Fuel injector assembly for fuel-injected engine

A fuel injector assembly in an engine having a plurality of cylinders and intake passages opening respectively into the cylinders includes a housing mounted in each of the intake passages, and a plurality of solenoid-operated fuel injection valves connected to a fuel supply source for injecting fuel through the intake passage into each of the cylinders. The solenoid-operated fuel injection valves are accommodated in the housing. The housing has a magnetic shield layer such as an air gap disposed between the fuel injection valve means. The fuel injection valves are supplied with fuel from the fuel supply source through a common fuel supply passage defined in the housing.

BACKGROUND OF THE INVENTION 
The present invention relates to a fuel injector assembly for a 
fuel-injected engine, which has a plurality of intake passages opening 
into each combustion chamber having respective fuel injection valves 
disposed therein, and more particularly to a fuel injector assembly in 
which fuel injection valves are assembled together with a magnetic shield 
layer therebetween. 
Some recent high-performance engines have two intake passages independently 
opening into each combustion chamber and associated with respective fuel 
injection valves for increased charging efficiency and independent fuel 
control required by the intake passages. One known fuel injection assembly 
for use with such a fuel-injected engine is disclosed in Japanese 
Laid-Open Patent Publication No. 60-32957. In the disclosed arrangement, 
the intake passages have respective solenoid-operated fuel injection 
valves disposed therein. One of the intake passages is opened and closed 
dependent on the rotational speed of the engine or the load on the engine, 
and at the same time the fuel injection valve disposed in said one intake 
passage is controlled in timed relation to the opening and closing of the 
intake passage for improved engine performance, such as greater engine 
output torque. 
Since the fuel injection valves are disposed respectively in the intake 
passages, however, a cylinder head or an intake manifold in which the 
intake passages are defined must have delivery passages defined therein 
for distributing fuel to the respective fuel injection valves. Therefore, 
the cylinder head is complex in configuration, high in cost, and has to be 
assembled through an increased number of steps. 
SUMMARY OF THE INVENTION 
In view of the aforesaid drawbacks of the conventional fuel injector 
arrangement, it is an object of the present invention to provide a fuel 
injector assembly which can be manufactured at a low cost and assembled 
through a small number of steps. 
According to the present invention, there is provide a fuel injector 
assembly in an engine having a plurality of cylinders and intake passages 
opening respectively into the cylinders, comprising a housing mounted in 
each of the intake passages, and a plurality of solenoid-operated fuel 
injection valve means connected to a fuel supply source for injecting fuel 
through the intake passage into each of the cylinders, the plurality of 
solenoid-operated fuel injection valve means being accommodated in the 
housing, the housing having a magnetic shield layer disposed between the 
fuel injection valve means. 
All the solenoid-operated fuel injection valve means associated with each 
cylinder are assembled in the single housing and placed in the 
corresponding intake passage. Since fuel can be supplied through a common 
fuel supply passage to the fuel injection valve means associated with each 
cylinder the cost of manufacture of the fuel injector assembly is reduced, 
and the fuel injection valve means can easily be installed in place. 
Because the magnetic shield layer is disposed between the fuel injection 
valve means, even when solenoids of the fuel injection valve means are 
selectively energized, they are not subjected to magnetic interference and 
can reliably be operated. 
The above and further objects, details and advantages of the present 
invention will become apparent from the following detailed description of 
preferred embodiments thereof, when read in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 through 3 show a fuel injector assembly according to an embodiment 
of the present invention. An intake passage 11 for introducing air is 
defined in the intake manifold or cylinder head of an engine (not shown) 
and has an inlet passage 12 and a pair of first and second branch passages 
13a, 13b branched from the inlet passage 12 and opening into a combustion 
chamber (not shown) in an engine cylinder. The first and second branch 
passages 13a, 13b house therein respective intake valves 14a, 14b for 
selectively opening and closing intake ports of the first and second 
branch passages 13a, 13b. A shutter valve 15b is disposed in the first 
branch passage 13b for selectively opening and closing the first branch 
passage 13b. The intake valves 14a, 14b are openable and closable in 
synchronism with rotation of the crankshaft (not shown) of the engine 
through a known valve operating mechanism. The shutter valve 15a is 
openable and closable by an actuator (not shown) dependent on operating 
conditions of the engine in the manner disclosed in Japanese Laid-Open 
Patent Publication No. 60-32957 or 59-43922, for example. The inlet 
passage 12, or the upstream end of the intake passage 11, is connected to 
an air cleaner or the like for drawing in air. The intake passage 11 is 
provided in combination with one combustion chamber Therefore, a 
four-cylinder engine has four intake passages 11 coupled respectively to 
the four combustion chambers. 
Two fuel injection valves 17a, 17b which are encased in a single housing 16 
are disposed in the intake passage 11 just upstream of the point where the 
inlet passage 12 is branched into the first and second branch passages 
13a, 13b. As shown in FIG. 3, the housing 16 is fixed to a wall defining 
the intake passage 11 and has defined therein a fuel supply hole 18 and 
two housing holes 19a, 19b extending perpendicularly to the fuel supply 
hole 18. The fuel supply hole 18 is connected through a pipe or the like 
to the fuel injector assembly associated with an adjacent engine cylinder, 
and is coupled to a fuel pump (not shown). The housing holes 19a, 19b have 
ends directed toward the substantial centers of the branch passages 13a, 
13b and opposite ends opening into the fuel supply hole 18. The housing 
holes 19a, 19b accommodate therein the respective fuel injection valves 
17a, 17b which comprise springs 20a, 20b, solenoids 21a, 21b, and needle 
valves 22a, 22b. The solenoids 21a, 21b are annularly fixedly positioned 
centrally in the respectively housing holes 19a, 19b and electrically 
connected to a driver circuit 23 (described later). The needle valves 22a, 
22b have needles on their ends which are loosely fitted respectively in 
the end openings of the housing holes 19a, 19b, thus defining fuel 
injection nozzles 24a, 24b. The needle valves 22a, 22b also have 
respective tapered seats 22c, 22d near the needles and engageable with 
corresponding seats around the end openings of the housing holes 19a, 19b 
for closing the fuel injection valves 24a, 24b. The needle valves 22a, 22b 
are axially movably disposed in the housing holes 19a, 19b, respectively, 
and extend through the respective solenoids 21a, 21b. When the solenoids 
21a, 21b are energized, the needle valves 22a, 22b are axially displaced 
to close the fuel injection valves 24a, 24b. The springs 20a, 20b act on 
the respective needle valves 22a, 22b for normally urging them in a 
direction to close the fuel injection nozzles 24a, 24b. 
The housing 16 has a vacant hole or air gap 25 having a rectangular cross 
section defined therein between the housing holes 19a, 19b, the vacant 
hole 25 serving as a magnetic shield air layer The vacant hole 25 lies 
between the solenoids 21a, 21b and extend fully across the solenoids 21a; 
21b to provide a shield against magnetic fluxes produced by the solenoids 
21a, 21b. The vacant hole 25 is filled with air, but may be filled with a 
substance having a low magnetic permeability. 
The driver circuit 23 comprises a battery 26, a switching power transistor 
27a connected between the battery 26 and the solenoid 21a, a power 
transistor 27b connected between the battery 26 and the solenoid 21b, and 
a transistor 28b for controlling the power transistor 27b. The power 
transistor 27b has an emitter connected to the solenoid 21b, a collector 
to the battery 26, and a base to the collector of the transistor 28b. The 
power transistor 27a has an emitter connected to the solenoid 21a, a 
collector to the battery 26, and a base to a control circuit (not shown) 
to which the emitter and base of the transistor 28b are also coupled. 
Dependent on operating conditions of the engine, the control circuit 
produces a control signal to selectively turn on the power transistors 
27a, 27b for selectively energizing the solenoids 21a, 21b of the fuel 
injection valves 17a, 17b to inject fuel. When the engine rotates at a 
high speed, for example, the solenoids 21a, 21b of both of the fuel 
injection valves 17a, 17b are energized to enable the fuel injection 
valves 17a, 17b to inject fuel from the nozzles 24a, 24b into the branch 
passages 13a, 13b. 
When the engine rotates at a low speed, only the solenoid 21a of the fuel 
injection valve 17a is energized to inject fuel into the branch passage 
13a, whereas the other branch passage 13b is closed by the shutter valve 
15b. At this time, since the vacant hole 25 between the solenoids 21a, 21b 
shields the solenoid 21b from the magnetic flux produced by the solenoid 
21a, the fuel injection valve 17b is not triggered into operation by the 
energization of the solenoid 21a. 
Since the two fuel injection valves 17a, 17b are assembled in the single 
housing 16, the fuel injector assembly can easily be installed in place, 
does not make the cylinder head or intake manifold complex in 
configuration, and can be manufactured at a low cost. It is not necessary 
to connect fuel supply pipes respectively to the fuel injection valves 
17a, 17b because the fuel injection valves 17a, 17b share the fuel supply 
hole 18 defined in the housing 16. The cylinder head or intake manifold is 
therefore simple in construction and highly reliable in operation as there 
is no danger of fuel leakage which would otherwise be caused from separate 
fuel supply pipes. 
FIGS. 4 and 5 show a fuel injector assembly according to another embodiment 
of the present invention. Those parts shown in FIGS. 4 and 5 which are 
identical to those in FIGS. 1 through 3 are denoted by identical reference 
numerals. 
According to the embodiment of FIGS. 4 and 5, a housing 16 additionally 
defines therein an auxiliary air passage 29 connected to a region upstream 
of a throttle valve (not shown), and an auxiliary air injection hole 30 
extending from the auxiliary air passage 29 and opening toward one of the 
branch passages 13a. A driver circuit 23 energizes the solenoid 21a of the 
fuel injection valve 17a at all times, and energizes the solenoid 21b of 
the fuel injection valve 17b with the transistor 28b and the power 
transistor 27b based on a control signal from the control circuit. 
With this embodiment, when fuel is injected only from the fuel injection 
valve 17a, auxiliary air is injected from the air injection hole 30 toward 
the spray of fuel injected from the fuel injection valve 17a for promoting 
the atomization of the fuel for better fuel combustion efficiency. 
Although there have been described what are at present considered to be the 
preferred embodiments of the present invention, it will be understood that 
the invention may be embodied in other specific forms without departing 
from the essential characteristics thereof. The present embodiments are 
therefore to be considered in all aspects as illustrative, and not 
restrictive. The scope of the invention is indicated by the appended 
claims rather than by the foregoing description.