JPH066096B2 - Boiling detection device in rice cooker - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention obtains a boiling detection signal when the water in a pan is in a boiling state, and the boiling detection signal can be used for rice cooking control. The present invention relates to a boiling detection device in a vessel.

[Technical background of the invention and its problems] In recent rice cookers, various rice cooker controls, specifically, a large rice cooker heater is used until the water in the pan boils when rice is cooked, for example. By making the output generate heat,
In addition to satisfying the so-called "medium pappa" which is one of the well-known conditions for deliciously cooking rice,
After boiling, the heater output is reduced to prevent the rice from sticking to the rice so that the rice can be cooked deliciously. The control for lowering the temperature and preventing the spillage is performed. However, when performing such control, it is necessary to detect whether or not the water in the pot is in a boiling state. However, in the conventional rice cooker, it is most common to detect the temperature of the pan and judge that it is in a boiling state when the detected temperature rises to a predetermined upper limit temperature. In order to accurately detect the state, it is desirable to set the reference temperature near 100 ° C. However, the maximum temperature is 100
If the temperature is set near ℃, the contact condition between the temperature sensor and the pan for detecting the pan temperature, the variation of the circuit constants of the temperature sensor and its characteristics over time, the change in atmospheric pressure or the cooked rice. When making, due to fluctuations in the boiling point due to the addition of seasonings into the pan, etc., it may not be possible to detect the boiling state despite the boiling state inside the pan. In reality, the upper limit temperature is set to around 80 ° C. in anticipation of such fluctuation. Therefore, in the conventional boiling detection device, there is a problem that the boiling state in the pan is extremely inaccurately detected, which in turn makes it impossible to accurately control the rice cooking by the rice cooker.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object thereof is to be able to detect a boiling state of water in a pan extremely accurately regardless of the amount of rice cooked by the pan. , It is to provide a boiling detection device in a rice cooker capable of accurately controlling rice cooking based on the detection result.

[Summary of the Invention] In order to achieve the above object, the present invention determines a boiling state when a rising rate of a pot temperature is equal to or lower than a predetermined target change rate, and outputs a boiling detection signal by outputting a boiling detection signal. In addition, a rice cooking amount detecting means for outputting a rice cooking amount signal according to the rice cooking amount is provided, and the boiling detecting means is configured to change the target as the rice cooking amount indicated by the rice cooking amount signal increases. The configuration is such that the correction is performed so that the rate becomes smaller.

[Embodiment 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 a rice cooker body including an inner frame 2 and an outer frame 3 and the like, 4 is a lid, 5 is a pot removably housed in the inner frame 2, and 6 is for heating the pot 5. For example, a rice cooking heater having a rated output of 600 watts is installed in the space between the bottoms of the inner frame 2 and the pan 5. Reference numeral 7 denotes a heat-sensitive cap that is vertically movably arranged so as to penetrate the bottom of the inner frame 2. This is always urged upward by the spring force of the compression coil spring 8, and the pot 5 is It is arranged so as to come into pressure contact with the outer bottom portion of the pot 5 when it is housed inside.
9 is a thermistor as a heat-sensitive element provided to detect the temperature of the pan 5 in the heat-sensitive cap 7, and 10 is only when the pan 5 containing rice and water is contained in the inner frame 2. It is a pan switch for preventing empty cooking which is pressed by the heat-sensitive cap 7 and turned on. Also, 11 is a rice cooker body 1
An operation panel 12 is installed on the side surface of the rice cooker, and a case 12 is provided on the outer bottom of the rice cooker body 1. The case 12 has the heater based on the temperature detected by the thermistor 9 and the input from the operation panel 11. A control circuit 13 for controlling the on / off of 6 is housed.

FIG. 1 shows the configuration of the control circuit 13 and the portions related thereto, which are directly related to the gist of the present invention, which will be described below. In addition, in FIG.
Although the control circuit 13 is shown as hardware by combining the respective functional portions, the present invention is not limited to this, and it goes without saying that the respective functional portions may be replaced by a program of a microcomputer.

In FIG. 1, 14 is, for example, a triac as a switching element, which is connected between both terminals of an AC power supply 15 through the heater 6 and the pan switch 10 in series. Reference numeral 16 is a photocoupler including a light emitting diode 16a and a phototransistor 16b.
7 and the resistor 18 are provided.
Reference numeral 19 is a DC constant voltage circuit that receives the output of the AC power supply 15,
Power is supplied from the output lines La and Lb to each circuit section described below.

Reference numeral 20 denotes an initialization circuit which is composed of, for example, a differentiating circuit, and outputs an initialization pulse P ₀ each time the power is turned on. Reference numeral 21 is a waveform shaping circuit for shaping the output of the photocoupler 16 (voltage output corresponding to the half-wave output of the AC power supply 15) into a rectangular wave.
Is a first frequency dividing circuit for dividing the output of the waveform shaping circuit 21 to generate a time signal, for example, a clock pulse P ₁ having a cycle of 1 second, and 23 is a time signal obtained by dividing the clock pulse P ₁ by frequency division. For example, a clock pulse P having a cycle of 10 seconds
_{It is a second} frequency divider circuit that outputs 2. Reference numeral 24 is an A / D converter which constitutes the temperature detecting means 25 together with the thermistor 9 and which outputs a digital value temperature detection signal Sd corresponding to the temperature of the pot 5 detected by the thermistor 9. 26 and 2
Reference numeral 7 is a first and second temperature value storage unit which stores numerical values corresponding to the temperatures used for detecting the amount of cooked rice, for example 70 ° C. and 80 ° C., respectively, and 28 corresponds to a predetermined lower limit temperature, for example 90 ° C. A third temperature value storage unit for storing numerical values, 29
Is a fourth temperature value storage unit that stores a numerical value corresponding to 110 ° C., for example. Further, reference numerals 30 to 39 are fifth to fourteenth temperature value storage units, which store, for example, the respective numerical values described below, as described in FIG.
That is, the fifth temperature value storage unit 30 stores a numerical value corresponding to 2 ° C., and the sixth, eighth, and eleventh temperature value storage units 3 are stored.
Numerical values corresponding to 3 ° C. are stored in 1, 33 and 36, numerical values corresponding to 1 ° C. are stored in the seventh and tenth temperature value storage units 32 and 35, respectively. Numerical values corresponding to 5 ° C. are stored in the temperature value storage units 34 and 37, respectively, and numerical values corresponding to 112 ° C. are stored in the thirteenth temperature value storage unit 38 as the heater disconnection temperature Dz. The temperature value storage unit 39 stores the temperature D for heating twice and starting heating.
A numerical value corresponding to 103 ° C. is stored as r. Four
Numerals 0 and 41 are first and second time value storage units which store the numerical values corresponding to, for example, 2 minutes and 4 minutes, respectively, which serve as a reference when detecting the amount of cooked rice. Numerals 42 to 51 are third to twelfth time value storage sections, which store, for example, the respective numerical values described below as described in FIG. That is, the third time value storage unit 42 stores the numerical value corresponding to 7 minutes, the fourth time value storage unit 43 stores the numerical value corresponding to 9 minutes, and the fifth and eighth time values are stored. Numerical values corresponding to 0 seconds are stored in the storage units 44 and 47, and numerical values corresponding to 10 seconds are stored in the sixth and ninth time value storage units 45 and 48, respectively. Numerical values corresponding to 20 seconds are stored in the time value storage units 46 and 49, respectively.
The time value storage unit 50 stores a numerical value corresponding to 30 seconds as the twice-cooking heating reference time N, and the twelfth time value storage unit 51 corresponds to a numerical value corresponding to 15 minutes as the rolling operation time M. Is remembered.

Reference numerals 52 to 64 denote 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 have a relation of A ≧ B and output terminal C when the relation of A <B. Outputs a low level signal. Reference numeral 65 denotes a comparison circuit having an enable terminal En, which performs the same operation as the comparison circuits 52 to 64 only when the enable terminal En receives a high level signal, and the enable terminal En receives a low level signal. When receiving the signal, the output terminal C always outputs a low level signal. Reference numerals 66 and 67 denote 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. 68 to 71 are addition circuits, which 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 count value from the output terminal Q.
The count contents are initialized when the pulse signal is received. Reference numerals 76 to 79 are trigger circuits, which output the trigger pulse P ₃ only for a short time when the input signal rises. Reference numeral 80 denotes a delay circuit, which delays the input signal for a short time and outputs it. 81 is 2 for example
This is a shift register having four unit registers, and this is a data terminal D every time a pulse signal is received at the clock terminal φ.
The input to the first unit register 81a is read and stored, and the old storage data is sequentially shifted to the upper unit register every time new data is read, and a pulse signal is supplied to the reset terminal R. When the data is received, the stored data is initialized. The shift register 81 is configured to output the stored data of the 12th unit register 81b, the 18th unit register 81c, and the 24th unit register 81d. Reference numeral 82 denotes a memory circuit, which is adapted to be initialized when a pulse signal is received at its reset terminal R, and has a structure for storing a value first inputted to the input terminal D from such an initialized state. Has been done. The triac 1 outputs the gate signal Sg only when it receives a high level signal.
A heater drive circuit to be applied to the gate terminal of No. 4 and a heater output control circuit 84 which is driven only when a high level signal is received. This heater output control circuit 84, for example, has a duty ratio of 50% when driven. Signal Sc
Is output. 85 to 100 are transfer gates,
These are conductive only when the gate terminal receives a high level signal.

101 and 102 are a start switch for starting rice and a stop switch for stopping rice, which are provided on the operation panel 11, respectively, and these are composed of momentary type push button switches, and are connected to corresponding lines only when turned on. Pulse signal (high level signal) P ₄ and P ₅
Are output respectively. Further, 103 to 105 are RS flip-flops, 106 to 115 are AND circuits, 116
Reference numerals 118 to 118 are OR circuits, and 119 to 125 are inverters. The first and second frequency dividing circuits 22 and 23 and the AN
The D circuit 108 constitutes the time measuring means 126, and includes the first and second temperature value storage units 26 and 27, the first and second time value storage units 40 and 41, and the comparison circuits 52, 53, 56 and 5.
7, the counter 72, the AND circuits 106 and 109 and the inverters 119 and 120 constitute the rice cooking amount detecting means 127, and the fifth temperature value storage unit 30, the comparison circuit 65, the subtraction circuit 66, the shift register 81 and the transfer gate 85, The boiling detection means 128 is constituted by 86 and 87, and the fourth temperature value storage unit 29, the third and fourth time value storage units 42 and 43, the comparison circuits 58 and 59, the counter 73,
AND circuits 107 and 110 and inverters 121 and 12
The correction means 129 is composed of 2 and includes a fourteenth temperature value storage unit 39 and fifth to twelfth time value storage units 44 to 5.
1, comparison circuits 62, 63, 64, addition circuits 70, 71,
Counters 74 and 75, trigger circuits 78 and 79, transfer gates 95 to 100, AND circuits 114 and 115
And the control means 130 that cooks twice with the inverter 125.
And the sixth temperature value storage unit 31, the comparison circuit 60, the subtraction circuit 67, the storage circuit 82, and the transfer gate 88 constitute a boiling detection compensating means 131.

Next, the operation of the above configuration will be described with reference to FIGS. 3 and 4. 3 (A) and 3 (B) show the time-dependent characteristics of the temperature detected by the thermistor 9 (that is, the temperature of the pot 5) and the output of the heater 6, respectively, and FIG. 4 shows the comparison circuit 52. , 53, 54, 55, 60, 61, 6
2, 63, 64, 65, heater output control circuit 84, start switch 101, RS flip-flop 103,
Each set output terminal Q of 104 and 105, AND circuit 10
6, 107, 113, 115 and the output waveforms from the OR circuit 118 are shown in correspondence with the respective symbols.

That is, when the pan 5 containing rice and a required amount of water is stored in the inner frame 2, the pan switch 10 is turned on according to the storage. When the power is turned on in this state, the DC power supply circuit 19
The photocoupler 16 is driven and the initialization circuit 2
Since the initialization pulse P ₀ is output from ₀ , the RS flip-flop 103 is generated by the initialization pulse P ₀ .
Is reset and a high level signal is output from the reset output terminal thereof. The high level signal initializes the counters 72 and 74 and the memory circuit 82, and
The RS flip-flop 105 is reset. At this time, the RS flip-flop 103
Since the trigger pulse P ₃ is output from the trigger circuit 76 which receives the high level signal from the OR circuit 117, the shift register 81 is generated by the trigger pulse P ₃ .
Is initialized, and the RS flip-flop 104 is reset by the high level signal also output from the OR circuit 117. After this, at time t ₀ (third
(See FIG. 4 and FIG. 4), when the start switch 101 is turned on, a pulse signal P ₄ output in response to the turning on
Sets the RS flip-flop 103,
The high level signal from the set output terminal Q is given to the AND circuits 112 and 113. At this time, one AN
Since the D rotation 112 is supplied with the low level signal from the set output terminal Q of the RS flip-flop 104 in the reset state as described above, its output remains the low level signal. AND circuit 113
Is supplied with the low level signal from the set output terminal Q of the RS flip-flop 104 inverted by the inverter 124 to the high level signal, and the reset output of the RS flip-flop 105 also in the reset state. Since the high level signal is applied from the terminal, the AND circuit 113 consequently outputs the high level signal to the heater drive circuit 83. Therefore, the gate signal Sg is output from the heater drive circuit 83 to turn on the triac 14, and in response to this, the AC power source 15 energizes the heater 6 via the pan switch 10 and the triac 14 to heat the pan 5. Then, the rice cooking process is started. As the rice cooking process progresses, the temperature of the pan 5 rises as shown in FIG. 3, and the temperature detection circuit 25 outputs a temperature detection signal Sd corresponding to the temperature of the pan 5. Then, when the temperature of the pan 5 rises to 70 ° C. stored in the first temperature value storage unit 26 (time t ₁ ), first, the cooked rice amount detecting means 127 operates. That is, in the cooked rice amount detecting means 127, the comparison circuit 5
2 indicates that the temperature detection signal Sd input to the terminal A is input to the terminal B from the first temperature value storage unit 26.
The low level signal is output until time t ₁ when the temperature value corresponding to “0 ° C.” becomes equal, and the high level signal is output after the time t ₁ . Further, in the comparison circuit 53, the temperature detection signal Sd input to the terminal B is second
The high level signal is output until time t ₂ when the temperature value becomes larger than the temperature value corresponding to “80 ° C.” input from the temperature value storage unit 27, and the low level signal is output after the time t ₂ . Therefore, both the comparison circuits 52, 52 only during the period from time t _{1 to} t ₂ .
A high level signal is output from 53 and the AND circuit 106
Is applied to the first frequency divider circuit 22 only during this period.
The pulse signal P ₁ having a cycle of 1 second from is passed through the AND circuit 106 and given to the clock terminal CK of the counter 72. Therefore, as a result, the count value of the counter 72 is
The temperature of the pot 5 becomes a value corresponding to the time Ta (the time from time t ₁ to t ₂ ) required for the temperature of 70 ° C. to rise to 80 ° C. Therefore, the time Ta measured as described above has the property of increasing or decreasing in proportion to the amount of cooked rice, and 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 determined by the comparison circuits 56 and 57 from the first and second time value storage units 4.
It is compared with each numerical value (corresponding to 2 minutes and 4 minutes) stored in 0 and 41, respectively. At this time, the comparison circuit 56 causes the counter 7
When the count value of 2 is smaller than the value corresponding to 2 minutes (in other words, when the amount of cooked rice is relatively small), a low level signal is output, and the low level signal is inverted by the inverter 119 into a high level signal which is a cooked rice amount signal. Applied to line L ₁ . Further, the comparison circuit 57 outputs a high level signal which is a rice cooking amount signal and gives it to the line L ₃ when the count value of the counter 72 is equal to or greater than the value corresponding to 4 minutes (in other words, when the rice cooking amount is relatively large). 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, the amount of cooked rice is medium), the comparison circuit 5
A high level signal is output from 6 and this is the AND circuit 1
09 is applied to one of the input terminals, and a low-level signal is output from the comparison circuit 57.
Then, the signal is inverted to a high level signal and applied to the other input terminal of the AND circuit 109. As a result, the AND circuit 109 outputs a high level signal which is a rice cooking amount signal and is applied to the line L ₂ . In short, the cooked rice amount detecting means 127 determines the amount of cooked rice based on the time required for the temperature of the pan 5 to rise from 70 ° C. to 80 ° C., and the cooked rice amount signal (high level signal) indicating the determination result. )
Is selectively output to lines L ₁ , L ₂ and L ₃ . When the amount of cooked rice thus detected is relatively small, the transfer gates 85, 89, 95 whose gate terminals are connected to the line L ₁ are in a conductive state, and when the detected amount of cooked rice is medium. Has a gate terminal on line L ₂
When the transfer gates 86, 90 and 96 connected to the switch are in the conductive state and the detected rice cooking amount is relatively large, the transfer gates 87, 91 and 97 whose gate terminals are connected to the line L ₃ are in the conductive state. Come to present. At this time, the seventh, eighth, and eighth gates corresponding to the transfer gates 89, 90, and 91 that are selectively turned on as described above.
The temperature values stored in the ninth temperature value storage units 32, 33, 34 are for adjusting the heater power-off temperature Dz (the temperature value stored in the thirteenth temperature value storage unit 38, that is, 112 ° C.). These storage temperature values are selectively given to the input terminal Y of the adding circuit 68 according to the magnitude of the detected rice cooking amount, and in the adding circuit 68, the temperature thus input is inputted. The value is added to the numerical value (heater disconnection temperature Dz) stored in the thirteenth temperature value storage unit 38 and output. Also,
Similarly, the time values stored in the fifth, sixth, and seventh time value storage units 44, 45, 46 corresponding to the transfer gates 95, 96, 97 which are selectively turned on as described above are cooked twice. The heating reference time N (time value stored in the eleventh time value storage unit 50, that is, 30 seconds) is adjusted, and these storage time values are detected by the input terminal Y of the adder circuit 70. In the adding circuit 70, the time value that is selectively given according to the amount of cooked rice and is input in this way is stored in the eleventh time value storage unit 50 (double heating standard time). N) and output. After this, pan 5
If the temperature rises further and becomes equal to or higher than the lower limit temperature “90 ° C.” stored in the third temperature value storage unit 28 (time t ₃ ),
Each input value to the input terminals A and B of the comparison circuit 54 is A ≧
With the relationship of B, the output of the comparison circuit 54 is inverted into a high level signal. As a result, the AND circuit 108 receiving the high level signal at one input terminal inputs to the other input terminal, that is, the pulse signal P ₂ of the 10-second cycle from the second frequency dividing circuit 23 in the time counting means 126. The passage is allowed, and the comparison circuit 54 is also provided.
The comparator circuit 65 which receives the high level signal from the input terminal at the enable terminal En through the delay circuit 80 becomes operable, and accordingly, the boiling detection function of the boiling detection means 128 is activated. That is, the pulse signal P ₂ is AN
When the pulse signal P ₂ passes through the D circuit 108, the pulse signal P ₂ is given to the clock terminal φ of the shift register 81. Therefore, the shift register 81 receives the input to the data terminal D, that is, the temperature detection signal Sd for 10 seconds. Each time the new temperature detection signal Sd is read, the old temperature detection signal Sd is sequentially shifted to the upper unit register. As a result, the present temperature detection signal Sd is stored in the 12th unit register 81b.
The temperature detection signal Sd 120 seconds (2 minutes) before is stored, and the 18th unit register 81c stores the temperature detection signal Sd 180 seconds (3 minutes) before the current temperature detection signal Sd. The temperature detection signal Sd 240 seconds (4 minutes) before the current temperature detection signal Sd is stored in the 24th unit register 81d. At this time, the respective storage data of the unit registers 81b, 81c and 81d correspond to the transfer gates 85 and 8 respectively.
It is adapted to be applied to the input terminal E of the subtraction circuit 66 via 6 and 87. However, as described above, when the amount of cooked rice is comparatively small, the transfer gate 85 is in the conductive state, and the unit register 81b. Is given to the input terminal E of the subtraction circuit 66. Similarly, when the amount of cooked rice is medium or relatively large, the respective storage data of the unit registers 81c and 81d are input to the subtraction circuit 66, respectively. Given to terminal E. The temperature detection signal Sd is directly input to the other input terminal D of the subtraction circuit 66. Therefore, the subtraction circuit 66 uses the numerical value indicated by the current temperature detection signal Sd in the present invention. The numerical value indicated by the temperature detection signal Sd 2 minutes before, 3 minutes before, or 4 minutes before corresponding to the reference time in the embodiment is subtracted,
The subtraction result is a fixed reference time (2 minutes, 3 minutes or 4 minutes).
It becomes a value corresponding to the temperature rise rate of the pan 5 within (min).
The temperature of the pot 5, that is, the rate of increase of the temperature detection signal Sd, has a property of becoming substantially zero when the water in the pot 5 is in a boiling state, and therefore the pot 5 within the reference time.
When it is detected that the temperature rise value of 1 has become equal to or lower than the predetermined comparison temperature value, it is possible to determine whether or not the pot 5 is in a boiling state. In this case, since the rate of temperature rise of the pan 5 has a tendency to become dull as the amount of cooked rice increases, it is desirable to change the reference time according to the amount of cooked rice in order to accurately detect boiling. Then, in order to perform such accurate temperature detection, the reference time (that is, the sampling time of the temperature detection signal Sd) referred to here is 2 minutes as described above,
It is automatically changed to either 3 minutes or 4 minutes. Then, in the comparison circuit 65, the output from the subtraction circuit 66 (the temperature rise value of the pan 5 within the three-step reference time determined according to the amount of cooked rice) and the fifth temperature value storage unit 3
When the temperature rise value of the pot 5 within the above reference time is less than 2 ° C, the comparison is made with the numerical value (corresponding to 2 ° C) stored as 0 for the comparison temperature value. Boiling detection signal S consisting of high level signal from circuit 65
z is output (time t ₄ ).

Then, at the time t ₄ , the memory content of the memory circuit 82 is in the initialized state, and the numerical value (corresponding to 3 ° C.) stored in the sixth temperature value memory unit 31 from the memory value is stored.
The output of the subtraction circuit 67 for subtracting is a negative value, and the comparison circuit 60 is in a state of outputting a low level signal. Therefore, the comparison circuit 6 is connected to both input terminals of the OR circuit 117.
0 and a low level signal is applied from the reset output terminal of the RS flip-flop 103, and the low level signal is inverted by the inverter 123 into a high level signal and applied to one input terminal of the AND circuit 111. . Therefore, the boiling detection signal Sz as described above at time t ₄ (high level signal) is outputted, a high level signal is output R-S flip-flop 104 from the AND circuit 111 is set. Then, the output of the AND circuit 113, which has output the high level signal until then, is inverted to the low level signal, and the set output terminals Q and R of the RS flip-flops 103 and 104 are connected to the respective input terminals of the AND circuit 112. A high level signal is applied from the reset output terminal of the -S flip-flop 105, and the AND circuit 112 outputs a high level signal. In response to this, the heater output control circuit 84
Outputs a pulse-shaped control signal Sc having a duty ratio of 50% and is supplied to the heater drive circuit 83. As a result, the triac 14 is turned on and off at a duty ratio of 50%, and the rated output of the heater 6 is 6 at this time.
Since it is 00 watts, the heater 6 will generate heat with an output of 300 watts, that is, half the rated output. Further, when the RS flip-flop 104 is set at the time t ₄ , the trigger circuit 77 is driven and the trigger pulse P ₃ is output from this, so that the counter 73 is initialized by the trigger pulse P ₃ . At the same time, the transfer gate 88 becomes conductive, and the temperature detection signal Sd at the time t ₄ (corresponding to the temperature of the pot 5 at the time when the boiling state is detected) is stored in the storage circuit 82. become. Further, at this point, since sufficient water still remains in the pan 5 and the temperature does not exceed 100 ° C., the temperature detection signal Sd corresponding to the temperature of the pan 5 and the fourth temperature value storage Memory value of part 29 (110 ° C
(Corresponding to the above) and the comparison circuit 55 outputs a high level signal.
The AND circuit 107, which has received the high level signal from the reset output terminal of the flip-flop 105, is in a state in which passage of the pulse signal P ₁ (1 second cycle) from the first frequency dividing circuit 22 is permitted. Therefore, the count value of the counter 73 initialized as described above indicates the elapsed time from the time t ₄ . Then, when the rice cooking process further progresses and the inside of the pan 5 exhibits a so-called dry-up state, the temperature of the pan 5 suddenly rises. In this case, the temperature of the pan 5 is at time t _5. At 110 ° C., the inputs of the input terminals A and B of the comparison circuit 55 become A <
Since the output is inverted to the low level signal due to the relationship of B, the AND circuit 107 blocks the passage of the pulse signal P ₁ and the counting operation of the counter 73 is stopped. Thus consequently, the count value of the counter 73, the time required from the time t ₄ when boiling detection signal Sz is output to the time t ₅ the temperature of the pan 5 has reached 110 ° C. Tb
(Corresponding to the duration of the boiling state).

The time Tb measured as described above also has the property of increasing or decreasing in proportion to the amount of cooked rice as well as the time Ta from time t ₁ to t ₂ described above, and also affects the ratio of rice to water during cooking. The correction means 129 corrects the rice cooked amount detected by the rice cooked amount detecting means 127 based on the count value of the count 73 corresponding to the time Tb as follows. That is, the count value of the counter 73 is the comparison circuit 5
According to 8, 59, the third and fourth time value storage units 42, 43
The respective numerical values (corresponding to 7 minutes and 9 minutes) stored in are compared respectively. At this time, the comparison circuit 58 outputs a low level signal when the count value of the counter 73 is smaller than the value corresponding to 7 minutes (in other words, when the amount of cooked rice is relatively small), and the low level signal is output by the inverter 121 to a high level. It is inverted into a level signal and given to the line L ₄ . Further, the comparison circuit 59 outputs a high level signal to the line L ₆ when the count value of the counter 73 is 9 minutes or more (in other words, when the amount of cooked rice is relatively large). 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, the amount of cooked rice is medium), a high level signal is output from the comparison circuit 58 and this is ANDed. The low level signal is applied to one input terminal of the circuit 110 and is output from the comparison circuit 59. The low level signal is inverted by the inverter 122 to be the high level signal.
The signal is supplied to the other input terminal of the D circuit 110, and as a result, a high level signal is output from the AND circuit 110 and supplied to the line L ₅ . When the amount of cooked rice thus detected is relatively small, the transfer gate 9 whose gate terminal is connected to the line L ₄
When 2,98 are conductive and the detected cooked rice amount is medium, the transfer gates 93 and 99 whose gate terminals are connected to the line L ₅ are conductive, and the detected cooked rice amount is relatively large. Then, the transfer gates 94 and 100 whose gate terminals are connected to the line L ₆ become conductive. At this time, the tenth, eleventh, and twelfth temperature value storage units 35, 36 corresponding to the transfer gates 92, 93, 94 which are selectively made conductive as described above.
The temperature value stored in 37 is also the heater disconnection temperature Dz.
This is for correcting the temperature value stored in the thirteenth temperature value storage unit 38, that is, 112 ° C., and these stored temperature values are applied to the input terminal Y of the adder circuit 69 for the time Tb.
In the adding circuit 69, the temperature value thus input is selectively applied according to the length of the value of the value of the numerical signal from the adding circuit 68 (that is, the amount of cooked rice with respect to the temperature value Dz for turning off the heater). The temperature value corresponding to the magnitude of the cooked rice amount detected by the detection means 127 is further added), and the added temperature value by the cooked rice amount detection means 127 and thus the detected cooked rice amount is corrected. . Also, the eighth, ninth, and tenth time value storage units 47, 48, 49 corresponding to the transfer gates 98, 99, 100 which are also selectively turned on.
Also, the time value stored in the second heating standard time N (the time value stored in the eleventh time value storage unit 50, ie, 30
Seconds), and these storage time values are selectively given to the input terminal Y of the adder circuit 71 according to the length of the time Tb. In the adder circuit 71,
The time value thus input is added to the numerical signal from the adding circuit 70 (that is, the time value corresponding to the magnitude of the cooked rice amount detected by the cooked rice amount detecting means 127 is added to the double-cooking heating reference time N). )), And thus the added time value by the cooked rice amount detecting means 127 and thus the detected cooked rice amount are corrected.

Now, at the subsequent time t ₆ , the temperature of the pan 5 corresponds to the output from the adder circuit 69, ie, the cooked rice temperature (that is, the heater power cut temperature Dz (112 ° C.), the cooked rice amount detecting means 127). Temperature value corresponding to the amount of cooked rice detected by and the temperature obtained by adding the correction temperature value by the correction means 129), the input values to the input terminals A and B of the comparison circuit 61 have a relationship of A ≧ B. , Its comparison circuit 61
Since a high level signal is output from the RS flip-flop 105, the RS flip-flop 105 is set. Then, the low-level signal from the reset output terminal of the RS flip-flop 105 is given to the AND circuit 112 and the output of the AND circuit 112 is inverted to the low-level signal, so that the heater output control circuit 84 is stopped. In response to this, the heater drive circuit 83 stops the output of the gate signal Sg and holds the triac 14 in the turned-off state, that is, the heater 6 is turned off, and the rice cooking process is completed. Then, at this time, the high level signal from the set output terminal Q of the RS flip-flop 105 is the AND circuit 114.
And 115, the AND circuit 114 allows the pulse signal P ₁ to pass therethrough, and in response to this, the double-cooking control means 130 functions and shifts to the unevenness stroke. In summary, the temperature of the pan 5 is 112 ° C., which is the heater power-off temperature Dz, with respect to the cooked rice amount detecting means 12.
Temperature value (any one of the temperature values stored in the seventh, eighth, and ninth temperature value storage units 32, 33, and 34) according to the amount of cooked rice detected by No. 7, and the correction temperature by the correction unit 129 Value (10th, 11th, 12th temperature value storage unit 35,
When one of the temperature values stored in Nos. 36 and 37) is reached and the cooked temperature is reached, the rice cooking process is terminated and the Muramura process is started. The action in the process will be described. In the case of this embodiment, the cooked temperature is 114 ° C. to 12 ° C. depending on the stored contents of the seventh to thirteenth temperature value storage units 32 to 38.
Varies between 2 ° C.

The counter 75 in the twice-cooking control means 130 has counted the pulse signal P ₁ from the time when the power is turned on, and therefore the count value is at least the numerical signal output from the adder circuit 71 at the time t ₆ (main In the case of the embodiment, the maximum value is 100 seconds), and as a result, each input value to the input terminals A and B of the comparison circuit 64 has a relation of A <B, and the comparison circuit 64 outputs a low level signal. Is being output. Further, since the other counter 74 in the twice cooking control means 130 starts the counting operation from the time t ₆ , each numerical value input to the input terminals A and B of the comparison circuit 62 is A at this time. The high level signal is output from the comparison circuit 62 in the relation of ≧ B.
When the heater 6 is cut off at time t ₆ ,
As shown in FIG. 3, the temperature of the pot 5 gradually decreases after it overshoots, and at the time t _{7, the} pot 5 becomes hot.
When the temperature of No. 2 decreases to the double-cooking start temperature Dr (103 ° C.) stored in the fourteenth temperature value storage unit 39, each input value to the input terminals A and B of the comparison circuit 63 becomes A ≧ B. Since a high level signal is output, the trigger circuit 78 receiving the high level signal triggers the trigger pulse P ₃
Is output, and the counter 75 is initialized by the trigger pulse P ₃ . Then, the input values of the input terminals A and B of the comparison circuit 64 have a relation of A ≧ B, and a high level signal is output from the comparison circuit 64. In response to this, to all the input terminals of the AND circuit 115. When the high level signal is given, the output of the AND circuit 115 is inverted to the high level signal. As a result, the above-mentioned AN
The heater drive circuit 83 receiving the high-level signal from the D circuit 115 turns off the triac 14 to re-energize the heater 6, and accordingly, the heating is performed twice. At this time, the count value of the counter 75 shows the elapsed time from the time t ₇ when the temperature of the pan 5 has dropped to 103 ° C., and the count value corresponds to the output from the adding circuit 71 at the time t ₈ . (That is, a time obtained by adding only a time value corresponding to the amount of cooked rice detected by the cooked rice amount detection unit 127 and a correction time value by the correction unit 129 to the reference time N (30 seconds) for double cooking and heating) , The input values to the input terminals A and B of the comparison circuit 64 have a relationship of A <B, and the output of the comparison circuit 64 is inverted to a low level signal, so the output of the AND circuit 115 is also inverted. Heater drive circuit 83 is the triac 14
Then, the heater 6 is cut off and the heating is stopped by heating twice. After this,
After heating the pot 5 once by heating it twice
At each time t ₉ and t _{11 when the} temperature drops to 03 ° C., the heater 6 is re-energized and boiled and heated in the same manner as described above, and in such a boiled heating, the count value of the counter 75 is added by the addition circuit 71. Is stopped at each of the times T ₁₀ and t ₁₂ when the time corresponding to the output from 1 has passed. Then, at time t ₁₃ when the uneven running time M (15 minutes) stored in the twelfth time value storage unit 51 elapses after time t ₆ , the count value of the counter 74 corresponds to the uneven running time M. Since the output of the comparison circuit 62 is inverted to a low level signal when the value exceeds the above value, the state where the AND circuit 115 outputs the low level signal and thus the state where the heater drive circuit 83 is stopped is held, and the unevenness occurs. The process is finished. When the output of the comparison circuit 62 is inverted to the low level signal as described above, the output of the inverter 125 is inverted to the high level signal and the trigger pulse P ₃ is output from the trigger circuit 79. _The RS flip-flop 103 is reset by ₃ and thereafter, the process proceeds to a heat retention process by a heat retention heater (not shown). In summary, in the Murashi process, the temperature of the pan 5 is twice the starting temperature Dr 103
When the temperature drops to ℃, the heater 6 is re-energized, and the energization time is a time value (the first value corresponding to the amount of cooked rice detected by the cooked rice amount detecting means 127) for 30 seconds which is the reference time N for heating twice and N 5, fifth and seventh time value storage units 44, 4
5, any of the time values stored in 46) and the correction time value by the correction means 129 (any of the time values stored in the eighth, ninth, and tenth time value storage units 47, 48, 49). When the time obtained by adding (1) is reached, the control of turning off the heater 6 and terminating the heating by heating twice is repeated. In the case of the present embodiment, the above-mentioned heating time by heating twice is It is changed between 30 seconds and 70 seconds according to the storage contents of the fifth to eleventh time value storage sections 44 to 50.

Now, up to this point, the operation when the temperature of the pot 5 rises without lowering after the boiling detection signal Sz is output at time t _{4 and} the output of the heater 6 is dropped to half of the rated value will be described. However, in the following, the operation when the temperature of the pot 5 is lowered after the output of the heater 6 is reduced in this way is similar to FIGS. 3 and 4, and is similar to FIGS. 5 and 6 respectively. Description will be given with reference to the drawings. That is, the phenomenon that the temperature of the pot 5 drops when the output of the heater 6 is reduced to half is that the water in the pot 5 is not yet boiling (in other words, when the boiling detection signal Sz is erroneously output). Such a phenomenon may occur in the pot 5, for example, when the cooked rice is cooked, the seasoning such as soy sauce put in the pot 5 is scorched at the bottom of the pot 5, whereby water in the pot 5 is absorbed. It is believed that this is due to the large gap between the temperature and the temperature detected by the thermistor 9.
Then, at the time t _{4 in} FIGS. 5 and 6, the heater 6
When the output of the pot is halved, the temperature detection signal Sd corresponding to the temperature of the pot 5 at that time (that is, the temperature of the pot 5 when the boiling detection means 128 detects that the boiling state is in the boiling state) as described above. The storage circuit 82 in the boiling detection compensating means 131.
Memorized in. At this time, in the subtraction circuit 67 in the boiling detection compensating means 131, the stored value of the sixth temperature value storage unit 31 (corresponding to 3 ° C.) is subtracted from the stored value of the storage circuit 82, and the subtraction result To the input terminal A of the comparison circuit 60. Therefore, after that, when the temperature of the pan 5 is reduced to the temperature value Tp (time t ₄₁ ), the output of the comparison circuit 60 is inverted to a high level signal, and the RS flip-flop 10 is accordingly responsive.
4 is reset, the trigger circuit 76 is driven, and the shift register 81 is initialized by the trigger pulse P ₃ from the trigger circuit 76. Therefore, AND
The output of the circuit 112 is inverted to a low level signal,
The output of the AND circuit 113 is inverted to a high level signal,
A high level signal is continuously supplied to the heater drive circuit 83, and accordingly, the heater 6 generates heat at a rated output, that is, an output of 600 watts. Further, in response to the initialization of the shift register 81 as described above, the boiling detection means 128 performs the boiling state detection operation similar to that described above. For example, at the time t _{42, the} boiling detection signal is output from the comparison circuit 65. When Sz is output, the output of the heater 6 is halved again. When the temperature of the pan 5 is lowered again after this, the same operation as described above is repeated, and the boiling detection compensating means 131 makes the detecting operation of the boiling detecting means 128 more accurate as described above. Works like.

According to this embodiment described above, the following effects can be obtained. That is, the state in which the water in the pot 5 is boiling is not detected based on the absolute upper limit temperature which is predetermined as in the conventional case, but when the water in the pot 5 is in the boiling state, the pot 5 The rate of temperature rise of the pan is less than or equal to the target rate of change (specifically, the amount of change in the temperature of the pan 5 within a predetermined reference time is the constant comparison temperature stored in the fifth temperature value storage unit 30). Since the temperature is detected based on the value (2 ° C. or less), the contact state between the heat-sensitive cap 7 and the bottom of the pan 5 and the thermistor 9 or A-D forming the temperature detecting means 25 are detected. Even if there are variations in the circuit constants of the converter 24, changes in its characteristics over time, changes in atmospheric pressure, or fluctuations in the boiling point due to the addition of seasonings into the pan 5 when making cooked rice. The boiling state of water in the pan 5 can be accurately detected. . Further, when the boiling state is detected in this way, the above-mentioned boiling detection becomes inaccurate when the amount of cooked rice is different because the rate of temperature rise of the pan 5 changes depending on the amount of cooked rice. However, in this embodiment, the target change rate for boiling detection is corrected according to the amount of cooked rice detected by the cooked rice amount detecting means 127 (specifically, the rate of temperature rise of the pan 5). Configuration that changes the reference time required when measuring
Therefore, the boiling state of the water in the pan 5 can always be detected accurately even when the amount of cooked rice is different. Then, in this embodiment, after the heater 6 is heated at the rated output until the boiling state is detected, the heater 6 is heated.
In this case, the rice cooking control is performed by halving the output. However, in this case, since the boiling state is accurately detected as described above, the above rice cooking control can be strictly performed, so that the rice is cooked deliciously. The condition of so-called "medium papa", which is one of the conditions described above, can be sufficiently satisfied, and the rice can be cooked with less charring, so that the rice can be cooked well as a whole. Of course, the boiling state in the pan 5 is accurately detected in this way, and the output of the heater 6 is halved after the boiling is detected. Therefore, when this configuration is applied to porridge cooking control, It is possible to reliably prevent spillage. Further, in the present embodiment, the larger the amount of cooked rice detected by the cooked rice amount detecting means 127, in other words, the state in which a relatively large amount of unnecessary water remains in the pan 5 during dry-up, the power to the heater 6 is cut off. Since the temperature, that is, the temperature at which the rice is cooked is raised, the rice can be cooked well from this aspect. Moreover,
In this case, the correction means 129 is provided, and the cooked rice amount detection means 1
Since the amount of cooked rice detected by 27 is corrected according to the length of the period in which the water in the pan 5 is in the boiling state, the cooked rice control according to the size of the cooked rice and the ratio of rice and water during cooking is better. It can be done strictly. Further, the twice-boiled heating time in the Murashi process is also changed to a time according to the amount of cooked rice detected by the cooked rice amount detecting means 127 and corrected by the correcting means 129. The cooked rice can be made even more delicious as it can be fully and fully cooked. In addition, when making cooked rice, the boiling detection compensating means 131 compensates for an error in boiling detection due to burning of seasonings such as soy sauce put in the pan 5 and the like. Even when the temperature detected by the temperature detecting means 25 deviates from the actual temperature in the pot 5, such as when the pot 5 falls into a special state as described above, the boiling state of the water in the pot 5 Can be detected extremely accurately. Further, in each of the above embodiments, the function of the boiling detection means 128 is activated only when the temperature of the pan 5 reaches the lower limit temperature (90 ° C.) stored in the third temperature value storage unit 28. Because there is a third
There is no risk of erroneously detecting a period in which the temperature gradient is in a flat state as a boiling state, such as when the temperature of the pot 5 rises as indicated by G in the figure.

FIG. 7 shows a second embodiment of the present invention, and only the parts different from the first embodiment will be described below. That is, the second embodiment is characterized in that the boiling detection means 128 in the first embodiment is replaced with a boiling detection means 132 having a different function from that of the first embodiment. 132 will be described. In the boiling detection means 132, 133 is a shift register having, for example, 12 unit registers, and the storage data of the 12th unit register 133a is applied 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 first
The shift register 81, the subtraction circuit 66, and the comparison circuit 65 in the embodiment of FIG.
Further, 136, 137, 138 are the 15th, 16th, 1st
7 in the temperature value storage unit, which are the reference temperatures 2 ° C., 1.5 ° C., which are the reference temperatures in the embodiment of the present invention. The numerical value corresponding to 1 ° C is stored. Furthermore, 139, 140, 141
Is a transfer gate provided corresponding to each of the storage units 136, 137, 138, and its gate terminal is connected to the lines L ₁ , L ₂ , L ₃ .

In the present embodiment, the current temperature detection signal Sd is given to the input terminal D of the subtraction circuit 134, and the data stored in the unit register 133a of the shift register 133, that is, the temperature detection at the time point 120 seconds (2 minutes) before. The signal Sd is given to the input terminal E of the subtraction circuit 134, and therefore, the numerical signal given from the subtraction circuit 134 to the input terminal B of the comparison circuit 135 corresponds to the temperature rise value of the pan 5 for a fixed time of 2 minutes. It will be what you did. At this time, any one of the transfer gates 139 to 141 is in a conductive state according to the size of the cooked rice amount detected by the cooked rice amount detecting means 127, and the fifteenth, sixteenth, and seventeenth temperature value storage units 136, 136 are provided. Either of the stored numerical values 137 and 138 is applied to the input terminal A of the comparison circuit 135 as the reference temperature. Therefore, in the comparison circuit 135, the input terminals A,
When each input value of B has a relation of A ≧ B, in other words, when the temperature rise value of the pot 5 in 2 minutes becomes equal to or lower than the reference temperature, the boiling detection signal Sz including a high level signal.
Is output.

In short, also in the present embodiment, when the temperature rise rate of the pan 5 is equal to or lower than a predetermined target change rate (specifically, when the temperature change amount of the pan 5 is equal to or lower than a predetermined reference temperature within a certain period of time). ), The reference temperature is automatically changed according to the amount of cooked rice, and the same effect as the above embodiment can be obtained.

In each of the above examples, the temperature of the pot 5 is 70 ° C to 80 ° C.
The rice-cooking amount detecting means 127 configured to detect the rice-cooking amount based on the time required to rise to
The detection temperature value, that is, the first and second temperature value storage units 26,
The stored value of 27 is not limited to this, and the cooked rice amount detecting means having another configuration may be provided, such as one that detects the cooked rice amount by measuring the total weight of the pan 5. good. Of course, the other temperature value storage units 28 to 3
9, 136 to 138 and time value storage units 40 to 51
The storage content of is not limited to the above embodiments,
In particular, the numerical value stored in the fourteenth storage unit 39 for the double heating control may be replaced by the numerical value stored in the storage circuit 82. Furthermore, in each of the above-described embodiments, the measurement of the duration of the boiling state by the correction unit 129 is performed by the numerical value (110 ° C.) stored in the fourth temperature value storage unit 29.
However, instead of this, it is also possible to detect the time when the temperature of the pot 5 rises sharply and measure the boiling duration based on the detection result. Further, in each of the above-mentioned embodiments, the rice cooked amount detected by the rice cooked amount detecting means 127 is ranked in three stages, but it may be ranked in multiple stages. Of course, in this case, boiling detection is performed. The configurations of the means 128 or 132 and the correction means 129 are also changed accordingly.
With such a configuration, boiling detection can be performed more finely. In each of the above-mentioned embodiments, the electric power at the time of double heating is changed by time control. However, another structure may be used as long as the average electric power of the heater 6 is changed, and the heater at the time of double heating. The energization time of 6 does not have to be constant in each time as in the above-described embodiments, and may be set to be a short time sequentially when heating twice for each heating. In addition, instead of the heater output control circuit 84, a configuration in which the output of the heater 6 is reduced by a phase control method may be adopted, and instead of the triac 14, another switching element such as a relay may be used. You can Further, in the above-described embodiment, the case where only the normal rice cooking operation is performed has been described. However, in addition to this, other rice cooking functions such as rice porridge cooking and brown rice cooking may be added.

Besides, the present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be carried out without departing from the scope of the invention.

[Effects of the Invention] According to the present invention, as is clear from the above description, the boiling state of water in a pot can be detected extremely accurately regardless of the amount of cooked rice. It has an excellent effect that the rice cooking control based on the detection result can be accurately performed.

[Brief description of drawings]

1 to 6 show a first embodiment of the present invention. FIG. 1 is a block diagram of an electrical configuration, FIG. 2 is a side view showing a partially cutaway view of a rice cooker, and FIG. FIG. 4 is a change characteristic diagram of pan temperature and heater output, FIG. 4 is a timing chart showing output waveforms of respective parts in FIG. 1, and FIG. 5 is change of pan temperature and heater output in a state different from that of FIG. FIG. 6 is a timing chart showing the output waveform of each part in FIG. 1 in a state different from that of FIG. FIG. 7 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. In the figure, 1 is a rice cooker main body, 5 is a pan, 6 is a heater, 7 is a heat cap, 9 is a thermistor, 10 is a pan switch, 13 is a control circuit, 25 is a temperature detecting means, 83 is a heater drive circuit, and 84 is Heater output control circuit, 101 is a start switch, 102 is a stop switch, 126 is a time measuring means,
127 is a rice cooking amount detecting means, 128 and 132 are boiling detecting means, 129 is a correcting means, 130 is a double cooking control means, 1
Reference numeral 31 denotes a boiling detection compensating means.

Front page continuation (72) Inventor Teruo Aoshima 4-21, Yoshihara-cho, Nishi-ku, Nagoya-shi, Aichi Toshiba Corporation Nagoya factory (56) Reference JP-A-58-44012 (JP, A)

Claims (5)

[Claims] 1. A temperature detecting means for outputting a temperature detecting signal according to the temperature of a pot, a time measuring means for outputting a time signal indicating an elapsed time during a rice cooking operation, and a rice cooking amount signal according to a rice cooking amount. The amount of cooked rice is detected, and the rate of rise of the pot temperature is measured based on the temperature detection signal and the time signal, and the water in the pot boils when the measured rate of temperature rise falls below a predetermined target change rate. And a boiling detection unit that outputs a boiling detection signal, and the boiling detection unit corrects the target change rate such that the target rate of change becomes smaller as the rice cooking amount indicated by the rice cooking amount signal increases. A boiling detection device in a rice cooker, which is configured to perform an operation. 2. A large amount of cooked rice indicated by the cooked rice amount signal for the reference time, which is not provided for the boiling detection means so as to measure the rise rate of the pot temperature based on the amount of change in the temperature detection signal within the reference time. The boiling detection device in a rice cooker according to claim 1, wherein the boiling detection device is configured to correct the target change rate so as to be small by changing the time so that the target change rate becomes smaller. 3. The boiling detection means is provided so as to measure the rate of rise of the pot temperature by comparing the amount of change in the temperature indicated by the temperature detection signal within a certain period of time with the reference temperature. The rice cooker according to claim 1, wherein the rice cooker has a configuration in which the target change rate is corrected by changing the rice cooker so that the rice cooker has a lower rice cooker when the rice cooker has a larger amount. Detector for boiling water. 4. The boiling detection means is configured to activate the boiling detection function only when the temperature indicated by the temperature detection signal becomes equal to or higher than a predetermined lower limit temperature. A boiling detection device in the rice cooker according to item 1. 5. The cooked rice amount detecting means is configured to detect the cooked rice amount according to the magnitude of the amount of change per unit time of the temperature indicated by the temperature detection signal. A boiling detection device in the rice cooker according to item 1.