JPH08285286A - Microwave oven - Google Patents

Abstract

PURPOSE: To provide a microwave oven in which the generation of irregular heating attributable to differential frequencies is prevented by controlling heating based on a heating cycle responding to a 50Hz area and a 60Hz area. CONSTITUTION: A synchronous motor 4a, which turns synchronizing with a power supply frequency, turns a rotary antenna 4, and a rotary cycle, which is substantially equal to the product of one rotary cycle of the rotary antenna 4 in 50Hz and the number of revolution and the product of one rotary cycle of the rotary antenna 4 in 60Hz and the number of revolution, is stored in an ROM of a microcomputer 1a as a heating cycle. A magnetron 6 is controlled based on this heating cycle, which makes it possible to prevent the generation of irregular heating attributable to the difference between the frequencies by controlling the heating with the heating cycle corresponding to the 50Hz and 60Hz areas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven, and more particularly, to a microwave oven having a function of preventing uneven heating when microwave heating an object to be heated placed on a rotary antenna.

[0002]

2. Description of the Related Art Conventionally, in a microwave oven, for example, a rotating antenna or a stirrer is used in order to prevent uneven heating when an object to be heated is cooked by microwaves.

Further, in recent years, techniques for thawing food have been improved, and for example, an electronically controlled cooker has been proposed which can thaw food evenly by combining heating programs of a plurality of stages (Japanese Patent Laid-Open No. 61-134525).
Publication No.).

[0004]

However, in the conventional microwave oven, even if the rotating antenna and the stirrer for preventing the heating unevenness are used, the experiment is performed regardless of the rotating cycle of the rotating antenna or the rotating cycle of the stirrer. The uneven heating was confirmed and the heating conditions were improved.

Therefore, when heating is performed at a heating output of 50% or less, uneven heating may occur depending on the relationship between the rotation cycle of the rotary antenna and the heating output cycle.

FIG. 6 is an explanatory diagram showing the relationship between the rotation angle of the rotary antenna and the microwave radiation timing of the magnetron in the first conventional example. In FIG. 6, the heating cycle Tc = 25
(Second), the heating output ratio is 10% (2.5 seconds / ON, 22.5 seconds / OFF), and the case where the microwave heating source is ON / OFF-controlled is shown, and the hatched portion shows the microwave output state.

FIG. 6A shows the rotation angle and the microwave radiation timing of the rotation period T50 = 12 (seconds) of the rotary antenna at 50 Hz. FIG. 6B shows the rotation angle and the output state of the rotation period T60 = 10 (seconds) of the rotating antenna at 60 Hz.

In the period T60 of the rotating antenna at 60 Hz shown in FIG. 6 (b), the timing of microwave radiation is
The angle of the rotating antenna is 0 ° to 90 °, 180 ° to 270
Since the microwaves are radiated only during the period, the radiation direction of the microwaves becomes constant, which causes uneven heating.

Also, in the period T50 of the rotary antenna at 50 Hz shown in FIG. 6 (a), uneven heating is likely to occur because the heating portions are gradually shifted and the same portions are overlapped and heated.

FIG. 7 is an explanatory view showing the relationship between the rotation angle of the rotary antenna and the microwave radiation timing of the magnetron in the second conventional example. In FIG. 7, the heating cycle Tc = 25
(Second), heating output ratio 20% (5 seconds / ON, 20 seconds / OF
The case where the microwave heating source is ON / OFF controlled is shown in F), and the hatched portion shows the microwave output state.

FIG. 7A shows the rotation angle and the output state of the rotation period T50 = 12 (seconds) of the rotary antenna at 50 Hz. FIG. 8B shows the rotation antenna rotation period T60 = 60 (seconds) rotation angle and output state at 60 Hz.

In the rotation period T60 of the rotating antenna at 60 Hz shown in FIG. 7B, the first rotation is 0 ° to 180 ° ,.
180 ° to 360 ° on the 3rd lap, 0 ° to 180 on the 6th lap
° ... 180 ° to 360 ° on the 9th lap, 0 ° to 360 °
Since microwaves are evenly applied to the entire region of °, uneven heating is unlikely to occur.

However, 50 Hz shown in FIG.
In the rotation period T50 when the rotating antenna is used, since the one rotation period of the synchronous motor is different, the heating region in the first rotation is 0 ° to
150 °, ... 30 ° to 180 ° on the 3rd lap, 6 on the 5th lap
When the microwave heating source is ON-OFF controlled in the same heating cycle, the microwave irradiation timing is deviated with respect to the rotation angle of the rotating antenna, and a portion overlapping the previous microwave irradiation portion is detected. Irradiation results in uneven heating.

Therefore, as shown in FIG. 7, even in the microwave oven in the 60 Hz region, even if the heating cycle is set so that the microwave can be radiated on average over the entire region of 0 ° to 360 °, the rotary antenna is driven. Since a synchronous motor that rotates in synchronization with the power supply frequency is used in the
In the z area, one rotation cycle of the cycle motor is different.

Therefore, microwaves are emitted at the same heating cycle.
In the case of N-OFF, the heating cycle was deviated in the 50 Hz region and it was not possible to prevent uneven heating.

That is, the rotating antenna transmits microwave
The aim is to prevent heating unevenness by radiating the light in all directions at 60 °, but the purpose cannot be sufficiently fulfilled during 50 Hz operation, and heating unevenness occurs.

Further, in Japanese Patent Laid-Open No. 61-134525, a heating program of a plurality of stages is combined in order to thaw the food evenly. For example, the heating output is 100% in the first stage, and the heating output is 30 in the second stage.
%, In the third stage, it is thawed with a heating output of 10%.

Therefore, in the stage where the heating output is 100%, heating unevenness due to the deviation of the rotation cycle of the rotary antenna in the 50 Hz region and the 60 Hz region does not occur at all, but the second stage where the heating output is 30% and the heating output is 10%. In the third stage, microwaves may be radiated to the same place depending on the rotation period of the rotating antenna and the microwave output period, and the microwaves are radiated on average over the entire region of 0 ° to 360 °. Since it is not always the case, there is a risk of uneven thawing.

The present invention is intended to solve such problems.

[0020]

Means for Solving the Problems The means of the present invention for solving the above-mentioned problems include a heating chamber for containing food, a microwave generating means for supplying microwaves to the heating chamber, and a power supply frequency of 50 Hz. Frequency detecting means for detecting whether the frequency is 60 Hz, a synchronous motor that rotates in synchronization with the power source frequency, a radio wave agitating means that is connected to the synchronous motor and that is disposed in the heating chamber, and a frequency detecting means of the frequency detecting means. Heating control means for controlling the microwave generation means in synchronism with the rotation cycle of the radio wave stirring means based on the detection result, wherein the heating control means divides the heating operation time into a plurality of heating cycles. While controlling the microwave generation means, the heating cycle is the radio wave agitation when the product of one cycle of the radio wave agitation means and the rotation speed is 60 Hz when the power supply frequency is 50 Hz. Is a configuration that is set to the product and the rotation cycle to be substantially equal to the engine speed and one cycle means.

Further, a heating chamber for containing food, a microwave generating means for supplying microwaves into the heating chamber, a pulse signal generating means for generating a power source synchronizing pulse signal synchronized with a power source frequency, and the pulse signal generating means. A counter that counts the number of pulses of the means, a storage means that stores in advance the number of pulses of one heating cycle of the microwave generation means, and a synchronous motor that rotates in synchronization with the power supply frequency,
An electric wave agitation unit arranged in the heating chamber that rotates in connection with the synchronous motor, and a heating control unit that controls the microwave generation unit are provided, and the heating control unit sets the pulse number of the storage unit. As one cycle, the microwave generation means is driven until the number of pulses corresponding to the heating output of the microwave is counted by the counter, and then 1
The microwave generation means is controlled to be stopped until the cycle is counted.

Further, the radio wave agitating means is composed of a rotary antenna for radiating the microwave of the magnetron.

[0023]

In other words, although the number of revolutions of the synchronous motor that rotates the radio wave agitating means changes according to the power source frequency, the heating cycle of the microwave generating means is set to the radio wave agitating means when the power source frequency is 50 Hz. The product of one cycle and the number of revolutions and 60
Since the product of one cycle and the number of revolutions of the radio wave stirring means at Hz is changed according to the power supply frequency, even if the power supply frequency changes, the entire circumference of the radio wave stirring means is centered. The microwave can be agitated substantially uniformly over.

Further, by setting the heating cycle by the number of pulses synchronized with the power supply frequency, even if the power supply frequency changes, the pulse interval also changes accordingly. It can be stirred substantially uniformly.

[0025]

The present invention will be described in detail below based on the embodiments shown in the drawings. The present invention is not limited to this. INDUSTRIAL APPLICABILITY The present invention is mainly suitable for a microwave oven in which an object to be heated is microwave-heated by a rotating antenna, and each constituent element achieves “a heating unevenness prevention function of microwave heating due to a difference in frequency” to achieve a 50 Hz area. , 60
A microwave oven with high heating performance can be provided regardless of the Hz region.

FIG. 1 is a block diagram showing an embodiment of the microwave oven of the present invention. In FIG. 1, reference numeral 1 is a control unit, which is composed of a microcomputer 1a having a CPU, a ROM, a RAM, an I / O port, a timer, a counter, a frequency detection circuit, a relay drive circuit, a display drive circuit, and the like. There is.

Reference numeral 2 denotes a key input unit having a menu key for setting the type of heating and cooking and a cooking start key for starting cooking, which is composed of a key switch, a touch sensor and the like.

Reference numeral 3 denotes a display section for displaying a menu, a heating time, and a heating operation status, which are keyed in, and a fluorescent display tube is usually used.

Reference numeral 4 is a rotary antenna that agitates and radiates microwaves, and a synchronous motor (warren motor) 4a that drives the rotary antenna 4 is connected to an output port of the microcomputer 1 via a motor drive circuit 5. Instead of the rotating antenna, stirrer blades for microwave reflection stirring may be used.

The number of rotations of the synchronous motor is 50 Hz and 60
Different in the Hz region, it is 5: 6. Therefore, the rotation cycle of the rotary antenna 4 is 6: 5 in the 50 Hz region and the 60 Hz region.

6 is a magnetron for radiating microwaves,
Reference numeral 7 is a high voltage transformer for oscillating the magnetron 6, and 8 is a heating source control circuit for ON / OFF controlling the high voltage transformer 7, which is connected to the output port of the microcomputer 1a.

As the motor drive circuit 5 and the heating source control circuit 8, switching elements such as ON / OFF control relays and triacs are used.

Reference numeral 9 denotes a commercial power supply, which supplies AC power directly to the synchronous motor 4a and the high voltage transformer 7. Reference numeral 10 denotes a power supply waveform detection circuit, which is, for example, a sensor including an electromagnetic induction coil, a photocoupler, etc., which detects the frequency timing from the waveform of the commercial power supply 9 and is input as a power supply synchronization signal to the input port of the microcomputer 1a. The frequency is detected by the frequency detection circuit built in 1a.

Further, the ROM of the microcomputer 1a has 50H
The rotation cycle at which the product of one rotation cycle and the number of rotations of the rotating antenna at z and the product of one rotation cycle and the number of rotations of the rotating antenna at 60 Hz substantially match is stored as a heating cycle, and a heating output of 50 Hz and 60 Hz is stored. It stores a conversion program for converting into 5: 6 for each pulse signal, a heating control program for ON / OFF controlling the object to be heated with a set heating cycle or heating output ratio, and the like.

FIG. 2 is a perspective view showing the appearance of the microwave oven of the present invention. In FIG. 2, 11 is a microwave oven main body and 2
Is a key input unit for operating a microwave oven, 3 is a display unit, 12
Is a door, and the heating chamber 13 is provided behind the door 12.

FIG. 3 is an explanatory view showing the positional relationship between the rotary antenna and the magnetron. In FIG. 3, reference numeral 13 denotes a heating chamber of the microwave oven main body 11, and 14 is a waveguide for supplying the microwave from the magnetron 6 to the heating chamber, which is installed above the microwave oven main body 11.

A synchronous motor 4a for rotating the rotary antenna 4 is provided above the waveguide 14, and a metallic drive shaft 4b extending from the synchronous motor 4a penetrates through the waveguide 14 to heat it. It is projected in the room. And drive shaft 4
The rotating antenna 4 is fixed to the tip of b, and the rotating antenna 4 is rotated by rotating the synchronous motor 4a.

Now, a method 1 (embodiment 1) for preventing uneven heating due to a difference in power supply frequency will be described. The microcomputer 1
a is a rotation cycle in which the product of one rotation cycle and the number of rotations of the rotating antenna 4 at 50 Hz and the product of one rotation cycle and the number of rotation of the rotating antenna 4 at 60 Hz substantially match each other are stored in the microcomputer 1a as a heating cycle Tc. I'll do it.

That is, the heating cycle when the microwave is output by controlling the ON / OFF of the magnetron 6 is Tc, 50H.
When the rotation cycle of the rotary antenna 4 at z and 60 Hz is T50, T60, and the synchronous rotation speed is N, M (natural number), Tc≈ (N−1 / 2) × T50≈ (M−1 / 2) × T6
N and M are calculated from the equation 0 and stored in advance in the ROM of the microcomputer 1a. Here, T50 = 12 (seconds), T
60 = 10 (seconds).

Incidentally, 1 / in N-1 / 2 and M-1 / 2
2 indicates 1/2 rotation, and is because the heating cycle is set so as to first heat the region of 0 ° to 180 ° and then heat the region of 180 ° to 360 °. In other words, the heating cycle Tc is the first cycle and the second cycle with respect to the rotation cycle of the rotary antenna 4.
The rotating angle of the rotating antenna at each heating output for the first time is shifted by about 180 ° and averaged for heating.

Therefore, Tc≈ (N-1 / 2) × 12≈
From (M−1 / 2) × 10, (N, M) = (5,6),
A combination of (10, 12), (15, 18) ... Is required. If (N, M) = (5, 6), the heating cycle T
c≈54 to 55 (seconds). This heating cycle is stored in the ROM of the microcomputer 1a in advance, is called every time the magnetron 6 is controlled, and is used for controlling the magnetron 6.

FIG. 4 is an explanatory diagram showing the relationship between the rotation angle of the rotary antenna and the microwave radiation timing of the magnetron in the first embodiment. In FIG. 4, the heating cycle Tc = 54
(Second), heating output 10% (5.4 seconds / ON time, 48.6)
The case where the magnetron 6 is ON / OFF controlled in (second / OFF time) is shown, and the hatched portion shows the microwave output state.

FIG. 4A shows the rotary antenna 4 at 50 Hz.
Shows the rotation angle and the output state in the rotation cycle T50 = 12 (seconds). FIG. 4B shows the rotation angle and the output state of the rotating antenna 4 at a period T60 = 10 (seconds) at 60 Hz.

The microwave is radiated from the rotary antenna 4 at 50 Hz shown in FIG. 4 (a) at 0 ° in the first round.
~ 165 °, 180 ° to 345 ° on the 5th lap, 0 ° to 165 ° on the 10th lap, 180 ° to 345 ° on the 14th lap,
.., and the microwave is evenly applied to the entire region of approximately 0 ° to 360 °, so that heating unevenness does not occur.

The microwave is radiated from the rotary antenna 4 at 60 Hz shown in FIG. 4 (b) at 0 ° in the first round.
~ 198 °, 144th to 342 ° on the 6th lap, 288 ° to 126 ° on the 11th and 12th laps, 50H
Even when the magnetron is controlled to be turned on and off at the same heating cycle at z, heating unevenness does not occur because the microwave is evenly applied to the entire region of approximately 0 ° to 360 °.

Next, a method 2 for preventing uneven heating (Example 2) will be described as another example. Turn on magnetron 6 /
The heating output ratio at the time of OFF control and microwave output is set to be 6: 5 at 50 Hz and 60 Hz.

Assuming that the rotation period of the rotating antenna at 50 Hz and 60 Hz is T50 and T60, T50: T60 = 1.
2: 10 = 6: 5.

After determining whether the frequency is 50 Hz or 60 Hz by the frequency detection circuit built in the microcomputer 1a, the counter in the microcomputer 1a then pulses the power supply waveform for 1 second, and at 50 Hz, the number of pulses per second. 50 counts,
At 60 Hz, the number of pulses is 60 per second.
By converting the heating cycle from a time unit to a pulse signal unit (pulse number) synchronized with the power supply frequency, the microcomputer 1a calculates the counted pulse number itself as a heating cycle (output cycle).
By doing so, the heating cycle can be incorporated in the same program without time conversion.

FIG. 5 is an explanatory diagram showing the relationship between the rotation period of the rotating antenna and the heating period of the magnetron in the second embodiment. In FIG. 5, for example, the heating cycle Tc = 1500.
Pulse, heating output 20% (300 pulse / ON time, 1
ON / O of magnetron with 200 pulses / OFF time)
The case where FF control is performed is shown, and the hatched portion shows the output state of microwaves.

FIG. 5A shows the rotary antenna 4 at 50 Hz.
Shows the rotation angle and the output state in the rotation cycle T50 = 12 (seconds). Also, if converted into time, 50 Hz
Heating cycle Tc = 30 seconds (6.0 seconds / ON time, 24
Second / OFF time).

FIG. 5B shows the rotation angle and the output state in the rotation period T60 = 10 (seconds) of the rotating antenna at 60 Hz. Further, when converted into time, the heating cycle Tc is 25 seconds at 60 Hz (5.0 seconds / ON time, 20 seconds / OFF time).

When the microwave is radiated from the rotary antenna 4 at the time of 50 Hz and 60 Hz, the first lap is 0 ° to 180 °, the third lap is 180 ° to 360 °, and the sixth lap is 0. ° to 180 ° ... Can be set at an angle deviated from the eighth lap by 180 ° to 360 °. Therefore, the microwave is evenly applied to the entire region of 0 ° to 360 °, so that heating unevenness does not occur.

Further, by converting the time unit into a pulse signal unit synchronized with the power supply frequency, it is not necessary to prepare a special double heating control program for the program of the microcomputer 1a for 50 Hz and 60 Hz.

FIG. 5 shows Example 2 in which the heating cycle Tc = 1500 pulses and the heating output is 20%.
It is preferable that the heating cycle is 1500 pulses when the heating rate is 0% or less, and 3300 pulses when the heating output exceeds 30%. The pulse period fixed at all outputs is (N-1 / 2) times the rotation period of the rotating antenna.

[0055]

According to the present invention, 60H, 50H region, 60H
By controlling the heating with the heating cycle corresponding to the z area,
It is possible to prevent uneven heating due to the difference in frequency.

Also, by converting the time unit into a pulse signal unit synchronized with the power supply frequency, it is not necessary to prepare two special heating control programs for the microcomputer program for 50 Hz and 60 Hz.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a microwave oven of the present invention.

FIG. 2 is a perspective view showing the appearance of the microwave oven of the present invention.

FIG. 3 is an explanatory diagram showing a positional relationship between a rotating antenna and a magnetron.

FIG. 4 is an explanatory diagram showing the relationship between the rotation period of the rotating antenna and the heating period of the magnetron in the first embodiment.

FIG. 5 is an explanatory diagram showing the relationship between the rotation period of the rotating antenna and the heating period of the magnetron in the second embodiment.

FIG. 6 is an explanatory diagram showing the relationship between the rotation period of the rotating antenna and the heating period of the magnetron in Conventional Example 1.

FIG. 7 is an explanatory diagram showing the relationship between the rotation period of the rotating antenna and the heating period of the magnetron in Conventional Example 2.

[Explanation of symbols]

 1 control unit 1a microcomputer 2 key input unit 3 display unit 4 rotating antenna 4a synchronous motor 5 motor drive circuit 6 magnetron 7 high voltage transformer 8 heating source control circuit 9 commercial power supply 10 power supply waveform detection circuit

Claims (3)

[Claims] 1. A heating chamber for accommodating food, a microwave generation unit for supplying microwaves to the heating chamber, a frequency detection unit for detecting whether the power supply frequency is 50 Hz or 60 Hz, and a synchronization unit for the power supply frequency. A rotating synchronous motor,
Controlling the microwave generating means in synchronization with the rotation cycle of the radio wave agitating means based on the detection result of the radio wave agitating means arranged in the heating chamber, which is connected to the synchronous motor to rotate, and the frequency detecting means. And heating control means,
The heating control means controls the microwave generation means by dividing the heating operation time into a plurality of heating cycles,
The heating cycle is substantially the same as the product of one cycle of the radio wave stirring means and the rotation speed when the product of one cycle of the radio wave stirring means and the rotation speed when the power supply frequency is 50 Hz is 60 Hz. A microwave oven characterized by being set to. 2. A heating chamber for storing food, a microwave generating unit for supplying microwaves to the heating chamber, a pulse signal generating unit for generating a power source synchronizing pulse signal synchronized with a power source frequency, and the pulse signal generating unit. A counter that counts the number of pulses of the means, a storage unit that stores in advance the number of pulses of one heating cycle of the microwave generation unit, a synchronous motor that rotates in synchronization with the power supply frequency, and the synchronous motor. An electric wave agitating unit arranged in the heating chamber that is connected and rotating, and a heating control unit that controls the microwave generation unit are provided, and the heating control unit has the number of pulses of the storage unit as one cycle, The microwave generating means is driven until the number of pulses corresponding to the heating output of the microwave is counted by the counter, and then until one cycle is counted. A microwave oven which is controlled to stop the microwave generation means. 3. The microwave oven according to claim 1, wherein the radio wave agitating means is composed of a rotary antenna that radiates microwaves of the magnetron.