JPS6251610B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric rice cooker (including an electronic jar rice cooker; the same applies hereinafter) that automatically performs additional cooking and heating for a certain period of time after the rice reaches a predetermined temperature after the end of cooking. It is.

In order to cook rice deliciously, it is necessary to remove excess water that clings to the rice after it has finished cooking, and to remove the α of the starch in the rice grains even after the rice has finished cooking.
It is important to encourage this process and allow it to progress to the inside. The gelatinization of starch in rice grains has the property that the process stops when the temperature of the rice drops below a predetermined temperature, and once it stops for a while, it no longer occurs.

For this reason, in the past, motor cam time was used to perform additional cooking and heating at fixed time intervals after a predetermined period of time had elapsed after the rice was finished cooking, to remove the moisture around the rice and raise the temperature inside the rice cooker to a predetermined temperature or higher. By maintaining the rice, the gelatinization of starch progresses to the core of the rice grain, resulting in fluffier and more delicious rice.

However, with conventional electric rice cookers that use the motor cam timer mentioned above to perform additional heating, there was a problem that the power frequency was different between the Kanto region and the Kansai region, resulting in a difference in motor rotational speed and a change in the set time. . For this reason, as a business operator, it is necessary to display the timing and heating time of additional heating for each of the Kanto and Kansai regions.On the other hand, for consumers, if they move to an area with a different frequency, etc.
I had to be very careful when cooking rice.

In addition, if the motor cam timer stops operating midway due to a power outage or unplugging the outlet plug, the motor cam timer will stop operating after the above midway point when the power is turned on to keep warm. There was a problem in that the system started to operate and additional heating was performed in a timely manner.

In addition, conventional electric rice cookers are equipped with a movable non-returnable temperature-sensitive rice-cooking switch, which is made of members such as a temperature-sensitive magnetic material, a magnet, and a spring, and which detects the end of rice cooking, located in the lower part of the interior of the electric rice cooker. By operating a lever operating part protruding from the window of the outer case of the rice cooker, the movable non-returnable temperature-sensitive rice cooking switch was mechanically operated to start cooking rice. Therefore, it is necessary to provide a space at the bottom of the rice cooker for arranging members such as a lever and a bearing member that transmits the force applied to the lever operation part to the mechanical part of the temperature-sensitive rice cooking switch. They had no choice but to use rice cookers, which was one of the causes of increased costs.
In addition, the lever operation part has no choice but to protrude outside through a window provided at the bottom of the outer case of the rice cooker.
There was a problem with the design.

In view of the above-mentioned drawbacks of conventional electric rice cookers, the present invention uses a CR circuit to perform additional cooking and heating without using a motor cam timer, and also allows mechanical parts such as levers to be controlled by simply operating a manual operation switch. To provide an electric rice cooker that automatically starts cooking rice by applying current to a rice heater without using it.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric rice cooker according to the present invention (hereinafter referred to as the rice cooker of the present invention) will be explained below based on drawings showing embodiments thereof.

The rice cooker of the present invention is equipped with an electric circuit as shown in FIG. 1, where 1 is a rice cooker heater for heating cooked rice. The rice cooking heater 1 is embedded in a hot plate 2, as shown in FIG. In FIG. 2, SW ₁ is an automatic reset type heat-responsive switch such as a make-type thermostat that closes when the rice is cooked, and is heat-conductively attached to the bottom of the inner pot 4.
As shown in FIG. 1, it is connected in series with a first resistor R ₁ to form a first series circuit 3 . The first series circuit 3 is connected to an AC power source 4 via a rectifying and smoothing circuit 5. The rectifying and smoothing circuit 5 includes a rectifying diode 51, a smoothing capacitor 52, and a constant voltage Zener diode 53, and is a circuit that rectifies the AC voltage output from the AC power source 4 and maintains it smoothed to a constant voltage. In Figure 2, SW ₂ is the outer case 6.
A manually operated automatic return type switch that is installed at an appropriate location such as the front of the machine and closes only when operated.
As shown in FIG. 1, the capacitor 7 is connected in series to form a second series circuit 8. First series circuit 3
An intermediate connection point A between the first resistor R ₁ and the thermally responsive switch SW ₁ is connected to an intermediate connection point B between the manually operated automatic reset type switch SW ₂ of the second series circuit 8 and the capacitor 7; ₂ and a rectifying element 9. The rectifying element 9 is connected to the intermediate connection point B.
The connection is made in such a direction that current flows only from the side to the intermediate connection point A side. 10 is a main switch control circuit which inputs the voltage Va at the intermediate connection point A and the voltage Vb at the intermediate connection point B, and when both voltage values are high, the main switch control circuit is connected in series to the rice cooking heater 1. The circuit outputs a closing signal to the main switch SW ₃ to close it, and outputs an opening signal to the main switch SW ₃ to open it when at least one of the voltage values is low. is the voltage Va
The first comparator COM 1 inputs COM ₁ to its + side input terminal.
, a second comparator COM ₂ which inputs the voltage Vb to its + side input terminal, and an output c ₁ of the first comparator COM ₁ .
and a transistor 12 having an AND circuit function, which inputs the output Vc ₂ of the second comparator COM ₂ to its base, and a circuit such as a relay RY connected to the collector of the transistor 12 and opening/closing the main switch SW ₃ . Become. A voltage dividing resistor is connected to the negative input terminal of the first comparator COM ₁ to divide the voltage V ₀ obtained by converting the AC power supply voltage into a constant DC voltage by the rectifying and smoothing circuit 5.
A predetermined voltage Vk at point K divided by R ₃ and R ₄ is input, and the constant voltage V ₀ is input to the negative input terminal of the second comparator COM ₂ through voltage dividing resistors R ₅ and R ₆ . A predetermined voltage Vl at point L, which will be described later, is input. SW ₄ is a rice cooking release switch that is connected in parallel to the capacitor 7 and is used to discharge the charge in the capacitor 7 and stop rice cooking, and as shown in FIG. 2, the manual automatic return type switch SW ₂ It is located below. As shown in FIG. 2, the thermally responsive switch SW ₁ has a fitting 11 installed in a hole W drilled in the center of the hot plate 2.
It is located inside. As shown in FIG. 3, the fixture 11 has an upper closed box 113 in which a spring 1 is placed inside an open upper box 112 having a flange 111 on the upper part.
14, and the thermally responsive switch SW ₁ is fixed in contact with the lower surface of the ceiling of the upper closed box 113 as shown in the figure. . Therefore, the ceiling of the upper closed box 113 is in direct contact with the bottom of the inner pot 4, and the heat-responsive switch _SW1 can detect the rice temperature extremely well. In FIG. 1, 13 is a non-temperature heater, and 14 is a lid heater.

Next, the operation of the rice cooker of the present invention will be explained.

When the manually operated automatic reset switch SW ₂ is pressed and closed, the capacitor 7 is charged to a voltage close to the power supply voltage V ₀ . Therefore, the voltage Vb at intermediate connection point B
A voltage close to V ₀ is input to the + side input terminal of the second comparator COM ₂ [see Figure 4a]. Also, since the set voltage Vl is input to the negative input terminal, the second
A high voltage Vc ₂ is output from the comparator COM ₂ (see FIG. 4b). On the other hand, make type thermally responsive switch
Since the temperature of SW ₁ is low, it is opened [Figure 4 c
[see Figure 4 d], the voltage Va close to V ₀ at the intermediate connection point A is input to the + side input terminal of the first comparator COM ₁ [see Figure 4 d], and the set voltage lower than V ₀
Since Vk is input to the negative input terminal, the first
A high voltage Vc ₁ is output from the comparator COM ₁ (see FIG. 4e). As a result, a sufficiently high voltage is input to the base of the transistor 12, so that the transistor 12 becomes conductive, the relay RY operates, and the main switch _SW3 is closed (see FIG. 4f). Then, heat Q is generated from the rice cooking heater 1, and rice cooking starts (see Fig. 4g).

As rice cooking progresses, heat-responsive switch SW ₁
When the temperature T of the rice rises [see Figure 4 h] and the rice is cooked, the heat response switch SW ₁ closes [see Figure 4 c]. Therefore, the voltage Va becomes almost zero, and only the low voltage Vc ₁ is output from the first comparator COM ₁ (see FIGS. 4d and 4e). Therefore, a voltage sufficient to make the transistor 12 conductive is no longer applied to the base of the transistor 12, so the transistor 12 becomes non-conductive, the relay RY does not operate, and the main switch SW ₃ opens (Fig. 4 f). reference〕. In this way, cooking and heating the rice is completed [see Figure 4g]. Note that while the thermally responsive switch SW ₁ is closed, the charge in the capacitor 7 is discharged through the second resistor R ₂ , the rectifying element 9, and the thermally responsive switch SW ₁ , and the voltage is increased.
Vb gradually decreases as shown in FIG. 4a. Note that since the manually operated automatic reset switch _SW2 remains open, the power supply voltage has no effect on the discharge of the voltage Vb. When the rice cooking is finished and the temperature drops as shown in Figure 4h, the heat response switch is turned on again.
SW ₁ opens (see Figure 4c). As a result, the discharge stops (see Figure 4a) and the voltage Va becomes higher than Vk, causing the first comparator to
The output voltage Vc ₁ of COM ₁ increases [Fig. 4 d, e
(see FIG. 4f), the transistor 12 becomes conductive, the relay RY operates, and the main switch SW ₃ closes (see FIG. 4f). Then, heating by the rice cooking heater 1 starts again, that is, additional heating starts, and the temperature rises (see Figures 4g and 4h). When the temperature rises and reaches the operating temperature of thermal switch SW ₁ , the thermal switch SW 1 switches off.
SW ₁ is closed again (see FIG. 4c), the voltage Va becomes approximately zero, and the output Vc ₁ from the first comparator COM ₁ becomes a low voltage (see FIGS. 4d, e). As a result, relay RY stops operating, main switch SW ₃ opens, and heating ends [see Figure 4 f, g]. Further, while the thermal response switch _SW1 is closed, the charge in the capacitor 7 is discharged, and as shown in FIG. 4a, the voltage Vb starts to gradually decrease again, and _the - After the voltage becomes lower than the set voltage Vl input to the side input terminal [see Vl, point W in Figure 4 a], the low voltage is output from the second comparator COM ₂ .
Only Vc ₂ will be output (see Figure 4b). When the temperature drops, the thermal response switch SW ₁
is opened and the voltage Va becomes high voltage. Therefore, the first
The high voltage Vc ₁ is now output from the comparator COM ₁ [see Figure 4 d and e], but as mentioned above, the second
Since only the low voltage Vc ₂ is output from the comparator COM ₂ [see Figure 4b], sufficient voltage is not input to the base of the transistor 12 to operate the transistor 12.
The transistor 12 remains non-conductive, the relay RY does not operate, and the main switch SW ₃ also remains open (see Figures 4f and 4g). Therefore, the temperature further decreases as shown in FIG. 4h, and a heat retention state is reached. Note that the value of the voltage Vl is determined after the additional heating is completed, and when the thermal response switch SW ₁
The voltage of the capacitor 7 before it closes for the third time, that is, the value of the voltage Vb, for example, the value Vl at the point W
Set in advance to match.

As is clear from the above, since the rice cooker of the present invention performs additional heating using the CR circuit, the additional heating time can be adjusted regardless of whether the power supply frequency is different in Kanto or Kansai. There will be no difference in the results. Therefore, the rice will not burn. In addition, since it does not use a motor cam timer that requires a large space, the rice cooker is more compact and less costly.
CR circuits have the advantage of being cheaper.
Furthermore, since the rice cooker of the present invention does not require a space to house mechanical members such as levers and bearing members, the electric rice cooker can be small in size, and from this point of view as well, significant cost reductions can be achieved. Furthermore, since mechanical members such as levers and bearing members are not used, there is also the advantage that there is no need to assemble these members without dimensional deviations. Furthermore, since the manually operated automatic reset switch can be installed at any location on the outer case of the rice cooker, it has the advantage of being able to be installed at the most desirable location in terms of design. It also has the advantage of starting additional cooking as soon as possible.

[Brief explanation of the drawing]

The drawings are all for explaining the embodiments of the rice cooker of the present invention, and Figure 1 is a wiring diagram of the main electric circuit of the rice cooker of the present invention, Figure 2 is a longitudinal sectional view of the rice cooker of the present invention, Fig. 3 is a cross-sectional view of the heat-responsive switch fitting of the rice cooker of the present invention, Fig. 4a is a graph showing the change in voltage Vb (vertical axis) at intermediate connection point B over time (horizontal axis), Fig. 4 b is the output Vc ₂ of the second comparator COM ₂
(vertical axis) is a graph showing the change over time (horizontal axis), Fig. 4c is a graph showing the change over time (horizontal axis) of the opening/closing of thermal response switch SW ₁ (vertical axis), Fig. 4d is a graph showing the change over time (horizontal axis) A graph showing the change over time (horizontal axis) of the voltage Va (vertical axis) at connection point A, and Fig. 4e shows the change over time (horizontal axis) in the output Vc ₁ (vertical axis) of the first comparator COM ₁ . The graph shown in Figure 4 f shows the opening/closing of main switch SW ₃ (vertical axis).
Fig. 4g is a graph showing the change over time (horizontal axis) of the heat generated by the rice cooking heater Q (vertical axis), Fig. 4h is a graph showing the change over time (horizontal axis) in the heat generated by the rice cooking heater
It is a graph showing a change in temperature T (vertical axis) of SW ₁ over time (horizontal axis). 1... Rice cooking heater, 3... First series circuit, 4...
... AC power supply, 5 ... Rectifier smoothing circuit, 7 ... Capacitor, 8 ... Second series circuit, 9 ... Rectifier element, 1
0...Main switch control circuit, SW ₁ ...Thermal response switch, SW ₂ ...Manual operation automatic return type switch,
SW ₃ ...Main switch, _R1 ...First resistor, _R2 ...
Second resistance.

Claims (1)

[Claims] 1. In an electric rice cooker that is equipped with a heating circuit in which a main switch is connected in series to the rice heater, and that automatically stops heating the rice when the rice is cooked, and that heats the rice for additional cooking after a predetermined period of time, the AC power source Through a rectifier and smoothing circuit that rectifies and smoothes AC voltage,
A first series circuit consisting of a first resistor and an automatic reset type thermally responsive switch is connected, and a second series circuit consisting of a manually operated automatic reset type switch and a capacitor is connected to the DC power supply. The intermediate connection point A between the first resistor and the automatic reset type thermally responsive switch is connected to the intermediate connection point B between the manually operated automatic reset type switch and the capacitor in the second series circuit.
The voltage Va at the intermediate connection point A and the voltage Vb at the intermediate connection point B are input to a main switch control circuit, and the main switch control circuit controls the voltage Va and the voltage Vb. An additional cooking electric rice cooker characterized in that when both voltages are high, a closing signal is output to the main switch, and when at least one of the voltages is low, a closing signal is output to the main switch.