JPH021489B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a rice cooker in which a pot is heated by a rice cooking heater to perform a rice cooking operation.

(Prior art) In conventional rice cookers, a switch device that combines magnetic shunt steel as a temperature detection element, a permanent magnet, an operating lever, a micro switch, etc. is widely used to control the end time of rice cooking. Also,
As heating means for heating a pot for cooking rice, a high-output rice-cooking heater (with a low internal resistance value) and a low-output heat-retaining heater (with a large internal resistance value) are provided. In this case, the rice cooking heater is connected to both ends of the power plug via the micro switch in series,
The heat-retaining heater is usually connected in parallel with the microswitch. In fact, a thermal relay is provided in order to maintain the heat retention temperature by the heat retention heater at a constant temperature, and this thermal relay is interposed in series with the current conduction path of the heat retention heater.
The above switch device is generally constructed as follows.

In other words, a heat-sensitive cap is provided that presses against the outer bottom of the rice-cooking pot when it is installed in a predetermined position. Inside this heat-sensitive cap, magnetic shunt steel, which loses its magnetism at a certain Curie point temperature, conducts heat. The temperature of the rice to be cooked is detected as the temperature of the pot using the magnetic shunt steel. At this time, the Curie point temperature of the magnetic shunt steel is selected to be approximately equal to the temperature at which rice is cooked (generally around 130° C.). In addition, a permanent magnet is attached to the tip of an operating lever that is rotatable between two positions, and this operating lever can be used to attract the above-mentioned permanent magnet to magnetic shunt steel in response to an external operation. While being rotated to the first position, it is rotated back to the second position in response to the permanent magnet being released from attraction as the magnetic shunt steel loses its magnetism. The microswitch is turned on when the control lever is rotated to the first position, and turned off when the control lever is rotated to the second position.

Therefore, in a rice cooker equipped with a switch device configured as described above, when the operation lever is rotated to the first position, the rotation state is changed due to the attraction between the permanent magnet and the magnetic shunt steel. At the same time, the microswitch is turned on, and in response, the rice cooking heater generates heat at a high output to start the rice cooking operation. After this, as the rice cooking continues, the inside of the pot exhibits a so-called dry-up state, and when the temperature (detected temperature) of the magnetic steel becomes higher than the rice cooking temperature and its magnetism disappears, the permanent magnet's attraction is released. As a result, the operating lever is rotated back to the second position and the micro switch is turned off, so the rice cooking heater and the warming heater are energized in series and the load current becomes extremely small, resulting in cooking with a small internal resistance value. The heater is in a substantially power-off state, and the heat retention operation is performed by the heat generated by the heat retention heater.

(Problem to be solved by the invention) Thermal conductivity between the outer bottom of the pot and the heat-sensitive cap,
In addition, the thermal conductivity between the heat-sensitive cap and the magnetic shunt steel varies to some extent due to the processing accuracy and assembly accuracy of each of these parts, so the actual temperature of the pot and the temperature detected by the magnetic shunt steel may vary. It is inevitable that errors will occur between the two. On the other hand, since the Curie point temperature of magnetic shunt steel is constant, the temperature of the pot when the magnetic shunt steel loses its magnetism, that is, the temperature of the pot when the rice cooking operation is ended by the switch device, is the temperature of the pot when the rice cooking operation is terminated by the switch device. It will vary depending on the device. As a result, in the conventional rice cooker, there is a possibility that the control of the end timing of the rice cooking operation may become inaccurate.

One possible way to deal with these problems is to provide an adjustment mechanism to adjust the thermal conductivity of the magnetic shunt steel, but it is actually extremely difficult to provide such an adjustment mechanism. be. For this reason, conventionally, a predetermined tolerance temperature range is set for the operating temperature of the switch device (the temperature at which magnetic shunt steel loses its magnetism), and when manufacturing rice cookers,
Quality control is carried out so that the operating temperature of the switch device falls within the above-mentioned allowable error temperature range. In other words, in the conventional rice cooker, the actual situation is that the control of the end time of the rice cooking operation is relatively loose, and this point has been an unresolved problem.

In addition, in the conventional rice cooker described above, when the power plug is inserted into the power outlet, a series energization path of the rice cooking heater and the warming heater is formed, that is, it is in the warming state. Therefore, if the rice and water are stored in the pot and the power plug is left plugged into the electrode outlet, the warming operation will be performed inadvertently. In this case, especially when the ambient temperature is high such as in the summer, the temperature of the water in the pot will rise abnormally, which will have a negative effect on the rice inside, and the subsequent rice cooking will cause a strange odor to the cooked rice. This may cause problems such as sticking. In order to deal with such a problem, it is sufficient to add a function to selectively perform the heat-retaining operation by external operation, but conventionally, there has been no rice cooker equipped with such a function. Therefore, when starting or ending the heat-retaining operation, it is necessary to perform the troublesome operation of inserting and removing the power plug each time, which is inconvenient to use.

The present invention has been made in view of the above circumstances, and its purpose is to provide effects such as being able to accurately control the timing at which the rice cooking operation ends, as well as being able to selectively execute the warming operation, thereby improving usability. It is to provide a rice cooker that performs.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a heating means for heating a pot for cooking rice, a temperature detection means for outputting a temperature information signal according to the temperature of the rice to be cooked, and an amount of heating by the heating means. and a control means for controlling the end of the rice cooking operation by the heating means based on the temperature information signal and a pre-stored program, and the control means controls the heating amount by the heating means to The heat-retaining operation of maintaining the temperature at a low level by the adjusting means can be selectively executed in response to an external operation.

(Function) The temperature information signal used to control the end timing of the rice cooking operation changes depending on the temperature of the rice to be cooked detected by the temperature detection means and is not fixed. Even if the thermal conductivity between the object and the temperature detection means varies, the temperature detected by the temperature detection means can be easily compensated for. Therefore, it becomes possible to accurately control the end timing of the rice cooking operation. Further, since the control means selectively executes the heat-retaining operation to keep the amount of heating by the heating means low, there is no risk of the heat-retaining operation being performed carelessly as in the conventional case.

(Example) First, in FIG. 3, 1 is a substantially circular outer case, 2 is a bottom frame fitted to the lower part of the outer case 1, and 3
4 is a heat insulating material interposed between the outer case 1 and the inner case 3; 5 is an inner case disposed within the outer case 1;
is a pot detachably mounted inside the inner case 3. Further, 6 is a rice cooking heater which is a heating means arranged at the inner bottom of the inner case 3, 7 is a heat insulating heater which is also a heating means and is wrapped around the upper outer periphery of the inner case 3, and 8 is rotatable to the outer case 1. lid supported on,
Reference numeral 9 denotes a lock mechanism that holds the lid 8 in a locked state. Reference numeral 10 denotes a heat transfer cap which is provided so as to be in pressure contact with the outer bottom of the pot 5 by the force of a spring (not shown), and a thermistor 11, such as a thermistor 11, which is a temperature detecting means is disposed inside the cap in a heat transfer manner. ing. Therefore, this thermistor 11 detects the temperature of the rice to be cooked as the bottom temperature of the corresponding pot 5 (hereinafter referred to as pot bottom temperature D), and has a resistance value corresponding to the detected temperature. The change is output as a temperature information signal Sd.

In addition, in Fig. 4, 12 is a clock device disposed on the outside of the outer case, which indicates the hours and minutes.
It consists of a display section 13 that digitally displays the information, and an operation section 14. The clock device 12 has a normal clock function and a timer function for a well-known timer switch, and each function can be selected and adjusted using the operating section 14.
This is done using each operation button 14a. Furthermore, 15 is a heating pattern selection device which is an operation means also disposed on the outside of the outer case 1, and this has, for example, three operation buttons 15a, and these operation buttons 15a are used for cooking porridge, which will be described later. Any one of the heating pattern, double-cooking heating pattern, and warming heating pattern can be selected. At this time, the heating pattern selection device 15 outputs a pattern selection signal Sd that can specify the selected heating pattern. still,
Reference numeral 15b denotes an "off" button provided adjacent to the operation button 15a, and is configured to interrupt the heat retention operation in response to the operation of this button. Also, 1
Reference numeral 6 denotes a display device disposed on the outside of the outer case 1, which has, for example, four indicator lamps 16a, each of which indicates the current operating state by lighting. At this time, the display device 16 is adapted to display the operating states of "rice cooking", "double cooking", "uniform cooking", and "keep warm".

Next, the electrical configuration will be explained with reference to FIGS. 1 and 2. First, in FIG. 2 showing the outline of the electric circuit configuration, 17 is a bidirectional three-terminal thyristor (hereinafter simply referred to as thyristor), and a series circuit between this and the rice cooking heater 6 receives power from the power plug 17a. It is connected. Further, the warming heater 7 is connected in parallel with the thyristor 17, so when the thyristor 17 is turned off, the rice cooking heater 6 and the warming heater 7 are energized in series, and the rice cooking heater 6 is in a substantially power-off state. , and the fifth portion is heated over low heat. Further, when the thyristor 17 is turned on, only the rice cooking heater 6 is energized, which generates heat at a relatively high output and heats the pot 5 over high heat. Reference numeral 18 denotes a voltage regulating device which together with the thyristor 17 constitutes the regulating means 19, which is interposed in the energizing path of the rice cooking heater 6;
By controlling the voltage between the terminals of the rice cooking heater 6, the output amount (heating amount) is adjusted. Note that the output amount of the rice cooking heater 6 does not necessarily need to be adjusted by the voltage regulator 18 as described above, and can also be adjusted by, for example, phase control of the thyristor 17 or on/off duty ratio control.

Thus, the voltage regulator 18, together with the thyristor 17 and the clock device 12, is controlled by a control circuit device 20 serving as a control means. As shown in FIG. 1, this control circuit device 20 is configured as a microcopy unit including a storage section 21, a time control section 22, and an arithmetic processing section 23, and the storage section 21 includes a thyristor 17. and three types of programs (described later) for controlling the voltage regulator 18 in a predetermined manner are stored corresponding to the three types of heating patterns. Further, the time control section 22 is connected to an oscillator 24.
It is provided to receive the clock pulse Pc from the arithmetic processing section 23, and outputs a time information signal St for timing based on a command from the arithmetic processing section 23. The arithmetic processing section 23 is provided to receive the temperature information signal Sd from the thermistor 11, the pattern selection signal Sp from the heating pattern selection device 15, and the time information signal St from the time control section 23 as data inputs. and the input pattern selection signal
reads a program corresponding to Sp from the storage unit 21, and controls the thyristor 17 and the voltage regulator 18 based on this read program and the temperature information signal Sd and time information signal St;
In this way, a heating pattern corresponding to the program can be obtained. Further, the arithmetic processing section 23 is adapted to also control the clock device 12.

Now, below, the specific operation that the arithmetic processing section 23 executes based on the program read from the storage section 21 will be explained with reference to FIGS. 5 to 7 as well as the effects of each heating pattern. In addition, FIGS. 5A and 6 show temperature characteristic curves corresponding to time T and pan bottom temperature D (°C) on the horizontal and vertical axes, respectively, and FIGS. 5B and 7 show temperature characteristic curves on the horizontal and vertical axes, respectively. The vertical axis shows time T and output P of the rice cooking heater 6, respectively.
A temperature characteristic curve corresponding to (W) is shown.

()... Heating pattern for cooking porridge (see Fig. 5) When a heating pattern for cooking porridge is selected by the heating pattern selection device 15 and a pattern selection signal Sp that can identify the heating pattern is output, The arithmetic processing unit 23 turns on the thyristor 17 to energize only the rice cooking heater 6 based on the program from the storage unit 21 . Therefore, when the pot 5 is heated over high heat, the bottom temperature D of the pot rises relatively rapidly, and the thermistor 1 detects this.
1 outputs its own resistance value change as a temperature information signal Sd. Then, at time t ₁ , the pot bottom temperature D=
When the temperature information signal Sd corresponding to 80° C. is output, the arithmetic processing unit 23 operates the voltage regulator 18 in accordance with this to adjust the amount of heat generated by the rice cooking heater 6.
Heat the pot 5 over low heat, controlling the temperature to about 100 watts. As a result, the pot bottom temperature D is raised relatively slowly. Then, when the pot bottom temperature D reaches 98°C (time t ₂ ), the arithmetic processing unit 23 sends the time information signal St to the time control unit 22 after 20 minutes.
Issue a command to output.

When the above-mentioned time information signal St is output at time t _{3, which is 20 minutes after this time t 2 ,} the arithmetic processing unit 23 that has received it cancels the operation of the voltage regulator 18 and simultaneously turns off the thyristor 17. The rice cooking heater 6 and the heat-retaining heater 7 are then energized in series, and the pot 5 is further heated over a low heat. Due to the above-described actions, the rice stored in the pot 5 together with an appropriate amount of water can be cooked into porridge. In particular, during such "cooking porridge", the pot 5 is heated over a low heat of about 100 watts from time t ₂ when the pot bottom temperature D reaches 98°C to time t ₃ . This prevents the soup from boiling over due to excessive boiling.

()... Heating pattern for double-cooking (see Figure 6) A heating pattern for "double-cooking" is selected by the heating pattern selection device 16, and this serves as a rice-cooking start command signal that allows the heating pattern to be specified. When the pattern selection signal Sp is output, the arithmetic processing unit 23 turns on the thyristor 17 to start the rice cooking operation based on the program from the storage unit 21, and heats the pot 5 with high heat using the rice cooking heater 6. Bring the water in the pot 5 to a boil. During this boiling period, the bottom temperature D of the pot is maintained at approximately 100℃,
When the water in the pot 5 evaporates and is absorbed by the rice, resulting in a so-called dry-up condition, the bottom temperature D of the pot rises rapidly. As a result, when the thermistor 11 outputs the temperature information signal Sd corresponding to the pot bottom temperature D=130°C (time t ₄ ), the arithmetic processing unit 23 turns off the thyristor 17 in response to this and shifts to uneven operation. At the same time, a command is issued to the time control section 22 to output the time information signal St after 5 minutes have elapsed. this time t ₄
When the above-mentioned time information signal St is output at time _t5 , which is 5 minutes later, the arithmetic processing unit 23 that receives this turns on the thyristor 17 for only 1 minute, thereby turning on the pot 5 during this on period. It is reheated over high heat to perform so-called double cooking, and then the above-mentioned shading operation is performed. In other words, when a predetermined condition is established that 5 minutes have passed after the end of the rice cooking operation, the double cooking operation is controlled as described above, and as a result, the excess moisture in the cooked rice is removed. The food becomes delicious when it is blown away.

()...Heating pattern for keeping warm (see Figure ₇ ) This heating pattern is for keeping rice, etc. that has already been cooked, warm. When a pattern is selected and a pattern selection signal Sp is output that allows the heating pattern to be identified,
Based on the program from the storage unit 21, the arithmetic processing unit 23 maintains the thyristor 17 in an off state and maintains the control voltage by the voltage regulator 19 at a constant value. As a result, a heat-retaining operation is performed in which the outputs of the rice-cooking heater 6 and the heat-retaining heater 7 are controlled to be low, and the pot 5 is heated over low heat.

In the above embodiment, the time control section 11 may be configured to cause a buzzer or the like to sound when a predetermined period of time has elapsed after the automatic transition to the uneven operation.

As described above, in this embodiment, the thermistor 11 is provided to detect the temperature of the rice to be cooked through the pot 5, and the temperature information signal Sd from the thermistor 11 is provided.
Based on this, the heating pattern for porridge cooking and the heating pattern for double cooking are selectively controlled based on the pattern selection signal from the pattern selection device.
The present invention is characterized in that it is provided with a control circuit device 20 that selectively executes a heat-retaining operation using Sp. At this time,
Since the temperature information signal Sd is based on the resistance value, which is the easiest to handle as an electrical variable, it can be easily corrected. As a result,
Even if the thermal conductivity between the pot 5 and the heat-sensitive cap 10 and between the heat-sensitive cap 10 and the thermistor 11 vary during manufacturing, the temperature detected by the thermistor 11 corresponding to the temperature information signal can be compensated very easily. be able to. Therefore, it is possible to accurately control not only the end timing of the rice cooking operation but also the rice cooking operation for cooking porridge as described in the embodiment. Further, since a micro switch having a conventional mechanical contact point is not required for detecting the temperature of the pot 5, there is no problem such as a shortened lifespan due to wear of the contact point. Moreover, since the control circuit device 20 is configured to selectively execute the heat retention operation, the heat retention operation will not be started simply by inserting the power plug 17a into the power outlet, and unlike the conventional case, the heat retention operation will not be activated. User-friendliness improves as there is no need to do it in advance.

〔Effect of the invention〕

According to the present invention, as is clear from the above description, the amount of heating by the temperature detection means that detects the temperature of the rice to be cooked and outputs a temperature information signal according to the detected temperature, and the heating means for heating the pot. and a control means for controlling the termination of the rice cooking operation by the heating means based on the temperature information signal and a pre-stored program;
Since the control means is configured to be able to selectively execute a heat-retaining operation in which the amount of heating by the heating means is held in a low state by the adjustment means in response to an external operation, the end timing of the rice cooking operation can be controlled. This has excellent effects in that it is possible to improve accuracy and reliability over the lifespan, and furthermore, it is possible to selectively perform the heat-retaining operation by external operation, thereby improving usability.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, and FIG. 1 is a block diagram of the electrical configuration, FIG. 2 is a schematic electrical circuit diagram, and FIG. 3 is a partially cutaway front view of the entire device. Figure 4 is a front view of the whole, Figure 5A is a temperature characteristic diagram for explaining the effect, Figure 5B is an output characteristic diagram for explaining the effect, Figure 6 is a temperature characteristic diagram for explaining the effect, and Figure 6 is a temperature characteristic diagram for explaining the effect. FIG. 7 is an output characteristic diagram for explaining the action. In the figure, 5 is a pot, 6 is a rice cooker (heating means),
7 is a heat retention heater (heating means), 11 is a thermistor (temperature detection means), 15 is a heating pattern selection device,
17 is a bidirectional three-terminal thyristor, 18 is a voltage regulator, 19 is an adjustment means, 20 is a control circuit device (control means), 21 is a storage section, 22 is a time control section,
23 indicates an arithmetic processing section.

Claims (1)

[Claims] 1. A heating means for heating a pot for cooking rice, a temperature detection means provided to detect the temperature of the rice to be cooked and outputting a temperature information signal according to the detected temperature, and a heating amount by the heating means. and a control means for controlling the end of the rice cooking operation by the heating means based on the temperature information signal and a pre-stored program, the control means controlling the amount of heating by the heating means by adjusting the amount of heating by the heating means. 1. A rice cooker characterized by being configured to be able to selectively perform a heat retention operation in response to an external operation to maintain the temperature at a low level.