Low noise permanent magnet DC motor

Abstract

The application discloses a low-noise permanent magnet DC motor, which solves the technical problem of large noise of a permanent magnet DC motor in the prior art during operation, and comprises a shell and a rotating shaft extending out of the shell, a commutator fixed on the rotating shaft is arranged in the shell, and a carbon brush in contact with the commutator to transmit current is arranged in the shell, the inner side surface of the carbon brush comprises an axial arc surface and a connecting inclined surface connected in an axial direction, one end of the connecting inclined surface is connected with the axial arc surface, the other end of the connecting inclined surface is inclined to the outside of the shell and connected with the end surface of the carbon brush, and the axial arc surface is in surface-to-surface contact with the outer peripheral surface of the commutator.

Description

Technical field

[0001] The present invention relates to the technical field of permanent magnet DC motors, and in particular to a low-noise permanent magnet DC motor. [Background Technology]

[0002] Traditional permanent magnet DC motors used in push rods or column structures suffer from high noise levels. As living standards improve, consumers' expectations for motor noise levels are becoming increasingly stringent, and the noise levels of existing motors cannot meet these demands. Motor noise is caused by mechanical, electromagnetic, and aerodynamic noise. Since the motors in push rods and columns do not have fans, aerodynamic noise is very low, with mechanical and electromagnetic noise being the primary noise sources. Therefore, it is necessary to develop a low-noise permanent magnet DC motor to enhance the user experience. [Summary of the invention]

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a low-noise permanent magnet DC motor. By reducing the contact area between the carbon brush and the commutator, the noise generated by friction can be effectively reduced, thereby effectively reducing the motor noise.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A low-noise permanent magnet DC motor includes a housing and a rotating shaft with one end extending out of the housing. The housing is provided with a commutator fixed to the rotating shaft and a carbon brush that contacts the commutator to transmit current. The inner side surface of the carbon brush includes an axially connected axial arc surface and a connecting inclined surface. One end of the connecting inclined surface is connected to the axial arc surface, and the other end is inclined toward the outside of the housing and connected to the end face of the carbon brush. The axial arc surface forms a surface-to-surface contact with the outer peripheral surface of the commutator.

[0006] Furthermore, the vertical height of the axial arc surface is H, the axial height of the carbon brush is H1, and 0.05≤H / H1≤0.2. Furthermore, a lubricating oil layer is provided on the surface of the carbon brush.

[0007] Furthermore, the shell includes a casing, and a front cover and a rear cover for closing the front and rear ends of the casing. One end of the rotating shaft passes through the front cover and extends out of the casing. A bearing is provided between the other end of the rotating shaft and the rear cover, and lubricating grease is filled between the rotating shaft and the bearing.

[0008] Furthermore, the shell is provided with a rotor fixed on the rotating shaft and two magnets symmetrically sleeved on the outside of the rotor, the magnets include a first arc segment and a second arc segment provided at both ends of the first arc segment, and the thickness of the second arc segment is less than the thickness of the first arc segment.

[0009] Furthermore, the center of the second arc segment is offset from the center of the first arc segment.

[0010] Furthermore, the rotor includes a rotor core and a rotor winding. The rotor core is provided with a plurality of rotor skew slots for embedding the rotor winding at circumferential intervals. The rotor skew slots are skewed by half a rotor slot pitch.

[0011] Furthermore, the rotor chip includes a yoke fixed on the rotating shaft and T-shaped teeth evenly spaced circumferentially on the outside of the yoke. The T-shaped teeth are inclined in the same direction along the axial direction of the yoke, and the rotor skew slot is formed between two adjacent T-shaped teeth.

[0012] Furthermore, the T-shaped tooth includes a tooth root section extending radially along the yoke and a tooth crown section arranged concentrically with the yoke, the tooth root section is arranged between the yoke and the tooth crown section, and the outer side surface of the tooth crown section is provided with an axially penetrating groove; or, the thickness of the circumferential ends of the tooth crown section is less than the thickness of the middle part of the tooth crown section.

[0013] Furthermore, the T-shaped tooth includes a tooth root section extending radially along the yoke and a tooth crown section arranged concentrically with the yoke, the tooth root section is arranged between the yoke and the tooth crown section, the outer surface of the tooth crown section includes an arc surface arranged concentrically with the yoke and cutting edge bevels arranged at both ends of the arc surface, and an axially through groove is provided on the arc surface.

[0014] Beneficial effects of the present invention:

[0015] Compared with the prior art in which the entire inner side of the carbon brush is in surface contact with the outer peripheral surface of the commutator, the inner side of the carbon brush in the present invention only has the axial arc surface in contact with the outer peripheral surface of the commutator, thereby greatly reducing the contact area between the carbon brush and the commutator and reducing friction noise. Friction noise is mechanical noise, thereby reducing the noise of the motor and improving the user experience. In addition, it also ensures that the carbon brush can stably transmit current. Secondly, the inner side of the carbon brush in the present invention is composed of an axial arc surface and a connecting bevel, so the structure is relatively simple, which is conducive to the processing and forming of the inner side of the carbon brush and reduces the processing and manufacturing cost.

[0016] The vertical height of the axial arc surface is H, and the axial height of the carbon brush is H1, with 0.05≤H / H1≤0.2. This design ensures that the carbon brush can stably transmit current while effectively reducing the contact area between the carbon brush and the commutator, thereby effectively reducing friction noise.

[0017] The surface of the carbon brush is coated with a lubricating oil layer. This design effectively reduces the friction coefficient between the carbon brush and the commutator, thereby further reducing friction noise.

[0018] The housing consists of a casing, front and rear covers that enclose the front and rear ends of the casing. One end of the rotating shaft passes through the front cover and extends out of the casing. A bearing is located between the other end of the rotating shaft and the rear cover. Lubricating grease is filled between the rotating shaft and the bearing. This design effectively reduces the friction coefficient between the rotating shaft and the bearing, further reducing friction noise.

[0019] The housing houses a rotor fixed to the shaft and two magnets symmetrically sleeved around the rotor. The magnets comprise a first arc-shaped segment and second arc-shaped segments positioned at either end of the first segment. The thickness of the second arc-shaped segments is smaller than that of the first. This design, by changing the shape of the magnets, effectively improves the waveform of the motor's air gap magnetic flux density, making it closer to a sinusoidal distribution. This effectively reduces the spatial harmonics of the air gap magnetic flux density, minimizes electromagnetic torque fluctuations, and reduces the electromagnetic noise generated by the motor.

[0020] The center of the second arc segment is offset from the center of the first arc segment. This design can further make the air gap magnetic density close to a sinusoidal distribution, thereby further reducing electromagnetic torque fluctuations and reducing electromagnetic noise generated by the motor.

[0021] The rotor consists of a core and rotor windings. The core is circumferentially spaced with multiple rotor slots for mounting the rotor windings. The rotor slots are skewed at half the rotor slot pitch. This design reduces the motor's cogging torque, thereby weakening the parasitic torque and, consequently, reducing the motor's electromagnetic noise.

[0022] The T-shaped teeth consist of a root section extending radially along the yoke and a crown section concentrically positioned with the yoke. The root section is located between the yoke and crown sections, and the crown section's outer surface is provided with an axially extending groove. Alternatively, the crown section's circumferential ends are thinner than its center. This design effectively reduces the rotor's weight and moment of inertia, thereby lowering the motor's ripple torque, ensuring smooth operation and reducing electromagnetic noise.

[0023] The T-shaped teeth consist of a root section extending radially along the yoke and a crown section concentric with the yoke. The root section is located between the yoke and crown sections. The outer surface of the crown section includes an arcuate surface concentric with the yoke and chamfered edges at either end of the arcuate surface. The arcuate surface is provided with an axially extending groove. This design further reduces the weight and moment of inertia of the rotor, thereby further reducing the ripple torque of the motor and ensuring smoother operation.

[0024] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and drawings.

Brief Description of the Drawings

[0025] The present invention will be further described below with reference to the accompanying drawings:

[0026] Figure 1An exploded view of a portion of the structure of a permanent magnet DC motor in a preferred embodiment of the present invention;

[0027] Figure 2 A cross-sectional view of a permanent magnet DC motor in a preferred embodiment of the present invention;

[0028] Figure 3 A schematic diagram of the coordination between the carbon brush and the commutator in a preferred embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the cooperation between the magnet and the housing in a preferred embodiment of the present invention;

[0030] Figure 5 This is a schematic structural diagram of a commutator installed on a rotating shaft in a preferred embodiment of the present invention;

[0031] Figure 6 A top view of a commutator in a preferred embodiment of the present invention;

[0032] Figure 7 Schematic diagram of the structure of the commutator segment in a preferred embodiment of the present invention. [Specific implementation method]

[0033] The present invention provides a low-noise permanent magnet DC motor, comprising a housing and a rotating shaft with one end extending out of the housing. A commutator fixed to the rotating shaft and a carbon brush in contact with the commutator to transmit current are provided in the housing. The inner side surface of the carbon brush comprises an axially connected axial arc surface and a connecting inclined surface. One end of the connecting inclined surface is connected to the axial arc surface, and the other end is inclined toward the outside of the housing and connected to the end face of the carbon brush. The axial arc surface forms surface-to-surface contact with the outer peripheral surface of the commutator.

[0034] Compared with the prior art in which the entire inner side of the carbon brush is in surface contact with the outer peripheral surface of the commutator, the inner side of the carbon brush in the present invention only has the axial arc surface in contact with the outer peripheral surface of the commutator, thereby greatly reducing the contact area between the carbon brush and the commutator and reducing friction noise. Friction noise is mechanical noise, thereby reducing the noise of the motor and improving the user experience. In addition, it also ensures that the carbon brush can stably transmit current. Secondly, the inner side of the carbon brush in the present invention is composed of an axial arc surface and a connecting bevel, so the structure is relatively simple, which is conducive to the processing and forming of the inner side of the carbon brush and reduces the processing and manufacturing cost.

[0035] The following is an explanation and description of the technical solutions of the embodiments of the present invention in conjunction with the drawings of the embodiments of the present invention. However, the following embodiments are only preferred embodiments of the present invention and are not exhaustive. Based on the embodiments in the implementation manner, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0036] Reference Figures 1 to 3As shown, the low-noise permanent magnet DC motor in this preferred embodiment includes a housing 100 and a rotating shaft 200 with one end extending out of the housing 100. The housing 100 is provided with a commutator 300 fixed on the rotating shaft 200 and a carbon brush 400 in contact with the commutator 300 to transmit current. The carbon brush 400 is fixed in the housing 100 by a bracket. The inner side of the carbon brush 400 includes an axially connected axial arc surface 410 and a connecting inclined surface 420. The connecting inclined surface 420 is an inclined plane or The inclined arc surface, the axial arc surface 410 matches the outer peripheral surface of the commutator 300, the upper end of the axial arc surface 410 is flush with the upper end surface of the carbon brush, the upper end of the connecting inclined surface 420 is connected to the lower end of the axial arc surface 410, and the lower end of the connecting inclined surface 420 is inclined toward the outside of the shell and connected to the lower end surface of the carbon brush, that is, the inner side surface of the carbon brush is composed of the axial arc surface 410 and the connecting inclined surface 420, and the axial arc surface 410 forms a surface-to-surface contact with the outer peripheral surface of the commutator 300.

[0037] Compared with the prior art in which the entire inner side surface of the carbon brush is in surface-to-surface contact with the outer peripheral surface of the commutator, in this embodiment, only the axial arc surface 410 of the inner side surface of the carbon brush is in contact with the outer peripheral surface of the commutator 300, thereby greatly reducing the contact area between the carbon brush 400 and the commutator 300 and reducing friction noise, which is mechanical noise. This reduces the noise of the motor and improves the user experience. In addition, it also ensures that the carbon brush 400 can stably transmit current. Secondly, the structure of the inner side surface of the carbon brush in this embodiment is relatively simple, which is conducive to the processing and forming of the inner side surface of the carbon brush and reduces the processing and manufacturing cost.

[0038] Preferably, in this embodiment, the vertical height of the axial arc surface 410 is H, and the axial height of the carbon brush is H1. 0.05≤H / H1≤0.2. When H / H1 is less than 0.5, the contact area between the carbon brush 400 and the commutator 300 is too small, affecting the current transmission effect. When H / H1 is greater than 0.2, the contact area between the carbon brush 400 and the commutator 300 is too large, resulting in excessive mechanical noise. Therefore, in this embodiment, H / H1 is preferably 0.1. This design can not only ensure that the carbon brush 400 can stably transmit current, but also effectively reduce the contact area between the carbon brush 400 and the commutator 300, thereby effectively reducing friction noise. Of course, H / H1 can also be, but is not limited to, 0.05, 0.08, 0.12, 0.15, 0.18, 0.2, etc.

[0039] It can be understood that in other embodiments of the present invention, the axial arc surface is arranged at the bottom of the connecting bevel; or the inner side surface of the carbon brush includes an axially connected axial arc surface and two connecting bevels, the axial arc surface is connected between one ends of the two connecting bevels, and the other ends of the two connecting bevels are inclined toward the outside of the shell and are respectively connected to the end faces of the carbon brush.

[0040] In order to further reduce the friction noise between the carbon brush 400 and the commutator 300, a lubricating oil layer is provided on the surface of the carbon brush in this embodiment, thereby effectively reducing the friction coefficient between the carbon brush 400 and the commutator 300, thereby further reducing the friction noise.

[0041] The housing 100 in this embodiment includes a casing 110, a front cover 120, and a rear cover 130 for enclosing the front and rear ends of the casing 110. One end of the rotating shaft 200 extends through the front cover 120 and out of the casing 100. A bearing 140 is disposed between the other end of the rotating shaft 200 and the rear cover 130. Lubricating grease is filled between the rotating shaft 200 and the bearing 140. This design effectively reduces the coefficient of friction between the rotating shaft 200 and the bearing 140, thereby further reducing friction noise.

[0042] In addition, if Figure 4 As shown, in this embodiment, the housing 100 further includes a rotor 500 fixed to the rotating shaft 200 and two magnets 600 symmetrically sleeved around the outside of the rotor 500. The magnets 600 are arc-shaped, comprising a first arc segment 610 and second arc segments 620 disposed at either end of the first arc segment 610. The thickness of the second arc segments 620 is less than that of the first arc segment 610. This design, by changing the shape of the magnets 600, effectively improves the waveform of the motor's air gap flux density, making it closer to a sinusoidal distribution. This effectively reduces the spatial harmonics of the air gap flux density, reduces electromagnetic torque fluctuations, and reduces the electromagnetic noise generated by the motor.

[0043] Specifically, the inner and outer surfaces of the magnetic steel in this embodiment are both arc-shaped surfaces, and beveled surfaces 621 are provided at both ends of the outer surface. The portion corresponding to the beveled surfaces 621 forms the second arc segment 620, and the portion located between the two beveled surfaces 621 forms the first arc segment 610. Such a design can effectively reduce the processing difficulty of the magnetic steel 600.

[0044] Of course, it is understood that the inner and outer surfaces of the second arc segment are concentric arcs, the thickness of the second arc segment is less than that of the first arc segment, and the center of the second arc segment is offset from the center of the first arc segment. This design can further make the air gap magnetic flux density closer to a sinusoidal distribution, thereby further reducing electromagnetic torque fluctuations and lowering the electromagnetic noise generated by the motor.

[0045] In addition, if Figures 5 to 7 As shown, the rotor 500 in this embodiment includes a rotor lamination and a rotor winding (not shown). The rotor lamination is circumferentially provided with a plurality of rotor skew slots 510 for receiving the rotor winding. The rotor skew slots 510 are skewed at half the rotor slot pitch. This design reduces the cogging torque of the motor, thereby reducing torque ripple and, consequently, electromagnetic noise.

[0046] Specifically, the rotor chips in this embodiment are composed of multiple commutator segments 520 stacked axially. The commutator segments 520 include a yoke 521 fixed to the rotating shaft 200 and T-shaped teeth 522 arranged on the outside of the yoke 521 at evenly spaced circumferential intervals. When the commutator segments 520 are stacked, the T-shaped teeth 522 are tilted in the same direction along the axial direction of the yoke 521 so that the above-mentioned rotor skew slot 510 is formed between two adjacent T-shaped teeth 522. The T-shaped tooth 522 includes a tooth root section extending radially along the yoke 521 and a tooth crown section arranged concentrically with the yoke 521. The tooth root section is arranged between the yoke 521 and the tooth crown section. The outer side surface of the tooth crown section includes an arc surface arranged concentrically with the yoke 521 and a cutting bevel 5222 arranged at both ends of the arc surface. The cutting bevel 5222 makes the thickness of the tooth crown section at both ends in the circumferential direction smaller than the thickness of the middle part of the tooth crown section. An axially penetrating groove 5221 is provided on the arc surface. Such a design can effectively reduce the weight and rotational inertia of the rotor 500, thereby reducing the ripple torque of the motor, making it run smoothly, and further reducing the electromagnetic noise of the motor.

[0047] It can be understood that in other embodiments of the present invention, the outer side surface of the tooth crown segment is provided with at least one axially penetrating groove; or, the thickness of the circumferential ends of the tooth crown segment is less than the thickness of the middle part of the tooth crown segment. Such a design effectively improves the waveform of the air gap magnetic density of the motor, making the air gap magnetic density close to a sinusoidal distribution, thereby effectively weakening the spatial harmonics of the air gap magnetic density, reducing the ripple torque of the motor, and thereby reducing the electromagnetic noise generated by the motor.

[0048] In addition, the low-noise permanent magnet DC motor in this embodiment can be used in a push rod or lifting column structure to enhance the user experience.

[0049] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art will understand that the present invention includes, but is not limited to, the contents described in the drawings and the above specific embodiments. Any modifications that do not deviate from the functional and structural principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A low-noise permanent magnet DC motor comprising a housing and a rotating shaft with one end extending out of the housing, wherein a commutator fixed to the rotating shaft and carbon brushes contacting the commutator to transmit current are provided within the housing, characterized in that: The inner side surface of the carbon brush includes an axially connected axial arc surface and a connecting inclined surface, one end of the connecting inclined surface is connected to the axial arc surface, and the other end is inclined toward the outer side of the shell and connected to the end face of the carbon brush, the axial arc surface forms surface-to-surface contact with the outer peripheral surface of the commutator, the shell is provided with a rotor fixed on the rotating shaft and two magnets symmetrically sleeved on the outer side of the rotor, the magnet includes a first arc segment and a second arc segment provided at both ends of the first arc segment, the thickness of the second arc segment is less than the thickness of the first arc segment, the rotor includes a rotor chip and a rotor winding, the rotor chip is circumferentially spaced apart with a plurality of rotor skew slots for embedding the rotor winding, the rotor skew slots are inclined by half the rotor slot pitch, the rotor chip includes a yoke fixed on the rotating shaft and T-shaped teeth evenly spaced circumferentially on the outer side of the yoke, the T-shaped teeth are inclined in the same direction along the axial direction of the yoke, and the rotor skew slot is formed between two adjacent T-shaped teeth.

2. A low-noise permanent magnet DC motor according to claim 1, characterized in that: The vertical height of the axial arc surface is H, the axial height of the carbon brush is H1, and 0.05≤H / H1≤0.

2.

3. A low-noise permanent magnet DC motor according to claim 1, characterized in that: A lubricating oil layer is provided on the surface of the carbon brush.

4. A low-noise permanent magnet DC motor according to claim 1, characterized in that: The shell includes a casing, and a front cover and a rear cover for closing the front and rear ends of the casing. One end of the rotating shaft passes through the front cover and extends out of the casing. A bearing is provided between the other end of the rotating shaft and the rear cover. Lubricating grease is filled between the rotating shaft and the bearing.

5. A low-noise permanent magnet DC motor according to claim 1, characterized in that: The center of the second arc segment is offset from the center of the first arc segment.

6. A low-noise permanent magnet DC motor according to claim 1, characterized in that: The T-shaped tooth includes a tooth root section extending radially along the yoke and a tooth crown section arranged concentrically with the yoke, the tooth root section is arranged between the yoke and the tooth crown section, and the outer side surface of the tooth crown section is provided with an axially penetrating groove; or, the T-shaped tooth includes a tooth root section extending radially along the yoke and a tooth crown section arranged concentrically with the yoke, the tooth root section is arranged between the yoke and the tooth crown section, and the thickness of the circumferential ends of the tooth crown section is less than the thickness of the middle part of the tooth crown section.

7. A low-noise permanent magnet DC motor according to claim 1, characterized in that: The T-shaped tooth includes a tooth root section extending radially along the yoke and a tooth crown section arranged concentrically with the yoke. The tooth root section is arranged between the yoke and the tooth crown section. The outer side surface of the tooth crown section includes an arcuate surface arranged concentrically with the yoke and cutting edge bevels arranged at both ends of the arcuate surface. An axially penetrating groove is provided on the arcuate surface.

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