Fuel cell device

Abstract

To reduce electromagnetic noise radiated from a fuel cell device.SOLUTION: A fuel cell device 10 includes: a cell stack 12 in which fuel battery cells are stacked; a DC-DC converter 14 which boosts power generated in the cell stack 12; and a metal fuel cell case 16 which defines a cell stack chamber 20 in which the cell stack 12 is accommodated and a converter chamber 22 in which the DC-DC converter 14 is accommodated, the converter chamber being separated from the cell stack chamber 20. The cell stack 12 is wrapped by an electric insulation sheet 28 that electrically insulates between the cell stack 12 and the fuel cell case 16. The electric insulation sheet 28 has an electromagnetic wave absorption layer 40 on an outer surface or inside. Electromagnetic noise radiated from the cell stack 12 can be shielded by the electromagnetic wave absorption layer 40.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel cell device, and more particularly to reducing electromagnetic waves emitted from a fuel cell device. [Background technology]

[0002] The fuel cell device includes a cell stack in which fuel cells are stacked, and a fuel cell case that houses the cell stack. Furthermore, in order to reduce size and cost, a fuel cell device is also known in which electronic devices such as a converter and an inverter are housed in the fuel cell case together with the cell stack. The following Patent Document 1 shows a resin fuel cell stack case (50) having a conductive material (51) within its thickness. Examples of the conductive material (51) include aluminum filler or flake graphite filler contained in a base resin material (52), or an aluminum or flake graphite plate provided on the outer surface of the resin material (52) or sandwiched between the resin material (52). Note that the reference numbers in parentheses are those used in the following Patent Document 1, and are not related to the reference numbers used in the description of the embodiments of the present application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 046490 Summary of the Invention [Problem to be solved by the invention]

[0004] When a cell stack and electronic devices such as a converter are housed inside a metal fuel cell case, high-frequency (e.g., MHz band) electromagnetic waves and currents (hereinafter referred to as electromagnetic noise) generated by switching noise of the electronic devices are transmitted to the cell stack and then from the surface of the cell stack to the fuel cell case. The electromagnetic noise transmitted to the fuel cell case is then transmitted from the case surface to the surroundings.

[0005] The present invention aims to reduce electromagnetic noise emitted from a fuel cell device. [Means for solving the problem]

[0006] The fuel cell device according to the present invention includes a cell stack in which fuel cells are stacked, a converter that boosts the power generated in the cell stack, a metal fuel cell case that houses the cell stack and the converter, and an electrical insulation sheet that encases the cell stack and electrically insulates the cell stack from the fuel cell case. The fuel cell case defines a cell stack chamber that houses the cell stack and a converter chamber that houses the converter and is separated from the cell stack chamber. The electrical insulation sheet has an electromagnetic wave absorbing layer on its outer surface or inside that is arranged so as not to come into contact with the fuel cell case, and the electromagnetic wave absorbing layer has a thickness equal to or greater than the skin depth for the electromagnetic waves to be absorbed and is made of a ferromagnetic material. Effect of the Invention

[0007] By providing an electromagnetic wave absorbing layer on the electrical insulation sheet that encases the cell stack, it is possible to suppress electromagnetic noise radiated from the cell stack to the fuel cell case that houses the cell stack, thereby reducing the electromagnetic noise radiated from the fuel cell device. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view that illustrates a schematic configuration of a fuel cell device. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of an electrical insulating sheet. [Diagram 3] FIG. 4 is a cross-sectional view showing another example of the electrical insulating sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic cross section of a fuel cell device 10. The fuel cell device 10 includes a cell stack 12 in which fuel cells are stacked, a DC-DC converter 14 that boosts the power generated in the cell stack 12, and a fuel cell case 16 that houses the cell stack 12 and the DC-DC converter 14. The shape of the cell stack 12 is a substantially rectangular parallelepiped. The fuel cell case 16 has a partition wall 18 that divides the internal space into upper and lower halves. The space below the partition wall 18 of the fuel cell case 16 is a cell stack chamber 20 in which the cell stack 12 is disposed, and the space above the partition wall 18 is a converter chamber 22 in which the DC-DC converter 14 is disposed. The fuel cell case 16 including the partition wall 18 defines the cell stack chamber 20 that accommodates the cell stack 12, and also defines the converter chamber 22 that accommodates the DC-DC converter 14. The cell stack 12 and the DC-DC converter 14 are surrounded on six sides, top and bottom, left and right, front and rear, by a fuel cell case 16 including a partition wall 18. The fuel cell case 16 may be made of metal, for example, an aluminum alloy.

[0010] The cell stack 12 is supported by the fuel cell case 16 via support members 24, 26. The cell stack 12 is wrapped in an electrical insulating sheet 28 that electrically insulates the cell stack 12 from the fuel cell case 16. The electrical insulating sheet 28 is fixed to six side surfaces of the rectangular parallelepiped of the cell stack 12. For example, double-sided tape, adhesive, or the like can be used for fixing. The electrical insulating sheet 28 has an electrical insulating layer 30 formed of an electrically insulating organic material, such as resin, rubber, or the like. The electrical insulating layer 30 electrically insulates the cell stack 12 from the fuel cell case 16. The electrical insulating sheet 28 is disposed so as to leave a gap between the cell stack 12 and the fuel cell case 16, that is, in a non-contact state with the fuel cell case 16. In FIG. 1, the thickness of the electrical insulating sheet 28 and the distance between the sheet and the plate surface of the fuel cell case 16, including the partition wall 18, which the sheet faces, are drawn large and exaggerated. The electrical insulating sheet 28 will be described in detail later.

[0011] The DC-DC converter 14 includes a switching element 32. The fuel cell device 10 has an element cooler 34 that cools the switching element 32. The element cooler 34 is in contact with the switching element 32, and a cooling liquid flowing inside the element cooler 34 removes heat from the switching element 32 and cools the switching element 32. The cooling liquid circulates between the element cooler 34 and a heat sink (not shown) provided outside the fuel cell device 10, and dissipates heat generated by the switching element 32 to the outside.

[0012] Electromagnetic noise is generated by the switching operation of the switching element 32. This electromagnetic noise is transmitted to the cell stack 12 through the internal bus bar 36 that connects the switching element 32 and the cell stack 12. The electromagnetic noise is then radiated from the surface of the cell stack 12 to the plate surface of the fuel cell casing 16 that faces the cell stack 12. The electromagnetic noise then returns to the switching element 32 via the fuel cell casing 16 and the element cooler 34. This electromagnetic noise is radiated from the fuel cell casing 16 to the outside, or is transmitted to the outside via the output conductors 38 of the fuel cell device 10, etc.

[0013] The electrical insulation sheet 28 will now be described in detail. FIG. 2 shows an enlarged cross section of a portion of the electrical insulation sheet 28. The electrical insulation sheet 28 has an electromagnetic wave absorbing layer 40 to suppress the above-mentioned electromagnetic noise radiation. The electromagnetic wave absorbing layer 40 may be a ferromagnetic material such as ferrite, cobalt, or nickel, or may be based on one or more of these. The electromagnetic wave absorbing layer 40 is formed on the outer surface of the electrical insulation layer 30, i.e., the surface facing the fuel cell case 16, by a method such as coating, electrodeposition, or vapor deposition.

[0014] The electromagnetic wave absorbing layer 40 has a thickness equal to or greater than the skin depth. The skin depth d is defined by the following equation (1). d=√{1 / (π×f×μ×σ)} ···(1) f: frequency of the electromagnetic wave, μ: absolute permeability of the conductor, σ: conductivity The skin depth d represents the thickness of the conductor at which the attenuation of the electromagnetic waves passing through the conductor is about 8.7 dB. The electromagnetic noise band that is a problem in this fuel cell device 10 is in the MHz band, and it is empirically known that if an attenuation of 8.7 dB is obtained, there will be no problem with the influence on surrounding devices. Therefore, the thickness of the electromagnetic wave absorbing layer 40 is set to be equal to or greater than the skin depth for electromagnetic waves in the MHz band. The thicker the electromagnetic wave absorbing layer 40 is, the more material is used, and depending on the manufacturing method, the more time is required, so from these points of view, it is preferable that it is thinner. The upper limit of the thickness of the electromagnetic wave absorbing layer 40 may be set to 2 times or less of the skin depth, preferably 1.5 times or less, and more preferably 1.2 times or less.

[0015] It is possible to thin the electromagnetic wave absorbing layer 40 by using a ferromagnetic material for the electromagnetic wave absorbing layer 40. Ferromagnetic materials have high absolute magnetic permeability, and it is seen from formula (1) that the value of the skin depth d becomes small.

[0016] By providing the electromagnetic wave absorbing layer 40 on the outer surface of the electrical insulation sheet 28, it is possible to prevent foreign matter caused by the electromagnetic wave absorbing layer 40 from being mixed into the cell stack 12. Even if the electromagnetic wave absorbing layer 40 breaks into fine particles due to aging or the like and falls off from the electrical insulation sheet 28, it will not enter the cell stack 12 because it is on the outer surface. This makes it possible to prevent a decrease in the performance of the cell stack 12.

[0017] FIG. 3 is a diagram showing another example of the configuration of the electrical insulating sheet. The electrical insulating sheet 50 has a configuration in which an electromagnetic wave absorbing layer 56 is sandwiched between two electrical insulating layers 52, 54. The electrical insulating layers 52, 54 may be made of an electrically insulating organic material such as resin or rubber. The electromagnetic wave absorbing layer 56 may be made of a ferromagnetic material such as ferrite, nickel, or cobalt, and may be based on one or more of these. The electromagnetic wave absorbing layer 56 may be formed on one surface of the electrical insulating layers 52, 54 by a method such as coating, electrodeposition, or vapor deposition, and then the other electrical insulating layer may be superimposed to form the electrical insulating sheet 50. The thickness of the electromagnetic wave absorbing layer 56 is set to be equal to or greater than the skin depth for electromagnetic waves in the MHz band.

[0018] Since the electromagnetic wave absorbing layer 56 of the electrical insulating sheet 50 is present inside and not exposed, the amount of foreign matter generated can be significantly reduced compared to the aforementioned electrical insulating sheet 28, which has exposed electromagnetic wave absorbing layer 56. Also, unlike the aforementioned electrical insulating sheet 28, which required a gap between it and the fuel cell case 16, the electrical insulating sheet 50 can be fixed to the inner wall surface of the fuel cell case 16.

[0019] In still another embodiment of the electrical insulating sheet, the electromagnetic wave absorbing layers 40, 56 of the electrical insulating sheets 28, 50 described above may be formed by stacking a plurality of sheet-like electromagnetic wave absorbing sheets. [Explanation of symbols]

[0020] 10 fuel cell device, 12 cell stack, 14 DC-DC converter, 16 fuel cell case, 18 partition wall, 20 cell stack chamber, 22 converter chamber, 28, 50 electrical insulation sheet, 30, 52, 54 electrical insulation layer, 40, 56 electromagnetic wave absorbing layer.

Claims

[Claim 1] a cell stack in which fuel cells are stacked; a converter that boosts the power generated in the cell stack; a metal fuel cell case that defines a cell stack chamber that houses the cell stack and a converter chamber that houses the converter and is separated from the cell stack chamber; an electrical insulating sheet that wraps the cell stack and electrically insulates the cell stack from the fuel cell case; Including, the electrical insulation sheet has an electromagnetic wave absorbing layer disposed on an outer surface or inside thereof so as not to come into contact with the fuel cell case, the electromagnetic wave absorbing layer having a thickness equal to or greater than the skin depth of the electromagnetic waves to be absorbed, and formed of a ferromagnetic material; Fuel cell device.

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