WO2000063549A2

WO2000063549A2 - Fuel pressure delay cylinder

Info

Publication number: WO2000063549A2
Application number: PCT/US2000/010659
Authority: WO
Inventors: Ning Lei; Xilin Yang; James H. Yager; Puring Wei; Mark J. Glodowski
Original assignee: International Engine Intellectual Property Co LLC; International Truck and Engine Corp
Current assignee: International Engine Intellectual Property Co LLC; International Motors LLC
Priority date: 1999-04-19
Filing date: 2000-04-19
Publication date: 2000-10-26
Anticipated expiration: 2001-10-19
Also published as: WO2000063549A3; US6408829B1; BR0009841A; CA2367618A1; AU4364600A; KR20010111310A; MXPA01010277A; JP2002542426A; EP1169567A2

Abstract

A delay device (12) for an engine fuel injector (10) having a control valve (50) for controlling high pressure actuating fluid flow to an intensifier (204) responsive to an injection command defining the duration of an injection event to increase the pressure on a volume of fuel for injection. The delay device (12) includes a piston (18) shiftable between a first disposition and a second disposition over a period of time after initiation of the injection command to effect a delay in initiation of fuel injection after initiation of the injection command. A method of controlling a fuel injection event includes flowing actuating fluid from the controller (50) to an intensifier (204) responsive to an injection command, pressurizing the fuel by the intensifier (204), flowing pressurized fuel to an injector nozzle (16), and interposing a delay in the flow of fuel to the injector nozzle (16).

Description

FUEL PRESSURE DELAY CYLINDER

Related Application

The present application claims the benefit of U S Provisional Application No 60/129,999 filed

April 19, 1999, and incorporated herein in its entirety by reference

Technical Field

The present invention relates to fuel injectors for use with internal combustion engines and

particularly with diesel engines More particularly, the present invention relates to hydraulically actuated

fuel injectors

Background of the Invention

Referring to the drawings, Figs 5 and 5a show a prior art fuel injector 350 The prior art fuel

injector 350 is typically mounted to an engine block and injects a controlled pressurized volume of fuel into

a combustion chamber (not shown) The prior art injector 350 of the present invention is typically used to

inject diesel fuel into a compression ignition engine, although it is to be understood that the injector could

also be used in a spark ignition engine or any other system that requires the injection of a fluid

The fuel injector 350 has an injector housing 352 that is typically constructed from a plurality of

individual parts The housing 352 includes an outer casing 354 that contains block members 356, 358,

and 360 The outer casing 354 has a fuel port 364 that is coupled to a fuel pressure chamber 366 by a

fuel passage 368 A first check valve 370 is located within fuel passage 368 to prevent a reverse flow of

fuel from the pressure chamber 366 to the fuel port 364 The pressure chamber 366 is coupled to a nozzle

372 through fuel passage 374 A second check valve 376 is located within the fuel passage 374 to prevent

a reverse flow of fuel from the nozzle 372 to the pressure chamber 366

The flow of fuel through the nozzle 372 is controlled by a needle valve 378 that is biased into a

closed position by spring 380 located within a spring chamber 381 The needle valve 378 has a shoulder

382 above the location where the passage 374 enters the nozzle 378 When fuel flows into the passage 374 the pressure of the fuel applies a force on the shoulder 382. The shoulder force lifts the needle valve

378 away from the nozzle openings 372 and allows fuel to be discharged from the injector 350.

A passage 383 may be provided between the spring chamber 381 and the fuel - port 364 to drain

any fuel that leaks into the chamber 381. The drain passage 383 prevents the build up of a hydrostatic

pressure within the chamber 381 which could create a counteractive force on the needle valve 378 and

degrade the performance of the injector 350.

The volume of the pressure chamber 366 is varied by an intensifier piston 384. The intensifier

piston 384 extends through a bore 386 of block 360 and into a first intensifier chamber 388 located within

an upper valve block 390. The piston 384 includes a shaft member 392 which has a shoulder 394 that is

attached to a head member 396. The shoulder 394 is retained in position by clamp 398 that fits within a

corresponding groove 400 in the head member 396. The head member 396 has a cavity which defines a

second intensifier chamber 402.

The first intensifier chamber 388 is in fluid communication with a first intensifier passage 404 that

extends through block 390. Likewise, the second intensifier chamber 402 is in fluid communication with a

second intensifier passage 406.

The block 390 also has a supply working passage 408 that is in fluid communication with a supply

working port 410. The supply port is typically coupled to a system that supplies a working fluid which is

used to control the movement of the intensifier piston 384. The working fluid is typically a hydraulic fluid

that circulates in a closed system separate from the fuel. Alternatively the fuel could also be used as the

working fluid. Both the outer body 354 and block 390 have a number of outer grooves 412 which typically

retain O-rings (not shown) that seal the injector 350 against the engine block. Additionally, block 362 and

outer shell 354 may be sealed to block 390 by O-ring 414.

Block 360 has a passage 416 that is in fluid communication with the fuel port 364. The passage

416 allows any fuel that leaks from the pressure chamber 366 between the block bore 386 and piston 384 to be drained back into the fuel port 364 The passage 416 prevents fuel from leaking into the first

intensifier chamber 388

The flow of working fluid into the intensifier chambers 388 and 402 can be controlled by a four-

way solenoid control valve 418 The control valve 418 has a spool 420 that moves within a valve housing

5 422 The valve housing 422 has openings connected to the passages 404, 406 and 408 and a drain port

424 The spool 420 has an inner chamber 426 and a pair of spool ports that can be coupled to the drain

ports 424 The spool 420 also has an outer groove 432 The ends of the spool 420 have openings 434

which provide fluid communication between the inner chamber 426 and the valve chamber 434 of the

housing 422 The openings 434 maintain the hydrostatic balance of the spool 420

10 The valve spool 420 is moved between the first position shown in Fig 5 and a second position

shown in Fig 5a by a first solenoid 438 and a second solenoid 440 The solenoids 438 and 440 are

typically coupled to a controller which controls the operation of the injector When the first solenoid 438 is

energized, the spool 420 is pulled to the first position, wherein the first groove 432 allows the working fluid

to flow from the supply working passage 408 into the first intensifier chamber 388 and the fluid flows from

i s the second intensifier chamber 402 into the inner chamber 426 and out the drain port 424 When the

second solenoid 440 is energized the spool 420 is pulled to the second position, wherein the first groove

432 provides fluid communication between the supply working passage 408 and the second intensifier

chamber 402 and between the first intensifier chamber 388 and the drain port 424

The groove 432 and passages 428 are preferably constructed so that the initial port is closed

0 before the final port is opened For example, when the spool 420 moves from the first position to the

second position, the portion of the spool adjacent to the groove 432 initially blocks the first passage 404

before the passage 428 provides fluid communication between the first passage 404 and the drain port

424 Delaying the exposure of the ports reduces the pressure surges in the system and provides an

injector 350 which has more predictable firing points on the fuel injection curve The spool 420 typically engages a pair of bearing surfaces 442 in the valve housing 422 Both the

spool 420 and the housing 422 are preferably constructed from a magnetic matenal such as a hardened

52100 or 4140 steel, so that the hysteresis of the material will maintain the spool 420 in either the first or

second position The hysteresis allows the solenoids 438, 440 to be de-energized after the spool 420 is

pulled into position In this respect the control valve 418 operates in a digital manner, wherein the spool

420 is moved by a defined pulse that is provided to the appropriate solenoid 438, 440 Operating the

control valve 418 in a digital manner reduces the heat generated by the solenoids 438, 440 and increases

the reliability and life of the injector 350

In operation, the first solenoid 438 is energized and pulls the spool 420 to the first position, so that

the working fluid flows from the supply port 410 into the first intensifier chamber 388 and from the second

intensifier chamber 402 into drain port 424 The flow of working fluid into the intensifier chamber 388

moves the piston 384 and increases the volume of chamber 366 The increase in the chamber 366 volume

decreases the chamber pressure and draws fuel into the chamber 366 from the fuel port 364 Power to the

first solenoid 438 is terminated when the spool 420 reaches the first position

When the chamber 366 is filled with fuel, the second solenoid 440 is energized to pull the spool

420 into the second position Power to the second solenoid 440 is terminated when the spool reaches the

second position The movement of the spool 420 allows working fluid to flow into the second intensifier

chamber 402 from the supply port 410 and from the first intensifier chamber 388 into the drain port 424

The head 396 of the intensifier piston 396 has an area much larger than the end of the piston 384,

so that the pressure of the working fluid generates a force that pushes the intensifier piston 384 and

reduces the volume of the pressure chamber 366 The stroking cycle of the intensifier piston 384

increases the pressure of the fuel within the pressure chamber 366 The pressunzed fuel is discharged

from the injector 350 through the nozzle opening 372 The actuating fluid is typically introduced to the

injector at a pressure between 300 - 4000 psi In the preferred embodiment, the piston has a head-to-end

ratio of approximately 7 1 , wherein the pressure of the fuel discharged by the injector is between 2,000 - 28,000 psi The fuel is discharged from the injector nozzle openings 372 and the first solenoid 438 is again

energized to pull the spool 420 to the first position and the cycle is repeated

The prior art HEUI injection system 350 has a relatively quick rise of the injection pressure after

initiation of the injection event As the intensifier piston 384 travels downward under the influence of the

actuating fluid, injection pressure builds up very quickly Under higher actuation fluid pressure (oil

pressure), the injection pressure build-up process is abrupt, due to high acceleration of the intensifier

piston 384 With the high initial injection pressure of the HEUI injection system 350, the initial rate of the

injection is also relatively high and hence contributes to higher NOx emission in an internal combustion

engine As is known, high NOx emission is undesirable as a pollutant With stringent emission regulations

currently being imposed, there is a need in the diesel engine industry to control the initial injection rate so

that a gradual rise or rate-shaped injection rate profile can be obtained and the NOx emissions may be

favorably affected

U S Patent No 5,492,098 presents an invention which improves HEUI injection by adding a spill

port at bottom of the plunger With some spilling of the high pressure fuel at the beginning of the injection,

initial injection pressure rises more slowly, hence producing a rate shaping feature However, due to the

spilling of high injection pressure fuel, significant energy is lost to the low pressure fuel reservoir This loss

can not be recovered during the injection event Such high energy loss is not desirable It would be

advantageous to provide for rate shaping of the rate of fuel injection without significant loss of fuel

pressure energy

Summary of the Invention

An objective of the present invention is to use a delay device to postpone or slow down the initial

injection pressure build up while retaining high fuel pressure energy With slow initial pressure rising in the

injection nozzle chamber, rate shaping can be obtained and controllability of small pilot injection is

improved

Advantages of the present invention are as follows Placing a delay device between pressure generation chamber (plunger chamber) and nozzle

chamber allows delay of the initial injection pressure rise and tailoring the amount of rate shaping before

the main injection event commences A slow and controllable fuel pressure rise during the initial portion of

the injection event is very critical to the precision control of the initial small quantity fuel delivery, especially

during a pilot injection mode Such control further provides repeatability between injection events

This delay device can be applied to any fuel injection system and specifically is not limited to the

HEUI injection system

The present invention is a delay device for use with a fuel injector, the fuel injector having an

electric controller for controlling the flow of a high pressure actuating fluid responsive to initiation and

cessation of a pulse width command, the pulse width command defining the duration of an injection event,

and an intensifier being in fluid communication with the controller, the intensifier being translatable to

increase the pressure of a volume of fuel for injection into the combustion chamber of an engine, the delay

device includes an apparatus, shiftable between a first disposition and a second disposition over a certain

period of time after initiation of the pulse width command, the period of time effecting a delay in initiation of

fuel injection after initiation of the pulse width command The present invention is further a fuel injector

including a delay device Additionally, the present invention is a method of controlling a fuel injection

event, includes the steps of sending a pulse width command to a controller to define an injection event,

flowing an actuating fluid from the controller to affect an intensifier responsive to reception of the pulse

width command, pressurizing a volume of fuel by means of the intensifier, flowing a high pressure fuel

from the intensifier to an injector nozzle, and interposing a delay in at least a portion of the flow of fuel to

the injector nozzle

Brief Description of the Drawings

Fig 1 is a side sectional view of an injector incorporating the delay control means of the present

invention, the control portion of the injector being shown schematically,

Fig 2 is an enlarged, sectional view of the present invention as depicted in Fig 1 , Fig 2a is a sectional view of the present invention prior to injection commencement

Fig 2b is a sectional view of the present invention during pilot injection,

Fig 2c is a sectional view of the present invention during main injection,

Fig 3a is a sectional view of a further embodiment of the present invention during pilot injection,

Fig 3b is a sectional view of the embodiment of Fig 3a during mam injection,

Fig 3c is a sectional view of the present invention depicted in the circle 3c of Fig 3b,

Fig 4a is a sectional view of another embodiment of the present invention prior to pilot injection,

Fig 4b is a sectional depiction of the present invention as depicted in Fig 4a during main

injection, and

Fig 5 is a sectional view of a prior art fuel injector,

Fig 5a is a sectional view of a prior art fuel injector electrically actuated controller,

Fig 6 is a sectional view of an injector with an embodiment of the present invention having rate

shaping features,

Fig 6a is a sectional view of the delay device of Fig 6 taken along the circle 6a,

Fig 6b is a sectional view of the delay device of Fig 6a during main injection

Fig 7a is a sectional view of an alternative embodiment of the delay device depicted in the closed

disposition, and

Fig 7b is a sectional view of the delay device of Fig 6a during main injection

Description of the Preferred Embodiments

An exemplary HEUI injector incorporating the present invention is shown generally at 10 in Fig 1

It is understood that other fuel injectors may also incorporate the present invention The delay control

device 12 of the present invention is installed between the intensifier plunger chamber 14 and the nozzle

chamber 16 In a preferred embodiment, the delay control device 12 comprises a delay cylinder 18 and a

delay cylinder housing 20, in conjunction with associated fluid passageways, as will be described The

operation of the delay control device 12 is basically such that high pressure fuel flows from the plunger chamber 14 to the nozzle chamber 16 through two different paths, the pilot path 22 and the main path 24

The pilot path 22 is open at all times between the plunger bottom chamber 34 and the nozzle chamber 16

However, the pilot path 22 is relatively restrictive, having a flow area that is less than about 10% of the

mam path 24 The amount of high pressure fuel flow through the pilot path 22 to the nozzle chamber 16 is

therefore relatively limited The significant fuel flow to the nozzle chamber 16 occurs only when the mam

path 24 opens up The main path 24 opening and closing is controlled by the position of the delay cylinder

18 of the delay device 12

The delay cylinder 18 is translatable between two positions, a closed position, as depicted in Fig

2a, and an open position, as depicted in Fig 2c Interim positions of the delay cylinder 18 are depicted in

Figs 2 and 2b The mam path 24 of high pressure fuel is blocked when the lower portion 27 of the delay

cylinder 18 closes the fuel path between the upper mam path 24a and the lower main path 24b This

occurs when the delay cylinder 18 is at its topmost position (Fig 2a) and in the interim positions (Figs 2

and 2b) The mam path 24 is fully open when delay cylinder 18 is at its bottom stop 28 position (Fig 2c),

where the groove 26 (defined in the body of the delay cylinder 18) fully opens the upper main path 24a to

the lower main path 24b

The delay cylinder 18 has two opposed pressure surfaces 30, 32 The top surface 30 is exposable

to high pressure fuel in the control chamber 34 and the bottom surface 32 forms in part a reservoir 39 and

is exposable to venting pressure in the low pressure fuel passageway 36 The venting pressure is at the

same pressure as low pressure fuel reservoir 38 pressure of Fig 1 As the intensifier plunger 40 moves

downwards, pressure under the plunger 40 in the chamber 14 builds up and a small amount of high

pressure fuel flows into the delay cylinder control chamber 34 via the control chambers orifice 52 (see Fig

2)

The delay cylinder spring 42 acting upward on the delay cylinder 18 is relatively weak

Accordingly, the delay cylinder 18 starts to move downward virtually as soon as the pressure in the control

chamber 34 rises (See Fig 2b) As the delay cylinder 18 travels downward, the delay cylinder 18 gradually passes the delay overlap 44 and gradually opens up the main path 24, connecting upper main path 24a to

lower main path 24b. The delay overlap 44 is the distance from the bottom margin 46 of the groove 26 to

the top 48 margin of the main path 24 prior to commencing the downward stroke of the delay cylinder 18.

See Fig. 2a.

Once the main path 24 is open, fuel flow from the plunger chamber 14 to the nozzle chamber 16

will have a rate that is typical of the prior art injector 350. The opening of the main fuel flow path 24 is

delayed from the initiation of the flow of the high pressure actuating fluid to the intensifier plunger 40 as

controlled by the control valve 50. The delay is equal to the amount of time it takes the delay chamber 18

to travel from its topmost disposition to decrease the overlap amount 44 to zero where the groove 26

commence opening the main path 24. The amount of the delay overlap 44 may be adjusted to fit specific

injection system needs by adjusting the distance of the delay overlap 44 during manufacture of the

injector. Such adjustment, for example, may be made by increasing the distance from the bottom 46 of the

groove 26 to the top 48 (point of intersection with) of the main flow path 24. The delay time may be further

adjusted by changing the area of the top pressure surface 30, or by changing the flow area of control

chamber orifice 52, or changing the flow area of the drain orifice 54.

The control chamber orifice 52 extends between the high pressure fuel chamber 14 and delay

cylinder control chamber 34. The purpose of this orifice 52 is to control the rate of the fuel pressure rising

within the control chamber 34. The orifice 52 is used to control the speed of delay cylinder 18 motion by

throttling the admission of high pressure fuel to the control chamber 34. If the orifice 52 is relatively large,

the delay cylinder 18 moves very fast and main path 24 opening delay becomes nearly negligible. A

smaller orifice 52 throttles the high pressure fuel to the control chamber 34, thereby reducing the speed of

the downward motion of the delay cylinder 18. The pressure inside of control chamber 34 is preferably

lower than the fuel pressure at plunger chamber 14 due to the throttling effect of the orifice 52. As

indicated above, the throttling is effected by the relatively small flow area of orifice 52. A lower pressure in the control chamber 34 allows the delay cylinder 18 to move downward with a slower, more controllable

and more desirable velocity

A dram orifice 54 is at the venting (lower) side of the delay cylinder 18 and is fluidly coupled to the

bottom pressure surface 32 The orifice 54 is used to vent fuel pressure to the low pressure fuel reservoir

38 when the delay cylinder 18 is moving downward This orifice 54 purposely restricts the venting process

so that the delay cylinder 18 downward motion is damped Such damping slows down the delay cylinder

18 opening process (Figs 2a to 2c) Varying the flow area of the orifice 54 as desired varies the amount of

damping of the delay cylinder 18 and has a direct effect on the duration of the delay time

The delay cylinder spring 42 is primarily used to return the delay cylinder 18 to its topmost position

(Fig 2a) at the end of the injection event after the previously described downward motion of the delay

cylinder 18 Accordingly, the spring 42 has a relatively weak spring constant As long as there is a higher

pressure in the control chamber 34 acting downward on the delay cylinder 18 than the pressure in the low

pressure fuel reservoir 38 (Fig 1) pressure (preferably about 50 psi), the delay cylinder 18 will stay at its

bottom stop position Such downward pressure on top pressure surface 30 overcomes the upward bias of

the spring 42 Therefore, the closing of the mam path 24 can occur at very end of the injection event when

the pressure in the control chamber 34 drops to near the pressure in the low pressure fuel reservoir 38

(which is the pressure in reservoir 39) With substantially equal fuel pressure acting on both surfaces 30,

32, the spring 42 is free to return the delay piston 18 to its retracted initial disposition as noted in Fig 2a

The delaying effect of the delay cylinder 18 therefore only occurs at the initial portion of each injection

event as described below.

The pilot path 22 connects intensifier plunger chamber 14 to the lower main path 24b and to the

nozzle chamber 16 The pilot path 22 is used to allow a limited amount of high pressure fuel flow to the

nozzle chamber 16 of the needle valve 60 before the mam path 24 flow path opens to admit the high

pressure fuel for the main fuel injection event This small amount of initial flow to the nozzle chamber 16

acts to open the needle valve 60 a small amount to permit a small amount of initial fuel injection to occur and provides a rate shaped feature to the injection system prior to main injection Varying the flow area of

the pilot path 22 as desired affects the volume of high pressure fuel flow through the pilot path 22 and

therefore affects the rate shaping of the injection event as desired to fit particular application needs

Description of the Operation

5 Operation may be appreciated with reference to Figs 1 and 2-2c Before the injection event starts,

the injector control valve 50 is at its closed position and the intensifier plunger 40 is at its topmost position

The fuel pressure in the passageway 36, the chamber 14, the control chamber 34, the reservoir 39, and at

orifice 54 is all at the same pressure, such pressure being the pressure in the low pressure fuel reservoir

38 This pressure is about 50 psi The delay cylinder 18 of the delay control device 12 is at its topmost

10 position (Fig 2a) due to the upward bias of the spring 42 Initially, the fuel pressure on both surfaces 30,

32 of the delay cylinder 18 is balanced so that the upward bias of the spring 42 alone is affecting the delay

cylinder 18 position The needle valve 60 is also closed under the influence of the spring 62

Initiation of the injection event is controlled by the control valve 50 As the control valve 50 opens,

high pressure actuation fluid from an engine associated high pressure actuation fluid rail 51 flows, at a

i s pressure ranging from 500-3500 psi, into intensifier piston chamber 64 and drives the intensifier plunger

40 downwards against the bias of the return spring 66 Fuel pressure under intensifier plunger 40 in the

chamber 14 builds up due to compression of the fuel effected by the force exerted by the high pressure

actuation fluid acting on the plunger 40

A small amount of the increasing pressure fuel flows through the pilot path 22 to the lower mam

0 path 24b and then further down to the nozzle chamber 16 See Fig 2b Since the flow volume through the

pilot path 22 is very small, the injection pressure at nozzle chamber 16 rises relatively slowly Such

pressure acts to generate an upward directed force on the needle valve 60 and the needle valve 60 is

opened only a small amount to permit a small amount of fuel to be injected from orifices 61 Such small

injection may be either pilot injection or rate shaping as desired At the same time as the pilot injection or rate shaping noted above, a small amount of fuel flows

into the delay cylinder control chamber 34 through the orifice 52 The delay cylinder 18 moves downward

at a controlled rate against the bias of the spring 42 Since there is offset (delay overlap 44) between the

delay cylinder groove edge 46 and the top 48 of mam path bore 24, the mam path 24 does not start to

open until the travel of the delay cylinder 18 is more than the amount of the overlap 44 The opening of the

mam path is delayed by the time it takes for the travel of the delay cylinder 18 to reduce the overlap 44

amount to zero, which occurs the point where the groove 26 commences to intersect the main path 24

The mam path 24 then starts to open gradually as the groove increasingly intersects the main

path 24 after the delay cylinder 18 passes the overlap 44 As soon as the mam path 24 begins to open, a

significant amount of high pressure fuel flows to the nozzle chamber 16 and causes the needle valve 60 to

open fully, resulting in the main injection event The delay cylinder 18 continues downward until the mam

path 24 is fully opened as indicated in Fig 2c

The end of the injection event is also controlled by the control valve 50 The control valve 50

closes to cause the end of the injection event At such closing, the actuation fluid is vented to ambient

pressure at the low pressure reservoir 66 The intensifier plunger 40 starts to return to its top stop position

and the injection pressure in the main path 24 available to the needle valve 60 decays As injection

pressure drops, the needle valve 60 is closed by the spring 62 The refill check valve ball 68 starts to open

to refill the chamber 14 During the refilling process, the fuel pressure at top surface 30 of the delay

cylinder 18 is same (balanced) as the pressure at the bottom surface 32 (about 50 psi fuel reservoir 38

pressure) The delay cylinder spring 42 now starts to push the delay cylinder 18 upward to return the delay

cylinder 18 to top stop position (Fig 2a) to complete the injection cycle

It should be noted that the delay cylinder spring 42 has a very small initial load and spπng rate

This allows the delay cylinder 18 to stay at its bottom disposition until the pressure in the control chamber

34 goes substantially low during the end of an injection event This feature is desirable for dwell control of

a split injection event when the control valve makes two round trips Although the first injection (pilot injection) is delayed, the mam injection will not be delayed which causes an increase of dwell time

between the pilot injection and the mam injection

Alternative Preferred Embodiments

Push Pin Design

This further preferred embodiment of the delay control means 12 is used to minimize the total

amount of fuel used during retraction of the delay piston 18, as indicated in Figs 3a-3c As the delay piston

18 moves downward (translating between the position of Fig 3a to the position of Fig 3b), the delay piston

18 creates displacement in the control chamber 34 and therefore requires some additional amount of the

fuel to fill the control chamber 34 It is very desirable that this amount of the fuel should be minimized for

energy efficiency concerns Fuel used to drive the delay piston 18 is not available for injection into the

engine combustion chamber A small pin 70 is used to push the delay cylinder 18 during the downward

opening process This pin 70 can be designed much smaller than is possible with the control chamber 34

of the above embodiment of Figs 2 Accordingly, the volume of the control chamber 34 is minimized and

hence the amount of fuel used to cause translation of the delay piston 18 is substantially smaller This

increases the volume of fuel available for injection by needle valve 60 Referring to Fig 3c, there is a drain

hole 72 at center of the delay cylinder Together with the transverse slot 74 at bottom of the pin 70, the

drain hole 72 balances the pressure on both sides of the delay cylinder 18

Delayed Pilot Hole Design

Referring to Figs 4a and 4b, the pilot hole 80 of the pilot path 22 draws fuel from the delay cylinder

control chamber 34 The pilot hole 80 is covered by the delay cylinder 18 when delay cylinder 18 is at

topmost position See Fig 4a As the delay cylinder 18 travels downward, the pilot hole 80 is uncovered

and exposed to the fuel under pressure in the chamber 34 The uncovering occurs prior to the opening of

the main path 24 This is evident in Fig 4b The distance between pilot hole 80 and mam path 24 defines

the amount of rate shaping that will occur before the mam injection event occurs Rate shaping occurs

during the time that the pilot path 22 alone is supplying fuel to the needle valve Such fuel flow in the pilot path 22 commences only after the pilot hole 80 is uncovered and continues as the only source of fuel to

the needle valve 60 until the groove 26 of the delay cylinder 18 intersects the main path 24, at which time

the main injection event commences

Spool Cylinder Design

A further embodiment of the present invention is depicted in Figs 6, 6a, and 6b The injector of

Fig 6 is a HEUI type injector substantially as described with respect to the prior art injector 350 of Figs 5

and 5a

Ignoring the delay device 10 of the present invention, the injector 200 has four main components

control valve 202, intensifier 204, nozzle 206, and injector housing 208 The injector housing 208 may be

formed of several components such as housing 208a, housing 208b, or be made as a unitary housing

The control valve 202 initiates and ends an injection event The control valve 202 has a spool

valve 210 and an electric control 212 for shifting the spool valve 210 from a right closed disposition to a

left open disposition and return to the right closed seat The spool valve 210, responsive to electric inputs,

ports high pressure actuating fluid to and from the intensifier 204

To begin injection, a solenoid of the electric control 212 is energized, moving the spool valve 210

from its right closed seat to its left open seat This action admits high pressure actuating fluid via internal

passages (not shown) to the piston chamber 223 of the intensifier 204 As will be seen, absent the delay

device 10, fuel injection commences substantially simultaneously with the porting of the high pressure

actuating fluid to the intensifier 204 and continues until a solenoid of the electric control 212 is energized

and the spool valve 210 is shifted πghtward to its right closed seat Actuating fluid and fuel pressure within

the injector 200 then decrease as spent actuating fluid is discharged from injector 200 by the spool valve

210 Such discharge is typically to the valve cover area of the engine, which is at ambient pressure

The center segment of the injector 200 includes the intensifier 204 The intensifier 204 includes a

preferably unitary device comprising the hydraulic intensifier piston 236 and plunger 228, in addition to the

fuel chamber 230 and the plunger return spring 232 Intensification of the fuel pressure to a desired injection pressure level is accomplished by the

ratio of areas between the upper surface 234 of the intensifier piston 236, acted on by the high pressure

actuating fluid, and the lower surface 238 of the plunger 228 acting on the fuel in the chamber 230 The

intensification ratio can be tailored to achieve desired injection characteristics Fuel is admitted to chamber

230 through the passageway 240 past check valve 242 Injection begins as the high pressure actuating

fluid is supplied to the upper surface 234 of the intensifier piston 236, driving the intensifier piston 236

downward to compress the fuel in chamber 230

As the intensifier piston 236 and plunger 228 move downward responsive to the force exerted by

the high pressure actuating fluid, the pressure of the fuel in chamber 230 below the plunger 228 rises

dramatically Absent the delay device 10 of the present invention, the chamber 230 is directly fluidly

coupled to the passageway 244 High pressure fuel from the chamber 230 flows through the passageway

244 to act upwardly on the needle valve surface 248 The upward force on the surface 248 overcomes the

bias of the needle valve spring 256 and opens the needle valve 250 Fuel is then discharged from the

orifices 252 into the combustion chamber of the engine The intensifier piston 236 continues to move

downward and compressing the fuel in chamber 230 until a solenoid of the electric control 212 is

energized causing the spool valve 210 to shift πghtward to its closed right seat In such disposition, the

high pressure actuating fluid bearing on the surface 234 is discharged from the injector 200 to ambient

pressure At this point, the plunger return spring 232 returns the piston 236 and plunger 228 to their initial

upward seated position As the plunger 228 returns upward, the plunger 228 draws replenishing fuel into

the plunger chamber 230 across the ball check valve 242

The nozzle 206 is typical of other diesel fuel system nozzles Fuel is supplied to the nozzle orifices

252 through internal passages 244 As indicated above, the dramatic rise in fuel pressure to the nozzle

needle 250 acts to lift to the needle 250 to the open position, thereby allowing fuel injection to occur

through orifices 252 As fuel pressure decays at the end of the injection event, responsive to the πghtward

shift of the spool valve 210, the spring 256 returns the nozzle needle 250 to its upward closed disposition The imposition of the delay device 10 in the injector 200 has a dramatic effect on the

aforementioned injection process as will be described in greater detail below As best shown in Fig 6a

and 6b, the delay device 10 includes the following components piston assembly 300 and flow passage

assembly 302 The flow passage assembly 302 includes a cylinder 304 defined in the housing 306

Cylinder 304 has a dram passage 308 defined proximate the lower margin of the cylinder 304 The dram

passage 308 is typically vented exterior of the injector 200 to fuel supply pressure (50 psi) The dram

passage 308 is preferably defined between the housing 306 and the delay cylinder stop 310 The delay

cylinder stop 310 has a generally circular spring retainer groove 312 defined therein

The delay piston assembly 300 includes a delay piston 314 translatably disposed within the

l o cylinder 304 The delay piston 314 is biased to the upward disposition as depicted in Fig 6a by a return

spring 316 The return spring 316 resides in an axial chamber 318 defined within the delay piston 314 A

distal end of the return spring 316 is captured within the spring retainer groove 312

The delay piston 314 has a top surface 320 that is exposable to high pressure fuel The top

surface 320 has a centrally disposed return orifice 322 defined therein The return orifice 322 extends

15 between top surface 320 and the axial chamber 318 A circumferential groove 324 is defined around the

body of the delay piston 314 The groove 324 is spaced apart from the top surface 320 The delay piston

314 further has a lower margin 312 As depicted in Fig 6b, the lower margin 312 is in contact with the

delay cylinder stop 310 in the fully open disposition of the delay piston 314

The flow passage assembly 302 further includes a plurality of flow passages as will be described

0 The first such flow passage is the control chamber orifice 328 The control chamber orifice extends

between the plunger chamber 230 and the cylinder 304 High pressure fuel flowing from the plunger

chamber 230 through the control chamber orifice 328 bears on the top surface 320 of the delay piston

314

The mam path 330 has a substantially larger flow passageway than the control chamber orifice

2 328 The main path 330 is also fluidly connected to the plunger chamber 230 and is defined at least in part in the housing 306 alongside the delay piston 314 The mam path 330 is defined in part through the delay

cylinder stop 310 and in part in the housing 306 The mam path 330 is fluidly coupled to an upper groove

332 that is also defined in the housing 306 The upper groove 332 is circumferential about the center axis

of the delay piston 314 The upper groove 332 intersects and is fluidly coupled to the cylinder 304 A

5 second groove, the lower groove 334 is spaced apart from and immediately beneath the upper groove

332 Like the upper groove 332, the lower groove 334 is defined in the housing 306 circumferential to the

delay piston 314 The lower groove 334 intersects the cylinder 304

Where rate shaping is desired, a relatively small area pilot path 336 is defined in the housing 306

extending between and fluidly coupling the upper groove 332 and the lower groove 334 It is understood

l o that where delay alone is desired, the pilot path 336 would not be included As will be seen, the delay

overlap 338 is defined between the lower margin of the groove 324 and the upper margin of the lower

groove 334

Operation of the delay device 10 may be appreciated with reference to Figs 6a and 6b Fig 6a

shows the delay piston 314 at its uppermost disposition within the cylinder 304 This position is the

i s position and defines the status prior to initiation of the injection event The lower groove 334 is

substantially sealed by the wall of the delay piston 314 Accordingly, fuel may flow from the upper groove

332 to the lower groove 334 only through the pilot path 336 The dram passage 308 is fully open

Upon initiation of the injection event by the control valve 202, high pressure actuating fluid is

ported to the intensifier 204 The plunger 228 starts downward dramatically compressing the fuel in the

20 plunger chamber 230 The high pressure fuel flows through the control chamber orifice 328 to bear upon

the top surface 320 of the delay piston 314 and thereby to commence downward translation of the delay

piston 314

Simultaneously, high pressure fuel flows through the mam path 330, the upper groove 332, and

the pilot path 336 The limited amount of high pressure fuel passing through the pilot path 336 flows

2 through the lower groove 334 to the passageway 244 This limited amount of high pressure fuel acts to open the needle valve 250 to slightly open the orifices 252 resulting in the injection of a very limited

amount of fuel into the compression chamber The limited amount of fuel injected results in a gradual

ramping of the rate of injection into the combustion chamber, comprising the desired rate shaping of the

leading edge of the mam injection event

5 It should be understood that by not including the optional pilot path 336, no injection occurs during

the aforementioned described period of delay In such event, no high pressure fuel is admitted to the flow

passageway 244 until the delay cylinder 314 completes the transition through the delay overlap 338

When the delay piston 314 translates downward enough to complete the translation through the

region of the delay overlap 338 the groove 324 defined in the delay piston 314 intersects both the upper

10 groove 332 and the lower groove 334 permitting full flow of high pressure fuel from the plunger chamber

230 to the fuel passage 244 to fully open the needle valve 250, resulting in the mam injection portion of

the injection event The delay piston 314 continues downward under the influence of the force generated

on the top surface 320 by the high pressure fuel until the lower margin 326 comes into contact with the

delay cylinder stop 310 as depicted in Fig 6b At this lower disposition, dram passage 308 is completely

i s blocked by the delay piston body 314

Termination of the injection event is commanded by the control valve 202 An electric signal to the

control valve 202 shifts the spool valve 210 from the left open seat to the right closed seat Such shifting

vents the high pressure actuating fluid from the injector 200 The intensifier 204 ceases to pressurize fuel

in the plunger chamber 230 The plunger 228 commences its upward travel At this point, the delay piston

20 314 commences its upward travel from the lower open seat of Fig 6b to the upper closed seat of Fig 6a

Such translation is effected by the bias generated on the delay piston 314 by the return spring 316 As the

delay piston 314 translates upward, fuel captured within the cylinder 304 above the delay piston 314

passes through the return orifice 322 and out the dram passage 308 The delay piston 314 continues

upward until the top surface 320 is seated on the underside of the spacer 313 as depicted in Fig 6a The control chamber orifice 328 has a significant effect on the motion of the delay piston If the

control chamber orifice 328 is extremely small, the motion of the delay piston 314 will be very slow

resulting in a longer delay time The delay piston return spring 316 is relatively weak So that return of the

delay piston occurs only when the pressure in the plunger chamber 230 decays nearly to the fuel supply

5 pressure level (50 psi)

A further embodiment of the present invention is depicted in Figures 7a and 7b The concept of

the delay device of Figures 7a and 7b is similar to the embodiment described above with respect to

Figures 6a and 6b and may be readily installed in the injector 200 of Figure 6 Accordingly, like numbers in

the Figures 7a and 7b denote like components in Figures 6a and 6b The delay device 10 includes

l o components piston assembly 300 and flow passage assembly 302

The flow passage assembly 302 includes a cylinder 304 defined in the housing 306 Cylinder 304

has a drain passage 308 defined proximate the lower margin of the cylinder 304 The drain passage 308 is

typically vented exterior to the injector 200 to fuel supply pressure The dram passage 308 is preferably

defined between the housing 306 and the delay cylinder stop 310 The delay piston stop 310 has a

15 generally circular spring retainer groove 312 defined therein

The piston assembly 300 includes a delay piston 314 translatably disposed within the cylinder

304 The delay piston 314 is biased in the upward disposition as depicted in Fig 7a by a return spring

316 The return spring 316 is concentrically disposed with respect to a depending cylinder 318 of the delay

piston 314

0 The delay piston 314 has a top surface 320 that is exposable to high pressure fuel The top

surface 320 has a centrally disposed inlet orifice 321 defined therein The inlet orifice 321 extends

between top surface 320 and a circumferential groove 324 that is defined around the body of the delay

piston 314 The groove 324 is spaced apart from the top surface 320 The delay piston 314 further has a

lower margin 312 As depicted in Fig 7b, the lower margin 312 is in contact with the delay cylinder stop

25 310 in the fully open disposition of the delay piston 314 The flow passage assembly 302 further includes a plurality of flow passages as will be described

The first such flow passage is the mam path 330 The upper mam path 330a is fluidly connected to the

plunger chamber 230 and the lower mam path 334 is fluidly connected to the passage 244 to the nozzle

orifices 252 The upper main path 330a is fluidly coupled to an upper path extension 332 that is also

defined in the housing 306 The upper path extension 332 is intersects and is fluidly coupled to the groove

324 in the piston 314 and thence through an inlet orifice 350 to the inlet 321 The size of inlet orifice 350

can be varied to adjust the velocity of the delay piston 314 A second lower path extension 334 is spaced

apart from and immediately beneath the upper path extension 332 The lower path extension 334

intersects the cylinder 304 An axially symmetric drilled passage 334a is placed on the other side from

extension 334 to reduce the hydraulic side loading on the delay piston since the hydraulic pressure in

passages 334 and 334a are always the same

Where rate shaping is desired, a relatively small flow area pilot path 336 is defined in the housing

306 extending between and fluidly coupling the upper mam path 330a and the lower path extension 334 It

is understood that where delay alone is desired, the pilot path 336 would not be included As will be seen,

the delay overlap 338 is defined by the width of a land 337 of the delay piston 314 that, in Figure 7a,

spans the gap between intersections with the cylinder 304 respectively of the upper path extension 324

and the lower path extension 334

Operation of the delay device 10 may be appreciated with reference to Figs 7a and 7b Fig 7a

position and defines the status prior to initiation of the injection event The lower path extension 334 is

substantially sealed from the upper path extension by the land defining the delay overlap 338

Accordingly, fuel may flow from the chamber 230 in the injector 200 (see Figure 6) through the upper main

path 330a, the upper path extension 332 and to the inlet 321 to bear on the surface 320 Simultaneously,

high pressure fuel may flow from the upper main path 330a through the pilot path 336 to the lower mam

path 330b and thence to the orifices 252 for pilot injection The drain passage 308 is fully open Upon initiation of the injection event by the control valve 202, high pressure actuating fluid is

ported to the intensifier 204. The plunger 228 starts downward dramatically compressing the fuel in the

plunger chamber 230 and providing high pressure fuel to the upper main path 330a. The high pressure

fuel flows through the inlet 321 to bear upon the top surface 320 of the delay piston 314 and thereby to

commence downward translation of the delay piston 314.

Simultaneously, high pressure fuel flows through the main path 330a and the pilot path 336. The

limited amount of high pressure fuel passing through the restricted flow area of the pilot path 336 flows

through the lower path extension 334 and the lower main path 330b to the passageway 244. This limited

amount of high pressure fuel acts to open the needle valve 250 to slightly open the orifices 252, resulting

in the injection of a very limited amount of fuel into the compression chamber. The limited amount of fuel

injected results in a gradual ramping of the rate of injection into the combustion chamber, comprising the

desired rate shaping of the leading edge of the main injection event.

It should be understood that by not including the optional pilot path 336, no injection occurs during

the aforementioned described period of delay. In such event, no high pressure fuel is admitted to the flow

passageway 244 until the delay cylinder 314 completes the transition through the delay overlap 338.

region of the delay overlap 338, the groove 324 defined in the delay piston 314 intersects both the upper

path extension 332 and the lower path extension 334 permitting full flow of high pressure fuel from the

plunger chamber 230 to the fuel passage 244 to fully open the needle valve 250, resulting in the main

injection portion of the injection event. The delay piston 314 continues downward under the influence of

the force generated on the top surface 320 by the high pressure fuel until the lower margin 312 comes into

contact with the piston stop 310 as depicted in Fig. 7b.

It should be understood that by adjusting the length of the overlap 338, the size of the inlet orifice

350, and/or the size of the pilot passage 336, different rate shaping effects can be obtained. The optimum

combination will be determined empirically from engine performance testing. Termination of the injection event is commanded by the control valve 202 An electric signal to the

314 commences its upward travel from the lower open seat of Fig 7b to the upper closed seat of Fig 7a

passes through the inlet orifice 321 and out the dram passage 308 The delay piston 314 continues

upward until the top surface 320 is seated on the underside of the spacer 313 as depicted in Fig 7a

While a number of presently preferred embodiments of the invention have been illustrated and

described, it should be appreciated that the inventive principles can be applied to other embodiments falling

within the scope of the following claims

What is claimed is

Claims

1 A delay device for use with a fuel injector, the fuel injector having an electric controller for

controlling the flow of a high pressure actuating fluid responsive to initiation and cessation of a pulse width

command, the pulse width command defining the duration of an injection event, and an intensifier being in

fluid communication with the controller, the intensifier having a plunger chamber, and being translatable to

increase the pressure of a volume of fuel in the plunger chamber, the plunger chamber being in fluid

communication with an injector nozzle, the injector nozzle for injection of fuel into the combustion chamber

of an engine, the delay device comprising

an apparatus, shiftable between a first disposition and a second disposition over

a certain period of time after initiation of the pulse width command, the period of time

effecting a delay in initiation of fuel injection after initiation of the pulse width command

2 The delay device of claim 1 wherein the electric controller is shiftable between a closed disposition

and an open disposition, the delay in initiation of fuel injection being related to a period of time necessary

for the electric controller to complete a round trip between the closed disposition and the open disposition

3 The delay device of claim 1 further effecting rate shaping of the injection event

4 The fuel injector of claim 1 further effecting pilot injection prior to a main injection portion of the

injection event

5 The delay device of claim 1 being fluidly interposed between the intensifier and the injector nozzle

to affect the fluid communication between the intensifier and the injector nozzle

6 The delay device of claim 5 wherein the apparatus acts to delay the flow of high pressure fuel

from the intensifier to the injector nozzle

7 The delay device of claim 1 wherein the apparatus is biased in the first disposition

8 The delay device of claim 7 wherein the apparatus shifts from the first disposition responsive to

high pressure fuel generating a force on the apparatus in opposition to the bias

9 The delay device of claim 8 wherein the apparatus is disposed relative to a fluid passageway, the

fluid passageway being in fluid communication with the injector nozzle, such that shifting of the apparatus

acts to open and close the passageway

10 The delay device of claim 9 wherein the apparatus is a piston disposed in a cylinder, the fluid

passageway intersecting the cylinder

11 The delay device of claim 10 wherein the piston is biased in the first disposition

12 The delay device of claim 11 wherein the piston is translatably disposed at least in part in a

cylinder defined in an injector housing

13 A fuel injector, comprising

an electric controller for controlling the flow of a high pressure actuating fluid

responsive to initiation and cessation of a pulse width command, the pulse width

command defining the duration of an injection event, an intensifier being in fluid communication with the controller, the intensifier being

translatable to increase the pressure of a volume of fuel for injection into the combustion

chamber of an engine,

a delay device, shiftable between a first disposition and a second disposition over

14 The fuel injector of claim 13 wherein the electric controller is shiftable between a closed

disposition and an open disposition, the delay in initiation of fuel injection being related to a period of time

necessary for the electric controller to complete a round trip between the closed disposition and the open

disposition

15 The fuel injector of claim 13 further effecting rate shaping of the injection event

16 The fuel injector of claim 13 further effecting pilot injection prior to a main injection portion of the

injection event

17 The fuel injector of claim 13 being fluidly interposed between the intensifier and an injector nozzle

18 The fuel injector of claim 17 wherein the delay device acts to delay the flow of high pressure fuel

from the intensifier to the injector nozzle

19 The fuel injector of claim 13 wherein the delay device is biased in the first disposition

20 The fuel injector of claim 19 wherein the delay device shifts from the first disposition responsive to

high pressure fuel generating a force on the delay device in opposition to the bias

21 The fuel injector of claim 20 wherein the delay device is disposed relative to a fluid passageway,

the fluid passageway being in fluid communication with the injector nozzle, such that shifting of the delay

device acts to open and close the passageway

22 The fuel injector of claim 21 wherein the delay device is a piston disposed in a cylinder, the

passageway intersecting the cylinder

23 The fuel injector of claim 22 wherein the piston is biased in the first disposition by a spring acting

thereon

24 The fuel injector of claim 23 wherein the piston is translatably disposed at least in part in a cylinder

defined in an injector housing

25 A method of controlling fuel injection events, comprising the steps of

sending a pulse width command to a controller to define an injection event,

flowing an actuating fluid from the controller to affect an intensifier responsive to

reception of the pulse width command,

pressurizing a volume of fuel by means of the intensifier,

flowing a high pressure fuel from the intensifier to an injector nozzle, and

interposing a delay in at least a portion of the flow of fuel to the injector nozzle

26 The method of claim 25 wherein a small portion of the flow of fuel to the injector nozzle is not

delayed to provide pilot injection

27 The method of claim 25 wherein a period of injection rate shaping is concurrent with the period of

delay

28 The method of claim 25 wherein the delay is effected by selectively opening and closing an

actuating fluid passageway by means of the translatory motion of a delay piston

29 The method of claim 28 wherein the translatory motion of the delay piston is effected in part by the

high pressure fuel acting on the delay piston

30 A fuel injector, comprising

command defining the duration of an injection event,

an intensifier being in fluid communication with the controller, the intensifier being

translatable to increase the pressure of a volume of fuel in a plunger chamber for injection

into the combustion chamber of an engine, the intensifier having an intensifier piston

disposed in a cylinder defined in an injector housing,

an injector nozzle in fluid communication with the intensifier,

a delay device in fluid communication with the intensifier and the injector nozzle,

being shiftable between a first disposition and a second disposition over a certain period

of time after initiation of the pulse width command, the period of time effecting a delay in

initiation of at least a portion of the fuel injection from the injector nozzle after initiation of the pulse width command, the delay device including a delay piston transitionally

disposed in a delay piston cylinder defined at least in part in the injector housing

31 The injector of claim 30 further including a first actuating high pressure fuel passageway, the first

actuating fuel passageway fluidly coupling the plunger chamber to the delay piston, fluid pressure in the

first actuating fuel passageway acting to generate a force on the delay piston for imparting translatory

motion thereto

32 The injector of claim 31 and the first actuating fuel passageway providing a predetermined

restriction controlling the application of the fluid pressure to impart the translatory motion to the delay

piston

33 The injector of claim 31 further including a second fuel passageway, the second fuel passageway

fluidly coupling the delay piston to the injector nozzle, fluid pressure in the second fuel passageway acting

to generate a force on the injector nozzle for imparting translatory opening motion thereto

34 The injector of claim 33 wherein the second fuel passageway intersects the delay piston cylinder

between the delay device a first disposition and a second disposition

35 The injector of claim 34 wherein the second fuel passageway is substantially sealed by the delay

piston when the delay piston is in the first disposition

36 The injector of claim 35 wherein translation of the delay piston from the first disposition toward the

second disposition acts to open the second fuel passageway after a selected distance of delay piston

travel

37. The injector of claim 33 wherein a third fuel passageway intersects the second fuel passageway

for conveying a volume of pressurized fuel thereto, the third fuel passageway having a relatively small flow

area for restricting the volume of fuel flowing therein, such restriction effecting a rate shaped injection

event.

38. The injector of claim 37 wherein the third fuel passageway is in fluid communication with the

plunger chamber.

39. The injector of claim 37 wherein the third fuel passageway is open to the flow of fuel without

regard to the position of the delay piston.