JP6555169B2 - Control method of fuel cell system - Google Patents

Description

  The present invention relates to a control method for a fuel cell system.

  A fuel cell system generally includes a water storage unit that stores a certain amount of water generated by power generation. For example, in the fuel cell system described in Patent Document 1, it is determined using an acceleration sensor whether or not the water in the water reservoir is in a position where it can be discharged from a drain outlet in the water reservoir, and based on the determination result. Controls the opening and closing of the discharge valve.

JP 2008-262735 A

  In the fuel cell system described in Patent Document 1, if the drain is to be discharged when the drain port is not completely covered with water, the timing for discharging the water may be missed. When water is added, water that is not discharged may flow back to the hydrogen pump or the fuel cell stack. On the other hand, if the drain valve is opened when the drain port is not completely covered with water, water can be discharged, but the fuel gas may be wasted. In addition, if water moves to a position where high acceleration is applied and does not flow into the discharge port, the gas is discharged despite the remaining water, so it may be erroneously determined that drainage is complete and the discharge valve may be closed. is there. If so, water may remain in the reservoir. Therefore, in the fuel cell system, there has been a demand for a technique capable of suppressing wasteful discharge of fuel gas while effectively discharging water even when the water surface in the water storage portion is inclined due to acceleration.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a method for controlling a fuel cell system is provided. The control method of the fuel cell system includes a circulation flow path for circulating the anode off-gas of the fuel cell to the fuel cell; and is connected to the circulation flow path to separate generated water from the anode off-gas in the circulation flow path A water storage section for storing water; a discharge valve provided at a lower portion of the water storage section for draining the generated water stored in the water storage section and exhausting the anode off-gas in the water storage section; opening and closing of the discharge valve And a sensor for estimating the inclination angle of the water surface of the generated water in the water reservoir; a fuel cell having an inclined surface in which the water reservoir is inclined toward the discharge valve. A control method of a system, wherein (a) the control device opens the discharge valve when the generated water in the water storage section reaches a specified amount, and (b) after the step (a), The control device is When the inclination angle of the water surface estimated using the sensor is larger than the inclination angle of the inclined surface, the discharge valve is closed after the pressure drop in the circulation passage occurs, and (c) the step (b) ), The control device opens the discharge valve when the inclination angle of the water surface estimated using the sensor becomes equal to or less than the inclination angle of the inclined surface. According to the control method of the fuel cell system of this embodiment, by performing the steps (a), (b), and (c), water can be effectively discharged even when the water surface in the water storage section is inclined due to acceleration. While performing, it can suppress that fuel gas is discharged | emitted wastefully.

  It should be noted that the present invention can be realized in various modes, such as a vehicle equipped with a fuel cell, a fuel cell system mounted on the vehicle, a control device that executes a control method for the fuel cell system, and the like. Can be realized.

It is the schematic which shows schematic structure of a fuel cell system. It is a schematic diagram of a water storage part. It is a flowchart showing a waste water treatment. It is a figure which shows the mode in the water storage part when acceleration generate | occur | produces.

A. Embodiment:
FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell system 100 according to an embodiment of the present invention. The fuel cell system 100 includes a fuel cell 10, a control device 20, an oxidizing gas channel system 30, and a fuel gas channel system 50. In the present embodiment, the fuel cell system 100 is mounted on a vehicle 200 and used as a power source such as a traction motor (not shown) provided in the vehicle 200.

  The fuel cell 10 is a polymer electrolyte fuel cell that generates electricity by receiving supply of hydrogen (fuel gas) and air (oxidizing gas) as reaction gases. The fuel cell 10 has a stack structure in which a plurality of cells 11 are stacked. Each cell 11 has a membrane electrode assembly (not shown) in which electrodes are arranged on both surfaces of an electrolyte membrane (not shown), and a set of separators that sandwich the membrane electrode assembly. The electric power generated by the fuel cell 10 is stored in the battery 92 via the DC / DC converter 90. Various loads 93 are connected to the battery 92. Electric power is supplied from the fuel cell 10 or the battery 92 to the air compressor 32, the circulation pump 64, and various valves, which will be described later, and is driven.

  The oxidizing gas flow path system 30 includes an oxidizing gas pipe 31, an air compressor 32, an on-off valve 33, a cathode offgas pipe 41, and a regulator 42. The oxidizing gas flow path system 30 includes a flow path on the cathode side in the fuel cell 10.

  The air compressor 32 is connected to the fuel cell 10 via the oxidizing gas pipe 31. The air compressor 32 compresses air taken from outside in accordance with a control signal from the control device 20 and supplies the compressed air to the fuel cell 10 as an oxidizing gas.

  The on-off valve 33 is provided between the air compressor 32 and the fuel cell 10 and opens and closes according to the flow of supply air in the oxidizing gas pipe 31. Specifically, the on-off valve 33 is normally in a closed state and opens when air having a predetermined pressure is supplied from the air compressor 32 to the oxidizing gas pipe 31.

  The cathode offgas pipe 41 discharges the cathode offgas discharged from the cathode of the fuel cell 10 to the outside of the fuel cell system 100. The regulator 42 adjusts the cathode offgas pressure (back pressure on the cathode side of the fuel cell 10) in the cathode offgas piping 41 in accordance with a control signal from the control device 20.

  The fuel gas passage system 50 includes a fuel gas pipe 51, a hydrogen tank 52, an on-off valve 53, a regulator 54, an injector 55, a discharge valve 60, an anode off-gas pipe 61, a pressure sensor 62, and a circulation pipe. 63, a circulation pump 64, and a water storage unit 70. The fuel gas channel system 50 includes an anode-side channel in the fuel cell 10. In the following, the flow path constituted by the downstream side of the injector 55 of the fuel gas pipe 51, the flow path on the anode side in the fuel cell 10, the anode off-gas pipe 61, the circulation pipe 63, and the water reservoir 70. This is also referred to as a circulation channel 65. The circulation channel 65 is a channel for circulating the anode off gas of the fuel cell 10 to the fuel cell 10. A pressure sensor 62 for detecting the pressure in the circulation channel 65 is connected to the circulation channel 65.

  The hydrogen tank 52 is connected to the anode of the fuel cell 10 through the fuel gas pipe 51, and supplies the hydrogen filled inside to the fuel cell 10. The on-off valve 53, the regulator 54, and the injector 55 are provided in the fuel gas pipe 51 in this order from the upstream side, that is, the side close to the hydrogen tank 52.

  The on-off valve 53 opens and closes in response to a control signal from the control device 20 and controls the inflow of hydrogen from the hydrogen tank 52 to the upstream side of the injector 55. When the fuel cell system 100 is stopped, the on-off valve 53 is closed. The regulator 54 adjusts the hydrogen pressure on the upstream side of the injector 55 in accordance with a control signal from the control device 20. The injector 55 is an electromagnetically driven on / off valve in which the valve element is electromagnetically driven in accordance with the driving cycle and valve opening time set by the control device 20. The control device 20 controls the amount of hydrogen supplied to the fuel cell 10 by controlling the drive cycle and valve opening time of the injector 55.

  The anode off-gas pipe 61 is a pipe that connects the outlet of the anode of the fuel cell 10 and the water storage unit 70. The anode off gas pipe 61 guides the anode off gas containing fuel gas, nitrogen gas, and the like that has not been used for the power generation reaction to the water storage unit 70.

  The water reservoir 70 is connected between the anode off-gas pipe 61 and the circulation pipe 63 of the circulation channel 65. The water storage unit 70 separates and stores the generated water from the anode off gas in the circulation flow path 65. The water reservoir 70 is also referred to as a “gas-liquid separator”.

  The circulation pipe 63 is connected downstream from the injector 55 of the fuel gas pipe 51. The circulation pipe 63 is provided with a circulation pump 64 that is driven in accordance with a control signal from the control device 20. The anode off gas from which the generated water has been separated by the water reservoir 70 is sent out to the fuel gas pipe 51 by the circulation pump 64. Thus, in this fuel cell system 100, the anode off gas containing hydrogen is circulated and supplied to the fuel cell 10 again, thereby improving the utilization efficiency of hydrogen.

  The drain valve 60 is provided in the lower part of the water reservoir 70. The discharge valve 60 drains the generated water stored in the water storage unit 70 and exhausts the anode off gas in the water storage unit 70. During operation of the fuel cell system 100, the discharge valve 60 is normally closed and opens and closes in response to a control signal from the control device 20. In the present embodiment, the discharge valve 60 is connected to the cathode offgas pipe 41, and the generated water and the anode offgas discharged by the discharge valve 60 are discharged to the outside through the cathode offgas pipe 41.

  The control device 20 is configured as a computer including a CPU, a memory, and an interface circuit to which the above-described components are connected. The CPU executes a control program stored in the memory, thereby realizing drainage treatment described later and performing operation control of the fuel cell system 100. An acceleration sensor 80 is connected to the control device 20. The acceleration sensor 80 is a sensor that detects the direction of gravity acceleration. The control device 20 uses the acceleration sensor 80 to estimate the inclination angle of the water surface of the generated water in the water storage unit 70.

  FIG. 2 is a schematic diagram of the water reservoir 70. The water storage unit 70 includes an introduction port 71, a discharge port 72, a discharge unit 73, and an inclined surface 74. Anode off gas is introduced into the water reservoir 70 from an anode off gas pipe 61 connected to the inlet 71. Then, the anode off gas after separating the generated water 75 is discharged from the discharge port 72 connected to the circulation pipe 63. The discharge part 73 is provided in the lower part of the water storage part 70, and the discharge valve 60 is connected. An inclined surface 74 that is inclined toward the discharge portion 73 is provided inside the water reservoir 70. Due to the inclined surface 74, the water reservoir 70 can smoothly discharge the generated water 75 and the anode off gas. Hereinafter, the inclination angle of the inclined surface 74 from the horizontal direction is referred to as a water storage portion inclination angle D1.

  FIG. 3 is a flowchart showing the waste water treatment which is a part of the control method of the fuel cell system in the present embodiment. This process is a process repeatedly executed by the control device 20 during the operation of the system. When the wastewater treatment is started, first, the control device 20 estimates the amount of the generated water 75 accumulated in the water storage unit 70 based on the current value generated by the fuel cell 10, and the amount of stored water is defined. It is determined whether or not the amount has been exceeded (step S300). The control device 20 can estimate the amount of stored water based on a map or function in which the relationship between the current value of the fuel cell 10 and the amount of water generated is defined. If the amount of stored water is equal to or greater than the specified value (step S300: YES), the control device 20 opens the discharge valve 60 (step S310). On the other hand, if the amount of stored water is less than the specified value (step S300: NO), the process waits until the specified value is reached.

  FIG. 4 is a diagram illustrating a state in the water storage unit 70 when acceleration is generated in the vehicle 200. The controller 20 uses the acceleration sensor 80 to estimate the water surface inclination angle D2 of the water surface of the generated water 75 according to the generated acceleration (step S320), and the water storage portion inclination angle D1 and the estimated liquid surface inclination angle. D2 is compared (step S330). A method for calculating the liquid surface inclination angle D2 based on the acceleration is known as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-262735.

  When the liquid surface inclination angle D2 is equal to or smaller than the water storage section inclination angle D1 (step S330: NO), the water surface in the water storage section 70 becomes the water surface w1 shown in FIG. Will be broken. Therefore, the control device 20 opens the discharge valve 60 to perform drainage (step S380). Subsequently, the control device 20 uses the pressure sensor 62 to calculate the amount of pressure decrease in the circulation flow path 65 caused by the gas being discharged from the water storage unit 70 (step S390), and the pressure has decreased. Is calculated, it is determined that the drainage is completed, and the discharge valve 60 is closed (step S400). In step S400, the control device 20 resets the value of the water storage amount estimated in the next step S300.

  On the other hand, when the liquid surface inclination angle D2 is larger than the water storage section inclination angle D1 in step S330 (step S330: YES), depending on the amount of the generated water 75, the water surface in the water storage section 70 is the water surface shown in FIG. Since it becomes like w2, the discharge part 73 may not be covered with generated water. Therefore, first, the control device 20 calculates the amount of pressure drop in the circulation flow path 65 caused by the gas being discharged using the pressure sensor 62 (step S340).

  When it is not calculated that the pressure has decreased (step S340: NO), the discharge unit 73 is covered with the generated water 75, so the control device 20 keeps the discharge valve 60 open, Continue draining and wait until pressure drop occurs. On the other hand, if it is calculated that the pressure has decreased (step S340: YES), the control device 20 determines that the anode off-gas has been discharged, and temporarily closes the discharge valve 60 (step S350). Subsequently, the control device 20 again estimates the liquid surface inclination angle D2 using the acceleration sensor 80 (step S360), and compares the water storage section inclination angle D1 with the estimated liquid surface inclination angle D2 (step S370). ).

  When the estimated liquid surface inclination angle D2 is larger than the water storage section inclination angle D1 (step S370: NO), the process returns to step S360, and the above-described steps are performed until the liquid surface inclination angle D2 becomes equal to or less than the water storage section inclination angle D1. The processes of S360 and S370 are repeated. That is, the process waits until the discharge unit 73 is covered with the generated water 75.

  On the other hand, when the estimated liquid surface inclination angle D2 is equal to or smaller than the water storage section inclination angle D1 in step S370 (step S370: YES), the discharge section 73 is covered with the generated water 75, so the control device 20 Then, the discharge valve 60 is opened and drainage is performed (step S380). Subsequently, the control device 20 uses the pressure sensor 62 to calculate the amount of pressure drop in the circulation flow path 65 caused by the gas being discharged from the water storage unit 70 (step S390). When it is not calculated that the pressure has decreased (step S390: NO), the control device 20 stands by until the pressure decrease occurs with the discharge valve 60 open. On the other hand, when it is calculated that the pressure has decreased (step S390: YES), the control device 20 determines that the drainage is completed and closes the discharge valve 60 (step S400). As described above, in this step S400, the value of the water storage amount estimated in the next step S300 is reset.

  According to the control method of the fuel cell system 100 of the present embodiment described above, whether or not the discharge unit 73 is completely covered with the generated water 75 when the water storage amount of the water storage unit 70 reaches a specified amount. First, in step S310, the control device 20 opens the discharge valve 60. Therefore, the timing for discharging water is not missed. Then, after that, when the liquid surface inclination angle D2 of the water surface of the generated water 75 is larger than the water storage section inclination angle D1 of the water storage section, when the pressure drop in the circulation flow path 65 occurs, in step S350, the control device Since 20 closes the discharge valve 60, wasteful discharge of hydrogen gas can be suppressed. Thereafter, in step S370, by comparing the liquid surface inclination angle D2 of the generated water 75 with the water storage section inclination angle D1, it can be determined whether or not the discharge portion 73 is covered with the generated water. Therefore, when the liquid level inclination angle D2 is equal to or smaller than the water reservoir inclination angle D1, the remaining generated water 75 can be discharged by opening the discharge valve 60 by the control device 20 in step S380. Therefore, according to the control method of the fuel cell system 100 of the present embodiment, even when the water surface in the water storage section 70 is inclined due to acceleration, the fuel gas is discharged wastefully while effectively discharging water. This can be suppressed.

B. Variation:
<First Modification>
In the above embodiment, the acceleration sensor 80 is used for the estimation of the liquid surface inclination angle D2. However, the liquid surface inclination angle D2 may be estimated by providing a floating substance provided with a gyro sensor in the water reservoir 70.

<Second Modification>
In the above embodiment, the waste water treatment for draining water from the water storage unit 70 has been described in detail, but the control device 20 separately performs a process for exhausting impurities such as nitrogen from the circulation flow path 65, and the exhaust treatment In this case, the discharge valve 60 may be opened and closed at a timing different from the above-described waste water treatment.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the column of the summary of the invention are intended to solve the above-described problems or to achieve a part or all of the above-described effects. In order to achieve, it is possible to replace and combine as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 11 ... Cell 20 ... Control apparatus 30 ... Oxidation gas flow path system 31 ... Oxidation gas piping 32 ... Air compressor 33 ... On-off valve 41 ... Cathode off-gas piping 42 ... Regulator 50 ... Fuel gas flow path system 51 ... Fuel gas Piping 52 ... Hydrogen tank 53 ... Open / close valve 54 ... Regulator 55 ... Injector 60 ... Discharge valve 61 ... Anode off-gas piping 62 ... Pressure sensor 63 ... Circulation piping 64 ... Circulation pump 65 ... Circulation flow path 70 ... Water storage section 71 ... Inlet 72 ... Discharge port 73 ... Discharge part 74 ... Inclined surface 75 ... Generated water 80 ... Acceleration sensor 90 ... DC / DC converter 92 ... Battery 93 ... Load 100 ... Fuel cell system 200 ... Vehicle D1 ... Water storage part inclination angle D2 ... Liquid level Inclination angle w1, w2 ... water surface

Claims (1)

A circulation flow path for circulating the anode off gas of the fuel cell to the fuel cell;
A water storage unit connected to the circulation channel and separating and storing the generated water from the anode off-gas in the circulation channel;
A discharge valve provided at a lower portion of the water storage section, and configured to discharge the generated water stored in the water storage section and exhaust the anode off-gas in the water storage section;
A control device for controlling opening and closing of the discharge valve;
A sensor for estimating an inclination angle from a horizontal direction of the water surface of the generated water in the water reservoir,
A control method of a fuel cell system having an inclined surface inside the water storage portion inclined toward the discharge valve,
(A) the controller opens the discharge valve when the generated water in the reservoir reaches a specified amount;
(B) After the step (a), when the control device estimates an inclination angle of the water surface from the horizontal direction estimated using the sensor to be larger than an inclination angle of the inclined surface from the horizontal direction , the circulation A step of closing the discharge valve after a pressure drop in the flow path has occurred;
(C) After the step (b), when the tilt angle from the horizontal direction of the water surface estimated using the sensor is equal to or less than the tilt angle from the horizontal direction of the tilted surface, And a step of opening the discharge valve.

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