A fuel filter with multi-stage filtration

Abstract

This invention relates to the field of fuel filter technology, and particularly to a fuel filter with multi-stage filtration, comprising a housing, a drain pipe installed at the lower end of the housing, a support spring placed on the bottom wall of the housing, and a filter element placed on the support spring; the multi-stage fuel filter also includes a filter unit, which is placed inside the housing and outside the filter element, and the filter unit includes a conical filter frame placed inside the housing. The filter element and filter unit of this invention work together to achieve a multi-stage filtration architecture. The filter unit, as a primary filtration unit, pre-isolates large-sized contaminants in the fuel and pipeline, preventing large particles from directly clogging the filter element and significantly extending the effective service life of the filter element; the filter element, as a secondary fine filtration unit, achieves deep purification of the fuel, ensuring the cleanliness of the engine fuel supply.

Description

Technical Field

[0001] This invention relates to the field of fuel filter technology, and in particular to a fuel filter with multi-stage filtration. Background Technology

[0002] The fuel filter is a core safety component of a car's fuel supply system. Its core function is to filter solid impurities, gum, and water from the fuel, preventing wear, blockage, or corrosion of components such as precision fuel injectors and high-pressure fuel pumps. This directly determines the reliability and lifespan of the engine.

[0003] Currently, most fuel filters are single-stage filter structures, lacking a pre-interception mechanism for large particulate impurities. Large contaminants such as metal shavings and welding slag in the fuel directly impact the filter surface, easily causing rapid local clogging and reducing the filter's lifespan. Existing fuel filters are mainly divided into two types: integrated and separate. Integrated filters generally use a single O-ring end face seal for the filter element. The metal shell of an integrated fuel filter can typically last 5-8 years, while the filter element replacement cycle is only 10,000-20,000 kilometers. After the filter element reaches the end of its lifespan, it cannot be replaced individually. Replacing the entire filter results in the waste of more than 90% of the metal material and generates a large amount of non-biodegradable plastic waste, which not only increases the cost of using fuel filters but also does not conform to the concept of green and environmentally friendly development. While separate filters allow for individual filter element replacement, the sealing pre-tightening force of separate filters is fixed after assembly and cannot be dynamically adjusted with changes in the internal oil pressure of the filter. As the filter is used for longer periods, the filter element becomes increasingly clogged, and the internal oil pressure increases non-linearly. When the oil pressure exceeds the critical clamping force of the seal, the seal will be squeezed open or micro-gap will be created, leading to fuel leakage. This not only wastes fuel but also poses significant safety hazards such as fire.

[0004] Therefore, there is an urgent need to provide a fuel filter with high filtration efficiency, strong sealing reliability, low operating cost, and strong environmental friendliness. Summary of the Invention

[0005] Therefore, it is necessary to provide a fuel filter with multi-stage filtration to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a fuel filter with multi-stage filtration, comprising: a housing, a drain pipe installed at the lower end of the housing, a support spring placed on the bottom wall of the housing, and a filter element placed on the support spring.

[0007] The fuel filter with multi-stage filtration also includes a filter unit, which is placed inside the housing and located outside the filter element. The filter unit includes a conical filter frame placed inside the housing. Near the upper end of the conical filter frame, a molding ring located outside the conical filter frame is installed by multiple connecting rods. The molding ring is provided with multiple circumferentially evenly distributed tightening parts, and a pushing part is installed at the lower end of the molding ring.

[0008] The fuel filter with multi-stage filtration also includes an end cap unit, which is detachably installed at the end of the housing. The end cap unit includes a cover plate placed at the end of the housing, an inlet pipe installed on the cover plate, a sealing part for sealing the gap between the cover plate and the housing at the lower end of the cover plate, and multiple circumferentially evenly distributed insertion parts installed at the lower end of the cover plate.

[0009] The fuel filter with multi-stage filtration also includes a snap-fit ​​unit, which has multiple snap-fit ​​parts for snapping into corresponding insertion parts. The snap-fit ​​unit includes a snap-fit ​​frame installed at the end of the outer ring surface of the housing, with snap-fit ​​holes on the snap-fit ​​frame and snap-fit ​​parts inside the snap-fit ​​holes.

[0010] The cover plate is detached from the housing via a plug-in part and a snap-fit ​​part to facilitate filter element replacement; after the cover plate is fixedly connected to the housing, the sealing part cooperates with the molding ring to seal the gap between the cover plate and the housing; as the oil pressure inside the housing increases, the force-bearing pushing part pushes against multiple tightening parts, and the multiple tightening parts further tighten and limit the sealing part.

[0011] Preferably, the tightening part includes a sliding hole formed on the outer ring surface of the molding ring, a tightening plate is slidably connected in the sliding hole, and a moving rod is installed at one end of the tightening plate near the axis of the molding ring, the moving rod slidingly passing through the molding ring.

[0012] Preferably, the pushing part includes an airbag installed at the lower end of the molding ring, and a pushing ring with an upward opening and a U-shaped cross-section is installed at the lower end of the airbag, wherein the length of the inner section of the pushing ring is greater than the length of the outer section.

[0013] Preferably, the sealing part includes a mating ring installed at the lower end of the cover plate, a sealing rubber is installed at the lower end of the mating ring, and an insertion groove is opened at the lower end of the cover plate outside the mating ring. The insertion groove is inserted into the upper end of the outer shell, and a rubber ring is laid in the insertion groove.

[0014] Preferably, the insertion part includes an insertion arc plate installed at the lower end of the cover plate, the insertion arc plate is inserted and engaged with the corresponding snap-fit ​​hole, the insertion arc plate is provided with a limit hole, and the lower end of the insertion arc plate is provided with an inclined surface.

[0015] Preferably, the snap-fit ​​portion includes a sliding countersunk hole formed on the side wall of the snap-fit ​​hole near the outer shell, a limit rod is slidably connected in the sliding countersunk hole, and a limit spring is installed between the limit rod and the sliding countersunk hole.

[0016] Preferably, a positioning tube is installed in the middle of the upper part of the bottom wall of the outer casing, and the positioning tube has multiple oil passage holes.

[0017] Preferably, the limiting rod has a U-shaped structure with the opening away from the outer shell, the length of the upper section of the limiting rod is less than the length of the lower section, the end of the upper section of the limiting rod is provided with a slope, and the lower section of the limiting rod slides through the snap-fit ​​frame.

[0018] Preferably, a pressure relief valve for stabilizing the internal pressure of the housing is installed in the middle of the cover plate.

[0019] Preferably, the sealing rubber has an annular structure with a right-angled trapezoidal cross-section, and the sealing rubber tightly fills the gap between the molding ring and the inner annular surface of the outer shell.

[0020] In summary, the present invention has the following beneficial technical effects: 1. The filter element and filter unit used in the present invention work together to achieve a multi-stage filtration architecture. The filter unit, as a primary filtration unit, pre-isolates large-sized contaminants in the fuel and pipeline, preventing large particles of impurities from directly clogging the filter element and significantly extending the effective service life of the filter element. The filter element, as a secondary fine filtration unit, achieves deep purification of the fuel and ensures the cleanliness of the engine fuel supply.

[0021] 2. The filter unit and end cap unit used in this invention cooperate to construct a dual sealing system of end plug-in seal and internal annular surface seal, which effectively improves the overall sealing strength of the fuel filter. Furthermore, through the linkage between the pushing part and the tightening part, the sealing performance is automatically adjusted according to the internal oil pressure: when the filter element is clogged and the oil pressure inside the housing increases, the oil pressure pushes the pushing ring to squeeze the airbag. The pushing ring synchronously drives multiple tightening plates to tighten the sealing rubber outward through the inclined surface. The higher the oil pressure, the greater the adhesion strength between the sealing rubber and the inner wall of the housing, thus preventing the fuel filter from leaking under high pressure conditions.

[0022] 3. The outer shell and end cap unit of this invention are detachably connected. After the fuel filter is used, only the filter element, sealing rubber and rubber ring and other vulnerable parts need to be replaced periodically. The metal shell can be reused. This abandons the traditional whole replacement mode of integrated fuel filter, greatly reduces the use cost of fuel filter, and at the same time reduces the generation of metal waste, which has significant environmental value. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1A three-dimensional structural schematic diagram of the present invention is shown; Figure 2 A front view of the invention is shown; Figure 3 A cross-sectional view of the present invention is shown; Figure 4 It shows Figure 3 Enlarged view of region A in the middle; Figure 5 A schematic diagram of the filter element of the present invention is shown; Figure 6 A schematic diagram of the structure of the filter unit of the present invention is shown; Figure 7 A schematic diagram of the end cap unit of the present invention is shown; Figure 8 The diagram shows the working principle of the present invention: the push ring squeezes the moving rod and the top plate and presses the sealing rubber.

[0025] The above-mentioned figures include the following reference numerals: 1. Outer shell; 2. Support spring; 3. Filter element; 4. Filter unit; 40. Conical filter frame; 41. Molding ring; 42. Tightening part; 420. Sliding hole; 421. Tightening plate; 422. Moving rod; 43. Pushing part; 430. Airbag; 431. Pushing ring; 5. End cap unit; 50. Cover plate; 51. Liquid inlet pipe; 52. Sealing part; 520. Connecting ring; 521. Sealing rubber; 522. Insertion groove; 523. Rubber ring; 53. Insertion part; 530. Insertion arc plate; 531. Limiting hole; 6. Snap-fit ​​unit; 60. Snap-fit ​​frame; 61. Snap-fit ​​hole; 62. Snap-fit ​​part; 620. Sliding countersunk hole; 621. Limiting rod; 622. Limiting spring. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways not described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] See Figure 1 , Figure 2 , Figure 3 and Figure 5 A fuel filter with multi-stage filtration includes a housing 1, a drain pipe installed at the lower end of the housing 1, a support spring 2 placed on the bottom wall of the housing 1, a filter element 3 placed on the support spring 2, and a positioning tube installed at the middle of the upper end of the bottom wall of the housing 1, with multiple oil passage holes opened on the positioning tube.

[0028] In practice, when installing the fuel filter, first put the support spring 2 on the positioning tube and place it on the bottom wall of the outer shell 1. Then put the filter element 3 into the outer shell 1 and put it on the positioning tube. Then push the filter element 3 to the upper end of the support spring 2. The positioning tube centers the filter element 3.

[0029] See Figure 1 , Figure 4 and Figure 6 The fuel filter with multi-stage filtration also includes a filter unit 4 placed inside the housing 1 and located outside the filter element 3. The filter unit 4 includes a conical filter frame 40 placed inside the housing 1. Near the upper end of the conical filter frame 40, a molding ring 41 located outside the conical filter frame 40 is installed by multiple connecting rods.

[0030] In actual operation, after the filter element 3 is placed inside the outer shell 1, the conical filter frame 40 is placed inside the outer shell 1. The conical filter frame 40 is fitted on the outside of the filter element 3 and further centers and limits the filter element 3. The bottom outer diameter of the conical filter frame 40 is consistent with the inner diameter of the outer shell 1, that is, the bottom of the conical filter frame 40 is slidably connected to the outer shell 1. The conical filter frame 40 performs a primary filtration of the fuel, isolating large-sized stains in the fuel or pipeline, and improving the service life of the filter element 3. At the same time, the conical filter frame 40 drives the molding ring 41 to move into the outer shell 1 through multiple connecting rods. The cross-section of the molding ring 41 is a right-angled trapezoidal structure and the inclined surface faces the inner wall of the outer shell 1.

[0031] See Figure 1 , Figure 3 and Figure 7 The fuel filter with multi-stage filtration also includes an end cap unit 5 that is detachably installed at the end of the housing 1. The end cap unit 5 includes a cover plate 50 placed at the end of the housing 1, an inlet pipe 51 installed on the cover plate 50, and a pressure relief valve for stabilizing the internal pressure of the housing 1 installed in the middle of the cover plate 50.

[0032] In actual operation, after the conical filter frame 40 is placed inside the housing 1, the cover plate 50 is placed at the end of the housing 1 and the housing 1 is sealed. The inlet pipe 51 is used for fuel to enter. A one-way valve (not shown in the figure) is installed in the inlet pipe 51. The pressure relief valve is used to stabilize the pressure inside the housing 1. This is existing equipment.

[0033] See Figures 1-4The fuel filter with multi-stage filtration also includes a snap-fit ​​unit 6 with multiple snap-fit ​​parts 53 for snapping into each other. The snap-fit ​​unit 6 includes a snap-fit ​​frame 60 installed at the end of the outer ring surface of the housing 1. The snap-fit ​​frame 60 has a snap-fit ​​hole 61 and a snap-fit ​​part 62 is provided in the snap-fit ​​hole 61. The snap-fit ​​part 62 includes a sliding countersunk hole 620 opened on the side wall of the snap-fit ​​hole 61 near the housing 1. A limit rod 621 is slidably connected in the sliding countersunk hole 620. A limit spring 622 is installed between the limit rod 621 and the sliding countersunk hole 620.

[0034] See Figures 1-4 The limiting rod 621 has a U-shaped structure with an opening away from the outer shell 1. The length of the upper section of the limiting rod 621 is less than the length of the lower section. The end of the upper section of the limiting rod 621 is provided with a slope. The lower section of the limiting rod 621 slides through the snap-fit ​​frame 60.

[0035] See Figure 1 , Figure 3 , Figure 4 and Figure 7 The lower end of the cover plate 50 is also equipped with a plurality of circumferentially evenly distributed plug-in parts 53. Each plug-in part 53 includes a plug-in arc plate 530 installed at the lower end of the cover plate 50. The plug-in arc plate 530 is plugged into and cooperates with the corresponding snap-fit ​​hole 61. A limit hole 531 is provided on the plug-in arc plate 530, and a slope is provided at the lower end of the plug-in arc plate 530.

[0036] In actual operation, the cover plate 50 is detached from the outer shell 1 via the insertion part 53 and the snap-fit ​​part 62 to facilitate the replacement of the filter element 3. The specific steps are as follows: During the process of the cover plate 50 covering the end of the outer shell 1, the cover plate 50 drives multiple insertion arc plates 530 to insert into the snap-fit ​​holes 61 of the corresponding snap-fit ​​frame 60. The insertion arc plates 530 slide in the snap-fit ​​holes 61 and push against the slope of the upper end of the limiting rod 621 by the inclined surface at the lower end. The limiting rod 621 slides in the sliding countersunk hole 620 under force and limits the movement of the limiting rod 621. When the spring 622 is compressed, the limiting rod 621 releases its obstruction of the insertion arc plate 530. The insertion arc plate 530 continues to enter the snap-fit ​​hole 61 until the limiting hole 531 on the insertion arc plate 530 moves to the upper end of the limiting rod 621. At this time, the compressed limiting spring 622 resets and drives the upper end of the limiting rod 621 to insert into the limiting hole 531, thereby realizing the function of limiting the insertion arc plate 530 within the snap-fit ​​frame 60, and thus realizing the fixed connection between the cover plate 50 and the outer shell 1.

[0037] See Figure 1 , Figure 3 , Figure 4 and Figure 7The lower end of the cover plate 50 is provided with a sealing part 52 for sealing the gap between the cover plate 50 and the outer shell 1. The sealing part 52 includes a mating ring 520 installed at the lower end of the cover plate 50. A sealing rubber 521 is installed at the lower end of the mating ring 520. An insertion groove 522 is opened at the lower end of the cover plate 50 outside the mating ring 520. The insertion groove 522 is inserted and matched with the upper end of the outer shell 1. A rubber ring 523 is laid in the insertion groove 522.

[0038] See Figure 4 The sealing rubber 521 has an annular structure with a right-angled trapezoidal cross-section, and the sealing rubber 521 tightly fills the gap between the plastic ring 41 and the inner annular surface of the outer shell 1.

[0039] In specific operation, after the cover plate 50 is fixedly connected to the outer shell 1, the sealing part 52 cooperates with the molding ring 41 to seal the gap between the cover plate 50 and the outer shell 1. The specific steps are as follows: During the process of fixing the cover plate 50 to the outer shell 1, the mating ring 520 at the lower end of the cover plate 50 drives the sealing rubber 521 from the end of the outer shell 1 into the outer shell 1. The outer ring surface of the mating ring 520 fits against the inner ring surface of the outer shell 1. When the cover plate 50 covers the end of the outer shell 1, the mating ring 520 drives the sealing rubber 521 to move between the molding ring 41 and the inner wall of the outer shell 1, and simultaneously squeezes it tightly against the inclined surface of the molding ring 41 and the inner wall of the outer shell 1. The rubber ring 521 is used to seal the gap between the inner wall of the outer shell 1 and the mating ring 520, thereby sealing the gap between the cover plate 50 and the end of the outer shell 1. The molding ring 41 limits the sealing rubber 521, causing the sealing rubber 521 to deform, thereby improving the sealing effect of the sealing rubber 521 on the gap between the inner wall of the outer shell 1 and the mating ring 520. At the same time, the end of the outer shell 1 is inserted into the insertion groove 522 at the lower end of the cover plate 50, and the rubber ring 523 further seals the gap between the end of the outer shell 1 and the cover plate 50, further improving the sealing effect after the cover plate 50 and the outer shell 1 are fixedly connected.

[0040] After the cover plate 50 is fixedly connected to the housing 1, the entire fuel filter is fixedly installed in the pipeline between the vehicle engine and the fuel tank. The fuel supply pipe on the vehicle is connected to the inlet pipe 51. The drain pipe at the lower end of the housing 1 is connected to the pipeline connected to the engine. Then, the pressure relief valve on the cover plate 50 is connected to the inlet pipe 51 through the return pipe.

[0041] See Figure 1 , Figure 3 , Figure 4 and Figure 6The molding ring 41 is provided with a plurality of circumferentially evenly distributed tightening parts 42. Each tightening part 42 includes a sliding hole 420 formed on the outer ring surface of the molding ring 41. A tightening plate 421 is slidably connected in the sliding hole 420. A moving rod 422 is installed at one end of the tightening plate 421 near the axis of the molding ring 41. The moving rod 422 slides through the molding ring 41. A hemispherical protrusion is provided at one end of the moving rod 422 near the axis of the outer shell 1.

[0042] See Figure 1 , Figure 3 , Figure 4 and Figure 6 The lower end of the molding ring 41 is equipped with a pushing part 43, which includes an airbag 430 installed at the lower end of the molding ring 41. The airbag 430 is made of a material that is not easily corroded, is resistant to aging, and has a long service life, such as neoprene or fluororubber. The material of the airbag 430 is calculated based on the full life cycle cost. Compared with the case where all fuel filters are replaced, the overall usage cost is within a controllable range. The lower end of the airbag 430 is equipped with a pushing ring 431 with an upward opening and a U-shaped cross section. The length of the inner section of the pushing ring 431 is greater than the length of the outer section. The upper end of the inner section of the pushing ring 431 is provided with an inclined pushing surface.

[0043] In actual operation, as the oil pressure inside the outer casing 1 increases, the force-bearing pushing part 43 pushes against multiple clamping parts 42, and the multiple clamping parts 42 further clamp and limit the sealing part 52. The specific steps are as follows: fuel inside the fuel tank enters the outer casing 1 through the fuel supply pipe and the liquid inlet pipe 51, then undergoes primary filtration through the conical filter frame 40, followed by secondary filtration through the filter element 3. The fuel passing through the filter element 3 enters the drain pipe through multiple oil passages on the positioning tube, and finally flows into the engine. With prolonged use of the fuel filter, impurities inside the fuel gradually clog the filter element 3, and the oil pressure inside the outer casing 1 gradually increases. As the oil pressure gradually increases, the middle section of the push ring 431 is provided with a groove to facilitate the application of oil pressure to the push ring 431. As the oil pressure increases, the push ring 431 is subjected to force to compress the airbag 430, causing the airbag 430 to deform. The push ring 431 slides relative to the molding ring 41 and simultaneously pushes the hemispherical protrusions of multiple moving rods 422 through the pushing surface of the inner section. The multiple moving rods 422 are subjected to force to drive the corresponding top plate 421 to slide in the corresponding sliding hole 420 and simultaneously compress the sealing rubber 521, thereby increasing the tightness between the sealing rubber 521 and the inner wall of the outer shell 1 (e.g., Figure 8 As shown, the greater the internal oil pressure of the outer casing 1, the stronger the adhesion between the sealing rubber 521 and the inner wall of the outer casing 1, and the stronger the sealing between the outer casing 1 and the cover plate 50, effectively preventing fuel leakage. A spring can be installed inside the airbag 430 as needed to enhance its pressure resistance and ensure the stable connection between the airbag 430 and the push ring 431.

[0044] When the fuel filter reaches its replacement time or the vehicle reaches its rated working mileage, remove the fuel filter from the vehicle. Simultaneously press multiple limiting rods 621 to move the upper section of the limiting rods 621 out of the limiting hole 531, thereby releasing the restriction on the insertion arc plate 530. Then separate the cover plate 50 from the outer shell 1. Next, remove the conical filter frame 40 from the outer shell 1. During removal, the bottom of the conical filter frame 40 scrapes away dirt adhering to the inner wall of the outer shell 1, achieving the function of cleaning the inside of the outer shell 1. Clean the removed conical filter frame 40 with cleaning fluid. Then remove the used filter element 3 from the outer shell 1. The filter element 3 is placed inside the outer shell 1. By repeating the steps of assembling the fuel filter, the filter element 3 can be replaced. This effectively solves the problem that the entire metal shell of the traditional integrated fuel filter needs to be discarded every time it is replaced, avoiding serious waste of resources, effectively reducing the total life cycle cost of the fuel filter, reducing the generation of metal waste, and having significant long-term environmental value. It should be noted that the condition of the rubber ring 523 and sealing rubber 521 should be checked every time the fuel filter is replaced. If aging or damage is found, they should be replaced in time. The fuel filter also needs to be replaced as a whole after it reaches the end of its service life.

[0045] It should also be noted that although existing technologies can use traditional lip seals and multi-seals to achieve a seal between the cover plate 50 and the outer shell 1, multi-seals are passive constant-force seal structures. The sealing preload is fixed during assembly and cannot be dynamically adjusted according to internal operating conditions. When the filter element 3 is clogged and the oil pressure inside the outer shell 1 continues to rise, the fixed preload cannot match the high pressure differential conditions. The lip seal is directly set at the contact position between the cover plate 50 and the outer shell 1. When the pressure is high, the deformation of the lip seal can only adhere tightly to the inner wall of the outer shell 1, without rigid compression and limiting. Moreover, the deformation of the lip seal is limited. If the pressure exceeds the operating range, it is prone to sealing failure and fuel leakage. However, this solution achieves sealing of the rubber 52 through the deformation of the airbag 430. The dynamic matching of the sealing force of the filter element 3 with the internal oil pressure, under high pressure conditions when the filter element 3 is clogged, increases the rigidity of the sealing rubber 521 by the deformation of the airbag 430, thereby improving the sealing force of the sealing rubber 521. As the internal oil pressure of the housing 1 continues to rise, the rigidity of the sealing rubber 521 increases, and the sealing force of the sealing rubber 521 becomes stronger, thus preventing fuel leakage under high pressure. The structure has high reliability. At the same time, because the airbag 430 is deformable, it slows down the pressure rise rate inside the housing 1 when the filter element 3 is clogged and increases the upper limit of the operating pressure. Compared with lip seals and multi-channel fixed seals, the overall sealing performance under all operating conditions is better, which can effectively improve the operational reliability of the fuel filter and has strong practicality.

[0046] In the description of the embodiments of the present invention, it should be noted that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0047] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A fuel filter with multi-stage filtration, comprising a housing, a drain pipe is mounted at the lower end of the housing, a supporting spring is placed on the bottom wall of the housing, and a filter element is placed on the supporting spring, characterized in that, Also includes: A filter unit is placed inside the housing and located outside the filter element. The filter unit includes a conical filter frame placed inside the housing. A molding ring is installed near the upper end of the conical filter frame via multiple connecting rods. The molding ring is located outside the conical filter frame. Multiple tightening parts are provided on the molding ring. A pushing part is installed at the lower end of the molding ring. An end cap unit is detachably installed at the end of the housing. The end cap unit includes a cover plate placed at the end of the housing, an inlet pipe installed on the cover plate, a sealing part for sealing the gap between the cover plate and the housing at the lower end of the cover plate, and multiple plug-in parts installed at the lower end of the cover plate. The snap-fit ​​unit is provided with multiple corresponding plug-in parts. The snap-fit ​​unit includes a snap-fit ​​frame installed at the end of the outer ring surface of the housing. The snap-fit ​​frame has snap-fit ​​holes, and snap-fit ​​parts are provided in the snap-fit ​​holes. The cover plate is detached from the housing via a plug-in part and a snap-fit ​​part; after the cover plate is fixedly connected to the housing, the sealing part cooperates with the molding ring to seal the gap between the cover plate and the housing; as the oil pressure inside the housing increases, the force-bearing pushing part pushes against multiple tightening parts, and the multiple tightening parts further tighten and limit the sealing part.

2. A fuel filter with multi-stage filtration according to claim 1, characterized in that: The tightening part includes a sliding hole on the outer ring surface of the molding ring, a tightening plate is slidably connected in the sliding hole, and a moving rod is installed at one end of the tightening plate near the axis of the molding ring, the moving rod sliding through the molding ring.

3. A fuel filter with multi-stage filtration according to claim 1, characterized in that: The pushing part includes an airbag installed at the lower end of the molding ring. The lower end of the airbag is equipped with a pushing ring with an upward opening and a U-shaped cross-section. The length of the inner section of the pushing ring is greater than the length of the outer section.

4. A fuel filter with multi-stage filtration according to claim 1, characterized in that: The sealing part includes a mating ring installed at the lower end of the cover plate. A sealing rubber is installed at the lower end of the mating ring. An insertion groove is opened at the lower end of the cover plate outside the mating ring. The insertion groove is inserted into the upper end of the outer shell. A rubber ring is laid in the insertion groove.

5. A fuel filter with multi-stage filtration according to claim 1, characterized in that: The insertion part includes an insertion arc plate installed at the lower end of the cover plate. The insertion arc plate is inserted and engaged with the corresponding snap-fit ​​hole. A limit hole is provided on the insertion arc plate, and an inclined surface is provided at the lower end of the insertion arc plate.

6. A fuel filter with multi-stage filtration according to claim 1, characterized in that: The snap-fit ​​part includes a sliding countersunk hole on the side wall of the snap-fit ​​hole near the outer shell, a limit rod is slidably connected in the sliding countersunk hole, and a limit spring is installed between the limit rod and the sliding countersunk hole.

7. A fuel filter with multi-stage filtration according to claim 1, characterized in that: A positioning tube is installed in the middle of the upper part of the bottom wall of the outer shell, and multiple oil passage holes are opened on the positioning tube.

8. A fuel filter with multi-stage filtration according to claim 6, characterized in that: The limiting rod has a U-shaped structure with the opening away from the outer shell. The length of the upper section of the limiting rod is less than the length of the lower section. The end of the upper section of the limiting rod is provided with a slope. The lower section of the limiting rod slides through the snap-fit ​​frame.

9. A fuel filter with multi-stage filtration according to claim 1, characterized in that: A pressure relief valve for stabilizing the internal pressure of the outer shell is installed in the middle of the cover plate.

10. A fuel filter with multi-stage filtration according to claim 4, characterized in that: The sealing rubber has an annular structure with a right-angled trapezoidal cross-section, and the sealing rubber tightly fills the gap between the plastic ring and the inner annular surface of the outer shell.

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