Abstract:
A supercharged internal combustion engine embodying a construction for maintaining the desired supercharger pressure in the induction system and avoiding the objectionable noises that occur with conventional system wherein the bypass flow is all discharged into the induction system upstream of the supercharger. This is done by bypassing the intake air from the area between the supercharger and the combustion chamber to a point other than in said induction system an particularly to the engine exhaust system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to an intake air system for an internal combustion engine and more particularly to an improved pressure control arrangement for a supercharged internal combustion engine.  
           [0002]    In conjunction with engine design, it has been proposed to use some form of compressor or supercharger in the intake system so as to force more air into the combustion chamber to improve performance output. Various types of superchargers and/or turbochargers, generically called “superchargers” are utilized for this purpose. In conjunction with such systems, it has been the practice to provide an arrangement for relieving the pressure generated by the superchargers so that the full pressure is not introduced into the induction system under at least some running conditions.  
           [0003]    It has generally been the practice to reduce the pressure in the induction system downstream of the supercharger by utilizing a bypass valve that bypasses the air from the induction system downstream of the supercharger to a point in the induction system upstream of the supercharger. When this is done, however, the opening of the bypass valve causes a surge of air to flow into the induction system, which creates noise in the intake side. This can be objectionable to the operator.  
           [0004]    It is, therefore, a principal object to this invention to provide an improved pressure control arrangement for a supercharged internal combustion engine wherein pressure of control is accomplished without attendant noise during the time when pressure relief is occurring.  
           [0005]    It is a further object to this invention to provide an improved pressure relief system for a supercharged internal combustion engine.  
         SUMMARY OF THE INVENTION  
         [0006]    This invention is adapted to be embodied in a supercharged internal combustion engine having an induction system that includes a supercharger interposed between an air inlet device and the combustion chambers of the engine. A pressure relief system is provided having a bypass passageway interposed between the supercharger and the combustion chamber and which has a first branch having a pressure control valve therein for bypassing air from the supercharger back to the induction system between the air inlet device and the supercharger. In addition, there is provided a decompression device in the bypass passage for bypassing the intake air from the area between the supercharger and the combustion chamber to a point other than the induction system. The system is operated so that the flow through the bypass passage is initiated at least at the time the pressure relief valve is opened so as to reduce the pressure exerted in the intake system between the supercharger and the air inlet device. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0007]    [0007]FIG. 1 is a partially schematic view of an internal combustion engine constructed in accordance with an embodiment of the invention and showing two alternate discharge paths from the decompression valve.  
         [0008]    [0008]FIG. 2 is a graphical view showing the timing of the opening and closing of the pressure control and decompression valves. 
     
    
     DETAILED DESCRIPTION  
       [0009]    Referring now in detail to the drawings and initially to FIG. 1, an internal combustion engine constructed and operated in accordance with the embodiments of the invention is indicated generally by the reference numeral  11 . For the most part, the engine components are shown schematically because they can be of any type generally known or desired in the art.  
         [0010]    The engine  11  includes a main engine body  12  which may be comprised of a cylinder block, cylinder head, crankcase and the well known associated components. In the illustrated embodiment, the engine  11  is shown as an in-line four-cylinder type engine; however, the invention can be practiced with other types of engine constructions.  
         [0011]    An induction system, indicated generally by the reference numeral  13  is provided for the engine  11 . This induction system  13  includes an air inlet device  14  having an atmospheric air inlet opening  15  through which air is inducted as indicated by the air flow arrows A.  
         [0012]    A supercharger inlet pipe  16  forms a portion of the induction system and delivers the air from the air inlet device  14  to a supercharger, indicated schematically by the reference numeral  17 . This supercharger  17  may be of the type that is driven from the output shaft of the engine  11  and the drive therefore is indicated schematically by the phantom line  18 . Of course, other types of supercharger drives can be employed.  
         [0013]    An outlet passage  19  leads from the pressure side of the supercharger  17  to an intercooler, indicated generally by the reference numeral  21 . The intercooler  21 , in turn, discharges to a flow sensor  22 , which, in turn, discharges into a throttle, body  23  in which a flow controlling throttle valve is positioned. A suitable actuator  24  is provided for positioning the throttle valve of the throttle body  23 . This may be either a linkage system to an accelerator pedal or a “fly by the wire” type of control system.  
         [0014]    In turn, the throttle body  23  supplies air to a plenum chamber  25  of an intake manifold having individual runners  26  which extend to intake ports of the engine  11 .  
         [0015]    A suitable fuel supply is provided for introducing fuel to the engine  11  for mixture with the inducted air. This fuel supply system is shown schematically at  27  and can comprise either carburetors, fuel injectors or any other type of arrangement for supplying fuel. If fuel injectors are employed, they can be of the direct injection type or manifold injection.  
         [0016]    The charge, which is introduced to the combustion chambers of the engine  11 , is ignited by a suitable ignition system and the burnt exhaust gases are discharged to the atmosphere through an exhaust system, indicated generally by the reference numeral  28 .  
         [0017]    This exhaust system  28  is comprised of an exhaust manifold  29  having a discharge end  31  in which a catalyst bed of a suitable type  32  is provided. The flow of the exhaust gases is indicated by the arrow E and this also passes through a first silencer  33  forming an expansion chamber  34 . An additional silencing device or muffler  35  is positioned downstream of the expansion chamber  34 .  
         [0018]    It is to be understood that the construction of the engine  11  as thus far described is only intended to show the environment in which the invention can be practiced. As has been previously noted, the construction of the engine  11  at least in so far as the components thus far described may be considered to be of any known or conventional type.  
         [0019]    The invention, as should be apparent from the foregoing discussion, deals with the pressure control system for preventing too high a pressure from existing in the induction system downstream of the supercharger  17 . This comprises a pressure relief system, indicated generally by the reference numeral  36 , which communicates with the induction system in the conduit  19  at a point indicated at  37 .  
         [0020]    A bypass conduit  38  intersects the conduit  19  at this point. A pressure control valve, indicated generally by the reference numeral  39  communicates a portion  41  of the passage  38  back with the intake passage  16  when the bypass valve  39  is opened. Then, the bypass flow flows in the direction indicated by the dot dash arrows in FIG. 1.  
         [0021]    In addition to the bypass valve  39 , there is further provided a decompression valve  42  which communicates with the passage portion  41  and permits a bypass flow when opened in the direction indicated by the arrow  43  to a decompression manifold, indicated generally by the reference numeral  44  and which has branch portions  45  which communicate with each of the branch passages of the exhaust manifold  29 .  
         [0022]    The operation of the bypass valve  39  and the decompression valve  42  is controlled by an ECU, indicated generally by the reference numeral  46  and which may be the main ECU control for the engine. This ECU  46  receives input signals from the air flow or pressure sensor  22  and also from a throttle position sensor  47 , an intake manifold pressure sensor  48  and an engine speed sensor  49  so as to control servo-motors  51  and  52  associated with the bypass valve  39  and decompression valve  42 , respectively.  
         [0023]    As seen in FIG. 2, the control strategy of the ECU  46  is such that when pressure relief is required due to higher intake system pressure than required for good engine operation at the specific engine running conditions, the decompression valve  42  is opened at a time period T 3  which is preferably a short time period or simultaneously with the time of opening T 1  of the bypass valve  39 .  
         [0024]    By doing this, the pressure is relieved at least partially through the decompression manifold  44  into the exhaust system  28  so that any pressure pulse will be silenced by the silencing arrangement of the exhaust system  28  and not into the intake system where it could cause objectionable noise.  
         [0025]    The control strategy illustrated in the solid line view of FIG. 2 indicates that the decompression valve is closed at a time T 4  after the time interval T 0  and before the bypass valve is closed at the time T 2 . Since the initial pressure relief relieves the main pressure pulse and avoids the noise, it is not necessary to maintain the decompression valve open for a longer time period. Under other running conditions, as indicated by the broken line curves in FIG. 2, the bypass valve and decompression valve may be closed both at the same time. However, the decompression valve is never closed after the bypass valve is closed.  
         [0026]    In the solid line view of FIG. 1, the decompression valve discharges into the exhaust manifold  29 . However, the system also may be operated so as to cause the decompression gases to flow into the expansion chamber  34  and this alternate location is shown in phantom lines in FIG. 1 and the similar components identified by the same reference numerals with the suffix “a” added.  
         [0027]    Thus, from the foregoing description it should be readily apparent that the described construction provides a very effective way of maintaining the desired supercharger pressure in the induction system and avoiding the objectionable noises that occur with conventional system wherein the bypass flow is all discharged into the induction system upstream of the supercharger. Of course, the foregoing description is that of preferred embodiments of the invention and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.