Selective insulation of fuel cell stack monitoring device

Abstract

A fuel cell system includes: a housing; a fuel cell within the housing; and a stack monitoring device, wherein the stack monitoring device is installed on the housing. The stack monitoring device includes an enclosure and a cover connected to the enclosure to define a cavity. The lid defines an inner lid surface. The inner cap surface partially defines the cavity. The stack monitoring device also includes a metal oxide semiconductor field effect transistor (MOSFET) disposed in the cavity between the enclosure and the cover. An inner lid surface of the lid faces the MOSFET. The MOSFET includes a body and one or more pins protruding from the body. The system also includes an electrical insulator connected to the inner cover surface. The electrical insulator defines an inner insulator surface facing the MOSFET. The pins are spaced apart from the electrical insulator to define an air gap.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a selective insulation for a fuel cell stack monitor device. BACKGROUND

[0002] This section generally presents the background of the present disclosure. To the extent that specific experiments are discussed in this section, such discussion is intended to provide context for the described invention. To the extent that there are any discrepancies between descriptions of the methods, devices and materials of the background art and the descriptions of the state of the art in this section, the contents of the former shall be deemed incorrect.

[0003] Some vehicle systems use fuel cell systems for propulsion. The fuel cell system includes a stack monitor device (SMCD). The SMCD includes a printed circuit board, sensors, bus bars, cold plates, and power electronics arranged within a housing. The SMCD is mounted on a stack enclosure within a fuel cell power module. Some high-level functions of the housing include preventing accidental access to power paths, protecting electronics, component electrical insulation, shielding from external intrusion, and transferring heat to a cryogenic coolant loop. To meet grounding requirements, the SMCD housing should be electrically connected to the vehicle chassis.

[0004] For high voltage gaps, the air gap length between the electrical conductor (e.g., pin of MOSFET) and the SMCD cover should be greater than 3.0 mm. Therefore, there is a need to develop a system that electrically insulates the SMCD cover from the high voltage electrical conductor (e.g., pin of MOSFET). SUMMARY

[0005] The present disclosure describes a fuel cell system. In an aspect of the present disclosure, the fuel cell system includes an enclosure, a number of individual fuel cells stacked together within the enclosure, and a stack monitor device mounted on the enclosure. The stack monitor device includes an enclosure and a cover connected to the enclosure to define a cavity. The cover defines an inner cover surface. The inner cover surface partially defines the cavity. The stack monitor device further includes an electronic component (e.g., a metal oxide semiconductor field effect transistor (MOSFET)) arranged in the cavity between the enclosure and the cover. The inner cover surface of the cover faces the electronic component. The electronic component includes a body (e.g., a p-type substrate) and one or more pins protruding from the body. The system further includes an electrical insulator connected to the inner cover surface. The electrical insulator defines an inner insulator surface facing the electronic component. The pins are spaced apart from the electrical insulator to define an air gap.

[0006] In some aspects of the disclosure, an electrical insulator is disposed over a pin of a MOSFET. The electrical insulator can be made entirely of polytetrafluoroethylene (PTFE). The cap and the enclosure can each be made entirely of a metallic material. The cap defines a recess at least partially defined by an inner cap surface. The electrical insulator can be disposed entirely in the recess. The inner insulator surface can be flush with the inner cap surface. The air gap has a gap length defined from the pin to the inner insulator surface. The gap length is greater than 3.0 mm (e.g., 3.1 mm). The electrical insulator has an insulator thickness. The insulator thickness is between 0.2 mm and 1 mm (e.g., 0.3 mm). The electrical insulator has a dielectric strength. The dielectric strength of the electrical insulator is between 9 kV / mm and 280 kV / mm (e.g., 9 kV / mm). The electrical insulator can be made partially or entirely of a ceramic and / or polymeric material (e.g., polytetrafluoroethylene (PTFE)). The electrical insulator can be disposed entirely in the recess. The cap can be made entirely or partially of an aluminum alloy. The electrical insulator can be made entirely or partially of an elastomer and / or a glaze.

[0007] The inner cap surface has a sloped face portion and a horizontal face portion. The horizontal face portion is elongated along a horizontal direction. The horizontal direction is perpendicular to the vertical direction V. The pin of the MOSFET is spaced apart from the electrical insulator along the vertical direction. The sloped face portion is at an oblique angle relative to the horizontal face portion. The gap length is defined along a length axis from the pin of the MOSFET to the inner insulator surface of the electrical insulator. The length axis intersects the sloped face portion at a right angle. The gap length is parallel to the length axis. An angle is defined from the vertical direction V to the length axis 58, the angle being the oblique angle (e.g., 37 degrees).

[0008] Further areas of applicability of the present disclosure will become apparent from the detailed description provided below. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment, are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0009] The above features and advantages of the presently disclosed systems and methods, and other features and advantages, will be apparent from the detailed description, including the examples, which follows, when considered in conjunction with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0010] The present disclosure will be more fully understood from the detailed description and the specific examples, which follow, in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a schematic illustration of a vehicle including a fuel cell system.

[0012] Figure 2 is Figure 1 is an isometric schematic illustration of the fuel cell system of

[0013] Figure 3 isFigure 2 a bottom view of the cover of the SMCD of

[0014] Figure 4 is taken around Figure 3 the area A of Figure 3 a bottom view of the cover of the SMCD of

[0015] Figure 5 is taken along Figure 2 the cross-sectional line 5-5 of Figure 2 a cross-sectional view of the SMCD of

[0016] Figure 6 is taken around Figure 5 the area B of Figure 2 a cross-sectional view of the SMCD of DETAILED DESCRIPTION

[0017] Reference will now be made in detail to several examples of the present disclosure illustrated in the accompanying drawings. Wherever possible, the same or like reference numbers will be used throughout the drawings and the written description to refer to the same or like parts or steps.

[0018] Referring to Figure 1 , the vehicle 10 generally includes a vehicle body 12 and a plurality of wheels 14 connected to the vehicle body 12. The vehicle 10 can be an autonomous vehicle. In the depicted embodiment, the vehicle 10 can be a sedan, a truck, a coupe, a sport utility vehicle (SUV), a recreational vehicle (RV). The vehicle 10 further includes an electric motor 16 connected to one or more wheels 14. The electric motor 16 is configured to convert electrical energy into mechanical energy (e.g., torque) to drive the wheels 14. The vehicle 10 further includes a fuel cell system 18 electrically connected to the electric motor 16. The fuel cell system 18 is configured to generate electricity from hydrogen or other fuel. Thus, the fuel cell system 18 provides electrical power to the electric motor 16. The fuel cell system 18 includes an enclosure 20 and one or more fuel cells 22 located within the enclosure 20.

[0019] Referring to Figures 2-6 , the fuel cell system 18 includes a stack monitoring device (SMCD) 24 mounted on the enclosure 20. The SMCD 24 includes an enclosure 26 and a cover directly connected to the enclosure 26. One or more seals 30 seal the enclosure 26 and the cover 28. The enclosure 26 and the cover 28 collectively define a cavity 32. The SMCD 24 houses printed circuit boards, sensors, bus bars, cold plates, and power electronics in the cavity 32. The cover 28 and the enclosure 26 are each partially or entirely made of a metallic material to enhance the structural integrity of the SMCD 24. For example, the cover 28 can be partially or entirely made of an aluminum alloy.

[0020] The SMCD 24 includes electronic components, such as a metal oxide semiconductor field effect transistor (MOSFET) 34, switches, relays, capacitors, and the like, located in the cavity 32 between the enclosure 26 and the lid 28. The MOSFET 34 or other electronic components include a body 36 (e.g., a p-type substrate or an n-type substrate) and one or more pins 38 protruding from the body 36. The pins 38 are made entirely of conductive material and carry high voltage electricity. As such, it is desirable to electrically insulate the pins 38 from the lid 28 to prevent a short circuit.

[0021] The lid 28 defines an inner lid surface 40 that partially defines the cavity 32. The inner lid surface 40 faces the MOSFET 34 or other electronic components. The lid 28 defines a recess 42 that is at least partially defined by the inner lid surface 40. The SMCD 24 includes an electrical insulator 44 connected to the inner lid surface 40 to prevent the transmission of electrical current from the pins 38 of the MOSFET 34 (or other electronic components) to the lid 28. The electrical insulator 44 can be disposed entirely in the recess 42.

[0022] The electrical insulator 44 defines an inner insulator surface 46 that faces the MOSFET 34 or other electronic components. The inner insulator surface 46 is flush with the inner lid surface 40. The pins 38 are spaced apart from the electrical insulator 44 to define an air gap 48. The pins 38 are spaced apart from the electrical insulator 44 in the vertical direction V. As such, the electrical insulator 44 is disposed above the pins 38 of the MOSFET 34. The electrical insulator 44 is made partially or entirely of an electrically insulating material (e.g., a polymeric material, a ceramic, and / or an enamel) to electrically insulate the lid 28 from the pins 38 of the MOSFET 34 or other electronic components. As a non-limiting example, the electrical insulator 44 can be made entirely or partially of an elastomer and / or polytetrafluoroethylene (PTFE) to electrically insulate the lid 28 from the pins 38 of the MOSFET 34.

[0023] As described above, the pin 38 of the MOSFET 34 (or other electronic component) is spaced apart from the electrical insulator 44 to define the air gap 48. The air gap 48 has a gap length 50 defined from the pin 38 of the MOSFET 34 (or other electronic component) to the inner insulator surface 46 of the electrical insulator 44. The gap length 50 is greater than 3.0 mm (e.g., 3.1 mm) to prevent the transmission of electrical power from the pin 38 of the MOSFET 34 (or other electronic component) to the cover 28, thereby preventing a short circuit. The electrical insulator 44 has an insulator thickness 52. The insulator thickness 52 is between 0.2 mm and 1 mm (e.g., 0.3 mm) to prevent the transmission of electrical power from the pin 38 of the MOSFET 34 (or other electronic component) to the cover 28, thereby preventing a short circuit. The electrical insulator 44 has a dielectric strength. The dielectric strength of the electrical insulator 44 is between 9 kV / mm and 280 kV / mm (e.g., 9 kV / mm) to prevent the transmission of electrical power from the pin 38 of the MOSFET 34 (or other electronic component) to the cover 28, thereby preventing a short circuit.

[0024] The inner cover surface 40 has a sloped face 54 and a horizontal face 56. The horizontal face 56 extends along a horizontal direction H. The horizontal direction H is perpendicular to the vertical direction V. The sloped face 54 is at an oblique angle with respect to the horizontal face 56. The gap length 50 is defined along a length axis 58 from the pin 38 of the MOSFET 34 (or other electronic component) to the inner insulator surface 46 of the electrical insulator 44. The length axis 58 intersects the sloped face 54 at a right angle. The gap length 50 is parallel to the length axis 58. An angle Θ is defined from the vertical direction V to the length axis 58. The angle Θ is an oblique angle (e.g., 37 degrees).

[0025] The electrical insulator 44 electrically insulates the pin 38 of the MOSFET 34 (or other electronic component) with minimal changes without affecting the manufacturing process and cost. The electrical insulator 44 is partially or completely made of a material that is electrically insulating and has excellent dielectric strength at the areas in the SMCD 24 where short circuits are prone to occur. Manufacturing the SMCD 24 includes selectively machining the cover 28 (e.g., rectangular patches of different lengths and widths, orientation based on the location where electrical insulation is needed). Furthermore, manufacturing the SMCD 24 includes filling and / or coating the machined patches with the excellent electrical insulator 44. Manufacturing the SMCD 24 also includes achieving excellent adhesion (e.g., curing) between the electrical insulator 44 and the cover 28 that remains unchanged throughout the lifetime of the SMCD 24 subjected to harsh environmental, thermal, and mechanical conditions. As described above, the electrical insulator material can be ceramic, polymer, elastomer, and enamel. For example, PTFE can be used for the electrical insulator 44 due to its remarkable properties (i.e., excellent electrical insulation, durability, stability at extreme temperatures, chemical inertness, strong bonding with aluminum), cost, availability, and ease of use.

[0026] While the foregoing describes exemplary embodiments, it is not intended to describe all possible forms of the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, features of various embodiments can be combined to form further embodiments of the presently disclosed systems and methods that are not expressly described or illustrated. While various embodiments can be described as providing advantages or being more desirable or optimal than other embodiments or prior approaches, one of ordinary skill in the art will recognize that one or more features or characteristics can be substituted or removed and that the presently disclosed systems and methods can be altered to meet desired system attributes, depending on the specific application and implementation. These attributes can include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, suitability, weight, manufacturability, ease of assembly, and the like. Thus, embodiments described as being less desirable than other embodiments or prior approaches in one or more features are not outside the scope of the present disclosure and can be desirable for particular applications.

[0027] The drawings are in simplified form and are not drawn to precise scale. Directional terminology, such as top, bottom, left, right, upper, lower, above, below, inside, outside, rear, and front, is used for orientation only and is not intended to be limiting.

[0028] Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and can be carried out in various alternative forms. The drawings are not necessarily to scale; certain features can be exaggerated or minimized for purposes of clarity and precision in illustrating certain parts. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to employ the systems and methods of the present disclosure in variously different embodiments. As those skilled in the art will appreciate, the various features shown and described with reference to any one figure can be combined with features shown and described as part of one or more other figures to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments for typical applications. However, various combinations and modifications of features, consistent with the teachings of the present disclosure, can be desired for particular applications or implementations.

[0029] This description is merely illustrative in nature and is not intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be limited to such examples.

Claims

1. A fuel cell system, comprising: shell; Fuel cell, wherein the fuel cell is located within the housing; A stack monitoring device, mounted on the housing, wherein the stack monitoring device comprises: Sealing; A lid, connected to the housing to define a cavity, wherein the lid defines an inner cover surface, and the inner cover surface partially defines the cavity; An electronic component is disposed within the cavity between the housing and the lid, wherein the inner surface of the lid faces the electronic component, and the electronic component includes: Main body; and Pins, the pins protruding from the body; and An electrical insulator is attached to the inner cover surface, the electrical insulator defines an inner insulator surface facing the electronic component, and the pins are spaced apart from the electrical insulator to define an air gap.

2. The fuel cell system according to claim 1, wherein, The electronic component is a metal-oxide-semiconductor field-effect transistor (MOSFET), and the electrical insulator is disposed above the pin of the MOSFET.

3. The fuel cell system according to claim 1, wherein, The electrical insulator is made entirely of polytetrafluoroethylene (PTFE).

4. The fuel cell system according to claim 1, wherein, Both the lid and the cover are made entirely of metal, and the lid defines a recess at least partially defined by the inner cover surface, and the electrical insulator is completely disposed in the recess.

5. The fuel cell system according to claim 1, wherein, The surface of the inner insulator is flush with the surface of the inner cover.

6. The fuel cell system of claim 1, wherein the gas gap has a gap length defined from the pin to the surface of the inner insulator, and the gap length is greater than 3.0 mm.

7. The fuel cell system according to claim 6, wherein, The electrical insulator has an insulator thickness, and the insulator thickness is between 0.2 mm and 1 mm.

8. The fuel cell system according to claim 7, wherein, The electrical insulator has a dielectric strength, which is between 9 kV / mm and 280 kV / mm.

9. The fuel cell system according to claim 8, wherein, The electrical insulator is made entirely of ceramic.

10. The fuel cell system according to claim 8, wherein, The electrical insulator is made entirely of polymeric materials.

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