GB2551281A - Sirocco fan and indoor unit of air conditioner using this sirocco fan - Google Patents

Abstract

A sirocco fan 4 equipped with a scroll-type casing 1, which has a tongue section 3 that is the starting point of the scroll, and a multi-bladed centrifugal fan 2, which is accommodated within the casing. When a region in the casing located in the vicinity of 90° from the tongue section 3 in the fan rotation direction is set as a flat section 6, the shortest distance between the tongue section 3 and the fan 2 is X, and the shortest distance between the flat section 6 and the fan 2 is Z, the distance X and the distance Z are set in the range 1.0 ≤ X/Z ≤ 1.5.

Description

DESCRIPTION Title of Invention

SIROCCO FAN AND INDOOR UNIT OF AN AIR-CONDITIONING APPARATUS USING THE SIROCCO FAN

Technical Field [0001]

The present invention relates to a sirocco fan capable of reducing a height of a casing without increasing noise and fan input, and to an indoor unit of an air-conditioning apparatus using the sirocco fan.

Background Art [0002]

Hitherto, there has been known a sirocco fan that includes a casing of a scroll type having an air outlet formed therein and including a tongue portion being a scroll starting point, and includes a multiblade centrifugal fan accommodated in the casing. In such a sirocco fan, a distance between the fan and the casing is gradually increased toward the air outlet.

[0003]

Further, such a sirocco fan is required to achieve reduction in fan input and reduction in noise in order to save energy. An indoor unit of an air-conditioning apparatus is strongly required to achieve downsizing in addition to the reduction in fan input and noise.

[0004]

In order to meet the requirements, it is necessary to increase performance of the sirocco fan in the indoor unit of the air-conditioning apparatus.

[0005]

Hitherto, as an example of a method of increasing performance of the sirocco fan, there have been known a variety of methods of devising a casing shape.

However, none of those casing shapes can break through such a basic shape that the distance between the fan and the casing is gradually increased from the tongue portion in a fan rotating direction (for example, see Patent Literature 1).

Citation List Patent Literature [0006]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2006-233835 (Abstract and Fig. 1)

Summary of Invention Technical Problem [0007]

When such a sirocco fan is mounted in the indoor unit of the air-conditioning apparatus, there arises a problem in that fan input and noise are increased because of not only a dimensional limitation of the indoor unit but also a limitation of a size of the casing.

[0008]

The present invention has been made to overcome the above-mentioned problem, and has an object to obtain a sirocco fan capable of reducing a height of a casing without increasing noise and fan input and to obtain an indoor unit of an air-conditioning apparatus using the sirocco fan.

Solution to Problem [0009]

According to one embodiment of the present invention, there is provided a sirocco fan, including: a casing of a scroll type comprising a tongue portion being a scroll starting point; a multiblade centrifugal fan accommodated in the casing; and a flat portion formed in a region of the casing so as to be shifted from the tongue portion by approximately 90 degrees in a fan rotating direction, wherein 1,0<X/Z<1.5 holds where X is a minimum distance between the tongue portion and the multiblade centrifugal fan, and Z is a minimum distance between the flat portion and the multiblade centrifugal fan.

[0010]

According to one embodiment of the present invention, there is provided an indoor unit of an air-conditioning apparatus, which uses the above-mentioned sirocco fan.

Advantageous Effects of Invention [0011]

In the sirocco fan according to the present invention, where the flat portion is the region of the casing, shifted from the tongue portion by approximately 90 degrees in the fan rotating direction, and when the minimum distance between the tongue portion and the fan is represented by X, and the minimum distance between the flat portion and the fan is represented by Z, the distance X and the distance Z are set to satisfy 1,0<X/Z<1.5. Accordingly, without increasing noise and fan input, the height of the casing can be reduced.

[0012]

Further, the indoor unit of the air-conditioning apparatus according to the present invention uses the above-mentioned sirocco fan. Accordingly, the indoor unit can be downsized.

Brief Description of Drawings [0013] [Fig. 1] Fig. 1 is an explanatory view of the principle of a sirocco fan according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a side sectional view of an indoor unit of an air-conditioning apparatus in which the sirocco fan according to Embodiment 1 of the present invention is mounted.

[Fig. 3] Fig. 3 is a side sectional view of the indoor unit of the air-conditioning apparatus in which the sirocco fan according to Embodiment 1 of the present invention is mounted.

[Fig. 4] Fig. 4 is a side sectional view for illustrating the sirocco fan according to Embodiment 1 of the present invention.

[Fig. 5] Fig. 5 is a graph for showing a P-Q characteristic of the sirocco fan according to Embodiment 1 of the present invention.

[Fig. 6] Fig. 6 is a graph for showing a relationship between noise and a ratio X/Z at an operating point M of Fig. 5.

[Fig. 7] Fig. 7 is a graph for showing a relationship between noise and the ratio X/Z at an operating point N of Fig. 5.

[Fig. 8] Fig. 8 is a graph for showing a relationship between noise and a ratio D/H in the sirocco fan according to Embodiment 1 of the present invention.

[Fig. 9] Fig. 9 is a graph for showing the relationship between noise and the ratio D/H in the sirocco fan according to Embodiment 1 of the present invention.

[Fig. 10] Fig. 10 is an explanatory view of the principle of a sirocco fan according to Embodiment 2 of the present invention.

[Fig. 11] Fig. 11 is a front sectional view for illustrating the sirocco fan according to Embodiment 2 of the present invention.

[Fig. 12] Fig. 12 is a graph for showing a P-Q characteristic of the sirocco fan according to Embodiment 2 of the present invention.

Description of Embodiments [0014]

Embodiment 1

Fig. 1 is an explanatory view of the principle of a sirocco fan according to Embodiment 1 of the present invention.

As illustrated in Fig. 1, a sirocco fan 4 of Embodiment 1 includes a casing 1 of a scroll type having an air outlet 13 formed therein and including a tongue portion 3 being a scroll starting point. The sirocco fan 4 further includes a multiblade centrifugal fan 2 accommodated in the casing 1. Flere, a height of the casing 1 is represented by Fla, and a fan diameter is represented by D. A rotation center of the fan 2 is indicated by a point O. Further, a point on the tongue portion 3, which is least distant from the fan 2, is indicated by a point A, and an end point of the casing 1 is indicated by a point B. A freely-selected point on a curve AB is indicated by a point C, and a distance between the point C and the fan 2 is represented by Y. The distance Y is defined as "line segment OC length-D/2". Further, a distance between the point A on the tongue portion 3 and the fan 2 is represented by X.

[0015]

In general, in the sirocco fan 4, the closer the point C is to the point A, the closer the point C is to the fan 2, and the closer the point C is to the point B, the point C is more distant from the fan.

An inter-blade airflow rate in the vicinity of the point C increases as the point C is set closer to the point B. When a distance between the fan 2 and the casing 1 is small, airflow resistance is caused to affect the inter-blade airflow rate. Accordingly, a region where the inter-blade airflow rate is high requires that the distance between the casing 1 and the fan 2 is increased to reduce the airflow resistance.

[0016]

Fig. 2 is a side sectional view for illustrating an example of an indoor unit of an air-conditioning apparatus in which the sirocco fan according to Embodiment 1 of the present invention is mounted, and is an illustration of an example of arranging a heat exchanger downstream of the sirocco fan. Fig. 3 is a side sectional view for illustrating another example of the indoor unit of the air-conditioning apparatus in which the sirocco fan according to Embodiment 1 of the present invention is mounted, and is an illustration of an example of arranging the heat exchanger upstream of the sirocco fan.

As illustrated in Fig. 2 and Fig. 3, the sirocco fan 4 and a heat exchanger 16 are arranged in an air duct of an indoor unit 5 of the air-conditioning apparatus in which the sirocco fan 4 is mounted. When the sirocco fan 4 is mounted in the indoor unit 5 of the air-conditioning apparatus, a dimensional limitation is imposed on the height Fla of the casing 1 of the sirocco fan 4. In this case, the larger the height Fla is, the more the fan input and noise of the sirocco fan 4 can be reduced. Flowever, when the height Ha is increased, a size of the indoor unit 5 also needs to be increased. Accordingly, because of a limitation of an installation space for the indoor unit 5, the height Ha can be hardly increased.

[0017]

Next, description is made of increase in performance of the sirocco fan 4 with the height is limited to a height Ha.

Fig. 4 is a side sectional view for illustrating the sirocco fan according to Embodiment 1 of the present invention.

As described above with reference to Fig. 1, the closer the point C is to the point A, the smaller the distance between the point C and the fan 2 is, and the interblade airflow rate at the vicinity of the point C is decreased. Accordingly, when the point C is close to the point A, it is not necessary to increase the distance between the point C and the fan 2. As illustrated in Fig. 4, in the sirocco fan 4 of Embodiment 1, a region of the casing 1, which is shifted from the tongue portion 3 by approximately 90 degrees in a fan rotating direction, is formed as a flat portion 6 extending horizontally, and a distance between the flat portion 6 and the fan 2 is reduced as compared to that in a sirocco fan having a normal scroll shape. Thus, a height H of the casing is reduced.

[0018]

That is, in the sirocco fan 4 of Embodiment 1, a lowermost end point shifted from the tongue portion 3 by approximately 90 degrees in the fan rotating direction in the casing 1 having the height Ha of Fig. 1 is moved upward by an amount ΔΗ. Further, as illustrated in Fig. 4, intersection points of the casing 1 with a horizontal line passing the above-mentioned moved point are indicated by a point E and a point F, and a surface that contains a line segment EF and is perpendicular to the drawing sheet is formed as the flat portion 6. Further, the height H of the casing is defined by H=Ha-AH, that is, the height H of the casing is reduced by the amount ΔΗ from the height Ha.

[0019]

In the sirocco fan 4 of Embodiment 1, a perpendicular line is drawn from the point 0 to the flat portion 6, and an intersection point of the perpendicular line and the flat portion 6 is indicated by a point G. Further, a distance between the point G and the fan 2 is represented by Z, and the distance between the point A on the tongue portion 3 and the fan 2 is represented by X.

[0020]

Fig. 5 is a graph for showing a P-Q characteristic of the sirocco fan 4. Flere, P represents static pressure [Pa], and Q represents an airflow rate [m3/min]. The operating point M is an operating point on a closed side, and a region where an airflow rate is lower than an airflow rate at the operating point M is a surging region. An airflow is unstable in the surging region, and hence the surging region is normally unused. The operating point N is an operating point on an opened side, and static pressure is zero [Pa] at the operating point N.

[0021]

Fig. 6 is a graph for showing a relationship between noise and a ratio X/Z at the operating point M of Fig. 5. Fig. 7 is a graph for showing a relationship between noise and the ratio X/Z at the operating point N of Fig. 5. Flere, SPL represents noise [dB], and X/Z represents a ratio of the minimum distance X between the tongue portion 3 of the casing 1 and the fan 2 to the minimum distance Z between the fan 2 and the flat portion 6 formed in the region of the casing 1 shifted by approximately 90 degrees in the fan rotating direction from the tongue portion 3. The minimum distance Z is the distance between the point G and the fan 2. Further, here, the distance X between the point A and the fan 2 is fixed, and the distance Z between the point G and the fan 2 is varied by varying only the amount ΔΗΙ.

[0022]

As shown in Fig. 6, it is understood that noise is stable when X/Z>1.0 is satisfied at the operating point M. Therefore, fan input is also stable when X/Z>1.0 is satisfied at the operating point M.

[0023]

Further, as shown in Fig. 7, it is understood that noise is stable when X/Z>1.5 is satisfied at the operating point N at which static pressure is zero [Pa], Therefore, fan input is also stable when X/Z>1.5 is satisfied at the operating point N. Further, at the operating point N at which static pressure is zero [Pa], a noise difference between a case of X/Z=1.0 and a case of X/Z=1.5 is small, specifically, 0.2 dB, and substantially the same fan input is obtained in the both cases.

[0024]

Next, the reason is described.

The operating point M is the operating point on the closed side, and the operating point N is the operating point on the opened side. An airflow rate on the opened side is higher than an airflow rate on the closed side. Noise generated in the casing 1 is increased as a unit-time variation in static pressure on a wall surface of the casing 1 is increased. The unit-time variation in static pressure is large also in a case where the distance between the wall surface of the casing 1 and the fan 2 is small and a case where an inter-blade airflow rate at the vicinity of the wall surface of the casing 1 is high.

[0025]

Accordingly, the inter-blade airflow rate at the vicinity of the wall surface of the casing 1 is higher at the operating point N at which the airflow rate is higher than that at the operating point M at which the airflow rate is low. Thus, noise is increased.

In order to prevent increase in noise, for example, it is effective to increase the small distance X between the wall surface of the casing 1 and the fan 2, and to reduce the unit-time variation in static pressure on the wall surface of the casing 1.

[0026]

As described above, the flat portion 6 is formed in the region of the casing 1 so as to be shifted from the tongue portion 3 by approximately 90 degrees in the fan rotating direction, and the ratio X/Z of the minimum distance X between the tongue portion 3 and the fan 2 to the minimum distance Z between the flat portion 6 and the fan 2 is set to satisfy 1,0<X/Z<1.5. In this manner, without increasing noise and fan input, the height of the casing can be reduced, and the indoor unit 5 can be downsized. Further, when the indoor unit 5 is not downsized, for example, on a side opposed to the point G across the point O, the distance between the casing 1 and the fan 2 can be increased as compared to that in the related art. Thus, increase in performance of the sirocco fan 4 can be achieved.

[0027]

Next, description is made of a relationship between the fan diameter D and the height H of the casing 1 including the flat portion 6.

First, the operating point M is described.

Fig. 8 is a graph for showing a relationship between noise and a ratio D/H in the sirocco fan according to Embodiment 1 of the present invention. Specifically, there is shown the relationship between noise and the ratio D/H when the height H of the casing and the distance X between the point A and the fan 2 are fixed, Z=X is satisfied, and the fan diameter D is varied at the operating point M.

[0028]

As shown in Fig. 8, at the operating point M, noise is minimized when 0.66<D/H<0.75 is satisfied. The reason is as follows.

[0029]

At the operating point M, since the larger the fan diameter D is, the smaller the number of revolutions is , and an inter-blade passing speed is reduced at an interblade portion near the point B on the curve AB illustrated in Fig. 4, with the result that fan input and noise are reduced. However, the distance between the fan 2 and the casing 1 is small, and airflow resistance is increased.

Meanwhile, the larger the number of revolutions is, the smaller the fan diameter D is, and the inter-blade passing speed is increased at the inter-blade portion near the point B on the curve AB, with the result that the fan input and noise are increased. However, the distance between the fan 2 and the casing 1 becomes large, and airflow resistance is reduced.

[0030]

There are advantages and disadvantages in changing a size of the fan diameter D. When 0.66<D/H<0.75 is satisfied at the operating point M, effects cancel out each other so that noise is stable and minimized.

[0031]

Next, the operating point N is described.

Fig. 9 is a graph for showing the relationship between noise and the ratio D/H in the sirocco fan according to Embodiment 1 of the present invention. Specifically, there is shown the relationship between noise and the ratio D/H when the height H of the casing and the distance X between the point A and the fan 2 are fixed, Z=X is satisfied, and the fan diameter D is varied at the operating point N.

[0032]

As shown in Fig. 9, at the operating point N, noise is minimized when 0.65<D/H<0.74 is satisfied. The reason is as follows.

[0033]

At the operating point N, the larger the fan diameter D is, the smaller the number of revolutions is, and the inter-blade passing speed is reduced at the interblade portion near the point B on the curve AB, with the result that fan input and noise are reduced. However, the distance between the fan 2 and the casing 1 is reduced, and airflow resistance is increased.

The smaller the fan diameter D is, the larger the number of revolutions is , and the inter-blade passing speed is large at the inter-blade portion near the point B on the curve AB, with the result that the fan input and noise increase. However, the distance between the fan 2 and the casing 1 is larger, and airflow resistance is reduced.

[0034]

There are advantages and disadvantages in changing the size of the fan diameter D. When 0.65<D/H<0.74 is satisfied at the operating point N, effects cancel out each other so that noise is stable and minimized.

[0035]

Accordingly, when 0.66<D/H<0.75 is satisfied at the operating point M on the closed side and when 0.65<D/H^0.74 is satisfied at the operating point N on the opened side, noise is minimized. Therefore, when 0.65^D/H^0.75 is satisfied, noise is minimized at an operating point between the operating point M and the operating point N.

[0036]

Further, when 0.65<D/H<0.75 is satisfied, fan input can also be minimized at the operating point between the operating point M and the operating point N.

[0037]

As described above, in the sirocco fan 4 of Embodiment 1, the flat portion 6 is formed in the region of the casing 1 so as to be shifted from the tongue portion 3 by approximately 90 degrees in the fan rotating direction, and the ratio X/Z of the minimum distance X between the point A on the tongue portion 3 and the fan 2 to the minimum distance Z between the point G on the flat portion 6 and the fan 2 is set to satisfy 1,0<X/Z<1.5. Accordingly, without increasing noise and fan input, the height H of the casing can be reduced.

[0038]

Further, in the sirocco fan 4 of Embodiment 1, the ratio D/H of the fan diameter D to the height H of the casing is set to satisfy 0.65<D/FI<0.75. Accordingly, noise and fan input can be minimized.

[0039]

Further, the height FI of the casing can be reduced so that the indoor unit 5 of the air-conditioning apparatus using the sirocco fan 4 can be downsized. In addition, when the indoor unit 5 is not downsized, the height FI of the casing can be increased so that increase in performance of the sirocco fan 4 can be achieved.

[0040]

Further, the flat portion 6 is formed in the casing 1 of the sirocco fan 4 so that there can be increased a contact area with a casing of the indoor unit 5 arranged in a horizontal posture (Fig. 2) or a casing of the indoor unit 5 arranged in an upright posture (Fig. 3). Accordingly, during operation of the fan 2, even when the indoor unit 5 is vibrated by earthquake or other causes, a positional relationship among the indoor unit 5, the casing 1, and the fan 2 can be maintained. Thus, a collision between the fan 2 and the casing 1 can be avoided, and reduction in aerodynamic performance can be prevented.

[0041]

Embodiment 2

Fig. 10 is an explanatory view for illustrating the principle of a sirocco fan according to Embodiment 2 of the present invention. In Fig. 10, components corresponding to the above-mentioned components of Embodiment 1 are denoted by the same reference symbols. The sirocco fan according to Embodiment 2 is described below with reference to Fig. 2 to Fig. 4.

In Fig. 10, the sirocco fan 4 includes a rotation shaft 7, a main plate 15 mounted on the rotation shaft 7 through intermediation of a boss 8, the fan 2 mounted on the main plate 15, and bellmouths 9 mounted on the casing 1. Each of the bellmouths 9 defines an air inlet 14, and has a substantially quarter-arc shape.

Further, a gap 10 for interference prevention is defined between each of the bellmouths 9 and the fan 2. Further, a space 12 exists between the casing 1 and the fan 2. Here, a width dimension of the casing 1, a width dimension of the fan 2, and a width of the gap 10 are represented by Lc, Lf, and Δ, respectively.

[0042]

In the sirocco fan 4 described above, the larger the width dimension Lf of the fan 2 is, the more liable the fan 2 is to be eccentric to the rotation shaft 7 during operation. The reason for the eccentricity is as follows. Flexure of the fan due to gravity, and the inter-blade airflow rate are high at the vicinity of the main plate 15, but are low at the vicinity of the air inlet 14. Thus, for example, the more uneven the inter-blade airflow rate is in the rotation shaft direction, the larger the width dimension Lf is.

[0043]

As illustrated in Fig. 4, when the flat portion 6 is formed in the casing 1 and the distance between the flat portion 6 and the fan 2 is reduced as compared to that in a sirocco fan having a normal scroll shape, a region where the distance between the casing 1 and the fan 2 is small is increased as compared to a region in the sirocco fan having a normal scroll shape. In addition, when the fan 2 having the large width dimension Lf is used, an eccentric amount of the fan 2 is prone to be further increased. When the sirocco fan 4 described above is mounted in the indoor unit 5 as illustrated in Fig. 2 or Fig. 3, during assembling work, there easily occurs such misalignment that the rotation shaft 7 and the bellmouth 9 are slightly eccentric to each other. When a large degree of eccentricity and a large degree of misalignment occur at the same time, the fan 2 may collide with the casing 1, and thus a probability of breakage of the fan 2 is increased. As a result, quality of the indoor unit 5 is degraded.

[0044]

In order to reduce the probability of breakage of the fan 2, it is effective to increase the distance X between the point A and the fan 2. Flowever, in this case, leakage of the airflow is increased at the vicinity of the tongue portion 3, thereby leading to increase in fan input.

[0045]

Fig. 11 is a front sectional view for illustrating the sirocco fan according to Embodiment 2 of the present invention, and is an illustration of the sirocco fan 4 in which the width dimension Lc of the casing 1 and the width Δ of the gap 10 of Fig. 10 are maintained and the width dimension Lf of the fan 2 is reduced.

As illustrated in Fig. 11, to maintain the width Δ of the gap 10, the sirocco fan 4 includes a straight portion 11 extending in parallel to the rotation shaft 7 from each of the bellmouths 9 toward the fan 2. The straight portion 11 has a hollow cylindrical shape having a length W.

[0046]

Fig. 12 is a graph for showing a P-Q characteristic of the sirocco fan according to Embodiment 2 of the present invention, and for showing the P-Q characteristic obtained by varying a ratio Lc/Lf with the width dimension Lc of the casing 1 and the width Δ of the gap 10 being fixed and the width dimension Lf of the fan 2 and the length W of the straight portion 11 being varied.

[0047]

As shown in Fig. 12, the P-Q characteristic is unchanged when 1.05<Lc/Lf<1.45 is satisfied, and static pressure is reduced at the operating point on the opened side when Lc/Lf=1.55 is satisfied. The reason why the P-Q characteristic is unchanged when Lc/Lf^1.45 is satisfied is as follows.

That is, the smaller the width dimension Lf is, the smaller an inter-blade area is. Accordingly, an inter-blade speed is increased, and fan performance is degraded. Meanwhile, the smaller the width dimension Lf is, the larger the space 12 is. Part of an airflow blown out from an inter-blade portion is blown out from the air outlet 13 through the space 12. Accordingly, airflow resistance generated when the airflow passes through the space 12 is reduced, and an effect of increase in inter-blade airflow velocity and an effect of reduction in airflow resistance cancel out each other, with the result that the P-Q characteristic is not changed. When Lc/Lf=1.55 is satisfied, the effect of increase in inter-blade airflow velocity exceeds the effect of reduction in airflow resistance, with the result that static pressure is reduced at the operating point on the opened side.

[0048]

In a case of drawing a graph similar to the graph of Fig. 12 under a condition where 1,45<Lc/Lf<1.55 is satisfied, the maximum ratio Lc/Lf allowing the P-Q characteristic to be unchanged was 1.47.

[0049]

Further, when Lc/Lf<1.47 is satisfied, an η-Q characteristic and a Ks-Q characteristic are also unchanged. Here, the following relations are satisfied: n=(P[Pa]xQ[m3/s])/(T[Nm]xcju[rad/s]) Ks=SPL[dB]-10logio(P2[mmAq]xQ[m3/min]) where η represents fan efficiency; Ks, specific sound level; P, static pressure; Q, an airflow rate; T, torque; ω, angular velocity; and SPL, noise.

[0050]

As described above, the width Δ of the gap 10 is maintained, and the straight portion 11 is formed in the bellmouth 9 having a quarter-arc shape. Further, the width dimension Lf is reduced under a condition where 1,05<Lc/Lf<1.47 is satisfied. With this configuration, the P-Q, η-Q, and Ks-Q characteristics are maintained, and eccentricity of the fan 2 is prevented. Further, the probability of breakage of the fan 2 due to the collision between the casing 1 and the fan 2 is reduced, and quality of the indoor unit 5 can be enhanced.

[0051]

Further, when providing selections of models of the indoor unit 5 different in air-conditioning performance, in general, an airflow rate is higher in a model with higher air-conditioning performance. For example, in a case of providing selections of models of the indoor unit 5 of Fig. 2, which have the same height and are different in air-conditioning performance, when the width dimension Lc is varied in accordance with air-conditioning performance and the width dimension Lf is equalized, the airflow rate can be varied depending on a size of the width dimension Lc under a condition where 1,05<Lc/Lf<1.47 is satisfied. Accordingly, commonality of the fan 2 can be achieved. As a result, die cost can be reduced, and fan cost can be reduced. In addition, in a case where the straight portion 11 is formed and the width dimension Lf is reduced when the width Δ of the gap 10 is equalized, manufacturing cost of the fan 2 can be reduced as compared to a case where the straight portion 11 is not formed and the width dimension Lf is not reduced.

[0052]

In Embodiment 2, description is made of the sirocco fan 4 of a double suction type having two air inlets 14 as an example. However, the present invention is also applicable to the sirocco fan 4 of a single suction type having one air inlet 14.

Reference Signs List [0053] I casing 2 fan 3 tongue portion 4 sirocco fan 5 indoor unit 6 flat portion 7 rotation shaft 8 boss 9 bellmouth 10 gap II straight portion 12 space 13 air outlet 14 air inlet 15 main plate 16 heat exchanger

Claims (1)

1. CLAIMS [Claim 1] A sirocco fan, comprising: a casing of a scroll type comprising a tongue portion being a scroll starting point; and a multiblade centrifugal fan accommodated in the casing, wherein a flat portion is formed in a region of the casing at approximately 90 degrees in a fan rotating direction from the tongue portion, and wherein 1,0<X/Z<1.5 holds where X is a minimum distance between the tongue portion and the multiblade centrifugal fan, and Z is a minimum distance between the flat portion and the multiblade centrifugal fan. [Claim 2] The sirocco fan of claim 1, wherein 0.65<D/H<0.75 holds where H is a height of the casing and D is a diameter of the multiblade centrifugal fan. [Claim 3] The sirocco fan of claim 1 or 2, further comprising a bellmouth defining an air inlet and having a quarter-arc shape, the bellmouth comprising a straight portion extending toward the multiblade centrifugal fan, wherein the multiblade centrifugal fan has a width dimension Lf under a condition where 1,05<LC/Lf<1.47 holds where Lc is a width dimension of the casing and Lf is a width dimension of the multiblade centrifugal fan and a gap Δ between the bellmouth and the multiblade centrifugal fan is maintained. [Claim 4] An indoor unit of an air-conditioning apparatus, which uses the sirocco fan of any one of claims 1 to 3.