Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-04-02
2004-01-27
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S447000, C123S458000
Reexamination Certificate
active
06681743
ABSTRACT:
TECHNICAL FIELD
The present invention relates to actuators for use principally with internal combustion engines. More particularly, the present invention relates to hydraulic actuation of actuators, including fuel injectors and camless engine intake/exhaust valves.
BACKGROUND OF THE INVENTION
A prior art hydraulically actuated, intensified injection system (commonly a HEUI injection system)
10
is depicted in prior art FIG.
1
and consists of five major components:
1. Electronic Control Module (ECM)
20
2. Injector Drive Module (IDM)
30
3. High Pressure actuating fluid supply pump
40
4. Rail Pressure Control Valve (RPCV)
50
5. HEUI Injectors
60
Electronic Control Module (ECM)
20
The ECM
20
is a microprocessor which monitors various sensors
22
from the vehicle and engine as it controls the operation of the entire fuel system
10
. Because the ECM
20
has many more operational inputs than a mechanical governor, it can determine optimum fuel rate and injection timing for almost any condition. Electronic controls such as this are absolutely essential in meeting standards of exhaust emissions and noise.
Injector Drive Module (IDM)
30
The IDM
30
is communicatively coupled to the ECM
20
and receives commands therefrom. The IDM
30
sends a precisely controlled current pulse to energize the solenoid of each injector
60
. Such energization acts to port high pressure actuating fluid to the intensifier of the respective injector
60
. The timing and duration of the IDM
30
pulse are controlled by the ECM
20
. In essence, the IDM
30
acts like a relay.
High Pressure Actuating Fluid Supply Pump
40
The high pressure actuating fluid supply pump
40
is a single stage pump and is in the prior art, typically a seven piston fixed displacement axial piston pump and is driven by the engine. The high pressure actuating fluid supply pump
40
draws in low pressure actuating fluid (most commonly engine oil, but other actuating fluids could be used as well) from the reservoir
46
, elevates the pressure of the actuating fluid for pressurization of the accumulator or rail
42
. The rail
42
is plumbed to each injector
60
. During normal engine operation, pump output pressure of the high pressure actuating fluid supply pump
40
is controlled by the rail pressure control valve (RPCV)
50
, which dumps excess flow back to the return circuit
44
to the reservoir
46
. The reservoir
46
is at substantially ambient pressure and may be at the normal pressure of the lubricating oil circulating in the engine of about 50 psi. Pressures in the rail
42
for specific engine conditions are determined by the ECM
20
.
Rail Pressure Control Valve (RPCV)
50
The RPCV
50
is an electrically operated dump valve, which closely controls pump output pressure of the high pressure actuating fluid supply pump
40
by dumping excess flow to the return circuit
44
thence and to the reservoir
46
. A variable signal current from the ECM
20
to the RPCV
50
determines output pressure of the pump
40
. Pump output pressure is maintained anywhere between about 450 psi and 3,000 psi during normal engine operation. When the actuating fluid is engine lubricating oil, pressure while cranking a cold engine (below 50 degrees F.) is slightly higher because cold oil is thicker and components in the respective injectors
60
move slower. The higher pressure helps the injector
60
to fire faster until the viscosity of the actuating fluid (oil) is reduced.
HEUI Injector
60
Injectors
60
of the HEUI type are known and are representatively described in U.S. Pat. Nos. 5,460,329 and 5,682,858, incorporated herein by reference. The injector
60
includes an intensifier piston and plunger, the actuating fluid acting on the intensifier to pressurize a volume of fuel acted upon by the plunger. The injector
60
uses the hydraulic energy of the pressurized actuating fluid (preferably, lubricating oil) to dramatically increase the pressure of the volume of fuel and thereby to cause injection. Actuating fluid is ported to the intensifier by a valve controlled by a solenoid. The pressure of the incoming actuating fluid from the rail
42
controls the speed of the intensifier piston and plunger movement, and therefore, the rate of injection. The amount of fuel injected is determined by the duration of the pulse from the IDM
30
and how long it keeps the solenoid of the respective injector
60
energized. The intensifier amplifies the pressure of the actuating fluid and elevates the pressure of the fuel acted upon by the plunger from near ambient to about 20,000 psi for each injection event. As long as the solenoid is energized and the valve is off its seat, high pressure actuating fluid continues to translate the intensifier and plunger to continuously pressurize fuel for injection until the intensifier reaches the bottom of its bore.
In the prior art fuel injection system
10
, pressurized actuating fluid is used to control the injected fuel quantity by using pressure amplification in the injectors
60
. As noted above, a pressure source (pump
40
) pumps actuating fluid to a pressure rail
42
(accumulator) where pressure is regulated according to the engine load and speed requirement. The pressure regulation is done via the rail pressure control valve
50
that dumps some of the pressurized actuating fluid to ambient (reservoir
46
) in order to maintain the desired pressure in the rail
42
.
Prior Art Rail RPCV
50
The RPCV
50
is an electronically controlled, pilot operated valve. The basic components of the RPCV
50
are depicted in Prior Art FIG.
2
and include:
Body
51
Spool valve
52
Spool spring
53
Poppet
54
Push pin
55
Armature
56
Solenoid
57
Edge filter
58
Drain Port
59
The RPCV
50
controls pump outlet pressure of pump
40
in a range between about 450 and 3,000 psi. An electrical signal to the solenoid
57
from the ECM
20
creates a magnetic field which applies a variable force on the armature
56
, shifting the poppet
54
to control pressure. With the engine off, the valve spool
52
is held to the right by the return spring
53
and the drain ports
59
are closed.
Approximately 1,500 psi of oil pressure is required to start a relatively warm engine. If the engine is cold (coolant temperatures below 32° F.), 3,000 psi of oil pressure is typically commanded by the ECM
20
. Initially, pump outlet pressure enters the end of the body
51
and a small amount of oil flows into the spool valve
52
chamber through the pilot stage filter screen and control orifice in the end of the spool valve
52
. The electronic signal causes the solenoid
57
to generate a magnetic field which pushes the armature
56
to the right. The armature
56
exerts a force on the push pin
55
and poppet
54
holding the poppet
54
closed allowing spool chamber pressure to build. The combination of spool spring
53
force and spool chamber pressure hold the spool valve
52
to the right, closing the drain ports
59
. All oil is directed to the pressure rail
42
until the desired pressure is reached.
Once the engine starts, the ECM
20
sends a signal to the RPCV
50
to give the rail pressure desired. The injection control pressure sensor
22
monitors actual rail pressure. The ECM
20
compares the actual rail pressure to the desired rail pressure and adjusts the signal to the RPCV
50
to obtain the desired rail pressure. The pressure in the spool chamber is controlled by adjusting the position of the poppet
54
and allowing it to bleed off some of the oil in the spool chamber through the drain port
59
. The position on the poppet
54
is controlled by the strength of the magnetic field produced from the electrical signal from the ECM
20
. The spool valve
52
responds to pressure changes in the spool chamber (left side of the spool) by changing positions to maintain a force balance between the right and left side of the spool. The spool valve
52
position determines how much area of the drain ports
59
are open. The drain port
59
open area directly affects how much oil is bled off from the outlet of the pum
Calfa Jeffrey P.
International Engine Intellectual Property Company LLC
Lukasik Susan L.
Moulis Thomas N.
Sullivan Dennis Kelly
LandOfFree
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