JP2534763B2 - microwave - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a microwave oven capable of automatically determining the type of food and controlling heating accordingly.

(Prior Art) Conventionally, as a microwave oven of this type, for example, Japanese Patent Publication No.
There is one described in Japanese Patent No. 7453. This product is equipped with a temperature sensor that detects the exhaust temperature and a gas sensor that detects gases such as steam in the exhaust.The type of food is judged based on the change rate of the output voltage of the gas sensor, and based on the judgment result. Change the finish detection level of the temperature sensor, and then
The heating is stopped when the output voltage of the temperature sensor reaches the partition detection level.

(Problems to be Solved by the Invention) By the way, even if the food to be heated has the same weight, the state of change in the output voltage of the gas sensor is greatly different depending on whether the food is frozen food or not. The example is the sixth
As shown in the figure, A (solid line) is the frozen food,
B (dotted line) is the non-frozen food. In this case, if the weight of the non-frozen food becomes large, the output voltage of the gas sensor becomes C
Since it approaches the non-frozen food B as shown by (two-dot chain line),
As in the prior art, by simply determining the type of food based only on the rate of change of the output voltage of the gas sensor, whether it is a frozen food or a large non-frozen food cannot be distinguished at all, and is very It's a problem.

The present invention has been made in consideration of such circumstances.
Therefore, it is an object of the present invention to provide a microwave oven capable of distinguishing frozen foods from non-frozen foods and performing automatic cooking according to freezing / non-freezing without error.

[Configuration of the Invention] (Means for Solving the Problems) A microwave oven of the present invention is a microwave oven for heating food stored in a heating chamber by a magnetron, and a weight sensor for detecting the weight of the food, A gas sensor for detecting gas such as steam generated from the food is provided, and when cooking is started, a check time from heating start is determined based on the output of the weight sensor, and a refresh operation for ventilating the heating chamber is performed. To start heating, determine whether the food in the heating chamber is frozen food based on the amount of change from the extreme value of the output of the gas sensor when the check time is reached, and in the determination result Based on this, the subsequent heating conditions are determined and the operation of the magnetron is controlled.

(Operation) When cooking is started, the check time from the start of heating is determined based on the output of the weight sensor, and the heating chamber is ventilated by the refresh operation. Due to this ventilation, residual gas and residual heat in the heating chamber are discharged. Then, heating is started. This heating produces gas from the food,
Since the refresh operation is performed first, the gas generation status is changed according to the condition of the food. Therefore, when the food is frozen food, the amount of change from the gas output, that is, the extreme value of the output of the gas sensor, is small, whereas when it is non-frozen food, the output of gas, that is, the extreme value of the output of the gas sensor, is small. The amount of change from is large. However, this is under the same weight and the same time condition.

Then, when the check time is reached, it is determined whether or not the food is a frozen food based on the amount of change from the extreme value of the output of the gas sensor. In this case, the check time is determined based on the weight of the food, and since there are no error factors of the gas sensor such as residual gas and heating and the gas detection accuracy is good, whether or not the food is a frozen food can be determined without error. Then, since the subsequent heating conditions are determined based on the result of the determination and the operation of the magnetron is controlled, good heating control according to the food can be performed.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. Reference numeral 1 is a heating chamber in which a saucer 3 on which food 2 is placed is arranged. Reference numeral 4 denotes a magnetron for heating the food 2 at high frequency, which is connected to a power source 7 via a high voltage transformer 5 and a relay contact 6. On the other hand, 8 is the saucer 3
A weight sensor that detects the weight of the food 2 placed on the food, and its output signal is input to the control circuit 10 via the weight detection circuit 9. The control circuit 10 has a microcomputer (not shown), and controls the operation of the magnetron 4 by controlling the opening and closing of the relay contacts 6 according to the control programs shown in FIGS. 4 and 5 described later. 11a is a start key for inputting a cooking start signal to the control circuit 10, 11b is a "warm" key for automatically performing "warm" cooking, and this "warm" key 11b is used to "warm" non-frozen foods. Both "" and "warming" of frozen foods, that is, "thawing warming" can be automatically performed as described later. Reference numeral 12 is a display unit for displaying setting contents, 13 is a gas sensor for detecting gas such as steam generated from the food 2, and the gas sensor 13 is provided in an exhaust passage 14 for exhausting air in the heating chamber 1. . The output signal of the gas sensor 13 is input to the control circuit 10 via the gas detection circuit 15. The second
The figure shows the change over time in the output level of the gas sensor 13 after the start of cooking. The solid line A is a frozen food and the dotted line B is a non-frozen food, and the weights of both are equal.

Next, the control content of the control circuit 10 will be described with reference to FIGS. When warming the food 2, whether the food 2 stored in the heating chamber 1 is frozen food or non-frozen food, the user presses the "warm" key 11b and then the start key 11a. Just good. By pressing the start key 11a, first, the check time T ₁ (the time to judge whether or not the food is frozen) and the coefficients α and β (for these coefficients) are determined according to the output signal of the weight sensor 8, that is, the detected weight of the food 2. (Described later) is determined (steps P1-9).
Specifically, when the food weight is 0 to 400 g, T ₁ is 1 minute,
α is 0.05 and β is 0.2 (steps P1,2,3), and the weight is 4
When ₁ to 100g, T ₁ is 2 minutes, α is 0.06, β is 0.6 (steps P4,5,6), and when the weight is 1000g or more, T ₁
Is 4 minutes, α is 0.07 and β is 1.2 (steps P7,8,
9). The reason why the check time T ₁ is changed according to the food weight is that the food temperature rises faster and the gas (steam) is generated earlier as the food weight decreases.

After the determination of T ₁ , α, and β, the refresh operation is executed for t ₁ seconds (for example, about 10 seconds) (step P10). In this refresh operation, the magnetron 4 is not operated, only the fan (not shown) is operated to ventilate the inside of the heating chamber 1,
Eject residual gas. After this refresh operation, the operation of the magnetron 4 is started to heat the food 2 at a high frequency, and at the same time, a built-in counter (not shown) is started (step P11). This built-in counter is a hardware counter built into the microcomputer of the control circuit 10.
It measures t ₀ . The food 2 is heated by the above-described high-frequency heating, and thereby gas such as steam is generated from the food 2. In this case, since the refresh operation is performed first, there is no residual gas in the heating chamber 1, and the gas generated only from the food 2 is detected by the gas sensor 13. Further, the sensitivity of the gas sensor 13 is affected by the temperature, but since the residual heat is also removed by the refresh operation, there is no effect. Then, since the refresh operation is switched to heating, the amount of gas in the heating chamber 1 is
The gas sensor 13 has a characteristic that it decreases and then rises after reaching an extreme value, and the output of the gas sensor 13 increases and once reaches a peak value (extreme value) and then decreases. Then, when the integrated time by this counter reaches the check time T ₁ (step P12), the difference (Vs max-Vs) between the output level Vs of the gas sensor 13 and the peak value Vs max at that time is calculated, and Is compared with the comparison data D (step P13).
The comparison data D is previously stored in the microcomputer.

In this case, the peak value Vs max is determined as follows by the subroutine of FIG. That is, for example, every 2 msec after the start of cooking, the output level Vs of the gas sensor 13 is read and is set as data Vs new (step S1).
Compare ew with Vs old (step S2). The comparison data Vs old at this time is the maximum value of the output level of the gas sensor 13 up to that point. If YES is determined in step S2, that is, if Vs new> Vs old, Vs o
The data of ld is changed to Vs new, and the data of Vs max is changed to Vs new (step S3). On the other hand, step S2
When it is determined to be NO (NO), that is, when Vs new ≦ Vs old, Vold and Vs max are not changed, and the previous data is maintained.

On the other hand, when it is determined to be YES in step P13 of FIG. 4, that is, when (Vs max-Vs)> D, the amount of change in the output level Vs of the gas sensor 13 from the peak value Vs max is large. Therefore, it is determined that the food 2 in the heating chamber 1 is a non-frozen food. On the other hand, if it is determined to be NO in step P13, that is, if (Vs max −Vs) ≦ D, the amount of change from the peak value Vs max of the output level Vs of the gas sensor 13 is small, The food 2 in the room 1 is determined to be frozen food. Then, for both frozen foods and non-frozen foods, V ₀ = Vs max −Vs is calculated (steps P14, 18), and V ₀ and αVs max are compared (steps P15, 19). . After this, when V ₀ > αVs max,
The built-in counter is stopped and the accumulated time t
Read ₀ (see FIG. 2). In the case of non-frozen foods, in step P17, to determine the heating time [beta] t ₀ follow by multiplying the β in the integrated time t _0, executes the follow heating only that time [beta] t ₀ (step P23,24 ), The cooking is completed (step P25). On the other hand, in the case of frozen foods, in step P21, in terms of changing the value of beta is multiplied by 0.5 in beta, the heating time [beta] t ₀ follow by multiplying the beta after the change in the integration time t ₀ decide. Therefore, for frozen foods, the additional heating time βt ₀ is half the time for non-frozen foods. Then, when the additional heating time βt _{0 has} elapsed (steps P23, 24), the cooking is finished (step P2).
Five).

According to the above embodiment, the check time T ₁ is determined according to the weight detected by the weight sensor 8, and the change amount (Vs max-Vs) from the peak value of the output level Vs of the gas sensor 13 until the check time T ₁ is reached. It is determined whether the food 2 in the heating chamber 1 is a frozen food or a non-frozen food, depending on the amount of change (Vs max-Vs). It is possible to set the appropriate additional heating time βT ₀ according to freezing or non-freezing. Therefore, the finished state of automatic cooking can be surely made good regardless of whether it is frozen or unfrozen.

Moreover, "warm" of both frozen and non-frozen foods
Since the number of keys can be set with one key 11b, the number of keys can be reduced while being multifunctional, and the operability can be improved, and the operation panel can be downsized and the cost can be reduced.

In the above embodiment, the check time T ₁ is changed in 3 steps according to the weight of the food, but it may be changed in 2 steps, 4 steps or more, or stepless (continuous change). Alternatively, in the above-described embodiment, the additional heating time βt ₀ is changed according to freezing / non-freezing. However, other heating conditions such as heating temperature may be changed.

EFFECTS OF THE INVENTION As is apparent from the above description, the present invention can eliminate the detection error element of the gas sensor by ventilating the heating chamber by the refresh operation when cooking is started, and It is possible to detect the amount of gas including the extreme value according to the food, and further determine the check time based on the output of the weight sensor, and based on the amount of change from the extreme value of the output of the gas sensor when this check time is reached. Since the frozen or unfrozen food is judged, the output of the gas sensor becomes the information in which the food weight information is taken into consideration and the detection error factor is removed, and as a result, it is possible to accurately judge whether the food is frozen or unfrozen. The finish of automatic cooking can be surely improved regardless of whether it is frozen.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention.
FIG. 1 is an overall schematic configuration diagram, FIG. 2 is a change characteristic diagram of the output level of the gas sensor, and FIG. 3 is food weight and check time.
FIG. 4 is a flowchart showing the relationship with T ₁ , FIG. 4 is a flowchart showing a main program, and FIG. 5 is a flowchart showing a program for determining the peak value Vs max of the output level of the gas sensor. FIG. 6 is a change characteristic diagram of the output level of the gas sensor for explaining the conventional technique. In the drawing, 1 is a heating chamber, 2 is food, 4 is a magnetron, 8
Is a weight sensor, 10 is a control circuit, 11a is a start key, 11b
Is a "warm" key, and 13 is a gas sensor.

Claims (1)

(57) [Claims] 1. A food in which a food stored in a heating chamber is heated by a magnetron at high frequency, comprising a weight sensor for detecting the weight of the food and a gas sensor for detecting gas such as steam generated from the food. When cooking is started, a check time from the start of heating is determined based on the output of the weight sensor, and a refresh operation for ventilating the heating chamber is executed to start heating, and when the check time is reached, Based on the amount of change from the extreme value of the output of the gas sensor to determine whether the food in the heating chamber is frozen food, based on the result of the determination determines the subsequent heating conditions to control the operation of the magnetron A microwave oven characterized by being configured to.