JP2003302057A - Microwave oven - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an uneven heating in ON-OFF control with a simple structure. <P>SOLUTION: This microwave oven comprises an electromagnetic wave generating means for heating and cooking matter to be cooked in a heating chamber by electromagnetic wave, a turn table or placing the matter to be cooked thereon and rotated by a synchronous motor, and a controller for performing the ON-OFF control of the electromagnetic wave generating means at a pre-set heating frequency while driving the synchronous motor. The heating frequency is set so that the multiple of the integer thereof (n) (where n<50) is a time not matching any of the multiples of the rotation frequency of the turn table which varies according to a power frequency. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microwave oven for heating and cooking an object to be cooked on a turntable with electromagnetic waves.

[0002]

2. Description of the Related Art A microwave oven includes an electromagnetic wave generating means such as a magnetron for heating and cooking an object to be cooked in a heating chamber, and a turntable on which the object to be cooked is placed and rotated by a synchronous motor. A controller equipped with a microcomputer and the like is capable of heating and cooking such as thawing by ON-OFF controlling the magnetron at a preset heating cycle while driving the synchronous motor to rotate the turntable. However, the synchronous motor changes the rotation cycle depending on the power supply frequency (at 50 Hz, the rotation cycle is 12 seconds,
Since the rotation cycle is 10 seconds at 60 Hz), even if the heating cycle of the magnetron is constant, uneven heating occurs depending on the power supply frequency. FIG. 3 shows the heating area for the outer circumference of the turntable by the power supply frequency when the ON-OFF control is performed at a predetermined heating cycle in each output mode of the magnetron (here, 90 W, 110 W, and 200 W). Is a heating area during ON control (for example, 9
At 0 W, it takes 2.4 seconds), and one rotation including an arc becomes the rotation cycle. However, here, in order to make it easy to understand the deviation of the heating region, the diameter of the rotation cycle is gradually enlarged and displayed as time passes.

[0003]

As is apparent from the above, in the region where the power supply frequency is 50 Hz, when it is used at an output of 90 W, only a region of less than 1/4 is heated intensively and other regions are heated. It turns out that is not heated at all.
Further, in the region of the power supply frequency of 60 Hz, only the case where the output is 90 W is heated over substantially the entire circumference, and the output is 110 W.
In, a non-heated region occurs point-symmetrically, and at an output of 200 W, more than half is a non-heated region. In other words, in any of the output modes, there is no uniform heating at both the power source frequency of 50 Hz and 60 Hz, and the heating region is displaced due to the change of the rotation cycle due to the change of the power source frequency, resulting in uneven heating. . Therefore, in order to prevent the occurrence of this heating unevenness, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 8-42856, a frequency detecting means for detecting the power supply frequency, and one turn cycle of the turntable at 50 Hz based on the detected frequency are provided. A heating cycle calculation means for calculating, as a heating cycle, a rotating cycle in which the product of the rotating speed and the product of the rotating speed and the product of the rotating speed at 60 Hz substantially match each other is provided, and the heating cycle corresponding to the power supply frequency is turned on. An invention is known in which -OFF control is performed. However, since a detection circuit for frequency detection, a program for heating cycle calculation, etc. are newly required, the structure and control are complicated and the cost is increased.

Therefore, the invention according to claim 1 is the ON-type.
An object of the present invention is to provide a microwave oven capable of preventing uneven heating during OFF control with a simple configuration regardless of the power supply frequency.

[0005]

In order to achieve the above object, the invention according to claim 1 is one of the turntables in which the heating cycle is an integer multiple n (where n <50) of which varies depending on the power supply frequency. It is characterized in that it is set at a time that does not match a multiple of the rotation cycle of. According to the invention of claim 2, in addition to the object of claim 1, in order to obtain an appropriate heating cycle that is not likely to coincide with the rotation cycle of the turntable, the heating cycle is set from any rotation cycle of the turntable. Is larger and smaller than twice any of the above rotation cycles.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional explanatory view of a combination range 1 provided with a gas oven function as a microwave oven. The combination range 1 includes a turntable 4 on which a range plate 3 is mounted and which is rotated by a synchronous motor 12.
And a combustion chamber accommodating a burner (not shown), which is adjacent to the left and right, has a substantially cubic heating chamber 2 and an opening / closing door 5 capable of opening and closing the front surface of the heating chamber 2. An exhaust duct 6 for discharging the mixed hot air in the heating cabinet 2 to the outside of the body is connected to the center of the upper portion of the rear wall of the heating cabinet 2, and the thermistor 7 and the humidity sensor 8 are connected to the tip of the exhaust duct 6. It is provided so as to project into the exhaust duct 6. 9 is a magnetron as an electromagnetic wave generating means for oscillating an electromagnetic wave to the center of the upper surface of the heating chamber 2 by a waveguide not shown, and 10 is a controller,
The controller 10 has a well-known microcomputer provided with a CPU, a ROM, a timer, etc., a magnetron control circuit, a synchronous motor drive circuit, etc., and follows the instructions from the operation unit 11 provided on the front surface of the heating cabinet 2 and follows the thermistor. 7 and the output signal from the humidity sensor 8 while monitoring the burner combustion control,
The operation control of the magnetron 9 and the synchronous motor 12 is performed.

Further, the controller 10 turns the magnetron 9 at a constant cycle while rotating the turntable 4.
It is possible to execute ON-OFF control in which N is set and defrosting or the like is possible. Here, the microwave output is 90W,
Three output modes of 110 W and 200 W are selectable respectively, and the heating cycle for each output mode is stored in the ROM in the controller 10 according to the contents of Table 1 below. This heating cycle is 50Hz and 60H
z is also shared, and its integer multiple n (where n <50) is 50
Rotation cycle of the turntable 4 in the case of Hz (12 seconds)
And the rotation cycle of the turntable 4 at 60 Hz (1
It is set so that the time does not match any multiple of 0 seconds). It should be noted that when n = 50, a match occurs once every 500 seconds, but with such a match rate, normal cooking is not hindered. Therefore, n <50.

However, here, the heating cycle is longer than each rotation cycle (12 seconds and 10 seconds) and shorter than twice each rotation cycle (24 seconds and 20 seconds) within the above setting range. Is selected. The reason for this selection is that if the heating cycle is set too large, the multiple of the rotation cycle of the turntable 4 and the least common multiple match, so there is no such match within the above setting range. In the case where an appropriate heating cycle is selected, and when the output becomes too large with respect to the cooking time and the output is controlled by ON-OFF control, the output does not correspond to the target output and the same as the maximum or 0 output. This is because The ON time for each output mode is obtained by the duty ratio set in advance.

[0009]

[Table 1]

In the combination range 1 configured as described above, when defrosting or the like, when the output mode is selected on the operation unit 11 and the start button is pressed, the controller 10 causes the turntable 4 to rotate,
Heating cycle and ON in Table 1 according to the selected output mode
The magnetron 9 will be ON-OFF controlled depending on the time. The heating region of the turntable 4 by the ON-OFF control executed in this manner is shown in FIG. 2 for each power supply frequency in each output mode as described in FIG. As is clear here, in each of the output modes, no heating region is generated at both the power supply frequencies of 50 Hz and 60 Hz, and the entire circumference of the turntable 4 is uniformly heated.

As described above, according to the combination range 1 of the above embodiment, the heating cycle is set to an integral multiple n (where n <
Since 50) is set to a time that does not match any multiple of the rotation cycle of the turntable 4 that varies depending on the power supply frequency, it is possible to prevent uneven heating during ON-OFF control with a simple configuration. In particular, since heating unevenness is prevented by setting the heating cycle regardless of the power supply frequency, additional functions such as a power supply frequency detection circuit are unnecessary.
There is no cost increase. Further, since the heating cycle is set to be longer than any rotation cycle of the turntable 4 and smaller than twice any rotation cycle, it is appropriate that there is no possibility of coincidence with the rotation cycle of the turntable 4. Various heating cycles can be selected.

The heating cycle and the ON time thereof are not limited to the above-mentioned time, and can be appropriately increased or decreased without departing from the gist of the present invention. Moreover, in the above-mentioned form,
Although a combination range provided with a gas oven function has been described, it goes without saying that the present invention can be applied even to a single microwave oven without a gas oven function.

[0013]

According to the first aspect of the present invention, the heating cycle is set to a time such that the integer multiple n (where n <50) does not match the multiple of any rotation cycle of the turntable that differs depending on the power supply frequency. Since the setting is made, it is possible to prevent the heating unevenness from occurring in the ON-OFF control with a simple configuration.
In particular, since heating unevenness is prevented by setting the heating cycle regardless of the power supply frequency, additional functions such as a power supply frequency detection circuit are not required, and the cost does not increase. According to the invention described in claim 2, in addition to the effect of claim 1, the heating cycle is set to be longer than any rotation cycle of the turntable and less than twice any rotation cycle. Therefore, it is possible to select an appropriate heating cycle that is unlikely to match the rotation cycle of the turntable.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view of a combination range.

FIG. 2 is an explanatory view showing a heating region of a turntable for each power supply frequency, (A) output 90 W, (B) output 11;
The case where the output is 0 W and (C) is 200 W is shown respectively.

FIG. 3 is an explanatory view showing a heating region of a turntable in a conventional microwave oven for each power supply frequency, (A) output 90 W, (B) output 110 W, (C) output 200 W.
The case of is shown respectively.

[Explanation of symbols]

1 ... Combination range, 2 ... Heating chamber, 4 ...
Turntable, 9 ... Magnetron, 10 ... Controller, 12 ... Synchronous motor.

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Claims (2)

[Claims] 1. An electromagnetic wave generating means for heating and cooking an object to be cooked in a heating chamber with electromagnetic waves, a turntable on which the object to be cooked is placed and which is rotated by a synchronous motor, and the electromagnetic wave while driving the synchronous motor. A microwave oven provided with a controller that controls ON / OFF of a generating unit at a preset heating cycle, wherein the heating cycle has an integer multiple n (where n <50) that varies depending on a power supply frequency. The microwave oven set to a time that does not match a multiple of any of the rotation cycles. 2. The microwave oven according to claim 1, wherein the heating cycle is longer than any rotation cycle of the turntable and smaller than twice any rotation cycle of the turntable.