JPS62129648A - Method for controlling electric pot and device thereof - Google Patents

Abstract

PURPOSE:To simplify the structure of an electric pot and to make a work easy at the time of assembling, by constituting the pot in such a manner that a heater circuit is opened by detecting water boiling by vibration of water or that of a water container. CONSTITUTION:When the temperature in water is raised to reach about 60 deg.C, the output from a vibration sensor 3 is increased, the output voltage Va from an amplifier 4 exceeds a predetermined voltage V01, the output from a voltage comparator 12 is inverted, and the output voltage Ve from the voltage comparator 12 is also inverted, and then a relay Ry is turned ON. When the temperature in the water exceeds about 90 deg.C, the output voltage Va from the amplifier 4 gets gradually decreased, and when the water temperature gets to its boiling point, the output voltage Va gets to the predetermined voltage Vo, and the output from the comparator 12 is inverted from lower to higher level. Because a capacitor C3 is discharged at that time, the input voltage Vc to a comparator 14 is gradually raised. When the voltage reaches a predetermined voltage V02 after a predetermined time has passed, the output voltage Ve from the comparator 14 is inverted from lower to higher level, the relay Ry is turned OFF, and a circuit to a kettle heater 2a is opened to stop heating.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heater control method and apparatus for an electric kettle.

(Prior Art) Conventionally, as a heater control device for a boiling electric kettle, a temperature sensor is installed in the steam exhaust path of the electric kettle, and an output signal from the temperature sensor and a standard corresponding to the boiling temperature of water are used. The voltage is input to a comparator and compared, boiling is detected when the output signal becomes equal to the reference voltage, and the signal from the comparator stops the heater control circuit connected in series to the heater, and the heater A device that stops energizing is in practical use.

(Problem to be Solved by the Invention) However, in electric pots equipped with this type of heater control device, in order to transmit the output of the temperature sensor provided on the lid to the control circuit on the electric pot body side, the lead wire of the temperature sensor is This has the disadvantage of complicating the structure and assembly because it requires wiring through the hinge between the electric pot body and the lid, which has become a big problem as electric pots have become more compact in recent years. There is. In an electric kettle that uses a band heater as the heater, if you boil the water in the container with approximately the same amount of water as the top of the band heater, the top of the band heater will reach the top of the band heater before the water below reaches boiling temperature. There was also a problem in that only the water in contact with the nearby wall of the container reached boiling temperature and generated steam, and the power to the heater was stopped before the entire container was completely boiled.

(Means for Solving the Problems) As a means for solving the above problems, the present invention converts vibrations of a liquid or a container that occur due to an increase in the temperature of the liquid into an electrical signal, and Boiling of the liquid is detected by detecting the displacement point where the corresponding voltage changes from a higher state to a lower state than the reference voltage corresponding to the boiling of the liquid, and the heater circuit is turned off based on that signal. .

In the present invention, the reference voltage corresponding to the boiling of the liquid is defined as the output from the vibration sensor when the liquid reaches its boiling point and the time when the vibration level of the liquid reaches equilibrium after the liquid has completely boiled. This refers to the voltage set within the range between the output of

According to the present invention, the method includes sea urchin, j as shown in FIG.
A vibration sensor 3 that converts vibrations of the liquid or container caused by a rise in temperature of the liquid into electrical signals, and a reference voltage setting means 5 that sets a reference voltage corresponding to boiling of the liquid.
and a discriminator 6 for determining boiling of the liquid by comparing the voltage corresponding to the electrical signal from the vibration sensor 3 with the reference voltage from the reference voltage setting means 5; Heater control circuit 2 that stops energization to
This can be carried out by using an electric kettle control device consisting of 0.

In the embodiment of the boiling detection device according to the present invention, in order to prevent malfunctions caused by external vibrations and to utilize a frequency band in which the output voltage changes greatly as the water temperature increases, the signal from the vibration sensor 3 is Detection is performed using only frequency components including the frequency band at the time of boiling, which are passed through a noise filter such as a band-pass filter.

Further, in the embodiment of the present invention, a bandpass filter 20 is inserted between the vibration sensor 3 and the discriminator 6, which passes only output components of frequencies or frequency bands within a certain range. When the liquid is water, it is preferable to use a bandpass filter that only passes output components of frequencies or frequency bands within the range of 400 to 3000 Hz.

Note that instead of a bandpass filter, a filter with a frequency of 400 to 300
A piezoelectric vibration sensor having a resonant frequency within the range of 0 Hz may be used.

(Function) In the method according to the present invention, when the water in the container of an electric kettle is heated, vibrations are generated in the water or the container as the temperature of the water rises, and the vibrations are correlated with the temperature. , the vibration is converted into an electrical signal to detect the vibration level, while an arbitrary voltage between the output voltage when the water reaches the boiling point (VB) and the output voltage when the equilibrium level is reached (VL) is detected. is the reference voltage V. The detection voltage corresponding to the vibration level detected by the vibration sensor 3 is set as the reference voltage V by the reference voltage setting means 5. from a state higher than the reference voltage V. Complete boiling is detected by detecting the mutation point at which the discriminator 6 changes to a state lower than Switching components such as elements are operated to stop the supply of electricity to the heater.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a control device for a boiling electric kettle according to the present invention, in which 1 is a container, 2 is a heater, 3 is a vibration sensor, 4 is an amplifier, and 5 is a reference corresponding to the boiling temperature of the liquid. Voltage ■. 6 is a vibration level discriminator, 8 is a boiling discriminator consisting of a comparator 14, and the heater 2 is attached to the lower part of the side wall of the container 1, and includes a water boiling heater 2a and a warming heater 2b. There is.

A vibration sensor 3 is attached to the bottom wall of the inner container I, and its terminal is connected to an amplifier 4. As the vibration sensor 3, in addition to piezoelectric type vibration sensors made of piezoelectric ceramics, composite materials, rotund salt, plastic materials, etc., any type of vibration sensor such as electrodynamic type vibration sensors, semiconductor strain gauge type vibration sensors, etc. can be adopted, but small size A piezoelectric type is preferable in terms of weight reduction.

The amplifier 4 includes an operational amplifier 11 that amplifies the output signal of the vibration sensor 3, a field effect transistor FET, and a capacitor C that performs impedance conversion and smoothing of the output.
It is composed of 2.

The vibration level discriminator 6 is composed of a voltage comparator 12, the output from the amplifier 4 converted into a voltage corresponding to the vibration level is input to its inverting input terminal, and a resistor R5 and a variable resistor are input to its non-inverting input terminal. A reference voltage V is set by a reference voltage setting means 5 consisting of a series circuit of VR. I is input.

The heater control circuit 20 includes a voltage comparator 14 constituting a boiling discriminator, a relay Ry, and a thermostat T.
It consists of a parallel circuit with S+, and this circuit is connected in series with the water heater 2a.

Further, a thermal reed switch TR8 is connected in series with the heat-retaining heater 2b in order to control energization to the heat-retaining heater 2b. The thermostats TS, TS2 and the thermal reed switch TR3 are attached to the inner container 1, as shown in FIG.

Further, a reboiling switch SW is provided in the boiling discriminator so that boiling can be performed again if necessary.

In addition, Dl is a reverse voltage absorption diode, and 15 is a DC power supply circuit, which is composed of a power transformer PT, a bridge rectifier circuit DB consisting of diodes, a smoothing capacitor C4, a current limiting resistor R+o, and a stabilizing Zener diode ZD. ing.

The thermostat TS is used to turn off the power when the container is heated without water, and is usually set to 110
It is set at a temperature of about 0.degree. C. and is placed near the band heater 2 of the container.

The operation of the electric pot equipped with the control device having the above configuration will be explained.

When water is poured into the inner container 1 and electricity is turned on to the electric pot, as shown in Figure 2, the water temperature is low (A) and the thermostat TS is turned on.
Since both T S 2 and thermal reed switch TR8 are in the on state, power is supplied to the water boiling heater 2a and the warming heater 2b regardless of the heater control device, and power is supplied to the heater control device from the power supply circuit I5. Direct current is supplied.

At this time, since the output voltage of the vibration sensor 3 is small, the output of the vibration level discriminator 6 becomes a high level, but since the capacitor C3 is in a discharged state, the input terminal Vc to the voltage comparator 14 instantly becomes a high level. No, resistor R8
capacitor C3 according to the time constant determined by and 03.
gradually increases until it is charged. Therefore, the input voltage Vc is the reference voltage V set by the resistor R8 and the variable resistor VR3. 3, the output Ve of the voltage comparator 14
becomes low level, and relay Ry is turned on for a short time. The input voltage Vc is the reference voltage ■. Voltage comparator 1 reaches 3
Even if the output Ve of 4 is reversed and the relay RY is turned off,
Since the water temperature is not yet high, the thermostat T S + and the thermal reed switch TR8 remain in the on state, and the electricity supply to the water boiling heater 2a and the warming heater 2b is maintained.

When the water temperature rises and reaches around 60°C (c), the output from the vibration sensor 3 increases and the output voltage Va of the amplifier 4 increases.
is the reference voltage V. , the output of voltage comparator 12 is inverted, so that voltage comparator I4
Since the output voltage Ve of is also inverted, the relay Ry is turned on.

When the water temperature increases further by 1 and reaches around 90°C (d)
, thermostat TS, and thermal reed switch T
Both R8 are turned off, but since relay RY is closed, electricity to the water heater 2a is maintained.

When the water temperature exceeds around 90°C, the output voltage of the vibration sensor 3 gradually decreases, so the output voltage Va of the amplifier 4 also gradually decreases, and when the water temperature reaches the boiling point (e), the output voltage Va changes to the reference voltage. ■. The output of the voltage comparator 12 is inverted from low level to /S high level. At this time, since the capacitor C3 is discharging, the input terminal Vc to the voltage comparator 14 gradually rises and reaches the reference voltage ■ after a predetermined period of time, as in the case described above. 2, the output voltage Ve of the voltage comparator 14 is reversed from a low level to a high level, the relay RY is turned off, the power supply to the water heater 2a is stopped, the water heating is completed, and a warming operation is started.

During the heat retention operation, the thermal reed switch TR9 is designed to turn on when the water temperature drops below a predetermined temperature, e.g., 87°C, and turn off when it rises to a predetermined temperature, e.g., 90°C or higher. As the TR8 is turned on and off, electricity is turned on and off to the heat-retaining heater 2b, and the water temperature is maintained within a predetermined range. While the heat-retaining heater 2b is energized, the liquid or the container hardly vibrates, and the output of the vibration sensor 3 is extremely small, so the heater control device does not operate.

In addition, if you want to re-boil while keeping warm, press the re-boil switch SW.
Just press . That is, the operation at this time is B in Fig. 2.
As shown in the area, when the reboiling switch SW is temporarily turned on by manually pressing it, the charge in the capacitor C3 is discharged, so the output voltage of the voltage comparator 12 is inverted from high level to low level, and the output voltage is transferred to the voltage comparator 14. The input voltage VC tries to rise gradually by charging the capacitor C0, but since the temperature of the hot water is already high at around 90°C at this time, the output of the vibration sensor 3 increases immediately, and the output voltage of the amplifier 4 increases. Va is the reference voltage■. , the output of the voltage comparator 12 is maintained at a low level. Therefore, the input voltage Vc to the voltage comparator 14
Ve decreases during the rise and the output Ve of the voltage comparator 14
is maintained at a low level. Therefore, relay RY is turned on at the same time as reboiling switch SW is turned on, and energization of water heater 2a is maintained until the water is completely boiled. When it boils completely, the output voltage Va of the amplifier 4 becomes the reference voltage V. , the relay Ry is turned off by the same operation as before, and the electricity to the water heater 2a is turned off.

In addition, when cold water is replenished during keeping warm, as shown in area C of FIG. 2, the thermostat TS.

is turned on, and the boiling detection device performs the same operation as in area A.

In the embodiment shown in FIG. 1, the output voltage VB when the boiling point is reached is the reference voltage V. However, instead of the output voltage VB, the output voltage Vl when the equilibrium level is reached is used as the reference voltage V. The reference voltage V may be set as an arbitrary output voltage between the output voltage VB when the boiling point is reached and the output voltage VL when the equilibrium level is reached.

You may set it to be closed.

FIG. 3 shows another embodiment of the present invention, in which a reference voltage is set by a resistor R8 and a variable resistor VR3. 3, a temperature level discriminator 7 is used, and the temperature level discriminator 7 is a reference temperature setting means consisting of a temperature sensor 9 consisting of a thermistor, and a series circuit of a resistor R7 and a variable resistor VR. , and a voltage comparator 13, the output of the temperature sensor 9 is input to the inverting input terminal of the voltage comparator 13, and the non-inverting input terminal is connected to a resistor R7 and a variable resistor VR.
.

The reference voltage V set by 2 is input.

In this embodiment, the heater drive circuit is turned off only when the water in the electric pot boils, and as shown in FIG. 4, while the water temperature is low, the output voltage from the amplifier 4 is
a is the reference voltage V set by the reference voltage setting means 5; (a), the output voltage vb of the vibration level discriminator 6 becomes high level, but the resistance value of the temperature sensor 9 is large and the voltage applied to the inverting input terminal of the voltage comparator 13 is variable with the resistance R7. Reference voltage set by resistor VR,■. 2 and the output voltage Vc from the temperature level discriminator 7 becomes a low level, so the output of the boiling discriminator 8 becomes a low level.

When the water temperature rises and reaches around 60°C, the output voltage Va of the amplifier 4 begins to increase (b), and as the water temperature rises further, the output voltage Va becomes the reference voltage (2). When reaching (c), the output voltage of the vibration level discriminator 6 is inverted to low level, but the output of the boiling level discriminator 8 is maintained at low level. The temperature rises further and the base thread voltage ■. 2, e.g. 85°
When reaching C, the output of the temperature level discriminator 7 is inverted to high level, but the output voltage vb of the vibration level discriminator 6 is
Output voltage Va is reference voltage V. Since the output of the boiling discriminator 8 is not inverted to high level until it reaches 1 (e), the output of the boiling discriminator 8 is maintained at low level. Output voltage Va is reference voltage V. When the temperature reaches 1, the output of the boiling discriminator 8 is inverted to high level, the relay RY is energized, and the heater circuit is turned off.

Note that the output from the boiling discriminator 8 can also be used to sound a buzzer or the like to issue an alarm.

FIG. 5 shows another embodiment, and solves the problems in the above embodiment.
In other words, all of them work well when the electric kettle is full of water, but when the amount of water in the container changes, the reference voltage
. In order to maintain a constant temperature at which the heater circuit turns off regardless of the amount of water, the temperature at which it reaches 1 changes, and as a result, regardless of the water volume,
Reference voltage V. This solves the problem that the variable resistor VR, which is set at 1, needs to be adjusted according to the amount of water.

That is, in this embodiment, the reference voltage setting means 5 is constituted by a water amount detection means, and this water amount detection means includes a pair of water level detection electrodes 21 for electrically detecting the water level in the container.
and an operation amplifier 22 that converts the electrical resistance between both electrodes into an electrical signal and performs electrical processing such as amplification and voltage regulation.
The output voltage is the reference voltage of the vibration level discriminator 6. I am trying to use it as 1. In this way, the reference voltage is automatically set according to the amount of water in the container 1, so the temperature at which the heater circuit is turned off can be maintained constant regardless of the amount of water.

Note that the water amount detection means is not limited to the electric resistance type shown in the above embodiment, but any known type may be used.

For example, Japanese Unexamined Patent Publication No. 55-128123, Utility Model Application No. 57
- The capacitive type described in Publication No. 166537, or the photoelectric type that detects the amount of water by arranging a plurality of light emitting elements such as light emitting diodes and light receiving elements such as photosensors across a water level tube, or the one in the container 1. Examples include a gravimetric method that detects the amount of water by weight.

In the above embodiment, the control device is configured with a logic circuit, but it can also be configured using a microcomputer, and instead of configuring the heater control circuit with a relay, a switching element such as an IAC can be used. It can also be configured using

(Effects of the Invention) As is clear from the above description, the present invention stops the heater circuit by detecting the boiling of the liquid by vibration of the liquid or the container, so the boiling detection means is attached directly to the container. Therefore, it is possible to simplify the structure of the electric kettle, facilitate assembly during production, and downsize the electric kettle. Further, by configuring the reference voltage setting means with the water amount detection means, excellent effects such as being able to stop energizing the heater at the same temperature regardless of the amount of water are achieved. In addition, boiling can be detected reliably and accurately by extracting only a certain frequency within a specific frequency band or an output component of a frequency band from the output of the vibration sensor to detect boiling.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of a control device for an electric kettle according to the present invention, FIG. 2 is a diagram showing changes in voltage at each part during operation, and FIG. 3 is a diagram showing another embodiment of the present invention. Fig. 4 is a block diagram of the boiling detection circuit of the control device, and Fig. 4 is a time chart showing voltage changes and operations of each part during its operation.
The figure is a circuit diagram of reference voltage setting means of a control device showing another embodiment of the present invention. I...Container, 2...Electric heater, 3...Vibration sensor, 4...Amplifier, 5-Reference voltage setting means, 6...
Discriminator, 7... Temperature level discriminator, death/boiling discriminator,
9... Temperature sensor, 11... Operational amplifier, 12.1
3.14...Voltage comparator, FET...field effect transistor, CI~C4/capacitor, R1~RIQ
...Resistance, VR,, VR3...Variable resistor, VR2
~Reference temperature setting means.

Claims (4)

[Claims] (1) A state in which the vibration of the liquid or container caused by a rise in the temperature of the liquid is converted into an electrical signal, and the voltage corresponding to the electrical signal is higher than or lower than the reference voltage corresponding to boiling of the liquid. A method for controlling an electric kettle, characterized in that boiling of a liquid is detected by detecting a displacement point where the liquid changes to , and a heater circuit is turned off based on the signal. (2) a vibration sensor 3 that converts vibrations of the liquid or container caused by a rise in temperature of the liquid into electrical signals;
A reference voltage setting means 5 sets a reference voltage corresponding to the boiling of the liquid, and a voltage corresponding to the electrical signal from the vibration sensor 3 is compared with the reference voltage from the reference voltage setting means 5 to determine the boiling of the liquid. A control device for an electric kettle, which includes a vibration level discriminator 6 that makes a determination, and a heater control circuit 20 that stops energizing the heater based on a signal from the vibration level discriminator. (3) The control device according to claim 2, wherein the reference voltage setting means comprises water amount detection means. (4) The heater control circuit compares the reference temperature setting means, the temperature sensor 9 that detects the container temperature, and the output signal from the reference temperature setting means and the output signal from the temperature sensor 9 to determine the temperature level. The control device according to claim 2 or 3, comprising a temperature level discriminator 7.