JP2732954B2 - Electric pot boiling control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling boiling of an electric pot.

[0002]

2. Description of the Related Art In a conventional boiling control of an electric pot, a heating device including a main heater and a heat retention heater heats a liquid stored in a container to perform boiling water, and when the boiling detecting device detects boiling, the boiling water is heated. I'm trying to stop. In principle, the detection of boiling by this boiling detector is based on the phenomenon that the rise in water temperature reaches an equilibrium state when water boils, and the rate of increase in water temperature is periodically detected, and the value is a constant value. It was determined that boiling was complete when the following conditions were reached. For this reason, the boiling state was actually maintained for several tens of seconds. Further, in order to sufficiently disperse the calcium in the water, it has been performed that the main heater is turned off for one minute and then turned on again for one minute after the detection of boiling to continue the boiling state.

[0003]

However, in such a conventional boiling control method, since the strong boiling state by the main heater is continued for a while after the boiling, a large amount of steam is released, and the peripheral devices and the like are released. Had the adverse effect of dew condensation. An object of the present invention is to solve such a problem, and an object of the present invention is to provide a method for controlling the boiling of an electric pot that can be boiled in a weakly boiled state that emits little steam.

[0004]

According to the present invention, as shown in FIG. 1, the liquid stored in a container is heated by a heating device comprising a main heater and a heat retaining heater, thereby achieving water heating. When a predetermined temperature immediately before boiling is detected (step S2), the main heater is turned off to continue water heating by the heat keeping heater (step S3), and when boiling (step S4), the heat keeping heater is turned off. (Step S5).

The predetermined temperature immediately before the boiling can be detected by fuzzy inference. That is, the boiling degree obtained by integrating the difference between the detected temperature detected per unit time from the predetermined temperature near the boiling point and the predetermined temperature for a certain period of time, and the boiling degree obtained by calculating the increase in the degree of boiling after a certain period of time. With the speed as input, and with the boiling completion degree indicating the degree of completion of the current boiling as output, set the membership function corresponding to the fuzzy set of each stage of each input and output concept,
The output from the two inputs is fuzzy inferred in accordance with the fuzzy rules between them, and the degree of completion of the output boiling is sequentially added for each unit time. When the accumulated value becomes a predetermined value of 0 or less, the predetermined value is determined. Assume that a temperature has been detected. Also,
The detection of boiling after the main heater is turned off can be regarded as boiling when a predetermined time has elapsed since the main heater was turned off, and the boiling completion degree accumulated value is continuously calculated and calculated. It is also possible to boil when it reaches zero.

[0006]

FIG. 2 shows an electric pot to which the method according to the present invention is applied, 1 is an exterior body, 2 is a lid, 3 is an inner container,
Is a water pipe. Reference numerals 5, 6, and 7 denote heating devices, of which 5 and 6 are water heaters and warming heaters, respectively, disposed on the bottom outer surface of the inner container 3, and 7 is a band heater disposed on the outer peripheral side surface of the inner container 3. is there. Reference numeral 8 denotes a temperature detecting device including a thermistor for detecting the water temperature in the inner container 3, reference numeral 9 denotes a power switch, and reference numeral 10 denotes a reboiler switch. Also,
11 is a microcomputer constituting the control device, 12
Is a membership function adjusting circuit, and fixed resistors 13a, 13a are used to make constants P, Q that determine the form of the membership function in a fuzzy inference routine to be described later variable.
This is a circuit for inputting a divided voltage between the variable resistor b and the variable resistors 14a and 14b to an AD converter of the microcomputer 11.

[0007] The microcomputer 11 operates the water heater according to a built-in program based on a water temperature detection signal detected by the temperature detection device 8, a selection signal from the power switch 9, and an on signal from the reboiler switch 10. The heater 5, the heat retaining heater 6, and the band heater 7 are controlled to execute various modes as shown in FIG. The water amount discriminating mode is a mode for discriminating the amount of water in the inner container 3. The high power water heater mode is a mode in which the water heater 5 and the band heater 7 are used as main heaters to perform water heating with high power. The standard water heater mode is the water heater This is a mode in which only the main heater is used to perform water heating, and the heat retention mode is a mode in which the heat retention heater 6 retains hot water.

When the water temperature is low when the power is turned on, the mode is the water amount determination mode, and when the temperature is high, the mode is the heat retention mode. When the water amount discrimination mode ends, the mode is changed to the high power water heating mode or the standard water heating mode selected by the power switch 9. The high-power water heater mode and the standard water heater mode can be switched to each other by the power switch 9, and in any of these modes, when the water temperature reaches a predetermined temperature (94 ° C.) near the boiling point, the mode shifts to the boiling control mode. If it boils in the boiling control mode, it will transition to the heat retention mode,
When cold water is added to lower the water temperature, the mode transits to a mode selected from the high power water heating mode and the standard water heating mode. If the reboil switch 10 is turned on in the warming mode, the mode transits to the boiling control mode, and if cold water is added, the mode transits to the water amount determination mode.

In the boiling control mode, as shown in the flowchart of FIG. 4, a predetermined temperature T ₁ immediately before boiling is detected by fuzzy inference in steps S11 to S17. That is, in step S11, the initial value of j used in the calculation of the boiling completion degree accumulated value F described later is set to 1, the F value is calculated in step S12, and the F value is calculated in step S13.
It is determined whether or not the value is less than -10. If the value is not less than -10, j = j + 1 is set in step S14 and step S12 is performed.
Is repeated. If the F value is less than -10 in step S13, the calculation of the F value is further continued in step S16 with j = j + 1 in step S15, and it is determined in step S17 whether the F value is -10 or more. And
If it is less than -10, the process returns to step S15 to repeat the calculation of the F value. Then, F value in step S17, if the -10 or more, so that the predetermined temperature T ₁ of the near boiling has been detected. When the predetermined temperature T ₁ immediately before boiling is detected in this manner, only the main heaters 5 and 7 are turned off in step S18, the heat keeping heater 6 is kept on, and this is continued until 5 minutes elapse in step S19. The state is maintained, and after 5 minutes, the mode is shifted to the warming mode.

As shown in the flow chart of FIG. 5, the calculation of the boiling completion degree accumulated value F takes in the detected temperature T (i) from the temperature detecting device 8 in step S101 every second as an AD value, and executes step S102. And each of the detected temperatures T (i)
And a predetermined temperature T ₀ (94 ° C.) to determine a difference ΔT (i).
Then, in step S103, this ΔT (i) is integrated every 5 seconds for 10 seconds as shown in FIG.
, And in step S104, the degree of boiling B (j)
Is calculated, and a boiling speed V (j), which is an increase in the boiling degree after 10 seconds, is calculated. In step S105, fuzzy inference to be described later is performed by using the boiling degree B (j) and the boiling rate V (j) as inputs, and a boiling completion degree E (j) indicating the current degree of boiling completion is output.

In the fuzzy inference routine in step S105, as shown in FIGS. 8 to 10, membership functions corresponding to fuzzy sets at respective stages of the degree of boiling, the boiling speed, and the degree of completion of boiling are defined in advance. .
That is, the degree of boiling is classified into three stages of "small", "medium", and "large", and the degree of boiling "small" (indicated by S in FIG. 8) is the degree of boiling B (j) of 00H in hexadecimal. Sometimes at the maximum 40H,
It is a function that decreases linearly so that it becomes 0 at the time of P, and the boiling degree “medium” (indicated by M in FIG. 8) is the boiling degree B.
(J) is a triangular function which is 0 when 00H and 6EH, and becomes 40H at the maximum when it is intermediate P, and the boiling degree “large” (indicated by L in FIG. 8) is the boiling degree B. (J) is a function that linearly increases so as to be 0 when P is P and 40H at the maximum when it is 6EH. Similarly, the boiling speed is also classified into three stages of “small”, “medium”, and “large”, and is defined as indicated by S, M, and L in FIG. The values of the constants P and Q that determine the form of this membership function are
The variable resistor 14 of the membership function adjusting circuit 12
a, 14b to operate the microcomputer 11
It is set arbitrarily by changing the divided voltage to the D converter.

The degree of completion of boiling is “very small”,
"Small", "somewhat small", "medium", "somewhat large", "large",
It is classified into seven stages of "very large"
As shown by S, SL, MS, MM, ML, LS, and LL, adjacent functions are defined by overlapping triangular functions. The degree of completion of boiling is a value indicating whether or not the current boiling is completed, and takes a negative value if the boiling is not advanced, and takes a positive value as the boiling is advanced. In addition,
r indicates the distance from the reference point (the point where E (j) at the left end in FIG. 10 is −8). Fuzzy rules shown in Table 1 are defined between the membership functions. For example, in the fuzzy rule 1, if the boiling degree is S and the boiling rate is S, the boiling completion degree is SS.

Under the membership function and the fuzzy rules defined as described above, in the fuzzy inference routine, as shown in FIG. 6, based on the AD value of the divided voltage from the membership function adjustment circuit 12 in step S201, as shown in FIG. P
Set the value. Then, in steps S202 to S204, the degrees BS, BM, BL of the boiling degree “small”, the boiling degree “medium”, and the boiling degree “large” with respect to the input value of the boiling degree B (j) are calculated from the membership function. Ask. Similarly, a Q value is set in step S205, and steps S206 to S20
In step 8, the respective degrees VS, VM, and VL of the boiling speed “small”, the boiling speed “medium”, and the boiling speed “large” with respect to the input value of the boiling speed V (j) are obtained.

Table 1 Fuzzy rule Boiling degree Boiling rate Boiling completion degree 1 SSSS2SMMS3SLMM4MSSSL5MMMMMM6MLLLML7LSLMMMLMLLS9LLLL

Next, in step S209, for each fuzzy rule, the smaller one of the degree of boiling and the degree of boiling speed is taken as D (j), and this value is taken as D (j). The membership function of the degree of boiling completion is cut off to obtain a fuzzy output, and its area S is obtained. Then, in step S210, the position of the center of gravity G from the reference point of the sum of the areas of the membership functions of the degree of completion of boiling from SS to LL is calculated. In step S211 the degree of completion of boiling E () corresponding to the position of the center of gravity is obtained. The defuzzified output value of j) is obtained. When the degree of boiling completion E (j) is obtained by fuzzy inference in this manner, as shown in FIG. 5, a constant α is calculated from the degree of boiling completion E (j) in step S106.
(A predetermined value between 0 and 1) is subtracted, and step S107 is performed.
The degree of completion of boiling E (j) is converted to the degree of completion of boiling E (j−
F value is obtained by adding to 1).

In the electric pot having the above configuration, water heating is performed in either the high power water heating mode or the standard water heating mode corresponding to the power selected by the power switch 9, and the temperature detected by the temperature detecting device 8 is set to a predetermined value. When the temperature T ₀ (94 ° C.) is reached, a transition is made to the boiling control mode, where the predetermined temperature T ₁ immediately before boiling is detected by fuzzy inference. The detection of the predetermined temperature T ₁ by fuzzy inference is performed by _first detecting the temperature T ₁ from the temperature detection device 8.
It is taken in every second (step S101), and based on this, the degree of boiling B (j) and the boiling speed V (j) are calculated (steps S103, S104). Since the boiling speed B (j) is obtained by integrating the detected temperature for 10 seconds, it indicates a macroscopic boiling state and is not affected by instantaneous temperature fluctuations due to the influence of convection and the like. The boiling speed V (j) is an increase from the boiling degree V (j) 10 seconds before the current boiling degree, and indicates the speed at which the boiling state rises.

Now, the boiling degree B (j) and the boiling speed V
Assuming that the input values of (j) are B ₁ and V ₁ (same as Q) as shown in FIGS. 11 and 12, respectively, the membership function S of the boiling degree “small” and the boiling degree “medium” BS and BM are obtained from the membership function M of the above, and VM is obtained from the membership function of the boiling rate “medium”.
Therefore, first, the membership function MS of the boiling completion degree “slightly small” is truncated at the smaller of the BS and the VM from the fuzzy rule 2, that is, at the BS as shown in FIG. 13, and a trapezoidal fuzzy output is obtained. Next, fuzzy rule 5
The smaller of BM and VM, ie, BM, the membership function MM with the degree of boiling completion “medium” is truncated, and a trapezoidal fuzzy output is similarly obtained. Then, E is located at the center of gravity G of the area sum of the fuzzy outputs of these trapezoids.
By calculating the value of (j), -1 is obtained as a defuzzified output value.

Further, the boiling state further advances, and the boiling degree B
(J) and the input values of the boiling speed V (j) are shown in FIGS.
As shown in FIG. 3, if the respective functions become B ₂ and V ₂ , respectively, the membership functions M and B of the boiling degree “medium” and the boiling degree “large” are obtained.
BM and BL are obtained from L, and VS and VM are obtained from membership functions S and M of the boiling speed “small” and the boiling speed “medium”. Therefore, in this case, fuzzy rule 4,
5, 7, 8 are applied, and the degree of boiling completion is "small", "medium",
Each membership function SL, MM, LS of "large" is truncated by BM, BL, so that a trapezoidal fuzzy output is obtained, and 0 is obtained as a defuzzified output value. The output value E thus defuzzified
(J) is subsequently subtracted by a constant α (step S1).
06), and is added to the previous output value E (j-1) to obtain the F value.

The F value is, as described above, the degree of completion of boiling E
(J) takes a value from negative to positive as boiling progresses,
Negative values accumulate at the beginning of boiling and approach zero as boiling proceeds further. Therefore, immediately before the F value becomes zero, that is, when the F value becomes -10, it is determined that the temperature has reached the predetermined temperature T ₁ immediately before boiling. Thereafter, the main heaters 5 and 7 are turned off, and heating by the heat retaining heater 6 is performed for 5 minutes. Thus, just before boiling, the main heaters 5, 7
Is turned off, the remaining heaters of the main heaters 5 and 7 and the heating by the heat retaining heater 6 thereafter perform boiling water, resulting in a weak boiling state. In addition, since the emission of steam is extremely reduced by turning off the main heaters 5 and 7 immediately before boiling, there is no possibility that water vapor is condensed on peripheral devices or glass windows.

The reason why the constant α is subtracted from the degree of boiling completion E (j) is that the boiling in the water is released by continuing the boiling state assuming that the boiling is delayed. As described above, the P value and the Q value that determine the membership function can be changed by the membership function adjustment circuit 12, so that it can be quickly adapted to electric pots of other models having different capacities and heating means. can do.

In the above-described embodiment, three stages of "small", "medium" and "large" are provided for the degree of boiling and the boiling speed which are input concepts. However, the present invention is not limited to this. There may be two stages such as "medium" or "small" and "large". In this case, it is necessary to determine each membership function and fuzzy rules according to the stage. Further, in the above-described embodiment, a method based on fuzzy inference is employed to detect the predetermined temperature T ₁ immediately before boiling. However, the predetermined temperature T ₁ is directly detected by the temperature detection device 8 including a thermistor or the like. You may make it detect. Furthermore, in the above-described embodiment, the main heaters 5 and 7 are turned off, and the heater 6 is used for boiling water for 5 minutes. However, as shown in FIG. The calculation of the degree-of-completion cumulative value F may be continued, and the mode may be shifted to the warming mode when the F value becomes zero. Thus, the boiling operation is surely terminated at the time of boiling.

[0022]

As is apparent from the above description, according to the present invention, the main heater is turned off immediately before boiling, and thereafter the hot water is heated by the heat retaining heater. The adverse effect of condensation is eliminated. In particular, according to the second aspect of the present invention, since the predetermined temperature immediately before boiling is detected from the predetermined temperature near the boiling point by fuzzy inference, an accurate temperature rise is achieved regardless of the rate of temperature rise in the course of reaching the predetermined temperature. Detection can be performed.

[Brief description of the drawings]

FIG. 1 is a flowchart of a boiling control method according to the present invention.

FIG. 2 is a configuration diagram of an electric pot to which the method according to the present invention is applied.

FIG. 3 is a mode transition diagram of the electric pot.

FIG. 4 is a flowchart of a boiling control mode.

FIG. 5 is a flowchart of a calculation routine of a boiling completion degree accumulated value F;

FIG. 6 is a flowchart of a fuzzy inference routine.

FIG. 7 is an explanatory diagram of a degree of boiling.

FIG. 8 is an explanatory diagram of a membership function of a boiling degree.

FIG. 9 is an explanatory diagram of a boiling speed membership function.

FIG. 10 is an explanatory diagram of a boiling completion degree membership function.

FIG. 11 is an explanatory diagram showing values of membership functions with respect to specific input values of the boiling degree at the beginning of boiling.

FIG. 12 is an explanatory diagram showing a value of a membership function with respect to a specific input value of a boiling speed at the beginning of boiling.

FIG. 13 is an explanatory diagram showing a fuzzy output with respect to specific input values in FIGS. 11 and 12;

FIG. 14 is an explanatory diagram showing values of membership functions with respect to specific input values of the degree of boiling in a later stage of boiling.

FIG. 15 is an explanatory diagram showing values of a membership function with respect to specific input values of a boiling rate in a later stage of boiling.

FIG. 16 is an explanatory diagram showing a fuzzy output corresponding to specific input values in FIGS. 14 and 15;

FIG. 17 is a flowchart showing another embodiment of the boiling control mode.

[Explanation of symbols]

3 inner container, 5 water heater (main heater), 6 heat retaining heater, 7 band heater (main heater), 8 temperature detector, 11 microcomputer, B (j) boiling degree, V (j) ... boiling speed, E (j) ... degree of boiling completion, F ... cumulative value of degree of boiling completion.

Claims (4)

(57) [Claims] In a boiling control method for an electric pot, a liquid stored in a container is heated by a heating device including a main heater and a heat retaining heater to perform boiling water, and the boiling is stopped when the liquid is boiled. A method of controlling the boiling of an electric pot, wherein the main heater is turned off when the predetermined temperature is detected, and then the hot heater is turned off if the hot water is continuously heated by the warming heater. And calculating a boiling degree obtained by integrating a difference between the detected temperature detected from the predetermined temperature near the boiling point per unit time from the predetermined temperature for a predetermined time and an increase in the boiling degree after the predetermined time. The obtained boiling rate and the input, the degree of completion of the current boiling completion degree is output, and the membership function corresponding to the fuzzy set of each stage of each input and output concept is set, and those The output from the two inputs is fuzzy inferred in accordance with the fuzzy rule between them, and the degree of completion of boiling output is sequentially added for each unit time, and the main heater is turned off when the accumulated value becomes a predetermined value of 0 or less. 2. The method for controlling boiling of an electric pot according to claim 1, wherein: 3. The heat retaining heater is turned off after a predetermined time after turning off the main heater.
3. The method for controlling boiling of an electric pot according to item 1. 4. The method of controlling an electric pot according to claim 2, further comprising, after turning off the main heater, turning off the heat retaining heater when the cumulative value of the degree of completion of boiling reaches zero.