WO2014121986A1

WO2014121986A1 - Valve unit for a waste gate system and turbocharger

Info

Publication number: WO2014121986A1
Application number: PCT/EP2014/050690
Authority: WO
Inventors: Florian Arndt; Marko Künstner
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 2013-02-05
Filing date: 2014-01-15
Publication date: 2014-08-14
Also published as: DE102013001978A1; EP2954182A1

Abstract

The invention relates to a valve unit for a waste gate system of a turbocharger, comprising a valve element (28), an actuating element for the valve element (28) and a bearing sleeve (36) in which the actuating element is rotationally mounted. Said actuation element is pressurized by a spring element in the axial direction counter to the bearing sleeve (36). A passage for waste gas is provided in the region of the contact surfaces, pressed against each other, of the bearing sleeve (36) and the actuating element.

Description

description

Valve unit for a wastegate system and turbocharger

The invention relates to a valve unit for a wastegate system and such

Wastegate system comprehensive exhaust gas turbocharger.

Exhaust gas turbochargers serve to increase the efficiency and efficiency of

Internal combustion engines by the combustion chambers of the internal combustion engines, a compressed fuel-air mixture is supplied. As a result, the filling of the combustion chambers can be improved and a larger amount of fuel per combustion cycle can be burned.

Exhaust gas turbochargers include a turbine with a turbine runner, which by a

Exhaust gas flow, which is ejected from an internal combustion engine, flows and thereby driven in rotation. The rotational movement transmits the turbine wheel by means of a shaft to a compressor wheel. The rotation of the compressor wheel ensures the pressure increase of the fresh gas supplied to the internal combustion engine. In principle, the compressor output thus depends directly on the enthalpy of the exhaust gas flow, although the actual desired compressor output does not always correlate with the current exhaust gas flow.

It is therefore known to adapt the compressor performance by the integration of control means to the respective needs. Widely used is the integration of a so-called

Wastegate. This is a controllable or controllable bypass, over which a part of the exhaust gas can be guided past the turbine. To control or regulate the exhaust gas flow conducted via the wastegate, a valve element is used regularly, which more or less releases the bypass cross-section as a function of its position. The actuation of the valve body takes place by means of an actuator. However, this is usually arranged away from the turbine and integrated, for example, in the compressor part of the exhaust gas turbocharger to keep its thermal load low. The actuation of the valve element by the actuator then takes place by means of an actuating element. For this purpose, the actuating element may comprise a bearing section, which is rotatably mounted in a bearing shell integrated in the housing of the exhaust gas turbocharger and which extends with one end into the bypass of the wastegate system. At this end, an actuating portion may be fixed, which extends in the radial direction of the bearing portion and at the end of the

Valve element is attached. By a rotation of the bearing portion of the actuating element thus the valve element is moved. The rotational movement can be effected by means of an actuator portion of the actuating element, which is located on the other, outside the Housing of the exhaust gas turbocharger located end of the bearing portion is fixed and can also extend in the radial direction thereto. A translatory movement of the actuator section by the actuator is thus translated into a rotational movement of the bearing section and this then again in a translational movement of the valve element.

For precise control or regulation of the exhaust gas flow conducted via the wastegate, it is necessary for the actuator movement to be largely free from play on the exhaust gas flow

Valve element is transmitted. To this freedom of play in the field of storage of

To achieve actuating element in the bearing shell of the housing, is known

Bear bearing portion on one side of the bearing shell by a spring element in the axial direction, including a pair of a contact surface of the bearing shell and a contact surface of the actuating element are pressed against each other. These

Spring loading causes the desired backlash of storage in the axial direction, but at the same time allows to allow different, thermally induced elongations of the bearing shell and actuator.

Such an exhaust gas turbocharger with wastegate system is known from EP 1 644 625 B1. There, the spring element is arranged on the outside of the housing side of the bearing shell, while in the contact point on the inner side of the bearing shell, two sealing discs are provided, which are pressed against each other as a result of the spring load. As an additional advantage of this embodiment, the particularly good sealing is specified in EP 1 644 625 B1, whereby leakage of exhaust gas from the housing of the exhaust gas turbocharger via the bearing of the actuating element can be avoided.

Such an improvement of the seal in a comparably trained

Wastegate system are also devoted to JP 05248253 A and JP 08334030 A. There is provided, the different, thermally induced elongation of the bearing shell and

Take advantage of actuator to a warm-running exhaust gas turbocharger

to effect sufficient contact pressure of the two sealing washers. An axial

Spring load of the bearing of the actuating element in the housing of the exhaust gas turbocharger is not provided there. A disadvantage of this known system is that the

Contact pressure in the seals and thus the sealing effect and the frictional resistance and wear of the bearing of the actuator directly from the respective

Temperature level in the region of the turbine of the exhaust gas turbocharger depends, but is subject to load-dependent significant fluctuations even when the engine is operating warm.

Based on this prior art, the invention was based on the object, an improved or alternative valve unit for a wastegate system of an exhaust gas turbocharger specify. In particular, such a valve unit should be specified, which despite a backlash over a wide operating temperature range allows a leak in the storage of the actuator.

This object is achieved by a valve unit for a wastegate according to independent claim 1. An exhaust gas turbocharger comprising such a valve unit is the subject matter of independent patent claim 6.

The invention is based on the finding that a backlash of storage of the

Actuating element in the bearing shell of the housing in combination with a compensation of different, thermally induced elongations of actuator and bearing shell can best be achieved by an axial spring action, as is generally known from EP 1 644 625 B1. Another, the invention is based knowledge that such axial spring loading inevitably leads to a substantial tightness of storage by a support or a stop must be formed between the actuator and the bearing shell, which / counteracts the spring loading. This is especially true when the spring loading, as in the

EP 1 644 625 B1, is produced by a disc spring. In many cases, additional sealing disks, such as are provided in the area of the support in EP 1 644 625 B1, are not required for achieving a good seal (they can rather have a positive influence on the wear behavior.) A basic idea of the invention is also that a leak In the field of storage of the actuating element is not only unproblematic, but may also have advantages.

The basic idea of the invention is therefore to modify a bearing of the actuating element of a generic valve unit in such a way that, in spite of the axial

Spring loading, the maintenance of which is meaningful for a good backlash and the compensation of different, thermally induced elongations, a certain particular predetermined leak in the wastegate system is to be achieved.

A generic valve unit for a wastegate system, the (at least) one

Valve element, (at least) an actuating element for the valve element and (at least) a bearing shell in which the actuating element is rotatably mounted, wherein the actuating element by means of (at least) a spring element in the axial direction (ie in the direction of the axis of rotation) acts against the bearing shell is, is therefore

according to the invention characterized in that in the region (at least) one (by the spring action) against each other acted contact surface pairing (at least) a passage for exhaust gas is provided. It can preferably be provided that the passage is formed by the fact that at least one of the contact surfaces (at least) one from an outer edge of the

Contact surface inwards, i. more or less, substantially radially extending recess, e.g. in the form of a groove or recess. The course of the depression can be rectilinear or curved. Alternatively, it is also possible to use a leak-inducing intermediate element, such as, for example, a washer with recesses (grooves) or a toothed disk.

In a preferred embodiment of the valve unit according to the invention can be provided that the spring element is designed in the form of a plate spring. Advantages of this

Embodiment may be: Relatively large spring forces at relatively small

Installation space for the spring element; a selectable and possibly also adjustable spring characteristic (linear, degressive or even progressive); a comparatively long service life even under dynamic loads, which accommodates the use in an internal combustion engine, in particular of a motor vehicle. A wave washer may be a preferred alternative to a cup spring.

With regard to the inventively aimed at leaking storage of the

Actuating element of the valve device, the characteristic shape of a plate spring with a conical or conical annular shell be disadvantageous because it has a comparatively good sealing effect by a closed on both sides annular contact with the components on which it is supported. To achieve a leak of the wastegate, the one

Accordingly, it can be advantageously provided that the disc spring (at least) has a passage for exhaust gas, in particular in the form of a recess extending from an inner edge to an outer edge of the disc spring, e.g. in the form of a bead can be provided. Alternatively or additionally, however, the plate spring can also have, for example, (at least) one passage opening in its annular shell. Furthermore, it can also be provided that a depression in one or both

Contact surfaces on which the diaphragm spring is supported, forms a passage for the exhaust gas.

In a particularly preferred embodiment of the valve unit according to the invention may further be provided that bilaterally. at the inner and the outer end of the

Bearing each a spring element, preferably between the bearing shell and the actuating element, is supported. As a result, a relatively large compensation path for different, thermally induced elongations can be created in a simple manner. Also can be achieved in this way comparatively easy the desired leak on both sides of the bearing shell without this, for example, depressions or grooves in the

Contact surfaces would have to be introduced. Rather, appropriate leaks guaranteeing spring elements, such as the already mentioned disc springs with recess or through hole or even, for example. conventional coil springs are used.

An exhaust gas turbocharger according to the invention comprises (at least) one (single- or multi-part) housing, (at least) a turbine rotatably mounted within a turbine chamber of the housing, (at least) an inlet for supplying exhaust gas into the turbine chamber and an outlet for removing the exhaust gas from the exhaust gas Turbine space and a wastegate for the exhaust gas to bypass the turbine chamber, wherein the amount of exhaust gas passed through the wastegate system is controllable by means of a valve unit according to the invention. In this case, the bearing shell of the valve unit is preferably integrated into the housing (i.e., fixed in or integral with the housing).

The invention will be described below with reference to an illustrated in the drawing

Embodiment explained in more detail. In the drawings shows:

1 shows an embodiment of an exhaust gas turbocharger according to the invention in a partially sectioned, perspective view;

FIG. 2 shows the valve unit of the exhaust-gas turbocharger according to FIG. 1 in a front view; FIG.

3 shows a part of the valve unit according to FIG. 2 in a perspective illustration;

Fig. 4: a plate spring of the valve unit of FIG. 2;

5 shows a first embodiment of a bearing shell for possible use in one

Valve unit according to FIGS. 2 and 3; and

6 shows a second embodiment of a bearing shell for possible use in one

Valve unit according to FIGS. 2 and 3.

The embodiment of the exhaust gas turbocharger according to the invention shown in FIG. 1 comprises a turbine 10 and a compressor 12. The turbine 10 comprises a

Turbine housing 16, which forms a turbine inlet channel 18, a turbine outlet channel 20 and a turbine chamber 22, which merge into each other in a fluid-conducting manner. Within the

Turbine space 22 is a turbine wheel 24 rotatably mounted. Exhaust discharged from an internal combustion engine (not shown) may flow into the turbine chamber 22 via the turbine inlet passage 18 where it rotatively drives the turbine runner 24. After the flow around the turbine runner 24, the exhaust gas flows via the turbine outlet passage 20.

The rotation of the turbine runner 24 is transmitted via a (non-visible) shaft to a (non-visible) compressor impeller, which is rotatably mounted in a compressor chamber of the compressor 12. By rotating the compressor impeller, fresh gas supplied to the compressor via a (not visible) compressor inlet passage can be compressed. The compressed fresh gas can then be discharged via a compressor outlet channel 26 and fed to the combustion chamber of the internal combustion engine.

For power control, the exhaust gas turbocharger has a so-called wastegate system. Through the wastegate system, a defined portion of the exhaust gas supplied to the exhaust gas turbocharger can be guided past the turbine runner 24.

The wastegate system comprises a valve unit with a valve element 28 which, depending on the position of the valve unit, more or less closes a bypass channel of the wastegate system. Furthermore, the wastegate system comprises a multi-part actuating element. This comprises a bearing shaft 30, at one end of which one end of a valve arm 32 is secured against rotation. The other end of the valve arm 32 is connected to the valve element 28. At the other end of the bearing shaft 30, one end of an actuating arm 34 is rotatably attached. The bearing shaft 30 is rotatably supported within a tubular bearing shell 36. The bearing shell 36 itself is arranged in a bearing bore of the turbine housing 16.

The wastegate system further comprises an adjusting device 38. This comprises an actuator, for example, pneumatically or electrically actuated, which translates an actuator piston 40 as a function of a control signal, which is supplied for example by a motor control. This actuator piston 40 is rotatably connected at its free end to the other end of the actuating arm 34. A translational movement of the actuator piston 40 leads to a pivoting movement of the actuating arm 34, wherein the

Bearing shaft 30 serves as a rotation axis of this pivoting movement. The rotation of the bearing shaft 30 leads to a corresponding pivoting of the valve arm 32 and thus to a more or less wide lifting of the valve element 28 from its valve seat. The width of the thus released annular gap between the valve element 28 and the valve seat defines the amount of exhaust gas carried over the bypass passage. In order to keep the wear and the operating noise of the valve system low, the bearing of the actuating element in the bearing shell 36 should be as free of play as possible. The backlash should also be achieved over the wide range of temperatures which the exhaust-gas turbocharger can have, in particular on the turbine side during operation. For this purpose, it is provided that the actuating element by means of two disc springs 42 axially (relative to the longitudinal axis of the bearing shaft 30) is braced against the bearing shell 36. The plate springs 42 are arranged under prestress between the end faces of the bearing shell 36 and the valve arm 32 or the actuating arm 34. The plate springs 42 can compensate for different thermal elongations of the bearing shell 36 on the one hand and (in particular) the bearing shaft 30 on the other hand.

According to the invention, it is provided that the valve unit has a defined leak. For this purpose, the two disc springs 42 are each provided with two radially extending beads 44. Exhaust gas, which flows out of the bypass passage into the turbine outlet passage 18 when the valve element 28 is open via the beads 44 of the plate bushes 36 clamped between the bearing shell 36 and the actuation element, can firstly pass into the annular gap which extends between the valve seat

Bearing shell 36 and the bearing shaft 30 is formed, flow and flow from there via the beads 44 from the exhaust gas turbocharger.

In a further development, the inside of the bearing shell 36 and / or the outside of the bearing shaft 30 at least one recess which extends along the annular gap formed between the bearing shell 36 and bearing shaft 30 and extends axially from the inner to the outer end. This at least one depression can be straight or curved, e.g. run helically along the inside or the outside. In this way, a controlled predetermined leakage of the valve unit of the wastegate is additionally supported.

Additionally or alternatively to the introduced by means of the beads 44 leakage can also be provided, those contact surfaces of the bearing shell 36, the actuating arm 34 and / or the valve arm 32, against which the disc springs 42, with inwardly extending recesses 14 (eg grooves ), as shown in FIGS. 5 and 6 in two embodiments for the contact surfaces of the bearing shell 36. In the

Embodiment according to FIG. 5, four radially extending recesses 14 are provided per contact surface and, in the embodiment according to FIG. 6, a spiral-shaped or curved depression 14 is provided. Of course, other wells and any number of wells are possible. List of references Turbine

compressor

deepening

turbine housing

Turbine inlet channel

Turbinenauslasskanal

turbine room

turbine impeller

Verdichterauslasskanal

valve element

bearing shaft

valve arm

actuating arm

bearing shell

locking device

actuator piston

Belleville spring

Beading

Claims

claims

Valve unit for a wastegate system, with a valve element (28), a

Actuating element for the valve element (28) and a bearing shell (36) in which the actuating element is rotatably mounted, wherein the actuating element by means of a spring element in the axial direction against the bearing shell (36) is acted upon, characterized in that acted upon in the region of a mutually

Contact surface pairing is provided a passage for exhaust gas.

Valve unit according to claim 1, characterized in that at least one of the contact surfaces has a from an outer edge inwardly extending recess (14).

Valve unit according to claim 1 or 2, characterized in that the

Spring element in the form of a plate spring (42) is formed.

Valve unit according to claim 3, characterized in that the plate spring (42) has a recess extending from an inner edge to an outer edge.

Valve unit according to one of the preceding claims, characterized in that on both sides of the bearing shell (36) in each case a spring element between the bearing shell (36) and the actuating element is supported.

Exhaust gas turbocharger with a housing and a turbine runner (24) rotatably mounted within a turbine chamber (22) of the housing, an inlet for supplying exhaust gas into the turbine chamber (22) and an outlet for removing the exhaust gas from the turbine chamber (22) and a wastegate system for the exhaust gas for bypassing the turbine chamber (22), wherein the amount of exhaust gas passed through the wastegate system is controllable by means of a valve unit according to one of the preceding claims.