EP1111196B1 - Variable guide vane system for the turbine of a turbocharger - Google Patents

Description

The invention relates to an exhaust gas turbine of an exhaust gas turbocharger for an internal combustion engine according to the closer defined in the preamble of claim 1.

Such an exhaust gas turbine is known from US Pat. No. 4,502,836.

A generic exhaust gas turbine is also known from DE 195 43 190 C2. In this case, adjustable blocking bodies are provided in an annular nozzle in which a variable guide grid is arranged, which are intended to increase the operational reliability of the exhaust gas turbine when operated as an engine brake.

In DE 198 38 928 C1, a variably adjustable guide vane grille of a turbine of an exhaust gas turbocharger is described, wherein a sealing element is provided in each case in a pressure chamber per guide vane. The sealing elements are designed as a sealing cup and can be pressed sealingly against the free blade end. In this way, the Leitgitterspalt to be completely sealed at the blade ends. The disadvantage here is that according to the number The guide vanes a large number of sealing elements is required, which means a considerable effort and a susceptibility to operation. In addition, in an adjustment of the vanes due to the frictional forces, which are generated by the pressing of the sealing elements to the guide vanes, higher adjusting forces must be applied. Furthermore, there is the danger that due to the complete elimination of the gap, the permissible supercharger speed is exceeded in braking mode and at high engine speeds and thus can lead to damage. Another problem is that unavoidable thermal expansion of the blades can also lead to difficulties in operation.

From JP 001 130002 AA a Leitgitterverstelleinrichtung is known, which is to be adjusted by a spacer a precisely defined gap.

The present invention is therefore based on the object to provide an exhaust gas turbine of the aforementioned type, wherein the efficiency of the exhaust gas turbine or the exhaust gas turbocharger is always optimally adjustable depending on the operating condition of the internal combustion engine, in particular an improvement in the acceleration behavior of the turbine during engine braking. and the drive mode of operation is achieved even at low engine speeds and a rapid build-up of boost pressure and thus a faster build-up of a high braking or drive torque, and at the same time avoid overloading the exhaust turbine or the turbocharger under extreme conditions becomes.

According to the invention this object is achieved by the features mentioned in the characterizing part of claim 1.

By controlling or regulating the axial gap between a maximum gap and a zero gap, optionally with clamping, the efficiency of the exhaust gas turbine and thus also of the exhaust gas turbocharger can always be optimally adapted to the respective operating state of the internal combustion engine or adjust it. Thus, e.g. after a corresponding adjustment of the guide grid, the gap can be reduced to zero, which takes place advantageously by a corresponding clamping, so that even at low engine speeds an improvement in the acceleration behavior of the exhaust gas turbine during engine braking occurs. At the same time a faster build up of the boost pressure for the compressor and thus a faster construction of a high braking torque is achieved, because gap losses are avoided in this way.

When the guide vanes in an advantageous embodiment of the invention, e.g. are clamped by an annular piston between the annular wall surrounding the surrounding or forming housing wall parts, so vibration excitations of the guide vanes of the guide grid are effectively avoided.

Through a targeted generation of a gap between Zero and a maximum position, the exhaust gas turbine can be controlled in their efficiency in a simple way.

A particular advantage of the change or adjustment of the gap according to the invention lies in the fact that the exhaust gas turbine can be driven very close to its speed limit or the exhaust gas turbine can be designed to be correspondingly high. By a defined efficiency deterioration in the upper speed range of the engine, which can be achieved by a targeted opening of the gap, a corresponding deterioration in efficiency is achieved, so that damage to the exhaust gas turbine and the exhaust gas turbocharger can be prevented.

Advantageous embodiments and modifications of the invention will become apparent from the dependent claims and from the exemplary embodiment described in principle below with reference to the drawing.

Fig. 1

eine schematische Darstellung eines Abgasturboladers mit der erfindungsgemäßen Abgasturbine und deren Regelung;

Fig. 2

einen Schnitt durch die erfindungsgemäße Abgasturbine mit einem Ringkolben in einer ersten Ausführungsart;

Fig. 3

ausschnittsweise einen Ringkolben in einer zweiten Ausführungsart;

Fig. 4

ausschnittsweise einen Ringkolben in einer dritten Ausführungsart; und

Fig. 5

ausschnittsweise einen Ringkolben in einer vierten Ausführungsart.

It shows:

Fig. 1

a schematic representation of an exhaust gas turbocharger with the exhaust gas turbine according to the invention and its control;

Fig. 2

a section through the exhaust gas turbine according to the invention with an annular piston in a first embodiment;

Fig. 3

detail a ring piston in a second embodiment;

Fig. 4

detail a ring piston in a third embodiment; and

Fig. 5

detail a ring piston in a fourth embodiment.

Construction and operation of an exhaust gas turbocharger are well known, which is why will not be discussed in more detail below. With reference to Figures 1 and 2, a first embodiment of the invention will be described.

An exhaust gas turbocharger has an exhaust gas turbine 1 arranged in the exhaust gas flow, which is connected to a compressor 3 via a drive shaft 2. The compressor 3 is located in a leading to an internal combustion engine 4 intake 5 and leads to the internal combustion engine in this way pre-compressed air. The exhaust gas turbine 1 is located in an exhaust pipe 6. The exhaust gas turbine 1 has on the input side a spiral flow channel 7, from where the exhaust gas via an annular nozzle 8 leads to an impeller of a turbine 9, which is arranged on the drive shaft 2. The flow channel 7, the annular nozzle 8 and the turbine 9 are located in a common housing 10. The annular nozzle 8 is limited by axial walls. The guide grid 11 and the guide vanes 12 are in a known manner by a Leitgitterverstelleinrichtung 13 so adjustable that the effective flow cross section of the annular nozzle 8 between a maximum open position and a nearly closed Adjustable position or is adjustable.

On the side facing away from the Leitgitterverstelleinrichtung 13 is provided as a wall in the adjustment of the vanes 12, an annular piston 14 in the form of a disc. On the side facing away from the vanes 12 side of the annular piston 14 is a pressure chamber 15, which communicates via a pressure connection 16 with a pressure supply line 17. In general, one will fall back as the pressure medium on the Preßluftbordnetz, if this is available. However, it is of course also possible for this purpose to provide its own printing system with a pressure accumulator 18, wherein, of course, combinations are possible.

In order to achieve high braking performance especially in engine braking operation even at low engine speeds, the gap between the guide grid 11 and vanes 12 and the adjacent walls should be minimized or best eliminated completely. However, a complete elimination has not been readily possible in the prior art for reasons of thermal expansion of the vanes 12 and the operation of the Leitgitterverstelleinrichtung 13. By the annular piston 14, which now forms the axial wall in the movement or adjustment of the guide vanes 12, the gap between the guide vanes 12 and the adjacent wall can now be set variably.

The regulation or adjustment of the gap size works in the following way:

The pressure for the adjustment of the annular piston 14 via the pressure supply line 17 and the pressure accumulator 18 (or the Preßluftbordnetz), 19 corresponding pressure changes or pressure modulations can be performed via a pressure regulating or shut-off device. The pressure control device 19 is controlled by a motor control device 21 via a control line 20.

Alternatively, the pressurization can also take place via a branch line 22, which is connectable to the pressure port 16 via a not-shown 3-way valve 31 in the pressure supply line 17 (dashed line in Fig. 2).

The accumulator 18 is charged by the exhaust pressure in the exhaust pipe 6 via a check valve 23. The loading of the pressure accumulator or the pressure chamber 15 of the annular piston 14 can also take place via a motor compressor 24.

The gap adjustment is carried out in conjunction with the control device 21 and the control line 20 via the setting of the control device 19. Intermediate sizes of the gap and also the level of the contact pressure of the annular piston 14 to the guide vanes 12 is realized by a pressure modulation via the control device 19. If required, the annular piston 14 can also be configured with a spring 25 as a spring device, which is preferably arranged in the pressure chamber 15, which would ensure a neutral position or an output gap.

• 1. Beschleunigung des Abgasturboladers:
  Ausgehend von einer Klemmung der Leitschaufeln 12 durch eine entsprechende Anpreßkraft von Seiten des Ringkolbens 14 wird in einem ersten Schritt die Anpreßkraft des Ringkolbens 14 durch eine Belüftung des Druckregelventiles 19 zurückgenommen. Anschließend erfolgt eine Einstellung der Leitschaufeln 12 durch eine entsprechende Verstellung der Leitgitterverstelleinrichtung 13 in die gewünschte Position. Nach dieser Einstellung wird durch ein Durchschalten des Druckes in dem Speicher 18 über das Druckeinstellventil 19 eine Nullspalteinstellung durch die erfolgte Druckbeaufschlagung des Ringkolbens 14 und damit eine Anpressung bzw. Einklemmung der Leitschaufeln 12 zwischen den Ringkolben und den Wandungsteil auf der anderen Seite.
  Im Bedarfsfalle kann noch eine Druck-Taktung (Entlüfter/Belastung) während der Öffnungsbewegung des Leitgitters 11 bzw. der Leitschaufeln 12 über die Leitgitterverstelleinrichtung 13 erfolgen, um seitlich bzw. axial geringste Spalte zu erhalten.
• 2. Turbobremsen im Motorbremsbetrieb:
  In einem ersten Schritt wird hier ebenfalls die Klemmung der Leitschaufeln 12 reduziert durch Zurücknahme der Anpreßkraft des Ringkolbens 14 und ein Belüften der Druckregeleinrichtung 19. Bei einer niedrigen Motordrehzahl erfolgt ein entsprechendes Einstellen der motordrehzahlabhängigen Position des Leitgitters 1 bzw. der Leitschaufeln 12 über die Leitgitterverstelleinrichtung 13. Anschließend erfolgt über eine entsprechende Druckbeaufschlagung der Druckkammer 15 eine Nullspalteinstellung. Auch hier ist eine Druck-Belüftungs-Taktung bei einem Motordrehzahlanstieg zum Öffnen des Leitgitters 11 über eine entsprechende Betätigung der Leitgitterverstelleinrichtung 13 möglich, um den Spalt stets klein zu halten. Bei Erreichen einer bekannten Grenzdrehzahl und bei einem weiteren Motordrehzahlanstieg kann eine Spaltvergrößerung durch eine Druckreduktion in dem Druckraum 15 erfolgen, um eine gezielte Wirkungsgradverschlechterung und damit Schädigungen der Abgasturbine zu vermeiden bzw. diese damit unter einer zulässigen Grenze zu halten.

Two process examples or typical examples of the exhaust gas turbine according to the invention are described below.

• 1. acceleration of the exhaust gas turbocharger:
  Starting from a clamping of the guide vanes 12 by a corresponding pressing force from the side of the annular piston 14, the contact pressure of the annular piston 14 is withdrawn by aeration of the pressure control valve 19 in a first step. Subsequently, an adjustment of the guide vanes 12 by a corresponding adjustment of the Leitgitterverstelleinrichtung 13 in the desired position. After this setting is by switching the pressure in the memory 18 via the Druckeinstellventil 19 zero column setting by the successful pressurization of the annular piston 14 and thus a contact or clamping of the vanes 12 between the annular piston and the wall part on the other side.
  In case of need, a pressure-clocking (vent / load) during the opening movement of the guide grid 11 and the guide vanes 12 via the Leitgitterverstelleinrichtung 13 can be done to obtain laterally or axially smallest column.
• 2. Turbobarems in engine braking operation:
  In a first step, the clamping of the guide vanes 12 is also reduced here by withdrawal of the contact pressure of the annular piston 14 and a venting of the pressure control device 19. In a low engine speed is a corresponding setting of the engine speed-dependent position of the guide grid 1 and the guide vanes 12 via the Leitgitterverstelleinrichtung 13. Subsequently, via a corresponding pressurization of the pressure chamber 15, a zero-gap setting. Again, a pressure-ventilation timing at an engine speed increase to open the guide grid 11 via a corresponding operation of the Leitgitterverstelleinrichtung 13 is possible to keep the gap always small. Upon reaching a known limit speed and at a further engine speed increase, a gap enlargement by a pressure reduction in the pressure chamber 15 can be made in order to avoid a targeted deterioration in efficiency and thus damage the exhaust gas turbine and thus to keep it below an acceptable limit.

In order to achieve a reliable contact pressure of the annular piston on the end faces of the guide vanes 12, this can be formed elastically at least in its front the guide vanes 12 facing region or be provided with an elastic support 27 accordingly. One or more piston rings 28 take over the seal between the exhaust chamber or the annular nozzle 8 of the exhaust turbine 1 and the pressure chamber 15. The piston rings or the piston 28 can be arranged in the housing 10 or in the annular piston 14 itself. For simplicity, both possibilities are alternatively entered in FIGS. 2 to 4.

Advantageously, one can also provide the guide vanes 12 on the side remote from the Leitergitterverstelleinrichtung 13 side each with pin bearings 29, which are then each guided in holes 30 on the front side in the annular piston 14. By this measure, an additional Leitschaufellagerung on the side facing away from the guide grid device 13 side is created, which means that the guide vanes 12 and the guide grid 11 is mounted and guided on both sides, which leads to an increase in stability and freedom from vibration.

For centering the annular piston 14 axially directed pins 26 may be provided which engage in holes on the back of the annular piston 14, so that tilting of the annular piston 14 is avoided, which would be disadvantageous in terms of the two-sided support of the guide vanes 12 via the pin bearings 29 ,

In principle, the further exemplary embodiments described below with reference to FIGS. 3, 4 and 5 function in the same way as the exemplary embodiment explained above, for which reason the same reference numerals for the same parts have been retained and only the modifications are explained in more detail.

According to FIG. 3, the annular piston 14 has a very thin-walled thickness, in particular in the middle region, and has no guide pins 26. In this way you get a simplified Construction. The annular piston 14 in this case no longer serves as a second bearing point for the guide vanes 11. It is provided in particular for smaller exhaust forces acting on the guide vanes 11. A tilting moment of the guide vanes 11 can be neutralized by the clamping due to the adjacent annular piston 14.

As can be seen from Fig. 3, the annular piston 14 is particularly greatly tapered in the central region, so that it can create elastic by the high pressure forces in the piston chamber 15 to the vanes 11 and thus securely clamps all vanes 11 in the respective position. Also, the piston ring 14 in this embodiment can also be operated by the compressed air port 16 via the three-way valve 31 in the manner as has been explained in the first embodiment.

4, an embodiment of the annular piston 14 is described, which is provided with a damping device. For this purpose, another indicated by piston rings 32 damping ring 33 within the piston ring 14. Again, as an alternative in Fig. 4 indicated that the piston ring 32 in an annular groove of the damping ring 33 or in an annular groove of the annular piston 14 (see the lower illustration) may lie , Ring piston 14 and damping ring 33 are pressed apart by a spring means 34 and the gap 35 between the annular piston 14 and the damping ring 33 fills via one or more throttle bores 36 with compressed air from the piston chamber 15th

The damping of the annular piston 14 is thus achieved in the following manner: In pulsations of the exhaust gas flowing through the exhaust gas turbine, the piston ring 14 can only perform an inhibited or delayed movement axially to the turbine wheel. Thus, vibrations are prevented, because the throttle bores 36, which lead into the intermediate space 35, have only such a small diameter that the pressure medium can escape only very slowly from the intermediate space 35.

The embodiment shown in Fig. 5 also allows a two-sided mounting of the guide vanes 12 of the guide grid 11. In contrast to the two-sided bearing shown in FIG. 2, however, each of the bearing pins 29 is not stored in the annular piston 14, but in the underlying fixed housing 10th the turbine. For this purpose, located on a radially outwardly projecting shoulder 37 of the annular piston 14 each have a through hole 38 in the region of the guide vanes 12, through which the bearing pin 29 pushed through each with play and stored in a bearing bore 39 located behind the housing 10.

The advantage of this type of storage is that in this way a positionally stable mounting of the bearing pins 29 is achieved in the housing 10, whereby guide pins 26, as shown in FIG. 2, can be dispensed with. At the same time, the two-sided Storage an improved braking operation, with not actuated annular piston 14 and at high gas forces a very good support of the guide vanes 12 created. Also in this embodiment, both ways of attaching piston rings 28 for sealing the piston chamber 15 are shown for simplicity in the figure 5.

Claims (6)

1. Exhaust gas turbine of an exhaust gas turbocharger for an internal-combustion engine with a blade wheel arranged in a housing and at least one flow duct (7) surrounding the blade wheel and comprising an annular nozzle (8) opening onto the blade wheel, in which annular nozzle (8) at least one variable guide blade cascade (11) with guide blades (12) and guide blade cascade ducts is arranged, wherein the effective flow cross-section of the annular nozzle (8) can be adjusted by the guide blade cascade (11) via a guide blade cascade adjusting device (13), wherein an adjusting device (14, 15, 16, 17), by means of which the width of the gap between the guide blade cascade (11) and the housing wall parts (10) surrounding the guide blade cascade (11) can be adjusted between a maximum gap and a zero gap, and wherein at least some of the housing wall parts are located in the region of the guide blade cascade (11), is designed as an annular piston (14) which has a pressure space (15), owing to the pressure loading of which, the annular piston (14) can be pressed against the guide blades (12) of the guide blade cascade (11), characterised in that lying within the annular piston (14) is a sealed damping ring (33), the annular piston (14) and damping ring (33) being pressed apart by a spring device (34) and the interspace (35) between the annular piston (14) and damping ring (33) being connected to the piston space (15) via one or more throttle bores (36).
2. Exhaust gas turbine according to claim 1, characterised in that the pressure space (15) of the annular piston (14) is connected to a pressure regulating device and in that the pressure regulating device (19) is connected to an engine regulating device (21) for generating pressure modulations.
3. Exhaust gas turbine according to claim 1 or 2, characterised in that the annular piston (14), at least on the side facing the guide blades (12), is elastic in design or is provided with an elastic coating (27).
4. Exhaust gas turbine according to claim 3, characterised in that the annular piston (14) is thin-walled in design, at least in its central region.
5. Exhaust gas turbine according to any one of claims 1 to 4, characterised in that the guide blades (12) on the side remote from the guide blade cascade adjusting device (13) are provided with pin bearings (29) which are inserted through bores (38) in the extension portion (37) of the annular piston (14) and are mounted in the housing (10) in bearing bores (39).
6. Exhaust gas turbine according to claim 5, characterised in that the extension portion (37) of the annular piston (14) has a smaller wall thickness than the annular piston (14).