CN1056672C - Centrifugal blower - Google Patents

Abstract

A centrifugal blower, the longitudinal section of the casing along the axial direction of the centrifugal impeller is roughly oblong, its axial width gradually expands from the nose shape to the direction of rotation of the centrifugal impeller, and the maximum width part is between the discharge port , so the axial diffusivity of the shell can be expanded to compensate for the suppression of the radial diffusivity and ensure a substantial diffusivity. The present invention does not have the two-dimensional flow, ie, eddy current, etc. of the corners of the conventional casing. Large air volume and low noise can be achieved without increasing the volume. Even if thin ducts are used, the air volume will not be reduced and the noise will not be increased.

Description

centrifugal blower

The invention relates to a centrifugal blower with an improved casing.

As shown in FIG. 37, a conventional centrifugal fan of this type has a centrifugal impeller 1 and a housing 2 surrounding the impeller 1. By using a motor 3 to rotate the centrifugal impeller 1, the centrifugal impeller 1 rotates from the axial direction. After the air is sucked in, it is discharged in the circumferential direction. The housing 2 collects the discharged air and guides it to the discharge port 4, and sends it out after passing through the pipe interface part 5 and the pipe 6 in sequence.

When the above-mentioned centrifugal blower is used, for example, as a ventilating fan for ducts installed on the back of the ceiling, due to the limited space on the back of the ceiling, it is required to have a small volume, a large air supply volume, and low noise. However, it is very difficult to achieve such a large air volume and low noise in a small volume.

Also, when constructing in a narrow space behind the ceiling of a house, or to reduce costs, it is necessary to use thinner pipes. However, if thin pipes are used, the resulting pressure loss will increase, thereby reducing the air volume and increasing the noise.

In view of the above facts, the object of the present invention is to provide a centrifugal blower that can achieve high wind volume and low noise with a small overall volume, and even if thin ducts are used, the air volume will not decrease and the noise will increase.

In order to achieve the above object, the centrifugal blower of the present invention is characterized in that the casing is formed in such a structure that the longitudinal section along the axial direction of the centrifugal blower is approximately oblong, and the width in the axial direction extends from the nose portion to the centrifugal blower. The direction of rotation of the blower gradually expands, and its widest part is between the discharge port.

In this case, if the axial length of the centrifugal impeller is b, the outer diameter is d2, and the maximum axial width of the casing is Bmax, it can be determined as:

b/d2=0.45～0.70

b/Bmax＝0.55～0.75

In addition, it is preferable that the position where the maximum width portion in the axial direction of the casing is formed forms an angle of 200 to 310° from the nose portion to the rotation direction of the centrifugal blower.

Furthermore, the length formed by the smallest width portion in the axial direction of the casing is preferably within a range from the nose portion to the rotation direction of the centrifugal blower to the vicinity of the nose portion, especially at an angle of 45° or less from the nose portion. range.

The performance of centrifugal blowers is greatly influenced by the size of the housing. This effect is greater than that of the impeller outer diameter and axial length.

Centrifugal blowers generally form a vortex with a certain diffusion rate in the radial direction. The larger the diffusion rate, the greater the air volume and high static pressure can be obtained. However, if a ventilating fan for a duct using a centrifugal blower, for example, is mounted on the back of the ceiling, the radial diffusivity of the casing has to be suppressed to some extent due to limited space.

Regarding this point, as mentioned above, if the casing is formed by adopting the following structure, that is, the longitudinal section along the axial direction of the centrifugal impeller has an approximately oblong shape, and the width in the axial direction gradually expands from the nose portion to the rotational direction of the centrifugal blower. , and its widest part is between the discharge port, by increasing the axial diffusivity of the shell, the suppression of the radial diffusivity can be compensated to ensure the substantial diffusivity of the shell.

In addition, the substantially oblong casing along the longitudinal section of the axial direction of the centrifugal impeller can eliminate the two-dimensional flow, that is, the so-called vortex, which occurs at the corner of the conventional rectangular casing, thereby substantially expanding the wind flow. As a result, the centrifugal blower can achieve large air volume, low noise, and high static pressure.

Also, in this case, assume that the axial length of the centrifugal impeller is b, the outer diameter is d2, and the maximum axial width of the casing is Bmax, if it is set as:

b/d2=0.45～0.70

When b/Bmax=0.55～0.75, according to the actual test results, more ideal data can be obtained than other values.

In addition, if the maximum width in the axial direction of the casing is formed at an angle of 200° to 310° from the nose portion to the rotation direction of the centrifugal blower, more ideal data than other values can be obtained according to actual test results.

Moreover, if the length formed by the minimum width portion in the axial direction of the housing is within the range from the nose to the rotation direction of the centrifugal blower to the vicinity of the nose, the wind returning through the gap of the nose can be reduced, and achieve better results. Wherein, if the length formed by the smallest part of the housing is within the range of an angle of less than 45° from the nose, more ideal data can be obtained than other values according to actual test results.

The following is a brief description of the accompanying drawings.

Fig. 1 is a sectional development view along line I-I in Fig. 2 (showing the first embodiment of the present invention).

Fig. 2 is an overall longitudinal sectional view.

Fig. 3 is a cross-sectional view.

Fig. 4 is a front view.

Fig. 5 is a partial longitudinal sectional view of a casing portion of a conventional centrifugal blower.

Fig. 6 is a partial longitudinal sectional view of the casing of the centrifugal blower according to the present invention.

Fig. 7 is a partially enlarged sectional view of a centrifugal impeller.

Fig. 8 is an enlarged sectional view of a blade portion of a centrifugal impeller.

Fig. 9 is characteristic diagram 1.

Figure 10 is the second characteristic diagram.

Figure 11 is the third characteristic diagram.

Figure 12 is the fourth characteristic diagram.

Figure 13 is the fifth characteristic diagram.

Fig. 14 is characteristic diagram No. 6.

Fig. 15 is characteristic diagram No. 7.

Figure 16 is the eighth characteristic diagram.

Fig. 17 is characteristic diagram No. 9.

Fig. 18 is a view corresponding to Fig. 1 showing a second embodiment of the present invention.

Figure 19 is the tenth characteristic diagram.

Figure 20 is characteristic diagram 11.

Figure 21 is characteristic diagram 12.

Fig. 22 is a side view showing a third embodiment of the present invention.

Fig. 23 is a cross-sectional view showing a fourth embodiment of the present invention.

Fig. 24 is a sectional view along line II-II of Fig. 23 .

Fig. 25 is a sectional view along line III-III of Fig. 23 .

Fig. 26 is a sectional view taken along line IV-IV of Fig. 23 .

Fig. 27 is a sectional view taken along line V-V of Fig. 23 .

Fig. 28 is an enlarged vertical cross-sectional view showing a connection port body portion of a fifth embodiment of the present invention.

Fig. 29 is an enlarged perspective view of a windshield alone.

Fig. 30 is an enlarged longitudinal sectional view of the connecting port body.

Fig. 31 is a diagram corresponding to Fig. 30 showing a sixth embodiment of the present invention.

Fig. 32 is a half vertical sectional view showing the whole of a seventh embodiment of the present invention.

FIG. 33 is a diagram corresponding to FIG. 1 .

Fig. 34 is a view corresponding to Fig. 2 showing an eighth embodiment of the present invention.

Fig. 35 is a view corresponding to Fig. 2 showing a ninth embodiment of the present invention.

Fig. 36 is a view corresponding to Fig. 2 showing a tenth embodiment of the present invention.

Fig. 37 is a diagram equivalent to Fig. 2 showing a conventional example.

Embodiments of the present invention are described below in conjunction with the accompanying drawings.

First, a first embodiment of the present invention for a ventilation fan for ducts will be described with reference to Figs. 1 to 17 .

Shown in Fig. 2 is the outer frame 11, which is an open box-shaped bottom, with a motor 12 installed in the approximate center of its upper wall 11a, and a centrifugal impeller mounted on the rotating shaft 12a of the motor 12 inside the outer frame 11. 13.

The above-mentioned centrifugal impeller 13 is formed by arranging curved multi-blade blades 14 (see Fig. 8 ) in a cylindrical shape around the circular bottom plate 15, and each front end is surrounded by an end ring 16, and the whole body is reused by a shell. 17 surrounded.

The housing 17 is composed of the upper part mainly of the upper wall part 11a of the outer frame 11 and the cover 18 arranged in the upper and lower middle parts of the outer frame 11, and its longitudinal cross-sectional shape along the axis of the centrifugal impeller 13 is substantially oblong. Shaped, and as shown in FIG. 3 , it has a nose portion 19 close to the centrifugal impeller 13, and has a vortex-shaped ventilation passage 20 whose distance from the nose portion 19 to the centrifugal impeller 13 gradually expands. Also, as shown by Bmin and Bmax in FIG. 1, the width B of the axial direction (up and down in FIG. 2) of the housing 17 gradually expands from the above-mentioned nose-shaped portion 19 toward the direction of rotation of the centrifugal impeller 13 (indicated by arrow R). , and its maximum width Bmax part is between the discharge port 21 (see FIG. 3 ), and then gradually narrows toward the discharge port 21 from there.

Here if the maximum axial width Bmax of the housing 17 is set as b and the outer diameter of the centrifugal impeller 13 as b and d2 (see Fig. 2), then it can be defined as:

b/d2=0.45～0.70

b/Bmax＝0.55～0.75

In addition, the position where the axially maximum width Bmax of the casing 17 is formed forms an angle of 200° to 310° from the nose portion 19 toward the rotation direction of the centrifugal impeller 13 .

In addition, the cover 18 has a bell mouth 22 at a substantially central portion facing the centrifugal impeller 13 . In addition, the outer frame 11 is installed on the ceiling 23 of the house, and is provided on the back of the ceiling, and the open portion of the lower surface is covered with a decorative frame 24 . And the mounting plate 25 shown in Figure 4 is housed on the ceiling 23, makes the connecting port body 26 that forms one with this mounting plate 25 communicate with described outlet 21, and the cross section of connecting port body 26 is the circular front end portion connection. A pipe 28 having a circular cross-section that is thinner than the nominal diameter of the conventionally used pipe 27 is provided.

The operation of the centrifugal blower constructed as described above will be described below.

When the above-mentioned structure is adopted, once the centrifugal impeller 13 is rotated by the motor 12, the centrifugal impeller 13 will suck the air in the lower chamber facing the outer frame 11 from the axial direction through the decorative frame 24 and the bell mouth 22 of the cover 18, and The discharged air is discharged in the circumferential direction, and the discharged air is collected by the casing 1 ′ and then directed to the discharge port 21 , and discharged from the connecting port body 26 through the pipe 28 to the outside.

However, the performance of the centrifugal blower is greatly affected by the size of the housing 17 . This influence is greater than that of the outer diameter d2 or the axial length b of the centrifugal impeller 13 .

The casing 17 of the centrifugal blower is generally formed in a spiral shape with a certain radial diffusivity, and the larger the diffusivity, the greater the air volume and high static pressure can be obtained. That is, as shown in FIG. 3 , if the outer diameter d2 of the centrifugal impeller 13 is set to be D0 the inner diameter of the casing 17 that is parallel to the surface of the discharge port 21 and passes through the center of the centrifugal impeller 13, then D0/d2 is larger, The more you can get high performance. However, the current actual situation is that if a centrifugal blower such as a ventilation fan for ducts is installed on the back of the ceiling, the radial diffusivity of the housing 17 has to be reduced to some extent due to limited space, and D0/d2 is generally only It can be around 1.4 to 1.6, that is, it must be controlled below 2.0.

Regarding this point, as described above, if the casing 17 is formed by adopting the following structure, that is, the longitudinal section along the axis of the centrifugal impeller 13 has a substantially oblong shape, and the width B in the axial direction extends from the nose portion 19 to the center of the centrifugal impeller 13. The direction of rotation gradually expands, and its maximum width Bmax part is between the discharge port 21, then by increasing the axial diffusivity of the housing 17, the above-mentioned restraint on the radial diffusivity can be compensated, ensuring that the housing substantial diffusivity.

Again, the longitudinal section along the axis of the centrifugal impeller 13 is a substantially oblong housing 17 as shown in Figure 6, which can eliminate the two-dimensional arrow shown in Figure 5 that occurs at the corners of the traditional rectangular housing 2. The flow is the so-called vortex s, so that the air path can be substantially expanded, and thus the centrifugal blower can achieve high wind volume, low noise, and high static pressure.

Therefore, large air volume and low noise can be realized without increasing the volume, and high static pressure can also be realized, so even if thin ducts are used, the air volume will not decrease and the noise will not increase.

In addition, when adopting the above configuration, as shown below, the optimal size of the centrifugal impeller 13 and the optimal size of the casing 17 are further found out.

(1) b/d2 (axial length/outer diameter of the centrifugal impeller 13)

The suction area and discharge effective area of the centrifugal impeller 13 are preferably equal. The effective area of so-called centrifugal impeller 13 refers to removing the respective wall thicknesses of blades 14, bottom plate 15, and end ring 16 from the area of the circumferential side of the exhaust wind (air) of centrifugal impeller 13, and then removing the wall thickness in centrifugal impeller 13. The dead water area that occurs at the suction end of the impeller 13 (because the direction of the airflow does not change sharply, the part that cannot blow the wind occurs at the suction end of the centrifugal impeller 13...see Figure 7), and the area from the nose 19 to The circumferential side of the centrifugal impeller 13 at about 20% of the rotation direction (due to the wind returning from the discharge part of the casing 17 through the gap of the nose part 19 does not blow from the centrifugal impeller 13). 13 The area of the part where the wind is blown out from the side of the circumference...see Fig. 3). From this, the ratio of the axial length b and the outer diameter d2 where the suction area of the centrifugal impeller 13 is equal to the effective discharge area is calculated, then:

Suction area S1 of the centrifugal impeller 13=π×(d1/2) ²

Area S2 of the circumferential side of the centrifugal impeller 13 = π × d2 × b

The effective circumferential side area S2'=S2×A×C×E of the centrifugal impeller 13

d1: inner diameter of the centrifugal impeller 13 (see Figure 7)

A: The reduction rate of the circumferential side area of the centrifugal impeller 13 = 0.40 to 0.65

The circumference side area reduction rate A of the so-called centrifugal impeller 13 is actually the ratio of the effective area Se blown by the wind to the circumference side area S2, and the effective area Se is the distance p between the blades 14 (see Figure 8) and the effective length b '(see Fig. 7) and the product of the number Z of blade 14.

thereby,

A=Se/S2=(p×b′×Z)/(π×d2×b) Usually, the centrifugal impeller 13 made of plastic is A=0.40～0.55, while the centrifugal impeller 13 made of metal is A= 0.50～0.65.

C: The reduction rate of the effective peripheral side area of the centrifugal impeller 13 due to the dead water area = about 0.8

E: The area reduction rate of the centrifugal impeller 13 due to the portion of the nose portion 19 where the wind is hardly blown = about 0.8

From this it can be concluded that:

S1=S2'=S2×A×C×E

π＝(d1/2) ² ＝(π×d2×b)×(0.40～0.65)×0.8×0.8

And the inner and outer diameter ratio (d1/d2) of the centrifugal impeller 13 is usually designed to be 0.82, so d1=0.82×d2, if it is substituted into the above formula, then,

π×(0.82×d2/2) ² ＝(π×d2×b)×(0.40～0.65)×0.8×0.8

(0.82/2) ² ×d2＝b×(0.40～0.65)×0.8×0.8

b/d2=0.40～0.56

Figures 9 to 11 are characteristic diagrams made based on actual measured results. They are respectively made according to the results measured when the outer diameter d2 of the centrifugal impeller 13 is 10 [cm], 18 [cm], and 23 [cm]. It can be known from Fig. 9 to Fig. 11 that there is a range b/d2 in which the air volume and static pressure are the largest and the noise is the smallest, that is, 0.45-0.70. This range deviates slightly from the numerical value obtained from above-mentioned theory, and this is because the air-flow stripping that takes place at the back side of blade 14 makes the actual blowing effective circumference side area dwindle (it can be considered that the circumference side area reduction rate A is actually greater than the aforementioned value small).

Therefore, the present invention sets b/d2 as 0.45-0.70, which can achieve high performance, according to the actual test results.

(2) b/Bmax (axial length of the centrifugal impeller 13/maximum width of the casing 17)

Figures 12 to 14 are characteristic diagrams made according to the test results after using the centrifugal impeller 13 with a size close to the minimum noise value b/d2 in the above-mentioned performances and changing the maximum width Bmax of the housing 17 respectively. It can be seen from Fig. 12 to Fig. 14 that there is a range b/Bmax in which the air volume and static pressure are the maximum and the noise is the minimum, that is, 0.55-0.75. In this case, people tend to think that the larger the maximum width Bmax of the housing 17, the better the performance. In fact, this is not the case. Since the size of the discharge part of the housing 17 is limited, the larger the maximum width Bmax, the greater the reduction rate of the discharge part. Larger, and the greater the loss caused by the narrowing of the airflow, the result is that the performance deteriorates. Therefore, there must be an optimal maximum housing width Bmax that can achieve balance.

Therefore, the present invention also sets b/Bmax to 0.55 to 0.75, which can obtain high performance, based on the actual measured results.

Figures 15 to 17 are characteristic diagrams made according to the test results after using the centrifugal impeller 13 with a size close to the minimum noise value b/d2 and changing the position of the maximum width Bmax part of the casing 17 respectively. It can be seen from Fig. 15 to Fig. 17 that there is a position of the maximum width Bmax of the casing 17 where the air volume and static pressure are the maximum value and the noise is the minimum value, that is, the rotation direction from the nose-shaped part 19 to the centrifugal impeller 13 is 200°. ~310° angle position.

Therefore, according to the actual measured results, the present invention sets the position of the portion of the maximum width Bmax in the axial direction of the casing 17 at the above-mentioned 200-310° angle position where high performance can be obtained.

In this way, compared with our traditional models of the same size, the air volume can be increased by 4-8〔%〕, the static pressure can be increased by 5-10〔%〕, and the noise can be reduced by 0.8-1.3〔dB〕, effectively improving the performance .

18 to 21 show the second embodiment of the present invention, showing that the length of the minimum width Bmin in the axial direction of the housing 17 is from the nose-shaped portion 19 to the direction of rotation of the centrifugal impeller 13 to the vicinity of the nose-shaped portion 19. In the range, especially in the length range below the angle of 45° from the nose portion 19.

Once the minimum width Bmin in the axial direction of the housing 17 is formed so that the length is within the range from the nose 19 to the rotation direction of the centrifugal impeller 13 to the vicinity of the nose 19, the gap passing through the nose 19 can be reduced. The returned wind can achieve better results in terms of high wind quantization, low noise, and high static pressure.

Particularly, in this case, if the length formed by the minimum width Bmin in the axial direction of the housing 17 exceeds the range of an angle of 45° from the nose portion 19, the passage of the wind blown from the centrifugal impeller 13 will be narrowed. And as shown in the actual test results in Figure 19 to Figure 21, the performance will be reduced, and if the length is set below the 45° angle, high performance can be reliably obtained, especially in the case of maintaining large air volume and low noise increase the static pressure.

Fig. 22 is the 3rd embodiment of the present invention, nose-shaped part 19 forms curved shape, the suction end (end ring 16 side) part 19a of centrifugal impeller 13 and the opposite end (bottom plate 15 side) part 19b of suction from The discharge port 21 is extended to the circumferential side of the centrifugal impeller 13 or near the circumferential side. In this way, in the vicinity of the nose 19, the gap between the bell mouth 22 and the centrifugal impeller 13 and the gap opposite to it are respectively passed. The gap between the upper wall portion 11a of the outer frame and the centrifugal impeller 13 can reduce the air volume circulating in the casing 17, so better results can be achieved in terms of high wind volume, low noise, and high static pressure.

Fig. 23 to Fig. 27 are the 4th embodiment of the present invention, the side cross-sectional shape of each ventilation passage 20 of the extension part 19a19b of the above-mentioned curved nose-shaped part 19 is arc-shaped, and in the extension part 19a of the nose-shaped part 19 The shape of the casing 17 of the part 19b is toward the discharge port 21, and its cross section gradually changes from an oblong circle to an approximate circle. In this way, the wind flow can smoothly flow from the casing 17 into the connecting port body 26 with a circular cross section at the front end, and then flow into the pipe 28 with a circular cross section, thereby further increasing the air volume and static pressure and reducing noise.

28 to 30 are the fifth embodiment of the present invention. The anti-backflow windshield 29 provided in the connection port body 26 is in a curved shape. When opened, it is on the arc-shaped inner surface along the connecting port body 26 . Also, in this case, the pivotal portion 30 of the windshield 29 is located at substantially the same position as the upper edge of the front end of the connection port body 26, so that the air enters the connection port body 26 from the housing 17 and then enters the duct 28. The wind flow inside can flow in smoothly without being influenced by the windshield 29 and its pivotal branch 30, so the air volume and static pressure can be further increased, and the noise can be reduced. It is also possible to prevent the eddy sound that is likely to occur due to the pivotal portion 30 of the windshield 29 in this case.

Fig. 31 is the sixth embodiment of the present invention, the pivotal part 31 of the windshield 29 is set at a higher position than the upper edge of the front end of the connecting port body 26, so that the casing 17 enters the connecting port body 26 and the pipe 28 The wind flow inside can flow in smoothly without being affected by the windshield 29 and its pivotal part 31, and can more effectively prevent the eddy current sound that is likely to occur due to the pivotal part 31 of the windshield 29.

Fig. 32 and Fig. 33 are the 7th embodiment of the present invention, and the position of the nose-shaped part 19 of the housing 17 is staggered from the position of the discharge part according to the deviation of the central position between the centrifugal impeller 13 and the connecting port body 26, and The enlarged shape of the nose portion 19 side of the housing 17 is different from the reduced shape of the discharge portion side to correspond respectively.

In this case, since the duct adopting this centrifugal fan is mounted on the back of the narrow ceiling, the height of the product is limited. Therefore, as shown in FIG. 33, the highest position (dimension H) of the motor 12 is limited. Wherein, when the upper wall portion 11a of the outer frame 11 is made of metal, due to problems in processing (such as deep drawing), the depth G of the casing 17 cannot be too large, and the position of the centrifugal impeller 13 follows. must also be restricted.

In addition, the outer frame 11 is specifically fixed on the wooden frame 32 mounted on the ceiling 23 . Moreover, in order to connect the connecting port body 26 and the pipe 28, tapping work is required, and in order to improve workability, a sufficient space is required between the wooden frame 32 and the connecting port body 26. For this purpose, the mounting position of the connection opening 26 must be raised.

From the performance point of view, the vertical center positions of the centrifugal impeller 13 and the connecting port body 26 are preferably equal. 26 centers are staggered. For this reason, this misalignment should be compensated between the maximum width Bmax part of the housing 17 and the discharge part, and the shapes of different housings 17 can be made according to the above-mentioned method, thus making it possible to enter the connecting port body from the housing 17. The wind current in 26 and pipeline 28 still flows smoothly.

34 to 36 are eighth to tenth embodiments of the present invention, wherein the outer frame 33 in FIG. 34 is formed by connecting the outer frame main body 34 and another upper wall 35, and the cover 36 is embedded in the connecting portion. In addition, the outer frame 37 in FIG. 35 is formed by connecting the outer frame body 38 lower in height than the outer frame body 34 and the upper wall 39 deeper than the upper wall 35 , and the cover 40 is fitted into the connecting portion. In the cover 41 in FIG. 36 , due to the thickness of the components, the bell mouth 42 gradually narrows from the lower opening of the outer frame 11, thereby improving the air suction.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate changes within the scope not departing from the gist of the present invention.

The centrifugal fan of the present invention described above has the following effects.

First, this type of centrifugal blower has a centrifugal impeller that sucks air from the axial direction and discharges it to the circumferential direction by rotation, and has a nose portion close to the centrifugal impeller and concentrates the air discharged from the centrifugal impeller. The vortex-shaped ventilation path leads to the casing of the discharge port, and the longitudinal section of the casing along the axial direction of the centrifugal impeller is approximately oblong, and the width of the axial direction extends from the nose-shaped part to the centrifugal impeller. The rotation direction of the pipe gradually expands, and its largest part is between the above-mentioned discharge port, so that large air volume, low noise, and high static pressure can be realized without increasing the overall volume, so even if a thin pipe is used, it will not cause damage. Reduced air volume and increased noise.

Second, assuming that the axial length of the above-mentioned centrifugal impeller is b, the outer diameter is d2, and the maximum axial width of the casing is Bmax, it is set as follows, namely

b/d2=0.45～0.70

b, Bmax=0.55～0.75 can achieve more ideal effects of large air volume, low noise and high static pressure in practice.

Third, since the position of the maximum width in the axial direction of the casing is formed at an angle of 200° to 310° from the nose portion to the direction of rotation of the centrifugal impeller 13, ideal large air volume and low noise can also be obtained in practice. , and high static pressure effect.

Fourth, since the length of the minimum axial portion of the housing is within the range from the nose to the direction of rotation of the centrifugal impeller to the vicinity of the nose, the amount of air returning through the gap in the nose can be reduced. , can achieve better results in terms of increasing air volume, reducing noise, and increasing static pressure.

Fifth, since the length of the minimum width in the axial direction of the above-mentioned housing is within the range of 45° from the nose, ideal large air volume, low noise, and high static pressure can also be obtained in practice. pressure effect.

Claims (5)

1. A centrifugal blower, comprising a centrifugal impeller (13) that is discharged from the axial direction to the circumferential direction by rotating, having a nose (19) that is close to the centrifugal impeller (13) and will The air discharged by the centrifugal impeller (13) is concentrated in the vortex-shaped ventilation passage (20) and directed to the casing (17) of the discharge port (21), wherein the shape of the casing (17) is as follows: That is, the longitudinal section along the axial direction of the centrifugal impeller (13) is approximately oblong, and its width gradually expands from the nose portion (19) to the rotation direction of the centrifugal impeller (13), and its maximum width is at to the outlet (21). 2. The centrifugal blower according to claim 1, characterized in that, when the axial length of the centrifugal impeller (13) is b, the outer diameter is d2, and the axial maximum width of the housing (17) is Bmax , make the following settings: b/d2=0.45～0.70 b/Bmax＝0.55～0.75 3. The centrifugal blower according to claim 1, characterized in that the maximum width in the axial direction of the casing (17) is in the range of 200-310 from the nose-shaped part (19) to the rotation direction of the centrifugal impeller (13). ° angle position. 4. The centrifugal blower according to claim 1, characterized in that, the length of the smallest width portion in the axial direction of the casing (17) is from the nose (19) to the centrifugal impeller (13) to the nose (19) within the vicinity. 5. The centrifugal blower according to claim 4, characterized in that the length formed by the smallest width portion in the axial direction of the housing (17) is within the range of an angle of 45° or less from the nose portion (19).

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