Patent ID: 7146966

Claim:
A cylinder cutoff control apparatus of an internal combustion engine comprising: an intake-valve operating control mechanism capable of continuously reducing an intake-valve lift and valve open period characteristic of an intake valve to a zero lift and lifted-period characteristic; an exhaust-valve operating control mechanism capable of reducing an exhaust-valve lift characteristic of an exhaust valve to a zero lift characteristic; an engine-and-vehicle sensor that detects an engine-and-vehicle operating condition; and a control unit configured to be electronically connected to at least the engine-and-vehicle sensor and the valve operating control mechanisms for controlling the valve operating control mechanisms depending on the engine-and-vehicle operating condition; the control unit comprising (a) an intake-air quantity control circuit through which a quantity of intake air is controlled by the intake-valve operating control mechanism; (b) an intake-valve shutdown circuit that generates an intake-valve shutdown signal to the intake-air quantity control circuit, only when two necessary conditions are both satisfied for initiating, based on the engine-and-vehicle operating condition, a cylinder cutoff mode where at least one cylinder is cut off by shifting the intake and exhaust valves to their valve shutoff states, one of the two necessary conditions being a low load condition, and the other being a condition that an intake valve closure timing, varied by the intake-valve operating control mechanism, is controlled to a given timing value before a bottom dead center of a piston; (c) a fuel cutoff circuit that executes a fuel cutoff mode prior to the cylinder cutoff mode; and (d) an exhaust-valve shutdown circuit that reduces the valve lift amount of the exhaust valve included in the first group to the zero lift by the exhaust-valve operating control mechanism, depending on the valve lift amount of the intake valve included in the first group.