Patent Description:
Filters are widely used in vehicles. It is e.g. well known to provide an air filter for cleaning intake air for use in an internal combustion engine. Other equipment and components in the vehicle, such as a e.g. compressor for the brake system, may also use clean air from an air filter. Besides air filters, there are other types of filters in a vehicle, e.g. oil filters. The filters can be designed in many different shapes and have various configurations.

An air filter, or an air filter system, typically comprises an air filter element comprising a filter body through which the air is filtered, and a filter housing in which the air filter element is installed. The air filter element is typically replaced on a regular basis to keep the performance of the air filter system, and of the equipment and components utilizing the filtered air, at a desired level.

When the air filter element is to be replaced (or be subject to maintenance), the air filter element is removed from the filter housing, and a new (or cleaned) air filter element is inserted and installed into the filter housing. One particular problem when installing the air filter element in the filter housing is to align the air filter element within the filter housing. This is especially cumbersome for air filter systems in which the outlet of the air filter element needs to be aligned with the corresponding outlet of the filter housing, or when the air filter system comprises two oppositely arranged outlets supplying clean air to e.g. both the internal combustion engine and an auxiliary component, as e.g. disclosed in <CIT> and <CIT>, and the air filter element needs to be aligned in the filter housing so the first and second outlets of the air filter element aligns with the first and second housing outlets, respectively. For example, <CIT>, describes a filter element having a tubular shape defining an inner space, a first outlet in communication with the inner space and a second outlet in communication with the inner space, wherein the second outlet has an offset position in relation to the first outlet in a transversal direction of the filter element. Many air filter elements and corresponding filter housings, as e.g. disclosed in <CIT>, are also complex and bulky, leading to extended assembly time and inefficient use of space. Moreover, the bulkiness may also have a negative effect on noise optimized tuning of the intake system.

There is thus a need in the industry for an improved air filter system.

It is an object of the present disclosure to at least to some extent alleviate the shortcomings discussed above in relation to known filters, and to improve an air filter element and air filter housing, especially for the installation of the air filter element relative the air filter housing.

According to at least a first aspect of the present invention, an air filter housing is provided, according to claim <NUM>.

The air filter housing comprises an inner housing space adapted to receive an air filter element, the air filter housing comprising a first housing end and a second housing end located axially opposite the first housing end in relation to the inner housing space, and an outlet pipe extending from the second housing end axially into the inner housing space, the outlet pipe having a centre axis and an opening configured to receive clean air from the inner housing space, wherein at least an axial portion of the outlet pipe has a cross-sectional area along a geometrical plane perpendicular to the centre axis which is tapering.

Hereby, the air filter housing can be adapted to connect to air filter elements having a corresponding structure. Thus, at least the insertion and housing of an air filter element in/into the air filter housing is improved.

According to at least one example embodiment, the axial portion of the outlet pipe is configured and arranged to mate with a corresponding opening of the air filter element. According to at least one example embodiment, the outlet pipe, such as the whole outlet pipe, is configured and arranged to mate with the corresponding opening of the air filter element.

The inventors have realized that by having a tapering cross-sectional area of the outlet pipe, or as specified above, a tapering cross-sectional area of at least said axial portion of the outlet pipe, the outlet pipe acts as a fixation element relative an air filter element, when the air filter element is installed into the air filter housing. That is, the tapering cross-sectional area prevents the air filter element to move in the radial plane, such as e.g. prevents the air filter element to rotate within the air filter housing, and thus, fixates, or locks, the air filter element in the radial plane (i.e. a geometrical plane coinciding or being parallel to said cross-sectional area of the outlet pipe or axial portion of the outlet pipe). Hereby, the air filter element is locked in at least two directions being perpendicular to each other.

According to at least one example embodiment, the cross-sectional area is tapering with an inclination defined by an angle between two intersecting sides of the cross-sectional area smaller than <NUM> degrees, such as smaller than <NUM> degrees, e.g. between <NUM> degrees and <NUM> degrees.

Thus, according to at least one example embodiment, the axial portion of the outlet pipe is configured to prevent the air filter element to rotate, and/or move in the radial plane, when the air filter element is installed in the air filter housing. Thus, the outlet pipe is configured to at least radially fixate an air filter element installed in the air filter housing.

It should be understood that the axial portion is a portion of the outlet pipe extending axially into the inner housing space. Moreover, it should be understood that the geometrical plane perpendicular to the centre axis is typically a plane in the radial direction of the air filter housing.

It should be understood that the axial direction of the air filter housing is parallel to, or coinciding with, a longitudinal direction of the air filter housing, and that the axial direction of the outlet pipe is parallel to, or coinciding with a longitudinal direction of the outlet pipe. In the embodiment mentioned above, the longitudinal direction of the air filter housing is also parallel to, or coincides with, the longitudinal direction of the outlet pipe.

According to at least one example embodiment, the piping walls defining the cross-sectional area of the outlet pipe, or the axial portion of the outlet pipe, is shaped to have at least two oppositely wall portions angled relative each other. For example, the piping walls may comprise first and second wall portions being parallel to each other, and third and fourth wall portions connecting the first and second wall portions on opposite sides to each other. The first and second wall portions are typically of different lengths, whereby each one of, or at least one of, the third and fourth wall portions is inclined with respect to the longest of the first and second wall portion with an angle of less than <NUM> degrees, typically below <NUM> degrees, e.g. between <NUM> degrees and <NUM> degrees.

According to the invention, the cross-sectional area of the axial portion of the outlet pipe is shaped as a trapezoid, or truncated triangle. Hereby, fixation, or locking, in at least two directions are achieved.

According to at least one example embodiment, the cross-sectional area of the axial portion of the outlet pipe has rounded corners. Hereby, the flow conditions through the outlet pipe is improved.

It should be understood that the cross-sectional area is measured in a geometrical plane, e.g. the radial plane, extending perpendicular to the axial or longitudinal direction of the outlet pipe. Stated differently, the centre axis of the outlet pipe is a normal to said cross-sectional area.

According to at least one example embodiment, the opening of the outlet pipe is sized and dimensioned to match the tapering cross-sectional area of the axial portion.

According to at least one example embodiment, the outlet pipe comprises a first leading edge and a second leading edge, each one of the first and second leading edges at least partly defining the opening, wherein the first and second leading edges are arranged upstream of said axial portion of the outlet pipe.

That is, upstream in relation to the flow of air from the air filter housing, out through the outlet pipe, and further to e.g. auxiliary equipment, such as e.g. brake compressors. In other words, the first and second leading edges are arranged axially further away from the second housing end compared to the axial portion of the outlet pipe. Hereby, one portion of the outlet pipe, i.e. the opening of the outlet pipe, can be adapted based on a first criteria, e.g. noise reduction, while another portion of the outlet pipe, i.e. said axial portion arranged downstream of the opening, can be adapted based on a second criteria, e.g. mating with a corresponding opening/outlet of the air filter element.

According to at least one example embodiment, the first leading edge and/or the second leading edge is configured and arranged to fixate/lock an installed air filter element in the air filter housing, and configured to prevent the air filter element to move in the radial plane and/or rotate within the air filter housing.

According to at least one example embodiment at least one of the first and second leading edges comprises a sinusoidal portion.

A sinusoidal portion may reduce noise travelling through the outlet pipe. The sinusoidal portion is typically formed by peaks and valleys axially distant from each other. In other words, the portion is sinusoidal in a cross section along the axial direction of the outlet pipe.

Stated differently, the first and/or second leading edge is shaped to reduce noise travelling through the outlet pipe. This may e.g. be made by the sinusoidal portion mentioned above.

According to at least one example embodiment, the first leading edge is axially offset to said second leading edge, such that the opening is at least partly extending in the axial direction.

Hereby, the outlet pipe may be installed such that the opening is directed in the inner housing space in a desired manner.

According to at least one example embodiment, the second leading edge is arranged closer to the second housing end compared to the first leading edge. Thus, an axial distance between the second housing end and the first leading edge is larger than an axial distance between the second housing end and the second leading edge. By having the first leading edge axially offset to the second leading edge in this manner, the first leading edge will lead the alignment and interconnection with the corresponding opening of the air filter element. That is, the first leading edge will be the part of the outlet pipe which firstly interacts with the corresponding opening of the air filter element during installation of the air filter element in the air filter housing. Hereby, the fixation, or alignment, of the air filter element in the air filter housing may be carried out in a two-step procedure, firstly the first leading edge will interact with the corresponding opening of the air filter element, to initially align the air filter element in the air filter housing, and secondly, as the outlet pipe is inserted further into the corresponding opening of the air filter element, said axial portion of the outlet pipe will further, or finally, align the air filter element to the air filter housing owing to the matching cross-sectional areas of said axial portion and the corresponding opening of the air filter element.

Stated differently, the outlet pipe comprises a first portion, or an opening portion, which has an open (partly non-bounded) cross-sectional area in the geometrical plane being perpendicular to the axial direction of the outlet pipe, and being at least partly defined by the shape of the first leading edge, and comprises a second portion, or said axial portion, which has a closed (fully bounded) cross-sectional area in the geometrical plane being perpendicular to the axial direction of the outlet pipe. The open cross-sectional area may e.g. be "U-shaped" defined by two vertical legs, and a connecting horizontal leg, where at least one of the vertical legs are inclined relative the horizonal leg. By the combination of having a first portion with an open cross-sectional area leading the insertion of the outlet pipe into the corresponding opening of the air filter element, and having a second portion with a closed cross-sectional area trailing the insertion of the outlet pipe into the corresponding opening of the air filter element, the above mentioned two-step procedure of alignment and fixation of the air filter element to the air filter housing can be realized.

According to at least one example embodiment, the first leading edge comprises a first lateral portion, a second lateral portion, and a transversal portion connecting the first lateral portion with the second lateral portion such that the second lateral portion is located opposite to the first lateral portion in relation to the transversal portion, wherein at least one of the first and second lateral portions are inclined relative the transversal portion with an angle of less than <NUM> degrees, such as e.g. less than <NUM> degrees, e.g. between <NUM> degrees and <NUM> degrees. This arrangement may form the above-mentioned first portion, or opening portion, with the open cross-sectional area. This arrangement may furthermore form at least a sub-portion of the cross-sectional area of the axial portion of the outlet pipe.

By having the above mentioned arrangement wherein at least one of the first and second lateral portions are inclined relative the transversal portion with an angle of less than <NUM> degrees, such as e.g. less than <NUM> degrees, the air filter element may be fixated/aligned in at least two directions as soon as the first leading edge of the outlet pipe is inserted into the corresponding opening of the air filter element. Thus, the first portion, or opening portion, of the outlet pipe may align and fixate the air filter element in the air filter housing in at least two directions upon entering of the first portion into the corresponding opening of the air filter element.

It should be understood that the above mentioned fixation in at least two directions typically refer to as a fixation in the radial plane, or a geometrical plane perpendicular to the axial direction of the outlet pipe.

According to at least one example embodiment, the air filter housing further comprises a radial gasket arranged circumferentially of the outlet pipe, typically downstream of said axial portion. Hereby, the air filter element may be axially fixated to the air filter housing. The radial gasket is typically arranged on the outlet pipe close to, or adjacent to, the second housing end.

According to at least one example embodiment, outlet pipe further comprises a first axial edge portion connecting a first end of the first leading edge with a first end of the second leading edge, and a second axial edge portion connecting a second end of the first leading edge with a second end of the second leading edge, such that the first and second leading edges together with the first and second axial edge portions defines the opening of the outlet pipe. Both the first and second axial edge portions extending axially, or substantially axially, in the inner housing space.

According to at least one example embodiment, the opening is facing away from a centre axis of the air filter housing.

Hereby, the opening is arranged to face the air filter element when the latter is installed in the air filter housing, and may thus receive filtered air directly from the air filter element.

According to at least one example embodiment, the centre axis of the outlet pipe is arranged parallel to the centre axis of the air filter housing, wherein the centre axis of the outlet pipe is offset in relation to the centre axis of the air filter housing in a direction perpendicular to the centre axes.

According to at least one example embodiment, the outlet pipe is adapted for conveying clean air to an auxiliary component of a vehicle. The auxiliary component may e.g. be the brake compressors.

According to at least one example embodiment, the air filter housing further comprises a housing inlet for receiving air, and an engine outlet for conveying clean air to an engine of a vehicle, the engine outlet being located in the first housing end, wherein the outlet pipe and the engine outlet are in communication with the inner housing space, wherein the centre axis of the outlet pipe and the centre axis of the engine outlet are parallel, and arranged at an offset position in relation to one another in a direction perpendicular to the extension of the centre axes.

The engine outlet of the air filter housing may be referred to as a first housing outlet, and the outlet pipe of the air filter housing may be referred to as a second housing outlet.

According to at least one example embodiment, said offset position involves a distance, and preferably is a distance, in the transversal direction of said air filter housing. According to at least one example embodiment, said offset position is a mutual distance as seen in the transversal direction of the air filter housing between a centre point in engine outlet and a centre point in the outlet pipe.

According to at least one example embodiment, the first housing end is located in parallel relationship with the second housing end.

According to at least one example embodiment, a cross-sectional area of the outlet pipe is smaller than a cross-sectional area of the engine outlet. Such cross-sectional area is measured in the same manner as previously descried, i.e. in a geometrical plane being perpendicular to the centre axis of the outlet pipe and engine outlet, respectively. This improves the acoustic response of the air filter housing, and enables a compact design.

According to at least one example embodiment, the air filter housing has a cross-sectional shape which has a first extension in a first direction and a second extension in a second direction, wherein said first extension is greater than said second extension, said second extension preferably being perpendicular to said first extension and that said cross-sectional shape is generally elliptical. The first extension may alternatively be equal to the second extension.

According to at least one example embodiment, the housing inlet is located in an envelope surface of the air filter housing. This enables a compact design of the air filter housing. According to at least one example embodiment, the housing inlet is located in the envelope surface at a position coinciding with the first extension direction. According to at least one example embodiment, the housing inlet is located on an opposite side of a middle point of said air filter housing in relation to said outlet pipe. This enables an increase of the offset position between the housing inlet and of the outlet pipe or second housing outlet.

According to at least one example embodiment, the air filter housing has a tubular shape. This enables a compact design of the air filter housing. According to at least one example embodiment, a direction of said offset position between said engine outlet and the outlet pipe coincides with the first extension direction. According to at least one example embodiment, said engine outlet is located coaxially with said filter housing.

According to at least one example embodiment, the air filter housing further comprising a housing lid, the housing lid comprising, or encompassing, the second housing end of the air filter housing and encompassing the outlet pipe. Moreover, when the air filter element is installed into the air filter housing, and the housing lid closes the inner housing space. This provides for closing and possibly sealing of the air filter housing.

Thus, the air filter housing may be comprised of at least two parts, a first air filter housing part including the first housing end, and a second air filter housing part being the housing lid. Thus, the first air filter housing part is configured to house a majority of the air filter element, and the second air filter housing part is configured to close the air filter element in the inner housing space.

According to at least one example embodiment, the housing lid comprises a protruding pipe portion for connection to an adjoining pipe. The protruding pipe portion may have an extension away from the inner housing space. Having an adjoining pipe connected to the air filter housing provides for an easier attachment to an auxiliary component.

According to at least a second aspect of the invention, an air filter element is provided, according to claim <NUM>.

The air filter element comprising a first end and a second end located opposite to the first end in relation to a longitudinal direction of the air filter element, the air filter element being configured for axial insertion into an air filter housing with the first end leading the axial insertion, wherein the air filter element comprises a first outlet located in the first end and being configured to communicate with a corresponding first housing outlet in the air filter housing, and a second outlet located in the second end and being configured to communicate with a corresponding second housing outlet in the air filter housing, wherein a cross-sectional area of the second outlet is tapering.

Hereby, the air filter element can be adapted to connect to the air filter housing of the first aspect of the invention, as the second outlet is the above-mentioned corresponding opening of the air filter element, and thus has a corresponding cross-sectional area as the second housing outlet, being embodied by said axial portion of the outlet pipe as described in the first aspect of the invention. Thus, at least the insertion and housing of the air filter element in/into the air filter housing is improved. As mentioned above, the first housing outlet may be referred to as an engine housing outlet, and the second housing outlet may be referred to, and embodied by, the outlet pipe.

According to at least one example embodiment, the second outlet is configured and arranged to mate with the second housing outlet, or outlet pipe, of the air filter housing, such that air may flow via the second outlet of the air filter element and the opening of the outlet pipe of the air filter housing. According to at least one example embodiment, the second outlet is configured and arranged to mate with the outlet pipe, such as the whole outlet pipe, of the air filter housing. According to at least one example embodiment, the second outlet is provided with an axial gasket to seal against the outlet pipe.

The inventors have realized that by having a tapering cross-sectional area of the second outlet, the air filter element may be fixated against the air filter housing, as e.g. inner walls of the second outlet may act as a fixation element relative the outlet pipe, when the air filter element is installed into the air filter housing. That is, the tapering cross-sectional area prevents the air filter element to move in the radial plane, or rotate within the air filter housing and thus, fixates, or locks, the air filter element in at least two directions, e.g. locks the air filter element in the radial plane (i.e. a geometrical plane parallel to said cross-sectional area of the outlet pipe or axial portion of the outlet pipe).

Thus, according to at least one example embodiment, the second outlet is configured to prevent the air filter element to rotate, and/or move in the radial plane, when the air filter element is installed in the air filter housing. Thus, the second outlet is configured to at least radially fixate the air filter element when being installed in the air filter housing.

It should be understood that the axial direction of the air filter element is parallel to, or coinciding with, a longitudinal direction of the air filter element. The cross-sectional area of the second outlet is shaped as a trapezoid, or truncated triangle. Hereby, fixation, or locking, in at least two directions are achieved.

According to at least one example embodiment, the cross-sectional area of second outlet has rounded corners. Hereby, the flow conditions through the second outlet is improved.

It should be understood that the cross-sectional area is measured in a geometrical plane, e.g. the radial plane, extending perpendicular to the centre axis of the second outlet (the centre axis may run along the axial or longitudinal direction of a pipe, or axial portion encompassing the second outlet). Stated differently, the centre axis of the second outlet is a normal to said cross-sectional area.

According to at least one example embodiment, the second outlet is sized and dimensioned to match the tapering cross-sectional area of the axial portion of the outlet pipe.

It should be understood that the cross-sectional area of the second outlet is typically larger than that of the axial portion of the outlet pipe, as the outlet pipe is to be inserted into the second outlet during installation of the air filter element into the air filter housing.

According to at least one example embodiment, the air filter element comprises a filter body arranged between the first and second ends of the air filter element, the filter body forming an outer sleeve surface configured to receive unfiltered air. The filter body may further comprise an inner sleeve surface configured to discharge filtered air. That is, during use, the filter body is arranged in the air filter element to receive unfiltered air to said outer sleeve, filter the air through the filter body, and discharge or release the filtered air from said inner sleeve. The filter body may e.g. be shaped as a hollow cylinder or hollow cone (i.e. be cylindrical or conical in shape), wherein the outer and inner sleeves form the outer and inner envelope surfaces of such hollow cylinder or cone, respectively.

According to at least one example embodiment, the filter body may be pleated. Hereby, the contact surface between the air and the filter material in the filter body may be increase. Preferably, the filter body is made of a filter material chosen from the group of: paper and cellulose. These materials are common materials and enables low manufacturing costs.

According to at least one example embodiment, the air filter element further comprises a first end panel at the first end of the air filter element, and a second end panel at the second end of the air filter element.

The first outlet of the air filter element is typically adapted for conveying clean air to an internal combustion engine of a vehicle. The second outlet of the air filter element is typically adapted for conveying clean air to an auxiliary component of the vehicle.

According to at least one example embodiment, the air filter element has a tubular shape defining an inner space in communication with the first and second outlets, the first outlet having a first centre axis and the second outlet having a second centre axis parallel and arranged at an offset position in relation to the first centre axis in a direction perpendicular to the first and second centre axes.

This improves the acoustic response when using the air filter element. The offset position involves a distance, and preferably is a distance, in the transversal direction (e.g. radial direction) of the air filter element, the offset position is a mutual distance as seen in the transversal direction of the air filter element between a centre point in the first outlet and a centre point in the second outlet.

According to at least one example embodiment, the first end panel houses the first outlet, and is arranged to block any filtered fluid to exit the air filter element axially through the first end panel, other than through the first outlet. This provides a simple design and for enabling a proper sealing effect between the air filter element and a filter housing when installed therein. Moreover, this provides for a certain air flow and for a desired flow and filtration performance.

According to at least one example embodiment, the second end panel houses the second outlet, and is arranged to block any filtered fluid to exit the air filter element axially through the second end panel other than through the second outlet. This enables a correct fluid flow without any leakage, and thereby an improved filtering performance. Moreover, the acoustic response of the air filter element is improved, as well as a minimising of any interference between the respective flows of fluid through the first and second outlets is achieved. Thus, a controlled flow of filtered air, through the first and second outlets of the air filter element is provided.

According to at least one example embodiment, the air filter element has a cross-sectional shape with a first extension in a first direction and a second extension in a second direction which is perpendicular to said first direction. The first extension may according to one example embodiment greater than the second extension, such that the cross-sectional shape is oval, preferably generally elliptical. This enables locating the second outlet at an offset position in relation to the first outlet at an increased distance compared to for example a circular shape, thereby allowing for a further increased distance between the second outlet and the first outlet in order to improve the acoustic response. The first extension may alternatively be equal to the second extension.

According to at least one example embodiment, the above-mentioned offset position of the second outlet in relation to the first outlet is along the first extension direction. According to at least one example embodiment, the first outlet has a generally cylindrical cross-section. According to at least one example embodiment, the first outlet is located coaxially with the air filter element. According to at least one example embodiment, a cross-sectional shape and dimension of the first outlet is substantially the same as a cross-sectional shape and dimension of the inner space of the air filter element. According to at least one example embodiment, a cross-sectional area of the second outlet is substantially smaller than a cross-sectional area of the inner space of the air filter element. According to at least one example embodiment, a cross-sectional area of the second outlet is substantially smaller than a cross-sectional area of the first outlet. According to at least one example embodiment, a cross-sectional shape of the second outlet is tapering (i.e. substantially the same as a cross-sectional shape of the axial portion of the outlet pipe of the air filter housing), wherein a cross-sectional dimension of the second outlet is substantially smaller than a cross-sectional dimension of the first outlet. This improves the acoustic response of the air filter element, and enables a compact design.

According to at least one example embodiment, the air filter element is adapted to be removably arranged in the air filter housing.

Herby, the air filter element can be removed from the air filter housing, be subject to maintenance, and subsequently re-inserted into the air filter housing. Alternatively, a new air filter element, corresponding to the removed air filter element, can be inserted into the air filter housing. The air filter element may e.g. be configured to be supplied to a filter system of an internal combustion engine in a vehicle.

According to at least a third aspect of the invention, a filter system comprising an air filter element according to the second aspect of the invention, and an air filter housing according to the first aspect of the invention is provided. The second outlet of the air filter element is sized and dimensioned to mate with the outlet pipe of the air filter housing.

Effects and features related to this third aspect of the present invention are largely analogous to those described above in connection with the first and second aspects of the invention. Embodiments mentioned in the first and second aspects of the invention are applicable to this third aspect of the invention.

Thus, the first housing end is arranged adjacent to, and facing, the first end of the air filter element, and the second housing end is arranged adjacent to, and facing, the second end of the air filter element, when the air filter element is housed in said inner housing space of the air filter housing. The air filter element thus comprises an engine outlet (i.e. the first outlet) located in the first end of the air filter element and being configured to communicate with the engine outlet (i.e. the first housing outlet) of the air filter housing, and comprises an auxiliary equipment outlet (i.e. the second outlet) located in the second end of the air filter element and being configured to communicate with the outlet pipe (i.e. the second housing outlet) of the air filter housing. Hereby, the first outlet of the air filter element is coaxial and aligned with the engine outlet of the air filter housing, for conveying clean air to an internal combustion engine, and the above mentioned second outlet of the air filter element is coaxial and aligned with the outlet pipe of the air filter housing for conveying clean air to an auxiliary component.

According to at least one example embodiment, the inner housing shape of the air filter housing is adapted to match to an outer shape of the air filter element. This provides for the air filter housing to correspond to the air filter element, such that a fluid to be filtered is generally evenly spread between the air filter housing and the air filter element to fully utilize the filtering operation of the air filter element. Moreover, the air filter element can snuggly be fitted into the air filter housing.

According to at least one example embodiment, the cross-sectional area of said axial portion of the outlet pipe is sized and dimensioned to correspond to the cross-sectional area of the second outlet of the air filter element, such that the outlet pipe, upon installation of the air filter element in the air filter housing, is inserted into the second outlet.

Hereby, the air filter element is fixated in a radial plane, and is e.g. prevented from rotating relative the air filter housing.

According to at least a further aspect of the invention, a lid of an air filter housing having an inner housing space is provided, according to claim <NUM>. The lid comprises a first surface configured to face the inner housing space, and an outlet pipe extending axially outwardly from the first surface, the outlet pipe having a centre axis and an opening configured to receive clean air from the inner housing space, wherein at least an axial portion of the outlet pipe has a cross-sectional area along a geometrical plane perpendicular of the centre axis which is tapering.

Thus, the lid of the fourth aspect of the invention is analogous to the housing lid described in the first aspect of the invention. Effects and features related to this fourth aspect of the present invention are largely analogous to those described above in connection with the first aspect of the invention. Embodiments mentioned in the first aspect of the invention, applicable to the housing lid of the first aspect of the invention, are applicable to this fourth aspect of the invention.

According to at least one example embodiment, the lid may further comprise a second surface arranged opposite to the first surface, and thus arranged to face away from an inner housing space of the air filter housing.

According to at least a fifth aspect of the present invention, an internal combustion engine is provided. The internal combustion engine comprises a filter system according to the third aspect of the invention.

According to at least a sixth aspect of the present invention, a vehicle is provided, the vehicle comprising an internal combustion engine according to the fifth aspect of the present invention.

With reference to <FIG> a vehicle <NUM>, here embodied as a heavy duty truck <NUM>, is disclosed for which an internal combustion engine system <NUM> of a kind disclosed in the present disclosure is advantageous. However, the internal combustion engine system <NUM> may as well be implemented in other types of vehicles, such as in busses, light-weight trucks, passenger cars, marine applications etc. The internal combustion engine system <NUM> may be based on e.g. a diesel engine, which as such may be running on several different types of fuel, such as diesel or dimethyl ether, DME. Other fuel types are well suited, as well as hybrid systems. The internal combustion engine system <NUM> is provided with an air intake system <NUM> comprising a filter system <NUM> with a filter housing <NUM> holding an air filter element (as shown in e.g. <FIG>) of the kind disclosed herein. The air intake system <NUM> further comprises an air intake pipe <NUM> located upstream of the filter system <NUM>, configured to draw air from the ambient by an air intake <NUM>. The ambient air is most often in need of filtration before being directed towards an inlet of the internal combustion engine system <NUM> and/or any auxiliary use. Downstream the air intake <NUM> and air intake pipe <NUM> is a housing inlet <NUM> arranged in the air filter housing <NUM> to supply air to the air filter element. The air is then filtered by the air filter element and further directed through a housing outlet <NUM> and towards the internal combustion engine system <NUM>. The air filter system <NUM> may further provide filtered air to an auxiliary component (not shown). In such cases the housing outlet <NUM> is a first housing outlet and the air filter housing <NUM> further comprises a second outlet (as shown in e.g. <FIG>). The filter system <NUM> is located in a lower region of the vehicle <NUM> and the air intake <NUM> in a higher region of the vehicle <NUM>. In the depicted embodiment the filter system <NUM> is located directly behind the vehicle cab, whereas the air intake <NUM> is located on top of the vehicle cab at a rear end thereof. The air intake pipe <NUM> is located at the rear end in a generally vertical position of the vehicle cab, and the air filter housing <NUM> is located having its longitudinal, or axial, direction transversal to the driving direction of the vehicle <NUM>.

Initially a description of a first embodiment of the present disclosure will be provided based on <FIG> illustrating an air filter element <NUM>. The air filter element <NUM> is adapted to be removably arranged in a filter housing <NUM> (shown e.g. in <FIG>) and comprises a filter material body <NUM> made of any material that is suited for the filtering operation of the air to be filtered.

The air filter element <NUM> has an extension in a longitudinal direction along a longitudinal centre axis L (which may also be referred to as an axial axis of the air filter element <NUM>), and an extension in a transversal direction in a transversal plane which is perpendicular to the longitudinal direction and the longitudinal centre axis L. Such transversal plane typically includes a radial axis for a tubular, or circular cylindrical, air filter element <NUM> as shown in <FIG>.

The air filter element <NUM> in <FIG> comprising a first end <NUM> and a second end <NUM>. The second end <NUM> is located opposite to the first end <NUM> in relation to the air filter element <NUM> along the longitudinal centre axis L. The air filter element <NUM> further has a first end panel <NUM> at the first end <NUM> and a second end panel <NUM> at the second end <NUM>. As will be described in more detail with reference to <FIG>, but briefly mentioned here, the air filter element <NUM> is configured for axial insertion (i.e. along the longitudinal or axial direction of the air filter housing) into the air filter housing <NUM>, with the first end <NUM> leading the axial insertion. Moreover, the air filter element <NUM> in <FIG> has a circular cylindrical tubular shape defining an inner space <NUM>, wherein a first outlet <NUM> and a second outlet <NUM> are in communication with the inner space <NUM>, as shown in <FIG>. The second outlet <NUM> has here an offset position in relation to the first outlet <NUM> in the transversal direction of the air filter element <NUM>. As seen in <FIG>, the offset position involves a distance, and preferably is a distance, in the transversal direction of the air filter element <NUM>. The offset position is measured as a mutual distance as seen in the transversal direction of the air filter element <NUM> between a centre point in the first outlet <NUM> and a centre point in the second outlet <NUM>. The first outlet <NUM> is located coaxially with the air filter element <NUM>, or stated differently, the centre point of the first outlet <NUM> is located on the longitudinal centre axis L of the air filter element <NUM>. The offset position of the second outlet <NUM> in relation to the first outlet <NUM> is consequently in this embodiment measured as a distance in the transversal direction of the air filter element <NUM> between the longitudinal centre axis L of the air filter element <NUM> and the centre point of the second outlet <NUM>. The first outlet <NUM> is adapted for conveying clean air to the internal combustion engine system <NUM>, and the second outlet <NUM> is adapted for conveying clean air to an auxiliary component, such as brake compressor, which may be located within the internal combustion engine system <NUM>, or in another position in the vehicle <NUM>. In this embodiment, each one of the first outlet <NUM> and the second outlet <NUM>, has an axial extension. Consequently, the first outlet <NUM> has a first centre axis L1 coinciding with the longitudinal centre axis L and a centre point of the first outlet <NUM>, and the second outlet <NUM> has a second centre axis L2 coinciding with the centre point of the second outlet <NUM>, depicted in <FIG>, wherein the offset position of the second outlet <NUM> in relation to the first outlet <NUM> is measured as an offset position between the second centre axis L2 in relation to the first centre axis L1 in the transversal direction of the air filter element <NUM>.

In <FIG>, the first outlet <NUM> is located in the first end panel <NUM> and the second outlet <NUM> is located in the second end panel <NUM>. The first end panel <NUM> is arranged to block any filtered fluid to exit the air filter element <NUM> axially through the first end panel <NUM> other than through the first outlet <NUM>. The first end panel <NUM> is hence located at the first end <NUM> such that it covers both the filter material body <NUM> and any parts of the inner space <NUM> surrounding the first outlet <NUM> at this end. The second end panel <NUM> is arranged to block any filtered fluid to exit the air filter element <NUM> axially through the second end panel <NUM> other than through the second outlet <NUM>. The second end panel <NUM> is hence located at the second end <NUM> such that it covers both the filter material body <NUM> and any parts of the inner space <NUM> surrounding the second outlet <NUM> at this end. The first end panel <NUM> and the second end panel <NUM> may be made of a single panel as in the depicted embodiment, or of a combination of materials and/or sub-panels. Both the first end panel <NUM> and the second end panel <NUM> are made planar and parallel to the transversal direction of the air filter element <NUM>.

The first outlet <NUM> has a cylindrical cross-section, and the second outlet <NUM> has a cross-sectional area which is tapering, here tapering in direction perpendicular to the second centre axis L2, and away from the centre axis L of the air filter element <NUM>. The cross-sectional area and the hydraulic diameter of the second outlet <NUM> are substantially smaller than the cross-sectional area and the diameter of the inner space <NUM>. It should be noted that the cross-sectional area and the hydraulic diameter of the second outlet <NUM> is substantially smaller than the cross-sectional area and the diameter of the first outlet <NUM>, the latter being substantially the same as the cross-sectional shape and diameter of the inner space <NUM>. The first outlet <NUM> is located coaxially with the air filter element <NUM>. The air filter element <NUM> in <FIG> further comprises a sealing portion <NUM> arranged and configured for sealing engagement around the first outlet <NUM>. The sealing portion <NUM> is typically made of a flexible rubber material which may adapt in use to a surface of the air filter housing or of a pipe portion to which it abuts.

The tapering cross-section of the second outlet <NUM> is here formed as a trapezoid, or truncated triangle, having a base, or first cross section boundary/side, in the transversal (or radial) direction of the air filter element <NUM>, and two inclined cross section boundaries/sides joined by a fourth cross section boundary/side arranged opposite and parallel to the base. It should however be noted that other tapering cross-sections are within the scope of the invention. As seen in <FIG>, the cross-sectional area of second outlet <NUM> has rounded corners to provide beneficial flow conditions through the second outlet.

Furthermore, the air filter element <NUM> comprises a filter material body <NUM> arranged between the first and second ends <NUM>, <NUM> of the air filter element <NUM>. The filter material body <NUM> is arranged surrounding the inner space <NUM>, and comprises an outer sleeve surface 10A configured to receive unfiltered air and being bounded by an outer filter body radius Ro. Correspondingly, the filter material body <NUM> comprises an inner sleeve 10B, configured to discharge, or let out, filtered air (i.e. air that has been filtered through the filter material body <NUM>). As illustrated in <FIG>, the air filter element <NUM> of this embodiment comprises an inner portion <NUM> holding the filter material body <NUM> at the inner sleeve 10B for maintaining the shape of the air filter element <NUM> when air is filtered through the filter material body <NUM>, and to avoid collapsing of the filter material body <NUM> due to the air pressure during use. The inner portion <NUM> is tubular and air permeable, and is typically made of a plastic material. The inner portion <NUM> is in the present embodiment made as a rectangular net, configured to maintain the shape of the air filter element <NUM> and not interfere the air flow through the air filter element <NUM>. The thickness of the inner portion <NUM> is typically small in relation to the thickness of the filter material body <NUM>. When the air filter element <NUM> is used in connection with an internal combustion engine system <NUM>, i.e. when the filtering operation is performed on air such as ambient air, the filter material body <NUM> is typically made of a material such as paper or cellulose. The filter material body <NUM> of the depicted embodiments has a corrugated or pleated surface, but may be constructed differently and be of other suitable materials, or material combinations.

It should be understood, that the positioning the second outlet <NUM> in the depicted position improves the acoustic response of the air filter element <NUM>. The air filter element <NUM> may consequently be used as a noise reduction means. The larger the offset between the first center axis L1 and the second axis L2, the better from a noise reduction point of view. The best noise reduction properties will be achieved when a maximum distance is used for the offset. In the depicted embodiment the second outlet <NUM> is hence positioned as close as possible to the inner sleeve 10B of the filter material body <NUM>, which position is related to the hydraulic diameter of the second outlet <NUM>. This position is achieved when the outer periphery of the second outlet <NUM> is located adjacent to the periphery of the inner space <NUM> and consequently of the inner portion <NUM> or inner sleeve 10B of the filter material body <NUM>. In other words, the centre point of the second outlet <NUM> and thus the second centre axis L2 is located at a distance corresponding to half the hydraulic diameter of the second outlet <NUM> from the periphery of the inner space <NUM>.

Correspondingly, the outer periphery of the first outlet <NUM> is located adjacent to the periphery of the inner space <NUM>. Since the diameter of the first outlet <NUM> is substantially the same as the diameter of the inner space <NUM>, the first outlet <NUM> cannot be positioned otherwise in this embodiment and hence a maximum offset position of the second outlet <NUM> is achieved. If however the diameter of the first outlet <NUM> would be less than the diameter of the inner space <NUM>, then it would be possible to further increase the offset position between the first outlet <NUM> and the second outlet <NUM>. The maximum available offset position is set by the geometrical constraints of the air filter element <NUM>, such that the maximum available offset position equals a distance or length corresponding to the diameter of the inner space <NUM> subtracted by the radius, or hydraulic radius, of the outer periphery of the second outlet <NUM> and by the radius of the outer periphery of the first outlet <NUM>. The offset position should be at least <NUM> %, or preferably at least <NUM> %, or more preferably at least <NUM> % of the maximum available offset position.

Turning now to <FIG>, illustrating an air filter housing <NUM> and details thereof. In <FIG> a flow of air to be filtered through the filter system <NUM> and the air filter element <NUM> is disclosed in relation to the air filter housing <NUM>. The air filter housing <NUM> has an extension in a longitudinal direction along a longitudinal centre axis L, and an extension in a transversal direction (e.g. radial direction) in a transversal plane which is perpendicular to the longitudinal direction and the longitudinal centre axis L. The longitudinal centre axis L of the air filter housing <NUM> coincides with the longitudinal centre axis L of the air filter element <NUM>, when the air filter element <NUM> is inserted into the air filter housing <NUM>. The air filter housing <NUM> comprises a housing inlet <NUM>, a first housing outlet <NUM> and a second housing outlet <NUM>. The housing inlet <NUM> is located in the curved outer periphery, or in other words, in the envelope surface of the air filter housing <NUM>. The curved envelope surface is circular cylindrical. The housing inlet <NUM> is furthermore slightly inclined in relation to a normal to the outer periphery. The air filter housing <NUM> in <FIG> comprises a housing lid <NUM> for opening the air filter housing <NUM> to an inner housing space <NUM> which is adapted to receive the air filter element <NUM>. The housing lid <NUM> is also adapted to seal the opening in the air filter housing <NUM> when the housing lid <NUM> is closed. The air filter housing <NUM> further has a first end <NUM> and a second end <NUM>, at opposite ends of the inner housing space <NUM> along the longitudinal centre axis L. The housing lid <NUM> is part of, or even encompasses, the second end <NUM> of the air filter housing <NUM>. Both the first end <NUM> and the second end <NUM> of the air filter housing <NUM> are generally parallel to a transversal direction of the air filter housing <NUM>. The housing lid <NUM> is closed using e.g. otherwise known clips.

The first housing outlet <NUM> is located in the first end <NUM> and the second housing outlet <NUM> is in the embodiment shown in <FIG>, located in the in the second end <NUM> comprised in the housing lid <NUM>. In correspondence with the design of the air filter element <NUM>, the first housing outlet <NUM> is located coaxially with the envelope surface of the air filter housing <NUM>. The first housing outlet <NUM> has a first centre axis and the second housing outlet <NUM> has a second centre axis. Also, in correspondence with the design of the air filter element <NUM>, the offset position of the second housing outlet <NUM> in relation to the first housing outlet <NUM> is defined by an offset position between the second centre axis in relation to the first centre axis in the transversal direction of the air filter housing <NUM>. The offset position involves a distance, and preferably is a distance, in the transversal direction of the air filter housing <NUM>. The offset position is measured as a mutual distance as seen in the transversal direction of the air filter housing <NUM> between a centre point in the first housing outlet <NUM> to a centre point in the second housing outlet <NUM>. The second housing outlet <NUM> is furthermore located in a position the most far away from the housing inlet <NUM> in the air filter housing <NUM> in order to improve the acoustic response of the air filter housing <NUM>. In order for the air filter element <NUM> to be installable in the air filter housing <NUM>, the first housing outlet <NUM> is positioned within the air filter housing <NUM> in a position corresponding to the position of the first outlet <NUM> in the air filter element <NUM>, and the second housing outlet <NUM> is positioned within the air filter housing <NUM> in a position corresponding to the position of the second outlet <NUM> in the air filter element <NUM>.

In <FIG>, the air filter housing <NUM> further comprises an outlet pipe <NUM> extending from the second housing <NUM> end axially into the inner housing space <NUM> The outlet pipe <NUM> comprises the second housing outlet <NUM>. The outlet pipe <NUM> has a centre axis corresponding to the second centre axis of the second housing outlet <NUM>, and comprises an opening 25A configured and arranged to receive clean air from the inner housing space <NUM>. At least an axial portion 25B of the outlet pipe <NUM> has a cross-sectional area along a geometrical plane perpendicular of the centre axis which is tapering (which is better shown in <FIG>).

Turning to <FIG> illustrating the outlet pipe <NUM> in a perspective view. As shown, the outlet pipe <NUM> comprises a first leading edge <NUM>, a second leading edge <NUM>, a first axial edge portion <NUM> connecting a first end of the first leading edge <NUM> with a first end of the second leading edge <NUM>, and a second axial edge portion <NUM> connecting a second end of the first leading edge <NUM> with a second end of the second leading edge <NUM>. Hereby, the first and second leading edges <NUM>, <NUM> together with the first and second axial edge portions <NUM>, <NUM> define the opening 25A of the outlet pipe <NUM>. Moreover, in <FIG> the axial portion 25B is shown downstream of the first and second leading edges <NUM>, <NUM>. Stated differently, the axial portion 25B is arranged closer to the second housing end <NUM> compared to the first and second leading edges <NUM>, <NUM>. As also seen in <FIG>, the second leading edge <NUM> is arranged closer to the second housing end <NUM>, compared to first leading edge <NUM>. Stated differently, an axial distance between the second leading edge <NUM> and the second housing end <NUM> is smaller than an axial distance between the first leading edge <NUM> and the second housing end <NUM>. By having the first leading edge <NUM> arranged axially offset to the second leading edge <NUM> as shown in <FIG>, the opening 25A is at least partly extending in the axial direction. Thus, the opening 25A can be directed inside of the inner housing space <NUM>, e.g. facing away from the longitudinal centre axis L of the air filter housing <NUM>.

As seen in <FIG>, each one of the first and second leading edges <NUM>, <NUM> are sinusoidal or comprises sinus-shaped portions. The sinus-shaped portions are here arranged such that the peaks and valleys of the sinus-shape are axially distant from each other. That is, the sinus-shape extends in a transversal direction of the outlet pipe. Such sinusoidal shape may reduce noise travelling through the outlet pipe <NUM>.

In <FIG> a respective cross sectional view of the interaction between the second outlet <NUM> of the air filter element <NUM> of <FIG>, and the outlet pipe <NUM> of <FIG> is shown. In <FIG>, the outlet pipe <NUM> has been inserted into the second outlet <NUM> by the first leading edge <NUM>, and not yet by the second leading edge <NUM> and axial portion 25B. In <FIG>, the outlet pipe <NUM> has been further inserted into the second inlet and the axial portion 25B is fully encompassed by inner walls of the second outlet <NUM>. Thus, the second outlet <NUM> of the air filter element <NUM> is sized and dimensioned to mate with the outlet pipe <NUM> of the air filter housing <NUM>.

In <FIG>, is clear that the axial portion 25B of the outlet pipe <NUM> is configured and arranged to mate with the second outlet <NUM> of the air filter element <NUM>. Hereby, the axial portion 25B of the outlet pipe <NUM> is configured to prevent the air filter element to rotate, or even move in the radial plane, when the air filter element <NUM> is installed in the air filter housing <NUM>. As seen in <FIG>, the cross-sectional area of the axial portion 25B of the outlet pipe <NUM>, and the second outlet <NUM>, are shaped as trapezoids, or truncated triangles.

In <FIG>, it is shown how the first leading edge <NUM> leads the alignment and interconnection with the second outlet <NUM>. Thus, it is here shown how the first leading edge <NUM> firstly interacts with the second outlet <NUM>. As shown in <FIG>, the first leading edge comprises a first lateral portion 51A, a second lateral portion 51B, and a transversal portion 51C connecting the first lateral portion 51A with the second lateral portion <NUM> B such that the second lateral portion <NUM> B is located opposite to the first lateral portion 51A in relation to the transversal portion 51C. The first and second lateral portions 51A, 51B are inclined relative the transversal portion 51C with an angle of less than <NUM> degrees, such as about <NUM> degrees. Hereby, the air filter element <NUM> is fixated/aligned in at least two directions (typically in the radial plane) already when the first leading edge <NUM> has been inserted into second outlet <NUM>. Thus, the portion of the outlet pipe comprising the first leading edge <NUM> may align and fixate the air filter element <NUM> in the air filter housing <NUM> in at least two directions upon entering of first leading edge <NUM> into the second outlet <NUM>. Thus, the fixation, or alignment, of the air filter element <NUM> in the air filter housing <NUM> is carried out in a two-step procedure, firstly the first leading edge <NUM> interact with the inner walls of the second outlet <NUM> to initially align and fixate the air filter element <NUM> in the air filter housing <NUM>. Secondly, as the outlet pipe <NUM> is inserted further into the second outlet <NUM>, the axial portion 25B of the outlet pipe <NUM> will further, or finally, align and fixate the air filter element <NUM> to the air filter housing <NUM> owing to the matching cross-sectional areas of the axial portion 25B and the second outlet <NUM> of the air filter element <NUM>.

As shown in <FIG>, the housing lid <NUM> may further comprise a pipe portion 25C arranged on the opposite side of the second housing end <NUM> relative the outlet pipe <NUM>. Thus, the pipe portion 25C extends axially away from the inner housing space <NUM>. At least one of the outlet pipe <NUM>, and the pipe portion 25C may be made in one piece with the housing lid <NUM>.

When in use, the air to be filtered, represented by arrow <NUM>, enters the air filter housing <NUM> through the housing inlet <NUM>, spreads around the outside of the air filter element <NUM> and the outer sleeve 10A of the filter material body <NUM>, and penetrates through the air filter element <NUM> and the filter material body <NUM> such that the air is filtered. Finally, the filtered, and preferably generally cleaned, air leaves the air filter housing <NUM> through the first housing outlet <NUM> (represented by arrow <NUM>) and the second housing outlet <NUM> (represented by arrow <NUM>). The air intake pipe <NUM> which connects to the housing inlet <NUM> may be inclined such that the fluid has a flow component directed slightly towards the first housing outlet <NUM>.

It should be noted that the air filter housing <NUM> may have many other designs and still maintain the filtering, noise reduction and housing function in relation to the air filter element <NUM>.

Turning to <FIG> illustrating an exploded view of the filter system <NUM>, i.e. the air filter element <NUM> of <FIG> installed in the air filter housing <NUM> of <FIG>. Here, the air filter housing <NUM> and the inner housing space <NUM> is adapted for axial insertion and removal of the air filter element <NUM> into/from the inner housing space <NUM>.

The air filter housing <NUM> has generally the same curved shape as the air filter element <NUM> in order to distribute the air well around the air filter element <NUM>. An outer surface of the air filter element <NUM>, typically the outer sleeve 10A of the filter material body <NUM>, is adapted to be closely aligned with a curved inner surface of the air filter housing <NUM>, as depicted in <FIG>, in which the air filter element <NUM> is disclosed in a position installed in the air filter housing <NUM>. The air filter housing <NUM> has a curved inner surface which is slightly larger than the outer curved shape of the air filter element <NUM>, such that the air to be filtered may spread well around the air filter element <NUM> in order to utilise the full outer surface are of the air filter element <NUM>. Moreover, the first end <NUM> of the air filter housing <NUM>, i.e. the first housing end <NUM>, is arranged adjacent to the first end <NUM> of the air filter element <NUM> when housed in the inner housing space <NUM>. Correspondingly, the second end <NUM> of the filter housing <NUM>, i.e. the second housing end <NUM>, is located distant to, and opposite to, the first housing end <NUM> in relation to the longitudinal direction of the air filter housing <NUM>, and is arranged adjacent to the second end <NUM> of the filter element <NUM> when housed in the inner housing space <NUM>.

As shown in <FIG>, the cross-sectional area of the axial portion 25B of the outlet pipe <NUM> is sized and dimensioned to correspond to the cross-sectional area of the second outlet <NUM> of the air filter element <NUM>, as already described in relation to <FIG>. Hereby, the outlet pipe <NUM> is inserted into the second outlet <NUM> and thereby preventing the air filter element <NUM> from moving in the radial plane and also to rotate relative the air filter housing <NUM>.

In <FIG>, the sealing portion <NUM> at the first outlet <NUM> of the air filter element <NUM> is adapted in size and position to the first housing outlet <NUM> of the air filter housing <NUM> in order to seal off the inner housing space <NUM> from the ambient and the inner space <NUM> from the inner housing space <NUM>. Thus, in <FIG>, it is also clear that the first outlet <NUM>, located in the first end <NUM> of the air filter element <NUM> is configured to communicate with the corresponding first housing outlet <NUM> in the air filter housing <NUM>, and that the second outlet <NUM> located in the second end <NUM> of the air filter element <NUM> is configured to communicate with the outlet pipe <NUM>, and corresponding second housing outlet <NUM>, in the air filter housing <NUM>.

As depicted in <FIG> the air filter element <NUM> is disclosed installed in the air filter housing <NUM> with the housing lid <NUM> closed. Generally only the housing inlet <NUM>, and first and second housing outlets <NUM>, <NUM> are shown in <FIG>.

In <FIG> a lid <NUM> for an air filter housing <NUM> having an inner housing space <NUM> is shown. The lid <NUM> comprises a first surface <NUM> configured to face the inner housing space, and an outlet pipe <NUM> as disclosed in <FIG>, extending axially outwardly from the first surface <NUM>. Corresponding to the outlet pipe <NUM> of <FIG>, the outlet pipe <NUM> has a centre axis and an opening 125A configured to receive clean air from the inner housing space, and comprises an axial portion 125B having a cross-sectional area along a geometrical plane perpendicular of the centre axis, which is tapering. The lid <NUM> in <FIG> may be used as the housing lid <NUM> in <FIG>.

In the above disclosed embodiments the direction of fluid flow may be opposite to the one depicted, the size of the filter housing in relation to the air filter element may be different, the material of the filter body may be other such as e.g. made of a foam material, the thickness of the air filter element may be otherwise chosen, the size and position of the first outlet, and first housing outlet, the second outlet, and the outlet pipe may be otherwise chosen, without deviating from the scope of this disclosure.

The air filter element may alternatively be called filter cartridge, filter module or filter insert.

The alternative embodiments which have been disclosed above may be combined in any way which is found advantageous, unless anything else is explicitly stated, as long as the features of the main claims are fulfilled.

Claim 1:
An air filter element (<NUM>) comprising a first end (<NUM>) and a second end (<NUM>) located opposite to the first end in relation to a longitudinal direction of the air filter element, the air filter element being configured for axial insertion into an air filter housing (<NUM>), with the first end leading the axial insertion, wherein the air filter element comprises a first outlet (<NUM>) located in the first end and being configured to communicate with a corresponding first housing outlet (<NUM>) in the air filter housing, and a second outlet (<NUM>) located in the second end and being configured to communicate with a corresponding second housing outlet (<NUM>, <NUM>) in the air filter housing, characterized in that a cross-sectional area of the second outlet, along a geometrical plane perpendicular to the centre axis, is tapering, and is shaped as a trapezoid, or truncated triangle.