Direct-current brushless motor and positive and negative rotation electric fan
By using independent position sensors in DC brushless motors to work separately when the rotor is forward and reversed, the problems of low efficiency and abnormal start during reversal are solved, and efficient forward and reversed are achieved. Reversal.
Patent Information
- Application Number
- CN202323584072.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-26
- Publication Date
- 2025-01-10
- Estimated Expiration
- 2033-12-26
AI Technical Summary
Existing single-phase brushless motors usually sacrifice the working efficiency of forward rotation when achieving reversal, and the reversal speed is low, and even problems with abnormal start may occur.
A DC brushless motor is designed, and the at least one first position sensor is respectively in the working state when the rotor is forward and the at least one second position sensor is in the working state when the rotor is reversed, and the setting positions of the two sensors can be designed with reference to a single direction. , thereby achieving reversal while ensuring the forward working efficiency.
It realizes fan reversal while ensuring the forward working efficiency of the fan, and ensures the stability of reversal start-up and reversal working efficiency.
Smart Images
Figure CN222339287U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of power electronics, in particular to a brushless DC motor and a forward and reverse electric fan. Background Art
[0002] As the operating power of the whole machine increases, the air volume required for heat dissipation becomes larger and larger. When the whole machine is used outdoors, there will be debris such as catkins and cotton wool in the environment. These debris will be adsorbed on the surface of the heat sink or block the fan port, resulting in poor heat dissipation effect, and after a long time, the whole machine may cause derating.
[0003] In order to improve the dust accumulation of the whole machine, a fan capable of forward and reverse rotation is introduced to remove dust from the whole machine; however, for a fan using a single-phase DC brushless motor, achieving both forward and reverse rotation functions usually sacrifices the working efficiency during forward rotation, and the reverse rotation speed is also lower, and there may even be problems such as abnormal startup during reverse rotation.
[0004] Therefore, how to achieve fan reverse rotation while ensuring the working efficiency of the fan in forward rotation is a technical problem that needs to be solved urgently. Utility Model Content
[0005] In view of this, the utility model provides a brushless DC motor and a forward and reverse electric fan, so as to achieve the reverse rotation of the fan while ensuring the working efficiency of the forward rotation of the fan.
[0006] To achieve the above purpose, the present invention provides the following technical solutions:
[0007] On one hand, the present application provides a brushless DC motor, comprising: a motor body, a motor drive controller, at least one first position sensor and at least one second position sensor; wherein:
[0008] The output end of the motor drive controller is connected to the input end of the motor body;
[0009] The output end of the first position sensor and the output end of the second position sensor are respectively connected to the signal input end of the motor drive controller;
[0010] The first position sensor and the second position sensor both correspond to the silicon steel sheets of the stator in the motor body;
[0011] The angle between the axial section of the stator passing through the first position sensor and the axial section of the stator passing through the center line of the corresponding silicon steel sheet is a first angle;
[0012] The angle between the axial section of the stator passing through the second position sensor and the axial section of the stator passing through the center line of the corresponding silicon steel sheet is a second angle;
[0013] The first angle is not equal to the second angle;
[0014] At least one of the first position sensors is in an operative state when the rotor in the motor body rotates forward, and at least one of the second position sensors is in an operative state when the rotor rotates reversely.
[0015] Optionally, the first angle is equal to the first angle;
[0016] The first angle is an angle at which the first position sensor can first detect a change in polarity of the rotor when the rotor rotates forward.
[0017] Optionally, if the outer diameters of the two ends of the silicon steel sheet are different, the first angle is equal to the angle between the axial section of the stator passing through the end with a larger outer diameter of the silicon steel sheet and the axial section of the stator passing through the center line of the corresponding silicon steel sheet.
[0018] Optionally, the first angle is equal to the second angle;
[0019] The second angle is an angle at which the second position sensor can first detect a change in polarity of the rotor when the rotor is reversed.
[0020] Optionally, if the outer diameters of the two ends of the silicon steel sheet are different, the second angle is equal to the angle between the axial section of the stator passing through the end with the smaller outer diameter of the silicon steel sheet and the axial section of the stator passing through the center line of the corresponding silicon steel sheet.
[0021] Optionally, if the electrical connection lines between the components in the brushless DC motor are integrated into a printed circuit board PCB, and the PCB is arranged below or above the stator, the first position sensor and the second position sensor are both arranged on the PCB.
[0022] Optionally, the first position sensor and the second position sensor are both arranged on the silicon steel sheet.
[0023] Optionally, the inverter in the motor controller is a three-phase inverter or a single-phase inverter.
[0024] Optionally, if the inverter is a single-phase inverter, the number of the first position sensor and the number of the second position sensor are both 1;
[0025] If the inverter is a three-phase inverter, the number of the first position sensors and the number of the second position sensors are both 3.
[0026] Optionally, the positive rotation of the rotor means that the rotor rotates in a clockwise direction;
[0027] The rotor reverses direction when the rotor rotates in a counterclockwise direction.
[0028] Optionally, the position sensor is a Hall sensor.
[0029] On one hand, the present application provides a forward and reverse electric fan, comprising: a brushless DC motor as described in any one of the previous aspects of the present application, and fan blades installed on the driving shaft of the brushless DC motor.
[0030] It can be seen from the above technical solution that the utility model provides a brushless DC motor. In the brushless DC motor, the angle between the axial section of the stator passing through the first position sensor and the axial section of the stator passing through the center line of the corresponding silicon steel sheet is the first angle, and the angle between the axial section of the stator passing through the second position sensor and the axial section of the stator passing through the center line of the corresponding silicon steel sheet is the second angle; since at least one first position sensor is in a working state when the rotor in the motor is rotating forward, and at least one second position sensor is in a working state when the rotor is reversed, and the first angle is not equal to the second angle, the setting positions of the two position sensors can be designed with reference to a single direction, that is, the rotor in the motor can use independent position sensors when rotating forward and reverse, so the brushless DC motor can achieve reverse rotation while ensuring the working efficiency of forward rotation, so that the fan using the brushless DC motor can achieve its own reverse rotation while ensuring its own working efficiency of forward rotation; in addition, the stability and reverse working efficiency of the fan using the brushless DC motor are also guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.
[0032] Figure 1 This is a schematic diagram of the placement of Hall sensors in a brushless DC motor;
[0033] Figure 2 , Figure 3 They are schematic diagrams of the structures of two implementation modes of the brushless DC motor provided in the present application;
[0034] Figure 4 A schematic diagram of a connection method of the position sensor 100 provided in the present application;
[0035] Figure 5 A schematic diagram of a placement method of the first position sensor 30 and the second position sensor provided in the present application;
[0036] Figure 6 A schematic diagram of another placement method of the first position sensor 30 and the second position sensor provided in the present application;
[0037] Figure 7 , Figure 8 They are schematic structural diagrams of two other implementation modes of the brushless DC motor provided in the present application. DETAILED DESCRIPTION
[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0039] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.
[0040] In the prior art, Figure 1 As shown, in the single-phase DC brushless motor, only one Hall sensor 04 is arranged on the silicon steel sheet 03 of the electron 01 in the single-phase DC brushless motor; usually, the setting position of the Hall sensor 04 is the position where the polarity change of the rotor 02 can be first detected when the rotor 02 rotates forward. Under this setting mode, the current direction can be switched in time, that is, the polarity of the stator or the rotor can be reversed in time, so that the working efficiency of the motor when it rotates forward is optimized; however, under this setting mode, when the motor reverses, the Hall sensor 04 will detect the polarity change of the rotor 02 last, resulting in untimely switching of the current direction, that is, untimely reversal of the polarity of the stator or the rotor, which in turn leads to the problem that the single-phase DC brushless motor cannot be reversed normally or the reverse start is abnormal; in order to reverse, the setting position of the Hall sensor 04 can be close to the position where the polarity change of the rotor 02 can be first detected when the rotor 02 reverses.
[0041] However, in this case, the Hall sensor 04 cannot first detect the polarity change of the rotor 02 when the rotor 02 rotates forward, and thus cannot switch the current direction in time, which leads to a decrease in the forward rotation efficiency of the single-phase DC brushless motor.
[0042] In order to achieve fan reverse rotation while ensuring the working efficiency of the fan in forward rotation, the embodiment of the present application provides a brushless DC motor, the specific structure of which can be seen in Figure 2 ( Figure 2 Only one first position sensor 30 and one second position sensor 40 are used as examples for demonstration) or Figure 3 ( Figure 3 Only three first position sensors 30 and three second position sensors 40 are used as examples for display), specifically including: a motor body 10, a motor drive controller 20, at least one first position sensor 30 and at least one second position sensor 40; the connection relationship between the components is specifically described as follows:
[0043] An output terminal of the motor driving controller 20 is connected to an input terminal of the motor body 10 .
[0044] The output end of the first position sensor 30 and the output end of the second position sensor 40 are connected to the signal input end of the motor drive controller 20 respectively.
[0045] In a specific example, if Figure 4 As shown, the positive pole of the power supply end of the position sensor 100 receives the power supply voltage VCC, the negative pole of the power supply end of the position sensor 100 is grounded, and the output end of the position sensor 100 is connected to the input end of the controller in the motor controller 20; a resistor R is arranged between the positive pole of the power supply end of the position sensor 100 and the output end of the position sensor 100; and a capacitor C is arranged between the negative pole of the power supply end of the position sensor 100 and the output end of the position sensor 100.
[0046] The above example only shows a specific connection method of the position sensor 100. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific situation, all of which are within the scope of protection of this application.
[0047] The first position sensor 30 and the second position sensor 40 both correspond to the silicon steel sheets 03 of the stator 01 in the motor body 10 .
[0048] If the number of the first position sensors 30 is equal to 1, the first position sensor 30 corresponds to any silicon steel sheet 03, for example, Figure 5 or Figure 6 As shown, Figure 5 or Figure 6 In the figure, only the stator 01 including four silicon steel sheets 03 and the brushless DC motor including a first position sensor 30 are taken as an example for demonstration.
[0049] If the number of the first position sensors 30 is greater than 1, each first position sensor 30 may correspond to a different silicon steel sheet 03 , or at least two first position sensors 30 may correspond to the same silicon steel sheet.
[0050] If the number of the second position sensors 40 is equal to 1, the second position sensor 40 corresponds to any silicon steel sheet 03, for example, Figure 5 or Figure 6 As shown, Figure 5 or Figure 6 In the illustration, only the stator 01 including four silicon steel sheets 03 and the brushless DC motor including a second position sensor 40 are taken as an example.
[0051] If the number of the second position sensors 40 is greater than 1, each second position sensor 40 may correspond to a different silicon steel sheet 03 , or at least two second position sensors 40 may correspond to the same silicon steel sheet.
[0052] It should be noted that Figure 5 or Figure 6 The S is the south pole of the magnetic field and the N is the north pole of the magnetic field.
[0053] In a specific example, the first position sensor 30 and the second position sensor 40 are both arranged on the silicon steel sheet 03 of the stator 01 in the motor body 10 .
[0054] It should be noted that the arrangement of the position sensor on the silicon steel sheet 03 is already a very mature arrangement method in the prior art, and how to arrange the position sensor on the silicon steel sheet 03 will not be described in detail here.
[0055] In another specific example, the electrical connection lines between the components in the brushless DC motor are integrated into a printed circuit board PCB, and the PCB is arranged below or above the stator 01, and the first position sensor 30 and the second position sensor 40 are both arranged on the PCB.
[0056] The above two examples show two configuration methods of the first position sensor 30 and the second position sensor 40 in the DC brushless motor, which are not specifically limited here and can be determined according to specific circumstances, and are all within the scope of protection of this application.
[0057] The angle between the axial section of the stator 01 passing through the first position sensor 30 and the axial section of the stator 01 passing through the center line of the corresponding silicon steel sheet 03 is the first angle.
[0058] The angle between the axial section of the stator 01 passing through the second position sensor 40 and the axial section of the stator 01 passing through the center line of the corresponding silicon steel sheet 03 is the second angle.
[0059] The first included angle is not equal to the second included angle.
[0060] For example, Figure 5 As shown in or 6, the first angle is α, and the second angle is θ, wherein the above angles are positive in the counterclockwise direction, that is, α is negative and θ is positive.
[0061] It should be noted that the distance between the position sensor and the center of the stator 01 can be set according to the internal space of the brushless DC motor, and is not specifically limited here.
[0062] The at least one first position sensor 30 is in an operating state when the rotor 02 in the motor body 10 rotates forward, and the at least one second position sensor 40 is in an operating state when the rotor 02 rotates reversely.
[0063] The position sensor being in a working state refers to a state when the position sensor is working normally, that is, the position sensor can perform position detection normally.
[0064] Optionally, the position sensor may be a Hall sensor. In practical applications, this includes but is not limited to this, which is not specifically limited here and may be determined according to specific circumstances, all of which are within the scope of protection of this application.
[0065] In this embodiment, since at least one first position sensor 30 is in a working state when the rotor 02 in the motor rotates forward, and at least one second position sensor 40 is in a working state when the rotor 02 is reversed, and the first angle is not equal to the second angle, the setting positions of the two position sensors can be designed with reference to a single direction, that is, the rotor 02 in the motor can utilize independent position sensors when rotating forward and reversely. Therefore, the DC brushless motor can achieve reverse rotation while ensuring the working efficiency of forward rotation, so that the fan using the DC brushless motor can achieve its own reverse rotation while ensuring its own forward rotation working efficiency; in addition, the stability of the reverse start-up and the reverse working efficiency of the fan using the DC brushless motor are also guaranteed.
[0066] Another embodiment of the present application provides a specific arrangement of the first position sensor 30. The specific position of the first position sensor 30 can be found in Figure 5 or Figure 6 .
[0067] The first included angle is equal to the first angle.
[0068] The first angle is the angle at which the first position sensor 30 can first detect the polarity change of the rotor 02 when the rotor 02 rotates forward.
[0069] In a specific example, the forward rotation of the rotor 02 means that the rotor 02 rotates in a clockwise direction, and the reverse rotation of the rotor 02 means that the rotor 02 rotates in a counterclockwise direction.
[0070] The above example only shows a specific implementation method of the forward and reverse rotation of the rotor 02. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific circumstances, all of which are within the scope of protection of this application.
[0071] In a specific example, the outer diameters of the two ends of the silicon steel sheet 03 are different, and the first angle is equal to the angle between the axial section of the stator 01 passing through the end with a larger outer diameter of the silicon steel sheet 03 and the axial section of the stator 01 passing through the center line of the corresponding silicon steel sheet 03, for example, Figure 5 or Figure 6 α in .
[0072] The above example only shows one implementation of the first angle, etc. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances and is within the scope of protection of this application.
[0073] The above is only a specific setting method of the first position sensor 30. In practical applications, it includes but is not limited to this. No specific limitation is made here and it can be determined according to the specific situation. All of them are within the protection scope of this application.
[0074] In this embodiment, since the first angle is the angle at which the first position sensor 30 can first detect the change in polarity of the rotor 02 when the rotor 02 rotates forward, the first position sensor 30 can first detect the change in polarity of the rotor 02 when the rotor 02 rotates forward, thereby first changing the current mode, that is, the polarity of the stator 01 or the rotor 02 is reversed first, thereby achieving the best working efficiency when the motor rotates forward, thereby avoiding a large working current peak of the DC brushless motor when rotating forward, and thus the forward rotation speed can be made higher.
[0075] Another embodiment of the present application provides a specific arrangement of the second position sensor 40. The specific position of the second position sensor 40 can be found in Figure 5 or Figure 6 .
[0076] The first angle is equal to the second angle.
[0077] The second angle is the angle at which the second position sensor 40 can first detect the polarity change of the rotor 02 when the rotor 02 reverses.
[0078] In a specific example, the forward rotation of the rotor 02 means that the rotor 02 rotates in a clockwise direction, and the reverse rotation of the rotor 02 means that the rotor 02 rotates in a counterclockwise direction.
[0079] The above example only shows a specific implementation method of the forward and reverse rotation of the rotor 02. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific circumstances, all of which are within the scope of protection of this application.
[0080] In a specific example, the outer diameters of the two ends of the silicon steel sheet 03 are different, and the second angle is equal to the angle between the axial section of the stator 01 passing through the end with a smaller outer diameter of the silicon steel sheet 03 and the axial section of the stator 01 passing through the center line of the corresponding silicon steel sheet 03, for example, Figure 5 or Figure 6 θ in .
[0081] The above example only shows one implementation of the second angle. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances and is within the scope of protection of this application.
[0082] The above is only a specific setting method of the second position sensor 40. In practical applications, it includes but is not limited to this. No specific limitation is made here and it can be determined according to the specific situation. All of them are within the protection scope of this application.
[0083] In this embodiment, since the second angle is the angle at which the second position sensor 40 can first detect the change in polarity of the rotor 02 when the rotor 02 reverses, the second position sensor 40 can first detect the change in polarity of the rotor 02 when the rotor 02 reverses, thereby being able to change the current first, i.e., the polarity of the stator 01 or the rotor 02 is reversed first, thereby achieving the best working efficiency when the motor is reversed, thereby avoiding a large working current peak of the brushless DC motor when it is reversed, and thus the reversal speed can be made higher; in addition, since the second position sensor 40 can first detect the change in polarity of the rotor 02 when the rotor 02 reverses, there is no dead angle problem with the brushless DC motor when the brushless DC motor is reversed and started.
[0084] Another embodiment of the present application provides a specific implementation of a motor controller, and its specific structure can be found in Figure 7 ( Figure 7 Only in Figure 2 or Figure 8 ( Figure 8 Only in Figure 3 , specifically comprising: a controller 21 and an inverter 22; wherein:
[0085] The DC side of the inverter 22 is connected to the power supply as the input end of the motor controller; the AC side of the inverter 22 is connected to the input end of the motor body 10 as the output end of the motor controller.
[0086] Optionally, the inverter 22 may be a three-phase inverter 22 or a single-phase inverter 22. In practical applications, this includes but is not limited to the above. No specific limitation is made here and it may be determined according to the specific circumstances. All of them are within the protection scope of this application.
[0087] The control end of the inverter 22 is connected to the output end of the controller 21 , and the input end of the controller 21 is connected to the output end of the first position sensor 30 and the output end of the second position sensor 40 , respectively.
[0088] In a specific example, the inverter 22 is a single-phase inverter 22 , and the number of the first position sensor 30 and the number of the second position sensor 40 are both one.
[0089] The above example only shows one implementation method of the number of first position sensors 30 and second position sensors 40 when the inverter is converted into a single-phase inverter 22. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances and is within the scope of protection of this application.
[0090] In another specific example, the inverter 22 is a three-phase inverter, and the number of the first position sensor 30 and the number of the second position sensor 40 are both one.
[0091] The above example only shows one implementation method of the number of first position sensors 30 and second position sensors 40 when the inverter is a three-phase inverter. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific situation and is within the scope of protection of this application.
[0092] The above is only one implementation of the motor controller. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.
[0093] Another embodiment of the present application provides an easy-to-turn forward and reverse electric fan, which specifically includes: a brushless DC motor as provided in the above embodiment, and fan blades installed on the drive shaft of the brushless DC motor.
[0094] It should be noted that fan blades are already very mature in the prior art and will not be described in detail here.
[0095] For the above description of the disclosed embodiments, the features recorded in each embodiment in this specification can be replaced or combined with each other, so that professional and technical personnel in this field can implement or use this application. The above is only a preferred embodiment of the utility model, and does not limit the utility model in any form. Although the utility model has been disclosed as above with a preferred embodiment, it is not used to limit the utility model. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the utility model by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the utility model, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the utility model without departing from the content of the technical solution of the utility model still falls within the scope of protection of the technical solution of the utility model.
Claims
1. A brushless DC motor, characterized in that: include: A motor body, a motor drive controller, at least one first position sensor and at least one second position sensor; wherein: The output end of the motor drive controller is connected to the input end of the motor body; The output end of the first position sensor and the output end of the second position sensor are respectively connected to the signal input end of the motor drive controller; The first position sensor and the second position sensor both correspond to the silicon steel sheets of the stator in the motor body; The angle between the axial section of the stator passing through the first position sensor and the axial section of the stator passing through the center line of the corresponding silicon steel sheet is a first angle; The angle between the axial section of the stator passing through the second position sensor and the axial section of the stator passing through the center line of the corresponding silicon steel sheet is a second angle; The first angle is not equal to the second angle; At least one of the first position sensors is in an operative state when the rotor in the motor body rotates forward, and at least one of the second position sensors is in an operative state when the rotor rotates reversely.
2. The brushless DC motor according to claim 1, characterized in that: The first angle is equal to the first angle; The first angle is an angle at which the first position sensor can first detect a change in polarity of the rotor when the rotor rotates forward.
3. The brushless DC motor according to claim 2, characterized in that: If the outer diameters of the two ends of the silicon steel sheet are different, the first angle is equal to the angle between the axial section of the stator passing through the end with a larger outer diameter of the silicon steel sheet and the axial section of the stator passing through the center line of the corresponding silicon steel sheet.
4. The brushless DC motor according to claim 1, characterized in that: The first angle is equal to the second angle; The second angle is an angle at which the second position sensor can first detect a change in polarity of the rotor when the rotor is reversed.
5. The brushless DC motor according to claim 4, characterized in that: If the outer diameters of the two ends of the silicon steel sheet are different, the second angle is equal to the angle between the axial section of the stator passing through the end with the smaller outer diameter of the silicon steel sheet and the axial section of the stator passing through the center line of the corresponding silicon steel sheet.
6. The brushless DC motor according to any one of claims 1 to 5, characterized in that: If the electrical connection lines between the components in the brushless DC motor are integrated into a printed circuit board PCB, and the PCB is arranged below or above the stator, the first position sensor and the second position sensor are both arranged on the PCB.
7. The brushless DC motor according to any one of claims 1 to 5, characterized in that: The first position sensor and the second position sensor are both arranged on the silicon steel sheet.
8. The brushless DC motor according to any one of claims 1 to 5, characterized in that: The inverter in the motor drive controller is a three-phase inverter or a single-phase inverter.
9. The brushless DC motor according to claim 8, characterized in that: If the inverter is a single-phase inverter, the number of the first position sensor and the number of the second position sensor are both 1; If the inverter is a three-phase inverter, the number of the first position sensors and the number of the second position sensors are both 3.
10. The brushless DC motor according to any one of claims 1 to 5, characterized in that: The positive rotation of the rotor means that the rotor rotates in a clockwise direction; The rotor reverses direction when the rotor rotates in a counterclockwise direction.
11. The brushless DC motor according to any one of claims 1 to 5, characterized in that: The position sensor is a Hall sensor.
12. A forward and reverse electric fan, characterized in that: include: A brushless DC motor as claimed in any one of claims 1 to 11, and a fan blade mounted on a drive shaft of the brushless DC motor.