Single dump single solenoid fuel injector

A unit injector having a mechanically driven piston and a remotely situated metering piston situated in a bore. The interplunger volume defining a timing chamber and the volume below the metering piston defining a metering chamber. The injector further including a single electrically responsive valve for controlling the functions of injection timing and fuel metering and a single dump port fabricated in the walls of the bore for relieving the fuel pressure on the timing chamber which correspondingly permits the pressure of fuel in the metering chamber to be decreased.

BACKGROUND AND SUMMARY OF THE INVENTION 
The instant Application relates generally to fuel injection systems and 
more particularly to mechanically or electrically operated diesel fuel 
injectors having means for separately regulating each of the functions of 
timing of fuel injection and metering of fuel into the injector thereby 
permitting separate and independent adjustment to both the timing of fuel 
injection into an engine and the quantity of fuel metered into the fuel 
injector prior to injection. U.S. Pat. Nos. 4,235,374 to Walter et al 
which issued Nov. 25, 1978 and 4,281,792 to Sisson et al which issued Aug. 
4, 1971 disclose a single solenoid fuel injector. This fuel injector 
injects metered quantities of fuel into the cylinders of a diesel engine 
as well as to function as an engine driven pump to pressurize the fuel 
prior to injection into the engine. The above noted United States patents 
disclose a fuel injector which utilizes a primary pumping piston disposed 
to be actuated by a cam operated mechanism, a metering or floating piston 
slidably mounted within the interior of the injector and a nozzle portion 
contiguous with fuel injector or combustion chamber of the engine. A 
timing chamber is formed between the primary pumping piston and the 
metering piston. The injector includes a cooperating electronic control 
unit (ECU) which generates a signal to control the state of a single 
electronically controlled solenoid which when in an open condition permits 
fuel to flow into the timing chamber and which when closed initiates fuel 
injection. In addition to the formation of the timing chamber between the 
pumping piston and the metering piston, a metering chamber is formed 
between the lower portion of the metering piston and the bore which houses 
the floating piston. The quantity of fuel fed to the metering chamber 
determines the amount of fuel which thereafter will be injected into each 
engine cylinder. The control valve is utilized to control both the timing 
of injection and the quantity of fuel metered to the engine. In the above 
patents, a substantially unobstructed fuel passage is provided from a 
supply to the metering chamber. Consequently, the amount of fuel that 
resides within the metering chamber is determined by the volume of the 
metering chamber, hence, this method of metering has been called 
volumetric fuel metering. During the metering mode of operation of the 
Walter et al or the Sisson et al injectors, the pumping piston is caused 
to retract allowing the supply pressure in the metering chamber to force 
the metering piston upward to follow the pumping piston retraction. This 
causes the volume of the metering chamber to be increased. To terminate 
the metering process the control valve is opened allowing supply fuel to 
flow into the timing chamber, thereby breaking the hydraulic link between 
the two pistons. A spring is inserted within the timing chamber to bias 
the two pistons apart to insure that the motion of the metering piston is 
stopped and that no more fuel enters the metering chamber. The utilization 
of the spring within the metering piston increases the length of the 
injector therein consuming valuable engine space. It should be recalled 
that a unit injector is typically incorporated within the engine and 
driven by the cam shaft of the engine. 
The above noted fuel injectors are relatively complex in that they utilize 
check valves within the movable metering piston, in particular, a timing 
chamber check valve and a metering chamber check valve which are included 
within the movable floating or metering piston. The incorporation of the 
check valves within the moving element complicates the manufacture and 
assembly of the above noted fuel injectors and may cause non-repeatability 
in the injector performance. During the dumping mode of operation of these 
fuel injectors, fuel is dumped from the timing chamber to drain through 
the timing chamber check valve. By dumping the timing chamber through the 
restriction imposed by the check valve slows the dumping process. 
It is therefore an object of the present invention to provide a unit 
injector having a less massive metering piston to permit a more rapid 
initiation of the injection mode of operation. In addition, it is an 
object of the present invention to provide a unit injector having a 
shorter metering piston thus providing a more compact design. A further 
object of the present invention is to eliminate the check valves from the 
influence of the movable metering piston and to eliminate the necessity 
for the timing chamber check valve and biasing spring. Another object of 
the invention is to provide a unit injector having one dump port and to 
hydraulically bias the needle valve, with the dumped fuel to rapidly 
terminate injection. 
Accordingly, the invention comprises: a fuel injector comprising: a body 
having an axially extending bore, a pumping piston and a remotely 
positioned metering piston positioned within the bore. A timing chamber is 
defined within the bore between the pumping piston and the metering piston 
and a metering chamber defined between the metering piston and the lower 
portion of the bore. The injector includes first fuel passage having an 
electronically controlled valve situated therein for receiving pressurized 
fuel and for controllably transmitting the fuel to the timing chamber; a 
second fuel passage having a pressure regulator for receiving pressurized 
fuel for establishing the pressure level for fuel in the metering chamber 
and for transporting the received fuel to the metering chamber. The 
injector further includes a spring chamber and nozzle situated remotely 
from the metering chamber wherein the nozzle partially extends within the 
spring chamber. A biasing spring is located within the spring chamber for 
biasing the nozzle in a closed position during non-injecting modes of 
operation. The injector further includes a third fuel passage terminating 
at an open end at the wall of the bore, proximate said timing chamber 
forming in cooperation with the bore, a timing chamber dump port. The 
third fuel passage also communicates with the spring chamber and with a 
fourth passage having a restrictive orifice situated therein for 
establishing upstream thereto an increased pressure during the period of 
time that fuel in the timing chamber is being dumped through.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
Turning now to the drawings, FIG. 1 schematically depicts the major 
components of a diesel unit injector 10 and further shows the injector 10 
in its metering mode of operation. The injector includes a housing 20 
having a central bore 22 and further includes a plurality of fuel carrying 
passages 24, 26, 28, 30, 32, 36, 38. Fuel is received by the injector 10 
through a supply port 50 and returned through a drain port 52 to a low 
pressure reservoir such as a fuel tank which is exposed to atmosphere 
pressure. The injector 10 further includes a pumping piston 60 that may be 
formed as an integral part of a follower 62 which is biased upwardly by a 
heavy duty spring 64. The follower 62 and pumping piston 60 may be formed 
as separate or integral elements. The follower is urged downwardly by a 
rocker arm 40 driven by a cam 42. The relationship of the rocker arm 40 to 
the engine is more particularly defined in U.S. Pat. No. 4,281,792 which 
is expressly incorporated herein by reference. The central bore 22 also 
receives a metering piston 70. The volume between the pumping piston 60 
and the metering piston 70 forms a timing chamber 72. The volume above the 
bottom of the central bore 22 and below the metering piston 70 form a 
metering chamber 74. 
In order to prevent the metering piston 70 from moving too far upward 
within the central bore 22. The injector 10 further includes a mechanical 
means for prohibiting excessive metering piston travel. In the embodiment 
of the invention shown in FIG. 1 this excess travel means is accomplished 
by having the lower end of the bore 22 include an enlarged diameter bore 
90. The transition between the bore 90 and the upper portion of the bore 
22 form a shoulder 92. In addition, the metering piston 70 further 
includes an outwardly extending shoulder 94 which will physically contact 
the shoulder 92 after a determinable amount of upward travel of the 
metering piston 70. Other means for accomplishing this mechanical stop can 
be accomplished by utilizing pins and cooperating slots manufactured 
within the housing 20 and or metering piston 70. 
The injector 10 further includes a nozzle 100 situated remotely from the 
metering chamber 74. The nozzle 100 includes a needle valve 102 of a known 
variety which is loosely received within a passage 104. The nozzle 100 
further includes a plurality of flow orifices 106. A spring 110 is 
situated above the needle valve for biasing the needle valve 102 during 
non-injecting periods to prevent fuel from exiting from the flow orifices 
106. The spring 110 is situated withing a spring chamber or bore 112. The 
bore 112 is connected to one of the passages within the injector; more 
particularly, passage 24 termintes at an end at the bore 112. Passage 24 
terminates at its other end in the walls of the central bore 22 thus 
forming a timing chamber dump port 114. Fuel is communicated from the 
metering chamber 74 to the passage 104 surrounding the needle valve 102 
through the passage 32 which may optionally include a blow back check 
valve 120. The purpose of the check valve 120 is to prohibit the 
transmission of fumes within the combustion chamber of the engine from 
propagating back into the injector. The bore 112 which houses the spring 
110 is connected to the drain port 52 of the injector 10 through a passage 
36 having an orifice 122 situated therein. 
Fuel is communicated from an external pump 44 to the supply port 50 and 
thereafter distributed through passage 38, which contains a solenoid 
control valve 130, to the timing chamber 72. Additionally, fuel is 
supplied to the metering chamber 74 through the passage 28 which includes 
a fill pressure regulator 132. 
Reference is made to FIGS. 2, 3, 4 which illustrate further the various 
modes of operation of the present invention. FIG. 2 illustrates a 
pre-injection mode of operation. As a result of a prior metering mode of 
operation, as hereinafter described, a predetermined quantity of fuel 
resides within the metering chamber 74. The cam driven pumping piston 60 
is illustrated moving downwardly under the force exerted by the cam 42 and 
the follower arm 40. In this pre-injection mode of operation, the control 
valve 130 is open so that fuel can escape from the timing chamber 72 and 
flow through the passage 38 out through the supply port 50 to the supply 
pump. During this pre-injection mode, the fill pressure regulator 132 
closes passage 28 therein prohibiting additional fuel from flowing into 
the metering chamber 74. 
FIG. 3 illustrates the injection mode of operation for the injector 10. In 
this mode of operation, the solenoid control valve 130 is closed. Upon the 
closure of the solenoid control valves 130, the fuel within the timing 
chamber 72 is trapped therein, thereby establishing a hydraulic link 
between the pumping piston 60 and the metering piston 70. The continued 
downward motion of the pumping piston forces the metering piston downward 
compressing the fuel within the metering chamber as well as compressing 
the fuel within passages 32 and 104. At a determinable pressure level, the 
pressure force of the fuel within passage 104 urges the needle valve 
upwardly against the bias force exerted by the spring 110 therein causing 
the needle valve 102 to move from its seat permitting fuel to flow from 
the flow orifices 106. The operation of the fuel injector 10 in its 
pre-injection and injection modes of operation is relatively identical to 
the modes of operation as discussed in U.S. Pat. No. 4,281,792 which has 
been incorporated by reference. 
FIG. 4 illustrates the dumping mode of operation of the present invention 
wherein the pressure of the fuel within the timing chamber 72 and within 
the metering chamber 74 is relieved. During the dumping mode of operation, 
the control valve 130 remains closed and the fill pressure regulator 132 
resides in a position to prohibit flow through passage 28. The dumping 
mode of operation terminates the fuel injection mode of operation by 
relieving the pressure of the fuel surrounding the needle valve 102, thus 
permitting the needle valve to rapidly close the flow path to the orifices 
106. Just prior to the beginning of the dumping mode of operation, the 
pumping piston 60 operating through the hydraulic link established between 
the pumping piston and the metering piston has moved the metering piston 
into a position such that its upper edge 76 opens the timing chamber dump 
port 114. The opening of the dump port 114 permits the communication of 
the highly pressurized fuel from the timing chamber to be dumped through 
passages 24, bore 112 and orifice 122 to the drain therein substantially 
lessening the pressure of the fuel within the timing chamber 72. This 
dumping also disables the hydraulic link previously established linking 
the pumping piston 60 to the metering piston 70. The pressure in the 
metering chamber 74 is relieved as fuel continues to flow out from the 
nozzle 100. Due to inertia effects, this flow continues as the metering 
piston 70 moves further to increase the opening of the timing chamber dump 
port 114. As the needle valve 102 moves to terminate the nozzle flow, the 
metering piston 70 may move upward slightly further reducing the pressure 
in the metering chamber 74. During this process the pressure in the timing 
chamber 72 and the metering chamber 74 are substantially equal. As 
previously mentioned, the timing chamber 72 is dumped through the bore 
112, that houses the spring 110 and through which a part of the needle 
valve 102 extends. By incorporating this single dump feature to dump the 
timing chamber fuel to the spring chamber 112 and through the orifice 122, 
the pressure within the spring chamber 112 is caused to build rapidly 
because of the flow restriction imposed by the orifice 122. This increase 
in the fuel pressure (which during non-dumping modes of operation is 
maintained at the low drain pressure) exerts a hydraulic force on that 
portion of the needle valve 102 extending into the spring chamber 112 
therein exerting an additional biasing force upon the needle valve 102 to 
cause the needle valve 102 to rapidly close the flow orifices 106. 
During the dumping mode of operation, that is as the fuel within the timing 
chamber is being dropped to a relatively low pressure, there may exist a 
pressure differential across the metering piston 70. It can be seen that 
after the timing chamber 72 has been dumped, its pressure will approach 
the pressure of the drain line which is substantially atmospheric 
pressure. However, the pressure within the metering chamber 74, that is 
the pressure exerted on the bottom face of the metering piston, is at a 
level determined by any residual injection pressure plus the supply 
pressure minus the pressure drop across the fill pressure regulator 132. 
This pressure differential causes the metering piston 70 to move upwardly, 
thus causing the metering piston 70 to momentarily move to a reference 
position that is above the bottom of the bore 90 and to thereupon close 
off the dump port 114. Depending upon the restrictions in the lines and 
their inherent line dynamics, during certain instances there may not be 
sufficient time for the pressure within the timing chamber 72 to be 
relieved to a sufficiently low level below that which is established by 
the fill pressure regulator 132. Consequently, it may be desirable to 
include within the profile of the cam 42, a dwell, which will cause the 
pumping piston 70 to remain at the bottom of its stroke for a determinable 
period during this dump mode of operation to permit the fuel within the 
timing chamber to continue to be dumped to drain. It can be seen that if 
the pumping piston 60 moves upwardly prematurely, that is while the timing 
chamber dump port 114 is still open, a vacuum pressure may be created 
within the timing chamber which will cause fuel to flow into the timing 
chamber rather than to be desirably removed therefrom. It should be noted 
by utilizing a single dump port 114 and by controlling the pressure 
differential across the metering piston 70 the timing chamber check valve 
shown in U.S. Pat. No. 4,281,792 is eliminated. In addition, to cause the 
metering piston 70 to achieve its reference position during the dwell mode 
and thereby close off the timing chamber dump port 114, it is necessary to 
create a pressure differential across the metering piston 70 during the 
dwell mode of operation. This is achieved by insuring that the pressure 
within the metering chamber is higher than that of the timing chamber 
during the dwell mode and therefore necessitates the dumping of the timing 
chamber to a low pressure drain such as a fuel tank reservoir. 
The final mode of operation for the injector 10 is the metering mode which 
is illustrated in FIG. 1. This mode of operation is begun just after the 
metering piston 70 closes off the timing chamber dump port 114. During 
this mode of operation, the cam 42 causes the rocker arm to move upward. 
The spring 64 urges the follower 62 in an upward direction therein further 
moving the pumping piston 60. The motion of the pumping piston 60 creates 
a tendancy to lower the pressure within the timing chamber 72 and in 
cooperation with the positive pressure resident in the metering chamber 
causes the metering piston 70 to move upward. The metering piston 70 will 
substantially follow the motion of the pumping piston 60 until the control 
valve 130 is opened therein permitting fuel from the supply to enter the 
timing chamber, which thereafter creates a pressure nearly equal to the 
supply pressure in the timing chamber 72 which, combined with the pressure 
in the metering chamber 74 that is equal to the supply pressure reduced by 
the pressure drop across the pressure regulator 132, causes a net biasing 
force on the metering piston 70, terminating the upward motion of the 
meter piston. The metering chamber 74 is now charged with a determinable 
quantity of fuel and the operation of the injector continues again with 
the injector 10 entering its preinjection mode of operation as illustrated 
in FIG. 2. 
Many changes in modifications in the above described embodiment of the 
invention can of course be carried out without departing from the scope 
thereof. Accordingly, that scope is intended to be limited only by the 
scope of the appended claims.