JP3700217B2 - Centrifugal blower - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal blower used as, for example, a blower for an air conditioner, and more particularly to a centrifugal multiblade blower capable of suppressing a reverse flow phenomenon that occurs near a nose portion.
[0002]
[Prior art]
Conventionally, for example, a centrifugal blower used as a blower for an air conditioner, the shape of the bell mouth forming the suction port of the scroll casing is a perfect circle having a center on the rotating shaft of the centrifugal impeller. The height of the slope of the bell mouth was also uniform over the entire circumference.
[0003]
However, in the centrifugal blower having the above-described structure, the centrifugal impeller is spirally formed radially outward by the rotation of a large number of blades after being sucked into the centrifugal impeller through the suction port from the outside of the scroll casing. It is known that a reverse flow phenomenon that flows in the opposite direction to the suction air flow blown into the ventilation path occurs in the vicinity of the nose portion of the scroll casing. In a region where such a reverse flow phenomenon is likely to occur, a collision between the suction air flow and the reverse flow occurs, resulting in a problem that the generation of blowing noise and the deterioration of blowing characteristics occur.
[0004]
For the purpose of solving the above-mentioned problems, Japanese Utility Model Laid-Open No. 56-171699 discloses that a suction port is formed from a blade by forming a bow-shaped shielding plate within a range of 90 ° from the nose portion in the reverse rotation direction. A centrifugal blower (first conventional example) has been proposed in which a reverse flow phenomenon that blows back to the side is pressed by a shielding plate.
[0005]
Further, in Japanese Utility Model Laid-Open No. 63-128297, the center of the perfect circular suction port formed in the scroll casing is on the anti-nose portion side on the line connecting the nose portion of the scroll casing and the rotation center of the centrifugal impeller. There has been proposed a centrifugal blower (second conventional example) in which generation of high-frequency sound in the nose portion is suppressed by decentering by a predetermined amount of eccentricity.
[0006]
In JP-A-5-149297, without changing the center and suction area of the bell mouth, the radius of the bell mouth is gradually increased in a region where the back flow phenomenon hardly occurs, and in the region where the back flow phenomenon easily occurs, the bell mouth is increased. The radius of the mouse is gradually decreased, the height of the bell mouth is gradually decreased in the region where the reflux phenomenon is difficult to occur, and the height of the bell mouth is gradually increased in the region where the reflux phenomenon is likely to occur. Thus, a centrifugal blower (third conventional example) has been proposed in which the blowing noise generated due to the collision between the reverse flow and the suction air flow is reduced and the blowing characteristics are improved.
[0007]
[Problems to be solved by the invention]
However, in the centrifugal blower of the first conventional example and the centrifugal blower of the second conventional example, the bell mouth with the eccentric center of the bow-shaped shielding plate and the suction port greatly reduces the suction area of the suction port. From the viewpoint of air blowing performance, it is effective when backflow occurs, but in normal air blowing conditions, the total air pressure and air volume are reduced, and the flow rate of the suction part is increased due to the presence of the shielding plate. The problem of letting it happen has arisen. Further, in the centrifugal blower of the third conventional example, by gradually increasing or decreasing the inner diameter of the suction port and the height of the bell mouth in the region where the backflow phenomenon is unlikely to occur, the airflow characteristics in the region where the backflow phenomenon is unlikely to be deteriorated. The problem has arisen.
[0008]
OBJECT OF THE INVENTION
It is an object of the present invention to effectively prevent a collision between a suction air flow and a back flow, suppress the generation of blowing noise caused by the collision, and suppress the badness to a normal blowing state to a minimum. It is another object of the present invention to improve the blowing characteristics and reduce the blowing noise in an area where the backflow phenomenon easily occurs without reducing the blowing characteristics in the area where the backflow phenomenon hardly occurs.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, the backflow phenomenon that blows back from the blade to the suction port side of the scroll casing is a blowout from the upper surface of the blade, and that portion is a portion that hardly sucks air in a normal blowing state. Cover the entire upper surface of the blade in the region where the backflow phenomenon from −60 ° to + 60 ° is likely to occur with respect to the rotation direction of the centrifugal impeller from the nose portion with the bell mouth, and start the nose portion. By partially covering the upper surface of the blade in the region where the backflow phenomenon is difficult to occur from + 120 ° to + 270 ° with respect to the rotation direction of the centrifugal impeller, the generation of the backflow in the region where the backflow phenomenon easily occurs is suppressed. be able to. Thereby, by effectively preventing the collision between the suction air flow and the backflow, it is possible to reduce noise generation and improve the airflow characteristics without deteriorating the airflow characteristics in the region where the backflow phenomenon is difficult to occur. . Moreover, the effect that the badness to a normal ventilation state can be suppressed to the minimum is acquired. In addition, a minute gap is formed between the inner surface of the annular ridge of the bell mouth and the upper end of the annular shroud of the centrifugal impeller, so that a spiral shape passes between the bell mouth and the shroud. It is difficult to generate a backflow from the ventilation path toward the suction port, and the effect of improving the blowing efficiency and reducing blowing noise can be obtained.
In addition, by providing a large number of fixed wings on the inner surface of the bell mouth in the region where the backflow phenomenon from −60 ° to + 60 ° is likely to occur with respect to the rotation direction of the centrifugal impeller starting from the nose, A small and stable vortex is forcibly generated in a space surrounded by the blade and the upper surface of the blade. As a result, the pressure on the upper surface side of the blade is increased, and an effect that backflow hardly occurs is obtained.
[0012]
According to the second aspect of the present invention, the height of the slope where the reverse flow phenomenon is likely to occur from −60 ° to + 60 ° in the rotation direction of the centrifugal impeller from the nose portion as a starting point, and the centrifuge starting from the nose portion as a starting point. By making the height of the slope of the region where the backflow phenomenon hardly occurs from + 120 ° to + 270 ° in the rotation direction of the impeller, the flow of air flowing into the region where the backflow easily occurs is rectified, and the blade inlet The angle and the inflow angle of air coincide. Thereby, the effect that a ventilation characteristic can be improved and ventilation noise can be reduced is acquired.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
[Configuration of the first embodiment]
1 to 4 show a first embodiment in which the centrifugal blower of the present invention is applied to a centrifugal multiblade blower used in a vehicle air conditioner. FIGS. 1 and 2 show the centrifugal multi-blade. It is the figure which showed the whole structure of the blade air blower.
[0014]
The centrifugal multiblade blower 1 is integrally provided on the upstream side of the air duct of the vehicle air conditioner, and includes an electric motor 2 as a driving means, a centrifugal impeller 3 that is rotationally driven by the electric motor 2, and It is comprised from the scroll casing 4 etc. which accommodate the centrifugal impeller 3 grade | etc.,.
[0015]
The electric motor 2 is fixed to the scroll casing 4 with a lower end portion protruding outside from the scroll casing 4. A rotating shaft 5 fixed to the centrifugal impeller 3 protrudes from the upper end surface of the electric motor 2.
[0016]
The centrifugal impeller 3 is an impeller made of an integrally molded product of resin, and includes a bottom plate 6, a large number of blades 7, a shroud 8, and the like. The bottom plate 6 has a substantially conical shape with a central portion recessed inward in order to reduce the jumping-out of the electric motor 2 from the scroll casing 4, and the rotary shaft 5 of the electric motor 2 is fitted in the central portion. A boss portion 9 that is integrally meshed is provided.
[0017]
A number of blades 7 are rotor blades (rotary blades) having a circular cross-sectional shape, and are parallel to the rotation shaft 5 of the electric motor 2 on the annular flat plate portion of the bottom plate 6, in the circumferential direction. Are arranged at a constant pitch. These blades 7 suck in air from the suction side end face (suction side end part) 11 on the inner peripheral side, and blow out air radially outward from the blow side end face (blowing side end part) 12 on the outer peripheral side. .
[0018]
The shroud 8 is provided in an annular shape, and has a substantially arc-shaped cross section along the flow of the intake air while gradually changing the direction from the axial direction to the radially outward direction. The shroud 8 connects the upper ends of the blades 7 to hold the blades 7 at regular intervals, and is substantially spaced from the suction side end surface 11 of each blade 7 toward the blowout side end surface 12 between the blades 7. The ventilation path of the suction air flow that flows in an arc shape is formed. On the inner peripheral side of the shroud 8, a cylindrical protruding portion 13 that protrudes upward from the upper surface of each blade 7 is provided.
[0019]
The scroll casing 4 forms a spiral air passage 10 around the centrifugal impeller 3 and is divided into two in the width direction of the spiral air passage 10, and a bell mouth 15 that forms an air inlet 14. And a second casing (lower casing) 17 that supports the electric motor 2.
[0020]
As shown in FIG. 1, the scroll casing 4 has a spiral portion of the spiral air passage 10 starting from one point of the nose portion 18 that is the starting point of the spiral air passage 10, and starts from one point of the nose portion 18. It is composed of a scroll curve formed with a constant spread angle. A discharge port 19 having a rectangular opening cross section for discharging air to a cooling unit (not shown) is formed at the downstream end of the spiral air passage 10.
[0021]
The bell mouth 15 of the scroll casing 4 of this embodiment will be described in detail with reference to FIGS. The bell mouth 15 is provided closer to the suction port 14 than the spiral flat plate portion 20 of the first casing 16, and is formed to project outwardly so as to face the projecting portion 13 of the shroud 8. have. An annular recess 22 is formed on the inner surface of the protrusion 21. Between the inner surface of the bell mouth 15 and the shroud 8, a cylindrical minute gap 23 having a labyrinth seal structure that makes it difficult for air to pass therethrough is formed.
[0022]
Then, within the range of the scroll angle from −60 ° to + 95 ° in the rotational direction of the centrifugal impeller 3 starting from the nose portion 18, the ceiling portion of the ridge portion 21 is covered with the entire upper surface of many blades 7. The wide portion 24 is used. Further, the ceiling portion of the ridge portion 21 is partially covered on the upper surfaces of the blades 7 within the range of the scroll angle from + 115 ° to + 270 ° in the rotational direction of the centrifugal impeller 3 starting from the nose portion 18. The narrow portion 25 is used.
[0023]
Here, the positional relationship between the suction side and blow-out side end surfaces 11 and 12 of the blade 7 of this embodiment and the bell mouth 15 is determined as follows. The bell mouth 15 fluidly divides the inside and the outside of the scroll casing 4. The inner diameter of the substantially circular suction port 14 whose axis is the center of rotation of the centrifugal impeller 3 is Di, and the blade 7 When the inner diameter of the suction side end face 11 is D1 and the outer diameter of the outlet side end face 12 of the blade 7 is D2, the reverse flow phenomenon from −60 ° to + 95 ° in the rotational direction of the centrifugal impeller 3 starting from the nose portion 18. The region A in which the reverse flow phenomenon is satisfied satisfies the relationship expressed by the following formula 1, and the region B in which the backflow phenomenon from + 115 ° to + 270 ° hardly occurs in the rotation direction of the centrifugal impeller 3 starting from the nose portion 18 is as follows. The relationship of the formulas 2 to 4 is satisfied.
[Expression 1]
Di ≦ D1
[Expression 2]
D1 ≤ Di ≤ D2
[Equation 3]
Di / D2 ≈ 0.2
[Expression 4]
0.5 ≦ D1 / D2 ≦ 0.6
[0024]
That is, as shown in FIG. 3, the inner diameter of the mouth edge portion 26 of the suction port 14 of the bell mouth 15 having the wide portion 24 in the protruding portion 21 near the nose portion 18 is set on the suction side end surface 11 of the blade 7. It is made smaller than the inner diameter and covers the entire upper surface of the blade 7. The wide portion 24 is within a scroll angle range of −90 ° to −60 ° and within a scroll angle range of + 60 ° to + 120 ° in the rotational direction of the centrifugal impeller 3 starting from the nose portion 18. May also be provided.
[0025]
Further, as shown in FIG. 4, the inner diameter of the mouth edge portion 27 of the suction port 14 of the bell mouth 15 which is separated from the nose portion 18 and has the narrow portion 25 on the protruding portion 21 is the suction side of the blade 7. The diameter is larger than the inner diameter of the end surface 11 and smaller than the outer diameter of the outlet side end surface 12 of the blade 7, and partially covers the upper surface of the blade 7.
[0026]
As shown in FIG. 1, the two lip portions 28 and 29, which are connection portions between the lip portion 26 having the same inner diameter and the lip portion 27 having the same inner diameter, of the scroll casing 4 are 10 at a scroll angle. It is provided within the range of °, and the mouth edge part 26 and the mouth edge part 27 are connected at an acute angle.
[0027]
[Operation of the first embodiment]
Next, the operation of the centrifugal multiblade fan 1 of this embodiment will be briefly described with reference to FIGS.
[0028]
When an operating voltage is applied to the electric motor 2, the centrifugal impeller 3 rotates with the rotation of the rotating shaft 5 of the electric motor 2. As a result, air is sucked into the suction-side end surfaces 11 of the large number of blades 7 from the suction ports 14, and air is blown into the spiral ventilation path 10 from the discharge-side end surfaces 12 of the large number of blades 7 with a predetermined angle. . Thereby, the suction air is pressurized in the spiral air passage 10 and flows in the direction of the discharge port 19.
[0029]
At this time, the air that has entered between the adjacent blades 7 from the suction port 14 near −120 ° in the rotation direction of the centrifugal impeller 3 starting from the nose portion 18 enters the nose portion 18 by the rotation of the blades 7. The pressure increases as it approaches. The air whose pressure has increased over other air tends to cause a backflow phenomenon in which the air flows backward between adjacent blades 7 and blows back from the upper surface of the suction side end surface 11 of the blade 7 to the bell mouth 15 side. As shown in the example, the backflow phenomenon is suppressed by providing the bell mouth 15 having the wide portion 24 in the region A where the backflow phenomenon easily occurs. Thereby, it can suppress that the suction air flow and backflow which blow off from the blowing side end surface 12 of the braid | blade 7 through the circular arc-shaped space of the shroud 8 and the bottom plate 6 from the suction inlet 14 collide.
[0030]
[Effects of the first embodiment]
As described above, the centrifugal multi-blade blower 1 is provided with the wide portion 24 in the ridge portion 21 of the bell mouth 15 so as to suppress air blowback from the vicinity of the nose portion 18. By effectively preventing the collision with the reverse flow, the fan efficiency can be improved and the blowing noise can be reduced. Further, since the reverse flow phenomenon occurs only on the upper surface of the blade 7, only the upper surface (necessary portion) of the blade 7 in the region A where the reverse flow phenomenon easily occurs is covered, so that the suction area of the suction port 14 is reduced. It is possible to reduce the number of processing steps as well as restraining. And since the suction flow velocity from the suction inlet 14 does not become fast, bad influences, such as a noise increase in a normal ventilation state, a ventilation volume, and the fall of a ventilation total pressure, can be suppressed.
[0031]
Further, in this embodiment, by forming a minute gap 23 having a long flow path between the bell mouth 15 and the annular shroud 8, the spiral air passage 10 passes between the bell mouth 15 and the shroud 8. It is difficult to generate a reverse flow phenomenon from the air to the suction port 14 side, improving the air blowing efficiency and reducing the air blowing noise.
[0032]
FIG. 5 shows the effects (experimental results) of this example. In the graph of FIG. 5, the horizontal axis represents the flow coefficient (φ), and the vertical axis represents the specific noise (Ks) and the pressure coefficient (ψ). By using the bell mouth 15 of this embodiment, noise reduction of about 2 dB was partially possible without reducing the pressure coefficient. Therefore, by setting the shape of this embodiment according to the operating point of the centrifugal multiblade blower 1, the blowing noise can be effectively reduced. Incidentally, the decrease in the open air volume at this time is a change of about 2% before and after the implementation, and it has been found that there is virtually no adverse effect on the open air volume.
[0033]
[Second Embodiment]
FIG. 6 shows a second embodiment of the present invention, and is a diagram showing a region where a backflow phenomenon is likely to occur in a centrifugal multiblade fan.
[0034]
In this embodiment, a small and stable vortex is forcibly generated in a region A where a backflow phenomenon from −60 ° to + 60 ° is likely to occur in the rotational direction of the centrifugal impeller 3 starting from the nose portion 18. By increasing the pressure of the part, it is difficult to generate a backflow phenomenon.
[0035]
As a specific example, a fixed wing 31 that acts as a Wesco pump with the blade 7 is installed on the suction side of the inner surface of the bell mouth 15, so that the space surrounded by the blade 7 and the fixed wing 31 is small and stable. The vortex (shown by broken lines in FIG. 6) is forcibly generated. The stationary blade 31 can reduce the blowing noise without changing the blowing characteristics. The shape of the fixed blade 31 is determined by the shape of the blade, the strength of the required vortex action, and the operating point of the centrifugal multiblade fan 1.
[0036]
[Third embodiment]
FIG. 7 shows a third embodiment of the present invention and is a diagram showing a region where a backflow phenomenon is likely to occur in a centrifugal multiblade fan.
[0037]
In this embodiment, the flow of air flowing into the region A where the backflow phenomenon is likely to occur by bringing the air sucked again into the scroll casing 4 from the suction port 14 by the backflow phenomenon close to the designed entrance angle of the centrifugal multiblade blower 1. Is rectified so that the inlet angle of the blade 7 and the inflow angle of the intake air coincide with each other to prevent the generation of noise due to the deviation of the inlet angle of the blade 7.
[0038]
That is, the height of the slope of the bell mouth 15 in the region (re-inhalation portion) A where the backflow phenomenon easily occurs from −60 ° to + 60 ° in the rotation direction of the centrifugal impeller 3 starting from the nose portion 18 is determined as the backflow. By providing a tongue-like protrusion (projection) 32 that is set about 1.1 times higher than the region (see FIG. 4) B where the phenomenon is unlikely to occur, the blowing characteristics are improved and the blowing noise is reduced. . In addition, when it confirmed with the centrifugal multiblade blower 1 whose outer diameter of the centrifugal impeller 3 is φ180, the height of 20 to 30 mm was sufficient. However, this height differs depending on the blade shape, outer diameter, and height of the centrifugal multiblade fan.
[0039]
[Modification]
In this embodiment, the present invention is applied to the centrifugal multiblade fan 1 having forward blades. However, the present invention may be applied to a turbocharger having radial blades or a turbofan having backward blades.
[0040]
In place of the electric motor 2, driving means such as a fluid pressure motor such as an internal combustion engine or a hydraulic motor may be used. In addition, when used in a home air conditioner or a factory air conditioner, a driving means such as a water wheel or a windmill may be used instead of the electric motor 2.
[Brief description of the drawings]
FIG. 1 is a plan view showing the overall structure of a centrifugal multiblade fan (first embodiment).
FIG. 2 is a cross-sectional view showing the overall structure of a centrifugal multiblade fan (first embodiment).
FIG. 3 is a cross-sectional view showing a region where a reverse flow phenomenon is likely to occur in a centrifugal multiblade fan (first embodiment).
FIG. 4 is a cross-sectional view showing a region in which a reverse flow phenomenon hardly occurs in a centrifugal multiblade fan (first embodiment).
FIG. 5 is a graph showing changes in flow coefficient with respect to specific noise and pressure coefficient (first embodiment).
FIG. 6 is a cross-sectional view showing a region where a backflow phenomenon is likely to occur in a centrifugal multiblade fan (second embodiment).
FIG. 7 is a cross-sectional view showing a region where a backflow phenomenon is likely to occur in a centrifugal multiblade fan (third embodiment).
[Explanation of symbols]
A Area where backflow phenomenon is likely to occur B Area where backflow phenomenon is unlikely to occur 1 Centrifugal multiblade blower (centrifugal blower)
2 Electric motor (drive means)
3 Centrifugal impeller 4 Scroll casing 7 Blade 8 Shroud 10 Spiral air passage 11 Suction side end face (suction side end)
12 Outlet side end face (outlet side end)
14 suction port 15 bell mouth 18 nose part 21 ridge part 24 wide part 25 narrow part 31 fixed wing

Claims (2)

Many blades are arranged at regular intervals in the circumferential direction, and a centrifugal impeller that blows out sucked air radially outward;
A spiral air passage is formed around the centrifugal impeller with a nose as a starting point, and a spiral casing provided with a bell mouth that forms a suction port at one end in the axial direction of the centrifugal impeller. Prepared,
The centrifugal impeller has an annular shroud provided on the outlet side of the upper end surfaces of the multiple blades,
The shroud has a substantially arc-shaped cross-sectional shape along the flow of the intake air flow while gradually turning from the axial direction to the radially outward direction,
The bell mouth includes an annular ridge protruding outward so as to face the upper end of the shroud, and a cylinder formed between the inner surface of the ridge and the upper end of the shroud. A centrifugal blower having a microscopic gap,
The inner diameter of the suction port is Di,
The inner diameter of the suction side end of the blade is D1,
When the outer diameter of the blowing side end of the blade is D2,
The bell mouth is
The region where the back flow phenomenon from −60 ° to + 60 ° is likely to occur in the rotational direction of the centrifugal impeller starting from the nose portion is Di ≦ D1,
The region where the backflow phenomenon from + 120 ° to + 270 ° hardly occurs in the rotation direction of the centrifugal impeller starting from the nose portion is D1 ≦ Di ≦ D2.
Satisfied with the relationship
A centrifugal blower characterized in that a large number of fixed blades projecting toward a large number of blades of the centrifugal impeller are provided on the inner surface of the bell mouth where the reverse flow phenomenon is likely to occur. In the centrifugal blower according to claim 1 ,
The bell mouth has a height of a slope in a region in which a reverse flow phenomenon from −60 ° to + 60 ° is likely to occur in the rotation direction of the centrifugal impeller from the nose portion, and the centrifugal start from the nose portion. A centrifugal blower characterized in that it is higher than the height of a slope in a region where a backflow phenomenon from + 120 ° to + 270 ° hardly occurs in the rotational direction of the rotary impeller.

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