US20120230814A1

US20120230814A1 - Diffuser for a turbocharger having an adjustable turbine geometry and turbocharger for an internal combustion engine

Info

Publication number: US20120230814A1
Application number: US13/459,149
Authority: US
Inventors: Peter Fledersbacher; Torsten Hirth
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2009-10-28
Filing date: 2012-04-28
Publication date: 2012-09-13
Also published as: WO2011050874A3; JP5352012B2; CN102597460A; JP2013509521A; WO2011050874A2; DE102009050975A1

Abstract

In a diffuser for a turbocharger having an adjustable turbine geometry wherein the diffuser comprises an axial slide and an adjusting device for moving the axial slide and wherein the adjusting device comprises an adjusting fork having an opening with a guide axis for the accommodation of a guide element and the adjusting device further comprises an adjusting lever with a lever end, the lever end is accommodated in a recess of the adjusting fork which is disposed at a side of the adjusting fork facing the axial slide in order to minimize tilting forces and provide for smooth sliding movement of the fork.

Description

This is a Continuation-In-Part application of pending international patent application PCT/EP2010/005201 filed Aug. 25, 2010 and claiming the priority of German patent application 10 2009 050 975.5 filed Oct. 28, 2009.

BACKGROUND OF THE INVENTION

The invention relates to a diffuser for a turbocharger having an adjustable turbine geometry operated by an actuating lever and to a turbocharger for an internal combustion engine including a turbine having such an adjustable turbine geometry.
From the application document US 2009 277171 A1, a diffuser for a turbocharger having an adjustable turbine geometry is known. The diffuser comprises an axial slide and an adjusting device for the translational movement of the axial slide. The adjusting device in turn comprises an adjusting fork which encompasses the axial slide, a first fork arm and a second fork arm each having a contact surface by means of which a body contact with the axial slide can be established. A guide section of the adjusting device has an opening for the accommodation of a guide element. With the aid of the guide element, the axial slide can be moved by an adjusting fork along a guide axis of the guide element, and therefore positioned securely. A lever end of an adjusting lever of the adjusting device engages the guide section. By means of the adjusting lever, movement of the adjusting fork can be initiated.
It is the principal object of the present invention to provide a diffuser for a turbocharger having an adjustable turbine geometry with an axial slide and a turbocharger for an internal combustion engine in such a way that the axial slide can be moved without jamming in any operating range or operating directions while having a simple and cost-effective structure.

SUMMARY OF THE INVENTION

In a diffuser for a turbocharger having an adjustable turbine geometry wherein the diffuser comprises an axial slide and an adjusting device for moving the axial slide and wherein the adjusting device comprises an adjusting fork having an opening with a guide axis for the accommodation of a guide element and the adjusting device further comprises an adjusting lever with a lever end, the lever end is accommodated in a recess or groove of the adjusting fork which recess or groove is disposed at a side of the adjusting fork facing the axial slide in order to minimize tilting forces and provide for smooth sliding movement of the fork. The recess or groove has sidewalls forming guide surfaces in contact with the lever end.
The contact surface is designed to establish a contact between the axial slide and the adjusting fork. This means that there is a first point of force application at the contact surface as the axial slide is being moved. A second point of force application for positioning the axial slide lies in the engagement recess, in which the lever end of the adjusting lever is accommodated for transmitting forces. As both of the points of force application which are required for the positioning of the axial slide are positioned with conformal directions, the initiated momentums can be compensated partially or even fully. As a result of this partial or full compensation, a tilting tendency of the adjusting fork and therefore a jamming in operation or during the positioning of the axial slide can be minimized.
In an advantageous variant of the diffuser, the engagement recess is provided in a guide section of the adjusting fork, so that an adequate strength of the adjusting fork is ensured while the axial slide is being moved.
In a further advantageous variant of the diffuser, the guide section is immovably joined to the adjusting fork for further reducing the tilting tendency.
In an advantageous variant of the diffuser, the lever end is movably positioned in the engagement recess, so that, owing to this movable arrangement, a rotary movement of the adjusting lever and thus of the lever end can counteract a jamming of the lever end in the engagement recess.
The engagement recess is positioned between the guide axis and a longitudinal axis of the axial slide, whereby the momentums developing in the positioning process are relatively small.
The invention further relates to a turbocharger for an internal combustion engine, which turbocharger comprises a housing with an exhaust gas guide section and a wheel assembly with a turbine wheel, wherein a diffuser according to the invention is assigned to the exhaust gas guide section for controlling the admission of exhaust gas to the turbine wheel.
In a preferred variant of the turbocharger, a contact area having a certain length is formed between the adjusting fork and the guide element, the guide element having a certain diameter. To reduce wear and to ensure a long service life for the turbocharger, a ratio between the length and the diameter is advantageously greater than 2.
In a further variant of the turbocharger, the guide element is supported in a contoured sleeve on the side remote from the turbine wheel and in the exhaust gas guide section on the side facing the turbine wheel, thereby avoiding a distortion of the guide element if there are great temperature fluctuations during engine operation.
In a further preferred variant, the guide element and its openings are cylindrical for cost-effective manufacture and simple assembly.
In a further advantageous variant, the adjusting fork and the axial slide have a first body contact and a second body contact, the first body contact and the second body contact being arranged to be symmetrical with respect to a guide axis of the guide element, whereby a tilting movement of the axial slide can be avoided.
The invention will become more readily apparent from the following description of advantageous embodiments thereof with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in a longitudinal sectional view an exhaust gas guide section of a turbocharger according to the invention equipped with a diffuser;

FIG. 2 is a perspective view of a diffuser according to the invention;

FIG. 3 is a longitudinal sectional view of the exhaust gas guide section according to FIG. 1, with momentums acting on the diffuser while the axial slide is being moved in a first direction;

FIG. 4 is a longitudinal sectional view of the exhaust gas guide section according to FIG. 1, with momentums acting on the diffuser while the axial slide is being moved in a second direction;

FIG. 5 is a perspective view of a prior art diffuser;

FIG. 6 is a longitudinal sectional view of an exhaust gas guide section of a prior art turbocharger equipped with a diffuser according to FIG. 5, with momentums acting on the diffuser while the axial slide is being moved in a first direction; and

FIG. 7 is a longitudinal sectional view of the exhaust gas guide section according to FIG. 6, with momentums acting on the diffuser while the axial slide is being moved in a second direction;

In the figures, identical components or components of identical action are identified by the same reference numbers.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

An internal combustion engine has a cylinder block with a cylinder head and a crankcase. The cylinder head is connected to a fresh air supply line of the internal combustion engine and to an exhaust duct of the internal combustion engine.
Cylinders are disposed in the cylinder block, each cylinder having an axially movable piston supported therein. In addition, a crankshaft is rotatably mounted in the crankcase. Each piston is connected to the crankshaft by means of a connecting rod, so that relevant piston forces can be transmitted to the crankshaft and converted into a rotary motion of the crankshaft.
In the cylinders of the internal combustion engine, combustion chambers are formed for burning an air/fuel mixture. Each combustion chamber is bounded by an internal wall of a cylinder, by the piston movable in the cylinder and by a wall of the cylinder head, the wall of the cylinder head and the respective piston being arranged opposite one another. The volumes of the combustion chambers can be varied by means of the pistons, so that a known combustion process can be carried out therein.
The cylinder head comprises an intake system with intake ports and intake valves and an exhaust system with exhaust ports and exhaust valves, as well as an injection system for injecting fuel into the respective combustion chamber, the fuel being delivered by means of a fuel pump from a fuel tank. Each intake port preferably has at least one intake valve by means of which the intake port can be opened or closed, the intake valve being located at an end of the intake port which faces the combustion chamber. Via the intake port, combustion air or an air/fuel mixture can be fed to the combustion chamber while the intake valve is open. An end of the intake port which is remote from the combustion chamber is connected to an inlet manifold which is located in the fresh air line and has the purpose of steadying flow.
Each exhaust port preferably has at least one exhaust valve by means of which the exhaust port can be opened or closed, the exhaust valve being located at an end of the exhaust port which next to the combustion chamber. During the combustion of the air/fuel mixture formed in the combustion chamber, the internal combustion engine produces exhaust gas while in operation; this can flow into the exhaust duct through the exhaust port.
The fresh air line comprises a charge air line, the inlet manifold being located at an end of the charge air line next to the internal combustion engine. Upstream of the inlet manifold, an intercooler is provided in the charge air line for cooling compressed combustion air. An air filter for cleaning the combustion air is provided at the inlet end of the charge air line, remote from the internal combustion engine.
The exhaust tract comprises the exhaust manifold and an exhaust gas line, the exhaust manifold comprises exhaust gas passages and a header where the exhaust gas passages merge. The exhaust manifold is positioned downstream of the cylinder head exhaust system, one exhaust gas passage being assigned to each exhaust port. At an opening of the header, the exhaust gas line is connected to the exhaust manifold, the opening being positioned downstream of the exhaust gas passages. At an end of the exhaust gas passage which is remote from the internal combustion engine, an exhaust treatment system is provided for treating the exhaust gas, the exhaust treatment system including a particulate filter and/or a catalytic converter.
In addition, the internal combustion engine comprises an exhaust gas recirculation system, with a connecting line acting as an exhaust gas recirculation line being provided between the exhaust manifold and the intake manifold. In the exhaust gas recirculation line, an exhaust gas recirculation cooler is provided to cool recirculated exhaust gas. The recirculated amount of exhaust gas is adjusted by means of an exhaust gas recirculation valve.
For the closed- and open-loop control of many functions, a closed- and open-loop control system is assigned to the internal combustion engine. Via the closed- and open-loop control system, the fuel supply and the exhaust gas recirculation valve can be controlled in particular.
The internal combustion engine is provided with a turbocharger 1 with a housing 2 comprising an air duct section not shown in detail, through which air can flow, an exhaust gas duct section 3, through which exhaust gas can flow, and a bearing section, wherein the air duct section is located in a fresh air line not shown in detail and the exhaust gas duct section 3 is located in an exhaust not shown in detail.
The turbocharger 1 comprises a wheel assembly not shown in detail, which in turn comprises a compressor impeller for drawing in and compressing combustion air, a turbine wheel for expanding exhaust gas and a shaft which joins the compressor impeller to the turbine wheel for rotation about a common axis of rotation. The shaft is rotatably mounted in a bearing section of the turbocharger 1, which bearing section is not shown in detail and is positioned between the air duct section and the exhaust gas duct section 3.
In the air duct section, which is not shown in detail in the drawing, the compressor impeller is rotatably positioned in a first wheel chamber. Upstream of the first wheel chamber, an inflow passage is provided in the air duct section, the inflow passage and the compressor impeller being preferably coaxial. The inflow passage is used for conditioning the combustion air drawn in by the compressor impeller.
Downstream of the first wheel chamber, an outflow passage in the form of a diffuser is formed in the air duct section; this is designed for conditioning the combustion air drawn in and compressed by the compressor impeller. At the end remote from the first wheel chamber, the outflow passage is connected to a first spiral passage which forms part of the air duct section and which is used for providing a rotationally symmetric flow. The first spiral passage is further designed as a connecting passage between the outflow passage and an outlet passage formed in the air duct section.
In an alternative embodiment of the air duct section, the air duct section comprises a device for controlling the air flow to the compressor impeller. As a result of this air flow control, an expansion of the drawn-in combustion air is possible, so that the compressor impeller can operate in a cold air turbine mode.
For an exhaust gas flow into the exhaust gas duct section 3, an inlet passage 4 is formed in the exhaust gas duct section 3. The inlet passage 4 is used for conditioning the exhaust gas, which makes the turbine wheel rotate during operation of the internal combustion engine. The inlet passage 4 is preferably perpendicular to the axis 14 of rotation of the shaft.
Downstream of the inlet passage 4, a second spiral passage 5 is provided in the exhaust gas duct section 3; this is used for providing a rotationally symmetric flow. Downstream of the second spiral passage 5, a feed passage 6 is provided in the exhaust gas duct section 3, which feed passage 6 is generally designed for conditioning the flow of the exhaust gas. The second spiral passage 5 is further designed as a connecting passage between the inlet passage 4 and the feed passage 6. Downstream of the feed passage 6, a second wheel chamber 7 is provided in the exhaust gas duct section 3, the turbine wheel not shown in detail in the drawing being positioned in the second wheel chamber 7. At the end adjacent to the second wheel chamber 7, the feed passage has an orifice cross-section 8. Downstream of the second wheel chamber 7, an outlet passage 9 is provided in the exhaust gas duct section 3.
During the operation of the internal combustion engine, the turbine wheel is made to rotate as a result of the admission of the exhaust gas of the internal combustion engine, and in this process, the shaft rotates the compressor impeller as well, so that it draws in and compresses combustion air.
In order to achieve an efficiency of the turbocharger as high as possible both at low loads and speeds of the internal combustion engine and at high loads and speeds of the internal combustion engine, the exhaust gas can be conditioned by means of an adjustable diffuser 10 installed into the exhaust gas duct section 3.
As shown in FIG. 1, the diffuser 10 comprises a guide vane ring 11 through which exhaust gas flows, an annular axial slide 12 and a contoured sleeve 13 for conditioning the flow of exhaust gas in the outlet passage 9. The guide vane ring 11, the axial slide 12 and the contoured sleeve 13 are coaxial with the shaft, i.e. the axis of rotation of the shaft of the wheel assembly corresponds to a longitudinal axis 14 of the axial slide 12. The contoured sleeve 13 is immovably positioned in the exhaust gas duct section 3. The guide vane ring 11 is fixed in the exhaust gas duct section 3.
The guide vane ring 11 partially encloses the turbine wheel in the feed passage 6, the guide vane ring 11 projecting into the orifice cross-section 8. The axial slide 12 has a first recess 15 which faces the guide vane ring 11 and in which the guide vane ring 11 can be accommodated. By means of the axial slide 12, the size of the orifice cross-section 8 can be adjusted. The orifice cross-section 8 is preferably small at low loads and/or speeds of the internal combustion engine and large at high loads and/or speeds of the internal combustion engine.
An adjusting device 16 is assigned to the axial slide 12. The adjusting device 16 comprises an adjusting fork 17 with a guide section 18, a guide element 19 and an adjusting lever 20. A force acting on the adjusting lever 20 to initiate adjustment can be provided electrically and/or mechanically and/or pneumatically and/or hydraulically.
The adjusting fork 17 is U-shaped (see FIG. 2). A first curved fork arm 21 and a second curved fork arm 22 are joined to the guide section 18 at the ends adjacent to the guide section 18 for movement therewith. The first fork arm 21, and the second fork arm 22 are symmetrically arranged opposite each other and convex with respect to the guide section 18 between the first fork arm 21 and the second fork arm 22.
The guide section 18 has an opening 23 extending through the whole of the guide section 18, which opening 23 is parallel to the longitudinal axis 14. At right angles to the guide axis 24, the guide section 18 has a groove-shaped engagement recess 25 at the surface which faces the axial slide 12.
For the secure guidance of the adjusting fork 17, the guide element 19 has a cross-section complementing the opening 23. A symmetrical cross-section is preferred.
The guide element 19 is preferably cylindrical in design and has an effective diameter D. In order to ensure a secure guidance, the guide element 19 is firmly joined to the contoured sleeve 13 at its end remote from the spiral passage 5. At its end, facing the spiral passage 5, the guide element 19 is axially freely movable supported in the exhaust gas duct section 3, as a result of which a distortion of the guide element by temperature fluctuations can be avoided.
The adjusting fork 17 is bearing-mounted on the guide element 19, the guide element 19 extending through the preferably cylindrical opening 23. Owing to the bearing-mounted arrangement, a contact area 26 having the length L is formed between the guide element 19 and the adjusting fork 17. To avoid a tilting movement of the adjusting fork 17, the effective diameter D of the guide element 19 is preferably chosen such that the length L is greater than the effective diameter D; in particular, an L/D ratio greater than 2 should be chosen between the length L and the effective diameter D.
The adjusting lever 20 has a first lever arm 27 with a pin-shaped lever end 28 and a second lever arm 29. The first lever arm 27 and the second lever arm 29 are firmly joined together opposite each other by a connecting bar 30, the lever end 28 being arranged adjacent to the engagement recess 25. The adjusting lever 20 is rotatably mounted in the exhaust gas duct section 3 by means of the connecting bar 30, which is accommodated in a bushing 31, in order to absorb adjusting forces. Owing to the pin-shaped design of the lever end 28, any movement involves less friction as a result of a localized or linear contact between the pin-shaped lever end 28 and the engagement recess 25.
The lever end 28 is designed to engage the engagement recess 25, a positive guidance of the lever end 28 being provided in the engagement recess 25. The lever end 28 is preferably positioned movably and includes a sliding roller structure, so that wear and jamming in the engagement recess 25 in operation can be avoided.
As FIG. 2 shows, the adjusting fork 17 encompasses the axial slide 12, wherein a first end section 32 of the first fork arm 21, which is remote from the guide section 18, and a second end section 33 of the second fork arm 22, which is remote from the guide section 18, engage a groove-shaped second recess 34 of the axial slide 12, which recess extends around the axial slide 12. Between the second recess 34 and a first contact surface 35 of the first end section 32, which is accommodated in the second recess 34, a first body contact is formed. In order to counteract any tilting motion of the axial slide 12, a second body contact is formed between the second recess 34 and a second contact surface 36 of the second end section 33, which is accommodated in the second recess 34 and is concealed in the perspective view, wherein the first body contact and the second contact should be symmetrical with respect to the guide axis 24.
For positioning the axial slide 12, an adjusting force acting on the second lever arm 29 is generated by means of an actuator. As the adjusting lever 20 is mounted rotatably, the first lever arm 27 performs a rotational movement as a result of its fixed connection to the second lever arm 29. This rotational movement is converted into a translational movement of the adjusting fork 17 owing to the positive engagement of the lever end 28 in the recess 25. The adjusting fork 17 is displaced axially along the guide axis 24 on the guide element 19 in the direction of the longitudinal axis 14. In this process, the axial slide 12 performs an axial movement as a result of the first body contact and the second body contact with the adjusting fork 17.
According to the invention, the adjusting fork 17 is provided with the engagement recess 25 for the accommodation of the lever end 28, the engagement recess 25 and the first contact surface 35 and also the second contact surface 26 having conformal directions with respect to the guide axis 24. The engagement recess 25 is arranged in the guide section 18 of the adjusting fork 17.
FIGS. 3 and 4 are longitudinal sections of the exhaust gas duct section according to FIG. 1, wherein the momentums MV, MA acting on the diffuser 10, which are generated at the adjusting fork 17 and the axial slide 12, are indicated. FIG. 3 shows the momentums which occur as the axial slide 12 is moved in the direction of a first position, the so-called open position. In this position, the orifice cross-section 8 is completely open. FIG. 4 shows the momentums which occur as the axial slide 12 is moved in the direction of a second position, the so-called closed position. In this position, the axial slide 12 is partially or completely inserted into the orifice cross-section 8. In the embodiment according to the invention, the momentum MV applied by the adjusting lever 20 to the adjusting fork 17 is completely or partially compensated by the momentum MA generated at the axial slide 12.
FIG. 5 shows a diffuser from prior art. FIGS. 6 and 7 show the momentums which occur in a movement process. This indicates that a tilting tendency due to an addition of the momentums cannot only not be eliminated but added up increasing the filtering forces.
The second recess 34 is advantageously designed to complement the first end section 32 and the second end section 33 of the fork 17, wherein, for the location of the axial slide 12 in the adjusting fork 17, solid body contact due to cohesive friction between the second recess 34 and the first and second fork end sections 32 and 33 has to be provided.
In a further embodiment, the first fork arm 21 and the second fork arm 22 have a groove-shaped recess facing the axial slide 12 each, in which a ring which is annular or partially annular, which is permanently joined to the axial slide 12 and which complements the cross-section of the groove-shaped recess can be accommodated.
In a further alternative embodiment, the adjusting fork 17 is designed as a single piece with the axial slide 12, the adjusting fork 17 and the axial slide 12 each having a permanent connection at the first body contact and the second body contact.

Claims

1. A diffuser for a turbocharger having an adjustable turbine geometry, the diffuser (10) comprising an axial slide (12) and an adjusting device (16) for positioning the axial slide (12), the adjusting device (16) comprising an adjusting fork (17) having an opening (23) with a guide axis (24) accommodating a guide element (19) and further comprising an adjusting lever (20) with a lever end (28), the adjusting fork (17) having at least one contact surface (35, 36), in body contact with the axial slide (12),

the adjusting fork (17) having an engagement recess (25) for the accommodation of the lever end (28), the engagement recess (25) with its contact surfaces (35, 36) being positioned between the guide axis (24) and a longitudinal axis (14) of the axial slide (12).

2. The diffuser according to claim 1, wherein

the engagement recess (25) is provided at side of a guide section (18) of the adjusting fork (17) facing the axial slide (12).

3. The diffuser according to claim 2, wherein

the guide section (18) is firmly joined to the adjusting fork (17).

4. The diffuser according to claim 1, wherein

the lever end (28) is movably accommodated in the engagement recess (25).

5. A turbocharger for an internal combustion engine, comprising a housing (2) with an exhaust gas duct section (3) through which exhaust gas can flow to a turbine wheel space in the housing (2) and wherein a diffuser (10) for changing the admission of exhaust gas to the turbine wheel space is provided in the exhaust gas duct section (3), the diffuser (10) supporting an axial slide (12), and an adjusting device (16) for positioning the axial slide (12), the adjusting device (16) comprising an adjusting fork (17) having an opening (23) with a guide axis (24) for the accommodation of a guide element (19), the adjusting device (16) further comprising an adjusting lever (20) with a lever end (28), the adjusting fork (17) having at least one contact surface (35, 36), in body contact with the axial slide (12), the adjusting fork (17) further having an engagement recess (25) for the accommodation of the lever end (28), the engagement recess (25) with the lever end (28) being positioned between the guide axis (24) and a longitudinal axis (14) of the axial slide (12)

7. The turbocharger according to claim 5, wherein the guide element (19) is supported in a contoured sleeve (13) on the side remote from the second spiral passage (5) and in the exhaust gas guide section (3) on the side facing the second spiral passage (5).

8. The turbocharger according to claim 5, wherein the guide element (19) and the opening (23) are cylindrical.

9. The turbocharger according to claim 5, wherein the adjusting fork (17) and the axial slide (12) have a first body contact and a second body contact, the first body contact and the second body contact being arranged symmetrically with respect to the guide axis (24) of the guide element (19).