JP5224080B2 - Fuel cell system and off-gas purge method - Google Patents

Description

  The present invention relates to a fuel cell system in which a variable gas amount supply device is provided in a fuel supply system of a fuel cell, and an off-gas purge method.

  Currently, a fuel cell system including a fuel cell that receives a supply of reaction gas (fuel gas and oxidizing gas) and generates electric power has been proposed and put into practical use. Such a fuel cell system is provided with a fuel supply channel for flowing fuel gas supplied from a fuel supply source such as a hydrogen tank to the fuel cell.

In general, when the supply pressure of the fuel gas from the fuel supply source is extremely high, a pressure regulating valve (regulator) that reduces the supply pressure to a certain value is provided in the fuel supply passage (for example, , See Patent Document 1).
JP 2004-342386 A

  However, in the pressure regulating valve described in Patent Document 1, the supply pressure of the fuel gas is fixed due to its structure, so that it is difficult to quickly change the supply pressure of the fuel gas according to the operation state. (That is, the responsiveness is low), and high-precision pressure regulation that changes the target pressure in multiple stages is impossible.

  In addition, the fuel cell system supplies the fuel gas off-gas discharged from the fuel cell again to the fuel cell and reuses it. When the concentration of the fuel gas in the off-gas decreases (impurity concentration increases), the off-gas is released to the atmosphere. It is necessary to control to a target pressure value that can prevent backflow of off-gas during such purging. However, high-precision pressure adjustment is difficult with the pressure control valve, and redundancy has to be provided for the target pressure value.

  The present invention has been made in view of such circumstances, and it is possible to appropriately change the supply pressure of the fuel gas in accordance with the operating state of the fuel cell, and to release the off-gas discharged from the fuel cell ( An object of the present invention is to provide a fuel cell system and an off-gas purging method capable of optimizing a target pressure value when purging.

Emissions to achieve the object, to discharge the fuel cell, a fuel supply passage to the fuel cell, the gas amount variable supply device provided in the fuel supply channel, the off-gas from the fuel cell and the flow path, and control means for driving and controlling the gas amount variable supply device, the fuel cell system equipped with, provided with a atmospheric pressure measuring means, the control means, the gas amount variable supply device upon release of the off-gas the target pressure value of it is thought that a method of controlling based on the detection result of the atmospheric pressure measuring means.

  In this case, the discharge flow path includes a circulation flow path for returning the off gas discharged from the fuel cell to the fuel supply flow path, and a purge path connected to the circulation flow path for purging the off gas to the atmosphere. A purge passage and a purge valve provided in the purge passage, and the control means may increase the target pressure value of the gas amount variable supply device before the purge valve is opened. .

  According to this configuration, the amount of gas depends on the operating state of the fuel cell (power generation amount (power, current, voltage) of the fuel cell, temperature of the fuel cell, abnormal state of the fuel cell system, abnormal state of the fuel cell body, etc.). The operating state of the variable supply device (valve element opening (gas passage area), valve element opening time (gas injection time), etc.) can be set. Therefore, the supply pressure of the fuel gas can be appropriately changed according to the operating state of the fuel cell, and the responsiveness can be improved.

  As the gas amount variable supply device, for example, an injector that adjusts the gas state on the upstream side of the fuel supply channel and supplies the gas state to the downstream side, or a variable regulator can be adopted. The “gas state” means a gas state (flow rate, pressure, temperature, molar concentration, etc.), and particularly includes at least one of a gas flow rate and a gas pressure.

  Moreover, in order to control the target pressure value of the gas amount variable supply device in relation to the opening of the purge valve based on the detection result of the atmospheric pressure measuring means, the target is added with the estimated atmospheric pressure fluctuation of the outlet to the atmosphere. Even if the pressure value is not set, the differential pressure before and after the purge valve is stabilized, so that a lower target pressure value can be obtained and the redundancy can be reduced.

  In the fuel cell system, the target pressure value of the gas amount variable supply device may be increased before the purge valve is opened.

  By adopting such a configuration, it is possible to reduce the redundancy of the target pressure value while suppressing the backflow before and after the purge valve and the insufficiency of the purge amount.

On the other hand, Oite the present invention, a fuel cell, a fuel supply passage to the fuel cell, the gas amount variable supply device provided in the fuel supply channel, the off-gas discharged from the fuel cell the A circulation passage for returning to the fuel supply passage, a purge passage connected to the circulation passage for purging off-gas from the fuel cell, a purge valve provided in the purge passage, and the gas and control means for driving and controlling the amount variable supply device, the fuel cell system wherein the control means, the purge valve by increasing the target pressure value of the gas amount variable supply device before the opening of the purge valve The pressure on the upstream side is increased to the first target pressure value.

  According to the above configuration, the operating state of the variable gas amount supply device according to the operating state of the fuel cell (the operating state grasped by the current value and voltage value during power generation, the operating state at startup, the intermittent operating state, etc.) (The injection flow rate and injection time of the gas amount variable supply device) can be set. Therefore, the supply pressure of the fuel gas can be appropriately changed according to the operating state of the fuel cell, and the responsiveness can be improved. Further, it is possible to suppress the backflow before and after the purge valve during the purge operation and the insufficiency of the purge amount.

The control unit further increases the target pressure value of the variable gas amount supply device before opening the purge valve when the required output to the fuel cell is larger than a predetermined threshold value. the pressure upstream of the valve, in which is increased to the second target pressure value smaller than the first target pressure value.

  When such a configuration is adopted, when the output demand to the fuel cell becomes large and the consumption amount of the fuel gas becomes large, the pressure upstream of the purge valve is set to the second pressure smaller than the first target pressure value. Since the pressure is increased to the target pressure value, an event that the valve cannot be opened without reaching the target pressure value can be mitigated.

Another fuel cell system according to the present invention includes a fuel cell, a fuel supply channel to the fuel cell, a gas amount variable supply device provided in the fuel supply channel, and a discharge from the fuel cell. A circulation channel for returning the generated off-gas to the fuel supply channel, a pump provided in the circulation channel, and a purge channel connected to the circulation channel for purging off-gas from the fuel cell And a purge valve provided in the purge flow path, and a control means for driving and controlling the gas amount variable supply device and the pump, wherein the control means opens the purge valve. The pressure upstream of the purge valve is raised to the first target pressure value by raising the target pressure value of the gas amount variable supply device before, and the pressure upstream of the purge valve During the rise It may be one that stops the rotational speed feedback control of the pump.

  By adopting such a configuration, it is possible to suppress wasteful power consumption in the pump and improve the fuel consumption rate.

An off-gas purging method for a fuel cell system according to the present invention includes a fuel cell, a fuel supply channel to the fuel cell, a gas amount variable supply device provided in the fuel supply channel, and an exhaust gas from the fuel cell. A circulation passage for returning the off-gas to the fuel supply passage, a purge passage connected to the circulation passage for purging off-gas from the fuel cell, and a purge valve provided in the purge passage And an off-gas purge method for a fuel cell system, wherein the target pressure value of the variable gas amount supply device is increased before the purge valve is opened. Thus, a step of increasing the pressure upstream of the purge valve to the first target pressure value is provided.

In addition to this step, when the required output to the fuel cell is larger than a predetermined threshold value, the purge valve is increased by raising the target pressure value of the gas amount variable supply device before the purge valve is opened. A step of increasing the pressure upstream of the first target pressure value to a second target pressure value smaller than the first target pressure value.

Further, an off-gas purge method for another fuel cell system according to the present invention includes a fuel cell, a fuel supply channel to the fuel cell, a gas amount variable supply device provided in the fuel supply channel, and the fuel. A circulation passage for returning off-gas discharged from the battery to the fuel supply passage; a pump provided in the circulation passage; and a purge passage connected to the circulation passage for purging off-gas from the fuel cell. a purge flow path, a said the purge flow path provided with a purge valve, the off gas purging process of the fuel cell system and a control means for driving and controlling the gas amount variable supply device and the pump, the gas A step of increasing the pressure upstream of the purge valve to a first target pressure value by increasing a target pressure value of the variable amount supply device, and during the rise of the pressure upstream of the purge valve, Pong It is intended to cancel the rotational speed feedback control.

  Employing the above configuration makes it possible to stabilize the differential pressure before and after the purge valve during off-gas purge, and reduce the redundancy of the target pressure value.

  According to the present invention, the supply pressure of the fuel gas can be appropriately changed according to the operating state of the fuel cell, and the target pressure when the off gas discharged from the fuel cell is released (purged). The efficiency of the fuel cell system can be improved by reducing the redundancy of values.

Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the following description , an example in which the present invention is applied to an in-vehicle power generation system of a fuel cell vehicle (moving body) will be described.

First, with reference to FIG. 1, the configuration of the fuel cell system 1 according to Kazumi facilities embodiment of the present invention.

Fuel cell system 1, as shown in FIG. 1, the supply provided with a fuel cell 10 which generates electric power by being supplied with reaction gas (oxidation gas and fuel gas) to the fuel cell 10 the air as the oxidizing gas The system includes an oxidizing gas piping system 2, a hydrogen gas piping system 3 for supplying hydrogen gas as a fuel gas to the fuel cell 10, and a control device (control means) 4 for integrated control of the entire system.

  The fuel cell 10 has a stack structure in which a required number of unit cells that generate power upon receiving a reaction gas are stacked. The electric power generated by the fuel cell 10 is supplied to a PCU (Power Control Unit) 11. The PCU 11 includes an inverter, a DC-DC converter, and the like that are disposed between the fuel cell 10 and the traction motor 12. Further, the fuel cell 10 is provided with a current sensor 13 for detecting a current during power generation.

  The oxidant gas piping system 2 includes an air supply passage 21 that supplies the oxidant gas (air) humidified by the humidifier 20 to the fuel cell 10, and an air exhaust that guides the oxidant off-gas discharged from the fuel cell 10 to the humidifier 20. A flow path 22 and an exhaust flow path 23 for guiding the oxidizing off gas from the humidifier 20 to the outside are provided. The air supply passage 21 is provided with an air compressor 24 that takes in the oxidizing gas in the atmosphere and pumps it to the humidifier 20.

  The hydrogen gas piping system 3 includes a hydrogen tank 30 as a fuel supply source storing high-pressure (for example, 70 MPa) hydrogen gas, and hydrogen as a fuel supply passage for supplying the hydrogen gas from the hydrogen tank 30 to the fuel cell 10. A supply flow path 31 and a circulation flow path 32 for returning the hydrogen off-gas discharged from the fuel cell 10 to the hydrogen supply flow path 31 are provided. Instead of the hydrogen tank 30, a reformer that generates a hydrogen-rich reformed gas from a hydrocarbon-based fuel, a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state, and Can also be employed as a fuel supply source. A tank having a hydrogen storage alloy may be employed as a fuel supply source.

  The hydrogen supply channel 31 includes a shut-off valve 33 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 30, a regulator 34 that adjusts the pressure of the hydrogen gas, and an injector (variable gas amount supply device) 35. Is provided. A primary pressure sensor 41 and a temperature sensor 42 that detect the pressure and temperature of the hydrogen gas in the hydrogen supply flow path 31 are provided on the upstream side of the injector 35. Further, on the downstream side of the injector 35 and upstream of the junction between the hydrogen supply flow path 31 and the circulation flow path 32, a secondary pressure sensor (for detecting the pressure of hydrogen gas in the hydrogen supply flow path 31) ( Pressure detecting means) 43 is provided.

  The regulator 34 is a device that regulates the upstream pressure (primary pressure) to a preset secondary pressure. In the present embodiment, a mechanical pressure reducing valve that reduces the primary pressure is employed as the regulator 34. The mechanical pressure reducing valve has a structure in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. Thus, a publicly known configuration for the secondary pressure can be employed.

  In the present embodiment, as shown in FIG. 1, the upstream pressure of the injector 35 can be effectively reduced by arranging two regulators 34 on the upstream side of the injector 35. For this reason, the design freedom of the mechanical structure (a valve body, a housing, a flow path, a drive device, etc.) of the injector 35 can be increased.

  In addition, since the upstream pressure of the injector 35 can be reduced, it is possible to prevent the valve body of the injector 35 from becoming difficult to move due to an increase in the differential pressure between the upstream pressure and the downstream pressure of the injector 35. be able to. Accordingly, it is possible to widen the adjustable pressure width of the downstream pressure of the injector 35 and to suppress a decrease in responsiveness of the injector 35.

  The injector 35 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. The injector 35 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is movably accommodated and opens and closes the injection hole.

  In this embodiment, the valve body of the injector 35 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole is made two or more stages by turning on and off the pulsed excitation current supplied to the solenoid. It can be switched. The gas injection time and gas injection timing of the injector 35 are controlled by a control signal output from the control device 4, whereby the flow rate and pressure of hydrogen gas are controlled with high accuracy. The injector 35 directly opens and closes the valve (valve body and valve seat) with an electromagnetic driving force, and has a high responsiveness because its driving cycle can be controlled to a highly responsive region.

  Injector 35 changes the opening area (opening) and the opening time of the valve body provided in the gas flow path of injector 35 in order to supply the required gas flow rate downstream thereof, thereby reducing the downstream flow rate. The gas flow rate (or hydrogen molar concentration) supplied to the side (fuel cell 10 side) is adjusted.

  Since the gas flow rate is adjusted by opening and closing the valve body of the injector 35 and the gas pressure supplied downstream of the injector 35 is reduced from the gas pressure upstream of the injector 35, the injector 35 is controlled by a pressure regulating valve (pressure reducing valve, regulator). ). Further, in the present embodiment, a variable pressure control valve capable of changing the pressure adjustment amount (pressure reduction amount) of the upstream gas pressure of the injector 35 so as to match the required pressure within a predetermined pressure range in accordance with the gas requirement. (Variable regulator).

  As described above, the injector 35 of the present embodiment is the pressure-reducing device on the most downstream side in the hydrogen supply flow path 31, and functions as a flow rate adjustment valve and a variable pressure control valve. Control the pressure.

In the above-described configuration , the injector 35 is disposed upstream of the junction between the hydrogen supply channel 31 and the circulation channel 32. Further, when a plurality of hydrogen tanks 30 are employed as the fuel supply source, the injector 35 is disposed downstream of the portion where the hydrogen gas supplied from each hydrogen tank 30 merges (hydrogen gas merge portion). To do.

  A discharge channel (purge channel) 38 is connected to the circulation channel 32 via a gas-liquid separator 36 and an exhaust drain valve (purge valve) 37. The gas-liquid separator 36 collects moisture from the hydrogen off gas. The exhaust / drain valve 37 operates according to a command from the control device 4 to discharge (purge) the moisture collected by the gas-liquid separator 36 and the hydrogen off-gas containing impurities in the circulation flow path 32 to the outside. Is.

  In addition, the circulation channel 32 is provided with a hydrogen pump (pump) 39 that pressurizes the hydrogen off-gas in the circulation channel 32 and sends it to the hydrogen supply channel 31 side. The hydrogen off-gas discharged through the exhaust / drain valve 37 and the discharge passage 38 is diluted by the diluter 40 and merges with the oxidizing off-gas in the exhaust passage 23. A discharge flow path pressure sensor (atmospheric pressure measuring means) 44 that detects the pressure in the discharge flow path 38 is provided in the discharge flow path 38 between the exhaust drain valve 37 and the diluter 40.

  The pressure of the discharge flow path 38 fluctuates with respect to the atmospheric pressure when the exhaust drainage valve 37 is opened. However, when the predetermined time elapses after the exhaust drainage valve 37 is closed, the pressure becomes the atmospheric pressure. Barometric pressure can be detected. The secondary pressure sensor 43 described above detects the pressure of hydrogen gas in the hydrogen supply flow path 31, that is, detects the pressure upstream of the exhaust / drain valve 37.

  The control device 4 detects an operation amount of an acceleration operation device (accelerator or the like) provided in the vehicle, receives control information such as an acceleration request value (for example, a required power generation amount from a load device such as the traction motor 12), Control the operation of various devices in the system.

  In addition to the traction motor 12, the load device is an auxiliary device (for example, a compressor 24, a hydrogen pump 39, a cooling pump motor, or the like) necessary for operating the fuel cell 10, and various types of vehicles involved in traveling of the vehicle. It is a collective term for power consumption devices including actuators used in devices (transmissions, wheel control devices, steering devices, suspension devices, etc.), occupant space air conditioners (air conditioners), lighting, audio, and the like.

  The control device 4 is configured by a computer system (not shown). Such a computer system includes a CPU, ROM, RAM, HDD, input / output interface, display, and the like, and various control operations are realized by the CPU reading and executing various control programs recorded in the ROM. It is like that.

Specifically, as shown in FIG. 2, the control device 4 is consumed by the fuel cell 10 based on the operating state of the fuel cell 10 (current value during power generation of the fuel cell 10 detected by the current sensor 13). The flow rate of hydrogen gas (hereinafter referred to as “hydrogen consumption”) is calculated (fuel consumption calculation function: B1). In the above configuration , the hydrogen consumption is calculated and updated for each calculation cycle of the control device 4 using a specific calculation formula representing the relationship between the current value of the fuel cell 10 and the hydrogen consumption.

Further, the control device 4 determines the target of the hydrogen gas supplied to the fuel cell 10 on the downstream side of the injector 35 based on the operation state of the fuel cell 10 (current value at the time of power generation detected by the current sensor 13). A pressure value is calculated (target pressure value calculation function: B2). In the above configuration , the target pressure value is calculated and updated every calculation cycle of the control device 4 using a specific target pressure map that represents the relationship between the current value of the fuel cell 10 and the target pressure value.

Further, the control device 4 calculates a feedback correction flow rate based on the deviation between the calculated target pressure value and the detected pressure value downstream of the injector 35 detected by the secondary pressure sensor 43 (feedback correction flow rate calculation function). : B3). The feedback correction flow rate is a hydrogen gas flow rate (pressure difference reduction correction flow rate) added to the hydrogen consumption in order to reduce the deviation between the target pressure value and the detected pressure value. In the above configuration , the feedback correction flow rate is calculated and updated every calculation cycle of the control device 4 using a target tracking control law such as PI control.

Moreover, the control apparatus 4 calculates the feedforward correction | amendment flow volume corresponding to the deviation of the target pressure value calculated last time and the target pressure value calculated this time (feedforward correction | amendment flow volume calculation function: B4). The feedforward correction flow rate is a fluctuation amount of the hydrogen gas flow rate (pressure difference corresponding correction flow rate) caused by the fluctuation of the target pressure value. In the above configuration , the feedforward correction flow rate is calculated and updated every calculation cycle of the control device 4 using a specific calculation formula representing the relationship between the deviation of the target pressure value and the feedforward correction flow rate.

Further, the control device 4 determines the static flow rate upstream of the injector 35 based on the gas state upstream of the injector 35 (hydrogen gas pressure detected by the primary pressure sensor 41 and hydrogen gas temperature detected by the temperature sensor 42). (Static flow rate calculation function: B5). In the above configuration , the static flow rate is calculated and updated every calculation cycle of the control device 4 using a specific calculation formula representing the relationship between the pressure and temperature of the hydrogen gas upstream of the injector 35 and the static flow rate. To do.

Further, the control device 4 calculates the invalid injection time of the injector 35 based on the gas state upstream of the injector 35 (pressure and temperature of hydrogen gas) and the applied voltage (invalid injection time calculation function: B6). Here, the invalid injection time means the time required from when the injector 35 receives a control signal from the control device 4 until the actual injection is started. In the above configuration , the invalid injection time is calculated for each calculation cycle of the control device 4 using a specific map representing the relationship between the pressure and temperature of the hydrogen gas upstream of the injector 35, the applied voltage, and the invalid injection time. To update.

  Further, the control device 4 calculates the injection flow rate of the injector 35 by adding the hydrogen consumption amount, the feedback correction flow rate, and the feedforward correction flow rate (injection flow rate calculation function: B7). Then, the control device 4 calculates the basic injection time of the injector 35 by multiplying the value obtained by dividing the injection flow rate of the injector 35 by the static flow rate by the drive cycle of the injector 35, and the basic injection time and the invalid injection time. Are added to calculate the total injection time of the injector 35 (total injection time calculation function: B8). Here, the drive cycle means a stepped (on / off) waveform cycle representing the open / close state of the injection hole of the injector 35. The drive period is set to a constant value by the control device 4, for example.

  And the control apparatus 4 controls the gas injection time and gas injection timing of the injector 35 by outputting the control signal for implement | achieving the total injection time of the injector 35 computed through the above procedure, and fuel cell The flow rate and pressure of the hydrogen gas supplied to 10 are adjusted.

During normal operation of the fuel cell system 1, hydrogen gas is supplied from the hydrogen tank 30 to the fuel electrode of the fuel cell 10 through the hydrogen supply channel 31, and the air that has been subjected to humidification adjustment passes through the air supply channel 21. Then, power is generated by being supplied to the oxidation electrode of the fuel cell 10. At this time, the power (output request) to be drawn from the fuel cell 10 is calculated by the control device 4, and hydrogen gas and air in amounts corresponding to the amount of power generation are supplied into the fuel cell 10. In the above configuration , the pressure of the hydrogen gas supplied to the fuel cell 10 during such normal operation is controlled with high accuracy.

  Here, in the fuel cell system 1, the hydrogen off gas is returned to the hydrogen supply channel 31 by the hydrogen pump 39 in order to effectively use the hydrogen gas remaining in the hydrogen off gas discharged from the fuel cell 10. In order to prevent a decrease in the cell voltage due to an increase in the impurity concentration of the hydrogen gas on the fuel electrode side due to repeated circulation of the hydrogen off gas, the control device 4 opens the exhaust drain valve 37 at an appropriate timing to remove the hydrogen off gas from the outside. A purge process is performed to discharge (in the atmosphere).

The control device 4 executes the purge process every time a preset predetermined time elapses. In one control example , as shown in FIG. 3, when the start timing of the purge process is reached (step SA1). First, the target pressure map is changed from the target pressure map for normal operation to the target pressure map for purge (step SA2). Here, the start timing of the purge process is set to a predetermined time before the timing at which the exhaust / drain valve 37 is actually scheduled to be opened.

  After changing to the purge target pressure map, the control device 4 detects the atmospheric pressure with the discharge flow path pressure sensor 44, reads the target pressure value from the detected atmospheric pressure based on the purge target pressure map, The injector 35 is controlled so that the secondary pressure sensor 43 detects the same pressure value as the target pressure value corresponding to the detected atmospheric pressure. In the target pressure map for purging, a minimum target pressure that can discharge off-gas without causing a backflow with respect to the atmospheric pressure is set.

  When the secondary pressure sensor 43 detects the same pressure value as the target pressure value (step SA3), the control device 4 opens the exhaust / drain valve 37 that has been closed for a predetermined time. Then, the valve is closed (step SA4). Then, the control device 4 changes the target pressure map from the purge target pressure map to the target pressure map for normal operation (step SA5).

According to fuel cell system 1 described above, the operation state of the fuel cell 10 (the operating condition to be grasped by a current value or a voltage value at the time of power generation, start-up operating state, an intermittent operation state, etc.) in accordance with the injector The operating state of 35 (the injection flow rate and the injection time of the injector 35) can be set. Accordingly, the supply pressure of hydrogen gas can be appropriately changed according to the operating state of the fuel cell 10, and the responsiveness can be improved.

  Moreover, in order to control the target pressure value of the injector 35 based on the detection result of the atmospheric pressure in relation to the opening of the exhaust / drain valve 37, the target pressure regulation value added with the estimated amount of atmospheric pressure fluctuation at the discharge port to the atmosphere. Even if it is not set to, the differential pressure before and after the exhaust / drain valve 37 is stabilized, so that a lower target pressure value can be obtained and the redundancy can be reduced. As a result, cross leak can be reduced and efficiency can be improved, and the exhaust / drain valve 37 can be reduced in size and weight can be reduced, and freeze resistance can be improved.

  That is, conventionally, since the atmospheric pressure fluctuates from the low atmospheric pressure indicated by X1 in FIG. 4 to the high atmospheric pressure indicated by X2 in FIG. 4, this amount of fluctuation Y1 of the atmospheric pressure is added, Furthermore, it is necessary to set the target pressure value based on the pressure line X4 obtained by adding the required differential pressure Y3 to the pressure line X3 on which the error Y2 of the secondary side pressure sensor 43 and the like is added.

On the other hand, according to the above control example of the fuel cell system 1 , since the atmospheric pressure is detected and the target pressure value is set, there is no need to add an amount corresponding to the fluctuation of the atmospheric pressure. Since a target pressure value obtained by adding an error amount of the secondary side pressure sensor 43 and the like and adding a necessary differential pressure to the purge may be set, as shown by a broken line X5 in FIG. The target pressure value can be set based on the minimum pressure line. Such highly accurate control is also possible by using the injector 35.

  The control device 4 may increase the target pressure regulation value of the injector 35 by a predetermined value with respect to the target pressure value based on the purge target pressure map before the exhaust / drain valve 37 is opened. By controlling, the pressure on the upstream side of the exhaust / drain valve 37 can be increased with high responsiveness before the exhaust / drain valve 37 is opened.

Next, the fuel cell system 1 according to Kazumi facilities embodiment of the present invention will be described, centering on differences with respect to the control example.

In the present embodiment, the control content of the control device 4 during the purge process is different from the above control example . That is, in this embodiment, as shown in FIG. 5, the control device 4 sets the target pressure value L1 based on the target pressure map for normal operation (step SB1) during normal operation. The injector 35 is controlled so that the pressure upstream of the exhaust / drain valve 37 detected by the secondary pressure sensor 43 becomes the target pressure value L1.

  When the predetermined timing immediately before the exhaust drain valve 37 is opened (step SB2), the pressure upstream of the exhaust drain valve 37 detected by the secondary pressure sensor 43 is higher than the target pressure value L1. The first target pressure value L2 is set (step SB3). That is, the target pressure value of the injector 35 is set as the target pressure value L2, and the injector 35 is controlled so that the target pressure value L2 is detected by the secondary pressure sensor 43. Then, the control device 4 opens the exhaust / drain valve 37 after being opened for a predetermined time (step SB4).

According to the fuel cell system 1 of the present embodiment described above, the pressure on the upstream side of the exhaust / drain valve 37 is increased to the first target pressure value L2 with high responsiveness immediately before the exhaust / drain valve 37 is opened. Can do.

Here, in the present embodiment, as shown in FIG. 6, the pressure on the upstream side of the exhaust drain valve 37 detected by the secondary pressure sensor 43 in step SB3 is between step SB3 and step SB4. After setting the target pressure value to the first target pressure value L2, the pressure value P1 detected by the secondary pressure sensor 43 becomes the first target pressure value L2 (step SB3-1) and The exhaust drainage valve 37 may be opened in step SB4 on the condition that the opening timing of the exhaust drainage valve 37 for each predetermined time has passed (step SB3-2). Good (modified example 1).

  As in the first modification, the purge process waits until the pressure value P1 on the upstream side of the exhaust / drain valve 37 becomes the first target pressure value L2, and after the opening timing of the exhaust / drain valve 37 elapses. If the exhaust / drain valve 37 is opened, it is possible to correct cross leaks occurring in the fuel cell 10 and an increase in out leakage to the outside of the fuel cell system 1, thereby preventing erroneous opening such as backflow.

Further, in the present embodiment, as shown in FIG. 7, the pressure value P1 upstream from the exhaust drain valve 37 detected by the secondary pressure sensor 43 in step SB3 between step SB3 and step SB4. After the target pressure value is set to the first target pressure value L2, the pressure value P1 detected by the secondary pressure sensor 43 becomes the first target pressure value L2 (step SB3-1) and The exhaust drainage valve 37 is opened in step SB4 on the condition that the opening timing of the exhaust drainage valve 37 set every predetermined time has elapsed (step SB3-2). In this case, when the pressure value P1 detected by the secondary pressure sensor 43 does not become the first target pressure value L2 in step SB3-1, the waiting time W1 is added by ΔT for each determination, and a predetermined upper limit is set. Time (Step SB3-1-1, SB3-1-2), and when the waiting time reaches a predetermined upper limit time, the secondary pressure sensor 43 is higher than the first target pressure value L2 by a predetermined value. The injector 35 may be controlled so that the temporary target value is detected (step SB3-1-3).

  That is, if the pressure value P1 detected by the secondary pressure sensor 43 does not become the first target pressure value L2 even after waiting for a predetermined waiting time, the injector 35 is temporarily set higher than the first target pressure value L2. By controlling so as to obtain the target value, the control is forcibly performed so that the pressure value P1 detected by the secondary side pressure sensor 43 becomes the first target pressure value L2.

  However, also in this case, after the pressure value P1 detected by the secondary side pressure sensor 43 becomes the first target pressure value L2 (step SB3-1), the exhaust water drainage at every predetermined time point set in advance. On the condition that the valve opening timing of the valve 37 has passed (step SB3-2), the exhaust / drain valve 37 is opened in step SB4 (modified example 2).

  If the control is performed as in the second modification, the pressure value P1 detected by the secondary pressure sensor 43, which may occur due to cross leak occurring in the fuel cell 10 or increase in out leak to the outside of the fuel cell system 1, is first. The situation where the target pressure value L2 is not reached can be corrected, and the valve opening timing can be kept as much as possible.

Furthermore, in each of the first and second modifications of the present embodiment, as shown in FIG. 8, when the predetermined timing immediately before the exhaust drainage valve 37 is opened in step SB2 between step SB2 and step SB3, It is determined whether the output request to the fuel cell 10 is equal to or less than a predetermined threshold value set in advance (step SB2-1), and the output request to the fuel cell 10 is set to a predetermined value set in advance. If the output request to the fuel cell 10 becomes larger than a predetermined threshold value set in advance, there is an acceleration request or the like and hydrogen is consumed. A pressure value P1 upstream of the exhaust / drain valve 37 detected by the secondary pressure sensor 43 is set to a second target pressure value that is higher than the target pressure value L1 during normal control and lower than the first target pressure value L2. Set to L3 Which may be (step SB2-2).

  That is, when the output request to the fuel cell 10 is less than or equal to a predetermined threshold value, control is performed in the same manner as in the first and second modifications, and the output request to the fuel cell 10 is greater than the predetermined threshold value set in advance. In this case, the target pressure value of the injector 35 is set to the target pressure value L3, and the injector 35 is controlled so that the target pressure value L3 is detected by the secondary pressure sensor 43, and the secondary pressure sensor When the pressure value P1 of 43 becomes the target pressure value L3 (step SB3-1 ′), the valve opening timing of the exhaust / drain valve 37 at every preset predetermined time has passed (step SB3-2). As a condition, the exhaust / drain valve 37 is opened in step SB4.

  In FIG. 8, when the determination at step SB3-1 ′ is NO, step SB3-1 ′ is repeated as in Modification 1, but when the determination at step SB3-1 ′ is NO. , Step SB3-1-1, SB3-1-2 or Step SB3-1-1, SB3-1-3 of Modification 2 may be executed to return to Step SB3-1 ′ (as described above, Example 3).

  If the output demand is high, such as during acceleration, the hydrogen consumption will increase and the pressure increase rate will slow down. However, if controlled as in this modified example 3, the valve will open at a low target pressure value L3, and the exhaust will be exhausted forever. The event that the drain valve 37 cannot be opened can be alleviated.

Here, the control unit 4, during the purge process as described above, so that the rise in pressure upstream of the exhaust drainage valve 37 detected by the secondary pressure sensor 43, the rotational speed of the hydrogen pump 39 The feedback control may be stopped. Alternatively, the power supply to the hydrogen pump 39 may be stopped while the pressure upstream of the exhaust / drain valve 37 detected by the secondary pressure sensor 43 is increasing.

  By controlling in this way, wasteful power consumption in the hydrogen pump 39 can be suppressed, and the fuel consumption rate can be improved.

  That is, when the pressure on the upstream side of the exhaust / drain valve 37 increases in the purge process described above, a pressure change occurs. When the exhaust / drain valve 37 is opened, the flow rate and the suction pressure of the hydrogen pump 39 are reduced, and the exhaust / drain valve is further reduced. When the valve 37 is closed, the flow rate and the suction pressure of the hydrogen pump 39 are increased. In addition, when the normal process is resumed after the purge process is completed, a pressure change occurs.

  In such a situation, since the load of the hydrogen pump 39 fluctuates greatly, the rotation speed feedback control of the hydrogen pump 39 consumes more power, but the purge process increases the stoichiometric ratio. Since the fuel cell 10 can be stably operated, power consumption can be suppressed by stopping the rotational speed feedback control of the hydrogen pump 39 or by stopping the power supply to the hydrogen pump 39.

Further, the control unit 4, as the target pressure map for ordinary operation, the target pressure map of the high-pressure side to the target pressure map of the low-pressure side, may be provided a map of the plurality of stages, immediately after the purge process described above is Alternatively, the control may be performed using the target pressure map on the lowest pressure side, and the control may be performed by gradually changing to the target pressure map on the high pressure side over time (modified example 4).

  That is, immediately after the purge process, the hydrogen concentration is high, so that stable operation is possible even when the pressure is low as indicated by Z1 in FIG. 9, while the hydrogen concentration decreases as the operating time elapses. , Z3, and Z4, it is possible to always stably operate by changing the pressure to the target pressure map on the high pressure side and increasing the pressure step by step. By controlling in this way, the pressure can be minimized, so that cross leakage can be suppressed and power generation efficiency can be improved.

Further, since preferably from previously drained of water in exhaust drainage valve 37 for discharging the hydrogen off-gas, the control device 4 to control so as to stepwise increase from low pressure pressure for discharging Anyway.

In the above description , an example in which the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been shown. A battery system can also be installed. Further, the fuel cell system according to the present invention may be applied to a stationary power generation system used as a power generation facility for a building (house, building, etc.).

The “atmosphere” may be a predetermined space that is affected by atmospheric pressure. For example, it may be interpreted as including a hydrogen concentration reducing means such as a diluter 40 or a hydrogen treatment device provided on the exhaust flow path 23.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a control block diagram for demonstrating the control aspect of the control apparatus of the fuel cell system shown in FIG. It is a flowchart for explaining the purge processing of fuel cell systems. It is a characteristic diagram for demonstrating the pressure value of the purge process of a fuel cell system. It is a flowchart for demonstrating the purge process of the fuel cell system which concerns on one Embodiment of this invention. Is a flow chart for explaining a first modification of the purging process of the fuel cell system according to an embodiment of the present invention. Is a flow chart for explaining a second modification of the purging process of the fuel cell system according to an embodiment of the present invention. Is a flow chart for explaining a third modification of the purging process of the fuel cell system according to an embodiment of the present invention. It is a characteristic diagram for demonstrating control after the purge process of the fuel cell system which concerns on one Embodiment of this invention.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 4 ... Control apparatus (control means), 10 ... Fuel cell, 31 ... Hydrogen supply flow path (fuel supply flow path), 32 ... Circulation flow path, 35 ... Injector (gas amount variable supply apparatus), 37: exhaust drain valve (purge valve), 38: discharge channel (purge channel), 39: hydrogen pump (pump), 44: discharge channel pressure sensor (atmospheric pressure measuring means).

Claims (2)

A fuel cell, a fuel supply channel to the fuel cell, a gas amount variable supply device provided in the fuel supply channel, and a circulation for returning off-gas discharged from the fuel cell to the fuel supply channel A flow path, a purge flow path connected to the circulation flow path for purging off-gas from the fuel cell, a purge valve provided in the purge flow path, and a control for driving and controlling the gas amount variable supply device A fuel cell system comprising:
The control means raises the pressure upstream of the purge valve to a first target pressure value by increasing the target pressure value of the gas amount variable supply device before the purge valve is opened, When the required output to the fuel cell is larger than a predetermined threshold value, the target pressure value of the gas amount variable supply device is increased before the purge valve is opened, so that the upstream side of the purge valve. Is increased to a second target pressure value smaller than the first target pressure value. A fuel cell, a fuel supply channel to the fuel cell, a gas amount variable supply device provided in the fuel supply channel, and a circulation for returning off-gas discharged from the fuel cell to the fuel supply channel A flow path, a purge flow path connected to the circulation flow path for purging off-gas from the fuel cell, a purge valve provided in the purge flow path, and a control for driving and controlling the gas amount variable supply device And an off-gas purging method for a fuel cell system comprising:
Increasing the pressure upstream of the purge valve to a first target pressure value by increasing the target pressure value of the gas amount variable supply device before opening the purge valve;
When the required output to the fuel cell is larger than a predetermined threshold, the pressure on the upstream side of the purge valve is increased by increasing the target pressure value of the gas amount variable supply device before the purge valve is opened. Increasing to a second target pressure value smaller than the first target pressure value;
An off-gas purge method for a fuel cell system.

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