JPH0552204B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a heating control method for an electric rice cooker in which rice cooking is controlled based on a temperature detection signal indicating the temperature inside the pot.

[Technical background of the invention and its problems] In recent years, rice cookers have various rice cooking controls, specifically, for example, when cooking white rice, the rice cooking method is used as a heating means only until the water in the pot boils. By generating heat from the heater at a high output, it satisfies the well-known conditions for cooking rice deliciously, the so-called "maka-patsupa" condition, and the inside of the pot reaches a boiling state. When the temperature reaches a predetermined target temperature, the heater output is reduced to prevent boiling over and burning of the rice. However, in the above-mentioned conventional configuration, the target temperature when reducing the heater output is constant regardless of the amount of rice cooked, so when the amount of rice cooked is small, due to the influence of thermal inertia when the rice is cooked, The rice may sometimes burn, and this has been an unresolved issue. Further, in the conventional configuration, since the operation of reducing the heater output is performed after the inside of the pot reaches a boiling state, there is also a problem that the boiling over prevention effect cannot be sufficiently exhibited.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to effectively prevent boiling over from the inside of the pot when cooking rice, and to reduce the thermal inertia at the time of rice cooking by reducing the amount of cooked rice. To provide a heating control method for an electric rice cooker that can maintain constant heating regardless of the size of the rice and suppress the occurrence of burning.

[Summary of the Invention] In order to achieve the above object, the present invention heats a pot when the temperature inside the pot, which is indicated by a temperature detection signal from a temperature detection means, reaches a predetermined cooking temperature that is higher than the boiling temperature. In the electric rice cooker, the electric rice cooker is configured to cut off power to the heating means for cooking, the signal generation means outputting a rice cooking amount signal according to the amount of rice cooked, and the increase value of the pot temperature within a reference time based on the temperature detection signal. a detection means for measuring and detecting that the temperature inside the pot has reached a predetermined target temperature below the boiling temperature based on the amount of change in the measured temperature rise value; The apparatus is further provided with an output control means for reducing the heating output of the heating means, and is configured to change the target temperature so that the larger the amount of rice indicated by the rice cooking amount signal is, the higher the target temperature becomes.

[Embodiments of the Invention] A first embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

In Fig. 2, 1 is the main body of the rice cooker consisting of an inner frame 2 and an outer frame 3, 4 is a lid, 5 is a pot removably housed in the inner frame 2, and 6 is a device for heating this pot 5. The heating means installed in the space between the bottoms of the inner frame 2 and the outer frame 3 is, for example, a rice cooking heater with a rated output of 600 watts. Reference numeral 7 denotes a heat-sensitive cap that is arranged so as to be able to move up and down so as to penetrate through the bottom of the inner frame 2. This cap is always urged upward by the spring force of a compression coil spring 8, so that the pot 5 is not moved inside. It is arranged so as to come into pressure contact with the outer bottom of the pot 5 while being housed in the two frames. 9 is heat sensitive cap 7
For example, a thermistor 10 is a heat-sensitive element installed in the inner frame 2 to detect the temperature of the pot 5, and is pressed by the heat-sensitive cap 7 only when the pot 5 containing rice and water is housed in the inner frame 2. This is a pot switch that turns on the pot to prevent dry cooking. In addition, 11 is an operation panel installed on the side of the rice cooker main body 1;
Reference numeral 2 denotes a case disposed at the outer bottom of the rice cooker main body 1, and inside this case 12 there is a control for controlling power on/off of the heater 6 based on the temperature detected by the thermistor 9 and input from the operation panel 11. circuit 1
3 is stored.

FIG. 1 shows the configuration of the control circuit 13 and its related parts that are directly related to the gist of the present invention, and will be described below.
In FIG. 1, the control circuit 13 is shown in terms of hardware by combining various functional parts; however, the present invention is not limited to this, and each of the functional parts described above can be replaced by a program of a microcomputer. Of course, this is also a good thing.

In FIG. 1, 14 is a switching element, for example, a triax, which is connected to an AC power source 15.
The heater 6 and the pot switch 10 are connected in series between both terminals of the pot switch 10 . Reference numeral 16 denotes a photocoupler consisting of a light emitting diode 16a and a phototransistor 16b, and the half wave voltage of the AC power source 15 is applied to the light emitting diode 16a through a diode 17 and a resistor 18.
Reference numeral 19 denotes a DC constant voltage circuit that receives the output of the AC power supply 15, and power is supplied to each circuit section described below from its output lines La and Lb.

20 is an initialization circuit consisting of, for example, a differential circuit;
This outputs an initialization pulse P ₀ every time the power is turned on. 21 is a waveform shaping circuit that shapes the output of the photocoupler 16 (voltage output corresponding to the half-wave output of the AC power source 15) into a rectangular wave, and 22 is a waveform shaping circuit that divides the output of this waveform shaping circuit 21 to form a time signal, for example 1. A first frequency divider circuit 23 generates a clock pulse P ₁ with a period of seconds, and a second frequency divider 23 divides the frequency of the clock pulse P ₁ and outputs a clock pulse P ₂ with a period of 10 seconds, which is also a time signal. . Reference numeral 24 denotes an A-D converter which together with the thermistor 9 constitutes a temperature detection means 25, which outputs a digital temperature detection signal Sd corresponding to the temperature of the pot 5 detected by the thermistor 9. 26 and 27 are first and second temperature value storage units that store values corresponding to temperatures used to detect the amount of cooked rice, such as 70°C and 80°C, respectively; 28 is a predetermined lower limit temperature, such as 90°C; a third temperature value storage unit storing corresponding numerical values; 2;
Reference numeral 9 denotes a fourth temperature value storage section that stores a value corresponding to, for example, 110°C. Also, 30 to 39
1 are fifth to fourteenth temperature value storage sections, in which, for example, the following numerical values are stored as shown in FIG. That is, the fifth temperature value storage unit 30 stores a numerical value corresponding to 2°C, and the sixth temperature value storage unit 30 stores a value corresponding to 2°C.
Eighth and eleventh temperature value storage units 31, 33 and 36
are stored with numerical values corresponding to 3°C, respectively, and values corresponding to 1°C are stored in the seventh and tenth temperature value storage units 32 and 35, respectively.
The ninth and twelfth temperature value storage units 34 and 37 store numerical values corresponding to 5°C, respectively, and the thirteenth temperature value storage unit 38 stores the heater power-off temperature Dz. A numerical value corresponding to 112° C. is stored as the double-cooking heating start temperature Dr, and a numerical value corresponding to 103° C. is stored in the fourteenth temperature value storage section 39. Reference numerals 40 and 41 denote first and second time value storage units that store numerical values corresponding to, for example, 2 minutes and 4 minutes, respectively, which serve as standards when detecting the amount of cooked rice. Reference numerals 42 to 51 are third to twelfth time value storage sections, in which, as shown in FIG. 1, for example, the following numerical values are stored. That is,
The third time value storage section 42 stores a numerical value corresponding to 7 minutes, the fourth time value storage section 43 stores a numerical value corresponding to 9 minutes, and the fifth and eighth time value storage sections Numerical values corresponding to 0 seconds are stored in 44 and 47, respectively, and numerical values corresponding to 10 seconds are stored in the sixth and ninth time value storage sections 45 and 48, respectively.
The seventh and tenth time value storage units 46 and 49 respectively store numerical values corresponding to 20 seconds, and the eleventh time value storage unit 50 stores numerical values corresponding to 30 seconds as the double cooking heating reference time N. Numerical values are stored, and the twelfth time value storage section 51 stores a numerical value corresponding to 15 minutes as the uneven driving time M.

Reference numerals 52 to 64 are comparison circuits, which output a high level signal from the output terminal C when the respective input values to the input terminals A and B are in the relationship A≧B, and when A<B.
A low level signal is output from the output terminal C when the relationship is as follows. Further, 65 is a comparison circuit equipped with an enable terminal En;
It performs the same operation as the comparator circuits 52 to 64 only when receiving a high level signal at the enable terminal En, and always outputs a low level signal from the output terminal C when receiving a low level signal at the enable terminal En. 66 and 67 are subtraction circuits which subtract the input value to the input terminal E from the input value to the input terminal D, and output the subtraction result from the output terminal F. Addition circuits 68 to 71 add the input value to the input terminal X and the input value to the input terminal Y, and output the addition result from the output terminal Z. 72 to 75 are counters that count the number of input pulses to the clock terminal CK and output the counted value from the output terminal Q, and the count contents are initialized when a pulse signal is received at the reset terminal R. ing. 76
Trigger circuits 79 output a trigger pulse _P3 for a short time when the input signal thereof rises. 80 is a delay circuit, which delays the input signal for a short time and outputs the delayed signal. For example, 81 is 24
This is a shift register having unit registers 81a. Each time a pulse signal is received at the clock terminal φ, the input to the data terminal D is read and stored in the first unit register 81a, and each time new data is read, The structure is such that the old stored data is sequentially shifted to the upper unit register.
When the reset terminal R receives a pulse signal, the stored data is initialized. In the case of such a shift register 81, the 12th unit register 81b, the 18th unit register 81c, and the 24th unit register 81
It is configured to output each stored data of d. 82 is a memory circuit which is initialized when a pulse signal is received at its reset terminal R, and from this initialized state the input terminal D
The configuration is such that the value entered for the first time is stored. 83 outputs a gate signal Sg only when receiving a high level signal to connect the triac 14.
A heater drive circuit 84 is a heater output control circuit as an output control means that is driven only when receiving a high level signal, and this heater output control circuit 84 has a duty ratio of, for example, 50% when driven. outputs a pulse-like control signal Sc. Reference numerals 85 to 100 designate transfer gates, which are rendered conductive only when receiving a high level signal at their gate terminals.

Reference numerals 101 and 102 are a start switch for starting rice cooking and a stop switch for stopping rice cooking, respectively, which are provided on the operation panel 11, and these are constituted by momentary type push button switches.
Only when turned on, pulse signals (high level signals) _P4 and _P5 are output to the corresponding lines, respectively. Further, 103 to 105 are R-S flip-flops, 106 to 115 are AND circuits, and 116
118 to 118 are OR circuits, and 119 to 125 are inverters. Note that the first and second frequency dividing circuits 22,
23 and the AND circuit 108, the clock means 12
6 is configured, first and second temperature value storage sections 26,
27, first and second time value storage units 40, 41, comparison circuits 52, 53, 56, 57, counter 72,
AND circuits 106, 109 and inverter 119,
120 constitutes a rice cooking amount detection means 127, and the fifth temperature value storage section 30, comparison circuit 65, subtraction circuit 66, shift register 81, and transfer gates 85, 86, and 87 constitute a boiling detection means 128. and a fourth temperature value storage section 29, third and fourth time value storage sections 42 and 43, and a comparison circuit 5.
8, 59, counter 73, AND circuit 107, 1
10 and inverters 121 and 122 constitute a correction means 129, and the fourteenth temperature value storage section 3
9, fifth to twelfth time value storage units 44 to 51,
Comparison circuits 62, 63, 64, addition circuits 70, 7
1. Counters 74, 75, trigger circuits 78, 7
9, Transfer Gate 95 to 100, AND
The circuits 114, 115 and the inverter 125 constitute the double cooking control means 130, and further includes the sixth temperature value storage section 31, the comparison circuit 60, the subtraction circuit 67, the storage circuit 82, and the transfer gate 88.
The boiling detection compensating means 131 is constituted by.

Next, the effects of the above configuration will be explained in Figures 3 and 4.
This will be explained with reference to the drawings. In addition, Fig. 3 A and B
The temperature detected by the thermistor 9 (i.e. the pot 5
temperature) and the output of the heater 6, and FIG.
4,55,60,61,62,63,64,6
5. Heater output control circuit 84, start switch 101, R-S flip-flop 103, 10
4,105 each set output terminal Q, AND circuit 1
06, 107, 113, 115, OR circuit 118
Each output waveform is shown in correspondence with each code.

That is, the pot 5 containing rice and the required amount of water is placed in the inner frame 2.
When stored inside the pot switch 1
0 is turned on. When the power is turned on in this state, the DC power supply circuit 19 and the photocoupler 16 are driven, and the initialization pulse P ₀ is output from the initialization circuit ₂₀ .
This resets the R-S flip-flop 103 and outputs a high-level signal from its reset output terminal.This high-level signal initializes the counters 72, 74 and the memory circuit 82, and also resets the R-S flip-flop 103. 105 is reset. Also, at this time, the high level signal from the R-S flip-flop 103 is
Since the trigger pulse P ₃ is output from the trigger circuit 76 received via the OR circuit 117, the shift register 81 is initialized by the trigger pulse P ₃ and is also output via the OR circuit 117. The high level signal resets the R-S flip-flop 104. Thereafter, when the start switch 101 is turned on at time t ₀ (see FIGS. 3 and 4), the R-S flip-flop 103 is set by the pulse signal P ₄ output in response to the turn on. , the high level signal from the set output terminal Q is sent to the AND circuit 112,
113. At this time, one AND circuit 112 is given a low level signal from the set output terminal Q of the R-S flip-flop 104 which is in the reset state as described above, so its output remains a low level signal. Yes, but
The other AND circuit 113 is supplied with a low level signal from the set output terminal Q of the R-S flip-flop 104, inverted to a high-level signal by an inverter 124, and is also supplied with the R-S flip-flop 105, which is also in the reset state. As a result, the AND circuit 113 outputs a high level signal and the heater drive circuit 8
given to 3. Therefore, the heater drive circuit 83
The gate signal Sg is output from the triack 1
4 is turned on, and in response, AC power supply 15 is turned on.
Electricity is then applied to the heater 6 via the pot switch 10 and the triax 14 to heat the pot 5, thereby starting the rice cooking process. As the rice cooking process progresses, the temperature of the pot 5 rises as shown in FIG.
A temperature detection signal Sd corresponding to the temperature of is output.
Then, the temperature of the pot 5 is stored in the first temperature value storage section 2.
When the temperature rises to 70°C stored in step 6 (time t ₁ ),
First, the rice cooking amount detection section 127 operates. That is, in the rice cooking amount detection unit 127, the comparison circuit 52 determines that the temperature detection signal Sd input to the terminal A corresponds to "70°C" input to the terminal B from the first temperature value storage unit 26. A low level signal is output until time _t1 when the temperature value becomes equal to the temperature value, and a high level signal is output after that time _t1 . Further, the comparison circuit 53 receives a temperature detection signal input to its terminal B.
Sd outputs a high level signal to terminal A until time t ₂ when the temperature value corresponding to "80°C" inputted from the second temperature value storage section 27 becomes higher, and after that time t ₂ it outputs a low level signal. Output a signal. Therefore, both comparison circuits 52 and 53 only during the period from time _t1 to time _t2 .
A high level signal is output from AND circuit 10
6, therefore, only during this period, the 1 second period pulse signal P ₁ from the first frequency dividing circuit 22 is ANDed.
The signal passes through circuit 106 and is applied to clock terminal CK of counter 72. Therefore, as a result, the count value of the counter 72 changes from 70°C to 80°C.
The value corresponds to the time Ta (time from time t ₁ to t ₂ ) required for the temperature to rise to . Therefore, the time Ta measured as described above has a property of increasing or decreasing in proportion to the amount of cooked rice, and the magnitude of the amount of cooked rice is determined based on the count value of the counter 72 corresponding to this time Ta. That is, the count value of the counter 72 is calculated by the comparator circuits 56 and 57 into the respective numerical values (2 minutes, 2 minutes,
(equivalent to 4 minutes). At this time, the comparison circuit 56 outputs a low level signal when the count value of the counter 72 is smaller than the value equivalent to 2 minutes (in other words, when the amount of rice cooked is relatively small), and this low level signal is sent to the inverter 119 to cook the rice. The signal is inverted to a high level signal which is a quantity signal and is applied to line _L1 . Further, the comparison circuit 57 includes a counter 72
When the count value is equal to or more than 4 minutes (in other words, when the amount of cooked rice is relatively large), a high level signal as a rice cooking amount signal is outputted and applied to line _L3 . Further, when the count value of the counter 72 is equal to or greater than the value equivalent to 2 minutes and smaller than the value equivalent to 4 minutes (in other words, when the amount of rice cooked is medium), a high level signal is output from the comparator circuit 56 and this is ANDed. circuit 1
09, a low level signal is output from the comparator circuit 57, and this is inverted to a high level signal by the inverter 120.
The signal is then applied to the other input terminal of the AND circuit 109, and as a result, a high level signal, which is the rice cooking amount signal, is output from the AND circuit 109 and applied to line _L2 . In short, the rice cooking amount detection section 1
27 determines the amount of rice to be cooked based on the time required for the temperature of the pot 5 to rise from 70°C to 80°C, and sends a rice cooking amount signal (high level signal) indicating the determination result to line L ₁ , It selectively outputs to L ₂ and L ₃ . When the amount of cooked rice detected in this way is relatively small, the gate terminal is connected to the line.
Transfer gates 85, 89, connected to L ₁
95 is in a conductive state and the detected amount of cooked rice is medium, the transfer gates 86, 90, and 96 whose gate terminals are connected to the line _L2 are in a conductive state, and furthermore, when the detected amount of cooked rice is relatively large. for,
Transfer gates 87, 91, and 97 whose gate terminals are connected to line _L3 become conductive. At this time, the seventh, eighth, and ninth temperature value storage sections 32, 3 corresponding to the transfer gates 89, 90, 91 that are selectively turned on as described above.
The temperature values stored in 3 and 34 are for adjusting the heater power-off temperature Dz (the temperature value stored in the 13th temperature value storage unit 38, that is, 112°C,
Each of these stored temperature values is input to the input terminal Y of the adder circuit 68.
The temperature value inputted in this manner is selectively given to the temperature value according to the magnitude of the detected rice cooking amount, and the temperature value inputted in this way is given as the numerical value (heater cutoff) stored in the thirteenth temperature value storage section 38. It is added to the electric power temperature Dz) and output. Furthermore, fifth, sixth, and seventh time value storage units 44, 4 corresponding to the transfer gates 95, 96, 97 which are selectively turned on as described above are also provided.
The time values stored in 5 and 46 are for adjusting the double-cooking heating reference time N (the time value stored in the 11th time value storage unit 50, that is, 30 seconds), and each of these storage times A value is selectively given to the input terminal Y of the addition circuit 70 according to the magnitude of the detected rice cooking amount, and the addition circuit 70 stores the time value thus inputted in the eleventh time value storage section. The value is added to the value stored in 50 (double cooking heating reference time N) and output.

Thereafter, when the temperature of the pot 5 further increases and reaches the lower limit temperature "90° C." stored in the third temperature value storage section 28 (time t ₃ ), each of the input terminals A and B of the comparator circuit 54 When the input values meet the relationship A≧B, the output of the comparison circuit 54 is inverted to a high level signal. As a result, the AND circuit 108 receives the high level signal at one input terminal.
is the input to the other input terminal, that is, the clock means 1
In addition to allowing the passage of the pulse signal _P2 with a period of 10 seconds from the second frequency dividing circuit 23 in 26,
Similarly, the comparison circuit 65 which receives the high level signal from the comparison circuit 54 via the delay circuit 80 to the enable terminal En becomes operational, and accordingly, the boiling detection function of the boiling detection means 128 is enabled. Become. That is, when the pulse signal P ₂ begins to pass through the AND circuit 108, the pulse signal P 2 passes through the AND circuit 108.
Since P ₂ is now applied to the clock terminal φ of the shift register 81, the shift register 8
1 reads and stores the input to the data terminal D, that is, the temperature detection signal Sd every 10 seconds, and sequentially shifts the old temperature detection signal Sd to the upper unit register every time a new temperature detection signal Sd is read. Become. As a result, the 12th unit register 81b contains 120% of the current temperature detection signal Sd.
The temperature detection signal Sd seconds (2 minutes) ago is memorized and
The 18th unit register 81c stores the temperature detection signal 180 seconds (3 minutes) before the current temperature detection signal Sd.
Sd is stored in the 24th unit register 81d
240 seconds (4 seconds) from the current temperature detection signal Sd.
) The previous temperature detection signal Sd is now stored. At this time, the unit registers 81b, 81c
and 81d are supplied to the input terminal E of the subtraction circuit 66 via the corresponding transfer gates 85, 86 and 87, but as mentioned above, when the amount of rice to be cooked is relatively small, When the transfer gate 85 is in a conductive state and the data stored in the unit register 81b is applied to the input terminal E of the subtraction circuit 66, and similarly when the amount of cooked rice is medium or relatively large,
Each data stored in unit registers 81c and 81d is applied to input terminal E of subtraction circuit 66. The other input terminal D of the subtraction circuit 66 has a temperature detection signal.
Sd is directly input, therefore, the subtraction circuit 66 receives the current temperature detection signal Sd.
The value indicated by the temperature detection signal Sd 2 minutes before, 3 minutes before, or 4 minutes before, which corresponds to the reference time in the embodiment of the present invention, is subtracted from the value indicated by, and the result of the subtraction is: The value corresponds to the temperature rise value of the pot 5 within a certain reference time (2 minutes, 3 minutes, or 4 minutes) and the temperature gradient of the pot 5. Therefore, the temperature of the pot 5, that is, the temperature detection signal Sd
The rate of increase in the temperature of the pot 5 has a property of becoming approximately zero when the water in the pot 5 reaches a boiling state. Therefore, the rate of increase in the temperature of the pot 5 within the reference time is equal to or less than the predetermined comparative temperature value. If the temperature is detected, it can be determined whether or not the inside of the pot 5 has reached a boiling state. In this case, since the temperature increase rate of the pot 5 tends to be slower as the amount of rice cooked increases, in order to accurately detect boiling, it is desirable to change the above reference time according to the amount of rice cooked. Now, in order to perform accurate temperature detection, the reference time (i.e., the sampling time of the temperature detection signal Sd) is automatically changed to 2 minutes, 3 minutes, or 4 minutes as described above. That's what I do. Then, in the comparison circuit 65, the output from the subtraction circuit 66 (the temperature rise value of the pot 5 within the three-step reference time determined according to the amount of rice cooked) and the fifth temperature value storage section 30 are stored for comparison. The numerical value stored as the temperature value (equivalent to 2°C) is compared, and when the temperature increase value of the pot 5 within the above reference time is less than 2°C, in other words, the temperature of the pot 5 is When a predetermined target temperature below the boiling temperature (temperature when the temperature increase value of the pot 5 reaches 0°C within the reference time) is reached, the boiling detection signal Sz consisting of a high level signal is output from the comparator circuit 65. is output (time
_t4 ).

Therefore, at the time _t4 , the memory circuit 8
2 is in an initialized state, the output of the subtraction circuit 67 that subtracts the numerical value (corresponding to 3° C.) stored in the sixth temperature value storage section 31 from the stored value is a negative value. Yes, the comparison circuit 60 is in a state of outputting a low level signal. Therefore, OR circuit 1
The comparator circuit 60 and R
A low level signal is applied from the reset output terminal Q of the -S flip-flop 103, and this low level signal is inverted to a high level signal by an inverter 123 and applied to one input terminal of the AND circuit 111. Therefore, when the boiling detection signal Sz (high level signal) is output as described above at time _t4 , a high level signal is output from the AND circuit 111 and the R-S flip-flop 104
is set. Then, the output of the AND circuit 113, which had been outputting a high level signal, is inverted to a low level signal, and the AND circuit 112 outputs a high level signal.
An R-S flip-flop 103 is connected to each input terminal of the
High level signals from the set output terminals Q of 104 and the reset output terminal of R-S flip-flop 105 are applied to the AND circuit 112.
A high level signal is output from the heater output control circuit 84, and in response, a pulsed control signal Sc with a duty ratio of 50% is output from the heater output control circuit 84 and is applied to the heater drive circuit 83. As a result, the triax 14 is turned on and off at a duty ratio of 50%, and since the rated output of the heater 6 is 600 watts, the heater 6 has a rated output of 300 watts.
It starts to generate heat at watt output, which is half the rated output. Further, when the R-S flip-flop 104 is set at the above-mentioned time _t4 , the trigger circuit 77 is driven and a trigger pulse is generated from now on.
Since P ₃ is output, the counter 73 is initialized by the trigger pulse P ₃ and the transfer gate ₈₈ becomes conductive, and the temperature detection signal Sd ( (corresponding to the temperature of the pot 5 at the time when the boiling state was detected) is stored in the memory circuit 82. Also, at this point, there is enough water left in the pot 5 and the temperature does not exceed 100°C, so the temperature detection signal Sd corresponding to the temperature of the pot 5 and the fourth temperature value are The comparator circuit 55 that compares the value stored in the storage section 29 (corresponding to 110° C.) outputs a high level signal, and therefore the high level signal and the high level signal from the reset output terminal of the R-S flip-flop 105 The AND circuit 107 that received the
Pulse signal P ₁ from frequency dividing circuit 22 (1 second period)
is in a state where it is allowed to pass through. Therefore, the count value of the counter 73 initialized as described above indicates the elapsed time from time _t4 . When the rice cooking process further progresses and the inside of the pot 5 enters a so-called dry-up state, the temperature of the pot 5 will rise rapidly.In this case, the temperature of the pot 5 will rise at time _t5 . When the temperature reaches 110°C, the input terminals A and B of the comparator circuit 55 have a relationship of A<B, and the output is inverted to _a low level signal. As a result, the counting operation of the counter 73 is stopped. Therefore, as a result, the count value of the counter 73 is equal to the boiling detection signal.
This corresponds to the time Tb (corresponding to the duration of the boiling state) from time _t4 when Sz is output to time _t5 when the temperature of pot 5 reaches 110°C.

Like the time Ta from time t ₁ to t ₂ mentioned above, the time Tb measured as above has the property of increasing or decreasing in proportion to the amount of rice cooked, and also affects the ratio of rice to water during cooking. The correction means 12 has the property of
9 corrects the rice cooking amount detected by the rice cooking amount detection means 127 as follows based on the count value of the counter 73 corresponding to the time Tb. That is,
The count value of the counter 73 is the comparator circuit 58, 59
are compared with the numerical values (corresponding to 7 minutes and 9 minutes) stored in the third and fourth time value storage sections 42 and 43, respectively. At this time, the comparator circuit 58 outputs a low level signal when the count value of the counter 73 is smaller than the value equivalent to 7 minutes (in other words, when the amount of rice cooked is relatively small), and this low level signal is raised by the inverter 121. It is inverted to a level signal and applied to line _L4 . Further, the comparison circuit 59
When the count value of the counter 73 is equal to or greater than the value equivalent to 9 minutes (in other words, when the amount of cooked rice is relatively large), a high level signal is output and applied to the line _L6 . When the count value of the counter 73 is equal to or greater than the value equivalent to 7 minutes and smaller than the value equivalent to 9 minutes (in other words, when the amount of rice cooked is medium), a high level signal is output from the comparison circuit 58 and this is ANDed. circuit 11
0 to one input terminal of the comparator circuit 5.
9 outputs a low level signal, which is inverted to a high level signal by the inverter 122.
The signal is applied to the other input terminal of the AND circuit 110, and as a result, a high level signal is output from the AND circuit 110 and applied to the line _L5 . When the amount of cooked rice detected in this way is relatively small, the transfer gates 92 and 98 whose gate terminals are connected to the line _L4 are in a conductive state, and when the detected amount of cooked rice is medium, When the transfer gates 93 and 99 whose gate terminals are connected to the line _L5 are in a conductive state and the detected amount of cooked rice is relatively large, the transfer gates 94 and 1 whose gate terminals are connected to the line _L6 are in a conductive state.
00 becomes conductive. At this time,
The tenth, eleventh, and
The temperature values stored in the 12 temperature value storage units 35, 36, and 37 are also used to correct the heater power-off temperature Dz (the temperature value stored in the 13th temperature value storage unit 38, that is, 112°C). , and each of these stored temperature values corresponds to the input terminal Y of the adder circuit 69 for the above-mentioned time Tb.
is selectively given according to the length of , and the adder circuit 69
In the case of
Dz by the temperature value corresponding to the amount of cooked rice detected by the amount of cooked rice detected by the amount of cooked rice detected by the amount of rice detected by the amount of cooked rice 127). It acts to correct. Also, eighth, ninth, and tenth time value storage units 47 and 4 corresponding to transfer gates 98, 99, and 100 that are similarly selectively turned on.
The time values stored in 8 and 49 are also for correcting the double-cooking heating reference time N (the time value stored in the 11th time value storage unit 50, that is, 30 seconds). A time value is selectively given to the input terminal Y of the adder circuit 71 according to the length of the time Tb, and the adder circuit 71 receives the time value inputted in this manner as a numerical signal from the adder circuit 70. (that is, the time value corresponding to the size of the rice cooking amount detected by the rice cooking amount detection circuit 127 is added to the double-cooking heating reference time N), and then the rice cooking amount detection section 127 It acts to correct the added time value and thus the detected rice cooking amount.

Now, at the subsequent time t ₆ , the temperature of the pot 5 becomes the cooked rice temperature corresponding to the output from the adding circuit 69 (i.e., the heater power-off temperature Dz (112°C)).
, the temperature value corresponding to the amount of cooked rice detected by the amount of cooked rice detected by the amount of cooked rice detected by the amount of cooked rice detected by the amount of cooked rice and the temperature value corrected by the correction means 129 is reached), each input value to the input terminals A and B of the comparison circuit 61 is A
Since the relationship ≧B is established and a high level signal is output from the comparison circuit 61, the R-S flip-flop 105 is set. Then, a low level signal from the reset output terminal of the R-S flip-flop 105 is applied to the AND circuit 112, and the output of the AND circuit 112 is inverted to a low level signal, so that the heater output control circuit 84 is stopped. The heater drive circuit 83 stops outputting the gate signal Sg in response to
The heater 6 is kept in a turned-off state, that is, the heater 6 is turned off, and the rice cooking process is completed. At this time, the R-S flip-flop 10
The high level signal from the set output terminal Q of 5 is
is applied to AND circuits 114 and 115, and the
The AND circuit 114 now allows the pulse signal P ₁ to pass, and in response, the double cooking control means 1
30 will function and shift to uneven stroke. In short, the temperature of the pot 5 is determined by the temperature value (7th, 8th, 9th temperature value storage section any one of the temperature values stored in 32, 33, 34) and the correction means 1
29 (any one of the temperature values stored in the 10th, 11th, and 12th temperature value storage units 35, 36, and 37) is reached, and the rice cooking process starts. After this is completed, the process moves on to the uneven stroke, and the operation in this uneven stroke will be described below. In addition, in the case of this example,
The above-mentioned cooking temperature ranges from 114°C to 122°C depending on the contents stored in the seventh to thirteenth temperature value storage units 32 to 38.
Varies between ℃.

The counter 75 in the double cooking control means 130 is
The pulse signal _P1 is counted from the time the power is turned on, and therefore, at time _t6 , the count value is at least equal to the numerical signal output from the adder circuit 71 (in this embodiment, the pulse signal P1 corresponds to a maximum of 100 seconds). numerical value)
As a result, each input value to the input terminals A and B of the comparator circuit 64 has a relationship of A<B, and the comparator circuit 64 outputs a low level signal. Further, since the other counter 74 in the double-cooking control means 130 starts its counting operation from time _t6 , at this point each numerical value input to the input terminals A and B of the comparator circuit 62 is A.
Since the relationship is ≧B, a high level signal is output from the comparison circuit 62. Then, when the heater 6 is cut off at time t ₆ , the temperature of the pot 5 once overshoots as shown in _FIG . decreases to the double cooking start temperature Dr (103°C) stored in the 14th temperature value storage section 39, each input value to input terminals A and B of the comparator circuit 63 becomes A.
Since the relationship of ≧B is established and a high level signal is output, the trigger circuit 7 that receives the high level signal
8 starts outputting a trigger pulse _P3 , and the counter 75 is initialized by the trigger pulse _P3 . Then, the input terminal A of the comparator circuit 64,
Each input value of B has a relationship of A≧B, and a high level signal is output from the comparison circuit 64. In response, high level signals are given to all input terminals of the AND circuit 115, and the AND circuit 64 outputs a high level signal. circuit 115
The output of will be inverted to a high level signal.
As a result, the heater drive circuit 83 receiving the high level signal from the AND circuit 115 turns on the triac 14 to re-energize the heater 6, and in response, double cooking is performed. At this time, the count value of the counter 75 indicates the elapsed time from time _t7 when the temperature of the pot 5 decreased to 103°C, and at time _t8 , the count value corresponds to the output from the adder circuit 71. (i.e., the time obtained by adding the time value corresponding to the amount of cooked rice detected by the rice amount detection unit 127 and the time value corrected by the correction means 129 to the reference time N (30 seconds) for double cooking and heating) , each input value to the input terminals A and B of the comparison circuit 64 becomes A<
B, the output of the comparison circuit 64 is inverted to a low level signal, so the AND circuit 115
The output of is also reversed, and the heater drive circuit 83 turns off the triax 14, thereby cutting off the power to the heater 6 and stopping the double-cooking heating.
From this point on, by heating the pot twice,
At times t ₉ and t ₁₁ when the temperature rises once and then decreases to 103°C, the heater 6 is energized again to perform double heating in the same manner as described above, and such double heating is performed by the counter 75 It is stopped at each time T ₁₀ and t ₁₂ when the time period for which the count value corresponds to the output from the adder circuit 71 has elapsed. Then, at time t13, when the erratic driving time M (15 minutes) stored in the 12th time value storage unit ₅₁ has elapsed after time _t6 , the count value of the counter 74 corresponds to the erratic driving time M. Since the output of the comparator circuit 62 is inverted to a low level signal as the value exceeds the
The state in which the AND circuit 115 outputs a low level signal and the heater drive circuit 83 are maintained in a state in which the operation is stopped, and the uneven stroke is completed. Then, when the output of the comparison circuit 62 is inverted to a low level signal as described above, the inverter 125
The output of is inverted to a high level signal and the trigger circuit 7
Since the trigger pulse _P3 is output from 9, the R-S flip-flop 103 is reset by the trigger pulse _P3 , and from this point on, the process proceeds to a warming process using a warming heater (not shown). In short, in the process, the heater 6 is re-energized when the temperature of the pot 5 drops to 103°C, which is the double-cooking starting temperature Dr, and the energization time is set to the double-cooking heating standard time N. barrel 30
A time value corresponding to the rice cooking amount detected by the rice cooking amount detection means 127 in seconds (any one of the time values stored in the fifth, sixth, and seventh time value storage units 44, 45, and 46) and corrected time values by the correction means 129 (eighth, ninth, tenth time value storage units 47, 4
8 or 49) is reached, the heater 6 is cut off to end the double-cooking heating, and this embodiment repeats the control. In this case, the heating time for double cooking is stored in the fifth to eleventh time value storage units 44 to 50.
The time varies between 30 and 70 seconds depending on the memory contents.

So far, we have described the effect when the temperature of the pot 5 continues to rise without decreasing after the boiling detection signal Sz is output at time _t4 and the output of the heater 6 is reduced to half of the rated value. However, in the following, the effect when the temperature of the pot 5 decreases after the output of the heater 6 is reduced in this way will be explained using FIGS. 5 and 6, which are similar to FIGS. 3 and 4, respectively. This will be explained with reference to the figures. That is, the phenomenon in which the temperature of the pot 5 decreases when the output of the heater 6 is reduced by half occurs when the water in the pot 5 has not yet boiled (in other words, when the boiling detection signal Sz is erroneously output). Such a phenomenon can occur, for example, when seasonings such as soy sauce put into the pot 5 burn on the bottom of the pot 5 when making cooked rice, and this causes the contents of the pot 5 to burn. It is believed that this is caused by an increase in the gap between the temperature of the water and the temperature detected by the thermistor 9. Therefore, when the output of the heater 6 is halved at time _t4 in FIGS. 5 and 6, the temperature of the pot 5 at that time (i.e., the boiling detection means 128 is in the boiling state), as described above. The temperature detection signal Sd corresponding to the temperature of the pot 5 at the time when the temperature is detected is stored in the storage circuit 82 in the boiling detection compensating means 131. At this time, the subtraction circuit 67 in the boiling detection compensation means 131 subtracts the stored value (corresponding to 3° C.) in the sixth temperature value storage section 31 from the stored value in the storage circuit 82, and the subtraction result is temperature value corresponding to
Tp is applied to the input terminal A of the comparator circuit 60. Therefore, after that, the temperature of the pot 5 is set to the above temperature value.
When the voltage drops to Tp (time _t41 ), the output of the comparator circuit 60 is inverted to a high level signal, and in response to this, the R-S flip-flop 104 is reset and the trigger circuit 76 is driven to Shift register 81 is initialized by trigger pulse _P3 from 76. Therefore, the output of the AND circuit 112 is inverted to a low level signal, and the output of the AND circuit 113 is inverted to a high level signal, so that a high level signal is continuously given to the heater drive circuit 83.
In response to this, the heater 6 begins to generate heat at its rated output, that is, an output of 600 watts. In addition, in response to the shift register 81 being initialized as described above, the boiling detection means 127 starts to perform the boiling state detection operation similar to that described above, and for example, at time _t42 , the boiling detection signal is output from the comparator circuit 65. When Sz is output, the output of the heater 6 is halved again. Further, if the temperature of the pot 5 decreases again after this, the same operation as described above is repeated, and as described above, the boil detection compensation means 131 makes the detection operation of the boil detection means 128 more accurate. It works like this.

According to the present embodiment described above, the following effects can be achieved. That is, instead of detecting the boiling state of the water in the pot 5 based on a predetermined absolute upper limit temperature as in the conventional method, the boiling state of the water in the pot 5 is detected when the water in the pot 5 exhibits a boiling state. (specifically, the amount of change in the temperature of the pot 5 within a predetermined reference time is a constant comparison temperature value stored in the fifth temperature value storage section 30). (2°C) or below), the contact state between the heat-sensitive cap 7 and the bottom of the pot 5, the temperature detection means 25
This is caused by variations in the circuit logarithm of the thermistor 9 or the A-D converter 24 that constitute the thermistor 9 and changes in its characteristics over time, changes in atmospheric pressure, or seasonings added to the pot 5 when making cooked rice. Even if there is a fluctuation in the boiling point, the boiling state of the water in the pot 5 can be accurately detected. In addition, when detecting the boiling state in this way, the temperature rise gradient of the pot 5 changes depending on the amount of rice cooked, so the boiling detection described above may be inaccurate when the amount of rice cooked differs. However, in this embodiment, the target pot 5 at the time of boiling detection is determined according to the amount of cooked rice detected by the rice cooking amount detection means 127.
Since the temperature gradient of the pot 5 is changed (specifically, the reference time required when measuring the temperature gradient is changed), the boiling state of the water in the pot 5 can be detected by
Even if the amount of rice to be cooked differs, it can always be done accurately. In this embodiment, the rice cooking control is performed by causing the heater 6 to generate heat at the rated output until a boiling state is detected, and then reducing the output of the heater 6 by half. Since the boiling state is accurately detected, the rice cooking control described above can be performed strictly, and the so-called "medium-temperature" condition, which is one of the conditions for deliciously cooking rice, can be fully satisfied. At the same time, the rice can be cooked with less burning, and the rice can be cooked well overall. Of course, since the boiling state in the pot 5 is accurately detected in this way and the output of the heater 6 is halved after the boiling is detected, when this structure is applied to porridge cooking control, This can reliably prevent boiling over. moreover,
In this embodiment, the larger the amount of cooked rice detected by the rice cooking amount detecting means 127, in other words, the more unnecessary moisture remains in the pot 5 during dry-up, the more the cut-off temperature of the heater 6, ie the rice By raising the cooking temperature, you can improve the cooking of the rice from this aspect as well. Moreover, in this case,
A correction means 129 is provided, and the rice cooking amount detection means 127
Since the amount of cooked rice detected by the method is corrected according to the length of the period during which the water in the pot 5 is in a boiling state, the rice cooking control can be made more strictly according to the amount of cooked rice and the ratio of rice to water during cooking. can be done. Also, the heating time for double cooking during the uneven process is
Since the time is changed according to the amount of cooked rice detected by the rice cooking amount detection means 127 and corrected by the correction means 129, the rice can undergo the necessary and sufficient alpha conversion, and the rice can be fully cooked. You can make Tsuta rice even more delicious. In addition, the boiling detection compensating means 131 compensates for errors in boiling detection caused by scorching of seasonings such as soy sauce put into the pot 5 when cooking cooked rice. , the inside of the pot 5 may fall into a special state as described above, and the temperature detection means 25
Even if there is a difference between the detected temperature and the actual temperature inside the pot 5, the boiling state of the water in the pot 5 can be detected very accurately. Furthermore, in each of the above embodiments, the function of the boiling detection means 128 is activated only when the temperature of the pot 5 reaches the lower limit temperature (90° C.) stored in the third temperature value storage section 28. Therefore, there is no possibility that a period when the temperature gradient is flat, such as when the temperature of the pot 5 rises as indicated by G in FIG. 3, will be mistakenly detected as a boiling state.

A second embodiment of the present invention is shown in FIG. 7, and only the differences from the first embodiment will be described below. That is, in this second embodiment, instead of the boiling detection means 128 in the first embodiment, a boiling detection means 132 having a different function is used.
This boiling detection means 132 will be described below. In the boiling detection means 132, 133 is a shift register having, for example, 12 unit registers, and the data stored in the 12th unit register 133a is supplied to the input terminal E of the subtraction circuit 134.
The shift register 133, the subtraction circuit 134, and the comparison circuit 135 which receives the output of the subtraction circuit 134 at the input terminal B are the shift register 81, the subtraction circuit 66, and the comparison circuit 6 in the first embodiment.
5 and each has the same functions. Also,
Reference numerals 136, 137, and 138 are 15th, 16th, and 17th temperature value storage units, in which numerical values corresponding to 2°C, 1.5°C, and 1°C, which are reference temperatures in the embodiment of the present invention, are stored, respectively. ing. Furthermore, 139,14
0,141 are each of the above storage units 136, 137, 13
Transfer gates are provided corresponding to lines L 1 , L 2 , and L ₃ , respectively, and their gate terminals are connected to lines L ₁ , L ₂ , and L 3 .

In this embodiment, the current temperature detection signal
Sd is applied to the input terminal D of the subtraction circuit 134, and the unit register 13 of the shift register 133
The stored data 3a, that is, the temperature detection signal Sd at a time point 120 seconds (2 minutes) ago, is given to the input terminal E of the subtraction circuit 134;
4 to the input terminal B of the comparator circuit 135 corresponds to the temperature rise value of the pot 5 over a fixed period of 2 minutes. At this time, transfer gates 139 to 141 are selected according to the amount of cooked rice detected by the rice cooking amount detection means 127.
The 15th, 15th and 15th
16, 17th temperature value storage section 136, 137, 138
Comparison circuit 1 uses one of the stored numerical values as the reference temperature.
35 input terminal A. Therefore, in the comparator circuit 135, when each input value of input terminals A and B has a relationship of A≧B, in other words, 2
When the temperature rise value of the pot 5 per minute becomes below the reference temperature, a boiling detection signal Sz consisting of a high level signal is output.

In short, in this embodiment as well, when the temperature increase gradient of the pot 5 falls below a predetermined target temperature gradient (specifically, when the amount of change in the temperature of the pot 5 within a certain period of time falls below a predetermined reference temperature) ), the boiling detection signal Sz is outputted, and the reference temperature is automatically changed depending on the amount of rice cooked, thereby achieving the same effects as in the previous embodiment.

In addition, in each of the above embodiments, the temperature of the pot 5 is from 70°C.
Although the rice cooking amount detecting means 127 is configured to detect the rice cooking amount based on the time required for the rice to rise to 80° C., the temperature value for detection, that is, the first and second temperature value storage unit 26, The stored value of 27 is not limited to this, and it is also possible to provide a rice cooking amount detection means of another configuration, such as one that detects the rice cooking amount by measuring the entire weight of the pot 5. It's okay. Of course, each of the other temperature value storage units 28 to 39, 136 to 138 and each time value storage unit 40
The storage contents of 51 to 51 are not limited to the above-mentioned embodiments. In particular, the numerical values stored in the 14th storage section 39 for double-cooking heating control are stored in the storage circuit 8.
The numerical value stored in 2 may be substituted. Furthermore, in each of the above embodiments, the correction means 12
9, the duration of the boiling state is measured based on the value (110°C) stored in the fourth temperature value storage unit 29, but instead of measuring the duration of the boiling state at the point when the temperature of the pot 5 suddenly increases. The boiling duration may be measured based on the detection result. Furthermore, in each of the above embodiments, the amount of cooked rice detected by the amount of cooked rice detected by the rice cooking amount detecting means 127 is ranked in three stages, but this may be ranked in more stages. Means 128 or 132 and correction means 129
Although the configuration of 1 is also changed in accordance with this, by configuring it in this way, boiling detection can be performed more precisely. In each of the above embodiments, the electric power during double-cooking heating is changed by time control, but other configurations may be used as long as the average power of the heater 6 is changed. The energization time of the heater 6 does not need to be constant each time as in each of the above-mentioned embodiments, and may be made to become shorter in sequence during each double-cooking heating, for example. In addition, instead of the heater output control circuit 84, a circuit configured to reduce the output of the heater 6 using a phase control method may be adopted, and instead of the triax 14, another switching element such as a relay may be used. You can also do it. Furthermore, in the above embodiment, only the normal rice cooking operation was explained, but in addition to this, porridge cooking,
Of course, other rice cooking functions such as brown rice cooking may also be added.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without departing from the spirit thereof.

[Effects of the Invention] According to the present invention, as is clear from the above explanation, the heater output is reduced when the temperature inside the pot reaches a predetermined target temperature below the boiling temperature during rice cooking. , which can effectively prevent boiling over from the inside of the pot, and because the target temperature is configured to increase as the amount of rice cooked increases, the heater power is cut off according to the amount of rice that is cooked. The later thermal inertia becomes constant regardless of the amount of rice cooked, and the temperature inside the pot no longer rises excessively due to thermal inertia.
This has the excellent effect of reliably preventing the cooked rice from burning.

[Brief explanation of the drawing]

1 to 6 show a first embodiment of the present invention, in which FIG. 1 is a block diagram of the electrical configuration, FIG. 2 is a partially cutaway side view of the rice cooker, and FIG. The figure is a characteristic diagram of changes in pan temperature and heater output, Figure 4 is a timing chart showing the output waveforms of each part in Figure 1, and Figure 5 is a change in pan temperature and heater output under conditions different from those in Figure 3. The characteristic diagram, FIG. 6, is a timing chart showing the output waveforms of each part in FIG. 1 in a state different from that in FIG. 4. Further, FIG. 7 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention. In the figure, 1 is the rice cooker body, 5 is a pot, 6 is a heater (heating means), 7 is a thermal cap, 9 is a thermistor, 10 is a pot switch, 13 is a control circuit, 25 is a temperature detection means, and 83 is a heater drive circuit, 84 is a heater output control circuit (output control means), 101 is a start switch, 102 is a stop switch, 1
26 is a timing means, 127 is a rice cooking amount detection means, 12
8, 132 is boiling detection means, 129 is correction means,
Reference numeral 130 indicates double cooking control means, and reference numeral 131 indicates boiling detection compensation means.

Claims (1)

[Scope of Claims] 1. A device comprising a pot storing rice and water, heating means for heating the pot, and temperature detection means for outputting a temperature detection signal according to the temperature inside the pot. , in an electric rice cooker that cuts off power to the heating means when the temperature indicated by the temperature detection signal reaches a predetermined finished cooking temperature that is higher than the boiling temperature, a signal generation means that outputs a rice cooking amount signal corresponding to the amount of rice cooked; , measuring the increase value of the pot temperature within a reference time based on the temperature detection signal, and determining that the temperature inside the pot has reached a predetermined target temperature below the boiling temperature based on the amount of change in the measured temperature increase value; and an output control means that reduces the heating output of the heating means when the detection means is in the detection state, and the target temperature increases as the amount of cooked rice indicated by the rice cooking amount signal increases. A heating control method for an electric rice cooker, characterized by changing the temperature so that the temperature increases. 2. The signal generating means is configured to detect the amount of rice cooked according to the magnitude of the amount of change in temperature per unit time indicated by the temperature detection signal, and output the detection result as a rice cooking amount signal. A heating control method for an electric rice cooker according to claim 1.