JPH09228997A - Casing of centrifugal fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the reduction of pressure of discharge air at a discharge port and increase wind velocity and wind volume by forming a tapered face which is extended to a nose side in the inside on an anti-nose side of the discharge port in a casing of a centrifugal fan which is communicated with a small clearance part on the uppermost stream side on the nose side of the discharge port on the lowermost stream side. SOLUTION: A tapered face 3-1 which is extended to a side of a nose 2-2 is formed in the inside on an anti-nose side which is in proximity with a discharge port 2-4 in a casing 1 of a centrifugal fan, in particular, a centrifugal fan in which the discharge port is short. Consequently, it is possible to prevent abrupt expansion of a cross section of a passage in the vicinity of the short discharge port 2-4, stabilize a stream of air to be discharged, and suppress noise because area of a spiral passage 2 from a terminal part to an end of the discharge port 2-4 of the passage 2 is changed gently. Moreover, a straightening plate 4 may be provided in opposition to the tapered face 3-1 which is extended to the nose 2-2 side at the discharge port 2-4. In this case, it is possible to increase the maximum wind velocity further.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal fan, and more particularly to an improved casing of a centrifugal fan having a short discharge port.

[0002]

2. Description of the Related Art In the casing structure of a centrifugal fan, since the upstream side of a ventilation passage into which air flows in communicates with the downstream side of a ventilation passage from which air is discharged, turbulence in the flow of discharged air occurs, which not only causes noise but also discharges it. Various improvements have been made to cause pressure loss. Japanese Patent Laid-Open No. 7-91400 is also an example of this. As a means for preventing high pressure air to be discharged from the discharge port to the uppermost stream side of the ventilation passage having a low pressure, auxiliary suction is performed near the nose of the discharge port. This is a proposal for a structure with a mouth.

Referring to FIGS. 3 and 4, FIG. 5 is a vertical cross-sectional view of an example of a casing 1 of a centrifugal fan that has been conventionally used, showing the vicinity of a discharge port 2-4 where the same effect as the above-mentioned known example can be seen. The nose 2-2 is formed with a tapered surface 2-21 that expands to the edge of the discharge port 2-4. Nose of the discharge port 2-2
The taper surface 2-21 is formed on the side, as disclosed in the above-mentioned known example, generally, air having a high pressure to be discharged from the discharge port 2-4 to the outside is discharged from the discharge port 2-4. This is because it is possible to obtain the effect of preventing the air from going around to the small gap portion 2-1 on the most upstream side of the ventilation path that communicates with.

Although not shown in FIG. 5, the structure having the tapered surface 2-21 formed on the nose side as described above,
Even in the conventional structure in which the nose 2-2 is flat, a structure in which a rectifying plate is provided in the vicinity of the discharge port edge is in practical use.

[0006]

In the conventional configuration as described above, since the ventilation passage area near the discharge port is rapidly expanded,
The pressure distribution of the discharge air near the discharge port tends to be uneven,
Mere measures against the high-pressure air sneak in the nose portion are not always sufficient to avoid the turbulence and pressure drop of the discharge air, and further improvements have been desired.

[0007]

A centrifugal fan casing according to the present invention has a tapered surface extending to the nose side formed inside or connected to a nose side inside a discharge port located downstream of ventilation. A taper surface that expands toward the edge of the discharge port is formed, and / or a current plate is provided so as to face the taper surface.

With the above-mentioned structure, it is possible to improve the wind speed and the air volume by suppressing the pressure reduction of the discharge air at the discharge port.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view showing a first embodiment of a casing according to the present invention, in which a tapered surface 3 extending toward the nose 2-2 is provided inside a side of the casing 1 opposite to the discharge port 2-4 opposite to the nose. In this example, -1 is formed.

In this example, the air flow in the vicinity of the nose 2-2 is the same as in the prior art, but since the casing shape inside the anti-nose side has a tapered surface extending to the nose side, The discharged air is also prevented by preventing a rapid expansion of the cross section of the passage in the vicinity of the short discharge port 2-4 and grading the change in the passage area from the end of the spiral passage to the end of the discharge port. The effect of stabilizing the flow of air and suppressing noise is brought about. A comparison of the wind speed distribution with the prior art using the same size and same driving electric motor as that of the configuration, it was confirmed that the maximum wind speed ratio increased by about 13%.

FIG. 2 shows a second embodiment, in which the tapered surface 3-1 extending to the nose side inside the discharge nose 2-4 of the first example described above is enlarged near the edge of the discharge opening. Is formed so as to be connected to the second tapered surface 3-2, and the rectifying plate 4 is added to the discharge port 2-4, and in this example, compared to the above-described first configuration, A maximum wind speed increase of about 8% has been confirmed.

[0012]

EFFECTS OF THE INVENTION The centrifugal fan casing according to the present invention, particularly in a structure having a short discharge port, effectively realizes an improvement in terms of an increase in wind speed and volume by suppressing the pressure loss of the discharge air at the discharge port. it can.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a first example of a centrifugal fan casing according to the present invention.

FIG. 2 is a longitudinal sectional view of a second example of a centrifugal fan casing according to the present invention.

FIG. 3 is a partially transparent perspective view of the casing of the example of FIG.

FIG. 4 is a front view of the centrifugal fan viewed from the discharge port side using the casing of the example of FIG.

FIG. 5 is a vertical cross-sectional view of an example of a conventional casing.

[Explanation of Codes] 1 Casing 2 Ventilation path 2-1 Small air gap on the most upstream side of ventilation path 2-2 Nose 2-21 Tapered surface of nose 2-3 Ventilation path downstream 2-4 Discharge port 2-5 Suction Mouth 3 Taper forming part 3-1 Tapered surface that extends to the nose side 3-2 Tapered surface that expands to the edge of the discharge port 4 Straightening plate 5 Impeller

Claims (3)

[Claims] 1. A nose side of the most downstream discharge port, which has a shape in which the width of the ventilation passage formed by the inner peripheral surface of the casing and the outer peripheral edge of the impeller gradually increases from the upstream side toward the downstream side. In the casing of the centrifugal fan communicating with the uppermost stream side small gap portion, a taper surface extending to the nose side is formed inside the anti-nose side of the discharge port. 2. The centrifugal fan according to claim 1, wherein a taper surface extending to the nose side inside the anti-nose side of the discharge port is connected to an enlarged taper reaching an end edge of the discharge port. Casing. 3. The casing for a centrifugal fan according to claim 1, wherein a rectifying plate is provided side by side with the discharge port so as to face a tapered surface extending toward the nose side.