JPH0339689B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a rice cooker equipped with a control circuit that cuts off power to a heater for heating a pot to execute a rice cooking process based on the pot temperature detected by a temperature sensor. The present invention relates to rice cookers, and particularly to rice cookers equipped with a time display section.

[Technical background of the invention and its problems]

In this type of rice cooker, a thermistor is generally used as a temperature sensor, but if this thermistor malfunctions, rice cannot be cooked. For this reason, for example,
As disclosed in Publication No. 136015, when a contact failure or disconnection failure occurs in the temperature detection circuit including the thermistor body, lead wire, and connector, the temperature detected by the thermistor exceeds the normal detection temperature range. There is a known device that utilizes this to display a failure indication on a display device. However, in addition to the so-called "open circuit failure" disclosed in the above-mentioned publication, there are also "short circuit failures" as failures in temperature detection circuits including thermistors. This was an oversight, and in diagnosing failures, it was desired to be able to see the type of failure at a glance. Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 55-136015 had the problem of increasing the number of parts because it required a separate display device.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to be able to reliably notify the user of the details of the failure when a temperature sensor fails, and to prevent the number of parts for indicating the failure from increasing even with such a configuration. To provide a rice cooker that does not cause problems such as complication of assembly work.

[Summary of the invention]

The present invention includes a time display section provided on the outer surface of an outer case of the rice cooker main body, and a temperature sensor provided to detect the temperature of a pot housed in the inner case of the rice cooker main body. In the rice cooker, a conversion means converts a temperature value signal corresponding to the temperature sensed by the temperature sensor into a digital signal, and a control for controlling energization/disconnection of the heater for heating the pot based on the signal from the conversion means. means, detecting a short circuit failure and a disconnection failure of the temperature sensor based on a comparison between the signal from the converting means and a pre-stored temperature value for detecting a short circuit failure and a temperature value for detecting a disconnection failure, and generating an abnormal signal. The present invention is configured to include a detection means and a display control means for causing the time display section to display a failure display corresponding to the details of the failure when the abnormality signal is received.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is the main body of the rice cooker consisting of an inner case 2 and an outer case 3, 4 is a lid, 5 is a pot housed in the inner case 2, and 6 is a space between the bottoms of the inner case 2 and the pot 5. This is a heater placed in the space. 7
is a cup-shaped heat-sensitive part provided so as to be elastically pressed against the outer bottom of the pot 5, and a thermistor 8 serving as a temperature sensor is housed inside the heat-sensitive part 9.
The temperature of the pot 5 can be sensed by the thermistor 8. Reference numeral 10 denotes a case disposed on the outer bottom of the rice cooker body 1, and inside the case there are a control circuit 11 as a control means whose circuit configuration is shown in FIG. 3, a detection circuit 12 as a detection means, and a display control as a display control means. A circuit 13 and a timer 14 are housed. Further, 15 is a digital time display section disposed on the outer surface of the outer case 3, which has, for example, four 7-segment light emitting diodes 15a to 15d in a horizontal row as shown in FIG. The remaining time of the timer 14 is displayed.

Next, in FIG. 3, reference numeral 16 is an AC power source, and the heater 6 is connected between both terminals of the AC power source via a normally open relay switch 17. 18 is a drive circuit that turns on the relay switch 17 only when the signal "1" is input; 19 is a start switch for starting rice cooking; when the start switch 19 is turned on, a signal " ₁ " is sent to the line L1; ”
is output. Further, 20 is an auxiliary drive circuit which turns on the start switch 19 only when a signal "1" is input. 21 is a pulse generator, which consists of a shaping circuit 22 that shapes the waveform of the output of the AC power supply 16 and a frequency dividing circuit 23 that divides the frequency of the output of this shaping circuit 22;
is configured to output a clock pulse Pc to line _L2 at a cycle of, for example, one second, and output a clock pulse Pc to line _L3 at a cycle of, for example, one minute. 24 is an A-D converter which is a conversion means that receives the resistance value of the thermistor 8 as an input;
It digitally converts the input value each time it receives a clock pulse Pc from line _L2 at its terminal φ. A temperature converter 25 constitutes the temperature measuring section 26 together with the thermistor 8 and the A-D converter 24, and this converts the output of the A-D converter 24 into a digital temperature value every time a clock pulse Pc is received at its terminal φ. Convert the digital temperature value to the thermistor 8
Temperature value signal Sd corresponding to the temperature of the pot 5 detected by
output to line L ₄ as

Now, in the following, the control circuit 11, the detection circuit 12, the display control circuit 13, and the timer 14 will be explained in terms of hardware using logic circuits and functional blocks. 12. Of course, the same functions as the display control circuit 13 and the timer 14 may be obtained.

First, an overview of each functional block of the control circuit 11 will be explained. 27 is a calculation unit that receives the temperature value signal Sd at the input terminal I, and this calculates when the temperature gradient of the pot 5 corresponding to the temperature value signal Sd starts to rise from a flat state (the state where the water in the pot 5 is boiling). When the output of the output terminal _P0 is reversed from the previous signal "0" to the signal "1", the temperature value signal when the temperature gradient of the pot 5 starts to rise
Based on Sd, the finished cooking temperature value D ₁ and the double cooking temperature value D ₂ (however, D ₁ > D ₂ ) are outputted to the output terminals P 1 and ₂ , respectively.
Output from _P2 . A counter 28 counts the pulses input to the clock input terminal CK, and is cleared when a signal "1" is input to the clear terminal CL. Comparing units 29 to 31 output a signal "1" when the input value of the terminal A is greater than or equal to the input value of the terminal B, and output a signal "0" in other cases. Reference numeral 32 denotes a double-cooking storage section, in which a double-cooking time value T ₃₂ (for example, 900 (seconds) in this embodiment) is stored. Further, 33 is an R-S flip-flop, 34 to 36 are AND circuits, and 37 and 38 are
The OR circuit and 39 are NOT circuits.

Next, an overview of each functional block of the detection circuit 12 will be explained. Reference numerals 40 and 41 are constant storage parts, in which a temperature value T ₄₀ (for example, 300
(℃)) and the temperature value T ₄₁ (for example 0
(°C)) are respectively memorized. Comparing sections 42 and 43 have the same structure as the comparing sections 29 to 31 described above.

Next, an overview of each functional block of the display control circuit 13 will be explained. 44 to 47 are drivers for driving the light emitting diodes 15a to 15d, respectively, and these drivers cause the corresponding light emitting diodes to display characters or numbers according to display signals and numerical signals received at their terminals M and N, respectively. . 48 to 55 are display storage units, and the storage unit 48 stores display signals corresponding to “-”.
S ₄₈ and storage section 49 respectively store a display signal S ₄₉ corresponding to the alpha bet "0", storage sections 50 and 51 respectively store display signals S ₅₀ and S ₅₁ corresponding to the alpha bet "F",
Similarly, display signals S ₅₂ , S 53 , and S 55 corresponding to alpha alphabets "S", "H", "r", and "t" are stored in storage units 52, ₅₃ , 54, and ₅₅ , respectively. Reference numerals 56 and 57 are gate circuits for the display storage units 48 to 55, and these gate terminals G
Opens only when signal ``1'' is received. Also,
58 to 61 are OR circuits, 62 to 66 are NOT circuits, 67 to 74 are transfer gates,
These transfer gates 67 to 74 exhibit low impedance and allow the signal to pass only when a signal "1" is input to their gate terminals.

On the other hand, an outline of each functional block of the timer 14 is as follows. 75 is a count section, which is composed of a hexadecimal counter corresponding to the "hour" element and a sexagesimal counter corresponding to the "minute" element.The hexadecimal counter receives the pulses input to the clock input terminal _CK1 . The sexagesimal counter counts the pulses input to the clock input terminal _CK2 . 7
6 is the count content of the counting unit 75 which is transferred to 13
This is a down count section that is preset to a hexadecimal down counter and a sexagesimal down counter, respectively, and its output terminals P ₁ and P ₂ correspond to the upper and lower digits of the count contents of the hexadecimal down counter, respectively. ₃ and _P4 correspond to the upper and lower digits of the count contents of the sexagesimal down counter, respectively. still,
The above hexadecimal down counter is clock input terminal CK.
The 13-decimal down counter counts the carry signal of the 60-decimal down counter. Also,
The down-count unit 76 outputs a numerical signal "0" from the output terminal P ₀ when the counts of the hexadecimal down counter and the sexagenical down counter both reach zero, and otherwise outputs a numerical signal "0" from the output terminal P ₀ . Outputs a numerical signal other than "0". Reference numeral 77 denotes a comparator, which outputs a signal "1" only when the inputs to terminal A and terminal B become equal. Reference numeral 78 denotes a timer storage section in which a numerical value "0" is stored. 79 and 80 are switches for setting timer time, and when these are turned on, a signal "1" is output to the corresponding lines _L5 and _L6 , respectively. Further, 81 and 82 are AND circuits.

Next, the specific signal flow shown in FIG. 3 will be explained with reference to its effect and the temporal change characteristic diagram of the temperature of the pot 5 shown in FIG. 4. Now, if it is desired to start cooking rice after 12 hours, for example, the timer time of the timer 14 is set using the switches 79 and 80 with a predetermined amount of rice and water stored in the pot 5. That is, when switch 79 is turned on,
As the AND circuit 81 allows the clock pulse Pc to pass, the count of the hexadecimal counter in the counting section 75 progresses. Then, the count contents are transferred to the down-count section 76, and the count contents of the hexadecimal counter are output from the output terminals _P1 and _P2 of the down-count section 76. In this state, a numerical signal other than "0" is output from the output terminal P ₀ of the down-counting section 76 and this numerical signal is given to the terminal A of the comparing section 77.
7 outputs a signal "0" because the input to its terminal A and the input to its terminal B (the numerical value "0" stored in the timer storage section 78) do not match, and this signal "0" After the signal is inverted to “1” by the NOT circuit 66, the transfer gate 6
These gate terminals are applied to gate terminals 7 to 70 to allow signals to pass through. Also, at this point, as will be understood from the description below, the NOT circuits 62 to 65
Since the signal "1" is outputted from the transfer gate 7 and the signal "1" is given to the gate terminals of the transfer gates 71 to 74, these transfer gates 7
1 to 74 also allow the passage of signals. Therefore, the numerical signals from the output terminals P ₁ and P ₂ of the down-counting section 76 (corresponding to the count value of the hexadecimal counter in the counting section 75) are sent to the transfer gates 67 and 6.
8, 71, 72 and is applied to the terminals N of the drivers 44, 45, and the light emitting diodes 15a, 1
In 5b, the numbers corresponding to the time are "1", "2", "3",
... will be displayed sequentially, so if you release the on operation of the switch 79 when the display reaches "12", the hexadecimal down counter in the down count section 76 will be preset to "12". Thus, the timer time of the timer 14 is set to 12 hours. still,
To set the timer time of the timer 14 in minutes, the switch 80 may be turned on. When the timer time of the timer 14 is thus set, the down-counter 76 starts counting clock pulses Pc' with a period of 1 minute, and the counting output from its output terminals _P1 to _P4 gradually decreases. The display contents of the time display section 15 (timer 14
(remaining timer time) will gradually decrease every minute. After this, when the timer operation of the timer 14 ends at time t ₀ in FIG. 4, in other words, the count contents of the hexadecimal down counter and the sexagesimal down counter in the down counting section 76 both become zero and the time is displayed. When the display content of section 15 reaches 0:00, a numerical signal "0" is output from output terminal P ₀ of downcount section 76, so inputs to terminals A and B of comparison section 77 match and the comparison is performed. A signal “1” is output from the section 77. Then, the auxiliary drive circuit 20 that receives the signal "1" turns on the start switch 19, so that the signal "1" is output to the line _L1 , and this signal "1" causes the counter 2 to turn on.
8 is cleared, and R- receives the above signal "1" through the OR circuit 37 at the set input terminal
The S flip-flop 33 is set so that the signal "1" from its output terminal Q is applied to the drive circuit 18. Therefore, the relay switch 17 is turned on by the drive circuit 18, and the heater 6 is energized from the AC power source 16, so that the rice cooking operation of heating the pot 5 by the heater 6 is started. . With the start of such a rice cooking operation, the temperature of the pot 5 rises as shown in FIG. 4, and a temperature value signal Sd corresponding to the temperature is sent from the temperature converter 25 to
It will be output at a second period (period of clock pulse Pc). When the water in the pot 5 is boiling, the temperature gradient of the pot 5 becomes flat, but at time _t1 in FIG. 4, the temperature of the pot 5 is Ds.
℃ and the temperature gradient suddenly rises from a flat state, the calculation unit 27 outputs a signal "1" from its output terminal _P0 , and outputs the signal "1" from its output terminal _P1 , P2 _.
From this, a finished cooking temperature value D ₁ and a double cooking temperature value D ₂ corresponding to the temperature Ds are output, respectively. Then, since the signal "1" output from the output terminal _P0 is given to each input terminal of the AND circuits 34, 35, and 36, the AND circuit 36 allows the clock pulse Pc given to the other input terminal to pass through. The counter 28 then starts counting. On the other hand, the finished cooking temperature value D ₁ output from the output terminal P ₁ is compared with the temperature value signal Sd by the comparator 30, and when the temperature value signal Sd exceeds the finished cooking temperature value D ₁ at time t ₂ . , a signal “1” is output from the comparator 30 and applied to one input terminal of the AND circuit 35. At this time, since the signal "1" is given to the other input terminal of the AND circuit 35 from the output terminal _P0 of the calculation section 27, the AND circuit 35 outputs the signal "1", and this signal "1" is applied to the other input terminal of the AND circuit 35. ” is R− through the OR circuit 38
It is applied to the reset input terminal R of the S flip-flop 33. Therefore, R-S flip-flop 3
3 is reset and the supply of the signal "1" to the drive circuit 18 is stopped, so the relay switch 17 is turned off and the heater 6 is cut off, and after this, the operation shifts to double cooking operation (uneven operation). Ru. When the operation is shifted to double-cooking in this way, the temperature value for double-cooking D ₂ outputted from the output terminal P ₂ of the calculation section 27
is compared with the temperature value signal Sd in the comparator 29, and when the temperature value signal Sd becomes equal to the double-cooking temperature value _D2 at time _t3 as the temperature of the pot 5 decreases due to the power outage of the heater 6, A signal “1” is output from the comparator 29 and applied to the second input terminal of the three-input type AND circuit 34. At this time, since the signal "1" is applied to the first and third input terminals of the AND circuit 34 from the output terminal P ₀ of the calculation section 27 and the comparison section 31, respectively, the AND circuit 34 receives the signal "1". ”, and this signal “1” is sent to R via the OR circuit 37.
-S is applied to the set input terminal S of the flip-flop 33. Therefore, R-S flip-flop 3
3 is set and the signal "1" is sent to the drive circuit 18 again.
is given, relay switch 1
7 is turned on to re-energize the heater 6, which causes the pot 5 to
This is called double-cooking, where the rice is reheated. Thereafter, when the temperature value signal Sd exceeds the cooked temperature value _D1 in accordance with the temperature rise of the pot 5 due to the double cooking, the heater 6 is cut off in the same way as described above. When the temperature value signal Sd becomes equal to the double-cooking temperature value _D2 as the temperature of the pot 5 decreases due to the electric current, the heater 6 is energized in the same manner as described above, and this operation is repeated. and 900 seconds (i.e. 15 minutes) corresponding to the double-cooking time value T ₃₂ from time t ₁ .
When the elapsed time _t4 is reached, the count value of the counter 28 becomes equal to the double-cooking time value T32 stored in the double-cooking storage section ₃₂ , so the comparison section 31 outputs a signal "0". It becomes like this. Then, the signal "0" is inverted to signal "1" by the NOT circuit 39, and then applied to the reset input terminal R of the R-S flip-flop 33 via the OR circuit 38, so that the R-S flip-flop 33 is reset. , the two-motion cooking operation is completed.

By the way, the thermistor 8 often causes a short-circuit failure or a disconnection failure, and when such a failure occurs, the detection circuit 12 and the display control circuit 13 operate as follows. In other words, a state in which a short-circuit failure occurs in the thermistor 8 is equivalent to a state in which an abnormally high temperature is detected by the thermistor 8 such that its resistance value becomes zero, and the temperature value signal output from the temperature converter 25 Sd is the detection circuit 1
The temperature value T ₄₀ for short-circuit failure detection stored in the constant storage unit 40 in 2. Then, the comparator 42, which had been outputting a signal "0" before the short-circuit failure of the thermistor 8, now outputs a signal "1", which is an abnormal signal, and the signal "1" is sent to the gate terminal G.
The gate circuit 57 that receives the signal opens. When the gate circuit 57 is opened in this way, the storage sections 52, 53, 5
Display signal S ₅₂ stored in 4, 55,
S ₅₃ , S ₅₄ , and S ₅₅ are OR circuits 58, 59, and 6, respectively.
After passing through 0, 61, drivers 44, 45, 4
6 and 47, and NOT
The signal is inverted to "0" by circuits 62, 63, 64, 65 and transferred to transfer gates 71, 72, 7.
3,74 gate terminals. Therefore, as a result, the input of numerical signals to the terminals N of the drivers 44, 45, 46, 47 is cut off, and the display signals S ₅₂ , S ₅₃ , S ₅₄ , input to the terminals M are cut off.
Letters "S", "H", "r", "t" according to S ₅₅
(SHORT, which means short circuit) is displayed on the corresponding light emitting diodes 15a, 15b, 15c, and 15d as shown in FIG. 2b, thereby indicating a short circuit failure of the thermistor 8. Also, thermistor 8
The state in which a disconnection failure occurs is equivalent to the state in which the thermistor 8 detects an abnormally low temperature such that its resistance value becomes infinite, and the temperature value signal Sd from the temperature converter 25 is It becomes smaller than the temperature value _T41 for disconnection failure detection stored in . Then, the signal becomes "0" before the thermistor 8 breaks down.
Since the comparator 43 which had been outputting the signal "1" now outputs the abnormal signal "1", the gate circuit 5
6 is opened, and as a result, the storage units 48, 49, 50,
Display signals S ₄₈ , S ₄₉ , stored in 51
Characters "-", "0", "F", "F" according to S ₅₀ and S ₅₁
(OFF, meaning disconnection) is displayed on the corresponding light emitting diodes 15a, 15b, 15c, and 15d as shown in FIG. 2a, thereby indicating that the thermistor 8 is disconnected.

According to the present embodiment described above, when a short circuit or disconnection failure occurs in the thermistor 8, the details of the failure can be immediately displayed and notified to the user, so that the user can quickly deal with the situation in which rice cannot be cooked. It becomes like this. Furthermore, since the time display unit 15 for displaying the remaining timer time of the timer 14 can also be used to display such a failure, a dedicated display for failure indication is not required, and the number of parts increases. There is no risk of it being lost.

In the above embodiment, when a failure of the thermistor 8 is detected, the power to the heater 6 may be cut off in conjunction with a display to that effect.

〔Effect of the invention〕

According to the present invention, as explained above, when a short circuit or disconnection failure occurs in a temperature sensor, it is possible to reliably inform the user of the details of the failure, and even with such a configuration, it is possible to notify the user of the failure. The number of parts does not increase, and there is no risk of problems such as complication of assembly work.

[Brief explanation of the drawing]

The drawings relate to one embodiment of the present invention.
The figure is a partially cutaway side view of the rice cooker, Figure 2 is an enlarged view of the main parts, Figure 3 is a block diagram showing the electrical configuration, and Figure 4 is a diagram showing how the temperature of the pot changes. . In the figure, 5 is a pot, 6 is a heater, 8 is a thermistor (temperature sensor), 11 is a control circuit (control means), 1
2 is a detection circuit (detection means), 13 is a display control circuit (display control means), 14 is a timer, 15 is a time display section, 25 is an AD converter (conversion means), and 26 is a temperature measurement section.

Claims (1)

[Claims] 1. A rice cooker body consisting of an inner case and an outer case;
A time display section disposed on the outer surface of the outer case, a pot housed in the inner case, a temperature sensor provided to detect the temperature of the pot, and a temperature sensor according to the temperature sensed by the temperature sensor. a conversion means for converting a temperature value signal into a digital signal; a control means for controlling energization/disconnection of the heater for heating the pot based on the signal from the conversion means; a detection means for detecting a short circuit failure and a disconnection failure of the temperature sensor based on a comparison with a temperature value for short circuit failure detection and a temperature value for disconnection failure detection and generating an abnormal signal; A rice cooker comprising display control means for causing the time display section to display a failure display corresponding to the content. 2. The rice cooker according to claim 1, wherein the display control means is provided to display characters indicating the details of the failure.