Motor with busbar

Abstract

The invention relates to an electric motor with busbars, having a stator with a plurality of pairs of windings, the winding wire ends being in electrical contact at the ends with three busbars to form a three-phase, the three busbars having power supply connection terminals which are located next to one another, the second and third busbars extending over an angle of approximately 210° and having the same contact portion which has four contact points for contacting the winding wire ends which are arranged in succession in the circumferential direction, the second and third busbars being arranged offset in the circumferential direction by approximately 120°, the first busbar having a contact portion which differs from the contact portion of the second and third busbars, the first busbar comprising a first and a second portion, three contact points being located on the first portion and a further contact point being located on the second portion, the power supply connection terminals of the first busbar being arranged between the first and second portions, the first busbar extending over an angle of approximately 300°, the first contact point of the first busbar being offset by approximately 180° with respect to the first contact point of the second busbar.

Description

TECHNICAL FIELD

[0001] The invention relates to an electric motor. BACKGROUND

[0002] Here, a brushless DC motor of the relevant type is referred to as an inner rotor motor, which has a rotor connected to the motor shaft and rotatably mounted in a housing. The rotor is provided with permanent magnets. A stator is arranged around the motor, which carries a plurality of windings on its core. When controlled appropriately, the windings generate a magnetic field that drives the rotor to rotate. The windings are usually wound in three phases and are correspondingly provided with three electrical connections, by means of which the windings can be connected to a control unit (ECU). At low power levels, the busbar can be designed as a conductive foil busbar. For higher powers, as assumed here, the winding connection is made by means of a busbar made of copper sheet.

[0003] The parallel windings or coil groups, if applicable, are arranged uniformly in the circumferential direction in the stator. On the other hand, the electrical connections for the individual phases are usually not uniformly distributed, but are concentrated at one point of the stator. This leads to an asymmetry in the circuit diagram. The electrical resistance between the phase connections and the coils (groups) is not the same for all phases. This leads to different phase resistances and phase currents, which is undesirable. SUMMARY

[0004] It is an object of the invention to provide an electric motor, which, despite the asymmetric arrangement of its phase connections, achieves a low asymmetry value in the phase resistances of the busbar at low cost. This object is achieved by an electric motor having the following features.

[0005] For a geometric description of the electric motor, it is first assumed that the rotational axis of the electric motor is the central axis and the axis of symmetry. The stator is concentric with the rotational axis and the rotor. At the same time, the rotational axis defines the axial direction. Furthermore, with respect to the central axis, the radial direction is mentioned, which represents the distance from the central axis, and the circumferential direction, which is tangential to a certain radius arranged in the radial direction. The connection side of the stator, i.e. the position at which the winding wires are connected to the busbar arrangement, is described as the top of the stator.

[0006] Thus, an electric motor is provided, having a rotor rotatably mounted about an axis of rotation, and a stator externally surrounding the rotor, the stator having a stator core with stator teeth, the stator teeth each carrying a winding. Each two windings adjacent in the circumferential direction are formed by one winding wire having a winding wire end portion, the winding wire end portions electrically contacting at an end three busbars to form three phases, the three busbars each having a power connection terminal for electrically contacting the busbar with a power supply, and the three power connection terminals being located in close proximity to each other. The second and third busbars extend over an angular range of about 210° and have identical contact portions, with four contact points for contacting the winding wire end portions arranged in succession in the circumferential direction. The two busbars are offset from each other in the circumferential direction by about 120°. On the other hand, the first busbar has a different contact portion, the first busbar comprising a first portion and a second portion, three contact points being located at the first portion and one contact point being located at the second portion, the power connection terminal of the first busbar being arranged between the two portions, the first busbar extending over an angular range of about 300°, the first contact points of the first busbar being arranged offset from the first contact points of the second busbar by about 180°.

[0007] By making the first busbar different from the other two busbars, the electrical resistance of the busbars can be symmetrical, although the arrangement of the power connection terminals is asymmetrical, and an undesired asymmetry in the circuit diagram can be prevented.

[0008] Preferably, the winding pairs formed by adjacent windings each have the same winding pattern.

[0009] In order to accommodate the electrical resistance, it is also possible to provide that the second portion of the first busbar has a narrower width in the radial direction than the first portion of the first busbar. Preferably, the second and third busbars have the same width as the first portion of the first busbar.

[0010] Preferably, the electrical resistance of the second portion of the first busbar is between 0.9 mΩ and 1.3 mΩ.

[0011] In an advantageous embodiment, the second portion of the first busbar extends in the circumferential direction over about 90°.

[0012] In order to save costs, the second and third busbars are preferably identical, except for the arrangement of the respective power connection terminal. The power connection terminal of the second busbar is preferably located between the first and second contact points, and the power connection terminal of the third busbar is preferably located between the second and third contact points.

[0013] Advantageously, the busbars have a base portion from which coil connection terminal elements of the winding wire end portions extend, the busbars are stacked one above the other and overlap each other in the area of the base portion in plan view over a large (continuous) angular range.

[0014] For ease of contact, the power supply connections of the three phases extend parallel to each other in the direction of the longitudinal axis of the stator.

[0015] The busbars preferably have coil connection terminal elements for contacting the winding end portions, which have a substantially U-shaped or V-shaped configuration and extend substantially in a plane perpendicular to the longitudinal axis of the stator, wherein all openings of the coil connection terminal elements for inserting the winding wire end portions point in a common direction.

[0016] To ensure that the busbars occupy as little installation space as possible, the base portion of each busbar is preferably laid flat in a plane perpendicular to the longitudinal axis.

[0017] The busbars are preferably held in a busbar holder, which is preferably formed by injection molding, wherein the busbars are overmolded.

[0018] The stator preferably has six pairs of windings forming coils. BRIEF DESCRIPTION OF DRAWINGS

[0019] Preferred embodiments of the application will be explained in more detail below with reference to the drawings. Like or similar components are denoted by the same reference signs in the figures. They show:

[0020] Figure 1 is a plan view of a stator,

[0021] Figure 2 is Figure 1 is a schematic view of the busbars of a stator,

[0022] Figure 3 is Figure 2 is a top view of one busbar,

[0023] Figure 4 is Figure 2 is a top view of two busbars,

[0024] Figure 5 is Figure 2 is a top view of all three busbars, and

[0025] Figure 6 is a schematic view of an arrangement of busbars connected to each other in the form of an equivalent resistance. DETAILED DESCRIPTION

[0026] Figure 1 A stator 1 of an electric motor is shown. The stator 1 of the electric motor comprises a core and has winding wires 2 wound on stator teeth. Two winding 3 adjacent to each other in the circumferential direction form a winding pair, the two windings 3 form a coil, which are connected to form the three phases U, V, W. The first winding 3 of each winding pair 4 is formed by winding the teeth counterclockwise in a plan view from the inside to the outside. Subsequently, the second tooth of the winding pair 4 next to the first tooth is wound clockwise without interruption. The winding wire end 5 of the first winding is located radially on the outside, the winding wire end 6 of the second winding of the winding pair 4 is located radially on the inside. The winding wire ends 5, 6 are in electrical contact with a busbar unit 7. All six winding pairs 4 are wound in the same way. The necessary reversal of the magnetic poles within the winding pair 4 is achieved by the reversed electrical connection and the reversal of the current direction.

[0027] The stator 1 has a cylindrical free inner area 8, in which a rotor (not shown) of the electric motor rotates during operation.

[0028] The busbar unit 7 has a busbar carrier 9 and three not shown busbars arranged in the busbar carrier. The busbars are made of an electrically conductive material, preferably of a metal, in particular of copper. The busbar carrier is at least partially or completely composed of an electrically insulating material, so that short circuits between the busbars can be effectively prevented. The busbar carrier is preferably made by injection molding and extends onto the partial busbars. In this way, a firm and unambiguous physical connection between the busbar carrier and the busbars can be provided. The busbar unit is located on the shaft side (top) of the stator. Thus, the busbars are located above the winding pairs 4.

[0029] Figure 2 The busbars 10, 11, 12 without busbar carrier are shown in detail. The busbars 10, 11, 12 each have a power connection terminal 100, 110, 120 adapted to be electrically connected to a power source and four coil connection terminal elements 13 adapted to be electrically connected to the respective winding wire ends 5, 6 of the winding pairs of the stator. The power connection terminals 100, 110, 120 of the three phases U, V, W are arranged next to each other and extend parallel to each other in the longitudinal upward direction. They are designed as flat connectors to be soldered on the busbars. However, they can also be designed as cables, for example with plug units.

[0030] The coil connection terminal elements 13 have a generally U-shaped or V-shaped structure and extend in a plane perpendicular to the longitudinal axis 200 of the stator. In other words, the coil connection terminal elements 13 have a U-shaped or V-shaped profile in cross section with respect to the longitudinal axis 200 and each contain a winding wire end 5, 6 extending generally parallel to the longitudinal direction. All openings of the coil connection terminal elements 13 for inserting the winding wire ends 5, 6 thus all point in the circumferential direction.

[0031] The busbars 10, 11, 12 with the base portions 101, 111, 121 extend in the circumferential direction, but deviate from the circular shape. Starting from the base portions 101, 111, 121, the coil connection terminal elements 13 extend both inwards and outwards. The base portions 101, 111, 121 of each busbar lie in a plane perpendicular to the longitudinal axis 200, wherein the base portions 101, 111, 121 are flat or horizontal in the plane. The coil connection terminal elements 13 extend upwards out of the plane of the base portions 101, 111, 121. The base portions 101, 111, 121 of the individual busbars are arranged on top of each other in succession and partially overlap.

[0032] Figure 3 The busbar 12 of the third phase W is shown. The busbar 12 extends in the circumferential direction over approximately 210°. In total, four so-called contact points K1w, K2w, K3w, K4w are provided, each of which is formed by a coil connection terminal element 13. The first contact point K1w and the last, fourth contact point K4w in the circumferential direction are separated by six windings. These windings or coils are not shown here. In other words, the No. 1 winding is contacted at the first contact point K1w and the No. 8 winding is contacted at the fourth contact point K4w. The windings are numbered consecutively in the circumferential direction, whereby each two windings form a winding pair, wherein the No. 2 winding and the No. 3 winding form a winding pair, and so on. Thus, the No. 3 winding is contacted at the second contact point K2w and the No. 6 winding is contacted at the third contact point K3w. The power connection terminal 120 is located in the vicinity of the third contact point K3w. Since the second winding in the circumferential direction of a winding pair has an inwards directed line end, the contact points K1w, K2w and K4w are also inwards and the corresponding coil connection terminal elements 13 protrude inwards from the base portion 121.

[0033] Figure 4 The busbars 11, 12 of the third phase W and the second phase V are shown. The first contact point K1v of the second phase V is located between the second contact point K2w and the third contact point K3w of the third phase W. The busbar 11 of the second phase V also extends over approximately 210°, whereby the assignment of the respective windings to the contact points is identical to the third phase W, except for a shift, i.e. the No. 5 winding is contacted at the first contact point K1v, the No. 7 winding at the second contact point K2v, the No. 10 winding at the third contact point K3v and the No. 12 winding at the fourth contact point K4v. The power connection terminal 110 of the second phase is located between the first contact point and the second contact point of the second phase.

[0034] Figure 5The arrangement of all three busbars 10, 11, 12 is shown in a top view from above. The busbar 10 of the first phase U has a different contact scheme than the other two phases V, W in order to adapt the resistance of the busbar 10 to the resistance of the other two busbars 11, 12.

[0035] The base portion 101 of the first busbar 10 of the first phase U is divided into two portions 102, 103. The first portion 102 is formed corresponding to the other two busbars 11, 12 in width and course, the second portion 103 has a narrow width. The first portion 102 extends from the first contact point Klu to the power connection terminal 100, which is located behind the third contact point K3u in the circumferential direction. The fourth contact point K4u is connected to the power connection terminal 100 by the second portion 103. If an equal share approach is taken, the first contact point Klu would be the second contact point K2u, the fourth contact point K4u would be the first contact point Klu, the contact scheme and the base portion would be formed similar to the contact scheme and the base portion of the second phase V and the third phase W. However, a great asymmetry would occur in the circuit diagram, since the power connection terminal 100 would be located behind the fourth contact point K4u in the circumferential direction. This asymmetry is reduced by the division of the first portion 102 and the second portion 103. The busbar 10 of the first phase U extends over an angle of approximately 300°. The first contact point Klu and the last fourth contact point K4u in the circumferential direction are separated by 9 windings. The resistance can be further adjusted by the smaller width of the busbar 10 of the second portion 103. The second portion 103 extends at least over 90°. Although the busbar 10 of the first phase U is longer than the busbars of the other two phases V, W and requires more material, this division reduces the asymmetry of the resistance, so that the resistance of the first phase U is within an acceptable resistance range. The other two phases V, W do not need to be changed, since the distance to the respective power connection terminal 110, 120 is shorter.

[0036] Figure 6 An arrangement diagram of an interlinked winding pair 4 or coil and the equivalent resistance for the busbar portion between the contact points is shown. In this example, the busbar of the first phase U has a resistance Rhlu of approximately 1.3 mΩ for the second portion 103, the coil R spule contacts the fourth contact point of the second portion 103. This resistance Rhlu is preferably between 0.9 mΩ and 1.3 mΩ. The coil R spuleThe other side of the fourth contact point is in contact with a fourth contact point of the busbar 12 of the third phase W. The respective equivalent resistance of the busbar portion between the fourth contact point and the third contact point is designated Rh4w. The remaining interconnections are made in the manner already described in detail above. As can be seen from the overview, due to the chosen contact scheme of the busbars, the total resistance of the individual current paths (i.e. the coil resistance plus the resistance of the busbar plus the contact resistance at the contact points) deviates by approximately 0.5%.

Claims

1. An electric motor having busbars, comprising a rotor rotatably mounted about a rotation axis and a stator (1) surrounding the rotor from the outside, the stator having a stator core with stator teeth, each stator tooth carrying a winding (3), two adjacent windings (3) in the circumferential direction being formed by a winding wire (2) having winding wire ends (5, 6), and the winding wire ends (5, 6) being electrically contacted at their ends with three busbars (10, 11, 12) to form three phases (U, V, W), the three busbars (10, 11, 12) each having power connection terminals (100, 110, 120) for electrically contacting the busbars (10, 11, 12) with a power source, and the three power connection terminals (100, 110, 120) being adjacent to each other, characterized in that, The second bus (11) and the third bus (12) extend within an angle range of 210° and have the same contact portion, the contact portion having four contact points K1v, K2v, K3v, K4v, K1w, K2w, K3w, K4w arranged sequentially along the circumferential direction for contacting the ends (5, 6) of the winding wires. The second bus (11) and the third bus (12) are arranged to be offset from each other by 120° along the circumferential direction. The first bus (10) has another contact portion different from that of the second bus (11) and the third bus (12). A bus (10) includes a first part (102) and a second part (103), three contact points K1u, K2u, and K3u are located in the first part (102), another contact point K4u is located in the second part (103), and the power connection terminal (100) of the first bus is arranged between the first part (102) and the second part (103), wherein the first bus (10) extends over an angular range of 300°, and the first contact point K1u of the first bus is arranged to be offset by 180° from the first contact point K1v of the second bus.

2. The electric motor according to claim 1, characterized in that, The winding pairs (4) formed by adjacent windings (3) have the same winding method.

3. The electric motor according to claim 1 or 2, characterized in that, The second portion (103) of the first busbar has a narrower width in the radial direction than the first portion (102) of the first busbar.

4. The electric motor according to claim 1 or 2, characterized in that, The resistance (Rh1u) of the second part (103) is between 0.9mΩ and 1.3mΩ.

5. The electric motor according to claim 1 or 2, characterized in that, The second portion (103) of the first busbar extends 90°.

6. The electric motor according to claim 1 or 2, characterized in that, The second bus (11) and the third bus (12) are identical in design except for the arrangement of their respective power connection terminals (110, 120).

7. The electric motor according to claim 1 or 2, characterized in that, The busbars (10, 11, 12) have base portions (101, 111, 121) from which coil connection terminal elements (13) for contacting the ends (5, 6) of the winding wires extend. The busbars (10, 11, 12) are stacked upwards in sequence, and in a plan view, the base portions (101, 111, 121) partially overlap each other.

8. The electric motor according to claim 1 or 2, characterized in that, The power connection terminals (100, 110, 120) of the three phases (U, V, W) extend upward parallel to each other in the direction of the longitudinal axis (200) of the stator.

9. The electric motor according to claim 7, characterized in that, The coil connection terminal element (13) has a U-shaped or V-shaped structure and extends in a plane perpendicular to the longitudinal axis (200) of the stator. All openings of the coil connection terminal element (13) for inserting the ends (5, 6) of the winding wires are oriented in a common circumferential direction.

10. The electric motor according to claim 7, characterized in that, The base portion (101, 111, 121) of each busbar lies flat in a plane perpendicular to the longitudinal axis (200).

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