JP2009181925A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology which can stably supply air to a fuel cell by using an air compressor. <P>SOLUTION: A fuel cell system is provided with: the fuel cell; the air compressor for supplying air to the fuel cell; a pressure gauge for measuring inlet air pressure and outlet air pressure in the fuel cell; an action speed adjusting section for adjusting the action speed of the air compressor; a pressure ratio adjusting section which is arranged in an air passage in the fuel cell system for adjusting the pressure ratio between the inlet pressure and the outlet pressure of the air compressor by executing an operation which influences the outlet pressure of the air compressor; and a control section. The control section changes at least one of a first adjusting amount in adjusting the action speed by the action speed adjusting section or a second adjusting amount in adjusting the pressure ratio by the pressure ratio adjusting section according to a phase difference between the variation in the inlet air pressure and the variation in the outlet air pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for supplying air to a fuel cell.

  Some fuel cell systems supply air to a fuel cell using an air compressor (see Patent Document 1 below).

JP 2007-123006 A

  Surging may occur in a fuel cell system using an air compressor. Surging is a phenomenon in which the flow rate of air supplied to the fuel cell and the air pressure inside the fuel cell periodically fluctuate (pulsate). This surging is, for example, when the air compressor operates in an operating region in which the flow rate of air supplied to the fuel cell is small and the pressure ratio in the air compressor (ratio of inlet pressure to outlet pressure of the air compressor) is relatively high. Can happen. Therefore, in the conventional fuel cell system, the air compressor is not operated in an operating region where surging occurs (hereinafter referred to as “surging region”), but is operated in another operating region (hereinafter referred to as “normal region”). It was like that.

  However, when the air compressor operates in an operating region that is very close to the surging region even in the normal region (hereinafter referred to as “pseudo surging region”), the operation of the air compressor becomes unstable, and the air flow rate and air pressure As a result, hunting may occur and air may not be stably supplied to the fuel cell.

  An object of this invention is to provide the technique which can supply air stably to a fuel cell using an air compressor.

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

  Application Example 1 A fuel cell system, a fuel cell, an air compressor for supplying air to the fuel cell, a pressure gauge for measuring an inlet air pressure and an outlet air pressure of the fuel cell, and the air compressor An operating speed adjusting unit that adjusts the operating speed of the air compressor, and an inlet pressure and an outlet pressure of the air compressor that are arranged in an air path in the fuel cell system and that perform an operation that affects the outlet pressure of the air compressor. A pressure ratio adjustment unit that adjusts the pressure ratio of the control unit, and a control unit, wherein the control unit adjusts the operation speed adjustment unit according to a phase difference between the fluctuation of the inlet air pressure and the fluctuation of the outlet air pressure. A fuel cell system that changes at least one of a first adjustment amount when adjusting the operating speed and a second adjustment amount when the pressure ratio adjustment unit adjusts the pressure ratio. Beam.

  In the fuel cell system of Application Example 1, at least one of the first adjustment amount and the second adjustment amount is changed according to the phase difference between the inlet air pressure and the outlet air pressure of the fuel cell. In such a case, it is possible to change at least one of the first adjustment amount and the second adjustment amount to suppress an increase in hunting and to stably supply air to the fuel cell. it can.

  Application Example 2 In the fuel cell system according to Application Example 1, when the control unit changes at least one of the first adjustment amount and the second adjustment amount, the phase difference is When the value is larger than a certain value, the adjustment amount to be adjusted is made smaller than when the phase difference is smaller than the certain value.

  With such a configuration, when the phase difference is larger than a certain value and the air flow rate or air pressure is unstable, the adjustment amount to be adjusted becomes relatively small. It is possible to suppress an increase in. In addition, when the phase difference is smaller than a certain value and air is stably supplied, the adjustment amount to be adjusted is relatively large, so that the operation speed and pressure ratio of the air compressor are relatively short. Adjustment can be made so as to reach the target value over time, and the response performance of the air compressor can be improved.

  Application Example 3 In the fuel cell system according to Application Example 1, when the control unit adjusts at least one of the first adjustment amount and the second adjustment amount, the phase difference is The phase difference is less than or equal to the first value when the amplitude of the inlet air pressure or the amplitude of the outlet air pressure is greater than a certain second value, Or the fuel cell system which makes adjustment amount used as adjustment object small rather than the case where the amplitude of the said inlet air pressure or the amplitude of the said outlet air pressure is below the said 2nd value.

  By adopting such a configuration, when the air flow rate and air pressure become unstable and the hunting width becomes large and is unlikely to be settled immediately, the adjustment amount to be adjusted can be made relatively small. Therefore, when the hunting occurs immediately (when the hunting width is small), the adjustment amount to be adjusted is relatively increased, so the air compressor operating speed and pressure ratio can be reduced for a relatively short time. It is possible to adjust so as to reach the target value, and it is possible to improve the response performance of the operating speed of the air compressor.

  The present invention can be realized in various forms, for example, an air compressor control method, a computer program for realizing the function of the air compressor control method or the fuel cell system, and the computer program recorded therein. It can be realized in the form of a recording medium.

Hereinafter, the best mode for carrying out the present invention will be described in the following order based on examples.
A. First embodiment:
B. Second embodiment:
C. Third embodiment:
D. Variations:

A. First embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system as an embodiment of the present invention. The fuel cell system 1000 includes a fuel cell 100, an air cleaner 32, an air compressor 34, two pressure gauges 52 and 54, a flow meter 62, a pressure regulating valve 44, a control unit 20, an air supply channel. 72 and an air discharge channel 92. In this embodiment, the fuel cell system 1000 is used by being mounted on an electric vehicle provided with a drive motor (not shown), but it can also be used as a stationary fuel cell system.

  The fuel cell 100 is a polymer electrolyte fuel cell, and includes an anode 100a and a cathode 100c. Hydrogen gas as a fuel gas supplied from a hydrogen tank (not shown) is supplied to the anode 100a and used for an electrochemical reaction. The hydrogen gas that has not been used for the electrochemical reaction is discharged to the outside of the fuel cell 100 as an off gas. On the other hand, air as an oxidant gas is supplied to the cathode 100 c of the fuel cell 100 through the air supply channel 72. Air that has not been used for the electrochemical reaction at the cathode 100c is discharged to the outside (atmosphere) of the fuel cell 100 as off-gas. As the fuel cell 100, other types of fuel cells such as phosphoric acid fuel cells may be employed instead of the solid polymer fuel cells.

  The air cleaner 32 removes impurities from the air sucked by the air compressor 34. The air compressor 34 sucks air from the atmosphere through the air cleaner 32 and compresses it, and sends the compressed air toward the cathode 100 c of the fuel cell 100. The air compressor 34 is a so-called centrifugal air compressor that compresses air by rotating an impeller (not shown) in the housing. This impeller (not shown) is driven by an electric motor (not shown). Therefore, the output voltage of the air compressor 34 can be controlled by adjusting the rotation speed of the impeller by adjusting the voltage and current applied to the electric motor (not shown). In addition, it can also be set as a belt drive instead of the drive by an electric motor.

  The flow meter 62 is disposed in the air supply channel 72 and can measure the flow rate of air flowing through the air supply channel 72. The pressure gauge 52 is disposed in the air supply flow path 72 and can measure the outlet pressure of the air compressor 34. Since the air compressor 34 and the fuel cell 100 are disposed very close to each other, the pressure gauge 52 can also measure the inlet pressure on the cathode 100c side of the fuel cell 100. In addition to the pressure gauge 52, a pressure gauge may be arranged near the inlet of the cathode 100c to measure the inlet pressure on the cathode 100c side. The pressure gauge 54 is disposed in the air discharge channel 92 and can measure the outlet pressure on the cathode 100 c side of the fuel cell 100.

  The pressure regulating valve 44 is an electromagnetic valve and is disposed in the air discharge channel 92. The pressure regulating valve 44 can adjust the outlet pressure of the fuel cell 100. Here, since the pressure loss of the fuel cell 100 is substantially constant, the pressure regulating valve 44 can adjust the outlet pressure of the air compressor 34 by adjusting the outlet pressure of the fuel cell 100. Here, the inlet pressure (atmospheric pressure) of the air compressor 34 is substantially constant. Therefore, the pressure regulating valve 44 can adjust the pressure ratio in the air compressor 34 (ratio between the inlet pressure (atmospheric pressure) and the outlet pressure).

  The control unit 20 includes a CPU 20a, a RAM 20c, and a ROM 20d. The CPU 20a functions as the control unit 20b by executing a control program (not shown) stored in the ROM 20d. The control unit 20 is connected to the pressure regulating valve 44 by a cable. Similarly, the control unit 20 is connected to the air compressor 34, the flow meter 62, the pressure gauge 52, and the pressure gauge 54 with cables. The control unit 20b can control the pressure regulating valve 44 and the air compressor 34. Further, after the electric vehicle is activated (for example, the ignition key is turned on), the control unit 20b constantly monitors the air flow value notified from the flow meter 62 and stores it in the RAM 20c. Further, the control unit 20b constantly monitors the pressure values (inlet pressure value and outlet pressure value of the fuel cell 100) notified from the two pressure gauges 52 and 54, and stores them in the RAM 20c.

  FIG. 2 is an explanatory diagram showing operating characteristics of the air compressor 34 shown in FIG. In FIG. 2, the horizontal axis indicates the flow rate of air sent from the air compressor 34, and the vertical axis indicates the pressure ratio in the air compressor 34. In addition, operation lines La, Lb, Lc, Ld, and Le are described as examples of operation lines of the air compressor 34. In the fuel cell system 1000, when the outlet pressure of the fuel cell 100 is changed while keeping the rotation speed of the impeller constant, the air compressor 34 is moved along operation lines (for example, operation lines La, Lb, Lc) corresponding to the rotation speed. The operating point moves. Here, the rotation speed of the three operation lines La, Lb, and Lc decreases in this order. For example, when the outlet pressure is gradually lowered, each operating point moves from the upper left to the lower right on the operating lines La, Lb, and Lc. On the other hand, when the outlet pressure is gradually increased, the operation lines La, Lb, and Lc are moved from the lower right to the upper left.

  In the fuel cell system 1000, when the impeller pressure is changed while the impeller rotational speed is changed, the operating point moves along an operating line (for example, operating lines Ld and Le) corresponding to the outlet pressure. Here, the outlet pressure of the two operation lines Ld and Le decreases in this order. Then, when the rotational speed of the rotating body is gradually lowered, the operating point moves from the upper right to the lower left on the operating lines Ld and Le. As can be understood from the above description, the operating point of the air compressor 34 moves by adjusting the rotational speed of the air compressor 34 (impeller) and the outlet pressure of the fuel cell 100 (the opening degree of the pressure regulating valve 44). Can be made.

  Here, since the air compressor 34 is a centrifugal air compressor, surging can occur when the air flow rate is relatively small. Surging is a phenomenon in which the air flow rate and air pressure fluctuate significantly (pulsates) periodically.

  FIG. 3 is an explanatory diagram showing surging generation characteristics in the air compressor 34. In FIG. 3, the horizontal axis and the vertical axis are the same as those in FIG. In FIG. 3, the limit condition where surging does not occur is shown as surging line L1. The left side of the surging line L1 is a surging area, and the right side including the surging line L1 is a normal area. Such a surging line L1 can be obtained by experiments. However, as an operating characteristic of the air compressor 34, an operating region (pseudo surging region) AR1 in which the air flow rate and air pressure become unstable even in the normal region exists in the vicinity of the surging line L1.

  When the operating point of the air compressor 34 is within the pseudo surging area AR1, the supply of air flow rate and air pressure becomes unstable, and air flow rate and air pressure hunting may occur. However, the fuel cell system 1000 is configured to suppress the increase in hunting by executing an air compressor control process described later and to stably supply air to the cathode 100c.

  The control unit 20b described above corresponds to the control unit and the operation speed adjustment unit in the claims. The pressure regulating valve 44 corresponds to a pressure ratio adjusting unit in the claims.

  FIG. 4 is a flowchart showing a procedure of air compressor control processing executed in the fuel cell system 1000. After the electric vehicle is activated (for example, when the ignition key is turned on), the control unit 20b determines the fuel cell 100 based on the amount of depression of an accelerator (not shown) or an operation change of an auxiliary device such as an air conditioner (not shown). Calculate the required power generation amount. Then, when the required power generation amount to the fuel cell 100 is calculated, the control unit 20b executes an air compressor control process.

  In step S205, the control unit 20b determines a final target operating point and an operating line of the air compressor 34 based on the required power generation amount and the current operating point of the air compressor 34. In the ROM 20d, an operation map (not shown) in which the current operating point (air flow rate and pressure ratio) and the final target operating point are associated with each other according to the required power generation amount is stored in advance. The unit 20b can determine a final target operation point and an operation line with reference to the operation map. Such an operation map can be created by conducting an experiment in advance in the fuel cell system 1000. The current operating point can be obtained from the outlet pressure of the air compressor 34 obtained from the pressure gauge 52 and the air flow rate obtained from the flow meter 62.

  FIG. 5 is an explanatory diagram showing an example of the transition of the operating point of the air compressor 34 when executing the air compressor control process. In FIG. 5, the horizontal and vertical axes are the same as the horizontal and vertical axes in FIG. In the example of FIG. 5, the operating point at the start of the air compressor control process (the time when step S205 is executed) is the operating point pA, and the operating point pF is set as the final target operating point. An operation line L10 is set. A part of the operation line L10 is included in the pseudo surging area AR1.

  In step S210 (FIG. 4), the control unit 20b determines whether or not the current operating point has reached the final target operating point. When the final target operating point is reached, the control unit 20b adjusts the outlet pressure and the rotational speed so that the operating point of the air compressor 34 maintains the final target operating point (step S240).

  In step S210 described above, when it is determined that the current operating point has not reached the final target operating point, the control unit 20b determines the phase difference between the inlet pressure and the outlet pressure on the cathode 100c side of the fuel cell 100 (hereinafter, referred to as the following). Simply referred to as “phase difference”) (step S215). The phase difference can be obtained, for example, as a time difference between the peak time of the inlet pressure and the peak time of the outlet pressure. For example, it can also obtain | require as a phase (radian) of an outlet pressure when an inlet pressure becomes a peak. In step S220, the control unit 20b determines whether or not the phase difference obtained in step S215 is greater than a preset threshold value.

  FIG. 6 is an explanatory diagram schematically showing the transition of the inlet pressure and the outlet pressure of the fuel cell 100 when the operating point of the air compressor 34 changes on the operating line L10 shown in FIG. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates pressure. The start time of the air compressor control process is time 0.

  When air is stably supplied to the fuel cell 100, the phase difference is a slight phase difference (hereinafter referred to as “initial phase difference”) corresponding to the length of the air flow path in the fuel cell 100. Only occurs). However, when the operation of the air compressor 34 becomes unstable and hunting occurs, the phase of the inlet pressure and the phase of the outlet pressure are greatly shifted, and a phase difference larger than the initial phase difference may be generated. Therefore, in the fuel cell system 1000, by setting the threshold value of the phase difference used in the above-described step S220 to a value slightly larger than the initial phase difference, the presence or absence of hunting is determined by executing step S220. It is configured. In addition, as an example of the threshold value of the phase difference, for example, when the time difference between the peak time of the inlet pressure and the peak time of the outlet pressure is obtained as the phase difference, it can be set to 5 ms.

  In the example of FIG. 6, air is stably supplied to the fuel cell 100 at the start of the air compressor control process (time 0), and the phase difference is the initial phase difference. In this case, since the phase difference is smaller than the threshold value (step S220 in FIG. 4: NO), the control unit 20b is the operating point on the target operating line determined in step S205, and is the final target operating point. The operating point on the way is determined as a small target operating point (step S225a). At this time, the control unit 20b determines, as a small target operating point, an operating point that can be reached when the rotational speed of the air compressor 34 is changed from the current operating point by a predetermined first change width Δr1. As the first change width Δr1, for example, 10000 rpm can be set.

  In step S230, the control unit 20b adjusts the rotational speed of the air compressor 34 toward the determined small target operating point and adjusts the opening of the pressure regulating valve 44. Then, in the example of FIG. 5, the operating point of the air compressor 34 starts to move on the target operating line L10 from the operating point pA toward the operating point pF. As shown in FIG. 6, the inlet pressure of the fuel cell 100 gradually decreases from Pi1, and the outlet pressure also decreases.

  When a predetermined period has elapsed after the start of step S230 (FIG. 4) (step S235: YES), the control unit 20b executes steps S210 to S235 again. The “predetermined period” is 16 ms in the present embodiment, but may be an arbitrary length. In the example of FIG. 5, the operating point when executing step S210 at the second control timing (time 16 ms) is the operating point pB, and the input pressure of the fuel cell 100 at this time is Pi2 (FIG. 6). The operating point pB is an operating point included in the pseudo surging area AR1. At this operating point pB, no air flow rate or air pressure hunting occurs, and the phase difference is only the initial phase difference. Therefore, similarly to the first time, the control unit 20b again sets a small target operating point using the first change width Δr1 in step S225a executed for the second time, and in step S230, the new small target operating point. Adjust the outlet pressure and rotational speed toward.

  However, in the example of FIG. 6, after the operating point exceeds the operating point pB, the air flow rate and air pressure become unstable and hunting of the inlet pressure and outlet pressure of the fuel cell 100 occurs. As a result, the moving speed of the operating point slows down. In the example of FIG. 5, at the third control timing (time 32 ms), the operating point is an operating point pC that is relatively close to the operating point pB. At this time, the phase difference is relatively large as shown in FIG. If the phase difference is larger than the threshold value in step S220, the control unit 20b executes step S225b instead of step S225a.

  The process in step S225b is different from step S225a in that the second change width Δr2 is used instead of the first change width Δr1, and the other processes are the same as those in step S225a. Here, the second change width Δr2 is smaller than the first change width Δr1, and can be set to, for example, 3000 rpm. Therefore, the control unit 20b determines an operating point at a position relatively close to the current operating point as a small target operating point, as compared with the case where step S225a is executed.

  Thus, when the phase difference is larger than the threshold value, the small target operating point is determined using the relatively small second change width Δr2 for the following reason. When the small target operating point is determined using the second change width Δr2, an operating point relatively close to the current operating point can be determined as the small target operating point. Therefore, the degree of change in the rotational speed of the air compressor 34 and the degree of change in the opening degree of the pressure regulating valve 44 in step S230 can be reduced as compared with the case where the first change width Δr1 is used. This is because it works to suppress fluctuations in the air pressure and the air flow rate, and it can be expected that hunting will be settled. The degree of change in the rotational speed of the air compressor 34 described above corresponds to the first adjustment amount in the claims. Moreover, the change degree of the opening degree of the pressure regulating valve 44 described above corresponds to the second adjustment amount in the claims. )

  In the example of FIG. 6, in the movement from the operating point pC, the degree of change in the rotational speed of the air compressor 34 and the degree of change in the opening of the pressure regulating valve 44 are relatively small, but the fourth control timing (48 ms ) Still has some hunting, and the phase difference is relatively large. Therefore, at the operating point pD as well as the operating point pC, the operating point at a relatively close position is determined as the small target operating point using the second change width Δr2. Therefore, the degree of change in the rotational speed of the air compressor 34 and the degree of change in the opening degree of the pressure regulating valve 44 remain relatively small. The hunting is settled after a while after the operating point exceeds the operating point pD, and the phase difference is the initial phase difference at the fifth control timing (64 ms).

  In this case, step S225a (FIG. 4) is executed, and an operating point at a position relatively far from the operating point pE (FIG. 5) (for example, the final target operating point pF) is determined as the small target operating point. Therefore, as in the case of moving from the operating point pA to the operating point pB, the degree of change in the rotational speed of the air compressor 34 and the degree of change in the opening of the pressure regulating valve 44 in step S230 are relatively large. At this time, the operating point rapidly moves toward the final target operating point pF, and the inlet pressure and the outlet pressure (FIG. 6) of the fuel cell 100 rapidly decrease. In the example of FIG. 6, the operating point has reached the operating point pF at the sixth control timing (80 ms), and the movement of the operating point stops.

  As described above, in the fuel cell system 1000, when the flow rate of air supplied to the fuel cell 100 and the air pressure can cause hunting, the rotational speed of the air compressor 34 and the degree of change in the opening of the pressure regulating valve 44 are compared. It is configured to be small. Therefore, when hunting occurs, the air pressure and the air flow rate are suppressed, so that increase of hunting can be suppressed and air can be stably supplied to the fuel cell 100. Further, when air is stably supplied to the fuel cell 100, the degree of change in the rotational speed of the air compressor 34 and the degree of opening of the pressure regulating valve 44 is relatively large. Therefore, since the operating point of the air compressor 34 can be moved to the final target operating point in a relatively short time, the response performance of the air compressor 34 can be improved.

B. Second embodiment:
FIG. 7 is a flowchart showing the procedure of the air compressor control process in the second embodiment. In the fuel cell system 1000 of the second embodiment, in the air compressor control process, the step S215a is executed instead of the step S215, and the step S220a is executed instead of the step S220. Unlike FIG. 1), the other configurations are the same as those of the first embodiment. When the fuel cell system 1000 of the second embodiment determines the small target operating point based on the amplitude of the inlet pressure and the amplitude of the outlet pressure in addition to the phase difference between the inlet pressure and the outlet pressure of the fuel cell 100. The change width to be used (the first change width Δr1 or the second change width Δr2) is determined.

  Specifically, in step S215a (FIG. 7), the control unit 20b (FIG. 1), in addition to the phase difference between the inlet pressure and the outlet pressure of the fuel cell 100, the amplitude of the inlet pressure and the outlet pressure of the fuel cell 100. Are respectively obtained. The respective amplitudes of the inlet pressure and the outlet pressure can be obtained based on the inlet pressure value and the outlet pressure value stored in the RAM 20c. In step S220a, the controller 20b determines whether or not the phase difference obtained in step S215a is greater than a threshold value and at least one of the amplitude of the inlet pressure and the amplitude of the outlet pressure is greater than the threshold value. Determine. When the phase difference is larger than the threshold value and at least one of the amplitude of the inlet pressure and the amplitude of the outlet pressure is larger than the threshold value, the above-described step S225a is executed. On the other hand, when the phase difference is equal to or smaller than the threshold value, or when both the amplitude of the inlet pressure and the amplitude of the outlet pressure are equal to or smaller than the threshold value, the above-described step S225b is executed. The phase difference threshold used in step S220a is the same as the phase difference threshold used in step S220 (FIG. 4) in the first embodiment.

  The fuel cell system 1000 of the second embodiment having the above configuration has the same effects as the fuel cell system 1000 of the first embodiment. Further, with the above-described configuration, the phase difference between the inlet pressure and the outlet pressure of the fuel cell 100 is relatively large, and at least one of the amplitude of the inlet pressure or the amplitude of the outlet pressure. The degree of change in the rotational speed of the air compressor 34 and the opening degree of the pressure regulating valve 44 can be made relatively small only when is relatively large. The reason for this configuration is as follows. In the configuration in which the degree of change is relatively small irrespective of the magnitude of the amplitude (hunting width) of the inlet pressure or the outlet pressure, even if the hunting occurs and immediately falls, the rotational speed of the air compressor 34 The degree of change in the opening of the pressure regulating valve 44 is made relatively small. Therefore, reaching the final target operating point is relatively slow. On the other hand, in the second embodiment, when both the amplitude of the inlet pressure and the amplitude of the outlet pressure are relatively small and are settled immediately after hunting occurs, the rotational speed of the air compressor 34 The degree of change in the opening degree of the pressure regulating valve 44 can be made relatively large. Therefore, the target operating point can be reached relatively quickly, and the response performance of the air compressor 34 can be improved.

C. Third embodiment:
FIG. 8 is an explanatory diagram showing a schematic configuration of a vehicle to which the fuel cell system according to the third embodiment is applied. A vehicle 500 in the third embodiment is an electric vehicle, and includes a power supply unit 520 and a load unit 540. The power supply unit 520 supplies power as a power source to the load unit 540. The load unit 540 converts the supplied power into mechanical power for driving the vehicle 500.

  The power supply unit 520 includes a fuel cell system 1000a, a secondary battery 522, and a DC-DC converter 523. The fuel cell system 1000a differs from the fuel cell system 1000 (FIG. 1) in the first and second embodiments in that it includes a power supply control unit 20e instead of the control unit 20b (FIG. 1). The configuration is the same. The power supply control unit 20e is a functional unit that functions when the CPU 20a executes a power supply control program (not shown) stored in the ROM 20d. In the example of FIG. 8, for convenience, the control unit 20 is shown not to be included in the fuel cell system 1000a. However, the control unit 20 is actually included in the fuel cell system 1000a.

  The secondary battery 522 stores electric power generated in the fuel cell system 1000a and electric power regenerated in the load unit 540. The secondary battery 522 supplies power to an auxiliary machine (not shown) such as a load unit 540 and an air conditioner. The DC-DC converter 23 adjusts the output voltage of the secondary battery 522. The control unit 20 is connected to a flow meter 62 (FIG. 1) and two pressure gauges 52 and 54 constituting the fuel cell system 1000a. In addition, the control unit 20 is connected to the secondary battery 522, and the power supply control unit 20 e can acquire a charging power amount (SOC: State Of Charge) from the secondary battery 522.

  The load unit 540 includes a drive circuit 546, a motor 541, a gear mechanism 542, and wheels 544. The drive circuit 546 is a circuit for driving the motor 541. The power generated by the motor 541 is transmitted to the wheels 544 through the gear mechanism 542. The drive circuit 546 converts the DC power supplied from the power supply unit 520 into three-phase AC power and supplies it to the motor 541. The drive circuit 546 is electrically connected to the control unit 20 described above, and the power supply control unit 20e controls the drive circuit 546.

  In this vehicle 500, the power generation amount (required power generation amount) in the fuel cell system 1000a includes the amount of depression of an accelerator (not shown), the required power generation amount in an auxiliary device (not shown) such as an air conditioner, and the SOC of the secondary battery 522. Determined based on In the vehicle 500, even if the target operating point of the air compressor 34 when generating power for the required power generation amount is within the surging area, the motor 541 is executed by executing power supply control processing described later. And auxiliary equipment (not shown) can be stably supplied with power. Note that the SOC of the secondary battery 522 is also taken into consideration when determining the required power generation amount. If the secondary battery 522 has a free capacity, a part of the electric power generated in the fuel cell system 1000a is used as the secondary battery. This is because it is stored in 522. The purpose of this is to make it possible to supply power from the secondary battery 522 even when the power generation of the fuel cell 100 is stopped in the fuel cell system 1000a.

  In addition, as a case where the target operating point is in the surging area, for example, it is assumed that the required power generation amount is supplied in the highland so that the operating point of the air compressor 34 is in the normal area on a flat ground. Since the atmospheric pressure (inlet pressure in the air compressor 34) is lower in the highland than in the flatland, if the outlet pressure in the air compressor 34 is the same, the pressure ratio of the air compressor 34 is higher than that in the flatland. Therefore, the operating point may deviate from the normal region and may be within the surging region.

  FIG. 9 is a flowchart showing a procedure of power supply processing executed in vehicle 500. As described above, when the required power generation amount is determined based on the amount of depression of an accelerator (not shown) or the like, the power supply process is started in the vehicle 500.

  In step S305, the power supply control unit 20e determines a final target operation point and an operation line of the air compressor 34 based on the required power generation amount and the current operation point of the air compressor 34. In step S310, the power supply control unit 20e determines whether or not the final target operating point determined in step S305 is within the surging area. When the final target operating point is not within the surging area, the power supply control unit 20e moves the operating point along an operating line (not shown) to maintain the final target operating point. The fuel cell 100 is operated to generate power. Then, electric power is supplied from the fuel cell system 1000a to the motor 541 and the like (step S340).

  If it is determined in step S310 described above that the final target operating point is within the surging range, the power supply control unit 20e changes the final target operating point to an operating point within the normal range (step S315).

  FIG. 10 is an explanatory diagram showing an example of the operating point transition of the air compressor 34 in the third embodiment. 10, the vertical axis and the horizontal axis are the same as the vertical axis and the horizontal axis in FIG. In the example of FIG. 10, the operating point at the start of power supply processing (the time when step S205 is executed) is the operating point X, and the operating line L20 and the operating point Z in the surging area are set as the final target operating point. Has been. Then, after the process of step S315 described above, the final target operating point is changed from the operating point X to the operating point Y in the normal range. The operating point Y is an operating point on the operating line L20 and in the vicinity of the surging line L1. The operating point Y can be determined as an operating point on the operating line L20 where the air flow rate is increased by a predetermined amount from the intersection of the operating line L20 and the surging line L1, for example.

  In step S320 (FIG. 9), the power supply control unit 20e moves the operating point along the operating line L20 to operate the air compressor 34 so as to maintain the final target operating point and generate power in the fuel cell 100. To do. Then, electric power is supplied from the fuel cell system 1000a to the motor 541 and the like (step S320). In the example of FIG. 10, the operating point moves toward the target operating point Y after the change along the operating line L20 and stays at the operating point Y. At this time, since the operating point Y is in the normal range, the air compressor 34 can stably supply air to the fuel cell 100.

  In step S325, the power supply control unit 20e acquires the SOC of the secondary battery 522. In step S330, the power supply control unit 20e determines whether the obtained SOC of the secondary battery 522 is smaller than a preset threshold value. Here, as the threshold value used in step S330, a charging power amount that can sufficiently secure a free capacity for storing in the secondary battery 522 can be obtained by experiment and set. Therefore, when the SOC of the secondary battery 522 is smaller than the threshold value, the secondary battery 522 has sufficient free capacity for storing electricity. In this case, the power supply control unit 20e executes steps S320 to S330 again. Therefore, necessary power can be supplied to the motor 541 and the auxiliary machine (not shown), and the secondary battery 522 can be charged.

  On the other hand, when the SOC is equal to or higher than the threshold value, the secondary battery 522 has almost no free capacity for storing electricity. Therefore, if power generation is performed in the fuel cell 100 as it is, there is a risk of supplying excessive power to the motor 541 and the auxiliary machine. Therefore, in this case, the power supply control unit 20e stops the operation of the air compressor 34 to stop the power generation in the fuel cell 100, and the power required from the secondary battery 522 to the motor 541 and an auxiliary device (not shown). Is supplied (step S335). After step S335, the power supply control unit 20e executes steps S325 to S335 again. When electric power is supplied from the secondary battery 522, the SOC of the secondary battery 522 gradually decreases. When the SOC of the secondary battery 522 falls below the threshold value (step S330: YES), the secondary battery 522 has a sufficient free capacity for charging. In this case, since the process returns to step S320 again as described above, the air compressor 34 operates at the changed target operating point (the operating point Y in the example of FIG. 10), and power generation is resumed in the fuel cell 100. Is done.

  As described above, in the vehicle 500 according to the third embodiment, even when the target operating point determined based on the required power generation amount calculated from the depression amount of an accelerator (not shown) is within the surging range, the target Since the air compressor 34 is operated by changing the operating point to an operating point in the normal range, air can be stably supplied to the fuel cell 100. When the target operating point is changed and the charge amount of the secondary battery 522 exceeds the threshold value, the power supply from the fuel cell system 1000a is stopped and the power is supplied from the secondary battery 522. It is configured as follows. Therefore, it is possible to suppress excessive power supply to the motor 541 and the auxiliary machine (not shown).

D. Variations:
In addition, elements other than the elements claimed in the independent claims among the constituent elements in each of the above embodiments are additional elements and can be omitted as appropriate. The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

D1. Modification 1:
In the first and second embodiments described above, when the operating point is in the pseudo surging area AR1, hunting of the air flow rate or air pressure has occurred, but hunting occurs in an area other than the pseudo surging area AR1. Even in such a case, the effects of the fuel cell system 1000 can be obtained. That is, even if hunting occurs in an area other than the pseudo surging area AR1, the fuel cell system 1000 relatively reduces the degree of change in the rotational speed of the air compressor 34 and the opening of the pressure regulating valve 44. The increase can be suppressed. Therefore, air can be stably supplied to the fuel cell 100.

D2. Modification 2:
In the first embodiment described above, in step S220 (FIG. 4), step S225b is executed once the phase difference becomes larger than the threshold value. Step S225b is executed when N times (N is an integer equal to or greater than 2) that the threshold value is greater than the threshold value, and when the phase difference is greater than the threshold value does not continue N times, step S225b is executed. It can also be configured to execute S225a. By doing so, when the hunting is immediately settled, the degree of change in the rotational speed of the air compressor 34 and the opening of the pressure regulating valve 44 can be made relatively large. Response performance can be improved.

D3. Modification 3:
In the first and second embodiments described above, the movement of the operating point from the operating point (operating point pA) at the start of the air compressor control process to the final target operating point (operating point pF) has been described. The present invention can also be applied to the case where the operating point is maintained at the target operating point after reaching the final target operating point (when step S240 is executed). For example, after the operating point reaches the target operating point, the present invention can also be applied to the case where the operating point is returned to the target operating point because the operating point has deviated from the target operating point due to a change in environmental conditions (such as temperature). That is, when returning the operating point to the target operating point, if the phase difference is larger than the threshold value, a small target is determined using the second change width Δr2 (step S225b), and the phase difference is equal to or smaller than the threshold value. If so, it may be configured to determine the small target using the first change width Δr1 (step S225a). By doing so, air can be stably supplied to the fuel cell 100 when the operating point is maintained at the target operating point.

D4. Modification 4:
In each of the above-described embodiments, the air compressor 34 is used to supply air to the fuel cell 100. However, a blower can be used instead of the air compressor 34. In each embodiment, the air compressor 34 is a centrifugal compressor, but instead of this, an axial-flow compressor in which a moving blade (rotor) rotates to perform compression can be used. Further, a so-called positive displacement type air compressor such as a reciprocating type or a rotary type can be used instead of the centrifugal type or the axial flow type so-called turbo type air compressor. That is, in general, any type of air compressor whose operating speed can be adjusted can be used in the fuel cell system of the present invention.

D5. Modification 5:
In the first and second embodiments described above, the change width used when determining the small target operating point is two types of the first change width Δr1 and the second change width Δr2, but two or more. Any type of change width can be used. Specifically, for example, it can be configured as follows. In addition to the first change width Δr1 and the second change width Δr2, the third change width Δr3 is set in advance. The third change width Δr3 is a change width (for example, 1000 rpm) smaller than the second change width Δr2. In addition, as the phase difference threshold value, a relatively small first threshold value (for example, 2 ms) and a relatively large second threshold value (for example, 5 ms) are set. When the phase difference is larger than the second threshold value (for example, 10 ms), the third change width Δr1 is used, and the phase difference is between the first threshold value and the second threshold value. If the phase difference is smaller than the first threshold (for example, 1 ms), the first variation width Δr3 is used. It can also be configured as follows. In this configuration, for two phase differences (for example, 1 ms and 10 ms) within different phase difference ranges, as in the first and second embodiments, when the phase difference is relatively large. Is configured to use a relatively large change width. However, two phase differences (for example, 3 ms and 4 ms) within the same phase difference range are configured to use the same change width even when the phase difference is relatively large.

D6. Modification 6:
In the first and second embodiments described above, the rotation of the air compressor 34 when determining the small target operating point in order to vary the degree of change in the rotational speed of the air compressor 34 and the opening of the pressure regulating valve 44. Although the change width of the speed is different, it can be configured to change the rotational speed of the air compressor 34 and the degree of change of the opening degree of the pressure regulating valve 44 by another arbitrary method instead. . For example, a relatively large change degree and a relatively small change degree are set in advance for the rotation speed of the air compressor 34 and the opening degree of the pressure regulating valve 44. When the phase difference between the inlet pressure and the outlet pressure of the fuel cell 100 is larger than the threshold value, the rotational speed and pressure regulation of the air compressor 34 are adjusted so that a relatively small degree of change is set in advance. The opening degree of the valve 44 is changed. Further, when the phase difference is smaller than the threshold value, the rotational speed of the air compressor 34 and the opening degree of the pressure regulating valve 44 are changed so that a relatively large change degree set in advance is obtained. You can also In addition, in this structure, it can also comprise so that a change degree may be changed only according to a phase difference about either one among the rotational speed of the air compressor 34, and the opening degree of the pressure regulation valve 44. FIG.

  As another example, the rotational speed change rate of the air compressor 34 when determining the small target operating point is constant, and the “predetermined period” in step S235 is varied, so that the rotational speed and adjustment of the air compressor 34 are varied. The degree of change in the opening degree of the pressure valve 44 may be varied. Specifically, when the phase difference is larger than the threshold value, the aforementioned “predetermined period” is lengthened (for example, 32 ms), and when the phase difference is equal to or smaller than the threshold value, the “predetermined period” is shortened. (For example, 8 ms). In this configuration, the small target operating point is determined as an operating point that is scheduled to be reached after the aforementioned “predetermined period”. In such a configuration, when the phase difference is larger than the threshold value, the operating point is moved by a predetermined change width in a relatively long period, and the rotational speed of the air compressor 34 and the pressure regulating valve are achieved. The degree of change in the opening degree of 44 can be made relatively small. Further, when the phase difference is equal to or smaller than the threshold value, the operating point movement for a predetermined change width is achieved in a relatively short period, and the change in the rotation speed of the air compressor 34 and the opening degree of the pressure regulating valve 44 are achieved. Can be made relatively large. As can be understood from the above embodiments and modifications, generally, the degree of change in the operating speed of the air compressor and the degree of change in the pressure ratio in the air compressor according to the phase difference between the inlet pressure and the outlet pressure. Among these, the configuration for adjusting at least one of them can be employed in the fuel cell system of the present invention.

D7. Modification 7:
In the third embodiment described above, the secondary battery 522 is used as means for storing the electric power generated in the fuel cell system 1000a. However, any other power storage device can be employed instead of the secondary battery. . For example, a capacitor can be used.

D8. Modification 8:
In the third embodiment described above, the switching determination of the power supply source between the fuel cell system 1000a (fuel cell 100) and the secondary battery 522 is performed based on the SOC of the secondary battery 522 (FIG. 9: Step S330), the present invention is not limited to this. For example, the determination may be performed based on the required power amount. Specifically, instead of step S325, the required power generation amount (the power generation amount calculated based on the accelerator depression amount, the required power generation amount in an auxiliary machine such as an air conditioner, and the SOC of the secondary battery 522) is obtained again. Like that. Then, instead of step S330, it is determined whether or not the required power generation amount newly obtained is smaller than the power generation amount of the fuel cell 100 obtained when the air compressor 34 is operated at the operating point after the change. To do. When the required power generation amount is smaller than the power generation amount obtained when the air compressor 34 operates at the operating point after the change, the power supply source is the secondary battery 522 (step S335). Can be configured such that the power supply source is the fuel cell system 1000a. Even in such a configuration, when the amount of charge of the secondary battery 522 is small (when the SOC is smaller than the threshold value), the required power generation amount becomes relatively large, so the air compressor 34 is operated at the operating point after the change. Thus, it is possible to prevent surplus power from being generated even if the fuel cell 100 generates power.

D9. Modification 9:
In each of the embodiments described above, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. Good.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows schematic structure of the fuel cell system as one Example of this invention. Explanatory drawing which shows the operating characteristic of the air compressor 34 shown in FIG. Explanatory drawing which shows the generation characteristic of surging in the air compressor. 5 is a flowchart showing a procedure of air compressor control processing executed in the fuel cell system 1000. Explanatory drawing which shows an example of transition of the operating point of the air compressor 34 at the time of performing an air compressor control process. FIG. 6 is an explanatory diagram schematically showing changes in the inlet pressure and outlet pressure of the fuel cell 100 when the operating point of the air compressor 34 changes on the operation line L10 shown in FIG. The flowchart which shows the procedure of the air compressor control process in a 2nd Example. Explanatory drawing which shows schematic structure of the vehicle to which the fuel cell system 1000 in a 3rd Example is applied. 5 is a flowchart showing a procedure of power supply processing executed in vehicle 500. Explanatory drawing which shows an example of the operating point transition of the air compressor 34 in a 3rd Example.

Explanation of symbols

20 ... Control unit 20a ... CPU
20b ... Control unit 20c ... RAM
20d ... ROM
20e ... Electric power supply controller 32 ... Air cleaner 34 ... Air compressor 44 ... Pressure regulator 52 ... Pressure gauge 54 ... Pressure gauge 62 ... Flow meter 72 ... Air supply flow path 92 ... Air discharge flow path 100 ... Fuel cell 100a ... Anode 100c DESCRIPTION OF SYMBOLS ... Cathode 500 ... Vehicle 520 ... Electric power supply part 522 ... Secondary battery 523 ... DC-DC converter 540 ... Load part 541 ... Motor 542 ... Gear mechanism 544 ... Wheel 546 ... Drive circuit 1000 ... Fuel cell system 1000a ... Fuel cell system pA ~ PF, X ~ Z ... operating point L1 ... surging line La, Lb, Lc, Ld, Le, L10, L20 ... operating line AR1 ... pseudo surging area

Claims (3)

A fuel cell system,
A fuel cell;
An air compressor for supplying air to the fuel cell;
A pressure gauge for measuring an inlet air pressure and an outlet air pressure of the fuel cell;
An operation speed adjusting unit for adjusting an operation speed of the air compressor;
A pressure ratio adjusting unit that is disposed in an air path in the fuel cell system and adjusts a pressure ratio between the inlet pressure and the outlet pressure of the air compressor by performing an operation that affects the outlet pressure of the air compressor;
A control unit;
With
The control unit includes a first adjustment amount when the operation speed adjustment unit adjusts the operation speed according to a phase difference between a change in the inlet air pressure and a change in the outlet air pressure, and the pressure ratio adjustment unit. The fuel cell system changes at least one of the second adjustment amount when adjusting the pressure ratio. The fuel cell system according to claim 1,
When the phase difference is greater than a certain value when changing at least one of the first adjustment amount and the second adjustment amount, the control unit determines that the phase difference is the certain amount. A fuel cell system in which the adjustment amount to be adjusted is smaller than when the value is smaller than the value. The fuel cell system according to claim 1,
When the controller adjusts at least one of the first adjustment amount and the second adjustment amount,
When the phase difference is larger than a certain first value and the amplitude of the inlet air pressure or the amplitude of the outlet air pressure is larger than a certain second value, the phase difference is the first value. Or a fuel cell system in which an adjustment amount to be adjusted is made smaller than when the amplitude of the inlet air pressure or the amplitude of the outlet air pressure is less than or equal to the second value.

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