Propeller fan and axial flow blower

Abstract

A stagger angle of a rotor blade has a first stagger angle distribution having a local minimum value in a region from an inner circumferential edge to a first boundary position, and has a second stagger angle distribution that increases toward an outer circumferential edge and follows an n-dimensional function using the radius of the rotor blade as a parameter in a region from the first boundary position to the outer circumferential edge, where n is a value ranging from 1 to 2 and exclusive of 1. This can limit the height of the outer circumferential portion, and can achieve a reduced noise level and higher efficiency.

1 . A propeller fan including a boss portion that is driven rotationally, and more than one rotor blade radially attached to the boss portion to generate an airflow in a rotational axis direction, wherein
 a radial cross section of the rotor blade on an inner circumferential portion side of the rotor blade has a shape convex against a direction of the airflow, and a radial cross section of the rotor blade on an outer circumferential portion side of the rotor blade has a shape concave along the direction of the airflow,   the radial cross section of the rotor blade is inclined toward an upstream side of the airflow in a leading edge side region with an inclination angle increasing toward a leading edge, and is inclined toward a downstream side of the airflow in a trailing edge side region with the inclination angle increasing toward a trailing edge, and   a stagger angle of the rotor blade has a first stagger angle distribution having a local minimum value in a region from an inner circumferential edge to a first boundary position, and has a second stagger angle distribution that increases toward an outer circumferential edge and follows an n-dimensional function using a radius of the rotor blade as a parameter in a region from the first boundary position to the outer circumferential edge, where n is a value ranging from 1 to 2 and exclusive of 1.   
     
     
         2 . The propeller fan according to  claim 1 , wherein an angle of advance of the rotor blade has a first angle-of-advance distribution that linearly increases in a region from the inner circumferential edge to a second boundary position, and has a second angle-of-advance distribution that increases toward the outer circumferential edge and follows an m-dimensional function using the radius as a parameter in a region from the second boundary position to the outer circumferential edge, where m is a value ranging from 1 to 2 and exclusive of 1. 
     
     
         3 . The propeller fan according to  claim 1 , wherein a forward tilt angle of the rotor blade has a first forward tilt angle distribution having a constant value in a region from the inner circumferential edge to a third boundary position, and has a second forward tilt angle distribution that increases toward the outer circumferential edge and follows a p-dimensional function using the radius as a parameter in a region from the third boundary position to the outer circumferential edge, where p is a value ranging from 2 to 5. 
     
     
         4 . The propeller fan according to  claim 1 , wherein the second stagger angle distribution changes at a rate higher than a rate of change in the first stagger angle distribution. 
     
     
         5 . The propeller fan according to  claim 2 , wherein the second angle-of-advance distribution increases at a rate higher than a rate of increase in the first angle-of-advance distribution. 
     
     
         6 . An axial flow blower comprising:
 the propeller fan according to  claim 1 ;   a motor to rotationally drive the boss portion of the propeller fan; and   a body including a bell mouth disposed around the propeller fan.   
     
     
         7 . The propeller fan according to  claim 2 , wherein a forward tilt angle of the rotor blade has a first forward tilt angle distribution having a constant value in a region from the inner circumferential edge to a third boundary position, and has a second forward tilt angle distribution that increases toward the outer circumferential edge and follows a p-dimensional function using the radius as a parameter in a region from the third boundary position to the outer circumferential edge, where p is a value ranging from 2 to 5. 
     
     
         8 . The axial flow blower according to  claim 6 , wherein an angle of advance of the rotor blade has a first angle-of-advance distribution that linearly increases in a region from the inner circumferential edge to a second boundary position, and has a second angle-of-advance distribution that increases toward the outer circumferential edge and follows an m-dimensional function using the radius as a parameter in a region from the second boundary position to the outer circumferential edge, where m is a value ranging from 1 to 2 and exclusive of 1. 
     
     
         9 . The axial flow blower according to  claim 6 , wherein a forward tilt angle of the rotor blade has a first forward tilt angle distribution having a constant value in a region from the inner circumferential edge to a third boundary position, and has a second forward tilt angle distribution that increases toward the outer circumferential edge and follows a p-dimensional function using the radius as a parameter in a region from the third boundary position to the outer circumferential edge, where p is a value ranging from 2 to 5. 
     
     
         10 . The axial flow blower according to  claim 8 , wherein a forward tilt angle of the rotor blade has a first forward tilt angle distribution having a constant value in a region from the inner circumferential edge to a third boundary position, and has a second forward tilt angle distribution that increases toward the outer circumferential edge and follows a p-dimensional function using the radius as a parameter in a region from the third boundary position to the outer circumferential edge, where p is a value ranging from 2 to 5. 
     
     
         11 . The axial flow blower according to  claim 6 , wherein the second stagger angle distribution changes at a rate higher than a rate of change in the first stagger angle distribution. 
     
     
         12 . The axial flow blower according to  claim 8 , wherein the second angle-of-advance distribution increases at a rate higher than a rate of increase in the first angle-of-advance distribution.