centrifugal blower

Abstract

To provide a centrifugal blower that maintains the strength of a casing even when an exhaust port is provided on the radial side of the casing, ensures handleability and reliability, and, even when being small and flat, secures airflow and static pressure while capable of achieving quiet operation.SOLUTION: Among annular airflow passages 4f formed around the radial outer side of a casing 4 by combining a first casing 4a and a second casing 4b, the radial side of the second casing 4b is provided with an exhaust port 4m separated by a diffuser 4n that is connected to an annular end portion 4r uprightly formed on a bottom plate 4q forming a second airflow passage 4e and positioned radially outward.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a centrifugal blower used, for example, in seat air conditioning or HVAC (Heating, Ventilation, and Air Conditioning) equipment. [Background technology]

[0002] For example, when a driver is in contact with the seat back or seating area for a long period of time, such as when driving a car for a long distance, the hot and humid air clings to the driver, causing discomfort. For this reason, seat air conditioning systems are used to harmonize the hot and humid air that tends to accumulate in the seat back and seating area.

[0003] There are two types of seat air conditioning systems: one that blows air out of the seat, and one that sucks air in through the seat and then expels it. Here, we will explain the intake type seat air conditioning system, which is expected to provide a more comfortable air conditioning effect. The intake type seat air conditioning system achieves an air conditioning effect by sucking in hot and humid air trapped in the backrest and seat area and removing it from those areas.

[0004] For example, a seat air conditioning system has been proposed that suppresses noise generated when air flows from the seat into the air intake of a blower. The upper and lower case sections are assembled by screwing together the four corners of the case, and an intake port is formed in the upper case section. A motor equipped with a stator and a rotor, and a centrifugal multi-blade fan are rotatably supported in the lower case section. The rotor is assembled integrally with the centrifugal multi-blade fan. When the motor rotates, the centrifugal multi-blade fan rotates, drawing air from the seat side through the intake port in the upper case section and blowing it out through outlets opening on all four sides of the case (Patent Document 1: JP 2015-174580 A). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-174580 Summary of the Invention [Problem to be solved by the invention]

[0006] In the configuration of Patent Document 1, the case is open on all four sides, resulting in extremely low rigidity. This may result in reduced durability against stress loads on the seat, ease of assembly, and reliability. Specifically, tension on cables such as signal lines and power supply lines connected to the motor board may cause them to break, reducing reliability. Furthermore, providing ribs or other components to increase the rigidity of the case would increase costs and require ingenuity in securing the lead wires, making handling more difficult. Furthermore, if it is not possible to secure an exhaust port on the axial bottom of the case where the centrifugal fan is installed, it is necessary to provide an exhaust port on the radial side as in Patent Document 1. In this case, for example, for vehicle use, it is required to maintain the strength of the case body, make it small and flat, ensure air volume and static pressure, and also achieve quiet operation. [Means for solving the problem]

[0007] The present invention has been made to solve these problems, and its purpose is to provide a centrifugal blower that maintains the strength of the case body even when an exhaust port is provided on the radial side of the case body, is easy to handle and reliable, and is small and flat, yet ensures air volume and static pressure and is quiet.

[0008] In order to achieve the above object, the present invention has the following configuration. a centrifugal fan and a motor that drives and rotates the fan housed within a case body, the case body taking in air from the axial center of the case body and discharging air from a radial side surface of the case body, the case body comprising: a first case that is assembled to cover the centrifugal fan, has an intake opening in the axial center and a ring-shaped first air passage formed radially outward; and a second case that has an annular second air passage formed on the outer circumferential side of a bottom plate that rotatably supports the motor, the second case being formed with a ring-shaped second air passage combined with the first air passage radially outward of the outer circumferential end of the centrifugal fan, the motor being housed overlapping in the axial direction in a dome-shaped space formed on the side opposite the intake opening by a hub of the centrifugal fan and a main plate connected to the hub, and the second case having an exhaust port partitioned off by a diffuser that is formed upright on the bottom plate that forms the second air passage and is connected to an annular end positioned radially outward.

[0009] According to the above configuration, the diffuser is formed upright on the bottom plate that forms the second air passage of the second case and is connected to the annular end portion arranged radially outward, and the exhaust port is provided on the radial side surface of the second case, separated by the diffuser. This improves the strength even when the exhaust port is provided on the radial side surface of the second case, increases the rigidity of the case body, and improves handleability and reliability. Furthermore, even if the exhaust flow path from the centrifugal fan to the exhaust port is short, it is possible to ensure air volume and increase static pressure. In addition, because the motor is housed overlapping in the axial direction in a dome-shaped space formed on the opposite side of the intake opening by the centrifugal fan hub and the main plate connected to it, the axial dimension of the centrifugal fan can be reduced, making it possible to make a centrifugal fan smaller and flatter even with the same size. Also, by increasing the outer diameter of the centrifugal fan and expanding the areas of the intake opening and exhaust hole, it is possible to make the fan smaller and flatter in the axial direction, thereby increasing the flow rate even at low rotation speeds, and because there is no partition wall called a tongue in the annular air passage formed around the radial outside of the case body, peak noise is not generated, making it possible to achieve quieter operation.

[0010] The diffuser includes a plurality of diffusion plates formed at predetermined intervals on the bottom plate, and the diffusion plates are arranged so that, when the inner surface of the second case is viewed from above, the height of the diffusion plates gradually increases from the radially inner side to the radially outer side of the bottom plate that forms the second air passage. Along the rotation direction of the centrifugal fan Preferably, the annular end portions are formed to stand up and are connected to the annular end portions, respectively. As a result, the plurality of diffusion plates formed upright on the disk-shaped bottom plate are arranged so that, when the inner surface of the second case is viewed from above, the height gradually increases from the inner diameter side outer periphery of the bottom plate that forms the second air passage toward the radially outer side. Along the direction of rotation of the centrifugal fan Because they are raised and connected to the annular ends, the strength of the second case is improved and the peak noise of the frequency component obtained by multiplying the number of blades in the impeller by the rotational frequency is dispersed, thereby making the noise quieter.

[0011] The inner wall surface between the radially inner wall and the radially outer wall formed upright along the concentric circle that forms the first air passage has a circumferential groove formed thereon such that the height gradually increases from the radially inner wall to the radially outer wall when the first case is viewed from above. Along the rotation direction of the centrifugal fan A series of protrusions may be formed at predetermined intervals. This allows the air drawn in through the intake opening of the first case by the rotation of the centrifugal fan to be diffused by the ribs in the first air passage and guided to the second air passage, thereby increasing the static pressure in the low flow rate range compared to when only the second diffuser is provided in the second case. [Effects of the Invention]

[0013] By using the centrifugal blower described above, it is possible to provide a centrifugal blower that maintains the strength of the case body even when an exhaust port is provided on the radial side of the case body, is easy to handle, and is highly reliable, and is small and flat, ensures air volume and static pressure, and is quiet. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a centrifugal blower. [Figure 2] FIG. 2 is a front view of the centrifugal blower. [Figure 3] FIG. 3 is a cross-sectional view of a centrifugal blower. [Figure 4] 4 is a perspective view of the centrifugal blower of FIG. 1 with the first case removed. [Figure 5] FIG. 5 is a front view of FIG. [Figure 6] FIG. 6 is a plan view of the inner surface side of the second case. [Figure 7] FIG. 7 is a perspective view of the second case. [Figure 8] 8 is a partially enlarged perspective view of the second case of FIG. 6. FIG. [Figure 9] FIG. 9 is a front view of the second case. [Figure 10] FIG. 10 is a plan view of the first case. [Figure 11] FIG. 11 is a front view of the first case. [Figure 12] FIG. 12 is a perspective view of the inner surface of the first case. [Figure 13] 13 is a partially enlarged perspective view of the first case of FIG. [Figure 14] FIG. 14 is a graph showing the air volume-static pressure characteristics depending on whether or not the first and second cases of the centrifugal blower have diffusers. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, one embodiment of a centrifugal fan according to the present invention will be described with reference to the accompanying drawings. First, the schematic configuration of the centrifugal fan will be described with reference to Figs. 1 to 14. A DC brushless motor is used as the motor M, and in this embodiment, an outer rotor motor is used. However, an inner rotor motor may also be used.

[0016] As shown in Figure 3, centrifugal blower 1 has centrifugal fan 2 and rotor 3 assembled together, and motor M that rotates and drives them is housed in case body 4. Air is taken in from the axial center of case body 4, and pressurized air is exhausted from the radial side. As shown in Figure 1, case body 4 is formed by combining first case 4a assembled to cover centrifugal fan 2 and second case 4b that rotatably supports motor M (rotor 3 and stator 5: see Figure 3).

[0017] In FIG. 3, an intake opening 4c is provided in the center of the first case 4a, and a ring-shaped first air passage 4d is formed radially outward. A ring-shaped second air passage 4e is formed radially outward of the second case 4b, and is combined with the first air passage 4d. The first case 4a and the second case 4b are combined to form a ring-shaped air passage 4f radially outward of the case body 4. A bearing holder 6 and a motor board 7 are attached to the center of the second case 4b. The motor board 7 is connected to the lead wires of the stator coil 5b and is equipped with a Hall sensor or the like that detects the position of the rotor magnet 3c. If the motor M is a sensorless type, the position detection sensor can be omitted. The stator core 5a is fixed integrally to the outer periphery of the bearing holder 6, and the rotor shaft 3a is rotatably supported in the shaft hole of the bearing holder 6 via a bearing 6a. Stator coils 5b are wound around the pole teeth formed on the stator core 5a, and the tips of the pole teeth are positioned opposite the rotor magnets 3c. One end of the rotor shaft 3a is integrally attached to the hub of the cup-shaped rotor yoke 3b by press-fitting, shrink-fitting, adhesive bonding, or a combination of these. The other end of the rotor shaft 3a is supported by a shaft support 6b provided within the bearing holder 6. The shaft support 6b is supported by a board support 7a that supports the motor board 7. The rotor magnets 3c are integrally attached to the inner circumferential surface of the rotor yoke 3b. Note that the center of the intake opening 4c does not need to be strictly aligned with the axis of the rotor shaft 3a of the motor M; it is sufficient that the position of the intake opening 4c is near the axial center of the case body 4, within a range where the centrifugal fan 2 can operate without reducing efficiency.

[0018] As shown in FIG. 4, the centrifugal fan 2 has a dome-shaped main plate 2b extending radially outward from the hub 2a. The main plate 2b, which is continuous with the hub 2a, extends radially outward, tilting toward the downstream side in the airflow direction. Multiple curved impellers 2c are formed on the main plate 2b, extending from the inner to the outer radial direction. Auxiliary impellers 2d are formed on the outer periphery of the impellers 2c, each standing upright, at equal intervals (at the center between the impellers 2c) from adjacent impellers 2c. This reduces pressure pulsation between each blade, thereby suppressing peak noise due to interference with the diffuser. Air drawn in through an intake opening 4c facing the hub 2a of the centrifugal fan 2 is pressurized and sent out by the impellers 2c and auxiliary impellers 2d formed on the main plate 2b toward the annular air passage 4f, which is located radially outward. An annular shroud 2e is connected to the outer peripheral edges of the impeller 2c and the auxiliary impeller 2d, and the air pressurized by the impeller 2c and the auxiliary impeller 2d is straightened and sent out toward the annular air flow passage 4f (see Figure 3) on the outer peripheral side.

[0019] 3, the hub 2a of the centrifugal fan 2 and the main plate 2b connected thereto form a dome-shaped space 4g on the side opposite the intake opening 4c. This dome-shaped space 4g can be used to house tall components (such as the electrolytic capacitor 7b) mounted on the motor M and the motor board 7, allowing the centrifugal fan 2 and motor M to be assembled compactly. The rotor 3 and stator 5 of the motor M are housed in the dome-shaped space 4g, overlapping in the axial direction. This reduces the axial dimension of the centrifugal fan 1, allowing for a centrifugal fan 1 of the same size to be made smaller and flatter.

[0020] As shown in Fig. 1, the first case 4a and the second case 4b are assembled together by overlapping them with their openings facing each other and engaging locking pieces 4h provided on the outer periphery of the side of the first case 4a with locking portions 4i provided on the outer periphery of the side of the second case 4b. Wiring connection ports 4j are formed in the first case 4a and the second case 4b, through which wiring connected to the motor board 7 is taken out of the case (see Fig. 2). The wiring connection ports 4j are formed by fitting a fitting plate 4j1 protruding from a side surface of the first case 4a into a fitting groove 4j2 protruding from the corresponding side surface of the second case 4b (see Figs. 1 and 2).

[0021] As shown in Fig. 10, a first air passage 4d is formed in the outer peripheral side surface portion of the first case 4a, which is continuous with the upper surface portion where the intake opening 4c is provided (see Fig. 11). As shown in Figs. 12 and 13, a radially inner wall 4d1 and a radially outer wall 4d2, which form the first air passage 4d, are concentrically formed and stand upright on the inner surface radially outward from the intake opening 4c. Within this first air passage 4d, Projection 4k may be formed. Specifically, as shown in FIG. 12, the inclined wall surface between the radially inner wall 4d1 and the radially outer wall 4d2 has an arc-shaped inclined wall that gradually increases in height from the radially inner wall 4d1 to the radially outer wall 4d2 when the first case 4a is viewed from above. each The protrusions 4k1 are formed at a predetermined interval. The height of each protrusion 4k1 is formed so that the radially outer end is higher than the radially outer wall 4d2 (see FIG. 13). Projection 4k does not necessarily have to be provided and may be omitted.

[0022] As shown in FIG. 2, a radial side surface of the second case 4b is provided with an annular end portion 4r which is formed upright on a bottom plate 4q forming the second air passage 4b ​​and is arranged radially outward. De An exhaust port 4m separated by a diffuser 4n is provided (see FIG. 9). The annular end 4r is the open end of the second case 4b, whose upper end is formed with a concave-convex portion 4r1 that engages with the first case 4a (see FIGS. 3 and 8).

[0023] As shown in Figures 6 and 7, De The diffuser 4n has a plurality of diffusion plates 4n1 formed at predetermined intervals on the bottom plate 4q of the second case 4b. In a plan view of the inner surface of the second case 4b, the diffusion plates 4n1 stand in an arc shape so that their height gradually increases from the radially inner side of the bottom plate 4q that forms the second air passage 4b ​​toward the annular end 4r on the radially outer side, and are each connected to the annular end 4r at predetermined intervals. As a result, the multiple diffusion plates 4n1 formed upright on the circular bottom plate 4q rise in an arc shape so that their height gradually increases from the radially inner side to the radially outer side of the bottom plate 4q that forms the second air passage 4e when the inner surface of the second case 4b is viewed in plan, and are each connected to the annular end portion 4r.This improves the strength of the second case 4b and also makes it possible to decentralize the locations where peak sounds of frequency components obtained by multiplying the number of blades of the impeller 2 by the rotational frequency, thereby reducing noise.

[0024] in particular, De 6 and 7, the diffuser 4n has a plurality of diffusion plates 4n1 each having a curved surface whose downstream end in the exhaust direction is shifted a predetermined amount in the rotation direction E of the centrifugal fan 2 so that the air is exhausted in accordance with the rotation of the centrifugal fan 2 in the direction of the arrow. As shown in Fig. 8, the exhaust holes 4m are formed between adjacent diffusion plates 4n1.

[0025] In addition, a first air passage 4d of the first case 4a is provided Projection Configure 4k each The protrusion 4k1 and the second air passage 4e of the second case 4b are provided De The diffuser 4n has a diffuser plate 4n1 that is formed in an arc shape along the rotation direction of the centrifugal fan 2. When the first case 4a and the second case 4b are combined, each The ridges 4k1 and the diffusion plates 4n1 may be formed in opposing positions, or may be alternately arranged in positions where they mesh with each other. As a result, as the centrifugal fan 2 rotates, air flows from the first air passage 4d eachThe compressed air guided along the ridge 4k1 to the second air passage 4e can be efficiently exhausted from the exhaust port 4m partitioned by the diffusion plate 4n1.

[0026] As shown in FIGS. 4 and 5, the second air passage 4e is closed by a bottom plate 4q, and is partitioned by a plurality of diffusion plates 4n1 formed upright on the bottom plate 4q, and air is exhausted from an exhaust port 4m provided on the radially outer side of the second case 4b. Therefore, even if the centrifugal fan 1 is small and flat, a required air volume can be ensured. De Compared to the case where the diffuser 4n is not provided, the static pressure can be increased even if the exhaust flow path from the centrifugal fan 2 to the exhaust port 4m is short.

[0027] Here, in the first case 4a Projection With or without 4k, in the second case 4b De The air volume vs. static pressure characteristics (PQ characteristics) for different combinations with and without the Diffuser 4n are shown in the graph in Figure 14. In the dashed line graph in Figure 14, ▲ indicates Projection 4k and De Airflow vs. static pressure characteristics (PQ characteristics) when diffuser 4n is not present. ● indicates the first case 4a. Projection The air volume-static pressure characteristics (PQ characteristics) are shown when only 4k is installed. Dashed line ● As shown in the graph Projection It can be seen that the air volume-static pressure characteristics (PQ characteristics) are improved when 4k is installed compared to when it is not installed.

[0028] In the solid line graph in Figure 14, the black circles indicate the second case 4b. De Air volume vs. static pressure characteristics (PQ characteristics) when only the diffuser 4n is installed. ■ is the first case 4a. Projection 4k is provided, and the second case 4b De The figure shows the air volume-static pressure characteristics (PQ characteristics) when a 4n diffuser is installed.

[0029] First, it can be seen that the solid line graph (white line ● and black line ■) has improved air volume-static pressure characteristics (PQ characteristics) compared to the dashed line graph (dashed line ▲, dashed line ●). Projection In the second case 4b, De It can be seen that when the Diffuser 4n is installed, the air volume-static pressure characteristics (PQ characteristics) are improved overall.

[0030] In addition, in the solid line graph (white line ● and black line ■), in the first case 4a Projection 4k is provided, and the second case 4b De It can be seen that when the Diffuser 4n is installed, the air volume-static pressure characteristics (PQ characteristics) in the low flow rate range are improved.

[0031] As described above, the bottom plate 4q forming the second air passage 4e De The diffuser 4n is formed upright and connected to the annular end portion 4r arranged radially outward, so that the diffuser 4n is attached to the radial side surface of the second case 4b. De Since the exhaust port 4m is provided separated by the diffuser 4n, even if the exhaust port 4m is provided on the radial side surface of the second case 4b, the strength is improved, the rigidity of the case body 4 is high, and the handleability and reliability are improved. Furthermore, even if the exhaust flow path from the centrifugal fan 2 to the exhaust port 4m is short, the air volume can be secured and the static pressure can be increased.

[0032] Furthermore, since the motor M is housed overlapping in the axial direction in the dome-shaped space 4g formed on the opposite side of the intake opening 4c by the hub 2a of the centrifugal fan 2 and the main plate 2b connected thereto, it is possible to reduce the axial dimension of the centrifugal fan 1 and make it smaller and flatter even for a centrifugal fan of the same size. Also, by increasing the outer diameter of the centrifugal fan 2 and expanding the areas of the intake opening 4c and the exhaust port 4m, it is possible to make the fan smaller and flatter in the axial direction, thereby increasing the flow rate even at low rotation speeds, and since there is no partition wall called a tongue in the annular air flow passage 4f formed around the radial outside of the case body 4, peak noise is not generated, resulting in quieter operation.

[0033] Here, the effect of the centrifugal blower 1 of the present invention in vehicle air conditioning will be described in detail. When the centrifugal blower 1 of the present invention is installed in a vehicle seat for the purpose of suction-type seat air conditioning, the noise generated during the operation of the centrifugal blower 1 of the present invention—"the centrifugal fan 2 rotates, drawing in air from the axial direction, generating an airflow toward the periphery within the case body 4, changing direction near the periphery within the case body 4, and exhausting the air radially outward at the periphery"—constitutes a large proportion of noise generated by the entire seat air conditioning system. Because the flow path from the intake port on the seat surface to the centrifugal blower 1 of the present invention is short and the exhaust port of the centrifugal blower 1 of the present invention has a sufficient flow path cross-sectional area for the exhaust flow rate, noise sources other than the blower are limited. This makes it possible to clearly distinguish noise other than that generated by the blower from noise generated by the centrifugal blower 1 of the present invention. Since the noise generating factors and characteristics of the centrifugal blower 1 of the present invention, such as output, are contained within the case body 4, the characteristics (output and noise) of the blower are constant. Furthermore, since the case body 4 has high rigidity as described above, there is greater freedom in the position and shape of the mounting location for the seat to which the centrifugal blower 1 of the present invention is attached, making it applicable to many types of seats and achieving cost reductions through mass production effects. In addition, by stabilizing the characteristics (output and noise), the accuracy of simulating the seat air conditioning characteristics for passenger comfort can be improved from the vehicle design stage, which has the secondary effect of reducing the design man-hours required by vehicle manufacturers. Furthermore, compared to the suction-type seat air conditioning disclosed in the aforementioned prior art document (Patent Document 1: JP 2015-174580 A), the centrifugal blower 1 of the present invention has the advantage of enabling the seat to be made smaller.

[0034] Unlike the present invention, the blower disclosed in Patent Document 1 exhausts air in the radial direction (outer periphery) of the rotating shaft. Therefore, as mentioned above, there are concerns about the blower's durability against mechanical stress, requiring a mechanically robust design, which increases its size and weight. In addition, since the exhaust air is processed at the rear end of the seat (the rear end in the case of the back, or the lower end in the case of the seat cushion), the blower must be equipped with connections to an in-seat duct or an outlet on the rear side of the seat, further increasing its size and weight. In contrast, the centrifugal blower 1 of the present invention can be made smaller than the centrifugal blower of Patent Document 1 due to the high rigidity of the case body 4 and the omission of accessories. Conventionally, vehicle seats have not had components such as air conditioners, and seats equipped with air blowers essentially have a foreign object inside the seat cushion. In order to prevent seated occupants from perceiving the blower as a foreign object, the blower must be made smaller or the seat cushion must be thicker. Considering the recent trend toward lighter and smaller vehicles, it is clear that the centrifugal blower 1 of the present invention has an effect in line with this trend.

[0035] Furthermore, while the above embodiment has been described using an in-vehicle seat air conditioner as an example, the present invention is not limited to this and may also be used in centrifugal blowers for HVAC (heating, ventilation, and air conditioning). For example, the centrifugal blower 1 of the present invention can also be used in vehicle HVAC systems other than seat air conditioners. Conventionally, air conditioning blowers (such as those with a scroll-type casing with a tongue) have been placed in surplus space in automobiles. However, due to the recent downsizing of automobiles and the expansion of passenger space, surplus space has been reduced, and electric vehicles have a different body structure from conventional automobiles, so considering the space in which to place air conditioning blowers has become a difficult issue for automobile designers. By adopting a blower with characteristics such as a thin profile, high pressure, and intake and exhaust directions opposite to each other, such as the centrifugal blower 1 of the present invention, automobile design flexibility can be improved. In conventional automobiles, HVAC-related devices are concentrated around the knees of the front seats due to the installation location of the blowers, but the centrifugal blower 1 of the present invention allows multiple blowers to be distributed and placed on the ceiling, side walls, doors, etc. By combining it with a thermoelectric element such as a Peltier element, space-saving distributed air conditioning can be realized, which can also be used to help design automobiles with high space utilization efficiency.It goes without saying that the present invention is equally effective in places other than vehicles where there is little excess space and it is difficult to secure space for installing a conventional air conditioning blower. [Explanation of symbols]

[0036] REFERENCE SIGNS LIST 1 Centrifugal blower 2 Centrifugal fan 2a Hub 2b Main plate 2c Impeller 2d Auxiliary impeller 2e Shroud 3 Rotor 3a Rotor shaft 3b Rotor yoke 3c Rotor magnet 4 Case body 4a First case 4b Second case 4c Intake opening 4d First air passage 4d1 Radially inner wall 4d2 Radially outer wall 4e Second air passage 4f Annular air passage 4g Dome-shaped space 4h Locking piece 4i Locking portion 4j Wiring connection port 4j1 Fitting plate 4j2 Fitting groove 4k Projection 4k1 each Protrusion 4m Exhaust port 4n DeDiffuser 4n1 Diffusion plate 4r Annular end 4r1 Concave and convex portion 4q Bottom plate 5 Stator 5a Stator core 5b Stator coil 6 Bearing holder 6a Bearing 6b Shaft support 7 Motor board 7a Board support 7b Electrolytic capacitor M Motor

Claims

1. A centrifugal blower in which a centrifugal fan and a motor for rotating the fan are housed in a case body, and air is taken in from a central part of the case body in the axial direction and exhausted from a side surface of the case body in the radial direction, the case body is assembled to cover the centrifugal fan, the first case having an intake opening at its axial center and a first annular air passage formed on its radially outer side; a second case having an annular second air passage formed on an outer circumferential side of a bottom plate that rotatably supports the motor, the second air passage being combined with the first air passage radially outward from an outer circumferential end of the centrifugal fan, the motor is housed in a dome-shaped space formed on the opposite side of the intake opening by a hub of the centrifugal fan and a main plate connected thereto, the motor overlapping the motor in the axial direction, A centrifugal blower characterized in that an exhaust port is provided on the radial side of the second case, separated by a diffuser that is formed upright on a bottom plate that forms the second air passage and connects to an annular end portion arranged radially outward.

2. 2. The centrifugal blower according to claim 1, wherein the diffuser comprises a plurality of diffusion plates formed at predetermined intervals on the bottom plate, the diffusion plates being formed to rise along the rotation direction of the centrifugal fan so that their heights gradually increase from the radially inner side to the radially outer side of the bottom plate that forms the second air passage when the inner surface of the second case is viewed from above, and the diffusion plates are each connected to the annular end portion.

3. 3. The centrifugal blower according to claim 1, wherein an inner wall surface between a radially inner wall and a radially outer wall formed upright along a concentric circle that forms the first air passage has ridges formed at predetermined intervals along the rotation direction of the centrifugal fan so that their height gradually increases from the radially inner wall toward the radially outer wall when the first case is viewed in plan.

Images