JP5652863B2 - Centrifugal fan - Google Patents

Description

  The present invention relates to a centrifugal fan used for a blower or the like.

In general, a centrifugal fan is disposed on an air suction side with respect to an impeller having blades fixed on a main plate (also referred to as a hub) that rotates around a central axis at intervals in the circumferential direction. And a bell mouth that forms a mouth (see, for example, JP-A-2006-194235). The impeller includes a shroud (closed impeller) provided opposite to the main plate across the blade (closed impeller) and a shroud not provided (open impeller).
JP 2006-194235 A

  In the centrifugal fan as described above, depending on the place where the centrifugal fan is used, there is a case where there is a demand to widen the gap (tip clearance) between the bell mouth (particularly the portion closest to the blade of the air suction port) and the blade. . For example, when a centrifugal fan with a narrow chip clearance is used in a refrigerator, there is a possibility that the blades may be fixed to the bell mouth due to freezing. Therefore, it is required to make the chip clearance wide enough not to be fixed due to freezing. .

  However, when the tip clearance is widened, there is a large space from the inside of the air suction port to the impeller, and this space becomes an unstable negative pressure space as the air flow, and the volume of such space increases, so that There is a problem that noise during operation of the fan (when the impeller rotates) increases.

  The present invention has been made in view of such a point, and an object of the present invention is to suppress deterioration of noise performance of the centrifugal fan even when the tip clearance is widened in the centrifugal fan. .

  In order to achieve the above object, a centrifugal fan of the present invention includes an impeller having blades fixed at a circumferential interval on a main plate rotating around a central axis, and an air suction side with respect to the impeller. And a bell mouth forming an air suction port having a portion whose inner diameter decreases toward the impeller side, and each of the blades protrudes toward the bell mouth side and enters the inside of the air suction port. Is formed.

  With the above configuration, the protrusion of the blade enters the inside of the air inlet of the bell mouth, and the suction work is promoted at the inner portion, so that the tip clearance between the bell mouth and the blade is widened to some extent. Even so, the air flow is stabilized at the inner portion of the air inlet. As a result, the volume of the negative pressure space unstable as the air flow is reduced. Therefore, even if the tip clearance is widened, an increase in noise during operation of the centrifugal fan can be suppressed.

  According to an embodiment of the present invention, each blade is bent toward the rear side in the rotation direction of the main plate from the inner end in the main plate radial direction toward the outer side in the main plate radial direction when viewed from the central axis direction. ing. That is, each blade has a shape generally used in a so-called turbo fan.

  As a result, the efficiency of the centrifugal fan is improved, a large output (air volume and static pressure) can be obtained with a small amount of power, and the noise performance of the centrifugal fan can be further improved.

  According to another embodiment of the present invention, the impeller is an open impeller that is not provided with a shroud that faces the main plate across the blade.

  This facilitates resin molding of the impeller. That is, with a simple two-part type of a fixed type and a movable type, the main plate and blades of the impeller can be integrally formed with resin, and the manufacturing cost of the centrifugal fan can be reduced.

  According to another embodiment of the present invention, the front end surface of the protruding portion of each blade is substantially the same as the reduced diameter start position at which the inner diameter starts to decrease toward the impeller side in the air suction port in the central axis direction. Located in the same position.

  As a result, the volume of the negative pressure space that is unstable as the air flow can be reduced as much as possible, and an increase in noise during operation of the centrifugal fan can be more effectively suppressed.

  According to another embodiment of the present invention, serrations for suppressing the generation of air eddy currents at the tip surfaces are formed at the tip surfaces of the protrusions of the blades.

  As a result, the air introduced into the impeller is rectified by the serration, so that the air flow is further stabilized at the inner portion of the air intake port, thereby further improving the noise performance of the centrifugal fan.

  According to the centrifugal fan of the present invention, even if the tip clearance between the bell mouth and the blades is widened, an increase in noise during operation of the centrifugal fan can be suppressed, and the noise performance of the centrifugal fan is maintained well. can do.

It is sectional drawing which shows the state which has arrange | positioned the centrifugal fan which concerns on embodiment of this invention in the fan arrangement | positioning space of a refrigerator. It is the figure which looked at the centrifugal fan from the air suction side. It is the perspective view which looked at the centrifugal fan from the slanting air suction side. It is the figure which looked at the impeller of the centrifugal fan from the air suction side. It is the perspective view which looked at the impeller of a centrifugal fan from the diagonal air suction side. FIG. 6 is a view corresponding to FIG. 5, showing a modified example in which serrations are formed on the front end surface of the protrusion of each blade. It is a graph which shows the PQ characteristic and noise characteristic of an Example (with a wall), an Example (without a wall), a comparative example (with a wall), and a comparative example (without a wall).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a centrifugal fan 1 according to an embodiment of the present invention. In this embodiment, the centrifugal fan 1 blows cooling air to the freezer compartment 51 of the refrigerator, and is arranged in a fan arrangement space 52 partitioned on the back side of the freezer compartment 51. Further on the far side of the fan arrangement space 52, a cooler arrangement space 53 in which a cooler (not shown) is arranged is defined. The fan arrangement space 52 and the cooler arrangement space 53 are partitioned by a first partition wall 54 that extends in the vertical direction, and the freezer compartment 51 and the fan layout space 52 extend in a vertical direction parallel to the first partition wall 54. It is partitioned by two partition walls 55.

  An attachment member 57 to which the centrifugal fan 1 is attached is arranged in the fan arrangement space 52 so as to extend in the vertical direction. A portion between the mounting member 57 and the first partition wall 54 serves as a first passage 58 through which cooling air passes, and a portion between the mounting member 57 and the second partition wall 55 passes through cooling air. A second passage 59 is formed. The first passage 58 and the second passage 59 extend in the vertical direction that is perpendicular to the central axis J of the main plate 3 to be described later.

  The cooling air cooled by the cooler is sent from the cooler arrangement space 53 to the first passage 58 of the fan arrangement space 52, and flows in the first passage 58 in the vertical direction to reach the centrifugal fan 1. Then, the cooling air is sent by the centrifugal fan 1 to the second passage 59 of the fan arrangement space 52 and flows in the second passage 59 in the vertical direction, and then is formed in the second partition wall 55 (not shown). It blows out to the freezer compartment 51 from a blower outlet. Hereinafter, the cooling air is simply referred to as air.

  As shown in FIGS. 1 to 5, in the present embodiment, the centrifugal fan 1 is fixed to a main plate 3 that rotates about a central axis J that extends in the horizontal direction and is spaced apart on the main plate 3 in the circumferential direction. The impeller 2 having a plurality (11 in this embodiment) of blades 4 is provided. The impeller 2 is an open impeller that is not provided with a shroud that faces the main plate 3 with the blades 4 interposed therebetween. Hereinafter, the central axis J of the main plate 3 (also the central axis of the impeller 2) is simply referred to as the central axis J, and the direction in which the central axis J extends (the left-right direction in FIG. 1) is referred to as the central axis direction. A direction perpendicular to the central axis direction is referred to as a radial direction.

  The blades 4 rotate around the central axis J together with the main plate 3, so that the air suction side (the left side in FIG. Air is sucked in from the 58 side), and the air is discharged from the radially outer end of the impeller 2 to the radially outer side (second passage 59) (see the air flow indicated by arrows in FIG. 1).

  As shown in FIGS. 4 and 5, the plurality of blades 4 are connected to each other by a ring member 5 on the air suction side and the radially outer end of the blade 4. The main plate 3, the blades 4 and the ring member 5 are made of resin and are integrally formed with each other.

  The central portion of the main plate 3 protrudes toward the air suction side. Correspondingly, a motor 11 that rotates the main plate 3 is located on the opposite side of the main plate 3 from the air suction side (right side in FIG. 1). A space that can be disposed is formed. The motor 11 includes a rotor 12 that rotates about a central axis J, and a stator 13 that is disposed inside the rotor 12.

  The rotor 12 includes a covered cylindrical rotor holder 15 in which only the air suction side of both sides in the central axis direction is closed, a field magnet 16 fixed to the inner surface of the side wall of the rotor holder 15, and the air suction side of the rotor holder 15. The shaft 17 is fixed to the central portion of the end face portion of the rotor and rotates integrally with the rotor holder 15.

  The shaft 17 extends from the end surface portion on the air suction side of the rotor holder 15 to the side opposite to the air suction side on the central axis J, and is rotatably supported by two bearings 20. Further, the end surface portion on the air suction side of the rotor holder 15 is attached and fixed to a portion of the main plate 3 protruding to the air suction side. As a result, the main plate 3 rotates integrally with the rotor holder 15 (rotor 12) around the central axis J.

  A substantially disc-shaped base portion 21 is provided on the opposite side of the rotor holder 15 from the air suction side. A cylindrical bearing holding portion 22 that extends toward the air suction side is integrally formed at the center of the air suction side surface of the base portion 21. The two bearings 20 are respectively fixed at two locations in the central axis direction inside the bearing holding portion 22. The base portion 21 is supported by a bell mouth support member 32 described later via a connecting member 35 described later.

  The stator 13 includes a substantially cylindrical stator core 25 that is provided on the outer peripheral surface of the bearing holding portion 22 and is formed by laminating steel plates in the central axis direction, and a coil 26 wound around the stator core 25. A substrate holding part 27 for holding the circuit board 28 is provided on the surface of the stator 13 opposite to the air suction side. By supplying a drive current to the coil 26 via the circuit board 28, a rotational torque is generated between the field magnet 16 and the stator core 25, whereby the impeller 2 (main plate 3 and blade 4) is centered. It will rotate around the axis J. The rotation direction of the impeller 2 is indicated by an arrow R in FIGS. 4 and 5 (the same applies to FIG. 6 showing a modified example described later).

  In the present embodiment, the centrifugal fan 1 is a turbo fan. That is, each blade 4 of the impeller 2 has a turbofan shape. Specifically, each blade 4 is bent to the rear side in the rotational direction R of the impeller 2 (main plate 4) from the radially inner end of the blade 4 toward the radially outer side when viewed from the central axis direction. Yes.

  On the air suction side with respect to the impeller 2, a bell mouth 31 that forms an air suction port 31a having a portion whose inner diameter decreases toward the impeller side is disposed. The bell mouth 31 is integrally formed with a bell mouth support member 32 that supports the bell mouth 31 on its outer peripheral side. The center of the air inlet 31a of the bell mouth 31 coincides with the central axis J. In the present embodiment, the air suction port 31a is formed so that the inner diameter decreases toward the impeller side over the entire center axis direction, but a part of the air suction port 31a in the center axis direction (particularly, The end portion on the impeller 2 side) is a portion where the inner diameter is constant or the inner diameter increases toward the impeller side, and other portions are portions where the inner diameter decreases toward the impeller side. Good.

  The base portion 21 and the bell mouth support member 32 include a plurality of (four in the present embodiment) arranged at intervals in the circumferential direction through the side opposite to the air suction side and the radially outer side with respect to the impeller 2. ) Are connected to each other by a connecting member 35. As a result, the base portion 21 is supported by the bell mouth support member 32 via the connecting member 35. A flange portion 32 a is formed at the outer peripheral edge of the bell mouth support member 32, and the centrifugal fan 1 is attached and fixed to the attachment member 57 via the flange portion 32 a. In the mounted state of the centrifugal fan 1, the bell mouth support member 32 (bell mouth 31) is located in the first passage 58, while the radially outer end from which air is discharged in the impeller 2 is located in the second passage 59. doing.

  A protruding portion 4a that protrudes toward the bell mouth 31 and enters the inside of the air suction port 31a is formed on the air suction side of each blade 4 and on the radially inner end (the portion facing the air suction port 31a). Yes.

  Here, the space | interval (tip clearance) between the bellmouth 31 and the blade | wing 4 containing the said protrusion part 4a is set so that the blade | wing 4 may not adhere to the bellmouth 31 by freezing. In the case where the tip clearance is such a width, if there is no protrusion 4a, noise during operation of the centrifugal fan 1 (when the impeller rotates) increases. However, even if the tip clearance is set as described above by forming the protrusions 4a as described above on each blade 4 as in the present embodiment, the noise during operation of the centrifugal fan 1 is increased. Can be suppressed. That is, since the projecting portion 4a promotes the suction work in the inner portion of the air suction port 31a, the air flow is generated in the inner portion of the air suction port 31a even if the tip clearance is as wide as described above. As a result, the volume of the negative pressure space that is unstable as the air flow is reduced. Therefore, an increase in noise during operation of the centrifugal fan 1 can be suppressed.

  The front end surface of the protruding portion 4a of each blade 4 is substantially the same as the reduced diameter starting position (in this embodiment, the end on the air suction side) where the inner diameter starts to decrease toward the impeller side in the air suction port 4a in the central axis direction. It is preferable that they are located at the same position. Thereby, the volume of the negative pressure space unstable as the air flow can be reduced as much as possible. Or the deviation | shift amount in the central-axis direction of the position of the front end surface of the protrusion part 4a and the said diameter reduction start position may exceed 0, and may be below a predetermined value. The predetermined value is, for example, 10% of the length of the air inlet 4a in the central axis direction. Particularly preferably, the distal end surface of the protruding portion 4a is displaced toward the air suction side from the reduced diameter starting position, and the amount of deviation in the central axis direction between the position of the distal end surface of the protruding portion 4a and the reduced diameter starting position is 0 Is less than the predetermined value (see FIG. 1). That is, it is particularly preferable that the protruding portion 4a protrudes from the air suction port 31a to the outer space (first passage 58) on the air suction side at the predetermined value or less.

  In addition, as shown in FIG. 6, serrations 4 b may be formed on the tip surfaces of the protrusions 4 a of the blades 4 for suppressing the generation of air eddy currents at the tip surfaces. The serrations 4b are continuously uneven along the length direction of the blades 4 on the tip surface of the protrusion 4a. Since the air introduced into the impeller 2 is rectified by such serration 4b, the air flow is further stabilized at the inner portion of the air suction port 31a, and thereby the noise performance of the centrifugal fan 1 is further improved. become.

  The present invention is not limited to the above-described embodiment, and can be substituted without departing from the scope of the claims.

  For example, in the above-described embodiment, each blade 4 of the impeller 2 has a turbofan shape, but is not limited thereto. For example, each blade 4 extends straight in the radial direction (all blades 4 are arranged radially). May be).

  Moreover, in the said embodiment, although the impeller 2 is an open impeller, the closed impeller provided with the casing which hold | maintained the shroud may be sufficient.

  Furthermore, in the said embodiment, although the centrifugal fan 1 was used in order to ventilate cooling air to the freezer compartment 51 of a refrigerator, it is not restricted to this, For example, even if it uses as a cooling blower, such as an electronic device Good. When the centrifugal fan 1 is used for a fan that requires a large chip clearance as in the above-described embodiment, a large silent effect can be expected.

  Further, in the embodiment, the first partition wall 54 exists in the vicinity of the air suction side with respect to the centrifugal fan 1 (expressed as “with wall” in the following examples and comparative examples). The present invention can also be applied to the case where the first partition wall 54 does not exist (the second partition wall 55 may be omitted) (expressed as “no wall” in the following examples and comparative examples). Thus, even if the tip clearance is widened, an increase in noise during operation of the centrifugal fan 1 can be suppressed.

  The above embodiments are merely examples, and the scope of the present invention should not be interpreted in a limited manner. The scope of the present invention is defined by the scope of the claims, and all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  Here, a centrifugal fan similar to that of the above-described embodiment is prepared, and for the centrifugal fan, the change in static pressure (PQ characteristic) relative to the flow rate (air volume) on the side from which air is discharged and the side from which air is discharged. The change of noise level (noise characteristics) with respect to the flow rate (air volume) of the air was investigated. In the prepared centrifugal fan, each blade 4 is provided with a protrusion 4a, the tip surface of the protrusion 4a is shifted to the air suction side with respect to the diameter reduction start position, and the position of the tip surface of the protrusion 4a The amount of deviation in the central axis direction from the diameter reduction start position is not more than the predetermined value. Further, the tip clearance is set to the same size as in the above embodiment. When the centrifugal fan is disposed in a space between two walls similar to the first partition wall 54 and the second partition wall 55 of the embodiment (Example (with walls)), these two walls The PQ characteristic and the noise characteristic were examined for the case (Example (no wall)) in which there is no space.

  In addition, for comparison, a centrifugal fan in which the protrusions 4a are not formed on each blade 4 (the other configurations are the same as those in the above embodiment) is disposed in the space between the two walls ( PQ characteristics and noise characteristics were examined for a comparative example (with walls) and a case in which these two walls are not provided (comparative example (without walls)).

  The result is shown in FIG. Comparing the example (with walls) and the comparative example (with walls), it can be seen that the noise level in the example (with walls) is lower in any flow rate region than the comparative example (with walls). As for the PQ characteristics, the difference between the two is hardly seen, and it can be seen that the PQ characteristics have the desired performance. In addition, when comparing the example (no wall) and the comparative example (no wall), the noise level of the example (no wall) is reduced in most of the flow rate range compared to the comparative example (no wall). I understand. As for the PQ characteristics, both have desired performance.

  Therefore, it can be seen that by forming the protrusions 4a on each blade 4, the noise reduction during the operation of the centrifugal fan is realized even if the tip clearance is widened.

DESCRIPTION OF SYMBOLS 1 Centrifugal fan 2 Impeller 3 Main plate 4 Blade 4a Protruding part 4b Serration 31 Bell mouth 31a Air inlet J Central axis

Claims (1)

A motor, an impeller that is rotated by the motor, and has a plurality of blades fixed at intervals in the circumferential direction on an outer peripheral portion of the concave portion on a main plate having a concave portion that accommodates the motor in a central portion; and the impeller A bell mouth that forms an air suction port that is disposed on the air suction side and has an inner diameter that decreases toward the impeller side, and a plurality of columnar members that connect the bell mouth and the motor. A centrifugal fan, wherein each blade is formed with a protruding portion that protrudes toward the bell mouth side and enters the inside of the air suction port, and a tip surface of the protruding portion of each blade is in the direction of the central axis. The centrifugal fan is located at substantially the same position as the diameter reduction start position at which the inner diameter starts to decrease toward the impeller side at the air suction port .

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