JPH094593A - Electric centrifugal blower - Google Patents

Abstract

PURPOSE: To provide a multi-stage centrifugal blower at a low cost in which the blowing efficiency is improved and the variance of the properties is suppressed by improving the assembly accuracy in the axial direction, and whose fabricability is sufficiently improved with a casing structure of excellent maintainability CONSTITUTION: Stud bolts 5 are used to fit an impeller casing 2 in which an impeller 1 and a return 4 part are housed and an impeller casing 21 in which an impeller 11 is housed to an end bracket 6 of a motor 8. The impeller casings 2, 21 and the return part 4 are positioned relative to the end bracket 6 by interposing a cylindrical member 7. Because the assembly accuracy can be determined irrespective of the shape accuracy of the impeller casings 2, 21, the tolerance of each part is suppressed, and the fan efficiency is improved. As a result, the impeller casings 2, 21 which are made of pressed sheets can be available.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal multistage electric blower, and more particularly to an electric centrifugal blower suitable as a vacuum source for pneumatic transportation such as a dust collector and an air shooter.

[0002]

2. Description of the Related Art Centrifugal blowers have been generally used as a vacuum source for pneumatic transportation, but in this case, a vacuum cleaner for home use is an exception, and a high pressure is used for industrial purposes. , Mainly multi-stage centrifugal blowers are used. Therefore, the conventional technique of such a multi-stage centrifugal blower will be described. First, the conventional example of FIG. 2 is an example of a three-stage centrifugal blower using an impeller casing made of cast metal, and the rotary shaft 8a of the electric motor 8 is sequentially arranged. The three attached impellers 1, 11, 12 and the same three-stage impeller casings 2, 21, 22 sequentially attached to the load-side end bracket 6 of the electric motor 8 and these impeller casings 2,
21. Disc-shaped return parts 4 and 41 for separating the space 21
And return vanes 4a and 41a provided therein, and by rotating the impellers 1, 11 and 12 by the electric motor 8, the fluid such as air sucked in axially from the suction port 2a is The fluid pressurized by the wheel 1 and discharged from the impeller 1 turns around in the return section 4 and is guided to the next-stage impeller by the return vanes 4a and 41a. The fluid sent by the impeller 13 at the final stage is discharged from the discharge port 6a.

In this conventional example, each impeller casing 2, 21, 22 is provided with a flange on the outer periphery of the joint end portion thereof, and the bolts are formed at the joint portions 2b, 2c formed by these flanges. Assembled in
It is constructed so that it can be removed for maintenance.

By the way, in such a centrifugal blower, if the rotation speed can be increased, the diameter of the impeller can be reduced,
As a result, miniaturization is possible. Therefore, in recent years, a centrifugal blower has been used in which an electric motor is driven at a frequency higher than that of a commercial power source and is rotated at a high speed by using an inverter device. An example of a conventional technique of such a centrifugal blower is shown in FIG. Shown in. The structure of each part is the same as that of the conventional example of FIG.

In this case, since the diameters of the impellers 1, 11 and 12 can be made small, as is apparent from FIG. 3, the impeller casings 2, 21 and 22 are formed by pressing or drawing a thin metal material. The return sections 4 and 41 are made by plastic deformation processing, and are attached to the outer sides of the bottom portions of the downstream side impeller casings 21 and 22 by the return vanes 4a and 41a, respectively.

At this time, the outer diameters of the impeller casings 2, 21, 22 are made substantially equal to each other according to the outer shape of the bracket 6, and these are sequentially press-fitted and assembled as shown in the drawing. As a result, the size and weight are reduced, and the cost is reduced.

[0007]

The above-mentioned prior art cannot be said to be small in size, light in weight, maintain accuracy during assembly, and are easy to maintain. However, there was a problem in that the cost associated with the increase in cost was increased. That is, in such a centrifugal blower, there is a problem of fluid leakage from the outlet side of the impeller to the inlet part,
As the leakage flow rate increases, the efficiency decreases and the temperature of the discharged fluid increases. Therefore, in order to improve its performance, it is necessary to keep this leakage flow rate as small as possible.

By the way, the fluid leakage from the outlet side to the inlet portion of the impeller is determined by the dimension δ and the dimension t shown in FIG. 4, and in order to suppress the leakage flow rate, the dimension δ and the dimension t.
It is necessary to keep the ratio δ / t of .DELTA. / T sufficiently large. Therefore, it is necessary for the product to maintain these dimensions .delta., T within a predetermined tolerance. 4 is an enlarged view of a portion A surrounded by a broken line in FIG.
Therefore, in order to maintain the dimensions δ and t at the predetermined tolerances, it is necessary to maintain the dimensional accuracy of the impeller and the casing alone at the predetermined tolerances.

Since the assembly accuracy of the multi-stage centrifugal blower is determined by the stacking tolerance of the axially stacked parts, it is necessary to further improve the accuracy of each part.

In the prior art shown in FIG. 2, however, the impeller casings 2, 21 and 22 are made of cast metal and are therefore machined, so that it is easy to maintain accuracy, but the cost is reduced. With up and weight gain. On the other hand, in the prior art shown in FIG. 3, since the impeller casing made by pressing a plate material is used, it is advantageous in terms of cost reduction. In this case, however, the impeller casing having a large radius cannot be pressed. It is difficult to finely specify the accuracy in the height direction, and it becomes difficult to secure the overlapping length dimension δ in the axial direction to a length effective for preventing leakage.

Further, in this case, since the impeller casings are in line contact with each other when they are fitted together, it is necessary to take into consideration the collapse of the casings during assembly and the change in length due to the change in wall thickness. However, there is a limit to the high precision. Also, if the radial gap between the rotary shaft and the shaft hole of the return part increases, the leakage flow also increases, but if the leakage flow in this part increases, it will also affect the aerodynamic performance. Although the positioning is required, in the conventional technique of FIG. 3, the return vane is fixed to the downstream side impeller casing, and the accuracy of assembly of the return part with respect to the shaft is determined by the accuracy of the downstream side impeller casing. .

As a result, when the impeller casing is tilted, the shaft part of the return part may come into contact with the shaft, so that the tolerance cannot be sufficiently reduced, and the improvement in performance is limited. Will end up. Therefore, in the above-mentioned conventional technology, it cannot be said that consideration is given to downsizing and weight reduction, accuracy retention at the time of assembly, and ease of maintenance. There is a problem in terms.

Further, as a method of fixing the impeller casing in such a blower, a screw-fastening method, which is easy to remove, is preferable to the press-fitting method in consideration of maintainability and reliability. On the other hand, in order to reduce costs and reduce the size and weight, it is desirable to use a plate impeller casing rather than a cast impeller casing. For this purpose, even if a plate impeller casing is used, a fixed alternative to the press-fitting method is used. It will be necessary to consider the method.

Also, regarding the method of fixing the impeller casing and the return portion, in the case of the multi-stage type, the number of assembling steps such as fixing the individual impeller casings is large and the workability is deteriorated. Moreover, at this time, since it is necessary to position the return portion in the radial direction, more man-hours are required for positioning, and workability is further deteriorated.

The present invention has been made to solve the above problems, and an object thereof is to improve the ventilation efficiency and suppress the characteristic variation by improving the axial assembly accuracy.
It is an object of the present invention to provide a multistage centrifugal blower, which has a casing structure with good maintainability and whose assembly property can be sufficiently improved, at low cost.

[0016]

The object is to provide at least two impeller casings each containing an impeller, and these at least two impeller casings are sequentially superposed and attached to an end bracket of an electric motor. Type electric centrifugal blower, at least two studs extending parallel to a rotation axis of the electric motor from a surface of the end bracket opposite to the electric motor and penetrating a bottom portion of the impeller casing on an outer peripheral side of the impeller. This is accomplished by providing bolts and attaching the impeller casing to the end brackets with the at least two stud bolts.

[0017]

The stud bolt extending from the end bracket works so that when the impeller casing is attached to the end bracket, it is not affected by the shape precision of the impeller casing and the axial assembly precision is sufficiently given. As a result, the number of integrated parts can be reduced and the accuracy in the axial direction can be relatively easily obtained, so that the assembly tolerance in the axial direction can be set small.

As mentioned above, in order to improve the efficiency of the blower,
It is effective to reduce the leakage of the flow boosted by the impeller, and the leakage flow at the impeller inlet at this time flows from the impeller outlet through the back of the impeller shroud to the inlet,
Not only does the volume loss increase, but it also impedes the flow of fluid at the inlet of the impeller, making it easier for the fluid to separate, resulting in a significant loss of fan efficiency. Furthermore, since the flow circulates, the temperature of the working fluid rises, which adversely affects the grease life of the output shaft side bearing of the blower.

To prevent the leakage flow at the inlet of the impeller,
The axial overlap dimension δ at the inlet of the impeller and the impeller casing is important, and the longer the axial overlap, the smaller the leakage flow rate. Here, since the stud bolt is not affected by the shape accuracy of the impeller casing, the stacking tolerance can be made relatively small, and the predetermined seal overlap length δ.
It is possible to reduce variations in characteristics.

On the other hand, the leakage flow from the gap between the shaft hole portion of the return portion and the shaft is as follows. That is,
This return part is also positioned directly from the end bracket end face by the stud bolt, so it is easier to prevent deterioration of radial assembly accuracy than when it is fixed to the impeller casing, and the gap between the shaft hole and shaft is small. Yes, and therefore less leakage flow.

Further, since the stud bolt extending from the end bracket is used, the return portion is fixed inside the impeller casing, separately from this.
Therefore, even if the impeller casing is made of a thin-walled casing formed by pressing a plate material or the like, the impeller casing and the return portion can be reliably fixed. As described above, since the thin casing can be adopted, cost reduction and size and weight reduction can be obtained.

At this time, since the stud bolts bear the fixing force necessary for mounting the impeller casing, the casing material is less likely to settle, and the casing is internally fixed, so that the casing can be miniaturized. Further, as compared with the case where it is fixed on the outer peripheral side, since it is fixed within the outer shape of the impeller casing,
The rigidity of the impeller casing is increased, a structure that does not easily vibrate is obtained, the impeller casing can be easily removed, and a compact and lightweight structure is obtained in consideration of maintainability.

Further, since the same stud bolt is used for fixing, the number of man-hours required for working is small, and at the time of assembling, the stud bolt is set up in advance and the assembling process is carried out. With the above operation, the assembling accuracy in the axial direction can be improved, the fan efficiency can be improved, the characteristic variation can be reduced, and the assembling performance can be improved with the structure having good maintainability.

[0024]

The electric centrifugal blower according to the present invention will be described in detail below with reference to the illustrated embodiments. 1 is a first embodiment of the present invention, in which 5 is a stud bolt,
Reference numerals 7 and 71 denote tubular members, and the other components are the same as those of the conventional example shown in FIG. 3 except that they have a two-stage configuration having two impellers 1 and 11. The stud bolt 5
As shown in the figure, the end bracket 6 on the output rotary shaft side of the electric motor 8 extends parallel to the rotary shaft 8a, passes through the outer peripheral sides of the impellers 1 and 11, and bottoms 2a of the impeller casings 2 and 21,
21a is penetrated, respectively, and it is embedded in the end bracket 6 so that it may reach these outer sides. Although only one stud bolt 5 is visible in FIG. 1, at least two stud bolts 5 are necessary, and the determination of the number of stud bolts 5 requires that the impeller be in a neat and disjoint state. When the number of stud bolts is a factor or multiple of the number of impellers, the noise (number of blades) x (rotation frequency)
This is because the components increase and the noise increases. In this embodiment, three pieces are embedded in the end bracket 6 at substantially equal intervals around the rotary shaft 8a. The stud bolt is also called a stud bolt.

The tubular members 7 and 71 are formed into a tubular shape as the name suggests, and when assembled, they are respectively between the end bracket 6 and the bottom portion 21a of the impeller casing 21, and between the bottom portion 21a of the impeller casing 21 and the blade. It is inserted into the stud bolt 5 so as to be interposed between the bottom portion 2 a of the vehicle casing 2. The tubular members 7 and 71 have a function as a distance piece (positioning piece).
The position of the bottom 21a of the impeller casing 21 with respect to
The position of the bottom 2a of the impeller casing 1 can be accurately determined.

Further, in this embodiment, among the tubular members 7 and 71, the tubular member 7 located at a position apart from the end bracket 6 is not provided alone but in the drawing. As shown in FIG. 5, it is integrally formed with the return section 4. In addition, in this FIG. 5 embodiment, the cylindrical member 7
5, a lower portion in FIG. 5 is formed integrally with the return vane 4a, and thus is shown slightly different from FIG.

Next, the order of assembling the electric centrifugal blower according to this embodiment will be described with reference to FIG. First here
It is assumed that the electric motor 8 is completed using the end bracket 6. Then, the ball bearing 8b of the electric motor 8 is fitted into the bearing insertion portion of the end bracket 6,
The protruding size of the rotary shaft 8a from the end bracket 6 is determined.

Hereinafter, as shown in FIG. 6, first, the stud bolt 5 is embedded in the end bracket 6. In this embodiment, the stud bolt 5 is implanted by press fitting, but it may be screwed or may be implanted before the end bracket 6 is assembled to the electric motor 8.

Next, the second-stage impeller 11 is inserted into the rotary shaft 8a, and together with this, the tubular member 71 is inserted into the stud bolt 5. Therefore, in this embodiment, as shown in FIG. 6, that is, with the left side of FIG. 1 facing upward,
It is advisable to carry out the assembly work with the electric motor 8 standing up. After that, first, the impeller casing 21 of the second stage is put on the impeller 11 such that the stud bolts 5 are inserted into the mounting holes provided in the peripheral portion of the bottom portion 21a in advance. At this time, the cylindrical portion 21b of the impeller casing 21 is fitted into the fitting portion 6b formed in the end bracket 6 in advance.

Next, the return part 4 is put on the impeller casing 21 so that the hole of the tubular member 7 is inserted into the stud bolt 5. After this, the rotary shaft 8
By inserting the first-stage impeller 1 into a and engaging and rotating the nut with a male screw portion provided at the tip of the rotary shaft 8a through a washer as shown in FIG. The cars 1 and 11 are fixed to the rotating shaft 8a. At this time, if necessary, well-known key engagement or spline engagement may be applied to withstand the required torque transmission.

Finally, as shown in FIG. 6, the first-stage impeller casing 2 is configured so that the stud bolt 5 is inserted into a mounting hole which is provided in advance in the peripheral portion of the bottom portion 2a thereof.
After covering the impeller 1 and the return part 4, as shown in FIG. 1, the nut 5a is screwed into the male screw part provided at the tip of the stud bolt 5 to complete the assembly. In addition, as shown in the figure, the nut 5a is doubled to prevent loosening, which is a kind of a loosening prevention technique called a double nut.

Next, regarding the embodiment assembled as shown in FIG. 1, first, the positional accuracy of the impellers 1 and 11 with respect to the end bracket 6 in the axial direction is as described above. By fitting the ball bearing 8b into the bearing insertion portion of the end bracket 6, the rotation shaft 8a
Since the projecting dimension from the end bracket 6 is determined, it depends on the processing accuracy of the end bracket 6 and the rotary shaft 8a. Since the end bracket 6 and the rotary shaft 8a are machined, their machining accuracy can be easily increased.

On the other hand, regarding the positional accuracy of the second-stage impeller casing 21 in the axial direction with respect to the end bracket 6, this is determined only by the length accuracy of the tubular member 71. Therefore, also in this case, the positional accuracy can be kept sufficiently high by cutting the tubular member 71.

Next, regarding the positional accuracy of the return section 4 and the first-stage impeller casing 2 in the axial direction with respect to the end bracket 6, the length accuracy of the tubular member 71 and the two-step accuracy are shown. It is determined by the cumulative accuracy of the thickness accuracy of the bottom portion 21a of the eye impeller casing 21 and the accuracy of the length of the tubular member 7. In this case, the tubular member 7 is the tubular member 71.
As described above, it is easy to maintain the accuracy of the length accuracy without any problem, as described above.

Next, the thickness accuracy of the bottom portion 21a of the second stage impeller casing 21 is as follows. First, the metal plate material is generally supplied by rolling, and therefore, the thickness accuracy thereof is extremely high. Next, looking at the change in thickness accuracy when the plate material is processed into the impeller casing 21, as is clear from the shape, the bottom portion 21a is hardly extended and deformed.
Therefore, it can be said that the thickness accuracy here is the same as that of the material, and in the end, the thickness accuracy of the bottom portion 21a of the second-stage impeller casing 21 can be kept sufficiently high. As a result, the positional accuracy of the return portion 4 and the first-stage impeller casing 2 in the axial direction with respect to the end bracket 6 can be maintained sufficiently high.

Next, regarding the positional accuracy of the impellers 1 and 11 and the impeller casings 2 and 21 and the return portion 4 with respect to the rotary shaft 8a in the present embodiment in the direction perpendicular to the rotary shaft 8a, first, , The impellers 1 and 11 are
Since it is only inserted and attached to the rotary shaft 8a, it is possible to easily maintain high accuracy in view of the ordinary processing and assembly technology level.

Next, regarding the positional accuracy of the impeller casings 2 and 21, and the return portion 4, these are the impeller casing 2 of the outer peripheral portion 2b of the impeller casing 2.
1 and the fitting state of the outer peripheral portion 21b of the impeller casing 21 with respect to the fitting portion 6b of the end bracket 6 are completely independent of each other, and both are simply the stud bolt 5
Since it is determined only by the positional accuracy of the end bracket 6 with respect to the end bracket 6, the problem of cumulative accuracy is eliminated, and therefore highly accurate holding can be easily obtained.

Therefore, according to this embodiment, the impeller 1,
11 and impeller casings 2, 21 and return section 4
The positional accuracy of each is determined based on the end bracket 6, and as described above, all of them can be easily maintained with sufficiently high accuracy. Therefore, the dimension t shown in FIG. It is possible to sufficiently reduce the accumulated tolerance. As a result, according to this embodiment, the dimension t can be set to a sufficiently small value, variation in characteristics can be suppressed, and fan efficiency can be greatly improved.

Further, in the above embodiment, as shown in FIG. 5, the tubular member 7 is the return vane 4 of the return section 4.
Since it is formed integrally with a and these positions match, the loss due to the obstruction of the fluid flow is suppressed and the return vane 4a is compared with the case where the tubular member 7 is present alone. It is also useful for reinforcement. As a result, the number of parts does not increase, and the number of tubular members 7 at this time can be made to have a prime relationship with the number of blades 1b of the impeller. Resonance due to fluctuation does not occur, and vibration and noise can be reduced. Further, as shown in FIG. 6, since it is fixed by the stud bolts 5, the number of working steps is small, and the stud bolts 5 are set up in advance at the time of assembly, and the assembly work of the impeller casing 2 and the return section 4 is performed. Assembly workability is improved.

In addition, in this embodiment, since the stud bolts 5 are used, it is not necessary to give the impeller casings 2 and 21 high strength. As a result, as shown in FIG. 2, 21 can be formed by molding a thin plate, and further cost reduction and size and weight reduction can be obtained. Moreover, at this time, since the tubular members 7 and 71 are used for positioning, a large fixing area can be obtained, and as a result, the impeller casing hits due to stress concentration due to the pressing force at the time of fixing. It is possible to prevent the settling of the surface, and it is possible to further reduce the thickness of the impeller casing and thereby reduce the cost and the weight.

Further, according to this embodiment, since the impeller casings 2 and 21 are fixed at their bottom portions 2a and 21a by the plurality of stud bolts 5 located inside thereof, these bottom portions 2a are fixed. , 21a has a sufficiently high rigidity, and vibration and noise can be reduced.

Next, another embodiment of the present invention will be described. First, FIG. 7 shows a second embodiment of the present invention in which the cross-sectional shape of the cylindrical member 7 in the first embodiment is changed from the cylindrical shape, and the return part 4 is sucked in. It is the figure which showed the state seen from the upper part of the mouth (upper part of FIG. 6).
Note that the other configurations are the same. The fluid sent out from the periphery of the impeller 1 by centrifugal force, in the return section 4,
It flows at high speed as indicated by arrow 3. Therefore, if this collides with the tubular member 7, the flow is obstructed and there is a possibility that a large loss will occur. Therefore, in this embodiment, the tubular member 7
Is a streamlined shape along the arrow 3.

Therefore, according to this embodiment, since the tubular member 7 has a streamlined shape, even if it is present in the flow path of the fluid, the degree of obstructing the flow is small, so that a large loss may occur. Since this is eliminated and the role of a guide is also obtained, the flow becomes smooth, so that the loss can be further reduced and a great improvement in efficiency can be obtained.

Further, the streamline has a larger cross-sectional area as compared with the case of a simple circle even if the area opposed to the fluid is the same, so that the contact area with the impeller casing 2 can be increased,
Effective in preventing the contact surface of the impeller casing 2 from settling,
In addition, it has an effect of increasing the strength of itself and increasing the rigidity.

Next, FIG. 8 shows a third embodiment of the present invention.
A stepped bolt is used as the stud bolt 5, and the large-diameter portion 51 of the stud bolt 5 is used instead of the cylindrical member 71 for positioning at the final stage in the first embodiment, and the impeller casing 21 of the second stage is used. Is positioned, and other configurations are the same as those in the first embodiment described with reference to FIG. Since the large-diameter portion 51 is cut, it is easy to maintain the dimensional accuracy. Therefore, also in the third embodiment, the assembly accuracy can be easily increased, and the fan efficiency can be sufficiently improved. Will be done. Further, according to this embodiment, since the cylindrical member 71 is not necessary, the number of parts can be reduced and therefore workability can be improved.

FIG. 9 shows the fourth embodiment of the present invention.
Similarly, instead of the cylindrical member 71 for positioning at the final stage in the first embodiment described above, the end bracket 6 is previously provided with 2 pieces.
Cylindrical protrusion 6 for positioning the second stage impeller casing 21
1 is formed in advance, and other configurations are the same.

The cylindrical protruding portion 61 of the end bracket 6
Also serves as an implantation seat for the stud bolt 5, and its end surface is machined, so that it is easy to maintain dimensional accuracy. Therefore, also in the fourth embodiment, the assembly accuracy can be easily increased. As a result, the pump efficiency can be sufficiently improved, and the cylindrical member 71 is not required, so that the number of parts can be reduced and therefore the workability can be improved.

Further, in the fourth embodiment, the fact that the end bracket 6 is made by die casting is utilized,
As shown in FIG. 10, the cross-sectional shape of the cylindrical protrusion 61 is streamlined along the flow of the fluid indicated by the arrow 3. Therefore, according to the fourth embodiment, even if the cylindrical protruding portion 61 is present in the fluid flow path, there is no possibility of obstructing the flow, and the role of a guide can be obtained. As a result, the loss can be further reduced and a great improvement in efficiency can be obtained as in the case of the suction side of the return section 4 in the second embodiment described with reference to FIG.

Further, the streamline has a larger cross-sectional area as compared with the case of a simple circle even if the area opposed to the flow of fluid is the same. Therefore, this is also the case of the second embodiment described in FIG. Similarly, the area of contact with the impeller casing 21 can be increased, which is effective in preventing sagging on that surface, and also has the effect of increasing the strength of itself and increasing the rigidity.

Next, FIG. 11 shows a fifth embodiment of the present invention, in which the cylindrical projecting portion 61 (FIG. 9) in the fourth embodiment is moved to the outer peripheral side of the end bracket 6, as shown in FIG. To
In order to fit the cylindrical portion 21b of the impeller casing 21, the fitting portion 6b previously formed on the end bracket 6 is fitted.
The bulging portion 6c formed integrally with the above is provided, and the other structure is the same as that of the fourth embodiment shown in FIG.

In this embodiment, the fitting portion 6b of the end bracket 6 has the same height (in FIG. 11) as the bulging portion 6c over the entire circumference, as shown in FIG. It is made, and the fitting portion 6b provides a positioning function over the entire circumference. Portion of the stud bolt 5 that serves as an implantation hole, that is, a bulge portion 6c
Is formed in an ear shape inside the fitting portion 6b as shown in FIG. On the other hand, as shown in FIG. 13, the tubular member 7 has a cross-sectional shape of an ear shape protruding from the outer periphery of the return portion 4.

In the case of the above-mentioned fourth embodiment, the fitting portion 6b
It is necessary to process the cylindrical protrusion 61 and the cylindrical protrusion 61 separately, which requires a lot of man-hours. However, in the fifth embodiment, the fitting portion 6b is used.
Since the bulging portion 6c and the bulging portion 6c have the same height, the cutting process only needs to be performed once, and the number of steps can be reduced. Further, in this embodiment, since the positions of the stud bolt 5 and the bulging portion 6c are far from the outlet of the impeller 12, it is possible to obtain a reduction in flow loss and a reduction in noise.

As is apparent from FIG. 1, according to the embodiment of the present invention, the discharge port 6a of the end bracket 6 is formed.
Therefore, as shown by an arrow 3, a fluid (air) is jetted out, and this fluid flows along the outer peripheral surface of the electric motor 8. Therefore, according to this embodiment, the effect of cooling the electric motor 8 by the flow of the fluid can be obtained, and as a result, the effect of reducing the size and weight of the electric motor 8 can be expected.
At this time, an appropriate cover may be provided or a cooling fin may be provided so that the air ejected from the discharge port 6a flows sufficiently along the outer peripheral surface of the electric motor 8.
According to these, an even greater cooling effect can be obtained.

[0054]

According to the present invention, the following effects can be obtained. Since it is not affected by the shape accuracy of the impeller casing, the stacking tolerance in the axial direction can be kept low, and since each part is positioned directly from the end bracket end face by the stud bolt, the assembly accuracy in the radial direction can be improved. Deterioration can be suppressed, and the gap between the shaft hole and the shaft can be reduced, so that the improvement of the blower performance due to the reduction of leak flow can be sufficiently obtained.

Since the stud bolts extending from the end brackets are used, the return portion is separately fixed inside the impeller casing, and therefore the impeller casing is made into a thin casing structure such as a pressed product of a plate material. However, the impeller casing and the return part can be reliably fixed. Further, since a thin casing can be adopted, cost reduction and size and weight reduction can be obtained.

Since the stud bolt takes charge of the fixing force required for mounting the impeller casing, the casing material has little settling and the casing is internally fixed, so that the casing can be miniaturized. Rigidity of the impeller casing is higher than when it is fixed on the outer peripheral side, and a structure that does not vibrate is obtained.Furthermore, the impeller casing can be easily removed, and a compact and lightweight structure that allows for easy maintenance is obtained. To be

Further, since the same stud bolt is used for fixing, the number of working steps is small, and at the time of assembling, the stud bolt is set up in advance and the assembling work is carried out. Therefore, the assembling workability is improved.

[Brief description of drawings]

FIG. 1 is a side view with a partial cross-section showing a first embodiment of an electric centrifugal blower according to the present invention.

FIG. 2 is a side view with a partial cross section showing an example of an electric centrifugal blower according to a conventional technique.

FIG. 3 is a partial cross-sectional view showing another example of the electric centrifugal blower according to the conventional technique.

FIG. 4 is a partial cross-sectional view for explaining a leak of the centrifugal blower.

FIG. 5 is a perspective view of a return unit used in an embodiment of the present invention.

FIG. 6 is an exploded perspective view showing a first embodiment of the electric centrifugal blower according to the present invention.

FIG. 7 is an enlarged view showing a part of a return section in the second embodiment of the electric centrifugal blower according to the present invention.

FIG. 8 is a partial cross-sectional view showing a third embodiment of the electric centrifugal blower according to the present invention.

FIG. 9 is a partial sectional view showing a fourth embodiment of the electric centrifugal blower according to the present invention.

FIG. 10 is an enlarged view showing a part of an end bracket in a fourth embodiment of the electric centrifugal blower according to the present invention.

FIG. 11 is a partial cross-sectional view showing a fifth embodiment of the electric centrifugal blower according to the present invention.

FIG. 12 is an enlarged view showing a part of an end bracket in a fifth embodiment of the electric centrifugal blower according to the present invention.

FIG. 13 is an enlarged view showing a part of a return section in the fifth embodiment of the electric centrifugal blower according to the present invention.

[Explanation of symbols]

 1, 11 Impeller 2, 21 Impeller casing 3 Arrow indicating fluid flow 4 Return part 5 Stud bolt 6 End bracket 7, 71 Cylindrical member 8 Electric motor

Claims (4)

[Claims] 1. At least two impellers each included
A multi-stage electric centrifugal blower comprising a plurality of impeller casings and sequentially stacking these at least two impeller casings on an end bracket of an electric motor, wherein the end bracket has a surface opposite to the electric motor. At least two stud bolts extending parallel to the rotation axis of the impeller and penetrating the bottom portion of the impeller casing on the outer peripheral side of the impeller, and attaching the impeller casing to the end bracket by attaching the at least two stud bolts to the end bracket. An electric centrifugal blower characterized by being configured with stud bolts. 2. The invention according to claim 1, wherein the positioning of the impeller casing with respect to the end bracket in the rotation axis direction is provided by a tubular member inserted into the stud bolt. An electric centrifugal blower characterized in that. 3. The electric centrifugal blower according to claim 2, wherein the tubular member is formed by a part of a return member arranged inside the impeller casing. 4. The invention according to claim 2, wherein among the cylindrical members, a member arranged between the end bracket and the impeller casing is integrally formed with the end bracket. A characteristic electric centrifugal blower.