Patent Publication Number: US-10316860-B2

Title: Centrifugal fan having impeller with blades between annular shroud and main plate

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     The present invention relates to a centrifugal fan, and more particularly to a centrifugal fan which is reduced with a thickness and a noise. 
     2. Description of the Related Art 
     In the related art, as a fan widely used for cooling, ventilating, air conditioning of household electrical appliances, OA (Office Automation) equipment, and industrial equipment, air conditioning for vehicles, blowing, etc., a centrifugal fan has been known. As a related-art centrifugal fan, a centrifugal fan in which a casing is configured by an upper casing and a lower casing, an impeller is housed between the upper casing and the lower casing, and air suctioned from an inlet with rotation of the impeller is discharged from an outlet formed in a lateral surface between the upper casing and the lower casing toward the outside has been known (for example, see JP-A-2012-207600). 
       FIG. 5  illustrates a centrifugal fan  100  described in JP-A-2012-207600, where a quadrangular casing  120  is configured by an upper casing  121  and a lower casing  122 , and an impeller  130  is housed between the upper casing  121  and the lower casing  122 . The impeller  130  is provided with an annular shroud  131 . The annular shroud  131  is configured to have a cylindrical part  132  in the center thereof and to be warped toward the upper casing  121  from the cylindrical part  132  to a periphery of the annular shroud  131 , and is configured such that a shape of an upper surface from an end of the cylindrical part  132  of the annular shroud  131  to the periphery of the annular shroud  131  is formed in a shape of a curved surface in which four circular arcs having different radii of curvature are connected, and a cross-sectional area of an air flow passage up to the periphery of the annular shroud  131  is gradually increased. Thus, air is increased in pressure, and blows out from a periphery of the impeller  130  to the outside. 
     Air suctioned from an inlet  110  by high-speed rotation of the impeller  130  passes between the blades  135 , blows out from the periphery of the impeller  130  to the outside, and is discharged from an outlet  111 , which is formed in a lateral surface between the upper casing  121  and the lower casing  122 . However, since the centrifugal fan  100  described in JP-A-2012-207600 has the shape in which the periphery of the annular shroud  131  is warped toward the upper casing  121 , part of the air blowing out from the periphery of the impeller  130  may flow back from a gap  125  between the annular shroud  131  and the upper casing  121  toward the inlet  110 , and a disturbance may occur at a flow of the air in the vicinity of the inlet  110  due to the air flowing backward, which is responsible for a noise. 
     When the full height the centrifugal fan is designated from restriction of a space mounted on the equipment or apparatus, the centrifugal fan  100  described in JP-A-2012-207600 may not meet a demand for reduction in thickness due to a height dimension of electronic components such as control IC, etc. mounted on a circuit board  140 . 
     SUMMARY OF THE INVENTION 
     One of objects of the present invention is to provide a centrifugal fan in which an outlet is formed in a lateral surface of a quadrangular casing between an upper casing and a lower casing and which reduces a thickness and inhibits part of air blowing out from a periphery of an impeller from flowing backward to reduce a noise. 
     According to an illustrative embodiment of the present invention, there is provided a centrifugal fan including: a casing including an upper casing, a lower casing, and struts disposed between the upper casing and the lower casing; and an impeller that is provided in the casing, the impeller having an annular shroud, a plurality of blades, and a main plate, wherein the main plate of the impeller has an inclined surface between an inner circumference side and an outer circumference side of the impeller, and wherein the inner circumference side of the impeller is located at an upward position in an axial direction of the impeller, and the outer circumference side of the impeller is located at an downward position in the axial direction of the impeller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a cross-sectional view illustrating a centrifugal fan according to an embodiment of the invention; 
         FIG. 2  is a partially enlarged view of the centrifugal fan illustrated in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the centrifugal fan illustrated in  FIG. 1 ; 
         FIG. 4  is an explanatory view illustrating a flow of air blowing out from an outlet in the centrifugal fan according to the embodiment of the invention; and 
         FIG. 5  is a cross-sectional view illustrating a centrifugal fan of the related art. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a mode for carrying out the invention (hereinafter referred to as “embodiment”) will be described on the basis of the attached drawings. Throughout the description of the embodiment, the same reference numeral is given the same element. 
     The basic structure of the centrifugal fan  1  is as follows. As illustrated in  FIGS. 1 and 2 , a casing  2  is configured by an upper casing  3  and a lower casing  4 , and an impeller  8  is housed between the upper casing  3  and the lower casing  4 . Air suctioned from an inlet  35  with the rotation of this impeller  8  passes between blades  10 , and is discharged from an outlet  36 , which is formed in a lateral surface from which struts  7  installed between the upper casing  3  and the lower casing  4  are removed, toward the outside of the casing  2 . 
     A motor  21  is an outer rotor type brushless DC motor, and is mounted on a bottom of a recess part  5   a  formed in the motor base  5 . A circuit board  30  mounted on a lower insulator  24   b  (to be described below) of the motor  21  is also housed in the recess part  5   a . An electronic component  31  is mounted on the circuit board  30 . 
     As illustrated in  FIG. 2 , bearings  27  and  28  are mounted on an inner side of a bearing holder part  26 , and rotatably support a shaft  16 . A stator  22  is set up on an outer side of the bearing holder part  26 . The stator  22  is provided with a stator core  23  that is obtained by laminating a predetermined number of cores, an insulator  24  made up of an upper and lower insulators  24   a  and  24   b  that are mounted from opposite sides in an axial direction that is a direction of the shaft  16  of the motor  21 , and a coil  25  that is wound around teeth of the stator core  23  via the insulator  24 . The stator core  23  is configured by laminating cores having a plurality of teeth (see  FIG. 3 , six teeth are exemplified in  FIG. 3 ) that extend outward from an annular yoke in a radial direction. Thus, the bearing holder part  26  is fitted into an opening formed in the center of the stator core  23 , and the stator  22  is set up at the outer side of the bearing holder part  26 . 
     A rotor  15  is configured by the shaft  16 , a boss part  17  mounted on the shaft  16 , a cup-shaped rotor yoke  18  mounted on the boss part  17 , and an annular magnet  19  fixed at an inner side of the rotor yoke  18 . The rotor yoke  18  is caulked to the boss part  17 , and the circuit board  30  is mounted on the lower insulator  24   b.    
     The impeller  8  is configured by an annular shroud  9 , a plurality of blades  10 , and a main plate  11 . The blades  10  and the main plate  11  are formed by integrally molding a resin. The blades  10  are extended from the main plate  11  in the axial direction, have a shape curved and inclined in a direction opposite to a rotational direction, and become backward blades (a so-called turbo type) with respect to the rotational direction. All of the blades  10  have the same shape, and both of the blades  10  and the annular shroud  9  are coupled by ultrasonic welding. 
     The main plate  11  of the impeller  8  has an inclined surface  11   a  between an inner circumference side and an outer circumference side. That is, the inner circumference side of the impeller  8  is located at an axial upper side, and the outer circumference side of the impeller  8  is located on an axial lower side. As a result, the inclined surface  11   a  is formed between these inner and outer circumference sides. 
     The impeller  8  and the rotor  15  are coupled in the following procedure. That is, first, an annular flange  20  is welded to an outer circumferential surface of the rotor yoke  18  by, for instance, resistance welding. Next, pins (not shown) formed on a lower surface of an inner circumference side of the main plate  11  by integral molding are fitted into through-holes formed in the flange  20 , and tips of the pins are crushed by heat, and are thermally caulked. Thereby, both are coupled, and the impeller  8  is mounted on the rotor  15 . 
     Coupling of each member will be described with reference to  FIG. 3 . A plurality of recess parts (thinned portions)  3   a  are formed at an upper surface side of the upper casing  3 . The upper casing  3  and the lower casing  4  are coupled by installing the struts  7  between the upper casing  3  and the lower casing  4  and fastening the struts  7  with fasteners such as screws. To be specific, the struts  7  are formed by integral molding of a resin with the upper casing  3 , and are fastened by tightening tapping screws to lower holes formed in the struts  7 . The fastening means is not limited thereto. For example, a configuration in which screws (or bolts) are inserted into through-holes of the struts  7  from the lower casing  4  side and are fixed from the upper casing  3  side by nuts may be naturally adopted. 
     The lower casing  4  is configured by the motor base  5  made of a metal (for example, a steel sheet) and a base plate  6  made of a resin, and is formed by superimpose both. The motor  21  is mounted on the bottom of the recess part  5   a  formed in the motor base  5 . Lateral portions  6   a  extending downward are formed at four places of an outer circumferential end of the base plate  6 . Inner sides of these lateral portions  6   a  are in contact with outer circumferences of four sides of the motor base  5 , and are positioned. Reference numerals  5   d  and  6   d  indicate through-holes. 
     In the present embodiment, as described above, the main plate  11  is provided with the inclined surface  11   a . This is intended to reduce a thickness of the centrifugal fan  1 . As illustrated in  FIG. 1 , components for controlling driving of the motor  21  and the electronic component  31  such as the control IC are mounted on the circuit board  30 . For this reason, to prevent contact between the electronic component  31  mounted on the circuit board  30  and the impeller  8  in a limited space, the inclined surface  11   a  is formed at the main plate  11 . Thereby, since a part of the electronic component  31  is housed at a position covered with this inclined surface  11   a , the contact between the electronic component  31  and the impeller  8  can be prevented, and an axial reduction in thickness is achieved. 
     In the present embodiment, to reduce a noise, the upper casing  3  and the lower casing  4  is configured as follows. An upper end of the cylindrical part in which an opening serving as the inlet  35  of the annular shroud  9  is formed is located within an annular groove of the upper casing  3 . Thereby, the upper casing  3  has a shape in which the upper end of the cylindrical part of the annular shroud  9  is covered. For this reason, even when air flows backward from an outer circumferential edge of the impeller  8 , a backflow entering the inlet  35  can be suppressed by resistance at this place. 
     As illustrated in  FIG. 4 , an outer diameter of the upper casing  3  and an outer diameter of the base plate  6  of the lower casing  4  are larger than an outer diameter of the impeller  8 . A lower surface  3   b  of an outer circumferential end of the upper casing  3  is formed into an arcuate curved surface in its cross section such that it protrudes toward an upper surface side of the upper casing  3 . An outer circumferential end  6   b  of the base plate  6  of the lower casing  4  is also formed into an arcuate curved surface in its cross section such that it protrudes toward a lower surface side of the upper casing  3 . For this reason, when air blowing out from the outer circumferential end of the impeller  8  blows out from a space, which becomes the outlet  36  formed between the upper casing  3  and the base plate  6  of the lower casing  4 , to the outside of the casing  2 , the blowout air blows out in an axial downward direction. Afterwards, the air changes the direction to a slight upward direction, and blows out in a horizontal direction. In this way, since the air blowing out from the outlet  36  blows out in the axial downward direction, air flowing backward from a gap  3   c  between the upper casing  3  and the annular shroud  9  to the inlet  35  side can be suppressed, and a disturbance of the air does not occur. As a result, a noise can be reduced. Cross sections of the lower surface  3   b  and the outer circumferential end  6   b  may not necessarily be in an arcuate shape of a complete circle or an oval circle, and may be a curved surface that protrudes toward the upper surface side of the upper casing  3 . 
     Here, since the outer diameters of the upper casing  3  and the base plate  6  of the lower casing  4  are larger than the outer diameter of the impeller  8 , and the outlet  36  is directed in the axial downward direction, a structure in which foreign materials hardly enter the outlet  36  due to the upper casing  3  and the outer circumferential edge  6   b  of the base plate  6  of the lower casing  4  is obtained, and an effect of the measures for safety can also obtained. 
     As described above, the motor base  5  formed of the metal and the base plate  6  formed of the resin, which constitute the lower casing  4  have been separately described, but the outlet may be configured to be formed of a resin by insert molding of the motor base. 
     In this way, the invention is not limited to the specific embodiment, and includes various modifications. Those are apparent to those skilled in the art from the description of the claims. 
     As described with reference to the embodiment, according to the invention, it is possible to provide the centrifugal fan in which an outlet is formed in a lateral surface of the quadrangular casing between the upper casing and the lower casing and which reduces a thickness and inhibits part of air blowing out from the periphery of the impeller from flowing backward to reduce a noise.