High pressure fuel injection unit

Abstract: The present invention relates to a high pressure fuel injection unit comprising a feeder wire take-out structure for supplying a drave current to a lower electromagnetic coil of a solenoid regulating the stroke of an injection valve member disposed in a pressurized fuel chamber of the injection unit. Specifically, an axial passageway means is provided to receive a feeder wire assembly structure extending axially through the high pressure fuel injection unit.

Description: The present invention relates to a high pressure fuel injection unit comprising a housing of generally cylinderical shape extending from an upper supply portion to a lower fastening portion thereof, accommodating a partitioning wall member therein to define an upper chamber comprising a first fuel injection control and/or detection means, and a lower chamber comprising a second fuel injection control and/or detection means, said lower chamber being supplied with pressurised fuel through a fuel supply line extending substantially axially from an upper end side of the housing to said lower chamber which, in turn, is communicated to an injection nozzle adapted to engage a tip end of an injection valve body, said injection valve body being reciprocable in between an advanced injection valve closing position and a retracted injection valve opening position, and a power supply passageway means extending substantially axially from the rear end side of the housing to the lower chamber thereof, adapted to receive a power supply assembly to connect and supply power to the second fuel injection control and/or detetection means . A high pressure fuel injection unit as indicated above (being of a so called reservoir or accumulator type), particularly suited to be used for high speed diesel engines is well known in the art (Japan Patent Application No. Hei 1-36971). A similar fuel injection unit is shown in US-A-4 870 943. Such a fuel injection unit of the fuel storage or accumulator type has a structure comprising a generally tubular housing comprising a tubular main body, a cover insert received therein and closing cap to reliably hold the cover insert fitted in the tubular main body of the housing and closing the fuel injection unit to the outside. The tubular main body of the housing is sub-divided through a partitioning wall member into an upper chamber wherein an injection timing control solenoid is disposed and a back pressure relief chamber is formed, and a lower accumulator or fuel storage chamber communicated to the fuel injection nozzle, filled with pressurized fuel and, moreover, receiving a lift regulating solenoid therein. The pressurized fuel collecting chamber surrounds an injection valve body for opening or closing an injection nozzle at the lower end of the fuel injection unit and, moreover, is fluidly connected to a back pressure chamber formed ahead of the rear end portion of the injection valve body. A back pressure prevailing in said back pressure chamber is effective to urge the injection valve body in its injection valve closing position. The rear end portion of the injection valve member is slideably received by means of the partitioning wall member. Moreover, the back pressure chamber is communicated to the back pressure relief chamber in response to a valve operation performed by the upper injection timing solenoid disposed in the upper chamber of the fuel injection unit. The lower electromagnetic lift regulating solenoid is provided in order adjust a lift regulating member to a lift regulating position which is effective to delimit the retractive opening movement of the injection valve pin to establish a condition wherein a small amount of fuel is injected per injection cycle. On the other hand, such a lower electromagnetic coil or lift regulating actuator could also be used to detect the operation of the injection valve pin etc. Due to the provision of the lower electromagnetic coil of the lift regulating solenoid in the lower chamber subject to the fuel pressure there is a problem of providing a reliable power supply to said lower electromagnetic coil taking appropriate sealing requirements into consideration, arising due to the fuel pressure in said lower chamber of the fuel injection unit. Moreover, care should be taken to avoid any interference of a power supply feeding system with other systems in the vicinity of the fuel injection unit. In order to supply power to an electromagnetic coil in a lower pressurized fuel chamber of a fuel injector the applicant has already proposed to provide a wiring structure of a feeder wire harness to supply a drive current to the lower electromagnetic coil by means of providing the side wall of the lower fuel accumulator chamber of the housing with a through hole to take out the wire harness from the coil outwards through this through hole i.e. disposing the wire harness substantially perpendicularly to the axis of the housing to connect to the electromagnetic coil in the lower chamber of the high pressure fuel injection unit (Japan Patent Application S63-259563). On the other hand, taking the very high pressure prevailing in the fuel storage chamber into consideration, main needs to be met for wiring the feeder wire harness to the associated electromagnetic coil leaves the following main problems to be solved: 1. Sealing structure needs to be provided and secured capable of enduring the high pressure resulting from the pressurized fuel. 2. The passing through of the wire harness from the electromagnetic coil in the lower pressurized chamber of the fuel injection unit to the outside should not reduce the installation freedom for disposing the high pressure fuel injection unit on the engine. 3. Finally, the wire harness should be fed to the outside without enlarging the outer diameter of the fuel injection unit. In view of the afore-mentioned requirements which should be met, the previously proposed radial passing through of the feeder wire through a side wall of the housing implies several difficulties, namely a radial passing through of the drive wire structure leads to an insufficient sealing length so that a reliable sealability cannot be assured due to the relatively small thickness of the side wall of the fuel chamber of the fuel injection unit. Moreover, the insulation freedom is undesirably limited as the wire harness is to be installed such as to avoid any interference with the engine side and, accordingly, the freedom of insulation is affected. Moreover, the previously suggested structure leads to an enlarged diameter of the fuel injection unit which, in some cases, is unacceptable. Taking the difficulties comprised in the art into consideration, it is an objective of the present invention to provide a high pressure fuel injection unit as indicated in the intorductory portion of this specification comprising a convenient power supply to a fuel injection control and/or detection means disposed therein which is disposed in a chamber containing highly pressurized fuel and, therefore, is not readily accessible from the outside, assuring that the outside diameter of the high pressure fuel injection unit can be maintained, installation freedom for disposing the high pressure fuel injection unit on the engine is guaranteed and a high sealability of the high pressure fuel injection unit is obtained. In order to perform the afore-indicated objectives, the high pressure fuel injection unit according to the present invention is characterised in that said housing accommodates an insert comprising axially extending take-out holes accommodating an electrical conductor of the power supply assembly therein and having axially extending sealing portions, said electrical conductor being embedded in said sealing portion by means of a substantially axially extending sealing adhesive. Specifically, the power supply passageway means extends axially through a member, preferably through a peripheral wall portion thereof, which also forms a receipt member for axially leading a fuel supply passage, preferably through a peripheral wall portion thereof, circumferentially offset from the power supply passageway means. Specifically, the high pressure fuel injection unit according to the present invention is designed in such a manner that said second fuel injection control and/or detection means comprises an electromagnetic solenoid including an electromagnetic coil which is adapted to be energized by a drive current supplied through said power supply assembly. According to yet another preferred embodiment of the present invention the high pressure fuel injection unit comprises an injection timing solenoid actuator performing a relief valve control of a pressure release orifice passageway to operate a valve pin of a fuel injection valve of the unit whereas said second fuel injection control and/or detection means as indicated above is a lift regulating solenoid adapted to perform a lift control of the injection valve body by means of a regulator member. Thus, according to yet another preferred embodiment of the present invention, the power supply assembly is designed to form a feeder wire assembly to supply a drive current to the lift regulating solenoid disposed in the lower chamber of the high pressure fuel injection unit, said chamber being charged with pressurized fuel and is communicated to the fuel injection valve of the system, said feeder wire assembly being axially feed through the high pressure fuel injection unit disposed in a wiring passage means. According to yet another preferred embodiment of the present invention said wiring passage means comprises first and second wiring passages each being adapted to receive a feeder wire assembly therein which, in turn, comprises an upper feeder rod and a lower wire harness wherein at least the feeder rod extends through a member, preferably a cover insert of hollow cyclindrical structure, which also forms a pathway means for the fuel supply line terminating into the lower fuel storage chamber. Further preferred embodiments of the present invention are laid down in the other sub-claims. The power supply assembly, specifically the feeder wire structure, according to the present invention, leading a power supply line such as a feeder wire axially through the high pressure fuel injection unit, specifically at least partially through a peripheral wall of a cover insert or the housing thereof is advantageous as, in this way, it is possible to seal the wiring passage along its entire length. Accordingly, a very long and sufficient sealing length can be easily assured. Thus, in contrast to other structures the sealability of the high pressure fuel injection unit is not limited or determined by the radial wall thickness of the housing of the high pressure fuel injection unit and, accordingly, is significantly improved. Moreover, as the wiring passage is formed in axial direction the outer surface of the high pressure fuel injection unit remains completely free and unoccupied through any wiring structures or terminals for radially approaching power supply systems. Accordingly, the insulation freedom remains completely unaffected and the outer diameter of the fuel injection unit can be kept unamended or even reduced in comparison to previously suggested structures. In view of the provision that, according to the preferred embodiment of the present invention, the power supply or wiring passages are formed through a member through which the fuel supply passage extends as well as member for feeding electrical power to the lower electromagnetic coil is selected which in any case has a sufficient wall thickness. Thus, any need is removed to provide a specifically adapted wall portion having increased thickness, specifically adapted to receive a feeder wire assembly to connect to a lower electromagnetic coil. The latter aspect, as well, contributes to avoid the outside diameter of the fuel injection unit to become increased. Further objectives, features and advantages of the present invention will become more apparent from the following description of a specific embodiment thereof in conjunction with the accompanied drawings, wherein: Figure 1 is a sectional front view of a high pressure fuel injection unit according to an embodiment of the present invention showing a feeder wire structure for a certain electromagnetic component thereof, Figure 2 is a sectional side view of the high pressure fuel injection unit as shown in Figure 1, Figure 3 is a sectional view of a back pressure chamber area of the high pressure fuel injection unit of Figure 1, shown in larger scale, Figure 4(a) is a bottom view of a shim member associated to the rear end portion of an injection valve body of the high pressure fuel injection unit as shown in Figures 1 and 3, Figure 4(b) is a sectional view according to Figure 4(a), Figure 5 is a bottom view of a cover insert serving as a fuel and electric power feeding member as shown in Figures 1 and 2, Figure 6(a) is a plan view of a partitioning wall member as shown in Figures 1 and 2, Figure 6(b) is a bottom view of the partitioning wall member of Figure 6(a). In the following an embodiment of the present invention is described in detail referring to the appended drawings, Figures 1 to 6 as explained above. In Figs. 1 to 6 the reference numeral 1 generally denotes a high pressure fuel injection unit according to this embodiment of the present invention which, in its basic structure, comprises a housing 2 partitioned into an upper fuel injection timing control chamber 4 and a lower pressurized fuel storage chamber 5 (wherein the pressurized fuel is accumulated) by means of a partitioning wall member 3 disposing an injection valve body 6. Within the fuel storage chamber 5 a lift regulating solenoid actuator 7 for regulating the amount of the lift of the injection valve body 6 is disposed while an axial projection 3a of the partitioning wall member 3 is adapted to support an injection timing solenoid actuator 8 (hereinafter referred to as injection timing control valve 8) disposed in the fuel injection timing control chamber 4 and adapted to control the timing of fuel injection by controlling the resultant force urging the injection valve body 6 in its injection valve closing position, as explained in full detail as description proceeds. Generally the housing 2 is composed of a tubular main body 9 and a cover insert 10 for closing the insert opening 9a of the main body 9. The tubular main body 9 has a generally cylindrical shape with its diameter reducing in three steps from a top portion thereof to the lower injection nozzle side portion of the injection 1. The size of the injection timing control chamber 4 is substantially determined by the diameter of the insert opening 9a at the upper portion of the fuel injection unit 1, whereas a step portion or shoulder 9b projects inwardly at approximately half the axial extension of the fuel injection unit and is adapted to hold a plurality of members accommodated in said main body 9 as described hereinafter. Another accommodation opening 9h is formed to extend downwardly from the shoulder 9b, thus defining an upper part 5a of the pressurized fuel storage chamber 5 accommodating the lift regulating solenoid actuator 7 (hereinafter referred to as lift solenoid 7) and terminating into a lower part 5b of the fuel storage chamber 5 with a step 9d in betwen both parts 5a and 5b of the fuel chamber storage chamber 5. A fuel injection nozzle cap 11 is screwed from below into a holding opening 9c of the lower extension of the main body 9 of the injection unit 1 and, moreover, provided to complete the lower wall of the fuel storage chamber 5. Along an axis portion of the nozzle cap 11 a guide hole 11c for guiding the slide section 6c of the injection valve body 6 is provided, the tip end portion of the guide hole 11c constitutes the fuel injection nozzle 11a. A selectively applicable intermediate shim 11b is provided to adjust a minimal amount of the lift of the injection valve body 6 whereas reference numeral 9d denotes a mounting screw portion for fastening the complete high pressure fuel injection 1 on the engine, for example a high speed diesel engine. The afore-mentioned cover insert 10 has the shape of a flanged hollow cylindrical member integrally established from a cylindrical tube portion 10a and a top plate portion 10b, said cover insert 10 is adapted to accommodate the injection timing control valve 8 and to form a fastening and guide member for other elements. The top plate portion 10b is provided with a connecting pipe portion 10c projecting upwardly through an upper closing cap 12, said connecting pipe portion 10c is adapted to fasten a fuel supply tube 17a through a connector nut 17b. A fuel passage 10d extends axially through the connector portion 10c and through a portion of the cover insert 10, specifically through the cylindrical tube portion 10a (see Fig. 2) and through a flange portion of the partitioning wall member 3 to terminate into a back pressure chamber 4a as described later on. The cylindrical tubular portion 10a of the cover insert 10 is inserted into the insert opening 9a of the main body 9 and the top plate portion 10b of the cover insert 10 is pressed down by the closure cap 12 screwed and mounted onto the upper end portion of the main body 9 of the housing 2. Accordingly, a peripheral portion of the partitioning wall member 3 and a radially projecting upper rim portion of a coil holder 18 of the lift solenoid 7 are pressed against and fixed on the step portion 9b by a lower end portion of the tubular portion 10a of the cover insert 10, as shown in Figs. 1 and 2. Reference numeral 30 denotes a spacer disposed in between a circumferential rim portion of the partioning wall member 3 and the coil holder 18. As shown in Figure 6, the partitioning wall member 3 is of a generally disc-shaped configuration having a guide hole 3a formed at its centre portion into which an upper end 6a of the injection valve body 6 having an increased diameter is slideably received. A space in the upper portion of this guide hole 3a defined at its one side by an upper rear end face 6h of the injection valve body 6 constitutes a back pressure chamber 3b which is communicated with a pressure release chamber 4a of the fuel injection timing control chamber 4 through an orifice passage 3c and, moreover, is communicated with the fuel storage chamber 5 through a throttle hole 6f and a communicating hole 6b both formed through the upper rear end portion 6a of the injection valve body 6 (see Figure 3). Again, referring to Figure 6 the peripheral flange portion of the partitioning wall member 3 has a fuel supply groove 3d forming an axial passageway and, moreover, performing also a radial offset of said passageway for supplying fuel downwards to the fuel storage chamber 5 of the high pressure fuel unit 1 i.e. through said fuel groove 3d the fuel passage 10d of the cover insert 10 is comminucated to the pressurized fuel accumulator or storage chamber 5. The above injection timing control valve 8 comprises a bisectional coil holder 13 screwed and mounted on the central projection 3a of the partioning wall member 3, a ring shaped electromagnetic coil 14, supported within the coil holder 13 and an axially movable valve body 15, comprising a valve stem 15a slidably inserted through a coaxial hole of the coil holder 13 and a disk shaped abutment portion 15b as shown in greater detail in Fig. 3. The orifice passageway 3c is controlled by a central protrusion 15c of the valve member 15 of the injection timing control valve, as shown in Figure 3. In order to assist an injection valve opening retracting force being applied to the injection valve body 6 through the static pressure of the pressurized fuel a transition range from a middle portion of the injection valve body 6 to the rear end portion 6a thereof having an increased diameter forms a cone portion 6g as shown in Fig. 3. A feeder terminal 31 (Fig. 2) is disposed and supported through the top plate portion 10b of the cover insert 10 to electrically connect the ring coil 14 to an external power source. An upper end of the valve stem 15a is in engagement with a pushing spring 16 urging the valve member 15 into a downwardly advanced valve closing position as described later on. Accordingly, an orifice passageway 3c of a back pressure chamber 3c is usually kept closed by the central valve protrusion 15c formed at the lower end of the valve stem 15a and said orifice passageway 3d is adapted to be opened by attracting the disk-shaped abutment portion 15b fixed on the valve stem 15a by means of the electromagnetic coil 14. Moreover, the injection valve body 6 is provided with a guide portion 6c formed at its lower portion and comprising a helical fuel supply groove and a tip end 6d formed at its lower end for opening or closing the associated injection nozzle 11a thus forming an injection valve. Moreover, a stopper portion 6e is formed at the middle part of the injection valve body 6 having a cross-shaped cross-section. The upper face of said stopper portion 6e is adapted to be disposed engageably opposite to the lower end face of the guide portion 20a of the shift regulating member 20. Accordingly, the engagement position between the stopper portion 6e and the facing end of the guide portion 20a of the shift regulating member 20 determines the stroke of the injection valve body 6. An urging spring 22 is disposed between a lower spring seat 21b mounted on the guide portion 6c of the injection valve body 6 and an upper spring seat 21a inserted in a receipt section 18b formed at the lower portion of the guide hole 18a of the coil holder 18. By means of said urging spring 22 the injection valve body 6 is kept urged in the direction for closing the injection nozzle 11a. Finally, as already mentioned above and shown in Fig. 3 on the upper rear end face 6h of the rear end portion 6a of the injection valve body 6, said portion 6a having an increased diameter, the annular lift amount adjusting shim plate 28 is disposed ad the distance between the upper surface of said shim plate 28 and the opposite facing surface 3f of the back pressure chamber 3b constitutes the maximum amount of the lift of the injection valve body 6. As shown in Figs. 3a and 3b said shim plate 28 is an annular plate and its lower surface is provided with abuting faces 28a projected every 90° forming recessed portions 28b for introducing the fuel pressure to act upon the rear end face 6h of the rear end portion 6a of the injection valve body 6, said recessed portions 28b being constituted in between adjacent abutting faces 28a in circumferential direction of the shim plate 28. As shown in Fig. 3, preferably, said shim plate 28 can be installed upside down. On the other hand the electromagnetic lift solenoid 7 disposed downstream of the partioning wall member 3 in the upper part 5a of the fuel storage chamber 5 comprises a bisectional coil holder 18, a ring shaped electromagnetic coil 19 supported within the coil holder 18 and a lift regulating member 20 for regulating the amount of the lift of the injection valve body 6, specifically delimiting the lift of the injection valve body to a smaller value (smaller amount of fuel injection) when the lift regulating member 20 assumes it lift regulating position. The upper peripheral rim portion of the coil holder 18 is pressed against and fixed on the step portion 9b of the main body 9 of the housing 2 through the tubular portion 10a of the cover inset 10 as indicated above. The lift regulating member 20, comprises a tubular guide portion 20a slidably inserted into a guide hole 18a of the coil holder 18 and a disk-shaped abutment portion 20b fixed on the upper end of the cylindrical guide portion 20a. The guide hole 18a extending coaxially through the coil holder 18 comprises the receipt section 18b formed at the lower end portion of the guide hole 18a with a diameter somewhat increased. As already indicated, said receipt section 18b serves to support the upper spring seat 21a of the urging spring 22 whereas the lower spring seat 21b is provided on the upper end of the guide portion 6c of the injection valve body. The lower end face of the guide 20a of the lift regulating member 20 is disposed engagably opposite to the upper face of a stopper portion 6e of the injection valve body 6. In Figures 1 and 2 the reference numeral 32 denotes a stopper plate made of non-magnetic material provided as a magnetic shield to prevent a magnetic circuit from being generated through the partitioning wall member 3 under the condition that the lift regulator member 20 is in its unbiased raised position and the lift solenoid 7 is energized to attract the lift regulating member 20. Generally the lift electromagnetic 19 of the lift solenoid 7 is of a small current type formed by winding a wire having a small diameter by a large number of turns and, accordingly the start-up of the magnetic force and the movement of the lift regulating member 20 is relatively slow. In contrast hereto, the characteristics of the electromagentic coil 14 of the upper injection timing control valve 8 is of a big current type formed by winding a wire having a larger diameter by a smaller number of turns, thus employing a big current type coil having quick start-ups of the magnetic force and of the valve member 15. For example, the injection electromagentic coil 14 is of the type A > T in terms of its ampere turn characteristics. In this way it is possible to improve the control accuracy of the injection timing by rendering the start-up characteristics of the magnetic force curve as steep and quick as possible driving a large current through the coil 8. On the other hand as indicated above, the electromagnetic lift coil 19 of the lift solenoid 7 employs a coil of the type formed of electric wire having a smaller diameter wound by a large number of turns that is the coil 19 is of the type A < T in terms of its ampere turn characteristics. Such a design is selected as a slow start-up characteristics is sufficient for the lift electromagnetic coil 19 and the operation of the lift regulating member 20 of the lift solenoid 7 as there is a sufficient time available for energizing and attracting the lift regulating member 20 in its attracted lift regulating position. Moreover, the cylindrical tube portion 10a of the cover insert 10 comprises a pair of knock pin holes 10f at the leading end thereof with knock pins 29 fitted therein to engage knock pin holes 9f at the step portion 9b and extending through knock pin grooves 3g, 30c and 29e formed to penetrate the peripheries of the partioning wall member 3, the spacer 20 and the coil holder 18, respectively. In order to supply energy to the coil 19 of the lower lift solenoid 7 wiring passages are formed through the high pressure fuel injection unit 1 substantially extending in an axial direction thereof from the top of the fuel injection unit extending axially through the closure cap 12 and the cylindrical tube portion 10a of the cover insert 10 to connect to the lift electromagentic coil 19 of the lower lift regulating solenoid 7 from below. Such a structure is preferred and particularly advantageous in order to avoid a space-consuming radially extending wiring harness for feeding the lower electromagnetic coil 19, thus increasing the installation freedom and assuring a high sealability of the pressurized fuel storage chamber 5. Specifically, the wiring passages for feeder wires assemblies connected to the coil 19 of the lift solenoid 7 are constituted by guide holes 18c of a portion of the coil holder 18 beneath the lower end of the electromagnetic coil 19, guide grooves 9e, 18d, 30a and 3e along a portion of the housing's main body 9 surrounding the lift solenoid 7, the coil holder 18 and the spacer 30 as well as of the peripheral portion of the partitioning wall member 3 terminating into take out holes 10h of the cylindrical tubular portion 10a of the cover insert 10 through the top plate portion 10b thereof to the outside at the top portion of the high pressure fuel injection unit 1. The take out hole 10h respectively, comprises a holding portion 10g formed by its upper half, and a sealing portion 10e formed by its lower half forming a receipt structure for an insulating pipe 23 made of insulating material which is screwed into the holding portion 10g respectively and is fixed therein with an adhesive. The insulating pipe 23 is adapted to receive a feeder rod 24 which is, for example, a rod made of copper inserted into the insulating pipe 23 and constituting a part of a feeder wire. Said conductive rod is fixed to the inner surface of the insulating pipe 23 with an adhesive and its upper end portion axially projecting out of the housing 2 is fixed by a lock nut 25. A soft sealing adhesive 24 is filled in between a portion 24b of the feeder rod 24 having a smaller diameter and the sealing portion 10e of the take out hole 10h. The lower end of the portion 24b of the feeder rod 24 is positioned near to the guide groove 30a of the spacer 20. The wire harness 27 which is drawn out from both ends of the winding of the electromagnetic coil 19 is fed through the guide hole 18c and the guide groove 9h to the vicinity of the spacer 30 to be connected at that position through soldering with the lower end of the thinner portion 24b of the feeder rod 24. In the following the action and effects of the high pressure fuel injection unit according to the present invention will be explained. Generally, the high pressure fuel injection unit 1 according to this embodiment of the present invention provides a fuel injection cycle opening or closing the fuel injection nozzle 11a and, thus, starting or terminating the fuel injection by energizing or deenergizing the electromagnetic coil 14 of the above injection timing controlling solenoid 8. Specifically, when the electromagnetic coil 14 of said injection timing control solenoid 8 is energized the valve body 15 thereof is attracted and raised to the coil holder 13 of said solenoid 8 opening the orifice passageway 3c, as shown in Figure 3. In this way, the fuel back pressure prevailing within the back pressure chamber 3b is released to the back pressure relief chamber 4a and, driven by the highly pressurized fuel in the fuel storage chamber 5 the injection valve body 6 rises to open the fuel injection nozzle 11a and the fuel from the fuel storage chamber 5 through the helical groove of the guide section 6c of the injection valve body 6 flows downwardly to be injected. When, on the other hand, the injection timing control solenoid 8, specifically the electromagnetic coil 14 thereof is deenergized the valve body 15 forming part of the relief control valve is lowered by the urging force of the pre-biasing spring 16 to close the orifice passageway 3c. Again, then a back pressure is built up within the back pressure chamber 3b which, assisted by the force of the urging spring 22 is effective to lower the injection valve body 6 to close the injection nozzle 11a with its valve tip portion 6d. Moreover, with the high pressure fuel injection unit 1 according to this embodiment as a present invention, the amount of fuel injection can be changed and altered in two steps by changing the amount of the lift of the injection valve body 6 either to a small lift or to a larger lift. Firstly, in case the lift amount is to be regulated to a larger one injecting a larger amount of fuel the electromagnetic coil 19 of the lift regulating solenoid 7 disposed in the fuel storage chamber 5 and beneath the injection timing control solenoid 8 with respect to the axial direction of the fuel injection unit 1, is deenergized and, according, the regulating member 20 is freely movable within the space available which allows the amount of lift of the injection valve 6 to be the larger one regulated by the distance between the top face of the shim plate 28 disposed on the rear end face of the rear end portion 6a of the valve body 6 and the opposite facing wall 3f of the back pressure chamber 3b. Of course, a certain shim plate 28 having a certain thickness can selectively be replaced by another shim plate 28 having a different thickness, thus, enabling to adjust the maximum lift of the injection valve body 6. In case the lift amount is regulated to the smaller one, firstly, the electromagnetic coil 19 of the lift regulating solenoid 7 is energized to attract the disc shaped abutment portion 20b to the coil holder 18 and, accordingly, the guide portion 20a of the lift regulating member 20 is lowered regulating the amount of the lift of the valve injection body 6 and, consequently, the amount of fuel being injected, to a smaller valve determined by distance in between the lower end face of the guide portion 20a and upper face of the stopper portion 6e of the injection valve body 6. The provision of such a lift regulating assembly comprising the solenoid 7 and lift regulating member 20 enables to adjust the amount of fuel being injected in response to the operational perimeter of the engine and, therefore, the freedom of the injection pattern can be enlarged providing optimal fuel injection conditions. On the other hand, the fuel supply of highly pressurized fuel necessitates to dispose an electromagnetic coil 19 of the lift regulating solenoid 7 to be disposed within the fuel storage chamber 5 wherein the highly pressurized fuel is accumulated and, accordingly, several problems to be solved with respect to the energy supply or disposing of a feeder wire structure serving the electromagnetic coil arise such as the need to assure a sealability which withstands high fuel pressure, the need to maintain the freedom of installation of the fuel injection unit which might be reduced by an enlarged diameter of the fuel injection unit which would result from radial electrical terminals or wiring harnesses taking the limited space in the vicinity of the cylinder head of an internal combustion engine into consideration. According to the present invention the sealing performance and sealing capabilities of the fuel injection system are considerably improved in that the take-out hole 10h is resepctively formed axially penetrating the cylindrical tube portion 10a of the insert cover 10, i.e. that portion surrounding the injection timing control solenoid 8. This take-out hole 10h, respectively, is adapted to receive a feeder rod 24 through an insulating pipe 23 and the upper portion of this feeder rod 24 is fixed to the inner surface of the insulating pipe 23 with a high strength adhesive effective to withstand the load caused by the fuel pressure. Moreover, a soft sealing adhesive 26 is filled between the lower portion 24b of the feeder rod 24, having a reduced diameter, and the sealing portion 10e of the surrounding take-out hole 10h. This sealing adhesive 26 becomes readily expanded by being longitudinally compressed and densified in response to the fuel pressure prevailing within the fuel storage chamber 5 acting on the lower end of said sealing adhesive 26. Accordingly, the fuel pressure applied longitudinally to the sealing adhesive 26 resulting in said sealing adhesive 26 to become densified and radially expanded and an improved sealability is obtained. In this embodiment the take-out hole 10h respectively extends axially through the cylindrical tube portion 10a of the cover insert 10,thus a sufficient sealing length can be assured and high sealing performance is achieved. Moreover, it is not necessary to specifically increase the wall thickness of the member, specifically of the cylindrical tube portion 10a of the cover insert 10 as said wall thickness is already designed to accommodate the fuel supply passage 10d therethrough in axial direction and, accordingly, the wiring passage means according to the present invention can easily be formed. Of course, the present invention is not limited to such a design including a cover insert. Specifically in those cases said other member such as the main body of the housing is already adapted to axially guide the fuel supple passage therethrough as well. As the feeder rod 24 and, accordingly, the feeder wire assembly according to the present invention is drawn out from the upper rear end face of the fuel injection unit 1 said feeder wire assembly for the lower lift regulating solenoid 7 does not interfere with the engine side nor does expand the axial dimension of the injection unit 1 and, accordingly, the degree of freedom for the installation of the high pressure fuel injection 1 on the engine is not effected by the wiring of the feeder wire assembly. As mentioned, the wiring of the feeder wire assembly in no way increase the outer diameter of the fuel injection unit, neither due to any electrical side terminals at the radial outside of the fuel injection unit nor through an increased diameter of the fuel injection unit itself as preferably, the take-out holes 10h for receiving the feeder rods 24 are formed through the cylindrical tube portion 10a with the cover insert 10 which is originally designed to have an appropriate thickness to accommodate the fuel passage 10d. Thus, the axial feeding of the feeder wire assembly or wiring passages adapted to accommodate same needs not to be designed with an increased wall thickness and, therefore, the diameter of the fuel injection unit 1 is not increased in an undesirable manner. Preferrably, the present embodiment sets out the cover insert 10, the partitioning wall member 3, the spacer 20 and the coil holder 18 of the solenoid 7 to be joined to the main body 9 of the housing 2 by a pair of knock pins 29 which prevent said components from being rotated relatively to each other so that the fuel suppy passage 10d and the wiring passages are reliably fixed in their circumferential position in the housing 1. Of course, the present invention is not limited to the specific embodiment in as far a lift regulating solenoid adapted to preadjust the stroke of the injection valve pin of a fuel injection valve disposed in a pressurized fuel storage chamber of the fuel injection unit but can be applied to an electromagnetic coil of any type disposed under the same or similar conditions used for example to actuate the valve pin or for performing other purposes. Moreover, the present invention is not delimited to the specific structure of a cover insert to form the guide member for the wiring passages as well as for the fuel supply passage 10d. The present invention suggests to provide a feeder wire take-out structure or passing through structure of a high pressure fuel injection unit in such a manner that at least one wiring passage through which the feeder wire extends to an electromagnetic coil disposed in a pressurized fuel accumulator chamber is formed axially, communicating with said fuel storage chamber through a cover member of a housing which simultaneously serves to define a fuel supply passage. In this way, not only an advantageous bridging of an injection timing control solenoid by means of the casing wall or hollow cylindrical tube portion of the cover member can be obtained but the afore-indicated structure has the effects that it provides high performance sealability characteristics by improving the sealing length and, simultaneously, assuring a desirable high degree of freedom for installing the high pressure fuel injection unit on an engine.

Claims: High pressure fuel injection unit comprising a housing (2) of generally cylindrical shape extending from an upper supply portion to a lower fastening portion thereof, accommodating a partitioning wall member (3) therein to define an upper chamber (4) comprising a first fuel injection control and/or detection means, and a lower chamber (5) comprising a second fuel injection control and/or detection means, said lower chamber (5) being supplied with pressurized fuel through a fuel supply line extending substantially axially from an upper end side of the housing (2) to said lower chamber (5) which, in turn, is communicated to an injection nozzle (119) adapted to engage a tip end of an injection valve body (6), said injection valve body (6) being reciprocable in between an advanced injection valve closing position and a retracted injection valve opening position, and a power supply passageway means extending substantially axially from the rear end side of the housing (9, 12) to the lower chamber (5) thereof, adapted to receive a power supply assembly (24, 27) to connect and supply power to the second fuel injection control and/or detection means (7), characterised in that said housing (2) accomodates an insert (10) comprising axially extending take-out holes (10h) accommodating an electrical conductor (24) of the power supply assembly therein and having axially extending sealing portions (10a), said electrical conductor (24) being embedded in said sealing portion (10a) by means of a substantially axially extending sealing adhesive (26). High pressure fuel injection unit as claimed in claim 1, characterised in that , said power supply passageway means extends axially through said insert (10) which also contains the fuel supply line (10d) extending axially therethrough. High pressure fuel injection unit as claimed in claim 1 or 2, characterized in that , said power supply passageway means and said fuel supply line (10) both extend axially, circumferentially offset, through a wall portion of a hollow member (10) of the high pressure fuel injection unit. High pressure fuel injection unit as claimed in at least one of the preceding claims 1 to 3, characterized in that , said second fuel injection control and/or detection means comprises an electromagnetic solenoid (7) including an electromagnetic coil (19) adapted to be energized by a drive current supplied through said power supply assembly (24, 27). High pressure fuel injection unit as claimed in at least one of the preceding claims 1 to 4, characterized in that , said first fuel injection control and/or detection means is an injection timing solenoid actuator (8) performing a relief valve control of a pressure release orifice passageway (3c) communicated to a rear end (6a, 6h) of the injection valve body (6) whereas said second fuel injection control and/or detection means is a lift regulating solenoid (7) performing a lift control of the injection valve body (6). High pressure fuel injection unit as claimed in at least one of the preceding claims 1 to 5, characterized in that , said power supply passageway means receiving the power supply assembly comprising a wiring passage means adapted to receive a feeder wire assembly (24, 27) therein. High pressure fuel injection unit as claimed in claim 6, characterized in that , said wiring passage means comprises first and second wiring passages (10h, 3e, 30a, 18d, 9e, 18c) to receive the feeder wire assembly therein, respectively, adapted to connect to the end of the electromagnetic coil (19) of the lift regulating solenoid (7). High pressure fuel injection unit as claimed in at least one of the preceding claims 1 to 7, characterized in that , the feeder wire assembly comprising a feeder rod (24) and wire harness (27). High pressure fuel injection unit as claimed in claim 7, characterised in that , said first and second wiring passages extend axially through said insert (10) which, circumferentially offset, also contains said fuel supply line (10d). High pressure fuel injection unit as claimed in at least one the preceding claims 1 to 9, characterized in that , the housing (1, 12) comprises a stepped tubular main body (9) supporting the partitioning wall member (3) which, in turn, has a peripherial flange portion and a projecting central portion, and a cover insert (10) having a hollow cylindrical structure to be received upside down in said tubular mean body (9) secured therein to a closure cap (12) urging said cover insert (10) downwardly to abut against the peripheral flange portion of the partitioning wall member (3). High pressure fuel injection unit as claimed in claim 10, characterized in that , the partitioning wall member (3) is held inside the housing's tubular main body (9) at an inwardly projecting step (9b) with a spacer (30) and an upper rim portion of a coil holder (18) of the lift regulating solenoid (7) in between, said partitioning wall member (3) is adapted to support the injection timing solenoid actuator (8) by means of its centre portion and, internally, to slideably receive a rear end (6a) of the injection valve (6) exposed to a back pressure chamber (3b) communicated to a back pressure relief chamber (4a) through an orifice passageway (3c) to establish a fluid passageway in between the back pressure chamber (3b) and back pressure relief chamber (4a) in response to a valve operation of the injection timing solenoid actuator (8). High pressure fuel injection unit as claimed in at least of the preceding claims 7 to 11, characterized in that , said wiring passages (10h, 3e, 30a, 18d, 9e, 18c) substantially extend axially, preferably diametrically opposite to each other, through the closure cap (12) and a cylindrical tube portion (10a) of the cover insert (10) and through guide grooves of the partitioning wall member (3) downwardly to establish access to the electromagnetic coil (19) of the lift regulating solenoid (7) from below. High pressure fuel injection unit as claimed in claim 12, characterised in that , each wiring passage comprises said take-out holes (10h) extending axially through the cylinderical tube portion (10a) of the cover insert (10) and guide grooves (3e, 30a, 18d, 9e, 18c) extending through a peripheral flange portion of the partitioning wall member (3), a spacer (30), an upper rim portion of a coil holder (18) of the lift regulating solenoid (7), a step portion (9b) of th tubular main body (9) along the lift regulating solenoid (7) and through a portion of the coil holder (18) of said lift regulating solenoid actuator (7) to terminate at an end of the electromagentic coil (19) of said lift regulating solenoid (7). High pressure fuel injection unit as claimed in claim 13, characterized in that , the take-out holes (10h) comprise an upper holding portion (10g) and a lower sealing portion (10e), respectively and that an insulating pipe (23) is received, preferrably threadingly engaged, in said upper holding portion (10g) fixed by an adhesive. High pressure fuel injection unit as claimed in claim 14, characterised in that , the insulating pipe (23) is provided to receive a feeder rod (24) of a highly conductive material, perferably copper, said feeder rod (24) comprising an upper portion (24a) of larger diameter accommodated by said insulating pipe (23) and fixed therein by an adhesive, and a lower portion (24b) of smaller diameter received in the lower sealing portion (10e) of the respective take-out hole (10h) surrounded by the soft sealing adhesive (26). High pressure fuel injection unit as claimed in claim 15, characterized in that , a lower end of the lower portion (24b) of the feeder rod (24) is positioned near the guide groove (30a) of the spacer (30) to form a conntecting end for a wire harness (27) drawn out from the respective end of the electromagnetic coil (19), said wire harness (27) being fed through the guide hole (18c) of the coil holder (18) and the guide groove (9e) of the main body (9) to the vicinity of the spacer (30) to be connected, preferably by soldering, to the lower end of the lower portion (24b) of the feeder rod (24) having a smaller diameter. High pressure fuel injection unit as claimed in claims 15 or 16, characterized in that , the feeder rod (24) comprises an upper rearwardly projecting connector section extending outwards beyond the upper surface of the closure cap (12) threadingly engaging a fastening nut structure (25), respectively.

Inventors: SUZUKI MINORU, YOSHIDA TAKEO, SUZUKI, MINORU, YOSHIDA, TAKEO
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1990
Main classification: F02M47
IPC codes: F02M47, F02M61, F02M51