WO2018050236A1

WO2018050236A1 - Air filter

Info

Publication number: WO2018050236A1
Application number: PCT/EP2016/071884
Authority: WO
Inventors: Alexandre LUCHESI DE ALMEIDA; Edson VALDOMIRO DE AZEVEDO JUNIOR; Pedro BASSO; Marcos José DANTAS DE OLIVEIRA
Original assignee: Mahle International Gmbh; Mahle Metal Leve S/A
Priority date: 2016-09-15
Filing date: 2016-09-15
Publication date: 2018-03-22

Abstract

The present invention relates to an air filter (1) for a fresh air system of an internal combustion engine, comprising a filter housing (2), a filter element (15) which has an annular filter body (17), a first end plate (18) and a second end plate (19), and an inner frame (16) which has an annular grid body (24) which is arranged within the filter body (15) coaxially with respect to the filter body (15). An inexpensive construction for the filter element results if the inner frame (16) is a separate component with regard to the filter element (15) and the filter housing (2),if the inner frame (16) is arranged in the filter housing (2) such that it can be rotated about the longitudinal center axis (11) of the filter housing (2), and if a first torque coupling (29) for transmitting torques between the filter element (15) and the inner frame (16) is configured between the inner frame (16) and the filter element (15).

Description

Air filter

The present invention relates to an air filter or an air filter device for a fresh air system of an internal combustion engine, having the features of the preamble of claim 1 . Moreover, the invention relates to a filter element for an air filter of this type.

An air filter of the generic type is known, for example, from DE 100 20 538 A1 . The air filter has a filter housing which has a housing pot with a pot bottom, a housing lid for closing the housing pot, a raw air inlet for feeding in unfiltered fresh air, and a pure air outlet for discharging filtered fresh air. A filter element is arranged in the filter housing, which filter element has an annular filter body made from filter material, a first end plate which faces the housing lid on a first axial end side of the filter body, and a second end plate which faces the pot bottom on a second axial end side of the filter body. In the filter housing, the filter element separates a raw side which is connected fluidically to the raw air inlet from a pure side which is connected fluidically to the pure air outlet. Furthermore, an inner frame is provided which has an annular grid body which is arranged within the filter body coaxially with respect to the filter body. The inner frame serves to radially support the filter body. Accordingly, the grid body is permeable for the fresh air flow. In the known air filter, the inner frame is integrated into the filter element, that is to say is connected fixedly to the two end plates. As a result, the filter element is comparatively expensive. Moreover, the recycling of the filter element is made more difficult, since the inner frame usually consists of a different material than the end plates and the filter body. In order to provide a remedy here, it is fundamentally possible to provide the inner frame as a separate component with regard to the filter element. It can be necessary to lock the filter element to the housing pot for certain applications, in order to fix predefined positioning of the filter element in the filter housing. Here, a locking means of this type can expediently interact between the housing pot and the leading second end plate during the introduction of the filter element. In order to lock and unlock the locking means, a rotational movement of the second end plate relative to the filter housing can be necessary. Said rotational movement can require a corresponding torque. The cause for the required torque can lie, for example, in a seal which acts between the second end plate and the housing pot and generates a corresponding frictional force which counteracts a rotational movement. The locking and unlocking of the locking means can likewise take place counter to a certain resistance, which also contributes to the fixing of the predefined rotary position between the filter element and the filter housing. If a filter element without an integrated inner frame is then to be used, there is the risk of the filter body being damaged when the filter element is rotated in the filter housing about the longitudinal center axis of the filter housing, in order to apply the required torque to the second end plate. This applies, in particular, to filter elements which are of comparatively great dimensions axially. Since the filter material, from which the filter body consists, does not have any great rigidity, the risk of twisting of the filter body is produced during rotation of the filter element, which can cause damage of the filter body.

The present invention is concerned with the problem of specifying an improved embodiment for an air filter of the type mentioned at the outset or for an associated filter element, which improved embodiment is distinguished firstly by an inexpensive filter element, whereas secondly the risk of damage to the filter element is reduced.

According to the invention, said problem is solved by way of the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims. The invention is based on the general concept of configuring the inner frame as a separate component both with regard to the filter element and with regard to the filter housing, of arranging the inner frame in the filter housing such that it can be rotated about the longitudinal center axis of the filter housing, and of configuring a first torque coupling between the inner frame and the filter element, by way of which first torque coupling it is possible to transmit torques between the filter element and the inner frame. As a result of this proposal, it is possible to introduce torques into the filter element via the inner frame. Here, said introduction of torque can be carried out, in particular, in such a way that twisting of the filter body can be avoided here.

The grid body of the inner frame has a first axial end which faces the housing lid and a second axial end which faces the pot bottom. In accordance with one advantageous embodiment, the first torque coupling can be configured between the second end plate and the second axial end of the grid body, with the result that it makes a transmission of torque possible between the second end plate and the second axial end. In the case of said embodiment, the transmission of torque from the inner frame to the filter element takes place directly at the second end plate, with the result that torques can be generated at the second end plate without torsional loading of the filter body. For example, it is therefore possible to bring about a locking means of the abovementioned type which requires a corresponding torque at the second end plate for unlocking and for locking.

It is therefore in principle possible to introduce the torque which is required for rotating the filter element in the filter housing, for example, manually into the inner frame. The inner frame then transmits said torque to the second end plate, which leads to rotation of the filter element, without the filter body being torsionally loaded in the process. In accordance with one particularly advantageous embodiment, in addition to the first torque coupling, a second torque coupling can be provided which is configured between the first end plate and the first axial end of the grid body and accordingly makes a transmission of torque possible between the first end plate and the first axial end. As a result of said design, it is possible to introduce the torque which is necessary for rotating the filter element, for example, manually into the first end plate. Said torque is then transmitted by the second torque coupling to the inner frame. Furthermore, the torque is then transmitted via the first torque coupling from the inner frame to the second end plate. Accordingly, the torque which is introduced at the first end plate can act on the second end plate via a force path or torque path which bypasses the filter body, without the filter body being loaded torsionally in the process. As a result, the handling of the filter element during rotation in the filter housing is simplified. In particular, the first end plate can be configured as a closed end plate. As a result of the second torque coupling, the torque-transmitting function of the inner frame can be utilized, even if the inner frame itself is manually not accessible.

In one advantageous embodiment, the inner frame can have, at the second axial end of the grid body, a radially outwardly protruding annular collar which runs around in a closed manner in the circumferential direction. The first torque coupling has at least one driver contour on said annular collar. Furthermore, the first torque coupling has, for each driver contour, a driver counter-contour which is complementary with respect to said driver contour on the second end plate. For the transmission of torque, the respective driver contour and the associated driver counter-contour are in engagement with one another axially. As a result of the axial engagement, a positively locking connection which efficiently makes the transmission of torque possible is realized in the circumferential direction. In one advantageous development, one of the driver contour and the driver counter-contour can be an axially protruding projection, whereas the other of the driver contour and the driver counter-contour is a receptacle, into which the projection engages axially. The driver contour is preferably said projection, whereas the driver counter-contour is preferably said receptacle. The reverse construction is likewise possible, as is a mixed construction.

One development provides that the respective projection is formed by way of a web structure which has at least two webs which run in an inclined manner with respect to one another and/or which cross one another. Here, the webs which support one another mutually can be at any desired angles of inclination with respect to one another. They preferably run perpendicularly with respect to one another.

Another development provides that the respective receptacle has two stops which lie opposite one another in the circumferential direction and between which a gap is configured. The respective projection can then engage axially into said gap. The respective stop can also be formed here by way of a web structure with at least two webs which run in an inclined manner with respect to one another.

Here, for example, the webs can have a T-profile in a cross section which is oriented perpendicularly with respect to the axial direction. The above-described embodiments for the projections and/or receptacles can be realized comparatively simply using injection molding technology and are distinguished by a high stability and/or stiffness.

In another embodiment, a locking means can be configured between the second end plate and the housing pot, which locking means is unlocked in a first rotary position between the housing pot and the second end plate and is locked in a second rotary position between the housing pot and the second end plate. As has been mentioned multiple times, the filter element can be fixed in the housing in a predefined rotary position with the aid of a locking means of this type. Here, axial fixing is of increased significance in the case of rotationally symmetrical filter elements. The axial fixing in the region of the second end plate can, for example, assist the function of a seal which is provided in the region of the second end plate with respect to the filter housing, in order to avoid leaks.

According to one advantageous development, the locking means can be configured as a bayonet closure. A bayonet closure is distinguished by the combination of two different rotational movements, in order to adjust the filter element relative to the filter housing between an open state of the bayonet closure and a closed state of the bayonet closure. In the open state, the filter element can be introduced axially into the housing pot and can be pulled out of the latter. In the closed state, the filter element can no longer be pulled axially out of the housing pot.

In one advantageous development, the bayonet closure can have at least one slotted guide on the second end plate and at least one bar element which interacts with the slotted guide on the housing pot. As a result, the bayonet closure or the locking means is integrated largely into the second end plate. The associated bar element can also be realized simply on the housing pot, for example by way of a projection which protrudes radially to the inside from a pot wall.

The respective slotted guide can expediently have an inlet for axial introduction of the bar element into the slotted guide, and an end stop, into which the bar element can be introduced in the circumferential direction and in which the bar element is secured axially. The slotted guide therefore defines at least one two- stage adjusting movement between the filter element and the housing pot. During the insertion of the filter element, it first of all has to be adjusted axially, in order for it to be possible to introduce the bar element through the inlet into the slotted guide. At the end of the locking operation or closing operation, a rotational movement of the filter element takes place about the longitudinal center axis of the filter housing, in order to transfer the bar element into the end stop in the circumferential direction. The end stop at the same time defines the predefined end rotary position between the filter element and the housing pot.

In one advantageous embodiment, the respective slotted guide can have a ramp, moreover, which guides the bar element along a helical track from the inlet to the end stop. In said embodiment, the slotted guide therefore defines a three-stage adjusting movement, in which the axial adjusting movement at the beginning and the rotational movement at the end are coupled to one another by means of a screwing movement which positively couples an axial adjustment with a rotational adjustment. As a result, for example, an axial force can be generated on the second end plate via the torque. An axial force of this type can be necessary, for example, for prestressing an axial seal or for pressing a radial seal. The axial movement for guiding the bar element through the inlet is to be understood to be a pure axial movement which does not contain any rotational movement. The rotational movement for transferring the bar element into the end stop is to be considered to be a pure rotational movement in the circumferential direction which does not contain any axial movement. In contrast to this, the screwing movement contains both a rotational movement in the circumferential direction and an axial movement which is positively coupled to it.

In one embodiment which presupposes the second torque coupling, the inner frame can have an end bottom at the first axial end of the grid body. The second torque coupling is then expediently configured between the first end plate and said end bottom, and makes a transmission of torque possible between the first end plate and the end bottom as a result. The inner frame is significantly stiffened at the first axial end of the grid body by way of the end bottom, which improves, in particular, the introduction of torque at the first axial end.

In one development, the second torque coupling can have a coupling contour on the end bottom and a coupling counter-contour which is complementary with respect to the coupling contour on the first end plate. The coupling contour and the coupling counter-contour engage axially into one another for the transmission of torque. The first end plate is expediently configured as a closed end plate for said embodiment, which facilitates the realization of the coupling counter-contour on the first end plate. The components of the second torque coupling which engage axially into one another bring about a positively locking connection in the circumferential direction, which positively locking connection makes an efficient transmission of torque possible.

One development provides that, on an outer side which faces away from the second end plate, the first end plate has a handle for the manual introduction of torques into the first end plate. The manipulation of the filter element in the filter housing is simplified as a result. When the filter housing is open, the housing lid is removed from the housing pot, as a result of which the filter element is accessible in the region of the first end plate. A fitter can then introduce the torque which is required to release the filter element into the filter element via the handle. The filter element can be unlocked as a result, for example, in order for it to be possible to pull it axially out of the housing pot. This then also applies correspondingly in the reverse direction for the insertion of the filter element.

A filter element according to the invention is distinguished by the fact that it is provided for use in an air filter of the above-described type. To this end, the filter element has constituent parts of the first torque coupling which are configured in a complementary manner with respect to constituent parts of the first torque cou- pling which are configured on the inner frame. If the filter element is used in the air filter, torques can be introduced into the second end plate of the filter element via the inner frame. The second end plate of the filter element leads during the introduction of the filter element into the housing pot.

In the present context, the axial direction, the radial direction and the circumferential direction relate to the longitudinal center axis of the filter housing, which will be explained in greater detail further below in the description of the figures.

Further important features and advantages of the invention arise from the sub claims, from the drawings and from the associated description of the figures using the drawings.

It goes without saying that the features which are mentioned in the above text and are still to be described in the following text can be used not only in the respectively specified combination, but rather also in other combinations or on their own, without departing from the scope of the present invention.

Preferred embodiments of the invention are shown in the drawings and will be explained in greater detail in the following description, identical designations relating to identical or similar or functionally identical components.

In the drawings, in each case diagrammatically: fig. 1 shows an isometric view of an air filter, shows an isometric view of a housing pot of a filter housing of the air filter, fig. 3 shows an isometric view of a filter element of the air filter, fig. 4 shows an isometric view of an inner frame of the air filter, fig. 5 shows an enlarged detail V from fig. 4, fig. 6 shows an enlarged detail VI from fig. 3, fig. 7 shows an axial view of an end plate of the filter element, fig. 8 shows an axial view of the inner frame, fig. 9 shows a sectional view of the air filter in the region of the first torque coupling, fig. 10 shows a view of another end plate of the filter element, fig. 1 1 shows a detailed view of the inner frame from fig. 4, fig. 12 shows a sectional view of the filter device in the region of a second torque coupling, and fig. 13 shows an isometric view of the filter element as in fig. 3, but from another viewing direction.

In accordance with fig. 1 , an air filter device 1 or an air filter 1 which is used in a fresh air system of an internal combustion engine for filtering fresh air comprises a filter housing 2 which has a housing pot 3, a housing lid 4, a raw air inlet 5 and a pure air outlet 6. The housing 2 can be opened by way of removal of the lid 4. The housing pot 3 has a pot bottom 7 axially opposite the housing lid 4. The pure air outlet 6 is situated on said pot bottom 7 and faces away from the observer in fig. 1 and correspondingly cannot be seen. Moreover, the filter housing 2 can be equipped with a bracket 8 and with a discharge stub 9, on which a discharge valve 10 is arranged in the example which is shown. The filter housing 2 has a longitudinal center axis 1 1 which is defined by a cylindrical pot wall 12 of the housing pot 3. The longitudinal center axis 1 1 for its part defines an axial direction of the air filter 1 . The axial direction runs parallel to the longitudinal center axis 1 1 . A radial direction of the air filter 1 runs transversely with respect to the axial direction. A circumferential direction of the air filter 1 rotates around the longitudinal center axis 1 1 and is indicated in the figures by way of a double arrow and is denoted by 13.

Fig. 2 shows the filter pot 3 without the pot bottom 7 and with a raw air inlet 5 which is mirrored with regard to a longitudinal center plane. An interior space 14 of the filter housing 2 can be seen in fig. 2. A filter element 15 which is shown in fig. 3 and an inner frame 16 which is shown in fig. 4 are arranged in said interior space 14.

In accordance with fig. 3, the filter element 15 has an annular filter body 17, a first end plate 18 and a second end plate 19. Here, the first end plate 18 is arranged on a first axial end side 20 of the filter body 17 and faces the housing lid 4 in the installed state of the filter element 15. The second end plate 19 is attached on a second axial end side 21 of the filter body 17 and faces the pot bottom 5 in the installed state. In the installed state, the filter element 15 separates a raw side 22 which is connected fluidically to the raw air inlet 5 and is situated outside the filter body 17 in fig. 3 from a pure side 23 which is connected politically to the pure air outlet 6 and is situated within the filter body 17 in fig. 3, in a customary manner. The filter body 17 consists of a filter material which is not denoted in greater de- tail. Here, this can be a folded web material. Since, in the example which is shown here, the filter body 17 is flowed through radially from the outside toward the inside during operation of the air filter 1 , the differential pressure which prevails on the filter body 17 leads to the filter body 17 being pressed radially inward. In order to avoid damage of the filter body 17 and/or for stabilization of the filter body 17, the inner frame 16 is arranged within the filter body 17 coaxially with respect to the filter body 17 in the installed state. The filter body 17 can be supported radially on the inner frame 16 radially on the inside at least during the operation of the air filter 1 .

According to fig. 4, the inner frame 16 has an annular grid body 24 which is permeable for the air flow and is arranged concentrically in the filter body 17 in the installed state, with the result that the filter body 17 can be supported radially on the grid body 24. Said grid structure 24 has a first axial end 25 which faces the housing lid 4 and a second axial end 26 which faces the pot bottom 7. At the first axial end 25, the inner frame 16 has an end bottom 27 which is configured here as a closed end bottom 27. The inner frame 16 is therefore axially impermeable at the first axial end 25. At the second axial end 26, the inner frame 16 has a radially protruding annular collar 28 which runs around in a closed manner in the circumferential direction 13. Both said annular collar 28 and the end bottom 27 bring about significant stiffening of the inner frame 16. The inner frame 16 represents a separate component with regard to the filter element 15 and with regard to the filter housing 2.

In the installed state, the inner frame 16 is arranged in the filter housing 2 such that it can be rotated about the longitudinal center axis 1 1 . Furthermore, a first torque coupling 29 is configured between the inner frame 16 and the filter element 15, via which first torque coupling 29 a transmission of torque is possible between the filter element 15 and the inner frame 16. Said first torque coupling 29 has components 30 on the side of the inner frame and components 31 on the filter element side which interact for the transmission of torque. The components 30 on the side of the inner frame will also be called a driver contour 30 in the following text. The components 31 on the filter element side will also be called a driver counter-contour 31 in the following text.

The first torque coupling 29 is preferably configured between the second end plate 19 of the filter element 15 and a second axial end 26 of the grid body 24. The transmission of torque therefore takes place between the second axial end 26 and the second end plate 19.

Moreover, a second torque coupling 32 is provided between the inner frame 16 and the filter element 15, which second torque coupling 32, independently of the first torque coupling 29, likewise makes a transmission of torque possible between the filter element 15 and the inner frame 16. The second torque coupling 32 also has components 33 on the side of the inner frame and components 34 on the filter element side. The components 33 on the side of the inner frame of the second torque coupling 32 can also be called a coupling contour 33 in the following text, whereas the second components 34 of the second torque coupling 32 can also be called a coupling counter-contour 34 in the following text.

The second torque coupling 32 is preferably configured between the first end plate 18 and the first axial end 25 of the grid body 24, with the result that a transmission of torque is made possible between the first end plate 18 and the first axial end 25 via the second torque coupling 32. If both torque couplings 29, 32 are present, a torque which is introduced on the first end plate 18 can be transmitted via the second torque coupling 32 to the inner frame 16 and can be transmitted from the inner frame 16 via the first torque coupling 29 to the second end plate 19. The torque therefore passes from the first end plate 18 to the second end plate 19 bypassing the filter body 17, with the result that the filter body 17 is not loaded torsionally during a rotational actuation of the filter element 15 when it is plugged as intended onto the inner frame 16 in the filter housing 2.

According to figs. 3 to 9, the first torque coupling 29 has at least one driver contour 30 on the annular collar 28 of the inner frame 16. In the preferred example which is shown, precisely two driver contours 30 are provided which lie diametrically opposite one another. For each driver contour 30, the first torque coupling 29 has a driver counter-contour 31 which is complementary with respect to the former on the second end plate 19. In the installed state which can be seen in fig. 9, the respective driver contour 30 engages axially into the associated driver counter-contour 31 . As a result, a positively locking connection is produced in the circumferential direction 13 between the driver contour 30 and the driver counter- contour 31 . In the examples which are shown here, the driver contour 30 is configured as a projection 35 which protrudes axially from the annular collar 28 in the direction of the end bottom 27. In contrast, the driver counter-contour 31 is configured as a receptacle 36, into which the respective projection 35 engages axially. As can be gathered from figs. 4, 5, 8 and 9, the respective projection 35 can be formed by way of a web structure which, according to fig. 5, has a plurality of webs 37 which extend in an inclined manner with respect to one another or which cross one another. In fig. 5, a radially extending web 37 can be seen which is crossed perpendicularly by two webs 37 which run parallel to one another. According to figs. 3, 6, 7 and 9, the respective receptacle 36 can have two stops 38 which lie opposite one another in the circumferential direction 13 in the manner of bookends, between which a gap 39 is configured. The projection 35 can engage into said gap 39.

According to fig. 6, a locking means 40 can be configured between the second end plate 19 and the housing pot 3, of which locking means 40 only one constitu- ent part on the filter element side can be seen in fig. 6, however. A component on the housing pot side of the locking means 40 is indicated in fig. 2. The locking means 40 is configured in such a way that it is unlocked in a first rotary position between the housing pot 3 and the second end plate 19, whereas it is locked in a second rotary position which is different than said first rotary position between the housing pot 3 and the second end plate 19. The second rotary position expediently corresponds to an end rotary position between the filter element 15 and the housing pot 3, which end rotary position is to exist when the filter element 15 is inserted as intended into the filter housing 2. In the preferred example which is shown here, the locking means 40 is configured as a bayonet closure 41 . The bayonet closure 41 has at least one slotted guide 42 on the second end plate 19. In a complementary manner with respect to the slotted guide 42, the bayonet closure 41 has at least one bar element 43 on the housing pot 3. According to the views of figs. 3 and 7, a total of four slotted guides 42 of this type are arranged uniformly distributed in the circumferential direction 13 on the second end plate 19, in order to form the bayonet closure 41 or the locking means 40. According to fig. 6, the respective slotted guide 42 has an inlet 44 and an end stop 45. In the particularly advantageous embodiment which is shown here, moreover, the slotted guide 42 has a ramp 46. The bar element 43 can be introduced axially into the slotted guide 42 through the inlet 44. The ramp 46 forces a helical transfer of the bar element 43 from the inlet 44 to the end stop 45. Here, a rotational movement in the circumferential direction 13 is positively coupled to an axial movement. Finally, the bar element 43 can move into the end stop 45 in the circumferential direction 13 in a manner which is guided within the slotted guide 42. The bar element 43 is secured axially in the end stop 45. The end stop 45 at the same time defines the abovementioned end rotary position between the filter element 15 and the housing pot 3. According to figs. 3, 4, 8 and 10 to 12, the second torque coupling 32 can expediently be configured between the first end plate 18 of the filter element 15 and the end bottom 27 of the inner frame 16. To this end, the coupling contour 33 is configured on the end bottom 27, for example in the form of a depression on an outer side 47 of the end bottom 27 which faces away from the second axial end 26. The coupling counter-contour 34 is configured on the first end plate 18, to be precise on an inner side 48 of the first end plate 18, which inner side 48 faces the second end plate 19. Here, the first end plate 18 is configured as a closed end plate which has an annular region 49 and a core region 50. The annular region 49 is attached on the first end side 20 on the filter body 17 and encloses the core region 50 in the circumferential direction 13. The coupling counter-contour 34 is formed within said core region 50, for example in the form of a projection which protrudes axially on the inner side 48 in the direction of the second end plate 19. In the example which is shown, moreover, an axial driver 51 which protrudes axially from the projection is formed on said projection, which axial driver 51 engages axially into an axial receptacle 52 which is formed in the depression of the coupling contour 33. Here, a central receptacle 53 can be configured within the axial driver 51 , into which central receptacle 53 a mandrel 54 which protrudes within the axial recess 52 can engage axially. Moreover, two radial drivers 55 which lie diametrically opposite one another can emanate radially from the projection of the coupling counter-contour 34, which radial drivers 55 engage axially into radial cutouts 56 which are complementary with respect to them and are configured within the depression of the coupling contour 33.

According to figs. 12 and 13, the first end plate 18 can have a handle 58 on an outer side 57 which faces away from the second end plate 19, via which handle 58 a torque can be introduced manually into the first end plate 18. Here, in the example of figs. 12 and 13, the handle 58 bridges a depression 59 which is produced on the outer side 57 during the configuration of the projection for the cou- pling counter-contour 34. As a result, the handling of the handle 58 is facilitated at the same time. Furthermore, the handle 58 can in this way be arranged substantially within the outer contour of the first end plate 18 in a largely recessed manner.

In contrast to this, the second end plate 19 is configured as an open end plate, with the result that it is of annular configuration and has a central through opening 60. The inner frame 16 penetrates coaxially through said through opening 60 during placing of the filter element 15 into the filter body 17.

In a first rotary position between the housing pot 3 and the filter element 15 or second end plate 19, the bar element 43 is arranged axially flush with respect to the inlet 44, with the result that the bar element 43 can be introduced through the inlet 44 into the slotted guide 42 by way of an axial adjustment. In a second rotary position which is different than the first rotary position between the housing pot 3 and the filter element 15 or second end plate 19, the bar element 43 has moved completely into the end stop 45, with the result that the bar element 43 is secured axially in the end stop 45. In said second rotary position, the predefined end rotary position between the filter element 15 and the filter housing 2 prevails at the same time. In said second rotary position, the filter element 15 can no longer be pulled axially out of the housing pot 34.

Claims

1 . An air filter for a fresh air system of an internal combustion engine,

- having a filter housing (2) which has a housing pot (3) with a pot bottom (7), a housing lid (4), a raw air inlet (5) and a pure air outlet (6),

- having a filter element (15) which has an annular filter body (17) made from filter material, a first end plate (18) which faces the housing lid (4) on a first axial end side (20) of the filter body (17), and a second end plate (19) which faces the pot bottom (7) on a second axial end side (21 ) of the filter body (17), and which, in the filter housing (2), separates a raw side (22) which is connected fluidically to the raw air inlet (5) from a pure side (23) which is connected fluidically to the pure air outlet (6),

- having an inner frame (16) which has an annular grid body (24) which is arranged within the filter body (15) coaxially with respect to the filter body (15), characterized

- in that the inner frame (16) is a separate component with regard to the filter element (15) and the filter housing (2),

- in that the inner frame (16) is arranged in the filter housing (2) such that it can be rotated about the longitudinal center axis (1 1 ) of the filter housing (2), and

- in that a first torque coupling (29) for transmitting torques between the filter element (15) and the inner frame (16) is configured between the inner frame (16) and the filter element (15).

2. The air filter as claimed in claim 1 ,

characterized - in that the grid body (24) has a first axial end (25) which faces the housing lid (4) and a second axial end (26) which faces the pot bottom (7), and

- in that the first torque coupling (29) is configured between the second end plate (19) and the second axial end (26) of the grid body (24), and makes a transmission of torque possible between the second end plate (19) and the second axial end (26).

3. The air filter as claimed in claim 2,

characterized

in that, in addition to the first torque coupling (29), a second torque coupling (32) is provided which is configured between the first end plate (18) and the first axial end (25) of the grid body (24), and makes a transmission of torque possible between the first end plate (18) and the first axial end (25).

4. The air filter as claimed in claim 2 or 3,

characterized

- in that the inner frame (16) has, at the second axial end (26) of the grid body (24), a radially outwardly protruding annular collar (28) which runs around in the circumferential direction (13),

- in that the first torque coupling (29) has at least one driver contour (30) on the annular collar (28) of the inner frame (16),

- in that the first torque coupling (29) has at least one driver counter-contour (31 ) which is complementary with respect to the driver contour (30) on the second end plate (19), and

- in that the respective driver contour (30) and the associated driver counter- contour (31 ) are in engagement axially with one another for the transmission of torque.

5. The air filter as claimed in claim 4, characterized

in that one of the driver contour (30) and the driver counter-contour (31 ) is an axi- ally protruding projection (35), whereas the other of the driver contour (30) and the driver counter-contour (31 ) is a receptacle (36), into which the projection (35) engages axially.

6. The air filter as claimed in claim 5,

characterized

in that the respective projection (35) is formed by way of a web structure which has at least two webs (37) which cross one another and/or run in an inclined manner with respect to one another.

7. The air filter as claimed in claim 5 or 6,

characterized

in that the respective receptacle (36) has two stops (38) which lie opposite one another in the circumferential direction (13) and between which a gap (39) is configured, into which the respective projection (35) engages axially.

8. The air filter as claimed in one of claims 1 to 7,

characterized

in that a locking means (40) is configured between the second end plate (19) and the housing pot (3), which locking means (40) is unlocked in a first rotary position between the housing pot (3) and the second end plate (19) and is locked in a second rotary position between the housing pot (3) and the second end plate (19).

9. The air filter as claimed in claim 8,

characterized

in that the locking means (40) is configured as a bayonet closure (41 ).

10. The air filter as claimed in claim 9,

characterized

in that the bayonet closure (41 ) has at least one slotted guide (42) on the second end plate (19) and at least one bar element (43) which interacts with the slotted guide (42) on the housing pot (3).

1 1 . The air filter as claimed in claim 10,

characterized

in that the respective slotted guide (42) has an inlet (44) for axial introduction of the bar element (43) into the slotted guide (42), and an end stop (45), into which the bar element (43) can be introduced in the circumferential direction (13) and in which the bar element (43) is secured axially.

12. The air filter as claimed in claim 1 1 ,

characterized

in that the respective slotted guide (42) has a ramp (46) which guides the bar element (43) along a helical track from the inlet (44) to the end stop (45).

13. The air filter as claimed in claim 3 or as claimed in claim 3 and one of claims 4 to 12,

characterized

- in that the inner frame (16) has an end bottom (27) at the first axial end (25) of the filter body (24), and

- in that the second torque coupling (32) is configured between the first end plate (18) and the end bottom (27), and makes a transmission of torque possible between the first end plate (18) and the end bottom (27).

14. The air filter as claimed in claim 13, characterized

in that the second torque coupling (32) has a coupling contour (33) on the end bottom (27) and a coupling counter-contour (34) which is complementary with respect to the coupling contour (33) on the first end plate (18) which is configured as a closed end plate, which coupling contours (33, 34) engage axially into one another for the transmission of torque.

15. The air filter as claimed in claim 13 or 14,

characterized

in that, on an outer side (57) which faces away from the second end plate (19), the first end plate (18) has a handle (58) for the manual introduction of torques into the first end plate (18).

16. A filter element for an air filter (1 ) as claimed in one of the preceding claims.

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