Electromagnetic fuel injection valve assembly

A fuel injection valve assembly has a construction less expensive in production and applicable for automated assembling. A cylindrical stem portion of a movable core is movably arranged within a movable core guide bore with opposing the rear end thereof with a tip end of a cylindrical core portion of a stationary core and opposing a conical valve head portion to a valve seat. A movable core spring is arranged between the movable core and an inner collar which is arranged within a fuel passage of the housing in pre-loaded fashion. A valve head portion is seated on the valve seat and a gap corresponding to a fully open stroke of said movable core is defined between the rear end of the movable core and the tip end of the cylindrical core portion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a fuel injection valve assembly 
to be employed in a fuel injection system for an internal combustion 
engine for an automotive vehicle and so forth. 
2. Description of the Related Art 
Japanese Unexamined Patent Publication (Kokai) No. Showa 59-136560 
discloses a conventional electromagnetic fuel injection valve assembly. 
The electromagnetic fuel injection valve assembly, as disclosed in the 
above-identified publication, is illustrated in FIG. 9. In the discussion 
given hereinafter, the electromagnetic fuel injection valve will be simply 
referred to as a fuel injection valve. For the purpose of disclosure, the 
upper side in the drawing will be referred to as rear side and the lower 
side will be referred to as front side. 
The reference numeral 70 denotes a housing which is formed with a large 
diameter flange receptacle bore 70C located in the vicinity of a rear end 
70A. A coil bobbin receptacle bore 70E is defined at front side of a 
shoulder 70D of the flange receptacle bore 70C. The coil bobbin receptacle 
bore 70E is continuously formed with a smaller diameter movable core guide 
bore 70G via a shoulder 70F. A valve seat 70J is defined at the radially 
inner end of a shoulder 70H extending from the movable core guide bore 
70G. A fuel injection cavity 70K extending to a tip end 70B is defined at 
the front side of the valve seat 70J. 
The flange receptacle bore 70C, the coil bobbin receptacle bore 70E, the 
movable core guide bore 70G and the fuel injection cavity 70K are 
coaxially formed within the housing 70 in axial alignment. Furthermore, an 
injection aperture 70L is formed to extend from the fuel injection cavity 
70G to the tip end 70B. At the axially intermediate portion of the movable 
core guide bore 70G there is an annular groove 70M having greater diameter 
than that of the movable core guide bore 70G. 
Reference numeral 71 denotes a stationary core the construction of which is 
described below. Reference numeral 71A denotes an annular flange portion 
radially extending from a core body of the stationary core 71 and engaging 
with the flange receptacle bore 70C. A fuel introducing cylindrical 
portion 7lB is formed at the rear side of the annular flange portion 71A. 
A cylindrical core portion 71C is formed in the core body and extending to 
the tip end 71E of the stationary core 71. 
Reference numeral 72 denotes a coil bobbin which is constructed as set out 
below. Reference numeral 72A denotes a cylindrical portion formed into a 
cylindrical-shaped configuration. At the rear end of the cylindrical 
portion 72A, a read end A side radial flange portion 72B is formed, and at 
the front end thereof, a front end B side radial flange portion 72C is 
formed. On the other hand, a coil 72D is wound around the outer periphery 
of the cylindrical portion 72A. The coil 72D is terminated to a terminal 
72E extending radially from the rear end side radial flange portion 72B. 
Reference numeral 73 denotes a movable core which is constructed as set out 
below. Reference numeral 73A denotes a cylindrical portion. The 
cylindrical portion 73A has a conical valve head portion 73C at a tip end 
73B thereof. Also, the cylindrical portion 73A has a radially extending 
flange portion 73D. In the movable core 73, a fuel flow path 73F extends 
from a rear end 73E of the cylindrical portion 73A to the tip end 73B and 
further extends in the radial direction for flowing fuel in the vicinity 
of a fuel metering valve portion formed by the valve seat 70J and the 
valve head 73C. 
The components set forth above are assembled in the following manner. 
First, the movable core 73 is arranged within the movable core guide bore 
70G via the larger diameter rear portion of the housing 70. At this time, 
the valve head portion 73C is arranged in contact with the valve seat 70J, 
and the annular flange portion 73D is disposed within the annular groove 
70M. The width (length in the longitudinal direction) is set to be greater 
than the thickness of the annular flange portion 73D. Thus, a stroke of 
the movable core 73 to a fully open position of the fuel metering valve 
portion is determined by a difference between the width of the annular 
groove 70M and the thickness of the annular flange portion 73D. 
Next, the coil bobbin 72 is disposed within the coil bobbin receptacle hole 
70E. At this time, the terminal 72E is externally extended sidewardly from 
the housing 70. 
Then, the annular flange 71A of the stationary core is inserted into the 
flange receptacle bore 70C and thus arranged above the shoulder 70D. At 
this time, the cylindrical core portion 71C is disposed within the 
cylindrical portion 72A of the coil bobbin 72. Also, between the 
cylindrical core portion 71C and the movable core 73, a movable core 
spring 73J is disposed in preloaded fashion. In such condition, the rear 
end 70A of the housing 70 is clamped inwardly toward the annular flange 
portion 71A. 
Thus, the stationary core 71 and the coil bobbin 72 are fixedly arranged 
within the housing 70. However, the movable core 73 is movably arranged 
within the movable core guide bore 70G. At this position, the rear end 73E 
of the movable core 73 is placed in opposition to the tip end 71E of the 
stationary core 73. The valve head portion 73C is urged toward the valve 
seat 70J by means of the movable core spring 73J. 
When current is not supplied to the coil 72D, no magnetic force is 
generated in a magnetic circuit formed by the stationary core 71, the 
housing 70 and the movable core 73. Therefore, the movable core 73 is 
urged toward the tip end B by a spring force of the movable core spring 
73J so that the valve head portion 73 is seated on the valve seat 70J in 
closing position for closing the fuel metering Valve portion. Accordingly, 
the fuel supplied within the movable core guide bore 70G and reaching to 
the valve seat 70J from the fuel flow passage 71F of the stationary core 
71 and the fuel flow passage 73F of the movable core 73, is shut-off at 
the fuel metering valve portion of the valve seat 70J and the valve head 
portion 73C. Therefore, no fuel is injected toward outside from the 
injection aperture 70L. 
When current is supplied to the coil 72D, a magnetic force is generated 
within the magnetic circuit to draw the movable core 73 toward the 
stationary core 71 against the spring force of the movable core spring 
73J. At the condition where the annular flange 73D of the movable core 73 
is in contact with the rear end surface 70N of the annular groove 70M, 
motion of the movable core 73 toward the rear end A is stopped to open the 
fuel metering valve portion of the valve head portion 73C and the valve 
seat 70J. Accordingly, the fuel supplied into the movable core guide bore 
70G via the fuel flow passages 71F and 73F passes the fuel metering valve 
portion and the fuel injection cavity 70K to be injected through the fuel 
injection aperture 70L. 
The conventional fuel injection valve assembly constructed as set forth 
above has the following drawbacks. 
(1) It is not possible to lower production cost of the housing. The housing 
is normally formed by forging, and a press reduction process, etc. 
However, in the foregoing construction, since the annular groove having 
greater diameter is located at the axially intermediate portion of the 
movable core guide bore, the foregoing process cannot be employed, and the 
production process can be complicated to make it difficult to improve 
production efficiency. On the other hand, it is important to form the 
annular groove with high precision since the axial width of the annular 
groove determines the stroke of the movable core at fully open position. 
Since the recessed groove is formed by expanding the diameter of the 
movable core guide bore, it is difficult to form the groove width with 
high precision. It is also difficult to measure the groove width. This is 
one of causes for degradation of production efficiency. 
(2) It is not possible to lower production cost of the movable core. The 
diameter of the movable core is univocally determined by the area of the 
magnetic passage formed between the surface of the tip end of the 
cylindrical core portion of the stationary core and the surface of the 
read end of the movable core. For improved dynamic characteristics of the 
movable core, the diameter of the movable core should to be as small as 
possible. On the Other hand, at the intermediate portion of the 
cylindrical portion of the movable core, the annular flange portion 
extends radially outward. This inherently requires that the diameter of 
the material of the movable core before processing has to be greater than 
that external diameter of the annular flange portion. Thus, the cost of 
material for the movable core is increased. Furthermore, since the 
diameter of the cylindrical portion other than the annular flange portion 
has to be reduced for obtaining necessary magnetic passage area, the 
production cost of the movable core can be further increased. 
(3) It is not possible to lower the cost of assembling the fuel injection 
valve assembly. To lower the cost of assembling the fuel injection valve 
assembly, it has been customary to automatically assemble the components 
with the housing by inserting them from one direction. However, in case of 
the conventional device described above, since the movable core has the 
annular flange portion extending radially outward, the movable core can 
not be simply inserted into the movable core guide bore. Accordingly, 
special arrangement is required in assembling the fuel injection valve 
assembly. Thus, automatic assembling by inserting the components from one 
direction is difficult. This increases assembling cost. 
(4) It is not possible to satisfy both the requirements for dynamic 
characteristics and durability of the movable core. The cylindrical 
portion of the movable core is formed to have constant diameter through 
the entire length from the rear end to the tip end, and, on the outer 
periphery of the cylindrical portion of the movable core in the vicinity 
of the tip end thereof, fuel flow conduits are opened. The fuel flowing 
from the fuel flow conduits flows toward the fuel metering valve portion 
constituted by the valve seat and the valve head portion with an annular 
gap between the outer periphery of the cylindrical portion at the tip end 
side of the movable core and the inner periphery of the movable core guide 
bore at the tip end side. In order to permit the fuel to flow, the annular 
gap between the outer periphery of the cylindrical portion at the tip end 
side of the movable core and the inner periphery of the movable core guide 
bore at the tip end side has to be greater than or equal to 1 mm. Then, an 
identical annular gap is inherently formed between the outer periphery of 
the cylindrical portion at the rear end side of the movable core and the 
inner periphery of the movable core guide bore at the rear end side. Such 
relatively large gap at the rear end side permits tilting of the movable 
core to cause local contact between the outer periphery of the movable 
core and the inner periphery of the movable core guide bore to cause 
friction force serving as resistance for smooth axial movement of the 
movable core. Also, reciprocation of the movable core while maintaining 
local contact between the outer periphery of the movable core and the 
inner periphery of the movable core guide bore should cause wearing of the 
contacting portion to make it difficult to stably control fuel for a long 
period. It should be noted that, in order to prevent tilting of the 
movable core, the gap between the between the outer periphery of the 
movable core and the inner periphery of the movable core guide bore has to 
be quite small, i.e., on the order of 10 .mu.m. 
SUMMARY OF THE INVENTION 
The present invention has been developed in view of the problem set forth 
above. It is therefore an object of the present invention to provide a 
fuel injection valve assembly which can be produced with lower cost of the 
major components and that can be easily assembled so as to provide an 
inexpensive fuel injection valve assembly. 
Another object of the present invention is to provide a fuel injection 
valve assembly which can achieve satisfactory high dynamic characteristics 
and durability. 
In order to accomplish and other objects, according to one aspect of the 
invention, an electromagnetic fuel injection valve assembly comprising: 
a housing coaxially defining a flange receptacle bore of a large diameter, 
a coil bobbin receptacle bore of a medium diameter, a movable core guide 
bore of a small diameter, a conical valve seat having smaller diameter 
than that of the movable core guide bore and a fuel injection cavity 
having smaller diameter than the valve seat, in order from a rear end to a 
tip end; 
a stationary core having an annular flange portion to be inserted into the 
flange receptacle bore of the housing, a fuel induction cylinder portion 
projecting from the annular flange portion to the rear end, a cylindrical 
core portion projecting from the annular flange portion to the tip end, a 
fuel passage defined from the rear end of the fuel induction cylinder 
portion to the tip end of the cylindrical core portion, and a terminal 
insertion hole defined perpendicularly to the annular flange portion; 
a coil bobbin having a coil wound around the outer periphery of a 
cylindrical portion and a terminal connected to the coil and extending 
from the rear end side flange portion of the cylindrical portion toward 
the rear end; 
a movable core having a cylindrical portion movably arranged within the 
movable core guide bore, a smaller diameter cylindrical stem portion 4C 
extending from a tip end of the cylindrical stem portion toward the tip 
end of sad housing and having smaller diameter than that of the 
cylindrical stem portion, a conical valve head portion extended from a tip 
end of the smaller diameter cylindrical portion toward the tip end of the 
housing and a fuel flow passage defined from a rear end of the cylindrical 
stem portion toward the smaller diameter cylindrical portion and opening 
to an outer periphery of the smaller diameter cylindrical portion; 
the annular flange portion of the stationary core being disposed within the 
flange receptacle bore, 
the cylindrical core portion being extended into the coil bobbin receptacle 
bore of the housing; 
the coil bobbin being disposed between the coil receptacle bore of the 
housing and the outer periphery of the cylindrical core portion, 
the terminal being extended rearwardly from the rear end of the housing 
through a terminal insertion hole defined in the annular flange portion of 
the stationary core, 
the cylindrical stem portion of the movable core being movably arranged 
within the movable core guide bore with opposing the rear end thereof with 
the tip end of the cylindrical core portion of the stationary core and 
opposing the conical valve head portion to the valve seat, and 
a movable core spring being arranged between the movable core and an inner 
collar which is arranged within the fuel passage of the housing in 
pre-loaded fashion, the valve head portion being seated on the valve seat 
and a gap corresponding to a fully open stroke of the movable core being 
defined between the rear end of the movable core and the tip end of the 
cylindrical core portion. 
In the preferred construction, a liquid state bond is applied between the 
flange receptacle bore of the housing and the outer periphery of the 
annular flange portion of the stationary core, and between the terminal 
insertion hole of the annular flange portion and the outer periphery of 
the terminal, and subsequently, the rear end of the housing is clamped 
radially inward toward the annular flange portion. In the alternative, the 
liquid state bond is applied between the flange receptacle bore and the 
outer periphery of the annular flange portion of the stationary core and 
between the terminal insertion hole of the annular flange and the outer 
periphery of the terminal. 
The fuel injection cavity defined in the housing may be a hemisphere shaped 
configuration. A wall thickness of the hemispherical fuel injection cavity 
may be less than or equal to 0.5 mm, and a fuel injection aperture may be 
formed substantially perpendicularly to the hemisphere surface of the fuel 
injection cavity. A plurality of the fuel injection apertures may be 
arranged in circumferential alignment about the center of the hemisphere. 
Also, a given number of the fuel injection apertures may be arranged at a 
regular interval to form a fuel injection aperture group, and a plurality 
of fuel injection aperture groups may be arranged along the circumference 
about the center of the hemisphere. 
The electromagnetic fuel injection valve assembly may further comprise a 
protective cylindrical portion provided on the tip end of the housing, the 
protective cylindrical portion extending toward the tip end of the housing 
beyond the fuel injection cavity and surrounding the outer periphery of 
the fuel injection cavity. 
Also, a ring-shaped groove may be defined on the outer periphery of the 
annular flange portion of the stationary core. Alternatively, a plurality 
of vertically extending grooves extending from the tip end of the 
cylindrical stem portion to the portion in the vicinity of the rear end of 
the cylindrical stem portion may be formed on the outer periphery of the 
cylindrical stem portion. 
The electromagnetic fuel injection valve assembly may further comprise a 
hemisphere-shaped projection formed integrally with the valve head portion 
of the movable core and extending from the tip end of the valve head 
portion, the hemisphere-shaped projection having a shape that is 
substantially complementary with that of the fuel injection cavity for 
defining a substantially uniform hemisphere-shaped fine gap therebetween. 
With the construction described above, since the flange receptacle bore, 
the coil bobbin receptacle bore, the movable core guide bore, the valve 
seat and the fuel injection cavity are coaxially arranged within the 
housing with reducing respective diameter in order, manufacture of the 
housing is facilitated. Also, the cylindrical stem portion of the movable 
core can be selected to have the minimum possible diameter satisfying the 
requirement for the magnetic path area and have no larger diameter 
portion, thereby reducing material cost of the movable core. Furthermore, 
since the movable core, the coil bobbin and the stationary core are 
sequentially inserted into the housing and since the terminal can be 
inserted through the terminal receptacle hole, the fuel injection valve 
assembly can be easily assembled. Thus, the production cost of the fuel 
injection valve assembly can be lowered. Also, the cylindrical stem 
portion of the movable core is movably guided with a fine clearance with 
the inner periphery of the movable core guide bore, tilting of the movable 
core can be restricted to improve dynamic characteristics and durability. 
On the other hand, since the liquid state bond is applied between the 
flange receptacle bore of the housing and the outer periphery of the 
annular flange portion of the stationary core, and between the terminal 
insertion hole of the annular flange portion and the outer periphery of 
the terminal, and subsequently, the rear end of the housing is clamped 
radially inward toward the annular flange portion, a seal in the gap 
portion can be securely maintained without requiring special sealing 
material. Thus, workability in assembling can be significantly improved to 
contribute to lowering of the production cost. 
In the alternative, since the liquid state bond is applied between the 
flange receptacle bore and the outer periphery of the annular flange 
portion of the stationary core and between the terminal insertion hole of 
the annular flange and the outer periphery of the terminal, a seal in the 
gap portion can be certainly maintained without requiring special sealing 
material. Furthermore, since the inner periphery of the flange receptacle 
bore and the outer periphery of the annular flange are fixedly bonded, 
clamping the rear end of the housing radially inward toward the annular 
flange portion is facilitate. This makes assembly even easier contributing 
to lowering of the production cost. 
Also, since the fuel injection aperture is formed perpendicularly to the 
hemisphere-shaped fuel injection cavity having wall thickness of less than 
or equal to 0.5 mm, the fuel injection aperture having a quite fine 
diameter can be made quite accurately and satisfactorily. 
Since a plurality of said fuel injection apertures are arranged in 
circumferential alignment about the center of the hemisphere, fuel can be 
injected from respective fuel injection apertures in oblique direction. 
Thus, finely atomized fuel may form conical spray configuration. 
Since a given number of fuel injection apertures are arranged at a regular 
interval to form a fuel injection aperture group, and a plurality of fuel 
injection aperture groups are arranged along the circumference about the 
center of the hemisphere, a conical spray of atomized fuel can be injected 
toward one predetermined direction from one fuel injection aperture group. 
Also, a conical spray of atomized fuel can be injected toward the other 
predetermined direction from another fuel injection aperture group. This 
is suitable as the fuel injection valve assembly in a multi-induction type 
engine having a plurality of suction valves. 
The electromagnetic fuel injection valve assembly further comprises a 
protective cylindrical portion provided on the tip end of said housing. 
The protective cylindrical portion extends toward the tip end of said 
housing beyond said fuel injection cavity and surrounds the outer 
periphery of said fuel injection cavity. Thus, the fuel injection aperture 
can be protected. Therefore, the fuel injection aperture can be certainly 
protected upon production of the fuel injection valve assembly and in 
loading on the engine. Furthermore, deposition of the deposit on the fuel 
injection aperture can be effectively restricted. 
By depressing the annular flange portion from the rear end side toward the 
tip end side after insertion of the annular flange portion of the 
stationary core into the flange receptacle bore of the housing, the ring 
groove is crushed to permit accurate adjustment of the fully open stroke 
of the movable core. 
By providing the vertical groove, the movable core can be supported a 
centered position without varying the sliding gap in the longitudinal 
direction between the outer periphery of the cylindrical stem portion of 
the movable core and the movable core guide bore. Furthermore, sliding 
resistance between the outer periphery of the cylindrical stem portion of 
the movable core and the movable core guide bore is reduced. Thus, dynamic 
characteristics of the movable core and toughness of movable core in 
biting of the foreign matter is improved. 
Upon closure of a fuel metering valve portion formed by the valve head 
portion of the movable core and the valve seat, the volume of the chamber 
of the fuel injection cavity can be effectively reduced. Therefore, 
after-dripping of the fuel (upon stopping fuel injection) and deposition 
of deposits on the fuel injection aperture are effectively reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention will be discussed hereinafter in detail in terms of 
preferred embodiments with reference to the accompanying drawings, 
particularly to FIGS. 1 to 8. In the following description, numerous 
specific details are set forth in order to provide a thorough 
understanding of the present invention. It will be obvious, however, to 
those skilled in the art that the present invention may be practiced 
without these specific details. In other instances, well-known structures 
are not shown in detail in to not unnecessary obscure the present 
invention. 
The first embodiment of a fuel injection valve assembly according to the 
present invention will be discussed with reference to FIG. 1. The 
reference numeral 1 denotes a housing formed of a magnetic material, 1A 
denotes a large diameter flange receptacle bore opening toward the rear 
end 1B of the housing 1. 1C denotes a coil bobbin receptacle bore 
continuous with the large diameter flange receptacle bore across a stepped 
portion 1D and extends toward a tip end B. The diameter of the coil bobbin 
receptacle bore 1C is smaller than the diameter of the flange receptacle 
bore 1A. The diameter of the coil bobbin receptacle bore 1C will be 
referred to hereinafter as "medium diameter). 1E denotes a movable coil 
guide bore continuous to the coil bobbin receptacle bore 1C across a 
stepped portion 1F and has a diameter smaller than the diameter of the 
coil bobbin receptacle bore 1C. 1G denotes a valve seat of truncated 
conical-shaped configuration. The valve seat 1G is continuous to the 
movable core guide bore 1E across a stepped portion 1H. The largest 
diameter of the truncated conical valve seat 1G is smaller than the 
diameter of the movable core guide bore 1E. 1J denotes a fuel injection 
cavity formed as extension of the truncated conical valve seat 1G toward 
the tip end 1K. 
Namely, within the housing 1, the flange receptacle bore 1A, the coil 
bobbin receptacle bore 1C, the movable core guide bore 1E, the valve seat 
1G and the fuel injection cavity. 1J are coaxially arranged from the rear 
end 1B to the tip end 1K. Furthermore, the diameters of respective bores 
are gradually reduced from the rear end 1B to the tip end 1K. Also, a fuel 
injection conduit 1L communicated with the fuel injection cavity 1J and 
opening to the tip end 1K of the housing 1, is formed. 
A stationary core 2 is formed of a magnetic material, and constructed as 
follow. The reference numeral 2A denotes an annular flange portion 
inserted into the flange receptacle bore 1A. From the annular flange 
portion 2A, a fuel introduction cylindrical portion 2B is extended toward 
the rear end A. Also, a cylindrical core portion 2C entering into the coil 
bobbin receptacle bore 1C is extended from the annular flange portion 2A 
toward the tip end B. A fuel passage 2F is formed from the read end 2D to 
the tip end 2E through the fuel introduction cylindrical portion 2B. On 
the other hand, in the annular flange portion 2A, a terminal insertion 
hole 2G is formed in a direction perpendicularly to the annular flange 
portion 2A. In other words, the terminal insertion hole 2G is formed along 
the longitudinal axis of the stationary core 2. It should be noted that 2H 
denotes a pipe-shaped inner collar arranged within the fuel passage 2F by 
way of press fitting. 
A coil bobbin 3 is formed of a synthetic resin material. 3A denotes a 
cylindrical portion formed with a through hole therein. An annular rear 
end side flange portion 3B is formed at the rear end A side of the 
cylindrical portion 3A. An annular tip end side flange portion 3C is 
formed at the tip end B side. A coil 3D is wound around the outer 
periphery of the cylindrical portion 3A. On the rear end side flange 
portion 3B, a terminal 3E oriented toward the read end A is provided. The 
terminal 3E is connected to the coil 3D. As shown, the terminal 3E is 
implanted in a terminal post 3F extending toward the rear end A side from 
the rear end side flange portion 3B. Before assembling the coil bobbin 3 
within the housing 1, the terminal 3E extends substantially 
perpendicularly toward the rear end A. 
A movable core 4 is formed of a magnetic material. 4A denotes a cylindrical 
portion movably arranged with a fine gap in the order of 10 .mu.m, for 
example, with respect to the movable core guide bore 1E. From the tip end 
4B of the cylindrical portion 4A, a small diameter cylindrical portion 4C 
having sufficiently smaller diameter than the diameter of the cylindrical 
portion 4A, is extended toward the tip end B. A truncated conical valve 
head portion 4E is formed at the tip end B side of the tip end 4D of the 
small diameter cylindrical portion 4C. Cylindrical portion 4A, the small 
diameter cylindrical portion 4C and the valve head portion 4E are 
coaxially formed in series. From the rear end 4F of the cylindrical 
portion 4A, a fuel passage 4G is formed toward the small diameter 
cylindrical portion 4C. The downstream of the fuel passage 4G opens to the 
outer periphery of the small diameter cylindrical portion 4C. 
The first embodiment of the fuel injection valve assembly, according to the 
present invention is assembled in the following manner. From the opening 
at the rear end 1B of the housing 1, the movable core 4 having a movable 
core spring 5 of a coil spring within the fuel passage 4G is inserted into 
the movable core guide bore 1E of the housing 1 from the opening at the 
rear end 1B of the housing 1. By this, the cylindrical portion 4A and the 
small diameter cylindrical portion 4C of the movable core 4 are arranged 
within the movable core guide bore 1E. Then, the valve head portion 4E is 
arranged in opposition to the valve seat 1G. 
Next, the coil bobbin 3 is inserted into the coil bobbin receptacle bore 1C 
from the opening of the rear end 1B. By this, the tip end side flange 
portion 3C of the coil bobbin 3 is abutted onto the stepped portion 1F, 
and the a part of the outer periphery at the read end 4F side of the 
cylindrical portion 4A of the movable core 4 is arranged in opposition 
within the cylindrical portion 3A of the coil bobbin 3. 
Next, the annular flange portion 2A of the stationary core 2 is inserted 
within the flange receptacle bore 1A of the housing 1 from the opening at 
the rear end 1B. The annular flange portion 2A is abutted on the stepped 
portion 1D of the flange receptacle bore 1A. The cylindrical core portion 
2C is arranged within the cylindrical portion 3A of the coil bobbin 3. 
Furthermore, the terminal 3E including the terminal boss 3F of the coil 
bobbin 3 is arranged to project toward the rear end A through the terminal 
insertion hole 2G of the annular flange portion 2A. In such condition, the 
rear end 5A of the movable core spring is abutted on the tip end of the 
inner collar 2H. Thus, the movable core 4 is urged toward the tip end B by 
the spring force of the movable core spring 5. The valve head portion 4E 
abuts against the valve seat 1G. Then, a gap corresponding to the fully 
open stroke of the movable core 4 is defined between the rear end 4F of 
the cylindrical portion 4A of the movable core 4 and the tip end 2E of the 
cylindrical core portion 2C of the stationary core 2 opposing to the 
former. 
After thus arranging the movable core 4, the coil bobbin 3, the movable 
core spring 5 and the stationary core 2 within the housing, the rear end 
1B of the housing 1 is clamped radially inward toward the annular flange 
portion 2A of the stationary core 2. Thus, respective components set forth 
above are retained within the housing 1. 
Then, the terminal 3E extending toward rear end A beyond the rear end 1B of 
the housing 1 is bent in the desired direction. Thereafter, by way of out 
molding of a synthetic resin material, a coupler on the outer periphery of 
the rear end 1B of the housing 1 and a part of the outer periphery of the 
fuel introduction cylinder portion 2B are surround together with a coupler 
for the terminal 3E, in integral fashion. Thus assembling of the fuel 
injection valve assembly can be completed. 
Fuel supplied into the fuel passage 2F of the fuel introduction cylindrical 
portion 2B reaches the fuel passage 4G of the movable core 4 via the fuel 
passage 2F of the cylindrical core portion 2C. The fuel within the fuel 
passage 4G reaches an annular fuel passage 6 defined by the small diameter 
cylindrical portion 4C of the movable core 4 and the movable core guide 
bore 1E. While a current is not supplied to the coil 3D, the valve head 
portion 4E is seated on the valve seat 1G to maintaining the fuel metering 
valve portion defined therebetween in shut-off position. Therefore, no 
fuel is injected through the fuel injection aperture 11. 
On the other hand, when the current is supplied to the coil 3D via the 
terminal 3E, a magnetic force is generated in the magnetic circuit formed 
by the housing 1, the movable core 4 and the stationary core 2. By the 
magnetic force thus generated, the movable core 4 is drawn toward the 
stationary core 2 against the spring force of the movable core spring 5. 
Then, the rear end 4F of the movable core 4 abuts onto the tip end 2E of 
the cylindrical core portion 2 to release the valve head portion 4E from 
the valve seat 1G and whereby the fuel metering valve is opened to 
introduce the fuel into the fuel injection cavity. Then, the controlled 
amount of fuel is injected through the fuel injection aperture 1L. 
By the shown embodiment of the fuel injection valve, (1) a production cost 
of the housing 1 can be lowered. Namely, in the housing, the flange 
portion receptacle bore 1A, the coil bobbin receptacle bore 1C, the 
movable core guide bore 1E, the valve seat 1G and the fuel injection 
cavity 1J are formed in continuous fashion, in order from the rear end 1B 
to the tip end 1K, and the diameters of respective bores are gradually 
reduced from the rear end 1B to the tip end 1K. Thus, the housing 1 can be 
formed in simple process such as forging, press reduction process or so 
forth to lower the production cost of the housing. 
Machining may be performed for the movable core guide bore 1E and the valve 
seat G which are must have high precision in the bore diameter and 
improvement of the surface roughness. In such case, since the guide hole 
has already been formed by forging or so forth, machining thickness as can 
be quite small. Therefore, such machining will not significantly affect 
for lowering of the production cost. 
On the other hand, the fully open stroke of the movable core 4 is defined 
by a gap between the rear end 4F of the movable core 4 and the tip end 2E 
of the cylindrical core portion 2C. Therefore, it is not necessary to 
provide a recessed groove for controlling the fully open stroke of the 
movable core within the peripheral wall of the housing 1. Thus, 
productivity of the housing can be significantly improved. (2) The 
production cost of the movable core 4 can be lowered. The diameter of the 
movable core 4 is determined depending upon the magnetic path area formed 
between the surface of the tip end 2E of the cylindrical core portion 2C 
and the rear end 4F thereof. In view of improvement of the dynamic 
characteristics of the movable core 4 with reduction of the weight as 
light as possible, the diameter of the movable core 4 is selected at 
possible smallest diameter. In case of the movable core to be employed in 
the shown embodiment, no flange portion extends radially outward for 
controlling the fully open stroke of the movable core, the diameter of the 
movable core 4 can be minimum while still satisfying the requirement for 
the magnetic path area. Accordingly, the diameter of the elemental 
material of the movable core 4 can be slightly greater than the diameter 
of the cylindrical portion 4A of the movable core 4. Therefore, in case of 
the movable core to be formed of a relatively expensive material, such as 
magnetic stainless steel material or so forth, material cost can be 
lowered to contribute for reduction of the production cost. 
On the other hand, the small diameter cylindrical portion 4C formed at the 
tip end B side of the cylindrical portion 4A is formed to have smaller 
diameter than that of the cylindrical portion 4. Therefore, the smaller 
diameter cylindrical portion 4C never affects selection of the diameter of 
the cylindrical portion. Also, the smaller diameter cylindrical portion 4C 
may contribute for reduction of the weight of the movable core 4. (3) It 
is also possible to reduce assembling cost of the fuel injection valve 
assembly. Assembling of the fuel injection valve assembly is performed by 
disposing the movable core 4, the movable core spring 5, and the coil 
bobbin 5 into the housing 1 through the flange receptacle bore portion 1A. 
Subsequently, the annular flange portion 2A is inserted into the flange 
receptacle bore 1A with inserting the terminal 3E including a terminal 
boss 3F of the coil bobbin 3 into a terminal insertion hole 2G of the 
annular flange portion 2A of the stationary core 2. Then, the rear end 1B 
of the housing 1 is clamped radially inward toward the annular flange 
portion 2A. With the construction set forth above, since respective 
components are inserted in the same orientation within the housing 1 from 
the rear end A to the tip end B, automatic assembling can be easily 
performed. Accordingly, assembling can be facilitated to significantly 
reduce assembling cost. 
As set forth above, since the production cost of the housing 1 can be 
lowered, the production cost of the movable core 4 can be lowered and the 
assembling cost of the fuel injection valve assembly can be lowered, 
overall production cost of the fuel injection valve assembly can be 
significantly lowered. 
On the other hand, the movable core 4 is formed with the cylindrical 
portion 4A of larger diameter and the smaller diameter cylindrical portion 
4C located at the tip end B side of the cylindrical portion 4A and having 
smaller diameter. Therefore, the cylindrical portion 4A can be movably 
guided within the movable core guide bore 1E, and the smaller diameter 
cylindrical portion 4C can be placed within the annular fuel passage 6 
having a large annular gap defined by the movable core guide bore 1E. As 
set forth above, the gap between the cylindrical portion 4A and the 
movable core guide bore 1E can be set at fine gap of approximately 10 
.mu.m, for example, irrespective of the dimensions of other components. 
By supporting the cylindrical portion 4A of the movable core 4 with a quite 
fine gap by the movable core guide bore 1E, tilting of the movable core 4 
in reciprocating action can be completely avoided. Thus, the movable core 
4 can smoothly act to improve dynamic characteristics. On the other hand, 
by avoidance of tilting of the movable core 4, there will never be a local 
collision between the movable core 4 and the movable core guide bore 1E. 
Therefore, wearing of the movable core 4 and the movable core guide bore 
1E can be minimized and stable fuel control can be performed over a long 
period of time. 
On the other hand, the fuel within the fuel passage 4G of the movable core 
4 can be supplied into the annular fuel passage 6 from the fuel passage 4G 
opening to the outer periphery of the smaller diameter cylindrical portion 
4C. Therefore, fuel supply toward the fuel metering valve portion will 
never be interfered and thus can be smoothly performed. 
Then, in assembling, the flange receptacle bore 1A, the annular flange 
portion 2A, the terminal insertion bore 2G and the terminal boss 3F at the 
rear end 1B of the housing 1 can be maintained with a seal. This prevents 
internal fuel from externally leaking. The present invention proposes the 
following construction for maintaining seal. 
At first, a liquid state bond can be employed. The liquid state bond is a 
single liquid type silicon denaturated polymer base bond, denaturated 
silicon epoxy matrix type bond or dual liquid type denaturated silicon 
epoxy matrix type bond or so forth can be employed. The set article of the 
liquid state bond has a bonding ability and becomes a rubber-like elastic 
body after application on a bonding portion and setting thereon. 
Then, from the opening at the rear end 1B of the housing 1, the liquid 
state bond is applied into the gap between the flange receptacle bore 1A 
and the outer periphery of the annular flange portion 2A of the stationary 
core 2 and the gap between the terminal insertion hole 2G of the annular 
flange portion 2A and the outer periphery of the terminal boss 3F of the 
coil bobbin 3. Since the bond is in liquid state, the bond penetrates over 
the entire area in the gap and set therein. As set forth above, the gaps 
between the flange receptacle bore 1A and the annular flange portion 2A 
and between the terminal insertion hole 2G and the terminal boss 3F can be 
certainly sealed by the rubber-like elastic body. Thereafter, the rear end 
1B of the housing 1 is clamped radially inward toward the annular flange 
portion 2A. 
With the construction set forth above, it becomes unnecessary to provide 
sealing member, such as an O-ring, square-ring or so forth, arranged 
within the gap portion. Therefore, number of parts can be reduced and 
loading operation of such sealing member becomes unnecessary. This is 
effective for lowering of the production cost of the fuel injection valve 
assembly. Furthermore, it is possible to automatically meter the bond into 
the gap by employing a bond metering and ejecting device having a 
sun-and-planetary type rotor mechanism. Therefore, it becomes possible to 
automatically apply the bond. 
Secondly, another liquid state bond is employed. The liquid state bond is a 
bond containing alkyl-.alpha.-cyanoacrylate as a primary component, a 
compound containing epoxy group or so forth. This type liquid state bond 
has a high bonding force by setting in quite short period. 
Then, from the opening of the rear end 1B of the housing, the liquid state 
bond can be applied into the gap between the flange receptacle bore 1A and 
the outer periphery of the annular flange portion 2A of the stationary 
core 2 and between the gap between the terminal insertion hole 2G and the 
terminal boss 3F of the coil bobbin 3. Since the bond is in liquid state, 
the bond penetrates over the entire area in the gap and set therein. As 
set forth above, the gaps between the flange receptacle bore 1A and the 
annular flange portion 2A and between the terminal insertion hole 2G and 
the terminal boss 3F can be certainly sealed by the rubber-like elastic 
body and bonded at high bonding force. 
With the construction set forth above, it becomes unnecessary to provide 
sealing member, such as an O-ring, square-ring or so forth, arranged 
within the gap portion. Therefore, number of parts can be reduced and 
loading operation of such sealing member becomes unnecessary. Furthermore, 
by bonding the gap portions with high bonding force, it becomes 
unnecessary to clamp the rear end 1B of the housing 1. Therefore, it 
becomes possible to further lower the production cost of the fuel 
injection valve assembly. 
The second embodiment of the fuel injection valve assembly according to the 
present invention will be discussed with reference to FIG. 2. In this 
embodiment, like components are represented by like reference numerals. 
The fuel injection cavity 1J formed at the tip end B side of the valve 
seat 1G of the housing is formed into a hemisphere-shaped configuration. 
The thickness of the fuel injection cavity 1J is less than or equal to 0.5 
mm. Then, the fuel injection aperture 1L is formed substantially 
perpendicularly to the hemisphere surface 1M of the fuel injection cavity 
1J. The hemisphere-shaped fuel injection cavity 1J including the fuel 
injection aperture is illustrated in enlarged fashion in FIG. 3. 
With the construction as set forth above, the following particular effect 
can be achieved. (1) Since the fuel injection cavity 1J is formed into a 
hemisphere-shaped configuration, the wall thickness of the fuel injection 
cavity 1J is less than or equal to 0.5 mm, and the fuel injection aperture 
1L is formed substantially perpendicular to the hemisphere surface 1M of 
the fuel injection cavity 1J, machining precision of the fuel injection 
hole 1 can be remarkably improved to make it possible to obtain accurate 
and uniform fuel atomization. Particularly, since the fuel injection 
aperture having quite fine diameter in the extent of 0.2 mm can be formed 
without edge loss. Thus, improvement of fuel atomization characteristics 
and improvement of fuel metering precision by the fuel injection aperture 
1L can be achieved. (2) When fuel supply to the coil 3D is shut off, the 
valve head portion 4E is seated on the valve seat 1G to shut off the fuel 
metering valve. Thus, fuel supply into the fuel injection cavity via the 
fuel metering valve portion of the valve head portion 4E and the valve 
seat 1G is shut off. However, immediately before shutting off of the fuel 
metering valve portion, the fuel flows into the fuel injection cavity 1J 
by inertia. Then, the fuel flowing into the fuel injection cavity 1J 
concentrates at the tip end side of the hemisphere-shaped fuel injection 
cavity 1J and instantly ejected cavity 1J via the fuel ion cavity 1J via 
the fuel injection aperture 1L. As set forth above, a problem that the 
fuel retained in the fuel injection cavity is evaporated by atmospheric 
temperature of the engine to deposit gummy matter in the fuel in the 
vicinity of the fuel injection aperture 1L for causing reduction of the 
open area of the fuel injection aperture 1L, can be solved completely. 
On the other hand, concerning the fuel injection aperture 1L, when a 
plurality of fuel injection apertures 1L are formed in alignment in the 
circumferential direction C about a center IN of the hemisphere fuel 
injection cavity 1J. Thus, the fuel can be effectively atomized into 
conical configuration (fuel injection aperture 1L is formed substantially 
perpendicularly to the hemisphere surface 1M). In the shown embodiment, 
twelve fuel injection apertures 1L of 0.3 mm diameter are formed on the 
circumferential direction C at 30.degree. interval. 
As set forth above, the fuel is injected relatively linearly toward oblique 
direction from respective fuel injection apertures 1L. By arranging a 
plurality of the fuel injection apertures along the circumference C, the 
conical fuel injected from respective fuel injection apertures is well 
mixed with the air for promoting atomization in comparison with the 
conical fuel injected from single fuel injection aperture. Thus, fuel 
supply characteristics for the engine is improved and whereby combustion 
ability of the engine can be improved. 
Another arrangement of a plurality of fuel injection apertures is 
illustrated in FIG. 5. As shown in FIG. 5, a plurality of fuel injection 
apertures 1L are formed along a circle D to form one fuel injection 
aperture group 1P. When a plurality of fuel injection apertures groups 1P 
are formed in alignment in the circumferential direction C about a center 
IN of the hemisphere fuel injection cavity 1J. Thus, the fuel can be 
effectively atomized into conical configuration (fuel injection aperture 
1L is formed substantially perpendicularly to the hemisphere surface 1M). 
In the shown embodiment, each fuel injection aperture group six fuel 
injection apertures arranged with 60.degree. of angular interval, and two 
fuel injection aperture groups 1P are formed on the circle C with 
180.degree. of angular interval. In other words, one of the fuel injection 
aperture group 1P and the other fuel injection aperture group 1P are 
arranged symmetrically with respect to the center IN. 
Fuel is injected relatively linearly toward oblique direction from 
respective fuel injection apertures groups 1P. By arranging a plurality of 
the fuel injection aperture groups along the circumference C, the conical 
fuels injected from respective fuel injection apertures groups in 
different directions. Such fuel injection valve assembly may be 
effectively employed in a multi-induction valve type engine. From one of 
the fuel injection aperture group 1P, the conical spray of fuel is 
accurately injected toward the first suction valve. From the other fuel 
injection aperture group 1P, the conical spray of fuel is accurately 
injected toward the second suction valve. In particular, in case of the 
multi-induction valve type engine, good engine performance can be 
attained. It should be noted that the number of the fuel injection 
apertures 1L and number of the fuel injection aperture groups may be 
appropriately or arbitrarily selected. 
The third embodiment of the fuel injection valve assembly according to the 
present invention will be discussed with reference to FIG. 6. In the 
following discussion, like reference numerals to those in FIG. 1 identify 
like components. A protective cylinder portion 1R is formed integrally 
with the housing 1, at the tip end B of the housing 1. The protective 
cylinder portion 1R surrounds the outer periphery of the fuel injection 
cavity and extends toward the tip end B from the tip end of the fuel 
injection cavity 1J. In other words, the tip end 1S of the protective 
cylinder portion 1R is extended beyond the tip end B from the fuel 
injection cavity for defining a protective space 1T within the protective 
cylinder portion 1R. 
By providing the protective cylindrical portion 1R, during transportation 
of the fuel injection valve assembly, assembling operation and loading to 
the engine, possibility that the fuel injection aperture and the fuel 
injection cavity 1J are directly subject to external force, can be reduced 
and thus avoid possibility of damaging of the fuel injection aperture 1L 
and the fuel injection cavity 1J to certainly protect them. This is 
desirable from the viewpoint of quality assurance. On the other hand, it 
is known that gummy matter contained in a low quality fuel deposited on 
the circumference of the fuel injection aperture 1L together with dust in 
the air, make it difficult to open the fuel injection aperture 1L within a 
recessed portion of the protective cylindrical portion 1R. Here, in the 
shown embodiment, since the fuel injection aperture 1L is arranged with 
opening in the protective cylinder portion, the deposit effect can be 
efficiently avoided. Furthermore, it becomes unnecessary to prepare the 
cap of other material for forming the protective cylindrical portion 1R. 
The protective cylindrical portion can be formed simultaneously with 
formation of the housing. 
The fourth embodiment of the fuel injection valve assembly according to the 
invention will be discussed with reference to FIG. 2. A ring groove 2J is 
formed on the outer periphery of the annular flange portion 2A of the 
stationary core 2. By providing the ring groove 2J, the ring groove 2J is 
deformed to reduce the groove width by application of the external force 
in the direction from the rear end A to the tip end B for the rear end 
surface of the annular flange portion 2A or the rear end 2D of the fuel 
induction cylindrical portion 2B, in the condition, where the annular 
flange portion 2A of the stationary core 2 is inserted into the flange 
receptacle bore 1A of the housing 1 and the tip end surface 2K of the 
annular flange portion 2A is abutted onto the stepped portion 1D of the 
flange receptacle bore 1A. As set forth above, the tip end 2E of the 
stationary cylindrical core portion 2C of the stationary core 2 is shifted 
toward the tip end B corresponding to the reduction amount of the recessed 
groove. Thus, the gap between the tip end 2E of the stationary cylindrical 
core portion 2C is reduced to permit adjustment of the magnitude of the 
fully open stroke of the movable core 4. On the other hand, the direction 
where the external force for the annular flange portion 2A acts, is the 
direction from the rear end A toward the tip end B and the same as the 
inserting direction of the parts into the housing. Therefore, the 
assembling operation can be automated. 
The fifth embodiment of the fuel injection valve assembly will be discussed 
with reference to FIGS. 2 and 7. The reference numeral 4H denotes a 
plurality of vertical grooves formed on the movable core 4. The vertical 
groove 4H extends from the tip end 4A of the cylindrical portion 4A to 
reach the position in the vicinity of the rear end 4F of the cylindrical 
portion. As can be seen, a plurality of vertical grooves 4H are formed on 
the outer periphery of the cylindrical portion. In the shown embodiment, 
three vertical grooves are formed with 120.degree. of angular interval. 
By providing the vertical groove 4H, sliding resistance between the 
cylindrical portion 4A and the movable core guide bore 1E guiding the 
former can be reduced to achieve improvement of the dynamic 
characteristics of the movable core 4. Also, within the annular fuel 
passage 6, fuel is supplied via the fuel passage 4G opening to the small 
diameter cylindrical portion 4C of the movable core 4. The fine foreign 
matter contained in the fuel in the annular fuel passage 6 tends to be 
retained in the portion of the tip end 4B of the cylindrical portion 4A 
opposing to the fuel passage 6 during reciprocal motion of the movable 
core 4. On the other hand, by opening the vertical grooves 4H to the tip 
end 4B of the cylindrical portion 4A, the foreign matter to be retained 
within the portion of the tip end 4B can penetrate into the vertical 
grooves 4H. Thus, introduction of the foreign matter into the fine gap 
between the cylindrical portion 4A and the movable core guide bore 1E can 
be restricted. Accordingly, good dynamic characteristics of the movable 
core 4 can be maintained for a long period. On the other hand, not forming 
the vertical grooves 4H to the rear end 4F of the cylindrical portion is 
preferred in viewpoint of reduction of the magnetic path area of the 
movable core 4 relative to the cylindrical core portion 2C. 
The sixth embodiment of the fuel injection valve assembly according to the 
present invention will be discussed with reference to FIG. 8. The shown 
embodiment has a hemisphere projection 4K to enter into the fuel injection 
cavity 1J, is integrally extended from the tip end 4J of the valve head 
portion 4E of the movable core 4 toward the tip end B. The hemisphere 
projection 4K is shaped into substantially complementary configuration to 
the hemisphere fuel injection cavity 1J. At the condition where the 
hemisphere projection 4K enters into the fuel injection cavity 1J, a 
substantially uniform hemisphere fine gap 4L is formed by the hemisphere 
projection 4K and the hemisphere surface 1M of the fuel injection cavity 
1J. The hemisphere projection should not contact with the hemisphere 
surface 1M of the fuel injection cavity 1J. With the construction set 
forth above, the volume within the fuel injection cavity 1J corresponds to 
the volume of the hemisphere projection 4K to reduce the volume. 
With the construction set forth above, the fuel introduced into the fuel 
injection cavity 1J via the fuel metering valve portion enters into a 
small volume chamber, a fuel pressure may not be lowered in the fuel 
injection cavity and can be injected through the fuel injection aperture 
1L at an appropriate pressure. Thus, fuel with excellent atomizing 
characteristics can be supplied to the engine. 
On the other hand, the hemisphere fine gap 4L defined by the hemisphere 
surface 1M of the fuel injection cavity 1J and the hemisphere projection 
4K can have substantially uniform gap width. Therefore, when a plurality 
of fuel injection apertures 1L are formed, the fuel pressure to exerted 
upon respective fuel injection apertures 1L from the fine gap 4L becomes 
uniform. Thus, fuel amount to be injected from respective fuel injection 
apertures 1L can be made uniform. 
Furthermore, since the volume of the fuel injection cavity becomes small, 
response of fuel supply through the fuel injection apertures 1L upon 
initiation of opening operation of the movable core 4 can be higher. On 
the other hand, upon closing of the movable core 4, after-dripping of fuel 
from the fuel injection cavity can be reduced. Also, when the valve head 
portion 4E of the movable core 4 abuts onto the valve seat 1G, fuel amount 
retained within the fuel injection cavity can be reduced. By this, 
deposition on the fuel injection aperture 1L can be reduced. 
Although the invention has been illustrated and described with respect to 
exemplary embodiment thereof, it should be understood by those skilled in 
the art that the foregoing and various other changes, omissions and 
additions may be made therein and thereto, without departing from the 
spirit and scope of the present invention. Therefore, the present 
invention should not be understood as limited to the specific embodiment 
set out above but to include all possible embodiments which can be 
embodies within a scope encompassed and equivalents thereof with respect 
to the feature set out in the appended claims.