JPH0534607Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an electric pot, and particularly to a heat-retaining electric pot equipped with a control device that prevents the heater from heating partially or completely dry.

Conventional technology In general, in thermal electric pots, when the amount of water in the container is small or there is no water at all, local or complete heating occurs, which reduces the durability of the heater, discolors the container, and deteriorates corrosion resistance. The problem is that it brings about For this reason, in recent years, electric pots that issue a warning to the user when the water level in the container falls below a certain level have been introduced, for example, in the 1980s.
It has been proposed in Publication No. 166537 and Japanese Utility Model Application Publication No. 179043/1983. In addition, one of the present inventors, together with other co-inventors, has developed an electric pot equipped with a control device that detects the water level in the container and stops energizing the heater when the water level is below a certain level, for example. , was proposed in Japanese Patent Application Laid-Open No. 58-103418.

Problems to be Solved by the Invention However, electric pots that issue warnings have a problem in that they are of little use if the user is not near the electric pot.
In addition, for electric pots that stop energizing by detecting the water level, setting the lowest electrode position above the top of the band heater has the advantage of preventing local or completely dry heating; however, if the side wall of the container Since a plurality of water level detection electrodes must be installed at predetermined intervals in the depth direction, it is complicated to attach the electrodes to the container, insulate and seal between the container and the control device. If the power supply is turned on with no water due to failure,
There is an unavoidable problem of localized dry firing or complete dry firing.

Therefore, an object of the present invention is to make it possible to prevent the heater or container from being partially or completely heated even when the user is not nearby.

Means for Solving the Problems As a means for solving the above problems, the present invention provides a temperature sensor for detecting the temperature of the container, a boiling detection means for detecting boiling of water, and a signal from the boiling detection means. In the electric pot, the electric pot is equipped with a control device comprising a first power control means for turning off the heater, and a second power control means for controlling the sub-heater on and off based on a signal from the temperature sensor, wherein the electric pot comes into contact with water in the container. A reference water level setting electrode is provided to set a reference water level that allows water boiling operation, and the control device detects the water level in the container based on a signal from the reference water level setting electrode, and detects that the detected water level is less than the reference water level. water level detection means for outputting a signal to stop energizing only the main heater when and outputs a signal to the first and second power control means to stop energizing the main heater and the sub-heater and maintain them in the energized state when the detected temperature is equal to or higher than the dry firing prevention reference temperature. A means for preventing dry heating is provided.

In other words, in the present invention, when boiling water in an electric kettle, the water level and temperature of the container are constantly detected by the water level detection means and the empty heating detection means, and when the water level in the container is below a predetermined level, , the water level detection means stops the operation of the first power control means, and the main heater is maintained in a stopped state; In this case, the dry heating detection means detects that the container has reached the dry heating prevention temperature, the dry heating detection means stops the operation of the first power control means and the second power control means, and the main heater is turned off. By maintaining the energization to the auxiliary heater in a stopped state, it is possible to prevent the container and the heater from being heated partially or completely dry.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1 showing an electric pot according to the present invention, 1 is a conductive container made of a metal material such as stainless steel, 2 is a conductive water pipe, 3 is an insulating tube, and 4a and 4b are negative characteristic thermistors. The conductive water pump 2 is arranged so that its lower end is at least approximately at the same level as the upper end of the band heater 5, and communicates with the inside of the container via the insulating tube 3. It constitutes a water level setting electrode. The band heater 5 is composed of a main heater 5a of high power and a sub-heater 5b of low power.

As shown in FIG. 1, the control device basically includes a water level detection means 1 that detects the water level in the container 1 and outputs an output when the water level is below a preset reference water level.
3, and the water level detection means 13 or boiling detection means 3
a first power control means 14a that stops energization to the main heater in response to a signal from 5; and a second power control means 14b that controls on/off energization to the sub-heater 5b in accordance with a signal from the heat retention temperature detection means 30; Dry heating that maintains the first power control means 14a and the second power control means 14b in a heater stopped state when the temperature detected by the temperature sensor 4a reaches a preset dry heating prevention reference temperature T2 _or higher. Detecting means 24.

Further, as another function, a timer 15 is provided which starts energizing the heaters 5a and 5b after a set time has elapsed.

The water level detecting means 13 includes a reference water level setting electrode (in the embodiment, the container 1 and the pumping pipe 2) that sets a reference water level at which energization to the heaters 5a and 5b is stopped, and a pulse voltage that applies a pulse voltage between both electrodes. A generation circuit 16 and a voltage detection circuit 1 that detects the voltage between the two.
7, a filter 18 for removing noise included in the output of the voltage detection circuit 17, and a temporary memory for sequentially updating and storing the detected voltage from the filter 18 in synchronization with the pulse voltage and outputting it to the first control means 14a. It is composed of a circuit 19.

The filter 18 receives a detection voltage input from the voltage detection circuit 17 (for example, the n-th pulse voltage) and a detection voltage input next (for example, (n+1)).
th pulse voltage) match, and when two consecutive pulse voltages match, it is output to the temporary memory circuit 19. It is designed to improve the stability of operation against noise such as changes in detection voltage. In addition, the detected voltage is temporarily stored in the memory circuit 19.
By keeping the control means 14a in the same state, even when the voltage during one cycle of the pulse voltage becomes zero, the control means 14a can be maintained in the same state. The reason why a pulse voltage is applied between the reference water level setting electrodes is to prevent the taste from changing due to electrolysis or the like if current is constantly passed through the water.

The first power control means 14a and the second power control means 14b are connected to the triaxes 12a and 12, respectively.
B and AND circuits 20 and 23, which turn on and off electricity to the main heater 5a and sub-heater 5b connected in series to the triaxes 12a and 12b, respectively.

The first power control means 14a includes a boiling detection means 35
The boiling detection means 35 stops energizing the main heater 5a in response to a signal from the temperature sensor 4a, and the boiling detection means 35 detects the detected temperature T' at the steam outlet of the container 1 detected by the temperature sensor 4a and the reference temperature T at the time of boiling. ₃ is compared with the boiling reference temperature _T3 from the heat retention temperature setting means 36, and when the detected temperature T' is less than the boiling reference temperature _T3 , the output is high level, and when it is higher than the boiling reference temperature _T3 , the output is low level. The comparator 37 includes a comparator 37, and a storage circuit 40 that stores the output thereof.

In a normal state, the second power control means 14b operates in response to a signal from the heat retention temperature detection means 30, but the heat retention temperature detection means 30 is connected to a temperature sensor 4a that detects the temperature at the bottom of the container 1, a heat retention temperature setting means 27 for setting a reference temperature _T1 for the time;
The comparator 28 compares the heat retention reference temperature _T1 and the detected temperature T from the temperature sensor 4a, and outputs a high level output when the detected temperature T is lower than the heat retention reference temperature _T1 .

In addition, the timer 15 is a timer switch SW.
Each time the timer is pressed, the timer operation is set and canceled repeatedly, and the first power control means 1 outputs a low level when the timer is set and a high level when the timer is released.
4a, and when a low level output is input from the water level detection means 13, timer setting is prohibited.

The dry-heating detection means 24 includes a temperature sensor 4a attached to the bottom of the container 1 to detect its temperature, a dry-heating prevention reference temperature setting means 25 for setting a dry-heating prevention reference temperature _T2 , a temperature sensor 4a, and a dry-heating prevention reference temperature setting means 25. It is comprised of a comparator 26 that compares signals from the prevention reference temperature setting means 25 to determine whether the temperature of the container 1 is higher than the reference temperature, a memory circuit 21 that holds the output thereof, and an inverter 22.

When the dry heating detection means 24 detects dry heating, it outputs an output to the first power control means 14a and the second power control means 14b, and turns the main heater drive circuit 12a and the sub-heater drive circuit 12b into the heater-off state, respectively. maintain it.

The operation of the electric pot equipped with the control device will be explained. First, a level lower than the reference water level set by the container 1 as a water level detection electrode and the lower end of the water pump 2 in the container 1 of the electric pot, for example,
When an amount of tap water (for example, less than 600 ml) is poured into the container 1 so that the water level is below the upper end of the band heater 5, and electricity is applied, the pulse voltage generation circuit 16 generates a voltage of 1 mS at a rate of, for example, once every 4 seconds. A pulse voltage of is applied between the water level detection electrodes, that is, the container 1 and the water pump 2 via the resistor _R1 .

At this time, since there is no water between the container 1 and the pumping pipe 2, the resistance between them becomes infinite, and since it is much larger than the resistance _R1 , the voltage detection circuit 17
A high level pulse voltage is detected. The pulse voltage is input to the filter 18. This filter 18 outputs a low level signal when two continuously inputted pulse voltages match,
The output signal is stored in the temporary storage circuit 19, and is also stored in the AND circuit 20 of the first power control means 14a.
is input.

In addition, since the water temperature in the container is low, and therefore the temperature of the container 1 detected by the temperature sensor 4a is lower than the dry firing reference temperature _T2 , a low level output from the comparator 26 is sent to the inverter via the storage circuit 21. 22, and the high level signal inverted there is sent to the AND circuit 2 of the first power control means 14a.
0, and the high level output from the timer 15 is also input to the AND circuit 20 of the first power control means 14a, but as mentioned above, since the output level from the water level detection means 13 is low level,
Its output level becomes low level, the triac 12a does not operate, and the supply of electricity to the main heater 5a is prohibited.

Note that since the output level from the heat retention temperature detection means 30 is high level, the second power control means 14
The output level of the AND circuit 23 of b becomes a high level, and only the triax 12b operates to supply electricity to the sub-heater 5b, and only heat retention is performed.

In the unlikely event that the water level detection means 13 malfunctions and the first power control means 14a turns on the tri-attack 12a to perform empty heating even though the water in the container 1 is empty, the temperature of the container 1 becomes normal. Dry firing prevention standard temperature T ₂ that cannot be reached during operation,
For example, when the temperature reaches 105°C, the output of the comparator 26 of the dry firing detection means 24 is inverted from low level to high level, and a low level signal is sent from the inverter 22 to the first and second power control means 14a, 14b.
Since it is input to AND circuits 20 and 23, its output level becomes low level, and both triax 1
In order to stop heaters 2a and 12b, power supply to all heaters is stopped. At this time, a warning may be issued to the user using a lamp or a buzzer. Thereafter, even if the temperature of the container 1 decreases, the output level of the inverter 22 is maintained at a low level by the function of the memory circuit 21, so unless the power supply to the control device is temporarily stopped and the memory in the memory circuit 21 is updated. Energization to both heaters is not resumed.

On the other hand, when there is a sufficient amount of cold water in the container 1, there is continuity between the container 1 and the pumping pipe 2 through the water, so a voltage drop occurs due to the resistance R ₁ , and the voltage between them is almost zero. Since the voltage becomes zero and the detection voltage detected by the voltage detection circuit 17 becomes a low level, the output level of the water level detection means 13 becomes a high level, and the output is inputted to the first power control means 14a and the timer 15. As a result, if the timer switch SW is not turned on, the output of the AND circuit 20 of the first power control means 14a becomes high level and the triax 12a is turned on, and the signal from the AND circuit 23 of the second power control means 14b is turned on. In response, the sub-heater 5b drive circuit 12b is also turned on, so power is supplied to the main heater 5a and the sub-heater 5b, and both heaters boil water.

When the water boils, a low level signal is input to the first power control means 14a in response to a signal from the boil detection means 35, turning off the triax 12a and completing the boiling of water. In addition, the second power control means 14b receives a low level signal from the heat retention temperature detection means 30 when the temperature T detected by the temperature sensor 4a becomes equal to or higher than the heat retention reference temperature _T1 , so that the second power control means 14b starts boiling the water before the water boiling is completed. Triack 12b
is turned off, and power supply to the sub-heater 5b is stopped. Note that the power supply to the sub-heater 5b may not be stopped until boiling is detected by the temperature sensor 4b.

During keeping warm, each time the temperature detected by the temperature sensor 4a drops to the preset keeping temperature _T1 ,
The output level of the heat retention temperature detection means 30 becomes high level, the second power control means 14b is activated, the sub-heater 5b is turned on, and the water temperature is maintained at a predetermined temperature.

In the above embodiment, an electric pot equipped with a control device consisting of a logic circuit has been described. The means 30 can also be configured using a microcomputer.

In this case, the control device mainly includes a central processing unit (CPU) 6, as shown in FIG.
The microcomputer 11 includes a read only memory (ROM) 7, a random access memory (RAM) 8, a clock pulse generator 9, and an input/output interface 10. In the diagram, 4
a and 4b are temperature sensors consisting of thermistors,
The temperature sensor 4a is placed at the bottom of the container 1, and the other temperature sensor 4b is placed in the steam exhaust passage provided at the top of the container 1 to detect boiling.

When this electric pot is used, the power supply to the heater 5 is controlled according to the program contents written in the memory (ROM), for example, according to the flowchart shown in FIG.

First, when the power is turned on, the temperature sensor 4a
A voltage corresponding to the temperature T detected by is input to the central processing unit (CPU) 6 via the interface 10, and the detected temperature T is
Dry firing prevention standard temperature T ₂ read from ROM7
It is determined whether there is an abnormality such as an empty state of the container 1. Detection temperature T is dry firing prevention temperature T ₂
If higher than
Warn the user using a display device, light emitting element, buzzer, etc.

In addition, before determining the dry firing state, the temperature detected by the temperature sensors 4a and 4b is checked in advance.
It compares the temperature with the reference temperature read from the ROM and determines whether there is an abnormality such as a disconnection in the temperature sensors 4a and 4b. If there is an abnormality, the system switches to abnormality notification mode and alerts the user using a display device, light emitting element, or buzzer. It may also be possible to issue a warning.

If it is determined in step 1 that there is no abnormality, the process proceeds to step 2, where it is determined whether or not the timer is set.If the timer is not set, the process proceeds to step 3, where it is determined whether or not there is a water shortage. In this embodiment as well, as in the _embodiment shown in FIG. In other words, if the detected voltage is high between the water level L in the container 1 and the pump pipe 2
If it is lower than the reference water level L ₀ set by
Determining that there is a water shortage, the system shifts to step 12, the water supply notification mode, and notifies the user with a water supply lamp, buzzer, etc., and maintains the heater drive circuit 12, which consists of triaxes, relays, etc., in an OFF state, and supplies water to the main heater 5a. The process returns to step 1 and repeats the above flow while prohibiting energization. Even in this case,
Even if the water level L temporarily becomes lower than the reference water level _L0 due to pouring, etc., by using the detection voltage in calculations only when the two detection voltages detected every 4 seconds are equal, It is desirable to prevent malfunctions.

If it is determined that the water level L is higher than the reference water level _L0 , the process moves to step 4, and if the timer switch _SW1 is not turned on, the process proceeds to step 5.
After step 6, move to step 8, boiling water mode.
Power to both heaters 5a and 5b is started to boil water.

When boiling water is started, the supply of electricity to the sub-heater 5b is stopped when the detected temperature T reaches the heat retention temperature _T1 , but the temperature T detected by the steam temperature sensor 4b disposed at the steam port of the container 1 The main heater 5a continues to be energized until the temperature reaches the preset boiling reference temperature _T3 , and the flow from step 1 to step 8 is repeated.

In the above flow, even if there is no water in the container 1 due to a failure of the water level detection electrode, etc., the process moves from step 1 to step 8, and both heaters 5
When power is applied to a and 5b, the temperature T detected by the temperature sensor 4a is constantly compared with the dry firing prevention reference temperature _T2 in step 1, so the temperature T of the container 1 will never reach it during normal operation. When the temperature reaches, for example, 105.degree. C., the system shifts to the abnormality notification mode of step 11 as described above, and the supply of electricity to both heaters 5a and 5b is stopped, and a warning is issued to the user.

Moreover, once the dry firing prevention reference temperature T ₂ is reached, even if the container temperature drops after the power supply to the heater is stopped, the current state is maintained, so the power is not re-energized. In addition, in order to restart the operation, it is necessary to erase the memory of RAM8 by unplugging the power outlet or by installing a power switch in the power supply circuit of the control device and turning off the operation of the control device itself. .

Furthermore, if it is determined in step 4 that the timer switch SW1 is pressed, the mode shifts to the timer mode in step 13, after which a preset time is set.
For example, step 1, 2, etc. until 6 hours have passed.
The judgments in steps 13, 14, and 15 are repeated, and if the timer switch SW ₁ is pressed during the process, the timer operation is canceled and the process moves to step 8 via steps 5 and 6 to boil water. Timer is running. The heater drive circuit 12 is maintained in an off state.

During boiling water, when the temperature T' detected by the temperature sensor 4b reaches the boiling reference temperature _T3 written in the ROM 7 or higher, it is determined in step 5 that the water boiling has been completed, and in response to this signal, the heater drive circuit 12, the power supply to the heater 5 is stopped, and the mode shifts from step 5 to the heat retention mode of step 9, and thereafter the flow from steps 1 to 7 to step 9 is repeated.

Temperature T detected by temperature sensor 4a during warming
is lower than the insulation temperature T ₁ , step 6
The process moves to step 8, where the heater drive circuit 12 supplies power to the sub-heater 5b, and the detected temperature T
When the temperature reaches T1 or _higher , the process goes through step 7 and shifts to the heat retention mode. In this case, unless the reboiling switch SW ₂ is pressed, the main heater 5a
No power is supplied to the terminal, so the determination at step 5 is not made.

Further, when the reboiling switch _SW2 is turned on during the heat retention, the mode shifts to the reboiling mode and the boiling operation from step 1 is repeated, and when the water boils, it stops.

FIG. 4 shows another embodiment of the electric pot according to the present invention, in which a plurality of short pipes 2a, 2 of the conductive water pump 2
Divided into b and 2c, mutually insulating tube 31
a, 31b, and 31c, and the lower end of the lowest short pipe 2a is aligned with the upper end of the band heater 5, while the lower end of the highest short pipe 2c is aligned with the full water level in the container. and each short pipe 2a,
A pulse voltage is applied to 2b and 2c from a pulse voltage generation circuit via resistors _R4 to _R6 , respectively, and the voltage between each short tube 2a, 2b, 2c and container 1 is detected and input to the control circuit. This is how it was done.

This embodiment operates in the same way as the embodiment shown in FIG. 2, and also prevents the main heater 5a from being energized even when the container 1 and the amount of water in the container are above the full water level. This prevents boiling water from scattering from the container, and also allows the water level in the container to be displayed in multiple stages by omitting a water level tube.

In the above-mentioned embodiment, the water level detection electrode is composed of the water pump and the container, but it may have the structure of a conventionally known water level detection electrode.

(Effects of the invention) As is clear from the above explanation, according to the invention, by detecting the water level, when the water level in the container is lower than the upper end of the band heater or at the full water level during use or during use, If the water level is higher than that, the main heater is prohibited from being energized, but even if the water level detection circuit does not operate and the water level becomes dry, the dry heating detection circuit will prevent the main heater and auxiliary heater from being energized. A double safety device is installed to prevent local or completely dry heating, which reduces the lifespan of the heater, discolors the container, or reduces corrosion resistance, and prevents overfilling with water. Excellent effects can be obtained, such as preventing boiling water from scattering.

In addition, if the present invention is applied to a boiling electric pot that has a temperature sensor installed at the steam outlet to detect boiling in the steam and stop power to the heater, even if you start boiling water with a small amount of water, Since electricity to the heater is prohibited, there is no problem with the conventional method where the water boils completely before the water temperature at the bottom reaches 100°C.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an electric pot according to the present invention, FIG. 2 is a block diagram of an electric pot showing another embodiment, FIG. 3 is a flowchart thereof, and FIG. 4 is a diagram showing the structure of the electric pot according to the present invention. 1 is a schematic diagram of an electric pot showing another embodiment of the invention. 1... Conductive container, 2... Conductive pumping pipe (reference water level setting electrode), 3... Insulating tube, 4, 4
a, 4b...Temperature sensor, 5...Band heater, 5a...Main heater, 5b...Sub-heater, 11
...Microcomputer, 12...Switching element, 13...Water level detection means, 14a...First
Power control means, 14b...Second power control means, 1
5...Timer, 24...Dry firing detection means, 25
...Dry firing prevention reference temperature setting means, 26...Comparator.

Claims (1)

[Claims for Utility Model Registration] 1. A temperature sensor that detects the temperature of the container, boiling detection means that detects boiling of water, and a first heater that turns off the main heater in response to a signal from the boiling detection means.
An electric kettle comprising a control device comprising a power control means and a second power control means for controlling the sub-heater on and off based on a signal from the temperature sensor, which contacts water in the container to permit a water boiling operation. A reference water level setting electrode for setting a reference water level is provided, and the control device detects the water level in the container based on a signal from the reference water level setting electrode, and when the detected water level is less than the reference water level, the main heater is Water level detection means outputs a signal to stop only energization; dry-heating prevention reference temperature setting means sets a dry-heating prevention reference temperature; and the detected temperature is determined by comparing the detected temperature of the temperature sensor with the dry-heating prevention reference temperature. dry heating prevention means for outputting a signal to the first and second power control means to stop energizing the main heater and the auxiliary heater and maintain them in the energized state when the temperature is equal to or higher than the dry heating prevention reference temperature. An electric pot characterized by the following: 2. A conductive water pumping pipe 2 in which the water level detection means 13 is electrically insulated from the container and whose lower end terminates at a position approximately equal to the upper end of the band heater.
, a pulse voltage generation circuit 16 that applies a voltage between the lifting pipe 2 and the container, and a voltage detection circuit 17 that detects the voltage between the container and the lifting pipe 2. The electric pot described in paragraph 1. 3. The electric pot according to claim 2, wherein the water level detecting means 13 is provided with a filter 18 that outputs an output only when two consecutive signals outputted intermittently from the voltage detection circuit 17 match. 4. The dry heating detection means 24 includes a temperature sensor 4a attached to the bottom of the container, and a dry heating prevention reference temperature setting means 25 for setting a dry heating prevention reference temperature.
The second power control means 14 compares the temperature detected by the temperature sensor with the dry-heating prevention reference temperature, and when the detected temperature reaches the dry-heating prevention reference temperature or higher.
An electric pot according to any one of claims 1 to 3 of the utility model registration claim, comprising a comparator 26 that outputs an output to