Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2000-09-25
2002-12-10
Vo, Hieu T. (Department: 3754)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C123S480000
Reexamination Certificate
active
06493627
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to establishing a fuel value limit for diesel engines, and more specifically to establishing such a limit based on the ambient conditions in which the diesel engine operates.
Large self-propelled traction vehicles such as locomotives commonly use a diesel engine to drive an electrical transmission system comprising generating means for supplying electric current to a plurality of direct current traction motors whose rotors are drivingly coupled through speed-reducing gearing to the respective axle-wheel sets of the vehicle. The generating means typically comprises a main 3-phase traction alternator whose rotor is mechanically coupled to the output shaft of the engine, typically a 16-cylinder turbo-charged diesel engine. When excitation current is supplied to field windings on the rotating rotor, alternating voltages are generated in the 3-phase stator windings of the alternator. These voltages are rectified and applied to the armature windings of the traction motors.
During the “motoring” or propulsion mode of operation, a locomotive diesel engine tends to deliver constant power from the traction alternator to the traction motors, depending on the throttle setting and ambient conditions, regardless of locomotive speed. For maximum performance, the electrical power output of the traction alternator must be suitably controlled so that the locomotive utilizes fall engine power. For proper train handling, intermediate power output levels are provided to permit graduation from minimum to fall output. But the traction alternator load on the engine must not exceed the level of power the engine is designed to develop for a given speed. Overloads can cause premature wear, engine stalling or “bogging,” or other undesirable effects. Historically, locomotive control systems have been designed so that the operator can select the desired level of traction power, in discrete steps between zero and maximum, so that the traction and auxiliary alternator, driven by the engine, can supply the power demanded by the traction load and the auxiliary loads, respectively.
In the prior art locomotives, when the throttle is advanced from one position to the next (commonly referred to as notches) the diesel engine speed and the load (or excitation) applied to the traction motors are simultaneously increased to the next speed and horsepower point established for the new notch position. The engine acceleration to the new speed point is controlled by the electronic fuel injection controller which adjusts the quantity of pressurized diesel fuel (i.e., fuel oil) injected into each of the engine cylinders so that the actual speed (in rpm) of the crankshaft corresponds to a desired speed. The locomotive control system applies more excitation to the main alternator, which in turn supplies more current to the traction motors, increasing the motor horsepower.
In the prior art locomotive systems, the electronic fuel injection controller acts as the speed governor in response to speed changes requested by the locomotive control system. In the prior art, the speed governor does not receive any signals from the throttle when it is changed from one notch position to another and therefore does not know when a notch change has occurred; the speed governor knows only the speed demand as requested by the locomotive control system. In fact, there are multiple notch settings that vary the horsepower delivered by the traction motors without changing the engine speed.
For each of its eight different notch settings, the engine is capable of developing a corresponding constant amount of horsepower (assuming maximum output torque). When the throttle notch
8
is selected, maximum speed (e.g., 1,050 rpm) and maximum rated gross horsepower (e.g., 4,500) are realized. Under normal conditions, the engine power at each notch equals the power demanded by the electric propulsion system, which is supplied by the engine-driven traction alternator, plus the power consumed by the electrically driven auxiliary equipment.
The electronic fuel injection controller calculates the fuel mass required to maintain the desired engine speed, then converts this value to a pulse duration, through a series of look-up tables. The pulse duration determines the fuel mass that is injected into each cylinder, as measured in mm
3
/injection. The pulse is input to the pump solenoids that control the injection of fuel into each cylinder. The leading edge of the pulse determines the start of fuel injection, and the pulse length determines the duration during which fuel is injected into the cylinder. The look-up tables provide the required duration of fuel injection (i.e., the pulse duration) as a function of engine speed, speed demand, and start of injection timing. Before the diesel engine is placed in service, the tables are empirically created based on calibration tests performed on a test stand, during which the fuel delivery quantity is measured, while varying fuel injector cam speed (which is a function of engine speed), the start of injection timing, and the pulse duration. The tables are necessarily based on the fuel temperature during the test and the fact that when the test is performed the fuel pumps and injectors are new. Thus, the actual fuel temperature and the fuel pump and injector integrity during the bench test serve as the calibration point for the look-up tables.
It is possible, but not practical, to perform a series of calibration tests at various fuel temperatures and fuel pump and injector conditions. That is, a first calibration test could be performed based on a first fuel temperature and fuel pump and injector conditions based on one year of wear. The second test could be based on the first fuel temperature and a fuel pump and injector condition based on two years of wear. In this way, a series of tables could be created for later use when the diesel engine is placed into service. The appropriate table would be consulted, as a function of fuel temperature and fuel pump/injector wear, to determine the pulse duration. As the fuel temperature changes or the fuel pumps and injectors wear, the appropriate table would be selected from among those available. However, it is well known that it is not practical to create nor store such a large number of tables. Therefore, the prior art has developed certain techniques for determining the fuel value when actual conditions are different from those conditions extant when the calibration tests were conducted. It is known that under changed conditions of fuel temperature and fuel pump and injector wear, a different fuel value (i.e., a different pulse duration) must be commanded to inject the same fuel mass into each cylinder so that the engine speed under the current conditions equals the engine speed during the calibration tests. Another recognized disadvantage of the prior art scheme is the fact that the tables are generic and that one table is used for all engines in the same engine family. Thus subtle variations between individual diesel engines are not accounted for in the fuel tables.
There is a fuel value limit (expressed in mm
3
/injection) associated with a diesel engine. This limit represents the maximum amount of fuel that can be injected into each cylinder without raising the cylinder pressure above its design value or causing excessive smoke. When the fuel injection controller commands a fuel value at the fuel limit, the diesel engine is derated (i.e., the engine cannot deliver more horsepower) and higher fuel values are prohibited by the controller. For example, assume that a fuel mass of 80 pounds must be injected into each cylinder, per hour, to maintain an engine speed of 1050 rpm at 4500 hp. Using the look-up tables, the electronic fuel injection controller generates a pulse having a duration such that a fuel volume of 1400 mm
3
is injected into each cylinder per stroke, to maintain this speed. Now, if the fuel temperature increases by 20° F., the fuel density decreases and thus a greater fuel volume must be injected during
Dillen Eric R.
Dunsworth Vincent F.
Gallagher Shawn M.
Beusse Brownlee Bowdoin & Wolter P.A.
DeAngelis Jr. John L.
General Electric Company
Rowold Carl A.
Vo Hieu T.
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