Household appliance precise temperature control method and system

Abstract

The present application relates to a precise temperature control method and system for household appliances, comprising the following steps: system power-on; presetting a first heating mode, a second heating mode, a third heating mode, a fourth heating mode and a constant temperature holding mode in the system, the temperature ranges corresponding to the five heating modes are continuous in turn, and the corresponding PWM duty cycle values decrease in turn; preliminary heating: automatically switching the heating mode; when T 当前 falls into the temperature range of the constant temperature holding mode, entering the constant temperature holding mode. By detecting the initial temperature of the liquid in the container body first, selecting the corresponding heating power for preliminary heating, then judging the water quantity in the container body according to the temperature rising condition and the temperature rising efficiency, further selecting the appropriate heating power for different water quantities, and finally setting a smaller constant temperature range to control the start and stop of the heating element, the temperature is stabilized in the set range, avoiding temperature overshoot and too large temperature adjustment range, and both the rapid heating efficiency and the constant temperature control are considered, which is especially suitable for containers with fast heat conduction and small thermal inertia.

Description

Technical Field

[0001] This invention relates to the field of home appliance temperature control technology, and in particular to a method and system for precise temperature control of home appliances. Background Technology

[0002] Home appliances with heating functions, such as electric kettles, need to safely and accurately heat milk to the set temperature and maintain it within a certain constant temperature range.

[0003] Traditional home appliances typically place NTC sensors and PTC heating elements in close proximity. When the PTC heating element operates, it generates continuous heat radiation and conduction, leading to the NTC sensor registering higher temperatures and experiencing significant temperature drift. Furthermore, if the container is made of a material with high thermal conductivity and low thermal inertia, ordinary temperature control algorithms, which only set an endpoint temperature, are prone to overshoot and large temperature fluctuations, making it difficult to maintain a stable temperature within a safe range and negatively impacting the user experience.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses a method and system for precise temperature control of home appliances, in order to solve the problems that temperature control algorithms of home appliances are prone to overshoot, large temperature fluctuations, and negative impacts on user experience.

[0006] The technical solution adopted in this invention is as follows: A method for precise temperature control of home appliances, comprising the following steps: System power on; The system has five preset heating modes: first heating mode, second heating mode, third heating mode, fourth heating mode, and constant temperature heat preservation mode. The temperature ranges corresponding to the five heating modes are sequentially continuous, and the corresponding PWM duty cycle values ​​decrease sequentially. Preliminary heating: The first temperature sensor collects the initial temperature T0 of the liquid inside the container; Determine the temperature range to which T0 belongs and enter the corresponding heating mode; Automatic switching of heating modes: At set intervals, the first temperature sensor collects the current temperature T of the liquid inside the container. 当前 Calculate the heating efficiency k; According to T 当前 The water volume is determined by the temperature range and the heating efficiency range of k, and the corresponding heating mode is entered. Constant temperature insulation: When T 当前Once the temperature falls within the range of the constant temperature insulation mode, the mode will be activated, including the following steps: The first temperature sensor collects the current temperature T in real time. 当前 ; If T 当前 If the temperature exceeds the constant temperature point, the heating element will stop heating. If T 当前 If the temperature is below the lower limit of the constant temperature insulation mode, the heating element will restart.

[0007] The further technical solution involves determining the temperature range to which T0 belongs and then entering the corresponding heating mode, including the following steps: If T0 < 15℃, enter the first heating mode; If 15℃≤T0<25℃, enter the second heating mode; If 25℃≤T0<30℃, enter the third heating mode; If 30℃≤T0<35℃, enter the fourth heating mode; If 35℃≤T0, enter constant temperature insulation mode.

[0008] The further technical solution is that the first PWM duty cycle of the first heating mode is 100%, the second PWM duty cycle of the second heating mode is 80%, the third PWM duty cycle of the third heating mode is 50%, the fourth PWM duty cycle of the fourth heating mode is 30%, and the fifth PWM duty cycle of the constant temperature heat preservation mode is 10%.

[0009] Its further technical solution is, according to T 当前 The steps for determining the water volume and entering the corresponding heating mode, based on the temperature range and the heating efficiency range of k, include: If k < 0.2, 15℃ > T 当前 The system is determined to be at low temperature and full water volume, and then enters the first heating mode. If k < 0.2, 20℃ > T 当前 If the temperature reaches ≥15℃, it is determined that there is too much water, and the second heating mode is activated. If k < 0.2, 30℃ > T 当前 If the temperature is ≥20℃, the water volume is considered appropriate. The system will first enter the second heating mode and then the third heating mode. If 0.4 > k ≥ 0.2, 30℃ > T 当前 If the temperature is ≥20℃, it is determined that the water volume is too low, and the system will switch to the third heating mode. If 0.4 > k ≥ 0.2, T 当前 If the temperature is ≥30℃, it is determined that there is insufficient water and the system will switch to the fourth heating mode.

[0010] A further technical solution is that the formula for calculating the heating efficiency is: k= ; Among them, T 上一时刻 The temperature last collected by the first temperature sensor. t is the time interval between two temperature acquisitions.

[0011] A further technical solution is to set the interval between each heating cycle to 30 seconds.

[0012] The further technical solution is that the first temperature sensor collects the temperature in real time at a frequency of 20ms / time; and the collected temperature of the first temperature sensor is processed by a sliding window averaging filter.

[0013] A further technical solution involves, after calculating the heating efficiency k, the following steps: If k ≥ 0.4, it is determined that the container is dry-burning, and the power supply to the heating element is cut off.

[0014] A further technical solution is that, after the system power-on step, a failure detection step is also included, which includes: The resistance value across the first temperature sensor is detected. If it is within the set value range, it is considered normal. If it is greater than the set value, it is considered that the first temperature sensor is open-circuited. If it is less than the set value, it is considered that the first temperature sensor is short-circuited. After the system power-on procedure, an over-temperature detection procedure is also included, which includes: When the first temperature sensor detects that the current temperature exceeds 45°C, the power supply to the heating element is immediately disconnected.

[0015] The present invention also discloses a system for realizing the aforementioned precise temperature control method for home appliances, characterized in that: the system includes a container body, a heating element is disposed at the bottom of the inner side of the container body, a first temperature sensor is embedded at the upper end of the heating element, and a heat insulation plate is disposed between the heating element and the first temperature sensor; the system also includes a controller, which is electrically connected to the heating element and the first temperature sensor.

[0016] The beneficial effects of the embodiments of the present invention are as follows: (i) The precise temperature control method for household appliances in this invention first detects the initial temperature of the liquid in the container, selects the corresponding heating power for initial heating, then determines the amount of liquid in the container based on the heating situation and heating efficiency, and further selects the appropriate heating power for different amounts of water. Finally, the start and stop of the heating element are controlled by setting a small constant temperature range to stabilize the temperature within the set range, avoiding temperature overshoot and excessive temperature fluctuation range, and taking into account both rapid heating efficiency and constant temperature control. It is especially suitable for containers with fast heat conduction and low thermal inertia.

[0017] (ii) Furthermore, a high-temperature resistant rigid heat insulation plate is installed between the temperature sensor and the heating element to achieve complete thermal isolation, eliminate the interference of the heat source of the heating element with temperature measurement, and improve the temperature measurement accuracy of the temperature sensor.

[0018] (III) Furthermore, a triple overheat protection system is adopted. The first layer utilizes the self-limiting temperature physical properties of PTC ceramic in the heating element, automatically reducing power when the temperature exceeds the limit. The second layer uses a first temperature sensor to collect the temperature, disconnecting the power supply to the heating element when the temperature exceeds the limit. The third layer uses a mechanical temperature sensor at the bottom of the heating element, triggering a mechanical action to disconnect the circuit when the temperature exceeds the limit. By setting up a triple overheat protection system, it is ensured that the failure of any single component will not affect the normal operation of the system, resulting in high safety and reliability. Attached Figure Description

[0019] Figure 1 This is a flowchart of the precise temperature control method for home appliances according to the present invention.

[0020] Figure 2 This is a data graph showing the heating of low-temperature milk using the precise temperature control method for home appliances of this invention.

[0021] Figure 3 This is a structural diagram of the system of the present invention.

[0022] Figure 4 This is a connection diagram of the system of the present invention.

[0023] In the picture: 1. Container body; 2. Heating element; 3. Heat insulation plate; 4. First temperature sensor; 5. Second temperature sensor; 6. Controller. Detailed Implementation

[0024] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0025] First embodiment: This embodiment discloses a method for precise temperature control of home appliances.

[0026] In this embodiment, the liquid in container 1 is described using milk as an example. Of course, the precise temperature control method for household appliances of this application can also be used to heat other fluid foods, and the present invention does not impose further limitations on this.

[0027] Figure 1 This is a flowchart of the precise temperature control method for home appliances according to the present invention. Figure 1 As shown, the method for precise temperature control of home appliances includes the following steps: Step S1: Power on the system.

[0028] Step S2: The system has preset a first heating mode, a second heating mode, a third heating mode, a fourth heating mode, and a constant temperature heat preservation mode. The temperature ranges corresponding to the five heating modes are sequentially continuous, and the corresponding PWM duty cycle values ​​decrease sequentially.

[0029] Specifically, the first PWM duty cycle of the first heating mode is 100%, the second PWM duty cycle of the second heating mode is 80%, the third PWM duty cycle of the third heating mode is 50%, the fourth PWM duty cycle of the fourth heating mode is 30%, and the fifth PWM duty cycle of the constant temperature heat preservation mode is 10%.

[0030] Step S3, initial heating: Step S31: The first temperature sensor 4 collects the initial temperature T0 of the liquid inside the container 1.

[0031] Step S32: Determine the temperature range to which T0 belongs and enter the corresponding heating mode.

[0032] Specifically, the steps for determining the temperature range to which T0 belongs and entering the corresponding heating mode include: Step S321: If T0 < 15℃, enter the first heating mode.

[0033] Step S322: If 15℃≤T0<25℃, enter the second heating mode.

[0034] Step S323: If 25℃≤T0<30℃, enter the third heating mode.

[0035] Step S324: If 30℃≤T0<35℃, enter the fourth heating mode.

[0036] Step S325: If 35℃≤T0, enter the constant temperature insulation mode.

[0037] Step S4, automatically switch heating modes: Step S41: At a set interval, the first temperature sensor 4 collects the current temperature T of the liquid inside container 1. 当前 Calculate the heating efficiency k.

[0038] Specifically, the interval between each heating cycle is set to 30 seconds.

[0039] The first temperature sensor 4 acquires temperature data in real time at a frequency of 20ms / time. Preferably, the temperature acquired by the first temperature sensor 4 is processed by a sliding window averaging filter. A sliding window of length 5 is used to preprocess the continuously acquired temperature data, calculate the average value as the effective temperature value, and eliminate random noise and electromagnetic interference.

[0040] The formula for calculating heating efficiency is: k= ; Among them, T 上一时刻 The temperature measured by the first temperature sensor 4 in the previous test. t is the time interval between two temperature acquisitions.

[0041] Step S42, according to T 当前 The system determines the water volume by analyzing the temperature range and the heating efficiency range of k, and then enters the corresponding heating mode.

[0042] Specifically, according to T 当前 The steps for determining the water volume and entering the corresponding heating mode, based on the temperature range and the heating efficiency range of k, include: Step S421, if k < 0.2, 15℃ > T 当前 If the water level is determined to be at low temperature and full capacity, the system will enter the first heating mode.

[0043] Step S422, if k < 0.2, 20℃ > T 当前 If the temperature reaches ≥15℃, it is determined that there is too much water, and the second heating mode will be activated.

[0044] Step S423, if k < 0.2, 30℃ > T 当前 If the temperature is ≥20℃, the water volume is considered appropriate. The system will first enter the second heating mode and then the third heating mode.

[0045] Step S424: If 0.4 > k ≥ 0.2, 30℃ > T 当前 If the temperature is ≥20℃, it is determined that the water volume is too low, and the system will switch to the third heating mode.

[0046] Step S425, if 0.4 > k ≥ 0.2, T 当前 If the temperature is ≥30℃, it is determined that there is insufficient water and the system will switch to the fourth heating mode.

[0047] According to the heat absorption formula: Where, Q: absorbed heat (J); c: specific heat capacity of milk, 3900 J / (kg·℃); m: milk mass (kg), 1L milk ≈ 1.03kg; ΔT: temperature difference, ΔT = T_final - T_initial (℃) Formula for power doing work: Where P: heating power (W); t: heating time (s).

[0048] Combining the above formulas, we get: Due to t, c, P, T 当前 T 上一时刻 Since all parameters are known, m can be deduced from them.

[0049] Step S5, constant temperature insulation: When T 当前Once the temperature falls within the range of the constant temperature insulation mode, the mode will be activated, including the following steps: Step S51, the first temperature sensor 4 collects the current temperature T in real time. 当前 .

[0050] Step S52, if T 当前 If the temperature exceeds the constant temperature point, heating element 2 will stop heating.

[0051] Step S53, if T 当前 If the temperature is below the lower limit of the constant temperature insulation mode, the heating element 2 will restart.

[0052] Specifically, controller 67 can dynamically fine-tune the PWM duty cycle. When T 当前 When the temperature reaches ≥37℃, immediately stop heating with heating element 22. When the temperature drops to 34℃, restart heating with heating element 22 and stabilize the temperature within the range of 37℃±3℃.

[0053] Furthermore, after calculating the heating efficiency k, the following steps are also included: Step S43: If k≥0.4, it is determined that container 1 is dry-burning, and the power supply to heating element 2 is cut off.

[0054] Furthermore, after the system power-on procedure, a failure detection procedure is also included, which includes: Step S11: Detect the resistance value across the first temperature sensor 4. If it is within the set value range, it is considered normal. If it is greater than the set value, it is considered that the first temperature sensor 4 is open-circuited. If it is less than the set value, it is considered that the first temperature sensor 4 is short-circuited.

[0055] After the system power-on procedure, an over-temperature detection procedure is also included, which includes: Step S12: When the first temperature sensor 4 detects that the current temperature exceeds 45°C, the power supply to the heating element 2 is immediately disconnected.

[0056] The milk was heated using the precise temperature control method for household appliances described in this embodiment. The temperature was measured during the warming process, and the results are as follows: Figure 2 As shown, the average power variation matches the method of this application. Figure 2 This is a data graph showing the heating of low-temperature milk using the precise temperature control method for home appliances of this invention.

[0057] In this embodiment, the initial temperature of the liquid in container 1 is detected first, and the corresponding heating power is selected for initial heating. Then, the amount of liquid in container 1 is determined based on the heating situation and heating efficiency. Then, a suitable heating power is selected for different amounts of liquid. Finally, the start and stop of the heating element 2 is controlled by setting a small constant temperature range to stabilize the temperature within the set range. This avoids temperature overshoot and excessive temperature fluctuation range, and takes into account both rapid heating efficiency and constant temperature control. It is especially suitable for container 1 with fast heat conduction and low thermal inertia.

[0058] Second embodiment: This embodiment discloses a system for implementing the precise temperature control method for home appliances in the first embodiment.

[0059] Figure 3 This is a structural diagram of the system of the present invention. Figure 4 This is a connection diagram of the system of the present invention. For example... Figure 3 and Figure 4 As shown, the system includes a container body 1, a heating element 2 disposed at the bottom inner side of the container body 1, a first temperature sensor 4 embedded at the upper end of the heating element 2, and a heat insulation plate 3 disposed between the heating element 2 and the first temperature sensor 4. The system also includes a controller 6, which is electrically connected to the heating element 2 and the first temperature sensor 4.

[0060] For example, the container body 1 is made of metal, preferably stainless steel, and the PWM duty cycle and heating time are adjusted accordingly based on the material. The controller 6 can be a commercially available PLC controller 6. The first temperature sensor 4 is an NTC temperature sensor. The heating element 2 is made of PTC ceramic with a Curie point temperature of 120°C. Above this temperature, the resistance increases sharply, and the power automatically drops to an extremely low level.

[0061] like Figure 3 and Figure 4 As shown, a second temperature sensor 55 is further provided at the lower end of the heating element 22. The second temperature sensor 55 is a mechanical temperature sensor with a trigger temperature of 120°C. When the temperature reaches 120°C, the bimetallic strip activates, physically disconnecting the main circuit. In other embodiments of the present invention, the second temperature sensor 55 may also be a fuse or a manually reset temperature limiter, etc., as long as it can generate mechanical action and disconnect the circuit according to temperature changes. The present invention does not impose further limitations on this.

[0062] In this embodiment, a high-temperature resistant rigid heat insulation plate 3 is provided between the temperature sensor and the heating element 2 to achieve complete thermal isolation, eliminate the interference of the heat source of the heating element 2 with temperature measurement, and improve the temperature measurement accuracy of the temperature sensor.

[0063] It should be noted that the steps described in this manual do not necessarily have a strict sequential order. Without affecting the implementation of the relevant functions, the steps can be adjusted, combined, or split according to actual needs, and some steps can be selected for execution based on the specific application scenario; steps that can be executed in parallel can also be executed simultaneously or alternately. Unless otherwise explicitly specified, the numbering or order of the steps should not be construed as a limitation on the order of execution.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for precise temperature control in home appliances, characterized by: The precise temperature control method for home appliances includes the following steps: System power-on; The system has five preset heating modes: first heating mode, second heating mode, third heating mode, fourth heating mode, and constant temperature heat preservation mode. The temperature ranges corresponding to the five heating modes are sequentially continuous, and the corresponding PWM duty cycle values ​​decrease sequentially. Preliminary heating: The first temperature sensor collects the initial temperature T0 of the liquid inside the container; Determine the temperature range to which T0 belongs and enter the corresponding heating mode; Automatic switching of heating modes: At set intervals, the first temperature sensor collects the current temperature T of the liquid inside the container. 当前 Calculate the heating efficiency k; According to T 当前 The water volume is determined by the temperature range and the heating efficiency range of k, and the corresponding heating mode is entered. Constant temperature insulation: When T 当前 Once the temperature falls within the range of the constant temperature insulation mode, the mode will be activated, including the following steps: The first temperature sensor collects the current temperature T in real time. 当前 ; If T 当前 If the temperature exceeds the constant temperature point, the heating element will stop heating. If T 当前 If the temperature is below the lower limit of the constant temperature insulation mode, the heating element will restart.

2. The method for precise temperature control of household appliances according to claim 1, characterized in that: The steps for determining the temperature range to which T0 belongs and entering the corresponding heating mode include: If T0 < 15℃, enter the first heating mode; If 15℃≤T0<25℃, enter the second heating mode; If 25℃≤T0<30℃, enter the third heating mode; If 30℃≤T0<35℃, enter the fourth heating mode; If 35℃≤T0, enter constant temperature insulation mode.

3. The method for precise temperature control of household appliances according to claim 2, characterized in that: The first PWM duty cycle of the first heating mode is 100%, the second PWM duty cycle of the second heating mode is 80%, the third PWM duty cycle of the third heating mode is 50%, the fourth PWM duty cycle of the fourth heating mode is 30%, and the fifth PWM duty cycle of the constant temperature heat preservation mode is 10%.

4. The method for precise temperature control of household appliances according to claim 3, characterized in that: According to T 当前 The steps for determining the water volume and entering the corresponding heating mode, based on the temperature range and the heating efficiency range of k, include: If k < 0.2, 15℃ > T 当前 The system is determined to be at low temperature and full water volume, and then enters the first heating mode. If k < 0.2, 20℃ > T 当前 If the temperature reaches ≥15℃, it is determined that there is too much water, and the second heating mode is activated. If k < 0.2, 30℃ > T 当前 If the temperature is ≥20℃, the water volume is considered appropriate. The system will first enter the second heating mode and then the third heating mode. If 0.4 > k ≥ 0.2, 30℃ > T 当前 If the temperature is ≥20℃, it is determined that the water volume is too low, and the system will switch to the third heating mode. If 0.4 > k ≥ 0.2, T 当前 If the temperature is ≥30℃, it is determined that there is insufficient water and the system will switch to the fourth heating mode.

5. The method for precise temperature control of household appliances according to claim 1, characterized in that: The formula for calculating the heating efficiency is: k= ; Among them, T 上一时刻 The temperature last collected by the first temperature sensor. t is the time interval between two temperature acquisitions.

6. The method for precise temperature control of household appliances according to claim 1, characterized in that: The interval between each heating cycle is set to 30 seconds.

7. The method for precise temperature control of household appliances according to claim 1, characterized in that: The first temperature sensor acquires the temperature in real time at a frequency of 20ms / time; the acquired temperature is processed by a sliding window averaging filter.

8. The method for precise temperature control of household appliances according to claim 1, characterized in that: After calculating the heating efficiency k, the following steps are also included: If k ≥ 0.4, it is determined that the container is dry-burning, and the power supply to the heating element is cut off.

9. The method for precise temperature control of household appliances according to claim 1, characterized in that: Following the system power-on procedure, a failure detection procedure is also included, which includes: The resistance value across the first temperature sensor is detected. If it is within the set value range, it is considered normal. If it is greater than the set value, it is considered that the first temperature sensor is open-circuited. If it is less than the set value, it is considered that the first temperature sensor is short-circuited. After the system power-on procedure, an over-temperature detection procedure is also included, which includes: When the first temperature sensor detects that the current temperature exceeds 45°C, the power supply to the heating element is immediately disconnected.

10. A system for implementing the precise temperature control method for household appliances according to any one of claims 1 to 9, characterized in that: The system includes a container body, a heating element is disposed at the bottom inside the container body, a first temperature sensor is embedded at the upper end of the heating element, and a heat insulation plate is disposed between the heating element and the first temperature sensor; the system also includes a controller, which is electrically connected to the heating element and the first temperature sensor.

Images