JP2021028057A - Air filter unit - Google Patents

Abstract

To provide an air filter unit which can widely secure an area into which dust in a filter material can be collected while holding a pleat shape of the filter material.SOLUTION: An air filter unit has a main collection layer (31b) and an air permeability support layer (31c) higher than the main collection layer (31b) in rigidity, and arranged at a leeward side of an airflow rather than the main collection layer (31b), and also comprises a filter pack (20) being a pleat-shaped air-filter filter material (30), and interval holding members for holding a pleat interval of the filter pack (20). The air filter unit sets a value which is obtained by dividing an area ratio of a portion contacting with a windward holding member (50) at a face at a windward side of the air-filter filter material (30) by an area rate of a portion not contacting with a leeward holding member (60) at a face at a leeward side of the air-filter filter material (30) to a value which is larger than 0 and smaller than 1.0 while having the leeward holding member (60) and the windward holding member (50) as the interval holding members, or the air filter unit has the leeward holding member (60) as the interval holding member, and does not has the windward holding member (50).SELECTED DRAWING: Figure 6

Description

Regarding the air filter unit.

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 collection efficiency of particles having a predetermined particle size. These are used for different purposes depending on their performance.

These air filters may be used in a pleated shape in order to secure an effective area that can be collected as wide as possible.

As a structure for maintaining the pleated shape of the air filter in this way, for example, as described in Patent Document 1 (Japanese Patent Publication No. 03-054711), the upstream side and the downstream side of the air flow with respect to the pleated filter medium A structure in which a pleated shape is maintained by inserting comb-tooth-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 leeward 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 stabilizer and the filter medium The area where the leeward side surface is in contact with the leeward side stabilizer has the same structure.

However, it is difficult to contribute to the collection of dust in the part of the filter medium covered by the stabilizer on the windward side.

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 medium layer and is arranged on the leeward side of the air flow from the filter medium layer. The spacing member holds the pleated spacing of the filter media. The interval holding member includes an upwind holding member arranged on the leeward side of the filter medium and a leeward holding member arranged on the leeward side of the filter medium, and the upwind holding member on the leeward side surface of the filter medium The value obtained by dividing the area ratio of the contacted portion by the area ratio of the portion in contact with the leeward holding member on the leeward side surface of the filter medium is greater than 0 and less than 1.0, or the interval is maintained. The member has a leeward holding member arranged on the leeward side of the filter medium, and is not arranged on the leeward side of the filter medium.

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 protruding or recessed in the thickness direction.

Further, it is preferable that the distribution of the pressure loss of the filter medium has little variation and the pleated shapes are evenly spaced. If the pleated shape can be maintained at the same distance even during use by using the leeward holding member, the need to use the leeward holding member can be further reduced, and in some cases, it is not used. Will be done. When the upwind holding member is not used, it is not necessary to attach the upwind holding member while adjusting the pleats spacing on the windward side with a jig at the time of assembly.

The upwind holding member has a flat plate shape whose normal direction is the direction in which the pleated crease extends, and is at least on the upstream side of the air flow between the upwind side surfaces of the filter media and the surfaces facing each other. It is preferable that it is located.

In this air filter unit, the pleated shape of the filter medium is held by the leeward holding member, and the area where the leeward holding member is in contact with the leeward surface of the filter medium is the area where the leeward holding member is in contact with the leeward surface of the filter medium. Since the area is smaller than the area covered or the windward holding member is not provided, it is possible to secure a wide surface of the filter medium that contributes to the collection of dust while maintaining the pleated shape of the filter medium. ..

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

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 of the filter medium is reduced or the pleating interval is narrowed as compared with the case where the thickness of the filter medium is less than 0.3 mm. It will be. When the number of pleats is reduced, the area of the filter medium is reduced, but the area where the leeward holding member and the upwind holding member are in contact with the filter medium is suppressed to a small size, and the degree of decrease in the effective filter medium area is suppressed to a small extent. The degree of increase in loss can be kept small. In addition, when the pleats interval is narrowed, the flow velocity in the pleated gap (the part between adjacent pleats) increases, but the pressure loss due to these is reduced by reducing the surface area of the leeward holding member and the leeward holding member. The degree of increase can be suppressed to a small level. Further, since the area on the upstream side of the filter medium has a large effect on the amount of dust retained, it is desirable that the closed area on the upstream side of the filter medium (closed area by the windward holding member or the like) is small. The presence or absence of the leeward 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 of the first aspect or the second aspect, and the leeward holding member is adhered on the leeward side surface of the airflow in the filter medium.

When the shape-retaining member has an upwind-holding member, the upwind-holding member may or may not be adhered to the filter medium.

It should be noted that the adhesion is not limited to the case where the adhesive is cured and cannot be peeled off, or the case where the intervening resin is melted and then cured and cannot be peeled off, and the adhesive is peeled off by applying an external force. Adhesives that can be used are also included.

This air filter unit can suppress changes in the pleated shape by enhancing the holding function by the shape holding member. As a result, it is possible to reduce the situation in which the distance between the surfaces facing each other on the windward side of the filter medium is narrowed and the function as the filter medium is suppressed.

The air filter unit according to the fourth aspect is any of the air filter units from the first aspect to the third aspect, and the leeward holding member has a plurality of plate-shaped members. The plate-shaped member has a flat plate shape whose normal direction is the direction in which the pleated fold extends. The plate-shaped member has a shape that is narrower toward the upstream side of the air flow. The plurality of plate-shaped members are arranged side by side at a pitch of 15 mm or more and 35 mm or less in the plate thickness direction.

It is more preferable that the plurality of plate-shaped members are arranged side by side at a pitch of 17 mm or more and 31 mm or less in the plate thickness direction.

For the plurality of plate-shaped members, the value obtained by dividing the pitch of arrangement in the plate thickness direction by the plate thickness of the plate-shaped members 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 keep the structural resistance small.

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

Since the thickness of the plate-shaped member of this air filter unit is 0.8 mm or more, it is advantageous for maintaining the shape of the filter medium, and since the thickness of the plate-shaped member is 2.0 mm or less, the plate-shaped member itself has ventilation resistance. Can be suppressed.

The air filter unit according to the sixth aspect is the air filter unit of the fourth aspect or the fifth aspect, and the filter medium has a crease on the leeward side. The filter medium has first pleats, second pleats, and third pleats arranged so as to be adjacent to each other. The plurality of plate-shaped members include a first plate-shaped member and a second plate-shaped member which is a separate member independent of the first plate-shaped member. The first plate-shaped member maintains a distance between the first pleats and the second pleats. The second plate-shaped member maintains a distance between the second pleats and the third pleats.

In this air filter unit, since the first plate-shaped member and the second plate-shaped member are separate members independent of each other, the shape of each pleat formed by each plate-shaped member is maintained while each pleat is sequentially formed. It becomes possible to make it.

When a plurality of plate-shaped members independent of each other are adhered only to the leeward side of the pleats to maintain the pleated shape, for example, the filter media can be expanded and contracted in the pleated folding direction (the direction in which the filter media folds in the pleated pack state). Therefore, when the air filter unit is incorporated into the housing, it is possible to absorb an error in the direction in which the filter media folds.

The air filter unit according to the seventh aspect is the air filter unit of the sixth aspect, and the plate-shaped member does not come into contact with the contact portion that contacts the leeward surface of the filter medium and the leeward surface of the filter medium. It has a contact portion and. 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-shaped member and joining it to the filter medium.

The air filter unit according to the eighth aspect is any of the air filter units from the first aspect to the seventh aspect, and the interval holding member has an upwind holding member. The windward holding member has a plurality of spacing holding portions and a connecting portion. Spacing portions are located between the pleats. The connecting portion connects a plurality of spaced portions to each other.

This air filter unit is capable of maintaining a pleated-shaped pleated spacing in the windward portion of the filter medium.

The air filter unit according to the ninth aspect is the air filter unit according to the eighth aspect, and the windward holding member is located only on the upstream side of the center of the filter medium in the passing direction of the air flow.

The windward holding member is preferably located only on the upstream side of the center of the air filter unit in the airflow passing direction.

The windward holding member is preferably provided only in a range of 20% or less of the total length of the filter medium in the passage direction of the air flow from the upstream end of the filter medium, and only in a range of 10% or less of the total length. It is more preferable that it is provided.

In this air filter unit, it is possible to keep the pleated spacing at the upstream end of the filter medium by the windward holding member, and to keep the degree to which the windward holding member itself becomes ventilation resistance small.

The air filter unit according to the tenth viewpoint is any of the air filter units from the first viewpoint to the ninth viewpoint, and the area ratio of the portion of the windward side surface of the filter medium to which the windward holding member is in contact is determined. It is 1.0% or less.

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

The air filter unit according to the eleventh viewpoint is any of the air filter units from the first viewpoint to the tenth viewpoint, and the area ratio of the portion of the leeward side surface of the filter medium in contact with the leeward holding member is 2. It is 5.5% or more and 6.0% or less.

This air filter unit can sufficiently support the pleated shape from the leeward side even when the pleated filter medium is ventilated, and secure a sufficiently wide area through which the air flow can pass in the filter medium.

The air filter unit according to the twelfth viewpoint is any of the air filter units from the first viewpoint to the eleventh viewpoint, and the filter medium layer is on the windward side of the main collection layer and the airflow with respect to the main collection layer. It has an arranged windward filter medium layer.

This air filter unit can capture relatively large dust by the windward filter medium layer arranged on the windward side with respect to the main collection layer, so that clogging of the main collection layer can be suppressed. Will be possible.

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

This air filter unit can capture even relatively small dust.

The external perspective view of the inflow port side which shows one Embodiment of an air filter unit. The external perspective view of the outlet side which shows one Embodiment of an air filter unit. External perspective view of the air filter pack. Schematic cross-sectional configuration diagram of the air filter filter medium. A side view showing how the air filter pack is held by the upwind holding member and the leeward holding member. Top view showing how the air filter pack is held by the upwind holding member and the leeward holding member. Top view of the upwind holding member. Top view of the leeward holding member.

Hereinafter, the air filter unit will be specifically described with reference to examples, but these descriptions do not limit the contents of the present disclosure.

(1) Air filter unit 1
FIG. 1 shows an overview perspective view of the air filter unit 1 on the inflow port side. FIG. 2 shows an overview perspective view of the air filter unit 1 on the outlet side.

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

The frame body 10 may be made of aluminum, an aluminum alloy, or a resin, as long as it can store and hold the air filter pack 20 inside.

The frame 10 has large openings on the front side (inlet) and the rear side (outlet) in the ventilation direction so that the waveform of the air filter pack 20, which will be described later, appears when viewed from the direction perpendicular to the ventilation direction. Accommodates the air filter pack 20. The accommodation direction of the air filter pack 20 is not particularly limited, but the air filter pack 20 is accommodated so that the waveform of the air filter pack 20 appears in the top view, that is, the pleated peaks and valleys extend vertically. It is preferably contained.

Here, the air filter pack 20 is housed in the frame body 10 so that the pleated intervals of the air filter filter media 30 are narrowed. Although not particularly limited, it is preferable to improve the sealing property by providing a sealing agent between the end portion of the air filter filter medium 30 and the inner peripheral portion of the frame body 10. Examples of such a sealing agent include those made of resins 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 filter medium 30 has a predetermined shape (pleated filter medium), and has a pleated shape (corrugated shape). ing. In the present embodiment, the mountain fold line extends at the leeward end and the valley fold line extends at the leeward end.

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

The air filter pack 20 preferably has a pleated pitch of 5.5 mm or more and 9.0 mm or less. By setting the pleated pitch within this range, it is possible to secure a sufficiently wide area of the air filter filter medium that can be accommodated in the frame 10 and function while suppressing an increase in the structural resistance of the air filter unit 1. become.

From the viewpoint of securing a sufficiently wide filter medium area, the air filter pack 20 can have a folding height (length L shown in FIG. 5), which is a length in the air flow passing direction, of 50 mm or more, and is 100 mm or more. It is preferably 200 mm or more, and more preferably 200 mm or more. The upper limit of the folding height of the air filter pack 20 can be, for example, 500 mm or less, preferably 400 mm or less. In the air filter unit 1 of the present embodiment, even if the structure is such that the folding height is sufficiently long and the area of the filter medium is secured so that the structural resistance tends to be a problem, the structural resistance is suppressed to a small value. Is possible. Further, when the folding height of the air filter pack 20 is long as described above, the leeward surfaces facing each other are excessively close to each other, especially in the portion downstream from the center in the airflow direction. It is easy for things to come into contact with each other, but even in such a case, by providing the leeward holding member 60, which will be described later, excessive approach and contact between the leeward surfaces can be avoided. While suppressing the increase in pressure loss, it is possible to reduce the locations where the filtration function cannot be exhibited.

The size of the upstream end portion of the air filter pack 20 (inner portion of the inflow port of the frame body 10) and the size of the downstream end portion (inner portion of the outflow port of the frame body 10) are equivalent. It is preferable to have a size.

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

The air filter 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, for example, a porous membrane. The main collection layer 31b is preferably, for example, a porous membrane containing a fluororesin, and more preferably a porous membrane of a fluororesin containing polytetrafluoroethylene as a main component. The polytetrafluoroethylene as the fluororesin may be modified or unmodified. Further, such a porous membrane may be used as a single membrane, or a plurality of such porous membranes may be used in layers. In this case, the plurality of porous membranes may be of the same type or different types.

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

The method for producing 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 used as an example for production. The method will be described. First, in step 1, an unfired film or a semi-fired film made of polytetrafluoroethylene or the like is prepared. Then, in step 2, the unfired film is stretched in the first direction at a predetermined stretching speed under a predetermined temperature environment, and then stretched in the second direction perpendicular to the first direction to form holes. The main collection layer 31b is obtained. Here, in the film of step 1, for example, modified PTFE fine particles and / or homo-PTFE fine particles are mixed with an extrusion aid (liquid lubricant) such as liquid paraffin and naphtha, and a rod-shaped product obtained by paste extrusion is obtained. It is obtained by rolling with a calendar roll or the like and forming it into a film. If necessary, a step of removing the extrusion aid (liquid lubricant) may be provided.

The breathable support material 31c is not particularly limited as long as it is breathable and can support the main collection layer 31b from the downstream side of the air flow and has a higher rigidity (flexural rigidity) than the main collection layer 31b. However, it is preferably a non-woven fabric. The breathable support 31c is preferably adhered to the main collection layer 31b. As for the flexural rigidity, for example, a long test sample having a size of 150 mm × 20 mm is cut out, and a region in the range of 40 mm from one end in the longitudinal direction of the test sample is used as a holding allowance to project horizontally from a horizontal table. Let it stand still, and with the protrusion length of 110 mm at this time as the measurement length, measure the displacement in the vertical direction hanging from the horizontal table due to its own weight, and use the following equation (flexural rigidity [g weight / mm] = packing of filter media). × (measured length) ^4/8 / displacement) may flexural rigidity those calculated by.

Examples of the non-woven fabric include polyethylene terephthalate (PET) fiber non-polyethylene, polybutylene terephthalate (PBT) fiber non-woven, and core-sheath-structured non-woven (PET / PE core / sheath non-woven) in which the core component is PET and the sheath component is polyethylene (PE). ), Core-sheathed non-woven fabric (PET / PBT core / sheathed non-woven) with core component PET and sheath component PBT, core-sheathed non-woven fabric with core component high melting point PET and sheath component low melting point PET (high) Melting point PET / low melting point PET core / sheath non-woven fabric), non-woven fabric made of composite fibers of PET fiber and PBT fiber, non-woven fabric made of composite fiber of high melting point PET fiber and low melting point PET fiber, and the like. As the non-woven fabric, one type or a combination of a plurality of types can be used. As the non-woven fabric, one having heat-sealing property is preferable.

The basis weight of the non-woven 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, more preferably 30 g / m ^2. More than 100 g / m ² or less. The film thickness of the non-woven fabric used for the breathable support material 31c is preferably 0.10 mm or more and 0.60 mm or less.

Further, with respect to the breathable support material 31c, the pressure loss when air is passed 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 is substantially 0. Is more preferable.

Although not particularly limited, for example, the air filter filter medium 30 is a pre-collection layer on the windward side of the main collection layer 31b from the viewpoint of reducing the dust collection load in the main collection layer 31b and suppressing clogging. It is preferable to have 31a (an example of a windward filter medium layer). Specifically, the air filter filter medium 30 preferably has a pre-collection layer 31a, a main collection layer 31b, and a breathable support material 31c in this order from the windward side.

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

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

As for the air filter filter medium 30 as a whole, the pressure loss when air is passed at a flow rate of 5.3 cm / sec is, for example, 60 Pa or more and 200 Pa or less for a flat state having no pleated shape. In addition, the air filter filter medium 30 as a whole, which is not in a pleated shape but in a flat state, collects particles when air containing NaCl particles having a particle diameter of 0.3 μm is passed through at a flow rate of 5.3 cm / sec. The efficiency is preferably 99.99% or more, and the one used as a HEPA filter is preferable. The total thickness of the air filter filter medium 30 is preferably 0.3 mm or more and 1.0 mm or less.

From the viewpoint of suppressing damage caused by the air filter filter medium 30 and suppressing leakage, the air filter filter medium 30 is not embossed to form an uneven shape protruding or dented in the thickness direction. Is preferable.

The air filter filter medium 30 may have a winding habit, for example, by being wound into a roll during manufacturing. When the air filter unit 1 having a high folding height is manufactured by using a relatively thick air filter filter medium 30 having a curl, the air filter filter medium 30 having a pleated shape due to the curl is opposed to the air filter unit 1. The uniformity of the pleated spacing tends to decrease and the structural resistance tends to increase, such as the inflow port inside the part to be narrowed unintentionally, but according to this structure, it is caused by the curl. It is possible to suppress such an increase in structural resistance to a small extent.

(4) Spacing member The pleated shape of the air filter pack 20 is held by a spacing member that holds the spacing between the surfaces of the opposing filter media. Specifically, in the present embodiment, the interval holding member includes 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 the plurality of upwind holding members 50 and the 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) Upwind holding member 50
FIG. 7 shows a plan view of the upwind holding member 50.

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

The upwind connecting portion 51 (an example of the connecting portion) extends in a direction orthogonal to the direction in which the pleated mountain fold line of the air filter pack 20 extends.

The plurality of leeward protrusions 52 (an example of the interval holding portion) are provided side by side at predetermined intervals along the longitudinal direction of the leeward connecting portion 51, and are further leeward side from the leeward side of the leeward connecting portion 51. It extends so as to protrude toward it, and is a part corresponding to the insertion allowance. A portion of the air filter pack 20 in the vicinity of the pleated mountain fold line is held between the plurality of windward protrusions 52. The length of the leeward protrusion 52 in the longitudinal direction of the leeward connecting portion 51 becomes slightly shorter toward the leeward side, whereby the leeward protrusion 52 has a trapezoidal shape. The shape and size of each windward protrusion 52 are the same. Here, both edges of the windward protrusion 52 in the longitudinal direction of the windward connecting portion 51 are in contact with the windward side surface of the air filter filter medium 30, but the downstream end of the windward protrusion 52 is the air filter filter medium. It does not touch 30.

It is preferable that the windward protrusion 52 is provided only on the upstream side 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 folding height of the air filter pack 20, preferably 10% or less, and may be 3% or more. As a result, it is possible to keep the contact area between the upwind holding member 50 and the air filter filter medium 30 small while keeping the pleated spacing at the windward end of the air filter pack 20 constant. The upwind holding member 50 is applied so as to be orthogonal to the pleated folds of the conventionally used pleated shape because the ability to hold the gap is low when the pleated spacing of the air filter pack 20 is wide. It is preferable that it is not like 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 upwind holding member 50 to 0.8 mm or more, the pleated spacing can be stably maintained, and by setting the thickness of the upwind holding member 50 to 2.0 mm or less, the upwind holding member It is possible to suppress the degree to which the 50 itself becomes the structural resistance of the air filter unit 1.

The plurality of windward holding members 50 are preferably arranged side by side at intervals of 15 mm or more and 35 mm or less in the plate thickness direction from the viewpoint of keeping the structural resistance small while stably maintaining the pleated spacing. It is more preferable that they are arranged 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 the 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 surface of the air filter filter medium 30 / the area of the windward surface of the air filter filter medium 30 is preferably 1.0% or less. More preferably, it is 5% or less. As a result, it is possible to reduce the area of the area on the windward side of the air filter filter medium 30 that is less likely to contribute to the collection of dust due to the contact of the plurality of windward holding members 30.

The windward holding member 50 may be fixed to the air filter pack 20 via an adhesive, or may be fixed to the air filter pack 20 without 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 has a plurality of leeward holding members 60 arranged in a direction orthogonal to the direction in which the pleated mountain fold lines and valley fold lines of the air filter pack 20 extend. Further, when the air filter unit 1 is a set of a plurality of leeward holding members 60 arranged in a direction orthogonal to the direction in which the pleated mountain fold line or valley fold line extends, the set is pleated. It is provided side by side along the direction in which the mountain fold line and valley fold line extend.

The leeward holding member 60 is a plate-shaped member whose normal direction is the direction in which the pleated mountain fold line or valley fold line of the air filter pack 20 extends, and is from the direction in which the pleated mountain fold line or valley fold line extends. When viewed, the upstream side has a thin trapezoidal shape. The leeward holding member 60 may have a thin triangular shape on the upstream side.

The leeward holding member 60 is perpendicular to the airflow in a direction perpendicular to the direction in which the pleated mountain fold line or valley fold line of the air filter pack 20 extends from the upstream side edge portion 61 and the upstream side edge portion 61. It has a downstream side edge portion 62 having a long width in the direction, and a first side edge portion 63 and a second side edge portion 64 extending between the upstream side edge portion 61 and the downstream side edge portion 62. Here, the downstream side edge portion 62 of the leeward holding member 60 is not in contact with the downstream surface of the air filter filter medium 30, and the first side edge portion 63 and the second side edge portion of the leeward holding member 60. 64 is in contact with the downstream surface of the air filter filter medium 30. The upstream side edge portion 61 of the leeward holding member 60 may or may not be in contact with the surface on the downstream side of the air filter filter medium 30.

When the upwind holding member 50 is used, the area ratio of the portion of the air filter filter medium 30 on the leeward side where the upwind holding member 50 is in contact is set on the leeward side of the air filter filter medium 30. The value obtained by dividing by the area ratio of the portion of the surface where the leeward holding member 60 is in contact is greater than 0 and less than 1.0.

The first side edge portion 63 and the second side edge portion 64 of the leeward holding member 60 maintain the pleated shape of the air filter pack 20, and the distance between the leeward surfaces of the air filter filter medium 30 is shortened. From the viewpoint of suppressing (the shape of the airflow inlet is narrowed), it is preferable that the air filter is adhered to the downstream surface of the filter medium 30. Here, the state in which the leeward holding member 60 and the air filter filter medium 40 are adhered to each other is not particularly limited, and depending on the application of airflow during use, they are adhered to each other to the extent that they are not separated from each other and can be peeled off without being destroyed. It may be in a state where it is adhered with an adhesive to the extent that it can be formed, it may be in a state where it is hardened with an adhesive and cannot be peeled off, or the intervening resin is melted. It may be in a state where it is cured later and cannot be peeled off from each other. When an adhesive is used, for example, polyester resin, polyurethane resin, polyamide resin and the like can be used. In the case where the resin is melted and cured, the first side edge portion 63 and the second side edge portion 64 of the leeward holding member 63 are separated from the main body portion separately from the resin constituting the main body portion of the leeward holding member 60. May be composed of a resin having a low melting point. As a result, when the leeward holding member 60 is heated, only the resin portions constituting the first side edge portion 63 and the second side edge portion 64 are melted and air is suppressed while suppressing the deformation of the main body portion of the leeward holding member 60. It can be adhered to the filter medium 30 and can be easily manufactured.

A plurality of the leeward holding members 60 are arranged so as to be arranged in the plate thickness direction on the leeward side of each mountain fold line of the air filter pack 20 in order to maintain the pleated shape of the air filter pack 20. Specifically, on the leeward side of one pleated portion of the air filter pack 20, a plurality of leeward holding members 60 are arranged at predetermined intervals in the plate thickness direction. As a result, it is possible to prevent the space between the surfaces on the downstream side of the air filter filter medium 30 of the air filter pack 20 from being narrowed when the air flow passes through.

The length of the leeward holding member 60 in the airflow direction is preferably half or more, more preferably 80% or more of the folding height of the air filter pack 20, and is substantially the same as the folding height of the air filter pack 20. It is more preferable that they are the same. As a result, it becomes possible to more reliably suppress the contact between the wind surfaces of the air filter pack 20 facing each other.

The plate thickness of the plurality of leeward holding members 60 can be, for example, 0.8 mm or more and 2.0 mm or less, and may be the same as the leeward holding member 50. By setting the thickness of the leeward holding member 60 to 0.8 mm or more, the pleated spacing can be stably maintained, and the bonding state is stabilized by sufficiently securing the bonding surface when bonding to the filter medium. Can be made. Further, by setting the thickness of the leeward holding member 60 to 2.0 mm or less, it is possible to suppress the degree to which the leeward holding member 60 itself becomes the structural resistance of the air filter unit 1.

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

From the viewpoint of suppressing the total structural resistance of the plurality of leeward holding members 60 and the plurality of leeward holding members 50 to be small, each leeward holding member 60 is attached to each leeward holding member 50 when viewed from the airflow direction. On the other hand, it is preferable that they are arranged at overlapping positions on the leeward side.

Further, the contact area between the plurality of leeward holding members 60 and the leeward surface of the air filter filter medium 30 / the area of the leeward surface of the air filter 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 the narrowing of the distance between the facing surfaces on the leeward side of the air filter filter medium 30, and by setting it to 6.0% or less, the air filter filter medium 30 It is possible to keep the area of the portion that is difficult to contribute to the collection of dust small.

In addition, in the plurality of leeward holding members 60, for example, like the leeward holding member 50, the portions holding the adjacent pleats spacing (each leeward holding member 60) are integrated via a connecting portion or the like. It may be configured. However, for example, when the air filter filter medium 30 is conveyed while being tensioned by a tension roller to manufacture the air filter pack in a continuous process, the plurality of leeward holding members 60 are individually separated without damaging the air filter filter medium 30. From the viewpoint that it can be adhered and fixed to the air filter filter medium 30 and mass production is easy, it is preferable that the plurality of leeward holding members 60 are provided as independent members. Specifically, first, either the first side edge portion 63 or the second side edge portion 64 of the leeward holding member 60 is placed on the surface of the flat air filter filter medium 30 which is conveyed while applying tension. The plurality of leeward holding members 60 are fixed on the surface of the air filter filter medium 30 while fixing the portion of the leeward through an adhesive or the like. After that, an adhesive or the like is applied to the other portion of the first side edge portion 63 or the second side edge portion 64 of the leeward holding member 60 that is not fixed, and the upstream side of the leeward holding member 60 of the air filter filter medium 30 is applied. By folding the portion facing the edge portion 61, it is possible to realize a state in which both the first side edge portion 63 and the second side edge portion 64 of the leeward holding member 60 are adhered to the air filter filter medium 30. preferable.

(5) Features The conventional air filter unit is provided with a pre-filter layer that collects coarse particles on the upstream side of the collection layer of the high-performance filter medium that collects fine particles from the viewpoint of extending the life of the air filter filter medium. May be done. However, if the thickness of the entire filter medium increases, the number of folds in the air filter unit decreases and the pressure loss of the filter medium also increases, so that the pressure loss also increases as the air filter unit and the operating cost increases. It ends up.

Further, the air filter filter medium is usually manufactured in a roll shape by being wound around a core material, but the roll-shaped filter medium may have a curl habit. In particular, the thicker the filter medium, the greater the curl tendency. When an air filter unit having a pleated shape is manufactured using this filter medium having a curl, a holding member is used in order to suppress the curl 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 that it is required to maintain the pleated shape while suppressing an increase in the pressure loss of the air filter filter medium.

Here, a separator filter, a V-bank filter, an embossed filter, and a stabilizer filter will be examined as a conventionally used pleated air filter unit. The separator filter maintains the pleated spacing by inserting an aluminum separator in which a thin aluminum plate is woven into an uneven shape between the pleats. The V-bank filter is a filter frame in which a plurality of pleated filters having a low folding height, in which the pleated intervals are maintained by hot melt beads applied to the surface of the filter medium, are inclined to each other and housed in the filter frame. The embossed filter is obtained by processing the embossed filter medium into a pleated shape to maintain the pleated distance between the filter media facing each other by the embossed protrusions. The stabilizer filter is one in which the stabilizer is inserted to maintain the pleating interval.

Of the above, with regard to the "separator filter", the presence of the aluminum separator increases the resistance to the air flow, and it is difficult to keep the pressure loss of the air filter unit low.

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

Further, in the case of using an "embossed filter" using a filter medium having a roll-shaped curl, it is difficult to suppress an increase in structural resistance due to the curl, and the pressure loss of the air filter unit also occurs. It becomes difficult to keep it low.

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

However, when a stabilizer is used in an air filter unit having a large pleated folding height, it may be difficult to sufficiently insert the stabilizer into the pleated filter medium. Specifically, it is relatively easy to insert the stabilizer into the pleated air filter filter medium at the stage of first inserting it, but the stabilizer to be inserted later is pushed in so as to correct the filter medium. Therefore, a relatively large insertion force is required when inserting. Specifically, for example, when the stabilizer is inserted first on the leeward side of the pleats and then the stabilizer is also inserted at the opposite position on the leeward side, a large insertion force is required to insert the stabilizer to be inserted later. Become. In particular, the larger the pleated folding height, the more remarkable this tendency becomes. When such a large insertion force is required, a stabilizer having high rigidity is required in consideration of the material and thickness of the filter medium in order to prevent the pleated shape from being deformed. Moreover, when inserting the stabilizer, especially when inserting the stub riser from both the leeward side and the leeward side, the surface of the filter medium may be damaged. Further, the upstream surface of the filter medium is blocked by the stabilizer arranged on the upstream side, and the life of the filter medium is shortened accordingly.

On the other hand, in the air filter unit 1 of the present embodiment, the pleated shape of the air filter filter medium 30 is held by a plurality of leeward holding members 60, and the leeward holding member 50 is the windward surface of the air filter filter medium 30. The area in contact with the leeward holding member 60 is smaller than the area in which the plurality of leeward holding members 60 are in contact with the leeward side surface of the air filter filter medium 30, or the leeward holding member 50 is not provided in the first place. is there. For this reason, the windward surface of the air filter filter medium 30 can be kept to a small extent covered with members other than the filter medium, such as a holding member, and a wide surface that contributes to the collection of dust can be secured, and pleats. The shape is sufficiently held by a plurality of leeward holding members 60, the uniformity of each pleated interval is ensured even during ventilation, and the structural resistance is suppressed to be small, so that the pressure loss as the air filter unit 1 can be suppressed to a low level. ing. Moreover, the plurality of leeward holding members 60 are provided in groups of pleats so as to be independent of each other, and if each leeward holding member 60 is inserted into and attached to the pleated air filter filter medium 30. Even if there is, it can be easily performed with a smaller force than when a comb-shaped stabilizer is used, and damage to the air filter filter medium 30 can be suppressed. Further, even when the pleated shape is neatly secured by using the air filter filter medium 30 having a curl, the damage can be suppressed to a small extent.

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

On the other hand, as the shape holding member, the upwind holding member 50 in the above embodiment may not be provided, and the shape may be held by a plurality of leeward holding members 60.

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

On the other hand, for example, the means for maintaining the pleated shape on the windward side is not limited to the case of using a member such as resin, and is hot so as to intersect the mountain fold line of the air filter pack 20, for example. The pleated shape may be maintained by applying a melt resin.

(6-3) Other Embodiment C
In the above embodiment, 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 filter medium 30, is used as one member has been described as an example.

On the other hand, for example, one pleated interval in the pleated shape of the air filter filter medium 30 may be secured by a plurality of members such as two members. Specifically, in the pleated air filter filter medium 30, the first member fixed to one surface of the filter media surfaces facing each other by adhesion or the like and the first member fixed to the other surface of the facing filter media surfaces by adhesion or the like. By connecting with the fixed second member, the same function as the leeward holding member 60, which is one member of the above embodiment, may be exhibited. Here, the first member and the second member may be, for example, right-angled triangular plate-shaped members having the same size and shape.

In this case, the first bonded portion of the first member other than the portion bonded to the filter medium surface and the second bonded portion of the second member other than the portion bonded to the filter medium surface are , Will be bonded to each other via an adhesive or the like. In this case, the opposite relationship (with the S pole) is made so that the first bonded portion of the first member and the second bonded portion of the second member can be attracted to each other by magnetic force and bonded to each other. An adhesive or the like containing a magnetic material to which a magnetic force of (N-pole relationship) is applied may be applied.

Further, for example, when the air filter pack is manufactured in a continuous process by transporting the air filter pack while applying tension by a tension roller, the air filter filter medium 30 in a flat state is crossed and orthogonal to the crease. , A hot melt resin having magnetism or containing a magnetic material may be applied. Then, after that, the magnetic materials to be bonded to each other may be magnetized so as to be subjected to magnetic forces having opposite relationships to each other so as to be bonded.

As a result, those located at the portions facing each other through the crease can be attracted to each other by magnetic force and joined to each other. This makes it possible to easily perform the folding work when the pleated shape is secured by the continuous process.

Hereinafter, the contents of the present disclosure will be specifically described with reference to Examples.

There were two types of air filter filter media used in each Example and Comparative Example (excluding Comparative Example 2), one having a thickness of 0.35 mm and the other having a thickness of 0.81 mm. The air filter filter medium having a thickness of 0.35 mm was obtained by laminating PET / PE core-sheath spunbonded non-woven fabric, PTFE stretched membrane (thickness 10 μm), and PET / PE core-sheath spunbonded non-woven fabric (thickness 0.2 mm) in this order from the wind side. It was a thing. The air filter filter medium having a thickness of 0.81 mm was a laminate of PP melt blown non-woven fabric, PTFE stretched film (thickness 100 μm), and PET thermal bond non-woven fabric (thickness 0.3 mm) in this order from the windward side.

The frame of the air filter unit of each of the examples and the comparative examples is rectangular as described in the above embodiment, has a rectangular inflow port and an outflow port, and has a pleated mountain fold line. A structure was used in which the pleated valley fold line extended in the vertical direction near the inlet and the pleated valley fold line extended in the vertical direction near the outlet.

Further, 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 embodiment, the one having the shape of the leeward holding member 60 described in the above embodiment is used, and the arrangement pitch in the plate thickness direction is changed while the thickness is 1 mm. The leeward holding member 60 in each embodiment has an upstream side edge portion 61 having a width of 0.44 mm, a downstream side edge portion 62 having a width of 5.34 mm, and a length in the airflow direction of 274.38 mm. there were. Further, in each embodiment, the actual width of the air filter pack 20 was 116 mm, and 3 mm on the left and right was used for sealing the frame body.

In Comparative Example 1, instead of the upwind holding member 50 in Example 3, an aluminum separator was used on the leeward side of the air filter filter medium, and on the leeward side of the air filter filter medium, the same leeward holding member 60 as in Example 3 was used. It was assumed that it was used. This aluminum separator had a length of 264 mm in the airflow direction, 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 adopts 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 generated in the inner height of 110 mm, and in the downstream part, 3 on the upstream side is formed in the inner height of 110 mm. The zigzag shape was formed so as to generate twice as many peaks. 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 having a thickness of 0.38 mm was used. In Comparative Example 2, the same aluminum separator as that used in Comparative Example 1 was used on the windward side of the air filter filter medium as in Comparative Example 1. In Comparative Example 2, on the leeward side of the air filter 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 leeward side of the air filter filter medium was used in a different direction. There was.

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

The terms in the table are as follows.

The "pressure loss of the filter unit" (Df) is ^{obtained by accommodating the air filter filter medium 30 having an area of Af (m 2} ) in the frame 10 in the form of an air filter pack 20. This is the pressure difference between the front and rear of the air filter unit 1 when 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). 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 is set to 2.9 (m / s).

The “filter medium pressure loss” (D0) is the pressure before and after the air filter filter medium 30 when air is passed through the flat air filter filter medium 30 which does not have a pleated shape at a flow rate of 0.053 m / s. The difference is D0.

The "filter medium resistance" (Dm) is the pressure difference between the air filter filter medium 30 having an ^{area of Af (m 2} ) and the air filter filter medium 30 before and after passing air at a rated air volume Q (m ^{3 / s).} This is a value obtained as filter media resistance (Dm) = D0 × (Q / Af) /0.053.

The “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 with Comparative Example 1, in the above-mentioned Example 3, since the upwind support member 50 is changed to the aluminum separator as described above, the contact area with the air filter filter medium is different, and the contact area / air filter filter medium is different. The value of the area of was 0.12% in Example 1 and 14.4% in Comparative Example 1. Here, the windward support member 60 is common to the third embodiment and the first comparative example, and the contact area with the air filter filter medium is 3.3%. Then, the ratio of the area ratio between the leeward side and the leeward side (the ratio of the contact area on the leeward side / the ratio of the contact area on the leeward side) is 0.036 (= 0.12% / 3.3) in Example 3. %), Which is 4.36 (= 14.4% / 3.3%) in Comparative Example 1 and a small value in Example 3. Then, in this Example 3, the structural resistance can be suppressed to be smaller than that in Comparative Example 1. In Comparative Examples 2 to 4, aluminum separators are arranged on both the leeward and leeward tails, but the value of the structural resistance is larger than that of Examples 1 to 11.

In Example 5-8, only the pitch of the leeward holding member 60 is different, but it can be seen that the structural resistance is the minimum in the case of Example 7 in which the pitch is 22 mm.

Although the embodiments of the present disclosure have been described above, it will be understood that various modifications of the forms and details are possible without departing from the purpose and scope of the present disclosure described in the claims. ..

1 Air filter unit 10 Frame 20 Air filter pack (filter medium)
30 Air filter filter medium (filter medium)
31a Pre-collection layer (filter medium layer, windward filter medium layer)
31b Main collection layer (filter medium layer)
31c Breathable support material (support layer)
50 Windward holding member (interval holding member)
51 Upwind connecting part (connecting part)
52 Windward protrusion (interval holding part)
60 Downwind holding member (interval holding member)

Jikkenhei 03-054711

Claims (13)

A pleated filter medium (30, 20) having a filter medium layer (31b) and a support layer (31c) having a higher rigidity than the filter medium layer and arranged on the leeward side of the air flow than the filter medium layer. When,
At least one spacing member (50, 60) for holding the pleated spacing of the filter medium, and
With
The interval holding member includes an upwind holding member (50) arranged on the leeward side of the filter medium and a leeward holding member (60) arranged on the leeward side of the filter medium. The value obtained by dividing the area ratio of the portion in contact with the leeward holding member on the leeward side surface by the area ratio of the portion in contact with the leeward holding member on the leeward side surface of the filter medium is from 0. Greatly less than 1.0
Or
The interval holding member has a leeward holding member (60) arranged on the leeward side of the filter medium, and is not arranged on the leeward side of the filter medium.
Air filter unit (1). The thickness of the filter medium is 0.3 mm or more.
The air filter unit according to claim 1. The leeward holding member is adhered on the leeward side surface of the airflow in the filter medium.
The air filter unit according to claim 1 or 2. The leeward holding member has a plurality of plate-shaped members having a normal direction in which the pleated crease extends and having a narrower width toward the upstream side of the air flow.
The plurality of plate-shaped members are arranged side by side at a pitch of 15 mm or more and 35 mm or less in the plate thickness direction.
The air filter unit according to any one of claims 1 to 3. The thickness of the plate-shaped member is 0.8 mm or more and 2.0 mm or less.
The air filter unit according to claim 4. The filter medium has creases on the leeward side, and has first pleats, second pleats, and third pleats arranged so as to be adjacent to each other.
The plurality of plate-shaped members maintain a distance between the first plate-shaped member that holds the distance between the first pleats and the second pleats, and the distance between the second pleats and the third pleats, and the first plate. Includes a second plate-shaped member, which is a separate member independent of the shaped member.
The air filter unit according to claim 4 or 5. The plate-shaped member has a contact portion that contacts the leeward surface of the filter medium and a non-contact portion that does not contact the leeward 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 claim 6. The space holding member has the windward holding member (50).
The windward holding member has a plurality of spacing holding portions (52) located between the pleats, and a connecting portion (51) connecting the plurality of spacing portions.
The air filter unit according to any one of claims 1 to 7. The windward holding member (50) is located only on the upstream side of the center of the filter medium in the passing direction of the air flow.
The air filter unit according to claim 8. The area ratio of the portion in contact with the windward holding member on the windward surface of the filter medium is 1.0% or less.
The air filter unit according to any one of claims 1 to 9. The area ratio of the portion of the leeward surface of the filter medium to which the leeward holding member is in contact is 2.5% or more and 6.0% or less.
The air filter unit according to any one of claims 1 to 10. The filter medium layer has a main collection layer (31b) and a windward filter medium 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 11. The main collecting layer is a porous membrane containing a fluororesin.
The air filter unit according to claim 12.

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