JP7397279B2 - air filter unit - Google Patents

Description

Regarding air filter units.

Air filters are classified into ULPA (Ultra Low Penetration Air) filters, HEPA (High Efficiency Particulate Air) filters, medium-performance filters, and the like, depending on the efficiency of collecting particles having a predetermined particle size. These are used for different purposes depending on their performance.

These air filters are sometimes used in a pleated state in order to ensure as wide an effective area as possible where air can be collected.

As a structure for maintaining the pleated shape of the air filter in this way, for example, as described in Patent Document 1 (Japanese Utility Model Publication No. 03-054711), there is a structure in which the pleated filter medium is formed on the upstream side and the downstream side of the airflow. A structure in which the pleat shape is maintained by inserting comb-shaped stabilizers from both sides has been proposed.

In the air filter described in Patent Document 1, stabilizers having the same shape are provided on the windward side and the leeward side of the filter medium, and the area where the windward side surface of the filter medium is in contact with the windward side stabilizer, The area where the leeward side surface of the leeward side is in contact with the leeward side stabilizer is of the same structure.

However, the part of the filter medium covered by the stabilizer on the windward side does not easily contribute to the collection of dust.

The air filter unit according to the first aspect includes a filter medium and at least one spacing member. The filter medium has a pleated shape. The filter medium has a filter medium layer and a support layer. The support layer has higher rigidity than the filter layer and is disposed on the leeward side of the airflow than the filter layer. The spacing member maintains the pleat spacing of the filter medium. The spacing holding member has an upwind holding member placed on the windward side of the filter medium and a leeward holding member placed on the leeward side of the filter medium, and the windward holding member on the windward side of the filter medium is The value obtained by dividing the area ratio of the contacting part by the area ratio of the part of the leeward side of the filter medium that is in contact with the leeward holding member is greater than 0 and less than 1.0, or the interval is maintained. The member has a leeward holding member disposed on the leeward side of the filter medium, and is not disposed on the windward side of the filter medium.

In addition, from the viewpoint of suppressing damage to the filter medium, it is preferable that the filter medium is not embossed to form an uneven shape that is protruding or recessed in the thickness direction.

Further, it is preferable that there is little variation in the pressure loss distribution of the filter medium and that the intervals between the pleat shapes are uniform. If the interval between the pleat shapes can be maintained even during use by using the leeward holding member, the need to use the upwind holding member can be further reduced, and in some cases, it may not be necessary to use it. It will also be done. When the windward holding member is not used, it is not necessary to attach the windward holding member while adjusting the pleat interval on the windward side using a jig during assembly.

The windward holding member has a flat plate shape whose normal direction is the direction in which the folds of the pleat shape extend, and is attached to at least the upstream side of the airflow between the windward side surfaces of the filter medium that face each other. It is preferable that the

In this air filter unit, the pleated shape of the filter medium is held by the leeward holding member, and the area where the upwind holding member is in contact with the windward side of the filter medium is the area where the leeward holding member is in contact with the leeward side of the filter medium. The area of the filter is smaller than that of the filter, or the upwind holding member is not provided, making it possible to maintain the pleated shape of the filter while securing a wide surface area of the filter that contributes to collecting dust. .

The air filter unit according to the second aspect is the air filter unit according to the first aspect, and the thickness of the filter medium is 0.3 mm or more.

Note that the thickness of the filter medium here can be, for example, 1.0 mm or less.

In this air filter unit, when the thickness of the filter medium is 0.3 mm or more, the number of folds in the filter medium is reduced or the pleat interval is narrowed compared to when the thickness of the filter medium is less than 0.3 mm. It turns out. When reducing the number of pleats, the area of the filter medium decreases, but the area in which the leeward holding member and the upwind holding member contact the filter medium is kept small, and the degree of decrease in the effective filter medium area is suppressed to a small extent, which increases the pressure accordingly. The degree of increase in loss can be suppressed to a small level. In addition, when the pleat spacing is narrowed, the flow velocity in the pleat gap (the area between adjacent pleats) increases, but by reducing the surface area of the leeward holding member and the upwind holding member, the pressure loss due to these The degree of increase in can be suppressed to a small level. Furthermore, since the area of the upstream side of the filter medium has a large influence on the amount of dust retained, it is desirable that the area of occlusion on the upstream side of the filter medium (the area of occlusion by the windward holding member, etc.) is small. Note that the presence or absence of the leeward side holding member has almost no effect on the amount of dust retained in the filter medium.

The air filter unit according to the third aspect is the air filter unit according to the first aspect or the second aspect, and the leeward holding member is bonded to the filter medium at a surface on the leeward side of the airflow.

In addition, when the shape retaining member has an upwind retaining member, the upwind retaining member may or may not be adhered to the filter medium.

Note that adhesion can be achieved not only by curing the adhesive to a state where it cannot be removed, or by melting the intervening resin and then curing it to a state where it cannot be removed, but also by applying an external force to remove it. It also includes adhesives that can be used.

This air filter unit can suppress changes in pleat shape by enhancing the holding function of the shape holding member. This makes it possible to reduce the situation in which the distance between the surfaces facing each other on the windward side of the filter medium narrows and the performance of the filter medium is suppressed.

The air filter unit according to the fourth aspect is the air filter unit according to any one of the first to third aspects, and the leeward holding member has a plurality of plate-like members. The plate member has a flat plate shape whose normal direction is the direction in which the folds of the pleat shape extend. The plate-like member has a shape whose width becomes narrower toward the upstream side of the airflow. The plurality of plate-like members are arranged in a line in the thickness direction at a pitch of 15 mm or more and 35 mm or less.

In addition, it is more preferable that the plurality of plate-like members are arranged in a line in the thickness direction at a pitch of 17 mm or more and 31 mm or less.

Note that the value obtained by dividing the arrangement pitch in the thickness direction of the plurality of plate-like members by the thickness of the plate-like member is preferably 15 or more and 35 or less, and more preferably 17 or more and 31 or less.

This air filter unit makes it possible to suppress structural resistance to a low level.

The air filter unit according to the fifth aspect is the air filter unit according to the fourth aspect, and the thickness of the plate member is 0.8 mm or more and 2.0 mm or less.

This air filter unit has a plate-shaped member with a thickness of 0.8 mm or more, which is advantageous in maintaining the shape of the filter medium, and since the plate-shaped member has a thickness of 2.0 mm or less, the plate-shaped member itself has ventilation resistance. It is possible to prevent this from happening.

The air filter unit according to the sixth aspect is the air filter unit according to the fourth or fifth aspect, and the filter medium has a crease on the leeward side. The filter medium has first pleats, second pleats, and third pleats that are arranged next to each other. The plurality of plate-like members include a first plate-like member and a second plate-like member that is a separate member independent of the first plate-like member. The first plate member maintains a distance between the first pleat and the second pleat. The second plate member maintains the interval between the second pleat and the third pleat.

In this air filter unit, since the first plate-like member and the second plate-like member are separate members that are independent from each other, the shape of each pleat formed by each plate-like member is maintained while forming each pleat in sequence. It becomes possible to do so.

In addition, if multiple independent plate members are adhered only to the leeward side of the pleats to maintain the pleat shape, for example, it is possible to expand and contract in the pleat folding direction (the direction in which the filter media is folded in the pleat pack state). Therefore, when the air filter unit is assembled into a casing of the air filter unit, it is possible to absorb errors in the direction in which the filter medium is folded.

The air filter unit according to the seventh aspect is the air filter unit according to the sixth aspect, in which the plate member has a contact portion that contacts the leeward side surface of the filter medium and a non-contact portion that does not contact the leeward side surface of the filter medium. It has a contact part. The melting point of the contact portion is lower than the melting point of the non-contact portion.

This air filter unit can be easily manufactured by melting the contact portion of the plate member and joining it to the filter medium.

The air filter unit according to the eighth aspect is the air filter unit according to any one of the first to seventh aspects, and the interval holding member includes an upwind holding member. The windward holding member has a plurality of spacing holding parts and a connecting part. A spacing portion is located between each pleat. The connecting portion connects the plurality of spaced portions.

This air filter unit is capable of maintaining pleat-shaped pleat intervals in the windward side portion of the filter medium.

The air filter unit according to the ninth aspect is the air filter unit according to the eighth aspect, in which the upwind holding member is located only upstream of the center of the filter medium in the airflow passing direction.

Note that the windward holding member is preferably located only upstream of the center of the air filter unit in the airflow passing direction.

In addition, it is preferable that the windward holding member is provided only in a range of 20% or less of the total length of the filter media in the airflow passing direction from the upstream end of the filter media, and only in a range of 10% or less of the total length of the filter media in the airflow passing direction. More preferably, it is provided.

In this air filter unit, it is possible to maintain the pleat interval at the upstream end of the filter medium by the upwind holding member, while minimizing the degree to which the upwind holding member itself causes ventilation resistance.

The air filter unit according to the tenth aspect is the air filter unit according to any one of the first to ninth aspects, and the area ratio of the portion of the windward side surface of the filter medium that is in contact with the windward holding member is as follows: It is 1.0% or less.

In this air filter unit, it is possible to reduce the area where the windward side surface of the filter medium comes into contact with the windward holding member, thereby making it difficult to contribute to dust collection.

The air filter unit according to the eleventh aspect is the air filter unit according to any one of the first to tenth aspects, and the area ratio of the portion of the leeward side surface of the filter material that is in contact with the leeward holding member is 2. .5% or more and 6.0% or less.

This air filter unit makes it possible to sufficiently support the pleated shape from the leeward side even when ventilating the pleated filter medium, and to secure a sufficiently large area of the filter medium through which airflow can pass.

The air filter unit according to the twelfth aspect is the air filter unit according to any one of the first to eleventh aspects, and the filter layer includes a main collection layer and a main collection layer on the upwind side of the airflow. and a windward side filter medium layer arranged therein.

This air filter unit is able to trap relatively large amounts of dust with the windward filter layer placed upwind of the main collection layer, thereby suppressing clogging of the main collection layer. becomes possible.

The air filter unit according to the thirteenth aspect is the air filter unit according to the twelfth aspect, in which the main collection layer is a porous membrane containing a fluororesin.

This air filter unit can trap even relatively small dust particles.

FIG. 1 is an external perspective view of an inlet side showing an embodiment of an air filter unit. FIG. 2 is an external perspective view of the outlet side showing an embodiment of the air filter unit. FIG. 2 is a perspective view of the air filter pack. A schematic cross-sectional configuration diagram of an air filter medium. FIG. 3 is a side view showing how the air filter pack is held by a windward holding member and a leeward holding member. A plan view showing how the air filter pack is held by a windward holding member and a leeward holding member. FIG. 3 is a plan view of the windward holding member. FIG. 3 is a plan view of the leeward holding member.

Hereinafter, the air filter unit will be specifically explained while giving examples, but these descriptions do not limit the content of the present disclosure.

(1) Air filter unit 1
FIG. 1 shows a perspective view of the air filter unit 1 on the inlet side. FIG. 2 shows a perspective view of the air filter unit 1 on the outflow port side.

The air filter unit 1 includes an air filter pack 20 and a frame 10 in which the air filter pack 20 is housed.

The frame 10 may be of any material as long as it can house and hold the air filter pack 20 therein, and may be made of aluminum, aluminum alloy, or resin, for example.

The frame body 10 has large openings at the front side (inflow port) and rear side (outflow port) in the ventilation direction, so that the waveform of the air filter pack 20 described later appears when viewed from a direction perpendicular to the ventilation direction. The air filter pack 20 is housed therein. The direction in which the air filter pack 20 is housed is not particularly limited, but it must be housed so that the waveform of the air filter pack 20 appears when viewed from above, that is, the pleat-shaped peaks and valleys extend vertically. Preferably, it is accommodated.

Here, the air filter pack 20 is accommodated in the frame 10 so that the pleat intervals of each air filter medium 30 are narrowed. Note that, although not particularly limited, it is preferable to provide a sealant between the end of the air filter medium 30 and the inner peripheral portion of the frame 10 to improve sealing performance. Examples of such sealants include those made of resin such as epoxy, acrylic, and urethane.

(2) Air filter pack 20
FIG. 3 shows an external perspective view of the air filter pack 20.

The air filter pack 20 is formed by repeating mountain folds and valley folds so that the air filter medium 30 has a predetermined shape (pleated filter medium), and has a pleated shape (wavy shape). ing. In this embodiment, the mountain fold line extends at the windward end, and the valley fold line extends at the leeward end.

The air filter pack 20 is not particularly limited, but can be obtained, for example, by folding the air filter medium 30 using a reciprocating folding machine or the like.

It is preferable that the air filter pack 20 has a pleat pitch of 5.5 mm or more and 9.0 mm or less. By setting the pleat pitch within this range, it is possible to suppress an increase in the structural resistance of the air filter unit 1 while ensuring a sufficiently large area of the air filter medium that can be housed in the frame 10 and function. become.

The air filter pack 20 can have a folded height (length L shown in FIG. 5), which is the length in the airflow passage direction, of 50 mm or more, and 100 mm or more, from the viewpoint of ensuring a sufficiently large filter area. It is preferable that it is, and it is more preferable that it is 200 mm or more. The upper limit of the folded height of the air filter pack 20 can be, for example, 500 mm or less, and preferably 400 mm or less. In the air filter unit 1 of this embodiment, the folding height is sufficiently long and the area of the filter medium is wide enough to keep the structural resistance low even in structures where structural resistance tends to be a problem. It is possible. In addition, when the air filter pack 20 has a long folding height, the leeward sides facing each other become too close to each other, especially in the downstream side of the center in the airflow direction. However, even in such a case, the provision of the leeward holding member 60, which will be described later, prevents the leeward surfaces from coming too close to each other or coming into contact with each other. While suppressing the increase in pressure loss, it is possible to reduce the number of locations where the filtration function cannot be performed.

Note that the size of the upstream end of the air filter pack 20 (inner part of the inlet of the frame 10) and the size of the downstream end (inner part of the outlet of the frame 10) are equivalent. It is preferable that it has a certain size.

(3) Air filter media 30
FIG. 3 shows a schematic cross-sectional configuration diagram of the air filter medium 30.

The air filter medium 30 has a main collection layer 31b and a breathable support material 31c.

The main collection layer 31b is not particularly limited, and may have a porous film, for example. This main collection layer 31b is preferably a porous membrane containing, for example, a fluororesin, and more preferably a porous membrane of a fluororesin containing polytetrafluoroethylene as a main component. Polytetrafluoroethylene, which is a fluororesin, may be modified or unmodified. Moreover, such a porous membrane may be used as a single membrane, or may be used in a plurality of layers. In this case, the plurality of porous membranes may be of the same type or of different types.

Further, it is preferable that the main collection layer 31b has a pressure loss of 20 Pa or more and less than 160 Pa when air is passed through it at a flow rate of 5.3 cm/sec. Further, the main trapping layer 31b preferably has a trapping efficiency of 70% or more and 99.9999% or less for NaCl having a particle size of 0.3 μm. Further, the thickness of the main collection layer 31b is not particularly limited, but is preferably 1 μm or more and 300 μm or less, more preferably 5 μm or more and 150 μm or less. Further, when the main collection layer 31b has a porous membrane, the average fiber diameter is preferably 0.1 μm or less.

The method of manufacturing the main collection layer 31b is not particularly limited, but here, the main collection layer 31b of a porous membrane containing polytetrafluoroethylene as a fluororesin as a main component is taken as an example. Explain how. First, in step 1, an unfired film or a semi-fired film made of polytetrafluoroethylene or the like is prepared. Thereafter, in step 2, the green film is stretched in a first direction at a predetermined stretching speed in a predetermined temperature environment, and then in a second direction perpendicular to the first direction to form holes. A main collection layer 31b is obtained. Here, the film in step 1 is produced by mixing modified PTFE fine particles and/or homo-PTFE fine particles with an extrusion aid (liquid lubricant) such as liquid paraffin or naphtha, and then forming a rod-like product by paste extrusion. It is obtained by rolling it with a calendar roll or the like to form it into a film. Note that a step of removing the extrusion aid (liquid lubricant) may be provided as necessary.

The breathable support material 31c is not particularly limited as long as it has breathability and can support the main collection layer 31b from the downstream side of the airflow, and has higher rigidity (flexural rigidity) than the main collection layer 31b. However, it is preferably a non-woven fabric. The breathable support material 31c is preferably adhered to the main collection layer 31b. As for the bending rigidity, for example, a long test sample of size 150 mm x 20 mm is cut out, and a region of 40 mm from one longitudinal end of the test sample is used as a holding margin to protrude horizontally from a horizontal table. Then, using the protruding length of 110 mm as the measurement length, measure the vertical displacement of the hanging body due to its own weight from the horizontal stand, and calculate the following equation (bending rigidity [g weight / mm] = basis weight of filter medium). x (measured length) ⁴ /8/displacement) may be used as the bending rigidity.

Examples of the nonwoven fabric include polyethylene terephthalate (PET) fiber nonwoven fabric, polybutylene terephthalate (PBT) fiber nonwoven fabric, and nonwoven fabric with a core-sheath structure in which the core component is PET and the sheath component is polyethylene (PE) (PET/PE core/sheath nonwoven fabric). ), a nonwoven fabric with a core-sheath structure in which the core component is PET and the sheath component is PBT (PET/PBT core/sheath nonwoven fabric), a nonwoven fabric with a core-sheath structure in which the core component is high melting point PET and the sheath component is low melting point PET (high Nonwoven fabrics made of composite fibers of PET fibers and PBT fibers, nonwoven fabrics made of composite fibers of high melting point PET fibers and low melting point PET fibers, and the like. As the nonwoven fabric, one type or a combination of multiple types can be used. In addition, as a nonwoven fabric, the thing which has heat-fusibility is preferable.

The basis weight of the nonwoven fabric used for the breathable support material 31c is not particularly limited, but is usually 10 g/m ² or more and 600 g/m ² or less, preferably 15 g/m ² or more and 300 g/m ² or less, and more preferably 30 g/m ² It is not less than 100 g/m ² or less. Further, the thickness of the nonwoven fabric used for the breathable support material 31c is preferably 0.10 mm or more and 0.60 mm or less.

In addition, the pressure loss of the breathable support material 31c when air is passed through it at a flow rate of 5.3 cm/sec is smaller than that of the main collection layer 31b, preferably 10 Pa or less, and substantially 0. is more preferable.

Although not particularly limited, for example, the air filter medium 30 may include a pre-collection layer on the windward side of the airflow relative to the main collection layer 31b from the viewpoint of reducing the dust collection load on the main collection layer 31b and suppressing clogging. 31a (an example of a windward side filter medium layer). Specifically, it is preferable that the air filter medium 30 has, in order from the windward side, a pre-trapping layer 31a, a main trapping layer 31b, and an air-permeable support material 31c.

The pre-collection layer 31a is not particularly limited, but for example, one obtained by a melt-blown method can be used. The material of the pre-trapping layer 31a is, for example, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polyacrylonitrile (PAN), polyvinylidene fluoride. (PVdF), polyvinyl alcohol (PVA), polyurethane (PU), etc. The pre-trapping layer 31a can be bonded to the main trapping layer 31b, for example, by thermal lamination using hot melt resin.

Further, it is preferable that the pre-collection layer 31a has a pressure loss of 15 Pa or more and less than 55 Pa when air is passed through it at a flow rate of 5.3 cm/sec. Further, it is preferable that the pre-trapping layer 31a has a trapping efficiency of 25% or more and less than 80% for NaCl having a particle size of 0.3 μm. Further, the thickness of the pre-trapping layer 31a is preferably thicker than the main trapping layer 31b, preferably from 0.1 mm to 0.8 mm, and more preferably from 0.2 mm to 0.5 mm. preferable.

As for the air filter medium 30 as a whole, the pressure loss when air is passed through it at a flow rate of 5.3 cm/sec is, for example, 60 Pa or more and 200 Pa or less when the air filter medium 30 is not pleated and is in a flat state. In addition, when the air filter medium 30 as a whole is not pleated and is in a flat state, particles are collected when air containing NaCl particles with a particle size of 0.3 μm is passed through the air filter medium 30 at a flow rate of 5.3 cm/sec. It is preferable that the efficiency is 99.99% or more, and it is preferable to use it as a HEPA filter. Note that the overall thickness of the air filter medium 30 is preferably 0.3 mm or more and 1.0 mm or less.

Note that, from the viewpoint of suppressing damage caused to the air filter medium 30 and suppressing leakage, the air filter medium 30 is not embossed to form an uneven shape that is protruding or recessed in the thickness direction. It is preferable.

For example, the air filter medium 30 may be wound into a roll during manufacturing, so that the air filter medium 30 has a curling tendency. When manufacturing an air filter unit 1 with a high folded height using a relatively thick air filter medium 30 that has a curl, the air filter medium 30 that is pleated due to the curl may be However, with this structure, the uniformity of the pleat spacing tends to decrease and the structural resistance increases, such as when the inflow port on the inside of the part where the pleats narrow unintentionally. It becomes possible to suppress such an increase in structural resistance to a small level.

(4) Spacing member The pleated shape of the air filter pack 20 is maintained by a spacing member that maintains the spacing between the opposing surfaces of the filter media. Specifically, in this embodiment, the spacing members include a plurality of upwind holding members 50 and a plurality of leeward holding members 60.

FIG. 5 is a side view showing how the air filter pack 20 is held by a plurality of upwind holding members 50 and a plurality of leeward holding members 60. FIG. 6 is a plan view showing how the air filter pack 20 is held by the upwind holding member 50 and the leeward holding member 60.

(4-1) Windward holding member 50
FIG. 7 shows a plan view of the windward holding member 50.

The windward holding member 50 has a windward connecting portion 51 and a plurality of windward protrusions 52, and has a plate shape whose normal direction is the direction in which the mountain fold line of the pleat shape of the air filter pack 20 extends. It is a member.

The windward connecting portion 51 (an example of a connecting portion) extends in a direction perpendicular to the direction in which the pleated mountain fold lines of the air filter pack 20 extend.

The plurality of windward protrusions 52 (an example of a spacing maintaining portion) are provided in line at predetermined intervals along the longitudinal direction of the windward connecting portion 51, and extend further from the leeward side of the windward connecting portion 51 to the leeward side. This is a portion that protrudes towards the user and corresponds to the insertion allowance. A portion of the air filter pack 20 near the mountain fold line of the pleat shape is held between the plurality of windward protrusions 52 . Note that the length of the windward projection 52 in the longitudinal direction of the windward connecting portion 51 becomes slightly shorter toward the leeward side, so that the windward projection 52 has a trapezoidal shape. The shape and size of each windward protrusion 52 are the same. Here, both edges of the windward projection 52 in the longitudinal direction of the windward connecting portion 51 are in contact with the windward side surface of the air filter medium 30, but the downstream end of the windward projection 52 is in contact with the windward side surface of the air filter medium 30. It is not close to 30.

Note that the windward protrusion 52 is preferably provided only upstream of the center of the length of the air filter pack 20 in the airflow direction. Further, the length of the windward protrusion 52 in the airflow direction may be 20% or less of the folded height of the air filter pack 20, preferably 10% or less, and may be 3% or more. This makes it possible to maintain a constant pleat interval at the windward end of the air filter pack 20 while keeping the contact area between the windward holding member 50 and the air filter medium 30 small. Note that when the air filter pack 20 has a wide pleat interval, the windward holding member 50 has a low ability to maintain the interval. It is preferable that the resin is not a hot melt resin.

The plate thickness of the plurality of windward holding members 50 can be, for example, 0.8 mm or more and 2.0 mm or less. By setting the thickness of the windward holding member 50 to 0.8 mm or more, the pleat interval can be stably maintained, and by setting the thickness of the windward holding member 50 to 2.0 mm or less, the windward holding member It becomes possible to suppress the extent to which the air filter unit 50 itself becomes a structural resistance of the air filter unit 1.

It is preferable that the plurality of windward holding members 50 are arranged side by side with an interval of 15 mm or more and 35 mm or less in the thickness direction from the viewpoint of suppressing structural resistance to a low level while stably maintaining the pleat interval. It is more preferable to arrange them side by side at a pitch of 17 mm or more and 31 mm or less (note that the pitch includes the plate thickness, not the interval). Further, for the plurality of windward holding members 50, the value of arrangement pitch/plate thickness in the plate thickness direction is preferably 15 or more and 35 or less, and more preferably 17 or more and 31 or less.

Further, the contact area between the plurality of windward holding members 50 and the windward side surface of the air filter medium 30/area of the windward side surface of the air filter medium 30 is preferably 1.0% or less, and 0.0% or less. More preferably, it is 5% or less. This makes it possible to reduce the area of the part of the windward side surface of the air filter medium 30 that is less likely to contribute to dust collection due to contact between the plurality of windward holding members 30.

Note that the windward holding member 50 may be fixed to the air filter pack 20 with an adhesive or without using an adhesive.

(4-2) Downwind holding member 60
FIG. 8 shows a plan view of the leeward holding member 60.

The air filter unit 1 includes a plurality of leeward holding members 60 arranged in a direction perpendicular to the direction in which the pleat-shaped mountain fold lines and valley fold lines of the air filter pack 20 extend. Further, in the air filter unit 1, when a plurality of leeward holding members 60 arranged in a direction perpendicular to the direction in which the pleated mountain fold lines and valley fold lines extend are made into a set, the set has a pleated shape. They are arranged along the direction in which the mountain fold lines and valley fold lines extend.

The leeward holding member 60 is a plate-like member whose normal direction is the direction in which the pleated mountain fold lines and valley fold lines of the air filter pack 20 extend, and is When viewed, it has a trapezoidal shape with the upstream side narrower. Note that the leeward holding member 60 may have a triangular shape that is narrower on the upstream side.

The leeward holding member 60 has an upstream edge 61 and a direction perpendicular to the direction in which the mountain fold lines and valley fold lines of the pleat shape of the air filter pack 20 extend, and which is perpendicular to the airflow. It has a downstream edge 62 having a long width in the direction, and a first side edge 63 and a second side edge 64 extending between the upstream edge 61 and the downstream edge 62. Here, the downstream side edge 62 of the leeward holding member 60 is not in contact with the downstream side surface of the air filter medium 30, and the first side edge 63 and the second side edge of the leeward holding member 60 are not in contact with the downstream side surface of the air filter medium 30. 64 is in contact with the downstream surface of the air filter medium 30. Note that the upstream edge 61 of the leeward holding member 60 may or may not be in contact with the downstream surface of the air filter medium 30.

In addition, when the windward holding member 50 is used, the area ratio of the part of the windward side surface of the air filter medium 30 that is in contact with the windward holding member 50 is calculated as the area ratio of the portion on the windward side of the air filter medium 30 The value divided by the area ratio of the portion of the surface that is in contact with the leeward holding member 60 is greater than 0 and less than 1.0.

Note that the first side edge portion 63 and the second side edge portion 64 of the leeward holding member 60 maintain the respective pleated shapes of the air filter pack 20, and the distance between the windward side surfaces of the air filter medium 30 is reduced. From the viewpoint of suppressing (the shape in which the airflow inflow port becomes narrow), it is preferable that the air filter material 30 is bonded to the downstream surface of the air filter medium 30. Here, the state in which the leeward holding member 60 and the air filter medium 40 are adhered is not particularly limited, and may be such that they adhere to each other to the extent that they do not separate from each other depending on the application of airflow during use, and can be peeled off without being destroyed. They may be in a state where they are stuck together using an adhesive to the extent that they can be bonded together, or they may be in a state where they are hardened together using an adhesive so that they cannot be removed, or they may be in a state where the intervening resin is melted. They may be cured later so that they cannot be peeled off from each other. When using an adhesive, for example, polyester resin, polyurethane resin, polyamide resin, etc. can be used. In addition, in the case where the resin is melted and hardened, the first side edge 63 and the second side edge 64 of the leeward holding member 63 are separated from the main body part of the leeward holding member 60, in addition to the resin that constitutes the main body part of the leeward holding member 60. It may also be made of a low melting point resin. As a result, when the leeward holding member 60 is heated, only the resin portions forming the first side edge 63 and the second side edge 64 are melted while suppressing deformation of the main body portion of the leeward holding member 60. It can be adhered to the filter medium 30, and manufacturing can be facilitated.

A plurality of leeward holding members 60 are arranged so as to be lined up in the thickness direction on the leeward side of each mountain fold line of the air filter pack 20 in order to maintain each pleat shape of the air filter pack 20. Specifically, on the leeward side of one pleat-shaped portion of the air filter pack 20, a plurality of leeward holding members 60 are arranged at predetermined intervals in the thickness direction. This makes it possible to suppress narrowing of the distance between the downstream surfaces of the air filter media 30 of the air filter pack 20 when airflow passes through.

The length of the leeward holding member 60 in the airflow direction is preferably at least half the folded height of the air filter pack 20, more preferably 80% or more, and is substantially equal to the folded height of the air filter pack 20. More preferably, they are the same. This makes it possible to more reliably prevent the mutually opposing leeward surfaces of the air filter pack 20 from coming into contact with each other.

The plate thickness of the plurality of leeward holding members 60 may be, for example, 0.8 mm or more and 2.0 mm or less, and may be the same as that of the windward holding member 50. By setting the thickness of the leeward holding member 60 to 0.8 mm or more, the pleat interval can be stably maintained, and the adhesive state is stabilized by ensuring a sufficient adhesive surface when adhering to the filter medium. can be made into Further, by setting the thickness of the leeward holding member 60 to 2.0 mm or less, it is possible to suppress the extent to which the leeward holding member 60 itself becomes a structural resistance of the air filter unit 1.

The plurality of leeward holding members 60 are preferably arranged in line in the thickness direction at a pitch of 15 mm or more and 35 mm or less, and preferably 17 mm or more and 31 mm or less, from the viewpoint of keeping the structural resistance small while stably maintaining the pleat interval. It is more preferable that they be arranged side by side at a pitch of (note that the pitch includes the plate thickness, not the interval). Further, for the plurality of leeward holding members 60, the value of arrangement pitch/plate thickness in the plate thickness direction is preferably 15 or more and 35 or less, and more preferably 17 or more and 31 or less.

In addition, from the viewpoint of suppressing the total structural resistance of the plurality of leeward holding members 60 and the plurality of windward holding members 50, each leeward holding member 60 is On the other hand, it is preferable that they be arranged in an overlapping position on the leeward side.

Further, the contact area between the plurality of leeward holding members 60 and the leeward side surface of the air filter medium 30/the area of the leeward side surface of the air filter medium 30 may be 2.5% or more and 6.0% or less. It is preferably 0.5% or less, and more preferably 0.5% or less. By setting it to 2.5% or more, it is possible to suppress narrowing of the interval between opposing surfaces on the leeward side of the air filter medium 30, and by setting it to 6.0% or less, the air filter medium 30 In this case, it is possible to keep the area of the portion that is difficult to contribute to dust collection small.

Note that the plurality of leeward holding members 60, for example, similarly to the windward holding member 50, parts that maintain the interval between adjacent pleats (each leeward holding member 60) are integrated via a connecting part or the like. It may also be a configuration. However, for example, when manufacturing an air filter pack in a continuous process by transporting the air filter medium 30 while applying tension with a tension roller, the plurality of leeward holding members 60 are individually moved without damaging the air filter medium 30. It is preferable that the plurality of leeward holding members 60 be provided as mutually independent members from the viewpoint that they can be adhesively fixed to the air filter medium 30 and mass production is easy. Specifically, first, either the first side edge 63 or the second side edge 64 of the leeward holding member 60 is placed on the surface of the flat air filter medium 30 that is being conveyed while applying tension. The plurality of leeward holding members 60 are fixed on the surface of the air filter medium 30 while fixing the portions with an adhesive or the like. After that, an adhesive or the like is applied to the other portion of the leeward holding member 60 that is not fixed, of the first side edge 63 or the second side edge 64, and the upstream side of the leeward holding member 60 of the air filter medium 30 is By folding in the portion facing the edge 61, it is possible to realize a state in which both the first side edge 63 and the second side edge 64 of the leeward holding member 60 are bonded to the air filter medium 30. preferable.

(5) Features Conventional air filter units have a pre-filter layer that collects coarse particles upstream of the collection layer of high-performance filter media that collects fine particles in order to extend the life of the air filter media. There may be cases where However, as the overall thickness of the filter medium increases, the number of folding ridges in the air filter unit decreases, and the pressure loss of the filter medium also increases, which increases the pressure loss of the air filter unit and increases operating costs. Put it away.

Moreover, air filter media are usually manufactured in a roll shape by being wound around a core material, but the filter media formed into a roll shape may have a tendency to curl. In particular, the thicker the filter medium is, the more likely it is to curl. When manufacturing an air filter unit having a pleated shape using a filter medium having a curling tendency, a holding member is used to suppress the curling tendency and maintain the pleated shape. Moreover, when the thickness of the filter medium is large, the effective area of the filter medium decreases as described above, so it is required to maintain the pleated shape while suppressing the increase in pressure loss of the air filter medium.

Here, as conventionally used pleated air filter units, a separator filter, a V-bank filter, an emboss filter, and a stabilizer filter will be considered. Note that the separator filter maintains the pleat spacing by inserting an aluminum separator, which is made by weaving aluminum thin plates into a convex-concave shape, between the pleats. A V-bank filter is a filter frame in which a plurality of low folded pleated filters, whose pleat spacing is maintained by hot melt beads applied to the surface of the filter medium, are arranged at an angle to each other and housed in a filter frame. An embossed filter is a filter in which embossed filter media is processed into a pleated shape so that the pleat spacing between opposing filter media is maintained by embossed protrusions. The stabilizer filter is made by inserting a stabilizer to maintain the pleat spacing.

Among the above, regarding the "separator filter", the presence of the aluminum separator increases the resistance to the airflow, making it difficult to keep the pressure loss of the air filter unit low.

Further, although a conventional relatively thin filter medium can be applied to a "V bank filter", if a thick filter medium is used, the area of the filter medium that can be folded is small, resulting in high pressure loss.

Furthermore, when manufacturing embossed filters using filter media with roll-like curls, it is difficult to minimize the increase in structural resistance due to the curls, and this also results in pressure loss in the air filter unit. It becomes difficult to keep it low.

On the other hand, a "stabilizer filter" as proposed in the above-mentioned Patent Document 1, that is, a stabilizer filter having the same shape on the windward side and the leeward side of the filter medium (lined up in the longitudinal direction of the edges) A stabilizer including a plurality of comb teeth extending from the edge is provided, and the area in which the windward side of the filter medium is in contact with the windward side stabilizer, and the area in which the leeward side surface of the filter medium is in contact with the leeward side stabilizer are provided. If the area in contact with the stabilizer is of the same structure, it is thought that the pressure loss in the air filter unit can be suppressed to a low level.

However, when a stabilizer is employed in an air filter unit with a large pleat height, it may be difficult to fully insert the stabilizer into the pleated filter medium. Specifically, when inserting a stabilizer into a pleated air filter medium for the first time, it is relatively easy to insert it, but when inserting the stabilizer later, the filter medium must be pushed in to straighten it. Therefore, a relatively large insertion force is required when inserting. Specifically, for example, if a stabilizer is first inserted on the leeward side of the pleats, and then the stabilizer is also inserted in the opposite position on the windward side, a large insertion force is required to insert the stabilizer that is inserted later. Become. In particular, this tendency becomes more pronounced as the pleat fold height increases. When such a large insertion force is required, a highly rigid stabilizer is required in consideration of the material and thickness of the filter medium in order to prevent deformation of the pleat shape. Furthermore, when inserting the stabilizer, particularly when inserting the stabilizer from both the leeward and windward sides, there is a risk that the surface of the filter medium may be damaged. Furthermore, since the upstream surface of the filter medium is blocked by the stabilizer disposed on the upstream side, the life of the filter medium is shortened accordingly.

In contrast, in the air filter unit 1 of the present embodiment, the pleated shape of the air filter medium 30 is held by a plurality of leeward holding members 60, and the upwind holding member 50 is attached to the windward surface of the air filter medium 30. The area in contact with the leeward holding member 60 is smaller than the area in contact with the leeward side surface of the air filter medium 30, or the upwind holding member 50 is not provided in the first place. be. Therefore, the windward side surface of the air filter medium 30 is not covered with parts other than the filter medium, such as the holding member, to a small extent, ensuring a wide surface that contributes to collecting dust. The shape is sufficiently maintained by the plurality of leeward holding members 60, uniformity of the pleat intervals is ensured even during ventilation, and structural resistance is kept low, so pressure loss as the air filter unit 1 can also be kept low. ing. Moreover, the plurality of leeward holding members 60 are provided in groups between the pleats so as to be independent from each other, and even if each leeward holding member 60 is inserted and attached to the pleated air filter medium 30, Even if there is, it can be easily performed with a smaller force than when using a comb-like stabilizer, and damage to the air filter medium 30 can also be suppressed. Moreover, even when the air filter medium 30 with curling tendency is used to secure a neat pleat shape, damage to the air filter medium 30 can be kept small.

(6) Other embodiments (6-1) Other embodiments A
In the above embodiment, the case where both the windward holding member 50 and the leeward holding member 60 are included as shape holding members has been described as an example.

On the other hand, the shape retaining member may be one in which the windward retaining member 50 in the above embodiment is not provided and the shape is retained by a plurality of leeward retaining members 60.

(6-2) Other embodiment B
In the above embodiment, the case where the windward holding member 50 is used to hold the pleat shape on the windward side has been described as an example.

On the other hand, the means for maintaining the pleat shape on the windward side, for example, is not limited to the use of a member such as resin; The pleated shape may be maintained by applying melt resin.

(6-3) Other embodiment C
In the embodiment described above, the case where the leeward holding member 60, which is a plate-shaped member or the like located between the pleats of the air filter medium 30, is used as one member has been described as an example.

On the other hand, for example, one pleat interval in the pleated shape of the air filter medium 30 may be ensured by a plurality of members such as two members. Specifically, in the pleated air filter medium 30, a first member is fixed to one of the mutually opposing filter medium surfaces by adhesive or the like, and a first member is fixed to the other of the opposing filter medium surfaces by adhesive or the like. By combining the fixed second member with the second member, the same function as the leeward holding member 60, which is one member of the above embodiment, may be exerted. Here, the first member and the second member may be, for example, right triangular plate members having the same size and shape.

In this case, the first joined part other than the part of the first member that is adhered to the filter medium surface and the second joined part of the second member other than the part that is adhered to the filter medium surface are , are bonded to each other via an adhesive or the like. In this case, the first part of the first member to be joined and the second part to be joined of the second member are in an opposite relationship (S pole and An adhesive or the like containing a magnetic material to which a magnetic force (N-pole relationship) is applied may be applied.

For example, when manufacturing an air filter pack in a continuous process by conveying the air filter while applying tension with a tension roller, the air filter medium 30 in a flat state may be Alternatively, a hot melt resin having magnetism or containing a magnetic material may be applied. Then, the magnetic materials to be bonded to each other may be magnetized and bonded so that magnetic forces having opposite relationships are applied to the magnetic materials.

This makes it possible for the parts located at mutually opposing portions with the fold line in between to be attracted to each other by magnetic force and to be combined. This makes it possible to easily perform the folding operation when securing a pleated shape through a continuous process.

Hereinafter, the content of the present disclosure will be specifically explained with reference to Examples.

Two types of air filter media were used in each of the Examples and Comparative Examples (excluding Comparative Example 2): one with a thickness of 0.35 mm and one with a thickness of 0.81 mm. The air filter medium with a thickness of 0.35 mm was laminated with PET/PE core/sheath spunbond nonwoven fabric, PTFE stretched membrane (thickness 10 μm), and PET/PE core/sheath spunbond nonwoven fabric (thickness 0.2 mm) in order from the windward side. It was something. The air filter medium with a thickness of 0.81 mm was made by laminating, in order from the windward side, a PP melt-blown nonwoven fabric, a PTFE stretched membrane (thickness 100 μm), and a PET thermal bond nonwoven fabric (thickness 0.3 mm).

Note that the frame of the air filter unit of each example and comparative example is rectangular as described in the above embodiment, and has a rectangular inlet and an outlet, and the pleated mountain fold line A structure was used in which the pleat-shaped valley fold line extended in the vertical direction near the inlet, and the pleat-shaped valley fold line extended in the vertical direction near the outlet.

In addition, in each example and comparative example 1, the shape of the windward holding member 50 described in the above embodiment is used, the thickness is 1 mm, the arrangement pitch in the plate thickness direction is 30 mm, and the insertion allowance is It was set to 10 mm. Further, in each example, the shape of the leeward holding member 60 described in the above embodiment was used, and while the thickness was 1 mm, the arrangement pitch in the thickness direction was varied. In addition, in the leeward holding member 60 in each example, the width of the upstream edge 61 is 0.44 mm, the width of the downstream edge 62 is 5.34 mm, and the length in the airflow direction is 274.38 mm. there were. Further, in each example, the actual width of the air filter pack 20 was 116 mm, and 3 mm on the left and right sides were used for sealing to the frame.

Comparative Example 1 uses an aluminum separator on the windward side of the air filter medium instead of the windward holding member 50 in Example 3, and uses the same leeward holding member 60 as in Example 3 on the leeward side of the air filter medium. It was assumed that it was used. This aluminum separator had a length in the airflow direction of 264 mm, and a height in side view of 4.2 mm at the upstream end and 1.4 mm at the downstream end. The aluminum separator has a relatively large zigzag shape in the upstream portion and a relatively small zigzag shape in the downstream portion. Specifically, in the upstream part, a zigzag shape is formed so that 8.5 peaks are formed in the internal height of 110 mm, and in the downstream part, 3 peaks on the upstream side are formed in the internal height of 110 mm. A zigzag shape was formed so that twice as many peaks were formed. Note that the length of the downstream portion of the aluminum separator in the airflow direction was 198 mm.

In Comparative Example 2, a commercially available glass fiber filter medium with a thickness of 0.38 mm was used. In addition, in Comparative Example 2, similarly to Comparative Example 1, an aluminum separator similar to that used in Comparative Example 1 was used on the windward side of the air filter medium. In Comparative Example 2, on the leeward side of the air filter medium, instead of the leeward holding member 60, an aluminum separator having the same shape and structure as the aluminum separator used on the windward side of the air filter medium was used in a different direction. there was.

Note that in Comparative Examples 3 and 4, the same air filter media as in Examples 9 to 11 were used, and aluminum separators were used on both the windward side and the leeward side, as in Comparative Example 2.

In addition, each term in the table is as follows.

"Pressure loss of the filter unit" (Df) is the air filter unit 1 obtained by accommodating the air filter medium 30 having an area Af (m ² ) in the frame 10 in the form of the air filter pack 20 at a predetermined front wind speed (Df). This is the pressure difference between the front and rear of the air filter unit 1 when it is placed in an environment of (m/s). The pressure loss (Df) of the filter unit is the sum of the filter medium resistance (Dm) and the structural resistance (Ds). Note that the front wind speed (m/s) here is the rated air volume front wind speed (m ³ /s) divided by the opening area on the windward side, and was set to 2.9 (m/s).

"Filter media pressure loss" (D0) is the pressure before and after the air filter media 30 when air is passed through the flat air filter media 30 that is not pleated at a flow rate of 0.053 m/s. The difference is D0.

“Filter media resistance” (Dm) is the pressure difference before and after the air filter media 30 when air is passed through the air filter media 30 having an area Af (m ² ) at a rated air flow rate Q (m ³ /s). This is a value obtained as filter medium resistance (Dm)=D0×(Q/Af)/0.053.

“Structural resistance” (Ds) is a value obtained by structural resistance (Ds)=Df−Dm=Df−D0×(Q/Af)/0.053.

Details of each of the above examples and comparative examples are shown in the table below.

Compared to Comparative Example 1, the upwind support member 50 in Example 3 is changed to an aluminum separator as described above, so the contact area with the air filter material is different, and the contact area/air filter material is different. The value of the area was 0.12% in Example 1 and 14.4% in Comparative Example 1. Here, Example 3 and Comparative Example 1 have the same windward support member 60, and both have a contact area with the air filter medium of 3.3%. Then, the ratio of the area ratio between the windward side and the leeward side (ratio of the contact area on the windward side / ratio of the contact area on the leeward side) is 0.036 (= 0.12% / 3.3 %), 4.36 (=14.4%/3.3%) in Comparative Example 1, and a small value in Example 3. In Example 3, it is possible to suppress the structural resistance lower than in Comparative Example 1. In Comparative Examples 2 to 4, aluminum separators were placed on both the windward and leeward sides, and the structural resistance values were larger than those in Examples 1 to 11.

Note that in Examples 5-8, only the pitch of the leeward holding members 60 differs, but it can be seen that the structural resistance is the minimum in the case of Example 7 where the pitch is 22 mm.

Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as described in the claims. .

1 Air filter unit 10 Frame body 20 Air filter pack (filter material)
30 Air filter material (filter material)
31a Pre-collection layer (filter layer, windward filter layer)
31b Main collection layer (filter layer)
31c Breathable support material (support layer)
50 Windward holding member (spacing holding member)
51 Windward connection part (connection part)
52 Windward projection (space maintaining part)
60 Downwind holding member (spacing holding member)

Utility Model Publication No. 03-054711

Claims (12)

A filter medium (30, 20) having a pleated shape and having a filter medium layer (31b) and a support layer (31c) having higher rigidity than the filter medium layer and disposed on the leeward side of the airflow from the filter medium layer. and,
at least one spacing member (50, 60) that maintains the pleat spacing of the filter medium;
Equipped with
The spacing member includes an upwind holding member (50) disposed on the windward side of the filter medium, and a leeward holding member (60) disposed on the leeward side of the filter medium. The value obtained by dividing the area ratio of the part of the windward side surface that is in contact with the windward holding member by the area ratio of the part of the leeward side surface of the filter medium that is in contact with the leeward holding member is less than 0. Is it significantly less than 1.0?
or
The spacing member has a leeward holding member (60) disposed on the leeward side of the filter medium, and is not disposed on the windward side of the filter medium,
The leeward holding member has a plurality of plate-like members whose normal direction is the direction in which the folds of the pleat shape extend, and whose width is narrower toward the upstream side of the airflow,
The plurality of plate-like members are arranged in a line in the thickness direction at a pitch of 15 mm or more and 35 mm or less,
The filter medium has a fold on the leeward side, and has first pleats, second pleats, and third pleats arranged next to each other,
The plurality of plate-like members include a first plate-like member that maintains a distance between the first pleat and the second pleat, a first plate-like member that maintains a distance between the second pleat and the third pleat, and a first plate member that maintains a distance between the second pleat and the third pleat. a second plate-shaped member that is a separate member independent of the shaped member ;
The area ratio of the portion of the windward side surface of the filter medium that is in contact with the windward holding member is 1.0% or less,
The area ratio of the portion of the leeward side surface of the filter medium that is in contact with the leeward holding member is 2.5% or more and 6.0% or less,
Air filter unit (1). The spacing member includes the windward holding member (50),
The windward holding member has a plurality of spacing holding parts (52) located between each pleat, and a connecting part (51) that connects the plurality of spacing holding parts.
The air filter unit according to claim 1. A filter medium (30, 20) having a pleated shape and having a filter medium layer (31b) and a support layer (31c) having higher rigidity than the filter medium layer and disposed on the leeward side of the airflow from the filter medium layer. and,
at least one spacing member (50, 60) that maintains the pleat spacing of the filter medium;
Equipped with
The spacing member includes an upwind holding member (50) disposed on the windward side of the filter medium, and a leeward holding member (60) disposed on the leeward side of the filter medium. The value obtained by dividing the area ratio of the part of the windward side surface that is in contact with the windward holding member by the area ratio of the part of the leeward side surface of the filter medium that is in contact with the leeward holding member is less than 0. It is largely less than 1.0,
The windward holding member has a plurality of spacing holding portions (52) located between each pleat, and a connecting portion (51) connecting the plurality of spacing holding portions,
The area ratio of the portion of the windward side surface of the filter medium that is in contact with the windward holding member is 1.0% or less,
The area ratio of the portion of the leeward side surface of the filter medium that is in contact with the leeward holding member is 2.5% or more and 6.0% or less,
Air filter unit (1). The leeward holding member has a plurality of plate-like members whose normal direction is the direction in which the folds of the pleat shape extend, and whose width is narrower toward the upstream side of the airflow,
The plurality of plate-like members are arranged in a line in the thickness direction at a pitch of 15 mm or more and 35 mm or less,
The air filter unit according to claim 3. The filter medium has a fold on the leeward side, and has first pleats, second pleats, and third pleats arranged next to each other,
The plurality of plate-like members include a first plate-like member that maintains a distance between the first pleat and the second pleat, a first plate-like member that maintains a distance between the second pleat and the third pleat, and a first plate member that maintains a distance between the second pleat and the third pleat. a second plate-shaped member that is a separate member independent of the shaped member;
The air filter unit according to claim 4. The plate member has a contact portion that contacts the leeward side surface of the filter medium, and a non-contact portion that does not contact the leeward side surface of the filter medium,
The melting point of the contact portion is lower than the melting point of the non-contact portion.
The air filter unit according to any one of claims 1, 2, 4, and 5. The thickness of the plate member is 0.8 mm or more and 2.0 mm or less,
The air filter unit according to any one of claims 1, 2, 4, 5, and 6. The windward holding member (50) is located only upstream of the center of the filter medium in the airflow passing direction.
The air filter unit according to any one of claims 1 to 7. The thickness of the filter medium is 0.3 mm or more,
The air filter unit according to any one of claims 1 to 8. The leeward holding member is bonded to a surface of the filter medium on the leeward side of the airflow.
The air filter unit according to any one of claims 1 to 9. The filter layer includes a main collection layer (31b) and an upwind filter layer (31a) arranged on the windward side of the airflow with respect to the main collection layer.
The air filter unit according to any one of claims 1 to 10 . The main collection layer is a porous membrane containing a fluororesin,
The air filter unit according to claim 11 .

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