Abstract:
An engine control system transitions between activated and deactivated modes in a vehicle equipped with a manual transmission. The engine control system includes a clutch plate position sensor and a shifter shaft position sensor in communication with a controller. The controller determines if conditions to increase or reduce the number of active cylinders based on data collected from the position sensors, engine speed, and manifold absolute pressure. Prediction of the driver&#39;s next movements is the basis of the control. The sensors provide the history, averages, acceleration data, and velocity data, which lead to the driver&#39;s intent.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to internal combustion engines and, more particularly, to control systems that command transitions in a displacement on demand engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     Some internal combustion engines include engine control systems that deactivate cylinders under low load situations. For example, an eight cylinder can be operated using four cylinders to improve fuel economy by reducing pumping losses. This process is generally referred to as displacement on demand or DOD. Operation using all of the engine cylinders is referred to as an activated mode. A deactivated mode refers to operation using less than all of the cylinders of the engine (one or more cylinders not active).  
         [0003]     To smoothly transition between the activated and deactivated modes, the internal combustion engine must produce sufficient drive torque with a minimum of disturbances. Otherwise, the transition will not be transparent to the driver. In other words, excess torque will cause engine surge and insufficient torque will cause engine sag, which degrades the driving experience.  
         [0004]     Conventional engine control systems have been somewhat successful in transitioning between the activated and deactivated modes in vehicles equipped with automatic transmissions. Torque converter slip algorithms are used to help smooth the transitions between DOD modes.  
         [0005]     Engine control of vehicles equipped with manual transmissions is more challenging because the driver intent is unknown. Specifically, the control system does not have enough data to accurately determine if the driver is about to upshift and increase the load on the engine, downshift and decrease the load, or simply maintain the current gear. Due to this uncertainty, it is very difficult to determine if the engine may be placed in the deactivated mode.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides an engine control system for controlling transitions between activated and deactivated modes in a vehicle equipped with a manual transmission. The engine control system includes a clutch plate position sensor and a shifter shaft position sensor in communication with a controller. The controller determines if conditions exist to increase or reduce the number of active cylinders based on data collected from the position sensors, engine speed, and manifold absolute pressure. Prediction of the driver&#39;s next movements is the basis of the control. The sensors provide the history, averages, acceleration data, and velocity data, which lead to the driver&#39;s intent.  
         [0007]     One feature of the present invention includes a clutch plate position sensor which provides an indication of clutch engagement or disengagement.  
         [0008]     In another feature, the position of the shifter shaft is measured. Additionally, the speed at which the shifter shaft is being moved and the direction the shaft is heading is also determined.  
         [0009]     In another feature of the present invention, brake pedal position and throttle pedal position are determined. The monitored inputs are analyzed by the controller to predict the driver&#39;s next actions. The control system maintains a smooth output torque during transitions between activated and deactivated modes in the displacement on demand engine.  
         [0010]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0012]      FIG. 1  is a functional block diagram illustrating a vehicle powertrain including a DOD transition control system according to the present invention;  
         [0013]      FIG. 2  is an exploded perspective view of an exemplary manual transmission and clutch assembly equipped with a clutch plate position sensor and a shifter shaft position sensor constructed in accordance with the teachings of the present invention;  
         [0014]      FIG. 3  is an exemplary shifter shaft position map used by the control system of the present invention for a five speed manual transmission with reverse;  
         [0015]      FIGS. 4-7  are schematic diagrams depicting the relation between the shifter shaft position sensors and the shifter shaft at various locations within a shift pattern; and  
         [0016]      FIG. 8  is a flowchart illustrating steps performed by the DOD control system of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, activated refers to operation using all of the engine cylinders. Deactivated refers to operation using less than all of the cylinders of the engine (one or more cylinders not active).  
         [0018]     Referring now to  FIG. 1 , a vehicle  4  includes an engine  6  drivingly coupled to a transmission  8 . Transmission  8  is either an automatic or a manual transmission that is driven by the engine  6  through a corresponding torque converter or clutch assembly  9 . Air flows into the engine  6  through an intake manifold  10  having a first passageway  12  and a second passageway  14 . The first and second passageways are separated from one another. A first set of engine cylinders  16  is in communication with first passageway  12  to receive an air/fuel mixture. A second set of engine cylinders  18  is in communication with second passageway  14 .  
         [0019]     A first throttle A is positioned in communication with first passageway  12  to provide an individually controlled air/fuel mixture to first set of cylinders  16 . A second throttle B is in communication with second passageway  14  and second set of cylinders  18 . Preferably, the number of sets of cylinders equals the number of throttles present. The air/fuel mixture is subsequently combusted within cylinders  16  and  18 . Accessories  22  such as a hydraulic pump, HVAC compressor, and/or alternator are driven by the engine  6 .  
         [0020]     The engine  6  includes N cylinders. One or more of the cylinders may be selectively deactivated during engine operation. Although  FIG. 1  depicts eight cylinders (N=8), it can be appreciated that the engine  6  may include additional or fewer cylinders. For example, engines having 4, 5, 6, 8, 10, 12 and 16 cylinders are contemplated. It should be appreciated that engines having more than two throttles are also contemplated. An eight cylinder engine may likely include 2, 4 or 8 throttles without departing from the scope of the present invention.  
         [0021]     A controller  24  communicates with the engine  6  and various sensors discussed herein. An air flow sensor  26  generates a signal based on the rate of air flow through intake manifold  10 . An engine speed sensor  28  generates a signal based on engine speed. An engine temperature sensor  30  generates a signal based on engine temperature. A first intake manifold pressure sensor  32  generates a signal based on a vacuum pressure within first passageway  12 . A second intake manifold pressure sensor  34  generates a signal based on vacuum pressure within second passageway  14 . An intake air temperature sensor  40  generates a signal based on intake air temperature. An accelerator pedal position sensor  42  generates a signal based on accelerator pedal position. A brake pedal position sensor  43  generates a signal based on brake pedal position. A clutch plate position sensor  44  generates a signal based on clutch plate position. First and second shifter shaft position sensors,  46  and  48 , respectively, generate signals based on shifter shaft position.  
         [0022]     When proper conditions exist, the controller  24  transitions the engine  6  to the deactivated mode. In an exemplary embodiment, N/2 cylinders are deactivated, although one or more cylinders may be deactivated. Upon deactivation of the selected cylinders, the controller  24  increases the power output of the remaining cylinders. The controller  24  provides DOD transition by evaluating the output of the clutch plate position sensor and shifter shaft position sensors as will be described below.  
         [0023]     Referring to  FIG. 2 , clutch assembly  9  includes a clutch plate  50 , a pressure plate  52 , a throw-out bearing  54  and a clutch fork  56 . Clutch plate  50  is selectively engageable with a flywheel  58  of engine  6 . Clutch assembly  9  is operable in an engaged mode where engine torque is transferred from flywheel  58  to transmission  8  and a disengaged mode where torque is not transferred from engine  6  to transmission  8 . Clutch fork  56  extends through an aperture  60  formed in a bell housing  62  coupled to transmission  8 . A boot  64  sealingly engages clutch fork  56  and bell housing  62  to prevent contaminant ingress to clutch assembly  9 . Clutch fork  56  is pivotable relative to the housing  62 . A bifurcated end  66  of clutch fork  56  is positioned within an annular groove  68  of throw-out bearing  54 . Accordingly, movement of clutch fork  56  causes axial displacement of throw-out bearing  54 . As throw-out bearing  54  moves, pressure plate  52  also moves causing clutch plate  50  to drivingly engage or disengage flywheel  58 .  
         [0024]     Clutch plate position sensor  44  is mounted to an external surface  70  of bell housing  62 . Clutch plate position sensor includes a reel  72  having a wire  74  wound thereon. One end of wire  74  is coupled to shifter fork  56 . As clutch fork  56  moves, a length of wire  74  is paid out from reel  72 . The linear length of wire paid out from reel  72  is measured and an appropriate signal is output to controller  24 . An encoder or other measurement device may be sued to determine the length of wire  74  extended from reel  72 . The length of wire paid out at any one time correlates to the position of clutch plate  50 . A look-up table or an algorithm may be created for controller  24  to correlate the data provided by clutch plate position sensor  44  and the true position of clutch plate  50 . As an additional feature, clutch wear may be monitored throughout the length of the vehicle by monitoring changes in output of clutch plate position sensor  44 .  
         [0025]     First shifter shaft position sensor  46  and second shifter shaft position sensor  48  are preferably coupled to an outer surface  76  of transmission  8 . First shifter shaft position sensor  46  includes a reel  78  having a length of wire  80  wound thereon. Similarly, second shifter shaft position sensor  48  includes a reel  82  and a wire  84 . Wires  80  and  84  are coupled to a shifter shaft  86 . Shifter shaft  86  is selectively moveable by operator to obtain a number of drive ratios.  
         [0026]      FIG. 3  depicts a shift pattern for a five-speed manual transmission. The extreme positions of each column correspond to a desired speed ratio. Specifically, position  00  corresponds to reverse gear. Position  010  corresponds to first gear. Position  40  corresponds to second gear. Position  410  corresponds to third gear. Position  80  corresponds to fourth gear, and position  810  is indicative of fifth gear. When the manual transmission is in neutral, the shifter shaft is located at position  45 . Shifter shaft positions intermediate the gear positions previously mentioned are also identified in  FIG. 3 . The data output from first shifter shaft position sensor  46  and second shifter shaft position sensor  48  allows controller  24  to determine at which location of the shift pattern the shifter shaft is located.  
         [0027]      FIG. 4  represents shifter shaft  86  as being located in neutral at position  45 . Controller  24  receives an output from first shifter shaft position sensor  46  that a certain length of wire  80  is extended from reel  78 . Similarly, second shifter shaft position sensor  48  provides a signal to controller  24  indicating the length of wire  84  presently extended from reel  82 . Because the length of wire  80  and the length of wire  84  are equal and of a certain magnitude, controller  24  correlates the location of shifter shaft  86  with neutral position  45 .  
         [0028]      FIG. 5  depicts shifter shaft  86  as being within the gate between reverse and first gears. Based on the lengths of wires  80  and  84 , controller  24  is able to determine that shifter shaft  86  is positioned at location  03  in  FIG. 5 . Controller  24  is operable to continuously monitor the length of wires  80  and  84  and track the movement of shifter shaft  86  during vehicle operation. In this manner, controller  24  may determine the direction in which shifter shaft  86  is being moved and the speed at which the shaft is being moved by comparing shifter shaft location versus time.  
         [0029]      FIGS. 6 and 7  provide additional examples of alternate shifter shaft locations and the corresponding lengths of wires  80  and  84 . In particular,  FIG. 6  relates to a shifter shaft position between fourth and fifth gears corresponding to position  87 .  FIG. 7  depicts wires  80  and  84  being of equal length. The length of wires  80  and  84  corresponds to position  410  indicating that the transmission is in third gear.  
         [0030]     It should be appreciated that the clutch plate position sensor and shifter shaft position sensor embodiments previously described are merely exemplary and that any number of position determining techniques may be used without departing from the scope of the present invention. Specifically, it is contemplated that optical measurement systems, hall effect sensors, switches, proximity sensors or other devices may be used to output a signal to controller  24  indicative of the position of a clutch plate and/or a shifter shaft. Additionally, other components within the clutch may be instrumented to provide an indication of clutch engagement or disengagement.  
         [0031]     In operation, controller  24  determines if the engine is exhibiting characteristic indicating that it may be transitioned from an activated mode to a deactivated mode based on the signals generated by accelerator pedal position sensor  42 , engine speed sensor  28 , first and second intake manifold pressure sensors  32  and  34  and brake pedal position sensor  43 . If the aforementioned data indicates that a transition is possible, controller  24  monitors clutch plate position sensor  44  to determine if clutch plate  50  is becoming disengaged from flywheel  58 . At the time clutch plate  50  begins to disengage flywheel  58 , data output from first shifter shaft position sensor  46  and second shifter shaft position sensor  48  is monitored to determine if the operator is shifting into a higher gear, also known as upshifting. If so, engine  6  is transitioned into the deactivated mode. One skilled in the art will appreciate that the transition may occur before the higher gear is actually engaged by the driver. This differs from commonly known automatic transmission algorithms where the transition occurs only after the shift is fully completed.  
         [0032]     The design of manifold  10  further enhances the operation of the engine control system of the present invention by allowing throttle A in communication with first passageway  12  to be individually controlled in relation to throttle B in communication with second passageway  14 . The presence of multiple throttles in communication with separate intake passageways allows DOD transitions to be made without fluctuations in the engine torque output curve. Ideally, a transition may occur when clutch assembly  9  is fully engaged, fully disengaged or partially engaged with flywheel  58 .  
         [0033]     One skilled in the art will appreciate that the dual throttle, multiple passageway intake system previously described is merely exemplary and that the control system of the present invention is operable with any number of intake systems including singular or multiple throttles. For example, an eight cylinder engine equipped with four throttles having four intake passageways would be desirable. Each of the throttles and intake passageways provide air and fuel to two of the combustion chambers. Accordingly, implementation of the control system of the present invention should not be limited based on the examples described herein.  
         [0034]     Referring to  FIG. 8 , steps of a DOD control method according to the present invention are shown. In step  100 , the outputs from intake manifold pressure sensors  32  and  34  are converted to manifold vacuum. Manifold vacuum is an indicator of engine load. The higher the intake manifold vacuum, the lower the engine load.  
         [0035]     In step  102 , engine speed sensor  28  provides a signal indicative of the engine speed. In step  104 , controller  24  determines whether deactivation conditions have been met. For example, transitioning to the deactivated mode would be allowed to occur when the manifold vacuum exceeds a predetermined value. The predetermined vacuum value may vary with engine speed. As such both parameters are measured. If the deactivation conditions are met, controller  24  continues with step  106 .  
         [0036]     In step  106 , controller  24  determines whether engine  6  is currently operating in a deactivated mode. If false, controller  24  continues with step  108 . If the engine is presently operating in a deactivated mode, controller  24  proceeds with step  118 .  
         [0037]     In step  108 , clutch plate position sensor  44  provides a signal indicative of the location of clutch plate  50 . Based on the output from clutch plate position sensor  44 , controller  24  determines if clutch assembly  9  is in a disengaged, engaged, or partially engaged mode with flywheel  58  at step  110 . If the clutch is in a disengaged or at least partially disengaged position, controller  24  continues to step  112 .  
         [0038]     In step  112 , first shifter shaft position sensor  46  and second shifter shaft position sensor  48  provide signals indicative of the length of wires  80  and  84  extending therefrom. Controller  24  correlates the wire lengths to a shifter shaft position.  
         [0039]     In step  114 , controller  24  determines if an upshift is about to occur. If so, controller  24  continues at step  116 . In step  116 , transitioning from activated mode to deactivated mode begins. In the example presented, throttle A begins to close while throttle B begins to open. Both throttles move until throttle A is completely closed. At this time, the fuel supply to throttle A may be discontinued.  
         [0040]     To complete the control logic analysis, reference is once again made to step  106 . If the engine is presently in the deactivated mode, controller  24  continues to operate at step  118 .  
         [0041]     In step  118 , controller  24  determines if conditions exist to transition engine  6  from the deactivated mode to the activated mode. If so, controller  24  proceeds to step  120 .  
         [0042]     At step  120 , the deactivated cylinders are activated. During activation, fuel supply is returned to throttle A. Throttle A slowly opens as throttle B slowly closes to maintain a smooth torque output curve. Both throttles continue to move until throttle A and throttle B are at substantially the same position.  
         [0043]     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.