JP4630040B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art In recent years, a fuel cell stack (also referred to as a fuel cell) in which a plurality of single cells are stacked has been actively developed as a power source for fuel cell vehicles. When a fuel cell generates electricity, water is generated mainly on the cathode (air electrode) side. Part of the generated water diffuses in the solid polymer electrolyte membrane (hereinafter referred to as electrolyte membrane) constituting the single cell and permeates to the anode (fuel electrode) side. In order to maintain the wet state of the electrolyte membrane, a method of supplying humidified oxidant gas (for example, humidified air) to the cathode side is generally employed.

  Thus, the water content of the gas flowing through the fuel cell is high due to water generated by power generation and humidification. Therefore, when the temperature of gas falls, the water contained in gas will condense. Therefore, when the fuel cell is used in the winter or in a cold region, if the fuel cell is exposed to below freezing after being stopped, the inside of the fuel cell may freeze.

  Therefore, in order to prevent such freezing in the fuel cell, when the fuel cell is stopped or started, the fuel gas channel and the oxidant gas channel in the fuel cell are made of non-humidified air (scavenging gas). A fuel cell system that performs scavenging (air purging) has been proposed (see Patent Document 1).

Japanese Patent Laying-Open No. 2003-331893 (paragraph numbers 0012 to 0033, FIG. 1)

  However, the fuel cell system described in Patent Document 1 includes two on-off valves for supplying the scavenging gas to the fuel gas flow path and the oxidant gas flow path, thereby reducing weight and size. This was not preferable in the field of required fuel cell vehicles.

  Accordingly, an object of the present invention is to provide a fuel cell system that can suitably scavenge the fuel cell with a simple configuration.

As means for solving the above-mentioned problems, the present invention provides a fuel cell having a fuel gas flow channel and an oxidant gas flow channel, which generates power by the reaction of the fuel gas and the oxidant gas, and the fuel gas flow from the fuel gas tank. A fuel gas supply pipe through which fuel gas flows to the road, an ejector provided in the fuel gas supply pipe, and a fuel that circulates the fuel gas by returning the fuel off-gas discharged from the fuel gas flow path to the ejector A gas circulation pipe, a compressor that discharges a scavenging gas that is a non-humidified oxidant gas, and one end connected to the compressor and branched at an intermediate branch point, and the other end is between the ejector and the fuel gas flow path . the fuel gas supply pipe and the scavenging gas supply pipe connected respectively to said oxidant gas passage includes a time of stopping the fuel cell or at startup, the fuel gas stream And wherein a fuel cell system for scavenging supplying scavenging gas into the oxidant gas flow path, downstream of the oxidant gas flow path, by controlling the pressure, from the branch point and the fuel gas flow the A pressure control means for distributing scavenging gas toward the oxidant gas flow path; and the fuel gas supply pipe includes a confluence of the scavenging gas supply pipe and the fuel gas supply pipe and the fuel gas flow path. during a fuel cell system characterized that it is a pipe without the device.

  Here, the “scavenging gas” is a gas having a predetermined pressure for extruding water or the like in the fuel cell to the outside of the fuel cell and cleaning the inside of the fuel cell, such as air and nitrogen. “To scavenge” means to introduce the scavenging gas into the fuel gas flow path and the oxidant gas flow path of the fuel cell and push out the water in the fuel cell to the outside of the fuel cell.

According to such a fuel cell system, the system can be simply configured by including the pressure control means on the downstream side of the branch point of the scavenging gas supply pipe and on one side of the fuel gas channel and the oxidant gas channel. it can.
Then, the pressure control means controls the pressure to distribute the scavenging gas to one side and the other side of the fuel gas flow path and the oxidant gas flow path at the branch point of the scavenging gas supply pipe. Scavenging can be suitably performed.
Further, according to such a fuel cell system, since the pressure control means is located on the downstream side of the oxidant gas flow path, in addition to the above-described effects, the pressure control means can perform the normal power generation of the fuel cell. The back pressure, that is, the pressure in the oxidant gas flow path of the fuel cell can be adjusted. That is, the balance between the pressure in the oxidant gas flow path of the fuel cell and the pressure in the fuel gas flow path across the electrolyte membrane can be adjusted.

Further, in the fuel cell system, the minimum flow path cross-sectional area of the flow path between the pressure control means and the branch point is the minimum flow path breakage of the flow path between the branch point and the fuel gas flow path. When the pressure control means is not controlled, the scavenging gas flow rate to the pressure control means is preferably larger than the area.

  Here, “when the pressure control means is not controlled” means that the pressure is not controlled and “the pressure on the upstream side and the downstream side of the pressure control means are the same”.

According to such a fuel cell system, the minimum flow path cross-sectional area of the flow path on the pressure control means side (one side) is larger than the minimum flow path cross-sectional area on the other side, and pressure control is performed when the pressure control means is not controlled. A large amount of scavenging gas flows on the means side.
Thereby, for example, when the initial state of the pressure control means is set so that the pressure on the upstream side and the downstream side of the pressure control means is the same (for example, when the back pressure valve as the pressure control means is fully open) ) When the pressure control means controls the pressure to increase the back pressure, the scavenging gas hardly flows on the pressure control means side (one side) and the scavenging gas flows on the other side. That is, by controlling the pressure control means, the distribution of the scavenging gas to the one side and the other side of the fuel gas channel and the oxidant gas channel can be more suitably controlled in a wide range.
On the other hand, when the initial state of the pressure control means is set so that the pressure on the upstream side of the pressure control means is higher than that on the downstream side (for example, when the back pressure valve as the pressure control means is substantially fully closed), the pressure When the control means is controlled in a direction to reduce the back pressure, the scavenging gas easily flows to the pressure control means side.

  The fuel cell system further includes control means for controlling the compressor and the pressure control means so that the actual scavenging gas flow rate matches the target scavenging gas flow rate and the actual scavenging gas pressure matches the target scavenging gas pressure. It is preferable.

  Further, in the fuel cell system, provided between the compressor and the branch point, provided between the flow point sensor for detecting the actual scavenging gas flow rate, the branch point and the pressure control means, and the actual And a pressure sensor for detecting the scavenging gas pressure.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which enables scavenging of a fuel cell suitably with a simple structure can be provided.

Embodiments of the present invention will be described below with reference to the drawings as appropriate.
In the description of each embodiment, the same constituent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

<< First Embodiment >>
The fuel cell system according to the first embodiment will be described with reference to FIGS. 1 and 2. In the drawings to be referred to, FIG. 1 is a configuration diagram of a fuel cell system according to a first embodiment. FIG. 2 is a flowchart showing the operation of the fuel cell system according to the first embodiment.

≪Configuration of fuel cell system≫
As shown in FIG. 1, the fuel cell system 1A according to the first embodiment is a system mounted on a fuel cell vehicle. When the fuel cell vehicle is stopped (when the fuel cell 2 is stopped), the back pressure valve 24A ( By controlling the back pressure (pressure) with the pressure control means), the scavenging gas (non-humidified air) is separated from the oxidant gas flow path 5 side (one side) of the fuel cell 2 at the connection point C (branch point). This is a system that distributes the fuel gas flow path 4 side (the other side).

  As shown in FIG. 1, a fuel cell system 1A includes a fuel cell 2, an anode system for supplying and discharging hydrogen gas (fuel gas, reaction gas) to the anode side of the fuel cell 2, and a cathode side of the fuel cell 2. A cathode system that supplies and discharges humidified air (oxidant gas, reactive gas) or scavenging gas (non-humidified air), a scavenging system that guides the scavenging gas from the cathode system to the anode system during scavenging, a temperature sensor 51, and The ECU 60 (Electronic Control Unit, control device) to be controlled is mainly provided.

<Fuel cell>
The fuel cell 2 (fuel cell stack) is mainly configured by stacking a plurality of single cells each having both surfaces of the electrolyte membrane 3 sandwiched between an anode (fuel electrode) and a cathode (air electrode) via a separator. Has been. In the separator, a groove for supplying hydrogen gas (fuel gas) and humidified air (oxidant gas) to the entire surface of the electrolyte membrane 3, a through hole for supplying each single cell, and the like are formed in a complicated manner. These grooves and the like function as the fuel gas channel 4 and the oxidant gas channel 5. Hydrogen gas flows through the fuel gas flow path 4, and this flowing hydrogen gas is supplied to each anode. On the other hand, humidified air circulates in the oxidant gas flow path 5, and this circulated humidified air is supplied to each cathode.
When hydrogen gas is supplied to each anode and humidified air is supplied to each cathode, an electrochemical reaction occurs in each anode and each cathode, and a predetermined potential difference is generated in each single cell. This single cell is generally connected in series. Therefore, it is possible to take out large electric power from the fuel cell 2.

<Anode system>
The anode system is a system that is arranged on the anode side of the fuel cell 2 and supplies / discharges hydrogen gas. The anode system mainly includes a hydrogen tank 11 that stores hydrogen gas, an ejector 12, and an open / close purge valve 13. .

  First, the anode hydrogen gas supply side will be described. The hydrogen tank 11 is connected to a downstream ejector 12 via a pipe 11a, and the ejector 12 is connected to the hydrogen inlet 4a of the fuel cell 2 via the pipe 12a. Connected. Then, hydrogen gas can be supplied from the hydrogen tank 11 to the fuel gas passage 4 of the fuel cell 2 via the ejector 12. In addition, the piping 11a between the hydrogen tank 11 and the ejector 12 is provided with a shut-off valve and a pressure reducing valve (both not shown) in order toward the ejector 12, so that the hydrogen gas is appropriately shut off and depressurized to a predetermined level. It is possible.

  Next, the anode-side hydrogen gas discharge side will be described. The purge valve 13 is connected to a hydrogen discharge port 4b communicating with the fuel gas passage 4 via a pipe 13a. Further, the purge valve 13 is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can open and close the purge valve 13 appropriately.

  The pipe 13a is branched at a midway position, and the branched portion is connected to the ejector 12 on the hydrogen gas supply side. Thereby, at the time of normal power generation of the fuel cell 2, the purge valve 13 is closed, and the hydrogen gas (anode offgas, fuel gas) discharged from the fuel cell 2 is returned (circulated) to the hydrogen gas supply side. Hydrogen gas can be used efficiently. On the other hand, when the moisture in the anode off gas increases due to power generation, the purge valve 13 is opened, and the anode off gas having a high water content can be discharged (purged) out of the system.

<Cathode system>
The cathode system is disposed on the cathode side of the fuel cell 2 and mainly supplies and discharges air (a scavenging gas that is humidified air during normal power generation and non-humidified air during scavenging), and is a pump 21 (compressor). The flow meter 22, the pressure gauge 23, and the back pressure valve 24A (pressure control means, back pressure control means) are mainly provided.

  First, the cathode system air supply side will be described. The pump 21 is connected to a downstream flow meter 22 via a pipe 21a, and the flow meter 22 is connected to the air inlet 5a of the fuel cell 2 via the pipe 22a. Connected.

The pump 21 is a device for taking outside air, compressing it to a predetermined level, and sending it to the fuel cell 2. The pump 21 is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can control the pump 21 as desired.
The pump 21 according to the first embodiment corresponds to a “ scavenging gas source”.

  The flow meter 22 includes a flow rate of the anode scavenging gas that actually flows to the fuel gas flow channel 4 side (anode scavenging gas flow rate Q11) and a cathode scavenging gas that actually flows to the oxidant gas flow channel 5 side when scavenging the fuel cell 2. The total scavenging gas flow rate Q13, which is the sum of the flow rates (cathode scavenging gas flow rate Q12), can be detected. The flow meter 22 is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can monitor the total scavenging gas flow rate Q13.

  A humidifier (not shown) is provided in the middle of the pipe 21a. During normal power generation of the fuel cell 2, the humidifier can humidify the air from the pump 21 to a predetermined degree. On the other hand, when the fuel cell 2 is scavenged, humidification by the humidifier is stopped, and scavenging gas (non-humidified air) can be supplied downstream.

  The pressure gauge 23 is provided in the pipe 22a and can detect the pressure of the scavenging gas that actually flows (scavenging gas pressure P1) when scavenging the fuel cell 2. The pressure gauge 23 is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can monitor the scavenging gas pressure P1.

  A scavenging system pipe 41 to be described later is connected to a connection point C between the flow meter 22 and the pressure gauge 23 and in the middle of the pipe 22a. Therefore, during scavenging of the fuel cell 2, the scavenging gas from the pump 21 is purged from the anode scavenging gas toward the fuel gas channel 4 and the cathode scavenging toward the oxidant gas channel 5 at the connection point C (branch point). It can be distributed to gas.

  Next, the cathode air discharge side will be described. The back pressure valve 24A is connected to an air discharge port 5b communicating with the oxidant gas flow path 5 through a pipe 24a. The air discharged from the fuel cell 2 (cathode off-gas during power generation and scavenging gas during scavenging) is discharged out of the system via the pipe 24a and the back pressure valve 24A. Further, the back pressure (= the pressure on the upstream side of the back pressure valve 24A) can be appropriately controlled by adjusting the opening of the back pressure valve 24A. The back pressure valve 24A is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can control the back pressure valve 24A as desired.

  Further, since the back pressure valve 24A is positioned on the downstream side of the oxidant gas flow path, the back pressure of the back pressure valve 24A, that is, within the oxidant gas flow path 5 of the fuel cell 2 during normal power generation of the fuel cell 2 is achieved. The pressure can be adjusted. That is, during normal power generation of the fuel cell 2, the back pressure valve 24A adjusts the balance between the pressure in the oxidant gas flow channel 5 of the fuel cell 2 and the pressure in the fuel gas flow channel 4 across the electrolyte membrane 3. You can also.

<Scavenging system>
The scavenging system is a system that guides scavenging gas (non-humidified air) from the cathode system to the anode system when scavenging the fuel cell 2, and mainly includes a pipe 41 and an opening / closing valve 42.

One end of the pipe 41 is connected to the connection point C (branch point) of the cathode system pipe 22a. The other end of the pipe 41 is connected to the anode pipe 12a.
The on-off valve 42 is provided in the middle of the pipe 41 and can appropriately block the flow in the pipe 41. Further, the on-off valve 42 is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can control the on-off valve 42 as desired.

  Accordingly, the open / close valve 42 is closed during normal power generation of the fuel cell 2, while the scavenging gas (non-humidified air) from the connection point C (branch point) is opened by opening the open / close valve 42 during scavenging of the fuel cell 2. Can be introduced into the pipe 41 and supplied to the fuel gas flow path 4 via the pipe 41 and the pipe 12a.

Therefore, in the fuel cell system 1A according to the first embodiment, the “ scavenging gas supply piping” includes the cathode piping 21a and the piping 22a, the scavenging piping 41, and a part of the anode piping 12a. Has been. That is, one end side of the “scavenging gas supply pipe” according to the first embodiment is connected to the pump 21 that is a scavenging gas source. The “scavenging gas supply pipe” branches off at an intermediate connection point C (branch point), and the other end is connected to the fuel gas passage 4 and the oxidant gas passage 5 respectively.

The piping 41 is set to be narrower than the cathode piping 21a, 22a, 24a. More specifically, the minimum flow path cross-sectional area in the cathode piping 21 a, 22 a, 24 a is set larger than the minimum flow path cross-sectional area in the pipe 41.
In other words, when the anode purge valve 13, the cathode back pressure valve 24A, and the scavenging system open / close valve 42 are fully open, the pressure loss from the connection point C to the air outlet downstream of the anode purge valve 13; The pressure loss from the connection point C to the air outlet on the downstream side of the cathode back pressure valve 24A is set so that the pressure loss on the cathode side is smaller.

  Thereby, when the back pressure valve 24A is not controlled, the cathode scavenging gas flow rate Q12 from the connection point C to the oxidant gas flow path 5 side (= back pressure valve 24A side) is changed from the connection point C to the fuel gas flow path 4 side. It is larger than the anode scavenging gas flow rate Q11. Therefore, by controlling the back pressure with the back pressure valve 24A, the distribution of the cathode scavenging gas flow rate Q12 and the anode scavenging gas flow rate Q11 can be adjusted in a wide range.

<Temperature sensor for outside air>
The temperature sensor 51 is provided at an appropriate position of the fuel cell vehicle and can detect the outside air temperature T0. The temperature sensor 51 is electrically connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can monitor the outside air temperature T0.

<ECU>
The ECU 60 mainly has a function of controlling scavenging of the fuel cell 2. The ECU 60 includes a CPU, ROM, RAM, various interfaces, electronic circuits, various storage media, and the like, and mainly includes a control unit 61 (back pressure valve control unit) and a scavenging data storage unit 62 (scavenging data storage unit). In preparation. The ECU 60 is linked to an ignition switch (hereinafter referred to as IGSW) that is a start switch of the fuel cell vehicle.

[Control unit]
The output side of the control unit 61 is electrically connected to the cathode back pressure valve 24A, and the control unit 61 can appropriately adjust the back pressure by appropriately controlling the opening of the back pressure valve 24A. ing. Note that the controller 61 does not control the back pressure valve 24A (the back pressure valve 24A is fully open), and the pressure on the upstream side and the downstream side of the back pressure valve 24A can be the same. Thus, when the opening degree of the back pressure valve 24A is fully open, in the first embodiment, it is referred to as “initial state when the back pressure valve 24A is not controlled”.

  In addition, the output side of the control unit 61 is electrically connected to the cathode pump 21, and the control unit 61 can control the pump 21 as desired. Further, the output side of the control unit 61 is electrically connected to the anode purge valve 13 and the scavenging system opening / closing valve 42, and the control unit 61 can control them as desired.

The input side of the control unit 61 is electrically connected to the cathode-type flow meter 22 and pressure gauge 23 and the temperature sensor 51. The control unit 61 performs actual total scavenging gas flow rate Q13, scavenging gas pressure P1. The outside air temperature T0 can be monitored.
Then, the control unit 61 compares the actual total scavenging gas flow rate Q13 with a target total scavenging gas flow rate Q3, which will be described later, an actual scavenging gas pressure P1, and a target scavenging gas pressure P0, which will be described later. According to the control of the pressure valve 24A, it has a function of determining whether the anode scavenging gas or the cathode scavenging gas is supplied as scheduled.
The control unit 61 has a function of determining whether scavenging is necessary based on the outside air temperature T0.

  Further, the control unit 61 is electrically connected to the scavenging data storage unit 62 and can appropriately refer to “scavenging data A” to be described later. The control unit 61 can control the pump 21 and the back pressure valve 24A based on the referred “scavenging data A”.

[Scavenging data storage]
The scavenging data storage unit 62 stores “scavenging data A”. The “scavenging data A” is “target scavenging gas pressure P 0, target anode scavenging gas flow rate Q 1, target cathode scavenging gas flow rate Q 2, target total scavenging gas flow rate Q 3” obtained during preliminary scavenging of the fuel cell 2. Is included.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1A according to the first embodiment will be described with reference to FIG. 2 in addition to FIG.

  When the IGSW (not shown) of the fuel cell vehicle is turned off (S1), the control unit 61 closes the anode shutoff valve (not shown) and stops the supply of hydrogen gas to the fuel cell 2. Further, the control unit 61 stops humidification by a cathode humidifier (not shown) while the pump 21 is operating, and supplies scavenging gas (non-humidified air) to the downstream side.

  In step S2, the control unit 61 determines whether scavenging of the fuel cell 2 is necessary. Specifically, it is determined whether or not the outside air temperature T0 detected by the temperature sensor 51 is 0 ° C. or less. This is because there is a high possibility that the inside of the fuel cell 2 will freeze when the outside air temperature T0 is 0 ° C. or lower.

When it is determined that “the outside air temperature T0 is 0 ° C. or less and scavenging is necessary” (S2, Yes), the control unit 61 opens the anode purge valve 13 and the scavenging system open / close valve 42 to perform scavenging. Gas is supplied to the fuel gas flow path 4. Thereafter, the process proceeds to step S3.
On the other hand, when it is determined that “the outside air temperature T0 is higher than 0 ° C. and scavenging is not necessary” (S2, No), the control unit 61 stops the pump 21 and the fuel cell 2 stops.

  In step S3, the control unit 61 reads from the scavenging data storage unit 62 “scavenging data A (target scavenging gas pressure P0, target anode scavenging gas flow rate Q1, target cathode scavenging gas flow rate Q2, target scavenging data A "Total scavenging gas flow rate Q3)" is read.

  In step S4, the rotational speed of the pump 21 and the opening of the back pressure valve 24A are determined based on the “target scavenging gas pressure P0” and “target total scavenging gas flow rate Q3” of the read “scavenging data A”. .

  In step S5, the control unit 61 controls the pump 21 and the back pressure valve 24A according to the rotation speed of the pump 21 determined in step S4 and the opening degree of the back pressure valve 24A. Then, the back pressure (= scavenging gas pressure P1) is adjusted according to the rotational speed of the pump 21 and the opening of the back pressure valve 24A. The scavenging gas from the pump 21 is distributed in a predetermined manner at the connection point C (branch point), and the cathode scavenging gas is supplied to the oxidant gas channel 5 side and the anode scavenging gas is supplied to the fuel gas channel 4 side. Is done.

More specifically, on the downstream side of the connection point C and the oxidant gas flow path 5 side, the cathode scavenging gas is supplied to the oxidant gas flow path 5 of the fuel cell 2 via the downstream side of the pipe 22a, and the oxidant The gas flow path 5 is scavenged.
On the other hand, on the downstream side of the connection point C and on the fuel gas flow path 4 side, the anode scavenging gas is supplied to the fuel gas flow path 4 of the fuel cell 2 via the pipe 41 and the downstream portion of the pipe 12a, and the fuel gas The flow path 4 is scavenged.

  In step S <b> 6, the control unit 61 sets the “total scavenging gas flow rate Q <b> 13” and “scavenging gas pressure P <b> 1” of the total scavenging gas actually flowing via the flow meter 22 and the pressure gauge 23 to “target total scavenging gas flow rate”. It is determined whether or not “Q3” and “target scavenging gas pressure P0” are satisfied.

  When it is determined that the actually flowing scavenging gas satisfies the “target total scavenging gas flow rate Q3” and “target scavenging gas pressure P0” (S6, Yes), the process proceeds to step S7, and scavenging is performed for a predetermined time. Then go to the end.

  On the other hand, when it is determined that the actually flowing scavenging gas does not satisfy at least one of “target total scavenging gas flow rate Q3” and “target scavenging gas pressure P0” (S6, No), the process returns to step S5, and the controller 61 Controls the pump 21 and the back pressure valve 24A again.

  Thus, according to the fuel cell system according to the first embodiment, the opening degree of one back pressure valve 24A on the oxidant gas flow path 5 side, which is downstream of the connection point C (branch point), is controlled. As a result, the back pressure is adjusted, and the scavenging gas is changed to the cathode scavenging gas on the oxidant gas channel 5 side (one side) and the anode scavenging gas on the fuel gas channel 4 side (the other side) at the connection point C. Can be distributed.

≪First Reference Form≫
Next, the fuel cell system according to the first reference embodiment will be described with reference to FIG. FIG. 3 is a configuration diagram of the fuel cell system according to the first reference embodiment.

≪Configuration of fuel cell system≫
As shown in FIG. 3, the fuel cell system 1B according to the first reference embodiment includes a back pressure valve 24B at a position different from the back pressure valve 24A according to the first embodiment. The fuel cell system 1 </ b> B further includes a current / voltage detector 52.

<Back pressure valve>
The back pressure valve 24 </ b> B is disposed on the pipe 22 a and between the pressure gauge 23 and the oxidant gas flow path 5. That is, the back pressure valve 24 </ b> B is disposed between the connection point C (branch point) and the oxidant gas flow path 5. The back pressure valve 24 </ b> B is electrically connected to the control unit 61 and can be controlled as desired by the control unit 61.
The scavenging gas distribution at the connection point C when the back pressure valve 24B is not controlled is similar to the first embodiment in that the cathode scavenging gas flow rate Q12 on the oxidant gas flow path 5 side (one side) is the fuel gas flow. It is set to be larger than the anode scavenging gas flow rate Q11 on the path 4 side (the other side).

  Thus, even if the back pressure valve 24B is disposed between the connection point C (branch point) and the oxidant gas flow path 5, the back pressure is adjusted by controlling the back pressure valve 24B. The scavenging gas from the pump 21 can be distributed to the cathode scavenging gas and the anode scavenging gas.

<Current / voltage detector>
The current / voltage detector 52 is a device that detects the output current and output voltage of the fuel cell 2, and includes an ammeter, a voltmeter, and the like, and is connected to the output terminal of the fuel cell 2. The current / voltage detector 52 is connected to a control unit 61 of the ECU 60 described later, and the control unit 61 can monitor the output current and output voltage of the fuel cell 2.

  Therefore, when the fuel cell 2 is stopped, the control unit 61 estimates the power generation status from, for example, the output current / output voltage of the fuel cell 2 immediately before the stop, and the estimated power generation status (that is, the water generation status by power generation). Corresponding to the above, the target anode scavenging gas flow rate Q1 and the target cathode scavenging gas flow rate Q2 can be set.

  In this case, “scavenging data B” associated with “output current, output voltage” and “target anode scavenging gas flow rate Q1, target cathode scavenging gas flow rate Q2” in advance is stored in the scavenging data storage unit 62 of the ECU 60. Has been. When scavenging the fuel cell 2, the controller 61 refers to the “scavenging data B” based on the output current / output voltage, and sets the target anode scavenging gas flow rate Q 1 and the target cathode scavenging gas required for scavenging. The flow rate Q2 can be determined.

  Next, the controller 61 adds the target anode scavenging gas flow rate Q1 and the target cathode scavenging gas flow rate Q2 determined based on the output current and the like to obtain a target total scavenging gas flow rate Q3, and this and the target scavenging gas pressure P0. Therefore, the rotational speed of the pump 21 and the opening degree of the back pressure valve 24B can be determined.

Thus, according to the fuel cell system 1B according to the first reference embodiment, it is possible to suitably determine the scavenging conditions in accordance with the power generation state of the fuel cell 2 before the stop, and to suitably scavenge the fuel cell 2. it can.

≪Second reference form≫
Next, a fuel cell system according to a second reference embodiment will be described with reference to FIG. FIG. 4 is a configuration diagram of the fuel cell system according to the second reference embodiment.

≪Configuration of fuel cell system≫
As shown in FIG. 4, the fuel cell system 1C according to the second reference embodiment includes a back pressure valve 24C at a position different from the back pressure valve 24A according to the first embodiment.

In the fuel cell system 1C according to the second reference form and the fuel cell system 1D according to the third reference form described later, the fuel gas flow path 4 side is downstream of the connection point C (branch point) . Corresponds to “ one side”. The downstream side of the connection point C and the oxidant gas flow path 5 side corresponds to the “ other side”.
When the back pressure valve 24C (back pressure valve 24D in the third reference form described later) is not controlled, the anode scavenging gas flow rate Q11 to the fuel gas flow path 4 side (one side) is set to the oxidant gas flow path 5 side (the other side). Side) to be larger than the cathode scavenging gas flow rate Q12.

<Back pressure valve>
The back pressure valve 24C is arranged in the anode-side hydrogen gas discharge side pipe 13a in place of the purge valve 13 (see FIG. 1), and also has a function as a purge valve. The back pressure valve 24 </ b> C is electrically connected to the control unit 61 of the ECU 60 and can be controlled as desired by the control unit 61.

  Thus, even if the back pressure valve 24C is arranged downstream of the anode fuel gas passage 4 of the fuel cell 2, the back pressure is controlled by controlling the opening of the back pressure valve 24C during scavenging of the fuel cell 2. The scavenging gas from the pump 21 is suitably distributed to the anode scavenging gas to the fuel gas channel 4 side (one side) and the cathode scavenging gas to the oxidant gas channel 5 side (the other side). It is possible.

≪Third reference form≫
Next, a fuel cell system according to a third reference embodiment will be described with reference to FIG. FIG. 5 is a configuration diagram of the fuel cell system according to the third reference embodiment.

≪Configuration of fuel cell system≫
As shown in FIG. 5, the fuel cell system 1D according to the third reference embodiment includes a back pressure valve 24D at a position different from the back pressure valve 24C according to the second reference embodiment.

<Back pressure valve>
The back pressure valve 24 </ b> D is provided on the pipe 41 and between the connection point C (branch point) and the on-off valve 42. That is, the back pressure valve 24 </ b> D is disposed between the connection point C and the fuel gas channel 4. The back pressure valve 24 </ b> D is electrically connected to the control unit 61 of the ECU 60 and can be controlled as desired by the control unit 61.

  In this way, even if the back pressure valve 24D is disposed between the connection point C and the fuel gas flow path 4, the back pressure is adjusted by controlling the back pressure valve 24D as desired. This scavenging gas can be suitably distributed to the anode scavenging gas to the fuel gas channel 4 side (one side) and the cathode scavenging gas to the oxidant gas channel 5 side (the other side).

  As mentioned above, although an example was described about each suitable embodiment of the present invention, the present invention is not limited to the above-mentioned each embodiment, and the composition concerning each above-mentioned embodiment is combined in the range which does not deviate from the meaning of the present invention, In addition, for example, the following changes can be made.

  In the first embodiment described above, scavenging is performed when the fuel cell 2 is stopped. However, scavenging may be performed when the fuel cell 2 is started.

  In the first embodiment described above, the case where the initial state of the back pressure valve 24A is fully opened and the back pressure valve 24A is throttled to increase the back pressure during control has been described. However, the initial state of the back pressure valve 24A is substantially fully closed. In this case, the back pressure valve 24A may be opened during control to reduce the back pressure.

  In the first embodiment described above, the on-off valve 42 is provided in the middle of the pipe 41 and the flow in the pipe 41 is controlled by the on-off valve 42. In addition, for example, by providing a three-way valve at the connection point C, the pipe The distribution in 41 may be controlled.

  In the first embodiment described above, the pipe 41 is made thinner than the cathode pipes 21a, 22a, and 24a, so that the sword scavenging gas flow rate of the back pressure valve 24A becomes larger than the anode scavenging gas flow rate. If the pressure loss on the downstream side can be adjusted, the pipe 41 is not limited to be thin. For example, the pipe 41 may be lengthened to increase the pressure loss on the fuel gas channel 4 side.

1 is a configuration diagram of a fuel cell system according to a first embodiment. FIG. It is a flowchart which shows operation | movement of the fuel cell system which concerns on 1st Embodiment. It is a block diagram of the fuel cell system which concerns on a 1st reference form. It is a block diagram of the fuel cell system which concerns on a 2nd reference form. It is a block diagram of the fuel cell system which concerns on a 3rd reference form.

Explanation of symbols

1A, 1B, 1C, 1D Fuel cell system 2 Fuel cell 4 Fuel gas flow path 5 Oxidant gas flow path 12a, 21a, 22a, 41 Piping (scavenging gas supply piping)
21 Pump (scavenging gas source)
22 Flow meter 23 Pressure gauge 24A, 24B, 24C, 24D Back pressure valve (pressure control means, back pressure control means)
60 ECU
61 Control unit 62 Scavenging data storage unit C Connection point (branch point)

Claims (4)

A fuel cell having a fuel gas flow path and an oxidant gas flow path, and generating power by a reaction between the fuel gas and the oxidant gas;
A fuel gas supply pipe through which fuel gas flows from the fuel gas tank toward the fuel gas flow path;
An ejector provided in the fuel gas supply pipe;
A fuel gas circulation pipe for returning the fuel off-gas discharged from the fuel gas flow path to the ejector and circulating the fuel gas;
A compressor that discharges a scavenging gas that is a non-humidifying oxidant gas;
Scavenging gas supply having one end connected to the compressor and branched at an intermediate branch point, and the other end connected to the fuel gas supply pipe and the oxidant gas flow path between the ejector and the fuel gas flow path, respectively. Piping,
A fuel cell system for supplying a scavenging gas to the fuel gas flow path and the oxidant gas flow path when the fuel cell is stopped or started,
Pressure control means for distributing scavenging gas from the branch point toward the fuel gas flow path and the oxidant gas flow path by controlling the pressure downstream of the oxidant gas flow path ;
The fuel gas supply pipe is a pipe that does not include a device between the scavenging gas supply pipe and the confluence of the fuel gas supply pipe and the fuel gas flow path.
The fuel cell system which is characterized a call. The minimum flow path cross-sectional area of the flow path between the pressure control means and the branch point is larger than the minimum flow path cross-sectional area of the flow path between the branch point and the fuel gas flow path, and the pressure control means 2. The fuel cell system according to claim 1, wherein the scavenging gas flow rate toward the pressure control means is large when the control is not performed.   Control means for controlling the compressor and the pressure control means is provided so that the actual scavenging gas flow rate matches the target scavenging gas flow rate and the actual scavenging gas pressure matches the target scavenging gas pressure.
  The fuel cell system according to claim 1 or 2, characterized by the above.   A flow rate sensor provided between the compressor and the branch point for detecting the actual scavenging gas flow rate;
  A pressure sensor provided between the branch point and the pressure control means for detecting the actual scavenging gas pressure;
  With
  The fuel cell system according to claim 3.

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