Abstract:
Methods and arrangements are described for controlling transitions between firing fractions during skip fire operation of an engine in order to help smooth the transitions. Generally, firing fractions transitions are implemented gradually, preferably in a manner that relatively closely tracks manifold filling dynamics. In some embodiments, the commanded firing fraction is altered each firing opportunity. Another approach contemplates altering the commanded firing fraction by substantially the same amount each firing opportunity for at least a portion of the transition. These approaches work particularly well when the commanded firing fraction is provided to a skip fire controller that includes an accumulator functionality that tracks the portion of a firing that has been requested, but not delivered, or vice versa. In various embodiments, commanded firing fraction changes are delayed relative to initiation of the change in throttle position to help compensate for inherent delays associated with changing the manifold air pressure.
Abstract:
A variety of methods and devices for mitigating power train vibration during skip fire operation of an engine are described. In one aspect, the slip of a drive train component (such as a torque converter clutch) is based at least in part upon a skip fire characteristic (such as firing fraction, selected firing sequence/pattern, etc.) during skip fire operation of an engine. The modulation of the drive train component slip can also be varied as a function of one or more engine operating parameters such as engine speed and/or a parameter indicative of the output of fired cylinders (such as mass air charge).
Abstract:
Various methods and arrangements for operating a skip fire engine control system are described. In one aspect of the invention, a distinct firing sequence is determined for each bank of working chambers that is used to operate the bank in a skip fire manner. Each firing sequence uses a different firing fraction. In another aspect of the invention, a determination is made as to whether a firing sequence should be dynamically generated or selected from a set of predefined firing sequences.
Abstract:
A variety of methods and arrangements for reducing noise, vibration and harshness (NVH) in a skip fire engine control system are described. In one aspect, a firing sequence is used to operate the engine in a skip fire manner. A smoothing torque is determined that is applied to a powertrain by an energy storage/release device. The smoothing torque is arranged to at least partially cancel out variation in torque generated by the skip fire firing sequence. Various methods, powertrain controllers, arrangements and computer software related to the above operations are also described.
Abstract:
A variety of methods and arrangements for reducing noise, vibration and harshness (NVH) in a skip fire engine control system are described. In one aspect, a firing sequence is used to operate the engine in a skip fire manner A smoothing torque is determined that is applied to a powertrain by an energy storage/release device. The smoothing torque is arranged to at least partially cancel out variation in torque generated by the skip fire firing sequence. Various methods, powertrain controllers, arrangements and computer software related to the above operations are also described.
Abstract:
Various methods and arrangements for determining a combustion control parameter for a working chamber in an engine are described. In one aspect, an engine controller includes a firing counter that stores a firing history for the working chamber. A combustion control module is used to determine a combustion control parameter, which is used to help manage combustion in the working chamber. The combustion control parameter is determined based at least in part on the firing history.
Abstract:
Arrangements for stabilizing valve timing adjustment mechanisms such as cam phasers during operation of an engine are described. The described approaches are particularly well suited for use during skip fire control, although they may be used advantageously in other applications as well. In general, the phase of an adjustable phase camshaft is controlled relative to a crankshaft of an engine. In one aspect, at least one of (i) firing events in a skip fire firing sequence, and (ii) dynamically determined valve actuation events are used in the control of the camshaft phase during operation of the engine. In some embodiments, hydraulic pressure within a cam phaser is varied in a manner that maintains the phase of the camshaft substantially more stable through transitory variations in torque applied to the camshaft by the actuation of the valves than would occur without the variations in hydraulic pressure.
Abstract:
Methods and devices are described that utilize skip fire techniques to rapidly meet requests for transitory changes in the output of an engine. Specifically, the fraction or percentage of the working cycles that are fired can be changed during a transitory event so that the engine delivers the desired transitory engine output. Once the transitory event is over, normal engine operation may be restored. The described techniques are useful in a variety of applications that require a relatively quick, but transitory, reduction in engine output to meet vehicle control requirements. One particularly useful application is during transmission shift events. Other representative applications include: loss of traction events, stability control events, wheel hop prevention events, etc.
Abstract:
A system and method for operating an ICE by (a) generating a running history of one or more-cylinder events per cylinder, and (b) using the running history to select a least-used non-rotating firing pattern, among a plurality of non-rotating firing patterns, provided for each firing fraction less than one (1). By making the least used selection based on the running history, unequal usage among cylinders of the ICE can be mitigated.
Abstract:
Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO may begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. The number of pumping cycles, if any, is based on intake manifold absolute pressure (MAP).