JPH11324984A - Multi-blade fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the blowing performance in a narrow and long cylindrical multi-blade fan for blowing a wide air flow. SOLUTION: Plural multi-blade centrifugal fan units 23 are connected to each other with a space along the same rotary shaft through a rotary core 25 so as to form a narrow and long cylindrical multi-blade fan 21 as a whole. A casing 29 for covering the multi-blade fan 21 is formed with a blowing flow passage 31 for blowing the air discharged outside from the multi-blade fan 21. This blowing flow passage 3 is a common flow passage connected to all plural centrifugal fan units 23. Each centrifugal fan unit 23 is formed of a first centrifugal fan formed of multiple wide impellers cylindrically arranged around a core 25 and having a small inner diameter and a second centrifugal fan formed of multiple narrow impellers cylindrically arranged around the rotary core 25 and having a large inner diameter, and the second centrifugal fan is fitted to a tip of the first centrifugal fan at a part close to the periphery thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-blade fan having a slender cylindrical shape as a whole and capable of blowing a wide band of wind, and more particularly to an improvement for increasing the air volume and static pressure.

[0002]

2. Description of the Related Art A multi-blade fan which has a slender cylindrical shape as a whole and blows out a wide band of wind is used for various types of units such as an air conditioner indoor unit, a warm air indoor heater, a wall-mounted bathroom clothes dryer, an air purifier and the like. It is used favorably in blowers. The most common type of multi-blade fan is a once-through fan. FIG. 1 illustrates the principle of a once-through fan. The cross-flow fan 1 has a large number of elongated blades 3 arranged on a circumference to form an elongated cylindrical body as a whole, and is disposed in an air flow path 5 having a suction port 5A and an air outlet 5B. The once-through fan 1 takes in air from the outside on the suction port side and discharges the taken-in air to the outside on the outlet side.

One problem with once-through fans is that, in principle,
The air volume is small (that is, the efficiency is low), and the static pressure is also low. In addition, there is also a problem that the number of rotations cannot be increased so much because the elongated shape easily bends. To solve this drawback, Japanese Utility Model Laid-Open No. 56-8897 discloses an elongated cylindrical multi-blade fan using a centrifugal fan instead of a once-through fan. As shown in FIG. 2, this device is configured by connecting a plurality of multi-blade centrifugal fan units 7 via a spacer 9 along the same rotation axis. Each centrifugal fan unit 7 has a large number of blades 13 laid in a cylindrical shape between a pair of end rings 11, 11, and the end rings 11, 1 of adjacent centrifugal fan units 7, 7 are arranged.
1 are connected by a plurality of rod-shaped spacers 9. Also, the casing 15 of this elongated cylindrical multi-blade fan
Form independent blowing channels 17 for each individual multi-blade centrifugal fan unit 7. When this elongated cylindrical multi-blade fan rotates, air is taken into the centrifugal fan units 7, 7 from the space between the centrifugal fan units 7, 7 as indicated by arrows, and each centrifugal fan unit 7, 7 It is discharged to the outside of the fan units 7 and 7.

This elongated cylindrical multi-blade fan utilizes the principle of a centrifugal fan and has a high rigidity by connecting the centrifugal fans to each other with a plurality of spacers, so that the number of revolutions can be increased. There is an advantage that the blowing capacity is higher than that of a general once-through fan.

[0005]

Problems to be Solved by the Invention
One problem with the No. multi-blade fan is that the spacers cut off the wind and produce loud noise. Another problem is that the multi-blade centrifugal fan is connected by spacers, which has a somewhat complicated structure, which increases the manufacturing cost.However, the improvement in air blowing performance is not large for the cost increase. Is a point. One of the reasons for the poor improvement of the blowing performance is that the air flow path is independent for each centrifugal fan unit, and the air resistance in this flow path is large. As a second cause, the performance of the centrifugal fan unit itself can be considered. That is, the centrifugal fan is
The outside air is sucked into the inside from the opening at the axial front end side, and the sucked air is blown outward by centrifugal force. It has the disadvantage of low efficiency. To remedy this drawback, it is conceivable to reduce the length of the individual centrifugal fan units. However, this requires a larger number of fan units, which causes a problem that the manufacturing cost is further increased in addition to the above.

In order to solve the above-mentioned drawbacks, a single centrifugal fan is disclosed, for example, in Japanese Patent Application Laid-Open No. 7-233798.
As shown in FIG. 2, there is known a fan in which a portion near the low-efficiency suction port is replaced with a diagonal flow fan that sucks air from the front end and diagonally outwards. However, the performance of the mixed flow fan is not so high in principle, so that a remarkable effect of increasing the air volume cannot be expected.

[0007] It is, therefore, an object of the present invention to provide an improved multi-blade fan capable of providing a better air blowing performance than the prior art.

[0008]

A multi-blade fan according to a first aspect of the present invention includes a plurality of multi-blade centrifugal fan units connected along the same rotational axis with a space therebetween. A casing accommodating a plurality of multiblade centrifugal fan units. The casing forms a blowing channel for blowing air discharged from the plurality of multiblade centrifugal fan units to the outside, and the blowing channel is continuous for the plurality of multiblade centrifugal fan units. It is a common channel.

This multi-blade fan uses a centrifugal fan, and the blow-out passage is not independent for each centrifugal fan unit, but is a common common passage for a plurality of centrifugal fan units. Therefore, the resistance of the flow path for blowing is small, and the blowing performance is high.

In a preferred embodiment, except for the air inlet opening at the end face of the centrifugal fan unit and the outlet channel,
Each of the centrifugal fan units is individually covered with a scroll plate. Thus, each centrifugal fan unit can effectively exert its air blowing performance without being significantly affected by other centrifugal fan units.

In a preferred embodiment, each of the centrifugal fan units has a rotating mandrel having a circular cross section centered on the rotating shaft, and is connected to each other with the rotating mandrel.
According to this configuration, there is no problem of the spacer wind noise in the conventional fan shown in FIG. 2, and thus the noise is small.

A multi-blade fan according to a second aspect of the present invention comprises:
A plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space therebetween are provided, and at least one of the centrifugal fan units has a large number of sheets arranged in a cylindrical shape with the rotation axis as a central axis. A first centrifugal fan having a relatively small inner diameter having a first blade, and a second centrifugal fan having a relatively large inner diameter having a plurality of second blades also arranged in a cylindrical shape. A centrifugal fan,
Is attached to the tip of the first centrifugal fan.

A multi-blade fan according to a third aspect of the present invention comprises:
A plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space between each other, and at least one of the centrifugal fan units has a plurality of centrifugal fans having different inner peripheral diameters, Another centrifugal fan having a relatively large inner diameter is attached to the distal end side of the centrifugal fan having a small inner diameter.

In the multi-blade fan according to the second and third aspects, the portion of the first centrifugal fan having a small inner peripheral diameter, which is an inefficient part of the first centrifugal fan, is located closer to the outer periphery of the tip. The centrifugal fan compensates for the efficiency and improves the blowing performance. By using such a centrifugal fan unit with high blowing performance, to achieve the same blowing performance, the number of revolutions can be reduced compared to the conventional fan, the size can be reduced, and the rigidity of the fan material can be reduced, thus reducing noise. , Miniaturization or cost reduction.

In a preferred embodiment, the blades of the first centrifugal fan are wide and the second centrifugal fan has a second blade attached to its tip.
Of the centrifugal fan is narrow. It is desirable for the width of the gap between the blades to be in the range of 1 to 3 mm in order to obtain a large air flow. This gap is smaller than that of the conventional multi-blade fan.

In a preferred embodiment, the distal end surface of the first centrifugal fan has a surface inclined with respect to the rotation axis from the inner peripheral side toward the outer peripheral side toward the proximal end side. A second centrifugal fan is mounted on the inclined surface near the outer periphery. In this structure, it can be said that the inefficient portion of the first centrifugal fan near the outer periphery of the tip is removed and replaced with the second centrifugal fan. Further, the inclined front end face of the first centrifugal fan also plays a role of smoothing the airflow entering the second centrifugal fan. Therefore, the blowing capacity is further improved.

Further, in a preferred embodiment, an annular air guide plate is joined to at least a part of the front end face of the first centrifugal fan. This air guide plate effectively guides the air flow to the second centrifugal fan, and contributes to the improvement of the blowing capacity.

A blower according to a fifth aspect of the present invention comprises an air flow path having an air inlet and an air outlet, a multi-blade fan according to the present invention disposed in the air flow path, An air processor disposed in the road. The blower is
Specifically, it is an air conditioner, a warm air room heater, a wall-mounted bathroom clothes dryer, an air purifier, or the like. Depending on the purpose of each blower, the air processor may include a heat exchanger for heating or cooling air, a heater, a cooler, a cleaning unit for cleaning air, an ozone generation unit, or an ion generation unit. A suitable air conditioner is located in the flow path. Since this blower uses the multi-blade fan of the present invention, the noise is small, the blow capacity is high, and if the blow capacity is the same, the size is smaller than the conventional blower,
Cost reduction is easy.

[0019]

FIG. 3 shows an overall configuration of a multi-blade fan according to an embodiment of the present invention. FIGS. 4 and 5 are taken along lines AA and BB in FIG. 3, respectively. 2 shows a cross-sectional view of the same fan.

The multi-blade fan 21 is obtained by connecting a plurality of multi-blade centrifugal fan units 23 along the same rotation axis with a space therebetween. Each centrifugal fan unit 23 has a cylindrical rotating mandrel 25,
5, the rotating mandrel 2 of the adjacent centrifugal fan unit 23
5. A motor 37 is connected to the rotating shaft 26 of the centrifugal fan unit 23 at one end. The rotating mandrel 25 connecting the centrifugal fan units 23 is sufficiently thick and has sufficient rigidity so that the multi-blade fan 21 does not bend in the operating speed range.

Each multi-blade centrifugal fan unit 23 has a large number of blade plates 27 arranged in a cylindrical shape coaxial with the rotating shaft 25. As will be described in detail later, the blade plate 27 has a unique shape in which a narrow upper blade plate and a wide blade plate are combined.

The casing 29 accommodating the multi-blade fan 21 comprises the following several parts. First, a pair of outer plates 29A, 29A cover both end faces of the multi-blade fan 21 from outside. As shown in FIG. 4, a curved outer scroll plate 29B surrounds the outer periphery of each multi-blade centrifugal fan unit 23. The outer scroll plate 29B is opened in a predetermined direction, and is provided therewith.
1 are formed. This blowing channel 31 is not independent for each centrifugal fan unit 7 like the blowing channel 17 of the conventional device shown in FIG. It is formed as a continuous common single channel. Further, as shown in FIG. 5, the curved inner curved plate 29 </ b> C makes the space between the adjacent multiblade centrifugal fan units 23, 23 substantially equal to the inner peripheral diameter of the cylindrical row of the blade plates 27 of the centrifugal fan unit 23. It is enclosed along a circumference of the same diameter and coaxial with the fan rotation axis. The inner curved plate 29C is opened in a predetermined direction different from that of the blowing channel 31, and forms a suction channel 33 therein.
In addition, as shown in FIG. 5, a roughly crescent-shaped partition plate 2
9D divides the space outside each multi-blade centrifugal fan unit 23 surrounded by the outer scroll plate 29B into a suction passage 33.
Is separated from.

As shown in FIG. 5, between the inner curved plate 29C and the partition plate 29D, a circular suction hole having substantially the same diameter as the inner diameter of the cylindrical row of the blade plates 27 of the centrifugal fan unit 23 is provided. 35 are formed. A similar suction hole 35 is provided in the outer plate 2.
9A and 29A are also formed.

When the multi-blade fan 21 rotates, as shown by arrows, air is sucked from each suction passage 33 through each suction hole 35 into each centrifugal fan unit 23,
The sucked air is blown out of each centrifugal fan unit 23 through a gap between the blade plates 27 by centrifugal force. The air blown from the plurality of centrifugal fan units 23 is collected in a common blowing channel 31, and is discharged as a wide band-like wind through the passage.

According to the structure shown in FIGS. 3 to 5, since the plurality of centrifugal fan units 23 are connected by the cylindrical rotating mandrel 25, the wind noise of the spacer as in the conventional fan shown in FIG. No problem and noise is small. Further, since the blow-out flow passages 31 are all formed as one continuous common flow passage for the centrifugal fan unit 23, the flow passage resistance is smaller than that of the conventional fan shown in FIG. Is obtained.

FIG. 6 is a cross-sectional view of the centrifugal fan unit 23 of the multi-blade fan 21 of the present embodiment along the rotation axis F. 7 and 8 are cross-sectional views of the centrifugal fan unit 23 taken along lines CC and DD in FIG. 6, respectively. Note that the cross section in FIG. 6 is along the line EE in FIGS. 7 and 8. In the following description, the left side of FIG. 6 will be referred to as “distal side” and the right side will be referred to as “proximal side”.

As shown in the figure, the rotating mandrel 25 of the centrifugal fan unit 23 has irregularities on both end faces so that it can be fitted to and connected to the rotating mandrel 25 of another centrifugal fan unit 23. The desired number of centrifugal fan units 23 can be connected. The rotating shaft 25 has a double pipe structure in order to obtain high rigidity. In addition,
The rigidity of the rotating mandrel 25 may be further increased by fitting a metal pipe or the like inside the rotating mandrel 25.
This is useful, for example, when a long rotating mandrel 25 is required, such as an apparatus that creates an air curtain.

On the outer periphery of the rotating mandrel 25, a cylindrical rotating plate 4 is provided.
A large number of (for example, about 100) wide blade plates 27A are connected to the periphery of the rotating plate 41 in a direction parallel to the rotation axis F. The large number of wide blade plates 27A are arranged at a constant pitch in a cylindrical shape around the rotation axis F. The width W of the gap between the wide blades 27A
1 is about 1 to 3 mm, preferably about 2 to 3 mm, which is an appropriate range for obtaining a large air volume. The base angle at the outer peripheral side of the cylindrical row of these wide blades 27A is
3 are connected. The cylindrical row of the wide blades 27A functions as a “first centrifugal fan”, and as shown by arrows, from the distal opening 45 and the proximal opening 47 of the centrifugal fan unit 23 to the inside spaces 49 and 51, respectively. Air is blown outward through the gap of the wide blade plate 27A.

In order to improve the intake of air, the inner and outer ends of the wide blade plate 27A are advanced blades which are curved so as to form an acute angle with respect to the rotation direction G. Is composed. However, this is not necessarily required, and the wide blade plate 27A may be a flat plate to constitute a “radial fan”, or the wide blade plate 27A may constitute a “turbo fan” with swept wings. You may.

As shown in FIG. 6, a portion of the wide blade plate 27A from the outer periphery of the distal end portion is inclined with respect to the rotation axis F from the inner peripheral side toward the outer peripheral side toward the proximal end side. It is as if it had been cut along the cut line. On the leading edge of the wide blade plate 27A that is inclined as described above,
An annular air guide plate 53 is joined. A large number of sheets (for example, 80
(Approximately one sheet) of narrow blades 27B are erected in parallel with the rotation axis F, and are arranged in a cylindrical shape at a constant pitch. The width W2 of the gap between the narrow blade plates 27B is about 1 to 3 mm, preferably about 2 to 3 mm, which is an appropriate range for obtaining a large air volume. The width of these narrow blades 27B is wide blade 2
Clearly narrower than 7A, the cylindrical row of narrow blades 27B has a larger inner circumference than the cylindrical row of wide blades 27A, forming an inner space 55 inside. I have. The tip angles on the outer peripheral side of the narrow blade plate 27B are connected by a reinforcing ring 57. The cylindrical row of narrow blade plates 27B functions as a "second centrifugal fan", sucks air into the inner space 55 from the front end side opening 45 as shown by the arrow, and transfers the sucked air to the narrow blades. It blows out through the gap between the plates 27B. The air guide plate 53 is a narrow blade plate 27B.
To guide the air sucked into the inner space 55 to the narrow blade plate 27B side.

The tip of the narrow blade plate 27B is connected to the wide blade plate 27.
A protrudes from the front end of A to the front end side, so that the suction of air into the inner space 49 of the wide blade plate 27A becomes good. Further, the air guide plate 53 is inclined and curved along the flow of air as shown in FIG.
Can be smoothly guided to the narrow blade plate 27B side. Further, the narrow blade plate 27B is also curved, but this is not always necessary.
The inner / outer diameter ratio (inner diameter / outer diameter) of the cylindrical row of the wide blades 27A is, for example, about 60% to 65%, and the width of the narrow blades 27A is large.
The inner / outer diameter ratio of the cylindrical row of B is, for example, about 85% to 90%, but this is not always necessary.

When such a centrifugal fan unit 23 is rotated, as described above, both the cylindrical row of the wide blades 27A and the cylindrical row of the narrow blades 27B function as a "centrifugal fan". Here, the place where the centrifugal fan action of the narrow blade board 27B is effectively exhibited is the wide blade board 2
The “end portion of the end portion of FIG. 7A as if cut along an oblique line” and the portion near the outer periphery described above. This part has been regarded as a problem in that the efficiency is relatively low and the air flow rate is small. In the present embodiment, the low-efficiency portion of the “first centrifugal fan” of the wide blade 27A is cut off and replaced with the “second centrifugal fan” of the narrow blade 27B having a larger inner diameter. I have. As a result, the efficiency of the low-efficiency portion is improved, so that the air volume and the static pressure can be increased. Furthermore, the air guide plate 53 further improves the flow of air in the “second centrifugal fan”, and further enhances the effects of increasing the air volume and increasing the static pressure.

As a result, the blowing capacity is significantly improved. Due to the high air blowing capacity, the number of rotations required to obtain the same air volume and static pressure is lower than that of the conventional multi-blade fan, and the size is smaller. There are few problems. This also has the advantage that, in the present embodiment, it can be made of inexpensive synthetic resin, whereas conventionally it had to be made of a highly rigid metal in order to obtain the desired air blowing performance. Furthermore, lowering the number of rotations leads to lower noise. In addition, reducing the size of the fan leads to a reduction in the size and cost of the entire blower.

FIGS. 9 to 13 show the centrifugal fan unit 23.
Are shown below. 9 to 13, the same reference numerals are given to the same elements as those in the above-described drawings.

In the modification shown in FIG. 9, the wide blade plate 27A
Is projected to the distal end side up to the distal end and the height of the narrow blade plate 27B. Furthermore, the wide blade board 27
The design may be made such that the tip of the inner peripheral side of A protrudes further toward the tip than the tip of the narrow blade 27B. Both designs have varying degrees of effectiveness,
As described above, an effect is obtained in which the “second centrifugal fan” of the narrow blade plate 27B improves efficiency by replacing the inefficient outer peripheral portion of the tip of the “first centrifugal fan” of the wide blade plate 27A. Can be

In the modification shown in FIG. 10, the wide blade 27
A is connected at its base end to the rotating plate 41, so that the centrifugal fan unit 23
Inhale only from 5. Also, the rotating plate 41 is inclined and curved substantially along the flow of air, so that
The air flow in the "first centrifugal fan" is improved.

In the modification shown in FIG. 11, a combination of a cylindrical row of wide blades 27A and a cylindrical row of narrow blades 27B is formed on both the distal end side and the proximal end side of the rotary plate 41. Similarly, air is sucked in from the proximal opening 47 from the distal opening 45 of the centrifugal fan 23.

In the modified example shown in FIG.
B is disposed so as to protrude outward from the wide blade plate 27A, and the inner peripheral diameter of the cylindrical row of the narrow blade plates 27B is larger than in the above-described embodiment.

In the modification shown in FIG.
A has a different width (that is, a different amount of protrusion to the inner peripheral side)
There are two types of blade plates 27AL and 27S, and the two types of blade plates 27AL and 27S are alternately arranged. Thereby, the air in the internal space 49 is easily taken into the gap between the wide blades 27A.

In addition, the specific configuration of the centrifugal fan unit 23 may be combined with the features of the above-described modification,
For example, simplification such as omitting the baffle plate 53 or providing a “third centrifugal fan” using a narrower blade plate near the outer periphery on the tip side of the “second centrifugal fan” Various modifications can be considered.

FIG. 14 shows a blower using the multi-blade fan 21 according to the above embodiment, which is partially cut away.

The blower 61 is, for example, an air conditioner indoor unit, a warm air indoor heater, an air curtain generator, a wall-mounted bathroom clothes dryer, or an air purifier. The outer case 63 sucks air. It has a suction port 65 and an air outlet 67 for discharging air. An air passage is formed in the outer case 63, and the multi-blade fan 21 according to the present invention is arranged in the air passage. Although not shown in FIG. 14, the multi-blade fan 21 is housed in a casing 29 as shown in FIG. 3, and the blowing passage 31 formed by the casing 29 It is connected to the exit 67. A heat exchanger for heating or cooling air, a heater, a cooler, a purifying unit for purifying air, ozone, at a point 69 on the upstream side or a point 71 on the downstream side of the multi-blade fan 21 along the air flow path. An air processor according to the purpose of each blower, such as a generation unit or an ion generation unit, is arranged.

Although the embodiments of the present invention have been described above, these embodiments are merely examples for describing the present invention, and are not intended to limit the present invention only to these embodiments. Therefore, the present invention can be implemented in various forms other than the above-described embodiment.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conventional general once-through fan.

FIG. 2 is an overall configuration diagram of a multi-blade fan using a conventional centrifugal fan.

FIG. 3 is an overall configuration diagram of a multi-blade fan according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view of the same embodiment taken along line AA of FIG. 3;

FIG. 5 is a sectional view of the same embodiment taken along line BB of FIG. 3;

FIG. 6 is a sectional view taken along a rotation axis of the centrifugal fan unit constituting the embodiment;

FIG. 7 is a sectional view of the centrifugal fan unit taken along line CC of FIG. 6;

FIG. 8 is a sectional view of the centrifugal fan unit taken along line DD of FIG. 6;

FIG. 9 is a sectional view showing a first modification of the centrifugal fan unit.

FIG. 10 is a sectional view showing a second modification of the centrifugal fan unit.

FIG. 11 is a sectional view showing a third modification of the centrifugal fan unit.

FIG. 12 is a sectional view showing a fourth modification of the centrifugal fan unit.

FIG. 13 is a sectional view showing a fifth modification of the centrifugal fan unit.

FIG. 14 is a perspective view of a blower using the multi-blade fan of the present invention.

[Explanation of symbols]

 Reference Signs List 21 multi-blade fan 23 multi-blade centrifugal fan unit 27 blade 25 rotating mandrel 27A wide blade (first blade) 27B narrow blade (second blade) 29 casing 31 blow-out channel 33 suction flow Road 35 Suction hole (air suction opening) 53 Baffle plate 61 Blower

Claims (12)

[Claims] 1. A plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space therebetween, and a casing accommodating the connected plurality of multi-blade centrifugal fan units, wherein the casing Forms a blowing channel for blowing air discharged from the plurality of multi-blade centrifugal fan units to the outside, and the blowing channel is continuous common for the plurality of multi-blade centrifugal fan units. Multi-blade fan that is the flow path of. 2. The casing has a scroll plate,
The multi-blade centrifugal fan unit according to claim 1, wherein the scroll plate individually covers the outer periphery of each of the multi-blade centrifugal fan units except for the air suction opening and the blow-out channel of each of the multi-blade centrifugal fan units. Tsubasa fan. 3. At least one of the plurality of centrifugal fan units includes a plurality of first blade plates arranged in a cylindrical shape with the rotation axis as a central axis, and has a relatively small inner peripheral diameter. 1
A second centrifugal fan having a relatively large inner peripheral diameter, the second centrifugal fan having a plurality of second blade plates arranged in a cylindrical shape around the rotation axis.
The multi-blade fan according to claim 1, further comprising: a centrifugal fan, wherein the second centrifugal fan is attached to a tip of the first centrifugal fan. 4. The multi-blade fan according to claim 3, wherein said second blade has a narrower width than said first blade. 5. A gap between the first blades and the second blade.
The multi-blade fan according to claim 3, wherein the width of the gap between the blade plates is in the range of 1 to 3 mm. 6. A front end surface of the first centrifugal fan has a surface inclined with respect to the rotation axis so as to go from the front end side to the base end side from the inner peripheral side to the outer peripheral side. The multi-blade fan according to claim 3, wherein the second blade plate is arranged near an outer periphery on an inclined surface. 7. The multi-blade fan according to claim 3, further comprising an annular air guide plate joined to at least a part of a front end surface of said first centrifugal fan. 8. The multi-blade fan according to claim 1, wherein each of the plurality of centrifugal fan units has a rotating mandrel having a circular cross section centered on the rotating shaft, and is interconnected by the rotating mandrel. . 9. A plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space therebetween, wherein at least one of the plurality of centrifugal fan units is a cylinder having the rotation axis as a central axis. Having a relatively small inner peripheral diameter, having a large number of first blades arranged in a circle
A second centrifugal fan having a relatively large inner peripheral diameter, the second centrifugal fan having a plurality of second blade plates arranged in a cylindrical shape around the rotation axis.
And a centrifugal fan, wherein the second centrifugal fan is attached to a tip of the first centrifugal fan. 10. A centrifugal fan unit comprising a plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space therebetween, wherein at least one of the plurality of centrifugal fan units has a plurality of centrifugal fans having different inner peripheral diameters. A multi-blade fan having a fan and a centrifugal fan having a relatively small inner peripheral diameter and another centrifugal fan having a relatively large internal diameter attached to the distal end side. 11. An air passage having an air inlet and an air outlet, a multi-blade fan disposed in the air passage, a casing accommodating the multi-blade fan, and an air passage in the air passage. The multi-blade fan includes a plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space therebetween, and the casing includes the multi-blade fan. A blowing device, wherein a blowing channel for guiding air discharged from a fan to the air outlet is formed, and the discharging channel is a continuous common channel for the plurality of multiblade centrifugal fan units. 12. An air flow path having an air inlet and an air outlet, a multi-blade fan disposed in the air flow path, and an air processor disposed in the air flow path. The multi-blade fan has a plurality of multi-blade centrifugal fan units connected along the same rotation axis with a space therebetween, and at least one of the plurality of centrifugal fan units has a center axis about the rotation axis. A first having a relatively small inner peripheral diameter, having a plurality of first blades arranged in a cylindrical shape formed in a cylindrical shape;
A second centrifugal fan having a relatively large inner peripheral diameter, the second centrifugal fan having a plurality of second blade plates arranged in a cylindrical shape around the rotation axis.
And a centrifugal fan, wherein the second centrifugal fan is attached to a tip of the first centrifugal fan.