US20160190609A1

US20160190609A1 - Applying a seal to a fuel cell component

Info

Publication number: US20160190609A1
Application number: US15/064,454
Authority: US
Inventors: Kristoffer Ridgeway; John F. Hoffman
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2010-05-12
Filing date: 2016-03-08
Publication date: 2016-06-30
Also published as: US20130052565A1; US9312547B2; DE112010005551B4; WO2011142750A1; DE112010005551T5

Abstract

An exemplary method of applying a seal to a fuel cell component includes providing a release layer on one side of a seal. The release layer has reinforcing fibers. Another side of the seal is placed against a selected portion of the fuel cell component. The seal, release layer and fuel cell component are heated. The release layer is then removed after the seal is secured to the fuel cell component.

Description

BACKGROUND

Fuel cells are useful for generating electric power. Typical fuel cell arrangements include a plurality of individual cells in a stack that is referred to as a cell stack assembly (CSA). There are various challenges associated with manufacturing and operating CSAs. For example, different fluids are introduced into to or removed from the CSA during fuel cell operation. It is necessary to maintain those fluids within specified areas in the CSA.
Typical CSAs include a significant number of components. Each individual cell includes multiple layers. There are interfaces between the different layers of each cell and between adjacent cells. Some of those interfaces require a seal to maintain the fluids within the CSA appropriately to achieve desired fuel cell operation.
The various materials that are used for fuel cell components make it difficult to achieve an adequate seal.

BRIEF SUMMARY

An exemplary method of applying a seal to a fuel cell component includes providing a release layer on one side of a seal. The release layer has reinforcing fibers. Another side of the seal is placed against a selected portion of the fuel cell component. The seal, release layer and fuel cell component are heated. The release layer is then removed after the seal is secured to the fuel cell component.
The reinforcing fibers in the release layer have a coefficient of thermal expansion that is very close to the coefficient of thermal expansion of the material used for the fuel cell component. This effectively prevents the seal material from expanding beyond a desired location during the heating portion of the process for securing the seal to the fuel cell component.
An exemplary fuel cell component includes a plate. A seal is received against a selected portion of the plate. A fiber reinforced release layer is on a side of the seal that faces away from the plate.
The various features and advantages of a disclosed example will be apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 diagrammatically illustrates an exemplary fuel cell component designed according to an embodiment of this invention.

FIG. 2 is a cross-sectional illustration taken along the lines 2-2 in FIG. 1.

FIG. 3 schematically illustrates an exemplary procedure for assembling a fuel cell component.

FIG. 4 schematically illustrates another portion of the exemplary procedure.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary fuel cell component 20 that comprises a plate 22 and a seal 24. In one example, the fuel cell component 20 comprises a bipolar plate. In one example the plates 22 comprises carbon. The seal 24 comprises an elastomer. One example seal comprises rubber.
As shown in FIG. 2, the seal 24 is at least partially received within a recess or groove 26 that is formed in the plate 22. One challenge associated with providing the plate 22 with the seal 24 is maintaining the material of the seal 24 within the selected area on the plate 22 during the process of securing the seal in place. The illustrated example includes a release layer 30 that is reinforced with fibers. The release layer 30 facilitates removing the fuel cell component from a fixture used for securing the seal 24 in place. The release layer in this example also facilitates maintaining the material of the seal 24 in the desired location relative to the plate 22.
FIG. 3 schematically illustrates an arrangement for securing the seal 24 in place. In this example, a fixture or mold 32 has one portion 34 that includes a groove 36 that is configured to at least partially receive a portion of the seal 24. In this example, the release layer 30 is received against the groove 36. Another portion 38 of the fixture 32 supports the plate 22 during the assembly process.
The example of FIG. 3 includes a thermoplastic bond film 40 on a side of the seal 24 that faces opposite the side on which the release layer 30 is positioned. When the various portions of the fuel cell component 20 are appropriately positioned within the fixture 32, heat and pressure are applied as schematically shown at 42. The heat causes the thermoplastic bond film 40 to melt to thereby secure the seal 24 to the plate 22.
During the heating portion of the process the materials tend to expand. A significant challenge associated with providing an elastomer seal on a carbon plate, for example, is that the coefficient of thermal expansion of carbon is much less than that of an elastomer such as rubber. The release film 30 includes reinforcing fibers 50 (schematically shown in FIG. 4) to maintain the material of the seal 24 in the desired location during the process of securing the seal 24 to the plate 22. The reinforcing fibers 50 have a coefficient of thermal expansion that is very close to the coefficient of thermal expansion of the material of the plate 22 (e.g., carbon). In one example, the coefficient of thermal expansion of the reinforcing fibers 50 approximately equals that of the material of the plate 22. Having reinforcing fibers within the release layer 30 with a coefficient of thermal expansion similar to that of the material of the plate 22 prevents the seal material from expanding in a manner where the seal would leave the desired area of the plate 22.
In one example, the reinforcing fibers 50 comprise carbon. The carbon fibers 50 and the carbon material of the plate 22 in such an example have the same coefficient of thermal expansion. Another example includes fibers 50 that comprise glass, which has a coefficient of thermal expansion similar to that of carbon. For example, glass typically has a linear coefficient of thermal expansion of 8.5 and the coefficient of thermal expansion of carbon graphite may be 0.5 and up to 6.5. For purposes of this description 8.5 and 0.5 are considered similar especially when compared to that of an elastomer seal material, which may be approximately 75. Any reinforcing fibers that have a coefficient of thermal expansion that is close to that of the material used for the plate 22 will effectively compensate for the difference in coefficient of thermal expansion of the seal material and the plate material.
The arrangement of the fibers 50 holds the material of the seal 24 from expanding throughout the path of the seal 24 so that it remains in the correct position on the plate 22. Some examples include fibers 50 arranged in a raised matrix or grid pattern. Other examples include a weave of the fibers 50. The arrangement of the fibers 50 is operative to constrain the material of the seal material during the bonding process.
Another feature of the release layer 30 is that it protects the seal 24 from contamination that may exist on the fixture 32.
After the plate 22 and the seal 24 have cooled, the seal 24 is secured in place. The release layer 30 can then be removed as schematically shown in FIG. 4. The seal 24 and plate 22 are then ready for the fuel cell component 20 to be incorporated into a CSA.
In one example, the release layer 30 comprises a polymer film including the reinforcing fibers 50. One example includes using polytetraflouroethylene and glass reinforcing fibers for the release layer 30. Another example includes a low surface energy plastic as the polymer with an appropriate reinforcing fiber material selected for its coefficient of thermal expansion to correspond to that of the material used for the plate 22. In one example, the fibers 50 are generally continuous along the release layer 30. The orientation and length of the fibers 50 provide sufficient control over expansion of the material of the seal 24 during the bonding process. The illustrated example allows for bonding an elastomer seal with a high coefficient of thermal expansion to a fuel cell component such as a bipolar plate that has a low coefficient of thermal expansion. In this example, the seal is effectively trapped between materials having a similar coefficient of thermal expansion, which works against the tendency the seal material would have to expand in an undesired manner. The illustrated example provides a reliable assembly process that results in a seal having desired characteristics and placement relative to the fuel cell component.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.

Claims

1. A fuel cell component, comprising:

a plate;

a seal positioned against the plate; and

a release layer including reinforcing fibers, the release layer positioned against the seal, the seal encapsulated between the plate and the release layer.

2. The fuel cell component of claim 1 wherein the seal includes an elastomer and the release layer includes a polymer.

3. The fuel cell component of claim 2 wherein the elastomer includes rubber, the polymer includes polytetrafluoroethylene, the reinforcing fibers include glass, and the plate includes carbon.

4. The fuel cell component of claim 2 wherein the elastomer includes rubber, the polymer includes polytetrafluoroethylene, the reinforcing fibers include carbon, and the plate includes carbon.

5. The fuel cell component of claim 1 wherein the plate has a first coefficient of thermal expansion and the reinforcing fibers have a second coefficient of thermal expansion that is approximately equal to the first coefficient of thermal expansion.

6. The fuel cell component of claim 1 wherein the plate has a first coefficient of thermal expansion and the reinforcing fibers have a second coefficient of thermal expansion that corresponds to the first coefficient of thermal expansion.

7. The fuel cell component of claim 1 wherein the plate has a first coefficient of thermal expansion, the reinforcing fibers have a second coefficient of thermal expansion that is approximately equal to the first coefficient of thermal expansion, and the seal has a third coefficient of thermal expansion that is greater than the first and second coefficients of thermal expansion.

8. The fuel cell component of claim 1 wherein the plate includes a groove and the seal is positioned at least partially within the groove.

9. The fuel cell component of claim 1, further comprising a thermoplastic bond film positioned between the seal and the plate.

10. The fuel cell component of claim 1 wherein the seal includes a looped seal that extends around a peripheral portion of a surface of the plate.

11. The fuel cell component of claim 1 wherein the release layer includes fibers arranged in a raised grid pattern.

12. The fuel cell component of claim 1 wherein the release layer includes weaved fibers.

13. The fuel cell component of claim 1 wherein the release layer includes fibers that are continuous along a length of the release layer.

14. A system, comprising:

a first mold portion having a first opening configured to receive a fuel cell plate, the fuel cell plate having a groove;

a second mold portion having a second opening aligned with the groove of the fuel cell plate, the second opening being sized and shaped to provide a release layer that covers a seal in the grove of the fuel cell plate, the second opening being wider than the groove.

15. The system of claim 14 wherein at least a portion of the seal is above the groove.

16. The system of claim 15 wherein the release layer includes reinforcing fibers and the first mold portion and the second mold portion are configured to apply heat and pressure to the release layer.

17. The system of claim 16 wherein the release layer is in contact with a top surface of the fuel cell plate and with top and side surfaces of the seal.

18. A system, comprising:

a fuel cell plate;

a seal positioned against the fuel cell plate; and

a fiber-reinforced release layer positioned against the seal, the fiber-reinforced release layer in contact with top and side surfaces of the seal and in contact with a surface of the fuel cell plate.

19. The system of claim 18 wherein the fuel cell plate includes a groove and the seal is positioned at least partially within the groove.

20. The system of claim 18 wherein the fiber-reinforced release layer is in direct contact with the top and side surfaces of the seal and in direct contact with the surface of the fuel cell plate.