Flap device for an internal combustion engine

Abstract

Proposed is a flap device for an internal combustion engine, comprising: a flow housing (12) which delimits at least one flow channel (14, 16); a flap shaft (18) which is mounted rotatably on the flow housing (12) by means of at least one plain bearing element, wherein the plain bearing element is fastened to the flow housing (12) by means of a press-fit connection between an outer circumferential surface of the plain bearing element and an inner circumferential surface of an opening formed in the flow housing; and at least one flap element (20, 22) which is supported on the flap shaft (18) and is arranged in the flow channel (14, 16), wherein the flap element (20, 22) is rotatable conjointly with the flap shaft (18) about a longitudinal axis (24) of the flap shaft (18) between different positions; wherein a recess (80) is provided in the outer circumferential surface (46) of the plain bearing element (41) and / or in the inner circumferential surface (31) of the opening (30), wherein, when a hot gas flows through the flow channel (14, 16), the contact pressure between the outer circumferential surface (46) of the plain bearing element (41) and the inner circumferential surface (31) of the opening (30) provided in the flow housing increases, owing to the thermal expansion of the plain bearing element (41) and the thermal expansion of the flow housing (12), such that a portion (82) of one circumferential surface (31, 46) protrudes, in the region of the recess (80) provided in the other circumferential surface (31, 46), into said recess (80) and plastically deforms to form a projection (84), wherein, when the plain bearing element (41) and the flow housing (12) have cooled, the plain bearing element (41) is held interlockingly in the axial direction by the projection (84) protruding into the recess (80).

Description

[0001] DESCRIPTION

[0002] Flap device for an internal combustion engine

[0003] The invention relates to a flap device for an internal combustion engine, comprising a flow housing which delimits at least one flow channel, a flap shaft which is rotatably mounted on the flow housing via at least one plain bearing element, wherein the plain bearing element is fastened to the flow housing via a press connection between an outer circumferential surface of the plain 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 channel, wherein the flap body can be rotated together with the flap shaft about a longitudinal axis of the flap shaft between different positions.

[0004] Such flap devices are used, for example, as exhaust gas dampers or as exhaust gas recirculation valves in low-pressure or high-pressure exhaust 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 valve.

[0005] Such a flap device is disclosed, for example, in WO 2017 / 182233 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 and is fastened to a flap shaft which is rotatably mounted on the exhaust gas flow housing and projects into the exhaust gas flow channel. For rotatable mounting, two plain bearing elements are provided which are arranged in alignment with one another and on opposite sides of the flap body. Such plain bearing elements are usually pressed into each opening of the flow housing, such that the plain bearing elements are fastened to the flow housing via a press connection between an outer peripheral surface and an inner peripheral surface of the opening, i.e. by a press fit.

[0006] The disadvantage of attaching the plain bearing element to the flow housing exclusively through a press connection is that there is a risk that the fixation of the plain bearing element cannot be reliably ensured under certain conditions. The different thermal expansions of the flow housing and the plain bearing element caused by the different materials lead to the flow housing and / or the plain bearing element undergoing plastic deformation under high thermal loads on the flow housing and the plain bearing element, particularly due to the hot gas flowing through the flow channel of the flow housing.When the flow housing and the plain bearing element are subsequently subjected to slight thermal stress, the compression established when the housing was new is eliminated by the shrinkage of the flow housing and the plain bearing element, so that the plain bearing element is no longer fixed to the flow housing. In particular, a lack of axial securing of the plain bearing element to the flow housing causes the plain bearing element to move axially back and forth, striking adjacent components, resulting in undesirable noise.

[0007] The object is therefore to provide a flap device for an internal combustion engine of a motor vehicle in which the plain bearing element can be reliably secured axially to the flow housing in a simple and cost-effective manner, in particular without additional components and without an additional assembly step, even under different thermal loads.

[0008] This object is achieved by a flap device for an internal combustion engine of a motor vehicle having the features of claim 1.

[0009] For the axial fixing of the plain bearing element, a recess is provided on the outer circumferential surface of the plain 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 plain bearing element and the inner circumferential surface of the opening provided on the flow housing increases due to the thermal expansion of the equal bearing element and the thermal expansion of the flow housing in such a way that a section of one circumferential surface in the region of the recess penetrates the other circumferential surface into the recess and is plastically deformed, wherein in the cooled state of the plain bearing element and the flow housing the formed projection, i.e. the plastically deformed portion, is retained and the equal bearing element is held in a form-fitting manner in the axial direction by the plastically deformed section projecting into the recess.

[0010] When the flap device is new, the plain bearing element pressed into the opening is held axially to 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, particularly during initial operation of the flap device, the plain bearing element and the flow housing, particularly in the area of ​​the plain bearing element, heat up to such an extent that the plain bearing element and the flow housing expand due to the thermal stress and undergo elastic and plastic deformation. The deformation in the area of ​​the recess is such that the deformation creates a projection on the circumferential surface not having the recess, which engages into the recess.In the cooled state, the projection is formed exclusively by the plastic component of the deformation, with the projection having a radial extension such that it engages the recess. In other words, the positive connection between the flow housing and the plain bearing element is automatically established upon commissioning of the flap device, with the formation of the section or projection projecting into the recess occurring exclusively through the thermal load present during operation of the flap device and the resulting thermal expansion of the flow housing and the plain bearing element.

[0011] In this way, the plain bearing element can be fixed to the flow housing reliably and under different thermal loads of the flow housing and the plain bearing element, whereby no additional components or additional assembly steps are required.

[0012] Preferably, the recess is a circumferential groove. The 360° circumferential groove allows the plain bearing element to be axially fixed evenly to the flow housing over its entire circumference. This allows the plain bearing element to be reliably secured to the flow housing with a positive fit in the axial direction of the valve shaft. The groove can be manufactured easily and cost-effectively, particularly during the manufacturing process of the plain bearing element or during mechanical post-processing of the plain bearing element.

[0013] In a preferred embodiment, the flow housing has a higher coefficient of thermal expansion than the plain bearing element. In this case, in particular, there is a risk that the press connection between the flow housing and the plain bearing element will be lost when cooled, resulting in unwanted noises caused by the axial displacement of the plain bearing element. This can be reliably prevented by the additional positive connection in the axial direction between the plain bearing element and the flow housing. In a preferred embodiment, the flow housing is made of a metallic cast material, and the plain bearing element is made of a sintered material.

[0014] Preferably, the recess has a width of several millimeters. The projection resulting from the plastic deformation thus also has a width of several millimeters. Thus, the plain bearing element and / or the peripheral surface of the opening of the flow housing has a macroscopic recess.

[0015] 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 sliding bearing element arranged at a first axial end, a second sliding bearing element arranged at a second axial end and a third sliding bearing element arranged between the two flap bodies, wherein the third sliding bearing element has the recess.Due to the arrangement of the third plain bearing element in a through-hole between the two flow channels, the third plain bearing element is subjected to particularly high thermal stress, resulting in a particularly high risk of the press connection between the third plain bearing element and the flow housing becoming loose. The positive connection reliably prevents axial displacement of the third plain bearing element when cooled.

[0016] 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 plain bearing element and the flow housing are exposed to a relatively high thermal load.

[0017] The object is also achieved by a method for assembling a sliding bearing element of a flap device according to one of claims 1 to 7, the method comprising the following steps:

[0018] Pressing the plain bearing element into an opening of a flow housing,

[0019] 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 coefficients in such a way that a section of one circumferential surface in the region of the recess of the other circumferential surface penetrates into the recess and is plastically deformed into a projection, wherein in the cooled state of the sliding bearing element and the flow housing, the sliding bearing element is fastened to the flow housing in an axially form-fitting manner by an engagement of the projection in the recess.

[0020] This provides a flap device for an internal combustion engine in which the plain bearing element can be fixed to the flow housing reliably and under different thermal loads of the flow housing and the plain bearing element, without the need for additional components or additional assembly steps.

[0021] An embodiment of a flap device according to the invention for an internal combustion engine is shown in the figures and is described below.

[0022] Figure 1 shows a sectional view of a flap device according to the invention, and

[0023] Figures 2a, 2b and 2c show a temporal sequence of the operation of the flap device from Figure 1.

[0024] 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 flap or as an exhaust gas recirculation valve.

[0025] The flap device 10 comprises a flow housing 12, which defines a first flow channel 14 and a second flow channel 16. The flow housing 12 is made of a metallic material, in particular in one piece and from a cast material.

[0026] The flap device 10 further comprises a flap shaft 18 which is rotatably mounted on the flow housing 12 and 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 designed in one piece and extends through the two flow channels 14, 16, wherein the flow housing 12 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 in the flow housing 12. An actuator (not shown in the figure) engages the protruding portion of the flap shaft 18, by means of which 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. By attaching the flap bodies 20, 22 to a single flap shaft 18, the flow cross-section in both flow channels 14, 16 must be adjusted simultaneously.

[0027] The flap shaft 18 is mounted on the flow housing 12 axially on the one hand and radially on the other hand, ie rotatably.

[0028] For the radial support of the valve shaft 18, a radial bearing 40, 42, 44 in the form of a plain bearing element 41, 43, 45 is provided in the opening 30, in the blind hole 34, and in the through-hole 32. A first plain bearing element 43, a second plain bearing element 45, and a third plain bearing element 41 are sleeve-shaped and made of a sintered material. The sleeve-like plain bearing elements 41, 43, 45 are each fastened to the flow housing 12 via a press connection, wherein the plain bearing elements 41, 43, 45 are pressed into the respective opening 30, 32, 34 during assembly in such a way that in the assembled state there is a surface pressure between the outer circumferential surfaces 46, 47, 48 of the plain bearing elements 41, 43, 45 and the inner circumferential surfaces 31, 33, 35 of the openings 30, 32, 34 and the plain bearing elements 41, 43, 45 are fastened axially, radially and tangentially, ie in the circumferential direction, to the flow housing 12.

[0029] The axial bearing is provided 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 to 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 finally assembled state, bears against a complementary, conical counter-contact surface 60 of the bearing element 52.The conical design of the contact surfaces 58, 60 allows the contact area to be increased and thus the sealing to be improved.

[0030] A spring receiving element 70 is fastened to the protruding section of the flap shaft 18, with a spring element 72 being preloaded 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 initial assembly, there is such a high surface pressure between the outer peripheral surface 46, 47, 48 of the plain bearing elements 41, 43, 45 and the corresponding peripheral surface 31, 33, 35 of the openings 30, 32, 34 that the plain bearing elements 41, 43, 45 are radially, axially, and tangentially fixed to the flow housing 12. During operation of the flap device 10, the flow channels 14, 16 are flowed through by an exhaust gas which has a temperature of several 100°C.Due to the high temperatures of the exhaust gas, the plain bearing elements 41, 43, 45 and the flow housing 12 heat up and expand according to their thermal expansion coefficient. The third plain bearing element 41 arranged in the opening 30 and the area of ​​the flow housing 12 around the third plain bearing element 41 are subjected to the greatest thermal stress. Due to the thermal expansion, in particular of the third plain bearing element 41 and the flow housing 12, the surface pressure between the outer peripheral surface 46 of the third plain bearing element 41 and the peripheral surface 31 of the opening 30 increases such that the third plain bearing element 41 and the flow housing 12 undergo plastic deformation in the area of ​​the opening 30.Due to the plastic deformation, in the cooled state of the third plain bearing element 41 and the flow housing 12, a radial gap 49 exists between the outer circumferential surface 46 of the third plain bearing element 41 and the circumferential surface 31 of the opening 30, whereby the surface pressure is eliminated at least in the cooled state and a fixation of the third plain bearing element 41 to the flow housing 12 is no longer ensured.

[0031] According to the invention, a macroscopic recess 80 in the form of a groove is provided on the outer peripheral surface 46 of the third plain bearing element 41. The recess 80 causes a portion 82 of the flow housing 12 to penetrate into the recess 80 upon thermally induced expansion of the third plain bearing element 41 and the flow housing 12 and the resulting plastic deformation of the plain bearing element 41 and the flow housing 12. The portion 82 penetrating the recess 80 and still present in the cooled state is created by plastic deformation and forms a projection 84, which remains intact even in the cooled state of the flow housing 12 and engages in the recess 80. In this case, the projection 84 has a radial extension a in the case of a thermal expansion of the plain bearing element 41 and the flow housing 12, which is composed of an elastic and a plastic component.In the cooled state, only the plastic component of the deformation is retained, so that the projection 84 has a radial extent b which is less than the radial extent a. In the cooled state of the flow housing 12 and the plain bearing element 41, the radial extent b of the projection 84 created by the plastic deformation is so high that the projection 84 rests against the side surfaces 86, 88 of the recess 80 over a section d. The projection 84 and the recess 80 thus form a positive connection between the third plain bearing element 41 and the flow housing 12 in the axial direction, the positive connection being established automatically by the activation 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 manufacture of the projection 84 is illustrated in Figures 2a, 2b, and 2c, wherein Figure 2a illustrates the new state and the plain bearing element 41 is merely pressed into the opening 30. Figure 1 also illustrates the new state. Figure 2b shows a state in which the exhaust gas flows through the flow channels 14, 16, and as a result, the third plain bearing element 41 and the flow housing 12 in the region of the third plain bearing element 41 have thermally expanded. Figure 3c shows the cooled state after the thermal expansion of the plain bearing element 41 and 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 plain bearing elements 43, 45 can also be provided with a recess.The recess could also be formed on the peripheral surface 31 of the opening 30.

Claims

P A T E N T A N S P R Ü C H E 1. A flap device for an internal combustion engine, comprising a flow housing (12) which defines 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, wherein the sliding bearing element is fastened to the flow housing (12) via a press connection between an outer circumferential surface of the sliding bearing element and an inner circumferential surface of an opening formed on the flow housing, 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) is rotatable together with the flap shaft (18) about a longitudinal axis (24) of the flap shaft (18) between different positions, characterized in that on the outer circumferential surface (46) of the sliding bearing element (41) and / or on the inner circumferential surface (31) of the opening (30) a recess (80) is provided,wherein, when a hot gas flows through the flow channel (14, 16), the surface pressure between the outer circumferential surface (46) of the plain 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 equal 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) in the region of the recess (80) provided on the other circumferential surface (31, 46) penetrates into the recess (80) and plastically forms a projection (84), deformed, wherein in the cooled state of the plain bearing element (41) and the flow housing (12), the equal bearing element (41) is held in a form-fitting manner in the axial direction by the projection (84) projecting into the recess (80).

2. Flap device according to claim 1, characterized in that the recess (80) is a circumferential groove.

3. Flap device according to claim 1 or 2, characterized in that the flow housing (12) has a larger coefficient of thermal expansion than the sliding bearing element (41).

4. Flap device according to one of the preceding claims, characterized in that the flow housing (12) is made of a cast material and the sliding bearing element (41) is made of a sintered material.

5. Flap device according to one of the preceding claims, characterized in that the recess (80) has a width of several millimeters.

6. 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 The flap body (22) is arranged in a second flow channel (16) delimited by the flow housing (12), the flap body (22) having a first sliding bearing element (43) arranged at a first axial end, a second sliding bearing element (45) arranged at a second axial end, and a third sliding bearing element (41) arranged between the two flap bodies (20, 22), the third sliding bearing element (41) having the recess (80).

7. Flap device according to one of the preceding claims, characterized in that the flow channel (14, 16) is an exhaust gas flow channel.

8. A method for assembling a sliding bearing element of a flap device according to one of claims 1 to 7, comprising the following steps: Pressing the plain bearing element (41) into an opening (30) of a flow housing (12), Flow through the flow channel (14, 16) of the Flow housing (12) with a hot gas, wherein the flow housing (12) and the sliding bearing element (41) expand based on the corresponding thermal expansion coefficients in such a way that a section (82) of one circumferential surface (31, 46) in the region of the recess (80) of the other circumferential surface (31, 46) penetrates into the recess (80) 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 fastened to the flow housing (12) in an axially form-fitting manner by an engagement of the projection (84) in the recess (80).

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