JPH0419844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a rice cooker, and particularly to a rice cooker using a microcomputer as a control circuit.

Conventional technology: ROM is used in rice cookers with a built-in microcomputer.
By presetting a predetermined rice cooking program in the read-on memory, the rice cooking operation according to the program can be automatically performed. However, with this type of rice cooker, if you accidentally start cooking rice with the inner pot empty,
The rice cooker operates according to the same program as when cooking rice normally. As a result, temperatures in various parts may rise beyond the specified limits, and there is a risk that accidents such as melting of temperature fuses may occur. Therefore, in such a rice cooker, it is necessary to provide some kind of dry-cooking prevention means or dry-cooking detection means.

Purpose In view of such problems, an object of the present invention is to provide a rice cooker with a built-in microcomputer that is equipped with a means for preventing dry cooking.

The present invention is capable of controlling the temperature of the inner pot within a certain period of time after the start of the rice cooking operation or until reaching the predetermined rice cooking mode, even though the temperature of the inner pot cannot reach the predetermined temperature if there is food in the rice cooker. The above purpose is achieved by determining that the inner pot is empty and taking appropriate measures when the inner pot is reached.

composition FIG. 1 schematically shows the configuration of the present invention.

1 is a rice cooking heater provided to heat the bottom surface of the inner pot 2 of the rice cooker A via an electric heating member 3; 4 is a heat-retaining heater; It is provided to heat the sides.

Reference numeral 6 denotes temperature detection means including a thermistor (hereinafter referred to as a first thermistor) 6-1 as an example of a temperature measuring element, and the first thermistor 6-1 is provided so as to be in contact with the bottom surface of the inner pot 2. Reference numeral 7 denotes a rice cooking mode setting means which stores a rice cooking mode program using temperature and time as parameters, and is usually constituted by a ROM. 8 is a rice cooking mode control means which inputs the temperature signal from the temperature detection means 6 and the time signal from the time measurement means 9, and controls the rice cooking heater 1 and the heat retention heater according to the rice cooking mode program set in the rice cooking mode setting means 7. It outputs a signal that controls the on/off operation of rice cooker 4 and the amount of electricity supplied to rice cooking heater 1. 10
is heater energization amount control means, which inputs a signal from the rice cooking mode control means 8 and determines the amount of energization to the rice cooking heater 1. Reference numeral 11 denotes a switch means which inputs a signal from the rice cooking mode control means 8 and controls the ON/OFF operation of energizing the rice cooking heater 1 and the warming heater 4.

In the present invention, if a temperature signal higher than a predetermined temperature is sent from the temperature detection means 6 to the rice cooking mode control means 8 before reaching a predetermined rice cooking mode or within a certain period of time, the rice cooking mode control means 8 switches the rice cooking mode to the switch means 1.
1, the power supply to the rice cooking heater 1 is turned off, and the power supply to the heat-retaining heater 4 is controlled to shift to the heat-retaining mode.

In addition, in a preferred embodiment of the present invention,
As shown in FIG. 1, a thermistor (hereinafter referred to as a second thermistor) 12-1 for detecting the side temperature of the inner pot 2, a temperature detecting means 12 including the second thermistor 12-1, and a rice cooking power determining means 13 are provided.

The rice cooking power determining means 13 measures the temperature rise rate over a certain period of time from the temperature detecting means 12, determines the content amount of the inner pot 2, and controls the heater energization amount control means to set the heater energization amount according to the content amount. 10. Further, the heater energization amount control means 10
inputs a signal from the temperature detecting means 12 at the start of rice cooking, and performs control such that if the starting temperature is high, the amount of electricity applied to the heater is reduced, and conversely, if the starting temperature is low, the amount of electricity applied to the heater is increased. Further, in the initial state (when the power is turned on), the rice cooking mode control means 8 inputs a signal from the temperature detection means 12, and if the inner pot temperature is 55°C or higher, turns off the electricity to the rice cooking heater 1 and enters the warming mode. It is also possible to control the transition.

FIG. 2 shows a schematic sectional view of one embodiment.

Reference numeral 20 denotes a control unit installed on the outer body of the rice cooker, and a microcomputer 21 as a control circuit for realizing each means shown in FIG. 1 is built inside the control unit. 22 to 24 are various switches for operating this microcomputer 21.

First thermistor 6-1 and second thermistor 12
-1 are brought into contact with the bottom and side surfaces of the inner pot 2, respectively, by the pressing force of a spring, and are connected so that the detection signals of both thermistors 6-1 and 12-1 are input to the microcomputer 21. . 2
5 is a power supply circuit which receives a control signal from the microcomputer 21 and energizes the rice cooking heater 1 and the warming heater 4.

The rice cooking heater 1 has a heat transfer member 3 in contact with the bottom of the inner pot so that the heat generated therein is effectively transferred to the bottom of the inner pot.
It is buried inside. The heat retaining heater 4 is provided surrounding the upper side surface of the outer container 5 so that heat is transferred to the inner pot 2 via the outer container 5. 26 is the lid of the inner pot. Although omitted in the figure, a heat insulating material is filled around the outer container 5 to keep it warm.
Further, the lid 26 may be provided with a known pressure regulating device. 19 is a micro switch that detects the presence or absence of the inner pot 2, and if the inner pot 2 is present, it turns on and turns on the power supply circuit 25; until the inner pot 2 is placed, the power supply circuit 25 is turned off and dry cooking is performed. It is prevented.

FIG. 3 shows an electric circuit system directly related to the operation of the rice cooking heater 1 in this embodiment. The first thermistor 6-1 on the bottom side of the inner pot and the second thermistor 12-1 on the side side are connected to the power supply via resistors _R1 and _R2, respectively.
It is provided between Vdd and ground, and each detection signal is input to A/D converter input ports K ₂ and K ₁ of the microcomputer 21 and converted into a digital signal.

Switch 22 is a rice cooking switch for operating the rice cooking operation, and switch 23 is a timer switch for setting the timer since this embodiment has a timer function as described later. Signals from the respective switches 22 and 23 are also input to the microcomputer 21.

The microcomputer 21 controls the gate signal of the triac 28 via the driver 27 by sending an on/off signal to the driver 27. The rice cooking heater 1 is connected to an AC power source 29 via its triax 28, and is controlled to be turned on and off.

In this embodiment, the amount of electricity supplied to the rice cooking heater 1 is controlled by the duty ratio of the on-time controlled via the triax 28. That is, when the microcomputer 21 inputs the temperature signals from the first thermistor 6-1 and the second thermistor 12-1, the microcomputer 21 inputs the temperature signals from the first thermistor 6-1 and the second thermistor 12-1, and then the microcomputer 21 inputs the temperature signals from the first thermistor 6-1 and the second thermistor 12-1. (for example, 15 seconds), the driver 27 turns on the triac 28 by outputting an on signal for an appropriate period of time. Since the rice cooking heater 1 is energized and heated only during the time when the triax 28 is on, the desired amount of energization (rice cooking power) can be achieved by changing the energized time.

FIG. 4 shows a panel of the control unit 20 in this embodiment. There are three switches that the operator can operate: a rice cooker switch 22 for starting and stopping the rice cooking operation, a timer switch 23 for setting the time until the start of the rice cooking operation, and a browning switch 24 for adjusting the degree of browning according to preference. be. Reference numeral 30 denotes a display panel that displays the progress of rice cooking as it progresses according to the program, and LEDs (lighting diodes) 31 to 38 are provided for each step. The lights are turned on one after another.

41 and 42 are time display panels that display the remaining time until the rice cooking operation starts when the timer switch 23 sets the timer;
0 is a single digit 7 segment LED element that represents time,
41 is a surface emitting element on which the number 30 (minutes) is displayed.

motion Next, the operation of one embodiment will be explained.

FIG. 5 shows the relationship between the rice cooking mode program executed in one embodiment and the bottom temperature of the inner pot.

The beginning of the rice cooking operation is a stage at a low temperature to allow the rice to sufficiently absorb moisture, for example, for 6 minutes. This stage is called preheating mode. Next, increase the power of the rice cooking heater 1 to the maximum. This stage is called the middle Patsupa mode. When the temperature detected by the second thermistor 12-1 exceeds 50 DEG C., the content amount is determined from the temperature gradient as described above, and the supplied power is controlled according to the content amount. This stage is called power control mode. In this mode it will eventually boil over. After a certain period of time after starting the power control mode, the rice cooking heater power is reduced to a predetermined percentage (for example, 70%) to maintain the boiling state. This stage is called boiling maintenance mode.

As the water continues to boil, the water will eventually disappear and the temperature will begin to rise. The temperature is a predetermined temperature (e.g.
When the temperature reaches 137°C, the temperature shifts to uneven mode. In the uneven mode, after the rice cooking heater 1 is turned off for a certain period of time, the rice cooking heater 1 is turned on for a time corresponding to the set value of the burn switch 24, and then turned off again to complete the rice cooking operation and shift to the heat retention mode. In the heat retention mode, the rice temperature is controlled to be a constant temperature (for example, 70°C) by turning on and off the heat retention heater 4.

The above is a normal rice cooking operation, but for example, in the power control mode, the first thermistor 6-
When the detected temperature of No. 1 reaches a predetermined value (137° C.) or higher, it is determined that the inner pot is empty, and the subsequent program steps are omitted and the mode is shifted to the keep-warm mode. Furthermore, if the second thermistor 12-1 provided on the side of the inner pot is not normal, the rice cooking operation according to the program cannot be performed, so the normal rice cooking mode in which the power of the rice cooking heater 1 is constant is executed. In that case, after starting the normal rice cooking mode,
The temperature detected by the first thermistor 6-1 within a certain period of time
If the temperature reaches 137 degrees Celsius or higher, it is assumed that the inner pot is empty, and the system switches to keep-warm mode.

The above operation will be explained in more detail according to the flowchart.

FIG. 6 shows the initial state, and when the power is turned on, an abnormality in the first thermistor 6-1 on the bottom of the inner pot is detected (step S1). Abnormality detection is performed as follows. If the thermistor is disconnected, it will have high resistance and will be in the same state as at low temperatures, and if it is shorted, it will be low in resistance and will be in the same state as at high temperatures. Therefore, in the initial state, the first thermistor 6
-1 resistance value corresponds to -20℃ or less, high resistance value,
Alternatively, if the resistance value is low corresponding to 150° C. or higher, it is determined that the first thermistor 6-1 is abnormal, and the abnormality is notified. Next, temperature is detected by the second thermistor 12-1 on the side surface of the inner pot (step S2). If the detected temperature is 55°C or higher, the mode shifts to the heat retention mode, and if it is lower than 55°C, the timer switch 23 and rice cooking switch 22 are read. If the timer switch 23 is on, the rice cooker shifts to the timer set mode (step S3), and if the timer set switch 23 is off and the rice cooking switch 22 is on, the rice cooker shifts to the preheating mode (step S3).
4).

FIG. 7 shows an operational flowchart of the heat retention mode. The insulating heater 4 is controlled so that the rice temperature reaches 70°C (step s5). When the rice cooking switch 22 is pressed during the heat retention mode, the rice cooking is stopped (step s6). Also, the second thermistor 1 is
2-1 abnormality is detected (step s7). Second
Abnormality detection for thermistor 12-1 is the same as for the first thermistor 6-1, but in this case, it is determined that there is an abnormality if it becomes a high resistance value corresponding to 20°C or lower or a low resistance value corresponding to 130°C or higher. do.

A flowchart of the timer set operation is shown in FIG. When the timer switch 23 is pressed, the set time of 30 minutes is displayed (step s11), and each time the timer switch 23 is pressed, the time display changes to 30 minutes.
It is incremented by minutes.
(Steps s12, s13).

When the rice cooking switch 22 is pressed (step s10), the timer operation is started.

A flowchart of the timer operation is shown in FIG. The elapsed time is subtracted from the displayed set time, and the remaining time is displayed (step s15). When the remaining time reaches 0, the mode shifts to preheating mode (step s16). When the rice cooking switch 22 is pressed during this timer mode (step s14), the timer set is canceled and the process returns to the initial state.

Next, the rice cooking operation will be explained with reference to FIGS. 10 to 14.

In the preheating mode (Fig. 10), the inner pot temperature is first measured by the second thermistor 12-1, and the temperature is lower than 20℃.
Depending on whether the temperature is 20 to 33°C or over 33°C, the rice cooking heater 1 is heated with appropriate electric power (steps s20 and s21). After preheating for a certain period of time (for example, 6 minutes), rice cooking heater 1
The power is increased to the maximum and the mode is shifted to the next medium power mode (steps s23, s24).

If the rice cooking switch 22 is pressed in this preheating mode, if the timer switch 23 is not turned on when the rice cooking switch 22 is released and turned off, the rice cooking operation is canceled and returns to the initial state (step s22→ s40, s41). This operation is performed when you have started cooking rice but want to stop it for some reason. If the timer switch 23 is pressed when the pressed rice cooking switch 22 is released, the mode shifts to the normal rice cooking mode (step s22).
→s40, s41). This operation is performed in an inspection process before shipment at a factory.

In the medium-temperature mode (Fig. 11), if the temperature detected by the second thermistor 12-1 is less than 37°C, the medium-temperature operation will continue, but if the second thermistor 12-1 detects a temperature of 37°C or higher at this point. If so, the mode shifts to normal rice cooking mode (step s25).

During normal operation, the thermistor 12-1 becomes 50% within a certain period of time (for example, 10 minutes) after the start of the medium-temperature operation.
℃ is detected (steps s26, s27).

However, even after a certain period of time has passed, the second thermistor 1
When 2-1 does not detect 50°C, it is determined that there is an abnormality in the second thermistor 12-1 and others, and the mode shifts to normal rice cooking mode (step s26).

At step s27, the second thermistor 12-1 becomes 50.
Once the temperature is detected, the second thermistor 12-1 detects the temperature again after a certain period of time (for example, 2 minutes) from that point (steps s28, s29).
Then, the content amount is determined based on the rate of temperature increase over a certain period of time, and the amount of electricity supplied to the rice cooking heater 1 is controlled to be electric power corresponding to the content amount, and the process moves to the next power control mode (step s30). .

In the power control mode (FIG. 12), electricity is applied and heated for a certain period of time (for example, 4 minutes) with a controlled amount of electricity (step s32). Normally it will boil at this stage, but since there is still water left, it will boil at this stage.
The temperature detected by the thermistor 6-1 never exceeds the boiling point of water. If the first thermistor 6-1 detects a temperature of 137°C or higher in this power control mode, it is determined that the inner pot is empty, and the mode shifts to the heat retention mode (step s31).

After a certain period of time has elapsed in step s32, the boiling maintenance mode is entered and the power is reduced to 70% of the control power value (step s33). When the boiling is completed and the moisture disappears, the temperature of the rice will rise, so if the first thermistor 6-1 detects a temperature of 137°C or higher, the next mode will be shifted to the uneven mode (step s34).
If an abnormality occurs in the first thermistor 6-1,
If 137°C is not detected, the process shifts to the uneven mode after a certain period of time (for example, 25 minutes) has elapsed after starting the boiling maintenance mode (step s35).

The normal rice cooking mode will be explained with reference to FIG. 13. In this mode, the electric power applied to the rice cooking heater 1 is set to 70% of the maximum electric power, and the rice is heated for a certain period of time _T1 , and then the rice cooker shifts to the uneven mode (steps s37, s38).
In this case, after switching to normal rice cooking mode,
Before T ₁ elapses, the temperature detected by the first thermistor 6-1 is
When 137℃ is detected, if the time until detecting 137℃ is longer than a certain time T _{2, it will shift to uneven mode, but if this time is less than T 2 ,} it will assume that the inner pot is empty. After making a judgment, the mode is shifted to the heat retention mode (step s39). Here, the fixed time T ₂ is the time during which the temperature never rises to 137°C unless the inner pot is empty.

Finally, the operation in uneven mode is shown in FIG.

After turning off the electricity to the rice cooking heater 1 for a certain period of time (steps s50 and s51), the on time is determined according to whether the burn switch is set to dark, medium, or light, and the electricity is turned on to the rice cooking heater 1 for that period. Heating (steps s52 to s54). The degree of burntness can be changed by adjusting the energization time. After a certain period of time, the rice cooking heater 1 is turned off and the mode is shifted to the heat retention mode (step s55).

Effects As described above, in a rice cooker equipped with a microcomputer, the inner pot is empty if the inner pot temperature rises to a predetermined temperature or higher within a certain period of time or by a predetermined mode after the rice cooking operation is started. Since the rice cooker is configured to determine that the rice is hot and immediately shift to the warming mode, it is now possible to easily realize a rice cooker that can prevent empty cooking. Furthermore, by utilizing the above-mentioned transition to the heat retention mode, the rice cooker of the present invention can also reheat cold rice when it is placed in the inner pot.

[Brief explanation of drawings]

Figure 1 is a schematic diagram explaining the configuration of the present invention, Figure 2 is a schematic diagram explaining the configuration of the present invention.
The figure is a schematic sectional view showing one embodiment of the present invention, FIG. 3 is a main circuit diagram of one embodiment, FIG. 4 is a diagram showing a panel of a control unit used in one embodiment, and FIG. 5 is one embodiment. Figures 6 to 14 showing the example rice cooking program are flowcharts showing the operation of one embodiment. 1...Rice cooking heater, 2...Inner pot, 4...Warmth retention heater,
6, 12... Temperature detection means, 6-1, 12-1... Thermistor, 7... Rice cooking mode setting means, 8 Rice cooking mode control means, 9... Timing means, 10... Heater energization amount control means, 11... Switch means, 21 ...microcomputer.

Claims (1)

[Scope of Claims] 1. Temperature detection means including a temperature measuring element provided so as to be in contact with the bottom surface of the inner pot, a rice cooking heater provided on the bottom surface of the inner pot, a heat retention heater that heats the inner pot from the side, and rice cooking. a rice cooking mode setting means storing a mode; a clocking means; inputting a temperature signal from the temperature detection means and a time signal from the clocking means, and controlling the rice cooking heater according to a rice cooking mode program of the rice cooking mode setting means; and a rice cooking mode control means that outputs a signal for controlling the on/off operation of the warming heater and the amount of electricity applied to the rice cooking heater, and a signal from the rice cooking mode control means is inputted to determine the amount of electricity applied to the rice cooking heater. It comprises at least a heater energization amount control means, and a switch means for inputting a signal from the rice cooking mode control means to control the on/off operation of energization to the rice cooking heater and the warming heater, and the temperature detected by the temperature detection means. If the temperature of the rice rises above a predetermined temperature within a certain period of time or before reaching the predetermined cooking mode, the rice cooking heater is configured to cut off electricity to the rice cooking heater and shift to the heat retention mode. rice cooker.