Welding fixture for joining bar-wound stator conductors

A fixture assembly for welding a plurality of stator wire end pairs may include an anvil, a movable clamp configured to translate between an unclamped state and a clamped state, a first grounding electrode, and a second grounding electrode. The movable clamp may be configured to urge the plurality of stator wire ends against the anvil when in the clamped state. The moveable clamp includes a separator feature that generally extends toward the anvil. Each of the first grounding electrode and second grounding electrodes may be configured to translate between a clamped state and an unclamped state. When in the clamped state, each of the first and second grounding electrodes is configured to urge a pair of the plurality of stator wire end pairs against the separator feature.

TECHNICAL FIELD

The present disclosure relates to welding fixtures for joining the stator wires of electric devices.

BACKGROUND

Electric devices such as motors and generators having a stator secured within a housing of the motor/generator are well known. A rotor mounted on a shaft is coaxially positioned within the stator and is rotatable relative to the stator about the longitudinal axis of the shaft to transmit the force capacity of the motor. The passage of current through the stator creates a magnetic field tending to rotate the rotor and shaft.

Some stators are generally configured as an annular ring and are formed by stacking thin plates, or laminations, of highly magnetic steel. A copper winding of a specific pattern is configured, typically in slots of the lamination stack, through which current is flowed to magnetize sections of the stator assembly and to create a force reaction that causes the rotation of the rotor.

Bar pin stators are a particular type of stator that include a winding formed from a plurality of bar pins, or bar pin wires. The bar pin wires are formed from a heavy gauge copper wire with a rectangular cross section and generally configured in a hairpin shape having a curved section and typically terminating in two wire ends. The bar pins are accurately formed into a predetermined shape for insertion into specific rectangular slots in the stator, and are typically coated with an insulating material prior to insertion, such that the adjacent surfaces of the pins within the slots are electrically insulated from each other.

Typically, the curved ends of the bar pins protrude from one end of the lamination stack and the wire ends of the bar pins protrude from the opposite end of the lamination stack. After insertion, the portions of the wire protruding from the lamination stack are bent to form a complex weave from wire to wire, creating a plurality of wire end pairs. Adjacent paired wire ends are typically joined to form an electrical connection, such as through a welding operation. The resultant weave pattern and plurality of joints determines the flow of current through the motor, and thus the motive force of the rotor.

SUMMARY

A welding fixture assembly may be utilized for separating, crowding, and grounding a plurality of stator wire ends to receive a weld. The fixture assembly may include an anvil, a movable clamp configured to translate between an unclamped state and a clamped state, a first grounding electrode, and a second grounding electrode. The movable clamp may be configured to urge the plurality of stator wire ends against the anvil when in the clamped state.

The moveable clamp may include a separator feature that generally extends toward the anvil. In one configuration, the separator feature may include a wedge-shaped protrusion. Each of the first grounding electrode and second grounding electrode may be configured to translate between a clamped state and an unclamped state. When in the clamped state, the first grounding electrode is configured to urge a first pair of the plurality of stator wire ends against the separator feature. Likewise, when in a clamped state, the second grounding electrode may be configured to urge a second pair of the plurality of stator wire ends against the separator feature. Each of the first grounding electrode and the second grounding electrode may be electrically coupled with an electrical ground, and may be in electrical communication with the plurality of stator wire end pairs when in a clamped state.

The fixture may further include an electrode actuator that is configured to movably translate each of the first grounding electrode and the second grounding electrode between the respective unclamped and clamped states. Likewise, a similar actuator may be configured to movably translate the movable clamp.

The above mentioned fixture assembly may be used in a system for welding a plurality of stator wire end pairs that further includes an electric welding apparatus including a current source and a welding electrode.

Similarly, a method of fixturing a plurality of stator wire end pairs to receive an electrical weld may include: crowding the plurality of stator wire end pairs between a movable clamp and an anvil, wherein the movable clamp including a separator feature extending toward the anvil; crowding a first pair of the plurality of stator wire end pairs against a first side of the separator feature using a first translatable grounding electrode; crowding a second pair of the plurality of stator wire end pairs against a second side of the separator feature using a second translatable grounding electrode; and electrically coupling each of the first translatable grounding electrode and the second translatable grounding electrode with an electrical ground.

DETAILED DESCRIPTION

Referring to the drawings, wherein like reference numerals are used to identify like or identical components in the various views,FIG. 1schematically illustrates a stator assembly10of an electric machine having a plurality of bar-wound electrical conductor windings (generally at12). The stator10may generally be configured as an annular ring and may be formed from a lamination stack16(i.e., a plurality of individual laminations stacked in an ordered manner). Each lamination may include a plurality of radially distributed slots which may be oriented during assembly of the lamination stack16to define a plurality of generally rectangular slots18through the stator10. Each slot18may be particularly adapted to receive one or more of the conductor windings12.

As generally illustrated inFIG. 1, the stator10may be configured as a bar pin stator, wherein the conductor windings12are formed from a plurality of bar pins24(also referred to as “bar pin wires24”). The conductor windings12may further include terminals or connections20a,20band20c, for connecting the various phases of the windings12to an electrical controller such as a power inverter module. The bar pin wires24are typically formed from a heavy gauge, high conductivity copper wire with a rectangular cross section. Each bar pin wire24may generally be configured in a hairpin-type shape that has a curved section22at one end and typically terminates in two wire ends28at the opposing end. Prior to insertion, the bar pins24may be accurately formed into a predetermined shape to construct a predetermined weave pattern after insertion into the slots18. In one configuration, the bar pins24may be coated with an insulating material26prior to insertion, such that the adjacent surfaces of the bar pins24within the slots18are electrically insulated from each other. To facilitate joining of the wire ends28to form an electrical connection, the wire ends28of the bar pins24may be stripped of the insulating layer26prior to insertion into the slots18of the lamination stack16and prior to bending to form a weave pattern such as the weave pattern shown inFIG. 1and in additional detail inFIG. 2. Each slot18may be lined with a slot liner, to insulate the bar pins24from the lamination stack16, and to prevent damage to the insulating layer26during insertion of the bar pins24in the slots18.

FIG. 1shows the curved ends22of the bar pins24protruding from one end of the lamination stack16and the wire ends28of the bar pins24protruding from the opposite end of the lamination stack16. The plurality of bent wire ends28may generally be referred to as the wire end portion14of the stator10. After insertion, the wire ends28protruding from the lamination stack16may be bent to form a complex weave of bar pins24on the wire end portion14of the stator10. As such, each respective wire end28may be paired with and joined to a different wire end28according to the connection requirements of the winding12.

FIG. 2shows, by way of non-limiting example, a perspective view of the wire end portion14of stator10. As illustrated, the collective wire ends28of the bar pins24may be arranged in four layers, with each layer being disposed radially outward of the previous layer. For example, the outermost layer may include a plurality of wire ends28closest to the outer diameter of the lamination pack16, and the innermost layer may include a plurality of wire ends28closest to the inner diameter of the lamination stack16. Additionally, the wire ends28may be aligned in a plurality of rows30that each extend radially outward from the center of the stator10. As shown inFIGS. 2 and 3, the plurality of wire ends forming the innermost or first layer of the winding12are identified as wire ends34. The second layer of the winding12, which is proximate to the first layer, is formed of a plurality of wire ends identified as wire ends36. The third layer of the winding12is formed of a plurality of wire ends identified as wire ends44. The outermost or fourth layer is formed of a plurality of wire ends identified as wire ends46.

FIG. 2shows each of the wire ends34in the first layer being bent such that it is proximate to and paired with a wire end36in the second layer, forming a first, or inner wire end pair32. The wire ends34,36of the inner wire end pair32may be fused together through an electric welding process such as gas tungsten arc welding (GTAW or TIG welding), plasma arc welding (PAW), electric resistance welding (ERW) or other similar processes that may create a mechanical and electrical bond via the delivery of an electrical current.

Similar to the inner wire pair32, the wire ends44of the third layer may be bent such that they are each proximate to, and paired with a wire end46in the fourth layer, forming a second, or outer wire end pair42. The wire ends44,46of the outer wire end pair44may be fused together through a welding process that may be similar to the one used to form the inner wire end pair32.

FIGS. 3-5illustrate a fixture apparatus60that may be utilized when welding the wire ends28together to form end pairs32,42. As illustrated, the fixture60may be selectively transitionable between an unclamped state (FIG. 3) and a clamped state (FIG. 4). When in the clamped state, the fixture60may be operative to separate the second wire end36from the third wire end44, to crowd the first wire end34against the second wire end36, and to crowd the third wire end44against the fourth wire end46. Additionally, the fixture60may be operative to electrically ground both wire end pairs32,42to facilitate an electrical welding process. As used herein, “crowding” involves forcibly contacting the adjoining wire ends such that a welding operation may be effective in mechanically and/or electrically coupling the ends.

FIG. 3schematically illustrates an embodiment of the fixture apparatus60in the unclamped state. Conversely,FIG. 4schematically illustrates the same apparatus60in a clamped state. Said another way, inFIG. 4, the fixture apparatus has sufficiently been clamped against the wire ends28to separate, crowd, and ground the wire pairs32,42. Finally,FIG. 5illustrates a partial schematic cross-sectional view of the apparatus ofFIG. 4, taken along line5-5, and further including an electric welding apparatus100.

As generally illustrated inFIGS. 3 and 4, the fixture apparatus60may include an anvil62, a movable clamp64, a first grounding electrode66, and a second grounding electrode68. The fixture apparatus60may be adapted to generally surround one row30of wire ends28, such that the first grounding electrode66is disposed on a radially inward side of the row30, the second grounding electrode68is disposed on a radially outward side of the row30, and the movable clamp64and anvil62are disposed on opposite circumferential sides of the row30. In one configuration, the fixture apparatus60may be lowered onto the row30in a direction generally parallel to the longitudinal axis of the stator10. In another configuration, however, various components of the fixture assembly60(e.g., the clamp64and anvil62) may move into position relative to the wire ends28by translating along a radial axis.

During a fixturing operation, as shown inFIG. 4, the movable clamp64may translate in a direction70toward the anvil62(i.e., from the unclamped state to the clamped state). This translation may correspondingly trap and/or compress the wire ends34,36,44,46between the clamp64and the anvil62while urging them to align along a single row. The translation of the movable clamp64may be caused by an actuator72, which may be either a manual actuator or an electronically controlled actuator. Examples of manual actuators may include spring clamps, toggle clamps, or other such manually actuated clamping devices. Examples of electronically controlled actuators include pneumatic actuators, hydraulic actuators, screw-drive actuators, or other such electronically controlled actuators.

The movable clamp64may include a separator feature74that may urge the second wire end36to remain physically separated from the third wire end44. The separator feature74may be, for example, a wedge-shaped protrusion that may extend from a contact surface of the clamp64. As the movable clamp64is translated toward the anvil62, the protrusion may either urge the second and third wire ends36,44apart (if they are initially in contact), or may maintain a minimum separation distance between them (if they are initially apart). In one configuration, the anvil62may include a similar separator feature or wedge-shaped protrusion (not shown) that may oppose the separator feature74of the movable clamp64.

While the movable clamp64is aligning and/or separating the wire ends against the anvil62, the first and second grounding electrodes66,68may respectively translate toward the wire ends34,36,44,46from the unclamped state to the clamped state (i.e., along respective directions76,78). In this manner, the first grounding electrode66may contact the first wire end34and urge it against the second wire end36. Likewise the second grounding electrode68may contact the fourth wire end46and urge it against the third wire end44. The compressing translation of the first and second grounding electrodes66,68may also urge the inner and outer wire pairs32,42against opposing sides of the separator feature74.

Each grounding electrode66,68may linearly translate under the control of a respective electrode actuator80. The electrode actuator80may be either a mechanical actuator or an electrical actuator, and may enable each grounding electrode66,68to either translate independently, or in unison. Additionally, each grounding electrode66,68may be coupled to an electrical ground82that may be capable of receiving a large amount of electrical current (e.g., greater than 250 Amperes). Grounding the electrodes may enable automated welding processes and eliminate the need to separately ground the wire ends.

Once the fixture assembly60engages the plurality of wire ends to separate, crowd and ground the end pairs32,42, as shown inFIG. 4, a welding apparatus100(shown inFIG. 5) may then apply high current electrical energy to each pair32,42in a manner that welds the respective wire ends together. For example, an electrode, such as a tungsten welding electrode102may conduct electricity supplied by a current source104to the grounded wire ends. The electrode102may be surrounded by a continuous flow of inert gas106(e.g., argon) that may flow through a nozzle108surrounding the electrode106. In one embodiment, the current source104may be electrically coupled with the grounding electrodes66,68either through a direct electrical connection or by way of a common electrical ground82. As may be appreciated, the electric welding apparatus100may weld each pair32,42independent from the other pair. For example, the welding apparatus100may first weld the inner wire end pair32, and may subsequently weld the outer wire end pair42.

The motion and actuation of the electric welding apparatus100may be controlled by a welding controller110. In one embodiment, the welding controller110may include a three-axis positioning device that may be configured to move the electrode102in Cartesian directions relative to the wire end pairs32,42. Once in proper position (i.e., approximately 1-2 mm separated from the wire ends in the case of a GTAW) the welding controller110may selectively energize the current source104to create the weld.

Referring toFIG. 6, once the welding apparatus100has fused the wire end pairs of one row120together, the various actuators may translate the grounding electrodes66,68and movable clamp64away from the wire ends28(i.e., from the clamped state to the unclamped state) and the fixture apparatus60may lift off of the row30. In one configuration, the stator10may be indexed on a rotatable table or fixture, such that an adjacent row (e.g., row122) may be welded following the welding of row30. This may be accomplished by controllably rotating the table (and stator assembly) in a corresponding angular direction124until the adjacent row122is disposed under the fixture assembly60. In this manner, all end-pairs of the bar wound stator assembly may be welded in an automated manner.

While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not as limiting.