A brushed DC motor

Abstract

The present invention relates to a brushed DC motor, comprising: a housing, one or both ends of the housing are open, and a receiving space is formed inside the housing; a stator, the stator is arranged in the receiving space; a rotor, the rotor has a rotor hub, rotor teeth extending radially outward from the rotor hub, tooth slots are formed between adjacent rotor teeth, and the rotor hub can be connected to an output component to output power; a winding is located in the tooth slot; the ratio of the number of the rotor teeth to the magnetic poles of the brushed DC motor is a non-integer, and the number of windings located in different tooth slots is not completely the same. The present invention designs the motor as a scheme of matching non-integer multiple pole slots, and designs the number of windings per slot of the motor to be a regular and non-complete number of windings, so that the motor running current waveform is more obvious, which is convenient for the electronic controller to identify the rotor position.

Description

Technical Field

[0001] The invention belongs to the technical field of motors, and in particular relates to a brushed DC motor. Background Art

[0002] During the operation of the motor, in order to facilitate the controller circuit to accurately change phase and commutate, closed-loop control is generally used to control the motor. Therefore, it is necessary to set a position sensor such as a Hall sensor in the motor to determine the rotor position of the motor, thereby monitoring the operating status of the motor.

[0003] However, installing sensors will increase the complexity of the circuit, and due to the structure of the motor or the installation location, the position sensor may be difficult to install, and the Hall sensor is easily affected by external environments such as temperature and magnetic fields, and has a high failure rate. As a result, motors without position sensors came into being. Compared with the solution with position sensors, the most obvious advantage of motors without position sensors is that they reduce costs, reduce volume, and correspondingly improve reliability.

[0004] In order to make the motor meet the requirements of sensorless positioning / controls (hereinafter referred to as SLP for convenience of description), most motor products in the prior art adopt the traditional solution of motor pole slot matching in integer multiples, that is, the solution of full-pitch winding, such as 4 poles and 12 slots, 2 poles and 8 slots. The motor using this design solution generates periodic sparks due to the commutation of the rotor full-pitch winding and the periodic symmetrical magnetic pull generated by the rotor structure, and the motor is prone to vibration, noise and electromagnetic interference. When the motor is especially used in automobiles, such as when the motor is used for seat adjustment of the vehicle, the above shortcomings will significantly increase the noise in the car, causing discomfort to the user, affecting the customer experience, and affecting the electromagnetic compatibility requirements of the entire vehicle due to electromagnetic interference.

[0005] In the prior art, there are motors with non-uniform pitch windings, which have relatively reduced vibration and noise, and improved electromagnetic compatibility to a certain extent, but the operating current waveform of the motor cannot meet the requirements of position control without position sensors. 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.

[0007] A brushed DC motor, comprising:

[0008] A shell, one or both ends of which are open to form a receiving space inside the shell;

[0009] a stator, wherein the stator is arranged in the accommodation space;

[0010] A rotor, the rotor comprising a rotor hub, rotor teeth extending radially outward from the rotor hub, tooth grooves formed between adjacent rotor teeth, and the rotor hub being connectable to an output component to output power;

[0011] A winding located in the tooth slot;

[0012] The ratio of the number of the rotor teeth to the magnetic poles of the brushed DC motor is a non-integer, and

[0013] The number of windings in different slots is not exactly the same.

[0014] According to an improvement of the present invention, the tooth widths of the rotor teeth are not completely the same.

[0015] According to an improvement of the present invention, the shapes of the tooth grooves are not completely the same.

[0016] According to an improvement of the present invention, the slot shape of each slot is adjusted based on the number of windings accommodated in the slot, so that the center of gravity position of the rotor equipped with the winding meets the dynamic balance requirements, thereby reducing vibration and noise during the operation of the motor.

[0017] According to an improvement of the present invention, adjusting the slot shape includes changing the radial dimension of the rotor hub between two adjacent rotor teeth defining the slot, or changing the shape of the top of the rotor tooth corresponding to the slot.

[0018] According to an improvement of the present invention, the tooth width of each rotor tooth is adjusted based on the number of windings accommodated in the tooth slots so that the center of gravity position of the rotor equipped with the windings meets the dynamic balance requirements, thereby reducing vibration and noise during the operation of the motor.

[0019] According to an improvement of the present invention, the rotor is in the following form: formed by stacking a plurality of rotor laminations, or formed into an integral body by stamping, casting or extrusion of magnetic conductive material.

[0020] According to an improvement of the present invention, the rotor laminations are silicon steel sheets made of soft magnetic material or carbon steel sheets made of soft magnetic material.

[0021] According to an improvement of the present invention, the conductor material in the winding is copper, aluminum, silver or a composite material containing copper and aluminum.

[0022] According to an improvement of the present invention, the brushed DC motor has 2 poles and 7 slots, 4 poles and 14 slots, or 6 poles and 21 slots.

[0023] In order to make the motor running current waveform meet the requirements of position sensorless position control, the present invention designs the motor to be a scheme with non-integer multiple pole slots (for example, 4 poles and 14 slots, 2 poles and 7 slots, 6 poles and 21 slots, etc.), and designs the number of coils per slot of the motor to be regular and not completely the same. Through this modification, the motor running current waveform is more obvious, which is convenient for the electronic controller to identify the rotor position.

[0024] The present invention also proposes to make corresponding changes to the slot shape and tooth width in combination with the changed number of winding coils, so as to achieve the requirements of low noise, low vibration, excellent electromagnetic radiation interference and high performance.

[0025] The detailed features and advantages of the present invention will be apparent from the following description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Exemplary embodiments of the present invention are described with reference to the accompanying drawings, in which:

[0027] Figure 1 It is a cross-sectional diagram of the motor.

[0028] Figure 2 It is a periodic variation diagram of the motor current in the prior art.

[0029] Figure 3 FIG. 4 is a diagram showing periodic changes in the motor current using the motor structure according to the present invention.

[0030] All the drawings are only schematic and not necessarily drawn to scale, and they only show those parts necessary for explaining the present invention, and other parts are omitted or only mentioned. That is, in addition to the parts shown in the drawings, the present invention may also include other parts. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0032] Figure 1 A schematic cross-section of the motor is shown. Figure 1 As can be seen in the figure, 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 is arranged at the outermost radial side, and a cavity is formed inside the housing for accommodating the rotor 100, the stator 200 and the winding 400. The housing 300 is generally made of metal. The housing 300 can be configured to have openings at both ends and end covers for closing the openings.

[0033] The stator 200 is made of magnetic material. The stator 200 is fixedly arranged relative to the housing 100 to provide a magnetic field. Figure 1In the example shown, the stator 200 includes four magnetic poles, forming two magnetic pole pairs. The stator 200 can be configured as a structure that is inherently magnetic, but can also be configured in a structure in which one or more permanent magnets are fixedly arranged on a stator made of a non-magnetic material, such as by bonding, to form a magnetic field.

[0034] The material of the stator 200 can be a ferrite magnetic material or a rare earth permanent magnet material. In order to obtain the desired shape, during manufacturing, ferrite magnetic powder or anisotropic or isotropic bonded NdFeB magnetic powder can be mixed with epoxy resin glue and then pressed into shape by a mold with a corresponding shape, or ferrite magnetic powder or anisotropic or isotropic NdFeB magnetic powder can be mixed with PA or PPS and other thermoplastic adhesives to form granules, and then the granules can be injection molded into a magnet with the desired structure by an injection molding machine.

[0035] The rotor 100 is disposed inside the stator 200. Figure 1 As can be seen in the figure, the rotor 100 includes a rotor hub 101 located in the center, and a hole is provided in the rotor hub 101 for connecting with the shaft component. For example, a spline can be provided in the hole to be fixedly connected with the shaft component. A plurality of rotor teeth 102 are provided to extend radially outward from the rotor hub 101. The rotor teeth 102 have a certain width, which is called the tooth width. A top 103 is provided at the end of the rotor tooth 102 away from the rotor hub 101, and the top 103 extends roughly in a direction perpendicular to the rotor tooth 102, but its surface facing the stator 200 is arc-shaped so as 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, and for the sake of simplicity of description, the shape of the tooth slot is called a slot shape.

[0036] The rotor 100 may be formed by stacking a plurality of rotor laminations, for example, made of silicon steel sheets, and the rotor laminations may be stacked to form a rotor. Of course, the rotor 100 may also be formed in other forms, for example, by forming a magnetic conductive material into a whole by a molding method such as stamping, casting or extrusion. In addition, the rotor laminations may also be made of other soft magnetic materials other than silicon steel sheets, for example, carbon steel plates.

[0037] A winding 400 is arranged between the teeth. When current passes through the winding 400 in the magnetic field of the stator 200, the rotor 100 starts to rotate under the action of electromagnetic force, thereby driving the shaft component fixedly connected to the rotor hub 101, thereby outputting power to the outside. The conductor material in the winding 400 is preferably copper. In addition, the conductor material can also be a material, such as aluminum or silver, or a composite material containing copper and aluminum, such as a copper-aluminum alloy.

[0038] exist Figure 1In the motor shown, the rotor 100 is provided with 14 rotor teeth and 4 magnetic poles. In the existing motor, the tooth widths of the rotor teeth 102 of the rotor are equal, and the slot shapes of the tooth slots are also the same. That is, the 14 rotor teeth 102 are evenly distributed in the radial direction, and the rotor 100 itself is symmetrical about the straight line where the two rotor teeth 102 located on the same straight line are located.

[0039] In the motor, the number of poles of the motor can also be set accordingly as required. For example, it can also be set to a form where the pole-slot ratio is a non-integer multiple, such as 2 poles and 7 slots, 6 poles and 21 slots.

[0040] Figure 2 The current waveform of a 4-pole 14-slot motor in the prior art is shown. Figure 2 The motor in the prior art is a 4-pole 14-slot motor, and the number of coils in each slot is the same, which is 78. In this case, the running current of the motor is as follows: Figure 2 As shown. Figure 2 It can be seen that in the existing motor with 4 poles and 14 slots and 78 turns per slot, the running current amplitude of the motor output is between 11-12 A, the minimum value is 11.0153 A, the maximum value is 11.9390 A, and the average value is 11.5572 A. This form of output current waveform fluctuation is too small, and the electronic controller cannot identify the rotor position, so it cannot meet the requirements of sensorless position control.

[0041] To this end, the present invention proposes the following solution: the number of coils in different tooth slots is set to be different, thereby changing the output operating current waveform to meet the requirements of sensorless position control.

[0042] Figure 3 The figure shows the periodic variation of the motor current using the motor structure according to the present invention. Figure 3 The motor based on Figure 2 The difference between the motors is that the number of coils in each tooth slot is not exactly the same. Specifically, as an example, the number of coils in the 14 slots is set to 76-56-76-87-62-62-87-76-56-76-87-62-62-87 in sequence. When this coil number setting method is adopted, the measured motor running current waveform is as follows Figure 3 As shown. Figure 3 It can be seen that the maximum value of the running current output by the motor is 13.1183A, the minimum value is 11.5665A, and the average value is 12.1997A. Figure 2 The waveform change of the current is increased in comparison, making it easier for the electronic controller to identify the rotor position, thus facilitating sensorless position control.

[0043] According to the above ideas of the present invention, technicians in this field can also improve the solutions of other types of non-integer multiple pole slots, and set the number of coils in the tooth slots to be not exactly the same, thereby changing the current waveform therein, which is conducive to sensorless position control.

[0044] Although the above only proposes a specific winding number setting for a 4-pole 14-slot motor as an example, those skilled in the art can improve motors with other numbers of poles and slots based on the concept of the present invention. For example, corresponding improvements can be made to motors with 2 poles and 7 slots, 6 poles and 21 slots, etc., as long as the current waveform of the operation can meet the requirements of SLP by changing the number of windings.

[0045] As a further improvement of the present invention, the structure of the rotor is also adjusted according to the number of windings. Specifically, the tooth width of the rotor and the slot shape of the rotor can be adjusted accordingly. This adjustment is made considering that after the number of coils in each tooth slot is changed, the mass distribution and center of gravity position of the rotor assembly of the motor are changed, which may cause other problems during the operation of the motor. Therefore, it is necessary to adaptively adjust the tooth width of the rotor and the slot shape of the rotor.

[0046] For example, in order to improve the overall operating performance of the motor and reduce the vibration and noise during the operation of the motor, the slot shape of the rotor can be changed in combination with the number of coils in each slot, and it can be set to be not completely the same. For example, for slots with a small number of coils, the area corresponding to the slot shape of the slot can be reduced. Reducing the slot shape of the slot can make the center of gravity position of the rotor equipped with coils meet the dynamic balance requirements to reduce the vibration and noise during the operation of the motor. In addition, reducing the slot shape of the slot can also increase the slot fill rate in the slot, which can also enhance the performance of the motor. Reducing the slot shape of the slot can be achieved, for example, by increasing the radial dimension of the rotor hub between two adjacent rotor teeth that define the slot. In addition, the slot shape can also be changed by changing the shape of the top of the rotor tooth. "Fewer number of coils" in the present invention refers to a relative relationship compared to the number of coils in other slots. For example, for the winding number of 76-56-76-87-62-62-87-76-56-76-87-62-62-87 mentioned above, 76 is less than 87, but more than 62. 62 is less than 76, but more than 56. The slot shape can be adjusted by considering the number of coils in the slots, as long as the vibration and noise during the operation of the motor can be reduced.

[0047] In addition, the tooth width of the rotor can also be changed to improve the performance of the motor. Based on a similar idea, for a tooth slot with a small number of coils, the width of the rotor teeth on both sides of the tooth slot can be appropriately increased. This will also substantially reduce the area corresponding to the slot shape of the tooth slot. When designing the specific size of the tooth width, the tooth width flux should also be considered.

[0048] From the above, it can be seen that in the present invention, in order to make the current waveform of the motor running meet the requirements of position sensorless position control and achieve the requirements of low noise, low vibration, low electromagnetic interference and high performance, the present invention is based on the scheme that the motor has a non-integer number of pole slots, and designs the number of winding coils per slot of the motor to be regular and not completely the same, and designs the slot shape and tooth width of the motor rotor to different sizes and widths to match the corresponding number of winding coils, so as to simultaneously meet the requirements of SLP control, low noise, low vibration, excellent electromagnetic radiation interference and high performance.

[0049] The present invention has been clearly and completely described with reference to the above exemplary embodiments, and it should be understood by those skilled in the art that various other embodiments can be conceived by modifying the disclosed technical solutions without departing from the spirit and scope of the present invention. These embodiments should be understood to fall within the scope of the present invention determined based on the claims and any equivalent technical solutions thereof.

Claims

1. A brushed DC motor, comprising: A shell, one or both ends of which are open to form a receiving space inside the shell; a stator, wherein the stator is arranged in the accommodation space; A rotor, the rotor comprising a rotor hub, rotor teeth extending radially outward from the rotor hub, tooth grooves formed between adjacent rotor teeth, and the rotor hub being connectable to an output component to output power; A winding located in the tooth slot; It is characterized in that The ratio of the number of the rotor teeth to the magnetic poles of the brushed DC motor is a non-integer, and The number of windings in different tooth slots is not exactly the same, which increases the variation of the motor running current waveform, making it easier for the electronic controller to identify the rotor position, and The tooth widths of the rotor teeth are not exactly the same, and the shapes of the tooth grooves are not exactly the same. Based on the number of windings contained in the tooth slots, the slot shape of each tooth slot is adjusted so that the center of gravity of the rotor equipped with the windings meets the dynamic balance requirements, thereby reducing vibration and noise during the operation of the motor. Based on the number of windings accommodated in the tooth slots, the tooth width of each rotor tooth is adjusted so that the center of gravity position of the rotor equipped with the windings meets the dynamic balance requirements, thereby reducing vibration and noise during the operation of the motor.

2. A brushed DC motor according to claim 1, characterized in that: Adjusting the slot shape includes changing the radial dimension of the rotor hub between two adjacent rotor teeth defining the slot, or changing the shape of the top of the rotor tooth corresponding to the slot.

3. A brushed DC motor according to any one of claims 1-2, characterized in that: The rotor takes the following form: Made up of multiple rotor laminations, or It is formed into a whole by stamping, casting or extrusion of magnetic conductive material.

4. A brushed DC motor according to claim 3, characterized in that: The rotor laminations are silicon steel sheets made of soft magnetic material or carbon steel sheets made of soft magnetic material.

5. A brushed DC motor according to any one of claims 1-2, characterized in that: The conductor material in the winding is copper, aluminum, silver or a composite material containing copper and aluminum.

6. A brushed DC motor according to any one of claims 1-2, characterized in that: The brushed DC motor has 2 poles and 7 slots, 4 poles and 14 slots, or 6 poles and 21 slots.

Images