JPH0570914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an electromagnetic cooking device in which when a metal cooking container is placed in a place where alternating magnetic lines of force are generated, an eddy current flows through the container and generates heat due to the resistance.

<Prior art> In recent years, electromagnetic cookers have become popular due to their safety and cleanliness, but their functions are almost the same as gas stoves, and some models are equipped with a fry warming function and a timer function to easily control the temperature. It's just that it's being done. Therefore, if an electromagnetic cooker has a function such as automatically boiling water, detecting the boiling state, and then keeping the water warm, it would be a very convenient heating appliance.

However, the temperature of an induction cooker is indirectly detected by a temperature sensor placed on the back of the ceramic plate on which the pot (cooking container) is placed, and it is difficult to accurately detect the absolute temperature of the pot. This is extremely difficult because the shape of the object and the amount of the object to be heated cannot be determined.

<Purpose> Therefore, the present invention aims to provide an electromagnetic cooker that can recognize a temperature state such as a boiling state from a pattern of changes in values detected by a temperature sensor during heating, and can control the heating.

In order to achieve the above object, the present invention includes: input current detection means A for detecting the input current value to the magnetic force generating coil 1; and container temperature detection means B for detecting the temperature of the cooking container.
, an arithmetic/control circuit C connected to the output side of the input current detection means A and input current detection means B, and a magnetic force generating coil drive means D connected to the output side of the arithmetic/control circuit C. The arithmetic and control circuit C includes a first setting means for setting a sampling interval Ts1 for detecting the temperature of the container at the initial stage of heating according to the material shape of the container, and a sampling interval Ts1 once set by the first setting means. , a second setting means for changing the setting to a new sampling interval Ts2 according to the amount of the object to be heated from the middle; and a temperature measurement value Te( obtained at the sampling interval based on the first setting means and the second setting means). n) and a previous temperature measurement value Te (n-1) that is equal to or less than a predetermined value of 8, it recognizes that the object to be heated has boiled and changes the heating output; One setting means includes a material shape determination function that determines the material shape of the container based on the input current value from the input current detection means A, and container temperature detection according to the material shape of the container determined by the material shape determination function. sampling interval Ts1
and an initial setting function for initializing the sampling interval set by the first setting means.
A rising time in which the container temperature is detected by the container temperature detection means B every Ts1 and the actual time t required for the temperature to rise by a predetermined set value (Te2 - Te1) from the temperature Tel, which has risen to a certain extent at the initial stage of heating, is measured. a measurement function; and a sampling interval Ts1 once set by the first setting means is changed to a new sampling interval Ts proportional to the actual time t measured by the rise time measurement function.
It is equipped with a proportional change function to change the settings to 2.

In the above configuration, for the time series values Te(1)...Te(n) of the container temperature detection means B detected at a certain sampling interval, if Te(n)−Te(n−1)<δ, then At that point, the temperature is saturated and recognized as a boiling state, and the heating output is changed.

By the way, the materials and shapes of cooking containers (pots) used in electromagnetic cookers vary, and the heating power also varies accordingly. In other words, a standard iron pot will give you maximum heating power, while a high-end stainless steel pot will usually only produce about half the heating power.

Therefore, in the present invention, the material shape determination function of the first setting means cuts the material shape of the container based on the input current value from the input current detection means A, and the initial setting function cuts the material shape of the container. A corresponding sampling interval Ts1 for container temperature detection is initially set, and temperature detection is performed at each sampling interval Te1.

Therefore, for example, when heating an iron pot with a high heating output, if the temperature is detected at the sampling interval for a stainless steel pot with a low heating output, the interval will be large, so the food cooked in the iron pot will be detected at the next sampling interval. However, in the present invention, the material, size, etc. of the cooking container are determined based on the input current value to the magnetic force generating coil, and the sampling interval is determined. Prevents cooking from spilling.

Next, the temperature increase pattern changes depending on the amount of the object to be heated and its initial temperature. However, the time required to reach a certain temperature Te2 from a certain temperature Te1 is proportional to the amount, assuming that the specific heat of the object to be heated is constant.

Focusing on this, in the present invention, the sampling interval Ts1 once set by the first setting means is changed to a new sampling interval Ts2 according to the amount of the object to be heated by the second setting means. There is.

That is, first, the container temperature is detected by the container temperature detection means B at every sampling interval Ts1 set by the first setting means, and the temperature Te1, which has risen to a certain extent at the initial stage of heating, is detected by the rise time measuring function of the second setting means.
The actual time t required for the temperature to rise by a predetermined set value (Te2 - Te1) is measured. Next, with the proportional change function, the sampling interval Ts1 once set by the first setting means is changed to a new sampling interval proportional to the actual time t measured by the rise time measurement function.
Change the setting to Ts2.

This can prevent the sampling interval from being incorrectly set due to the amount of food to be heated or the initial temperature.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. Fig. 1 is a combination diagram of the electronic circuit and block diagram circuit of the entire embodiment of the electromagnetic cooker of the present invention, Fig. 2 is a diagram showing the correction of the sampling interval according to the input current, and Fig. FIG. 4 is a flowchart of the arithmetic and control circuit.

Therefore, as shown in these figures, the present invention includes an input current detection means A consisting of a current transformer CT for detecting the input current value to the magnetic force generating coil 1 and a current detection circuit 2 connected to the current transformer CT. , a temperature sensor 3 such as a thermistor that indirectly detects the temperature of a cooking container such as a pot through a ceramic plate.
, a container temperature detection means B consisting of a temperature detection circuit 4 connected thereto, an A/D conversion circuit 5 connected to the output sides of the current detection circuit 2 and temperature detection circuit 4, and a container temperature detection means B consisting of a temperature detection circuit 4 connected thereto; A microcomputer-made arithmetic/control circuit C connected to the output side, that is, the output side of the input current detection means A and container temperature detection means B, and a drive for a magnetic force generating coil connected to the output side of the arithmetic/control circuit C. and means D.

The driving means D includes a driving circuit 6, an oscillation circuit 7 connected to the input side thereof, and an output changing switching element connected to the output side of the driving circuit 6.
It is composed of Tr.

The arithmetic/control circuit C also stores a predetermined value δ of the difference between the temperature measurement value Te(n) obtained at an appropriate sampling interval and the previous temperature measurement value Te(n-1).
It is equipped with a function that recognizes that the object to be heated has boiled when the temperature is below and changes the heating output. That is, the sampling interval (Ts1 or
If Te(n)-Te(n-1)<δ for the time-series value Te(1)...Te(n) detected by the temperature sensor 3 every Ts2), the temperature is saturated and the state is boiling. Recognize that it is.

Here, as a means for setting the above-mentioned appropriate sampling interval, a first setting means for setting a sampling interval Ts1 for detecting the temperature of the container at the initial stage of heating according to the material shape of the container, and a first setting means are used to set the sampling interval once. From the middle of the sampling interval Ts1,
New sampling interval according to the amount of heated material
A second setting means for changing the setting to Ts2 is provided.

The first setting means is the input current detection means A.
A material shape determination function that determines the material shape of the container based on the input current value (which differs depending on the type of cooking container), and a sampling interval for container temperature detection according to the material shape of the container determined by the material shape determination function. It also has an initial setting function for initializing Ts1.

The second setting means detects the container temperature using the container temperature detection means B at every sampling interval Ts1 set by the first setting means, and changes the temperature from the temperature Te1, which has risen to a certain extent at the initial stage of heating, to a predetermined set value (Te2-
A rise time measurement function that measures the actual time t required for the temperature to rise by Te1), and a sampling interval Ts1 once set by the first setting means, which is proportional to the actual time t measured by the rise time measurement function. It is equipped with a proportional change function to change the setting to a new sampling interval Ts2.

Note that 8 is an AC power supply, 9 is a rectifier circuit, and L is a smoothing coil.

Note that the materials and shapes of the cooking containers (pots) used in electromagnetic cookers vary, and the heating power also varies accordingly. In other words, a standard iron pot will give you maximum heating power, while a high-end stainless steel pot will usually only produce about half the heating power. Therefore, in order to correct the fluctuation in temperature change due to this heating output, the first setting means of the arithmetic/control circuit C detects the input current from the current transformer CT, and uses the output to adjust the temperature at each constant power as shown below. Determine the sampling interval to perform detection.

I×Ts1=c c: constant, I: input current, Ts1: sampling interval FIG. 2 shows how the temperature change pattern is corrected in this way. The steps in the flowchart of the arithmetic/control circuit C that performs the correction are S1 to S5.

Next, adding an explanation to the fact that the temperature rise pattern changes depending on the amount of the object to be heated, the amount cannot be automatically measured, and it is not preferable to have the user set it, as it would make it difficult to use. Therefore, we have focused on the fact that the time it takes to reach a certain temperature is proportional to the amount of heat, assuming that the specific heat of the object to be heated is constant.

In FIG. 3, for example, it is assumed that water is boiled, so the specific heat can be considered to be always constant. In order to eliminate the influence of the initial temperature of the heated water, the second setting means is used to calculate the actual time required for the temperature to rise by a certain value (Te2 - Te1) from the value Te1 at which the temperature has risen to a certain extent. t is measured, and a value proportional to the time t is set as the subsequent sampling interval Ts2. That is, the temperature Te1 to Te2
If the time to reach temperature is t, then Ts2 = k x Ts1 x t Ts2: New sampling time k: Coefficient Ts1: Previous sampling time t: Actual time required for temperature rise. Figure 3 shows how this is corrected. shown. The flowchart steps of the arithmetic/control circuit C that performs the correction are S6 to S10. If Te(n)−Te(n−1)<δ for the time series values Te(1)...Te(n) of the temperature sensor 3 detected at a certain sampling interval, the temperature is saturated and boiling occurs. Recognize it as a state. And this is the arithmetic/control circuit C
This is shown in steps S11 to S14 of the flowchart. By combining the two corrections as described above, good boiling detection becomes possible.

Note that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that many modifications and changes can be made to the above-mentioned embodiments within the scope of the present invention.

<Effects> As is clear from the above explanation, according to the present invention, when the difference between the temperature measurement value obtained at a certain sampling interval and the previous temperature measurement value becomes equal to or less than a predetermined value, the object to be heated boils. Since the heating output is changed based on the recognition, the temperature state such as boiling state can be reliably recognized and the heating control can be performed.

For example, when heating an iron pot with a high heating output, if the temperature is detected at the sampling interval for a stainless steel pot with a low heating output, the food in the iron pot will be detected at the next sampling interval because the interval is long. However, in the present invention, the first setting means determines the material of the cooking container based on the input current value to the magnetic force generating coil.
By determining the size and other factors and determining the sampling interval, you can prevent food from spilling before the next sampling time.

Here, depending on the amount of material to be heated and its initial temperature,
The pattern of temperature rise will change. However, in the present invention, the second setting means measures the actual time required for the temperature to rise by a predetermined set value from the temperature that has risen to a certain extent at the initial stage of heating, and then calculates a new value proportional to the measured real time. Since the sampling interval is changed to a certain sampling interval, it is possible to prevent the sampling interval from being incorrectly set due to the amount of food to be heated or the initial temperature.

[Brief explanation of the drawing]

FIG. 1 is a combination diagram of an electronic circuit and a block circuit of an embodiment of the electromagnetic cooker of the present invention, and FIG. 2 is a diagram showing correction of the sampling interval according to the input current.
FIG. 3 is a diagram showing the correction of the sampling interval based on the amount of heated material (load amount), and FIG. 4 is a flowchart of the calculation/control circuit. A: Input current detection means, B: Container temperature detection means, C: Arithmetic/control circuit, CT: Current transformer,
D: driving means, Tr: switching element, TS1,
TS2: Sampling interval for detection, T(n): Temperature measurement value, δ: Predetermined value, 1: Magnetic force generating coil, 2: Current detection circuit, 3: Temperature sensor, 4: Temperature detection circuit, 5: Conversion circuit, 6 : Drive circuit, 7: Oscillation circuit.

Claims (1)

[Scope of Claims] 1. Input current detection means for detecting the input current value to the magnetic force generating coil; Container temperature detection means for detecting the temperature of the cooking container; The input current detection means and the container temperature detection means It is equipped with an arithmetic and control circuit connected to the output side, and a driving means for a magnetic force generating coil connected to the output side of the arithmetic and control circuit, and the arithmetic and control circuit has a heating function according to the material shape of the container. a first setting means for setting an initial sampling interval for detecting the container temperature; and a first setting means for changing the sampling interval once set by the first setting means to a new sampling interval according to the amount of the object to be heated. a second setting means; and when the difference between the temperature measurement value obtained at the sampling interval based on the first setting means and the second setting means and the previous temperature measurement value becomes equal to or less than a predetermined value, the object to be heated boils. and a means for changing the heating output by recognizing that the first setting means has: a material shape determining function for determining the shape of the material of the container based on the input current value from the input current detecting means; and an initial setting function for initially setting a sampling interval for container temperature detection according to the material shape of the container determined by the shape determining function, and the second setting means is configured to detect the container at each sampling interval set by the first setting means. a rising time measurement function that detects the temperature of the container with the temperature detection means and measures the actual time required for the temperature to rise by a predetermined set value from the temperature that has risen to a certain extent at the initial stage of heating; An electromagnetic cooking device characterized by comprising a proportional change function that changes the set sampling interval to a new sampling interval that is proportional to the real time measured by the rise time measurement function.