JP6445391B2 - Fuel cell stack - Google Patents

Description

  The present invention includes a power generation cell having an electrolyte / electrode structure in which electrodes are arranged on both sides of an electrolyte and a separator, and a terminal plate on both sides in a stacking direction of the stacked body in which a plurality of the power generation cells are stacked. The present invention relates to a fuel cell stack in which an insulating member and an end plate are disposed.

  For example, a solid polymer fuel cell employs a solid polymer electrolyte membrane made of a polymer ion exchange membrane. This fuel cell comprises an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode each having an electrode catalyst (electrode catalyst layer) and porous carbon (gas diffusion layer) are disposed on both sides of a solid polymer electrolyte membrane ( MEA). The electrolyte membrane / electrode structure constitutes a power generation cell by being sandwiched between separators (bipolar plates).

  In general, a fuel cell stack is configured by including a stack in which a predetermined number of power generation cells are stacked, and terminal plates, insulating plates, and end plates are disposed on both sides of the stack in the stacking direction. This fuel cell stack is used as, for example, an in-vehicle fuel cell stack mounted on a fuel cell electric vehicle.

  In the fuel cell stack, there is a power generation cell in which a temperature drop is likely to be caused by heat radiation to the outside as compared with other power generation cells. For example, a power generation cell (hereinafter also referred to as an end power generation cell) arranged at the end in the stacking direction has a large amount of heat released from a terminal plate, an end plate, etc. adjacent to the power generation cell, and the above temperature decrease is remarkable. It has become.

  In particular, in a low temperature environment, the amount of heat release increases, and the power generation performance on the low temperature side may deteriorate. In addition, when the in-plane of the end power generation cell is dewed by heat dissipation, a decrease in power generation performance due to the generation of condensed water is caused, and there is a concern about a decrease in stack durability such as film deterioration.

  Therefore, for example, a fuel cell stack disclosed in Patent Document 1 is known. The fuel cell stack includes a stacked body in which power generation cells are stacked, and terminal plates, insulating members, and end plates are disposed on both sides in the stacking direction of the stacked body. At least one of the insulating members is provided with a recess in which an end on the laminated body side is opened, and a heat insulating member and a terminal plate are accommodated in the recess. And the heat insulation member is laminated | stacked between the terminal plate and the laminated body.

  Therefore, in Patent Document 1, it is possible to reliably prevent the temperature drop of the end cell arranged at the end of the laminated body with a simple configuration and maintain good power generation performance.

Japanese Patent No. 5608713

  The present invention has been made in connection with this type of technology, and can suppress heat dissipation from the end power generation cells as much as possible, and can reliably maintain desired power generation performance. An object is to provide a battery stack.

  The fuel cell stack according to the present invention includes a power generation cell having an electrolyte / electrode structure in which electrodes are disposed on both sides of an electrolyte, and a separator. A terminal plate, an insulating member, and an end plate are disposed on both sides in the stacking direction of the stacked body in which a plurality of power generation cells are stacked.

  In the fuel cell stack, a conductive plate is disposed between the insulating member and the terminal plate. A cooling medium passage is formed between the conductive plate and the insulating member to distribute the cooling medium along the plate surface direction of the conductive plate.

  Further, in the fuel cell stack, it is preferable that a cooling medium flow path for flowing the cooling medium along the electrode surface direction is formed between the power generation cells, and the cooling medium path communicates with the cooling medium flow path. .

  Further, in the fuel cell stack, it is preferable that the insulating member is formed with a recess for accommodating the conductive plate and the terminal plate, and the cooling medium passage is formed on the bottom surface of the insulating member that forms the recess. .

  According to the present invention, a cooling medium passage is formed between the conductive plate and the insulating member for circulating the cooling medium along the plate surface direction of the conductive plate. For this reason, the heat radiation from the end power generation cells arranged at the end of the laminate can be suppressed as much as possible, and the desired power generation performance can be reliably maintained.

  In addition, a conductive plate is provided separately from the terminal plate, and a cooling medium circulates along the plate surface of the conductive plate. Therefore, the terminal plate does not always come into contact with the cooling medium, ion elution can be reliably suppressed, and the durability of the terminal plate can be easily improved.

1 is an exploded schematic perspective view of a fuel cell stack according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the fuel cell stack taken along line II-II in FIG. 1. It is a disassembled perspective explanatory drawing of the electric power generation cell which comprises the said fuel cell stack. It is front explanatory drawing of one insulating member which comprises the said fuel cell stack. It is front explanatory drawing of the other insulating member which comprises the said fuel cell stack. It is a perspective explanatory view of the end plate which constitutes the fuel cell stack.

  As shown in FIG. 1, a fuel cell stack 10 according to an embodiment of the present invention includes a stacked body 12M in which a plurality of power generation cells 12 are stacked in a horizontal direction (arrow A direction) or a vertical direction (arrow C direction). Prepare.

  A terminal plate 14a, a conductive plate 16a, an insulating member 18a, and an end plate 20a are sequentially arranged at one end in the stacking direction (arrow A direction) of the stacked body 12M. At the other end in the stacking direction of the stacked body 12M, a terminal plate 14b, a conductive plate 16b, an insulating member 18b, and an end plate 20b are sequentially disposed outward (see FIGS. 1 and 2).

  The fuel cell stack 10 is integrally held by, for example, a box-like casing (not shown) including end plates 20a and 20b configured in a rectangular shape as end plates. The fuel cell stack 10 may be integrally clamped and held by a plurality of tie rods (not shown) extending in the direction of arrow A, for example.

  As shown in FIGS. 2 and 3, the power generation cell 12 includes a first metal separator 22, a first electrolyte membrane / electrode structure (electrolyte / electrode structure) (MEA) 24a, a second metal separator 26, and a second electrolyte. A membrane / electrode structure (MEA) 24b and a third metal separator 28 are provided. The 1st metal separator 22, the 2nd metal separator 26, and the 3rd metal separator 28 are formed by forming a cross section of a vertically long metal plate such as a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, etc. into irregularities, for example. However, a carbon separator may be used. The power generation cell may be configured by sandwiching the MEA between the first separator and the second separator.

  As shown in FIG. 2, the first electrolyte membrane / electrode structure 24a and the second electrolyte membrane / electrode structure 24b include, for example, a solid polymer electrolyte membrane 30 in which a perfluorosulfonic acid thin film is impregnated with water. . The solid polymer electrolyte membrane 30 is sandwiched between an anode electrode 32 and a cathode electrode 34. The anode electrode 32 constitutes a step MEA having a smaller planar dimension than the cathode electrode 34, but on the contrary, it can have a larger planar dimension than the cathode electrode 34.

  The anode electrode 32 and the cathode electrode 34 are obtained by uniformly applying a gas diffusion layer (not shown) made of carbon paper or the like and porous carbon particles carrying a platinum alloy on the surface thereof to the surface of the gas diffusion layer. And an electrode catalyst layer (not shown) to be formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 30.

  As shown in FIG. 3, the oxidant gas inlet communication hole 36a and the fuel gas inlet are communicated with each other in the direction of arrow A, which is the stacking direction, at the upper edge of the long side direction (arrow C direction) of the power generation cell 12. A communication hole 38a is provided. The oxidant gas inlet communication hole 36a supplies an oxidant gas, for example, an oxygen-containing gas. The fuel gas inlet communication hole 38a supplies a fuel gas, for example, a hydrogen-containing gas.

  The lower end edge of the power generation cell 12 in the long side direction (arrow C direction) communicates with each other in the direction of arrow A, and the fuel gas outlet communication hole 38b for discharging the fuel gas and the oxidant gas outlet for discharging the oxidant gas. A communication hole 36b is provided. A pair of cooling medium inlet communication holes 40a that communicate with each other in the direction of arrow A and supply a cooling medium are provided on the upper side of both edge portions in the short side direction (arrow B direction) of the power generation cell 12. A pair of cooling medium outlet communication holes 40 b that communicate with each other in the direction of arrow A and discharge the cooling medium are provided on the lower side of both edge portions in the short side direction of the power generation cell 12. The fuel gas inlet communication hole 38a and the fuel gas outlet communication hole 38b may be interchanged.

  A surface 22a of the first metal separator 22 facing the first electrolyte membrane / electrode structure 24a is formed with a first fuel gas flow path 42 that connects the fuel gas inlet communication hole 38a and the fuel gas outlet communication hole 38b. .

  The fuel gas inlet communication hole 38a and the first fuel gas flow path 42 communicate with each other via a plurality of inlet connection flow paths 43a, while the fuel gas outlet communication hole 38b and the first fuel gas flow path 42 have a plurality of numbers. Communicated via the outlet connection flow path 43b. The inlet connection channel 43a is covered with a lid 45a, and the outlet connection channel 43b is covered with a lid 45b. A part of the cooling medium flow path 44 that connects the pair of cooling medium inlet communication holes 40 a and the pair of cooling medium outlet communication holes 40 b is formed on the surface 22 b of the first metal separator 22.

  On the surface 26a of the second metal separator 26 facing the first electrolyte membrane / electrode structure 24a, there is a first oxidant gas channel 46 that communicates the oxidant gas inlet communication hole 36a and the oxidant gas outlet communication hole 36b. It is formed.

  A second fuel gas channel 48 that connects the fuel gas inlet communication hole 38a and the fuel gas outlet communication hole 38b is formed on the surface 26b of the second metal separator 26 facing the second electrolyte membrane / electrode structure 24b. . The fuel gas inlet communication hole 38a and the second fuel gas flow path 48 communicate with each other via a plurality of inlet connection flow paths 47a, while the fuel gas outlet communication hole 38b and the second fuel gas flow path 48 include a plurality of Through the outlet connection channel 47b. The inlet connection channel 47a is covered with a lid 49a, and the outlet connection channel 47b is covered with a lid 49b.

  A second oxidant gas flow path 50 communicating the oxidant gas inlet communication hole 36a and the oxidant gas outlet communication hole 36b is formed on the surface 28a of the third metal separator 28 facing the second electrolyte membrane / electrode structure 24b. It is formed. A part of the cooling medium flow path 44 is formed on the surface 28 b of the third metal separator 28.

  A first seal member 52 is integrally formed on the surfaces 22 a and 22 b of the first metal separator 22 around the outer peripheral edge of the first metal separator 22. A second seal member 54 is integrally formed on the surfaces 26 a and 26 b of the second metal separator 26 around the outer peripheral edge of the second metal separator 26. A third seal member 56 is integrally formed on the surfaces 28 a and 28 b of the third metal separator 28 around the outer peripheral edge of the third metal separator 28.

  Examples of the first seal member 52, the second seal member 54, and the third seal member 56 include EPDM, NBR, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroprene, or acrylic rubber. A sealing member having elasticity such as a sealing material, a cushioning material, or a packing material is used.

  As shown in FIG. 1, the terminal plates 14a and 14b have a rectangular shape and are set to have outer diameters that can be accommodated in recesses 62a and 62b of insulating members 18a and 18b described later. Terminal portions 58a and 58b extending outward in the stacking direction are provided at positions separated from the in-plane center of the terminal plates 14a and 14b (or in-plane center).

  The conductive plates 16a and 16b are formed of, for example, a porous or dense carbon plate, and are set to a rectangle having substantially the same outer diameter as the terminal plates 14a and 14b. Hole portions 60a and 60b into which the terminal portions 58a and 58b are inserted are formed at positions separated from the in-plane center of the conductive plates 16a and 16b (or the in-plane center).

  The insulating members 18a and 18b are made of an insulating material such as polycarbonate (PC) or phenol resin. On the surface of the insulating member 18a facing the conductive plate 16a, a rectangular recess 62a is provided at the center. A hole 64a into which the terminal portion 58a of the terminal plate 14a is inserted communicates with the recess 62a. The insulating member 18a is formed with an oxidant gas inlet communication hole 36a, an oxidant gas outlet communication hole 36b, a fuel gas inlet communication hole 38a, and a fuel gas outlet communication hole 38b located outside the recess 62a.

  As shown in FIG. 4, a cooling medium passage 66a is formed on the bottom surface 62af that forms the recess 62a of the insulating member 18a. In the cooling medium passage 66a, for example, one (or two or more) flow grooves form a serpentine flow path and extend vertically, and the cooling medium supply port 68a communicates with the upper end portion. The cooling medium discharge port 70a communicates with the lower end portion. In the recess 62a, a seal member 71a is disposed around the cooling medium passage 66a.

  The cooling medium supply port 68a is disposed between the oxidant gas inlet communication hole 36a and the fuel gas inlet communication hole 38a, extends to substantially the center in the thickness direction of the insulating member 18a, and then bends upward by 90 °. It extends and is opened to the upper surface of the insulating member 18a (see FIG. 1). The cooling medium discharge port 70a is disposed between the oxidant gas outlet communication hole 36b and the fuel gas outlet communication hole 38b, extends to substantially the center in the thickness direction of the insulating member 18a, and then bends by 90 ° to the lower side. It extends and opens to the lower surface of the insulating member 18a.

  On the surface of the insulating member 18b facing the conductive plate 16b, a rectangular recess 62b is provided at the center. A hole 64b into which the terminal portion 58b of the terminal plate 14b is inserted communicates with the recess 62b. As shown in FIGS. 1 and 5, the insulating member 18b is formed with a cooling medium inlet communication hole 40a and a cooling medium outlet communication hole 40b located outside the recess 62b. In the recess 62b, a seal member 71b is disposed around the cooling medium passage 66b.

  As shown in FIG. 5, a cooling medium passage 66b is formed on the bottom surface 62bf that forms the recess 62b of the insulating member 18b. In the cooling medium passage 66b, for example, one (or two or more) flow grooves form a serpentine flow path and extend vertically, and a cooling medium supply port 68b communicates with the upper end portion. The cooling medium discharge port 70b communicates with the lower end portion.

  The cooling medium supply port 68a is disposed in the vicinity of one cooling medium inlet communication hole 40a side, extends to substantially the center in the thickness direction of the insulating member 18b, then bends by 90 ° and extends upward, The insulating member 18b is opened to the upper surface portion. The cooling medium discharge port 70b is disposed close to the other cooling medium outlet communication hole 40b side (a position diagonal to the one cooling medium inlet communication hole 40a). The cooling medium discharge port 70b extends to substantially the center in the thickness direction of the insulating member 18a, then bends by 90 ° and extends downward, and is opened to the lower surface portion of the insulating member 18b.

  As shown in FIG. 1, a conductive plate 16a is accommodated in the recess 62a of the insulating member 18a, and the conductive plate 16a covers the open surface of the cooling medium passage 66a. A conductive plate 16b is accommodated in the recess 62b of the insulating member 18b, and the conductive plate 16b functions as a seal member for sealing the cooling medium passage 66b.

  An oxidant gas inlet manifold 72a, an oxidant gas outlet manifold 72b, a fuel gas inlet manifold 74a, and a fuel gas outlet manifold 74b are formed in the end plate 20a. The oxidant gas inlet manifold 72a communicates with the oxidant gas inlet communication hole 36a, and the oxidant gas outlet manifold 72b communicates with the oxidant gas outlet communication hole 36b. The fuel gas inlet manifold 74a communicates with the fuel gas inlet communication hole 38a, and the fuel gas outlet manifold 74b communicates with the fuel gas outlet communication hole 38b.

  As shown in FIGS. 1 and 6, the end plate 20b includes a cooling medium inlet manifold 76a communicating with the pair of cooling medium inlet communication holes 40a and a cooling medium outlet manifold 76b communicating with the pair of cooling medium outlet communication holes 40b. And are provided. A cooling medium supply port 78a is formed in the cooling medium inlet manifold 76a, and a cooling medium discharge port 78b is formed in the cooling medium outlet manifold 76b. The cooling medium supply port 78a and the cooling medium discharge port 78b are preferably arranged at diagonal positions.

  One end of a cooling medium supply pipe 80a is connected to the cooling medium inlet manifold 76a. The other end of the cooling medium supply pipe 80a is connected to the cooling medium supply port 68a of the insulating member 18a and the cooling medium supply port 68b of the insulating member 18b. The other end of the cooling medium supply pipe 80a may be divided into two parts, or two cooling medium supply pipes 80a may be used. The cooling medium supply port 68a and the cooling medium supply port 68b may be connected by a pipe provided inside the insulating member 18b and the end plate 20b without using the cooling medium supply pipe 80a which is an external pipe. Further, the cooling medium discharge port 70a and the cooling medium discharge port 70b described below may be configured similarly to the cooling medium supply port 68a and the cooling medium supply port 68b.

  One end of a cooling medium discharge pipe 80b is connected to the cooling medium outlet manifold 76b. The other end of the cooling medium discharge pipe 80b is connected to the cooling medium discharge port 70a of the insulating member 18a and the cooling medium discharge port 70b of the insulating member 18b. The other end of the cooling medium discharge pipe 80b may be divided into two parts, or two cooling medium discharge pipes 80b may be used. The cooling medium passages 66a and 66b communicate with the respective cooling medium flow paths 44 via the cooling medium inlet manifold 76a and the cooling medium outlet manifold 76b.

  As shown in FIGS. 1 and 2, the conductive plate 16b, the terminal plate 14b, and the conductive heat insulating member 82 are accommodated in the recess 62b of the insulating member 18b. The heat insulating member 82 includes, for example, at least a first heat insulating member 84 and a second heat insulating member 86, which are made of different materials, and the first heat insulating member 84 and the second heat insulating member 86 are stacked in this order from the terminal plate 14b side. . The first heat insulating member 84 is made of, for example, a corrugated metal plate, while the second heat insulating member 86 is made of, for example, a carbon plate. Similarly, a heat insulating member 82 is disposed in the recess 62a of the insulating member 18a.

  The heat insulating member 82 may be configured by, for example, laminating two types (or three sets) of two corrugated metal plates alternately. The heat insulating member 82 may be any member that retains pores and has electrical conductivity, and is a foam metal, honeycomb-shaped metal (honeycomb member), or porous carbon (for example, carbon paper) having electrical conductivity. You may comprise either. One heat insulating member 82 may be used, or a plurality of heat insulating members 82 may be stacked.

  The operation of the fuel cell stack 10 configured as described above will be described below.

  First, as shown in FIG. 1, an oxidant gas such as an oxygen-containing gas is supplied from the oxidant gas inlet manifold 72a of the end plate 20a to the oxidant gas inlet communication hole 36a. Fuel gas such as hydrogen-containing gas is supplied from the fuel gas inlet manifold 74a of the end plate 20a to the fuel gas inlet communication hole 38a. On the other hand, as shown in FIG. 6, a cooling medium such as pure water, ethylene glycol, or oil is supplied from the cooling medium inlet manifold 76a of the end plate 20b to the pair of cooling medium inlet communication holes 40a.

  As shown in FIG. 3, the oxidant gas flows from the oxidant gas inlet communication hole 36 a to the first oxidant gas channel 46 of the second metal separator 26 and the second oxidant gas channel 50 of the third metal separator 28. be introduced. The oxidant gas moves in the direction of arrow C and is supplied to the cathode electrodes 34 of the first electrolyte membrane / electrode structure 24a and the second electrolyte membrane / electrode structure 24b.

  On the other hand, the fuel gas is introduced into the first fuel gas channel 42 of the first metal separator 22 and the second fuel gas channel 48 of the second metal separator 26 from the fuel gas inlet communication hole 38a. The fuel gas moves in the direction of arrow C along the first fuel gas flow path 42 and the second fuel gas flow path 48, and each of the first electrolyte membrane / electrode structure 24a and the second electrolyte membrane / electrode structure 24b. It is supplied to the anode electrode 32.

  Therefore, in the first electrolyte membrane / electrode structure 24a and the second electrolyte membrane / electrode structure 24b, the oxidant gas supplied to each cathode electrode 34 and the fuel gas supplied to each anode electrode 32 are electrodes. Electricity is generated by being consumed by an electrochemical reaction in the catalyst layer.

  Next, the oxidant gas consumed by being supplied to the cathode electrode 34 is discharged in the direction of arrow A along the oxidant gas outlet communication hole 36b. Similarly, the fuel gas consumed by being supplied to the anode electrode 32 is discharged in the direction of arrow A along the fuel gas outlet communication hole 38b.

  Further, as shown in FIG. 3, the cooling medium supplied to each cooling medium inlet communication hole 40a is introduced into the cooling medium flow path 44 between the first metal separator 22 and the third metal separator 28 adjacent to each other. After that, first, it circulates in the direction of arrow B so as to be close to each other. The cooling medium flows in the direction of the arrow C (the separator long side direction), cools the first electrolyte membrane / electrode structure 24a and the second electrolyte membrane / electrode structure 24b, and then separates them from each other in the direction of the arrow B And is discharged from each cooling medium outlet communication hole 40b.

  In this case, in this embodiment, as shown in FIGS. 1, 2, and 5, a cooling medium is provided between the conductive plate 16b and the insulating member 18b along the plate surface direction of the conductive plate 16b. A cooling medium passage 66b to be circulated is formed. Therefore, the cooling medium supplied to the cooling medium inlet manifold 76a flows through the cooling medium supply pipe 80a and is supplied to the cooling medium supply port 68b of the insulating member 18b.

  As shown in FIG. 5, the cooling medium supplied to the cooling medium supply port 68b is introduced into the cooling medium passage 66b formed in the bottom surface 62bf of the recess 62b of the insulating member 18b. Then, after the cooling medium flows along the cooling medium passage 66b, that is, along the serpentine flow path, the cooling medium is discharged to the cooling medium discharge port 70b. The cooling medium discharged to the cooling medium discharge port 70b flows through the cooling medium discharge pipe 80b and is discharged to the cooling medium outlet manifold 76b (see FIGS. 1 and 6).

Therefore, in this embodiment, the heat radiation from the _end power generation cell 12 _end disposed at the end of the stacked body 12M can be suppressed as much as possible, and the desired power generation performance can be reliably maintained. (See FIG. 2).

  In addition, the conductive plate 16b is provided separately from the terminal plate 14b, and the cooling medium flows along the plate surface of the conductive plate 16b. As a result, the terminal plate 14b does not always come into contact with the cooling medium, and ion elution can be reliably suppressed, and the durability of the terminal plate 14b can be easily improved.

  Further, a cooling medium passage 66a is provided on the terminal plate 14a side, and the same effect as the cooling medium passage 66b on the terminal plate 14b side can be obtained. Note that at least one of the cooling medium passages 66a and 66b may be provided as necessary.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 12 ... Power generation cell 12 _end ... End part power generation cell 12M ... Laminated body 14a, 14b ... Terminal plate 16a, 16b ... Conductive plate 18a, 18b ... Insulation member 20a, 20b ... End plate 22, 26, 28 ... Metal separators 24a, 24b ... electrolyte membrane / electrode structure 30 ... solid polymer electrolyte membrane 32 ... anode electrode 34 ... cathode electrode 36a ... oxidant gas inlet communication hole 36b ... oxidant gas outlet communication hole 38a ... fuel gas inlet communication Hole 38b ... Fuel gas outlet communication hole 40a ... Cooling medium inlet communication hole 40b ... Cooling medium outlet communication hole 42, 48 ... Fuel gas flow path 44 ... Cooling medium flow path 46, 50 ... Oxidant gas flow path 52, 54, 56 ... Seal members 62a and 62b ... Recesses 66a and 66b ... Cooling medium passages 68a and 68b ... Cooling medium supply port 70a 70b ... coolant discharge port 76a ... coolant inlet manifold 76 b ... coolant outlet manifold 80a ... coolant supply pipe 80b ... coolant discharge pipe 82, 84, 86 ... heat insulating member

Claims (3)

A power generation cell having an electrolyte / electrode structure in which electrodes are disposed on both sides of the electrolyte and a separator, and a terminal plate, an insulating member, and an end are provided on both sides in the stacking direction of the stacked body in which the plurality of power generation cells are stacked A fuel cell stack in which a plate is disposed,
A conductive plate is disposed between the insulating member and the terminal plate,
A fuel cell stack, characterized in that a cooling medium passage is formed between the conductive plate and the insulating member for flowing a cooling medium along a plate surface direction of the conductive plate. The fuel cell stack according to claim 1, wherein a cooling medium flow path for flowing a cooling medium along the electrode surface direction is formed between the power generation cells.
The fuel cell stack, wherein the coolant passage communicates with the coolant passage. 3. The fuel cell stack according to claim 1, wherein the insulating member is formed with a recess for accommodating the conductive plate and the terminal plate,
The fuel cell stack, wherein the cooling medium passage is formed on a bottom surface of the insulating member that forms the recess.

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