Direct current motor
By adjusting the phase difference between the armature torque and the cogging torque, the problem of vibration and noise in DC motors caused by uneven timing of the power supply brush rectification was solved, resulting in lower vibration and noise levels and improved vehicle ride comfort.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DENSO CORP
- Filing Date
- 2022-03-28
- Publication Date
- 2026-06-05
AI Technical Summary
The uneven rectification timing between the power brushes in existing DC motors leads to an imbalance in the magnetic field of the armature coil, resulting in vibration and noise, which makes it difficult to meet the requirements for low vibration and low noise in vehicle structural components.
By adjusting the phase difference between the armature torque and the cogging torque, specifically by adjusting the combined shift angle S of angles C, D, E, and F, the phase difference between the armature torque and the cogging torque is made to be 180 degrees ± 80 degrees, preferably 180 degrees ± 60 degrees, in order to reduce the deviation of the rectification timing.
It effectively reduces the vibration and noise of DC motors, improving vehicle comfort and the low vibration and low noise performance of structural components.
Smart Images
Figure CN117223203B_ABST
Abstract
Description
[0001] Cross-references to related applications
[0002] This application is based on the interest of claiming priority to Japanese Patent Application No. 2021-075818, filed on April 28, 2021, the entire contents of which are incorporated herein by reference. Technical Field
[0003] This disclosure relates to DC motors. Background Technology
[0004] For example, in vehicles equipped with ABS (Anti-lock Braking System), a DC motor is used as the drive source for the ABS. As disclosed in Patent Document 1, this DC motor includes an armature mounted on the shaft, a commutator, and multiple power brushes sliding on multiple commutator segments. If a timing deviation in rectification occurs among these multiple power brushes, an imbalance in the magnetic field is generated in the armature coil, resulting in vibration and noise during rotation.
[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-158359
[0006] Patent Document 1 proposes a technique to reduce armature resonance by improving the balance of the winding method of the coil forming the armature in order to reduce vibration and noise in a DC motor. However, in recent years, with the shift of vehicle power sources from engines to electric motors, there is a growing demand for lower vibration and noise levels in vehicle structural components to improve passenger comfort. Therefore, further reductions in vibration and noise are needed for DC motors assembled in vehicles. Summary of the Invention
[0007] The purpose of this disclosure is to provide a DC motor that can further reduce vibration and noise compared to the past.
[0008] The DC motor disclosed herein comprises: a rotor having an armature core and a commutator, the armature core having a plurality of teeth arranged axially around an axis, with slots formed between adjacent teeth, and the commutator having a plurality of commutator segments arranged axially adjacent to the armature core; a stator having a plurality of excitation magnets having a plurality of magnetic poles arranged axially around an axis; and brush holders having a plurality of power supply brushes arranged in contact with the commutator segments axially around an axis. When the natural number is n, the relationship between the number of slots A and the number of magnetic poles B is A = n × B. When viewed from the output side of the shaft and with the axis as a reference, a first hypothetical center position is defined in the circumferential direction passing through the teeth. When the angle C of the line intersects with the second imaginary line at the center position of the undercut circumference between the adjacent pair of commutator segments corresponding to the tooth, the angle D of the third imaginary line passing through the non-magnetic flux region of the excitation magnet and the fourth imaginary line at the center position of the circumference of the power supply brush, the angle E of the third imaginary line intersects with the fifth imaginary line at the center position of the circumference of the magnetic pole, and the angle F of the stator reference line intersects with the sixth imaginary line passing through the reference point of the brush gripping the stator assembly position, the shift angle S, represented by angle C + angle D - angle E + angle F, is adjusted so that the phase difference between the armature torque and the cogging torque is 180 degrees ± 80 degrees.
[0009] In a DC motor with this structure, the timing of rectification can be adjusted among multiple power brushes by adjusting the shift angle S, which is a composite of angles C to F, which are related to the phase of the armature torque and the cogging torque. According to the inventors' verification, considering the output characteristics of the DC motor, it was confirmed that if the shift angle S is set such that the phase difference between the armature torque and the cogging torque is 180 degrees ± 80 degrees, the vibration and noise of the DC motor can be further reduced compared to the past. Furthermore, the shift angle S is more preferably adjusted to achieve a phase difference of 180 degrees ± 60 degrees.
[0010] In the DC motor of this disclosure, the preferred ranges for angle C are 0° ± 3°, angle D is 30° ± 3°, angle E is 30° ± 3°, angle F is 0° ± 3°, and shift angle S is 0° ± 3°. Furthermore, it is preferable that, when the number of magnetic poles B is 6 and the natural number n is 3, each winding is wound across 3 teeth at equal intervals of 120° to form 3 coils. The DC motor of this disclosure is used to control a brake.
[0011] According to this disclosure, a DC motor is provided that can further reduce vibration and noise compared to the past. Attached Figure Description
[0012] Figure 1 This is an exploded perspective view that schematically shows the structure of the DC motor of this embodiment.
[0013] Figure 2This is a side view of the rotor as seen from the output side of the shaft.
[0014] Figure 3 This is a side view of the stator as seen from the output side of the shaft.
[0015] Figure 4 This is a side view of the brush holder, viewed from the side opposite to the output side of the shaft.
[0016] Figure 5 This is a side view of the DC motor as seen from the output side of the shaft.
[0017] Figure 6 It is a graph showing the relationship between the shift angle and torque pulsation based on the analytical results.
[0018] Figure 7 It is a graph showing the relationship between the shift angle and the phase of torque pulsation (armature torque and cogging torque) based on the analytical results. Detailed Implementation
[0019] The following is a reference to the appendix. Figure 1 The following description will explain this embodiment. To facilitate understanding, the same structural elements will be labeled with the same reference numerals as much as possible in the accompanying drawings, and repeated descriptions will be omitted.
[0020] Figure 1 This is an exploded perspective view schematically showing the structure of the DC motor 10 in this embodiment. The DC motor 10 is, for example, a DC motor that is assembled into a drive source of a control brake such as an ABS (anti-lock braking system). Specifically, the hydraulic pressure is controlled by converting the driving force of the rotation of the DC motor 10 into the linear reciprocating motion of the piston of a hydraulic pump (not shown), thereby controlling the braking force of the brake disc (not shown).
[0021] The DC motor 10 includes a rotor 20, a stator 30, and a brush assembly 40. The rotor 20 includes: a shaft 21 that functions as an output shaft; an armature core 22 fixed to the shaft 21; a commutator 23 also fixed to the shaft 21 adjacent to its output side; and multiple windings 24 wound around the armature core 22. One end of the shaft 21 protrudes outward from the brush assembly 40 and is connected to a driven device (not shown). Thus, the shaft 21 transmits rotational driving force to the driven device.
[0022] Figure 2 This is a side view of the rotor 20 as seen from the output side of shaft 21. Furthermore, in Figure 2 Only a portion of winding 24 is shown in the diagram. Please refer to the diagram as well. Figure 1 as well as Figure 2The armature core 22 includes a cylindrical annular portion 22a that is pressed into and fixed to a shaft 21, and a plurality of teeth 22b extending radially from the outer peripheral surface of the annular portion 22a. A groove 22c is formed between adjacent pairs of teeth 22b. The armature core 22 is made of a magnetic material.
[0023] The teeth 22b are arranged at equal intervals in the circumferential direction around the axis X of the shaft 21. When viewed from the output side of the shaft 21, the teeth 22b form a T-shape. In this embodiment, the armature core 22 has 18 teeth 22b arranged at 20-degree intervals around the axis X, and therefore, 18 slots 22c are formed on the outer peripheral surface of the armature core 22, arranged at equal intervals in the circumferential direction around the axis X.
[0024] Multiple windings 24 are wound around the armature core 22 via so-called distributed winding. Specifically, as... Figure 2 As shown, a winding 24 is wound multiple times across three teeth 22b to form the first coil 25. The same winding 24 is wound multiple times across three teeth 22b separated by 120 degrees around the axis X to form the second coil 25. This winding 24 is further wound multiple times across three teeth 22b separated by 120 degrees around the axis X to form the third coil 25.
[0025] In this embodiment, the armature core 22 has 18 teeth 22b, so the process of forming three coils 25 by winding based on one winding 24 is repeated 18 times while staggering the teeth 22b. That is, coils 25 are further stacked on top of the already formed coils 25. Thus, the final number of coils 25 in the armature core 22 is 3 × 18 = 54. The ends of each winding 24 are electrically connected to the commutator segments 23a of the commutator 23 (described later) (not shown).
[0026] The commutator 23 is pressed into the shaft 21 and fixed in place. The commutator 23 has a plurality of commutator segments (rectifier segments) 23a arranged at equal intervals in the circumferential direction around the axis X. The number of commutator segments 23a is 18, corresponding to the number of teeth 22b and slots 22c. Adjacent commutator segments 23a are arranged in an electrically insulated manner, with grooves (undercuts 23b) formed between adjacent segments. Each commutator segment 23a is electrically connected to the end of its corresponding winding 24 (not shown).
[0027] Figure 3 This is a side view of the stator 30 as seen from the output side of shaft 21. Furthermore, in Figure 3 The rotor 20 and brush assembly 40 are omitted from the diagram. Please refer to the diagram for further details. Figure 1 as well as Figure 3 The stator 30 has a magnetic yoke housing 31.
[0028] The yoke housing 31 includes: a circular bottom 31a; a cylindrical sidewall portion 31b extending from the outer periphery of the circular bottom 31a along the axis X; an opening 31c in the sidewall portion 31b defined on the opposite side to the bottom 31a; and a flange 31d extending outward from the outer periphery of the opening 31c, orthogonal to the sidewall portion 31b. A rotor 20 is housed within the yoke housing 31, and a bearing member (not shown) rotatably supports one end of a shaft 21 of the rotor 20 at the bottom 31a. The central axis of the cylindrical sidewall portion 31b coincides with the axis X of the shaft 21. A brush device 40 is mounted at the opening 31c.
[0029] Multiple excitation magnets 32 are fixed to the inner circumferential surface of the sidewall portion 31b. In this embodiment, three excitation magnets 32, which are bent along the inner circumferential surface of the sidewall portion 31b, are arranged at equal intervals of 120 degrees. Each excitation magnet 32 is a magnet with an integrated structure of an N-pole magnet 32N and an S-pole magnet 32S, forming a non-magnetic flux region 32a at the center position of the circumferential axis X around the axis 21. Alternatively, the excitation magnet 32 can also be an excitation magnet composed of separate N-pole magnet 32N and S-pole magnet 32S.
[0030] Each excitation magnet 32 is arranged radially outside the tooth 22b of the rotor 20, opposite to the tooth 22b. Based on the current flowing through the coil 25, an electromagnetic force is generated in the armature core 22, which becomes the torque that rotates the rotor 20. Furthermore, the three excitation magnets 32 have six poles; therefore, the DC motor 10 of this embodiment is a motor with six poles. That is, when the natural number n is 3, the relationship between the number of slots 22c (A) and the number of poles (B) (A) = n × (B) becomes 18 = 3 × 6.
[0031] Return to Figure 1 The brush device 40 includes a brush holder 41 that is installed in the opening 31c of the magnetic yoke housing 31, for example by riveting, to seal the opening 31c. The brush holder 41 has an opening 41a that accommodates the other end of the shaft 21 of the rotor 20, and a bearing member (not shown) that supports the other end of the shaft 21 for rotation is disposed in the opening 41a.
[0032] Figure 4 This is a side view of the brush holder 41, viewed from the side opposite to the output side of shaft 21. Furthermore, in Figure 4 The diagram of rotor 20 is omitted. Please refer to the diagram as well. Figure 1 as well as Figure 4 A plurality of brush holders 42 are held on the inner surface of the brush holder 41, and a power supply brush 43 is supported in each brush holder 42. In this embodiment, six brush holders 42, i.e., power supply brushes 43, are arranged at equal intervals (60-degree intervals) around the axis X of shaft 21. See also... Figure 3 as well as Figure 4Each power supply brush 43 is positioned at the circumferential center of the N pole magnet 32N and the S pole magnet 32S of each excitation magnet 32, i.e., at the center of the magnetic pole.
[0033] Each power brush 43 is a sintered body mainly comprising graphite powder and bulk powder, and is connected to a power supply component (not shown) disposed on the brush holder 41. Thus, current is supplied to the power brush 43 from an external power source through the power supply component. On the other hand, the brush holder 41 and the brush box 42 are formed of electrically insulating materials such as resin.
[0034] The power supply brushes 43 are arranged radially outside the commutator segment 23a of the commutator 23. Through a coil spring (not shown) arranged within the brush holder 42, force is applied radially towards the commutator segment 23a of the DC motor 10 in a retractable manner. As a result, the radially inner ends of the power supply brushes 43 are pressed against the commutator segment 23a and make contact. As the rotor 20 rotates, each power supply brush 43 slides on the commutator segment 23a, supplying current to the winding 24, i.e., the coil 25, which is electrically connected to the commutator segment 23a.
[0035] Figure 5 This is a side view of the DC motor 10 as seen from the output side of shaft 21. (See also...) Figure 1 as well as Figure 5 A reference line RL is defined in the yoke housing 31, passing through the axis X of the shaft 21. The reference line RL is a line passing through the center of one of the three openings 31e formed in the flange 31d of the yoke housing 31. Furthermore, the three openings 31e are arranged at equal intervals of 120 degrees around the axis X. In this embodiment, the reference line RL coincides with the non-magnetic flux region 32a of the excitation magnet 32 within the yoke housing 31.
[0036] On the other hand, three bottomed holes 41b are arranged at 120-degree intervals around the axis X on the outer surface of the brush holder 41. The center of each bottomed hole 41b serves as a reference point RP for the assembly position when the brush holder 41, i.e., the brush device 40, is assembled onto the yoke housing 31. Specifically, the assembly position of the brush holder 41 relative to the yoke housing 31 around the axis X is defined by adjusting the position of the reference line RL of the yoke housing 31 and the reference point RP of the brush holder 41.
[0037] Here, we will explain the torque variations that are easily caused by the construction of DC motors. The key factors contributing to these torque variations are the armature torque, based on the electromagnetic force generated by the armature core 22 when the coil 25 is energized, and the cogging torque, resulting from the influence of the magnetic lines of force exerted on the armature core 22 by the excitation magnet 32. Both the armature torque and the cogging torque vary depending on the rotational position of the rotor 20; specifically, the magnitude of the torque variation based on the rotational angle is represented by a beautiful sine curve.
[0038] The torque ripple is obtained by adding the armature torque and the cogging torque. Therefore, if the phase of the sine curve of the armature torque coincides with the phase of the sine curve of the cogging torque, the torque ripple increases, thus increasing the vibration and noise of the DC motor. In this invention, the torque ripple is reduced and the vibration and noise of the DC motor 10 are reduced by adjusting the phases of the armature torque and the cogging torque, i.e., by shifting their phases.
[0039] The inventors focus on adjusting the timing of rectification among multiple power supply brushes 43 by adjusting a shift angle S, which is a composite of the following angles related to the phase of armature torque and cogging torque, when torque pulsation is reduced.
[0040] From the first perspective, such as Figure 2 As shown, when viewed from the output side of shaft 21 and with shaft center X as the reference, the angle C between the first imaginary line L1 passing through the circumferential center position of the tooth 22b of armature core 22 and the second imaginary line L2 passing through the circumferential center positions of the adjacent pair of commutator segments 23a, 23a corresponding to the tooth 22b is defined. The size of this angle C is adjusted within the range of 0 degrees ± 3 degrees to account for tolerances.
[0041] As a second perspective, such as Figure 4 As shown, when viewed from the output side of shaft 21 and with the axis X as the reference (in... Figure 4 In the diagram, (representing the angle observed from the side opposite to the output side), the angle D is defined as the angle at which a third imaginary line L3 passing through the non-magnetic flux region 32a of the excitation magnet 32 intersects with a fourth imaginary line L4 passing through the circumferential center of the power supply brush 43, for example, the N-pole magnet 32N adjacent to the third imaginary line L3. This angle D is adjusted within a range of 30 degrees ± 3 degrees to account for tolerances. Furthermore, the fourth imaginary line L4 can also be defined by a line that passes through the circumferential center of the brush box 42 instead of the power supply brush 43.
[0042] As a third perspective, such as Figure 3 As shown, when viewed from the output side of shaft 21 and with the shaft center X as a reference, the angle E between the third imaginary line L3 passing through the non-magnetic flux region 32a of the excitation magnet 32 and the fifth imaginary line L5 passing through the circumferential center position (pole center) of, for example, the N-pole magnet 32N adjacent to the third imaginary line L3 is defined. The size of this angle E is adjusted within a range of 30 degrees ± 3 degrees to take tolerance.
[0043] As a fourth perspective, such as Figure 5As shown, when viewed from the output side of shaft 21 and with the shaft center X as a reference, the angle F between the reference line RL of stator 30 (i.e., yoke housing 31) and the sixth imaginary line L6 passing through brush holder 41 to the assembly position of yoke housing 31 is defined. Furthermore, in Figure 5 In this case, angle F is set to 0 degrees, so the baseline RL coincides with the sixth imaginary line L6. The angle F is adjusted within a range of 0 degrees ± 3 degrees to account for tolerances.
[0044] In this embodiment, since the timing of rectification is adjusted, the shift angle S, represented by angle C + angle D - angle E + angle F, is set. When setting this shift angle S, the inventors conducted verification based on analytical simulation. In the analytical simulation, in the DC motor 10 of this embodiment, the relationship between the shift angle S and torque pulsation (armature torque and cogging torque) when the rotor 20 rotates at an unloaded vibration rate of 1500 rpm was verified.
[0045] Figure 6 This is a graph showing the relationship between the shift angle S and torque ripple based on analytical simulation results. The DC motor 10 used for analysis has 18 teeth 22b and 6 magnetic poles; therefore, the vertical axis on the right side of the graph represents the analytical value (N·m) of torque ripple under 18 vibration modes. On the other hand, the vertical axis on the left side of the graph represents the measured value (m / s) of the DC motor 10 under 18 vibration modes. 2 The average value of the torque ripple. The analytical value of the torque ripple and the measured value of 18 vibrations both show roughly the same result. Specifically, it is confirmed that the torque ripple is minimized when the displacement angle S is set to 0 degrees, and increases as the displacement angle S increases or decreases from 0 degrees.
[0046] Figure 7 This is a graph showing the relationship between the shift angle S and the phase of torque pulsations (armature torque and cogging torque) based on the same analytical simulation results. From this graph, it can be confirmed that when the shift angle S is 0 degrees, i.e., when the phase difference between the armature torque and the cogging torque is 180 degrees, the phases of the two torque sine curves are most effectively canceled out. It is also confirmed that as the shift angle S increases or decreases from 0 degrees, the phase difference between the two torques increases or decreases from 180 degrees.
[0047] Based on the above analytical simulation results, it was confirmed that setting the shift angle S to 0 degrees minimizes torque ripple, resulting in reduced vibration and noise. Furthermore, it is common knowledge that reducing torque ripple leads to improved output characteristics of the DC motor 10. Therefore, considering the output characteristics of the DC motor 10, it is preferable to set the shift angle S within a range of 0 degrees ± 4 degrees, with a phase difference of 180 degrees ± 80 degrees. Moreover, to further reduce vibration and noise of the DC motor 10, it is more preferable to set the shift angle S within a range of 0 degrees ± 3 degrees, with a phase difference of 180 degrees ± 60 degrees.
[0048] The present embodiment has been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Any technology obtained by those skilled in the art through appropriate design modifications to these specific examples, provided it possesses the features of this disclosure, is also included within the scope of this disclosure. The elements, their configurations, conditions, shapes, etc., of each of the above-described specific examples are not limited to the illustrated content and can be appropriately modified. The elements of each of the above-described specific examples can be appropriately combined, provided they do not create technical contradictions.
Claims
1. A DC motor, wherein, have: The rotor has an armature core and a commutator, the armature core having a plurality of teeth arranged around an axis with slots formed between adjacent teeth, and the commutator having a plurality of commutator segments arranged around the axis adjacent to the armature core; The stator has a plurality of excitation magnets, each having multiple magnetic poles, arranged around the said axis; and A brush holder holds multiple power supply brushes arranged in contact with the commutator segment around the axis. When the natural number is n, the relationship between the number of slots A and the number of magnetic poles B is A = n × B. When viewed from the output side of the shaft and with the shaft center as a reference, When the angle C of the intersection of the first imaginary line and the second imaginary line, the angle D of the intersection of the third imaginary line and the fourth imaginary line, the angle E of the intersection of the third imaginary line and the fifth imaginary line, and the angle F of the intersection of the stator's reference line and the sixth imaginary line are defined, Adjust the shift angle S, represented by angle C + angle D - angle E + angle F, so that the phase difference between the armature torque and the cogging torque is 180 degrees ± 80 degrees, wherein... The first imaginary line passes through the circumferential center of the tooth, and the second imaginary line passes through the circumferential center of the undercut between the adjacent pair of commutator segments corresponding to the tooth. The third imaginary line passes through the non-magnetic flux region of the excitation magnet, and the fourth imaginary line passes through the circumferential center of the power supply brush. The fifth imaginary line passes through the circumferential center of the magnetic pole. The sixth imaginary line passes through the reference point of the brush gripping the stator assembly position.
2. The DC motor according to claim 1, wherein, Adjust the shift angle S so that the phase difference is 180 degrees ± 60 degrees.
3. The DC motor according to claim 2, wherein, The range of angle C is 0 degrees ± 3 degrees, the range of angle D is 30 degrees ± 3 degrees, the range of angle E is 30 degrees ± 3 degrees, the range of angle F is 0 degrees ± 3 degrees, and the range of displacement angle S is 0 degrees ± 3 degrees.
4. The DC motor according to any one of claims 1 to 3, wherein, When the number of magnetic poles B is 6 and the natural number n is 3, each winding is wound across 3 teeth at equal intervals of 120 degrees to form 3 coils.
5. The DC motor according to any one of claims 1 to 3, wherein, The DC motor is used to control the brake.