Abstract: Disclosed is a door closer provided with a unit for adding door-closing force inside a housing. The disclosed door closer comprises a force-adding unit, which is included inside the housing, for adding the door-closing force. The force-adding unit comprises a cam which coaxially rotates with a link shaft inside the housing, and a cam pusher which is elastically compressed so as to come into close contact with the outer circumferential surface of the cam. The outer circumferential surface of the cam comprises an arc surface portion which is separated apart from a rotary axis of the cam at an equal distance, a concave surface portion which is separated apart from the rotary axis of the cam at a distance shorter than that to the arc surface portion, and one pair of protruding corner portions for connecting the arc surface portion and the concave surface portion.

Abstract: Disclosed is a door closer of which the inside of a housing is made compact and thus is easily made smaller. The disclosed door closer is comprised so that movement of one end of a coil spring, which is relatively close to a link shaft, toward the link shaft inside of the housing is limited, and the other end of the coil spring, which is relatively far from the link shaft, moves toward the link shaft by being pushed by a piston base portion, thereby compressing the coil spring.

Abstract: Disclosed is a door closer provided with a unit for adding door-closing force inside a housing. The disclosed door closer comprises a force-adding unit, which is included inside the housing, for adding the door-closing force. The force-adding unit comprises a cam which coaxially rotates with a link shaft inside the housing, and a cam pusher which is elastically compressed so as to come into close contact with the outer circumferential surface of the cam. The outer circumferential surface of the cam comprises an arc surface portion which is separated apart from a rotary axis of the cam at an equal distance, a concave surface portion which is separated apart from the rotary axis of the cam at a distance shorter than that to the arc surface portion, and one pair of protruding corner portions for connecting the arc surface portion and the concave surface portion.

Abstract: Disclosed is a door closer of which the inside of a housing is made compact and thus is easily made smaller. The disclosed door closer is comprised so that movement of one end of a coil spring, which is relatively close to a link shaft, toward the link shaft inside of the housing is limited, and the other end of the coil spring, which is relatively far from the link shaft, moves toward the link shaft by being pushed by a piston base portion, thereby compressing the coil spring.