Abstract:
A system for selectively intensifying fuel for injection utilizing a fuel injector having an intensifier piston connected to a drain and a pressurized fuel source. The intensifier piston includes a control chamber co-axially positioned opposite from an intensification chamber, and a pressurization chamber co-axially positioned between the control chamber and the intensification chamber. The control chamber selectively fluidly communicates with the pressurized fuel source and the drain. The intensification chamber fluidly communicates with the pressurized fuel source and the pressurization chamber fluidly communicates with the pressurized fuel source and a nozzle assembly.

Description:
This application claims the benefit of U.S. provisional application No. 60/752,408, filed Dec. 22, 2005, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to fuel injectors for internal combustion engines, and more particularly to a fuel injector providing variable intensification. 
     BACKGROUND 
     Precisely controlling the quantity and timing of the fuel delivered to a combustion chamber of an internal combustion engine may lead to an increase in engine efficiency and/or a reduction in the generation of undesirable emissions. To improve control over the quantity and timing of fuel delivery, a typical fuel injection system, and in particular, a fuel injector, may include an intensifier assembly that pressurizes the fuel for use in the combustion chamber. Intensifier assemblies may be of the dual-fluid type or the single-fluid type. 
     In a dual-fluid type intensifier assembly, fuel enters a pressurization chamber of the intensifier assembly and a relatively high pressure actuation fluid, such as engine lubricating oil, enters a control chamber of the intensifier assembly. A controllable valve, usually a solenoid type valve, controls the flow of high pressure actuation fluid to the control chamber by opening and closing a high pressure inlet. Activating the solenoid valve opens the high pressure inlet allowing the high pressure activation fluid to act on one end of the intensifier piston. The other end of the intensifier piston is in contact with the fuel in the pressurization chamber. Because the high pressure activation fluid in the control chamber has a higher pressure than the fuel and because the high pressure activation fluid acts on a surface area of the intensifier piston that is larger than the surface area in contact with the fuel, the high pressure activation fluid drives the intensifier piston towards an advanced position. As the intensifier piston moves towards its advanced position, it acts on the fuel in the pressurization chamber, increasing the fuel pressure. When the pressure caused by the intensifier piston reaches a valve opening pressure, a spring biased needle check opens to commence fuel injection into a combustion chamber of the engine. Deactivating the solenoid valve ends the injection cycle and releases pressure in the control chamber of the intensifier assembly. Releasing the pressure in the control chamber drops the fuel pressure in the pressurization chamber causing the needle check, under the influence of its return spring, to close. Closing the needle check ends fuel injection. 
     Single-fluid type intensifier assemblies do not utilize high pressure engine oil as the actuation fluid. Rather single-fluid intensifier assemblies utilize the same fluid (fuel) for use in both the pressurization chamber and the control chamber. In a single-fluid intensifier assembly, the engine supplies pressurized fuel to the fuel injector from a high pressure supply, such as a high pressure common rail. The fuel injector selectively supplies the pressurized fuel to the control chamber to act on one end of the intensifier piston. Fuel is also supplied to the pressurization chamber of the intensifier assembly. When the fuel is selectively supplied to the control chamber, it acts on the intensifier piston. The intensifier piston then acts on the fuel in the pressurization chamber increasing the pressure of the fuel in the pressurization chamber above the pressure of the fuel supplied to the control chamber. This occurs because the fuel in the control chamber acts on a larger surface area of the intensifier piston than the fuel in the pressurization chamber. 
     U.S. Pat. No. 6,453,875 (“the &#39;875 patent”), for example, discloses a single-fluid type intensifier assembly for a fuel injector. The &#39;875 patent discloses a fuel injection system including a pressure step-up unit having a pressure chamber in communication with a nozzle chamber via a pressure line and a pressure storage chamber. Control of the pressure step-up unit is effected hydraulically by imposition of pressure from a differential chamber of the pressure step-up unit. The &#39;875 patent however, requires a bypass line parallel to the step-up unit to provide fuel to the nozzle. The addition of the bypass line utilizes valuable space in such tightly confined systems, and adds to the cost and complexity of the system. 
     The method and apparatus of the present disclosure solves one or more of the problems set forth above. 
     SUMMARY OF THE INVENTION 
     In accordance with one exemplary embodiment, a fuel injector includes an intensifier connected to at least one drain and a pressurized fuel source. The intensifier includes a control chamber co-axially positioned opposite from an intensification chamber, and a pressurization chamber co-axially positioned between the control chamber and the intensification chamber. The control chamber selectively fluidly communicates with the drain and the pressurized fuel source, the intensification chamber communicates with the pressurized fuel source, and the pressurization chamber communicates with the pressurized fuel source and a nozzle assembly. 
     In accordance with another exemplary embodiment, a fuel injector includes an intensifier connected to at least one drain and a pressurized fuel source. The intensifier includes an internal chamber housing an intensifier piston separating the internal chamber into a control chamber, an intensification chamber, and a pressurization chamber. The control chamber selectively fluidly communicates with the pressurized fuel source and the drain, the intensification chamber fluidly communicates with the pressurized fuel source, and the pressurization chamber fluidly communicates with a flow control valve and a nozzle assembly The flow control valve allows continuous supply of fluid to the pressurization chamber. 
     In yet another exemplary embodiment, a method for selectively intensifying fuel for injection utilizing a fuel injector includes communicating fuel to a control chamber, an intensification chamber and a pressurization chamber of an intensifier piston from a pressurized fuel source. The control chamber selectively fluidly communicates with the drain and the pressurized fuel source, the intensification chamber communicates with the pressurized fuel source, and the pressurization chamber communicates with the pressurized fuel source and a nozzle assembly. The method further includes pressurizing fuel in the pressurization chamber by selectively connecting the control chamber to the drain, and controlling injection by selectively connecting the nozzle assembly to the drain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . is a schematic illustration of a fuel injector with an intensifier piston in a starting position in accordance with an exemplary embodiment of the present disclosure; 
         FIG. 2 . is a schematic illustration of the fuel injector of  FIG. 1  injecting intensified fuel; and 
         FIG. 3  is a schematic illustration of the fuel injector of  FIG. 1  injecting non-intensified fuel. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the disclosure, illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     A fuel injector  10  according to the present disclosure is shown generally in the schematic of  FIG. 1 . Fuel injector  10  may include an intensifier assembly  12  including a barrel  14 , an internal chamber  16  housing a piston  18  and a piston spring  20 . Piston  18  may be T-shaped. Alternatively, piston  18  may take on another shape. Internal chamber  16  may be shaped to receive piston  18  such that piston  18  separates internal chamber  16  into an intensification chamber  22 , a pressurization chamber  24 , and a control chamber  26 . This separation of internal chamber  16  by piston  18  allows the surface area of piston  18  in contact with intensification chamber  22  to be greater than the surface area of piston  18  in contact with pressurization chamber  24 . It also allows surface area of piston  18  in contact with intensification chamber  22  to be greater than the surface area of piston  18  in contact with control chamber  26 . Piston spring  20  may be positioned co-axially within the pressurization chamber  24  for biasing piston  18  towards a first or starting position. 
     Intensification chamber  22  may be fluidly connected to a fuel line  28 . The fuel line  28  may be fluidly connected to a high pressure fuel source  30 , such as a high pressure fuel accumulator or common rail. Intensification chamber  22  may be co-axially located on one end of piston  18 , opposite from control chamber  26 . In the exemplary embodiment, intensification chamber  22  may be positioned between a piston head  19  of piston  18  and internal chamber  16 . 
     Control chamber  26  may be selectively fluidly connected to fuel line  28  or low pressure drain  34  by a first control valve  32 . Control chamber  26  may be co-axially positioned at one end of piston  18 , opposite from intensification chamber  22 . In the exemplary embodiment, control chamber  26  may be positioned opposite from piston head  19 , between piston  18  and internal chamber  16 . 
     First control valve  32  may be a solenoid actuated control valve. Solenoid actuated control valves typically control the movement of a valve member from a closed position to an open position using a bias spring and an electromagnetic force created by a solenoid. It should be understood, however, that other types of control valve assemblies, such as piezoelectric valves, may be used with the present disclosure. Accordingly, energization of first control valve  32  allows communication between control chamber  26  and a low pressure drain  34  and prevents communication between fuel line  28  and control chamber  26 . De-energization of first control valve  32  allows communication between fuel line  28  and control chamber  26 . 
     Pressurization chamber  24  may be fluidly connected both with fuel line  28  and a nozzle assembly  52 . Pressurization chamber  24  may be co-axially positioned between control chamber  26  and intensification chamber  22 . In the exemplary embodiment, pressurization chamber  24  may be located between piston head  19  and internal chamber  16 . 
     A one-way valve  36  allows communication from fuel line  28  to pressurization chamber  24  and prevents communication from pressurization chamber  24  to fuel line  28 . One-way valve  36  may be a ball check valve or another similar check valve. One-way valve  36  may be operate passively. For example, a ball check valve allows fluid to flow in one direction and passively prevents fluid from flowing in the other direction. This occurs because the fluid will push the ball against the valve opening, and the ball will prevent fluid from flowing. 
     Nozzle assembly  52  may include a second control valve  38 , a nozzle chamber  48 , a nozzle spring  46 , and a nozzle check piston  40 . Nozzle check piston  40  may be T-shaped or it may take another shape. Nozzle check piston  40  may be deposed in nozzle chamber  48  separating nozzle chamber  48  into a check cavity  49  and a nozzle cavity  50 . Second control valve  38  may be directly connected to check cavity  49  through a nozzle check passage  42 . Nozzle check piston  40  can move between a first or closed position ( FIG. 1 ) and a second or open position ( FIG. 2 ). In its closed position, nozzle check piston  40  prevents communication between one or more flow orifices  44  and high pressure fuel in nozzle cavity  50 . In its open position, nozzle check piston  40  allows communication between high pressure fuel in nozzle cavity  50  and flow orifice  44 . High pressure fuel in nozzle check passage  42  and nozzle spring  46  bias nozzle check piston  40  towards its closed position. 
     Second control valve  38  may be a solenoid actuated control valve. As noted above, typical solenoid actuated control valves control the movement of a valve member from a closed position to an open position using a bias spring and an electromagnetic force created by a solenoid. It should be understood, however, that other types of control valve assemblies, such as piezoelectric valves, may be used with the present disclosure. Energization of second control valve  38  allows communication between nozzle check passage  42  and low pressure drain  34 . Furthermore, energization of second control valve  38  prevents communication between pressurization chamber  24  and nozzle check passage  42 . De-energization of second control valve  38  allows communication between a pressurization chamber  24  and nozzle check passage  42  ( FIG. 1 ). 
     A control unit (not shown) for fuel injector  10  controls the activation of first control valve  32  and second control valve  38 . Alternatively, more than one control unit may be utilized to control activation of first control valve  32  and second control valve  38 . 
     It should be understood that the present disclosure may utilize end of injection rate shaping as is practiced in the art, in order to reduce unwanted emissions and improve fuel efficiency. For example, the control unit may operate second control valve  38  in a manner to create various fuel injection rate shapes, including square, boot, ramp, or and other similar rate shapes, to match particular operating conditions of the work machine with particular rate shapes to improve fuel efficiency and reduce unwanted emissions. 
     It should be understood that each of the above described components may be included in a single unit fuel injector  10 . Alternatively, fuel injector  10  may include separate components forming the nozzle assembly  52 . 
     Each of the components described above may be fabricated from any rigid material, such as steel, aluminum, or cast iron. 
     INDUSTRIAL APPLICABILITY 
     Before injection, first control valve  32  allows communication between fuel line  28  and control chamber  26 . Fuel enters pressurization chamber  24  from fuel line  28  after passing through one-way valve  36 . Fuel also enters intensification chamber  22  from fuel line  28 . Piston spring  20 , along with pressure from pressurization chamber  24  and pressure from control chamber  26 , act on piston  18 , urging piston  18  to a fully open position as seen in  FIG. 1 . 
     Referring to  FIG. 2 , to pressurize fuel in pressurization chamber  24 , the control unit activates first control valve  32  to allow fluid communication between control chamber  26  and low pressure drain  34 . When activated, first control valve  32  prevents communication between fuel line  28  and control chamber  26 . As can be seen in  FIG. 2 , when first control valve  32  is activated, fuel in control chamber  26  may communicate with low pressure drain  34  and flow out when the pressure in the low pressure drain  34  is less than the pressure of the fuel in control chamber  26 . As the fuel in control chamber  26  flows out to low pressure drain  34 , fuel in intensifier chamber  22  will urge piston  18  away from its starting position and decrease the size of pressurization chamber  24 . This decrease in size of pressurization chamber  24  will pressurize or intensify the fuel in pressurization chamber  24 . 
     To inject the intensified fuel into the combustion chamber (not shown), the control unit activates second control valve  38  to allow communication between nozzle check passage  42  and low pressure drain  34 . As the pressure in nozzle check passage  42  decreases, pressure from fuel in nozzle cavity  50  urges nozzle check piston  40  towards its open position as illustrated in  FIG. 2  against the force of nozzle spring  46 . In its open position, nozzle check piston  40  allows communication between the one or more flow orifices  44  and nozzle cavity  50 , allowing fuel to enter the combustion chamber. 
     To stop injection, the control unit deactivates second control valve  38  allowing communication between nozzle check passage  42  and pressurization chamber  24 . Pressure from fuel in check cavity  48  and from nozzle spring  46  urge nozzle check piston  40  towards its closed position, ending injection. 
     Alternatively, injection can occur without activating first control valve  32 . In this operation, non-intensified fuel can be injected into the combustion chamber. Referring to  FIG. 3 , high pressure fuel enters pressurization chamber  24  from fuel line  28  after passing through one-way valve  36 . Fuel also enters intensifier chamber  22  from fuel line  28 . When deactivated, first control valve  32  allows communication between fuel line  28  and control chamber  26 . Piston spring  20 , along with pressure from pressurization chamber  24  and pressure from control chamber  26 , act on piston  18 , urging piston  18  towards its starting position, as shown in  FIG. 1 . To start injection, the control unit activates second control valve  38  to allow communication between nozzle check passage  42  and low pressure drain  34 . Pressure from fuel in nozzle cavity  50  urges nozzle check piston  40  towards its open position as the pressure in nozzle check passage  42  decreases. In its open position, nozzle check piston  40  allows fluid communication between flow orifice  44  and nozzle cavity  50 , allowing fuel to flow into the combustion chamber as illustrated in  FIG. 3 . This arrangement allows for fuel from high pressure fuel source  30  to flow through the pressurization chamber  24  of the intensifier assembly  12  and into the combustion chamber without intensifying the fuel. To stop injection, the control unit deactivates second control valve  38  allowing communication between nozzle check passage  42  and pressurization chamber  24 . Pressure from fuel in nozzle check passage  42  and nozzle spring  46 , urge nozzle check piston  40  towards its closed position, ending injection. 
     This arrangement of first, second and one-way valves  32 ,  38 , and  36  with the intensifier assembly  12  and utilization of internal chamber  16  allows for non-intensification, without requiring a separate bypass fuel line to connect the high pressure fuel source  30  to the nozzle cavity  50 . As described above, high pressure fuel flows from high pressure fuel source  30  to one-way valve  36  through pressurization chamber  24  to nozzle cavity  50 . By selectively activating first control valve  32 , the control unit for the fuel injector  10  can send intensified or non-intensified fuel to the nozzle check piston  40  for injection into the combustion chamber. This arrangement of components is less complex than bypass arrangements that allow for non-intensified fuel injection. In addition, reducing the number of components and/or fuel passages needed to get both intensified and non-intensified fuel injected into the combustion chamber may reduce the cost. 
     Between injections, the control unit deactivates first control valve  32 , allowing communication between fuel line  28  and control chamber  26 . Pressure from fuel in pressurization chamber  24  and pressure from fuel in control chamber  26  along with force from piston spring  30 , cause piston  18  to return to its fully open position as illustrated in  FIG. 1 . 
     For some applications, selectively controlling the amount of intensifier piston reset may prove advantageous. For example, the control unit can control activation of first control valve  32  to control the amount of piston  18  reset and cause piston  18  to only partially return to its fully open position. To accomplish this, the control unit deactivates first control valve  32  for a certain period of time between injections. The length of deactivation of control valve  32  would correspond to a certain amount of high pressure fuel allowed to communicate with control chamber  26 . The fuel in control chamber  26  causes an increase in fuel pressure acting on piston  18 . This increase in pressure in control chamber  26  would add to the force from piston spring  20  and pressure from fuel in pressurization chamber  24  to urge piston  18  towards its starting position. The amount of force from the fuel in control chamber  26  would be less than the amount needed to urge the piston to its starting position because only a certain amount of fuel would be allowed to communicate with the control chamber  26 . When the first control Valve  32  is activated and fuel from control chamber  26  flows out to low pressure drain  34 , the reduction in the size of pressurization chamber  24  will be less than the reduction in the pressurization chamber  24  when the piston  18  is in its starting position. To control the amount of intensification using first control valve  32 , the manufacturer of fuel injector  10  can test a nominal fuel injector  10  to determine the amount of intensification for each activation duration of first control valve  32 . Based on these tests, the manufacturer can create a map of intensification as a function of first control valve  32  activation duration for use by the control unit. Controlling the amount of intensification would allow the control unit to match a certain amount of intensification with a particular operating condition to improve fuel efficiency and/or reduce unwanted emissions. 
     It should be understood that alternative flow configurations may be implemented provided a control valve controls activation of the intensifier piston, another control valve directly controls injection, and fuel flows through the intensifier to the nozzle tip. Further, while the present disclosure is described in connection with one fuel injector  10 , it is appreciated that the disclosure may be applied to multiple fuel injectors. 
     Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims and their equivalents.