Fluid filtration device

Abstract

To provide a fluid filtration device capable of absorbing cubical dilatation for preventing damage on a device, when internal fluid is frozen to cause the cubical dilatation.SOLUTION: A fluid filtration device 10 comprises: lower and upper housings 11, 15 which have an inlet part 11a and an outlet part 15a, respectively; and a filter element 30 provided in an internal space of the housings. The filter element 30 is arranged in the internal space 20 so that the internal space 20 is partitioned into primary fluid spaces 21, 22 connected to the inlet part 11a, and secondary fluid spaces 23, 24, 25 connected to the outlet part 15a, respectively. A fluid introduced into the primary fluid spaces from the inlet part 11a is filtrated and is made flow into the secondary fluid spaces, then the fluid passes through the outlet part 15a and is discharged. The outlet part 15a is open toward the secondary fluid spaces below an air reservoir space. A bleeding device 40 is provided disconnectably connecting the secondary fluid spaces and an internal path of the outlet part 15a. Air in the air reservoir space is discharged to the internal path of the outlet part 15a so that a formation region of the air reservoir space is provided.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a fluid filtration device for filtering foreign matters such as dust and dirt in a fluid, and particularly to a fluid filtration device having a function for preventing fluid freezing.

Background Art

[0002] Fluid filtration devices for filtering foreign matters such as dust and dirt in a fluid have been widely used. However, depending on the type of fluid to be filtered, there is a problem that the fluid in the filtration device freezes at a low temperature, causing volume expansion and damaging the filtration device. For example, in a urea SCR system for purifying nitrogen oxides in the exhaust gas of a diesel engine, there is a problem that the urea aqueous solution freezes at a low temperature and damages the urea aqueous solution filtration device before the urea aqueous solution is injected into the exhaust gas by a urea water injector after filtering dust and dirt in the urea aqueous solution.

[0003] To address such problems, as disclosed in Patent Document 1, there is a liquid filter device in which an element that can be contracted by gas encapsulation is disposed in a filter housing. According to this liquid filter device, when freezing of the fluid occurs in the filter housing and volume expansion occurs, the contractable element contracts in response to the pressure caused by this volume expansion, thereby preventing damage to the filter device. Further, as disclosed in Patent Document 2, there is also a liquid filter device in which a filter element is composed of an annular filter body and a support body surrounded thereby, and the material of the support body is 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 to prevent damage to the filter device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] According to the liquid filter devices disclosed in Patent Document 1 and Patent Document 2 described above, even if the liquid to be filtered (for example, an aqueous urea solution) freezes and volume expansion occurs, damage to the filter can be prevented. However, in the filter device of Patent Document 1, it is necessary to arrange an element that can be contracted by gas encapsulation in the filter housing. Further, in the filter device of Patent Document 2, it is necessary to use an elastomer as the material of the support surrounded by the annular filter body. For this reason, there are problems that the configuration of the filter device becomes complicated and the cost increases.

[0006] The present invention has been made in view of such problems, and an object thereof is to provide a fluid filtration device having a configuration that can utilize the configuration of a conventionally used fluid filtration device without requiring additional devices or mechanisms, and can absorb volume expansion when the internal fluid freezes to prevent damage to the device.

MEANS FOR SOLVING THE PROBLEMS

[0007] To achieve the above object, a fluid filtration device according to the present invention includes a housing (for example, the lower and upper housings 11 and 15 in the embodiment) having an internal space (for example, the internal space 20 in the embodiment) with an inlet passage (for example, the internal passage of the inlet portion 11a in the embodiment) and an outlet passage (for example, the internal passage of the outlet portion 15a in the embodiment) for the filtered fluid, and , and a filter element disposed in the internal space, configured to partition the internal space into a primary fluid space (e.g., the first and second internal spaces 21 and 22 in the embodiment) connected to the inlet passage and a secondary fluid space (e.g., the third to fifth internal spaces 23 to 25 in the embodiment) connected to the outlet passage. The filter element is disposed in the internal space of the housing so that the fluid introduced from the inlet passage into the primary fluid space passes through the filter medium of the filter element, is filtered, and flows into the secondary fluid space, and is discharged through the outlet passage. And an air accumulation space closed at the upper part of the secondary fluid space is provided to store air generated by bubbles and the like from the filtered fluid in the air accumulation space. The outlet passage opens into the secondary fluid space below the air accumulation space, and an air venting device is provided to connect the secondary fluid space and the outlet passage in a cut-off manner. The air venting device is configured to discharge the air in the air accumulation space into the outlet passage to set the formation region of the air accumulation space.

[0008] The above According to the present invention In the fluid filtration device, Furthermore The air venting device includes an air venting passage connecting the secondary fluid space and the outlet passage, and a float valve disposed movably up and down in the air venting passage. When the air accumulation space becomes larger and its lower end surface position moves downward to move the float valve downward, the float valve opens the air venting passage to discharge the air in the air accumulation space into the outlet passage. When the air accumulation space becomes smaller and its lower end surface position moves upward to float the float valve, the float valve closes the air venting passage to hold the air in the air accumulation space.

[0009] In the above fluid filtration device, preferably, the filter element includes a cylindrical inner support member, a filter medium wound around the outer periphery of the inner support member in a bellows-like bent state, an upper end plate member attached to cover the upper end of the filter medium at the upper end of the inner support member, and a lower end plate member attached to cover the lower end of the filter medium at the lower end of the inner support member. The lower end plate member is attached to the housing so as to vertically partition the internal space. The inlet passage communicates with a lower space (e.g., the first internal space 21 in the embodiment) below the lower end plate in the internal space. A lower communication hole (e.g., the opening 32b of the lower end plate 32 in the embodiment) is formed in the end plate to communicate the lower space with an inner support space (e.g., the second internal space 22 in the embodiment) of the inner support member surrounded by the filter medium. The primary fluid space is formed by the lower space and the inner support space.

[0010] In the above fluid filtration device, preferably, an upper communication hole (e.g., the opening 31b of the upper end plate 31 in the embodiment) is formed in the upper end plate. An outlet space forming member that forms a recessed space (e.g., the fifth internal space 25 in the embodiment) extending downward in communication with the upper communication hole is provided on the inner support member. The recessed space communicates with the secondary fluid space through the upper communication hole. A passage forming member (e.g., the suction pipe 16 in the embodiment) that forms the outlet passage protrudes downward from above into the recessed space of the outlet space forming member and has a lower end opening into the recessed space. It is configured to allow the fluid in the secondary fluid space to flow into and be discharged from the lower part of the recessed space to the outlet passage.

Advantages of the Invention

[0011] According to the fluid filtration device of the present invention, in a fluid filtration device configured to filter the fluid introduced from the inlet passage into the primary fluid space by passing it through the filter medium of the filter element and causing it to flow into the secondary fluid space, and then discharging it through the outlet passage, an air storage space closed at the upper part of the secondary fluid space is provided, and air generated by bubbles or the like in the filtered fluid is stored in the air storage space. The outlet passage opens into the secondary fluid space below the air storage space, and an air venting device is provided to connect the secondary fluid space and the outlet passage in a cut-off manner. The air venting device is configured to discharge the air in the air storage space to the outlet passage to set the formation region of the air storage space. Therefore, air is constantly stored in the air storage space. Even if the fluid in the internal space freezes at a low temperature and volume expansion occurs, the air in the air storage space can be compressed to absorb this volume expansion, preventing an increase in internal pressure and preventing damage to the fluid filtration device. Since the outlet passage opens into the secondary fluid space below the air storage space, there is no risk of sucking in the air in the air storage space through the outlet passage. A venting device is provided to connect the secondary fluid space and the outlet passage in a cut-off manner. The venting device is configured to discharge the air in the air storage space to the outlet passage to set the formation region of the air storage space. For this reason, air is constantly stored in the air storage space. Even if the fluid in the internal space freezes at a low temperature and volume expansion occurs, the air in the air storage space can be compressed to absorb this volume expansion, preventing an increase in internal pressure and preventing damage to the fluid filtration device. Since the outlet passage opens into the secondary fluid space below the air storage space, there is no risk of sucking in the air in the air storage space through the outlet passage.

[0012] In the fluid filtration device according to the present invention, when the air storage space becomes large and the position of its lower end surface moves downward to move the float valve downward, the float valve opens the air venting passage to discharge the air in the air storage space into the outlet passage. When the air storage space becomes small and the position of its lower end surface moves upward to float the float valve, it is preferable that the float valve closes the air venting passage to hold air in the air storage space. Thereby, the region of the air storage space, that is, the boundary position with the filtered fluid can be set at an appropriate position.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the schematic configuration of a urea SCR system to which the urea aqueous solution filtration device 10 as a fluid filtration device according to the present invention is applied will be described with reference to FIG. 1. This system supplies a urea aqueous solution to a urea SCR catalyst device 3 provided in an exhaust passage 2a connected to an exhaust pipe 2 of a diesel engine 1 to purify nitrogen oxides in the exhaust gas. The purified exhaust gas is released into the atmosphere from an exhaust pipe 2b. The urea SCR system includes a urea aqueous solution storage tank 5 for storing a urea aqueous solution, and a urea aqueous solution injection device 6 that sucks the urea aqueous solution from the urea aqueous solution storage tank 5 via introduction pipes 7 and 8 and injects the urea aqueous solution into the urea SCR catalyst device 3 via an injection supply pipe 9. At this time, a urea aqueous solution filtration device 10 is provided between the introduction pipes 7 and 8 in order to purify dust and dirt in the urea aqueous solution.

[0015] As shown in FIGS. 2 and 3, the urea aqueous solution filtration device 10 is configured by detachably disposing a filter element 30 in an internal space 20 surrounded by a lower housing 11 and an upper housing 15. The lower housing 11 is connected to the introduction pipe 7 through an inlet portion 11a, and introduces the urea aqueous solution stored in the urea tank 5 into the internal space 20 through the introduction path 7a of the introduction pipe 7. As can be understood from this, the internal passage of the inlet portion 11a corresponds to the inlet passage defined in the claims. The upper housing is connected to the introduction pipe 8 through an outlet portion 15a, and sends out the filtered urea aqueous solution to the introduction path 8a of the introduction pipe 8. The lower housing 11 and the upper housing 15 are hermetically held in the internal space 20 by fitting the lower housing flange portion 11b and the upper housing flange portion 15b with a seal ring 12. The lower housing 11 is provided with attachment flange portions 13, 13 on the left and right, and the urea aqueous solution filtration device 10 can be fixed at a predetermined attachment position. The lower housing 11 is provided with attachment flange portions 13, 13 on the left and right, and the urea aqueous solution filtration device 10 can be fixed at a predetermined attachment position.

[0016] As shown in FIG. 4, the filter element 30 includes a disk-shaped upper end plate 31, a disk-shaped lower end plate 32, a substantially 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 peripheral side of the inner support member 35 in a bellows-like bent state. In a state where the filter element 30 is 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 through a locking projection 31a provided on its upper surface. In this way, the filter element 30 is attached in the internal space 20. In this state, the lower end plate 32 fits on the inner periphery of the lower housing 11 and is sealed by a seal 32a, forming a first internal space 21 as a part of the internal space 20. The first internal space 21 is connected to the introduction pipe 7 through the inlet portion 11a, and the urea aqueous solution is introduced into the first internal space 21 through the introduction path 7a of the introduction pipe 7. A heater 50 is provided in the lower side portion of the first internal space 21, which will be described later.

[0017] As shown in FIG. 7, the inner support member 35 has a substantially cylindrical support frame 36 and a wedge-shaped recess space forming portion 38 formed by partitioning a part of the support frame into a wedge shape. The support frame 36 has ring-shaped support frames 36a, 36a located at the upper and lower ends, a plurality of ring-shaped intermediate frames 36b located in the middle, and a plurality of vertical frames 36c extending vertically to connect the upper and lower support frames 36a, 36a and the plurality of intermediate frames 36b, and is formed in a cylindrical frame shape. Inside the support frame 36, a cylindrical outlet space forming member 37 connected via a support flange 37a extends along the inner circumference of the upper support frame 36a. The outlet space forming member 37 is a cylindrical hollow container-shaped member that opens upward, and is connected to the central opening of the support flange 37a and has an open upper end. The wedge-shaped recess forming portion 38 has a bottom wall 38c extending vertically and connected to the outer peripheral surface of the outlet space forming member 37, and left and right walls 38a, 38b that extend vertically while expanding radially outward from the bottom wall 38c. A wedge-shaped recess space 38d surrounded by the left and right walls 38a, 38b and the bottom wall 38c and open to the outer peripheral side is formed. As shown in FIGS. 2 and 4, communication small holes 39 are 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 through the communication small holes 39.

[0018] Around the outer periphery of the substantially cylindrical support frame 36 of the inner support member 35, the filter medium 33 bent in a bellows shape is wound and attached as shown in FIG. 5 (and FIG. 6 showing the shape as viewed from the bottom surface). At this time, one end side bent surface 33a of the filter medium 33 is welded and joined to the outer wall surface of the right wall 38a, and the other end side bent surface 33b is welded and joined to the outer wall surface of the left wall 38b. This welding and joining is performed using an ultrasonic welding tool 60 (comprising a welding horn 61 and an ultrasonic welding receiving jig 62) as shown in FIG. 8. For example, as shown in FIG. 8, the ultrasonic welding receiving jig 62 is applied to the inner surface of the right wall 38a, the end bent surface 33a of the filter medium 33 is applied to the outer surface of the right wall 38a, and the welding horn 61 is pressed, and the right wall 38a and the end bent surface 33a of the filter medium 33 are clamped by the ultrasonic welding receiving jig 62 and the welding horn 61. In this state, ultrasonic waves are applied from the welding horn 61 to thermally weld the end bent surface 33a of the filter medium 33 to the outer surface of the right wall 38a. The right wall 38a (inner support member 35) is made of resin and is thermally welded to the resin fibers forming the filter medium 33. This welding is performed in the same manner for the left wall 38b and the other end of the filter medium 33. As a result, as shown in FIGS. 5 and 6, the filter medium 33 bent in a bellows shape is wound and attached around the outer periphery of the substantially cylindrical support frame 36 of the inner support member 35. Note that, instead of thermal welding, joining by other methods such as adhesion may be performed.

[0019] In this way, the filter medium 33 is wound around the outer periphery of the support frame 36 of the inner support member 35 to obtain the state shown in FIG. 5 and FIG. 6. After that, the upper end plate 31 is attached to cover the upper ends of the inner support member 35 and the filter medium 33, and the lower end plate is attached to cover the lower ends. Thereby, the filter element 30 shown in FIG. 4 is produced. An opening 31b is formed in the upper end plate 31, and through this opening 31b, the internal space of the outlet space forming member 37 of the inner support member 35 communicates with the outside. An opening 32b is also formed in the lower end plate 32, and through this opening 32b, the first internal space 21 communicates with the inside of the inner support member 35. Note that this filter element 30 is mounted in the internal spaces 20 of the lower and upper housings 11 and 15 as described above.

[0020] Returning to FIG. 2, the description will be continued. A heater 50 is mounted at the lower part of the internal space of the lower housing 11. The heater 50 has an upper cover 51 fitted and attached to the inner peripheral surface of the lower housing 11, and a disposition space 55 in a liquid-tight state is formed by seals 52a and 52b. An engine coolant inlet 53 and an outlet 54 are provided leading to the disposition space 55. Engine coolant is introduced into the internal space 55 from the coolant inlet 53 and discharged from the internal space 55 through the coolant outlet 54. Thereby, the heat of the engine coolant is transmitted to the aqueous urea solution in the first internal space 21 through the upper cover 51, warming the aqueous urea solution to be filtered in a low-temperature environment. Note that the seal 52a is for maintaining the liquid tightness between the internal space 20 and the outside, and the seal 52b is for maintaining the liquid tightness between the internal space of the heater 50 and the outside. Therefore, even if there is a problem with either seal, the aqueous urea solution and the engine coolant will not mix.

[0021] On the other hand, an air venting device 40 is provided inside the upper housing. The air venting device 40 includes an air vent hole 41 formed by a small hole connecting the internal space 20 and the internal passage of the outlet portion 15a, and a float 42. The float 42 has a specific gravity that causes it to float in the aqueous urea solution. When the internal space 20 is filled with the aqueous urea solution and the float floats, the air vent hole 41 is blocked. When bubbles (air) mixed in the aqueous urea solution accumulate in the upper part of the internal space 20, an air layer space 24a is formed. When the water surface 24c (indicated by a two-dot chain line in FIG. 2) of the aqueous urea solution below the air layer space 24a rises above the position where the float 42 floats, the float 42 blocks the air vent hole 41, so that the bubbles (air) mixed in the aqueous urea solution accumulate in the upper part of the internal space 20. Thereby, the air layer space 24a becomes larger. When the water surface 24c of the aqueous urea 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 portion 15a. In this way, the air venting device 40 forms an air layer space 24a in the internal space 20, sets the position of the water surface 24c of the aqueous urea solution at a predetermined position, and maintains the size of the air layer space 24a at a predetermined size.

[0022] Inside the upper interior of the upper housing 15, a suction pipe 16 that is connected to the internal passage of the outlet portion 15a and protrudes downward is attached. As shown in FIG. 2, this suction pipe 16 protrudes into the internal space of the outlet space forming member 37 of the inner support member 35 through the opening 31b of the upper end plate 31 of the filter element 30 mounted in the internal space 20. The internal passage of the outlet portion 15a and the internal passage of the suction pipe 16 correspond to the outlet passage in the claims.

[0023] In the urea aqueous solution filtration device 10 shown in FIG. 2 configured as described above, since the internal space 20 is partitioned into a plurality of internal spaces by the filter element 30, this will be described. First, as described above, a first internal space 21 is formed below the lower end plate 32, and the urea aqueous solution is sent into this space from the introduction pipe 7. An opening 32b is formed in the lower end plate 32, and the first internal space 21 is connected to an internal space (referred to as a second internal space 22) surrounded by the filter medium 33 attached to the outer periphery of the inner support member 35, and the urea aqueous solution is directly sent into the second internal space 22. These first and second internal spaces 21 and 22 correspond to the primary fluid space in the claims. Note that the outlet space forming member 37 protrudes into the space within the support frame 3 6 of the inner support member 35, but this internal space is blocked from the second internal space 22. Similarly, the wedge-shaped recess space 38d of the wedge-shaped recess space forming portion 38 is also blocked from the second internal space 22.

[0024] In the space on the outer peripheral side of the filter medium 33 of the filter element 30 (referred to as the third internal space 23), the urea aqueous solution filtered by passing through the filter medium 33 flows in. The third internal space 23 is a space located on the outer periphery of the filter element 30, and the wedge-shaped recess space 38d of the wedge-shaped recess space forming portion 38 communicates with the third internal space 23 and forms a part of the third internal space 23. This third internal space 23 communicates with the internal space of the upper housing 15 (referred to as the fourth internal space 24). Since the air layer space 24a is formed in the fourth internal space 24 as described above, the fourth internal space 24 is divided into an air layer space 24a and a urea aqueous solution filling space 24b, and the boundary surface 24c thereof becomes the water surface of the urea aqueous solution.

[0025] 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 upward into the fifth internal space 25, and the fifth internal space 25 communicates with the internal passage space of the suction pipe 16 (referred to as the sixth internal space 26). The sixth internal space 26 is connected to the internal passage of the outlet portion 15a (referred to as the seventh internal space 27). As can be understood from this, the third to fifth internal spaces 23 to 25 correspond to the secondary fluid space defined in the claims, and the sixth and seventh internal spaces correspond to the outlet passage.

[0026] The filtration of the aqueous urea solution by the aqueous urea solution filtration device 10 configured as described above will be explained. The aqueous urea solution (which is in the state before filtration and is thus referred to as the primary aqueous urea solution) sucked from the aqueous urea solution storage tank 5 by the aqueous urea solution injection device 6 flows into the first internal space 21 from the introduction pipe 7 through the inlet portion 11a. The primary aqueous urea solution further flows from the first internal space 21 into the second internal space 22 through the opening 32b, passes through the filter medium 33 and is filtered, and then flows into the third internal space 23. The aqueous urea solution thus filtered is referred to as the secondary aqueous urea solution. The secondary aqueous 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 space located at the uppermost position, and an air layer is formed at the upper part, for example, by the bubbles (air) contained in the aqueous urea solution gathering. The size of this air layer is adjusted by the air venting device 40 as described above, and the boundary surface 24c shown by the two-dot chain line in Fig. 2 is set.

[0027] The secondary aqueous urea solution in the fourth internal space 24 flows into the fifth internal space 25, which is the internal space of the outlet space forming member 37 of the inner support member 35 through the opening 31b of the upper end plate 31. Then, it passes through the sixth internal space 26, which is the internal passage space of the suction pipe 16, and through the 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, since the suction pipe 16 protrudes downward from above in the fifth space 25 and the lower end opening is located at the lower part of the fifth space 25, it is configured not to suck the air in the air layer space 24a.

[0028] The urea SCR system equipped with the urea aqueous solution filtration device 10 configured as described above is mounted on a vehicle or the like in which a diesel engine is used, and this vehicle may be used in a cold region. When used in a cold region, there is a problem that the urea aqueous solution freezes, but the urea aqueous solution filtration device 10 takes measures against freezing. That is, an air layer space 24a is formed in the fourth internal space 24, and even if the urea aqueous solution in the internal space 20 freezes and volume expansion occurs, the air in the air layer space 24a is compressed and shrunk to prevent an increase in internal pressure. Thereby, damage to internal members can be efficiently prevented.

[0029] In the air bleeding device 40, the air in the air layer space 24a of the fourth internal space 24 flows out to the seventh internal space 27 through the air bleeding hole 41. At this time, some of the urea aqueous solution in the fourth internal space 24 also flows out. However, since there is a filtered and purified secondary urea aqueous solution in the fourth internal space 24, this outflow does not cause any problems.

[0030] In the urea SCR system described with reference to FIG. 1, as a measure to prevent freezing of the aqueous urea solution at low temperatures, when the engine stops, the aqueous urea solution is made to flow backward by the aqueous urea solution injector 6, and the aqueous urea solution inside the system is recovered into the aqueous urea solution storage tank 5. At this time, since the fifth internal space 25 is the internal space of the outlet space forming member 37 and is a container-shaped space with an open upper end, there is a possibility that the aqueous urea solution may remain in the lower part of the fifth internal space 25. Therefore, as described above, communication small holes 39 are 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 with each other through the communication small holes 39. Thereby, the aqueous urea solution inside the fifth internal space 25 flows out through the communication small holes 39 into the wedge-shaped recessed space 38d, thus solving the problem that the aqueous urea solution remains in the lower part of the fifth internal space 25. Note that the size of the communication small holes 39 is suppressed to the minimum size necessary for allowing the aqueous urea solution remaining inside the fifth internal space 25 to flow out into the wedge-shaped recessed space 38d, and during the use of the urea SCR system, the amount of the secondary aqueous urea solution directly flowing from the wedge-shaped recessed space 38d through the communication small holes 39 into the fifth internal space 25 is suppressed. Thereby, the flow is ensured such that after the filtered secondary aqueous urea solution flows from the third internal space 23 to the upper fourth internal space 24, it then flows into the fifth internal space.

[0031] As described above, an example of the aqueous urea solution filtration device 10 as an embodiment to which the present invention is applied has been described. However, the fluid filtration device according to the present invention is not limited thereto. For example, the fluid to be filtered is not limited to the aqueous urea solution, and the present invention is applicable to filtration devices for various fluids containing water, particularly fluids that have a problem of freezing at low temperatures. Further, the wedge-shaped recess forming member 38 provided on the inner support member of the filter element is not limited to such a shape, and may have various shapes that form a wedge-shaped recessed space expanding in a sector shape in cross section. For example, it may be one that forms a semi-cylindrical recessed space.

Explanation of Reference Numerals

[0032] 10 Aqueous urea solution filtration device 11 Lower housing Inner space of the upper housing 20 21 to 27 First to seventh inner spaces, filter element 30 Upper end plate 31, lower end plate 32 Filter medium 33, inner support member 35 Support frame 36, outlet space forming member 37 Wedgelike recess forming member 38, air venting device 40 Air venting hole 41, float 42 Heater 50, upper cover 51 Ultrasonic welding tool 60

Claims

1. A fluid filtration device comprising a housing having an internal space with an inlet passage and an outlet passage for the filtered fluid, and a filter element disposed within the internal space, The filter element is disposed within the internal space of the housing such that the internal space is partitioned into a primary fluid space connected to the inlet passage and a secondary fluid space connected to the outlet passage, The fluid introduced from the inlet passage into the primary fluid space is filtered by passing through the filter medium of the filter element and then flows into the secondary fluid space and is discharged through the outlet passage. An air reservoir space closed at the upper part of the secondary fluid space is provided to store air generated by bubbles or the like from the filtered fluid within the air reservoir space. The outlet passage opens into the secondary fluid space below the air reservoir space. An air bleeding device is provided to connect the secondary fluid space and the outlet passage in a cut-off manner. The air bleeding device is configured to discharge the air within the air reservoir space to the outlet passage to set the formation region of the air reservoir space. The air bleeding device includes an air bleeding passage connecting the secondary fluid space and the outlet passage, and a float valve disposed movably up and down within the air bleeding passage. When the air reservoir space becomes larger and its lower end face position moves downward to move the float valve downward, the float valve opens the air bleeding passage to discharge the air within the air reservoir space into the outlet passage. When the air reservoir space becomes smaller and its lower end face position moves upward to float the float valve, the float valve closes the air bleeding passage to hold the air within the air reservoir space.

2. The filter element includes a cylindrical inner support member, a filter medium wound around the outer periphery of the inner support member in a bellows-like bent state, an upper end plate member attached to cover the upper end of the filter medium at the upper end of the inner support member, and a lower end plate member attached to cover the lower end of the filter medium at the lower end of the inner support member. The lower end plate member is attached to the housing so as to partition the internal space vertically. The inlet passage communicates with the lower space below the lower end plate in the internal space. The end plate is formed with a lower communication hole that communicates the lower space with the inner support space of the inner support member surrounded by the filter medium, and the primary fluid space is formed by the lower space and the inner support space. The fluid filtration device according to claim 1, characterized in that.

3. An upper communication hole is formed in the upper end plate, and an outlet space forming member that forms a recessed space communicating with the upper communication hole and extending downward is provided in the inner support member. The recessed space communicates with the secondary fluid space through the upper communication hole. The passage forming member that forms the outlet passage protrudes from above downward into the recessed space of the outlet space forming member, and the lower end thereof opens into the recessed space. The fluid filtration device according to claim 2, characterized in that it is configured to allow the fluid in the secondary fluid space to flow into and be discharged from the recessed space to the outlet passage.

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