Fuel injection valve

Information

  • Patent Grant
  • 6601786
  • Patent Number
    6,601,786
  • Date Filed
    Friday, May 11, 2001
    23 years ago
  • Date Issued
    Tuesday, August 5, 2003
    21 years ago
Abstract
In a fuel injection valve, a cylindrical valve body has a valve seat protruding radially inward out of an inner wall thereof and a needle supporting cylindrical inner wall. A nozzle needle is fixed to the armature so as to move together with the armature, while being supported slidably by the needle supporting cylindrical inner wall. The nozzle needle is provided with a valve portion to be seated on the valve seat when a coil is de-energized and inside thereof with a cavity into which fuel is introduced. A fuel accumulation bore is provided between inner circumference of the cylindrical valve body and outer circumference of the nozzle needle. With the construction mentioned above, the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore.
Description




CROSS REFERENCE TO RELATED APPLICATION




This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2000-139702 filed on May 12, 2000, the content of which is incorporated herein by reference.




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a fuel injection valve for an internal combustion engine (hereinafter called as an engine).




2. Description of Related Art




As shown in

FIG. 6

, a conventional fuel injection valve


100


has a nozzle needle


101


that is slidably and reciprocatingly supported by a sliding portion


102


. The sliding portion


102


is provided with a plurality of cuts for forming fuel passages. The cuts of the sliding portion


102


also serve as vapor passages through which vapor generated by heat near injection holes moves toward a side of fuel upstream. A contact portion


103


formed at an end of the nozzle needle


101


on a side of fuel injection may be seated on a valve seat


105




a


formed in a valve body


105


.




An armature


111


is connected with the nozzle needle


101


at a position facing a stator


110


and is biased in a valve closing direction by a spring


112


. Since the armature


111


and the sliding portion


102


are slidably and reciprocatingly supported by the valve body


105


, the nozzle needle


101


can make a reciprocating movement accurately along a center axis thereof. Generally, the stator


110


and the armature


111


are made of lower toughness material and are plated with, for example, chromium to form thin film thereon. When a coil


115


is energized, the armature


111


is attracted toward the stator


110


against biasing force of the spring


112


. Accordingly, the nozzle needle


101


leaves the valve seat


105




a


so that fuel is injected from the injection holes. When the coil


115


is de-energized, the contacting portion


103


is seated on the valve seat


105




a


to finish fuel injection.




It is important for better fuel consumption that fuel is supplied to the engine at an adequate timing during a period when an intake port of the engine is opened. Therefore, the fuel injection valve is required to have quick response characteristic that is largely affected by mass of a moving member including the nozzle needle


101


.




According to the conventional fuel injection valve


100


, the nozzle needle


101


is integrally provided with the sliding portion


102


having the cuts, whose maximum outer diameter is larger than that of the contact portion


103


, for securing the fuel and vapor passages. Accordingly, among the nozzle needle


101


, the sliding portion


102


and the armature


111


, which constitute the moving member, the sliding portion


102


adversely affects on the quick response characteristic of the fuel injection valve because of larger mass thereof.




Further, formation of the chromium thin film on portions where the stator


110


and the armature


111


come in contact with each other results in higher manufacturing cost of the fuel injection valve.




SUMMARY OF THE INVENTION




An object of the invention is to provide a fuel injection valve in which weight of a nozzle needle is relatively light and mass of a movable member constituted by the nozzle needle and an armature is smaller so that quicker response characteristic of the injection valve is secured.




To achieve the above object, in the injection valve having a housing, a stator, an armature and a coil for exerting electromagnetic attracting force on the armature, a cylindrical valve body, which is provided with at least an injection hole, has a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat. A nozzle needle is fixed to the armature so as to move together with the armature in the cylindrical valve body, while being supported slidably by the needle supporting cylindrical inner wall. The nozzle needle is provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced. A fuel accumulation bore is provided between inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and outer circumference of the nozzle needle.




With the construction mentioned above, the nozzle needle is further provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing coil, the fuel accumulation bore communicates with the injection hole for fuel injection.




Since the nozzle needle is provided inside thereof with the cavity and with the opening through which the cavity communicates with the fuel accumulation bore, weight of the nozzle needle is lighter than that of the conventional fuel injection valve in which the nozzle needle has the cuts for forming the fuel and vapor passages between the armature accommodation bore and the fuel accumulation bore.




Preferably, the opening of the nozzle needle is opened to the highest position in the fuel accumulation bore to evacuate vapor smoothly.




It is preferable that the housing has a hollow into which fuel is flown from outside and the stator is provided with a penetrating bore communicating with the hollow of the housing at an axial end thereof and communicating with an armature accommodation bore at another axial end thereof, and the armature has a through-hole for making the armature accommodation bore on a side of the stator communicate with the cavity so that fuel is introduced from the hollow of the housing into the cavity. With this construction, the fuel injection valve becomes further lighter and more compact.




It is preferable that the nozzle needle penetrates axially along the through-hole of the armature until an axial end thereof protrudes out of an axial end of the armature toward the stator so that fuel is introduced into the cavity from the hollow of the housing via the penetrating bore. This will make it possible to manufacture the fuel injection valve at lower cost, since an air gap is automatically formed between the stator and the armature by the axial end of the nozzle needle protruding out of the end of the armature and coming in contact with the stator and, further, it is not necessary to cover the axial end of the nozzle needle with chromium thin film for reinforcement because the nozzle needle is inherently made of material having relatively higher stiffness.




Preferably, the opening of the nozzle needle is formed to axially stride over the needle supporting cylindrical inner wall so that the cavity communicates not only with the fuel accumulation bore but also with the armature accommodation bore on a side of the cylindrical valve body. With this construction, vapor generated by heat is easily evacuated from the fuel accumulation bore to the armature accommodation bore through the opening. Accordingly, fluctuation of injection characteristic due to vapor is limited.




Further, it is preferable that the needle cylindrical inner wall, whose diameter is larger than a diameter of the valve seat, is formed to protrude radially inward out of the inner wall of the cylindrical valve body. Since a diameter of the valve seat are smaller than that of the needle supporting cylindrical inner wall, the seat valve, on which the valve portion of the nozzle needle is seated, is easily and accurately machined by inserting a cutting tool from a side of the needle supporting cylindrical inner wall into an inside of the cylindrical valve body.




Moreover, preferably, the nozzle needle is provided with a small diameter column portion whose axial end on a side of the injection hole constitutes the valve portion and with a large diameter column portion whose diameter is larger than that of the small diameter column portion and which is slidably supported by the needle supporting cylindrical inner wall.











BRIEF DESCRIPTION OF THE DRAWING




Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:





FIG. 1

is across sectional part view of a fuel injection valve according to a first embodiment of the present invention;





FIG. 2

is a cross sectional whole view of the fuel injection valve according to the first embodiment;





FIG. 3

is a cross sectional part view of a fuel injection valve according to a second embodiment of the present invention;





FIG. 4

is a cross sectional part view of a modified fuel injection valve according to the second embodiment;





FIG. 5

is a cross sectional part view of a fuel injection valve according to a third embodiment of the present invention; and





FIG. 6

is a cross sectional whole view of a conventional fuel injection valve as a prior art.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




(First Embodiment)




A fuel injection valve according to a first embodiment is described with reference to

FIGS. 1 and 2

.




As shown in

FIG. 2

, a valve body


29


, a nozzle needle


26


, an armature


25


, a stator


22


, an adjusting pipe


21


, a spring


24


and a filter


11


are accommodated in a cylindrical member


14


.




The cylindrical member


14


, for example, made of composite magnetic material, is formed in pipe shape to have both of magnetic and non-magnetic portions. The cylindrical member


14


has the non-magnetic portion partly changed by heating and is provided with a magnetic pipe portion


14




c


, a non-magnetic pipe portion


14




b


and a magnetic pipe portion


14




a


, which are positioned upward in order from a lower end thereof on a side of fuel injection. The armature


25


is housed in an armature accommodation bore


14




e


of the cylindrical member


14


in a vicinity of a boundary between the non-magnetic pipe portion


14




b


and the magnetic pipe portion


14




c


. The valve body


29


and an injection hole plate


28


are housed in the magnetic pipe portion


14




c


on a side of fuel injection. The filter


11


, which filters foreign material in fuel, is installed in the cylindrical member


14


at an upper end on a fuel upstream side.




As shown in

FIG. 1

, the valve body


29


, which is formed in pipe shape, is press fitted into and fixed by laser welding to an inner wall of the magnetic pipe portion


14




c


. An inner circumferential wall of the valve body


29


has a conical surface wall


29




a


, a large diameter cylindrical surface wall


29




b


, a conical surface wall


29




c


, a small diameter cylindrical surface wall


29




d


and a conical surface wall


29




e


, which are positioned in order from a side of fuel injection toward a side of fuel upstream. The conical surface wall


29




a


, whose diameter is smaller toward a side of fuel injection, is provided to form a valve seat on which a contact portion


26




c


of the nozzle needle


26


can be seated. The large diameter cylindrical surface wall


29




b


is provided to form a fuel accumulation bore


29




f


. A diameter of the conical surface wall


29


is smaller toward a side of fuel upstream. The small diameter cylindrical surface wall


29




d


constitutes a nozzle needle supporting hole whose diameter is smaller than that of the fuel accumulation bore


29




f


. A diameter of the conical surface wall


29




e


is larger toward a side of fuel upstream.




The injection hole plate


28


in cup shape is press fitted into and fixed by laser welding to an inner wall of the magnetic pipe portion


14




c


. The injection hole plate


28


is in contact with an end of the valve body


29


on a side of fuel injection. The injection hole plate


28


is formed in thin plate shape and provided in a center thereof with a plurality of injection holes


28




a.






The nozzle needle


26


is made of stainless steel and formed in cylindrical shape having a bottom. The nozzle needle


26


is provided on a side of fuel upstream with a large diameter column portion


26




e


whose diameter is slightly smaller than an inner diameter of the small diameter cylindrical surface wall


29




d


and provided on a side of fuel injection with a small diameter column portion


26




d


whose diameter is smaller than that of the large diameter column portion


26




e


on a side of fuel upstream. It is preferable that a diameter difference between the large and small diameter column portions


26




e


and


26




d


is more than 0.1 mm in view of obtaining lighter weight of the nozzle needle


26


and easily manufacturing the valve seat.




An end corner of the small diameter column portion


26




d


on a side of fuel injection is chamfered or tapered to form a conical surface that constitutes the contact portion


26




c


. A diameter of the contact portion


26




c


, that is, a seat diameter, is smaller than that of the small diameter cylindrical surface wall


29




d


. To bring an outer wall of the large diameter column portion


26




e


in slidable contact with the small diameter cylindrical surface wall


29




d


, a slight clearance is formed therebetween. Most part of the large diameter column portion


26




e


is formed in thin cylinder shape and an inner circumferential wall


26




a


thereof constitutes an interior passage


26




f


. The interior passage


26




f


is formed by drilling a hole from an end of the large diameter column portion


26




e


on a side of fuel upstream. Length of the drilled hole is deep to an extent that a bottom of the nozzle needle


26


sufficiently endures a shock caused on seating itself on the valve seat.




An axial length of the large diameter column portion


26




e


is long to an extent that, when centerless machining forms the small diameter column portion


26




d


and the contact portion


26




c


, an outer circumferential wall of the large diameter column portion


26




e


can be held tightly by a chuck so that a center axis of the valve body does not deviate throughout a whole axial length thereof.




The large diameter column portion


26




e


is provided with outlet holes


26




b


that constitute openings of the interior passage


26




f


. The outlet holes


26




b


are positioned circumferentially at 180-degree angular intervals so as to perforate the large diameter column portion


26




e


radially. One outlet hole


26




b


, instead of the two outlet holes


24


, is sufficient enough to perform an operation of the present invention. Each of the outlet holes


26




b


is formed in shape of oval or flat oval whose major axis extends axially and whose major axis length is longer than axial length of the small diameter cylindrical surface wall


29




d


. A periphery of the outlet hole


26




b


on a side of fuel injection is located at a position lower than an axial end of the small diameter cylindrical surface wall


29




d


on a side of fuel injection and opened to the fuel accumulation bore


29




f


. Another periphery of the outlet hole


26




b


on a side of fuel upstream is located at a position higher than an axial end of the small diameter cylindrical surface wall


29




d


on a side of fuel upstream and opened to the armature accommodation bore


14




e


. The shape of the outlet hole


26




b


is not limited to oval or flat oval but may be circular.




The armature


25


is fixed by laser welding to an outer wall of the large diameter column portion


26


on a side of fuel upstream. The armature


25


is made of ferromagnetic material such as magnetic stainless steel and is formed in pipe shape having steps. Inner circumferential wall


25




b


of the armature


25


is provided in middle thereof with a ring shaped projection so as to form steps on axially opposite sides thereof. Inner diameter of the armature


25


at the ring shaped projection is smallest. The step of the armature


25


on a side of fuel upstream serves as a spring seat


25




c


. An interior passage


25




e


of the armature


25


and the interior passage


26




f


of the nozzle needle


26


communicate with each other. The armature is further provided at an end on a side of fuel upstream with a flange


25




a


. An outer circumferential wall of the flange


25




a


and an inner circumferential wall of the cylindrical member


14


are in slidable contact with each other so that a slight clearance is formed therebetween.




As the outer circumferential wall of the large diameter column portion


26




e


and the small diameter cylindrical wall


29




d


are in slidable contact with each other and the outer circumferential wall of the flange


25




a


and the inner circumferential wall of the cylindrical member


14


are in slidable contact with each other, the nozzle needle


26


moves reciprocatingly along a predetermined orbit. The armature


25


is provided at an axial end thereof on a side of fuel upstream with a ring shaped projection


25




d


which comes in contact with the stator


22


with an air gap between the axial end of the armature


25


other than the ring shaped projection


25




d


and an axial end of the stator


22


. A surface of the ring shaped projection


25




d


that comes in contact with the stator


22


is coated with chromium thin film.




As shown in

FIG. 2

, the stator


22


is made of ferromagnetic material such as magnetic stainless steel and is formed in cylindrical shape. A surface of the stator


22


that comes in contact with the armature


25


is coated with chromium thin film. The adjusting pipe


21


is press fitted and fixed into an inner wall of the stator


22


. Adjusting a press fitting amount of the adjusting pipe


21


allows to change preset biasing force of the spring


24


, whose one end contacts the spring seat


25




c


of the armature


25


and whose another end contacts an end of the adjusting pipe


21


. The adjusting pipe


21


may be fastened to stator


22


by screws instead of being press fitted thereto.




As shown in

FIG. 2

, a resin spool


30


is attached to outer circumference of the cylindrical member


14


. A coil


31


is wound on outer circumference of the spool


30


. An outer circumference of the cylindrical member


14


is covered with a resin mold


13


and provided with a connector portion


16


protruding out of the outer wall of the resin mold


13


. A terminal


12


, which is connected in circuit with the coil


31


, is embedded in the connector portion


16


. The terminal is partly covered with a resin rib


17


.




A magnetic member


23


covers around outer circumference of the coil


31


. A fan shaped magnetic member


18


is disposed on a fuel upstream side of the coil


31


circumferentially at an angle of about 250 degrees not to interfere with the rib


17


. A resin mold


15


is formed around outer circumferences of the magnetic members


18


and


23


and connected with the resin mold


13


. The nozzle needle


26


, the stator


22


, the magnetic pipe portions


14




a


and


14




c


and the magnetic members


18


and


23


constitute a magnetic circuit through which magnetic flux passes on energizing the coil


31


.




Fuel, which is flown into the cylindrical member


14


through the filter


11


, is introduced to the fuel accumulation bore


29




f


from the outlet hole


26




b


via an interior of the adjusting pipe


21


, an interior of the stator


22


, the interior passage


25




e


of the armature


25


and the inner passage


26




f


of the nozzle needle


26


so that fuel reaches a portion where the contact portion


26




c


of the nozzle needle


26


is seated on the valve seat. When the contact portion


26




c


is seated on the valve seat, communication between the fuel accumulation bore


29




f


and the injection holes


28




a


is interrupted and, when the contact portion


26




c


leaves the valve seat, the fuel accumulation bore


29




f


communicates with the injection holes


28




a.






Next, an operation of the fuel injection valve


1


is described.




Upon energizing the coil


31


, the nozzle needle


26


is attracted toward the stator


22


against the biasing force of the spring


24


. Accordingly, the contact portion


26




c


leaves the valve seat so that fuel is injected from the injection holes


28




a.






Upon de-energizing the coil


31


, the nozzle needle


26


receives the biasing force of the spring


24


acting in the valve closing direction so that the contact portion


26




c


is seated on the valve seat to finish the fuel injection from the injection holes


28




a.






According to the fuel injection valve


1


mentioned above, As the outer circumferential wall of the large diameter column portion


26




e


and the small diameter cylindrical wall


29




d


are in slidable contact with each other and the outer circumferential wall of the flange


25




a


and the inner circumferential wall of the cylindrical member


14


are in slidable contact with each other, the nozzle needle


26


moves reciprocatingly along the predetermined orbit without offsetting the center axis thereof. Accordingly, the contact portion


26




c


of the small diameter column portion


26




d


comes in contact accurately with a predetermined seat position on the conical surface wall


29




a.






During engine operation, vapor tends to be generated in fuel by heat in the fuel accumulation bore


29




f


. According to the fuel injection valve


1


, the vapor moves toward the fuel upstream side from the fuel accumulation bore


29




f


through the outlet hole


26




b


so that generation of the vapor does not affect adversely on fuel injection characteristic. Further, the outlet hole


26




b


makes it possible to reduce frictional resistance between the nozzle needle


26


and the valve body


29


so that the quick response characteristic of the nozzle needle


26


is secured since a surface area where the nozzle needle


26


and the valve body


29


are in slidable contact with each other is relatively small.




Furthermore, as the interior passage


26




f


of the nozzle needle


26


constitutes a fuel passage, the outer diameter of the large diameter column portion


26




e


is relatively small and is slightly larger than or nearly equal to that of the contact portion


26




c


. A large part of the nozzle needle


26


is constituted by the large diameter column portion


26




e


whose wall thickness is relatively thin. Accordingly, mass of the movable member integrally composed of the nozzle needle


26


and the armature


25


becomes smaller, resulting in improving the quick response characteristic of the nozzle needle


26


.




Moreover, as the small diameter column portion


26




d


is formed on the nozzle needle


26


on a side of fuel injection, the valve seat can be easily and accurately manufactured. In more details, it is generally required to highly accurately machine the seat portion on the conical surface wall


29




a


on which the contact portion


26




c


is fluid-tightly seated. Since the seat diameter is smaller than an inner diameter of the small diameter cylindrical surface wall


29




d


of the valve body which slidably supports the nozzle needle


26


, the seat portion on the conical surface wall


29




a


can be accurately machined by inserting a cutting tool into the fuel accumulation bore


29




f


from a side of fuel upstream after the small diameter cylindrical surface wall


29




d


, the conical surface wall


29




c


, the large diameter cylindrical surface wall


29




b


and conical surface wall


29




a


are machined.




As the fuel injection valve


1


has a construction that the valve body


29


supports the large diameter column portion


26




e


of the nozzle needle


26


on a side of fuel upstream, the nozzle needle


26


can be easily and accurately machined. That is, it is necessary to machine coaxially and accurately the large diameter column portion


26




e


and the contact portion


26




c


for securing valve fluid-tightness. Since the large diameter column portion


26




e


, whose axial length is relatively long, is firmly fixed by the chuck, centerless machining can accurately form the contact portion


26




c.






(Second Embodiment)




A fuel injection valve according to a second embodiment is described with reference to

FIG. 3. A

construction of the fuel injection valve not shown in

FIG. 3

is substantially same as the fuel injection valve


1


of the first embodiment. The construction of the second embodiment substantially similar as that of the first embodiment is described with the same reference number as the first embodiment.




A valve body


41


is formed in shape of a cylinder whose peripheries of both opening ends protrude radially and inwardly. An inner circumferential wall of the valve body


41


has a conical surface wall


41




a


, a large diameter cylindrical surface wall


41




b


, a step surface wall


41




c


and a small diameter cylindrical surface wall


41




d


, which are positioned in order from a side of fuel injection toward a side of fuel upstream. The conical surface wall


41




a


, whose diameter is smaller toward a side of fuel injection, is provided to form a valve seat on which a contact portion


42




b


of the nozzle needle


42


can be seated. The large diameter cylindrical surface wall


41




b


is provided to form a fuel accumulation bore


41




e


. The small diameter cylindrical surface wall


41




d


constitutes a nozzle needle supporting hole whose diameter is smaller than that of the fuel accumulation bore


41




e.






The nozzle needle


42


is made of stainless steel and formed in cylindrical shape having a bottom. The nozzle needle


42


has a column wall


42




d


whose diameter is identical from a side of fuel injection to a side of fuel upstream. To bring the column wall


42




d


in slidable contact with the small diameter cylindrical surface wall


41




d


, a slight clearance is formed therebetween. An interior passage


42




c


is formed by drilling a hole from an end of the nozzle needle


42


on a side of fuel upstream. Length of the drilled hole is deep to an extent that a bottom of the nozzle needle


42


sufficiently endures a shock caused on seating itself on the valve seat. An outlet hole


42


, which constitute an opening of the interior passage


42




c


, is formed in oval or flat oval shape.




An interior space


40




d


, which is formed by an inner circumferential wall


40




b


of an armature


40


, and the interior passage


42




c


of the nozzle needle


42


communicate with each other. Outer circumference of a flange


40




c


on the outer circumference of the armature


40


is in slidable contact with the inner circumferential wall


14




d


of the cylindrical member


14


A. The armature


40


is provided at a step portion thereof with vapor passages


40




a


, through which an armature accommodation bore


14




e


and the interior space


40




d


of the armature


40


communicate with each other. The vapor passages


40




a


serve to move vapor included in fuel toward a side of fuel upstream in the armature accommodation bore


14




e.






According to the second embodiment, it is easy to form accurately the contact portion


42




b


by centerless machining since the nozzle needle


42


has the column wall


42




d


whose diameter is identical axially. Further, as the fuel passage extending from the interior space


40




d


of the armature


40


to the fuel accumulation bore


41




e


is formed through the interior passage


42




c


and the outlet hole


42




a


of the nozzle needle


42


, the mass of the nozzle needle


42


is smaller so that the quicker response of the nozzle needle


42


may be secured.




As an alternative, the nozzle needle


43


may be formed to penetrate axially the armature


40


, as shown in FIG.


4


. An axial end


43




a


of the nozzle needle


42


protrudes out of the end of the armature


40


on a side of the stator so as to come in contact with stator


22


. With this construction, as it is not necessary to cover the axial end


43




a


with the chromium thin film for reinforcement, the fuel injection valve is manufactured at lower cost.




(Third Embodiment)




A fuel injection valve according to a third embodiment is described with reference to

FIG. 5. A

construction of the fuel injection valve not shown in

FIG. 5

is substantially same as the fuel injection valve


1


of the first embodiment. The construction of the third embodiment substantially similar as that of the first embodiment is described with the same reference number as the first embodiment.




A valve body


52


is formed in shape of a cylinder whose opening end on a side of fuel injection protrudes radially and inwardly. The valve body


52


is provided on an inner circumferential wall thereof with a conical surface wall


52




b


on a side of fuel injection and a cylindrical surface wall


52




a


on a side of fuel upstream. The conical surface wall


52




b


, whose inner wall diameter is smaller toward a side of fuel injection, constitutes a valve seat on which a contact portion


51




c


of a nozzle needle


51


is seated. The cylindrical surface wall


52


constitutes a fuel accumulation bore


52




c.






The nozzle needle


42


, which is made of stainless steel, is formed in cylindrical shape having a bottom. The nozzle needle


51


is provided on a side of fuel upstream with a large diameter column portion


51




e


whose diameter is slightly smaller than an inner diameter of the cylindrical surface wall


52




a


and provided on a side of fuel injection with a small diameter column portion


51




d


whose diameter is smaller than that of the large diameter column portion


51




e


. An end corner of the small diameter column portion


51




d


on a side of fuel injection is chamfered or tapered to form a conical surface that constitutes the contact portion


51




c


. A diameter of the contact portion


51




c


, that is, a seat diameter, is smaller than that of the cylindrical surface wall


52




a.






An axial end


51




g


of the large diameter column portion


51




e


on a side of fuel upstream penetrates an armature


50


so as to protrude out of the end of the armature on a side of the stator. The axial end


51




g


comes in contact with the stator


22


with an air gap between the axial end of the armature and an axial end of the stator


22


. An outer circumferential wall of the large diameter column portion


51




e


and the cylindrical surface wall


52




a


are in slidable contact with each other so that a slight clearance is formed therebetween. An interior passage


51




a


is formed by drilling a hole from an end of the large diameter column portion


51




e


on a side of fuel upstream. Length of the drilled hole is deep to an extent that a bottom of the nozzle needle


51


sufficiently endures a shock caused on seating itself on the valve seat.




Outlet holes


51




b


, which extends from the large diameter column portion


51




e


to the small diameter column portion


51




d


, are positioned circumferentially at 180-degree angular intervals so as to perforate the large diameter column portion


51




e


radially. The outlet hole


51




b


is formed in oval or flat oval shape. A periphery of the outlet hole


51




b


on a side of fuel injection is formed on an outer circumferential wall of the small diameter column portion


51




d


and another periphery thereof on a side of fuel upstream is formed on an outer circumferential wall of the large diameter column portion


51




e


at a position on a side of fuel upstream with respect to an axial end


52




d


of an valve body


52


.




According to the third embodiment, the interior passage


51




a


of the nozzle needle


51


communicates with injection holes


28




a


via a fuel accumulation bore


52


which is formed between the valve body


52


and the small diameter column portion


51




d


. Wall thickness of most part of the nozzle needle


51


is thinner. Accordingly, mass of a movable member composed of the nozzle needle


51


and the armature


50


is relatively small so that the nozzle needle


51


has quicker response characteristic.



Claims
  • 1. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the housing has a hollow into which fuel is flown from outside and the stator is provided with a penetrating bore communicating with the hollow of the housing at an axial end thereof and communicating with the armature accommodation bore at another axial end thereof, and the armature has a through-hole for making the armature accommodation bore on a side of the stator communicate with the cavity so that fuel is introduced from the hollow of the housing into the cavity.
  • 2. A fuel injection valve according to claim 1, wherein the nozzle needle penetrates axially along the through-hole of the armature until an axial end thereof protrudes out of an axial end of the armature toward the stator so that fuel is introduced into the cavity from the hollow of the housing via the penetrating bore.
  • 3. A fuel injection valve according to claim 1, wherein the through hole of the armature communicates with the armature accommodation bore on the side of the stator at an axial end thereof and communicates with the cavity at another axial end thereof so that fuel is introduced into the cavity from the hollow of the housing via the penetrating bore and the through-hole.
  • 4. A fuel injection valve according to claim 3, wherein the armature is provided at an axial end thereof on a side of the nozzle needle with an aperture through which the armature accommodation bore communicates with the through-hole.
  • 5. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the opening is formed to axially stride over the needle supporting cylindrical inner wall so that the cavity communicates not only with the fuel accumulation bore but also with the armature accommodation bore on a side of the cylindrical valve body.
  • 6. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the nozzle needle is provided with a small diameter column portion whose axial end on a side of the injection hole constitutes the valve portion and with a large diameter column portion whose diameter is larger than that of the small diameter column portion and which is slidably supported by the needle supporting cylindrical inner wall.
  • 7. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the needle supporting cylindrical inner wall, whose diameter is larger than a diameter of the valve seat, is formed to protrude radially inward out of the inner wall of the cylindrical valve body.
  • 8. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and an outer circumference of the armature is in slidable contact with a circumferential wall constituting the armature accommodation bore in the housing so that the armature is slidably supported by axially spaced two supporting points.
  • 9. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle, wherein the nozzle needle is provided on an outer circumference thereof with an opening at least part of which is opened to the fuel accommodation bore from the cavity so that the fuel introduced into the cavity flows through the opening to the fuel accumulation bore, and when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection.
  • 10. A fuel injection valve according to claim 9, wherein another part of the opening is radially opposed to the needle supporting cylindrical wall.
  • 11. A fuel injection valve according to claim 9, wherein the valve seat and the needle supporting cylindrical inner wall are integrally formed into a single piece.
  • 12. A fuel injection valve according to claim 9, wherein another part of the opening is opened to the armature accommodation bore from the cavity so that the opening axially strides over the needle supporting cylindrical inner wall.
Priority Claims (1)
Number Date Country Kind
2000-139702 May 2000 JP
US Referenced Citations (12)
Number Name Date Kind
4944486 Babitzka Jul 1990 A
4967966 Babitzka et al. Nov 1990 A
5232166 Reiter Aug 1993 A
5285969 Greiner et al. Feb 1994 A
5314122 Winter May 1994 A
5462231 Hall Oct 1995 A
5544816 Nally et al. Aug 1996 A
5944262 Akutagawa et al. Aug 1999 A
6131826 Teiwes Oct 2000 A
6209806 Pace et al. Apr 2001 B1
6360960 Nally, Jr. et al. Mar 2002 B1
6422481 Ren et al. Jul 2002 B2
Foreign Referenced Citations (2)
Number Date Country
0 602 001 Jun 1994 EP
8-303327 Nov 1996 JP