The invention relates to a turbocharger with a variable nozzle device for regulating the flow of exhaust gas driving a turbine.
In turbochargers comprising a turbine for driving a compressor impeller or the like, it is necessary to control the flow of the exhaust gas driving the turbine in order to achieve different operational conditions. Such a control is possible by arranging a plurality of vanes in a circular manner between a nozzle ring and the exhaust housing of the turbocharger. The vanes form a plurality of nozzle passages, wherein by arranging the vanes in a pivotablie manner, it becomes possible to vary the throat area of the nozzle passages.
According to document WO 01/96713 A1, there is disclosed a turbocharger arrangement comprising a vane area formed between a nozzle ring and a ring member which is axially slidable with respect to the vanes.
It is the object of the invention to provide an improved turbocharger arrangement.
According to one aspect of the invention, the above object is achieved by a turbocharger defined in claim 1. Preferable embodiments of this turbocharger are set forth in the subclaims.
According to the technical solution defined in claim 1, the turbocharger comprises vanes interposed in a nozzle between a nozzle element and a floating insert supported axially slidably on the exhaust housing or turbine housing. By means of this arrangement, a gap between the turbine housing and the nozzle element can be kept closed at any operational condition in order to increase the overall turbine efficiency of the turbocharger and the regulation thereof, while at the same time, the risk of vane sticking is avoided.
In the turbocharger the floating insert can be urged against the vanes in said nozzle by a difference in the pressure in the exhaust gas inlet and the nozzle and/or by a biasing member supported on the exhaust housing. As biasing member a spring washer can be used which is placed preferably in a recess formed in the gas outlet or shroud portion of the turbine housing.
Alternatively, the biasing member can also be interposed in a recess formed in the floating insert. In this case, the floating insert is formed preferably of a sheet metal and has a C-shaped cross-section with the open portion facing the turbine housing.
In the turbocharger construction where the floating insert is arranged to be urged against the vanes in the nozzle by a difference in the pressures in the exhaust gas inlet and the nozzle, the space or recess formed between the insert and the turbine housing is communicated to the exhaust gas inlet of said exhaust housing preferably by cut-out portions in the insert.
For mounting the variable nozzle device, its nozzle element carrying a vane pivoting mechanism is preferably clamped between a step portion of an inner periphery of the turbine and a disc-shaped member supported on the center housing. According to an alternative construction of the turbocharger, the nozzle ring is abutted against the turbine housing by means of spacer elements passing through the floating insert and thus serving also as guiding means for guiding the movement of the floating insert.
For providing a pressure-free pivoting of the vanes at the initial stage of operation of the turbocharger, a spacer element is arranged on the nozzle ring for limiting the displacement of the insert towards the vanes. Furthermore, a piston ring can be provided between the floating insert and a gas outlet portion of the turbine housing.
In the following, further technical solutions of the object of the invention are described in detail with reference being made to the enclosed drawings.
In the drawings:
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As shown in
On the nozzle ring 21, a plurality of vanes particularly shown in
In the embodiment shown in
For actuating the unison ring an actuating system is used which is not particularly shown in the Figures. As such a system, e.g. a bell crank system described in the document U.S. Pat. No. 4,804,316 can be used.
The ring-shaped insert 17 is provided at its outer peripheral portion with at least one dowel pin 37 slidingly accommodated in a corresponding hole of the exhaust housing 7. On the inner periphery of the ring-shaped insert 17, a circumferential recess is formed in order to accommodate a piston ring 39. Radially inwardly of the hole accommodating the dowel pin 37 there is provided a circumferential recess 41 in the exhaust housing, said recess accommodating an elastic spring washer 43 by means of which the ring-shaped insert 17 is urged against the side faces of the vanes 27 so that the vanes are sandwiched between the nozzle ring 21 and the ring-shaped insert with a well balanced pressure. Thus, the clearances of the contact portions between the vanes and the nozzle ring and the vanes and the ring-shaped insert can be reduced, and at the same time, the risk of vane sticking at these contact surfaces can be minimised due to the resilient contacting of these surfaces.
The thickness of the insert ring 17 can be dimensioned such that there remains a small clearance between the insert ring and the outlet portion 19 of the turbine housing for communicating the circumferential recess 41 with the volute 11. Due to this communication and preferably by using the piston ring 39 as a seal between the recess 41 and the nozzle 13, during operation of the turbocharger, the pressure within the circumferential recess 41 becomes higher than the dynamic flow pressure within the nozzle 13 so that the pressure difference creates an additional force urging the insert 17 toward the vanes forming the nozzle passages.
In the second embodiment of the turbocharger shown in
A ring-shaped insert according to one of the embodiments shown in
As shown in
In the second embodiment, the spacer elements 145 extend with their ends in both the turbine housing 107 and the nozzle ring 121 so that the provision of a locking element similar to the locking pin 26 used in the first embodiment shown in
The third embodiment of the turbocharger according to the invention shown in
In this embodiment, the same modifications of the ring-shaped insert shown in
The turbocharger according to the fourth embodiment shown in
According to the above description, a substantial advantage of the invention is that the outer wall of the nozzle can be constituted by a relative small separate element which is not only exchangeable separately from the turbine housing, which as such integrally forms the volute and the outlet shroud encompassing the turbine, but is also flexibly adjustable towards the vanes, thus providing a limited clearance to the vanes and avoiding sticking hindering movement of the vanes.
The turbocharger according to a fifth embodiment is shown in
The flange 518 is fitted in an inner recess 541 formed in the exhaust housing 507. The axial width of the flange 518 is smaller than the axial width of the inner recess 541 such that also a spring member 543 can be accommodated within the recess 541. The spring member 543 axially urges the floating insert 517 towards the vanes 527.
The floating insert 517 is formed with a wall 516 which abuts against the vanes 527. Thereby, the vanes 527 are sandwiched between the floating insert 517 and the nozzle ring 521 by means of the spring member 543 in a floating manner in order to keep a constant nozzle width.
Such a construction provides a variable nozzle device which is not only arranged in a floating manner between the center housing 51 and the exhaust housing 507 but which also incorporates a nozzle ring 521 and the floating insert 517 being axially movable for floating with respect to each other, thus enabling a widening of the nozzle and therefore more efficiently avoiding sticking and binding of the vanes 527.
This embodiment advantageously facilitates the axial guiding of the floating insert 517 and reduces the component parts thereof.
The fifth embodiment may be modified as follows.
A modification of such a floating arrangement of the variable nozzle device can use the center housing design mentioned above, where the center housing is provided with an inner recess, with the floating insert 517 being accommodated in an axially movable manner within said recess.
The locking pin 537 may be attached to the exhaust housing.
Instead of the locking pin 537, another locking means may be provided. For instance, the inner recess in the exhaust housing may be provided with an irregular inner shape matching an outer shape of the floating insert so as to prevent the floating insert from rotating relative to the exhaust housing.
The spring member 543 may be omitted. In this case, an elastic disk shroud similar to the elastic disk shrouds 23, 123 of the preceding embodiments is used to urge the vanes 527 against the floating insert 517 via the nozzle ring 521.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB02/03835 | 9/18/2002 | WO | 11/8/2005 |