Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
1999-03-05
2001-01-09
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406470, C701S104000, C701S115000
Reexamination Certificate
active
06170463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to adjusting fuel and timing operations of an engine to optimize desired operating characteristics of the engine and in particular to a method and apparatus for adjusting the fuel flow and ignition timing for each engine cylinder individually to optimize desired operating characteristics of the engine as a whole.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98
In order to optimize engine performance with today's technology, it is well known to inject fuel into engine cylinders in a known quantity while monitoring desired engine operating characteristics such as torque, emissions, and the like. These tests are made for a plurality of engine operating RPM settings and throttle positions. Thus, for a given throttle position and engine speed, a voltage is applied to the fuel injector for a period of time known as the pulse width. The duration of the voltage pulse determines the amount of fuel injected into a cylinder. This pulse-width is varied until the optimum desired operating engine conditions that are being monitored are achieved. Then the throttle position and engine speed are changed to a new throttle position and engine speed and the desired engine operating characteristics are monitored again while the pulse-width is varied to vary the amount of fuel being injected into the cylinders and the optimum pulse-width is again noted. When this is accomplished for a desired number of throttle positions and RPM settings over a given range, the gross pulse-width data value for each throttle position versus engine RPM is stored in a two-dimensional data storage cell array. A microprocessor is coupled to the data storage cell and during engine operation, when the throttle is in a given position and the RPM is at a given setting, the microprocessor selects the pulse-width value stored in the table for that throttle position and RPM setting and causes the same desired amount of fuel to be injected into each cylinder. Thus, optimum operation of the engine as a whole is achieved based upon the desired engine operating characteristics to be achieved and, at each throttle position and RPM setting, the same pulse-width stored for that throttle position and RPM setting causes the same amount of fuel to be applied to all cylinders to cause optimum operation of the engine.
Also, for the same throttle positions and RPM settings, the timing of the ignition is varied and the desired operating characteristics of the engine are monitored until the proper ignition timing is obtained for each of the throttle positions and RPM settings to achieve the desired optimum engine operating conditions. These settings are again stored in a second two-dimensional table representing throttle position versus RPM setting. The microprocessor, again, at any given throttle position and RPM setting will look into the table and pick the ignition timing value stored therein and cause that same ignition timing to be applied to all of the cylinders to again achieve the desired optimum engine operating conditions.
It has been found, however, that a number of conditions exists which may cause a variation between the operation of one cylinder with respect to another. Thus, for instance, in a four-cycle or two-cycle engine, it has been found that the volume of the combustion chamber varies from cylinder-to-cylinder and causes variable compression rates. In addition, it has been found that there is a difference between “in-cylinder” temperatures because of a variation in cooling paths to each cylinder and the like. Further, the length of the path of the air intake and of the exhaust also varies from cylinder-to-cylinder which causes a variation in the optimum operation of one cylinder with respect to another. In addition, in two-cycle engines, exhaust tuning as well as intake and exhaust port location vary from cylinder-to-cylinder and thus create differences in operation between cylinders.
Therefore, if the same fuel control pulse width is used to cause the same amount of fuel to be applied to each cylinder and if the same ignition timing is applied to each cylinder at each given throttle position and RPM setting to cause the ignition to occur at identical crankshaft positions, the engine may not operate at its ultimate optimum operating conditions because of the variation in operation between cylinders.
Therefore, it would be advantageous if the operating characteristics of an engine could be optimized by adjusting the amount of fuel flow and ignition timing to each cylinder individually.
SUMMARY OF THE INVENTION
The present invention relates to the optimization of engine operation wherein each engine cylinder has a coefficient of variance, represented by a pressure-versus-time curve, during each ignition of fuel therein. The intent of the invention is to cause, as nearly as possible, the optimum coefficient of variance for all cylinders at any given throttle position and RPM setting. A first two-dimensional data storage cell array represents a throttle position versus engine RPM setting and stores a gross pulse-width data value in each cell representing the same amount of fuel to be charged into each of the engine cylinders for each given throttle position and RPM setting to optimize operation of the engine as a whole. A microprocessor is coupled to the first two-dimensional array for retrieving the stored gross pulse-width data for any given throttle position and RPM setting and causing the same amount of fuel to be injected to all of the cylinders at the proper time.
By adjusting the pulse-width data value for each cylinder individually, a specific pulse-width data value is obtained for each cylinder that represents the amount of fuel for each cylinder in order to achieve the optimum coefficient of variance of that specific cylinder at corresponding RPM settings used in the first two-dimensional data storage cell array. Therefore, each cylinder can be caused to operate at its optimum coefficient of variance to provide optimized engine operation as a whole. A first at least one-dimensional array of data storage cells is created for each cylinder with each cell corresponding to an RPM setting used in the first two-dimensional data storage cell array. Stored in each data storage cell of each of the first one-dimensional arrays for each cylinder is a correction pulse-width data value representing the difference between the gross data pulse-width value and the specific pulse-width data value for a corresponding cylinder at each of the RPM settings. By coupling each of the one-dimensional data arrays to the microprocessor along with a two-dimensional array, the microprocessor can algebraically add each of the gross pulse-width data values to the correction pulse-width values for each cylinder at each corresponding RPM setting to optimize operation of each cylinder individually with respect to fuel injection.
The same thing can be done with the ignition timing. Again, there is a second two-dimensional data storage cell array coupled to the microprocessor that stores gross ignition timing data values representing the same relative time of ignition of the fuel in all of the cylinders for any given throttle position and RPM setting. The present method adjusts the ignition timing of each cylinder individually to obtain a specific ignition timing data value for each cylinder that represents the optimum coefficient of variance of that specific cylinder at corresponding RPM settings stored in the second two-dimensional data storage cell array. A second at least one-dimensional array of data storage cells for each cylinder is created with each cell corresponding to an RPM setting used in the second two-dimensional data storage cell array. A correction ignition timing data value representing the difference between the gross timing data value and the specific ignition timing data value for the corresponding cylinder at each of the RPM settings is stored in each data storage cell of each of the secon
Armstrong Teasdale LLP
Outboard Marine Corporation
Wolfe Willis R.
LandOfFree
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