JP2019005714A - Filter unit for air cleaner - Google Patents

Abstract

To provide a filter unit of an air cleaner of which attachment/detachment operation for replacement is easy, and on which a commercially available filter member can be mounted easily.SOLUTION: A filter unit 1 includes: an approximately flange shaped outer frame 11 which is air-tightly mounted on a wall surface of an intake port of an air cleaner, and of which a front surface shape is an approximately rectangular annular shape; an inner frame 12 which is vertical to a rear surface of the outer frame 11, is extended to a rear side of a back surface, and has an approximately square cylindrical shape longer than at least a filter member 13, the filter member 13 of which a total length is housed and held inside the inner frame 12, and a filter pressing member 16 which supports the filter member 13 held by the inner frame 12 at a rear end part of the inner frame 12.SELECTED DRAWING: Figure 3

Description

  The present invention is installed for the purpose of isolation of pharmaceuticals and cosmetics manufacturing factories and research facilities clean rooms, or biohazard countermeasures and radioactive substance countermeasures that handle substances that are harmful or harmful to the human body and the environment. A device equipped with an air filter that cleans and recirculates the air in the space used in spaces such as hazard prevention rooms, hazard prevention cabinets, draft chambers, etc. The present invention relates to a filter unit that is replaceably attached to an air purifier.

BACKGROUND ART An air cleaning device has been conventionally used in various industrial fields as a device for cleaning air in equipment such as a hazard countermeasure room and a draft chamber.
As an example of a known air cleaning device, a casing made of a vertically long wall structure, a suction port formed in the lower portion of the front wall of the casing, an exhaust port formed in the top wall of the casing, A unitized HEPA filter (High Efficiency Particulate Air Filter, hereinafter referred to as a filter unit), which is an intermediate part in the height direction of the casing above the intake port and is detachably installed on the gantry in a posture crossing the inside of the housing. And a filter exchange port with a lid provided on the front wall of the housing above the filter unit. There is also an air cleaning device using a unitized ULPA filter (Ultra Low Penetration Air Filter, hereinafter referred to as included in the filter unit) instead of the filter unit.

  In the conventional air cleaning device, an air inlet is formed in the lower part of the front wall, and a frame for horizontally supporting the filter unit is provided above the air inlet in the housing, and the filter unit is mounted on the frame. The following problems have been pointed out due to the horizontal installation.

  Since the filter unit is disposed inside the housing in a horizontal posture, the housing needs to have a depth amount that can accommodate at least the front-rear width of the filter unit in the horizontal posture. That is, a filter unit having an air filtration surface of a required area has a front-rear width (depth amount) corresponding to the filtration area in a horizontal posture, and therefore the front-rear width (depth amount) of the housing must be increased. This is a factor that the equipment space of the exhaust unit including the air cleaning device for the entire hazard countermeasure room must be enlarged, particularly in the depth direction of the apparatus, and the space in the hazard countermeasure room is reduced. is there.

  Further, in the conventional air cleaning device, since the air inlet is installed at the lower part of the front wall of the housing, the air filtration surface (primary side) of the filter unit installed horizontally from the air inlet to the housing. The inside of the casing up to becomes a contaminated area in the air cleaning device. When the filter unit is replaced, in order to prevent scattering of harmful substances adhering to the contaminated area including the air filtration surface (primary side) of the filter unit, the contaminated area is removed with water or chemicals prior to replacing the filter unit. However, since the portion to be cleaned is inside the housing downstream from the intake port, it is difficult to visually check the cleaning status, and the housing includes the air filtration surface of the filter unit from the intake port. There is a problem that it is difficult to perform the cleaning work together with the fact that the inside is difficult to visually check.

Furthermore, in the conventional air cleaning device, the filter unit is installed in a horizontal posture inside the housing. Therefore, for replacement or inspection of the filter unit, a filter replacement port with a lid is connected to the filter unit. It is indispensable to be provided on the front wall of the casing above the installation height.

  The inventors of the present invention have proposed a novel air cleaning device that has solved the above problems in the conventional air cleaning device by patent application. That is, the proposed air purifying device has a wall structure housing as a main body of the air purifying device, an air inlet formed in the front wall of the housing, and the air inlet is closed on the front surface of the air inlet. The filter unit includes a filter unit that is detachably mounted in a vertically-facing front posture, and an exhaust port that is connected to an external blower provided on the top wall of the housing via a duct.

  In the proposed air purifying apparatus, if the vertical and horizontal sizes of the front wall of the housing are formed so that the filter unit fits in a vertically-facing front shape (upright posture), There is an advantage that the front-rear width can be formed to a depth amount (front-rear width) smaller than the vertical width (vertical width) of the upright filter unit.

  As described above, the proposed air purifying apparatus has a casing as a main body, an intake port provided on the front surface (wall) of the casing, and a vertical front posture so as to block the intake port on the front surface of the intake port. Since the filter unit is detachably arranged and the exhaust port connected to the external blower provided on the upper surface (wall) of the housing through a duct is formed, the front-rear width (depth amount) of the housing is reduced. It was possible to obtain an effect that the size of the installation space of the exhaust equipment in the hazard countermeasure room can be suppressed in the depth direction of the casing.

  In addition, since the filter unit is detachably provided in the vertical position on the front surface of the housing, the interior of the housing does not become a contaminated area, and cleaning such as washing with water inside the housing is unnecessary, and the filter unit is mounted on the front wall of the housing. Because it is placed in an upright vertical position, all operations such as filter unit maintenance, filter unit replacement, and water washing when necessary can be performed in the external area of the housing, improving work accuracy and working efficiency. There is also an effect.

Here, the filter unit used in the proposed air purifying apparatus needs to be able to be installed airtightly from the front surface of the intake port in an upright posture on the intake port provided on the front wall of the housing, and In exchanging the filter unit, it is necessary that the filter unit can be easily attached and detached.
Incidentally, in the conventional air cleaning devices described in the following Patent Documents 1 to 3, since the filter unit is provided in a horizontal posture on the filter mount provided in the inside of the casing, There is no mention of mounting the filter unit in an upright position in an airtight manner in an air intake port and mounting it easily.
Patent Document 4 describes an example in which the filter unit is installed in the vertical direction (upright posture), but this filter unit is not particularly touched on means for facilitating mounting of the filter member to the filter unit. It was. .

Japanese Patent Laid-Open No. 2006-10793 Japanese Patent Application Laid-Open No. 2006-10895 Japanese Patent No. 4627310 Japanese Patent No. 5554553

  Accordingly, the present invention provides an air filter that recirculates air that has been purified by filtering air in a room or space such as a hazard prevention room or a hazard prevention cabinet through a filter unit, or exhausts the air outside. The filter unit in the air cleaning device, that is, the filter unit in the air cleaning device can be mounted airtight in an upright posture on the air inlet formed in the air cleaning device, and the attachment / detachment operation for replacing the filter unit is easy. It is an object of the present invention to provide a filter unit formed so that a commercially available filter member can be easily attached.

The first configuration of the filter unit of the present invention made for the purpose of solving the above problems is as follows.
A filter unit that is detachably attached to the wall surface of the air inlet of the air purifier, and has a substantially flange-shaped outer frame in which the front surface that is airtightly attached to the wall surface of the air inlet of the air cleaner has a substantially rectangular ring shape. An inner frame that is perpendicular to the rear surface of the outer frame and extends rearwardly at the rear and has a substantially rectangular tube shape that is at least longer than the filter member, a filter member that is housed and held in its entirety inside the inner frame, And a filter pressing member that supports the filter member held by the frame at the rear end of the inner frame.

  In the filter unit, the substantially flange-shaped outer frame has a substantially inverted L-shaped side sectional shape and a substantially rectangular annular shape on the front surface, and the substantially rectangular tube-shaped inner frame is on the back surface of the vertical side of the outer frame. The front end portion of the substantially L-shaped side section is airtightly joined, and the rear end side is formed in a substantially rectangular tube shape extending rearward and rearward of the outer frame, and the substantially entire length of the filter member is stored inside the inner frame, The filter member housed in the inner frame is supported by a filter pressing member at the rear end portion of the inner frame, and passes through the packing and an airtight packing disposed over the entire back surface of the substantially inverted L-shaped portion of the outer frame. A plurality of holes for screw rods and screw rods screwed into the inlet side from the screw holes are attached airtightly to the wall surface of the inlet port on the back surface of the outer frame.

  In the present invention, the second configuration of the filter unit of the present invention that can solve the above-mentioned problems is that the outer frame having a substantially flange-like shape in which the side cross-sectional shape is a substantially inverted L shape and the front shape is a substantially rectangular ring shape, and the perpendicular to the outer frame. A front end portion having a substantially L-shaped side cross section is airtightly joined to the rear surface of the side, and a rear end side is extended to the rear rear side of the outer frame. A filter member that is partially retained in the longitudinal direction inside the inner frame, a support member for the filter frame that couples the filter frame to the inner frame, and an abbreviation for the outer frame. An air-tight packing disposed in the entire back surface of the inverted L-shaped portion, a plurality of screw rod holes provided through the packing, and a screw rod screwed through the holes, the wall surface of the intake port on the back surface of the outer frame Mounted airtight to And wherein the door.

  The filter unit of the present invention having the first configuration and the second configuration is provided in the filter unit mounting portion having a bottomed screw hole corresponding to the screw hole provided to protrude from the wall surface of the intake port. Fit in the packing of the outer frame, screw the screw rods into the screw holes from the holes for the screw rods, respectively, and tighten the screw rods to be airtightly attached to the intake port to loosen the screw rods. Therefore, it can be removed from the intake port, and can be attached and detached quickly and easily.

  When the filter unit is removed from the wall surface of the intake port after use, the screw rod is loosened after fitting a sealing plate on the inner peripheral side edge of the outer frame in order to prevent scattering of contaminants. In this way, it is possible to prevent scattering of contaminants from the used filter unit when replacing the filter unit. Before fitting the sealing plate, water or glue may be applied to the filtration surface.

  The filter unit is formed by an outer frame and an inner frame, but there are some formed in a substantially square shape and a substantially rectangular shape in front view. It is preferable that the holes for attaching the screw rods of the outer frame are provided at equal pitches on each side on the outer periphery. In this way, the square filter unit has no direction in all directions when attached to the intake port, and the rectangular filter unit has no direction in the vertical or horizontal direction, so that the mounting work becomes easy.

  When the substantially rectangular tube-shaped portion of the inner frame is formed to a length that can cover the entire outer surface of the filter member housed therein, the entire side surface of the filter member accommodated in the inner frame Since it is covered by the inner frame, the side surface of the filter member is hardly damaged when the filter unit is transported, stored, or mounted. The rear end portion of the filter member housed in the inner frame is supported at the rear end portion of the inner frame by a presser frame that has a substantially L-shaped side cross section and closely fits into the substantially rectangular tube-shaped portion of the inner frame.

  Although the said filter member made from multiple manufacturers is marketed, there exists a subtle difference in a form (size, shape), and the cover aspect of a filter member also differs. For filter members of the commercially available type where the entire side surface is covered with a filter frame such as a metal material, the front-rear length of the inner frame is the total length of the filter member side surface (the entire front-rear length). The thing of the length which does not cover may be sufficient.

  The filter unit mounting portion formed along the outer periphery of the suction port is formed in a frame portion that protrudes in a substantially convex shape from the front side of the wall (standing wall) provided with the suction port, and is formed on the front surface of the frame portion. A bottomed screw hole is provided. This is because the screw hole with the bottom does not allow the screw hole to pass through the inside of the wall, and if the screw hole penetrates inside, a hermetic seal is required at that portion, so that this is avoided.

The present invention is a filter unit that is detachably attached to a wall surface of an air inlet of an air cleaning device, and a front flange that is airtightly attached to the wall surface of the air inlet of the air cleaning device has a substantially rectangular annular shape. Outer frame, an inner frame that is perpendicular to the rear surface of the outer frame and extends rearwardly and has a substantially rectangular tube shape that is at least longer than the filter member, and a filter member in which the entire length is stored and held inside the inner frame And a filter pressing member that supports the filter member held by the inner frame at the rear end of the inner frame, and is formed in the filter unit, so that the filter member is inserted into the inner frame and the rear end Is supported by the filter holding member, so that the filter member can be easily attached to the filter unit, and the filter member, particularly the filter medium, is protected by the inner frame, and thus is damaged. No kicking risk.
In particular, after a substantially flange-shaped outer frame having a substantially inverted L-shaped side cross-sectional shape and a substantially rectangular annular shape on the front surface, and a front end portion having a substantially L-shaped side cross-section joined to the back surface of the vertical side of the outer frame. An inner frame having a substantially rectangular tube shape whose end side extends to the rear rear side of the outer frame, a filter member that holds the substantially entire length inside the inner frame, and a filter member that is held by the inner frame A filter pressing member supported at the rear end of the outer frame, an airtight packing disposed over the entire back surface of the substantially inverted L-shaped portion of the outer frame, and a plurality of screw rods provided through the packing on the entire circumference of the outer frame. Since the filter unit is formed in the filter unit with the holes for mounting, the filter unit is mounted on the air cleaning device for the screw rod provided so as to protrude along the outer periphery of the intake port formed in the standing wall of the device. In front of the filter unit mounting part that has a screw hole corresponding to the hole, In the packing, the filter unit is fitted, and screw holes are screwed into the screw holes from the holes for the screw holes, and each screw hole is tightened to be tightly attached to the intake port. Since the filter unit loosened and airtightly attached to the air inlet is removed from the air inlet, the filter unit can be attached and detached easily and simply.

The front view of an example of this invention filter unit. The enlarged right view of the filter unit of FIG. The center longitudinal cross-section expansion right side view of the filter unit of FIG. The enlarged plan view of the filter unit of FIG. Part A enlarged view of FIG. The front view of another example of this invention filter unit. FIG. 4 is an enlarged right side view of the filter unit of FIG. 3. The enlarged plan view of the filter unit of FIG. The B section expanded sectional view of FIG. The C section expanded sectional view of FIG. The perspective view of an example of the air purification apparatus which mounted | wore the filter unit of this invention of FIGS. FIG. 12 is a right side end view of the center longitudinal section of FIG. 11. The A section enlarged view of FIG.

Next, embodiments of the filter unit of the present invention will be described with reference to the drawings.
In the filter unit 1 illustrated in FIGS. 1 to 5, 11 has a bent edge portion 11 a having a substantially inverted L-shaped side section whose outer peripheral edge portion is bent substantially 90 degrees horizontally toward the rear, as viewed from the front. A rectangular flange-shaped outer frame 12 is a short substantially rectangular tube-shaped inner frame arranged so as to extend from the back surface of the vertical inner periphery 11 b of the outer frame 11 toward the back surface of the outer frame 1. The front end side of the inner frame 12 is provided with a vertical joining surface 12a that rises in a substantially L-shaped side section so as to be joined to the back surface of the inner periphery 11b.

  As an example, a filter member 13 made of a HEPA filter is loaded in the inner frame 12 having a substantially rectangular short cylindrical shape when viewed from the front. The filter member 13 has a configuration in which a filter medium 13b mainly composed of a glass fiber material or the like is accommodated in a cylindrical filter frame 13a having a size that can be accommodated in the square cylindrical inner frame 12. It is. The filter member 13 is inserted into the inner frame 12 from the rear end side of the rectangular tubular inner frame 12, and the front end of the filter member 13 contacts the back surface of the inner peripheral edge 11 b of the outer frame 11. It is pushed in until it touches.

  In the filter unit 1, an airtight packing 14 made of an elastic resin foam or the like is provided on the back surface of the substantially inverted L-shaped section formed by the outer frame 11 and the bent edge portion 11 a. On the entire circumference of the outer frame 11, screw mounting holes 15 (also referred to as screw holes 15) that penetrate the packing 14 are provided at a substantially equal pitch.

  The filter member 13 held on the outer frame 11 and the inner frame 12 as described above has a substantially L-shaped side section loaded on the inner surface of the rear end of the inner frame 12 and a ring-shaped presser member 16. Pressed and supported. The holding member 16 having a substantially L-shaped side cross section has a portion parallel to the inner frame 12 fixed to the inner frame 12 by a stopper 16a such as a screw, so that the entire filter member 13 is stored inside the inner frame 12. Hold in a state (see FIGS. 3 and 5). Although the filter member 13 has a slightly different form depending on the manufacturer, the inner frame 12 is formed so as to be able to accommodate all the filter members 13 having a subtle form difference due to the manufacturer.

  As described above, the filter member 13 is held by the inner frame 12 by the ring-shaped pressing member 16 in a state of being accommodated by the outer frame 11 and the inner frame 12, and the air illustrated in FIGS. Since this is detachably attached to the air inlet 3 formed in the front wall 20 of the housing 2 that forms the main body of the cleaning device AC, this point will be described below with reference to FIGS.

In FIG. 11 to FIG. 13, the inner frame 12 of the filter unit 1 can be inserted with a margin in the substantially central region of the front wall 20 that is the standing wall of the housing 2 of the air cleaning device AC, but the outer frame 11 is inserted. An intake port 3 having a diameter (size) that cannot be formed is formed.

The casing 2 has a front wall 20, a rear wall 21, left and right side walls 22, 23, and upper and lower walls 24, 25 made of a metal plate such as a stainless steel plate as an example. It is formed in a box shape with a small front-rear width (depth amount). Reference numeral 26 denotes a base disposed in the lower part of the housing 2.
An exhaust port 4 is formed in the upper surface wall 24 of the housing 2, a differential pressure gauge box 5 to be described later is disposed on the front surface of the exhaust port 4 of the upper surface wall 24, and a filter unit on the front wall 20. Above 1, a filter measurement nozzle Fn for detecting the substance to be filtered that has passed through the filter unit 1 is provided.
The filter unit 1 of the present invention described above with reference to FIGS. 1 to 5 is detachably and airtightly attached to the intake port 3 and will be described below.

  On the outer periphery of the air inlet 3, a substantially cross-sectional substantially L-shaped packing 14 provided at the bent edge portion 11 a of the outer frame 11 in the filter unit 1 is projected from the front surface of the front wall 20. An engaging filter support frame 31 (hereinafter referred to as a support frame 31) is provided. On the front surface of the support frame 31, bottomed screw holes 32 are provided at positions corresponding to the plurality of screw holes 15 provided on the front surface of the outer frame 11 in the filter unit 1. The reason why the screw hole 32 is bottomed is to prevent the screw hole 32 from passing into the inside of the housing 2.

  The filter unit 1 is first engaged with the support frame 31 from the front surface of the support frame 31 in the packing 14 on the back surface of the outer frame 11. Next, a screw rod 15a such as a screw is screwed into a screw hole 32 of the support frame 31 from each screw hole 15 provided in the outer frame 11, and is engaged with the support frame 31. The filter unit 1 is fixed to the support frame 31 and is detachably and airtightly attached to the intake port 3.

  The first example of the filter unit 1 is formed by the outer frame 11 having a substantially square shape when viewed from the front and the inner frame 12 having a substantially rectangular tube shape with a cross-sectional shape along the front shape of the outer frame 11. 1 also includes a second example of the filter unit 1 shown in FIGS.

  The filter unit 1 of the second example of the present invention shown in FIGS. 6 to 10 includes the filter unit 1 of the first example shown in FIGS. 1 to 5, the front shapes of the outer frame 11 and the inner frame 12, and the inner There is a difference in the shape seen from the side surface (or plane) of the frame 12. That is, the filter unit 1 of the second example has a rectangular front shape (the outer frame 11 is rectangular), and the inner frame 12 has a shorter length than that of the first example. However, the structure, function, and action of housing the filter member 13 by the outer frame 11 and the inner frame 12 are substantially the same as those in the first example. In addition, in this invention filter unit 1 shown to FIGS. 6-10, the same code | symbol is used for the same member and site | part as the filter unit of a 1st example.

  In the filter unit 1 of the second example, the length (front-rear width) of the inner frame 12 is smaller than the thickness (width in the front-rear direction) of the filter member 13 (approximately half as short in the example in the figure). The reason why the length of the filter body 13 may be short is that the substantially entire area of the outer peripheral surface of the filter body 13 is covered with a strong filter frame 13a made of metal or the like, so that the entire filter member 13 does not fit inside the inner frame 12. There is no problem. The filter member 13 of the second example is fixed to the inner frame 12 by a screw 13c serving as a support member in the frame 13a, and is coupled to the inner frame 12.

As described above, in the first example of the filter unit 1 of the present invention, the filter member 13 is housed entirely in the inner frame 12 and is held in the inner frame 12 by the filter pressing member 16. Even if there is a subtle difference in form depending on the manufacturer, it can be easily attached and detached, and in addition, the risk of damage to the filter member 13 (filter medium 13b) can be avoided when the filter unit 1 is attached.
Furthermore, a substantially flange-shaped outer frame 11 having a substantially inverted L-shaped side cross-section and a substantially rectangular annular shape on the front surface, and a front end portion having a substantially L-shaped side cross-section are joined airtightly to the back surface of the vertical side of the outer frame 11 The inner frame 12 having a substantially rectangular tube shape whose rear end side extends to the rear rear side of the outer frame 11, the filter member 13 that holds the substantially entire length inside the inner frame 12, and the inner frame 12 hold A filter holding member 16 that supports the filter member 13 at the rear end of the inner frame 12, an airtight packing 14 disposed over the entire back surface of the substantially inverted L-shaped portion of the outer frame 11, Since the plurality of holes 15 for screw rods provided through the packing 14 are formed on the entire circumference, for example, the screw rod 15a is simply fastened to the intake port 3 provided on the front surface of the air purifier AC. It can be installed airtight, and the filtration surface is sealed with a sealing plate. The filter unit 1 can be removed easily and quickly by simply removing by loosening the rod 15a.

  The air cleaning device AC used above is provided with a differential pressure gauge Dm for measuring the change in performance of the filter unit 1 and inspecting the filter performance as in the conventional device. The differential pressure gauge Dm is not installed on the front wall 20 of the housing 2 as in the prior art, but is disposed in a differential pressure gauge box 5 formed as a sealed container separate from the housing 2.

  The differential pressure gauge box 5 is provided separately from the housing 2 because the primary side air (contaminated air in the room) before entering the filter unit 1 introduced into the differential pressure gauge Dm leaks to the secondary side inside the housing 2. In this case, the air cleaned by the filter unit 1 is prevented from being recontaminated.

  Further, in the above air cleaning device AC, the height of the front wall 20 of the housing 2 is more preferably formed to be higher than approximately twice the height (vertical width) of the vertically oriented filter unit 1. In addition, three air inlets are formed in the lower half of the front wall 20 of the housing 2 so that the filter unit 1 is mounted in a vertically-facing front posture, and the filter unit 1 is formed in the upper half of the front wall 20 of the housing 2. There is also a case using a housing provided with an inspection port (not shown) with a lid for inspecting.

  Since the present invention is as described above, in an air cleaning device for cleaning the air in the space in a hazard countermeasure room or a draft chamber used in each industrial field, for example, in a standing wall provided with an intake port. It can be mounted in an upright position in an airtight manner, and it can be attached and detached and the filter member itself can be mounted very easily. On the other hand, it is extremely useful as a filter unit that is designed to avoid damage to the filter member during handling such as mounting and replacement. It is.

AC air purifying apparatus 1 The present invention filter unit 11 Outer frame 12 Inner frame 13 Filter member 14 Packing 15 Screw hole 15a Screw rod 16 Holding member 2 Housing 20 Front wall (standing wall)
21 Back walls 22, 23 Side wall 24 Top wall 25 Bottom wall 26 Base
3 Inlet 31 Filter unit support frame 32 Screw hole 4 in support frame 4 Exhaust port 5 Differential pressure gauge box

Claims (5)

  A filter unit that is detachably attached to the wall surface of the air inlet of the air purifier, and has a substantially flange-shaped outer frame in which the front surface that is airtightly attached to the wall surface of the air inlet of the air cleaner has a substantially rectangular ring shape. An inner frame that is perpendicular to the rear surface of the outer frame and extends rearwardly at the rear and has a substantially rectangular tube shape that is at least longer than the filter member, a filter member that is housed and held in its entirety inside the inner frame, A filter unit comprising: a filter pressing member that supports a filter member held by a frame at a rear end portion of the inner frame.   The substantially flange-shaped outer frame has a substantially inverted L-shaped side cross-section and a substantially rectangular annular front shape, and the substantially rectangular tube-shaped inner frame has a substantially L-shaped side cross section on the back surface of the vertical side of the outer frame. The front end portion of the filter frame is hermetically joined and the rear end side is formed in a substantially rectangular tube shape extending rearwardly from the back of the outer frame, and the filter member is accommodated in the inner frame so that the substantially entire length of the filter member is accommodated in the inner frame. The filter member is supported by a filter pressing member at the rear end portion of the inner frame, and has a plurality of airtight packings arranged in the entire back surface of the substantially inverted L-shaped portion of the outer frame and a plurality of holes penetrating the packing. 2. The filter unit according to claim 1, wherein the filter unit is hermetically attached to a wall surface of the air intake port on a back surface of the outer frame by a screw rod hole and a screw rod screwed into the air intake side from the screw hole.   A substantially flange-shaped outer frame having a substantially inverted L-shaped side cross-sectional shape and a substantially rectangular annular shape on the front surface, and a front end portion having a substantially L-shaped side cross-section is airtightly joined to the back surface of the vertical side of the outer frame. An inner frame having a short substantially rectangular tube shape extending rearward and rearward of the outer frame, and a filter member having a substantially entire side surface covered by the filter frame, and a part in the length direction is formed inside the inner frame. A filter member to be held, a support member for the filter frame for coupling the filter frame to the inner frame, an airtight packing disposed over the entire back surface of the substantially inverted L-shaped portion of the outer frame, and a through hole through the packing A filter unit, wherein the filter unit is hermetically attached to the wall surface of the intake port on the back surface of the outer frame by a plurality of holes for screw rods and screw rods screwed through the holes.   The filter unit according to claim 2 or 3 is fitted in a filter unit mounting portion having a bottomed screw hole corresponding to the screw hole provided so as to protrude from the wall surface of the intake port in the packing of the outer frame, Screw holes are respectively inserted into the screw holes from the holes for the screw holes, and each screw hole is tightly attached to the air inlet, and the screw holes are loosened to be removed from the air inlet. Filter unit. The filter unit according to any one of claims 1 to 4, wherein when the filter unit is removed from the wall surface of the intake port after use, a sealing plate for preventing scattering of contaminants is fitted to the inner peripheral side edge of the outer frame.

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