Abstract:
A bypass ( 26 ) around a charge air cooler ( 20 ) and a control system ( 28 ) for apportioning the amounts of charge air passing through the bypass and the charge air cooler.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to internal combustion engines in motor vehicles, especially to an engine intake system that delivers charge air and a method for charge air temperature control in a diesel engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     The diesel engine industry is facing increasingly strict limits on certain undesirable constituents in diesel engine exhaust, such as oxides of nitrogen (NO x ) and particulate matter (PM) emissions. After-treatment devices such as diesel particulate filters (DPF&#39;s) and NO x  adsorbers are potential solutions for reducing PM and NO x  emissions by physically trapping them. Alternative diesel combustion processes such as HCCI are also potential solutions because of their capability to limit formation of undesirable constituents.  
         [0003]     An important factor in the use of such potential solutions is the ability to control the temperature of the air that enters the engine cylinders for combustion. Diesel engines are today typically turbocharged, and that consideration lends added importance to the control of the temperature of the charge air that a turbocharger creates to impart boost to an engine. When a diesel engine is equipped with a turbocharger, cooling of the charge air is needed when the engine is being operated in certain ways. Hence, the intake system of a turbocharged diesel engine contains some form of heat exchanger disposed between the turbocharger compressor and the engine intake manifold. Today that heat exchanger is frequently referred to as a charge air cooler.  
         [0004]     Even in the absence of exhaust emission considerations, the ability to control charge air temperature independently of the engine coolant temperature is an important consideration in engine and vehicle operation.  
         [0005]     For many years many large diesel-powered vehicles like heavy trucks and highway tractors have had shutters in front of their engine compartment opening. When the shutters are maximally open, they present minimal restriction to airflow entering the engine compartment through the radiator and charge air cooler. When they are substantially closed, they present maximal restriction to the entering airflow.  
         [0006]     Because the radiator of the engine cooling system and the heat exchanger for cooling the charge air are disposed substantially directly behind the shutters when a vehicle is so equipped, shutters have historically served to control the airflow through the radiator and charge air heat exchanger hence controlling engine coolant and charge air temperature.  
         [0007]     One form of charge air cooler occupies some of the space in the engine compartment opening that is not occupied by the radiator. When a vehicle that has such a charge air cooler is also equipped with shutters, the opening and closing of the shutters modulates not only the airflow through the radiator, but also the airflow through the charge air cooler. Charge air from the turbocharger is piped to and through the charge air cooler, and then piped to the engine intake manifold. The temperature of the charge air is controlled to some extent by the shutters which, as they open and close, modulate cooling air entering the engine compartment through the front-end engine compartment opening and passing across cooling fins of the charge air cooler.  
         [0008]     The shutters are open at various times such as when the cab air conditioning is turned on to allow maximum outside airflow through the air conditioning condenser which is disposed in the engine compartment opening, possibly fully or partially overlapping the radiator. Certain engine coolant temperature conditions also call for the shutters be open. Conditions like these may result in the charge air temperature being less than optimal for best engine operation during such conditions.  
         [0009]     The use of shutters for control of charge air temperature is often desired by users of large diesel-powered vehicles because they can improve operating performance. This is borne out by the fact that certain customers continue to order shutters on new trucks. Shutters that cover only the charge air cooler, and not the engine cooling system radiator, have made possible an increase in the average temperature in the interior of a diesel-powered vehicle during cold weather operation. This is especially true in school buses. Further increases in avergae interior temperature would be desirable, particularly if they could be accomplished without the use of shutters.  
         [0010]     For various reasons, including regulations that are expected to become effective in the not too distant future, cooling systems of large diesel powered vehicle must have significantly larger cooling capacity. This means that more front end engine compartment space must be allocated to cooling system components. That in turn infringes on space that would be occupied by shutters. Consequently, certain customers of new vehciles are ordering shutters that cover only the charge air cooler portion of the opening. The effectiveness of such shutters however depends on how well they are sealed to the charge air cooler.  
         [0011]     For reasons such as these, some existing vehicle design packages may require major front end redesign in order to accommodate the needs of customers who desire shutters. That involves outlays not just for design services, but also for new tooling of various parts, and the costs incurred will have to be passed on, at least in part, to customers through price increases, an undesirable consequence in a competitive marketplace.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention is directed toward a novel system and method for enabling charge air temperature to be controlled without the use of shutters, thereby avoiding not only the cost of the shutters but also the need for major front-end redesign in existing vehicles. This will continue to make the benefit of charge air temperature control available to customers who want it, but without incurring the expense of shutters just for that purpose.  
         [0013]     The invention can be readily adapted to the requirements of virtually any engine and vehicle model combination to obtain the added performance benefits to charge air temperature control heretofore attempted by using shutters.  
         [0014]     Briefly, the invention is embodied by providing a bypass around the charge air cooler and a control system for apportioning the amounts of charge air passing through the bypass and the charge air cooler.  
         [0015]     The disclosed control system comprises a valve, preferably a deflector valve having a deflector that is selectively positioned to control the relative amounts of air through the charge air cooler and the bypass, for blending some amount of uncooled charge air that has passed through the bypass with some amount of charge air that has been cooled by virtue of having passed through the charge air cooler. The relative amounts blended to form the charge air entering an engine intake manifold may span large ranges. At one extreme, essentially 0% uncooled air and 100% cooled air, and at the opposite extreme, 100% uncooled air and 0% cooled air.  
         [0016]     The invention provides improved temperature control in various ways. Unlike the effect of opening the shutters, the invention allows the charge air temperature entering the engine combustion chambers to remain substantially unaffected by operation of the air conditioning system. Temperature can be optimized for prevailing engine operating conditions largely independent of the cooling load imposed on the radiator. At cold-start, temperature can be controlled to provide faster engine warm-up. The ability to better control temperature provides benefits for engine and vehicle performance and for exhaust after-treatment control.  
         [0017]     Specific implementations of the invention may be made in various ways. The bypass can be packaged with the charge air cooler to facilitate assembly procedures. It can be located remote from the charge air cooler but operatively associated with the charge air cooler by fittings, preferably “Y-fittings”, connecting into pipes leading to and from the charge air cooler. A deflector valve can be incorporated internally of one of the Y-fittings for manufacturing and assembly synergy, and an actuator for operating the valve can be mounted on the exterior of the Y-fitting.  
         [0018]     Control is accomplished using certain sensors that may already be available in the base vehicle and engine to provide data to an electronic controller, such as an existing ESC (engine system controller). For example, a thermistor disposed to sense charge air temperture into an engine intake manifold indicates that temperature to the ESC. The ESC comprises an algorithm that processes the temperature data to develop an output for control of the deflector valve via the valve actuator.  
         [0019]     The valve actuator may be an air cylinder. Air pressure at an existing air manifold is modulated to the air cylinder by an air solenoid in accordance with the output of the ESC to properly position the deflector valve. A pulse width modulated motor may create a better blend-air effect than an air valve.  
         [0020]     Generally speaking, the present invention relates to engines, to their intake systems, and to methods involving control of charge air temperature.  
         [0021]     One generic aspect of the present invention relates to a motor vehicle comprising an internal combustion engine, a drivetrain, and wheels for propelling the vehicle on land, an intake system for creating charge air and delivering the charge air to an engine intake manifold comprising a charge air cooler, a bypass around the charge air cooler, and a control system for apportioning the charge air flow through the charge air cooler and the bypass.  
         [0022]     Another generic aspect of the invention relates to an internal combustion engine comprising an air intake system including a turbocharger for creating and delivering charge air to engine combustion chambers, wherein the air intake system further comprises a charge air cooler for cooling charge air created by the turbocharger before the charge air enters the combustion chambers, a bypass for shunting charge air from the turbocharger around the charge air cooler, and a control system for apportioning the charge air flow through the charge air cooler and the bypass.  
         [0023]     Still another generic aspect of the invention relates to a method for controlling charge air cooling in an internal combustion engine having an air intake system including a turbocharger for creating and delivering charge air to engine combustion chambers wherein the air intake system further comprises a charge air cooler for cooling charge air created by the turbocharger before the charge air enters the combustion chambers. The method comprises shunting charge air from the turbocharger through a bypass around the charge air cooler, and apportioning the charge air flow through the charge air cooler and the bypass.  
         [0024]     The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  is a perspective view of a portion of the contents of an engine compartment in a large motor vehicle, such as a heavy truck, relevant to an explanation of principles of the invention.  
         [0026]      FIG. 2  is an enlarged view in circle  2  in  FIG. 1 .  
         [0027]      FIG. 3  is an enlarged view in circle  3  in  FIG. 1  with a portion broken away for illustrative purposes.  
         [0028]      FIG. 4  is a schematic diagram relevant to certain principles of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]      FIG. 1  shows contents of an engine compartment  10  of a heavy truck comprising a diesel engine  12  having an intake manifold  14  that is part of an air intake system  16 . Additional components of air intake system  16  include a turbocharger  18  and a charge air cooler  20 .  
         [0030]     Turbocharger  18  is conventional and comprises a compressor operated by engine exhaust to draw ambient air into the intake system and create charge air that provides boost for engine  12 . For removing at least some of the heat of compression from the charge air, the charge air can pass through charge air cooler  20  before it is delivered to intake manifold  14 . Charge air cooler  20  is an air-to-air type heat exchanger, meaning one that utilizes air that passes through an air intake opening  22  into engine compartment  10  at the front of the truck to cool the charge air. A radiator  24  that cools engine coolant is also disposed in a portion of the engine compartment opening not occupied by charge air cooler  20 . An air conditioning condenser (not shown) may also be present at opening  22  in front of the radiator  24  for cooling refrigerant in the air conditioning system. Certain customers may order new vehicles equipped with shutters that are only over the charge air cooler  20  because they believe that shutters over the radiator make little or no difference in helping the engine produce more heat on cold days. With the present invention, shutters over the charge air cooler become unnecessary, and that is the preferred configuration when the present invention is practiced.  
         [0031]     In accordance with principles of the invention, a bypass  26  is provided around charge air cooler  20 , and a control system  28  (to be described with reference to  FIG. 4 ) serves to apportion the charge air flow through charge air cooler  20  and bypass  26 .  
         [0032]     Bypass  26  comprises a conduit  30  disposed within engine compartment  10  rearward of charge air cooler  20 . A supply conduit  32  serves to supply charge air from turbocharger  18  to an inlet  34  of charge air cooler  20 . A delivery conduit  36  serves to deliver charge air from an outlet  38  of charge air cooler  20  to intake manifold  14 , fitting to an inlet  40  of manifold  14 .  
         [0033]     An inlet fitting  42  provides for an inlet of bypass conduit  30  to have communication with supply conduit  32 . An outlet fitting  44  provides for an outlet of bypass conduit  30  to have communication with delivery conduit  36 .  
         [0034]     Each fitting  42 ,  44  is preferably a Y-type fitting, meaning that it has two ports arranged at an acute angle with the flows through these two ports being in the same direction. In the case of fitting  42 , the two flows are out of the fitting while in the case of fitting  44 , they are into the fitting.  
         [0035]      FIG. 3  shows a control element  46  disposed within fitting  44  to comprise a diverter that can swing about an axis  48 . As portrayed by  FIG. 3 , the diverter can swing over a range  51  of positions between a position  46 A at least partially restricting flow from bypass conduit  30  and a position  46 B at least partially restricting flow from charge air cooler  20 . Position  46 A actually shows substantially complete obturation of the bypass while position  46 B shows substantially complete obturation of flow from charge air cooler  20 . In the medial position (solid line) neither incoming flow is significantly obstructed by the diverter.  
         [0036]     The diverter is selectively positioned over the range of swinging between positions  46 A and  46 B by an actuator  50  that is disposed on the exterior of fitting  44  and secured by any suitable means. Actuator  50  is a pulse width modulated electric motor providing movement of control element  46  in incremental steps to provide a blend air effect, or actuator  50  is as shown in the drawings an air cylinder whose linearly movable element is spring-biased in one direction. When air pressure is applied to an inlet port  52  of actuator  50 , the linearly movable element is displaced against the spring bias in an amount correlated with the applied air pressure. The movable element acts on a crank arm  54  that is externally attached to a shaft that extends into the inside of the fitting to turn the diverter. Consequently, the diverter is swung about axis  48  to an extent correlated with the air pressure applied to the actuator.  
         [0037]      FIG. 2  shows that air pressure for operating actuator  50  is obtained from a pressure source  56 , as modulated by an air solenoid  58 . The modulated air pressure to actuator  50  is supplied through a conduit  60 . While engine coolant temperature may not be used for control of the diverter, engine coolant temperature data as measured by a sensor  62  is transmitted through a connection  64  to an engine control system (ESC) module  66  of system  28  as shown in  FIG. 4 . Also, inlet air temperature as measured by a thermistor  70  in the delivery conduit  36  downstream of the diverter is transmitted through a connection  72  to the engine system controller (ESC) module  66 . ESC module  66  controls actuator  50  through a driver  68  that delivers current to actuator control  58 , which is the air solenoid when the actuator is an air cylinder. When the actuator is an electric motor, the driver delivers pulse width modulated current to the motor.  
         [0038]     When engine charge air inlet temperature, as sensed by thermistor  70 , is below a certain temperature, such as 180° F. for example, all the charge air could be conveyed through the bypass. When engine charge air inlet temperature is above a certain temperature, such as 185° F. for example, all the charge air could be conveyed through the charge air cooler.  
         [0039]     With control being provided by ESC module  66 , the temperature settings can be adjusted by suitable programming of ESC module  66  for regions or customer preference.  
         [0040]     The inventive system can provide faster engine warm-ups and accurately control temperature of charge air entering the engine, thus providing improved performance and emissions control over the use of shutters. The system will cycle to help maintain the engine charge air inlet temperature within the above range of 180° F.-185° F. or a range for optimum engine performance.  
         [0041]     While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention apply to all embodiments falling within the scope of the following claims.