JPH064049B2 - rice cooker - Google Patents

Description

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

(Prior Art) In a conventional rice cooker, in order to control the end time of the rice cooking,
A mechanical switch device, which is a combination of a degaussing steel as a temperature detecting element, a permanent magnet, an operating lever, a micro switch, and the like, is widely used, and such a switch device is generally configured as follows.

That is, there is a heat-sensitive cap that presses against the bottom of the outer surface of the rice cooker with the rice cooker attached at a predetermined position, and the heat-damping steel loses magnetism at a certain Curie point temperature. The temperature of the rice to be cooked is detected as the temperature of the pot by the demagnetizing steel.
At this time, the Curie point temperature of the magnetic shunt steel is selected to be substantially equal to the cooking temperature of rice (generally around 130 ° C.). In addition, a permanent magnet is attached to the tip of the operation lever that is rotatably provided between the two positions, and this operation lever causes the permanent magnet to be attracted to the degaussing steel according to an external operation. In addition to being rotated to the first position, it is returned to the second position in response to the demagnetization of the magnetic compensating steel due to the demagnetization of the permanent magnet. The micro switch is adapted to be turned on when the operation lever is rotated to the first position and turned off when it is rotated to the second position. In the on state, the energizing path of the electric heater is turned on. It is configured to be formed.

Therefore, in the rice cooker provided with the switch device having the above configuration, when the operation lever is rotated to the first position,
The rotating state is held by the attraction between the permanent magnet and the magnetic shunting steel, and the micro switch is turned on, and accordingly the rice cooking operation by the electric heater is started. After this, when the rice cooking operation continues, the inside of the pot is in a so-called dry-up state, and when the temperature of the magnetic shunting steel (detection temperature) exceeds the rice cooking temperature and the magnetism disappears, the permanent magnet is attracted. With the release, the operation lever is returned and rotated to the second position to turn off the micro switch, so that the electric heater is turned off and the rice cooking operation is ended.

(Problems to be Solved by the Invention) The thermal conductivity between the outer bottom of the pot and the heat-sensitive cap and the heat conductivity between the heat-sensitive cap and the magnetic compensating steel depend on the machining accuracy and assembly accuracy of each of these parts. Because of this, there is an unavoidable difference between the actual temperature of the kettle and the temperature detected by the magnetic shunting steel, because it fluctuates to some extent. On the other hand, since the Curie temperature of the magnetic shunt is constant, the temperature of the rice cooker when it loses magnetism, that is, the temperature of the rice cooker when the rice cooking operation is terminated by the switch device, It will vary from vessel to vessel. Moreover, since the magnetic shunting steel has a heat capacity, it has poor responsiveness to a rapid temperature rise such as dry-up. Therefore, as a result, the conventional rice cooker has a problem that the control of the end time of the rice cooking operation becomes inaccurate.

Further, in the rice cooker, a delicious plate can be cooked by changing the heat generation capacity of the electric heater such as so-called medium heat, high heat, and low heat during the rice cooking operation. It is impossible to carry out control at a plurality of different time points by temperature detection.

Furthermore, since the conventional rice cooker requires a mechanical contact such as a micro switch for detecting the temperature of the pot, it also has a problem of shortening the life due to wear of the contact.

The present invention has been made in view of the above circumstances, and an object thereof is to enable accurate control of the end time of rice cooking operation and control of the heating capacity of an electric heater at a plurality of times. Another object of the present invention is to provide a rice cooker having the effects of increasing the reliability over the life of the rice cooker.

[Structure of the Invention] (Means for Solving the Problems) The rice cooker of the present invention is provided with a temperature sensitive element for converting temperature information of the pot heated by the electric heater into an electric signal, and the temperature sensitive element detects the temperature. A control means is provided for converting an electric signal corresponding to the temperature information into a digital signal, and the electric heater is controlled to have a predetermined heating capacity at a plurality of time points during the rice cooking operation according to the temperature information supplied by the conversion means. It is characterized by the configuration of the means.

(Operation) According to the rice cooker of the present invention, the temperature information from the temperature sensing element is processed as an electric signal, and the electric heater is controlled by the control means based on the electric signal to have a predetermined heating capacity at a plurality of time points. Therefore, the conventional mechanical switch device becomes unnecessary.

(Embodiment) An embodiment will be described below with reference to the drawings.

First, the electrical configuration will be described with reference to FIG. 1 and 2 are power supply terminals connected to an AC power supply (not shown), one power supply terminal 1 is connected to a bus bar 3, the other power supply terminal 2 is connected to a bus bar 4, and the bus bar 3 is a rectifying diode 5 And a voltage dividing resistor 6 and a bus bar 7. Reference numeral 8 is an electric heater for heating a kettle (not shown), which is connected between the busbars 3 and 4 via a bidirectional three-terminal thyristor 9 in series. Reference numeral 10 denotes a thermistor, which is a temperature-sensitive element arranged so as to detect the temperature of, for example, the bottom of the outer surface of a pot (not shown), which is connected between the buses 7 and 4 via a resistor 11 in series. 12 is a bus bar 7,4
Is a constant voltage diode connected in between. Reference numeral 13 denotes an analog-digital conversion circuit which is conversion means connected between the bus lines 7 and 4, and its input terminal is connected to a common connection point of the resistor 11 and the thermistor 10, and thus the temperature detection unit 14 is configured. . Reference numeral 15 is a microcomputer as a control means connected between the bus lines 7 and 4, the input terminal of which is connected to the output terminal of the analog-digital conversion circuit 13 and the output terminal of which is connected via the buffer circuit 16 to the bidirectional three-way circuit. It is connected to the gate terminal of the terminal thyristor 9.

Next, the operation of this embodiment will be described with reference to the temperature characteristic diagram of FIG. 2, the voltage characteristic diagram of FIG. 3 and the flowchart of FIG.

AC power supply voltage between power supply terminals 1 and 2 is rectifying diode 5
Is rectified by and divided by the voltage dividing resistor 6 and applied between the bus bars 7 and 4.

Then, when the microcomputer 15 is started by operating a start switch (not shown), the microcomputer 15 first comes to the output step (a) of "set to medium heat generation capacity", and the bidirectional three-terminal thyristor 9 A gate signal is applied to the device so that the conduction angle becomes medium. As a result, the electric heater 8 generates heat with a medium heat generation capacity that is a predetermined heat generation capacity to heat the pot, and rice cooking is started by so-called medium heat. At the beginning of rice cooking, the temperature of the pot is low as shown by the characteristic curve shown in FIG. 2, and the resistance value of the thermistor 10 that senses this is large and the resistance 1
The detection voltage V, which is the voltage across the terminals of the thermistor 10 that is energized via 1, becomes high as shown in FIG. in this case,
The detection voltage V of the thermistor 10 due to the temperature change of the kettle is given to the analog-digital conversion circuit 13, and the analog-digital conversion circuit 13 outputs a digital signal according to the change of the detection voltage V, and the microcomputer 15 Captures this digital signal as a function of time, detects the temperature of the kettle, and operates as described below. That is, after the electric heater 8 starts heating the kettle, when the heat exchange with the rice water in the kettle becomes relatively active, the kettle temperature rises rapidly toward a predetermined temperature (for example, 100 ° C.). (Indicated as the first rising edge a in FIG. 2) (time t ₁ ), the detection voltage V
Falls sharply. The microcomputer 15 repeats the process of shifting to the judgment step (b) of “a?” After the output step (a), judges “NO” here and returns to the judgment step (b). As described above, when the temperature of the kettle shows the first rising a, it is determined to be "YES" in the determination step (b), and the process proceeds to the "set to large heat generation capacity" output step (c). Then, in this output step (c), the microcomputer 15 gives a gate signal to the bidirectional three-terminal thyristor 9 so that its conduction angle becomes large. As a result, the electric heater 8 generates heat with a large heat generation capacity, so that rice is cooked by so-called high heat, heat exchange with rice water is actively performed, and the temperature of the pot is kept substantially constant at a predetermined temperature. Become. In this state, the detection voltage V also becomes substantially constant. After that, when it reaches a so-called dry-up state in which the water in the pot disappears at the time when the rice cooking is almost finished (time t ₂ ),
The temperature of the kettle again rises sharply (shown as the second rising b in FIG. 2), and the detection voltage V also falls sharply. After the output step (c), the microcomputer 15 repeatedly moves to the judgment step (d) of "b?", Judges "no" here and returns to the judgment step (d). When the temperature of the kettle shows the second rise b, it is determined "YES" in the determination step (d) to shift to the output step (e) of "set to medium or small heat generation capacity". Then, in this output step (e), the microcomputer 15 gives a gate signal to the bidirectional three-terminal thyristor 9 so that its conduction angle becomes medium or small. As a result, the electric heater 8 comes to generate heat with a medium or small heat generation capacity, and the pot is heated with medium or low heat. After that, the microcomputer 15 shifts to the “setting temperature?” Determination step (f), initially determines “NO” and returns to the determination step (f), but the temperature of the kettle is dried up. When the set temperature (for example, 130 ° C.) in the state is reached (time t ₃ ), it is determined as “YES” in the determination step (f) and the output step of the next “set heat generation capacity to zero” (g)
Move to. Then, in this output step (g), the microcomputer 15 receives the bidirectional three-terminal thyristor 9
To stop giving the gate signal to. As a result, the bidirectional three-terminal thyristor 9 is brought into a non-conducting state, the electric heater 8 is cut off, and the rice cooking is completed.
As a result, as shown in FIG. 2, the time t ₁ earlier medium heat by the first region A, the high heat by the second region B and the time t ₂ after between times t ₁ and t ₂ medium heat Alternatively, the rice is cooked in a three-stage predetermined control mode of the third area C by low heat.

As described above, according to the embodiment, the thermistor 10 that senses the temperature of the kettle and detects it as an analog signal (detection voltage V) that is an electric signal is provided, and the detection voltage V that indicates the sensed temperature information of the thermistor 10 is analog-digital. The conversion circuit 13 converts the signal into a digital signal and the microcomputer 15
Since the rice-cooking operation is controlled based on the temperature information given as the digital signal by the microcomputer 15, unlike the conventional mechanical switch device, the parts such as the heat-sensitive cap and the magnetic shunt steel are processed. There is no problem that an error occurs between the actual temperature of the kettle and the temperature detected by the magnetic shunting steel due to variations in thermal conductivity due to precision and assembly accuracy, etc. There is no problem of poor responsiveness. Therefore, the temperature of the cooker can be detected with good responsiveness and without variation, and the control of the completion time of the rice cooking operation can be accurately performed, which causes problems such as burning the rice. There is no. Moreover, since the thermistor 10 is provided to detect the temperature information of the kettle,
Unlike the conventional one using a mechanical contact such as a micro switch, there is no decrease in the life due to wear, and the reliability for the life can be improved.

In particular, in the present embodiment, the temperature detector 14 and the microcomputer 15 detect the rise of the temperature of the pot, and the electric heater 8 is controlled to a predetermined heat generation capacity at a plurality of time points. Specifically, at the beginning of rice cooking, the microcomputer 15 causes the electric heater 8 to generate heat with a medium heating capacity to cook rice over medium heat.
Microcomputer 1 when the first rising edge a is detected
5 causes the electric heater 8 to generate heat with a large heat generation capacity to cook rice with high heat, and when the second rising b is detected thereafter, the microcomputer 15 causes the electric heater 8 to generate heat with a medium or heat generation capacity to generate medium or low heat. The rice is cooked in the first area A,
Rice can be cooked in a three-step control mode including the second region B and the third region C, and delicious rice can be cooked.

In the above embodiment, the first rising a of the temperature of the kettle is detected and the heating capacity of the electric heater 8 is switched so that the temperature of the kettle changes from the first area A to the second area B. However, when the absolute value of the temperature of the kettle is detected when switching from the first area A to the second area B, for example, when the temperature of the kettle reaches a predetermined value (for example, 60 ° C.), it is sufficiently practical. It can be used for.

Besides, the present invention is not limited to the embodiments described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[Effects of the Invention] As described above, the rice cooker of the present invention includes a plurality of electric heaters that detect temperature information of the pot as an electric signal by the temperature sensitive element and that heat the pot by the control means based on the electric signal. Since the heat generation capacity is controlled to a predetermined value at the time of, it becomes possible to accurately control the end time of the rice cooking operation, and it becomes possible to control the heat generation capacity of the electric heater at a plurality of times. In addition, it has an excellent effect such that the reliability with respect to the life can be improved.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is an electrical configuration diagram, FIG. 2 is a temperature characteristic diagram, FIG. 3 is a voltage characteristic diagram, and FIG. 4 is a flow chart. In the drawings, 8 is an electric heater, 10 is a thermistor (temperature sensitive element), 13 is an analog-digital conversion circuit (conversion means), and 15 is a microcomputer (control means).

Claims (1)

[Claims] 1. A pot heated by an electric heater, a temperature sensitive element for converting temperature information of the pot into an electric signal, and an electric signal corresponding to the temperature information detected by the temperature sensitive element into a digital signal. And a control means for controlling the electric heater to a predetermined heat generation capacity at a plurality of points during the rice cooking operation according to the temperature information supplied by the conversion means. .