Abstract:
A fuel injector an internal combustion engine includes a filter for filtering fuel flowing into the control valve, the filter includes multiple filter orifices, provided on a sleeve surrounding the control valve, or on a filter element integral to the sleeve, or a filter element or plate located between an entry to the INO (inlet orifice) from a main fuel supply passage and the control valve, thereby filtering fuel contaminant particles from the flow of fuel entering the control valve, thereby reducing or eliminating control valve seat wear and subsequent leakage.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage application under 35 USC 371 of PCT Application No. PCT/EP2015/058022 having an international filing date of Apr. 14, 2015, which is designated in the United States and which claimed the benefit of EP Patent Application No. 14166770.9 filed on May 1, 2014 the entire disclosures of each are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to fuel injector for delivering fuel such as diesel to a combustion space of an internal combustion engine, and more particularly to a filter for a control flow of a fuel injector. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates to a fuel injector used in the delivery of fuel to a cylinder of an internal combustion engine of the type in which fuel such as diesel is supplied from a high pressure accumulator, e.g. a common rail, to fuel injectors. 
         [0004]    Such fuel injectors generally comprise a needle which is slidable within a body and engageable with a needle valve seat to control the flow of fuel from a high pressure fuel supply line through the injector body. 
         [0005]    The injector is indirectly controlled by means of a control valve arrangement which controls the pressurising or discharging of a nozzle control chamber located above the injector needle. When the control valve arrangement is closed, the valve member is in contact with a valve seat under the action of a spring. Upon actuation of an actuator such as a solenoid, the spring force is overcome and the control valve opens by movement of the valve member away from the valve seat, thereby opening a flow path between the nozzle control chamber and a low pressure drain. As the pressure reduces within the nozzle control chamber, the needle leaves a needle valve seat due to pressure acting against a portion of the needle adjacent the valve seat. 
         [0006]    When the control valve is closed, the valve seat must be perfectly sealed for the correct operation of the injector. In prior art embodiments, static leakage at the control valve seat is a known problem. Leakage of the valve seat leads to a reduction in efficiency, or possible failure of the injector. Static leaks are significant since the control valve is closed more often than it is open, and are particularly relevant in view of the continuing trend towards higher operating pressures (for example 2200 to 3000 bar) for fuel injected into the combustion chamber. 
         [0007]    Leakage at the control valve seat can be caused by hard contaminant particles in the flow of fuel flowing through the control valve causing damage to the valve seat. 
         [0008]    Furthermore, leakage can occur due to distortion of the control valve body and/or the control valve member, caused by radial loading applied to the control valve body/control valve member. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to at least mitigate some of the problems associated with prior art fuel injectors and control valves. 
         [0010]    Accordingly the present invention provides, in a first aspect, a fuel injector for use in delivering fuel in an internal combustion engine, the fuel injector comprising a nozzle, a control valve body, a fuel supply line, and a needle moveable to control ejection of fuel through at least one nozzle hole, the fuel supply line supplying fuel to the nozzle control chamber via an inlet orifice and to the nozzle; the needle being controlled by variation of pressure of fuel within in a nozzle control chamber; the pressure of fuel within the nozzle control chamber being controlled by a control valve in the control valve body, the control valve being movable between an open position wherein a fuel path is provided between the nozzle control chamber and a low pressure fuel return line, via a spill orifice and the control valve, and a closed position wherein the control valve closes the flow path; wherein a filter is provided at a position between an entry to the inlet orifice from the fuel supply line, and the control valve, such that fuel passes through the filter before entering the control valve. 
         [0011]    The present invention provides filtration of the flow entering the control valve, thereby preventing hard contaminant particles likely to cause wear to the control valve seat from passing through the control valve seat, thereby reducing the risk of leakage, reduction in performance, or failure of the injector. 
         [0012]    The filter orifices may be provided on a sleeve surrounding the control valve, and may comprise slots or micro-drilled holes, the of which may be coincident or non-coincident with a radial axis of the sleeve. 
         [0013]    The filter orifices may be arranged symmetrically around the sleeve. 
         [0014]    The sleeve may comprise an annular filter element on which the filter orifices are provided, wherein the filter element is attached to at least one further sleeve element. 
         [0015]    The filter may be located between an entry to the inlet orifice from the fuel supply line, and the spill orifice channel. 
         [0016]    In an alternative embodiment the filter may be provided by a filter element comprising a plurality of filter orifices, which may be located between the nozzle control chamber and the spill orifice channel, or between the entry to the inlet orifice from the fuel supply line, and the nozzle control chamber. 
         [0017]    The filter element may comprise a filter plate comprising a plurality of filter orifices. The filter plate may be integral with an electrically insulating separating plate which separates the control valve body and a further section of the injector containing the nozzle control chamber. 
         [0018]    The filter plate is located between the nozzle control chamber and the spill orifice channel, or between the entry to the inlet orifice from the fuel supply line, and the nozzle control chamber. 
         [0019]    The fuel injector may further comprise a nozzle path orifice through which fuel from the fuel supply line flows into the nozzle control chamber, wherein the nozzle path orifice is formed by a filter plate. 
         [0020]    In a further alternative embodiment, the filter may be provided by a plurality of micro-drilled channels located between the nozzle control chamber and the spill orifice channel. 
         [0021]    The filter may forms a spill orifice or the inlet orifice. 
         [0022]    In a further alternative embodiment, the filter may be provided by a filter tube located in the spill orifice channel. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0023]      FIGS. 1 to 4  are cross-sectional views of an injector in accordance with the prior art; 
           [0024]      FIG. 5  is a cross-sectional view of an injector in accordance with a first embodiment of the present invention; 
           [0025]      FIG. 6  is a cross-sectional view of the control valve arrangement of the injector of  FIG. 5 ; 
           [0026]      FIG. 7  is a partially cross-sectional view of the control valve arrangement of the injector  FIG. 5 ; 
           [0027]      FIG. 8  is an isometric partial view of the control valve arrangement of the injector of  FIG. 5  with the annular chamber and SPO channel shown as transparent; 
           [0028]      FIG. 9  is a partially cross-section view of a control valve arrangement in accordance with a second embodiment of the first group of the present invention; 
           [0029]      FIG. 10  is a detailed partial view of the control valve arrangement of  FIG. 8  with the annular chamber and SPO channel shown as transparent; 
           [0030]      FIG. 11  is a partially cross-sectional view of a control valve arrangement in accordance with a third embodiment of the first group of the present invention; 
           [0031]      FIG. 12  is cross-sectional view of the control valve arrangement of  FIG. 11 ; 
           [0032]      FIG. 13  is an isometric partial view of the control valve arrangement of  FIG. 11  with the annular chamber and SPO shown as transparent; 
           [0033]      FIG. 14  is a cross-sectional view of a control valve arrangement in accordance with a first embodiment of a second group of the present invention; 
           [0034]      FIG. 15  is an isometric partial view of the filter element of the control valve arrangement of  FIG. 14  with surrounding injector components shown in cross-section; 
           [0035]      FIG. 16  is a cross-sectional view of a control valve arrangement in accordance with a second embodiment of a second group of the present invention; 
           [0036]      FIG. 17  is a detailed isometric view of the filter element of the control valve arrangement of  FIG. 16  with surrounding injector components shown in cross-section; 
           [0037]      FIG. 18  is a detailed view of an alternative control valve assembly in accordance the second embodiment of the second group of the present invention including two filter elements, with surrounding injector components shown as transparent; 
           [0038]      FIG. 19  is a cross-sectional view of a control valve arrangement in accordance with a third embodiment of the second group of the present invention; 
           [0039]      FIG. 20  is a cross-section view of a control valve arrangement in accordance with a fourth embodiment of the second group of the present invention; 
           [0040]    and 
           [0041]      FIG. 21  is an isometric partial view of the injector of  FIG. 20  with components shown as transparent. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    A known fuel injector  1  as illustrated in  FIGS. 1 to 4 , comprises an injector body  10  including a first region of relatively narrow diameter (the nozzle body  8 ) and a second, enlarged region. A bore  11  extends through the nozzle body  8  and the second region of the injector  1 . An elongate injector needle  12  is slidable within the bore  11 , the injector needle  12  including a tip region  14  which is arranged to engage a needle seat defined by an inner surface of the nozzle body  8  adjacent a distal end of the bore  11 . The nozzle body  8  is provided with one or more nozzle holes (not shown) communicating with the bore  11 , the nozzle holes being positioned such that engagement of the needle tip  14  with the needle seat prevents fluid escaping from the injector body  10  through the apertures, and when the needle tip  14  is lifted from the needle seat, fuel may be delivered through the nozzle holes. 
         [0043]    As shown in  FIG. 1 , the injector needle  12  is shaped such that the region thereof which extends within the injector nozzle body  8  is of smaller diameter than the bore  11  to permit fuel to flow between the injector needle  12  and the inner surface of the nozzle body  8 . Within the second region of the injector body  10 , the injector needle  12  is of a relatively larger diameter, thereby substantially preventing fluid flowing between the injector needle  12  and the injector body  10 , except for a fluted region, which allows fuel to flow from an annular gallery  16  provided in the second region to the nozzle body  8 . 
         [0044]    The annular gallery  16  communicates with a fuel supply line  18  via an NPO  58  (nozzle path orifice, also referred to as an injection supply orifice), the fuel supply line being arranged to receive high pressure fuel from an accumulator of an associated fuel delivery system (not shown). 
         [0045]    A nozzle control chamber/spring chamber  22  is provided within the second region of the injector body  10  at a position remote from the tip region of  14  of the needle  12 . The fuel supply line  18  also provides fuel to the nozzle control chamber  22 , via an INO  54  (inlet orifice, also referred to as a chamber filling orifice). The INO  54  meets the fuel supply line  18  at an entry  19 . A main flow of fuel enters the injector  1  along the fuel supply line  18 , and at the entry  19  to the INO  54 , the main flow is split into two, such that part of the flow enters the INO  54  and the remainder of the main flow continues along the fuel supply line  18  to the NPO  58 . 
         [0046]    A compression spring  30  is provided in the nozzle control chamber  22  for biasing the needle  12  towards the needle seat. 
         [0047]    The injector in  FIG. 1  further comprises an electromagnetic actuator arrangement  44  located above a control valve arrangement  50  comprising a valve body  51 . 
         [0048]    The control valve arrangement  50  comprises a control valve member  60  carrying an armature  62  at one end of the control valve member  60 . The control valve member  60  is slidable within a bore  64  of the control valve arrangement  50 . At the armature end of the valve member  60  is provided a sealing face  66  which is engageable with a seat  68  at an end of the bore  64 . When the sealing face  66  is brought into contact with the seat  68  a contact a pressure seal is formed. A valve spring  46  is located above the armature  62  provides a closing force for the control valve, acting to urge the sealing face  66  into engagement with its seat  68  and maintain a contact pressure on the valve seat  68  when the valve arrangement  50  is closed. 
         [0049]    The control valve arrangement  50  may further comprise a sleeve  80  surrounding the control valve member  60 , as illustrated in  FIGS. 3 and 4 . 
         [0050]    The control valve arrangement  50  is also in fluid communication with the fuel supply line  18  via the INO  54 , an SPO  56  (spill orifice, also referred to as a control chamber discharge orifice), and an SPO channel  55 . 
         [0051]    When the control valve arrangement  50  is closed and the sealing face  66  is engaged with the seat  68 , there is no fluid communication between the nozzle control chamber  22  and a low pressure fuel return line  27 . The nozzle control chamber  22  is subjected to the pressure of fuel within the common rail (not shown). This high pressure fuel exerts a force on the top of the needle  12  which, in combination with pressure from the spring  30 , biases the needle into a seated position, such that there is no injection through the nozzle holes. 
         [0052]    Energising of the actuator  44  causes the armature  62  to lift such that the valve arrangement  50  opens, i.e. the sealing face  66  lifts from the seat  68 . Fuel contained within the nozzle control chamber  22  now has a flow path through the SPO  56  and the SPO channel  55 , through typically two communication holes (not shown) into a control valve control chamber  53 , past the control valve seat  68  and to the low pressure fuel return line  27 . Consequently, fuel flows from the nozzle control chamber  22  to the low pressure fuel return line  27 , resulting in a reduction in the fuel pressure in the nozzle control chamber  22 . The fuel pressure in the nozzle body  8  is subsequently higher than the fuel pressure in the nozzle control chamber  22  and a pressure force applied to the injector needle  12  overcomes the bias of the spring  30 . The injector needle  12  lifts from its seated position and opens the nozzle holes allowing fuel flowing into the nozzle body  8  via the NPO  58  to be injected into a combustion chamber (not shown). 
         [0053]    To stop injection, the electromagnetic actuator  44  is de-energised and the valve spring closes the control valve arrangement  50 . High pressure fuel from the supply line  18  through the INO  54  and into the nozzle control chamber  22  causes the pressure in the nozzle control chamber  22  to increase until the needle  12  is urged towards the seated position again, thereby causing injection through the nozzle holes to cease. 
         [0054]    The embodiments of injector of the present invention are characterised from the above prior art embodiments by provision of a filter which filters flow entering the control chamber  53  of the control valve assembly  50 . The filter can be located at various positions between the entry to the INO or SPO from the fuel supply line, and the control valve, to provide the necessary filtration of the flow of fuel entering the control valve. 
         [0055]    Group 1 
         [0056]    In the first group of the present invention, a particulate filter is located on, or formed by, the control valve sleeve. 
         [0057]    Referring to  FIG. 5 , in common with the prior art injector, the injector  101  of the present invention comprises an injector body  110  including a nozzle body  108 , a fuel supply line  118  into which a main supply of fuel enters the injector  101  and separates at an entry  119  to an INO  154 , and within a bore  111 , a needle  112  which is biased into a seated position by a compression spring  130 . Other components of, and operation of the injector are identical to those of the prior art embodiment of  FIGS. 2 and 3 . 
         [0058]    The first embodiment of Group 1 of the present invention further comprises a filter provided on the sleeve  180 . The SPO channel  155  is in fluid communication with the sleeve  180  via an annular chamber  182 . The filter comprises a plurality of filter orifices, which in the embodiment illustrated in  FIGS. 5 to 8  are formed by micro-drilled holes  202 . When the control valve arrangement  150  is open, i.e. when the actuator arrangement  144  acts on the valve spring  146 , causing the armature  162  to lift thereby lifting the sealing surface  166  thereof away from the control valve seat  168 , a fuel path is opened along the SPO  156 , SPO channel  155 , and the low pressure fuel return  127  via the control valve arrangement  150 . Fuel flowing from the SPO channel  155  into the annular chamber  182  must subsequently pass through the filter orifices before reaching the control valve seat  168 . Therefore, any fuel contaminant particles which are too large to pass though the filter orifices are trapped upstream of the control valve seat  168 , i.e. such particles do not reach the control valve seat  168  and thereby damage to the control valve seat  168  by these particles is prevented. 
         [0059]    The micro-drilled holes  202  may each have a radial axis which is coincident with a radial axis of the sleeve  180 . Alternatively, the micro-drilled holes  202  may have an axis which is offset relative to a radial axis of the sleeve  180 , thereby generating a swirl/rotating flow of fuel passing through the holes into the valve control chamber  153 . 
         [0060]    The number of filter orifices  202  is selected such that the total flow area provided by the filter orifices  202  is greater than the upstream restriction provided by the SPO  156 . 
         [0061]    The micro-drilled holes  202  are located symmetrically around the sleeve  180  and therefore stress generated is significantly lower than in prior art embodiments comprising two communication holes into the valve control chamber which generate a mechanical stress concentration. The present invention prevents the deformation of the control valve member  160 , and thereby further reducing the possibility of leakage at the valve seat  168 . 
         [0062]    Furthermore, the hydraulic volume of the micro-drillings  202  is less than the hydraulic volume of the two communication holes of prior art embodiments, providing a more suitable embodiment for a multi-injection process. 
         [0063]    A retention zone for contaminant particles may be created at the base of the area provided with micro-drilled holes  202 . The particle retention zone is indicated generally at ‘P’ in  FIG. 8 . 
         [0064]      FIGS. 9 and 10  illustrate a second embodiment of Group 1. The second embodiment is similar to the first embodiment and differs only in that the modified sleeve  180 ′ is provided with a plurality of grooves  204  instead of the holes  202  of the first embodiment. Fuel contaminant particles which are smaller than the width of the grooves  204  cannot pass through the sleeve  180 ′ and are thereby prevented from reaching the valve seat  168 . 
         [0065]    In a similar manner to the first embodiment, a particle retention zone is created, as indicated generally by ‘P’ in  FIG. 10 . 
         [0066]    In a third embodiment of Group 1 as illustrated in  FIGS. 11 to 13 , an annular filter element  206  is integrated into the modified sleeve  180 ″. The annular filter element  206  is located between a first annular sleeve part  184  and a second annular sleeve part  186 , and comprises a plurality of filter orifices  208 . In further alternative embodiments, either the first sleeve part  184  or the second sleeve part  186  may be omitted; the filter element  206  may be located above or below (in the orientation shown in the figures) the remaining sleeve part  184 ,  186 . 
         [0067]    Group 2 
         [0068]    The second group of embodiments in accordance with the present invention is generally similar to the first embodiment; like numerals will be referred to below. 
         [0069]    In the embodiments of Group 2, a particulate filter is provided in the region of the SPO  156  or INO  154 , or in the SPO channel  155 . All embodiments of Group 2 could be applied to an injector with or without a sleeve  180 . 
         [0070]    Referring to  FIGS. 14 and 15 , the first embodiment of Group 2 comprises a filter provided by a filter element  190 , located in a chamber  194  provided in the valve body  151  adjacent to the SPO  156 . The filter element  190  comprises a plurality of filter orifices  192 . 
         [0071]    In the embodiment illustrated in  FIGS. 14 and 15 , the filter element  190  is provided in addition to the SPO  156 . However, the number and size of the filter orifices  192  or the filter element  190  could be selected to provide a restriction having the same effect as the original SPO  156 , i.e. to provide the same flow area, and therefore the same pressure drop across the filter element  190  as would be provided by the SPO  156 . Therefore, the filter element  190  could replace the SPO  156 . 
         [0072]    The same principle can be applied to the INO  154 , i.e. the INO  154  could be replaced by a filter element, provided with a plurality of filter orifices, the number and size of which is selected to provide the same flow area as the standard singular INO  154 . Alternatively, a filter could be provided only at, or by, the INO  154 , thereby filtering particles arriving at the INO  154  before the fuel flow enters the nozzle control chamber  122 , i.e. before the fuel flow enters the SPO  156 , SPO channel  155  and control valve arrangement  150 . 
         [0073]    A second embodiment of the Group 2 of the present invention, as illustrated in  FIGS. 16 to 18 , comprises a filter formed by a filter plate  196  integrated into a separating plate  198 , which may be electrically insulating, located between the control valve body  151  and a lower section  103  of the injector containing the nozzle control chamber  122 . 
         [0074]    In this embodiment, the relative positioning of the filter is simplified in comparison to the first embodiment of Group 2 of the present invention. Furthermore, the integrated filter plate  196  can allow an improved sealing interface between the control valve body  151  and the lower injector section  103  thereby reducing or eliminating leakage between the two sections. 
         [0075]    The filter plate  196  can also act as a restriction, thereby allowing removal of the current SPO  156 . A similar filter plate could also be used to replace the current INO  154 , in addition to, or instead of the filter place  196  provided at/in replacement of the SPO  156 .  FIG. 16  illustrates a similar plate filter  196 ′ located at the INO  154  in addition to the filter plate  196  located at the SPO  156 . 
         [0076]    Similarly, the current NPO  158  could be replaced by a filter plate similar to the filter plate  196 . 
         [0077]    Referring to  FIG. 19 , in a third embodiment of Group 2 of the present invention, a filter is formed by a filter tube  210  located in the SPO channel. Therefore, contaminant particles in the fuel flowing through the SPO channel  155  which are larger than the filter holes of the filter tube  210  are prevented from passing through the filter tube  210  and into the control valve arrangement  150 . 
         [0078]      FIGS. 20 and 21 , a filter is provided by a plurality of micro-drilled channels  212  between the chamber  194  in the control valve body  151  and the SPO channel  155 . In this embodiment, the micro-drilled channels  212  replace the SPO  156 ; the number and diameter of micro-drilled channels  212  is selected to provide the same restriction as the original SPO  156 . This embodiment allows calibration of the SPO  156 , in addition to allowing regulation of the size of contaminant particles arriving at the control valve seat  168  through control of the diameter of the micro-drilled channels  212 . 
         [0079]    It will be appreciated that various changes and modifications can be made to the injector and control valve assembly described herein without departing from the scope of the present invention. 
       REFERENCES 
     Prior Art 
       [0000]    
       
         
           
             fuel injector  1   
             injector nozzle  8   
             injector body  10   
             bore  11   
             injector needle  12   
             tip region  14   
             annular gallery  16   
             fuel supply line  18   
             entry (from fuel supply line to INO)  19   
             nozzle control chamber  22   
             low pressure fuel return line  27   
             compression spring  30   
             electromagnetic actuator arrangement  44   
             valve spring  46   
             control valve arrangement  50   
             control valve body  51   
             valve control chamber  53   
             INO  54   
             SPO channel  55   
             SPO  56   
             NPO  58   
             control valve member  60   
             armature  62   
             bore  64   
             valve member sealing face  66   
             seat  68   
             control valve sleeve  80   
             Invention 
             fuel injector  101   
             injector lower section  103   
             injector/valve body  110   
             injector nozzle  108   
             injector body/nozzle holder body  110   
             bore  111   
             injector needle  112   
             tip region  114   
             annular gallery  116   
             fuel supply line  118   
             entry (from fuel supply line to INO)  119   
             control chamber  122   
             low pressure fuel return line  127   
             compression spring  130   
             electromagnetic actuator arrangement  144   
             valve spring  146   
             control valve arrangement  150   
             control valve body  151   
             control valve control chamber  153   
             spacer component  152   
             INO  154   
             SPO channel  155   
             SPO  156   
             NPO  158   
             control valve member  160   
             armature  162   
             bore  164   
             valve member sealing face  166   
             seat  168   
             control valve sleeve  180 ,  180 ′,  180 ″ 
             annular chamber  182   
             first annular sleeve part  184   
             second annular sleeve part  186   
             filter element (in control valve body chamber)  190   
             filter orifices (of filter element)  192   
             chamber (in valve body)  194   
             filter plate  196 ,  196 ′ 
             separating plate  198   
             micro-drilled holes  202   
             slots  204   
             filter element (of sleeve)  206   
             filter orifices (of filter element)  208   
             filter tube  210   
             micro-drilled channels  212   
             particle retention zone P