MULTI-VANE CENTRIFUGAL AIR TRANSMITTER

Abstract

A multi-blade centrifugal air ejection device includes a fan having a main plate, a plurality of blades, and a side plate that is annular and secures ends of the plurality of blades opposite to the main plate; and a scroll casing having a peripheral wall that is spiral-shaped and at least one side wall that has a bell mouth forming an intake opening, the scroll casing housing the fan. The fan includes a rear blade portion that forms a rear blade of each of the plurality of blades located on an inner periphery of the plurality of blades, a front blade portion that forms a front blade of each of the plurality of blades located on an outer periphery of the plurality of blades, and an inflection point portion that forms an inflection point between the rear blade portion and the front blade portion.The inflection point portion is formed over an entire length of a portion of each of the plurality of blades. The inflection point portion is located between a proximal end of each of the plurality of blades closest to the main plate and a distal end of each of the plurality of blades closest to the side plate. An entire axial direction portion of the inflection point portion is located further inward in the radial direction of the fan than an inner peripheral end portion constituting an inner edge of the bell mouth.

Description

Field of TechnologyThe present disclosure relates to a centrifugal multi-vane air transmission device having a scroll casing.General State of the ArtA centrifugal multi-blade air transmission device is provided with a fan having a circular disk-shaped main plate, a plurality of blades installed at the peripheral portion of the main plate, and a side plate to which end portions of the blades are fixed. Further, such a centrifugal multi-blade air transmission device is provided with a scroll casing having a spiral peripheral wall covering the fan, and at a suction port of the scroll casing, a bell mouth for smoothly guiding an air flow to the fan is provided. Such a centrifugal multi-blade air transmission device often has, as blades, front blades inclined in the rotational direction of the fan to increase the pressure of an air flow flowing out through an enlarged air passage inside the scroll casing between the blades by the rotation of the fan. However, the air flow drawn into the volute along the bell mouth often flows at an angle to the vanes that does not match the inlet angles of the front vanes. Such a multi-blade centrifugal air-sending device may result in a separation of the air flow at the suction surfaces of the leading edges and the adjacent areas of the blades, which may result in a reduction of the air flow. As a countermeasure, there has been proposed a centrifugal multi-blade air transmission device provided on the inner peripheries of the front blades with rear blades facing in the opposite direction to the rotational direction of the fan. This structure thus weakens the reduction in the air flow by smoothly guiding an air flow drawn from the bell mouth to the blades and preventing the air flow generated at the suction surfaces of the leading edges and the adjacent areas of the blades from separating. Such a centrifugal multi-vane air transmission device is disclosed in, for example, Patent Literature 1.Reference listPatent LiteraturePatent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-70793Summary of the InventionTechnical TaskHowever, the centrifugal multi-vane air transmission device disclosed in Patent Literature 1 has rear vanes on the inner peripheries of the vanes and front vanes on the outer peripheries of the vanes. This structure results in substantial changes in the angles of the vane surfaces between the inner peripheries of the vanes and the outer peripheries of the vanes, which may cause air flow to be re-separated at the suction surfaces of the vanes and thus may result in a reduction in the air flow.The present disclosure is intended to solve the problems described above and provide a centrifugal multi-vane air transmission device configured to prevent separation of the air flow at the suction surfaces of the vanes and thereby mitigate the reduction of the air flow.Solution of the ProblemA centrifugal multi-blade air transmission device according to an embodiment of the present disclosure includes a fan having a main plate that is circular when the main plate is viewed in an axial direction of a rotation axis, a plurality of blades installed around a circumferential portion of the main plate, and a side plate that is annular and fixes ends of the plurality of blades that oppose the main plate in the axial direction of the rotation axis; and a scroll casing having a peripheral wall that is spiral and at least one side wall having a bell mouth that forms a suction opening, the scroll casing having a discharge opening through which an airflow generated by the fan is discharged, the scroll casing accommodating the fan. The fan includes a rear blade portion forming a rear blade of each of the plurality of blades located on an inner periphery of the plurality of blades in a radial direction of the fan, a front blade portion forming a front blade of each of the plurality of blades located on an outer periphery of the plurality of blades in the radial direction of the fan, and a inflection point portion forming an inflection point between the rear blade portion and the front blade portion when the inflection point portion is viewed in the axial direction of the rotational axis. The inflection point portion is formed over an entire length of a portion of each of the plurality of blades in the axial direction of the rotation axis. The inflection point portion is located between a proximal end of each of the plurality of blades closest to the main plate and a distal end of each of the plurality of blades closest to the side plate. An entire portion of the inflection point portion in the axial direction in the radial direction of the fan is disposed more inward than an inner circumferential end portion that forms an inner edge of the bell mouth.Advantageous Effects of the InventionA centrifugal multi-blade air transmission device according to an embodiment of the present disclosure includes a fan having a rear blade portion, a front blade portion, and a inflection point portion forming an inflection point between the rear blade portion and the front blade portion. The inflection point portion is formed over the entire length of a portion of each blade of a plurality of blades in the axial direction of a rotational axis between a proximal end closest to a main plate and a distal end closest to a side plate of the blade. In addition, an entire portion of the inflection point portion in the axial direction of the rotation axis is formed to be located more inward in the radial direction of the fan than an inner circumferential end portion forming an inner edge of the bell mouth. In a structure in which the entire portion of the inflection point portion is disposed more inward than the inner circumferential end portion of the bell mouth, the proportion of the blade occupied by the front blade portion is larger than in a structure in which at least a portion or the entire portion of the inflection point portion is disposed more outward than the inner circumferential end portion. For this reason, the centrifugal multi-vane air transmission device is configured to compensate for the angular changes of the vanes from the respective leading edge side portions to the trailing edge side portions, prevent the separation of the air flow at the suction surfaces, and thus mitigate the reduction of the air flow.Brief Description of the Drawings[FIG. 1 ] FIG. 1 is an external view schematically showing a configuration of a centrifugal multi-vane air transmission device 1 according to Embodiment 1, the configuration being viewed parallel to a rotation axis RA. [FIG. 2 ] FIG. 2 is a perspective view illustrating the centrifugal multi-vane air transmission device according to Embodiment 1.[FIG. 3] FIG. 3 is a perspective view illustrating a fan of the centrifugal multi-blade air transmission device according to Embodiment 1.[FIG. 4] FIG. 4 is a plan view illustrating the fan of the centrifugal multi-blade air transmission device according to Embodiment 1.[FIG. 5 ] FIG. 5 is a partial enlarged view illustrating the fan of the centrifugal multi-blade air transmission device according to Embodiment 1.[FIG. 6 ] FIG. 6 is a partial cross-sectional view illustrating the centrifugal multi-vane air transmission device according to Embodiment 1.[FIG. 7 ] FIG. 7 is a partial cross-sectional view illustrating a centrifugal multi-vane air transmission device according to Embodiment 2.[FIG. 8] FIG. 8 is a partial cross-sectional view illustrating a centrifugal multi-vane air transmission device according to Embodiment 3.[FIG. 9] FIG. 9 is a partial enlarged view illustrating a fan of a centrifugal multi-blade air transmission device according to Embodiment 4.DESCRIPTION OF EMBODIMENTSCentrifugal multi-vane air transmission devices according to the embodiments will be described below with reference to drawings and other references. Moreover, in the following drawings, to which FIG. 1 also pertains, the relative dimensions, shapes, and other details of various components may vary from those of the actual components. Also, the components denoted by the same reference numerals in the following drawings are the same or equivalent to each other, and these reference numerals are the same throughout the text of the specification. Also, directional terms such as "top", "bottom", "right", "left", "front", and "rear" used for convenience are written so only for convenience, and the placement or orientation of a device or a component is not limited by the directional terms.Embodiment 1Multi-Vane Centrifugal Air Transmission Device 1FIG. 1 is an external view schematically showing a configuration of a centrifugal multi-vane air transmission device 1 according to Embodiment 1, the configuration being viewed parallel to a rotation axis RA. FIG. 2 is a perspective view illustrating the centrifugal multi-vane air transmission device 1 according to Embodiment 1. An arrow R shown in FIG. 1 indicates the rotational direction of a fan 2, and a broken arrow CD indicates the circumferential direction of the fan 2. In addition, FIG. 2 shows the external view of the centrifugal multi-vane air transmission device 1 and illustrates only the internal configuration of the centrifugal multi-vane air transmission device 1.The centrifugal multi-blade air transmission device 1 is a device such as a Schirocco fan that transmits air by the centrifugal force generated by the rotation of the fan 2. The centrifugal multi-blade air transmission device 1 is a one-side suction type centrifugal air transmission device through which air is sucked from one side of a scroll casing 4 in the axial direction of the virtual rotation axis RA of the fan 2. Moreover, the multi-blade centrifugal air transmission device 1 is not limited to a one-side suction type centrifugal air transmission device, but may be a double-side suction type centrifugal air transmission device through which air is sucked from both sides of the scroll casing 4 in the axial direction of the rotation axis RA. As illustrated in FIGS. 1 and 2, the centrifugal multi-blade air transmission device 1 includes the fan 2 configured to generate an air flow and the scroll casing 4 accommodating the fan 2.Fan 2FIG. 3 is a perspective view illustrating the fan 2 of the centrifugal multi-blade air transmission device 1 according to Embodiment 1. FIG. 4 is a plan view illustrating the fan 2 of the centrifugal multi-blade air transmission device 1 according to Embodiment 1. Further, FIG. 4 is a drawing showing the fan 2 as viewed in the axial direction of the rotation axis RA. The fan 2 will be described below with reference to 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 driven to rotate by the motor. By the rotation, a centrifugal force is generated, which causes the fan 2 to forcibly emit air in the radial directions outward. The fan 2 is driven by the motor or other drive source and rotates in the rotational direction indicated by the arrow R.As shown in FIG. 1, the fan 2 includes, as viewed in the direction of the rotation axis RA, a circular main plate 2 a, an annular side plate 2 c, and a plurality of blades 2 darranged radially around the rotation axis RA with the rotation axis RA as a center on a peripheral portion 2 a 1 of the main plate 2 a. The fan 2 is formed by the main plate 2 aand the plurality of blades 2 darranged on the main plate 2 ain a bottomed circular cylindrical shape.The fan 2 has a fan suction port 2 eformed adjacent to the side plate 2 cwhich is opposite to the main plate 2 ain the axial direction of the rotation axis RA. The fan suction port 2 eis a recess of the fan 2 through which air flows into the fan 2 and gas can flow into the spaces surrounded by the main plate 2 aand the plurality of blades 2 d.Main plate 2aThe main plate 2 ais formed in a circular shape as viewed in the axial direction of the rotational axis RA. The main plate 2 aincludes the peripheral portion 2 a 1 formed at its outer portion and a central portion 2 a 2 formed at its inner portion in the radial directions centered on the rotation axis RA.The peripheral portion 2 a 1 is formed farther outward than the central portion 2 a 2, and is formed in a circular ring shape as viewed in the axial direction of the rotational axis RA. The peripheral portion 2 a 1 is formed in a plate shape. The central portion 2 a 2 is formed more inside than the peripheral portion 2 a 1, and is formed such that the central portion 2 a 2 protrudes from an inner edge portion of the peripheral portion 2 a 1. The central portion 2a2 is formed by a plate material formed in the shape of a mountain. The central portion 2 a 2 is formed inside the plurality of blades 2 d.The peripheral portion 2 a 1 and the central portion 2 a 2 of the main plate 2 amay also be formed integrally with each other. The main plate 2a may also be formed in the shape of a flat plate as a whole. The main plate 2a may also be formed in another shape, for example, a circular disk or a polygonal shape. The main plate 2 amay also be formed such that its wall thickness increases toward its center in the radial directions centered on the rotation axis RA. The main plate 2 amay alternatively be formed so that its thickness is constant in the radial directions centered on the rotation axis RA. Also, the main plate 2a is not limited to a single plate material, but may be made of a plurality of plate materials firmly joined together. Moreover, the radial directions centered on the rotation axis RA are directions perpendicular to the axial direction of the rotation axis RA.In the central portion of the main plate 2a, a boss portion 2b to which the drive shaft of the engine is connected is provided. In the boss portion 2 b, a shaft hole is formed into which the drive shaft of the engine is inserted. The boss portion 2 bis formed in a circular cylindrical shape, for example, but the shape of the boss portion 2 bis not limited to such a circular cylindrical shape. The boss portion 2 bneeds only to be formed in a columnar shape, and may also be formed in a polygonal columnar shape, for example. The main plate 2a is driven to rotate by the motor by means of the boss portion 2b.Side plate 2cThe fan 2 has the annular side plate 2 cfixed to end portions of the plurality of blades 2 dopposing the main plate 2 ain the axial direction of the rotation axis RA. The end portions of the plurality of blades 2 d, which are opposed to the main plate 2 c, are fixed to the side plate 2 c, in the axial direction of the rotation axis RA. The side plate 2 cis provided on an outer circumferential surface 2 fof the fan 2. The side plate 2 cis provided at an outer portion of the vanes 2 din the radial directions centered on the rotation axis RA. The side plate 2 cmay also be provided at the distal ends 2 gof the plurality of blades 2 dprotruding from the main plate 2 atoward the rotation axis RA. The side plate 2c connects the plurality of blades 2d to each other, thus maintaining the positional relationship between the tips of the blades 2d. In addition, the side plate 2 cthus connects the plurality of blades 2 dto each other, thereby reinforcing the plurality of blades 2 d.Wing 2dThe plurality of blades 2 dare installed on the peripheral portion 2 a 1 of the main plate 2 a. The plurality of blades 2 dare each connected to the main plate 2 a, and to the side plate 2 c, at the other edge, and are arranged centered on the rotation axis RA in the circumferential direction. The plurality of blades 2d are respectively located at least between the main plate 2a and the side plate 2c. The plurality of blades 2 dare arranged in a circular pattern and centered on the boss portion 2 b, and the base ends of the blades 2 dare fixed to a plate surface of the main plate 2 a. As shown in FIG. 3, one surface of the vane 2 dfacing the rotational direction is a pressing surface 2 d 1 and the other surface opposite to the rotational direction is a suction surface 2 d 2.Each vane 2d is spaced apart from another vane 2d in the circumferential direction on the circumferential portion 2a1 of the main plate 2a at a regular interval. Each vane 2 dis provided so as to stand upright from the main plate 2 aand is formed in a plate shape. Each wing 2 dis provided so as to stand upright and substantially perpendicular to the main plate 2 a, but is not limited to this structure. Each wing 2 dmay also be provided to be inclined in the vertical direction from the main plate 2 a.As shown in FIG. 3, the blade 2d is inclined so that a leading edge 25a is farther from the rotation axis RA from its portion adjacent to the main plate 2a to its portion adjacent to the side plate 2c. The leading edge 25a is formed by the inner circumferential ends 25 of the blades 2d. The inner circumferential ends 25 are the inner ends of the vanes 2 din a cross section perpendicular to the rotation axis RA. The front edge 25 ais a portion where the inner circumferential ends 25 are arranged one behind the other in the axial direction of the rotational axis. The leading edge 25a of the blade 2d is inclined so that the inner diameter of the blade increases from the main plate 2a to the side plate 2c.FIG. 5 is a partially enlarged view showing the fan 2 of the centrifugal multi-blade air transmission device 1 according to Embodiment 1. FIG. 5 is an enlarged view showing the fan 2 as viewed in the axial direction of the rotation axis RA. Figure 5, intended to illustrate the shape of the wing 2d, shows the wing 2d as viewed through a bell mouth 3. As shown in FIG. 5, an inner portion of the vane 2 dis formed to be disposed inside an inner circumferential end portion 35 of the bell mouth 3. In the blade 2 dof the fan 2 illustrated in FIG. 5, a front blade portion 21 and a rear blade portion 22 are formed integrally with each other.The wings 2 deach have the front wing portion 21 including an outer circumferential end 24 and formed as a front wing and the rear wing portion 22 including the inner circumferential end 25 and formed as a rear wing. In addition, the blades 2 deach have a inflection point portion 26 forming the inflection point between the rear blade portion 22 and the front blade portion 21 as viewed in the axial direction of the rotation axis RA of the fan 2. In the blade 2 d, the rear blade portion 22, the inflection point portion 26, and the front blade portion 21 are integrally formed with each other in this order from the rotation axis RA toward the outer periphery in the radial direction of the fan 2.The rear blade portion 22 is an inner portion of each of the plurality of blades 2 dforming the rear blade in the radial direction of the fan 2. The front blade portion 21 is an outer portion of each of the plurality of blades 2 dforming the front blade in the radial direction of the fan 2.In the blade 2 dwhere an inner portion is formed by the rear blade and an outer portion is formed by the front blade, the inflection point portion 26 forms the transition portion where the rear blade portion 22 transitions to the front blade portion 21. That is, in the blade 2 dwhere an inner portion is formed by the rear blade and an outer portion is formed by the front blade, the inflection point portion 26 forms, as viewed in the axial direction of the rotation axis RA of the fan 2, the inflection point between the rear blade portion 22 and the front blade portion 21, where the connection points between the rear wing section 22 and the front wing section 21 are arranged in series.The not-shown motor drives the fan 2, which rotates about the rotation axis RA as the center. When the fan 2 rotates, gas outside the centrifugal multi-blade air sending device 1 passes through a suction port 5 formed in the scroll casing 4 and the fan suction port 2 eof the fan 2 shown in FIG. 1, and is sucked into the spaces surrounded by the main plate 2 aand the plurality of blades 2 d. When the fan 2 rotates, air sucked into the spaces surrounded by the main plate 2 aand the plurality of blades 2 dpass through, then, the spaces between the adjacent blades 2 d, and is sent to the outside in the radial directions of the fan 2.Scroll Case 4The scroll case 4 will be described below with reference to FIGS. 1 to 2. The scroll casing 4 accommodates the fan 2 inside and aligns the air blown out from the fan 2. The scroll 4 is a one-side suction type housing having a side wall 4 ain which the suction port 5 described later is formed on one side of the main plate 2 ain the axial direction of the rotation axis RA. The scroll casing 4 is not limited to a one-side suction casing, but may be a two-side suction casing in which the side walls 4 aeach having the suction ports 5 described later are located on both sides of the main plate 2 ain the axial direction of the rotation axis RA.The scroll 4 has a scroll portion 41 and an outlet portion 42. The scroll casing 4 has a peripheral wall 4 cformed spirally and the corresponding side walls 4 aprovided on both sides of the fan 2 in the axial direction of the rotation axis RA.Spiral Portion 41The scroll portion 41 forms an air passage that converts the dynamic pressure of the air flow generated by the fan 2 into static pressure. The scroll portion 41 has the side walls 4 athat cover the fan 2 in the axial direction of the rotation axis RA and the peripheral wall 4 cthat surrounds the fan 2 in the radial directions of the rotation axis RA of the boss portion 2 b.The scroll portion 41 also includes a tongue portion 43 that is disposed between the scroll portion 41 and the outlet portion 42, forms a curved surface, and guides an air flow generated by the fan 2 to an outlet opening 42 athrough the scroll portion 41. The inner space of the scroll portion 41 defined by the peripheral wall 4 cand the side walls 4 ais a space in which the air blown out from the fan 2 flows along the peripheral wall 4 c.Side walls 4aIn Embodiment 1, the scroll 4 includes the two side walls 4 a. Of the two side walls 4 a, a side wall 4 athat has the bell mouth 3 forming the suction port 5 is referred to as a first side wall 4 a 1, and a side wall 4 ain which no suction port 5 and no bell mouth 3 are formed is referred to as a second side wall 4 a 2. The two respective side walls 4a located on both sides of the fan 2 are formed to face each other across the peripheral wall 4c.The scroll case 4 according to Embodiment 1 includes, as illustrated in FIG. 2, the first side wall 4 a 1 and the second side wall 4 a 2 as its side walls 4 a. That is, the scroll casing 4 has at least one side wall 4a provided with the bell mouth 3 forming the suction port 5 communicating with the spaces formed by the main plate 2a and the plurality of vanes 2d.The first side wall 4 a 1 is a side wall 4 aarranged closer to the side plate 2 cthan to the main plate 2 a. The second side wall 4a2 is a side wall 4a which is disposed closer to the main plate 2a than to the side plate 2c. The first side wall 4 a 1 and the second side wall 4 a 2 are collectively referred to as side wall 4 a.On the first side wall 4 a 1 of the scroll 4, the suction port 5 is formed so that air can flow between the fan 2 and the outside of the scroll 4. The suction port 5 communicates with the fan suction port 2 e, and is an air intake port through which gas can flow into the spaces surrounded by the main plate 2 aand the plurality of blades 2 d. The suction port 5 is located at a position facing a plate surface of the main plate 2a.The suction port 5 provided in the first side wall 4 a 1 is formed by the bell mouth 3. That is, the bell mouth 3 forms the suction port 5 through which a space outside the scroll 4 and the spaces formed by the main plate 2 aand the plurality of vanes 2 dcommunicate with each other. The bell mouth 3 aligns the gas flow to be sucked into the fan 2 and causes the gas to flow into the fan suction opening 2 eof the fan 2.The bell mouth 3 is formed with an opening having a diameter gradually decreasing from the outside to the inside of the scroll 4. The bell mouth 3 is formed to extend in the axial direction of the rotational axis RA. The inner circumferential end portion 35 forming the inner edge of the bell mouth 3 is disposed inside the scroll 4. The air around the suction port 5 flows smoothly along the bell mouth 3 and efficiently flows from the suction port 5 into the fan 2.Peripheral wall 4cThe peripheral wall 4 cis a wall having a curved wall surface along which an air flow generated by the fan 2 is guided to the outlet opening 42 a. The peripheral wall 4c is formed spirally. The peripheral wall 4 cis formed such that the distance to the rotation axis RA from the tongue portion 43 as a starting point gradually increases as viewed in the rotation direction of the fan 2. The peripheral wall 4 cis formed such that the clearance between the peripheral wall 4 cand the outer periphery of the fan 2 expands at a predetermined rate from the tongue portion 43 to the outlet portion 42 in the rotational direction of the fan 2, and the flow channel area for air gradually increases also in the same direction.The spiral shape of the peripheral wall 4 cis based on, for example, a shape such as a logarithmic spiral, an Archimedes spiral, and an involute curve. The inner peripheral surface of the peripheral wall 4c forms a smooth arc-shaped surface along the circumferential direction of the fan 2 from the tongue portion 43 at which the spiral winding starts to a winding end portion 41b at which the spiral winding ends. Such a structure enables the air emitted from the fan 2 to smoothly flow through the clearance between the fan 2 and the peripheral wall 4 cin the direction from the fan 2 to the outlet portion 42. In the scroll casing 4, therefore, the static air pressure increases efficiently from the tongue portion 43 to the outlet portion 42.The peripheral wall 4 cis provided between the side walls 4 afacing each other, and forms the arc-shaped surface extending along the rotational direction of the fan 2. The peripheral wall 4 cis parallel to the axial direction of the rotation axis RA and covers the fan 2. Moreover, the peripheral wall 4 cmay also be formed to be inclined toward the axial direction of the rotation axis RA of the fan 2, and is not limited to be disposed parallel to the axial direction of the rotation axis RA.The peripheral wall 4 cconstitutes the inner wall surface facing the outer peripheral surface 2 fof the fan 2. The peripheral wall 4 cfaces the outer peripheral end portions of the plurality of blades 2 dforming the outer peripheral surface 2 fof the fan 2. The peripheral wall 4c faces the side of the blades 2d of the fan 2 from which the air is blown. As illustrated in FIG. 1, the peripheral wall 4 cis provided from the tongue portion 43, which is a winding start portion at which the winding of the spiral shape starts, to the winding end portion 41 bdisposed at the boundary between the spiral portion 41 and a portion of the outlet portion 42 that is away from the tongue portion 43 in the rotation direction of the fan 2.The tongue portion 43 is the upstream end portion of the peripheral wall 4 cthat forms the arc-shaped surface in the direction in which the gas is caused to flow into the inside of the scroll casing 4 by the rotation of the fan 2 along the peripheral wall 4 c. The coil end portion 41 bis the downstream end portion of the peripheral wall 4 cthat forms the arc-shaped surface in the direction in which the gas is caused to flow into the inside of the scroll casing 4 by the rotation of the fan 2 along the peripheral wall 4 c.Tongue portion 43The scroll casing 4 has a tongue portion 43 that forms the curved surface at the beginning portion of the winding of the peripheral wall 4 cin the vicinity of the rotation axis RA of the fan 2 and guides the air flow generated by the fan 2 to the outlet opening 42 a. The peripheral wall 4 cincludes the tongue portion 43 at one end portion of the peripheral wall 4 cthat is closer to the outlet portion 42 than the other end portion. The tongue portion 43 is formed at the beginning portion of the turn of the peripheral wall 4c which is formed spirally.The tongue portion 43 is provided at the boundary portion between the tongue portion 43 and a baffle plate 42 cof the outlet portion 42, which will be described later. The tongue portion 43 is formed with a curved surface and is formed in an arc shape as viewed in the axial direction of the rotational axis RA. The tongue portion 43 is formed with a predetermined radius of curvature, and the peripheral wall 4c is smoothly connected to the baffle plate 42c with the tongue portion 43 interposed therebetween. The tongue portion 43 has substantially the same shape in the axial direction of the rotation axis RA as viewed from the outlet opening 42 aand is formed along the axial direction of the rotation axis RA.The tongue portion 43 reduces the air supply inside the scroll 4 from the end of the spiral flow passage where its turn ends to its beginning. The tongue portion 43 is provided upstream in the air passage and serves to separate one air flow moving in the rotational direction of the fan 2 from the other air flow moving from a downstream portion of the air passage to the outlet opening 42 a. As the air flow passes through the scroll 4, its static pressure rises to a high pressure as it flows into the outlet portion 42. For this reason, the tongue portion 43 is designed so that the pressures are separated with such a difference. The tongue portion 43, which is thus configured to separate the pressures with a difference, is also configured to guide, with its curved surface, the air to flow into the outlet portion 42 to each flow passage.Outlet portion 42The outlet portion 42 forms the outlet opening 42 athrough which an air flow generated by the fan 2 and having passed through the scroll portion 41 is discharged. The outlet portion 42 is formed of a hollow pipe having a rectangular cross section and perpendicular to the direction of flow of air along the peripheral wall 4c. Moreover, such a cross-sectional shape of the outlet portion 42 is not limited to a rectangular shape. The outlet portion 42 forms a flow passage through which air, which is emitted from the fan 2 and which flows through the clearance between the peripheral wall 4 cand the fan 2, is guided to the outside of the scroll casing 4 for discharge.An end portion of the outlet portion 42 forms an inlet port, not shown, through which air flows from the scroll 4 into the outlet portion 42. In addition, the other end portion of the outlet portion 42 forms the outlet opening 42 athrough which air that has passed through the flow passage inside the outlet portion 42 is discharged to outside air.As shown in FIG. 2, the outlet portion 42 includes an extension plate 42 b, the deflector plate 42 c, a first side plate portion 42 d, and a second side plate portion 42 e. The extension plate 42 binterlaced smoothly with the coil end portion 41 blocated downstream of the peripheral wall 4 cand formed integrally with the peripheral wall 4 c. The baffle plate 42 cis formed integrally with the tongue portion 43 of the scroll 4 and faces the extension plate 42 b. For example, the baffle plate 42 cis formed at a predetermined angle to the extension plate 42 bsuch that the cross-sectional area of the flow channel gradually increases along the direction in which the air flows inside the outlet portion 42, but is not limited to this structure.The first side plate portion 42 dis integrally formed with the first side wall 4 a 1 of the scroll 4, and the second side plate portion 42 eis integrally formed with the opposite second side wall 4 a 2 of the scroll 4. Moreover, the first side plate portion 42 dand the second side plate portion 42 eare formed between the extension plate 42 band the deflector plate 42 c. Thus, the outlet portion 42 forms a flow channel of rectangular cross section defined by the extension plate 42 b, the deflector plate 42 c, the first side plate portion 42 d, and the second side plate portion 42 e.Relationship between fan 2 and scroll casing 4FIG. 6 is a partial cross-sectional view illustrating the centrifugal multi-vane air transmission device 1 according to Embodiment 1. FIG. 6 is a cross-sectional view of the centrifugal multi-vane air transmitter 1 taken in the direction of arrows A-A shown in FIG. 1. FIG. 6 is a cross-sectional view of the centrifugal multi-vane air transmission device 1 viewed in the radial direction of the rotational axis RA. The inflection point portion 26 is formed over the entire length of each blade 2d. The total length of each vane 2 dis the length of the vane 2 dalong the axial direction of the rotational axis RA, and is the length of the portion between a proximal end 2 hof the vane 2 dwhich is closest to the main plate 2 aand the distal end 2 gof the vane 2 dwhich is closest to the side plate 2 c. The proximal end 2 his an end portion of the vane 2 din the axial direction of the rotation axis RA, and is the end portion closest to the main plate 2 a. The distal end 2 his the other end portion of the vane 2 din the axial direction of the rotation axis RA, and is the end portion that is opposite to the main plate 2 a.As shown in FIG. 6, the centrifugal multi-vane air transmission device 1 is configured such that the entire portion of the inflection point portion 26 is located more inward than the inner circumferential end portion 35 constituting the inner edge of the bell mouth 3 as viewed in the radial direction of the rotational axis RA. That is, as illustrated in FIG. 6, the centrifugal multi-vane air transmission device 1 is configured such that the entire portion of the inflection point portion 26 is disposed closer to the rotation axis RA than the inner circumferential end portion 35 of the bell mouth 3 as viewed in the radial direction of the rotation axis RA. The centrifugal multi-vane air transmission device 1 is configured such that the entire portion of the inflection point portion 26 is disposed more inward in the radial direction of the fan 2 in the axial direction of the rotation axis RA than the inner circumferential end portion 35 forming the inner edge of the bell mouth 3.The centrifugal multi-blade air transmission device 1 is formed such that an imaginary line B defined by the inflection point portion 26 extending from the proximal end 2h closest to the main plate 2a to the distal end 2g closest to the side plate 2c of each blade 2d extends parallel to the rotational axis RA of the fan 2. When the imaginary line B is formed parallel to the rotation axis RA of the fan 2, for example, as viewed in the radial direction of the rotation axis RA, the imaginary line B is formed at an angle of ±1 degree to the rotation axis RA.Operation of a Multi-Vane Centrifugal Air Transmitter 1The operation of the centrifugal multi-vane air transmission device 1 will be described with reference to FIG. 2. In the centrifugal multi-vane air transmission device 1, when driven by a motor, not shown, the main plate 2 ato which a motor shaft is connected rotates, and through the main plate 2 a, the plurality of vanes 2 drotate about the rotation axis RA. By the rotation of the fan 2, air is sucked from outside the scroll 4 into the scroll 4 through the suction port 5.The air to be sucked into the scroll casing 4 is guided to the bell mouth 3 and sucked into the fan 2. In the process in which the air sucked into the fan 2 passes through the gaps between the plurality of blades 2 d, the air turns into an air flow on which dynamic pressure and static pressure act, and the air flow is blown out in the radial directions of the fan 2. The air flow to be blown out by the fan 2 is blown into the scroll casing 4 by the increase in the pressure of the fan 2.The air flow flowing inside the scroll casing 4 increases the pressure by passing through the air passage gradually expanding through the spiral peripheral wall 4 cfrom the winding start portion toward the winding end portion. The air blown out from the fan 2 into the scroll 4 is decelerated in the expanding air passage partially formed by the peripheral wall 4 cof the scroll 4, recovers the static pressure, and is blown out to the outside from the outlet opening 42 aillustrated in FIG. 1.Mechanism and Action of Multi-Vane Centrifugal Air Transmitter 1The centrifugal multi-blade air transmission device 1 includes the fan 2 including the rear blade portion 22, the front blade portion 21, and the inflection point portion 26 forming the inflection point between the rear blade portion 22 and the front blade portion 21. The inflection point portion 26 is formed over the entire length of a portion of each of the plurality of blades 2 din the axial direction of the rotational axis RA between the proximal end 2 h, which is closest to the main plate 2 a, and the distal end 2 g, which is closest to the side plate 2 cof the blade 2 d. The entire portion of the inflection point portion 26 in the axial direction of the rotation axis RA is also formed to be located more inward in the radial direction of the fan 2 than the inner circumferential end portion 35 that forms the inner edge of the bell mouth 3.Here, a structure in which the entire portion of the inflection point portion 26 is located more inward than the inner circumferential end portion 35 of the bell mouth 3 is defined as structure A. A structure in which at least a portion or the entire portion of the diffraction point portion 26 is disposed more outward than the inner circumferential end portion 35 is defined as Structure B. In a case where the structure A and the structure B are compared with each other in the same-diameter fan 2, the proportion of the blade 2 dacquired by the front blade portion 21 along the radial distance of the fan 2 is larger in the structure A than in the structure B. For this reason, the centrifugal multi-blade air transmission device 1 is configured to compensate for changes in the blade angles from the respective front edges 25 ato the rear edges 24 a, prevent separation of the air flow at the suction surfaces 2 d 2, and thereby mitigate a reduction in the air flow, compared with the structure where at least a portion or the entire portion of the inflection point portion 26 is disposed more outward than the inner circumferential end portion 35.In addition, the fan 2 is formed such that the imaginary line B defined by the inflection point portion 26 extending from the proximal end 2 h, which is closest to the main plate 2 a, to the distal end 2 g, which is closest to the side plate 2 cof each of the plurality of blades 2 d, is parallel to the rotation axis RA. Thus, the centrifugal multi-vane air transmission device 1 is configured such that the imaginary line B is parallel to the rotation axis RA. Consequently, compared with a case where the imaginary line B is not parallel to the rotation axis RA, the fan 2 can be more easily taken out of the mold in manufacturing the fan 2, so that the production process is simpler.Embodiment 2FIG. 7 is a partial cross-sectional view illustrating a centrifugal multi-vane air transmission device 1 according to Embodiment 2. FIG. 7 is a cross-sectional view of the centrifugal multi-vane air transmitter 1 taken in the direction of arrows A-A shown in FIG. 1. A portion having the same structure as that of the centrifugal multi-vane air transmission device 1 shown in Figs. 1 to 6 is denoted by the same reference numeral, and description thereof is omitted.The centrifugal multi-vane air transmission device 1 according to Embodiment 2 is further specified with respect to the shape of the vane 2 d. The centrifugal multi-vane air transmission device 1 according to Embodiment 2 is further also specified with respect to the positional relationship between the vane 2 dand the bell mouth 3. Structures other than the shape of the vane 2 dand the positional relationship between the vane 2 dand the bell mouth 3 are the same as those of the centrifugal multi-vane air transmission device 1 according to Embodiment 1.Each vane 2d of the centrifugal multi-vane air transmission device 1 according to Embodiment 2 is formed so that a notch-shaped step portion 27 is formed at a portion of the leading edge 25a closest to the side plate 2c. More specifically, the blade 2d has a notch-shaped step portion 27 formed at the front edge 25a of the blade 2d and at the distal end 2g closest to the side plate 2c.The step portion 27 is a portion formed in a state in which a wall defining the front edge 25 aand the distal end 2 gis notched. The step portion 27 is formed at a portion of the leading edge 25 aand also formed at a portion of the distal end 2 g. At the step portion 27, an end portion of the front edge 25a closest to the side plate 2c is notched, and an end portion of the distal end 2g closest to the rotation axis RA is also notched. The step portion 27 is a portion formed in a state in which a corner portion connecting the front edge 25 aand the distal end 2 gis notched. The step portion 27 is formed, as shown in FIG. 7, on the rear wing portion 22 and on the distal end 2g of the front wing portion 21 closest to the side plate 2c.The step portion 27 is formed by a side portion edge portion 27A extending in the axial direction of the rotation axis RA of the fan 2 and an upper portion edge portion 27B extending in the radial direction of the fan 2. In the fan 2, the upper portion edge portion 27B is an edge portion that is disposed closer to the main plate 2 athan the distal end 2 g. The fan 2 has a step formed between the upper portion edge portion 27B and the distal end 2 gin the axial direction of the rotation axis RA. In addition, the fan 2 is formed such that the side portion edge portion 27A is disposed closer to the outer periphery of the fan 2 than an imaginary extension line C of the front edge 25 ato the step portion 27.The step portion 27 is not limited to the structure formed by the side portion edge portion 27A extending in the axial direction of the rotation axis RA of the fan 2 and the upper portion edge portion 27B extending in the radial direction of the fan 2. The step portion 27 may also be formed as an arcuate edge portion in which the side portion edge portion 27A and the upper portion edge portion 27B are seamlessly connected and integrated with each other, for example.The centrifugal multi-vane air transmission device 1 according to Embodiment 2 is configured such that an outer diameter of the vanes defined by the respective outer circumferential ends 24 of the plurality of vanes 2 dis larger than the inner diameter of the bell mouth 3. that is, the centrifugal multi-vane air transmission device 1 according to Embodiment 2 is configured, as viewed in the axial direction of the rotational axis RA, such that the outer circumferential ends 24 of the vanes 2 dare disposed more outward than the inner circumferential end portion 35 of the bell mouth 3 as viewed in the radial direction of the fan 2. that is, the centrifugal multi-vane air transmission device 1 according to Embodiment 2 is configured, as viewed in the axial direction of the rotational axis RA, at least portions of the leading edges 25 aof the blades 2 dare disposed more inward than the inner circumferential end portion 35 of the bell mouth 3 in the radial directions of the fan 2.The boundary portion between the distal end 2 gand the step portion 27 of the blade 2 dis referred to as a step start point 27C. The step start point 27C of the blade 2 dis the boundary portion between the distal end 2 gand the side portion edge portion 27A of the blade 2 d. The step start point 27C is the corner portion of the blade 2 dformed between the distal end 2 gand the side portion edge portion 27A. The centrifugal multi-blade air transmission device 1 according to Embodiment 2 is configured such that the step start points 27C of the blades 2 dare located more outward than the inner circumferential end portion 35 of the bell mouth 3 in the radial direction of the fan 2.As illustrated in FIG. 7, in the centrifugal multi-vane air transmission device 1 according to Embodiment 2, the inner circumferential end portion 35 of the bell mouth 3 is located above the step portion 27. the centrifugal multi-vane air transmission device 1 according to Embodiment 2 is configured such that the inner circumferential end portion 35 of the bell mouth 3 faces the step portion 27 in the axial direction of the rotational axis RA. More specifically, in the centrifugal multi-vane air transmission device 1 according to Embodiment 2, the inner circumferential end portion 35 of the bell mouth 3 is disposed to face the upper portion edge portion 27B in the axial direction of the rotation axis RA. In the centrifugal multi-vane air transmission device 1 according to Embodiment 2, a gap is formed between the inner circumferential end portion 35 of the bell mouth 3 and the upper portion edge portion 27B.Further, in the centrifugal multi-blade air transmission device 1 according to Embodiment 2, the inner circumferential end portion 35 of the bell mouth 3 may also be disposed to face the side portion edge portion 27A in the radial direction of the fan 2. In the centrifugal multi-vane air transmission device 1 according to Embodiment 2, the gap is formed between the inner circumferential end portion 35 of the bell mouth 3 and the upper portion edge portion 27B in the axial direction of the rotation axis RA, and a gap may also be formed between the inner circumferential end portion 35 of the bell mouth 3 and the side portion edge portion 27A in the radial direction of the rotation axis RA.Mechanism and Action of Multi-Vane Centrifugal Air Transmitter 1Each of the plurality of blades 2 dis formed such that the notch-shaped step portion 27 is formed at a portion of the front edge 25 a, which is closest to the side plate 2 c. In a case where the boundary portion between the distal end 2 gand the step portion 27 is defined as the step start point 27C, the structure is formed such that the step start point 27C is located more outward in the radial direction of the fan 2 than the inner circumferential end portion 35 of the bell mouth 3. The centrifugal multi-vane air transmission device 1 according to Embodiment 2 is configured so that even if the height of the vane 2 dis increased to extend the vane surface by the provision of the step portion 27, the vane 2 dis prevented from engaging with the inner circumferential end portion 35 of the bell mouth 3.The centrifugal multi-vane air transmission device 1 is therefore configured such that the step start points 27C are located more outward than the inner circumferential end portion 35 of the bell mouth 3 and are configured such that the height of each vane 2 dis increased in the axial direction of the rotational axis RA while the distance between the inner circumferential end portion 35 of the bell mouth 3 and the vane 2 dis secured. The centrifugal multi-vane air transmission device 1 according to Embodiment 2 enables the distal ends 2 gof the vanes 2 dto be closer to the corresponding side wall 4 acompared to the vanes 2 dwhich do not have step portions 27, thereby increasing the vane area and thus achieving a large amount of airflow.Embodiment 3FIG. 8 is a partial cross-sectional view showing a centrifugal multi-vane air transmission device 1 according to Embodiment 3. FIG. 8 is a cross-sectional view of the centrifugal multi-vane air transmitter 1 taken in the direction of arrows A-A shown in FIG. 1. A portion having the same structure as that of the centrifugal multi-vane air transmission device 1 shown in Figs. 1 to 6 is denoted by the same reference numeral, and description thereof is omitted.The centrifugal multi-vane air transmission device 1 according to Embodiment 3 is specified with respect to the positional relationship between each vane 2 dand the bell mouth 3. Structures other than the positional relationship between the vane 2 dand the bell mouth 3 are the same as those of the centrifugal multi-vane air transmission device 1 according to Embodiment 1.The centrifugal multi-blade air transmission device 1 according to Embodiment 3 is configured such that the outer diameter of the blades defined by the respective outer circumferential ends 24 of the plurality of blades 2 dis larger than the inner diameter of the bell mouth 3.The centrifugal multi-vane air transmission device 1 according to Embodiment 3 is configured such that at least portions of the leading edges 25 aof the vanes 2 dare disposed more inward than the inner circumferential end portion 35 of the bell mouth 3 in the radial directions of the fan 2 as viewed in the axial direction of the rotational axis RA. The centrifugal multi-vane air transmission device 1 according to Embodiment 3 is configured such that the rear vane portions 22 are disposed more inward than the inner circumferential end portion 35 of the bell mouth 3 in the radial directions of the fan 2.In the fan 2, a portion of the leading edge 25 adisposed at the boundary portion between the leading edge 25 aand the distal end 2 gof the blade 2 dis referred to as a side plate-side leading edge portion 25 b. The side plate side front edge portion 25 bdefines a portion of the corner portion of the blade 2 dformed between the distal end 2 gand the front edge 25 a. The centrifugal multi-blade air transmission device 1 according to Embodiment 3 is configured such that the side plate side leading edge portions 25 bof the blades 2 dare disposed more outward than the inner circumferential end portion 35 of the bell mouth 3 in the radial directions of the fan 2.Mechanism and Action of Multi-Vane Centrifugal Air Transmitter 1The centrifugal multi-blade air transmission device 1 according to Embodiment 3 is configured such that the side plate side leading edge portions 25 bare disposed more outward than the inner circumferential end portion 35 of the bell mouth 3 in the radial directions of the fan 2. the centrifugal multi-blade air transmission device 1 according to Embodiment 3 is therefore configured such that the side plate side leading edge portions 25 bare disposed more outward than the inner circumferential end portion 35 of the bell mouth 3, and is thereby configured such that even if the height of the blade 2 dis increased to extend the blade surface, the blade 2 dis prevented from engaging the inner circumferential end portion 35 of the bell mouth 3.The centrifugal multi-vane air transmission device 1 is therefore configured such that the side plate side leading edge portions 25 bare located more outward than the inner circumferential end portion 35 of the bell mouth 3, and is configured such that the height of each vane 2 dis increased in the axial direction of the rotation axis RA while the distance between the inner circumferential end portion 35 of the bell mouth 3 and the vane 2 dis secured. The centrifugal multi-vane air transmission device 1 enables the distal ends 2 gof the vanes 2 dto be closer to the corresponding side wall 4 a, as compared with the vanes 2 dformed such that the side plate-side leading edge portions 25 bare disposed more inward than the inner circumferential end portion 35 of the bell mouth 3, thereby increasing the vane area and thus achieving a large airflow.Embodiment 4FIG. 9 is a partially enlarged view showing a fan 2 of a centrifugal multi-blade air transmission device 1 according to Embodiment 4. FIG. 9 is an enlarged view showing the fan 2 as viewed in the axial direction of the rotation axis RA. Figure 9, intended to illustrate the shape of the wing 2d, shows the wing 2d as viewed through the bell mouth 3. A portion having the same structure as that of the centrifugal multi-vane air transmission device 1 shown in Figs. 1 to 8 is denoted by the same reference numeral, and description thereof is omitted.The centrifugal multi-vane air transmission device 1 according to Embodiment 4 is further specified with respect to the shape of the vane 2 d. Structures other than the shape of the vane 2 ddescribed below are the same as those of the centrifugal multi-vane air transmission device 1 according to Embodiment 1.In a case where the vane 2 dis viewed in the axial direction of the rotational axis RA, a portion of the vane 2 dformed in the shape of a circular arc is referred to as a circular arc portion AR. In each vane 2 dof the centrifugal multi-vane air transmission device 1 according to Embodiment 4, a portion of the vane 2 dfrom the inflection point portion 26 to the trailing edge 24 aas illustrated in FIG. 3 is formed by the single circular arc portion AR as illustrated in FIG. 9 or by a plurality of circular arc portions AR. That is, in each vane 2 dof the centrifugal multi-vane air transmission device 1 according to Embodiment 4, the front vane portion 21 is formed by the single circular arc portion AR as illustrated in FIG. 9 or by the plurality of circular arc portions AR. In each blade 2 dof the centrifugal multi-blade air transmission device 1 according to Embodiment 4, the portion of the blade 2 dfrom the inflection point portion 26 to the trailing edge 24 ais formed by the at least one circular arc portion AR as illustrated in FIG. 3.The circular arc portion AR is a circular arc-shaped portion of the blade 2 dwhen viewed in the axial direction of the rotational axis RA. The trailing edge 24a is formed by the outer circumferential ends 24. The outer circumferential ends 24 are the outer ends of the blades 2 din a cross section perpendicular to the rotation axis RA. The trailing edge 24 ais a portion where the outer circumferential ends 24 are arranged one behind the other in the axial direction of the rotational axis.Mechanism and Action of Multi-Vane Centrifugal Air Transmitter 1In each of the plurality of blades 2 d, the portion of the blade 2 dfrom the inflection point portion 26 to the trailing edge 24 ais formed by the at least one circular arc portion AR. Therefore, the centrifugal multi-blade air transmission device 1 according to Embodiment 4 is configured such that the portion of each blade 2 dfrom the inflection point portion 26 to the trailing edge 24 ais formed by the at least one circular arc portion AR, thereby reducing a steep change in the angle of the blade 2 din the radial direction of the fan 2. for this reason, the centrifugal multi-blade air transmission device 1 prevents the separation of the air flow at the suction surfaces 2 d 2 and thus suppresses the reduction of the air flow.Preferred embodiments and other concepts are described in detail above. The embodiments are not limited to the above-described preferred embodiments and other concepts. Various configurations and substitutions may be applied to the above-described preferred embodiments and other concepts without departing from the scope described in the claims.In the following description, various aspects of the present disclosure are set forth as appendices.Appendix 1A centrifugal multi-vane air transmitter comprising:a fan having a main plate that is circular when the main plate is viewed in an axial direction of a rotation axis, a plurality of blades installed around a peripheral portion of the main plate, and a side plate that is annular and fixes ends of the plurality of blades that oppose the main plate in the axial direction of the rotation axis; anda scroll casing having a peripheral wall that is spiral and at least one side wall having a bell mouth that forms a suction port, the scroll casing having a discharge port through which an air flow generated by the fan is discharged, the scroll casing accommodating the fan,wherein the fan comprisesa rear blade portion forming a rear blade of each of the plurality of blades located on an inner periphery of the plurality of blades in a radial direction of the fan,a front blade portion forming a front blade of each of the plurality of blades located on an outer periphery of the plurality of blades in the radial direction of the fan, anda inflection point portion that forms an inflection point between the rear blade portion and the front blade portion when the inflection point portion is viewed in the axial direction of the rotation axis,wherein the inflection point portion is formed over an entire length of a portion of each of the plurality of blades in the axial direction of the rotational axis,wherein the inflection point portion is located between a proximal end of each of the plurality of blades closest to the main plate and a distal end of each of the plurality of blades closest to the side plate,wherein an entire portion of the inflection point portion is disposed more inward in the axial direction in the radial direction of the fan than an inner circumferential end portion forming an inner edge of the bell mouth.Appendix 2The centrifugal multi-vane air transmission device described in Appendix 1, wherein the fan is formed such that an imaginary line defined by the inflection point portion extending from the proximal end closest to the main plate to the distal end closest to the side plate of each of the plurality of vanes extends parallel to the rotation axis.Appendix 3The centrifugal multi-blade air transmission device described in Appendix 1 or 2, wherein, in each of the plurality of blades, a step portion that is notch-shaped is formed at a portion of a leading edge that is closest to the side plate, and in a case where a boundary portion between the distal end and the step portion is defined as a step start point, a structure is formed that is such that the step start point is located more outward in the radial direction of the fan than the inner circumferential end portion of the bell mouth.Appendix 4The centrifugal multi-blade air transmission device as described in any one of Claims 1 to 3, wherein, in a case where, in the fan, a portion of a leading edge located at a boundary portion between the leading edge and the distal end of each of the plurality of blades is defined as a side plate side leading edge portion, a structure is formed such that the side plate side leading edge portion is located more outward in the radial direction of the fan than the inner circumferential end portion of the bell mouth.Appendix 5The centrifugal multi-vane air transmission device as described in any one of Claims 1 to 4, wherein, in a case where, as viewed in the axial direction of the rotational axis, a portion of each of the plurality of vanes formed in the shape of a circular arc is defined as a circular arc portion, in each of the plurality of vanes, a portion of each of the plurality of vanes from the inflection point portion to a trailing edge is formed by the at least one circular arc portion.List of reference characters1: Centrifugal multi-blade air transmission device, 2: fan, 2 a: main plate, 2 a 1: peripheral portion, 2 a 2: central portion, 2 b: boss portion, 2 c: side plate, 2 d: blade, 2 d 1: pressure surface, 2 d 2: suction surface, 2 e: fan suction port, 2 f: outer peripheral surface, 2 g: distal end, 2 h: proximal end, 3: bell mouth, 4: scroll casing, 4 a: side wall, 4 a 1: first side wall, 4 a 2: second side wall, 4 c: peripheral wall, 5: suction port, 21: front blade portion, 22: rear blade portion, 24: outer peripheral end, 24 a: rear edge, 25: inner peripheral end, 25 a: front edge, 25 b: side plate-side front edge portion, 26: inflection point portion, 27: step portion, 27A: side portion edge portion, 27B: upper portion edge portion, 27C: step start point, 35: inner circumferential end portion, 41: spiral portion, 41 b: turn end portion, 42: outlet portion, 42 a: outlet opening, 42 b: extension plate, 42 c: deflector plate, 42 d: first side plate portion, 42 e: second side plate portion, 43: tongue portion, AR: circular arc portion, B: imaginary lineReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2002-70793

[0003]

Claims

A centrifugal multi-blade air transmission device comprising: a fan having a main plate that is circular when the main plate is viewed in an axial direction of a rotation axis, a plurality of blades installed around a circumferential portion of the main plate, and a side plate that is annular and fixes ends of the plurality of blades that oppose the main plate in the axial direction of the rotation axis; and a scroll casing having a peripheral wall that is spiral and at least one side wall having a bell mouth that forms a suction opening, the scroll casing having an outlet opening through which an air flow generated by the fan is discharged, the scroll casing accommodating the fan, the fan having a rear blade portion that forms a rear blade of each of the plurality of blades, which are located on an inner periphery of the plurality of blades in a radial direction of the fan, a front blade portion which forms a front blade of each of the plurality of blades which are located on an outer periphery of the plurality of blades in the radial direction of the fan, and a inflection point portion which forms an inflection point between the rear blade portion and the front blade portion when the inflection point portion is viewed in the axial direction of the rotational axis, the inflection point portion being formed over an entire length of a portion of each of the plurality of blades in the axial direction of the rotational axis, the inflection point portion being located between a proximal end of each of the plurality of blades closest to the main plate and a distal end of each of the plurality of blades closest to the side plate, wherein an entire portion of the inflection point portion is disposed more inward in the axial direction in the radial direction of the fan than an inner circumferential end portion forming an inner edge of the bell mouth.The centrifugal multi-blade air transmission device according to claim 1, wherein the fan is configured such that an imaginary line defined by the inflection point portion extending from the proximal end closest to the main plate to the distal end closest to the side plate of each of the plurality of blades is parallel to the rotation axis.The centrifugal multi-blade air transmission device according to claim 1 or 2, wherein, in each of the plurality of blades, a step portion that is notch-shaped is formed at a portion of a front edge that is closest to the side plate, and in a case where a boundary portion between the distal end and the step portion is defined as a step start point, a structure is formed that is such that the step start point is located more outward in the radial direction of the fan than the inner circumferential end portion of the bell mouth.The centrifugal multi-blade air transmission device according to any one of claims 1 to 3, wherein, in a case where, in the fan, a portion of a leading edge disposed at a boundary portion between the leading edge and the distal end of each of the plurality of blades is defined as a side plate-side leading edge portion, a structure is formed such that the side plate-side leading edge portion is disposed more outward in the radial direction of the fan than the inner circumferential end portion of the bell mouth.The centrifugal multi-vane air transmission device according to any one of claims 1 to 4, wherein, in a case where, as viewed in the axial direction of the rotational axis, a portion of each of the plurality of vanes formed in the shape of a circular arc is defined as a circular arc portion, in each of the plurality of vanes, a portion of each of the plurality of vanes from the inflection point portion to a trailing edge is formed by the at least one circular arc portion.

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