JP2019183817A - Filter device - Google Patents

Abstract

To provide a filter device capable of suppressing occurrence of air voids and preventing failure such as abnormal combustion of an engine resulting from the air voids.SOLUTION: A fuel filter 1 configured to allow fuel introduced from the outside to an inflow space 42A through an inflow passage 16 to pass through a filter material 52 of a filter element 50 and to flow out from an outflow space 42B to the outside through an outflow passage 17 comprises: a communication hole 21 having one end opened to the inflow passage 16 and the other end opened to the outflow passage 17; and a porous sintered metal body 20 provided in the communication hole 21 and having air permeability. The fuel filter is configured to discharge air accumulated in the inflow space 42A from the inflow passage 16 to the outflow passage 17 through holes of the sintered metal body 20.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a filter device used for filtering liquid such as fuel.

  As a conventional technique, some engines of power machines that operate on liquids such as light oil, kerosene, and gasoline are equipped with a fuel injection system that supplies this fuel in the form of a mist into the cylinder or intake port. ing. This fuel injection system is configured to include a fuel tank, a fuel pump, an injection nozzle, and the like, and in the fuel flow path between the fuel tank and the injection nozzle, garbage contained in the fuel in the fuel tank. A fuel filter for capturing and removing foreign substances such as dust is provided (see, for example, Patent Document 1).

  The fuel filter disclosed in the above-mentioned patent document is divided into a filter case having an element disposition space inside, an inflow space that connects the element disposition space to the fuel inflow passage, and an outflow passage that connects to the fuel outflow passage. The filter element is detachably mounted in the element arrangement space. This fuel filter removes foreign matters (combustion products and metal powder) contained in the fuel by filtering the fuel introduced from the outside into the inflow space through the inflow passage with a filter medium included in the filter element. . The fuel filter introduces the fuel from which foreign matters have been removed by the filter medium into the outflow space in a clean state, and causes the fuel to flow out from the outflow space to the outside (fuel flow path) through the outflow path. .

JP 2009-125737 A

  The fuel supplied to the fuel filter contains fine bubbles of air (bubbles) that are invisible, and when the fuel passes through the filter element (filter medium), the bubbles in the fuel are removed. Easy to adhere to the surface of the filter medium. The fine bubbles adhering to the surface of the filter medium gradually gather to form large bubbles, float away from the surface of the filter medium, and form an air pocket above the inflow space (the space on the outer periphery side of the filter medium). When the fuel flow rate suddenly increases due to the rapid acceleration of the engine in the state where the air pool is formed in the fuel filter in this way, the pressure loss when passing through the filter element (filter medium) increases and the outflow occurs. Since the space side has a relatively large negative pressure with respect to the inflow space side, the air reservoir formed in the upper part of the inflow space passes through the filter element (filter medium) and is sucked into the outflow space side, and the fuel It is carried into the flow path downstream of the filter. Then, the fuel flow path is filled with bubbles, so that air is temporarily supplied instead of fuel, fuel supply becomes insufficient, and problems such as abnormal combustion of the engine may occur. was there.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a filter device that can suppress the occurrence of air accumulation and prevent problems such as abnormal combustion of the engine due to this. .

  In order to solve the above problems, a filter device according to the present invention has an element arrangement space inside, and a filter case in which an inflow path and an outflow path for communicating the element arrangement space and the outside are formed, A filter element attached to the element arrangement space by dividing the element arrangement space into an inflow space connected to the inflow path and an outflow space connected to the outflow path; and from the outside through the inflow path, the inflow A filter device configured to allow the liquid introduced into the space to pass through the filter element and to flow out from the outflow space through the outflow passage, and the filter case has one end side of the inflow passage. A communicating hole whose other end opens to the outflow passage, and a porous sintered metal body provided in the communicating hole and having air permeability. Characterized in that the air accumulated in the inlet space and dischargeable configured to the outlet channel through the sintered metal body from the inlet passage.

  In the filter device according to the present invention, the filter case is formed in a bottomed cylindrical shape having an open top, and has an element case having the element arrangement space, and the inflow path and the outflow path are formed. A filter head attached to an upper portion of the element case, the case head being provided on the outer peripheral side of the first cylindrical portion, the hollow first cylindrical portion in which the outflow path is formed on the inner peripheral side, and The communication hole includes a hollow second cylindrical portion in which the inflow passage is formed between the inner peripheral side of the first cylindrical portion, and connects the inflow passage and the outflow passage to an upper portion of the first cylindrical portion. Is preferably formed.

  In the filter device according to the present invention, a male screw is formed on the outer peripheral side of the second cylindrical portion in the filter head, and a female screw is formed on the inner peripheral side of the element arrangement space in the element case. Preferably, the element case is detachably attached to the filter head by forming the male screw and the female screw.

  According to the filter device of the present invention, the porous sintered metal body is provided in the communication hole connecting the inflow path and the outflow path, and the air staying in the inflow space is discharged through the pores of the sintered metal body. By discharging a minute amount to the inside, it is possible to prevent the occurrence of air accumulation in the inflow space. As a result, the liquid to be filtered can be introduced into the entire filter element surface of the filter element in a substantially uniform flow (the entire filter medium can be used almost uniformly), and the engine abnormality caused by the air pool Problems such as combustion can be effectively suppressed.

  Further, according to the filter device of the present invention, the male screw formed on the outer peripheral surface of the second cylindrical portion of the filter head and the female screw formed on the inner peripheral surface of the element case are screwed together to filter the filter device. Since there is a structure that joins the head and element case (that is, a structure that covers only the outermost periphery of the upper end opening of the element case), there is nothing that blocks between the inflow path of the filter head and the inflow space of the element case Therefore, it is difficult to generate an oil film that hinders the discharge of air, so that the air staying in the inflow space can be quickly and surely moved to the inflow path (sintered metal body). Occurrence can be prevented more reliably.

It is a front view which shows the fuel filter which concerns on this embodiment. It is sectional drawing shown along the arrow II-II in FIG. It is a top view of the said fuel filter. FIG. 4 is a sectional view taken along arrows IV-IV in FIG. 2. FIG. 5 is a cross-sectional view taken along arrows VV in FIG. 3. It is sectional drawing shown along arrow VI-VI in FIG. It is sectional drawing of the filter head of the said fuel filter. It is a figure for demonstrating the effect | action of the said fuel filter.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. A fuel filter 1 to which a filter device according to the present invention is applied is shown in FIGS. 1 to 7. First, the overall configuration of the fuel filter 1 will be described with reference to these drawings.

  The fuel filter 1 includes a filter head 10 disposed in the middle of a fuel passage (negative pressure line) between a fuel tank and a fuel pump, and an element assembly (cartridge assembly) 30 detachably attached to the filter head 10. It is mainly composed.

  The filter head 10 is configured with a body 11 formed in a cylindrical shape using a metal material such as aluminum or cast iron or a resin material as a base. The body 11 communicates with the outside (upstream side of the fuel passage) to allow the fuel to flow into the fuel filter 1, and communicates with the outside (downstream side of the fuel passage) and outside the fuel filter 1. And an outlet port 13 for allowing fuel to flow out. The body 11 is provided with an outer cylindrical portion 14 and an inner cylindrical portion 15 that protrude vertically downward and are formed in a double cylindrical shape. An inflow passage (outer passage) 16 extending vertically is formed between the inner peripheral surface of the outer cylindrical portion 14 and the outer peripheral surface of the inner cylindrical portion 15, and the inflow passage 16 communicates with the inlet port 12 in the upper portion. . An outflow passage (inner passage) 17 is formed which is surrounded by the inner peripheral surface of the inner cylindrical portion 15 and extends vertically. The outflow passage 17 communicates with the outlet port 13 in the upper portion. The inflow path 16 and the outflow path 17 are open at the lower portion, and communicate with the element arrangement space 42 formed inside the element assembly 30 in the vertical direction. A male screw 18 for screwing the element assembly 30 is formed on the outer peripheral surface of the outer cylindrical portion 14. The inner cylindrical portion 15 is formed in a stepped cylindrical shape having a small diameter portion 15a and a large diameter portion 15b. The small diameter portion 15 a of the inner cylindrical portion 15 protrudes downward from the lower end of the outer cylindrical portion 14 and is formed so as to be able to be fitted into a seal ring 54 attached to the element assembly 30. A seal surface 19 is formed on the outer peripheral side of the outer cylindrical portion 14 of the body 11 so as to protrude outward and in close contact with the seal ring 44 attached to the element assembly 30.

  A stepped cylindrical communication hole 20 that connects between the outer inflow passage 16 and the inner outflow passage 17 penetrates in the upper part of the large diameter portion 15b of the inner cylindrical portion 15 (near the outlet port 13) in the radial direction. Is formed. As shown in FIG. 7, the communication hole 20 is formed of a first communication hole portion 20 a that communicates with the outer inflow passage 16 and a second communication hole portion 20 b that communicates with the inner outflow passage 17. A sintered metal body 21 for air bleeding formed in substantially the same shape (cylindrical shape) as the first communication hole 20a is press-fitted and fixed to the first communication hole 20a. The sintered metal body 21 is formed in a state where the contact points of the metal powder are connected to each other. The sintered metal body 21 is a porous body in which a large number of fine pores are formed between powder metals on the surface and inside thereof, and pores having a predetermined pore diameter (for example, about 40 μm) are isotropic. Exhibits breathability through communication. Thereby, as will be described in detail later, the stagnant air that has floated and accumulated upward (upper part of the inflow path) due to the difference in specific gravity with the fuel in the fuel filter 1 passes through the pores of the sintered metal body 21 and flows into the inflow path 16. It is possible to discharge from the outlet to the outflow passage 17 in small amounts. Therefore, the sintered metal body 21 is disposed in the vicinity of the uppermost portion of the inflow path 16 where air (bubbles) is most easily collected. Further, the sintered metal body 21 is disposed in the vicinity of the outlet port 13 so that the retained air can be efficiently discharged under the action of the negative pressure of the outlet port 13. Note that the porosity of the sintered metal body 21 (the ratio of the voids in the total volume) can be appropriately set according to the amount of air discharged or the like. Moreover, the material of the metal powder that forms the sintered metal body 21 is not particularly limited, but, for example, bronze, stainless steel, iron, various alloys, and composite materials thereof can be applied.

  The element assembly 30 includes an element case 40 that is detachably attached to the filter head 10 and a filter element 50 that is inserted and held in the element case 40.

  The element case 40 includes a case main body 41 that houses the filter element 50, a fixing plate 43 that is attached to the upper end of the case main body 41, and a tapping plate 45 that is coupled to the lower end of the fixing plate 43. . The case main body 41 is formed in a bottomed cylindrical shape opened upward, and has an element arrangement space 42 in which the filter element 50 can be accommodated. A fixing plate 43 is joined to the upper end portion of the case body 41 so as to cover a part of the upper end opening. The fixed plate 43 is formed in a thin disk shape that bends and extends in a substantially U-shaped cross section. The peripheral edge of the fixing plate 43 is integrally bent and joined outward together with the upper end of the case body 41. A seal ring 44 formed of an elastic member such as synthetic rubber is attached to the fixed plate 43. The seal ring 44 is held in a state of protruding upward from the upper end of the fixed plate 43. A tapping plate 45 is joined and fixed to the lower end of the fixed plate 43 by spot welding. The tapping plate 45 is formed in an annular shape coaxial with the case main body 41, and a female screw 46 that is screwed with the male screw 18 of the filter head 10 is formed on the inner peripheral surface thereof. Therefore, the element assembly 30 can be assembled to the filter head 10 by screwing the female screw 18 with the male screw 46.

  The filter element 50 is formed by winding a chrysanthemum-shaped filter medium 52 folded in a bellows shape around a thin cylindrical inner cylinder 51 made of a punch sheet or the like having a large number of small holes 51a. A disc-shaped upper end plate 53 is fixed to the portion, and a disk-shaped lower end plate 55 is also fixed to the lower end portion, so that both ends of the inner cylinder 51 and the filter medium 52 in the cylindrical axial direction are upper and lower ends. It is configured to be sandwiched between plates 53 and 55.

  The filter medium 52 is configured by winding a filter medium sheet capable of collecting foreign substances in the fuel into a bellows shape with a certain bending width so as to be substantially cylindrical. In addition, about this filter medium 52, for example, those formed in a cylindrical shape by glass fiber or nonwoven fabric having a predetermined thickness, those formed by combining these materials, or sintered in a cylindrical shape The optimal material and shape can be selected in accordance with the liquid to be filtered or the solid matter to be removed.

  A seal ring 54 formed of an elastic member such as synthetic rubber is attached to the center portion (center opening) of the upper end plate 53. When the small diameter portion 15a of the filter head 10 is inserted into the inner diameter portion of the seal ring 54, the small diameter portion 15a of the filter head 10 is fitted and held by the elastic force of the seal ring 54 (the filter element 50 and the small diameter portion 15a). Is maintained in a liquid-tight state).

  A coil spring (compression coil spring) 47 for urging the filter element 50 accommodated in the element arrangement space 42 upward is abutted on the lower portion of the lower end plate 55. The coil spring 56 is supported by a spring receiving portion 48 erected on the bottom of the element disposition space 42 of the case main body 41.

  Next, in the fuel filter 1 according to this embodiment, a procedure for assembling the filter element 50 in the element case 40 (a procedure for assembling the element assembly 30) will be described.

  First, the filter element 50 is inserted into the element arrangement space 42 of the case body 40, and the filter element 50 is placed on the coil spring 47. Subsequently, the two plates (fixed plate 43 and tapping plate 45) in a state of being integrated in advance by a joining means such as spot welding are directed to the upper end opening of the case main body 41, and the peripheral portion of the fixed plate 43 is set to the case main body 41. The filter element 50 is assembled in the case main body 41 in a state of being prevented from being detached, and the element assembly 30 is completed. At this time, the lower end portion of the fixed plate 43 abuts on the upper end portion (upper end plate 53) of the filter element 50 and presses downward, so that the coil spring 47 is compressed and deformed in the axial direction. Accordingly, the filter element 50 receives the elastic force of the coil spring 47 and is urged upward, and the upper end portion (upper end plate 53) of the filter element 50 is firmly in contact with the lower end portion of the tapping plate 45. Retained.

  As a result, the element arrangement space 42 in the element case 40 includes a space on the outer peripheral side of the filter element 50 (referred to as “inflow space 42A”) and a space on the inner peripheral side of the filter element 50 (“outflow space 42B”). Called). The inflow space 42A is a dirty side through which fuel before filtration flows, and the outflow space 42B is a clean side through which fuel after filtration flows.

  Next, a procedure for attaching the element assembly 30 to the filter head 10 will be described. First, the element assembly 30 is aligned substantially coaxially with the filter head 10, and the upper portion of the element assembly 30 is brought close to the lower portion of the filter head 10. Then, the upper part of the element assembly 30 is rotated around the center axis while pressing the lower part of the filter head 10, and the male screw 18 of the filter head 10 is screwed into the female screw 46 of the element assembly 30. The element assembly 30 is attached to the filter head 10. When the element assembly 30 is attached to the filter head 10, the filter element 50 is pressed downward by the filter head 10 against the urging force of the coil spring 47 (the filter element 50 is relative to the element case 40. The lower end of the tapping plate 45 and the upper end of the upper end plate 53 are separated from each other and a gap is formed between them, so that the inflow path 16 of the filter head 10 and the inflow of the element assembly 30 are generated. The space 42A communicates vertically, and the small diameter portion 15a of the inner cylindrical portion 15 is fitted into the seal ring 54, so that the outflow passage 17 of the filter head 10 and the outflow space 42B of the element assembly 30 communicate vertically. To do. At this time, since the inner cylindrical portion 15 of the filter head 10 is elastically fitted to the seal ring 54 of the filter element 50 and the two are sealed in a liquid-tight manner, the fuel in the inflow space 42A passes through the filter medium 52. Unless it passes, it cannot reach the outflow space 42B. Further, since the seal surface 19 of the filter head 10 is elastically adhered to the seal ring 44 of the element assembly 30, the space between the two is liquid-tightly sealed, and the filter head 10 and the element case 40 are joined from the joint portion. The internal fuel is prevented from leaking outside.

  Next, the flow of fuel filtered by the fuel filter 1 will be described with reference to FIG. In FIG. 8, the flow of fuel is represented by solid arrows, and the flow of air in the fuel (retained air) is represented by broken arrows.

  When a negative pressure is applied to the fuel filter 1 by a suction operation of a fuel pump (not shown), fuel from the outside (fuel tank side) passes through the inlet port 12 and flows into the inflow path, as indicated by the solid line arrow in FIG. 16 is introduced into the inflow space 42A and passes through the filter medium 52 of the filter element 50 from the outside to the inside. At this time, foreign matters such as dust contained in the fuel are captured and removed by the filter medium 52 and cleaned. It becomes. The fuel filtered by the filter medium 52 flows into the outflow space 42 </ b> B through a large number of small holes 51 a formed in the inner cylinder 51. In addition, since the inner peripheral part of the filter medium 52 is in contact with the outer peripheral part of the inner cylinder 52, the filter medium 52 is not deformed even if fuel flows in from the outer peripheral direction. The fuel flowing into the outflow space 42B flows out from the outlet port 13 to the outside (fuel pump side) via the outflow path 17.

  Here, when the fuel passes through the filter medium 52, small bubble-like air (bubbles) contained in the fuel is likely to adhere to the surface of the filter medium 52, and this aggregates and gradually grows into large bubbles, thereby the filter medium. When separated from the surface of 52, the bubbles may move upward due to the difference in specific gravity (buoyancy) with the fuel and form an air pocket at the upper part of the inflow side (inflow path 16 and outflow space 42A). When the air pool expands and the occupied volume of the air pool in the inflow side increases, the flow of fuel in the inflow space 42A is obstructed, and the fuel is filtered in the portion where the air pool is formed. There is a possibility that the fuel cannot pass through 52 (the fuel can pass through only a partial region (lower region) of the filter medium 52). However, in the fuel filter 1 of the present embodiment, the air staying at the upper part of the inflow side (retained air) is affected by the negative pressure on the outflow side (the outflow path 17 and the outflow space 42B) side in FIG. As shown by the broken arrows in FIG. 3, the small amount is discharged from the inflow path 16 to the outflow path 17 through the holes of the sintered metal body 51 provided in the inner cylindrical portion 15 that partitions the inflow path 16 and the outflow path 17. As a result, it is possible to prevent the occurrence of air accumulation on the inflow side. As a result, the fuel is introduced into the entire surface of the filter medium 52 without being disturbed by air accumulation (bubbles) in the inflow space 42A, so that the filtration area of the filter medium 52 is effectively utilized. can do. The air discharged to the outflow passage 17 through the pores of the sintered metal body 21 is mixed as fine bubbles in the fuel (purified fuel) flowing through the outflow passage 17 and directly into the fuel pump. Supplied. Therefore, the air in the fuel is not supplied to the fuel pump in the form of large bubbles, and the fuel supply to the fuel pump is not temporarily stopped, so abnormal combustion such as knocking occurs in the engine. Can be prevented.

  As described above, according to the fuel filter 1 according to the present embodiment, the porous sintered metal body 21 is provided in the communication hole 20 that connects the inflow path 16 and the outflow path 17, and the air staying in the inflow space 42 </ b> A is burned. By discharging a small amount to the outflow path 17 through the holes of the metal body 21, it is possible to prevent the occurrence of air accumulation in the inflow space 42A. As a result, the fuel to be filtered can be introduced into the entire surface of the filter medium 52 in a substantially uniform flow (the entire filter medium 52 can be used almost uniformly), and even if it is temporary, the fuel can be replaced. It is possible to prevent the occurrence of a situation in which air is supplied to the fuel (large bubbles are mixed into the supplied fuel) and to effectively suppress problems such as abnormal combustion of the engine caused by the situation.

  In the structure of the prior art (Patent Document 1), a male screw formed on the outer peripheral surface of the inner cylindrical portion of the filter head and a female screw formed on the inner peripheral surface of the tapping plate of the element assembly are screwed together. As a result, the filter head and the element assembly are coupled to each other (that is, the tapping plate substantially covers the portion other than the central portion of the upper end opening of the case body). A tapping plate with an oil passage hole penetrating vertically is interposed between the space and the fuel that flows from the inflow space to the inflow space through the oil passage port, but cannot pass through the oil passage port. May stay on top of the tapping plate and form an oil film (fuel layer) at the oil passage port. When an oil film is formed at the oil passage port, the movement (rise) of air from the inflow space to the inflow path is hindered. Therefore, even if a sintered metal body is provided in this conventional structure (Patent Document 1), the air in the inflow space cannot move to the inflow path through the oil passage port, and the air is discharged from the inflow path to the outflow path. Results that cannot be done. In contrast, in the fuel filter 1 according to this embodiment, the male screw 18 formed on the outer peripheral surface of the outer cylindrical portion 14 of the filter head 10 and the inner peripheral surface of the tapping plate 45 of the element assembly 30 are formed. Since the female head 46 is screwed together, the filter head 10 and the element assembly 30 are coupled (that is, the tapping plate 45 covers only the outermost peripheral portion of the upper end opening of the case body 41). There is nothing that blocks between the inflow path 16 of the filter head 10 and the inflow space 42A of the element assembly 30, and an oil film that hinders the discharge of air is less likely to occur, so that the air staying in the inflow space 42A Can be quickly and reliably moved to the inflow passage 16 (sintered metal body 21), and the occurrence of air pockets can be prevented more reliably. Theft is possible.

  Conventionally, a floating member for releasing air (for example, Japanese Patent Application Laid-Open No. 2006-46142) that moves up and down according to the height of the liquid level of the fuel is well known. There was a risk of causing dust outflow (dust removal) from the inflow side to the outflow side by moving up and down (running out). On the other hand, since the sintered metal body 21 of the present embodiment is used in a state of being fixed in the communication hole 20, there is no fear that the sintered metal body 21 behaves due to vehicle vibration or the like. Since the filter itself has a filtering performance for trapping and removing foreign substances (impurities), dust does not escape.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, If it is a range which does not deviate from the summary of this invention, it can improve suitably.

  In the said embodiment, although the structure which provided only one sintered metal body 21 (communication hole 20) for air bleeding in the inner side cylinder part 15 of the filter head 10 was demonstrated and demonstrated, it is limited to this structure Instead, a plurality of sintered metal bodies 21 (communication holes 20) may be provided in the circumferential direction or the vertical direction.

  In the above-described embodiment, the case where the filter device according to the present invention is applied to a fuel filter has been described as an example. However, the present invention is not limited to this, and other liquids (for example, lubricating oil, hydraulic oil, Even when applied to a filter device that filters water, etc., such as an oil filter, a suction filter, and a return filter, the same effect can be obtained.

1 Fuel filter (filter device)
10 Filter head 11 Body 12 Inlet port 13 Outlet port 14 Outer cylindrical part (second cylindrical part)
15 Inner cylindrical part (first cylindrical part)
16 Inflow path 17 Outflow path 18 Male thread 20 Communication hole 21 Sintered metal body 30 Element assembly 40 Element case 41 Case body 42 Element arrangement space 42A Inflow space 42B Outflow space 43 Fixing plate 45 Tapping plate 46 Female thread 50 Filter element 51 Inner cylinder 52 Filter medium 53 Upper end plate 55 Lower end plate

Claims (3)

A filter case having an element arrangement space inside, and having an inflow path and an outflow path communicating with the element arrangement space and the outside;
A filter element attached to the element arrangement space by dividing the element arrangement space into an inflow space connected to the inflow path and an outflow space connected to the outflow path;
A filter device configured to allow liquid introduced from the outside through the inflow path to the inflow space to pass through the filter element and to flow out from the outflow space to the outside through the outflow path,
The filter case includes a communication hole having one end opened to the inflow passage and the other end opened to the outflow passage, and a porous sintered metal body provided in the communication hole and having air permeability,
A filter device characterized in that the air accumulated in the inflow space can be discharged from the inflow passage to the outflow passage through the sintered metal body. The filter case is formed in a bottomed cylindrical shape having an open top and has the element arrangement space, and a filter head in which the inflow path and the outflow path are formed and attached to the upper part of the element case With
The case head is provided between a hollow first cylindrical portion in which the outflow passage is formed on an inner peripheral side and an inner peripheral side of the first cylindrical portion provided on the outer peripheral side of the first cylindrical portion. A hollow second cylindrical portion in which an inflow path is formed,
The filter device according to claim 1, wherein the communication hole that connects the inflow path and the outflow path is formed in an upper portion of the first cylindrical portion. On the outer peripheral side of the second cylindrical portion in the filter head, a male screw is formed,
On the inner peripheral side of the element arrangement space in the element case, a female screw is formed,
The filter device according to claim 2, wherein the element case is detachably attached to the filter head by screwing the male screw into the female screw.

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