Centrifugal fan

Abstract

Provided is a centrifugal fan with which an improvement in the cooling performance of a motor can be achieved.　In this centrifugal fan 1, a first gap part S1, which is obtained by separating a portion of a motor support wall 93 from a motor wall 31 in the axial direction of a drive shaft 35 over a range from an outer peripheral edge 31E of the motor wall 31 to a boss part 33, is formed between the motor support wall 93 and the motor wall 31. A second gap part S2, which is obtained by separating an inner peripheral edge 97E of an opening part 97 from the boss part 33 in the radial direction of the drive shaft 35, is formed between the opening part 97 and the boss part 33. A gap region E3 that communicates with the first gap part S1 and the second gap part S2 is formed between the motor support wall 93 and a main plate 51. A communication hole 50C that allows the gap region E3 to communicate with the inside of an impeller 50 is provided to pass through the main plate 51 on the radial inside of each blade 53.

Description

centrifugal fan

[0001] The present invention relates to a centrifugal fan.

[0002] An example of a conventional centrifugal fan is disclosed in Patent Document 1. This centrifugal fan includes a casing, a motor, and an impeller.

[0003] The casing defines a snail-shaped accommodation space and has a motor support wall. An opening is formed through the motor support wall. The motor is disposed on the opposite side of the accommodation space from the motor support wall and has a motor wall, a boss portion, and a drive shaft. The motor wall is supported by the motor support wall. The boss portion is formed in the center of the motor wall and protrudes toward the accommodation space and enters the opening. The drive shaft protrudes from the boss portion and is located within the accommodation space. The impeller is disposed within the accommodation space and has a main plate and multiple blades. The main plate is fixed to the drive shaft so as to be rotatable together with the main plate. The multiple blades are arranged along the outer periphery of the main plate.

[0004] A first gap is formed between the motor support wall and the motor wall. The first gap extends from the outer peripheral edge of the motor wall to the boss portion, with a portion of the motor support wall spaced apart from the motor wall in the axial direction of the drive shaft. A second gap is formed between the opening and the boss portion. The second gap is formed by spacing the inner peripheral edge of the opening away from the boss portion in the radial direction of the drive shaft. A gap region communicating with the first gap and the second gap is formed between the motor support wall and the main plate.

[0005] In a conventional centrifugal fan having the above-described configuration, the pressure in the gap between the rotating impeller main plate and the stationary motor support wall decreases due to the airflow in the gap, and the air around the motor tends to flow into the gap via the first and second gaps. In this case, the flowing air removes heat from the motor wall and boss, thereby cooling the motor.

[0006] Japanese Patent Application Laid-Open No. 2020-90913

[0007] However, there is a demand for improved motor cooling performance in the conventional centrifugal fans.

[0008] The present invention has been made in view of the above-mentioned conventional circumstances, and an object to be achieved is to provide a centrifugal fan that can improve the cooling performance of a motor.

[0009] a motor disposed on the opposite side of the motor support wall from the accommodation space, the motor having a motor wall supported by the motor support wall, a boss formed in the center of the motor wall and projecting toward the accommodation space to enter the opening, and a drive shaft projecting from the boss and positioned within the accommodation space; and an impeller disposed within the accommodation space, the impeller having a main plate fixed to be rotatable integrally with the drive shaft and a plurality of blades arranged along the outer circumferential edge of the main plate, wherein a first gap is formed between the motor support wall and the motor wall, extending from the outer circumferential edge of the motor wall to the boss, and wherein a part of the motor support wall is spaced apart from the motor wall in the axial direction of the drive shaft; and a second gap is formed between the opening and the boss, the inner circumferential edge of the opening being spaced apart from the boss in the radial direction of the drive shaft. A gap region communicating with the first gap portion and the second gap portion is formed between the motor support wall and the main plate, and a communication hole communicating the gap region with the inside of the impeller is provided radially inward of each of the blades in the main plate.

[0010] As a result of extensive research into the above-mentioned conventional centrifugal fans, the inventors realized that when air around the motor flows into the gap region via the first gap and the second gap, the narrowness of the gap region tends to increase the passage resistance in the gap region downstream of the second gap, and that it is important to reduce this passage resistance.The inventors then avoided widening the gap region because it would increase the size of the fan, and after considering other means, they came up with the present invention.

[0011] In the centrifugal fan of the present invention, communication holes formed in the main plate radially inward of the blades communicate the gap region with the interior of the impeller. As a result, when air around the motor flows into the gap region via the first and second gaps, some of the flowing air passes through the communication holes and flows into the interior of the impeller, reducing the passage resistance of the gap region. As a result, the air around the motor is less likely to stagnate in the first and second gaps and flows smoothly into the gap region, allowing the flowing air to reliably remove heat from the motor wall and boss.

[0012] Therefore, the centrifugal fan of the present invention can achieve improved motor cooling performance.

[0013] It is desirable that the plurality of communication holes be formed at equal angular intervals along an imaginary circle centered on the drive shaft.

[0014] In this case, the effect of reducing the passage resistance in the gap region due to each communication hole can be prevented from fluctuating or varying in the circumferential direction of the drive shaft, thereby further improving the cooling performance of the motor with this centrifugal fan.

[0015] It is desirable that a recessed portion recessed in a substantially truncated cone shape be formed radially inward of the communication hole in the main plate so as to be spaced apart in the axial direction from the boss portion and the opening portion.

[0016] In this case, the relief portion can reduce the curvature of the path that the air around the motor takes when it passes through the first and second gaps and flows into the clearance region, forming a generally U-shaped curve in cross section. As a result, the air around the motor is less likely to stagnate in the first and second gaps and flows more smoothly into the clearance region, allowing the flowing air to more reliably remove heat from the motor wall and boss. As a result, this centrifugal fan can further improve the cooling performance of the motor.

[0017] The casing preferably has an outlet located on the outer periphery of the snail-shaped housing space for discharging air from the housing space. The area of ​​the second gap as viewed in the axial direction is preferably 13% or more of the opening area of ​​the outlet. The inner diameter of the opening is preferably 2 / 3 or less of the outer diameter of the motor wall.

[0018] In a configuration in which a communication hole is provided in the main plate, if the area of ​​the second gap when viewed in the axial direction is small, the passage resistance of the second gap is likely to be large, resulting in air around the motor easily stagnating in the first and second gaps. In this regard, by making the area of ​​the second gap when viewed in the axial direction 13% or more of the opening area of ​​the outlet port, the passage resistance of the second gap can be reliably reduced. On the other hand, if the area of ​​the second gap when viewed in the axial direction is too large, it becomes difficult to ensure the radial length of the first gap, which tends to reduce the effectiveness of the air flowing through the first gap in removing heat from the motor wall. In this regard, by making the inner diameter of the opening 2 / 3 or less of the outer diameter of the motor wall, it becomes easy to ensure the radial length of the first gap, and this effect is less likely to be reduced. As a result, this centrifugal fan can further improve the cooling performance of the motor.

[0019] According to the centrifugal fan of the present invention, the cooling performance of the motor can be improved.

[0020] FIG. 1 is a schematic diagram of a water heater to which a centrifugal fan according to an embodiment of the present invention is applied. FIG. 2 is a front view of the centrifugal fan according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing the A-A cross section of FIG. 2. FIG. 4 is an exploded perspective view of the centrifugal fan according to an embodiment of the present invention. FIG. 5 is a partial side view of the centrifugal fan as viewed from the direction of arrow Z in FIG. 2. FIG. 6 is a rear view of the impeller as viewed from the opposing plate side. FIG. 7 is an enlarged cross-sectional view of a main portion of FIG. 3, showing a schematic diagram of the air flow passing through the first gap, the second gap, the gap region, and each communication hole. FIG. 8 is a graph showing the relationship between the area of ​​the second gap as viewed along the drive shaft and the decrease in motor temperature. FIG. 9 is a graph showing the relationship between the total area of ​​each communication hole and the decrease in motor temperature.

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0022] 1, a centrifugal fan 1 according to the embodiment is an example of a specific aspect of the centrifugal fan of the present invention, and is applied to a water heater 8. After describing the general configuration of the water heater 8, the specific configuration of the centrifugal fan 1 will be described.

[0023] <General configuration of water heater> The water heater 8 is a forced intake / exhaust type water heater. The water heater 8 includes a housing 80, a combustion chamber 82, and a double pipe 89. The combustion chamber 82 is housed inside the housing 80. An air supply space 81 is formed between the inner wall surface of the housing 80 and the combustion chamber 82.

[0024] The double pipe 89 has an air intake pipe 87 and an exhaust pipe 88 housed inside the air intake pipe 87. The lower end of the air intake pipe 87 is connected to the upper part of the housing 80 and communicates with the air intake space 81. The lower end of the exhaust pipe 88 passes through the upper part of the housing 80 and communicates with the combustion chamber 82. The double pipe 89 extends upward from the housing 80, then bends, passes through the wall W1, and protrudes outdoors.

[0025] The water heater 8 also includes a centrifugal fan 1. The specific configuration of the centrifugal fan 1 will be described in detail later, but the centrifugal fan 1 is connected to the bottom of the combustion chamber 82. The centrifugal fan 1 includes a casing 9, a motor 3, and an impeller 50.

[0026] The casing 9 defines an accommodation space 90 by a side wall 92, a motor support wall 93, etc. An intake port 9A is formed in the side wall 92, which connects the air supply space 81 to the accommodation space 90. An outlet port 9B is formed in the upper part of the casing 9, which discharges air from the accommodation space 90. The outlet port 9B connects the accommodation space 90 to the combustion chamber 82.

[0027] The motor 3 is disposed on the opposite side of the motor support wall 93 from the accommodation space 90. The impeller 50 is disposed within the accommodation space 90 and is connected to the drive shaft 35 of the motor 3.

[0028] Furthermore, the water heater 8 includes a burner 83 and a heat exchanger 84, each housed in the combustion chamber 82. A gas supply pipe (not shown) is connected to the burner 83. The heat exchanger 84 is disposed above the burner 83. A water supply pipe (not shown) that supplies water from outside the housing 80 and a hot water outlet pipe (not shown) that discharges hot water to outside the housing 80 are connected to the heat exchanger 84.

[0029] <Hot Water Supply Operation of Water Heater> In water heater 8 configured as described above, when hot water supply operation starts, motor 3 of centrifugal fan 1 is activated to rotate impeller 50. As a result, outdoor air is drawn into accommodation space 90 of centrifugal fan 1 via air supply pipe 87, air supply space 81, and intake port 9A, and is forcibly supplied to combustion chamber 82 via discharge port 9B.

[0030] The burner 83 generates combustion exhaust gas by mixing and igniting air supplied to the combustion chamber 82 with fuel gas supplied from a gas supply pipe (not shown). The heat exchanger 84 heats water supplied from a water supply pipe (not shown) by heat exchange with the combustion exhaust gas from the burner 83. The hot water thus heated to the desired temperature by the heat exchanger 84 is discharged outside the housing 80 via a hot water outlet pipe (not shown) and supplied to the hot water outlet destination.

[0031] The combustion exhaust gas used for heat exchange in the heat exchanger 84 is discharged outdoors via an exhaust pipe 88. At this time, heat exchange occurs between the air flowing through the air intake pipe 87 and the combustion exhaust gas flowing through the exhaust pipe 88. Therefore, the air flowing through the air intake pipe 87 is heated to a high temperature before being introduced into the air intake space 81.

[0032] <Specific Configuration of Centrifugal Fan> Next, the centrifugal fan 1 will be described in detail with reference to Figures 2 to 7. In the following description, the axis of the drive shaft 35 of the motor 3 is defined as the drive axis X35, and the shape and the like will be described based on the direction of the drive axis X35 and the radial direction of the drive axis X35. The direction of the drive axis X35 is an example of the "axial direction of the drive shaft" in the present invention. The radial direction of the drive axis X35 is an example of the "radial direction of the drive shaft" in the present invention.

[0033] 2 to 4, in the centrifugal fan 1, the casing 9 has a peripheral wall 91, a side wall 92, and a motor support wall 93, each of which is made of steel plate. The side wall 92 and the motor support wall 93 face each other at a predetermined distance in the direction of the drive axis X35, and the peripheral wall 91 is joined to the outer periphery of the side wall 92 and the outer periphery of the motor support wall 93, thereby defining a snail-shaped accommodation space 90, as shown in FIG.

[0034] As shown in Figures 3 and 4, the side wall 92 is formed by combining two metal plates. The suction port 9A is a circular hole that penetrates the side wall 92 and is centered on the drive axis X35. As shown in Figures 2 and 4, the discharge port 9B is located on the outer periphery of the snail-shaped housing space 90. The discharge port 9B is formed between a first discharge wall 91E and a second discharge wall 91F of the peripheral wall 91, a third discharge wall 92E of the side wall 92, and a fourth discharge wall 93E of the motor support wall 93. As shown in Figure 5, the discharge port 9B is a rectangular opening.

[0035] 3 and 4, the motor support wall 93 has a motor support wall main body 94 and a motor mounting plate 95. The motor support wall main body 94 includes an outer periphery to which the peripheral wall 91 of the motor support wall 93 is joined, and has an impeller insertion hole 94H formed in the center thereof.

[0036] The impeller insertion hole 94H is a large-diameter circular hole centered on the drive axis X35. The impeller insertion hole 94H is set to a size such that the motor support wall main body 94 does not interfere with the impeller 50 when the impeller 50 is disposed in the accommodation space 90.

[0037] The motor mounting plate 95 has a generally disk-like shape centered on the drive axis X35, and has an opening 97 formed in the center thereof. The opening 97 is a circular hole centered on the drive axis X35. The opening 97 is set to a size sufficient to ensure a sufficient gap between the opening 97 and the outer peripheral surface of the boss portion 33, which will be described later.

[0038] As shown in Figure 4, the motor mounting plate 95 has set screws 95F inserted into screw holes formed at multiple locations on its outer periphery, and as shown in Figures 2 and 3, the set screws 95F are screwed into the motor support wall main body 94, thereby assembling the motor mounting plate 95 to the motor support wall main body 94 and closing the impeller insertion hole 94H.

[0039] 4, three mounting portions 96 are formed on the motor mounting plate 95. The mounting portions 96 are arranged at equal angular intervals around the drive axis X35 between the outer periphery of the motor mounting plate 95 and the opening 97.

[0040] Each mounting portion 96 is a small bulge formed by drawing into a generally truncated cone shape so as to approach the motor 3 in the direction of the drive axis X35. A screw hole is formed in each mounting portion 96. The rest of the motor mounting plate 95, excluding each mounting portion 96, is a flat plate with no irregularities.

[0041] 3, the motor 3 has a motor housing 32, a motor wall 31, a boss portion 33, and a drive shaft 35. The motor housing 32 is made of steel plate and has a generally cylindrical shape with a bottom and is centered on the drive axis X35. A bearing 32T is attached to the bottom of the motor housing 32.

[0042] The motor wall 31 and the boss portion 33 are integrally formed by drawing, cutting, or the like, a steel plate. The motor wall 31 has a generally circular flat plate shape centered on the drive axis X35, and the boss portion 33 is formed in the center thereof. The boss portion 33 has a generally cylindrical shape centered on the drive axis X35. A bearing 33T is assembled inside the boss portion 33.

[0043] The opening edge of the motor housing 32 and the outer peripheral edge 31E of the motor wall 31 are joined together to form a motor chamber 3A surrounded by the motor housing 32, the motor wall 31, and the boss portion 33.

[0044] The drive shaft 35 is supported by the motor housing 32, the motor wall 31, and the boss portion 33 via bearings 32T and 33T, and is thereby rotatable around a drive axis X35.

[0045] A stator 3S is fixed to the inner peripheral surface of the motor housing 32. A rotor 3R is fixed to a portion of the drive shaft 35 located inside the motor chamber 3A so as to be rotatable together with the rotor 3R. The rotor 3R is disposed within the stator 3S. A control board 3C is fixed to the surface of the motor wall 31 facing the motor chamber 3A. The control board 3C includes a control IC, power transistors, resistors, etc. The motor 3 rotates the rotor 3R and drive shaft 35 about the drive axis X35 by supplying power to the stator 3S via the control board 3C.

[0046] 2 and 4 , three small pieces 31F are formed on the motor wall 31, protruding radially outward from the outer circumferential edge 31E of the motor wall 31 about the drive axis X35. Set screws 3F are inserted into threaded holes formed in the small pieces 31F and screwed into threaded holes formed in each mounting portion 96 of the motor mounting plate 95, thereby attaching the motor wall 31 to each mounting portion 96 and supporting it on the motor mounting plate 95 of the motor support wall 93.

[0047] 3 , with the motor wall 31 supported by the motor mounting plate 95, the boss portion 33 protrudes toward the accommodation space 90 and enters an opening 97 of the motor mounting plate 95. The tip surface of the boss portion 33 is substantially flush with the inner surface of the motor mounting plate 95 that faces the accommodation space 90. The drive shaft 35 protrudes from the boss portion 33 and is located within the accommodation space 90.

[0048] <First Gap and Second Gap> As shown in FIGS. 3 and 7 , a first gap S1 is formed between the motor mounting plate 95 of the motor support wall 93 and the motor wall 31 .

[0049] The first gap S1 extends from the outer peripheral edge 31E of the motor wall 31 to the outer peripheral surface of the boss portion 33, and is formed by a part of the motor support wall 93, i.e., the motor mounting plate 95, being spaced apart from the motor wall 31 in the direction of the drive axis X35.

[0050] A second gap S2 is formed between the opening 97 of the motor mounting plate 95 and the boss portion 33.

[0051] The second gap S2 is formed by spacing the entire inner peripheral edge 97E of the opening 97 of the motor mounting plate 95 from the outer peripheral surface of the boss portion 33 in the radial direction of the drive axis X35.

[0052] 3, 4, and 6, the impeller 50 has a main plate 51, an opposing plate 52, and a plurality of blades 53. In this embodiment, the main plate 51, the opposing plate 52, and the plurality of blades 53 are made of steel plates.

[0053] The main plate 51 has a generally disk-like shape centered on the drive axis X35, and has a shaft hole 51H formed through its center.

[0054] 3, the opposing plate 52 has a generally annular shape centered on the drive axis X35, and has a large-diameter hole 52H formed in the center thereof. The large-diameter hole 52H has a diameter larger than that of the suction port 9A in the side wall 92. The opposing plate 52 faces the main plate 51 in the direction of the drive axis X35.

[0055] 3 and 4 , the blades 53 are arranged side by side along the outer peripheral edge 51E of the main plate 51. The impeller 50 is configured such that one end of each blade 53 in the direction of the drive axis X35 is joined to the main plate 51 and the other end of each blade 53 in the direction of the drive axis X35 is joined to the opposing plate 52.

[0056] The impeller 50 is formed with a plurality of auxiliary blades 54. A portion of each auxiliary blade 54 penetrates the main plate 51 and protrudes toward the opposite side of the opposing plate 52. The cross-sectional shape of the auxiliary blade 54 is the same as that of the blade 53, except that the portion of the cross-sectional shape of the blade 53 located radially inward of the drive axis X35 is removed.

[0057] 3, with the impeller 50 disposed in the accommodation space 90, the drive shaft 35 is inserted into the shaft hole 51H of the main plate 51, and a nut 35F is screwed onto the tip of the drive shaft 35 with a washer or the like interposed therebetween, thereby fixing the main plate 51 to be rotatable integrally with the drive shaft 35. In this state, the main plate 51 faces the motor mounting plate 95 of the motor support wall 93, the opposing plate 52 faces the side wall 92, and each auxiliary blade 54 protrudes toward the motor mounting plate 95.

[0058] A gap region E3 is formed between the motor mounting plate 95 of the motor support wall 93 and the main plate 51. The gap region E3 communicates with the first gap portion S1 and the second gap portion S2.

[0059] 3, 4, and 6, a plurality of communication holes 50C are formed in the main plate 51 radially inward of the drive axis X35 relative to each blade 53. As shown in Fig. 6, the communication holes 50C are circular holes formed at equal angular intervals along an imaginary circle K1 centered on the drive shaft 35, and have the same inner diameter. As shown in Fig. 3, the communication holes 50C communicate between the gap region E3 and the interior of the impeller 50.

[0060] 3 and 4, a recess 51A is formed in the area surrounding the shaft hole 51H in the main plate 51. The recess 51A is formed radially inward of each of the communication holes 50C in the main plate 51 with respect to the drive axis X35. The recess 51A is recessed in a generally truncated cone shape so as to be spaced away from the boss portion 33 and the opening 97 in the direction of the drive axis X35. The portion of the main plate 51 excluding the recess 51A is flat and has no irregularities.

[0061] In the centrifugal fan 1 configured as described above, when the motor 3 is operated, the impeller 50 rotates in a rotational direction R1 shown in FIG. 4. Each blade 53 is inclined in the rotational direction R1 as it moves radially outward from the drive axis X35. In other words, the impeller 50 is a sirocco fan. Like each blade 53, each support blade 54 is also inclined in the rotational direction R1 as it moves radially outward from the drive axis X35.

[0062] The centrifugal fan 1 draws air into the housing space 90 through the intake port 9A by the rotation of the impeller 50. The drawn air rotates together with the blades 53 of the impeller 50 inside the impeller 50, and is subjected to centrifugal force, being drawn toward the peripheral wall 91 of the housing space 90 and compressed, before being discharged from the discharge port 9B.

[0063] As shown in FIG. 5, the opening area A1 (mm 2 ) is a vertical length L1 (mm) × a horizontal length L2 (mm). In this embodiment, as an example, the opening area A1 of the discharge port 9B is 2300 (mm 2)

[0064] As shown in Fig. 2, the outer diameter of the motor wall 31 is defined as DM1 (mm). As shown in Fig. 3, the outer diameter of the boss portion 33 is defined as DM2 (mm). The inner diameter of the opening 97 is defined as DH1 (mm).

[0065] In this embodiment, for example, the outer diameter DM1 of the motor wall 31 is approximately 100 mm, the outer diameter DM2 of the boss portion 33 is approximately 24 mm, and the inner diameter DH1 of the opening 97 is approximately 31 mm or more.

[0066] The inner diameter DH1 of the opening 97 is equal to or less than two-thirds the outer diameter DM1 of the motor wall 31. In this embodiment, for example, it is equal to or less than 66 mm. This makes it easier to ensure the radial length of the drive axis X35 in the first gap S1.

[0067] Opening area A3 of the opening 97 (mm 2 ) is π × (inner diameter DH 1 / 2 of opening 97) 2 is.

[0068] Cross-sectional area A4 of the boss portion 33 (mm 2 ) is π × (outer diameter DM2 / 2 of the boss portion 33) 2 is.

[0069] The area A2 (mm when viewed along the drive axis X35 direction) of the second gap S2 2 ) is the opening area A3 - the cross-sectional area A4.

[0070] In this embodiment, the area A2 of the second gap S2 when viewed along the drive axis X35 is 13% or more of the opening area A1 of the discharge port 9B. 2 ) or more and is 13.04% or more of the opening area A1. This makes it possible to reduce the passage resistance of the second gap S2 with high reliability.

[0071] As shown in FIG. 6, the inner diameter of each communication hole 50C is DH2 (mm). The total area of ​​each communication hole 50C is A5 (mm 2 ) is the number of communicating holes 50C × π × (inner diameter DH2 of communicating holes 50C / 2) 2 In this embodiment, as an example, the total area A5 of the communication holes 50C is 100 to 500 (mm 2) is within the range.

[0072] 3 , in the centrifugal fan 1 of the embodiment, when the motor 3 is operated to rotate the drive shaft 35 and the impeller 50, the pressure in the housing space 90 is higher in an outer region E2 located radially outward of the drive axis X35 than the blades 53 of the impeller 50, compared to an inner region E1 located radially inward of the drive axis X35 than the blades 53 of the impeller 50. The air with increased pressure in the outer region E2 is then discharged from the housing space 90 via the discharge port 9B.

[0073] 5, the pressure in the gap region E3 decreases due to the airflow generated in the gap region E3 between the stationary motor mounting plate 95 of the motor support wall 93 and the main plate 51 of the rotating impeller 50. The air around the motor 3 then flows into the gap region E3 via the first gap S1 and the second gap S2, merges with the air in the outer region E2 within the housing space 90, and is then discharged from the housing space 90. In this case, the air around the motor 3 comes into contact with the motor wall 31 while flowing through the first gap S1, and then comes into contact with the boss portion 33 while flowing through the second gap S2, thereby effectively removing heat from the motor 3.

[0074] Furthermore, a plurality of communication holes 50C formed through the main plate 51 radially inward of the drive axis X35 relative to each blade 53 communicate the gap region E3 with the interior of the impeller 50. As a result, when air around the motor 3 flows into the gap region E3 via the first gap S1 and the second gap S2, part of the flowing air passes through the communication holes 50C and flows into the interior of the impeller 50, thereby reducing the passage resistance of the gap region E3. As a result, the air around the motor 3 is less likely to stagnate in the first gap S1 and the second gap S2 and flows smoothly into the gap region E3, allowing the flowing air to reliably remove heat from the motor wall 31 and the boss portion 33.

[0075] Therefore, the centrifugal fan 1 of the embodiment can improve the cooling performance of the motor 3.

[0076] 6, the centrifugal fan 1 has a plurality of communication holes 50C formed at equal angular intervals along an imaginary circle K1 centered on the drive shaft 35. This configuration prevents the effect of each communication hole 50C in reducing the passage resistance in the clearance region E3 from fluctuating or varying circumferentially around the drive shaft 35. As a result, the centrifugal fan 1 can further improve the cooling performance of the motor 3.

[0077] Furthermore, as shown in FIG. 5 , the centrifugal fan 1 includes a recess 51A, which is recessed into a generally truncated cone shape and spaced away from the boss 33 and the opening 97 toward the drive axis X35, located radially inward of each communication hole 50C in the main plate 51. This configuration helps to smooth the U-shaped cross-sectional curve of the air flowing around the motor 3 as it passes through the first gap S1 and the second gap S2 and into the gap region E3. This reduces the likelihood of the air around the motor 3 stagnating in the first gap S1 and the second gap S2 and allows the air to flow more smoothly into the gap region E3, thereby more reliably removing heat from the motor wall 31 and the boss 33. As a result, the centrifugal fan 1 achieves improved cooling performance for the motor 3.

[0078] Furthermore, in this centrifugal fan 1, the area A2 of the second gap S2 when viewed along the drive axis X35 is 13% or more of the opening area A1 of the discharge port 9B. The inner diameter DH1 of the opening 97 is 2 / 3 or less of the outer diameter DM1 of the motor wall 31. In a configuration in which the main plate 51 is provided with a communication hole 50C, if the area A2 of the second gap S2 when viewed along the drive axis X35 is small, the passage resistance of the second gap S2 is likely to increase, and as a result, the air around the motor 3 is likely to stagnate in the first gap S1 and the second gap S2. In this regard, by having the area A2 of the second gap S2 when viewed along the drive axis X35 be 13% or more of the opening area A1 of the discharge port 9B, the passage resistance of the second gap S2 can be reliably reduced. On the other hand, if the area A2 of the second gap S2 when viewed along the drive axis X35 becomes too large, it becomes difficult to ensure the radial length of the first gap S1 about the drive axis X35, and the effect of the air flowing through the first gap S1 in absorbing heat from the motor wall 31 is likely to be reduced. In this regard, by setting the inner diameter DH1 of the opening 97 to be no more than two-thirds of the outer diameter DM1 of the motor wall 31, it becomes easier to ensure the radial length of the first gap S1 about the drive axis X35, and this effect is unlikely to be reduced. As a result, this centrifugal fan 1 can further improve the cooling performance of the motor 3.

[0079] Graphs illustrating the improvement in cooling performance due to the area A2 of the second gap S2 when viewed along the drive axis X35 being 13% or more of the opening area A1 of the discharge port 9B are shown in Figures 8 and 9.

[0080] In FIG. 8 , the five white circles represent the test results of evaluating the temperature drop (°C) of the motor 3 under specified operating conditions for five centrifugal fans 1 with different areas A2 of the second gap S2 when viewed along the drive axis X35.

[0081] Area A2 is 300 mm 2 The above range corresponds to the range in which the area A2 is 13% or more of the opening area A1 of the discharge port 9B. The line GL1 is an approximate line based on the test results shown by the five white circles. The line GL1 is the approximate line based on the test results in which the area A2 is 300 mm 2 In the above range, the value is a negative value indicating that the temperature of the motor 3 is likely to decrease.

[0082] In FIG. 9, the three white circles represent the area A2 of the second gap S2 when viewed along the drive axis X35 direction, which is 300 mm 2 Less than (approximately 120 mm 2 1 shows test results for evaluating the temperature drop (°C) of the motor 3 under specified operating conditions for three centrifugal fans 1 with a constant total area A5 of the communication holes 50C and different total areas A5 of the communication holes 50C. Line GL2 is an approximate line based on the test results indicated by the three white circles. Line GL2 takes a positive value, indicating that the temperature of the motor 3 increases more easily as the total area A5 of the communication holes 50C increases.

[0083] In FIG. 9, the four black circles represent the area A2 of the second gap S2 when viewed along the drive axis X35 direction, which is 300 mm 2 or more (approx. 400 mm 2 1 shows test results for evaluating the temperature drop (°C) of the motor 3 under specified operating conditions for four centrifugal fans 1 with a constant total area A5 of the communication holes 50C and different total areas A5 of the communication holes 50C. Line GL3 is an approximate line based on the test results indicated by the four black circles. Line GL3 takes a negative value, indicating that the temperature of the motor 3 decreases more easily as the total area A5 of the communication holes 50C increases.

[0084] From the test results shown in Figures 8 and 9, it is clear that it is preferable that the area A2 of the second gap S2 when viewed along the direction of the drive axis X35 be 13% or more of the opening area A1 of the discharge port 9B.

[0085] 5, the impeller 50 of the centrifugal fan 1 is formed with a plurality of auxiliary blades 54, each of which has a portion of each blade 53 penetrating the main plate 51 and protruding into the gap region E3. With this configuration, the auxiliary blades 54 rotate together with the drive shaft 35 and the impeller 50 and cooperate with the communication holes 50C to further promote the flow of air in the gap region E3. As a result, the air around the motor 3 flows more smoothly into the gap region E3 via the first gap S1 and the second gap S2, and the flowing air can more reliably remove heat from the motor wall 31 and the boss portion 33.

[0086] Although the present invention has been described above with reference to the examples, it goes without saying that the present invention is not limited to the above examples and can be modified and applied as appropriate within the scope of the invention.

[0087] In the embodiment, the tip surface of the boss portion 33 is substantially flush with the inner surface of the motor mounting plate 95 that faces the accommodation space 90, but the present invention is not limited to this configuration. For example, a configuration in which the boss portion 33 protrudes into the accommodation space 90 is also included in the present invention.

[0088] It is also possible to employ a configuration in which the first gap is formed by interposing a spacer between the motor support wall and the motor wall, or by providing a leg on the motor wall.

[0089] The present invention can be used, for example, in forced-air combustion devices, water heaters, heating heat source devices, and the like.

[0090] DESCRIPTION OF SYMBOLS 1...Centrifugal fan 90...Accommodation space 9...Casing 97...Opening 93...Motor support wall 31...Motor wall 33...Boss portion 35...Drive shaft 3...Motor 51...Main plate 51E...Outer edge of main plate 53...Blade 50...Impeller 31E...Outer edge of motor wall S1...First gap 97E...Inner edge of opening S2...Second gap E3...Gap area 50C...Communication hole K1...Imaginary circle 51A...Relief portion 9B...Discharge port A2...Area of ​​second gap when viewed along the axial direction A1...Opening area of ​​discharge port DH1...Inner diameter of opening DM1...Outer diameter of motor wall

Claims

1. A casing defining a snail-shaped storage space, the casing having a motor support wall with an opening formed therethrough; a motor arranged on the opposite side of the storage space from the motor support wall, the motor having a motor wall supported by the motor support wall, a boss formed in the center of the motor wall and protruding toward the storage space and entering the opening, and a drive shaft protruding from the boss and positioned within the storage space; and an impeller arranged within the storage space, the impeller having a main plate fixed to be rotatable integrally with the drive shaft and a plurality of blades lined up along the outer periphery of the main plate, wherein a first gap is formed between the motor support wall and the motor wall, spanning the range from the outer periphery of the motor wall to the boss, with a part of the motor support wall spaced apart from the motor wall in the axial direction of the drive shaft; and a second gap is formed between the opening and the boss, with the inner periphery of the opening spaced apart from the boss in the radial direction of the drive shaft. a gap region communicating with the first gap portion and the second gap portion is formed between the motor support wall and the main plate, and a communication hole is provided in the main plate radially inward of each of the blades, communicating the gap region with the inside of the impeller.

2. A centrifugal fan according to claim 1, wherein a plurality of said communication holes are formed at equal angular intervals along an imaginary circle centered on said drive shaft.

3. A centrifugal fan according to claim 1 or 2, wherein a recessed portion recessed in a substantially truncated cone shape is formed radially inward of the communication hole in the main plate so as to be spaced apart from the boss portion and the opening in the axial direction.

4. A centrifugal fan according to claim 1 or 2, wherein the casing is located on the outer periphery of the snail-shaped storage space and has an outlet port for discharging air from within the storage space, the area of ​​the second gap when viewed along the axial direction is 13% or more of the opening area of ​​the outlet port, and the inner diameter of the opening is 2 / 3 or less of the outer diameter of the motor wall.

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