Abstract:
A spin-on filter for a filtering device for fluid, the spin-on filter including: a housing pot, in which at least one filter element is arranged; a connecting body, which is arranged at an end face of the housing pot, the connecting body having a central opening; and a coupling device including a filter-side coupling part configured for detachably coupling the spin-on filter to a filter head of the filtering device; wherein the coupling part is arranged on the central opening; wherein the filter-side coupling part is configured to detachably couple to a connector of a head-side coupling part of the filter head by way of a plug-in and/or rotational movement with respect to a coupling axis; and wherein the filter-side coupling part includes a plurality of coupling ribs which are distributed in the circumferential direction of a coupling axis on the central opening and projecting radially inwardly.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a spin-on filter for a filtering device for fluid, in particular liquid, in particular oil or fuel, in particular of an internal combustion engine, in particular of a motor vehicle. 
         [0002]    The invention further relates to a filtering device for fluid, in particular liquid, in particular oil or fuel, in particular of an internal combustion engine, in particular of a motor vehicle. The invention moreover relates to a filter head of a filtering device for fluid, in particular liquid, in particular oil or fuel, in particular of an internal combustion engine, in particular of a motor vehicle, in particular of a filtering device according to the invention. 
       BACKGROUND OF THE INVETION 
       [0003]    A filtering device including a filter head and a filter cartridge is known from EP 0 830 885 A1. The filter cartridge is secured to the filter head. The filter head includes a plurality of outwardly extending ramped projections constituting a first component of a bayonet-type coupling. The ramped projections are cooperable with similar projections of the cartridge to secure the filter cartridge to the filter head. 
       SUMMARY OF THE INVENTION 
       [0004]    It is the object of the invention to devise a spin-on filter, a filtering device, and a filter head of the type mentioned above, in which securing of the filter, in particular of the spin-on filter, to the filter head can be simplified. Moreover, a stability of the coupling of the filter, in particular of the spin-on filter, to the filter head is to be improved. 
         [0005]    The object is achieved according to the invention by the spin-on filter including:
       a housing pot, in which at least one filter element is arranged;   a connecting body, which is arranged at the end face of the housing pot and is provided with a central opening; and   a filter-side coupling part of a coupling device for detachably coupling the spin-on filter to a filter head of the filtering device, the coupling part being arranged on the central opening,       
 
         [0009]    wherein the filter-side coupling part can be detachably coupled to a connector of a head-side coupling part of the filter head by way of a plug-in and/or rotational movement with respect to a coupling axis, and wherein the filter-side coupling part comprises multiple coupling ribs, which are distributed in the circumferential direction of the coupling axis on the central opening and project radially inwardly. 
         [0010]    Such spin-on filters are also known to be referred to as easy-change filters or screw-on filters. At least one filter element is arranged in the housing pot of the filter housing in the case of the spin-on-filter. The spin-on filter is replaced entirely together with the filter housing and the at least one filter element contained therein. Advantageously, the at least one filter element may be fixedly arranged in the filter housing. 
         [0011]    The connecting ribs can be implemented as ramp sections. 
         [0012]    The connecting ribs can advantageously be continuous circumferentially with respect to the coupling axis. The connecting ribs can also include interruptions circumferentially with respect to the coupling axis. 
         [0013]    The spin-on filter or the filtering device is in particular designed such that unfiltered fluid is fed on one end face, and the filtered fluid is discharged on the same end face. 
         [0014]    Against this background, the connecting body can preferably also comprise at least one eccentric fluid opening, which advantageously can be a fluid inflow opening. The fluid can reach an interior space of the spin-on filter through the fluid inflow opening. The filtered fluid can flow back from the spin-on filter into the filter head via the central opening. Alternatively, however, it is also possible for both the untreated fluid and the treated fluid to flow via the central opening into the filter or out of the filter. 
         [0015]    The connecting body can advantageously be a connecting plate. 
         [0016]    The head-side coupling part can advantageously be designed as a connector. The head-side coupling part can alternatively also comprise a section that has the function and/or shape of a connector. 
         [0017]    In an advantageous embodiment, the coupling ribs, on the side thereof facing away from the filter head or on the side thereof facing the filter interior, can include at least one respective filter-side retaining surface extending obliquely with respect to the coupling axis, and on the side thereof facing the filter head or the side thereof facing away from the filter interior, they can include at least one respective feed ramp extending obliquely with respect to the coupling axis, which can be used to feed head-side retaining surfaces on the head-side coupling part to the filter-side retaining surfaces when the spin-on filter is being mounted to the filter head, while rotating the spin-on filter. 
         [0018]    In a further advantageous embodiment, the coupling ribs can be arranged on a radially inner circumferential side of the connecting body and project radially inwardly into the central opening. 
         [0019]    In this way, a stable and compact shape can be implemented. The coupling ribs can be arranged on an inner circumference of the central opening. 
         [0020]    In a further advantageous embodiment, starting sections of the coupling ribs facing the filter head may be distributed, in particular uniformly distributed, circumferentially with respect to the coupling axis. 
         [0021]    In this way, the risk of the spin-on filter tilting during attachment to the filter head can be reduced, and preferably prevented. 
         [0022]    In a further advantageous embodiment, starting sections of the coupling ribs facing the filter head may be spaced axially, with respect to the coupling axis, from a head-side radially inner edge of the connecting body surrounding the central opening. 
         [0023]    In this way, a section of the radially inner circumferential side of the connecting body, which delimits the central opening, can act as an axial insertion aid for the connector on the side of the filter head between the corresponding starting sections of the coupling ribs and the edge of the coupling body. 
         [0024]    The starting sections of the coupling ribs facing the filter head can advantageously be arranged with axial offset in relation to the head-side edge of the central opening. 
         [0025]    In a further advantageous embodiment, the coupling device can comprise at least one locking device having at least one filter-side locking part, which in the closed position of the coupling device can form an unlockable connection with at least one head-side locking part. 
         [0026]    In a further advantageous embodiment, the at least one filter-side locking part can comprise an in particular elastically movable, in particular deformable, lug, in particular a catch lug. 
         [0027]    The at least one filter-side locking part can advantageously be designed as a radially elastically deformable lug. 
         [0028]    In a further advantageous embodiment, the at least one filter-side locking part can be arranged on the connecting body, in particular on the side facing the filter head. 
         [0029]    The at least one filter-side locking part can advantageously be arranged on the side of the connecting plate facing the filter head. 
         [0030]    In a further advantageous embodiment, multiple filter-side locking parts may be distributed, in particular uniformly distributed, circumferentially with respect to the coupling axis. 
         [0031]    In a further advantageous embodiment, the coupling device can comprise at least one circumferential, with respect to the coupling axis, inner seal. 
         [0032]    In a further advantageous embodiment, the inner seal can be arranged offset axially with respect to the coupling axis in relation to the filter-side coupling part toward the interior of the spin-on filter. 
         [0033]    The inner seal can advantageously provide at least axial sealing with respect to the coupling axis between the filter head and the spin-on filter. The inner seal can advantageously separate a dirty side of the spin-on filter, in particular of the filter element, from a clean side. 
         [0034]    In a further advantageous embodiment, the coupling device can comprise at least one circumferential, with respect to the coupling axis, outer seal. 
         [0035]    In a further advantageous embodiment, the outer seal can be arranged on the connecting body. 
         [0036]    In a further advantageous embodiment, the outer seal can be oriented radially outwardly with respect to the coupling axis. 
         [0037]    In a further advantageous embodiment, the outer seal can surround the central opening, and optionally the at least one eccentric fluid opening. 
         [0038]    The outer seal can advantageously provide at least radial sealing with respect to the coupling axis between the filter head and the spin-on filter. It may separate a fluid-conducting area of the filtering device from the surroundings. 
         [0039]    The object is further achieved by the filtering device according to the invention in that the same comprises an easy-change filter, and more particularly a spin-on-filter according to the invention, which comprises:
       a housing pot, in which a filter element is arranged;   a connecting body, which is arranged at the end face of the housing pot and is provided with a central opening; and   a filter-side coupling part of a coupling device for detachably coupling the easy-change filter to a filter head of the filtering device, the coupling part being arranged on the central opening,       
 
         [0043]    wherein the filter-side coupling part can be detachably coupled to a connector of a head-side coupling part of a filter head of the filtering device by way of a plug-in and/or rotational movement with respect to a coupling axis, 
         [0044]    and wherein the filter-side coupling part comprises multiple coupling ribs, which are distributed in the circumferential direction of the coupling axis on the central opening and project radially inwardly. 
         [0045]    The easy-change filter can advantageously be a spin-on filter or screw-on filter. 
         [0046]    In an advantageous embodiment, at least one first of the coupling parts can comprise at least two first ramp sections extending helically with respect to the coupling axis, which overlap at least over a portion of the circumference with respect to the coupling axis such that they delimit a helically extending first ramp groove on sides that are axially opposite each other with respect to the coupling axis, and the second coupling part comprises at least two second ramp sections extending helically with respect to the coupling axis, of which at least one is guided at least partially in one of the first ramp grooves for closing the coupling device. 
         [0047]    The filtering device is suitable for filtering fluid. In particular liquids, in particular oil or fuel, can be filtered therewith. 
         [0048]    The filtering device can be used in internal combustion engines of motor vehicles. It can also be used in different internal combustion engines, in particular industrial motors. The invention can also be used outside of internal combustion engines, in particular in motor vehicle technology. 
         [0049]    The filtering device comprises a filter head, on which the easy-change filter can be mounted. The filter head can advantageously have at least one inflow and/or at least one outflow for the fluid. The filter head can preferably be rigidly fixed to a frame. The frame can in particular be part of the internal combustion engine and/or of the motor vehicle. 
         [0050]    The filter head comprises a head-side coupling part of a coupling device for the easy-change filter. The filter head can advantageously comprise the first coupling part. 
         [0051]    The easy-change filter comprises a filter-side coupling part of the coupling device. The easy-change filter can advantageously comprise the second coupling part. 
         [0052]    The second coupling part can be detachably coupled to the first coupling part. The coupling device can advantageously be closable and releasable by way of a combined plug-in movement and rotational movement (plug-in and/or rotational movement) with respect to a coupling axis. Combined plug-in/rotational connections are easy and quick to close and open. Moreover, they are robust to tensile loads. In this way, a quick-release fastener can be easily implemented with the coupling device according to the invention, which is easy and quick to close and open. 
         [0053]    The first coupling part can advantageously comprise at least two first, in particular head-side, ramp sections that extend helically with respect to the coupling axis. The second coupling part can comprise at least two second, in particular filter-side, ramp sections that extend helically with respect to the coupling axis. By using the helical ramp sections, an installation space-optimized coupling device can be implemented. By each of the coupling parts having at least two respective ramp sections, the ramp sections of the coupling parts can circumferentially abut each other in multiple locations when the coupling parts are plugged together by way of a plug-in movement in the direction of the coupling axis. In this way, the coupling parts can be attached to each other uniformly, in particular without tilting. During a subsequent rotational movement about the coupling axis, the ramp sections of the coupling parts can mutually guide each other. In this way, a closing process can be carried out easily and precisely. 
         [0054]    The first ramp sections can advantageously overlap at least over a portion of the circumference. Advantageously, they can delimit a helically extending first, in particular head-side, ramp groove on sides that are axially opposite each other with respect to the coupling axis. The at least one first ramp groove can advantageously have a U-shaped profile. In this way, it can serve as a guide for the second ramp sections on three sides, these being a radially outer or inner side and two axial sides. One of the axial sides can advantageously serve as a retaining surface, in particular a head-side retaining surface. 
         [0055]    So as to close the coupling device, at least one of the second ramp sections can be guided at least partially in one of the first ramp sections. With the aid of the cooperation between the ramp sections and the ramp grooves, it is possible to achieve precise, exact and stable guidance in the axial, radial and circumferential directions during closing of the coupling device. The corresponding second ramp sections can also be retained in a stable manner within the first ramp grooves. It is thus possible to implement a connection that is highly resilient axially with respect to the coupling axis, in particular when it comes to tensile forces. 
         [0056]    Multiple helical threads may be implemented by way of the multitude of ramp sections on each of the coupling parts. The coupling device can thus be closed using relatively small rotational movements. Advantageously, the coupling device can be closed by way of a rotational movement of no more than 360°. 
         [0057]    The slopes of the helical ramp sections can be uniform, in particular constant. They may also vary along the ramp sections. 
         [0058]    The first ramp sections can be identical. However, it is also possible to use differing first ramp sections. Correspondingly, the second ramp sections may be identical or different. The ramp sections of a respective one of the coupling parts can start at the same axial height with respect to the coupling axis. However, they may also start at differing axial heights. 
         [0059]    The coupling parts can each be made of a single material or of a material mix. The coupling parts can advantageously be made of plastic material, aluminum and/or sheet metal or comprise such a material. The two coupling parts can be made of the same material or of differing materials. 
         [0060]    The easy-change filter can advantageously have a round cross-section. The easy-change filter can advantageously be coaxial with respect to a filter axis. The filter axis can advantageously coincide with the coupling axis. The easy-change filter can advantageously comprise a filter element. The filter element can advantageously comprise a filter medium that is closed circumferentially. The filter medium can advantageously be pleated in a star-shaped or zigzag manner. The filter medium can advantageously be sealingly coupled to an end body, in particular an end cap, on at least one end face. The filter element can advantageously be coaxial with respect to the filter axis. The filter element can advantageously comprise a supporting body. The supporting body can advantageously be a center pipe. The center pipe can advantageously be located in an element interior of the filter element. The center pipe may extend between the end bodies. 
         [0061]    Advantageously, the filter-side, in particular second, coupling part may be a carrying and/or supporting part of the easy-change filter, in particular of a housing of the easy-change filter. 
         [0062]    Advantageously, the filter-side, in particular second, coupling part can be designed with a cover part, in particular a connecting body, for closing the housing of the easy-change filter. The filter-side coupling part can advantageously be integrally joined to the cover part. In this way, a complexity in terms of components can be reduced. The cover part can advantageously include at least one passage, in particular an inlet and/or an outlet, for the fluid into the easy-change filter or out of the same. The cover part can advantageously be fixed to a further housing part, in particular a filter bowl, of the easy-change filter by way of a fixation element. The fixation element can advantageously comprise a sheet metal ring, which may be coupled to the further housing part. The sheet metal ring can advantageously be coupled to the further housing part by way of a crimped joint. 
         [0063]    The coupling device can advantageously comprise at least one stop. The at least one stop can be used to prevent the coupling device from being moved beyond the closed position thereof during the plug-in and/or rotational movement. In this way, the closed position can be precisely defined. At least one of the stops can be located at the end of one of the ramp grooves. In this way, the corresponding facing end of the ramp section guided in the corresponding ramp groove can abut the stop and thus prevent further rotation. 
         [0064]    Advantageously, each of the two coupling parts can have at least two ramp sections that extend helically with respect to the coupling axis. The ramp sections of the same coupling part can overlap over at least part of the circumference with respect to the coupling axis. The ramp sections of the same coupling part can each delimit a helically extending ramp groove on sides that are axially opposite each other with respect to the coupling axis. So as to close the coupling device, each of the coupling parts can guide at least one of the ramp sections at least partially in one of the ramp grooves of the respective other coupling part. 
         [0065]    The coupling device can advantageously be located between a dirty side and a clean side of a filter element of the easy-change filter. The coupling device can thus advantageously be arranged within an outer seal, which can then seal the fluid-conducting area of the filtering device with respect to the surroundings. A retaining function/coupling function of the coupling device, and a sealing function between the fluid-conducting area of the filtering device and the surroundings, can thus be separated from each other. In this way, the retaining function/coupling function and the sealing function can each be optimized, in particular independently of one another. 
         [0066]    In an advantageous embodiment, at least one of the first ramp sections can comprise, outside the corresponding first ramp groove, an insertion ramp surface which can transition into the corresponding first ramp groove. The insertion ramp surface can serve as an insertion aid so as to achieve exact insertion of the respective second ramp sections into the corresponding ramp grooves. Advantageously, the at least one first ramp section, together with the insertion ramp surface, may be located on the filter head side. The at least one second ramp section on the easy-change filter side, in particular the spin-on filter side, can advantageously comprise, on a side located axially opposite the retaining surface, a feed ramp for the corresponding insertion ramp surface of the at least one first ramp section. 
         [0067]    At least one of the insertion ramp surfaces can advantageously extend helically with respect to the coupling axis. In this way, guidance of the corresponding second ramp sections during the plug-in and/or rotational movement for closing/opening the coupling device can be improved. 
         [0068]    Advantageously, the at least one insertion ramp surface can transition steplessly into the corresponding ramp groove. In this way, uniform guidance can be achieved. 
         [0069]    Advantageously, the at least one insertion ramp surface can be arranged on the side of the at least one first ramp section which axially faces the second coupling part. 
         [0070]    Advantageously, at least two of the first ramp sections can be circumferentially offset in relation to each other at least in some sections In this way, each of the second ramp sections can be placed against a corresponding insertion ramp surface when the coupling parts are plugged into each other in any rotational orientation of the easy-change filter with respect to the filter head. Guidance of the ramp sections can thus be achieved in any rotational position of the easy-change filter relative to the filter head. 
         [0071]    In a further advantageous embodiment, at least one of the first ramp sections may extend over only a portion of the circumference with respect to the coupling axis. In this way, the coupling device can be opened or closed by way of a rotation of the easy-change filter of no more than 360° relative to the filter head. The coupling device can be opened and closed quickly in this way. 
         [0072]    Advantageously, at least the first ramp sections can each extend across the same angle of circumference. The coupling device can thus be symmetrical with respect to the coupling axis. In this way, the easy-change filter can be mounted to the filter head in multiple rotational orientations. During closing of the coupling device, it is easier to find a starting position from which controlled closure of the coupling device is possible. The attachment of the easy-change filter can thus be simplified. 
         [0073]    Advantageously, an angle of circumference, across which each of the ramp grooves extends circumferentially, can correspond approximately to an angle of 360° divided by the number of first ramp sections. This can improve the symmetry of the coupling device. Mounting of the easy-change filter can be further simplified. Moreover, the circumferential extension of the ramp grooves in relation to the overall size of the coupling device can thus be optimized. It is thus possible to simplify the coupling device as a whole. Moreover, the guidance and retention of the corresponding second ramp sections during assembly of the coupling device can be improved. 
         [0074]    Advantageously, three first, in particular head-side, ramp sections may be provided in each case. Advantageously, three second, in particular filter-side, ramp sections may be provided in each case. Three ramp sections allow the second coupling part to be easily and precisely applied, guided and retained. 
         [0075]    The second ramp sections can advantageously each extend across the same angle of circumference as the ramp grooves. In this way, each of the second ramp sections can be lowered completely into the corresponding ramp grooves. The ramp grooves can implement a force transmission across the entire circumferential extension thereof, together with the second ramp sections. The mechanical load-bearing capacity of the coupling device can thus be improved. 
         [0076]    If three first ramp sections are used, the corresponding ramp grooves can advantageously each extend across an angle of circumference of approximately between 100° and 140°, and preferably 120°. The ramp grooves can thus overall encompass the entire circumference. In this way, the coupling parts can be coupled along the entire circumference. 
         [0077]    Advantageously, an angle of circumference, across which each of the insertion ramp surfaces extends, can correspond approximately to an angle of 360° divided by the number of first ramp sections. Advantageously, the second ramp sections can each extend across the same angle of circumference as the insertion ramp surfaces of the first ramp sections. The second ramp sections can thus each be uniformly and precisely placed against the corresponding insertion ramp surfaces and guided there. 
         [0078]    If three first ramp sections are used, the three second ramp sections can advantageously each extend across an angle of circumference of approximately between 100° and 140°, and preferably 120°. 
         [0079]    Advantageously, the first ramp sections can circumferentially delimit half of each insertion ramp surface and half of each ramp groove. In this way, the second ramp sections can be uniformly seated against and be guided on the insertion ramp surfaces. Moreover, the second ramp sections can be held half in the ramp grooves approximately across the entire circumferential extension of the same. In this way, a stable, and more particularly a tensile-resistant, coupling can be achieved. 
         [0080]    A very large supporting surface can be implemented in a coupling device having three respective ramp sections on the head side and on the filter side. In this way, high mechanical loads, and more particularly tensile loads, can be compensated for. 
         [0081]    The ramp grooves can advantageously adjoin each other circumferentially with respect to the coupling axis. The ramp grooves can thus be consecutively arranged with respect to the rotational movement for closing/opening the coupling device. The ramp grooves may be arranged without circumferential overlap. The ramp grooves can thus extend on the circumferential sides of the first coupling part in a space-saving manner. 
         [0082]    Advantageously, the insertion ramp surfaces may optionally adjoin each other circumferentially with respect to the coupling axis. The insertion ramp surfaces can be arranged without circumferential overlap. 
         [0083]    In a further advantageous embodiment, the coupling device can comprise at least one locking device having at least one head-side locking part and at least one filter-side locking part, which in the closed position of the coupling device can form an unlockable connection with each other. In this way, the closed coupling device can be mechanically secured at least when it is closed. The coupling device can thus be prevented from opening in an uncontrolled manner. The unlockable connection can advantageously be closed and/or opened without the use of a separate tool. 
         [0084]    The unlockable connection can advantageously be a detent connection. A detent connection is easy to close and open. The detent connection can advantageously implement a mechanical resistance, which must be overcome to open the unlockable connection. The unlockable connection can thus be prevented from opening in an uncontrolled manner. 
         [0085]    The unlockable connection, in particular the detent connection, can advantageously generate a signal, in particular a signal that can be detected acoustically and/or in a tactile manner, during locking. In this way, the closed state of the coupling device is easy to detect. 
         [0086]    At least one of the locking parts, and more particularly at least one of the filter-side locking parts, can advantageously comprise a spring arm. The spring arm can advantageously be bent radially outwardly and/or radially inwardly in a spring-loaded manner with respect to the coupling axis. A catch lug or a detent seat can advantageously be provided at one free end of the spring arm. The at least one corresponding other locking part, and more particularly at least one of the head-side locking parts, can advantageously correspondingly comprise a detent seat or a catch lug. The detent seat or catch lug of the spring arm can advantageously latchingly engage with the catch lug or detent seat of the other locking part in the locked position of the unlockable connection. 
         [0087]    The at least one other locking part can advantageously have a guide surface. The guide surface can ascend in a ramp-like manner in the axial direction. The detent seat or catch lug may optionally be located at the end of the guide surface. During the rotational movement for closing the coupling device, the spring arm of the one locking part, in particular optionally the catch lug, can be guided on the guide surface of the other locking part. 
         [0088]    The at least one spring arm can advantageously be arranged on the easy-change filter side. In this way, the spring arm can be replaced jointly with the easy-change filter. This allows fatigue on the movable spring arm to be prevented, which may occur as a result of multiple instances of opening and closing of the coupling device. The other locking part can advantageously be arranged on the filter head side. 
         [0089]    The spring arm of the one coupling part can advantageously extend against a closing rotational direction of the easy-change filter relative to the filter head. 
         [0090]    The spring arm can advantageously be preloaded, the preload being directed radially inwardly with respect to the coupling axis. The other locking part can advantageously be arranged on a circumferential side of the corresponding coupling part which is located radially outside with respect to the coupling axis. 
         [0091]    The unlockable connection can advantageously be located outside an interior of the easy-change filter. Advantageously, it can be located on the outside of a cover body, in particular of a filter cover, of the easy-change filter. It may be visible from the outside when the easy-change filter is separated from the filter head. It is thus possible to identify before mounting the easy-change filter whether the at least one filter-side locking part, and more particularly the spring arm, is functional, in particular undamaged. The at least one filter-side locking part, and more particularly the at least one spring arm, can advantageously project beyond the cover body in the axial direction. The filter-side locking part can advantageously be located in a circumferential extension of ribs extending circumferentially. The filter-side locking part can thus be protected. 
         [0092]    In a further advantageous embodiment, the coupling device can comprise at least one circumferential, with respect to the coupling axis, inner seal, which can provide sealing between the filter head and the easy-change filter at least axially with respect to the coupling axis and can separate a dirty side of the easy-change filter from a clean side. The inner seal can advantageously be an annular seal. It may have a round or angular, in particular rectangular, profile. The profile may be flat. 
         [0093]    The inner seal can advantageously contribute to axial bracing of the coupling device. In this way, it is possible to damp vibrations between the easy-change filter and the filter head. Any potential noise development, in particular rattling, may thus be reduced. 
         [0094]    The inner seal can advantageously be arranged coaxially with respect to the coupling axis. The axial sealing action can be improved during closing of the coupling device by a corresponding compression axially with respect to the coupling axis. 
         [0095]    The inner seal may additionally act as a screw-on protector. After compression of the inner seal, a rotation of the easy-change filter relative to the filter head against the closing rotational direction may be made more difficult as a result of friction. In this way, the likelihood of the coupling device opening in an uncontrolled manner can be reduced. 
         [0096]    The inner seal can advantageously be coupled to the easy-change filter. It may advantageously be secured to the easy-change filter. It may advantageously be arranged in an appropriate sealing groove on the easy-change filter. In this way, it is easy to captively preassemble. 
         [0097]    Advantageously, the inner seal can be arranged on an end body of a filter element, and more particularly of a round filter element, of the easy-change filter. It may advantageously surround a through-opening to an element interior of the filter element. The element interior can be located on the clean side or the dirty side of the filter element. Correspondingly, the dirty side or the clean side can be located on the outside of the filter element. 
         [0098]    The through-opening can advantageously be coaxial with respect to the coupling axis. It can advantageously be connected to a connecting channel. The connecting channel can advantageously extend coaxially with respect to the coupling axis at least in some sections. The connecting channel may be part of the filter head and/or of the head-side coupling part. The connecting channel can advantageously be connected to the at least one inflow or the at least one outflow for the fluid. This depends on whether a flow through the filter element from radially outside to radially inside, or vice versa, is possible. 
         [0099]    A sealing surface for the inner seal can advantageously be provided on the filter head side. The sealing surface can advantageously be coaxial with respect to the coupling axis. The inner seal can be seated against the sealing surface in a planner and circumferentially closed manner. The sealing surface can advantageously surround the connecting channel. 
         [0100]    The inner seal can advantageously be coaxial with respect to a potential center pipe of the easy-change filter. In this way, the inner seal can be supported against the center pipe in a stable manner in the axial direction. 
         [0101]    In a further advantageous embodiment, the coupling device can comprise at least one circumferential, with respect to the coupling axis, outer seal which can provide sealing between the filter head and the easy-change filter at least radially with respect to the coupling axis and can separate a fluid-conducting area of the filtering device from the surroundings. The outer seal can be used to separate the fluid-conducting areas, and more particularly areas between the easy-change filter and the filter head, from the surroundings in a sealed manner. The outer seal can be located on the dirty side or the clean side of the filter element of the easy-change filter. This depends on the flow direction of the fluid through the easy-change filter. 
         [0102]    The outer seal can provide sealing in the radial direction with respect to the coupling axis. In this way, any potential compression of the outer seal can be substantially independent of a degree with which the coupling device is closed. Mechanical loading of the outer seal can thus be decreased. 
         [0103]    The outer seal can advantageously be an O-ring seal. Alternatively, an angular, in particular flat, seal may be used. An O-ring seal has the advantage that it is able to roll more easily off the corresponding radially inner and/or radially outer sealing surfaces during a plug-in movement in the direction of the coupling axis. The radial sealing action can be better defined and/or set with the O-ring seal than with a flat seal. 
         [0104]    The outer seal can advantageously be secured on the easy-change filter side. It can advantageously be seated against the radial inside of a corresponding surface of the easy-change filter. Alternatively, it may also be seated against the radial outside of a corresponding surface of the easy-change filter. 
         [0105]    A corresponding sealing surface, with which the outer seal can sealingly cooperate, can advantageously be arranged on the filter head side. The sealing surface can be located radially outside or inside the outer seal. The sealing surface can advantageously be arranged on a corresponding outer sealing section on the filter head side. The outer sealing section can advantageously be cylindrical. The outer sealing section can advantageously be coaxial with respect to the coupling axis. A diameter of the sealing surface on the side facing the outer seal can widen in the axial direction toward the end face from which the outer seal is moved toward the sealing surface during coupling of the coupling device. In this way, an insertion of the outer seal into the sealing surface or an attachment of the outer seal onto the sealing surface can be simplified. Moreover, the outer seal can be continuously, in particular uniformly, compressed during the closing process of the coupling device. 
         [0106]    The outer seal can advantageously be arranged in a seal seat. The seal seat can advantageously be located on the easy-change filter side. The seal seat can advantageously be a sealing groove. The sealing groove can advantageously be open to the radial outside or to the radial inside. The sealing groove can advantageously be arranged on a cover element of the easy-change filter. The cover element can advantageously be annular. Advantageously, the cover element can be a sheet metal ring. The sealing groove can advantageously be implemented by crimping of the sheet metal ring. The cover element can advantageously be coupled to a housing element, in particular a housing pot, of the easy-change filter, in particular by way of a crimp. 
         [0107]    On the side facing the open side of the sealing groove, the cover element can comprise a seat, in particular an annular groove, for the outer sealing section of the filter head. 
         [0108]    The outer seal can additionally or alternatively also provide axial sealing. 
         [0109]    Advantageously, a progression of the ramp sections can be adapted to an arrangement of a circumferential, with respect to the coupling axis, outer seal of the coupling device such that, during closing of the coupling device by way of a plug-in and/or rotational movement, during an early closing phase, in particular during which the second ramp sections are located in a respective starting region of the ramp grooves, the outer seal is located axially outside one of two sealing sections, in particular of a cylindrical outer sealing section, between which the outer seal provides sealing in the radial direction in the closed position of the coupling device, and during a later closing phase, during which the second ramp sections in particular engage in a respective end region of the ramp grooves, the outer seal is compressed between the two sealing sections. In this way, the outer seal can be relieved during the closing phase when the ramp sections are located outside or in the starting region of the ramp grooves. Loading, in particular compression, of the outer seal does not take place until the later closing phase when the ramp sections engage in the respective ramp grooves, and more particularly in the end regions of the same. In this way, a circumferential movement, in particular chafing, of the outer seal between the sealing sections, in particular between the head-side outer sealing section and the filter-side sealing groove, can be minimized. Mechanical loading of the outer seal, in particular wear, can thus be decreased. The slopes and/or the corresponding circumferential extensions of the ramp grooves and/or optionally of the insertion ramp surfaces can advantageously be adapted to the arrangement, in particular the position, of the outer seal. 
         [0110]    The earlier closing phase can advantageously take place as the second ramp sections enter the ramp grooves. A first rotational angle during the rotation of the easy-change filter relative to the filter head, between the time at which the second ramp sections enter the ramp grooves and the early closing phase transitions to the late closing phase, can advantageously correspond approximately to a second rotational angle between the time at which the earlier closing phase transitions to the later closing phase and the later closing phase is completed. 
         [0111]    If three ramp sections are used, the compression of the outer seal can advantageously begin following the time at which the second ramp sections enter the ramp grooves, subsequent to a rotation of the easy-change filter by approximately 60°. After the easy-change filter is rotated another 60°, the outer seal can be completely compressed. 
         [0112]    In addition, the advantages and features described above in connection with the spin-on filter according to the invention and the advantageous embodiments thereof apply in corresponding fashion to the filtering device according to the invention and the advantageous embodiments thereof, and vice versa. 
         [0113]    The object is further achieved by the filter head according to the invention in that the filter head comprises a head-side coupling part having a connector, to which a filter-side coupling part of an easy-change filter, and more particularly of a spin-on filter according to the invention, can be detachably coupled by way of a plug-in and/or rotational movement with respect to a coupling axis, wherein the head-side coupling part comprises at least one fluid channel which can communicate with a fluid opening of the easy-change filter, and wherein the head-side coupling part comprises multiple head-side coupling ribs, which are distributed in the circumferential direction of the coupling axis and implement seats for corresponding filter-side coupling ribs of the filter-side coupling part of the easy-change filter. 
         [0114]    The easy-change filter can advantageously be a spin-on filter. 
         [0115]    In addition, the advantages and features described above in connection with the spin-on filter according to the invention and the filtering device according to the invention and the respective advantageous embodiments of the same apply in corresponding fashion to the filter head according to the invention and the advantageous embodiments thereof, and vice versa. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0116]    Additional advantages, features and details of the invention will be apparent from the description provided hereafter, which describes one exemplary embodiment of the invention in more detail based on the drawings. A person skilled in the art will expediently also individually consider the features that are disclosed in combination in the drawings, the description and the claims and combine them to form meaningful further combinations. In the schematic drawings: 
           [0117]      FIG. 1  shows a longitudinal section of a filter system for engine oil of an internal combustion engine of a motor vehicle, including a filter head to which an easy-change filter is secured by way of a releasable coupling device; 
           [0118]      FIG. 2  shows a detailed view of another longitudinal section of the filter system of  FIG. 1  in the region of the coupling device; 
           [0119]      FIG. 3  shows an isometric representation of the filter head of  FIGS. 1 and 2  without the easy-change filter, with a view onto the coupling side; 
           [0120]      FIG. 4  shows a top view onto the coupling side of the filter head of  FIGS. 1 to 3  without the easy-change filter; 
           [0121]      FIG. 5  shows an isometric representation of the easy-change filter of  FIGS. 1 and 2 , with a view onto the coupling side; and 
           [0122]      FIG. 6  shows a top view onto the coupling side of the easy-change filter of  FIGS. 1,2 and 5 . 
       
    
    
       [0123]    In the figures, identical components are denoted by the same reference numerals. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0124]      FIGS. 1 to 6  show a filter system  10  for engine oil of an internal combustion engine of a motor vehicle in different perspectives, sections and detailed views. 
         [0125]    The filter system  10  comprises a filter head  12 , to which an easy-change filter  14  is detachably secured. The filter head  12  is made of metal. The filter head  12  is rigidly coupled to the internal combustion engine and serves as a connecting part for the easy-change filter  14 . The filter head  12  comprises an inlet  16  and an outlet  18  for the engine oil. The inlet  16  and the outlet  18  are connected to corresponding oil lines of the internal combustion engine in a manner that is not of further interest here. 
         [0126]    The filter head  12  moreover comprises a head-side coupling part  20  of a releasable coupling device for coupling the easy-change filter  14  to the filter head  12 , the coupling device being denoted in the overall by reference numeral  22 . The head-side coupling part  20  is made of metal. The side of the head-side coupling part  20  facing the easy-change filter  14  has the shape and function of a connector. The head-side coupling part  20  is screwed into a hollow connecting cylinder  24 , which is integrally joined to the filter head  12 . The connecting cylinder  24  includes an internal thread. The connecting cylinder  24  is coaxial with respect to a filter axis  26 . Instead of being screwed as a separate component to the filter head  12 , the head-side coupling part  20  can also be integrally joined thereto. 
         [0127]    When referring hereafter to “axial,” “radial,” “coaxial” or “circumferential,” this description relates to the filter axis  26 , unless indicated otherwise. 
         [0128]    The head-side coupling part  20  comprises a cylindrical connecting sleeve section  28  having an external thread matching the internal thread of the connecting cylinder  24 . When the easy-change filter  14  is attached, the connecting sleeve section  28  is likewise coaxial with respect to the filter axis  26 . 
         [0129]    An interior of the connecting sleeve section  28  is connected to the outlet  18  of the filter head  12 . The connecting sleeve section  28  has a single step on the radially inner circumferential side thereof. The inside cross-section of the connecting sleeve section  28  is approximately hexagonal on the expanded side facing the easy-change filter  14 , wherein the corners are slightly rounded. The inside cross-section of an imaginary incircle on the side of the outlet  18  is smaller than the inside cross-section of the connecting sleeve section  28  on the side facing the easy-change filter  14 . 
         [0130]    The connecting cylinder  24  is surrounded on the radial outside by an inlet ring chamber  30  of the filter head  12 . 
         [0131]    An end face of the connecting sleeve section  28  facing the easy-change filter  14  forms an annular coaxial sealing surface  32 . 
         [0132]    The connecting sleeve section  28  of the head-side coupling part  20  is surrounded on the radial outside by an outer cylinder section  34 . The circumferential wall of the outer cylinder section  34  has approximately the shape of a hollow circular cylinder. The outer cylinder section  34  is coaxial with respect to the filter axis  26 . It extends in the axial direction approximately from the axial center plane of the connecting sleeve section  28  in the direction toward the end face of the connecting sleeve section  28  which faces the easy-change filter  14 . On the side facing the filter head  12 , the outer cylinder section  34  is integrally joined to the radially outer circumferential side of the connecting sleeve section  28  by way of a radial ring disk section  36 . 
         [0133]    A plurality of radial connecting walls  40  are arranged in an annular chamber  38  between the radially inner circumferential side of the outer cylinder section  34  and the radially outer circumferential side of the connecting sleeve section  28 . The radial connecting walls  40  are each integrally joined on the radial outside to the outer cylinder section  34 , and on the radial inside to the connecting sleeve section  28  and to a bottom side of the radial ring disk section  36 . The radial connecting walls  40  each extend radially and axially. They are arranged in an approximately star-shaped manner seen in the direction of the filter axis  26 . 
         [0134]    A total of three head-side ramp sections  42  are arranged on the radially outer circumferential side of the outer cylinder section  34 . The head-side ramp sections  42  are identical in terms of the expanses and shapes thereof. The head-side ramp sections  42  each extend helically with respect to the filter axis  26 . A slope direction of the head-side ramp sections  42  corresponds to a known right-handed thread. 
         [0135]    A closing rotational direction  43  of the easy-change filter  14  relative to the filter head  12 , which is indicated by an arrow in  FIGS. 1, 2, 4 and 6 , corresponds to that of a known right-handed thread. The closing rotational direction  43  extends clockwise from the easy-change filter  14  toward the filter head  12  seen in the axial direction. 
         [0136]    The head-side ramp sections  42  each extend approximately across an angle of circumference of 240°. The head-side ramp sections  42  are arranged offset in relation to each other. Two of the head-side ramp sections  42  in each case overlap across half of the circumferential extensions thereof. The starting sections of the head-side ramp sections  42  are each located on the free end face of the outer cylinder section  34  which faces the easy-change filter  14 . The ends of the head-side ramp sections  42  are each circumferentially located where the next but one head-side ramp section  42  begins, seen against the closing rotational direction  43 . 
         [0137]    Each head-side ramp section  42  is composed of two regions seen circumferentially. A first region including a respective insertion ramp surface  44  extends circumferentially from the starting section of a respective head-side ramp section  42  to the starting section of the respective next head-side ramp section  42 , seen against the closing rotational direction  43 . The insertion ramp surfaces  44  are freely accessible in the axial direction, seen from the easy-change filter  14 . They each extend in the radial direction and helically in the circumferential direction. The insertion ramp surfaces  44  each extend in the radial direction across the entire radial wall thickness of the outer cylinder section  34 . 
         [0138]    A respective region including a groove ramp surface  46  adjoins the respective insertion ramp surface  44 . The circumferential extension of the insertion ramp surface  44  corresponds to the circumferential extension of the groove ramp surfaces  46 . They each extend across an angle of circumference of 120°. The groove ramp surfaces  46  are located on the radial outside of the outer cylinder section  34 . The regions including the groove ramp surfaces  46  each overlap the subsequent head-side ramp sections  42 , seen against the closing rotational direction  43 . The groove ramp surface  46  of the front head-side ramp section  42 , seen in the closing rotational direction  43 , in each case overlaps the insertion ramp surface  44  of the subsequent head-side ramp section  42 . The groove ramp surfaces  46  extend in the radial direction approximately across half the radial wall thickness of the outer cylinder section  34 . The insertion ramp surfaces  44  transition without steps into the groove ramp surfaces  46 . The groove ramp surfaces  46  have the same slope as the insertion ramp surfaces  44 . Each of the groove ramp surfaces  46  starts, in the circumferential direction, at the level of the starting section of the respective subsequent clockwise head-side ramp section  42 . The groove ramp surfaces  46  end at the level of the starting section of the respective circumferentially next but one head-side ramp section  42 . 
         [0139]    The groove ramp surfaces  46  delimit a respective ramp groove  48  on an axial side. On the axially opposing side, the ramp grooves  48  are each delimited by a head-side retaining surface  49  of the corresponding region of the subsequent head-side ramp section  42 , the retaining surface being located axially opposite the insertion ramp surface  42 . The ramp grooves  48  have a constant axial extension in the circumferential direction. Seen in the circumferential direction, the radial extension of the same is likewise constant. 
         [0140]    Three detent elements  50  of a locking device of the coupling device  22  are arranged on the radially outer circumferential side of the outer cylinder section  34 , the locking device being denoted in the overall by reference numeral  52 . Each of the detent elements  50  is integrally joined to the outer cylinder section  34 . The detent elements  50  are radial elevations. The detent elements  50  are arranged in the axial direction approximately at the level of the radial ring disk section  36 . 
         [0141]    Each of the detent elements  50  is approximately wedge-shaped. In a rear region with respect to the closing rotational direction  43  of the coupling device  22 , each detent element  50  has a sloping guide surface  54 . The guide surface  54  is provided at the radially outer circumferential side of the detent elements  50 . A respective detent recess  56  adjoins the end of the guide surface  54 . The radial expansion of the detent elements  50  is smaller in the region of the detent recess  54  than in the region of the end of the guide surface  54  which is elevated in the radial direction. Each detent element  50  extends circumferentially across an angle of circumference of approximately 25° to 30°. The transition from the guide surface  54  to the corresponding detent recess  56 , seen circumferentially, is located approximately at one level with the end of one of the head-side ramp sections  42  and the start of the next but one head-side ramp section  42 , seen against the closing rotational direction  43 . 
         [0142]    The connecting cylinder  24  and the head-side coupling part  20  are surrounded by a coaxial circular cylindrical outer sealing section  58 . The free end face of the outer sealing section  58  faces the easy-change filter  14 . The inside cross-section of this section increases toward the free end face thereof. The radially inner circumferential side of the outer sealing section  58  forms an outer sealing surface  60 . 
         [0143]    Furthermore, the filter bowl  12  comprises an outer collar  62 , which extends in sections coaxially with respect to the filter axis  26  and surrounds the radial outside of the outer sealing section  58  over a portion of the circumference. 
         [0144]    The easy-change filter  14  is designed as a spin-on filter having a round cross-section. It is substantially coaxial with respect to the filter axis  26 . The easy-change filter  14  comprises a filter bowl  64 , in the open side of which a filter cover  66  is secured. The filter bowl  64  has an outwardly curved filter bottom  68 . 
         [0145]    A coaxial filter element  70  is arranged in the filter bowl  64 . The filter element  70  comprises a circumferentially closed filter medium  72  that is pleated in a zigzag manner. At the respective end faces, the filter medium  72  is sealingly connected to a connecting end cap  74 , at the top, see  FIG. 1 , and a counter end cap  76 , at the bottom. 
         [0146]    The connecting end cap  74  is shown in detail in  FIGS. 2, 5 and 6 . It is located on the side of the filter element  70  facing the filter cover  66 . The filter medium  72  surrounds an element interior  78  of the filter element  70 . The element interior  78  is located on a clean side of the filter element  70 . 
         [0147]    The counter end cap  76  closes the element interior  78  on the end face of the filter element  70  facing the filter bottom  68 . Multiple spring elements  80  are supported on the outside of the counter end cap  76  which faces the filter bottom  78 , and are supported on the other side on the spring bottom  68 . 
         [0148]    The filter element  70  is surrounded on the radial outside by a dirty-side annular chamber  82 , which is delimited by the radially inner circumferential side of the filter bowl  64 . 
         [0149]    A coaxial center pipe  84  extends in the element interior  78  between the counter end cap  76  and the connecting end cap  74 . A circumferential wall of the center pipe  84  is pervious to the engine oil. A radially inner circumferential side, which is to say radially inner pleated edges, of the filter medium  72  is supported on the radially outer circumferential side of the center pipe  84 . 
         [0150]    The connecting end cap  74  comprises a coaxial outlet opening  86  for the filtered engine oil. A coaxial seal seat cylinder  88  is integrally provided on the axially outer side of the connecting end cap  74 . A radially inner circumferential side of the seal seat cylinder  88  is stepped. On the end face facing away from the element interior  78 , the seal seat cylinder  88  comprises a coaxial sealing groove  90  including an annular inner seal  92 . The inner seal  92  is arranged offset axially with respect to the filter axis  26  in relation to the filter-side coupling part  108  toward the interior of the easy-change filter  14 . The inner seal  92  is designed as a flat seal. When the easy-change filter  14  is mounted, the side of the inner seal  92  facing away from the element interior  78  is sealingly seated against the sealing surface  32  of the connecting sleeve section  28  of the head-side coupling part  20 . The inner seal  92  acts in the axial direction. The inner seal  92  separates a dirty side of the filter element  70 , radially outside the seal seat cylinder  88 , in a sealed manner from a clean side, radially inside the seal seat cylinder  88 . The smallest inside radius of the seal seat cylinder  88  corresponds approximately to the inside radius of an imaginary incircle of the connecting sleeve section  28  on the side having an expanded cross-section. 
         [0151]    On the radial outside, the seal seat cylinder  88  is braced by way of supporting elements  94  against the radially extending section of the connecting end cap  74 . The supporting elements  94  each extend radially and axially. In addition, inner supporting elements  96  are provided on the radially inner circumferential side of the seal seat section  88 , bracing a ring section of the seal seat cylinder  88  that surrounds the sealing groove  90  on the radial inside. 
         [0152]    The filter cover  66  has the shape of a ring having an approximately rectangular profile. The filter cover  66  is made of metal. The filter cover  66  has the function of a connecting plate for coupling the easy-change filter  14  to the filter head  12 . The filter cover  66  includes a receiving opening  98  that is coaxial with respect to the filter axis  26 , for receiving the outer cylinder section  34  of the head-side coupling part  20 . Within the radially outer edge of the filter cover  66 , a coaxial annular groove  100  for accommodating a cover sheet metal ring  102  is arranged on the outside facing away from the filter bottom  68 . A plurality of inlet through-ports  104  are arranged radially between the annular groove  100  and the receiving opening  98 . The inlet ports  104  each extend in parallel to the filter axis  46 . They connect the inlet ring chamber  30  of the filter head  12  to the interior of the filter bowl  64 , or the dirty-side annular chamber  82 . 
         [0153]    Three filter-side ramp sections  106  are arranged on the radially inner circumferential side of the filter cover  66 . The ramp sections  106  implement respective coupling ribs. The filter-side ramp sections  106  each extend radially inwardly from the radially inner circumferential side of the filter cover  66 . The extension and the circumferential progression of the filter-side ramp sections  106  are substantially identical. The sides of the filter-side ramp sections  106  facing the interior of the filter bowl  64  form respective filter-side retaining surfaces  107 . The sides of the filter-side ramp sections  106  facing away from the interior of the filter bowl  64  form respective filter-side feed ramps  109 . The filter-side retaining surfaces  107  and the feed ramps  109  run approximately parallel to each other. The filter-side ramp sections  106  each extend helically with respect to the filter axis  26 , analogously to the head-side ramp sections  42 . The slopes of the same correspond to those of the head-side ramp sections  42 . The filter-side ramp sections  106  each extend across an angle of circumference of 120° with respect to the filter axis  26 . The filter-side ramp sections  106  do not overlap. The starting sections  111  of the filter-side ramp sections  106  are located on the axial side facing away from the interior of the filter bowl  64 . The starting sections  111  face the filter head  12  when the easy-change filter  14  is mounted. The starting sections  111  are spaced from a head-side radially inner edge of the filter cover  66  which faces away from the element interior  78  and surrounds the outlet opening  86 . Seen circumferentially, the starting section  111  of each filter-side ramp section  106  is located at one level with the end of the preceding filter-side ramp section  106  in the closing rotational direction  43 . The axial heights of the filter-side ramp sections  106  are constant across the circumference. They correspond to the axial heights of the ramp grooves  48  of the head-side ramp sections  42 . The filter-side ramp sections  106  and the receiving opening  98  together form a filter-side coupling part  108  of the coupling device  22 . 
         [0154]    Three detent spring elements  110  are arranged on the outside of the filter cover  66  facing away from the interior of the filter bowl  64 . The detent spring elements  110  are part of the locking device  52 . Each of the detent spring elements  110  has a retaining section  112 . The retaining section  112  is integrally joined to the filter cover  66  radially between the annular groove  100  and the receiving opening  98 . A respective spring arm section  114  of the detent spring elements  110  is integrally joined to the retaining section  112 . The spring arm sections  114  are each located on the front side of the retaining sections  112 , seen in the closing rotational direction  43 . The spring arm sections  114  each extend circumferentially across an angle of circumference of approximately 30°. The spring arm sections  114  can be bent outwardly in a spring-loaded manner on the retaining sections  112  in the radial direction. At the respective free ends facing away from the retaining sections  112 , each of the spring arm sections  114  transitions into a catch lug  116 . The catch lugs  116  extend radially inwardly. Each of the catch lugs  116  is located on the same circumferential side as a starting section  111  of one of the filter-side detent sections  106  and an end of the respective preceding filter-side ramp section  106 . 
         [0155]    The cover sheet metal ring  102  has a profile that is bent multiple times. The radially outer circumferential side of the ring is rigidly connected to a free edge of the filter bowl  64  by way of a crimped joint  120 . Radially inside the crimped joint  120 , the cover sheet metal ring  102  has an approximately rectangular, circumferentially closed first bending section. In the region of the first bending section, the cover sheet metal ring  102  comprises a collar  122 , which engages in the annular groove  100  of the filter cover  66 , on the side facing the filter cover  66 . 
         [0156]    On the outside of the cover sheet metal ring  102  facing away from the filter cover  66 , the collar  122  forms a receiving groove  124  for the outer sealing section  58  of the filter head  12 . 
         [0157]    The radially inner circumferential side of the cover sheet metal ring  102  is bent to form a U-shaped profile, the opening of which points radially outwardly. The U-shaped profile includes a coaxial, circumferentially closed sealing groove  126 . An outer seal  128  is arranged in the sealing groove  126 . The outer seal  128  is an O-ring seal. The outer seal  128  is oriented radially outwardly with respect to the filter axis  26 . The outer seal  128  acts in the radial direction. 
         [0158]    On the inside edge facing axially away from the filter cover  66 , the cover sheet metal ring  102  comprises a plurality of notches  130  distributed over the circumference. 
         [0159]    When the easy-change filter  14  is mounted, the outer seal  128  is sealingly seated against the outer sealing surface  60  of the outer sealing section  58 . The outer seal  128  separates the dirty side of the filter element  70 , or the inlet ring chamber  30 , from the surroundings  132 . 
         [0160]    For coupling to the filter head  12 , the easy-change filter  14  is initially moved, with the filter cover  66  first, axially with respect to a coupling axis, which in the exemplary embodiment coincides with the filter axis  26 , toward the head-side coupling part  20  of the filter head  12  in a plug-in movement. The outer cylinder section  34  is plugged into the receiving opening  98  of the filter cover  66  until the filter-side ramp sections  106  axially abut the insertion ramp surfaces  44  of the head-side ramp sections  42 . The outer sealing section  58  is located axially remote from the outer seal  128 . 
         [0161]    Using a rotational movement of the easy-change filter  14  in the closing rotational direction  43 , the filter-side coupling part  108  is screwed into the head-side coupling part  20 . In this process, the respective filter-side ramp sections  106  engage in one of the ramp grooves  48 . Following a rotational angle of 60° from the time at which the filter-side ramp sections  106  begin to be lowered into the ramp grooves  48 , the outer seal  128  begins to be seated against the outer sealing surface  60  of the outer sealing section  58  and is guided in the inlet region having an expanded cross-section when the easy-change filter  14  is rotated further. 
         [0162]    Following further rotation by 60°, the front ends, in the closing rotational direction  43 , of the filter-side ramp sections  160  abut the rear ends of the ramp grooves  48 . The ends of the ramp grooves  48  form stops, which prevent the easy-change filter  14  from being rotated further when the coupling device  22  is closed. 
         [0163]    When the coupling device  22  is closed, the inner seal  92  is sealingly seated against the sealing surface  32  of the connecting sleeve section  28  in a radially compressed manner. 
         [0164]    In an end phase of the closing movement, the catch lugs  116  of the spring arm sections  114  of the detent spring elements  110  furthermore abut the respective rear ends, in the closing rotational direction  43 , of the guide surfaces  54  of the detent elements  50 . When the easy-change filter  14  is rotated further in the closing rotational direction  43 , the catch lugs  116  are guided on the guide surfaces  54 . When the coupling device  22  is closed, the catch lugs  116  latchingly engage the respective detent recesses  56  of the detent elements  50 . The latching engagement of the catch lugs  116  generates an audible sound. 
         [0165]    The latchingly engaged catch lugs  116  make it more difficult to open the coupling device  22  by rotating the easy-change cylinder  14  against the closing rotational direction  43 . Moreover, the compressed inner seal  92  makes it more difficult to open the coupling device  92  as a result of friction. 
         [0166]    The easy-change filter  14  is removed from the filter head  12  by rotating the easy-change filter  14  against the closing rotational direction  43 . For this purpose, initially the spring force of the spring sections  114  and the frictional force between the inner seal  92  and the sealing surface  32  must be overcome. 
         [0167]    During operation of the filter system  10 , the engine oil to be filtered is fed through the inlet  16  of the filter head  12  to the inlet ring chamber  30 . From there, the engine oil reaches the dirty-side annular chamber  82  of the easy-change filter  14  through the inlet ports  104 . The engine oil to be filtered flows through the filter medium  72  from the radial outside to the radial inside and is purified. The purified engine oil leaves the element interior  78  through the outlet opening  86  and reaches the interior of the connecting sleeve section  28 , which serves as an oil duct. The interior of the connecting sleeve section  28  thus fluidically communicates with the outlet opening  86 . From there, the purified engine oil flows into the outlet  18  of the filter head  12  and leaves the filter system  10 . 
         [0168]    In an alternative design of the filtering device, it is possible to provide inlet ports on the filter head  20 , and specifically on the ring disk section  36  of the connecting sleeve section  28 , so that the untreated fluid can flow through the head-side inlet ports into the filter, as an alternative or in addition to the inlet via the inlet ports  104 .