DC Brush Motor

Abstract

The present invention relates to a DC brush motor, which includes a housing, one or both ends of the housing are open and a receiving space is formed in the housing, a stator disposed in the receiving space, a rotor with a rotor hub and rotor teeth extending radially outward from the rotor hub, where teeth slots are formed between adjacent rotor teeth, and the rotor hub can be connected to an output element for outputting electric power, and windings disposed in the teeth slots. The ratio of the number of rotor teeth to the number of magnetic poles of the DC brush motor is not an integer, and the number of windings in different teeth slots is not strictly equal. According to the design of the motor of the present invention, the pole-slot ratio is not an integer, and the number of turns of the winding per slot is regular but not strictly equal, which makes the waveform of the operating current of the motor clearly visible, which makes it easy for an electronic controller to identify the position of the rotor.

Description

[Technical field]

[0001] The present invention relates to the technical field of motors, and more particularly to DC brush motors. [Background technology]

[0002] In order to ensure that phase and direction changes can be accurately implemented in the control circuit during the operation of the motor, closed-loop control is usually adopted for controlling the motor. Therefore, in order to monitor the operating state of the motor, a position sensor such as a Hall sensor needs to be arranged in the motor to determine the position of the rotor of the motor.

[0003] However, the introduction of a sensor increases the complexity of the circuit, and the position sensor may be difficult to introduce due to the constraints of the motor structure or the introduction scenario. In addition, the Hall sensor is easily affected by external environments such as temperature and magnetic field, and therefore has a high failure rate. Under such circumstances, motors without position sensors have appeared. Compared with motors with position sensors, motors without position sensors have the following significant advantages: low cost, small volume, and high reliability.

[0004] In order to make the motor meet the requirements of Sensorless Positioning / Control (hereinafter referred to as SLP), the traditional solution of the pole-slot ratio being an integer is applied to most motor products in the prior art. That is, a full pitch winding solution including 4 poles 12 slots or 2 poles 8 slots, etc. is adopted. The motor using this design solution is prone to generate vibration, noise, and electromagnetic interference, because the direction change of the full pitch winding of the rotor generates periodic sparks, and the rotor structure generates periodic symmetric magnetic pulling force. Especially when the motor is used in automobiles, such as for adjusting automobile seats, the above shortcomings will make the noise inside the automobile very large, causing discomfort to users, affecting the customer experience, and also affecting the electromagnetic compatibility of the entire automobile through electromagnetic interference.

[0005] It is known in the prior art that there exist non-full pitch motors, which reduce vibration and noise and improve electromagnetic compatibility, but the waveform of their operating current cannot meet the requirements of SLP. Summary of the Invention

[0006] In order to solve the above technical problems to a certain extent, the present invention proposes the following technical solutions: A DC brush motor, comprising: a housing, the housing having one or both ends open and a receiving space formed therein; A stator disposed in the receiving space; and a rotor including a rotor hub and rotor teeth extending radially outward from the rotor hub, wherein adjacent rotor teeth have tooth slots formed therebetween, and the rotor hub is connectable to an output element for outputting electrical power; a winding disposed in the tooth slot; A DC brush motor is proposed in which the ratio of the number of rotor teeth to the number of magnetic poles of the DC brush motor is not an integer, and the number of turns of the windings in different teeth slots are not all equal.

[0007] According to a refinement of the invention, the teeth widths of the rotor teeth are not all equal.

[0008] According to one refinement of the invention, the shapes of the teeth slots are not all equal.

[0009] According to one improvement of the present invention, based on the number of turns of the winding contained in each tooth slot, the slot shape of the tooth slot is adjusted so that the position of the center of gravity of the rotor with windings meets the dynamic balance requirements and reduces vibration and noise during operation of the motor.

[0010] According to one improvement of the invention, adjusting the slot shape includes changing the radial size of the rotor hub between two adjacent rotor teeth that define the tooth slot, or changing the shape of the top portion of the rotor tooth that corresponds to the tooth slot.

[0011] According to one improvement of the invention, based on the number of turns of the winding contained in each tooth slot, the tooth width of each rotor tooth is adjusted so that the position of the center of gravity of the rotor with windings meets the dynamic balance requirements and reduces vibration and noise during operation of the motor.

[0012] According to one refinement of the invention, the rotor is formed by stacking a number of rotor laminations or is formed entirely by pressing, casting or extruding a magnetic conductive material.

[0013] According to one refinement of the invention, the rotor laminations are soft magnetic silicon steel sheets or soft magnetic carbon steel sheets.

[0014] According to one refinement of the invention, the conductive material of the windings is copper, aluminum, silver or a composite material containing copper and aluminum.

[0015] According to a refinement of the invention, the DC brush motor comprises 2 poles and 7 slots, 4 poles and 14 slots, or 6 poles and 21 slots.

[0016] To ensure that the waveform of the motor's operating current can meet the SLP requirements, the motor of the present invention is designed with a non-integer pole-slot ratio (e.g., 4 poles, 14 slots, 2 poles, 7 slots, 6 poles, 21 slots) and with a regular but not all equal number of winding turns per slot. This modification makes the waveform of the motor's operating current clearly visible, making it easier for the electronic controller to determine the rotor position.

[0017] The present invention also proposes to modify the slot shape and teeth width based on the modified number of windings to achieve the requirements of low noise, low vibration, excellent electromagnetic interference, and high performance.

[0018] Detailed features and advantages of the present invention are also set forth in the following detailed description taken in conjunction with the accompanying drawings.

[0019] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view of a motor. [Diagram 2] FIG. 2 is a diagram showing periodic oscillations of a motor current in the prior art. [Diagram 3] FIG. 3 is a diagram showing periodic oscillations of the motor current using a motor structure according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] All the drawings are only schematic and are not necessarily drawn to scale. In addition, the drawings only show parts necessary for explaining the present invention, and other parts are omitted or only mentioned. That is, the present invention may include other parts in addition to the parts shown in the drawings.

[0022] The technical solutions of the present invention will be described in detail below in combination with the accompanying drawings.

[0023] Fig. 1 shows a schematic cross-sectional view of a motor. As can be seen from Fig. 1, the motor mainly includes a rotor 100, a stator 200, a housing 300, and a winding 400. As an exemplary structure, the housing 300 is cylindrical and disposed on the outermost side in the radial direction, and a cavity for receiving the rotor 100, the stator 200, and the winding 400 is formed therein. The housing 300 is generally made of metal. The housing 300 may be configured to have openings at both ends and end covers for closing the openings.

[0024] The stator 200 is made of a magnetic material. The stator 200 and the housing 100 are arranged fixedly relative to each other to create a magnetic field. In the example shown in Fig. 1, the stator 200 comprises four magnetic poles forming two pole sets. The stator 200 may be designed as a magnetic structure or may be designed as a non-magnetic structure having one or more permanent magnets fixed thereto, for example stacked thereto, to create a magnetic field.

[0025] The material of the stator 200 can be ferrite magnetic material or rare earth permanent magnet material. During manufacturing, ferrite magnetic powder or isotropic or anisotropic bond NdFeB magnet powder may be mixed with epoxy resin adhesive and pressed in a mold to produce a desired shape. Alternatively, ferrite magnetic powder or isotropic or anisotropic bond NdFeB magnet powder may be mixed uniformly with a thermoplastic rubber material such as PA or PPS to form granules, and the granules are injection molded by an injection molding machine into a magnet with a desired structure.

[0026] The rotor 100 is disposed inside the stator 200. As can be seen from FIG. 1, the rotor 100 comprises a centrally disposed rotor hub 101, which is provided with holes for connection with a shaft element. For example, splines may be provided in the holes for fixed connection to the shaft element. A number of rotor teeth 102 are provided extending radially outward from the rotor hub 101. The rotor teeth 102 have a certain width, which is called the "teeth width." At the end of the rotor teeth 102 remote from the rotor hub 101, a top portion 103 is provided. The top portion 103 extends in a direction generally perpendicular to the rotor teeth 102, but the surface facing the stator 200 is arc-shaped to match the inner contour of the stator 200, thereby forming an air gap between the rotor 100 and the stator 200. A tooth slot is formed between two adjacent rotor teeth 102. For simplicity, the shape of the teeth slots will be described as being slot shaped.

[0027] Rotor 100 may be formed by stacking multiple rotor laminations, such as made from silicon steel, into a single unit. Of course, rotor 100 may be formed into a single unit in other ways, such as by forming a magnetic conductive material through pressing, casting, extrusion, etc. Additionally, rotor laminations may be made from other soft magnetic materials, such as carbon steel, in addition to silicon steel.

[0028] The windings 400 are disposed in the teeth slots. When current flows through the windings 400 in the magnetic field of the stator 200, the rotor 100 starts to rotate under the action of electromagnetic force, driving a shaft element fixedly connected to the rotor hub 101 to output power to the outside. The conductive material of the windings 400 is preferably copper. In addition, the conductive material may be aluminum or silver, or a composite material containing copper and aluminum, such as a copper-aluminum alloy.

[0029] 1, the rotor 100 has 14 rotor teeth and 4 magnetic poles. In the existing motor, the rotor teeth 102 of the rotor have equal tooth widths and the tooth slots have equal slot shapes. That is, the 14 rotor teeth 102 are uniformly distributed in the radial direction, and the rotor 100 is symmetrical with respect to a line passing through two rotor teeth 102.

[0030] The number of poles in the motor may also be set as needed, for example, non-integer pole-slot ratios are possible, such as 2 poles, 7 slots and 6 poles, 21 slots.

[0031] FIG. 2 shows a diagram of the current waveform of a 4-pole, 14-slot motor in the prior art. The prior art motor in FIG. 2 is a 4-pole, 14-slot motor, with each slot having 78 windings. In FIG. 2, the starting current of the motor in this example is shown. As can be seen from FIG. 2, in the existing 4-pole, 14-slot motor with 78 windings per slot, the amplitude of the operating current output by the motor ranges from 11 A to 12 A, with a minimum value of 11.0153 A, a maximum value of 11.9390 A, and an average value of 11.5572 A. The variation of the output current waveform in this form is so small that the electronic controller cannot identify the rotor position, and therefore cannot meet the SLP requirements.

[0032] Under this situation, the present invention proposes the following solution: the numbers of windings in different teeth slots are not strictly equal, so that the waveform of the output starting current is changed to meet the SLP requirements.

[0033] FIG. 3 shows the periodic variation of the current of the motor having the structure according to the present invention. The difference between the motor according to FIG. 3 and the motor according to FIG. 2 is that the number of windings in each slot is not all equal. Specifically, as an example, the number of windings in the 14 slots is set in sequence as follows: 76-56-76-87-62-62-87-76-56-76-87-62-62-87. When this setting is adopted, the measured waveform of the starting current of the motor is shown in FIG. 3. As can be seen from FIG. 3, the maximum starting current output by the motor is 13.1183 A, the minimum is 11.5665 A, and the average value is 12.1997 A. Compared with FIG. 2, FIG. 3 shows an increase in the waveform variation of the current, which allows the electronic controller to easily identify the rotor position, facilitating SLP control.

[0034] Those skilled in the art can improve other types of solutions with non-integer pole-slot ratios according to the above inventive concept. The current waveform can be varied by setting the number of windings in the teeth slots not all equal, which facilitates SLP control.

[0035] The above winding mode is only provided as an example for a 4-pole, 14-slot motor, and those skilled in the art can improve motors with different numbers of poles and slots according to the concept of the present invention. For example, corresponding improvements can be made to a 2-pole, 7-slot motor and a 6-pole, 21-slot motor, as long as the waveform of the operating current can meet the SLP requirements by changing the number of windings.

[0036] As a further improvement of the present invention, the structure of the rotor is also adjusted according to the number of windings. Specifically, the teeth width and slot shape of the rotor can be adjusted accordingly. After the number of windings in each teeth slot is changed, the mass distribution and center of gravity of the rotor assembly of the motor are changed, which results in other problems during the operation of the motor. Considering this situation, the teeth width and slot shape of the rotor should also be adjusted adaptively.

[0037] In terms of improving the overall performance of the motor and reducing vibration and noise during operation of the motor, the rotor slot shape can be changed according to the number of windings in each teeth slot, i.e., the rotor slot shapes can be made not all equal. For example, for teeth slots with fewer coil turns, the area corresponding to the teeth slot can be made smaller. The reduction of the teeth slots can make the position of the center of gravity of the rotor with the coils meet the requirements of dynamic balance, reducing vibration and noise during operation of the motor. In addition, the reduction of the teeth slots can increase the slot filling rate / slot filling factor of the teeth slots, which can also improve the motor performance. The shape of the teeth slots can be made smaller, for example, by increasing the radial size / dimension of the rotor hub between two adjacent rotor teeth that define the teeth slot. The slot shape can also be changed by changing the shape of the top of the rotor teeth. In the present invention, the expression "fewer coil turns" refers to a relative relationship compared to the number of coil turns in other teeth slots. For example, for the above mentioned winding of 76-56-76-87-62-62-87-76-56-76-87-62-62-87, 76 is less than 87 but more than 62, and 62 is less than 76 but more than 56. The slot shape can be adjusted according to the number of turns in the teeth slot as long as it can reduce vibration and noise during the operation of the motor.

[0038] In addition, the performance of the motor can be improved by changing the tooth width of the rotor. Based on a similar idea, the width of the rotor teeth on both sides of the tooth slot can be appropriately increased for the tooth slot with fewer coil turns. This also reduces the area corresponding to the slot shape of the tooth slot. When the size of the tooth width is designed, the magnetic flux of the tooth width should also be considered.

[0039] As can be seen from the above, in the present invention, the pole-slot ratio of the motor is not an integer, the number of turns of the winding per slot is regular but not all equal, the teeth slots of the rotor are differently sized and the teeth are designed to have different widths to match the corresponding number of windings, so that the current waveform during the operation of the motor can meet the requirements of SLP, low noise, low vibration, low electromagnetic interference, and high performance.

[0040] The present invention has been clearly and completely described above with reference to exemplary embodiments, and those skilled in the art can understand that various other embodiments can be conceived by modifying the technical solutions of the present disclosure without departing from the spirit and scope of the present invention. It is also understood that the embodiments determined by the claims and any technical solutions equivalent thereto fall within the scope of the present invention.

Claims

1. A DC brush motor, comprising: a housing, the housing having one or both ends open and a receiving space formed therein; A stator disposed in the receiving space; and a rotor including a rotor hub and rotor teeth extending radially outward from the rotor hub, wherein adjacent rotor teeth have tooth slots formed therebetween, and the rotor hub is connectable to an output element for outputting electrical power; A winding disposed in the tooth slot; In a DC brush motor including: A DC brush motor, characterized in that the ratio of the number of rotor teeth to the number of magnetic poles of the DC brush motor is not an integer, and the numbers of turns of the windings in different tooth slots are not strictly equal.

2. 2. The DC brush motor according to claim 1, wherein the tooth widths of the rotor teeth are not strictly equal.

3. 2. The DC brush motor as claimed in claim 1, wherein the shapes of the teeth slots are not strictly equal.

4. 4. A DC brush motor as claimed in any one of claims 1 to 3, characterized in that the slot shape of the tooth slot is adjusted based on the number of turns of the winding contained in each tooth slot so that the position of the center of gravity of the rotor with the winding meets the dynamic balance requirements and reduces vibration and noise during operation of the motor.

5. 5. The DC brush motor of claim 4, characterized in that adjusting the slot shape includes changing the radial size of the rotor hub between two adjacent rotor teeth that define the tooth slot, or changing the shape of the top portion of the rotor tooth corresponding to the tooth slot.

6. 4. A DC brush motor as claimed in claim 1, wherein the tooth width of each rotor tooth is adjusted based on the number of turns of the winding contained in each tooth slot so that the position of the center of gravity of the rotor with the winding meets the dynamic balance requirements and reduces vibration and noise during operation of the motor.

7. 4. The DC brush motor of claim 1, wherein the rotor is formed by stacking a plurality of rotor laminations, or is formed by stamping, casting, or extruding entirely from a magnetic conductive material.

8. 8. The DC brush motor as claimed in claim 7, wherein the rotor laminations are soft magnetic silicon steel sheets or soft magnetic carbon steel sheets.

9. 4. The DC brush motor according to claim 1, wherein the conductive material of the winding is copper, aluminum, silver, or a composite material containing copper and aluminum.

10. 4. The DC brush motor of claim 1, wherein the motor comprises 2 poles and 7 slots, 4 poles and 14 slots, or 6 poles and 21 slots.

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