Patent Publication Number: US-7913929-B2

Title: Modular outward opening piezo direct fuel injector

Description:
TECHNICAL FIELD 
     The present disclosure relates to a direct fuel injector for supplying fuel to an engine of a vehicle. 
     BACKGROUND 
     In today&#39;s automotive engine systems, there is an increased demand for low cost, direct fuel injectors with coking resistance. Typical piezo-type fuel injectors for automobiles have outward opening valves that are very fast responding but are costly. Typical direct injector solenoid valves have inward opening valves but they are not resistant to fuel coking. Injector coking is a problem in direct injected internal combustion engines because the injectors are in contact with the harsh environment of the combustion chamber. Due to high temperatures, fuel decomposes in the injector nozzle and lays down a deposit which both restricts flow, and distorts the symmetry of the spray. As this deposit grows with operation, the internal dimensions of the nozzle change. 
     The buildup of deposits in the combustion chamber can alter engine performance by impairing fuel economy, regulated emissions, and drivability, and in the worst case scenario cause engine damage. 
     Another disadvantage of conventional fuel injectors is the occurrence of scrap during the manufacturing of the injector. 
     SUMMARY 
     There is a need to provide a modular direct fuel injector for an automobile having a piezo stack coupled to an outwardly opening needle valve that allows for fast opening and closing response as well as the ability to measure the combustion pressure using the piezo stack as a sensor. 
     An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing a module, direct fuel injector including a fuel side sub-assembly having valve body structure defining a main flow passage there-through and an outlet opening. The valve body structure includes a seating surface at a distal end thereof. A needle is disposed in the main flow passage. The needle has first and second ends, with the second end having a sealing surface associated with the seating surface. The needle is movable between a closed position with the sealing surface engaging the seating surface to prevent fuel from passing through the outlet opening, and an open position with at least a portion of the needle moving outwardly from the distal end of the valve body structure with the sealing surface being disengaged from the seating surface to permit fuel to pass through the outlet opening. A spring, disposed in the main flow passage, is constructed and arranged to bias the needle to the closed position. A manifold structure is coupled to the valve body structure. A portion of the manifold structure has a bore there-through with the first end of the needle extending outwardly from the bore and beyond an end surface of the portion of the manifold structure. The manifold structure includes inlet passage structure in communication with the bore and with the main fuel passage so that fuel supplied to the inlet passage structure will pass through the main flow passage and through the outlet opening when the needle is in the open position. Bellows is provided in the bore and is constructed and arranged to prevent fuel from exiting the bore near the first end of the needle. The injector includes a dry side sub-assembly including a piezo stack coupled to the manifold structure and constructed and arranged to change length when voltage is applied thereto. The piezo stack is associated with the first end of the needle so that when the length of the piezo stack changes, the needle moves from the closed position to the open position thereof. 
     In accordance with another aspect of an embodiment, the invention, a method of assembling a module, direct fuel injector provides a fuel side sub-assembly having valve body structure defining a main flow passage there-through and an outlet opening. The valve body structure includes a seating surface at a distal end thereof. A needle is disposed in the main flow passage and has first and second ends, with the second end having a sealing surface associated with the seating surface. The needle is movable between a closed position with the sealing surface engaging the seating surface to prevent fuel from passing through the outlet opening, and an open position with at least a portion of the needle moving outwardly from the distal end of valve body structure with the sealing surface being disengaged from the seating surface to permit fuel to pass through the outlet opening. A spring, disposed in the main flow passage, is constructed and arranged to bias the needle to the closed position. Manifold structure is coupled to the upper valve body. A portion of the manifold structure has a bore there-through with the first end of the needle extending outwardly from the bore and beyond an end surface of the portion of the manifold structure. The manifold structure includes inlet passage structure in communication with the bore and with the main fuel passage so that fuel supplied to the inlet passage structure will pass through the main flow passage and through the outlet opening when the needle is in the open position. A pre-deformed crush ring is provided adjacent to the end surface of the portion of the manifold structure. A piezo stack, separate from the fuel side sub-assembly, is coupled to the manifold structure with an end of the piezo stack engaging the crush ring thereby setting a lift of the needle. The piezo stack is constructed and arranged to change length when voltage is applied thereto and being associated with the first end of the needle so that when the length of the piezo stack changes, the needle moves from the closed position to the open position thereof. 
     Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which: 
         FIG. 1  is a view of a modular, outward opening piezo direct fuel injector provided in accordance with an example embodiment of the present invention. 
         FIG. 2  is a sectional view taken along the line  2 - 2  of  FIG. 1 . 
         FIG. 3  is an enlarged sectional view of the needle seated in the lower valve body of the injector  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Referring to  FIG. 1 , a module, outward opening piezo direct fuel injector is shown, generally indicated at  10 , for supplying fuel to an internal combustion engine (not shown) of an automobile. The direct fuel injector  10  includes an upper valve body  12 , coupled preferably by a laser weld, at one end to a lower valve body  14 . The valve bodies  12  and  14  can be considered to be valve body structure that defines a main flow passage  16  of the injector  10 . A needle  18  is provided in the flow passage  16  of the valve bodies  12  and  14 . The needle  18  is moveable between a first, seated, i.e., closed, position and a second, open position for controlling the flow of fuel through the injector  10 . In the closed position as best shown in  FIG. 3 , an annular sealing surface  20  of an end  22  of the needle  18  is engaged with a mating annular seating surface  24  of the lower valve body  14  thereby closing an outlet opening  26  and preventing fuel flow from the injector  10 . In the open position, the needle  18  moves outwardly from the distal end  28  of the lower valve body  14  so that the sealing surface  20  is moved away and disengaged from the seating surface  24  to allow fuel flow through the outlet opening  26 . The seating surface  24  is defined at the distal end  28  of the lower valve body  14 . A seal  29  is provided near the distal end  28  of the lower valve body  14  in the conventional manner. 
     An end of a spring  30  rests on an end  32  of the lower valve housing  14  and surrounds a portion of the needle  18  in the upper valve body  14 . A retainer  34  retains the other end of the spring  30 . The spring  30  biases the needle  18  to the closed position thereof. The retainer  34  and spring  30  are in the main flow passage  16  and when the needle  18  is in the open position, fuel flow about the periphery of the needle  18 , the retainer  34  and the spring  30 . Since the valve body structure is module due to the separate upper valve body  12  and lower valve body  14 , the force of spring  30  on the needle  18  can advantageously be set prior to final assembly of the injector  10 . 
     A body manifold  36  is coupled, preferably by a laser weld, to the other end of the upper valve body manifold  12 . The body manifold  36  includes an axially extending bore  38  there-through and an end  40  of the needle  18  extends through the bore  38  and from end surface  41  of the body manifold  36  to engage a piezo stack  42 , the function of which will be explained below. The body manifold  36  includes manifold passages  44 . One of the manifold passages  44  communicates with an inlet passage  46  in a fuel manifold  48  that is coupled to the body manifold  36 , preferably by a laser weld. Passages  44  and  46  can be considered to be inlet passage structure in communication with the main flow passage  16  of the injector  10  so that fuel can pass through the injector when the needle is in an opened position. An inlet fitting  50  is coupled to the fuel manifold  48  and is sealed with respect thereto via an O-ring  52 . Fuel is supplied to the injector  10  via the inlet fitting  50 . The fuel manifold  48  also includes mounting structure  54  constructed and arranged to mount the fuel injector  10  to a fuel rail (not shown). The mounting structure  54  is disposed generally 180° from the inlet fitting  50 . 
     The fuel manifold surrounds the body manifold  36 . Two inlet passages  46  are provided 180° apart so that the fuel manifold  48  can be mounted 180° from the position shown in  FIG. 2 , for alternative mounting purposes. The body manifold  36 , the fuel manifold  48 , and inlet fitting  50  can be considered to be manifold structure and need not be separate parts as in the embodiment. 
     A thrust nut  56  is provided over the periphery of the piezo stack  42  and external threads  58  of the nut  56  are engaged with internal threads  59  of the fuel manifold  48 . A thrust ring  60  is provided such that during assembly, the thrust nut  56  pushes down on the thrust ring  60 , which pushes down on the piezo stack  42 . An O-ring  62  provides a seal between the piezo stack  42  and the fuel manifold  48 . A crush ring  64  is provided in a bore  65  of the fuel manifold  48  and is disposed between an end  66  of the piezo stack  42  and the end  41  of the body manifold  36 . The crush ring  64  is preferably pre-deformed to set the blind lift of the needle  18  by controlling the gap  68  between the end surface  41  of the body manifold  36  and the end surface  66  of the piezo stack  42 . Blind lift is defined as the small clearance between the needle  18  and the end of the piezo stack  42 . As the thrust nut  56  is tightened, minor adjustments to the lift can be made due to minor deformation of the crush ring  64 . 
     A metal bellows  70 , disposed in the bore  38  of the body manifold  36 , has a first end welded to the needle  18  near end  40  thereof and a second end welded to the body manifold  36 . The bellows  70  seals a fuel chamber  72  off hermetically from the unpressurized air filed gap  68 . In other words, the bellows  70  separates the dry, piezo stack side from the wet, fuel side of the injector  10 . The bellows  70  also permits axial movement of the needle  18 . In addition, the bellows diameter and the needle outlet diameter are equal to make the needle pressure balanced. As pressure changes, the force on the needle remains balanced; thus the opening of the needle is not pressure sensitive. 
     The piezo stack  42  is conventionally used in diesel-type fuel injectors to actuate a valve member and can be of the type disclosed in U.S. Pat. No. 7,222,424, the content of which is hereby incorporated by reference into this specification. More particularly, the piezo stack  42  includes a plurality of stacked, individual piezoelectric elements  43  (only one shown in  FIG. 2 ). Electrical voltage is applied to the piezo stack  42  causing a longitudinal expansion thereof to move the needle  18  downwardly in  FIG. 2 , to the open position. Removing the voltage returns the piezo stack  42  to its original length and the spring  30  biases the needle  18  back to the closed position thereof. An electrical connector  74  houses the leads  76  for providing the voltage to the piezo stack  42 . 
     The direct fuel injector  10  is of modular configuration so as to reduce parts and to reduce scrap during manufacturing. The assembly of the direct fuel injector  10  includes first building a fuel side sub-assembly, generally indicating at  78 , by welding the bellows to the needle and body manifold  36 , assembling the upper and lower valve bodies  12 ,  14  with the needle  18 , spring  30  and retainer  34  therein, joining the upper valve body  12  to the body manifold  36 , and joining the fuel manifold  48 , with inlet fitting  50  attached, to the body manifold  36 . The force of spring  30  is set by adjusting the retainer  34  during constructing the fuel side sub-assembly  78 . Next, the dry side-sub assembly, generally indicated at  80 , is built by assembling the thrust nut  56 , the thrust ring  60 , and O-ring  62  with respect to the piezo stack  42  and placing the crush ring  64  in the bore  65  of the fuel manifold  48 . The threads  58  of thrush nut  56  are engaged with the threads  59  of the fuel manifold  48 , with the end surface  66  of the piezo stack  42  engaging the crush ring  64 , thereby setting the blind lift of the needle  18  and completing the assembly of the injector  10 . Thus, the dry side sub-assembly  80  is separate from the fuel side sub-assembly  78 , but coupled therewith. 
     The fuel manifold  48 , body manifold  36 , and upper and lower valve bodies  12  and  14  are of stainless steel, thereby defining a stainless steel fuel passage through the injector  10 . The modular configuration allows the injector  10  to be calibrated and tested on a sub-assembly basis. In addition, the piezo stack  42  can be manufactured in a place different from where the fuel side sub-assembly  78  is assembled. In addition, the modular configuration enables easy change of fuel injector length and for change in connector types. 
     Since the injector  10  is outward opening, cocking resistance is improved. The injector  10  can be used in alcohol, gasoline, and flex fuel applications, but conveniently uses a diesel piezo stack  42  mounted above the fuel the passage  16 . The injector  10  is of lower cost than conventional outward opening injectors since it has fewer components, less welds, and fewer manufacturing steps than conventional injectors. The use of the dry piezo stack  42  directly coupled to the outwardly opening needle  18  allows for fast opening and closing response as well as the ability to measure the combustion pressure using the piezo stack as a sensor. 
     The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.