Patent Application
20070196206
Not Applicable.
1 Field of the Invention (Technical Field)
The present invention relates to turbocharger compressor vaned diffusers, specifically to a diffuser plate that is axially movable in response to pressure from the compressor housing volute so that, as the compressor housing moves, an effective seal is maintained on the open side of the compressor's vaned diffuser.
2. Description of Related Art
Note that where the following discussion refers to a number of publications by author(s) and year of publication, because of recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Turbochargers for pressurizing or boosting the intake air stream into an internal combustion engine include an exhaust gas turbine through which the engine's exhaust gas is routed so that the exhaust gas turbine spins within the turbocharger housing. The exhaust gas turbine is connected via a shaft to a radial air compressor impeller disposed within the compressor housing so that as the exhaust gas turbine turns, the compressor impeller also turns within the compressor housing and causes intake air to axially enter the compressor housing, go past the impeller, then change direction past a diffuser before entering a compressor housing volute. After the intake air is pressurized or boosted, it exits the turbocharger to be mixed with fuel then sent to the engine combustion chamber.
The diffuser in the compressor housing can either be part of the compressor housing or it can be a separate component attached within the compressor housing. By slowing down the air that is taken into the compressor housing, the diffuser converts the velocity energy to pressure energy and produces air boost pressure in the turbocharger. The diffuser can include one or more vanes that project outwardly from the diffuser surface and that extend in a generally radial direction in line with the direction of air flow coming from the compressor impeller. The vanes force the air leaving the compressor impeller to flow in a particular direction, reducing air flow velocity in a way that favors a particular application demand such as a particular engine speed or torque requirement. Thus, turbocharger compressors use vaned diffusers to increase compressor stage efficiency.
Vane diffusers include those constructed as a separate component of the compressor housing and that are shaped in the form of an annular ring designed to fit against a backplate axial wall surface. Typically, at least one pin is placed axially between the vane diffuser and the backplate to prevent the vane diffuser from rotating within the compressor hosing.
Typically, vaned diffusers are open sided and take advantage of either the backplate or compressor housing to form the sealing side of the diffuser. However, as compressor outlet pressures are increased, the compressor housing tends to move, and the clamp load that clamps the diffuser against the back plate is decreased thereby impacting the effectiveness of the diffuser seal and resulting in leakage around the diffuser. The loss of sealing effectiveness and the resulting leakage causes a significant loss of compressor efficiency.
Also typical in the prior art is an elastomeric O-ring that is interposed, for example, between the vane diffuser and the backplate to both provide an air leakage seal and to pressure load the vane diffuser away from the backplate. This pressure loading is used to urge the vane diffuser away from the backplate as the compressor housing moves axially away from the backplate during operation. Therefore, pressure loading is intended to keep the vane diffuser in contact with the housing during such axial movement to prevent compressor performance losses caused by air flow restrictions between the compressor housing and the vane diffuser. However, the O-ring energizer cannot provide both the range and consistent degree of pressure loading that is required because the ring force provided by the O-ring energizer decreases rapidly as the vane diffuser is moved away from the backplate (thus effective for only a very limited range of motion), and the known elastomers are known to degrade and creep at high compressor operating temperatures so that the energizer spring rate decreases over time.
Another approach to ensure that the vane diffuser remains in contact with the compressor housing as the compressor housing moves during compressor operation is provided by U.S. Pat. No. 6,168,375 wherein the vaned diffuser is spring-loaded.
Other approaches to ensure for an effective seal of the vane diffuser are desirable, particularly those that involve simple components having few or no moveable parts.
The present invention provides a movable diffuser loading plate to provide a sealing surface against the open side of a compressor vaned diffuser. Thus, an embodiment of the present invention provides a turbocharger compressor comprising a housing having a volute, a backplate attached to an exterior surface of the housing, an impeller rotatably mounted within the housing, an annular vaned diffuser disposed in the housing between the volute and the impeller, said vaned diffuser axially facing an axially facing surface of said backplate, and a diffuser loading plate adjacent to the vaned diffuser, said loading plate in communication with the volute via a pressure port, and said diffuser loading plate moveable in response to pressure from the volute so that the diffuser loading plate imposes an axially directed pressure load to provide a seal on an open end of the vaned diffuser.
The compressor further comprises a pressure loading cavity adjacent to the diffuser loading plate and in fluid communication with the pressure port.
In an embodiment, the vaned diffuser and the diffuser loading plate are integral.
In an embodiment, the vaned diffuser is located between the back plate and the diffuser loading plate. In an alternative embodiment, the diffuser loading plate is located between the backplate and the vaned diffuser.
The diffuser loading plate may comprise a disc.
Another embodiment provides a compressor diffuser assembly for placement in a fluid passageway between a compressor impeller and a compressor volute, said assembly comprising an annular vaned diffuser adapted to be placed between the volute and the impeller so that the vaned diffuser axially faces an axially facing surface of a compressor backplate, a diffuser loading plate adjacent to the vaned diffuser, and a pressure port in communication with the volute and the diffuser loading plate, said diffuser loading plate moveable in response to pressure from the volute so that the diffuser loading plate imposes an axially directed pressure load to provide a seal on an open end of the vaned diffuser. The assembly preferably further comprises a pressure loading cavity adjacent the diffuser loading plate and in communication with the pressure port.
In an embodiment, the vaned diffuser and the diffuser loading plate are integral.
The diffuser loading plate preferably comprises a disc.
Still another embodiment provides a vaned diffuser assembly for use in a turbocharger compressor, said assembly comprising a diffuser loading plate in contact with a vaned diffuser, and said assembly positionable between a housing and a backplate of the compressor. The diffuser loading plate and the vaned diffuser may be integral.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The accompanying drawings, which are incorporated into, and form a part of, the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings:
The present invention provides a movable compressor diffuser loading plate. The diffuser loading plate may be integral with a vaned compressor diffuser so that the diffuser loading plate loads the diffuser against the backplate or against the compressor housing. Alternatively, the diffuser loading plate and the diffuser may be non-integral so that the diffuser loading plate provides a sealing surface against the open side of a vaned diffuser. In any of these embodiments, the diffuser loading plate communicates with the compressor outlet pressure via a pressure port. The diffuser loading plate is free to move within the compressor stage assembly. As the compressor outlet pressure increases, the pressure exerted against the diffuser loading plate increases thus providing the necessary load to provide a seal at the open side of the diffuser. Even if the compressor housing moves, the pressure loading maintains the sealing of the diffuser.
As used in the specification and claims herein, the terms “a”, “an”, and “the” mean one or more.
Turning now to the figures, which describe a non-limiting embodiment of the present invention that is illustrative of the various embodiments within the scope of the present invention,
In another embodiment, shown in
As noted above, utilizing the same principles wherein diffuser loading plate 130 can move within compressor assembly 100, and as easily visualized referring to
In yet another embodiment using the principles described above and wherein diffuser loading plate 130 and diffuser 120 are not integral, and as easily visualized referring to
In all embodiments, as compressor outlet pressure is increased (and compressor housing 102 moves axially away from backplate 106) pressure is increased on diffuser loading plate 130 to maintain contact/sealing of an open side of diffuser 120 thus maintaining high compressor efficiency.
It is also understood that pressure cavity 140 may be comprise a continuous, generally annular cavity, or may comprise open sections arranged in an annular configuration. The geometry and orientation of cavity 140 may vary as understood by those skilled in the art. Pressure port 142 may likewise vary in orientation, geometry, etc.
It is also understood that in other embodiments, loading other than pneumatic loading, such as, but not limited to, mechanical loading of diffuser loading plate 130, may be utilized.
The compressor housing, vaned diffuser, and backplate, in accordance with the present invention, are attached together according to conventional practice and are combined with other parts conventionally associated with turbochargers to provide a turbocharger for internal combustion engines that incorporates the pressure loaded compressor diffuser of the present invention. Thus, the present invention provides for the axial movement of an integrated diffuser loading plate/vaned diffuser combination and, alternatively, for the axial movement of a diffuser loading plate that is not integral to the diffuser. In all embodiments/applications, an effective seal of the open side of a diffuser is maintained to thereby maintain a smooth air flow transition with the compressor housing such that improved compressor performance is provided.
The preceding examples can be repeated with similar success by substituting the generically or specifically described components, mechanisms, materials, and/or operating conditions of this invention for those used in the preceding examples.
Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.
