JPS63153016A - Electric rice cooker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Statement of the Invention] (Industrial Application Field) The present invention automatically controls energization of a heater for heating a pot until rice cooking is completed based on a temperature signal from a heat-sensitive element that detects the temperature of a pot. The present invention relates to an electric rice cooker that uses a cooking method, and particularly relates to an electric rice cooker that has a dry cooking prevention function.

(Prior Art) Conventionally, there is an electric rice cooker that can automatically control the process from the start of rice cooking to the completion of rice cooking using a control circuit having a heat-sensitive element such as a thermistor.

(Problem to be solved by the invention) However, with something like this, there is no rice in the pot.

Even when the start switch is turned on without filling the pot with water, the heater for heating the pot is energized and controlled in the same way as in normal rice cooking, resulting in dry cooking. In dry cooking, the heat capacity is small, so even after the heater is turned off, the pot temperature rises to a considerable value, causing thermal deformation of various parts and shortening the service life. In particular, in the recently developed so-called double-cooking method (a method in which the heater is re-energized for a short time after rice cooking is completed), the above phenomenon is repeated twice, making the situation even more serious. In addition, such dry cooking operates in the same way as the rice cooking cycle, and therefore consumes a large amount of energy.

The present invention has been made to eliminate the above-mentioned drawbacks.
The purpose of this is to be able to determine the presence or absence of dry cooking at a low temperature after the pot starts heating, thereby preventing abnormal situations caused by dry cooking. It is on offer.

[Structure of the Invention] (Means for Solving the Problem) When the electric rice cooker of the present invention is energized for rice cooking at the beginning, the heater is turned off for a certain period of time by a timer element, and the temperature of the pot is determined within the power cut-off time. The configuration is such that the degree of rise is judged by a judgment element and the presence or absence of dry cooking is detected.

(Function) In this rice cooker, when electricity is started to be applied to the heater to start cooking rice, the heater is turned off for a certain period of time after a while. During this power outage period, the temperature of the pot continues to rise due to thermal inertia, and if the degree of temperature rise is greater than the set value, it is determined to be "dry cooking", and if the set value is not reached, the heater is re-energized and the rice is cooked. Continue the operation.

(Example) An example of the present invention will be described below with reference to the drawings. 1 is a power source; 2 is a rice-cooking heater circuit consisting of a rice-cooking heater 3 for heating a pot and a normally open contact 4a of a relay 4; 5;
is a heat-sensitive element, for example formed by a thermistor, which is brought into contact with the outer bottom surface of the pot in order to detect the temperature of the pot. 6 is a control section, which will be explained below. Reference numerals 7 to 9 designate temperature determiners, which each receive a temperature signal S1 from the heat-sensitive cable 5, and the detected temperatures are TI and T2, respectively.

When T3 or higher, a logic value "1" is output to lines 7a, 8a, and 9a, and at other times, a logic value rOJ is output. Here, TI is set to, for example, 50°C, which is lower than the gelatinization temperature of starch, 55°C, and Tl < Tg <
It is in the relationship of T3. Temperature T3 is the temperature at which rice cooking is completed, and T2 is set to a reference temperature in the range that occurs in an empty pot among the temperatures at which the pot heats up immediately after the heater 3 is turned off. 10 is a clock pulse generator which obtains a pulse synchronized with the frequency from power supply 1 and outputs it as clock pulse P1 to line 10a; 11 is an initial value storage element in which time data X of 10 minutes, for example, is stored; , the time data X is transferred to a subtraction counter 14 by a transfer gate 13 which is opened upon receiving a pulse from the one-shot multi 12. This subtraction counter 14 forms a part of a timer element, and outputs rOJ to the line 14a when the count value becomes zero, and otherwise outputs "1". In other configurations, 15 is a start switch, 16 is a flip-flop, 17 to 20 are ant gates, 21 is an or gate, and 22 is an inverter, especially an and gate 19.
constitutes an element for determining the degree of temperature rise.

Next, the operation of the above configuration will be explained. First, the rice cooking operation in a normal state when water and rice are stored in a pot will be explained using FIG. Now, if you turn on the start switch 15 to start cooking rice, the flip-flop 16 will be set and "1" will be output from its Q output terminal to the line 16a.
This state will be maintained thereafter. When "1" is output to the line 16a, the one-shot multi 12 generates a pulse and gives it to the transfer gate 13, which transfers the 10-minute time data X in the initial value storage element 11 to the subtraction counter 14. Count to 1. As a result, "1" is output to the line 14a, while the brightest pot temperature is T.
Since it is less than 1, the line 7a is "0", therefore the output of the AND gate 18 is "O", the output of the inverter 22 is "1", the output of the AND gate 20 is "1", and the relay 4 is output. Electricity is supplied, and the normally open contact 4a is closed at approximately the same time as the start switch 15 is turned on, and the rice cooking operation is started at time to in FIG.

Thereafter, as a result of energizing the heater 3 via the normally open contact 4a,
The pot temperature gradually rises as shown by curve A in FIG.

When the pot temperature reaches TI at time t1 during the initial energization of the heater 3 for this rice cooking, the output of the temperature determiner 7 becomes "1", and as a result, the clock pulse P1 passes through the antge 1 and 17. The subtraction counter 14 subtracts and counts this clock pulse P1, and at time t2, 10 minutes after time t1, the count value becomes zero and outputs "0" to line 14a. Since the lines 7a and 14a are both "1" between the times t and -t2, the output of the AND gate 18 is "1", and therefore the output of the inverter 22 is "1".
0'', the output of the AND gate 20 is ``0'', and the relay 4 is de-energized. That is, the heater 3 has a pot temperature of approximately 50°C (T1
), the time t! The power was cut off at time t.
2 for approximately 10 minutes. Then, when time t2 is reached and the output of the subtraction counter 14 becomes rOJ, the output of the AND gate 17 is kept at "0" to prevent the sending of the clock pulse P1.・Since the output of 18 is also rOJ, the output of AND gate 20 is "1"
As a result, the relay 4 is activated, and the power supply to the heater 3 is restarted. As a result, the temperature of the pot rises and the actual rice cooking operation starts, and when the pot temperature exceeds the temperature T2 midway through and reaches the rice cooking completion temperature T3, the output of the temperature determiner 9 is r.
lJ, and as a result, the flip-flop 16 receives the output "1" of the temperature determiner 9 through the OR gate 21 to the reset input terminal and is inverted to the reset state, and the line 1
6a is set to "O", the output of Antoge 1 and 20 is "0", so the relay 4 is cut off, its normally open contact 4a is opened, the heater 3 is cut off, and the rice cooking is completed. .

Next, using FIG. 3, we will explain the case where the start switch 15 is turned on when the pot is empty with no rice or water in it. In this case, m? Time t when H degree reaches T1
1, the heater 3 is cut off, and from this point on, the subtraction counter 1
4 is the subtraction count of the clock pulse Pl, and therefore, the start of the operation at the :L time of the temporary power-off period of 10 minutes of the heater 3 is the same as the above-mentioned normal rice cooking operation. However, even after the heater 3 is cut off at time t1, the temperature of the pot rises due to thermal inertia or residual heat in the surroundings, but in an empty state with no load, the heat capacity is small, so the curve B in Fig. 3 As shown in , the degree of rise is high, and therefore, at time t11 before reaching time t2, the temperature reaches the predetermined reference temperature 12 or higher, and the output of the temperature judger 8 becomes rlJ, while at this time the subtraction counter Since the output of 14 is still at "1", the time t
At 11, an output of "1" is generated from the AND gate 19 as a conduction blocking signal. This causes flip-flop 16
is reversed to the reset state, the heater 3 is cut off by the same operation as explained in the section of normal rice cooking, and the temperature of the pot is kept at around T2, which prevents the pot from becoming essentially dry-cooked. #-, I can do it.

In particular, in this embodiment, the start temperature T1 of the temporary power cutoff described as the heater power cutoff operation between tl and t2 is set at a temperature lower than the gelatinization temperature of starch at the initial stage of energization of the heater 3, so tl It is possible to prevent the phenomenon in which starch begins to gelatinize during the temporary power cutoff period between -t2 and water becomes difficult to penetrate from the surface of the rice to the inside.

[Effects of the Invention] According to the present invention, the following effects can be obtained as can be understood from the embodiments described above.

That is, a temporary power-off period is interposed by a timer element at the beginning of the heater's energization, and the temperature of the pot immediately after the heater is turned off during this period.
It detects the presence or absence of dry cooking by determining the degree of rise, and can reliably prevent dry cooking of the pot.
The above-mentioned temporary power-off period for determining whether the rice is cooked dry has the benefit of exerting a chilling effect during normal rice cooking.

[Brief explanation of the drawing]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are pan temperature characteristic diagrams under different load conditions in this embodiment. In the figure, 3 is a heater, 5 is a heat-sensitive element, 6 is a control unit, 14 is a subtraction counter (timer element), and 19 is an anime game 1 (
(judgment factor).

Claims (1)

[Claims] 1. Consisting of a heater that heats a pot, a heat-sensitive element that detects the temperature of the pot, and a control unit that controls energization of the heater based on a temperature signal output from the heat-sensitive element. , a timer element that temporarily cuts off the power to the heater for a certain period of time at the beginning of power supply, and a determination element that judges the degree of temperature rise of the pot during the temporary power cutoff period based on the temperature signal from the heat sensitive element and outputs a power supply blocking signal. An electric rice cooker equipped with 2. The electric rice cooker according to claim 1, wherein the pot temperature at the start of the temporary power cut is set to a temperature lower than the gelatinization temperature of starch.