JPH0569528B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heating control method for an electric pot.

(Conventional technology and its problems) In conventional electric pots, once the water boiling operation is started, the heater is driven at full power until the water boils. Internal pressure may rise and hot water may overflow from the outlet.

In order to prevent this, a space is required between the hot water surface (water surface) and the inner container to prevent the hot water from overflowing, and the contents must be made larger by that amount. As a result, electric pots become bulky, which becomes a major hindrance to the recent trend of miniaturization and compactness, and requires a large amount of material, which increases the cost of the product. Ta.

In order to solve this problem, the inventors of the present invention conducted various studies and found that if the heater is energized intermittently from just before boiling to gradually heat it, the increase in internal pressure can be alleviated. I discovered that the overflowing of hot water was eliminated.

(Means for solving the problems) The present invention was made based on the above findings, and
In an electric pot that heats water by installing a temperature detection element to detect a rise in water temperature, multiple temperature ranges are set from the temperature just before boiling, and the temperature raising process is repeated in which one cycle is a heating state and a heating stop state. The water temperature is raised while running the water, and when the water temperature is detected at least twice within the same temperature range, the water boiling operation is then terminated without executing a new temperature raising process.

(Example) The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an electric pot A, in which a heater 4 as a heating means and a temperature detection element TH are attached to the outer surface of the bottom of the inner container 10, and a microcomputer MC and a relay 3 are attached to the bottom of the outer case 11. Each of these devices constitutes the circuit shown in FIG.

The control circuit shown in FIG. 2 will be explained below.

In the figure, reference numeral 1 indicates an AC power source, and a contact 31 of a relay 3 is connected to this AC power source 1 via a heater 4.

Further, the AC power source 1 is transformed into a predetermined voltage by a transformer (not shown), and then rectified into a DC voltage by a rectifier circuit 2. The - terminal of the rectifier circuit 2 is grounded, and a microcomputer is connected between the + terminal of the rectifier circuit 2 and the ground.
In addition to MC, a coil 32 and a switching transistor 5 in the electromagnetic device (not shown) of the relay 3 are directly connected, and the base of the transistor 5 is connected to the output terminal B ₀ of the microcomputer MC.
It is connected to the.

Therefore, when the transistor 5 is turned on and off by a signal from the microcomputer MC, the current to the coil 32 is turned on and off, and the electromagnetic device is excited and demagnetized.
1 and heater 4 are turned on and off.

The microcomputer MC has a built-in timer Tm and a comparator 6, which is a comparator.
The comparison input terminal 6a of the comparator 6 has the +
Temperature sensing element connected in series between terminal and ground
Contact a between TH and resistor _R1 is connected.

Note that the resistance value of the built-in resistor in the temperature detection element TH decreases as the hot water temperature (water temperature) increases, and the comparison voltage Vi input to the comparator 6 gradually increases.

On the other hand, the reference input terminal 6b of the comparator 6 has a resistor connected in series between the + terminal and the ground.
Contact b of R ₂ and R ₃ is connected, and the resistors R ₂ and R ₃
Connect one end to the terminal of the microcomputer MC.
The other ends of resistors R ₄ , R ₅ , and R ₆ connected to A ₄ , A ₅ , and A ₆ are connected in parallel, respectively.

By appropriately switching the combination of resistors R ₂ , ~, R ₆ inside the microcomputer MC, the reference voltage input to the comparator 6 is
It is possible to switch Vj to a predetermined set voltage (V ₁ , . . . , Vn).

Note that the set voltage (V ₁ , ~, Vn) indicates that the water temperature detected by the temperature detection element is the set temperature (T ₁ , Vn).
~, Tn), it is the comparison voltage Vi that is input to the comparator 6. More specifically, _T1 is 98℃,
Tn is set at 103° C., and the temperature therebetween is divided into (n-1) temperature regions.

Therefore, in the comparator 6 of the microcomputer MC, during operation, the comparison input terminal 6
A comparison voltage (Vi) that changes from moment to moment as the water temperature rises is input from the reference input terminal 6b, while any of the set voltages (V ₁ , ~, V ₄ ) is input as the reference voltage (Vj) from the reference input terminal 6b. is entered, and these two
The two voltages (Vi) and (Vj) are compared, and if Vi<Vj, a "Hi" signal is output to the microcomputer MC, and if Vi≧VJ, a "Lo" signal is output to the microcomputer MC.

Note that the comparator 6 is set to start when the water boiling operation is started, and to be driven and controlled by the timer Tm described below once the water temperature reaches _T1 .

The timer Tm built in the microcomputer MC is in a standby state from when the heater 4 is started until the first "Lo" signal is output from the comparator 6.
It is set to start driving when a signal is output, and there is an OFF state in which the transistor 5 is operated for ₁ hour (30 seconds) and the heater 4 is stopped, and an OFF state in which the transistor 5 is operated _{for 2} hours (t 20 seconds) to stop the heater 4. A temperature raising process is performed in which one cycle is the on state in which the transistor 4 is driven.

Then, when the timer Tm starts operating, the microcomputer MC turns off the heater 4 for t ₁ hour, then drives the comparator 6 again, and if the output signal is "Lo", the reference voltage Vj is compared with the voltage Set the set voltage to a higher level than Vi, and operate the timer Tm again after the timer Tm ends.If the output signal is “Hi”, the timer
After Tm ends, the water boiling operation is ended without executing a new temperature raising process.

Furthermore, when the water temperature reaches Tn = 103°C, which is the dry boiling level, the water boiling operation is immediately stopped.

A heating control method for the electric pot A having the above configuration will be explained with reference to graphs and time charts shown in FIGS. 3a to 3d.

First, when water is poured into the inner container 10 and a power switch (not shown) is turned on, the voltage of the AC power supply 1 is lowered by a transformer (not shown), and the voltage transformed into DC by the rectifier circuit 2 is transferred to the microcomputer.
MC and a circuit having resistors R ₁ and R ₂ .

Then, when the water boiler switch (not shown) is turned on, the transistor 5 is operated by a signal from the microcomputer MC, a current is applied to the coil 32 of the relay 3, and the electromagnetic device (not shown) is excited to turn on the contact 31. Then, the water boiling operation by the heater 4 starts.

On the other hand, at the same time as the water boiling operation starts, the microcomputer MC
Inside, comparator 6 is turned on, and
By combining _resistors R _{2 ,} .

When the water boiling operation is started, the temperature of the water heated by the heater 4 gradually rises, and the comparison voltage Vi also rises accordingly. However, until the first set temperature T ₁ is reached (from the start), the voltages Vi and Vj have a relationship of Vi<Vj (=V ₁ ), so the comparator 6 does not output a “Hi” signal during this time. output and keep the heater 4 on.

When the water temperature reaches the first set temperature _T1 (state of step), the comparison voltage Vi of the comparator 6 becomes equal to the first set voltage _V1 (Vi=Vj), and the comparator 6 outputs a "Lo" signal for the first time. Output. As a result, as shown in FIGS. 3c and 3d, the comparator 6 is turned off and the temperature raising process by the timer Tm is started.

When timer Tm starts, heater 4 is activated for t ₁ hour.
Power is cut off.

However, even if the power supply to the heater 4 is cut off, until the heat of the heater 4 itself is radiated,
As the water temperature rises slightly, the comparison voltage Vi rises.

Then, after t ₁ hour (step state),
Inside the microcomputer MC, heater 4
At the same time as turning on the comparator 6 (see Figure 3c), the comparison voltage Vi and the reference voltage Vj (=
V ₁ ). And at this time, Vi>Vj(=
V ₁ ), the comparator 6 outputs a "Lo" signal, and the microcomputer MC receives the "Lo" signal and changes the combination of resistors R ₂ , ~, R ₆ to determine whether the comparison voltage Vi is currently Search whether the voltage is within the set voltage (temperature range).

As a result, as shown in FIG. 3a, V ₁ <Vi<
If V ₂ , the reference voltage Vj is set to a second set voltage V ₂ one rank higher than Vi, the heater 4 is driven for t ₂ hours, and then the timer Tm is driven again. At this time, if V ₂ <Vi < V ₃ , Vj is set to V ₃ , which is one rank higher than Vi.

Hereinafter, the above temperature raising process [1 cycle is (t ₁ +
_t2 ) time] while repeatedly turning the heater 4 on and off intermittently to raise the temperature of the hot water.

Then, as shown in FIG. 3a, a similar operation is performed at the time of step to change the reference voltage Vj to V ₄
Set to . Then, the temperature (resistance) rise subsides until the next step in the temperature raising process.
In the step, when Vi<Vj, the comparator 6 outputs a "Hi" signal.

As a result, it is determined that the water temperature detected in the previous step and the water temperature detected in the current step are in the same temperature range [T ₃ -T ₄ (:V ₃ -V ₄ )]. As a result, it is assumed that the water is already in a boiling state, and after t ₂ hours have elapsed, the water boiling operation is stopped and the warming operation is started, without performing a new temperature raising process.

Furthermore, even if you accidentally start boiling water when there is no water in the electric kettle, all boiling operations will stop immediately when the empty cooking level Vn (set temperature Tn: 103°C) is reached. however,
Before the dry cooking level is reached, the timer Tm operates at least once and the power supply to the heater 4 is cut off. As a result, the temperature rise rate is moderated, and the heater 4 is stopped when the dry cooking level is detected. Then, the amount of subsequent temperature rise is small. As a result, the temperature of the atmosphere around the heater 4 does not become high, and there is little risk of damaging electrical equipment such as the microcomputer MC and the relay 3 provided around the heater 4.

In the embodiment described above, the comparator 6 is operated to check the water temperature after ₁ hour after the timer Tm starts operating and the power supply to the heater 4 is cut off, but the present invention is not limited to this. , t When the heater 4 has been turned on for ₂ hours, the water temperature may be checked.

In addition, in the above example, _T1 was 98°C and Tn was 103°C.
℃, and _t1 of timer Tm is 30sec,
Although t ₂ is set to 20 seconds, the above setting values are not limited to that value.

(Effects of the Invention) As is clear from the above explanation, in the boiling control method for an electric pot according to the present invention, the heating means is intermittently turned on and off in a constant cycle from just before boiling, and at least When the water temperature is detected twice, the boiling operation is ended without executing a new temperature raising process.

Therefore, the internal pressure of the electric kettle will not suddenly rise and hot water will not overflow from the discharge port, making it possible to fill the inner container with water to near the upper end, making effective use of the internal space of the inner container. I can do it. Therefore, it is possible to reduce the bulk of the electric pot while maintaining its capacity, making it smaller and more compact, and reducing material costs.
It becomes possible to supply inexpensive products to consumers.

Additionally, the limescale contained in tap water cannot be released unless the water is boiled for a certain period of time; however, according to the present invention, the water is heated at least twice in a boiling state, which removes limescale. can be released reliably. As a result, delicious hot water without the odor peculiar to tap water can be provided for drinking.

Furthermore, one temperature detection element can serve as temperature detection functions for boiling, keeping warm, and dry cooking.
It will be cheaper that much.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of the electric pot, FIG. 2 is a control circuit diagram, and FIGS. 3a to 3d are graphs and time charts showing boiling control of the electric pot. A... Electric pot, 1... AC power supply, 2... Rectifier circuit, 3... Relay, 4... Heater, 5... Transistor, 6... Comparator, 10... Inner container, 11... Exterior body, TH...Temperature detection element,
MC...Microcomputer, Tm...Timer.

Claims (1)

[Claims] 1. In an electric pot that heats water while detecting a rise in water temperature by installing a temperature detection element, multiple temperature ranges are set from the temperature just before boiling, and a temperature raising process is performed in which one cycle is a heating state and a heating stop state. An electric kettle characterized in that the water temperature is repeatedly raised while the water temperature is increased, and when the water temperature is detected at least twice within the same temperature range, the water boiling operation is terminated without performing a new temperature raising process. Heating control method.