JP7476735B2 - Centrifugal Blower - Google Patents

Description

This disclosure relates to a centrifugal blower.

Centrifugal blowers such as multi-blade blowers are used for ventilation in buildings, apartment buildings, stores, etc. Centrifugal blowers tend to generate a lot of noise due to the structure of their impeller and the method of boosting pressure. For this reason, there has been a demand for reducing noise in centrifugal blowers, and techniques for reducing noise are known. For example, Patent Document 1 describes a centrifugal blower with a multi-blade fan equipped with an inducer section as a configuration that can prevent an increase in noise.

JP 2002-70793 A (paragraph 0010, Figures 1 and 2)

However, the centrifugal blower described in Patent Document 1 has an inducer section inside the multi-blade fan, which makes the structure of the multi-blade fan complex and increases manufacturing costs.

This disclosure has been made to solve the problems described above, and provides a centrifugal blower that is simple in structure and capable of reducing noise.

The centrifugal blower according to the present disclosure comprises: an outer casing provided with an intake port and an exhaust port; a fan casing housed inside the outer casing and provided with a fan-side intake port communicating with the intake port, a motor-side intake port communicating with the intake port and arranged opposite the fan-side intake port, and an outlet port communicating with the exhaust port; a multi-blade fan having a plurality of blades arranged in a circumferential direction about a rotation axis, housed inside the fan casing and arranged so as to be sandwiched between the fan-side intake port and the motor-side intake port; and a rotor arranged on the motor-side intake port side of the multi-blade fan and configured to rotate the rotor. The fan comprises a motor that rotates the multi-blade fan around a rotation axis, and a straightening member that is fixed to at least one of the outer casing and the fan casing and extends from at least the fan side suction port into the interior of the multi-blade fan, and is arranged with a gap between the edge of the fan side suction port and the multiple blades to allow air to flow in from the fan side suction port.The motor comprises a motor main body supported by at least one of the outer casing and the fan casing, and a drive shaft to which the multi-blade fan is fixed, and the motor main body and the straightening member are arranged with a gap in between in the direction of the rotation axis.
In addition, the centrifugal blower according to the present disclosure comprises a fan casing provided with a fan side suction port, a motor side suction port arranged opposite the fan side suction port, and an outlet port, a multi-blade fan having a plurality of blades arranged in a circumferential direction centered on a rotation axis and housed inside the fan casing and arranged to be sandwiched between the fan side suction port and the motor side suction port, a motor arranged on the motor side suction port side of the fan casing with respect to the multi-blade fan and rotating the multi-blade fan around the rotation axis, and a straightening member fixed relatively to the fan casing and extending from at least the fan side suction port into the interior of the multi-blade fan and arranged at a distance from the edge of the fan side suction port and the plurality of blades, the motor comprising a motor main body supported by the fan casing and a drive shaft to which the multi-blade fan is fixed, and the motor main body and the straightening member are arranged at a distance in the direction of the rotation axis.

According to the present disclosure, the generation of vortexes that cause noise can be suppressed by the straightening member, making it possible to reduce noise with a simple structure.

1 is a perspective view of a centrifugal blower showing a first embodiment. FIG. 1 is a cross-sectional view of a centrifugal blower according to a first embodiment of the present invention; 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 1 is an analytical model diagram of a conventional centrifugal blower. FIG. 5 is a diagram showing an analysis result of a cross section taken along line VV in FIG. 4. FIG. 5 is a diagram showing an analysis result in a cross section taken along line VI-VI in FIG. 4. 10 is a cross-sectional plan view showing another example of the airflow straightening member of the centrifugal blower according to the first embodiment. FIG. FIG. 11 is a cross-sectional view of a centrifugal blower according to a second embodiment of the present invention; 13 is a cross-sectional plan view showing another example of the straightening member of the centrifugal blower according to the second embodiment. FIG. FIG. 11 is a cross-sectional view of a centrifugal blower according to a third embodiment of the present invention;

The following describes the embodiments with reference to the attached drawings. The same or corresponding parts in each drawing are denoted by the same reference numerals.

Embodiment 1.
Fig. 1 is a perspective view of a centrifugal blower 1 in the first embodiment. Fig. 2 is a cross-sectional view in a plan view of the centrifugal blower 1. The centrifugal blower 1 includes an outer casing 10, a fan casing 20, a multi-blade fan 30, a motor 40, and a straightening member 50. The centrifugal blower 1 is installed in a space such as the ceiling of a building, for example, and performs ventilation by sucking in indoor air through a duct provided in the ceiling or the like and discharging it to the outside.

In this embodiment, the outer casing 10 forms the exterior of the centrifugal blower 1 and is formed in a substantially rectangular box shape. The outer casing 10 is provided with an intake port 12 and an exhaust port 14. The intake port 12 and the exhaust port 14 are provided on two opposing side surfaces of the outer casing 10, side surface 10a and side surface 10b, respectively. The outer casing 10 is also provided with two duct connection parts 16. The duct connection parts 16 are used to connect to an external duct (not shown) and are formed in a cylindrical shape. One of the duct connection parts 16 is disposed so as to surround the periphery of the intake port 12 on side surface 10a, and the other is disposed so as to surround the periphery of the exhaust port 14 on side surface 10b.

The fan casing 20 is housed inside the outer casing 10. In this embodiment, the fan casing 20 is formed in a box shape with a hollow interior. The fan casing 20 has a first side plate 20a, a second side plate 20b, and a peripheral wall 20c, and constitutes a so-called spiral casing. The first side plate 20a and the second side plate 20b are arranged to face each other in the direction of the rotation axis A of the multi-blade fan 30. The peripheral wall 20c is provided between the first side plate 20a and the second side plate 20b, and is formed in a spiral shape along the outer periphery of the multi-blade fan 30, and a part of it forms the air outlet 28. The first side plate 20a, the second side plate 20b, and the peripheral wall 20c may be integrally molded or may be composed of a combination of multiple parts.

The fan casing 20 is also provided with an intake port 22 and an outlet port 28. In this embodiment, two intake ports 22 are provided: a fan-side intake port 24 and a motor-side intake port 26. The fan-side intake port 24 is formed in the first side plate 20a of the fan casing 20, and is, for example, a circular opening centered on the rotation axis A of the multi-blade fan 30. The fan-side intake port 24 has a bell-mouth shape whose inner diameter decreases from the first side plate 20a to the second side plate 20b. The motor-side intake port 26 is formed in the second side plate 20b of the fan casing 20, and is, for example, a circular opening centered on the rotation axis A of the multi-blade fan 30. The motor-side intake port 26 has a bell-mouth shape whose inner diameter decreases from the second side plate 20b to the first side plate 20a. Inside the outer casing 10, between the outer casing 10 and the fan casing 20, there are formed an air passage from the intake port 12 to the fan side intake port 24, and an air passage from the intake port 12 to the motor side intake port 26, and the fan side intake port 24 and the motor side intake port 26 are each connected to the intake port 12. The air outlet 28 is connected to the exhaust port 14 of the outer casing 10. The air outlet 28 is an opening surrounded by the first side plate 20a, the second side plate 20b, and the peripheral wall 20c of the fan casing 20.

The multi-blade fan 30 is an impeller of the centrifugal blower 1, and is housed inside the fan casing 20 and is arranged opposite the suction port 22 of the fan casing 20. In this embodiment, the multi-blade fan 30 is a so-called double-suction type fan, and is arranged so as to be sandwiched between the fan-side suction port 24 and the motor-side suction port 26 of the fan casing 20. The multi-blade fan 30 has a main plate 32, a first ring member 34, a second ring member 36, and a plurality of blades 38. The main plate 32 is formed in a disk shape. The center of the main plate 32 is provided on the rotation axis A. The center of the main plate 32 is provided with a boss portion 33 having a drive shaft hole into which the drive shaft 42 of the motor 40 is inserted. The main plate 32 is connected to the drive shaft 42 of the motor 40 via the boss portion 33, and can rotate around the rotation axis A together with the drive shaft 42. The first ring member 34 and the second ring member 36 are formed in an annular shape. The first ring member 34 and the second ring member 36 are provided as reinforcing members that maintain the spacing between the tips of the multiple blades 38. The multiple blades 38 are arranged between the main plate 32 and the first ring member 34 at the outer periphery of the surface of the main plate 32 that faces the fan-side suction port 24, and are arranged at equal intervals in the circumferential direction centered on the rotation axis A. The multiple blades 38 are also arranged between the main plate 32 and the second ring member 36 at the outer periphery of the surface of the main plate 32 that faces the motor-side suction port 26, and are arranged at equal intervals in the circumferential direction centered on the rotation axis A.

The motor 40 rotates the multi-blade fan 30 around the rotation axis A. In this embodiment, the motor 40 has a drive shaft 42. The drive shaft 42 is formed in a cylindrical shape centered on the rotation axis A. The main plate 32 of the multi-blade fan 30 is fixed to the drive shaft 42 via a boss portion 33. When the motor 40 rotates, the drive shaft 42 rotates around the rotation axis A, and the multi-blade fan 30 rotates around the rotation axis A. The motor 40 is disposed on the motor side suction port 26 side of the fan casing 20 with respect to the multi-blade fan 30. The motor 40 is supported on the fan casing 20 by, for example, a mounting member not shown. The motor 40 may be supported on the outer casing 10 by a mounting member not shown.

The straightening member 50 is provided extending from the suction port 22 of the fan casing 20 into the inside of the multi-blade fan 30, and is arranged with a gap between the edge of the suction port 22 and the multiple blades 38 of the multi-blade fan 30 so that air from the suction port 22 flows in. In this embodiment, the straightening member 50 is fixed to the outer casing 10 and is provided extending from the outer casing 10 through the fan side suction port 24 of the fan casing 20 into the inside of the multi-blade fan 30. Here, the inside of the multi-blade fan 30 is the inner part of the multiple blades 38 arranged in the circumferential direction centered on the rotation axis A. The straightening member 50 is arranged on the opposite side of the motor 40 with respect to the multi-blade fan 30. The straightening member 50 is formed in a cylindrical shape extending into the inside of the multi-blade fan 30. The central axis of the straightening member 50 is arranged to be the same as the rotation axis A of the multi-blade fan 30. The straightening member 50 is disposed at a distance from the edge of the fan-side suction port 24 and the plurality of blades 38, so that air can flow between the edge of the fan-side suction port 24 and the straightening member 50, and between the plurality of blades 38 and the straightening member 50. In addition, the tip of the straightening member 50, i.e., the end facing the main plate 32 of the multi-blade fan 30, is disposed at a distance from the boss portion 33 of the main plate 32 in the direction of the rotation axis A.

Figure 3 is a cross-sectional view taken along line III-III in Figure 2. As shown in Figure 3, in a cross section perpendicular to the rotation axis A of the multi-blade fan 30, there is a certain relationship between the ratio of the area occupied by the straightening member 50 to the area inside the multi-blade fan 30. Here, the area inside the multi-blade fan 30 is the area inside the multiple blades 38 arranged in a circumferential direction centered on the rotation axis A. More specifically, the area inside the multiple blades 38 is the area of a circle (shown by a dashed line in Figure 3) with a radius R1 being a line segment connecting the radial inner end 38a of the blade 38 with the rotation axis A as the central axis and the rotation axis A. In addition, the area occupied by the straightening member 50 is an area defined by the outer periphery of the straightening member 50 in a cross section perpendicular to the rotation axis A, and this area is smaller than the area inside the multiple blades 38. In this case, the ratio of the area occupied by the straightening member 50 to the area inside the multiple blades 38 is 0.4 or more. Preferably, the ratio of the area occupied by the flow straightening member 50 to the area inside the blades 38 is 0.5 or more and 0.7 or less.

When the centrifugal blower 1 is in operation, the motor 40 is driven to rotate the multi-blade fan 30, and air is drawn into the outer casing 10 from the intake port 12 of the outer casing 10. The flow of air drawn into the outer casing 10 branches into two directions just before the fan casing 20, and is drawn into the multi-blade fan 30 from the fan-side intake port 24 and the motor-side intake port 26 of the fan casing 20, respectively. The air drawn into the multi-blade fan 30 is pressurized by the multi-blade fan 30 and sent into the fan casing 20. The air sent into the fan casing 20 passes through the exhaust port 14 of the outer casing 10 from the air outlet 28 of the fan casing 20 and is discharged to the outside of the outer casing 10.

Figure 4 is an analytical model diagram of a conventional centrifugal blower 90. Unlike the centrifugal blower 1 in embodiment 1, the conventional centrifugal blower 90 does not have a straightening member 50. The results of airflow analysis of the conventional centrifugal blower 90 are shown in Figures 5 and 6. Figure 5 is a diagram showing the analysis results in a cross section taken along line V-V in Figure 4. Figure 6 is a diagram showing the analysis results in a cross section taken along line VI-VI in Figure 4. Figure 5 shows the results of airflow analysis of the fan side intake port 92 of the fan casing 91 of the conventional centrifugal blower 90. As shown by the solid arrow in Figure 5, in the conventional centrifugal blower 90, a vortex is generated near the center of the fan side intake port 92. Also, Figure 6 shows the results of airflow analysis inside the multi-blade fan 93 of the conventional centrifugal blower 90. As shown by the solid arrow in Figure 6, in the conventional centrifugal blower 90, a vortex is also generated near the center inside the multi-blade fan 93. These vortexes are thought to be one of the causes of noise from conventional centrifugal blowers 90.

Unlike the conventional centrifugal blower 90 described above, the centrifugal blower 1 in this embodiment is provided with a straightening member 50. The straightening member 50 extends from the inner wall surface of the outer casing 10 through the vicinity of the center of the fan side suction port 24 to the vicinity of the center inside the multi-blade fan 30, and smoothly guides the air sucked from the fan side suction port 24 to the multi-blade fan 30, thereby suppressing the generation of vortexes near the center of the fan side suction port 24 and near the center inside the multi-blade fan 30. In addition, the straightening member 50 extends from at least the fan side suction port 24 to the inside of the multi-blade fan 30, thereby suppressing the generation of vortexes near the center of the fan side suction port 24.

As described above, the centrifugal blower 1 according to this embodiment includes an outer casing 10 having an intake port 12 and an exhaust port 14, a fan casing 20 housed inside the outer casing 10 and having an intake port 22 communicating with the intake port 12 and an exhaust port 28 communicating with the exhaust port 14, a multi-blade fan 30 having a plurality of blades 38 arranged in a circumferential direction around the rotation axis A, housed inside the fan casing 20 and arranged opposite the intake port 22, a motor 40 that rotates the multi-blade fan 30 around the rotation axis A, and a straightening member 50 fixed to at least one of the outer casing 10 and the fan casing 20, extending from at least the intake port 22 into the interior of the multi-blade fan 30, and arranged with a gap between the edge of the intake port 22 and the plurality of blades 38 so that air from the intake port 22 flows in.

With this configuration, the straightening member 50 extends from at least the suction port 22 of the fan casing 20 into the inside of the multi-blade fan 30, so that the air sucked in from the suction port 22 is guided along the surface of the straightening member 50 into the multi-blade fan 30, thereby suppressing the generation of vortexes inside the suction port 22 and inside the multi-blade fan 30. In this way, a simple structure such as the straightening member 50 can suppress the generation of vortexes that cause noise, making it possible to reduce noise with a simple structure.

In addition, in a cross section perpendicular to the rotation axis A, the ratio of the area occupied by the straightening member 50 to the area inside the plurality of blades 38 is 0.4 or more. In Figs. 5 and 6, which are the results of airflow analysis of a conventional centrifugal blower 90, the area where vortices are mainly generated is near the center of the inside of the suction port 22 and near the center of the inside of the multi-blade fan 30, and occupies about 40% of the area inside the plurality of blades 38. Therefore, by setting the ratio of the area occupied by the straightening member 50 to the area inside the plurality of blades 38 to 0.4 or more, it is possible to effectively suppress the generation of vortices near the center of the inside of the suction port 22 and near the center of the inside of the multi-blade fan 30. This makes it possible to reduce noise. Furthermore, by setting the ratio of the area occupied by the straightening member 50 to the area inside the plurality of blades 38 to 0.5 or more and 0.7 or less, vortexes that occur in the area outside the area that is 40% of the area inside the plurality of blades 38 described above can also be suppressed, and noise can be reduced more reliably, while the external shape of the straightening member 50 does not become too large, so as not to interfere with the work of the plurality of blades 38.

The straightening member 50 has a cylindrical shape that extends from the suction port 22 into the interior of the multi-blade fan 30. This configuration makes it easier to manufacture the straightening member 50, improving the workability of the manufacturing process.

The central axis of the straightening member 50 is aligned with the rotation axis A. With this configuration, the straightening member 50 is aligned coaxially with the multi-blade fan 30, which makes it easier to assemble the product and reduces the likelihood of mistakes, compared to when the central axis of the straightening member 50 is offset from the rotation axis A.

In this embodiment, the intake port 12 and the exhaust port 14 are provided on two opposing side surfaces of the outer casing 10, namely, side surface 10a and side surface 10b, respectively, but this is not limited to the above. The intake port 12 and the exhaust port 14 do not necessarily have to be provided on opposing surfaces of the outer casing 10.

In addition, although the straightening member 50 is described as being fixed to the outer casing 10, this is not limited thereto. The straightening member 50 may be fixed to the fan casing 20, for example, using an attachment member not shown. In this case, as in the example of the straightening member 50A shown in FIG. 7, the straightening member 50A may not be in contact with the outer casing 10, and may be disposed at a distance from the outer casing. In addition, although the straightening member 50 is described as being formed in a cylindrical shape extending inside the multi-blade fan 30, it may also be formed in a hollow cylindrical shape.

Furthermore, although the centrifugal blower 1 is described as having an outer casing 10, this is not limiting, and the outer casing 10 may not be included. In this case, the straightening member 50 may be fixed to the fan casing 20 using a mounting member (not shown) or may be fixed to another member, as long as it is fixed relative to the fan casing 20.

The centrifugal blower 1 is configured as a double-suction type in which the fan casing 20 is provided with a fan-side suction port 24 and a motor-side suction port 26, but is not limited to this. For example, it may be a single-suction type centrifugal blower in which only the fan-side suction port 24 is provided as the suction port 22.

Embodiment 2.
Next, a second embodiment will be described with reference to Fig. 8. Fig. 8 is a cross-sectional plan view of a centrifugal blower 101 according to the second embodiment. Note that, in this embodiment, the description of the same parts as those in the above-mentioned embodiment will be omitted.

As shown in FIG. 8, in the centrifugal blower 101 of this embodiment, the shape of the straightening member 150 is different from the shape of the straightening member 50 of the centrifugal blower 1 of the first embodiment. Specifically, the straightening member 150 has a truncated cone shape that spreads from the suction port 22 of the fan casing 20 toward the inside of the multi-blade fan 30. In this embodiment, the straightening member 150 is fixed to the outer casing 10, and has a truncated cone shape that spreads from the fan-side suction port 24 of the fan casing 20 toward the inside of the multi-blade fan 30. In addition, the central axis of the straightening member 150 is aligned with the rotation axis A.

In addition, when the cross section perpendicular to the rotation axis A of the straightening member 150 is not constant as in this embodiment, it is preferable that in the portion of the straightening member 150 extending from the fan-side inlet 24 to the inside of the multi-blade fan 30, the ratio of the area occupied by the straightening member 150 to the area inside the multiple blades 38 is 0.4 or more.

In the centrifugal blower 101 according to this embodiment, the straightening member 150 has a truncated cone shape that expands from the suction port 22 toward the inside of the multi-blade fan 30. With this configuration, the air sucked in from the suction port 22 flows into the inside of the multi-blade fan 30 along the inclined surface of the truncated cone shape of the straightening member 150, so that the direction of the air flow can be changed radially more smoothly compared to a cylindrical shape, and the air can be sent to the multiple blades 38.

The shape of the straightening member is not limited to the cylindrical shape of the straightening member 50 in embodiment 1 or the truncated cone shape of the straightening member 150 in embodiment 2. Another example of the shape of the straightening member is the straightening member 150A shown in FIG. 9. The straightening member 150A has a shape in which the radial dimension about the rotation axis A decreases from the outer casing 10 to a certain portion inside the multi-blade fan 30 and then increases again from that portion, i.e., the middle portion is narrowed.

Embodiment 3.
Next, a third embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view of a centrifugal blower 201 according to the third embodiment in a plan view. Note that, in this embodiment, the description of the same parts as those in the above-mentioned embodiments will be omitted.

As shown in FIG. 10, in the centrifugal blower 201 of this embodiment, the shape of the straightening member 250 is different from the shape of the straightening member 50 of the centrifugal blower 1 of the first embodiment. Specifically, the straightening member 250 extends from the outer casing 10 through the fan-side inlet 24 of the fan casing 20 to the boss portion 33 of the multi-blade fan 30. The straightening member 250 is supported by the boss portion 33 via a bearing 239.

At the tip of the straightening member 250, a hole 252 is formed that is recessed toward the outer casing 10. A bearing 239 is provided inside the hole 252. The bearing 239 is provided in the boss portion 33 so as to surround the drive shaft 42 of the motor 40. In this embodiment, a tip portion 254 having a smaller radial dimension with the rotation axis A as the central axis is provided on the outer periphery of the tip of the straightening member 250. The tip portion 254 is provided to prevent the straightening member 250 from coming into contact with a rivet or the like (not shown) provided on the main plate 32.

In the centrifugal blower 201 according to this embodiment, the straightening member 250 is provided extending to the boss portion 33 of the multi-blade fan 30 and is supported by the boss portion 33 via a bearing 239. With this configuration, the straightening member 250 can be supported at both ends without interfering with the rotation of the multi-blade fan 30. This reduces the possibility that the straightening member 250 will come off due to aging or the like and damage the multi-blade fan 30, etc., compared to when it is supported at one end by the outer casing 10, etc., and allows the straightening member 250 to be supported more stably.

In addition, appropriate combinations, modifications, and omissions of each embodiment are also within the scope of the technical ideas presented in the embodiments.

1, 101, 201 Centrifugal blower, 10 Outer casing, 10a, 10b Side, 12 Intake port, 14 Exhaust port, 16 Duct connection part, 20 Fan casing, 20a First side plate, 20b Second side plate, 20c Peripheral wall, 22 Intake port, 24 Fan side intake port, 26 Motor side intake port, 28 Outlet port, 30 Multi-blade fan, 32 Main plate, 33 Boss portion, 34 First ring member, 36 Second ring member, 38 Blade, 38a Inner end, 40 Motor, 42 Drive shaft, 50, 50A, 150, 150A, 250 Straightening member, 90 Conventional centrifugal blower, 239 Bearing, 252 Hole portion, 254 Tip portion, A Rotating shaft, R1 Radius.

Claims (8)

an outer casing having an intake port and an exhaust port;
a fan casing accommodated inside the outer casing and provided with a fan-side suction port communicating with the intake port, a motor-side suction port communicating with the intake port and disposed opposite the fan-side suction port, and an air outlet communicating with the exhaust port;
a multi-blade fan having a plurality of blades arranged in a circumferential direction around a rotation axis, the multi-blade fan being housed inside the fan casing and disposed between the fan-side suction port and the motor-side suction port;
a motor that is disposed on a motor-side inlet side of the fan casing with respect to the multi-blade fan and rotates the multi-blade fan about the rotation shaft;
a straightening member fixed to at least one of the outer casing and the fan casing, extending from at least the fan-side suction port into the interior of the multi-blade fan, and disposed between an edge of the fan-side suction port and the plurality of blades with a gap provided therebetween through which air from the fan-side suction port flows in;
Equipped with
the motor includes a motor body supported by at least one of the outer casing and the fan casing, and a drive shaft to which the multi-blade fan is fixed,
A centrifugal blower in which the motor body and the straightening member are arranged at an interval in the direction of the rotation shaft. The centrifugal blower according to claim 1, wherein the ratio of the area occupied by the straightening member to the area inside the blades in a cross section perpendicular to the rotation shaft is 0.4 or more. The centrifugal blower according to claim 2, wherein the ratio of the area occupied by the straightening member to the area inside the blades in a cross section perpendicular to the rotation shaft is 0.5 to 0.7. the multi-blade fan has a boss portion to which a drive shaft of the motor is connected,
4. The centrifugal blower according to claim 1, wherein the flow straightening member is provided to extend to the boss portion and is supported by the boss portion via a bearing. The centrifugal blower according to any one of claims 1 to 4, wherein the straightening member has a cylindrical shape extending from the fan-side suction port into the interior of the multi-blade fan. The centrifugal blower according to any one of claims 1 to 4, wherein the straightening member has a truncated cone shape that expands from the fan-side intake port toward the inside of the multi-blade fan. The centrifugal blower according to claim 5 or 6, wherein the central axis of the straightening member is aligned with the rotating shaft. a fan casing provided with a fan-side suction port, a motor-side suction port arranged opposite the fan-side suction port, and an air outlet;
a multi-blade fan having a plurality of blades arranged in a circumferential direction around a rotation axis, the multi-blade fan being housed inside the fan casing and disposed between the fan-side suction port and the motor-side suction port;
a motor that is disposed on a motor-side inlet side of the fan casing with respect to the multi-blade fan and rotates the multi-blade fan about the rotation shaft;
a straightening member that is fixed relatively to the fan casing, extends from at least the fan side inlet into the multi-blade fan, and is disposed at a distance from an edge of the fan side inlet and the plurality of blades;
Equipped with
the motor includes a motor body supported by the fan casing and a drive shaft to which the multi-blade fan is fixed,
A centrifugal blower in which the motor body and the straightening member are arranged at an interval in the direction of the rotation shaft.