阅读说明：本技术 离心式鼓风机 (Centrifugal blower ) 是由 宇佐美宏行 酒井雅晴 小坂翔 神谷洋平 于 2016-12-14 设计创作，主要内容包括：一种离心式鼓风机,该离心式鼓风机包括旋转轴(20)、叶轮(3)、壳体。叶轮包括多个叶片(31)和侧板(32)。壳体容纳叶轮并且包括定位成邻近于侧板的进气部(41)。进气部包括下游端部(411)和内壁表面(412)。侧板包括上游端部(321)和内板表面(323),该内板表面是侧板的内表面。下游端部和上游端部在一定角度范围内彼此间隔地面对。进气部的内壁表面的最小内径(Db)和内板表面的最小内径(Ds)之间的差异在该角度范围内小于或者等于侧板的厚度。(A centrifugal blower includes a rotary shaft (20), an impeller (3), and a housing. The impeller includes a plurality of blades (31) and a side plate (32). The housing houses the impeller and includes an air intake (41) positioned adjacent to the side plate. The intake portion includes a downstream end portion (411) and an inner wall surface (412). The side plate includes an upstream end portion (321) and an inner plate surface (323) that is an inner surface of the side plate. The downstream end portion and the upstream end portion face each other at a distance in a certain angular range. The difference between the minimum inner diameter (Db) of the inner wall surface of the air intake portion and the minimum inner diameter (Ds) of the inner plate surface is less than or equal to the thickness of the side plate within the angular range.)

1. A centrifugal blower, comprising:

a rotating shaft (20);

an impeller (3) that has a cylindrical shape and rotates around an axis (C L) of the rotating shaft so as to suck air in an axis direction (AX) of the rotating shaft and discharge the air outward in a Radial Direction (RD) of the rotating shaft, the impeller including a plurality of blades (31) and a side plate (32), the plurality of blades (31) being arranged radially around the axis of the rotating shaft, the side plate (32) having an annular shape and connecting end portions of the plurality of blades in the axis direction of the rotating shaft, and

a housing (4), the housing (4) housing the impeller and including an air intake portion (41), the air intake portion (41) being positioned adjacent to the side plate, the air intake portion having a bell mouth shape through which drawn air is guided to an inside of the impeller; wherein

The air intake portion includes: a downstream end portion (411), the downstream end portion (411) being an end portion of the intake portion that is downstream of an airflow; and an inner wall surface (412), the inner wall surface (412) being located inside the air intake portion in the radial direction of the rotation shaft;

the side plate includes: an upstream end portion (321), the upstream end portion (321) being an end portion of the side plate located upstream of the air flow; and an inner plate surface (323), the inner plate surface (323) being an inner surface of the side plate located inside the side plate in the radial direction of the rotation shaft;

the downstream end portion and the upstream end portion face each other at a spacing in the axial direction of the rotary shaft at least within a certain angular range (SE1) in a direction of rotation (CD);

a difference between a minimum inner diameter (Db) of the inner wall surface of the intake portion and a minimum inner diameter (Ds) of the inner panel surface is smaller than or equal to a thickness of the side panel at least in the angular range;

the centrifugal blower further includes a deflecting passage (5) between the air intake portion and the side plate, the deflecting passage (5) deflecting a direction of a backflow flowing through a gap between the downstream end portion and the upstream end portion toward an air intake side of the impeller to be deflected closer to a main flow flowing from the air intake portion toward the air intake side of the impeller;

a portion of the downstream end portion (411) facing the upstream end portion (321) of the side plate (32) is inclined at an acute angle to intersect with the inner wall surface (412).

2. The centrifugal blower of claim 1, wherein,

said deflection channel including said gap between said downstream end and said upstream end; and is

The downstream end portion includes a downstream end surface facing the upstream end portion, the downstream end surface being inclined toward the inner wall surface such that a radius of the downstream end surface with respect to the rotational axis decreases in a downstream direction of the main flow.

3. The centrifugal blower of claim 2, wherein the upstream end portion includes an upstream end surface facing the downstream end portion, the upstream end surface being inclined toward the inner plate surface such that a radius of the upstream end surface with respect to the rotational axis increases in an upstream direction of the main flow.

Technical Field

The present invention relates to a centrifugal blower that sucks in internal air from one side in an axial direction of a rotating shaft and discharges the sucked air outward in a radial direction of the rotating shaft.

Background

Conventionally, a centrifugal blower in which air leakage from a gap between a bell mouth and a cover of a centrifugal fan is reduced in order to reduce separation noise on a negative pressure surface of a blade due to interference of a main flow has been proposed (for example, refer to patent document 1: JP2001-115991 a). Patent document 1 discloses a labyrinth seal portion provided in a portion of an intake side end portion of a bell mouth in a region of a shroud facing a negative pressure surface of a vane.

Disclosure of Invention

According to the study of the inventors of the present invention, in patent document 1, the cover is positioned radially outside the bell mouth, and a head difference is formed between the bell mouth and the cover in the radial direction. Thus, the air flowing along the inner surface of the bell mouth is separated therefrom at the downstream end of the bell mouth, and the air may not flow along the inner surface of the cover. Accordingly, turbulence is generated in the air flowing from the surface of the bell mouth into the vicinity of the shroud of the fan. When the air moves to the downstream side of the fan, turbulence increases and may cause an increase in noise and a decrease in blowing efficiency.

An object of the present invention is to provide a centrifugal blower capable of reducing noise and improving blowing efficiency.

According to an aspect of the invention, a centrifugal blower comprises: a rotating shaft; an impeller that has a cylindrical shape and rotates around an axis of the rotary shaft so as to suck internal air in an axis direction of the rotary shaft and discharge the air outward in a radial direction of the rotary shaft, the impeller including a plurality of blades arranged radially around the axis of the rotary shaft and a side plate having an annular shape and connecting end portions of the plurality of blades in the axis direction of the rotary shaft; and a housing that houses the impeller and includes an air intake portion positioned adjacent to the side plate, the air intake portion having a bell mouth shape through which the drawn air is guided to an inside of the impeller. The air intake portion includes: a downstream end portion that is an end portion of the air intake portion located downstream of the air flow; and an inner wall surface located inside the air intake portion in a radial direction of the rotation shaft. The side plate includes: an upstream end portion which is an end portion of the side plate located upstream of the air flow; and an inner plate surface that is an inner surface of the side plate located inside the side plate in a radial direction of the rotation axis. The downstream end portion and the upstream end portion face each other at a spacing in the axial direction of the rotary shaft at least within a certain angular range in the rotational direction. The difference between the minimum inner diameter of the inner wall surface of the air intake portion and the minimum inner diameter of the inner plate surface is smaller than or equal to the thickness of the side plate at least in the angular range.

Thus, since the difference between the minimum inner diameter of the inner wall surface of the air intake portion and the minimum inner diameter of the inner panel surface is smaller than or equal to the thickness of the side panel at least in the angular range, there is substantially no head difference in the radial direction between the inner wall surface of the air intake portion and the inner panel surface portion of the side panel. Therefore, the air flowing along the intake portion can smoothly flow to the side plate. Thereby, the centrifugal blower can reduce noise and improve blowing efficiency. The air intake portion having a bell mouth shape means a bell mouth-shaped air intake portion in which the diameter of the air intake portion becomes larger toward the upstream side of the airflow.

Drawings

The invention, together with additional objects, features and advantages thereof, will best be understood from the following description, the appended claims and the accompanying drawings, in which:

fig. 1 is a sectional view taken in an axial direction illustrating a centrifugal blower according to a first embodiment of the invention;

fig. 2 is a sectional view illustrating a centrifugal blower according to the first embodiment;

fig. 3 is a sectional view illustrating a centrifugal blower according to the first embodiment;

fig. 4 is a sectional view illustrating a centrifugal blower according to a comparative example;

fig. 5 is a sectional view illustrating a centrifugal blower according to the first embodiment;

FIG. 6 is a graph showing the relationship between the air flow rate and the air blowing efficiency of the centrifugal blowers of the first embodiment and the comparative example;

fig. 7 is a graph showing a relationship between an air flow rate and a specific noise level (specific noise level) of the centrifugal blowers of the first embodiment and the comparative example;

fig. 8 is a sectional view illustrating a centrifugal blower according to a first modification of the first embodiment;

fig. 9 is a sectional view illustrating a centrifugal blower according to a first modification of the first embodiment;

fig. 10 is a sectional view illustrating a centrifugal blower according to a second modification of the first embodiment;

fig. 11 is a sectional view illustrating a centrifugal blower according to a second modification of the first embodiment;

fig. 12 is a sectional view illustrating a centrifugal blower according to a second embodiment;

fig. 13 is a sectional view illustrating a centrifugal blower according to a second embodiment;

fig. 14 is a sectional view illustrating a centrifugal blower according to a second embodiment;

fig. 15 is a sectional view illustrating a centrifugal blower according to a second embodiment;

fig. 16 is a sectional view illustrating a centrifugal blower according to a third embodiment;

fig. 17 is a sectional view illustrating a centrifugal blower according to a third embodiment;

fig. 18 is a sectional view illustrating a centrifugal blower according to a fourth embodiment;

FIG. 19 is a sectional view taken along line XIX-XIX of FIG. 18;

fig. 20 is a top view illustrating the centrifugal blower as viewed in the direction of arrow XX of fig. 18;

fig. 21 is a top view illustrating a centrifugal blower according to the first embodiment;

fig. 22 is a sectional view taken along line XXII-XXII of fig. 21;

fig. 23 is a sectional view taken along line XXIII-XXIII of fig. 21;

fig. 24 is a sectional view taken along line XXIV-XXIV of fig. 20;

fig. 25 is a sectional view taken along line XXV-XXV of fig. 20; and

fig. 26 is a sectional view illustrating a centrifugal blower according to the fourth embodiment.

Detailed Description

Embodiments of the present invention will be explained hereinafter with reference to the accompanying drawings. In these embodiments, portions corresponding to the matters described in the previous embodiments may be assigned the same reference numerals, and repeated descriptions for the portions may be omitted. While only a part of the configuration is explained in the embodiment, another previous embodiment may be applied to other parts of the configuration. These parts may be combined even if there is no explicit indication that these parts may be combined. These embodiments may be partially combined if there is no harm in the combination, even if it is not explicitly stated that these embodiments may be combined.

(first embodiment)

The first embodiment will be explained below with reference to fig. 1 to 7. The centrifugal blower 1 of the present embodiment shown in fig. 1 is used in an air blowing unit that sends air to an internal unit of an air conditioning apparatus such as a vehicle.

The centrifugal blower 1 includes a motor 2 having a rotary shaft 20, an impeller 3 rotationally driven by the motor 2 to discharge air, and a casing 4 housing the impeller 3, arrow AX shown in fig. 1 indicates an axial direction along an axis C L of the rotary shaft 20, arrow CD shown in fig. 2 indicates a rotational direction of the rotary shaft 20, arrow RD shown in fig. 2 indicates a radial direction perpendicular to the axial direction AX of the rotary shaft 20, which are the same in other drawings.

The impeller 3 has a cylindrical shape and rotates about an axis C L of the rotating shaft 20 the impeller 3 includes a plurality of blades 31 arranged radially about the rotating shaft 20, a side plate 32 having a circular ring shape and connecting end portions of the plurality of blades on one side in the axis direction AX, and a main plate 33 having a disk shape and connecting end portions of the plurality of blades on the other side in the axis direction AX.

The impeller 3 of the present embodiment includes a multi-blade centrifugal fan (sirocco fan) in which each of the blades 31 is a forward curved blade the blades 31 are radially arranged about the axis C L of the rotary shaft 20.

The side plate 32 is formed of a circular ring-shaped member having an opening at a central portion. In order to reduce the weight, the thickness Th of the side plate 32 of the present embodiment is set within 1-3mm, for example.

The side plate 32 of the present embodiment includes: a first end 321, which is the end upstream of the gas flow; and a second end 322, which is the end located downstream of the gas flow. In addition, the side plate 32 includes: an inner plate surface portion 323 that is an inner surface in the radial direction RD of the rotary shaft 20; and an outer surface portion 324, which is an outer surface in the radial direction RD. In the present embodiment, the first end 321 of the side plate 32 is the upstream end. The side plate 32 is connected to an end portion of the blade 31 on one side in the axial direction AX. The inner panel surface portion 323 may be an inner panel surface of the side panel 32.

The inner plate surface portion 323 defines a guide opening that guides air drawn from the air intake portion 41 of the housing 4 into the impeller 3. The inner plate surface portion 323 of the present embodiment is inwardly convex in the radial direction RD of the rotary shaft 20 so that the air sucked in the axial direction AX of the rotary shaft 20 is outwardly directed in the radial direction RD of the rotary shaft 20. Specifically, the radius of the inner panel surface portion 323 gradually increases in size from the first end 321 toward the second end 322. In the present embodiment, the radius at the first end 321 is the smallest in the inner panel surface portion 323.

The main plate 33 is connected to the rotation shaft 20 at a central portion thereof. A portion of the main plate 33 facing the side plate 32 is connected to an end portion of the other side of the blade 31 in the axial direction AX. The main plate 33 of the present embodiment has a flat circular shape. The main plate 33 may have a conical shape that is convex toward the side plate 32 in the axis direction AX.

The housing 4 accommodates the impeller 3. The housing 4 of the present embodiment is a scroll-shaped housing defining an air flow channel 40 having a spiral shape outside the impeller 3. The housing 4 includes an air intake portion 41 having a bell mouth shape and guiding air into the impeller 3.

The intake portion 41 is provided in a portion of the case 4 on one side in the axial direction AX, the portion being adjacent to the side plate 32 of the impeller 3. The intake portion 41 includes: a downstream end 411, which is the end located downstream of the gas flow; and an inner wall surface portion 412 which is an inner wall in the radial direction RD of the rotation shaft 20. The inner wall surface portion 412 may be an inner wall surface of the air intake portion 41.

The intake portion 41 of the present embodiment is provided in the case 4 such that the downstream end portion 411 is spaced from the first end portion 321 of the side plate 32 in the axial direction AX and faces the first end portion 321. Therefore, the intake portion 41 does not overlap the side plate 32 in the radial direction RD of the rotary shaft 20.

The inner wall surface portion 412 is inwardly convex to guide air into the impeller 3. Specifically, the radius of the inner wall surface portion 412 is gradually reduced in size from the upstream side toward the downstream end portion 411 of the gas flow. In the present embodiment, the radius at the downstream end 411 of the intake portion 41 is the smallest in the inner wall surface portion 412.

In the centrifugal blower 1 of the present embodiment, there is substantially no head difference between the air intake portion 41 and the side plate 32 in the radial direction RD, thereby restricting separation of the main flow of air flowing from the air intake portion 41 toward the side plate 32. The separation may mean that air is separated from the intake portion 41 or the side panel 32.

As shown in fig. 2, the dimensional difference between the radius Db of the portion of the air intake part 41 having the smallest radius in the inner wall surface part 412 and the radius Ds of the portion of the side panel 32 having the smallest radius in the inner panel surface part 323 is set to be equal to or smaller than the thickness Th. of the side panel 32, the radius of the inner wall surface part 412 of the air intake part 41 means the distance (e.g., radius) from the inner wall surface part 412 of the air intake part 41 to the axis C L of the rotary shaft 20. the radius of the inner panel surface part 323 of the side panel 32 means the distance (e.g., radius) between the inner panel surface part 323 of the side panel 32 and the axis C L of the rotary shaft 20. the radius Db may be a first radius and the radius Ds may be a second radius in a cross section including the rotary shaft 20 taken in the axial direction, the first radius may be the smallest radius in the inner wall surface part 412, and in the cross section, the smallest radius Db may be the smallest inner diameter of the inner panel surface part 323.

In the present embodiment, as described above, a portion of the intake portion 41 having the smallest radius among the inner wall surface portions 412 is the downstream end portion 411, and a portion of the side plate 32 having the smallest radius among the inner plate surface portions 323 is the first end portion 321.

Thereby, the dimensional difference between the radius Db of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 is set to be equal to or smaller than the thickness Th of the side plate 32. The thickness Th of the side plate 32 is the thickness of a portion of the side plate 32 adjacent to the intake portion 41.

In the present embodiment, the radius Db of the downstream end portion 411 of the air intake portion 41 is set to be equal to or smaller than the radius Ds of the first end portion 321 of the side plate 32 in the entire dimension in the rotation direction CD. Specifically, the radius Db of the downstream end portion 411 of the air intake portion 41 is set to be substantially equal in overall size in the rotation direction CD to the radius Ds of the first end portion 321 of the side plate 32.

The air intake portion 41 and the side plate 32 are set such that a tangent to the air intake portion 41 at the downstream end 411 and a tangent to the side plate 32 at the first end 321 are substantially parallel. Specifically, in the present embodiment, a tangent to the intake portion 41 at the downstream end portion 411 and a tangent to the side plate 32 at the first end portion 321 are both set to extend along the axial direction AX of the rotary shaft 20. Thereby, even if the air flow separation occurs at the downstream end portion 411 of the air intake portion 41, the separated air flow can be reattached at the first end portion 321 of the side plate 32.

The intake side of the impeller 3 and the exhaust side of the impeller 3 communicate with each other through the gap between the intake portion 41 and the side plate 32. Therefore, the air discharged from the exhaust side of the impeller 3 can be returned to the intake side of the impeller 3 through the gap between the intake portion 41 and the side plate 32. In the present embodiment, the gap between the intake portion 41 and the side plate 32 is a return passage through which air flows from the exhaust side to the intake side of the impeller 3.

In the present embodiment, a portion of the downstream end portion 411 facing the first end portion 321 extends in the radial direction RD of the rotary shaft 20. The first end 321 of the side plate 32 of the present embodiment faces the downstream end 411 of the air intake portion 41 and extends in the radial direction RD of the rotary shaft 20. Thereby, the gap between the intake portion 41 and the side plate 32 as the return passage extends in the radial direction RD of the rotary shaft 20.

Next, the action of the centrifugal blower 1 of the present embodiment will be explained below. The impeller 3 of the centrifugal blower 1 rotates in accordance with the rotation of the rotary shaft 20 of the motor 2. Therefore, the air drawn into the impeller 3 from one side in the axial direction AX of the rotary shaft 20 is discharged outward in the radial direction RD of the rotary shaft 20 by the centrifugal force, as shown in fig. 3.

Fig. 4 illustrates the air flow near the side plate 32 of the centrifugal blower CE according to the comparative example of the present invention. The centrifugal blower CE is different from the centrifugal blower 1 of the present embodiment in that: the side plate 32 is positioned outside the intake portion 41 in the radial direction RD.

In the centrifugal blower CE of the comparative example, air is drawn from one side of the axis direction AX of the rotary shaft 20 into the impeller 3 by the rotation of the impeller 3. In the centrifugal blower CE of the comparative example, since there is no large head difference between the intake portion 41 and the side plate 32 in the radial direction RD, the air flowing along the surface of the intake portion 41 is separated at the downstream end portion 411 of the intake portion 41. Thereby, turbulence including parallel vortices is generated in the air flowing from the surface of the intake portion 41 into the vicinity of the side plate 32 of the impeller 3. As the airflow moves to the downstream side of the impeller 3, turbulence increases. Therefore, noise may be increased, and blowing efficiency may be reduced. A parallel vortex is a vortex having a central axis of rotation that intersects the flow direction of the main flow of air.

On the other hand, in the centrifugal blower 1 of the present invention, the dimensional difference between the radius Db of the portion having the smallest dimension in the inner wall surface portion 412 of the air intake portion 41 and the radius Ds of the portion having the smallest dimension in the inner plate surface portion 323 of the side plate 32 is set to be equal to or smaller than the thickness Th.

Therefore, in the centrifugal blower 1 of the present embodiment, the air flowing along the surface of the air intake portion 41 reattaches to the side plate 32 after separating from the downstream end portion 411 of the air intake portion 41, as shown in fig. 5. The airflow near the side panel 32 flows along the side panel 32 without being separated from the side panel 32. In the centrifugal blower 1 of the present embodiment, the air flowing along the air intake portion 41 can smoothly flow to the side plate 32.

Fig. 6 is a graph showing the relationship between the discharged air amount and the air blowing efficiency of the centrifugal blower 1 of the present embodiment and the centrifugal blower CE of the comparative example. In fig. 6, the air blowing efficiency of the centrifugal blower CE of the comparative example is illustrated by a solid line a, and the air blowing efficiency of the centrifugal blower 1 of the present embodiment is illustrated by a broken line B.

Fig. 7 is a graph showing a relationship between the amount of air discharged and a specific noise level of the centrifugal blower 1 of the present embodiment and the centrifugal blower CE of the comparative example. In fig. 7, the specific noise level of the centrifugal blower CE of the comparative example is illustrated by a solid line a, and the specific noise level of the centrifugal blower 1 of the present embodiment is illustrated by a broken line B.

As shown in fig. 6, the blowing efficiency of the centrifugal blower 1 of the present embodiment is higher than that of the centrifugal blower CE of the comparative example over the entire range of the discharged air amount. As shown in fig. 7, the centrifugal blower 1 of the present embodiment generates less noise over the entire range of the air volume than the noise generated by the centrifugal blower CE of the comparative example. The centrifugal blower 1 of the present embodiment can reduce noise and improve blowing efficiency.

In the centrifugal blower 1 of the present embodiment, the difference in size between the radius of a portion of the inner wall surface portion 412 of the air intake portion 41 having the smallest radius of the inner wall surface portion 412 and the radius of a portion of the inner plate surface portion 323 of the side plate 32 having the smallest radius of the inner plate surface portion 323 is equal to or smaller than the thickness Th of the side plate 32, as described above.

Thereby, there is substantially no head difference in the radial direction RD between the inner wall surface portion 412 of the intake portion 41 and the inner plate surface portion 323 of the side plate 32. Accordingly, the air flowing along the intake portion 41 can smoothly flow to the side plate 32. Therefore, according to the centrifugal blower 1 of the present embodiment, it is possible to reduce noise and improve air blowing efficiency.

Further, in the centrifugal blower 1 of the present embodiment, the radius Db of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 are set to be equal in size to each other. Accordingly, since the air flowing along the intake portion 41 is prevented from impacting the side plate 32, the air flowing along the intake portion 41 can flow more smoothly to the side plate 32.

(first modification of the first embodiment)

A first modification of the first embodiment will be explained below with reference to fig. 8 and 9. In the first modification, the radius of a portion of the inner wall surface portion 412 having the smallest radius is different in size from the radius of a portion of the inner panel surface portion 323 having the smallest radius.

In this modification, the radius Db of the downstream end portion 411 of the air intake portion 41 is set smaller than the radius Ds of the first end portion 321 of the side plate 32 (Db < Ds), as shown in fig. 8. Also in this modification, the dimensional difference Δ D between the radius of the portion having the smallest radius in the inner wall surface portion 412 of the intake portion 41 and the radius of the portion having the smallest radius in the inner plate surface portion 323 of the side panel 32 is set to be equal to or smaller than the thickness Th of the side panel 32.

The other configuration is the same as that of the first embodiment. In the centrifugal blower 1 of this modification, the air flowing along the surface of the air intake portion 41 reattaches to the side plate 32 after separating from the downstream end portion 411 of the air intake portion 41, and the air flows along the side plate 32 without separating from the side plate 32, as shown in fig. 9. Thereby, the centrifugal blower 1 of this modification can also reduce noise and improve air blowing efficiency.

(second modification of the first embodiment)

In the second modification of the present embodiment, the shapes of the inner wall surface portion 412 and the inner panel surface portion 323 of the side panel 32 are modified, as shown in fig. 10 and 11.

In the intake portion 41 of this modification, a portion of the inner wall surface portion 412 having the smallest radius is positioned upstream of the downstream end portion 411, as shown in fig. 10. Thus, the radius of the downstream end portion 411 is larger than the radius of a portion of the inner wall surface portion 412 located upstream of the downstream end portion 411.

In the side panel 32 of this modification, a portion of the inner panel surface portion 323 having the smallest radius is positioned between the first end 321 and the second end 322. Thus, in the inner panel surface part 323 of this modification, the radius of the first end 321 or the second end 322 of this modification is larger than the radius of a portion between the first end 321 and the second end 322.

The difference in size between the radius Db of the portion having the smallest radius in the inner wall surface portion 412 of the air intake part 41 and the radius Ds of the portion having the smallest radius in the inner panel surface portion 323 of the side panel 32 is set to be equal to or smaller than the thickness Th of the side panel 32.

In this modification, a tangent to the intake portion 41 at a portion having the smallest radius in the inner wall surface portion 412 and a tangent to the side plate 32 at a portion having the smallest radius in the inner plate surface portion 323 are set to be substantially parallel to each other. Specifically, in this modification, both a tangent to a portion having the smallest radius in the inner wall surface portion 412 and a tangent to a portion having the smallest radius in the inner panel surface portion 323 are set to extend in the direction along the axial direction AX of the rotary shaft 20.

The other configuration of this modification is the same as that of the first embodiment. The air flowing along the intake portion 41 is reattached to the side plate 32 after being separated from the downstream end portion 411 of the intake portion 41, and the air flows along the side plate 32 without being separated from the side plate 32, as shown in fig. 11. Thereby, the centrifugal blower 1 of this modification can reduce noise and improve air blowing efficiency.

(second embodiment)

A second embodiment of the present invention will be explained below with reference to fig. 12 and 13. In the present embodiment, the direction of the backflow flowing in the gap between the intake portion 41 and the side plate 32 is deflected to be closer to the direction of the main flow.

In the centrifugal blower 1 of the present embodiment, the deflecting passage 5 is provided between the air intake portion 41 and the side plate 32, as shown in fig. 12. The deflecting passage 5 deflects the backflow flowing through the gap between the downstream end 411 of the intake portion 41 and the first end 321 of the side plate 32 so that the direction of the backflow becomes closer to the direction of the main flow. This backflow is an airflow from the gap between the downstream end portion 411 of the intake portion 41 and the first end portion 321 of the side plate 32 toward the intake side of the impeller 3. The main flow is an airflow from the intake portion 41 to the intake side of the impeller 3.

The deflection channel 5 comprises: an upstream passage 51 defined between the outer surface portion 324 of the side plate 32 and the inner wall surface of the casing 4; and a downstream passage 52 defined between the downstream end 411 of the intake portion 41 and the first end 321 of the side plate 32.

The downstream end portion 411 of the air intake portion 41 according to this embodiment is inclined toward the inner wall surface portion 412 such that a radius of a part of the downstream end portion 411 is reduced in size toward the first end portion 321. A portion of the downstream end portion 411 facing the first end portion 321 of the side plate 32 is inclined at an acute angle to intersect the inner wall surface portion 412.

In the upstream passage 51 of the present embodiment, a part of the inner wall surface of the housing 4 connected to the downstream end portion 411 is inclined toward the inner wall surface portion 412, similarly to a part of the downstream end portion 411 facing the first end portion 321 of the side plate 32.

A portion of the first end 321 of the side plate 32 facing the downstream end 411 of the air intake portion 41 extends in the radial direction RD of the rotary shaft 20. Thereby, the cross-sectional area of the downstream passage 52 decreases in size toward the downstream side of the airflow.

The other configuration is the same as that of the first embodiment. In the centrifugal blower 1 of the present embodiment, the air flowing along the air intake portion 41 flows along the side plate 32 without being separated from the side plate 32, as shown in fig. 13.

In addition, in the centrifugal blower 1 of the present embodiment, the deflecting passage 5 is provided between the air intake portion 41 and the side plate 32, and the deflecting passage 5 deflects the backflow from the gap between the downstream end portion 411 of the air intake portion 41 and the first end portion 321 of the side plate 32 so that the backflow becomes closer to the main flow.

Therefore, the direction of the backflow from the gap between the intake portion 41 and the side plate 32 becomes the direction along the main flow, whereby interference of the main flow and the backflow can be restricted. Thereby, the air flow along the air intake portion 41 becomes able to smoothly flow to the side plate 32, and therefore it is possible to reduce noise and improve the air blowing efficiency.

(modification of the second embodiment)

In this modification, an example in which the deflecting channel 5 of the downstream channel 52 of the second embodiment is modified will be explained below with reference to fig. 14 and 15.

When the cross-sectional area of the downstream passage 52 is reduced in size toward the downstream side of the gas flow as described in the second embodiment, the passage of the backflow is throttled, whereby turbulence may be generated in the backflow. This can result in the main flow being disturbed when the main flow and the backflow are combined.

In this modification, a part of the first end portion 321 of the side plate 32 facing the downstream end portion 411 is inclined toward the inner plate surface portion 323, as shown in fig. 14. Specifically, the radius of a portion of the first end 321 facing the downstream end 411 of this modification increases in size toward the downstream end 411. A portion of the first end 321 of the side plate 32 facing the downstream end 411 is inclined to intersect the inner panel surface portion 323 at an obtuse angle. Thus, the downstream passage 52 has a cross section whose area size on the upstream side is similar to that on the downstream side.

The other configuration is the same as that of the second embodiment. In the centrifugal blower 1 of this modification, the air flowing along the surface of the air intake portion 41 flows along the side plate 32 without being separated from the side plate 32, as shown in fig. 15.

In the centrifugal blower 1 of this modification, the downstream passage 52 of the deflecting passage 5 has a cross section whose area size on the upstream side is similar to that on the downstream side. Since the turbulence of the backflow flowing through the gap between the intake portion 41 and the side plate 32 is restricted, the turbulence of the main flow generated when the main flow and the backflow are combined together can be effectively restricted.

(third embodiment)

A third embodiment will be explained below with reference to fig. 16 and 17. In the present embodiment, the shape of the deflection duct 5 is different from that of the second embodiment.

In the centrifugal blower 1 of the present embodiment, the upstream passage 51 of the deflecting passage 5 has a circular shape, and the upstream passage 51 is located between the outer surface portion 324 of the side plate 32 and the inner wall surface of the housing 4, as shown in fig. 16.

Specifically, the inner wall surface of the housing 4 defining the upstream passage 51 has a semicircular shape protruding to one side of the rotation shaft 20. The first end 321 of the side plate 32 facing the downstream end 411 of the air intake part 41 has a circular shape.

The other configuration is the same as that of the second embodiment. In the centrifugal blower 1 of the present embodiment, the air flowing along the surface of the air intake portion 41 flows along the side plate 32 without being separated from the side plate 32, as shown in fig. 17.

In the centrifugal blower 1 of the present embodiment, the upstream passage 51 of the deflecting passage 5 has a circular shape. Therefore, the backflow can smoothly flow into the upstream passage 51 of the deflecting passage 5. Since the turbulence of the backflow flowing through the gap between the intake portion 41 and the side plate 32 is restricted, the turbulence of the main flow generated when the main flow and the backflow are combined together can be effectively restricted.

(fourth embodiment)

A fourth embodiment will be explained below with reference to fig. 18 to 26. In the centrifugal blower 1A of the present embodiment, the difference in size between the radius of a portion of the inner wall surface portion 412 of the air intake portion 41 having the smallest radius of the inner wall surface portion 412 and the radius of a portion of the inner plate surface portion 323 of the side plate 32 having the smallest radius of the inner plate surface portion 323 is set to be equal to or smaller than the thickness Th of the side plate 32 in the rotational direction CD. A portion of the inner wall surface portion 412 and a portion of the inner panel surface portion 323 may face each other.

Similar to the centrifugal blower 1 of the first embodiment, the housing 4 of the centrifugal blower 1A according to this embodiment is a curl-shaped housing that includes a side wall portion 43, the side wall portion 43 defining the air flow passage 40 having a spiral shape outside the impeller 3, as shown in fig. 18 to 20. The housing 4 includes a nose 42 as a starting point of the airflow path.

The side wall portion 43 of the housing 4 extends from the curl start portion 431 to the curl end portion 432, which are positioned at the nose portion 42 of the side wall portion 43, such that the distance (radius) from the axis C L of the rotary shaft 20 increases in a logarithmic spiral shape, the cross-sectional area of the housing 4 increases in size from the curl start portion 431 of the side wall portion 43 toward the curl end portion 432, the curl start portion 431 may be a curl start point, and the curl end portion 432 may be a curl end point.

When the casing 4 is configured by a scroll-shaped casing as in the present embodiment, the distance between the trailing edge of the blade 31 of the impeller 3 and the side wall portion 43 increases from the curl start portion 431 toward the curl end portion 432. Specifically, the distance between the trailing edge of the blade 31 and the side wall portion 43 is shortest at the curl start portion 431 of the side wall portion 43 and greatest at the curl end portion 432.

Therefore, in the housing 4 of the present embodiment, a region where the air flow is likely to be disturbed and a region where the air flow on the exhaust side of the impeller 3 in the rotation direction CD is less likely to be disturbed are included.

For example, because the side wall portion 43 constitutes resistance to the airflow in the region SE1 extending from the curl start portion 431 to the intermediate portion 433 in the rotation direction CD, as shown in fig. 19 and 20, the airflow on the exhaust side of the impeller 3 may generate turbulence. The middle portion 433 may be a middle point.

On the other hand, since the side wall portion 43 hardly constitutes resistance to the airflow in the area SE2 from the intermediate portion 433 to the curl end portion 432, as shown in fig. 19 and 20, the airflow on the exhaust side of the impeller 3 is less likely to generate turbulence.

As described in the first embodiment, the centrifugal blower 1 of the first embodiment can reduce noise and improve air blowing efficiency as compared with the centrifugal blower CE of the comparative example.

In order to further reduce the noise, the inventors of the present invention made studies on the loudness of the noise generated in the centrifugal blower 1. As a result, the inventors found that the noise in the vicinity of the curl end portion 432 of the side wall portion 43 as shown in fig. 21 is larger than the noise in the area SE1 extending from the curl start portion 431 to the intermediate portion 433 of the side wall portion 43 in the rotation direction CD.

Next, the inventors made studies on the air flow in the region SE1 extending from the curl start portion 431 to the middle portion 433 of the side wall portion 43 in the rotation direction CD and in the vicinity of the curl end portion 432 of the side wall portion 43.

As a result, the inventors found that, in the centrifugal blower 1 of the first embodiment, the air flowing into the vicinity of the surface of the air intake portion 41 flows along the side plate 32 in the area SE1 extending from the curl start portion 431 of the side wall portion 43 in the rotational direction CD, as shown in fig. 22.

The inventors further found that, in the region SE1 extending from the curl start portion 431 of the side wall portion 43 to the intermediate portion 433 in the rotation direction CD, a part of the air discharged from the exhaust side of the impeller 3 easily flows back to the intake side of the impeller 3 through the gap between the intake portion 41 and the side plate 32. This is because, as described above, the side plate 32 constitutes resistance to the airflow in the region SE1 extending from the curl start portion 431 to the intermediate portion 433 in the rotation direction CD.

On the other hand, the inventors found that the air flowing into the vicinity of the surface of the intake portion 41 flows along the side plate 32 in the vicinity of the curl end portion 432 of the side wall portion 43.

In addition, the inventors found that a part of the air flowing into the vicinity of the surface of the intake portion 41 easily flows to the exhaust side of the impeller 3 through the gap between the intake portion 41 and the side plate 32 in the vicinity of the curl end portion 432 of the side wall portion 43. This is because the number of elements constituting the resistance on the exhaust side of the impeller 3 in the vicinity of the curl end portion 432 of the side wall portion 43 is small compared to the region SE1 extending from the curl start portion 431 to the intermediate portion 433 of the side wall portion 43 in the rotation direction CD.

The inventors have further found that the air flowing into the vicinity of the intake portion 41 and the air flowing through the gap between the intake portion 41 and the side plate 32 easily collide with each other in the separation area DA where the airflow near the side plate 32 may be separated. Air flow collisions like this may cause noise.

According to the study of the inventors of the present invention, the direction of the air flowing through the gap between the intake portion 41 and the side plate 32 is easily changed according to the rotation direction CD.

According to the results of the investigation by the inventors of the present invention, it is inferred that noise may be large in the vicinity of the curled ending portion 432 of the side wall portion 43 because the airflows that are opposite to each other collide with each other in the separation region DA.

In the centrifugal blower 1A of the present embodiment, there is substantially no head difference in the radial direction RD between the air intake portion 41 and the side plate 32 in the rotational direction.

Specifically, in the centrifugal blower 1A according to the present embodiment, in the region SE1 extending from the curl start portion 431 to the intermediate portion 433 of the side wall portion 43 in the rotational direction CD, there is substantially no head difference between the air intake portion 41 and the side plate 32 in the radial direction RD, as shown in fig. 19 and 20. In the centrifugal blower 1A of the present embodiment, in the region SE1 extending from the curl start portion 431 to the intermediate portion 433 of the side wall portion 43 in the rotational direction CD, the difference in size between the radius Db1 of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 is equal to or smaller than the thickness Th of the side plate 32.

On the other hand, in the centrifugal blower 1A of the present embodiment, there is no head difference in the radial direction RD between the air intake portion 41 and the side plate 32 in a part in the rotation direction CD of the rotary shaft 20.

Specifically, in the vicinity of the curl end portion 432 of the side wall portion 43 of the centrifugal blower 1A according to the present embodiment as shown in fig. 19 and 20, there is a head difference between the air intake portion 41 and the side plate 32, as shown in fig. 25. In the vicinity of the curl end portion 432 of the side wall portion 43 of the centrifugal blower 1A according to the present embodiment, the difference in size between the radius Db2 of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 is larger than the thickness Th of the side plate 32. The radius Db2 of the downstream end 411 of the intake portion 41 is sized smaller than the radius Ds of the first end 321 of the side plate 32.

In the centrifugal blower 1A according to the present embodiment, in the region SE2 from the intermediate portion 433 of the side wall portion 43 to the vicinity of the curl end portion 432, the difference in size between the radius Db of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 continuously increases in the rotational direction CD of the rotary shaft 20.

In the centrifugal blower 1A according to the present embodiment, in the region extending from the curl end portion 432 to the curl start portion 431 of the side wall portion 43 in the rotational direction CD, the difference in size between the radius Db of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 continuously decreases in the rotational direction CD. The difference in size between the radius Db of the downstream end portion 411 of the intake part 41 and the radius Ds of the first end portion 321 of the side plate 32 may vary discontinuously, rather than continuously.

Next, the action of the centrifugal blower 1A of the present embodiment will be explained below with reference to fig. 26. In fig. 26, a cross section near the curl start portion 431 of the side wall portion 43 is shown on the right-hand side, and a cross section near the curl end portion 432 of the side wall portion 43 is shown on the left-hand side.

As shown in fig. 26, in the vicinity of the curl start portion 431 of the centrifugal blower 1A according to the present embodiment, the dimensional difference between the radius Db1 of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 is equal to or smaller than the thickness Th of the side plate 32.

Therefore, in the vicinity of the curl start portion 431 of the centrifugal blower 1A according to the present embodiment, the air flowing along the air intake portion 41 can smoothly flow to the side plate 32. In addition, in the vicinity of the curl start portion 431 of the centrifugal blower 1A according to the present embodiment, the airflow on the exhaust side of the impeller 3 flows back to the intake side of the impeller 3 through the gap between the intake portion 41 and the side plate 32.

In the vicinity of the curl end portion 432 of the centrifugal blower 1A according to the present embodiment, the dimensional difference between the radius Db2 of the downstream end portion 411 of the air intake portion 41 and the radius Ds of the first end portion 321 of the side plate 32 is larger than the side plate 32 thickness Th.

Thus, in the vicinity of the curl completion portion 432 of the side wall portion 43, the air flowing along the intake portion 41 is separated from the side plate 32, but the airflow in the vicinity of the surface of the intake portion 41 does not flow to the exhaust side of the impeller 3 through the gap between the intake portion 41 and the side plate 32. In the vicinity of the curl end portion 432 of the centrifugal blower 1A according to the present embodiment, air on the exhaust side of the impeller 3 flows back to the intake side of the impeller 3 through the gap between the intake portion 41 and the side plate 32.

The other configuration is the same as that of the first embodiment. Therefore, the centrifugal blower 1A can obtain the effects obtained by the same configuration as the first embodiment. In the centrifugal blower 1A according to the present embodiment, in the region SE1 extending from the curl start portion 431 to the intermediate portion 433 of the side wall portion 43 in the rotation direction CD, the difference in size between the radius of a portion of the inner wall surface portion 412 of the air intake portion 41 having the smallest radius of the inner wall surface portion 412 and the radius of a portion of the inner wall surface portion 323 of the side plate 32 having the smallest radius of the inner wall surface portion 323 is equal to or smaller than the thickness Th of the side plate 32.

Accordingly, in the region SE1 where turbulence of the air flow is likely to occur, extending from the curl start portion 431 of the side wall portion 43 to the intermediate portion 433 in the rotational direction CD, there is substantially no head difference in the radial direction RD between the inner wall surface portion 412 of the air intake portion 41 and the inner plate surface portion 323 of the side plate 32. Thereby, since the air flowing along the air intake portion 41 can smoothly flow to the side plate 32 in the region of the housing 4 where the turbulent flow of the air flow is likely to be generated, it is possible to reduce noise in the centrifugal blower 1A and improve the blowing efficiency.

In the centrifugal blower 1A of the present embodiment, in the vicinity of the curl end portion 432 of the side wall portion 43, the difference in size between the portion having the smallest radius in the air intake portion 41 and the portion having the smallest radius in the side plate 32 is larger than the difference in size in the region extending from the curl start portion 431 to the intermediate portion 433 in the rotational direction CD. A dimensional difference between a portion having the smallest radius in the intake portion 41 and a portion having the smallest radius in the side plate 32 in a cross section taken along the axial direction including the rotary shaft 20 and the curl end portion 432 is larger than the dimensional difference in a cross section taken along the axial direction including the rotary shaft 20 and a portion of the region SE 1.

In the vicinity of the curl end portion 432 of the side wall portion 43, there is a level difference in the radial direction RD between the inner wall surface portion 412 of the intake portion 41 and the inner plate surface portion 323 of the side plate 32. Therefore, the flow of air flowing to the exhaust side of the impeller 3 through the gap in the axial direction between the intake portion 41 and the side plate 32 in the vicinity of the intake portion 41 can be restricted. In the centrifugal blower 1A of the present embodiment, noise caused by collision of the air flows in the vicinity of the curl end portion 432 of the side wall portion 43 can be restricted. Thus, the centrifugal blower 1A of the present embodiment can reduce noise compared to the centrifugal blower 1 of the first embodiment.

In the vicinity of the curl end portion 432 of the centrifugal blower 1A according to the present embodiment, the difference in size between the radius of a portion of the inner wall surface portion 412 of the air intake portion 41 having the smallest radius of the inner wall surface portion 412 and the radius of a portion of the inner plate surface portion 323 of the side plate 32 having the smallest radius of the inner plate surface portion 323 is larger than the thickness Th of the side plate 32.

Accordingly, in the vicinity of the curl end portion 432 of the side wall portion 43, a difference in the radial direction RD between the inner wall surface portion 412 of the intake portion 41 and the inner plate surface portion 323 of the side plate 32 is larger than the thickness Th of the side plate 32. Therefore, the flow of air flowing to the exhaust side through the intake portion 41 and the side plate 32 near the surface of the intake portion 41 can be further restricted.

In the present embodiment, an example is explained in which, in the vicinity of the curl end portion 432, the difference in size between the radius of a portion having the smallest radius in the inner wall surface portion 412 and the radius of a portion having the smallest radius in the inner panel surface portion 323 is larger than the thickness Th of the side panel 32. However, the present invention is not limited thereto. For example, the difference in size between the radius of the portion having the smallest radius in the inner wall surface portion 412 and the radius of the portion having the smallest radius in the inner panel surface portion 323 may be equal to or smaller than the thickness Th of the side panel 32 as long as there is a head difference in the radial direction between the intake portion 41 and the side panel 32 in the vicinity of the curl end portion 432.

While the present invention has been fully described in connection with the preferred embodiments and with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art.

In the above-described embodiments, the centrifugal blower 1, 1A is used in the air blowing unit of the air conditioner for a vehicle. However, the present invention is not limited thereto. For example, the centrifugal blower 1, 1A may be used in a seat air conditioner of a vehicle. In addition, the centrifugal blower 1, 1A is not limited to use for vehicles, but may be used in stationary air conditioners or ventilators.

In the above-described embodiment, the impeller 3 is formed of a multi-blade centrifugal fan (sirocco fan) in which blades bent in the forward direction are used as the blades 31, but the impeller 3 is not limited thereto. The impeller 3 may be formed of a turbo fan using backward curved blades as each blade 31.

In the above embodiment, the case 4 is a curl-shaped case, however, the case 4 is not limited thereto. A 360 degree blow-off type housing 4 may be employed. When the housing 4 is configured by a 360-degree blow-off type housing, the direction of air flowing through the gap between the air intake portion 41 and the side plate 32 is less likely to change to the rotation direction of the rotation shaft 20. Therefore, when the housing 4 is constructed of a 360-degree blow-off type housing, it is preferable that there is substantially no head difference between the air intake portion 41 and the side plate 32 in the entire rotational direction, as in the first to third embodiments.

The radius Db of the downstream end portion 411 of the air intake portion 41 may preferably be equal to or smaller than the radius Ds of the first end portion 321 of the side plate 32, as in the first to third embodiments. However, the present invention is not limited thereto. The radius Db of the downstream end portion 411 may be set to a size larger than the radius Ds of the first end portion 321 as long as the size difference between the radius size of the minimum radius of the inner wall surface portion 412 and the radius size of the minimum radius of the inner panel surface portion 323 is equal to or smaller than the thickness Th.

A tangent to the downstream end portion 411 of the intake portion 41 and a tangent to the first end portion 321 of the side plate 32 may both be preferably set to extend in a direction along the axial direction AX of the rotary shaft 20. However, the present invention is not limited thereto. A tangent to the downstream end portion 411 of the intake portion 41 and a tangent to the first end portion 321 of the side plate 32 may both extend in a direction slightly inclined with respect to the axial direction AX of the rotary shaft 20.

In the second and third embodiments, the deflector channel 5 is provided between the intake portion 41 and the side plate 32. However, the present invention is not limited thereto. For example, a backflow restricting portion, such as a labyrinth seal, may be provided between the intake portion 41 and the side plate 32.

Except where expressly specified or clearly necessary in principle, it is needless to say that no components in the embodiments described above are necessary.

In the above-described embodiments, when the number, value, amount, numerical range, and the like of components are mentioned, it is not intended to be limited to a specific number except in a case where it is obvious that the components are limited to the specific number in principle or where it is necessary to explicitly describe.

Further, in the above-described embodiments, when the shape, positional relationship, and the like of the components are mentioned, it is not intended to be limited to a specific shape or positional relationship except in the case where the components are apparently limited to the specific shape or positional relationship or are explicitly described as being necessary in principle.

According to the first aspect of some or all of the embodiments described above, in the centrifugal blower, the downstream end portion of the air intake portion and the upstream end portion of the side plate are spaced apart from each other in the axial direction of the rotary shaft and face each other in the axial direction. A dimension difference between a radius of a portion of the inner wall surface portion having the smallest radius and a radius of a portion of the inner panel surface portion having the smallest radius is set to be equal to or smaller than a thickness of the side panel.

According to the second aspect, the radius of a portion of the inner wall surface portion having the smallest radius is set to a size equal to or smaller than the radius of a portion of the inner panel surface portion. Accordingly, the air flowing along the intake portion can be restricted from colliding with the side panel.

According to a third aspect, a casing of a centrifugal blower is configured by a scroll-shaped casing including a side wall portion defining an air flow passage having a spiral shape outside an impeller. In at least a part of a region extending from the curl starting portion to the intermediate portion in the rotational direction, a dimensional difference between a radius of a portion having a smallest radius in the inner wall surface portion and a radius of a portion having a smallest radius in the inner panel surface portion is set to be equal to or smaller than a thickness of the side panel.

Accordingly, in at least a part of the region extending from the curl start portion to the intermediate portion in the rotational direction, there is substantially no head difference in the radial direction between the inner wall surface portion and the inner panel surface portion, and the at least a part may generate turbulence of the air flow. Since the air flowing along the air intake portion can smoothly flow to the side plate in a portion of the case where turbulence may be generated, it is possible to reduce noise and improve blowing efficiency.

According to the fourth aspect, in the vicinity of the curl ending portion of the side wall portion, the difference in size between the portion having the smallest radius in the air intake portion and the portion having the smallest radius in the side plate is larger than the difference in size in the region extending from the curl starting portion to the intermediate portion in the rotational direction.

Accordingly, in the vicinity of the curl finishing portion of the side wall portion, a difference in level in the radial direction is provided between the inner wall surface portion of the air intake portion and the inner plate surface portion of the side plate. Therefore, it is possible to reduce the flow of the air near the surface of the intake portion to the exhaust side of the impeller through the gap between the intake portion and the side plate. Since noise in the vicinity of the curl end portion caused by collision of the air flow can be restrained, noise in the centrifugal blower can be further reduced.

According to the fifth aspect, in the portion of the side panel and the intake portion corresponding to the curl finish portion of the side wall portion, the difference in size between the radius of the portion having the smallest radius in the inner wall surface portion and the radius of the portion having the smallest radius in the inner panel surface portion is larger than the thickness of the side panel.

Accordingly, a position difference having a dimension larger than the thickness of the side plate in the radial direction is present in the vicinity of the curl end portion. Therefore, the airflow near the surface of the intake portion is further restricted from flowing to the exhaust side of the impeller through the gap between the intake portion and the side plate.

According to the sixth aspect, the deflecting passage is provided between the air intake portion and the side plate. The deflecting passage deflects a backflow flowing from a gap between the downstream end portion and the upstream end portion to an intake side of the impeller so as to be closer to a main flow flowing from the intake portion to the intake side of the impeller. When the deflecting portion deflects the backflow so as to be closer to the main flow, interference of the main flow and the backflow can be restricted. Since the air flowing along the air intake portion becomes able to smoothly flow to the side plate, noise can be reduced, and the blowing efficiency can be improved.

According to the seventh aspect, a specific configuration of the deflection channel is explained. Specifically, the deflection channel includes a gap between the downstream end and the upstream end. The downstream end portion is inclined toward the inner wall surface portion so that a radius of a portion facing the upstream end portion becomes smaller as the portion becomes closer to the upstream end portion.

If the facing surface of the upstream end facing the downstream end portion extends in the radial direction of the rotary shaft, the cross-sectional area of the gap between the upstream end portion and the downstream end portion becomes smaller toward the downstream. In this case, the backflow flowing in the gap between the upstream end portion and the downstream end portion may be disturbed.

In view of this, the upstream end portion is inclined such that the radius of a portion of the upstream end portion facing the downstream end portion becomes larger as the upstream end portion becomes closer to the downstream end portion. Accordingly, interference of the main flow and the backflow can be restricted because of turbulence of the backflow in the gap between the upstream end portion and the downstream end portion. Since the air flowing along the air intake portion becomes able to smoothly flow to the side plate, noise can be reduced, and the blowing efficiency can be improved.

Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the broader concepts of the invention are not limited to the specific details, representative apparatus, and illustrative examples shown and described.