Intake system for multi-cylinder engine

An intake system for a multi-cylinder engine, comprising:

• independent intake passages, each defined in an intake pipe, which supply air to a corresponding one of cylinders of said multi-cylinder engine, and an intake port disposed on a downstream side of said intake pipe;
• intake valves each adapted to be open and closed a corresponding one of said intake ports in said independent intake passages;
• a valuable valve timing system adapted to change an open timing of each of said intake valves;
• a rotary valve serving as a valve of an impulse charging device adapted to be open in association with an intake stroke in each of said cylinders and at least during a term from the middle of an intake stroke to a compression stroke in said multi-cylinder engine so as to generate a high pressure wave in each of said cylinders;
• and
• a hollow cylindrical-shaped collecting portion disposed at respective upstream ends of said intake pipes and fluidically connected with said intake pipes,
• wherein:
• said rotary valve is disposed inside said collecting portion in a concentric arrangement;
• said rotary valve has a diameter larger than a sectional width of each of said intake pipes, and a peripheral wall formed in an opening;
• and each of said intake pipes has an upstream end which is fluidically connected to said collecting portion in such a manner as to be disposed to face said opening of said rotary valve so as to be selectively open and closed by said rotary valve.

An intake system for a multi-cylinder engine, comprising:

• intake pipes which respectively supply air to cylinders of said multi-cylinder engine;
• intake ports disposed on a downstream side of said intake pipes and respectively, fluidically connected to said intake pipes;
• intake valves each adapted to be open and closed a corresponding one of said intake ports;
• a valuable valve timing system adapted to change an open timing of each of said intake valves in such a manner that said intake valve has a relatively low lift and a relatively high lift, respectively, in a low engine-speed range in intermediate and high engine speed ranges;
• an impulse charging device adapted to have a valve function in association with an intake stroke in each of said cylinders and at least during a term from the middle of an intake stroke to a compression stroke in said multi-cylinder engine so as to generate a high pressure wave in each of said cylinders;
• engine-speed detection means for detecting an engine speed of said multi-cylinder engine;
• and
• valve timing control means operable to control an open timing of said impulse charging device and a valve-open timing of said valuable valve timing system, in accordance with a detection value of said engine-speed detection means, in such a manner as to advance the open timing of said impulse charging device and delay the open timing of said intake-valve, when the engine speed in an intermediate engine-speed range of said multi-cylinder engine becomes higher, and to maximize a term during which said impulse charging device and said intake valve are concurrently open, in low and high engine-speed ranges.