Bypass valve and electric indicator integrated low-pressure fuel filter and detection method

Abstract

The invention discloses a bypass valve and electric indicator integrated low-pressure fuel filter and a detection method. The low-pressure fuel filter comprises a bypass valve shell, an annunciator shell and an electric appliance socket. A valve is arranged in a bypass valve shell, the valve and the inner wall of the shell form a two-stage sealing / two-stage triggering structure, first-stage sealing is formed by linear contact of a valve cone part and an annular inner boss, and second-stage sealing is formed by matching of a guide sleeve and a sealing section of an annular guide block; when the filter element is blocked to cause the differential pressure to reach a first threshold value, the first-stage sealing is released to trigger an alarm; according to the detection method, double-contact and liquid leakage electrical parameters are collected through the electrical appliance socket, and stability confirmation, sequence consistency judgment, alarm priority control, alarm output, bypass confirmation, sealing failure alarm and fault diagnosis alarm are carried out. And the contact event interval can be counted for prompting the blockage trend.

Description

Technical Field

[0001] This invention relates to the field of fuel filtration, bypass protection, and condition detection technology for unmanned aerial vehicle (UAV) engines, specifically a low-pressure fuel filter and detection method integrating a bypass valve and an electrical indicator. Background Technology

[0002] Unmanned aerial vehicles (UAVs) are unmanned aerial vehicles that do not require human passengers and can perform missions through remote control or pre-set flight plans. Since 2010, China's military-civilian integration industry has developed rapidly, and by 2019, the domestic UAV industry had undergone rapid upgrading, becoming a major global UAV production base. In the military field, my country has made significant progress in aviation unmanned systems technology, developing several high-performance UAVs such as the Rainbow series, Wing Loong series, and a certain "Peng" series. In the civilian field, UAVs are widely used in aerial photography, express delivery and logistics, environmental monitoring, and agricultural plant protection. With the expansion of application scale and the increasing complexity of mission conditions, UAVs are placing higher demands on the reliability, lightweight design, and maintainability of their power systems.

[0003] Drone engine fuel systems typically include low-pressure fuel filters to remove particulate impurities from the fuel, ensuring proper functioning of fuel supply components and preventing system malfunctions. As the filter element ages, impurities accumulate, increasing filter resistance and widening the pressure difference between the filter inlet and outlet. To prevent insufficient fuel supply or filter damage due to excessive clogging, a bypass valve is usually installed: when the pressure difference reaches a set threshold, the bypass valve opens, allowing fuel to flow around the filter element to maintain fuel supply. Simultaneously, to facilitate maintenance personnel monitoring the degree of filter clogging and scheduling replacements, an electrical indicator (remote electrical signal output) is usually required to provide alerts for statuses such as "approaching clogging" or "bypass open."

[0004] Currently, most low-pressure filters on the market design the bypass valve and electrical indicator separately. This type of split design typically has the following drawbacks: First, the dispersed arrangement of the bypass valve and electrical indicator often leads to an increase in internal pressure tapping and connection structures, complicating the internal flow channels of the filter and increasing product flow resistance; Second, split installation usually increases the external dimensions and the number of assembly parts, making the overall product weight larger, which is not conducive to the compact, lightweight, and refined design of UAV platforms; Third, when the bypass valve and electrical indicator are separated, there is a risk of inconsistency in their actions, that is, the triggering of the indicator does not necessarily mean that the bypass valve is in a true bypass state, and the short-term opening of the bypass valve may not be accurately indicated, affecting the reliability of maintenance decisions.

[0005] Furthermore, the fuel pump output in the low-pressure fuel system of UAVs often exhibits periodic pulsations, and sudden changes in engine operating conditions can easily generate transient pressure differential spikes. If the bypass valve or electrical indicator is overly sensitive to pressure differential changes, the threshold may drift under dynamic operating conditions, leading to alarms or false triggering of bypass confirmations. This can cause signal instability, contact jitter, and repeated critical opening and closing of the bypass port, thereby affecting system stability and reducing the lifespan of electrical switches. On the other hand, bypass valves and electrical indicators typically require an electrical installation space (dry zone) and rely on a sealing structure to isolate them from the fuel chamber. If the seals leak, allowing fuel to enter the dry zone, there is a risk of electrical failure. Existing products often lack the ability to diagnose and alarm for seal leaks / fuel ingress into the dry zone, potentially resulting in "silent failure," which is detrimental to the reliability and maintenance of UAVs.

[0006] There is already a domestic patent for a differential pressure signaler solution that integrates oil filter blockage alarm and bypass function into one unit. For example, patent document CN114109610A / B discloses an "integrated small differential pressure signaler for alarm bypass," which integrates the signaler component, differential pressure component, and housing. When the differential pressure across the oil filter reaches the alarm threshold, the valve core drives the magnet to trigger a micro switch to output an alarm signal. The disadvantages of this solution are that the action boundary depends more on the stroke / opening change, and contact jitter or malfunction may occur when encountering differential pressure pulsation or vibration, resulting in unclear distinction between alarm and bypass states. When the pressure tapping / bypass path is compact, it may also be affected by flow pulsation, resulting in limited stability of the action point. Foreign patent document US20220401859A1 uses the change of current of a magnetic sensor to realize the "nearby bypass" alarm. Although it can provide an alarm signal, it also has the following shortcomings: it mainly provides "nearby bypass" type alarm signals and it is difficult to give two clear outputs of "alarm-bypass confirmation" at the same time. Moreover, the magnetic sensing solution is more sensitive to gap tolerance, temperature drift, electromagnetic environment, and power supply line, and the signal stability and consistency may be affected under operating condition fluctuations.

[0007] The existing domestic patent document CN202991719U uses a mechanical linkage mechanism such as a linkage rod to link the bypass valve action with the detection switch, and drives an indicator light / buzzer to sound an alarm, embodying the overall concept of "bypass / byoff + switch linkage alarm". Its shortcomings are: the application object and structural system of this solution differ from the low-pressure fuel filter of UAVs, and it does not optimize the structural design for the L-shaped compact arrangement and low flow resistance channel inside the fuel filter of this application; its linkage detection is usually a single action or single threshold alarm, failing to form the dual threshold and dual contact output of alarm and bypass confirmation of this application; it also does not disclose the differential pressure sampling buffer / throttling low-pass filter and displacement chain damping set up in this application to suppress false triggering caused by pump pulsation; nor does it address the dry area intrusion monitoring and seal failure alarm priority for electrical dry area risks, as well as reliability improvement measures such as consistency diagnosis / debouncing based on contact sequence, as in this application; similarly, patent document CN119097985B also adopts the overall concept of switch linkage alarm, but it also has the above-mentioned problems.

[0008] Foreign patent document US4574836A discloses a structure that integrates a bypass valve and an indicator, used to provide an indication when a filter bypasses, improving the reliability of "bypass occurrence - indication trigger". Its disadvantages are: this solution is mainly aimed at the reliable triggering of mechanical / magnetic indicating mechanisms, and does not provide a structured design for the compact L-shaped arrangement of UAV low-pressure fuel filters and the standard output of electrical sockets; it also does not disclose the dual-threshold (alarm + bypass confirmation) electrical signal output mechanism used in this application, nor the differential pressure pulsation suppression structure (buffer chamber + throttling orifice / damping) set to adapt to pump pulsation and sudden changes in operating conditions; at the same time, it does not involve the reliability design proposed in this application for dry area oil intrusion detection and seal failure alarm priority for electrical dry area risks; another document US2015 / 0128906A1 proposes an indication / alarm system for "imminent bypass and actual bypass" for aviation fuel filter scenarios, which realizes the output of different states through differential pressure detection and logic judgment, and links the bypass valve state with the indication strategy at the system level. This type of solution emphasizes the monitoring and alarm approach in aviation applications, but its implementation usually relies on sensor measurement and signal processing links; document number US4574728A can distinguish between different states such as "differential pressure is close to the bypass threshold (about to bypass)" and "bypass has occurred", which reflects the idea of ​​multi-threshold / multi-state indication; but it also has the above-mentioned problems.

[0009] Therefore, under the premise of meeting the installation requirements of low-pressure fuel filters and the coordination and connection requirements of various functional components, there is an urgent need for an integrated product that can achieve a compact structure, low opening pressure, integration of bypass valve and electric indicator, good linkage consistency and high reliability under the constraints of device principle, function, performance, weight and strength, and can improve the stability of indication and fault diagnosability under dynamic operating conditions, so as to solve the problems existing in the above-mentioned existing technologies. Summary of the Invention

[0010] The technical problem this invention aims to solve is to overcome existing defects and provide a low-pressure fuel filter and detection method that integrates a bypass valve and an electrical indicator. This invention achieves a compact L-shaped integration of the bypass valve housing, the indicator housing, and the electrical socket, reducing the complexity of the outer contour and internal flow channels and decreasing flow resistance while ensuring structural strength and lightweight layout. Through the valve's two-stage sealing / two-stage triggering structure combined with a dual-contact microswitch, a stable alarm is output when the pressure difference reaches ΔP1, and a bypass confirmation signal is output when it reaches ΔP2. This makes the "about to bypass / already bypassed" state boundary clear and strongly consistent with the actual valve action, effectively solving the problems in the background technology.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a low-pressure fuel filter and detection method integrating a bypass valve and an electrical indicator, comprising a bypass valve housing, an indicator housing, and an electrical socket. The bypass valve housing, indicator housing, and electrical socket are fixedly connected and arranged in an L-shape. They can be connected by flanges and fixed with screws. This structure helps to reduce vertical space, thereby increasing the internal space of the product and reducing the outer contour size. With ample internal space, optimizing the internal flow channel of the low-pressure fuel filter can effectively reduce the flow resistance of the product. A valve is installed inside the bypass valve housing, and a two-stage triggering structure is formed between the valve and the inner wall of the bypass valve housing. The two-stage triggering structure includes a cone part, a guide sleeve, and an annular guide block. The cone part is an integral structure with the valve. The cone part makes linear contact with the annular inner boss on the inner wall of the bypass valve housing, achieving a hard seal structure under the action of the main spring. This linear contact is a first-stage sealing structure. By controlling the machining accuracy of the parts, both sealing performance and the number of parts can be reduced. The product is designed to ensure reliability. A guide sleeve is located on the right side of the cone section. The guide sleeve and valve can be machined as a single unit or separately and fixed by bonding to reduce processing difficulty. An annular guide block is located on the inner circumference of the bypass valve housing. An annular groove is located on the left side of the annular guide block, which slides with the guide sleeve, achieving a two-stage contact seal and guiding the valve. A flow channel is located at the right end of the guide sleeve, arranged in an L-shape, connecting the circumferential surface of the guide sleeve and the right end. A through hole is located at the bottom of the annular groove, communicating with the flow channel for liquid flow. On the left side of the flow channel, the outer circumferential surface of the guide sleeve and the inner circumferential surface of the annular guide block form a sealing section. The guide sleeve and the annular guide block form a two-stage sealing structure. When the pressure difference reaches ΔP1, the valve displaces by S1, the cone section separates from the annular inner boss, and the first-stage sealing structure opens. This first-stage sealing structure is the first actuation point, triggering the microswitch contact group to activate an alarm.Furthermore, due to the presence of the sealing section, the secondary sealing structure will not open. When the pressure difference reaches ΔP2, the valve will displace S2, where S2 > S1. The flow channel connects the high-pressure oil chamber and the low-pressure oil chamber, triggering the second action point. The second contact group of the microswitch actuates, opening the bypass. An auxiliary spring is provided inside the guide sleeve. This auxiliary spring is used to compensate for and adjust the elasticity of the main spring, thereby adjusting the opening pressure difference of the bypass. The auxiliary spring is located between the annular guide block and the valve. This auxiliary spring can be set according to the actual situation or not. The spring increases the flexibility of the bypass mechanism and improves its practicality. A microswitch is installed inside the signal device housing; two microswitches can be used, or a double-contact microswitch can be employed. A magnet is installed at the right end of the valve, and the right end of the valve is inserted into the countersunk hole at the right end of the bypass valve housing. A movable cover is slidably connected to the right end of the bypass valve housing. A second magnet, which cooperates with magnet one, is installed on the movable cover. Magnets one and two are magnetically engaged. As magnet one moves to the left, magnet two moves to the right under the influence of the magnetic force, thereby causing the movable cover to contact the microswitch.

[0012] The signal receiver housing and the bypass valve housing are assembled to form an electrical installation space. The electrical socket is connected to the micro switch via a cable and is used to output status signals.

[0013] In the low-pressure fuel system of UAVs, the fuel pump output exhibits periodic pulsations, and sudden changes in engine operating conditions can cause transient pressure difference spikes. If the bypass valve is "too sensitive" to pressure difference changes, it can cause: the ΔP1 / ΔP2 threshold to drift under dynamic operating conditions, triggering alarms or bypass confirmations due to spikes, resulting in false alarms; reduced lifespan of microswitch contacts and unstable signals; and repeated micro-opening and closing of the bypass valve, i.e., critical opening and closing of the bypass port, affecting system stability.

[0014] Therefore, low-pass filtering / damping needs to be introduced into the "path of differential pressure to valve" or "displacement transmission link: from the moving cover to the micro switch" to make the valve response closer to the average blockage level rather than transient spikes, thereby stabilizing ΔP1 / ΔP2 and the switching action.

[0015] The differential pressure sampling passage of the valve is located between the cone and the guide sleeve, and a differential pressure pulsation suppression structure is provided on this passage; the structure includes a buffer cavity formed between the guide sleeve and the annular inner boss, and throttling orifices are provided on the left and right sides of the buffer cavity respectively. The throttling orifice on the left side is connected to the high-pressure side oil cavity to limit the flow of fuel into the buffer cavity; and the throttling orifice on the right side of the buffer cavity is connected to the low-pressure side oil cavity to controllably release the pressure in the buffer cavity.

[0016] Furthermore, a liquid inlet is provided on the right end of the bypass valve housing in the circumferential direction to form a liquid inlet end, and a bypass port is provided in the middle of the bypass valve housing for oil bypass. An O-ring is provided on the circumferential direction of the bypass valve housing for isolating the oil chamber and the bypass chamber.

[0017] Furthermore, a main spring is provided at the left end of the valve, which is used to apply an elastic force to the valve to make it tend to close the bypass port. A plug is provided at the right end of the bypass valve body, and the plug abuts against the left end of the main spring.

[0018] Furthermore, a positioning plate is provided inside the signal device housing. The positioning plate is fixedly connected to the bypass valve housing by long screws. A micro switch is installed on the positioning plate. A central hole is provided in the center of the positioning plate. The contacts of the micro switch are located in the central hole, and the right end of the movable cover corresponds to the central hole.

[0019] Furthermore, the buffer chamber consists of throttling ring one and throttling ring two, which are fixedly connected to the guide sleeve. During processing, throttling ring one, throttling ring two, and the guide sleeve can be machined into a single structure. The outer circumference of throttling ring one and throttling ring two slides in contact with the annular inner boss, forming a buffer chamber between throttling ring one and throttling ring two. Throttling orifices are respectively opened on throttling ring one and throttling ring two, and the throttling orifices are staggered. A damping ring is set at the sliding fit between the movable cover and the bypass valve housing. The movable cover can also be equipped with a pre-tightening elastic element for applying pre-tightening force to the damping ring. The specific setting is selected according to the actual situation and will not be detailed here. This is to dissipate energy and suppress jitter when the movable cover undergoes high-frequency small-amplitude reciprocating displacement.

[0020] Furthermore, a leakage guiding structure is provided at the isolation interface between the signal device housing and the bypass valve housing and / or the installation interface between the electrical socket and the signal device housing to guide fuel leakage at the seal. Specifically, an O-ring is provided at the isolation interface, and an O-ring is provided at the installation interface. Fuel leakage generated by O-ring one and / or O-ring two and / or the sealing section is guided to a predetermined collection location. Additionally, a leakage detection circuit is provided at the bottom of the dry area of ​​the signal device housing. This leakage detection circuit is electrically connected to the electrical socket and is used to output a seal failure alarm signal via the electrical socket when fuel leakage enters the dry area and causes a change in the electrical parameters of the leakage detection circuit.

[0021] Specifically, at the interface between the bypass valve housing and the signal housing, a leakage guiding structure is set around the sealing position of O-ring one; and / or at the installation interface between the electrical socket and the signal housing, a leakage guiding structure is set around the sealing position of O-ring two. This leakage guiding structure can be an annular or semi-annular guiding groove, a confluence slope, or a drainage channel connected to the outside on the mating surface. When leakage occurs at the seal, the leaking fuel is directed to flow and collect preferentially along a predetermined path, preventing the leaking fuel from spreading disorderly within the electrical installation space of the signal housing. The specific setting is adjusted in practice according to the housing structure.

[0022] A liquid collection point is set at the lowest point of the dry area inside the signal device housing, and a leakage detection circuit is arranged therein. The leakage detection circuit may include two electrodes (or equivalent conductive detection structures) arranged at intervals between each other. The two electrodes are electrically connected to an electrical socket through wires or conductive lines. An external controller can detect the continuity or equivalent resistance between the two electrodes through the electrical socket.

[0023] When O-ring one and / or O-ring two and / or the sealing section leak, the leaking fuel first enters the leakage guiding structure and is guided to a predetermined collection location. Simultaneously, a small amount of leaking fuel can be guided to the collection location at the lowest point of the dry area of ​​the signaler housing, thereby changing the electrical parameters between the two electrodes of the leak detection circuit. Based on this, the external controller determines that there is a risk of fuel intrusion / seal failure in the dry area and outputs a seal failure alarm signal through the electrical socket. This allows for early diagnosis and maintenance reminders before the microswitch and electrical components experience silent failure due to fuel intrusion.

[0024] By combining the aforementioned leakage diversion structure with the leakage detection circuit, the sealing leakage can be transformed from "invisible and undiagnosable" to "guided, detectable, and alarmable," thereby significantly reducing the risk of silent failure caused by oil ingress into the electrical installation space of the signal device housing, improving system reliability and maintainability, and is especially suitable for application scenarios such as UAVs that have high requirements for condition diagnosis and airworthiness reliability.

[0025] Furthermore, the external controller acquires the status signals of contact group one and contact group two of the micro switch via the electrical socket, and performs debouncing confirmation and sequence consistency judgment on the status signals; when it is detected that the action of contact group two does not meet the sequential constraint that contact group one should act first and / or contact group one is not in the acted state when contact group two acts, a diagnostic fault alarm is output; and the external controller statistically analyzes the time interval between the action events of contact group one and contact group two to output filter clogging trend or maintenance reminder information.

[0026] Furthermore, in step S101, during power-on or operation, the external controller simultaneously collects the status signals of contact group one and contact group two of the micro switch via the electrical socket, and also collects the electrical parameters of the leakage detection circuit.

[0027] S102, determine whether the micro switch is triggered based on the state signals of contact group one and contact group two; wherein, when the pressure difference of the low-pressure fuel filter causes the valve to shift and triggers the micro switch through the movable cover, contact group one and / or contact group two will operate; and compare the electrical parameters of the leakage detection circuit with the dry state criterion to determine whether the electrical parameters are in the high resistance or non-conducting range corresponding to the dry state;

[0028] S103, when it is determined that contact group one has acted and the electrical parameter is in the high resistance or non-conducting range, the external controller outputs a blockage alarm signal through the electrical socket and returns to execute step S101 for cyclic monitoring.

[0029] S104, when the second contact group is activated, the external controller determines that the low-pressure fuel filter has entered the bypass confirmation state and generates a bypass confirmation signal; and when the electrical parameters are not in the high resistance or non-conducting range, the external controller determines that there is a risk of fuel intrusion or seal failure in the dry area of ​​the signal housing, and sets the seal failure alarm to a higher alarm priority than the alarm signal and / or the bypass confirmation signal.

[0030] S105, the external controller outputs the bypass confirmation signal through the electrical socket, and when it is determined that there is a risk of fuel intrusion or seal failure, it outputs a seal failure alarm signal with the alarm priority, and continues to output the seal failure alarm signal until the reset condition is met.

[0031] Furthermore, a stability confirmation step is included between step S101 and step S102. The stability confirmation step includes de-jittering the status signals of contact group one and contact group two, and / or sampling the electrical parameters multiple times within a preset confirmation time window, and only executing step S102 when the results of multiple samplings meet the consistency condition, so as to suppress false triggering caused by differential pressure pulsation or vibration and false alarms caused by transient interference.

[0032] Furthermore, the external controller performs a sequence consistency judgment on the actions of contact group one and contact group two. The sequence consistency judgment includes at least the requirement that the action of contact group two should occur after the action of contact group one. When it is detected that the action of contact group two does not meet the sequence constraint and / or contact group one is not in the activated state when contact group two is activated, the external controller outputs a diagnostic fault alarm signal.

[0033] Furthermore, the external controller adaptively adjusts the confirmation time window and / or consistency conditions based on the operating condition parameters; wherein the operating condition parameters include at least one of engine speed, fuel pump drive frequency or duty cycle, fuel temperature, and fluctuation amplitude or short-time variance of the differential pressure sampling signal.

[0034] Furthermore, the external controller performs statistics on the state flipping of contact group one and / or contact group two. Within a preset statistical window, when the contact closing / opening duration is less than the preset minimum holding time and the number of flipping reaches a preset threshold, a contact chatter diagnostic signal is output.

[0035] Furthermore, the leakage alarm signal is a graded alarm signal. The external controller outputs at least a first-level leakage alarm and a second-level leakage alarm according to the different penetration criteria based on the electrical parameters of the leakage detection circuit. The graded method includes: at least two sets of detection electrodes at different heights or positions trigger graded outputs respectively, and / or the same set of detection electrodes corresponds to at least two penetration threshold intervals for graded output.

[0036] Furthermore, the controller performs a self-test on the leakage detection circuit to determine whether the leakage detection circuit is open-circuited, short-circuited, or abnormally drifting, and outputs a leakage detection circuit fault diagnosis signal when a self-test abnormality is determined; wherein the self-test includes power-on self-test and / or operation interval self-test performed according to a preset cycle.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] 1. This invention integrates the bypass valve housing, signal housing, and electrical socket into a single unit with a compact L-shaped arrangement. This allows the bypass function and remote electrical indication output to be completed within the same component, reducing the additional connectors, installation interfaces, and pressure tapping structures commonly found in split-type solutions. This helps to reduce vertical space occupation and external dimensions, lighten the overall weight, and improve the layout flexibility of the UAV platform. At the same time, the integrated structure makes the internal space and flow channel organization of the fuel filter more controllable, facilitating the optimization of fuel passages, reducing the additional pressure drop caused by the detour flow channel, and improving low-pressure fuel supply margin and engine operating condition adaptability.

[0039] 2. Through the two-stage triggering structure and two-stage sealing structure formed by the valve and the inner wall of the housing, a dual-threshold output logic of "alarm-bypass confirmation" is realized: when the differential pressure reaches the first threshold, the first-stage seal is released and the contact group one of the micro switch is triggered to output a blockage alarm signal. When the differential pressure further increases to the second threshold, the second-stage seal is released and the flow channel is connected to enter the bypass state, while the contact group two is triggered to output a bypass confirmation signal. This structure makes the boundary between the "about to bypass" and "already bypassed" states clear, avoiding misjudgments caused by single threshold or inconsistency between the indication and the valve state. Furthermore, the opening differential pressure can be compensated and adjusted by the cooperation of the main spring and the auxiliary spring, improving batch consistency and adaptability under different temperature, viscosity, and flow conditions.

[0040] 3. To address the transient differential pressure spikes caused by fuel pump pulsation and sudden changes in operating conditions in drones, this invention incorporates a differential pressure pulsation suppression structure consisting of a buffer chamber and a throttling orifice in the differential pressure sampling path of the valve. This structure enables the differential pressure action to exhibit a controlled low-pass response, preventing transient peaks from driving the valve to generate high-frequency small displacements. Furthermore, a damping structure is installed at the relative sliding contact between the movable cover and the housing to dissipate high-frequency reciprocating energy. This significantly reduces the probability of false alarm and bypass confirmation triggers, minimizes microswitch contact jitter and wear, improves signal stability and contact lifespan, and suppresses repeated micro-opening and closing of the bypass port in critical states. This improves system pressure fluctuations and fuel supply stability, making it particularly suitable for applications with more demanding dynamic operating conditions, such as drones.

[0041] 4. This invention further addresses the reliability issues of electrical installation spaces by incorporating leakage guidance structures at the isolation interface between the signal device housing and the bypass valve housing, and / or at the installation interface between the electrical socket and the signal device housing. A leakage detection circuit is also installed at the bottom of the dry area. This allows seal leakage to be guided, collected, and converted into detectable changes in electrical parameters, which are then output as a seal failure alarm signal via the electrical socket. This reduces the risk of short circuits, corrosion, or "silent failure" caused by oil ingress into the dry area. The external controller can also perform debouncing confirmation and sequence consistency judgment on the dual-contact status. In cases of abnormal contact action sequence or contact inconsistency, it outputs diagnostic fault alarms and can statistically analyze the time interval between alarms and bypass confirmation events to generate blockage trends and maintenance prompts. Simultaneously, the seal failure alarm is prioritized higher than the alarm and bypass confirmation outputs, allowing critical risks to be exposed earlier and handled more easily, thus improving overall system safety, diagnosability, and maintainability. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the internal structure of the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of the present invention from a bottom view;

[0044] Figure 3 This is an enlarged structural diagram of point A in the present invention;

[0045] Figure 4 This is an isometric view of the entire invention;

[0046] Figure 5 This is a flowchart of the dry zone oil inlet / seal failure monitoring process of the leakage detection circuit of the present invention;

[0047] Figure 6 This is the overall flowchart of the low-pressure fuel filter status detection and alarm output of the present invention.

[0048] In the diagram: 1. Plug, 2. Main spring, 3. O-ring I, 4. Valve, 5. Bypass valve housing, 6. Movable cover, 7. Positioning plate, 8. Micro switch, 9. Cylindrical head screw, 10. Signal device housing, 11. Cable, 12. Long screw, 13. Electrical socket, 14. Locking screw, 15. Fixing screw, 16. O-ring II, 17. Magnet I, 18. Magnet II, 19. Bypass port, 20. Liquid inlet, 21. Auxiliary spring, 22. Sealing section, 23. Flow channel, 24. Annular guide block, 25. Guide sleeve, 26. Conical part, 27. Through hole, 28. Annular groove, 29. Annular inner boss, 30. Throttling ring I, 31. Throttling orifice, 32. Buffer chamber, 33. Throttling ring II, 34. Damping ring. Detailed Implementation

[0049] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0050] Example 1

[0051] Please see Figure 1-6 This invention provides a technical solution: a low-pressure fuel filter and detection method integrating a bypass valve and an electrical indicator, comprising a bypass valve housing 5, an indicator housing 10, and an electrical socket 13; the bypass valve housing 5, the indicator housing 10, and the electrical socket 13 are fixedly connected to form an integrated assembly, arranged in an L-shape; the three components can be connected by flanges and fixed with screws to achieve compact installation and reduce external connection interfaces; an inlet 20 is provided on the right circumferential direction of the bypass valve housing 5, and a bypass port 19 is provided in the middle of the bypass valve housing 5; an O-ring 3 is provided on the outer circumference of the bypass valve housing 5 for sealing and isolating the oil chamber and the bypass chamber; and an O-ring 16 can be provided at the installation interface between the electrical socket 13 and the indicator housing 10 to form an additional sealing interface in the electrical connection area.

[0052] A valve 4 is installed inside the bypass valve housing 5. A two-stage triggering structure is formed between the valve 4 and the inner wall of the bypass valve housing 5. The two-stage triggering structure includes a cone portion 26, a guide sleeve 25, and an annular guide block 24.

[0053] 1. Primary sealing structure

[0054] The cone portion 26 is an integral structure with the valve 4. The cone portion 26 is in linear contact or narrow ring contact with the annular inner boss 29 on the inner wall of the bypass valve housing 5 to form a primary sealing structure; a hard seal is achieved under the action of the main spring 2.

[0055] 2. Secondary sealing structure and guiding structure

[0056] The guide sleeve 25 is located on the right side of the cone portion 26. The guide sleeve 25 and the valve 4 can be machined as a single piece or machined separately and then fixedly connected. The annular guide block 24 is located in the circumferential direction inside the bypass valve housing 5. The annular guide block 24 and the guide sleeve 25 slide together to guide the valve 4 and form a secondary sealing fit. An annular groove 28 is provided on the left side of the annular guide block 24. The bottom of the annular groove 28 is provided with a through hole 27 that communicates with the flow channel 23. The flow channel 23 is provided at the right end of the guide sleeve 25. The flow channel 23 is arranged in an L-shape to connect the circumferential surface of the guide sleeve 25 with the right end of the guide sleeve 25. The flow channel 23 is connected to the annular groove 28 through the through hole 27 to form a controlled communication path. A sealing section 22 is provided on the left side of the flow channel 23 for the guide sleeve 25 and the annular guide block 24. The guide sleeve 25 and the annular guide block 24 form a secondary sealing structure through the sealing section 22.

[0057] A main spring 2 is installed at the left end of valve 4, and a plug 1 is installed at the end of the bypass valve body 5. The plug 1 abuts against the left end of the main spring 2. The main spring 2 is used to apply an elastic force to valve 4 to make it tend to close the bypass port 19. An auxiliary spring 21 is installed inside the guide sleeve 25. The auxiliary spring 21 is located between the annular guide block 24 and valve 4 and is used to compensate for and adjust the elastic force of the main spring 2 in order to adjust the bypass opening pressure difference. The auxiliary spring 21 can be configured or not configured according to calibration requirements.

[0058] A microswitch 8 is installed inside the signal receiver housing 10. The microswitch 8 has a double-contact structure to form contact group one and contact group two (two microswitches can also be used to achieve two-level signal output respectively). A magnet 17 is installed on the right end of the valve 4, and the right end of the valve 4 is inserted into the countersunk hole on the right end of the bypass valve housing 5. The right end of the bypass valve housing 5 is slidably connected to the movable cover 6, and a magnet 28 is installed on the movable cover 6 and magnetically coupled to the magnet 17. When the valve 4 moves under the action of pressure difference, the magnet 17 moves with the valve 4 and drives the magnet 28 and the movable cover 6 to move through magnetic coupling, thereby triggering the microswitch 8 and outputting a corresponding status signal. The signal receiver housing 10 and the bypass valve housing 5 are assembled to form an electrical installation space. The electrical socket 13 is connected to the microswitch 8 through the cable 11 for outputting status signals to the outside.

[0059] To suppress transient differential pressure spikes caused by fuel pump pulsation and sudden changes in operating conditions in the UAV, this embodiment sets up a differential pressure pulsation suppression structure in the differential pressure sampling passage of valve 4. The differential pressure pulsation suppression structure includes: a buffer cavity 32 formed between the guide sleeve 25 and the annular inner boss 29, and throttling orifices 31 set on the left and right sides of the buffer cavity 32 respectively; the left throttling orifice 31 is connected to the high-pressure side oil cavity, and the right throttling orifice 31 is connected to the low-pressure side oil cavity, so as to limit the transient transmission of high-pressure side pressure to valve 4 and control the release of pressure in the buffer cavity 32; the high-pressure side is the pre-filter (upstream) oil cavity; the low-pressure side is the post-filter (downstream) oil cavity.

[0060] During operation, a dual-threshold linkage logic is adopted. In this embodiment, valve 4 is displaced under the action of the pressure difference before and after the filter, and the "alarm-bypass confirmation" linkage output is realized through a two-stage triggering structure.

[0061] When the pressure difference reaches the first threshold ΔP1, valve 4 overcomes the spring force to generate the first displacement S1, causing the cone part 26 to separate from the annular inner boss 29, and the primary sealing structure to open; at this time, since the sealing section 22 still remains sealed, the secondary sealing structure does not open, and the bypass oil circuit is not yet connected; the displacement of valve 4 drives the movable cover 6 to move through the magnetic coupling of magnet 17 and magnet 2 18, triggering the action of the contact group 1 of micro switch 8, and outputting an alarm signal through electrical socket 13.

[0062] When the pressure difference further increases to the second threshold ΔP2, valve 4 generates a second displacement S2, S2>S1. The flow channel 23 on the guide sleeve 25 forms an effective connection with the annular groove 28 through the through hole 27, so that the flow channel 23 connects to the oil chamber and the bypass port 19 enters the bypass open state; the movable cover 6 moves further, triggering the second contact group of the micro switch 8 to act, and outputs a bypass confirmation signal through the electrical socket 13.

[0063] In this embodiment, the electrical socket 13 is detachably connected to the signal housing 10 via a fixing screw 15. The fixing screw 15 passes through the mounting hole of the electrical socket 13 and engages with the threaded hole on the signal housing 10 to achieve the positioning and fixing of the electrical socket 13. The locking screw 14 is provided on the electrical socket 13 or the signal housing 10 and engages with the fixing screw 15 to form an anti-loosening structure, for example, to tighten the fixing screw 15 or to lock it, so as to prevent the fixing screw 15 from loosening under vibration conditions and causing electrical connection failure. The electrical socket 13 is electrically connected to an external controller via a cable 11. The cable 11 is used to transmit the contact group one status signal C1, the contact group two status signal C2, and the electrical signal corresponding to the leakage detection circuit electrical parameter L of the micro switch 8.

[0064] In one embodiment, O-ring 3 is disposed at the connection and mating point between the bypass valve housing 5 and the signal housing 10, preferably disposed in the outer circumferential sealing groove of the bypass valve housing 5 or the corresponding sealing groove of the signal housing 10, for circumferential static sealing of the assembly and connection interface between the two, preventing fuel from leaking or cross-leaking along the housing mating surface; O-ring 16 is disposed at the mating point between the electrical socket 13 and the signal housing 10, preferably disposed in the annular sealing groove on the outer circumference of the electrical socket 13 or the signal housing 10, for sealing the installation interface of the electrical socket 13, reducing the risk of fuel vapor, moisture or dust entering the electrical connection area, thereby improving the reliability of the electrical connection.

[0065] In this embodiment, to facilitate early identification and location of sealing failures of O-ring 3 and / or O-ring 16, the signal housing 10 and / or the bypass valve housing 5 are provided with a leakage guiding structure at the corresponding sealing interface to guide fuel leaking from O-ring 3 and / or O-ring 16 to a predetermined collection location; the leakage guiding structure includes at least one or more of a guiding groove, a guiding channel, and a collection cavity, and structurally satisfies that the fuel flows along a predetermined path and does not diffuse disorderly at the joint surface; surrounding O-ring 3... At the sealing position, an annular or semi-annular guide groove is provided on the inner wall of the signal housing 10 or the outer wall of the bypass valve housing 5. The guide groove is continuously formed in the circumferential direction and arranged around the O-ring 3. The cross-section of the guide groove can be U-shaped or V-shaped, and its width can be 0.5mm to 3mm and its depth can be 0.3mm to 2mm, so as to form a preferred flow path when the O-ring 3 has a slight leakage. The guide groove is connected to the drainage channel, which can be a groove or channel extending in the axial or radial direction and connected to the collection cavity inside the signal housing 10.

[0066] The collecting cavity is located at the bottom or lowest point of the dry area of ​​the signal housing 10, and the elevation of the lowest point of the collecting cavity is lower than the elevation of the lowest point of the guide groove, so as to use gravity or capillary action to promote the leakage fuel into the collecting cavity; around the sealing position of O-ring 2 16, the signal housing 10 is provided with a circumferential guide groove or annular confluence cavity at the installation interface of the electrical socket 13. The circumferential guide groove or annular confluence cavity is connected to at least one drainage hole or drainage channel, which extends radially or axially and leads to the collecting cavity; preferably, the guide groove around O-ring 1 3 and the circumferential guide groove around O-ring 2 16 are respectively connected to the same collecting cavity through their respective drainage channels, so as to realize the centralized collection and unified detection of leakage at different sealing positions. Alternatively, they can be configured to be connected separately. The system connects to different collection chambers to differentiate and locate the source of leakage. A detection electrode group for the leakage detection circuit is set at the collection chamber. The detection electrode group includes a first detection electrode and a second detection electrode. The distance between the first detection electrode and the second detection electrode can be 0.5mm to 5mm. The detection electrode group is arranged at or near the lowest point of the collection chamber, so that the leaking fuel preferentially covers the detection electrode group. The external controller collects the electrical parameter L of the leakage detection circuit. When the electrical parameter L changes from the range corresponding to the dry state to the range corresponding to the seepage state and meets the consistency condition within the preset confirmation time window, a seal failure alarm signal is output. This realizes directional flow, rapid collection and reliable detection around the sealing position of O-ring 3 and / or O-ring 16.

[0067] Furthermore, the leakage guiding structure can be processed as needed according to the actual assembly interface and installation space. It can be set on the corresponding surfaces of the signal housing 10 and / or the bypass valve housing 5 and the electrical socket 13. For example, it can be processed by turning, milling, drilling, stamping or injection molding to form a guiding groove, a guiding hole, a guiding channel or a collecting cavity. It should be understood that the technical solution of the present invention does not require all guiding features to be set at the same time in all embodiments. Under the premise of not affecting the basic function of the bypass valve and the signal, it is only necessary to set a guiding structure that can guide the leaked fuel to the predetermined collecting position near the sealing position of O-ring 1 3 and / or O-ring 2 16. Since the guiding structure is mostly a local groove or channel, it is not necessary to draw them one by one in the figure for the purpose of simplification of the figure, but it does not affect the ability of those skilled in the art to process and implement it in the actual product based on the above description. Moreover, the leakage guiding structure can be set or not set according to actual needs.

[0068] Parameter settings: To ensure clear two-level action points, stable action, and adaptability to dynamic working conditions, this embodiment provides recommended engineering ranges and adjustable methods for threshold, displacement, temperature, and key coordination.

[0069] 1. Threshold ΔP1, ΔP2 range and adjustment

[0070] The first threshold ΔP1 and the second threshold ΔP2 satisfy ΔP2>ΔP1; ΔP1 is recommended to be 0.03~0.12MPa, preferably 0.05~0.10MPa; ΔP2 is recommended to be 0.10~0.30MPa, preferably 0.15~0.25MPa; ΔP2−ΔP1 is recommended to be 0.05~0.15MPa;

[0071] ΔP1 and ΔP2 can be determined by the stiffness and preload of the main spring 2, the effective pressure area of ​​the valve 4, and the matching parameters of the secondary sealing structure; the auxiliary spring 21 is used to compensate or fine-tune the elastic force to achieve the calibration adjustment of ΔP2 and improve batch consistency.

[0072] 2. Displacement ranges S1 and S2 and limit / hysteresis

[0073] The first displacement S1 is used to reliably release the primary seal, and the second displacement S2 is used to ensure stable connection of the flow channel 23 and form a bypass opening, and S2>S1 is satisfied; S1 is recommended to be 0.2~0.8mm, preferably 0.3~0.6mm; S2 is recommended to be 1.0~3.0mm, preferably 1.5~2.5mm;

[0074] To reduce high-frequency jitter and false triggering near the threshold, a valve stroke limiting structure (such as a valve step, retaining ring, or housing limiting shoulder) can be set to limit the maximum displacement; and hysteresis characteristics are formed by the magnetic coupling gap, the trigger stroke of the movable cover 6, and the action hysteresis of the micro switch 8, so that the contact action is closer to the average degree of blockage rather than transient spikes.

[0075] 3. Temperature range and media compatibility

[0076] This embodiment is applicable to the fuel medium of the low-pressure fuel system of UAV engine; the recommended operating temperature range is -40℃ to +85℃; in more severe environments, it can be extended to -55℃ to +125℃; the increased viscosity at low temperatures leads to an increase in pressure difference, so ΔP1 and ΔP2 need to be checked or calibrated under the lowest temperature conditions to ensure that the alarm and bypass confirmation are reliable and consistent.

[0077] 4. Guide clearance, sealing section dimensions, and sealing surface quality

[0078] The radial clearance of the sliding fit between the guide sleeve 25 and the annular guide block 24 is recommended to be 0.01 to 0.05 mm to balance low-friction sliding and guiding stability; the axial length of the sealing section 22 is recommended to be 1 to 5 mm, preferably 2 to 4 mm, to ensure that the secondary seal does not open in stage S1 and a stable connection is formed in stage S2; the surface roughness of the sealing mating surface between the cone portion 26 and the annular inner boss 29 is recommended to be Ra≤0.8μm, preferably Ra≤0.4μm, and the coaxiality / circular runout of the two should be controlled to meet the sealing and repeatability requirements.

[0079] Pressure differential pulsation suppression and displacement chain damping: The fuel pump output in the low-pressure fuel system of the UAV has periodic pulsations, and sudden changes in engine operating conditions can easily generate transient pressure differential spikes. If valve 4 and micro switch 8 are too sensitive to pressure differential changes, false alarm / bypass confirmation triggering, contact jitter, and critical repeated micro-opening and closing of bypass port 19 can easily occur. This embodiment suppresses the above problems by using pressure differential sampling low-pass and displacement chain damping.

[0080] The buffer chamber 32 is located between the guide sleeve 25 and the annular inner boss 29. Throttling holes 31 are respectively provided on the left and right sides of the buffer chamber 32. The left throttling hole 31 is connected to the high-pressure side oil chamber to limit the flow of fuel into the buffer chamber 32. The right throttling hole 31 is connected to the low-pressure side oil chamber to release the pressure of the buffer chamber 32 in a controlled manner, so that the pressure change in the buffer chamber 32 is controlled and thus suppresses the transient drive of the valve 4 by the pressure difference peak.

[0081] The throttling orifice 31 can be implemented using micro-orifices or equivalent throttling grooves; the recommended equivalent orifice diameter of the throttling orifice 31 is 0.2 to 1.0 mm. The effective volume of the buffer chamber 32 is designed in conjunction with the pump pulsation frequency and the target response time constant to reduce the driving amplitude of high-frequency components and maintain the ability to respond to continuous clogging trends.

[0082] like Figure 3 As shown, the buffer cavity 32 is formed by throttling ring 30 and throttling ring 33. Throttling ring 30 and throttling ring 33 are fixedly connected to the guide sleeve 25, and their outer circumferences are in sliding contact with the annular inner boss 29. Throttling holes 31 are respectively opened on throttling ring 30 and throttling ring 33 and are staggered to reduce direct flushing and improve filtering stability.

[0083] A damping ring 34 is provided at the sliding fit between the movable cover 6 and the bypass valve housing 5. The damping ring 34 is used to dissipate energy and suppress jitter when the movable cover 6 undergoes high-frequency small-amplitude reciprocating displacement. The movable cover 6 can be further provided with a pre-tightening elastic element to apply a pre-tightening force to the damping ring 34, so that the damping force is within a controllable range, thereby improving the anti-jitter capability and triggering consistency without significantly increasing the steady-state triggering force.

[0084] Leakage guiding structures are provided at the isolation interface between the signal housing 10 and the bypass valve housing 5 and / or at the installation interface between the electrical socket 13 and the signal housing 10. These structures guide the leaking fuel generated by O-ring 1 (isolation interface) and / or O-ring 2 16 (installation interface) and / or the sealing section 22 to a predetermined collection location, preventing the leaking fuel from spreading disorderly within the electrical installation space of the signal housing 10. A guide groove, a confluence slope, and a drainage channel connecting to the outside are provided around the sealing position of O-ring 13 at the isolation interface and / or around the sealing position of O-ring 2 16 at the installation interface. The leaking fuel at the seal flows and collects along a predetermined path, reducing the risk of fuel intrusion into electrical components in the dry area. A liquid collection position is provided at the lowest point of the dry area inside the signal housing 10, and a leak detection circuit is arranged therein. The leak detection circuit includes two electrodes (or equivalent conductive detection structures) spaced apart from each other, and the two electrodes are electrically connected to the electrical socket 13. An external controller detects the continuity or equivalent resistance between the two electrodes through the electrical socket 13. When… When leaking fuel enters the dry area collection point and causes a change in the electrical parameters of the leak detection circuit (which can be a change in resistance / conduction, capacitance / dielectric constant), the external controller determines that there is a risk of fuel intrusion / sealing failure in the dry area and outputs a sealing failure alarm signal via electrical socket 13. This allows for early diagnosis and maintenance reminders before the microswitch 8 and electrical components experience silent failure due to fuel intrusion. The external controller obtains the status signals of contact group one and contact group two of microswitch 8 via electrical socket 13 and performs debouncing confirmation and sequence consistency judgment on the status signals. The sequence consistency judgment includes at least the following: the action of contact group two should occur after the action of contact group one. When the action of contact group two does not meet the sequential constraint that contact group one should act first, and / or contact group one is not in an activated state when contact group two acts, the external controller outputs a diagnostic fault alarm. The external controller statistically analyzes the time interval between the action events of contact group one and contact group two to output filter clogging trend or maintenance reminder information.

[0085] Example 2: Detection Method

[0086] like Figure 6 As shown, and in combination Figure 5 The present invention also provides a detection method for a low-pressure fuel filter with an integrated bypass valve and an electrical indicator, using the low-pressure fuel filter of Example 1, specifically including the following steps:

[0087] S101: During power-on or operation, the external controller simultaneously acquires the contact group one status signal C1 and the contact group two status signal C2 of the micro switch 8 via the electrical socket 13, and also acquires the electrical parameter L of the leakage detection circuit.

[0088] Stability confirmation is set between step S101 and step S102: de-jitter confirmation is performed on C1 and C2, and / or the electrical parameter L is sampled multiple times within a preset confirmation time window, and step S102 is only entered when the sampling results meet the consistency condition, so as to suppress false triggering and false alarm caused by differential pressure pulsation, vibration or transient interference.

[0089] S102: Compare the electrical parameter L with the drying state criterion to determine whether the electrical parameter L is in the high resistance or non-conducting range corresponding to the drying state; when the valve 4 is displaced under the action of pressure difference and triggers the micro switch 8 through the movable cover 6, the contact group one and / or contact group two will operate.

[0090] S103: When it is determined that the contact group 1 has been activated and the electrical parameter L is in the high resistance or non-conducting range, the external controller outputs an alarm signal through the electrical socket 13 and returns to step S101 for cyclic monitoring.

[0091] S104: When the electrical parameter L is not in the high resistance or non-conducting range, the external controller determines that there is a risk of fuel intrusion or seal failure in the dry area of ​​the signal housing 10, and sets the seal failure alarm to a higher alarm priority than the alarm signal and / or bypass confirmation signal.

[0092] When it is determined that contact group two has acted effectively, the external controller performs a sequence consistency judgment. The sequence consistency judgment includes at least the following conditions: the action of contact group two should occur after the action of contact group one, and contact group one should be in the acted state when contact group two acts. If the sequence consistency condition is met, the external controller determines that the low-pressure fuel filter has entered the bypass confirmation state and generates a bypass confirmation signal. If the sequence consistency condition is not met, the external controller outputs a diagnostic fault alarm signal.

[0093] S105: The external controller outputs a bypass confirmation signal via electrical socket 13; when it is determined that there is a risk of fuel intrusion or seal failure, the external controller outputs a seal failure alarm signal according to the alarm priority and keeps outputting until the reset conditions are met; the reset conditions include power failure reset, manual reset, or the electrical parameter L returning to the corresponding range of the dry state and continuously meeting the preset stability time window, etc. Figure 6 The "Output: Bypass Confirmation Signal" box corresponds to the output action of the bypass confirmation signal.

[0094] In a further embodiment, the external controller simultaneously acquires the contact group one status signal C1 and the contact group two status signal C2 of the micro switch 8 via the electrical socket 13, and acquires the electrical parameters L of the leakage detection circuit; during the execution of steps S101 to S105 of the detection method, the external controller further introduces adaptive confirmation, contact chatter diagnosis, graded seal failure alarm and leakage detection circuit self-test strategy to improve signal stability and diagnosability under conditions such as differential pressure pulsation, vibration and temperature drift.

[0095] (1) Adaptive confirmation time window and consistency condition

[0096] A stability confirmation is set between steps S101 and S102: debouncing confirmation is performed on C1 and C2, and / or the electrical parameter L is sampled multiple times within a preset confirmation time window, and step S102 is only entered when the sampling results meet the consistency condition; furthermore, the preset confirmation time window and consistency condition can be adaptively adjusted according to the operating conditions, including at least one of engine speed, fuel pump drive frequency / duty cycle, fuel temperature, and fluctuation amplitude / short-time variance obtained from the statistics of electrical parameter L or C1 / C2 events: when the operating condition is determined to be high pulsation or high vibration, the external controller increases the preset confirmation time window and raises the consistency condition threshold to suppress false triggering caused by differential pressure pulsation and false alarms caused by transient interference; when the operating condition is determined to be low pulsation or steady state, the external controller shortens the preset confirmation time window and lowers the consistency condition threshold to improve the response speed.

[0097] (2) Diagnosis of contact chatter (jitter)

[0098] Based on the external controller's confirmation of debouncing and sequence consistency judgment of C1 and C2, the external controller can also perform statistical analysis on the state flipping of contact group one and / or contact group two to form contact chatter diagnosis: within the preset statistical window, if multiple rapid flipping of C1 or C2 is detected, and the duration of a single closing / opening is less than the preset minimum holding time and the number of flipping exceeds the preset threshold, the external controller outputs contact chatter diagnosis prompt information or diagnostic fault alarm signal; among them, contact chatter diagnosis can be associated with the fluctuation amplitude of electrical parameter L to distinguish between "critical instability caused by differential pressure pulsation" and structural / assembly abnormalities such as "stuck cover 6, damping component wear, spring fatigue or microswitch 8 assembly deviation", and can also link to increase the above-mentioned stability confirmation threshold.

[0099] (3) Graded seal failure alarm

[0100] In step S102, the external controller compares the electrical parameter L with the dryness condition criterion to determine whether the electrical parameter L is in the high resistance or non-conducting range corresponding to the dryness condition. When the electrical parameter L is not in the high resistance or non-conducting range, the external controller determines that there is a risk of fuel intrusion or seal failure in the dry area of ​​the signal housing 10. The seal failure alarm signal can be set to graded output to distinguish between micro-leakage trends and obvious fuel intrusion risks. The grading method includes at least one or a combination of the following:

[0101] 1) Grading threshold of electrical parameter L: When electrical parameter L enters the first penetration range, output "Level 1 seal failure alarm"; when electrical parameter L enters the more serious second penetration range or continues to meet more stringent consistency conditions, output "Level 2 seal failure alarm".

[0102] 2) Multi-detection point classification: At least two sets of leakage detection circuits (or equivalent conductive detection structures) are set at different heights or positions in the dry area. When the first detection point is triggered, a first-level seal failure alarm is output, and when the second detection point is also triggered, a second-level seal failure alarm is output.

[0103] 3) Trend classification: When the electrical parameter L rapidly crosses the threshold range in a short period of time, an "emergency oil ingress risk warning" is output; when the electrical parameter L slowly approaches the threshold and remains in the critical range for a long time, a "micro-leakage trend warning" is output.

[0104] Tiered alarms can also be combined with preset confirmation time windows and consistency conditions for stability verification, so as to reduce false alarms and improve alarm reliability.

[0105] (4) Leakage detection circuit self-test and open / short circuit diagnosis

[0106] To prevent the leakage detection circuit from failing silently due to broken wires, poor contact of connectors, electrode corrosion, or short circuit in the wiring harness, the external controller can perform a self-test on the leakage detection circuit. The self-test includes at least a power-on self-test and / or an intermittent self-test.

[0107] Power-on self-test: During the system power-on or initialization phase, the external controller applies test excitation to the leakage detection circuit and reads the response to determine open circuit, short circuit or abnormal drift.

[0108] Operating interval self-check: During operation, a rapid consistency check is performed at a preset cycle. If a long-term fixed value, an obviously unreasonable jump, or an inconsistency with the reference response is detected, a leak detection circuit fault diagnosis signal is output.

[0109] When the self-test determines that the leakage detection circuit is faulty, the external controller can set the "seal failure alarm signal" to an unavailable state and report the circuit fault diagnosis, or adopt a more conservative protection strategy to reduce the system risk caused by the unavailability of the leakage detection function.

[0110] In this embodiment, the external controller outputs alarm signals, bypass confirmation signals, seal failure alarm signals, and diagnostic fault alarm signals via electrical socket 13, and performs priority / parallel reporting control according to the following rules:

[0111] 1) When it is determined that there is a risk of fuel intrusion or seal failure in the dry zone of the signal housing 10, the external controller sets the seal failure alarm signal to a higher alarm priority than the alarm signal and / or bypass confirmation signal, and maintains the output until the reset conditions are met (including power failure reset, manual reset, or electrical parameter L recovers to the corresponding range of dry state and continues to meet the preset stability time window).

[0112] 2) When C2 performs a valid action, the external controller performs a sequence consistency judgment, which includes at least "C2's action should occur after C1's action, and C1 should be in an already activated state when C2 takes action"; if the sequence consistency condition is met, a bypass confirmation signal is generated and output; if not, a diagnostic fault alarm signal is output.

[0113] 3) When the interface supports multiple parallel outputs, the seal failure alarm signal can be reported in parallel with the bypass confirmation signal / alarm signal, and at the same time, contact chatter diagnosis prompts or maintenance prompts are output; when the interface does not support parallel output or requires single-channel encoded output, the external controller overwrites the low-priority alarm with the highest priority alarm, or outputs secondary status information using a preset encoding / time-division reporting method.

[0114] In this embodiment, the determination and output of leakage / dry zone intrusion are implemented as follows: In the step of "collecting electrical parameters of the leakage detection circuit", the controller samples the detection circuit with a sampling period of 1ms to 100ms, preferably 5ms to 20ms; the electrical parameters can be the equivalent resistance, equivalent capacitance, or a combination thereof between the detection electrodes, and the sampled values ​​can be simply filtered / moving averaged to suppress transient noise, with a filtering window of 3 to 20 sampling points; in the step of "judging according to the drying state criterion", the drying state criterion can be set as follows: when the electrical parameters meet the "drying threshold"... When the "value condition" is met, the state is determined to be dry; when the "penetration threshold condition" is met, the state is determined to be non-dry (fuel penetration exists). The dryness threshold condition and the penetration threshold condition are preferably set as dual thresholds with hysteresis (i.e., different thresholds are used for entering non-dry and restoring dryness) to avoid repeated jumps near the thresholds. In the step of "confirming stability within the confirmation time window", the confirmation time window can be 0.1s to 10s, preferably 0.3s to 2s; the confirmation time window for "confirming the triggering of the leak alarm" can be 0.1s to 5s (preferably 0.3s to 1.5s), and the confirmation time window for "clearing the alarm / ..." The confirmation time window for "restoring drying" can be 0.2s to 10s (preferably 1s to 5s) to reduce false alarms and improve the reliability of the restoration. In the step of "outputting the judgment result only when the consistency condition is met", the consistency condition can adopt at least one of the following rules: First, the criterion must be met consecutively a preset number of times within the confirmation time window (e.g., 3 to 50 times consecutively, preferably 8 to 20 times); Second, majority voting is used within the sliding window corresponding to the confirmation time window (e.g., the success rate reaches 60% to 95%, preferably 80% to 90%); Third, a minimum holding time is set (e.g., entering non-drying state). After the status is established, it should be maintained for at least 0.5s to 30s, preferably 2s to 10s, before it can be released, to suppress transient misjudgments caused by vibration, pulsation, or electromagnetic interference. Finally, in the step of "outputting alarm signal / status signal", a leak alarm signal is output when the consistency condition is met within the confirmation time window; the leak alarm is released when the dry recovery consistency condition is met within the confirmation time window. Priority or parallel reporting strategies can be set for alarm / bypass confirmation signals according to system requirements. The above thresholds and time parameters can be calibrated and adjusted according to fuel dielectric characteristics, ambient humidity, vibration level, and installation tolerance.

[0115] In terms of assembly and verification, after assembly, the pressure difference test is used for verification: the pressure difference before and after the filter is measured under rated flow and maximum flow conditions to verify that the pressure loss meets the system allowable value; the pressure difference is gradually increased and the ΔP1 and ΔP2 corresponding to the action points of contact group one and contact group two, as well as the repeatability of valve 4 displacement S1 and S2 are recorded; the test is repeated under normal temperature and low temperature conditions to verify the influence range of temperature on the threshold, thereby ensuring signal stability and batch consistency under dynamic conditions.

[0116] The most significant feature of this invention compared to existing low-pressure fuel filter bypass alarm schemes is that, in the integrated structure of the bypass valve and electrical indicator, a dual-threshold working link of "alarm-bypass confirmation" is established through the graded release of the primary and secondary seals. When the pressure difference reaches the first threshold ΔP1, the first contact group outputs a blockage warning, while when the pressure difference reaches the second threshold ΔP2, the secondary sealing section is released and bypass connection is formed, simultaneously triggering the second contact group to output a bypass confirmation signal. Combined with the structural cooperation of guide sleeve-annular guide block-sealing section-flow channel / through hole, the two-stage signals and the bypass state have a structurally necessary correspondence, thereby avoiding the problems of misjudgment and missed judgment caused by relying on a single threshold or a single contact, and can simultaneously achieve reliable output of "early warning" and "bypass state confirmation".

[0117] This invention further achieves synergistic improvements in reliability: on the one hand, a buffer chamber and its two sides of throttling orifices (or equivalent damping structures) are set in the differential pressure sampling path to provide low-pass filtering for fuel pump pulsation and transient spikes, significantly reducing the probability of contact jitter and malfunction; on the other hand, a leakage guiding structure is set at the isolation interface between the signal device housing and the bypass valve housing and / or the electrical socket installation interface to guide the leaking fuel generated by the O-ring and / or sealing section to a predetermined collection location, and a leak detection circuit is arranged at the bottom of the dry zone to convert the leakage into a detectable change in electrical parameters and output a seal failure alarm; combined with the controller-side de-jitter confirmation, sequence consistency diagnosis, and alarm priority strategy, a hierarchical discrimination and robust output of "blockage warning - bypass confirmation - seal failure - fault diagnosis" is achieved. The combination of the above structure and method is not a simple splicing of existing technologies, but rather establishes a mutually supportive technical closed loop between differential pressure triggering, bypass confirmation, anti-pulsation, and leakage diagnosis, resulting in higher overall state recognition accuracy and system reliability.

[0118] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A low pressure fuel filter with a by-pass valve and an integral electric indicator, comprising a by-pass valve housing (5), a signaler housing (10), an electric socket (13), characterized in that: The bypass valve shell (5), the signaler shell (10) and the electric appliance socket (13) are fixedly connected and arranged in L shape, the bypass valve shell (5) is internally provided with a valve (4), the valve (4) and the inner wall of the bypass valve shell (5) form a two-stage triggering structure, the two-stage triggering structure comprises a cone part (26), a guide sleeve (25) and an annular guide block (24), the cone part (26) is an integral structure with the valve (4), the cone part (26) is in linear contact with an annular inner boss (29) on the inner wall of the bypass valve shell (5), the linear contact is a primary sealing structure, the guide sleeve (25) is arranged on the right side of the cone part (26), the annular guide block (24) is arranged in the circumferential direction of the bypass valve shell (5), an annular recess (28) is arranged on the left side surface of the annular guide block (24), the annular recess (28) is in sliding fit with the guide sleeve (25), a flow channel (23) is arranged at the right end of the guide sleeve (25), the flow channel (23) is arranged in L shape, the flow channel (23) is communicated with the circumferential surface and the right end of the guide sleeve (25), a through hole (27) communicated with the flow channel (23) is arranged at the bottom of the annular recess (28), the through hole (27) is correspondingly communicated with the flow channel (23), on the left side of the flow channel (23), the outer circumferential surface of the guide sleeve (25) and the inner circumferential surface of the annular guide block (24) form a sealing section (22), the guide sleeve (25) and the annular guide block (24) form a secondary sealing structure, an auxiliary spring (21) is arranged on the inner side of the guide sleeve (25), the auxiliary spring (21) is arranged between the annular guide block (24) and the valve (4), a micro switch (8) is arranged in the signaler shell (10), a magnetic steel (17) is arranged at the right end of the valve (4), the right end of the valve (4) is inserted into a right end counterbore of the bypass valve shell (5), a movable cover (6) is slidably connected to the right end of the bypass valve shell (5), a magnetic steel (18) is arranged on the movable cover (6) and matched with the magnetic steel (17), a pressure difference pulsation suppression structure is arranged on the pressure difference sampling passage of the valve (4), the pressure difference pulsation suppression structure comprises a buffer cavity (32) formed between the guide sleeve (25) and the annular inner boss (29), throttle holes (31) are arranged on the left and right sides of the buffer cavity (32), the throttle hole (31) on the left side is communicated with a high-pressure side oil cavity, and the throttle hole (31) on the right side of the buffer cavity (32) is communicated with a low-pressure side oil cavity.

2. A low pressure fuel filter with a by-pass valve and an electric indicator in one piece according to claim 1, characterized in that: An inlet (20) is arranged in the circumferential direction of the right end of the bypass valve shell (5), a bypass opening (19) is arranged in the middle of the bypass valve shell (5), and an O-shaped ring (3) is arranged in the circumferential direction of the bypass valve shell (5).

3. A low pressure fuel filter with an integrated bypass valve and electric indicator according to claim 1 or 2, characterized in that: A main spring (2) is arranged at the left end of the valve (4), a plug cover (1) is arranged at the right end of the bypass valve shell (5), and the plug cover (1) abuts against the left end of the main spring (2).

4. A low pressure fuel filter with an integrated bypass valve and electric indicator according to any one of claims 1-3, characterized in that: The inside of the signal housing (10) is provided with a positioning disc (7), which is fixedly connected with the bypass valve shell (5) through long screws (12), the micro switch (8) is installed on the positioning disc (7), the center of the positioning disc (7) is provided with a center hole, the contact of the micro switch (8) is located in the center hole, and the right end of the movable cover (6) corresponds to the center hole.

5. A low pressure fuel filter with a by-pass valve and an electric indicator in one piece according to claim 2, characterized in that: The buffer cavity (32) is composed of the throttle ring one (30) and the throttle ring two (33), the throttle ring one (30) and the throttle ring two (33) are fixedly connected with the guide sleeve (25) respectively, the outer circumferences of the throttle ring one (30) and the throttle ring two (33) are in sliding contact with the annular inner boss (29), the buffer cavity (32) is formed between the throttle ring one (30) and the throttle ring two (33), the throttle holes (31) are arranged on the throttle ring one (30) and the throttle ring two (33) respectively, and the throttle holes (31) are staggered with each other, and the movable cover (6) is arranged with the damping ring (34) at the position of the sliding fit with the bypass valve shell (5).

6. A low pressure fuel filter with a by-pass valve and an integrated electric indicator according to claim 5, characterized in that: The leakage flow guide structure is arranged at the isolation interface between the signal housing (10) and the bypass valve shell (5) and / or the installation interface between the electric appliance socket (13) and the signal housing (10); wherein, the O-shaped ring one (3) is arranged at the isolation interface, and the O-shaped ring two (16) is arranged at the installation interface; the leaked fuel generated by the O-shaped ring one (3) and / or the O-shaped ring two (16) and / or the sealing section (22) is guided to the predetermined collection position; and the dry area bottom of the signal housing (10) is provided with a leakage detection loop, the leakage detection loop is electrically connected with the electric appliance socket (13), and is used for outputting a sealing failure warning signal through the electric appliance socket (13) when the leaked fuel enters the dry area and causes the electrical parameter change of the leakage detection loop.

7. A low pressure fuel filter with a by-pass valve and an electric indicator in one piece according to claim 6, characterized in that: The external controller acquires the state signals of the contact group one and the contact group two of the micro switch (8) through the electric appliance socket (13), and performs debounce confirmation and sequence consistency judgment on the state signals; when it is detected that the action of the contact group two does not satisfy the sequence constraint of the action of the contact group one and / or the contact group one is not in the action state when the contact group two acts, a diagnostic fault warning is output; and the external controller counts the time interval of the contact group one action event and the contact group two action event to output the filter clogging trend or maintenance prompt information.

8. A method of detecting a low pressure fuel filter with an integrated bypass valve and electric indicator, characterized in that, The bypass valve and electric indicator integrated low-pressure fuel filter of claim 7 comprises the following steps: S101, during power-on or operation, the external controller simultaneously acquires the state signals of the contact group one and the contact group two of the micro switch (8) through the electric appliance socket (13), and acquires the electrical parameter of the leakage detection loop; S102, whether the micro switch (8) is triggered is judged according to the state signals of the contact group one and the contact group two; wherein, when the differential pressure of the low-pressure fuel filter causes the displacement of the valve (4) and triggers the micro switch (8) through the movable cover (6), the contact group one and / or the contact group two act; and the electrical parameter of the leakage detection loop is compared with the dry state criterion to judge whether the electrical parameter is in the high resistance or non-conduction interval corresponding to the dry state; S103, when it is determined that the contact group 1 has acted and the electrical parameter is in the high resistance or non-conducting range, the external controller outputs a blockage alarm signal through the electrical socket (13) and returns to the execution step S101 to perform cyclic monitoring; S104, when the second contact group is activated, the external controller determines that the low-pressure fuel filter has entered the bypass confirmation state and generates a bypass confirmation signal; and when the electrical parameters are not in the high resistance or non-conducting range, the external controller determines that there is a risk of fuel intrusion or seal failure in the dry area of ​​the signal housing (10), and sets the seal failure alarm to a higher alarm priority than the alarm signal and / or the bypass confirmation signal. S105, the external controller outputs the bypass confirmation signal through the electrical socket (13), and when it is determined that there is a risk of fuel intrusion or seal failure, it outputs a seal failure alarm signal with the alarm priority, and continues to output the seal failure alarm signal until the reset condition is met.

9. A low pressure fuel filter with a by-pass valve and an electric indicator in one piece according to claim 8, characterized in that: Between step S101 and step S102, there is also a stability confirmation step. The stability confirmation step includes de-jittering the status signals of contact group one and contact group two, and / or sampling the electrical parameters multiple times within a preset confirmation time window, and only executing step S102 when the results of multiple samplings meet the consistency condition, so as to suppress false triggering caused by differential pressure pulsation or vibration and false alarms caused by transient interference.

10. The low pressure fuel filter with integrated bypass valve and electric indicator according to claim 8, characterized in that The external controller performs a sequence consistency judgment on the actions of contact group one and contact group two. The sequence consistency judgment includes at least the requirement that the action of contact group two should occur after the action of contact group one. When it is detected that the action of contact group two does not meet the above sequence constraints and / or contact group one is not in the activated state when contact group two is activated, the external controller outputs a diagnostic fault alarm signal.

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