Multi-blade centrifugal blower

Abstract

A multi-blade centrifugal blower is provided with: a fan having a main plate, a plurality of blades, and an annular side plate for fixing the ends of the plurality of blades on the opposite side from the main plate; and a volute having a peripheral wall formed in a scroll shape and at least one side wall having a bell mouth forming a suction port, the volute housing accommodating the fan, the fan having: a rearward blade portion constituting a rearward blade at a portion on the inner peripheral side of each of the plurality of blades; a forward vane part that constitutes a forward vane in a portion on the outer peripheral side of each of the plurality of vanes; and an inflection point portion forming an inflection point between the rearward blade portion and the forward blade portion, the inflection point portion being formed throughout the entire length of the blade, which is a portion between the base end portion on the main plate side and the tip end portion on the side plate side of each of the plurality of blades. All parts of the inflection point part in the axial direction are formed to be closer to the inner circumferential side than the inner circumferential end part of the inner edge forming the horn mouth in the radial direction of the fan.

Description

Technical Field

[0001] The present disclosure relates to a multi-blade centrifugal blower having a scroll casing. Background Art

[0002] Conventional multi-blade centrifugal blowers include a fan having a disc-shaped main board, a plurality of blades arranged on the peripheral portion of the main board, and a side plate for fixing the ends of the blades. In addition, conventional multi-blade centrifugal blowers include a volute having a vortex-shaped peripheral wall covering the fan, and a bell mouth for smoothly guiding the airflow to the fan is provided at the suction port of the volute. Conventional multi-blade centrifugal blowers utilize an expanded air path inside the volute to increase the pressure of the airflow flowing out from between the blades through the rotation of the fan, so that most of the blades become forward blades inclined in the direction of rotation of the fan. However, the airflow angle toward the blade of the airflow guided to the inside of the volute along the bell mouth is mostly inconsistent with the inlet angle of the forward blade, and conventional multi-blade centrifugal blowers produce airflow separation at the negative pressure surface on the leading edge side of the blade, which may reduce the air volume. Therefore, the following multi-blade centrifugal blower is proposed: by providing a backward blade on the inner circumferential side of the forward blade in the direction opposite to the fan rotation direction, the airflow guided from the bell mouth is smoothly guided to the blade, thereby suppressing the separation of the airflow generated at the negative pressure surface on the leading edge side of the blade, and suppressing the reduction of air volume (for example, refer to patent document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-70793 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, the inner side of the blade of the multi-blade centrifugal blower of Patent Document 1 becomes a backward blade, and the outer side of the blade becomes a forward blade. The angle of the blade surface between the inner side portion and the outer side portion of the blade changes greatly, so new airflow separation is generated at the negative pressure surface of the blade, and the air volume may be reduced.

[0008] The present disclosure aims to solve the above-mentioned problems and provides a multi-blade centrifugal blower capable of suppressing separation of airflow at the negative pressure surface of the blade and suppressing a decrease in air volume.

[0009] Means for solving problems

[0010] The multi-blade centrifugal blower disclosed in the present invention comprises: a fan having a main plate which is circular when viewed along the axial direction of a rotating shaft, a plurality of blades arranged on the peripheral edge of the main plate, and an annular side plate, the side plate fixing the ends of the plurality of blades on the opposite side of the main plate in the axial direction of the rotating shaft; and a volute having a peripheral wall formed in a vortex shape, and at least one side wall, the at least one side wall having a bell mouth forming an inlet, the volute forming an outlet for discharging the airflow generated by the fan and accommodating the fan, the fan having: a backward blade portion, which is formed in the radial direction of the fan at the plurality of blades The inner circumferential side portions of each of the plurality of blades constitute the backward blade; the forward blade portion, which, in the radial direction of the fan, is the outer circumferential side portion of each of the plurality of blades and constitutes the forward blade; and the inflection point portion, which, when observed along the axial direction of the rotating shaft, forms the inflection point of the backward blade portion and the forward blade portion, the inflection point portion is formed in the axial direction of the rotating shaft and extends over the portion between the base end portion on the main board side and the terminal end portion on the side plate side of each of the plurality of blades, that is, the entire length of the blade, and all axial portions of the inflection point portion are formed to be located on the inner circumferential side of the inner circumferential end portion forming the inner edge of the bell mouth in the radial direction of the fan.

[0011] Effects of the Invention

[0012] The fan of the multi-blade centrifugal blower disclosed in the present invention has a backward blade portion, a forward blade portion, and an inflection point portion forming an inflection point between the backward blade portion and the forward blade portion. The inflection point portion is formed in the axial direction of the rotating shaft, covering the portion between the base end portion on the main board side and the terminal end portion on the side plate side of each of the multiple blades, that is, the entire length of the blade. In addition, all portions of the inflection point portion in the axial direction of the rotating shaft are formed to be located at a position closer to the inner circumference than the inner peripheral end portion forming the inner edge of the bell mouth in the radial direction of the fan. In a structure in which all portions of the inflection point portion are located at a position closer to the inner circumference than the inner peripheral end portion of the bell mouth, the proportion of the forward blade portion in the blade becomes larger than the structure in which at least a portion or all portions of the inflection point portion are located at a position closer to the outer circumference than the inner peripheral end portion. Therefore, the multi-blade centrifugal blower can make the change of the blade angle from the portion on the leading edge side to the portion on the trailing edge side smooth, and can suppress the separation of the airflow at the negative pressure surface and suppress the reduction of the air volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is an external view schematically showing the structure of the multi-blade centrifugal fan 1 according to the first embodiment when viewed parallel to the rotation axis RA.

[0014] Figure 2 This is a perspective view of the multi-blade centrifugal fan according to Embodiment 1.

[0015] Figure 3 This is a perspective view of a fan of the multi-blade centrifugal blower according to Embodiment 1.

[0016] Figure 4This is a plan view of the fan of the multi-blade centrifugal blower according to Embodiment 1.

[0017] Figure 5 This is a partially enlarged view of the fan of the multi-blade centrifugal blower according to the first embodiment.

[0018] Figure 6 This is a partial cross-sectional view of the multi-blade centrifugal fan according to the first embodiment.

[0019] Figure 7 This is a partial cross-sectional view of the multi-blade centrifugal fan according to the second embodiment.

[0020] Figure 8 This is a partial cross-sectional view of the multi-blade centrifugal blower according to the third embodiment.

[0021] Fig. 9 This is a partially enlarged view of a fan of the multi-blade centrifugal blower according to the fourth embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, the multi-blade centrifugal blower of the embodiment will be described with reference to the drawings and the like. Figure 1 In the following drawings, there are cases where the relative size relationship and shape of each component are different from the actual ones. In addition, in the following drawings, the parts marked with the same reference numerals are the same or equivalent parts, which are common to the entire text of the specification. In addition, for easy understanding, terms indicating directions (such as "upper", "lower", "right", "left", "front", "back", etc.) are used appropriately, but these expressions are recorded only for the convenience of explanation and do not limit the configuration and orientation of the device or components.

[0023] Implementation method 1.

[0024] [Multi-blade centrifugal blower 1]

[0025] Figure 1 This is an external view schematically showing the structure of the multi-blade centrifugal fan 1 according to the first embodiment when viewed parallel to the rotation axis RA. Figure 2 It is a perspective view of the multi-blade centrifugal fan 1 according to the first embodiment. Figure 1 The arrow R indicates the rotation direction of the fan 2, and the dotted arrow CD indicates the circumferential direction of the fan 2. Figure 2 1 is a diagram for explaining the appearance of the multi-blade centrifugal fan 1, and a simplified diagram showing the internal structure of the multi-blade centrifugal fan 1. Figure 1 and Figure 2 , the basic structure of the multi-blade centrifugal blower 1 is described.

[0026] The multi-blade centrifugal blower 1 is a device that uses the centrifugal force generated by the rotation of the fan 2 to blow air, such as a Sirocco fan. The multi-blade centrifugal blower 1 is a single-suction centrifugal blower that draws air from one side of the volute 4 in the axial direction of the imaginary rotation axis RA of the fan 2. In addition, the multi-blade centrifugal blower 1 is not limited to a single-suction centrifugal blower, and may also be a double-suction centrifugal blower that draws air from both sides of the volute 4 in the axial direction of the rotation axis RA. Figure 1 and Figure 2 As shown, a multi-blade centrifugal fan 1 includes a fan 2 for generating airflow and a scroll casing 4 for accommodating the fan 2 therein.

[0027] (Fan 2)

[0028] Figure 3 This is a perspective view of the fan 2 of the multiblade centrifugal fan 1 according to the first embodiment. Figure 4 This is a top view of the fan 2 of the multi-blade centrifugal blower 1 according to the first embodiment. Figure 4 FIG. 2 is a diagram of the fan 2 viewed along the axial direction of the rotation axis RA. Figure 1 to Figure 4 The fan 2 will be described.

[0029] 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 driven by the motor to force air to be sent radially outward by the centrifugal force generated by the rotation. The fan 2 is rotated in the direction indicated by the arrow R by the motor or the like.

[0030] like Figure 1 As shown, when viewed along the direction of the rotation axis RA, the fan 2 has a circular main plate 2a, an annular side plate 2c, and a plurality of blades 2d radially arranged around the rotation axis RA at the peripheral portion of the main plate 2a. The fan 2 is formed into a bottomed cylindrical shape by the main plate 2a and the plurality of blades 2d arranged on the main plate 2a.

[0031] The fan 2 is provided with a fan inlet 2e in the axial direction of the rotation axis RA at a portion of the side plate 2c on the side opposite to the main plate 2a. The fan inlet 2e is an opening of the fan 2 into which the air flowing into the inside of the fan 2 flows, so that the gas flows into the space surrounded by the main plate 2a and the plurality of blades 2d.

[0032] (Motherboard 2a)

[0033] The main plate 2a is formed in a circular shape when viewed in the axial direction of the rotation axis RA, and has a peripheral edge portion 2a1 formed on the outer peripheral side and a central portion 2a2 formed on the inner peripheral side in the radial direction centered on the rotation axis RA.

[0034] The portion of the peripheral portion 2a1 formed on the outer peripheral side relative to the central portion 2a2 is formed in an annular shape when viewed along the axial direction of the rotation axis RA. The peripheral portion 2a1 is formed in a plate shape. The central portion 2a2 is formed in a manner protruding from the edge portion of the inner peripheral side of the peripheral portion 2a1 relative to the peripheral portion 2a1. The central portion 2a2 is formed by a plate-shaped member formed in a mountain shape. The central portion 2a2 is formed on the inner side of the plurality of blades 2d.

[0035] The main board 2a may also be formed integrally with a peripheral portion 2a1 and a central portion 2a2. The main board 2a may also be formed as a flat plate as a whole. The main board 2a may also be formed in a disc shape or a polygonal shape, etc. The thickness of the main board 2a may be formed in a radial direction with the rotation axis RA as the center so that the wall thickness becomes thicker toward the center, or may be formed in a fixed thickness in a radial direction with the rotation axis RA as the center. In addition, the main board 2a is not limited to being composed of a single plate-like component, but may also be composed of a plurality of plate-like components fixed integrally. In addition, the radial direction with the rotation axis RA as the center refers to a direction perpendicular to the axial direction of the rotation axis RA.

[0036] A boss portion 2b connected to the drive shaft of the motor is provided at the center of the main board 2a. An axial hole for inserting the drive shaft of the motor is formed in the boss portion 2b. The boss portion 2b is formed in a cylindrical shape, for example, but the shape of the boss portion 2b is not limited to a cylindrical shape. The boss portion 2b only needs to be formed in a columnar shape, for example, it can also be formed in a polygonal column shape. The main board 2a is driven to rotate by the motor via the boss portion 2b.

[0037] (Side panel 2c)

[0038] The fan 2 has an annular side plate 2c, which is mounted on the end of the plurality of blades 2d on the side opposite to the main board 2a in the axial direction of the rotation axis RA. The side plate 2c fixes the end of the plurality of blades 2d on the side opposite to the main board 2a in the axial direction of the rotation axis RA. The side plate 2c is disposed on the outer peripheral surface 2f of the fan 2. The side plate 2c is disposed on the outer portion of the blade 2d in the radial direction centered on the rotation axis RA. The side plate 2c may also be disposed on the end portion 2g of the plurality of blades 2d protruding from the main board 2a in the direction of the rotation axis RA. The side plate 2c maintains the positional relationship of the ends of the blades 2d by connecting the plurality of blades 2d. In addition, the side plate 2c strengthens the strength of the plurality of blades 2d by connecting the plurality of blades 2d.

[0039] (Blade 2d)

[0040] The plurality of blades 2d are arranged at the peripheral edge 2a1 of the main plate 2a. One end of the plurality of blades 2d is connected to the main plate 2a, and the other end is connected to the side plate 2c, and the plurality of blades 2d are arranged in a circumferential direction with the rotation axis RA as the center. The plurality of blades 2d are respectively arranged at least between the main plate 2a and the side plate 2c. The plurality of blades 2d are arranged in a circular shape with the boss portion 2b as the center, and the base ends are fixed to the plate surface of the main plate 2a. Figure 3 As shown, in the blade 2d, the surface on the rotation direction side is a positive pressure surface 2d1, and the surface on the side opposite to the rotation direction is a negative pressure surface 2d2.

[0041] Each blade 2d is arranged in the circumferential direction at a fixed interval on the peripheral edge 2a1 of the main board 2a. Each blade 2d is arranged in a manner of standing up from the main board 2a and is formed in a plate shape. Each blade 2d is arranged in a manner of standing up substantially vertically relative to the main board 2a, but is not particularly limited thereto, and each blade 2d may also be arranged in a manner of being inclined relative to the vertical direction of the main board 2a.

[0042] like Figure 3 As shown in FIG. 1 , the blade 2d is inclined in such a manner that the leading edge 25a of the blade 2d moves away from the rotation axis RA as it moves from the portion on the main plate 2a side toward the portion on 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 the end of the inner peripheral side of the blade 2d in a cross section perpendicular to the rotation axis RA, and the leading edge 25a is the portion formed by connecting the inner peripheral end 25 in the axial direction of the rotation axis. The leading edge 25a of the blade 2d is inclined in such a manner that the inner diameter of the blade increases as it moves from the portion on the main plate 2a side toward the portion on the side plate 2c side.

[0043] Figure 5 This is a partially enlarged view of the fan 2 of the multi-blade centrifugal fan 1 according to the first embodiment. Figure 5 FIG. 2 is an enlarged view of the fan 2 viewed along the axial direction of the rotation axis RA. Figure 5 In order to show the shape of the blade 2d, the blade 2d is shown through the bell mouth 3. Figure 5 As shown in FIG. 2 , a portion of the inner peripheral side of the blade 2 d is formed so as to be located inside the inner peripheral end portion 35 of the bell mouth 3. Figure 5 As shown, the blade 2d of the fan 2 is integrally formed with a forward blade portion 21 and a backward blade portion 22.

[0044] The blade 2d has a forward blade portion 21 including an outer peripheral end 24 and configured as a forward blade, and a backward blade portion 22 including an inner peripheral end 25 and configured as a backward blade. In addition, when viewed in the axial direction of the rotation axis RA of the fan 2, the blade 2d has an inflection point portion 26 that forms an inflection point between the backward blade portion 22 and the forward blade portion 21. The blade 2d is continuously formed as a whole in the radial direction of the fan 2 from the rotation axis RA toward the outer peripheral side in the order of the backward blade portion 22, the inflection point portion 26, and the forward blade portion 21.

[0045] The backward blade portion 22 is a portion of the backward blade on the inner circumference of each of the plurality of blades 2d in the radial direction of the fan 2. The forward blade portion 21 is a portion of the forward blade on the outer circumference of each of the plurality of blades 2d in the radial direction of the fan 2.

[0046] In the blade 2d in which the inner peripheral part is formed by the rearward blade and the outer peripheral part is formed by the forward blade, the inflection point portion 26 forms the portion that changes from the rearward blade portion 22 to the forward blade portion 21. That is, in the blade 2d in which the inner peripheral part is formed by the rearward blade and the outer peripheral part is formed by the forward blade, the inflection point portion 26 forms the inflection point of the rearward 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 other words, in the blade 2d in which the inner peripheral part is formed by the rearward blade and the outer peripheral part is formed by the forward blade, the inflection point portion 26 forms the connection point of the rearward 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 formed by connecting the inflection point of the boundary between the rearward blade portion 22 and the forward blade portion 21 in the axial direction of the rotation axis RA, and is a portion formed by connecting the connection point of the rearward blade portion 22 and the forward blade portion 21.

[0047] The fan 2 is driven by a motor (not shown) to rotate about the rotation axis RA. As the fan 2 rotates, the air outside the multi-blade centrifugal blower 1 passes through the Figure 1 The air inlet 5 of the volute 4 and the fan inlet 2e of the fan 2 are sucked into the space surrounded by the main plate 2a and the plurality of blades 2d. The air sucked into the space surrounded by the main plate 2a and the plurality of blades 2d is sent radially outward of the fan 2 through the space between the blade 2d and the adjacent blade 2d by the rotation of the fan 2.

[0048] (Voltage 4)

[0049] use Figure 1 and Figure 2 , the volute 4 is described. The volute 4 accommodates the fan 2 inside and rectifies the air blown out from the fan 2. The volute 4 is a single-suction housing having a side wall 4a on one side of the main board 2a in the axial direction of the rotation axis RA, on which a suction port 5 described later is formed. The volute 4 is not limited to a single-suction housing, and may be a double-suction housing having a side wall 4a on both sides of the main board 2a in the axial direction of the rotation axis RA, on which a suction port 5 described later is formed.

[0050] The scroll housing 4 has a scroll portion 41 and a discharge portion 42. The scroll housing 4 has a circumferential wall 4c formed in a scroll shape and side walls 4a provided on both sides of the fan 2 in the axial direction of the rotation axis RA.

[0051] (Scroll 41)

[0052] Scroll portion 41 forms an air passage that converts dynamic pressure of airflow generated by fan 2 into static pressure. Scroll portion 41 includes side wall 4a covering fan 2 in the axial direction of rotation axis RA and peripheral wall 4c surrounding fan 2 in the radial direction of rotation axis RA of boss portion 2b.

[0053] In addition, the vortex portion 41 has a tongue portion 43, which is located between the discharge portion 42 and forms a curved surface, and guides the airflow generated by the fan 2 to the discharge port 42a via the vortex portion 41. The internal space of the vortex portion 41 formed by the peripheral wall 4c and the side wall 4a becomes a space where the air blown out from the fan 2 flows along the peripheral wall 4c.

[0054] (Side wall 4a)

[0055] In the first embodiment, the volute 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 the first side wall 4a1, and the side wall 4a not forming the suction port 5 and the bell mouth 3 is referred to as the second side wall 4a2. The two side walls 4a disposed on both sides of the fan 2 are formed in a manner of being opposed to each other with the peripheral wall 4c interposed therebetween.

[0056] like Figure 2 As shown, the volute 4 of Embodiment 1 includes a first side wall 4a1 and a second side wall 4a2 as the side wall 4a. That is, the volute 4 has at least one side wall 4a having a bell mouth 3 forming a suction port 5 communicating with a space formed by the main plate 2a and the plurality of blades 2d.

[0057] The first side wall 4a1 is located on the side where the side plate 2c is arranged relative to the main board 2a. The second side wall 4a2 is located on the side where the main board 2a is arranged relative to the side plate 2c. The side wall 4a is a general term for the first side wall 4a1 and the second side wall 4a2.

[0058] The first side wall 4a1 of the volute 4 is provided with an inlet 5 so that air can flow between the fan 2 and the outside of the volute 4. The inlet 5 is connected to the fan inlet 2e and is an air intake for allowing gas to flow into the space surrounded by the main board 2a and the plurality of blades 2d. The inlet 5 is formed at a position facing the plate surface of the main board 2a.

[0059] The suction port 5 provided on the first side wall 4a1 is formed by the bell mouth 3. That is, the bell mouth 3 forms the suction port 5 that connects the space outside the volute 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 flows into the fan suction port 2e of the fan 2.

[0060] The bell mouth 3 is formed so that the opening diameter gradually decreases from the outside toward the inside of the volute 4. The bell mouth 3 is formed to extend along the axial direction of the rotation axis RA. The inner peripheral end 35 forming the inner edge of the bell mouth 3 is located inside the volute 4. The 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.

[0061] (Surrounding wall 4c)

[0062] 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 vortex shape. The peripheral wall 4c is formed so that the distance from the rotation axis RA starts from the tongue portion 43 and gradually becomes farther as it moves in the rotation direction of the fan 2. The peripheral wall 4c is formed so that in the rotation direction of the fan 2, from the tongue portion 43 to the discharge portion 42, the gap between the peripheral wall 4c and the outer periphery of the fan 2 is expanded at a predetermined ratio, and the air flow path area gradually becomes larger.

[0063] As the spiral shape of the peripheral wall 4c, there are shapes based on logarithmic spirals, Archimedean spirals, or involute curves, for example. The inner peripheral surface of the peripheral wall 4c constitutes a curved surface that smoothly bends along the circumference of the fan 2 from the tongue portion 43 at the beginning of the spiral winding to the winding end portion 41b at the end of the spiral winding. With such a structure, the air sent from the fan 2 flows smoothly in the gap between the fan 2 and the peripheral wall 4c in the direction from the fan 2 to the discharge portion 42. Therefore, in the volute 4, the static pressure of the air efficiently rises from the tongue portion 43 toward the discharge portion 42.

[0064] 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. In addition, the peripheral wall 4c may be inclined relative to the axial direction of the rotation axis RA of the fan 2, and is not limited to the form arranged parallel to the axial direction of the rotation axis RA.

[0065] The peripheral wall 4c forms an inner wall surface opposite to the outer peripheral surface 2f of the fan 2. The peripheral wall 4c is opposite to the outer peripheral end of the plurality of blades 2d constituting the outer peripheral surface 2f of the fan 2. The peripheral wall 4c is opposite to the air blowing side of the blades 2d of the fan 2. Figure 1 As shown, the peripheral wall 4c is provided along the rotation direction of the fan 2 from the tongue portion 43 which is the spiral winding start portion to the winding end portion 41b which is the boundary between the discharge portion 42 and the spiral portion 41 which is located on the side away from the tongue portion 43.

[0066] The tongue portion 43 is an end portion of the peripheral wall 4c constituting the curved surface, which is located on the upstream side in the flow direction of the gas flowing along the peripheral wall 4c in the internal space of the volute 4 by the rotation of the fan 2. The winding end portion 41b is an end portion of the peripheral wall 4c constituting the curved surface, which is located on the downstream side in the flow direction of the gas flowing along the peripheral wall 4c in the internal space of the volute 4 by the rotation of the fan 2.

[0067] (tongue 43)

[0068] The scroll housing 4 has a tongue 43 which forms a curved surface at the winding start portion of the peripheral wall 4c close to the rotation axis RA of the fan 2, and guides the airflow generated by the fan 2 to the discharge port 42a. The end of the peripheral wall 4c on the discharge portion 42 side includes the tongue 43. The tongue 43 is formed at the winding start portion of the peripheral wall 4c formed in a spiral shape.

[0069] The tongue 43 is provided at a boundary portion connected to a diffuser plate 42c of the discharge portion 42 described later. The tongue 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 43 is formed with a predetermined curvature radius, and the peripheral wall 4c is smoothly connected to the diffuser plate 42c via the tongue 43. The tongue 43 has a substantially uniform shape in the axial direction of the rotation axis RA when viewed from the discharge port 42a, and is a shape along the axial direction of the rotation axis RA.

[0070] The tongue 43 suppresses the inflow of air from the end of the winding of the spiral flow path to the beginning of the winding inside the volute 4. The tongue 43 is arranged at the upstream part of the ventilation path, and has the function of separating the air flow in the rotation direction of the fan 2 from the air flow in the discharge direction from the downstream part of the ventilation path toward the discharge port 42a. In addition, the static pressure of the air flow flowing into the discharge part 42 rises and becomes high pressure during the period of passing through the volute 4. Therefore, the tongue 43 has the function of separating such a pressure difference. The tongue 43 has the function of separating the pressure difference, and has the function of guiding the air flowing into the discharge part 42 to each flow path through the curved surface.

[0071] (Discharge portion 42)

[0072] The discharge portion 42 forms a discharge port 42a for discharging the airflow generated by the fan 2 and passing through the vortex portion 41. The discharge portion 42 is composed of a hollow tube, and the cross section of the hollow tube perpendicular to the flow direction of the air flowing along the peripheral wall 4c is rectangular. In addition, the cross-sectional shape of the discharge portion 42 is not limited to a rectangle. The discharge portion 42 forms a flow path that guides the air sent from the fan 2 and flowing in the gap between the peripheral wall 4c and the fan 2 to be discharged to the outside of the vortex housing 4.

[0073] One end of the discharge portion 42 forms an inlet (not shown) for air to flow from the scroll 4 into the discharge portion 42. The other end of the discharge portion 42 forms a discharge port 42a for discharging air flowing in the flow path in the discharge portion 42 to the outside air.

[0074] like Figure 2 As shown, the discharge portion 42 includes an extended plate 42b, a diffuser plate 42c, a first side plate portion 42d, and a second side plate portion 42e. The extended plate 42b is smoothly continuous with the winding end portion 41b on the downstream side of the peripheral wall 4c, and is formed integrally with the peripheral wall 4c. The diffuser plate 42c is formed integrally with the tongue portion 43 of the volute 4, and is opposed to the extended plate 42b. The diffuser plate 42c is formed at a predetermined angle relative to the extended plate 42b, for example, in a manner that the cross-sectional area of ​​the flow path gradually expands along the flow direction of the air in the discharge portion 42, but is not limited to this structure.

[0075] The first side plate portion 42d is formed integrally with the first side wall 4a1 of the volute 4, and the second side plate portion 42e is formed integrally with the second side wall 4a2 on the opposite side of the volute 4. Furthermore, the first side plate portion 42d and the second side plate portion 42e are formed between the extended plate 42b and the diffuser plate 42c. In this way, the discharge portion 42 is formed with the extended plate 42b, the diffuser plate 42c, the first side plate portion 42d, and the second side plate portion 42e to form a flow path having a rectangular cross section.

[0076] (Relationship between fan 2 and volute 4)

[0077] Figure 6 This is a partial cross-sectional view of the multi-blade centrifugal fan 1 according to the first embodiment. Figure 6 Observe in the direction of the arrow Figure 1 FIG. 5 is a diagram of a cross section of a multi-blade centrifugal fan 1 at the position of line AA. Figure 6 2 is a cross-sectional view of the multi-blade centrifugal blower 1 observed along the radial direction of the rotation axis RA. The inflection point 26 is formed over the entire length of the blade 2d. The entire 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 of the portion between the base end 2h on the main board 2a side of the blade 2d and the terminal end 2g on the side plate 2c side of the blade 2d. The base end 2h is one end of the blade 2d in the axial direction of the rotation axis RA, and is the end on the main board 2a side. The terminal end 2g is the other end of the blade 2d in the axial direction of the rotation axis RA, and is the end on the side opposite to the main board 2a.

[0078] like Figure 6 As shown, the multi-blade centrifugal blower 1 is formed such that, when viewed in the radial direction of the rotation axis RA, all parts of the inflection point 26 are located on the inner peripheral side of the inner peripheral end 35 forming the inner edge of the bell mouth 3. Figure 6As shown, the multi-blade centrifugal blower 1 is formed so that, when viewed in the radial direction of the rotation axis RA, all parts of the inflection point portion 26 are located closer to the rotation axis RA side than the inner peripheral end portion 35 of the bell mouth 3. The multi-blade centrifugal blower 1 is formed so that all parts of the inflection point portion 26 in the axial direction of the rotation axis RA are located closer to the inner peripheral side than the inner peripheral end portion 35 forming the inner edge of the bell mouth 3 in the radial direction of the fan 2.

[0079] The multi-blade centrifugal blower 1 is formed so that the imaginary line B formed by the inflection point portion 26 of the blade 2d from the base end portion 2h on the main plate 2a side to the terminal end portion 2g on the side plate 2c side is parallel to the rotation axis RA of the fan 2. The imaginary line B is formed to be parallel to the rotation axis RA of the fan 2, which means that, for example, when viewed in the radial direction of the rotation axis RA, the imaginary line B is formed to be at an angle within ±1 degree relative to the rotation axis RA.

[0080] [Operation of the multi-blade centrifugal blower 1]

[0081] use Figure 2 The operation of the multi-blade centrifugal blower 1 is described. In the multi-blade centrifugal blower 1, when the motor (not shown) is driven, the main board 2a connected to the motor shaft rotates, and through the main board 2a, the plurality of blades 2d rotate around the rotation axis RA. When the fan 2 rotates, the air outside the volute 4 is sucked into the inside of the volute 4 through the suction port 5.

[0082] The air sucked into the volute 4 is guided by the bell mouth 3 and sucked into the fan 2. The air sucked into the fan 2 becomes an airflow with dynamic pressure and static pressure in the process of passing between the plurality of blades 2d and is blown out toward the radially outer side of the fan 2. The airflow blown out from the fan 2 is blown out from the fan 2 into the volute 4 by the pressure-boosting effect of the fan 2.

[0083] The airflow flowing in the volute 4 is pressurized by flowing in the air passage that gradually expands from the winding start side to the winding end side by using the spiral shaped peripheral wall 4c. The air blown from the fan 2 into the volute 4 is decelerated in the expanded air passage formed by the peripheral wall 4c of the volute 4 to restore the static pressure, and then Figure 1 The exhaust port 42a shown blows out to the outside.

[0084] [Effects of the multi-blade centrifugal blower 1]

[0085] The fan 2 of the multi-blade centrifugal blower 1 has a backward blade portion 22, a forward blade portion 21, and an inflection point portion 26 forming an inflection point between the backward blade portion 22 and the forward blade portion 21. The inflection point portion 26 is formed in the axial direction of the rotation axis RA over the portion between the base end portion 2h on the main board 2a side and the terminal end portion 2g on the side of the side plate 2c of each of the plurality of blades 2d, that is, the entire length of the blade 2d. In addition, all portions of the inflection point portion 26 in the axial direction of the rotation axis RA are formed to be located at a position closer to the inner peripheral side than the inner peripheral end portion 35 forming the inner edge of the bell mouth 3 in the radial direction of the fan 2.

[0086] Here, the case where all parts of the inflection point 26 are formed to be located on the inner peripheral side of the inner peripheral end 35 of the bell mouth 3 is referred to as structure A, and the case where at least a part or all of the inflection point 26 is formed to be located on the outer peripheral side of the inner peripheral end 35 is referred to as structure B. When comparing structure A and structure B in the fan 2 of the same diameter, in structure A, the proportion of the forward blade portion 21 in the radial distance of the fan 2 in the blade 2d is larger than that in structure B. Therefore, compared with the structure in which at least a part or all of the inflection point 26 is formed to be located on the outer peripheral side of the inner peripheral end 35, the multi-blade centrifugal blower 1 can make the change of the blade angle from the part on the leading edge 25a side to the part on the trailing edge 24a side smooth, and can suppress the separation of the airflow at the negative pressure surface 2d2 and suppress the reduction of the air volume.

[0087] In addition, the fan 2 is formed so that the imaginary line B formed by the inflection point portion 26 from the base end portion 2h on the main plate 2a side to the terminal end portion 2g on the side plate 2c side of each of the plurality of blades 2d is parallel to the rotation axis RA. Since the multi-blade centrifugal blower 1 is formed with the imaginary line B parallel to the rotation axis RA, it is easier to pull the fan 2 out of the mold when manufacturing the fan 2, and manufacturing becomes easier than when the imaginary line B is not parallel to the rotation axis RA.

[0088] Implementation method 2.

[0089] Figure 7 It is a partial cross-sectional view of the multi-blade centrifugal fan 1 according to the second embodiment. Figure 7 Observe in the direction of the arrow Figure 1 A cross-sectional view of the multi-blade centrifugal blower 1 at the AA line position. Figure 1 to Figure 6 The same structural parts of the multi-blade centrifugal blower 1 are denoted by the same reference numerals and their description is omitted.

[0090] The multi-blade centrifugal blower 1 of the second embodiment further defines the relationship between the shape of the blade 2d. In addition, the multi-blade centrifugal blower 1 of the second embodiment further defines the positional relationship between the blade 2d and the bell mouth 3. The structure of the other parts except 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 of the first embodiment. Therefore, in the following description, the multi-blade centrifugal blower 1 is used. Figure 7 The following description will focus on the structures of the blades 2d and the bell mouth 3 of the multi-blade centrifugal fan 1 according to the second embodiment.

[0091] The blade 2d of the multiblade centrifugal blower 1 of Embodiment 2 has a notch-like step 27 formed at the front edge 25a on the side plate 2c. More specifically, the blade 2d has a notch-like step 27 formed at the front edge 25a of the blade 2d at the end 2g on the side plate 2c.

[0092] The step portion 27 is a portion formed by cutting out the wall constituting the front edge 25a and the terminal portion 2g. The step portion 27 is formed at a portion of the front edge 25a and at a portion of the terminal portion 2g. In the step portion 27, the end portion on the side plate 2c side of the front edge 25a is cut out, and the end portion on the side of the rotation axis RA of the terminal portion 2g is cut out. The step portion 27 is a portion formed by cutting out the continuous corner portion of the front edge 25a and the terminal portion 2g. Figure 7 As shown, a step portion 27 is formed at a tip end portion 2g of the rearward blade portion 22 and the forward blade portion 21 on the side plate 2c side.

[0093] The step portion 27 is formed by a side edge portion 27A extending in the axial direction of the rotation axis RA of the fan 2 and an upper edge portion 27B extending in the radial direction of the fan 2. In the fan 2, the upper edge portion 27B is an edge portion located at a position closer to the main board 2a side than the terminal portion 2g. The fan 2 is formed with a step between the upper edge portion 27B and the terminal portion 2g in the axial direction of the rotation axis RA. In addition, the fan 2 is formed so that the side edge portion 27A is located on the outer peripheral side of the fan 2 with respect to the imaginary extension line C of the leading edge 25a at the step portion 27. The fan 2 is formed with a step between the leading edge 25a and the side edge portion 27A in the radial direction of the rotation axis RA.

[0094] The step portion 27 is not limited to a structure formed by the side edge portion 27A extending in the axial direction of the rotation axis RA of the fan 2 and the upper edge portion 27B extending in the radial direction of the fan 2. For example, the step portion 27 may be formed as an arc-shaped edge portion in which the side edge portion 27A and the upper edge portion 27B are continuously and integrally formed.

[0095] The outer diameter of the blades formed by the outer peripheral ends 24 of each of the plurality of blades 2d of the multi-blade centrifugal blower 1 of the second embodiment is formed to be larger than the inner diameter of the bell mouth 3. That is, the multi-blade centrifugal blower 1 of the second embodiment is formed so that, when viewed along the axial direction of the rotation axis RA, the outer peripheral ends 24 of the blades 2d are located at a position closer to the outer peripheral side than the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2. In addition, the multi-blade centrifugal blower 1 of the second embodiment is formed so that, when viewed along the axial direction of the rotation axis RA, at least a portion of the leading edge 25a of the blade 2d is located at a position closer to the inner peripheral side than the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2.

[0096] In the blade 2d, the boundary portion between the tip 2g and the step portion 27 is called the step start point 27C. The step start point 27C is the boundary portion between the tip 2g and the side edge 27A of the blade 2d in the blade 2d. The step start point 27C is the corner portion of the blade 2d formed by the tip 2g and the side edge 27A. The multi-blade centrifugal blower 1 of the second embodiment is formed so that the step start point 27C of the blade 2d is located at a position closer to the outer peripheral side than the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2.

[0097] like Figure 7 As shown, the inner peripheral end 35 of the bell mouth 3 of the multi-blade centrifugal blower 1 of the second embodiment is arranged above the step portion 27. The multi-blade centrifugal blower 1 of the second embodiment is configured so that the inner peripheral end 35 of the bell mouth 3 and the step portion 27 are opposite in the axial direction of the rotation axis RA. More specifically, the multi-blade centrifugal blower 1 of the second embodiment is configured so that the inner peripheral end 35 of the bell mouth 3 and the upper edge 27B are opposite in the axial direction of the rotation axis RA. The multi-blade centrifugal blower 1 of the second embodiment has a gap formed between the inner peripheral end 35 of the bell mouth 3 and the upper edge 27B.

[0098] The multi-blade centrifugal blower 1 of embodiment 2 may also be configured such that the inner peripheral end 35 of the bell mouth 3 is opposite to the side edge 27A in the radial direction of the fan 2. The multi-blade centrifugal blower 1 of embodiment 2 may also form a gap between the inner peripheral end 35 of the bell mouth 3 and the upper edge 27B in the axial direction of the rotation axis RA, and form a gap between the inner peripheral end 35 of the bell mouth 3 and the side edge 27A in the radial direction of the rotation axis RA.

[0099] [Effects of the multi-blade centrifugal blower 1]

[0100] The plurality of blades 2d are respectively formed with a notch-shaped step portion 27 at the leading edge 25a on the side of the side plate 2c. When the boundary portion between the terminal portion 2g and the step portion 27 is set as the step starting point 27C, the step starting point 27C is formed to be located at a position closer to the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3 in the radial direction of the fan 2. Even if the multi-blade centrifugal blower 1 of the second embodiment increases the height of the blade 2d in order to expand the blade surface, the blade 2d does not interfere with the inner peripheral end portion 35 of the bell mouth 3 due to the presence of the step portion 27.

[0101] The multi-blade centrifugal blower 1 is formed such that the step starting point 27C is located at a position closer to the outer peripheral side than the inner peripheral end 35 of the bell mouth 3, thereby being able to increase the height of the blade 2d in the axial direction of the rotation axis RA while ensuring the interval between the inner peripheral end 35 of the bell mouth 3 and the blade 2d. Compared with the blade 2d without the step portion 27, the multi-blade centrifugal blower 1 of embodiment 2 can make the tip 2g of the blade 2d close to the side wall 4a, and can increase the blade area, so that a larger air volume can be obtained.

[0102] Implementation method 3.

[0103] Figure 8 It is a partial cross-sectional view of the multi-blade centrifugal fan 1 according to the third embodiment. Figure 8 Observe in the direction of the arrow Figure 1 A cross-sectional view of the multi-blade centrifugal blower 1 at the AA line position. Figure 1 to Figure 6 The same structural parts of the multi-blade centrifugal blower 1 are denoted by the same reference numerals and their description is omitted.

[0104] The multi-blade centrifugal blower 1 of the third embodiment defines the positional relationship between the blade 2d and the bell mouth 3. The structure of other parts except the positional relationship between the blade 2d and the bell mouth 3 is the same as that of the multi-blade centrifugal blower 1 of the first embodiment. Therefore, in the following description, the term " Figure 8 The description will be mainly based on the structures of the blades 2d and the bell mouth 3 of the multi-blade centrifugal fan 1 according to the third embodiment.

[0105] The outer diameter of the blades formed by the outer peripheral ends 24 of each of the plurality of blades 2d of the multi-blade centrifugal blower 1 of the third embodiment is formed to be larger than the inner diameter of the bell mouth 3. That is, the multi-blade centrifugal blower 1 of the third embodiment is formed such that, when viewed along the axial direction of the rotation axis RA, in the radial direction of the fan 2, the outer peripheral ends 24 of the blades 2d are located at a position closer to the outer peripheral side than the inner peripheral end 35 of the bell mouth 3.

[0106] The multi-blade centrifugal blower 1 of the third embodiment is formed such that, when viewed along the axial direction of the rotation axis RA, a portion of the leading edge 25a of the blade 2d is located at a position closer to the inner circumference than the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2. The multi-blade centrifugal blower 1 of the third embodiment is formed such that, when viewed along the axial direction of the rotation axis RA, the rearward blade portion 22 is located at a position closer to the inner circumference than the inner peripheral end 35 of the bell mouth 3 in the radial direction of the fan 2.

[0107] In the fan 2, the front edge 25a located at the boundary portion between the front edge 25a of the blade 2d and the terminal portion 2g is referred to as the side plate side front edge portion 25b. The side plate side front edge portion 25b constitutes a part of the corner portion of the blade 2d formed by the terminal portion 2g and the front edge 25a. The multi-blade centrifugal blower 1 of the third embodiment is formed so that, in the radial direction of the fan 2, the side plate side front edge portion 25b of the blade 2d is located at a position closer to the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3. That is, the multi-blade centrifugal blower 1 of the third embodiment is formed so that, in the axial direction of the rotation axis RA, the inner peripheral end portion 35 of the bell mouth 3 is opposed to a part of the front edge 25a of the blade 2d.

[0108] [Effects of the multi-blade centrifugal blower 1]

[0109] The multi-blade centrifugal blower 1 of the third embodiment is formed so that, in the radial direction of the fan 2, the side plate side front edge portion 25b is located at a position closer to the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3. In the multi-blade centrifugal blower 1 of the third embodiment, the side plate side front edge portion 25b is formed so as to be located closer to the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3, so that even if the height of the blade 2d is increased in order to expand the blade surface, the blade 2d does not interfere with the inner peripheral end portion 35 of the bell mouth 3.

[0110] The multi-blade centrifugal blower 1 is formed so that the side plate side front edge portion 25b is located at a position closer to the outer peripheral side than the inner peripheral end portion 35 of the bell mouth 3, thereby being able to increase the height of the blade 2d in the axial direction of the rotation axis RA while ensuring the interval between the inner peripheral end portion 35 of the bell mouth 3 and the blade 2d. Compared with the blade 2d formed so that the side plate side front edge portion 25b is located at a position closer to the inner peripheral side than the inner peripheral end portion 35 of the bell mouth 3, the multi-blade centrifugal blower 1 can make the tip portion 2g of the blade 2d close to the side wall 4a, and can increase the blade area, so that a larger air volume can be obtained.

[0111] Implementation method 4.

[0112] Fig. 9 It is a partially enlarged view of the fan 2 of the multi-blade centrifugal fan 1 according to the fourth embodiment. Fig. 9 FIG. 2 is an enlarged view of the fan 2 viewed along the axial direction of the rotation axis RA. Fig. 9In order to show the shape of the blade 2d, the blade 2d is shown through the bell mouth 3. Figures 1 to 8 The same structural parts of the multi-blade centrifugal blower 1 are denoted by the same reference numerals and their description is omitted.

[0113] The multi-blade centrifugal blower 1 of the fourth embodiment further defines the shape of the blade 2d. The structure other than the shape of the blade 2d described below is the same as that of the multi-blade centrifugal blower 1 of the first embodiment. Therefore, in the following description, Fig. 9 The description will be centered on the shape of the blades 2d of the multi-blade centrifugal fan 1 according to the fourth embodiment.

[0114] When the blade 2d is viewed along the axial direction of the rotation axis RA, the portion of the blade 2d formed in an arc shape is referred to as an arc portion AR. Fig. 9 As shown, from the inflection point 26 to the trailing edge 24a of the blade 2d (refer to Figure 3 ) is composed of one arc portion AR or a plurality of arc portions AR. Fig. 9 As shown, the forward blade portion 21 of the blade 2d of the multi-blade centrifugal blower 1 of the fourth embodiment is composed of one arc portion AR or a plurality of arc portions AR. The blade 2d of the multi-blade centrifugal blower 1 of the fourth embodiment has a radius from the inflection point 26 to the trailing edge 24a of the blade 2d (see Figure 3 ) to the portion is composed of at least one arc portion AR.

[0115] The arc portion AR is a portion formed in an arc shape in the blade 2d when viewed along the axial direction of the rotation axis RA. The trailing edge 24a is formed by the outer peripheral end 24. The outer peripheral end 24 is an end portion 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 portion formed by connecting the outer peripheral end 24 in the axial direction of the rotation axis.

[0116] [Effects of the multi-blade centrifugal blower 1]

[0117] The portion from the inflection point 26 of each of the plurality of blades 2d to the trailing edge 24a of the blade 2d is composed of at least one arc portion AR. In the multi-blade centrifugal blower 1 of Embodiment 4, the portion from the inflection point 26 of the blade 2d to the trailing edge 24a of the blade is composed of at least one arc portion AR, thereby suppressing a sharp angle change of the blade 2d in the radial direction of the fan 2. Therefore, the multi-blade centrifugal blower 1 can suppress the separation of the airflow at the negative pressure surface 2d2 and suppress the reduction of the air volume.

[0118] As mentioned above, although the preferred embodiments and the like have been described in detail, the present invention is not limited to the above-mentioned embodiments and the like, and various modifications and substitutions can be added to the above-mentioned embodiments and the like without departing from the scope described in the claims.

[0119] Hereinafter, each aspect of the present disclosure will be collectively described as a supplementary note.

[0120] (Note 1)

[0121] A multi-blade centrifugal blower, comprising:

[0122] A fan having a main plate which is circular when viewed in the axial direction of a rotating shaft, a plurality of blades provided on the peripheral edge of the main plate, and an annular side plate which fixes the ends of the plurality of blades on the side opposite to the main plate in the axial direction of the rotating shaft; and

[0123] A volute having a peripheral wall formed in a vortex shape and at least one side wall, wherein the at least one side wall has a bell mouth forming a suction port, the volute forming an exhaust port for exhausting the airflow generated by the fan and accommodating the fan,

[0124] The fan has:

[0125] A backward blade portion, which constitutes a backward blade at a portion on the inner circumference side of each of the plurality of blades in the radial direction of the fan;

[0126] a forward blade portion, which constitutes a forward blade at a portion on an outer peripheral side of each of the plurality of blades in a radial direction of the fan; and

[0127] an inflection point portion which forms an inflection point between the rearward blade portion and the forward blade portion when viewed along the axial direction of the rotation shaft,

[0128] The inflection point portion is formed in the axial direction of the rotating shaft over the portion between the base end portion on the main board side and the terminal end portion on the side plate side of each of the multiple blades, that is, the entire length of the blade, and all axial portions of the inflection point portion are formed to be located on the inner side of the inner circumferential end portion forming the inner edge of the bell mouth in the radial direction of the fan.

[0129] (Note 2)

[0130] The multi-blade centrifugal blower according to Supplement 1, wherein:

[0131] The fan is formed such that an imaginary line formed by the inflection point from the base end portion on the main plate side to the tip end portion on the side plate side of each of the plurality of blades is parallel to the rotation axis.

[0132] (Note 3)

[0133] The multi-blade centrifugal blower according to Supplement 1 or 2, wherein:

[0134] The plurality of blades are respectively provided with a notch-shaped step portion at the front edge of the side plate.

[0135] When a boundary portion between the terminal portion and the step portion is defined as a step start point, the step start point is formed to be located on the outer peripheral side of the inner peripheral end portion of the bell mouth in the radial direction of the fan.

[0136] (Note 4)

[0137] The multi-blade centrifugal blower according to any one of Supplementary Notes 1 to 3, wherein:

[0138] In the fan, when the leading edge located at the boundary between the leading edge of each of the plurality of blades and the tip portion is set as the side plate side leading edge portion,

[0139] The side plate side front edge portion is formed to be located on the outer peripheral side of the inner peripheral end portion of the bell mouth in the radial direction of the fan.

[0140] (Note 5)

[0141] The multi-blade centrifugal blower according to any one of Supplementary Notes 1 to 4, wherein:

[0142] When a portion of the blade that is formed in an arc shape when viewed in the axial direction of the rotation shaft is defined as an arc portion,

[0143] A portion of each of the plurality of blades from the inflection point to the trailing edge of the blade is formed by at least one of the arc portions.

[0144] Description of symbols

[0145] 1: Multi-blade centrifugal blower, 2: Fan, 2a: Main board, 2a1: Peripheral part, 2a2: Central part, 2b: Boss part, 2c: Side plate, 2d: Blade, 2d1: Positive pressure surface, 2d2: Negative pressure surface, 2e: Fan inlet, 2f: Outer peripheral surface, 2g: Terminal part, 2h: Base end, 3: Bell mouth, 4: Scroll casing, 4a: Side wall, 4a1: First side wall, 4a2: Second side wall, 4c: Peripheral wall, 5: Inlet, 21: Forward blade part, 22: Rear blade part, 24: Outer peripheral surface End, 24a: trailing edge, 25: inner peripheral end, 25a: leading edge, 25b: side plate side leading edge, 26: inflection point, 27: step portion, 27A: side edge, 27B: upper edge, 27C: step starting point, 35: inner peripheral end, 41: vortex portion, 41b: winding end portion, 42: discharge portion, 42a: discharge port, 42b: extension plate, 42c: diffuser, 42d: first side plate portion, 42e: second side plate portion, 43: tongue, AR: arc portion, B: imaginary line.

Claims

1. A multi-blade centrifugal blower, comprising: A fan having a main plate which is circular when viewed along the axial direction of a rotating shaft, a plurality of blades provided on the peripheral edge of the main plate, and an annular side plate which fixes the ends of the plurality of blades on the side opposite to the main plate in the axial direction of the rotating shaft; as well as A volute having a peripheral wall formed in a vortex shape and at least one side wall, wherein the at least one side wall has a bell mouth forming a suction port, the volute forming an exhaust port for exhausting the airflow generated by the fan and accommodating the fan, The fan has: A backward blade portion, which constitutes a backward blade at a portion on the inner circumference side of each of the plurality of blades in the radial direction of the fan; A forward blade portion, which constitutes a forward blade at a portion on an outer peripheral side of each of the plurality of blades in a radial direction of the fan; as well as an inflection point portion which forms an inflection point between the rearward blade portion and the forward blade portion when viewed along the axial direction of the rotation shaft, The inflection point portion is formed in the axial direction of the rotating shaft over the portion between the base end portion on the main board side and the terminal end portion on the side plate side of each of the multiple blades, that is, the entire length of the blade, and all axial portions of the inflection point portion are formed to be located on the inner side of the inner circumferential end portion forming the inner edge of the bell mouth in the radial direction of the fan.

2. The multi-blade centrifugal blower according to claim 1, wherein: The fan is formed such that an imaginary line formed by the inflection point from the base end portion on the main plate side to the tip end portion on the side plate side of each of the plurality of blades is parallel to the rotation axis.

3. The multi-blade centrifugal blower according to claim 1 or 2, wherein: The plurality of blades are respectively provided with a notch-shaped step portion at the front edge of the side plate. When a boundary portion between the terminal portion and the step portion is defined as a step start point, the step start point is formed to be located on the outer peripheral side of the inner peripheral end portion of the bell mouth in the radial direction of the fan.

4. The multi-blade centrifugal blower according to any one of claims 1 to 3, wherein: In the fan, when the leading edge located at the boundary between the leading edge of each of the plurality of blades and the tip portion is set as the side plate side leading edge portion, The side plate side front edge portion is formed to be located on the outer peripheral side of the inner peripheral end portion of the bell mouth in the radial direction of the fan.

5. The multi-blade centrifugal blower according to any one of claims 1 to 4, wherein: When a portion of the blade that is formed in an arc shape when viewed in the axial direction of the rotation shaft is defined as an arc portion, A portion of each of the plurality of blades from the inflection point to the trailing edge of the blade is formed by at least one of the arc portions.

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