Patent ID: 8418791

Claim:
An air-intake structure of an engine comprising: a duct structure configured to take in air from outside; an air cleaner including an air filter configured to clean the air guided to the air cleaner through the duct structure; a throttle device including a throttle valve for controlling a flow rate of the air guided to the throttle device through the air cleaner; an engine including an intake port configured to suction the air guided to the engine through the throttle device; and an on-off valve provided in the duct structure; the duct structure including: a main inlet configured to take in air therethrough from outside by utilizing a ram pressure; a main passage extending from the main inlet to the air filter; a sub-inlet configured to take in air therethrough from outside; and a joint section located upstream of the air filter, the air flowing from the sub-inlet being joined to the air in the main passage, at the joint section; wherein the on-off valve is configured to permit and inhibit air communication between the sub-inlet and the joint section; wherein the on-off valve includes a valve body positioned to permit and inhibit air flow through the sub-inlet of the duct structure; and wherein the valve body is configured to open by an air pressure directly applied to the valve body during running of the engine.