Variable valve timing
AssigneeGeneral Motors Corporation
InventorKo-Jen Wu
Life of this patent
Estimating the term…
Abstract
Intake valve timing information is provided for control and diagnostics in a variable valve timing internal combustion engine application in which check valves are disposed in intake passages connecting engine cylinders to an intake plenum for impeding backflow out of the intake passages and into the intake plenum, by timed sampling of intake passage pressure and a determination of pressure change over an intake valve closing event indicating an amount of backflow out of the cylinder and into the intake passage. The amount of backflow indicates intake valve timing as the crank angle at the time of intake valve closing.
Claims7
In an internal combustion engine having at least one cylinder with an intake valve which opens to allow inlet air passing through an intake air passage having a check valve to enter the cylinder, the cylinder having a piston disposed therein and coupled to a crankshaft for timed reciprocation, the timing of the intake valve being variably controlled relative to the crank angle of the piston, a method of determining the intake valve timing relative to the crank angle of the piston, comprising the steps of:
- determining when the piston is substantially at a predetermined crank angle providing an inlet air region within the cylinder of a known volume;
- sampling pressure in the intake air passage between the check valve and the intake valve when the piston is determined to substantially be at the predetermined crank angle;
- while the intake valve is closed, sampling pressure in the intake air passage;
- determining the intake valve timing as a predetermined function of the samples of pressure.
In an internal combustion engine having at least one cylinder with an intake valve which opens to allow inlet air passing through an intake air passage having a check valve to enter the cylinder, the cylinder having a piston disposed therein and coupled to a crankshaft for timed reciprocation, the timing of the intake valve relative to the crank angle of the piston being variably controlled, a method of determining the time of intake valve closing relative to the crank angle of the piston, comprising the steps of:
- when the piston is approximately at a predetermined crank angle at which the cylinder intake volume is substantially known, sampling air pressure in the intake passage between the check valve and the intake valve;
- when the intake valve is closed, sampling air pressure in the intake passage;
- calculating a pressure ratio between the samples of air pressure;
- determining a decrease in cylinder intake volume from the substantially known volume to the cylinder intake volume when the intake valve is closed, as a predetermined function of the pressure ratio;
- generating a crank angle difference between the predetermined crank angle and the crank angle at the time of intake valve closing as the amount of crank angle required to displace a volume substantially corresponding to the determined decrease in cylinder intake volume out of the cylinder and into the intake air passage;
- and
- calculating the crank angle at the time of intake valve closing to indicate time of intake valve closing relative to crank angle of the piston, by combining the generated crank angle difference with the predetermined crank angle.
In an internal combustion engine having at least one cylinder with an intake valve which opens to allow inlet air and inlet fuel passing through an intake air passage having a check valve to enter the cylinder, the cylinder having a piston disposed therein and coupled to a crankshaft for timed reciprocation, the timing of the intake valve relative to the crank angle of the piston being variably controlled, a method of determining the time of intake valve closing relative to the crank angle of the piston, comprising the steps of:
- when the piston is approximately at a predetermined crank angle at which the cylinder intake air and fuel volume is substantially known, sampling pressure in the intake passage between the check valve and the intake valve;
- when the intake valve is closed, sampling pressure in the intake passage;
- calculating a pressure ratio between the samples of pressure;
- estimating an amount of backflow of intake air and fuel out of the cylinder and into the intake passage as a predetermined function of the calculated pressure ratio;
- generating a crank angle difference between the predetermined crank angle and the crank angle at the time of intake valve closing as the amount of crank angle required to displace the estimated backflow amount of fuel and air out of the cylinder;
- and
- calculating the crank angle at the time of intake valve closing to indicate time of intake valve closing relative to crank angle of the piston, by combining the generated crank angle difference with the predetermined crank angle.
Dependencies are inferred from the claim text.