JP5113634B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  In recent years, a polymer electrolyte fuel cell (Polymer Electrolyte Fuel Cell) that generates electricity by supplying hydrogen (fuel gas, reactive gas) to the anode and oxygen-containing air (oxidant gas, reactive gas) to the cathode, respectively. The development of fuel cells such as PEFC is active.

Conventionally, in this type of fuel cell, when power generation is stopped for a long time, nitrogen contained in the air supplied to the cathode electrode permeates the solid polymer electrolyte membrane and enters the anode electrode. If such nitrogen is present in the anode electrode at the start of the fuel cell, the voltage is unlikely to rise, so that stable start-up cannot be obtained.
Therefore, when the fuel cell is started, a process of discharging impurities such as nitrogen remaining in the anode electrode is performed. For example, in Patent Document 1, when the fuel cell is started, a purge valve provided on the outlet side of the anode electrode is opened to perform hydrogen replacement, and after the voltage is increased to a predetermined value, power generation is started. It has been broken.

JP-A-11-97047

  By the way, in a situation where the inside of the anode system is not completely replaced with hydrogen, if the generated current is pulled high from the fuel cell toward the external load, the fuel cell may be burdened and the fuel cell may deteriorate, for example, It has been found that there is a risk of deterioration (corrosion) of the electrodes (catalyst, etc.) of the anode and cathode of the fuel cell.

  Therefore, the present invention has been made to solve such a new problem, and suppresses deterioration of the fuel cell by power generation until the inside of the anode system is completely replaced with hydrogen. It is an object of the present invention to provide a fuel cell system that can be used.

In order to achieve the above object, a fuel cell system according to the present invention includes a fuel cell that generates electric power by a reaction between a fuel gas and an oxidant gas, fuel gas supply means for supplying the fuel gas to the fuel cell, and the fuel. A replacement means for replacing the inside of the fuel gas flow passage through which the fuel gas flows with the fuel gas when the battery is started, and a fuel cell starting means for starting the power generation of the fuel cell after performing the gas replacement by the replacement means; A fuel cell system comprising: concentration specifying means for obtaining the concentration of the fuel gas in the fuel cell; and temperature detecting means for detecting the temperature in the fuel cell, wherein the control controls the fuel cell system. The control means further includes a control means for controlling the inside of the fuel cell detected by the temperature detecting means after the fuel cell starting means starts power generation of the fuel cell. When the temperature has reached the warm-up completion temperature at which the warm-up has been completed, it is determined that the warm-up of the fuel cell has been completed. When the warm-up completion temperature has not been reached, it is determined whether or not the specified concentration value of the fuel gas has reached a predetermined value, and the concentration value of the fuel gas has reached a predetermined value. If you are permits the rated power generation of the fuel cell, when it has not reached limits the power generation current of the fuel cell, when control for limiting the generated current, the lower the said concentration values specified controlled so that the current value of the generated current reduces temperature within said detected fuel cell current value a higher power generation current and controls so as to decrease.

According to this fuel cell system, when the warm-up of the fuel cell is not completed, that is, when the power generation stability of the fuel cell is not ensured, the concentration value of the fuel gas is detected and the concentration value is When the concentration value is a low concentration value that does not reach the predetermined value, the power generation of the fuel cell is limited, so that it is possible to generate power with a current value that matches the concentration and temperature of the fuel gas. Accordingly, Ki out to reduce the burden on the fuel cell, it is possible to suitably suppress degradation of the fuel cell.

The fuel cell system of the present invention includes a fuel cell that generates electric power by a reaction between a fuel gas and an oxidant gas, fuel gas supply means for supplying the fuel gas to the fuel cell, and when the fuel cell is activated, A replacement means for replacing the inside of the fuel gas flow passage through which the fuel gas flows with the fuel gas; a fuel cell starting means for starting the power generation of the fuel cell after performing the gas replacement by the replacement means; wherein a density identifying means for determining the concentration of the fuel gas, a fuel cell system having a to that temperature detecting means detecting the temperature in the fuel cell, further have a control means for controlling the fuel cell system The control means, after the fuel cell starting means starts the power generation of the fuel cell, the temperature inside the fuel cell detected by the temperature detecting means is warmed up. It is determined whether or not the warm-up completion temperature has been reached. If the warm-up completion temperature has been reached, it is determined that the fuel cell has been warmed up, and the warm-up completion temperature has been reached. If not, it is determined whether or not the specified concentration value of the fuel gas has reached a predetermined value. If the concentration value of the fuel gas has reached a predetermined value, the fuel cell When the rated power generation of the fuel cell is permitted and not reached, the generated current of the fuel cell is limited, and the flow rate of the refrigerant flowing through the fuel cell is increased during the control for limiting the generated current. It is characterized by controlling.

According to this fuel cell system, when the warm-up of the fuel cell is not completed, that is, when the power generation stability of the fuel cell is not ensured, the concentration value of the fuel gas is detected and the concentration value is In the case of a low concentration value that does not reach the predetermined value, control is performed so as to increase the flow rate of the refrigerant flowing in the fuel cell, so that the reactivity in the fuel cell can be reduced. Thereby, the burden on the fuel cell can be reduced, and the deterioration of the fuel cell can be suitably suppressed.

The front Symbol control means, when control for limiting the generated current, it is preferable to configured to control so as to increase the passing flow rate of the refrigerant flowing through the inside of the fuel cell.

According to this fuel cell system, since the flow rate of the refrigerant flowing through the fuel cell is increased and the reactivity within the fuel cell is lowered, the burden on the fuel cell can be reduced and the deterioration of the fuel cell can be reduced. It becomes possible to suppress suitably.

Also, the control unit, when the density value becomes a predetermined value, until the temperature in the detected said fuel cell reaches a warm-up completion temperature, to reduce the passing flow rate of the refrigerant restriction It is good to set it as the structure to do.

  According to this fuel cell system, when the concentration value reaches a predetermined value, the flow rate of the refrigerant is reduced, so that warm-up is promoted and the deterioration of the fuel cell is suppressed. Suitable power generation can be performed.

Also, the control unit, when the temperature in the detected the fuel cell has reached the warm-up completion temperature, it is preferable to configured to remove the restriction of passage flow rate of the coolant.

  According to this fuel cell system, suitable power generation can be performed while suppressing deterioration of the fuel cell.

  In addition, a purge unit that purges the fuel gas discharged from the fuel cell is provided, and the control unit controls to increase the amount of the fuel gas discharged by the purge unit during the control for limiting the generated current. It is good to have a configuration.

  According to this fuel cell system, the control means performs control so as to increase the amount of the fuel gas discharged by the purge means, so that the inside of the fuel cell is suitably replaced with the fuel gas. The burden is reduced, and the deterioration of the fuel cell can be more suitably suppressed. In addition, the activation time can be shortened.

  Further, the control means releases the restriction of the generated current when the concentration value reaches a predetermined value.

According to this fuel cell system, when the concentration value reaches a predetermined value, the limit of the generated current is released, and the generated current is drawn from the fuel cell toward the external load with a rating. Thereby, suitable power generation can be performed while suppressing deterioration of the fuel cell.
The apparatus further comprises a refrigerant temperature detecting means for detecting a temperature of the refrigerant flowing through the fuel cell, wherein the temperature detecting means uses the temperature of the refrigerant detected by the refrigerant temperature detecting means as a temperature inside the fuel cell. It is good to set it as the structure to do.
In addition, a purge unit that purges the fuel gas discharged from the fuel cell is provided, and the control unit determines the amount of the fuel gas discharged by the purge unit during the control for permitting rated power generation of the fuel cell. It is preferable to perform control so as to reduce the flow rate of the refrigerant after purging as a normal amount smaller than that at the time of control for limiting the generated current of the fuel cell.
Further, the concentration specifying means obtains a hydrogen concentration at start-up of the fuel cell based on an elapsed time since the fuel cell stopped and a refrigerant temperature detected by the refrigerant temperature detecting means. The hydrogen concentration obtained by the start-up hydrogen concentration calculating means is preferably configured such that the hydrogen concentration becomes lower as the elapsed time is longer and the refrigerant temperature is higher.

  According to the present invention, it is possible to obtain a fuel cell system capable of suppressing deterioration of the fuel cell by power generation until the inside of the anode system is completely replaced with hydrogen.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
≪Configuration of fuel cell system≫
A fuel cell system 1 according to this embodiment shown in FIG. 1 is mounted on a fuel cell vehicle (moving body) (not shown). The fuel cell system 1 includes a fuel cell stack 10, an anode system that supplies and discharges hydrogen (fuel gas and reaction gas) to and from the anode of the fuel cell stack 10, and air that contains oxygen with respect to the cathode of the fuel cell stack 10. (Cathode system for supplying and discharging (oxidant gas, reaction gas), power consumption system for consuming power generated by the fuel cell stack 10, refrigerant circulation system for circulating a radiator liquid (heat exchange fluid), and electronic control of these systems ECU 60 (Electronic Control Unit) which mainly performs.

<Fuel cell>
The fuel cell stack 10 is a stack configured by stacking a plurality of (for example, 200 to 400) solid polymer type single cells 11, and the plurality of single cells 11 are electrically connected in series. Yes. The single cell 11 includes an MEA (Membrane Electrode Assembly) and two conductive anode separators and cathode separators sandwiching the MEA.

  The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane (for example, perfluorosulfonic acid type), and an anode and a cathode sandwiching the electrolyte membrane. The anode and the cathode are mainly composed of a conductive porous material such as carbon paper, and contain a catalyst (Pt, Ru, etc.) for causing an electrode reaction in the anode and the cathode.

The anode separator is formed with a through-hole (referred to as an internal manifold) extending in the stacking direction of the single cells 11 and a groove extending in the surface direction of the single cells 11 in order to supply and discharge hydrogen to the anode of each MEA. These through holes and grooves function as the anode flow path 12 (fuel gas flow path).
The cathode separator is formed with a through-hole (called an internal manifold) extending in the stacking direction of the single cells and a groove extending in the surface direction of the single cell 11 in order to supply and discharge air to and from the cathode of each MEA. These through holes and grooves function as the cathode channel 13 (oxidant gas channel).

When hydrogen is supplied to each anode via the anode flow path 12, an electrode reaction of the following formula (1) occurs, and air is supplied to each cathode via the cathode flow path 13. Then, an electrode reaction of the following formula (2) occurs, and a potential difference (OCV (Open Circuit Voltage), open circuit voltage) is generated in each single cell 11. When the fuel cell stack 2 and an external circuit such as a travel motor are electrically connected and current is taken out, the fuel cell stack 10 generates power.
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

  The fuel cell stack 10 has a unique warm-up transition hydrogen concentration (for example, a hydrogen concentration after hydrogen replacement is 95%) and a warm-up completion temperature (for example, 60 ° C. or more). The warm-up transition hydrogen concentration is a concentration at which hydrogen replacement of the fuel cell stack 10 is almost completed, and the metal material (separator, catalyst, etc.) of the fuel cell stack 10 can be protected. This is a concentration that can suppress 10 degradation. The warming-up completion temperature is a temperature at which the warming-up of the fuel cell stack 10 is completed. At this temperature, the activity of the catalyst contained in the anode and the cathode is improved satisfactorily. It is supposed to proceed to. The setting of the warm-up completion temperature depends on the specifications of the fuel cell stack 10, for example, the heat-resistant temperature of the electrolyte membrane, etc., but is activated well.

<Anode system>
The anode system mainly includes a hydrogen tank 21 in which hydrogen is stored at a high pressure, a normally closed shut-off valve 22, an ejector 23, and a purge valve 24.

The hydrogen tank 21 is connected to the inlet of the anode channel 12 through a pipe 21a, a shutoff valve 22, a pipe 22a, an ejector 23, and a pipe 23a in this order. The piping 21a is provided with a pressure reducing valve (not shown) for reducing hydrogen to a predetermined pressure. The pressure of the air toward the cathode flow path 13 is input to the pressure reducing valve as a signal pressure (pilot pressure). The pressure reducing valve corresponds to the pressure of the air and the pressure of hydrogen in the anode flow path 12. Control is performed so as to fluctuate. The shutoff valve 22 is connected to the ECU 60 and is controlled by the ECU 60.
When the IG (ignition) 60a of the fuel cell vehicle is turned on, the activation of the fuel cell stack 10 is requested, and the shutoff valve 22 is opened by the ECU 60, the hydrogen in the hydrogen tank 21 flows through the pipe 21a and the like. It is supplied to the path 12.

  The outlet of the anode channel 12 is connected to the suction port of the ejector 23 through the pipe 23b. The anode off-gas returned to the ejector 23 is mixed with hydrogen from the hydrogen tank 21 and then supplied again to the anode flow path 12. In other words, in the present embodiment, the piping 23b constitutes a hydrogen circulation path that circulates and reuses hydrogen.

[Purge valve]
The purge valve (purge means) 24 is a normally closed electromagnetic valve that discharges impurities (water vapor, nitrogen, etc.) contained in the anode off-gas (hydrogen) circulating through the pipe 23b when the fuel cell stack 10 generates power ( When purging), the ECU 60 opens the ECU 60 and, as will be described later, when the gas in the anode passage 12 is replaced (replacement to increase the hydrogen concentration) in the OCV check (OCV purge: replacement means), the ECU 60 appropriately It has been opened. The anode off-gas discharged through the purge valve 24 is sent to the diluter 32 through the pipe 24b, diluted with the diluter 32, and then discharged to the outside.

  The gas replacement in the anode flow path 12 will be further described. When the purge valve 24 is appropriately opened by the ECU 60 with the shut-off valve 22 open, the hydrogen in the anode flow path 12 is discharged and the hydrogen tank A high concentration of hydrogen flows into the anode channel 12 from 21, and the hydrogen concentration in the anode channel 12 increases. That is, the inside of the fuel cell stack 10 is replaced with a hydrogen concentration at which good power generation is possible, specifically, a hydrogen concentration at which the electrode reaction proceeds favorably on the anode catalyst.

<Cathode system>
The cathode system mainly includes a compressor 30 (supercharger), a back pressure valve 31, and a diluter 32.
The compressor 30 is connected to the inlet of the cathode flow path 13 via the pipe 30a. When the compressor 30 is operated according to the command rotational speed sent from the ECU 60, the air containing oxygen is taken in and supplied to the cathode flow path 13. It has become. Note that the rotational speed of the compressor 30 is normally set to be increased to supply air at a large flow rate and high pressure when the amount of depression (accelerator opening) of an accelerator pedal (not shown) increases.

  The pipe 30 a is provided with a humidifier (not shown) that humidifies the air toward the cathode flow path 13. This humidifier is equipped with a hollow fiber membrane capable of exchanging moisture, and through this hollow fiber membrane, moisture is exchanged between the air toward the cathode flow path 13 and the humid cathode off gas. .

  The outlet of the cathode channel 13 is connected to a diluter 32 via a pipe 31a, a back pressure valve 31, and a pipe 31b. The humid cathode offgas discharged from the cathode channel 13 (cathode) is discharged to the diluter 32 through the pipe 31a and the like, and the diluter 32 is in the anode offgas introduced from the pipe 24b by the cathode offgas. After diluting the hydrogen, it is discharged out of the car.

  The back pressure valve 31 is a normally closed valve composed of a butterfly valve or the like, and its opening degree is controlled by the ECU 60. Specifically, when the amount of depression of the accelerator pedal increases, the ECU 60 controls the opening of the back pressure valve 31 to be small so as to supply air at a high pressure.

<Power consumption system>
The power consumption system includes a traveling motor 51, a VCU (Voltage Control Unit) 52, a battery (charging / discharging device) 53, a contactor 54, and a current sensor 55.
The travel motor 51 is connected to an output terminal (not shown) of the fuel cell stack 10 via a VCU 52 and a contactor 54. The battery 53 is connected to the VCU 52. Note that an inverter (PDU: Power Drive Unit) disposed between the traveling motor 51 and the VCU 52 is omitted.

The travel motor 51 is an external load that is a power source of the fuel cell vehicle.
The VCU 52 is a device that controls (limits) the generated power (output current, output voltage) of the fuel cell stack 10 in accordance with a command from the ECU 60 (generated current control means 67 (see FIG. 2) described later), and is a DC / DC chopper. And an electronic circuit such as a DC / DC converter. That is, as the command current to the VCU 52 increases, the current extracted from the fuel cell stack 10 increases (the restriction on current extraction is relaxed), and the consumption of hydrogen and air consumed by the fuel cell stack 10 increases. When the upper limit value of the generated current is set by the generated current control means 67 described later, the VCU 52 controls the output current of the fuel cell stack 10 so as not to exceed the set upper limit value of the generated current. .

The VCU 52 also includes an electronic circuit that controls the power of the battery 53 in accordance with a command from the ECU 60, that is, controls charging / discharging of the battery 53.
The battery 53 includes, for example, a plurality of lithium ion secondary batteries.

  The contactor 54 is a switch for turning on / off the electrical connection between the fuel cell stack 10 and the VCU 52. Further, the contactor 54 is connected to the ECU 60. When the contactor 54 is turned off by the ECU 60, the current cannot be taken out from the fuel cell stack 10, and the fuel cell stack 10 does not generate power. On the other hand, when the contactor 54 is turned on by the ECU 60, current can be taken out from the fuel cell stack 10, that is, the fuel cell stack 10 can generate power. That is, when the contactor 54 is in the ON state and the VCU 52 is appropriately controlled, the fuel cell stack 10 generates power.

  The current sensor 55 detects a current value when the fuel cell stack 10 is generating power. The current value detected by the current sensor 55 is output to the ECU 60 and used for operation control of the fuel cell stack 10 by the ECU 60 described later.

<Refrigerant circulation system>
In the following description of the refrigerant circulation system, “upstream” and “downstream” are based on the direction in which the refrigerant flows.
The refrigerant circulation system includes a refrigerant pump 40, a flow rate adjustment valve 41, a radiator 42, and an electromagnetic switching valve 43. That is, the fuel cell stack 10 is connected to the downstream side of the refrigerant pump 40 via the pipe 40a, the flow rate adjusting valve 41, and the pipe 41a, and the radiator 42 is connected to the downstream side of the fuel cell stack 10 via the pipe 41b. The switching valve 43 is connected to the downstream side of the radiator 42 through a pipe 42a, and the refrigerant pump 40 is connected to the downstream side of the switching valve 43 through a pipe 43a. In addition, a refrigerant temperature sensor 44 as temperature detection means (refrigerant temperature detection means) is provided in the pipe 41b on the downstream side of the fuel cell stack 10.

  The refrigerant pump 40 pumps the coolant in the clockwise direction in FIG. 1, that is, pumps the cooling water to the refrigerant passage 14 of the fuel cell stack 10 through the pipe 40 a, and is driven by a command from the ECU 60.

  The flow rate adjusting valve 41 has a butterfly valve (not shown) as a valve body, and controls the flow rate of the refrigerant by adjusting the opening of the butterfly valve. The degree of opening adjustment is performed according to a command from the ECU 60, thereby controlling the flow rate of the refrigerant sent to the fuel cell stack 10.

  The radiator 42 exchanges heat with the outside air via a refrigerant flowing through the pipe 41b, and radiates heat from the fuel cell stack 10.

The switching valve 43 is a valve that performs switching control of the direction in which the refrigerant flows, and is a valve that switches the refrigerant so that the refrigerant flows through the radiator 42 and the radiator 42 so that the refrigerant bypasses and flows. That is, the switching valve 43 includes a bypass mode in which the refrigerant flows from the downstream pipe 41b of the fuel cell stack 10 through the pipe 41c to the refrigerant pump 40, and a radiator from the downstream pipe 41b of the fuel cell stack 10. 42 and a radiator flow mode for switching the refrigerant to flow to the refrigerant pump 40 through the pipe 42a. Switching between these modes is performed by control of a refrigerant flow rate adjusting unit 69 (see FIG. 2) described later of the ECU 60.
In this embodiment, after the OCV purge described later, when the hydrogen concentration is lower than a predetermined value in a state where the inside of the fuel cell stack 10 is not completely replaced with hydrogen, the radiator flow mode is selected, and the hydrogen concentration When the value reaches a predetermined value, the bypass mode is selected. Details of the control will be described later.

  The refrigerant temperature sensor 44 is a sensor that detects the temperature of the refrigerant on the outlet side of the fuel cell stack 10, and the detected temperature value is acquired by the ECU 60. In the present embodiment, the temperature value detected by the refrigerant temperature sensor 44 is used as a temperature value in the fuel cell stack 10 for the control of the control means 61 (see FIG. 2) described later.

<ECU>
The ECU 60 is a control device that electronically controls the fuel cell system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like. The ECU 60 appropriately controls various devices in accordance with programs stored therein.

The ECU 60 controls the power generation unit 61 (see FIG. 6) for controlling power generation until the anode system is completely replaced with hydrogen after the start of the fuel cell stack 10 and after hydrogen replacement by the OCV purge described above. 2).
As shown in FIG. 2, the control means 61 includes a hydrogen concentration calculating means 61A (concentration specifying means) that is specified by calculating a hydrogen concentration, and a fuel cell stack based on the hydrogen concentration calculated by the hydrogen concentration calculating means 61A. And an operation control means 61B for controlling 10 operations.

  The hydrogen concentration calculation means 61A includes a startup hydrogen concentration calculation means 62, a timer 62b, a purge integrated amount calculation means 63, a hydrogen concentration increase amount calculation means 64, and an estimated hydrogen concentration calculation means 65.

The startup hydrogen concentration calculating means 62 calculates the hydrogen concentration at startup of the fuel cell stack 10 from the elapsed time since the fuel cell stack 10 stopped, the so-called soak time, and the refrigerant temperature. Specifically, here, the hydrogen concentration is acquired based on a map or function stored in advance in the map storage unit 62a.
The map stored in the map storage unit 62a is, for example, as shown in FIG. 3. For example, the relationship between the soak time and the hydrogen concentration is expressed by a function represented by a curve that takes into account the temperature of the refrigerant. A corresponding one can be used. FIG. 3 shows that the hydrogen concentration tends to be higher as the soak time is shorter and the refrigerant temperature is lower, and the hydrogen concentration is lower as the soak time is longer and the refrigerant temperature is higher. The hydrogen concentration calculated by the startup hydrogen concentration calculating means 62 is output to the estimated hydrogen concentration calculating means 65.
The calculation of the hydrogen concentration by the start time hydrogen concentration calculation means 62 is performed immediately after the start, that is, before the OCV purge is performed.

  Here, the soak time is measured by a timer 62 b connected to the startup hydrogen concentration calculating means 62. The timer 62b is reset by the ECU 60 when the driving of the fuel cell stack 10 is stopped, and measures the elapsed time from the reset time.

  The purge integrated amount calculation means 63 calculates the integrated amount of hydrogen used for purging after the fuel cell stack 10 is started. Specifically, for example, the pressure after the shutoff valve 22 (see FIG. 1) is detected by a sensor (not shown), and the purge integrated amount can be obtained from the pressure value and the purge time. The calculated purge integrated amount is output to the hydrogen concentration increase amount calculating means 64.

The hydrogen concentration increase amount calculating means 64 calculates the hydrogen concentration increase amount from the input purge integrated amount. Specifically, here, the hydrogen concentration increase amount is acquired based on a map or function stored in advance in the map storage unit 64a.
As the map stored in the map storage unit 64a, for example, a function as shown in FIG. 4 can be used. The calculated hydrogen concentration increase amount is output to the estimated hydrogen concentration calculation means 65.

  The estimated hydrogen concentration calculation means 65 is a currently estimated hydrogen concentration from the hydrogen concentration at startup calculated by the startup hydrogen concentration calculation means 62 and the hydrogen concentration increase calculated by the hydrogen concentration increase calculation means 64. Is calculated. Specifically, the hydrogen concentration increase amount is added to the hydrogen concentration at the time of startup to calculate the currently estimated hydrogen concentration. The calculated hydrogen concentration value is output to the hydrogen concentration determination means 66 of the operation control means 61B.

  The hydrogen concentration determination means 66 of the operation control means 61B determines whether or not the calculated hydrogen concentration value is larger than a predetermined value set in advance. That is, it is determined whether the hydrogen concentration after hydrogen replacement by the OCV purge is higher than a predetermined value (whether the hydrogen concentration is such that power generation that does not impose a burden on the fuel cell stack 10) is possible.

The generated current control unit 67 controls the VCU 52 based on the determination by the hydrogen concentration determination unit 66. For example, when the hydrogen concentration value (concentration value) is smaller than a predetermined value, a power generation current upper limit value capable of generating power is calculated from the hydrogen concentration value and the detected refrigerant temperature value.
Here, the generated current control means 67 is configured so that the current value of the generated current decreases as the specified hydrogen concentration value is lower than the predetermined value, and the generated current value increases as the detected temperature value is higher than the predetermined value. The current value is controlled to be small. Specifically, here, the generated current upper limit value is acquired based on a map or function stored in advance in the map storage unit 67a.
The map stored in the map storage unit 67a is, for example, as shown in FIG. 5, and for example, the relationship between the hydrogen concentration and the generated current upper limit value is represented by a straight line that takes into account the refrigerant temperature. The one corresponding to the function can be used. In FIG. 5, as the hydrogen concentration value is lower than the predetermined value, the upper limit value of the generated current tends to be lower, and the current value of the generated current is controlled to be smaller, and the detected temperature value is lower than the predetermined value. The higher the value, the lower the generated current upper limit value, and the smaller the generated current value is controlled. The calculated generated current upper limit value is output to the VCU 52.
When the hydrogen concentration determination unit 66 determines that the above-described hydrogen concentration value is greater than a predetermined value, the generated current control unit 67 outputs a signal permitting rated power generation to the VCU 52.

The purge control unit 68 controls the purge valve 24 based on the determination by the hydrogen concentration determination unit 66. For example, when the hydrogen concentration value is smaller than a predetermined value, control is performed to increase the purge frequency (number of times / hour) more than before so that the purge amount is increased, or the purge time per time is increased. Control to change the setting.
In addition, when the hydrogen concentration determination means 66 determines that the above-described hydrogen concentration value is larger than a predetermined value, the control is performed so that the purge amount becomes a normal purge amount without performing control to increase the purge amount.

The refrigerant flow rate adjustment unit 69 controls the purge valve 24 based on the determination by the hydrogen concentration determination unit 66. For example, when the value of the hydrogen concentration is smaller than a predetermined value, the flow rate adjustment valve 41 is controlled in the opening direction in order to keep the temperature of the refrigerant low and lighten the burden on the fuel cell stack 10.
Further, when the hydrogen concentration determination means 66 determines that the hydrogen concentration value is larger than a predetermined value, it is determined that the fuel cell stack 10 is not burdened, and the flow rate adjustment valve 41 is to perform warm-up operation. Is controlled in the closing direction.

Further, as necessary, the refrigerant flow rate adjusting unit 69 controls the purge valve 24 based on the determination by the hydrogen concentration determination unit 66. For example, when the value of the hydrogen concentration is smaller than a predetermined value, the switching valve 43 is controlled to keep the temperature of the refrigerant low and lighten the burden on the fuel cell stack 10, and the refrigerant is supplied to the radiator 42 (see FIG. 1). ) (Radiator flow mode).
Further, when the hydrogen concentration determination means 66 determines that the above-described hydrogen concentration value is larger than the predetermined value, it is determined that the fuel cell stack 10 is not burdened, and the switching valve 43 is set to perform warm-up operation. Control is performed so that the refrigerant flows through the radiator 42 (see FIG. 1) (bypass mode).

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1 will be described with reference to each drawing as appropriate with reference mainly to FIG.
When the IG 60a is turned on in step S1, the ECU 60 that has detected this on signal executes various processes at the time of activation, and in step S2, the hydrogen concentration calculation means 61A of the control means 61 determines the hydrogen concentration at the time of activation. calculate. That is, the hydrogen concentration is acquired from FIG. 3 based on the soak time measured by the timer 62 b and the temperature value from the refrigerant temperature sensor 44.

In step S3, OCV purge is executed. Here, the OCV purge is a procedure necessary for determining whether or not the fuel cell stack 10 is in a state where power generation is possible before the fuel cell stack 10 performs power generation. This is an operation to replace with hydrogen and increase the hydrogen concentration. The OCV purge is determined using, for example, an open circuit voltage (also referred to as an open end voltage). This OCV is determined by a voltage value V obtained from a voltmeter (not shown). The OCV purge is performed by opening the purge valve 24. This is because the hydrogen concentration in the anode system may decrease during the soak (while the system is stopped), and if the hydrogen concentration is low, stable power generation of the fuel cell stack 10 cannot be performed.
The condition for completing the OCV check can be determined, for example, when the voltage value V exceeds a predetermined voltage.

  In step S4, the fuel cell stack 10 starts power generation upon completion of the OCV check. That is, the ECU 60 turns on the contactor 54 and issues a command for taking out current from the fuel cell stack 10 to the VCU 52 (fuel cell starting means).

  In step S5, the integrated amount calculation unit 63 calculates the integrated amount of hydrogen used for purging after the fuel cell stack 10 is started.

  In step S6, the hydrogen concentration increase amount calculating means 64 calculates the hydrogen concentration increase amount from the input purge integrated amount.

  In step S <b> 7, the estimated hydrogen concentration calculation unit 65 currently estimates from the hydrogen concentration at startup calculated by the startup hydrogen concentration calculation unit 62 and the hydrogen concentration increase calculated by the hydrogen concentration increase calculation unit 64. Calculate the hydrogen concentration.

  In step S8, the ECU 60 determines whether the warm-up has been completed. Here, it is determined whether or not the temperature value T of the refrigerant has reached a warm-up completion temperature (for example, 60 ° C. or higher) inherent in the fuel cell stack 10.

  When the temperature value T of the refrigerant has not reached the warm-up completion temperature (for example, 60 ° C. or higher) (step S8: No), the hydrogen concentration is determined by the hydrogen concentration determination unit 66 of the operation control unit 61B in step S9. It is determined whether or not the value (calculated in step S7) is larger than a predetermined value (warm-up transition hydrogen concentration, for example, hydrogen concentration is 95%).

  When the value of the hydrogen concentration (calculated in step S7) is smaller than the predetermined value (step S9: No), the generated current upper limit value is calculated by the generated current control means 67 in step S10. That is, a power generation current upper limit value that can be generated is acquired from the hydrogen concentration value and the refrigerant temperature value T based on FIG. 5, and the VCU 52 is controlled so as not to exceed the acquired power generation current upper limit value. That is, the VCU 52 is configured such that the current value of the generated current decreases as the hydrogen concentration value is lower than the predetermined value, and the current value of the generated current decreases as the detected temperature value T is higher than the predetermined value. To control.

  In step S11, the purge control means 68 controls the purge valve 24 so that the purge amount increases.

Further, in step S12, the flow rate adjusting valve 41 is controlled in the opening direction in order to reduce the burden on the fuel cell stack 10 by keeping the refrigerant temperature value T low by the refrigerant flow rate adjusting means 69. If the hydrogen concentration decreases, the refrigerant flow may be in either the bypass mode or the radiator flow mode.
Thereafter, step S8 and subsequent steps are repeated.

  On the other hand, in step S9, when the hydrogen concentration (calculated in step S7) is larger than the predetermined value (Yes), in step S13, the power generation current control means 67 permits the rated power generation of the VCU 52.

  In step S14, the purge control means 68 controls the purge valve 24 to a normal purge amount. In step S15, the refrigerant flow rate adjusting means 69 assumes that the fuel cell stack 10 is not burdened. In order to perform machine operation, the flow rate adjustment valve 41 is controlled in the opening direction. Thereafter, step S8 and subsequent steps are repeated.

  Thereafter, in step S8, when the temperature value T of the refrigerant reaches the warm-up completion temperature (for example, 60 ° C. or higher) (Yes), the warm-up is completed in step S16, and the refrigerant flow rate adjustment is performed in step S17. The control of the flow rate adjustment valve 41 by the means 69 is released, and then the process ends.

According to the fuel cell system of the present embodiment described above, when the warm-up of the fuel cell stack 10 is not completed (when the warm-up completion temperature is not reached (step S8: No)), that is, the fuel cell. When the power generation stability of the stack 10 is not ensured, the value of the hydrogen concentration is detected, and when the value of the hydrogen concentration is a low concentration that does not reach the predetermined value (step S9: No), Since the power generation of the fuel cell stack 10 is limited, power generation is performed at a current value corresponding to the hydrogen concentration and the temperature in the fuel cell stack 10 in a situation where the anode system is not completely replaced with hydrogen after gas replacement. Can do. Accordingly, Ki out to reduce the burden on the fuel cell stack 10, so that the deterioration of the fuel cell stack 10 can be suitably suppressed.

Further, the control unit 61, the value of the specified hydrogen concentration is lower than the predetermined value, and, when the temperature value T is lower than the predetermined value, and controls so as to increase the passing flow rate of the refrigerant, the fuel cell In the situation where the temperature in the stack 10 is lowered and the inside of the anode system after the gas replacement is not completely replaced with hydrogen, the reactivity can be lowered, and the electrodes (catalyst, etc.) can be protected. Thereby, deterioration of the fuel cell stack 10 can be suitably suppressed.

  Further, since the control means 61 performs control so as to increase the amount of anode off-gas discharged by the purge valve 24, the inside of the fuel cell stack 10 is suitably replaced with hydrogen, and the burden on the fuel cell stack 10 is increased. Can be reduced, and the deterioration of the fuel cell stack 10 can be more suitably suppressed. In addition, the activation time can be shortened.

  Further, since the control means 61 releases the limit of the generated current when the value of the hydrogen concentration reaches a predetermined value, the generated current is drawn from the fuel cell stack 10 toward the external load at a rating. Thereby, suitable electric power generation can be performed while suppressing deterioration of the fuel cell stack 10.

Further, the control unit 61, even if the value of the hydrogen concentration reaches a predetermined value, until the temperature of the fuel cell stack 10 reaches the warm-up completion temperature, because it limits to reduce the passing flow rate of the refrigerant, Warm-up is promoted, and suitable power generation can be performed while suppressing deterioration of the fuel cell stack 10.

Further, the control unit 61, when the temperature of the fuel cell stack 10 has reached the warm-up completion temperature, so to release the restriction of the passage flow rate of the refrigerant, while suppressing the fuel cell stack 10 from deteriorating Suitable power generation can be performed.

  In the above-described embodiment, the flow rate of the refrigerant is adjusted mainly using the flow rate adjustment valve 41. However, the present invention is not limited to this, and by appropriately controlling the rotational speed of the refrigerant pump 40 by the control of the ECU 60. The flow rate of the refrigerant may be adjusted in the same manner as when the flow rate adjustment valve 41 is used.

  The flow rate of the refrigerant may be adjusted by singly or in combination of the opening / closing control of the flow rate adjustment valve 41, the switching control of the switching valve 43, and the control of the rotation speed of the refrigerant pump 40.

  Further, instead of the refrigerant temperature sensor 44, the temperature of the membrane electrode assembly (MEA) may be directly measured and used as a temperature value.

  In the above embodiment, the hydrogen concentration is calculated by calculating the hydrogen concentration using the hydrogen concentration calculation means 61A. However, the present invention is not limited to this, and a hydrogen concentration sensor may be provided to detect the hydrogen concentration. Good. Alternatively, an oxygen concentration sensor may be provided in the cathode system, and the hydrogen concentration may be estimated based on the value.

It is a block diagram which shows the fuel cell system of one Embodiment of this invention. It is a block diagram which shows a control means. It is a figure which shows the relationship between soak time and hydrogen concentration. It is a figure which shows the relationship between purge integrated amount and hydrogen concentration raise amount. It is a figure which shows the relationship between hydrogen concentration and an electric power generation upper limit. It is a flowchart which shows operation | movement of a fuel cell system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell stack 24 Purge valve (purge means)
41 Flow Control Valve 43 Switching Valve 44 Refrigerant Temperature Sensor 52 VCU
55 Current sensor 60 ECU
61 Control means

Claims (10)

A fuel cell that generates electricity by a reaction between the fuel gas and the oxidant gas;
Fuel gas supply means for supplying the fuel gas to the fuel cell;
Replacement means for replacing the inside of the fuel gas flow path through which the fuel gas flows with the fuel gas when the fuel cell is activated;
Fuel cell starting means for starting power generation of the fuel cell after performing gas replacement by the replacement means;
A concentration specifying means for determining the concentration of the fuel gas in the fuel cell;
A temperature detecting means for detecting the temperature in the fuel cell, and a fuel cell system comprising:
A control means for controlling the fuel cell system;
The control means includes
Whether or not the temperature in the fuel cell detected by the temperature detection means has reached the warm-up completion temperature at which the warm-up has been completed after the fuel cell start-up means starts the power generation of the fuel cell. Judgment,
If the warm-up completion temperature has been reached, it is determined that the fuel cell has been warmed-up,
When the warm-up completion temperature has not been reached, it is determined whether or not the specified concentration value of the fuel gas has reached a predetermined value,
If the concentration value of the fuel gas has reached a predetermined value, the rated power generation of the fuel cell is permitted, and if not, the power generation current of the fuel cell is limited,
When control for limiting the generated current, and controlled so that the current value of the generator current the lower the density values specified decreases, the current value of the temperature in said detected fuel cell The higher generated current A fuel cell system that is controlled to be small. A fuel cell that generates electricity by a reaction between the fuel gas and the oxidant gas;
Fuel gas supply means for supplying the fuel gas to the fuel cell;
Replacement means for replacing the inside of the fuel gas flow path through which the fuel gas flows with the fuel gas when the fuel cell is activated;
Fuel cell starting means for starting power generation of the fuel cell after performing gas replacement by the replacement means;
A concentration specifying means for determining the concentration of the fuel gas in the fuel cell;
A fuel cell system having a temperature detecting means that detect the temperature in the fuel cell,
A control means for controlling the fuel cell system;
The control means includes
Whether or not the temperature in the fuel cell detected by the temperature detection means has reached the warm-up completion temperature at which the warm-up has been completed after the fuel cell start-up means starts the power generation of the fuel cell. Judgment,
If the warm-up completion temperature has been reached, it is determined that the fuel cell has been warmed-up,
When the warm-up completion temperature has not been reached, it is determined whether or not the specified concentration value of the fuel gas has reached a predetermined value,
If the concentration value of the fuel gas has reached a predetermined value, the rated power generation of the fuel cell is permitted, and if not, the power generation current of the fuel cell is limited,
A fuel cell system, wherein control is performed so as to increase a flow rate of a refrigerant flowing through the fuel cell at the time of control for limiting a generated current . Before SL control means, the fuel cell system according to claim 1, wherein when control for limiting the generated current, the controller controls so as to increase the passing flow rate of the refrigerant flowing through the inside of the fuel cell. Wherein, when the density value becomes the predetermined value, the temperature of the detected said fuel cell until it reaches the warm-up completion temperature is limited to reduce the passing flow rate of the coolant The fuel cell system according to claim 2 or claim 3, wherein Wherein, when the temperature in the detected the fuel cell has reached the warm-up completion temperature, the fuel cell according to claim 4, characterized in that to release the restriction of the passage flow rate of the coolant system. Purge means for purging the fuel gas discharged from the fuel cell;
6. The control unit according to claim 1, wherein the control unit performs control so as to increase an amount of fuel gas discharged by the purge unit during control for limiting the generated current. 7. Fuel cell system.   The fuel cell system according to any one of claims 1 to 6, wherein the control unit releases the restriction of the generated current when the concentration value reaches a predetermined value. Refrigerant temperature detection means for detecting the temperature of the refrigerant flowing through the fuel cell,
The fuel cell according to any one of claims 1 to 7, wherein the temperature detection means uses the temperature of the refrigerant detected by the refrigerant temperature detection means as a temperature inside the fuel cell. system. Purge means for purging the fuel gas discharged from the fuel cell;
The control means performs purging by setting the amount of fuel gas discharged by the purge means at a normal amount smaller than that at the time of control for limiting the power generation current of the fuel cell during control for permitting rated power generation of the fuel cell. 6. The fuel cell system according to claim 4, wherein the control is performed so that the flow rate of the refrigerant is reduced. The concentration specifying means is a start-time hydrogen concentration calculation means for obtaining a hydrogen concentration at the start-up of the fuel cell based on an elapsed time since the fuel cell was stopped and a refrigerant temperature detected by the refrigerant temperature detection means. With
9. The fuel cell system according to claim 8, wherein the hydrogen concentration obtained by the start-up hydrogen concentration calculating means is such that the hydrogen concentration decreases as the elapsed time is longer and the temperature of the refrigerant is higher.

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