Flap device for an internal combustion engine and method for mounting a plain bearing element of a flap device

Abstract

Flap device for an internal combustion engine, with a flow housing (12) which delimits at least one flow channel (14, 16), a flap shaft (18) which is rotatably mounted on the flow housing (12) via at least one sliding bearing element (41, 43, 45), wherein the sliding bearing element (41, 43, 45) is fastened to the flow housing (12) via a press connection between an outer peripheral surface of the sliding bearing element (41, 43, 45) and an inner peripheral surface of an opening formed on the flow housing (12), and at least one flap body (20, 22) which is mounted on the flap shaft (18) and is arranged in the flow channel (14, 16), wherein the flap body (20, 22) can be rotated together with the flap shaft (18) about a longitudinal axis (24) of the flap shaft (18) between different positions, characterized in that a recess (80) is provided on the outer circumferential surface (46) of the sliding bearing element (41) and / or on the inner circumferential surface (31) of the opening (30), wherein, when a hot gas flows through the flow channel (14, 16), the surface pressure between the outer circumferential surface (46) of the sliding bearing element (41) and the inner circumferential surface (31) of the opening (30) provided on the flow housing increases due to the thermal expansion of the sliding bearing element (41) and the thermal expansion of the flow housing (12) in such a way that a section (82) of one circumferential surface (31, 46) penetrates into the recess (80) in the region of the recess (80) provided on the other circumferential surface (31, 46) and is plastically deformed into a projection (84), wherein in the cooled state of the sliding bearing element (41) and the flow housing (12), the sliding bearing element (41) is held in a form-fitting manner in the axial direction by the projection (84) projecting into the recess (80).

Description

The invention relates to a flap device for an internal combustion engine, having a flow housing which delimits at least one flow duct, a flap shaft which is rotatably mounted on the flow housing via at least one slide bearing element, wherein the slide bearing element is fastened to the flow housing via a press connection between an outer circumferential surface of the slide bearing element and an inner circumferential surface of an opening formed on the flow housing, and at least one flap body which is mounted on the flap shaft and is arranged in the flow duct, wherein the flap body can be rotated together with the flap shaft about a longitudinal axis of the flap shaft between different positions.Flap devices of this type are used, for example, as exhaust gas back-up flaps or as exhaust gas recirculation valves in low-pressure or high-pressure exhaust gas circuits. It is also known to provide such flap devices in an air intake duct of an internal combustion engine, in particular as a throttle flap.Such a flap device is disclosed, for example, in WO 2017 / 182 233 A1. The flap device comprises an exhaust gas flow housing which delimits an exhaust gas flow channel. A flap body is arranged in the exhaust gas flow channel, which is fastened to a flap shaft rotatably mounted on the exhaust gas flow housing and projecting into the exhaust gas flow channel. For rotatable mounting, two slide bearing elements are provided, which are arranged in alignment with one another and on the opposite sides of the flap body. Such slide bearing elements are usually pressed into an opening of the flow housing in each case, so that the slide bearing elements are fastened to the flow housing via a press connection between an outer circumferential surface and an inner circumferential surface of the opening, i.e. by a press fit.DE 10 2013 013 387 A1 discloses an elastically deformed bearing sleeve for mounting a flap shaft of a flap device.DE 198 57 957 A1 discloses a bearing sleeve for mounting a flap shaft of a flap device, which bearing sleeve has wedge ribs on an outer circumferential surface, wherein the wedge ribs cause a plastic deformation of the plastic housing during a pressing-in process of the bearing sleeve into a plastic housing.DE 10 2016 204 440 A1 and US 2005 / 0 189 513 A each disclose a bearing sleeve for mounting a flap shaft of a flap device, which bearing sleeve is pressed into a housing and has positive locking means on the outer circumferential surface.The disadvantage of the fastening of the slide bearing element to the flow housing d, which fastening is exclusively realized by the press connection, is that there is the risk that the fixing of the slide bearing element cannot be reliably ensured in certain states. The different thermal expansions of the flow housing and of the sliding bearing element caused by the different materials lead to the flow housing and / or the sliding bearing element being plastically deformed in the event of a high thermal load of the flow housing and of the sliding bearing element, in particular by the hot gas flowing through the flow channel of the flow housing. In the event of a subsequent low thermal load on the flow housing and the sliding bearing element, the pressure set in the new state is canceled by the shrinkage of the flow housing and the sliding bearing element, so that the sliding bearing element is no longer fixed to the flow housing. In particular, a lack of axial securing of the slide bearing element on the flow housing leads to the slide bearing element moving axially to and fro and thereby abutting against adjacent components, which results in undesirable noises.The object therefore arises to provide a flap device for an internal combustion engine of a motor vehicle, in which the sliding bearing element can be reliably secured axially on the flow housing in a simple and cost-effective manner, in particular without additional components and without an additional assembly step, even in the case of different thermal loads.This object is achieved by a flap device for an internal combustion engine of a motor vehicle having the features of claim 1.For axially fixing the sliding bearing element, a cutout is provided on the outer circumferential surface of the sliding bearing element and / or on the inner circumferential surface of the opening, wherein, when a hot gas flows through the flow channel, the surface pressure between the outer circumferential surface of the sliding bearing element and the inner circumferential surface of the opening provided on the flow housing increases as a result of the thermal expansion of the sliding bearing element and the thermal expansion of the flow housing in such a way that a section of the one circumferential surface in the region of the cutout penetrates the other circumferential surface into the cutout and plastically deforms, wherein, in the cooled state of the sliding bearing element and of the flow housing, the formed protrusion, i.e. the plastically deformed portion, is retained and the sliding bearing element is retained in an axial direction in a positive-locking manner by the plastically deformed portion projecting into the cutout.In the new state of the flap device, the sliding bearing element pressed into the opening is held axially on the flow housing almost exclusively by the press connection. When a hot gas flows through the flow channel of the flow housing for the first time, in particular when the flap device is operated for the first time, the slide bearing element and the flow housing heat up, in particular in the region of the slide bearing element, in such a way that the slide bearing element and the flow housing expand due to the thermal loads and deform elastically and plastically. The deformation in the region of the recess is such that a projection is produced on the circumferential surface not having the recess as a result of the deformation, which projection engages into the recess. In the cooled state, the projection is formed exclusively by the plastic portion of the deformation, wherein the projection has a radial extension such that it engages in the recess. In other words, the positive connection between the flow housing and the sliding bearing element is produced automatically by the starting operation of the flap device, wherein the shaping of the section or projection projecting into the recess takes place exclusively by the thermal load present during operation of the flap device and the resulting thermal expansion of the flow housing and of the sliding bearing element.In this way, the sliding bearing element can be fixed to the flow housing reliably and in the event of different thermal loads of the flow housing and of the sliding bearing element, wherein no additional components or additional assembly steps are required.Preferably, the recess is a circumferential groove. By means of the groove running around 360°, the sliding bearing element can be fixed axially on the flow housing uniformly over the entire circumference. As a result, the slide bearing element can be reliably fastened to the flow housing in a positively locking manner in the axial direction of the flap shaft, wherein the groove can be produced easily and cost-effectively, in particular already during the production process of the slide bearing element or during a mechanical post-processing of the slide bearing element.In a preferred embodiment, the flow housing has a greater coefficient of thermal expansion than the sliding bearing element. In particular in this case, there is the risk that in the cooled state the press connection between the flow housing and the sliding bearing element is canceled and undesirable noises result therefrom due to the axial displacement of the sliding bearing element. This can be reliably prevented by the additional form-fitting connection in the axial direction between the slide bearing element and the flow housing. In a preferred embodiment, the flow housing is produced from a metallic cast material and the sliding bearing element is produced from a sintered material.The recess preferably has a width of several millimeters. The protrusion resulting from the plastic deformation thus also has a width of several millimeters. The slide bearing element and / or the circumferential surface of the opening of the flow housing thus has a macroscopic cutout.Preferably, a first flap body and a second flap body are fastened to the flap shaft, wherein the first flap body is arranged in a first flow channel delimited by the flow housing and the second flap body is arranged in a second flow channel delimited by the flow housing, wherein the flap body has a first slide bearing element arranged at a first axial end, a second slide bearing element arranged at a second axial end and a third slide bearing element arranged between the two flap bodies, wherein the third slide bearing element has the recess. Due to the arrangement of the third slide bearing element in a through-opening between the two flow channels, the third slide bearing element is subject to particularly severe thermal stress, so that the risk of the press connection between the third slide bearing element and the flow housing being released is particularly high on the third slide bearing element. By means of the form-fit connection, an axial displacement of the third slide bearing element in the cooled state can be reliably prevented.In a preferred embodiment, the flow channel is an exhaust gas flow channel, wherein the exhaust gas has a temperature of several 100 C° and the sliding bearing element and the flow housing are exposed to a relatively high thermal load.The object is also achieved by a method for mounting a sliding bearing element of a flap device according to one of claims 1 to 6, wherein the method comprises the following steps:pressing the sliding bearing element into an opening of a flow housing,A hot gas flows through the flow channel of the flow housing, wherein the flow housing and the sliding bearing element expand based on the corresponding thermal expansion coefficient such that a portion of the one circumferential surface in the region of the recess of the other circumferential surface penetrates into the recess and plastically deforms to form a protrusion, wherein in the cooled state of the sliding bearing element and of the flow housing the sliding bearing element is axially positively fastened to the flow housing by an engagement of the protrusion into the recess.This provides a flap device for an internal combustion engine, in which the slide bearing element can be fixed to the flow housing reliably and at different thermal loads of the flow housing and of the slide bearing element, without additional components or additional assembly steps being required for this purpose.An exemplary embodiment of a flap device according to the invention for an internal combustion engine is illustrated in the figures and is described below. FIG. 1 shows a sectional view of a flap device according to the invention, and FIGS. 2 a, 2 band 2 c show a time sequence of the operation of the flap device from FIG. 1.The figure shows a flap device 10 for an internal combustion engine of a motor vehicle, wherein the flap device 10 is designed as an exhaust flap device and serves, for example, as an exhaust gas retaining flap or as an exhaust gas recirculation valve.The flap device 10 comprises a flow housing 12 which delimits a first flow channel 14 and a second flow channel 16. The flow housing 12 is produced from a metallic material, in particular in one piece and from a cast material.The flap device 10 further comprises a flap shaft 18 rotatably mounted on the flow housing 12, to which two flap bodies 20, 22 are fastened, wherein a first flap body 20 is arranged in the first flow channel 14 and the second flap body 22 is arranged in the second flow channel 16. The flap shaft 18 is embodied in one piece and extends through the two flow channels 14, 16, wherein the flow housing 12 here has an opening 30 in the form of a through opening between the two flow channels 14, 16, a blind hole opening 34 on a side of the second flow channel 16 facing away from the first flow channel 14, and a through opening 32 on a side of the first flow channel 14 facing away from the second flow channel 16. The flap shaft 18 protrudes from the through-opening 32 out of the flow housing 12, wherein an actuator, not shown in the figure, acts on the protruding section of the flap shaft 18, by means of which actuator the flap shaft 18 and the flap bodies 20, 22 can be rotated between different positions. By adjusting the flap shaft 18 and the flap bodies 20, 22, the flow cross section defined by the respective flap body 20, 22 and an inner circumferential surface of the flow channels 14, 16 can be changed, wherein by fastening the flap bodies 20, 22 to a single flap shaft 18 the flow cross section in both flow channels 14, 16 is necessarily adjusted simultaneously.The flap shaft 18 is mounted on the flow housing 12 on the one hand axially and on the other hand radially, i.e. rotatably.For the radial mounting of the flap shaft 18, a radial bearing 40, 42, 44 in the form of a slide bearing element 41, 43, 45 is provided in each of the opening 30, the blind hole opening 34 and the through opening 32. A first slide bearing element 43, a second slide bearing element 45 and a third slide bearing element 41 are sleeve-like and manufactured from a sintered material. The sleeve-like slide bearing elements 41, 43, 45 are fastened to the flow housing 12 via a respective press connection, wherein the slide bearing elements 41, 43, 45 are pressed into the respective opening 30, 32, 34 during the assembly in such a way that, in the assembled state, a surface pressure is present in each case between the outer circumferential surfaces 46, 47, 48 of the slide bearing elements 41, 43, 45 and the inner circumferential surfaces 31, 33, 35 of the openings 30, 32, 34, and the slide bearing elements 41, 43, 45 are fastened to the flow housing 12 axially, radially and tangentially, i.e. in the circumferential direction.The axial mounting is effected by an axial bearing 50, which has a bearing element 52, a counter bearing element 54 and a ceramic element 56. The bearing element 52 is arranged within the through-opening 32 and fastened to the flow housing 12. The bearing element 52 has an annular cross section and is pressed into the flow housing 12 via an outer circumferential surface, so that the bearing element 52 is fixedly arranged on the flow housing 12 at least in the axial direction. The counter bearing element 54 is fastened to the flap shaft 18, for example via a press connection. The ceramic element 56 is arranged between the bearing element 52 and the counter bearing element 54 and is fastened on a side of the counter bearing element 54 facing the bearing element 52. The ceramic element 56 has a conical contact surface 58, which in the final assembled state abuts a conical counter-contact surface 60 of the bearing element 52 complementary thereto. The conical design of the contact surfaces 58, 60 allows the contacting surface to be enlarged and the sealing can thereby be improved.A spring receiving element 70 is fastened to the protruding portion of the flap shaft 18, wherein a spring element 72 is arranged pretensioned between the spring receiving element 70 and the flow housing 12. The spring element 72 exerts such a load on the flap shaft 18 that the counter bearing element 54 is loaded in the direction of the bearing element 52 of the axial bearing 50.In the new state of the flap device 10, i.e. in the state after the initial assembly, there is such a high surface pressure between the outer circumferential surface 46, 47, 48 of the slide bearing elements 41, 43, 45 and the corresponding circumferential surface 31, 33, 35 of the openings 30, 32, 34 that the slide bearing elements 41, 43, 45 are arranged radially, axially and tangentially fixedly on the flow housing 12. During operation of the flap device 10, an exhaust gas having a temperature of several 100 C° flows through the flow channels 14, 16. Due to the high temperatures of the exhaust gas, the slide bearing elements 41, 43, 45 and the flow housing 12 heat up and expand according to their thermal expansion coefficient. The third slide bearing element 41 arranged in the opening 30 and the region of the flow housing 12 around the third slide bearing element 41 are subjected to the greatest thermal load. Due to the thermal expansion, in particular of the third slide bearing element 41 and the flow housing 12, the surface pressure between the outer circumferential surface 46 of the third slide bearing element 41 and the circumferential surface 31 of the opening 30 increases in such a way that the third slide bearing element 41 and the flow housing 12 deform plastically in the region of the opening 30. As a result of the plastic deformation, in the cooled state of the third slide bearing element 41 and of the flow housing 12, a radial gap 49 is present between the outer circumferential surface 46 of the third slide bearing element 41 and the circumferential surface 31 of the opening 30, as a result of which the surface pressure is canceled at least in the cooled state and fixing of the third slide bearing element 41 to the flow housing 12 is no longer possible.According to the invention, a macroscopic cutout 80 in the form of a groove is provided on the outer circumferential surface 46 of the third slide bearing element 41. The recess 80 has the effect that during the thermal expansion of the third slide bearing element 41 and of the flow housing 12 and the plastic deformation of the slide bearing element 41 and of the flow housing 12 caused thereby, a section 82 of the flow housing 12 penetrates into the recess 80. The portion 82 penetrating into the recess 80 and still present in the cooled state is formed by a plastic deformation and forms a protrusion 84, which is retained even in the cooled state of the flow housing 12 and engages into the recess 80. In this case, the projection 84 has a radial extension a in the event of a present thermal expansion of the slide bearing element 41 and of the flow housing 12, which is composed of an elastic and a plastic component. In the cooled state, only the plastic portion of the deformation is retained, so that the projection 84 has a radial extension b which is less than the radial extension a. The radial extension b of the protrusion 84 produced by the plastic deformation is so high in the cooled state of the flow housing 12 and of the sliding bearing element 41 that the protrusion 84 abuts the side surfaces 90, 92 of the recess 80 via a section d with the side surfaces 86, 88. The projection 84 and the recess 80 thus form a positive connection between the third slide bearing element 41 and the flow housing 12 in the axial direction, wherein the positive connection is automatically established by the starting operation of the flap device 10, i.e. by the exhaust gas flowing through the flow channels 14, 16, and no additional components are required for this. The production of the projection 84 is illustrated in FIGS. 2 a, 2 band 2 c, wherein FIG. 2 ashows the new state and the sliding bearing element 41 is pressed only into the opening 30. The new state is also shown in FIG. 1. FIG. 2 bshows a state in which the exhaust gas flows through the flow channels 14, 16 and the third slide bearing element 41 and the flow housing 12 have thereby expanded in the region of the third slide bearing element 41 in a thermally induced manner. FIG. 3 cshows the cooled state after the thermal expansion of the slide bearing element 41 and of the flow housing 12.It should be clear that the scope of protection of the main claim is not limited to the described embodiment, but various modifications are possible. For example, the other slide bearing elements 43, 45 can also be provided with a cutout. The recess could also be formed on the circumferential surface 31 of the opening 30.

Claims

Flap device for an internal combustion engine, having a flow housing (12) which delimits at least one flow duct (14, 16), a flap shaft (18) which is rotatably mounted on the flow housing (12) via at least one slide bearing element (41, 43, 45), wherein the slide bearing element (41, 43, 45) is fastened to the flow housing (12) via a press connection between an outer circumferential surface of the slide bearing element (41, 43, 45) and an inner circumferential surface of an opening formed on the flow housing (12), and at least one flap body (20, 22) which is mounted on the flap shaft (18) and is arranged in the flow duct (14, 16), wherein the flap body (20, 22) can be rotated together with the flap shaft (18) about a longitudinal axis (24) of the flap shaft (18) between different positions, characterized in that, a cutout (80) is provided on the outer circumferential surface (46) of the sliding bearing element (41) and / or on the inner circumferential surface (31) of the opening (30), wherein, when a hot gas flows through the flow channel (14, 16), the surface pressure between the outer circumferential surface (46) of the sliding bearing element (41) and the inner circumferential surface (31) of the opening (30) provided on the flow housing increases on account of the thermal expansion of the sliding bearing element (41) and the thermal expansion of the flow housing (12) such that a portion (82) of the one circumferential surface (31, 46), in the region of the cutout (80) provided on the other circumferential surface (31, 46), penetrates into the cutout (80) and plastically deforms to form a projection (84), wherein, in the cooled state of the slide bearing element (41) and of the flow housing (12), the slide bearing element (41) is held in the axial direction in a positive fit by the projection (84) projecting into the recess (80).Flap device according to claim 1, characterised in that the recess (80) is a circumferential groove.Flap device according to claim 1 or 2, characterised in that the flow housing (12) has a greater coefficient of thermal expansion than the sliding bearing element (41).Flap device according to one of the preceding claims, characterized in that the flow housing (12) is produced from a casting material and the sliding bearing element (41) is produced from a sintered material.Flap device according to one of the preceding claims, characterized in that a first flap body (20) and a second flap body (22) are fastened to the flap shaft (18), wherein the first flap body (20) is arranged in a first flow channel (14) delimited by the flow housing (12) and the second flap body (22) is arranged in a second flow channel (16) delimited by the flow housing (12), wherein the flap body (22) has a first slide bearing element (43) arranged at a first axial end, a second slide bearing element (45) arranged at a second axial end and a third slide bearing element (41) arranged between the two flap bodies (20, 22), wherein the third slide bearing element (41) has the cutout (80).Flap device according to one of the preceding claims, characterized in that the flow channel (14, 16) is an exhaust gas flow channel.Method for mounting a slide bearing element of a flap device according to one of Claims 1 to 6, having the following steps: pressing the slide bearing element (41) into an opening (30) of a flow housing (12), a hot gas flowing through the flow duct (14, 16) of the flow housing (12), wherein the flow housing (12) and the slide bearing element (41) expand on the basis of the corresponding coefficient of thermal expansion in such a way that a portion (82) of the one circumferential surface (31, 46), in the region of the cutout (80), penetrates the other circumferential surface (31, 46) into the cutout (80) and plastically deforms to form a projection (84), wherein, in the cooled state of the slide bearing element (41) and of the flow housing (12), the slide bearing element (41) is fastened axially form-lockingly to the flow housing (12) by engagement of the projection (84) into the cutout (80).

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