Abstract:
An engine with cylinder deactivation (Displacement on Demand or DOD™) includes standard (STD) cylinders which are not deactivated and DOD cylinders which can be deactivated by closing their intake and exhaust valves and shutting off their fuel supply. To provide smooth transitions, the STD and DOD cylinders form separate groups each supplied with charge air through one or more separate throttles. When switching to DOD operation, the throttles are oppositely actuated to cut out the DOD cylinders and maintain torque in the active cylinders prior to deactivation of the cylinder valves. When returning to STD operation, the valves are reactivated before oppositely actuating the throttles to enable full cylinder operation. In DOD operation, a small supercharger may be operated to boost torque of the operating STD cylinders and thus increase the DOD operating range.

Description:
TECHNICAL FIELD 
     This invention relates to automotive engines with cylinder deactivation and to improved means and methods for operation of such engines. 
     BACKGROUND OF THE INVENTION 
     Cylinder deactivation (also called Displacement on Demand or DOD™), generally involves deactivating the intake and exhaust valves of up to half of the cylinders of a vehicle engine. Simultaneously, fuel flow to those cylinders is cut off, at the same time increasing air and fuel supplied to the remaining engine cylinders, which continue to operate and provide power for driving the vehicle. During the changeover, a torque bump or sag may be noticeable to the vehicle operator under at least certain conditions of operation of the engine. 
     In the development of automotive engines, DOD is of current interest for providing engine operation with higher efficiency during highway cruising and at lower speeds and loads. However, it is desired to provide smooth transitions between standard (STD) full cylinder operation and DOD (cylinder deactivation) operation, which will make the changeover essentially unnoticeable to the vehicle operator. In addition, it is desired to provide an increase in engine torque output during cylinder deactivation operation on less then all the engine cylinders in order to permit continued DOD operation when the vehicle operator calls for a moderate torque increase, or operation at a higher speed within the capabilities of the engine. 
     SUMMARY OF THE INVENTION 
     The present invention provides improved means and operating methods for use in obtaining improvements in DOD operation. To avoid a noticeable change in engine torque during changeover to and from DOD operation, the present invention divides the engine cylinders into two or more groups, one including DOD cylinders to be deactivated when efficient running at partial engine power is desired and another including STD cylinders to remain activated and powering the engine when the DOD cylinders of the first group are deactivated. 
     The separate groups of cylinders are provided with separate manifold passages or ports so that one or more separate throttles may be provided for controlling the operation of each cylinder group. A control is provided for selectively actuating the throttles to smoothly control the changeover of airflow before cylinder valve deactivation and after cylinder valve reactivation. During the changeover processes, the throttles are controlled to concurrently and progressively close the throttles of one group while opening further the throttles of the other group in order to maintain constant torque output during the full changeover in either direction. Deactivation of the engine valves of the deactivated DOD cylinders thus occurs after the throttle adjustments have been made, and reactivation of the engine valves occurs before readjustment of the throttles to provide full engine cylinder activation. 
     In a further feature of the invention, the engine is provided with a small boost compressor or supercharger that is connected for use during cylinder deactivation on only the STD cylinders that remain in operation. The supercharger is preferably operated only when the operating cylinders are running near their maximum load or torque condition so that the boost, or increased cylinder pressure, provided by the supercharger produces extra power in the operating cylinders. This provides additional performance from the engine while in DOD operation without requiring switchover to operation of all the engine cylinders. This will provide increased efficiency with savings in fuel cost by extending the range of engine operation during cylinder deactivation. In addition, the transitions between full cylinder operation and cylinder deactivation in both directions will be smooth with throttle coordination control and boost coordination control. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a transverse cross-sectional view of an engine including features in accordance with the invention; 
         FIG. 2  is a schematic view of the engine air system including individual cylinder throttles and a supercharger for supplemental boost during cylinder deactivation; 
         FIG. 3  is an end view of an alternative embodiment of V-type engine having separate intake manifolds and a turbocharger boost system according to the invention; and 
         FIGS. 4-6  are schematic views of alternative cylinder arrangements showing various cylinder groups which may be selected for each arrangement. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIG. 1  of the drawings, numeral  10  generally indicates a V8 automotive internal combustion engine equipped for operation on cylinder deactivation, also called Displacement on Demand or DOD™, the engine further including features according to the present invention. Engine  10  conventionally includes a cylinder block  12  including two banks of cylinders  14 ,  15  closed at their outer ends by cylinder heads  16 . Pistons  18 , reciprocating in the cylinders, act through connecting rods  20  to rotate a crankshaft  22 , conventionally supported in the cylinder block. 
     A centrally-mounted camshaft  24  actuates both conventional valve lifters  26  and so called switching valve lifters  28 . These act through push rods  30  and rocker arms  32  to actuate intake and exhaust valves  34 ,  36  carried in the engine cylinder heads  16 . The conventional hydraulic lifters  26  actuate intake and exhaust valves  34 ,  36  of the standard (STD) cylinders  14 . The switching lifters  28  are hydraulically actuated, in known manner through electrically controlled solenoid valves  38 , to operate the intake and exhaust valves of the deactivation or DOD cylinders  15  to either operate normally in STD engine operation or to deactivate the valves, which remain closed in DOD operation. 
     The cylinder heads  16  further include exhaust ports  40  which connect with exhaust manifolds, not shown, to carry away exhaust products from the cylinders  14 ,  15 . Cylinder head intake ports  42  deliver intake air from an intake manifold  44  to the engine cylinders  14 ,  15  upon opening of the intake valves  34 . Fuel injectors  46  also supply fuel to the intake ports for admission to the cylinders. 
     Referring also to  FIG. 2 , the intake manifold  44  includes an intake opening  48  into a plenum which feeds individual STD and DOD intake runners  50 ,  51  that connect with the cylinder head intake ports  42 . In accordance with the invention, the intake runners  50 ,  51  are controlled by individual throttles  52 ,  54  (FIG.  2 ). The throttles are arranged in separate groups for controlling air flow respectively to the DOD cylinders  15 , which may be deactivated, and the conventional cylinders  14 , which remain always activated during engine operation. The throttles  52 ,  54  may be actuated in any suitable manner such as, for example, by lever arms  56 ,  58  ( FIG. 1 ) which may be connected with separate linkages, not shown, for operation by a control  59  in a manner to be subsequently described. 
     In accordance with the invention, engine  10  may be additionally provided with a supplemental supercharger  60  shown in FIG.  2 . Supercharger  60  is selectively operable during DOD operation to pressurize air to the STD cylinders  14  in a manner to be subsequently described. 
     Referring particularly to  FIG. 2  of the drawings, there is shown one possible embodiment of an air system  62  for use with the engine of FIG.  1  and in which like numerals indicate components corresponding to those of the embodiment of FIG.  1 . 
     Intake air system  62  includes an air filter  64 , intake conduit  66 , intake throttle  68  and the intake manifold  44  into which intake air is inducted or delivered. For air delivery from the intake manifold  44 , the cylinders are divided into first and second cylinder groups. The first cylinder group includes STD or non-deactivating cylinders  14  which receive air from the manifold  44  through intake runners  50  and individual throttles  52 . The second cylinder group includes deactivating or DOD cylinders  15  which receive air from the manifold through intake runners  51  and throttles  54 . 
     The air system  62  further includes exhaust ports  70 , which connect with common exhaust manifolds  72  cross-connected at their ends by a crossover pipe  74 . Thus, the exhaust gas from all the cylinders passes through the exhaust manifold system and out through an exhaust pipe  76 . 
     In accordance with the invention, the air system  62  optionally additionally includes a supercharger  60 . The supercharger may be of any suitable type and may be driven in any desired fashion, such as electrically, mechanically, or hydraulically.  FIG. 2  illustrates, as an example, an exhaust driven turbocharger  60 . As is known in the art, the turbocharger  60  includes an exhaust turbine  78  and a centrifugal compressor  80  connected by a common shaft, not shown. 
     To operate the turbocharger  60 , the exhaust manifold outlet is provided with an exhaust shutoff valve  82 . A bypass passage  84  extends around the shutoff valve  82  and includes a bypass shutoff valve  86 . The bypass passage  84  connects with the exhaust turbine  78  of the turbocharger to direct exhaust gases through the turbine for driving the compressor  80 . Similarly, the air intake conduit  66  includes the air intake throttle  68  and a bypass conduit  88  which extends around the intake throttle  68 . Conduit  88  connects with the compressor  80  to deliver air through the compressor from the air filter  64  directly to the intake manifold  44  downstream of the intake throttle  68 . A bypass valve or throttle  90  in the bypass conduit  88  controls the delivery of air to the turbocharger compressor  80 . 
     Following is an example of the operation of the engine embodiment of  FIG. 1  incorporating the air system  62  shown in FIG.  2 . In this example, it is assumed that the engine has been started and is running on the full complement of eight cylinders, including both the first (STD) and second (DOD) cylinder groups containing cylinders  14  and  15 , respectively. However, it should be understood that it may be practical to start and initially operate the engine with the cylinders  15  of the second cylinder group deactivated. 
     With the engine operating conventionally on all cylinders, the bypass valves  86  and  90  will be closed and the exhaust shutoff valve  82  and inlet throttle  68  will be fully open, allowing engine operation without operation of the supercharger  60 . In this conventional operating mode, the individual intake throttles  52  and  54  of the first and second cylinder groups respectively will be operated together to provide the desired amount of air flow equally to all the engine cylinders  14 ,  15 , fuel being injected in the conventional manner into the intake ports  42  for burning in the engine cylinders to provide power. 
     When conditions exist in which it is desired to switch to the cylinder deactivation or DOD mode, the throttles  52 ,  54  will be adjusted concurrently and progressively at a controlled rate by closing the throttles  54  of the second (DOD) cylinder group and correspondingly increasing the openings of the throttles  52  of the first (STD) cylinder group, which is not to be deactivated. As the throttles  52  of the first group are opened farther, the throttles  54  of the second DOD group of cylinders are closed until the engine is operating entirely on the cylinders of the first STD group. During this changeover, engine torque continues to be controlled to the vehicle operator&#39;s request as determined by the position of the accelerator pedal. 
     After the throttles  54  of the second group are closed, the switching lifters  28  are actuated to deactivate the valves of the cylinders  15  of the second DOD group. Because actuation of the throttles is coordinated to provide a constant torque, the changeover to cylinder deactivation is smooth and unnoticeable to the vehicle operator while actual deactivation of the engine valves occurs only after the throttles of the deactivated cylinders are closed. 
     While the cylinders  15  of the second group remain deactivated, the engine torque requirement may be increased near to a value that would cause a switch back to full engine operation in a standard operating mode. To defer the switch, the engine supercharger may be operated to increase cylinder pressure in the STD cylinders  14 . This will allow an increase in engine power sufficient to allow continued operation at a slightly higher level without requiring switchover to the standard operating mode. 
     Operation of the supercharger  60  is determined by the type of unit being used. In the illustrated embodiment, the turbocharger  60  is operated by opening the bypass valves  86  and  90  and closing the exhaust shutoff valve  82  and the intake throttle  68 . Exhaust gas is then directed through the bypass conduit  84  and turbine  78  to drive the turbocharger while intake air is directed through the bypass conduit  88  and the compressor  80 , which increases the air pressure delivered to the intake manifold  44 . The pressurized intake air in the manifold is delivered only to the operating STD cylinders  14  of the first group, since the cylinders  15  of the second group have been deactivated so that no air is delivered to these cylinders. When the requirement for extra engine torque is no longer needed, the turbocharger is deactivated by returning the control valves  80 ,  86 ,  68 ,  90  to their original positions and the engine operates normally in the DOD deactivation mode. 
     When the vehicle operator actuates the accelerator pedal to call for additional engine torque and a return to full cylinder STD operation is required, the switching valve lifters  28  of the deactivated cylinders will first be operated to again activate the valves in the second group of cylinders  15 . Then the throttles  52 ,  54  of the first and second cylinder groups will be actuated concurrently and progressively at a predetermined rate to return to their original positions. This requires that the throttles  54  of the second cylinder group be opened while the throttles  52  of the first cylinder group are correspondingly partially closed until both sets of throttles are positioned properly to provide equal air charges to all the operating cylinders of the engine. With this mode of changeover from DOD cylinder deactivation operation to STD all cylinder operation, the torque is again controlled during adjustment of the cylinder throttles so that there is no discontinuity or bump in the engine torque curve and the change in operation is unnoticeable to the vehicle operator. 
     While the embodiment of  FIGS. 1 and 2  contemplates the use of individual cylinder throttles in the manifold runners or intake ports of each of the cylinders, it should be understood that alternative arrangements of cylinder throttling may equally well be utilized. For example, suitable manifolding may be provided so that a single throttle is utilized for each of the two cylinder groups and each throttle controls the air flow through manifolding to all the cylinders of its respective group. 
     Furthermore, the turbocharger form of supercharger illustrated in  FIG. 2  may be replaced if desired by any other suitable form of boost device, such as an electrically driven air pump or compressor or a mechanically driven positive displacement air pump, as examples. Additional known forms of supercharging devices may equally well be substituted as they may be suited to a particular engine application. It is intended, however, that the supercharger or boost device applied should be used only when higher torque is needed during DOD operation with cylinders deactivated. Thus, the time in the DOD cylinder mode may be extended and the efficiencies of operation of this mode may be realized over a larger portion of the engine operating period. 
     Referring now to  FIG. 3  of the drawings, an alternative embodiment of V engine arrangement is illustrated, generally indicated by numeral  92 . Engine  92  includes the usual cylinder block, heads and other equipment of the main engine body  94  but is equipped with dual air intake manifolds  96 ,  98  positioned one above the other and each having an inlet throttle  100 ,  102  respectively. 
     Intake manifold  96  has intake runners  104  connecting with a first group of cylinders, not shown, which are STD cylinders not capable of being deactivated. Intake manifold  98  has intake runners  106  which connect with a second cylinder group of DOD deactivation cylinders, not shown. 
     Engine  92  also includes exhaust manifolds  108  connected by a crossover pipe  110  to feed a turbocharger  112  driven by exhaust gas. The turbocharger  112  draws in air through an intake tube  113  and delivers pressurized air through a conduit  114  to the intake manifold  96  for delivery to the STD cylinders when needed in the deactivation mode. In operation, a shutoff valve  116  in an exhaust outlet pipe  118  redirects exhaust gas from the exhaust outlet pipe for driving the turbocharger. 
     In a standard operating mode, the valve  116  is open, deactivating the turbocharger, and the throttles  100 ,  102  are operated together to provide equal amounts of air to each of the engine cylinders, all of which are supplying power. When switching to cylinder deactivation, the throttles are moved in opposite directions concurrently and progressively until the DOD throttle  102  is completely closed and the STD throttle  100  is opened further in order to smoothly transfer power from all eight cylinders to the four cylinders continuing to operate in the DOD mode. In this regard, operation of the throttles is similar to that described relative to the engine of  FIGS. 1 and 2 , except that only one throttle is utilized for each cylinder group. 
     In like manner, operation of the engine turbocharger is reserved for the deactivation mode under conditions when additional torque is needed. This is supplied by slightly boosting the cylinder air charge in manifold  96  connected with the first group of cylinders, which remain operational during deactivation of the second group of cylinders. 
     Referring now to  FIGS. 4-6 , there are shown three examples of engine cylinder arrangements for deactivation. The embodiment of engine  92  is schematically illustrated in  FIG. 4  wherein two manifolds  96 ,  98  controlled by two throttles  100 ,  102  are connected to respectively control a first group of cylinders  120  and a second group of DOD cylinders  122  provided in a V8 engine. 
       FIG. 5  schematically illustrates an alternative V8 engine arrangement wherein four separate manifolds  126 - 129  are controlled respectively by throttles  130 - 133  and feed air to four separate cylinder groups  134 ,  135 ,  136 ,  137 . In this arrangement, STD cylinder groups  134  and  135  remain operational under all engine conditions and are controlled by their separate throttles to provide equal amounts of power. 
     DOD cylinders  136  are controlled by throttle  132  and DOD cylinders  137  are controlled by throttle  133  to provide for two modes of cylinder deactivation. The cylinders of group  137  may first be deactivated in order to provide operation of the engine on six cylinders, including the cylinders of group  136 . Then, if further cylinder deactivation is desired, the cylinders of group  136  are also deactivated, leaving only the cylinders of groups  134  and  135  operational. Thus, the engine in  FIG. 5  is capable of two separate deactivation steps in addition to the normal full operational mode. 
       FIG. 6  illustrates a V6 engine arrangement wherein manifolds  138  and  139  are controlled respectively by throttles  140  and  141 . Manifold  138  connects with a first group of three STD cylinders  142  located in one bank of the V6 engine while manifold  139  connects with a second group of three DOD cylinders  143  located in an opposite bank of the engine. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.