Abstract: A brushless DC motor including a rotor capable of minimizing demagnetization of a magnet even when a short-circuit brake operation is performed by short-circuiting motor coils includes two kinds magnets differing in coercive force from each other which are alternately arranged into an annular shape along a circumferential direction. A magnet having a high coercive force is arranged in the portion where a diamagnetic flux is strongly generated. The portion where a diamagnetic flux is generated is the salient pole portion of a stator. A counter electromotive force becomes greatest when the center of the salient pole portion of the stator comes closer to the border of an N-pole and an S-pole of the magnet. Since the diamagnetic flux has a maximum value in that position, the magnet having a high coercive force is arranged near the border of an N-pole and an S-pole.

Abstract: In an axial flow fan, a line extending from a center axis and passing a corner where a following edge and a radially outer edge of a blade of an impeller meet is arranged forwardly in a rotational direction from an another corner where a leading edge of the blade and a radially outer surface of a hub meet. Furthermore, a camber ratio of the blade, which is minimum at a joint with the hub across the blade, monotonically increases to be maximum at the radially outer edge of the blade.

Abstract: A serial axial fan unit includes a first axial fan arranged to rotate about a central axis, a flow control device connected to the first axial fan along the central axis, and a second axial fan connected to the flow control device along the central axis. The flow control device preferably includes a wind tunnel portion, a base portion, and a plurality of flow control vanes. A flow of air caused by rotation of first blades has a whirl velocity component in substantially the same direction as the rotation direction thereof. This whirl velocity component is converted to a velocity component in a direction parallel or substantially parallel to the central axis by interference of first stationary vanes. The above arrangement provides an improvement in air volume characteristics of a serial axial fan unit including two axial fans arranged in series.

Abstract: An serial axial fan unit includes a first axial fan arranged to rotate about a central axis, a flow control device connected to the first axial fan along the central axis, and a second axial fan connected to the flow control device along the central axis. The flow control device preferably includes a wind tunnel portion, a base portion, and a plurality of flow control vanes. A flow of air caused by rotation of first blades has a whirl velocity component in substantially the same direction as the rotation direction thereof. This whirl velocity component is converted to a velocity component in a direction parallel or substantially parallel to the central axis by interference of first stationary vanes. The above arrangement provides an improvement in air volume characteristics of a serial axial fan unit including two axial fans arranged in series.

Abstract: In an axial flow fan, a line extending from a center axis and passing a corner where a following edge and a radially outer edge of a blade of an impeller meet is arranged forwardly in a rotational direction from an another corner where a leading edge of the blade and a radially outer surface of a hub meet. Furthermore, a camber ratio of the blade, which is minimum at a joint with the hub across the blade, monotonically increases to be maximum at the radially outer edge of the blade.

Abstract: Multiple fans of cascade connection comprises at least two fans of cascade connection, and a commutation device arranged between the two fans. The commutation device is composed of a cylindrical case and a plurality of planar plates, each extending radially from the center axis of the cylindrical case to an inner peripheral wall of the cylindrical case, and extending axially in the cylindrical case. The two fans are connected coaxially and identical substantially in design with each other.