Patent Publication Number: US-7712445-B2

Title: Fuel pressure boost method and apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/865,006 filed on Nov. 9, 2006 which is hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure is related to internal combustion engine fuel delivery. 
     BACKGROUND 
     During engine starting events, a fuel rail operative to channel pressurized fuel to the engine may not have enough pressure to deliver fuel in quantity and quality required to accurately meet engine fuel demands due to an increased response time of the fuel pump and system. This is particularly acute in all direct injection engines which rely on cam driven fuel pumps to establish the high pressures required for direct in-cylinder fuel injection. Such high pressure fuel pumps struggle to achieve adequate pressure at the typically low engine cranking speeds. Inherent advantages of direct injection gasoline engines, such as direct engine start and combustion-assisted engine start, are lost due to low fuel pressure issues at engine starting events. In addition, low fuel pressure in conventional engine start maneuvers may result in several misfire events prior to robust combustion and therefore result in poor engine startability, undesirably increased tailpipe emissions and undesirably decreased fuel economy. Similarly, during fuel/power enrichment maneuvers—especially in E85 spark-ignited direct-injection (SIDI) engines which require higher fuel flow rates due to the relatively lower power density of E85 relative to other fuels—fuel pressure can drastically drop due to transient high fueling rate requirements, resulting in lower power output and higher engine out emission due to inadequate fuel delivery. 
     Solutions to low fuel pressure include the addition of a second fuel pump. Additional pumps and the machinery required to drive them may be bulky and require a large number of additional parts, exacerbating package space issues, adding unnecessary weight to the vehicle, and adding additional parts that may eventually require service. Additionally, fuel pumps driven by electric motors frequently require a large gear reduction factor in order for both the motor and the fuel pump to operate in normal operating ranges, and such gear reduction devices are typically bulky and require a particular orientation to the attached devices. 
     SUMMARY 
     An apparatus for providing pressurized fuel for an engine includes an engine starting apparatus including an electric motor operative to crank the engine and a fuel pump operatively coupled to the electric motor. The electric motor is preferably operable independent from the starting function such that the fuel pump is selectively operable during or independent of engine cranking. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic depiction of a fuel pressure boosting apparatus and control in accordance with the present disclosure; 
         FIG. 2  is a schematic depiction of a fuel pressure boosting apparatus utilizing a cam and worm gear assembly in accordance with the present disclosure; 
         FIG. 3  is a cross-sectional depiction of a cam and worm gear assembly in accordance with the present disclosure; 
         FIG. 4  is a high level control routine depicting fuel pressure boosting control during certain exemplary engine operating scenarios in accordance with the present disclosure; 
         FIG. 5  is a more detailed depiction of a control routine depicting fuel pressure boosting control in conjunction with engine cranking in accordance with the present disclosure; 
         FIG. 6  is a more detailed depiction of a control routine depicting fuel pressure boosting control in conjunction with engine running in accordance with the present disclosure; and 
         FIG. 7  is a more detailed depiction of a control routine depicting fuel pressure boosting control in conjunction with a failed cam pump in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same, a fuel pressure boosting apparatus  10  is depicted in  FIG. 1  and includes an exemplary engine starting apparatus  12  and exemplary high pressure fuel delivery apparatus  14 . The starting apparatus  12  includes electric motor  41 . Motor  41  includes armature  18  coupled to motor output shaft  16 . Output shaft  16  is coupled to a reduction gearset  37 . Gearset  37  has an output shaft  20  which is slidably engaged with pinion gear  39 , for example through conventional screw spline coupling. Pinion gear  39  is controllably engaged and disengaged with the engine flywheel, in this particular embodiment, with gear teeth on its outer circumference (not shown) and imparts rotation thereto when engine cranking is desired. Pinion gear  39  also includes an overrun device or one-way clutch to prevent the engine, once started, from back driving the starter motor  41 . Alternatively, gearset  37  may be adapted to include such overrun functionality. Pinion gear  39  position is established by mechanical linkages including drive lever  35  and plunger arm  27  coupled to one end thereof. Linear motion of plunger arm  27  is imparted to one end of drive lever  35  which drives the end of drive lever  35  which is coupled to pinion gear  39 . Engagement and disengagement of pinion gear  39  with the engine flywheel is therefore controllable in accordance with the linear positioning of plunger arm  27 . Plunger arm  27  is biased by a return spring (not shown) toward a disengaged position with respect to the engine flywheel. Plunger arm  27  position is controllable in accordance with a pair of solenoid coils—a pull-in coil  15  and a hold coil  13 . Pull-in and hold coils are both initially energized by battery  29  when cranking is called for and plunger  27  moves in the direction of the associated arrow in the figure to effect engagement of the pinion gear  39  with the engine flywheel. Energization of the coils is effected by closure of switch  30  which may take any suitable form including mechanical, electromechanical or solid-state. During engagement motion of the plunger arm  27 , motor  41  is powered through pull-in coil  15  to effect a low power rotation during engagement owing to the voltage drop across pull-in coil  15 . Once plunger arm  27  is fully engaged, corresponding contact pad  23  bridges contacts  21 A and  21 B to short pull-in coil  15  and directly couple starter motor  41  to full battery voltage for full power rotation. Continued energization of hold coil  13  maintains engagement of pinion gear  39 . Deenergization of hold coil  13  results in release of plunger arm  27  under force of the return spring which opens the contacts  21 A and  21 B to deenergize the motor  41  and disengage the pinion gear  39  from the flywheel. One having ordinary skill in the art will recognize a number of variations respecting a starter motor arrangement and control as described herein above in the exemplary apparatus. For example, hold-in coil  13  may magnetically latch the plunger arm, the motor  41  may provide direct drive of the flywheel absent any reduction gearset, and different engagement linkages may be employed. Additionally, the switching function provided by contact pad  23  and contacts  21 A and  21 B may alternatively be provided by a controlled switch such as a controlled electromechanical or solid state switch. 
     With continued reference to  FIG. 1 , high pressure fuel delivery apparatus  14  includes high pressure fuel supply  49  from a primary fuel pump (not shown). High pressure fuel is supplied to a high pressure fuel rail  47  which supplies a plurality of fuel injectors (not shown). 
     In accordance with the present disclosure, a fuel pump in the form of high pressure boost pump  43 , which may be a piston-type pump, is coupled to the output shaft  16  of the starter motor  41 . In the exemplary embodiment, this coupling is through a reduction gearset  45  and is at the end of the starter motor  41  opposite the pinion gear  39 . Any alternative arrangement, including directly driving the high pressure boost pump  43  from the output shaft  16  without an intervening gearset, driving the high pressure boost pump off of a gearset shared with the pinion gear drive, etc., is contemplated. It is only necessary in accordance with the present disclosure that the high pressure boost pump  43  be drivable by the starter motor  41 . High pressure boost pump  43  is in fluid communication with the fuel reservoir (not shown) on a suction side thereof and is effective when operative to supply high pressure fuel to fuel rail  47 . As can be appreciated from the foregoing description, the high pressure boost pump  43  supplies high pressure fuel to fuel rail  47  any time starter motor  41  is operative. Therefore, during the engagement period of operation when the pull-in  15  and hold  13  coils are energized and during the subsequent engaged period of operation when only the hold coil  13  remains energized, the high pressure boost pump is providing high pressure fuel to fuel rail  47  thereby compensating additively the characteristically low fuel pressure from the cam driven fuel pump during engine cranking. And, once engine ignition has taken hold, engine idle speed attained and cranking is no longer required, further energization of the starter motor  41  is terminated. The termination of starter motor energization ceases forced rotation of the starter motor  41  and disengages the mechanical coupling of the starter motor  41  output shaft  16  and armature  18  from the engine. Therefore, subsequent to engine cranking, the starter motor armature  18  and output shaft  16  remains static. Hence, the high pressure boost pump remains static and is not contributing any parasitic load upon the engine of electrical system of the vehicle. 
     In accordance with a further embodiment of the disclosure, and one in which additional extended fuel boost functionality is attained, high pressure boost pump is operative by the starter motor  41  independently of the cranking functionality of the starting apparatus  12 . Boost coil  17  is controllable to pull plunger arm  25  in the direction of the associated arrow in the figure against the bias of a return spring (not shown). Energization of boost coil  17  is effected by closure of switch  34  which may take any suitable form including mechanical, electromechanical or solid-state. Plunger arm  25  has a corresponding contact pad  19  which is forced into contact with and bridging contacts  21 A and  21 B. The shorted contact pads  21 A and  21 B effect the direct coupling of full battery voltage to the starter motor  41  for full power rotation of the armature, output shaft and high pressure boost pump. One having ordinary skill in the art will recognize that the switching function provided by contact pad  19  and contacts  21 A and  21 B may alternatively be provided by a controlled switch such as a controlled electromechanical or solid state switch. Such an arrangement advantageously makes full use of the significant torque capacity of the and almost instantaneous response of the otherwise unloaded starter motor  41  to provide high pressure fuel to the fuel rail  47  during periods of engine operation. For example, such high pressure boost pump operation may be beneficial during periods of exceptionally significant or sustained periods of fuel consumption, such as during fuel enrichment or heavy loads. As another example, such high pressure boost pump operation may also be beneficial to alleviate anomalous operation of the primary cam driven fuel pump. In other words, a system so mechanized with a high pressure boost pump advantageously enables continued operation, perhaps at decreased levels of performance, of the engine in the event of an improperly operative (e.g. low pressure) or wholly inoperative high pressure fuel supply  49  to the fuel rail  47 . 
     Preferably, the control of switches  30  and  34 , as well as any alternative implementations of the functionality of contact pads  23  and  19  and contacts  21 A and  21 B, is by way of computer based controller  11  as illustrated with respect to switches  30 ,  34  by respective control lines  31 ,  33 . Controller  11  is preferably a general-purpose digital computer including a microprocessor or central processing unit, read only memory (ROM), random access memory (RAM), electrically programmable read only memory (EPROM), high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry, and input/output circuitry and devices (J/O) and appropriate signal conditioning and buffer circuitry. The controller has a set of control routines, comprising resident program instructions and calibrations stored in ROM. 
     Routines for engine control, including cranking, are typically executed during preset loop cycles such that each algorithm is executed at least once each loop cycle. Routines stored in the non-volatile memory devices are executed by the central processing unit and are operable to monitor inputs from sensing devices and execute control and diagnostic routines to control operation of the engine using preset calibrations. Loop cycles are typically executed at regular intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing engine operation. Alternatively, algorithms may be executed in response to occurrence of an event or interrupt request such as, for example, operator request for engine ignition. 
     As previously described, high pressure boost pump  43  is coupled to output shaft  16  of starter motor  41 . In one exemplary embodiment as depicted in  FIG. 1 , this coupling is through reduction gearset  45  and is at the end of starter motor  41  opposite pinion gear  39 . The use of reduction gearset  45  enables the use of a known starter motor that runs at a high speed with a known fuel pump that runs at a low speed by introducing a gear reduction factor. However, many embodiments of reduction gearset  45  require significant package space and must be located proximately to starter motor  41  and output shaft  16 . Package space within an engine compartment and particularly in close proximity to starter motor  41  is not always readily available and may pose serious engine design issues.  FIGS. 2 and 3  illustrate an exemplary embodiment that utilizes a cam and worm wheel assembly  60  in place of reduction gearset  45  in order to accomplish the gear reduction factor described above while gaining flexibility in package space. However, it will be appreciated that many alternative embodiments of reduction gearset  45  are contemplated, including common gears and planetary gear sets well known in the art. 
       FIG. 2  illustrates an exemplary fuel pressure boosting apparatus  10 , including engine starting apparatus  12 , high pressure boost pump  43  in the form of piston pump  90 , high pressure fuel delivery apparatus  14 , and cam and worm wheel assembly  60 . Cam and worm wheel assembly  60  includes a worm wheel  70 , a cam  80 , and a shaft  72 . Electric motor  41  of engine starting apparatus  12  turns a worm  50  which, in this particular embodiment, is fixedly attached to output shaft  16 . It will be appreciated that worm  50  may be attached to output shaft  16 , or worm  50  may exist on its own shaft, coupled to output shaft  16  through some coupling device. Worm  50  uses spiral threading around a cylindrical core and mechanically interacts with worm wheel  70  such that as output shaft  16  turns, worm  50  turns worm wheel  70 . 
     Worm gear mechanisms such as the one utilized the exemplary system of  FIG. 2  are especially advantageous for use in applications requiring high gear reduction factors and also requiring package space flexibility. Those having ordinary skill in the art will appreciate that worm gears are known to accomplish high gear reduction factors. Also, worm  50  is a compact component and may be only relatively minimally larger than the shaft on which it is mounted, and worm wheel  70  can be flexibly located in any orientation around the worm that supports the mechanical contact between worm  50  and worm wheel  70 . As a result of these features of the worm gear design which accommodate gear reduction and package space issues, the connection of high pressure boost pump  43  to starter motor  41  in close proximity to the engine block and other large, immovable engine components and the gear reducing function inherent to a worm gear are made possible. 
     Worm  50  and worm wheel  70  accomplish the transmission of torque and provide a gear reduction factor for the purpose of driving high pressure boost pump  43 . The torque provided through worm wheel  70  may be utilized in a number of ways. In the exemplary embodiment depicted in  FIG. 2 , worm wheel  70  is attached to shaft  72  for the purpose of transferring torque from worm  50  to some fuel pump driving mechanism, in this case, cam  80 .  FIG. 3  depicts an exemplary embodiment whereby cam and worm wheel assembly  60  is held in contact with worm  50 . Shaft  72  is axially held in place by bearings  74  and  76  and is allowed to rotate. Cam  80  is fixedly attached to shaft  72 , such that when worm wheel  70  is turned by worm  50 , shaft  72  spins, causing cam  80  to spin in unison with worm wheel  70 . Returning to  FIG. 2 , cam  80  is a rotating disk and is well known in the art. Cam  80  is formed in shape such that, as cam  80  spins, lobes  82  on the circumference of cam  80  spin around the center of cam  80 . Lobes  82  interact with piston pump  90  to drive the piston mechanism in and out, thereby powering piston pump  90 . Cams may utilize a single lobe, for example, as is widely used in camshaft applications, or cams may utilize a plurality of lobes. Cam  80  utilized in this exemplary embodiment utilizes three lobes  82 . In this particular exemplary embodiment of piston pump  90 , the piston mechanism includes piston  92 , piston spring  94 , and flat face plate  96 . Flat face plate  96  is located such that the lobes  82  around the circumference of cam  80  interact with and push outward with each lobe  82  on flat face plate  96  as cam  80  spins. Flat face plate  96  is attached to piston  92 , which axially transfers force from flat face plate  96  to the internal mechanisms of piston pump  90  to perform fuel pumping work. Piston  92  and flat face plate  96  are biased towards an out position by piston spring  94  which is located around piston  92  and is compressed between flat face plate  96  and the body of piston pump  90 . The bias of piston spring  94  is counteracted by lobes  82  rotating around the circumference of cam  80 , causing the in and out motion described above used to power piston pump  90 . In this way, cam and worm wheel assembly  60  transfers power from high speed output shaft  16  to piston pump  90 , utilizing different package space options and accomplishing the gear reduction factor required to utilize piston pump  90 . It will be appreciated by those having ordinary skill in the art that a multitude of arrangements for converting the high speed output shaft  16  into a low speed input for a fuel pump may be utilized with different package space effects, and the disclosure is not intended to be limited to the embodiments listed herein. 
     Having thus described operative embodiments for effecting fuel boost, the remaining  FIGS. 4 through 7  are now referenced and depict exemplary routines suitable for execution by controller  11  in carrying out certain functions in accordance with the present disclosure.  FIG. 4  depicts a high level control routine for fuel pressure boosting control during certain exemplary engine operating scenarios in accordance with the present disclosure as implemented in conjunction with the exemplary apparatus herein before described. The routine determines through logical decisions at blocks  201  through  205  whether a mode of engine operation or control requires operation of the high pressure boost pump and attendant fuel pressure boost through execution of an appropriately more detailed boost control routine  207 . Where no call for high pressure boost pump operation is required, block  215  is executed whereat all coils  13 ,  15  and  17  are deenergized by deactivation or opening of switches  30  and  34 . 
     The three exemplary scenarios illustrating the utility of the disclosure and demonstrative of various inventive control aspects are respectively illustrated in decision blocks  201 ,  203 , and  205  and corresponding detailed boost routines  209 ,  211 , and  213 , respectively. In a first scenario of desired high pressure boost pump operation when engine cranking is desired or active in accordance, for example, with operator initiation or subsequent controller crank operation, decision block  201  would pass control to crank boost control routine further illustrated in  FIG. 5 . Similarly, in a second scenario of desired high pressure boost pump operation when the engine is running and fuel enrichment is desired in accordance, for example, with vehicle throttle pedal position, decision block  203  would pass control to run boost control routine further illustrated in  FIG. 6 . And, in a third scenario of desired high pressure boost pump operation when engine operation is desired in accordance, for example, with a diagnosed faulty cam driven pump or low pressure fuel supply, decision block  205  would pass control to run boost control routine further illustrated in  FIG. 7 . 
     Taking the first exemplary scenario of high pressure boost pump operation during engine cranking described above as boost routine  209  and with more particular reference to  FIG. 5 , an exemplary routine for execution by controller  11  includes a determination at block  301  to provide an initial period at the inception of the engine cranking control during which the high pressure boost pump is caused to spin up and establish pressure. Therefore, if this initial timeout period has not expired, block  301  passes control to block  303  whereat only the boost coil  17  is energized to establish adequate pressure in the fuel rail prior to engine cranking. Subsequent to block  303 , the routine is exited. When the initial timeout period has expired, block  301  passes control to block  305  whereat the boost coil is deenergized since continued energization will no longer be required to maintain the rotation of the high pressure boost pump in accordance with the subsequently illustrated blocks to be described. Subsequently, the hold and pull-in coils are energized at blocks  307  and  309  to effect engine cranking and the continued operation of the high pressure boost pump. Block  311  next represents fuel pressure regulation as may be implemented, for example, by way of pressure bleed off and fuel return to the fuel reservoir to maintain a desired fuel rail pressure. Subsequently, the routine is exited. When cranking is no longer desired, and assuming other high pressure boost pressure operational modes are not called for, block  215  of  FIG. 4  will effect deenergization of all coils resulting in the termination of pinion to flywheel engagement and starter motor rotation. 
     Taking next the second exemplary scenario of high pressure boost pump operation during engine operation described above as boost routine  211  and with more particular reference to  FIG. 6 , an exemplary routine for execution by controller  11  includes block  401  whereat only the boost coil  17  is energized to establish pressure in the fuel rail in conjunction with the pressure being established independently by the cam driven fuel pump. Block  401  passes control to block  403  which represents fuel pressure regulation as may be implemented, for example, by way of pressure bleed off and fuel return to the fuel reservoir to maintain a desired fuel rail pressure. Subsequently, the routine is exited. When boosting fuel pressure by the high pressure boost pump is no longer desired, and assuming other high pressure boost pressure operational modes are not called for, block  215  of  FIG. 4  will effect deenergization of all coils resulting in the termination of starter motor rotation and high pressure boost pump operation. 
     Taking next the third exemplary scenario of high pressure boost pump operation during engine operation in response to diagnosis of a faulty cam driven pump described above as boost routine  213  and with more particular reference to  FIG. 7 , an exemplary routine for execution by controller  11  includes block  501  whereat only the boost coil  17  is energized to establish pressure in the fuel rail in conjunction with the pressure being established independently by the cam driven fuel pump, which pressure has been diagnosed as being inadequate. Block  501  passes control to block  503  which represents fuel pressure regulation as may be implemented, for example, by way of pressure bleed off and fuel return to the fuel reservoir to maintain a desired fuel rail pressure. Subsequently, the routine is exited. When boosting fuel pressure by the high pressure boost pump is no longer desired, and assuming other high pressure boost pressure operational modes are not called for, block  215  of  FIG. 4  will effect deenergization of all coils resulting in the termination of starter motor rotation and high pressure boost pump operation. 
     The disclosure has described certain preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.