This invention relates generally to the field of turbochargers and, more particularly, to a variable geometry turbocharger having a center housing that is specially engineered to provide liquid cooling to a compressor side of the turbocharger to control the temperature along a wall structure in the compressor housing adjacent to a variable geometry member disposed therein during turbocharger operation, thereby reduce the formation of oil deposits along the wall structure that could interfere with the desired movement of the variable geometry member and adversely impact compressor efficiency.
Turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting the intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Specifically, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine to spin within the housing. The exhaust gas-driven turbine is mounted onto one end of a shaft that is common to a radial air compressor mounted onto an opposite end of the shaft and housed in a compressor housing. Thus, rotary action of the turbine also causes the air compressor to spin within a compressor housing of the turbocharger that is separate from the turbine housing. The spinning action of the air compressor causes intake air to enter the compressor housing and be pressurized or boosted a desired amount before it is mixed with fuel and combusted within the engine combustion chamber.
In a turbocharger it is often desirable to control the flow of exhaust gas to the turbine to improve the efficiency or operational range of the turbocharger. Variable geometry turbochargers have been configured to address this need. A type of variable geometry turbocharger is one having a variable exhaust nozzle, referred to as a variable nozzle turbocharger. Different configurations of variable nozzles have been employed in variable nozzle turbochargers to control the exhaust gas flow. One approach taken to achieve exhaust gas flow control in such variable nozzle turbochargers involves the use of multiple pivoting vanes that are positioned annularly around the turbine inlet. The pivoting vanes are commonly controlled by a unison ring, that is movably disposed within the turbocharger, to alter the throat area of the passages between the vanes, thereby functioning to control the exhaust gas flow into the turbine.
In such turbochargers, a center housing is interposed between the turbocharger turbine housing and compressor housing, and is configured internally to carry and provide lubrication to the common shaft. While oil is circulated through the center housing to provide lubrication to the shaft, air surrounding the external surface of the center housing is used for cooling the center housing and portions of the center housing adjacent the turbine and compressor housings. In some turbochargers the center housing is constructed having an internal passage, in addition to the oil lubrication passage, that is configured to receive a cooling liquid therein to reduce the extent of heat transfer from the turbine housing. Such liquid-cooled center housings, are configured having an internal liquid cooling passage intentionally positioned adjacent the turbine housing for this purpose.
Some turbochargers are known to have variable geometry members disposed both in the turbine housing, as described above, and in the compressor housing. The variable geometry members that are disposed in the compressor housing are controlled in a manner similar to that described above to achieve a desired result with respect to the air circulating through the compressor housing. In an example embodiment, the variable geometry members disposed in the compressor housing comprise a plurality of pivoting vanes positioned adjacent a wall portion of the compressor housing.
A problem known to exist with such turbochargers, comprising variable geometry members disposed within the compressor housing, is that at temperatures above about 180° C. any oil that has entered the compressor housing, e.g., coming from blow by recirculation, deposits itself on the compressor wall that is adjacent the variable geometry members. At these temperatures, the deposited oil can operate to jam or otherwise impair movement of the variable geometry members. For example, it is not uncommon for the oil deposits to cause the variable geometry members to become jammed or stuck, thereby impairing their ability to operate properly to have a desired impact on the air circulating through the compressor housing reducing compressor efficiency.
It is, therefore, desired that a turbocharger assembly be constructed in a manner that reduces or eliminates the potential for any such variable geometry members disposed within the compressor housing becoming jammed or stuck during turbocharger operation by the formation or presence of oil deposits therein.
A turbocharger assembly constructed according to the present invention includes a center housing having a shaft disposed therethrough, a compressor housing attached to one side of the center housing and having an impeller rotatably disposed therein and attached to one end of the shaft, and a turbine housing attached to another side of the center housing and having a turbine wheel rotatably disposed therein and attached to an opposite end of the shaft. The center housing is specially engineered having an internal liquid cooling passage disposed therein.
The center housing liquid cooling passage includes a compressor section that is positioned adjacent a wall section of the center housing that is connected with and that forms a portion of the compressor housing. The liquid cooling passage also includes a turbine section that is positioned adjacent a wall section of the center housing opposite the compressor housing and that is connected with and that forms a portion of the turbine housing. In an example embodiment, the turbine and/or compressor housings include one or more variable geometry members disposed therein.
Configured in this manner, the liquid-cooled center housing comprising the compressor section operates to maintain the compressor housing wall structure at a temperature below about 180° C. to minimize or eliminate the unwanted occurrence of oil deposits thereon, which ensures the unimpaired operation of variable geometry members within the compressor, thereby improving compressor efficiency and reducing needed variable geometry member actuation loads.
The details and features of the present invention will be more clearly understood with respect to the detailed description and drawings in which:
Turbocharger assemblies constructed according to principles of this invention comprise a center housing that is interposed between a turbine housing and a compressor housing. In an example embodiment, the turbocharger assembly comprises one or more variable geometry members disposed within the compressor housing for controlling the circulation of air therein. The turbocharger assembly center housing is specially engineered having an internal liquid cooling passage disposed therein and includes a compressor section that is positioned adjacent a wall structure connecting with the compressor housing. The internal liquid cooling passage can also extend along a wall structure of the center housing connecting with the turbine housing. Constructed in this manner, the center housing operates to maintain a desired wall structure temperature within the compressor housing during turbocharger operation to minimize or eliminate the formation or presence of oil deposits on the wall structure that can impair desired movement of the variable geometry member and reduce compressor efficiency.
The turbine housing 14 includes a volute 26 that is in gas flow communication with an exhaust inlet for receiving exhaust gas and directing it to the turbine wheel. The turbine housing includes a nozzle wall 28 interposed between the volute and the turbine wheel. The nozzle wall 28 is configured to accommodate placement of the plurality of vanes. The center housing 12 includes a wall structure 32 opposite the nozzle wall that together operate to define a flow passage 34 from the volute to the turbine wheel.
The liquid cooling passage 58 in this prior art center housing 50 is one that is intentionally located within the center housing body 60 at a position adjacent and extending along an inside portion of the wall structure 32 to receive heat generated from the turbine housing. As illustrated in
The center housing 64 includes an oil inlet port 78 that is in communication with an oil inlet passage 80, for facilitating the transport of a lubricating oil to the bearing assembly 72, and includes an oil outlet passage 82 and oil out port 84 for facilitate passage of oil from the bearing assembly and the center housing. Additionally, the center housing 64 is specially configured to accommodate passage of a liquid cooling medium therethrough for the purposes of controlling the temperature of the turbocharger assembly. Specifically, the center housing 64 is constructed having an internal cooling passage 86 that is configured comprising a turbine housing section 88 and, unlike the turbocharger assembly of
The internal cooling passage turbine housing section 88 is positioned within the center housing body 92 so that it is adjacent the wall structure 94 of the center housing that forms a portion of the turbine housing. In an example embodiment, the cooling passage turbine housing section 88 is provided in the form of an annular passage that extends at least a partially around a shaft opening 96 through the center housing, and that extends axially into a neck portion 98 of the wall section that is adjacent the turbine wheel 74. Configured in this manner, the cooling passage turbine housing section operates to control amount of heat generated in the turbine housing and transferred to the center housing.
As shown in
The placement position of the cooling liquid inlet and outlet radially along the center housing body 92 is understood to vary depending on the particular use application. In an example embodiment, the placement position is dependent on a number of factors such as the packaging of the turbocharger assembly and the need to provide connection points that are located in places that do not interfere with other elements that will be attached to the turbocharger assembly, such as oil lines, vacuum lines, actuator assemblies and the like. Additionally, the placement position of the cooling liquid inlet and outlet ports will also be determined by heat transfer and liquid flow considerations of the cooling liquid within the center housing, e.g., to obtain the desired cooling liquid flow path within the internal passage.
In an example embodiment, the cooling liquid outlet is preferably mounted above the cooling liquid inlet for the purpose of bleeding or removing by gravity any air from within the internal cooling passage. Placing the cooling liquid inlet at a position along the center housing body that is lower than the cooling liquid outlet also facilitates thermosyphon liquid cooking when the internal combustion engine connected with the turbocharger assembly is off. In an example embodiment, the liquid cooling inlet and outlet ports are positioned at least about 45 degrees apart from one another.
As best shown in FIG, 6B, the internal passage compressor section 90 is shown to have a core that extends at least partially around a center housing central opening. The exact configuration of the internally passage compressor section 90 can and will vary depending on the desired heat transfer and/or cooling liquid flow characteristics within the center housing. I an example embodiment, the compressor section 90 is configured so that it does not extend a full 360 degrees around the central opening, thus does not extend along the full surface of the compressor wall structure, for the purpose of providing a desired cooling liquid flow path within the center housing that produces a maximized heat transfer surface exchange and a minimized pressure drop within the internal passage. For example, in the embodiment illustrated in
In an example embodiment, the compressor section 90 comprises a core that extends partially around the central opening at least about 180 degrees, and more preferably approximately 270 degrees. While a particular example embodiment has been illustrated having a particularly configured compressor section core, it is to be understood that turbocharger assemblies having liquid cooled center housings with liquid passage compressor sections configured differently that that illustrated in
A factor driving the configuration of the compressor section core is the amount of heat transfer necessary to keep the wall structure of the compressor below about 180° C. during turbocharger operation. As noted above, it has been discovered that at above this temperature oil can deposit on the compressor wall structure and interfere with the proper movement of the variable geometry member that is positioned thereagainst. Accordingly, it is desired that the internal passage compressor section be configured in a manner that provides an amount of heat transfer reducing or eliminating the presence of such oil deposits.
Liquid-cooled center housings of this invention can be formed from conventional methods such as by machining, molding or casting, and can be formed from conventional materials used to make turbocharger assembly center housings, e.g., metallic materials. In an example embodiment, the center housing is made by mold process out of a metallic material.
A feature of turbocharger assemblies constructed in accordance with the principles of this invention, and as illustrated in FIGS. 4 to 6B, is the use of a liquid-cooled center housing having an internal liquid cooling passage comprising a compressor section that is configured to keep a wall structure of the compressor below a temperature of about 180° C. during turbocharger operation, thereby minimizing or eliminating the formation of oil deposits along the wall structure that could impair proper movement of a variable geometry member disposed within the compressor housing, e.g., positioned adjacent the wall structure. The impairment of proper variable geometry member movement within the compressor housing is not desired because it can both reduce compressor housing efficiency and require an increased actuation load to move the member.
Although specific embodiments of turbocharger assemblies comprising liquid-cooled center housings have been described above and illustrated, it is to be understood that modifications and variations of this configuration may be apparent to those skilled in the art, and that such modifications and variations are intended to be within the scope of this invention.