Method and code for determining event-based control delay of hydraulically-deactivatable valve train component

#The invention relates generally to methods and computer-executable code for controlling the operation of an internal combustion engine for a motor vehicle that features deactivatable cylinders.

#The prior art teaches equipping vehicles with “variable displacement,” “displacement on demand,” or “multiple displacement” internal combustion engines in which one or more cylinders may be selectively “deactivated,” for example, to improve vehicle fuel economy when operating under relatively low-load conditions. Typically, in a multi-displacement system, the engine's cylinders are deactivated through use of deactivatable valve train components, such as the deactivating valve lifters as disclosed in U.S. patent publication no. U.S. 2004/0244751 A1, in which a supply of pressurized engine oil is selectively delivered from an engine oil gallery to a deactivatable valve lifter through operation of a solenoid valve under the control of an engine control module.

#With the intake and exhaust valves of each deactivated cylinder remaining in their closed positions during engine operation in the cylinder-deactivation mode, combustion gases are trapped within each deactivated cylinder, whereupon the deactivated cylinders operate as “air springs” to reduce engine pumping losses. When vehicle operating conditions are thereafter deemed to require an engine output torque greater than that achievable without the contribution of the deactivated cylinders, as through a heightened torque request from the vehicle operator (based upon a detected position of the vehicle's accelerator pedal), the deactivatable valve train components are returned to their nominal activated state to thereby “reactivate” the deactivated cylinders. More specifically, under one prior art approach,

#FIG. 1 is a flow chart illustrating the main steps of a method for determining an event-based hydraulic deactivation or reactivation delay for a multi-displacement system of an internal combustion engine;

#FIG. 2 shows an exemplary computer-executable process for determining an event-based hydraulic deactivation or reactivation delay for a multi-displacement system of an internal combustion engine, in accordance with the invention;

#FIG. 3 is a plot illustrating three “sections” of a first three-dimensional lookup table from which to retrieve a first value for a time-based hydraulic deactivation or “fill” delay using current engine speed and current oil temperature, for use in the exemplary process of FIG. 2; and

#A method 10 for determining an event-based hydraulic control delay in a multi-displacement system for an internal combustion engine, with which to adjust the triggering a solenoid in hydraulic communication with a hydraulically-deactivatable valve train component, is illustrated generally in FIG. 1. Preliminarily, it is noted that the invention contemplates any suitable systems and methods for deactivating selected cylinders to thereby enable engine operation in a partial-displacement mode, such as the multi-displacement system disclosed in U.S. patent publication no. U.S. 2004/0244751 A1, the teachings of which are hereby incorporated by reference. Significantly, such a multi-displacement system is characterized both by a generally negligible oil pressure impact on hydraulic delay over the engine's nominal operating range, and a generally negligible amount of oil aeration at normal engine operating speeds.

#As seen in FIG. 1, the method 10 generally includes retrieving, at block 12, a value representative of a time-based hydraulic delay from a lookup table based on a current engine speed and a current oil temperature. Preferably, one lookup table is provides mapped values for the hydraulic deactivation (oil gallery “fill”) time-based delay, while another lookup table provides mapped values for the hydraulic reactivation (oil gallery “drain”) time-based delays. In a constructed embodiment, the mapped values contained in each table are derived empirically, for example, by running the multi-displacement engine in a test cell over predetermined engine speed and oil temperature ranges (the latter perhaps being inferred from a detected engine coolant temperature range) while proximity probes determine valve lifter response to solenoid-generated hydraulic “fill” and “drain” commands.

#Referring again to FIG. 1, the method 10 further includes determining, at block 14, a current time period between generated crankshaft position pulses and, at block 16, dividing the retrieved time-based value for hydraulic delay by the first time period to obtain the desired event-based hydraulic deactivation or reactivation delay. The event-based delays are thereafter used to synchronize the timing of solenoid operation when deactivating or reactivating a given deactivatable cylinder.