Base oil filtering system and filtering method

Abstract

The base oil filtering system comprises a tank body, a multi-stage filtering cylinder, a rotating mechanism, a first scraping plate unit and a fine filtering unit, the tank body comprises a tank body and a tank cover arranged on the tank body, an oil inlet is formed in the upper end of the tank body, and an oil outlet is formed in the bottom end of the tank body. The multi-stage filter cartridge is arranged at the middle upper part of the tank body and comprises a plurality of conical filter cartridges which are coaxially sleeved, the axes of the conical filter cartridges are coaxial with the axis of the tank body, and the apertures of meshes of the plurality of conical filter cartridges are gradually reduced from the inner side to the outer side. By arranging the inverted conical filter cartridges which are coaxially arranged in a sleeving manner and of which the pore diameters are gradually reduced from inside to outside, a progressive physical filtering gradient is formed, when oil liquid naturally flows under the action of gravity, large particles are firstly intercepted by the inner-layer coarse filtration pores, and small particles are captured by the outer-layer fine filtration pores, so that the oil liquid can be effectively filtered by virtue of a multi-stage synergistic filtering manner; compared with a single-precision filter screen, the filter screen has the advantages that impurities in a wider particle size range can be efficiently removed in a single process, and the cleanliness of a final oil product is improved.

Description

Technical Field

[0001] This invention relates to the field of base oil filtration technology, specifically to a base oil filtration system and filtration method. Background Technology

[0002] During production and storage, base oil inevitably mixes with solid and semi-solid impurities such as metal shavings, dust, and gum. Its purity directly affects the performance of subsequent lubricating products and the life of equipment, so filtration devices are needed for purification.

[0003] Currently, the most common filtration method involves installing static filter screens or cartridges inside storage tanks or pressure vessels. This method relies primarily on the direct collision and surface interception of impurities with the filter medium as the oil passes through it. However, this filtration method causes trapped impurities to accumulate rapidly on the surface of the filter medium, forming a dense filter cake. This leads to clogging of the filtration channels and a sharp increase in resistance, resulting not only in a rapid decline in filtration efficiency but also necessitating frequent shutdowns for disassembly and cleaning. Summary of the Invention

[0004] To address the technical problems existing in the background art, the present invention provides a base oil filtration system and filtration method.

[0005] The technical solution of this invention is as follows: A base oil filtration system, comprising: The tank body includes the tank body and the tank cover installed thereon. The upper end of the tank body is provided with an oil inlet and the lower end is provided with an oil outlet. A multi-stage filter cartridge is located in the upper part of the tank body and includes multiple coaxially sleeved conical filter cartridges. The axis of the conical filter cartridges is coaxial with the axis of the tank body. The mesh diameter of the multiple conical filter cartridges decreases from the inside to the outside. The outermost conical filter cartridge is connected to the inner wall of the tank body through a support. The conical filter cartridge located on the inner side is connected to its adjacent outer conical filter cartridge through a support leg. The body of the inner conical filter cartridge is provided with multiple coarse filtration holes, and the body of the outermost conical filter cartridge is provided with fine filtration holes. The lower part of the body of the outermost conical filter cartridge forms an impurity collection area. The rotating mechanism includes a rotating shaft and a drive motor connected thereto. The rotating motor is mounted on the tank cover, and the rotating shaft is mounted inside the tank along the axial direction of the tank body. Its lower end passes through a multi-stage filter cylinder and is rotatably connected to the oil guide support at the lower inner side of the tank body. Multiple first scraper units are arranged circumferentially along the rotation axis. Each first scraper unit includes a connecting rod and a first scraper. The first scraper is provided with a flexible first scraper strip. One end of the connecting rod is connected to the rotation axis, and the other end is connected to the upper part of the first scraper. The first scraper is disposed between two adjacent conical filter cylinders, and the first scraper strip abuts against the surface of the adjacent conical filter cylinder.

[0006] The external inlet and internal outlet fine filtration unit is located below the multi-stage filter cartridge and has a central clean chamber that is connected to the oil outlet.

[0007] The structure of the multiple conical filter cylinders is as follows: the multiple conical filter cylinders include an inner filter cylinder and an outer filter cylinder sleeved on the outside. Both the inner filter cylinder and the outer filter cylinder are inverted frustum-shaped cylindrical structures with the large end facing up and the small end facing down.

[0008] The first scraper unit is structured such that the first scraper is disposed in the annular gap formed between the inner filter cylinder and the outer filter cylinder. Multiple first scraper strips are symmetrically arranged on opposite sides of the first scraper. One side of the first scraper strip abuts against the outer wall of the inner filter cylinder, and the other side of the first scraper strip abuts against the inner wall of the outer filter cylinder.

[0009] Preferably, the connecting rod is also provided with a second scraper parallel to the first scraper. The second scraper is located inside the inner filter cylinder, and the second scraper is provided with a flexible second scraper along its length direction. The second scraper abuts against the inner wall of the inner filter cylinder.

[0010] Furthermore, the inner filter cartridge and the outer filter cartridge are connected by support legs. Multiple support legs are provided, all located at the bottom of the outer filter cartridge, and arranged in a circumferential direction.

[0011] Preferably, the plane at the lower end of the first scraper is higher than the horizontal plane at the highest position of the support leg.

[0012] To ensure stable rotation of the lower part of the first scraper, a guide wheel is provided at the lower end of the first scraper, and the wheel surface of the guide wheel abuts against the inner wall of the outer filter cylinder.

[0013] Preferably, the lower end of the second scraper extends above the upper bottom surface of the inner filter cylinder, and a third scraper is provided at the lower end of the second scraper. The third scraper is provided with a third scraping strip that abuts against the upper bottom surface of the inner filter cylinder. The third scraping strip is arranged parallel to the upper bottom surface of the inner filter cylinder, and the end of the third scraping strip away from the second scraper is connected to the rotating shaft.

[0014] Preferably, the fine filtration unit includes a filter housing and a cylindrical filter element disposed therein, the cylindrical filter element being connected to the filter housing via a perforated bracket.

[0015] A filtration method for a base oil filtration system includes the following steps: S1. The base oil to be filtered is introduced through the oil inlet at the top of the tank, so that it enters the top area of ​​the multi-stage filter cartridge. S2. Start the drive motor to drive the rotating shaft and the first scraper unit fixed on it to rotate. Under the influence of gravity, the base oil flows sequentially through the inner and outer filter cartridges of the multi-stage filter cartridges, achieving gradient filtration from coarse to fine. The first scraper on the first scraper continuously scrapes the outer wall of the inner filter cartridge and the inner wall of the outer filter cartridge, the second scraper continuously scrapes the inner wall of the inner filter cartridge, and the third scraper continuously scrapes the top and bottom surfaces of the inner filter cartridge, removing impurities attached to the corresponding mesh. S3. After being processed by the multi-stage filter cartridges, the oil flows downward into the external inlet and internal outlet fine filtration unit. The oil passes through the outside of the cylindrical filter cartridge and enters the central clean chamber inside it to complete fine filtration. S4. The clean oil collected in the central clean chamber is guided by the oil outlet groove of the oil guide support and finally discharged continuously from the oil outlet at the bottom of the tank.

[0016] The beneficial effects of this invention are as follows: By setting up an inverted conical filter cartridge with coaxially nested holes and decreasing pore size from the inside to the outside, a gradual physical filtration gradient is formed. When the oil flows naturally under the action of gravity, larger particles are first intercepted by the inner coarse filter holes, while smaller particles are captured by the outer fine filter holes. This multi-stage synergistic filtration method, compared with a single-precision filter screen, can achieve efficient removal of impurities with a wider range of particle sizes in a single process, thereby improving the cleanliness of the final oil product.

[0017] When the drive mechanism rotates the scraper, the first, second and third scrapers can continuously clean the impurities on the inner and outer walls of the filter cartridge, reducing the problems of rapid accumulation of impurities and blockage of filter holes in traditional static filtration, which can lead to a sudden increase in pressure drop and flow rate attenuation. This allows the filtration process to operate stably for a long time and reduces downtime caused by cleaning the filter screen.

[0018] While cleaning the filter screen, the rotating scraper also agitates and guides the oil, which helps to separate and settle impurities. Attached Figure Description

[0019] In the attached diagram: Figure 1 This is a schematic diagram of the cross-sectional structure; Figure 2 for Figure 1 Enlarged structural diagram at point A in the middle; Figure 3 for Figure 1 Enlarged structural diagram at point B; Figure 4 A schematic diagram of the multi-stage filter cartridge, the first scraper unit, and the oil guide support structure; Figure 5 for Figure 4 Enlarged structural diagram at point C; Figure 6 This is a partial structural diagram of the first scraper unit; The components represented by the various reference numerals in the diagram are: 1. Tank body; 101. Tank body; 102. Tank cover; 103. Oil inlet; 104. Oil outlet; 2. Multi-stage filter cartridge; 201. Inner filter cartridge; 202. Outer filter cartridge; 203. Support; 204. Support leg; 205. Impurity collection area; 3. Rotating mechanism; 301. Rotating shaft; 302. Drive motor; 4. Oil guide support; 401. Oil outlet groove; 5. First scraper unit; 501. Connecting rod; 502. First scraper; 503. First scraper strip; 504. Second scraper; 505. Second scraper strip; 506. Third scraper; 507. Third scraper strip; 508. Reinforcing rib; 6. Guide wheel; 7. Fine filtration unit; 701. Filter element housing; 702. Cylindrical filter element; 703. Central clean chamber. Detailed Implementation

[0020] Example 1 See Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, a base oil filtration system includes: a tank 1, a multi-stage filter cartridge 2, a rotating mechanism 3, a first scraper unit 5, and a fine filtration unit 7.

[0021] The tank body 1 includes a tank body 101 and a tank cover 102 disposed thereon. The upper end of the tank body 1 is provided with an oil inlet 103 and the lower end is provided with an oil outlet 104.

[0022] A multi-stage filter cartridge 2 is located in the upper part of the tank body 101, comprising multiple coaxially sleeved conical filter cartridges. The axis of the conical filter cartridges is coaxial with the axis of the tank body 101. The mesh diameter of the multiple conical filter cartridges decreases from the inside to the outside. Two conical filter cartridges do not interfere with each other. The outermost conical filter cartridge is connected to the inner wall of the tank body 101 through a bracket 203. The inner conical filter cartridge is connected to its adjacent outer conical filter cartridge through a support leg 204. The cylinder body of the inner conical filter cartridge... Each filter has multiple coarse filter holes, and the outermost conical filter cylinder has fine filter holes. The lower part of the outermost conical filter cylinder forms an impurity collection zone 205. When the oil flows naturally under gravity, larger particles are first intercepted by the inner coarse filter holes, while smaller particles are captured by the outer fine filter holes. This multi-stage synergistic filtration method, compared with a single-precision filter screen, can achieve efficient removal of impurities with a wider particle size range in a single process, thereby improving the cleanliness of the final oil product.

[0023] The rotating mechanism 3 includes a rotating shaft 301 and a drive motor 302 connected thereto. The rotating motor is mounted on the tank cover 102. The rotating shaft 301 is mounted inside the tank body 1 along the axial direction of the tank body 1. Its lower end passes through the multi-stage filter cylinder 2 and is rotatably connected to the oil guide support 4 at the lower inner side of the tank body 101. The oil guide support 4 is located near the oil outlet 104, and its lower part is provided with multiple oil outlet grooves 401 that communicate with the oil outlet 104. The bottom surface of the oil outlet grooves 401 is flush with the upper surface of the oil outlet 104.

[0024] See Figure 4 , Figure 5 and Figure 6 As shown, multiple first scraper units 5 are arranged circumferentially along the rotation axis 301. In this embodiment, two sets of first scraper units 5 are symmetrically arranged on both sides of the rotation axis 301. Each first scraper unit 5 includes a connecting rod 501 and a first scraper 502. The first scraper 502 is provided with a flexible first scraper strip 503. One end of the connecting rod 501 is connected to the rotation axis 301, and the other end is connected to the upper part of the first scraper 502. In this embodiment, the rotation axis 301 and the connecting rod 501 are also connected by a reinforcing rib 508 to improve the connection strength. The reinforcing rib 508 is inclined downward to form a rib. The first scraper 502 is set in the annular gap between two adjacent conical filter cylinders. The first scraper strip 503 abuts against the surface of the adjacent conical filter cylinder. The rotation axis 301 can drive the first scraper 502 and the first scraper strip 503 to rotate in the annular gap between the inner filter cylinder 201 and the outer filter cylinder 202. The first scraper strip 503 cleans the impurities on the surface of the corresponding filter cylinder, reducing the clogging of the filter cylinder mesh.

[0025] An externally inlet, internally outlet fine filtration unit 7 is located below the multi-stage filter cartridge 2 and has a central clean chamber 703, which is connected to the oil outlet 104. The fine filtration unit 7 includes a filter cartridge housing 701 and a cylindrical filter element 702 housed within it. Both the filter cartridge housing 701 and the cylindrical filter element 702 are existing technologies. The cylindrical filter element 702 can be a high-precision pleated glass fiber filter element or a filter element of other materials. The cylindrical filter element 702 is connected to the filter cartridge housing 701 via a perforated bracket 203 or a stainless steel mesh. The base oil to be filtered enters the inner side of the cylindrical filter element 702 from the outside, while impurities are filtered onto the outside of the cylindrical filter element 702. After filtration, the filtered oil flows from the central clean chamber 703 in the middle of the cylindrical filter element 702 to the oil outlet 104.

[0026] The axis of the rotating shaft 301 is coaxial with the axis of the filter element housing 701. The rotating shaft 301 extends through the filter element housing 701 to the upper part of the oil guide support 4. The rotating shaft 301 is rotatably connected to the filter element housing 701 and the oil guide support 4 respectively through bearings.

[0027] A single conical filter cartridge includes an inner filter cartridge 201 and an outer filter cartridge 202 fitted around it. Both the inner filter cartridge 201 and the outer filter cartridge 202 are inverted frustum-shaped cylindrical structures with the larger end facing upwards and the smaller end facing downwards. The upper ends of both the inner filter cartridge 201 and the outer filter cartridge 202 are open, and the lower ends of both the inner filter cartridge 201 and the outer filter cartridge 202 have perforated mesh plates. The aperture of the perforated mesh plate of the inner filter cartridge 201 is the same as the aperture of the mesh of the inner filter cartridge 201. The perforated mesh plate of the outer filter cylinder 202 has the same aperture as the mesh aperture of the outer filter cylinder 202. The inner filter cylinder 201 and the outer filter cylinder 202 are spaced apart to avoid interference. The outer filter cylinder 202 is connected to the inner wall of the tank body 101 through the bracket 203. The lower part of the inner filter cylinder 201 is connected to the outer filter cylinder 202 through multiple legs 204. The multiple legs 204 are arranged in the circumferential direction. The inner filter cylinder 201 and the outer filter cylinder 202 are fixedly installed.

[0028] The inner filter cartridge 201 and the outer filter cartridge 202, together with the cylindrical filter element 702, form a multi-stage filtration system for base oil, which filters the base oil that needs to be filtered layer by layer. The pore size of the cylindrical filter element 702 is smaller than that of the outer filter cartridge 202, further filtering the base oil.

[0029] The first scraper unit 5 has the following structure: the first scraper 502 is disposed in the annular gap formed between the inner filter cylinder 201 and the outer filter cylinder 202. Multiple first scraper strips 503 are symmetrically arranged on opposite sides of the first scraper 502. The first scraper strip 503 on one side abuts against the outer wall of the inner filter cylinder 201 to clean impurities on the outer wall of the inner filter cylinder 201. The first scraper strip 503 on the other side abuts against the inner wall of the outer filter cylinder 202 to clean impurities on the inner wall of the outer filter cylinder 202. The horizontal plane at the lower end of the first scraper 502 is higher than the horizontal plane at the highest position of the support leg 204 to prevent the first scraper 502 and the first scraper strip 503 from colliding with the support leg 204 when rotating.

[0030] The connecting rod 501 is also provided with a second scraper 504 parallel to the first scraper 503. The second scraper 504 is located inside the inner filter cylinder 201. The second scraper 504 is provided with a plurality of flexible second scrapers 505 along its length direction. The plurality of second scrapers 505 are arranged along the length direction of the second scraper 504. The second scrapers 505 face the inner wall of the inner filter cylinder 201 and abut against the inner wall of the inner filter cylinder 201.

[0031] To ensure stable rotation of the lower part of the first scraper 502, a guide wheel 6 is provided at the lower end of the first scraper 502, and the wheel surface of the guide wheel 6 abuts against the inner wall of the outer filter cylinder 202.

[0032] The lower end of the second scraper 504 extends above the upper bottom surface of the inner filter cylinder 201. A third scraper 506 is provided at the lower end of the second scraper 504. A third scraper 507 is provided on the third scraper 506 that abuts against the upper bottom surface of the inner filter cylinder 201. The third scraper 507 is arranged parallel to the upper bottom surface of the inner filter cylinder 201, and the end of the third scraper 507 away from the second scraper 504 is connected to the rotating shaft 301.

[0033] The filtration system of this invention constructs a highly efficient continuous anti-clogging mechanism through the synergy of "gravity flow" and "dynamic scraping". Specifically, the inverted conical filter cylinder assembly provides a natural diffusion and drainage channel for the oil, while the first scraper 503, the second scraper 505, and the third scraper 507 driven by the rotating shaft 301 simultaneously and continuously scrape the inner wall, outer wall, and top surface of the filter cylinder. This synergy combines filtration and cleaning. When the oil flows through the filter screen under gravity, the impurities intercepted are immediately scraped off by the rotating flexible scraper and slide down the conical surface to the impurity collection area 205 at the bottom. The whole process realizes the transformation from "static interception-clogging" to "dynamic interception-instant removal-automatic collection", thereby ensuring that the system can operate stably for a long time and reducing downtime caused by cleaning or replacing the filter screen.

[0034] The coaxially mounted conical filter cartridges with decreasing pore size from the inside to the outside form a highly efficient physical filtration gradient. In a single process, the oil can remove various particulate impurities from large to small step by step, reducing the impurity load on the cylindrical filter element 702 of the downstream external inlet and internal outlet fine filtration unit 7. This not only extends the service life of the core fine filter element and reduces operating resistance, but also reliably ensures that the oil obtained from the oil outlet 104 can reach an extremely high cleanliness standard.

[0035] Example 2 Based on the filtration system in Example 1, this embodiment provides a filtration method for a base oil filtration system, comprising the following steps: S1. The base oil to be filtered is introduced through the oil inlet 103 at the top of the tank 1, so that it enters the top area of ​​the multi-stage filter cartridge 2. S2. Start the drive motor 302 to drive the rotating shaft 301 and the first scraper unit 5 fixed thereon to rotate. Under the influence of gravity, the base oil flows sequentially through the inner filter cylinder 201 and the outer filter cylinder 202 of the multi-stage filter cylinder 2, achieving gradient filtration from coarse to fine. The first scraper 503 on the first scraper 502 continuously scrapes the outer wall of the inner filter cylinder 201 and the inner wall of the outer filter cylinder 202, the second scraper 505 continuously scrapes the inner wall of the inner filter cylinder 201, and the third scraper 507 continuously scrapes the top and bottom surfaces of the inner filter cylinder 201 to remove impurities attached to the corresponding mesh. S3. The oil after being processed by the multi-stage filter cartridge 2 flows downward into the external inlet and internal outlet fine filtration unit 7. The oil passes through the cylindrical filter element 702 from the outside and enters the central clean chamber 703 inside it to complete fine filtration. S4. The clean oil collected in the central clean chamber 703 is guided by the oil outlet groove 401 of the oil guide support 4 and finally discharged continuously from the oil outlet 104 at the bottom of the tank 1.

Claims

1. A base oil filtration system characterized by, include: The tank body (1) includes the tank body (101) and the tank cover (102) provided thereon. The upper end of the tank body (1) is provided with an oil inlet (103) and the lower end is provided with an oil outlet (104). A multi-stage filter cartridge (2) is disposed in the upper part of the tank body (101), comprising multiple coaxially sleeved conical filter cartridges. The axis of the conical filter cartridges is coaxial with the axis of the tank body (101). The mesh diameter of the multiple conical filter cartridges decreases from the inside to the outside. The outermost conical filter cartridge is connected to the inner wall of the tank body (101) through a bracket (203). The conical filter cartridges located on the inner side are spaced apart from their adjacent outer conical filter cartridges. The conical filter cartridges located on the inner side are provided with multiple coarse filtration holes, and the conical filter cartridges located on the outermost side are provided with fine filtration holes. The lower part of the conical filter cartridge of the outermost side forms an impurity collection area (205). The rotating mechanism (3) includes a rotating shaft (301) and a drive motor (302) connected thereto. The rotating motor is mounted on the tank cover (102). The rotating shaft (301) is mounted in the tank body (1) along the axial direction of the tank body (1). Its lower end passes through the multi-stage filter cylinder (2) and is rotatably connected to the oil guide support (4) on the lower inner side of the tank body (101). Multiple first scraper units (5) are arranged circumferentially along the rotation axis (301). Each first scraper unit (5) includes a connecting rod (501) and a first scraper (502). The first scraper (502) is provided with a flexible first scraper strip (503). One end of the connecting rod (501) is connected to the rotation axis (301), and the other end is connected to the upper part of the first scraper (502). The first scraper (502) is disposed between two adjacent conical filter cylinders, and the first scraper strip (503) abuts against the surface of the adjacent conical filter cylinder. An externally inlet and internally outlet fine filtration unit (7) is located below the multi-stage filter cylinder (2) and has a central clean chamber (703) that is connected to the oil outlet (104).

2. The base oil filtration system of claim 1, wherein, The plurality of conical filter cylinders include an inner filter cylinder (201) and an outer filter cylinder (202) sleeved thereon. Both the inner filter cylinder (201) and the outer filter cylinder (202) are inverted frustum-shaped cylindrical structures with the large end facing up and the small end facing down.

3. The base oil filtration system of claim 1, wherein, The first scraper (502) is disposed in the annular gap formed between the inner filter cylinder (201) and the outer filter cylinder (202). A plurality of first scraper strips (503) are symmetrically arranged on the first scraper (502) on opposite sides. One side of the first scraper strip (503) abuts against the outer wall of the inner filter cylinder (201), and the other side of the first scraper strip (503) abuts against the inner wall of the outer filter cylinder (202).

4. The base oil filtration system of claim 1, wherein, The connecting rod (501) is also provided with a second scraper (504) parallel to the first scraper (503). The second scraper (504) is located inside the inner filter cylinder (201). The second scraper (504) is provided with a flexible second scraper (505) along its length direction. The second scraper (505) abuts against the inner wall of the inner filter cylinder (201).

5. The base oil filtration system of claim 2, wherein, The inner filter cartridge (201) and the outer filter cartridge (202) are connected through the supporting legs (204), the supporting legs (204) are provided in plurality, the plurality of supporting legs (204) are located at the lower part of the outer filter cartridge (202) and are arranged along the circumferential direction of the outer filter cartridge (202).

6. The base oil filtration system of claim 5, wherein, The plane where the lower end of the first scraper (502) is located is higher than the horizontal plane where the supporting leg (204) in the highest position is located.

7. The base oil filtration system of claim 6, wherein, The lower end of the first scraper (502) is rotationally provided with a guide wheel (6), and the wheel surface of the guide wheel (6) is in contact with the inner wall of the outer filter cartridge (202).

8. The base oil filtration system of claim 4, wherein, The lower end of the second scraper (504) extends above the upper bottom surface of the inner filter cartridge (201), the lower end of the second scraper (504) is provided with a third scraper (506), the third scraper (506) is provided with a third scraper strip (507) in contact with the upper bottom surface of the inner filter cartridge (201), the third scraper strip (507) is parallelly arranged with the upper bottom surface of the inner filter cartridge (201), and the end of the third scraper strip (507) away from the second scraper (504) is connected with the rotating shaft (301).

9. The base oil filtration system of claim 1, wherein, The fine filter unit (7) comprises a filter core shell (701) and a cylindrical filter core (702) arranged in the filter core shell (701), and the cylindrical filter core (702) is connected with the filter core shell (701) through a perforated support (203).

10. The filtration method of a base oil filtration system according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: S1, introducing the base oil to be filtered into the tank body (1) through the oil inlet (103) at the upper end of the tank body (1) so that the base oil enters the top region of the multi-stage filter cartridge (2); S2, starting the driving motor (302) to drive the rotating shaft (301) and the first scraper unit (5) fixed thereon to rotate; The base oil flows through the inner filter cartridge (201) and the outer filter cartridge (202) of the multi-stage filter cartridge (2) under the action of gravity, realizing gradient filtration from coarse to fine; the first scraper strip (503) on the first scraper (502) continuously scrapes the outer wall of the inner filter cartridge (201) and the inner wall of the outer filter cartridge (202), the second scraper strip (505) continuously scrapes the inner wall of the inner filter cartridge (201), and the third scraper strip (507) continuously scrapes the upper bottom surface of the inner filter cartridge (201), thereby removing impurities attached to the corresponding mesh holes; S3, the oil liquid treated by the multi-stage filter cartridge (2) flows downward into the fine filter unit (7) of the outer-in and inner-out type, and the oil liquid penetrates through the cylindrical filter core (702) from the outside of the cylindrical filter core (702) into the central clean cavity (703) in the inside of the cylindrical filter core (702), completing fine filtration; S4, the clean oil collected in the central clean cavity (703) is guided through the oil outlet groove (401) of the oil guiding support (4) and finally continuously discharged from the oil outlet (104) at the bottom end of the tank body (1).

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