Intake system for internal combustion engine

An intake system of components of an internal combustion engine, which supplies combustion air to the internal combustion engine having a combustion chamber and an intake valve that opens and closes the combustion chamber, the internal combustion engine having a cylinder block in which the combustion chamber is formed, a cylinder head provided with a cylinder head cover on an upper side of the cylinder head and with a plurality of intake ports to introduce the combustion air into the combustion chamber, a motor provided on an upper side of the cylinder head cover and exerting drive force to a cam slide mechanism that axially moves a solid cam driving the intake valve, and a cam position sensor provided on the upper side of the cylinder head cover and detecting an axial position of the solid cam, the intake system comprising:

• an air cleaner that is provided on an upper side of the cylinder head cover, the motor and the cam position sensor, and takes in and cleans the combustion air from outside, wherein:
• the air cleaner comprises
• a body which has a box-shaped configuration inside which a space is formed and has a bottom wall portion,
• a side wall portion that extends from a periphery of the bottom wall portion toward an upper side, and
• an upper wall portion that covers an upper side of the body;
• a concave portion is provided with the bottom wall portion at a center portion in a horizontal direction of the bottom wall portion, the concave portion having a larger depth in a vertical direction compared to an edge portion of the bottom wall portion, surrounding the center portion, and bulging toward a cylinder head cover side;
• an inlet for taking in air from outside is provided with the side wall portion at both sides in the horizontal direction of the side wall portion;
• the inlet has a cylindrical configuration extending substantially diagonally forward from the both sides of the side wall portion;
• the air taken in from the inlet flows into a space enlarged by the concave portion;
• openings are provided with the bottom wall portion of the air cleaner so as to be arrayed in series, each of the openings communicating with each of the intake ports, respectively;
• and
• the concave portion is provided between the motor and the cam position sensor.