filter element

Abstract

To provide a filter element which is used for a fluid filtration device and which allows a space not surrounded by a filter medium, to be provided in an outer periphery portion of an inner support member.SOLUTION: A filter element 30 comprises: an inner support member which has a substantially cylindrical support frame; a filter medium 33 which is fitted so as to cover an outer periphery of the support frame; an upper end plate member 31 which is fitted to an upper end of the inner support member so as to cover an upper end of the filter medium; and a lower end plate member 32 which is fitted to a lower end of the inner support member so as to cover a lower end of the filter medium. The inner support member comprises: a pair of right and left side walls 38a, 38b which extends radially outward from the support frame, inner peripheral ends of the side walls are connected via a bottom wall 38c, and an outer periphery opening space is formed surrounded by these side walls and the bottom wall and being open toward an outer peripheral side. Both ends of the filter medium are provided joined to the pair of right and left side walls, and the filter medium is fitted so as to cover an outer periphery of the support frame, except for a place formed with the opening space of the pair of right and left side walls.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a filter element used in a fluid filtering device that filters foreign matter such as dirt and dust from a fluid. [Background technology]

[0002] Fluid filtration devices that filter foreign matter such as dirt and dust from fluids have been widely used for some time, but they are known to pose a problem in that, depending on the type of fluid being filtered, the fluid inside the filtration device freezes at low temperatures, causing volume expansion and damaging the filtration device.For example, in a urea SCR system that purifies nitrogen oxides from the exhaust gas of a diesel engine, a urea aqueous solution filtration device that filters dirt and dust from the urea aqueous solution before the urea aqueous solution is injected into the exhaust gas by a urea aqueous solution injector has a problem in that the urea aqueous solution freezes at low temperatures and causes damage to the urea aqueous solution filtration device.

[0003] To address this problem, as disclosed in Patent Document 1, there is a liquid filter device in which a contractible element that can be contracted by gas is disposed within the filter housing. According to this liquid filter device, when fluid freezes within the filter housing and volumetric expansion occurs, the contractible element contracts in response to the pressure caused by this volumetric expansion, thereby preventing damage to the filter device. Furthermore, as disclosed in Patent Document 2, there is also a liquid filter device in which the filter element is composed of an annular filter body and a support body surrounded by the annular filter body, and the support body is made of an elastomer. In this liquid filter device, when the urea aqueous solution to be filtered freezes, the support body made of an elastomer deforms inward, preventing damage to the filter device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2013-510712 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-214367 Summary of the Invention [Problem to be solved by the invention]

[0005] The liquid filter devices disclosed in Patent Document 1 and Patent Document 2 mentioned above can prevent damage to the filter even if the liquid to be filtered (e.g., a urea aqueous solution) freezes and expands in volume. However, the filter device of Patent Document 1 requires an element to be placed inside the filter housing that can contract when gas is sealed in it. Furthermore, the filter device of Patent Document 2 requires the support surrounded by the annular filter body to be made of an elastomer. This leads to problems such as a complicated configuration of the filter device and increased costs.

[0006] For this reason, the present applicant has been considering a fluid filtration device that does not require additional devices or mechanisms, can utilize the configuration of conventional fluid filtration devices, and can absorb the volume expansion caused by freezing of the internal fluid to prevent damage to the device.At this time, it has been found that the filter element used in the fluid filtration device may not be able to meet the desired requirements if it is configured as a conventional filter element in which a folded filter material is wrapped cylindrically around an inner support member.Specifically, it has been found that there are cases where it is required to communicate the outer space of the filter material with the internal space of the inner support member (the inner space of the filter material) without using a filter material.

[0007] In addition, the fluid filtration device generally has a folded filter material wound cylindrically around an inner support member. This configuration uses a bayonet-type filter element, and the outer periphery of the inner support member is covered with filter material, but there is also a demand for providing a space on the outer periphery of the inner support member that is not surrounded by filter material.

[0008] The present invention has been made in consideration of these problems, and aims to provide a filter element having a configuration in which a folded filter material is wound cylindrically around an inner support member, while allowing a space on the outer periphery of the inner support member that is not surrounded by the filter material. Another aim of the present invention is to provide a filter element having a configuration in which the outer space of the filter material and the internal space of the inner support member (the inner space of the filter material) can be communicated without the need for a filter material. [Means for solving the problem]

[0009] In order to achieve the above object, the filter element according to the present invention comprises: Allows fluid to pass through The inner support member has a substantially cylindrical support frame, a filter medium attached to the outer periphery of the support frame, an upper end plate attached to the upper end of the inner support member to cover the upper end of the filter medium, and a lower end plate attached to the lower end of the inner support member to cover the lower end of the filter medium. The inner support member has a pair of left and right side walls (for example, left and right walls 38a, 38b in the embodiment) extending radially outward from the support frame, and the pair of left and right side walls Inner ends in the radial direction are connected by a bottom wall (for example, bottom wall 38c in the embodiment), The pair of left and right side walls and the bottom wall are configured so that fluid cannot pass through, and upper ends of the pair of left and right side walls and the bottom wall are covered by the upper end plate, and lower ends of the pair of left and right side walls and the bottom wall are covered by the lower end plate, and the pair of left and right side walls, the bottom wall, the upper end plate, and the lower end plate An outer peripheral open space (for example, a wedge-shaped recessed space 38d in the embodiment) is formed, which is surrounded by the filter material and is open to the outer periphery, and both ends of the filter material are respectively joined to the pair of left and right side walls, and the filter material is attached to cover the outer periphery of the support frame except for the part of the pair of left and right side walls where the open space is formed (for example, the wedge-shaped recessed space forming part 38 in the embodiment).

[0010] In the above filter element, preferably, the filter material is formed by folding a strip of filter paper, and the folded surface at one end of the filter material is joined to one of the pair of left and right side walls, and the folded surface at the other end of the filter material is joined to the other of the pair of left and right side walls. In the above filter element, preferably, a communication opening (e.g., opening 31b formed in upper end plate 31 in the embodiment) is formed in the upper end plate, a recessed space forming member (e.g., outlet space forming member 37 in the embodiment) is provided inside the support frame of the inner support member and forms a recessed space that communicates with the communication opening and extends downward, and a part of the wall of the recessed space forming member is formed to overlap with the bottom wall, a wall of the recessed space forming member at the bottom wall configured so that fluid cannot pass through; The overlapping portion is configured to connect the recessed space and the outer peripheral open space. to allow fluid to pass through A communication hole (for example, the small communication hole 39 in the embodiment) is formed.

[0011] Furthermore, in the manufacturing method of the above-mentioned filter element according to the present invention, the filter material is formed by folding a strip of filter paper, and the folded surface at one end of the filter material is joined to one of the pair of left and right side walls, and the folded surface at the other end of the filter material is joined to the other of the pair of left and right side walls. The above filter element Manufacturing method Preferably, the joining of the bent surface at one end of the filter material to one of the pair of left and right side walls and the joining of the bent surface at the other end of the filter material to the other of the pair of left and right side walls are performed by ultrasonic welding.

[0012] The above filter element Manufacturing method In the present invention, preferably, the filter material contains heat-melting resin fibers, the pair of left and right side walls are made of a resin material, and the ultrasonic welding joint is a joint in which the resin fibers and the resin material are melted and heat-welded.

[0013] In the method for manufacturing the filter element described above, preferably, a communication opening (e.g., opening 31b formed in upper end plate 31 in the embodiment) is formed in the upper end plate, a recessed space forming member (e.g., outlet space forming member 37 in the embodiment) is provided inside the support frame of the inner support member and forms a recessed space that communicates with the communication opening and extends downward, a wall of the recessed space forming member is formed to overlap with the bottom wall, and a portion where a portion of the wall of the recessed space forming member overlaps with the bottom wall communicates with the recessed space and the outer peripheral open space. to allow fluid to pass through A communication hole (for example, the small communication hole 39 in the embodiment) is formed. [Effects of the Invention]

[0014] According to the filter element of the present invention, an outer peripheral open space is formed that is surrounded by the pair of left and right side walls and the bottom wall and is open to the outer periphery, and both ends of the filter material are respectively joined to the pair of left and right side walls, and the filter material is attached to cover the outer periphery of the support frame except for the portions of the pair of left and right side walls where the open space is formed. Furthermore, in the area where the open space is formed, it is possible to easily connect the space on the outer periphery of the filter material with the space on the inner periphery of the filter material without being obstructed by the filter material. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing the configuration of a urea SCR system using a urea aqueous solution filtering device 10 having a filter element according to the present invention. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the urea aqueous solution filtration device. [Figure 3] FIG. 2 is a cross-sectional view showing the urea aqueous solution filtering device. [Figure 4] FIG. 2 is a perspective view showing a filter element used in the urea aqueous solution filtering device. [Figure 5] FIG. 2 is a perspective view showing an inner support member and a filter medium attached to its outer periphery in the filter element. [Figure 6] FIG. 10 is a bottom view showing the inner support member and the filter medium attached to its outer periphery. [Figure 7] FIG. 2 is a perspective view showing an inner support member. [Figure 8] 10 is a cross-sectional view showing a method of joining a filter medium to an inner support member. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] A preferred embodiment of the present invention will now be described with reference to the drawings. First, a schematic configuration of a urea SCR system using a urea solution filtration device 10 having a filter element according to the present invention will be described with reference to FIG. 1. This system purifies nitrogen oxides in exhaust gas by supplying a urea solution to a urea SCR catalytic device 3 provided in an exhaust passage 2a connected to an exhaust pipe 2 of a diesel engine 1. The purified exhaust gas is released into the atmosphere through an exhaust pipe 2b. The urea SCR system includes a urea solution storage tank 5 for storing the urea solution, and a urea solution injector 6 that draws the urea solution from the urea solution storage tank 5 via inlet pipes 7 and 8 and injects the urea solution into the urea SCR catalytic device 3 via an injection supply pipe 9. A urea solution filtration device 10 is provided between the inlet pipes 7 and 8 to purify dirt and dust from the urea solution.

[0017] As shown in Figures 2 and 3, the urea aqueous solution filtration device 10 is configured with a replaceable filter element 30 disposed in an internal space 20 surrounded by a lower housing 11 and an upper housing 15. The lower housing 11 is connected to the inlet pipe 7 via an inlet portion 11a, and the urea aqueous solution stored in the urea tank 5 is introduced into the internal space 20 through an inlet passage 7a of the inlet pipe 7. The upper housing is connected to the inlet pipe 8 via an outlet portion 15a, and the filtered urea aqueous solution is sent to the inlet passage 8a of the inlet pipe 8. The lower housing 11 and the upper housing 15 have a lower housing flange portion 11b and an upper housing flange portion 15b fitted together, and the internal space 20 is kept airtight by a seal ring 12. The lower housing 11 is provided with left and right mounting flange portions 13, 13, which allow the urea aqueous solution filtration device 10 to be fixed in a predetermined mounting position.

[0018] As shown in Figure 4, the filter element 30 is composed of a disk-shaped upper end plate 31, a disk-shaped lower end plate 32, a generally cylindrical inner support member 35 extending vertically and sandwiched between the upper and lower end plates 31, 32, and a filter medium 33 wound around the outer periphery of the inner support member 35 in a bellows-like manner. With the filter element 30 disposed in the internal space 20, the lower end plate 32 is fitted and held on the inner periphery of the lower housing 11, and the upper end plate 31 is fixed to the upper inner surface of the upper housing 15 via a locking projection 31a provided on its upper surface. In this manner, the filter element 30 is attached to the internal space 20. In this state, the lower end plate 32 is fitted on the inner periphery of the lower housing 11 and sealed by a seal 32a, forming a first internal space 21 as part of the internal space 20. The first internal space 21 is introduced and arranged through the inlet portion 11a. The inlet pipe 7 is connected to the inlet passage 7a of the inlet pipe 7, and the urea aqueous solution is introduced into the first internal space 21. A heater 50 is provided in the lower part of the first internal space 21, which will be described later.

[0019] As shown in FIG. 7 , the inner support member 35 includes a substantially cylindrical support frame 36 and a wedge-shaped recessed space-forming portion 38 formed by partitioning a portion of the support frame into a wedge shape. The support frame 36 includes ring-shaped support frames 36a, 36a located at the upper and lower ends, multiple ring-shaped intermediate frames 36b located in the middle, and multiple vertical frames 36c extending vertically and connecting the upper and lower support frames 36a, 36a to the multiple intermediate frames 36b, forming a cylindrical frame shape. A cylindrical outlet space-forming member 37, connected to the inner periphery of the upper support frame 36a via a support flange 37a, is provided extending into the support frame 36. The outlet space-forming member 37 is a cylindrical hollow container-like member that opens upward and is connected to the central opening of the support flange 37a, and its upper end is open. The wedge-shaped recess-forming portion 38 has a bottom wall 38c that extends vertically and is connected to the outer circumferential surface of the outlet space-forming member 37, and left and right walls 38a, 38b that extend vertically and radially outward from the bottom wall 38c, and a wedge-shaped recess space 38d that is open to the outer circumferential side is formed by being surrounded by the left and right walls 38a, 38b and the bottom wall 38c. As shown in Figures 2 and 4, a small communication hole 39 is formed in the lower part of the bottom wall 38, and the internal space of the outlet space-forming member 37 communicates with the wedge-shaped recess space 38d via the small communication hole 39.

[0020] The filter medium 33, bent like a bellows, is wound around and attached to the outer periphery of the substantially cylindrical support frame 36 of the inner support member 35, as shown in FIG. 5 (and FIG. 6, which shows the shape as viewed from the bottom). At this time, one end bent surface 33a of the filter medium 33 is welded to the outer wall surface of the right wall 38a, and the other end bent surface 33b is welded to the outer wall surface of the left wall 38b. This welding is performed using an ultrasonic welding tool 60 (comprising a welding horn 61 and an ultrasonic welding support jig 62), as shown in FIG. 8. For example, as shown in FIG. 8, the ultrasonic welding support jig 62 is placed against the inner surface of the right wall 38a, and the end bent surface 33a of the filter medium 33 is placed against the outer surface of the right wall 38a while the welding horn 61 is pressed against it, so that the right wall 38a and the end bent surface 33a of the filter medium 33 are sandwiched between the ultrasonic welding support jig 62 and the welding horn 61. In this state, ultrasonic waves are applied from the welding horn 61 to heat-weld the end bent surface 33a of the filter material 33 to the outer surface of the right wall 38a. The right wall 38a (inner support member 35) is made of resin and is heat-welded to the resin fibers that form the filter material 33. This welding is similarly performed on the left wall 38b and the other end of the filter material 33, and as a result, as shown in Figures 5 and 6, the accordion-shaped bent filter material 33 is wrapped and attached to the outer periphery of the approximately cylindrical support frame 36 of the inner support member 35. Note that instead of heat welding, other methods of joining, such as adhesive bonding, may be used.

[0021] After wrapping the filter medium 33 around the outer periphery of the support frame 36 of the inner support member 35 in this manner, as shown in FIGS. 5 and 6, an upper end plate 31 is attached to cover the upper ends of the inner support member 35 and the filter medium 33, and a lower end plate is attached to cover the lower ends. This completes the filter element 30 shown in FIG. 4. An opening 31b is formed in the upper end plate 31, and the internal space of the outlet space-forming member 37 of the inner support member 35 communicates with the outside through this opening 31b. An opening 32b is also formed in the lower end plate 32, and the first internal space 21 communicates with the interior of the inner support member 35 through this opening 32b. The filter element 30 is then installed within the internal space 20 of the lower and upper housings 11 and 15 as described above.

[0022] Returning to Figure 2, the explanation will continue. A heater 50 is mounted in the lower part of the internal space of the lower housing 11. The heater 50 is attached by fitting an upper cover 51 to the inner peripheral surface of the lower housing 11, and an installation space 55 that is liquid-tight is formed by seals 52a and 52b. An engine cooling water inlet 53 and an outlet 54 are provided in communication with this installation space 55, and engine cooling water is introduced from the cooling water inlet 53 into the internal space 55 and discharged from the internal space 55. The engine coolant is discharged through the coolant outlet 54. This transfers heat from the engine coolant to the urea solution in the first internal space 21 through the upper cover 51, warming the urea solution to be filtered in a low-temperature environment. The seal 52a maintains a liquid-tight seal between the internal space 20 and the outside, and the seal 52b maintains a liquid-tight seal between the internal space of the heater 50 and the outside. Therefore, even if a malfunction occurs in either seal, the urea solution and the engine coolant will not mix.

[0023] Meanwhile, an air vent device 40 is provided inside the upper housing. The air vent device 40 consists of a float 42 and an air vent hole 41, which is a small hole connecting the internal space 20 and the internal passage of the outlet portion 15a. The float 42 has a specific gravity that causes it to float in the urea aqueous solution. When the internal space 20 is filled with the urea aqueous solution and the float floats, it blocks the air vent hole 41. When bubbles (air) mixed in the urea aqueous solution accumulate in the upper part of the internal space 20, an air layer space 24a is formed. When the water surface 24c of the urea aqueous solution (shown by a two-dot chain line in FIG. 2 ) below this air layer space 24a rises above the position that would allow the float 42 to float, the float 42 blocks the air vent hole 41, and the bubbles (air) mixed in the urea aqueous solution accumulate in the upper part of the internal space 20. This increases the size of the air layer space 24a, and when the water level 24c of the urea aqueous solution drops, the position of the float 42 is lowered, the air vent hole 41 is opened, and the air in the air layer space 24a is discharged to the outlet 15a. In this way, the air vent device 40 forms the air layer space 24a in the internal space 20 and sets the position of the water level 24c of the urea aqueous solution to a predetermined position, thereby maintaining the size of the air layer space 24a at a predetermined size.

[0024] A suction pipe 16 that connects to the internal passage of the outlet portion 15a and protrudes downward is attached to the upper interior of the upper housing 15. As shown in Figure 2, this suction pipe 16 passes through an opening 31b in an upper end plate 31 of a filter element 30 installed in the internal space 20 and protrudes into the internal space of an outlet space-forming member 37 of an inner support member 35.

[0025] In the urea aqueous solution filtration device 10 shown in FIG. 2 configured as described above, the internal space 20 is divided into multiple internal spaces by the filter element 30, which will now be described. First, as described above, the first internal space 21 is formed below the lower end plate 32, and the urea aqueous solution is fed into this space from the inlet pipe 7. An opening 32b is formed in the lower end plate 32, and the first internal space 21 connects to an internal space (referred to as the second internal space 22) surrounded by the filter media 33 attached to the outer periphery of the inner support member 35, and the urea aqueous solution is fed directly into the second internal space 22. Note that the outlet space-forming member 37 protrudes into the space within the support frame 36 of the inner support member 35, but this internal space is isolated from the second internal space 22. Similarly, the wedge-shaped recessed space 38d of the wedge-shaped recessed space-forming portion 38 is also isolated from the second internal space 22.

[0026] The urea aqueous solution that has been filtered through the filter medium 33 flows into a space (referred to as the third internal space 23) on the outer periphery of the filter medium 33 of the filter element 30. The third internal space 23 is a space located on the outer periphery of the filter element 30, and the wedge-shaped recessed space 38d of the wedge-shaped recessed space-forming portion 38 communicates with the third internal space 23 and forms part of the third internal space 23. The third internal space 23 communicates with the internal space of the upper housing 15 (referred to as the fourth internal space 24). As described above, the air layer space 24a is formed within the fourth internal space 24, so the fourth internal space 24 is divided into the air layer space 24a and the urea aqueous solution filling space 24b, and the boundary surface 24c between them is the water surface of the urea aqueous solution.

[0027] The fourth internal space 24 further communicates with the internal space of the outlet space forming member 37 of the inner support member 35 (referred to as the fifth internal space 25) through the opening 31b of the upper end plate 31 of the filter element 30. As described above, the suction pipe 16 protrudes from above into the fifth internal space 25, and the fifth internal space 25 is the internal passage space of the suction pipe 16 (the This is referred to as a sixth internal space 26. The sixth internal space 26 is connected to an internal passage of the outlet portion 15a (this is referred to as a seventh internal space 27).

[0028] The filtration of urea solution using the urea solution filtration device 10 configured as described above will now be described. The urea solution (referred to as the primary urea solution because it is in a state before filtration) drawn from the urea solution storage tank 5 by the urea solution sprayer 6 flows from the inlet pipe 7 through the inlet 11a into the first internal space 21. The primary urea solution then flows from the first internal space 21 through the opening 32b into the second internal space 22, passes through the filter medium 33 for filtration, and then flows into the third internal space 23. The urea solution filtered in this manner is referred to as the secondary urea solution. The secondary urea solution that has entered the third internal space 23 is sent upward from the outer periphery of the filter element 30 to the fourth internal space 24. The fourth internal space 24 is the uppermost space, and an air layer forms at the top due to the accumulation of bubbles (air) contained in the urea solution. The size of this air layer is adjusted by the air vent device 40 as described above, and the boundary surface 24c indicated by the two-dot chain line in FIG. 2 is set.

[0029] The secondary urea aqueous solution in the fourth internal space 24 flows through the opening 31b of the upper end plate 31 into a fifth internal space 25, which is the internal space of the outlet space forming member 37 of the inner support member 35. Then, from the fifth internal space 25, the secondary urea aqueous solution passes through a sixth internal space 26, which is the internal passage space of the suction pipe 16, and through a seventh internal space 27, which is the internal passage of the outlet portion 15a, and is sent out to the introduction pipe 8. In this case, the suction pipe 16 protrudes from above to below in the fifth space 25, and the lower end opening is located below the fifth space 25, so that the suction pipe 16 does not suck in air from the air layer space 24a.

[0030] A urea SCR system equipped with the urea solution filtration device 10 configured as described above is installed in a vehicle using a diesel engine, which may be used in cold climates. When used in cold climates, freezing of the urea solution can be a problem, but the urea solution filtration device 10 has anti-freezing measures in place. Specifically, an air layer space 24a is formed in the fourth internal space 24, and even if the urea solution in the internal space 20 freezes and expands in volume, the air in the air layer space 24a is compressed and contracted, preventing an increase in internal pressure. This effectively prevents damage to internal components.

[0031] The air vent device 40 is configured to allow air in the air layer space 24a of the fourth internal space 24 to flow out into the seventh internal space 27 through the air vent hole 41, and at this time, a small amount of the urea aqueous solution in the fourth internal space 24 also flows out. However, since there is filtered and purified secondary urea aqueous solution in the fourth internal space 24, this outflow does not cause any problems.

[0032] In the urea SCR system described with reference to FIG. 1 , as part of a measure to prevent the urea solution from freezing at low temperatures, the urea solution injection device 6 is configured to reverse the flow of urea solution inside the system and recover the urea solution inside the system into the urea solution storage tank 5 when the engine is stopped. At this time, because the fifth internal space 25 is the internal space of the outlet space forming member 37 and is a container-like space with an open upper end, there is a risk that the urea solution may remain in the lower part of the fifth internal space 25. Therefore, as described above, the small communication hole 39 is formed in the lower part of the bottom wall 38, and the internal space of the outlet space forming member 37 and the wedge-shaped recessed space 38d are communicated through the small communication hole 39. As a result, the urea solution inside the fifth internal space 25 flows out through the small communication hole 39 into the wedge-shaped recessed space 38d, eliminating the problem of the urea solution remaining in the lower part of the fifth internal space 25. The size of the small communicating holes 39 is kept to the minimum size necessary to allow the urea aqueous solution remaining inside the fifth internal space 25 to flow out into the wedge-shaped recessed space 38d, thereby limiting the amount of secondary urea aqueous solution that flows directly into the fifth internal space 25 from the wedge-shaped recessed space 38d through the small communicating holes 39 when the urea SCR system is in use. As a result, the filtered secondary urea aqueous solution flows from the third internal space 23 to the fourth internal space 24 above, and then flows into the fifth internal space 25. This ensures that there is a flow between them.

[0033] Although the urea aqueous solution filtration device 10 has been described above as an example of an embodiment to which the present invention is applicable, the fluid filtration device according to the present invention is not limited to this. For example, the fluid to be filtered is not limited to urea aqueous solution. It may also be applied to filtration devices for various fluids, including water, particularly fluids that have the problem of freezing at low temperatures. Furthermore, the wedge-shaped recess-forming member 38 provided in the inner support member of the filter element is not limited to this shape and may have various shapes that form a wedge-shaped recess space with a sectorial cross section. For example, it may be formed as a semi-cylindrical recess space. Furthermore, in the above embodiment, the communicating small hole 39 is formed in the lower part of the bottom wall 38, and the internal space of the outlet space-forming member 37 is connected to the wedge-shaped recess space 38d through the communicating small hole 39. However, the communicating small hole 39 may be omitted so that the wedge-shaped recess space (open space) can be effectively utilized without being obstructed by the filter material. [Explanation of symbols]

[0034] 10 urea aqueous solution filtration device 11 lower housing 15 upper housing 20 internal space 21-27 First to seventh internal spaces 30 Filter element 31 Upper end plate 32 Lower end plate 33 Filter material 35 Inner support member 36 Support frame 37 Exit space forming member 38 Wedge-shaped recess forming member 40 Air vent device 41 Air vent hole 42 Float 50 Heater 51 Upper cover 60 Ultrasonic welding tools

Claims

1. The filter is configured to include an inner support member having a substantially cylindrical support frame through which a fluid can pass, a filter medium attached to cover the outer periphery of the support frame, an upper end plate member attached to the upper end of the inner support member to cover the upper end of the filter medium, and a lower end plate member attached to the lower end of the inner support member to cover the lower end of the filter medium, the inner support member has a pair of left and right side walls extending radially outward from the support frame, radial inner ends of the pair of left and right side walls are connected to each other by a bottom wall, the pair of left and right side walls and the bottom wall are configured to be impermeable to fluid, upper ends of the pair of left and right side walls and the bottom wall are covered by the upper end plate, lower ends of the pair of left and right side walls and the bottom wall are covered by the lower end plate, and an outer peripheral open space is formed that is surrounded by the pair of left and right side walls, the bottom wall, the upper end plate, and the lower end plate and is open to the outer periphery, A filter element characterized in that both ends of the filter material are joined to the pair of left and right side walls, and the filter material is attached to cover the outer periphery of the support frame except for the areas where the open space is formed on the pair of left and right side walls.

2. The filter element according to claim 1, characterized in that the filter material is formed by folding a strip of filter paper, and the folded surface at one end of the filter material is joined to one of the pair of left and right side walls, and the folded surface at the other end of the filter material is joined to the other of the pair of left and right side walls.

3. a communication opening is formed in the upper end plate, a recessed space forming member is provided inside the support frame of the inner support member and forms a recessed space that communicates with the communication opening and extends downward, and a wall of the recessed space forming member is formed so as to overlap with the bottom wall, 3. The filter element according to claim 1, wherein a communication hole is formed in the bottom wall, which is configured to prevent fluid passage, at a portion where the bottom wall overlaps with the wall of the recessed space forming member, thereby connecting the recessed space and the outer peripheral open space and allowing fluid to pass through.

4. A method for manufacturing the filter element according to claim 1, comprising the steps of: A method for manufacturing a filter element, characterized in that the filter material is formed by folding a strip of filter paper, and the folded surface at one end of the filter material is joined to one of the pair of left and right side walls, and the folded surface at the other end of the filter material is joined to the other of the pair of left and right side walls.

5. 4. The method for manufacturing a filter element according to claim 3, wherein the joining of the bent surface at one end of the filter material to one of the pair of left and right side walls and the joining of the bent surface at the other end of the filter material to the other of the pair of left and right side walls are performed by ultrasonic welding.

6. 5. The method for manufacturing a filter element according to claim 4, wherein the filter material contains heat-melting resin fibers, the pair of left and right side walls are made of a resin material, and the ultrasonic welding is a joining in which the resin fibers and the resin material are melted and heat-welded.

7. a communication opening is formed in the upper end plate, a recessed space forming member is provided inside the support frame of the inner support member and forms a recessed space that communicates with the communication opening and extends downward, and a wall of the recessed space forming member is formed so as to overlap with the bottom wall, 7. The method for manufacturing a filter element according to claim 4, wherein a communication hole is formed in a portion where a part of the wall of the recessed space forming member and the bottom wall overlap, the communication hole connecting the recessed space and the outer peripheral open space and allowing a fluid to pass through.

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