Abstract:
A method for controlling a direct injection fuel system of a vehicle, the method comprising generating fuel pressure via an electronically controlled lift pump and a second pump, the electronically controlled lift pump actuated responsive to a command during an initial start-up duration, translating the fuel pump command via a first mapping to drive the fuel pump, where the first mapping includes mapping a default signal to active pump operation and after the initial start-up duration, translating the fuel pump command via a second mapping to drive the fuel pump where the second mapping includes mapping the default signal to pump deactivation. This method may achieve near immediate lift pump actuation upon system power-up while preserving favorable degradation modes and maintaining a simple, cost-effective inter-module communication scheme.

Description:
BACKGROUND AND SUMMARY 
     During a vehicle start operation, it may be advantageous to provide fuel pressure to the fueling system of the engine as fast as possible, especially in a direct injection engine system. Various approaches have been described to achieve such a feature. 
     While low pressure (e.g., port injection) single speed (single pump voltage) mechanical returnless fuel systems may achieve lift pump operation with no minimal delays in application of the fuel lift pump using a default, on-command, for the lift pump. However, such a lift pump system may operate ineffectively in higher pressure, direct injection systems since a single speed fuel system results in design tradeoffs that injure lift pump durability and increase lift pump energy consumption. Thus, variable speed/voltage pumps have been applied in direct injection applications. 
     Furthermore, when using a variable speed electronically controlled pump in direct injection applications, prior approaches have utilized a default, off-command, for the pump to address various degradation conditions (so that inadvertent pump operation is less likely to occur). However, this default-off state adds to delays in providing sufficient fuel pump pressure, since various systems must first initialize before the fuel pump may be reliably activated. Other solutions use complex wiring and communications between the PCM and lift pump control module to achieve the goal of rapid lift pump voltage application with favorable behaviors in degraded states. 
     The inventors herein have recognized the above issues, and attempted to address the conflicting requirements of the prior art, in one embodiment, by a method for controlling a fuel system of a vehicle. The method may comprise generating fuel pressure via an electronically controlled pump, the electronically controlled pump actuated responsive to a command; during an initial start-up duration, translating the fuel pump command via a first mapping to drive the fuel pump, where the first mapping includes mapping a default signal to active pump operation; and after the initial start-up duration, translating the fuel pump command via a second mapping to drive the fuel pump where the second mapping includes mapping the default signal to pump deactivation. 
     In one example, it is thus possible to provide a system that does not activate the fuel pump when a command is absent, avoids activating the fuel pump in response to various system degradation conditions, yet still provides variable speed pump operation with pump activation upon control system initialization without waiting for initialization of the control system. Note, however, that various other alternative and/or additional functions may be achieved. Further, note that various approaches may provide a first and second mapping, such as via an algorithm in a processor, an electrical circuit, etc. Further, note than the initial duration may include a time limit, or a non-time-based limit (e.g., it may include a limit related to a number of calculations performed by a processor, etc). 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows an example system diagram including a fuel system for an engine of a vehicle. 
         FIG. 2  shows an example high level flow chart for controlling system operation. 
         FIG. 3  show example mappings for enabling control of the fuel system. 
         FIG. 4  shows an example fuel system timing diagram. 
         FIGS. 5A-5B  shows additional system details for various default configurations. 
     
    
    
     DETAILED DESCRIPTION 
     As will be described in further detail herein, the present application relates to achieving a low costs fuel system for a vehicle that can enable improved starting with earlier application of a fuel pump following initial key-on operation. In one example, such operation is achieved with reduced wiring requirements while still achieving acceptable default operation in the presence of degradation. 
     Referring now to  FIG. 1 , an example fuel system  100  is illustrated in communication with a control system  110 , and vehicle powertrain system  112 . The vehicle powertrain system may include an engine  142 , which may be a gasoline engine, manual and/or automatic transmission  144 , and other components. 
     Fuel system  100  may be a direct injection high pressure fuel system, including an electronic multi-speed lift pump  120  and a mechanical high pressure pump  122 . Lift pump  120  may be coupled upstream of the high pressure pump  122 , and may be located with a fuel tank  130  containing fuel  132 . Lift pump  120  may be a two-speed pump, continuously variable speed pump, etc., and may operate to increase fuel pressure from tank pressure to an intermediate pressure, before fuel pressure is raised to an injection pressure via pump  122 . Various check valves, filters, and other devices may further be included in the fuel system, such as check valve  134  coupled downstream of pump  120 , and check valve  136  coupled around pump  122 . Check valve  134  operates to prevent backflow into pump  120 , and check valve  136  operates as a path around pump  122 . Further, a filter  138  may be positioned downstream of check valve  134 , but upstream of a bypass regulator  139  coupled in the tank  130 . 
     The high pressure pump  122  lead to a fuel rail  140 , which delivers fuel to a plurality of direct injection, in-cylinder, fuel injectors of engine  142 . Further, a pressure sensor  144  may be coupled to the fuel rail, and deliver a signal to the control system indicative of fuel rail pressure that is used to control the fuel pumps, and/or other operations, such as engine operation, etc. 
     Continuing with  FIG. 1 , a portion of the control system  110  may include a powertrain control module (PCM)  150  and a lift pump control module  160 , as well as various sensor and/or actuator signals. The PCM may include various components, such as RAM, ROM, I/O, processors, etc. The PCM may further include instructions executable by the processor to carry out various operations, as described in further detail herein. PCM  150  specifically includes a microcontroller  152  communicating with a driver  154 . While only a single processor and driver are illustrated, various others may be included. 
     In this example, microcontroller  152  may include code for controlling engine and/or transmission operation response to various vehicle sensors, operator commands, etc., including controlling fuel injection, exhaust components, and others. Further, microcontroller  152  may proceed through an initialization sequence upon vehicle starting, such as initiated responsive to a vehicle operator key-on operation through ignition interface  170 . In one example, PCM  150  receives power upon a key-on event. Note that while this example illustrate key-on operation via a physical key  172 , various other approaches may be used, such as digital signatures, wireless communications, etc. Further, various other power-on events may be used, such as a door-ajar signal, a key insertion signal, etc. The initialization sequence may include initial power up and initializing before taking active control and adjustment of various output signals that may be set at default levels during such conditions. After initialization, PCM  152  adjusts the various output signals responsive to measured operating conditions, code contained therein, etc. Also, as indicated in  FIG. 1 , in this embodiment, there is no need to route an ignition signal (e.g.,  170 ) to module  160 , although such a modification may be used, if desired. 
     Driver  154  enables translation of microcontroller level control signals (e.g., lower current, 0-5V signals) to inter-module communication level control signals (e.g., high current, 0-12V signals) Specifically, driver  154  generates a lift pump control signal  180  that is transmitted to module  160 . Signal  180  may be a pulse width (duty cycle, frequency, etc.) modulated signal, and be either active high or active low. An active high signal indicates that when the signal  180  is high (e.g., 12V), this corresponds to applying pump voltage and supplying electrical energy to the lift pump  120  driven by the signal (via module  160 , as noted below). Similarly, an active low signal indicates that when the signal  180  is low (e.g., 0V, ground), this corresponds to applying pump voltage and supplying electrical energy to the lift pump  120  driven by the signal (via module  160 , as noted below). 
     Module  160  includes a microprocessor  162  or other application specific integrated circuit (ASIC) configured to translate incoming signal  180  coupled via pull down resistor  168  into a driving signal  164  delivered to pump  120  for controlling pump actuation (e.g., pump speed). Further, module  160  may communicate diagnostic information back to PCM  150  via signal  182 . Module  160  translates the incoming command signal  180  to the driving signal  164  to enable earlier application of the lift pump during and following PCM initialization, yet still retain adequate control and degradation operation. Further, module  160  receives a restraint deployment signal (RCM)  190 . The table below illustrates example operation of the restraint deployment operation. 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 RCM to  
                   
                   
               
               
                   
                 Module 160 
                   
                   
               
               
                   
                 Signal  
                   
                 Module 160  
               
               
                   
                 Frequency 
                 Definition 
                 “Read” 
               
               
                   
                   
               
             
             
               
                   
                 Open or  
                 No 
                 Enable pump output 
               
               
                   
                 no signal 
                 communication 
                   
               
               
                   
                  10 Hz 
                 Normal  
                 Enable pump  
               
               
                   
                   
                 operation 
                 output and clear 
               
               
                   
                   
                   
                 disable/override flags 
               
               
                   
                 250 Hz 
                 Deployment 
                 Enable pump  
               
               
                   
                   
                 Event 
                 output 
               
               
                   
                 500 Hz-250  
                 Valid “Off” 
                 Disable pump output  
               
               
                   
                 Hz 
                 command 
                 if and only if: 
               
               
                   
                 alternating 
                   
                 A total of three (3)  
               
               
                   
                   
                   
                 500 Hz pulses and a 
               
               
                   
                   
                   
                 total of three (3)  
               
               
                   
                   
                   
                 250 Hz pulses are 
               
               
                   
                   
                   
                 detected in any order  
               
               
                   
                   
                   
                 within any 30 msec 
               
               
                   
                   
                   
                 window. 
               
               
                   
                   
                   
                 500 Hz pulse  
               
               
                   
                   
                   
                 determined by: 
               
               
                   
                   
                   
                 V high  &gt;=4.5 V  
               
               
                   
                   
                   
                 for 1.0 ± 0.1 msec 
               
               
                   
                   
                   
                 followed by 
               
               
                   
                   
                   
                 V low  &lt;2.5 V for  
               
               
                   
                   
                   
                 1.0 ± 0.1 msec 
               
               
                   
                   
                   
                 within 2.0 ± 0.2 msec.; 
               
               
                   
                   
                   
                 250 Hz pulse  
               
               
                   
                   
                   
                 determined by: 
               
               
                   
                   
                   
                 V high  &gt;=4.5 V for  
               
               
                   
                   
                   
                 2.0 ± 0.1 msec 
               
               
                   
                   
                   
                 followed by 
               
               
                   
                   
                   
                 V low  &lt;2.5 V for  
               
               
                   
                   
                   
                 2.0 ± 0.1 msec 
               
               
                   
                   
                   
                 within 4.0 ± 0.2 msec. 
               
               
                   
                   
                   
                 Set pump control output  
               
               
                   
                   
                   
                 duty cycle to 0 
               
               
                   
                   
                   
                 within 10 msec  
               
               
                   
                   
                   
                 following the 
               
               
                   
                   
                   
                 detection of the three  
               
               
                   
                   
                   
                 500 Hz and three 
               
               
                   
                   
                   
                 250 Hz pulses  
               
               
                   
                   
                   
                 within any 30 msec 
               
               
                   
                   
                   
                 window. 
               
               
                   
                   
               
             
          
         
       
     
     The lift pump control module further communicates the restraint deployment to the PCM via the diagnostic signal  182 , which is a redundant communication path. 
     In one particular example, to enable improved vehicle starting, driver  154  is configured to be in the active state by default (including before any command from the microcontroller  152  is generated), where if the signal is active, the fuel pump is actuated. In one embodiment, the active state corresponds to 100% active duty cycle. Specifically, a 100% active duty cycle received by module  160  is translated to command the fuel pump duty cycle to 100% during an initial duration after key-on; but then alternatively translated thereafter so that as soon as the microcontroller  152  was powered up, initialized, and performing control so that the PCM was issuing a duty cycle, such signal would control the pump. In this way, even before the PCM is powered up, initialized, and performing control, voltage can be applied to the fuel pump. I.e., fuel pump voltage can be applied immediately because the fuel pump command  180  would be in the active state at PCM power-up. Then, once the PCM dynamically controls the command signal, the module enables the dynamic control to be passed to the pump so that the pump follows the dynamic PCM control. 
     Further, to address various degradation conditions, module  160  operates to modify the received command signal differently before and after an initial duration, which in one example includes an initial time-out. Specifically, after the initial time-out, the module does not provide pump activation responsive to the default command. The translation and time-out operation of module  160  is described further with regard to  FIG. 2-3 , for example. 
     Referring now to  FIG. 2 , a high level flow chart illustrates various operation. Note that the flow chart may represent code and/or instructions encoded in one or both of  152  and  162 , as indicated. 
     Responsive to key-on operation at  210 , both processors receive power and commence operating. Specifically, PCM  150  operates as indicated at  220  and module  160  operates as indicated at  222 . However, in various alternative examples, the functions may be combined and/or further divided. 
     At  230 , the PCM powers-up, initializes, and determines a desired fuel pump command signal based on various operating parameters, such as rail pressure, engine operation, ambient temperature, ambient pressure, etc. Then, at  232 , the PCM sends the fuel pump command via signal  180  to module  160 . Such operation is repeatedly performed to provide variable lift pump actuation responsive to operating conditions. Further, because the default state of the driver  154  corresponds to activation (which may be full, or maximum, actuation of the fuel pump  120 ), the above operation results in activation of the fuel pump after key-on limited only by the start-up/initialization of processor/ASIC  162 , which can be significantly faster than processor  152 , since processor/ASIC  162  may be considerably simpler than processor  152 . 
     At  242 , module  160  determines whether a time since activation is greater than a limit time T 1 , which in one example may be set to approximately 0.4 seconds. If so, in  244  module  160  sends a fuel pump a driving signal  164  using a first mapping based on signal  180  received from the PCM. Alternatively, in  246  module  160  sends the fuel pump driving signal  164  using a second mapping based on signal  180  received from the PCM. The mapping may be illustrated via the following table. Note that in this example, it is only the 100% duty cycle meaning that differs depending on time since power was applied to the fuel pump module. 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Fuel Pump 
                 Pump Module  
                 Pump Module  
               
               
                   
                 Command 180 
                 power-up timer 
                 power-up timer 
               
               
                   
                 (duty cycle) 
                 &lt;0.4 second 
                 &gt;0.4 second 
               
               
                   
                   
               
             
             
               
                   
                 FPC = 0% 
                 Pump Duty  
                 Pump Duty  
               
               
                   
                   
                 Cycle 164 = 0% 
                 Cycle = 0% 
               
               
                   
                  0% &lt; FPC &lt; 4% 
                 Pump Duty  
                 Pump Duty  
               
               
                   
                   
                 Cycle = 0% 
                 Cycle = 0% 
               
               
                   
                  4% &lt;= FPC &lt;= 50% 
                 Pump Duty  
                 Pump Duty  
               
               
                   
                   
                 Cycle = 2 * FPC 
                 Cycle = 2 * FPC 
               
               
                   
                 50% &lt; FPC &lt; 55% 
                 Pump Duty  
                 Pump Duty  
               
               
                   
                   
                 Cycle = 100% 
                 Cycle = 100% 
               
               
                   
                 55% &lt; FPC &lt; 100% 
                 Pump Duty  
                 Pump Duty  
               
               
                   
                   
                 Cycle = 0% 
                 Cycle = 0% 
               
               
                   
                 FPC = 100% 
                 Pump Duty  
                 Pump Duty  
               
               
                   
                   
                 Cycle = 100% 
                 Cycle = 0% 
               
               
                   
                   
               
             
          
         
       
     
     Thus, upon power-up, the fuel pump module  160  receives a steady “on” command from the PCM (where the PCM microcontroller  162  is not yet dynamically controlling the signal outputs). Within the first second of operation, the PCM duty cycle begins dynamic control, and the fuel pump module  160  passes this dynamic command through to the pump. However, should the fuel pump module get an “on command” but not see a duty cycle within the time limit (T 1 ), it times out and the fuel pump is effectively disabled. 
       FIG. 3  further illustrates the first and second mapping/translation performed by module  160 . Specifically, the dashed line shows the first mapping, and the solid line shows the second mapping. As noted above, depending on the duration (which may be a timer, number of calculations, number of clock pulses, etc.) the different mappings are applied to drive the fuel pump. The mappings effectively enable the module to pass through mid-range duty cycles before and after time reaches the limit, but before the limit, pass through a fully active default command, whereas after the limit, such default commands are not passed through. Further, the mapping accounts for degradation where the command signal is stuck high, and/or stuck low. 
       FIG. 4  shows key-on behavior according to operation as described herein as a prophetic example. The top graph shows the fuel pump command signal from the PCM (e.g., signal  180 ) and the bottom graph shows the fuel pump voltage (e.g., via signal  164 ). As illustrated in the figure, the fuel pump module  160  does not apply voltage to the fuel pump without a corresponding PCM command. Further, in a situation where no degradation is present, fuel pump voltage is applied almost immediately (e.g., less than 10 ms). Finally, should a short-to-power degradation exist in signal  180 , fuel pump voltage is only applied for the limit time, e.g. 0.4 seconds. 
       FIG. 5  shows further details comparing the configuration for active high and active low embodiments. Specifically,  FIG. 5A  shows a scheme where the PCM  150  has a high-side driver and the module  160  has a pull-down resistor to ground, with driver  154  illustrated via a switch. In this scenario an short to ground or an open of signal  180  during the initial period during which the PCM initializes (e.g., 150 milliseconds in this example) results in no un-commanded fuel pump voltage application, and an short to power of signal  180  during the initial period during which the PCM initializes results in up to 150 milliseconds of un-commanded fuel pump voltage application. 
     Alternatively, as shown in  FIG. 5B , the PCM  150  includes a low-side driver and module  160  has a pull-up resistor to power. In this scenario a short to ground or an open of signal  180  during the initial 150 milliseconds results in up to 150 milliseconds of un-commanded fuel pump voltage application, and a short to power of signal  180  during the initial 150 milliseconds results in no un-commanded fuel pump voltage application. 
     While the above examples illustrate various configurations to enable faster fuel pump activation, while managing cost and degradation performance, still other variations may be used. For example, the PCM may be configured to generate mid-range signals as a default signal (e.g., output signal  180  having a 150 Hz square-wave as its default state, which can operate while PCM microcontroller is in rest or being initialized). In this case, module  160  can utilize alternative first and second mappings to accept such a state. Further, the PCM may be configured to issue a constant analog voltage on signal  180  between 0 and battery as its default state. Module  160  can then be configured to identify such a command as a pump on command during first 150 milliseconds of operation. However, such an example may include various modifications to module  162 , for example. 
     Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts may graphically represent code to be programmed into the computer readable storage medium in the engine control system. 
     It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied with various combinations of different engine, transmission, motor configurations. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
     The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.