JP3227962B2 - Electric water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to controlling the temperature of an electric water heater for heating and maintaining the temperature of a liquid contained in a container.

[0002]

2. Description of the Related Art Heretofore, for setting a temperature for keeping an electric water heater warm, a temperature at which there is no fear of continuous boiling is set in advance, and the temperature is controlled so as to reach this set temperature. This is because it was difficult to determine a value lower by a certain temperature than the temperature at the time of boiling detection.

That is, the temperature of the liquid detected by the temperature detecting means indirectly detects the temperature of the liquid via the container, and the heating means is arranged so as to surround the temperature detecting means, and receives the heat of the heating means. This is because the difference between the actual liquid temperature and the actual liquid temperature occurs due to the easy configuration. FIG.
As shown in (a) and (b), when the amount of water is large and when the amount of water is small, a difference occurs in the follow-up of the temperature detecting means at the time of boiling detection.
In addition to this, there is a difference depending on the watt of the heating means and the room temperature. Therefore, the temperature detected by the temperature detecting means when the liquid boils contains a lot of variation.

[0004]

Therefore, in such a conventional configuration, it is difficult to determine the heat retaining temperature based on the temperature detected by the temperature detecting means at the time of boiling. For this reason, since the temperature is kept at a constant temperature regardless of the boiling temperature, it is necessary to reboil when hot water is required. In addition, it is desired to boil in as short a time as possible during re-boiling.

SUMMARY OF THE INVENTION It is a first object of the present invention to set the heat retention temperature higher than the conventional one and to a temperature that does not boil by bringing the temperature detected by the temperature detecting means closer to the boiling temperature in order to solve the above problem. .

A second object is to set a more stable temperature by setting a correction value based on the amount of water.

It is a third object of the present invention to increase the heat retention temperature to a predetermined high temperature that does not continuously boil when the set heat retention temperature becomes too low to keep the temperature.

A fourth object of the present invention is to lower the set temperature and keep the temperature at a high temperature that does not cause continuous boiling when the set temperature is too high and the boiling is continuous.

[0009]

In order to solve the above-mentioned first object, a first means of the present invention comprises a container for containing a liquid, a heating means for heating the liquid in the container, A heat retaining means for heating and retaining the liquid, an energizing means for controlling energization of the heating means and the heat retaining means, a temperature detecting means for detecting the temperature of the liquid in the container, and the heating means when power is turned on. A heating start unit to be driven; a boiling detection unit that stops the heating unit when a temperature rise gradient detected by the temperature detection unit becomes a predetermined value or less; and the heating unit stops according to a detection result of the boiling detection unit. Thereafter, the heat retaining means is driven until the second predetermined time has elapsed after the first predetermined time has elapsed, and a preset value is subtracted from the temperature detected by the temperature detecting means at the time when the second predetermined time has elapsed. Determine the heat retention temperature A temperature setting means for the output of said temperature detecting means from the retained temperature said set is that a comparator means for driving the lower between the heat insulating means.

In order to solve the second object, the second means of the present invention includes a water amount detecting means for detecting a liquid amount in the container and determining the set value according to the water amount. Things.

Further, in order to solve the third object, a third means of the present invention compares the heat retention temperature set by the temperature setting means with a predetermined temperature which is a high temperature which does not cause continuous boiling. A change means is provided for changing the predetermined temperature to the heat retaining temperature if the set heat retaining temperature is lower.

In order to solve the fourth object, a fourth means of the present invention comprises a time measuring means for measuring a time during which the comparing means continuously drives the heat retaining means, and a time measuring means for measuring the time. Continuous boiling when the time has passed the third predetermined time
It is provided with control means for changing a predetermined temperature, which is a high temperature not to be maintained, to a warming temperature.

[0013]

According to the present invention, when the temperature rise gradient disappears while the heating means is being driven, the heating means is deemed to be boiling, the heating means is stopped, and the heating means is waited for a first predetermined time. Since the influence of heat is eliminated, the output of the temperature detecting means can be gradually brought closer to the temperature of the container bottom. In addition, in order to obtain a temperature following the water temperature after a certain period of time from the detection of boiling, the power is supplied to the heat retaining means having less influence on the temperature detecting means than the heating means until the second predetermined time, so that the output of the temperature detecting means can be early. The temperature can be approximated to the water temperature, and the heat retention temperature can be obtained by subtracting a preset value in consideration of the temperature at which there is no risk of continuous boiling.

Further, the output of the temperature detecting means at the time when the second predetermined time has elapsed is corrected by the amount of water which is the largest cause of the variation in the detected temperature at the time of boiling detection, thereby shortening the second predetermined time. In addition, a stable high temperature keeping temperature can be set.

Further, when the temperature is not increased due to the addition of water during the heating and the temperature is set to a low temperature because the boiling is erroneously detected, the temperature may be maintained at a predetermined temperature at which there is no danger of continuous boiling. it can.

[0016] Then, the relationship between the temperature detecting means and the liquid following property changes due to factors such as the addition of water immediately before boiling, and the set heat retaining temperature becomes too high, so that the heat retaining means is continuously energized. Even if this occurs, the temperature can be maintained at a high temperature close to the boiling temperature by setting the set temperature to a predetermined temperature at which there is no danger of continuous boiling if it continues for a certain period of time.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an electric water heater according to an embodiment of the present invention, wherein 1 is a container for containing a liquid, 2 is a heating means for contacting the container and heating the liquid in the container, and 3 is a container for the liquid. , A temperature detecting means for heating and keeping the liquid in the container in contact with the container 4; a temperature detecting means 4 for contacting with the container 1 for detecting the temperature of the liquid in the container; and 5 for energizing the heating means 2 and the heat keeping means 3. It is an energizing means.

Reference numeral 10 denotes a water amount detecting means which connects the lower part and the upper part of the container 1 and is attached to a water level pipe through which the liquid in the container passes, and measures the amount of water in the container.

Reference numeral 6 denotes a heating start means for driving the heating means 2 by the energizing means 5 when the power is turned on, and 7 denotes a change in the temperature rise gradient by the output of the temperature detecting means 4 when the heating means 2 is driven. The boiling detecting means 8 which stops the heating means 2 when the amount is measured and considered as boiling, waits for a first predetermined time to elapse when the boiling detecting means 7 detects boiling, and then waits for a second predetermined time. Driving the heat retaining means 3,
The temperature detecting means 4 when the heat retaining means 3 is stopped
Temperature setting means for determining the heat retention temperature to a value obtained by subtracting a preset value from the value of the water amount detection means 10 from the value of the water amount detection means 10, 9 is a temperature determined by the temperature setting means 8 and 9 This is control means for controlling the heat retaining means 3 so as to reach a temperature determined by comparing the outputs.

Further, 11 is changing means for changing the value of the temperature setting means 8 to a predetermined temperature if the heat retention temperature set by the temperature setting means 8 is lower than a predetermined temperature. When the heat retaining means 3 is driven, the time is measured, and when it is stopped, the time keeping means keeps clearing the time. When the time keeping means measures a predetermined time, the set temperature at that time is a predetermined value. This is control means for changing the value to a value that has been lowered by just one.

FIG. 2 is a circuit diagram of an electric water heater showing one embodiment of the present invention. In the figure, reference numeral 14 denotes an AC power supply. The heating means 2 is constituted by a first heating element for heating the liquid in the container, and the heat retaining means 3 is constituted by a second heating element having a smaller heating power than the heating means 2 for heating and retaining the liquid in the container. You. The energizing means 5 has relay contacts 5a and 5b connected in series with the heating elements of the heating means 2 and the heat retaining means 3 and an AC power supply 10, and a relay for controlling the relay contacts 5a and 5b. It is composed of coils 5c and 5d, and a current flows through this relay coil to close the relay contact.

A temperature sensing element 4a for converting a temperature into a resistance value by the temperature detecting means 4, and an AD converter for forming a divided voltage value by the temperature sensing element 4a and the resistance 4b and converting the divided voltage value into a binary code. 4c and the comparator 4d. The output of the comparator 4d is configured so that the output of the temperature sensing element 4a is inverted at a predetermined temperature as a boundary. The AD converter 4c is configured to be able to detect a range of about 70 to 120 ° C. in steps of 0.5 ° C., thereby enabling detection of a temperature gradient or the like.
The second is set to a first predetermined value, and when the temperature rise gradient becomes smaller than this, it is determined that boiling has occurred.

The water amount detecting means 10 includes an electrode mounted at an equally divided position of a water level tube connecting the upper and lower parts of the container.
10a, 10b, and 10c (in this embodiment, three equal parts). When the electrode reaches the position of the electrode to which water is attached, the electrode is energized and outputs "H" to the temperature setting means 8. The temperature setting means 8 can detect the water level by determining which electrode has output the signal.

Reference numeral 15 denotes a microcomputer (hereinafter abbreviated as "microcomputer") that executes a program to execute the heating starting means 6, the boiling detecting means 7, the temperature setting means 8, the comparing means 9, the changing means 11, The control method of the timer 12 and the controller 13 is realized.

FIG. 3 is a flowchart of a program stored in the microcomputer 15 according to the first embodiment.
The operation will be described with reference to FIG.

In this embodiment, when the power is turned on, the heating means 2 is driven until boiling is detected with the above-mentioned temperature rise gradient (steps 21 and 22). When the boiling is detected, the heating means 2 is stopped, and a first predetermined time (5 minutes in this embodiment) elapses (steps 22, 23, 24). After the first predetermined time has elapsed, the heat retaining means 3 is driven for a second predetermined time (3 minutes in this embodiment) (steps 25 and 2).
6). Then, when the second predetermined time has elapsed, the value of the temperature detecting means 4 at that time is input, and a value obtained by subtracting a preset value from the value is set as the heat retention temperature (step 2).
7). After the temperature is set, if the value of the temperature detecting means 4 is higher than the set value, the temperature keeping means 3 is stopped, and if the value of the temperature detecting means 4 is low, the temperature keeping means 3 is set.
Is driven (steps 28-30).

As described above, the present invention can maintain a high heat retaining temperature with a simple structure. FIG. 4 shows a flowchart of a program stored in the microcomputer 15 according to the second invention, and the operation will be described with reference to FIG.

In this embodiment, when the power is turned on, the heating means 2 is driven until boiling is detected with the above-mentioned temperature rise gradient (steps 31 and 32). When the boiling is detected, the heating means 2 is stopped, the value of the water amount detecting means 10 is inputted, and the elapse of a first predetermined time (5 minutes in this embodiment) is waited (steps 33, 34, 35). After the first predetermined time has elapsed, the heat retaining means 3 is turned on for a second predetermined time (in this embodiment, 1 second).
Min) (step 37). Then, when the second predetermined time has elapsed, the value of the temperature detecting means 4 at that time is input, and a value obtained by subtracting a preset value according to the detected water amount is set as the heat retaining temperature (step 38). . After the temperature is set, if the value of the temperature detecting means 4 is higher than the set value, the temperature keeping means 3 is stopped, and if the value of the temperature detecting means 4 is low, the temperature keeping means 3 is driven (step 39-41).

As described above, according to the present invention, by further reducing the set value according to the amount of water, it is possible to maintain the heat retention temperature at a stable high temperature in a short time from the detection of boiling.

FIG. 5 is a flowchart of a program stored in the microcomputer 15 according to the third embodiment.
The operation will be described with reference to FIG.

In this embodiment, the configuration is the same as that of the first embodiment until the heat retention temperature is set based on the temperature and the amount of water after the second predetermined time, but when the heat retention temperature is set, the value becomes the predetermined value. When the temperature is set lower than the temperature (about 92 ° C. in this embodiment), the predetermined temperature is set as the heat retention temperature (steps 59 and 60). If the value of the temperature detecting means 4 is higher than the set value thereafter, the heat retaining means 3 is stopped, and if the value of the temperature detecting means 4 is low, the heat retaining means 3 is driven (steps 61-63).

As described above, according to the present invention, the heat retention temperature can be set to a higher temperature than the predetermined temperature with a simple configuration.

FIG. 6 is a flowchart of a program stored in the microcomputer 15 according to the fourth invention.
The operation will be described with reference to FIG.

In this embodiment, the structure is the same as that of the first and second embodiments until the heat retaining temperature is set and the heat retaining means 3 is turned on and off in order to maintain the temperature. 3 is driven, the timer 12 measures time (step 82), and while the heat retaining means 3 is stopped, the timer 12 is kept cleared (step 8).
3) After the third predetermined time (one hour in this embodiment) has elapsed, the timer 12 lowers the set value of the heat retention temperature to the predetermined temperature (step 84).

As described above, when the time measuring means 12 times the third predetermined time, the set temperature is lowered to maintain a high temperature at which continuous boiling does not occur.

[0037]

As is apparent from the above embodiment, according to the first aspect of the present invention, when the temperature detecting means approaches the water temperature and stabilizes after a certain period of time has passed while controlling the heat retaining means after the detection of boiling. Since the heat retention temperature is set by the value, the temperature can be kept at a temperature close to the boiling point where there is no danger of continuous boiling by a simple method, hot water can be used immediately, and an easy-to-use electric water heater can be provided. .

Further, according to the second aspect of the present invention, the second predetermined time during which the water temperature maintains the boiling point and the temperature detecting means approaches the water temperature can be shortened while controlling the heat retaining means. Intermittent time can be shortened, and a safer and more convenient one can be provided.

According to the third aspect of the present invention, even when the amount of water is changed during heating or the like, the characteristics of the temperature detecting means at the time of normal boiling detection cannot be obtained and the set heat retaining temperature becomes low. It is possible to prevent the temperature from lowering than the maintained temperature.

According to the fourth aspect, when the amount of water is changed during heating or the like, the characteristics of the temperature detecting means at the time of normal boiling detection cannot be obtained, and the set heat retention temperature becomes high, resulting in continuous boiling. In this case, the conventional temperature that does not continuously boil after a certain period of time is maintained, so that a more convenient product can be provided.

[Brief description of the drawings]

FIG. 1 is a specific block diagram of an electric water heater in one embodiment of the present invention.

FIG. 2 is a specific circuit diagram of the electric water heater.

FIG. 3 is a flowchart showing processing of the electric water heater in the first invention.

FIG. 4 is a flowchart showing the processing of the electric water heater in the second invention.

FIG. 5 is a flowchart showing processing of the electric water heater in the third invention.

FIG. 6 is a flowchart showing processing of the electric water heater in the fourth invention.

FIG. 7 shows a temperature characteristic during heating of the electric water heater.

[Explanation of symbols]

 2 heating means 3 warming means 4 temperature detecting means 5 energizing means 6 heating start means 7 boiling detecting means 8 temperature setting means 9 comparing means 10 water amount detecting means 11 changing means 12 timing means 13 control means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-17813 (JP, A) JP-A-64-68213 (JP, A) JP-A-4-17814 (JP, A) JP-A-4-17813 35621 (JP, A) JP-A-63-315009 (JP, A) JP-A-6-155408 (JP, A) JP-A-7-177970 (JP, A) JP-A-2-109527 (JP, U) Japanese Utility Model Showa 16-1624 (JP, U) Japanese Utility Model Showa 16-1625 (JP, U) Japanese Utility Model Hei 5-95424 (JP, U) Japanese Utility Model Utility Model 6-52725 (JP, U) (58) (Int.Cl. ⁷ , DB name) A47J 27/21

Claims (4)

(57) [Claims] 1. A container for accommodating a liquid, a heating unit for heating the liquid in the container, a heat retaining unit for heating and retaining the liquid in the container, and a power supply for controlling the energization of the heating unit and the heat retaining unit. Means, a temperature detecting means for detecting the temperature of the liquid in the container, a heating start means for driving the heating means when the power is turned on, and a temperature rising gradient detected by the temperature detecting means falling below a predetermined value. Boiling detection means for stopping the heating means, and the heat retention means until a second predetermined time elapses after a first predetermined time has elapsed since the heating means was stopped according to a detection result of the boiling detection means. A temperature setting means for determining a heat retention temperature by subtracting a preset set value from a temperature detected by the temperature detection means when the second predetermined time has elapsed, and an output of the temperature detection means from the set heat retention temperature. An electric kettle comprising comparison means for driving said heat retaining means while power is low. 2. The electric water heater according to claim 1, further comprising a water amount detecting means for detecting the amount of liquid in the container and determining the set value according to the amount of water. 3. A heat retaining temperature set by said temperature setting means.
3. The electric water heater according to claim 1, further comprising a change unit configured to compare a predetermined temperature which is a high temperature that does not continuously boil, and to change the predetermined temperature to the heat retention temperature if the set heat retention temperature is lower. 4. A timer means for counting the time during which the comparing means continuously drives the heat retaining means, and the boiling means does not continuously boil when a third predetermined time has elapsed.
The electric water heater according to any one of claims 1 to 3 , further comprising control means for changing a predetermined high temperature to a heat retaining temperature.