JP2577503B2 - microwave - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a microwave oven that performs automatic finishing control of food using a sensor.

[Prior art]

Conventionally, this type of microwave oven measures the weight of food in a container using, for example, a weight sensor, calculates a heating time according to the measured weight, and energizes the magnetron for the heating time. It has been known.

However, the above-mentioned conventional microwave oven heats food for a time corresponding to the weight of the food in the container, so that a light container and a heavy container are heavy. Putting the food in the container has the disadvantage that the heating time per unit weight of the food becomes longer, the finishing temperature becomes higher, and a uniform finishing of the food cannot be obtained. Further, in this heating control method, since the initial temperature of the food is not taken into consideration at all, the food taken out of the refrigerator (initial temperature of 5 ° C.) and the food left in the summer room (initial temperature of 30 ° C.) However, there is a drawback that the finishing temperature becomes high and a uniform finishing cannot be obtained. Furthermore, the weight sensor used is
Since it is more expensive than other humidity sensors and optical sensors, there is a problem that the manufacturing cost of the microwave oven is increased. Therefore, an object of the present invention is to pay attention to a relatively inexpensive and highly sensitive humidity sensor, and to control the heating time while monitoring the steam generated from the food at the time of heating by using the humidity sensor, whereby the weight of the container and the weight of the food are controlled. An object of the present invention is to provide a microwave oven that can obtain a uniform finish regardless of the initial temperature and can reduce manufacturing costs.

[Means for Solving the Problems]

In order to achieve the above object, a microwave oven of the present invention includes a magnetron for irradiating microwaves on food on a turntable in a heating chamber to heat the food, a humidity sensor for detecting humidity in the heating chamber, and a microwave placed on the turntable. An optical sensor that detects reflected light from the food that is swirled and turned, and a detection signal from the optical sensor is monitored over the rotation cycle of the turntable, and the number of the food is determined by the number of minimum values appearing in the detection signal. Discriminating means for discriminating, target value setting means for setting an optimal target humidity in the heating chamber at the time of finishing the cooking, according to the number of foods discriminated by the discriminating means and the type of food given in advance; When the detection signal reaches the optimum target humidity level, the power supply control means for stopping power supply to the magnetron is provided. In addition, the target value setting means sets the lower limit time and the upper limit time of energization based on the number and type of foods, and the energization control means controls the energization regardless of the detection signal from the humidity sensor. The energization may be performed for the lower limit time or longer, and may not be performed for the energization upper limit time or longer.

[Action]

When microwave heating starts due to the start of energization of the magnetron, the optical sensor detects reflected light from the food that turns on the turntable in the heating chamber. The determination means monitors the detection signal from the optical sensor, and determines the number of foods based on the number of minimum values appearing in the detection signal during one rotation of the turntable. Next, the target value setting means sets an optimum target humidity in the heating chamber at the time of finishing the cooking according to the number of foods determined by the determination means and a type of food given in advance from the operation panel, for example. When the detection signal from the humidity sensor that detects the humidity in the heating chamber reaches the optimal target humidity level,
Power supply to the magnetron is stopped. Thus, the cooking by the microwave heating is completed, and the food is always finished in a uniform and optimum state irrespective of the weight of the container or the initial temperature. If the target value setting means sets the lower limit time and the upper limit time of energization, and the energization control means performs the energization based on the upper and lower limit times, if the humidity sensor breaks down halfway, Even if the operation becomes poor due to noise or the like, the heating is not insufficient or excessive, and an appropriate finished state can always be obtained.

【Example】

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a longitudinal sectional view showing one embodiment of a microwave oven according to the present invention, wherein 1 is a heating chamber, 2 is provided at the bottom of the heating chamber 1 and milk as food A in a cup 3 is provided. A turntable that is mounted and rotated by a motor (not shown);
Is a magnetron for irradiating microwaves to the food A from obliquely above, 5 is a humidity sensor for detecting humidity in the heating chamber 1, 6 is emitted from a light source (not shown) at a fixed position, and is reflected by the turntable 2 or the food A. An optical sensor (for example, a CdS photoconductive element) that detects the reflected light. The microwave oven has a control circuit as shown in FIG. The control circuit includes a bridge circuit 7 including a pair of the humidity sensors 5 and a pair of resistors.
And a microcomputer 9 that controls power supply to the magnetron 4 based on an output signal of the amplifier 8 and a detection signal of the optical sensor 6. The microcomputer 9 monitors a detection signal from the optical sensor 6 over a rotation cycle Tr of the turntable 2 stored in advance as shown in FIG. 3 and determines a minimum value appearing in the detection signal as a determination unit. The number of foods A is determined based on the number. The minimum value of the waveform of the detection signal shown in FIG. 3 indicates a state where the light of the light source is absorbed by the food A and the amount of light received by the optical sensor 6 is reduced. The solid lines and broken lines in the figure indicate the case where there are two and one cup 3 containing milk, respectively, since the reflected light increases the amount of light received by the optical sensor 6, respectively. Further, the microcomputer 9 serves as a target value setting unit in accordance with the number of foods A determined by the determination unit and data representing the type of food input from an operation panel (not shown) or the like. At the same time, the optimal target humidity in the heating chamber 1 is set, and the lower limit time of power supply and the upper limit time of power supply are set. That is, as the number of cups 3 containing milk increases, the amount of water vapor generated due to microwave heating also increases. Therefore, the level of the detection signal to be output from the humidity sensor 5 at the time of finishing the cooking is K in FIG. as shown in ₁ and K _4, different in the case cups of one and four. Therefore, the goal setting means:
As shown in FIG. 5, the optimal target humidity is set as K ₁ , K ₂ , K ₃ , K ₄ according to the number of cups. In addition, energization lower limit time Tmin
And energizing the upper limit time Tmax, as shown in FIG. 6, the optimum target humidity is set to K _1, as appropriate finishing state is obtained around the heating time T ₁ corresponding to the K ₁ The left and right sides of the lever are set at a constant width. Further, the microcomputer 9 as an energization control unit stops the energization to the magnetron 4 when the detection signal from the humidity sensor 5 reaches the optimum target humidity level set by the target value setting unit, and Irrespective of the detection signal, the current is supplied for the current supply lower limit time Tmin or more, and is not supplied for the current supply upper limit time Tmax or more. The operation of the microwave oven having the above configuration will be described next with reference to FIG. Food A (milk) by starting power supply to magnetron 4
When the microwave heating starts, the optical sensor 6 detects the reflected light of the food A turning on the turntable 2, and the microcomputer 9 monitors the detection signal of the optical sensor 6, and the turntable 2 The number of cups 3 is determined based on the number of minimum values appearing in the detection signal during one rotation (see FIG. 3) (see step S1). Next, the microcomputer 9 determines the optimum target humidity Ki (for example, i = 1 to 4) in the heating chamber 1 at the time of finishing the cooking in accordance with the determined number and the type of the food A input by the keys on the operation panel. ), And the lower and upper limit times Tmin, Tmax (6th
(See the figure) (see step S2). The microcomputer 9 keeps energizing the magnetron 4 for the energizing lower limit time Tmin (see step S3), and then the detection signal from the humidity sensor 5 that detects the humidity in the heating chamber 1 becomes the optimal target humidity Ki. It is determined whether or not it has reached (see step S4).
While stopping the energization to terminate the microwave heating,
If not, it is determined whether or not the energization time has become equal to or greater than the above-described energization upper limit time Tmax (see step S5). Then, while the energization is continued as long as it does not exceed Tmax, the determination process of the above-described step S4 is performed, and when it becomes Tmax or more, the energization is immediately stopped to end the microwave heating. As described above, in the present invention, the heating time (Ti ← Ki) is optimally controlled according to the number i of the foods A while detecting the water vapor generated from the foods A by the heating with the relatively inexpensive humidity sensor 5. Therefore, unlike the control by the conventional weight sensor, it is possible to always obtain a uniform and best cooked finish regardless of the weight of the container (3) or the initial temperature of the food A, and to obtain a microwave oven. Manufacturing costs can be reduced. In the above embodiment, the microcomputer 9 sets the lower limit and the upper limit time Tmin, Tmax together with the optimum target humidity Ki, and continues the power supply at least during the lower limit time Tmin.
Also, since the energization is always stopped when the energization upper limit time Tmax is exceeded, even if the humidity sensor malfunctions due to failure or noise during heating, the heating does not become insufficient or excessive, There is an advantage that an appropriate finished state can always be obtained. In the above embodiment, the microcomputer is provided with the discriminating means, the target value setting means, and the energization control means collectively, but these may be provided separately.

【The invention's effect】

As is clear from the above description, the microwave oven of the present invention detects water vapor emitted from food by microwave heating with a humidity sensor, and detects reflected light from food rotating on a turntable with an optical sensor, The number of foods is determined by the number of minimum values appearing in the detection signal of the optical sensor by the determining means, and the optimum target humidity in the heating chamber at the time of finishing the cooking is set by the target value setting means according to the determined number and the like. When the sensor detection signal reaches this optimal target humidity level,
Since the power supply to the magnetron is stopped by the power supply control means, unlike the heating time control by the conventional weight sensor, a uniform and best cooked finish is always obtained regardless of the weight of the container or the initial temperature of the food. Thus, the manufacturing cost of the microwave oven can be reduced.

[Brief description of the drawings]

1 is a longitudinal sectional view showing one embodiment of a microwave oven according to the present invention, FIG. 2 is a control circuit diagram of the above embodiment, FIG. 3 is a diagram showing detection signals of an optical sensor, and FIG. FIG. 5 is a diagram showing an example of setting an optimum target humidity, FIG. 6 is a diagram showing an example of setting an upper limit and a lower limit time of energization, and FIG. 7 is a diagram showing a control flow of the control circuit. It is a flowchart. 1 ...... the heating chamber, 2 ...... turntable, 3 ...... cups, 4 ...... magnetron, 5 ...... humidity sensor, 6 ...... light sensor, 9 ...... microcomputer, K ₁ ~K ₄ ...... optimum target humidity , Tmin: Lower energization time, Tmax: Upper energization time, A: Food.

Claims (2)

(57) [Claims] A magnetron for irradiating microwaves to a food on a turntable in the heating chamber to heat the food; a humidity sensor for detecting humidity in the heating chamber; and reflected light from the food rotating on the turntable. An optical sensor for detecting the number of the foods by monitoring a detection signal from the optical sensor over the rotation cycle of the turntable, and determining the number of the foods by the number of minimum values appearing in the detection signal; Target value setting means for setting an optimum target humidity in the heating chamber at the time of finishing the cooking according to the number of foods determined in advance and the type of food given in advance, and a detection signal from the humidity sensor is used to determine the optimum target humidity level. A microwave oven comprising an energization control means for stopping the energization of the magnetron when the temperature of the microwave oven is reached. 2. The target value setting means sets an energization lower limit time and an energization upper limit time based on the number and type of foods, and the energization control means sets the energization lower limit regardless of a detection signal from a humidity sensor. 2. The microwave oven according to claim 1, wherein the energization is performed for the energization lower limit time or more and the energization is not performed for the energization upper limit time or more.