JP2002190380A - High-frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce more than the power consumption higher than required by suppressing the calorific value of a high-voltage transformer itself in a microwave oven. SOLUTION: After a fixed time has passed following the start of heating, control timing is shifted after a prescribed time for a power which is smaller than that obtained at a control timing set by a user, with the control timing shift being conducted, irrespective of the control timing set by the user, so that the calorific value of the high-voltage transformer is suppressed and the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating apparatus provided with a power relay for intermittently supplying power to a high-voltage transformer.

[0002]

2. Description of the Related Art In a high-frequency heating apparatus such as a microwave oven in recent years, a user can set a high-frequency output to an appropriate level in accordance with demands such as a kind, a quality, and a finished condition of an object to be heated. .

As a method for setting the high-frequency output to an appropriate level, a method using a power relay for interrupting the primary side of a high-voltage transformer for supplying a high-voltage to a high-frequency oscillator is known. This power relay is composed of a relay drive coil that is excited by a voltage signal from a control unit, and a relay contact that is connected to the primary side of the high-voltage transformer and that opens and closes when the relay drive coil is deenergized. The operation timing of the relay drive coil is controlled by a signal to control the opening and closing of the relay contact, thereby controlling the power supplied to the high-voltage transformer.

FIG. 3 is a diagram showing the timing at which a conventional relay contact turns on and off. 3A, 3B, and 3C, the following control is performed, respectively. (A) When the user sets 100% power, the heating time set by the user from the beginning to the end is set to 100%.
Power is output at the rate of%. (B) When the user sets the 90% power, a rate of 90% (for example, power ON for 30 seconds, power OFF for 2 seconds, from the beginning to the end of the heating time set by the user, for 2 seconds)
ON and OFF are repeated in the cycle of F), and power is output. (C) When the user sets the 80% power, the heating time set by the user is set to 80% from the beginning to the end of the heating time.
(For example, power ON for 26 seconds, power O for 6 seconds)
ON and OFF are repeated in the cycle of FF), and power is output.

As described above, in the conventional high-frequency heating apparatus, when the user sets 100% power, the voltage is always supplied to the relay drive coil until the end of the heating time set by the user, and the relay contacts are turned on during the heating time. Because of the "closed" state, the high-frequency transformer supplies 100% of the high-frequency power to the high-frequency oscillator.

When the user sets the power to 90% or 80%, the voltage of the drive coil of the relay is repeatedly turned on and off at a rate set by the user, and the relay contacts are set accordingly until the end of the heating time. It opens and closes at the timing, and the high-frequency transformer supplies the high-frequency power to the high-frequency oscillator by the ratio.

[0007]

By the way, in a model having a high rated power, the power of the high-voltage transformer is large, so that the high-frequency output from the high-frequency oscillator driven by the high-voltage power supplied from the high-voltage transformer is large. Therefore, there is a tendency that the cooking of the target food is finished earlier than the time set by the user. Therefore, 100% of users
When the power is set to 90% or 80%, the object to be heated is continuously heated for the required heating time or longer, and more power is consumed than necessary.

[0008] Further, if the heating is performed for a time longer than the required time, a load is applied to the high-voltage transformer, the amount of heat generated by the transformer itself increases, and the life of the high-voltage transformer is affected.

[0009]

Therefore, according to the present invention, even when the power is initially set by the user, for example, at 100%, 90% and 80% power, a predetermined time after the start of heating is automatically set to a predetermined value. By switching to power (for example, 70% power), the amount of heat generated by the high-voltage transformer itself is suppressed, and unnecessary power consumption is reduced.

That is, according to the present invention, a high-frequency oscillator for high-frequency heating, a high-voltage transformer for supplying high-frequency power to the high-frequency oscillator, a power relay for intermittently supplying power to the high-voltage transformer, and a relay drive coil of the power relay are turned on. A control unit that controls the timing of turning off, after a predetermined time has elapsed from the start of heating,
The control timing is changed to a predetermined control timing regardless of the control timing set by the user.

In this case, the control timing according to the user setting can be set in a plurality of steps, for example, 100%, 90%, and 80% power.
0% power) to drive the high voltage transformer.

Further, the timing of switching the control timing set by the user to the predetermined control timing depends on the time set by the user or the model of the high-frequency heating device, that is, the rated value of the mounted high-voltage transformer. If it is changed accordingly, further power consumption can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a microwave oven as an example of a high-frequency heating device according to an embodiment of the present invention. As shown in the figure, a microwave oven 1 includes a high-frequency oscillator (magnetron) 2 that outputs a high frequency, a high-voltage transformer 3 that supplies a high voltage to the magnetron 2, a high-voltage transformer 3, a cooking chamber lamp 4, a turntable motor 5, and A control unit 7 for controlling the fan motor 6, a temperature fuse 9 and a temperature thermostat 10 interposed in a power supply line for supplying power from a commercial AC power supply 8 to these members.
And a safety switch 11 for short-circuiting the power supply line to cut the thermal fuse 9, and a door switch 12 for opening the power supply line by opening the door.

The magnetron 2 includes a high-voltage condenser 13
The high-voltage rectifier is connected to a secondary winding of a high-voltage transformer via a high-voltage rectifier, and outputs a high frequency in accordance with a high-voltage DC voltage input from the high-voltage rectifier.

The high-voltage transformer 3 has a secondary winding connected to the magnetron 2 via a high-voltage rectification unit, and the primary winding receives power from an AC power supply 8 through a control unit 7 and a power relay 15 described later. The supplied voltage is boosted by the secondary winding and supplied to the magnetron 2.

The control unit 7 includes a control unit 16 such as an LSI.
A low-voltage transformer 17 for supplying the driving voltage; a relay coil for turning on and off by a voltage signal from the control unit 16 to drive the cooking chamber lamp 4, the turntable motor 5, the fan motor 6, and the high-voltage transformer 3; A start relay 20 including a relay contact and a power relay 15 for controlling the voltage of the high-voltage transformer by intermittently supplying power to the high-voltage transformer 2 are provided.

The low-voltage transformer 17 steps down the AC voltage input through the temperature fuse 9 and the thermostat 10 and supplies the AC voltage as a drive voltage for the control unit 16 and also supplies the stepped-down voltage to the relay 20 and the like.

The power relay 15 includes a relay contact 15a interposed in the AC power supply line and connected in series with the primary winding of the high-voltage transformer 3, and a relay drive coil 15b for opening and closing the relay contact. .

The relay drive coil 15b is driven by a control signal from the control unit 16 and a DC voltage that has been dropped and rectified by the low-voltage transformer 17, and the relay contact 15a is closed by the excitation of the relay drive coil 15b to close the relay contact coil 15b. AC power is supplied to the primary winding of the transformer 3, and the relay contact 15a is opened by the demagnetization of the coil 15b, so that the AC power supply to the primary winding of the high-voltage transformer 3 is cut off. I have.

Accordingly, the power supplied to the high voltage transformer 3 is determined by the timing of opening and closing the relay contact 15a, and the power supplied to the high voltage transformer is controlled by the timing of opening and closing.

A power supply line to the relay drive coil 15b has a door open / close detection switch 2 for detecting door open / close.
3 are connected in series, and when the door is opened, the relay drive coil 15b is turned off and the power supply to the high voltage transformer 3 is cut off.

The control unit 16 is composed of a microcomputer, and receives a command signal from the setting unit 22 to control the relay 2.
0 and the power relay 15 to control the driving of the cooking chamber lamp 4, the turntable motor 5 and the fan motor 6, and the voltage of the high-voltage transformer 3.

In the setting unit 22, the user operates the
For example, it is possible to set the power in a plurality of steps, for example, 100%, 90%, 80%, and the like.
The high-frequency output of the magnetron 2 can be controlled.

In response to a power command signal set by the user, the control section 16 controls the timing of turning on and off the power relay 15 and, after a lapse of a predetermined time from the start of heating, uses the power stored in advance. The on / off control timing of the power relay 15 is changed so as to drive the high-voltage transformer 3.

That is, the control unit 16 receives the power command signal from the setting unit 22, calculates the ON / OFF timing of the relay drive coil 15b, measures the time from the start of heating, A drive timing changing means for receiving a signal from the measuring means and outputting a previously stored on / off timing signal of the relay drive coil 15b to the drive control means after a predetermined time has elapsed from the start, an arithmetic means or a drive timing changing means And a drive control means for applying a voltage to the relay drive coil 15b at a predetermined timing in response to a signal from the relay drive coil 15b.

The control timing signal stored in advance in the control unit 16 is based on the power (100
%, 90%, 80% power), for example, 7
A control timing signal capable of outputting 0% power is stored.

In the drive timing changing means, the timing for changing from the start of heating to the predetermined control timing can be set uniformly. However, the timing change timing is calculated according to the time set by the user input from the setting unit 22, A mode in which the output is output to the drive control means is preferable. For example, it is preferable that the timing of change from the heating end time is calculated in response to the input of the user set time, and the timing change signal is output to the drive control means when the timing has reached from the start of heating.

The control unit 16 may be configured to change the timing of switching to a predetermined control timing stored in advance according to the rated value of the high-voltage transformer 3.

FIGS. 2A and 2B are control timing charts for turning on and off the relay contact 15a of the power relay 15 in the circuit of this embodiment. FIG. 2A shows the case of 100% power, and FIG. FIG. 3C shows the case of 80% power.

(A) When the user sets 100% power, the power does not come out at the rate of 100% from the beginning of the heating time set by the user until the end thereof, but when a certain time elapses after heating. , The control section 16 receives a command from the drive timing changing means to change the power supply from 100% to 70% (8 seconds power off, 2
OFF and ON are repeated at a power-on cycle of 4 seconds), and power is output and continues until the end.

(B) When the user sets the 90% power, the power does not come out at the rate of 90% from the beginning of the heating time set by the user until the end of the heating time.
After a certain period of time has elapsed after heating, 90% to 70% of the rate (power OFF for 8 seconds, power O for 24 seconds)
(OFF and ON are repeated in a cycle of N), and power is output, and this continues until the end.

(C) When the user sets the 80% power, the power does not come out at the rate of 80% from the beginning of the heating time set by the user until the end, and a certain time after the heating elapses, 80% to 7 from the middle
0% rate (8 seconds power off, 24 seconds power on
OFF and ON are repeated in the cycle of), power is output, and this continues until the end.

In either case, the ON / OFF voltage signal is output from the drive control means of the control unit 16, the relay drive coil 15b is de-energized, and the relay contact 15a is opened and closed by the de-energization of the drive coil 15b. Relay contact 15a
Is closed, AC power is supplied to the primary winding of the high-voltage transformer 3 and boosted, and the power set by the setting unit 22 and after a predetermined time elapses, the power stored in the control unit 16 is used by the magnetron 2. High frequency output is provided.

As described above, in the high-frequency heating device of the present embodiment, the heat of the high-voltage transformer 3 itself is automatically switched to 70% power after a certain period of time by heating to turn on and off the relay drive coil 15b. The amount is reduced. By suppressing the amount of heat generated by the high-voltage transformer 3, the wire diameter of the winding coil, which is a component of the high-voltage transformer, can be reduced, and the material cost can be reduced.

Further, since a model having a high power as a rated value has a large power, there is a tendency that heating and cooking of an object to be cooked end earlier than a time set by a user. By performing the switching at an early time and automatically changing the power to 70% power, further power consumption can be prevented.

[0036]

As is apparent from the above description, according to the present invention, after the elapse of a predetermined time after the start of heating, the control timing is changed to the predetermined control timing regardless of the control timing set by the user. Power consumption can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a control timing chart for turning on and off a relay contact according to the present invention.

FIG. 3 is a conventional control timing chart for turning on and off a relay contact.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High frequency heating device 2 High frequency oscillator 3 High voltage transformer 7 Control unit 8 AC power supply 9 Thermal fuse 13 High voltage capacitor 14 High voltage diode 15 Power relay 15a Relay contact 15b Relay drive coil 16 Control part 17 Low voltage transformer 20 Relay 22 Setting part

Claims (4)

[Claims] 1. A high-frequency oscillator for high-frequency heating, a high-voltage transformer for supplying high-frequency power to the high-frequency oscillator, a power relay for intermittently supplying power to the high-voltage transformer, and a timing for turning on and off a relay driving coil of the power relay. A high-frequency heating device, wherein after a predetermined time has elapsed from the start of heating, the control unit changes the control timing to a predetermined control timing regardless of a control timing set by a user. 2. The control timing of the user setting can be set in a plurality of stages, and the predetermined control timing is:
2. The high-frequency heating apparatus according to claim 1, wherein the power is at a timing smaller than the user-set power. 3. The high-frequency heating apparatus according to claim 1, wherein the control section calculates and outputs a change timing to a predetermined control timing according to a time set by a user. 4. The high-frequency heating apparatus according to claim 1, wherein the change timing to the predetermined control timing can be changed according to a rated value of the high-voltage transformer.