JP2715839B2 - Centrifugal blower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower,
In particular, the present invention relates to a centrifugal blower effective for use in an air conditioner for a vehicle.

[0002]

2. Description of the Related Art Conventionally, a centrifugal blower used in an air conditioner for a vehicle has a centrifugal fan 20 having a number of blades 25 in a case 21 having a bell mouth 31 as shown in FIG. It is configured to be stored in. The centrifugal fan 20 has a structure in which a number of blades 25 are arranged between the bottom plate 24 and the holding ring 42.

According to this type of centrifugal blower, when the centrifugal fan 20 is driven by a motor, an air flow is generated in the direction indicated by an arrow in the drawing, and air taken in from an air inlet 36 passes between the blades 25. Out of the discharge port of the case 21.

[0004]

However, FIG.
As shown as a wind speed distribution curve in (B), the wind speed distribution at the outlet of the blade 25 of the above-described conventional centrifugal blower is such that the wind speed is large below the blade 25 and is high above the blade 25. Little air flows in the upper space 38 in the case 21 as a result.
0 was found to occur.

The vortex 50 is generated irrespective of the air volume of the centrifugal blower, and disturbs the discharge flow 49 from between the blades 25 to increase the noise of the centrifugal blower and reduce the fan efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a centrifugal blower capable of preventing a vortex generated in a space above a case, reducing noise and improving fan efficiency.

[0007]

In order to achieve the above object, the present invention provides a case having an air intake port in an axial direction,
A large number of circumferentially arranged
Blades, formed at the air intake side end of the multiple blades
Annular shroud, and the counteraction of the multiple blades
A centrifugal fan that has a bottom plate formed at an end of the air intake side , sucks air from the air intake and blows out radially outward, and the case has a second side having the air intake. 1 wall, made from the outer circumferential wall surface for connecting the outer peripheral end portion of the first and second walls facing each other, and the first wall and the second wall and the outer peripheral end portion of the Shura
Udo has a fan shaft between the air intake and the blade.
To the incoming air flow that changes direction from the fan diameter to the outside
The first wall surface is formed in a cross-sectional shape substantially along ,
Inclined to said second wall side as it goes radially outward direction, and
Further, the air intake of the case out of the first wall surface
The inner wall cross-sectional shape near the mouth is minute between the shroud
Through the gap, along the cross-sectional shape of the shroud
The centrifugal blower thus formed is employed.

[0008] As a preferred embodiment, there is provided a centrifugal blower in which the inclination angle θ1 of the first wall surface is in the range of 5 to 30 °.

[0009]

According to the centrifugal blower of the present invention having the above-described structure, the first wall having the air intake is inclined toward the second wall as it goes radially outward, so that the centrifugal fan can be used. The shape of the case conforms to the wind speed distribution of the air blown out in the radial direction, so that a space with a small wind speed distribution on the first wall surface side can be reduced. Therefore, the centrifugal fan
Smooths the flow of air blown outward in the radial direction
Thus, it is possible to prevent eddy currents from being generated. Also the case
The inner wall cross-sectional shape near the air intake of the
Along the shroud's cross-sectional shape through a small gap
By forming, from the outlet of the blade (centrifugal fan)
Reduces the amount of air flowing back to the inner diameter side through this gap
can do.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment A first embodiment in which the present invention is applied to a blower that takes in air of a vehicle air conditioner is shown in FIGS. FIGS. 1 and 3A are half sectional views showing a blower according to the present invention, and FIG. 2 is a schematic structural view of the present embodiment. As shown in FIG. The air taken in from the outside air intake 2 to be taken in or the inside air intake 3 to take in the air in the passenger compartment is taken into the case 21 from the air intake 36 of the blower 6, and guided to the evaporator 7 by the centrifugal fan 20. The outside air inlet 2 and the inside air inlet 3 are opened and closed by a rotatable inside / outside air switching damper 5. An air mix damper 8 is provided on the outlet side of the evaporator 7, and the first flow path 1 partitioned by the air mix damper 8 is provided.
The heater core 17 is attached to the second flow path 19 on one side of the second flow path 8 and the second flow path 19. Air mix damper 8
The air mix chamber 9 formed on the outlet side of the heater core 17 has an upper outlet 13 that blows out upward in the passenger compartment, and an upper outlet 12 that blows out toward the upper part of the vehicle occupant.
And a foot outlet 1 that blows out toward the feet of the vehicle occupants
It communicates with 0. On the inlet side of each of the outlets 10, 12, and 13, a damper 14, which adjusts the opening of each outlet,
15 and 16 are attached rotatably.

The specific structure of the blower 6 is shown in FIG.
Is shown in The blower 6 includes a centrifugal fan 20 and a case 2
It consists of 1. The case 21 is formed by integrally assembling a resin-formed upper case 22 and a lower case 23 with a clamp, a screw, or the like, and is formed in a well-known scroll shape (see FIG. 10). (See FIG. 2), and this air outlet 37 is connected to the air inlet side of the evaporator 7. In addition,
FIG. 10 is a perspective view corresponding to the third embodiment of the present invention shown in a half sectional view in FIG.

A fan driving motor 33 (see FIG. 2) is supported and fixed to the lower case 23 of the case 21. The fan 20 includes a bottom plate 24, a number of blades 25,
And a shroud 26 formed annularly on the top of the blade 25 and also serving as a reinforcing ring. The bottom plate 24 has a boss 28 to which the driving force from the motor 33 shown in FIG. 2 is transmitted. The top surface 241 of the bottom plate 24 is formed into a curved surface that smoothly curves from the center to the outer periphery. The blade 25 is attached to the bottom plate 2
4 are formed so as to rise from the vicinity of the outer peripheral end 242 of the bottom plate 24, and are arranged in the vicinity of the outer peripheral end 242 of the bottom plate 24 at predetermined arc intervals along the circumferential direction.
The shroud 26 is joined to the top of the blade 25, and a line connecting the inner peripheral end 261 of the shroud and the outer peripheral end 242 of the bottom plate coincides with the parting line 30. An annular projection 262 is formed above the inner peripheral end 261 of the shroud. A top surface 263 having a substantially arc-shaped cross section is formed radially outward from the shroud inner peripheral end 261.

A bell mouth 31 that forms the air intake 36 is formed in the upper case 22 above the case 21 that houses the fan 20.
Is formed in a semicircular cross section so as to surround the projection 262 of the shroud 26. There is a minute constant interval δ between the inner wall 311 of the bell mouth 31 and the projection 262, for example, about 3 mm. The case inner wall 221 near the base of the bell mouth 31 is formed at a substantially constant minute interval δ, for example, about 3 mm from the top surface 263 of the shroud 26. Such a substantially constant minute interval δ corresponds to the radially outer end 2 of the top surface 263 formed so as to be smoothly curved radially outward from the outer peripheral wall of the projection 262 of the shroud 26.
Up to 64 are formed.

As described above, the case inner wall 221 is formed along the shroud 26, and from the case inner wall 221,
A case upper surface 222 corresponding to a first wall surface of the present invention up to an upper end portion 224 of an upper wall portion 223 of an outer periphery of the upper case 22.
Are formed at an angle θ1 with respect to the horizontal plane.
That is, to case upper surface 222 toward the radially outward direction, are formed to be inclined at an angle θ1 in the case the lower surface 232 side corresponding to the second wall of the present invention. Here, the horizontal plane is a plane perpendicular to the axial direction in which the centrifugal fan 20 rotates by receiving the driving force of the motor 33.

The lower central portion 231 of the center of the lower case 23
(Corresponding to the plane portion of the present invention) is formed horizontally in the radial direction up to the radially outer end 264 of the shroud 26 and at the same position in the radial direction. The case lower surface 232 from the outer peripheral side of the lower central portion 231 to the lower end portion 234 of the lower wall portion 233 of the outer periphery of the lower case 23 (corresponding to the outer peripheral portion of the present invention).
Is formed at an angle θ2 with respect to the horizontal plane. That is, the case lower surface 232 is formed to be inclined at an angle θ2 in the same direction as the case upper surface 222 as going outward in the radial direction.

The upper wall portion 223 of the outer periphery of the upper case 22
And the lower wall portion 233 of the outer periphery of the lower case 23 form the outer peripheral wall surface of the present invention. Next, the operation of the first embodiment of the present invention will be described based on FIGS. 3A and 3B in comparison with a conventional example.

FIG. 3A simultaneously shows the wind speed distribution curve in the embodiment shown in FIG. FIG. 3 (B)
As shown in the figure, in the conventional example in which the blade 25 is fixed by the retaining ring 42 and the upper surface 211 of the case 21 is not inclined, from the result of the visualization experiment by the spark tracking method of the present inventor, the exit of the blade 25 It was found that the wind speed distribution was biased to the lower side of the blade 25, and almost no air flowed above the blade 25. As a result, FIG.
In the above conventional example, the vortex 50 is generated in the upper space 38 in the case 21 and at the same time, the upper backflow 5 between the blades 25 is formed.
It has been found that a backflow 52 that passes through the upper portion of the retaining ring 42 from between the blades 25 and flows in the direction of the suction flow 48 occurs.

On the other hand, in the first embodiment of the present invention shown in FIG. 3A, a shroud 26 formed in the flow direction of the air flowing into the centrifugal blower 6 is formed in the centrifugal fan 20. Since the gap between the shroud 26, the bell mouth 31 and the case inner wall 221 is narrow at a minute interval δ and is formed over a long distance, the blade 2
The amount of air flowing backward from the outlet 5 to the inner diameter side through this gap is reduced.

Due to the shape in the vicinity of the shroud 26, the wind speed distribution at the outlet of the blade 25 becomes substantially uniform from the upper part to the lower part of the outer end of the blade 25, and no backflow occurs between the blades 25 on the upper side.

The blowers according to the first embodiment of the present invention and the conventional example are blowers applied to a ventilation system of a vehicle air conditioner. Such a blower has a relatively large air volume as compared with a static pressure. . Therefore, in the conventional example, as shown in the wind speed distribution curve of FIG. 3B, since there is the upper space 38 where almost no air flows inside the case above the position of the blade 25, a vortex 50 is generated, This vortex 50 is the discharge flow 4
9, the noise of the centrifugal blower 6 is increased, and the fan efficiency is reduced.

On the other hand, in this embodiment, the blade 25
The upper part on the radially outer side where air hardly flows is formed to be narrow, and the case upper surface 222 is further inclined at an angle of θ1 with respect to the horizontal plane along the direction in which air is blown out from the blade 25. Formed inclined to the lower surface 232 side,
Since the flow of the discharge flow 49 is made smooth, no swirl occurs. Therefore, it is possible to effectively improve the fan efficiency and reduce the noise.

In the conventional example, it has been found that the downward wind flowing out of the blade 25 colliding with the lower surface 212 of the case is also one of the causes for increasing the turbulence of the air flow in the case 21. . In this embodiment, the lower surface 232 is also inclined at an angle of θ2 with respect to the horizontal plane in the same direction as the upper surface 222 of the case, so that the collision can be eliminated and a further noise reduction effect can be obtained.

Next, an example of a centrifugal blower according to another embodiment of the present invention will be described with reference to FIGS. The second embodiment shown in FIG. 6 is not the centrifugal fan with the shroud 26 shown in the first embodiment but an example of the centrifugal fan 20 in which the blade 25 is fixed by a conventionally known holding ring 42. In the second embodiment, the cross section of the bellmouth 31 is formed in a semicircular shape, and the case upper surface 222 is formed at an angle θ1 with respect to the horizontal plane from the bellmouth end 312. Similarly, the case lower surface 232 is formed at an angle .theta.2 with respect to the horizontal plane from the same position as the radially outer end of the blade 25.

The third embodiment shown in FIG. 7 will be described with reference to the perspective view shown in FIG. 10. This embodiment is an example in which the connection from the bell mouth 31 to the upper surface 222 of the case is smoothed in the second embodiment. . That is, the cross section of the bellmouth 31 is formed in an arc shape, and the bellmouth end 31 is formed.
2, the case upper surface 222 is connected smoothly. The case upper surface 222 is formed at an angle θ1 with respect to the horizontal plane, and the case lower surface 232 is inclined at an angle θ2 with respect to the horizontal plane from the same position as the radial end of the blade 25, as in the above-described embodiment. This is an example of forming.

As described above, the case 21 has a scroll shape as shown in FIG.
The air that has flowed in from the air inlet 36 on the upper surface in the drawing is blown out in the radial direction of the centrifugal fan 20 by the blade 25. The air blown out in the radial direction is blown out along the circumferential direction of the scroll-shaped case 21,
The air passes through the internal space 40 and is blown out from the air outlet 37 connected to the case 21.

The ventilation path of the case 21 (the space 4
The radius from the center of the centrifugal fan 20 to the outer peripheral wall 27 of the case 21 gradually increases in the circumferential direction in which air is blown by the blade 25 from the nose N, which is the starting point of 0), toward the air outlet 37. The shape is taken. this is,
This is because the flow rate of air from the nose N toward the air outlet 37 increases.

In the fourth embodiment shown in FIG. 8, a shroud 26 is formed on the centrifugal fan 20 as in the first embodiment.
The case 21 is also formed along the shroud 26 from the bell mouth 31 to the case inner wall 221. The case inner wall 221 is formed at a distance δ from the shroud 26 up to an outer peripheral end 226 in a radially outward direction. An outer wall 225 that keeps the above-mentioned interval δ with the shroud 26 is formed from a radially outer peripheral end 226 of the case inner wall 221 toward the case lower surface. Then, the radial outer end 26 of the shroud 26
An outer wall 225 is formed up to a lower end 227 of the outer wall having the same height as that of the case 4, and an upper surface 222 of the case is formed from the lower end 227 of the outer wall at an angle θ1 with respect to a horizontal plane. The case lower surface 232 is formed at an angle θ2 in the same direction as the case upper surface 222 from the same position as the radially outer end of the blade 25.

The fifth embodiment shown in FIG. 9 is an example in which the shape of the shroud is formed in a conical shape having a linear cross section in the fourth embodiment. The shroud 35 is formed in a conical slope as described above, and corresponds to the shape of the shroud 35,
The case inner wall 221 is formed to extend substantially in a straight line and obliquely with a small interval δ. An outer wall 225 that keeps the above-mentioned distance δ with the shroud 26 from the radially outer end 226 of the case inner wall 221 toward the case lower surface.
Are formed. An outer wall 225 is formed up to an outer wall lower end 227 having the same height as the radially outer end 264 of the shroud 26, and a case upper surface 222 is formed from the outer wall lower end 227 at an angle of θ1 with respect to a horizontal plane. The case lower surface 232 is formed at an angle θ2 in the same direction as the case upper surface 222 from the same position as the radially outer end of the blade 25.

Although the present invention described in the first to fifth embodiments is effective when applied to a centrifugal blower in general, it is relatively advantageous especially in a ventilation system of a vehicle air conditioner. The effect is remarkable when applied to a ventilation system having a large ventilation resistance.

In the above embodiment, the upper and lower surfaces of the case are simultaneously inclined to obtain the effect.
Even if only the upper surface of the case is tilted, eddy currents are less likely to be generated in the case, so that fan efficiency can be effectively improved and noise can be effectively reduced.

Next, experimental data will be shown. The experimental conditions are shown in FIG.
In the second embodiment shown in FIG.
m, fan width: 85 mm, scroll spread angle: 5.0
°, the blower motor voltage: 12 V (constant), and the inclination angles θ1 and θ2 of the upper and lower surfaces of the case were both 10 °. As a result, the relationship between the flow coefficient Φ, the specific noise Ks and the pressure coefficient ψ is shown in FIG.
Was as shown in FIG. Compared to the conventional example shown in FIG. 3B, in the second embodiment, the specific noise Ks was relatively low, and a noise reduction effect of 3 to 4 dB was obtained as a whole. Further, it can be seen that the pressure coefficient ψ is relatively large.

Then, an experiment was conducted on how the minimum specific noise Ks and the fan efficiency ηf are changed by changing the inclination angles of the upper and lower surfaces of the case. The conditions such as the fan diameter and the width were the same as the above experimental conditions. Where the lowest specific noise K
s is a value at which the specific noise when the flow coefficient is changed is minimized. The result is shown in FIG.

The minimum specific noise Ks of the conventional example shown in FIG.
Is about 20 dB from the experimental results shown in FIG. FIG.
(A), the minimum specific noise Ks when the case upper surface inclination angle θ1 is 20 ° and the case lower surface inclination angle θ2 is 0 ° is about 15.8 dB.
In the first embodiment shown in FIGS. 1 and 3, when only the upper surface of the case is inclined, there is a difference of about 4.2 dB.

Also in the second embodiment shown in FIG. 6, when the case upper surface inclination angle θ1 is 20 ° and the case lower surface inclination angle θ2 is 0 °, the minimum specific noise Ks is about 16.0 dB, which is about the same as the conventional example. There is a 4.0 dB difference.

On the other hand , in the second embodiment, the case upper surface inclination angle θ1 is 0 ° and the case lower surface inclination angle θ2 is 20 degrees.
The minimum specific noise Ks at the time of ° is about 17.4 dB. Compared with the above result in which only the case upper surface 222 is inclined by 20 °, the case where the case upper surface 222 is inclined has a reduction of about 1.4 dB. is there.

In each of these cases, the lowest specific noise Ks is further reduced by providing the case lower surface inclination angle θ2. The optimum value is when the case lower surface inclination angle θ2 is 5 to 20 ° in the first embodiment, and when the case lower surface inclination angle θ2 is 5 to 30 ° in the second embodiment.

FIG. 5B shows that the case lower surface inclination angle θ 2 is 2
The effect of the case top angle θ1 when fixed at 0 ° was examined. According to the experimental results, when the case upper surface inclination angle θ1 is 5 to 20 ° in the first embodiment, and when the case upper surface inclination angle θ1 is 5 to 40 ° in the second embodiment, an effect is exerted on the lowest specific noise Ks. .

Looking at the fan efficiency ηf, about 57% is obtained when the inclination angle between the upper surface and the lower surface of the case is 0 ° in the second embodiment. When the tilt angle θ1 of the upper surface of the case is 20 °, the efficiency can be obtained when the tilt angle θ2 of the lower surface of the case is approximately 0 to 30 °. When the tilt angle θ2 of the lower surface of the case is 20 °, the efficiency of the upper surface of the case can be improved. When the inclination angle .theta.1 is about 5 DEG to 30 DEG, an efficiency exceeding this can be obtained.

Considering both the minimum specific noise K S and the fan efficiency η f, the inclination angle θ 1 of the upper surface of the case is 5 to 5.
At 30 °, the inclination angle θ2 of the lower surface of the case is 5 to 40 °
It can be seen that the effect appears in

Next, the relationship between the blowing angle θf of the airflow flowing out of the fan 20 and the angles of the case upper surface 222 and the case lower surface 232 will be described with reference to FIG. As shown in FIG. 11A, in the case 21 used for the fan 20 in which the airflow flowing out of the fan 20 flows out at an angle θf with respect to a horizontal plane perpendicular to the axial direction of the fan 20, the case upper surface 222 and the case lower surface 232 an optimum angle θs is with respect to the horizontal plane (in the first to fifth embodiments described above, each of the inclination angle theta _1, corresponding to theta _2), 11
(B) shows the optimum tilt angle.

This optimum tilt angle is an angle at which the specific noise ks is the lowest in the experiment shown in FIG. 5, for example, in the first embodiment, as shown in FIG.
When the angle θ _{2 of 2} is 10 °, the optimum inclination angle is obtained. In addition,
Fan efficiency? F is substantially proportional to the minimum specific noise ks, it may determine the optimum inclination angle theta _s at the fan efficiency? F.

In this experiment, a fan 20 having a different blowing angle θf was formed by changing the diameter of the fan 20 and the height h of the blade 25, and an experiment was conducted using the fan 20 having a different blowing angle θf. But the optimum inclination angle θ of the case 21 with respect to the fans 20
_s is the fan 20 as shown by the hatched portion in FIG.
Θ _s = (θf
-5) The angle is in the range of ° to θf °.

It should be noted that the first to fifth data shown in FIGS.
In the embodiment, as shown in FIG. 10, the case 21 has a scroll shape. In this case 21, the case upper surface 2
22 are inclined at an angle θ1. This inclination angle θ
Reference numeral 1 denotes a shape which is substantially constant over the entire circumference from the nose N of the scroll case and spreads outwardly from the nose N toward the air outlet 37.

Further, in the present embodiment, an example has been described in which the case upper surface 222 is formed linearly with a constant inclination angle θ1, but the present invention is not limited to this, and the cross section may be inclined in a curved shape. .

Further, the starting point on the inner diameter side of the inclination provided in the upper case 22 and the lower case 23 is not limited as in the present embodiment, and may be configured to be inclined from the radially outer side.

[0046]

As described above, according to the centrifugal blower of the present invention, the first wall surface having the air intake is inclined toward the second wall surface toward the radially outward direction. The shape of the case conforming to the wind speed distribution of the air blown radially outward by the centrifugal fan can be reduced, and a space with a small wind speed distribution on the first wall surface side can be reduced. Accordingly
Of the air blown outward by the centrifugal fan.
Smoothing the flow and preventing eddy currents.
To improve fan efficiency while reducing noise.
it can. Also, the cross-sectional shape of the inner wall near the air intake of the case
Between the shroud and the shroud
By forming it along the cross-sectional shape, the blade (centrifugal
Back through the gap from the outlet of the
The amount of air to be blown (hereinafter, this backflowing air is referred to as backflow air
Call. ) Can be reduced. Therefore, air intake
Interference (friction) between the air sucked from the inlet and the backflow air
The fan can be reduced while reducing noise.
Efficiency can be improved. As mentioned above,
According to the present invention, the noise of the centrifugal blower is reliably reduced.
In addition, fan efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a centrifugal blower showing a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a first embodiment in which the centrifugal blower of the present invention is applied to an air conditioner for a vehicle.

FIG. 3A is a schematic configuration diagram illustrating a main part of a centrifugal blower according to a first embodiment of the present invention. (B) is a schematic block diagram showing a main part of a conventional centrifugal blower.

FIG. 4 is a characteristic diagram comparing a flow rate coefficient, a specific noise, and a pressure coefficient between the second embodiment of the present invention and a conventional example.

[Fig. 5] Angle θ1 of case upper surface and angle θ2 of case lower surface
FIG. 4 is a characteristic diagram showing an influence of the relationship with the fan efficiency and the lowest specific noise.

FIG. 6 is a half sectional view of a centrifugal blower showing a second embodiment of the present invention.

FIG. 7 is a half sectional view of a centrifugal blower showing a third embodiment of the present invention.

FIG. 8 is a half sectional view of a centrifugal blower showing a fourth embodiment of the present invention.

FIG. 9 is a half sectional view of a centrifugal blower showing a fifth embodiment of the present invention.

FIG. 10 is a perspective view of a centrifugal blower according to a third embodiment of the present invention shown in FIG.

FIG. 11 is a diagram illustrating a relationship between a case tilt angle and a fan blowing angle.

[Explanation of symbols]

 6 Centrifugal blower 20 Centrifugal fan 21 Case 222 Case upper surface (first wall surface) 224 Upper end (outer peripheral end) 232 Case lower surface (second wall) 234 Lower end (outer peripheral end) 223, 233 External wall 24 Bottom plate 25 blade 26 shroud 31 bellmouth

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Uemura 1-1-1, Showa-cho, Kariya-shi, Aichi, Japan Inside Denso Corporation (72) Inventor Sugi Hikari 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Nihon Denso Co., Ltd. (56) References Japanese Utility Model Sho 57-134399 (JP, U) JP 3-4747 (JP, Y2)

Claims (6)

(57) [Claims] 1. A case having an air inlet in an axial direction, and a plurality of circumferentially arranged air-conditioners housed in the case.
Blades, formed at the air intake side end of the multiple blades
Annular shroud, and the counteraction of the multiple blades
A centrifugal fan having a bottom plate formed at an end of the air intake side and sucking air from the air intake and blowing out in a radially outward direction, wherein the case has a side having the air intake. A first wall, a second wall facing the first wall, and an outer wall connecting an outer end of the first wall and an outer end of the second wall ; From the air intake to the blade
Inflow from the fan axis direction to the outside of the fan diameter
The first wall surface is formed to have a cross-sectional shape substantially along the air flow, and the first wall surface is inclined toward the second wall surface toward the radially outward direction, and further, the air of the case is included in the first wall surface. Taking
The cross-sectional shape of the inner wall near the inlet is slightly different from the shroud.
Along the cross-sectional shape of the shroud via a small gap
Centrifugal blower formed in . 2. An inclination angle θ1 of the first wall is 5 to 30.
The centrifugal blower according to claim 1, which is in the range of °. 3. The second wall surface includes an annular flat portion corresponding to the centrifugal fan, and an outer peripheral portion connecting the flat surface portion and the outer peripheral wall surface. The centrifugal blower according to claim 1 or 2, wherein the blower is inclined in the same direction as the first wall surface as going toward. 4. The inclination angle θ2 of the second wall is 5 to 40.
The centrifugal blower according to claim 3, which is in the range of °. Wherein said shroud, said in the incoming air flow <br/> along Migihitsuji, claims 1 to 4 Izure of centrifugal blower stated is formed in a substantially arc-shaped cross section. 6. The centrifugal blower according to claim 1, wherein the inclination angle θ1 of the first wall surface is an angle corresponding to a blowing angle of air blown outward by the centrifugal fan.