Abstract:
A fuel economy (FE) indicator lamp regulation system for a hybrid electric vehicle having an internal combustion engine includes an FE indicator lamp, a first module that calculates an instantaneous FE of the hybrid electric vehicle and a second module that determines a velocity of the hybrid electric vehicle. A third module switches the FE indicator lamp between an on state and an off state based on the instantaneous FE and the vehicle speed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/816,686, filed on Jun. 27, 2006. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to hybrid vehicles, and more particularly to a fuel economy indicator lamp control system for a hybrid vehicle. 
     BACKGROUND 
     Hybrid vehicles are driven by multiple powerplants including, but not limited to an internal combustion engine and an electric machine. The electric machine functions as a motor/generator. In a generator mode, the electric machine is driven by the engine to generate electrical energy used to power electrical loads or charge batteries. In a motor mode, the electric machine supplements the engine, providing drive torque to drive the vehicle drivetrain. 
     Improved fuel economy (FE) and ecological sentiment are motivating factors for hybrid vehicle purchase. Traditionally, hybrid manufacturers provide a labeled FE ratings including city and highway FE ratings. Although the label FE, as well as real-world fuel economy, of hybrid vehicles is usually higher than those of their non-hybrid counterparts, hybrid vehicles have been criticized for lower than expected FE. 
     SUMMARY 
     Accordingly, the present disclosure provides a fuel economy (FE) indicator lamp regulation system for a hybrid electric vehicle having an internal combustion engine. The FE indicator lamp regulation system includes an FE indicator lamp, a first module that calculates an instantaneous FE of the hybrid electric vehicle and a second module that determines a velocity of the hybrid electric vehicle. A third module switches the FE indicator lamp between an on state and an off state based on the instantaneous FE and the vehicle speed. 
     In another feature, the FE indicator lamp is switched to the off state when the velocity is outside of a velocity range that is defined between a minimum velocity threshold and a maximum velocity threshold. 
     In another feature, the third module determines an FE threshold based on the velocity and switches the FE indicator lamp to the on state when the instantaneous FE remains above the FE threshold for a threshold time period. 
     In another feature, the third module determines an FE threshold based on the velocity and switches the FE indicator lamp to the off state when the instantaneous FE remains below the FE threshold for a threshold time period. 
     In another feature, the third module initiates an off timer upon switching the FE indicator lamp to the off state, wherein switching of the indicator lamp to the on state is inhibited until the off timer achieves a threshold time. 
     In still another feature, the FE indicator lamp regulation system further includes a fourth module that selectively initiates a hybrid engine off mode. The third module switches the FE indicator lamp to the on state when in the hybrid engine off mode for a threshold time period. 
     In yet other features, the FE indicator lamp regulation system further includes a fourth module that monitors an accelerator pedal position. The third module switches the FE indicator lamp to the off state when the instantaneous FE is below a threshold FE for a threshold time. The threshold time is determined based on the accelerator pedal position. More specifically, the threshold time is reduced when the accelerator pedal position exceeds a threshold accelerator pedal position. 
     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, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of an exemplary hybrid vehicle that is operated based on the fuel economy (FE) indicator lamp illumination control according to the present disclosure; 
         FIG. 2  is a graph illustrating FE indicator lamp illumination areas in accordance with the FE indicator lamp illumination control of the present disclosure; 
         FIG. 3  is a graph illustrating exemplary control parameters implemented by the FE indicator lamp illumination control of the present disclosure; 
         FIG. 4  is a flowchart illustrating exemplary steps executed by the FE indicator lamp control of the present disclosure; and 
         FIG. 5  is a functional block diagram of exemplary modules that execute the FE indicator lamp illumination control of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiment 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 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, or other suitable components that provide the described functionality. 
     Referring now to  FIG. 1 , an exemplary hybrid vehicle  10  includes an engine  12  and an electric machine  14 , which drive a transmission  16 . More specifically, the electric machine  14  supplements the engine  12  to produce drive torque to drive the transmission  16 . In this manner, fuel efficiency is increased and emissions are reduced. The engine  12  and electric machine  14  are coupled via a belt-alternator-starter (BAS) system  18 . More specifically, the electric machine  14  operates as a starter (i.e., motor) and an alternator (i.e., generator) and is coupled to the engine  12  through a belt and pulley system. The engine  12  and the electric machine  14  include pulleys  20 ,  22 , respectively, that are coupled for rotation by a belt  24 . The pulley  20  is coupled for rotation with a crankshaft  26  of the engine  12 . 
     In one mode, the engine  12  drives the electric machine  14  to generate power used to recharge an energy storage device (ESD)  28 . In another mode, the electric machine  14  drives the engine  12  using energy from the ESD  28 . The ESD  28  can include, but is not limited to, a battery or a super-capacitor. Alternatively, the BAS system  18  can be replaced with a flywheel-alternator-starter (FAS) system (not shown), which includes an electric machine operably disposed between the engine and the transmission or a chain or gear system that is implemented between the electric machine  14  and the crankshaft  26 . 
     The transmission  16  can include, but is not limited to, a manual transmission, an automatic transmission, a continuously variable transmission (CVT) and an automated manual transmission (AMT). Drive torque is transferred from the engine crankshaft  26  to the transmission  16  through a coupling device  30 . The coupling device  30  can include, but is not limited to, a friction clutch or a torque converter depending upon the type of transmission implemented. The transmission  16  multiplies the drive torque through one of a plurality of gear ratios to drive a driveshaft  32 . 
     A control module  34  regulates operation of the vehicle  10 . The control module  34  controls fuel injection and spark to selectively activate and deactivate cylinders of the engine  12 . More specifically, when the vehicle  10  is at rest, none of the cylinders of the engine  12  are firing (i.e., are deactivated) and the engine  12  is stopped. During vehicle launch (i.e., acceleration from rest), the electric machine  14  drives the crankshaft to spin-up the engine  12  to an idle RPM and to initiate vehicle acceleration. During periods where low drive torque is needed to drive the vehicle (i.e., a hybrid engine off (HEOff) mode), drive torque is provided by the electric machine  14 . When in the HEOff mode, fuel and spark are cut-off to the cylinders of the engine. Further, opening and closing cycles of the intake and exhaust valves can be prevented to inhibit air flow processing within the cylinders. 
     An accelerator pedal  36  is provided. A pedal position sensor  36  is sensitive to a position of the accelerator pedal  36  and generates a pedal position signal based thereon. A brake pedal  40  is provided. A brake pedal position sensor  42  is sensitive to a position of the brake pedal  40  and generates a pedal position signal based thereon. The control module  34  operates a brake system  43  based on the brake pedal position signal to adjust a pressure within the brake system, which in turn regulates a braking force of brakes (not shown). A speed sensor  44  is responsive to the rotational speed (RPM EM ) of the electric machine  44 . The speed sensor  44  generates a speed signal. The control module  34  operates the vehicle  10  based on the pedal position signals generated by the pedal position sensors  38 ,  42  and the speed signal generated by the speed sensor  44 , as described in further detail below. The engine speed (RPM ENG ) can be determined based on the speed signal. More specifically, RPM EM  can be multiplied by the known pulley ratio to provide RPM ENG . 
     An instrument panel is also provided and includes a fuel economy (FE) telltale or indicator lamp  50  that is selectively lit when the vehicle is operating within a desired FE range. More specifically, the FE indicator lamp control of the present disclosure recognizes that FE feedback from the vehicle&#39;s instrument panel can be helpful in improving customers&#39; driving style to achieve better fuel economy. Accordingly, the FE indicator lamp control determines whether the vehicle is operating at good or desired FE and illuminates the indicator lamp  50  accordingly. Anti-busy control is also implemented to inhibit flashing of the FE indicator lamp  50 . 
     The FE indicator lamp illumination control qualifies the good or desired FE using one or more pre-determined criteria. For example, the good FE is based on the vehicle&#39;s ideal capabilities as a function of vehicle speed. As shown in  FIG. 2 , the vehicle&#39;s ideal (e.g., no wind, grade or acceleration) FE as a function of vehicle speed (V VEH ) is provided. Whenever the instantaneous FE is greater than a threshold value at the respective V VEH , the FE indicator lamp  50  is illuminated. More specifically, the FE indicator lamp  50  is illuminated whenever the FE is within the shaded region. Although an indicator lamp  50  is described, it is also anticipated that a digital read-out of the instantaneous FE can also be provided, so that the driver is aware of the actual FE value at any moment. 
     In one alternative, if the vehicle is able to achieve the HWY label value at the ideal condition, the HWY label value is used as the threshold. If only the CITY label value can be achieved under the ideal condition, the CITY label value is used as the threshold. In another alternative, the CITY label value is used as the threshold at lower speeds, and the HWY label value is used as the threshold at higher speeds. For example, below a city speed (e.g., 45 mph), the CITY label value is the threshold, and at speeds above a highway speed (e.g., 60 mph), the HWY label value is the threshold. At speeds between the city and highway speeds, the threshold value is linearly interpolated across the CITY and the HWY label values. 
     In addition to steady FE thresholds, the indicator lamp  50  is also illuminated during operation in hybrid fuel-off, regenerative braking, HEOff, electric creep and the like, to coach the vehicle operator to achieve better FE. More specifically, when the fuel is cut, for example, the calculated FE saturates at an upper limit (e.g., 199.9 mpg). For fuel-on operation, the indicator lamp  50  is not illuminated for vehicle speeds under a lower threshold (V MIN ) (e.g., 20 mph), because the instantaneous FE value changes very rapidly with vehicle speed and driver input. However, the indicator lamp  50  is illuminated at vehicle speeds at or under the lower threshold if the fuel is off. On the other end of the speed spectrum, the indicator lamp  50  is not illuminated during fuel-on operation at speeds at or above an upper threshold (V MAX ) (e.g., 75 mph). In this manner, the vehicle operator is not encouraged to drive at over speed limits. 
     The FE indicator lamp control implements an anti-busy control to prevent flashing of the indicator lamp. The anti-busy calibrations include, but are not limited to, a minimum/maximum V VEH  and hysteresis on the minimum/maximum V VEH , a minimum off time (t OFFTHR ), a minimum on time (t ONTHR ), minimum wait times (t WAIT1 , t WAIT2 ), upper and lower FE thresholds as a function of V VEH  and FE value freezing during transmission shifts. 
     Once the indicator lamp  50  is turned off, it remains off for t OFFTHR . Similarly, once the indicator lamp  50  is turned on, it remains on for t ONTHR . In this manner, flashing of the indicator lamp  50  is prohibited. When entering the HEOff mode, and assuming that the indicator lamp  50  is not on, the indicator lamp  50  is turned on after t WAIT . Again, flashing of the indicator lamp  50  is prohibited in the event that the HEOff mode is exited shortly upon being initiated. 
     Under conditions where the driver steps into the accelerator and the accelerator pedal position is deemed high, t OFFTHR  is replaced by an accelerator pedal related time (t AP ), which is less than t OFFTHR . In this manner, the indicator lamp  50  is turned off more rapidly when the driver steps into the accelerator pedal. It is also anticipated that the instantaneous FE value is frozen during transmission shifts, to prevent the transient shift condition from influencing the indicator lamp on/off decision. 
     Referring now to  FIG. 3 , an exemplary driving cycle is illustrated, wherein an FE of 29 miles-per-gallon (mgp) is provided as an upper FE threshold and an FE of 27 mpg is provided as a lower FE threshold. During an initial period A, the indicator lamp  50  is illuminated, as indicated by an indicator lamp flag (FLAG IL ) being set equal to 1. A first wait timer (t WAIT1 ) trace has achieved a maximum (t MAX1 ) because the indicator lamp  50  has been illuminated for t MAX1 , indicating that that the indicator lamp  50  could be immediately turned off if the FE falls below the lower FE threshold for a sufficient time, as discussed in further detail below. 
     During a subsequent period B, the FE oscillates between the upper and lower FE thresholds. Each time the FE falls below the lower FE threshold, a second wait timer (t WAIT2 ) is initiated. If the FE goes back above the lower FE threshold, t WAIT2  is reset to zero. During the period C, the FE remains below the lower FE threshold for a sufficient time (i.e., t WAIT2  is equal to t MAX2 ), and the indicator lamp  50  is switched off, as indicated by FLAG IL  going to zero. At the same point, t WAIT1  is reset to zero and begins running again toward t MAX1 . 
     At the beginning of the period D, the FE has remained above the upper FE threshold for a sufficient time period, and the indicator lamp  50  is again illuminated. t WAIT2  is concurrently reset to zero. At the beginning of the period E, the FE has remained below the lower FE threshold for a sufficient time period (i.e., t WAIT2  is equal to t MAX2 ), and the indicator lamp is switched off. 
     Referring now to  FIG. 4 , exemplary steps executed by the indicator lamp illumination control will be described in detail. In step  400 , control determines whether the HEOff mode is active. If the HEOff mode is active, control continues in step  402 . If the HEOff mode is not active, control continues in step  404 . Control determines whether V VEH  is within a velocity range that is defined between V MAX  and V MIN  in step  404 . If V VEH  is not within the velocity range, control continues in step  402 . If V VEH  is within the velocity range, control continues in step  406 . 
     In step  402 , control determines whether the indicator lamp  50  is illuminated. If the indicator lamp  50  is not illuminated, control ends. If the indicator lamp  50  is illuminated, control initiates a timer (t) in step  408 . In step  410 , control determines whether t is equal to t OFFTHR . If t is not equal to t OFFTHR , control increments t in step  412  and loops back to step  410 . If t is equal to t OFFTHR , control turns the indicator lamp  50  off in step  414  and control ends. By delaying the turning off of the indicator lamp  50  by t OFFTHR , it is ensured that the indicator lamp  50  remains on for at least t OFFTHR  to prohibit flashing of the indicator lamp  50 . 
     In step  406 , control determines whether the FE is sufficiently good to warrant illumination of the indicator lamp  50 . A good FE is determined as described above. More specifically, a good threshold is provided based on one of the ideal FE for a given V VEH , the HWY label or the CITY label. If the FE is deemed not good, control continues in step  402 . If the FE is deemed good, control continues in step  416 . 
     In step  416 , control determines whether the indicator lamp  50  is illuminated. If the indicator lamp  50  is illuminated, control ends. If the indicator lamp  50  is not illuminated, control initiates t in step  418 . In step  420 , control determines whether t is equal to t ONTHR . If t is not equal to t ONTHR , control increments t in step  422  and loops back to step  420 . If t is equal to t ONTHR , control turns the indicator lamp  50  on in step  424  and control ends. By delaying the turning off of the indicator lamp  50  by t ONTHR , it is ensured that the indicator lamp  50  remains on for at least t ONTHR  to prohibit flashing of the indicator lamp  50 . 
     Referring now to  FIG. 5 , exemplary modules that execute the indicator lamp illumination control will be described in detail. The exemplary modules include a V VEH  determining module  500 , an FE determining module  502 , an indicator lamp control module  504 , a HEOff module  506  and an accelerator pedal module  508 . The V VEH  determining module  500  determines V VEH  based on a vehicle operating parameter or parameters. For example, V VEH  can be determined based on a transmission output shaft speed signal (TOSS) and or ABS signals provided by ABS sensors associated with each wheel of the hybrid vehicle. 
     The FE determining module  502  determines the instantaneous FE based on a plurality of vehicle operating conditions including, but not limited to, an engine RPM, a manifold absolute pressure (MAP), a throttle position signal (TPS) and V VEH . The indicator lamp control module  504  regulates the on and off state of the indicator lamp  50  based on the signals from the various other modules, in accordance with the indicator lamp illumination control described in detail above. 
     The HEOff module  506  regulates whether to operate the hybrid electric vehicle in the HEOff mode and generates corresponding control signals, as well as a signal that is received by the indicator lamp control module  504 . The accelerator pedal module  508  monitors an accelerator pedal position signal (APS) and generates a signal that is received by the indicator lamp control module  504  when the APS exceeds a threshold value. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, 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.