Patent Description:
In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drivetrains into their vehicle line-ups. To meet consumer expectations, however, the automobile industry must not only achieve a greener drivetrain, but must do so while maintaining reasonable levels of performance, range, reliability, safety and cost.

In recent years, electric vehicles have proven to be not only environmentally friendly, but also capable of meeting, if not exceeding, consumer desires and expectations regarding performance. While early electric vehicles used DC motors in order to achieve the variable levels of speed and torque required to drive a vehicle, the advent of modern motor control systems utilizing direct torque control have allowed AC motors to deliver the same level of performance while providing the many benefits associated with AC motors including small size, low cost, high reliability and low maintenance.

In an AC motor a rotating magnetic field is generated within the motor's stator assembly, resulting in rotation of the motor's rotor assembly. The rotating magnetic field is generated by a plurality of circumferentially distributed windings that are mounted within a plurality of circumferentially distributed stator slots and teeth. The windings, which may be comprised of round or rectangular wire, are divided into coil groups, each of which represents a single pole of a single phase. Each phase of the coil windings terminate into a connector, commonly referred to as a lug, which is used to couple the coil windings to an AC power source. Thus, for example, in a typical three phase stator assembly there are three winding lugs that connect the stator windings to the three phases of an AC inverter.

In a typical stator manufacturing process, distributing the windings within the stator assembly is a rapid process utilizing an automated CNC (computer numerical control) winding machine. Once the stator windings are completed, they must be coupled to the stator lugs. During this portion of the stator manufacturing process the wire bundles are routed, insulation sleeves are added, and the lugs are resistance welded to the wire bundles. As this portion of the process is performed by hand, it is quite slow and adds considerable expense to the stator assembly. Accordingly, what is needed is a stator manufacturing process that minimizes or eliminates the need for manually performing the final steps associated with coupling the windings to the lugs, thereby providing a more cost effective stator assembly. The present invention provides a system and manufacturing process that achieves these goals while also providing a more versatile stator assembly that may be configured to meet a variety of torque and power requirements.

<CIT> discloses a stator assembly according to the preamble of claim <NUM>.

Furthermore, <CIT> discloses an electrical, essentially ringshaped connection device for a stator of an electric motor with a retracted round wire winding, comprising: an electrically insulating base ring ; an electrically conductive star ring resting thereon and having a plurality of radially outwardly extending outer connection contacts; three structurally identical pairs, each having a lower, electrically insulating intermediate ring and an upper electrically conductive connection ring resting thereon with outer connection contacts extending radially outward and with one extending from its radially inner side in the axial direction upwardly extending, upper connection contact; and a substantially annular cover which covers the upper connection ring, from which the three upper connection contacts of the electrically conductive connection rings protrude upwards and which covers the outer connection contacts radially outwards; wherein the three pairs of electrically insulating intermediate rings and electrically conductive connection rings are arranged offset from one another in the circumferential direction so that their outer connection contacts are each at connection positions spaced from one another in the circumferential direction and that their upper connection contacts are at Circumferentially spaced contact positions lie.

Additionally, <CIT> discloses a phase busbar unit provided with: a busbar holder made of an insulator and supporting a plurality of phase busbars of a motor that rotates around the center axis thereof; and a busbar cover made of an insulator and fixed to the busbar holder while covering at least one axial side of each of the busbars. Each of the busbars includes: a base part; a plurality of extension parts extending radially outward from the base part; and terminals provided on radially outer end portions of the extension parts. The busbar cover includes a plurality of protrusion parts protruding toward the other axial side, wherein the plurality of the protrusion parts contact the busbars, and at least one of the protrusion parts contacts the base part in the vicinity of the extension parts.

Moreover, <CIT> discloses wire connection member for connecting a first wire to a second wire by crimping includes a partition for dividing a first housing space for housing tip portions of the first wire from a second housing space for housing a tip portion of the second wire, a first housing portion that, together with the partition, forms the first housing space, and a second housing portion that, together with the partition, forms the second housing space. The partition is arranged between the first and second housing portions.

In addition, <CIT> discloses a busbar unit which is arranged on an axial end portion of a stator, and electrically connected with a plurality of coil wire terminals arranged to project in an axial direction above the axial end portion of the stator. The busbar unit includes a plurality of busbars each including a body portion defined by an electrically conductive wire shaped in a ring or the letter "C", the body portion being arranged around an axis of the stator; a holder member arranged on the axial end portion of the stator to hold the busbars; and a plurality of terminal members each including a busbar connection portion connected with the body portion of one of the busbars, and a coil connection portion connected with one of the coil wire terminals.

The present invention provides a stator assembly as claimed in claim <NUM>.

In one aspect, each termination coupling member of each termination coupling member group may be (i) laser welded, (ii) TIG welded, (iii) resistance welded, and/or (iv) brazed to a different winding termination of the plurality of winding terminations during attachment of the pre-fabricated connector to the stator.

In another aspect, each of the plurality of electrically insulating coupling member overlays may include a U-shaped end portion that is configured to partially surround a corresponding winding termination, and which may be crimped onto the corresponding winding termination during attachment of the pre-fabricated connector to the stator.

In another aspect, the pre-fabricated connector as fabricated may further include a second plurality of termination coupling members divided into a second plurality of termination coupling member groups, where each termination coupling member of each termination coupling member group of the second plurality of termination coupling member groups is configured to be mechanically and conductively coupled to a different winding termination of the plurality of winding terminations, where each termination coupling member group of the second plurality of termination coupling member groups is mechanically and conductively coupled to one of a plurality of lugless bus bars, and where the electrically insulating material is configured to prevent electrical contact or partial discharge between the plurality of lugless bus bars, and to prevent electrical contact or partial discharge between the plurality of bus bars and the plurality of lugless bus bars. Each termination coupling member of each termination coupling member group may be (i) laser welded, (ii) TIG welded, (iii) resistance welded, and/or (iv) brazed to a different winding termination of the plurality of winding terminations during attachment of the pre-fabricated connector to the stator. The plurality of electrically insulating coupling member overlays may be configured to prevent electrical contact or partial discharge between the second plurality of termination coupling members, and between the first and second pluralities of termination coupling members. Each of the plurality of electrically insulating coupling member overlays may include a U-shaped end portion that is configured to partially surround a corresponding winding termination, and which may be crimped onto the corresponding winding termination during attachment of the pre-fabricated connector to the stator.

In another aspect, the first plurality of termination coupling members and the plurality of bus bars may be fabricated from a copper material.

In another aspect, at least a portion of the plurality of bus bars may be over-molded with the electrically insulating material (e.g., plastic) to form the pre-fabricated connector.

In another aspect, the plurality of windings may be comprised of (i) copper wire with a round cross-section, or (ii) copper wire with a rectangular cross-section.

In another aspect, each bus bar of the plurality of bus bars may correspond to a phase of the electric motor.

A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.

It should be understood that the accompanying figures are only meant to illustrate, not limit, the scope of the invention and should not be considered to be to scale. Additionally, the same reference label on different figures should be understood to refer to the same component or a component of similar functionality.

The terms "comprises", "comprising", "includes", and/or "including", as used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" and the symbol "/" are meant to include any and all combinations of one or more of the associated listed items. Additionally, while the terms first, second, etc. may be used herein to describe various steps or calculations, these steps or calculations should not be limited by these terms, rather these terms are only used to distinguish one step or calculation from another. For example, a first calculation could be termed a second calculation; similarly a first step could be termed a second step; similarly a first component could be termed a second component, all without departing from the scope of this disclosure.

The stator assembly described and illustrated herein is generally designed for use in a vehicle utilizing an electric motor, e.g., an electric vehicle (EV), although it should be understood that it is equally applicable to electric motors designed for use in other applications. As used herein, the terms "electric vehicle" and "EV" are interchangeable and may refer to an all-electric vehicle, a plug-in hybrid vehicle, also referred to as a PHEV, or a hybrid vehicle, also referred to as a HEV, where a hybrid vehicle utilizes multiple sources of propulsion including an electric drive system.

The stator assembly of the present invention provides a connector that simplifies the process of connecting the wire windings of the stator to the stator lugs. The connector is preferably used with a stator in which the stator windings terminate in a relatively small number of terminations, and preferably in which those winding terminations are adjacent or in close proximity to one another.

<FIG> provides a perspective view of an exemplary stator <NUM> that may be used with the connector. As shown, the windings of stator <NUM> terminate in <NUM> terminals <NUM>-<NUM>. Additionally and as preferred, winding terminations <NUM>-<NUM> are immediately adjacent to one another as shown, thereby simplifying their connection to the connector described below. <FIG> provides a detailed perspective view of portion <NUM> of stator <NUM>.

<FIG> provides a perspective view of a connector <NUM> comprised of an electrically conductive connector portion, preferably fabricated from copper, which couples to winding terminations <NUM>-<NUM> via termination coupling members <NUM>-<NUM>. In the present exemplary embodiment, and as described further below, the conductive connector portion couples a first subset of the stator winding terminations to lug <NUM>; a second subset of the stator winding terminations to lug <NUM>; and a third subset of the stator winding terminations to lug <NUM>. Additionally, and as described further below, the conductive connector portion of connector <NUM> also performs the function of the central node for four sets of winding circuits.

<FIG> provides a perspective view of the electrically conductive connector portion <NUM> of connector <NUM>. <FIG> provides a rear perspective view of connector portion <NUM>. As shown in <FIG> and <FIG>, in this configuration there are seven bus bars <NUM>-<NUM>. Bus bars <NUM>-<NUM> are connected to lugs <NUM>-<NUM>, respectively. In this embodiment, each bus bar <NUM>-<NUM> is connected to four winding terminations. For example and as shown, bus bar <NUM> and therefore lug <NUM> is connected to termination coupling members <NUM>-<NUM> which, in turn, are connected to winding terminations <NUM>-<NUM> when the connector is attached to the stator windings. Thus for this aspect of the illustrated connector, termination coupling members <NUM>-<NUM> form an electrically conductive link between lug <NUM> and stator winding terminations <NUM>-<NUM>. Each bus bar <NUM>-<NUM> is lugless (i.e., does not include a connecting lug) and is connected to three winding terminations and thus acts as the central node of the corresponding winding circuits. For example, in the figures bus bar <NUM> is shown connected to termination coupling members <NUM>, <NUM> and <NUM> which, in turn, are connected to winding terminations <NUM>, <NUM> and <NUM> after attachment of the connector to the stator windings.

In addition to the electrically conductive portion <NUM>, connector <NUM> includes an electrically insulating portion. <FIG> provides a perspective view of electrically insulating portion <NUM>. As shown in <FIG> and <FIG>, electrically insulating portion <NUM> is configured to separate bus bars <NUM>-<NUM> from each other, and to prevent termination coupling members <NUM>-<NUM> from inadvertently shorting to the wrong bus bar. Preferably insulating portion <NUM> is formed by inserting electrically conductive connector portion <NUM> into a plastic injection mold and over-molding portion <NUM> with a suitable electrically insulating plastic such as a thermosetting polyester material or an engineered thermoplastic (e.g., polypropylene).

In the embodiment of the electrically insulating portion <NUM> shown in <FIG>, a plurality of insulating coupling member overlays <NUM>-<NUM> are provided that correspond to, and partially surround, corresponding termination coupling members <NUM>-<NUM>. As a result of the approximately U-shaped design of each coupling member overlay, an electrically insulating barrier is provided between adjacent termination coupling members. Additionally, at least a portion of each overlay may be configured to extend beyond the sides of the corresponding winding termination, thereby further simplifying connector alignment relative to the stator winding terminations. In at least one embodiment, each overlay is sized such that it may be pinched or crimped onto the corresponding winding termination, thus helping to hold each coupling member to its corresponding winding termination during the process of attaching the connector to the stator windings.

It should be understood that the connector does not require the inclusion of insulating coupling member overlays (e.g., overlays <NUM>-<NUM>). For example, <FIG> provides a perspective view of an alternate electrically insulating portion <NUM>, equally applicable to the electrically conductive portion <NUM> of connector <NUM>. As shown, this example electrically insulates bus bars <NUM>-<NUM> from one another but does not include the insulating coupling member overlays.

After fabrication of connector <NUM>, it is placed on top of stator assembly <NUM> such that each of the winding terminations (e.g., terminations <NUM>-<NUM>) are aligned with, and in contact with, the corresponding termination coupling members (e.g., coupling members <NUM>-<NUM>). <FIG> provides a perspective view of connector <NUM> attached to stator <NUM>. <FIG> provides a detailed perspective view of portion <NUM> of stator assembly <NUM>. Note that in the embodiment illustrated in <FIG> and <FIG>, the connector utilizes the insulating member shown in <FIG> that includes insulating coupling member overlays <NUM>-<NUM>. As previously noted, while overlays <NUM>-<NUM> may aid during the connector alignment process, these overlays are not required.

Once connector <NUM> and termination coupling members <NUM>-<NUM> are properly positioned relative to winding terminations <NUM>-<NUM>, each winding termination is then permanently coupled to the corresponding termination coupling member. Preferably the winding terminations are attached to the corresponding termination coupling members by laser welding. Alternately, tungsten inert gas (TIG) welding, resistance welding or brazing may be used to attach each termination coupling member to the corresponding winding termination. As previously noted, in at least one preferred embodiment connector <NUM> includes the approximately U-shaped coupling member overlays (e.g., overlays <NUM>-<NUM>). In addition to electrically insulating adjacent winding terminations and adjacent winding coupling members, the termination coupling member overlays simplify connector alignment and can aid during the connector attachment process.

The connector offers a number of advantages over conventional techniques for connecting the stator windings of a motor to the coupling lugs. First and foremost, since the connector is designed to be fabricated as a separate component and then attached to the stator windings via a relatively quick process, a process that can be automated, the resultant stator assembly can be rapidly fabricated and at a lower cost. Thus the slow and tedious process of connecting the winding terminations to the stator lugs is replaced with a rapid manufacturing process that can be automated. Second, different connectors that couple the winding terminations to the bus bars in different configurations can be used to achieve different motor torque and power characteristics for the same set of stator windings. Similarly, different connectors can be used to alter the number of phases for a particular stator winding configuration, for example switching the number of phases from three to six. Third, the connector is very compact, thereby allowing the connector assembly to have minimal impact on the overall stator assembly diameter and length. Fourth, the connector is equally applicable to windings fabricated from round or rectangular wire.

Claim 1:
A stator assembly for an electric motor, comprising:
a stator (<NUM>) with a plurality of windings circumferentially distributed about said stator (<NUM>), wherein said plurality of windings terminate in a plurality of winding terminations (<NUM>-<NUM>); and
a pre-fabricated connector (<NUM>) attached to said stator (<NUM>) via said plurality of winding terminations (<NUM>-<NUM>), said pre-fabricated connector (<NUM>) fabricated prior to attachment to said stator (<NUM>), said pre-fabricated connector (<NUM>) as fabricated comprising:
a first plurality of termination coupling members (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) divided into a first plurality of termination coupling member groups, wherein each termination coupling member of each termination coupling member group of said first plurality of termination coupling member groups is configured to be mechanically and conductively coupled to a different winding termination of said plurality of winding terminations (<NUM>-<NUM>), wherein each termination coupling member group is mechanically and conductively coupled to one of a plurality of bus bars (<NUM>-<NUM>), and wherein each bus bar of said plurality of bus bars (<NUM>-<NUM>) includes an independent lug (<NUM>-<NUM>); and
an electrically insulating material (<NUM>) overlaying portions of said plurality of bus bars (<NUM>-<NUM>), said electrically insulating material (<NUM>) configured to prevent contact between said plurality of bus bars (<NUM>-<NUM>);
characterized by
a plurality of electrically insulating coupling member overlays (<NUM>-<NUM>), said plurality of electrically insulating coupling member overlays (<NUM>-<NUM>) configured to prevent contact between said first plurality of termination coupling members (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>).