the contact contact 9b. The diode 16
Short switches 17 are provided on the cathode side of both a and 16b.
Is connected to one end of. The short switch 17
Turns off when the door switches 14a and 14b turn on, and turns on when the door switches 14a and 14b turn off. The short switch 17 is
It is connected to the second terminal N of the power source via the current limiting resistor 18.

FIG. 2 is a cross-sectional view of the high frequency heating apparatus of the present invention, wherein the door switches 14a and 14b are provided on the right side wall of the heating chamber 19, and the short switch 17 is provided on the left side wall of the heating chamber 19. Has been.

The operation of the high-frequency heating device configured as above will be described.

First, when the power switch is turned on, the control circuit 8 is activated, both the contact points 9a and 9b are closed at the same time, and the high frequency oscillation circuits 10a and 10b can be supplied with power. In this state, when the object to be heated is put in the heating chamber 19 and the door 15 is closed, the door switches 14a and 14b are closed and the short switch 17 is opened. Since the door switch 14a is closed, the fuse 13a, the door switch 14a,
A voltage is applied to the primary winding of the power transformer 12a via the contact point 9a, and power is supplied from the secondary winding of the power transformer 12a to the high frequency oscillation circuit 10a to start oscillation. Similarly, the door switch 1
By closing 4b, a voltage is applied to the power transformer 12b through the fuse 13b, the door switch 14b, and the contact 9b, and power is supplied to the high frequency oscillation circuit 10b to start oscillation. When the operator opens the door 15 after heating and cooking of the object to be heated, the door switches 14a and 14b are opened and the short switch 17 is closed. The door switches 14a, 14b
The power supply to the power supply transformers 12a and 12b is stopped by the opening of the high frequency oscillators 10a and 10b.
The oscillation of b stops.

However, when the door 15 is opened, the door switch 14a may be closed (abnormally closed) due to an abnormality such as welding. At this time, the short switch 17 is in the closed state because the door 15 is open. Thereby, the fuse 13a, the door switch 14a, the diode 16a, the short switch 1
7. A closed circuit a is formed by the current limiting resistor 18. The impedance of the closed circuit a is much smaller than the impedance on the power transformer 12a side, almost no electric power is applied to the power transformer 12a, and the oscillation from the high-frequency oscillator circuit 10a is generated. The action stops. At this time, a large current flows through the closed circuit a, but due to the forward resistance of the diode 16a and the current limiting resistor 8, the closed circuit a is damaged by the short switch 17 being burned or the power source being damaged. The applied current does not flow. Due to this current, the fuse 13a is melted, the closed circuit a is opened, and the high-frequency oscillator circuit 10a cannot oscillate until the fuse 13a is repaired. The current flowing through the closed open circuit a is the diode. Due to the reverse current characteristic of 16b, it is not applied to the high frequency oscillation circuit 10b.

Similarly, when the door switch 14b is abnormally closed even though the door 15 is open, the fuse 13b, the door switch 14b, the diode 16b, the short switch 17, and the current limiting resistor 18 are used. A closed circuit b is formed, almost no electric power is applied to the power supply transformer 12b, and the high frequency oscillation circuit 10b is formed.
The oscillating action of stops. In the closed circuit b, due to the forward resistance of the diode 16b and the current limiting resistance 18,
No current flows that burns the short switch 17 or damages the power supply. Also, due to this current, the fuse 1
3b is blown, the closed circuit b is opened, and the fuse 1
The high frequency oscillation circuit 10b cannot oscillate until 3b is repaired. Further, the current flowing in the closed circuit b is not applied to the high frequency oscillation circuit 10a due to the reverse current characteristic of the diode 16a.

Next, when both the door switches 14a and 14b are abnormally closed even though the door 15 is opened, the fuse 13a, the door switch 14a,
A closed circuit including a diode 16a, a short switch 17, and a current limiting resistor 18, the fuse 13b, a door switch 14b, a diode 16b, a short switch 17,
A closed circuit is formed by the current limiting resistor 18, and almost no electric power is supplied to the high frequency oscillation circuits 10a and 10b.
Stop oscillation. Further, the forward resistance of each of the diodes 16a and 16b and the current limiting resistance 18 can prevent an excessive current from flowing in the both closed circuits. Further, this current causes the fuses 13a,
The high-frequency oscillator circuit 10a, 10b becomes unusable until the fuse 13a is blown and the fuses 13a, 13b are repaired.

With the above configuration, an interlock monitor circuit can be configured with one short switch and one current limiting resistor for each of the two high-frequency oscillation circuits, and the space required for providing the short switch can be reduced. Will be

Further, due to the reverse current characteristic of the diode, it is possible to prevent the application of (short-circuit) current from the short circuit (closed circuit including the short switch) to a circuit system other than the circuit system including the short circuit, and the accompanying oscillation.

The current limiting resistor 18 includes the diode 16a,
One end may be connected to the commonly connected poles of 16b, the other end may be connected to one end of the short switch 17, and the other end of the short switch 17 may be connected to the second terminal N of the power supply.

Next, when the current limiting resistor 18 is not used, that is, one end of the short switch 17 is connected to the commonly connected poles of the diodes 16a and 16b, and the other end is connected to the second terminal N of the power source. The operation will be described for the case of connection. Since the operation when the door switches 14a and 14b do not cause welding or the like is the same as when the current limiting resistor 18 is used, the door switch 1 will be described here.
The operation when 4a and 14b cause abnormal closure such as welding will be described.

First, when the door switch 14a is closed abnormally even though the door 15 is opened, the fuse 13a, the door switch 14a, the diode 16a,
The closed circuit c is formed by the short switch 17, and the high frequency oscillation circuit 10a is not supplied with sufficient power to cause the oscillation action, and the oscillation action is stopped. Then, a large current flows through the closed circuit c, but due to this large current, the fuse 13a is melted and the diode 1
The junction of 6a is destroyed and the semiconductor becomes a conductor (short state). When the door 15 is closed and cooking is started from this state, a voltage is applied to the power transformer 12b through the fuse 13b, the door switch 14b, and the contact 9b, and the fuse 13b, the door switch 14b, Diode 16b,
A half-wave rectified current is applied to the power transformer 12a via the diode 16a in the short-circuited state.
The power supply transformer 12a has an extremely small impedance with respect to a half-wave rectified current, and a large current flows through the fuse 13b to melt it. Therefore, without knowing that the fuse 13a is blown and the diode 16a is in a short-circuited state, when used, the fuse 13b is also blown and the door switch 14a, fuses 13a, 1
This radio frequency heating device is disabled until 3b and diode 16a are repaired.

Next, when the door switch 14b is abnormally closed even though the door 15 is open, the fuse 13b, the door switch 14b, and the diode 16 are provided.
b, a closed circuit d is formed by the short switch 17,
The high-frequency oscillator circuit 10b is not supplied with sufficient power to cause the oscillation action, and the oscillation action is stopped. A large current flows through the closed circuit d, but due to this large current,
While the fuse 13b is blown, the junction of the diode 16b is destroyed and the diode 16b is brought into a short circuit state. From this state, when the door 15 is closed and cooking is started, the fuse 13a and the door switch 14
a, the contact 9a, and then the power transformer 12
a voltage is applied to a and the fuses 13a,
Through the door switch 14a, the diode 16a, and the short-circuited diode 16b, the power transformer 1
A half-wave rectified current is applied to 2b. The power supply transformer 12b has an extremely small impedance with respect to a half-wave rectified current, and a large current flows through the fuse 13a to melt it. Therefore, when the fuse 13b is blown and the diode 16a is used without being aware that the diode 16a is in a short-circuited state, the fuse 13a is also blown and the door switch 14b, the fuses 13a and 13b and the diode 16b are repaired. Until then, this high frequency heating device will be disabled.

With this configuration, it is possible to prevent oscillation when the door 15 is opened without using the current limiting resistor 18, and to prevent the current limiting resistor 18 from occurring in the interlock monitor circuit when the current limiting resistor 18 is used. It is possible to solve the problem of high frequency leakage due to disconnection.

The diodes 16a and 16b need only have the same commonly connected poles, and the direction of connection in the circuit is opposite to that shown in FIG. 1, that is, the diodes 16a and 16b are both cathodes. Side is connected between the door switches 14a and 14b and the contact contacts 9a and 9b, and the anode side is connected to the short switch 1 together.
7 may be connected.

Further, in this embodiment, two high frequency oscillating circuits are used, but it is needless to say that even if the number of high frequency oscillating circuits is more than that, it can be realized with a single short switch and a current limiting resistor. .

Further, although the diode is used as the semiconductor rectifying element in the present embodiment, an element having a current control characteristic similar to that of the diode (thyristor, transistor, etc.) may be used.

EFFECTS OF THE INVENTION As is clear from the above description of the embodiments, according to the present invention, (1) in a high-frequency heating device having a plurality of high-frequency oscillation circuits, only one short switch is required, and the short switch is provided. The space required is small, the overall size of the device can be reduced, and the cost can be reduced by reducing the number of parts.

(2) Due to the reverse current characteristics of the semiconductor rectifier, current is applied to the circuit system other than the circuit system including the short circuit (closed circuit including the short switch), and the resulting oscillation,
That is, it is possible to completely prevent the electric wave leakage when the door is opened and improve the safety of the device.

(3) The timing adjustment of the door switch and short switch during product assembly is facilitated by the fact that only one short switch is required, improving productivity and the reliability of the product.

That is, an excellent high frequency heating device can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the high-frequency heating device of the present invention, FIG. 2 is a sectional view of the same plane, FIG. 3 is a circuit diagram of a conventional high-frequency heating device, and FIG. 4 is a sectional view of the same plane. is there. 10a, 10b ... High-frequency oscillator circuit, 13a, 13b ...
… Fuses, 14a, 14b… Door switches, 16
a, 16b ... Diode, 17 ... Short switch.

Claims (2)

[Claims] 1. A plurality of high frequency oscillating circuits, each of which is connected to a power supply circuit for supplying electric power from a common power source, said power supply circuit comprising a door switch interlocking with each door. A high-frequency heating device comprising a fuse that operates when an abnormality occurs in the power supply circuit, and a common short switch connected to the power supply circuit via a semiconductor rectifier. 2. The high-frequency heating device according to claim 1, wherein a diode is used as the semiconductor rectifying element.