Abstract:
A fuel delivery system for an engine. The fuel delivery system includes a fuel tank, at least one fuel injector, a fuel pump, a pressure sensor, a temperature sensor, and an engine control module. The fuel pump is configured to draw fuel from the fuel tank and provide the fuel to the at least one fuel injector. The pressure sensor is configured to sense a pressure of the fuel being provided to the at least one fuel injector. The temperature sensor is configured to sense a temperature of the engine. And the engine control module is configured to control the fuel pump based on the sensed pressure and the sensed temperature.

Description:
BACKGROUND 
   Internal combustion engines, such as used in motorcycles or automobiles, require fuel to operate. The fuel is generally stored in a fuel tank, located a distance from the engine, and is pumped to the engine. Fuel delivery systems for pumping the fuel to the engine are either closed-loop systems or open-loop systems. In an open-loop system, a fuel pump is operated at a constant rate to provide sufficient fuel to the engine for all operating conditions. When less fuel is required than is provided by the fuel pump, the excess fuel is returned to the fuel tank. 
   In a closed-loop system, there is no return path for fuel back to the fuel tank. Instead, the fuel pump is controlled to provide fuel to the engine at a constant pressure regardless of the quantity of fuel used by the engine. 
   SUMMARY 
   The present invention provides a closed-loop fuel delivery system that optimizes performance of and emissions from an engine by varying the pressure of fuel in a fuel line based on an operating mode and one or more engine characteristics. 
   In one embodiment, the invention provides a fuel delivery system including a fuel tank, at least one fuel injector, a fuel pump, a pressure sensor, a temperature sensor, and an engine control module. The fuel pump is configured to draw fuel from the fuel tank and provide the fuel to the at least one fuel injector. The pressure sensor is configured to sense a pressure of the fuel being provided to the at least one fuel injector. The temperature sensor is configured to sense a temperature of the engine. And the engine control module is configured to control the fuel pressure based on the sensed pressure and the sensed temperature. 
   In another embodiment, the invention provides a motorcycle including an engine, a fuel tank, a fuel delivery system, a temperature sensor, and an engine control module. The engine includes at least one fuel injector. The fuel delivery system includes a pressure sensor and a fuel pump configured to draw fuel from the fuel tank and provide the fuel to the at least one fuel injector. The temperature sensor is configured to sense a temperature of the engine and the engine control module is configured to control the fuel pump based on the sensed pressure and the sensed temperature. 
   In another embodiment the invention provides a method of delivering fuel to an engine. The method includes the acts of detecting a fuel pressure, detecting engine temperature, determining a fuel pressure set-point based on the detected temperature, and controlling the fuel pressure based on the detected fuel pressure and the fuel pressure set-point. 
   Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a motorcycle embodying the present invention. 
       FIG. 2  schematically illustrates an ignition switch of the motorcycle of  FIG. 1 . 
       FIG. 3  illustrates a schematic diagram of a fuel delivery system embodying the present invention. 
       FIG. 4  illustrates a flow chart of a start routine of the fuel delivery system of  FIG. 3 . 
       FIG. 5  illustrates a flow chart of a run routine of the fuel delivery system of  FIG. 3 . 
       FIG. 6  illustrates a flow chart of a stop routine of the fuel delivery system of  FIG. 3 . 
   

   DETAILED DESCRIPTION 
   Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
     FIG. 1  illustrates a motorcycle  10  including a frame  12 , a seat  14 , a front wheel  16  supported by a front fork  18 , a rear wheel  20  supported by a swing arm  22 , and an engine  24 . The engine  24  provides power to the rear wheel  20  through a transmission. The engine  24  includes two cylinders  26  for combusting an air-fuel mixture. In the illustrated motorcycle  10 , a portion of the frame  12  comprises a fuel tank  40  that stores fuel. 
   The motorcycle  10  also includes an ignition switch  42 . As shown in  FIG. 2 , the ignition switch  42  has two positions, off  44  and run  46 . An operator can use a valid key inserted in the ignition switch  42 , along with a start button (not shown), to operate the motorcycle  10  in a known manner. In other embodiments, the function of the ignition switch  42  can be performed using a start button, a stop button, and a wireless security device. 
     FIG. 3  is a schematic illustration of a fuel delivery system  100 , according to one embodiment of the invention, for delivering fuel from the fuel tank  40  to the first and second cylinders  26 . The fuel delivery system  100  includes a fuel pump  105 , a fuel pressure sensor  110 , a first fuel injector  115 , a second fuel injector  120 , an engine control module  125  (“ECM”), an ignition switch position indicator  130 , a start button indicator  132 , an engine temperature sensor  135 , a throttle position sensor  140 , and an engine speed sensor  145 . 
   In some embodiments, the ECM  125  can be dedicated to controlling the fuel delivery system  100 . In other embodiments, the ECM  125  can control other functions of the motorcycle  10  (e.g., ignition/spark) in addition to controlling the fuel delivery system  100 . In the embodiment shown, the ECM  125  monitors the ignition switch position indicator  130  to determine the position of the ignition switch  42  (e.g., stop, run) and the start button indicator  132  to determine if the start button is pressed. The ECM  125  also receives an indication of the temperature of the engine  24  from the engine temperature sensor  135  (e.g., a temperature of an engine coolant). The indication can be in any suitable form, such as an analog signal, a digital signal, or an electrical resistance. 
   The ECM  125  also receives an indication of a throttle position from the throttle position sensor  140 . The throttle position sensor  140  can provide the ECM  125  with a byte of data indicative of a percentage the throttle is open (e.g., between 0 and 100 percent). In a preferred embodiment, the throttle travels between 0 degrees (fully closed) and 85 degrees (fully open). The throttle position sensor  140  provides the byte of data with the values of 0 h when the throttle is at 0 degrees, 80 h when the throttle is at 42.5 degrees, and FFh when the throttle is at 85 degrees. In some embodiments, the throttle position sensor  140  can provide an analog signal (e.g., 0-10 volts) to indicate the position of the throttle. 
   The engine speed sensor  145  provides an indication of the speed of the engine  24  in rotations-per-minute (“RPM”) to the ECM  125 . The engine speed sensor  145  can provide the indication as an analog or a digital signal. A span of the signal can be chosen to provide sufficient precision such that the ECM  125  can accurately control the fuel delivery system  100 . For example, an engine may have an operating range between 1000 RPM and 8000 RPM. If the operating precision of the fuel delivery system  100  requires precision to 1000 RPM, the engine speed sensor  145  can have a data range of 0 to 8. However, if the fuel delivery system  100  requires precision to 50 RPM, the engine speed sensor  145  can have a data range of 0 to 160. 
   In some embodiments, the fuel pump  105  is positioned in the fuel tank  40  of the motorcycle  10 . In other embodiments, the fuel pump  105  can be positioned on an external wall of the fuel tank  40  or at a position a distance from the fuel tank  40 . The fuel pump  105  receives a signal from the ECM  125  indicative of a speed and/or torque at which the fuel pump  105  should operate. The signal from the ECM  125  to the fuel pump  105  can be analog or digital. In one preferred embodiment, the signal from the ECM  125  to the fuel pump  105  is a pulse-width modulated signal having a duty cycle proportional to a desired speed/torque of the fuel pump  105 . 
   The fuel pump  105 , based on the signal received from the ECM  125 , draws fuel from the fuel tank  40  and provides the fuel through a fuel line  150  to the first and second fuel injectors  115  and  120 . A speed/torque of the fuel pump  105 , along with a frequency and duration that the first and second fuel injectors  115  and  120  are open determines the pressure of fuel in the fuel line  150 . The fuel pressure sensor  110  detects the pressure of the fuel in the fuel line  150  and provides an indication of that pressure to the ECM  125 . The fuel pressure sensor  110  can provide the indication of the pressure of the fuel in the fuel line  150  as any appropriate signal, such as an analog signal, a digital signal, or an electrical resistance. 
   The ECM  125  sends a signal to the first and second fuel injectors  115  and  120  to control the opening and closing of each. In some embodiments, the signal is a digital signal (i.e., on or off) indicating that the fuel injector  115  or  120  should either fully open or fully close. It is anticipated that, in some embodiments, the signal from the ECM  125  to the fuel injectors  115  and  120  can be an analog or a digital signal indicating an amount the fuel injector  115  or  120  should open (e.g., 75 percent). 
   The ECM  125  controls the fuel pump  105  and the first and second fuel injectors  115  and  120  to optimize a quantity of fuel delivered to the engine based on engine parameter data received from the sensors and indicators (e.g., engine temperature, engine load, engine speed, etc.). The optimization of fuel delivery can, among other things, reduce exhaust emissions, improve engine performance, and/or prevent vapor lock. The fuel delivery system  100  operates in one of three modes: engine start, engine stop, or engine run. It is anticipated that, in some embodiments, the fuel delivery system  100  includes additional operating modes. 
     FIG. 4  is a flow chart of an embodiment of the operation of the fuel delivery system  100  in the engine start mode. To operate the motorcycle  10 , an operator puts a key in the ignition switch  42  which is in the off position  44 . The operator turns the key to the on position  46  causing power to be applied to the ECM  125  which initializes and begins functioning (block  300 ). The ECM  125  monitors the ignition switch  42  and the start button to determine if the operator has turned the key to the run position  46  and pressed the start button (block  305 ). When the operator turns the key to the engine run position  46  and presses the start button, the ECM  125  obtains an indication of engine temperature from the temperature sensor  135  (block  310 ). Next, the ECM  125  determines a fuel pressure set-point, in pounds-per-square-inch (“psi”), based on the engine temperature (block  315 ). In some embodiments, the ECM  125  selects the pressure set-point based on a look-up table such as shown in Table 1. The fuel pressure set-point can be chosen to prevent vapor lock and to optimize a fuel droplet size to improve an atomization of the fuel, which can result in less fuel being necessary to start the engine  24 . 
   
     
       
             
           
             
             
             
           
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Start Fuel Pressure 
             
           
        
         
             
                 
               Engine Temperature (° C.) 
               Fuel Pressure Set-point (psi) 
             
             
                 
                 
             
           
        
         
             
                 
               −10 
               70 
             
             
                 
               20 
               70 
             
             
                 
               60 
               68 
             
             
                 
               80 
               65 
             
             
                 
                 
             
           
        
       
     
   
   The ECM  125  then operates the fuel pump  105  to achieve and maintain the fuel pressure at the fuel pressure set-point (block  317 ). Once the fuel pressure is at the set-point, the ECM  125  starts the engine  24  (block  320 ). The fuel pressure set-point, when the engine  24  is starting, can be different from the fuel pressure set-point during normal operation (e.g., run mode). Therefore, the ECM  125  can transition from the starting fuel pressure set-point to a running fuel pressure set-point over a predetermined period of time or a predetermined number of steps. The larger the difference between the starting fuel pressure set-point and the operating fuel pressure set-point, the more time and/or steps the transition takes to complete. 
   The ECM  125  determines the operating fuel pressure set-point, as described in more detail below (block  325 ), and determines the transition time period and/or steps (block  330 ). Embodiments of the invention include, but are not limited to, (1) a fixed transition time period wherein the number and/or size of the steps is modified, (2) a fixed number and/or size of the steps wherein the time period can be modified, and (3) wherein the time period and the number and/or size of the steps are all modified. The ECM  125  then delays for the time period determined in block  330  (block  333 ), and modifies the fuel pressure set-point by the predetermined amount (block  335 ). Next, the ECM  125  determines if the transition period is complete (block  340 ) continuing by delaying at block  333  if the transition is not complete or continuing with the engine run routine (block  345 ) if the transition is complete. 
   In some embodiments, the ECM  125  can operate the fuel pump  105  to achieve and maintain a starting fuel pressure, based on engine temperature, as soon as the operator turns the key to the on position. 
     FIG. 5  is a flow chart of an embodiment of an engine run routine. The ECM  125  checks whether the operator has turned the ignition switch  42  to the off position  44  (block  400 ). If the ignition switch  42  is in the off position  44 , the ECM  125  executes a stop routine (block  405 ) as described in more detail below. If the ignition switch  42  is not in the off position  44 , the ECM determines the engine speed (block  410 ) based on information from the engine speed sensor  145 ; the throttle position (block  415 ) based on information from the throttle position indicator  140 ; and the engine temperature (block  420 ) based on information from the engine temperature sensor  135 . Next, the ECM  125  determines a desired fuel pressure based on the engine temperature (P t ) and a desired fuel pressure based on the throttle position (i.e., engine load) and the engine speed (P l-s ) (block  425 ). The ECM  125  can calculate the desired fuel pressures or can select the desired fuel pressures from look-up tables. Table 2 below is an exemplary look-up table for P t  and table 3 is an exemplary look-up table for P l-s . 
   The ECM  125  then compares the fuel pressures, P t  and P l-s  (block  430 ) and sets a fuel pressure set-point to the greater of P t  or P l-s  (blocks  435  and  440 ). For example, if the temperature of the engine  24  is 20° C., the throttle position is 10%, and the engine speed is 1000 RPM (such as when the motorcycle  10  is first started and idling), from table 2 P t =58 psi and from table 3 P l-s =0 psi. Therefore, the desired fuel pressure is 58 psi (P t  is greater than P l-s ). The ECM  125  then determines the actual fuel pressure (block  445 ) based on information from the fuel pressure sensor  110  and compares the actual fuel pressure to the desired fuel pressure (block  450 ). Based on the difference between the actual and desired fuel pressures, the ECM  125 , using a suitable control method (e.g., proportional-integral-derivative), increases or decreases the speed/torque of the fuel pump  105  to bring the actual fuel pressure in line with the desired fuel pressure. Next the ECM  125  sets an injector pulse-width (i.e., a time period that the injector is open) based on the actual fuel pressure (block  455 ). Table 4 below is an exemplary look-up table for adjusting the injector pulse-width based on the actual fuel pressure. The table indicates a percentage of normal injector pulse-width based on the fuel pressure. For example, if the actual fuel pressure is 58 psi, the injector pulse-width is not modified (i.e., is equal to 100% of the normal pulse-width). If the actual fuel pressure is 64 psi, the injector pulse-width is reduced to 95% of the normal pulse-width. The ECM  125  then continues processing at block  400  with checking the position of the ignition switch  42 . 
   
     
       
             
           
             
             
             
           
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               Pressure Set-point - Engine Temperature 
             
           
        
         
             
                 
               Engine Temperature (° C.) 
               Fuel Pressure Set-point (psi) 
             
             
                 
                 
             
           
        
         
             
                 
               −10 
               70 
             
             
                 
               0 
               65 
             
             
                 
               10 
               65 
             
             
                 
               20 
               58 
             
             
                 
               95 
               58 
             
             
                 
               100 
               65 
             
             
                 
               110 
               70 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
             
             
             
             
             
             
             
           
             
             
             
             
             
             
             
           
         
             
               TABLE 3 
             
           
           
             
                 
             
             
               Pressure Set-point - Load vs. Speed 
             
           
        
         
             
                 
               Throttle 
               Engine Speed (RPM) 
             
           
        
         
             
                 
               Position (%) 
               8000 
               6000 
               4000 
               2000 
               1000 
             
             
                 
                 
             
           
        
         
             
                 
               10 
               0 
               0 
               00 
               0 
               0 
             
             
                 
               15 
               0 
               0 
               0 
               0 
               0 
             
             
                 
               20 
               0 
               0 
               0 
               0 
               0 
             
             
                 
               30 
               0 
               0 
               0 
               0 
               0 
             
             
                 
               40 
               60 
               60 
               0 
               0 
               0 
             
             
                 
               70 
               68 
               65 
               60 
               0 
               0 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
             
             
             
           
         
             
               TABLE 4 
             
           
           
             
                 
             
             
               Injector Pulse-width 
             
           
        
         
             
                 
                 
               Injector Pulse-width 
             
             
                 
               Fuel Pressure (Actual) 
               (% of normal) 
             
             
                 
                 
             
           
        
         
             
                 
               25 
               152 
             
             
                 
               58 
               100 
             
             
                 
               64 
               95 
             
             
                 
               80 
               85 
             
             
                 
                 
             
           
        
       
     
   
   If the ECM  125  determines that the ignition switch  42  is in the stop position (block  400 ), the ECM  125  executes a stop routine.  FIG. 6  illustrates a flow chart of an embodiment of a stop routine. The stop routine begins with the ECM  125  obtaining an indication of the engine temperature from the engine temperature sensor  135  (block  500 ). The ECM  125  then determines a desired fuel pressure based on the engine temperature (block  505 ). In some embodiments, the ECM  125  determines the desired fuel pressure based on a look-up table such as shown in Table 5. The desired pressure is chosen such that, based on the temperature of the engine, the pressure of fuel in the fuel line  150  and at the injectors  115  and  120  is sufficient to prevent the fuel from vaporizing and thereby creating a situation wherein the engine  24  is difficult to start. In other embodiments, the ECM  125  sets the desired fuel pressure to a constant (e.g., 70 psi) chosen to be sufficient to prevent fuel from vaporizing under most expected engine temperatures. The ECM  125  then determines the actual fuel pressure (block  510 ) based on information for the fuel pressure sensor  110  and compares the actual fuel pressure to the desired fuel pressure (block  515 ). Based on the difference between the actual and desired fuel pressures, the ECM  125 , using a suitable control method (e.g., proportional-integral-derivative), increases or decreases the speed/torque of the fuel pump  105  to bring the actual fuel pressure in line with the desired fuel pressure (block  520 ). Next the ECM  125  checks if the actual fuel pressure equals the desired fuel pressure (block  525 ). If it does not, the ECM  125  continues at block  510  with determining the actual fuel pressure and adjusting the fuel pump as described above. If, at block  525 , the actual fuel pressure equals the desired fuel pressure, the ECM  125  briefly continues to operate the fuel pump to maintain the desired fuel pressure. 
   
     
       
             
           
             
             
             
           
             
             
             
           
         
             
               TABLE 5 
             
           
           
             
                 
             
             
               Stop Fuel Pressure 
             
           
        
         
             
                 
               Engine Temperature (° C.) 
               Fuel Pressure Set-point (psi) 
             
             
                 
                 
             
           
        
         
             
                 
               30 
               65 
             
             
                 
               40 
               68 
             
             
                 
               80 
               70 
             
             
                 
               100 
               72 
             
             
                 
                 
             
           
        
       
     
   
   Various features and advantages of the invention are set forth in the following claims.