Fuel injection valve assembly

Abstract: A two-stage opening fuel injection valve assembly, including a valve element (42) having an initial position providing a zero flow rate of fuel through the valve assembly, a first critical position displaced a predetermined distance from the initial position and providing a first flow rate of fuel through the valve assembly, a second critical position further displaced a predetermined distance from the first critical position and providing a second flow rate of fuel through the valve assembly, first and second movable members (76, 104) engageable with the valve element (42) independently of each other, a flange member (102) constantly engaged by the valve element (42) and engageable with each of the first and second movable members (76, 104), a first spring (66) urging the first movable member (76) to engage the flange member (102) when the valve element (42) is held in the initial position, the first spring (66) being operative to maintain the engagement between the first movable member (76) and the flange member (102) when the valve element (42) is located between the initial position and the first critical position, and a second spring (64) urging the second movable member (104) to engage the flange member (102) when the valve element (42) is moved from the initial position to one of the first and second critical positions, the second spring (64) being operative to maintain the engagement between the second movable member (104) and the flange member (102) when the valve element (42) is located between the first and second critical positions.

Description: FIELD OF THE INVENTION The present invention relates to a fuel injection valve for use in a diesel engine and, particularly, to a fuel injection valve of a two-stage opening type which has two successive steps of fuel injection for each cycle of operation of a power cylinder of a diesel engine according to the preambel of claim 1. BACKGROUND OF THE INVENTION A diesel engine using a fuel injection valve of the two-stage valve opening type is used to suppress the instability of operation typically represented by the diesel knock caused during injection of fuel. A diesel engine of this nature is also useful for precluding the delay in firing timings and controlling the emission of nitrogen oxides. A conventional fuel injection valve of the two-stage valve opening type has two successive fuel discharge steps for each cycle of fuel injection (see Fig 1 and 2). Fuel is injected into the associated one of the power cylinders of the engine in quantities respectively predetermined for the two fuel discharge steps. The quantities of the fuel to be discharged from the fuel injection valve assembly during the two fuel discharge steps are dictated by the amounts of movement of a needle valve element 42 incorporated in the fuel injection valve assembly. Specifically, the quantity of fuel to be discharged from the fuel injection valve assembly during the first or earlier fuel discharge step is determined by the preliminary valve lift PL of the fuel injection valve assembly, that is, the period of time for which the needle valve element 42 is moved from its initial axial position to a predetermined first critical axial position of the valve element. Likewise, the quantity of fuel to be discharged from the fuel injection valve assembly during the second or later fuel discharge step is determined by the full valve lift FL of the fuel injection valve assembly, that is, the period of time for which the needle valve element 42 is moved from the first critical axial position to a predetermined second critical axial position of the valve element. A fuel injection valves of this type is disclosed in, for example, Japanese Provisional Utility Model Publication (Kokai) No. 56-129568. The two-stage opening fuel injection valve assembly disclosed in the Provisional Utility Model Publications No. 56-129568 uses two pressure springs which control the movements, respectively, of the needle valve element 42 for the two fuel discharge steps of each cycle of fuel injection. These two pressure springs are arranged in series and are seated on movable spring seat elements which are respectively associated with the pressure springs. One of the pressure springs contributes to the primary valve lift for the earlier fuel discharge step and the other to the main valve lift for the later fuel discharge step. The prior-art fuel injection valve assembly has a drawback which results from the fact that the movable spring seat element contributing to the preliminary valve lift of the fuel injection valve assembly is intricate in shape. Extremely high techniques are thus required for controlling the dimensional accuracies of the spring seat element and the associated members and elements during machining, assembling and adjusting of these members and elements to provide a preliminary valve lift PL with a satisfactorily high degree of preciseness. It may be noted that generally more exacting control is required over the preliminary valve than over the main valve lift in a fuel injection valve assembly of the two-stage opening type. Attempts have therefore been made to provide useful solutions to this problem of the prior-art fuel injection valve of the described construction. Typical of such attempts include those which have resulted in fuel injection valves disclosed in the Japanese Provisional Utility Model Publications (Kokai) No. 56-173757 and No. 61-184866. The prior-art fuel injection valve shown in each of these publications is characterized in that the pressure springs providing the preliminary and main valve lifts, respectively, are arranged in parallel. The parallel arrangement of the two pressure springs is useful for reducing the number of members and elements which affect the degree of accuracy of, particularly, the preliminary valve lift and alleviating the requirement for high techniques in machining, assembling and adjusting the component members and elements of the fuel injection valve assembly. The improvement achieved by the prior-art two-stage opening fuel injection valve assembly taught in these publications are however not fully satisfactory. From DE-U-86 08 650, a two-stage opening fuel injection valve assembly is known, comprising a valve element having an initial position providing a substantially zero flow rate of fuel through the valve assembly, a first critical position displaced a first predetermined distance from the initial position in a predetermined direction and providing a first flow rate of fuel through the valve assembly, a second critical position further displaced a second predetermined distance from the first critical position in said predetermined direction and providing a second flow rate of fuel through the valve assembly. First and second movable members which are engageable with said valve element independently of each other. Intermediate means constantly engaged by said valve element and engageable with each of said first and second movable members. First biasing means urging said first movable member toward a predetermined position to engage said intermediate means when said valve element is held in said initial position, the first biasing means being operative to maintain the engagement between said first movable member and said intermediate means when the valve element is located between said initial position and said first critical position. Second biasing means urging said second movable member toward a predetermined position to engage said intermediate means when said is moved from said initial position to one of said first and second critical positions, the second biasing means being operative to maintain the engagement between said second movable member and said intermediate means when the valve element is located between said first and second critical positions. Displacement limiting means preventing movement of said valve element beyond said second critical position in said predetermined direction, wherein said intermediate means comprises a flange member formed separately of and constantly engaged by said valve element and said first movable member. The two-stage opening fuel injection valve assembly of DE-U-86 08 650 shows the disadvantage that the second moveable member which comprises a flange configuration may, to some extent, pivot together with said first moveable member, so that some incorrect positioning of the flange may occur leading incorrect positioning of the valve element. Accordingly, it is an object of the present invention to provide a two-stage opening fuel injection assembly of the above described kind, in which any inclination of the flange member with respect to said second moveable member is avoided, so that the initial degree of preciseness of, particularly, the preliminary valve lift PL of the valve assembly, can be maintained throughout use of the valve assembly. The solution of this object is achieved by the characterising features of the single claim. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The drawbacks of a prior-art two-stage opening fuel injection valve assembly of the nature to which the present invention appertains and the features and advantages of a two-stage opening fuel injection valve assembly according to the present invention over such a prior-art two-stage opening fuel injection valve assembly will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals and characters designate essentially similar or corresponding units, members, elements and portions and in which: Fig. 1 is a longitudinal sectional view showing an example of a conventional fuel injection valve assembly of the type to which the present invention generally appertains; Fig. 2 is a sectional view showing, to an enlarged scale, the detailed construction of a portion of the valve assembly of Fig. 1 indicated at II in Fig. 1; Fig. 3 is a longitudinal sectional view showing a preferred embodiment of a fuel injection valve assembly according to the present invention; Fig. 4 is a sectional view showing, to an enlarged scale, the detailed construction of a portion of the valve assembly of Fig. 6 indicated at VII in Fig. 3; DETAILED DESCRIPTION OF THE PRIOR ART Description will be hereinafter made with reference to Figs. 1 and 2 to more clearly show the drawbacks of a prior-art two-stage opening fuel injection valve assembly of the type to which the present invention generally appertains. Referring first to Fig. 1, a conventional two-stage opening fuel injection valve assembly is largely made up of a nozzle holder 10 and a nozzle member 12 projecting from the nozzle holder 10 through an annular spacer element 14. The nozzle member 12 has a sleeve portion 16 and a tip portion 18 projecting from the sleeve portion 16 and is formed with an axial valve chamber 20 in the sleeve portion 16 and a fuel discharge passageway 22 in the tip portion 18 of the nozzle member 12. The fuel discharge passageway 22 in the tip portion 18 communicates with the axial valve chamber 20 in the sleeve portion 16 and terminates in nozzle orifices 24 located at the leading end of the tip portion 18. The nozzle member 12 is fastened to the nozzle holder 10 by means of a retaining nut member 26 with locating pins 28 secured into the nozzle holder 10 and nozzle member 12 through the spacer element 14 as shown. The nozzle holder 10 has a lug portion 29 protruding sidewise from the nozzle holder 10 and has formed therein an axial bore 30 having threadedly received therein an axial end portion of a connector 32 formed with an axial fuel passageway 34. A fuel feed pipe leading from a fuel injection pump terminates in this connector 32, though not shown in the drawings. The nozzle holder 10 is formed with a fuel passageway 36 leading from the fuel passageway 34 in the connector 32 to an aperture 38 formed in the spacer element 14 so that the fuel directed into the fuel passageway 36 in the nozzle holder 10 is passed through the aperture 38 in the spacer element 14 into a fuel passageway 40 formed in the sleeve portion 16 of the nozzle member 12. The fuel passageway 40 in the sleeve portion 16 of the nozzle member 12 terminates in the fuel discharge passageway 22 in the nozzle member 12 so that the fuel passed to the fuel passageway 40 in the nozzle member 12 is discharged through the nozzle orifices 24 in the nozzle member 12. The nozzle member 12 has received therein a needle valve element 42 having a guide portion 44 and a rod portion 46 axially projecting from the guide portion 44. The guide portion 44 is axially slidable in the valve chamber 20 in the nozzle member 12 and the rod portion 46 extends through the fuel discharge passageway 22 in the nozzle member 12 and is needle-pointed toward the leading end of the fuel discharge passageway 22. The fuel discharge passageway 22 in the nozzle member 12 is thus closed or opened at its leading end by the pointed end of the rod portion 46 of the valve element 42 as the valve element 42 is axially moved in the nozzle member 12. The needle valve element 42 further has a stem portion 50 projecting from the opposite end of the guide portion 44 of the valve element 42. The stem portion 50 of the needle valve element 42 extends through a central opening 52 formed in the spacer element 14 as illustrated to an enlarged scale in Fig. 2 and projects into the nozzle holder 10. The nozzle holder 10 is formed with an axial bore extending from one end of the nozzle holder 10 to the other and having a bore portion forming a first spring chamber 54 terminating at the end of the nozzle holder 10 close to the spacer element 14, and a bore portion forming a second spring chamber 56 terminating at the opposite end of the nozzle holder 10. The axial bore in the nozzle holder 10 further has an intermediate bore portion 58 axially intervening between the first and second spring chambers 54 and 56 as shown. In the intermediate bore portion 58 of the nozzle holder 10 is closely received a sleeve member 60 formed with an axial bore 62 extending throughout the length of the sleeve member 60. The sleeve member 60 projects at one end into the first spring chamber 54 and at the other into the second spring chamber 56. In the first and second spring chambers 54 and 56 of the nozzle holder 10 are incorporated first and second pressure springs 64 and 66, respectively. The first pressure spring 64 axially extends in the first spring chamber 54 of the nozzle holder 10 and is seated at one end on an adjustment shim 68 received on one end face of the sleeve member 60. The pressure spring 64 is seated at the other end on a movable spring seat element 70 located close to the spacer element 14 as shown. As will be better seen in Fig. 2, the movable spring seat element 70 has a flange portion 72 located close to the spacer element 14 and an axial lug portion 74 axially projecting from the flange portion 72 in a direction opposite to the spacer element 14. The stem portion 50 of the needle valve element 42 axially projects through the opening 52 in the spacer element 14 into the first spring chamber 54 of the nozzle holder 10 and engages at its leading end with the flange portion 72 of the spring seat element 70. The first pressure spring 64 thus seated on the movable spring seat element 70 urges the spring seat element 70 toward the inner end face of the spacer element 14. In the presence of fuel under pressure in the in the fuel discharge passageway 22 in the nozzle member 12, the needle valve element 42 is forced by the fuel pressure to axially move toward the movable spring seat element 70 and has its stem portion 50 engaged at its leading end by the flange portion 72 of the spring seat element 70. The force of the first pressure spring 64 urging the spring seat element 70 toward the spacer element 14 is transmitted through the spring seat element 70 to the needle valve element 42 and urges the needle valve element 42 to stay in an "initial" axial position closing the fuel discharge passageway 22 in the nozzle member 12, opposing the force of the fuel under pressure forcing the needle valve element 42 to axially move in a direction to open the fuel discharge passageway 22 in the needle valve element 42. Within the nozzle holder 10 is further incorporated a push rod 76 having a boss portion 78 and a rod portion 80 projecting from the boss portion 78. The boss portion 78 of the push rod 76 is axially movable in the second spring chamber 56 and has one end face engageable with an adjustment shim 82 received on the other end face of the sleeve member 60. The second pressure spring 66 provided in the second spring chamber 56 is seated at one end on the other end face of the boss portion 78 of the push rod 76 and at the other end on an adjustment shim 84 received on a fixed spring seat element 86. The fixed spring seat element 86 is secured by a cap member 88 to the nozzle holder 10 at its end opposite to the spacer element 14 as shown. The cap member 88 has an opening 90 through which a plug member 92 is fitted to the cap member 88. The plug member 92 has an axial bore 94 communicating with the second spring chamber 56 in the nozzle holder 10 through an axial bore 96 in the spring seat element 86 and drain ports 98 sidewise leading from the axial bore 94. The axial bore 94 and drain ports 98 thus formed in the plug member 92 allow leakage fuel out of the fuel injection valve assembly therethrough. The rod portion 80 of the push rod 76 projects from the boss portion 78 of the push rod 76 and extends through the axial bore 62 in the sleeve member 60 into the first spring chamber 54. The rod portion 80 extends toward the lug portion 74 of the movable spring seat element 70 and has an end face engageable with the end face of the lug portion 74 of the spring seat element 70. The second pressure spring 66 seated on the boss portion 78 of the push rod 76 urges the push rod 76 toward the lug portion 74 of the movable spring seat element 70 until the boss portion 78 of the push rod 76 is received on the sleeve member 60 through the adjustment shim 82. When the movable spring seat element 70 is engaged by the stem portion 50 of the needle valve element 42 in the presence of fuel under pressure in the fuel discharge passageway 22 in the nozzle member 12, the spring seat element 70 will be caused to move into engagement at the end of its axial lug portion 74 with the end face of the rod portion 80 of the push rod 76. The force of the second pressure spring 66 urging the push rod 76 toward the spring seat element 70 is transmitted through the push rod 76 to the spring seat element 70 and further through the spring seat element 70 to the needle valve element 42, thus further opposing the force of the fuel under pressure forcing the needle valve element 42 to axially move in the direction to open the fuel discharge passageway 22 in the needle valve element 42. The needle valve element 42 moved in the direction to open the fuel discharge passageway 22 in the nozzle member 12 by the force of fuel under pressure is thus subjected first to the opposing force of the first pressure spring 64 and thereafter to the opposing forces of both of the first and second pressure springs 64 and 66. During each cycle of operation of the diesel engine, the fuel under pressure supplied from the fuel injection pump is admitted through the fuel feed pipe into the fuel passageway 34 in the connector 32 and is directed through the fuel passageway 36 in the nozzle holder 10, the aperture 38 in the spacer element 14 and the fuel passageway 40 in the nozzle member 12 into the fuel discharge passageway 22 in the nozzle member 12. The fuel pressure thus developed in the fuel discharge passageway 22 in the nozzle member 12 acts on the needle valve element 42 and forces the needle valve element 42 to axially move toward the movable spring seat element 70, that is, in the direction to open the fuel discharge passageway 22 in the needle valve element 42 until the needle valve element 42 has its stem portion 50 engaged at its end by the flange portion 72 of the spring seat element 70. The force of the first pressure spring 64 urging the movable spring seat element 70 toward the spacer element 14 is transmitted through the spring seat element 70 to the needle valve element 42 and opposes the force of the fuel under pressure acting on the needle valve element 42. The needle valve element 42 is accordingly caused to move with the spring seat element 70 against the force of the first pressure spring 64 until the lug portion 74 of the spring seat element 70 has its end face brought into pressing engagement with the end face of the rod portion 80 of the push rod 76. The distance of movement of the needle valve element 42 which is thus moved from its initial axial position to a first "critical" axial position having the movable spring seat element 70 brought into pressing engagement with the rod portion 80 of the push rod 76 provides the preliminary valve lift of the fuel injection valve assembly under consideration as indicated by PL in Fig. 2. The needle valve element 42 being moved the distance providing the preliminary valve lift PL, the fuel discharge passageway 22 in the nozzle member 12 is allowed to open so that the fuel which has been passed to the fuel discharge passageway 22 is discharged through the nozzle orifices 24 in the nozzle member 12 at a rate dictated by the preliminary valve lift PL of the fuel injection valve assembly. By the fuel pressure developed in the fuel discharge passageway 22 in the nozzle member 12, the needle valve element 42 is caused to further move, now together with the push rod 76, in the direction to wider open the fuel discharge passageway 22 in the nozzle member 12. The force of the fuel under pressure urging the needle valve element 42 to move in this direction is now opposed by not only the force of the first pressure spring 64 but also the force of the second pressure spring 66. The needle valve element 42 is thus caused to further move against the forces of the first and second pressure springs 64 and 66 until the guide portion 44 of the needle valve element 42 has its inner end face brought into contact with the outer end face of the spacer element 14. The distance of movement of the needle valve element 42 which is thus moved from its first critical axial position to a second "critical" axial position having the guide portion 44 thus brought into contact with the spacer element 14 provides the full valve lift FL of the fuel injection valve assembly under consideration as indicated by ML in Fig. 2. The needle valve element 42 being further moved the distance providing by the full valve lift FL, the fuel discharge passageway 22 in the nozzle member 12 is allowed to wider open so that the fuel in the fuel discharge passageway 22 in the nozzle member 12 is further discharged through the nozzle orifices 24 in the nozzle member 12 at an increased rate dictated by the full valve lift FL of the fuel injection valve assembly. The full valve lift FL of the fuel injection valve assembly is defined as the sum of the preliminary valve lift PL and the full valve lift FL of the valve assembly as shown in Fig. 2. As has been described, the prior-art fuel injection valve assembly of the two-stage opening type has two successive fuel discharge steps for each cycle of operation of the associated power cylinder of the diesel engine. The quantity of fuel discharged from the nozzle member 12 into the power cylinder during the first or earlier fuel discharge step is dictated by the preliminary valve lift PL of the fuel injection valve assembly, that is, the period of time for which the needle valve element 42 is moved from the initial axial position to the first critical axial position of the valve element 42. Likewise, the quantity of fuel discharged from the nozzle member 12 into the power cylinder during the second or later fuel discharge step is dictated by the full valve lift FL of the fuel injection valve assembly, that is, the period of time for which the needle valve element 42 is moved from the first critical axial position to the second critical axial position of the valve element 42. The various measurements of the fuel injection valve assembly that are predominant over these periods of time, that is, the preliminary and main valve lifts PL and ML of the valve assembly are selected so that the preliminary valve lift PL is smaller than the full valve lift FL. The preliminary valve lift PL is determined by the initial spacing between the end face of the lug portion 74 of the movable spring seat element 70 and the end face of the rod portion 80 of the push rod 76 and depends for its preciseness on the flatness and smoothness of each of these end faces of the spring seat element 70 and push rod 76, and the degree of parallelism between the end faces of the spring seat element 70 and push rod 76. The movable spring seat element 70 used in the shown prior-art fuel injection valve assembly being intricate in shape, extremely high techniques are required for controlling the dimensional accuracies of the spring seat element 70 and the associated members and elements during machining, assembling and adjusting of these members and elements to provide a preliminary valve lift PL with a satisfactorily high degree of preciseness. Various attempts have therefore been made to provide useful solutions to this problem of the prior-art fuel injection valve of the described construction. Examples of the prior-art fuel injection valves which have resulted from these attempts are disclosed in the previously named Japanese Provisional Utility Model Publications (Kokai) No. 56-173757 and No. 61-184866. The prior-art fuel injection valve shown in each of these publications is characterized, inter alia , by the parallel arrangement of the first and second pressure springs providing the preliminary and main valve lifts, respectively, of the valve assembly. The parallel arrangement of the two pressure springs is useful for reducing the number of members and elements which affect the degree of accuracy of, particularly, the preliminary valve lift and accordingly for alleviating the requirement for the extremely high techniques in machining various members and elements of the fuel injection valve assembly. The improvement achieved by the prior-art two-stage opening fuel injection valve assembly taught in the Provisional Utility Model Publication No. 56-173757 uses a movable spring seat element constantly engaged by the needle valve element 42 and associated with one of the pressure springs arranged in parallel. The movable spring seat element used in this prior-art fuel injection valve assembly is identical in shape to its counterpart in the fuel injection valve assembly hereinbefore described with reference to Figs. 1 and 2 and, for this reason, the fuel injection valve assembly proposed by this publication also has the problem hereinbefore pointed out of the prior-art fuel injection valve assembly shown in Figs. 1 and 2 and is not fully acceptable. The fuel injection valve assembly disclosed in this publication further a drawback in that the needle valve element 42 included therein could not be utilized without modification in a fuel injection valve assembly of the type to which the present invention generally appertains such as the prior-art valve assembly of Figs. 1 and 2. On the other hand, the two-stage opening fuel injection valve assembly disclosed in the Japanese Provisional Utility Model Publication No. 61-184866 uses a fixed spring seat clement common to both of the pressure springs arranged in parallel. The dimensional accuracy of the fixed spring seat element thus provided commonly to the two pressure springs contributes to the degrees of preciseness of both of the preliminary and main valve lifts. A dimensional error, if any, of the common fixed spring seat element would thus result in an error in each of the preliminary and main valve lifts and would thus amplify the error in the total valve lift which is given as the sum of the preliminary and main valve lifts. PREFERRED EMBODIMENT OF THE INVENTION Figs. 3 and 4 show a preferred embodiment of a two-stage opening fuel injection valve assembly to overcome these and other drawbacks of a prior-art two-stage opening fuel injection valve assembly. The two-stage opening fuel injection valve assembly embodying the present invention as herein shown is in various respects similar in construction to the prior-art fuel injection valve assembly hereinbefore described with reference to Figs. 1 and 2. Thus, the two-stage opening fuel injection valve assembly embodying the present invention comprises a valve casing structure composed of an elongated, generally cylindrical nozzle holder 10 and a nozzle member 12 projecting from the nozzle holder 10 through an annular spacer element 14. The annular spacer element 14 thus axially intervening between the nozzle holder 10 and nozzle member 12 has opposite, parallel flat end faces which consist of a first or inner end face 14 a contiguous to the nozzle holder 10 and a second or outer end face 14 b contiguous to the nozzle member 12 as illustrated to an enlarged scale in Fig. 4. These inner and outer end faces 14 a and 14 b of the spacer element 14 provide first and second fixed internal surface portions, respectively, of a two-stage opening valve assembly according to the present invention. The nozzle member 12 has a generally cylindrical sleeve portion 16 and a tip portion 18 axially projecting from the sleeve portion 16 in a direction opposite to the nozzle holder 10. The nozzle member 12 is formed with an axial valve chamber 20 extending in the sleeve portion 16 and a fuel discharge passageway 22 extending longitudinally in the tip portion 18 of the nozzle member 12. The axial valve chamber 20 in the sleeve portion 16 terminates at the end of the nozzle member 12 close to the outer end face 14 b of the spacer element 14. The fuel discharge passageway 22 in the tip portion 18 of the nozzle member 12 communicates with the axial valve chamber 20 in the sleeve portion 16 and terminates in nozzle orifices 24 located at the leading end of the tip portion 18. The nozzle member 12 is fastened to the nozzle holder 10 by means of an internally threaded retaining nut member 26 fitted to an externally threaded axial portion of the nozzle holder 10. During assembling of the fuel injection valve assembly herein shown, the nozzle holder 10, nozzle member 12 and spacer element 14 are correctly positioned with respect to each other by the aid of parallel locating pins 28 each having opposite end portions fitted into the nozzle holder 10 and nozzle member 12, respectively, through the spacer element 14 as shown. The nozzle holder 10 has a lateral lug portion 29 protruding sidewise from an intermediate axial portion of the nozzle holder 10 and has formed therein an internally threaded axial bore 30. The axial bore 30 has threadedly received therein an axial end portion of a connector 32 formed with an axial fuel inlet passageway 34 extending between the opposite ends of the connector 32. The connector 32 is herein assumed to form part of the casing structure of the valve assembly under consideration and connects the fuel injection valve assembly to a fuel feed pipe leading from a source of high-pressure fuel typically implemented by a fuel injection pump, though not shown in the drawings. High-pressure fuel is thus supplied from the fuel injection pump and is admitted into the fuel injection valve assembly through the fuel inlet passageway 34 in the connector 32. The nozzle holder 10 is formed with a fuel passageway 36 leading from the fuel inlet passageway 34 in the connector 32 to the end of the nozzle holder 10 close to the spacer element 14. The fuel passageway 36 in the nozzle holder 10 terminates in an aperture 38 formed in the spacer element 14 so that the fuel directed into the fuel passageway 36 in the nozzle holder 10 by way of the passageway 34 in the connector 32 is passed through the aperture 38 in the spacer element 14 into a fuel passageway 40 formed in the sleeve portion 16 of the nozzle member 12. The fuel passageway 40 thus formed in the sleeve portion 16 of the nozzle member 12 terminates in the fuel discharge passageway 22 in the tip portion 18 of the nozzle member 12. The fuel which has been passed to the fuel passageway 40 in the nozzle member 12 is thus discharged through the nozzle orifices 24 in the tip portion 18 of the nozzle member 12. The nozzle member 12 has received therein a needle valve element 42 having a cylindrical guide portion 44 and an elongated rod portion 46 axially projecting from one end of the guide portion 44 in a direction opposite to the spacer element 14. The guide portion 44 of the needle valve element 42 is axially slidable in the valve chamber 20 in the sleeve portion 16 of the nozzle member 12 and has a flat end face 44 a parallel with and confronting the outer end face 14 b of the spacer element 14 as illustrated in Fig. 4. The rod portion 46 of the needle valve element 42 axially extends through the fuel discharge passageway 22 in the tip portion 18 of the nozzle member 12 and is needle-pointed toward the leading end of the fuel discharge passageway 22 in the tip portion 18. The fuel discharge passageway 22 is thus closed or opened at its leading end by the pointed end of the rod portion 46 of the valve element 42 as the valve element 42 is axially moved in the nozzle member 12. The needle valve element 42 further has a stem portion 50 axially projecting from the opposite end of the guide portion 44 of the valve element 42. The stem portion 50 of the needle valve element 42 extends into a central opening 52 formed in the spacer element 14 as illustrated to an ellarged scale in Fig. 4. The nozzle holder 10 is formed with an axial bore extending from one end of the nozzle holder 10 to the other. The axial bore thus formed in the nozzle holder 10 has a bore portion forming a first spring chamber 56 terminating at the end of the nozzle holder 10 remote from the spacer element 14, and a bore portion forming a second spring chamber 54 terminating at the opposite end of the nozzle holder 10 and axially aligned with the first spring chamber 56. It may be noted that the "first" and "second" spring chambers 56 and 54 of the nozzle holder 10 forming part of the embodiment herein shown are referred to conversely to the first and second spring chambers 54 and 56 provided in the nozzle holder 10 of the prior-art fuel injection valve assembly described with reference to Figs. 1 and 2. The axial bore in the nozzle holder 10 further has an intermediate bore portion 58 axially intervening between these first and second spring chambers 56 and 54 as shown. In this intermediate bore portion 58 of the nozzle holder 10 is closely received a cylindrical sleeve member 60 formed with an axial bore 62 extending throughout the length of the sleeve member 60. The sleeve member 60 axially projects at one end into the first spring chamber 56 and at the other into the second spring chamber 54. Thus, the sleeve member 60 provides at one end thereof a first fixed seat portion projecting into the first spring chamber 56 and at the other end thereof a second fixed seat portion projecting into the second spring chamber 54 of the nozzle holder 10. In the first and second spring chambers 56 and 54 of the nozzle holder 10 are incorporated first and second pressure springs 66 and 64, respectively, each in the form of a preloaded helical compression spring. It may be noted that the "first" and "second" pressure springs 66 and 64 of the embodiment herein shown are also referred to conversely to the first and second pressure springs 64 and 66 in the nozzle holder 10 of the prior-art fuel injection valve assembly described with reference to Figs. 1 and 2. Within the nozzle holder 10 is further incorporated a push rod 76 having a cylindrical boss portion 78 and an elongated rod portion 80 axially projecting from the boss portion 78. The boss portion 78 of the push rod 76 is axially movable in the first spring chamber 56 and has one end face engageable with an annular adjustment shim 82 received on the first fixed seat portion of the sleeve member 60. The rod portion 80 of the push rod 76 axially extends through the axial bore 62 in the sleeve member 60 into the second spring chamber 54. The fuel injection valve assembly comprises a flange member 110, which is provided as intervening means of the needle valve element 42 and is formed separately of the needle valve element 42. The flange member 110 used in the embodiment shown is thus held in engagement with the stem portion 50 of the needle valve element 42 or may be secured to the needle valve element 42 by means of any adhesive or by mechanical fastening means such as a screw or a stud. The flange member 110 has an end face 110 a opposite to the stem portion 50 of the needle valve element 42 and is formed with a circular concavity 110 b in which is closely received a leading end portion of the stem portion 50 of the needle valve element 42. In the embodiment shown in Figs. 3 and 4, the flange member 110 engaged by or secured to the stem portion 50 of the needle valve element 42 has a hemispherically dished concavity 110 c which is axially open at its end face 110 a opposite to the stem portion 50 of the needle valve element 42 as illustrated to an enlarged scale in Fig. 4. The concavity 110 c may be press forged into the flange member 110. The rod portion 80 of the push rod 76 has a rounded end portion 112 shaped conformingly to the hemispherical concavity 110 c and slidably received in the concavity 110 c . The needle valve element 42, flange member 110 and push rod 76 have respective center axes aligned with each other so that, when the push rod 76 or, particularly, the rod portion 80 of the push rod 76 happens to incline with respect to the flange member 110 during its axial movement in the nozzle holder 10, the inclination of the push rod 76 or the rod portion thereof is taken up by the sliding movement of the rounded end portion of the rod portion 80. The flange member 110 is thus prevented from being inclined with respect to the movable spring seat element 104 and is enabled to maintain its correct position with respect to the spring seat element 104 so that the initial degree of preciseness of, particularly, the preliminary valve lift PL of the valve assembly can be maintained throughout use of the valve assembly. In the embodiment shown in Figs. 3 and 4, furthermore, the bore portion forming the first spring chamber 56 in the nozzle holder 10 is significantly longer than the bore portion forming the second spring chamber 54 in the nozzle holder 10. There is provided a generally cylindrical externally threaded member fixedly fitted into the bore portion forming the spring chamber 56 to implement an adjustment screw 114. The adjustment screw 114 has an externally threaded axial portion engaged by an internally threaded axial portion of the nozzle holder 10 as indicated at 116 in Fig. 3 and is secured to the nozzle holder 10 at its end opposite to the spacer element 14 by means of a cap member 88. The cap member 88 has an end portion formed with an opening 90 through which a plug member 92 is fitted to the cap member 88. The plug member 92 has an axial bore 94 communicating with the first spring chamber 56 in the nozzle holder 10 through an axial bore 118 formed in the adjustment screw 114 and extending throughout the length of the screw 114. The push rod 76 extending into the first spring chamber 56 in the embodiment herein shown has a flange portion 78'. Furthermore, the sleeve member 60 extending between the first and second spring chambers 56 and 54 through the bore portion 58 of the nozzle holder 10 in each of the first and second embodiments of the present invention is dispensed with in the embodiment herein shown. Thus, the elongated rod portion 80 of the push rod 76 axially projects from the flange portion 78' of the push rod 76 and extends directly through the axial bore portion 58 in the nozzle holder 10 into the second spring chamber 54. The adjustment screw 114 has an axial end portion projecting into the first spring chamber 56 to form an annular spring seat portion 114 a around the end portion. The first pressure spring 66 provided in the first spring chamber 56 is seated at one end on one end face of the flange portion 78 of the push rod 76 and at the other end on the flange portion 78' of the push rod 76. The force of the pressure spring 66 thus extending longitudinally in the first spring chamber 56 in a preloaded state is thus determined by the length to which the adjustment screw 114 projects into the spring chamber 56 and can be readily adjusted by varying the length to which the screw 114 is threadedly fitted into the nozzle holder 10. In the embodiment of Figs. 3 and 4, the preliminary valve lift PL of the valve assembly is also defined between the end face 110 a of the flange member 110 attached to the needle valve element 42 held in the initial axial position and the end face 104 a of the movable spring seat element 104 seated on the inner end face 14 a of the spacer element 14. The full valve lift FL is defined between the end face 44 a of the guide portion 44 of the needle valve element 42 in the initial axial position and the outer end face 14 b of the spacer element 14. The full valve lift FL of the valve assembly is defined between the outer end face 14 b of the spacer element 14 and the end face 44 a of the guide portion 44 of the needle valve element 42 moved to the first critical axial position thereof. It will have been understood from the foregoing description that the embodiment of the present invention hereinbefore described with reference to Figs. 3 and 4 is characterized inter alia by the slidable engagement between the rounded end portion of the rod portion 80 of the push rod 76 and the helispherically dished concavity 110 c in the movable spring seat element 104. By reason of such engagement between the push rod 76 and movable spring seat element 104, the flange member 110 intervening between the needle valve element 42 and push rod 76 is allowed to maintain its correct position with respect to the spring seat element 104 so that the initial degree of preciseness of, particularly, the preliminary valve lift PL of the valve assembly is maintained throughout use of the valve assembly. The embodiment of Figs. 3 and 4 is further advantageous in that the needle valve element 42 used in the valve assembly is per se also similar to that used in the prior-art valve assembly hereinbefore described with reference to Figs. 1 and 2 and, for this reason, the needle valve element 42 fabricated for use in the prior-art valve assembly can be utilized without modification in the fuel injection valve assembly of Figs. 3 and 4. Another advantage of the fuel injection valve assembly shown in Figs. 3 and 4 is that the amount of preliminary valve lift PL can be readily varied through selection of the thickness of the flange member 110 which is formed separately of the needle valve element 42.

Claims: A two-stage opening fuel injection valve assembly, comprising a) a valve element (42) having an initial position providing a substantially zero flow rate of fuel through the valve assembly, a first critical position displaced a first predetermined distance from the initial position in a predetermined direction and providing a first flow rate of fuel through the valve assembly, a second critical position further displaced a second predetermined distance from the first critical position in said predetermined direction and providing a second flow rate of fuel through the valve assembly, b) first and second movable members (76, 104) which are engageable with said valve element (42) independently of each other, c) intermediate means (110) constantly engaged by said valve element (42) and engageable with each of said first and second movable members (76, 104), d) first biasing means (66) urging said first movable member (76) toward a predetermined position to engage said intermediate means (110) when said valve element (42) is held in said initial position, the first biasing means being operative to maintain the engagement between said first movable member (76) and said intermediate means (110) when the valve element (42) is located between said initial position and said first critical position. e) second biasing means (64) urging said second movable member (104) toward a predetermined position to engage said intermediate means (110) when said valve element (42) is moved from said initial position to one of said first and second critical positions, the second biasing means being operative to maintain the engagement between said second movable member (104) and said intermediate means (110) when the valve element (42) is located between said first and second critical positions, and f) displacement limiting means (114a) preventing movement of said valve element (42) beyond said second critical position in said predetermined direction, wherein said intermediate means comprises a flange member (110) formed separately of and constantly engaged by said valve element (42), and said first movable member (76) characterised in that said flange member (110) has a substantially hemispherically dished concavity (110c) which is open toward said first movable member (76) and which has a center axis substantially parallel with said predetermined direction, said first movable member having a generally hemispherically rounded end portion (112) slidably received in said concavity (110c).

Inventors: KUROSAWA SHIRO C O DIESEL KIKI, SATO KAZUHIKO C O DIESEL KIKI, SHINDO TAKASHI C O DIESEL KIKI, KUROSAWA, SHIRO C/O DIESEL KIKI COMPANY LIMITED, SATO, KAZUHIKO C/O DIESEL KIKI COMPANY LIMITED, SHINDO, TAKASHI C/O DIESEL KIKI COMPANY LIMITED
Applicants: DIESEL KIKI CO, DIESEL KIKI CO., LTD.
Application year: 1989
Main classification: F02M45
IPC codes: F02M45, F02M61