Abstract:
A fuel injector having a reduced bounce armature is disclosed. The fuel injector includes an upstream end, a downstream end, and a valve seat located at the downstream end. The armature located between the upstream end and the downstream end and includes an upstream armature end; a downstream armature end; and a longitudinal channel extending therethrough. The longitudinal channel includes an upstream portion having a first cross-sectional area and a downstream portion having a second cross-sectional area, with the second cross-sectional area being smaller than the first cross-sectional area. The downstream portion includes at least one interior wall. The armature also includes a flow restrictor element inserted into the downstream portion of the longitudinal channel such that liquid flow from the downstream armature end to the upstream armature end is restricted. The fuel injector further includes a needle located in the longitudinal channel downstream of the transverse channel. The needle extends from the longitudinal channel and is reciprocably engageable with the valve seat in a closed position. A method of reducing the bounce of the armature is also disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an apparatus and a method for reducing and/or eliminating armature/needle bounce during operation. 
     BACKGROUND OF THE INVENTION 
     During operation of High Pressure Direct Injection (HPDI) fuel injectors, armature/needle assembly closing action during the closing phase of the duty cycle is followed immediately by a secondary shorter reopen and closing phase called “bounce”. During this secondary reopen phase, additional, unwanted fuel is dispensed from the fuel injector. To improve high pressure fuel injector performance, the bounce must be minimized, or more preferably, eliminated. 
     One aspect of injector performance which has been addressed to reduce or eliminate bounce has been the flow of fuel through the armature. To solve the bounce problem, an anti-bounce orifice disk has been installed in the armature. The anti-bounce disk has a shape which provides a fuel path for fuel flow downstream toward the tip of the injector, but which obstructs fuel flow in the opposite, or upstream direction. Different anti-bounce orifice disks with different internal diameters are used to provide different flow rates. An anti-bounce orifice disk with a specific internal diameter is used to provide a desired flow rate. However, the specific internal diameter required is generally determined on a trial-and-error basis. This procedure requires different anti-bounce disks with different internal diameters which must be individually installed in and removed from the injector until the desired performance parameters of the injector are achieved. This process is time consuming and expensive. 
     It would be beneficial to provide an anti-bounce orifice disk with a single internal diameter that can be adjusted to provide different flow rates based on the axial position of the anti-bounce orifice disk within the armature/needle assembly, eliminating the costly insertion and removal of anti-bounce disks having different internal diameters. 
     BRIEF SUMMARY OF THE INVENTION 
     An armature is provided. The armature comprises an upstream end, a downstream end and a longitudinal channel extending therethrough. The longitudinal channel includes an upstream portion having a first cross-sectional area and a downstream portion having a second cross-sectional area, with the second cross-sectional area being smaller than the first cross-sectional area. The downstream portion includes at least one interior wall. The armature further comprises a flow restrictor element inserted into the downstream portion of the longitudinal channel such that liquid flow from the downstream end to the upstream end is restricted. 
     An armature/needle assembly is provided. The assembly includes an armature and a needle. The armature comprises an upstream end, a downstream end and a longitudinal channel extending therethrough. The longitudinal channel includes an upstream portion having a first cross-sectional area and a downstream portion having a second cross-sectional area, with the second cross-sectional area being smaller than the first cross-sectional area. The downstream portion includes at least one interior wall. The armature further comprises a flow restrictor element inserted into the downstream portion of the longitudinal channel upstream of the at least one transverse channel such that liquid flow from the downstream end to the upstream end is restricted. The needle is located in the downstream portion of the longitudical channel such that the needle extends from the longitudinal channel. 
     A fuel injector is also provided. The fuel injector comprises an upstream end, a downstream end, a valve seat located at the downstream end, and an armature located between the upstream end and the downstream end. The armature includes an upstream armature end, a downstream armature end, and a longitudinal channel extending therethrough. The longitudinal channel includes an upstream portion having a first cross-sectional area and a downstream portion having a second cross-sectional area, with the second cross-sectional area being smaller than the first cross-sectional area. The downstream portion includes at least one interior wall. The armature further includes a flow restrictor element inserted into the downstream portion of the longitudinal channel such that liquid flow from the downstream armature end to the upstream armature end is restricted. The fuel injector further includes a needle located in the longitudinal channel downstream of the transverse channel, with the needle extending from the longitudinal channel. The needle is reciprocably engageable with the valve seat in a closed position. 
     A restrictor is provided. The restrictor comprises an upstream portion including at least a first leg and a second leg. Each of the first and second legs includes an upstream end and a downstream end. The upstream end of the first and second legs are connected by a transverse connector. The upstream portion further includes an upstream opening extending between the first and second legs. The restrictor further includes a downstream portion connected to the downstream end of each of the first and second legs. The downstream portion includes a generally central opening fluidly communicating with the upstream opening. 
     A method of reducing reverse fluid flow through an armature in a solenoid valve is provided. The method comprises providing an armature reciprocably located within the solenoid valve, the armature having an upstream end, a downstream end, and a channel extending therethrough; inserting a flow restrictor element into the channel, the flow restrictor element allowing flow from the upstream end toward the downstream end, but restricting flow from the downstream end toward the upstream end; and operating the solenoid valve. 
     A method of reducing bounce in an armature/needle assembly of a fuel injector is provided. The method comprises providing an armature reciprocably located within the fuel injector, the armature having an upstream end, a downstream end, and a channel extending therethrough; inserting a flow restrictor element into the channel, the flow restrictor element allowing flow from the upstream end toward the downstream end, but restricting flow from the downstream end toward the upstream end; and operating the fuel injector. 
     A method of setting a fuel flow rate in a fuel injector is provided. The method comprises: a) providing a fuel injector having an armature, the armature including an upstream end, a downstream end, and a channel extending therethrough; b) inserting a flow restrictor into the channel, the flow restrictor restricting fuel flow through the channel; c) operating the fuel injector; d) measuring a fuel flow rate through the fuel injector; e) adjusting a location of the flow restrictor in the channel; f) repeating steps c-e until a desired fuel flow rate is achieved; and g) securing the flow restrictor to the armature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention. 
     FIG. 1 is a side profile view, in section, of a fuel injector which incorporates an armature/needle assembly with the anti-bounce orifice disk according to a preferred embodiment of the present invention; 
     FIG. 2 is an enlarged side profile view, in section, of the armature/needle assembly with the anti-bounce orifice disk according to a first embodiment of the present invention, with the anti-bounce orifice disk in a first position; 
     FIG. 3 is a side profile view, in section, of the armature/needle assembly with the anti-bounce orifice disk according to a preferred embodiment of the present invention, with the anti-bounce orifice disk in a first position; 
     FIG. 4 is a side profile view, in section, of the armature/needle assembly with the anti-bounce orifice disk according to the preferred embodiment of the present invention, with the anti-bounce orifice disk in the first position, taken along line  3 — 3  of FIG. 2; 
     FIG. 5 is a side profile view, in section, of the armature/needle assembly with the anti-bounce orifice disk according to the preferred embodiment of the present invention, with the anti-bounce orifice disk in a second position; 
     FIG. 6 is a side profile view, in section, of the armature/needle assembly with the anti-bounce orifice disk according to a preferred embodiment of the present invention, with the anti-bounce orifice disk in the second position, taken along line  6 — 6  of FIG. 5; and 
     FIG. 7 is a perspective view of the anti-bounce orifice disk according to the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An armature/needle assembly  10  (hereinafter “assembly  10 ”) according to the present invention is used in a high pressure direct injection (HPDI) fuel injector  2 , and is shown in FIG.  1 . As used herein, like numbers indicate like elements throughout. An HPDI fuel injector in which the present invention may be used is disclosed in U.S. patent application Ser. No. 09/482,059, now U.S. Pat. No. 6,257,508, which is incorporated herein by reference in its entirety. Although the present invention is preferably used in fuel injectors, those skilled in the art will recognize that the present invention can be used for other devices such as solenoid valves in which adjustable metering of a fluid is desired and/or required. 
     The fuel injector  2  includes an upstream end  4 , and a downstream end  6 . As used herein, the terms “upstream” and “downstream” refer to directions toward the top and bottom of FIGS. 1-5, respectively. The fuel injector  2  includes an armature/needle assembly  10  (hereinafter “assembly  10 ”) located therein between the upstream end  4  and the downstream end  4 . An enlarged cross-sectional view of the assembly  10  according to the present invention is shown in FIG.  2 . The assembly  10  includes an armature  20 , a needle  30  and an anti-bounce orifice disk  40  (hereinafter “disk  40 ”). The disk  40  restricts flow of fuel from the downstream end  6  to the upstream end  4  after the fuel injector  2  closes during its operating cycle, reducing bounce of the assembly  10  after closing. 
     A biasing element, preferably a helical spring  50 , having an upstream end  510  and a downstream end  520 , is partially located within the armature  20  and biases the assembly  10  away from a fuel inlet tube  60 , which is located proximate to the upstream end  4  of the fuel injector  2 . The armature  20  includes an upstream end  202  and a downstream end  204 . The armature  20  also includes a longitudinal axis  206  which extends through the armature  20  between the upstream end  202  and the downstream end  204 . A longitudinal channel  210  extends through the armature  20  along the longitudinal axis  206  between the upstream end  202  and the downstream end  204 . The longitudinal channel  210  includes an upstream portion  212  which has a first cross-sectional area A 1 , and a downstream portion  214  which has a second cross-sectional area A 2 . The downstream end  204  of the armature includes a ledge or lip  205  which reduces the cross-sectional size of the longitudinal channel  210  such that the second cross-sectional area A 2  is smaller than the first cross-sectional area A 2 . Preferably, the second cross-sectional area A 2  is circular so that the downstream portion  214  of the longitudinal channel  210  includes a single, circular wall  216 . However, those skilled in the art will recognize that the downstream portion  214 , as well as the upstream portion  212  of the longitudinal channel  210  can be shapes other than circular, such as oblong or polygonal, and that the downstream portion  214  will have at least one wall  216 . 
     The downstream end  204  of the armature  20  includes at least one transverse channel  220  which extends through the downstream end  204  and into the longitudinal channel  210 , such that the at least one transverse channel  220  communicates the longitudinal channel  210  to the outside of the armature  20 . 
     The needle  30  is inserted into the downstream end  204  of the armature  20  such that the needle  30  is located wholly downstream of the at least one transverse channel  220 . Preferably, the needle  30  fills up the entire longitudinal channel  210  in the portion of the armature  20  in which the needle  30  is located so that any fuel or other fluid which flows downstream through the longitudinal channel  210  is directed out of the armature  20  through the at least one transverse channel  220 . However, those skilled in the art will recognize that at least one longitudinal channel (not shown) can be present between the needle  30  and downstream end  204  of the armature  20 , allowing some fuel or other fluid to flow out the armature  20  from other than the at least one transverse channel  220 . Referring back to FIG. 1, a downstream end of the needle  30  engages a valve seat  50  at the downstream end  6  of the fuel injector  2  when the needle  30  is in a closed position. 
     Referring back to FIG. 3, the disk  40  is inserted into the armature  20  from the upstream end  202 . A perspective view of the disk  40  is shown in FIG.  7 . The disk  40  acts as a variable flow restrictor, restricting fuel or other fluid flow through the assembly  10 . The disk  40  includes a downstream, or radial portion  410  and an upstream, or longitudinal portion  420 . The radial portion  410  is preferably annularly shaped, with a generally circular sidewall  412  which is sized to conform to the at least one wall  216  which forms the downstream portion  214  of the longitudinal channel  210 . Preferably, the sidewall  412  engages the wall  216  with an interference fit as will be discussed in more detail later herein. The radial portion  410  also includes a generally circular central opening  414 , which is coaxial with the longitudinal axis  206  of the armature  20 . The annular shape of the radial portion  410  matches the preferred circular internal diameter of the wall  216  of the downstream portion  214  of the longitudinal channel  210  so that the fuel or other fluid can flow only through the central opening  414  in the radial portion  410 . However, those skilled in the art will recognize that the radial portion  410  can be any shape that allows the disk  40  to snugly engage the wall  216  so that the fuel or other fluid can flow only through the central opening  414 , yet allow the disk  40  to be adjusted longitudinally in the downstream portion  214  of the longitudinal channel  210  as will be discussed in more detail later herein. 
     The longitudinal portion  420  is preferably generally arch shaped and includes first and second longitudinal legs  422 ,  424 , which extend upstream from the radial portion  410 . The longitudinal legs  422 ,  424  are connected by a transverse connector  426 . Preferably, the transverse connector  426  includes a generally flat top surface, for reasons that will be explained. Although two longitudinal legs  422 ,  424  are preferred, those skilled in the art will recognize that additional legs (not shown) connected to the radial portion  410  and the transverse connector  426  can be used. Preferably, exterior sides  423 ,  425  of the longitudinal legs  422 ,  424 , respectively, are arcuately shaped to conform with the wall  216  in an interference fit as described above with regard to the sidewall  412 . A longitudinal opening  428  is located axially between the transverse connector  426  and the radial portion  410 , and transversely between the two longitudinal legs  422 ,  424 . The longitudinal opening  428  is in communication with the central opening  414 . 
     With the above described configuration of the disk  40 , fuel flows along either side of the upstream portion  420 , through the longitudinal opening  428  and into the central opening  414 . The length of the longitudinal legs  422 ,  424  is preferably selected so as not to obstruct fuel flow between the internal area of the spring  50  and the outer diameter of the disk  40 . 
     Using an insertion tool (not shown), the restrictor  40  is inserted into the longitudinal channel  210  from the upstream end  202  of the armature  20  such that the sidewall  412  engages the wall  216  which forms the downstream portion  214  of the longitudinal channel  210 . 
     As shown in FIGS. 3 and 4, the radial portion  410  of the disk  40  is located in the uppermost end of the downstream portion  214  of the longitudinal channel  210 , proximate to the lip  205 . In this position, the radial portion  410  does not enter into the transverse channel  220  to reduce the cross-sectional area of the transverse channel  220 . Additionally, the longitudinal opening  428  communicates a maximum amount with the upstream portion  212  of the longitudinal channel  210 . The position of the disk  40  in the armature  20  as shown in FIGS. 1 and 2 provides maximum flow through the assembly  10 , as indicated by the flow arrows “F 1 ”. 
     To reduce fluid flow through the assembly  10  as required by the performance requirements of the particular injector, the disk  40  is preferably moved to a position in the longitudinal channel  210  downstream of the locations shown in FIGS. 3 and 4, such as to position shown in FIGS. 5 and 6. The insertion tool, or an adjusting tool (not shown) is inserted into the upstream end  202  of the armature  20  and engaged with the top, flat surface of the transverse connector  426 . The adjusting tool then forces the disk  40  downstream to a desired location in the longitudinal channel  210 . After the disk  40  has been moved to the desired location in the longitudinal channel  210 , the tool is removed from the armature  20 . The disk  40  in its new location relative to the armature  20  is shown in FIGS. 5 and 6. 
     As can be seen in FIGS. 5 and 6, the disk  40  is located farther downstream in the longitudinal channel  210  than in FIGS. 3 and 4. As a result, the radial portion  410  extends into the transverse channel  220 , reducing the cross-sectional area of the transverse channel  220  in the area of the disk  40 . Additionally, the longitudinal opening  428  is located farther downstream of the upstream portion  212  of the longitudinal channel  210 , restricting flow into the longitudinal opening  428  from the longitudinal channel  210 , as shown by the flow arrows “F 2 ”. 
     In the event that the injector performance actually obtained after setting the disk  40  in the longitudinal channel  210  is not the desired injector performance, the disk  40  can be adjusted in the longitudinal channel  210  by moving the disk  40  upstream or downstream in the longitudinal channel  210  until the desired performance of the injector is achieved. The movement of the disk  40  in the longitudinal channel  210  can be performed by trial and error without the need to remove the disk  40  and replace the disk  40  with a different sized disk. 
     Once the disk  40  is set in a final position in the armature  20 , the disk can be permanently fixed to the armature  20  by one of several known methods, including swaging, furnace brazing, gluing, or other known methods to permanently join the parts. Alternatively, the interference fit between the disk  40  and the armature  20  may be sufficient to permanently fix the disk  40  to the armature  20 . 
     Referring back to FIG. 2, it is seen that the downstream end  520  of the spring  50  circumscribes the longitudinal portion  420  of the disk  40 . In addition to the flow regulating and anti-bounce features of the disk  40  as described above, the disk  40  can also serve to center the spring  50  in the upstream portion  212  of the longitudinal channel  210 . This centering ability prevents unwanted contact between the coils in the spring  50  and the wall  211 , as well as the inlet tube  60 , eliminating unwanted friction during operation, and improving performance of the injector  2 . 
     During operation of the injects  2 , when the assembly  10  lifts from a valve seat (not shown), the fuel flows through the upstream portion  212  of the longitudinal channel  210 , as shown by the flow arrows F 1 , F 2  in FIGS. 3,  4  and  5 ,  6 , respectively. If the disk  40  is located sufficiently far into the downstream portion  214  of the longitudinal channel  210  so that the downstream portion  214  is in communication with the upstream portion  212 , as shown in FIGS. 5 and 6, the fuel flows into the downstream portion  214  prior to entering the disk  40 . 
     The fuel enters the longitudinal opening  428  in the disk  40  between the longitudinal legs  422 ,  424 , and then flows downstream through the central opening  414 . If the disk  40  is in the position shown in FIGS. 3 and 4, the fuel exits from the disk  40  and enters the downstream portion  214  of the longitudinal channel  210  prior to entering the transverse channel  220 . The fuel then enters the transverse channel  220  and is directed out of the armature  20  through the transverse channel  220 . If the disk  40  is in the position shown in FIGS. 5 and 6, the fuel exits from the disk  40  directly into the transverse channel  220 , where the fuel is directed out of the armature  20 . 
     The shape of the disk  40  facilitates fuel flow toward the downstream end  204  of the armature  20 , but restricts fuel flow toward the upstream end  202  of the armature  20  (i.e. reverse flow). 
     The use of a single disk  40  which can provide a wide range of fuel flows to obtain a variety of injector performance capabilities is a significant improvement over the prior known disk method which required a separate sized disk for different injector performance parameters. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.