JP3203147B2 - microwave - Google Patents

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 heating an object placed on a rotary antenna by microwave heating.

[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 heating an object to be heated by microwaves.

Further, in recent years, the technology relating to thawing of food has been improved, and for example, an electronically controlled cooker capable of thawing food evenly by combining a plurality of heating programs has been proposed (Japanese Patent Application Laid-Open No. 61-135525).
Publication No.).

[0004]

However, in a conventional microwave oven, even if a rotating antenna and a stirrer for preventing uneven heating are used, an experiment is performed irrespective of the rotation period of the rotating antenna and the rotation period of the stirrer. , Heating unevenness 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 rotating antenna and the microwave radiation timing of the magnetron in the first conventional example. In FIG. 6, the heating cycle Tc = 25
(Seconds), a heating output ratio of 10% (2.5 seconds / ON, 22.5 seconds / OFF) indicates a case where the microwave heating source is ON / OFF controlled, and a hatched portion indicates a microwave output state.

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

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

In addition, even in the period T50 of the rotating antenna at 50 Hz shown in FIG. 6A, heating unevenness is liable to occur because the same portion is overlapped and heated only because the heating region is gradually shifted.

FIG. 7 is an explanatory diagram showing the relationship between the rotation angle of the rotating 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
F) shows a case where the microwave heating source is ON / OFF controlled, and a hatched portion shows a microwave output state.

FIG. 7A shows the rotation angle and output state of the rotating antenna at a rotation period T50 = 12 (seconds) at 50 Hz. FIG. 8B shows the rotation antenna rotation cycle T60 = 10 (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 degrees to 360 degrees on the third lap, 0 degrees to 180 on the sixth lap
° 9th lap is 180 ° to 360 °, 0 ° to 360 °
The microwaves are evenly applied to the entire region of °, so that uneven heating is unlikely to occur.

However, 50 Hz shown in FIG.
In the rotation period T50 at the time of the rotating antenna, since the one rotation period of the synchronous motor is different, the heating area is 0 ° to 1 rotation.
150 °, # 3 lap 30 ° ~ 180 °, # 5 lap 6
When the microwave heating source is ON-OFF controlled at the same heating cycle from 0 ° to 210 °, the microwave irradiation timing with respect to the rotation angle of the rotating antenna is shifted, and the portion overlapping with the previous microwave irradiation portion is removed. Irradiation causes uneven heating.

Therefore, as shown in FIG. 7, even if the heating period is set so that microwaves can be irradiated on the entire region from 0 ° to 360 ° in a microwave oven in a 60 Hz area, the driving of the rotating antenna can be performed. Uses a synchronous motor that rotates in synchronization with the power supply frequency.
In the z region, one rotation cycle of the periodic motor is different.

For this reason, the microwaves are turned on at the same heating cycle.
When N-OFF was performed, the heating cycle was shifted in the region of 50 Hz, and the occurrence of uneven heating could not be prevented.

In other words, the rotating antenna transmits microwaves to 3
The purpose is to prevent heating unevenness by radiating the light in all directions at 60 °. However, when the operation is performed at 50 Hz, the purpose cannot be sufficiently satisfied, and the heating unevenness occurs.

In Japanese Patent Application Laid-Open No. 61-134525, a heating program of a plurality of stages is combined in order to thaw the food without unevenness. For example, in the first stage, the heating output is 100%, and in the second stage, the heating output is 30%.
%, And the third stage is defrosting with a heating output of 10%.

Therefore, in the stage where the heating output is 100%, there is no heating unevenness due to the difference between the rotation periods of the rotating antennas in the 50 Hz region and the 60 Hz region, but the second stage with the heating output of 30% and the heating stage with the heating output of 10%. In the third stage, the microwave may be applied to the same place depending on the rotation cycle of the rotating antenna and the output cycle of the microwave, and the microwave is applied to the entire region from 0 ° to 360 ° on average. May not be always present, so that thawing unevenness may occur.

The present invention is intended to solve such a problem.

[0020]

According to the present invention, there is provided a heating chamber for storing food, a microwave generating means for supplying a microwave into the heating chamber, and a power supply frequency of 50 Hz. Frequency detecting means for detecting whether the frequency is 60 Hz or less, a synchronous motor rotating in synchronization with the power supply frequency, a radio wave stirring means disposed in the heating chamber rotating in connection with the synchronous motor, and in synchronization with the rotation period of the radio wave stirring means based on a detection result and a, a heating control means for controlling said microwave generating means.

The heating control means operates during the heating operation.
Dividing the interval into a plurality of heating cycles,
And the heating cycle is controlled by the radio wave stirring means.
Is shifted from the integral multiple of the rotation cycle by approximately half the rotation cycle.
It is characterized by being set.

Further, the radio wave stirring means is constituted by a rotating antenna for radiating microwaves of the magnetron.

[0023]

That is, the rotation speed of the synchronous motor rotating the radio wave stirring means changes according to the power supply frequency, but the heating cycle of the microwave generation means is set to the rotation cycle of the radio wave stirring means.
It is set to be shifted from the integer multiple by approximately half the rotation cycle.
Substantially can uniformly stirring the microwaves entire circumference around the wave stirring means also changes the power supply frequency for that.

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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. The present invention is not limited by this. INDUSTRIAL APPLICABILITY The present invention is suitable mainly for a microwave oven in which an object to be heated is microwave-heated by a rotating antenna, and each component achieves “a function for preventing heating unevenness of microwave heating due to a difference in frequency” to achieve a 50 Hz region. , 60
A microwave oven with high heating performance can be provided regardless of the Hz region.

FIG. 1 is a block diagram showing one embodiment of the microwave oven of the present invention. In FIG. 1, reference numeral 1 denotes a control unit, which is configured by a microcomputer (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. I have.

Reference numeral 2 denotes a key input unit provided with a menu key for setting the type of heating cooking and a cooking start key for starting cooking, and includes a key switch, a touch sensor, and the like.

Reference numeral 3 denotes a display unit for displaying a key-input menu, a heating time, and a heating operation status, and usually uses a fluorescent display tube.

Reference numeral 4 denotes a rotary antenna for stirring and radiating microwaves. A synchronous motor (Warren motor) 4a for driving the rotary antenna 4 is connected to an output port of the microcomputer 1 via a motor drive circuit 5. Note that a stirrer blade for microwave reflection stirring may be used instead of the rotating antenna.

The rotation speed of the synchronous motor is 50 Hz and 60 Hz.
In the Hz region, it is 5: 6. Therefore, the rotation cycle of the rotating antenna 4 is 6: 5 in the 50 Hz region and the 60 Hz region.

6 is a magnetron for irradiating a microwave,
Reference numeral 7 denotes a high-voltage transformer that oscillates the magnetron 6, and reference numeral 8 denotes a heating source control circuit that controls ON / OFF of the high-voltage transformer 7 and is connected to an output port of the microcomputer 1a.

As the motor drive circuit 5 and the heating source control circuit 8, switching elements such as a relay for controlling ON / OFF and a triac 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 a sensor composed of, for example, an electromagnetic induction coil, a photocoupler, and the like. The sensor detects a frequency timing from the waveform of the commercial power supply 9 and is input to the input port of the microcomputer 1a as a power supply synchronization signal. The frequency is detected by a frequency detection circuit built in 1a.

The ROM of the microcomputer 1a has 50H
The rotation period in which the product of the rotation antenna's one rotation period and the number of rotations at z and the product of the rotation antenna's one rotation period and the number of rotations at 60 Hz substantially match is stored as the heating period, and the heating output at 50 Hz and 60 Hz And a heating control program for ON / OFF-controlling the object to be heated at a set heating cycle and heating output ratio.

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

FIG. 3 is an explanatory diagram showing the positional relationship between the rotating antenna and the magnetron. In FIG. 3, reference numeral 13 denotes a heating chamber of the microwave oven main body 11, and reference numeral 14 denotes a waveguide for supplying microwaves from the magnetron 6 to the heating chamber, and 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 metal drive shaft 4b extending from the synchronous motor 4a penetrates through the waveguide 14 and heats. It protrudes from the room. And the drive shaft 4
The rotating antenna 4 is rotated by rotating the synchronous motor 4a while fixing the rotating antenna 4 to the tip of b.

Here, 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 stored in the microcomputer 1a as a heating period Tc, as a heating period Tc, a rotation period in which the product of one rotation period of the rotating antenna 4 at 50 Hz and the number of rotations substantially coincides with the product of one rotation period of the rotating antenna 4 at 60 Hz and the number of rotations. Keep it.

That is, when the magnetron 6 is ON / OFF controlled to output a microwave, the heating cycle is Tc, 50H.
Tc 回 転 (N-／) × T50 ≒ (M- ／), where T50 and T60 are the rotation periods of the rotating antenna 4 at z and 60 Hz, and N and M (natural numbers) are the synchronous rotation speeds. × T6
N and M are obtained from the equation of 0 and stored in advance in the ROM of the microcomputer 1a. Here, T50 = 12 (seconds), T
60 = 10 (seconds).

It should be noted that 1 / N in N-1 / 2 and M-1 / 2
No. 2 indicates 回 転 rotation, and 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 °. That is, the heating cycle Tc is the first time, the second time,
The heating is performed by shifting the rotation angle of the rotary antenna at the time of each heating output by approximately 180 ° on average.

Therefore, Tc {(N-1 / 2) × 12}
From (M-1 / 2) × 10, (N, M) = (5, 6),
A combination of (10, 12), (15, 18)} is obtained. 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, and is recalled every time the magnetron 6 is controlled and 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
(Second / OFF time) shows the case where the magnetron 6 is ON / OFF controlled, and the hatched portion shows the output state of the microwave.

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

The timing at which microwaves are radiated from the rotating antenna 4 at 50 Hz shown in FIG.
~ 165 °, 180 ° ~ 345 ° on the 5th lap, 0 ° ~ 165 ° on the 10th lap, 180 ° ~ 345 ° on the 14th lap,
‥, and microwaves are irradiated on the entire region of approximately 0 ° to 360 ° on average, so that heating unevenness does not occur.

The microwaves are radiated from the rotating antenna 4 at 60 Hz shown in FIG.
198 °, ‥ 6th lap is 144 ° to 342 °, ‥ 11th lap, 12th lap is 288 ° to 126 °, ‥, 50H
Even when the magnetron is ON-OFF controlled in the same heating cycle at the time of z, the microwaves are averagely applied to almost the entire range of 0 ° to 360 °, so that uneven heating does not occur.

Next, a method 2 for preventing uneven heating (embodiment 2) will be described as another embodiment. Magnetron 6 ON /
The heating output ratio when the microwave is output by performing the OFF control is set to be 6: 5 at 50 Hz and 60 Hz.

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

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

FIG. 5 is an explanatory diagram showing the relationship between the rotation cycle of the rotary antenna and the heating cycle 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
Magnetron ON / O at 200 pulses / OFF time)
A case where the FF control is performed is shown, and a hatched portion indicates a microwave output state.

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

FIG. 5B shows the rotation angle and the output state at a rotation period T60 = 10 (seconds) of the rotating antenna at 60 Hz. In terms of time, at 60 Hz, the heating cycle Tc = 25 seconds (5.0 seconds / ON time, 20 seconds / OFF time).

When the microwaves are radiated from the rotating 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 ° ‥ The 8th round can be set at an angle shifted by 180 degrees to 360 ° by half a circle. Therefore, the microwave is irradiated on the entire region from 0 ° to 360 ° on average, so that uneven heating does not occur.

Further, by converting the time unit into a pulse signal unit synchronized with the power supply frequency, there is no need to create a special double heating control program for the microcomputer 1a for 50 Hz and 60 Hz.

FIG. 5 shows Embodiment 2 in which the heating cycle Tc = 1500 pulses and the heating output is 20%.
The heating cycle is preferably 1500 pulses at 0% or less, and 3300 pulses at heating power exceeding 30%. The pulse period fixed at the time of all outputs is (N-1 / 2) times the rotation period of the rotating antenna.

[0055]

According to the present invention, 50 Hz area, 60 H
By controlling the heating at a heating cycle corresponding to the z region,
The occurrence of uneven heating due to the difference in frequency can be prevented.

Further, by converting the time unit into a pulse signal unit synchronized with the power supply frequency, there is no need to create two special heating control programs for the microcomputer for 50 Hz and 60 Hz.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a microwave oven according to 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 illustrating a relationship between a rotation cycle of the rotating antenna and a heating cycle of the magnetron in the first embodiment.

FIG. 5 is an explanatory diagram illustrating a relationship between a rotation cycle of a rotary antenna and a heating cycle of a magnetron in a second embodiment.

FIG. 6 is an explanatory diagram showing a relationship between a rotation cycle of a rotary antenna and a heating cycle of a magnetron in Conventional Example 1.

FIG. 7 is an explanatory diagram showing a relationship between a rotation cycle of a rotary antenna and a heating cycle of a magnetron in Conventional Example 2.

[Explanation of symbols]

 Reference Signs List 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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-54967 (JP, A) JP-A-50-42355 (JP, A) JP-A-5-312333 (JP, A) JP-A-5-42333 312332 (JP, A) JP-A-3-163788 (JP, A) JP-A-59-58781 (JP, A) JP-A-2-114804 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) F24C 7/02 H05B 6/64-6/80

Claims (2)

(57) [Claims] 1. A heating chamber for storing food, microwave generating means for supplying microwaves into the heating chamber, frequency detecting means for detecting whether the power frequency is 50 Hz or 60 Hz, and synchronizing with the power frequency. A rotating synchronous motor,
The electromagnetic wave stirring means disposed in the heating chamber which rotates while being connected to the synchronous motor, and controls the microwave generation means in synchronization with a rotation cycle of the radio wave stirring means based on a detection result of the frequency detecting means. 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 an integral multiple of the rotation cycle of the radio wave stirring means .
Characterized in that the microwave oven is set so as to be shifted by about a half cycle of the rotation cycle . 2. The magnetron stirring means according to claim 1 , wherein:
Composed of a rotating antenna that emits microwaves
2. The microwave oven according to claim 1, wherein: