Fuel injection quantity adjustment apparatus for fuel injection pump

A pair of solenoids are disposed coaxially with and around a hollow cylindrical cut-off valve. The valve includes an inner non-magnetic sleeve and an outer permanent magnet sleeve. The cut-off valve slidably engages a fuel distributing plunger which injects fuel according to its axial reciprocation. The cut-off valve controls fuel injection quantity via timing of exposure of a fuel injection cut-off port in the plunger. When the pair of solenoids are energized in accordance with operating parameters of the engine, the cut-off valve is moved to a corresponding position along the plunger. A sensor senses the actual position of the cut-off valve for feedback control thereof. A pair of disc-like permanent magnets may be disposed opposite either extreme of travel of the cut-off valve in spaced relationship thereto. A pair of non-magnetic discs may be disposed in place of the pair of disc-like permanent magnets. A biasing member may be disposed between the cut-off valve and the plunger housing to prevent the cut-off valve from being attracted by the plunger housing and for preventing rotation of the cut-off valve relative to the plunger housing. The biasing member may be diaphragm, coil spring or a leaf spring.

BACKGROUND OF THE INVENTION 
The present invention relates to a fuel injection pump for an internal 
combustion engine, and more particularly to a fuel injection adjusting 
apparatus for the pump in which a hollow cylindrical fuel cut-off valve 
opens and closes a fuel escape port in a fuel distributing plunger which 
is rotationally and reciprocally driven therethrough. 
U.S. Pat. No. 3,630,643 to Eheim et al discloses a fuel injection pump 
which includes a fuel distributing plunger which is rotationally and 
reciprocally driven by the rotation of a cam disc connected to a drive 
shaft of an internal combustion engine. When the plunger is in its 
rarefaction stroke, an intake groove in the plunger can communicate with a 
fuel inlet passage so that fuel is drawn into a working space which is 
compressed during the compression stroke of the plunger, so that fuel in 
the plunger working space is injected via an axial passage in the plunger, 
one of a plurality of check valves and a corresponding injector into the 
corresponding cylinder when the axial passage in the plunger communicates 
during its rotation with a corresponding fuel passage leading to the check 
valve. 
Fuel injection by the pump terminates when fuel in the working space is 
vented into a chamber within the pump housing via a cut-off port provided 
in the plunger. The part opens and closes via axial displacement of a 
hollow cylindrical cut-off valve slidably fitted over the plunger. 
A mechanism which controls the cut-off valve includes a pair of 
electromagnetic windings or solenoids wound around a C-shaped core and a 
magnet disposed pivotably within the magnetic field of the core. The 
magnet is supported by a shaft, the lower end of which carries an 
eccentrically mounted ball-and-socket joint in conjunction with the 
cut-off valve, whereby rotation of the magnet is transmitted to axially 
move the cut-off valve. 
The electric current flowing through the pair of electromagnetic windings 
or solenoids and therefore the angular motion of the magnet are controlled 
by an amplifier in accordance with the output of a controller which 
receives signals indicative of operating parameters of the internal 
combustion engine, for example, engine speed, accelerator pedal position, 
air intake pressure, engine temperature, atmospheric temperature, etc. 
With this conventional fuel injection pump, since the torque of the 
pivotting magnet is transmitted to the cut-off valve via its shaft and the 
eccentrically mounted ball-and-socket joint, the mechanism is considerably 
complicated. Also design tolerances and normal wear on the ball-and-socket 
joint produce errors in the displacement of the cut-off valve. 
In addition, a conventional position sensor senses the position of the 
cut-off valve indirectly in such a manner that instead of sensing the 
axial displacement of the cut-off valve, the rotation of the magnet is 
converted into linear displacement of a ferrite core, which linear 
displacement is sensed by a pair of inductance coils wound around the 
ferrite core and energized by an oscillator. This does not result in good 
control accuracy. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a fuel injection 
quantity adjusting apparatus for a fuel injection pump with improved 
control accuracy. 
According to the present invention, the hollow cylindrical cut-off valve 
fitting slidably over the fuel distributing plunger includes a permanent 
magnet. A pair of drive solenoids are coaxially disposed around the 
cut-off valve and supplied with a control current determined in accordance 
with engine operating parameters. Energization of the solenoid 
magnetically moves the cut-off valve along the plunger. A position sensor 
electromagnetically senses the actual position of the cut-off valve to 
produce a signal indicative thereof for feedback control of the cut-off 
valve position.

DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATIVE EMBODIMENTS 
Referring to FIGS. 1 to 4 of the drawings, there is shown a fuel injection 
pump in which a preferred embodiment of a fuel injection quantity 
adjusting apparatus according to the present invention is incorporated. 
When an internal combustion engine, not shown, operates, the shaft 30 of a 
feed pump 32 (reference 32a shows feed pump rotor 32b rotated through 
90.degree. for ease of understanding) is driven synchronously with the 
engine. As a result, fuel is drawn via an inlet 34 and passageways 36 and 
38 into a reservoir chamber 40 within the pump housing. Reference numeral 
42 denotes a pressure regulating valve to regulate the pressure of fuel 
supplied to the chamber 40. A cam disc 44 is rotated by shaft 30 and 
simultaneously displaced axially by interaction with a set of 
substantially stationary rollers 46. A fuel distributing plunger 48 is 
connected at one end to disc 44 so that it is also driven rotationally and 
reciprocally within a plunger housing 50. In the fuel intake stroke, i.e., 
when plunger 48 starts to move to the left as seen in FIG. 1, one of a 
plurality of intake grooves 52 arranged radially symmetrically around the 
free end of plunger 48 can communicate with a fuel intake passageway 54, 
at which time fuel within the pump housing is drawn into a working space 
56 at the enclosed end of plunger housing 50. By the time the plunger 48 
has finished its intake stroke, it has been rotated so that the intake 
groove 52 no longer communicates with the intake passageway 54 so that the 
fuel previously admitted into the working space 56 is confined 
therewithin. The plunger 48 then begins its compression stroke in which 
fuel within working space 56 is forced via an axial passageway 58, an 
outlet groove 60, one of a plurality of injection passageways 62 
communicating with outlet groove 60, and a corresponding check valve 64 
into a corresponding injector, not shown. 
When a cut-off port 66, communicating with axial passageway 58 and covered 
by a cut-off valve 68 through part of the stroke of the plunger 48, is 
exposed to the chamber 40, fuel in working space 56 is vented via axial 
passageway 58 and cut-off port 66 into chamber 40. Accordingly, although 
plunger 48 is moving to the right in FIG. 1, fuel is not forced out via 
check valve 64 into the corresponding cylinder. By changing the timing at 
which cut-off valve 68 exposes cut-off port 66, the timing of the end of 
fuel injection and therefore fuel injection quantity can be adjusted. 
In this particular embodiment, cut-off valve 68 includes an inner 
non-magnetic sleeve 92 and an outer permanent magnet sleeve 94 and a pair 
of pole pieces 70, one attached to each end face of permanent magnet 
sleeve 94, as best seen in FIG. 2. Non-magnetic sleeve 92 is made of 
stainless steel, ceramic, aluminum plated with rigid chromium or sapphire 
and prevents magnetic attraction between outer sleeve 94 and plunger 48 to 
facilitate the axial movement of cut-off valve 68. 
In order to displace cut-off valve 68 axially along plunger 48, a pair of 
axially spaced drive solenoids 72, 74 are coaxially disposed around 
cut-off valve 68 at an appropriate distance therefrom. The outer 
circumferences of drive solenoids 72, 74 are surrounded by a yoke 76 which 
serves to define the limits of the magnetic field produced by solenoids 
72, 74 and to protect solenoids 72, 74. 
Cut-off valve 68 and drive solenoids 72, 74 constitute the essential 
portion of the fuel injection quantity adjusting apparatus. 
A position sensor 78 which may be a magnetic sensor is provided in the 
vicinity of one end of an elongated ferromagnetic extension 79, the other 
end of which is connected to left-hand pole piece 70 to magnetically sense 
the axial displacement of cut-off valve 68 without contacting same. A pair 
of members, not shown, are provided one on each side of extension 79 so as 
to limit the rotation of extension 79 around plunger 48 to within a small 
range, thereby allowing sensor 78 to sense the position of cut-off valve 
68. The output of sensor 78 is supplied as a feedback signal via leads 86 
to an input terminal of a controller 80, another input terminal of which 
receives the output of a calculating unit 82 calculated in accordance with 
different operating engine parameters; engine speed, accelerator pedal 
position, intake air vacuum, etc. Controller 80 controls the energizing 
currents flowing through drive solenoids 72, 74 via a drive unit 84 to 
magnetically displace cut-off valve 68 to a position at which the two 
inputs to controller 80 are equal. The outgoing lead 86 over which the 
output of sensor 78 is transmitted and an ingoing lead 88 over which the 
output of drive unit 84 is transmitted are threaded through a common 
connector 90 received in the pump housing to be connected to drive 
solenoids 72, 74 and sensor 78. Reference numeral 100 denotes a 
non-magnetic spring disposed between cut-off valve 68 and plunger housing 
50 around plunger 48, which biases cut-off valve 68 to the left as seen in 
FIG. 1, and reference numeral 93 denotes a spring which urges plunger 48 
against cam disc 44 via a push plate 95. 
As will be best seen in FIGS. 3 and 4, non-magnetic spring 100 may include 
a diaphragm 100 which is provided with a pair of diametrically opposed 
arcuate openings 104 which allow fuel to pass therethrough and thereby 
facilitate the reciprocal movement of cut-off valve 68. Diaphragm is 
secured along the periphery of one side therof to plunger housing 50 and 
the other side thereof to a magnetic ring 102. This magnetic ring 102 has 
spaced pegs 106 tightly received in corresponding grooves 108 provided in 
the adjacent pole piece 70 of cut-off valve 68 so that magnetic ring 102 
is rigidly connected by magnetic attraction to cut-off valve 68. Thus, 
diaphragm 100, magnetic ring 102 and cut-off valve 68 do not rotate 
relative to plunger housing 50, thereby preventing misalignment of 
magnetic extension 79 with sensor 78 to perform accurate control of 
positioning of cut-off valve 68. 
To avoid magnetic coupling between pole piece 70 and plunger housing 50, 
diaphragm 100 is designed to have a spring constant large enough to cancel 
the magnetic coupling force. That is, as shown in FIG. 5, the resultant 
force of the magnetic attraction force and the spring force of diaphragm 
100 has a positive value, thereby stabilizing the positioning of cut-off 
valve 68. The spring force of diaphragm 100 is exerted on cut-off valve 68 
so as to force cut-off valve 68 to the left in FIG. 2 so that if solenoids 
72, 74 should fail and produce no magnetic force, cut-off valve 68 will be 
moved to the left in FIG. 2 to expose port 66, thereby decreasing the fuel 
injection quantity and therefore preventing the engine from running wild. 
In FIGS. 6 and 7, there is shown a ring-like non-magnetic leaf spring 110, 
connected at upper and lower ends to magnetic ring 102, which may be used 
in place of diaphragm 100 of FIGS. 3 and 4. Use of this leaf spring 110 
reduces manufacturing cost compared to use of diaphragm 100. 
Referring to FIGS. 8 and 9, there is shown the details of the controller 80 
associated with other elements 78, 82, 84. Controller 80 includes a 
high-frequency generator 114 which produces a high-frequency square-wave 
pulse signal, a triangular waveform generator 116 which produces a 
triangular waveform signal, which may be an equilateral-triangular 
waveform signal, the top vertices of which coincide with the rising edges 
of the pulses of the signal from high-frequency generator 114 and the 
other vertices of which coincide with the falling edges of the pulses from 
high-frequency generator 114, and a comparator 118 which compares the 
triangular waveform signal to the output of an error amplifier 120 which 
amplifies the absolute value of the difference between the output S.sub.0 
of calculating unit 82, which outputs a signal indicative of a desired 
position of cut-off valve 68, and the output S.sub.R of position sensor 
78. The output of comparator 118 goes high while the output signal of 
error amplifier 120 is higher than the output of triangular waveform 
generator 116 during which the output of high-frequency generator 114 is 
inputted via an AND gate 122 to selector 124. Selector unit 124, which may 
be an analog switch, connects the output of AND gate 122 to one of a pair 
of drive units 126, 128 which energizes solenoids 72, 74 with current 
either in one pair of polarities or in the other pair of polarities in 
accordance with the output of a comparator 130. When the desired value 
S.sub.0 from calculating unit 82 is higher than the output S.sub.R of 
position sensor 78, the output of comparator 130 serves to connect the 
output A of AND gate 122 to an output terminal B of selector 124 at which 
time transistors Tr.sub.1 and Tr.sub.2 of drive units 126, 128 are 
rendered conductive and therefore solenoids 72, 74 are energized so as to 
have the polarities shown in FIG. 10, thereby moving cut-off valve 68 to 
close cut-off port 66 for fuel injection. On the other hand, when the 
desired value S.sub.0 from calculating unit 82 is lower than the output 
S.sub.R of position sensor 78, the output of comparator 130 serves to 
connect the output A of AND gate 122 to an output terminal C of selector 
124 at which time transistors Tr.sub.3 and Tr.sub.4 are rendered 
conductive and therefore solenoids 72, 74 are energized so as to have the 
polarities shown in FIG. 11, thereby moving cut-off valve 68 to open 
cut-off port 66 for stopping fuel injection. 
When a signal indicative of a desired position of cut-off valve 68 is 
outputted from calculating unit 82 in the initial stage of pump operation, 
the output of position sensor 78 is zero since cut-off valve 68 is at its 
left-hand extreme. Accordingly, the output of comparator 130 goes high, in 
which case selector unit 124 supplies energizing current to drive unit 126 
via contact A-B; rendering transistors Tr.sub.1 and Tr.sub.2 conductive to 
supply solenoids 72, 74 with energizing current so that solenoids 72, 74 
will have the polarities shown in FIG. 10 to move cut-off valve 68 in the 
direction of arrow P in FIG. 10. When cut-off valve 68 arrives at the 
desired position, the output of error amplifier 120 is zero because the 
output of position sensor 78 equals the desired value so that the outputs 
of comparator 118 and therefore AND gate 122 are zero. Thus, no current 
will flow through solenoids 72, 74. On the other hand, when cut-off valve 
68 goes beyond the desired position, the output of comparator 130 goes low 
so that selector unit 124 switches to contacts A-C to render transistors 
Tr.sub.3 and Tr.sub.4 conductive and therefore solenoids 72, 74 are 
supplied with energizing current which produces polarities as shown in 
FIG. 11 which propel cut-off valve 68 in the direction of arrow Q as shown 
in FIG. 11. If one solenoid 72 should fail when cut-off valve 68 is being 
driven in the direction Q in FIG. 11, no current would flow therethrough, 
but solenoid 74 would still be supplied with energizing current so as to 
produce polarities such as shown in FIG. 12, thereby producing 
electromagnetic force which moves cut-off valve 68 in the direction of 
arrow Q and opening cut-off port 66 to stop fuel injection. On the other 
hand, if solenoid 74 should fail when cut-off valve 68 is being driven in 
the direction Q in FIG. 11, no current would flow therethrough, but 
solenoid 72 would be supplied with energizing current so as to produce 
polarities such as shown in FIG. 13, thereby moving cut-off valve 68 in 
the direction of arrow Q and opening cut-off port 66 to stop fuel 
injection. 
Referring to FIG. 14, there is shown a second alternative embodiment which 
is the same as the FIG. 1 embodiment except that the second embodiment 
includes a coil spring 130 disposed around plunger 48 between cut-off 
valve 68 and plunger housing 50 in place of spring 100 of FIG. 2. Coil 
spring 130 tends to bias cut-off valve 68 to the left in FIG. 14 to 
uncover port 66, thereby allowing fuel to vent into chamber 40 to stop 
fuel injection when at least one of solenoids 72, 74 fails or the 
controller 80 malfunctions. 
Referring to FIG. 15, there is shown a third alternative embodiment of the 
present invention which is the same as the FIG. 1 embodiment except that 
the third embodiment includes a pair of permanent magnet discs 96, one 
disposed coaxially on each side of cut-off valve 68, separated therefrom, 
and oriented such that the polarities of the opposing faces of the 
permanent magnet discs 96 and of cut-off valve 68 are the same. The 
magnetic discs 96 serves to isolate cut-off valve 168 from the possible 
attractive force of plunger housing 50. Ferromagnetic extension 79 can 
move through a notch 81 provided in magnet 98 without being significantly 
influenced by the magnetic force produced by the left-hand magnet 98. 
Referring to FIG. 16, there is shown a fourth alternative embodiment of the 
present invention which is the same as the FIG. 15 embodiment except that 
the fourth embodiment includes a pair of discs 98 made of a non-magnetic 
material such as aluminum or stainless steel, one disposed and spaced from 
each end of cut-off valve 68 and coaxial with cut-off valve 68 for 
preventing the occurrence of a magnetic coupling between cut-off valve 68 
and plunger housing 50, thereby improving the control accuracy of cut-off 
valve 68, and that the pair of solenoids 72, 74 are energized such that 
the polarities of the opposing ends thereof are the same. The magnetic 
field produced by solenoids 72, 74 magnetically drives cut-off valve 68. 
The cut-off valve 68 accordingly moves relatively quickly in a direction 
determined by the polarities of magnet 94 and the direction of current 
flow. When energizing current flows in the opposite direction, cut-off 
valve 68 is moved in the opposite direction at a relatively high speed. 
While the present invention has been described and shown in terms of 
preferred and alternative embodiments thereof, it should be noted that the 
present invention is not limited to these embodiments. Various changes and 
modifications could be made by those skilled in the art without departing 
from the spirit and scope of the present invention as set forth in the 
accompanying claims.