Electric drive unit including capacitor bleeder

Abstract

An electric drive unit having an electric motor received in a housing assembly includes an inverter received in the housing assembly and electrically coupled to the electric motor, and a bleed transistor assembly. The inverter includes a field capacitor and an inverter mount. The bleed transistor assembly includes a heat sink coupled to the housing assembly, a bleed transistor positioned in the inverter mount, which is assembled in the housing assembly, and a housing coupling adapted to link the heat sink on the housing assembly. Further, the bleed transistor is coupled to the heat sink. The housing coupling is configured to position the heat sink in an XY-plane and provide compliance in a Z-direction to allow for misalignment of the bleed transistor assembly.

Description

ELECTRIC DRIVE UNIT INCLUDING CAPACITOR BLEEDERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119 to United States Provisional Application No. 63 / 655,647, filed June 4, 2024, the content of which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to electric drive units used in vehicles and, more particularly, to capacitor bleeders used in the electric drive units of the vehicle.BACKGROUND

[0003] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0004] While there is increasing interest in the electrification of vehicle driveline, there are significant issues that overcome before vehicles with electrified drivelines substantially displace vehicle drivelines that are powered solely by internal combustion engines. Some of these issues include the cost of the electrified driveline, the volume of the electrified driveline and its ability to be packaged into available space within a vehicle, as well as the robustness of the electronics that are employed to operate and control the electrified driveline.SUMMARY

[0005] The present disclosure provides an electric drive unit that includes a multi-phase electric motor and an inverter. According to an exemplary form of the present disclosure, a bleed transistor assembly for operation in an electric drive unit having a housing assembly and an inverter received in the housing assembly includes a heat sink coupled to the housing assembly, a bleed transistor electrically connected to the inverter and securely coupled to the heat sink, and a housing coupling adapted to link the heat sink on the housing assembly.

[0006] According to a further aspect of the present disclosure, the housing coupling is substantially planar shape with a plurality of apertures for receiving fasteners to couple to one or more attachment points on both the heat sink and the housing assembly. The housing coupling is configured to position the heat sink in an XY-plane and provided compliance ina Z-direction to allow for misalignment of the bleed transistor assembly. The housing coupling is formed of a metallic material and also formed by a stamping method.

[0007] According to a further aspect of the present disclosure, the bleed transistor assembly includes a retaining plate formed as a springy clip and releasably coupled to a first attachment point of the heat sink. The springy clip is configured to leverage the first attachment point to exert a force on the bleed transistor biasing the bleed transistor against the heat sink such that the springy clip maintains the bleed transistor in a desired position. The springy clip includes at least one V-shaped groove on a first surface of the bleed transistor.

[0008] According to a further aspect of the present disclosure, the bleed transistor assembly includes a thermal grease coating applied to each of an outer surface of the housing assembly and a second surface of the bleed transistor such that the coating layer is disposed between the housing assembly and the heat sink, and the heat sink and the bleed transistor.

[0009] According to a further aspect of the present disclosure, the heat sink is fixedly attached to an outer surface of the housing assembly, adjacent to the bleed transistor positioned in an inverter mount, which is assembled with the housing assembly such that the heat sink abuts both the bleed transistor and the housing assembly. The heat sink includes one or more apertures extending through a body of the heat sink such that one or more fasteners pass through the one or more apertures to fixedly attach to the housing assembly. In another approach, the heat sink is fixedly secured to the housing assembly using a bonding method with an adhesive material. The heat sink is formed of a conductive material such as copper or aluminum.

[0010] According to a further aspect of the present disclosure, the heat sink is positioned on an outer surface of the housing assembly, adjacent to a fluid passage of the housing assembly such that a fluid medium passing through the fluid passage is configured to provide a cooling effect of the heat sink.

[0011] According to another aspect of the present disclosure, an electric drive unit having an electric motor received in a housing assembly includes an inverter received in the housing assembly and electrically coupled to the electric motor and a bleed transistor assembly. The inverter comprises a field capacitor and an inverter mount. The bleed transistor assembly includes a heat sink coupled to the housing assembly, a bleed transistor positioned in the inverter mount, which is assembled in the housing assembly and coupledto the heat sink, and a housing coupling adapted to link the heat sink on the housing assembly.

[0012] Further details and benefits will become apparent from the following detailed description of the appended drawings. The drawings are provided herewith purely for illustrative purposes and are not intended to limit the scope of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

[0014] FIG. 1 is a perspective view depicting an implementation of power electronics used with an electric drive unit;

[0015] FIG. 2 is a perspective view depicting an implementation of a portion of the power electronics used with an electric drive unit;

[0016] FIG. 3 is a perspective view depicting an implementation of a portion of the power electronics used with an electric drive unit;

[0017] FIG. 4 is a perspective view depicting an implementation of a portion of the power electronics used with an electric drive unit;

[0018] FIG. 5 is a perspective view depicting an implementation of a portion of the power electronics used with an electric drive unit;

[0019] FIG. 6 is a perspective view depicting an implementation of a portion of the power electronics used with an electric drive unit; and

[0020] FIG. 7 is a perspective view depicting an implementation of a portion of the power electronics used with an electric drive unit.

[0021] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.DETAILED DESCRIPTION

[0022] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0023] Electric drive units typically include a battery, supplying direct current (DC) electrical power to a rotating electrical machine or electric motor through a bus bar assembly, and power electronics that include an inverter. An example of such an electric drive unit is described in U.S. Patent No. 11 ,863,046 the entire contents of which are incorporated by reference. The electric drive unit includes a housing assembly, a motor assembly, a transmission, and at least one output shaft. The housing assembly includes cavities that at least partially house elements of the electric drive unit. For example, the motor assembly, the transmission, the differential assembly, and the at least one output shaft may be at least partly housed. The motor assembly includes an electric motor and a motor control unit that includes an inverter. The electric motor may be a multi-phased electric motor and includes a stator and a rotor that is rotatable about a motor output axis. The stator has a stator core and a plurality of field windings that are wound about the stator core. Each of the field windings is associated with a corresponding phase of electrical power. The housing assembly includes one or more fluid passages, within the housing assembly, that receive cooling fluid from a fluid source and pass the cooling fluid through the housing assembly to cool components within or attached to the housing assembly.

[0024] The power electronics and inverter includes a plurality of power semiconductors or switches that regulate electrical power from the battery to the rotating electrical machine. The power semiconductors / switches may be implemented using any one of a variety of different switches, such as MOSFETs or binary junction transistors (BJTs). The inverter uses the plurality of power semiconductors to receive DC electrical power stored in the battery and invert the DC electrical power into alternating current (AC) supplied to the field windings of the stator of the rotating electrical machine or electric motor. The electric drive unit includes a DC link having electrical conductors electrically coupled to a field capacitor and an input to the inverter receiving DC electrical power. The field capacitor stores an electrical charge that may be selectively discharged using a bleed transistor. The bleed transistor is electrically coupled between the field capacitor and a ground; in a non- conductive state, the bleed transistor permits the field capacitor to carry an electrical charge. A gate signal may be selectively sent to the gate of the bleed transistor rendering is conductive and discharging the bleed transistor.

[0025] Given the amount of electrical charge stored in the field capacitor, rendering the bleed transistor conductive to discharge the field capacitor may generate a significant amount of heat in a relatively short amount of time. A bleed transistor assembly may help compensate for the heat generation using a dedicated heat sink coupled to a housingassembly on the electric drive unit. The heat sink is positioned relative to the housing using a housing coupling (e.g., a coupling plate) that may position the heat sink in an XY plane but provide compliance in a Z direction. And the heat sink may be positioned on a surface of the housing assembly to be in close proximity to the fluid passages to amplify cooling performance. A retaining plate (i.e., springy clip) releasably coupled to the heat sink may maintain the bleed transistor in a desired position.

[0026] FIG. 1 depicts a portion of an electric drive unit 10 carrying an inverter 12. The inverter 12 can be electrically coupled to an electric motor and a battery (not shown). The battery can store electrical charge as DC voltage and supply DC current to the inverter 12. The inverter 12 can invert DC electrical current into AC electrical current that is selectively supplied to the electric motor. The inverter 12 includes an inverter mount 14, a plurality of power semiconductors 16, a plurality of busbars 18 (e.g., a positive busbar, a ground busbar, and a plurality of phase busbars), a plurality of insulating layers (not specifically shown), an inverter circuit board 20, a field capacitor 22, and a bleed transistor assembly 24. The inverter 12 is configured to control the power semiconductors 16, which may be MOSFETs or IGBTs, for example, to control the switching of DC electricity to create three AC electric outputs, with each AC electric output being associated with a given phase of the windings of the stator. The power semiconductors 16 may be electrically coupled to field windings via the phase busbars 18a, 18b, and 18c (shown in more detail by FIG. 6). The positive busbar 18d and the ground busbar 18e may collectively form a DC link 26 and couple the DC voltage output from the battery to the inverter 12 and the field capacitor 22 that may be implemented as bulk capacitance having a plurality of individual capacitors. The inverter mount 14 may have a generally annular configuration and define a plurality of semiconductor mounts (not specifically shown) that may be formed into the radially outer portion on a wall of the inverter mount 14. Each of the semiconductor mounts may define a plurality of semiconductor terminal apertures (not specifically shown) and may be disposed in a ring- shaped arrangement about the outer perimeter of the inverter mount 14.

[0027] With reference to FIGS. 2-7, the bleed transistor assembly 24 can include a heat sink 28 configured to couple to a housing assembly 30 of the electric drive unit 10 adjacent a fluid passage 32, a bleed transistor 34 that abuts the heat sink 28, a retaining plate 36 configured to releasably couple with the heat sink 28 to hold the bleed transistor 34 against the heat sink 28, and a housing coupling (e.g., a coupling plate) 38. The bleed transistor 34 may be implemented using any one of a number of switches, such as MOSFETs or BJTs. In this implementation, the bleed transistor 34 can be implemented using a TO-247 transistorhaving a source terminal, a gate terminal, and a drain terminal (not shown). The bleed transistor 34 may be received by the inverter mount 14 at a location adjacent to the DC link 26 such that the terminals may be potted in a dielectric potting compound, such as epoxy. The source terminal may be electrically coupled to the field capacitor 22 and the drain terminal may be electrically coupled to ground. The gate terminal may be electrically coupled to the inverter circuit board 20 having one or more microprocessors carrying out computer-readable instructions that render the bleed transistor 34 conductive, or “on” as well as non-conductive, or “off.” During operation, the bleed transistor 34 may be maintained in a non-conductive state and, when discharging the field capacitor 22 is desired, the bleed transistor 34 may be rendered conductive. The bleed transistor 34 may be positioned in the inverter mount 14 such that when the inverter mount 14 is assembled with the housing assembly 30, the bleed transistor 34 may be positioned adjacent an outer surface of the housing assembly 30 in close proximity to fluid passages 32 flowing cooling fluid.

[0028] The heat sink 28 may be affixed to the outer surface of the housing assembly 30 in between the bleed transistor 34 and the housing assembly 30 such that the heat sink 28 abuts both the bleed transistor 34 and the housing assembly 30 while the inverter mount 14 is coupled to the housing assembly 30. The heat sink 28 may be implemented as a material that has a high thermal conductivity coefficient, such as copper or aluminum. The heat sink 28 includes one or more apertures (not shown) extending through the body of the heat sink 28 through which threaded fasteners 40 pass and engage with threaded receptacles (not shown) formed in the housing assembly 30. However, it should be appreciated that the heat sink 28 may be attached to the housing assembly 30 using other physical attachment mechanism, such as by bonding with an adhesive. The heat sink 28 also includes an attachment point 42 for coupling the retaining plate 36 to the heat sink 28. The attachment point 42 in this implementation may be a location for a threaded receptacle (not shown) that can receive a threaded fastener 40, but other mechanisms may be possible.

[0029] The retaining plate 36 may be implemented as a planar springy clip attached to the attachment point 42 in the heat sink 28. The shape of the retaining plate 36 may be chosen so that the springy clip 36 leverages the attachment point 42 to exert a force on the bleed transistor 34 biasing the bleed transistor 34 against the heat sink 28. At least one V- shaped groove 44 may be formed in the retaining plate 36 that engages a first surface 33 of the bleed transistor 34. The retaining plate may be formed in other shapes as well, such that the springy clip is non-planar and formed from one or more wires that couple with the attachment point and bias the bleed transistor into engagement with the heat sink. Duringassembly, a coating 52 of thermal grease can be applied to the outer surface of the housing assembly 30 between the heat sink 28 and the housing assembly 30 as well as a second surface 35 of the bleed transistor 34 where the bleed transistor 34 abuts the heat sink 28.

[0030] The housing coupling 38 (e.g., the coupling plate) may link the heat sink 28 to an attachment point 46 on the housing assembly 30 and to another attachment point 48 on the heat sink 28. In this implementation, the housing coupling 38 is substantially planar with a plurality of apertures 50 for receiving threaded fasteners 40 such that the threaded fasteners 40 are received by threaded receptacles (not shown) in the housing assembly 30 and the heat sink 28. The housing coupling (i.e. , the coupling plate) 38 may be formed from a metal sheet and may be stamped into a particular form. However, other shapes and methods of forming the housing coupling may be possible.

[0031] The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

[0032] As used in this specification and claims, the terms "e.g.," “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

CLAIMSWhat is claimed is:1 . A bleed transistor assembly for operation in an electric drive unit having a housing assembly and an inverter received in the housing assembly, the bleed transistor assembly comprising: a heat sink coupled to the housing assembly; a bleed transistor electrically connected to the inverter, the bleed transistor securely coupled to the heat sink; and a housing coupling adapted to link the heat sink on the housing assembly.

2. The bleed transistor assembly of claim 1 , wherein the housing coupling is substantially planar shape with a plurality of apertures for receiving fasteners to couple to one or more attachment points on both the heat sink and the housing assembly.

3. The bleed transistor assembly of claim 1 , wherein the housing coupling is configured to position the heat sink in an XY-plane and provide compliance in a Z-direction to allow for misalignment of the bleed transistor assembly.

4. The bleed transistor assembly of claim 1 , wherein the housing coupling is formed of a metallic material and also formed by a stamping method.

5. The bleed transistor assembly of claim 1 , further comprising a retaining plate formed as a springy clip and releasably coupled to a first attachment point of the heat sink.

6. The bleed transistor assembly of claim 5, wherein the springy clip is configured to leverage the first attachment point to exert a force on the bleed transistor biasing the bleed transistor against the heat sink such that the springy clip maintains the bleed transistor in a desired position.

7. The bleed transistor assembly of claim 5, wherein the springy clip includes at least one V-shaped groove engages on a first surface of the bleed transistor.

8. The bleed transistor assembly of claim 1 , further comprising a thermal grease coating applied to each of an outer surface of the housing assembly and a second surface of the bleed transistor such that the coating layer is disposed between the housing assembly and the heat sink, and the heat sink and the bleed transistor.

9. The bleed transistor assembly of claim 1 , wherein the heat sink is fixedly attached to an outer surface of the housing assembly, adjacent to the bleed transistor positioned in an inverter mount, which is assembled with the housing assembly such that the heat sink abuts both the bleed transistor and the housing assembly.

10. The bleed transistor assembly of claim 9, wherein the heat sink includes one or more apertures extending through a body of the heat sink such that one or more fasteners pass through the one or more apertures to fixedly attach to the housing assembly.11 . The bleed transistor assembly of claim 1 , wherein the heat sink is positioned on an outer surface of the housing assembly, adjacent to a fluid passage of the housing assembly such that a fluid medium passing through the fluid passage is configured to provide a cooling effect to the heat sink.

12. An electric drive unit having an electric motor received in a housing assembly, the electric drive unit comprising: an inverter received in the housing assembly and electrically coupled to the electric motor, the inverter comprising a field capacitor and an inverter mount; and a bleed transistor assembly, comprising: a heat sink coupled to the housing assembly; a bleed transistor positioned in the inverter mount, which is assembled in the housing assembly, the bleed transistor coupled to the heat sink; and a housing coupling adapted to link the heat sink on the housing assembly.

13. The electric drive unit of claim 12, wherein the housing coupling is substantially planar shape with a plurality of apertures for receiving fasteners to couple to one or more attachment points on both the heat sink and the housing assembly.

14. The electric drive unit of claim 12, wherein the housing coupling is configured to position the heat sink in an XY-plane and provide compliance in a Z-direction to allow for misalignment of the bleed transistor assembly.

15. The electric drive unit of claim 12, further comprising a retaining plate formed as a springy clip and releasably coupled to a first attachment point of the heat sink.

16. The electric drive unit of claim 15, wherein the springy clip is configured to leverage the first attachment point to exert a force on the bleed transistor biasing the bleed transistor against the heat sink such that the springy clip maintains the bleed transistor in a desired position.

17. The electric drive unit of claim 12, further comprising a thermal grease coating applied to each of an outer surface of the housing assembly and a second surface of the bleed transistor such that the coating layer is disposed between the housing assembly and the heat sink, and the heat sink and the bleed transistor.

18. The electric drive unit of claim 12, wherein the heat sink is fixedly attached to an outer surface of the housing assembly, adjacent to the bleed transistor such that the heat sink abuts both the bleed transistor and the housing assembly.

19. The electric drive unit of claim 12, wherein the heat sink is formed of a conductive material such as copper or aluminum.

20. The electric drive unit of claim 12, wherein the heat sink is positioned on an outer surface of the housing assembly, adjacent to a fluid passage of the housing assembly such that a fluid medium passing through the fluid passage is configured to provide a cooling effect to the heat sink.

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