Liquid level detection method and device and automatic liquid injection equipment

Abstract

The invention provides a liquid level detection method and device and automatic liquid injection equipment. The liquid level detection method is applied to a detection electrode circuit, a detection electrode comprises an inner-layer electrode and an outer-layer electrode, the inner-layer electrode is attached to the outer wall of a detected container, the outer-layer electrode and the inner-layer electrode are designed in a back-to-back attaching mode, and the liquid level detection method comprises the steps that ground capacitance values of the inner-layer electrode and the outer-layer electrode are obtained; calculating a difference value between the ground capacitance value of the inner-layer electrode and the ground capacitance value of the outer-layer electrode to obtain a capacitance difference value; and determining the liquid level of the measured container according to the variation trend of the capacitance difference value. According to the invention, the influence of time drift interference factors such as temperature drift and position change on the liquid level detection accuracy of the small container can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid level detection, and in particular to a liquid level detection method, device and automatic liquid injection equipment. Background Art

[0002] Environmental protection issues are increasingly valued in more and more countries. In the e-cigarette industry, refillable e-cigarettes are gradually becoming a trend, so a small automatic filling device is needed to efficiently fill the cartridges.

[0003] To realize the automatic liquid filling operation, the liquid level inside the cartridge needs to be detected in real time. At present, the common types of liquid level sensors on the market include float type, photoelectric type, capacitive type and ultrasonic type. Among them, the prior art proposes a solution to realize liquid level detection based on capacitive detection method. Specifically, any object has capacitance, and its size is related to the dielectric constant and volume size. Therefore, by detecting the size of the capacitance, the change of the liquid level height can be sensed.

[0004] How to improve the accuracy of liquid level detection in small containers such as cigarette cartridges has become a technical problem that needs to be urgently solved in this field. Summary of the invention

[0005] The object of the present invention is to provide a liquid level detection method, device and automatic liquid injection equipment to solve the above-mentioned technical problems in the prior art.

[0006] On the one hand, to achieve the above objectives, the present invention provides a liquid level detection method.

[0007] The liquid level detection method is applied to a detection electrode circuit, wherein the detection electrode comprises an inner electrode and an outer electrode, wherein the inner electrode is attached to the outer wall of the container to be measured, and the outer electrode and the inner electrode are designed to be in close contact with each other back to back. In the liquid level detection method, the capacitance values ​​of the inner electrode and the outer electrode to the ground are first obtained, and then the difference between the capacitance value of the inner electrode to the ground and the capacitance value of the outer electrode to the ground is calculated to obtain the capacitance difference, and then the liquid level of the container to be measured is determined according to the variation trend of the capacitance difference.

[0008] On the other hand, to achieve the above objective, the present invention provides a liquid level detection device.

[0009] The liquid level detection device comprises: a detection electrode, comprising an inner electrode and an outer electrode, wherein the inner electrode is used to be attached to the outer wall of the container to be detected, and the outer electrode and the inner electrode are designed to be closely attached back to back; a detection circuit, connected to the detection electrode, and used to detect the capacitance value of the detection electrode to the ground; and a control module, connected to the detection circuit, and used to execute any one of the liquid level detection methods provided in the present application.

[0010] On the other hand, to achieve the above object, the present invention also provides an automatic liquid injection device.

[0011] The automatic liquid injection device includes: a liquid level detection device, which is any one of the liquid level detection devices provided by the present invention; a liquid storage tank for storing the liquid to be injected into the container to be measured; and a liquid injection control box for setting the control module, wherein the control module is further configured to control the liquid storage tank to stop injecting liquid into the container to be measured when the liquid level of the container to be measured reaches a preset maximum liquid level.

[0012] For the liquid level detection method, device and automatic liquid injection device provided by the present invention, the inner electrode is attached to the outer wall of the container to be measured, and the outer electrode and the inner electrode are designed to be closely attached back to back. When performing liquid level detection, the capacitance value of the inner electrode to the ground and the capacitance value of the outer electrode to the ground are obtained, and the difference between the two capacitance values to the ground is calculated to obtain a capacitance difference. Then, the liquid level of the container to be measured is determined according to the change trend of the capacitance difference. Through the present invention, the change trend of the capacitance difference between the two layers of electrodes is used to determine the liquid level, effectively improving the sensitivity to the change of the liquid level in a small container, and is particularly suitable for scenarios where the liquid volume is small or the space is limited. At the same time, the inner electrode is close to the container to be measured, and the change of the liquid level in the container significantly affects the magnitude of the capacitance value of the inner electrode to the ground. The capacitance value of the outer electrode to the ground is used as a reference signal, and the change trend of the capacitance difference is used to reflect the liquid level, which can significantly reduce the influence of time drift interference factors such as temperature drift and position change on the accuracy of liquid level detection in a small container. It has a wide range of application scenarios and is suitable for scenarios such as e-cigarette liquid injection, medical liquid injection equipment, and food processing, which require high-precision liquid level detection for small containers. Description of the Drawings

[0013] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings: Figure 1 is a flowchart of the liquid level detection method provided by an embodiment of the present invention; Figure 2 is a schematic block diagram of the liquid level detection device provided by an embodiment of the present invention; Figure 3 and Figure 4 is a schematic diagram of the wiring of the detection electrode in the liquid level detection device provided by an embodiment of the present invention; Figure 5 is a schematic diagram of the automatic liquid injection device provided by an embodiment of the present invention; Figure 6 is Figure 5 an exploded view of the automatic liquid injection device shown; Figure 7 Schematic diagram of the detection electrode settings of the automatic liquid injection device provided by the embodiment of the present invention; Figure 8 Schematic diagram of the change in the liquid level line-capacitance difference in the automatic liquid injection device provided by the embodiment of the present invention; Figure 9 Flow chart of the liquid injection process of the automatic liquid injection device provided by the embodiment of the present invention; Figure 10 Flow chart of the dynamic threshold selection of the automatic liquid injection device provided by the embodiment of the present invention; Figure 11 Flow chart for judging the change trend of the capacitance difference of the automatic liquid injection device provided by the embodiment of the present invention; Figure 12 Schematic diagram of another automatic liquid injection device provided by the embodiment of the present invention. Detailed implementation manners

[0014] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0015] The inventors have found that when detecting the liquid level in a small container such as an e-cigarette cartridge, the following challenges are faced: on the one hand, due to cost and food safety considerations, the detection electrode cannot be directly placed in the liquid, but can only be set on the outer wall of the container, which increases the distance between the two poles of the capacitance sensor; on the other hand, limited by the container size, the electrode area of the capacitance sensor is also limited. Considering these two factors comprehensively, there is a problem of relatively small capacitance values in the liquid level detection of small containers by the capacitive detection method. Even when the liquid in the container is full, the capacitance value detected by the sensor is still relatively small.

[0016] On this basis, during the e-cigarette refilling process, users usually perform an automatic refilling operation immediately after using the e-cigarette. During this process, rapid temperature changes may occur, and different ambient temperatures will directly affect the size of the capacitance value. Therefore, there is a problem of temperature drift in capacitance detection. Combining the characteristics of relatively small capacitance values in the liquid level detection of small containers, the temperature drift has a particularly significant impact on the accuracy of liquid level detection.

[0017] In addition, there is a certain gap between the cartridge of the electronic cigarette and the refueling seat. During the use of the electronic cigarette, each time the user plugs and unpluggs the cigarette rod, the distance between the capacitance detection positions will change. This position change causes the capacitance values measured at different times to be inconsistent at the same liquid level and the same temperature, thus having a greater impact on the accuracy of the liquid level detection in a small container.

[0018] In order to effectively reduce the influence of time drift interference factors such as temperature drift and position change on the accuracy of the liquid level detection in a small container, the present invention provides a liquid level detection method, device and automatic liquid filling device. Regarding various embodiments of the liquid level detection method, device and automatic liquid filling device provided by the present invention, the details are described as follows.

[0019] Embodiment 1 of the present invention provides a liquid level detection method. The inner electrode is attached to the outer wall of the container to be measured. The outer electrode and the inner electrode are designed to be closely attached back to back. The change trend of the capacitance difference formed by the inner electrode and the ground and the outer electrode and the ground is used to sense the height of the liquid, reducing the influence of temperature drift and time drift interference factors on the liquid level detection in a small container, improving the anti-interference ability of the liquid level detection in a small container, and enhancing the detection accuracy. Specifically, Figure 1 is a flowchart of the liquid level detection method provided by the embodiment of the present invention. As Figure 1 shown, the liquid level detection method provided by this embodiment includes the following steps S101 to step S103.

[0020] Step S101: Obtain the capacitance values of the inner electrode and the outer electrode with respect to the ground.

[0021] Specifically, the inner electrode is attached to the outer wall of the container to be measured, forming a capacitance with the ground. The container wall serves as an insulating layer. The inner electrode indirectly senses the change in the height of the liquid in the container through the container wall. The change in the height of the liquid will change the electric field distribution on the other side of the container wall, thereby affecting the capacitance value of the inner electrode with respect to the ground. The outer electrode forms another capacitance with the ground through the container wall. At the same time, the outer electrode is designed to be closely attached back to back with the inner electrode, maintaining the same temperature and environmental conditions as the inner electrode. The capacitance value of the outer electrode with respect to the ground is mainly determined by the container wall and the external environment (such as air, electromagnetic field, temperature, etc.). The capacitance signal between the outer electrode and the ground is not sensitive to the change in the liquid height, but is highly sensitive to environmental changes such as temperature drift and the instability of the position of the container relative to the electrode. The container to be measured is arranged in a metal cavity, and the outer shell of the metal cavity is grounded and can be used as the ground for the above capacitance, or other ground wires can be set. The present application does not limit this.

[0022] Step S102: Calculate the difference between the capacitance value of the inner electrode with respect to the ground and the capacitance value of the outer electrode with respect to the ground to obtain a capacitance difference.

[0023] Specifically, the capacitance difference is the difference between the capacitance value of the inner electrode with respect to the ground and the capacitance value of the outer electrode with respect to the ground. Since the capacitance value of the inner electrode with respect to the ground reflects the liquid level change and environmental change, while the capacitance value of the outer electrode with respect to the ground mainly reflects the environmental change, calculating the capacitance difference between the two can effectively eliminate the influence of the external environment.

[0024] Step S103: Determine the liquid level of the container to be measured according to the change trend of the capacitance difference.

[0025] Specifically, if the liquid level is outside the detection range of the detection electrode, the change in the liquid level basically does not affect the capacitance value of the inner electrode with respect to the ground. If the liquid level is within the detection range of the detection electrode, when the liquid level rises, the interaction area between the inner electrode and the liquid increases, and the capacitance value of the inner electrode with respect to the ground increases; when the liquid level drops, the interaction area between the inner electrode and the liquid decreases, and the capacitance value of the inner electrode with respect to the ground decreases. The capacitance value of the outer electrode with respect to the ground basically does not change with the change in the liquid level. Therefore, the change trend of the capacitance difference mainly reflects the change in the liquid level, increasing as the liquid level rises and decreasing as the liquid level drops. When injecting liquid (filling) into the container to be measured or discharging the liquid in the container to be measured (releasing), the liquid level of the container to be measured can be determined through the change trend of the capacitance difference.

[0026] In the liquid level detection method provided in this embodiment, the inner electrode is attached to the outer wall of the container to be measured, and the outer electrode and the inner electrode are designed to be back-to-back and closely attached. When performing liquid level detection, the capacitance values of the inner electrode and the outer electrode with respect to the ground are obtained, and the difference between the two capacitance values is calculated to obtain the capacitance difference. Then, the liquid level of the container to be measured is determined according to the change trend of the capacitance difference. By using the change trend of the capacitance difference between the two layers of electrodes to determine the liquid level in the liquid level detection method provided in this embodiment, the sensitivity to the change in the liquid level of a small container is effectively improved, which is particularly suitable for scenarios where the liquid volume is small or the space is limited. At the same time, the inner electrode is close to the container to be measured, and the change in the liquid level in the container significantly affects the magnitude of the capacitance value of the inner electrode with respect to the ground. The capacitance value of the outer electrode with respect to the ground is used as a reference signal, and the change trend of the capacitance difference is used to reflect the liquid level, which can significantly reduce the influence of time drift interference factors such as temperature drift and position change on the accuracy of liquid level detection of small containers. It has a wide range of application scenarios and is suitable for scenarios such as e-cigarette liquid injection, pharmaceutical liquid injection equipment, and food processing that require high-precision liquid level detection for small containers.

[0027] In one embodiment, the inner electrode includes an upper line and a lower line. Determining the liquid level of the container to be measured according to the change trend of the capacitance difference includes: determining whether the change trend of the capacitance difference is in a stable state or a changing state; if the capacitance difference is in a stable state within a preset time, determining that the liquid level of the container to be measured is above the upper line or below the lower line; if the capacitance difference is in a changing state within a preset time, determining that the liquid level of the container to be measured is between the upper line and the lower line.

[0028] Specifically, in the case of real-time liquid level changes, by classifying the change trend of the capacitance difference (stable state or changing state), and then based on whether the capacitance difference is in a stable state or a changing state within a preset time, the liquid level of the container to be measured is judged. When the liquid level change is outside the detection range of the inner electrode, the magnitude of the capacitance difference fluctuates within a small range, and at this time the capacitance difference is in a stable state; when the liquid level changes within the detection range of the inner electrode, the capacitance difference shows an obvious change trend (increase or decrease) over time, that is, the capacitance difference is in a changing state. Therefore, for the scenarios of liquid injection or liquid release, starting from the initial moment, when the detected and calculated capacitance difference is in a stable state, it indicates that the liquid level has not reached the detection range of the inner electrode, that is, the liquid level of the container to be measured is above the upper edge line or below the lower edge line of the inner electrode; when the detected and calculated capacitance difference is in a changing state, it indicates that the liquid level has reached the detection range of the inner electrode and is rising or falling, that is, the liquid level of the container to be measured is between the upper edge line and the lower edge line of the inner electrode. The interval where the liquid level is located can be quickly and accurately obtained through the state of the capacitance difference. Further, the inner electrode can be arranged in the area of the outer wall of the container corresponding to the liquid level attention range, so that the detection range of the inner electrode is the liquid level attention range. When the capacitance difference is in a stable state, the liquid level changes outside the liquid level attention range; when the capacitance difference is in a changing state, the liquid level change is within the liquid level attention range, that is, it is determined that the liquid level is within the liquid level attention range.

[0029] Applying the liquid level detection method provided in this embodiment to an e-cigarette liquid injection device, when the liquid injection starts, the capacitance difference is in a stable state, and the liquid injection speed can be set to a relatively fast speed; after the capacitance difference enters a changing state, the system adjusts to a slower liquid injection speed; when the capacitance difference enters a stable state again, the system judges that the liquid level reaches the full liquid level and the liquid injection is completed.

[0030] Using the liquid level detection method provided in this embodiment, by determining whether the capacitance difference is in a stable state or a changing state, the system can quickly determine the liquid level area and improve the real-time detection ability. At the same time, determining the liquid level based on the difference between the stable state and the changing state can reduce the interference of environmental changes and ensure the reliability of liquid level judgment.

[0031] In one embodiment, the changing state of the capacitance difference includes an increasing state and a decreasing state.

[0032] In the liquid injection scenario, the liquid level of the container under test gradually increases. The initial liquid level of the container under test is lower than the lower edge line of the inner electrode. The steps for determining the liquid level of the container under test based on the state of the capacitance difference include: when the capacitance difference is in a stable state, determining that the liquid level of the container under test is lower than the lower edge line of the inner electrode; when the capacitance difference changes from the stable state to the rising state, determining that the liquid level of the container under test is between the upper and lower edge lines of the inner electrode; when the capacitance difference changes from the rising state back to the stable state again, determining that the liquid level of the container under test is above the upper edge line of the inner electrode.

[0033] Specifically, in the liquid injection scenario, the liquid level of the container under test gradually rises. Through the change in the state of the capacitance difference, the distribution position of the liquid level relative to the upper and lower edge lines of the inner electrode can be judged in real time. This embodiment describes a method for gradually determining the liquid level of the container under test based on the state conversion of the capacitance difference. The initial liquid level of the container under test is lower than the lower edge line of the inner electrode. At this time, the liquid has not entered the detection range of the inner electrode, and the capacitance difference is in a stable state. If it is detected that the state of the capacitance difference is stable within the preset time, it can be determined that the liquid level is lower than the lower edge line of the inner electrode.

[0034] As the liquid is injected, the liquid level gradually rises and enters the detection range of the inner electrode. The relative permittivity of the liquid is high, and the characteristics of the medium coupled with the inner electrode change. At this time, the capacitance difference begins to change from the stable state to the rising state. If it is detected that the capacitance difference changes from the stable state to the rising state, it can be determined that the liquid level has entered the detection range of the inner electrode, that is, between the upper and lower edge lines of the inner electrode.

[0035] As the liquid level continues to rise, the liquid covers the upper edge line of the inner electrode, and the effective electric field region induced by the inner electrode no longer changes significantly. The capacitance value of the inner electrode to the ground tends to be stable, and the capacitance difference changes from the rising state back to the stable state. If it is detected that the capacitance difference changes from the rising state to the stable state, that is, is stable again within the preset time, it can be determined that the liquid level has exceeded the upper edge line of the inner electrode, and it can be confirmed that the liquid has completely left the detection range of the inner electrode according to the final stable state of the capacitance difference.

[0036] When applied to the e-cigarette liquid injection scenario, the upper edge line of the inner electrode is determined according to the target position of the liquid in the cartridge. For example, the upper edge line of the inner electrode is set slightly lower than the target position. In the initial state, the liquid level in the cartridge is lower than the detection range of the detection electrode, and the capacitance difference is stable within the preset time; when the liquid level in the cartridge enters the detection range of the detection electrode, the capacitance difference enters a changing state, and at this time, the liquid injection speed can be slowed down; when it is detected again that the capacitance difference enters a stable state within the preset time and the liquid level covers the upper edge line of the inner electrode, the liquid level is close to the liquid target position at this time, and the liquid injection is stopped. It can also be applied to the medical liquid injection equipment scenario to achieve accurate liquid injection, ensure that the liquid volume reaches the established target, and monitor the liquid level change in real time through the state conversion process to prevent the liquid from being excessive or insufficient.

[0037] Using the liquid level detection method provided by this embodiment, by utilizing the change trend of the capacitance difference, the liquid level position is judged in stages without the need for continuous complex calculations. In addition, since the state transition of the capacitance difference has clear signal characteristics, the influence of temperature drift and time drift in the environment can be effectively reduced. In a dynamic liquid injection scenario, the dynamic change of the liquid level can be monitored in real time, and it is applicable to various application scenarios that require precise control of the liquid level.

[0038] In the liquid discharging scenario, the liquid level of the measured container gradually decreases, and the initial liquid level of the measured container is higher than the upper edge line of the inner electrode. The steps of determining the liquid level of the measured container according to the state of the capacitance difference include: when the capacitance difference is in a stable state, it is determined that the liquid level of the measured container is higher than the upper edge line of the inner electrode; when the capacitance difference changes from the stable state to the decreasing state, it is determined that the liquid level of the measured container is between the upper and lower edge lines of the inner electrode; when the capacitance difference changes from the decreasing state to the stable state, it is determined that the liquid level of the measured container is below the lower edge line of the inner electrode.

[0039] Specifically, in the liquid discharging scenario, as the liquid flows out of the measured container, the liquid level gradually decreases. Through the state change of the capacitance difference, the distribution position of the liquid level relative to the upper and lower edge lines of the inner electrode can be judged in real time. This embodiment describes that by monitoring the state transition of the capacitance difference, the distribution of the liquid level can be accurately determined. The initial liquid level of the measured container is higher than the upper edge line of the inner electrode, the liquid completely covers the detection range of the inner electrode, and the capacitance difference is in a stable state. When it is detected that the state of the capacitance difference is stable within a preset time, it can be determined that the liquid level is higher than the upper edge line of the inner electrode.

[0040] As the liquid gradually flows out, the liquid level drops below the upper edge line of the inner electrode, and the change in the liquid height causes the liquid in the detection range of the inner electrode to gradually decrease. At this time, the capacitance difference changes from the stable state to the decreasing state. When it is detected that the capacitance difference changes from the stable state to the decreasing state, it can be determined that the liquid level has entered the detection range of the inner electrode, that is, between the upper and lower edge lines of the inner electrode.

[0041] The liquid continues to flow out, the liquid level drops below the lower edge line of the inner electrode, the change in the liquid height is no longer within the detection range of the inner electrode, the capacitance value of the inner electrode to the ground tends to be stable, and the capacitance difference changes from the decreasing state to the stable state again. When it is detected that the capacitance difference changes from the decreasing state to the stable state, that is, is stable again within a preset time, it can be determined that the liquid level is lower than the lower edge line of the inner electrode, and the fact that the liquid has completely left the detection range of the inner electrode can be confirmed according to the final stable state of the capacitance difference.

[0042] When applied to the monitoring scenario of medical liquid discharge, the lower edge line of the inner electrode is determined according to the target position of the liquid in the medical container. For example, the lower edge line of the inner electrode is set slightly higher than the target position. In the initial state, the liquid level in the medical container is higher than the detection range of the inner electrode, and the capacitance difference is in a stable state within a preset time; when the liquid level in the medical container enters the detection range of the detection electrode, the capacitance difference enters a changing state; when it is detected again that the capacitance difference enters a stable state within a preset time, the liquid level is lower than the lower edge line of the inner electrode. At this time, the liquid level is close to the target position of the liquid, and the discharge is stopped or an alarm is issued.

[0043] In a chemical reaction, it is necessary to control the liquid discharge amount. By monitoring the change trend of the capacitance difference to monitor the liquid level in real time, it can be applied to the scenario of chemical reagent discharge equipment. After the discharge is completed, by detecting again that the capacitance difference is in a stable state within a preset time, it is further confirmed that the remaining liquid in the container has dropped to the target range.

[0044] Using the liquid level detection method provided by this embodiment, by monitoring the stable state or changing state of the capacitance difference, it can provide a clear dynamic change of the liquid level. During the whole process of the liquid level from higher than the upper edge line to lower than the lower edge line, the change of the liquid level can be tracked in real time to ensure the control of the discharge process. In addition, since the state conversion of the capacitance difference has a clear signal characteristic, it can effectively reduce the influence of temperature drift and time drift in the environment. In the dynamic liquid discharge scenario, it can monitor the dynamic change of the liquid level in real time and is applicable to various application scenarios that require precise control of the liquid level.

[0045] In one embodiment, determining that the change trend of the capacitance difference is a stable state or a changing state includes: calculating the capacitance difference at the initial moment of the measured container to obtain the initial capacitance difference; calculating the capacitance difference at the current moment of the measured container to obtain the current capacitance difference; calculating the difference between the current capacitance difference and the initial capacitance difference to obtain the capacitance difference change amount; determining whether the capacitance difference change amount is greater than or equal to a first threshold; when the capacitance difference change amount is greater than or equal to the first threshold, determining that the change trend of the current capacitance difference is a changing state; when the capacitance difference change amount is less than the first threshold, calculating the capacitance difference change rate, where the capacitance difference change rate is the ratio of the capacitance difference change amount to the time duration from the initial liquid level to the current moment; determining whether the capacitance difference change rate is greater than or equal to a second threshold, where the second threshold is less than the first threshold; when the capacitance difference change rate is greater than or equal to the second threshold, determining that the change trend of the current capacitance difference is a changing state; when the capacitance difference change rate is less than the second threshold, determining that the change trend of the current capacitance difference is a stable state.

[0046] Specifically, during the liquid level detection process, by monitoring the change amount and change rate of the capacitance difference, the stable state and changing state of the capacitance difference are distinguished. In this embodiment, by calculating the initial capacitance difference and the current capacitance difference and comparing them with the preset threshold, the change trend of the capacitance difference is judged.

[0047] In the initial stage of liquid level detection (e.g., before the start of liquid injection or liquid release), the initial value of the capacitance difference is measured and recorded, which is called the initial capacitance difference. The initial capacitance difference represents the reference value of the capacitance difference under the initial liquid level condition. During the dynamic change of the liquid level, the capacitance difference at the current moment is collected and calculated in real time, which is called the current capacitance difference. The current capacitance difference obtained at each acquisition moment changes with the liquid level and is the core parameter for judging the change state of the liquid level. At each acquisition moment, the difference between the current capacitance difference and the initial capacitance difference is calculated to obtain the change amount of the capacitance difference. The first threshold is the absolute value threshold of the set capacitance difference change amount, which is used to quickly determine whether the capacitance difference enters the change state. In one embodiment, the first threshold is set to be able to identify the capacitance difference corresponding to a significant change in the liquid level. If the change amount of the capacitance difference has reached the magnitude of the first threshold, it indicates that the capacitance difference has undergone a large change, and it can be directly determined that the current capacitance difference is in the change state.

[0048] Otherwise, it indicates that the change amount of the capacitance difference during this period is not sufficient to determine whether it is in the change state. At this time, the next step is to calculate the capacitance difference change rate. The capacitance difference change rate reflects the speed of the change amount of the capacitance difference changing with time. The second threshold is used to judge the magnitude of the capacitance difference change rate to capture a more subtle change trend. In one embodiment, the second threshold is set to be able to identify the capacitance difference change rate corresponding to a slow change in the liquid level. If the capacitance difference change rate has reached the magnitude of the second threshold, it indicates that although the overall change amount of the capacitance difference in this time period is not large, there is a certain change fluctuation, and it is determined that the current capacitance difference is in the change state. If the capacitance difference change rate has not reached the magnitude of the second threshold, it indicates that the change fluctuation of the capacitance difference is extremely small, and it is determined that the current capacitance difference is in the stable state. Since the change of temperature or humidity will cause the capacitance value to drift slowly, and this drift may be confused with the real capacitance change when it accumulates to a certain extent, by using the judgment of the capacitance difference change rate, the slow drift is identified and ignored, avoiding the misjudgment of the change state.

[0049] The inventor's research found that the influence of environmental factors such as temperature fluctuations (temperature drift), humidity changes, electromagnetic interference (such as radiation from surrounding electronic devices), or the non-uniformity or aging of the container wall material, as well as the influence of random noise or drift of the device, will still cause the capacitance difference to fluctuate when the liquid level does not change, thereby affecting the accuracy of liquid level judgment. By using the liquid level detection method provided in this embodiment, combining the dual judgment mechanisms of the capacitance difference change amount and the capacitance difference change rate, the first threshold is used to quickly capture the significant change of the liquid level, and the second threshold is used to identify the subtle change, effectively distinguishing the fluctuation caused by interference from the real liquid level change, and being able to identify the state of the capacitance difference at different change rates in various liquid level change scenarios, improving the anti-interference ability and accurately identifying the liquid level dynamics.

[0050] In one embodiment, the following steps are used to calculate the first threshold and the second threshold: Obtain the capacitance difference after a predetermined time duration starting from the initial moment to get the reference capacitance difference; Calculate the difference between the reference capacitance difference and the initial capacitance difference to obtain the reference change amount of the capacitance difference; Calculate the first threshold THDL: THDL = THD0 + Δ * K 1 , where THD0 is the initial value of the first threshold, Δ is the reference change amount of the capacitance difference, and K 1 is the first preset coefficient; Calculate the second threshold THDS: THDS = K 2 * Δ / T0, where T0 is the predetermined time duration, and K 2 is the second preset coefficient.

[0051] Specifically, in liquid level detection, by reasonably setting the first threshold (THDL) and the second threshold (THDS), the accuracy of judging the state of the capacitance difference can be improved. In this embodiment, the first threshold and the second threshold are dynamically generated to ensure that the first threshold and the second threshold adapt to different liquid level change stages.

[0052] At the initial moment, the liquid level is the height of the liquid level in the container at the start of liquid level detection, and the corresponding capacitance difference is recorded as the initial capacitance difference. In the liquid level change scenario, starting from the initial moment, the liquid level gradually increases. After a predetermined time duration T0, the liquid level reaches a certain height between the initial liquid level and the lower edge line of the inner electrode; starting from the initial moment, the liquid level gradually decreases. After a predetermined time duration T0, the liquid level reaches a certain height between the initial liquid level and the upper edge line of the inner electrode. Whether the liquid level increases or decreases, the capacitance difference after the predetermined time duration is measured and recorded as the reference capacitance difference. Calculate the difference between the reference capacitance value and the initial capacitance difference to obtain the reference change amount Δ of the capacitance difference, and calculate the first threshold and the second threshold according to the reference change amount Δ of the capacitance difference.

[0053] Among them, set the initial value THD0 of the first threshold, the first preset coefficient K 1 and the second preset coefficient K 2 , and both of these two preset coefficients are dimensionless coefficients. The first threshold is the sum of the initial value THD0 and Δ * K 1 , and the second threshold is K 2 * Δ / T0.

[0054] By using the liquid level detection method provided in this embodiment, the first threshold and the second threshold are dynamically generated according to the drift of the capacitance from the initial moment to the moment T0, enhancing the adaptability of the system to various liquid level change scenarios. The initial values of the thresholds are set using experimental measurement data, and then the thresholds are dynamically adjusted in combination with the change of the capacitance difference within a predetermined time period, significantly reducing the influence of environmental interference on liquid level detection. For example, in the actual use process, there is a scenario where the e-cigarette cartridge is refilled immediately after it is used up. At this time, the temperature of the e-cigarette cartridge itself changes violently. For this scenario, the liquid level detection method provided in this embodiment can further alleviate the above-mentioned temperature drift problem and improve the accuracy of liquid level recognition.

[0055] In one embodiment, the inner layer electrode includes a first inner layer electrode and a second inner layer electrode, and the outer layer electrode further includes a first outer layer electrode corresponding to the first inner layer electrode and a second outer layer electrode corresponding to the second inner layer electrode. The first inner layer electrode is closer to the bottom of the container to be measured than the second inner layer electrode. The difference between the capacitance value of the first inner layer electrode to the ground and the capacitance value of the first outer layer electrode to the ground is the first capacitance difference, and the difference between the capacitance value of the second inner layer electrode to the ground and the capacitance value of the second outer layer electrode to the ground is the second capacitance difference. Determining the liquid level of the container to be measured according to the change trend of the capacitance difference includes: determining the liquid level of the container to be measured according to the change trend of the first capacitance difference and the change trend of the second capacitance difference.

[0056] Specifically, to further improve the accuracy of liquid level detection, this embodiment adopts a multi-group electrode design: the first inner layer electrode and the first outer layer electrode are designed to be closely attached back-to-back to form a group, and the second inner layer electrode and the second outer layer electrode are designed to be closely attached back-to-back to form another group. These two groups of electrodes respectively detect the liquid level changes at different heights, and the liquid level position is jointly determined through the change trends of the two groups of capacitance differences, further enhancing the resolution and applicability of liquid level detection. It should be noted that this application only takes two groups of electrodes as an example for illustration. In practical applications, three groups or more groups can also be used, which belong to the equivalent embodiments of this application, and this application does not limit this. The first capacitance difference obtained through the first group of electrodes can reflect the liquid level change within the height range where the first inner layer electrode is located; the second capacitance difference obtained through the second group of electrodes can reflect the liquid level change within the height range where the second inner layer electrode is located. The two groups of electrodes cover different liquid level ranges. The first group of electrodes is used to detect the low liquid level, and the second group of electrodes is used to detect the high liquid level. When the liquid level gradually rises or falls, the state changes of the two groups of capacitance differences can accurately reflect the position of the liquid level.

[0057] By adopting the liquid level detection method provided in this embodiment, the design of multiple groups of electrodes realizes segmented monitoring of the liquid level, enhancing the adaptability to complex liquid level change scenarios. Each group of electrodes works independently and can refer to each other when judging the liquid level, reducing the influence of abnormal signals of a single electrode on the system judgment. The electrode positions are flexibly configured according to different container heights and liquid level change ranges to meet various application requirements.

[0058] In one embodiment, the first inner electrode includes a first lower line and a first upper line, and the second inner electrode includes a second lower line and a second upper line. Determining the liquid level of the container to be measured according to the change trends of the first capacitance difference and the second capacitance difference includes: determining whether the change trend of the capacitance difference is a stable state or a changing state; if both the first capacitance difference and the second capacitance difference are in a stable state within a preset time, determining that the liquid level of the container to be measured is above the second upper line or below the first lower line or between the first upper line and the second lower line; if the first capacitance difference is in a changing state and the second capacitance difference is in a stable state, determining that the liquid level of the container to be measured is between the first lower line and the first upper line; if the second capacitance difference is in a changing state and the first capacitance difference is in a stable state, determining that the liquid level of the container to be measured is between the second lower line and the second upper line.

[0059] Specifically, if the changing state is defined as an increasing state and a decreasing state according to the liquid injection or liquid discharge scenarios respectively, the steps of determining the liquid level of the container to be measured are as follows: For the scenario where the liquid level of the container to be measured gradually increases, the initial liquid level of the container to be measured is lower than the first lower line. During the liquid level measurement process, when both the first capacitance difference and the second capacitance difference are in a stable state within a preset time, it is determined that the liquid level of the container to be measured is lower than the first lower line; when the first capacitance difference changes from a stable state to an increasing state and the second capacitance difference remains in a stable state, it is determined that the liquid level of the container to be measured is between the first lower line and the first upper line; when the first capacitance difference changes from an increasing state to a stable state again and the second capacitance difference remains in a stable state, it is determined that the liquid level of the container to be measured is between the first upper line and the second lower line; when the second capacitance difference changes from a stable state to an increasing state and the first capacitance difference remains in a stable state, it is determined that the liquid level of the container to be measured is between the second lower line and the second upper line; when the second capacitance difference changes from an increasing state to a stable state and the first capacitance difference remains in a stable state, it is determined that the liquid level of the container to be measured is higher than the second upper line.

[0060] For the scenario where the liquid level of the container under test gradually increases, the initial liquid level of the container under test is higher than the second upper line. During the liquid level measurement process, when both the first capacitance difference and the second capacitance difference are in a stable state within a preset time, it is determined that the liquid level of the container under test is higher than the second upper line; when the second capacitance difference changes from the stable state to the decreasing state and the first capacitance difference remains in the stable state, it is determined that the liquid level of the container under test is between the second upper line and the second lower line; when the second capacitance difference changes from the decreasing state to the stable state and the first capacitance difference remains in the stable state, it is determined that the liquid level of the container under test is between the second lower line and the first upper line; when the first capacitance difference changes from the stable state to the decreasing state and the second capacitance difference remains in the stable state, it is determined that the liquid level of the container under test is between the first upper line and the second lower line; when the first capacitance difference changes from the decreasing state to the stable state and the second capacitance difference remains in the stable state, it is determined that the liquid level of the container under test is lower than the first lower line.

[0061] By using the liquid level detection method provided in this embodiment, based on the cooperation of the change trends of multiple groups of electrode capacitance differences, the segmented monitoring of the liquid level of the container is realized. By using two groups of capacitance difference signals for cross-verification, the liquid level position can be accurately located. Especially in the dynamic change scenarios where the liquid level gradually rises or falls, the detection accuracy is significantly improved. During the liquid level change process, the conversion of the capacitance difference state (from stable to rising / falling and then back to stable) can reflect the gradual change of the liquid level between different liquid level lines. Whether the liquid level rises or falls, the specific position of the liquid level relative to the upper and lower edges of the two groups of inner electrodes can be judged in real time, which is applicable to complex scenarios of dynamic liquid injection or liquid release. At the same time, by using the combination of the change trends of the two groups of capacitance differences to judge the liquid level, the influence of the fluctuation of a single capacitance signal or environmental interference on the detection result can be reduced, and the system can also support multi-level liquid level judgment, which is particularly crucial in scenarios where precise liquid level control is required (such as e-cigarette liquid injection equipment, medical liquid injection systems).

[0062] The embodiment of the present invention also provides a liquid level detection device. The inner electrode is arranged to be attached to the outer wall of the container under test, and the outer electrode and the inner electrode are designed to be closely attached back to back. The change trend of the capacitance difference formed by the inner electrode and the ground and the outer electrode and the ground is used to sense the height of the liquid, reducing the influence of temperature drift and time drift interference factors on the liquid level detection of small containers, improving the anti-interference ability of the liquid level detection of small containers, and improving the detection accuracy. Specifically, Figure 2 is a schematic block diagram of the liquid level detection device provided by the embodiment of the present invention, as Figure 2 shown, the liquid level detection device provided by this embodiment includes: a detection electrode 201, a detection circuit 202, and a control module 203.

[0063] Among them, the detection electrode 201 includes an inner layer electrode and an outer layer electrode. The inner layer electrode is used to be attached to the outer wall of the container to be measured, and the outer layer electrode is designed to be in back-to-back close contact with the inner layer electrode; the detection circuit 202 is connected to the detection electrode 201 and is used to detect the capacitance value of the detection electrode 202 to the ground; the control module 203 is connected to the detection circuit 202 and is used to execute any one of the liquid level detection methods provided by the present invention. The specific process and corresponding technical effects can be referred to the above text and will not be elaborated here.

[0064] In one embodiment, the inner layer electrode includes a first inner layer electrode and a second inner layer electrode, and the outer layer electrode further includes a first outer layer electrode corresponding to the first inner layer electrode (that is, designed to be in back-to-back close contact with the first inner layer electrode), and a second outer layer electrode corresponding to the second inner layer electrode (that is, designed to be in back-to-back close contact with the second inner layer electrode); the first inner layer electrode is relatively closer to the bottom of the container to be measured than the second inner layer electrode, that is, when the top of the container to be measured is upward and the bottom is downward, the setting position of the first inner layer electrode is lower than the setting position of the second inner layer electrode. The detection circuit 202 is used to detect the capacitance value of the inner layer electrode and the outer layer electrode to the ground and output a detection signal. In one embodiment, the detection circuit 202 may include circuit units such as a capacitance measurement module, a differential amplifier, and a signal filter to ensure the accuracy and stability of the signal. The control module 203 is connected to the detection circuit 202 and is used to receive the detection signal, execute the above liquid level detection method, judge the liquid level position, and output liquid level information or trigger a control action (such as stopping liquid injection or alarming).

[0065] By using the liquid level detection circuit provided in this embodiment, the change trend of the capacitance difference between two or more groups of inner and outer layer electrodes is utilized to jointly determine the liquid level, alleviate measurement interference, and achieve high-sensitivity detection of the liquid level. Through the high-speed sampling of the detection circuit and the real-time processing of the control module, the liquid level change can be quickly captured and judged. The detection device has a simple design, does not require direct contact between the liquid and the electrode, is applicable to various liquids and containers, has a small volume, and can be easily integrated into various liquid level detection scenarios.

[0066] In one embodiment, the detection electrode is disposed on top of an isolation layer, and the isolation layer uses grid copper for bottom layer copper plating.

[0067] Specifically, Figure 3 and Figure 4 are the wiring diagrams of the detection electrode in the liquid level detection device provided by the embodiment of the present invention. As Figure 3 and Figure 4As shown in the figure, the detection electrode includes a first inner layer electrode A1, a second inner layer electrode A2, a first outer layer electrode B1, and a second outer layer electrode B2. Each electrode is disposed above the isolation ground layer and is respectively connected to the detection circuit IC. The isolation ground layer uses grid copper for bottom copper plating. While isolating human interference, it can increase the magnitude of the capacitance difference and improve the accuracy of liquid level detection.

[0068] An embodiment of the present invention provides an automatic liquid injection device, which includes a liquid level detection device, a liquid storage tank, and a liquid injection control box. Among them, the liquid level detection device is any one of the liquid level detection devices provided by the present invention, including a detection electrode, a detection circuit, and a control module. For specific reference, please refer to the above description and will not be elaborated here. The liquid storage tank is used to store the liquid to be injected into the container to be measured; the liquid injection control box is used to set the control module. Among them, on the basis of executing any of the above liquid level detection methods, the control module is further used to control the liquid storage tank to stop injecting liquid into the container to be measured when it detects that the liquid level of the container to be measured reaches the preset highest liquid level. In one embodiment, the liquid injection control box includes a first cavity, a second cavity, and a third cavity; the first cavity is used to set the container to be measured and the detection electrode, and the housing of the first cavity is made of metal, and the capacitance to the ground is the capacitance between the detection electrode and the housing of the first cavity; the second cavity is used to set the control module, and the detection circuit is disposed on the outer wall of the second cavity; the third cavity is used to set the liquid storage tank. Hereinafter, taking the cartridge of an electronic cigarette as an example of the container to be measured, the automatic liquid injection device provided by the present application will be described in detail.

[0069] Figure 5 is a schematic diagram of the automatic liquid injection device provided by the embodiment of the present invention, Figure 6 is Figure 5 an exploded view of the automatic liquid injection device shown in the figure, as shown in Figure 5 and Figure 6 shown, the automatic liquid injection device includes a liquid injection control box (i.e., an oil injection control box), a liquid storage tank (i.e., an oil storage bin), a detection electrode, a detection circuit, and a control module (not shown in the figure). The cartridge of the electronic cigarette (provided with an oil injection hole) is installed in the cigarette rod, and the detection electrode is installed on the liquid injection control box at a position corresponding to the liquid level of the e-liquid in the cartridge. Among them, the liquid injection control box includes a first cavity for setting the cartridge and the detection electrode, and the housing of the first cavity is made of metal; it also includes a second cavity for setting the control module, and the detection circuit is disposed on the outer wall of the second cavity; it also includes a third cavity for accommodating the liquid storage tank.

[0070] The detection circuit is used to detect the capacitance between the detection electrode and the metal outer shell (grounded) of the liquid injection control box, that is, the capacitance to the ground value, and obtain a capacitance signal to feedback to the control module. The control module judges the liquid level inside the cartridge based on the difference in the capacitance to the ground value of the inner and outer layer electrodes, that is, the change trend of the capacitance difference, so as to control the operation of the liquid injection control box and ensure that each oil injection reaches the full oil level of the cartridge.

[0071] Figure 7 Schematic diagram of the detection electrode settings of the automatic liquid injection device provided by the embodiment of the present invention. Refer to Figure 7 , due to restrictions such as the size of the cartridge and food safety, both the size and spacing of the detection electrodes are limited, resulting in a small change in capacitance when the cartridge goes from less oil to full oil, and a large difference in the capacitance values measured multiple times for cartridges at the same liquid level. From the perspective of the absolute capacitance of the cartridge, the boundary between the less oil and full oil states of the cartridge is not obvious. Additionally, affected by time drift and temperature drift, the boundary is even more blurred. To solve the above problems, the embodiment of the present application adopts a recognition scheme for identifying the change in liquid level and the related trend change in capacitance while using the signal differential method.

[0072] As Figure 3 and Figure 4 shown, the inner electrodes (electrodes A1, B1) are close to the cartridge to be measured, and the outer electrodes (electrodes A2, B2) serve as the reference channels for the inner electrodes. In electrode design, the size of the electrode plates is kept the same. Additionally, a back-to-back and close design is adopted between the inner and outer electrodes to ensure that the temperatures of the two layers of electrodes are basically the same (electrode A1 corresponds to electrode A2, and electrode B1 corresponds to electrode B2). When no oil injection is carried out, due to external interference, the ground capacitances of the two layers of electrodes drift with time respectively, but their trends are the same. Also, because the temperatures of the two layers of electrodes are nearly the same, the difference in the ground capacitances of the inner and outer electrodes alleviates the time drift problem caused by unstable capacitance values and the temperature drift problem caused by temperature changes to a certain extent. The isolated ground uses grid copper with a 50% ratio for bottom copper plating, which can increase the size of the capacitance to be measured while isolating human interference.

[0073] This embodiment adopts the design of upper and lower electrodes, with the upper electrodes (B1, B2) as the main judgment basis and the lower electrodes (A1, A2) as the auxiliary judgment basis. As Figure 7 shown, the liquid level detection range of the lower electrodes is from line A to line B, and the liquid level detection range of the upper electrodes is from line C to line D. Line A is the lower edge line corresponding to electrodes A1 and A2, line B is the upper edge line corresponding to electrodes A1 and A2, line C is the lower edge line corresponding to electrodes B1 and B2, line D is the upper edge line corresponding to electrodes B1 and B2, and line X is the liquid level line of the e-liquid in the cartridge. By adjusting the electrode width and / or the spacing between line B and line C, line D can be set as the highest liquid level, and line C is located at 3 / 4 of the highest liquid level.

[0074] Figure 8 Schematic diagram of the change in the difference between the liquid level line and capacitance in the automatic liquid injection device provided by the embodiment of the present invention. As Figure 8 shown, assume that the initial liquid level is below line A. Starting from time 0, the oil injection control box starts the oil injection operation, and the oil enters the cartridge through the oil injection hole of the cartridge.

[0075] Before the liquid level reaches line A (at time T1), the e-liquid level keeps rising. Since the medium between detection electrodes A1 and A2 and the reference ground does not change, and the medium between detection electrodes B1 and B2 and the reference ground also does not change, both capacitance difference A (i.e., the first capacitance difference) and capacitance difference B (i.e., the second capacitance difference) remain unchanged.

[0076] When the liquid level X rises from line A (at time T1) to line B (at time T2), since the medium between detection electrodes A1 and A2 and the reference ground changes, and the area facing the e-liquid continuously increases, capacitance difference A also continuously increases, and capacitance difference A is in a changing state. While the medium between detection electrodes B1 and B2 and the reference ground does not change, capacitance difference B remains unchanged, and capacitance difference B is in a stable state.

[0077] When the liquid level X rises from line B (at time T2) to line C (at time T3), since the medium between detection electrodes A1 and A2 and the reference ground does not change, and the medium between detection electrodes B1 and B2 and the reference ground also does not change, both capacitance difference A and capacitance difference B remain unchanged and are both in a stable state.

[0078] When the liquid level X rises from line C (at time T3) to line D (at time T4), since the medium between detection electrodes A1 and A2 and the reference ground does not change, capacitance difference A remains unchanged. While the medium between detection electrodes B1 and B2 and the reference ground changes, and the area facing it continuously increases, capacitance difference B continuously increases, and capacitance difference B is in a changing state.

[0079] When the liquid level X is higher than line D (at time T4), since the medium between detection electrodes A1 and A2 and the reference ground does not change, and the medium between detection electrodes B1 and B2 and the reference ground also does not change, both capacitance difference A and capacitance difference B remain unchanged and are again both in a stable state.

[0080] From the above analysis, it can be seen that by observing the change trends of capacitance difference A and capacitance difference B, the position corresponding to the liquid level can be accurately judged. Then, according to this judgment logic, the main control can control the start and end of the oil injection system.

[0081] At time T3, the control module recognizes that capacitance difference B rises and is in a changing state, while capacitance difference A is stable and in a stable state. It can be considered full of oil, and at this time, the oil injection tank is controlled to stop injecting oil. Then line C is the full-oil demarcation line, that is, controlling the position of line C controls the full-oil position. In actual use, in order to take into account multiple oil injection situations, line C is controlled at 3 / 4 of the e-liquid volume in the cartridge.

[0082] In addition, during actual use, there is a scenario where the e-cigarette cartridge is refilled immediately after it is used up. At this time, the temperature of the e-cigarette cartridge itself changes significantly. For this scenario, in order to further improve the accuracy of recognition, a dynamic threshold method is used, and different dynamic thresholds are selected according to the drift speed of the capacitance from the 0th moment to the T0th moment.

[0083] Figure 9 The flowchart of the liquid injection process of the automatic liquid injection device provided by the embodiment of the present invention is as Figure 9 shown. After starting the oil injection, control the oil injection control box to inject oil into the e-cigarette cartridge, collect the capacitance values of the detection electrodes A1, A2, B1, and B2 to the ground, calculate the difference between the capacitance values of A1 and A2 to the ground to obtain the capacitance difference A, calculate the difference between the capacitance values of B1 and B2 to the ground to obtain the capacitance difference B, and respectively obtain the dynamic threshold corresponding to the capacitance difference A (that is, the first threshold and the second threshold corresponding to the lower electrode) and the dynamic threshold corresponding to the capacitance difference B (that is, the first threshold and the second threshold corresponding to the upper electrode) according to the change of the capacitance difference from the 0th moment to the T0th moment. Then, judge whether the capacitance difference A is in a changing state according to the capacitance difference A and its corresponding dynamic threshold. If the capacitance difference A is in a changing state, it indicates that the oil surface is between the A line and the B line and has not reached the C line, and the e-cigarette cartridge is in a state of less oil, and continue to control the oil injection control box to inject oil into the e-cigarette cartridge; if the capacitance difference A is in a stable state, it indicates that the oil surface is not between the A line and the B line. At this time, further judge whether the capacitance difference B changes according to the capacitance difference B and its corresponding dynamic threshold. If the capacitance difference B is in a stable state, it indicates that the oil surface has not reached the C line and the e-cigarette cartridge is in a state of less oil, and continue to control the oil injection control box to inject oil into the e-cigarette cartridge. If the capacitance difference B is in a changing state, it indicates that the oil surface has reached the C line and the e-cigarette cartridge is in a full oil state, and end the oil injection.

[0084] Among them, when obtaining the dynamic threshold corresponding to the capacitance difference according to the change of the capacitance difference from the 0th moment to the T0th moment, the dynamic threshold selection logics of the upper and lower electrodes are the same. The following electrode is taken as an example for illustration. Figure 10 The flowchart of the dynamic threshold selection of the automatic liquid injection device provided by the third embodiment of the present invention is as Figure 10 shown. First, initialize the long-time threshold (that is, the first threshold) THDL and the short-time threshold (that is, the second threshold) THDS, obtain the initial capacitance difference C0 at the 0th moment, obtain the capacitance difference C1 of the lower electrode at the T0th moment, that is, the reference capacitance difference C1, calculate Δ = C1 - C0, and then update the long-time threshold THDL = THD0 + Δ * K 1 , update the short-time threshold THDS: THDS = K 2 *Δ / T0, where K 1 is the first preset coefficient, and K 2 is the second preset coefficient.

[0085] Whether the capacitance difference changes depends on the long-term condition (i.e., the change in capacitance difference between the current moment and the moment 0) and the short-term condition (i.e., the change rate of the capacitance difference change per unit time). The long-term condition reflects how much the capacitance changes, that is, how much the liquid level in the detection area changes, and its judgment threshold is usually large; the short-term condition reflects how fast the capacitance changes, that is, the liquid level change rate in the detection area, and its judgment threshold is usually small. The long-term condition is the change in capacitance difference from the start of oil injection to the current moment. This long-term condition is to prevent the situation of missed detection caused by too slow oil injection or other reasons resulting in too slow change rate of capacitance difference, and it belongs to a guarantee condition, and its threshold is generally on the large side.

[0086] For the judgment logic of the rising capacitance difference, the upper and lower electrodes are the same. Taking the lower electrode as an example for illustration. Figure 11 This is the flowchart for judging the change trend of the capacitance difference of the automatic liquid injection device provided in the third embodiment of the present invention. As Figure 11 shown, obtain the initial capacitance difference C0, select a dynamic threshold, obtain the current capacitance difference Ct in real time, calculate the current capacitance difference change amount Δ0 = Ct - C0, calculate the current capacitance difference change rate Δk = (Ct - C0) / t, where t is the time length from zero to the current moment. Judge whether Δ0 is greater than or equal to the long-term threshold THDL. If Δ0 ≥ THDL, it can be determined that the capacitance difference is in a changing state; if Δ0 < THDL, then judge whether Δk is greater than or equal to the short-term threshold THDS. If Δk ≥ THDS, it can be determined that the capacitance difference is in a changing state. If Δk < THDS, it can be determined that the capacitance difference is in a stable state.

[0087] Figure 12 This is a schematic diagram of another automatic liquid injection device provided in the embodiment of the present invention. In another embodiment, as Figure 12 shown, a design with three groups of electrodes is adopted, including the lower electrodes (A1, A2), the middle electrodes (B1, B2) and the upper electrodes (C1, C2). The capacitance difference between the lower electrodes with respect to the ground is the capacitance difference A, the capacitance difference between the middle electrodes with respect to the ground is the capacitance difference B, and the capacitance difference between the upper electrodes with respect to the ground is the capacitance difference A. The liquid level detection range of the lower electrodes is from line A to line B, the liquid level detection range of the middle electrodes is from line C to line D, and the liquid level detection range of the upper electrodes is from line E to line F. Line A is the lower side line corresponding to electrodes A1 and A2, line B is the upper side line corresponding to electrodes A1 and A2, line C is the lower side line corresponding to electrodes B1 and B2, line D is the upper side line corresponding to electrodes B1 and B2, line E is the lower side line corresponding to electrodes C1 and C2, line F is the upper side line corresponding to electrodes C1 and C2, and line X is the liquid level line of the e-liquid in the cartridge.

[0088] Assume that the initial liquid level is below line A. Starting from the moment 0, the oil injection control box starts the oil injection action and enters the cartridge through the oil injection hole of the cartridge.

[0089] Before the liquid level reaches line A, the e-liquid level keeps rising. Since the medium between each group of detection electrodes and the reference ground remains unchanged, at this time, capacitance difference A, capacitance difference B, and capacitance difference C all remain unchanged and are in a stable state.

[0090] During the process of the liquid level X rising from line A to line B, since the medium between detection electrodes A1 and A2 and the reference ground changes, and the area facing the liquid level continuously increases, capacitance difference A also continuously increases and is in a changing state. However, the medium between detection electrodes B1 and B2 and the reference ground, as well as the medium between detection electrodes C1 and C2 and the reference ground, remains unchanged, and capacitance difference B and capacitance difference C still remain unchanged.

[0091] When the liquid level X rises from line B to line C, the medium between detection electrodes A1 and A2 and the reference ground no longer changes, and the medium between detection electrodes C1 and C2 and the reference ground, as well as the medium between detection electrodes B1 and B2 and the reference ground, also remains unchanged. At this time, capacitance difference A, capacitance difference B, and capacitance difference C are in a stable state again.

[0092] When the liquid level X rises from line C to line D, the medium between detection electrodes A1 and A2 and the reference ground no longer changes, and capacitance difference A still remains in a stable state. The medium between detection electrodes C1 and C2 and the reference ground also does not change, and capacitance difference C still remains in a stable state. However, the medium between detection electrodes B1 and B2 and the reference ground changes, and the area facing the liquid level continuously increases, and capacitance difference B continuously increases and is in a changing state.

[0093] When the liquid level X rises from line D to line E, the medium between detection electrodes A1 and A2 and the reference ground, and the medium between detection electrodes B1 and B2 and the reference ground both no longer change, and the medium between detection electrodes C1 and C2 and the reference ground also remains unchanged. At this time, capacitance difference A, capacitance difference B, and capacitance difference C are in a stable state again.

[0094] When the liquid level X rises from line E to line F, the medium between detection electrodes A1 and A2 and the reference ground, and the medium between detection electrodes B1 and B2 and the reference ground no longer change, and capacitance difference A and capacitance difference C still remain in a stable state. However, the medium between detection electrodes C1 and C2 and the reference ground changes, and the area facing the liquid level continuously increases, and capacitance difference C continuously increases and is in a changing state.

[0095] When the liquid level X is higher than line F, since the medium between the three groups of electrodes and the reference ground no longer changes, capacitance difference A, capacitance difference B, and capacitance difference C all return to a stable state.

[0096] As can be seen from the above analysis, by using the capacitance differences A, B, and C, the relative position relationship between the liquid level and lines A - F can be determined, and multiple sets of electrodes are provided to increase the precision of liquid level position determination.

[0097] It should be noted that in this document, the terms "include", "comprise" or any other variant thereof are intended to cover non - exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising such element.

[0098] The serial numbers of the above - mentioned embodiments of the present invention are only for description and do not represent the superiority or inferiority of the embodiments.

[0099] Through the description of the above - mentioned embodiments, those skilled in the art can clearly understand that the above - mentioned embodiment methods can be implemented by means of software plus a necessary general - purpose hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method.

[0100] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A liquid level detection method, applied to a detection electrode circuit, characterized in that: The detection electrode comprises an inner electrode and an outer electrode, the inner electrode is attached to the outer wall of the container to be detected, and the outer electrode and the inner electrode are designed to be closely attached back to back. The liquid level detection method comprises: Obtaining capacitance values ​​of the inner electrode and the outer electrode to ground; Calculating a difference between a capacitance value of the inner electrode to ground and a capacitance value of the outer electrode to ground to obtain a capacitance difference; and The liquid level of the measured container is determined according to the variation trend of the capacitance difference.

2. The liquid level detection method according to claim 1, characterized in that: The inner electrode includes an upper sideline and a lower sideline, and determining the liquid level of the measured container according to the change trend of the capacitance difference includes: Determining whether the variation trend of the capacitance difference is a stable state or a varying state; If the capacitance difference is in the stable state within the preset time, it is determined that the liquid level of the measured container is above the upper boundary or below the lower boundary; If the capacitance difference is in the changing state within the preset time, it is determined that the liquid level of the measured container is located between the upper boundary line and the lower boundary line.

3. The liquid level detection method according to claim 2, characterized in that: Determining whether the variation trend of the capacitance difference is a stable state or a varying state comprises: Calculating the capacitance difference of the measured container at the initial moment to obtain an initial capacitance difference; Calculating the capacitance difference of the measured container at the current moment to obtain a current capacitance difference; Calculating the difference between the initial capacitance difference and the current capacitance difference to obtain a capacitance difference change; Determining whether the capacitance difference change is greater than or equal to a first threshold; If the capacitance difference change is greater than or equal to the first threshold, determining that the change trend of the current capacitance difference is a changing state; If the capacitance difference change is less than the first threshold, calculating the capacitance difference change rate, wherein the capacitance difference change rate is a ratio of the capacitance difference change to the time from the initial moment to the current moment; Determining whether the capacitance difference change rate is greater than or equal to a second threshold, wherein the second threshold is less than the first threshold; If the capacitance difference change rate is greater than or equal to the second threshold, determining that the change trend of the current capacitance difference is a changing state; If the capacitance difference change rate is less than the second threshold, it is determined that the current capacitance difference change trend is in a stable state.

4. The liquid level detection method according to claim 3, characterized in that: The first threshold and the second threshold are calculated by the following steps: Calculating the capacitance difference after a predetermined period of time from the initial moment to obtain a reference capacitance difference; Calculating the difference between the reference capacitance difference and the initial capacitance difference to obtain a capacitance difference reference variation; Calculate the first threshold THDL: THDL=THD0+Δ*K1, wherein THD0 is the first threshold initial value, Δ is the capacitance difference reference change, and K1 is the first preset coefficient; The second threshold THDS is calculated: THDS=K2*Δ / T0, wherein T0 is the predetermined time length, and K2 is a second preset coefficient.

5. The liquid level detection method according to claim 1, characterized in that: The inner electrode comprises a first inner electrode and a second inner electrode, and the outer electrode comprises a first outer electrode corresponding to the first inner electrode and a second outer electrode corresponding to the second inner electrode, wherein the first inner electrode is closer to the bottom of the container to be measured than the second inner electrode; The difference between the capacitance value of the first inner electrode to ground and the capacitance value of the first outer electrode to ground is a first capacitance difference, and the difference between the capacitance value of the second inner electrode to ground and the capacitance value of the second outer electrode to ground is a second capacitance difference; Determining the liquid level of the measured container according to the variation trend of the capacitance difference includes: determining the liquid level of the measured container according to the variation trend of the first capacitance difference and the variation trend of the second capacitance difference.

6. The liquid level detection method according to claim 5, characterized in that: The first inner electrode includes a first lower edge and a first upper edge, the second inner electrode includes a second lower edge and a second upper edge, and the determining the liquid level of the measured container according to the change trend of the first capacitance difference and the change trend of the second capacitance difference includes: Determining whether the variation trend of the capacitance difference is a stable state or a varying state; If the first capacitance difference and the second capacitance difference are both in the stable state within a preset time, it is determined that the liquid level of the measured container is above the second upper edge line or below the first lower edge line or between the first upper edge line and the second lower edge line; If the first capacitance difference is in a changing state and the second capacitance difference is in a stable state, determining that the liquid level of the measured container is between the first lower edge line and the first upper edge line; If the second capacitance difference is in a changing state and the first capacitance difference is in a stable state, it is determined that the liquid level of the measured container is located between the second lower edge line and the second upper edge line.

7. A liquid level detection device, characterized in that: include: The detection electrode comprises an inner electrode and an outer electrode, wherein the inner electrode is arranged on the outer wall of the container to be detected, and the outer electrode and the inner electrode are designed to be closely attached back to back; A detection circuit, connected to the detection electrode, for detecting the capacitance value of the detection electrode to ground; A control module is connected to the detection circuit and is used to execute the liquid level detection method according to any one of claims 1 to 6.

8. The liquid level detection device according to claim 7, characterized in that: The inner electrode includes a first inner electrode and a second inner electrode, and the outer electrode includes a first outer electrode corresponding to the first inner electrode and a second outer electrode corresponding to the second inner electrode; The first inner electrode is closer to the bottom of the measured container than the second inner electrode.

9. An automatic liquid injection device, characterized in that: include: A liquid level detection device, wherein the liquid level detection device is the liquid level detection device according to claim 7 or 8; A liquid storage tank, used for storing the liquid injected into the container to be tested; The liquid injection control box is used to set the control module, wherein the control module is also used to control the liquid storage box to stop injecting liquid into the container under test when the liquid level of the container under test reaches a preset maximum liquid level.

10. The automatic liquid injection device according to claim 9, characterized in that: The container to be tested is a cigarette cartridge of an electronic cigarette.

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