JPS6314967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a rice cooker that switches the heat generation capacity of an electric heater that heats a pot during rice cooking.

In rice cookers, it is generally known that delicious rice can be cooked by switching the heat generation capacity of the electric heater that heats the pot midway through cooking. Conventionally, when switching the heat generation capacity of this electric heater, Two configurations are being considered: one that uses a timer to switch when a predetermined time has elapsed from the start of rice cooking, and the other that uses a temperature switch to switch when the temperature of the pot reaches a predetermined value. However, in the former configuration that uses a timer, the switching point is constant, which causes problems when the rice cooking capacity differs, and in the latter configuration that uses a temperature switch, setting the temperature at the time of manufacturing is troublesome, resulting in variations in the set temperature. There are some simple problems, and all of them have defects that prevent them from achieving their intended purpose of cooking delicious rice.

The present invention has been made in view of the above circumstances, and its purpose is to provide a temperature detection section that senses the temperature of the pot and detects the rise of the sensed temperature, and when the temperature detection section detects the rise of the sensed temperature. A control unit is installed to switch the heat generation capacity of the electric heater that heats the pot.
The control section controls the electric heater to move from a first region of a predetermined heat generation capacity to a second region of a larger heat generation capacity by a first rise in the temperature sensed by the temperature detection section.
By adopting a configuration in which the electric heater is switched so that it is in the region of It is possible to accurately detect the optimal switching point of the heat generating capacity and cook delicious rice.Moreover, it is easy to manufacture as high precision is not required at the time of manufacturing, and it is not affected by performance deterioration due to changes over time. An object of the present invention is to provide a temperature control device for a rice cooker which can also improve reliability such as not being exposed to heat.

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

1 and 2 are power terminals connected to an AC power source (not shown), one of which, power terminal 1, is connected to a bus bar 4 via a rice cooking switch 3 consisting of a temperature switch, and the other power terminal 2 is connected to a bus bar 5. is,
Furthermore, the bus 4 is connected to the bus 7 via a rectifying diode 6.
The bus 7 is connected to the bus 9 via a voltage dividing resistor 8. Reference numerals 10 and 11 are electric heaters (not shown) that heat the pot, and these are connected in series between the bus bars 4 and 5. 12 is a smoothing capacitor connected between bus bars 7 and 5.
Reference numerals 13 and 14 denote a control transistor and a flip-flop circuit constituting a control section 15, and the flip-flop circuit 14 is connected between bus lines 9 and 5. Further, in the control transistor 13, its collector is connected to the bus 7 via a relay 16, its emitter is connected to the bus 5, and its base is connected to the set output terminal Q of the flip-flop circuit 14 via a resistor 17. . The reset input terminal R of the flip-flop circuit 14 is divided into two branches, the first branch end of which is connected to the bus bar 9 via a resistor 18, and the second branch end thereof to the bus bar 5 via a capacitor 19. There is. Furthermore, a surge absorbing diode 2 is connected in parallel to the relay 16.
0 is connected, and the normally open contact 16a of the relay 16 is connected in parallel to the electric heater 10. 21 is a temperature detection section, which will be described below. 22 is a detection transistor whose collector is branched into two, the first branch end being connected to the bus line 9 via a resistor 23, and the second
The branch end of
The branch end of is connected to the bus bar 9 via the resistor 26,
The second branch end is connected to the bus bar 5 via a first thermistor 27 with negative characteristics, the base is branched into two via a resistor 28, and the first branch end is connected to the bus bar 5 via a capacitor 29. The second branch end is connected to a common connection point of a resistor 30 and a second thermistor 31 having a negative characteristic, which are connected in series between the bus bars 9 and 5, via a diode 32 having the polarity shown. 33 is an output transistor, its emitter is connected to the bus 9, and its collector, which is an output terminal, is branched into two, the first branch end being connected to the trigger input terminal T of the flip-flop circuit 14, and the second branch end being connected to the trigger input terminal T of the flip-flop circuit 14; The branch end is connected to the bus bar 5 via the resistor 34, and the base is connected to the common connection point of the resistors 24 and 25. In this case, the thermistors 27 and 31 are arranged at the same position to sense the temperature of, for example, the bottom of a pot (not shown) and are set to have the same characteristics, and the resistance values of the resistors 26 and 30 are set to be the same. ing. Note that 35 is a constant voltage diode connected between bus bars 9 and 5.

Next, the operation of this embodiment having the above configuration will be explained. When the rice cooker switch 3 is turned on manually, the AC power voltage between the power supply terminals 1 and 2 is rectified by the rectifying diode 6 and smoothed by the smoothing capacitor 12, and is converted into a DC voltage to the buses 7 and 5. The voltage is applied between the busbars 9 and 5, and the voltage is divided by the voltage dividing resistor 8 and applied between the busbars 9 and 5. Therefore, the capacitor 19 is charged via the resistor 18, and the charged voltage is applied to the reset input terminal R to reset the flip-flop circuit 14, and the set output signal at its set output terminal Q becomes low level. As a result, the control transistor 13 is turned off, the relay 16 is in an inoperative state, and the normally open contact 16
a is off. Therefore, the electric heaters 10 and 11 are connected in series and are energized, and as a whole, they generate heat with a small heat generation capacity that is a predetermined heat generation capacity to heat the pot, and rice cooking is started over a so-called medium heat. At the beginning of rice cooking, the temperature of the pot is low as shown by the characteristic curve l shown in Fig. 2, and the resistance values of the thermistors 27 and 31 that sense this are large.
A first thermistor 2 energized via a resistor 26
The first detected voltage _V1 , which is the voltage between the terminals of the second thermistor 31, is high as shown in FIG. capacitor 29
The second detection voltage V ₂ which is the voltage between the terminals of is also high, and the first detection voltage V ₁ and the second detection voltage V ₂ are approximately the same value. After that, as heat exchange with the rice water in the pot becomes relatively active, the temperature of the pot will rapidly rise toward a predetermined temperature (for example, 100℃) (in Figure 2, the first (shown as rising la), and along with this, the first detection voltage V ₁
decreases rapidly, but the second detection voltage _V2 , which is the voltage between the terminals of the capacitor 29, begins to decrease more gently than the first detection voltage _V1 , and when the value between the two reaches a predetermined value △V. (time t ₁ ), the detection transistor 22 is turned on, and along with this, the output transistor 33 is turned on, and the resistor 34 is turned on.
The voltage across the terminals of the flip-flop circuit 14 is applied as a high-level output voltage to the trigger input terminal T of the flip-flop circuit 14, and the flip-flop circuit 14 enters the set state, and the set output signal of the set output terminal Q becomes high level and is used for control. Applied to the base of transistor 13. Then, the control transistor 13 is turned on and the relay 16 is energized, and the relay 16 is activated to make the normally open contact 16a.
is turned on to short-circuit the electric heater 10. Therefore, only the electric heater 11 is energized and generates heat with a large heat generating capacity, so that rice is cooked over high heat, and heat exchange with the rice water is actively carried out to maintain the temperature of the pot at a predetermined temperature. remains approximately constant. In this state, the first detection voltage V ₁ and the second detection voltage V ₂ are approximately equal, the detection transistor 22 is turned off, and accordingly the output transistor 33 is also turned off. After that, when the rice cooking reaches the end and the water in the pot runs out, the so-called dry-up state occurs, and the temperature of the pot starts to rise again (shown as the second rise lb in Fig. 2), and as described above. When the difference between the first detection voltage V ₁ and the second detection voltage V ₂ reaches a predetermined value △V (time t ₂ ),
The detection transistor 22 and the output transistor 33 are turned on, and the flip-flop circuit 14 is reset by applying a high-level output voltage to the trigger input terminal T. The control transistor 13 is turned off and the relay 16 is turned on. Recover from power outage. This causes the normally open contact 16 of the relay 16 to
a is turned off, the electric heaters 10 and 11 are again connected in series and energized, and the entire heater generates heat with a small heat generation capacity. Thereafter, rice cooking is completed when the rice cooking switch 3 detects that the temperature of the pot has reached the set temperature and is turned off. As a result, as shown in FIG. 2, there is a first area A due to medium heat before time t ₁ , a second area B due to high flame between times t ₁ and t ₂ , and a medium flame after time t ₂ . Three stages of rice cooking in the third area C will be performed.

As described above, according to this embodiment, the temperature detection section 21
detects the rise in the temperature of the pot, and at the beginning of rice cooking, the control section 15 turns on the electric heaters 10 and 11.
By energizing the electric heaters 11 in series, rice is cooked with a medium heat with a small heat generating capacity, and when the temperature detecting section 21 detects the first rise la, the control section 15 energizes only the electric heater 11 to cook rice with a large heat generating capacity. The rice is cooked with a high heat with a high heat generating capacity, and then when the temperature detection unit 21 detects the second rise lb, the control unit 15 connects the electric heaters 10 and 11 in series again and energizes the rice, thereby cooking rice with a high heat generating capacity. This device is designed to cook rice using fire, and therefore can cook rice in three stages, consisting of the first area A, the second area B, and the third area C, and cook delicious rice. In addition, since the heat generation capacity of the electric heater is switched by detecting the first rise la and the second rise LB, the optimum switching point of the electric heater can be detected with high accuracy, and the absolute temperature of the pot can be detected accurately. Since it does not detect the temperature, it is not affected by the set temperature, does not require high precision during manufacturing, is easy to manufacture, and is reliable as it is not affected by performance deterioration due to changes over time. It can also improve sexual performance.

FIG. 4 shows a second embodiment of the present invention, in which the same parts as in FIG. 1 are denoted by the same reference numerals, and only the different parts will be described below. That is, the electric heater 36 is interposed and connected between the bus bar 4 and the electric heater 10, and the normally open contact 16a of the relay 16 is connected in parallel to the series circuit of the electric heaters 36 and 10. 37 is a control transistor, the collector of which is connected to the bus 7 via the relay 38, and the emitter connected to the bus 5;
Further, a surge absorbing diode 39 is connected in parallel to the relay 38. A normally closed contact 38b of the relay 38 is connected in parallel to the electric heater 36. 40 is a flip-flop circuit connected between bus bars 9 and 5, and its reset input terminal R
is connected to the common connection point of the resistor 18 and the capacitor 19, and the set output terminal Q is connected to the base of the control transistor 37 via the resistor 41. Furthermore, the output terminal of the temperature detection section 21 (collector of the output transistor 33 in FIG. 1) is connected to the first input terminal of the AND circuit 42 and the trigger input terminal T of the flip-flop circuit 14, and The reset output terminal of the AND circuit 42 is connected to the second input terminal of the AND circuit 42, and the output terminal of the AND circuit 42 is connected to the trigger input terminal T of the flip-flop circuit 40, thereby forming a control section 43.

When the rice cooker switch 3 is turned on, the flip-flop circuits 14 and 40 are reset by the charging voltage of the capacitor 19, and therefore the relay 1 is turned on.
6 and 38 are inoperative, the normally open contact 16a is off, and the normally closed contact 38b is on, and the electric heaters 10 and 11 are connected in series and energized, and the whole generates heat with a small heat generation capacity, and it does not heat at medium heat. Cooking begins.
Thereafter, when the temperature detection section 21 detects the first rise la of the pot temperature (see FIG. 2), the output voltage is applied to the trigger input terminal T of the flip-flop circuit 14.
and the flip-flop circuit 40
The signal is now applied to the trigger input terminal T of the circuit via the AND circuit 42, and both are inverted to the set state. Therefore, the control transistors 13 and 37 are turned on, the relays 16 and 38 are activated, the normally open contact 16a is turned on and the normally closed contact 38b is turned off, and only the electric heater 11 is energized and generates heat with a large heat generating capacity. , rice is cooked over high heat. Furthermore, after that, the temperature detection section 21 detects the second rise in the temperature of the pot.
When lb is detected and a high-level output voltage is generated, the flip-flop circuit 14 receives this high-level output voltage to the trigger input terminal T and enters the reset state, but the flip-flop circuit 40 is in the set state and resets. Since the low-level reset output signal at the output terminal is applied to the AND circuit 42, the AND circuit 42 is in a disconnected state, and the flip-flop circuit 40 receives a high-level output voltage at its trigger input terminal T. It remains in the set state. As a result, the control transistor 13 is turned off, the relay 16 is restored, and its normally open contact 16a is turned off, but the control transistor 37 remains on, and the relay 38 is in the operating state, and its normally closed contact 38b is turned off. remains off,
The electric heaters 36, 10, and 11 are connected in series and energized, and the entire heater generates heat with an even smaller heat generation capacity than the above-mentioned small heat generation capacity, and rice is cooked over low heat. As a result, the first area A, the second area B, and the third area C (see FIG. 2) are heated to medium heat, respectively.
Rice can now be cooked over high heat and low heat, and the same effects as in the previous embodiment can be obtained.

FIG. 5 shows a third embodiment of the present invention, in which the same parts as in FIG. 1 are denoted by the same reference numerals, and different parts will be explained below. That is, power terminals 1 and 2
A series circuit of a bidirectional three-terminal thyristor 44 and an electric heater 11 is connected between them. 45 is an analog-to-digital conversion circuit connected between bus bars 9 and 5, and its input terminal is connected to a resistor 26 and a thermistor 27.
is connected to the common connection point of the temperature detection section 46.
is configured. Reference numeral 47 denotes a control section consisting of a microcomputer or the like connected between the busbars 9 and 5, the input terminal of which is connected to the output terminal of the analog-to-digital conversion circuit 45, and the output terminal connected to the bidirectional signal via the buffer circuit 48. The gate terminal of the three-terminal thyristor 44 is connected to the gate terminal.

Thus, the detected voltage _V1 , which is the voltage between the terminals of the thermistor 27 due to a change in the temperature of the pot, is given to an analog-to-digital conversion circuit 45, and the analog-to-digital conversion circuit 45 converts a digital signal according to the change in the detected voltage _V1 . is now output, and the control unit 47
takes this digital signal as a function of time and calculates the first rise la and second rise lb of the pot temperature.
(see Fig. 2), and the gate signal of the bidirectional three-terminal thyristor 44 is controlled accordingly to adjust the heating capacity of the electric heater 11 so that the temperature of the pot is in the first area A, the first area The second area B and the third area C are switched. Therefore,
This embodiment also provides the same effects as the previous embodiment.

In addition, in the above embodiment, the first rise of the temperature of the pot la
is detected and the temperature of the pot changes from the first area A to the second area A.
The heat generation capacity of the electric heater is switched so that the temperature is in the region B. However, when switching from the first region A to the second region B, the absolute value of the temperature of the pot is detected and the temperature of the pot is changed, for example. Even if it is carried out when the temperature reaches a predetermined value (for example, 60° C.), it can be sufficiently put to practical use.

In addition, the present invention is not limited only to the embodiments described above and shown in the drawings, and it goes without saying that the present invention can be implemented with appropriate modifications within the scope of the invention.

As explained above, the present invention can accurately detect the optimum switching point of the heat generating capacity of the electric heater and cook delicious rice, and can be manufactured without requiring high precision during manufacturing. It is possible to provide a temperature control device for a rice cooker that is easy to control and has improved reliability, such as not being affected by performance deterioration due to changes over time.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention, FIGS. 2 and 3 are a temperature characteristic diagram and a voltage characteristic diagram, respectively, for explaining the operation of the same embodiment, and FIGS. FIG. 5 is an electrical circuit diagram showing second and third embodiments of the present invention, respectively. In the drawing, 10 and 11 are electric heaters, 14 is a flip-flop circuit, 15 is a control section, 16 is a relay, 21 is a temperature detection section, 27 and 31 are thermistors, 39 is a relay, 40 is a flip-flop circuit, 43 is a control section, 45 is an analog-digital conversion circuit, 46 is a temperature detection section, and 47 is a control section.

Claims (1)

[Scope of Claims] 1. A pot heated by an electric heater, a temperature detection section that senses the temperature of the pot and detects a rise in the sensed temperature, and a temperature detection section that detects a rise in the sensed temperature. and a control section that switches the heat generation capacity of the electric heater at the same time, and the control section switches the electric heater from a first region of a predetermined heat generation capacity to a higher temperature region according to a first rise in the temperature sensed by the temperature detection section. The electric heater is configured to switch so as to be in a second region with a heat generating capacity equal to or smaller than the second region, and to switch the electric heater from the second region to a third region with a smaller heat generating capacity by the second rise. A temperature control device for a rice cooker characterized by: 2. The control unit is configured to cause the temperature of the pot to change from the first region to the second region by the first rise at which the temperature sensed by the temperature detection unit reaches a predetermined value, and to cause the temperature of the pot to change from the first region to the second region by the second rise of the sensed temperature. 2. The temperature control device for a rice cooker according to claim 1, wherein the heat generation capacity of the electric heater is switched so that the temperature of the electric heater changes from the second region to the third region. 3. The rice cooker according to claim 1 or 2, wherein the control unit switches the electric heater in the first, second, and third regions so that the electric heaters have different heat generation capacities, respectively. Temperature control device.