EP4431748A1

EP4431748A1 - Centrifugal fan

Info

Publication number: EP4431748A1
Application number: EP23878371.6A
Authority: EP
Inventors: Azumi Terakawa; Takashi Kashihara; Rintaro TADA; Nobuhito TOMIYAMA
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2023-01-25
Filing date: 2023-12-18
Publication date: 2024-09-18
Anticipated expiration: 2043-12-18
Also published as: CN120435624A; JP7457268B1; WO2024157652A1; CN120435624B; EP4431748B1; JP2024104998A; EP4431748A4

Abstract

A centrifugal fan, having a blade rotating at a high speed, desirably has a further increased bonding strength between the blade and a plate. The centrifugal fan includes a plate, a ring, and a plurality of blades (43) including a first blade (43a). A first bond surface (51) is a bond surface of the first blade (43a) with the plate. The first bond surface (51) has a second bond surface (52) and a third bond surface (53). The second bond surface (52) is a part of the first bond surface (51) closer to a front end (91) than a second straight line (L2). The third bond surface (53) is a part of the first bond surface (51) closer to a rear end (92) than the second straight line (L2). A first width dimension (D1) is the largest dimension of width dimensions of the second bond surface (52) along the second straight line (L2). A second width dimension (D2) is the largest dimension of width dimensions of the third bond surface (53) along the second straight line (L2). The first width dimension (D1) is 1.3 times or more the second width dimension (D2).

Description

TECHNICAL FIELD

The present disclosure relates to a centrifugal fan.

BACKGROUND ART

As disclosed in Patent Document 1 ( JP 2019-100209 A ), there is known a centrifugal fan including a plate disposed such that a thickness direction of the plate is along a direction of an axis, a ring disposed apart from the plate in the direction of the axis and having a ring shape when viewed from the direction of the axis, and a plurality of blades disposed between the plate and the ring and having one end bonded to the plate and the other end bonded to the ring.

SUMMARY OF THE INVENTION

Since the centrifugal fan has a blade rotating at a high speed, a large centrifugal force acts on the blade. It is therefore desirable to further increase a bonding strength between the blade and the plate.

A centrifugal fan according to a first aspect includes a plate, a ring, and a plurality of blades. The plate is disposed such that a thickness direction of the plate is along a direction of an axis. The ring is disposed apart from the plate in the direction of the axis. The ring has a ring shape when viewed from the direction of the axis. The plurality of blades is disposed between the plate and the ring. The plurality of blades has one end bonded to the plate and the other end bonded to the ring. The plurality of blades includes a first blade. A first bond surface is a bond surface of the first blade with the plate. The first bond surface has a second bond surface and a third bond surface. The second bond surface is a part of the first bond surface closer to a front end than a second straight line. The second straight line is a straight line that passes through a center of a first straight line and is orthogonal to the first straight line. The first straight line connects the front end and a rear end of the first blade in a rotation direction. The third bond surface is a part of the first bond surface closer to the rear end than the second straight line. A first width dimension is the largest dimension of width dimensions of the second bond surface along the second straight line. A second width dimension is the largest dimension of width dimensions of the third bond surface along the second straight line. The first width dimension is 1.3 times or more the second width dimension.
By expanding the second bond surface as a part of the first blade near the front end in the rotation direction toward the axis, the value of a maximum normal stress generated on the first bond surface by a centrifugal force tends to decrease. In the centrifugal fan according to the first aspect, the first width dimension is 1.3 times or more the second width dimension. A first width dimension is the largest dimension of width dimensions of the second bond surface along the second straight line. A second width dimension is the largest dimension of width dimensions of the third bond surface along the second straight line. As a result, the centrifugal fan can increase a bonding strength between the first blade and the plate.
A centrifugal fan according to a second aspect is the centrifugal fan according to the first aspect, in which the first width dimension is three times or less the second width dimension.
A centrifugal fan according to a third aspect is the centrifugal fan according to the first or second aspect, in which the first width dimension is 1.6 times or more the second width dimension.
A centrifugal fan according to a fourth aspect is a centrifugal fan according to any of the first to third aspects, in which an area of a fourth bond surface as a part of the second bond surface closer to the axis than the first straight line is larger than an area of a fifth bond surface as a part of the second bond surface opposite to the axis.
The first blade 43a tends to be peeled off from the fourth bond surface as a part of the second bond surface near the axis due to the centrifugal force. In the centrifugal fan according to the fourth aspect, by making the area of the fourth bond surface larger than the area of the fifth bond surface in the second bond surface, the bonding strength between the first blade and the plate can be increased.
A centrifugal fan according to a fifth aspect is the centrifugal fan according to any of the first to fourth aspects, in which an area of a fourth bond surface as a part of the second bond surface closer to the axis than the first straight line is larger than an area of a sixth bond surface as a part of the third bond surface closer to the axis than the first straight line.
The first blade 43a tends to be peeled off from the fourth bond surface as a part of the second bond surface near the axis due to the centrifugal force. In the centrifugal fan according to the fifth aspect, by making the area of the fourth bond surface larger than the area of the sixth bond surface, the bonding strength between the first blade and the plate can be increased.
A centrifugal fan according to a sixth aspect is the centrifugal fan according to any of the first to fifth aspects, in which when the first blade extending from the plate to the ring is viewed along the first straight line, a shape of the first blade includes a first concave portion.
A centrifugal fan according to a seventh aspect is the centrifugal fan according to the sixth aspect, in which the first concave portion is formed at a position closer to the plate than the ring.
With such a configuration, the centrifugal fan according to the seventh aspect can secure the first width dimension without affecting performance of the centrifugal fan.
A centrifugal fan according to an eighth aspect is the centrifugal fan according to any of the first to seventh aspects, in which the plurality of blades includes a second blade adjacent to the first blade. The first bond surface has a shape in which a second concave portion is formed near the axis. A seventh bond surface is located outside a region surrounded by the second concave portion and a third straight line connecting both ends of the second concave portion. The seventh bond surface is a bond surface of the second blade with the plate.
When the first blade and the second blade are deformed by the centrifugal force, the plate tends to be deformed accordingly. At this time, if the first blade and the second blade are in close contact with each other, the plate cannot be deformed, and a large load is applied to the first bond surface and the seventh bond surface. In the centrifugal fan according to the eighth aspect, the seventh bond surface is located outside a region surrounded by the second concave portion and the third straight line connecting both ends of the second concave portion. Therefore, in the centrifugal fan, the plate can be deformed in accordance with the deformation of the first blade and the second blade due to the centrifugal force, and thus, a large load is not applied to the first bond surface and the seventh bond surface. As a result, the centrifugal fan can increase the bonding strength between the first blade and the plate and between the second blade and the plate.
A centrifugal fan according to a ninth aspect is the centrifugal fan according to any of the first to eighth aspects, in which the first bond surface is located around a hollow portion formed near the plate in the first blade.
The centrifugal fan according to the ninth aspect, which is provided with the hollow portion to lighten the first blade, can weaken the centrifugal force acting on the first blade.
A centrifugal fan according to a tenth aspect is the centrifugal fan according to any of the first to ninth aspects, in which the first blade is molded with resin.
The centrifugal fan according to the tenth aspect, in which the first blade is molded by injection molding or the like, can increase a degree of freedom of the shape of the first blade.
A centrifugal fan according to an eleventh aspect is the centrifugal fan according to any of the first to tenth aspects, in which the plate and the ring are molded with aluminum or an aluminum alloy.
A centrifugal fan according to a twelfth aspect is the centrifugal fan according to any of the first to eleventh aspects, in which the plate and the first blade are bonded by a method other than welding.
The centrifugal fan according to the twelfth aspect does not require a space for accommodating a welding torch, so that the number of the plurality of blades can be increased to eliminate Nz sound.
A centrifugal fan according to a thirteenth aspect is the centrifugal fan according to any of the first to twelfth aspects, in which the number of the plurality of blades is from seven to eleven.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of an indoor unit.
FIG. 2 is a schematic sectional view of a centrifugal fan.
FIG. 3 is a perspective view of an impeller.
FIG. 4 is a diagram of the impeller viewed along a direction of an axis from a plate.
FIG. 5 is a diagram of a first bond surface which is a bond surface of a first blade with the plate.
FIG. 6 is a diagram of the first bond surface which is a bond surface of the first blade with the plate.
FIG. 7 is a diagram of the first bond surface which is a bond surface of the first blade with the plate.
FIG. 8 is a diagram of an eighth bond surface which is a bond surface of the first blade with a ring.
FIG. 9 is a diagram of the first blade extending from the plate to the ring as viewed along a first straight line.
FIG. 10 is a diagram of a first bond surface which is a bond surface of a conventional blade with a plate.
FIG. 11 is a diagram of the first bond surface which is a bond surface of the conventional blade with the plate.
FIG. 12 is a diagram of a fourth bond surface and a fifth bond surface.
FIG. 13 is a diagram of the fourth bond surface and a sixth bond surface.
FIG. 14 is an enlarged view of the first bond surface of the first blade and a seventh bond surface of a second blade.

DESCRIPTION OF EMBODIMENTS

(1) Air conditioner

An air conditioner 1 performs air conditioning of a target space by using a vapor compression refrigeration cycle. In the present embodiment, the air conditioner 1 is a central air conditioner. The air conditioner 1 mainly includes an indoor unit 10 and a heat source unit 20.

(2) Indoor unit

FIG. 1 is a schematic configuration diagram of the indoor unit 10. In the present embodiment, the indoor unit 10 is an air handling unit. As shown in FIG. 1, the indoor unit 10 mainly includes a casing 11, a centrifugal fan 30, a heat exchanger 12, an electric heater 13, and a humidifier 14. The indoor unit 10 and the heat source unit 20 are connected via a pipe 94 through which a heat medium (for example, refrigerant, water, and the like) flows.
The casing 11 mainly accommodates the centrifugal fan 30, the heat exchanger 12, the electric heater 13, and the humidifier 14. The casing 11 is provided with a first opening 11a, a second opening 11b, and a third opening 11c. The first opening 11a is an opening for sucking outdoor air OA from outdoors into the casing 11. The second opening 11b is an opening for sucking indoor air RA into the target space from the target space into the casing 11. The third opening 11c is an opening for blowing out air-conditioned supply air SA from inside of the casing 11 toward the target space.
The centrifugal fan 30 sucks the outdoor air OA and the indoor air RA into the casing 11 from the first opening 11a and the second opening 11b, and blows the supply air SA toward the target space from the third opening 11c. The centrifugal fan 30 generates, in the casing 11, an air flow AF flowing from the first opening 11a and the second opening 11b to the third opening 11c. The air flow AF passes through the heat exchanger 12, the electric heater 13, and the humidifier 14 in that order in the casing 11.
The heat exchanger 12, the electric heater 13, and the humidifier 14 are disposed in a flow path of the air flow AF. The heat exchanger 12 causes heat exchange between the air flow AF and the heat medium in the pipe 94 supplied from the heat source unit 20. The electric heater 13 heats the air flow AF that has passed through the heat exchanger 12. The humidifier 14 humidifies the air flow AF by spraying water in a tank (not shown) installed outside the casing 11 from a nozzle.

(3) Centrifugal fan

FIG. 2 is a schematic sectional view of the centrifugal fan 30. In the present embodiment, the centrifugal fan 30 is a turbofan. As shown in FIG. 2, the centrifugal fan 30 mainly includes a fan motor 31 and an impeller 40. The impeller 40 is connected to the fan motor 31 via a boss member 44. The impeller 40 rotates around rotation an axis A1 by using the fan motor 31 as power. In FIG. 2, a rotation direction of the impeller 40 is indicated as "A2".
FIG. 3 is a perspective view of the impeller 40. As shown in FIG. 3, the impeller 40 mainly includes a plate 41, a ring 42, and a plurality of blades 43. In FIG. 3, the ring 42 is depicted as translucent.

(3-1) Plate

As shown in FIGS. 2 and 3, the plate 41 is disposed such that a thickness direction of the plate is along a direction of the axis A1. The plate 41 is molded with aluminum or an aluminum alloy. As shown in FIG. 2, the plate 41 has a first plate surface 41a facing the ring 42 and a second plate surface 41b opposite to the ring 42. FIG. 4 is a diagram of the impeller 40 viewed along the direction of the axis A1 from the plate 41. As shown in FIG. 4, the plate 41 has a ring shape when viewed from the direction of the axis A1. An opening 41c for fixing the boss member 44 is formed at a center of the plate 41. A hole 41d for fixing the boss member 44 with a bolt is formed around the opening 41c. As shown in FIG. 4, in the present embodiment, six holes 41d are formed. The plate 41 is connected to the fan motor 31 via the fixed boss member 44.

(3-2) Ring

As shown in FIGS. 2 and 3, the ring 42 is disposed apart from the plate 41 in the direction of the axis A1. The ring 42 is molded with aluminum or an aluminum alloy. As shown in FIG. 3, the ring 42 has a ring shape when viewed from the direction of the axis A1. As shown in FIG. 2, the ring 42 has a first ring surface 42a facing the plate 41 and a second ring surface 42b opposite to the plate 41.

(3-3) Blade

As shown in FIGS. 2 and 3, the plurality of blades 43 is disposed between the plate 41 and the ring 42. The number of the plurality of blades 43 is from seven to eleven. As shown in FIGS. 3 and 4, in the present embodiment, the number of blades 43 is nine. As shown in FIG. 2, one end of the plurality of blades 43 is bonded to the first plate surface 41a of the plate 41, and the other end is bonded to the first ring surface 42a of the ring 42. As shown in FIGS. 3 and 4, the plurality of blades 43 are arranged at unequal pitches along the rotation direction A2 of the impeller 40 (the rotation direction A2 of the plurality of blades 43).
Hereinafter, any one of the plurality of blades 43 will be referred to as a first blade 43a. The first blade 43a is molded with resin.
FIGS. 5 to 7 are diagrams each showing a first bond surface 51 which is a bond surface of the first blade 43a with the plate 41 (a bond surface between the first blade 43a and the first plate surface 41a). As shown in FIG. 5, a hollow portion 71 is formed near the plate 41 in the first blade 43a. The first bond surface 51 is located around the hollow portion 71. The first bond surface 51 has a shape in which a second concave portion 74 is formed near the axis A1. In FIG. 5, the first bond surface 51 is indicated by hatching. The first blade 43a has, on the first bond surface 51, a pin 81 for determining the position of the first blade 43a, and a hole 82 for bringing the first blade 43a into close contact with the first plate surface 41a by passing a screw. As shown in FIG. 5, in the present embodiment, the first blade 43a has two pins 81 and three holes 82 on the first bond surface 51. The plate 41 and the first blade 43a are bonded by a method other than welding. In the present embodiment, the position of the first blade 43a is determined by the pin 81, the first blade 43a is brought into close contact with the first plate surface 41a by passing a screw, and the plate 41 and the first blade 43a are bonded by an adhesive.
The first bond surface 51 has a second bond surface 52 and a third bond surface 53. Here, in order to describe the second bond surface 52 and the third bond surface 53, a first straight line L1 and a second straight line L2 are defined. In FIGS. 6 and 7, the structure of the hollow portion 71 is omitted and the first bond surface 51 is depicted so that the first straight line L1, the second straight line L2, and the like can be easily seen. As shown in FIG. 6, the first straight line L1 is a straight line connecting a front end 91 and a rear end 92 of the first blade 43a in the rotation direction A2. The second straight line L2 is a straight line that passes through a center 93 of the first straight line L1 and is orthogonal to the first straight line L1. The second bond surface 52 is a part of the first bond surface 51 closer to the front end 91 than the second straight line L2. The third bond surface 53 is a part of the first bond surface 51 closer to the rear end 92 than the second straight line L2. In FIG. 6, the second bond surface 52 and the third bond surface 53 are indicated by hatching. In FIG. 6, the second bond surface 52 and the third bond surface 53 are distinguished by distinguishing the inclination of the hatched line.
Furthermore, the first bond surface 51 has a first width dimension D1 and a second width dimension D2. As shown in FIG. 7, the first width dimension D1 is the largest dimension of the width dimensions of the second bond surface 52 along the second straight line L2. The second width dimension D2 is the largest dimension of the width dimensions of the third bond surface 53 along the second straight line L2. The first width dimension D1 is 1.3 times or more and 3 times or less the second width dimension D2. The first width dimension D1 is preferably 1.6 times or more the second width dimension D2.
FIG. 8 is a diagram showing an eighth bond surface 58 which is a connection surface of the first blade 43a with the ring 42 (a bond surface between the first blade 43a and the first ring surface 42a). As shown in FIG. 8, a hollow portion 72 is formed near the ring 42 in the first blade 43a. The eighth bond surface 58 is located around the hollow portion 72. In FIG. 8, the eighth bond surface 58 is indicated by hatching. The first blade 43a has, on the eighth bond surface 58, a pin 83 for determining the position of the first blade 43a, and a hole 84 for bringing the first blade 43a into close contact with the first ring surface 42a by passing a screw. As shown in FIG. 8, in the present embodiment, the first blade 43a has one pin 83 and one hole 84 on the eighth bond surface 58. The plate 41 and the first blade 43a are bonded by a method other than welding. In the present embodiment, the position of the first blade 43a is determined by the pin 83, the first blade 43a is brought into close contact with the first ring surface 42a by passing a screw, and the ring 42 and the first blade 43a are bonded by an adhesive.
FIG. 9 is a diagram of the first blade 43a extending from the plate 41 to the ring 42 as viewed along the first straight line L1. As shown in FIG. 9, when the first blade 43a extending from the plate 41 to the ring 42 is viewed along the first straight line L1, the shape of the first blade 43a includes the first concave portion 73. The first concave portion 73 is formed at a position closer to the plate 41 than the ring 42.

(4) Verification

Here, by using the first blade 43a in the present embodiment and a blade 43' used in a conventional turbofan, the number of rotations (number of breaking rotations) when the blade is broken by a centrifugal force has been verified. For this verification, simulation software "ANSYS" is used.

The specifications of the first blade 43a and the blade 43' in this verification are shown in Table 1 below.

[Table 1]

	First blade 43a	Blade 43'
Diameter of impeller [mm]	500
Number of blades	9
Mass [g]	1200	1324
Area of first bond surface [mm²]	9250.63	9341.27
First width dimension [mm]	82.29	57
Second width dimension [mm]	49.99	53.06
First width dimension/Second width dimension	1.65	1.07

As shown in Table 1, in this verification, the diameter of the impeller 40 having the first blade 43a and the diameter of the conventional impeller having the blade 43' are unified to 500 mm. The number of the first blades 43a and the number of the blades 43' are unified to nine. The arrangement of the first blades 43a in the impeller 40 is substantially the same as the arrangement of blades 43' in the conventional impeller.
The mass of the first blade 43a is 1200 g, and the mass of the blade 43' is 1324 g.
FIGS. 10 and 11 are diagrams showing a first bond surface 51' which is a bond surface of the conventional blade 43' with the plate. As shown in FIG. 10, unlike the first blade 43a, no hollow portion is formed near the plate in the blade 43'. In FIG. 10, a rotation direction of the blade 43' is indicated as "A2"'. In FIG. 10, the first bond surface 51' is indicated by hatching. Similarly to the first blade 43a, the blade 43' is molded by resin, and the plate and the blade 43' are bonded by an adhesive. FIG. 11 shows a first straight line L1', a second straight line L2', a first width dimension D1', and a second width dimension D2' of the first bond surface 51'. For later description, in FIG. 11, a second bond surface 52' is indicated by hatching. The area of the first bond surface 51 of the first blade 43a is 9250.63 mm², and the area of the first bond surface 51' of the blade 43' is 9341.27 mm². The first width dimension D1 of the first blade 43a is 82.29 mm, and the first width dimension D1' of the blade 43' is 57 mm. The second width dimension D2 of the first blade 43a is 49.99 mm, and the second width dimension D2' of the blade 43' is 53.06 mm. In the first blade 43a, the first width dimension D1 is 1.65 times the second width dimension D2, and in the blade 43', the first width dimension D1' is 1.07 times the second width dimension D2'.

The verification results are shown in Table 2 below.

[Table 2]

	First blade 43 a	Blade 43'
Number of breaking rotations [rpm]	3500	2300
Maximum stress generated on surface of blade [MPa]	25 (At 2300 rpm)	28 (At 2300 rpm)
Maximum stress generated on surface of blade [MPa]	44 (At 3100 rpm)	28 (At 2300 rpm)
Maximum normal stress generated on first bond surface [MPa]	8.25 (At 2300 rpm)	17.8 (At 2300 rpm)
Maximum normal stress generated on first bond surface [MPa]	15 (At 3100 rpm)	17.8 (At 2300 rpm)

As shown in Table 2, the number of breaking rotations of the first blade 43a is 3500 rpm, and the number of breaking rotations of the blade 43' is 2300 rpm.
When the number of rotations is 2300 rpm, a maximum stress generated on a surface of the first blade 43a (excluding the bond surface with the plate 41 and the ring 42) is 25 MPa, and a maximum stress generated on a surface of the blade 43' (excluding the bond surface with the plate and the ring) is 28 MPa. When the number of rotations is 3100 rpm, the maximum stress generated on the surface (excluding the bond surface between the plate 41 and the ring 42) of the first blade 43a is 44 MPa.
When the number of rotations is 2300 rpm, a maximum normal stress generated on the first bond surface 51 of the first blade 43a is 8.25 MPa, and a maximum normal stress generated on the first bond surface 51' of the blade 43' is 17.8 MPa. When the number of rotations is 3100 rpm, the maximum normal stress generated on the first bond surface 51 of the first blade 43a is 15 MPa. In FIG. 7, a location where the maximum normal stress is generated on the first bond surface 51 of the first blade 43a is indicated as "P". In FIG. 11, a location where the maximum normal stress is generated on the first bond surface 51' of the blade 43' is indicated as "P"'.
As shown in FIGS. 7 and 11, in the first bond surfaces 51 and 51', the locations P and P' where the maximum normal stress occurs are both located near the axes A1 and A1' on the second bond surfaces 52 and 52'.
On the other hand, the value of the "maximum normal stress (Table 2) generated on the first bond surface" is smaller in the first blade 43a than in the blade 43' (even the value of the maximum normal stress occurring on the first bond surface 51 when the number of rotations is 3100 rpm is smaller than the value of the maximum normal stress occurring on the first bond surface 51' when the number of rotations is 2300 rpm). Since the location P where the maximum normal stress is generated on the first bond surface 51 is closer to the axis than the location P' where the maximum normal stress is generated on the first bond surface 51', it is presumed that the value of the maximum normal stress decreases as the location where the maximum normal stress is generated is closer to the axis.
Therefore, the blade is peeled off from the second bond surface near the axis due to the centrifugal force. However, it is presumed that when the second bond surface is expanded toward the axis, a location where the maximum normal stress is generated becomes closer to the axis, and the value of the maximum normal stress also decreases, and thus, the blade is less likely to be peeled off.
As a result, it is presumed that one of the factors that the first blade 43a has a larger value of "number of breaking rotations (Table 2)" than the blade 43' is that the first blade 43a has a larger value of "first width dimension/second width dimension (Table 1)" than the blade 43'.

(5) Characteristics

(5-1) Conventionally, there is known a centrifugal fan including a plate disposed such that a thickness direction of the plate is along a direction of an axis, a ring disposed apart from the plate in the direction of the axis and having a ring shape when viewed from the direction of the axis, and a plurality of blades disposed between the plate and the ring and having one end bonded to the plate and the other end bonded to the ring.
Since the centrifugal fan has a blade rotating at a high speed, a large centrifugal force acts on the blade. It is therefore desirable to further increase the bonding strength between the blade and the plate.
The centrifugal fan 30 according to the present embodiment includes the plate 41, the ring 42, and the plurality of blades 43. The plate 41 is disposed such that the thickness direction of the plate 41 is along the direction of the axis A1. The ring 42 is disposed apart from the plate 41 in the direction of the axis A1. The ring 42 has a ring shape when viewed from the direction of the axis A1. The plurality of blades 43 is disposed between the plate 41 and the ring 42. The plurality of blades 43 has one end bonded to the plate 41 and the other end bonded to the ring 42. The plurality of blades 43 includes the first blade 43a. The first bond surface 51 is a bond surface of the first blade 43a with the plate 41. The first bond surface 51 has a second bond surface 52 and a third bond surface 53. The second bond surface 52 is a part of the first bond surface 51 closer to the front end 91 than the second straight line L2. The second straight line L2 passes through a center 93 of the first straight line L1 and is orthogonal to the first straight line L1. The first straight line L1 connects the front end 91 and the rear end 92 of the first blade 43a in the rotation direction A2. The third bond surface 53 is a part of the first bond surface 51 closer to the rear end 92 than the second straight line L2. The first width dimension D1 is the largest width dimension of the width dimensions of the second bond surface 52 along the second straight line L2. The second width dimension D2 is the largest width dimension of the width dimensions of the third bond surface 53 along the second straight line L2. The first width dimension D1 is 1.3 times or more the second width dimension D2.
By expanding the second bond surface 52 as a part of the first blade 43a near the front end 91 in the rotation direction A2 toward the axis A1, the value of the maximum normal stress generated on the first bond surface 51 by the centrifugal force tends to decrease. In the centrifugal fan 30 according to the present embodiment, the first width dimension D1 is 1.3 times or more the second width dimension D2. The first width dimension D1 is the largest width dimension of the width dimensions of the second bond surface 52 along the second straight line L2. The second width dimension D2 is the largest width dimension of the width dimensions of the third bond surface 53 along the second straight line L2. As a result, the centrifugal fan 30 can increase the bonding strength between the first blade 43a and the plate 41.

(5-2) In the centrifugal fan 30 according to the present embodiment, the first width dimension D1 is three times or less the second width dimension D2.
(5-3) In the centrifugal fan 30 according to the present embodiment, the first width dimension D1 is 1.6 times or more the second width dimension D2.
(5-4) In the centrifugal fan 30 according to the present embodiment, when the first blade 43a extending from the plate 41 to the ring 42 is viewed along the first straight line L1, the shape of the first blade 43a includes the first concave portion 73.
(5-5) In the centrifugal fan 30 according to the present embodiment, the first concave portion 73 is formed at a position closer to the plate 41 than the ring 42. As a result, the centrifugal fan 30 can secure the first width dimension D1 without affecting performance of the centrifugal fan 30.
(5-6) In the centrifugal fan 30 according to the present embodiment, the first bond surface 51 is located around the hollow portion 71 formed near the plate 41 in the first blade 43a. As a result, the centrifugal fan 30, which is provided with the hollow portion 71 to lighten the first blade 43a, can weaken the centrifugal force acting on the first blade 43a.
(5-7) In the centrifugal fan 30 according to the present embodiment, the first blade 43a is molded with resin. As a result, the centrifugal fan 30, in which the first blade 43a is molded by injection molding or the like, can increase a degree of freedom of the shape of the first blade 43a.
(5-8) In the centrifugal fan 30 according to the present embodiment, the plate 41 and the ring 42 are molded with aluminum or an aluminum alloy.
(5-9) In the centrifugal fan 30 according to the present embodiment, the plate 41 and the first blade 43a are bonded by a method other than welding. As a result, the centrifugal fan 30 does not require a space for accommodating a welding torch, so that the number of the plurality of blades 43 can be increased to eliminate Nz sound.
(5-10) In the centrifugal fan 30 according to the present embodiment, the number of the plurality of blades 43 is from seven to eleven.

(6) Modifications

(6-1) Modification 1A

The area of a fourth bond surface 54 as a part of the second bond surface 52 closer to the rotation axis A1 than the first straight line L1 may be larger than the area of a fifth bond surface 55 as a part of the second bond surface 52 opposite to the axis A1.
FIG. 12 is a diagram of the fourth bond surface 54 and the fifth bond surface 55. In FIG. 12, the fourth bond surface 54 and the fifth bond surface 55 are indicated by hatching. In FIG. 12, the fourth bond surface 54 and the fifth bond surface 55 are distinguished by distinguishing the inclination of the hatched line.
The first blade 43a tends to be peeled off from the fourth bond surface 54 as a part of the second bond surface 52 near the axis A1 due to the centrifugal force. Therefore, in the centrifugal fan 30, by making the area of the fourth bond surface 54 larger than the area of the fifth bond surface 55 in the second bond surface 52, the bonding strength between the first blade 43a and the plate 41 can be increased.

(6-2) Modification 1B

The area of a fourth bond surface 54 as a part of the second bond surface 52 closer to the rotation axis A1 than the first straight line L1 may be larger than the area of a sixth bond surface 56 as a part of the third bond surface 53 closer to the axis A1 than the first straight line L1.
FIG. 13 is a diagram of the fourth bond surface 54 and the sixth bond surface 56. In FIG. 13, the fourth bond surface 54 and the sixth bond surface 56 are indicated by hatching. In FIG. 13, the fourth bond surface 54 and the sixth bond surface 56 are distinguished by distinguishing the inclination of the hatched line.
The first blade 43a tends to be peeled off from the fourth bond surface as a part of the second bond surface 52 near the axis A1 due to the centrifugal force. Therefore, in the centrifugal fan 30, by making the area of the fourth bond surface 54 larger than the area of the sixth bond surface 56, the bonding strength between the first blade 43a and the plate 41 can be increased.

(6-3) Modification 1C

Hereinafter, any one blade adjacent to the first blade 43a of the plurality of blades 43 will be referred to as a second blade 43b. The bond surface of the second blade 43b with the plate 41 (bond surface between the second blade 43b and the first plate surface 41a) is referred to as a seventh bond surface 57. FIG. 14 is an enlarged view of the first bond surface 51 of the first blade 43a and the seventh bond surface 57 of the second blade 43b.
At this time, as shown in FIG. 14, the seventh bond surface 57 may be located outside a region surrounded by the second concave portion 74 of the first bond surface 51 and the third straight line L3 connecting both ends of the second concave portion 74.
When the first blade 43a and the second blade 43b are deformed by the centrifugal force, the plate 41 tends to be deformed accordingly. At this time, if the first blade 43a and the second blade 43b are in close contact with each other, the plate 41 cannot be deformed, and a large load is applied to the first bond surface 51 and the seventh bond surface 57. In the centrifugal fan 30 according to the present embodiment, the seventh bond surface 57 is located outside a region surrounded by the second concave portion 74 and the third straight line L3 connecting both ends of the second concave portion 74. Therefore, in the centrifugal fan 30, the plate 41 can be deformed in accordance with the deformation of the first blade 43a and the second blade 43b due to the centrifugal force, and thus, a large load is not applied to the first bond surface 51 and the seventh bond surface 57. As a result, the centrifugal fan 30 can increase the bonding strength between the first blade 43a and the plate 41 and between the second blade 43b and the plate 41.

(6-4) Modification 1D

In the present embodiment, the plate 41 and the ring 42 are molded with aluminum or an aluminum alloy. However, the plate 41 and the ring 42 may be molded with resin, similarly to the blades 43.

(6-5) Modification 1E

In the present embodiment, the centrifugal fan 30 is a turbofan used for an air handling unit. However, the centrifugal fan 30 may be used in any device as a turbofan such as, for example, a turbofan used for a fan coil unit, or a turbofan used as a ventilation fan or a humidification fan in a household outdoor unit.
(6-6) The embodiment of the present disclosure has been described above. Various modifications to modes and details should be available without departing from the gist and the scope of the present disclosure recited in the claims.

REFERENCE SIGNS LIST

30: centrifugal fan
41: plate
42: ring
43: blade
43a: first blade
43b: second blade
51 to 57: first bond surface to seventh bond surface
71: hollow portion
73: first concave portion
74: second concave portion
91: front end
92: rear end
93: center of first straight line
A1: axis
A2: rotation direction
D1: first width dimension
D2: second width dimension
L1 to L3: first straight line to third straight line

CITATION LIST

PATENT LITERATURE

Patent Literature 1: JP 2019-100209 A

Claims

A centrifugal fan (30) comprising:
a plate (41) disposed such that a thickness direction of the plate is along a direction of an axis (A1);

a ring (42) that is disposed apart from the plate in the direction of the axis and has a ring shape when viewed from the direction of the axis; and

a plurality of blades (43) disposed between the plate and the ring, having one end bonded to the plate and another end bonded to the ring, and including a first blade (43a),

wherein a first bond surface (51) that is a bond surface of the first blade with the plate includes

a second bond surface (52) that is a part of the first bond surface closer to a front end (91) of the first blade in a rotation direction (A2) than a second straight line (L2) that passes through a center (93) of a first straight line (L1) connecting the front end and a rear end (92) of the first blade in the rotation direction and is orthogonal to the first straight line, and

a third bond surface (53) that is a part of the first bond surface closer to the rear end than the second straight line, and

a first width dimension (D1) that is a largest width dimension of width dimensions of the second bond surface along the second straight line is 1.3 times or more a second width dimension (D2) that is a largest width dimension of width dimensions of the third bond surface along the second straight line.
The centrifugal fan (30) according to claim 1, wherein the first width dimension is three times or less the second width dimension.
The centrifugal fan (30) according to claim 1 or 2, wherein the first width dimension is 1.6 times or more the second width dimension.
The centrifugal fan (30) according to any one of claims 1 to 3, wherein an area of a fourth bond surface (54) as a part of the second bond surface closer to the axis than the first straight line is larger than an area of a fifth bond surface (55) as a part of the second bond surface opposite to the axis.
The centrifugal fan (30) according to any one of claims 1 to 4, wherein an area of a fourth bond surface (54) as a part of the second bond surface closer to the axis than the first straight line is larger than an area of a sixth bond surface (56) as a part of the third bond surface closer to the axis than the first straight line.
The centrifugal fan (30) according to any one of claims 1 to 5, wherein when the first blade extending from the plate to the ring is viewed along the first straight line, a shape of the first blade includes a first concave portion (73).
The centrifugal fan (30) according to claim 6, wherein the first concave portion is formed at a position closer to the plate than the ring.
The centrifugal fan (30) according to any one of claims 1 to 7, wherein
the plurality of blades includes a second blade (43b) adjacent to the first blade,

the first bond surface has a shape in which a second concave portion (74) is formed near the axis, and

a seventh bond surface (57) that is a bond surface of the second blade with the plate is located outside a region surrounded by the second concave portion and a third straight line (L3) connecting both ends of the second concave portion.
The centrifugal fan (30) according to any one of claims 1 to 8, wherein the first bond surface is located around a hollow portion (71) formed near the plate in the first blade.
The centrifugal fan (30) according to any one of claims 1 to 9, wherein the first blade is molded with resin.
The centrifugal fan (30) according to any one of claims 1 to 10, wherein the plate and the ring are molded with aluminum or an aluminum alloy.
The centrifugal fan (30) according to any one of claims 1 to 11, wherein the plate and the first blade are bonded by a method other than welding.
The centrifugal fan (30) according to any one of claims 1 to 12, wherein a number of the plurality of blades is from seven to eleven.