Abstract:
Turbochargers are disclosed that have a braking system to brake the rotation of an electrically conductive compressor wheel within the turbocharger. The brake system includes the electrically conductive compressor wheel, which is connected to a turbine by a common shaft, one or more electromagnets positioned proximate to the compressor wheel, and a control circuit electrically coupled to the one or more electromagnets to turn the one or more electromagnets on or off to provide braking action to the compressor wheel. Systems including such a turbocharger and methods utilizing such turbochargers are also included herein.

Description:
TECHNICAL FIELD 
       [0001]    This application relates to turbocharger systems within internal combustion engines, more particularly, to exhaust-driven turbochargers having a magnetic brake. 
       BACKGROUND 
       [0002]    Internal combustion engines, its mechanisms, refinements and iterations are used in a variety of moving and non-moving vehicles or housings. Today, for example, internal combustion engines are found in terrestrial passenger and industrial vehicles, marine, stationary, and aerospace applications. There are generally two dominant ignition cycles commonly referred to as gas and diesel, or more formally as spark ignited and compression ignition, respectively. More recently, exhaust-driven turbochargers have been incorporated into the system connected to the internal combustion engine to improve the power output and overall efficiency of engine. 
         [0003]    Turbochargers are generally incorporated to increase engine performance. In such applications, turbochargers often require control of their speed (the RPMs at which the turbine or compressor wheel rotates) so that either compressor surge or over speed does not occur. Typically, turbo speed control is accomplished by valves, levers and/or actuated devices that bypass exhaust gas around the turbine housed in the turbine section of the turbocharger. These types of controls include several moving parts that can wear over the life of the turbocharger and ultimately wear out. 
         [0004]    There is a need to continue to improve the exhaust-driven turbochargers, including the efficiency, power, and control thereof, in particular the turbo speed control. 
       SUMMARY 
       [0005]    In one aspect, turbochargers are disclosed herein that can replace or augment the turbo speed control previously existing, such as that accomplished by valves, levers, and actuated devices, by including a braking system for the compressor wheel utilizing Lenz&#39;s law. Here, a non-contacting, non-friction brake system is disclosed that includes one or more electromagnets positioned proximate to the compressor wheel, which is electrically conductive, and a control circuit electrically coupled to the one or more electromagnets to turn the one or more electromagnets on or off to provide braking action to the compressor wheel. When the electromagnet(s) are activated the magnetic field generated thereby brakes the compressor wheel and as a result reduces the turbo speed of the turbocharger. 
         [0006]    In another aspect, a system is disclosed that includes the turbocharger described in the preceding paragraphs and an internal combustion engine in fluid communication therewith. The system may also include an engine control unit that communicates with the control circuit of the brake system to turn the electromagnet(s) on or off as needed. In one embodiment, the control circuit receives commands from the engine control unit to activate the electromagnet(s) to brake the compressor wheel in coordination with at least one engine function to avoid a surge in the compressor section of the turbocharger or over revving of the turbine. 
         [0007]    In another aspect, methods for controlling the rotational speed of a turbocharger are disclosed. The method may include providing a turbocharger such as those described herein having electromagnet(s) and a control circuit, and operating the control circuit to allow electric current to flow to the one or more electromagnets to create a magnetic field to slow the rotations of the compressor wheel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a diagram including flow paths and flow directions of one embodiment of an internal combustion engine turbo system. 
           [0009]      FIG. 2  is a side, perspective view of one embodiment of a turbocharger. 
           [0010]      FIG. 3  is an end, perspective, partially assembled view of the turbocharger of  FIG. 2 . 
           [0011]      FIG. 4  is a longitudinal cross-sectional view of the turbocharger of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The following detailed description will illustrate the general principles of the invention, examples of which are additionally illustrated in the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
         [0013]      FIG. 1  illustrates one embodiment of an internal combustion engine turbo system, generally designated  100 . The turbo system  100  includes the following components in controlling the operating parameters of a turbocharger: an exhaust-driven turbocharger  102  having a turbine section  104  that includes a housing  112  having an inlet opening  113  and an exhaust outlet  114  and a compressor section  106  that includes a housing  116  having an ambient air inlet  118  and a discharge opening  119 . Housed within housing  112  of the turbine section  104  is a turbine wheel  124  that harnesses and converts exhaust energy into mechanical work through a common shaft  125  to turn a compressor wheel  126  that ingests air from an air induction system  150 , compresses it and feeds it at higher operating pressures into the engine inlet  162  of the internal combustion engine  160 . 
         [0014]    Still referring to  FIG. 1 , the compressor section  106  of the turbocharger  102  is in fluid communication with various parts of the system as follows: (1) the ambient air inlet  118  of the compressor section  106  is in fluid communication with the air induction system  150  and, optionally, return passages  138  from a compressor bypass valve  140 ; and (2) the discharge opening  119  is in fluid communication with the intake manifold of the internal combustion engine  160 . The intake manifold is represented by passageway  152 , engine inlet  162 , and intake valves contained therein (not shown). The turbine section  104  of the turbocharger  102  is in fluid communication with other parts of the system as follows: (1) the exhaust inlet  113  is in fluid communication with an exhaust manifold of the internal combustion engine; and (2) the exhaust outlet  114  is in fluid communication with passage  174  (also referred to as the exhaust line) exhausting to a catalytic converter  176 . The exhaust manifold is represented in  FIG. 1  by engine exhaust  164  and passageway  172 . Additionally, a turbine bypass valve  130 , commonly referred to as a wastegate, may be present. The turbine bypass valve  130  may be in fluid communication with a source of fluid to operate an actuator, such as actuator  134  in  FIG. 2 , that controls the opening and closing of the bypass valve  130 . When the bypass valve  130  is opened, wasted exhaust gas from the internal combustion engine  160  bypasses the turbine section  104  of the turbocharger  102  by being diverted through the bypass valve  130  and flowing directly to the exhaust line  174 . As such the turbine bypass valve  130  controls the amount of exhaust gas entering the turbine section  104  of the turbocharger  102 . 
         [0015]    Now referring to  FIGS. 2-4 , one embodiment of the turbocharger  102  is shown. As discussed above, the turbocharger  102  has a turbine section  104  and a compressor section  106 , both having respective housings  112 ,  116 . As illustrated in  FIGS. 3 and 4 , an electrically conductive compressor wheel  126  is enclosed within housing  116  of the compressor section  106 . The electrically conductive compressor wheel  126  is connected to the turbine  124 , enclosed within housing  112  of the turbine section  104 , by a common shaft  125 . Here, the added feature is a braking system that includes one or more electromagnets  128  positioned proximate to the compressor wheel  126 , and a control circuit  120  electrically coupled to the one or more electromagnets  128 , for example by wires, cables, and/or electrical connectors  122 , to turn the one or more electromagnets  128  on or off to provide braking action to the compressor wheel  126 . The electromagnets  128 , when on (i.e., activated), create a magnetic field that will slow down the electrically conductive compressor wheel  126  per Lenz&#39;s law. Accordingly, the electromagnets  128  act as a non-contact, non-friction brake to control the rotational speed of the compressor wheel  126  and hence the common shaft  125  and the attached turbine  124 . 
         [0016]    As seen in  FIGS. 2 and 4 , the control circuit  120  may independently control the electromagnets  128  to provide the braking action to the compressor wheel  126  or may be electrically coupled to an engine&#39;s engine control unit  166 , from which the control circuit  120  will receive commands or signals directing the operations of the control circuit. The engine control unit  166  can send signals to control circuit  120  to activate the electromagnets  128  under an engine condition likely to cause a surge of the compressor wheel  126  or under an engine condition that would over rev the turbine, thereby avoiding the surge or the over rev. Similarly, the engine control unit  166  can send signals to control circuit  120  to de-activate the electromagnets  128  under selected engine conditions when boost is demanded, for example, rapid vehicle acceleration. 
         [0017]    As seen in  FIGS. 3 and 4 , the one or more electromagnets  128  are positioned proximate the compressor wheel  126  at a location between the ambient air inlet  118  and a side of the compressor wheel  180  facing the ambient air inlet  118 . The electromagnets may be embedded in a surface  117  of the housing  116  enclosing the compressor wheel  126 . In another embodiment, the electromagnets  128  may be mounted to a surface, such as surface  117 , of housing  116  by any means. Also, the electromagnets  128  may be positioned more proximal to an edge  182  of the compressor wheel  126  defining the compressor wheel&#39;s outer diameter than a bore  184  defining the compressor wheel&#39;s inner diameter, and may be mounted or embedded equally distant from one another in a concentric arrangement about the central longitudinal axis A of the turbocharger. 
         [0018]    In one embodiment, the electromagnets  128  may be composed of an iron core with coils of wire wound around the core. The electromagnets provide the ability to control the strength of the magnetic flux density, the polarity of the field, and the shape of the field. The strength of the magnetic flux density is controlled by the magnitude of the current flowing in the coil, the polarity of the field is determined by the direction of the current flow, and the shape of the field is determined by the shape of the iron core around which the coil is wound. Additionally, the braking system may be controlled and/or adjusted by changing the number of electromagnets, their spacing, orientation, and location relative to the compressor wheel. 
         [0019]    The braking system in the turbocharger  102  has many benefits over conventional methods of turbine speed control, especially over by-pass systems using valves, levers and actuators. One benefit is the utilization of the magnetic fields created by the electromagnets in that the electromagnets act very fast to provide braking, which reduces response time and allow increased turbo performance. Accordingly, the turbo speed (surge) safety margins can be reduced due to the instantaneous turbo speed braking action. Another benefit is that the braking system has no moving parts other than the compressor wheel, which was already present. The electromagnetic braking system provides the additional benefit of being a variable controlled system by electronically controlling the strength of the magnetic field. This proportional braking provides greater turbo speed control by applying only the minimum braking required to maintain proper turbine/compressor wheel speed. 
         [0020]    As discussed above, the braking system can avoid surge or over revving, which could result in catastrophic failure of the turbocharger. This in turn would prevent engine catastrophic damage from the engine ingesting debris from the turbocharger failure. 
         [0021]    Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention which is defined in the appended claims.