Filter system and filter element unit for a fluid

Abstract

The invention relates to a filter system (100) for a fluid, in particular oil or fuel, in particular of an internal combustion engine, comprising a filter housing (110) with a fluid inlet (102), a first fluid outlet (104), and a second fluid outlet (106), and comprising a main-flow filter element (10) arranged in the filter housing (110) and a bypass filter element (30) arranged in series therewith in the flow direction (82). The main-flow filter element (10) surrounds a central tube (14). The bypass filter element (30) is arranged in an element housing (34) with a central inlet tube (50) and a central outlet tube (52), wherein the element housing (34) has at least one outflow opening (54) for the fluid filtered by the bypass filter element (30). The element housing (34) is coupled to the central tube (14) of the main filter element (10) in a rotationally fixed manner about a longitudinal axis (80).The outlet pipe (52) is fluidly connected to the first fluid outlet (104) and the drain opening (54) is fluidly connected to the second fluid outlet (106). Furthermore, the invention relates to a filter element unit (1).

Description

Technical area

[0001] The invention relates to a filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine, and a filter element unit for a filter system. State of the art

[0002] Filter systems with main flow filter elements and bypass filter elements arranged parallel in the fluid flow are known.

[0003] EP 0 487 231 A2 discloses an oil filter comprising a housing open at one end, a first separation unit arranged in the housing for removing solid contaminants from an oil, and a second separation unit for removing gaseous contaminants. The first separation unit comprises cylindrical primary and secondary filter elements aligned with one another, with the secondary filter element being finer than the primary filter element. The unfiltered oil flows through the primary filter element and the secondary filter element in parallel. The oil filtered by the primary filter element is supplied to an engine, and the oil filtered by the secondary filter element flows into an oil pan.

[0004] US 2003 / 0168397 A1 describes a filter system for filtering a pressurized liquid, such as oil, having a closed housing that has an inlet and main and secondary outlets for this liquid. The filter system further comprises a main filter element exposed to the majority of the liquid flow, the flow being directed through the main filter element to the main outlet of the housing; and a secondary filter element exposed to a portion of the liquid flow supplied to the housing inlet. The liquid flow through the secondary filter element is directed to the secondary outlet out of the housing. The main filter element offers less resistance to the liquid flowing through it than the secondary filter element, so that most of the liquid flowing through the inlet is filtered by the main filter element and the remainder by the secondary filter element. Disclosure of the invention

[0005] An object of the invention is to provide an improved filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine.

[0006] A further object of the invention is to provide an improved filter element unit for such a filter system according to one of the preceding claims for a fluid, in particular oil or fuel, in particular of an internal combustion engine.

[0007] The above-mentioned object is achieved according to one aspect of the invention with a filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine, with a filter housing having a fluid inlet, a first fluid outlet and a second fluid outlet and with a main flow filter element arranged in the filter housing and a secondary flow filter element arranged in series therewith in the flow direction, wherein the filter housing comprises at least a first housing part and a second housing part, which are connected to one another, wherein the first fluid outlet and the second fluid outlet are arranged in the second housing part, wherein the main flow filter element surrounds a central tube and has a first end plate with a first central opening on a first end face and a second end plate with a second central opening on a second end face axially opposite the first end face,wherein the central tube engages the first and second openings, wherein the bypass filter element is arranged in an element housing having a central inlet tube and a central outlet tube, wherein the element housing has at least one outlet opening for the fluid filtered by the bypass filter element, wherein the element housing is rotationally fixedly coupled to the central tube of the main filter element about a longitudinal axis, wherein the outlet tube is fluidically connected to the first fluid outlet and the outlet opening is fluidically connected to the second fluid outlet.

[0008] According to a further aspect of the invention, the further object is achieved by a filter element unit for a filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine, at least comprising a main flow filter element and a bypass filter element, wherein the bypass filter element is arranged serially downstream of the main flow filter element in the flow direction for a portion of the fluid filtered by the main flow filter element to flow through, wherein the main flow filter element surrounds a central tube and has a first end plate with a first central opening on a first end face, and a second end plate with a second central opening on a second end face axially opposite the first end face, wherein the central tube engages in the first and second openings,wherein the bypass filter element is arranged in an element housing having a central inlet pipe and a central outlet pipe, wherein the element housing has at least one discharge opening for the fluid filtered by the bypass filter element, wherein the element housing is rotationally fixedly coupled to the center pipe of the main filter element about a longitudinal axis.

[0009] Advantageous embodiments and advantages of the invention emerge from the further claims, the description and the drawing.

[0010] According to one aspect of the invention, a filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine, is proposed, comprising a filter housing with a fluid inlet, a first fluid outlet and a second fluid outlet and with a main flow filter element arranged in the filter housing and a bypass filter element arranged in series therewith in the flow direction, wherein the filter housing comprises at least a first housing part and a second housing part which are connected to one another, wherein the first fluid outlet and the second fluid outlet are arranged in the second housing part.The main flow filter element surrounds a central tube and has a first end plate with a first central opening on a first end face and a second end plate with a second central opening on a second end face axially opposite the first end face, wherein the central tube engages in the first and second openings. The bypass filter element is arranged in an element housing with a central inlet tube and a central outlet tube, wherein the element housing has at least one outflow opening for the fluid filtered by the bypass filter element. The element housing is coupled to the central tube of the main filter element in a rotationally fixed manner about a longitudinal axis. The outlet tube is fluidically connected to the first fluid outlet and the outflow opening is fluidically connected to the second fluid outlet.

[0011] The proposed filter system comprises a serially connected filter element unit, in which the volume flow of the fluid to be filtered is first filtered through the main-flow filter element. The bypass filter element is arranged downstream of the main-flow filter element so that a portion of the fluid filtered by the main-flow filter element can flow through it. In the bypass flow, a portion of the filtered oil is thus diverted to the bypass filter element.

[0012] The filter medium for the bypass filter element is significantly finer than that of the main flow filter element. The fluid flows through this bypass filter element from the inside to the outside. The filtered fluid can flow back through a dedicated channel, for example, into the oil pan.

[0013] The bypass filter element is positioned below the main flow filter element in the direction of gravity. The fluid to be filtered has already been filtered through the main flow filter element, partially flows to the bypass filter element, and is finely filtered from radially inside to outside as it flows through the bypass filter element.

[0014] The fluid then flows radially inwards through fine channels in the lower end plate and then axially in the longitudinal direction through a drainage channel back into the oil pan.

[0015] To prevent unfiltered fluid from entering the bypass flow, the bypass filter element is equipped with an element housing. The element housing is completely enclosed and engages with the center tube of the main flow filter element. Furthermore, torque can be introduced from the filter housing cover into the main flow filter element and then transmitted via the element housing of the bypass filter element to the end plate of the bypass filter element.

[0016] In contrast to the prior art, the proposed filter system has a full-flow filter element and a bypass filter element arranged in series in the flow direction. As a result, the bypass filter element, acting as a fine filter, is not located on the contaminant side of the filter system and is therefore not exposed to coarse contaminants.

[0017] This allows the bypass filter element to be operated with significantly less pressure loss.

[0018] According to a favorable embodiment of the filter system, the second fluid outlet can be arranged radially outside the first fluid outlet. This allows the fluid filtered by the bypass filter element to be easily discharged, for example, into the oil pan without interfering with the main fluid flow line.

[0019] According to a favorable embodiment of the filter system, the second housing part can have a connecting piece for receiving the outlet pipe of the bypass filter element, wherein the connecting piece encompasses the first fluid outlet. This allows the larger portion of the main flow that does not flow through the bypass filter element to be easily diverted from the filter system.

[0020] According to a favorable embodiment of the filter system, the connecting piece can have at least one radially inner wall and one radially outer wall, wherein the outlet pipe of the bypass filter element engages between the inner and outer walls when the bypass filter element is arranged as intended. The inner wall can form a sealing surface, in particular a radially outer one, and the outer wall can form a sealing surface, in particular a radially inner one, for sealing the outlet pipe. The connecting piece can have at least one shoulder arranged radially between the inner and outer walls, wherein the shoulder can form a sealing surface, in particular a radially inner one. In this way, the main flow and the bypass flow can be expediently diverted separately from one another. At the same time, a tight connection is provided between the element housing of the bypass filter element and the filter housing.

[0021] According to a favorable embodiment of the filter system, the connecting piece can have a circumferential annular channel, which is fluidically connected to the discharge opening of the bypass filter element and to the second fluid outlet. The annular channel can be formed between the inner and outer walls. In particular, the annular channel can be formed between the shoulder and the outer wall. The fluid filtered by the bypass filter element can be collected in the annular channel and easily discharged from the filter system.

[0022] Advantageously, the first housing part can have a bypass valve, with the interior of the center tube being fluidly connected to the bypass valve. In particular, the bypass valve can engage the interior of the center tube. This allows a bypass to be opened in the event of sudden pressure surges in the fluid flow, preventing damage to the filter elements.

[0023] According to a favorable design of the filter system, the inlet pipe and outlet pipe of the bypass filter element can be formed as a single piece. This reduces the number of individual parts required for the filter system's production, thereby resulting in cost savings.

[0024] According to a further aspect of the invention, a filter element unit for a filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine, is proposed, comprising at least a main flow filter element and a bypass filter element, wherein the bypass filter element is arranged serially downstream of the main flow filter element in the flow direction for a portion of the fluid filtered by the main flow filter element to flow through. The main flow filter element surrounds a central tube and has, on a first end face, a first end plate with a first central opening, and, on a second end face axially opposite the first end face, a second end plate with a second central opening, wherein the central tube engages in the first and second openings.The bypass filter element is arranged in an element housing with a central inlet tube and a central outlet tube, wherein the element housing has at least one outlet opening for the fluid filtered by the bypass filter element. The element housing is rotationally fixedly coupled to the center tube of the main filter element about a longitudinal axis.

[0025] The proposed filter element unit is connected in series, so that the volume flow of the fluid to be filtered is first filtered through the main-flow filter element. The bypass filter element is arranged downstream of the main-flow filter element so that a portion of the fluid filtered by the main-flow filter element can flow through it. In the bypass flow, a portion of the filtered oil is thus diverted to the bypass filter element.

[0026] The filter medium for the bypass filter element is significantly finer than that of the main flow filter element. The air flow through this bypass filter element is radially directed from the inside to the outside.

[0027] The bypass filter element is located below the main flow filter element in the direction of gravity. The fluid to be filtered has already been filtered through the main flow filter element, partially flows to the bypass filter element, and is finely filtered from radially inside to outside as it flows through the bypass filter element.

[0028] The fluid then flows radially inwards through fine channels in the lower end plate and then axially in the longitudinal direction through a drainage channel out of the filter element unit.

[0029] To prevent unfiltered fluid from entering the bypass flow, the bypass filter element is provided with a housing. The housing is completely enclosed and connected to the center tube of the main flow filter element in a rotationally fixed manner, for example, by locking or firmly connecting it, in particular by forming a single piece. Furthermore, torque can be introduced from the housing cover of the filter housing into the main flow filter element and then transmitted via the housing of the bypass filter element to the end plate of the bypass filter element.

[0030] In contrast to the prior art, the proposed filter element unit has the main-flow filter element and the bypass filter element arranged in series in the direction of flow. As a result, the bypass filter element, as a fine filter, is not located on the contaminant side of the filter system and is therefore not exposed to coarse contaminants. This allows the bypass filter element to be operated with significantly lower pressure loss.

[0031] According to a favorable embodiment of the filter element unit, the drain opening can be arranged in the outlet pipe. In particular, the drain opening can be arranged radially outside a central opening in the outlet pipe. In this way, the main flow and the secondary flow can be effectively discharged separately.

[0032] According to a favorable embodiment of the filter element unit, the outlet pipe can have at least one radially inner and one radially outer sealing element for sealing against respective sealing surfaces of a radially inner and radially outer wall of a connection piece of a filter housing. The outlet pipe can have at least one further, in particular radially outer, sealing element for sealing against a sealing surface of a shoulder of the connection piece arranged radially between the inner and outer walls. This allows the bypass filter element to be effectively sealed against the filter housing, thus allowing the main flow and the bypass flow to be safely discharged separately.

[0033] According to a favorable embodiment of the filter element unit, the bypass filter element can be terminated with a first end plate on a first end face facing the main filter element and with a second end plate on a second end face opposite the first end face. In particular, an elastic disc, particularly made of rubber, can be arranged between the first end plate and the element housing. The additional rubber disc can also be used to appropriately support axial loads on the filter medium body, for example, during collapse pressures.

[0034] In particular, a flow channel can be formed in the second end plate, which is fluidically connected to the outlet opening. The fluid filtered in the bypass filter element can be conveniently directed to the outlet opening through the flow channel.

[0035] According to a favorable embodiment of the filter element unit, the bypass filter element can have a radially outer support device. This allows the filter medium body to be effectively supported against the fluid pressure. The support device can, for example, be designed in the form of a casing element and surround the filter medium body of the bypass filter element from the outside.

[0036] According to a favorable embodiment of the filter element unit, the support device can be arranged on an inner wall of the element housing. In particular, the support device can be formed integrally with the wall of the element housing. This allows the support force to be absorbed by the element housing.

[0037] According to a favorable embodiment of the filter element unit, the element housing can have at least a first element housing part and a second element housing part, which are connected to one another in a rotationally secure manner along the longitudinal axis via connecting elements, in particular locking elements, of one of the two element housing parts and connecting counter-elements, in particular recesses, of the other of the two element housing parts. This allows the bypass filter element to be securely connected to the center tube and also transmit torque during assembly of the filter element unit.

[0038] According to a favorable embodiment of the filter element unit, the inlet pipe can be arranged in the first element housing part and the outlet pipe in the second element housing part. The inlet pipe can have a toothing device oriented along its longitudinal axis, which is designed to interact with a toothing counter-device of the center pipe. In particular, the toothing device and the toothing counter-device can mesh complementarily. This allows the bypass filter element to be connected to the center pipe and thus to the main flow filter element in a rotationally fixed manner, and during assembly / disassembly, a torque can be transmitted for proper positioning in the filter housing.

[0039] According to a favorable embodiment of the filter element unit, the first element housing part can be formed integrally with the center tube. Alternatively or additionally, the inlet tube and the outlet tube can be formed integrally and arranged in the second element housing part (70). In this way, the number of individual parts in the manufacture of the filter element unit can be reduced, thereby saving manufacturing costs. Short description of the drawings

[0040] Further advantages will become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will conveniently consider the features individually and combine them into useful further combinations. Examples include: Fig. 1 an isometric representation of a filter system for a fluid, in particular oil or fuel, in particular of an internal combustion engine, according to an embodiment of the invention; Fig. 2 a longitudinal section through the filter system according to Fig. 1; Fig. 3 an enlarged view of a section of the filter system according to Fig. 2 with the bypass filter element; Fig. 4 an isometric view of a filter element unit according to an embodiment of the invention; Fig. 5 an isometric, partially sectioned view of the bypass filter element coupled to the center tube; Fig. 6 an isometric view of the bypass filter element; Fig. 7 shows a longitudinal section through a filter system according to a further embodiment of the invention; Fig. 8 an enlarged view of a section of the filter system according to Fig. 7 with the bypass filter element; Fig. 9 an exploded view of the filter system according to Fig. 7; Fig. 10 an isometric view of the center tube with the first element housing part; Fig. 11 an isometric view of the center tube with the first element housing part with a view into the first element housing part; and Fig. 12 an isometric view of the second element housing part. Embodiments of the invention

[0041] In the figures, identical or similar components are numbered with the same reference numerals. The figures show only examples and are not to be understood as limiting.

[0042] To explain the invention, Fig. 1 an isometric representation of a filter system 100 for a fluid, in particular oil or fuel, in particular of an internal combustion engine, according to an embodiment of the invention, while in Fig. 2 shows a longitudinal section through the filter system 100. Fig. 3 shows an enlarged view of a portion of the filter system 100 according to Fig. 2 with the bypass filter element 30.

[0043] The filter system 100 comprises a series-connected filter element unit 1, in which the volume flow 82 of the fluid to be filtered is first filtered through the main flow filter element 10. In the secondary flow 84, a portion of the filtered fluid, for example, oil, is diverted to the secondary flow filter element 30. The fineness of the filter medium for the secondary flow filter element 30 is significantly finer than that of the main flow filter element 10. The flow through this secondary flow filter element 30 is from radially inside to outside. The fluid filtered in the secondary flow filter element 30 can flow back into the oil pan through its own annular channel 130.

[0044] The bypass filter element 30 is arranged below the main flow filter element 10. The fluid to be filtered has already been filtered by the main flow filter element 10 and is finely filtered from radially inside to outside as it flows through the bypass filter element 30.

[0045] The fluid then flows through fine flow channels in the second end plate 42, first radially and then axially through a drainage channel as a drain opening 54 back into the oil pan.

[0046] To prevent unfiltered fluid from entering the bypass flow 84, the bypass filter element 30 is enclosed. The element housing 34 is completely closed and engages the center tube 14 of the main flow filter element 10. Furthermore, a torque can be introduced into the main flow filter element 10 via the hexagon 132 of the first housing part 112 of the filter housing 110 and further transmitted via the element housing 34 of the bypass filter element 30 into the first end plate 40 of the bypass filter element 30. In the second end plate 42, which is designed with a drainage control, sealing rings 57, 58, 59 seal off both the raw fluid region 60 from the clean fluid region 62 and the second fluid outlet 106 to the oil pan.

[0047] Due to the flow direction from the inside to the outside of the bypass filter element, a support device 66 in the form of an outer shell is integrated around the filter medium body 32 in order to achieve support of the filter medium body 32 under corresponding load under cold start conditions.

[0048] The filter system 100 has a filter housing 110 with a fluid inlet 102, a first fluid outlet 104 and a second fluid outlet 106. The filter housing 110 comprises a first housing part 112 and a second housing part 114, which, as in Fig. 2, are connected via a screw connection 134. The connection between the housing parts 112, 114 is sealed by a sealing element 136, for example, an O-ring. To enable the filter housing 110 to be opened by rotation, a hexagon 132 is formed on the first housing part 112 along the longitudinal axis 80, to which a tool can be attached for this purpose.

[0049] The first fluid outlet 104 and the second fluid outlet 106 are arranged in the second housing part 114. The second fluid outlet 106 is arranged radially outside the first fluid outlet 104. The fluid inlet 102 is not visible in the illustrations.

[0050] The filter element unit 1 comprising the main flow filter element 10 and the secondary flow filter element 30 arranged in series therewith in the flow direction 82 is arranged in the filter housing 110.

[0051] The filter bellows 12 of the main flow filter element 10 surrounds the central tube 14 and has a first end plate 20 with a first central opening 24 on a first end face 16 and a second end plate 22 with a second central opening 26 on a second end face 18 axially opposite the first end face 16. The central tube 14 engages in the first and second openings 24, 26.

[0052] The bypass filter element 30 is arranged downstream of the main flow filter element 10 for a portion of the fluid filtered by the main flow filter element 10 to flow through.

[0053] The bypass filter element 30, with its hollow cylindrical filter medium body 32, is arranged in the element housing 34 with a central inlet tube 50 and a central outlet tube 52. The element housing 34 further has at least one outflow opening 54 for the fluid filtered by the bypass filter element 30. The at least one outflow opening 54 is arranged radially outside the central opening 53 of the outlet tube 52.

[0054] The filter bellows 32 of the bypass filter element 30 is terminated at a first end face 36 facing the main filter element 10 by a first end plate 40 and at a second end face 38 opposite the first end face 36 by a second end plate 42. An elastic disc 55, particularly made of rubber, is arranged between the first end plate 40 and the element housing 34. The additional rubber disc 55 can be used to appropriately support axial loads on the filter medium body 32, for example, during collapse pressures.

[0055] The bypass filter element 30 has a radially outer shell as a support device 66 in order to support the filter medium body 32 against the flow pressure of the fluid flowing radially from the inside to the outside.

[0056] In the second end plate 42, a flow channel 64 is further formed, which is fluidically connected to the discharge opening 54.

[0057] The element housing 34 is coupled to the central tube 14 of the main filter element 10 via the inlet tube 50 of the bypass filter element 30, in a rotationally fixed manner about a longitudinal axis 80. For this purpose, the inlet tube 50 has a toothing device 56 directed along the longitudinal axis 80, which is designed to interact with a counter-toothing device 15 of the central tube 14. The toothing device 56 and the counter-toothing device 15 mesh complementarily with one another.

[0058] The outlet pipe 52 is fluidly connected to the first fluid outlet 104 and the drain opening 54 is fluidly connected to the second fluid outlet 106.

[0059] The second housing part 114 has a connecting piece 116 for receiving the outlet pipe 52 of the bypass filter element 30. The connecting piece 116 includes the first fluid outlet 104 through which the main flow 82 is discharged.

[0060] As particularly in Fig. 3, the connecting piece 116 has a radially inner wall 118 and a radially outer wall 120. The outlet pipe 52 of the bypass filter element 30 engages between the inner and outer walls 118, 120. The inner wall 118 forms a radially outer sealing surface 122, and the outer wall 120 forms a radially inner sealing surface 124 for sealing the outlet pipe 52. The outlet pipe 52 has a radially inner and a radially outer sealing element 57, 58 for sealing against the respective sealing surfaces 122, 124.

[0061] The connecting piece 116 further has a shoulder 126 arranged radially between the inner and outer walls 118, 120 and directed toward the filter element unit 1. The shoulder 126 forms a radially inner sealing surface 128. The outlet pipe 52 also has a further radially outer sealing element 59 for sealing against the sealing surface 128.

[0062] The connecting piece 116 has a circumferential annular channel 130, which is fluidically connected to the at least one discharge opening 54 of the bypass filter element 30 and to the second fluid outlet 106. The annular channel 130 is formed between the shoulder 126 and the outer wall 120.

[0063] As in Fig. 2, the first housing part 112 has a bypass valve 140, which, when the filter element unit 1 is properly installed, engages the interior 28 of the center tube 14, so that the interior of the center tube 14, which represents the clean fluid area 62, is fluidly connected to the bypass valve 140. Thus, in the event of sudden pressure surges in the fluid flow, a bypass can be opened, preventing damage to the filter elements 10, 30.

[0064] The fluid to be filtered, for example, oil, is fed through the invisible fluid inlet 102 into the filter housing 110 and flows through the filter bellows 12 of the main-flow filter element 10 from radially outside to inside into the interior 28 of the center tube 14 as the clean fluid region 62. The main flow 82 is indicated by a thick black arrow. The fluid filtered by the main-flow filter element 10 flows through the center tube 14 toward the first outlet 104.

[0065] However, a portion of the main flow 82 exits as a secondary flow 84, indicated by thin black arrows, from the radial inside to the outside through the filter bellows 32 of the secondary flow filter element 30 and is additionally filtered there. This secondary flow 84 exits on the radial outside of the filter bellows 32 and flows through the flow channel 64 formed in the second end plate 42 to the at least one discharge opening 54 in the outlet pipe 52 of the secondary flow filter element 30. From there, the secondary flow 84 enters the annular channel 130 formed in the outlet pipe 116 of the second filter housing 114 and can flow through the second outlet 106, for example, into the oil pan.

[0066] Fig. 4 shows an isometric view of a filter element unit 1 according to an embodiment of the invention.

[0067] Main flow filter element 10 and secondary flow filter element 30 are connected via the Fig. 4 not visible, the toothing device 56 of the inlet pipe 50 and the toothing counter device 15 on the central pipe 14 are coupled together.

[0068] As in Fig. 4, the element housing 34 has a first element housing part 68 and a second element housing part 70, which are connected to one another in a rotationally secure manner in the longitudinal axis 80 via connecting elements 72 of the second element housing part 70, which, as shown in the exemplary embodiment, can be designed as locking elements or clip elements, with connecting counter-elements 74 of the first element housing part 68, for example recesses.

[0069] The second element housing part 70 has the outlet pipe 52, which with its opening 53 serves to discharge the main flow 82. Furthermore, in the outlet pipe 52, radially outside the central opening 53, a plurality of circumferentially arranged outlet openings 54 for the secondary flow 84 can be seen. From the outlet openings 54, the secondary flow 84 enters the annular channel 130 of the connecting piece 116 (see Fig. 3).

[0070] The second element housing part 70 is formed integrally with the outlet pipe 52, as shown in the Fig. 3 and Fig. 4 is recognizable.

[0071] In Fig. 5, the bypass filter element 30 coupled to the center pipe 14 is shown partially in section.

[0072] The center tube 14 is shown with the first end plate 20 and the second end plate 22, which are connected to the center tube 14. The bypass filter element 30 is connected to the center tube 14 via the toothing device 56 of the bypass filter element 30, which engages with the counter toothing device 15 of the center tube 14, so that the bypass filter element 30 is connected to the center tube 14 in a rotationally fixed manner.

[0073] The bypass filter element 30 is shown partially in section. This shows the inlet tube 50 with the toothing device 56, which is formed integrally with the first element housing part 68.

[0074] Fig. 6 shows an isometric view of the bypass filter element 30. The toothing device 56, which is formed on the inlet pipe 50, with the individual teeth 51, which engage in the toothing counter device 15 of the center pipe 14 and thus enable a rotationally fixed connection between the bypass filter element 30 and the center pipe 14, can be seen.

[0075] In Fig. 7 shows a longitudinal section through a filter system 100 according to a further embodiment of the invention. Fig. Figure 8 shows an enlarged view of a portion of the filter system 100 with the bypass filter element 30.

[0076] In this filter system 100, the number of individual parts of the filter element unit 1 is smaller than in the Fig. 1 to 6. Furthermore, some of the individual components have been simplified.

[0077] The first element housing part 68 of the element housing 34 is formed integrally with the center tube 14. This eliminates the need for the gearing device 56 and the counter-gearing device 15 of the previous embodiment, since the first element housing part 68 is thus firmly connected to the center tube 14.

[0078] Furthermore, the inlet pipe 50 and the outlet pipe 52 are also formed in one piece and arranged in the second element housing part 70.

[0079] As a further simplification, the support device 66 is formed integrally with the first element housing part 68. This allows the filter medium body 32 of the bypass filter element 30 to be supported against the flow pressure on the wall 67 of the first element housing part 68.

[0080] Fig. 9 shows an exploded view of the filter system 100 according to Fig. 7 and Fig. 8. It can be seen that the first element housing part 68 is connected to the center tube 14. The second element housing part 70 has the central inlet tube 50, onto which the filter medium body 32 of the bypass filter element 30 can be placed.

[0081] The elastic disc 55 is arranged between the filter medium body 32 and the first element housing part 68. The filter medium body 12 of the main flow filter element 10 can be placed on the center tube 14.

[0082] Furthermore, the sealing elements 57, 58, 59 are shown, which are applied to the outlet pipe 52 (not shown) in order to ensure sealing with respect to the second housing part 114 of the filter system 100.

[0083] In Fig. 10 is an isometric view of the center tube 14 with the first element housing part 68.

[0084] The center tube 14 is closed at its free end with a sealing element 13. The sealing element 13 can, for example, be a felt ring welded to the center tube 14.

[0085] Fig. 11 shows an isometric view of the center tube 14 with the first element housing part 68 with a view into the first element housing part 68, while in Fig. 12 an isometric view of the second element housing part 70 is shown.

[0086] In Fig. 11, the support device 66 can be seen on the inner wall 67 as projections running all around the wall 67. This allows the filter medium body 32 of the bypass filter element 30 to be effectively supported against the flow pressure on the wall 67.

[0087] In Fig. 10 to 12 also show how the two element housing parts 68, 70 can be connected to one another in a rotationally fixed manner. For this purpose, the second element housing part 68 has connecting elements 72 in the form of locking elements or clip elements, which interact with counter-connecting elements 74 of the first element housing part 68, for example, recesses. In this way, the two element housing parts 68, 70 can be connected to one another in a rotationally fixed manner along the longitudinal axis 80. Thus, the element housing 34 is also connected to the center tube 14 in a rotationally fixed manner in the assembled state.

[0088] In Fig. 12, the radially extending flow channels 64 can be seen on the inside of the second element housing part 70, through which the fluid filtered in the bypass filter element 30 can flow away. Reference symbol 1 filter element unit 10 Main flow filter element 12 filter medium bodies 13 Sealing element 14 Center pipe 15 Gear counter device 16 first front side 18 second front side 20 first end plate 22 second end plate 24 Opening 26 Opening 28 Interior 30 bypass filter element 32 filter medium bodies 34 element housings 36 first front side 38 second front side 40 first end plate 42 second end plate 44 Opening 46 Opening 48 Interior 50 Inlet pipe 51 tooth 52 Outlet pipe 53 Opening 54 Drain opening 55 elastic disc 56 Gear cutting device 57 Sealing element 58 Sealing element 59 Sealing element 60 Raw fluid area 62 Clean fluid area 64 flow channel 66 Support device 67 wall 68 first element housing part 70 second element housing part 72 connecting element 74 Connecting counter element 80 Longitudinal axis 82 Main stream 84 bypass 100 filter system 102 Fluid inlet 104 first fluid outlet 106 second fluid outlet 110 housings 112 first housing part 114 second housing part 116 connecting pieces 118 inner wall 120 outer wall 122 Sealing surface 124 Sealing surface 126 paragraph 128 Sealing surface 130 ring canal 132 hexagon 134 screw connection 136 Sealing element 140 Bypass valve QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 0 487 231 A2

[0003] US 2003 / 0168397 A1

[0004]

Claims

[1] Filter system (100) for a fluid, in particular oil or fuel, in particular of an internal combustion engine, with a filter housing (110) with a fluid inlet (102), a first fluid outlet (104) and a second fluid outlet (106) and with a main flow filter element (10) arranged in the filter housing (110) and a secondary flow filter element (30) arranged in series therewith in the flow direction (82), wherein the filter housing (110) comprises at least a first housing part (112) and a second housing part (114) which are connected to one another, wherein the first fluid outlet (104) and the second fluid outlet (106) are arranged in the second housing part (114), wherein the main flow filter element (10) surrounds a central tube (14) and has a first end plate (20) with a first central opening (24) on a first end face (16) and a second end plate (22) with a second central opening (26) on a second end face (18) axially opposite the first end face (16), wherein the central tube (14) engages in the first and second openings (24, 26), wherein the bypass filter element (30) is arranged in an element housing (34) with a central inlet pipe (50) and a central outlet pipe (52), wherein the element housing (34) has at least one discharge opening (54) for the fluid filtered by the bypass filter element (30), wherein the element housing (34) is coupled to the central tube (14) of the main filter element (10) in a rotationally fixed manner about a longitudinal axis (80), wherein the outlet pipe (52) is fluidly connected to the first fluid outlet (104) and the drain opening (54) is fluidly connected to the second fluid outlet (106). [2] The filter system of claim 1, wherein the second fluid outlet (106) is disposed radially outward of the first fluid outlet (104). [3] Filter system according to claim 1 or 2, wherein the second housing part (114) has a connecting piece (116) for receiving the outlet pipe (52) of the bypass filter element (30), wherein the connecting piece (116) comprises the first fluid outlet (104). [4] Filter system according to claim 3, wherein the connecting piece (116) has at least one radially inner wall (118) and one radially outer wall (120), wherein the outlet pipe (52) of the bypass filter element (30) engages between the inner and outer walls (118, 120) when the bypass filter element (30) is arranged as intended, wherein the inner wall (118) forms a, in particular radially outer, sealing surface (122) and the outer wall (120) forms a, in particular radially inner, sealing surface (124) for sealing the outlet pipe (52), wherein the connecting piece (116) has at least one shoulder (126) arranged radially between the inner and outer walls (118, 120), wherein the shoulder (126) forms a, in particular radially inner, sealing surface (128). [5] Filter system according to claim 3 or 4, wherein the connecting piece (116) has a circumferential annular channel (130) which is fluidically connected to the discharge opening (54) of the bypass filter element (30) and to the second fluid outlet (106), wherein the annular channel (130) is formed between the inner and outer walls (118, 120), in particular wherein the annular channel (130) is formed between the shoulder (126) and the outer wall (120). [6] Filter system according to one of the preceding claims, wherein the inlet pipe (50) and the outlet pipe (52) of the bypass filter element (30) are formed in one piece. [7] Filter element unit (1) for a filter system (100) according to one of the preceding claims for a fluid, in particular oil or fuel, in particular of an internal combustion engine, at least comprising a main flow filter element (10) and a bypass filter element (30), wherein the bypass filter element (30) is arranged serially downstream of the main flow filter element (10) in the flow direction (82) for a part of the fluid filtered by the main flow filter element (10) to flow through, wherein the main flow filter element (10) surrounds a central tube (14) and has a first end plate (20) with a first central opening (24) on a first end face (16), and a second end plate (22) with a second central opening (26) on a second end face (18) axially opposite the first end face (16), wherein the central tube (14) engages in the first and second openings (24, 26), wherein the bypass filter element (30) is arranged in an element housing (34) with a central inlet pipe (50) and a central outlet pipe (52), wherein the element housing (34) has at least one discharge opening (54) for the fluid filtered by the bypass filter element (30), wherein the element housing (34) is coupled to the central tube (14) of the main filter element (10) in a rotationally fixed manner about a longitudinal axis (80). [8] Filter element unit according to claim 7, wherein the drain opening (54) is arranged in the outlet pipe (52), in particular wherein the drain opening (54) is arranged radially outside a central opening (53) of the outlet pipe (52). [9] Filter element unit according to claim 7 or 8, wherein the outlet pipe (52) has at least one radially inner and one radially outer sealing element (57, 58) for sealing against respective sealing surfaces (122, 124) of a radially inner and radially outer wall (118, 120) of a connecting piece (116) of a filter housing (110), wherein the outlet pipe (52) has at least one further, in particular radially outer, sealing element (59) for sealing against a sealing surface (128) of a shoulder (126) of the connecting piece (116) arranged radially between the inner and outer walls (118, 120). [10] Filter element unit according to one of claims 7 to 9, wherein the bypass filter element (30) is closed at a first end face (36) directed towards the main filter element (10) by a first end plate (40) and at a second end face (38) opposite the first end face (36) by a second end plate (42), in particular wherein an elastic plate (55), in particular made of rubber, is arranged between the first end plate (40) and the element housing (34), in particular wherein a flow channel (64) is formed in the second end plate (42), which flow channel is fluidically connected to the discharge opening (54). [11] Filter element unit according to one of claims 7 to 10, wherein the bypass filter element (30) has a radially outer support device (66) which surrounds a filter medium body (32) of the bypass filter element (30) on its outer side. [12] Filter element unit according to claim 11, wherein the support device (66) is arranged on an inner wall (67) of the element housing (34), in particular wherein the support device (66) is formed integrally with the inner wall (67). [13] Filter element unit according to one of claims 7 to 12, wherein the element housing (34) has at least a first element housing part (68) and a second element housing part (70), which are connected to one another in a rotationally secure manner in the longitudinal axis (80) via connecting elements (72), in particular locking elements, of one of the two element housing parts (68, 70) and connecting counter-elements (74), in particular recesses, of the other of the two element housing parts (68, 70). [14] Filter element unit according to one of claims 7 to 13, wherein the inlet pipe (50) is arranged in the first element housing part (68) and the outlet pipe (52) is arranged in the second element housing part (70), wherein the inlet pipe (50) has a toothing device (56) directed in the longitudinal axis (80) which is designed to cooperate with a toothing counter-device (15) of the central pipe (14), in particular wherein the toothing device (56) and the toothing counter-device (15) mesh complementarily with one another. [15] Filter element unit according to one of claims 7 to 14, wherein the first element housing part (68) is formed integrally with the central tube (14), and / or wherein the inlet tube (50) and the outlet tube (52) are formed integrally and are arranged in the second element housing part (70).

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