The invention relates in general to turbochargers and, more particularly, to preventing oil leakage into the compressor of a turbocharger.
Turbochargers can have a turbine wheel that is connected by a shaft to a compressor wheel. The turbine wheel is driven by exhaust gas exiting an internal combustion engine. The rotation of the turbine wheel is communicated to the compressor wheel by the shaft. The compressor wheel is used to increase the pressure of intake air prior to mixing with fuel and combustion in the engine. The speeds at which the shaft, turbine wheel and compressor wheel are rotated is very high, and can be in excess of 250,000 rpm. Therefore, bearings used to support the shaft must be lubricated with pressurized oil. During normal operation of the turbocharger, pressure within the compressor is sufficient to retard the flow of oil from the area of the bearings into the compressor. However, during certain operational states, pressure is reduced in the compressor and pressurized oil can be drawn into the compressor area where the oil will contaminate the intake air.
This lubricant is ultimately emitted into the environment via the exhaust, contributing to emissions that may not be in compliance with the increasingly stringent emissions standards that turbocharged vehicles are required to meet. Further, such emissions can potentially harm certain downstream components (i.e., catalytic converters). However, it is a challenge to prevent the flow of lubricant into the compressor, considering that lubricating oil is pumped in under pressure, at a high flow rate, to lubricate and remove heat from a turbine shaft rotates at high speeds.
One example of such a system for containing the flow of lubricant into the compressor is shown in
Lubrication is provided by oil passageway 60 which receives oil from the oil intake 30. Oil escaping from the interface between the first radially outwardly extending wall 44 and the thrust bearing 50 is prevented from reaching the compressor wheel 18 by the provision of a seal assembly including an oil deflector 64 and an insert 68. The deflector 64 has an irregular form to facilitate the drainage of oil. Oil passing the deflector 64 is contacted by an oil thrower 72. The oil thrower 72 is connected to the shaft 22 and rotates therewith. Oil is thrown by the thrower 72 into the chamber 76 where it contacts a deflecting surface 80. The deflecting surface 80 collects the oil and the oil flows gravitationally to the outlet 84.
However, this configuration is mechanically complicated because it introduces an additional component (the oil deflector 64) to the assembly. Further, oil can become stuck between two surfaces due to surface tension and capillary action, preventing the oil from draining due to gravity and potentially blocking the drainage of other oil. Any oil trapped in the area increases the likelihood that it will be drawn into the compressor. Despite the tortuous path created by the presence of the insert 68, the oil deflector 64 and the oil thrower 72, the oil can nevertheless flow past the interstices between the insert 68 and the oil thrower 72 to reach the compressor wheel 18.
The prior art is replete with additional systems for preventing lubricant flow into the compressor. For instance, many references are directed to systems with double ring seals. Some references use pressurized gas or venting to air in combination with the seals to prevent undesired migration of the lubricant. Examples of such systems are disclosed in U.S. Pat. Nos. 3,825,311; 4,196,190; 5,076,765; and 5,890,881 as well as in International Publication No. WO2004/063535 and European Patent Specification No. EP0941431. However, these systems can be overly complicated, unreliable, expensive to incorporate and thus not universally adopted, and liable to wear out. Thus, there is a need for a turbocharger assembly that can minimize such concerns.
A turbocharger assembly according to aspects of the invention includes a thrust collar, a thrust bearing and an insert. The thrust collar has a first radially outwardly extending wall and a second radially outwardly extending wall. The first and second radially outwardly extending walls are axially spaced such that an annular channel is defined therebetween. The first radially outwardly extending wall has a proximal face and a distal face. Likewise, the second radially outwardly extending wall has a proximal face and a distal face. The annular channel is formed in part by the distal face of the first radially outwardly extending wall and the proximal face of the second radially outwardly extending wall.
A thrust bearing has a first axial face and a second axial face. The thrust bearing further has a radially outer end and a radially inner end. At least a portion of the thrust bearing including the radially inner end is received in the annular channel.
The insert has an outer axially extending lip and an inner axially extending lip. The outer lip is radially spaced from the inner lip. The inner lip has a radially outwardly extending tip. The inner lip defines an annular drainage channel. The insert annularly surrounds a portion of the thrust collar such that the tip of the inner lip directly engages the proximal face of the first radially outwardly extending wall and such that the outer lip directly engages the first axial face of the thrust bearing proximate the radially outer end.
An oil collection chamber is defined at least in part by the drainage channel of the insert, the first radially outwardly extending wall of the thrust collar and the first axial face of the thrust bearing. The chamber is in fluid communication with an oil release interface defined between the first radially outwardly extending wall and the thrust bearing. Thus, pressurized oil discharged from the oil release interface is permitted to be centrifugally propelled toward a radially outer region of the oil collection chamber and to collect in the oil collection chamber for subsequent drainage.
The insert can include a deflecting surface. The deflecting surface can form a part of the oil collection chamber. The deflecting surface can be angular, or it can be substantially curvilinear.
The first radially outwardly extending wall can have an associated diameter and the radially outwardly extending tip can have an associated second diameter. In one embodiment, the second diameter can be greater than the first diameter. In another embodiment, the second diameter can be less than the first diameter. In such case, the first radially outwardly extending wall can be at a first diameter at the proximal face and at a second diameter at the distal face. The first diameter can be greater than the second diameter such that a sharp edge is formed at the proximal face.
Embodiments of the invention are directed to an oil discharge assembly for a turbocharger. Aspects of the invention will be explained in connection with one possible oil discharge assembly, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in
Referring to
The turbocharger 100 can further include a thrust collar 124. The thrust collar 124 can be generally cylindrical with a first radially outwardly extending wall 130 and a second radially outwardly extending wall 134. The first radially outwardly extending wall 130 has a proximal face 131 and a distal face 133. The second radially outwardly extending wall 134 has an proximal face 135 and a distal face 137. It should be noted that the terms “proximal” and “distal,” as used herein, are intended to mean relative to the compressor assembly 110. The first and second radially outwardly extending walls 130, 134 are axially spaced such that an annular channel 160 is formed therebetween. The annular channel 160 can be defined in part by the distal face 133 of the first radially outwardly extending wall 130 and the proximal face 135 of the second radially outwardly extending wall 134.
The assembly further includes a thrust bearing 140. The thrust bearing 140 has a first axial face 144 and a second axial face 148. The thrust bearing 140 has a radially outer end 152 and a radially inner end 156. At least a portion of the thrust bearing 140, including the radially inner end 156, is received in the annular channel 160.
Pressurized oil is provided through an oil intake 170 and through a passageway 174 to the thrust bearing 140. Oil is transported through a passageway 178 to the first journal bearing 116 and through a passageway 182 to the second journal bearing 120. Oil making its way toward the compressor 110 is blocked by an insert 200. The insert 200 is generally annular and has an outer axially extending lip 204 and an inner axially extending lip 208. The inner lip 208 has a radially outwardly extending tip 212 such that the inner lip 208 defines an annular drainage channel 216. The insert 200 can be made of any suitable material, such as iron.
The insert 200 annularly surrounds the thrust collar 124. A portion of the outer lip 204 of the insert 200 can directly engage the housing 102. A portion of outer lip 204 can directly engage the first face 144 of the thrust bearing 140 proximate the radially outer end 152. The inner lip 208 of the insert 200 can directly engage the thrust collar 124. The tip 212 of the inner lip 208 can directly engage the proximal face 131 of the first radially outwardly extending wall 130 of the thrust collar 124. In one embodiment, the diameter of the outwardly extending tip 212 can be greater than the diameter of the first radially outwardly extending wall 130 of the thrust collar 124, as shown in
An oil collection chamber 240 is defined at least in part by the drainage channel 216 of the insert 200, the first radially outwardly extending wall 130 of the thrust collar 128 and the first axial face 144 of the thrust bearing 140. The chamber is in fluid communication with an oil release interface between the distal face 133 of the first radially outwardly extending wall 130 and the first axial face 144 of the thrust bearing 140.
Oil discharged from the oil release interface is centrifugally propelled from the interface as generally indicated by arrow 250. In cases where the first radially outwardly extending wall 130 provides a sharp edge 138, as described above, the oil can be broken apart by the edge 138 as it is propelled outward. The oil can be propelled toward a radially outer region of the oil collection chamber 240 as indicated by arrow 251. The oil can strike a deflecting surface 206 of the insert 200 and can follow the path of arrows 252-255 to the drainage channel 216. The deflecting surface 206 can be contoured to generally direct the oil downward. In one embodiment, the deflecting surface 206 can be substantially curvilinear or otherwise smooth, as shown in
According to aspects of the invention, it is preferred for the oil collection chamber 240 to be as large as possible. The larger the chamber 240, the more difficult it is for oil to stick between two surfaces of the chamber 240. Thus, the likelihood that the oil will drain out of the oil collection chamber 240 can be increased.
There is shown in
The foregoing description is provided in the context of one possible oil discharge assembly for a turbocharger. Thus, it will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.