JP7747966B2 - water heater - Google Patents

Description

The present invention relates to a water heater.

In the past, a liquid heating container has been proposed that includes a container body, a spout, a heating means for heating the liquid in the container body, a lid attached to the top of the container body, and a handle attached to the opposite side of the spout, with a bimetal switch, equivalent to a boiling detection means that detects vapor generated from the liquid in the container body and turns off the power supply, attached to the interior space of the handle (see, for example, JP 2016-165494 A).

JP 2016-165494 A

In electric kettles like the one described above, when the liquid in the container body is heated and boils, the steam generated from the liquid reaches the bimetal switch and heats it. When the bimetal switch is heated to the set temperature and deforms, the heating means turns off. However, if less than the maximum amount of liquid is poured into the container body, the distance from the liquid surface to the bimetal switch becomes greater, and it takes time for the bimetal switch to heat up to the set temperature. As a result, the heating means may remain on even when the liquid is boiling, resulting in high power consumption.

The objective of the present invention is to provide a water heater that can reduce power consumption when a liquid volume less than the maximum liquid volume is placed in the liquid container.

The water heater according to the present invention comprises:
A liquid container;
a heating unit that heats the liquid stored inside the liquid container;
a vapor temperature measuring unit for measuring the temperature of vapor generated from the liquid;
a boiling determination unit that determines that the liquid has boiled when the temperature of the vapor reaches or exceeds a boiling determination temperature;
a liquid amount determination unit that determines the amount of the liquid,
The boiling determination unit changes the boiling determination temperature based on the amount of liquid determined by the liquid amount determination unit.

With the above configuration, the boiling threshold temperature can be lowered as the amount of liquid decreases. Therefore, with this water heater, power consumption can be reduced when less than the maximum amount of liquid is placed in the liquid container.

In the present invention,
a liquid temperature measuring unit for measuring the temperature of the liquid;
a time measurement unit that measures time,
It is preferable that the liquid amount determining unit determines the amount of the liquid based on a temperature gradient calculated from the temperature measured by the liquid temperature measuring unit and the time measured by the time measuring unit.

With the above configuration, the amount of liquid can be determined without using a liquid level sensor, which is relatively more expensive than liquid temperature measurement units such as thermocouples or thermistors. This allows for the manufacturing costs of this water heater to be kept as low as possible.

In the present invention,
the time measurement unit includes a first time measurement unit that measures a first time during which the liquid temperature measurement unit measures a first liquid temperature when the temperature of the liquid becomes equal to or higher than a first reference temperature, and a second time measurement unit that measures a second time during which the liquid temperature measurement unit measures a second liquid temperature when the temperature of the liquid becomes equal to or higher than a second reference temperature that is higher than the first reference temperature,
It is preferable that the liquid amount determination unit determines the amount of the liquid based on (the second liquid temperature - the first liquid temperature)/(the second time - the first time).

When the liquid in the liquid container is heated, convection begins to occur within the liquid container. As a result, in low-temperature regions where the liquid temperature is relatively low, the liquid temperature measured by the liquid temperature measurement unit may become unstable. With the above configuration, the first liquid temperature and second liquid temperature can be set taking into account the temperature region where the liquid temperature is stable. As a result, this water heater can determine the temperature gradient as accurately as possible.

1 is a perspective view of an electric kettle according to an embodiment of the present invention; 1 is a plan view of an electric kettle according to an embodiment of the present invention. 3 is a cross-sectional view taken along line AA in FIG. 2. This is a cross-sectional view taken along the line BB in Figure 2. Note that in this figure, the lid unit portion is shown enlarged. FIG. 4 is an enlarged view of the lid unit portion shown in FIG. 3 . 1 is a control block diagram of an electric kettle according to an embodiment of the present invention. FIG. 2 is a diagram showing a temperature gradient used to determine the amount of liquid in an electric kettle according to an embodiment of the present invention.

<Configuration of the electric kettle according to the embodiment of the present invention>
1 and 3, the electric kettle 100 according to the embodiment of the present invention is mainly composed of a kettle body 200 and a power base 600. Each of these components will be described in detail below.

1. Kettle Body The kettle body 200 is detachably mounted on the power supply base 600. A user of the electric kettle 100 places the kettle body 200 on the power supply base 600 when he or she wants to boil water, and can remove the kettle body 200 from the power supply base 600 to pour the hot water into a cup, teacup, or other container. As shown in Figures 1 to 3, the kettle body 200 is primarily composed of a main body unit 300, a handle unit 400, and a lid unit 500. Each of these components will be described in detail below. As shown in Figures 1 to 3, a spout (discharge port) 301 for hot water or other liquids is formed in the upper front portion of the kettle body 200.

1 to 3, main body unit 300 is mainly composed of sidewall member 310, liquid container 320, bottom member 330, heater unit 340, ejection port forming portion 350, bottom sensor BS, etc. Each of these components will be described in detail below.

(1-1) Sidewall Member The sidewall member 310 is a member formed of resin, metal such as stainless steel, or the like, and is generally cylindrical as shown in FIGS. 1 and 3. It forms the outer peripheral surface of the main body unit 300. As shown in FIG. 3, the sidewall member 310 houses the liquid container 320, the discharge port forming portion 350, and the like. Also as shown in FIG. 3, the sidewall member 310 houses the heater unit 340 together with the bottom member 330. The upper end of the sidewall member 310 supports the upper end of the discharge port forming portion 350 as shown in FIGS. 1, 3, and 4. A notch is formed in the upper end of the rear portion of the sidewall member 310, and as shown in FIG. 3, the main body connecting portion 402 of the handle unit 400 is fitted into this notch. A front protrusion 311 that slopes forward is formed at the top of the front portion of the sidewall member 310.

(1-2) Liquid Container The liquid container 320 is a member capable of storing liquid therein and is housed within the side wall member 310 as described above. As shown in FIG. 3 , the liquid container 320 is formed from an inner wall member 321 and a heater plate 322. The inner wall member 321 is a member formed from resin or a metal such as stainless steel, and is generally cylindrical. As shown in FIG. 3 , the inner wall member 321 forms the side wall of the liquid container 320. As shown in FIGS. 3 and 4 , the lower end of the discharge port forming portion 350 is attached to the upper end of the inner wall member 321. The inner circumferential surface of the inner wall member 321 may be coated with a corrosion-resistant resin (not shown) such as fluororesin. The heater plate 322 is a metal plate that covers the lower opening of the inner wall member 321 so as to close it, as shown in FIG. 3 . In other words, the heater plate 322 forms the bottom of the liquid container 320. As shown in FIG. 3, a print heater 341, which is one component of the heater unit 340, is disposed on the underside of the heater plate 322, and the detection portion of the bottom sensor BS protrudes from the rear of the heater plate 322 into the internal space of the liquid container 320.

1 and 3, bottom member 330 constitutes the bottom of main unit 300, is attached to the lower side of side wall member 310, and covers liquid container 320, heater unit 340, etc. from below. Bottom member 330 has an opening formed therein that exposes the lower end of power supply terminal 342.

(1-4) Heater Unit As shown in FIG. 3 , the heater unit 340 is attached to the heater plate 322 of the liquid container 320 and is primarily composed of a print heater 341 and a power supply terminal 342. The print heater 341 heats the heater plate 322 of the liquid container 320, thereby heating the liquid in the liquid container 320. When the electric kettle 100 is turned on with the kettle body 200 placed on the power supply base 600 and the power supply terminal 342 is electrically connected to the connection terminal 602 provided on the power supply base 600, power is supplied from the connection terminal 602 to the print heater 341. The output of the print heater 341 is then controlled by the control device CO (see FIG. 6 ), enabling it to heat the liquid in the liquid container 320. A heater unit from a conventionally known electric kettle can be used as the heater unit 340.

(1-5) Spout Forming Port The spout forming portion 350 is a generally cylindrical member and is attached to the main unit 300 as shown in FIGS. 1 to 3 . As described above, the upper end of the spout forming portion 350 is supported by the upper end of the sidewall member 310, and the lower end of the spout forming portion 350 is attached to the upper end of the inner wall member 321 of the liquid container 320. Also, as shown in FIGS. 1 to 3 , a front protrusion 351 that slopes upward toward the front is formed at the top of the front of the spout forming portion 350. As shown in FIGS. 1 and 3 , the front protrusion 351 is supported by the front protrusion 311 of the sidewall member 310. In this way, in the electric kettle 100 according to the embodiment of the present invention, the spout 301 is formed by a part of the spout forming portion 350 (i.e., the front protrusion 351). As shown in Fig. 4, an outwardly recessed claw receiving portion 352 is formed in the middle of the left and right portions of the discharge port forming portion 350. A locking lever RL of the locking mechanism LM of the lid unit 500 is locked onto this claw receiving portion 352 (see Fig. 4). As shown in Fig. 4, an outwardly sloping portion 353 is formed on the upper side of the claw receiving portion 352. The sloping portion 353 comes into contact with the locking lever RL of the locking mechanism LM of the lid unit 500 when the lid unit 500 is attached to or detached from the main unit 300.

(1-6) Bottom Sensor Bottom sensor BS is a general temperature sensor (e.g., a thermocouple or a thermistor) for measuring the temperature of the liquid in liquid container 320 of main unit 300. As described above, the detection portion of bottom sensor BS protrudes from the rear of heater plate 322 of liquid container 320 into the internal space of liquid container 320.

1 to 3, the handle unit 400 is mainly composed of a grip portion 401, a main body connection portion 402, a dial mechanism 403, a control device CO, and a steam sensor SS. Each of these components will be described in detail below.

(2-1) Grip Portion Grip portion 401 is a member formed of resin or the like, and serves as a handle when a user carries kettle body 200. As shown in Figures 1 to 3, grip portion 401 extends downward from the rear of main body connecting portion 402.

(2-2) Main Body Connection Portion The main body connection portion 402 is used to connect the handle unit 400 to the main body unit 300. As described above, the main body connection portion 402 is fitted into the notch at the upper end of the rear portion of the side wall member 310. As shown in FIG. 3, a sensor installation space 402a is formed in the front portion of the main body connection portion 402. As shown in FIG. 3, a steam sensor SS is installed in the sensor installation space 402a. Furthermore, as shown in FIG. 3, the sensor installation space 402a communicates with the steam circulation space SP1 (described below) via a steam guide hole OP in the side wall portion 521 of the bottom plate member 520 of the lid unit 500.

(2-3) Dial Mechanism Dial mechanism 403 is used to adjust the temperature of print heater 341 of heater unit 340 (i.e., the temperature of the liquid in liquid container 320). As shown in Figures 1 to 3, dial mechanism 403 is disposed at the rear of main body connection part 402. Note that dial mechanism 403 also functions as a switch for turning the power of electric kettle 100 on and off when kettle main body 200 is placed on power base 600.

(2-4) Control Device The control device CO has electronic components such as a microcomputer, and as shown in FIG. 6 , is connected to the bottom sensor BS of the main unit 300, the heater unit 340 of the main unit 300, the steam sensor SS, the dial mechanism 403, and the like. The microcomputer is equipped with memory in which various programs and data are stored. When the electric kettle 100 is turned on, the control device CO turns on the print heater 341 of the heater unit 340, measures time, calculates a temperature gradient based on the temperature of the liquid in the liquid container 320 measured by the bottom sensor BS of the main unit 300 and the time for which that temperature was measured, changes the boiling threshold temperature according to the calculated temperature gradient, and determines that the liquid in the liquid container 320 has boiled when the temperature of the steam measured by the steam sensor SS reaches or exceeds the boiling threshold temperature.

(2-5) Steam Sensor The steam sensor SS is a general temperature sensor (e.g., a thermocouple or a thermistor) for measuring the temperature of the steam generated from the liquid in the liquid container 320 of the main unit 300, and as described above, is arranged in the sensor arrangement space 402a of the main body connection part 402.

(3) Lid Unit As shown in FIGS. 1 to 4 , the lid unit 500 is a removable, generally cylindrical lid that covers the top of the main unit 300. The user can remove the lid unit 500 from the main unit 300 by operating a locking member 550 (described below) via an operating lever 560 provided on the lid unit 500. This allows the user to pour liquid into the liquid container 320 after removing the lid unit 500 from the main unit 300. When heating the liquid contained in the liquid container 320, the user attaches the lid unit 500 to the main unit 300 to create a closed space inside the liquid container 320. As shown in FIGS. 1 to 5 , the lid unit 500 is mainly composed of a top member 510, a bottom plate member 520, an opening/closing button 530, an opening/closing valve 540, a locking member 550, a locking mechanism LM, an operating lever 560, a sealing member 590, and a packing PK. Each of these components will be described in detail below.

(3-1) Top Surface Member As shown in FIGS. 1 to 5, the top surface member 510 is a substantially annular-shaped member and constitutes the top surface of the lid unit 500. That is, an opening is formed in the center of this top surface member 510. As shown in FIGS. 3 to 5, the open/close button 530, the cylindrical wall portion of the locking member 550, the base portion 561 of the operating lever 560, and the like are fitted into the opening of the top surface member 510. In addition, as shown in FIG. 4, spring mounting portions 512 are formed on the left and right ends of the bottom surface of the top surface member 510. As shown in FIG. 4, one end of a coil spring CS2 that biases the locking member 550 downward is fitted into the spring mounting portion 512.

(3-2) Bottom Plate Member As shown in FIGS. 3 to 5, the bottom plate member 520 primarily constitutes the lower portion of the lid unit 500 and is formed from a side wall portion 521 and a bottom wall portion 522. The side wall portion 521 has a generally cylindrical shape. As shown in FIGS. 3 to 5, a top surface member 510 (described below) is placed on the upper side of the side wall portion 521. This forms a steam flow space SP1 surrounded by the top surface member 510 and the bottom plate member 520 (see FIGS. 3 and 5). The steam flow space SP1 forms a flow path for steam generated in the liquid container 320 (see the bold arrow in FIG. 5). As shown in FIGS. 3 and 5, a flow path forming portion 523 is formed in the front portion of the side wall portion 521. The flow path forming portion 523 is a portion that forms a flow path extending toward the spout 301 of the kettle body 200, i.e., the discharge path DP. The flow path forming portion 523 guides the liquid in the liquid container 320 to the spout 301. Furthermore, as shown in FIG. 4, openings 521a are formed in the lower left and right portions of the side wall portion 521, allowing the tip of the locking mechanism LM to protrude through these openings 521a. Furthermore, as shown in FIGS. 3 and 5, a steam guide hole OP is formed in the rear portion of the side wall portion 521. As shown in FIG. 3, this steam guide hole OP connects the sensor placement space 402a of the main body connection portion 402 of the handle unit 400 to the steam flow space SP1 when the lid unit 500 is attached to the main body unit 300. The bottom wall portion 522 has a generally annular shape in plan view and, as shown in FIGS. 3 to 5, forms a stepped structure in vertical cross section. As shown in FIGS. 3 to 5, an on-off valve 540 is disposed below the bottom wall portion 522. As shown in FIGS. 3 to 5, bottom wall portion 522 abuts against packing 543 of on-off valve 540 when on-off valve 540 is closed. Bottom wall portion 522 does not abut against packing 543 of on-off valve 540 when on-off valve 540 is open. This allows liquid in liquid container 320 to be guided to discharge path DP when on-off valve 540 is open. Also, as shown in FIGS. 3 to 5, a central opening is formed in the center of bottom wall portion 522, and shaft portion 542 of on-off valve 540 is fitted into this central opening. Also, as shown in FIGS. 3 and 5, a rear communication hole 522a is formed in the rear of bottom wall portion 522 (i.e., slightly rearward of the central opening). The rear communication hole 522a is in a closed state by abutting against a packing 543 of the on-off valve 540 when the on-off valve 540 is closed, and is in an open state when the on-off valve 540 is open, thereby communicating the interior space of the liquid container 320 with the vapor flow space SP1. As shown in FIGS. 3 and 5 , a steam vent 522c is formed in the bottom wall 522 at a position rearward of the rear communication hole 522a. Unlike the rear communication hole 522a, the steam vent 522c is always open, thereby communicating the interior space of the liquid container 320 with the vapor flow space SP1. As shown in FIGS. 3 and 5 , a front communication hole 522b is formed in the bottom wall 522 at a position forward of the central opening and rearward of the flow path forming portion 523. As shown in FIGS. 3 and 5 , the front communication hole 522b communicates the vapor flow space SP1 with the discharge path DP.

(3-3) Open/Close Button As shown in FIGS. 3 to 5, the open/close button 530 is fitted into the opening of the top member 510 and is connected to the tip of the shaft 542 of the open/close valve 540. As shown in FIGS. 2 to 5, a cylindrical wall portion of a locking member 550 is disposed around the side wall portion of the open/close button 530. The open/close button 530 is also biased upward by a coil spring CS1 (see FIGS. 3 to 5) disposed so as to surround the shaft 542 of the open/close valve 540. When the user presses the open/close button 530 downward against the biasing force of the coil spring CS1, the open/close valve 540 moves downward in conjunction with the pressing action. This causes the open/close valve 540 to enter an open state.

(3-4) On-Off Valve As shown in FIGS. 3 to 5, the on-off valve 540 is composed of a valve main body 541, a shaft 542, and a packing 543. The valve main body 541 has a generally disk shape and is disposed below the bottom plate member 520 of the lid unit 500 as shown in FIGS. 3 to 5. The shaft 542 is a rod-shaped member extending upward from the rear of the upper surface of the valve main body 541 as shown in FIGS. 3 to 5. As described above, the shaft 542 is fitted into the central opening of the bottom wall portion 522 of the bottom plate member 520, and the tip of the shaft 542 is connected to the on-off button 530. The packing 543 has a generally annular shape and is attached to the outer edge of the valve main body 541 as shown in FIGS. 3 to 5.

(3-5) Locking Member The locking member 550 is used to lock the lid unit 500 to the main unit 300 (see FIG. 4) when the lid unit 500 is attached to the main unit 300. When the lid unit 500 is locked to the main unit 300 (hereinafter referred to as the "locked state"), the locking member 550 is biased downward by the coil spring CS2 and engages with the locking lever RL of the locking mechanism LM. Furthermore, as shown in FIGS. 3 to 5, the cylindrical wall portion extending upward from the center of the locking member 550 is sandwiched between the open/close button 530 and the operating lever 560, and is connected only to the operating lever 560. Therefore, the operating lever 560 and the locking member 550 move in conjunction with each other, but the open/close button 530 and the locking member 550 do not move in conjunction with each other.

(3-6) Locking Mechanism The locking mechanism LM is mainly composed of a locking lever RL (see FIG. 4) and a torsion spring (not shown). The locking lever RL is rotatable around an axis AX (see FIG. 4) fixed within the lid unit 500, and can be locked to the claw receiving portion 352 of the outlet forming portion 350 of the main unit 300 (see FIG. 4). In the locked state, the locking lever RL is engaged with a locking member 550 and cannot be rotated from the state where it is locked to the claw receiving portion 352 of the outlet forming portion 350 of the main unit 300. The torsion spring biases the locking lever RL in the direction of locking it to the claw receiving portion 352 of the outlet forming portion 350 of the main unit 300, and is disposed on the outer periphery of the axis AX.

Here, we will explain how to unlock the electric kettle 100 according to an embodiment of the present invention. First, the user hooks the fingers of one hand around the flange 562 of the operating lever 560 and, while holding down the main unit 300 with the other hand, lifts the operating lever 560 upward. At this time, in conjunction with the movement of the operating lever 560, the locking member 550 is also lifted upward against the biasing force of the coil spring CS2. This releases the engagement between the locking member 550 and the locking lever RL of the locking mechanism LM, allowing the locking lever RL of the locking mechanism LM to rotate about the axis AX, thereby releasing the locked state. Then, while keeping the fingers hooked on the flange 562 of the operating lever 560, the user further lifts the operating lever 560 upward, thereby lifting the entire lid unit 500 upward, and can remove the lid unit 500 from the main unit 300.

(3-7) Operation Lever The operation lever 560 is operated by the user to release the locked state, and as described above, is connected to the locking member 550. As shown in FIGS. 3 to 5, the operation lever 560 is formed from a base portion 561 and a flange portion 562. The base portion 561 is generally cylindrical and, as shown in FIGS. 3 to 5, is fitted into the opening in the upper surface member 510. The flange portion 562 is a generally disk-shaped portion that allows the user to support the operation lever 560 with their fingers, and as shown in FIGS. 3 to 5, extends outward from the upper end of the base portion 561. As shown in FIGS. 3 to 5, an opening is formed in the center of the flange portion 562, and the open/close button 530 is exposed through this opening. In addition, a groove is formed on the underside of the flange portion 562. This groove functions as a non-slip surface for the user's fingers.

(3-8) Sealing Member Sealing member 590 is an annular member made of an elastic material such as rubber or elastomer, and as shown in Figures 3 to 5, is attached to the outer periphery of the lower surface of bottom wall portion 522 of bottom plate member 520. As shown in Figures 3 and 4, sealing member 590 serves to close the gap between liquid container 320 and bottom plate member 520 (in other words, to keep liquid container 320 and bottom plate member 520 tightly sealed) when lid unit 500 is attached to main body unit 300.

(3-9) Packing The packing PK is a member made of a flexible material and serves as a check valve that blocks the front communication hole 522b of the bottom plate member 520 from below (see FIGS. 3 and 5). When steam generated in the liquid container 320 flows into the steam flow space SP1 through the steam port 522c of the bottom plate member 520 and flows to the front side of the steam flow space SP1 (see the thick arrow in FIG. 5), the packing PK is pushed by the steam and bends downward, opening the front communication hole 522b of the bottom plate member 520.

2. Power Supply Base The power supply base 600 serves as a power supply unit that supplies electricity to the kettle body 200 and also serves as a base for the kettle body 200. As shown in FIGS. 1 and 3 , the power supply base 600 is mainly composed of a power cord 601, a power plug (not shown), and a connection terminal 602. When the kettle body 200 is placed on the power supply base 600 and the power supply terminal 342 of the heater unit 340 is connected to the connection terminal 602, a power supply circuit is formed. When the electric kettle 100 is turned on, electricity can be applied to the heater unit 340 and the control device CO. Note that the power supply base 600 can have a configuration similar to that of power supply bases for conventionally known electric kettles.

<Processing of the control device in the electric kettle according to the embodiment of the present invention>
Here, we will explain the process of calculating a temperature gradient based on the temperature of the liquid in the liquid container 320 measured by the bottom sensor BS of the main unit 300 and the time the temperature was measured, and the process of changing the boiling threshold temperature based on the calculated temperature gradient, performed by the control device CO of the electric kettle 100 according to an embodiment of the present invention. Because the temperature gradient changes depending on the amount of liquid contained in the liquid container 320, calculating the temperature gradient is equivalent to determining the amount of liquid contained in the liquid container 320. First, the user removes the lid unit 500 from the main unit 300 and fills the liquid container 320 with liquid up to the maximum amount. Then, the user attaches the lid unit 500 to the main unit 300 and locks it, places the kettle body 200 on the power supply base 600, and turns on the dial mechanism 403 to power on the electric kettle 100. This connects the heater unit 340 and the control device CO to the power supply base 600, and the print heater 341 of the heater unit 340 is turned on by the control device CO, starting to heat the liquid in the liquid container 320. The liquid temperature is measured by the bottom sensor BS. The control device CO receives the liquid temperature information and measures the time at which the bottom sensor BS measured the liquid temperature (see FIG. 7). The control device CO then measures the first time at which the bottom sensor BS measured the first liquid temperature when the liquid temperature reached 60°C or higher, and the second time at which the bottom sensor BS measured the second liquid temperature when the liquid temperature reached 80°C or higher (see FIG. 7). The control device CO then calculates the temperature gradient (rate of temperature rise) by calculating (second liquid temperature - first liquid temperature) / (second time - first time). The reference temperature gradient is calculated by calculating (second liquid temperature - first liquid temperature) / (second time - first time) when the maximum amount of liquid is poured into the liquid container 320, and is pre-stored in the memory of the control device CO. The control device CO then changes the boiling threshold temperature depending on the magnitude of the calculated temperature gradient relative to the reference temperature gradient. More specifically, the control device CO changes the boiling threshold temperature so that the larger the calculated temperature gradient becomes compared to the reference temperature gradient (i.e., the smaller the amount of liquid), the lower the boiling threshold temperature becomes compared to the reference boiling threshold temperature. The reference boiling threshold temperature is the temperature of the vapor measured by the vapor sensor SS when the maximum amount of liquid in the liquid container 320 is heated by the print heater 341 of the heater unit 340 to generate vapor, and is pre-stored in the memory of the control device CO. When the liquid in the liquid container 320 continues to be heated by the print heater 341 of the heater unit 340 and vapor is generated from the liquid, this vapor flows into the vapor flow space SP1 through the vapor port 522c of the bottom plate member 520 of the lid unit 500 and further flows into the sensor placement space 402a through the vapor guide hole OP of the bottom plate member 520 of the lid unit 500. The temperature of the vapor is then measured by the vapor sensor SS. The control device CO receives the vapor temperature information and determines that the liquid has boiled when the vapor temperature reaches or exceeds the boiling threshold temperature. After determining that the liquid has boiled, the control device CO controls the print heater 341 of the heater unit 340 to be in an OFF state.

<Method for confirming that the process for changing the boiling threshold temperature is functioning in the electric kettle according to the embodiment of the present invention>
Here, a method for verifying that the boiling threshold temperature has been changed in response to the amount of liquid contained in the liquid container 320 in the electric kettle 100 according to an embodiment of the present invention will be described. First, when the control unit CO determines that the maximum amount of liquid contained in the liquid container 320 has boiled, the resistance value of the steam sensor SS measured by the resistance meter is set as the reference resistance value. Then, when a quantity of liquid less than the maximum amount is placed in the liquid container 320 and the control unit CO determines that the liquid has boiled, the resistance value of the steam sensor SS is measured by the resistance meter. If the measurement results in a change in the resistance value of the steam sensor SS from the reference resistance value (more specifically, if the resistance value of the steam sensor SS changes significantly as the amount of liquid decreases below the maximum amount), this indicates that the control unit CO has changed the boiling threshold temperature. In this way, by measuring the resistance value of the steam sensor SS, which changes in response to the amount of liquid when the control unit CO detects that the liquid in the liquid container 320 has boiled, it is possible to verify that the control unit CO has changed the boiling threshold temperature.

<Features of the electric kettle according to the embodiment of the present invention>
(1)
In the electric kettle 100 according to the embodiment of the present invention, the control device CO changes the boiling threshold temperature so that the boiling threshold temperature becomes lower relative to the reference boiling threshold temperature as the calculated temperature gradient increases. Therefore, in this electric kettle 100, when the amount of liquid contained in the liquid container 320 is less than the maximum liquid amount, the print heater 341 is prevented from remaining on because the vapor generated from the liquid has not reached the reference boiling temperature, even though the liquid is actually boiling. Therefore, in this electric kettle 100, power consumption can be reduced compared to conventional electric kettles when boiling an amount of liquid contained in the liquid container 320 that is less than the maximum liquid amount.

(2)
In the electric kettle 100 according to this embodiment of the present invention, the control device CO measures the first time when the first liquid temperature is measured when the liquid temperature reaches 60°C or higher, and the second time when the second liquid temperature is measured when the liquid temperature reaches 80°C or higher. The control device CO then calculates the temperature gradient using (second liquid temperature - first liquid temperature) / (second time - first time). This allows the electric kettle 100 to calculate the temperature gradient as accurately as possible. Furthermore, in this electric kettle 100, the first and second liquid temperatures are measured using a bottom sensor BS, which is a common temperature sensor such as a thermocouple or thermistor. This allows the electric kettle 100 to minimize manufacturing costs by avoiding the use of a liquid level sensor, which is relatively more expensive than the bottom sensor BS.

<Modification>
(A)
In the electric kettle 100 according to the previous embodiment, the control device CO measures the first time when the bottom sensor BS measures the first liquid temperature when the liquid temperature reaches 60°C or higher, and the second time when the bottom sensor BS measures the second liquid temperature when the liquid temperature reaches 80°C or higher. The control device CO then calculates the temperature gradient using the formula (second liquid temperature - first liquid temperature) / (second time - first time) and changes the boiling threshold temperature based on the magnitude of the calculated temperature gradient relative to the reference temperature gradient. However, the control device CO may change the boiling threshold temperature in other ways. For example, the electric kettle 100 may be equipped with a liquid level sensor that measures the amount of liquid contained in the liquid container 320. The control device CO may then change the boiling threshold temperature based on the amount of liquid in the liquid container 320 measured by the liquid level sensor.

Furthermore, for example, the control device CO may calculate the gradient as (second time - first time) / (second liquid temperature - first liquid temperature). In such a case, the control device CO may set the boiling judgment temperature lower than the reference boiling judgment temperature as the calculated gradient becomes smaller compared to the reference gradient (the gradient calculated using this formula when the maximum amount of liquid is placed in the liquid container 320).

Furthermore, for example, the control device CO may measure time A when a first reference time or more has passed since the electric kettle 100 was turned on, and time B when a second reference time or more has passed.The control device CO may then calculate the gradient based on the liquid temperature A measured by the bottom sensor BS at time A and the liquid temperature B measured by the bottom sensor BS at time B.

Furthermore, the first liquid temperature is not limited to the temperature when the liquid temperature reaches 60°C or higher, and the second liquid temperature is not limited to the temperature when the liquid temperature reaches 80°C or higher. For example, the first liquid temperature may be the temperature when the liquid temperature reaches 50°C or higher, and the second liquid temperature may be the temperature when the liquid temperature reaches 60°C or higher.

(B)
In the electric kettle 100 according to the previous embodiment, the detection portion of the bottom sensor BS protrudes from the heater plate 322 of the liquid container 320 into the interior space of the liquid container 320. However, the detection portion of the bottom sensor BS may protrude from the inner wall member 321 of the liquid container 320 into the interior space of the liquid container 320, as long as it is positioned below the liquid level of the liquid contained in the liquid container 320.

(C)
In the electric kettle 100 according to the previous embodiment, the bottom sensor BS measures the temperature of the liquid in the liquid container 320. However, the bottom sensor BS may be disposed below the heater plate 322 of the liquid container 320 so as to be in contact with the heater plate 322 of the liquid container 320, and measure the temperature of the heater plate 322 of the liquid container 320. The temperature gradient may then be calculated using the temperature of the heater plate 322 of the liquid container 320 instead of the temperature of the liquid in the liquid container 320.

(D)
In the electric kettle 100 according to the previous embodiment, the dial mechanism 403 functions as a switch for turning on/off the power of the electric kettle 100. However, the switch for turning on/off the power of the electric kettle 100 may be disposed on the power base 600.

(E)
In the electric kettle 100 according to the previous embodiment, the control device CO adjusted the boiling threshold temperature so that the boiling threshold temperature was lower than the reference boiling threshold temperature as the calculated temperature gradient increased relative to the reference temperature gradient. The reference temperature gradient was the temperature gradient when the maximum amount of liquid was placed in the liquid container 320, and the reference boiling threshold temperature was the temperature of the vapor measured by the vapor sensor SS when the maximum amount of liquid was heated to generate steam. However, the control device CO may also use the temperature gradient when an amount of liquid other than the maximum amount was placed in the liquid container 320 as the reference temperature gradient, and use the temperature of the vapor measured by the vapor sensor SS when that amount of liquid was heated to generate steam as the reference boiling threshold temperature. The boiling threshold temperature may then be adjusted depending on the magnitude of the calculated temperature gradient relative to the reference temperature gradient. For example, when the control device CO sets the reference temperature gradient and the reference boiling judgment temperature based on an amount of liquid that is somewhat smaller than the maximum liquid amount, the control device CO may make the boiling judgment temperature lower than the reference boiling judgment temperature as the calculated temperature gradient becomes larger compared to the reference temperature gradient, and may make the boiling judgment temperature higher than the boiling judgment temperature as the calculated temperature gradient becomes smaller compared to the reference temperature gradient.

Also, a table relating the temperature gradient numerical range to the boiling judgment temperature may be stored in advance in the memory of the control device CO, and the control device CO may change the boiling judgment temperature based on this table after calculating the temperature gradient. For example, if the table indicates that "temperature gradient numerical range: x or more and less than 2x → boiling judgment temperature: S°C, temperature gradient numerical range: 2x or more and less than 3x → boiling judgment temperature: T°C, ...", the control device CO will change the boiling judgment temperature to S°C if the calculated temperature gradient is 1.5x.

The above modifications may be applied alone or in combination.

100 Electric kettle (water heater)
320 Liquid container 341 Print heater (heating unit)
BS Bottom sensor (liquid temperature measurement part)
CO control device (boiling determination unit, liquid volume determination unit, time measurement unit)
SS Steam sensor (steam temperature measurement part)

Claims (3)

A liquid container;
a heating unit that heats the liquid stored inside the liquid container;
a vapor flow passage for passing vapor generated from the liquid;
a steam temperature measuring unit that is provided in a space communicating with the steam flow passage and that comes into contact with the steam to measure the temperature of the steam ;
a boiling determination unit that determines that the liquid has boiled when the temperature of the vapor reaches or exceeds a boiling determination temperature;
a liquid amount determination unit that determines the amount of the liquid,
The boiling determination unit changes the boiling determination temperature based on the amount of liquid determined by the liquid amount determination unit. a liquid temperature measuring unit for measuring the temperature of the liquid;
a time measurement unit that measures time,
The water heater according to claim 1 , wherein the liquid amount determining unit determines the amount of the liquid based on a temperature gradient calculated from the temperature measured by the liquid temperature measuring unit and the time measured by the time measuring unit. the time measurement unit includes a first time measurement unit that measures a first time during which the liquid temperature measurement unit measures a first liquid temperature when the temperature of the liquid becomes equal to or higher than a first reference temperature, and a second time measurement unit that measures a second time during which the liquid temperature measurement unit measures a second liquid temperature when the temperature of the liquid becomes equal to or higher than a second reference temperature that is higher than the first reference temperature,
The water heater according to claim 2, wherein the liquid amount determination unit determines the amount of the liquid based on (the second liquid temperature - the first liquid temperature)/(the second time - the first time).