Abstract:
An apparatus and method for multi-mode fuel injection is disclosed. A sleeve is disposed about a fuel injector tip movable between a first and second position and wherein the sleeve is capable of impinging the fuel spray as it enters into the combustion chamber. By impinging the fuel spray, different spray profiles or plumes can be obtained allowing the fuel injector to inject in different modes, including homogenous charge compression ignition.

Description:
TECHNICAL FIELD 
   The present invention is directed to fuel injector nozzle assemblies and specifically to fuel injectors with dual mode capability. 
   BACKGROUND 
   Emission plays an important role in engine development. In particular, engine manufactures have learned that fuel injection plays a crucial role in determining the amount of emissions that an engine produces. Traditionally, a fuel injector would only operate in one mode of operation, injecting fuel towards the side of the cylinder when the piston approached top dead center. At this point, the compressed air is hot enough to cause combustion. However, engineers have learned that injecting in dual modes during the same engine cycle may substantially reduce the amount of the emissions created during the combustion process. Specifically, it has been learned that it is desirable to inject a small amount of fuel while the piston is near bottom dead center. As the piston moves closer to top dead center position, the fuel mixes with the air, as it is being compressed, to form a relatively lean homogeneous mixture. Traditional fuel injection also occurs near top dead center and combustion occurs as a result of the temperature of the compressed air. This process is commonly referred to as homogeneously charge compression ignition (HCCI). 
   The prior art has attempted to create dual mode injectors; however, improvement is still necessary for more viable dual mode operation. U.S. Pat. No. 6,186,419 B1, issued to Kampman et al., discloses an injector that is capable of injecting, in different modes based upon engine operating conditions. Specifically, a sleeve is disposed around a fuel injector that is capable of impinging the fuel spray as it is injected into the cylinder. By moving the sleeve up and down, the degree of impingement can be changed. At the fully retracted position, the injector injects towards the side of the cylinder without any impingement and at the fully advanced position, the injection spray is completely impinged and directed towards the bottom of the cylinder. However, in this patent, the sleeve is moved through a rack and pinion approach, and the sleeve is not capable of quickly transitioning between multiple modes during a single engine cycle. Further, the sleeve disposed around the injection tip provides only a vertical surface of impingement which limits the flexibility of the injector and limits the ability to achieve homogenous mixtures. 
   In other attempts to achieve dual mode operation, engine manufacturers have placed two fuel injector nozzles into a cylinder, each operating in a different mode. The first nozzle performs the initial homogenous charge injection, directed toward the bottom of the cylinder when the piston is near bottom dead center, and the second nozzle, with different orifice angles injects in the traditional fashion when the piston is near top dead center. Unfortunately, this approach requires numerous extra components, adding cost and taking up additional packaging space. 
   The present invention is directed to overcome one or more of the problems set forth above. 
   SUMMARY OF THE INVENTION 
   In one embodiment, a fuel injector tip has an inner surface and a outer surface and at least one orifice having an axis and being disposed within the injector tip and opening between the inner and outer surfaces. A sleeve has an angled portion and is disposed about the tip and is axially movable relative to the injector tip between a first position at which the orifice axis is free from intersection with the sleeve and a second position in which the orifice axis intersects the sleeve. 
   In another embodiment, a method of multi-mode fuel injection during an single engine cycle comprises: positioning an impingement sleeve having an angled portion and being disposed about a fuel injector tip at a first position to direct a fuel spray from the tip to a first cylinder position, injecting the first fuel spray, repositioning the sleeve to a second position to direct fuel spray from the tip to a second cylinder position, and injecting a second fuel spray. 
   In another embodiment, an injector tip has inner and outer surfaces and longitudinal axis. The tip also has at least one orifice having an axis wherein the orifice is disposed within the injector tip and opening at the inner and outer surfaces. A sleeve having an angled portion is disposed concentrically about the longitudinal axis of the tip and is axially movable relative to the injector tip between a first position and a second position, wherein the first and second positions are spread apart relative to the longitudinal axis. 
   Finally, in another embodiment, a fuel injector comprises an injector tip having an inner surface an outer surface and at least one orifice having an axis and being disposed within said injector tip and opening at the inner and outer surfaces. A sleeve having an angled portion and being disposed about said tip and being axially movable relative to said injector tip between a first position at which said sleeve is at a first predetermined retracted position relative to said orifice and a second position at which said sleeve is at a second predetermined advanced position at which said orifice act as intersects said sleeve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic cross section of an injector nozzle incorporating the present invention. 
       FIG. 2  is a diagrammatic cross section of an injector nozzle incorporating the present invention. 
       FIG. 3  is a diagrammatic cross section of an injector nozzle incorporating the present invention. 
       FIG. 4  is a diagrammatic cross section of an injector nozzle incorporating the present invention. 
       FIG. 5  is a diagrammatic cross section of an injector nozzle incorporating the present invention. 
       FIG. 6  is a diagrammatic cross section of an injector nozzle incorporating the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a diagrammatic cross section of an injector nozzle  20  incorporating the present invention. The injector nozzle includes an injector tip  32  having a blind bore which creates a fuel passage  46 . At the lower end of the injector tip  32 , there is at least one orifice  36  which allows fuel to communicate between the fuel passage  46 , and the combustion cylinder (not shown). Within the injector tip  32 , a check valve  34  is movable between an open position and a closed position thereby regulating fuel communication between fuel passage  46  and orifice  36 . 
   The injector tip is at least partially enclosed by the injector&#39;s lower body  30 . Further, a sleeve is disposed around the injector tip and slideable between a fully retracted position and a filly advanced position. The sleeve  38  is used to impinge fuel being injected through orifice  36 . By impinging the spray, sleeve  38  can change the direction and shape of the spray plume that is created. The inner-diameter of the sleeve  38  is angled to allow different degrees of impingement. In  FIG. 1 , the inner-diameter of sleeve  38  is shown with two different angled surfaces. The first surface creates an angle α designated by  40  and the second angle creates an angle β designated by  42 . In  FIG. 2 , a different variation of the sleeve  38  is shown. In  FIG. 2 , an angle θ, designated by  44 , is illustrated through steps. In this particular case, the angle is measured as the line running through the points of each step. It is possible to create an “angle”, using a curved surface. The curve is the tangent line at any single point on the curved surface. 
     FIGS. 1 and 2  illustrate sleeve  38  in the fully advanced position. 
     FIG. 3  illustrates sleeve  38  in a fully retracted position. It is possible for sleeve  38  to be stopped anywhere between its fully advanced and fully retracted positions, thereby changing the point of fuel impingement and therefore, the spray plume. 
   In  FIG. 4 , one embodiment of the present application is illustrated. Specifically, a passive control system is illustrated in which cylinder pressure controls the position of sleeve  38 . Spring  48  provides a biasing force against sleeve  38  to place the sleeve in its fully advanced position. As the piston  50  compresses air in cylinder  52 , cylinder pressure increases and causes the sleeve  38  to push against spring  48  and move upwards. When the piston  50  is near top dead center, sleeve  38  is in its fully retracted position. After, the piston  50  reaches top dead center, and moves back down, cylinder pressure is reduced and sleeve  38  also moves back down as the spring  48  strength becomes greater than the cylinder pressure. 
   In  FIGS. 5 and 6 , additional embodiments of the present application are illustrated, specifically incorporating active control of sleeve  38 . In  FIG. 5 , sleeve  38  is biased in the retracted position by a hydraulic bias spring  56 . The spring  56  is located in spring cavity  54 . Sleeve  38  is moved to the advanced position by introducing pressurized fluid into control cavity  58 , through fluid passage  60 . As pressure builds in control cavity  58 , the sleeve is pushed downward, into its advanced position, against spring  56 . When it is desired to return sleeve  38  to its retracted position, control cavity  58  is vented, releasing the pressure in control cavity  58  and allowing the spring  56  to return sleeve  38  to its retracted position. It should be noted that although  FIG. 5  illustrates spring  56  biasing sleeve  38  in the retracted position, the design could be altered such that the spring  56  biased sleeve  38  in the advanced position and that pressurized fluid was used to move the sleeve upwards into its retracted position. 
   In  FIG. 6 , sleeve  38  is completely hydraulically controlled. Once again pressurized fluid from fluid passage  60  can work on the top of sleeve  38  through control cavity  58  however, a second control cavity  64 , fed with pressurized fluid from second fluid passage  62  acts on the underside of sleeve  38 . Depending upon the desired position of sleeve  38 , pressurized fluid is either introduced into or, vented from the control cavity&#39;s  58  and  64 . It should be noted that a variety of pressurized fluids could be used in control cavities  58  and  64  including oil, fuel, air, and water. 
   As it can be seen from  FIGS. 5 and 6 , the sleeves  38  position can be infinitely varied by controlling the flow of pressurized fluid into control cavities  58  and  64 . It should also be noted that control of pressurized fluid flowing into the control cavity&#39;s  58  and  64  through fluid passages  60  and  62  is well known in the art and need not be described here however, for example only, a solenoid controlled valve could be used to regulate pressurized fuel flowing into and out of control cavities  58  and  64 . 
   In the descriptions, it should be noted that fully advanced and fully retracted position are discussed and that these forms could have various meanings depending on the application. In order to define these terms, in another manner, the orifice  36  of tip  32  has an axis. In the advanced position, the orifice axis intersects the sleeve  38 . In the retracted position, the orifice axis preferably is free form intersecting the sleeve  38  but this is not necessary. The sleeve  38  only needs to be retracted enough to avoid contacting the piston and providing an impinged spray plume that avoids putting fuel on the piston or cylinder walls. 
   INDUSTRIAL APPLICABILITY 
   Sleeve  38  allows a fuel injector to inject in multiple modes during the same engine cycle. In its most basic operation, the sleeve  38  helps control the fuel spray plume being injected into the cylinder  52 . For example, a homogenous charge for compression ignition is desirable to reduce emissions. To achieve a homogenous charge, fuel needs to be injected toward the bottom of the cylinder  52  when the piston  50  is near bottom dead center; however injectors generally are designed to inject towards the side of the cylinder  52  when the piston is near top dead center. Sleeve  38  can be used to impinge the fuel spray and direct the spray plume towards the bottom of the cylinder  52 . 
   High-pressure fuel is provided through fuel passage  46 . Check  34  controls when the fuel is injected into cylinder  50 . (Check  34  can be controlled in a variety of ways including direct control, such as with a solenoid or piezo). The Sleeve  38  can have any rest or start position but must be moveable between its advanced and retracted positions based upon fuel injection needs. To obtain the homogenous charge, the sleeve  38  needs to be placed in a position, preferably fully advanced, that directs the fuel spray plume toward the bottom of the cylinder  52 . When injection is desired, check  34  opens the communication between fuel passage  46  and orifice  36 . As the fuel is injected into the cylinder  52 , it hits sleeve  38  and is redirected towards the bottom of the cylinder  52 . As piston  50  moves up and compresses the air/fuel mixture, a homogenous charge is obtained. When the piston  50  is near top dead center, another traditional injection can occur by moving the sleeve  38  to its retracted position and again moving check  34  to allow injection. The injector has now injected in two modes during one engine cycle. 
   It is necessary to move sleeve  38  and inject in different modes to; 1) obtain proper homogenous mixing and 2) avoiding unnecessary emissions by spraying fuel on the cylinder walls (normal injection when the piston  50  is near bottom dead center) or spraying the piston  50  (by directing the spray down when the piston is near top dead center). It should be noted that the nozzle  20  can inject in numerous modes, besides just the two outlined above. The sleeve  38  can be positioned anywhere between the fully advanced and fully retracted positions to achieve different plume shape and direction based upon the sleeve&#39;s  38  angle. As illustrated in  FIGS. 1 and 2  the sleeve  38  can have multiple angles or shapes to provide a variety of injection characteristics depending on where sleeve  38  impinges the injected fuel. 
   Control of sleeve  38  can be achieved in a variety of ways. In one embodiment of the present application, a passive control system is used, as illustrated in  FIG. 4 . The sleeve  38  is placed in it fully advanced position by a spring  48  when cylinder pressure is low (when piston  50  is near bottom dead center). As combustion pressure increases the pressure pushes sleeve  38  upwards, compressing spring  48 . When the piston  50  reaches top dead center, sleeve  38  is in a retracted position. As the piston moves back down, cylinder pressure is reduced and the spring  48  again pushes sleeve  38  down to an advanced position. With this type of control system, injection may be based upon piston position, which has a relationship to cylinder pressure and therefore sleeve  38  position. For example, when operating in a HCCI mode, a first injection would be made when the sleeve  38  is in an advanced or down position. Check  34  would open communication between fuel passage  46  and orifice  36 , allowing fuel to spray into cylinder  52 . (NOTE—Varied methods of check  34  control are well known in the art and are not discussed here.) With cylinder pressure low, spring  48  has biased sleeve  38  in the advanced position causing fuel to contact sleeve  38  on its first angled position, forming angle α  40 . This causes the fuel spray to be directed toward the bottom of the cylinder  52 . This injection is then stopped by closing check  34 . As the piston  50  advances, and builds cylinder pressure, the initial injection creates a homogeneous charge in cylinder  52 . As cylinder pressure builds, pressure becomes greater than spring&#39;s  48  strength, causing sleeve  38  to retract or move up. This allows for two things, first, sleeve  38  may need to retract to avoid contacting piston  50  when it reaches top dead center. Second, when sleeve  38  retracts, other injection profiles can be obtained. It is describe to inject again when the piston  50  is near top dead center by again moving check  34 . Depending on the timing of the injection, the fuel spray could impinge sleeve  38  on the second angle position, forming angle β  42 , or the sleeve  38  could be completely retracted and the injection may not be impinged sleeve at all. With the sleeve  38  moving with the piston  50 , it is possible to obtain various injection profiles based upon the timing of the injection event and the number of different angles on sleeve  38 . 
   Another alternative embodiment, an active control system can be for sleeve  38  can be implemented. In  FIG. 5 , a hydraulic bias spring  56  and pressurized fluid are used to control the position of sleeve  38 . Specifically, spring  56 , located in spring cavity  54  can biases sleeve  38  in the retracted position. In order to perform HCCI operation, pressurized fluid is introduced to fluid passage  60  and subsequently control cavity  58 . As pressure builds in control cavity  58 , sleeve  38  is pushed down into in its advanced position against biases spring  56 . Check  34  would then open communication between fuel passage  46  and orifice  36  allowing the fuel spray to impinge sleeve  38  and be directed toward the bottom of cylinder  52 . Check  34  would then be closed and fluid pressure from control cavity  58  would be vented to allow sleeve  38  to move to its retracted position as piston  50  advances. A second injection could occur while sleeve  38  is advancing or when sleeve  38  reaches is fully retracted position. In fact multiple injections could occur whenever desired as sleeve  38  is moved towards its retracted position. By retracting sleeve  38  and continuing to have multiple injections, different injection profiles can be obtained depending upon the angle of sleeve  38  that fuel spray impinges upon. As sleeve  38  comes closer to its fully retracted position the fuel spray is directed less to the bottom of the cylinder and more towards the side until finally sleeve  38  is fully retracted and unimpinged fuel spray can be obtained. 
   In yet another embodiment of an active control system for sleeve  38 ,  FIG. 6  illustrates a fully hydraulic control system. Injection occurs in the same primary way by impinging the fuel spray along the different angles of sleeve  38  however control of sleeve  38  is slightly different. In this embodiment, hydraulic fluid in control cavity  58  and control cavity  64  positions sleeve  38 . The control cavity  58  receives pressurized fluid from fluid passage  60  and control cavity  64  receives pressurized fluid from fluid passage  62 . When its desirable to have the sleeve  38  in its advanced position, fluid pressure is allowed build in control cavity  58  and at the same time, pressurized fluid is vented from the second control cavity  64 . In just the opposite scenario, when it is desirable to have sleeve  38  in its retracted position, pressurized fluid is directed into the second control cavity  64  and vented from control cavity  58 . If it is desirable to have a intermediate position, sleeve  38  could be pressure balanced by putting pressurized fluid in both control cavities  58  and  64 . 
   Other aspects, features, advantages of the present application may be obtained from a study of this disclosure and drawings, along with the appended claims.