CN220302366U - Electric fan - Google Patents

Abstract

The application discloses an electric fan, which comprises a shell with a bearing chamber and a storage chamber, a stator and rotor assembly positioned in the storage chamber, a bearing positioned in the bearing chamber, a rotating shaft with one end part penetrating through the bearing, a fan cover positioned at the front side of the shell, a first movable impeller positioned at the inner side of the fan cover and fixedly connected with the rotating shaft, and an exhaust port communicated with the outside; the device is characterized in that a second impeller is fixedly connected to one end part of the rotating shaft, the second impeller is positioned between the bearing chamber and the first impeller, the second impeller is provided with an inlet end and an outlet end, the inlet end faces the bearing chamber, the outlet end is in fluid communication with the exhaust port, and the second impeller is configured to generate a positive pressure area near the outlet end for preventing working wind flowing out of the first impeller from flowing towards the bearing chamber when being driven to rotate; according to the scheme of the electric fan, working wind carrying liquid can be effectively prevented from flowing towards the position where the bearing is located, and the electric fan is safer to use.

Description

Electric fan

Technical Field

The application relates to the technical field of electric fans, in particular to a dry-wet electric fan for cleaning equipment.

Background

When the wet and dry electric fan in the cleaning electric appliance industry works, working air with water vapor or water drops is isolated from the inside of the motor main body; this can lead to water resistance problems for wet and dry cleaners.

The shaft in the rotor assembly, typically occurring both in the region of the working wind and inside the motor body; the bearing arranged on the rotating shaft is a weak link in the whole waterproof process; in the practical use of test and product, the fan damages the bearing water damage the most, i.e. the working wind with steam or water drops enters the motor main body through the bearing.

In the existing dry-wet dual-purpose electric fan, the waterproof treatment method of the bearing is generally as follows: firstly, an oil seal is arranged at the front part of a bearing, the interference fit of a rotating shaft and an oil seal hole is utilized to achieve a waterproof effect, and the rotating shaft is a rotating part, the oil seal is a static part, so that the relative movement speed between the rotating shaft and the oil seal is high, and in addition, the pressure difference exists at the two sides of the oil seal, so that the waterproof requirement of the whole life cycle of the electric fan is hardly met; secondly, the rotating shaft and the bracket through hole are in small clearance fit, and grease is filled in the rotating shaft and the bracket through hole; the functions of small clearance fit and grease filling are respectively as follows: the front end of the bearing is decompressed, sealed and lubricated; however, under the working condition of using the cleaning agent, grease is gradually cleaned by the cleaning agent solution, and the waterproof requirement of the whole life cycle of the electric fan cannot be met; thirdly, the maze is waterproof; the bushing and the bracket are matched with each other to form a labyrinth structure; the pressure difference between the front and the rear of the bearing can be greatly reduced, but the labyrinth is essentially a communicated structure, and water can still be 'twisted' through the labyrinth by a water film form after long-time operation.

The waterproof method generally adopted above can play a waterproof effect under certain time or working condition, but once water enters the front end of the bearing, the water can be collected at the front end of the bearing and finally damage the bearing because of no outlet, and once the water passes over the bearing, the service life of the electric fan is finished.

Disclosure of Invention

In order to solve the problem that the waterproof effect of the bearing in the prior art cannot reach the expectations, the purpose of the application is to provide an electric fan with reliable waterproof effect of the bearing.

In order to achieve the above purpose, the present application adopts the following technical scheme: an electric fan comprises a shell provided with a bearing chamber and a containing chamber, a stator and rotor assembly positioned in the containing chamber, a bearing positioned in the bearing chamber, a rotating shaft with one end penetrating through the bearing, a fan cover positioned at the front side of the shell, a first movable impeller positioned at the inner side of the fan cover and fixedly connected with the rotating shaft, and an exhaust port communicated with the outside; the rotary shaft is characterized in that a second movable impeller is fixedly connected to one end of the rotary shaft, the second movable impeller is located between the bearing chamber and the first movable impeller, the second movable impeller is provided with an inlet end and an outlet end, the inlet end faces the bearing chamber, the outlet end is in fluid communication with the exhaust port, and the second movable impeller is configured to generate a positive pressure area near the outlet end for preventing working wind flowing out of the first movable impeller from flowing towards the bearing chamber when being driven to rotate.

According to the scheme, the second movable impeller is additionally arranged between the bearing chamber of the electric fan and the first movable impeller, and a positive pressure area for preventing working wind from flowing towards the bearing chamber is generated near the outlet end of the second movable impeller through rotary acting, so that the bearing chamber can be protected by the positive pressure area, namely, when the electric fan works, moist working wind or water solution cannot enter the bearing through the positive pressure area; and even after the electric fan is stopped, in certain extreme cases, liquid enters the area, and when the electric fan is started next time, the second movable impeller can apply work to quickly remove the liquid, so that the situation that more liquid is accumulated is avoided.

In a specific embodiment, the first impeller is configured to be driven to rotate to generate a first positive pressure greater than atmospheric pressure at a region proximate to the second impeller, the positive pressure region having a second positive pressure, the second positive pressure being at least 30Pa greater than the first positive pressure. The differential force values of the first and second positive pressures provided in this embodiment are such that the working wind does not cross the second impeller and enter the region of the bearing chamber.

In a specific embodiment, the casing includes a front end wall and a rear end wall, the bearing chamber is located at the front end wall, the rear end wall is provided with a plurality of heat dissipation air inlets communicated with the outside atmosphere, the front end wall is provided with a plurality of heat dissipation air outlets communicated with the storage chamber, and the inlet end is close to the plurality of heat dissipation air outlets. The position design scheme of a plurality of heat dissipation wind outlets, heat dissipation wind outlets and with the entry end that provide in this embodiment for under the effect of second impeller, the indoor heat dissipation air current of accomodating of flow through can flow to the gas vent via the exit end, thereby make the electric fan structure of this example can satisfy waterproof and radiating dual demand simultaneously.

In a specific embodiment, the plurality of cooling air outlets are located at the bearing chamber. The design scheme of the heat dissipation air outlets provided in the embodiment can be completed together with the step of processing the bearing chamber, and is simple to manufacture.

In a specific embodiment, the electric fan further comprises a side passage, and the outlet end is in fluid communication with the exhaust port through the side passage. The side channel solution provided in this embodiment enables the air flow out of the side channel to flow out of the exhaust port together with the working wind.

In a specific embodiment, the electric fan further comprises a diffuser, the diffuser being located downstream of the first impeller; an exhaust passage is arranged between the diffuser and the exhaust port, and the side passage is connected with the exhaust passage. The diffuser provided in this embodiment can collect and guide the working wind flowing through the first impeller to the exhaust passage; the design scheme of the side channel and the exhaust channel enables the electric fan to generate negative pressure between the side channel and the exhaust channel when in operation, thereby further helping the airflow flowing out from the outlet end of the second movable impeller to flow to the exhaust channel.

In a specific embodiment, a second diffusion vane is disposed in the exhaust passage, and the junction between the side passage and the exhaust passage is located upstream of the second diffusion vane. The second diffuser vane arrangement provided in this embodiment is capable of simultaneously collecting and directing the working wind flowing through the first impeller and the heat dissipating airflow flowing through the second impeller toward the exhaust.

In a specific embodiment, the housing includes a front bracket having an inner side wall and an outer side wall, the hood is abutted to a front end of the outer side wall, at least a portion of the receiving chamber is located inside the inner side wall, the diffuser and the exhaust port are both located inside the outer side wall and the exhaust port is located at a rear side of the diffuser, and at least a portion of the side passage is defined by the diffuser and the inner side wall.

In a specific embodiment, the first movable impeller comprises a first end plate, a second end plate opposite to the first end plate, and a plurality of first movable blades positioned between the first end plate and the second end plate; the second movable impeller comprises a third end plate, a central column protruding backwards from the central part of the third end plate, an axial check ring extending towards the rear side from the outer edge of the third end plate, a plurality of second movable blades positioned on the inner side of the axial check ring and an opening opposite to the third end plate, and the central column is fixedly connected with the rotating shaft.

In a specific embodiment, the first impeller and the second impeller are an integral component.

In a specific embodiment, the rotating shaft outputs a total shaft power to the outside when being driven to rotate, and the shaft power consumed by the second movable impeller when being driven to rotate is not more than 10% of the total shaft power. In this embodiment, by limiting the shaft power of the second impeller, it reduces the impact on the performance of the first impeller due to the addition of the second impeller.

Other advantages of the present utility model will be apparent from the following detailed description of the utility model when taken in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a front view of an electric fan according to an embodiment of the present application;

FIG. 2 is a front cross-sectional view of the electric blower of FIG. 1;

FIG. 3 is an exploded view of the electric fan of FIG. 1; wherein the front bracket is partially cut;

fig. 4 is a perspective view of a front bracket according to an embodiment of the present application at a rear-to-front viewing angle;

fig. 5 is a perspective view of a front bracket according to an embodiment of the present application at a front-to-rear viewing angle;

fig. 6 is a front cross-sectional view of a front bracket provided in an embodiment of the present application;

FIG. 7 is a perspective view of a diffuser according to an embodiment of the present disclosure;

FIG. 8 is a second perspective view of a diffuser according to an embodiment of the present disclosure;

FIG. 9 is a perspective view of a second impeller according to an embodiment of the present disclosure;

fig. 10 is a perspective view of an integrated design of a first impeller and a second impeller according to an embodiment of the present disclosure;

FIG. 11 is a front cross-sectional view of a first movable impeller, a second movable impeller, a diffuser, and a front support according to an embodiment of the present disclosure;

fig. 12 is an enlarged view of fig. 11 at a;

fig. 13 is a schematic flow diagram of working wind and heat dissipation airflow of an electric fan in operation according to an embodiment of the present application;

fig. 14 is an enlarged view of fig. 13 at B.

Wherein: 100. an electric fan; 10. a housing; 11. a storage chamber; 1. a front bracket; 2. a rear bracket; 3. a rear end cover; 41. a stator-rotor assembly; 42. a control board; 43. a rotating shaft; 44. a bearing; 5. a diffuser; 6. a fan housing; 7. a first impeller; 8. a second impeller; 31. a rear end wall; 32. a heat dissipation wind inlet; 33. a wiring hole; 61. a working wind suction port; 71. a first end plate; 72. a second end plate; 73. a first rotor blade; 12. a front end wall; 13. an inner sidewall; 14. an outer sidewall; 15. a second diffuser vane; 90. an exhaust port; 91. an exhaust passage; 16. a bearing chamber; 161. a heat radiation air outlet; 162. a through groove; 51. a diffusion bracket; 52. a first diffuser vane; 53. an axial collar; 81. a third end plate; 82. a center column; 83. an axial retainer ring; 84. a second rotor blade; 85. an opening; 801. an inlet end; 802. an outlet end; 50. a diffusion passage; 92. side channels.

Detailed Description

In order to describe the technical content, constructional features, objects and effects of the application in detail, the technical solutions of the embodiments of the application will be described in conjunction with the accompanying drawings in the embodiments of the application, and it is apparent that the described embodiments are only some embodiments of the application, not all embodiments. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a detailed description of various exemplary embodiments or implementations of the utility model. However, various exemplary embodiments may be practiced without these specific details or with one or more equivalent arrangements. Furthermore, the various exemplary embodiments may be different, but are not necessarily exclusive. For example, the specific shapes, configurations, and characteristics of the exemplary embodiments may be used or implemented in another exemplary embodiment without departing from the inventive concept.

Hereinafter, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

The terms "front", "back" and "front and back" as used herein refer to the front and back as shown in FIG. 1.

In the present application, unless explicitly specified and limited otherwise, the term "coupled" is to be construed broadly, and for example, "coupled" may be either fixedly coupled, detachably coupled, or integrally formed; can be directly connected or indirectly connected through an intermediate medium.

The present application provides an electric fan that can be used with either a dry cleaning machine or a wet cleaning apparatus that uses a cleaning fluid to clean a surface; and is particularly suited for use with wet cleaning apparatus.

Referring to fig. 1 to 3, there is illustrated an electric fan 100, and the electric fan 100 includes a casing 10 composed of a front bracket 1, a rear bracket 2, and a rear cover 3, a stator-rotor assembly 41, a control board 42, a rotating shaft 43, a bearing 44, a diffuser 5, a fan housing 6, a first moving impeller 7, and a second moving impeller 8.

The housing 10 has a housing 11, and the stator/rotor assembly 41, the control board 42 and a part of the rotating shaft 43 are located in the housing 11. The bearing 44, the first impeller 7 and the second impeller 8 are all connected to the front portion of the rotating shaft 43. The inside of the fan housing 6 is located at the front side of the casing 10, the first impeller 7 is located inside the fan housing 6, and the second impeller 8 is located between the first impeller 7 and the bearing 44.

The rear end cover 3 includes a rear end wall 31, and a plurality of heat dissipation air inlets 32 communicating with the outside atmosphere are formed in the rear end wall 31. The inside and the outside of the housing chamber 11 can be penetrated through the heat radiation air inlets 32. The middle part of the rear end cover 3 is also provided with a wiring hole 33 through which the power supply connection wires pass.

The fan housing 6 has an integrated housing structure, and has a working air intake port 61 at its front end. When the first impeller 7 rotates, external working air flows into the first impeller 7 through the working air intake port 61.

The first moving impeller 7 includes a first end plate 71 and a second end plate 72 arranged one behind the other, and a plurality of circumferentially arranged first moving blades 73 between the first end plate 71 and the second end plate 72.

Referring to fig. 4, 5 and 6, a front bracket 1 is illustrated. The front bracket 1 is cylindrical and includes a front end wall 12, an inner side wall 13, an outer side wall 14, and a second diffuser vane 15. The second diffuser vane 15 is located between the inner and outer sidewalls 13 and 14. The front bracket 1 has an exhaust port 90 communicating with the outside atmosphere, and the exhaust port 90 is located at the rear end portions of the inner side wall 13 and the outer side wall 14. An exhaust passage 91 is formed between the inner sidewall 13 and the outer sidewall 14 that extends forward and aft to the exhaust port 90 and past the second diffuser vane 15. The front end wall 12 has a bearing chamber 16 in the middle thereof, and a bearing 44 is mounted in the bearing chamber 16. The bearing chamber 16 has a plurality of heat radiation air outlets 161 formed in the inner wall thereof and arranged in the circumferential direction, and the inside and the outside of the housing chamber 11 can be penetrated through the heat radiation air outlets 161. The front surface of the front end wall 12 and the outer surface of the inner side wall 13 are further provided with a plurality of through grooves 162 arranged in the circumferential direction, and these through grooves 162 communicate fluid into the exhaust passage 91.

Referring to fig. 7-8, a diffuser 5 is illustrated. The diffuser 5 is located downstream of the first movable impeller 7 and includes an annular diffuser bracket 51, first diffuser vanes 52 located at the periphery of the diffuser bracket 51, and an axial collar 53 integrally formed on the diffuser bracket 51.

Referring to fig. 9, a second impeller 8 is schematically shown. The second moving impeller 8 includes a third end plate 81, a center post 82 protruding rearward from a center portion of the third end plate 81, an axial check ring 83 extending from an outer edge of the third end plate 81 toward the rear side, a plurality of second moving blades 84 located inside the axial check ring 83, and an opening 85 opposite to the third end plate 81. The center post 82 will be fixedly connected to the front end of the spindle 43. The second rotor wheel 8 has an inlet end 801 and an outlet end 802 located inside and outside the second rotor blade 84. When the second impeller 8 rotates, a negative pressure region will be formed near the inlet end 801, a positive pressure region will be formed near the outlet end 802, and air flow can flow from the inlet end 801 to the outlet end 802.

The second impeller 8 adopted in the example is a semi-open centrifugal impeller; indeed, in other embodiments, the second impeller may be a mixed flow impeller, and the impeller may be closed or open. The second movable impeller can be independent or integrally designed with the first movable impeller.

Referring to fig. 10, an example of integrally designing the first impeller 7 and the second impeller 8 is illustrated. In this example, the first impeller 7 and the second impeller 8 are constructed as an integral member, and the second end plate 72 of the first impeller 7 is fixed integrally with the third end plate 81 of the second impeller 8.

As further shown in fig. 2, the front end of the fan housing 6 abuts against the first end plate 71 of the first impeller 7, and the rear end of the fan housing 6 abuts against the front end of the outer sidewall 14.

The second impeller 8 is located on the front side of the front end wall 12 with the inlet end 801 facing the bearing 44, the bearing chamber 16 and the plurality of cooling air outlets 161 and the outlet end 802 abutting the through slot 162.

Between the diffuser 5 and the outer side wall 14, a diffuser passage 50 is formed from front to rear, and the diffuser passage 50 is located upstream of the exhaust passage 91. The working air flowing out of the first movable vane 7 can first enter the diffuser passage 50 and then flow to the exhaust passage 91. Due to the presence of the through slot 162, the diffuser bracket 51 forms a side passage 92 with the front end wall 12 and the inner side wall 13. The side channel 92 will communicate the outlet end 802 with the exhaust channel 91, i.e. will be able to divert the flow of air flowing out from the outlet end 802 to the exhaust channel 91. In this example, the junction between the side passage 92 and the exhaust passage 91 is located upstream of the second diffuser vane 15, that is, the air flow flowing into the exhaust passage 91 from the side passage 92 merges with the working air flowing out of the diffuser passage 50, and is first diffused by the second diffuser vane 15 and then discharged from the exhaust port 90.

The front end of the rear bracket 2 is connected with the rear end of the inner side wall 13, and the rear end cover 3 covers the rear opening of the rear bracket 2.

In other embodiments, the side channel may not directly interface with the exhaust channel, but the end of the side channel may be directly introduced into the upstream diffusion channel, or even directly introduced into the air outlet of the first impeller; the side channel for discharging the heat dissipation air flow is led to the junction with the path for discharging the working air, so that when the working air flows, negative pressure is generated at the junction of the side channel and the path for discharging the working air (such as the junction of the side channel 92 and the exhaust channel 91), thereby further helping the flow of the heat dissipation air flow. In other embodiments, a side channel or the like may not be provided, but the heat dissipation air flow flowing out from the outlet end of the second movable impeller may flow to the area with low pressure, that is, the heat dissipation air flow may be discharged from the exhaust port together with the working air after being combined, or may be discharged independently.

In other embodiments, the cooling air outlet may not be provided, but the inlet end of the second moving impeller is in fluid communication with the external air through a separate channel, and when the second moving impeller rotates, the external air is continuously sucked into the inlet end; the scheme of the embodiment is particularly suitable for the situation that the corresponding parts in the shell do not need to be radiated by utilizing radiating airflow; such as the case where the electric fan is arranged with a highly efficient heat dissipation housing.

As shown in fig. 11-12, the front bracket 1, the fan housing 6, the first impeller 7, the second impeller 8, and the diffuser 5 are assembled together.

The diffuser 5 is fixedly arranged on the inner side of the outer side wall 14; the axial collar 53 is located at the periphery of the axial collar 83. The outlet end 802 of the second impeller 8 faces the through slot 162.

In order to reduce interference of the axial collar 53 with the rotation of the second impeller 8, a clearance fit is preferably provided between the axial collar 53 and the axial collar 83.

The axial collar 53 and the axial collar 83 used in this example are located on the stationary diffuser 5 and the rotating second moving impeller 8, respectively, and cooperate with each other. In other embodiments, the functional components bearing the axial collar and the axial collar may also be arranged entirely on the stationary component, for example as part of the diffuser or front support; or all arranged on the rotating member; in some embodiments of the electric fan, these functional components may also be omitted, where the pressure generated by the work done by the second impeller is required to be sufficient to balance the pressure generated by the first impeller of the electric fan in the vicinity of the second impeller; such as in a radial air-out electric fan.

In order to enable the first impeller 7 to maintain a certain vacuum pumping capacity, it is assumed that the rotating shaft 43 is capable of outputting a total shaft power P to the outside when driven to rotate by the stator assembly in the stator-rotor assembly 41, and the shaft power P1 consumed when the second impeller 8 is driven to rotate is preferably not more than 10%, such as 8%, 5%, etc., of the total shaft power P.

In addition, the second impeller 8 is configured such that, when driven to rotate by the rotating shaft 43, the positive pressure region pressure formed near the outlet end 802 is sufficient to prevent the working wind flowing out from the first impeller 7 from flowing toward the bearing chamber 16. Assuming that the first impeller 7 is configured to be driven in rotation to generate a first positive pressure P1 greater than atmospheric pressure at a region proximate to the second impeller 8 (e.g., a region proximate to or near the outlet end 802), the positive pressure region pressure formed proximate to the outlet end 802 is a second positive pressure P2, the second positive pressure P2 preferably being at least 30Pa greater than the first positive pressure P1; such as 50Pa,80Pa, or even 100Pa.

As shown in fig. 13 and 14, the electric fan 100 is shown in operation, in which the working air and the heat dissipation air flow in the electric fan 100; wherein the flow path of the working wind is a path shown by a hollow arrow; the flow path of the heat dissipation air flow is a path shown by a solid arrow; the method comprises the following steps:

when the rotating shaft 43 of the electric fan 100 rotates under the action of the stator and rotor assembly 41, the first movable impeller 7 and the second movable impeller 8 are driven to rotate at the same time; wherein, the rotation of the first movable impeller 7 will make the external working wind enter the first movable impeller 7 through the working wind suction inlet 61, then flow from the first movable impeller 7 and enter the diffuser 5, continue to flow to the rear exhaust channel 91 after being diffused in the diffusion channel 50 of the diffuser 5, and be discharged from the exhaust port 90 after being secondarily diffused in the exhaust channel 91; at the same time, the rotation of the second impeller 8 will form a negative pressure zone at the inlet end 801 facing the cooling air outlet 161 and a positive pressure zone at the butt-joint through groove 162; in this case, the air in the housing chamber 11 will continuously flow from the cooling air outlet 161 to the inlet end 801, and the outside air will only enter the housing chamber 11 through the cooling air inlet 32, and after passing through the control board 42 and the stator-rotor assembly 41, will further flow to the inlet end 801 through the cooling air outlet 161, so that a flowing cooling air flow is formed among the cooling air inlet 32, the housing chamber 11 and the cooling air outlet 161; the heat radiation air flow entering the inlet end 801 continuously flows towards the outlet end 802 and then flows into the side channel 92 from the through groove 162, and the heat radiation air flow further flows towards the exhaust channel 91 due to the pressure effect of the heat radiation air flow, so that the heat radiation air flow is combined with working air and flows towards the exhaust port 90 together; during the flow of working wind and heat dissipating air, working wind does not flow over the second impeller 8 to the bearing 44 due to the presence of the positive pressure region near the outlet end 802 of the second impeller 8.

The rotating second moving impeller 8 will form a "moving seal" effect on the front side of the bearing chamber 16, thereby effectively preventing the working air from flowing to the vicinity of the bearing chamber 16, and the rotating second moving impeller 8 will simultaneously cause the heat radiation air flow to continuously flow through the control board 42 and the stator-rotor assembly 41 and the like in the housing chamber 11, thereby achieving heat radiation of the control board 42 and the stator-rotor assembly 41.

Therefore, the second movable impeller is arranged at the front end of the bearing of the electric fan, a relatively independent acting area is formed at the front side of the bearing by the second movable impeller, a positive pressure area and a negative pressure area are generated in the area, the pressure of the positive pressure area is larger than that of the adjacent area generated by the first movable impeller, and when the electric fan works, moist working wind or water solution cannot enter the bearing through the relatively independent acting area due to the existence of the pressure difference; even after the electric fan is stopped, in certain extreme cases, liquid enters the area, and when the electric fan is started up next time, the electric fan can be rapidly discharged into the exhaust channel through the side channel by applying work through the second movable impeller, so that the situation that more liquid is accumulated is avoided. In addition, due to the existence of the negative pressure area, flowing heat dissipation airflow is formed among the heat dissipation air inlet, the accommodating chamber and the heat dissipation air outlet, so that heat generated on the control panel and the stator and rotor assembly is taken away; therefore, the design of the scheme can simultaneously meet the dual requirements of water resistance and heat dissipation.

The foregoing has outlined and described the basic principles, main features and advantages of the present application. It will be appreciated by persons skilled in the art that the present application is not limited to the embodiments described above, and that the embodiments and descriptions described herein are merely illustrative of the principles of the application, and various changes and modifications may be made therein without departing from the spirit and scope of the application, which is defined in the appended claims, specification and their equivalents.

Claims (11)

1. An electric fan comprises a shell provided with a bearing chamber and a containing chamber, a stator and rotor assembly positioned in the containing chamber, a bearing positioned in the bearing chamber, a rotating shaft with one end penetrating through the bearing, a fan cover positioned at the front side of the shell, a first movable impeller positioned at the inner side of the fan cover and fixedly connected with the rotating shaft, and an exhaust port communicated with the outside; the rotary shaft is characterized in that a second movable impeller is fixedly connected to one end of the rotary shaft, the second movable impeller is located between the bearing chamber and the first movable impeller, the second movable impeller is provided with an inlet end and an outlet end, the inlet end faces the bearing chamber, the outlet end is in fluid communication with the exhaust port, and the second movable impeller is configured to generate a positive pressure area which can prevent working wind flowing out of the first movable impeller from flowing towards the bearing chamber near the outlet end when being driven to rotate.

2. The electric fan of claim 1, wherein the first impeller is configured to be driven to rotate to generate a first positive pressure greater than atmospheric pressure at a region proximate the second impeller, the positive pressure region having a second positive pressure, the second positive pressure being at least 30Pa greater than the first positive pressure.

3. The electric fan as claimed in claim 1, wherein the housing includes a front end wall and a rear end wall, the bearing chamber is located at the front end wall, the rear end wall is provided with a plurality of heat dissipation air inlets communicating with the outside atmosphere, the front end wall is provided with a plurality of heat dissipation air outlets communicating with the storage chamber, and the inlet end is close to the plurality of heat dissipation air outlets.

4. An electric fan as claimed in claim 3, wherein said plurality of cooling air outlets are located at said bearing housing.

5. The electric fan of claim 1, further comprising a side passage, wherein the outlet port is in fluid communication with the exhaust port via the side passage.

6. The electric fan of claim 5, further comprising a diffuser, the diffuser being downstream of the first impeller; an exhaust passage is arranged between the diffuser and the exhaust port, and the side passage is connected with the exhaust passage.

7. The electric fan as claimed in claim 6, wherein a second diffuser is disposed in the exhaust passage, and the junction of the side passage and the exhaust passage is located upstream of the second diffuser.

8. The electric fan of claim 6, wherein the housing includes a front frame having an inner side wall and an outer side wall, the hood is abutted against a front end of the outer side wall, at least a portion of the receiving chamber is located inside the inner side wall, the diffuser and the exhaust port are both located inside the outer side wall and the exhaust port is located on a rear side of the diffuser, and at least a portion of the side passage is defined by the diffuser and the inner side wall.

9. The electric fan of claim 1, wherein the first rotor comprises a first end plate, a second end plate opposite the first end plate, and a plurality of first rotor blades positioned between the first end plate and the second end plate; the second movable impeller comprises a third end plate, a central column protruding backwards from the central part of the third end plate, an axial check ring extending towards the rear side from the outer edge of the third end plate, a plurality of second movable blades positioned on the inner side of the axial check ring and an opening opposite to the third end plate, and the central column is fixedly connected with the rotating shaft.

10. The electric fan as claimed in claim 1 or 9, wherein the first impeller and the second impeller are an integral member.

11. The electric fan as claimed in claim 1, wherein the rotation shaft is driven to rotate to output a total shaft power to the outside, and the shaft power consumed by the second impeller is driven to rotate is not more than 10% of the total shaft power.