Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-04-09
2004-03-30
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S458000
Reexamination Certificate
active
06712043
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to control of actuating fluid for use in an intensified fuel injection system for internal combustion engines. More particularly, the present invention controls a variable output pump that provides pressurized actuating fluid to an accumulator.
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:
Electronic Control Module (ECM)
20
Injector Drive Module (IDM)
30
High Pressure actuating fluid supply pump
40
Rail Pressure Control Valve (RPCV)
50
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. 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 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
and to the reservoir
46
. A variable signal current from the ECM
20
to the RPCV
50
determines pump output pressure. Pump pressure can be maintained anywhere between about 450 psi and 4000 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 this 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 push down the intensifier and plunger to continuously pressurize fuel for injection until the intensifier reaches the bottom of its bore.
Fuel economy is becoming more and more important. More efficiency in fuel usage is needed. The fuel consumption of the engine varies with engine speed and load. The need for actuating fluid also varies with engine speed and load, a higher volume of actuating fluid being required to develop sufficient high pressure fuel in the injector
60
at higher engine speeds and load. The actuating fluid pump
40
is engine driven and develops the same output at a given engine speed without regard for the volume of actuating fluid needed by the injectors
60
. The volume is selected to ensure that the rail
42
is always fully charged with high pressure actuating fluid at the highest demand for actuating fluid. As noted above, excess actuating fluid is vented by the RPCV
50
to the reservoir
46
. This means some engine power is used unnecessarily at lower to intermediate engine loads to run the actuating fluid pump
40
. As noted above, in the prior art engines, the actuating fluid pump
40
is a one stage actuating fluid pump delivering actuating fluid to the pressurized rail
42
. Under certain engine operating conditions, typically relatively low engine load, the unneeded actuating fluid is dumped to ambient (reservoir
46
), resulting in energy loss.
In the prior art fuel injection system
10
, pressurized actuating fluid (engine lubricating oil) is used to control the injected fuel quantity by using pressure amplification in the injectors
60
. As noted above, a pressure source 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 pressure-regulating valve
50
that dumps excess pressurized actuating fluid to ambient in order to maintain the desired pressure in the rail
42
. Although it is desirable to minimize the damped flow for efficiency purposes, the required demand must be maintained in order to assure stability of desired rail pressure.
In order to achieve a more efficient system, the delivery of the pump
40
must be controlled depending on the engine requirement. A continuous supply of actuating fluid to the rail is needed in order to maintain the desired rail pressure at any engine condition. Further, the engine power used to drive the actuating fluid pump should more nearly reflect the actuating fluid needed in the rail for the present engine operating condition.
SUMMARY OF THE INVENTION
The actuating fluid control system of the present invention is capable of meeting the aforementioned needs. By matching the power consumption of the actuating fluid pump to the engine needs, the engine fuel consumption is reduced, especially at lower engine load conditions. Further, a continuous supply of actuating fluid is supplied to the rail.
The pressure dynamics quality in the pressure rail
42
is a key player in such systems. The impact of transient flow discontinuity in the rail
42
has to be minimized. Dumping flow from a single actuating fluid pump as done in the past created objectionable high pressure fluctuations which were a significant source of transient flow discontinuity in the rail
42
. Hence, a continuous steady flow from a pump stage to the rail
42
as provided for in the present invention
Calfa Jeffrey P.
International Engine Intellectual Property Company LLC
Lukasik Susan L.
Moulis Thomas N.
Sullivan Dennis Kelly
LandOfFree
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