A brushless DC motor

Abstract

The present invention provides a direct current brushless motor, comprising a stator, a rotor, a front shaft sleeve and a rear shaft sleeve, wherein the rotor is fixedly arranged in the inner hole of the stator with a coil winding through the clamping grooves of the front shaft sleeve and the rear shaft sleeve, the rotor comprises a rotor core, a rotating shaft and a magnetic tile, the rotor core is connected to the rotating shaft, the magnetic tile is arranged on the outer surface of the rotor core, the rotor core comprises rotor false teeth and rotor slots, and the stator comprises stator slots and teeth. The present invention abandons the traditional method of providing a braking device externally, increases the tooth slot width on the basis of the existing direct current brushless motor, improves the pole slot ratio, realizes self-braking by utilizing the tooth slot effect, and reduces magnetic resistance. In addition, the stator is stamped from silicon steel sheets, which reduces the eddy current effect and hysteresis loss, prolongs the service life, reduces the later maintenance cost, and improves the use efficiency of the equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of solar thermal power generation, and in particular to a brushless DC motor. Background Art

[0002] With the adjustment of energy structure, traditional energy has revealed its shortcomings such as weak supply, high cost and serious pollution. The concepts of "new energy" and "green energy" have been gradually gaining popularity. As we all know, solar energy is not only a clean and pollution-free green energy, but also a renewable energy. Concentrating Solar Power (CSP) is an effective way to convert solar energy. In recent years, it has set off a new wave of research and development and construction around the world.

[0003] The CSP system uses heliostats to reflect sunlight, which is then focused on the energy receiving device and exchanges heat with the medium therein, and then uses the energy absorbed by the medium to heat water vapor to generate electricity. This method of power generation is clean and pollution-free, and the energy can be stored, achieving the "continuous, stable, and controllable" and "good grid connection" effects of power output. Therefore, solar thermal power generation with a long heat storage capacity can effectively improve the system's peak-shaving capacity, which in turn plays an important role in improving the overall new energy consumption capacity.

[0004] An important link in the CSP system is the control of the light field heliostat. The energy source of the entire system is completely provided by the sunlight reflected by the heliostat. The heliostat is used to track the reflected sunlight, so the angle of the mirror must be constantly adjusted to ensure that the sunlight is reflected to the specified position. This causes the motor used to drive the heliostat to start and stop frequently. The electromagnetic brake used on the traditional motor is difficult to use for a long time under frequent starts and stops due to the wear of the mechanical brake. Since the number of heliostats is as many as 10,000, the maintenance cost is huge. Therefore, in view of this special situation, the present invention has developed a DC brushless motor without affecting the normal operation of the motor itself. By increasing the tooth slot width and improving the pole slot ratio on the basis of the normal DC brushless motor, the tooth slot torque of the motor is increased, which has the effect of increasing the braking torque. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a brushless DC motor, which aims to achieve static braking when the motor is frequently started and stopped. The present invention abandons the traditional method of relying on an external braking device and achieves self-braking through the "slot effect", thereby extending the service life of the motor, reducing the subsequent maintenance cost, and improving the utilization efficiency of the equipment.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A brushless DC motor, the motor comprising a rotor, a stator, a front sleeve and a rear sleeve, the rotor being fixedly arranged in an inner hole of the stator through slots of the front sleeve and the rear sleeve, the rotor comprising a rotor core, a rotating shaft and a magnetic tile, the rotor core being connected to the rotating shaft, and the magnetic tile being arranged on the outer surface of the rotor core;

[0008] Furthermore, the stator generates an alternating rotating magnetic field through an external driving circuit, the magnetic shoe is subjected to force in the rotating magnetic field, and then drives the rotating shaft to rotate and output torque, and by adjusting the ratio of the number of poles and the number of slots, the width of the stator tooth slot is increased, thereby increasing the tooth slot torque;

[0009] Further, the rotor core comprises rotor false teeth and rotor slots, the arc between the rotor false teeth is 38°, and the magnetic shoe is arranged on the outer surface of the rotor slot;

[0010] Furthermore, the stator comprises stator slots and teeth, the stator slots are straight slots, the stator slots are 6 mm wide and 13.5 mm deep, the tooth spacing is 5 mm, and the stator is an 8-pole 12-slot single-layer winding structure;

[0011] Furthermore, the rotor is a radial rotor structure, the outer surface of the rotor is provided with 8 arc-shaped permanent magnets, and the rotor yoke is provided with a lightening hole with a diameter of 6 mm;

[0012] Furthermore, the thickness of the magnetic tile is 3 mm and the number is 8;

[0013] Furthermore, the stator is formed by pressing and welding stator punching sheets, has a thickness of 0.5 mm, and a maximum iron loss of 4.7 W / kg; the rotor is formed by pressing and welding rotor punching sheets, and the materials of the stator punching sheets and the rotor punching sheets are both silicon steel sheets;

[0014] Furthermore, the ratio between the number of poles and the number of slots is:

[0015] ,

[0016] Where A is an integer, is an irreducible fraction, P represents the number of poles, T represents the number of slots, and q represents the braking torque. The larger the denominator D is, the smaller the braking torque q is. When the number of poles P is constant, the change of the number of slots T will cause the change of the braking torque q.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The present invention adopts a tooth slot structure, and provides a magnetic field conduction circuit through the tooth structure, thereby reducing magnetic resistance. The stator with coil winding is stamped from silicon steel sheets, which reduces eddy current effect and hysteresis loss. The present invention abandons the traditional method of providing an external braking device, and realizes self-braking by increasing the tooth slot effect, thereby extending the service life of the motor, reducing the later maintenance cost, and improving the use efficiency of the equipment;

[0019] 2. Based on the existing DC brushless motor, the present invention increases the tooth slot width, improves the pole slot ratio, and increases the tooth slot torque of the motor. It enhances the effect of the braking torque without affecting the normal operation of the motor itself, and improves the working stability of the motor. Moreover, the magnetic shoe is made of neodymium iron boron, which reduces the loss of rotor material and reduces the weight of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a general assembly diagram of a brushless DC motor according to the present invention;

[0021] Figure 2 This is a schematic diagram of a stator punching sheet of a brushless DC motor according to the present invention;

[0022] Figure 3 This is a schematic diagram of a DC brushless motor rotor punching sheet according to the present invention;

[0023] Figure 4 A cross-sectional view of a stator of a brushless DC motor according to the present invention;

[0024] Figure 5 The figure is a schematic diagram of a brushless DC motor rotor according to the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. On the contrary, the present invention encompasses any substitutions, modifications, equivalent methods and schemes made on the essence and scope of the present invention as defined by the claims. Further, in order to enable the public to have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. For those skilled in the art, the present invention can be fully understood without the description of these details.

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings:

[0027] like Figure 1-Figure 5As shown, the present invention provides a brushless DC motor, including a rotor 1, a stator 3, a front sleeve 7 and a rear sleeve 8, wherein the rotor 1 is fixedly arranged in the inner hole of the stator 3 through the slots of the front sleeve 7 and the rear sleeve 8, and the rotor 1 includes a rotor core 4, a rotating shaft 2 and a magnetic tile 6, wherein the rotor core 4 is connected to the rotating shaft 2, and the magnetic tile 6 is arranged on the outer surface of the rotor core 4.

[0028] The stator 3 generates an alternating rotating magnetic field after being energized by an external driving circuit. The magnetic tile 6 is subjected to force in the rotating magnetic field, and then drives the rotating shaft 2 to rotate and output torque. The increase in the tooth slot width of the stator 3 and the improvement in the ratio of the number of poles to the number of slots increase the tooth slot torque, which has the effect of enhancing the braking torque.

[0029] The rotor core 4 includes rotor false teeth 9 and rotor slots 10 , the arc between the rotor false teeth 9 is 38°, and the magnetic shoe 6 is arranged on the outer surface of the rotor slot 10 .

[0030] The stator 3 includes stator slots 11 and teeth 12. The stator slots 11 are straight slots with a width of 6 mm and a depth of 13.5 mm. The spacing between the teeth 12 is 5 mm. The stator 3 is an 8-pole 12-slot single-layer winding structure.

[0031] The rotor 1 is a radial rotor structure. Eight arc-shaped permanent magnets are arranged on the outer surface of the rotor 1. A lightening hole with a diameter of 6 mm is arranged on the yoke of the rotor 1.

[0032] The magnetic tiles 6 are 3 mm thick and 8 in number.

[0033] The rotating shaft 2 is connected to the reducer for outputting driving torque.

[0034] The stator 3 is formed by pressing and welding stator punching sheets with coil windings, has a thickness of 0.5 mm, and a maximum iron loss of 4.7 W / kg. The rotor 1 is formed by pressing and welding rotor punching sheets, and the stator punching sheets and rotor punching sheets are both made of silicon steel sheets.

[0035] The proportional relationship between the number of poles and the number of slots is:

[0036] ,

[0037] Where A is an integer, It is an irreducible fraction, P represents the number of poles, T represents the number of slots, and q represents the braking torque. The larger the denominator D is, the smaller the braking torque q is. When the number of poles P is constant, the change of the number of slots T will cause the change of the braking torque q.

[0038] When the inner diameter of the stator 3 is determined, the outer diameter of the rotor 1 can be appropriately increased.

[0039] The brushless DC motor provided by the present invention has no carbon brush commutation. The position signal is fed back to the drive circuit through the Hall sensor, the frequency and waveform of the stator input current with the coil winding are changed, and a circular magnetic field rotating around the geometric center of the motor is formed around the coil, thereby realizing the change of the direction and speed of the motor.

[0040] like Figure 2 As shown, the permanent magnet steel on the rotor 1 is subjected to force in the rotating magnetic field to drive the rotor to rotate and output torque. Under the condition that the performance of the external drive circuit is constant, the operating performance of the motor is closely related to its own pole pair number, the magnetic permeability and thickness of the magnet steel.

[0041] The stator 3 adopts a tooth structure, and the tooth structure is used to provide a circuit for magnetic field conduction to reduce magnetic resistance, and the stator slot 11 is used to embed and fix the coil winding, and a magnetic field is generated around the coil to cross-link with the magnetic field in the rotor core 4. Since the magnetic flux passing through the teeth 12 and the stator slot 11 is different, the magnetic field strength is also different. The permanent magnets on the rotor 1 are affected by the alternating magnetic field and are attracted to the teeth with stronger magnetic field strength, hindering the rotation of the rotor, which is usually called "tooth effect" or "tooth torque".

[0042] The number of slots in the stator 3 is T=12, which is an integer slot design, and the number of motor poles 2P=8. The silicon steel sheet used for the rotor punching is the same as the material of the stator with coil winding, and the magnetic steel material is NdFeB 35SH. The slot effect is affected by factors such as the pole arc coefficient, slot width and stator-rotor gap when the motor itself has a certain size. Specific measures can be taken to increase the slot width and reduce the gap between the stator and rotor to change the air gap magnetic field distribution so that the braking torque meets the use requirements.

[0043] The stator 3 generates an alternating rotating magnetic field after the external driving circuit is energized, and the magnetic shoe 6 is subjected to force in the changing magnetic field, driving the rotating shaft 2 to rotate, and the reducer connected thereto outputs torque to do work.

[0044] like Figure 4 As shown, the present invention increases the cogging torque, the stator winding with the coil winding is in the form of a single-layer winding, the external power supply is a 24V DC power supply, which is converted into a three-phase AC circuit by a driver switch circuit to form a rotating magnetic field. The outer diameter of the stator 3 core is determined according to the output power, and the length of the stator 3 core is also related to the output power. Specifically, the electric load A and the magnetic load B are first determined, and the cost, service life, copper loss and iron loss of the selected material are also considered before determination.

[0045] like Figure 5 As shown, when the electric load A and the magnetic load B are determined, the shape of the rotor 1 can be represented by the ratio λ of the rotor length La to the rotor outer diameter Dz, In order to increase the cogging torque, the value of λ can be appropriately reduced, thereby increasing the value of the outer diameter Dz.

[0046] According to the given technical indicators including output power, rated torque, braking torque, rated speed and other specific indicators, first of all, the outer diameter Da, inner diameter Di and length La of the stator core are determined. The outer diameter Da of the stator core can be obtained according to the characteristic curve of Da and unit speed output power, and then the value of La is calculated. In order to reduce the gap between the stator and the rotor, the outer diameter Dz of the rotor can be appropriately increased when the inner diameter Di of the stator with coil winding is determined.

[0047] Because the special application of the brushless DC motor of the present invention requires frequent start and stop, the purpose of self-braking is to be achieved by increasing the cogging torque. Therefore, the design should consider the matching relationship between the number of poles P and the number of slots T. The specific influencing factor is the selection of the pole arc coefficient σ. Increasing the number of poles P can reduce the amount of copper and iron used, and can reduce the size of the motor, but the leakage flux per pole will increase, resulting in a smaller pole arc coefficient σ, which cannot meet the requirements. In order to meet the torque requirements, a reasonable pole-slot matching ratio must be designed. The relationship between the number of poles P and the number of slots T can be expressed by the following formula: , where A is an integer, is an irreducible fraction; practice has proved that the larger the denominator D is, the smaller the braking torque of the motor is. Therefore, when the number of poles is constant, the change in the number of slots will cause a change in the braking torque. After the number of poles and slots is determined, the air gap flux is adjusted by adjusting the width of the slot and the gap between the stator and rotor to affect the cogging torque. The magnetic density of the no-load armature is inversely proportional to the tooth width and directly proportional to the tooth pitch. The air gap flux is related to the gap between the stator and rotor. As the gap increases, the area through which the leakage flux passes increases, and the total magnetic flux decreases. Theoretical calculations and experiments have shown that increasing the tooth width and reducing the gap between the stator and rotor can increase the cogging torque. The stator and rotor dimensions of the present invention meet the requirements of a rated power of 0.4KW, a rated torque of 2.55Nm, and a braking torque (static resistance torque) of 1.3Nm-1.5Nm. After repeated tests, a 12-slot 8-pole motor structure with a slot width of 6mm and a slot pitch of 5mm is adopted to meet actual use requirements.

[0048] The present invention is applied to the control of heliostats in a mirror field of a solar thermal power station. Each heliostat requires one motor to drive the azimuth axis and the elevation axis respectively. There are more than 10,000 heliostats in the entire mirror field and more than 20,000 motors. If the motors are controlled by traditional braking methods, the initial investment cost and subsequent maintenance costs are huge. The present invention solves the problem of subsequent maintenance and reduces the investment cost of solar thermal power generation projects.

[0049] In the description of the present application, it should be noted that the directions or positional relationships indicated by terms such as center, up, down, left, right, vertical, horizontal, inside, and outside are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present application.

Claims

1. A brushless DC motor, characterized in that: The motor comprises a rotor, a stator, a front sleeve and a rear sleeve, wherein the rotor is fixedly arranged in the inner hole of the stator through the slots of the front sleeve and the rear sleeve, and the rotor comprises a rotor core, a rotating shaft and a magnetic tile, wherein the rotor core is connected to the rotating shaft, and the magnetic tile is arranged on the outer surface of the rotor core; the magnetic tile is made of neodymium iron boron; The stator generates an alternating rotating magnetic field through an external driving circuit. The magnetic shoe is subjected to force in the rotating magnetic field, and then drives the rotating shaft to rotate and output torque. By adjusting the ratio of the number of poles and the number of slots, the width of the stator tooth slot is increased, thereby increasing the tooth slot torque, and self-braking is achieved through the tooth slot effect; The proportional relationship between the number of poles and the number of slots is: ， Where A is an integer, is an irreducible fraction, 2P represents the number of poles, T represents the number of slots, and q represents the braking torque. The larger the denominator D is, the smaller the braking torque q is. When the number of poles P is constant, the change of the number of slots T will cause the change of the braking torque q. The stator comprises stator slots and teeth, the stator slots are straight slots, the stator slots are 6 mm wide and 13.5 mm deep, the tooth spacing is 5 mm, and the stator is an 8-pole 12-slot single-layer winding structure; The stator is formed by pressing and welding stator punching sheets, has a thickness of 0.5 mm, and a maximum iron loss of 4.7 W / kg. The rotor is formed by pressing and welding rotor punching sheets. Both the stator punching sheets and the rotor punching sheets are made of silicon steel sheets.

2. The motor according to claim 1, characterized in that: The rotor core comprises rotor false teeth and rotor slots, the arc between the rotor false teeth is 38°, and the magnetic shoe is arranged on the outer surface of the rotor slot.

3. The motor according to claim 1, characterized in that: The rotor is a radial rotor structure, and eight arc-shaped permanent magnets are arranged on the outer surface of the rotor. A lightening hole with a diameter of 6 mm is arranged on the rotor yoke.

4. The motor according to claim 1, characterized in that: The thickness of the magnetic tiles is 3 mm and the number is 8.

Images