JPH0228057B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to microwave ovens and food preparation methods.

BACKGROUND OF THE INVENTION Microwave ovens can cook, defrost, or reheat food extremely quickly, but because the heat energy is generated within the food itself by stirring the food molecules, the outer edges of the food may brown. does not reach the required temperature. This drawback has been addressed by providing known microwave ovens with some kind of heating means that is different from the microwave generator. For example, UK patent application no. 1172918
No. 1 and No. 1332122 describe ovens that have a thermal heating element in addition to a microwave generator.

Known microwave ovens employ different methods of using two forms of energy: microwave energy and thermal energy. One known oven generates thermal energy only during a first cooking period and subsequently generates microwave energy only during a second cooking period, and the conversion from thermal energy to microwave energy is automatic. It is done. During the first period, the food is not internally cooked by the thermal energy;
The surface is baked to a crispy or golden brown color. During the second period, when only microwave energy is applied to the oven, the core of the food is heated, resulting in the generation of steam, which is passed through the periphery of the already crispy or browned food to the outside. I have to run away. As a result, the outer periphery of the food contains steam and becomes soft and unpalatable. The oven is vented during the second period to remove steam. As a result, the heat already generated during the first period is lost and the temperature in the cooking chamber decreases, leading to a reduction in the quality of cooking of certain foods, especially pies and the like.

A second known microwave oven is characterized in that only microwave energy is generated during the first cooking period;
Subsequently, only thermal energy is generated within a second cooking period, operating in the opposite order to the first one. 1st
During this period, the oven cooking chamber is vented to remove steam by forced air flow. At the beginning of the second period, the vent is closed and heat energy is applied to bake the food product.

Both of these known microwave ovens are
Because vapor removal occurs during the period of generation of microwave energy, problems associated with vapor dispersion cannot be successfully addressed. Excessive steam condenses on cold oven surfaces and also makes food soft or mushy. Increasing ventilation to remove steam will reduce the temperature of the oven, while providing more heat energy will cause the outer edges of the food to burn before the center of the food is cooked.

The present invention provides a microwave oven and food cooking direction in which sufficient heat is provided within the cooking chamber of the oven to dispose of the steam emanating from the food when the food is cooked by microwave energy. purpose. To achieve this purpose, thermal energy is used simultaneously with microwave energy.
Provided continuously for at least the majority of the cooking period.

Microwave ovens are known in which microwave energy is applied simultaneously with thermal energy. However, in general, such known ovens are
It was a large commercial or industrial oven designed for high power. This means that the power required for microwave generators and thermal heating elements for various types of cooking is
This means that the power input level to the oven has been severely limited. In contrast, the present invention is a compact, home-use designed
It relates to ovens that can be connected to household electrical outlets, which have specific power limitations that vary from country to country. This invention relates to the provision of an oven designed for operation in countries such as Japan where household electrical outlets have a power limit of 1500 watts.

Microwave ovens are also known which have a fan so that hot air heated by the thermal heating means is distributed over the food being cooked. The success of cooking in such a microwave depends on the precise selection of many factors, such as the air convection pattern within the oven cooking chamber. One commercially available oven introduces heated air into the cooking chamber through a central portion of the back wall of the cooking chamber;
The air is directed forward and then split into two streams, flowing back along the side walls of the oven galley and then exiting the galley at two locations on the back wall of the galley. This airflow pattern is
When food is being cooked by microwave energy, steam generated from the food is not always removed satisfactorily. If the steam produced as a result of cooking is not removed by a stream of hot air,
Pies in particular become soft or mushy,
That's a problem.

SUMMARY OF THE INVENTION In accordance with one aspect of the invention, a small microwave oven designed to be powered from a household electrical plug rated not to exceed 1500 watts is provided with microwave energy in the cooking chamber of the oven. a rotatable turntable at the bottom of the cooking chamber and a thermal heating means capable of heating the air inside the oven cooking chamber and simultaneously supplying thermal energy to the oven cooking chamber. control means operative to continuously supply microwave energy to the cooking chamber, whereby the microwave energy heats the interior of the food;
The thermal energy also removes the resulting steam and browns the external surface of the food product, the thermal heating means comprising an electrical heating element and fan means for circulating air through the element and through the cooking chamber, the fan means heating the food. A forced stream or air heated by a heating element enters the cooking chamber from one side of the cooking chamber, passes over the turntable, and exits the cooking chamber from the other side of the cooking chamber. .

Preferably, the oven cooking chamber has a back wall, the rear side of which is a chamber containing an electrical heating element;
The back wall has an opening on said one side, which allows heated air to enter the cooking chamber from a portion of the cooking chamber which is forced by a fan and which occupies the majority of the height of the cooking chamber; A fan constituting the fan means is provided near the bottom corner of the other end.

Preferably, the control means is operative to provide a continuous supply of microwave energy simultaneously with a continuous supply of thermal energy during a first cooking period which is a major part of the total cooking period; The cooking period is followed by a final cooking period in which only thermal energy is applied to the cooking chamber. This is achieved by control means comprising two timers, one for the microwave generator and one for the thermal heating means, respectively.

The supply of thermal energy is advantageously increased at the beginning of the final cooking period in order to take advantage of the power that becomes available as a result of the cessation of the generation of microwave energy at the end of the first cooking period. Preferably,
The electric heating element and fan means are activated throughout the cooking period, and the oven further includes another electric heating element that is activated only during the final cooking period when the microwave generator is deactivated. . This further electrical heating element may be attached to the top of the oven cooking chamber to form a grill element.

In accordance with another aspect of the invention, a method of cooking food in a small microwave oven designed to be powered from a household electrical outlet rated not to exceed 1500 watts continues into the cooking chamber of the oven in which the food is cooked. and simultaneously supplying microwave energy to the cooking chamber, whereby the microwave energy heats the interior of the food product and the thermal energy removes the resulting steam and heats the exterior of the food product. Brown the surface,
Thermal energy is supplied by circulating air convection;
The flow is forced by a fan to pass through an electric heating element, enters the oven cooktop from one side of the oven cooktop, passes through the food being rotated on the turntable, and passes through the oven cooktop. exit.

Preferably, cooking begins in a cold oven, in other words the food product is placed in a cold oven before the start of the cooking chamber. Microwave energy is supplied at levels from 175 watts to 225 watts,
Preferably it is supplied in the order of 200 watts. microwave energy is provided during a first cooking period;
Only thermal energy is then supplied to the cooking chamber during the final cooking period to completely remove the steam and to finally brown the food. Preferably,
When the microwave energy supply ends, the thermal energy supply is increased, so that the oven derives substantially maximum power throughout the cooking period. For example, if microwave energy is being delivered at 200 watts, the final cooking period will require an extra 400 watts of thermal energy, considering that typical microwave energy sources are approximately 50% efficient. Available.

The microwave oven according to the invention will be described by way of example with reference to the accompanying drawings.

Referring to Figure 1, the microwave oven:
It has a casing 1 fitted with a hinged door 2 for sealing a cooking chamber 3. The upper wall of the cooking chamber is fitted with an electric heating element 4 (grill element), and the bottom of the cooking chamber is provided with a turntable 5 for rotating the food during cooking. A shelf guide 6 is provided on the side wall of the cooking chamber 3, and a perforated plate 9 is provided on the back wall of the cooking chamber 3 via a main heat convection element 8 (FIG. 2).
A fan 7 is provided for circulating air through.

FIG. 2 shows the components of the oven's electrical circuit. Power from the mains is supplied to a 15 amp fuse 1
2, magnetron cutout 13, and mains on/off switch 14. When switch 14 is closed, 100V power at 50/60Hz is applied to galley lamp 15 and cooking magnetron 1.
7 air blower motor 16. The thermal convection timer switch has interlocking contacts 18, 18a. The contacts 18 include a motor 19 for the fan 7, a galley thermostat 20 connected in series with the main heat convection element 8 of approximately 1 kW, a relay coil 22, and a relay contact 23 connected in series with the grill element 4 of 400 watts.
connected to.

Door switch 24, microwave timer switch 25, and cooking start switch 26 are connected in series by a power supply line 27 that conducts power to magnetron 17 for supplying microwave energy to the cooking chamber. The contact 18a and the thermal convection timer motor 36 are connected to the power supply line 27 and the neutral line 32.
The same applies to a relay coil 33 connected between and controlling the relay contact 23 and another contact 34. A thermal convection "on" lamp 30 is connected in parallel across the timer motor 36. A microwave timer motor 37 and a microwave "on" lamp 38 are connected between power line 27 and neutral line 32 at the locations shown. A turntable motor 39 for the turntable 5 is connected between the center contact of the relay contact 34 and the neutral line 32.

Relay 22 controls normally closed relay contacts 40 connected between power line 27 and neutral line 32 along with microwave energy selector switch 42 and relay coil 35 . The transformer 44 takes out power to the magnetron 17. Switch 45 is controlled by relay coil 35. Switch 45 isolates one of the two parallel connected capacitors 46 when open, thereby causing the magnetron to draw low power. When the relay switch 45 is closed, the two capacitors 46 are in circuit and the magnetron 17 draws high power. At low power, the magnetron supplies approximately 200 watts into cavity 3, and at high power, the magnetron supplies approximately 650 watts into cooking chamber 3. Magnetrons are about 50% efficient, so the power drawn by the magnetron is about 2 times the energy delivered to the galley in each case, low power and high power.
It's double. To provide 200 watts of output into the cooking chamber, the magnetron requires 360 watts of input power.

Returning to FIG. 1, control panel 10 controls the following: switch 42 for selecting high and low microwave energy, motor 37;
a rotation timer 50 for setting the time up to a maximum of 60 seconds that the magnetron is operated accordingly; a microwave "on" lamp 38; a heat convection "on" lamp 30;
Main switch 14, rotary knob 5 that changes the setting of thermostat 20 between 50°C and 250°C
2. It has another rotary timer 53 which controls the motor 36 and thus sets the time up to a maximum of 60 seconds during which thermal energy is generated, and a push button 54 which controls the switch 26.

The oven is used from a cold start in a "mixed facility" mode, ie thermal energy and microwave energy, as follows.

(a) Microwave timer 50 is set to a desired time, for example 10 minutes.

(b) Knob 52 is rotated to set thermostat 20 to maximum.

(c) The convection timer 53 is activated for a desired time, e.g.
It is set in minutes.

(d) Door 2 is closed and cooking button 54 is pressed to close switch 26.

The turntable 5 rotates and both timers operate simultaneously so that microwave energy and thermal energy are generated simultaneously.

After a first cooking period of 10 minutes, when microwave timer 50 reaches zero, switch 25 opens, thereby isolating magnetron 17 and relay coil 33. When current no longer flows through coil 33, normally open contacts 23 are closed and contacts 34 are changed to maintain power to turntable motor 39. When the contact 23 closes, the element 4 is activated, whereby during the second heating period, the thermal heating from the element 4 is maintained for the remaining cooking time, i.e. 5 minutes, during which the thermal convection timer 53 must operate. is added to the thermal heating of element 8.

Therefore, when magnetron 17 is switched off, approximately 360 watts of available power is available to the second
is consumed by element 4 during the cooking period to ensure that the oven takes its full power rate during the entire cooking period (in this case 15 minutes).

As long as relay 22 is active (contact 18 is closed), contact 40 is open, so that regardless of the position of switch 42, the magnetron will reliably produce low power.

When convection timer 53 reaches zero, switch contacts 18, 18a open, thermal convection heating elements 8 and 4 are rendered inactive, and the cooking period ends. Lamp 38 is lit (preferably green) as long as microwave energy is being generated, and lamp 30 is lit (preferably orange) as long as thermal energy is being generated. When oven door 2 is opened, switch 24 is opened, thereby cutting off the power supply to magnetron 17 and turning off both lamps 30 and 38. A conventional shorting switch 47 is connected between lines 27 and 32 to short the magnetron 17.

Relay coil 22 also operates a shutter (or valve) 48 for venting oven cooking chamber 33 under certain conditions. The shutter 48 is the third
As shown in the figure, it is located near the top front corner of the right side wall of the cooking chamber 3. When convective heat is being supplied to the cooking chamber 3, the relay coil 22 is activated to close the shutter 48 and prevent the air flow provided by the blower motor 16 from reaching the cooking chamber 3. When convective heat is not being supplied to the cooking chamber 3, the coil 22 is deactivated, thereby opening the shutter 48 and allowing venting of the cooking chamber. During venting, air carried by the motor 16 is forced into the cooking chamber and from there into the atmosphere to remove steam from the cooking chamber.

Preferably, the power rates of the various elements may be varied. Ovens according to the invention can be designed with selected power input levels. For example, 1100,
For total inputs of 1300 and 1450 watts, the component wattage rates can be determined as follows:

1100 Watts Element 8 700 Magnetron 17 200 (360 inputs) Element 4 380 Attachments 50 1300 Watts Element 8 900 Magnetron 17 200 (360 inputs) Element 4 380 Attachments 50 1450 Watts Element 8 1050 Magnetron 17 200 (360 inputs) element 4 380 Attachments 50 This invention enables microwave ovens to operate at 100V, 50/60Hz, 1450 or
Runs very efficiently with a maximum power input of 1500 watts. By applying thermal energy and microwave energy simultaneously, when steam is generated from within the food being cooked by the microwave energy, it is removed by forcing circulation of hot air. can be done. This means that
This is particularly useful for products such as pies, which are particularly sensitive to excessive steam during cooking.

The discussion so far has been about the possibility of continuing to supply thermal energy at an increased level after the supply of microwave energy has been stopped. For some cooking items, it may be advantageous to instead continue to supply microwave energy, preferably at an increased power level, after the supply of thermal energy has ceased. When the supply of thermal energy is stopped, the cooking chamber remains hot for a period during which the supply of microwave energy may be continued. For example, when cooking foods such as daikon that require additional cooking to soften, the supply of microwave energy may be continued for a period of about one minute after the supply of thermal energy is stopped. The residual heat in the oven is sufficient to evacuate steam from the food product, thus maintaining a good balance between the generation of steam by microwave energy and the removal of this steam by thermal energy. This last minute of microwave energy may also use the full power available to the oven, thereby causing the oven to draw approximately maximum power throughout the cooking period.

The control plate 10 may be designed with touch-sensitive pads for controlling the operation of the oven instead of the control knobs described above. In this case, level settings, such as power or temperature, can be set by repeatedly touching the pad to indicate the level by increasing steps, and the level reached is indicated by display means. be done. Such a control board may be coupled to a microprocessor that provides the necessary control functions for the thermal heating elements, microwave generator, and other operational components of the oven.

A perforated plate 9 is arranged at the right end of the back wall 3a and is elongated in the vertical direction so that hot air enters the cooking chamber 3 from almost all parts with respect to the height of the cooking chamber. The fan 7 is arranged near the lower left corner of the back wall 3a,
It is electrically driven and forces the convection of the hot air so that it hits the entire food placed on the rotary turntable 5.

FIG. 3 shows the convection pattern of air within the oven. The hot air passes through the perforated plate 9 into the cooking chamber 3 (arrow 50), passes over the turntable 5 (arrow 52) and is drawn through the fan 7 into the chamber 56 behind the cooking chamber 3. A thermal heating element 8 (shown diagrammatically in FIG. 3) is arranged within the chamber 56 to heat the air before it re-enters the cooking chamber 3. The turntable 5 rotates counterclockwise as shown in FIG. 3 to maximize the relative velocity between the hot air entering the cooking chamber through the perforated plate 9 and the food rotating on the turntable 5. .

Although the air convection pattern described above is effective in heating food, the walls of the oven galley remain cool compared to known air convection patterns in which air is directed along the galley walls.

Above the fan 7, the back wall 3a has vent holes (not shown) for steam and ventilation outside the oven.

If the door is opened during cooking, the switch 24 opens, resulting in the magnetron being deactivated and the relay coil 33 causing the contacts 23 to close, thereby activating the grill element 4. Figure 2 can be understood from the circuit diagram. Therefore, the oven continues to draw full power.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an oven. FIG. 2 is an electrical circuit diagram of the oven. FIG. 3 is a schematic plan view of the oven showing the convection pattern of hot air within the oven. In the figure, 1 is a casing, 2 is a door, 3 is an oven cooking chamber, 4 is a thermal heating element, 5 is a turntable, 6 is a shelf guide, 7 is a fan, 8 is a thermal convection element, 9 is a perforated plate, 10 is a control board, 15 is a galley lamp, 16 is a blower motor, 17 is a cooking magnetron, 19 is a fan motor, 20 is a galley thermostat, 22 is a relay coil, 23 is a relay contact, 24 is a door switch, and 25 is a micro Wave timer switch, 26 is start switch, 30
is the heat convection on-lamp, 35 is the relay coil, 36
37 is a timer motor, 37 is a microwave timer motor, 38 is a microwave on-lamp, 39 is a turntable motor, 40 is a relay contact, 44 is a transformer, and 45 is a relay switch.

Claims (1)

[Scope of Claims] 1. A small microwave oven designed to be powered from a household electrical outlet rated not to exceed 1500 watts, the microwave oven for supplying microwave energy to the cooking chamber of the oven. a generator; a rotatable turntable provided at the bottom of the oven cooking chamber; thermal heating means capable of heating the air in the oven cooking chamber; and simultaneously supplying thermal energy to the oven cooking chamber and the oven. control means operative to supply continuous microwave energy to the cooking chamber, whereby the microwave energy heats the interior of the food product, and the thermal energy comprises steam generated by internal heating of the food product. and browning the external surface of the food product, the thermal heating means comprising an electrical heating element and fan means for circulating air through the heating element and through the cooking chamber, the fan means , the heating is performed such that air heated by the thermal heating means enters the cooking chamber from one side of the cooking chamber, passes over the turntable, and exits the cooking chamber from the other side of the cooking chamber. producing a forced flow of air, said control means effecting a continuous supply of said microwave energy simultaneously with said continuous supply of thermal energy during a first cooking period forming the majority of the total cooking time; and operates so that only the thermal energy is supplied to the cooking chamber in a final cooking period after the first cooking period, and the control means operates to supply the microwave at the end of the first cooking period. A microwave oven comprising means for increasing said thermal energy at the beginning of said final cooking period by utilizing power made available as a result of the cessation of energy production. 2. The oven cooking chamber has a back wall, and behind the back wall is a room in which the electric heating element is provided, and an opening is provided on the one side of the back wall, and the heated air is supplied to the fan. the cooking chamber is forced to enter the cooking chamber from an area that occupies most of the height of the cooking chamber, and a fan constituting the fan means is provided near the bottom corner of the other side of the rear wall; A microwave oven according to claim 1, wherein the microwave oven is provided with: 3. The microwave oven according to claim 1, wherein the control means includes two timers, one for the microwave generator and one for the thermal heating means. 4. said electric heating element and said fan means are in operation throughout said cooking time, and said oven is in a separate state in which said oven is in operation only during said final cooking time when said microwave generator is in an inoperative state. A microwave oven according to claim 1, comprising an electric heating element. 5. A microwave oven according to claim 4, wherein the further electrical heating element is located at the top of the oven cooking chamber to form a grill element. 6. A method of cooking food in a small microwave oven designed to be powered from a domestic power outlet rated not to exceed 1,500 watts, which comprises supplying continuous microwave energy to the cooking chamber of said oven in which the food is placed. Simultaneously supplying thermal energy to the cooking chamber, such that the microwave energy heats the interior of the food product, and the thermal energy removes steam generated by the internal heating and browns the exterior surface of the food product. ,
said thermal energy is provided by a circulating convection of air, said circulating convection being forced by a fan to pass through an electrical heating element and enter said oven cooking chamber from one side of said oven cooking chamber; passing over the food being rotated on a turntable;
exiting the oven cooking chamber from the other side of the oven cooking chamber, the supply of microwave energy being stopped after a first cooking period and only thermal energy being supplied to the cooking chamber during a subsequent final cooking period; wherein the steam is completely removed and the food product is finally browned, and the supply of thermal energy is available as a result of the discontinuation of the supply of microwave energy when the supply of microwave energy is discontinued. the oven uses approximately maximum power throughout the cooking period of the food;
Food preparation methods. 7. The method of claim 6, wherein the cooking begins with the oven cold, and the food is placed in the cold oven before cooking begins. 8. The microwave energy is from 175 Watts.
7. A method according to claim 6, wherein the cooking chamber is supplied with a level of between 225 Watts.