Apparatus for controlling multi-cylinder internal combustion engine with partial cylinder switching-off mechanism

An apparatus for controlling a multi-cylinder internal combustion engine with partial cylinder switch-off mechanism, said engine being switchable between an all-cylinder operation in which all cylinders are operated and a partial-cylinder operation in which operation of partial cylinders is suspended, said apparatus comprising:

• hydraulically operated valve switching means on an intake side and on an exhaust side, respectively, for switching intake valves and exhaust valves of the partial cylinders between a driving state and a drive-free state, wherein said intake valves and said exhaust valves of the partial cylinders are switched, during the partial-cylinder operation, into the drive-free state;
• a control valve on the intake side for switching a hydraulic pressure inputted to said hydraulically operated valve switching means on the intake side between a hydraulic pressure to bring said intake valves into the driving state and a hydraulic pressure to bring said intake valves to the drive-free state;
• a control valve on the exhaust side for switching a hydraulic pressure inputted to said hydraulically operated valve switching means on the exhaust side between a hydraulic pressure to bring said exhaust valves into the driving state and a hydraulic pressure to bring said exhaust valves to the drive-free state;
• and
• control means for performing the following steps when the intake valves and the exhaust valves of the partial cylinders are switched from one of the driving state and the drive-free state to the other of said states, said steps including:
• performing hydraulic pressure switching by one of said control valve on the intake side and said control valve on the exhaust side ahead of hydraulic pressure switching by the other of said control valves;
• counting a subsequent number of rotations of a crankshaft of the engine;
• and, when the counted number of rotations has reached a predetermined value, performing hydraulic pressure switching by the other of said control valves, said predetermined value being set such that driving of, or resumption of driving of, said intake valves and said exhaust valves for all suspended cylinders is made in a given order irrespective of a rotational frequency of the engine.