JP2010272537A - Fuel battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly diagnose a factor of the output reduction of a fuel battery in a fuel battery system. <P>SOLUTION: The fuel battery system has current measurement means 134, 153, 163, 166, 174 for measuring currents flowing through portions D where fuel gases of the inside of a fuel battery 10 tend to become insufficient and a diagnosis means 40 for diagnosing insufficient states of the fuel gases of the fuel battery based on current values measured by the current measurement means. When the currents measured by the current measurement means are smaller than measured current values, and current reduction speed measured by the current measurement means is not lower than fixed reduction speed, the diagnosis means 40 diagnoses that a fuel-gas feeding quantity to the fuel battery is insufficient. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric energy by an electrochemical reaction between hydrogen and oxygen. The present invention relates to a generator for a mobile body such as a vehicle, a ship, and a portable generator, or a household generator. It is effective to apply.

  In a fuel cell system that generates electricity using an electrochemical reaction between hydrogen and oxygen, the electrolyte membrane dries and the battery output decreases when moisture is insufficient, while the electrode is covered with water when moisture is excessive. As a result, gas permeation is hindered and the output of the battery is reduced. Therefore, it is necessary to accurately diagnose the water retention state of the electrolyte membrane and the wet state of the electrode and to appropriately control the water retention state and the wet state. Further, since the output of the battery is lowered even when the supply amount of the reaction gas is insufficient, it is necessary to appropriately diagnose the lack of the reaction gas and appropriately control the reaction gas supply amount.

  By the way, in order to diagnose the operating state of the fuel cell, a method of diagnosing an abnormal state from a decrease in cell voltage can be considered. In addition, there has been proposed one that diagnoses the excess or deficiency of the reaction gas from the current distribution in the fuel cell and controls the reaction gas flow rate or load current to prevent the destruction of the fuel cell (for example, Patent Document 1). reference).

JP-A-9-259913

  However, in the case of a method of diagnosing an abnormal state from a decrease in cell voltage, the cell voltage decreases due to drying of the electrolyte membrane, reaction inhibition due to excessive water, and insufficient supply of reaction gas, so the output of the fuel cell decreases. There is a problem that the factor cannot be specified, and therefore, it is not possible to perform accurate control according to the output reduction factor.

  On the other hand, in the system described in Patent Document 1, since only the excess or deficiency of the reaction gas is diagnosed, it is impossible to accurately diagnose the output reduction factor. For this reason, it is not possible to distinguish between the excess water state other than the reaction gas flow rate and the dry state of the electrolyte membrane, and thus there arises a problem that accurate control according to the output reduction factor cannot be performed.

  In view of the above points, an object of the present invention is to enable accurate diagnosis of a fuel cell output reduction factor.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a fuel cell (10) that generates electrical energy by an electrochemical reaction between an oxidant gas and a fuel gas, and a fuel gas in the fuel cell (10). Current measurement means (134, 153, 163, 166, 174) for measuring the current flowing through the portion (D) that is likely to be insufficient, and the fuel gas shortage state of the fuel cell based on the current value measured by the current measurement means A diagnostic means (40) for diagnosing is provided. According to this, when the supply amount of hydrogen to the fuel cell is insufficient, it can be accurately diagnosed.

  Specifically, as in the invention described in claim 2, the diagnostic means (40) is configured such that the current measured by the current measuring means is less than a predetermined current value, and the rate of decrease in the current measured by the current measuring means. Can be diagnosed as insufficient fuel gas supply to the fuel cell.

  In the invention according to claim 3, the fuel cell (10) that generates electric energy by the electrochemical reaction between the oxidant gas and the fuel gas, the water tends to be excessive in the fuel cell (10), and the fuel gas is insufficient. Based on the current measurement means (134, 153, 163) for measuring the current flowing through the part (D) that is easy to perform, and the rate of decrease in the current measured by the current measurement means, the fuel cell has excessive moisture and the fuel cell has insufficient fuel gas. And a diagnostic means (40) for making a distinction and making a diagnosis.

  According to this, when the fuel cell becomes excessive in water, it can be diagnosed accurately, and when the supply amount of hydrogen to the fuel cell is insufficient, it is diagnosed accurately. be able to. In addition, it is possible to specify whether the output reduction factor of the fuel cell is excessive water or insufficient hydrogen supply based on the current decrease rate, and therefore it is possible to perform accurate control according to the output decrease factor.

  Specifically, in the invention according to claim 4, the diagnosis unit is configured such that the current measured by the current measurement unit is less than a predetermined current value, and the rate of decrease in current measured by the current measurement unit is less than the predetermined decrease rate. When the fuel cell is in excess of water, the current measured by the current measuring means is less than the predetermined current value, and the current decreasing speed measured by the current measuring means is the predetermined decreasing speed. When it is above, it can be diagnosed that the amount of fuel gas supplied to the fuel cell is insufficient.

  Incidentally, when the invention according to any one of claims 1 to 4 is carried out, as in the invention according to claim 5, the fuel cell (10) has a pair of electrodes disposed on both sides of the electrolyte membrane. An electrolyte-electrode assembly (100), a first separator (110) formed outside the electrolyte-electrode assembly and having an oxidizing gas channel (113) serving as an oxidizing gas channel, and an electrolyte A second separator (120) disposed outside the electrode assembly and having a fuel gas flow path (123) serving as a fuel gas flow path; and current measuring means (134, 153, 163, 166) 174) may measure the current at a position closer to the fuel gas outlet (122) than the fuel gas inlet (121) in the fuel gas flow path.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

It is a mimetic diagram showing the whole fuel cell system composition concerning a 1st embodiment of the present invention. It is a typical perspective view which shows the single cell of the fuel cell 10 of FIG. FIG. 3 is a perspective view of an air side separator 110 viewed from the right side of FIG. 2. FIG. 3 is a perspective view of a hydrogen separator 120 viewed from the right side of FIG. 2. FIG. 3 is an enlarged view of a main part on the negative side in FIG. 2. It is sectional drawing which follows the AA line of FIG. It is a characteristic view which shows the change of the electric current I when drying of an electrolyte membrane generate | occur | produced. It is a characteristic view which shows the change of the electric current I when the water | moisture-content excess generate | occur | produces by the amount of water droplets of a hydrogen exit part. It is a characteristic view which shows the change of the electric current I when hydrogen supply amount is insufficient. It is a characteristic view which shows the change of the electric current I at the time of water | moisture-content excess generation | occurrence | production and hydrogen shortage generation | occurrence | production. It is a characteristic figure which shows the fall rate of the electric current I at the time of water | moisture-content excess generation | occurrence | production and hydrogen shortage generation | occurrence | production. It is a flowchart which shows the control processing performed in the control part 40 of FIG. It is a characteristic view which shows the relationship between the total electric current value at the time of drying determination, and a predetermined electric current value. It is a schematic diagram which shows the whole structure of the fuel cell system which concerns on 2nd Embodiment of this invention. It is a typical perspective view which shows the fuel cell 10 of FIG. It is a typical perspective view which shows the single cell of the fuel cell 10 of FIG. It is a characteristic view which shows the change of the electric power generation electric current I of a fuel cell when the moisture state of 3rd Embodiment fluctuates. It is a characteristic view which shows the change of the difference voltage (DELTA) I when a moisture state fluctuates. It is a flowchart which shows the content of the moisture content control of 3rd Embodiment. It is a characteristic view which shows the change of the electric power generation electric current I of the fuel cell when the moisture condition of 4th Embodiment fluctuates. It is a characteristic view which shows the change of the difference voltage (DELTA) I when a moisture state fluctuates. It is a flowchart which shows the content of the moisture content control of 4th Embodiment. It is a characteristic view which shows the relationship between the local internal resistance of the fuel cell of 5th Embodiment, and internal moisture content. It is a characteristic view which shows the change of the local internal resistance I of a fuel cell when the moisture state of 6th Embodiment fluctuates. It is a characteristic view which shows the change of differential resistance (DELTA) I when a moisture state fluctuates. It is a flowchart which shows the content of the moisture content control of 6th Embodiment. It is a characteristic figure showing change of local internal resistance I of a fuel cell when the moisture state of a 7th embodiment changes. It is a characteristic view which shows the change of differential resistance (DELTA) I when a moisture state fluctuates. It is a flowchart which shows the content of the moisture content control of 7th Embodiment.

(First embodiment)
FIG. 1 is a schematic diagram showing a fuel cell system according to the first embodiment, and this fuel cell system is applied to, for example, an electric vehicle.

  As shown in FIG. 1, the fuel cell system of this embodiment includes a fuel cell 10 that generates electric power by utilizing an electrochemical reaction between hydrogen and oxygen. The fuel cell 10 supplies electric power to electric devices such as an electric load 11 and a secondary battery (not shown). Incidentally, in the case of an electric vehicle, an electric motor as a vehicle driving source corresponds to the electric load 11.

  In the present embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of fuel cells serving as basic units are stacked and electrically connected in series. In the fuel cell 10, the following electrochemical reaction between hydrogen and oxygen occurs to generate electric energy.

(Negative electrode side) H ₂ → 2H ⁺ + 2e ⁻
(Positive electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
A cell monitor 12 for detecting an output voltage for each cell is provided, and a cell voltage signal detected by the cell monitor 12 is input to the control unit 40 described later.

  The fuel cell system includes an air flow path 20 for supplying air (oxygen) to the air electrode (positive electrode) side of the fuel cell 10 and hydrogen for supplying hydrogen to the hydrogen electrode (negative electrode) side of the fuel cell 10. A flow path 30 is provided. Air corresponds to the oxidizing gas of the present invention, and hydrogen corresponds to the fuel gas of the present invention.

  An air pump 21 is provided at the most upstream portion of the air flow path 20 to pump air sucked from the atmosphere to the fuel cell 10. Between the air pump 21 and the fuel cell 10 in the air flow path 20. A humidifier 22 for humidifying the air is provided, and an air pressure regulating valve 23 for adjusting the pressure of the air supplied to the fuel cell 10 is provided on the downstream side of the fuel cell 10 in the air flow path 20. ing.

  A hydrogen cylinder 31 filled with hydrogen is provided in the uppermost stream portion of the hydrogen flow path 30, and hydrogen supplied to the fuel cell 10 is interposed between the hydrogen cylinder 31 and the fuel cell 10 in the hydrogen flow path 30. A hydrogen pressure regulating valve 32 for adjusting the pressure and a humidifier 33 for humidifying the hydrogen are provided.

  The downstream side of the fuel cell 10 in the hydrogen flow path 30 is connected to the downstream side of the hydrogen pressure regulating valve 32 so that the hydrogen flow path 30 is configured in a closed loop, thereby circulating hydrogen in the hydrogen flow path 30, Unused hydrogen in the fuel cell 10 is resupplied to the fuel cell 10. A hydrogen pump 34 for circulating hydrogen in the hydrogen channel 30 is provided on the downstream side of the fuel cell 10 in the hydrogen channel 30.

  The control unit (ECU) 40 corresponds to the diagnostic means of the present invention, and is composed of a well-known microcomputer comprising a CPU, ROM, RAM, etc. and its peripheral circuits. The control unit 40 receives a cell voltage signal from the cell monitor 12 and a signal from a current sensor described later. Further, the control unit 40 outputs a control signal to the air pump 21, the humidifiers 22, 33, the air pressure regulating valve 23, the hydrogen pressure regulating valve 32, and the hydrogen pump 34 based on the calculation result.

  FIG. 2 is a schematic perspective view showing a single cell of the fuel cell 10, and the single cell of the fuel cell 10 is an MEA (Membrane Electrode Assembly) in which electrodes are arranged on both sides of the electrolyte membrane. 100, and an air-side separator 110 and a hydrogen-side separator 120 that sandwich the MEA 100. Further, a negative electrode current collector plate 130 is disposed adjacent to the hydrogen side separator 120. Incidentally, the air-side separator 110 also serves as a positive electrode current collector plate.

  3 is a perspective view of the air-side separator 110 viewed from the right side of FIG. 2. The air-side separator 110 includes an air inlet portion 111 and an air outlet portion 112 connected to the air flow path 20, and an air inlet portion 111. And an air flow path groove 113 for flowing air toward the air outlet portion 112. The air-side separator 110 corresponds to the first separator of the present invention, the air flow path groove 113 corresponds to the oxidizing gas flow path of the present invention, and the air inlet 111 corresponds to the oxidizing gas inlet of the present invention. The air outlet 112 corresponds to the oxidizing gas outlet of the present invention.

  4 is a perspective view of the hydrogen side separator 120 as viewed from the right side of FIG. 2. The hydrogen side separator 120 includes a hydrogen inlet part 121 and a hydrogen outlet part 122 connected to the hydrogen flow path 30, and a hydrogen inlet part 121. And a hydrogen passage groove 123 for flowing hydrogen toward the hydrogen outlet portion 122. The hydrogen separator 120 corresponds to the second separator of the present invention, the hydrogen channel groove 123 corresponds to the fuel gas channel of the present invention, and the hydrogen inlet 121 corresponds to the fuel gas inlet of the present invention. The hydrogen outlet 122 corresponds to the fuel gas outlet of the present invention.

  5 is an enlarged view of the main part on the negative electrode side in FIG. 2, and FIG. 6 is a cross-sectional view taken along the line AA in FIG. As shown in FIGS. 2, 5, and 6, the current collector 130 is divided into a main current collector 131 and three sub current collectors 132 to 134. The main current collecting plate 131 and the three sub current collecting plates 132 to 134 are mounted in an insulated frame 140 made of an insulating material while being insulated from each other.

  The first sub collector plate 132 is closer to the air inlet portion 111 than the air outlet portion 112 in the air flow channel 113 of the air-side separator 110, more specifically, near the air inlet portion 111 (reference symbol B in FIG. 3). (Part shown), more specifically, the air inlet 111 is disposed at a position where it partially overlaps. The first sub collector plate 132 and the main collector plate 131 are connected by a conductive first collector wire 151. A first current sensor 161 that detects a current flowing through the first current collecting line 151 is attached to the first current collecting line 151.

  The second sub collector plate 133 is located closer to the hydrogen inlet 121 than the hydrogen outlet 122 in the hydrogen flow channel 123 of the hydrogen separator 120, more specifically, near the hydrogen inlet 121 (reference symbol C in FIG. 4). (Part shown), more specifically, the hydrogen inlet portion 121 is disposed so as to be opposed to a part of the hydrogen inlet portion 121. The second sub current collector 133 and the main current collector 131 are connected by a conductive second current collector 152. A second current sensor 162 that detects a current flowing through the second power collection line 152 is attached to the second power collection line 152.

  The third sub-current collector plate 134 is closer to the hydrogen outlet portion 122 than the hydrogen inlet portion 121 in the hydrogen flow channel 123 of the hydrogen side separator 120, more specifically, near the hydrogen outlet portion 122 (reference symbol D in FIG. 4). (Part shown), more specifically, the hydrogen outlet portion 122 is disposed so as to face the portion where it partially overlaps. The third sub collector plate 134 and the main collector plate 131 are connected by a conductive third collector wire 153. A third current sensor 163 that detects a current flowing through the third power collection line 153 is attached to the third power collection line 153.

  Each of the current sensors 161 to 163 can use, for example, a Hall element as a magnetic sensor. In this case, an iron core having a gap may be disposed around the collector wires 151 to 153, and a Hall element may be disposed in the gap. When a current flows through the current collectors 151 to 153, a magnetic field proportional to the current is generated around the current collectors 151 to 153. The Hall element detects a magnetic field generated by the current and converts it into a voltage. In addition to the Hall element, an MR element, MI element, flux gate, or the like can be used as the magnetic sensor. Furthermore, a current sensor using a shunt resistor can also be used.

  In addition, the first sub current collector 132, the first current collector 151, the first current sensor 161, the second sub current collector 133, the second current collector 152, the second current sensor 162, the third sub current collector 134, Each of the third power collection line 153 and the third current sensor 163 constitutes a current measuring means of the present invention.

  The operation of the fuel cell system having the above configuration will be described.

  First, the air supply amount and the hydrogen supply amount to the fuel cell 10 are controlled according to the power demand from the load 11. Specifically, the air supply amount is controlled by controlling the rotational speed of the air pump 21, and the hydrogen supply amount is controlled by controlling the rotational speed of the hydrogen pump 34. At this time, the air supply amount is set in advance to a supply amount that does not cause voltage variation. With the supply of air and hydrogen, the fuel cell 10 generates power by an electrochemical reaction, and the generated power is supplied to the load 11.

  The current passing through the load 11 flows into the negative collector plate 131. The current flowing into the main current collecting plate 131 is the current flowing into the MEA 100 as it is, the current flowing into the MEA 100 via the first current collecting wire 151 and the first sub current collecting plate 132, and the second current collecting wire 152 and the second sub current collecting. The current flows into the MEA 100 via the current plate 133 and the current flows into the MEA 100 via the third current collecting wire 153 and the third sub current collecting plate 134.

  And since the electric current which flows through the 1st current collection line 151 is equivalent to the local electric current (henceforth the air inlet side electric current Ia * in) which flows through the site | part close | similar to the air inlet part 111 in MEA100, the 1st electric current sensor 161 makes air The inlet side current Ia · in can be detected.

  In addition, since the current flowing through the second power collecting line 152 corresponds to a local current flowing through a portion near the hydrogen inlet 121 in the MEA 100 (hereinafter referred to as hydrogen inlet side current Ih · in), the second current sensor 162 The inlet side current Ih · in can be detected.

  Furthermore, since the current flowing through the third power collection line 153 corresponds to a local current flowing through a portion close to the hydrogen outlet portion 122 in the MEA 100 (hereinafter, referred to as hydrogen outlet side current Ih · out), the third current sensor 163 causes the hydrogen The outlet side current Ih · out can be detected.

  By the way, when the humidification amount to the air supplied to the fuel cell 10 decreases, the portion near the air inlet 111 in the electrolyte membrane of the MEA 100 is dried. FIG. 7 shows the change over time of the current I in the drying generation portion when the electrolyte membrane dries as the air humidity ψa decreases. The proton conduction resistance increases at the drying portion in the electrolyte membrane and the current flows. descend.

  Similarly, when the amount of humidification to the hydrogen supplied to the fuel cell 10 decreases, the vicinity of the hydrogen inlet 121 in the electrolyte membrane of the MEA 100 is dried, and the proton conduction resistance increases and the current decreases at the dry portion. It should be noted that the change in current in the drying portion when the electrolyte membrane is dried along with the decrease in the amount of humidification to hydrogen is the same as in the case of the decrease in air humidity ψa shown in FIG.

  From this, the fuel cell 10 is measured by measuring the current I in the vicinity of the air inlet 111 and the hydrogen inlet 121, that is, the air inlet side current Ia · in and the hydrogen inlet side current Ih · in, which are likely to be dried. It is possible to diagnose the dry state of the electrolyte membrane. Specifically, when the air inlet side current Ia · in and the hydrogen inlet side current Ih · in are less than a predetermined current value, it can be estimated that there is a dry portion of the electrolyte membrane. The predetermined current value is set to about 90% of the current value when the electrolyte membrane is not dried.

  On the contrary, when the humidification amount to air or hydrogen becomes excessive, the wet state of the electrode with excessive moisture occurs. At that time, the liquid droplets are most likely to stay in the vicinity of the hydrogen outlet portion 122 to cause excess water, and thus are prominently generated at a portion near the hydrogen outlet portion 122 in the electrode of the MEA 100. The reason why water tends to be excessive in the vicinity of the hydrogen outlet portion 122 is that water is transported from the hydrogen inlet portion 121 to the hydrogen outlet portion 122 via the hydrogen passage groove 123, and hydrogen is consumed, so that the hydrogen flow rate is increased. It is reduced and the water discharge capacity is reduced. FIG. 8 shows a change in the local current I in the excess water portion when the electrode is in an excessive water state with an increase in the water drop amount Vw at the hydrogen outlet 122, and as the water drop amount Vw increases. The permeation of gas is hindered and the output of the battery decreases.

  In addition, even when the hydrogen supply amount is insufficient with respect to the power generation amount, a shortage of hydrogen occurs from the vicinity of the hydrogen outlet portion 122, so that the current in a portion near the hydrogen outlet portion 122 in the MEA 100 decreases. FIG. 9 shows a change in the current I at a portion close to the hydrogen outlet 122 in the MEA 100 when the hydrogen supply amount Qh is insufficient. When the hydrogen shortage occurs, the current I immediately and rapidly decreases.

  From this, when the current I near the hydrogen outlet portion 122 in the MEA 100, that is, the hydrogen outlet side current Ih · out is less than a predetermined current value, it can be estimated that water is excessively generated or hydrogen is insufficiently generated. The predetermined current value is set to about 90% of the current value in the moisture excess state and the hydrogen deficiency state.

  Here, since the current I at the portion near the hydrogen outlet 122 in the MEA 100 decreases when the moisture excess occurs and when the hydrogen shortage occurs, it is necessary to specify which is the cause of the decrease in the current I.

  FIG. 10 shows changes in the current I near the hydrogen outlet 122 in the MEA 100 when excessive moisture occurs, and changes in the current I near the hydrogen outlet 122 in the MEA 100 when hydrogen shortage occurs. is there. FIG. 11 shows the rate of decrease in current I (hereinafter referred to as the current rate of decrease) at a site close to the hydrogen outlet 122 in the MEA 100 when excess moisture and insufficient hydrogen occur. It should be noted that the current decrease rate in this specification is the absolute value of the current change amount per unit time. In FIGS. 10 and 11, the solid line is the characteristic at the time of excess water generation, the broken line is the characteristic at the time of hydrogen shortage occurrence, and t1 is the time when the water excess or hydrogen shortage occurs.

As shown in FIGS. 10 and 11, the current I when hydrogen shortage occurs is drastically reduced as compared to when water is excessive. From this, it is possible to specify the cause of the decrease in the current I by the current decrease rate when the current decrease occurs. Specifically, when the hydrogen outlet-side current Ih · out is less than a predetermined current value and the current decrease rate is less than the predetermined decrease rate dI1 (see FIG. 11), it is estimated that moisture is excessively generated, and the hydrogen outlet-side current Ih · out When out is less than the predetermined current value and the current decrease rate is equal to or greater than the predetermined decrease rate dI1, it can be estimated that hydrogen shortage has occurred. The predetermined decrease rate dI1 is set to about 1.0 (mA / SEC / cm ² ).

  Next, the diagnosis of the output reduction factor of the fuel cell 10 will be described based on FIG. FIG. 12 is a flowchart of the portion of the control process executed by the control unit 40 (see FIG. 1) relating to the diagnosis of the output reduction factor of the fuel cell 10.

  First, the total current flowing from the fuel cell 10 to the load 11 is measured by a current sensor (not shown) (step 101), and the air inlet side current Ia · in is measured by the first current sensor 161 (step 102). Next, it is determined whether or not the air inlet side current Ia · in is less than a first predetermined current value (step 103). This “first predetermined current value” is a value set in advance for diagnosing the dry state of the fuel cell 10 in the vicinity of the air inlet 111. As shown in FIG. 13, the first predetermined current value is mapped in association with the total current of the fuel cell 10 and can be obtained based on the total current measured in step 100.

  If the air inlet side current Ia · in is less than the first predetermined current value (YES in step 103), it is diagnosed that there is a dry portion of the electrolyte membrane (step 104). If the air inlet side current Ia · in is equal to or greater than the first predetermined current value (NO in step 103), it is diagnosed that there is no dried portion of the electrolyte membrane (step 105). Incidentally, when it is diagnosed in step 104 that there is a dry portion of the electrolyte membrane, it is estimated that the humidity ψa of the air supplied to the fuel cell 10 is low, so the amount of humidification to the air by the humidifier 22 is increased. To do.

  Next, the hydrogen inlet side current Ih · in is measured by the second current sensor 162 (step 106). Next, it is determined whether or not the hydrogen inlet side current Ih · in is less than a second predetermined current value (step 107). This “second predetermined current value” is a value set in advance for diagnosing the dry state of the fuel cell 10 in the vicinity of the hydrogen inlet 121. Similar to the first predetermined current value, the second predetermined current value is mapped in association with the total current of the fuel cell 10, and can be obtained based on the total current measured in step 100.

  If the hydrogen inlet side current Ih · in is less than the second predetermined current value (YES in step 107), it is diagnosed that there is a dry portion of the electrolyte membrane (step 108). If the hydrogen inlet side current Ih · in is equal to or greater than the second predetermined current value (NO in step 107), it is diagnosed that there is no dried portion of the electrolyte membrane (step 109). Incidentally, when it is diagnosed in step 108 that there is a dry portion of the electrolyte membrane, it is estimated that the amount of humidification to hydrogen supplied to the fuel cell 10 is small, so the amount of humidification to hydrogen by the humidifier 33 is reduced. To increase.

  Next, the hydrogen outlet side current Ih · out is measured by the third current sensor 163 (step 110). Next, it is determined whether or not the hydrogen outlet side current Ih · out is less than a third predetermined current value (step 111). This “third predetermined current value” is a value set in advance for diagnosing the excessive water state of the fuel cell 10 in the vicinity of the hydrogen outlet 122. Similarly to the first predetermined current value, the third predetermined current value is mapped in association with the total current of the fuel cell 10 and can be obtained based on the total current measured in step 100.

  If the hydrogen outlet side current Ih · out is equal to or greater than the third predetermined current value (NO in step 111), it is diagnosed that there is no excess moisture or no shortage of hydrogen (step 112). When the hydrogen outlet side current Ih · out is less than the third predetermined current value (YES in step 111) and the current decreasing rate of the hydrogen outlet side current Ih · out is less than the predetermined decreasing rate (YES in step 113), moisture It is diagnosed that the state is excessive (step 114). Incidentally, if it is diagnosed in step 114 that the moisture is excessive, it is estimated that the amount of humidification to air or hydrogen is excessive, or that the discharge capacity of water is reduced due to a decrease in the hydrogen flow rate. Both the humidification amount to air and the humidification amount to hydrogen by the humidifier 33 are decreased, and the hydrogen flow rate is increased.

  Further, when the hydrogen outlet side current Ih · out is less than the third predetermined current value (YES in step 111) and the current decreasing rate of the hydrogen outlet side current Ih · out is equal to or higher than the predetermined decreasing rate (NO in step 113). Then, it is diagnosed that the hydrogen supply amount is insufficient (step 115). Incidentally, if it is determined in step 115 that the hydrogen supply amount is insufficient, the hydrogen flow rate is increased.

  According to the above-described embodiment, the dry state of the electrolyte membrane is diagnosed based on the air inlet side current Ia · in and the hydrogen inlet side current Ih · in, and the hydrogen outlet side current Ih · out and the hydrogen outlet side current Ih · in Since the excess moisture and the lack of hydrogen are diagnosed based on the current reduction rate of out, the output reduction factor of the fuel cell 10 can be diagnosed accurately. In addition, it is possible to specify the output reduction factor of the fuel cell 10, and therefore it is possible to perform accurate control according to the output reduction factor.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in the configuration of the current measuring means.

  FIG. 14 is a conceptual diagram showing the configuration of the fuel cell system of the second embodiment, FIG. 15 is a perspective view of the fuel cell of the present embodiment, and FIG. 16 is a perspective view of the fuel cell.

  As shown in FIG. 16, in the second embodiment, current collecting members 171 to 174 are provided on the first current collecting plate 140. The current collecting members 171 to 174 are made of a rod-shaped conductive member, and are provided so as to protrude from the plate surface of the first current collecting plate 140. The main current collecting plate 131 is provided with a first current collecting member 171, the first sub current collecting plate 132 is provided with a second current collecting member 172, and the second sub current collecting plate 133 is provided with a third current collecting member. 173 is provided, and a fourth current collecting member 174 is provided on the third sub-current collector plate 134. Through holes 170 a to 170 d are formed in the second current collector plate 170 at portions corresponding to the current collectors 171 to 174 of the first current collector plate 140.

  As shown in FIG. 14, the current generated by the fuel cell 10 flows to the electric load 11 via the current collecting members 171 to 174. As shown in FIGS. 14 and 15, current sensors 164, 165, 166 that measure current values flowing through current collecting members 172, 173, 174 provided on the sub current collector plates 132, 133, 134 are fuel cell 10. It is provided outside. As each of the current sensors 164 to 166, a Hall element or other current sensor can be used as in the first embodiment.

  Since the current flowing through the first current collecting member 172 corresponds to the air inlet-side current Ia · in in the MEA 100, the first current sensor 164 can detect the air inlet-side current Ia · in. Further, since the current flowing through the second current collecting member 173 corresponds to the hydrogen inlet side current Ih · in, the second current sensor 165 can detect the hydrogen inlet side current Ih · in. Further, since the current flowing through the third current collecting member 174 corresponds to the hydrogen outlet side current Ih · out, the third current sensor 166 can detect the hydrogen outlet side current Ih · out.

  Also, the first sub current collector 132, the first current collector 172, the first current sensor 164, the second sub current collector 133, the second current collector 173, the second current sensor 165, and the third sub current collector. Each of the 134, the third current collecting member 174, and the third current sensor 166 constitutes a current measuring means of the present invention.

  Also with the configuration using the current measuring means with the above configuration, it is possible to accurately diagnose the output reduction factor of the fuel cell 10 as in the first embodiment.

(Third embodiment)
Next, a third embodiment of the present invention will be described. The third embodiment is different from the above embodiments in the content of moisture control when the inside of the fuel cell is in a dry state.

FIG. 17 shows a change in the generated current I when the moisture state fluctuates in the vicinity of the air inlet 111, which is a portion B of the fuel cell 10 that is easily dried. In the example shown in FIG. 17, when the current I of the fuel cell 10 becomes equal to or higher than a predetermined reference current I ₁ , the inside of the fuel cell 10 is assumed to be in a wet state, and the current I of the fuel cell 10 changes the reference current I ₁ . When it falls below, it is supposed that the inside of the fuel cell 10 is in a dry state. When the inside of the fuel cell 10 is in a dry state, the power generation current I of the fuel cell 10 decreases as the amount of water in the fuel cell 10 decreases.

FIG. 18 shows a difference current ΔI (= I−I ₁₎ that is a difference between the generated current I and the reference current I ₁ when the moisture state fluctuates in the vicinity of the air inlet 111, which is a portion B of the fuel cell 10 that is easily dried. ) Changes. As shown in FIG. 18, the difference current ΔI is zero or more when the fuel cell 10 is in a wet state, and the difference current ΔI is less than zero when the fuel cell 10 is in a dry state. Further, as described above, since the generated current I of the fuel cell 10 changes in accordance with the amount of moisture in the fuel cell 10, the degree of moisture state inside the fuel cell 10 is estimated based on the magnitude of the differential current ΔI. be able to. That is, when the differential current ΔI is negative, it can be determined that the moisture shortage in the fuel cell 10 is larger as the absolute value of the differential current ΔI is larger, and that it is more dry.

  Next, the water content control of the fuel cell system of this embodiment will be described based on the flowchart of FIG.

First, the local current I of the dry part B is measured by a current sensor (step 200), and a differential current ΔI that is a difference from the reference current I ₁ is calculated (step 201). Next, it is determined whether or not the differential current ΔI is less than zero (step 202). As a result, when it is determined that the difference current ΔI is equal to or greater than zero, it can be estimated that the inside of the fuel cell 10 is in a wet state, so the humidification amount to the air by the humidifier 22 is set to zero (step 203). On the other hand, when it is determined that the difference current ΔI is less than zero, it can be estimated that the inside of the fuel cell 10 is in a dry state, so the amount of humidified water to the fuel cell 10 by the humidifier 22 is K1 × | ΔI |. Control (step 204). K1 is a coefficient for calculating the amount of humidified water.

As described above, by controlling the amount of humidified water by estimating the dry state inside the fuel cell 10 based on the difference current ΔI that is the difference between the local current I of the fuel cell 10 and the reference current I ₁ , The inside of the fuel cell 10 can be brought into a more appropriate moisture state.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. The fourth embodiment is different from the above embodiments in the content of the water content control when the fuel cell is in an excessive water state.

FIG. 20 shows a change in the generated current I when the moisture state fluctuates in the vicinity of the hydrogen outlet portion 122, which is the portion D where the moisture in the fuel cell 10 tends to be excessive. In the example shown in FIG. 20, when the current I of the fuel cell 10 is equal to or greater than a predetermined reference current I ₂ , the inside of the fuel cell 10 is assumed to be in a proper moisture state, and the current I of the fuel cell 10 is the reference current I _2. It is assumed that the inside of the fuel cell 10 is in an excessive water state. When the inside of the fuel cell 10 is in an excessive water state, the power generation current I of the fuel cell 10 decreases as the amount of water in the fuel cell 10 increases.

FIG. 21 shows a difference current ΔI (= I−I), which is the difference between the generated current I and the reference current I ₂ when the moisture state fluctuates in the vicinity of the hydrogen outlet 122, which is a portion D of the fuel cell 10 where the moisture tends to be excessive. ₂ ) shows changes. As shown in FIG. 21, the differential current I ₂ is zero or more when the water content in the fuel cell 10 is in an appropriate state, and the differential current ΔI is less than zero when the fuel cell 10 is in an excessive water state. Further, as described above, since the generated current I of the fuel cell 10 changes in accordance with the amount of moisture in the fuel cell 10, the degree of moisture state inside the fuel cell 10 is estimated based on the magnitude of the differential current ΔI. be able to. That is, when the difference current ΔI is negative, it can be determined that the excess amount of water in the fuel cell 10 is larger as the absolute value of the difference current ΔI is larger.

  Next, the water content control of the fuel cell system of the present embodiment will be described based on the flowchart of FIG.

First, the current sensor measures the local current I of overhydration site D (step 300), it calculates the differential current ΔI is the difference between the reference current I ₂ (step 301). Next, it is determined whether or not the differential current ΔI is less than zero (step 302). As a result, when it is determined that the difference current ΔI is zero or more, it can be estimated that the inside of the fuel cell 10 is in a proper moisture state, so the increase rate of the hydrogen flow rate is set to zero (step 303). On the other hand, if it is determined that the differential current ΔI is less than zero, it can be estimated that the fuel cell 10 is in an excessive water state, so the rate of increase in the hydrogen flow rate is controlled to K2 × | ΔI | (step 304). ). K2 is a coefficient for calculating the hydrogen flow rate increase rate.

  Then, the hydrogen supply flow rate to the fuel cell 10 is controlled to the required hydrogen flow rate × (1 + flow rate increase rate) (step 305). The hydrogen required flow rate is a hydrogen flow rate required for generating the required power. By supplying hydrogen excessively in this way, it is possible to push out the water in the excessive water portion D with the hydrogen gas flow.

As described above, the hydrogen supply amount is controlled by estimating the excess water state in the fuel cell 10 based on the magnitude of the difference current ΔI that is the difference between the local current I of the fuel cell 10 and the reference current I _2. Thus, the inside of the fuel cell 10 can be brought into a more appropriate moisture state.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. The fifth embodiment is different from the above embodiments in that the moisture state of the fuel cell is diagnosed based on the resistance value inside the fuel cell.

  FIG. 23 shows the relationship between the internal resistance of the fuel cell 10 and the internal moisture content. As shown in FIG. 23, the internal resistance decreases until a certain stage when the internal water content of the fuel cell 10 increases, and the internal resistance increases when the internal water content decreases.

Therefore, based on the local current of the portions B and C that are easily dried of the fuel cell 10 measured by the current sensors 161, 162, 164, 165, and the cell voltage of the fuel cell 10 measured by the cell monitor 12, A local internal resistance R (= cell voltage / local current) at a portion that is easily dried can be calculated, and the dry state inside the fuel cell 10 can be diagnosed based on the local internal resistance R. Specifically, when the local internal resistance R is the reference internal resistance R ₁ smaller than a preset, the fuel cell 10 is diagnosed as being dry. When it is diagnosed that the inside of the fuel cell 10 is in a dry state, it is estimated that the amount of humidification to hydrogen supplied to the fuel cell 10 is small, so the amount of humidification to hydrogen by the humidifier 33 is increased.

  Similarly, the fuel cell 10 becomes excessively water based on the local current of the part D that is likely to be excessively watery measured by the current sensors 163 and 166 and the voltage of the fuel cell 10 measured by the cell monitor 12. It is possible to calculate the local internal resistance R at an easy site and diagnose the excess water state inside the fuel cell 10 based on the local internal resistance R. Specifically, when the local resistance value R is larger than a preset reference internal resistance, the fuel cell 10 is diagnosed as being in an excessive water state. When it is diagnosed that the moisture is excessive, it is estimated that the amount of humidification to the air or hydrogen is excessive or the water discharge capacity is reduced due to the decrease in the hydrogen flow rate. Both the amount of humidification to hydrogen by the humidifier 33 is decreased and the hydrogen flow rate is increased.

  Even with the above configuration, the output reduction factor of the fuel cell 10 can be accurately diagnosed. In addition, it is possible to specify the output reduction factor of the fuel cell 10, and therefore it is possible to perform accurate control according to the output reduction factor.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described. The sixth embodiment is different from the above embodiments in that the degree of dryness of the fuel cell is diagnosed based on the resistance value inside the fuel cell and the amount of water is controlled.

FIG. 24 shows a change in the local resistance value R when the moisture state fluctuates in the vicinity of the air inlet 111, which is a portion B of the fuel cell 10 that is easily dried. In the example shown in FIG. 24, when the local internal resistance R of the fuel cell 10 exceeds the predetermined reference internal resistance R _1, the fuel cell 10 is to be dry, the reference local internal resistance R of the fuel cell 10 when it becomes an internal resistance R ₁ or less, the fuel cell 10 is to be wet. When the inside of the fuel cell 10 is in a dry state, the local internal resistance R of the fuel cell 10 increases as the amount of water in the fuel cell 10 decreases.

FIG. 25 shows a differential resistance ΔR (= R−) which is the difference between the local internal resistance R and the reference internal resistance R ₁ when the moisture state fluctuates in the vicinity of the air inlet 111, which is the portion B of the fuel cell 10 that is easy to dry. The change in R ₁ ) is shown. As shown in FIG. 18, when the inside of the fuel cell 10 is in a wet state, the differential resistance ΔR is not more than zero, and when the inside of the fuel cell 10 is in a dry state, the differential resistance ΔR exceeds zero. Further, as described above, since the local internal resistance R of the fuel cell 10 changes according to the amount of water inside the fuel cell 10, the degree of the moisture state inside the fuel cell 10 is estimated based on the magnitude of the differential resistance ΔR. can do. That is, when the differential resistance ΔR is positive, it can be determined that the moisture shortage in the fuel cell 10 is larger as the absolute value of the differential resistance ΔR is larger, and that the dryness is more dry.

  Next, the water content control of the fuel cell system of the present embodiment will be described based on the flowchart of FIG.

First, the local current of the dry region B is measured by the current sensor (step 400), the cell voltage is measured by the cell monitor 12 (step 401), and the local internal resistance R is calculated by dividing the cell voltage by the local current (step 401). 402). Next, a differential resistance ΔR that is a difference between the local resistance R and the reference internal resistance R ₁ is calculated (step 403).

  Next, it is determined whether or not the differential resistance ΔR exceeds zero (step 404). As a result, when it is determined that the differential resistance ΔR is equal to or less than zero, it can be estimated that the inside of the fuel cell 10 is in a wet state, so the humidification amount to the air by the humidifier 22 is made zero (step 405). On the other hand, if it is determined that the differential current ΔI is greater than zero, it can be estimated that the inside of the fuel cell 10 is in a dry state, so the amount of humidified water to the fuel cell 10 by the humidifier 22 is expressed as K3 × | ΔR | (Step 406). K3 is a coefficient for calculating the amount of humidified water.

As described above, the amount of humidified water is controlled by estimating the dry state inside the fuel cell 10 based on the difference resistance ΔR, which is the difference between the local resistance I of the fuel cell 10 and the reference internal resistance R _1. The interior of the fuel cell 10 can be brought into a more appropriate moisture state.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described. The seventh embodiment is different from the above-described embodiments in that the degree of moisture excess state of the fuel cell is diagnosed based on the resistance value inside the fuel cell, and the moisture amount is controlled.

FIG. 27 shows a change in local internal resistance R when the moisture state fluctuates in the vicinity of the hydrogen outlet portion 122, which is a portion D that tends to be excessive in the fuel cell 10. In the example shown in FIG. 27, when the local internal resistance R of the fuel cell 10 is equal to or less than a predetermined reference internal resistance R ₂ , it is assumed that the inside of the fuel cell 10 is in a proper moisture state, and the local internal resistance R of the fuel cell 10 is When the value exceeds a predetermined reference internal resistance R ₂ , the inside of the fuel cell 10 is assumed to be in an excessive water state. When the inside of the fuel cell 10 is in an excessive water state, the local internal resistance R of the fuel cell 10 increases as the amount of water in the fuel cell 10 increases.

FIG. 28 shows a differential resistance ΔR (= R) which is the difference between the local internal resistance R and the reference internal resistance R ₂ when the water state fluctuates in the vicinity of the hydrogen outlet portion 122, which is the portion D where the water content of the fuel cell 10 tends to be excessive. -R ₂ ) change. As shown in FIG. 28, when the water content in the fuel cell 10 is in an appropriate state, the differential resistance R ₂ becomes zero or less, and when the fuel cell 10 has an excessive water content, the differential resistance R ₂ exceeds zero. Further, as described above, since the local internal resistance R of the fuel cell 10 changes according to the amount of water inside the fuel cell 10, the degree of the moisture state inside the fuel cell 10 is estimated based on the magnitude of the differential resistance ΔR. can do. That is, when the differential resistance ΔR is positive, it can be determined that the excess amount of water in the fuel cell 10 is larger as the absolute value of the differential resistance ΔR is larger.

  Next, the water content control of the fuel cell system of this embodiment will be described based on the flowchart of FIG.

First, the local current I of the excessive water portion D is measured by the current sensor (step 500), the cell voltage is measured by the cell monitor 12 (step 501), and the local internal resistance R is calculated by dividing the cell voltage by the local current. (Step 502). Next, a differential resistance ΔR that is a difference between the local resistance R and the reference internal resistance R ₂ is calculated (step 503).

  Next, it is determined whether or not the differential resistance ΔR exceeds zero (step 504). As a result, if it is determined that the differential resistance ΔR is equal to or less than zero, it can be estimated that the inside of the fuel cell 10 is in a proper moisture state, and therefore the rate of increase in the hydrogen flow rate is set to zero (step 505). On the other hand, if it is determined that the differential resistance ΔR is greater than zero, it can be estimated that the fuel cell 10 is in an excessive water state, so the rate of increase in the hydrogen flow rate is controlled to K4 × | ΔI | (step 506). ). K4 is a coefficient for calculating the hydrogen flow rate increase rate.

  Then, the hydrogen supply flow rate to the fuel cell 10 is controlled to the hydrogen required flow rate × (1 + flow rate increase rate) (step 507). The hydrogen required flow rate is a hydrogen flow rate required for generating the required power. By supplying hydrogen excessively in this way, it is possible to push out the water in the excessive water portion D with the hydrogen gas flow.

As described above, the hydrogen supply amount is controlled by estimating the excess water state in the fuel cell 10 based on the magnitude of the differential resistance ΔR, which is the difference between the local internal resistance R of the fuel cell 10 and the reference internal resistance R _2. By doing so, the inside of the fuel cell 10 can be brought into a more appropriate moisture state.

(Other embodiments)
In each of the above embodiments, the fuel cell including the solid polymer electrolyte membrane is used. However, the present invention is not limited to this, and the present invention can be applied to, for example, a fuel cell including an inorganic material electrolyte.

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 12 ... Cell monitor, 40 ... Control part (diagnosis means), 161-166 ... Current sensor which makes the principal part of an electric current measurement means.

Claims (5)

A fuel cell (10) for generating electrical energy by an electrochemical reaction between an oxidant gas and a fuel gas;
Current measuring means (134, 153, 163, 166, 174) for measuring a current flowing through a portion (D) where the fuel gas is likely to be insufficient in the fuel cell (10);
A fuel cell system comprising diagnostic means (40) for diagnosing a shortage of fuel gas in the fuel cell based on a current value measured by the current measuring means.   When the current measured by the current measuring unit is less than a predetermined current value and the rate of current decrease measured by the current measuring unit is equal to or higher than a predetermined rate, the diagnostic unit (40) The fuel cell system according to claim 1, wherein the fuel cell system is diagnosed as having insufficient fuel gas supply amount. A fuel cell (10) for generating electrical energy by an electrochemical reaction between an oxidant gas and a fuel gas;
Current measuring means (134, 153, 163) for measuring a current flowing through a portion (D) in the fuel cell (10) that is likely to be excessive in water and short of fuel gas;
A fuel cell comprising diagnostic means (40) for distinguishing and diagnosing excess water in the fuel cell and insufficient fuel gas in the fuel cell based on a current decrease rate measured by the current measuring means. system.   When the current measured by the current measuring unit is less than a predetermined current value and the rate of decrease in current measured by the current measuring unit is less than a predetermined rate of decrease, When the current measured by the current measuring unit is less than the predetermined current value and the current decreasing rate measured by the current measuring unit is equal to or higher than the predetermined decreasing rate, The fuel cell system according to claim 3, wherein a diagnosis is made that the amount of fuel gas supplied to the fuel cell is insufficient. The fuel cell (10) includes an electrolyte / electrode assembly (100) in which a pair of electrodes are arranged on both sides of an electrolyte membrane, and an outside of the electrolyte / electrode assembly and a flow path for the oxidant gas. A first separator (110) in which an oxidant gas flow path (113) is formed, and a fuel gas flow path (123) that is disposed outside the electrolyte-electrode assembly and serves as a flow path for the fuel gas A second separator (120) formed with
The current measuring means (134, 153, 163, 166, 174) measures current at a position closer to the fuel gas outlet (122) than the fuel gas inlet (121) in the fuel gas flow path. The fuel cell system according to any one of claims 1 to 4, wherein:

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