1. An air cleaner (1) comprising:
a casing (2) including an inlet (4) for drawing in air in a room and an outlet (5) for blowing the air out;
air blowing means (6) for drawing air from the inlet (4) into the casing (2) and blowing out the air from the outlet (5);
cleaning means (8) for cleaning air flowing inside the casing (2);
an air blow direction changing mechanism (9, 10, 13, 14; 15) having a function of changing a direction of air blown out from the outlet (5) and including a horizontal rotation mechanism (15) rotating the outlet (5) substantially horizontally;
person detection means (21) for detecting a direction in which a person is present; and
control means (23) for controlling the air blowing means (6) and the air blow direction changing mechanism (9, 10, 13, 14; 15),
characterized in that
the control means (23) have an air blow direction control function of performing control so as to, upon detection of a person present in the room by the person detection means (21), make a front-back direction component of an air blow direction vector in a maximum air blow rate part of the air blow direction point in a direction in which the person is present and make a total vector of all direction components of the air blow direction vector in the maximum air blow rate part of the air blow direction point in a direction in which no person is present.
2. The air cleaner (1) as claimed in claim 1, wherein the person detection means (21) has a function of detecting a height of the person in addition to the direction in which the person is present, and the control means (23) performs control so as to blow the air toward an area above the height of the person detected by the person detection means (21), via the air blow direction changing mechanism (9, 10, 13, 14; 15).
3. The air cleaner (1) as claimed in claim 1 or claim 2, wherein the air blow direction changing mechanism (9, 10, 13, 14; 15) includes a movable louver capable of changing the direction of the air blown from the outlet (5) in a top-bottom direction.

4. The air cleaner (1) as claimed in any one of claims 1 to 3, wherein:
the person detection means (21) includes
a person detection sensor (40) detecting a direction in which a person is present and a height of the person, and
a sensor operation mechanism (44) changing a direction of the person detection sensor (40); and
the control means (23) controls the sensor operation mechanism (44) independently from the air blow direction changing mechanism (9, 10, 13, 14; 15).
5. The air cleaner (1) as claimed in claim 4, wherein the person detection means (21) includes a plurality of detection elements (41a – 41h) aligned in a top-bottom direction, the detection elements (41a – 41h) being capable of individually detecting a person and the sensor operation mechanism (44) performs horizontal rotation operation.
6. The air cleaner (1) as claimed in claim 3, wherein:
the horizontal rotation mechanism (15) further has a function of horizontally rotating the inlet (4) together with the outlet (5); and
the control means (23) controls the horizontal rotation mechanism (15) so as to, upon detection of a person present in a room by the person detection means (21), horizontally turn the inlet (4) to face a direction in which the person is present.
7. The air cleaner (1) as claimed in claim 6, comprising pollution degree
information detection means (20) for detecting information serving as an index of a
pollution degree of the air drawn in from the inlet (4),
wherein if the pollution degree becomes equal to or below a threshold value during execution of the air blow direction control function, the control means (23) ends the air blow direction control function.
8. The air cleaner (1) as claimed in claim 7, wherein upon detection of a direction
of a person that is in a condition different from that of the previous time by the person
detection means (21) after the end of the air blow direction control function, the

control means (23) executes the air blow direction control function based on the detected direction in which the person is present.
9. The air cleaner (1) as claimed in claim 7, wherein after the end of the air blow direction control function, the control means (23) horizontally rotates a direction of the inlet (4) to detect the pollution degree and upon detection of a pollution degree that is larger than the threshold value, the control means (23) performs control to horizontally turn the direction of the blown air to the direction of the inlet (4).
10. The air cleaner (1) as claimed in any one of claims 1 to 9, comprising room information acquisition means for acquiring room information relating to a layout of the room or an obstacle in the room,
wherein the control means (23) controls the air blowing means (6) and the air blow direction changing mechanism (9, 10, 13, 14; 15) based on the room information.
11. The air cleaner (1) as claimed in claim 10, wherein the room information acquisition means acquires the room information relating to the layout of the room or the obstacle in the room from an external device installed inside the room.
12. The air cleaner (1) as claimed in any one of claims 1 to 11, wherein the casing (2) is installed on a floor surface.