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(11) | EP 1 304 447 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Turbocharger flow control |
| (57) A turbocharger for an internal combustion engine is described, which is provided
in the exhaust gas flow stream and which is provided with a turbine. The effective
surface of a ring aperture (6) between the exhaust gas flow channel (2) and a turbine
wheel (8) is reduced via an axial valve (1) with a grating ring (13) for the braking
operation of the internal combustion engine. The axial displacement of the axial valve
(1) necessary therefore is achieved pneumatically using a pressure space (3) in combination
with a piston (4). The total size of the turbocharger can thereby be reduced and the
frictional wear of parts can be reduced. |
[0001] The invention concerns a turbocharger which is provided in the exhaust gas stream of an internal combustion engine, wherein a turbine is driven using an exhaust gas flow channel and wherein the effective flow cross section thereof is adjustable in the transition between the flow channel and the turbine wheel via an axial valve.
[0002] An internal combustion engine turbocharger system is known for example from DE 197 27 141 C1 (US Patent 6,269,643). In an annular-shaped area beginning at the flow channel and communicating with the turbine wheel, a ring shaped insert is provided to be axially displaceable. The insert, formed in part as a guide device with guide blades or vanes, is generally referred to as an axial valve. The axial valve includes a tubular sleeve part for guiding the displacement, carrying at its end associated with the annular nozzle a guide vane system formed by guide vanes, which can be displaced into a position in which the guide vanes of the guide vane system are in the cross section of the annular nozzle, reducing the free cross section of flow. The guide vane system is dimensioned to form a restriction which lies in the region of the annular nozzle, throttling the flow of exhaust gasses to the turbine rotor. This throttling, with reference to the coverage, can be constant and maximal or could also be variable. Thereby high braking characteristics can be achieved, combined with low thermal load of the internal combustion engine.
[0003] The adjustment or shifting of the axial valve in accordance with the state of the art, in particular the adjusting out of the rest position into the work position, exhibits certain shortcomings. The operation of the axial valve has occurred until now as a rule using mechanical adjusting cams or adjusting rods, which are driven by an external pneumatic cylinder. During mechanical operation of the axial valve it is however not ensured that the cams, generally provided pair-wise, are equally loaded. This results in excessive wear. The cause for the uneven force acting on the cams can be attributed to either the deformation of a control rod as a result of temperature influence or the unsymmetrical geometry of an adjusting rod as a result of certain constructional variations.
[0004] The invention is concerned with the task of simplifying the design and construction of the adjusting elements for the movement of an axial valve for introduction of a braking effect into a turbocharger of an internal combustion engine, and to make it more resistant to wear.
[0005] This task is solved by the combination of characteristics set forth in claim 1. Advantageous embodiments can be seen in the dependent claims.
[0006] In accordance with the invention a turbocharger for an internal combustion engine with an axial valve is modified in such a manner, that the control of the axial valve can occur in reproducible manner. This is achieved thereby, that in the housing of the turbocharger there is provided at least one system comprising a pressure space and a therewith operatively associated piston, by means of which the axial valve can be moved into the working or operating position. For return, there is provided a system comprised of at least one pressure spring, wherein the piston is returned to the rest position via the spring force when the pressure is reduced in the pressure space. There is a form-fitting or interlocking connection between the piston and the axial valve. The essentially cylinder or ring-shaped piston is constructively adapted or associated with the cylindrical shaped axial valve, so that when pressure acts on the pressure space an even movement of the piston in the direction of the axis of the turbocharger is achievable.
[0007] The subsequent return of the piston, actuated by one or more pressure springs, can in advantageous manner likewise occur pneumatically or, as the case may be, by compressed air. For this a further system of piston and pressure space is necessary, which upon pressure actuation returns the piston into the return position, which corresponds to the operating direction of the return pressure spring system. Preferred is the use of one single piston with two opposing pressure spaces. Therewith a pneumatic control system is provided which permits the movement of the axial valve out of its rest position into a work position and the reverse.
[0008] Further advantages are comprised therein, that a large number of mechanical construction components can be dispensed with, as well as that by external pneumatic cylinders the total or overall size of the turbocharger can be reduced. Further associated herewith is a turbocharger design, which is less liable to frictional wear.
[0009] In the following an illustrative embodiment will be described on the basis of the figures which should be understood as not limiting the scope of the invention:
- Figure 1
- shows a section through a turbocharger and
- Figure 2
- shows an embodiment of the turbocharger according to Figure 1 with pneumatic return.
[0010] Figure 1 shows a turbocharger with an axial valve 1 in a housing 10. The flow channel 2 forms a ring surrounding an area of the turbocharger which contains a turbine wheel 8. The effective cross section of the ring aperture or nozzle 6, via which the exhaust gas is directed upon the turbine wheel 8, is then reduced via a throttle or restrictor device, which in this case can be formed as a grating or restrictor ring 13 and which is provided on the end of the axial valve 1. For this, the axial valve 1 is partially or completely inserted into the annular nozzle or ring aperture 6. The blocking device can be in the form of a guide device with guide blades or a grating ring 13, which exhibits surface openings defined for example by a number of boreholes. The complete turbocharger unit is fastened to an internal combustion engine via at least one flange 7. Seals 9 seal the pneumatic part.
[0011] It can be seen from Figure 1 that the axial channel 11, the turbine wheel 8 and the ring aperture 6, as well as the axial valve 1 are provided co-axially. The axial valve 1 is guided in the axial direction essentially by the housing 10. The sleeve or tube-shaped part of the axial valve 1 carries a grating ring 13 on its end nearest the ring aperture.
[0012] If the exhaust gas supply from the flow channel 2 to the turbine wheel 8 through the ring aperture 6 is to be throttled or restricted, then the axial valve is slid into the area of the ring aperture 6. This occurs via the co-axially provided and ring shaped piston 4. This piston 4 is axially moved by a pressure actuatable pressure space 3 in such a manner, that the axial valve 1, which is form fittingly connected with the piston 4, is displaced axially in the desired direction. If the grating ring 13 is positioned in the area of the ring aperture 6, wherein this advanced into this area up to an abutment, so there results a maximal cross-sectional reduction in the ring aperture 6, which corresponds to a maximal braking effect for the turbocharger. By the operation of the axial valve via compressed air in association with appropriate clearance or tolerance fittings, it is ensured that the grating ring 13 always comes to be seated evenly axially. This is achieved by the ring shaped co-axial design of pressure space 3, piston 4 and longitudinally extending axial valve 1. In comparison to operation with mechanical adjustment devices, the pneumatic piston 4 moves without axial tilting or tipping, since a filling of the pressure space 3, for example with compressed air via the compressed air supply line 12, provides an even force distribution in the axial direction upon the piston 4.
[0013] The return of the axial valve into its rest position occurs in one embodiment of the invention by return springs 5, which, supported against housing 10, exercise a return force upon the piston 4. This should act upon the piston 4 in the axial direction distributed as evenly as possible, so that also in the return movement no tilting or tipping occurs. The coupling between axial valve 1 and piston 4 is form-locking in both directions.
[0014] In an advantageous further development of the invention it is envisioned that the return movement of the axial valve 1, shown as being via pressure springs 5, is also carried out pneumatically. For this, the pressure springs 5 are replaced by a further pressure space 14. This serves to apply the necessary return force pneumatically upon the piston 4. The compressed air supply 12, as well as appropriate controls for a one-way or two-way pressure space design, occurs via generally well known compressed air control means.
[0015] Independently of whether the grating ring 13 or the axial valve 1 are formed overall as a closed ring, the pressure actuation, which is evenly distributed about the circumference in the pressure space 3, 14, results in an even slide movement of the piston 4. The pressure actuated surfaces of the piston 4 are thereby preferably formed as continuous ring. It is however conceivable that separate individual pressure spaces 3 are distributed evenly about the circumference of the piston 4.
Reference Number List
1. Turbocharger for an internal combustion engine with at least one turbine provided
in the exhaust gas flow stream of the internal combustion engine, with a flow channel
(2) which communicates with the turbine wheel (8) via a ring shaped area, in which
communicating cross section an axial valve (1) is introducible for a braking operation,
via which the flow cross section in the transition to the turbine wheel (8) can be
controlled, thereby characterized, that
in the housing (10) of the turbocharger a pneumatic pressure space (3) and a therewith operatively associated ring shaped piston (4) is provided, wherein the piston (4) is form fittingly connected with the axial valve (1) for moving the axial valve into the working position, and at least one pressure means (5) is provided for returning the piston (4) or, as the case may be, the axial valve (1), into a rest position.
in the housing (10) of the turbocharger a pneumatic pressure space (3) and a therewith operatively associated ring shaped piston (4) is provided, wherein the piston (4) is form fittingly connected with the axial valve (1) for moving the axial valve into the working position, and at least one pressure means (5) is provided for returning the piston (4) or, as the case may be, the axial valve (1), into a rest position.
2. Turbocharger according to Claim 1, thereby characterized, that the least one pressure means (5) for return of the axial valve (1) into the
rest position comprises a pressure space operatively associated with the piston (4),
which has the same working direction as the pressure means (5).
3. Turbocharger according to Claim 2, thereby characterized, that for movement of the axial valve (1) the piston (4) is alternatively moveable
into a work position or as the case may be into a rest position.
4. Turbocharger according to one of the preceding claims, thereby characterized, that a pneumatic pressure space is connected to a controllable compressed air system.