WO1995035019A1

WO1995035019A1 - Low cost fluid-cooled housing for electric vehicle system control unit

Info

Publication number: WO1995035019A1
Application number: PCT/US1995/006976
Authority: WO
Inventors: Brian H. Smith
Original assignee: Westinghouse Electric Corporation
Priority date: 1994-06-10
Filing date: 1995-06-01
Publication date: 1995-12-21

Abstract

An electric vehicle propulsion system cooling assembly for channeling cooling fluid is provided and comprises a base member having two planar surfaces, and a cap member having an opening therein. The cap member is secured to one of the surfaces of the base member so that the surface covers the opening. Also provided are an inlet for admitting the fluid to the opening, and an outlet for emitting the fluid from the opening. The cap member channels the fluid sequentially through the inlet, the opening, and the outlet. At least one of the base member and the cap member is formed of the thermally conductive material to permit transfer of thermal energy to the fluid while the fluid is in the opening.

Description

LOW COST FLUID-COOLED HOUSING FOR ELECTRIC VEHICLE SYSTEM CONTROL UNIT RELATED APPLICATIONS The following identified U.S. patent applications are filed on the same date as the instant application and are relied upon and incorporated by reference in this application.

U.S. patent application entitled "Flat Topping Concept" bearing attorney docket No. 58,295, and filed on the same date herewith;

U.S. patent application entitled "Electric Induction Motor And Related Method Of Cooling" bearing attorney docket No. 58,332, and filed on the same date herewith;

U.S. patent application entitled "Automotive 12 Volt System For Electric Vehicles" bearing attorney docket No. 58,333, and filed on the same date herewith;

U.S. patent application entitled "Direct Cooled Switching Module For Electric Vehicle Propulsion System" bearing attorney docket No. 58,334, and filed on the same date herewith; U.S. patent application entitled "Electric

Vehicle Propulsion System" bearing attorney docket No. 58,335, and filed-on the same date herewith; U.S. patent application entitled "Speed Control and Bootstrap Technique For High Voltage Motor Control" bearing attorney docket No. 58,336, and filed on the same date herewith; U.S. patent application entitled "Vector Control

Board For An Electric Vehicle Propulsion System Motor Controller" bearing attorney docket No. 58,337, and filed on the same date herewith;

U.S. patent application entitled "Digital Pulse Width Modulator With Integrated Test And Control" bearing attorney docket No. 58,338, and filed on the same date herewith;

U.S. patent application entitled "Control Mechanism For Electric Vehicle" bearing attorney docket No. 58,339, and filed on the same date herewith;

U.S. patent application entitled "Improved EMI Filter Topology for Power Inverters" bearing attorney docket No. 58,340, and filed on the same date herewith; U.S. patent application entitled "Fault Detection Circuit For Sensing Leakage Currents Between Power Source And Chassis" bearing attorney docket No. 58,341, and filed on the same date herewith;

U.S. patent application entitled "Electric Vehicle Relay Assembly" bearing attorney docket No. 58,342, and filed on the same date herewith;

U.S. patent application entitled "Three Phase Power Bridge Assembly" bearing attorney docket No. 58,343, and filed on the same date herewith;

U.S. patent application entitled "Electric Vehicle Propulsion System Power Bridge With Built-in Test" bearing attorney docket No. 58,344, and filed on the same date herewith;

U.S. patent application entitled "Method For Testing A Power Bridge For An Electric Vehicle Propulsion System" bearing attorney docket No. 58,345, and filed on the same date herewith; U.S. patent application entitled "Electric Vehicle Power Distribution Module" bearing attorney docket No. 58,346, and filed on the same date herewith;

U.S. patent application entitled "Electric Vehicle Chassis Controller" bearing attorney docket No. 58,347, and filed on the same date herewith;

U.S. patent application entitled "Electric Vehicle System Control Unit Housing" bearing attorney docket No. 58,348, and filed on the same date herewith; U.S. patent application entitled "Electric

Vehicle Coolant Pump Assembly" bearing attorney docket No. 58,350, and filed on the same date herewith;

U.S. patent application entitled "Heat Dissipating Transformer Coil" bearing attorney docket No. 58,351, and filed on the same date herewith;

U.S. patent application entitled "Electric Vehicle Battery Charger" bearing attorney docket No. 58,352, and filed on the same date herewith.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a housing for electronic components of an electric vehicle. More particularly, the present invention relates to an electric vehicle propulsion system cooling assembly. While the invention is subject to a wide range of applications, it is especially suited for use in electric vehicles that utilize batteries or a combination of batteries and other sources, e.g., a heat engine coupled to an alternator, as a source of power, and will be particularly described in that connection.

Description of the Related Art Due to the importance currently placed on conserving petroleum reserves, achieving energy efficiency, and reducing air pollution, development of electric vehicles has become a priority. Ultimately, to be successful, these vehicles must be safe, inexpensive. efficient, and acceptable to consumers as an alternative to gasoline-powered vehicles.

Conventional electric vehicles include a motor, a battery, and electronic components for charging the battery and operating the motor. Although electric vehicles have been designed to be generally lighter than gasoline-powered vehicles, the weight of a typical electric vehicle is such that a substantial amount of power must be utilized in the motor to propel the vehicle. Because of friction within the motor, and because of resistance to electric current flow through various parts of the motor, heat is generated in the motor during use. If this heat is not removed, the potential for failure of the motor components exists. To remove heat from a motor, conventional electric vehicles have included a cooling system to cool the motor. Such a cooling system included a pump which circulated cooling fluid through the motor and a radiator. As the fluid passed through the motor, heat was absorbed by the fluid, and as the fluid passed through the radiator, heat was removed from the fluid. Alternately, a first fluid, such as ethylene glycol, was pumped through a housing in thermal contact with the motor to receive heat from the motor, and a second fluid, such as motor oil, was pumped through the motor to reduce friction. In this system, two fluid cycles were required.

In addition to the motor, the electrical components of conventional electrical vehicles can experience an undesirable build-up of heat due to the large electric currents used. For example, the motor controller within an electric vehicle system control unit may include a number of electronic switches such as insulated gate bipolar transistors (IGBT's). The IGBT's rapidly switch on and off to provide AC current flow to the motor, generating a substantial amount of heat.

Therefore, some method of removing thermal energy from the IGBT's is required to prevent their potential failure, as well as the potential failure of other electrical components located nearby. A directed flow of air has been used to cool electrical components in conventional electric vehicles. However, such air flow provides insufficient cooling in some situations. Further, use of two separate cooling systems (one for the motor and another for the electrical components) is costly to manufacture and service.

Another difficulty with conventional electric vehicles is electromagnetic interference (EMI) generated by electrical components of the vehicle propulsion system. While it may be desirable to mount many of the electrical components together for ease of manufacturing and servicing, doing so can increase the intensity of generated EMI, and may even cause the electrical components to interfere with each other. For example, the IGBT's cause a substantial amount of EMI during operation, which, if not attenuated, can cause unacceptable interference with other electrical components, both on and off the vehicle. Conventional electric vehicles have therefore utilized complicated shielding elements to prevent EMI disruption of closely spaced electrical components. These shields proved expensive and were complicated to manufacture. Alternately, electrical components have been spread out within an electric vehicle to reduce the intensity of generated EMI and make it less likely that EMI generated by one electrical component will disrupt other electrical components. However, spreading out various electrical components requires more wiring to connect the components, more housings to hold the components, and more labor to manufacture and service the components, than does mounting the components together.

Another drawback of conventional electric vehicles is that some vehicle components could not withstand the typical jolts and vibrations caused by driving. Many of-the critical parts of the system control unit are relatively fragile electrical components, and the components occasionally were broken during operation. Therefore, a sturdy support for such components is required.

One drawback of system control unit housings of related art electric vehicles is that' the housings can be expensive to manufacture. A cold plate of such a housing may comprise a base member and a cap member, both made of metal plates, which are preferably brazed together. An inlet and an outlet are provided in the base member for admitting and emitting fluid to and from a machined groove. Corrugated aluminum lanced offset finstock is brazed between the base member and cap member to improve thermal conduction of heat to the fluid in the groove. Ridges are disposed in the groove to secure the base member and cap member together. While performing its intended function well, the above cold plate is expensive to manufacture. Specifically, the machining of the groove and the brazing together of the base member and the cap member are expensive, thus making the cost of manufacture of the cold plate high. Therefore, a cold plate having similar performance capabilities as the above cold plate, but which is less expensive and complicated to manufacture, is desired.

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to an electric vehicle system control unit housing that substantially obviates one or more of the above problems

« due to the limitations and disadvantages of the related art. Features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus particularly pointed out in the written description and claims thereof as well as the appended drawings. To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, an electric vehicle propulsion system cooling assembly for channeling cooling fluid is provided. The assembly comprises a base member having two planar surfaces, and a cap member having means defining an opening therein. The cap member is secured to one of the surfaces of the base member so that the surface covers the opening. Inlet means is provided for admitting the fluid to the opening, and outlet means is provided for emitting the fluid from the opening. The cap member channels the fluid sequentially through the inlet means, the opening, and the outlet means. At least one of the base member and the cap member is formed of the thermally conductive material to permit transfer of thermal energy to the fluid while the fluid is in the opening.

In accordance with another aspect of the present invention, an electric vehicle propulsion system cooling assembly for channeling cooling fluid is provided. The assembly comprises a base member having two planar surfaces, and a first cap member having means defining a first opening therein. The first cap member is secured to one of the surfaces of the base member so that the surface covers the first opening. First inlet means is provided for admitting the fluid to the first opening, and first outlet means is provided for emitting the fluid from the first opening. A second cap member is provided having means defining a second opening therein, and is secured to one of the surfaces of the base member so that the surface covers the second opening. Second inlet means is provided for admitting the fluid to the second opening, and second outlet means is provided for emitting the fluid from the second opening. The first and second cap members channel the fluid sequentially through the first inlet means, the first opening, the first outlet means, the second inlet means, the second•opening, and the second outlet means. At least either the base member or the first and second cap members is formed of thermally conductive material to permit transfer of thermal energy to the fluid while the fluid is in the first and second openings.

As an option, with the second aspect of the present invention, the first inlet means includes an inlet hole formed through the base member, the first outlet means includes an outlet hole formed through the first cap member, the second inlet means includes an inlet hole formed through the second cap member, and the second outlet means includes an outlet hole formed through the base member.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate a presently preferred embodiment of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: Fig. 1 is a block diagram of an electric vehicle propulsion system in accordance with a preferred embodiment of the invention;

Fig. 2 is an exploded perspective view of a cold plate assembly of the electric vehicle propulsion system of Fig. 1;

Fig. 3 is a sectional view of the cold plate assembly taken along lines 3-3 in Fig. 2;

Fig. 4 is a sectional view of an alternate embodiment of a cold plate assembly of the electric vehicle propulsion system of Fig. 1; and

Fig. 5 is a perspective view of a plurality of cold plate assemblies mounted in various configurations. DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made in detail to a present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. As broadly represented in Fig. 1, an electric vehicle propulsion system 10 comprises a system control unit 12, a motor assembly 24, a cooling system 32, a battery 40, and a DC/DC converter 38. The system control unit 12 includes a cold plate 14, a battery charger 16, a motor controller 18, a power distribution module 20, and a chassis controller 22. The motor assembly 24 includes a resolver 26, a motor 28, and a filter 30. The cooling system 32 includes an oil pump unit 34 and a radiator/fan 36.

In accordance with the present invention, an electric vehicle propulsion system cooling assembly for channeling fluid is provided. The assembly comprises a base member having two planar surfaces, and a cap member having means defining an opening therein, the cap member being secured to one of the surfaces of the base member so that the surface covers the opening. As broadly embodied in Figs. 2-5, an electric vehicle propulsion system cooling assembly 70 comprises a base member 72 and a cap member 74. The base member 72 has top and bottom surfaces 76,78. As shown in Figs. 2-5, the cap member 74 is secured to the top surface 76. However, the cap member may also be secured to the bottom surface 78, if desired. The base member 72 and cap member 74 form the cold plate 14 of Fig. 1, when they are joined together.

As shown in Figs. 2-4, the cap member 74 is formed with an opening 88 for receiving the cooling fluid, which will be described below. As shown in Figs. 2-4, when the cap member 74 is secured to the base member 72, the top surface 76 of the base member covers the opening 88, thereby creating a passage for fluid flow through the base member and cap member.

Preferably, the cap member and base member are secured together by screws. As shown in Figs. 2 and 3, screws 80 are provided through screw holes 82 in the base member 72 to engage threaded holes 84 in the cap member 74. In Figs. 2 and 3, two representative screws 80 are provided through two of the screw holes 82 into a corresponding two of the threaded holes 84. It should be understood that the number of screws and holes shown in Figs. 2 and 3 is illustrative only, and screws are to be placed through each of the corresponding holes in the base member and cap member. Therefore, any suitable number of each may be employed as long as the cap member and base member are secured together thereby.

As an alternative to the screws, the base member 72 and the cap member 74 may be bonded together. If the base member 72 and cap member 74 are bonded together, a film adhesive 86, as shown in Fig. 4, may be employed to secure them together. Attaching the base member 72 and cap member 74 together with screws or a film adhesive is less expensive than brazing them together, and thus provides an easy to assemble and inexpensive heat sink.

Preferably, the cooling assembly further comprises a sealing member disposed around the opening between the base member and the cap member. As shown in

Figs. 2 and 3, an O-ring 94 is provided in a groove in the cap member 74 so as to form a seal between the base member 72 and cap member 74 when they are joined to preclude leakage. As shown in Fig. 4, it may be possible to eliminate the O-ring 94 if the base member 72 and the cap member 74 are joined together by bonding. However, the O-ring 94 may still be required to be added to the device of Fig. 4 in order to preclude leakage of fluid from the opening 88. In accordance with the present invention, at least one of the base member and the cap member are formed of thermally conductive material to permit transfer of thermal energy to the cooling fluid. Preferably, the base member and cap member comprise electrically conductive material, such as aluminum. Use of thermally and electrically conductive material allows for efficient heat transfer and prevention of EMI caused by electrical components which are mounted on the base member 72 and cap member 74. Covers (not shown) may be placed over the electrical components to form an improved EMI barrier surrounding the components. Preferably, the cap member is formed by a casting process. Casting the cap member 74 is less expensive than forming it by other conventional methods. While casting the cap member 74 limits its size due to the inherent characteristics of the casting process, a plurality of cap members can be provided in one assembly to provide accurately-targeted, localized cooling of individual components or groups of components which generate heat.

Preferably, the cap member includes at least one extending member disposed in the opening for improving transfer of thermal energy from the cap member to the fluid. As broadly shown in Figs. 2-4, the extending member may comprise a fin 90 extending into the opening 88 of the cap member 74. The fin 90 Improves heat transfer from the cap member to the fluid passing through the opening 88.

Preferably, the at least one extending member comprises a plurality of fins extending from the cap member into the opening, each of the fins having a truncated cone shape. As shown in Figs. 2-4, each of the plurality of fins 90 has a frustoconical truncated cone shape. This shape is employed because it can be formed readily in a casting process and provides efficient heat transfer. The fins 90 may be arranged in any suitable manner, and any number of fins may be utilized, in order to improve heat transfer. Generally, the more fins 90 employed, the better the heat transfer to the fluid, since heat transfer is a function of surface area. However, the number, size, and placement of the fins 90 may be limited by the constraints of the casting process.

Preferably, the base member includes protrusions which extend into the opening. More preferably, the protrusions comprise ridges. As broadly shown in Figs. 3 and 4, the protrusions on the sheet metal base member 72 may include beaded ridges 92 formed in a portion thereof covered by the cap member 74. The beaded ridges 92, as do the fins 90, improve heat transfer to the fluid. The ridges 92 are simple to form in the sheet metal base member 74, and thus provide an inexpensive way to improve heat transfer to the fluid. While in Figs. 3 and 4, the protrusions in the base member 72 are shown to be ridges 92, other shapes of protrusions may be employed within the scope of the invention. For example, these protrusions may comprise fins formed on the base member 72, within the scope of the invention.

In accordance with the invention, the assembly further comprises inlet means for admitting fluid to the opening, and outlet means for emitting fluid from the opening, the cap member channeling the fluid sequentially through the inlet means, the opening, and the outlet means. Preferably the inlet means comprises an inlet hole formed through one of the base member and the cap member, and the outlet means comprises an outlet hole formed through one of the base member and the cap member. As broadly embodied in Fig. 2, the inlet means comprises an inlet hole 96 formed in the base member 72 and in fluid communication with an inlet tube 98. As broadly shown in Fig. 2, the outlet means comprises an outlet hole 100 formed in the base member 72 and in fluid communication with an outlet tube 102. With the cap member 74 secured to the base member 72, the cooling fluid flows in the inlet tube 98, through the inlet hole 96, through the opening 88, through the outlet hole 100, and out the outlet tube 102, thereby permitting transfer of thermal energy to the fluid while the fluid is in the opening. While, in the assembly shown in Fig. 2, the inlet hole 96 and the outlet hole 100 are both formed in the base member 72, such an arrangement need not be employed within the scope of the invention. For example. as shown in Fig. 5, one of the holes (the inlet hole 112) feeding the cap member 74a is formed in the base member 72, but the other hole (the outlet hole 100) is formed in the cap member 74a. Alternately, both the inlet hole and outlet hole of the cooling assembly may be formed through the cap member, within the scope of the invention.

Preferably, the assembly further comprises electrical components mounted in thermal contact with the cap member, the cap member being formed of thermally conductive material, whereby thermal energy generated by the electrical components is transferred to the fluid by the cap member. As broadly shown in Figs. 3 and 4, electrical components comprising insulated gate bipolar transistors (IGBT's) are mounted atop the cap member 74 in thermal contact therewith. IGBT's can generate a large amount of heat during operation of the electric vehicle, and therefore are mounted directly on the cap member 74 for maximum heat transfer to the fluid. Electrical components other than the IGBT's may also be mounted on the cap member 74 within the scope of the invention.

As shown in Fig. 5, electrical components may be mounted on each of the cap members 74a-74c, for example, within the areas 108 marked by dotted lines on the cap members. Such an arrangement provides improved heat transfer from the electrical components. In order to further improve transfer of thermal energy from the electrical components, to the fluid, thermal gaskets 106 (see Figs. 3 and 4) may be provided between the electrical components and the cap member 74 to provide for better heat transfer from the component to the cap member. Such an arrangement is described in U.S. patent application entitled "Direct Cooled Switching Module For Electric Vehicle Propulsion System" attorney docket No. 58,334. Preferably, the assembly further comprises electrical components mounted in thermal contact with the base member, the base member being formed of thermally conductive material, whereby thermal energy generated by electrical components is transferred to the fluid via the base member. As shown in Figs. 2 and 5, electrical components may be mounted on the base member 72, for example, within the dotted-lined areas 110. Electrical components mounted within these areas 110 transfer thermal energy through the base member 72 to the fluid flowing through the opening 88.

Most preferably, electrical components are mounted in thermal contact with both the cap member and the base member to maximize heat transfer to the fluid, as shown in Fig. 5. If desired, electrical components may be mounted on both sides of the base member 72, and cap members 74 may be mounted on both sides of the base member for holding at least some of the electrical components. The fluid used in the assembly may comprise water, turbine oil, motor oil, or any other suitable fluid which can receive and transmit thermal energy without thermal breakdown, and which is of a suitable viscosity for pumping through a heat-cycle system. For example, applicants have obtained satisfactory results using Exxon 2389 Synthetic Lubricant.

In accordance with another aspect of the invention, an electric vehicle propulsion system cooling assembly for channeling cooling fluid is provided. The assembly comprises a base member having two planar surfaces, a first cap member having means defining a first opening therein, the cap member being secured to one of the surfaces of the base member so that the surface covers the first opening. First inlet means for admitting the fluid to the first opening, and first outlet means for emitting the fluid from the first opening. As broadly shown in Fig. 5, a cooling assembly 70 includes a base member 72, and a cap member 74a, as described above. A first inlet means comprising a hole 112 in the base member 72 is provided. The hole 112 is in communication with an inlet tube 98. The first outlet means comprises an outlet hole 100 formed in the cap member 74. In accordance with the second aspect of the invention, the assembly further comprises a second cap member having means defining a second opening therein, the second cap member being secured to one of the surfaces of the base member so that the surface covers the second opening, second inlet means for admitting fluid to the second opening, and second outlet means for emitting fluid from the second opening. As broadly shown in Fig. 5, cap member 74b is provided adjacent cap member 74a. Cap member 74b is essentially similar to cap member 74a and cap member 74 shown in Figs. 2-4. The second inlet means comprises an inlet hole 114 formed in the cap member 74b. The second outlet means comprises an outlet hole 100 formed in the base member 72 and in communication with an outlet tube 102.

Preferably, the first inlet means comprises an inlet hole formed through one of the base member and the first cap member, the second inlet means comprises an inlet hole formed through one of the base member and the second cap member, the first outlet means comprises an outlet hole formed through one of the base member and the second cap member, and the second outlet means comprises an outlet hole formed through one of the base member and the second cap member. Most preferably, the first inlet means comprises an inlet hole formed through the base member, the first outlet means comprises an outlet hole formed through the first cap member, the second inlet means comprises an inlet hole formed through the second cap member, and the second outlet means comprises an outlet hole formed through the base member. As broadly shown in Fig. 5, first inlet hole 112, first outlet hole 100, second inlet hole 114, and second outlet hole 100 are provided.

Preferably, the assembly further comprises tubing connecting the first outlet means and the second inlet means. As broadly shown in Fig. 5, connection tubing 116 is provided between the first outlet hole 100 and the second inlet hole 114.

In accordance with the second aspect of the present invention, the first and second cap members described above, along with the connection tubing, channel the fluid sequentially through the first inlet means, the first opening, the first outlet means, the second inlet means, the second opening, and the second outlet means, at least one of, the base member, the first cap member, and the second cap member being formed of thermally conductive material to permit transfer of thermal energy to the fluid while the fluid is in the first and second openings.

In operation, the cold plate 14 described above is employed within the cooling cycle of an electric vehicle. The pump unit 34 pumps the fluid through the cold plate 14, the radiator/fan 36, and optionally, the motor 28. As the fluid travels through the cold plate 14, heat is added to the fluid. As the fluid travels through the radiator/fan 36, heat is removed from the fluid. If desired, the fluid can also be pumped through the motor 28 and receive heat there, as well.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the .specification and practice of the invention disclosed herein. It is intended that the specification be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims, and their equivalents.

Claims

CLAIMS:

1. An electric vehicle propulsion system cooling assembly for channeling cooling fluid, the assembly comprising: a base member having two planar surfaces; a cap member having means defining an opening therein, the cap member being secured to one of the surfaces of the base member so that the surface covers the opening; inlet means for admitting the fluid to the opening; and outlet means for emitting the fluid from the opening, the cap member channeling the fluid sequentially through the inlet means, the opening, and the outlet means, at least one of the base member and the cap member being formed of the thermally conductive material to permit transfer of thermal energy to the fluid while the fluid is in the opening.

2. The assembly of claim 1, wherein the cap member is secured to the base member with screws.

3. The assembly of claim 2, wherein the cap member defines a plurality of threaded holes, and the base member defines a plurality of screw holes therethrough positioned to correspond to the threaded holes, for receiving the screws.

4. The assembly of claim 1, wherein the cap member is bonded to the base member.

5. The assembly of claim 1, wherein the cap member includes at least one extending fin disposed in the opening for improving transfer of thermal energy from the cap member to the fluid.

6. The assembly of claim 5, wherein the at least one fin includes a plurality of fins extending from the cap member into the opening, each of the fins having a truncated cone shape.

7. The assembly of claim 1, wherein the base member and the cap member comprise electrically conductive material.

8. The assembly of claim 7, wherein the base member and the cap member comprise aluminum.

9. The assembly of claim 1, wherein the cap member is formed by casting.

10. The assembly of claim 1, further including a sealing member disposed around the opening between the base member and the cap member.

11. The assembly of claim 1, wherein the inlet means includes an inlet hole formed through one of the base member or the cap member, and the outlet means includes an outlet hole formed through one of the base member or the cap member.

12. The assembly of claim 1, wherein the base member includes protrusions which extend into the opening.

13. The assembly of claim 12, wherein the protrusions include fins.

14. The assembly of claim 13, wherein the protrusions include ridges.

15. The assembly of claim 1, further including electrical components mounted in thermal contact with the cap member, the cap member being formed of thermally conductive material, whereby thermal energy generated by the electrical components is transferred to the fluid via the cap member.

16. The assembly of claim 1, further including electrical components mounted in thermal contact with the base member, the base member being formed of thermally conductive material, whereby thermal energy generated by the electrical components is transferred to the fluid via the base member.

17. The assembly of claim 1, further including electrical components mounted in thermal contact with the cap member and base member, the cap member and base member being formed of thermally conductive material, whereby thermal energy generated by the electrical components is transferred to the fluid via the cap member and base member.

18. An electric vehicle propulsion system cooling assembly for channeling cooling fluid, the assembly comprising: a base member having two planar surfaces; a first cap member having means defining a first opening therein, the first cap member being secured to one of the surfaces of the base member so that the surface covers the first opening; first inlet means for admitting the fluid to the first opening; first outlet means for emitting the fluid from the first opening; a second cap member having means defining a second opening therein, the second cap member being secured to one of the surfaces of the base member so that the surface covers the second opening; second inlet means for admitting the fluid to the second opening; and second outlet means for emitting the fluid from the second opening, the first and second cap members channeling the fluid sequentially through the first inlet means, the first opening, the first outlet means, the second inlet means, the second opening, and the second outlet means, at least either the base member or the first and second cap members being formed of thermally conductive material to permit transfer of thermal energy to the fluid while the fluid is in the first and second openings.

19. The assembly of claim 18, wherein the first inlet means includes an inlet hole formed through one of the base member or the first cap member, the second inlet means includes an inlet hole formed through one of the base member or the second cap member, the first outlet means includes an outlet hole formed through one of the base member or the second cap member, and the second outlet means includes an outlet hole formed through one of the base member or the second cap member.

20. The assembly of claim 18, wherein the first inlet means includes an inlet hole formed through the base member, the first outlet means includes an outlet hole formed through the first cap member, the second inlet means includes an inlet hole formed through the second cap member, and the second outlet means includes an outlet hole formed through the base member.

21. The assembly of claim 20, further including tubing connecting the first outlet means and the second inlet means.