The present invention relates to a fuel cell usable as electric sources and electric generators for outdoor, pleasure trip, household, business machines, or the like, and more particular, to an airbreathing fuel cell capable of removing moisture generated in a pollution-free solid polymer type fuel cell.
Among fuel cells, solid polymer electrolyte fuel cells with hydrogen as a main fuel have been given attention and developed because of low working temperature and high power density. Examples of such fuel cells are described in U.S. Pat. No. 5,595,834 or Japanese Patent Application No. 2001-66109 filed by the applicant of the present application.
As an example of such fuel cells, the inventors of the present application have proposed an airbreathing fuel cell, in which single cells 10 are stacked as shown in FIG. 3. Concretely, the airbreathing fuel cell comprises, as shown in FIG. 8, a fuel electrode 13a provided on an outer periphery thereof with an outer seal 16, an oxygen electrode 13b, an inside of which is sealed by an inner seal 22, and an oxygen passage plate 18 provided adjacent to the oxygen electrode 13b, the fuel electrode, and the oxygen electrode and the oxygen passage plate being provided on both sides of a polymer electrolyte membrane 12. Separator plates 34 arranged on both sides of the fuel electrode 13a and the oxygen passage plate 18 make these elements unitary to form a single cell 10, and a plurality of such single cells 10 are stacked together. In addition, the separator plates 34 are provided with terminals, through which electricity generated is taken out, and serve as collecting plates. Further, a fuel distribution manifold 32 communicated to the fuel electrodes 13a and composed of a sleeve of hydrophilic synthetic fiber yarns is provided to extend through central holes of the single cells 10, end plates 24 are further provided on both ends of a tie bolt 26, which extends centrally through the sleeve, to interpose end gaskets 28 between the end plates 24 and the separator plates 34, and one nut 40 having fuel flow passages 44 and the other nut 50 having a breeder valve 52 interpose O-rings 36 between them and the end plates 24 to clamp and fix the single cells integrally. Since such fuel cell can be made small in size and lightweight, it is suited to a fuel cell of low power.
Also, such a solid polymer electrolyte fuel cell is configured such that a fuel is fed from a center of the one nut 40 to be distributed to the fuel electrodes 13a through the hydrophilic sleeve of the fuel distribution manifold 32.
Thus, with such conventional solid polymer electrolyte fuel cell, moisture is generated in chemical reaction at the time of electrical power generation and discharged to the atmosphere outside and around the respective cells at the initial stage, thus affording supplying a fuel and generating a high electric current. However, with the lapse of time, the generated moisture collects in a portion downstream of the fuel distribution manifold in a fuel inflowing direction, so that a fuel cannot be adequately supplied to the fuel electrodes arranged in a downstream area and the generated electric current will be rapidly decreased since it is generally dominated by electrical power generation in the fuel electrodes.
Also, with solid polymer electrolyte fuel cells, moisture having collected in a fuel distribution manifold is removed by opening a breeder valve 52 provided on a nut 50. Labor for such removal, or provision of a device therefor results in addition of articles of excess configuration to decrease a size of a cell part, which gives rise to a need of taking account of an external shape of the device and cannot be simply coped with in terms of design.