Injection rate shaping nozzle assembly for a fuel injector

An injection rate shaping nozzle assembly for a fuel injector is provided which includes a closed nozzle valve element and a rate shaping control device including an injection spill circuit for spilling a portion of the fuel to be injected to produce a predetermined time varying change in the flow rate of fuel injected into a combustion chamber. The spill circuit includes a spill passage integrally formed in the nozzle valve element. The rate shaping control device may include a spill accelerating chamber in formed in the nozzle valve element for creating a rapid increase in the spill flow rate. A spill circuit purge device is provided to remove fuel from the spill circuit and accelerating chamber between each of the injection events thereby ensuring an unimpeded, effective spill fuel flow during the next spill event. The purge device includes a purge passage formed of a predetermined size for restricting the flow of purge gas to ensure sufficient fuel removal from the injection spill circuit while avoiding excessive purge gas flow. The purge passage may include an annular clearance gap formed between the nozzle valve element and the nozzle housing wall, or alternatively, may include an orifice passage formed in the inner portion of the nozzle valve element. An improved method for forming a nozzle valve element having an axial center passage is also disclosed.

TECHNICAL FIELD 
This invention relates to an improved nozzle assembly for fuel injectors 
which effectively controls the flow rate of fuel injected into the 
combustion chamber of an engine. 
BACKGROUND OF THE INVENTION 
In most fuel supply systems applicable to internal combustion engines, fuel 
injectors are used to direct fuel pulses into the engine combustion 
chamber. Fuel injection into the cylinders of an internal combustion 
engine is most commonly achieved using either a unit injector system or a 
fuel distribution type system. In the unit injector system, fuel is pumped 
from a source by way of a low pressure rotary pump or gear pump to high 
pressure pumps, known as unit injectors, associated with corresponding 
engine cylinders for increasing the fuel pressure while providing a finely 
atomized fuel spray into the combustion chamber. Such unit injectors 
conventionally includes a positive displacement plunger driven by a cam 
which is mounted on an engine driven cam shaft. The fuel distribution type 
system, on the other hand, supplies high pressure fuel to injectors which 
do not pump the fuel but only direct and atomize the fuel spray into the 
combustion chamber. 
A commonly used injector in both the unit and fuel distribution systems is 
a closed-nozzle injector. Closed-nozzle injectors include a nozzle 
assembly having a spring-biased nozzle valve element positioned adjacent 
the nozzle orifice for resisting blow back of exhaust gas into the pumping 
or metering chamber of the injector while allowing fuel to be injected 
into the cylinder. The nozzle valve element also functions to provide a 
deliberate, abrupt end to fuel injection thereby preventing a secondary 
injection which causes unburned hydrocarbons in the exhaust. The nozzle 
valve is positioned in a nozzle cavity and biased by a nozzle spring to 
block the nozzle orifices. When the pressure of the fuel within the nozzle 
cavity exceeds the biasing force of the nozzle spring, the nozzle valve 
element moves outwardly to allow fuel to pass through the nozzle orifices. 
Internal combustion engine designers have increasingly come to realize 
that substantially improved fuel supply systems are required in order to 
meet the ever increasing governmental and regulatory requirements of 
emissions abatement and increased fuel economy. It is well known that the 
level of emissions generated by the diesel fuel combustion process can be 
reduced by decreasing the volume of fuel injected during the initial stage 
of an injection event while permitting a subsequent unrestricted injection 
flow rate. As a result, many proposals have been made to provide injection 
rate control devices or modifications in or adjacent to the fuel injector 
nozzle assemblies. One method of controlling the initial rate of fuel 
injection is to spill a portion of the fuel to be injected during the 
injection event. For example, U.S. Pat. Nos. 4,811,715 to Djordjevic et 
al. and 3,747,857 to Fenne each disclose a fuel delivery system for 
supplying fuel to a closed nozzle injector which includes an expandable 
chamber for receiving a portion of the high pressure fuel to be injected. 
The diversion or spilling of injection fuel during the initial portion of 
an injection event decreases the quantity of fuel injected during this 
initial period thus controlling the rate of fuel injection. A subsequent 
unrestricted injection flow rate is achieved when the expandable chamber 
becomes filled causing a dramatic increase in the fuel pressure in the 
nozzle cavity. Therefore these devices rely on the volume of the 
expandable chamber to determine the beginning of the unrestricted flow 
rate. Moreover, the use of a separate expandable chamber device mounted on 
or near an injector increases the costs, size and complexity of the 
injector. U.S. Pat. No. 5,029,568 to Perr discloses a similar injection 
rate control device for an open nozzle injector. 
U.S. Pat. No. 4,804,143 to Thomas discloses another fuel injector nozzle 
assembly incorporating a passage in the nozzle assembly for diverting the 
fuel from the nozzle assembly. The injection nozzle unit includes a 
restricted passage formed in the injector adjacent the nozzle valve 
element for directing fuel from the nozzle cavity to a fuel outlet 
circuit. However, the restricted passage is used to maintain fuel flow 
through the nozzle unit so as to effect cooling. The Thomas patent nowhere 
discusses or suggests the desirability of controlling the injection rate. 
Moreover, the restricted passage is closed by the nozzle valve element 
upon movement from its seated position to prevent diverted flow during 
injection. 
U.S. Pat. No. 4,993,926 to Cavanagh discloses a fuel pumping apparatus 
including a piston having a passage formed therein for connecting a 
chamber to an annular groove for spilling fuel during an initial portion 
of an injection event. The piston includes a land which blocks the spill 
of fuel after the initial injection stage to permit the entirety of the 
fuel to be injected into the engine cylinder. However, this device is 
incorporated into a piston pump positioned upstream from an injector. 
Another method of reducing the initial volume of fuel injected during each 
injection event is to reduce the pressure of the fuel delivered to the 
nozzle cavity during the initial stage of injection. For example, U.S. 
Pat. No. 5,020,500 to Kelly discloses a closed nozzle injector including a 
passage formed between the nozzle valve element and the inner surface of 
the nozzle cavity for restricting or throttling fuel flow to the nozzle 
cavity so as to provide rate shaping capability. U.S. Pat. No. 4,258,883 
issued to Hofmann et al. discloses a similar fuel injection nozzle 
including a throttle passage formed between the nozzle valve element and a 
separate control supply valve for restricting fuel flow into the nozzle 
cavity thus limiting the pressure increase in the cavity and the rate of 
injection fuel flow through the injector orifices. However, the devices 
disclosed in both Kelly and Hofmann et al. require extremely close 
manufacturing tolerances which must be carefully controlled to create a 
throttling passage having the precise dimensions necessary to achieve 
effective, predictable rate shaping. As a result, because of the great 
difficulty associated with holding very close manufacturing tolerances, 
these devices greatly increase manufacturing costs. Moreover, this 
tolerance problem makes the production of fuel injectors having 
substantially identical characteristics both technically and economically 
unfeasible. 
U.S. Pat. Nos. 3,669,360 issued to Knight, 3,747,857 issued to Fenne, and 
3,817,456 issued to Schlappkohl all disclose closed nozzle injector 
assemblies including a high pressure delivery passage for directing high 
pressure fuel to the nozzle cavity of the injector and a throttling 
orifice positioned in the delivery passage for creating an initial low 
rate of injection. Moreover, the devices disclosed in Knight and 
Schlappkohl include a valve means operatively connected to the nozzle 
valve element which provides a substantially unrestricted flow of fuel to 
the nozzle cavity upon movement of the nozzle valve element a 
predetermined distance off its seat. 
U.S. Pat. Nos. 3,718,283 issued to Fenne and 4,889,288 issued to Gaskell 
disclose fuel injection nozzle assemblies including other forms of rate 
shaping devices. For example, Fenne '283 uses a multi-plunger and 
multi-spring arrangement to create a two-stage rate shaped injection. The 
Gaskell reference uses a damping chamber filled with a damping fluid for 
restricting the movement of the nozzle valve element. 
An improved injector nozzle assembly for effectively controlling the flow 
rate of fuel injected is disclosed in co-pending U.S. patent application 
Ser. No. 376,417, filed Jan. 23, 1995, now U.S. Pat. No. 5,647,536 
entitled Injection Rate shaping Nozzle Assembly for a Fuel Injector, and 
commonly assigned to Cummins Engine Co., Inc. The low cost, compact nozzle 
assembly disclosed in the '417 application includes a spring-biased needle 
valve having an integrally formed spill passage for controllably spilling 
fuel during injection events to thereby optimally minimize engine 
emissions. The nozzle assembly disclosed in the '417 application is of the 
valve-covered orifice type (VCO nozzle assembly) wherein the needle valve 
covers or blocks the injection orifices when in the closed position. 
Another type of conventional nozzle assembly is the "sac" or "mini-sac" 
type wherein the tip of the injector includes a sac or pocket between the 
valve element/seat and the injector orifices. In both the VCO and mini-sac 
type nozzle assemblies incorporating the rate shaping spill technology of 
the '417 application, the presence of fuel in the needle spill passage 
subsequent to a given spill/injection event, hinders the flow of fuel 
through the spill passage during the following injection event thereby 
preventing optimum injection rate shaping. 
U.S. Pat. No. 2,959,360 to Nichols discloses a nozzle valve element having 
an axial passage formed therein and a cross passage connecting the inner 
end of the axial passage to the nozzle cavity for diverting fuel from the 
nozzle cavity into an expansible chamber formed in the nozzle valve 
element. A plunger is positioned in the chamber to form a differential 
surface creating a fuel pressure induced seating force on the nozzle valve 
element to aid in rapidly seating the valve element. This system appears 
to be of the "mini-sac" design since it includes a smaller, coaxial duct 
positioned between the nozzle valve seat and the injector orifices. Also, 
U.S. Pat. No. 3,379,374 to Mekkes is noted for disclosing a closed nozzle 
injector including a valve element having an axial passage and a plurality 
of cross passages. However, the passages, formed in the valve elements of 
the Nichols and Mekkes devices, supply fuel for injection. Moreover, 
neither reference suggests the desirability of controlling the rate of 
injection. 
U.S. Pat. No. 5,421,521 to Gibson et al. discloses a fuel injection nozzle 
assembly including a needle element having an axial passage integrally 
formed therein for directing fuel, during an injection event, from the 
orifice end of the assembly to the actuator end. The tip portion of the 
valve element has an outer diameter which is slightly less than the 
diameter of the opposing injector tip wall so that a leakage path is 
established for fuel flow to the axial passage during an injection event. 
This arrangement is designed to balance the hydraulic forces on the 
element in the open position and, therefore, Gibson et al. no where 
suggest any form of fuel injection rate shaping during each injection 
event. 
Italian Patent No. 450,866 discloses a closed nozzle injector including a 
needle valve element having a passage formed therein for directing fuel to 
a pressure chamber formed by a piston. This arrangement is designed to 
cause the needle valve element to open during an initial stage, then 
momentarily close to interrupt injection, and subsequently reopen to 
continue injection thereby carrying out injection in two separate stages. 
The fuel pressure in the pressure chamber, formed by a spring loaded 
piston positioned in the needle valve element, necessarily increases to a 
high level to cause the closing of the needle valve element and thus the 
separate stages of injection. This reference fails to disclose a low 
pressure drain circuit for receiving fuel spilling from an injection spill 
circuit during the injection event so as to create a low injection flow 
rate followed by a high injection flow rate during the injection event. A 
fuel outlet extending from a spring chamber provides a leak-off path for 
fuel leaking by clearances between the piston elements and the nozzle body 
and does not function to control the injection characteristics of the 
valve. 
U.S. Pat. No. 5,133,645 to Crowley et al. discloses a nozzle valve assembly 
including passages for directing fuel from the nozzle cavity to a drain 
during injection wherein a stop formed on the needle valve element 
throttles the drain flow during injection. However, this arrangement is 
used to create a pressure differential across the nozzle valve element to 
initiate injection and, therefore, Crowley et al. no where suggest 
controlling the rate of fuel injection. 
German Patent Document No. 759,420 discloses a closed nozzle injector 
nozzle needle including an integral passage used to return leak-by fuel 
from the spring chamber to the interior of the atomizer head adjacent the 
injection orifices for injection into the combustion chamber. In this 
manner, fuel leaking through the slidable clearance formed between needle 
and nozzle body into the spring chamber is returned for injection. This 
reference fails to suggest the desirability of controlling the rate of 
injection. 
Consequently, there is a need for a fuel injector incorporating a simple, 
cost effective rate shaping device which minimizes the complexity of the 
nozzle assembly while controlling emissions by effectively controlling the 
rate of fuel injection during each injection event. 
SUMMARY OF THE INVENTION 
It is an object of the present invention, therefore, to overcome the 
disadvantages of the prior art and to provide an improved nozzle assembly 
for a fuel injector which effectively controls the flow rate of fuel 
injected into the combustion chamber of an engine so as to minimize engine 
emissions. 
It is another object of the present invention to provide both a valve 
covered orifice (VCO) type and a mini-sac type nozzle assembly capable of 
shaping the rate of fuel injection which are also simple and inexpensive 
to manufacture. 
It is yet another object of the present invention to provide a rate shaping 
nozzle assembly for an injector which effectively slows down the rate of 
fuel injection during the initial portion of an injection event while 
subsequently increasing the rate of injection to rapidly achieve a high 
injection pressure. 
It is a further object of the present invention to provide both a VCO and a 
mini-sac type rate shaping nozzle assembly for an injector including a 
nozzle valve element having a spill passage wherein fuel is effectively 
purged from the spill passage between each injection event to ensure 
effective control of the rate of injection. 
It is a still further object of the present invention to provide both a VCO 
and a mini-sac type rate shaping nozzle assembly for an injector including 
a nozzle valve element having a spill passage which provides an optimum 
amount of purge gas flow through the spill circuit to remove spill fuel 
while preventing an unnecessary amount of purge gas flow. 
Still another object of the present invention is to provide a rate shaping 
nozzle assembly for an injector which includes a spill circuit through 
which fuel flow is prevented when the nozzle valve element is closed 
between injection events. 
Yet another object of the present invention is to provide a mini-sac type 
injector assembly including a spill circuit for spilling fuel to create a 
low injection flow rate followed by a high injection flow rate while 
providing a purge gas flow for effectively removing a substantial portion 
of the fuel in the spill circuit before each injection event to ensure 
proper injection rate shaping while restricting the purge gas flow to an 
acceptable level. 
Another object of the present invention is to provide a rate shaping 
assembly having a spill circuit which effectively controls the rate of 
fuel injection while preventing the accumulation of gas or air bubbles in 
the spill circuit. 
A further object of the present invention is to provide a simple, 
inexpensive method for forming a rate shaping nozzle valve element having 
an integral spill passage. 
Still another object of the present invention is to provide a method for 
forming a rate shaping nozzle valve element having an integral spill 
passage which minimizes manufacturing costs, minimizes material removal by 
turning and grinding, eliminates an electro-discharge machining (EDM) 
"white" layer in highly stressed regions, minimizes EDM machining 
distances, maximizes material selection options, maximizes the available 
spill void volume while maintaining a high degree of rotational symmetry, 
and provides part handling and processing efficiencies. 
These and other objects are achieved by providing a closed nozzle fuel 
injector comprising an injector body containing an injector cavity 
communicating with an injector orifice for discharging fuel into a 
combustion chamber wherein the injector body includes a fuel transfer 
circuit for transferring supply fuel to the orifice and a low pressure 
drain circuit for draining fuel from the injector cavity. A nozzle valve 
element positioned in the injector cavity adjacent the injector orifice is 
movable between an open position in which fuel may flow from the transfer 
circuit through the orifice into the combustion chamber, and a closed 
position in which fuel flow through the injector orifice is blocked. The 
nozzle valve element moves from the closed position to the open position 
and back to the closed position to define an injection event. The injector 
includes a rate shaping control device for producing a predetermined time 
varying change in the flow rate of fuel injected into the combustion 
chamber during the injection event. The rate shaping control device 
includes an injection spill circuit for spilling a portion of the 
injection fuel from the transfer circuit to the low pressure drain circuit 
during the injection event. The closed nozzle fuel injection further 
includes a spill circuit purge device for providing a flow of purge gas 
through the injection spill circuit so as to remove fuel from the spill 
circuit between injection events. The purge device is capable of 
restricting the flow of purge gas to ensure sufficient fuel removal from 
the spill circuit while avoiding excessive purge gas flow. The spill 
circuit purge device may include a cylinder gas purge passage for 
directing cylinder gas from the combustion chamber of the engine into a 
spill passage formed in the nozzle valve element. 
The cylinder gas purge passage may be formed between the nozzle valve 
element and the injector body for directing cylinder gas from the injector 
orifice to the spill passage. The valve element may include an inner 
portion having a frusto-conically shaped valve surface while the injector 
body may include a nozzle housing having a frusto-conically shaped seating 
surface facing the valve surface. The valve surface and the seating 
surface may extend at different angles relative to the nozzle valve 
element center line so as to be positioned in a nonparallel relationship. 
As a result, the cylinder gas purge circuit includes an annular clearance 
gap formed between the valve surface and the seating surface created by 
the nonparallel relationship, and sized, when the nozzle valve element is 
in the closed position, to restrict the purge gas flow to achieve a 
predetermined optimum purge gas flow. 
The spill passage may include at least one axial passage extending 
longitudinally from an inner portion of the nozzle valve element to an 
outer portion. The spill passage may further include a plurality of 
connector passages extending from the axial passage through the inner 
portion of the nozzle valve element to communicate with the cylinder gas 
purge passage. The plurality of connector passages may include three 
passages evenly spaced around the nozzle valve element. The connector 
passages may also extend perpendicular to the axial spill passage or at an 
angle toward the injection orifice. A transverse passage, functioning as a 
spill acceleration device, may be provided in the outer portion of the 
nozzle valve element. The axial passage may be formed from the inner end 
of the nozzle valve element so that the outer end of the axial passage 
terminates at the transverse passage while the inner end of the axial 
passage includes a sealing plug. Alternatively, the axial spill passage 
may be formed from the outer end of the nozzle valve element and a sealing 
plug positioned in the outer end while the inner end of the passage 
terminates at, and communicates with, the plurality of connector passages 
in the inner portion of the nozzle valve element. 
The nozzle valve element may include an axial spill passage positioned a 
spaced transverse distance from a central longitudinal axis of the nozzle 
valve element. In this respect, two axial passages may be provided wherein 
each passage is spaced a respective transverse distance from the central 
longitudinal axis of the valve element. Whether one or more offset axial 
passages are provided, the inner end of one or more of the axial passages 
may form an opening in the valve surface of the nozzle valve element for 
directly communicating with the cylinder gas purge passage. In another 
embodiment, the cylinder gas purge passage may include an orifice passage 
formed integrally in the inner portion of the nozzle valve element for 
providing communication between an inner end of the spill passage and a 
mini-sac fuel reservoir formed in the injector body adjacent the injector 
orifice. 
In each of the embodiments, the nozzle valve element may block fuel flow 
through the spill circuit when positioned in the closed position. The rate 
shaping control device may include a spill valve for controlling the spill 
flow of fuel through the spill circuit to create the high injection flow 
rate. The spill valve may include an annular step integrally formed on the 
nozzle valve element and an annular valve seat formed on the injector body 
for sealing engagement by the annular step upon movement of the nozzle 
valve element into the open position to prevent spill flow through the 
spill circuit. The rate shaping control device may further include a spill 
accelerating device positioned along the spill circuit for creating a 
rapid increase in the spill flow rate during each injection event. The 
spill accelerating device may include a transverse spill chamber formed in 
the nozzle valve element and extending generally transverse to the axial 
passage for receiving spill fuel. The rate shaping control device may 
include a flow limiting orifice positioned in the spill circuit for 
limiting the spill flow through the spill passage to a predetermined 
maximum spill flow rate. The flow limiting orifice is formed at least 
partially by the nozzle valve element and positioned along the spill 
circuit downstream of the spill accelerating device. 
The present invention is also directed to an improved, less expensive 
method of forming a nozzle valve element having an axial center spill 
passage. One embodiment includes the formation of the nozzle valve element 
from a preformed, i.e. cast, tube having a central passage. A compressive 
force is applied to the outer surface of the tube, i.e. by roll forming. 
The central passage may be of the same size as the desired diameter of the 
spill passage or of a larger diameter which is compressed to the desired 
final size. Also, two nozzle valve elements may be formed from a single 
piece of tube stock using a single compression at the center of the tube 
length to form each of the valve seat portions. The tube may be formed 
from the a solid bar or rod wherein the spill passage is drilled from the 
inner end of the rod and terminates prior to the outer end to avoid 
leakage possibly experienced by a closed outer end of the spill passage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Throughout this application, the words "inward", "innermost", "outward", 
and "outermost" will correspond to the directions, respectively, forward 
and away from the point at which fuel from an injector is actually 
injected into the combustion chamber of the engine. The words "outer" and 
"inner" will refer to the portions of the injector or nozzle assembly 
which are, respectively, farthest away and closest to the engine cylinder 
when the injector is operatively mounted on the engine. 
FIGS. 1-10 disclose various embodiments of the rate shaping nozzle assembly 
of the present invention for use in fuel injectors of various types. For 
example, the rate shaping nozzle assembly of the present invention may be 
adapted for use in an injector designed to receive high pressure fuel from 
a high pressure source (not shown). Such an injector is disclosed in FIG. 
9 of U.S. patent application Ser. No. 376,417, filed Jan. 23, 1995, now 
U.S. Pat. No. 5,647,536 entitled Injection Rate Shaping Nozzle Assembly 
for a Fuel Injector and assigned to the assignee of the present 
application, Cummins Engine Co., Inc., and which is hereby incorporated by 
reference. The rate shaping nozzle assembly of the present invention can 
certainly be incorporated into other forms of injectors including a unit 
injector having a high pressure pump plunger incorporated into the 
injector body. 
Now referring to FIGS. 1a and 1b, there is shown the rate shaping nozzle 
assembly of the present invention indicated generally at 52 which includes 
a nozzle housing 54 containing a nozzle bore 56 opening into a nozzle 
cavity 58 at one end. The opposite end of nozzle bore 56 communicates with 
a spring cavity 60 via a through-hole 62 formed in, for example, an inner 
barrel 64. Although not shown, a conventional retainer is used to hold the 
inner barrel and nozzle housing 54 in compressive abutting relationship. 
Received in nozzle bore 56 is a nozzle valve element 66 sized to form a 
close sliding fit with the inside surface of bore 56 creating a fluid seal 
which substantially prevents fluid from leaking from the clearance between 
nozzle valve element 66 and the inner surface of bore 56. Nozzle valve 
element 66 is biased into the closed position blocking flow through 
injector orifices 68 by a biasing spring 70 positioned in spring cavity 
60. A connector button 72 functions as a spring seat and also to transmit 
the spring force to the outer end of nozzle valve element 66. A fuel 
transfer circuit 74 includes transfer passages 76 and 78 formed in the 
inner barrel and nozzle housing, respectively, for delivering high 
pressure fuel from a high pressure source (not shown) to nozzle cavity 58. 
A low pressure drain circuit 80 communicates with spring cavity 60 to 
provide a drain path for fuel leakage into spring cavity 60. 
Rate shaping nozzle assembly 52 includes a rate shaping control device 
indicated generally at 82 which includes an injection spill circuit 84 and 
a spill valve 86. Injection spill circuit 84 includes a spill passage 88 
formed integrally in, and extending through, nozzle valve element 66. 
Injection spill circuit 84 also includes an annular recess 90, 
through-hole 62, and spring cavity 60. Spill passage 88 includes an axial 
passage 92 extending from the inner end of nozzle valve element 66, along 
a central longitudinal axis of nozzle valve element 66, and terminating 
prior to the outer end of valve element 66. Spill passage 88 also includes 
a lateral passage 94 extending from the outer end of axial passage 92 to 
communicate with annular recess 90. Annular recess 90 communicates with 
spring cavity 60 via an annular clearance 96 formed between the outer end 
of valve element 66 and through-hole 62. Lateral passage 94 is sized to 
function as a flow limiting orifice so as to throttle the flow through 
injection spill circuit 84. Axial passage 92 and lateral passage 94 may be 
formed by drilling or electrical discharge machining the passages into a 
fully hardened and finished nozzle element. Also, a spill accelerating 
device may be provided to create a rapid increase in the spill flow rate 
at the beginning of the injection event and to minimize the formation of 
gas pockets along spill circuit 82 which may impair the spill flow. For 
example, the spill accelerating device may be a transverse chamber 97 
extending transversely through nozzle valve element 66 and communicating 
with axial passage 92. The insertion of nozzle valve element 66 into 
nozzle housing 54 permits nozzle bore 56 to close the opening of chamber 
97 so as to seal the injection spill circuit. The positioning of 
transverse chamber 97 along spill circuit 84 upstream of lateral orifice 
passage 94 permits chamber 97 to function effectively as a spill 
accelerating device while maintaining the flow control function of orifice 
passage 94. The spill accelerating device may, alternatively, include 
other large volume passages formed in nozzle valve element 66, such as the 
embodiments disclosed in U.S. patent application Ser. No. 376,417, filed 
Jan. 23, 1995, now U.S. Pat. No. 5,647,536 which is hereby incorporated by 
reference. In addition, instead of lateral passage 94, flats may be formed 
on the outer surface of nozzle element 66 so as to fluidically connect 
transverse chamber 97 with annular recess 90 and control the spill flow as 
disclosed in a co-pending U.S. patent application filed on the same date 
as the present application in the name of Peters et al. and entitled 
Injection Rate Shaping Nozzle Valve Assembly With Outer Spill Flow 
Restriction, the entire disclosure of which is hereby by reference. 
Spill valve 86 includes an annular step 98 formed on nozzle valve element 
66 adjacent annular recess 90. Spill valve 86 also includes an annular 
valve seat 100 formed opposite step 98 on inner barrel 64. When nozzle 
valve element 66 is in a closed position as shown in FIG. 1a blocking fuel 
flow through injector orifices 68, annular step 98 is positioned a spaced 
distance from annular valve seat 100 to provide a spill flow path from 
annular recess 90 to spring cavity 60 via clearance gap 96. However, 
during an injection event, when nozzle valve element 66 moves to a fully 
open position shown in FIG. 1b, annular step 98 sealingly engages annular 
valve seat 100 to prevent spill flow between annular recess 90 and spring 
cavity 60. Spill passage 88 is formed in nozzle valve element 66 so that 
the conventional valve arrangement formed on the inner end of element 66 
can be used as a spill valve. Specifically, the inner end of nozzle valve 
element 66 includes a valve surface 102 for sealingly engaging a valve 
seat 104 formed on the inner surface of nozzle cavity 58 upstream of 
injector orifices 68. The inner end of axial passage 92 opens relative to 
valve seat 104 so that nozzle valve element 66 blocks fuel flow from 
nozzle cavity 58 to axial passage 92 when nozzle valve element 66 is in 
the closed position against valve seat 104. As a result, no spill fuel 
flows through spill passage 88 between injection events. 
During operation, between injection events, nozzle valve element 66 is 
positioned in the closed position as shown in FIG. 1a blocking flow 
through injector orifices 68 and injection spill circuit 84. At the start 
of an injection event, high pressure fuel is delivered from fuel transfer 
circuit 74 to nozzle cavity 58. When the pressure of the fuel in nozzle 
cavity 58 reaches a predetermined maximum necessary to overcome the 
biasing force of spring 70, nozzle valve element 66 begins to lift off 
valve seat 104 permitting fuel flow from nozzle cavity 58 through fuel 
injector orifices 68 into the combustion chamber of an engine. Fuel also 
spills into axial passage 92 traveling outwardly through lateral passage 
94 into annular recess 90. During the initial outward movement of the 
nozzle valve element 66, annular step 98 is still positioned a spaced 
distance from annular valve seat 100. As a result, fuel flowing into 
annular recess 90 is permitted to spill through clearance gap 96 into 
spring cavity 60 and on to the low pressure drain (not shown) connected to 
spring cavity 60. 
Therefore, with the present rate shaping nozzle assembly 52, a portion of 
the fuel normally flowing through injector orifices 68 is instead directed 
into spill passage 88. This splitting of the fuel flow into an injection 
flow and a spill flow during the initial portion of the injection event 
creates a reduced or low injection rate as represented by Stage I in FIG. 
2. The size of the orifice formed in lateral passage 94 or, alternatively, 
the diameter of lateral passage 94, determines the maximum spill rate to 
the low pressure drain and thus controls the injection rate through 
orifices 68. Further outward movement of nozzle valve element 66 into a 
fully opened position as shown in FIG. 1b, causes annular step 98 to 
sealingly engage annular valve seat 100 blocking fluidic communication 
between annular recess 90 and annular clearance 96. Thus, once nozzle 
valve element 66 moves into the fully opened position, spill flow through 
injection spill circuit 84 is prevented thereby permitting full fuel flow 
through injector orifices 68. As indicated by Stage II in FIG. 2, blockage 
of the spill flow causes the injection flow rate through injector orifices 
68 to rapidly increase. 
At the end of the injection event, when the delivery of high pressure fuel 
to nozzle cavity 58 has ceased, nozzle valve element 66 begins to move 
inwardly toward the closed position shown in FIG. 1a. During this inward 
movement, annular step 98 moves away from valve seat 100 permitting spill 
flow of pressurized fuel from nozzle cavity 58 through injection spill 
circuit 84. This creation of an additional drain or spill path during the 
last portion of the injection event causes a rapid decrease in the 
injection flow rate through orifices 68 since a portion of the fuel is 
directed through spill circuit 84. This end of injection spill 
advantageously creates a sharper end to the injection event. 
The present invention also includes a spill circuit purge device 110 
indicated in FIG. 1a, but clearly illustrated in FIG. 3. Spill circuit 
purge device 110 includes a cylinder gas purge passage 112 formed between 
nozzle valve element 66 and nozzle housing 54 for directing gases from the 
combustion chamber into spill passage 92 so as to effectively remove spill 
fuel from spill circuit 82 between injection events when nozzle valve 
element 66 is in the closed position thus ensuring a more effective spill 
event during the next injection event resulting in consistent, reliable 
and more effective injection rate shaping. 
Specifically, cylinder gas purge passage 112 includes an annular clearance 
gap 114 formed between valve surface 102 of nozzle valve element 66 and 
valve seating surface 104 of nozzle housing 54. Valve surface 102 and 
valve seating surface 104 are both frusto-conically shaped so that the 
inner end of nozzle valve element 66 extends into the inner end of nozzle 
housing 54 in a generally complementary manner as shown in FIG. 3. 
However, the taper of the frusto-conically shaped valve surface 102 is 
slightly different than the taper of the frusto-conically shaped valve 
seating surface 104 so as to cause valve surface 102 abut valve seating 
surface 104 at a point above injection orifices 68 as shown in FIG. 3. In 
other words, the angle of inclination of valve surface 102 with respect to 
the central axis of nozzle valve element 66 is greater than that of the 
angle of inclination of frusto-conically shaped valve seating surface 104. 
As a result, a circular line of contact, i.e. a valve seat, 116 is formed 
between valve surface 102 and valve seating surface 104 upstream of 
injection orifices 68 forming a seal for preventing fuel flow to spill 
passage 92 and injection orifices 68 when nozzle valve element 66 is in 
its closed position as shown in FIG. 3. The included angle seat 
differential between valve seating surface 104 and valve surface 102 thus 
forms annular clearance gap 114. Annular clearance gap 114 thus 
fluidically connects injection orifices 68 with spill passage 92 
permitting combustion gas flow into spill circuit 82 between injection 
events. 
The flow of gas from the engine cylinder through annular clearance gap 114 
is extremely effective in ensuring a rapid spill event and thus a 
predictable and reliable reduced injection flow rate during the first 
portion of the injection event by supplying an adequate quantity of purge 
gas flow to spill circuit 82 necessary to remove fuel from the circuit. 
The cleared spill circuit, or void, created by the flow of purge gas in 
spill circuit 82 greatly improves the spill flow during the next injection 
event. However, Applicants have found that an excessive purge gas flow 
through spill circuit 82 creates adverse effects, such as pressurization 
of the fuel supply tank to which the spill fuel is drained, and 
overheating of the spill fuel and thus the supply fuel. In addition, an 
excessive purge gas flow quantity may also result in an accumulation of 
excessive combustion products, i.e. carbon deposits, in the fuel requiring 
frequent fuel filter replacement/maintenance. Therefore, the purge gas 
flow must be restricted to within a maximum predetermined limit to avoid 
these adverse effects. The air flow area, and thus the quantity of purge 
gas flow, is determined by the differential angle between valve surface 
102 and valve seating surface 104 and the position of the opening of 
injection orifices 68 along annular clearance gap 114. For a predetermined 
position of injection orifices 68, as the differential angle between valve 
surface 102 and valve seating surface 104 is increased, the size of the 
annular clearance gap 114 also increases to provide greater purge gas 
flow, and vice versa. As shown in FIG. 3, annular clearance gap 114 
increases in size from valve seat 116 inwardly toward the tip of nozzle 
valve element 66. Thus, for a given differential angle, the purge gas flow 
quantity can be reduced by forming injection orifices 68 closer to valve 
seat 116, and increased by forming orifices 68 outwardly toward the tip of 
nozzle valve element 66 where annular clearance gap 114 creates less of a 
restriction to the flow of purge gas. 
Referring to FIGS. 4a and 4b, another embodiment of the present invention 
is shown wherein the spill circuit purge device 110 is applied to a 
mini-sac type fuel injector including a reservoir or sac 118 formed in 
nozzle housing 54. Injection orifices 68 extend through nozzle housing 54 
to communicate with the lower portion of sac 118. Spill circuit purge 
device 110 includes the same purge passage 112 formed by the annular 
clearance gap 114 as described hereinabove with respect to the embodiment 
shown in FIG. 3. However, in this embodiment spill circuit 82 includes a 
plurality of connector passages, i.e. two, extending outwardly from spill 
passage 92 to communicate with annular clearance gap 114. A sealing plug 
122 is securely positioned in the inner end of spill passage 92 to prevent 
flow through this portion of spill passage 92. As a result, when nozzle 
valve element 66 is in the closed position as shown in FIG. 4b, cylinder 
purge gas may flow through injection orifices 68 into annular clearance 
gap 114 via sac 118 and then into connector passages 120. Thus, the 
direction of the flow of purge gas through annular clearance gap 114 is 
now reversed relative to the flow direction of the embodiment of FIG. 3. 
As described more fully hereinbelow, the purge gas flow rate can be 
controlled by controlling the size of annular clearance gap 114, the 
position of the opening of connector passages 120 along annular clearance 
gap 114, and the size, i.e. diameter, of connector passages 120. It should 
be noted that in the previous embodiment of FIG. 3, the quantity of purge 
gas flow is also determined by the size of injection orifices 68. However, 
the diameter of injection orifices 68 is usually determined by the fuel 
spray characteristics desired for a particular application. As shown in 
FIG. 4a, spill passage 92 is formed in nozzle valve element 66 by a 
drilling extending from the inner end of element 66 and terminating at 
transverse chamber 97. 
As shown in FIGS. 5a and 5b, another embodiment of the rate shaping nozzle 
assembly of the present invention is illustrated which is similar to the 
embodiment shown in FIGS. 4a and 4b except that axial spill passage 92 is 
formed by a drilling extending from the outer end of element 66 and 
terminating at connector passages 120. A sealing plug 126 is securely 
positioned in the outer end of spill passage 124 to seal against the flow 
of fuel and purge gas from the outer end. Consequently, as shown in FIG. 
5b, no sealing plug is required at the inner end of element 66. Spill 
circuit purge device 110 of the present embodiment is the same as 
discussed previously with respect to the embodiment of FIGS. 4a and 4b. 
FIGS. 6a and 6b illustrate yet another embodiment of the present invention 
which is similar to the embodiment of FIGS. 5a and 5b except that spill 
circuit 82 includes connector passages 128 which extend from the inner end 
of spill passage 126 at an angle toward valve surface 102. As shown in 
FIG. 6a, this embodiment includes two connector passages 128 along with 
six injection orifices 68. Like the previous embodiment, the purge gas 
flow rate is determined primarily by the purge gas flow area. Assuming a 
predetermined angle seat differential for given arrangement, the purge gas 
flow area, and thus the purge gas flow rate, for a given set of combustion 
chamber operating conditions, is determined by the position of the opening 
of the connector passage along annular clearance gap 114 and by the 
diameter of connector passages 128. FIG. 6c illustrates the effects of 
varying the diameter of the connector passages and the position of the 
connector passages along annular clearance gap 114, on the purge gas flow 
area. As can be seen, as the position of the opening of connector passage 
128 is moved outwardly along annular clearance gap 114 toward valve seat 
116, that is, when H is increased (where H equals the distance between the 
inner end of nozzle valve element 66 and the intersection of the central 
longitudinal axis of element 66 and the central axis of connector passage 
128), the purge gas flow area decreases as a result of the decreasing 
annular clearance gap 114. Also, for a given connector passage position, 
i.e. H=1.25, the purge gas flow area increases as the diameter of 
connector passages 128 increases. Thus, a certain combination of connector 
passage diameter and position can be chosen to achieve the desired purge 
gas flow area resulting in an optimum purge gas flow quantity or rate. The 
graph of FIG. 6c also illustrates the purge gas flow area for a VCO type 
injector nozzle as disclosed in FIG. 3 as calculated based on flow area 
dimensions and also measured based on test results for assemblies having 
both a very low force nozzle spring and a conventional nozzle spring 
force. The nozzle spring force acting on nozzle valve element 66 deforms 
the wall of nozzle housing 54 slightly inwardly toward valve surface 102 
so as to decrease the width of annular clearance gap 114 and thus reduce 
the purge gas flow area. Thus, the larger the biasing force of nozzle 
spring 70 (FIG. 1a), the greater the decreasing effect on the annular 
clearance gap and thus the purge gas flow area. 
FIGS. 7a and 7b illustrate yet another embodiment of the rate shaping 
nozzle assembly of the present invention which is the same as the 
embodiment shown in FIGS. 6a-6b, except that spill circuit 82 includes 
three connector passages 130 equally spaced around the circumference 
nozzle valve element 66 as specifically shown in FIG. 7a. Like the 
previous embodiment, the diameter of the openings of connector passages 
130 in valve surface 102 and the position of the connector passage 
openings along annular clearance gap 114, can be predetermined to achieve 
a desired purge gas flow area corresponding to a desired purge gas flow 
rate. FIG. 7c illustrates the effects of the size and positioning of the 
connector passages 130 on the air flow area. Comparing FIGS. 6c and 7c, it 
is clear that a nozzle assembly having three connector passages results in 
a larger air flow area than the two connector passage design of FIGS. 6a 
and 6b, for a given connector passage position and diameter. However, 
different combinations of connector passage diameters and positions can be 
chosen to achieve a similar air flow area for the two passage and three 
passage arrangements. 
FIGS. 8a and 8b illustrate another embodiment of the present rate shaping 
nozzle assembly including the cylinder gas purge passage 112 in the form 
of the annular clearance gap 114 discussed hereinabove with respect to the 
previous embodiments. However, in this mini-sac application, the connector 
passages discussed hereinabove with respect to the previous mini-sac 
embodiments, are avoided by forming an axial spill passage 150 offset a 
spaced distance from the center line of nozzle valve element 152. Axial 
spill passage 150 is formed from the inner end of nozzle valve element 152 
and terminates in the outer portion at transverse chamber 97. The inner 
end of spill passage 150 forms an opening 154 in valve surface 102. Thus, 
no additional connector passages are needed to connect spill passage 150 
to annular clearance gap 114. With the valve element 152 in the closed 
position as shown in FIGS. 8a and 8b, cylinder purge gas flows through 
injector orifices 68 into mini-sac 118, through annular clearance gap 114 
and into axial spill passage 150. When nozzle valve element 150 moves into 
an open position, annular valve seat 116 will open allowing fuel to flow 
through the annular gap between nozzle valve element 150 and nozzle 
housing 54. As discussed hereinabove, fuel will spill into axial passage 
150 during the initial portion of the injection event while also flowing 
into mini-sac 118 and through orifices 68 into the combustion chamber. The 
description of the rate shaping capability of the present embodiment is 
the same as that discussed hereinabove with respect to the embodiment of 
FIGS. 1a and 1b. Also, the flow of purge gas is determined by the size of 
annular clearance gap 114 i.e. the included angle seat differential, the 
position of the opening 154 of axial passage 150 and the size of opening 
154. 
FIGS. 9a and 9b disclose yet another embodiment of the present invention 
which is the same as the embodiment described hereinabove with respect to 
FIGS. 8a and 8b, except for the addition of a second axial spill passage 
156 offset a spaced distance from the center line of nozzle valve element 
152. Axial spill passage 156 likewise connects transverse chamber 97 to 
annular clearance gap 114 and forms an opening 160 in valve surface 102. 
The use of two axial spill passages 150 and 156 permits greater control 
over the purge gas flow area than the previous single axial spill passage 
embodiment of FIGS. 8a and 8b due to the difficulty in controlling the 
tolerances of a single opening and clearance gap flow area. 
FIG. 10 represents another embodiment of the present rate shaping nozzle 
assembly including a spill circuit purge device 170 integrally formed in a 
nozzle valve element 172. As shown in combination with a mini-sac type 
nozzle housing, an axial spill passage 174 extends longitudinally through 
nozzle valve element 172 to communicate with spill circuit purge device 
170 at its innermost end. Spill circuit purge device 170 includes a purge 
passage 176 extending from the inner end of spill passage 174 through 
nozzle valve element 172 to communicate with mini-sac 118. purge passage 
176 includes a restriction orifice 178 having a predetermined purge gas 
flow area for restricting the flow of purge gas between injection events. 
Therefore, orifice 178 functions in a similar manner to the annular 
clearance gap 114 discussed hereinabove with respect to the previous 
embodiments. However, the size of restriction orifice 178 can be more 
easily controlled during manufacture permitting more predictable control 
over the purge gas flow. On the other hand, purge passage 176 also 
functions as an integral part of the spill circuit, i.e. spill passage 
174, and thus all spill flow must pass through restriction orifice 178. As 
a result, the desired spill flow rate and thus rate shaping capability of 
the assembly must be considered in the selection of the appropriate size 
of restriction orifice 178 so as not to compromise the rate shaping 
ability of the assembly. 
FIGS. 11-13 illustrate an improved method of the present invention for 
forming the nozzle valve element for use with the rate shaping nozzle 
assembly of the present invention. As shown in FIG. 11, the method of the 
present invention includes a step of providing a tube 200 having a 
generally cylindrical outer surface 202 and an axial center passage 204 
extending therethrough. A compressive force is then applied to the outer 
surface of tube 200 by, for example, a conventional cold or warm forging 
process, i.e. roll forming, so as to reduce the initial diameter of outer 
surface 202 along preselected portions of tube 200. Specifically, an outer 
end 206 of tube 200 is compressed to a smaller diameter to form an annular 
step 208 which comprises a portion of the spill valve 86 discussed with 
respect to the first embodiment of FIGS. 1a and 1b. The compression of 
outer end 206 substantially closes the outer end of axial center passage 
204. Tube 200 is also compressed along a significant portion of its 
length, indicated at 210, corresponding to the length of an axial spill 
passage 212. Tube 200 is compressed along length 210 a predetermined 
amount until the diameter of axial center passage 204 has been reduced to 
the final desired diameter of spill passage 212. An end portion of tube 
200 is compressed even further so as to form angled valve seat portion 
214. As a result, the inner end of axial center passage 204 is 
substantially closed. A central portion 218 of tube 200 is not subjected 
to the roll forming forces so as to maintain the outer diameter of the 
tube along portion 218 while creating an accelerating chamber 215. The 
result of theses two steps is a partially completed nozzle valve element 
216. Nozzle valve element 216 is then heat treated in a conventional 
manner to relieve stresses and impart the required strength and hardness 
properties to the material. Nozzle valve element 216 is then subjected to 
a centerless grinding operation which finishes the exterior surface to 
ensure proper outer diameters are achieved while forming an effective 
valve seat surface 220 on valve seat portion 214. The inner end of axial 
spill passage 212 is then reopened by drilling or electrical discharge 
machining an axial passage in the inner end of valve seat portion 214. 
Also, a lateral passage 222 is formed by, for example, electrical 
discharge machining in central portion 218 so as to communicate with 
accelerating chamber 215. 
Tube 200 is selected with an initial predetermined outer diameter and an 
initial predetermined inner diameter forming axial center passage 204 
which are specifically sized so as to permit the effective formation of 
spill passage 212, section 206 and valve seat portion 214 upon the 
application of respective predetermined amounts of compressive force to 
outer surface 202. In addition, the outer diameter of tube 200 is chosen 
to correspond to the diameter of the guide bore of the nozzle housing so 
that the grinding step can effectively create the desired clearances 
necessary for a substantially sealed, slidable interface, if necessary. 
Also, the diameter of axial center passage 204 is chosen to correspond to 
the desired diameter of accelerating chamber 215. This method allows tube 
200 to be easily mass produced by any conventional process, for example, 
casting or extruding, thus minimizing the cost and difficulty associated 
with forming nozzle valve element 216 by conventional methods. 
Conventionally, the formation of spill passage 212 is extremely tedious 
and difficult due to the minimal size of both element 216 and passage 212. 
The present method provides an inexpensive yet effective alternative to 
conventional machining methods. 
FIG. 12 illustrates another embodiment of the method of the present 
invention for forming nozzle valve element 216. In this embodiment, a 
solid cylindrical rod 224 is provided which includes an outer 
predetermined diameter. An outer end 226 is worked or turned to form 
annual step 208. An axial center passage 228 is then formed from the inner 
end of rod 224 so as to terminate prior to the outer end 226. The hollow 
rod is then subjected to compressive forces, i.e. roll forming, along 
portion 210 and valve seat portion 214 to form axial spill passage 212 and 
close off the inner end of passage 212 as discussed hereinabove with 
respect to the embodiment of FIG. 11. However, this embodiment does not 
require roll forming the outer end 226. This embodiment ensures that all 
spill fuel is directed solely through lateral passage 222 thus avoiding 
any leakage through the outer end of the nozzle valve element of the 
previous embodiment in the event the outer end of the center passage is 
inadequately closed by compression, thus ensuring proper fuel spilling and 
effective rate shaping. After roll forming, nozzle valve element 216 is 
then heat treated, centerless ground and electrical discharge machined as 
described in the embodiment of FIG. 11. 
FIG. 13 illustrates yet another embodiment of the present method for 
forming nozzle valve elements to be used with the rate shaping nozzle 
assembly of the present invention which effectively produces two nozzle 
valve elements 230 and 232 for each piece of tube 234. The present 
embodiment is substantially the same as the embodiment of FIG. 11 except 
that tube 234 is provided with a predetermined length substantially 
corresponding to the combined length of the two nozzle valve elements 230 
and 232. Nozzle valve elements 230 and 232 are formed such that the 
respective valve seat portions 234 and 236, respectively, are positioned 
adjacent one another. As a result, a single portion of a compressive force 
producing machine, i.e. rollers, can be applied to a single portion of 
tube 232 to form both valve seat portions 234 and 236 in a single forming 
step thus decreasing the cost and time of the manufacturing process. 
FIG. 14 is directed to yet another embodiment of the present method for 
forming the rate shaping nozzle valve element of the present invention. In 
this embodiment, a tube 240 is provided with an axial center passage 242 
having a predetermined diameter corresponding to the desired diameter of 
the resulting spill passage. The outer end 244 and the inner valve seat 
end portion 246 are roll formed as discussed hereinabove with respect to 
the embodiment of FIG. 11 so as to form the conical valve seat portion 248 
and to close off the outer end of spill passage 242 while forming annular 
step 250. The nozzle valve element may then be heat treated and centerless 
ground as discussed hereinabove. The inner end of spill passage 242 is 
then reopened by electrical discharge machining and a lateral spill 
passage 252 formed as discussed hereinabove. In addition, a transverse 
accelerating chamber 254 may then be formed in the nozzle valve element. 
It should be noted that the previous embodiments of the present method as 
discussed hereinabove with respect to FIGS. 11-13 may also include a 
transverse accelerating chamber in lieu of, or in addition to, the 
disclosed axial accelerating chamber 215. 
INDUSTRIAL APPLICABILITY 
It is understood that the present invention is applicable to all internal 
combustion engines utilizing a fuel injection system and to all closed 
nozzle injectors including unit injectors. This invention is particularly 
applicable to diesel engines which require accurate fuel injection rate 
control by a simple rate control device in order to minimize emissions. 
Such internal combustion engines including a fuel injector in accordance 
with the present invention can be widely used in all industrial fields and 
non-commercial applications, including trucks, passenger cars, industrial 
equipment, stationary power plant and others.