Control method of liquid heater

Abstract

The invention provides a control method of a liquid heater, which relates to the liquid heater and comprises the following steps of: 1, heating a beverage by adopting first power until an overflow signal is detected, switching to a second step, 2, heating the beverage by adopting second power smaller than the first power until the overflow signal is not detected to meet a first time length, and switching to the first step, the first step and the second step are mutually switched for multiple times, and the positive difference value of the first power and the second power after the first step and the second step are mutually switched each time is smaller than the positive difference value of the first power and the second power before the first step and the second step are switched. The control method of the liquid heater is used for solving the technical problem in the prior art that in order to accurately measure the time required by power adjustment, the liquid heater frequently stops heating or uses single small power to heat the beverage for a long time, but the beverage cannot stably turn over for a long time before the power is adjusted to the target power.

Description

Technical Field

[0001] This invention relates to the technical field of liquid heaters, and more specifically, to a control method for a liquid heater. Background Technology

[0002] In daily life, more and more people are choosing to brew beverages using appliances such as health pots and blenders. To make an ideal beverage using a liquid heater, the heater needs to maintain the appropriate brewing time and temperature to fully dissolve the aromatic and nutrient components of the ingredients into the liquid, resulting in a richer and more flavorful drink. Therefore, during brewing, the liquid heater needs to maintain a high heating power to enhance the bubbling effect and duration of the beverage, thereby maximizing the release of the ingredients' components.

[0003] However, during the process of heating liquids in these devices, the high heating power will accelerate the rate of bubble formation. As the ingredients are released, the beverage becomes viscous, making it difficult for the bubbles to break and form foam. The accumulation of foam may lead to overflow, posing a safety hazard.

[0004] To address the issue of foam overflow, existing technology CN98105278.9 proposes using a rice soup detection device (float structure or optical sensor structure) to detect whether the beverage or foam is overflowing, and then controlling the heating device to turn on or off based on whether it is overflowing, so as to ensure that the rice soup does not overflow.

[0005] Specifically, once the device detects rising foam (referred to as rice porridge in the text) (i.e., an overflow signal is detected), it immediately stops heating; and when the foam is detected to be falling, the device restarts. However, this device cannot automatically adjust its heating power, so the foam may continue to rise after the heating restarts, making the device essentially intermittently heat the rice porridge, thus affecting the proper heating and taste of the food.

[0006] To address the technical problem of beverage surface or foam rising frequently and rapidly, causing liquid heaters to only heat the beverage intermittently and thus affecting the brewing effect, three main solutions are currently adopted:

[0007] The first method is time-controlled adjustment:

[0008] By recording the duration of the overflow signal and the interval between two signals, the heating power required to restore heating is calculated. The adjusted heating power is then used to reduce the frequency and number of overflow signals detected, thereby improving the heating effect.

[0009] For example, the existing technology CN200910016091.7 proposes a method for boiling soy milk and a soy milk maker. This solution dynamically adjusts the heating power by judging the duration after the anti-overflow electrode is touched, so that the beverage is kept in a heated state throughout the entire boiling process (the boiling stage is after the beverage boils or reaches 85℃ to 90℃ or above), avoiding the problem of insufficient boiling of beverage caused by intermittent heating.

[0010] For example, existing technologies CN201710034748.7 and CN201710035787.9 calculate the restored heating power based on the continuous detection time of foam. If the detection time is shorter than the preset time, the restored heating power is the power before stopping; if the detection time is longer than the preset time, the restored heating power is greater than the power before stopping. This effectively prevents overflow while ensuring that the food boils thoroughly, thereby improving the cooking effect.

[0011] The second method is the power increment method:

[0012] By gradually increasing the heating power, a power value that allows the beverage to swirl fully without causing it to overflow (hereinafter referred to as the target power) is found.

[0013] For example, according to existing technology CN201710035888.6, starting from the minimum power, the heating power of the electric cooker is gradually increased at preset time intervals until the foam detection device detects steam foam again, at which point heating stops. If the time for which steam foam is continuously detected exceeds the preset duration, the heating power is reduced from the previous power level.

[0014] The third method is the alternating heating method:

[0015] For example, in the prior art CN201710035297.9, when steam foam is detected, at least two different power ratios are obtained, and the electric cooker is controlled to heat alternately according to these two power ratios. The frequency of alternating heating is controlled according to the calculated time. This avoids overflow and ensures that the food boils fully.

[0016] In summary:

[0017] In summary, while time-based control and power adjustment methods can address the issue of foam overflow to some extent, in practical use, before adjusting to a cooking power that prevents overflow signals from being detected during prolonged heating, the liquid heater needs the foam to completely subside to ensure accurate power adjustment. This often results in the beverage being either stopped or heated at low power, preventing the beverage from achieving a stable, sustained boil. The ideal solution would be to maximize the cooking time of the beverage during power adjustment while preventing foam overflow. Summary of the Invention

[0018] The purpose of this invention is to provide a control method for a liquid heater. In order to accurately measure the time required for power adjustment, the existing technology involves the liquid heater frequently stopping heating or using a single low power to heat beverages for a long time. However, this leads to the technical problem that the beverage cannot achieve a stable bubbling effect for a long time before the target power is adjusted.

[0019] This application provides a control method for a liquid heater, wherein the liquid heater detects an overflow signal via a foam detection device, including:

[0020] The first step involves heating the beverage at the highest power until an overflow signal is detected, then switching to the second step.

[0021] The second step involves heating the beverage with a second power lower than the first power until no overflow signal is detected and the first time period is met, then switching back to the first step.

[0022] The first step and the second step are switched to each other multiple times. Each time the first step is switched to, the first power is reduced and the second power is switched to the second step. The positive difference between the first power and the second power after each switch between the first step and the second step is less than the positive difference between the first power and the second power before the switch.

[0023] Furthermore, in the third step, after the second step is applied for the last time, the process switches to the third step, where the beverage is heated with a third power and no overflow signal is detected continuously. The third power is less than the first power applied for the last time and greater than the second power applied for the last time. The control method terminates with the third step.

[0024] Furthermore, in the third step, after the second step is applied for the last time, the third step is switched to, and the beverage is heated with a third power while satisfying the condition that no overflow signal is continuously detected. The third power is less than the first power applied for the last time and greater than the second power applied for the last time. The third step does not detect an overflow signal and satisfies the second duration. The third power is then increased to heat the beverage.

[0025] Furthermore, in the fourth step, after the first step is applied for the last time, the process switches to the fourth step, where the beverage is heated with a fourth power and an overflow signal is continuously detected within a third time period. The fourth power is greater than the second power applied for the last time and less than the first power applied for the last time. The fourth power is then reduced until no overflow signal is detected.

[0026] Furthermore, the above control method terminates when the positive difference between the first power and the second power meets a preset condition, the first step and the second step are switched and applied alternately, and the first power and the second power are no longer adjusted.

[0027] Furthermore, the above control method terminates when the number of switching steps between the first step and the second step meets a preset condition, the first step and the second step are switched and applied alternately, and the first power and the second power are no longer adjusted.

[0028] Furthermore, the second step described above is applied by repeatedly increasing the second heating power.

[0029] Furthermore, during the switching process between the first and second steps, the change in the positive difference between the first power and the second power is set to a decreasing trend.

[0030] Furthermore, the power value of the first power is reduced each time the switch is made to the first step, and the power value of the second power is increased each time the switch is made to the second step.

[0031] Furthermore, the liquid heater is also equipped with a stirrer, which is used to switch to the third step after the first step is applied for the last time, and the stirrer rotates.

[0032] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0033] Alternating between a higher first power and a lower second power for swirling and heating the beverage achieves a balance between bubbling and preventing overflow. During the swirling process, the first power is reduced each time the process switches to the first step, extending the time before the liquid heater detects an overflow signal again. Conversely, the second power is increased each time the process switches to the second step. This second power is closer to the operating power for swirling without overflowing, preventing further foaming and helping to maintain the beverage's temperature and bubbling state. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of power changes during the power regulation process in existing technologies.

[0035] Figure 2 This is a schematic diagram of power changes during the power regulation process in an embodiment of this application.

[0036] Figure 3 This is a schematic diagram of the switching process between the first and second steps in an embodiment of this application.

[0037] Figure 4 This is a flowchart illustrating the transition from the second step to the third step in an embodiment of this application.

[0038] Figure 5 This is a schematic diagram of the adjustment process when the target power is higher than the third power in an embodiment of this application.

[0039] Figure 6 This is a flowchart illustrating the transition from the first step to the fourth step in an embodiment of this application.

[0040] Figure 7 This is a flowchart illustrating the process of switching between the first and second steps multiple times without adjusting the power when the target power is within a power range, according to an embodiment of this application.

[0041] Figure 8 This is a schematic diagram illustrating the application timing of repeatedly increasing the second power in an embodiment of this application.

[0042] Figure 9 This is a schematic diagram of the power change applied by repeatedly increasing the second power in the embodiments of this application. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] When a liquid heater is used to boil beverages, the process generally includes a pre-boiling stage and a post-boiling stage. In the pre-boiling stage, the beverage gradually reaches its boiling point; during the boiling stage, the nutrients in the ingredients are gradually released. The longer the beverage simmers during the boiling stage, the better the nutrient release and the better the boiling effect. Boiling can be at or near 100°C.

[0045] Therefore, existing technologies adjust the heating power in various ways to maximize the boiling time of beverages.

[0046] The first method is time-controlled adjustment. Existing technology adjusts the cooking power by measuring time values ​​and detecting overflow signals, thus avoiding the liquid heater stopping or intermittent heating. To ensure accurate power adjustment, existing technology adjusts power based on time values, requiring waiting for the foam or liquid level to completely drop before heating begins, thereby reducing errors in the duration and trigger interval of the overflow signal.

[0047] However, in actual use, adjusting the cooking power after detecting an overflow signal requires multiple adjustments to reach a power level where no overflow signal is detected. This means that existing technology still results in several periods where the beverage cannot fully boil. To reduce errors, existing technology uses extremely low heating power (often no more than 50W) after detecting an overflow signal to wait for the foam or liquid level to completely subside, further increasing the time the beverage cannot fully boil. Therefore, even when the cooking power is adjusted to a level where no overflow signal is detected during prolonged heating, the liquid heater still intermittently heats the beverage. The liquid heater spends much of the time either not heating the beverage or heating it at low power. The beverage does not receive sufficient heating power and adequate bubbling during the cooking process (especially in certain areas), resulting in an unsatisfactory cooking effect.

[0048] The second method, the incremental power method, requires gradually increasing the power from the minimum to a level sufficient to bring the food to a full boil without overflowing. This means the beverage will remain at a lower power level until the appropriate heating power is reached, thus requiring a longer cooking time to achieve full heating. If the power is increased too quickly, it may cause foam to grow rapidly, increasing the risk of overflow.

[0049] The third method, alternating heating, relies solely on setting specific heating time ranges for the first and second power ratios based on varying amounts of ingredients. This fails to allow for flexible adjustment of the liquid heater's power based on different heating environments and ingredients (especially unexpected amounts), thus failing to guarantee thorough heating of the beverage or prevent foam overflow. Furthermore, the frequency of alternating heating needs to be controlled by calculating the duration of the initial overflow signal.

[0050] In practical use, the second method requires a longer period of low-power heating, which visually creates the illusion that the beverage stops bubbling or only bubbling for an extended period, giving users the misconception that heating stops once the beverage reaches a boil. The third method cannot guarantee that the beverage will not overflow or that it will be fully heated. Therefore, consumers and manufacturers tend to choose the first method, which relies on time control and adjustable heating power.

[0051] However, the first method, in order to accurately determine the time required for power adjustment, involves frequent stopping of the liquid heater or prolonged use of a single low power to heat the beverage, which leads to a technical problem where the beverage cannot achieve stable bubbling over a long period before the target power is reached. Specifically, the existing technology causes this problem due to at least one or more of the following aspects.

[0052] Firstly, existing technologies typically stop heating the beverage or use a single low-power heating method after detecting an overflow signal. This requires waiting for the foam in the beverage to completely subside. However, the overflow detection device can only detect whether the foam has reached a set height (or whether the signal strength exceeds a threshold at the set height). Therefore, a relatively long safety time needs to be set to ensure that the foam completely subsides. As a result, the time for existing technologies to stop heating or use a single low-power heating method is significantly longer.

[0053] Secondly, existing technologies suggest that the reason beverages cannot be fully and prolongedly boiled is that higher heating power easily causes the beverage and foam to overflow. Therefore, only lower heating power can be used to ensure no overflow, but this results in poor cooking. To solve this problem, existing technologies gradually reduce the cooking power from a high level to a target power, stopping heating when an overflow signal is detected. Therefore, the technical approach and methods of existing technologies never consider adjusting the power when an overflow signal is detected during the beverage cooking process.

[0054] Thirdly, based on the second aspect, the power curve diagram of the prior art is as follows: Figure 1 As shown, as the cooking power approaches the target power, the beverage continuously switches between decreasing cooking power and stopping heating or a single low power. Before the cooking power reaches the target power, the average power of the beverage decreases rapidly, and the beverage cannot achieve long-term stable bubbling, ultimately affecting the cooking effect of the beverage.

[0055] Therefore, this embodiment differs from the prior art in at least the following ways.

[0056] Firstly, in this embodiment, the power value of the heating process is adjusted based on the number of cycles of the first and second steps. Therefore, this embodiment does not require ensuring that the foam has completely subsided before switching working steps, thus shortening the time the beverage is heated at a lower power.

[0057] Secondly, in this embodiment, during the cycle of the first and second steps, not only is the first power reduced, but the second power is also increased, so that the foam height is reduced but the foam does not need to completely fall back, thus preventing the beverage temperature from dropping rapidly and maintaining the bubbling of the beverage as much as possible.

[0058] Thirdly, the power curve of this embodiment is shown in the figure below. Figure 2 As shown, during the rolling process of the first and second steps, the first power decreases and the second power increases, the power difference gradually decreases, the average power of the beverage changes little, and the overall heating process of the beverage is more stable.

[0059] In summary, this implementation method alternates between the first and second steps multiple times to ensure the beverage boils thoroughly without overflowing. Before reaching the target power, the switching process gradually increases the second power. While reducing the foam height, the beverage temperature is maintained to ensure continued boiling, eliminating the need to stop heating or use a single low power for an extended period, thus improving the sustainability of the boiling. Furthermore, during the alternation of the first and second steps, the positive difference between the first and second power is gradually reduced, ensuring that the difference between the actual heating power (first or second power) and the target power gradually decreases throughout the heating process, allowing the beverage to boil stably for as long as possible.

[0060] To achieve the cyclic heating between the first and second steps of this invention, the invention includes: a first step of heating the beverage with a first power until an overflow signal is detected, then switching to the second step; and a second step of heating the beverage with a second power lower than the first power until no overflow signal is detected for a first duration, then switching back to the first step.

[0061] To prevent interference with the foam detection device or detection errors, the continuous overflow signal may be interrupted, causing an incorrect switch from the second step to the first step. Therefore, in the second step, it is necessary to wait until no overflow signal is detected and a first time period is met before switching to the first step. Even so, this embodiment does not need to ensure that the foam has completely fallen back before switching the working steps, so the first time period of the first step can still be less than the preset time period set by the prior art for foam falling back.

[0062] The first power and the second power are variables. To facilitate the description of the change process of the first power, the first power is divided into the initial first power, the adjusted first power, and the final first power; the second power is similarly divided.

[0063] The first step is used to thoroughly agitate the beverage, and the rising foam triggers an overflow signal from the foam detection device, thus switching to the second step. Therefore, the initial power is often set relatively high, causing the beverage to agitate significantly and triggering an overflow signal.

[0064] The second power in the second step is less than the first power. The second step is used to reduce the foam height and maintain the temperature and bubbling of the beverage as much as possible. Therefore, the initial second power is often set relatively low, so that the foam height is so low that no overflow signal can be detected.

[0065] The first and second steps switch back and forth multiple times, essentially using the detection and disappearance of an overflow signal as the switching condition. A higher first power and a lower second power are alternately used to tumble and heat the beverage, achieving a balance between bubbling and preventing overflow. During the tumbling process, the first power is reduced each time the beverage switches to the first step, extending the time before the liquid heater detects an overflow signal again. Conversely, the second power is increased each time the beverage switches to the second step. This second power is closer to the operating power for bubbling without overflowing, preventing further foaming and maintaining the beverage's temperature and bubbling state.

[0066] like Figure 3 As shown in the diagram, the control method for the liquid heater can be achieved by adjusting the first and second power according to the following process to maintain the bubbling state of the beverage as much as possible:

[0067] 1. The liquid heater heats the beverage using a first power P1 until an overflow signal is detected. The first power P1 ensures the beverage is fully heated, keeping it in a bubbling state.

[0068] 2. The liquid heater uses a second power P2 to heat the beverage. The second power P2 varies depending on the type and volume of the beverage, as detailed in Embodiments 1 and 2. At the second power P2, the foam will continuously and slowly descend. When no overflow signal is detected for a first duration, the number of switching events N is recorded (e.g., N=1 when the first overflow signal is detected). If an electrode-type foam detection device is used, the number of switching events can be recorded when the foam height drops to a point where it no longer contacts the electrode for a period exceeding the first duration. If a capacitive foam detection device is used, the number of switching events can be recorded when the foam height drops to a point where the signal strength no longer meets the threshold for a period exceeding the first duration.

[0069] 3. The liquid heater heats the beverage using a power level of P1 minus (number of switching times N * the difference in power level during a single adjustment). The power variation is expressed as a unit of power adjustment. This power variation can be a fixed or floating value in different implementations, as detailed in the embodiments.

[0070] 4. When the cooking device heats the beverage at the first power P1 - (number of switching times N * the difference in a single decrease of the first power) until an overflow signal is detected, the beverage is then heated at the second power P2 + (number of switching times N * the difference in a single increase of the second power). This process is repeated while the beverage is being cooked, reducing the positive difference between the first and second power, thus ensuring the beverage remains bubbly and stable for as long as possible during the cooking process.

[0071] When brewing different beverages, the main components of different ingredients vary, resulting in different variations in foam size and density with temperature. The initial first step, the initial second step, and the difference between lowering the first power and raising the second power in this invention primarily depend on the type of beverage.

[0072] Example 1

[0073] The initial power selection method and the adjustment method for the positive power difference in this embodiment are not limited to the application scenarios described below. This embodiment can be used to implement beverages such as rice porridge, soy milk, and rice paste. For ease of description, the following example is the preparation of white fungus soup.

[0074] When making white fungus soup, the main ingredient is white fungus. With a liquid heater and a maximum cooking capacity of 1.5L, using 1L of water and 10g of white fungus, the initial first power, the initial second power, and the positive difference between the first and second power after switching are selected based on the following reasons.

[0075] Initial power selection: The main component extracted from white fungus is soluble polysaccharide. The polysaccharides in white fungus need to be soaked and cooked in water for a long time to fully soften and extract. In the initial heating stage, the release of soluble polysaccharides is insufficient, the foam structure is relatively unstable, and the foam is difficult to accumulate and overflow. Therefore, a relatively high initial power can be used to heat the beverage to ensure it boils thoroughly. An initial power of 280W to 350W can be selected.

[0076] Selection of initial secondary power: Because the foam structure is relatively unstable and the foam is prone to bursting, a higher initial secondary power should be used to heat the beverage. This will help maintain the beverage's temperature and bubbling state as much as possible while preventing foam overflow. An initial secondary power of 30W to 60W can be selected.

[0077] Selection of the positive difference between the first and second power after switching: During the boiling stage of the beverage, most polysaccharides begin to dissolve and leach out, and the viscosity of the white fungus soup gradually increases and approaches its limit. As viscosity increases, the foam becomes increasingly difficult to break, gradually increasing the risk of overflow. Therefore, to prevent frequent overflow signals from being detected in the later stages of boiling, the positive difference between the first and second power after switching can be relatively large. The positive difference between the first and second power after switching can be selected from 5W to 20W.

[0078] Furthermore, during the cooking process, the polysaccharide precipitation from the white fungus is relatively gradual, and the dissolution rate is relatively constant (compared to free starch). The viscosity of the white fungus soup changes at a relatively stable rate, so a fixed positive difference between the first and second power can be used.

[0079] Furthermore, the polysaccharide extraction process of Tremella is relatively gradual. Therefore, in order to make the changes in the first power and the second power more stable, the power value of the first power is reduced each time the first step is switched to, and the power value of the second power is increased each time the second step is switched to.

[0080] For example, the liquid heater has a maximum cooking capacity of 1.5L, with 1L of water and 10g of white fungus. The power adjustment process during actual use is shown in Table 1.

[0081]

[0082] After the liquid level heater heats the beverage to 90°C at 650W, it switches to the first step, continuing to heat the beverage at the initial power of 350W until an overflow signal is detected.

[0083] Switch to the second step, heating the beverage with the second power. The second power is increased from 0W to 50W until no overflow signal is detected and the first time period is met, then switch back to the first step.

[0084] The first step is to continue heating the beverage using the first power, which is then reduced from 350W to 340W until an overflow signal is detected, at which point the process switches to the second step.

[0085] Switch to the second step, heating the beverage with the second power. The second power is increased from 50W to 60W until no overflow signal is detected and the first time period is met, then switch back to the first step.

[0086] The first step is to continue heating the beverage using the first power setting, which is then reduced from 340W to 330W until an overflow signal is detected, at which point the process switches to the second step.

[0087] When brewing the beverage, repeat the above process. During the switching between the first and second steps, the positive difference between the first and second power decreases, so that the beverage can churn as stably as possible during the brewing process.

[0088] Finally, after the second step is applied for the last time, the process switches to the third step, using a third power of 250W to heat the beverage while ensuring that no overflow signal is detected. This third power is less than the first power applied at the last time but greater than the second power applied at the last time. The control method terminates with this third step. (Detailed description follows.)

[0089] Example 2: When making rice porridge, or similar ingredients, or other ingredients such as white fungus soup, soy milk, or rice paste. For ease of description, the following example uses making rice porridge.

[0090] When making rice porridge, the main ingredient is rice. The maximum stewing power of the liquid heater is 850W, the maximum stewing capacity is 1.5L, and with 1L of water and 100g of rice, it is expected to be cooked in 45 minutes after boiling. The initial first power, the initial second power, and the positive difference between the first and second power after switching are selected based on the following reasons.

[0091] Initial power selection: Rice's main component is starch. In particular, some starch adheres to the rice surface in a free state. Therefore, when cooking rice, the free starch reduces the surface tension of the beverage, making rice porridge more prone to foaming in the early stages of cooking (compared to white fungus soup). Thus, when making rice porridge, the initial power should be relatively low, ideally between 250W and 320W.

[0092] Selection of the initial secondary power: Rice starch denatures and gelatinizes during heating, increasing the viscosity of the liquid. While this easily produces foam, its ability to stabilize the foam is limited. Therefore, an initial secondary power of 30W to 70W can be selected.

[0093] Selection of the positive difference between the first and second power after switching: After the beverage has been simmering for a period of time, it gradually becomes viscous, and the amount of starch and modified gelatinized starch gradually increases. However, according to the paper "Study on the Surface Tension of Proteins, Gelatinized Starch and its Relationship with Functional Properties," the effect of the modified gelatinized starch concentration on surface tension is limited after it reaches a certain concentration. To accurately adjust the first and second power, the positive difference between the first and second power after switching can be relatively small, selected as 5W to 15W.

[0094] Taking into account the fact that rice porridge is more prone to foaming, the power difference for the first power reduction can differ from the power difference for the second power increase. Specifically, the power difference for the first power reduction is greater each time the user switches to the first step than the power difference for the second power increase each time the user switches to the second step.

[0095] Specifically, when cooking a 1.5L maximum capacity rice with 1L of water and 100g of rice, the power adjustment process during actual use is as follows:

[0096] As shown in Table 2.

[0097]

[0098] After the liquid level heater heats the beverage to 90°C at 650W, it switches to the first step, continuing to heat the beverage at the initial power of 300W until an overflow signal is detected.

[0099] Switch to the second step, heating the beverage with the second power. The second power is increased from 0W to 30W until no overflow signal is detected and the first time period is met, then switch back to the first step.

[0100] The first step is to continue heating the beverage using the first power. The power difference between the first power and the lower power is 15W. The first power is reduced from 300W to 285W until an overflow signal is detected, then switch to the second step.

[0101] Switch to the second step, heat the beverage with the second power. The power difference of the second power is 10W. The second power is increased from 30W to 40W until no overflow signal is detected and the first time period is met. Then switch to the first step.

[0102] The first step is to continue heating the beverage using the first power setting, which is then reduced from 285W to 270W until an overflow signal is detected, at which point the process switches to the second step.

[0103] When brewing the beverage, repeat the above process. During the switching between the first and second steps, the positive difference between the first and second power decreases, so that the beverage can churn as stably as possible during the brewing process.

[0104] Finally, in the third step, after the second step is applied for the last time, the process switches to the third step, using a third power to heat the beverage while ensuring that no overflow signal is detected continuously. This third power is less than the first power applied at the last time but greater than the second power applied at the last time. The control method terminates at this third step. (This will be described in detail below.)

[0105] Example 3

[0106] In some cases, the change in surface tension of a beverage slows down as it is continuously boiled. For ease of description, rice porridge will be used as an example below, but it is not limited to boiling rice porridge.

[0107] During the cooking process, in rice porridge, the surface starch of the rice gelatinizes and sets, while the internal starch absorbs water and swells, creating pressure on the outside and causing the rice grains to "bloom." This "blooming" provides more channels for the internal starch to dissolve, allowing the porridge to thicken quickly. Overflow signals are easily detected in rice porridge at the very beginning of cooking. Therefore, for rice porridge, there is a specific stage at the beginning of cooking where foaming is extremely easy to occur. After cooking for a period of time, once the concentration of the gelatinized starch reaches a certain level, its effect on surface tension becomes limited.

[0108] Therefore, in order to further maintain the bubbling state of the beverage during the rolling switch and implementation process of the first and second stages, the change in the positive difference between the first power and the second power is set to a decreasing trend during the switching process between the first and second steps.

[0109] For example, the power difference for the first power reduction can be gradually decreased from 15W, decreasing by 1W each time it switches, until it reaches 10W. The power adjustment process is shown in Table 3 when cooking a maximum capacity of 1.5L, with 1L of water and 80g of rice.

[0110]

[0111] When brewing the beverage, repeat the above process until the power stabilizes at 205W. During the switching between the first and second steps, the positive difference between the first and second power decreases, ensuring that the beverage boils stably for as long as possible during the brewing process.

[0112] During the brewing process, there exists a power value that allows the beverage to boil fully without overflowing (hereinafter referred to as the target power). The magnitude of the target power depends on the following factors:

[0113] Beverage Types: Different types of beverages (such as white fungus soup, rice porridge, milk, etc.) exhibit different physical and chemical properties during heating. For example, white fungus soup may overflow more easily due to the formation of gelatinous substances, while rice porridge, containing starch, produces more foam and viscosity, affecting its overflow during boiling. For instance, white fungus soup may take longer to reach a boil than rice porridge, and the sudden change in starch concentration in rice porridge may make foam more difficult to control.

[0114] Beverage volume: The larger the volume, the greater the heat demand for the liquid to boil, requiring higher power to heat it to the boiling point and maintain boiling. However, a larger volume also means a higher risk of overflow, thus requiring more precise control of the heating power.

[0115] In the actual process of brewing beverages, the target power for heating different types and volumes of beverages using the same liquid heater will also be different. The following discussion will focus on the relationship between the first power, the second power, and the target power.

[0116] First, the target power is close to the first power.

[0117] As in Example 1, during the process of simmering white fungus, the target power of the white fungus soup in this example is close to the first power. The first step cannot be fully implemented initially, that is, no overflow signal can be detected when heating the beverage with the reduced first power. Therefore, for ease of description, the first step that cannot be implemented can be regarded as the third step, and the reduced first power can be regarded as the third power.

[0118] Therefore, in the implementation process of Example 1, as Figure 4As shown in Tables 1 and 2, after the second step is applied for the last time, the process switches to the third step, using the third power to heat the beverage while ensuring no overflow signal is detected. This third power is less than the first power applied at the last time but greater than the second power applied at the last time. The third power is generally the difference between the first power applied at the last time and the power difference caused by the reduction in the first power.

[0119] That is, in the third step, after the second step is applied for the last time, the third step is switched to, the beverage is heated with a third power and no overflow signal is detected continuously. The third power is less than the first power applied for the last time and greater than the second power applied for the last time. The control method terminates with the third step.

[0120] Example 4: When environmental changes cause the target power to be higher than the current third power.

[0121] In the third step, if there is wind or low temperature in the external environment, causing the target power to be higher than the current third power, the beverage may not be able to continue bubbling. To prevent this from happening, if the third step does not detect an overflow signal and the second duration is met, the third power is increased to ensure that the beverage continues to bubble.

[0122] That is, Figure 5 As shown, in the third step, after the last application of the second step, the process switches to the third step, using a third power to heat the beverage while ensuring no overflow signal is detected. This third power is less than the last applied first power but greater than the last applied second power. If no overflow signal is detected in the third step and the second duration is met, the third power is increased to heat the beverage. If, after increasing the third power, the foam detection device detects an overflow signal, the process returns to the third power level before the overflow signal was detected, and the second duration is checked again. This cycle continues until the preset cooking time ends.

[0123] Similarly, the third power is a variable. To facilitate the description of the change process of the third power, the third power is divided into the initial third power, the adjusted third power, and the final third power.

[0124] The initial value of the third power can generally be: the last applied first power minus the reduction value of the first power each time. Regardless of the adjustment, the third power must always be less than the last applied first power and greater than the last applied second power. Therefore, the value of each increase can also be less than the reduction value of the first power each time.

[0125] On the other hand, the second duration is mainly affected by the volume of the beverage. When the beverage volume is small, it is more sensitive to temperature changes. For example, when the beverage volume is 0.8L to 0.3L, the second duration is 1min to 5min. When the beverage volume is 1.5L to 0.8L, the second duration is 3min to 8min.

[0126] As shown in Table 4, the beverage is white fungus soup. The maximum capacity of the liquid heater is 1.5L, with 0.5L of water, 5g of white fungus, and a second cooking time of 3 minutes. In the third stage, the difference between the initial third power and the last first power is 10W, and the power increases by 3W each time the third power is used.

[0127] After heating the white fungus soup to 90℃ using 650W, switch to the first step and continue heating the beverage using the initial 350W power until an overflow signal is detected.

[0128] Switch to the second step, heating the beverage with the second power. The second power is increased from 0W to 50W until no overflow signal is detected and the first time period is met, then switch back to the first step.

[0129] The first step is to continue heating the beverage using the first power. The power difference between the first power and the lower power is 10W. The first power is reduced from 350W to 340W until an overflow signal is detected, then switch to the second step.

[0130] Switch to the second step, heating the beverage at the second power level. The power difference for the second power increase is 10W. The second power is increased from 50W to 60W until no overflow signal is detected, meeting the first time requirement. Then switch back to the first step. In the first step, continue heating the beverage at the first power level, decreasing the first power from 340W to 330W until an overflow signal is detected. Then switch back to the second step.

[0131] Repeat the above process until the second step is applied for the last time, then switch to the third step, using the initial third power (250W) to heat the beverage while ensuring no overflow signal is detected. After three minutes of no signal detection at the initial third power, increase the power from 250W to 253W. After three minutes of no signal detection at the third power of 253W, increase the power from 253W to 256W. If an overflow signal is detected at this point, revert to the previous third power of 253W where no overflow signal was detected.

[0132]

[0133] Example 5: The target power is close to the second power.

[0134] During use, it was found that existing technologies use a method of reducing the cooking power to find the target power. If the target power of the beverage is much lower than the cooking power, meaning the target power is closer to the second power of this embodiment, then existing technologies require a longer time and more frequent adjustments of the cooking power to reach the target power. Furthermore, each adjustment of the cooking power in existing technologies requires a longer heating stop time (or low-power heating). Therefore, when the target power is much lower than the cooking power, it is more difficult for existing technologies to achieve stable bubbling of the beverage over a long period.

[0135] Therefore, in some embodiments of this implementation, when the target power is low, after switching from the first step to the second step in actual use, the second step cannot be fully implemented. That is, the second power after the last power increase is too high, exceeding the target power and causing the foam to fail to descend, resulting in a continued risk of foam overflow. At this time, the second power cannot meet the requirements for the implementation of the original second step. For ease of description, this (incompletely implemented) second step is regarded as the fourth step, and the second power (when it cannot be fully implemented) is regarded as the fourth power. Specifically, the inability of the second step to be fully implemented can be manifested in some implementations as the continuous detection of an overflow signal, or the failure to detect an overflow signal and thus the inability to meet the first duration.

[0136] Similarly, the fourth power is a variable. To facilitate the description of the change process of the fourth power, the fourth power is divided into the initial fourth power, the adjusted fourth power, and the final fourth power.

[0137] Therefore, as Figure 6 As shown, if the second step cannot be fully implemented, the process switches to the fourth step after the last application of the first step. The fourth step uses a fourth power to heat the beverage; this fourth power is greater than the last applied second power but less than the last applied first power. The initial value of the fourth power can generally be: the last applied second power plus the increase in the second power value each time.

[0138] In practical use, it was found that when beverages are prone to foaming (such as starchy drinks like rice porridge) and when the volume of the beverage is close to the upper limit of the liquid heater's cooking capacity, the target power often approaches the second power. To prevent the overflow signal from lasting too long and causing foam overflow, a third duration is set. The third duration depends on the volume of the beverage, especially on the difference between the beverage's volume and the upper limit of the heater's cooking capacity. For example, if the difference between the beverage's volume and the upper limit of the heater's cooking capacity is 0.2L, it indicates that the distance between the liquid surface and the spout is relatively long, and the third duration can be 5S to 10S. For example, if the difference between the beverage's volume and the upper limit of the heater's cooking capacity is 0L, it indicates that the distance between the liquid surface and the spout is relatively short, and the third duration can be 1S to 3S.

[0139] The fourth step uses a fourth power level to ensure that an overflow signal is continuously detected within the third time period, then reduces the fourth power level until no overflow signal is detected. Specifically, the second stage can switch back to the first stage, indicating that the last second power level can ensure that the foam height is reduced; when using the fourth power level, an overflow signal is continuously detected. If an overflow signal is detected in the fourth stage, it means that the target power is between the last second power level and the fourth power level. Therefore, the reduction value of the fourth power level needs to be less than the increase value of the second power level each time.

[0140] As shown in Table 5, the maximum capacity of the liquid heater for stewing is 1.5L. For 1.5L of water and 136g of rice, heating to 85℃ at 500W with a third heating time of 2 seconds, or heating to 85℃ at 300W, the process switches to the first step, continuing to heat the beverage at the initial 300W power until an overflow signal is detected, at which point the process switches to the second step.

[0141] The second step involves heating the beverage at a second power level, increasing the power from 0W to 50W until no overflow signal is detected and the first duration is met, then switching back to the first step.

[0142] The first step is to continue heating the beverage using the first power. The power difference between the first power and the lower power is 10W. The first power is reduced from 300W to 290W until an overflow signal is detected, then switch to the second step.

[0143] The second step involves heating the beverage at a second power level, increasing the power by 10W at a time, from 50W to 60W, until no overflow signal is detected and the first time period is met, then switching back to the first step. The first step continues heating the beverage at the first power level, decreasing the power from 290W to 280W, until an overflow signal is detected, then switching back to the second step.

[0144] The above steps are repeated multiple times until the last application of the first step (first power is 210W). Afterwards, the fourth step is switched to an initial fourth power of 160W. At this power, an overflow signal is continuously detected, and the third duration of 2 seconds is met. The fourth power needs to be reduced, decreasing by 2W each time, from 160W to 158W. After adjustment, if an overflow signal is detected again and the third duration of 2 seconds is met, the fourth power is reduced from 158W to 156W. At 156W, no overflow signal is detected, and the fourth power is maintained to heat the beverage until the cooking process is complete.

[0145]

[0146] Furthermore, the fourth step, which uses a fourth power to heat the beverage and continuously detects an overflow signal within the third time period, may be due to detection errors caused by the foam detection device sticking together. The aforementioned liquid heater is also equipped with a stirrer; after the first step is applied for the last time, the system switches to the third step, using the stirrer to rotate, thereby avoiding the situation where foam sticking together causes an overflow signal to be detected.

[0147] Example 6: When the target power is within a power range.

[0148] During the brewing process, the beverage continuously evaporates, especially when it is constantly bubbling, where the evaporation rate is more significant (for example, when brewing white fungus soup at 250W for 30 minutes, the volume of the soup decreased from 1.5L to 1.3L). Furthermore, for the same beverage, the volume changes due to evaporation, resulting in different target power levels. On the other hand, as the brewing time increases, the viscosity of the beverage may increase (for example, white fungus soup becomes thicker after prolonged brewing), and the risk of foam formation and overflow also changes.

[0149] For liquid heaters with stirring functions, stirring has a significant impact on the target power during beverage heating. Stirring can make the temperature distribution inside the beverage more uniform, preventing localized overheating and rapid foaming. Since stirring reduces the risk of overflow, the target power is thus increased. On the other hand, stirring can promote even heating of ingredients or pulverize them; for example, large pieces of white fungus can be pulverized into smaller pieces. Since white fungus has a larger surface area, this actually increases the risk of overflow, thus increasing the target power.

[0150] Therefore, under the combined influence of the above factors, the target power can be a range.

[0151] Existing technology detects an overflow signal, stops heating, and reduces the cooking power, repeating this process until no more overflow signals are detected. When the target power is within a certain range, this technology frequently stops heating, leading to large temperature fluctuations and affecting the quality of the brewed beverage. Furthermore, reducing the cooking power to the lower limit of the target power range results in insufficient heating of the beverage.

[0152] To avoid frequent heating interruptions, and also to avoid the initial power level falling below the lower limit of the target power range. For example... Figure 7 As shown, in this embodiment, the process terminates when the positive difference between the first power and the second power meets a preset condition. The first step and the second step are switched and applied alternately, and the first power and the second power are no longer adjusted.

[0153] The positive difference between the first power and the second power satisfies the preset conditions, indicating that the difference between the first power, the second power, and the target power is within the expected range. In the first step, the first power is greater than the target power, but the difference is small, resulting in the beverage being in a state of strong bubbling with slowly rising foam until an overflow signal is detected. In the second step, the second power is less than the target power, but the difference is small, allowing the second power to better maintain the beverage temperature, resulting in a state of weak bubbling with slowly falling foam until no overflow signal is detected, satisfying the first time duration. Therefore, this embodiment can utilize the space of the foam moving up and down to fully heat the beverage, allowing it to quickly reach a state of general bubbling without overflowing.

[0154] As the first and second power continuously approach the target power, if the positive difference between the first and second power cannot be further adjusted, the first and second power are very small, and it can be considered that the first and second power are close to the target power. Therefore, during the switching process between the first and second steps, it can be assumed that the liquid heater is actually heating the beverage at the target power, and the beverage can simmer for a longer time during the power adjustment process. Therefore, the preset condition for termination can be: the positive difference between the first and second power is less than the decrease value of the first power each time or the increase value of the second power each time.

[0155]

[0156] As shown in Table 6, the maximum capacity of the liquid heater for stewing is 1.5L, with 1.2L of water and 15g of white fungus. Because of the high content of white fungus, the first power setting is adjusted down by 15W each time; the second power setting is adjusted up by 10W each time.

[0157] After the liquid heater heats the beverage to 90°C using 650W, it enters the first step, heating the beverage with the first power of 300W until an overflow signal is detected, then switches to the second step.

[0158] The second step involves heating the beverage at a second power level, increasing the power from 0W to 50W until no overflow signal is detected and the first duration is met, then switching back to the first step.

[0159] The first step is to continue heating the beverage using the first power, which is then reduced from 300W to 285W until an overflow signal is detected, at which point the process switches to the second step.

[0160] The second step involves heating the beverage at a second power level, increasing the power from 50W to 60W until no overflow signal is detected and the first duration is met, then switching back to the first step.

[0161] After repeatedly switching between the above steps, when the first power is 150W and the second power is 140W, the positive difference between the first power and the second power is 10W, which is less than the 15W reduction in the first power each time. Therefore, the first step and the second step can still be switched, but the first power and the second power will no longer be adjusted.

[0162] Example 7: Using the number of switching times as a preset condition.

[0163] In scenarios where the cooking time is limited and the target power needs to be adjusted as quickly as possible, the liquid heaters in existing technologies are in a state of frequent start-stop adjustment, which leads to unstable heating of beverages and affects the cooking effect.

[0164] This embodiment can also be adjusted based on the number of times the first power and the second power are switched. The process terminates when the number of switches between the first step and the second step meets a preset condition. The first step and the second step are switched and applied alternately, and the first power and the second power are no longer adjusted.

[0165] In this embodiment, for ease of description, switching from the first step to the second step and vice versa constitutes one switching operation. For example, as shown in Table 7, the maximum capacity of the liquid heater for stewing is 1.5L, with 1.2L of water and 15g of white fungus. Because of the high content of white fungus, the first power is adjusted down by 15W each time; the second power is adjusted up by 10W each time, and the liquid heater is heated to 90℃ using 650W.

[0166] First switch: Enter the first step, heat the beverage at the first power of 300W until an overflow signal is detected, then switch to the second step. Second step: Heat the beverage at the second power, increasing the power from 0W to 50W until no overflow signal is detected and the first time period is met, then switch back to the first step.

[0167] Second switching: First step, continue heating the beverage with the first power, which is reduced from 300W to 285W until an overflow signal is detected, then switch to the second step; Second step, heat the beverage with the second power, which is increased from 50W to 60W until no overflow signal is detected and the first time period is met, then switch back to the first step.

[0168] Repeat the above steps until the tenth switch is met. Eleventh switch: First step, continue heating the beverage with the first power, maintaining the first power at 165W, until an overflow signal is detected, then switch to the second step; Second step, heat the beverage with the second power, maintaining the second power at 140W, until no overflow signal is detected and the first duration is met, then switch to the first step.

[0169]

[0170] Example 8: The second step described above is applied by repeatedly increasing the second power.

[0171] After switching between the first and second steps multiple times, the positive difference between the first and second power decreases, and both the first and second power become very close to the target power. When rice porridge and white fungus are cooked together, the starch in the rice easily produces foam, while the polysaccharide structure of the white fungus makes the foam difficult to break. In this extreme case, after detecting an overflow signal, to avoid the foam decreasing at a slower rate than expected when the second power is directly applied, this embodiment switches to the second step and applies the second power by repeatedly increasing it to avoid a sudden foam burst.

[0172] To facilitate the description of applying the second power in two stages, the first increase in the second power is primarily to ensure that the foam is quickly eliminated, reducing the risk of overflow. The first increase in the second power is mainly to maintain the beverage temperature and its bubbling state.

[0173] Therefore, the initial and subsequent power increases depend on the ease with which the foam breaks and dissipates. For beverages like white fungus, where foam is difficult to eliminate, the initial power increase should not be too high; it is generally 10% to 50% of the power increase after multiple power increases. For beverages like rice porridge, where foam is easily generated and easily broken and eliminated, the initial power increase is generally 10% to 70% of the power increase after multiple power increases.

[0174] The following solutions can be referenced during implementation, such as... Figure 8 , Figure 9 As shown.

[0175] Option 1: When an overflow signal is detected, the second power is increased for the first time. The lower power prevents the foam from overflowing due to thermal inertia until the overflow signal is no longer detected. After the overflow signal is no longer detected, the second power is increased for the second time to heat until the first duration is met.

[0176] For example, for white fungus, the second power is increased to 110W, and the first heating time is 3 seconds. When an overflow signal is detected, the second power is increased to 50W to heat the beverage until no more overflow signals are detected. After no more overflow signals are detected, the second power is increased to 110W again, and heating continues until no more overflow signals are detected for 3 seconds, then the process returns to the first step.

[0177] Option 2 involves first increasing the second power upon detecting an overflow signal and maintaining this level for a preset time. After the preset time, the second power is increased a second time, heating until no more overflow signals are detected, satisfying the first time duration. The preset time is to ensure the second power is increased sufficiently during the first increase to prevent it from sticking to the foam.

[0178] The preset time ends before the overflow signal is no longer detected. For example, for white fungus, if the second power is increased to 110W, the preset time is 1 second, and the first duration is 3 seconds, when the overflow signal is detected, the second power is increased to 50W for 1 second, and then increased to 110W for 3 seconds until the overflow signal is no longer detected, then the process switches to the first step.

[0179] The preset time ends only after no more overflow signals are detected. For example, for white fungus, if the second power is increased to 110W, the preset time is 5 seconds, and the first duration is 3 seconds, when an overflow signal is detected, the second power is increased to 50W for 5 seconds, then the second power is increased to 110W for 3 seconds until no more overflow signals are detected, at which point the process switches to the first step.

[0180] Liquid heaters typically include a heating container and a foam detection device. The heating container has a cooking space for holding and heating beverages. The heating container may include common heating elements (such as heating plates or thick-film heating elements) and a vessel (which may be made of glass or metal). Specifically, the cooking space can be formed solely by the vessel or by the vessel and the heating elements together. The heating power of the liquid heater for the beverage can be adjusted by adjusting the heating elements. For electric kettles and rice cookers, the cooking space can be the space inside the inner pot where the beverage is heated. For soy milk makers and blenders, the cooking space can be the space for blending, grinding, and heating the beverage.

[0181] Foam detection devices can be used to detect overflow signals. Existing foam detection devices can be divided into capacitive and electrode types. Capacitive foam detection devices detect changes in dielectric constant and capacitance when the beverage or foam height changes. When the change in dielectric constant and capacitance exceeds a threshold, an overflow signal is detected. Common capacitive foam detection devices include contact and non-contact capacitor components. Contact capacitor components can be placed inside the cooking space, while non-contact capacitor components can be placed on the outside of the container. Electrode foam detection devices can also be placed inside the cooking space. When foam or beverage touches the foam detection device, the circuit closes, thus detecting an overflow signal.

[0182] Furthermore, it should be noted that the liquid heater of the present invention is not limited to the food processing machine with an integrated motor and cup body disclosed in the embodiments of the present invention. It can also be a soy milk maker with a top-mounted motor, a blender with a separate cup body and base, and a hand-washable food processing machine that can automatically discharge and clean itself. Moreover, the liquid heater of the present invention can also be applied to heating appliances that can perform boiling operations, rice paste making, etc., such as health pots and health cookers.

[0183] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a liquid heater, wherein the liquid heater detects an overflow signal via a foam detection device. Its features are, include: The first step involves heating the beverage at the highest power until an overflow signal is detected, then switching to the second step. The second step involves heating the beverage with a second power lower than the first power until no overflow signal is detected and the first time period is met, then switching back to the first step. The first step and the second step are switched multiple times. Each time the first step is switched to, the first power is reduced, and each time the second step is switched to, the second power is increased. The positive difference between the first power and the second power after each switching between the first step and the second step is less than the positive difference between the first power and the second power before the switching.

2. A control method for a liquid heater as claimed in claim 1, characterized in that, include: The third step involves switching to the third step after the last application of the second step, where the beverage is heated using a third power and no overflow signal is detected continuously. The third power is less than the first power applied at the last time and greater than the second power applied at the last time. The control method terminates with the third step.

3. The control method for a liquid heater according to claim 1, characterized in that: The third step involves switching to the third step after the second step is applied for the last time. The beverage is heated using the third power and no overflow signal is detected continuously. The third power is less than the first power applied at the last time and greater than the second power applied at the last time. No overflow signal is detected in the third step and the second duration is met. The third power is then increased to heat the beverage.

4. The control method of a liquid heater according to claim 1, wherein include: The fourth step involves switching to the fourth step after the first step is applied for the last time. The beverage is heated with the fourth power and an overflow signal is continuously detected within the third time period. The fourth power is greater than the second power applied at the last time and less than the first power applied at the last time. The fourth power is then reduced until no overflow signal is detected.

5. The control method for a liquid heater according to claim 1, characterized in that: The control method terminates when the positive difference between the first power and the second power meets a preset condition, the first step and the second step are switched and applied alternately, and the first power and the second power are no longer adjusted.

6. The control method for a liquid heater according to claim 1, characterized in that: The control method terminates when the number of switching steps between the first step and the second step meets a preset condition. The first step and the second step are switched and applied alternately, and the first power and the second power are no longer adjusted.

7. The control method for a liquid heater according to claim 1, characterized in that: The second step involves applying the second heating power by repeatedly increasing it.

8. The control method for a liquid heater according to claim 1, characterized in that: During the switching between the first and second steps, the change in the positive difference between the first power and the second power is set to a decreasing trend.

9. The control method of a liquid heater according to claim 1, characterized by: The power value of the first power is reduced each time the switch is made to the first step, and the power value of the second power is increased each time the switch is made to the second step.

10. The control method for a liquid heater according to claim 4, characterized in that: The liquid heater is further provided with a stirring member, and the third step is switched after the last application of the first step, and the stirring member is rotated.

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