Turbine for an exhaust gas turbocharger

Abstract

Turbine for an exhaust gas turbocharger, with a turbine housing through which exhaust gas from an internal combustion engine can flow, with a turbine wheel rotatably received in the turbine housing and driven by the exhaust gas, with at least one bypass channel via which the turbine wheel is to be bypassed by at least a portion of the exhaust gas, with a valve element (10) which is movable relative to the turbine housing between a closed position blocking the bypass channel and at least one open position releasing the bypass channel and has at least one first sealing surface (12) which, for blocking the bypass channel, bears against at least one corresponding second sealing surface of a wall of the turbine, and with a lever element (14) via which the valve element (10) is movable, characterized in that at least one point (18),on which the valve element (10) is supported on the lever element (14) in a direction (20) running obliquely or perpendicularly to the first sealing surface (12), is arranged upstream of the first sealing surface (12) with respect to a flow direction of the exhaust gas flowing into the bypass channel, and the valve element (10) has a hollow cross-section (28), and the lever element (14) has a first longitudinal region (30) and a second longitudinal region (32) running obliquely or perpendicularly thereto, which second longitudinal region (32) is at least partially received in the hollow cross-section (28), and the second longitudinal region (32) has an opening (40) designed as a through-opening, and the valve element (10) has a region (42) designed as a bolt or pin, which penetrates the opening (40).

Description

[0001] The invention relates to a turbine for an exhaust gas turbocharger according to the preamble of patent claim 1.

[0002] Such a turbine for an exhaust gas turbocharger, in particular of an internal combustion engine, is already known, for example, from DE 10 2013 002 894 A1, WO 2005 / 073 536 A1 and EP 2 444 626 A1. The turbine comprises a turbine housing through which the exhaust gas of the internal combustion engine can flow, and a turbine wheel rotatably received in the turbine housing and driven by the exhaust gas. The turbine further has at least one bypass channel via which at least a portion of the exhaust gas can bypass the turbine wheel. This means that the exhaust gas flowing through the bypass channel bypasses the turbine wheel and thus does not drive it. The bypass channel is usually also referred to as a bypass channel. The bypass channel is typically used to adjust a boost pressure that can be provided by the exhaust gas turbocharger.

[0003] The turbine further comprises a valve element, also referred to as a wastegate, which is movable, in particular pivotable, relative to the turbine housing between a closed position blocking the bypass channel and at least one open position releasing the bypass channel. The boost pressure can thus be adjusted by means of the valve element. The valve element has at least one first sealing surface which, in order to block the bypass channel, bears against at least one corresponding second sealing surface of a wall of the turbine. For example, the bypass channel has at least one inlet opening through which at least a portion of the exhaust gas can flow into the bypass channel. In the closed position, the sealing surfaces bear against one another such that the inlet opening is fluidically blocked by means of the sealing surfaces or by means of the valve element, and thus no exhaust gas can flow into or through the bypass channel.Furthermore, the turbine comprises a lever element, via which the valve element can be moved, in particular pivoted. EP 2 444 626 A1 further discloses a valve element having a hollow cross-section.

[0004] The valve element is also commonly referred to as a wastegate and is typically designed to be solid to fulfill its function. The lever element, for example, is part of an adjustment mechanism by which the valve element (wastegate) is moved. Particularly in the closed position, the valve element and, via it, the adjustment mechanism are typically subjected to high loads, making it challenging to achieve sufficient durability for the adjustment mechanism and thus for the turbine as a whole.

[0005] The object of the present invention is therefore to further develop a turbine of the type mentioned at the outset in such a way that a particularly high level of robustness of the turbine can be achieved.

[0006] This object is achieved by a turbine having the features of patent claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0007] In order to further develop a turbine of the type specified in the preamble of patent claim 1 such that a particularly high level of robustness of the turbine can be achieved, the invention provides that a point at which the valve element is supported on the lever element in a direction running obliquely or, in particular, perpendicular to the first sealing surface is arranged upstream of the first sealing surface with respect to a flow direction of the exhaust gas flowing into the bypass channel. In other words, the first sealing surface is arranged in an imaginary plane, wherein the valve element is supported on the lever element at this point in a direction running obliquely or, in particular, perpendicular to the first sealing surface and thus to this plane.

[0008] If the valve element is in its open position, the exhaust gas flows into the bypass channel in one flow direction. If the valve element is in its closed position, so that, for example, no exhaust gas flows into the bypass channel, the point is arranged upstream of the sealing surface, at least in the closed position of the valve element and relative to the flow direction in which the exhaust gas flows or would flow into the bypass channel when the valve element was in the open position. In contrast to the prior art, in which the first sealing surface is usually arranged downstream of the point, a particularly high level of robustness of the turbine can be achieved, since the arrangement of the point relative to the first sealing surface via the valve element onto the lever element and thus any loads acting on an adjustment mechanism of the turbine comprising the lever element, which may be provided, can be kept to a minimum.In particular, it is possible to achieve a particularly advantageous durability of the valve element and thus its function.

[0009] The aforementioned loads acting on the valve element and, via the valve element, on the lever element result, for example, from the exhaust gas flowing toward the valve element, particularly in its closed position, which, for example, causes a pressurization, particularly a pulsating pressurization, of the valve element. Typically, these pressurizations lead to high loads on the adjustment mechanism. However, since the location is located upstream and not downstream of the first sealing surface, the loads acting on the adjustment mechanism and resulting from the pulsating pressurization can be kept to a minimum.

[0010] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combinations, but also in other combinations or on their own, without departing from the scope of the invention.

[0011] The drawing shows: Fig. 1 a schematic sectional view of a valve element according to a first embodiment not belonging to the invention for a turbine of an exhaust gas turbocharger, wherein a bypass channel of the turbine can be blocked and released by means of the valve element; Fig. 2 is a schematic sectional view of the valve element according to a second embodiment; and Fig. 3 a schematic sectional view of the valve element according to a third embodiment.

[0012] In the figures, identical or functionally identical elements are provided with the same reference numerals.

[0013] Fig. 1 shows a schematic sectional view of a valve element 10 according to a first embodiment, not part of the invention, for a turbine of an exhaust gas turbocharger, in particular of an internal combustion engine. The valve element 10 is also referred to as a wastegate and—as will be explained below—is used to adjust a boost pressure to be provided by the exhaust gas turbocharger. The internal combustion engine is designed, for example, as a reciprocating piston internal combustion engine and comprises a plurality of combustion chambers in the form of cylinders, wherein the internal combustion engine is used to drive a motor vehicle, in particular a passenger car. During fired operation of the internal combustion engine, combustion processes take place in the cylinders, resulting in exhaust gas.

[0014] The turbine comprises a turbine housing (not visible in the figures) with a receiving space. A turbine wheel of the turbine is received in the receiving space, wherein the turbine wheel is rotatable about a rotation axis relative to the turbine housing. The turbine housing can be flowed through by the exhaust gas of the internal combustion engine and has at least two flows which are at least partially fluidically separated from one another and through which the exhaust gas of the internal combustion engine can flow. The exhaust gas is guided to the receiving space and thus to the turbine wheel by means of the flows, so that the turbine wheel can be driven by the exhaust gas. A first part of the cylinders is, for example, connected to a first of the flows or merged to form the first flow, wherein a second part of the cylinders, which is different from the first part, is fluidly connected to the second flow or merged to form the second flow.Thus, the exhaust gas from the cylinders belonging to the first section is fed to the first flow and not to the second flow, while the exhaust gas from the cylinders belonging to the second section is fed to the second flow and not to the first flow. In other words, the first section of cylinders feeds its exhaust gas to the first flow, while the second section of cylinders feeds its exhaust gas to the second flow.

[0015] By at least partially separating the flow channels, the exhaust gas volume between the cylinders and the turbine wheel is reduced overall compared to the cylinders, resulting in the effect of pulse-charging. In other words, the exhaust gas turbocharger and thus the internal combustion engine can be operated in pulse-charging mode by separating the flow channels, in which the internal combustion engine is charged, i.e., supplied with compressed air, by means of pulse-charging.

[0016] The turbine also comprises at least one bypass channel, via which at least a portion of the exhaust gas can be bypassed from the turbine wheel. In other words, at least a portion of the exhaust gas can be branched off at a branching point arranged upstream of the turbine wheel by means of the bypass channel, so that the branched exhaust gas flowing through the bypass channel bypasses the turbine wheel and thus does not drive it. Furthermore, the turbine has at least one overflow opening, via which the flows can be fluidly connected to one another at at least one connection point arranged upstream of the turbine wheel. By means of the valve element 10, a first quantity of exhaust gas flowing through the overflow opening and a second quantity of exhaust gas flowing through the bypass channel can be adjusted. The valve element 10 is movable, in particular pivotable, between a closed position and at least one open position relative to the turbine housing.In the closed position, the bypass channel is fluidically blocked by the valve element 10, so that no exhaust gas can flow through the bypass channel. In the open position, the valve element 10 releases the bypass channel, allowing at least a portion of the exhaust gas to bypass the turbine wheel.

[0017] The valve element 10 has a first sealing surface 12, which is designed, for example, as an annular surface or at least substantially annular surface. In the closed position, the first sealing surface 12 rests against a corresponding second sealing surface of a wall of the turbine, in particular of the turbine housing, such that the bypass channel is fluidically blocked by means of the sealing surfaces. In particular, the bypass channel has an inflow opening through which the exhaust gas can flow into the bypass channel. In the closed position, the inflow opening is fluidically blocked by means of the valve element 10 such that no exhaust gas can flow into the bypass channel. In the open position, however, the valve element 10 opens the inflow opening such that exhaust gas can flow through the inflow opening and thus exhaust gas can flow through the inflow opening and into the bypass channel.When the valve element 10 is in the open position, the exhaust gas flows in a direction toward and, in particular, into the bypass channel and thus through the inlet opening. This flow direction thus exists in the open position of the valve element 10, but can also be easily transferred to the closed position of the valve element 10 for reference purposes.

[0018] The turbine also includes an adjustment mechanism by which the valve element 10 can be pivoted between the closed position and the open position. The adjustment mechanism includes a lever element 14, which can be pivoted about a pivot axis 16 relative to the turbine housing. The lever element 14 is connected to the valve element 10, so that the valve element 10 is moved, i.e., pivoted, between the open position and the closed position by pivoting the lever element 14.

[0019] In order to create a particularly high level of robustness of the turbine, a point 18 at which the valve element 10 is inserted into a groove extending perpendicular to the first sealing surface 12 and in Fig. 1 by a directional arrow 20 is supported on the lever element 14, arranged upstream of the first sealing surface 12 with respect to the previously described flow direction of the exhaust gas flowing into the bypass channel. In Fig. 1 shows an imaginary plane 22, which is essentially perpendicular to the aforementioned flow direction and in which the point 18 is located. This means that the point 18 is arranged in the plane 22, with the plane 22 and thus the point 18 being arranged upstream of the first sealing surface 12.

[0020] In addition, a further point 24 is provided, arranged downstream of the point 18 with respect to the described flow direction, at which the valve element 10 is supported on the lever element 14 in the direction perpendicular to the first sealing surface 12. Furthermore, in Fig. 1 shows a plane 26 extending perpendicular to the aforementioned direction, in which the point 24 is arranged. The plane 26 and thus the point 24 are also arranged upstream of the first sealing surface 12 with respect to the aforementioned flow direction.

[0021] The valve element 10 has a hollow cross-section 28, designed, for example, as a closed hollow cross-section, in which the point 24 is arranged. Furthermore, the lever element 14 has a first longitudinal region 30 and a second longitudinal region 32, which extends at least substantially perpendicular to the first longitudinal region 30. The valve element 10 is supported in the aforementioned direction at the point 24 on the second longitudinal region 32 towards the longitudinal region 30. Furthermore, the lever element 14 has a third longitudinal region 34 which adjoins the second longitudinal region 32 and runs at least substantially parallel to the second longitudinal region 32 and is arranged coaxially to the second longitudinal region 32. The valve element 10 has an opening 36 designed as a through-opening, in which the third longitudinal region 34 is received. The valve element 10 is thus arranged on the third longitudinal region 34 via its opening 36.The longitudinal regions 32 and 34 thus have a longitudinal extension direction and are at least substantially cylindrical, so that they also have an axial direction. The planes 22, 26 extend perpendicular to the axial direction of the longitudinal regions 32 and 34, with said direction extending in the axial direction of the longitudinal regions 32 and 34. Thus, the valve element 10 is supported on the lever element 14 in the axial direction of the longitudinal regions 32 and 34, so that the respective point 18 or 24 is an axial interface at which the valve element 10 is supported on the lever element 14.

[0022] In the prior art, this axial interface is arranged downstream of the first sealing surface 12 with respect to the flow direction of the exhaust gas. However, in the valve element 10 and the lever element 14, the axial interface is now positioned upstream of the sealing surface 12. Fig. 1 shows that the second longitudinal region 32 is at least partially accommodated in the hollow cross-section 28. The valve element 10 is supported in the axial direction on the second longitudinal region 32.

[0023] To secure the valve element 10 on the third longitudinal section 34 in the axial direction, a fastening element 38 is provided, which is designed, for example, as a nut. The nut has, for example, an internal thread, while the third longitudinal section 34, designed as a pin, has, for example, an external thread corresponding to the internal thread. The nut is thus screwed onto the external thread of the longitudinal section 34 via its internal thread, whereby the valve element 10 is clamped in the axial direction against the second longitudinal section 32 and is thus secured on the third longitudinal section 34.

[0024] In the closed position, the exhaust gas flows against the valve element 10, with the exhaust gas flowing against the valve element 10, for example in a pulsating manner. This results in a pulsating pressurization of the valve element 10, which is also referred to as a wastegate or bypass valve. Bypassing the turbine wheel is also referred to as blow-off, so that the valve element 10 is also referred to as a blow-off valve. At one point in time, for example, a strongly one-sided pressure load is applied to the valve element 10, whereby this pressure load leads to a force F. This force F acts on the valve element 10 and thus leads to a load on the valve element 10, so that the lever element 14 and the adjustment mechanism as a whole are also loaded by the valve element 10.

[0025] The pressurization results in further forces F1, F2, and F3, for example, with force F1 acting in the axial direction of length regions 32 and 34 and force F2 acting in the radial direction of length regions 32 and 34. In particular, force F1, in the case of one-sided pressure loading, leads to a strong moment load on the axial interface in conventional turbines. However, since points 18 and 24 are now arranged upstream of the sealing surface 12, excessive moment load on points 18 and 24, and thus on the adjustment mechanism as a whole, can be avoided. In particular, the arrangement of points 18 and 24 upstream of the sealing surface 12 makes it possible, by design, to cancel out moments caused by pressure forces at the axial interface between the relief valve and the lever element 14. This ensures that the valve element 10 functions reliably and reliably over the long term.

[0026] For example, it is provided that the valve element 10 closes both the bypass channel and the aforementioned overflow opening in the closed position. Alternatively, it is conceivable that the valve element 10 closes the bypass channel in the closed position and at least partially opens the overflow opening, so that at least a portion of the exhaust gas can flow through the overflow opening both in the open position and in the closed position. Thus, for example, the flows are fluidically connected to one another via the overflow opening even in the closed position. If the valve element 10 is moved, for example, from the closed position to the open position, this is accompanied by a successive or increasing further opening of the overflow opening, so that the flows are successively or increasingly fluidically connected to one another as the valve element moves from the closed position to the open position.

[0027] It has proven advantageous if the valve element 10, in the closed position, exposes a first partial area of ​​the overflow opening and fluidically blocks a second partial area of ​​the overflow opening adjoining the first partial area. Preferably, the valve element 10 blocks the bypass channel in the closed position and, in the open position, exposes the bypass channel and not only the first partial area, but also the second partial area of ​​the overflow opening, so that the overflow opening is more exposed in the open position than in the closed position.

[0028] Furthermore, it has proven particularly advantageous if a first dimension by which the valve element 10 releases the bypass channel upon its movement from the closed position to the open position is greater, at least during part of the movement of the valve element 10, than a second dimension by which the valve element 10 releases the overflow opening. In other words, it is preferably provided that, upon opening the valve element 10, a more pronounced blow-off occurs as a flow connection, particularly at a small opening angle. Upon further opening of the valve element 10, an increasing or stronger blow-over occurs.

[0029] Blow-off is the process of bypassing the turbine wheel with exhaust gas. In other words, opening the bypass channel is also referred to as blowing off or blowing off, so that the exhaust gas flowing through the bypass channel is blown off. This is the case because the energy contained in the exhaust gas flowing through the bypass channel cannot be used to drive the turbine wheel. Blow-off is the process of connecting the streams via the overflow opening because by opening the overflow opening, which is also referred to as the throughflow opening, the streams are fluidically connected to one another. By fluidically connecting the streams, which is also referred to as the stream connection, exhaust gas can flow from the first stream to the second stream and vice versa. This exhaust gas is not blown off, for example, but can be used to drive the turbine wheel.The valve element 10 thus has a dual function, since it is used both to open and close the bypass channel and to adjust the amount of exhaust gas flowing through the overflow opening.

[0030] This allows for increased efficiency of the internal combustion engine compared to the prior art, as well as greater freedom in the design of a turbocharging system comprising the turbine and at least one compressor driven by the turbine, which supplies the cylinders with compressed air. Furthermore, the costs of the internal combustion engine can be kept low. Furthermore, efficient operation of the internal combustion engine can be achieved, so that fuel consumption and CO2 emissions of the internal combustion engine can be kept low. Furthermore, the demand-based flow connection and separation, as well as the demand-based opening and closing of the bypass channel, can create advantageous responsiveness. Improved torque characteristics can also be achieved.

[0031] Fig. Figure 2 shows a second embodiment of the valve element 10 and the lever element 14. In the second embodiment, the longitudinal region 30 is adjoined by the longitudinal region 32, which, however, is not solid as in the first embodiment, but is designed as a sleeve. The second longitudinal region 32 has an opening 40 designed as a through-hole. The valve element 10 has a region 42 designed as a bolt or pin, which penetrates the opening 40 and protrudes from the opening 40 on one side 44.

[0032] In the second embodiment, the valve element 10 is also supported on the lever element 14 at the point 18 arranged in the plane 22 in the direction running perpendicular to the sealing surface 12 and thus in the axial direction of the longitudinal region 32 and the region 42, wherein in the second embodiment the valve element 10 is supported in the axial direction on the longitudinal region 32 towards the longitudinal region 30. In a region 46 adjoining the region 42, the valve element 10 has an external thread corresponding to the internal thread of the nut (fastening element 38), onto which the nut is screwed. As a result, the valve element 10 is secured to the lever element 14 in the axial direction of the longitudinal region 32 or the region 42.As with the first embodiment, the axial interface can absorb compressive forces due to its design, allowing the adjustment mechanism and the valve element 10, and thus the turbine as a whole, to be designed with particularly low weight while still achieving sufficient functionality. Compared to the current technology, it is thus possible to reduce the weight of the turbine while maintaining the same functionality.

[0033] Fig. 3 shows a third embodiment of the valve element 10 and the lever element 14. The third embodiment differs from the second embodiment in particular in that the lever element 14 has a further hollow cross-section 48, particularly in the longitudinal region 32. The fastening element 38 is received in the hollow cross-section 48 and in the hollow cross-section 28 of the valve element 10 and is screwed onto the longitudinal region 46.

Claims

[1] Turbine for an exhaust gas turbocharger, with a turbine housing through which exhaust gas from an internal combustion engine can flow, with a turbine wheel rotatably received in the turbine housing and driven by the exhaust gas, with at least one bypass channel via which the turbine wheel is to be bypassed by at least a portion of the exhaust gas, with a valve element (10) which is movable relative to the turbine housing between a closed position blocking the bypass channel and at least one open position releasing the bypass channel and has at least one first sealing surface (12) which bears against at least one corresponding second sealing surface of a wall of the turbine to block the bypass channel, and with a lever element (14) via which the valve element (10) is movable, characterized byin that at least one point (18) at which the valve element (10) is supported on the lever element (14) in a direction (20) running obliquely or perpendicularly to the first sealing surface (12) is arranged upstream of the first sealing surface (12) with respect to a flow direction of the exhaust gas flowing into the bypass channel, and the valve element (10) has a hollow cross-section (28), and the lever element (14) has a first longitudinal region (30) and a second longitudinal region (32) running obliquely or perpendicularly thereto, which second longitudinal region (32) is at least partially received in the hollow cross-section (28), and the second longitudinal region (32) has an opening (40) designed as a through-opening, and the valve element (10) has a region (42) designed as a bolt or pin, which penetrates the opening (40). [2] Turbine according to claim 1, characterized bythat the turbine housing has at least two flows which are at least partially fluidically separated from one another and through which exhaust gas from an internal combustion engine can flow, via which the exhaust gas can be fed to the turbine wheel, wherein at least one overflow opening is provided, the flows are fluidically connectable to one another, and wherein a quantity of exhaust gas flowing through the overflow opening can be adjusted by means of the valve element (10). [3] Turbine according to claim 2, characterized by that the valve element (10) releases the overflow opening in the open position at least in part. [4] Turbine according to claim 2 or 3, characterized by that the valve element (10) in the closed position blocks the bypass channel and at least partially releases the overflow opening. [5] Turbine according to claim 4, characterized bythat the valve element (10) in the closed position releases a first partial area of ​​the overflow opening and fluidically blocks a second partial area of ​​the overflow opening adjoining the first partial area. [6] Turbine according to claim 5, characterized by that the valve element (10) in the open position releases the bypass channel and the second partial area. [7] Turbine according to one of claims 2 to 6, characterized by that a first dimension by which the valve element (10) releases the bypass channel when moving from the closed position to the open position is, at least in a partial range of the movement, greater than a second dimension by which the valve element (10) releases the overflow opening.

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