centrifugal fan

Abstract

A tangent touching a positive pressure surface (47) of a predetermined wing (4) from a plurality of wings (4) and passing through a trailing edge (45) of the predetermined wing (4) is defined as the first tangent (TL1). A virtual circle (C1) is centered at the midpoint of a rotation axis (CL) and passes through the trailing edge (45). A tangent tangent to the virtual circle (C1) and passing through the trailing edge (45) is defined as the second tangent (TL2). Among a plurality of angles defined between the first tangent (TL1) and the second tangent (TL2), an angle that is in front of the first tangent (TL1) in the direction of rotation and is located on an outside side of the virtual circle (C1) relative to the second tangent (TL2) is defined as the exhaust angle.When considering a change in the outlet angle at each of a plurality of locations arranged axially along the trailing edge (45), the trailing edge (45) has at least one inflection point (POI) at which the outlet angle changes to an increase or decrease. At least one of the outlet angles (θ3) measured at a corresponding adjacent location of the plurality of locations next to a main plate (3) along the trailing edge (45), and the outlet angle (θ1) measured at a corresponding adjacent location of the plurality of locations next to a cover (2) along the trailing edge (45), is smaller than the outlet angle (θ2) measured at a corresponding location of the plurality of locations where the outlet angle is largest among the plurality of locations arranged axially along the trailing edge (45).

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on and incorporates by reference Japanese Patent Application No. 2022-065872 filed on April 12, 2022. TECHNICAL FIELD

[0002] The present disclosure relates to a centrifugal fan. STATE OF THE ART

[0003] So far, a centrifugal fan is known that is used in a blower.

[0004] In the centrifugal fan described in Patent Literature 1, the helix angle of the trailing edge of a blade is smaller than the helix angle of the leading edge of the blade. With this configuration, the centrifugal fan reduces noise and improves pressure amplification characteristics by confining a secondary flow vortex generated in the airflow flowing in a flow passage (hereinafter referred to as an interblade passage) formed between two corresponding adjacent blades located side by side in a rotation direction. The helix angle is an angle defined between a main plate and a line connected between a portion of the blade joined to the main plate and a portion of the blade joined to a cover on a low-pressure side of the blade. CITATION LISTPATENT LITERATURE

[0005] PATENT LITERATURE 1: JP6981077B2 SUMMARY OF THE INVENTION

[0006] The centrifugal fan used in the blower may exhibit fluctuations in the airflow velocity distribution of the airflow exiting a blade outlet depending on the shape or size of individual components, such as the cover, the main plate, and the blades. When the variations in the flow velocity distribution of the airflow exiting the blade outlet in the centrifugal fan become large, noise increases and airflow efficiency deteriorates. Therefore, the centrifugal fan described in Patent Literature 1 has room for further improvement. It is an object of the present disclosure to provide a centrifugal fan that can reduce noise and improve airflow efficiency by making the flow velocity distribution of an airflow exiting from the outlet of a blade approximately uniform.

[0007] According to one aspect of the present disclosure, a centrifugal fan includes a shroud, a main plate, and a plurality of blades. The shroud is annular and has a suction-side port at a center point of the shroud. The main plate faces the shroud and is configured to rotate together with the shroud. The plurality of blades are arranged at predetermined intervals in a rotational direction between the shroud and the main plate and are joined to the shroud and the main plate. A tangent that is tangent to a positive pressure surface of a predetermined blade among the plurality of blades and passes through a trailing edge of the predetermined blade is defined as a first tangent.A virtual circle is centered on an axis of rotation and passes through the trailing edge of the predetermined wing, and a tangent tangent to the virtual circle and passing through the trailing edge of the predetermined wing is defined as a second tangent. Among a plurality of angles defined between the first tangent and the second tangent, an angle that is forward of the first tangent in the direction of rotation and on an outboard side of the virtual circle relative to the second tangent is defined as an outlet angle. When considering a change in the outlet angle at each of the plurality of locations arranged axially along the trailing edge, the trailing edge has at least one inflection point at which an increase or decrease in the outlet angle results.At least one of the outlet angles measured at a corresponding adjacent location of the plurality of locations adjacent the main plate along the trailing edge and the outlet angle measured at a corresponding adjacent location of the plurality of locations adjacent the cover along the trailing edge is smaller than the outlet angle measured at a corresponding location of the plurality of locations at which the outlet angle is greatest among the plurality of locations arranged axially along the trailing edge.

[0008] According to the above point of view, there are three possible configurations. The first configuration is that the exhaust angle measured at the corresponding adjacent position of the trailing edge adjacent to the main plate and the exhaust angle measured at the corresponding adjacent position of the trailing edge adjacent to the cover are both made relatively small. The second configuration is that the exhaust angle measured at the corresponding adjacent position of the trailing edge adjacent to the main plate is made relatively small. The third configuration is that the exhaust angle measured at the corresponding adjacent position of the trailing edge adjacent to the cover is made relatively small. In the description of the present disclosure, the trailing edge location adjacent to the main plate is defined as a trailing edge location located on the side of the main plate closest to the inflection point of the main plate. Furthermore, the cover-adjacent trailing edge location is defined as the trailing edge location located on the side of the cover closest to the inflection point.

[0009] The first configuration (that is, the configuration in which the outlet angle measured at the corresponding adjacent position of the trailing edge adjacent to the main plate and the outlet angle measured at the corresponding adjacent position of the trailing edge adjacent to the shroud are both made relatively small) is effective in a case where the airflow velocity in the shroud-side region and the airflow velocity in the main plate-side region at the wing outlet are both low, and the airflow velocity in an axial center region of the wing outlet is high in a hypothetical structure in which the trailing edge is formed parallel to the rotation axis. The airflow velocity in the main plate region of the wing outlet may become low due to the influence of a boundary layer formed, for example, by friction between the airflow and the main plate.Furthermore, the airflow velocity in the blade outlet region located on the shroud side may become low, e.g., due to a vortex generated near the shroud in the passage between the blades. In such a case, if the outlet angle measured at the corresponding adjacent point of the trailing edge adjacent to the shroud and the outlet angle measured at the corresponding adjacent point of the trailing edge adjacent to the main plate are both made relatively small, the airflow velocity in these regions will be accelerated compared to the other trailing edge regions.Furthermore, by increasing the outlet angle measured at a point at the axial center of the trailing edge, the airflow velocity in the region of the axial center of the trailing edge can be reduced compared to the other regions of the trailing edge. Therefore, with the centrifugal fan described above, the velocity distribution of the airflow exiting the blade outlet can be approximately uniform, thereby reducing noise and improving airflow efficiency.

[0010] The second configuration (i.e., the configuration in which the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the main plate is made relatively small) is effective in a case where the airflow velocity in the main plate-side region of the wing outlet is low in the hypothetical structure in which the trailing edge is formed parallel to the rotation axis. In such a case, if the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the main plate is made relatively small, the work applied by the main plate-side portion of the wing to the airflow is increased, and thereby the airflow velocity in the main plate-side region is accelerated compared to the other regions on the trailing edge.Therefore, with the centrifugal fan described above, the distribution of the speed of the air flow exiting from the outlet of the blade can be made almost uniform, making it possible to reduce the noise and improve the air flow efficiency.

[0011] The third configuration (i.e., the configuration in which the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the shroud is made relatively small) is effective in a case where the airflow velocity in the shroud-side region of the blade outlet is low in the hypothetical structure in which the trailing edge is formed parallel to the rotation axis. In such a case, if the outlet angle measured at the corresponding adjacent location of the trailing edge adjacent to the shroud is made relatively small, the amount of work applied to the airflow by the shroud-side region of the blade increases, and thereby the airflow velocity in the shroud-side region is accelerated compared to the other regions on the trailing edge.Therefore, with the centrifugal fan described above, the distribution of the speed of the air flow exiting from the outlet of the blade can be made almost uniform, making it possible to reduce the noise and improve the air flow efficiency.

[0012] The reference numeral in parentheses assigned to each component shows an example of correspondence between the component and the specific component described in the embodiment described later. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a centrifugal fan of a first embodiment. Fig. 2 is a cross-sectional view of the centrifugal fan of the first embodiment taken along a plane parallel to a rotation axis. Fig. 3 is a side view of the centrifugal fan of the first embodiment. Fig. 4 is an enlarged view of a section IV in Fig. 3. Fig. 5 is a cross-sectional view taken along the line VV in Fig. 4 to explain an outlet angle of the overpressure surface side measured at a position adjacent to a cover. Fig. 6 is a cross-sectional view along the line VI-VI in Fig. 4 for explaining an outlet angle of the overpressure surface side measured at a position of an axial section at the center in the axial direction. Fig. 7 is a cross-sectional view along the line VII-VII in Fig. 4 to explain an outlet angle of the overpressure surface side measured at a position adjacent to a main plate. Fig. 8 is a schematic diagram of a blade of a centrifugal fan of a comparative example in a rotation direction for explaining the air flow velocity of an airflow at an inter-blade passage and the air flow velocity of the airflow exiting from a blade outlet. Fig. 9 is a side view of the centrifugal fan of the comparative example for explaining the airflow velocity of the airflow at the inter-blade passage and the airflow velocity of the airflow exiting from the blade outlet. Fig. 10 is a view of the centrifugal fan of the first embodiment in the rotation direction for explaining the airflow velocity at an inter-blade passage and the airflow velocity of the airflow discharged from a blade outlet. Fig. 11 is a side view of the centrifugal fan of the first embodiment for explaining the airflow velocity of the airflow at the inter-blade passage and the airflow velocity of the airflow exiting from the blade outlet. Fig. 12 is a cross-sectional view taken along the line VV in Fig. 4 to explain the surface angle of the wings on the overpressure surface side, measured at the position adjacent to the cover. Fig. 13 is a cross-sectional view taken along line VI-VI in Fig. 4 to explain the surface angle of the wing on the overpressure surface side, which is measured at the position of the axial section at the center point, which is centered in the axial direction. Fig. 14 is a cross-sectional view taken along line VII-VII in Fig. 4 to explain the surface angle of the wing on the overpressure surface side, which is measured at the position adjacent to the main plate. Fig. 15 is a cross-sectional view taken along the line VV in Fig. 4 to explain an outlet angle on the vacuum surface side measured at the adjacent location adjacent to the cover. Fig. 16 is a cross-sectional view taken along line VI-VI in Fig. 4 to explain an outlet angle on the vacuum surface side, which is measured at the location of the axial center, which is centered in the axial direction. Fig. 17 is a cross-sectional view taken along the line VII-VII in Fig. 4 was taken to illustrate an outlet angle on the vacuum surface side measured at the adjacent location located next to the main plate. Fig. 18 is a cross-sectional view taken along the line VV in Fig. 4 was taken to explain a surface angle of the wing on the low pressure surface side measured at the adjacent location adjacent to the cover. Fig. 19 is a cross-sectional view taken along the line VI-VI in Fig. 4 was taken to explain a surface angle of the wing on the low pressure surface side, which is measured at the location of the axial section at the midpoint centered in the axial direction. Fig. 20 is a cross-sectional view taken along the line VII-VII in Fig. 4 was taken to illustrate a surface angle of the wing on the low pressure surface side measured at the adjacent location located next to the main plate. Fig. 21 is an enlarged side view of a portion of a centrifugal fan of a second embodiment, which is Fig. 4 corresponds. Fig. 22 is an enlarged side view of a portion of a centrifugal fan of a third embodiment, which is Fig. 4 corresponds. Fig. 23 is an enlarged side view of a portion of a centrifugal fan of a fourth embodiment, which is Fig. 4 corresponds. Fig. 24 is an enlarged side view of a portion of a centrifugal fan of a fifth embodiment, which is Fig. 4 corresponds. Fig. 25 is an enlarged side view of a portion of a centrifugal fan of a sixth embodiment, which is Fig. 4 corresponds. Fig. 26 is a schematic view of a blade of a centrifugal fan of the seventh embodiment in the rotation direction. Fig. 27 is a schematic view of a blade of a centrifugal fan of the eighth embodiment in the rotation direction. Fig. 28 is a schematic view of a blade of a centrifugal fan of the ninth embodiment in the rotation direction. Fig. 29 is a schematic view of a blade of a centrifugal fan of the tenth embodiment in the rotation direction. Fig. 30 is a schematic view of a blade of a centrifugal fan of an eleventh embodiment in the rotation direction. DESCRIPTION OF EMBODIMENTS

[0013] Embodiments of the present disclosure will be described below with reference to the drawings. In each of the following embodiments, portions that are the same or equivalent to each other are denoted by the same reference numerals. With reference to the drawings referred to in the respective embodiments, the shape of each component, the size of each component, the number of blades, and the thickness of each blade in a centrifugal fan are schematically described for clarity of explanation and do not limit the present disclosure. (First embodiment)

[0014] A first embodiment will be described with reference to the drawings. A centrifugal fan of the first embodiment is used in a blower of, for example, an air conditioner or a ventilation device.

[0015] As can be seen from the Fig. 1 to 3, the centrifugal fan 1 comprises: a cover 2 with a connection for the air intake; a main plate 3, which is opposite the cover 2; and a plurality of blades 4, which are arranged between the cover 2 and the main plate 3. In Fig. 2, a rotation axis CL of the centrifugal fan 1 is indicated by a dot-dash line. Hereinafter, a direction in which the rotation axis CL extends is referred to as an axial direction. A radially outer side of a circle perpendicular to the rotation axis CL and whose center is the rotation axis CL is referred to as a radially outer side or simply an outer side. The side of the cover 2 in the axial direction on which an air intake port 21 is located is referred to as an axial direction side, and the opposite side to one side is referred to as the other axial direction side.

[0016] The cover 2 is annular and includes the air intake port 21 configured to suck in air and formed at the center of the cover 2. The cover 2 is shaped such that the cover 2 increasingly approaches the other axial side as the cover 2 extends from the air intake port 21 toward the radially outer side.

[0017] The main plate 3 is formed in a circular disk shape and gradually approaches the other axial side as the main plate 3 extends from the central portion toward the radially outer side. In other words, the main plate 3 is formed such that the central portion of the main plate 3 protrudes toward the air intake port 21. A shaft of an electric motor (not shown) is attached to the central portion of the main plate 3.

[0018] The blades 4 are arranged at predetermined intervals in the rotation direction of the centrifugal fan 1 between the main plate 3 and the cover 2. A portion 41 of each blade 4, located on one side in the axial direction, is joined to the cover 2, and a portion 42 of each blade 4, located on the other side in the axial direction, is joined to the main plate 3. That is, the blades 4, the cover 2, and the main plate 3 are integrally formed. Each of the blades 4 is arranged so that a trailing edge 45 of the blade 4 lies behind (i.e., on a rear side) of a virtual plane having the rotation axis CL and a leading edge 46 of the blade 4 in the rotation direction. Therefore, the centrifugal fan 1 is a turbo fan.

[0019] The centrifugal fan 1 (ie the main plate 3, the cover 2 and the blades 4) is rotated by the electric motor (not visible) in the direction of rotation indicated by an arrow, for example Fig. 1. When the centrifugal fan 1 is rotated, the air sucked in by the air intake port 21 flows from the leading edge 46 of the corresponding blade 4 through a corresponding inter-blade duct 43 formed between two corresponding adjacent blades 4 and is discharged radially outward from a corresponding blade outlet 44 formed by the trailing edge 45 of the corresponding blade 4, the cover 2 and the main plate 3.

[0020] As can be seen from the Fig. 3 and Fig. 4, in the first embodiment, an axial center portion 453 of the trailing edge 45 of the blade 4, which is centered in the axial direction, is arranged rearward of a portion (joined portion) 451 of the trailing edge 45 joined to the cover 2 and a portion (joined portion) 452 of the trailing edge 45 joined to the main plate 3 in the rotation direction.

[0021] In contrast, the leading edge 46 of the wing 4 extends, as can be seen from the Fig. 1 and Fig. 2, generally parallel to the rotation axis CL from a portion 461 of the leading edge 46 connected to the shroud 2 to a portion 462 of the leading edge 46 connected to the main plate 3. Therefore, in the centrifugal fan 1, the axial center portion of each blade 4, centered in the axial direction, is displaced from a predetermined position located at the center of the blade 4 between the leading edge 46 and the trailing edge 45 in the rotation direction gradually rearward toward the trailing edge 45 relative to the portion 41 connected to the shroud 2 and the portion 42 connected to the main plate 3.

[0022] Now, an exit angle at the trailing edge 45 of the wing 4 is determined with reference to the Fig. 5 to 7. Fig. 5 is a cross-sectional view taken along the line VV in Fig. 4, ie a cross-sectional view of the wing 4 at the adjacent location adjacent to the cover 2. Fig. 6 is a cross-sectional view along the line VI-VI in Fig. 4, ie a cross-sectional view of the axial central portion of the wing 4, which is located at the center in the axial direction. In addition, Fig. 7 a cross-sectional view along the line VII-VII in Fig. 4, ie a cross-sectional view of the wing 4 at the adjacent location adjacent to the main plate 3.

[0023] As can be seen from the Fig. 5 to 7, in the following description, a tangent that touches a positive pressure surface 47 of a predetermined wing 4 among the plurality of wings 4 and passes through the trailing edge 45 of the wing 4 is defined as a first tangent TL1. In addition, a virtual circle (hereinafter referred to as a first virtual circle C1) is centered on the center of the rotation axis CL and passes through the trailing edge 45 of the predetermined wing 4. A tangent that touches the first virtual circle C1 and passes through the trailing edge 45 of the wing 4 is defined as a second tangent TL2. Among a plurality of angles defined between the first tangent TL1 and the second tangent TL2, an angle that is in front (ie,The angle of the positive pressure surface side that lies on the first tangent TL1 (on a forward side) and is located on an outboard side of the first virtual circle C1 relative to the second tangent TL2 is defined as the positive pressure surface side outlet angle. In the following description, the positive pressure surface side outlet angle is also referred to simply as the outlet angle.

[0024] In Fig. 5, the outlet angle, measured at the adjacent point of the trailing edge 45 next to the cover 2, is given as θ1. In Fig. 6, the outlet angle, measured at the axial center point 453 of the trailing edge 45, is given as θ2. In Fig. 7, the outlet angle measured at the adjacent position of the trailing edge 45 next to the main plate 3 is indicated by θ3. As described above, in the centrifugal fan 1 of the first embodiment, the outlet angle θ3 measured at the adjacent position of the trailing edge 45 next to the main plate 3 and the outlet angle θ1 measured at the adjacent position of the trailing edge 45 next to the cover 2 are smaller than the outlet angle θ2 measured at the position of the axial portion 453 of the trailing edge 45. The position of the axial center 453 of the trailing edge 45 can be referred to as a position at which the outlet angle is largest among the plurality of positions arranged axially along the trailing edge 45. In addition, as shown in FIG. Fig. 4, the trailing edge 45 is configured such that, when considering a change in the outlet angle at each of the multiple locations arranged axially along the trailing edge 45, the trailing edge 45 has at least one inflection point POI at which an increase or decrease in the outlet angle changes. In the first embodiment, the inflection point POI is located at the location of the axial section 453 at the center of the trailing edge 45.

[0025] The centrifugal fan 1 of the first embodiment is configured to have at least one inflection point POI at the trailing edge 45 of each blade 4. Furthermore, this centrifugal fan 1 is configured so that the outlet angle θ3 measured at the adjacent location of the trailing edge 45 adjacent to the main plate 3 and the outlet angle θ1 measured at the adjacent location of the trailing edge 45 adjacent to the cover 2 are both smaller than the outlet angle θ2 measured at the location of the axial portion 453 of the trailing edge 45. The significance of the above configuration of the centrifugal fan 1 of the present embodiment will be described below.

[0026] The Fig. 8 and Fig. 9 show a centrifugal fan of a comparative example (hypothetical example) different from the first embodiment.

[0027] As from Fig. As can be seen from Fig. 9, each of the blades 4 of the centrifugal fan of the comparative example is shaped such that the trailing edge 45 of the blade 4 is generally parallel to the rotation axis CL from the portion 451 of the trailing edge 45 connected to the cover 2 to the portion 452 of the trailing edge 45 connected to the main plate 3. Therefore, the outlet angle of the trailing edge 45 of the blade 4 is constant from the cover 2 side to the main plate 3 side.

[0028] In the Fig. 8 and Fig. 9, the magnitude of the airflow velocity of the airflow flowing at the flow passage 43 between the vanes and the magnitude of the airflow velocity of the airflow exiting from the vane outlet 44 are indicated by the length of the corresponding arrows.

[0029] In the centrifugal fan of the comparative example, as shown by the arrows FL1, FL2, FL3 in the Fig. 8 and Fig. 9, the air flow axially sucked into the air intake port 21 of the shroud 2 changes its direction along the main plate 3 and then flows from the leading edge 46 of the vane 4 into the space between the vanes 43. In addition, the air flow in the space between the vanes 43 is separated by the shroud 2, thereby directing a main air flow toward the side of the main plate 3. Due to the factors described above, the air flow velocity in the space between the vanes 43 in an axial center region and a region on the main plate 3 side of the axial center region is higher than the air flow velocity in the region adjacent to the shroud.However, as indicated by the arrow FL3, the air flow velocity in the area adjacent to the main plate 3 is reduced due to the influence of a boundary layer generated, for example, by friction between the air flow and the main plate 3.

[0030] Therefore, in the centrifugal fan of the comparative example, as indicated by arrows FL4 to FL8 and a dot-dash line, variations occur in the airflow velocity distribution of the airflow discharged from the outlet of the blades 44. This may potentially increase noise and deteriorate the pressure boosting characteristics.

[0031] In contrast, the Fig. 10 and Fig. 11 shows the centrifugal fan 1 of the first embodiment. Fig. 10 and Fig. 11, a magnitude of the airflow velocity of the airflow flowing at the passage between the vanes 43 and a magnitude of the airflow velocity of the airflow discharged from the vane outlet 44 are also indicated by the length of each corresponding arrow.

[0032] The blades 4 of the centrifugal fan 1 of the first embodiment have the configuration described above. That is, the trailing edge 45 has at least one inflection point POI, and the outlet angle θ3 measured at the adjacent position of the trailing edge 45 adjacent to the main plate 3 and the outlet angle θ1 measured at the adjacent position of the trailing edge 45 adjacent to the cover 2 are both smaller than the outlet angle θ2 measured at the position of the axial center portion 453 of the trailing edge 45. In other words, the outlet angle θ2 measured at the axial center point 453 of the trailing edge 45 is larger than the outlet angle θ3 measured at the adjacent position of the trailing edge 45 adjacent to the main plate 3 and the outlet angle θ1 measured at the adjacent position of the 45 adjacent to the cover 2.By increasing the outlet angle, the force applied by the blade 4 to the airflow flowing in the inter-blade flow passage 43 tends to be reduced, and thereby the amount of work applied by the blade 4 to the airflow is reduced to reduce the airflow velocity compared to the other regions. Therefore, in the first embodiment, as indicated by an arrow FL10 and a dot-dash line, by increasing the outlet angle θ2 measured at the location of the axial center portion 453 of the trailing edge 45, the airflow velocity in the axial center region of the inter-blade passage 43 can be slowed down compared to the other regions at the trailing edge 45. Thus, the centrifugal fan 1 of the first embodiment can provide a more uniform distribution of the airflow velocity of the airflow discharged from the blade outlet 44.

[0033] Furthermore, in the centrifugal fan 1 of the first embodiment, the outlet angle θ3 is small at the adjacent location of the trailing edge 45 next to the main plate 3, as described above. With this configuration, the force from the blade 4 is more likely to be applied to the airflow in the gap between the blades 43, thereby increasing the amount of work applied by the blade 4 to the airflow to increase the airflow velocity compared to the other locations. Therefore, in the first embodiment, as indicated by an arrow FL12, by reducing the outlet angle θ3 measured at the adjacent location of the trailing edge 45 next to the main plate 3, the airflow velocity, which is relatively low in the area next to the main plate 3 at the passage between the blades 43, can be accelerated compared to the other areas at the trailing edge 45.Thus, the centrifugal fan 1 of the first embodiment can provide a more uniform distribution of the airflow velocity of the airflow discharged from the blade outlet 44.

[0034] Next, with reference to the Fig. 12 to 14 a wing surface angle of the overpressure surface side of the wing 4 is described. Fig. 12 shows the cross section of the same section as in Fig. 5 (ie the section of the wing 4 next to the cover 2). Fig. 13 shows the cross section of the same section as in Fig. 6 (ie the axial center section of the wing 4). Fig. 14 shows the cross section of the same section as in Fig. 7 (ie the section of the wing 4 adjacent to the main plate 3).

[0035] As can be seen from the Fig. 12 to 14, in the following description, a tangent that is tangent to the positive pressure surface 47 of the predetermined wing 4 and passes through a predetermined position P1 (hereinafter referred to as the first predetermined position P1) between the leading edge 46 and the trailing edge 45 of the wing 4 is defined as a third tangent TL3. A virtual circle (hereinafter referred to as the second virtual circle C2) lies at the center of the rotation axis CL and passes through the first predetermined position P1, and a tangent that touches the second virtual circle C2 and passes through the first predetermined position P1 is defined as a fourth tangent TL4.Among a plurality of angles defined between the third tangent TL3 and the fourth tangent TL4, an angle that is forward of the third tangent TL3 in the direction of rotation and is located on an outboard side of the second virtual circle C2 relative to the fourth tangent TL4 is defined as a wing surface angle of the overpressure surface side.

[0036] In Fig. 12, the wing surface angle of the overpressure surface side, which is measured at the adjacent location of the wing 4 next to the cover 2 at the first predetermined position P1, is indicated by θ4. In Fig. 13, the wing surface angle of the overpressure surface side, which is measured at the position of the axial section of the wing 4 at the first predetermined position P1, is indicated by θ5. In Fig. 14, the positive pressure surface side wing face angle measured at the adjacent position of the wing 4 adjacent to the main plate 3 at the first predetermined position P1 is indicated by θ6. In the first embodiment, the positive pressure surface side wing face angle θ6 measured at the adjacent position of the wing 4 adjacent to the main plate 3 at the first predetermined position P1 is smaller than the positive pressure surface side wing face angle θ5 measured at the axial center position of the wing 4 at the first predetermined position P1. In addition, the positive pressure surface side wing face angle θ4 measured at the adjacent position of the wing 4 adjacent to the cover 2 at the first predetermined position P1 is smaller than the positive pressure surface side wing face angle θ5 measured at the axial center position of the wing 4 at the first predetermined position P1.The axial center of the wing 4 at the first predetermined position P1 may be referred to as a portion where the wing surface angle of the positive pressure surface side is the largest among the plurality of locations arranged axially along the wing 4 at the first predetermined position P1.

[0037] Now, an outlet angle of the negative pressure surface side on the wing 4 is determined with reference to the Fig. 15 to 17 described. Fig. 15 shows the cross section of the same section as in Fig. 5 (ie the section of the wing 4 next to the cover 2). Fig. 16 shows the cross section of the same section as in Fig. 6 (ie the axial center section of the wing 4). Fig. 17 shows the cross section of the same section as in Fig. 7 (ie the section of the wing 4 adjacent to the main plate 3).

[0038] As can be seen from the Fig. 15 to 17, in the following description, a tangent that is tangent to a negative pressure surface 48 of the predetermined wing 4 and passes through the trailing edge 45 of the wing 4 is defined as a fifth tangent TL5. Furthermore, a tangent that is tangent to the first virtual circle C1 and passes through the trailing edge 45 of the predetermined wing 4 is defined as a sixth tangent TL6. Among a plurality of angles defined between the fifth tangent TL5 and the sixth tangent TL6, an angle that is forward of the fifth tangent TL5 in the rotation direction and is located on the outboard side of the first virtual circle C1 relative to the sixth tangent TL6 is defined as a negative outlet angle of the negative pressure surface side.

[0039] In Fig. 15, the outlet angle of the vacuum surface side, measured at the adjacent point of the trailing edge 45 next to the cover 2, is given as θ7. In Fig. 16, the outlet angle of the vacuum surface side, measured at the location of the axial center 453 of the trailing edge 45, is given as θ8. In Fig. 17, the outlet angle of the negative pressure surface side, measured at the position of the trailing edge 45 adjacent to the main plate 3, is indicated by θ9. In the first embodiment, the outlet angle of the negative pressure surface side θ9 measured at the adjacent position of the trailing edge 45 adjacent to the main plate 3 is smaller than the outlet angle of the negative pressure surface side θ8 measured at the position of the axial center 453 of the trailing edge 45. Furthermore, the outlet angle of the negative pressure surface side θ7 measured at the adjacent position of the trailing edge 45 adjacent to the cover 2 is smaller than the outlet angle of the negative pressure surface side θ8 measured at the position of the axial center portion 453 of the trailing edge 45.The position of the axial center point 453 of the trailing edge 45 may be referred to as a position where the outlet angle of the negative pressure surface side is the largest among the plurality of positions arranged axially along the trailing edge 45.

[0040] Next, with reference to the Fig. 18 to 20 a wing surface angle of the negative pressure surface side of the wing 4 is described. Fig. 18 shows the cross section of the same section as in Fig. 5 (ie the section of the wing 4 next to the cover 2). Fig. 19 shows the cross section of the same section as in Fig. 6 (ie the axial center section of the wing 4). Fig. 20 shows the cross section of the same section as in Fig. 7 (ie the section of the wing 4 adjacent to the main plate 3).

[0041] As can be seen from the Fig. As can be seen from FIGS. 18 to 20, in the following description, a tangent line tangential to the negative pressure surface 48 of the predetermined wing 4 and passing through a predetermined position P2 (hereinafter referred to as the second predetermined position P2) between the leading edge 46 and the trailing edge 45 of the wing 4 is defined as the seventh tangent line TL7. A virtual circle (hereinafter referred to as the third virtual circle C3) is centered on the center point of the rotation axis CL and passes through the second predetermined position P2, and a tangent line tangential to the third virtual circle C3 and passing through the second predetermined position P2 is defined as the eighth tangent line TL8.Among a plurality of angles defined between the seventh tangent TL7 and the eighth tangent TL8, an angle that is forward of the seventh tangent TL7 in the direction of rotation and located on an outboard side of the third virtual circle C3 relative to the eighth tangent TL8 is defined as the wing surface angle of the low-pressure surface side.

[0042] In Fig. 18, the wing surface angle of the negative pressure surface side, which is measured at the adjacent location of the wing 4 next to the cover 2 at the second predetermined position P2, is indicated by θ10. In Fig. 19, the wing surface angle of the negative pressure surface side, which is measured at the location of the axial center of the wing 4 at the second predetermined position P2, is indicated by θ11. In Fig. 20, the blade surface angle of the negative pressure surface side measured at the adjacent position of the blade 4 adjacent to the main plate 3 at the second predetermined position P2 is indicated by θ12. In the first embodiment, the blade surface angle of the negative pressure surface side θ12 measured at the adjacent position of the blade 4 adjacent to the main plate 3 at the second predetermined position P2 is smaller than the blade surface angle of the negative pressure surface side θ11 measured at the position of the axial center point 453 of the blade 4 at the second predetermined position P2. In addition, the blade surface angle of the negative pressure surface side θ10 measured at the adjacent position of the blade 4 adjacent to the cover 2 at the second predetermined position P2 is smaller than the blade surface angle of the negative pressure surface side θ11 measured at the position of the axial center portion 453 of the blade 4 at the second predetermined position P2.The position of the axial center point 453 of the vane 4 at the second predetermined position P2 may be referred to as a position where the vane surface angle of the negative pressure surface side is the largest among the plurality of positions arranged axially along the vane 4 at the second predetermined position P2.

[0043] The blades 4 of the centrifugal fan 1 of the present embodiment are each shaped so that the outlet angle of the negative pressure surface side and the outlet angle of the positive pressure surface side are different from each other, and the blade surface angle of the negative pressure surface side and the blade surface angle of the positive pressure surface side are different from each other. With this configuration, it is possible to limit the separation of the airflow at the negative pressure surface 48 and also adjust the amount of work applied by the blade 4 to the airflow at the positive pressure surface 47, and thereby bring the airflow velocity distribution in the inter-blade duct 43 closer to uniformity.

[0044] The centrifugal fan 1 of the first embodiment described above implements the following actions and effects. (1) The centrifugal fan 1 of the first embodiment has at least one inflection point POI at the trailing edge 45 of the blade 4, where the increase or decrease of the outlet angle is changed. Furthermore, the outlet angle θ3 measured at the adjacent position of the trailing edge 45 adjacent to the main plate 3 and the outlet angle θ1 measured at the adjacent position of the trailing edge 45 adjacent to the cover 2 are both smaller than the outlet angle θ2 measured at the position of the trailing edge 45 where the outlet angle is largest.

[0045] Accordingly, the centrifugal fan 1 described above has a large effect in a case where the airflow velocity in the shroud 2 region and the airflow velocity in the main plate 3 region at the outlet of the blades 44 are both low, and the airflow velocity in the axial center of the outlet of the blades 44 is high in the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL. In this case, in the centrifugal fan 1 of the first embodiment, the outlet angle θ1 measured at the adjacent position of the trailing edge 45 adjacent to the shroud 2 and the outlet angle θ3 measured at the adjacent position of the trailing edge 45 adjacent to the main plate 3 are made small, thereby accelerating the airflow velocity in these regions compared to the other region(s) at the trailing edge 45.Furthermore, by increasing the outlet angle θ2 measured at the axial center portion 453 of the trailing edge 45, the airflow velocity in the axial center portion 453 region can be slowed down compared to the other regions on the trailing edge 45. Therefore, with the centrifugal fan 1 of the first embodiment, the velocity distribution of the airflow exiting the blade outlet 44 can be made closer to uniform, thereby making it possible to reduce noise and improve airflow efficiency.

[0046] (2) In the centrifugal fan 1 of the first embodiment, the blade face angle θ6 measured at the adjacent position of the blade 4 adjacent to the main plate 3 at the predetermined position P1 and the blade face angle θ4 measured at the adjacent position of the blade 4 adjacent to the cover 2 at the predetermined position P1 are smaller than the blade face angle θ5 measured at the corresponding position of the blade 4 at the predetermined position P1 where the blade face angle is the largest among the plurality of positions arranged axially along the blade 4 at the predetermined position P1.

[0047] According to this configuration, even for the air flow in the passage between the vanes 43, by changing the amount of work applied by the vane 4 to the air flow, the separation of the air flow from the vane surface can be limited, and the distribution of the air flow velocity can gradually become uniform starting from the upstream side of the vane outlet 44.

[0048] The configuration of the change in wing surface angle from the center of the wing 4 between the leading edge 46 and the trailing edge 45 and its actions and effects are the same in the second to eleventh embodiments described below.

[0049] (3) Each of the blades 4 of the centrifugal fan 1 of the first embodiment is shaped such that the outlet angle of the negative pressure surface side and the outlet angle of the positive pressure surface side are different from each other, and the blade surface angle of the negative pressure surface side and the blade surface angle of the positive pressure surface side are different from each other.

[0050] With this configuration, it is possible to limit the separation of the airflow at the negative pressure surface 48 and also adjust the amount of work applied by the vane 4 to the airflow at the positive pressure surface 47, and thereby bring the velocity distribution of the airflow discharged from the vane outlet 44 closer to uniformity. The above-described configuration and its actions and effects are the same in the second to eleventh embodiments described below. (Second embodiment)

[0051] Next, a second embodiment will be described. The second embodiment is a modification in which the shape of the trailing edge 45 of each blade 4 is changed from the first embodiment, while the rest of the second embodiment is the same as the first embodiment. Therefore, only the parts that differ from those of the first embodiment will be described in the following description.

[0052] As from Fig. As can be seen from Fig. 21, in the second embodiment, a portion of the trailing edge 45 of the vane 4, extending from the portion 451 connected to the cover 2 to the axial center portion 453, is generally parallel to the rotation axis CL. Furthermore, another portion of the trailing edge 45 of the vane 4, extending from the axial center 453 to the portion 452 connected to the main plate 3, is progressively displaced toward the front in the rotation direction. Therefore, in the second embodiment, the outlet angle measured at the portion (location) of the trailing edge 45 of the vane 4 extending from the portion 452 joined to the main plate 3 to the axial center portion 453 is smaller than the outlet angle measured at the portion (location) of the trailing edge 45 of the vane 4 extending from the portion 451 joined to the cover 2 to the axial center portion 453.The portion of the trailing edge 45 of the vane 4 extending from the portion 451 joined to the cover 2 to the axial center portion 453 may be referred to as a portion (location) where the outlet angle is largest among the plurality of locations arranged axially along the trailing edge 45.

[0053] Furthermore, the centrifugal fan 1 of the second embodiment is also configured such that, when considering a change in the outlet angle at each of the plurality of locations arranged axially along the trailing edge 45, the trailing edge 45 has at least one inflection point POI at which an increase or decrease in the outlet angle changes. In the second embodiment, the inflection point POI is located at the location of the axial center portion 453 of the trailing edge 45.

[0054] The centrifugal fan 1 of the second embodiment described above is configured to make the outlet angle large, measured at the portion (location) of the trailing edge 45 of the blade 4 extending from the portion 451 connected to the cover 2 to the axial center portion 453. Therefore, the centrifugal fan 1 can slow down the high speed of the airflow in the area extending from the cover 2 to the axial center in the space between the blades 43 compared to the other area(s) in the space between the blades 43. Furthermore, the centrifugal fan 1 is configured to make the outlet angle small, measured at the location of the trailing edge 45 adjacent to the main plate 3.Therefore, the centrifugal fan 1 can accelerate the low airflow velocity in the area adjacent to the main plate 3 in the space between the blades 43 compared to the other area(s) in the space between the blades 43. Therefore, with the centrifugal fan 1, the velocity distribution of the airflow exiting the outlet of the blades 44 can be made closer to uniform, making it possible to reduce noise and improve airflow efficiency. (Third embodiment)

[0055] Next, a third embodiment will be described. The third embodiment is a modification in which the shape of the trailing edge 45 of the wing 4 is changed from the first embodiment, while the rest of the third embodiment is the same as the first embodiment. Therefore, only the parts that differ from those of the first embodiment will be described in the following description.

[0056] As from Fig. As can be seen from Figure 22, in the third embodiment, the portion of the trailing edge 45 of the vane 4 extending from the portion 452 connected to the main plate 3 to the axial center portion 453 is generally parallel to the rotation axis CL. Furthermore, the portion of the trailing edge 45 of the vane 4 extending from the axial center 453 to the portion 451 connected to the cover 2 is progressively shifted toward the front in the rotation direction. Therefore, in the third embodiment, the outlet angle measured at the portion (location) of the trailing edge 45 of the vane 4 extending from the portion 451 joined to the cover 2 to the axial center portion 453 is smaller than the outlet angle measured at the portion (location) of the trailing edge 45 of the vane 4 extending from the portion 452 joined to the main plate 3 to the axial center portion 453.The portion (location) of the trailing edge 45 of the wing 4 extending from the portion 452 joined to the main plate 3 to the axial center portion 453 may be referred to as a portion (location) where the outlet angle is the largest among the portions (locations) arranged axially along the trailing edge 45.

[0057] Furthermore, the centrifugal fan 1 of the third embodiment is also configured such that, when considering a change in the outlet angle at each of the plurality of locations arranged axially along the trailing edge 45, the trailing edge 45 has at least one inflection point POI at which an increase or decrease in the outlet angle is changed. In the third embodiment, the inflection point POI is located at the location of the axial center 453 of the trailing edge 45.

[0058] The centrifugal fan 1 of the third embodiment described above is configured to make the outlet angle large, measured at the portion (location) of the trailing edge 45 of the blade 4 extending from the portion 452 joined to the main plate 3 to the axial center portion 453. Therefore, the centrifugal fan 1 can slow down the high speed of the airflow in the region extending from the main plate 3 to the axial center point in the space between the blades 43 compared to the other region(s) in the space between the blades 43. Furthermore, the centrifugal fan 1 of the third embodiment is configured to make the outlet angle small at the location of the portion 451 of the trailing edge 45 adjacent to the cover 2.Therefore, the centrifugal fan 1 can accelerate the low airflow velocity in the area adjacent to the cover 2 in the space between the blades 43 compared to the other areas in the space between the blades 43. Therefore, with the centrifugal fan 1 described above, the airflow velocity distribution of the airflow discharged from the blade outlet 44 can be made closer to uniform, thereby making it possible to reduce noise and improve airflow efficiency. (Fourth embodiment)

[0059] Next, a fourth embodiment will be described. The fourth embodiment is a modification in which the shape of the trailing edge 45 of the wing 4 is changed from the first embodiment, while the rest of the fourth embodiment is the same as the first embodiment. Therefore, only the parts that differ from those of the first embodiment will be described in the following description.

[0060] As from Fig. As can be seen from Figure 23, when considering a change in the outlet angle at each of a plurality of locations arranged axially along the trailing edge 45, the trailing edge 45 in the fourth embodiment has at least two inflection points POI at which an increase or decrease in the outlet angle is changed. Specifically, the trailing edge 45 in the fourth embodiment has four inflection points POI_1, POI_2, POI_3, POI_4. Each of the connecting portions of the trailing edge 45, each of which connects two corresponding adjacent ones of the four inflection points POI_1, POI_2, POI_3, POI_4, is straight.

[0061] The configuration of the fourth embodiment is effective in a case where a pressure drop element located on the upstream side of the centrifugal fan 1, or the shape or nature of each respective component of the centrifugal fan 1, causes fluctuations in the airflow velocity distribution in the respective outlet areas of the blades 44 in the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL. The pressure drop element refers to a member such as a casing of the blower in which the centrifugal fan 1 is installed or a filter mounted on the upstream side of the centrifugal fan 1, which causes a pressure drop in the airflow.In such a case, even in the fourth embodiment, the outlet angle measured at the position of the trailing edge 45 where the airflow velocity is low is made small, and the outlet angle measured at the position of the trailing edge 45 where the airflow velocity is high is made large. As described above, by decreasing the outlet angle, the amount of work applied by the vane 4 to the airflow can be increased, thereby increasing the airflow velocity compared to the other positions. In contrast, by increasing the outlet angle, the amount of work applied by the vane 4 to the airflow can be decreased, thereby decreasing the airflow velocity compared to the other positions.Therefore, even in a case where variations occur in the velocity distribution of the airflow exiting the vane outlet 44 in the regions of the vane outlet 44, in the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL, the velocity distribution of the airflow exiting the vane outlet 44 can be made closer to uniform. Therefore, with the centrifugal fan 1 of the fourth embodiment, it is possible to reduce noise and improve airflow efficiency. (Fifth embodiment)

[0062] Next, a fifth embodiment will be described. The fifth embodiment is a modification of the fourth embodiment.

[0063] As from Fig. As can be seen from Figure 24, even in the fifth embodiment, when considering a change in the outlet angle at each of a plurality of locations in an axial arrangement along the trailing edge 45, the trailing edge 45 has at least two inflection points POI at which an increase or decrease in the outlet angle is changed. Specifically, the trailing edge 45 in the fifth embodiment has three inflection points POI_1, POI_2, POI_3. Each of the connecting portions of the trailing edge 45, each of which connects two of the three corresponding adjacent inflection points POI_1, POI_2, POI_3, is curved.

[0064] Even with the configuration of the fifth embodiment, the flow velocity distribution of the airflow discharged from the vane outlet 44 can be made closer to uniform, even in the case where variations in the areas of the vane outlet 44 occur in the flow velocity distribution of the airflow discharged from the vane outlet 44 in the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL. Therefore, with the centrifugal fan 1 of the fifth embodiment, it is possible to reduce noise and improve airflow efficiency. (Sixth Embodiment)

[0065] Next, a sixth embodiment will be described. The sixth embodiment is a modification of the fourth or fifth embodiment.

[0066] As from Fig. As can be seen from Figure 25, even in the sixth embodiment, when considering a change in the outlet angle at each of a plurality of locations in an axial arrangement along the trailing edge 45, the trailing edge 45 has at least two inflection points POI at which an increase or decrease in the outlet angle is changed. Specifically, the trailing edge 45 in the sixth embodiment has four inflection points POI_1, POI_2, POI_3, POI_4. Each of the connecting portions of the trailing edge 45, each of which connects two corresponding adjacent ones of the four inflection points POI_1, POI_2, POI_3, POI_4, is curved.

[0067] Even with the configuration of the sixth embodiment, the flow velocity distribution of the airflow discharged from the vane outlet 44 can be made closer to uniform, even in the case where variations in the areas of the vane outlet 44 occur in the flow velocity distribution of the airflow discharged from the vane outlet 44 in the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL. Therefore, with the centrifugal fan 1 of the sixth embodiment, it is possible to reduce noise and improve airflow efficiency. (Seventh to eleventh embodiments)

[0068] Each of the seventh to eleventh embodiments is a modification in which the shape of the trailing edge 45 of the blade 4, as viewed in the rotational direction, is changed from the first embodiment, and the rest of each of the seventh to eleventh embodiments is the same as that of the first embodiment. Therefore, in the following description, only the parts different from those of the first embodiment will be described. Each of the configurations of the seventh to eleventh embodiments can be combined with any of the configurations of the first to sixth embodiments described above. (Seventh Embodiment)

[0069] As from the Fig. 26, in the seventh embodiment, a distance Db2 measured between the rotation axis CL and the portion 452 of the trailing edge 45 joined to the main plate 3 is longer than a distance Db1 measured between the rotation axis CL and the portion 451 of the trailing edge 45 joined to the cover 2. The trailing edge 45 is formed straight, so that the distance between the trailing edge 45 and the rotation axis CL is progressively reduced from the portion 452 joined to the main plate 3 to the portion 451 joined to the cover 2. The significance of the above configuration of the trailing edge 45 viewed in the rotation direction will be described below.

[0070] As indicated by the arrow FL21 in Fig. 26, the air flow in the space 43 between the vanes is detached from the cover 2 around the leading edge 46 and temporarily directed towards the main plate 3. However, as indicated by the arrow FL22, the air flow then flows such that the air flow in the middle of the space 43 between the vanes again rests against the cover 2. Therefore, the air flow at the outlet of the vane 44 can possibly be directed towards the cover 2, and thereby the air flow distribution can possibly be designed such that the air flow is directed in the axial direction.

[0071] In contrast, the centrifugal fan 1 of the seventh embodiment is configured to increase the amount of work applied to the airflow from the main plate side portion 3 of the blade 4, and thereby, as indicated by an arrow FL23, the airflow around the blade outlet 44 can be drawn again toward the main plate 3 at the inter-blade passage 43. Therefore, compared with the case of the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL, the velocity distribution of the airflow exiting the blade outlet 44 can be made closer to uniform, thereby making it possible to reduce noise and improve airflow efficiency.

[0072] The configuration of the centrifugal fan 1 of the seventh embodiment is more effective in a case where a relationship of 0.5 < Dsi / Dso < 0.7 is satisfied. Here, Dsi denotes an inner diameter of the cover 2, and Dso denotes an outer diameter of the cover 2. This is due to the following reasons.

[0073] In a hypothetical case where the Dsi / Dso ratio is equal to or less than 0.5, it is possible to ensure the sufficient length of the passage between the vanes 43 to guide the air flow after the air flow orientation toward the cover 2 occurs. In this case, even if the trailing edge 45 is parallel to the rotation axis CL when viewed in the direction of rotation, after the air flow orientation toward the cover 2 occurs, this air flow orientation is mitigated before reaching the trailing edge 45. In contrast, in another hypothetical case where the Dsi / Dso ratio is equal to or greater than 0.7, the air flow in the passage between the vanes 43 reaches the trailing edge 45 before a distortion of the air flow occurs, causing the air flow to re-adhere to the cover 2.In other words, the airflow indicated by arrows FL21, FL22 is cut off in the middle. Therefore, to make the configuration of the centrifugal fan 1 of the seventh embodiment more useful, it is desirable that the relationship 0.5 < Dsi / Dso < 0.7 be satisfied.

[0074] The centrifugal fan 1 of the seventh embodiment described above is configured such that the distance Db2 measured between the rotation axis CL and the portion 452 of the trailing edge 45 connected to the main plate 3 is longer than the distance Db1 measured between the rotation axis CL and the portion 451 of the trailing edge 45 connected to the cover 2.

[0075] In this configuration, the amount of work applied to the airflow from the main plate 3 portion of the wing 4 is increased, and thereby the airflow around the wing outlet 44 in the inter-wing duct 43 can be drawn toward the main plate 3 again. Therefore, compared with the case of the hypothetical structure in which the trailing edge 45 is formed parallel to the rotation axis CL, the velocity distribution of the airflow exiting the wing outlet 44 can be made closer to uniform, and thereby it is possible to reduce noise and improve airflow efficiency.

[0076] The centrifugal fan 1 of each of the eighth to eleventh embodiments described below is also configured such that the distance Db2 measured between the rotation axis CL and the portion 452 of the trailing edge 45 connected to the main plate 3 is longer than the distance Db1 measured between the rotation axis CL and the portion 451 of the trailing edge 45 connected to the cover 2. Therefore, the centrifugal fan 1 of each of the eighth to eleventh embodiments also has the same configuration as the seventh embodiment described above with reference to the above-described point, and thus can achieve the same actions and effects as the centrifugal fan 1 of the seventh embodiment. (Eighth Embodiment)

[0077] As from Fig. 27, in the eighth embodiment, the trailing edge 45 is formed in a step shape so that the distance between the trailing edge 45 and the rotation axis CL is gradually reduced from the portion 452 joined to the main plate 3 to the portion 451 joined to the cover 2. Specifically, the trailing edge 45 includes a first trailing edge portion 45a, a second trailing edge portion 45b, and a third trailing edge portion 45c. The first trailing edge portion 45a extends in the axial direction from the main plate 3 toward the cover 2. The second trailing edge portion 45b extends in the radial direction toward the rotation axis CL from an end of the first trailing edge portion 45a facing the cover 2.The third trailing edge portion 45c extends in the axial direction toward the cover 2 from one end of the second trailing edge portion 45b facing the rotation axis CL. Therefore, in the eighth embodiment, the trailing edge 45 is formed in a step shape, including two corners 45s, 45t, and three straight portions (i.e., the first to third trailing edge portions 45a to 45c).

[0078] The centrifugal fan 1 of the eighth embodiment described above can achieve the same actions and effects as the seventh embodiment. (Ninth Embodiment)

[0079] As from Fig. 28, the trailing edge 45 is also stepped in the ninth embodiment, so that the distance between the trailing edge 45 and the rotation axis CL is reduced from the portion 452 joined to the main plate 3 to the portion 451 joined to the cover 2. Specifically, the trailing edge 45 includes the first trailing edge portion 45a, the second trailing edge portion 45b, the third trailing edge portion 45c, a fourth trailing edge portion 45d, and a fifth trailing edge portion 45e. The first trailing edge portion 45a extends in the axial direction from the main plate 3 toward the cover 2. The second trailing edge portion 45b extends in the radial direction toward the rotation axis CL from one end of the first trailing edge portion 45a facing the cover 2.The third trailing edge portion 45c extends in the axial direction toward the cover 2 from one end of the second trailing edge portion 45b facing the rotation axis CL. The fourth trailing edge portion 45d extends in the radial direction toward the rotation axis CL from one end of the third trailing edge portion 45c facing the cover 2. The fifth trailing edge portion 45e extends in the axial direction toward the cover 2 from one end of the fourth trailing edge portion 45d facing the rotation axis CL. Therefore, in the ninth embodiment, the trailing edge 45 is formed in a step shape, having four corners 45s to 45v and five straight portions (i.e., the first to fifth trailing edge portions 45a to 45e).

[0080] The centrifugal fan 1 of the ninth embodiment described above can achieve the same actions and effects as the seventh and eighth embodiments. The number of corners and the number of straight sections of the stepped shape of the trailing edge 45 can be set to any number. (Tenth Embodiment)

[0081] As from Fig. As can be seen from Fig. 29, the trailing edge 45 in the tenth embodiment has an inclined portion 45f and a straight portion 45g. The inclined portion 45f is straight and extends from the portion 452 connected to the main plate 3 toward the axial center portion 453, so that the distance between the inclined portion 45f and the rotation axis CL is progressively reduced. The straight portion 45g extends parallel to the rotation axis CL from the axial center portion 453 to the portion 451 connected to the cover 2.

[0082] The centrifugal fan 1 of the tenth embodiment described above can also achieve the same actions and effects as the seventh to ninth embodiments. (Eleventh embodiment)

[0083] As from Fig. As can be seen from Fig. 30, in the eleventh embodiment, the trailing edge 45 is formed in a curved shape such that the distance between the trailing edge 45 and the rotation axis CL is progressively reduced from the portion 452 connected to the main plate 3 to the portion 451 connected to the cover 2. The shape of this curvature of the trailing edge 45 can be arbitrarily determined.

[0084] The centrifugal fan 1 of the eleventh embodiment as described above can also achieve the same actions and effects as the seventh to tenth embodiments. (Other embodiments)

[0085] In each of the embodiments described above, the centrifugal fan 1 is referred to as a turbofan. However, the present disclosure is not limited thereto. The centrifugal fan 1 may also be of another type, such as a radial fan.

[0086] In each of the above-described embodiments, although the configuration of the predetermined blade 4 among the plurality of blades 4 of the centrifugal fan 1 is described, the remaining two or more or all of the plurality of blades 4 of the centrifugal fan 1 may be formed in the same configuration as the configuration of the predetermined blade 4.

[0087] The present disclosure is not limited to the above embodiments, and the above embodiments may be appropriately modified. Furthermore, the above embodiments are not unrelated to each other and may be appropriately combined unless the combination is clearly impossible. Of course, in each of the above-described embodiments, the elements of the embodiment are not necessarily essential unless it is clearly stated that they are essential, and when they are clearly considered to be fundamentally essential.In each of the above-mentioned embodiments, when such a numerical value is mentioned, the present disclosure should not be limited to a numerical value such as the number, numerical value, amount, range, or the like of the constituent elements of the embodiment, unless it is clearly stated that it is essential and / or fundamentally required. In each of the above-mentioned embodiments, when the shape, position, or the like of the constituent elements of the embodiment is mentioned, the present disclosure should not be limited to the shape, position, or the like of the constituent elements of the embodiment, unless it is clearly stated that it is essential and / or fundamentally required. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022 - 065 872

[0001] JP 6981077B2

[0005]

Claims

[1] Centrifugal fan with: a cover (2) which is annular and has an air intake port (21) in a center of the cover; a main plate (3) opposite the cover and configured to be rotated together with the cover; and a plurality of vanes (4) arranged at predetermined intervals in a rotational direction between the cover and the main plate and joined to the cover and the main plate, wherein: a tangent that is tangent to a positive pressure surface (47) of a predetermined wing of the plurality of wings and passes through a trailing edge (45) of the predetermined wing is defined as a first tangent (TL1); a virtual circle (C1) is centered at the center of a rotation axis (CL) and passes through the trailing edge of the predetermined wing, and a tangent tangent to the virtual circle and passing through the trailing edge of the predetermined wing is defined as a second tangent (TL2); one of a plurality of angles defined between the first tangent and the second tangent, which lies in front of the first tangent in the direction of rotation and is located on an outer side of the virtual circle relative to the second tangent, is defined as the outlet angle; when considering a change in the outlet angle at each of a plurality of locations arranged axially along the trailing edge, the trailing edge has at least one point of inflection (POI) at which an increase or decrease in the outlet angle is changed; and at least one of the outlet angle (θ3) measured at a corresponding adjacent one of the plurality of locations adjacent to the main plate along the trailing edge and the outlet angle (θ1) measured at a corresponding adjacent one of the plurality of locations adjacent to the cover along the trailing edge is smaller than the outlet angle (θ2) measured at a corresponding one of the plurality of locations at which the outlet angle is greatest among the plurality of locations arranged axially along the trailing edge. [2] A centrifugal fan according to claim 1, wherein the at least one inflection point is at least two inflection points, wherein a connecting portion of the trailing edge connecting the at least two inflection points is curved or straight. [3] Centrifugal fan according to claim 1 or 2, wherein a tangent that is tangent to the overpressure surface of the predetermined wing and passes through a predetermined position (P1) between a leading edge (46) and the trailing edge of the predetermined wing is defined as a third tangent (TL3); a second virtual circle (C2) is centered at the center of the rotation axis and passes through the predetermined position, and a tangent tangent to the second virtual circle and passing through the predetermined position is defined as a fourth tangent (TL4); one of a plurality of angles defined between the third tangent and the fourth tangent, which lies in front of the third tangent in the direction of rotation and is located on an outside side of the second virtual circle relative to the fourth tangent, is defined as the wing surface angle; and among a plurality of locations arranged axially along the predetermined wing on the second virtual circle, at least one of the wing face angles (θ6) measured at a corresponding adjacent one of the plurality of locations adjacent to the main plate and the wing face angle (θ4) measured at a corresponding one of the plurality of locations adjacent to the cover is smaller than the wing face angle (θ5) measured at a corresponding one of the plurality of locations at which the wing face angle is the largest among the plurality of locations arranged axially along the predetermined wing on the second virtual circle. [4] Centrifugal fan according to claim 3, wherein: the outlet angle is referred to as the outlet angle of the overpressure surface side; the wing surface angle is called the wing surface angle of the overpressure surface side; a tangent touching a negative pressure surface (48) of the predetermined wing and passing through the trailing edge of the predetermined wing is defined as a fifth tangent (TL5); a tangent tangent to the virtual circle and passing through the trailing edge of the predetermined wing is defined as a sixth tangent (TL6); one angle among a plurality of angles defined between the fifth tangent and the sixth tangent, which is in front of the fifth tangent in the direction of rotation and is located on the outer side of the virtual circle relative to the sixth tangent, is defined as a negative outlet angle of the negative pressure surface side; a tangent that is tangent to the negative pressure surface of the predetermined wing and passes through a second predetermined position (P2) between the leading edge and the trailing edge of the predetermined wing is defined as a seventh tangent (TL7); a third virtual circle (C3) is at the center of the rotation axis and passes through the second predetermined position, and a tangent tangent to the third virtual circle and passing through the second predetermined position is defined as an eighth tangent (TL8); one angle among a plurality of angles defined between the seventh tangent and the eighth tangent, which lies in front of the seventh tangent in the direction of rotation and is located on an outboard side of the third virtual circle relative to the eighth tangent, is defined as a wing surface angle of the low-pressure surface side; and each of the plurality of vanes is shaped such that the outlet angle of the negative pressure surface side and the outlet angle of the positive pressure surface side are different from each other, and the vane surface angle of the negative pressure surface side and the vane surface angle of the positive pressure surface side are different from each other. [5] A centrifugal fan according to claim 1 or 2, wherein a distance (Db2) measured between the rotation axis and a portion (452) of the trailing edge joined to the main plate is longer than a distance (Db1) measured between the rotation axis and a portion (451) of the trailing edge joined to the cover. [6] A centrifugal fan according to claim 1 or 2, wherein the centrifugal fan is a turbo fan, and in each of the plurality of blades, the trailing edge of the blade is disposed behind a virtual plane including the rotation axis and a leading edge of the blade in the rotation direction.

Images