Motor unit

Abstract

A motor unit facilitates grounding of a circuit board outside a housing with a simple structure. The utility model relates to a motor unit, which is provided with a shell made of metal; the stator and the rotor are arranged in the shell; and a circuit board provided outside the housing and provided with a first terminal and an electronic component electrically connected to the first terminal, in which the first terminal is in contact with and electrically connected to the housing.

Description

TECHNICAL FIELD

[0001] The utility model relates to a motor unit. BACKGROUND

[0002] In the past, there is a motor unit, which has: a metal housing; a stator and a rotor, which are arranged in the housing; and a circuit substrate, which is arranged outside the housing and is provided with a plurality of electronic components.

[0003] In the above motor unit, in order to stabilize the current flowing through the plurality of electronic components with different potentials when working, each electronic component needs to be grounded. Therefore, in the case that the circuit substrate is a flexible substrate, the flexible substrate can be considered to be pulled to the vicinity of the housing, and a metal sheet is used to electrically connect the circuit substrate and the housing, so as to form the grounding of the circuit substrate. However, in the case that the circuit substrate is a rigid substrate, it is sometimes difficult to arrange the circuit substrate close to the housing, and it is also difficult to arrange the metal sheet to electrically connect the circuit substrate and the housing. SUMMARY

[0004] The utility model is completed in view of the above problems, and aims to provide a motor unit, which is helpful to realize the grounding of the circuit substrate outside the housing with a simple structure.

[0005] In order to achieve the above-mentioned purpose, the utility model provides a motor unit, which has: a metal housing; a stator and a rotor, which are arranged in the housing; and a circuit substrate, which is arranged outside the housing and is provided with a first terminal and an electronic component electrically connected with the first terminal, wherein the first terminal is in contact with the housing and is electrically connected.

[0006] According to the motor unit of the utility model, the first terminal of the circuit substrate is in contact with the housing and is electrically connected, so that the grounding of the circuit substrate outside the housing can be conveniently realized by using the first terminal.

[0007] In addition, in the motor unit of the utility model, preferably, the housing has a groove, and the first terminal is inserted into the groove.

[0008] According to the motor unit of the utility model, the housing has a groove, and the first terminal is inserted into the groove, so that the reliability of the electrical connection between the first terminal and the housing can be ensured.

[0009] In addition, in the motor unit of the utility model, preferably, the housing includes: a cylindrical portion extending in the axial direction; and a plate-shaped portion extending in a plane orthogonal to the axial direction, the cylindrical portion surrounds the stator and the rotor on the radial outer side, the plate-shaped portion overlaps at least one of the stator and the rotor in the axial direction, is electrically connected with the cylindrical portion, and has the groove opening to the radial outer side and penetrating in the axial direction.

[0010] According to the motor unit of the utility model, the plate-shaped part has a groove which opens to the radial outside and penetrates in the axial direction, thus, the installation freedom of the first terminal relative to the groove of the plate-shaped part can be improved.

[0011] In addition, in the motor unit of the utility model, preferably, the circuit board is provided with a plurality of terminals including the first terminal, the plurality of terminals are arranged in a direction orthogonal to the axial direction, and the terminals other than the first terminal are electrically connected to the winding of the stator.

[0012] In addition, in the motor unit of the utility model, preferably, the plurality of terminals are respectively strip-shaped and have the same length, the first terminal has a first part extending in a direction perpendicular to the axial direction and a second part bent from an end of the first part on the radial inside to one side in the axial direction, and the end of the first part on the radial inside is pressed into the groove to contact the inner surface of the groove.

[0013] According to the motor unit of the utility model, the plurality of terminals are respectively strip-shaped and have the same length, thus, compared with the case of using a plurality of terminals with different lengths, the types of raw materials of the terminals can be reduced, the terminal assembly equipment can be simplified or the terminal assembly process can be reduced, and the manufacturing cost can be reduced; and the first terminal has the first part extending in the direction perpendicular to the axial direction and the second part bent from the end of the first part on the radial inside to one side in the axial direction, thus, in the case that the plate-shaped part and the stator core are laminated and the recess for the first part of the first terminal to pass through in the axial direction is formed on the stator core, the depth (the size in the extension direction of the first part) of the recess can be reduced, the stator core is prevented from being disconnected in the middle into a ring shape, and the strength of the stator core can be improved.

[0014] In addition, in the motor unit of the utility model, preferably, the plurality of terminals respectively have a first part extending in a direction perpendicular to the axial direction and a second part bent from an end of the first part on the radial inside to one side in the axial direction, and the second part of the terminals other than the first terminal is longer than the second part of the first terminal and is electrically connected to the winding of the stator.

[0015] According to the motor unit of the utility model, the second part of the terminals other than the first terminal is longer than the second part of the first terminal and is electrically connected to the winding of the stator, thus, the winding of the stator can be conveniently wound on the second part of the terminals other than the first terminal, and the production efficiency can be improved.

[0016] Further, in the motor unit of the utility model, preferably, when viewed in the axial direction, the straight line where the first part of the terminal located on the two outer sides in the arrangement direction of the plurality of terminals is located on both sides of the rotation center line of the rotor, and the first terminal is located in the middle in the arrangement direction of the plurality of terminals.

[0017] According to the motor unit of the utility model, in the case that the plate-shaped part and the stator core are laminated and the recess for the first part of the first terminal to pass through in the axial direction when assembled is formed on the stator core, the width (the size in the extension direction of the first part) of the stator core at the recess can be ensured, the stator core is prevented from being disconnected in the middle into a ring shape due to the recess, and the strength of the stator core is helped to be improved.

[0018] Further, in the motor unit of the utility model, preferably, when viewed in the axial direction, the straight line where the first part of the terminal located on the two outer sides in the arrangement direction of the plurality of terminals is located on both sides of the rotation center line of the rotor, and the first terminal is located in the middle in the arrangement direction of the plurality of terminals.

[0019] Further, in the motor unit of the utility model, preferably, the stator has a stator core laminated with the plate-shaped part in the axial direction, and the stator core has a recess overlapping with the groove in the axial direction.

[0020] Further, in the motor unit of the utility model, preferably, the circuit board extends from the shell to the radial outer side.

[0021] Further, in the motor unit of the utility model, preferably, the circuit board is a rigid board.

[0022] Further, in the motor unit of the utility model, preferably, the terminal is provided with five, and the stator adopts a bipolar winding.

[0023] (utility model effect)

[0024] According to the utility model, the first terminal of the circuit board is in contact with the shell to be electrically connected, so that the ground of the circuit board outside the shell can be conveniently realized by the first terminal. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the perspective view of the motor unit of the embodiment 1 of the utility model.

[0026] Figure 2 is the perspective view of the motor unit of the embodiment 1 of the utility model, wherein a part of the shell and the cover is omitted.

[0027] Figure 3This is a top view schematically illustrating the motor unit of Embodiment 1 of the present invention, wherein the housing, cover, and part of the transmission mechanism are omitted.

[0028] Figure 4 This is a perspective view illustrating a portion of the structure of the motor unit according to Embodiment 1 of this utility model.

[0029] Figure 5 This is a perspective view schematically showing a portion of the structure of the motor unit in Embodiment 2 of this utility model.

[0030] Figure 6 This is a cross-sectional view schematically showing a portion of the structure of the motor unit according to Embodiment 2 of this utility model.

[0031] Figure 7 This is a top view schematically showing a portion of the structure of the motor unit according to Embodiment 2 of this utility model.

[0032] Figure 8 This is a perspective view illustrating a portion of the structure of the motor unit in Embodiment 3 of this utility model.

[0033] Figure 9 This is a cross-sectional view schematically showing a portion of the structure of the motor unit according to Embodiment 3 of this utility model.

[0034] Figure 10 This is a top view schematically showing a portion of the structure of the motor unit in Embodiment 3 of this utility model.

[0035] Figure 11 This is a perspective view illustrating a portion of the structure of the motor unit in Embodiment 4 of this utility model.

[0036] (Symbol Explanation)

[0037] 1 Motor Unit

[0038] 10. Shell

[0039] 11 cylindrical part

[0040] 111 Gap

[0041] 12 plate-shaped part

[0042] 121 Groove

[0043] 13 Top

[0044] 21 Stator

[0045] 211 Stator Core

[0046] 2111 concave part

[0047] 30 Circuit board

[0048] 31 terminal

[0049] 311 First Terminal

[0050] 32 Electronic Components

[0051] 40. Transmission Mechanism

[0052] 50 Output Shaft

[0053] 60 terminal block

[0054] 70 Shield

[0055] 71 First Cover

[0056] 72 Second Cover Detailed Implementation

[0057] Below, in conjunction with Figures 1 to 11 The motor unit of the present invention, including its embodiments and variations, will be described.

[0058] For ease of explanation, the three mutually orthogonal directions are designated as the X, Y, and Z directions. One side of the X direction is designated X1, and the other side as X2; one side of the Y direction is designated Y1, and the other side as Y2; one side of the Z direction is designated Z1, and the other side as Z2. Furthermore, the direction of extension of the rotor's rotation centerline is simply referred to as the "axial direction," and the circumferential and radial directions centered on the rotor's rotation centerline are simply referred to as the "circumferential" and "radial" directions, respectively.

[0059] <Implementation Method 1>

[0060] like Figures 1 to 4 As shown, the motor unit 1 has: a metal housing 10; a stator 21 and a rotor (not shown) disposed inside the housing 10; and a circuit board 30 disposed outside the housing 10, and having a first terminal 311 and an electronic component 32 electrically connected to the first terminal 311, the first terminal 311 being in contact with the housing 10 and electrically connected.

[0061] Here, as Figures 2 to 4 As shown, the motor unit 1 also has a transmission mechanism 40 and an output shaft 50, the transmission mechanism 40 transmitting the rotation of the rotor to the output shaft 50.

[0062] In addition, such as Figures 2 to 4 As shown, the motor unit 1 also has a terminal block 60, which is supported on the housing 10 and supports the first terminal 311.

[0063] In addition, such as Figures 1 to 3 As shown, the motor unit 1 also has a cover 70, which supports and houses the circuit board 30 and is assembled into the housing 10.

[0064] (Structure of the shell)

[0065] like Figures 2 to 4 As shown, the housing 10 has a groove 121, and the first terminal 311 is inserted into the groove 121.

[0066] Here, as Figures 1 to 4 As shown, the housing 10 includes: a cylindrical portion 11 extending axially (in the illustrated example, aligned with the Z direction); and a plate-like portion 12 extending in a plane orthogonal to the axial direction (in the illustrated example, the XY plane). The cylindrical portion 11 radially surrounds the stator 21 and the rotor. The plate-like portion 12 overlaps axially with at least one of the stator 21 and the rotor, is electrically connected to the cylindrical portion 11, and has a groove 121 opening radially outward (in the illustrated example, the X1 direction side) and extending axially. Specifically, a notch 111 is provided on one circumferential side of the cylindrical portion 11 (in the illustrated example, the X1 direction side), the notch 111 being recessed from one axial side of the cylindrical portion 11 (in the illustrated example, the Z1 direction side) toward the other axial side (in the illustrated example, the Z2 direction side). The plate-like portion 12 is disposed within the cylindrical portion 11 and located axially midway within the cylindrical portion 11. A portion of the periphery of the plate-shaped portion 12 contacts the inner surface of the cylindrical portion 11. The edge portion of the plate-shaped portion 12 facing the notch 111 has a protrusion projecting radially outward, which has a groove 121 that opens radially outward (in the illustrated example, the X1 direction side) and extends axially. The plate-shaped portion 12 divides the internal space of the cylindrical portion 11 into spaces for accommodating the stator 21 and rotor, and spaces for accommodating the transmission mechanism 40 and the output shaft 50.

[0067] In addition, such as Figure 1 As shown, the housing 10 also includes: a top 13 that closes an opening on one side of the cylindrical portion 11 in the axial direction; and a bottom that closes an opening on the other side of the cylindrical portion 11 in the axial direction.

[0068] (Structure of stator and rotor)

[0069] like Figure 4 As shown, the stator 21 has a stator core 211 that is stacked with the plate-shaped portion 12 in the axial direction.

[0070] Here, the stator core 211 has a recess 2111 that overlaps with the groove 121 in the axial direction (see reference). Figure 6 During assembly, the recess 2111 allows the first terminal 311 to pass through axially. Specifically, the stator core 211 includes: a plate portion stacked with the plate portion 12; and pole teeth rising axially from the plate portion. The recess 2111 is provided in the plate portion of the stator core 211.

[0071] In addition, although not shown in the figure, there is a winding wound on the stator core 211 with an insulator in between.

[0072] Furthermore, although not shown in the figure, the rotor is located radially inside the stator 21 and can rotate relative to the stator 21.

[0073] (Structure of the circuit board)

[0074] like Figures 2 to 4 As shown, the circuit board 30 is provided with a plurality of terminals 31, including a first terminal 311.

[0075] Here, as Figures 2 to 4 As shown, the stator 21 employs bipolar windings, and correspondingly, five terminals 31 are soldered onto the circuit board 30. The terminals 31 are arranged in a direction orthogonal to the axial direction (the Y direction in the illustrated example). Of the terminals 31, all except the first terminal 311 are electrically connected to the windings of the stator 21. Specifically, the circuit board 30 is a rigid substrate and extends radially outward from the housing 10 (the X1 direction side in the illustrated example). The terminals 31 are strip-shaped and of equal length. Each terminal 31 has an end that extends axially and inserts into the circuit board 30. When viewed axially, each end of the terminals 31 is arranged in a straight line extending in a direction perpendicular to the axial direction (the Y direction in the illustrated example) and spaced apart from the rotor's rotation center line. Of the plurality of terminals 31, each terminal other than the first terminal 311 has: a first portion extending in a direction perpendicular to the axial direction (X direction in the illustrated example); and a second portion bent axially from the radially inner end of the first portion. The first portion of each terminal other than the first terminal 311 extends from one end toward the rotation centerline of the rotor. The first terminal 311 has a first portion extending from one end toward the rotation centerline of the rotor, the radially inner end of which (X2 direction side in the illustrated example) is pressed into a groove 121 and contacts the inner surface of the groove 121. The second portion of each terminal other than the first terminal 311 is electrically connected to the windings of the stator 21. When viewed axially, the lines containing the first portions of the terminals located on the outermost sides of the arrangement direction of the plurality of terminals 31 lie on either side of the rotation centerline of the rotor, with the first terminal 311 located on the outermost side (Y1 direction side in the illustrated example).

[0076] In addition, such as Figures 2 to 4 As shown, multiple electronic components 32 are provided, and these electronic components 32 are electrically connected to multiple terminals 31 respectively.

[0077] (Structure of the transmission mechanism and output shaft)

[0078] like Figures 2 to 4 As shown, the transmission mechanism 40 is a reduction gear set.

[0079] Here, as Figures 2 to 4 As shown, the transmission mechanism 40 includes a plurality of gears disposed within the housing 10, which are rotatably supported on the plate-shaped portion 12 and the top 13 via support shafts.

[0080] In addition, such as Figures 2 to 4 As shown, the output shaft 50 has: a gear portion that meshes with the final stage gear in the transmission mechanism 40 and is disposed within the housing 10; and a shaft portion that extends axially upward from the gear portion to the outside of the housing 10.

[0081] (Structure of the terminal block)

[0082] like Figures 2 to 4 As shown, the terminal block 60 supports a plurality of terminals 31.

[0083] Here, as Figure 2 As shown, the terminal block 60 is provided at the notch 111 of the cylindrical portion 11. The terminal block 60 is located between the plate-shaped portion 12 and the circuit board 30.

[0084] In addition, such as Figures 2 to 4 As shown, the terminal block 60 is generally U-shaped and has: a first plate extending along the arrangement direction of the plurality of terminals 31 (the Y direction in the illustrated example); and two second plate portions extending from both ends of the first plate portion toward the rotation center of the rotor. The first portions of the plurality of terminals 31 pass through the first plate portion of the terminal block 60 in a direction orthogonal to the axial direction. The radially inner side of the first plate portion of the terminal block 60 (the X2 direction side in the illustrated example) is also provided with a plurality of slots spaced apart along the arrangement direction of the plurality of terminals 31, into which the second portions of the plurality of terminals 31 are engaged. The two second plate portions of the terminal block 60 clamp the protrusions of the plate-shaped portion 12 facing the notch 111 from both sides and abut against the edges of the plate-shaped portion 12 located on both sides of the protrusions.

[0085] (Structure of the cover)

[0086] like Figure 1 As shown, the cover 70 is generally rectangular in shape.

[0087] Here, as Figures 1 to 3As shown, the cover 70 has a first cover 71 and a second cover 72. A circuit board 30 is disposed on the other side of the first cover 71 in the axial direction, and is supported from the other side in the axial direction. The second cover 72 covers the circuit board 30 from one side in the axial direction and is assembled to the first cover 71. Specifically, the first cover 71 has: a first cover base plate that is generally rectangular when viewed axially; and a first cover side plate extending from two opposite sides of the first cover base plate toward one side in the axial direction. The second cover 72 has: a second cover top plate that is generally rectangular when viewed axially; and a second cover side plate extending from two opposite sides of the second cover top plate toward the other side in the axial direction and abutting against the first cover side plate. The first cover 71 and the second cover 72 are engaged with each other by a snap-fit ​​structure.

[0088] In addition, such as Figure 2 As shown, one end of the cover 70 is engaged at the notch 111 of the cylindrical part 11.

[0089] (Main effects of this implementation method)

[0090] According to the motor unit 1 of this embodiment, the first terminal 311 of the circuit board 30 is electrically connected to the housing 10 in contact with it. Therefore, the circuit board 30 outside the housing 10 can be conveniently grounded using the first terminal 311.

[0091] In particular, in existing stepper motors, regardless of whether the stator uses bipolar windings or bipolar windings, five terminals are usually provided on the circuit board. When the stator uses bipolar windings, only four of the terminals are used to connect the stator windings. Therefore, by using the remaining terminal (first terminal) to electrically connect the circuit board to the housing 10 in the motor unit 1 of this embodiment, grounding of the circuit board 30 outside the housing 10 can be achieved without adding any additional components.

[0092] <Implementation Method 2>

[0093] The motor unit of Embodiment 2 is basically the same as the motor unit of Embodiment 1. The motor unit of Embodiment 2 will be described below focusing on the differences from the motor unit of Embodiment 1.

[0094] In this embodiment, unlike in embodiment 1, such as... Figures 5 to 7 As shown, the first terminal 311 also has a first portion and a second portion, wherein the first portion extends in a direction perpendicular to the axial direction (the X direction in the illustrated example), and the second portion is bent from the radially inner end of the first portion toward the axially upward side. However, among the plurality of terminals 31, the second portion of the terminals other than the first terminal 311 is longer than the second portion of the first terminal 311 and is electrically connected to the winding of the stator 21.

[0095] Furthermore, in this embodiment, unlike embodiment 1, such as... Figures 5 to 7 As shown, one of the multiple slots on the radially inner side (X2 direction side in the illustrated example) of the first plate portion of the terminal block 60 is for the second portion of the first terminal 311 to be engaged.

[0096] The motor unit according to this embodiment can also achieve essentially the same effect as the motor unit of embodiment 1.

[0097] Furthermore, according to the motor unit of this embodiment, the depth of the recess 2111 of the stator core 211 (the dimension in the extending direction of the first portion of the first terminal 311) can be reduced, preventing the stator core 211 from becoming a broken ring due to the recess 2111, which helps to improve the strength of the stator core 211.

[0098] Furthermore, according to the motor unit of this embodiment, the stator 21 winding can be easily wound on the second part of the terminals other than the first terminal 311 among the plurality of terminals 31, thereby improving production efficiency.

[0099] <Implementation Method 3>

[0100] The motor unit of Embodiment 3 is basically the same as the motor unit of Embodiment 1. The motor unit of Embodiment 3 will be described below focusing on the differences from the motor unit of Embodiment 1.

[0101] In this embodiment, unlike in embodiment 1, such as... Figures 8 to 10 As shown, in the arrangement direction of the multiple terminals 31, the first terminal 311 is located in the center.

[0102] The motor unit according to this embodiment can also achieve essentially the same effect as the motor unit of embodiment 1.

[0103] <Implementation Method 4>

[0104] The motor unit of Embodiment 4 is basically the same as the motor unit of Embodiment 1. The motor unit of Embodiment 4 will be described below focusing on the differences from the motor unit of Embodiment 1.

[0105] In this embodiment, compared with embodiment 1, such as Figure 11 As shown, the two second plates of the terminal block 60 extending from both ends of the first plate portion toward the rotation center side of the rotor are longer. Compared with Embodiment 1, among the plurality of terminals 31, the second portion of each terminal other than the first terminal 311 is longer, and the first portion of the first terminal 311 is longer.

[0106] The motor unit according to this embodiment can also achieve essentially the same effect as the motor unit of embodiment 1.

[0107] Furthermore, according to the motor unit of this embodiment, the stator 21 winding can be easily wound on the second part of the terminals other than the first terminal 311 among the plurality of terminals 31, thereby improving production efficiency.

[0108] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above embodiments.

[0109] For example, in the above embodiment, the groove 121 opens radially outward and extends axially, but it is not limited to this. Depending on the situation, the opening of the groove 121 may also face other directions, and the groove 121 may not extend axially.

[0110] Furthermore, in the above embodiment, the housing 10 has a groove 121 and the first terminal 311 is pressed into the groove 121, but it is not limited to this. The groove 121 may not be provided, and the first terminal 311 may be in contact with the outer surface of the housing 10.

[0111] Furthermore, in the above embodiment, the stator 21 adopts a bipolar winding, but it is not limited to this and can also adopt a unipolar winding.

[0112] Furthermore, in the above embodiments, the circuit board 30 is a rigid board, but it is not limited to this and can also be a flexible board.

[0113] Furthermore, in the above embodiment, the circuit board 30 extends radially outward from the housing 10, but the extension direction of the circuit board 30 is not limited to this, and it may also extend axially.

[0114] Furthermore, in the above embodiment, five terminals 31 are provided, but it is not limited to this; the number of terminals 31 can also be more than five.

[0115] Furthermore, in the above embodiment, the lengths of the multiple terminals 31 are the same, but it is not limited to this, and the lengths of the multiple terminals 31 may also be different.

[0116] It should be understood that within the scope of this utility model, the various parts in the embodiments can be freely combined, or the various parts in the embodiments can be appropriately modified or omitted.

Claims

1. A motor unit comprising: a metal housing; a stator and a rotor disposed within the housing; and a circuit board disposed outside the housing, and having a first terminal and electronic components electrically connected to the first terminal, characterized in that, The first terminal is in contact with the housing and is electrically connected.

2. The motor unit as described in claim 1, characterized in that, The housing has grooves. The first terminal is inserted into the groove.

3. The motor unit as described in claim 2, characterized in that, The housing includes: a cylindrical portion extending axially; and a plate-like portion extending in a plane orthogonal to the axial direction. The cylindrical portion radially surrounds the stator and the rotor. The plate-shaped portion overlaps axially with at least one of the stator and the rotor, is electrically connected to the cylindrical portion, and has the groove that opens radially outward and extends axially.

4. The motor unit as described in claim 3, characterized in that, The circuit board is provided with multiple terminals, including the first terminal. The plurality of terminals are arranged in a direction orthogonal to the axial direction. Of the plurality of terminals, all of which are other than the first terminal are electrically connected to the windings of the stator.

5. The motor unit as described in claim 4, characterized in that, The plurality of terminals are strip-shaped and of the same length. The first terminal has: a first portion extending in a direction perpendicular to the axial direction; and a second portion bent from the radially inner end of the first portion toward an axially upward side. The radially inner end of the first portion of the first terminal is pressed into the groove and contacts the inner surface of the groove.

6. The motor unit as described in claim 5, characterized in that, Each of the plurality of terminals has: a first portion extending in a direction perpendicular to the axial direction; and a second portion bent from the radially inner end of the first portion toward an axially upward side. Of the plurality of terminals, the second portion of the terminals other than the first terminal is longer than the second portion of the first terminal and is electrically connected to the winding of the stator.

7. The motor unit as described in claim 6, characterized in that, When viewed along the axial direction, the straight line containing the first portions of the two outermost terminals in the arrangement direction of the plurality of terminals lies on both sides of the rotation center line of the rotor. In the arrangement direction of the plurality of terminals, the first terminal is located on the outermost side or in the middle.

8. The motor unit as described in claim 5, characterized in that, The stator has a stator core that is stacked axially with the plate-like portion. The stator core has a recess that overlaps with the groove in the axial direction.

9. The motor unit as described in claim 1, characterized in that, The circuit board extends radially outward from the housing. The circuit board is a rigid substrate.

10. The motor unit as claimed in claim 1, characterized in that, The terminal is provided with five. The stator employs bipolar windings.

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