JP2009054427A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system that prevents a local overheating of a fuel cell stack. <P>SOLUTION: The fuel cell system 1 is provided with a fuel cell stack 10, a coolant circulation means to circulate coolant so as to go through the fuel cell stack, and a butterfly valve 42 which restricts flow-rate of the coolant supplied to the fuel cell stack 10, and when the temperature T11 of the fuel cell stack 10 is a warming-up completion temperature or more, the butterfly valve 42 releases restriction of the flow-rate of the coolant. The fuel cell system 1 is provided with a reaction status estimating means to estimate reaction status of the fuel cell stack 10 and a limiting value setting means which sets a limiting value of the flow-rate of the coolant supplied to the fuel cell stack 10 based on the reaction status estimated by a reaction status estimating means so as to prevent over heating of the fuel cell stack 10, when the temperature T11 of the fuel cell stack 11 is less than the warming-up completion temperature, and gives a command to a coolant flow-rate restriction means so as to limit within the set limiting value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art In recent years, attention has been focused on fuel cell stacks configured by stacking fuel cells (single cells) such as polymer electrolyte fuel cells (PEFC). In such a fuel cell stack, hydrogen (fuel gas) and oxygen-containing air (oxidant gas) are supplied and discharged, and the refrigerant circulates through the fuel cell stack.

  For example, the flow path of the refrigerant in the fuel cell stack will be described. The refrigerant is introduced into the fuel cell stack from one refrigerant inlet, and is distributed to the refrigerant flow path of each single cell while proceeding in the stacking direction. Supplied. Further, the refrigerant from each single cell gathers while proceeding in the stacking direction inside the fuel cell stack, and is discharged to the outside from one refrigerant outlet. Such a supply / discharge system is the same for hydrogen and air.

  Further, the fuel cell stack has a temperature (warm-up completion temperature) at which power generation is favorably determined based on the type of the catalyst that promotes the electrode reaction, etc. It is important to manage the temperature of the stack.

In particular, when the fuel cell stack is started from a low temperature environment such as below freezing point, the flow rate of the refrigerant to the fuel cell stack is used to quickly raise the temperature of the fuel cell stack to the warm-up completion temperature by using self-heating by power generation. In other words, there has been proposed a technique for reducing the amount of cooling, that is, limiting the flow rate of the refrigerant and suppressing the degree of cooling by the refrigerant. And the technique which cancels | releases the restriction | limiting of a refrigerant | coolant flow volume when the temperature of a fuel cell stack reaches warming-up completion temperature is proposed (refer patent document 1).
Note that the temperature of the fuel cell stack is indirectly detected by detecting that the temperature of the refrigerant is substantially equal to, for example, the temperature of the refrigerant discharged from one refrigerant outlet.

JP 2005-116257 A

  However, in the fuel cell stack, depending on the shape and direction of the refrigerant flow path, there are portions where the refrigerant easily flows and portions where it is difficult to flow. Therefore, if the flow rate of the refrigerant is limited until the temperature of the fuel cell stack based on the temperature of the discharged refrigerant rises to the warm-up completion temperature, for example, the flow rate of the refrigerant is insufficient in a portion where the refrigerant is difficult to flow, There is a possibility that the single cell in the vicinity of this portion is locally overheated. In such an overheated state, for example, the electrolyte membrane or the like may deteriorate, and the durability of the fuel cell stack may be reduced.

  Then, this invention makes it a subject to provide the fuel cell system which prevents that a fuel cell stack will be in an overheating state locally.

  As means for solving the above-mentioned problems, the present invention provides a fuel cell stack that generates electric power when a reaction gas is supplied, a refrigerant circulation means that circulates a refrigerant through the fuel cell stack, and the fuel cell. Refrigerant flow restriction means for restricting the flow rate of the refrigerant supplied to the stack, and when the temperature of the fuel cell stack is lower than the warm-up completion temperature, the refrigerant flow restriction means executes restriction of the flow rate of the refrigerant. In the fuel cell system, when the temperature of the fuel cell stack is less than a warm-up completion temperature and the reaction state estimation means for estimating the reaction state of the fuel cell stack, overheating of the fuel cell stack is prevented As described above, the limit value of the flow rate of the refrigerant supplied to the fuel cell stack is changed based on the reaction state estimated by the reaction state estimating means, and the changed A limit changing means for instructing said refrigerant flow restricting means to limit in limit value, a fuel cell system comprising: a.

According to such a fuel cell system, the reaction state estimation means is based on the reaction state of the fuel cell stack, that is, in the embodiment described later, the temperature, the voltage, the IV characteristic, and the potential difference between the average cell voltage and the minimum cell voltage. Thus, the reaction state of the fuel cell (the progress of warm-up) is estimated.
Then, the limit value changing means changes the limit value of the flow rate of the refrigerant supplied to the fuel cell stack based on the estimated reaction state of the fuel cell stack so that overheating of the fuel cell stack is prevented. Then, the refrigerant flow restriction means is commanded to restrict the refrigerant flow path with the changed restriction value. Next, the refrigerant flow rate limiting means limits the refrigerant flow rate to the fuel cell stack so that the commanded limit value is reached.

  In this way, the limit value of the refrigerant flow rate is changed (set) based on the reaction state of the fuel cell, and the refrigerant flow rate is limited accordingly, so that the fuel cell stack is locally overheated. Can be prevented.

  The refrigerant circulation means includes a refrigerant pump that is operated by the generated power of the fuel cell stack and pumps the refrigerant, and the refrigerant flow restriction means adjusts a pressure loss received by the flowing refrigerant. When the pressure loss adjustment unit increases the pressure loss so as to limit the refrigerant supplied to the fuel cell stack, the refrigerant pump increases its rotational speed and increases its power consumption. This is a fuel cell system.

According to such a fuel cell system, when the pressure loss adjusting unit increases the pressure loss so as to limit the refrigerant supplied to the fuel cell stack, the refrigerant pump increases its rotational speed and increases its power consumption. As a result, the power generated by the fuel cell stack can be increased. Thereby, the self-heating amount of the fuel cell stack accompanying power generation can be increased, and warming up of the fuel cell stack can be promoted.
It should be noted that the degree of increasing the pressure loss (the opening degree of the butterfly valve in the embodiment described later) is set higher than the pressure loss when the number of revolutions of the refrigerant pump is not changed, and the refrigerant is limited to the refrigerant flow restriction means (pressure loss). It is preferable to increase the rotational speed of the refrigerant pump in response to the difficulty of passing through the adjusting unit).

  The system further includes a reaction gas replacement unit that replaces the inside of the fuel cell stack with a reaction gas when the system is started up. The reaction state estimation unit is based on the voltage of the fuel cell stack when the reaction gas is replaced by the reaction gas replacement unit. The fuel cell system is characterized by estimating a reaction state of the fuel cell stack.

According to such a fuel cell system, the reaction state estimation means can estimate the reaction state of the fuel cell stack based on the voltage of the fuel cell stack when the reaction gas is replaced by the reaction gas replacement means.
Here, even if the temperature of the fuel cell stack is lower than the warm-up completion temperature, for example, the fuel cell stack is new, the electrode reaction proceeds favorably, and a good voltage may be output. Therefore, even in such a case, the reaction state estimating means estimates the reaction state of the fuel cell stack based on the output voltage, and the limit value changing means changes the refrigerant flow rate limit value based on this. The refrigerant can be supplied appropriately.

  The reaction state estimation means estimates the reaction state of the fuel cell stack based on a voltage-current characteristic (IV characteristic) of the fuel cell stack.

According to such a fuel cell system, the reaction state estimation means can estimate the reaction state of the fuel cell stack based on the voltage-current characteristic (IV characteristic) of the fuel cell stack.
Here, even if the temperature of the fuel cell stack is lower than the warm-up completion temperature, for example, the fuel cell stack is new, the electrode reaction proceeds favorably, and good IV characteristics may be obtained. Therefore, even in such a case, the reaction state estimating means estimates the reaction state of the fuel cell stack based on the IV characteristics, and the limit value changing means changes the limit value of the refrigerant flow rate based on this, and appropriately It is possible to supply a refrigerant.

  Further, the reaction state estimation means is configured to provide a voltage difference (ΔV21) between a predetermined voltage (average cell voltage V21 in the embodiment described later) and a minimum cell voltage (V22) obtained from a plurality of single cells constituting the fuel cell stack. ) To estimate the reaction state of the fuel cell stack.

According to such a fuel cell system, the reaction state estimation means can estimate the reaction state of the fuel cell stack based on the voltage difference between the predetermined voltage obtained from the plurality of single cells and the minimum cell voltage.
Here, in general, when the warm-up of the fuel cell stack progresses and the temperature of the fuel cell stack increases, the voltage difference between the predetermined voltage and the minimum cell voltage decreases, and the power generation of the fuel cell stack is stabilized. Therefore, the reaction state estimation means estimates the reaction state of the fuel cell stack based on the voltage difference, and the limit value changing means changes the refrigerant flow rate limit value based on this, and supplies the refrigerant appropriately. can do.

  According to the present invention, it is possible to provide a fuel cell system that prevents the fuel cell stack from being overheated locally.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

≪Fuel cell system≫
A fuel cell system 1 shown in FIG. 1 is mounted on a fuel cell vehicle (mobile body) (not shown). The fuel cell system 1 includes a fuel cell stack 10, a cell voltage monitor 15, an anode system that supplies and discharges hydrogen (fuel gas and reactive gas) to and from the anode of the fuel cell stack 10, and a cathode of the fuel cell stack 10. On the other hand, a cathode system that supplies and discharges air (oxidant gas, reaction gas), a refrigerant circulation system (refrigerant circulation means) that circulates refrigerant (radiator liquid) through the fuel cell stack 10, and the fuel cell stack 10 A power consumption system that consumes the generated power, an IG 61 (ignition), and an ECU 70 (Electronic Control Unit) that electronically controls these are provided.

<Fuel cell stack>
The fuel cell stack 10 is a stack formed by stacking a plurality of (for example, 200 to 400) solid polymer type single cells, and the plurality of single cells are electrically connected in series. The single cell includes an MEA and two conductive separators sandwiching the MEA. The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane or the like, and an anode and a cathode sandwiching the electrolyte membrane.

  The anode and cathode are mainly composed of a conductive porous material such as carbon paper, and contain a catalyst (Pt, Ru, etc.) for causing an electrode reaction in the anode and cathode.

Each separator is formed with a groove for supplying hydrogen or air to the entire surface of each MEA, and through holes for supplying and discharging hydrogen or air to all single cells. It functions as a channel 11 (fuel gas channel) and a cathode channel 12 (oxidant gas channel). Then, when hydrogen is supplied to each anode via the anode flow path 11 and air is supplied to each cathode via the cathode flow path 12, an electrode reaction occurs, and an OCV (Open Circuit Voltage) in each single cell, Open circuit voltage).
Next, when the OCV is generated in this way, the fuel cell stack 10 is electrically connected to the traveling motor 51 and the like, and when the current is taken out, the fuel cell stack 10 generates power.

  Each separator is formed with a groove and a through-hole that constitute a refrigerant flow path 13 through which a refrigerant for cooling the fuel cell stack 10 flows. The refrigerant flows from one inlet in the stacking direction of the fuel cell stack 10 and is distributed and supplied to the refrigerant flow path 13 of each single cell. In addition, the refrigerant is collected from the refrigerant flow path 13 of each single cell while flowing in the stacking direction, and then discharged from one outlet to the outside.

<Cell voltage monitor>
The cell voltage monitor 15 is a device that detects a voltage (cell voltage) for each of a plurality of single cells constituting the fuel cell stack 10, and includes a monitor main body and a wire harness that connects the monitor main body and each single cell. ing.

  The monitor main body scans all single cells in a predetermined cycle, detects the cell voltage of each single cell, and calculates the average cell voltage V21 (predetermined voltage), the lowest cell voltage V22, and the average cell voltage V21 and the lowest cell voltage V22. The difference ΔV21 (V21−V22) is calculated. The monitor body outputs the voltage difference ΔV21 to the ECU 70.

<Anode system>
The anode system includes a hydrogen tank 21 and a shutoff valve 22.
The hydrogen tank 21 is connected to the inlet of the anode flow path 11 via a pipe 21a, a shutoff valve 22, and a pipe 22a. Then, when the shutoff valve 22 is opened by a command from the ECU 70, hydrogen is supplied from the hydrogen tank 21 to the anode flow path 11 via the shutoff valve 22 and the like.
The outlet of the anode flow path 11 is connected to a pipe 22b, and the anode off gas discharged from the anode flow path 11 is discharged to the outside through the pipe 22b.

<Cathode system>
The cathode system includes a compressor 31.
The compressor 31 is connected to the inlet of the cathode channel 12 via a pipe 31a. When the compressor 31 is operated in accordance with a command from the ECU 70, air containing oxygen is taken in and supplied to the cathode channel 12. Further, the pipe 31a is provided with a humidifier (not shown) so that the air supplied to the cathode channel 12 is appropriately humidified.
Note that the compressor 31 and a refrigerant pump 41 described later share a motor M serving as a power source, thereby simplifying the system configuration. That is, the impeller of the compressor 31 and the impeller of the refrigerant pump 41 are attached around the output shaft of the motor M.

  The outlet of the cathode channel 12 is connected to the pipe 31b, and the cathode off gas discharged from the cathode channel 12 is discharged to the outside through the pipe 31b.

<Refrigerant circulation system>
The refrigerant circulation system is a system that circulates refrigerant (cooling water, radiator liquid) so as to pass through the refrigerant flow path 13 of the fuel cell stack 10, and includes a refrigerant pump 41, a butterfly valve 42 (refrigerant flow restriction means), A radiator 43 (heat radiator) for radiating the refrigerant and a temperature sensor 44 are provided.

  The refrigerant pump 41 is a device that pumps the refrigerant, and a motor M that is a power source thereof is connected to the fuel cell stack 10 and the battery 52 via a contactor 53 and the like. The motor M operates with the fuel cell stack 10 and / or the battery 52 as a power source in accordance with a command from the ECU 70. That is, the refrigerant pump 41 is operated by the generated power of the fuel cell stack 10 and / or the charging power of the battery 52.

The discharge port of the refrigerant pump 41 is connected to the inlet of the refrigerant flow path 13 via the pipe 41a, the butterfly valve 42, and the pipe 42a. The outlet of the refrigerant flow path 13 is connected to the suction port of the refrigerant pump 41 via the pipe 43a, the radiator 43, and the pipe 43b.
When the refrigerant pump 41 is activated, the refrigerant circulates via the butterfly valve 42, the refrigerant flow path 13, and the radiator 43.

The butterfly valve 42 adjusts the pressure loss received by the refrigerant flowing through the refrigerant circulation system, specifically, the refrigerant supplied to the refrigerant flow path 13 by adjusting the opening degree of the valve body (pressure loss adjusting unit). And a refrigerant flow rate limiting means for limiting the flow rate of the refrigerant supplied to the refrigerant flow path 13. That is, when the opening degree of the valve body of the butterfly valve 42 becomes small, for example, the pressure loss received by the flowing refrigerant increases, and the flow rate of the refrigerant to the refrigerant flow path 13 decreases.
The butterfly valve 42 is connected to the ECU 70, and the opening degree of the butterfly valve 42 is appropriately controlled by the ECU 70.

  The temperature sensor 44 (temperature detection means) is disposed near the refrigerant flow path 13 of the pipe 43a. Here, it is assumed that the temperature in the pipe 43a is substantially equal to the temperature of the refrigerant flow path 13, that is, the current temperature T11 of the fuel cell stack 10, and the temperature sensor 44 detects the current temperature T11 of the fuel cell stack 10. . The temperature sensor 44 outputs the detected current temperature T11 of the fuel cell stack 10 to the ECU 70.

<Power consumption system>
The power consumption system includes a travel motor 51 (external load) that is a power source of the fuel cell vehicle, a battery 52 that charges and discharges power, a contactor 53 that is an ON / OFF switch, and an output detector 54. .

The travel motor 51 is connected to an output terminal (not shown) of the fuel cell stack 10 via a contactor 53 and an output detector 54.
Then, in a state where a predetermined OCV is generated in the fuel cell stack 10, the contactor 53 is turned on by the ECU 70, and a VCU (Voltage Control Unit) (not shown) for controlling the output of the fuel cell stack 10 is appropriately controlled by the ECU 70. Then, a current is taken out from the fuel cell stack 10 and the fuel cell stack 10 generates power.
On the other hand, when the contactor 53 is turned off, the electrical connection between the fuel cell stack 10 and the travel motor 51 is cut off, and the power generation of the fuel cell stack 10 is stopped.

The output detector 54 is a device that detects a voltage V11 (including OCV) and a current A11 that are currently output in the fuel cell stack 10, and includes a voltage sensor and a current sensor. The voltage sensor is arranged at an appropriate position so that the voltage V11 can be detected, and the current sensor can detect the current A11.
The output detector 54 outputs the detected voltage V11 and current A11 to the ECU 70.

The battery 52 is connected between the traveling motor 51 and the contactor 53 in parallel to the traveling motor 51 with respect to the contactor 53, and charges the surplus power of the fuel cell stack 10 or assists the fuel cell stack 10. It is like that.
In addition, a DC / DC converter (not shown) that reduces high-voltage power is connected between the traveling motor 51 and the contactor 53. The shut-off valve 22, the ECU 70, and the like are operated by this reduced power.

<IG>
The IG 61 is a start switch for the fuel cell vehicle and the fuel cell system 1 and is provided around the driver's seat. Moreover, IG61 is connected with ECU70, ECU70 detects the ON / OFF signal of IG61.

<ECU>
The ECU 70 is a control device that electronically controls the fuel cell system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and exhibits various functions according to programs stored therein. However, various processes are executed.

<ECU-Reaction state estimation function>
The ECU 70 (reaction state estimation means) functions to estimate the reaction state of the fuel cell stack 10, that is, the temperature T11, voltage V11, IV characteristics of the fuel cell stack 10, and the potential difference ΔV21 between the average cell voltage V21 and the minimum cell voltage V22. Based on the above, the fuel cell stack 10 has a function of estimating whether or not the degree of warm-up of the fuel cell stack 10 should be the degree to which the restriction on the flow rate of the refrigerant supplied to the fuel cell stack 10 should be changed.

<ECU-Limit value change function>
The ECU 70 (limit value changing means) changes the limit value of the refrigerant flow rate to the refrigerant flow path 13 based on the estimated reaction state of the fuel cell stack 10, that is, the degree of warm-up of the fuel cell stack 10. In addition, the refrigerant pump 41 and the butterfly valve 42 are instructed to be limited by the changed limit value.

<ECU—Warm-up completion determination, refrigerant flow rate restriction release function>
The ECU 70 determines whether or not the warm-up of the fuel cell stack 10 is completed based on the current temperature T11 of the fuel cell stack 10 and the warm-up completion temperature T3 (for example, 80 ° C.), and the warm-up is completed. When it is determined that the refrigerant flow rate has been determined, the function of releasing the restriction on the refrigerant flow rate to the refrigerant flow path 13 by the butterfly valve 42 is provided. That is, in the fuel cell system 1, when the temperature T11 of the fuel cell stack 10 is equal to or higher than the warm-up completion temperature T3, the refrigerant flow rate restriction is set to be released. In other words, when the temperature T11 of the fuel cell stack 10 is lower than the warm-up completion temperature T3, the refrigerant flow rate is limited.
The warm-up completion temperature T3 depends on the type of catalyst included in the anode or the like, is determined by a preliminary test or the like, and is stored in the ECU 70 in advance. Further, the relationship between the warm-up completion temperature T3, the refrigerant flow rate changing temperature T2 (for example, 30 ° C.), and the low-temperature starting start temperature T1 (for example, 0 ° C.) is “T1 <T2 <T3”.

≪Operation of fuel cell system≫
Next, with reference mainly to FIGS. 2 and 3, the operation of the fuel cell system 1 will be described together with the flow of a program (flow chart) set in the ECU 70.
When the IG 61 is turned on, the process shown in the flowchart of FIG. 2 starts. Further, before the IG 61 is turned on (initial state), the shutoff valve 22 is closed, the compressor 31 and the refrigerant pump 41 are stopped, the contactor 53 is turned off, and the power generation of the fuel cell stack 10 is stopped.

In step S101, when starting the fuel cell system 1, the ECU 70 determines whether or not it is necessary to start the fuel cell stack 10 at a low temperature in order to promote warm-up of the fuel cell stack 10.
Specifically, it is determined whether or not the current temperature T11 of the fuel cell stack 10 is equal to or lower than the low temperature start start temperature T1. The low temperature start start temperature T1 is a temperature (for example, 0 ° C.) at which it is determined that there is a possibility that the fuel cell stack 10 is frozen and it is necessary to start up at a low temperature and warm up. The low temperature start start temperature T1 is obtained by a preliminary test or the like and stored in the ECU 70 in advance.

  When the current temperature T11 of the fuel cell stack 10 is equal to or lower than the low temperature start start temperature T1 (S101 / Yes), it is determined that the low temperature start is necessary, and the processing of the ECU 70 proceeds to step S102. On the other hand, if the current temperature T11 of the fuel cell stack 10 is not equal to or lower than the low temperature start temperature T1 (No in S101), it is determined that there is no need to start at low temperature, and the processing of the ECU 70 proceeds to step S110.

In step S102, the ECU 70 starts control of the fuel cell system 1 in the low temperature startup mode in order to promote warm-up of the fuel cell stack 10.
Specifically, the ECU 70 opens the shut-off valve 22 and supplies hydrogen from the hydrogen tank 21 (reactive gas replacement means) to the anode flow path 11. Further, the motor M (compressor 31, refrigerant pump 41) is operated to supply air from the compressor 31 (reaction gas replacement means) to the cathode flow path 12 and to circulate the refrigerant. As a result, the anode channel 11 starts to be replaced with hydrogen and the cathode channel 12 starts to be replaced with air. At this time, the rotational speed of the motor M is set higher than the rotational speed of the motor M in the normal startup mode in step S110 described later. As a result, air is supplied to the cathode of the fuel cell stack 10 at a higher flow rate and higher pressure than the normal flow rate in the normal startup mode.

  Further, the ECU 70 opens the butterfly valve 42 at an opening for the low temperature starting mode (opening for the low temperature starting) smaller than the opening for the normal starting mode (the opening for normal starting) in Step S110 described later. Set to. As a result, the flow rate of the refrigerant to the refrigerant flow path 13 is controlled to be lower than that in the normal startup mode, and warming up of the fuel cell stack 10 by self-heating is promoted.

In step S103, the ECU 70 determines whether or not the current temperature T11 of the fuel cell stack 10 is lower than the refrigerant flow rate changing temperature T2 (see FIG. 4).
Although the refrigerant flow rate change temperature T2 is equal to or higher than the refrigerant flow rate change temperature T2 when the temperature T11 of the fuel cell stack 10 is lower than the warm-up completion temperature T3, the opening degree of the butterfly valve 42 is changed from the low temperature start-up opening degree. Even if it is changed to the normal starting opening (expanded) and the refrigerant flow rate to the refrigerant flow path 13 is increased (changed), the temperature T11 of the fuel cell stack 10 is warmed up by the subsequent self-heating of the fuel cell stack 10. The completion temperature T3 is set to a temperature that is estimated to rise without requiring much time. Note that such a refrigerant flow rate changing temperature T2 is obtained by a preliminary test or the like and stored in the ECU 70 in advance.

  When it is determined that the current temperature T11 of the fuel cell stack 10 is lower than the refrigerant flow rate changing temperature T2 (S103 / Yes), the process of the ECU 70 proceeds to step S104. On the other hand, when it is determined that the current temperature T11 is not less than the refrigerant flow rate changing temperature T2 (S103, No), the process of the ECU 70 proceeds to step S111.

In step S104, the ECU 70 determines whether or not the current voltage V11 (OCV) of the fuel cell stack 10 during the replacement of hydrogen and air is less than the refrigerant flow rate changing voltage V1 (see FIG. 5).
If the current voltage V11 of the fuel cell stack 10 is equal to or higher than the refrigerant flow rate change voltage V1, the refrigerant flow rate change voltage V1 changes the opening degree of the butterfly valve 42 from the low temperature start-up opening degree to the normal start-up opening degree. However, even if the refrigerant flow rate to the refrigerant flow path 13 is increased (changed), the temperature T11 of the fuel cell stack 10 increases to the warm-up completion temperature T3 due to the subsequent self-heating of the fuel cell stack 10. It is set to a voltage estimated to rise without taking time. Note that such a refrigerant flow rate changing voltage V1 is obtained by a preliminary test or the like and stored in the ECU 70 in advance.

  When it is determined that the current voltage V11 of the fuel cell stack 10 is less than the refrigerant flow rate change voltage V1 (Yes in S104), the process of the ECU 70 proceeds to step S200. On the other hand, when it is determined that the current voltage V11 is not less than the refrigerant flow rate changing voltage V1 (S104, No), the process of the ECU 70 proceeds to step S111.

In step S200, the ECU 70 limits the flow rate of the refrigerant supplied to the refrigerant flow path 13 for low temperature activation, that is, sets the opening degree of the butterfly valve 42 for low temperature activation.
Specifically, the processing of the ECU 70 proceeds to step S201 in FIG. 3, and in step S201, the ECU 70 controls the butterfly valve 42 in the closing direction to reduce its opening. At this time, the butterfly valve 42 has a current temperature T11 of the fuel cell stack 10, a voltage V11 (OCV), a time t from turning on the IG 61, and a voltage difference ΔV21 (V21−V22), as shown in FIGS. Control based on the map. Specifically, as shown in FIGS. 8 and 9, the opening of the butterfly valve 42 increases as the current temperature T11 is lower, the voltage V11 is lower, the time t from when the IG 61 is turned on is shorter, and the voltage difference ΔV21 is larger. It is controlled to be smaller.

In step S202, the ECU 70 increases the rotation speed of the motor M (refrigerant pump 41) based on the opening degree of the butterfly valve 42 after the control in the closing direction in step S201 and the map of FIG. Specifically, as shown in FIG. 10, the rotation speed of the motor M is controlled to be higher as the opening degree of the butterfly valve 42 is smaller. At this time, the rotation speed of the motor M is increased so that the refrigerant flow rate to the refrigerant flow path 13 does not change before and after the control of the opening degree of the butterfly valve 42 in the closing direction. Thereby, the power consumption of the motor M (refrigerant pump 41) becomes large.
Thereafter, the processing of the ECU 70 proceeds to step S105 in FIG. 2 via the end.

  In step S105, the ECU 70 determines whether or not the current voltage V11 (OCV) is equal to or higher than the power generation possible voltage V0. The power generation possible voltage V0 is a voltage at which the inside of the fuel cell stack 10 is satisfactorily replaced with hydrogen and air, is increased to a predetermined concentration, and is determined to be in a power generation enabled state. It is remembered.

  When it is determined that the current voltage V11 is equal to or higher than the power generation possible voltage V0 (Yes in S105), the process of the ECU 70 proceeds to step S106. On the other hand, when it is determined that the current voltage V11 is not equal to or higher than the power generation possible voltage V0 (S105, No), the process of the ECU 70 proceeds to step S103.

  In step S106, the ECU 70 starts power generation of the fuel cell stack 10. Specifically, the ECU 70 turns on the contactor 53, extracts current from the fuel cell stack 10 in response to a power generation request, and causes the fuel cell stack 10 to generate power. When power is generated in this manner, the fuel cell stack 10 is warmed up by the self-heating. In this case, the generated power of the fuel cell stack 10 is made larger than the generated power in step S113, which will be described later, corresponding to the air started to be supplied at a high flow rate and high pressure in step S102, and the self-heat generation amount is increased.

  In step S107, the ECU 70 determines whether or not the current temperature T11 of the fuel cell stack 10 is less than the refrigerant flow rate change temperature T2. When the current temperature T11 is lower than the refrigerant flow rate changing temperature T2 (S107 / Yes), the process of the ECU 70 proceeds to step S108. On the other hand, when the current temperature T11 is not less than the refrigerant flow rate changing temperature T2 (S107, No), the process of the ECU 70 proceeds to step S114.

In step S108, the ECU 70 determines whether or not the current IV characteristic (current-voltage curve) is lower than the determination IV characteristic.
Specifically, the current IV characteristic of the fuel cell stack 10 is obtained based on the current voltage V11 and current A11 of the fuel cell stack 10 detected via the output detector 54. Next, the ECU 70 determines whether or not the obtained IV characteristic is lower than the determination IV characteristic.

  If the current IV characteristic is equal to or higher than the determination IV characteristic, the opening degree of the butterfly valve 42 is changed (expanded) from the low temperature starting opening degree to the normal starting opening degree. Even if the refrigerant flow rate is increased (changed), it is estimated that the temperature T11 of the fuel cell stack 10 rises to the warm-up completion temperature T3 without much time due to subsequent self-heating of the fuel cell stack 10 IV characteristics to be set. Such a determination IV characteristic is obtained by a preliminary test or the like and stored in the ECU 70 in advance.

  If it is determined that the current IV characteristic is lower than the determination IV characteristic (Yes in S108), the process of the ECU 70 proceeds to step S109. On the other hand, when it is determined that the current IV characteristic is not lower than the determination IV characteristic (No in S108), the process of the ECU 70 proceeds to step S114.

In step S109, the ECU 70 determines whether or not the voltage difference ΔV21 (V21−V22) between the average cell voltage V21 and the lowest cell voltage V22 detected via the cell voltage monitor 15 is larger than the determination voltage difference ΔV20. To do.
If the voltage difference ΔV21 is equal to or smaller than the determination voltage difference ΔV20, the determination voltage difference ΔV20 is changed (expanded) from the low-temperature start opening to the normal start opening by expanding the butterfly valve 42. Even if the refrigerant flow rate to 13 is increased (changed), if the temperature T11 of the fuel cell stack 10 rises to the warm-up completion temperature T3 without taking much time due to subsequent self-heating of the fuel cell stack 10 Set to the estimated potential difference. Note that such a determination voltage difference ΔV20 is obtained by a preliminary test or the like and stored in the ECU 70 in advance.

  When it is determined that the current voltage difference ΔV21 is greater than the determination voltage difference ΔV20 (S109 / Yes), the process of the ECU 70 proceeds to step S300. On the other hand, when it is determined that the current voltage difference ΔV21 is not greater than the determination voltage difference ΔV20 (No in S109), the process of the ECU 70 proceeds to step S114.

In step S300, the ECU 70 limits the flow rate of the refrigerant supplied to the refrigerant flow path 13 as in step S200.
Specifically, the process of the ECU 70 proceeds to step S301 in FIG. 3, and in step S301, the ECU 70 controls the butterfly valve 42 in the closing direction to reduce its opening. At this time, the butterfly valve 42 has a current temperature T11 of the fuel cell stack 10, a time t from when the IG 61 is turned on, a difference between the current IV characteristic and the determination IV characteristic, a voltage difference ΔV21 (V21−V22), and FIG. Control is performed based on the map of FIG. Specifically, as shown in FIGS. 8 and 9, the current temperature T11 is low, the time t from turning on the IG 61 is short, the difference between the current IV characteristic and the determination IV characteristic is large, and ΔV21 is large, Control is performed so that the opening degree of the butterfly valve 42 is reduced.

In step S302, as in step S202, the ECU 70 determines the rotational speed of the motor M (refrigerant pump 41) based on the opening degree of the butterfly valve 42 after the control in the closing direction in step S301 and the map of FIG. Increase. Specifically, as shown in FIG. 10, the rotation speed of the motor M is controlled to be higher as the opening degree of the butterfly valve 42 is smaller. Thereby, the power consumption of the motor M (refrigerant pump 41) and the generated power of the fuel cell stack 10 are increased, and the warm-up of the fuel cell stack 10 due to self-heating is promoted.
Thereafter, the processing of the ECU 70 proceeds to step S107 in FIG. 2 via the end.

Next, step S110 that proceeds when the determination in step S101 is No will be described.
In step S110, the ECU 70 starts control in the normal activation mode of the fuel cell system 1.
Specifically, the ECU 70 opens the shut-off valve 22 and supplies hydrogen to the anode flow path 11. Further, the motor M (the compressor 31 and the refrigerant pump 41) is operated to supply air to the cathode channel 12 and to circulate the refrigerant.
The rotation speed for normal startup of the motor M is set lower than the rotation speed of the motor M for low temperature startup in step S102. Further, the opening degree for normal activation of the butterfly valve 42 is set in a range that is smaller than the opening degree after completion of warming up and larger than the opening degree of the butterfly valve 42 for low temperature activation in step S102.

In step S111, the ECU 70 sets the restriction on the flow rate of the refrigerant supplied to the refrigerant flow path 13 for normal activation. Specifically, the ECU 70 sets the opening degree of the butterfly valve 42 to the normal activation opening degree.
Specifically, when the process proceeds from step S110 to step S111, the opening degree of the butterfly valve 42 is maintained as the normal starting opening degree.
On the other hand, when the determination result of step S103 is No or the determination result of step S104 is No and the process proceeds to step S111, the opening degree of the butterfly valve 42 is changed to the normal activation opening degree. Thereby, the flow rate of the refrigerant to the refrigerant channel 13 is changed and increased, and local overheating in the fuel cell stack 10 is prevented.

In step S112, the ECU 70 determines whether or not the current V11 (OCV) is equal to or higher than the power generation possible voltage V0, as in step S105.
When it is determined that the current voltage V11 is equal to or higher than the power generation possible voltage V0 (S112 / Yes), the process of the ECU 70 proceeds to step S113. On the other hand, when it is determined that the current voltage V11 is not equal to or higher than the power generation possible voltage V0 (S112 · No), the ECU 70 repeats the determination in step S112.

  In step S113, the ECU 70 starts power generation of the fuel cell stack 10 as in step S106.

In step S114, as in step S111, the ECU 70 sets the restriction on the flow rate of the refrigerant supplied to the refrigerant flow path 13 for normal activation. Specifically, the opening of the butterfly valve 42 is set to the normal activation opening. Set.
Specifically, when the process proceeds from step S113 to step S114, the opening degree of the butterfly valve 42 is maintained as the normal starting opening degree.
On the other hand, when the determination result of step S107 is No, the determination result of step S108 is No, or the determination result of step S109 is No and the process proceeds to step S114, the opening degree of the butterfly valve 42 is normally activated. The opening is changed. Thereby, the flow rate of the refrigerant to the refrigerant channel 13 is changed and increased, and local overheating in the fuel cell stack 10 is prevented.

Next, in step S115, the ECU 70 determines whether or not the temperature T11 of the fuel cell stack 10 is equal to or higher than the warm-up completion temperature T3.
When the temperature T11 of the fuel cell stack 10 is equal to or higher than the warm-up completion temperature T3 (Yes in S115), the process of the ECU 70 proceeds to the end. When the process proceeds to the end in this way, the opening degree of the butterfly valve 42 is changed from the normal starting opening degree to the full opening. Thereby, the restriction | limiting of the refrigerant | coolant supply to the refrigerant flow path 13 is cancelled | released.
On the other hand, when the temperature T11 of the fuel cell stack 10 is not equal to or higher than the warm-up completion temperature T3 (No in S115), the process of the ECU 70 repeats the determination in step S115.

≪Effect of fuel cell system≫
According to such a fuel cell system 1, the following effects can be obtained.
When starting in the low temperature start mode, the temperature T11 of the fuel cell stack 10 is lower than the warm-up completion temperature T3, but the predetermined condition is satisfied (S103 No, S104 No, S107 No S108 · No, S109 · No), the opening degree of the butterfly valve 42 can be changed from the low temperature start to the normal start, and the refrigerant flow rate can be increased (changed) from the low temperature start to the normal start. Thereby, the fuel cell stack 10 can be prevented from being overheated locally.

  Further, in the case of starting in the low temperature starting mode, when the flow rate of the refrigerant is limited / changed (S200, S300), the current temperature T11, voltage V11, current IV characteristic and determination IV characteristic of the fuel cell stack 10 , The voltage difference ΔV21 (V21−V22), and the time t from when the IG 61 is turned on, the butterfly valve 42 is controlled in the closing direction, and the refrigerant pump 41 corresponds to the opening degree of the butterfly valve 42 after the control. By increasing the number of revolutions and increasing the power consumption, the power generated by the fuel cell stack 10 increases. As a result, it is possible to appropriately supply the refrigerant to the refrigerant flow path 13 while increasing the amount of self-heating of the fuel cell stack 10 and promoting warm-up.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to the said embodiment, For example, it can change as follows in the range which does not deviate from the meaning of this invention.

  In the above-described embodiment, the configuration in which the temperature sensor 44 that detects the temperature T11 of the fuel cell stack 10 is provided in the pipe 43a is exemplified, but the configuration in which the temperature sensor 44 is provided in the pipes 22b and 31b and the casing of the fuel cell stack 10 is also exemplified. Good. Further, a plurality of temperature sensors may be provided to prevent erroneous detection.

In the above-described embodiment, when the refrigerant flow rate is limited in steps S200 and S300, the configuration in which the opening degree of the butterfly valve 42 is reduced and the rotation speed of the refrigerant pump 41 is increased is exemplified. It is good also as a structure which restrict | limits a refrigerant | coolant flow volume by reducing the rotation speed of the pump 41. FIG.
In addition, when a bypass flow path for bypassing (reducing) the refrigerant flow path 13 is provided and a flow rate adjusting valve is provided in the bypass flow path to restrict the refrigerant flow rate, the refrigerant flow rate to the bypass flow path is increased. It is good also as a structure which controls the said flow regulating valve.

In the above-described embodiment, the case where the refrigerant flow rate change temperature T2 is constant as illustrated in FIG. 4 is exemplified, but as shown by the broken line in FIG. The change temperature T2 may be high. The same applies to the refrigerant flow rate changing voltage V1, as indicated by a broken line in FIG.
Further, as indicated by a broken line in FIG. 6, the determination IV characteristic may be configured to become higher as the time from when the IG 61 is turned on becomes longer. Furthermore, as indicated by a broken line in FIG. 7, the determination voltage difference ΔV20 may be reduced as the time from when the IG 61 is turned on becomes longer.

  In the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle is illustrated. However, for example, the fuel cell system 1 may be incorporated in a fuel cell system mounted on a motorcycle, a train, or a ship. Moreover, a stationary fuel cell system for home use or a fuel cell system incorporated in a hot water supply system may be used.

It is a figure which shows the structure of the fuel cell system which concerns on this embodiment. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment. It is a subflowchart of step S200 (S300) of FIG. It is a map which shows the relationship between time t from ON of IG, temperature T11 of a fuel cell stack, and the presence or absence of a restriction | limiting of a refrigerant | coolant flow rate. It is a map which shows the relationship between the time t from ON of IG, the voltage V11 (OCV) of a fuel cell stack, and the presence or absence of a restriction | limiting of a refrigerant | coolant flow volume. It is a map which shows the relationship between the time t from ON of IG, the IV characteristic of a fuel cell stack, and the presence or absence of a restriction | limiting of a refrigerant | coolant flow rate. It is a map which shows the relationship between time t from ON of IG, voltage difference (DELTA) V21 of the average cell voltage V21 and the minimum cell voltage V22, and the presence or absence of a restriction | limiting of a refrigerant | coolant flow volume. It is a map which shows the relationship between the temperature T11 of a fuel cell stack, voltage V11 (OCV), time t from ON of IG, and the opening degree of a butterfly valve. It is a map which shows the relationship between the difference of the present IV characteristic and determination IV characteristic of a fuel cell stack, voltage difference (DELTA) V21 of the average cell voltage V21 and the lowest cell voltage V22, and the opening degree of a butterfly valve. It is a map which shows the relationship between the opening degree of a butterfly valve, and the rotation speed of a motor (refrigerant pump).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell stack 11 Anode flow path 12 Cathode flow path 13 Refrigerant flow path 15 Cell voltage monitor 41 Refrigerant pump (refrigerant circulation means)
42 Butterfly valve (refrigerant flow restriction means, pressure loss adjustment unit)
43 Radiator 44 Temperature sensor (temperature detection means)
54 output detector 70 ECU (reaction state estimation means, limit value setting means)
T11 Current temperature of fuel cell stack T1 Low temperature start start temperature T2 Refrigerant flow rate change temperature T3 Warm-up completion temperature A11 Current current of fuel cell stack V11 Current voltage of fuel cell stack V0 Power generation potential V1 Refrigerant flow rate change voltage V21 Average Cell voltage (predetermined voltage)
V22 Minimum cell voltage ΔV21 Difference between average cell voltage and minimum cell voltage ΔV20 Judgment voltage difference

Claims (2)

A fuel cell stack that generates electricity by supplying reactive gas;
Refrigerant circulation means for circulating the refrigerant through the fuel cell stack;
Refrigerant flow rate limiting means for limiting the flow rate of the refrigerant supplied to the fuel cell stack;
And when the temperature of the fuel cell stack is lower than the warm-up completion temperature, the refrigerant flow rate limiting means executes a flow rate limitation of the refrigerant,
Reaction state estimation means for estimating a reaction state of the fuel cell stack;
When the temperature of the fuel cell stack is lower than the warm-up completion temperature, the fuel cell stack is supplied to the fuel cell stack based on the reaction state estimated by the reaction state estimation unit so that overheating of the fuel cell stack is prevented. Limit value changing means for instructing the refrigerant flow rate limiting means to change the limit value of the flow rate of the refrigerant to be performed and to limit the refrigerant flow limit value with the changed limit value;
A fuel cell system comprising: The refrigerant circulation means includes a refrigerant pump that is operated by generated power of the fuel cell stack and pumps the refrigerant,
The refrigerant flow rate limiting means includes a pressure loss adjusting unit that adjusts the pressure loss received by the flowing refrigerant,
The refrigerant pump increases the number of revolutions and increases the power consumption when the pressure loss adjustment unit increases the pressure loss so as to limit the refrigerant supplied to the fuel cell stack. 2. The fuel cell system according to 1.

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