Method for detecting inner liner of electric heating cooking utensil and inner liner of electric heating cooking utensil
By measuring the impedance of the inner pot of an electric heating cooking appliance and acquiring dynamic excitation signals, the problem of difficulty in detecting the electrical isolation characteristics between the heating element and the container is solved, enabling early identification of assembly deviations and poor fit, and improving the effectiveness and reliability of the detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG HUAQIANG ELECTRICAL APPLIANCE GROUP
- Filing Date
- 2026-03-04
- Publication Date
- 2026-05-29
Smart Images
Figure CN122109632A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of product testing technology, and in particular to a testing method for the inner pot of an electric heating cooking appliance and the inner pot of the electric heating cooking appliance. Background Technology
[0002] The inner pot of an electric cooker typically includes a container for holding food and liquids, and a heating element located at the bottom of the container. To meet safety and reliability requirements, the heating element is usually isolated from the container by insulating materials, such as mica sheets, during assembly. This ensures that the heating element can effectively transfer heat to the container during heating while preventing electrical connection between the heating element and the container, thus guaranteeing the product's electrical safety.
[0003] After the inner liner is manufactured, the performance of the heating element is usually tested to confirm whether it meets the factory requirements. Existing testing methods mainly focus on whether the heating element can operate normally by powering on. For example, by measuring the resistance value across the heating element or the operating current after power is applied, it can be determined whether there is an open circuit, short circuit, or abnormal resistance value in the resistance wire. This type of testing method can verify the basic conductivity of the heating element, but its testing object is mainly focused on the heating circuit itself.
[0004] However, since the heating element is isolated from the bottom of the container by a mica sheet after assembly and is fixed to the bottom of the container as a whole, the assembly status and isolation characteristics between the heating element and the container are difficult to observe directly in the finished inner liner. Relying solely on detecting the continuity of the heating circuit is insufficient to reflect whether the isolation between the heating element and the container is uniform and reliable, and it is also difficult to promptly detect potential problems caused by assembly deviations, poor local fitting, etc. Therefore, how to effectively test the electrical isolation characteristics between the heating element and the container during the production testing stage without disassembling the inner liner has become a technical problem that needs to be solved in the existing technology. Summary of the Invention
[0005] This application provides a method for detecting the inner pot of an electric heating cooking appliance. It aims to solve the problem that in existing electric heating cooking appliances, after the heating component is packaged, it is difficult to effectively detect the electrical isolation characteristics between the heating component and the container by only detecting the conduction status of the heating circuit. As a result, it is impossible to detect in time the technical problems that may be caused by assembly deviations or poor fit.
[0006] This invention is implemented as follows: a method for detecting the inner pot of an electrically heated cooking appliance, the inner pot comprising a container and a heating element disposed at the bottom of the container and electrically isolated therefrom, the heating element having a first power supply terminal and a second power supply terminal, the detection method comprising: Impedance measurements were performed between the first power supply terminal and the container, and between the second power supply terminal and the container, respectively, to obtain a first measurement value characterizing the electrical characteristics between the first power supply terminal and the container, and a second measurement value characterizing the electrical characteristics between the second power supply terminal and the container. The detection result of the inner liner is output based on the first measurement value and the second measurement value.
[0007] Optionally, the process of performing the impedance measurement includes: A dynamic excitation signal is applied to the first two-end network formed between the first power supply terminal and the container, the first dynamic response of the first two-end network is acquired, and the first measured value characterizing the equivalent impedance characteristics of the first two-end network is determined based on the first dynamic response. A dynamic excitation signal is applied to the second two-terminal network formed between the second power supply terminal and the container, the second dynamic response of the second two-terminal network is acquired, and the second measured value characterizing the equivalent impedance characteristics of the second two-terminal network is determined based on the second dynamic response.
[0008] Optionally, the dynamic excitation signal is a step excitation signal; The process of determining measured values based on dynamic response includes: The time required for the voltage or current response of the first two-terminal network to change from the initial response value at the moment the step excitation signal is applied to a preset threshold is used as the first measured value; The time required for the voltage or current response of the second two-terminal network to change from the initial response value at the moment the step excitation signal is applied to a preset threshold is measured as the second measured value.
[0009] Optionally, before applying the step excitation signal, the method further includes: The first power supply terminal, the second power supply terminal, and the container are connected to a reference potential through a preset discharge circuit and maintained for a preset time to eliminate residual charge in the first and second end networks. The preset discharge circuit is disconnected after the preset duration ends.
[0010] Optionally, the impedance measurement is performed when the container is subjected to at least two different pressures, including: Under the condition of applying a first preset pressure vertically downward to the bottom of the container, the impedance measurement is performed to obtain a first measurement value and a second measurement value under the first force state; Under the condition of applying a second preset pressure vertically downward to the bottom of the container, the impedance measurement is performed to obtain the first measurement value and the second measurement value under the second force state; Wherein, the first preset pressure is less than the second preset pressure.
[0011] Optionally, the output detection result includes: Determine whether the first measured value under the first stress state, the second measured value under the first stress state, the first measured value under the second stress state, and the second measured value under the second stress state are all within the preset qualified range; Determine whether the first measured value and the second measured value under the first stress state meet the preset consistency condition, and whether the first measured value and the second measured value under the second stress state meet the preset consistency condition; Determine whether the first change between the first measured value under the first stress state and the first measured value under the second stress state, and the second change between the second measured value under the first stress state and the second measured value under the second stress state, are both within a preset range of change. If all the above judgment conditions are met, output the test result that the inner liner is qualified; otherwise, output the test result that the inner liner is unqualified.
[0012] Optionally, the output detection result includes: Determine whether both the first measured value and the second measured value are within a preset acceptable range; Determine whether the first measured value and the second measured value meet a preset consistency condition; When both the first and second measured values are within the preset acceptable range and meet the preset consistency condition, the test result indicating that the inner liner is qualified is output; otherwise, the test result indicating that the inner liner is unqualified is output.
[0013] Optionally, the preset consistency condition includes: the difference or ratio between the first measured value and the second measured value is within a preset consistency range.
[0014] The present invention also provides an inner pot for an electrically heated cooking appliance, including a container and a heating element. The heating element is disposed at the bottom of the container and electrically isolated from the container. The heating element has a first power supply terminal and a second power supply terminal. The electrical characteristics formed between the first power supply terminal and the container, and between the second power supply terminal and the container, can be characterized by impedance measurement.
[0015] Optionally, the heating component includes an insulating base, an upper mica sheet, a middle mica sheet, a lower mica sheet, and a resistance wire. The insulating base is detachably fixed to the bottom of the container and forms an installation cavity with the container. The upper mica sheet, the middle mica sheet, and the lower mica sheet are all installed in the installation cavity, and the upper mica sheet, the middle mica sheet, and the lower mica sheet are stacked sequentially from the container to the insulating base. The resistance wire is wound around the middle mica sheet, and multiple parallel heating sections are formed on both sides of the middle mica sheet. The two extended ends of the resistance wire extend out of the insulating base to form the first power supply terminal and the second power supply terminal, respectively.
[0016] The technical solution provided in this application embodiment, under the condition that the inner liner remains assembled and its components are not disassembled, performs impedance measurements between the first power supply terminal and the container, and between the second power supply terminal and the container, respectively, to obtain the first and second measured values, and outputs the test results accordingly. This process shifts the detection object from the heating circuit body to the electrical isolation characteristics between the heating component and the container, so that even if the heating component is isolated by the mica sheet and fixed to the bottom of the container, it can still form a measurable two-end network with the container metal body through the externally accessible terminals, thereby indirectly characterizing the internal isolation state of the package. Since the terminal and the container are not electrically connected, but rather formed by an electrical coupling path through an insulating medium, the value obtained by the impedance measurement can reflect the overall state of the coupling path. When the isolation structure is in a normal assembly state, the coupling characteristics between the terminal and the container are relatively stable, and the measured impedance characteristics should fall within a preset range with product consistency. However, when there are assembly deviations or poor fits that cause deviations in local gaps, contact areas, or medium states, the electrical characteristics of the coupling path will change accordingly, thus showing a deviation in the impedance measurement value.
[0017] Simultaneously, measurements are taken on the first terminal and the container, and the second terminal and the container respectively, so that the detection does not rely on the value of a single path, but forms two sets of comparative characterization information. Since the two terminals correspond to the same heating component and are located within the same container structure, the two sets of measurements are usually similar and repeatable when the isolation structure is normal. If there is a local fitting abnormality or assembly difference in the terminal lead area on one side, it is more likely to show a significant deviation in the measurement value of the corresponding path. By comprehensively judging the above measurement values, the isolation-related status can be pre-diagnosed and health managed before the heating component has a conduction abnormality or safety failure. Thus, under the condition that the internal structure is not visible and inaccessible, the uniformity and reliability of the isolation between the heating component and the container can be assessed, making up for the insufficiency of simply detecting the conduction status of the heating circuit, which is difficult to cover potential risks. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of an embodiment of the detection method for the inner pot of an electrically heated cooking appliance of the present invention; Figure 2 This is a schematic diagram of the structure of an embodiment of the inner pot of the electric heating cooking appliance of the present invention; Figure 3 for Figure 2 Exploded view of the inner pot of a medium-electric heating cooking appliance; Figure 4 for Figure 3 A magnified view of a portion of point A in the middle.
[0020] Explanation of icon numbers: 1. Container; 2. Heating element; 21. Insulating base; 22. Upper mica sheet; 23. Middle mica sheet; 231. Limiting notch; 24. Lower mica sheet; 25. Resistance wire; 251. Heating section; 252. First power supply terminal; 253. Second power supply terminal.
[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0022] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0023] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.
[0024] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the term "and / or" throughout the text includes three solutions; taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that simultaneously satisfies A and B. Furthermore, the technical solutions of various embodiments can be combined with each other, provided that they are feasible for those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0025] Figure 1 The implementation flow of the detection method for the inner pot of an electrically heated cooking appliance provided in this embodiment is shown. For ease of explanation, only the parts relevant to this embodiment are shown, and are described in detail below: The inner liner includes a container and a heating element disposed at the bottom of the container and electrically isolated from the container. The heating element has a first power supply terminal and a second power supply terminal. The detection method includes: Please see Figure 1 Impedance measurements were performed between the first power supply terminal and the container, and between the second power supply terminal and the container, respectively, to obtain a first measurement value characterizing the electrical characteristics between the first power supply terminal and the container, and a second measurement value characterizing the electrical characteristics between the second power supply terminal and the container. The detection result of the inner liner is output based on the first measurement value and the second measurement value.
[0026] In one embodiment of the present invention, the process of performing the impedance measurement includes: A dynamic excitation signal is applied to the first two-end network formed between the first power supply terminal and the container, the first dynamic response of the first two-end network is acquired, and the first measured value characterizing the equivalent impedance characteristics of the first two-end network is determined based on the first dynamic response. A dynamic excitation signal is applied to the second two-terminal network formed between the second power supply terminal and the container, the second dynamic response of the second two-terminal network is acquired, and the second measured value characterizing the equivalent impedance characteristics of the second two-terminal network is determined based on the second dynamic response.
[0027] Specifically, in impedance measurement, the first two-terminal network refers to the electrical path formed between the first power supply terminal and the container (the container is a metal body), and the second two-terminal network refers to the electrical path formed between the second power supply terminal and the metal body of the container. Since the heating element is located at the bottom of the container and isolated from it by a mica sheet, the aforementioned two-terminal networks do not form a DC conductive loop. Instead, they form an electrical coupling relationship through the isolation medium and their contact state, allowing the two-terminal networks to exhibit measurable impedance characteristics when excited. The dynamic excitation signal is a time-varying electrical signal applied to the two-terminal networks. Its purpose is to induce a time-varying voltage or current response in the originally statically isolated two-terminal networks, thereby providing an observable signal basis for obtaining the impedance characteristics. The dynamic response refers to the process of voltage or current change in the two-terminal networks over time under the action of the dynamic excitation signal.
[0028] When measuring the first two-terminal network, the first power supply terminal and the container are respectively connected to the measurement channel, so that the dynamic excitation signal acts only between the first power supply terminal and the container. The dynamic excitation signal is preferably a step excitation signal, that is, the voltage or current applied to the first two-terminal network is rapidly switched from its initial value to a preset amplitude at a preset time, and maintained at that amplitude for a period of time. The amplitude of the step excitation signal is selected within a range that does not damage the isolation medium and does not introduce a risk of breakdown. While applying the step excitation signal, the voltage or current of the first two-terminal network is continuously sampled to obtain the first dynamic response. The first dynamic response reflects the charging, discharging, or attenuation process of the first two-terminal network under step excitation, a process influenced by factors such as the thickness of the isolation medium, the bonding area, and local gaps.
[0029] When determining the first measured value based on the first dynamic response, a threshold timing method can be used. Specifically, after applying a step excitation signal, the time required for the voltage or current response of the first two-terminal network to change from the initial response value to a preset threshold is recorded, and this time is used as the first measured value. The preset threshold is selected as the voltage or current value within the stable change range of the response curve, so that the measured value is neither affected by the initial transient jitter nor dependent on the accurate measurement of the final steady-state value. Time is used as the measured value because, under high insulation conditions, the coupling difference between the terminal and the container is often difficult to distinguish directly by amplitude, while the time characteristics in the step response process can stably reflect the change in equivalent impedance, giving the first measured value good repeatability and discriminability in production testing environments.
[0030] When measuring the second-terminal network, the application target of the dynamic excitation signal is switched from the first power supply terminal to the second power supply terminal, so that the dynamic excitation signal acts between the second power supply terminal and the container, while keeping other measurement conditions consistent. After applying the step excitation signal, the voltage dynamic response or current dynamic response of the second-terminal network is acquired to obtain the second dynamic response. Based on the second dynamic response, the second measurement value is determined using the same threshold timing method as the first measurement value. By acquiring the first and second measurement values under the same excitation conditions and processing methods, the two measurement paths are made comparable, thereby reflecting the isolation characteristics of the heating component in different terminal lead-out areas at the bottom of the container.
[0031] After obtaining the first and second measurement values, they can be used for the output of subsequent test results. Since the first and second end networks are under the same container structure and the same isolation medium, when the isolation between the heating element and the container is uniform and the assembly is reliable, the equivalent impedance characteristics of the two measurement paths are usually in a similar range. However, when there is a localized poor fit, a misalignment of the isolation medium, or an abnormal assembly in the lead-out area on one side, the dynamic response process of the corresponding path will change, resulting in a deviation in the measurement value. Through this method, the isolation-related characteristics between the heating element and the container can be measured practically without disassembling the inner liner or directly contacting the internal structure.
[0032] In other embodiments, the dynamic excitation signal may also be a pulse excitation signal, and the measured value may be determined based on the decay time of the current or voltage after pulse excitation; or a single-frequency sinusoidal excitation signal may be used, and the measured value may be determined based on the impedance amplitude under steady-state conditions.
[0033] In one embodiment of the present invention, the dynamic excitation signal is a step excitation signal; The process of determining measured values based on dynamic response includes: The time required for the voltage or current response of the first two-terminal network to change from the initial response value at the moment the step excitation signal is applied to a preset threshold is used as the first measured value; The time required for the voltage or current response of the second two-terminal network to change from the initial response value at the moment the step excitation signal is applied to a preset threshold is measured as the second measured value.
[0034] Specifically, when acquiring the first measured value, the voltage response or current response refers to the process by which the voltage or current in the first two-terminal network changes over time after a step excitation signal is applied to the first two-terminal network. The initial response value at the moment the step excitation signal is applied refers to the voltage or current value exhibited by the first two-terminal network at the instant the step excitation signal switches from its initial state to a preset amplitude. Since the first two-terminal network is formed between the first power supply terminal and the container, separated by an isolation medium such as a mica sheet, the application of the step excitation signal does not create DC conduction but instead triggers a charging / discharging or attenuation process determined by the coupling characteristics of the isolation medium. Therefore, this initial response value typically corresponds to the initial state at the instant the step excitation is applied and is used as the starting point for subsequent time measurements.
[0035] In the specific implementation process, while the step excitation signal is applied to the first two-terminal network, the voltage or current of the first two-terminal network is continuously sampled, and the trajectory of the voltage or current response over time is determined from the sampled data. The preset threshold is a pre-set voltage or current value that lies within the stable range of the response change process; it is higher than the initial response value but lower than the final steady-state response value, ensuring that the response curve remains in a monotonic change phase when it reaches this threshold. By judging the sampled data, the time point at which the voltage or current response first changes from the initial response value and reaches the preset threshold is determined, and the time length from the application of the step excitation signal to this time point is determined as the first measured value.
[0036] The reason for using the aforementioned time as the first measurement value is that the response speed of the first two-end network under step excitation is directly affected by its equivalent impedance characteristics. The bonding area of the insulating medium, the local gaps, and the structural state of the lead-out area in the first two-end network all affect the speed of this response process, thus manifesting in the difference in the time required to reach the same threshold. By selecting time rather than amplitude as the measurement result, the problem of insufficient amplitude variation under high insulation conditions, making stable differentiation difficult, can be avoided. This also reduces the requirements for measurement accuracy and environmental stability, making this measurement method more suitable for repeated implementation in production testing scenarios.
[0037] When measuring the second measured value, the implementation process is consistent with that of the first measured value, except that the application target of the step excitation signal is switched from the first power supply terminal to the second power supply terminal, so that the step excitation signal acts on the second-terminal network formed between the second power supply terminal and the container. Simultaneously with the application of the step excitation signal, the voltage or current response of the second-terminal network is continuously sampled, and the time required for the response value to change from the initial value at the moment the step excitation signal is applied to the same preset threshold is determined, which is then used as the second measured value. By obtaining the first and second measured values under the same excitation conditions, the same threshold conditions, and the same sampling method, the two values are well comparable, thereby reflecting the isolation-related electrical characteristics of the heating component at different terminal lead-out positions at the bottom of the container.
[0038] In one embodiment of the present invention, before applying the step excitation signal, the method further includes: The first power supply terminal, the second power supply terminal, and the container are connected to a reference potential through a preset discharge circuit and maintained for a preset time to eliminate residual charge in the first and second end networks. The preset discharge circuit is disconnected after the preset duration ends.
[0039] It should be noted that before applying the step excitation signal, connecting the first and second power supply terminals to the reference potential via a preset discharge circuit and maintaining this connection for a preset duration ensures that the first and second terminal networks are in a consistent and controllable initial electrical state before impedance measurement. Since the first and second terminal networks are formed by the power supply terminals and the container, and are electrically coupled through an isolation medium, residual charge may remain in these networks due to previous detection steps, handling processes, or environmental interference. This can lead to uncertainty in the initial state of the voltage or current response at the moment the step excitation signal is applied. If this residual charge is not addressed, the initial response values of different inner containers or the same inner container at different detection times may deviate, affecting the comparability and repeatability of subsequent time-based measurement results.
[0040] In practical implementation, the preset discharge circuit is used to connect the first power supply terminal, the second power supply terminal, and the container to a reference potential without introducing additional excitation, allowing residual charge in the networks at both ends to be gradually released through the discharge path. The reference potential can be a common reference point in the detection system, used to define a unified potential benchmark. Maintaining the preset duration ensures that the discharge process is fully completed, allowing the charge state formed by the coupling of the isolation medium in the networks at both ends to tend to stabilize. The preset duration is selected based on the detection cycle and network response characteristics, and its length should cover the time range required for the charge in the networks at both ends to decay to a stable state, thereby avoiding incomplete elimination of residual charge due to excessively short discharge, or impact on overall detection efficiency due to excessively long discharge.
[0041] After the preset duration, the preset discharge circuit is disconnected, causing the first and second power supply terminals to disconnect from the container and enter the test state. At this time, the first and second terminal networks are electrically unified and have repeatable initial conditions, providing a consistent starting point for applying a step excitation signal and acquiring the dynamic response. Through the above discharge and disconnection process, the influence of residual charge on the initial response value can be effectively avoided, and the time characteristics measured subsequently are mainly determined by the equivalent impedance characteristics of the terminal networks themselves, thereby improving the stability and repeatability of the impedance measurement results.
[0042] In one embodiment of the invention, the impedance measurement is performed when the container is subjected to at least two different pressures, including: Under the condition of applying a first preset pressure vertically downward to the bottom of the container, the impedance measurement is performed to obtain a first measurement value and a second measurement value under the first force state; Under the condition of applying a second preset pressure vertically downward to the bottom of the container, the impedance measurement is performed to obtain the first measurement value and the second measurement value under the second force state; Wherein, the first preset pressure is less than the second preset pressure.
[0043] In this embodiment, impedance measurements are performed separately when the container is subjected to at least two different pressures. This is to extend the measurement state from a lightly loaded, freely placed state to a compressed state that more closely resembles the actual assembly during the production testing phase, ensuring that the first and second end networks obtain comparable impedance measurement values under both stress conditions. Since the heating element is fixed to the bottom of the container and isolated from it by a mica sheet, the end networks between the terminals and the container depend not only on the isolation medium itself but also on the contact state between the heating element and the bottom of the container, local gaps, and the contact area after stress. When measuring only under a single stress state, if there are assembly deviations such as local warping, foreign matter inclusions, or uneven contact at the bottom of the container, some abnormalities may be masked by accidental contact in the free state. Extending the measurement to a higher compressive force allows for a more complete contact between the bottom of the container and the heating element or makes abnormal gaps more stable, thereby making the impedance measurement value more sensitive to assembly consistency and improving the repeatability of the test results.
[0044] When performing impedance measurements under a first preset downward pressure applied to the bottom of the container, this first preset pressure provides stable placement and contact conditions, ensuring a reliable electrical connection between the container and the measurement reference terminal, and making the initial state of the two-terminal networks repeatable. Specifically, the inner liner is placed at the testing station, and a preset volume of liquid is added to the container to create the first preset pressure. For example, a specified volume of water is added to the container, allowing the water's own weight to act on the bottom of the container, creating a stable and easily repeatable downward vertical pressure. Subsequently, impedance measurements are performed on the first and second-terminal networks under this pressure condition, yielding the first and second measured values under the first pressure condition. The advantage of using liquid pressure is that the pressure distribution formed by the liquid's own weight is relatively uniform, allowing for simple reproduction of light-load conditions without introducing additional local hard contact points, thus reducing the dispersion caused by manual force application. This measured value reflects the isolation-related impedance characteristics of the inner liner under light-load placement conditions and can be used to establish the acceptable range and terminal consistency reference under light-load conditions.
[0045] When performing impedance measurements under a second preset downward pressure applied to the bottom of the container, this second preset pressure is greater than the first preset pressure. This is used to reproduce a stress state closer to the actual assembly or installation clamping conditions, resulting in a more complete and stable fit between the container bottom and the heating element. Specifically, a first preset volume of liquid can be kept constant inside the container, and a reloadable weight or pressure plate can be placed at the container opening to generate an additional downward vertical force on the bottom of the container, thus forming the second preset pressure. Under this second stress state, impedance measurements are then performed again on the first and second end networks, respectively, yielding the first and second measured values under the second stress state. By keeping the excitation conditions, sampling conditions, and threshold conditions consistent for both measurements, and only changing the stress state, the variations in the measured values can be made primarily from differences in the contact area, local gaps, and structural clamping conditions. If the assembly is normal, the changes in the measured values under both light load and compression conditions will be stable and fall within the preset range. If there is local poor fit or assembly deviation, the compression condition will make the abnormal features more concentrated, manifested as abnormal deviations in the measured values or inconsistencies between terminals, thus providing more discriminative information for subsequent test results output.
[0046] In other embodiments, the first preset pressure and the second preset pressure can also be achieved in different ways. For example, the first preset pressure is generated by placing the container without a load, and the second preset pressure is generated by placing a specified mass of solid load in the container; or the first preset pressure is generated by a single liquid load, and the second preset pressure is generated by increasing the liquid volume or adding solid loads.
[0047] In one embodiment of the present invention, the output detection result includes: Determine whether the first measured value under the first stress state, the second measured value under the first stress state, the first measured value under the second stress state, and the second measured value under the second stress state are all within the preset qualified range; Determine whether the first measured value and the second measured value under the first stress state meet the preset consistency condition, and whether the first measured value and the second measured value under the second stress state meet the preset consistency condition; Determine whether the first change between the first measured value under the first stress state and the first measured value under the second stress state, and the second change between the second measured value under the first stress state and the second measured value under the second stress state, are both within a preset range of change. If all the above judgment conditions are met, output the test result that the inner liner is qualified; otherwise, output the test result that the inner liner is unqualified.
[0048] In embodiments where measurements are obtained under multiple stress states, the output of detection results is accomplished through multi-dimensional judgment. First, determining whether the first measurement under the first stress state, the second measurement under the first stress state, the first measurement under the second stress state, and the second measurement under the second stress state are all within a preset acceptable range is a judgment of the absolute effectiveness of each measurement path under different stress conditions. The preset acceptable range defines the allowable interval of the equivalent impedance characteristics between the terminal and the container. When a measurement value significantly deviates from this range, it indicates that the isolation-related state of the corresponding two-end networks has exceeded the normal fluctuation range, and even if other conditions are met, it is insufficient to conclude that the inner liner is in a healthy state. By performing range judgment on the four measurements separately, it is possible to avoid overlooking results due to a single stress state or an abnormal terminal path, thereby improving the comprehensiveness of the detection.
[0049] Based on the absolute range determination, it is further determined whether the first and second measured values under the first stress state, and the first and second measured values under the second stress state, meet the preset consistency conditions. This consistency condition is used to compare the relative relationship between the two measurement paths under the same stress state. Since the first and second end networks are located in the same container structure and isolation medium environment, under normal assembly conditions, the equivalent impedance characteristics of the two paths should have similar magnitudes and trends. If there is local misfitting, assembly deviation in the lead-out area, or local structural abnormalities on one side, it is more likely to manifest as inconsistencies in the measured values between the two paths. Through consistency determination, local anomalies can be identified by utilizing the comparative relationship of symmetrical structures without relying on absolute numerical accuracy, thereby enhancing the sensitivity of the detection to non-uniform assembly problems.
[0050] Under the premise of satisfying the above two conditions, it is further determined whether the change between the first stress state and the second stress state is within the preset change range. Specifically, the first change between the first measured value under the first stress state and the first measured value under the second stress state, and the second change between the second measured value under the first stress state and the second measured value under the second stress state are compared. This change reflects the degree of response of the equivalent impedance characteristics of the two-end network during the transition from a light load state to a compressed state. For an inner liner with normal assembly and stable fit, the changes in measured values under the two stress states should show a stable and repeatable amplitude; if there are problems such as local suspension, foreign matter inclusion, or uneven fit, the stress change will often cause abnormally amplified changes or abnormally sluggish changes, thus causing the change to exceed the preset range. By judging the change, it is possible to further exclude situations where the conditions are occasionally met under a single stress state, but abnormal behavior occurs during the stress change process.
[0051] When the above-mentioned judgment conditions regarding absolute range, consistency, and stress variation are all met, it indicates that the inner liner exhibits stable and consistent isolation-related impedance characteristics under different stress conditions and different terminal paths, and the test result of the inner liner being qualified can be output; when any judgment condition is not met, the test result of the inner liner being unqualified will be output.
[0052] In one embodiment of the present invention, the output detection result includes: Determine whether both the first measured value and the second measured value are within a preset acceptable range; Determine whether the first measured value and the second measured value meet a preset consistency condition; When both the first and second measured values are within the preset acceptable range and meet the preset consistency condition, the test result indicating that the inner liner is qualified is output; otherwise, the test result indicating that the inner liner is unqualified is output.
[0053] In this embodiment, the output detection result is no longer based on a comprehensive judgment of measurement values under multiple stress states, but rather on the first and second measurement values obtained under a single stress state, thus forming a parallel implementation method with a simpler structure and shorter detection cycle. The first and second measurement values respectively characterize the equivalent impedance characteristics of the first and second end networks under the same stress conditions. Their acquisition process is consistent with the aforementioned impedance measurement steps, except that it is completed under the same stress state.
[0054] When outputting test results, the first step is to determine whether both the first and second measured values are within a preset acceptable range. This preset acceptable range defines the permissible interval for the isolation-related impedance characteristics between the terminals and the container, and its range is determined by the sample measurement results under normal assembly conditions. When a measured value exceeds this range, it indicates that the electrical characteristics of the corresponding two-terminal network have deviated from the normal isolation state. Even if the other measured value is within a reasonable range, it is insufficient to determine that the inner liner as a whole is in a qualified state. By simultaneously determining the range of the first and second measured values, it is possible to avoid masking potential anomalies on the other side simply because a single path is normal.
[0055] Based on the above range determination, it is further necessary to determine whether the first and second measured values meet a preset consistency condition. This consistency condition is used to compare the relative relationship between the two measurement paths under the same stress state. Since the first and second end networks correspond to the same heating component and are located within the same container structure, under the condition of uniform isolation structure and normal assembly, the equivalent impedance characteristics of the two paths should have similar magnitudes or proportional relationships. If there is local poor fit, assembly deviation in the lead-out area, or abnormal position of the isolation medium on one side, it will often manifest as a significant inconsistency between the two measured values. Through consistency determination, local anomalies can be identified by utilizing structural symmetry without relying on multiple stress states.
[0056] When both the first and second measured values are within the preset acceptable range and meet the preset consistency condition, it indicates that under this stress state, the isolation-related impedance characteristics between the heating component and the container exhibit a stable and consistent state across different terminal paths, and a test result indicating that the inner liner is qualified can be output. If any judgment condition is not met, a test result indicating that the inner liner is unqualified is output. This embodiment achieves effective evaluation of the isolation-related state by combining the judgment of absolute range and path consistency without introducing multiple stress states, and is suitable for production testing scenarios with high requirements for testing efficiency or equipment simplification.
[0057] In one embodiment of the present invention, the preset consistency condition includes: the difference or ratio between the first measured value and the second measured value is within a preset consistency range.
[0058] In one specific embodiment, the detection station provides three electrical connection points: a first power supply terminal, a second power supply terminal, and the container metal body. The container metal body is connected to a reference potential, which serves as the common reference point for the detection system and is used as a zero-potential reference for voltage and current acquisition. The detection system has step excitation output, response acquisition, and timing functions, enabling it to apply a dynamic excitation signal between the terminal and the container and acquire the voltage or current response. To ensure controlled measurement energy and adaptability to high-impedance isolation scenarios, the step excitation signal preferably adopts a voltage step method, with an amplitude ranging from 3 V to 12 V, commonly 5 V. Simultaneously, a current-limiting resistor is connected in series at the excitation output terminal to limit the peak current and improve anti-interference capability. The current-limiting resistor can range from 100 kΩ to 1 MΩ, commonly 330 kΩ. The sampling channel can acquire the voltage response of either the first two-terminal network or the second two-terminal network. The sampling frequency can range from 10 kHz to 200 kHz, commonly 50 kHz, and the sampling window can range from 5 ms to 200 ms, commonly 50 ms, to cover the effective variation range of the response process.
[0059] A discharge step is performed before applying a step excitation signal. The preset discharge circuit refers to a circuit that connects the first power supply terminal, the second power supply terminal, and the container to a reference potential via a controlled conduction path. This circuit includes at least a discharge resistor and a switching device. The discharge resistor limits the discharge current, and the switching device is used to turn on during the discharge phase and off during the measurement phase. The discharge resistor can range from 10 kΩ to 200 kΩ, with 47 kΩ being commonly used to ensure sufficiently fast discharge without generating excessive transient current. The discharge process is as follows: the switching device is turned on, connecting the first and second power supply terminals to the reference potential via the discharge resistor and maintaining this connection for a preset duration. The preset duration can range from 20 ms to 500 ms, with 100 ms being commonly used, to eliminate residual charge in the first and second terminal networks and unify the initial potential state. After the preset duration, the switching device is turned off, allowing the first and second power supply terminals to enter the test state.
[0060] Subsequently, impedance measurements were performed sequentially on the first and second two-terminal networks to obtain the first and second measured values. Taking the first two-terminal network as an example, a step excitation signal was applied between the first power supply terminal and the capacitor. The capacitor maintained a reference potential, and the step excitation signal transitioned from 0 V to 5 V at a preset time and held for 50 ms. Simultaneously, the voltage response of the first two-terminal network was acquired. The initial response value at the moment the step excitation signal was applied was defined as the voltage response value sampled at the transition moment. The preset threshold was selected within the stable range of the response change to avoid the influence of initial transient jitter and terminal saturation. The preset threshold could be a fixed proportion of the step amplitude, such as 3.0 V to 4.0 V, with 3.5 V being a commonly used value. The timing process was as follows: timing started from the step transition moment, the sampled data was scanned, and the time point at which the voltage response changed from the initial response value and first reached the preset threshold was determined. The required time was taken as the first measured value. After completing the measurement of the first two-terminal network, the step excitation signal was switched to the second power supply terminal and the capacitor, keeping the step amplitude, sampling frequency, sampling window consistent with the preset threshold, and the same timing rules were used to obtain the second measured value.
[0061] In a parallel embodiment, impedance measurements can be performed separately when the container is subjected to at least two different pressures to enhance the detection capability of assembly misalignment. The first stress state can be formed by adding a predetermined volume of liquid into the container, such as 0.8 L of water, so that the liquid's own weight creates a stable and evenly distributed downward vertical pressure on the bottom of the container. Under this state, a first measurement and a second measurement are obtained sequentially. The second stress state is formed by adding an additional load while keeping the liquid level constant, such as placing a 2 kg flat pressure weight at the container opening, making the total pressure higher than the first stress state and closer to the assembly clamping condition. Under this state, the first and second measurements are again obtained under the second stress state. The next step is to determine the output test results: all four measured values must fall within a preset acceptable range. This preset acceptable range can be set based on production line sample statistics. For example, the first and second measured values should both be within 5 ms to 35 ms under the first stress state, and within 3 ms to 25 ms under the second stress state. Simultaneously, the consistency between the two ends must meet preset consistency conditions. For example, under the same stress state, the difference between the first and second measured values should not exceed 8 ms, or the ratio should be between 0.8 and 1.25. Furthermore, the stress change must be within a preset change range. For example, both the first and second changes should be within 0 ms to 12 ms. If all the above conditions are met, a qualified test result for the inner liner is output; otherwise, a failed test result is output.
[0062] Please see Figures 2 to 4 The present invention also proposes an inner pot for an electric heating cooking appliance. The inner pot for the electric heating cooking appliance is tested using the testing method for inner pots for electric heating cooking appliances described above. The inner pot for the electric heating cooking appliance includes a container 1 and a heating element 2. The heating element 2 is disposed at the bottom of the container 1 and is electrically isolated from the container 1. The heating element 2 has a first power supply terminal 252 and a second power supply terminal 253. The electrical characteristics formed between the first power supply terminal 252 and the container 1, and between the second power supply terminal 253 and the container 1, can be characterized by impedance measurement.
[0063] In one embodiment of the present invention, the heating component 2 includes an insulating base 21, an upper mica sheet 22, a middle mica sheet 23, a lower mica sheet 24, and a resistance wire 25. The insulating base 21 is detachably fixed to the bottom of the container 1 and forms an installation cavity with the container 1. The upper mica sheet 22, the middle mica sheet 23, and the lower mica sheet 24 are all installed in the installation cavity, and the upper mica sheet 22, the middle mica sheet 23, and the lower mica sheet 24 are stacked sequentially from the container 1 to the insulating base 21. The resistance wire 25 is wound around the middle mica sheet 23, and the resistance wire 25 has multiple parallel heating sections 251 formed on both sides of the middle mica sheet 23. The two extended ends of the resistance wire 25 extend out of the insulating base 21 to form the first power supply terminal 252 and the second power supply terminal 253, respectively.
[0064] Specifically, the insulating base 21 in the heating element 2 supports the mica sheet and the resistance wire 25, and serves as a structural connection between the heating element 2 and the container 1. The insulating base 21 can be made of a material that is resistant to high temperatures and aging, and has good electrical insulation properties, such as ceramic materials, high-temperature resistant engineering plastics, or high-strength insulating composite materials. The insulating base 21 is detachably fixed to the bottom of the container 1. On the one hand, it is used to position and support the internal mica sheet and the resistance wire 25; on the other hand, it is used to achieve a detachable connection between the heating element 2 and the container 1, so as to facilitate assembly, maintenance, or replacement.
[0065] The detachable connection between the insulating base 21 and the container 1 can adopt various structural forms. In a common embodiment, the outer periphery of the insulating base 21 is provided with a connection structure for mating with the bottom of the container 1. The bottom of the container 1 is provided with a corresponding mounting hole or mounting step, and the two can be detachably fixed by screws, bolts, or snap fasteners. For example, the insulating base 21 is provided with several threaded holes, and the bottom of the container 1 is provided with a through hole. Screws are inserted from the outside of the container 1 and screwed into the insulating base 21, thereby reliably fixing the insulating base 21 to the bottom of the container 1. When disassembly is required, the heating element 2 can be removed as a whole simply by loosening the screws. In addition to threaded connections, snap-fit or plug-in structures can also be used, allowing the insulating base 21 to form a detachable fit with the container 1 in the axial or radial direction to meet the assembly efficiency requirements of different products.
[0066] A sealing structure can also be provided in the mating area between the insulating base 21 and the container 1 to prevent liquid or vapor from seeping into the heating element 2. The sealing structure may include a silicone gasket, a rubber sealing ring, or a high-temperature resistant elastic seal. The seal may be disposed between the mating surfaces of the insulating base 21 and the container 1, or around the connecting structure. After the insulating base 21 is fixed to the bottom of the container 1, the seal is compressed, thereby forming a reliable seal between the insulating base 21 and the container 1. This sealing method not only improves the overall waterproof and moisture-proof performance of the inner liner but also does not affect the detachable nature of the insulating base 21 and the container 1.
[0067] Within the mounting cavity formed between the insulating base 21 and the container 1, an upper mica sheet 22, a middle mica sheet 23, and a lower mica sheet 24 are stacked sequentially. The upper mica sheet 22, located closer to the container 1, isolates the resistance wire 25 from the container 1 and serves as the primary insulating medium between the heating component 2 and the container 1. The middle mica sheet 23 supports and fixes the resistance wire 25. The lower mica sheet 24, located closer to the insulating base 21, provides auxiliary insulation and support for the resistance wire 25. This multi-layered arrangement of mica sheets ensures good insulation performance while allowing heat to be stably transferred towards the container 1.
[0068] The resistance wire 25 is a single continuous conductor wound around the middle mica sheet 23. Through this winding method, multiple parallel heating segments 251 are formed on both sides of the middle mica sheet 23. Although the resistance wire 25 appears as multiple parallel segments on both sides of the middle mica sheet 23, electrically they are still different spatially distributed portions of the same resistance wire 25. The two extended ends of the resistance wire 25 are respectively led out from the insulating base 21, forming a first power supply terminal 252 and a second power supply terminal 253 for connection to an external power supply line.
[0069] Through the above structural arrangement, a "surface-like" heating condition can be formed at the bottom of container 1, ensuring uniform heating of container 1. Furthermore, the heating component 2 forms an encapsulated structure at the bottom of container 1, with the resistance wire 25 and mica sheet located within the mounting cavity between the insulating base 21 and container 1, preventing direct external contact. Simultaneously, a stable electrical coupling path is formed between the first power supply terminal 252 and container 1, and between the second power supply terminal 253 and container 1, through the upper mica sheet 22. This allows for the characterization of the electrical properties through impedance measurement without disassembling the inner liner or exposing the internal structure, thereby enabling the detection of the inner liner's isolation status in conjunction with the aforementioned testing method. This structural design not only meets the safety and reliability requirements of electric heating cooking appliances but also provides a stable structural foundation for introducing impedance measurement-based testing methods during the production testing phase.
[0070] Furthermore, a plurality of limiting notches 231 are formed on the periphery of the middle mica sheet 23. The plurality of limiting notches 231 are distributed at intervals in the circumferential direction of the middle mica sheet 23. The limiting notches 231 are used to accommodate part of the resistance wire 25 to limit the sliding of the resistance wire 25 in the circumferential direction of the middle mica sheet 23 and improve the installation stability of the resistance wire 25.
[0071] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for detecting the inner pot of an electrically heated cooking appliance, characterized in that, The inner liner includes a container and a heating element disposed at the bottom of the container and electrically isolated from the container. The heating element has a first power supply terminal and a second power supply terminal. The detection method includes: Impedance measurements were performed between the first power supply terminal and the container, and between the second power supply terminal and the container, respectively, to obtain a first measurement value characterizing the electrical characteristics between the first power supply terminal and the container, and a second measurement value characterizing the electrical characteristics between the second power supply terminal and the container. The detection result of the inner liner is output based on the first measurement value and the second measurement value.
2. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 1, characterized in that, The process of performing the impedance measurement includes: A dynamic excitation signal is applied to the first two-end network formed between the first power supply terminal and the container, the first dynamic response of the first two-end network is acquired, and the first measured value characterizing the equivalent impedance characteristics of the first two-end network is determined based on the first dynamic response. A dynamic excitation signal is applied to the second two-terminal network formed between the second power supply terminal and the container, the second dynamic response of the second two-terminal network is acquired, and the second measured value characterizing the equivalent impedance characteristics of the second two-terminal network is determined based on the second dynamic response.
3. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 2, characterized in that, The dynamic excitation signal is a step excitation signal; The process of determining measured values based on dynamic response includes: The time required for the voltage or current response of the first two-terminal network to change from the initial response value at the moment the step excitation signal is applied to a preset threshold is used as the first measured value; The time required for the voltage or current response of the second two-terminal network to change from the initial response value at the moment the step excitation signal is applied to a preset threshold is measured as the second measured value.
4. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 3, characterized in that, Before applying the step excitation signal, the method further includes: The first power supply terminal, the second power supply terminal, and the container are connected to a reference potential through a preset discharge circuit and maintained for a preset time to eliminate residual charge in the first and second end networks. The preset discharge circuit is disconnected after the preset duration ends.
5. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 3, characterized in that, The impedance measurement is performed when the container is subjected to at least two different pressures, including: Under the condition of applying a first preset pressure vertically downward to the bottom of the container, the impedance measurement is performed to obtain a first measurement value and a second measurement value under the first force state; Under the condition of applying a second preset pressure vertically downward to the bottom of the container, the impedance measurement is performed to obtain the first measurement value and the second measurement value under the second force state; Wherein, the first preset pressure is less than the second preset pressure.
6. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 5, characterized in that, The output detection results include: Determine whether the first measured value under the first stress state, the second measured value under the first stress state, the first measured value under the second stress state, and the second measured value under the second stress state are all within the preset qualified range; Determine whether the first measured value and the second measured value under the first stress state meet the preset consistency condition, and whether the first measured value and the second measured value under the second stress state meet the preset consistency condition; Determine whether the first change between the first measured value under the first stress state and the first measured value under the second stress state, and the second change between the second measured value under the first stress state and the second measured value under the second stress state, are both within a preset range of change. If all the above judgment conditions are met, output the test result that the inner liner is qualified; otherwise, output the test result that the inner liner is unqualified.
7. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 3, characterized in that, The output detection results include: Determine whether both the first measured value and the second measured value are within a preset acceptable range; Determine whether the first measured value and the second measured value meet a preset consistency condition; When both the first and second measured values are within the preset acceptable range and meet the preset consistency condition, the test result indicating that the inner liner is qualified is output; otherwise, the test result indicating that the inner liner is unqualified is output.
8. The method for detecting the inner pot of an electrically heated cooking appliance according to claim 6 or 7, characterized in that, The preset consistency condition includes: the difference or ratio between the first measured value and the second measured value is within the preset consistency range.
9. An inner pot for an electrically heated cooking appliance, characterized in that, The inner pot of the electric heating cooking appliance is tested using the testing method for the inner pot of the electric heating cooking appliance according to any one of claims 1-8, and the inner pot of the electric heating cooking appliance comprises: container; A heating element is disposed at the bottom of the container and electrically isolated from the container. The heating element has a first power supply terminal and a second power supply terminal. The electrical characteristics formed between the first power supply terminal and the container, and between the second power supply terminal and the container, can be characterized by impedance measurement.
10. The inner pot of the electric heating cooking appliance according to claim 9, characterized in that, The heating component includes an insulating base, an upper mica sheet, a middle mica sheet, a lower mica sheet, and a resistance wire. The insulating base is detachably fixed to the bottom of the container and forms an installation cavity with the container. The upper mica sheet, the middle mica sheet, and the lower mica sheet are all installed in the installation cavity, and the upper mica sheet, the middle mica sheet, and the lower mica sheet are stacked sequentially from the container to the insulating base. The resistance wire is wound around the middle mica sheet, and multiple parallel heating sections are formed on both sides of the middle mica sheet. The two extended ends of the resistance wire extend out of the insulating base to form the first power supply terminal and the second power supply terminal, respectively.