WO2024038622A1

WO2024038622A1 - Multiblade centrifugal blower

Info

Publication number: WO2024038622A1
Application number: PCT/JP2022/039681
Authority: WO
Inventors: 弘恭林; 拓矢寺本; 優人浦辺; 奨太細見; 好孝明里; 優太 ▲高▼橋; 一夫乳井
Original assignee: 三菱電機株式会社
Priority date: 2022-08-19
Filing date: 2022-10-25
Publication date: 2024-02-22
Also published as: TW202417746A; JP2024027777A

Abstract

This multi-blade centrifugal blower comprises: a fan that includes a main plate, a plurality of blades, and a ring-shaped side plate that secures an end section of the plurality of blades on the opposite side from the main plate; and a scroll casing that houses the fan and that includes a peripheral wall formed in a spiral shape and at least one side wall including a bellmouth which forms an intake port. The fan comprises: rear-facing vane sections on the inner peripheral sides of the plurality of blades that serve as rearward blades; front-facing vane sections on the outer peripheral side of the plurality of blades that serve as front-facing blades; and inflection point sections that form inflection points between the rear-facing blade sections and the front-facing blade sections. The inflection point sections are formed along the entire length of each of the plurality of blades, that is, the portion between a base section on the main plate side and a tip section on the side plate side, and all portions of the inflection point sections in an axial direction are formed so as to be located, in the radial direction of the fan, further to the inner peripheral side than an inner peripheral end section that forms an inner edge of the bellmouth.

Description

multi-blade centrifugal blower

The present disclosure relates to a multi-blade centrifugal blower with a scroll casing.

A conventional multi-blade centrifugal blower includes a fan having a disc-shaped main plate, a plurality of blades installed on the peripheral edge of the main plate, and side plates that fix the ends of the blades. In addition, conventional multi-blade centrifugal blowers are equipped with a scroll casing that has a spiral peripheral wall that covers the fan, and a bell mouth is provided at the suction port of the scroll casing to smoothly draw airflow to the fan. . In conventional multi-blade centrifugal blowers, the airflow that flows out between the blades as the fan rotates is boosted by the expanded air passage inside the scroll casing, so the blades are forward-facing blades that are inclined in the direction of fan rotation. many. However, the angle of the airflow drawn inside the scroll casing along the bell mouth often does not match the inlet angle of the forward vane, and conventional multi-blade centrifugal blowers Separation of airflow may occur on the negative pressure surface on the edge side, resulting in a decrease in air volume. Therefore, by providing a rear vane facing opposite to the fan rotation direction on the inner circumferential side of the forward vane, the airflow induced from the bell mouth is smoothly guided to the vane, and the airflow generated on the negative pressure surface on the leading edge side of the vane. A multi-blade centrifugal blower has been proposed that suppresses separation of air and reduces air volume (for example, see Patent Document 1).

Japanese Patent Application Publication No. 2002-70793

However, in the multi-blade centrifugal blower of Patent Document 1, the inner circumferential side of the blade is the backward-facing blade, and the outer circumferential side of the blade is the forward-facing blade, and the angle of the blade surface between the inner circumferential side and the outer circumferential side of the blade is Because the change is large, there is a risk that new separation of airflow will occur on the suction surface of the blade, resulting in a decrease in air volume.

The present disclosure is intended to solve the above-mentioned problems, and provides a multi-blade centrifugal blower that can suppress separation of airflow on the negative pressure surface of the blade and suppress a decrease in air volume.

A multi-blade centrifugal blower according to the present disclosure includes a main plate that is circular when viewed in the axial direction of the rotating shaft, a plurality of blades installed on the peripheral edge of the main plate, and a plurality of blades in the axial direction of the rotating shaft. an annular side plate fixing an end opposite to the main plate of the fan, a peripheral wall formed in a spiral shape, and at least one side wall having a bell mouth forming a suction port; a scroll casing that forms a discharge port through which airflow generated by the fan is discharged and houses a fan, the fan having a rearward direction at the inner peripheral side of each of the plurality of blades in the radial direction of the fan. When viewed in the axial direction of the rotating shaft, the rearward blade part that constitutes the blade, the forward blade part that constitutes the forward blade at the outer peripheral side of each of the plurality of blades in the radial direction of the fan, , an inflection point part forming an inflection point between the rearward blade part and the forward blade part, and the inflection point part is located on the main plate side of each of the plurality of blades in the axial direction of the rotation shaft. It is formed over the entire length of the blade, which is the part between the base end of the fan and the tip of the side plate, and the entire axial part of the inflection point extends along the inner edge of the bell mouth in the radial direction of the fan. It is formed so as to be located on the inner peripheral side of the inner peripheral end portion to be formed.

The fan of the multi-blade centrifugal blower according to the present disclosure includes a backward blade portion, a forward blade portion, and an inflection point portion that forms an inflection point between the rearward blade portion and the forward blade portion. The inflection point portion is formed over the entire length of the blade, which is a portion between the base end portion on the main plate side and the tip portion on the side plate side of each of the plurality of blades in the axial direction of the rotating shaft. Further, all portions of the inflection point portion in the axial direction of the rotation shaft are formed so as to be located on the inner circumferential side of the inner circumferential end forming the inner edge of the bell mouth in the radial direction of the fan. . In a configuration in which all parts of the inflection point are located on the inner side of the inner circumferential end of the bell mouth, at least part or all of the inflection point part is located on the outer circumferential side of the inner circumferential end. Compared to a configuration in which the wing is located at Therefore, the multi-blade centrifugal blower can gradually change the blade angle from the leading edge side toward the trailing edge side, suppressing separation of airflow on the negative pressure surface and suppressing a decrease in air volume.

1 is an external view schematically showing a configuration of a multi-blade centrifugal blower 1 according to a first embodiment when viewed parallel to a rotation axis RA. FIG. 1 is a perspective view of a multi-blade centrifugal blower according to Embodiment 1. FIG. 1 is a perspective view of a fan of a multi-blade centrifugal blower according to Embodiment 1. FIG. 1 is a plan view of a fan of a multi-blade centrifugal blower according to Embodiment 1. FIG. FIG. 3 is a partially enlarged view of a fan in the multi-blade centrifugal blower according to the first embodiment. 1 is a partial cross-sectional view of a multi-blade centrifugal blower according to Embodiment 1. FIG. FIG. 2 is a partial cross-sectional view of a multi-blade centrifugal blower according to a second embodiment. FIG. 7 is a partial cross-sectional view of a multi-blade centrifugal blower according to Embodiment 3. FIG. 7 is a partially enlarged view of a fan in a multi-blade centrifugal blower according to Embodiment 4;

Hereinafter, a multi-blade centrifugal blower according to an embodiment will be described with reference to the drawings and the like. Note that in the following drawings including FIG. 1, the relative dimensional relationships, shapes, etc. of each component may differ from the actual ones. In addition, in the following drawings, parts with the same reference numerals are the same or equivalent, and this is common throughout the entire specification. In addition, to facilitate understanding, we use terms that indicate directions (for example, "top", "bottom", "right", "left", "front", "back", etc.), but these notations are as follows: This is only described for convenience of explanation, and does not limit the arrangement or orientation of the device or parts.

Embodiment 1.
[Multi-blade centrifugal blower 1]
FIG. 1 is an external view schematically showing the configuration of a multi-blade centrifugal blower 1 according to Embodiment 1, viewed parallel to the rotation axis RA. FIG. 2 is a perspective view of the multi-blade centrifugal blower 1 according to the first embodiment. The arrow R in FIG. 1 indicates the rotation direction of the fan 2, and the broken line arrow CD indicates the circumferential direction of the fan 2. Moreover, FIG. 2 explains the external appearance of the multi-blade centrifugal blower 1, and the internal configuration of the multi-blade centrifugal blower 1 is shown in a simplified manner. The basic structure of the multi-blade centrifugal blower 1 will be explained using FIGS. 1 and 2.

The multi-blade centrifugal blower 1 is a device that sends air using centrifugal force generated by the rotation of the fan 2, and is, for example, a sirocco fan. The multi-blade centrifugal blower 1 is a single-suction type centrifugal blower in which air is sucked in from one side of the scroll casing 4 in the axial direction of the imaginary rotational axis RA of the fan 2 . Note that the multi-blade centrifugal blower 1 is not limited to a single suction type centrifugal blower, but may be a double suction type centrifugal blower in which air is sucked in from both sides of the scroll casing 4 in the axial direction of the rotation axis RA. As shown in FIGS. 1 and 2, the multi-blade centrifugal blower 1 includes a fan 2 that generates airflow and a scroll casing 4 that houses the fan 2 therein.

(Fan 2)
FIG. 3 is a perspective view of the fan 2 of the multi-blade centrifugal blower 1 according to the first embodiment. FIG. 4 is a plan view of the fan 2 of the multi-blade centrifugal blower 1 according to the first embodiment. Note that FIG. 4 is a diagram of the fan 2 viewed in the axial direction of the rotation axis RA. The fan 2 will be explained using FIGS. 1 to 4.

The fan 2 is a centrifugal fan. The fan 2 is connected to a motor (not shown) having a drive shaft. The fan 2 is rotationally driven by a motor, and uses centrifugal force generated by the rotation to forcibly send air outward in the radial direction. The fan 2 is rotated in the direction of rotation indicated by an arrow R by a motor or the like.

As shown in FIG. 1, when viewed in the direction of the rotation axis RA, the fan 2 has a circular main plate 2a, an annular side plate 2c, and a peripheral edge 2a1 of the main plate 2a. It has a plurality of wings 2d arranged at. The fan 2 is formed into a bottomed cylindrical shape by a main plate 2a and a plurality of blades 2d arranged on the main plate 2a.

The fan 2 has a fan suction port 2e formed in a portion on the side plate 2c side opposite to the main plate 2a in the axial direction of the rotation axis RA. The fan suction port 2e is an opening of the fan 2 through which air flows into the fan 2, and allows gas to flow into a space surrounded by the main plate 2a and the plurality of blades 2d.

(Main plate 2a)
The main plate 2a is formed into a circular shape when viewed in the axial direction of the rotation axis RA. In the radial direction centered on the rotation axis RA, it has a peripheral portion two a1 formed on the outer circumferential side and a central portion two a2 formed on the inner circumferential side.

The peripheral portion two a1 is formed on the outer peripheral side of the central portion two a2, and is formed in an annular shape when viewed in the axial direction of the rotation axis RA. The peripheral portion two a1 is formed into a plate shape. The central portion two a2 is formed on the inner peripheral side of the peripheral edge two a1, and is formed to protrude from the inner peripheral edge portion of the peripheral edge two a1. The central portion 2a2 is formed of a plate-like member formed in a mountain shape. The central portion 2a2 is formed inside the plurality of wings 2d.

The main plate 2a may have a peripheral portion two a1 and a central portion two a2 integrally formed. The main plate 2a may be formed into a flat plate shape as a whole. The main plate 2a may be formed into a disk shape, a polygonal shape, or the like. The thickness of the main plate 2a may be formed such that the thickness of the wall becomes thicker toward the center in the radial direction centered on the rotation axis RA, or a constant thickness in the radial direction centered on the rotation axis RA. It may be formed in the same way. Further, the main plate 2a is not limited to being composed of a single plate-like member, but may be composed of a plurality of plate-like members fixed integrally. Note that the radial direction centered on the rotation axis RA is a direction perpendicular to the axial direction of the rotation axis RA.

A boss portion 2b to which the drive shaft of the motor is connected is provided at the center of the main plate 2a. A shaft hole into which the drive shaft of the motor is inserted is formed in the boss portion 2b. The boss portion 2b is formed, for example, in a cylindrical shape, but the shape of the boss portion 2b is not limited to the cylindrical shape. The boss portion 2b may be formed into a columnar shape, for example, a polygonal columnar shape. The main plate 2a is rotationally driven by a motor via the boss portion 2b.

(Side plate 2c)
The fan 2 has an annular side plate 2c attached to an end of a plurality of blades 2d opposite to the main plate 2a in the axial direction of the rotation axis RA. The side plate 2c fixes the ends of the plurality of blades 2d on the side opposite to the main plate 2a in the axial direction of the rotation axis RA. The side plate 2c is provided on the outer peripheral surface 2f of the fan 2. The side plate 2c is provided on the outer side of the blade 2d in the radial direction centered on the rotation axis RA. The side plate 2c may be provided at the tip portion 2g of a plurality of blades 2d that protrude from the main plate 2a in the direction of the rotation axis RA. The side plate 2c maintains the positional relationship of the tips of each wing 2d by connecting the plurality of wings 2d. Moreover, the side plate 2c reinforces the strength of the plurality of wings 2d by connecting the plurality of wings 2d.

(wing 2d)
The plurality of wings 2d are installed on the peripheral edge portion two a1 of the main plate 2a. The plurality of blades 2d have one end connected to the main plate 2a, the other end connected to the side plate 2c, and are arranged in a circumferential direction centered on the rotation axis RA. Each of the plurality of wings 2d is arranged at least between the main plate 2a and the side plate 2c. The plurality of wings 2d are arranged circumferentially around the boss portion 2b, and their base ends are fixed on the surface of the main plate 2a. As shown in FIG. 3, in the blade 2d, the surface on the rotation direction side is a pressure surface 2d1, and the surface on the opposite side to the rotation direction is a suction surface 2d2.

The blades 2d are arranged circumferentially at a constant interval from each other on the peripheral edge 2a1 of the main plate 2a. Each wing 2d is provided so as to rise from the main plate 2a, and is formed in a plate shape. Each wing 2d is provided so as to stand up almost perpendicularly to the main plate 2a, but the invention is not limited to this, and each wing 2d may be provided at an angle with respect to the vertical direction of the main plate 2a. .

As shown in FIG. 3, the blade 2d is inclined such that the leading edge 25a moves away from the rotation axis RA as it goes from the main plate 2a side to the side plate 2c side. The leading edge 25a is formed by the inner peripheral end 25 of the blade 2d. The inner peripheral end 25 is an end on the inner peripheral side of the blade 2d in a cross section perpendicular to the rotation axis RA, and the leading edge 25a is a part where the inner peripheral end 25 is continuous in the axial direction of the rotation axis. The leading edge 25a of the blade 2d is inclined such that the inner diameter of the blade increases from the main plate 2a side toward the side plate 2c side.

FIG. 5 is a partially enlarged view of the fan 2 in the multi-blade centrifugal blower 1 according to the first embodiment. FIG. 5 is an enlarged view of the fan 2 viewed in the axial direction of the rotation axis RA. In FIG. 5, the wing 2d is shown with the bell mouth 3 transparent in order to show the shape of the wing 2d. As shown in FIG. 5, a part of the inner circumferential side of the wing 2d is formed to be located inside the inner circumferential end portion 35 of the bell mouth 3. As shown in FIG. As shown in FIG. 5, the blade 2d of the fan 2 has a forward blade portion 21 and a backward blade portion 22 integrally formed.

The blade 2d has a forward blade portion 21 that includes an outer peripheral end 24 and is configured as a forward blade, and a backward blade portion 22 that includes an inner peripheral end 25 and is configured as a backward blade. Further, the blade 2 d has an inflection point portion 26 that forms an inflection point between the backward blade portion 22 and the forward blade portion 21 when viewed in the axial direction of the rotation axis RA of the fan 2 . In the radial direction of the fan 2, the blades 2d are integrally formed in the order of the backward blade portion 22, the inflection point portion 26, and the forward blade portion 21 from the rotation axis RA toward the outer circumferential side.

The backward blade portion 22 is a portion that constitutes a backward blade in the inner peripheral side of each of the plurality of blades 2d in the radial direction of the fan 2. The forward blade portion 21 is a portion that constitutes a forward blade on the outer peripheral side of each of the plurality of blades 2d in the radial direction of the fan 2.

The inflection point portion 26 changes from the backward blade portion 22 to the forward blade portion 21 in the blade 2d, in which the inner peripheral side portion is formed by the backward blade and the outer peripheral side portion is formed by the forward blade. form part. That is, when viewed in the axial direction of the rotation axis RA of the fan 2, the inflection point portion 26 is a blade in which the inner circumferential side portion is formed by backward-facing blades, and the outer circumferential side portion is formed by forward-facing blades. At 2d, an inflection point between the backward blade portion 22 and the forward blade portion 21 is formed. In other words, the inflection point portion 26 forms a connection point between the backward blade portion 22 and the forward blade portion 21 when viewed in the axial direction of the rotation axis RA of the fan 2 . The inflection point portion 26 is a portion where inflection points at the boundary between the backward blade portion 22 and the forward blade portion 21 are connected in the axial direction of the rotation axis RA, and the backward blade portion 22 and the forward blade portion This is a part where connection points with 21 are connected.

The fan 2 is driven to rotate around the rotation axis RA by being driven by a motor (not shown). As the fan 2 rotates, gas outside the multi-blade centrifugal blower 1 passes through the suction port 5 formed in the scroll casing 4 shown in FIG. It is sucked into the space surrounded by the two wings 2d. As the fan 2 rotates, the air sucked into the space surrounded by the main plate 2a and the plurality of blades 2d passes through the space between the blade 2d and the adjacent blade 2d, and passes in the radial direction of the fan 2. sent outward.

(Scroll casing 4)
The scroll casing 4 will be explained using FIGS. 1 and 2. The scroll casing 4 houses the fan 2 therein and rectifies the air blown out from the fan 2. The scroll casing 4 is a single suction type casing that has a side wall 4a in which a suction port 5 (described later) is formed on one side of the main plate 2a in the axial direction of the rotation axis RA. The scroll casing 4 is not limited to a single suction type casing, but may be a double suction type casing having side walls 4a in which suction ports 5, which will be described later, are formed on both sides of the main plate 2a in the axial direction of the rotation axis RA. But that's fine.

The scroll casing 4 has a scroll part 41 and a discharge part 42. The scroll casing 4 has a peripheral wall 4c formed in a spiral shape and side walls 4a provided on both sides of the fan 2 in the axial direction of the rotation axis RA.

(Scroll part 41)
The scroll portion 41 forms an air path that converts the dynamic pressure of the airflow generated by the fan 2 into static pressure. The scroll portion 41 has a side wall 4a that covers the fan 2 from the axial direction of the rotation axis RA, and a peripheral wall 4c that surrounds the fan 2 from the radial direction of the rotation axis RA of the boss portion 2b.

Further, the scroll portion 41 has a tongue portion 43 that is located between the scroll portion 41 and the discharge portion 42 and forms a curved surface, and that guides the airflow generated by the fan 2 to the discharge port 42a via the scroll portion 41. The internal space of the scroll portion 41 constituted by the peripheral wall 4c and the side wall 4a is a space through which air blown out from the fan 2 flows along the peripheral wall 4c.

(Side wall 4a)
In the first embodiment, the scroll casing 4 includes two side walls 4a. Of the two side walls 4a, the side wall 4a having the bell mouth 3 forming the suction port 5 is referred to as a first side wall 4a1, and the side wall 4a without the suction port 5 and the bell mouth 3 is referred to as a second side wall 4a2. Two side walls 4a arranged on both sides of the fan 2 are formed to face each other with a peripheral wall 4c interposed therebetween.

As shown in FIG. 2, the scroll casing 4 of the first embodiment includes a first side wall 4a1 and a second side wall 4a2 as the side walls 4a. That is, the scroll casing 4 has at least one side wall 4a provided with a bell mouth 3 that forms a suction port 5 that communicates with the space formed by the main plate 2a and the plurality of blades 2d.

The first side wall 4a1 is a side wall 4a located on the side where the side plate 2c is arranged with respect to the main plate 2a. The second side wall 4a2 is a side wall 4a located on the side where the main plate 2a is disposed with respect to the side plate 2c. The side wall 4a is a general term for the first side wall four a1 and the second side wall four a2.

A suction port 5 is formed in the first side wall 4a1 of the scroll casing 4 so that air can flow between the fan 2 and the outside of the scroll casing 4. The suction port 5 communicates with the fan suction port 2e, and is an air intake port that allows gas to flow into the space surrounded by the main plate 2a and the plurality of blades 2d. The suction port 5 is formed at a position facing the plate surface of the main plate 2a.

The suction port 5 provided in the first side wall 4a1 is formed by the bell mouth 3. That is, the bell mouth 3 forms a suction port 5 that communicates the space outside the scroll casing 4 with the space formed by the main plate 2a and the plurality of blades 2d. The bell mouth 3 rectifies the gas sucked into the fan 2 and causes it to flow into the fan suction port 2e of the fan 2.

The bell mouth 3 is formed so that the opening diameter gradually decreases from the outside to the inside of the scroll casing 4. The bell mouth 3 is formed to extend in the axial direction of the rotation axis RA. An inner circumferential end portion 35 forming an inner edge of the bell mouth 3 is located inside the scroll casing 4. Air near the suction port 5 flows smoothly along the bell mouth 3 and efficiently flows into the fan 2 from the suction port 5.

(peripheral wall 4c)
The peripheral wall 4c is a wall that guides the airflow generated by the fan 2 to the discharge port 42a along the curved wall surface. The peripheral wall 4c is formed in a spiral shape. The circumferential wall 4c is formed such that the distance from the rotation axis RA gradually increases in the rotational direction of the fan 2, starting from the tongue portion 43. In the rotation direction of the fan 2, the gap between the peripheral wall 4c and the outer periphery of the fan 2 increases at a predetermined rate from the tongue portion 43 to the discharge portion 42, and the air flow path area gradually increases. It is formed to be.

The spiral shape of the peripheral wall 4c includes, for example, a logarithmic spiral, an Archimedean spiral, or a shape based on an involute curve. The inner circumferential surface of the peripheral wall 4c constitutes a curved surface that curves smoothly along the circumferential direction of the fan 2 from the tongue portion 43 where the spiral winding begins to the winding end portion 41b where the spiral winding ends. With this configuration, the air sent out from the fan 2 smoothly flows through the gap between the fan 2 and the peripheral wall 4c from the fan 2 toward the discharge portion 42. Therefore, within the scroll casing 4, the static pressure of air increases efficiently from the tongue portion 43 toward the discharge portion 42.

The peripheral wall 4c is a wall provided between the side walls 4a facing each other, and forms a curved surface along the rotation direction of the fan 2. The peripheral wall 4c is arranged parallel to the axial direction of the rotation axis RA and covers the fan 2. Note that the peripheral wall 4c may have a form that is inclined with respect to the axial direction of the rotation axis RA of the fan 2, and is not limited to a form that is arranged parallel to the axial direction of the rotation axis RA.

The peripheral wall 4c constitutes an inner wall surface facing the outer peripheral surface 2f of the fan 2. The peripheral wall 4c faces the outer peripheral side ends of the plurality of blades 2d that constitute the outer peripheral surface 2f of the fan 2. The peripheral wall 4c faces the air blowing side of the blades 2d of the fan 2. As shown in FIG. 1, the peripheral wall 4c extends from a tongue portion 43 that is a spiral-shaped winding start portion to a winding end portion 41b that is located at the boundary between the discharge portion 42 and the scroll portion 41 on the side away from the tongue portion 43. , are provided along the rotation direction of the fan 2.

The tongue portion 43 is an upstream end of the peripheral wall 4c that forms a curved surface in the direction in which gas flows through the internal space of the scroll casing 4 along the peripheral wall 4c due to the rotation of the fan 2. The winding end portion 41b is a downstream end of the peripheral wall 4c that forms a curved surface in the direction in which gas flows through the internal space of the scroll casing 4 along the peripheral wall 4c due to the rotation of the fan 2.

(Tongue 43)
The scroll casing 4 forms a curved surface at a winding start portion of the peripheral wall 4c near the rotation axis RA of the fan 2, and has a tongue portion 43 that guides the airflow generated by the fan 2 to the discharge port 42a. The peripheral wall 4c includes a tongue portion 43 at the end on the discharge portion 42 side. The tongue portion 43 is formed at the beginning of the spiral-shaped peripheral wall 4c.

The tongue portion 43 is provided at the boundary between the discharge portion 42 and the diffuser plate 42c, which will be described later. The tongue portion 43 is formed to have a curved surface, and is formed in an arc shape when viewed from the axial direction of the rotation axis RA. The tongue portion 43 is formed with a predetermined radius of curvature, and the peripheral wall 4c is smoothly connected to the diffuser plate 42c via the tongue portion 43. The tongue portion 43 has substantially the same shape in the axial direction of the rotation axis RA when viewed from the discharge port 42a, and has a shape along the axial direction of the rotation axis RA.

The tongue portion 43 suppresses the inflow of air from the end of the spiral flow path to the beginning of the winding inside the scroll casing 4. The tongue portion 43 is provided at the upstream portion of the ventilation path, and has the role of separating the air flow in the rotation direction of the fan 2 and the air flow in the discharge direction from the downstream portion of the ventilation path toward the discharge port 42a. have Further, the static pressure of the air flowing into the discharge portion 42 increases while passing through the scroll casing 4, and becomes high pressure. Therefore, the tongue portion 43 has a function of partitioning off such a pressure difference. The tongue portion 43 has a function of partitioning a pressure difference, and also has a function of guiding air flowing into the discharge portion 42 to each flow path due to its curved surface.

(Discharge part 42)
The discharge part 42 forms a discharge port 42a through which the airflow generated by the fan 2 and passed through the scroll part 41 is discharged. The discharge portion 42 is constituted by a hollow tube having a rectangular cross section perpendicular to the direction in which air flows along the peripheral wall 4c. Note that the cross-sectional shape of the discharge portion 42 is not limited to a rectangle. The discharge part 42 forms a flow path that guides the air sent out from the fan 2 and flowing through the gap between the peripheral wall 4c and the fan 2 so as to be discharged to the outside of the scroll casing 4.

One end of the discharge section 42 forms an inlet (not shown) through which air flows into the discharge section 42 from the scroll casing 4. Further, the other end of the discharge section 42 forms a discharge port 42a through which the air that has flowed through the flow path within the discharge section 42 is discharged to the outside air.

As shown in FIG. 2, the discharge part 42 has an extension plate 42b, a diffuser plate 42c, a first side plate part 42d, and a second side plate part 42e. The extension plate 42b is formed integrally with the peripheral wall 4c so as to smoothly continue to the winding end portion 41b on the downstream side of the peripheral wall 4c. The diffuser plate 42c is formed integrally with the tongue portion 43 of the scroll casing 4, and faces the extension plate 42b. For example, the diffuser plate 42c is formed at a predetermined angle with respect to the extension plate 42b so that the cross-sectional area of the flow path gradually expands along the direction in which air flows in the discharge portion 42. It is not limited to this configuration.

The first side plate portion 42d is formed integrally with the first side wall 4a1 of the scroll casing 4, and the second side plate portion 42e is formed integrally with the second side wall 4a2 of the scroll casing 4 on the opposite side. The first side plate portion 42d and the second side plate portion 42e are formed between the extension plate 42b and the diffuser plate 42c. Thus, in the discharge section 42, a flow path having a rectangular cross section is formed by the extension plate 42b, the diffuser plate 42c, the first side plate part 42d, and the second side plate part 42e.

(Relationship between fan 2 and scroll casing 4)
FIG. 6 is a partial cross-sectional view of the multi-blade centrifugal blower 1 according to the first embodiment. FIG. 6 is a cross-sectional view taken along line AA of the multi-blade centrifugal blower 1 in FIG. 1, viewed in the direction of the arrows. FIG. 6 is a sectional view of the multi-blade centrifugal blower 1 viewed in the radial direction of the rotation axis RA. The inflection point portion 26 is formed over the entire length of the blade 2d. The total length of the blade 2d is the length of the blade 2d along the axial direction of the rotation axis RA, and is the length between the base end 2h of the blade 2d on the main plate 2a side and the tip 2g of the blade 2d on the side plate 2c side. is the length of the part. The base end portion 2h is one end portion of the blade 2d in the axial direction of the rotation axis RA, and is an end portion on the main plate 2a side. The tip portion 2g is the other end of the blade 2d in the axial direction of the rotation axis RA, and is the end on the opposite side from the main plate 2a.

As shown in FIG. 6, in the multi-blade centrifugal blower 1, when viewed in the radial direction of the rotation axis RA, all parts of the inflection point portion 26 form an inner circumferential end portion 35 that forms the inner edge of the bell mouth 3. It is formed so as to be located on the inner circumferential side. That is, in the multi-blade centrifugal blower 1, as shown in FIG. It is formed so as to be located on the rotation axis RA side. In the multi-blade centrifugal blower 1, all portions of the inflection point portion 26 in the axial direction of the rotation axis RA are inner than the inner peripheral end portion 35 forming the inner edge of the bell mouth 3 in the radial direction of the fan 2. It is formed to be located on the side.

In the multi-blade centrifugal blower 1, an imaginary line B formed by an inflection point 26 from a base end 2h on the main plate 2a side of the blade 2d to a tip end 2g on the side plate 2c side is parallel to the rotation axis RA of the fan 2. It is formed to be. When the imaginary line B is formed to be parallel to the rotation axis RA of the fan 2, for example, when viewed in the radial direction of the rotation axis RA, the imaginary line B is formed to be parallel to the rotation axis RA by ±1 degree. It is in a state where it is formed so that the angle is within the range.

[Operation of multi-blade centrifugal blower 1]
The operation of the multi-blade centrifugal blower 1 will be explained using FIG. 2. In the multi-blade centrifugal blower 1, when a motor (not shown) is driven, a main plate 2a to which a motor shaft is connected rotates, and a plurality of blades 2d rotate around a rotation axis RA via the main plate 2a. When the fan 2 rotates, air outside the scroll casing 4 is sucked into the scroll casing 4 through the suction port 5.

Air sucked into the scroll casing 4 is guided by the bell mouth 3 and sucked into the fan 2. The air sucked into the fan 2 becomes an airflow to which dynamic pressure and static pressure are added during the process of passing between the plurality of blades 2d, and is blown out toward the outside in the radial direction of the fan 2. The airflow blown out from the fan 2 is blown out into the scroll casing 4 from the fan 2 due to the pressure increasing action of the fan 2 .

The airflow flowing inside the scroll casing 4 is pressurized by flowing through an air path that gradually expands from the winding start side to the winding end side by the spiral-shaped peripheral wall 4c. The air blown into the scroll casing 4 from the fan 2 is decelerated in the enlarged air path formed by the peripheral wall 4c of the scroll casing 4, recovers static pressure, and is blown out from the discharge port 42a shown in FIG. Ru.

[Effects of multi-blade centrifugal blower 1]
The fan 2 of the multi-blade centrifugal blower 1 includes a backward blade portion 22, a forward blade portion 21, an inflection point portion 26 forming an inflection point between the backward blade portion 22 and the forward blade portion 21, has. The inflection point portion 26 is the entire length of the blade 2d, which is a portion between the base end 2h on the main plate 2a side and the tip end 2g on the side plate 2c side of each of the plurality of blades 2d in the axial direction of the rotation axis RA. It is formed over a period of time. Further, all portions of the inflection point portion 26 in the axial direction of the rotation axis RA are located on the inner circumferential side of the inner circumferential end portion 35 forming the inner edge of the bell mouth 3 in the radial direction of the fan 2. is formed.

Here, the case where all parts of the inflection point part 26 are formed so as to be located on the inner peripheral side than the inner peripheral end part 35 of the bell mouth 3 is referred to as configuration A, and at least the inflection point part 26 is A case in which a part or all of the inner circumferential end portion 35 is located on the outer circumferential side is referred to as configuration B. When comparing configuration A and configuration B for fans 2 of the same diameter, configuration A has a larger proportion of the forward blade portion 21 in the radial distance of the fan 2 in the blade 2d than configuration B. Become. Therefore, in the multi-blade centrifugal blower 1, compared to a configuration in which at least a part or all of the inflection point portion 26 is located on the outer peripheral side than the inner peripheral end portion 35, the multi-blade centrifugal blower 1 is closer to the leading edge 25a. It is possible to make the change in the blade angle gentle from the part toward the part on the trailing edge 24a side, and it is possible to suppress the separation of the airflow on the negative pressure surface 2d2 and suppress the decrease in the air volume.

Further, in the fan 2, a virtual line B formed by an inflection point 26 from a base end 2h on the main plate 2a side to a tip 2g on the side plate 2c side of each of the plurality of blades 2d is aligned with the rotation axis RA. They are formed to be parallel. In the multi-blade centrifugal blower 1, since the imaginary line B and the rotation axis RA are formed parallel to each other, compared to the case where the imaginary line B and the rotation axis RA are not parallel to each other, the fan 2 is made of metal during manufacturing. Easy to pull out from the mold and easy to manufacture.

Embodiment 2.
FIG. 7 is a partial cross-sectional view of the multi-blade centrifugal blower 1 according to the second embodiment. FIG. 7 is a cross-sectional view taken along line AA of the multi-blade centrifugal blower 1 in FIG. 1, viewed in the direction of the arrows. Components having the same configuration as the multi-blade centrifugal blower 1 shown in FIGS. 1 to 6 are designated by the same reference numerals, and the description thereof will be omitted.

The multi-blade centrifugal blower 1 according to the second embodiment further specifies the relationship between the shapes of the blades 2d. Furthermore, in the multi-blade centrifugal blower 1 according to the second embodiment, the positional relationship between the blades 2d and the bell mouth 3 is further specified. The configuration of other parts other than the shape of the blade 2d and the positional relationship between the blade 2d and the bell mouth 3 is the same as that of the multi-blade centrifugal blower 1 according to the first embodiment. Therefore, in the following description, the configurations of the blades 2d and the bell mouth 3 of the multi-blade centrifugal blower 1 according to the second embodiment will be mainly described using FIG.

The blade 2d of the multi-blade centrifugal blower 1 according to the second embodiment has a notch-shaped stepped portion 27 formed on the leading edge 25a on the side plate 2c side. More specifically, in the leading edge 25a of the blade 2d, a notch-shaped step portion 27 is formed at the tip 2g on the side plate 2c side.

The stepped portion 27 is a portion formed by cutting out the wall that constitutes the front edge 25a and the tip portion 2g. The step portion 27 is formed in a portion of the front edge 25a, and is also formed in a portion of the tip portion 2g. In the step portion 27, the end portion of the front edge 25a on the side plate 2c side is cut out, and the end portion of the tip portion 2g on the rotation axis RA side is cut out. The stepped portion 27 is a portion formed by cutting out a continuous corner portion between the front edge 25a and the tip portion 2g. As shown in FIG. 7, the stepped portion 27 is formed at the tip portion 2g of the rearward blade portion 22 and the forward blade portion 21 on the side plate 2c side.

The stepped portion 27 is formed by a side edge 27A extending in the axial direction of the rotation axis RA of the fan 2 and an upper edge 27B extending in the radial direction of the fan 2. In the fan 2, the upper edge 27B is an edge located closer to the main plate 2a than the tip 2g. The fan 2 has a step formed between the upper edge 27B and the tip 2g in the axial direction of the rotation axis RA. Further, the fan 2 is formed such that the side edge 27A is located on the outer peripheral side of the fan 2 with respect to an imaginary extension line C of the front edge 25a of the stepped portion 27. The fan 2 has a step formed between the front edge 25a and the side edge 27A in the radial direction of the rotation axis RA.

The stepped portion 27 is not limited to a configuration formed by a side edge 27A extending in the axial direction of the rotation axis RA of the fan 2 and an upper edge 27B extending in the radial direction of the fan 2. For example, the stepped portion 27 may be formed as an arcuate edge in which the side edge 27A and the upper edge 27B are continuously formed integrally.

In the multi-blade centrifugal blower 1 according to the second embodiment, the outer diameter of the blade formed by the outer peripheral end 24 of each of the plurality of blades 2d is larger than the inner diameter of the bell mouth 3. That is, in the multi-blade centrifugal blower 1 according to the second embodiment, when viewed in the axial direction of the rotation axis RA, the outer peripheral end 24 of the blade 2d is aligned with the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2. It is formed so as to be located on the outer peripheral side. Furthermore, in the multi-blade centrifugal blower 1 according to the second embodiment, at least a portion of the leading edge 25a of the blade 2d is inside the bell mouth 3 in the radial direction of the fan 2 when viewed in the axial direction of the rotation axis RA. It is formed so as to be located on the inner circumferential side of the circumferential end portion 35 .

In the blade 2d, the boundary between the tip 2g and the stepped portion 27 is referred to as a stepped starting point 27C. The step starting point 27C is the boundary between the tip 2g of the blade 2d and the side edge 27A in the blade 2d. The step starting point 27C is a corner portion of the blade 2d formed by the tip portion 2g and the side edge portion 27A. The multi-blade centrifugal blower 1 according to the second embodiment is formed such that the step start point 27C of the blade 2d is located closer to the outer circumferential side than the inner circumferential end 35 of the bell mouth 3 in the radial direction of the fan 2. .

As shown in FIG. 7, in the multi-blade centrifugal blower 1 according to the second embodiment, the inner peripheral end portion 35 of the bell mouth 3 is arranged above the stepped portion 27. The multi-blade centrifugal blower 1 according to the second embodiment is configured such that the inner peripheral end portion 35 of the bell mouth 3 faces the stepped portion 27 in the axial direction of the rotation axis RA. More specifically, the multi-blade centrifugal blower 1 according to the second embodiment is arranged such that the inner peripheral end 35 of the bell mouth 3 faces the upper edge 27B in the axial direction of the rotation axis RA. . The multi-blade centrifugal blower 1 according to the second embodiment forms a gap between the inner peripheral end 35 of the bell mouth 3 and the upper edge 27B.

The multi-blade centrifugal blower 1 according to the second embodiment may further be arranged such that the inner peripheral end 35 of the bell mouth 3 faces the side edge 27A in the radial direction of the fan 2. The multi-blade centrifugal blower 1 according to the second embodiment forms a gap between the inner peripheral end 35 and the upper edge 27B of the bell mouth 3 in the axial direction of the rotation axis RA, and also forms a gap in the radial direction of the rotation axis RA. A gap may be formed between the inner peripheral end 35 of the bell mouth 3 and the side edge 27A.

[Effects of multi-blade centrifugal blower 1]
Each of the plurality of blades 2d has a notch-shaped stepped portion 27 formed on a leading edge 25a on the side plate 2c side. When the boundary between the tip portion 2g and the stepped portion 27 is defined as the step starting point 27C, the step starting point 27C is located on the outer circumferential side of the inner circumferential end 35 of the bell mouth 3 in the radial direction of the fan 2. is formed. In the multi-blade centrifugal blower 1 according to the second embodiment, even if the height of the blade 2d is increased to increase the blade surface, the blade 2d does not fit inside the bell mouth 3 due to the stepped portion 27. It does not interfere with the peripheral end portion 35.

The multi-blade centrifugal blower 1 is formed such that the step starting point 27C is located on the outer peripheral side of the inner peripheral end 35 of the bell mouth 3, so that the inner peripheral end 35 of the bell mouth 3 and the blade 2d are The height of the blade 2d in the axial direction of the rotation axis RA can be increased while maintaining the interval . The multi-blade centrifugal blower 1 according to the second embodiment can bring the tips 2g of the blades 2d closer to the side walls 4a and increase the blade area compared to the blades 2d without the stepped portion 27. You can get the air volume.

Embodiment 3.
FIG. 8 is a partial cross-sectional view of the multi-blade centrifugal blower 1 according to the third embodiment. FIG. 8 is a cross-sectional view taken along line AA of the multi-blade centrifugal blower 1 in FIG. 1, viewed in the direction of the arrows. Components having the same configuration as the multi-blade centrifugal blower 1 shown in FIGS. 1 to 6 are designated by the same reference numerals, and the description thereof will be omitted.

The multi-blade centrifugal blower 1 according to the third embodiment specifies the positional relationship between the blades 2d and the bell mouth 3. The configuration of the other parts other than the positional relationship between the blades 2d and the bell mouth 3 is the same as that of the multi-blade centrifugal blower 1 according to the first embodiment. Therefore, in the following explanation, the configurations of the blades 2d and the bell mouth 3 of the multi-blade centrifugal blower 1 according to the third embodiment will be mainly explained using FIG.

In the multi-blade centrifugal blower 1 according to the third embodiment, the outer diameter of the blade formed by the outer peripheral end 24 of each of the plurality of blades 2d is larger than the inner diameter of the bell mouth 3. That is, in the multi-blade centrifugal blower 1 according to the third embodiment, when viewed in the axial direction of the rotation axis RA, the outer peripheral end 24 of the blade 2d is aligned with the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2. It is formed so as to be located on the outer peripheral side.

In the multi-blade centrifugal blower 1 according to the third embodiment, when viewed in the axial direction of the rotation axis RA, in the radial direction of the fan 2, a part of the leading edge 25a of the blade 2d is located at the inner peripheral end of the bell mouth 3. It is formed so as to be located on the inner circumferential side than 35. In the multi-blade centrifugal blower 1 according to the third embodiment, when viewed in the axial direction of the rotation axis RA, the backward blade portion 22 is located further inward than the inner circumferential end portion 35 of the bell mouth 3 in the radial direction of the fan 2. It is formed so as to be located on the circumferential side.

In the fan 2, the leading edge 25a located at the boundary between the leading edge 25a of the blade 2d and the tip 2g is referred to as a side plate side leading edge 25b. The side plate side leading edge portion 25b constitutes a part of the corner portion of the wing 2d formed by the tip portion 2g and the leading edge 25a. The multi-blade centrifugal blower 1 according to Embodiment 3 is formed such that the front edge portion 25b of the blade 2d on the side plate side is located on the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3 in the radial direction of the fan 2. ing. That is, in the multi-blade centrifugal blower 1 according to the third embodiment, the inner peripheral end 35 of the bell mouth 3 is formed so as to face a part of the leading edge 25a of the blade 2d in the axial direction of the rotation axis RA. ing.

[Effects of multi-blade centrifugal blower 1]
The multi-blade centrifugal blower 1 according to the third embodiment is formed such that the front edge portion 25b on the side plate side is located on the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3 in the radial direction of the fan 2. In the multi-blade centrifugal blower 1 according to Embodiment 3, even if the height of the blade 2d is increased to increase the blade surface, the front edge 25b on the side plate side is closer to the outer periphery than the inner periphery end 35 of the bell mouth 3. By being formed so as to be located on the side, the wings 2d do not interfere with the inner peripheral end portion 35 of the bell mouth 3.

The multi-blade centrifugal blower 1 is formed such that the front edge portion 25b on the side plate side is located on the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3, so that the inner peripheral end portion 35 of the bell mouth 3 and the blade The height of the blade 2d in the axial direction of the rotation axis RA can be increased while maintaining the distance from the blade 2d. The multi-blade centrifugal blower 1 has a tip portion 2g of the blade 2d that is formed such that the front edge portion 25b on the side plate side is located on the inner peripheral side of the inner peripheral end portion 35 of the bell mouth 3. Since it can be brought close to the side wall 4a and the blade area can be increased, a large amount of air can be obtained.

Embodiment 4.
FIG. 9 is a partially enlarged view of the fan 2 in the multi-blade centrifugal blower 1 according to the fourth embodiment. FIG. 9 is an enlarged view of the fan 2 viewed in the axial direction of the rotation axis RA. In FIG. 9, the wing 2d is shown with the bell mouth 3 transparent in order to show the shape of the wing 2d. Components having the same configuration as the multi-blade centrifugal blower 1 shown in FIGS. 1 to 8 are denoted by the same reference numerals, and the description thereof will be omitted.

In the multi-blade centrifugal blower 1 according to the fourth embodiment, the shape of the blades 2d is further specified. The configuration other than the shape of the blade 2d described below is the same as that of the multi-blade centrifugal blower 1 according to the first embodiment. Therefore, in the following explanation, the shape of the blade 2d of the multi-blade centrifugal blower 1 according to the fourth embodiment will be mainly explained using FIG.

When the blade 2d is viewed in the axial direction of the rotation axis RA, the arc-shaped portion of the blade 2d is referred to as an arc portion AR. In the blade 2d of the multi-blade centrifugal blower 1 according to the fourth embodiment, the portion from the inflection point 26 to the trailing edge 24a (see FIG. 3) of the blade 2d is one arcuate portion AR, as shown in FIG. Alternatively, it is composed of a plurality of arcuate portions AR. That is, in the blade 2d of the multi-blade centrifugal blower 1 according to the fourth embodiment, the forward vane portion 21 is composed of one circular arc portion AR or a plurality of circular arc portions AR, as shown in FIG. In the blade 2d of the multi-blade centrifugal blower 1 according to the fourth embodiment, the portion from the inflection point 26 to the trailing edge 24a (see FIG. 3) of the blade 2d is composed of at least one arcuate portion AR. There is.

The arc portion AR is a portion formed in an arc shape in the blade 2d when viewed in the axial direction of the rotation axis RA. The rear edge 24a is formed at the outer peripheral end 24. The outer peripheral end 24 is an end on the outer peripheral side of the blade 2d in a cross section perpendicular to the rotation axis RA, and the trailing edge 24a is a part where the outer peripheral end 24 is continuous in the axial direction of the rotation axis.

[Effects of multi-blade centrifugal blower 1]
In each of the plurality of blades 2d, a portion from the inflection point portion 26 to the trailing edge 24a of the blade 2d is constituted by at least one or more circular arc portions AR. In the multi-blade centrifugal blower 1 according to the fourth embodiment, the portion from the inflection point 26 of the blade 2d to the trailing edge 24a of the blade is configured with at least one arcuate portion AR, so that the fan 2 This suppresses sudden angle changes of the blade 2d in the radial direction. Therefore, the multi-blade centrifugal blower 1 can suppress separation of airflow on the negative pressure surface 2d2 and suppress a decrease in air volume.

Although the preferred embodiments have been described in detail above, they are not limited to the embodiments described above, and various modifications may be made to the embodiments described above without departing from the scope of the claims. Variations and substitutions can be made.

Hereinafter, various aspects of the present disclosure will be collectively described as supplementary notes.

(Additional note 1)
A main plate having a circular shape when viewed in the axial direction of the rotating shaft, a plurality of blades installed on the peripheral edge of the main plate, and a side opposite to the main plate of the plurality of blades in the axial direction of the rotating shaft. a fan having an annular side plate fixing an end;
It has a peripheral wall formed in a spiral shape and at least one side wall having a bell mouth forming an inlet, forming an outlet from which airflow generated by the fan is discharged, and housing the fan. scroll casing;
Equipped with
The fan is
In the radial direction of the fan, a rearward blade portion that constitutes a rearward blade at an inner peripheral side portion of each of the plurality of blades;
In the radial direction of the fan, a forward blade portion that constitutes a forward blade at an outer peripheral side portion of each of the plurality of blades;
an inflection point portion that forms an inflection point between the backward blade portion and the forward blade portion when viewed in the axial direction of the rotating shaft;
has
The inflection point portion is
In the axial direction of the rotating shaft, the inflection point is formed over the entire length of the blade, which is a portion between the base end on the main plate side and the tip end on the side plate side of each of the plurality of blades. A multi-blade centrifugal blower, wherein all portions in the axial direction of the fan are located on the inner peripheral side of an inner peripheral end forming an inner edge of the bell mouth in the radial direction of the fan.
(Additional note 2)
The fan is
An imaginary line formed by the inflection point from the base end on the main plate side to the tip end on the side plate side of each of the plurality of wings is formed so as to be parallel to the rotation axis. The multi-blade centrifugal blower described in Supplementary Note 1.
(Additional note 3)
Each of the plurality of wings is
A notch-like stepped portion is formed on the front edge of the side plate,
When the boundary between the tip end and the stepped portion is defined as a step starting point, the step starting point is located on the outer peripheral side of the inner peripheral end of the bell mouth in the radial direction of the fan. The multi-blade centrifugal blower according to

supplementary note

1 or 2, which is formed.
(Additional note 4)
In the fan, when the front edge located at the boundary between the front edge of each of the plurality of blades and the tip portion is a side plate side front edge,
The multi-blade according to any one of Supplementary Notes 1 to 3, wherein the front edge on the side plate side is formed to be located on the outer peripheral side of the inner peripheral end of the bell mouth in the radial direction of the fan. Centrifugal blower.
(Appendix 5)
When viewed in the axial direction of the rotating shaft, when the arc-shaped portion of the blade is defined as the arc portion,
Each of the plurality of wings is
The multi-blade centrifugal blower according to any one of appendices 1 to 4, wherein a portion from the inflection point to the trailing edge of the blade is constituted by at least one or more circular arc portions.

1 Multi-blade centrifugal blower, 2 Fan, 2a Main plate, 2a1 Periphery, 2a2 Center, 2b Boss, 2c Side plate, 2d Wing, 2d1 Positive pressure surface, 2d2 Negative pressure surface, 2e Fan suction port, 2f Outer surface, 2g Tip , 2h base end, 3 bell mouth, 4 scroll casing, 4a side wall, 4a1 first side wall, 4a2 second side wall, 4c peripheral wall, 5 suction port, 21 forward blade part, 22 backward blade part, 24 outer peripheral end, 24a rear edge, 25 inner peripheral end, 25a front edge, 25b side plate side front edge, 26 inflection point, 27 step part, 27A side edge, 27B upper edge, 27C step start point, 35 inner peripheral end Part, 41 scroll part, 41b winding end part, 42 discharge part, 42a discharge port, 42b extension plate, 42c diffuser plate, 42d first side plate part, 42e second side plate part, 43 tongue part, AR arc part, B virtual line.

Claims

A main plate having a circular shape when viewed in the axial direction of the rotating shaft, a plurality of blades installed on the peripheral edge of the main plate, and a side opposite to the main plate of the plurality of blades in the axial direction of the rotating shaft. a fan having an annular side plate fixing an end;
It has a peripheral wall formed in a spiral shape and at least one side wall having a bell mouth forming an inlet, forming an outlet from which airflow generated by the fan is discharged, and housing the fan. scroll casing;
Equipped with
The fan is
In the radial direction of the fan, a rearward blade portion that constitutes a rearward blade at an inner peripheral side portion of each of the plurality of blades;
In the radial direction of the fan, a forward blade portion that constitutes a forward blade at an outer peripheral side portion of each of the plurality of blades;
an inflection point portion that forms an inflection point between the backward blade portion and the forward blade portion when viewed in the axial direction of the rotating shaft;
has
The inflection point portion is
In the axial direction of the rotating shaft, the inflection point is formed over the entire length of the blade, which is a portion between the base end on the main plate side and the tip end on the side plate side of each of the plurality of blades. A multi-blade centrifugal blower, wherein all portions in the axial direction of the fan are located on the inner peripheral side of an inner peripheral end forming an inner edge of the bell mouth in the radial direction of the fan.
The fan is
An imaginary line formed by the inflection point from the base end on the main plate side to the tip end on the side plate side of each of the plurality of wings is formed so as to be parallel to the rotation axis. The multi-blade centrifugal blower according to claim 1.
Each of the plurality of wings is
A notch-like stepped portion is formed on the front edge of the side plate,
When a boundary between the tip end portion and the stepped portion is defined as a step starting point, the step starting point is located on the outer peripheral side of the inner peripheral end of the bell mouth in the radial direction of the fan. The multi-blade centrifugal blower according to claim 1 or 2, wherein the multi-blade centrifugal blower is formed.
In the fan, when the front edge located at the boundary between the leading edge of each of the plurality of blades and the tip portion is a side plate side front edge,
The fan according to any one of claims 1 to 3, wherein the front edge on the side plate side is formed to be located on the outer peripheral side of the inner peripheral end of the bell mouth in the radial direction of the fan. Wing centrifugal blower.
When viewed in the axial direction of the rotating shaft, when the arc-shaped portion of the blade is defined as the arc portion,
Each of the plurality of wings is
The multi-blade centrifugal blower according to any one of claims 1 to 4, wherein a portion from the inflection point to the trailing edge of the blade is comprised of at least one or more circular arc portions.