CENTRIFUGAL FAN, AND FAN EQUIPPED WITH SOUND-MUFFLING BOX AND USING CENTRIFUGAL FAN

Abstract

Centrifugal fan includes casing and impeller, and discharge duct is connected to casing. At least one of tongue-part-side wall surface on tongue part side extending from casing outlet of casing and opposite tongue-part-side wall surface on side opposite to tongue part side extending from casing outlet protrudes into the inside of discharge duct, and outlet gas flow is bent at predetermined angle and is formed into discharge duct internal gas flow.

Description

TECHNICAL FIELD

The present invention relates to a centrifugal fan, and a fan equipped with a sound-muffling box and using the centrifugal fan.

BACKGROUND ART

At a casing outlet of a centrifugal fan with a scroll casing, velocity of gas blown out from an outer peripheral side (opposite tongue-part-side) of a casing is high. Further, a gas flow blown out from the casing outlet is liable to be bent in a rotational direction of an impeller. Accordingly, in the centrifugal fan with a scroll casing, a pressure loss is generated due to bending of a gas flow toward an discharge duct from the casing outlet. For the reduction of such a pressure loss, in a conventional centrifugal fan the blowout direction of a gas flow at an outer peripheral portion of the casing where gas velocity is high is directed toward an area in the vicinity of a center portion of the discharge duct.

Hereinafter, the conventional centrifugal fan is described with reference to FIG. 10A and FIG. 10B. FIG. 10A is a side view of the centrifugal fan described in PTL 1, and FIG. 10B is a side view of a conventional centrifugal fan of a general type.

As shown in FIG. 10A, centrifugal fan 101a is constituted of casing 106a; and impeller 109 incorporated in casing 106a. Casing 106a is formed of side plate 104 provided with suction port 103, and scroll 105. Discharge duct 107a is provided at outlet 102a of casing 106a. Suction duct 108 is provided at suction port 103. When impeller 109 is rotated, a gas which passes through suction duct 108 flows into casing 106a from suction port 103 by way of impeller 109. Then, pressure of the gas is boosted in casing 106a, and the gas is blown out to discharge duct 107a from outlet 102a.

As shown in FIG. 10A, in centrifugal fan 101a, the gas supply direction (discharge duct internal gas flow 111a) of discharge duct 107a is parallel to a plane orthogonal to a rotation axis of impeller 109. A gas flow blown out from outlet 102a (outlet gas flow 110a) is bent toward an opposite tongue-part-side in an area in the vicinity of tongue part 112 by discharge duct 107a so that outlet gas flow 110a is formed into discharge duct internal gas flow 111a.

That is, a gas flow blown out from the opposite tongue-part-side of casing 106a does not flow along a wall surface of discharge duct 107a. The blowout direction of the gas flow is directed to a center portion between an upper side and a lower side of discharge duct 107a in FIG. 10A.

FIG. 10B shows a connection mode between centrifugal fan 101b of general type and discharge duct 107b. In FIG. 10B, symbols equal to symbols used in FIG. 10A indicate identical constitutional elements. As shown in FIG. 10B, a terminal end of casing 106b and discharge duct 107b are substantially horizontal. In such centrifugal fan 101b of a general type, discharge duct 107b is fixed such that the direction of outlet gas flow 110b at outlet 102b and the direction of discharge duct internal gas flow 111b are directed in the same direction. In other words, outlet gas flow 110b blown out from casing 106b advances into discharge duct 107b by keeping the straight linear movement.

On the other hand, velocity of outlet gas flow 110b is high at an outer peripheral side of casing 106b. Accordingly, in the inside of discharge duct 107b, gas velocity at an upper side is higher than gas velocity at the center portion between the upper side and a lower side of discharge duct 107b. As a result, when discharge duct 107b is bent in the same direction as rotational direction 114 at a downstream portion thereof, a gas flow having a high gas velocity passes at an outer peripheral side of a bent portion, and the gas flow smoothly flows along bending of discharge duct 107b. On the other hand, when discharge duct 107b is bent in the direction opposite to rotational direction 114 at the downstream portion thereof, a gas flow having high gas velocity passes an inner side of the bent portion and hence, the turbulence of gas flow is generated at the bent portion of discharge duct 107b. Thus, a pressure loss is increased.

In PTL 1, casing 106a is rotated in rotational direction 114 of impeller 109. Accordingly, in outlet gas flow 110a, outlet gas flow 110a having high gas velocity at an outer peripheral side of casing 106a flows into an area in the vicinity of a center portion between the upper side and the lower side of discharge duct 107a. Then, in the area in the vicinity of the center of discharge duct 107a, outlet gas flow 110a spreads over the whole discharge duct 107a, and flows in discharge duct 107a.

Outlet gas flow 110a having high velocity is collected to the center portion of discharge duct 107a and hence, whichever direction discharge duct 107a is bent, a pressure loss generated by bending discharge duct 107a is reduced. Accordingly, it is possible to provide centrifugal fan 101a having a small pressure loss irrelevant to the bending direction of discharge duct 107a.

However, when discharge duct 107a is bent in the direction opposite to the rotational direction of impeller 109 on a downstream side of discharge duct 107a, it is necessary to increase a distance between the bent portion and the outlet 102a.

CITATION LIST

Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 11-294393

SUMMARY OF THE INVENTION

In such a conventional centrifugal fan, a gas flow having high velocity can be collected to the center portion between the upper side and the lower side of discharge duct 107a shown in FIG. 10A. However, scroll 105 is formed into a shape where hatched portion 116 in the vicinity of outlet 102a is cut away, that is scroll 105 is formed into a shape where scroll 105 terminates half way. In scroll gas passage enlarging portion from an area in the vicinity of tongue part 112 of scroll 105 to outlet 102a, a velocity of a gas whose pressure is boosted by impeller 109 is lowered due to the enlargement of scroll gas passage. That is, the scroll gas passage enlarging portion is a portion which converts a gas into a static pressure from a dynamic pressure and makes the gas flow out into the inside of discharge duct 107a. However, in centrifugal fan 101a described in PTL 1, the scroll gas passage enlarging portion is short and hence, a velocity of the gas cannot be sufficiently dropped in the scroll gas passage enlarging portion. Accordingly, the centrifugal fan 101a described in PTL 1 has a drawback that performance (static pressure) of the centrifugal fan is lowered.

The centrifugal fan of the present invention includes: a casing having a scroll; and an impeller disposed inside the casing. The casing includes a side plate having a suction port. The scroll includes an outlet. An discharge duct is connected to the casing. An outlet gas flow blown out from the outlet is parallel to a plane orthogonal to a rotational axis of the impeller. At least one of a tongue-part-side wall surface on a tongue-part-side extending from a casing outlet of the casing and an opposite tongue-part-side wall surface on a side opposite to the tongue-part-side extending from the casing outlet protrudes into the inside of the discharge duct. As viewed from the direction orthogonal to the suction port, the outlet gas flow is bent toward the side opposite to the tongue-part-side from the tongue-part-side at a predetermined angle and the outlet gas flow is formed into an discharge duct internal gas flow.

The scroll gas passage enlarging portion is increased by the tongue-part-side wall surface, the opposite tongue-part-side wall surface or both the tongue-part-side wall surface and the opposite tongue-part-side wall surface and hence, a velocity of an outlet gas flow is sufficiently dropped so that the outlet gas flow is smoothly introduced into the discharge duct. Accordingly, in the outlet gas flow, the conversion into a static pressure from a dynamic pressure can be sufficiently performed and hence, a pressure loss is prevented whereby lowering of performance of the centrifugal fan can be prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a centrifugal fan according to a first exemplary embodiment of the present invention.

FIG. 2 is a graph comparing performance of the centrifugal fan of the present invention and performance of a conventional centrifugal fan.

FIG. 3A is a side view of a centrifugal fan according to a second exemplary embodiment of the present invention.

FIG. 3B is a front view of the centrifugal fan.

FIG. 4 is a side view of the centrifugal fan where a sound absorbing member is disposed inside an discharge adapter.

FIG. 5 is a perspective view of a casing when small holes are formed in a tongue-part-side wall surface and an opposite tongue-part-side wall surface of the centrifugal fan.

FIG. 6 is a side view for describing the duct connection of the centrifugal fan.

FIG. 7 is a side view of a fan equipped with a sound-muffling box which uses a centrifugal fan according to a third exemplary embodiment of the present invention.

FIG. 8 is a top plan view of the fan equipped with a sound-muffling box which uses the centrifugal fan.

FIG. 9 is an installation view of the fan equipped with a sound-muffling box.

FIG. 10A is a side view of a centrifugal fan described in PTL 1.

FIG. 10B is a side view of a conventional centrifugal fan of a general type.

DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention are described with reference to drawings.

First Exemplary Embodiment

FIG. 1 is a side view of a centrifugal fan according to the first exemplary embodiment of the present invention. As shown in FIG.1, centrifugal fan 1 is constituted of casing 6; and impeller 9 incorporated in casing 6. Casing 6 is formed of side plate 4 having suction port 3, and scroll 5 having outlet 2. Discharge duct 7 is connected to casing outlet 6a of casing 6, and suction duct 8 is connected to suction port 3.

Opposite tongue-part-side wall surface 14 of scroll 5 on an opposite tongue part 13b side and tongue-part-side wall surface 15 of scroll 5 on a tongue part 13a side protrude into the inside of discharge duct 7. Opposite tongue-part-side wall surface 14 does not reach the center of discharge duct 7, and an end portion of opposite tongue-part-side wall surface 14 is disposed at a position in an upper half of discharge duct 7 in FIG. 1. Open end of tongue-part-side wall surface 15a of tongue-part-side wall surface 15 is in contact with discharge duct wall surface 7a. Opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15 extend from casing outlet 6a.

Discharge duct 7 is connected to outlet 2 such that outlet gas flow 10 which flows in outlet 2 is bent parallel to a plane orthogonal to rotation axis 24 of impeller 9 and toward an opposite tongue part 13b side on a side opposite to tongue part 13a of scroll 5. That is, as viewed from the direction orthogonal to suction port 3, outlet gas flow 10 is bent at a predetermined angle θ′ toward the opposite tongue part 13b side from a tongue part 13a side, and forms discharge duct internal gas flow 11 which flows in discharge duct 7. Predetermined angle θ′ is larger than 0 degree and smaller than 45 degrees, and preferably more than or equal to 20 degrees and less than or equal to 30 degrees.

Since θ is expressed as θ=180−θ′ in FIG. 1, angle θ is a value exceeding 135 degrees and less than 180 degrees, and preferably more than or equal to 150 degrees and less than or equal to 160 degrees.

Discharge duct internal gas flow 11 is also parallel to a plane orthogonal to rotation axis 24 of impeller 9.

Tongue part opposedly facing position 13c is a position where a perpendicular extending downwardly to opposite tongue-part-side wall surface 14 from tongue part 13a intersects with opposite tongue-part-side wall surface 14. Connection portion 26 on an opposite tongue part 13b side between casing 6 and discharge duct 7 is provided closer to impeller 9 side than to tongue part opposedly facing position 13c.

The manner of operation and advantageous effects brought about by the above-mentioned constitution of centrifugal fan 1 are described. When impeller 9 is rotated, a gas which passes through suction duct 8 flows into the inside of casing 6 from suction port 3 by way of impeller 9, and a pressure of the gas is boosted inside casing 6, and the gas flows out into discharge duct 7 from outlet 2.

Here, the most characterizing part of the first exemplary embodiment is described. In the first exemplary embodiment, opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15 are formed inside discharge duct 7 such that scroll 5 protrudes into the inside of discharge duct 7, thus ensuring scroll gas passage enlarging portion 16. Accordingly, a gas which reaches casing outlet 6a lowers a velocity thereof sufficiently in scroll gas passage enlarging potion 16 and hence, the conversion into a static pressure from a dynamic pressure is accelerated, and the gas flows out into discharge duct 7.

Further, due to the formation of tongue-part-side wall surface 15, outlet gas flow 10 which impinges on tongue part 13a is guided to the inside of discharge duct 7 along tongue-part-side wall surface 15. Since outlet gas flow 10 is smoothly guided into discharge duct 7 by tongue-part-side wall surface 15 in this manner, a pressure loss caused by the sudden enlargement of the gas passage from tongue part 13a to discharge duct 7 can be prevented.

Accordingly, it is desirable that tongue-part-side wall surface 15 protruding into the inside of discharge duct 7 is configured such that open end of tongue-part-side wall surface 15a is brought into contact with discharge duct wall surface 7a. However, open end of tongue-part-side wall surface 15a is not necessarily brought into contact with discharge duct wall surface 7a.

A velocity of outlet gas flow 10 is higher on an outer peripheral side of casing 6, that is, on an opposite tongue part 13b side. Outlet gas flow 10 on the opposite tongue part 13b side is bent by opposite tongue-part-side wall surface 14 in the direction of discharge duct internal gas flow 11 at a center portion of discharge duct 7. In this manner, in centrifugal fan 1 of the first exemplary embodiment, the velocity of outlet gas flow 10 at the center portion in the inside of discharge duct 7 becomes high. Accordingly, whichever direction discharge duct 7 is bent at a bent portion thereof on a downstream side, the increase of a pressure loss can be suppressed. That is, compared with the case where outlet gas flow 10 flows straightly and forms discharge duct internal gas flow 11, a distance from outlet 2 to the bent portion of discharge duct 7 in the first exemplary embodiment can be made small.

Discharge duct 7 is connected to casing 6 such that discharge duct 7 is arranged closer to an impeller 9 side than tongue part facing position 13c is and hence, centrifugal fan 1 can be miniaturized.

Further, discharge duct 7 is connected to casing 6 such that a central axis of discharge duct 7 is arranged close to impeller 9 and hence, centrifugal fan 1 can be miniaturized.

From a viewpoint of miniaturizing centrifugal fan 1, it is desirable that discharge duct 7 is connected to casing 6 such that the central axis of discharge duct 7 passes rotation axis 24 (or a position in the vicinity of rotation axis 24) of impeller 9.

FIG. 2 is a graph comparing performance of the centrifugal fan according to the first exemplary embodiment of the present invention and performance of a conventional centrifugal fan. FIG. 2 is a graph comparing an amount of gas blown out from the centrifugal fan of the first exemplary embodiment which is indicated by graph (c), an amount of gas blown out from the centrifugal fan shown in FIG. 10A which is indicated by graph (b), and an amount of gas blown out from the centrifugal fan shown in FIG. 10B which is indicated by graph (a). An amount of gas is taken on an axis of abscissas, and a static pressure is taken on an axis of ordinates. Graph (a) indicates a case where an outlet gas flow from the centrifugal fan shown in FIG. 10B flows straightly and forms an discharge duct internal gas flow. Graph (b) indicates a case where an outlet gas flow from the centrifugal fan shown in FIG. 10A is bent to an opposite tongue part side and forms an discharge duct internal gas flow. Graph (c) indicates a case where opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15 protrude into the inside of discharge duct 7 in centrifugal fan 1 of the first exemplary embodiment, and outlet gas flow 10 is bent to the opposite tongue part 13b side and forms discharge duct internal gas flow 11.

Compared to the centrifugal fan shown in FIG. 10B, the centrifugal fan shown in FIG. 10A has a smaller scroll gas passage enlarging potion. Further, a gas passage leading to an discharge duct is suddenly enlarged at the tongue part in the centrifugal fan shown in FIG. 10A and hence, a static pressure is lowered as a whole. On the other hand, it is confirmed that centrifugal fan 1 according to the first exemplary embodiment has the substantially same performance as the general-type centrifugal fan shown in FIG. 10B.

As described above, according to the centrifugal fan 1 of first exemplary embodiment of the present invention, whichever direction discharge duct 7 is bent, the pressure loss caused by bending of discharge duct 7 can be reduced and, at the same time, casing 6 can be miniaturized while suppressing the lowering of performance (static pressure). Further, it is unnecessary to prepare two kinds of parts that is, a part for the rightward rotation and a part for the leftward rotation in conformity with the bending direction of discharge duct 7 with respect to the parts of centrifugal fan 1 such as casing 6. Accordingly, the lowering of the pressure loss can be suppressed irrespective of the bending direction of discharge duct 7.

In the first exemplary embodiment, both of opposite tongue-part-side wall surface 14 on an opposite tongue part 13b side and tongue-part-side wall surface 15 on a tongue part 13a side protrude into the inside of discharge duct 7 in casing 6. However, it is sufficient that either one of opposite tongue-part-side wall surface 14 on the opposite tongue part 13b side and tongue-part-side wall surface 15 on tongue part 13a side protrudes into the inside of discharge duct 7. In this case, the first exemplary embodiment can acquire advantageous effects brought about only either one of opposite tongue-part-side wall surface 14 on the opposite tongue part 13b side and tongue-part-side wall surface 15 on tongue part 13a side.

Second Exemplary Embodiment

In the second exemplary embodiment of the present invention, constitutional elements having the same constitution as the corresponding constitutional elements of the first exemplary embodiment are given the same symbols, and the detailed description of these constitutional elements is omitted and only different parts are described. FIG. 3A is a side view of a centrifugal fan according to the second exemplary embodiment of the present invention, and FIG. 3B is a front view of the centrifugal fan.

Centrifugal fan 1 shown in FIG. 3A and FIG. 3B is installed such that discharge adapter 17 having a circular shape covers an outer periphery of casing outlet 6a in connecting discharge duct 7 having a circular shape to casing outlet 6a. Discharge duct 7 having a circular shape is connected to discharge adapter 17. Opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15 protrude into the inside of discharge adapter 17. In this exemplary embodiment, tongue-part-side wall surface width 15c has the same size as impeller width 9a. Further, gaps 21 are formed between tongue-part-side wall surface sides 15b and both left and right sides of discharge adapter 17.

The manner of operation and advantageous effects brought about by the above-mentioned constitution of centrifugal fan 1 are described.

With respect to ensuring of scroll gas passage enlarging potion 16, the prevention of the sudden enlargement of the gas passage from tongue part 13a to discharge duct 7, and blowing of outlet gas flow 10 having high velocity at the outer peripheral portion of casing 6 into a center portion between an upper side and a lower side of discharge duct 7, the second exemplary embodiment has the constitution exactly same as the constitution explained in conjunction with the first exemplary embodiment. Impeller outlet gas flow 22 which is directly blown out from impeller 9 and has high velocity is liable to be influenced by the sudden enlargement of the gas passage. However, tongue-part-side wall surface width 15c and impeller width 9a have the same size and hence, impeller outlet gas flow 22 flows along tongue-part-side wall surface 15. Accordingly, impeller outlet gas flow 22 is smoothly guided to the inside of discharge duct 7 through discharge adapter 17.

On the other hand, velocity of side-plate-side outlet gas flow 23 on a side plate 4 side of impeller 9 is low. That is, side-plate-side outlet gas flow 23 is minimally influenced by a sudden enlarging portion of the gas passage formed in gap 21 portions so that side-plate-side outlet gas flow 23 flows into a lower side of discharge adapter 17 and is guided to discharge duct 7. In this manner, due to the formation of gaps 21, impeller outlet gas flow 22 having high velocity and side-plate-side outlet gas flow 23 having low velocity are smoothly guided into the inside of discharge duct 7 without colliding with each other and hence, the pressure loss of impeller outlet gas flow 22 and the pressure loss of side-plate-side outlet gas flow 23 can be prevented.

Discharge adapter 17 connects casing outlet 6a having a quadrangular shape following a shape of the extension of scroll 5 and discharge duct 7 having a circular shape. Discharge adapter 17 is configured such that discharge adapter 17 has a circular shape on a scroll 5 side, and a circular cross-sectional area of discharge adapter 17 is gradually decreased toward an discharge duct 7 side. Outlet gas flow 10 flows into the inside of casing 6 through impeller 9, pressure of outlet gas flow 10 is boosted inside casing 6, and outlet gas flow 10 reaches casing outlet 6a. Outlet gas flow 10 is smoothly guided to discharge duct 7 from casing outlet 6a by discharge adapter 17. At the same time, outlet gas flow 10 is directed to a center portion of discharge duct 7. Accordingly, a diameter of discharge duct 7 can be reduced. Discharge duct 7 is installed by being inserted into discharge adapter 17. A portion of casing 6 is inserted into discharge adapter 17 and hence, centrifugal fan 1 can be miniaturized.

In this manner, in centrifugal fan 1 according to the second exemplary embodiment of the present invention, casing 6 can be miniaturized, discharge duct 7 can be also miniaturized, and the installation workability can be also improved while suppressing the lowering of performance (static pressure).

In the second exemplary embodiment, tongue-part-side wall surface 15 has a flat planar shape. However, tongue-part-side wall surface sides 15b may be raised toward the opposite tongue part 13b side with respect to the gas supply direction or may be bent in the direction toward the tongue part 13a side.

FIG. 4 is a side view of the centrifugal fan according to the second exemplary embodiment of the present invention where a sound absorbing member is disposed inside an discharge adapter. In centrifugal fan 1 shown in FIG. 4, sound absorbing member 19 is disposed between discharge adapter inner surface 17a and opposite tongue-part-side wall surface 14 as well as between discharge adapter inner surface 17a and tongue-part-side wall surface 15.

The manner of operation and advantageous effects of centrifugal fan 1 shown in FIG. 4 are described. A gas flow whose pressure is boosted inside casing 6 is flown out into discharge duct 7 from casing outlet 6a. At this time, outlet gas flow 10 impinges on discharge adapter 17 so that gas flow noises are generated. Such gas flow noises are absorbed by sound absorbing members 19 disposed between discharge adapter 17 and casing outlet 6a of scroll 5.

FIG. 5 is a perspective view of a casing when small holes are formed in a tongue-part-side wall surface and an opposite tongue-part-side wall surface of the centrifugal fan according to the second exemplary embodiment of the present invention. As shown in FIG. 5, a plurality of small holes 20 are formed in opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15.

By forming the plurality of small holes 20 in opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15, an energy of gas flow noises passes through small holes 20 so that the energy propagates to spaces A, B shown in FIG. 4 disposed between scroll 5 and discharge adapter 17 or to sound absorbing members 19 whereby gas flow noises are absorbed. As a result, a sound absorbing rate in the inside of discharge adapter 17 is increased.

FIG. 6 is a side view for describing the duct connection of the centrifugal fan according to the second exemplary embodiment of the present invention. As shown in FIG. 6, central axis 25 of an opening of discharge adapter 17 passes rotation axis 24 of impeller 9 which constitutes the center of suction port 3.

As a result, a height of discharge duct 7 and a height of suction duct 8 can be set equal to each other. Accordingly, when discharge duct 7 and suction duct 8 are fixed to a floor or ceiling using members, a length of the members can be unified.

In the second exemplary embodiment, gaps 21 are disposed between tongue-part-side wall surface sides 15b and discharge adapter 17. However, gaps 21 may be disposed between tongue-part-side wall surface sides 15b and discharge duct 7.

Third Exemplary Embodiment

In a third exemplary embodiment of the present invention, constitutional elements having the same constitution as the corresponding constitutional elements of the first and second exemplary embodiments are given the same symbols, and the description of these constitutional elements is omitted and only different parts are described. FIG. 7 is a side view of a fan equipped with a sound-muffling box which uses a centrifugal fan according to a third exemplary embodiment of the present invention. FIG. 8 is a top plan view of the fan equipped with a sound-muffling box which uses the centrifugal fan.

The fan equipped with a sound-muffling box according to the third exemplary embodiment includes: either one of centrifugal fans 1 described in the first and second exemplary embodiments; and box-shaped body 50 which incorporates centrifugal fan 1 therein. As shown in FIG. 7 and FIG. 8, body 50 is constituted of: outlet panel 53; suction panel 56; and side panels 58. Body blowout port 51 and discharge adapter 52 are provided to outlet panel 53. Body suction port 54 and suction adapter 55 are provided to suction panel 56. Checkup panel 57 is fixed to side panel 58.

Casing outlet 6a is connected to discharge duct 59 by connecting discharge adapter 52 to discharge duct 59. Further, discharge adapter 52 is disposed at the center of outlet panel 53, and suction adapter 55 is disposed at the center of suction panel 56. Although opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15 are disposed inside discharge adapter 52 in the third exemplary embodiment, in the same manner as the first exemplary embodiment or the second exemplary embodiment, either one of opposite tongue-part-side wall surface 14 and tongue-part-side wall surface 15 may be disposed inside discharge adapter 52.

Top panel 60, bottom panel 61 and side panels 58 are positioned between outlet panel 53 and suction panel 56. Top panel 60 and bottom panel 61 are panels of body 50 which cover a top surface and a bottom surface of centrifugal fan 1, respectively. Checkup panel 57 detachably fixed to side panel 58 faces side plate 4 of centrifugal fan 1. Accordingly, after removing checkup panel 57 from side panel 58, an operator who enters from wall surface checkup opening 63 can observe impeller 9 and motor 62 fixed to side plate 4 through checkup panel opening 64.

Body blowout port 51 is formed at the center of outlet panel 53, and outlet panel 53 faces casing outlet 6a of centrifugal fan 1. In the third exemplary embodiment, outlet panel 53 and centrifugal fan 1 are connected and fixed to each other in a state where outlet panel 53 and centrifugal fan 1 are arranged close to each other. However, outlet panel 53 and centrifugal fan 1 may be connected and fixed to each other by way of an intermediate member.

Body suction port gas flow 66 supplied through body suction port 54 passes centrifugal fan 1 and flows out as body blowout port gas flow 67 through discharge duct 59 connected to discharge adapter 52 and suction duct 65 connected to suction adapter 55. Discharge adapter 52 is disposed at the center of outlet panel 53 and suction adapter 55 is disposed at the center of suction panel 56, and discharge adapter 52 faces suction adapter 55. Accordingly, discharge duct 59 and suction duct 65 are installed on the same central axis 68. By providing body suction port 54 at the center of suction panel 56, body suction port gas flow 66 from suction duct 65 smoothly flows into body suction port 54. For this reason, it is desirable that body suction port 54 be provided at the center of suction panel 56.

FIG. 9 is an installation view of the fan equipped with a sound-muffling box according to the third exemplary embodiment of the present invention. When centrifugal fan 1 shown in FIG. 9 is operated, air in room 70 is sucked through wall surface suction port 71, and is discharged to outdoors 73 from wall surface outlet 72 through suction duct 65, body 50 and discharge duct 59.

Wall surface checkup opening 63 is provided in the vicinity of checkup panel 57 so that centrifugal fan 1 can be checked up. Body 50 is disposed in attic 74 and hence, the miniaturization of centrifugal fan 1 leads to the miniaturization of body 50. Accordingly, even when attic 74 is narrow, body 50 can be easily installed.

The manner of operation and advantageous effects brought about by the fan equipped with a sound-muffling box which uses centrifugal fan 1 according to the third exemplary embodiment of the present invention are described.

As shown in FIG. 7, discharge adapter 52 is provided at the center of outlet panel 53, and suction adapter 55 is provided at the center of suction panel 56. Accordingly, when body 50 is installed upside down, that is, a top surface of body 50 is disposed on a lower side and a bottom surface of body 50 is disposed on an upper side, positions of discharge adapter 52 and suction adapter 55 relative to body 50 are not changed so that installation workability is improved.

The upside-down installation of body 50 is effectively applicable to a case where the inside of attic 74 shown in FIG. 9 is narrow so that the position of checkup panel 57 with respect to body 50 is set upside down, that is, a case where body 50 is installed with wall surface checkup opening 63 disposed upside down.

As shown in FIG. 7, body blowout port 51 is provided at the center of outlet panel 53. Accordingly, body blowout port gas flow 67 from body blowout port 51 is directed to discharge adapter 52 disposed at the center of outlet panel 53 so that body blowout port gas flow 67 is smoothly guided without collision. Thus, a pressure loss can be suppressed.

Further, a distance between outlet panel 53 and centrifugal fan 1 is minimized so that body 50 can be miniaturized. Accordingly, it is desirable that outlet panel 53 be in contact with casing outlet 6a of centrifugal fan 1. However, it is not always necessary to bring outlet panel 53 into contact with casing outlet 6a.

In this manner, according to the fan equipped with a sound-muffling box which uses centrifugal fan 1 according to the third exemplary embodiment of the present invention, the installation workability is improved and body 50 is miniaturized while suppressing the lowering of the performance (static pressure).

INDUSTRIAL APPLICABILITY

The present invention is applicable to a ventilation blower such as a duct fan and to a centrifugal fan used in an air conditioner or the like. The present invention is also applicable to cooling of installation equipment by using a gas flow from a body blowout port besides the conveyance of air by a ventilation blower or the like.

REFERENCE MARKS IN THE DRAWINGS

1 centrifugal fan

2 outlet

3 suction port

4 side plate

5 scroll

6 casing

6 a casing outlet

7 discharge duct

7 a discharge duct wall surface

8 suction duct

9 impeller

9 a impeller width

10 outlet gas flow

11 discharge duct internal gas flow

13 a tongue part

13 b opposite tongue part

13 c tongue part facing position

14 opposite tongue-part-side wall surface

15 tongue-part-side wall surface

15 a open end of tongue-part-side wall surface

15 b tongue-part-side wall surface side

15 c tongue-part-side wall surface width

16 scroll gas passage enlarging potion

17, 52 discharge adapter

17 a discharge adapter inner surface

19 sound absorbing member

20 small hole

21 gap

22 impeller outlet gas flow

23 side-plate-side outlet gas flow

24 rotation axis

25 central axis

26 connection portion

50 body

51 body blowout port

53 outlet panel

54 body suction port

55 suction adapter

56 suction panel

57 checkup panel

58 side panel

59 discharge duct

60 top panel

61 bottom panel

62 motor

63 wall surface checkup opening

64 checkup panel opening

65 suction duct

66 body suction port gas flow

67 body blowout port gas flow

68 same central axis

70 room

71 wall surface suction port

72 wall surface outlet

73 outdoor

74 attic

Claims

1. A centrifugal fan comprising: a casing having a scroll; andan impeller disposed inside the casing,whereinthe casing includes a side plate having a suction port,the scroll includes an outlet; andthe casing is connected to an discharge duct,an outlet gas flow which flows through the outlet is parallel to a plane orthogonal to a rotation axis of the impeller,at least one of a tongue-part-side wall surface on a tongue part side and an opposite tongue-part-side wall surface on another side opposite to the tongue part side extending from the casing outlet of the casing protrudes into the discharge duct, andas viewed from a direction orthogonal to the suction port, the outlet gas flow is bent from the tongue part side toward the side opposite to the tongue part side at a predetermined angle, and formed into an internal gas flow which flows through the discharge duct.

2. The centrifugal fan according to claim 1, wherein the predetermined angle is larger than 0 degree and smaller than 45 degrees.

3. The centrifugal fan according to claim 1, wherein an open end of the tongue-part-side wall surface is in contact with a wall surface of the discharge duct when the tongue-part-side wall surface protrudes into the discharge duct.

4. The centrifugal fan according to claim 1, wherein a gap is formed between a tongue-part-side wall surface side and the discharge duct when the tongue-part-side wall surface protrudes into the discharge duct.

5. The centrifugal fan according to claim 4, wherein a width of the tongue-part-side wall surface is equal to a width of the impeller.

6. The centrifugal fan according to claim 1, wherein a connection portion on the side opposite to the tongue part side between the casing and the discharge duct is closer to the impeller than a tongue part facing position at which a perpendicular extending downwardly to the opposite tongue-part-side wall surface from the tongue part intersects.

7. The centrifugal fan according to claim 1 further comprising an discharge adapter which covers the casing outlet, wherein the discharge duct and the discharge adapter are connected to each other, and the tongue-part-side wall surface and the opposite tongue-part-side wall surface protrude into the discharge adapter.

8. The centrifugal fan according to the claim 7, wherein a sound absorbing member is interposed between an discharge adapter inner surface and the tongue-part-side wall surface and between the discharge adapter inner surface and the opposite tongue-part-side wall surface.

9. The centrifugal fan according to the claim 8, wherein a plurality of small holes are formed in the tongue-part-side wall surface and the opposite tongue-part-side wall surface.

10. The centrifugal fan according to the claim 7, wherein a center axis of an opening of the discharge adapter passes the rotation axis.

11. A fan equipped with a sound-muffling box, the fan comprising: the centrifugal fan described in claim 1; anda body in which the centrifugal fan is incorporated,whereinthe body includes: an outlet panel provided with a body blowout port and an discharge adapter;a suction panel provided with a body suction port and a suction adapter; anda side panel to which a checkup panel is fixed,the discharge adapter is connected to the discharge duct such that the casing outlet is in communication with the discharge duct,the discharge adapter is disposed at a center of the outlet panel, andthe suction adapter is disposed at a center of the suction panel.

12. The fan equipped with a sound-muffling box according to claim 11, wherein the body blowout port is disposed at the center of the outlet panel.

13. The fan equipped with a sound-muffling box according to the claim 11, wherein the outlet panel is in contact with the casing outlet.