Blower fan

A blower fan configured to be rotated about a fan rotational axis, which is predetermined, in a fan rotational direction, the blower fan comprising:

• a hub that is placed on the fan rotational axis;
• a plurality of blades that are arranged along and extend outwardly from an outer periphery of the hub;
• and
• a ring that is shaped in a circular ring form and couples a distal end portion of each of the plurality of blades, wherein:
• the distal end portion of each of the plurality of blades has a separation limiting structure that is configured to limit separation of a flow of air from the blade;
• each blade among the plurality of blades has a shape that directs a flow direction of the air passing through each blade to the separation limiting structure of an adjacent blade which is an adjacent one of the plurality of blades located on a rear side of each blade in the fan rotational direction;
• at each blade among the plurality of blades, a base end portion is defined as an end portion of each blade that is joined to the outer periphery of the hub;
• at each blade among the plurality of blades, a reference line is defined as a straight line that intersects the fan rotational axis at a right angle and passes through a center point of the base end portion of each blade centered in the fan rotational direction;
• at each blade among the plurality of blades, a centerline is defined as a line that extends from the base end portion to the distal end portion along a center point of a width of each blade centered in the fan rotational direction;
• at each blade among the plurality of blades, a predetermined location line is defined as a straight line that intersects the fan rotational axis at the right angle and passes through a corresponding predetermined location along the centerline of each blade;
• at each blade among the plurality of blades, an angle of the predetermined location line relative to the reference line is defined as a skew angle at the corresponding predetermined location of each blade;
• in a case where the predetermined location line is displaced from the reference line in the fan rotational direction, the skew angle of the predetermined location line is expressed by a positive value, and in another case where the predetermined location line is displaced from the reference line in an opposite direction, which is opposite to the fan rotational direction, the skew angle of the predetermined location line is expressed by a negative value;
• each blade among the plurality of blades has a bent portion at a location that is on a base side, at which the base end portion is placed, of a center that is centered between the base end portion and the distal end portion;
• at each blade among the plurality of blades, as the shape, which directs the flow direction of the air passing through each blade to the separation limiting structure of the adjacent blade, each blade has a shape, with which the skew angle is progressively increased from the base end portion to the bent portion and reaches a maximum value at the bent portion, and the skew angle is progressively reduced from the bent portion to the distal end portion and becomes the negative value at the distal end portion;
• at each blade among the plurality of blades, an inner portion is defined as a portion of each blade that extends from the base end portion to the bent portion, and a rear-side airflow region is defined as a region that is formed by projecting a straight connecting line, which connects between one end of a leading edge of the inner portion located at the base end portion and another end of the leading edge of the inner portion located at the bent portion, in a direction that is perpendicular to the straight connecting line toward the rear side in the fan rotational direction;
• at least one of the plurality of blades has a shape, with which the rear-side airflow region of the inner portion does not overlap with an entire range of a leading edge of the adjacent blade;
• the plurality of blades are arranged at different angular intervals, respectively, in the fan rotational direction;
• the plurality of blades include:
• one or more primary blades, at each of which the rear-side airflow region of the inner portion does not overlap with the entire range of the leading edge of the adjacent blade;
• and
• one or more secondary blades, at each of which the rear-side airflow region of the inner portion overlaps with the leading edge of the adjacent blade;
• and
• a number of the one or more primary blades is larger than a number of the one or more secondary blades.

A blower fan configured to be rotated about a fan rotational axis, which is predetermined, in a fan rotational direction, the blower fan comprising:

• a hub that is placed on the fan rotational axis;
• a plurality of blades that are arranged along and extend outwardly from an outer periphery of the hub;
• and
• a ring that is shaped in a circular ring form and couples a distal end portion of each of the plurality of blades, wherein:
• the distal end portion of each of the plurality of blades has a separation limiting structure that is configured to limit separation of a flow of air from the blade;
• each blade among the plurality of blades has a shape that directs a flow direction of the air passing through each blade to the separation limiting structure of an adjacent blade which is an adjacent one of the plurality of blades located on a rear side of each blade in the fan rotational direction;
• at each blade among the plurality of blades, a base end portion is defined as an end portion of each blade that is joined to the outer periphery of the hub;
• at each blade among the plurality of blades, a reference line is defined as a straight line that intersects the fan rotational axis at a right angle and passes through a center point of the base end portion of each blade centered in the fan rotational direction;
• at each blade among the plurality of blades, a centerline is defined as a line that extends from the base end portion to the distal end portion along a center point of a width of each blade centered in the fan rotational direction;
• at each blade among the plurality of blades, a predetermined location line is defined as a straight line that intersects the fan rotational axis at the right angle and passes through a corresponding predetermined location along the centerline of each blade;
• at each blade among the plurality of blades, an angle of the predetermined location line relative to the reference line is defined as a skew angle at the corresponding predetermined location of each blade;
• in a case where the predetermined location line is displaced from the reference line in the fan rotational direction, the skew angle of the predetermined location line is expressed by a positive value, and in another case where the predetermined location line is displaced from the reference line in an opposite direction, which is opposite to the fan rotational direction, the skew angle of the predetermined location line is expressed by a negative value;
• each blade among the plurality of blades has a bent portion at a location that is on a base side, at which the base end portion is placed, of a center that is centered between the base end portion and the distal end portion;
• at each blade among the plurality of blades, as the shape, which directs the flow direction of the air passing through each blade to the separation limiting structure of the adjacent blade, each blade has a shape, with which the skew angle is progressively increased from the base end portion to the bent portion and reaches a maximum value at the bent portion, and the skew angle is progressively reduced from the bent portion to the distal end portion and becomes the negative value at the distal end portion;
• at each blade among the plurality of blades, an amount of change in the skew angle in a range from the bent portion to the distal end portion is set to be in a range of 25° to 40°;
• at each blade among the plurality of blades, a blade pitch is defined as a parameter that is obtained by normalizing a location along the centerline of the blade with a value in a range of 0 to 1, where 0 corresponds to a location of the base end portion, and 1 corresponds to a location of the distal end portion;
• at each blade among the plurality of blades, the bent portion is located in a range of each blade which corresponds to the blade pitch of 0.2 to 0.4;
• at each blade among the plurality of blades, the blade pitch, which corresponds to the location of the bent portion, is defined as Pc;
• and
• at each blade among the plurality of blades, an amount of change in a slope of the skew angle in a range of each blade, which corresponds to the blade pitch of Pc−0.1 to Pc+0.1, is set to be in a range of 60° to 90°.