Abstract:
An electrically controlled turbocharger having a substantially vertically oriented shaft interconnecting a turbine and a compressor. The vertical orientation serves to eliminate the effects of gravity on the rotating components. Placing the turbine vertically above the motor and compressor and provides additional cooling through convection of heat produced by hot exhaust gas flowing through the turbine. A lubricating system utilizes scavenged air from the compressor to draw lubricating oil through internal passages of the motor housing to maintain a desirable oil sump level, ventilate the auxiliary induction motor, and provide pressure to the oil seals of the motor cavity.

Description:
RELATED APPLICATION  
       [0001]     This application and the claimed subject matter is supported by Applicant&#39;s provisional application Ser. No. 60/669,598 to TURBOCHARGER, filed Apr. 9, 2005 and the benefit to priority of that date is hereby claimed. 
     
    
     BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to the field of turbochargers for use with internal combustion engines. More specifically the invention relates to specific improvements in a lubrication system for a turbocharger as well as the construction of an electrically controlled turbocharger.  
         [0004]     2. Description of the Prior Art  
         [0005]     Turbochargers are frequently employed in association with internal combustion engines to improve engine response under varying loads. Electrically assisted turbochargers provide the added advantage of, reducing transient lag, reducing fuel consumption and lowering emission levels. Typically, an electrically assisted turbocharger employs a motor engaged to supply supplemental power to rotate the shaft that extends between the turbine and the compressor. When the engine requires increased demand for intake air and the turbine is not turning at a fast enough speed to provide the demand, the motor is powered to drive the turbine and compressor at a sufficient speed to supply the required air.  
         [0006]     Such turbochargers described in the prior art are commonly structured so that the turbine, motor and compressor are mounted on a horizontal shaft. Additionally, the electric motors employed in prior art turbochargers contain magnets that become degraded due to exposure to the extreme heat inherent in such applications.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides several improvements to an electrically controlled turbocharger unit that result in lower vibration, cooler running temperatures and increased reliability. Such improvements are the result of orienting the unit so that the central shaft containing the turbine and the compressor is mounted to rotate on a substantially vertical axis. This orientation results in the elimination of gravitational effects on the rotating shaft and the elements mounted thereon. In addition, an induction motor having its rotor integrally mounted on the shaft that extends between the turbine and the compressor is found to provide highly responsive characteristics and greater endurance to the high temperatures inherent in turbochargers. Further, an improved lubricating system is described to enhance the flow of lubricating fluid through the turbocharger housing and the various bearings in the unit by utilizing air pressure scavenged from the compressor and injected into upper and lower oil reservoirs.  
         [0008]     It is an object of the present invention to provide a vertically oriented turbocharger that reduces and therefore improves the vibration characteristics of the turbo shaft at high speed rotations.  
         [0009]     It is another object of the present invention to provide an improved electrically controlled turbocharger that utilizes an induction motor for driving the compressor when exhaust gas flow from the associated internal combustion engine is insufficient to provide the necessary drive power.  
         [0010]     It is a further object of the invention to provide an improved lubricating system for vertically oriented turbochargers that is effective to provide lubricating fluid to the vertically spaced shaft bearings.  
         [0011]     It is a still further object of the present invention to provide improved cooling for an electrically controlled turbocharger through the use of air scavenged from the compressor and ducted into the motor and lubricating system that circulates lubricating fluid through the housing of the turbocharger. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a cross-sectional plan view of the preferred embodiment of the present invention.  
         [0013]      FIG. 2  is a 90 degree cross-sectional plan view of the embodiment shown in  FIG. 1 .  
         [0014]      FIG. 3  is a cross-sectional plan view of the preferred embodiment shown in  FIGS. 1 and 2 , taken along another vertical plane.  
         [0015]      FIG. 4  is a block diagram showing the functional inputs and outputs for the electrically controlled turbocharger of the present invention.  
         [0016]      FIG. 5  is a block diagram showing the flow of air and lubricating fluid into and through an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     In  FIG. 1 , the preferred embodiment of an electrically assisted turbocharger unit  100  is depicted in a substantially vertical orientation, intended to be mounted on or in close proximity to an associated internal combustion engine.  
         [0018]     In this embodiment, a turbine housing  102  in shown in the upper portion of  FIG. 1 , while a compressor housing  116  is shown in the lower portion. A motor housing  104  is shown as being intermediate the turbine and compressor housings.  
         [0019]     A turbocharger shaft  114  is at the core of the unit and provides the mechanical drive connection between an exhaust gas turbine rotor  110  and a compressor rotor  119 . In this case an induction motor  132  is provided in motor housing  104  to surround shaft  114  and a motor rotor  136  is formed to be preferably integral with shaft  114 .  
         [0020]     Turbine housing  102  provides an exhaust gas inlet port  116  that is connected to the exhaust manifold of an associated engine (not shown). Turbine housing  102  contains exhaust gas turbine rotor  110  and a volute  112  through which forced exhaust gas passes. Exhaust gas turbine rotor  110  is shown, in this embodiment, as being integrally forged to shaft  114 .  
         [0021]     An upper heat shield  109  and an insulation layer  108  are respectively provided between motor housing  104  and turbine housing  102  to resist the conduction of heat from the exhaust gas down to motor housing  104  and all the associated components that may be affected by such temperatures. Since convection heat tends to rise, some of the heat from exhaust gases is dissipated upwards from turbine housing  102  and away from motor housing  104 . In doing so, the rising air caused by the convection heat draws air upwards from below and helps cool the unit. The vertical stacking of the components takes advantage of this phenomenon.  
         [0022]     Motor housing  104  includes a motor cavity  133  and several passages for the flow of lubricating fluid and scavenged air. Induction motor  132  includes a stator  134  made up of copper wire windings and a rotor (laminate stack and windings)  136 , all within motor cavity  133 . The motor cavity  133  is configured to allow for the unobstructed rotation of the rotor  136  and for the flow of ventilation air scavenged from the compressor. Shaft  114  extends through motor cavity  133  of motor housing  104  and into compressor housing  116  where compressor rotor  119  is attached to shaft  114  by a retainer nut  120 .  
         [0023]     Compressor housing  116  includes a fresh air intake  118 , compressor rotor  119 , a volute air passage  122  and a compressed air outlet  124 .  
         [0024]     Shaft  114  is mounted for rotation along its substantially vertically oriented axis on upper bearing  130  and lower bearing  128 . Bearings  130  and  128  are lubricated by the lubrication system and are contained within oil reservoirs  144  and  145 , respectively. Upper oil reservoir  144  is separated from turbine housing  102  by a seal  111  and from motor cavity  133  by a bushing  131 . Lower oil reservoir  145  is the upper part of an oil sump  146  and is separated from compressor housing  116  by a lower compressor seal  121  and from motor cavity  133  by a bushing  129 .  
         [0025]     An oil inlet  138  is formed in the side of motor housing  104  and is in fluid communication with an upper oil passage  140  and a lower oil passage  142 . Upper oil passage  140  extends upwards to allow the delivery of oil to upper bearing  130  at its upper bearing oil injection port  141 . Lower oil passage  142  extends laterally through motor housing  104  towards lower bearing  128  to allow the delivery of oil to the lower bearing  128  at its lower bearing oil injection port  143 .  
         [0026]     Upper oil reservoir  144  is in fluid communication with drain passage  149  that is in turn connected to a drain outlet  148 . At the lower end of the unit, lower oil reservoir  145  is in fluid communication with an oil sump  146  that is formed between motor housing  104  and compressor housing  116 . Oil sump  146  is in fluid communication with a sump drain  147  that is connected to drain outlet  148 .  
         [0027]     In  FIG. 2 , a 90 degree cross-sectional plan view of the turbocharger embodiment shown in  FIG. 1  is presented. This view is taken along the vertical axis A-A. The left side of  FIG. 2  illustrates substantially the same components and features shown in  FIG. 1 , while the right side is a 90 degree rotation and shows the air injection portion of the lubricating system. A scavenged air inlet  150  is shown in communication with compressor volute passage  122 . A scavenged air passage  152  is in fluid communication with air inlet  150  and opens into motor cavity  133 . An air outlet passage  154  provides a path for air to flow from motor cavity  133  to upper oil reservoir  144 . Another air outlet passage  156  is formed at the lower portion of motor cavity  133  (added to left side of  FIG. 2 ) in fluid communication with lower oil reservoir  145  to allow for the scavenged air to escape from the motor cavity  133 .  
         [0028]     In  FIG. 3 , one of three electrical interconnections is illustrated for the turbocharger embodiment  100 . The interconnection is between a stud terminal  160 , mounted on motor housing  104 , and stator windings  134  through a lead wire  162 .  
         [0029]     In  FIG. 4 , the electrically controlled turbocharger is shown in its generic sense as receiving exhaust gas flowing from the associated engine and controlled electrical power from an associated controller. In this case, the controller provides alternating current or pulse width variable power to the electric induction motor to control its speed when required during cold start, other low idle conditions or acceleration demands in which the exhaust gas output from the engine is insufficient to cause the turbocharger to supply adequate amounts of fresh air to the intake manifold of the engine. As the engine increases its speed and produces more exhaust gas to drive the turbine, the controller responsively reduces power to the induction motor until the electric motor assist is no longer needed.  
         [0030]     The lubrication system of the preferred embodiment functions in accordance with the flow diagram of  FIG. 5 , with reference to the components shown in  FIGS. 1 and 2 . In this system, the oil is provided to oil inlet  138  from an auxiliary pump at a predetermined pressure and volume. It has been found that during cold starts or cold weather, the oil needs assistance to flow through the passages in an efficient manner. In addition, the location of the oil sump  146  at a level below the drain outlet requires positive pressure to keep the level below a predetermined level at all temperatures. The lubricating system utilizes pressurized scavenged air from compressor volute  122  to perform several tasks. First, the scavenged air flows into motor cavity  133  and provides a limited amount of ventilation to induction motor  132 . Second, the air in motor cavity  133  creates a positive pressure against upper motor cavity bushing  131  and lower motor cavity bushing  129  to prevent oil in the opposing reservoirs from entering motor cavity  133 . Third, as the air exits from motor cavity  133  through air outlet  154  and enters upper oil reservoir  144 , it provides additional pressure to the oil that has entered that same reservoir to drive the oil into the drain passage  149 . Fourth, the air that enters lower oil reservoir  145  from motor cavity  133  through air outlet  156  blows past the oil collected in the sump towards the drain oil outlet  148  and creates a vacuum. This vacuum in turn causes oil to be drawn from the sump and maintain the oil level therein at a desired level.  
         [0031]     It should be understood that the foregoing description of the embodiments is merely illustrative of many possible implementations of the present invention and is not intended to be exhaustive.