Abstract:
The movement of the intensifier piston in a fuel injector, to control the pressurization of fuel, can be controlled with a flow control valve. The flow control valve provides different flow rates depending upon the direction of flow. In a first direction, flow control valve has a first rate of flow and in the second direction flow control valve allows a second different rate of flow. Typically, this can be applied to a intensifier piston as follows: flow traveling to the intensifier piston, in the first direction, has a first flow rate, allowing the intensifier to move downward and pressurize fuel. When injection is over, and the intensifier piston is vented, the flow control valve allows a second flow rate which is greater than the first flow rate, allowing the intensifier piston to vent quickly and reset for another injection.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to fuel injection and specifically to the ability to control flow rates to and from an intensifier piston and the ability to reset the intensifier piston quickly.  
         BACKGROUND  
         [0002]    Reducing emissions is a top priority for today&#39;s engine manufacturers. As the government continues to tighten emission requirements, manufacturers must find new ways to reduce engine emissions while still providing powerful, economic engine operation. One area that engine manufacturers have focused on is fuel injection.  
           [0003]    Fuel injection plays a crucial role in the amount of emissions created during combustion. Numerous fuel injection variables, including fuel pressure, spray pattern, droplet size, number of injections and injection timing impact emissions. In order to properly control these parameters, fuel injectors have become more complicated and more precise. For example, one exemplary design of a fuel injector is a hydraulically actuated electronically controlled unit injector such as a Caterpillar HEUT™ B unit injector. This unit injector uses actuation fluid to pressurize fuel for injection. Specifically, a control valve and spool valve control the timing of high pressure actuation fluid acting upon an intensifier piston. When high pressure actuation fluid acts on the intensifier piston, the hydraulic force overcomes a biasing force from a piston spring and moves the piston downward, also moving a plunger, which pressurizes fuel in the pressurization cavity for injection. When injection is over, the control valve allows the high pressure actuation fluid acting on the intensifier piston to vent. This allows a piston spring to push the intensifier piston and plunger back to their original position and reset them for the next injection  
           [0004]    As emissions regulations have increased, injection strategies have become more complicated. For example, multiple injections, including pilots and posts, reduce emissions during combustion. However, it can be difficult for the injector to cycle quickly enough to perform multiple injections during a single combustion event. In the hydraulically actuated electronically controlled unit injector described above, multiple injections can be performed by cycling the control valve but depending on the dwell time between injections and the desired injection profile, the intensifier piston may not properly reset between injections.  
           [0005]    The present invention is intended to overcome one or more of the above problems.  
         SUMMARY OF THE INVENTION  
         [0006]    A fuel injector comprises a high pressure actuation fluid source, a lower pressure drain, at least one fluid line selectively to one of high pressure actuation fluid source and lower pressure drain, an intensifier piston fluidly connected to the fluid line and a flow control valve. The flow control valve is in fluid communication with the fluid line and the intensifier piston and position to control the rate of flow to and from the intensifier piston. The flow control valve has a first flow rate in the first direction and a second flow rate in a second direction, the second rate being different from the first.  
           [0007]    In another embodiment, a fuel injector comprises a high pressure actuation fluid source, a low pressure drain, flow control valve connected with the high pressure actuation fluid source and the low pressure drain and intensifier piston connected to flow control valve. The control flow valve controls the flow rate between the flow control valve and the intensifier piston and has a first flow rate in the first direction and a second flow rate in the second direction.  
           [0008]    In another embodiment, a method of controlling intensifier piston comprises pressurizing the intensifier piston at a first flow rate and venting the intensifier piston at a second flow rate, wherein the second flow rate is different than the first flow rate.  
           [0009]    In another embodiment of the present invention, a fuel injector comprises a high pressure actuation fluid source, low pressure drain, at least one fluid line selectively connected to one of the high pressure actuation fluid source and low pressure drain, and intensifier piston fluidly connected to the fluid line, and a flow control valve. The flow control is in fluid communication with the fluid line and the intensifier piston and position to control flow to and from the intensifier piston. Further, the flow control valve has a flow in a first direction and a second direction having a flow control valve having a flow restriction for flow in the first direction.  
           [0010]    In another embodiment, fuel injector comprises high pressure actuation fluid source, low pressure drain, at least one fluid line, means for selectively connecting the fluid line to one of the high pressure actuation fluid source and low pressure drain, an intensifier piston fluidly connected to the fluid line, and a flow control. The flow control valve is in fluid communication with the fluid line and the intensifier piston and in position to control a rate of flow to and from the intensifier piston. Further, the flow control valve has a first flow rate in the first direction and a second flow rate, different from the first flow rate, in the second direction. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a diagrammatic illustration of a cross section of a fuel injector according to one embodiment of the present invention.  
         [0012]    [0012]FIG. 2 is a diagrammatic illustration of a bottom view of a damper plate according to the embodiment of FIG. 1.  
         [0013]    [0013]FIG. 3 is a diagrammatic illustration of a cross section of a flow control valve along line  3 - 3  of the embodiment illustrated in FIG. 1.  
         [0014]    [0014]FIG. 4 is a diagrammatic illustration of a cross section of a flow control valve along line  3 - 3  of the embodiment illustrated in FIG. 1.  
         [0015]    [0015]FIG. 5 is a diagrammatic illustration of a cross section of a flow control valve along line  5 - 5  of the embodiment illustrated in FIG. 1.  
         [0016]    [0016]FIG. 6 is an enlarged diagrammatic illustration of a cross section of a flow control valve according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 is a diagrammatic illustration of a hydraulically actuated electronically controlled unit injector  10 . Fuel enters injector  10  through fuel inlet passage  12 , passes ball check  14  and enters fuel pressurization chamber  16 . High pressure actuation fluid enters injector  10  through actuation fluid inlet passage  18 . Actuation fluid then travels to control valve  20  and spool valve  22 .  
         [0018]    Control valve  20  controls the overall operation of injector  10  and operates as a pilot valve for spool valve  22 . Control valve  20  includes an armature  24  and a seated pin  26 . A solenoid (not shown) in control valve  20  controls movement of armature  24  and therefore the position of the seated pin  26 . In a first position, seated pin  26  allows high pressure actuation fluid to travel through upper check passage  28  and lower check passage  32  to check control cavity  34 . When seated pin  26  is in the first position, high pressure actuation fluid also travels through upper check passage  28  to spool passage  36  to balance spool valve  22  in its first position. When seated pin  26  is in its second position, high pressure actuation fluid from actuation fluid inlet passage is blocked and upper check passage  28 , lower check passage  32 , check control cavity  34  and spool passage  36  are open to low pressure drain  38 .  
         [0019]    When seated pin  26  is moved to its second position, the spool passage  36  is open to low pressure drain  38 , which unbalances spool valve  22  and allows high pressure actuation fluid to travel through upper intensifier passage  40 , into damper plate  42  where the flow is split in to two passages; middle intensifier passage  44  and upper rate shaping passage  46 . High pressure actuation fluid in middle intensifier passage  44  proceeds to lower intensifier passage  48 , in central body  50  where it acts upon piston hat  52  of intensifier piston  54 . Flow also travels from upper rate shaping passage  46  through flow control valve  56  to lower rate shaping passage  58  where the high pressure actuation fluid acts on the shoulder  60  of intensifier piston  54 .  
         [0020]    When high pressure actuation fluid acts upon intensifier piston  54 , intensifier piston  54  moves downward, against the force of piston spring  62 , causing plunger  64  to move downward and pressurize fuel in fuel pressurization chamber  16 . Fuel in fuel pressurization chamber  16  is pressurized to injection pressure and is directed through high pressure fuel passage  66  and into fuel cavity  68 .  
         [0021]    Check  70  is located in the nozzle assembly of injector  10  and controls the flow of fuel through orifices  72 , in nozzle tip  74 , into the combustion chamber (not shown). Check  70  is biased in the closed position by check spring  76 . High pressure fuel in fuel cavity  68  acts on an opening surface  78  of check  70  and pushes it upwards, against check spring  76 , into the open position, allowing injection through orifice  72 . Check opening and closing is also hydraulically controlled by check control cavity  34 . When high pressure actuation fluid is present in check control cavity  34 , it helps keep check  70  closed even when high pressure fuel is present in fuel cavity  68 . High pressure actuation fluid acts upon a closing surface  80  of check piston  82  and hydraulically offsets and, in fact overcomes, the pressure from the high pressure fuel in fuel cavity  68 . The high pressure actuation fluid helps close check  70  in combination with check spring  76 . Injection occurs when check control cavity  34  is opened to low pressure drain  38 , leaving the pressurized fuel to overcome only the check spring&#39;s  76  force. By controlling the high pressure actuation fluid in check control cavity  34 , injection timing and duration can be more accurately controlled.  
         [0022]    When injection is finished, seated pin  26  is returned to its first position, allowing high pressure actuation fluid into check control cavity  34  and spool passage  36 . As stated above, high pressure actuation fluid in check control cavity  34  closes check  56 . Further, high pressure actuation fluid in spool passage  36  causes spool valve  22  to return to its original position, stopping the flow of high pressure actuation fluid to the intensifier piston  54  and allowing the high pressure actuation fluid acting on the intensifier piston  54  from upper, middle, and lower intensifier passages  40 ,  44 ,  48  and upper and lower rate shaping passages  56 ,  58  to drain, allowing intensifier piston  54  and plunger  64  to return to their original positions.  
         [0023]    Flow control valve  56  controls the rate of flow through upper and lower rate shaping passages  46 ,  58 . FIGS.  2 - 5  are enlarged diagrammatic cross sections of flow control valve  56  illustrated in FIG. 1. In this embodiment, flow control valve  56  includes rate shaping orifice plate  84  and grooved damper plate  42 . Rate shaping orifice plate  84  is a circular disk that defines rate shaping orifice  86  through the center of plate  84 . Damper plate  42  defines a circular annulus  88  and a center passage  90  that is in fluid communication with circular annulus  88 . When high pressure fluid is moving from upper rate shaping passage  46  to lower rate shaping passage  58 , as illustrated in FIG. 4, rate shaping orifice plate  84  is pushed down, forming a seal with central body  50  and only allowing flow through rate shaping orifice  86 . When fluid is moving from lower rate shaping passage  58  to upper rate shaping passage  46 , as illustrated in FIG. 3, rate shaping orifice plate  84  is moved up, away from central body  50 , allowing flow through rate shaping orifice  86  and around rate shaping orifice plate  84  in annular plate passage  92 . This allows for a higher flow rate. As illustrated in this embodiment, flow control valve  56  results in a first flow rate to pressurize intensifier piston  54  and a faster flow rate for venting the fluid acting on intensifier piston  54 .  
         [0024]    Alternative flow control valve configurations can be implemented. Flow control valve  56  must simply allow different flow rates depending on the direction of the flow. FIG. 6 illustrates an alternative embodiment for flow control valve  56 . This embodiment comprises a flow orifice  92 , located in damper plate  42 , and a flow ball check  94  located in central body  50 . When flow is moving in the first direction, from upper rate shaping passage  46  to lower rate shaping passage  58 , actuation fluid travels through flow orifice  92  but flow ball check  94  is closed. This results in a slower flow rate and less pressure on shoulder  60 . When flow is moving in the second direction, from lower rate shaping passage  58  to upper rate shaping passage  46 , venting the cavity acting on shoulder  60 , flow travels through flow orifice  92  and also through flow ball check  94 , due to the ball coming of its seat. This allows a faster venting flow rate than filling flow rate.  
         [0025]    Industrial Applicability  
         [0026]    Controlling injection pressure and timing is important to reducing emissions. Further, multiple injections per engine cycle, such as pilots and posts, can also have a significant impact in emissions controls. Multiple injections could include two injections per cycle or as many as five or more. As the number of injections increase, injector speed must also increase. Unfortunately, many current injectors may have a difficult time cycling or resetting fast enough to allow multiple injections per engine cycle. For example, depending on the timing of the injection events and the desired quantity per event, an intensifier piston, used to pressurize fuel for injection, may not be able to reset quickly enough to perform all necessary injections.  
         [0027]    Flow control valve  56  allows different flow rates to and from the intensifier piston  54 . For example, flow control valve  56  allows a first flow rate to intensifier piston  54  to pressurize fuel at a desired rate (Note that this rate can adjusted and tuned by those skilled in the art by including rate shaping features, such as piston hats and rate shaping orifices.) Flow control valve  56  allows a second, faster flow rate away from intensifier piston  54  when the actuation passages are open to drain. This allows for quicker venting, allowing intensifier piston  54  to reset quicker. This allows the intensifier to handle multiple injection in the same engine cycle.  
         [0028]    As explained above, injector  10  starts in a closed or no-injection state. Control valve  20  is in its first position providing high pressure actuation fluid to the control cavity  34 . This insures that check  56  remains closed, preventing any fuel from entering the combustion chamber (not shown) through orifice  58 . Control valve  20  also provides high pressure actuation fluid to spool passage  36 , thereby biasing spool valve  22  in its first position, which prevents high pressure actuation fluid from acting on intensifier piston  46  and pressurizing fuel.  
         [0029]    When injection is desired, control valve  20  is actuated causing seated pin  26  to move to its second position. This opens spool passage  36  to low pressure drain  38 , allowing spool valve  22  to move to its second position. In its second position, spool valve  22  allows high pressure actuation fluid to act upon intensifier piston  46 , which causes intensifier piston  46  and subsequently plunger  50  to move downward and pressurize fuel in fuel pressurization chamber  16 . Specifically, high pressure actuation fluid travels through upper, middle and lower intensifier passages  40 ,  44 , and  48  to act upon the piston hat  52 . High pressure actuation fluid also travels through upper rate shaping passage  46 , flow control valve  56  and lower rate shaping passage  58  to act upon shoulder  60 . As the high pressure actuation fluid travels through flow control valve  56 , rate shape orifice plate  84  is pushed downward, forming a seal with central body  50 . This allows flow to only travel through rate shaping orifice  86 .  
         [0030]    The high pressure actuation fluid acting on hat  52  and shoulder  60  cause intensifier piston  54  to move downward, moving plunger  64 , and pressurize fuel at the desired rate. (Note the rate of pressurization can change if and when the piston hat  52  comes out of the bore.) Pressurized fuel from pressurization chamber  16  then moves to fuel cavity  54  where it acts on check  56 , trying to push check  56  up, into the open position, so that injection can occur. When seated pin  26  is in the second position, check control cavity  34  is also opened to low pressure drain  38 . This results in check spring  62  being the only thing that keeps check  56  closed; however, as fuel is pressurized, the force of pressurized fuel overcomes the force of the check spring  62  and moves check  56  to its open position.  
         [0031]    When end of injection is desired, control valve  20  is de-actuated and seated pin  26  is moved back to its first position. This results in high pressure actuation fluid traveling back in to spool passage  36  to bias spool valve  22  in its first position. Moving back to its first position, spool valve  22  blocks the high pressure actuation fluid and opens upper, middle and lower intensifier passages  40 ,  44 ,  48  to drain. Lower rate shaping passage  58  and upper rate shaping passage  46  are also opened to drain. As actuation fluid travels in this direction, back through flow control valve  56 , the flow rate is increased. Rate shape orifice plate  84  moves off of central body  50  allowing flow through rate shaping orifice  86  and around plate  84  in the annular plate passage  92 . By venting the high pressure actuation fluid acting on intensifier piston  56 , piston spring  62  can resent intensifier piston  56  back in its original, up position.  
         [0032]    Additionally, when the seated pin  26  moves back to its first position, high pressure actuation fluid is again directed through upper and lower check passages  28 ,  32  and back into check control cavity  34  to insure check closure.  
         [0033]    It should be noted that the valve arrangement in the injector shown provides a fast moving control valve  20  and a slow moving spool valve  22 . This can impact the rate shaping capabilities of the injector. For example, it may be possible to cycle control valve  20  quickly enough to stop and start injection without spool valve  22  ever really changing positions. In this senario, flow control valve  56  does not play much of a role, instead it just acts as a conventional rate shaping orifice. However, when multiple injections are sufficiently spaced apart, such that spool valve  22  has time to react, flow control valve  56  allows intensifier piston  54  to reset quickly.  
         [0034]    As illustrated above, flow control valve  54  could have alternative embodiments. Further, depending on the embodiment, more or less body parts could be used. For example, the flow control valve  54  embodiment shown in FIG. 6 could be implemented in one piece. Further, the size of the valve and its passages and orifices can be sized according to each injector&#39;s specific design. Those skilled in the art will understand that modeling and experimentation on valve and orifice sizes will achieve desired results.  
         [0035]    The present example has only illustrated a single injection event but multiple injections per engine cycle could be employed. Further, actuation fluid is preferably lubrication oil but could be any variety of other engine fluids, including fuel, coolant, or steering fluid.  
         [0036]    The present example also illustrates the use of the flow control valve in a hydraulically actuated electronically controlled unit injector; however, the flow control valve could be used in a variety of other injector types, including common rail systems, or other hydraulic devices.  
         [0037]    Other aspects, features, and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims.