Abstract:
An engine control system comprises a driver input module, a cylinder actuation module, and an active fuel management (AFM) module. The driver input module generates a fuel saver mode (FSM) signal having a first state based upon a driver input. The cylinder actuation module selectively disables at least one of a plurality of cylinders of an engine based upon a deactivation signal having a first state. The AFM module generates the deactivation signal based on at least one engine parameter and at least one threshold. The at least one threshold is modified when the FSM signal has the first state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/019,870, filed on Jan. 9, 2008. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to internal combustion engines and more particularly to engine control systems and methods that improve fuel economy. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Referring now to  FIG. 1 , a functional block diagram of an engine system according to the prior art is presented. An internal combustion engine  100  is controlled by a control module  104 . The control module  104  also controls a transmission  108 . The control module  104  receives driver input from an accelerator input module  1   10  and from a transmission input module  1   12 . 
         [0005]    The accelerator input module  110  may include an accelerator pedal and pedal position sensors. The transmission input module  112  may include a gearshift lever, gearshift paddles, and/or gearshift buttons. Based on the driver input, the control module  104  controls a throttle valve  116 . The throttle valve  116  regulates air intake into an intake manifold  118  of the engine  100 . The position of the throttle valve  116  may be measured by a throttle position sensor  120 . 
         [0006]    The amount of air flowing into the intake manifold  118  may be measured by a mass air flow (MAF) sensor  122 . The pressure inside the intake manifold  118  may be measured by a manifold absolute pressure (MAP) sensor  124 . Air from the intake manifold  118  is combined with fuel to create an air-fuel mixture in one or more cylinders  126 . For example only, eight cylinders  126  are shown in  FIG. 1 , although more or fewer cylinders may be present. 
         [0007]    Combusting the air-fuel mixture in the cylinders  126  produces torque to turn a crankshaft (not shown). The crankshaft is coupled to the transmission  108  via a torque transmitting device  130 , such as a torque converter or a clutch. The speed of the crankshaft may be measured by an RPM (revolutions per minute) sensor  132 . When maximum torque is not required, one or more of the cylinders  126  may be disabled to improve fuel economy. For example, the cylinders  126  having diagonal hash marks, such as the cylinder  126 - 1 , may be disabled. 
         [0008]    The control module  104  operates a lifter oil manifold assembly (LOMA)  134  to disable selected ones of the cylinders  126 . Valves (not shown) of each of the cylinders  126  may be actuated by rocker arms via pushrods driven off a camshaft. Lifters interface between the camshafts and pushrods. Alternatively, lifters may directly interface between the camshafts and valves in an overhead cam engine configuration. There is a hydraulically switchable lost motion portion of the lifters. In order to disable the selected cylinders, the LOMA  134  hydraulically decouples the lifters using solenoid-actuated valves. The intake and/or exhaust valves of the selected cylinders will then remain closed, disabling those cylinders. 
       SUMMARY 
       [0009]    An engine control system comprises a driver input module, a cylinder actuation module, and an active fuel management (AFM) module. The driver input module generates a fuel saver mode (FSM) signal having a first state based upon a driver input. The cylinder actuation module selectively disables at least one of a plurality of cylinders of an engine based upon a deactivation signal having a first state. The AFM module generates the deactivation signal based on at least one engine parameter and at least one threshold. The at least one threshold is modified when the FSM signal has the first state. 
         [0010]    A method of controlling an engine control system comprises generating a fuel saver mode (FSM) signal having a first state based upon a driver input; selectively disabling at least one of a plurality of cylinders of an engine based upon a deactivation signal having a first state; generating the deactivation signal based on at least one engine parameter and at least one threshold; and modifying the at least one threshold when the FSM signal has the first state. 
         [0011]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a functional block diagram of an engine system according to the prior art; 
           [0014]      FIG. 2A  is a graphical depiction of exemplary upper and lower pressure constraints for active fuel management (AFM) operation; 
           [0015]      FIG. 2B  is a graphical depiction of exemplary lower and upper pressure constraints for AFM operation when fuel saver mode (FSM) is engaged; 
           [0016]      FIG. 3A  is a graphical depiction of an exemplary mapping between accelerator pedal input and requested engine torque; 
           [0017]      FIG. 3B  is a graphical depiction of an exemplary mapping between accelerator pedal input and requested engine torque when FSM is engaged; 
           [0018]      FIG. 4A  is a graphical depiction of an exemplary shift map for a given transmission gear; 
           [0019]      FIG. 4B  is a graphical depiction of an exemplary shift map for a given transmission gear when FSM is engaged; 
           [0020]      FIG. 5  is a functional block diagram of an exemplary powertrain system according to the principles of the present disclosure; 
           [0021]      FIG. 6  is a functional block diagram of an exemplary implementation of the engine control module of  FIG. 5 ; 
           [0022]      FIG. 7  is a functional block diagram of an exemplary implementation of the navigation system; and 
           [0023]      FIG. 8  is a flowchart that depicts exemplary steps performed in engaging FSM. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, 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, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0025]    As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0026]    Internal combustion engines may be operated using fewer than all of their cylinders in order to improve fuel economy. For example, an eight-cylinder engine may be operated using four cylinders, thereby improving fuel economy by reducing pumping losses. This capability is herein referred to as active fuel management (AFM). AFM may deactivate one or more of the engine&#39;s cylinders. In various implementations, AFM may deactivate a predetermined number of the cylinders, such as half of the cylinders. In various implementations, AFM may disable cylinders individually. 
         [0027]    The use of AFM may be limited by noise, vibration, and harshness (NVH) concerns, as well as performance and drivability concerns. For example, at a given RPM, AFM operation may be disabled when manifold absolute pressure (MAP) is outside of a range defined between a first predetermined pressure and a second predetermined pressure. In various implementations, a table of lower and upper MAP limits for AFM operation as a function of RPM may be stored. 
         [0028]    Referring now to  FIG. 2A , exemplary upper and lower MAP constraints for AFM operation are graphically depicted. In this example, AFM may operate at points in the MAP-RPM plane above a lower limit  150  and below an upper limit  152 . There may be various RPM points and/or ranges where the lower and/or upper limits  150  and  152  are more restrictive. For example only, the lower limit  150  increases locally for a small RPM range as shown at  154 . 
         [0029]    When a driver desires to increase fuel economy, they may be willing to accept slightly degraded NVH, performance, and/or drivability performance. If the driver indicates that this is the case, a fuel saver mode (FSM) may be enabled. For example only, the driver may push a button to engage FSM. FSM may attempt to increase fuel economy by modifying, for example, AFM mapping, accelerator position mapping, and/or shift mapping. When FSM is engaged, AFM operation may be adapted, such as by increasing the MAP range in which AFM is employed. Alternatively or additionally, any other parameters used to regulate AFM operation may be adapted. 
         [0030]    Referring now to  FIG. 2B , exemplary lower and upper limits  156  and  158  for AFM operation when FSM is engaged are graphically depicted. The MAP range of AFM may be expanded for one or more RPM increments. In this example, the lower limit  156  does not have the local increase shown at  154  in  FIG. 2A . In addition, the upper limit  158  is increased compared to that shown in  FIG. 2A . 
         [0031]    Referring now to  FIG. 3A , an exemplary mapping  160  between accelerator pedal input and requested engine torque is graphically depicted. In this example, at a given vehicle speed, the torque request increases linearly with pedal position. 
         [0032]    In  FIG. 3B , an exemplary mapping  164  between accelerator pedal input and requested engine torque when FSM is engaged is graphically depicted. In this example, the derivative of the torque request increases approximately linearly with pedal position. This leads to an arc shape when graphed. In various implementations, the arc-shaped mapping  164  may share its endpoints with the line-shaped mapping  160  of  FIG. 3A , while at other pedal positions, the arc-shaped mapping  164  may be below the line-shaped mapping  160 . By sharing the endpoints, the response to minimum and maximum pedal position will be the same whether FSM is engaged or not. In this way, maximum pedal position can still result in advertised top speed and quickest acceleration. 
         [0033]    In various implementations, a constant position of the accelerator input may be translated to a torque that maintains the vehicle at its current speed, instead of at a greater torque, which may accelerate the vehicle. In this way, in order to accelerate the vehicle, a driver increases the accelerator input. 
         [0034]    Referring now to  FIG. 4A , an exemplary shift map for a given transmission gear is graphically depicted. For example, at a given RPM, the transmission may downshift when the pedal position increases above a predetermined threshold. In addition, at a given pedal position, the transmission may upshift when the RPM rises above a predetermined threshold. The downshift and upshift thresholds may be represented as lines  180  and  182  in the pedal-position-RPM plane. 
         [0035]    In  FIG. 4B , an exemplary shift map for the given transmission gear when FSM is engaged is graphically depicted. In various implementations, the shift map for every gear may be modified when FSM is engaged. Multiple sets of maps may be stored, corresponding to whether FSM is engaged or not. Alternatively, a single set of maps may be mathematically modified or combined with mathematical adjustments when FSM is either engaged or disengaged. When FSM is engaged, downshifts may require a greater pedal position. In addition, the pedal position at which an upshift occurs may be increased. In various implementations, the downshift and upshift maps may be lines  190  and  192  having slopes that are greater than the corresponding lines of the shift maps in  FIG. 4A . 
         [0036]    As an overview,  FIG. 5  shows an exemplary engine system that implements FSM, while  FIG. 6  shows an exemplary implementation of the engine control module of  FIG. 5 . FSM may be automatically engaged when the amount of fuel in the fuel tank decreases below a predetermined amount. For example, this may correspond to the low fuel indicator being illuminated on an instrument panel of the vehicle. 
         [0037]    In addition, when a low fuel level is detected, this fact may be communicated to a navigation system in the vehicle. The navigation system in the vehicle may then identify and display the location of fueling stations close to the vehicle.  FIG. 7  is an exemplary block diagram of a navigation system having this capability.  FIG. 8  is a flowchart depicting exemplary steps performed in engaging FSM. Now a more detailed discussion of the FIGs. will be presented. 
         [0038]    Referring now to  FIG. 5 , a functional block diagram of an exemplary powertrain system according to the principles of the present disclosure is shown. An internal combustion engine  200  is controlled by an engine control module (ECM)  204 . The ECM  204  interfaces with a transmission control module  208 , which controls a transmission  210 . The engine  200  is coupled to the transmission  210  by a torque coupling device  214 , such as a torque converter or clutch. 
         [0039]    The ECM  204  receives accelerator input from a driver via an accelerator input module  218 . For example, the accelerator input module  218  may include an accelerator pedal and a pedal position sensor. The ECM  204  receives transmission input from the driver via a transmission input module  220 . The transmission input module  220  may include a gearshift lever, buttons, and/or paddles, for example. 
         [0040]    The ECM  204  receives mode input from the driver via a driver mode input module  222 . The driver mode input module  222  allows the driver to indicate that increased fuel economy is desired. For example, the driver mode input module  222  may include a button, which may indicate that the driver desires increased fuel economy once depressed. In various implementations, the button may be located on a lever of the transmission input module  220 . In various implementations, the ECM  204  will activate fuel saver mode (FSM) when the driver mode input module  222  indicates that the driver desires increased fuel economy. 
         [0041]    In various implementations, the driver mode input module  222  may allow the driver to select other vehicle operating modes. For example, the driver mode input module  222  may allow the driver to select tow/haul mode (THM) for use when towing or hauling cargo. In various implementations, FSM and THM may be multiplexed on a single button, where successive button presses cycle through both of the modes being enabled, each of the modes being enabled, and neither mode being enabled. 
         [0042]    The ECM  204  may indicate the status of driver-selected modes via a driver indicator module  224 . In various implementations, the driver indicator module  224  may include lights on an instrument panel of the vehicle that are illuminated when the corresponding mode is activated. In various implementations, the indicator corresponding to FSM may be located within the button that engages FSM. The driver indicator module  224  may also indicate when a low fuel level has been detected in a fuel system  228  of the vehicle. 
         [0043]    Based on the selected modes and the accelerator and transmission inputs, the ECM  204  controls a throttle actuator module  232  and a cylinder actuator module  234 . The throttle actuator module  232  actuates a throttle valve  236  to a position instructed by the ECM  204 . The throttle actuator module  232  verifies the position of the throttle valve  236  via a throttle position sensor  238 . 
         [0044]    Air is drawn into an intake manifold  242  of the engine  200  via the throttle valve  236 . The amount of air entering the intake manifold  242  may be measured by a mass air flow (MAF) sensor  244 . Pressure within the intake manifold  242  may be measured using a manifold absolute pressure (MAP) sensor  246 . 
         [0045]    Air is mixed with fuel from the fuel system  228  in one or more cylinders  250 . For example only, eight cylinders  250  are shown in  FIG. 2 , although more or fewer are possible. The air-fuel mixture is combusted within the cylinders  250  to produce torque to rotate a crankshaft (not shown). The speed of the crankshaft may be measured by an RPM (revolutions per minute) sensor  254 . The cylinder actuator module  234  deactivates one or more of the cylinders  250  during active fuel management (AFM). 
         [0046]    In various implementations, ones of the cylinders  250  may be deactivated as a group. Alternatively, the cylinder actuator module  234  may deactivate individual ones of the cylinders  250 . The cylinder actuator module  234  may deactivate cylinders  250 , such as by halting supply of fuel to those cylinders and/or preventing the opening of the intake and/or exhaust valves of those cylinders. The ECM  204  may also communicate with a navigation system  270 , which may provide route information to the driver. 
         [0047]    Referring now to  FIG. 6 , a functional block diagram of an exemplary implementation of the engine control module (ECM)  204  is presented. The ECM  204  includes a driver input interpretation module  302 . The driver input interpretation module  302  receives accelerator input from the accelerator input module  218  and vehicle speed. In various implementations, vehicle speed may be calculated from RPM and transmission ratio. 
         [0048]    The driver input interpretation module  302  determines a desired torque based on pedal position and vehicle speed using a mapping from a mapping storage module  306 . The desired torque is output to a torque control module  310 . The torque control module  310  may receive other torque requests, such as from a cruise control system or a traction control system. 
         [0049]    Based on an arbitration of these torque requests, the torque control module  310  provides instructions to the cylinder actuator module  234  and the throttle actuator module  232  to produce the arbitrated torque. The torque control module  310  may receive a signal from an active fuel management (AFM) module  314  indicating whether and to what extent AFM can be used. Based on this signal, the torque control module  310  can control the cylinder actuator module  234 . 
         [0050]    The AFM module  314  may determine AFM availability based on MAP and RPM. The mapping from MAP and RPM to availability may be received from the mapping storage module  306 . A transmission control module  318  receives transmission input from the transmission input module  220 . Based on the transmission input, RPM, and accelerator input, the transmission control module  318  determines a desired ratio for the transmission  210 . 
         [0051]    The transmission input module  220  may specify to the transmission control module  208  which transmission ratios may be selected. For example only, the transmission input module  220  may specify whether an overdrive ratio is available. Based on a shift map from the mapping storage module  306 , the transmission control module  208  may determine when to upshift and downshift based on RPM and accelerator input. 
         [0052]    An OR gate  318  may output an active signal when FSM mode is activated in the driver mode input module  222  and/or when a low fuel level is indicated by the fuel system  228 . The mapping storage module  306  receives the output of the OR gate  318 . When the output signal is active, the mapping storage module  306  may select different mappings for the transmission control module  208 , the driver input interpretation module  302 , and the AFM module  314 . 
         [0053]    Referring now to  FIG. 7 , a functional block diagram of an exemplary implementation of the navigation system  270  is presented. The navigation system  270  includes a navigation control module  402 , which interfaces with the ECM  204 . The navigation system  270  also includes a global positioning system (GPS) receiver  406 , a mapping database  410 , an input module  414 , and a display  418 . 
         [0054]    The navigation control module  402  displays information on the display  418  and receives user input via the input module  414 . In various implementations, the display  418  may include a touch screen, which may also serve as part or all of the input module  414 . The navigation control module  402  receives positioning information from the GPS receiver  406 . The navigation control module  402  may also obtain position information in other ways, such as from terrestrial cellular networks. 
         [0055]    The navigation control module  402  may display routing information from the mapping database  410 . The routing information may include a course to a destination specified by the input module  414 , and may be dynamically updated as the vehicle moves. In addition, the mapping database  410  may include information about businesses, such as fueling stations. For example only, the information may include times of operation, fuel types offered, and prices. 
         [0056]    When the navigation control module  402  receives information from the ECM  204  that the fuel level is low, the navigation control module  402  may identify locations of nearby fueling stations from the mapping database  410  and present them on the display  418 . In various implementations, the display  418  may indicate a boundary beyond which fueling stations may not be reachable with the current amount of fuel. 
         [0057]    The mapping database  410  may be updated by a wireless interface module  422 . The wireless interface module  422  may receive updates of mapping information via wireless transmissions, such as from satellite and/or terrestrial networks. In various implementations, updates may be received from update media, such as CDs or DVDs. The navigation control module  402  may request fueling station position information from the wireless interface module  422  based upon the current position of the vehicle. 
         [0058]    The input module  414  may allow the user to specify desirable characteristics of fueling stations, such as corporation, facilities, and available fuel types. In addition, these preferences may be stored and/or preloaded into the navigation system  270 . The wireless interface module  422  may allow a mapping provider, which may include the vehicle&#39;s manufacturer, to select fueling stations of partner companies. 
         [0059]    For example, partnerships may be created between certain fueling station companies and the provider, and those fueling stations may be specially indicated. In addition, those fueling stations not owned by partner companies may be hidden on the display  418 . In various implementations, hidden fueling stations may be displayed when no partner stations are within the vehicle&#39;s current range. The user may select one of the displayed fueling stations via the input module  414  or the navigation control module  402  may select the nearest fueling station. A temporary route may then be created to reach that fueling station. 
         [0060]    Referring now to  FIG. 8 , a flowchart depicts exemplary steps performed in engaging fuel saver mode (FSM). Control begins in step  500 , where first mappings are selected for at least one of accelerator pedal mapping, AFM mapping, and transmission shift pattern mapping. Control then continues in step  502 , where control determines whether a low fuel condition is present. If so, control transfers to step  504 ; otherwise, control transfers to step  506 . In step  504 , control stops first and second timers. Control may also identify nearby fuel stations in a navigation system. Control then continues in step  508 . 
         [0061]    In step  506 , control determines whether FSM has been engaged by the driver. If so, control transfers to step  510 ; otherwise, control transfers to step  512 . In step  510 , the first timer is reset, and the second timer is stopped. Control then continues in step  512 . The first time measures the period after FSM is engaged, while the second timer measures the period after FSM is disengaged. 
         [0062]    After FSM has been engaged, the updated mappings may be delayed until the first timer has expired. In this way, if FSM is disengaged soon after it has been engaged, the updated mappings will not have been used. This prevents an abrupt change from normal mappings to FSM mappings and back to normal mappings. Engaging followed quickly by disengaging may occur frequently when a button is multiplexed between FSM and another function. In various implementations, the timer values may be less than approximately two seconds. 
         [0063]    In step  512 , control determines whether the first timer has expired. If so, control transfers to step  514 ; otherwise, control transfers to step  516 . In step  514 , the delay period after FSM was engaged has expired, and the first timer is stopped. Control continues in step  508 , where second mappings are selected for the accelerator progression, AFM, and transmission shifting. Control then continues in step  516 . 
         [0064]    In step  516 , control determines whether FSM has been disengaged. If so, control transfers to step  518 ; otherwise, control transfers to step  520 . In step  518 , the first timer is stopped, the second timer is reset, and control continues in step  520 . In step  520 , control determines whether the second timer has expired. If so, control transfers to step  522 ; otherwise, control returns to step  502 . In step  522 , the delay period after FSM being disengaged has expired and the second timer is stopped. Control then returns to step  500 , where the first mappings are selected. 
         [0065]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure 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.