Exhaust gas recirculation device for an internal combustion engine

Abstract

Exhaust gas recirculation devices for an internal combustion engine, comprising an inlet channel (10), a branch (12) at which the inlet channel (10) is divided into a first exhaust gas channel (14) and a second exhaust gas channel (16), a first flap (18) via which the first exhaust gas channel (14) can be closed or opened, a second flap (26) via which the second exhaust gas channel (16) can be closed or opened, a shaft (20) on which the two flaps (18, 26) are arranged and via which the two flaps (18, 26) can be rotated in the respective exhaust gas channel (14, 16), and a housing wall (24) via which the first exhaust gas channel (14) is separated from the second exhaust gas channel (16) and which has a shaft passage opening (22) through which the shaft (20) projects from the first exhaust gas channel (14) into the second exhaust gas channel (16), wherein in a first position of the shaft (20), the first exhaust gas channel (14) is closed by the first flap (18) and the second exhaust gas channel (16) is closed by the second flap (26), are known. In order to enable precise control without temperature overloads due to leakage flows, the invention proposes that, in the first position, the first flap (18) closes the first exhaust gas channel (14) downstream with respect to a leakage flow along the shaft (20) through the shaft passage opening (22) and the second flap (26) closes the second exhaust gas channel (16) downstream with respect to a leakage flow along the shaft (20) through the shaft passage opening (22).

Description

[0001] - 1 - / PL P.22044. WO / RÜ August 14, 2024

[0002] Pierburg GmbH, 41460 Neuss

[0003] DESCRIPTION

[0004] Exhaust gas recirculation device for an internal combustion engine

[0005] The invention relates to an exhaust gas recirculation device for an internal combustion engine comprising an inlet channel, a branch at which the inlet channel divides into a first exhaust channel and a second exhaust channel, a first flap by which the first exhaust channel can be closed or opened, a second flap by which the second exhaust channel can be closed or opened, a shaft on which the two flaps are arranged and by which the two flaps are rotatable in the respective exhaust channel, and a housing wall by which the first exhaust channel is separated from the second exhaust channel, wherein in a first position of the shaft the first exhaust channel is closed by the first flap and the second exhaust channel is closed by the second flap.

[0006] Such exhaust gas recirculation devices are used, for example, in exhaust gas recirculation systems with an exhaust gas cooler and bypass line to allow the recirculated exhaust gas flow to the bypass line or the exhaust gas cooler to be controlled separately. By opening the bypass line during the warm-up phase, this phase can be shortened, while after warm-up, a cooled exhaust gas flow can be regulated. In this way, a significantly reduced pollutant emission can be achieved.

[0007] Various designs have been implemented for this purpose. Besides the use of two separate channels in which separately controlled valve bodies are arranged, systems are also known in which both valves are coupled and controlled by a single actuator. This coupling can be achieved either via a gearbox, whereby both poppet valves and, for higher flow rates, flaps can be used to control the flow cross-section - 2 - / PL P.22044. WO / RÜ 14.08.2024, or a direct coupling is implemented, so that both valve bodies or flaps are arranged on a single shaft.

[0008] Such an exhaust gas recirculation device with two flaps arranged on a common shaft is disclosed, for example, in DE 10 2016 107 933 B4. The exhaust gas recirculation device has a housing with two channels, each containing a flap. Both flaps are fixed to a rotatably mounted shaft and are rotatable with the shaft. In a first angular position of the shaft, the first flap closes the first channel while the second channel is open; in a second angular position, the first channel is open while the second flap closes the second channel; and in a third angular position, the first flap closes the first channel and the second flap closes the second channel. To achieve this, a concave valve seat is arranged in the second channel, which surrounds the circumferential surface of the associated second flap in the second and third angular positions and allows rotation.The two flaps are arranged in such a way that the shaft can be rotated from the first angular position via the second angular position to the third angular position, and when the shaft is pivoted from the first angular position to the second angular position, the first channel opens while the second channel closes at the same time.

[0009] However, a problem with such an exhaust gas recirculation device is that it is no longer possible to regulate the amount of exhaust gas recirculated during the movement from the first to the second angular position.

[0010] On the other hand, it is known from DE 103 21 637 Al to regulate one of the channels at a time using lift valves, while the other channel remains closed. - 3 - / PL P.22044. WO / RÜ 14.08.2024

[0011] When using two rotatable flaps mounted on a common shaft, and thus potentially high exhaust gas recirculation rates, the disadvantage arises from possible leakage between the two exhaust channels. This can lead to increased temperatures in cooling mode or decreased temperatures in bypass mode, thereby reducing the efficiency of emissions reduction. This is especially true with low recirculated exhaust gas flows or outside of the intended recirculation times, and in the event of a leak in the bypass line. This results in undesirably significant temperature increases in the exhaust module. Furthermore, it has been shown that, in addition to leakage between the flap and the surrounding flap wall, leakage from one channel to the other is also relevant.

[0012] The task therefore is to provide an exhaust gas recirculation device for an internal combustion engine that allows both exhaust gas flows to be controlled separately and avoids temperature problems caused by leaks.

[0013] This problem is solved by an exhaust gas recirculation device for an internal combustion engine having the features of main claim 1.

[0014] The exhaust gas recirculation device according to the invention has an inlet channel which divides at a branch into a first exhaust gas channel and a second exhaust gas channel. A flap is arranged in each of these exhaust gas channels, such that the first exhaust gas channel can be closed or opened via a first flap, and the second exhaust gas channel can be closed or opened via a second flap. The two flaps are rotatably arranged on a common shaft in the two exhaust gas channels. Furthermore, the exhaust gas recirculation device has a housing wall that separates the first exhaust gas channel from the second exhaust gas channel. This - 4 - / PL P.22044. WO / RÜ 14.08.2024

[0015] The housing wall is thus located between the two exhaust channels. Either a shaft opening is formed in the housing wall, through which the shaft from the first exhaust channel protrudes into the second exhaust channel, or the shaft is located directly upstream of this housing wall. In a first position of the shaft, the first exhaust channel is closed by the first flap and the second exhaust channel is closed by the second flap, while by rotating the housing wall from this position, at least one of the exhaust channels is opened by the respective flap.

[0016] According to the invention, with respect to a flow along the shaft from the second exhaust channel to the first exhaust channel, in the first position the first flap closes the first exhaust channel downstream of this flow, and the second flap closes the second exhaust channel with respect to a flow along the shaft from the first exhaust channel to the second exhaust channel downstream of the latter flow. This does not necessarily mean that the entire flap must be arranged downstream of the shaft opening with respect to the exhaust flow through the exhaust channels, but rather that when the exhaust gas flows through the gap between the shaft and the housing wall, the flap prevents it from flowing further into the respective subsequent exhaust channel.

[0017] With flaps arranged at an angle on the shaft, the area facing the central housing wall is located behind the shaft section between the two flaps with respect to the normal exhaust gas flow when the flap is open. The area furthest from this shaft section, while located in front of the shaft opening with respect to the exhaust gas flow through the exhaust duct, is positioned in the described angled position. However, with respect to the flow along this shaft section, the entire flap is located downstream and is thus suitable for preventing further leakage. Accordingly, an exhaust gas flow passing through the gap between the shaft (5) and the housing wall from one exhaust duct into the other cannot penetrate further into the downstream area of ​​the other exhaust duct. In this way, increased temperatures caused by leakage behind the flaps are reliably prevented.This results in a complete seal of the area behind the flaps in the first position. The inclined arrangement means that in a cross-section through the shaft and the greatest extent of the flap mounted on it, a non-zero angle is formed between the shaft and the flap.

[0018] Accordingly, the first and second flaps are preferably mounted at an angle on the shaft. This angled arrangement means that in a cross-section through the shaft and the greatest extent of the flap mounted on it, a non-zero angle is formed between the shaft and the flap. This reduces the required installation space, since a flap aligned parallel to the shaft would have to be offset from the shaft, meaning that if the flap were to rotate, the space required for rotation would have to be significantly larger. Pressure loss is also reduced.

[0019] In a particularly preferred embodiment, the two flaps are arranged such that when the shaft is rotated from the first position in a first direction of rotation, the first flap continuously opens the first exhaust channel, while the second flap is rotatable with its entire circumference along a spherical valve seat bounding the second exhaust channel and closes and holds the second exhaust channel closed; and that when the shaft is rotated from the first position in the opposite second direction of rotation, the second flap continuously opens the second exhaust channel, while the first flap is rotatable with its entire circumference along a spherical valve seat bounding the first exhaust channel and closes and holds the first exhaust channel closed. This - 6 - / PL P.22044. WO / RÜ 14.08.2024

[0020] The arrangement and design of the spherical valve seat allow both exhaust gas flows to be controlled separately in terms of their mass flow, while the other exhaust gas channel is closed. This enables very precise control of recirculated exhaust gas flows.

[0021] Preferably, the first exhaust gas channel is connected downstream to an exhaust gas cooler, and the second exhaust gas channel is connected downstream to a bypass channel that bypasses the exhaust gas cooler. Accordingly, the exhaust gas can be recirculated uncooled to the internal combustion engine after a cold start and during the warm-up phase, and cooled after the warm-up phase. Complete flow control is possible with this exhaust gas recirculation device during both phases.

[0022] It is particularly advantageous if a sealing ring is arranged in a groove on the circumference of both the first and second flaps. This sealing ring is, in particular, a type of piston ring made of metal. This ensures a reliable closure of the respective exhaust duct by the flap, even in the event of thermal expansion, without the risk of the flap jamming in the duct. Furthermore, in the first position, it prevents leakage from bypassing the flap and entering the downstream area.

[0023] In an advantageous embodiment, the shaft is rotatable via an electric motor actuator attached to the housing forming the exhaust ducts. This actuator can also include a gearbox. By arranging it directly on the housing, the required installation space is reduced. The use of an electric motor actuator enables very precise and rapid control.

[0024] Preferably, the housing is formed in one piece and incorporates the inlet channel, the branch, and the two exhaust channels. The actuator for operating the shaft can then be attached to this housing. This simplifies assembly. The housing can be manufactured as a die-cast part. Assembly and the associated problems related to tolerances are thus eliminated.

[0025] In a further embodiment, the spherical valve seats are mounted as inserts in the housing forming the exhaust channels. This simplifies the manufacturing of the housing. The valve seats can be manufactured very precisely, even through post-processing, so that a high degree of tightness is achieved across the entire rotational range in which one valve closes the corresponding exhaust channel, while the other valve opens the corresponding bypass channel.

[0026] It is also advantageous if the shaft extends from the actuator through the housing and terminates in the second exhaust channel in front of a housing wall that borders the second exhaust channel on the side opposite the first exhaust channel. This prevents the shaft from becoming stiff due to slight misalignment and simplifies housing manufacturing.

[0027] In a further advantageous embodiment of the invention, the shaft is supported by a first radial bearing and a thrust bearing, which are arranged in the housing between the actuator and the first exhaust duct. Arranging the bearing in this area simplifies assembly.

[0028] In a further embodiment, the shaft is additionally supported by a second radial bearing, which is arranged in a shaft passage opening in the housing wall. This reduces the radial gaps while simultaneously reducing the friction that occurs.

[0029] This creates an exhaust gas recirculation device for an internal combustion engine, with which the effects of leaks at the shaft passage between the two - 8 - / PL P.22044. WO / RÜ 14.08.2024

[0030] The number of exhaust ducts is significantly reduced, thus preventing unwanted heating in a downstream area. Precise flow control is still possible via both exhaust ducts, while the other duct remains closed. A high level of airtightness is also achieved with this closure. The required installation space and effort are considerably reduced.

[0031] An embodiment of an invention according to the invention

[0032] The exhaust gas recirculation device for an internal combustion engine is shown in the figure and is described below.

[0033] The figure shows a side view of an exhaust gas recirculation device according to the invention in a cutaway view.

[0034] The exhaust gas recirculation device according to the invention consists of an inlet channel 10, through which an exhaust gas flow from an internal combustion engine is recirculated, so that this inlet channel 10 forms an upstream part of an exhaust gas recirculation channel.

[0035] The inlet channel 10 has a branch 12 at which it divides into a first exhaust channel 14 and a second exhaust channel 16. A first flap 18 is arranged in the first exhaust channel 14 and is mounted obliquely on a shaft 20, where obliquely means that, in the exemplary embodiment, the flap 18 forms an angle of approximately 20° with the shaft 20. The point of intersection of the flap 18 with the shaft 20 is located in the region of the central axis of the exhaust channel 14.

[0036] The shaft 20 extends through the first exhaust channel 14 and through a shaft passage opening 22, which is arranged in a housing wall 24 formed between the first exhaust channel 14 and the second exhaust channel 16, into the second exhaust channel 16. In the second exhaust channel 16, a second flap 26 is located on the shaft 20 for regulating the - 9 - / PL P.22044. WO / RÜ 14.08.2024

[0037] The second flap 26 is arranged in the flow cross-section of the second exhaust duct 16. It is also arranged obliquely on the shaft 20 and intersects it at an angle of approximately 20° in the region of the central axis of the second exhaust duct 16. The shaft 20 extends approximately to this central axis of the second exhaust duct 16 and thus does not project to the wall 28 of the second exhaust duct 16 opposite the shaft opening 22.

[0038] The inlet channel 10, the two exhaust channels 14 and 16, the housing wall 24, and the wall 28 are formed by a housing 30. On the side of the first exhaust channel opposite the second exhaust channel, the housing 30 has a projection 32, which serves as a stop for a return spring 33 of an electric actuator 34. The shaft 20 extends through a bore 35 in the housing 30 and is connected, in a torque-transmitting but thermally decoupled manner, to an output shaft 36 of the actuator 34, whose actuator housing 37 is attached to the housing 30 and which includes a gearbox 38 with an electric motor 40. The housing part 32 with the gearbox 38 arranged therein is closed by a cover 42. In the bore 36, a first radial bearing 44 and a thrust bearing 46 are arranged one behind the other for supporting the shaft 20. Furthermore, an additional radial bearing 48 is arranged in the shaft passage opening 22.

[0039] The first exhaust gas channel 14 is fluidically connected to a U-shaped exhaust gas cooler 50 (shown only schematically), at the downstream end of which a check valve 52 is arranged. The second exhaust gas channel 16 is fluidically connected to a bypass channel 54 that bypasses the exhaust gas cooler 50 and simultaneously forms an outlet channel 56 of the exhaust gas cooler 50. Accordingly, an exhaust gas flow either passes through the exhaust gas cooler 50 and the check valve 52 into the outlet channel 56 when the first exhaust gas channel 14 is open, or the exhaust gas flow passes directly into the outlet channel 56 via the second exhaust gas channel 16, which then serves as a bypass channel. - 10 - / PI.P.22044. WO / RÜ 14.08.2024

[0040] 54 serving outlet channel 56, whereby a flow into the associated exhaust gas cooler 50 is prevented by the check valve 52.

[0041] To reliably prevent leaks between the first exhaust duct 14 and the second exhaust duct 16, it must first be ensured that the first flap 18 and the second flap 26 are in contact with the opposite wall of the housing 30 with their outer circumference in the position closing the respective exhaust duct 14, 16.

[0042] A tight seal of the exhaust channels 14, 16 in a first position, in which both flaps 18, 26 close the two exhaust channels, is ensured by the fact that a groove 58 is formed on the outer circumference of the first flap 18 and the second flap 26, in which a sealing ring 60 is arranged. This sealing ring 60 is pre-tensioned outwards against the housing 30, similar to a piston ring, but can spring into the groove 58. To further ensure that complete exhaust gas control can take place when rotating from the first position, with the exhaust gas flow being regulated exclusively via the exhaust gas cooler 50 or exclusively via the bypass channel 54, spherical valve seats 62 are installed in the housing 30 in the area of ​​the two flaps 18, 26.These are designed such that, upon rotation from the first position in a first direction of rotation, the second flap 26, with its outer circumference or sealing ring 60, is guided directly opposite the valve seat 62 in the second exhaust channel 16, while the first flap 18 opens a continuously increasing flow cross-section in the first exhaust channel 14, thereby regulating the exhaust gas flow via the exhaust gas cooler 50, while the bypass channel 54 remains completely closed. Upon rotation from the first position in the opposite second direction of rotation, the first flap 18, with its outer circumference or sealing ring 60, is guided directly opposite the valve seat 62 in the first exhaust channel 16. - 11 - / PI.P.22044. WO / RÜ 14.08.2024.

[0043] Exhaust channel 14 is guided, while the second flap 26 releases a steadily increasing flow cross-section in the second exhaust channel 16, so that an exhaust flow in the bypass channel 54 is regulated.

[0044] In addition, leaks along the shaft 20 through the shaft passage opening 22 must be avoided, which could lead to exhaust gas entering the other exhaust channel 14, 16, especially when the exhaust gas recirculation flow is completely shut off, even though the flaps 18, 26 close the two exhaust channels 14, 16.

[0045] To prevent such leakage flows and any resulting temperature stresses downstream of the flaps 18, 26, the two flaps 18, 26 are aligned on the shaft 20 in the first position such that they close off an area downstream of the shaft opening 22 with respect to any leakage flow. This is achieved in particular by arranging the two flaps 18, 26 offset from each other by approximately 180° with respect to their position on the shaft 20 and by having their outer circumferences abut the housing wall 24 between the exhaust channels 14, 16 downstream of the shaft opening 22 with respect to any exhaust gas flow through the exhaust channels 14, 16. Accordingly, in this position an exhaust gas flow can pass along the shaft 20 through the shaft passage opening 22, but is prevented from flowing further because the two exhaust gas channels 14, 16 are closed over their entire circumference by the two flaps 18, 26.

[0046] Such a designed exhaust gas recirculation device thus prevents unwanted flow through the exhaust gas cooler or the bypass channel, so that the exhaust gas can be recirculated in a fully quantity-controlled manner even at defined temperatures, since mixing of the cooled exhaust gas stream with the uncooled exhaust gas stream is avoided. Undesirable leakage flows when both exhaust channels are completely closed are also prevented, thereby avoiding undesirable - 12 - / PI.P.22044. WO / RÜ 14.08.2024

[0047] Material stresses due to elevated temperatures can be prevented.

[0048] It should be clear that the bypass channel and exhaust gas cooler can be designed differently; in particular, a straight-flow exhaust gas cooler can also be used. The actuator can also be attached to the housing as a separate component. Most importantly, the flaps do not necessarily have to be positioned 180° apart on the shaft. It is also possible to reduce this offset, as long as the entire flap body is located downstream of the shaft opening and thus seals the exhaust channel against any downstream leakage through the shaft opening. Additionally, it should be noted that the shaft does not have to pass through a shaft opening; the shaft section between the two flaps can also be located directly upstream of the two separate exhaust channels and is therefore simply positioned directly upstream of the separating housing wall.

Claims

- 13 - / PI.P.22044. WO / RÜ August 14, 2024 Pierburg GmbH, 41460 Neuss PATENT CLAIMS 1. Exhaust gas recirculation device for an internal combustion engine with an inlet port (10), a branch (12) at which the inlet port (10) divides into a first exhaust port (14) and a second exhaust port (16), a first flap (18) by which the first exhaust port (14) can be closed or opened, a second flap (26) by which the second exhaust port (16) can be closed or opened, a shaft (20) on which the two flaps (18, 26) are arranged and by which the two flaps (18, 26) are rotatable in the respective exhaust ports (14, 16), a housing wall (24) by which the first exhaust port (14) is separated from the second exhaust port (16), wherein in a first position of the shaft (20) the first exhaust port (14) is closed by the first flap (18) and the second exhaust port (16) is closed by the second flap (26), thereby characterizedthat in the first position the first flap (18) closes the first exhaust channel (14) with respect to a flow along the shaft (20) from the second exhaust channel (16) to the first exhaust channel (14) downstream, and the second flap (26) closes the second exhaust channel (16) with respect to a flow along the shaft (20) from the first exhaust channel (14) to the second exhaust channel (16) downstream.

2. Exhaust gas recirculation device for an internal combustion engine according to claim 1, characterized in that - 14 - / PI.P.22044. WO / R.Ü 14.08.2024 the first flap (18) and the second flap (26) are attached at an angle to the shaft (20).

3. Exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2, characterized in that the two flaps (18, 26) are arranged such that when the shaft (20) is rotated from the first position in a first direction of rotation, the first flap (18) continuously opens the first exhaust gas channel (14), while the second flap (26) is rotatable with its entire circumference along a spherical valve seat (62) limiting the second exhaust gas channel (16) and closes the second exhaust gas channel (16), and that when the shaft (20) is rotated from the first position in an opposite second direction of rotation, the second flap (26) continuously opens the second exhaust gas channel (16), while the first flap (18) is rotatable with its entire circumference along a spherical valve seat (62) limiting the first exhaust gas channel (14) and closes the first exhaust gas channel (14).

4. Exhaust gas recirculation device for an internal combustion engine according to one of the preceding claims, characterized in that the first exhaust gas channel (14) is connected downstream to an exhaust gas cooler (50) and the second exhaust gas channel (16) is connected downstream to a bypass channel (54) bypassing the exhaust gas cooler (50).

5. Exhaust gas recirculation device for an internal combustion engine according to one of the preceding claims, characterized in that - 15 - / PI.P.22044. WO / RÜ 14.08.2024 on the circumference of the first flap (18) and the second flap (26) a sealing ring (60) is arranged in a groove (58).

6. Exhaust gas recirculation device for an internal combustion engine according to one of the preceding claims, characterized in that the shaft (20) is rotatable via an electric motor actuator (34) which is attached to the housing (30) forming the exhaust gas channels (14, 16).

7. Exhaust gas recirculation device for an internal combustion engine according to claim 6, characterized in that the housing (30) is formed in one piece and forms the inlet channel (10), the branch (24) and the two exhaust gas channels (14, 16).

8. Exhaust gas recirculation device for an internal combustion engine according to claim 6 or 7, characterized in that the spherical valve seats (62) are attached as inserts in the housing (30) forming the exhaust gas channels (14, 16).

9. Exhaust gas recirculation device for an internal combustion engine according to one of claims 6 to 8, characterized in that the shaft (20) extends from the actuator (34) through the housing (30) and terminates in the second exhaust gas channel (16) in front of a housing wall (24) which limits the second exhaust gas channel (16) on a side opposite to the first exhaust gas channel (14).

10. Exhaust gas recirculation device for an internal combustion engine according to one of claims 6 to 9, characterized in that - 16 - / PI.P.22044. WO / RÜ 14.08.2024 the shaft (20) is supported by a first radial bearing (44) and a thrust bearing (46), which are arranged in the housing (30) between the actuator (34) and the first exhaust gas channel (14).

11. Exhaust gas recirculation device for an internal combustion engine according to Claim 10, characterized in that the shaft (20) is additionally supported by a second radial bearing (48) which is arranged in a shaft passage opening (22) between the first exhaust duct (14) and the second exhaust duct (16).

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