JP2019145338A - Fuel cell system - Google Patents

Abstract

To prevent a turbo type compressor from operating in a request operation point which cannot be achieved.SOLUTION: A fuel cell system comprises: a fuel battery; a turbo type compressor supplying an oxidation gas to the fuel battery; a pressure regulator regulating a pressure of the oxidation gas in the fuel battery; and a control part that controls an operation of the turbo type compressor and the pressure regulator in accordance with at least an output request to the fuel battery. The control part sets a request operation point of the turbo type compressor by a target flow amount and a target pressure ratio of the turbo type compressor. If the target pressure ratio of the request operation point to be set is smaller than the minimum pressure ratio predetermined that is the minimum value of a pressure ratio achievable to the flow amount of the oxidation gas dischargable from the turbo type compressor, the target voltage ratio of the request operation point to be set is increased to the minimum pressure ratio corresponding to the target flow amount.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fuel cell system.

  Conventionally, a fuel cell system that supplies an oxidizing gas to a fuel cell using a compressor is known. A required operating point indicating a pressure ratio and a flow rate may be set for the compressor based on a fuel cell output request or the like. In the fuel cell system described in Patent Document 1, in order to avoid surging that may occur at a low flow rate, when the required operating point is in the surge region, the flow rate is increased and excess oxidizing gas is bypassed. It flows in the flow path.

JP 2009-123550 A

  The inventors of the present application have found that in a fuel cell system using a turbo compressor, there is an operating region in which the operating point of the compressor cannot be controlled to the target operating point, in addition to the surge region considered in Patent Document 1. It was. Such a region is an operation region of a high flow rate / low pressure ratio. In the turbo compressor, since the pressure loss in the downstream flow path increases when the flow rate is increased, there is a minimum value (lower limit value) of the pressure ratio that cannot be further reduced in the high flow rate region. When the valve provided in the flow path for supplying the oxidizing gas from the compressor to the fuel cell or the flow path for discharging the oxidizing gas from the fuel cell is fully open, the value of the pressure ratio to the flow rate at the operating point is the minimum value (lower limit value). ) For this reason, the required operating point at which the pressure ratio falls below the lower limit value cannot be realized by changing the valve opening. Further, if the rotational speed of the compressor is lowered in order to reduce the pressure ratio, the flow rate also decreases, so that the flow rate at the required operating point and the pressure ratio cannot be satisfied simultaneously. In this way, the inventors of the present application have found that the compressor may not be able to achieve the required operating point when the pressure ratio at the required operating point is smaller than the minimum value of the pressure ratio with respect to the flow rate at the required operating point. I found it.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

  According to one aspect of the present invention, a fuel cell system is provided. The fuel cell system includes: a fuel cell; a turbo compressor that supplies an oxidant gas to the fuel cell; a pressure regulating valve that adjusts the pressure of the oxidant gas in the fuel cell; and at least an output request to the fuel cell And a control unit that controls operations of the turbo compressor and the pressure regulating valve; and the control unit; a target flow rate that is a target value of the flow rate of the oxidizing gas discharged from the turbo compressor; A target pressure ratio that is a target value of a pressure ratio that is a ratio of a pressure of the oxidizing gas discharged from the turbo compressor to a pressure of the oxidizing gas sucked into the turbo compressor, and the turbo compressor The target pressure ratio of the set required operating point is before the turbo compressor can be discharged. The target pressure ratio of the set required operating point corresponds to the target flow rate when it is smaller than a predetermined minimum pressure ratio that is the minimum value of the pressure ratio that can be realized with respect to the flow rate of the oxidizing gas. Increase to the minimum pressure ratio. According to the fuel cell system of this aspect, the target pressure ratio at the required operating point is a predetermined minimum pressure ratio that is the minimum value of the pressure ratio that can be realized with respect to the flow rate of the oxidizing gas that can be discharged from the turbo compressor If it is smaller, the target pressure ratio of the set required operation point is increased to the minimum pressure ratio corresponding to the target flow rate, so that it is possible to suppress operating the turbo compressor at the required operation point that cannot be realized. Therefore, it is possible to suppress the performance of the fuel cell system from being impaired by continuously operating the turbo compressor at a required operating point that cannot be realized. For example, when feedback control including at least a proportional term and an integral term is performed with respect to the deviation between the required operating point and the actual operating point, accumulation of the feedback integral term can be suppressed. For this reason, it can suppress that control is delayed when changing a request | requirement operating point.

  The present invention can also be realized in various forms other than the fuel cell system. For example, it can be realized in the form of a control method of the fuel cell system, a vehicle including the fuel cell system, and the like.

It is explanatory drawing which shows schematic structure of a fuel cell system. It is explanatory drawing for demonstrating the operating characteristic of an air compressor. It is a flowchart which shows the procedure of a required operation point setting process. It is explanatory drawing for demonstrating the result of step S140. It is explanatory drawing for demonstrating the request | requirement operation | movement point changed by 2nd Embodiment.

A. First embodiment:
A-1. Configuration of fuel cell system:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system 10 as an embodiment of the present invention. The fuel cell system 10 is mounted on a fuel cell vehicle (not shown) as a system for supplying driving power. The fuel cell system 10 supplies electric power to loads such as a drive motor and an air compressor 50 of the fuel cell vehicle.

  The fuel cell system 10 includes a fuel cell 20, an oxidizing gas supply / discharge system 30, a fuel gas supply / discharge system 70, and a control unit 90.

  The fuel cell 20 is a power source of the fuel cell system 10 and is constituted by a so-called solid polymer fuel cell. The fuel cell 20 generates power by receiving supply of fuel gas and oxidizing gas. The fuel cell 20 may be configured by any other type of fuel cell such as a solid oxide fuel cell, instead of the solid polymer fuel cell. The fuel cell 20 has a stack structure in which a plurality of single cells (not shown) are stacked. Each single cell has a membrane electrode assembly (not shown) in which electrodes are arranged on both surfaces of an electrolyte membrane (not shown), and a set of separators (not shown) that sandwich the membrane electrode assembly. Each single cell constituting the fuel cell 20 is formed with an anode 22 supplied with fuel gas and a cathode 24 supplied with oxidizing gas via an electrolyte membrane. In FIG. 1, only the anode 22 and the cathode 24 of one single cell are schematically represented.

  The oxidizing gas supply / discharge system 30 supplies air as oxidizing gas to the fuel cell 20 and discharges it. The oxidizing gas supply / discharge system 30 includes an atmospheric pressure sensor 61, an oxidizing gas supply flow path 32, an air cleaner 42, an air flow meter 62, an air compressor 50, a pressure sensor 63, a flow sensor 64, and an oxidizing gas discharge flow. The passage 34, the pressure regulating valve 54, the cathode pressure sensor 65, the muffler 48, the bypass passage 36, and the bypass valve 56 are included.

  The oxidizing gas supply channel 32 constitutes a channel for air supplied to the fuel cell 20. The atmospheric pressure sensor 61 is disposed at the inlet of the oxidizing gas supply channel 32 and detects atmospheric pressure. The air cleaner 42 is disposed in the oxidizing gas supply flow path 32 and removes dust when taking in air. The air flow meter 62 detects the flow rate of the air taken into the air cleaner 42.

  The air compressor 50 compresses air and sends it to the fuel cell 20 in accordance with a command from the control unit 98. The air compressor 50 is configured as a so-called turbo-type air compressor that compresses air by rotating a rotating body (not shown) in the housing. As the air compressor 50, for example, a centrifugal compressor in which an impeller rotates and compresses, or an axial flow compressor in which a moving blade (rotor) rotates and compresses may be used. A rotating body such as an impeller is driven by a motor (not shown). Therefore, the drive of the air compressor 50 can be controlled by controlling the number of rotations of the rotating body by adjusting the voltage and current applied to the motor.

  The pressure sensor 63 is disposed on the downstream side of the air compressor 50 and measures the outlet pressure of the air compressor 50 in the oxidizing gas supply channel 32. The flow rate sensor 64 is disposed closer to the fuel cell 20 than the connection point A to the bypass flow path 36 in the oxidizing gas supply flow path 32. The flow sensor 64 measures the flow rate of the air supplied to the fuel cell 20.

  The oxidizing gas discharge flow path 34 constitutes a flow path for cathode exhaust gas discharged from the fuel cell 20. The pressure regulating valve 54 is disposed closer to the fuel cell 20 than the connection point B with the bypass flow path 36 in the oxidizing gas discharge flow path 34. The pressure regulating valve 54 adjusts the pressure of the cathode 24 by changing the opening according to a command from the control unit 98. The pressure of the cathode 24 decreases as the opening degree of the pressure regulating valve 54 increases, and increases as the opening degree of the pressure regulating valve 54 decreases. The cathode pressure sensor 65 is disposed between the pressure regulating valve 54 and the fuel cell 20 in the oxidizing gas discharge flow path 34. The cathode pressure sensor 65 detects the pressure of the cathode 24. The muffler 48 is disposed downstream of the connection point B with the bypass channel 36 in the oxidizing gas discharge channel 34. The muffler 48 reduces the exhaust noise of the cathode exhaust gas.

  The bypass channel 36 communicates the oxidizing gas supply channel 32 and the oxidizing gas discharge channel 34. The bypass channel 36 is connected to the oxidizing gas supply channel 32 at the connection point A, and is connected to the oxidizing gas discharge channel 34 at the connection point B. The bypass valve 56 is disposed in the bypass flow path 36 and adjusts the flow rate of air flowing through the bypass flow path 36 by changing the opening degree in accordance with an instruction from the control unit 98. Therefore, a part of the air discharged from the air compressor 50 flows into the bypass passage 36 according to the degree of opening of the bypass valve 56 and goes from the oxidizing gas discharge passage 34 to the atmosphere without passing through the fuel cell 20. And discharged. When the bypass valve 56 is closed, all the air discharged from the air compressor 50 is supplied to the fuel cell 20. The bypass valve 56 is normally closed and opened in response to a command from the control unit 98.

  The fuel gas supply / discharge system 70 supplies hydrogen as fuel gas supplied from the hydrogen tank 71 to the fuel cell 20 and discharges it. The fuel gas supply / discharge system 70 includes a hydrogen tank 71, a fuel gas supply flow path 72, a tank pressure sensor 73, a main stop valve 74, an anode pressure regulating valve 75, an injector 76, an anode pressure sensor 77, a fuel A gas discharge channel 82, a gas-liquid separator 83, a circulation pipe 84, a hydrogen pump 85, and an exhaust / drain valve 86 are provided.

  The hydrogen tank 71 stores high-pressure hydrogen. The fuel gas supply channel 72 constitutes a channel for hydrogen supplied from the hydrogen tank 71 to the fuel cell 20. The tank pressure sensor 73 detects the pressure in the hydrogen tank 71. The main stop valve 74, the anode pressure regulating valve 75, the injector 76, and the anode pressure sensor 77 are arranged in this order from the side close to the hydrogen tank 71 in the fuel gas supply flow path 72. The main stop valve 74 turns on and off the supply of hydrogen from the hydrogen tank 71 in accordance with an instruction from the control unit 98. The anode pressure regulating valve 75 adjusts the pressure of hydrogen supplied to the fuel cell 20. The injector 76 is configured by an electromagnetically driven on-off valve, and is driven according to the driving cycle and valve opening time set by the control unit 98 to inject hydrogen. The anode pressure sensor 77 is disposed closer to the fuel cell 20 than the connection portion with the circulation pipe 84 in the fuel gas supply channel 72, and detects the pressure of the anode 22.

  The fuel gas discharge passage 82 constitutes a passage for anode exhaust gas discharged from the fuel cell 20. The outlet of the fuel gas discharge channel 82 is connected to the downstream side of the connection point B with the bypass channel 36 in the oxidizing gas discharge channel 34. The gas-liquid separator 83 is disposed in the fuel gas discharge passage 82 and separates liquid water from the anode exhaust gas mixed with liquid water discharged from the fuel cell 20. The circulation pipe 84 connects the gas-liquid separator 83 and the fuel cell 20 side with respect to the injector 76 of the fuel gas supply flow path 72. The hydrogen pump 85 is arranged in the circulation pipe 84 and circulates anode exhaust gas containing hydrogen that has not been used in the electrochemical reaction to the fuel gas supply flow path 72. The exhaust drain valve 86 is disposed on the downstream side of the gas-liquid separator 83 in the fuel gas discharge channel 82. The exhaust / drain valve 86 is normally closed and opened in response to a command from the control unit 98. Thereby, the liquid water and impurity gas separated by the gas-liquid separator 83 are discharged to the outside of the fuel cell system 10.

  The control unit 90 is configured by an ECU (Electronic Control Unit), and includes a storage device 91 and a CPU 97. The storage device 91 is configured by a recording medium such as a ROM 92 and a RAM 95. The ROM 92 stores a control program 93 and a compressor map 94. The CPU 97 functions as the control unit 98 by developing and executing the control program 93. The compressor map 94 is created in advance as a map showing the operating characteristics of the air compressor 50. Detailed description of the compressor map 94 will be described later.

  The control unit 98 performs overall control of the fuel cell system 10. The control unit 98 includes an atmospheric pressure sensor 61, an air flow meter 62, a pressure sensor 63, a flow rate sensor 64, a cathode pressure sensor 65, a tank pressure sensor 73, an anode pressure sensor 77, and other sensors, a pressure regulating valve 54, and a bypass valve 56. In addition to various sensors included in the fuel cell system 10 and various opening sensors included in various valves such as the main stop valve 74, the anode pressure regulating valve 75, the injector 76, and the exhaust drain valve 86, an illustration of the fuel cell vehicle is illustrated. A detection signal is input from an accelerator opening sensor, a vehicle speed sensor, or the like. In addition, the control unit 98 supplies drive signals to various valves such as the pressure regulating valve 54, the bypass valve 56, the main stop valve 74, the anode pressure regulating valve 75, the injector 76, and the exhaust drain valve 86, the air compressor 50, the hydrogen pump 85, and the like. To control the operation of each part. In addition, the control unit 98 executes a requested operation point setting process described later.

  FIG. 2 is an explanatory diagram for explaining the operating characteristics of the air compressor 50. In FIG. 2, the vertical axis indicates the pressure ratio of the air compressor 50, and the horizontal axis indicates the flow rate of air discharged from the air compressor 50 (hereinafter also simply referred to as “flow rate”). The pressure ratio of the air compressor 50 means the ratio of the pressure of air discharged from the air compressor 50 to the pressure of air sucked into the air compressor 50. In the present embodiment, the pressure of the air sucked into the air compressor 50 approximates the atmospheric pressure detected by the atmospheric pressure sensor 61. In the present embodiment, the pressure of the air discharged from the air compressor 50 corresponds to the outlet pressure of the air compressor 50 detected by the pressure sensor 63.

  FIG. 2 shows the operating characteristics of the air compressor 50 when the bypass valve 56 is closed. The operating characteristics of the air compressor 50, which is a turbo type air compressor, are determined by the rotational speed of the rotating body of the air compressor 50 (hereinafter also simply referred to as “rotational speed”) and the opening of the pressure regulating valve 54, and the pressure ratio and flow rate. Means the relationship. FIG. 2 shows an equal rotation speed line L1 connecting a plurality of black dots indicating operating points when the rotation speed is kept constant and the opening of the pressure regulating valve 54 is changed. The plurality of black spots indicating the operating points are determined in advance by the fuel cell system 10 shown in FIG. As shown in FIG. 2, the pressure ratio and the flow rate of the air compressor 50 depend on each other. The pressure ratio decreases as the opening degree of the pressure regulating valve 54 increases, and increases as the rotational speed increases. Further, the flow rate increases as the opening of the pressure regulating valve 54 increases, and increases as the rotational speed increases. When the opening degree of the pressure regulating valve 54 is relatively small, the change in the pressure ratio with respect to the change in the flow rate is relatively small.

  In FIG. 2, in addition to a plurality of equal rotation speed lines L1 having different rotation speeds, a maximum rotation speed line L2, a maximum pressure ratio line L3, a surge line L4, and a stall line L5 are shown. In FIG. 2, a line obtained by extending the equal rotation speed line L1 to the lower side of the stall line L5 is indicated by a broken line.

  The maximum rotation speed line L2 means an equal rotation speed line at the maximum rotation speed determined according to the specifications of the air compressor 50. The maximum pressure ratio line L3 means the maximum pressure ratio determined according to the specifications of the air compressor 50. For this reason, the maximum pressure ratio line L3 is constant regardless of the flow rate. The surge line L4 is determined in advance in order to avoid surging that may occur at a low flow rate. The left side of the surge line L4 is also called a surge region and means a region where surging may occur. If surging occurs, there is a risk that an extreme impact will be applied to the air compressor 50, and adjustment of the flow rate may be difficult. The surge line L4 is obtained by measurement in advance in the fuel cell system 10 shown in FIG.

  The stall line L5 is formed by connecting a plurality of plots indicating operating points when the pressure regulating valve 54 is fully open. Below the stall line L5 is an operating region in which the air compressor 50 cannot be realized because it exceeds the upper limit of the opening of the pressure regulating valve 54. The stall line L5 is obtained by measurement in advance in the fuel cell system 10 shown in FIG. The stall line L5 may be determined in advance based on a pressure loss value calculated from an air flow rate in each part such as the fuel cell 20 and the oxidizing gas supply flow path 32. That is, the stall line L5 means the minimum pressure ratio that is the minimum value of the pressure ratio with respect to the flow rate in the operating characteristics of the air compressor 50.

  In FIG. 2, the area surrounded by the maximum rotation speed line L2, the maximum pressure ratio line L3, the surge line L4, and the stall line L5 is indicated by dot hatching as the operable area Ar1 of the air compressor 50. Yes. In the compressor map 94 shown in FIG. 1, each point in the operable area Ar <b> 1, that is, a combination of a pressure ratio and a flow rate is determined in advance as the operating characteristics of the air compressor 50. In the compressor map 94, equations representing the equal rotation speed line L1, the maximum rotation speed line L2, the maximum pressure ratio line L3, the surge line L4, and the stall line L5 are determined in advance.

  In the fuel cell system 10 of the present embodiment, the control unit 98 executes a required operation point setting process described below, thereby obtaining a required operation point that is an operation point commanded to the air compressor 50. Is set in the operable area Ar1.

  In the present embodiment, the air compressor 50 corresponds to a subordinate concept of the turbo compressor in the means for solving the problem. The stall line L5 is a subordinate concept of a predetermined minimum pressure ratio, which is a minimum value of the pressure ratio that can be realized with respect to the flow rate of the oxidizing gas that can be discharged from the turbo compressor, in the means for solving the problem. It corresponds to.

A-2. Required action point setting process:
FIG. 3 is a flowchart showing the procedure of the requested operation point setting process. The required operation point setting process is repeatedly executed when a starter switch (not shown) of the fuel cell vehicle is pressed and the fuel cell system 10 is activated.

  The control unit 98 receives the air flow rate and pressure ratio required by the fuel cell 20 (step S110). The air flow rate and pressure ratio required by the fuel cell 20 are determined based on the output request of the fuel cell 20 in accordance with detection signals from the accelerator opening sensor and the vehicle speed sensor. The control unit 98 sets a required operating point based on a target flow rate that is a target value of the flow rate of air discharged from the air compressor 50 and a target pressure ratio that is a target value of a pressure ratio before and after compression by the air compressor 50. (Step S120). At this time, the control unit 98 performs feedback control based on the flow rate measured by the flow rate sensor 64 and the pressure ratio specified from the pressure measured by the cathode pressure sensor 65, and the target flow rate and the target pressure ratio are determined. The required operating point is set so that the control deviation from the actual flow rate and pressure ratio can be eliminated. In this embodiment, PID (Proportional Integral Differential) control is used as feedback control. In PID control, control is performed using a control amount including a proportional term corresponding to the control deviation of the operating point, an integral term of the control deviation, and a differential term of the control deviation. In place of PID control, feedback control including at least a proportional term and an integral term may be used.

  The control unit 98 determines whether or not the target pressure ratio at the required operating point set in step S120 is smaller than the minimum pressure ratio corresponding to the target flow rate at the set required operating point (step S130). More specifically, the control unit 98 refers to the compressor map 94 in which the stall line L5 is set in advance, and determines whether or not the required operating point set in step S120 is located below the stall line L5. Determine whether.

  When it is determined that the target pressure ratio at the required operating point is not smaller than the minimum pressure ratio corresponding to the target flow rate at the set required operating point (step S130: NO), that is, the target pressure ratio at the required operating point is If it is determined that the pressure ratio is not less than the minimum pressure ratio, the process returns to step S110. Therefore, in this case, the control unit 98 controls the opening degree of the pressure regulating valve 54 and the rotation speed of the air compressor 50 so that the target flow rate and the target pressure ratio at the required operating point set in step S120 are obtained. More specifically, a command to output the opening corresponding to the required operating point to the pressure regulating valve 54 and a command to operate the air compressor 50 at the rotation speed corresponding to the required operating point. Is output. As a result, the pressure regulating valve 54 has the commanded opening, and the air compressor 50 supplies air to the cathode 24 of the fuel cell 20 at the target flow rate and target pressure ratio.

  On the other hand, when it is determined that the target pressure ratio of the required operating point is smaller than the minimum pressure ratio corresponding to the target flow rate of the set required operating point (step S130: YES), the control unit 98 is set in step S120. The target pressure ratio of the set required operation point is increased to the minimum pressure ratio corresponding to the set target flow rate of the required operation point (step S140). After step S140, the process returns to step S110.

  FIG. 4 is an explanatory diagram for explaining the result of step S140. In FIG. 4, the required operating point P1 set in step S120 is indicated by an asterisk, and the required operating point P2 increased to the minimum pressure ratio in step S140 is indicated by a large circle with respect to FIG. The requested operation point P1 set in step S120 is located below the stall line L5. Accordingly, in step S140, the requested operation point is changed from the requested operation point P1 set in step S120 to the requested operation point P2 on the stall line L5. Therefore, the required operating point is set in the operable area Ar1 of the air compressor 50. The control unit 98 controls the opening degree of the pressure regulating valve 54 and the rotation speed of the air compressor 50 so that the target flow rate and the target pressure ratio at the required operating point P2 changed in step S140 are obtained. More specifically, an opening degree corresponding to the required operating point P2, that is, a command to make the opening degree fully open is output to the pressure regulating valve 54, and the required operating point P2 is set to the air compressor 50. A command to operate at the corresponding rotation speed is output. As a result, the pressure regulating valve 54 is fully opened, and the air compressor 50 supplies air to the cathode 24 of the fuel cell 20 at the target flow rate and target pressure ratio.

  According to the fuel cell system 10 of the present embodiment described above, when the target pressure ratio at the set required operating point is smaller than the minimum pressure ratio corresponding to the target flow rate at the required operating point, the target at the required operating point is set. Since the pressure ratio is increased to the minimum pressure ratio, it is possible to suppress the setting of the required operating point in the operation region where the air compressor 50 cannot be realized, and it is possible to suppress the operation of the air compressor 50 at the required operating point which cannot be realized. Therefore, it is possible to suppress the performance of the fuel cell system 10 from being impaired by continuously operating the air compressor 50 at the required operating point that cannot be realized.

  Here, if the required operating point remains set below the stall line L5, the pressure regulating valve 54 is fully open, so the required operating point cannot be realized, and control is performed based on the difference between the required operating point and the actual operating point. Deviation occurs. That is, if the pressure ratio at the actual operating point is larger than the target pressure ratio at the required operating point, the pressure regulating valve 54 that has already been fully opened is further opened to reduce the pressure ratio. The feedback integral term to be controlled accumulates.

  However, according to the fuel cell system 10 of the present embodiment, the target pressure at the required operating point is set when the target pressure ratio at the set required operating point is smaller than the minimum pressure ratio corresponding to the target flow rate at the required operating point. Since the ratio is increased to the minimum pressure ratio, the required operating point can be realized when the pressure regulating valve 54 is fully opened, and accumulation of the feedback integral term can be suppressed. Therefore, when the requested operating point is further changed based on the output request of the fuel cell 20 or the like, it is possible to suppress the delay of control due to the accumulation of the feedback integral term.

  Further, since it is possible to suppress delay in the control for operating the pressure regulating valve 54 to close, the flow rate becomes excessive with respect to the required flow rate of the fuel cell 20 and the pressure is insufficient with respect to the required pressure of the fuel cell 20. Can be suppressed. For this reason, since it can suppress that the pressure of the cathode 24 falls, drying of the membrane electrode assembly of the fuel cell 20 can be suppressed, and it can suppress that the electric power generation performance of the fuel cell 20 falls.

  In addition, since only the target pressure ratio is changed without changing the target flow rate with respect to the required operating point set in step S120, it is possible to suppress that the flow rate required by the fuel cell 20 cannot be realized. It can be suppressed that the output request cannot be satisfied. Further, since the target pressure ratio is increased to the minimum pressure ratio (stall line L5) with respect to the required operating point set in step S120, the target pressure ratio is excessively increased beyond the minimum pressure ratio (stall line L5). This can suppress the deterioration of fuel consumption. In addition, since the target pressure ratio at the required operating point is increased to the minimum pressure ratio by referring to the predetermined compressor map 94, an increase in the processing load of the CPU 97 can be suppressed.

B. Second embodiment:
The fuel cell system 10 of the second embodiment is different from the fuel cell system 10 of the first embodiment in the required operation point setting process. Since other configurations including the device configuration are the same as those of the first embodiment, the same reference numerals are given to the same configurations, and detailed descriptions thereof are omitted.

  In the required operation point setting process of the second embodiment, in addition to the case where the pressure ratio of the required operation point is smaller than the minimum pressure ratio, that is, the required operation point is below the stall line L5, the required operation point is the air In any other case outside the operable area Ar1 of the compressor 50, the set required operating point is changed into the operable area Ar1.

  FIG. 5 is an explanatory diagram for explaining the requested operation point changed according to the second embodiment. FIG. 5 shows, in addition to FIG. 4, the set required operation points P11, P21, P31 and P41 by asterisks, and the operation points P12, P22, P32 and P42 changed in the operable region Ar1 are large circles. This is indicated by a mark.

  In the required operating point setting process in the second embodiment, the setting is performed when the required operating point P11 set based on the output request of the fuel cell 20 is located above the maximum rotational speed line L2 (case a). The target pressure ratio is decreased without changing the target flow rate at the requested operating point P11, and the operating point P12 on the maximum rotational speed line L2 is changed. Further, when the set required operating point P21 is located above the maximum pressure ratio line L3 (case b), the target pressure ratio is decreased without changing the target flow rate of the set required operating point P21. The operating point P22 is changed to the maximum pressure ratio line L3. In this manner, the control unit 98 changes only the target pressure ratio without changing the target flow rate with respect to the set required operating point.

  Further, when the set required operating point P31 is located on the left side of the surge line L4 (case c), the target flow rate is set on the surge line L4 without changing the target pressure ratio of the set required operating point P31. While changing to the operating point P32 on the increased surge line L4, the bypass valve 56 is opened to allow excess air to flow through the bypass passage 36. As a result, the air discharged from the air compressor 50 is divided into a part that is supplied to the fuel cell 20 and a part that passes through the bypass channel 36 without being supplied to the fuel cell 20. Therefore, it is possible to suppress the occurrence of surging while satisfying the flow rate and pressure ratio required by the fuel cell 20. When the set required operating point P41 is located above the maximum pressure ratio line L3 and on the left side of the surge line L4 (case d), the target flow rate at the required operating point P41 is set on the surge line L4. After increasing and opening the bypass valve 56, the target pressure ratio is decreased and changed to the operating point P42 on the maximum pressure ratio line L3.

  According to the fuel cell system 10 of the second embodiment described above, the same effects as the fuel cell system 10 of the first embodiment can be obtained. In addition, since it is possible to suppress the operation of the air compressor 50 at a rotation speed exceeding the predetermined maximum rotation speed and a pressure ratio exceeding the maximum pressure ratio, the motor of the air compressor 50 is prevented from excessively generating heat. The failure and deterioration of the air compressor 50 can be suppressed. Moreover, since it can suppress that the air compressor 50 operate | moves within a surge area | region, generation | occurrence | production of surging can be suppressed.

C. Other embodiments:
(1) In the required operation point setting process of the above embodiment, the required operation point is changed by referring to a predetermined compressor map 94, but the present invention is not limited to this. Instead of referring to the compressor map 94, the stall line L5 or the like may be calculated and specified based on detection signals of various sensors during operation of the fuel cell system 10. For example, one or a plurality of operating points are specified based on the detection signals of the pressure sensor 63 and the flow rate sensor 64 when the pressure regulating valve 54 is fully opened, and the flow rate and the pressure ratio at each operating point are applied to the model formula. Thus, the stall line L5 may be specified. Even with this configuration, the same effects as those of the above-described embodiment can be obtained. In addition, the capacity of the ROM 92 of the storage device 91 can be reduced. Further, since the stall line L5 can be specified in accordance with the manufacturing error of the components constituting the air compressor 50, the outside air temperature, the outside air pressure, the fluctuation of the pressure loss value caused by the moisture amount in the fuel cell 20, and the like, the stall line L5 Errors can be suppressed. For example, the control unit 98 controls the operation of the air compressor 50 and the pressure regulating valve 54 according to the rotation speed of the air compressor 50 required at the time of low temperature or hydrogen dilution in addition to the output request of the fuel cell 20. May be. Even with such a configuration, the same effects as those of the above embodiment can be obtained.

(2) The vertical axis of the compressor map 94 of the above embodiment is the pressure ratio of the air compressor 50. However, instead of the pressure ratio, the pressure of the air discharged from the air compressor 50 may be used. It may be. In such a configuration, the required operating point that calculates the pressure ratio of the air compressor 50 based on the pressure or pressure loss value of the air discharged from the air compressor 50 and indicates the target pressure ratio and the target flow rate that are target values of the pressure ratio. May be set. Even with this configuration, the same effects as those of the above-described embodiment can be obtained.

(3) The configuration of the fuel cell system 10 of the above embodiment is merely an example, and various changes can be made. For example, in the fuel cell system 10, the pressure regulating valve 54 is disposed in the oxidizing gas discharge flow path 34, but may be disposed in the oxidizing gas supply flow path 32 instead of the oxidizing gas discharge flow path 34. For example, the fuel cell system 10 may further include a refrigerant circulation system that cools the fuel cell 20 in order to keep the temperature of the fuel cell 20 within a predetermined range. Even with this configuration, the same effects as those of the above-described embodiment can be obtained.

(4) The requested operation point setting process in the second embodiment is merely an example, and various changes can be made. For example, in the compressor map 94, when the maximum flow rate line indicating the maximum flow rate according to the specifications of the air compressor 50 is further determined in advance and the set required operation point is located on the right side of the maximum flow rate line, the required operation is performed. The point target flow rate may be changed to the maximum flow rate line. Further, for example, when the set required operating point is larger than the maximum flow line and below the stall line L5, the target operating point is changed to the required flow point after changing the target flow rate of the required operating point to the maximum flow line. The target pressure ratio may be increased on the stall line L5. Further, for example, when the set required operating point is located above the maximum pressure ratio line L3 and on the left side of the surge line L4 (case d), the target pressure ratio is changed to the maximum pressure ratio line L3. After that, the target flow rate may be increased on the surge line L4 and the bypass valve 56 may be opened. Even with such a configuration, the same effects as those of the second embodiment can be obtained. Further, for example, in the compressor map 94, a zero slope line connecting a plot in which the pressure ratio does not substantially decrease with an increase in the flow rate in the constant rotation speed line L1 is further determined in advance, and the set required operating point is the zero slope line. When it is located on the left side, the target flow rate may be increased on the zero slope line and the bypass valve 56 may be opened. According to such a configuration, it is possible to prevent the required operating point from being set in a region where the flow rate changes suddenly with respect to minute pressure fluctuations. Therefore, when a control error of the air compressor 50 occurs, the actual operating point It is possible to suppress the flow rate from being significantly different from the target flow rate at the required operating point. Further, for example, when the set required operating point is located on the left side of the surge line L4 (case c), instead of increasing the target flow rate of the required operating point on the surge line L4, The opening degree of the bypass valve 56 may be further increased while increasing the target flow rate further than the flow rate of the surge line L4. According to such a configuration, when the control error of the air compressor 50 occurs, it is possible to suppress the actual operating point from being in the surge region, so that the failure and deterioration of the air compressor 50 can be further suppressed.

(5) In the above embodiment, the fuel cell system 10 is mounted and used in a fuel cell vehicle. However, the fuel cell system 10 may be mounted on any other moving body such as a ship or a robot instead of the vehicle. It may be used as a type fuel cell. Even with this configuration, the same effects as those of the above-described embodiment can be obtained.

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

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 20 ... Fuel cell 22 ... Anode 24 ... Cathode 30 ... Oxidizing gas supply / discharge system 32 ... Oxidizing gas supply channel 34 ... Oxidizing gas discharge channel 36 ... Bypass channel 42 ... Air cleaner 48 ... Muffler 50 ... Air Compressor 54 ... Pressure regulating valve 56 ... Bypass valve 61 ... Atmospheric pressure sensor 62 ... Air flow meter 63 ... Pressure sensor 64 ... Flow rate sensor 65 ... Cathode pressure sensor 70 ... Fuel gas supply / discharge system 71 ... Hydrogen tank 72 ... Fuel gas supply flow path 73 ... tank pressure sensor 74 ... main stop valve 75 ... anode pressure regulating valve 76 ... injector 77 ... anode pressure sensor 82 ... fuel gas discharge channel 83 ... gas-liquid separator 84 ... circulation piping 85 ... hydrogen pump 86 ... exhaust drain valve 90 ... Control unit 91 ... Storage device 92 ... ROM
93 ... Control program 94 ... Compressor map 95 ... RAM
97 ... CPU
98 ... Control unit a, b, c, d ... A, B ... Connection point Ar1 ... Operating range L1 ... Equivalent rotation speed line L2 ... Maximum rotation speed line L3 ... Maximum pressure ratio line L4 ... Surge line L5 ... Stall line P1, P2, P11, P21, P31, P41 ... required operating points P12, P22, P32, P42 ... operating points

Claims (1)

A fuel cell system,
A fuel cell;
A turbo compressor for supplying an oxidizing gas to the fuel cell;
A pressure regulating valve for adjusting the pressure of the oxidizing gas in the fuel cell;
A control unit for controlling operations of the turbo compressor and the pressure regulating valve in response to at least an output request to the fuel cell;
With
The controller is
A target flow rate that is a target value of the flow rate of the oxidizing gas discharged from the turbo compressor, and a pressure of the oxidizing gas discharged from the turbo compressor with respect to a pressure of the oxidizing gas sucked into the turbo compressor. The required operating point of the turbo compressor is set according to the target pressure ratio that is the target value of the pressure ratio that is the ratio,
The target pressure ratio at the set required operating point is smaller than a predetermined minimum pressure ratio that is a minimum value of the pressure ratio that can be realized with respect to the flow rate of the oxidizing gas that can be discharged from the turbo compressor. The target pressure ratio of the set required operating point is increased to the minimum pressure ratio corresponding to the target flow rate,
Fuel cell system.

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