JP2009283170A - Fuel cell system - Google Patents

Abstract

To reduce the pressure of hydrogen gas supplied from an ejector to a fuel cell with a simple configuration below an allowable pressure of the fuel cell.
A hydrogen gas supplied from a hydrogen tank to a fuel cell is merged with a hydrogen off-gas discharged from the fuel cell and supplied to the fuel cell, and a supply amount of the hydrogen gas to the ejector. The fuel cell system 1 includes an adjustment valve 44 for adjusting the upper limit value of the hydrogen gas pressure on the ejector inlet side even when the hydrogen gas pressure values on the inlet side and the outlet side of the ejector become equal after the system is stopped. The hydrogen gas pressure value on the ejector outlet side is determined to be equal to or lower than the allowable pressure value of the fuel cell.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system.

The fuel cell system generates electric power by an electrochemical reaction between a fuel gas supplied to the anode electrode and an oxidizing gas supplied to the cathode electrode. The fuel off-gas discharged from the anode electrode is returned to the fuel supply channel through the fuel circulation channel, mixed with the fuel gas supplied from the fuel supply source, and re-supplied to the anode electrode. In the fuel cell system described in Patent Document 1 below, the fuel off-gas discharged to the fuel circulation passage is returned to the fuel supply passage using an ejector and mixed with the fuel gas.
Japanese Patent Laid-Open No. 10-284098

  By the way, in general, an ejector discharges a fuel gas by utilizing a differential pressure of the fuel gas on the inlet side and the outlet side. Therefore, during operation of the fuel cell system, the pressure of the fuel gas on the inlet side of the ejector is higher than the pressure of the fuel gas on the outlet side. Further, during operation of the fuel cell system, the flow rate of the fuel gas supplied to the inlet side is controlled so that the pressure of the fuel gas on the outlet side of the ejector does not exceed the allowable pressure of the fuel cell.

  However, when the operation of the fuel cell system is stopped, the supply of the fuel gas to the ejector is shut off and the power generation of the fuel cell is stopped. When the power generation of the fuel cell stops, the consumption of the fuel gas discharged from the ejector stops. On the other hand, since a differential pressure is generated between the fuel gas on the inlet side and the outlet side of the ejector, the fuel gas is continuously discharged from the ejector even after the operation of the fuel cell system is stopped. In this case, the pressure of the fuel gas on the outlet side of the ejector may exceed the allowable pressure of the fuel cell.

  In the fuel cell system described in Patent Document 1 described above, a pressure gauge and a fuel discharge pipe are provided in order to keep the pressure of the fuel gas below a predetermined value. However, adding such a configuration complicates the system. End up.

  The present invention provides a fuel cell system capable of suppressing the pressure of the fuel gas supplied from the ejector to the fuel cell with a simple configuration below the allowable pressure of the fuel cell in order to eliminate the above-described problems caused by the prior art. The purpose is to provide.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of an oxidizing gas and a fuel gas, which are reaction gases, and generates electric power through an electrochemical reaction of the reaction gas, and a fuel gas. A fuel supply channel for supplying fuel to the fuel cell from the fuel supply source, and a fuel gas supplied to the fuel cell by combining the fuel gas supplied from the fuel supply source with the fuel off-gas discharged from the fuel cell. An ejector to be supplied, and a valve provided upstream of the ejector in the fuel supply flow path, for blocking or allowing the supply of the fuel gas to the ejector, and a pressure value of the fuel gas on the inlet side of the ejector; Even when the pressure value of the fuel gas on the outlet side of the ejector becomes equal, the pressure value of the fuel gas on the outlet side of the ejector is less than the allowable pressure value of the fuel cell. Wherein the upper limit value of the pressure of the fuel gas at the inlet side of the injector is determined.

  According to the present invention, in a fuel cell system that supplies fuel gas to a fuel cell using an ejector, the fuel gas pressure on the inlet side of the ejector is controlled to be within a predetermined upper limit value. Even if the fuel gas pressure value at the ejector inlet side and the fuel gas pressure value at the ejector outlet side become equal after the battery system operation is stopped and the valve is closed, The pressure value of the fuel gas on the outlet side can be suppressed below the allowable pressure value of the fuel cell.

  In the fuel cell system, the upper limit value of the pressure of the fuel gas on the inlet side of the ejector is the allowable pressure value of the fuel cell, the pressure value of the fuel gas on the outlet side of the ejector, and the closed pressure formed between the valve and the ejector. It may be determined based on the volume of the space and the volume of the closed space formed between the ejector and the fuel cell.

  In the fuel cell system, the upper limit value of the pressure of the fuel gas on the inlet side of the ejector is a supply amount of fuel gas supplied to the ejector after the valve closing command is sent to the valve until the valve is closed. May be determined using as a correction value.

  As a result, it is possible to suppress the fuel gas pressure at the outlet side of the ejector below the allowable pressure value of the fuel cell in consideration of the amount of fuel gas supplied to the ejector during the valve operation delay. Become.

  In the fuel cell system, the ejector is an ejector having a constant nozzle diameter, and when the pressure value of the fuel gas on the inlet side of the ejector exceeds the upper limit value of the pressure of the fuel gas on the inlet side of the ejector, Control means for reducing at least the excess pressure can be further provided.

  Thereby, even if the physical requirements cannot satisfy the design requirements and the pressure value of the fuel gas supplied to the ejector may exceed the upper limit value of the fuel gas pressure on the inlet side of the ejector, Since at least the excess pressure can be reduced, the degree of freedom in design can be increased.

  In the fuel cell system, the control means can reduce the excess pressure by causing the fuel cell to generate power. The fuel cell system further includes a fuel circulation passage for returning the fuel off-gas to the fuel gas supply passage, and a discharge valve for discharging the fuel off-gas and moisture in the fuel circulation passage to the outside. The control means can reduce the excess pressure by opening the discharge valve.

  In the fuel cell system, the ejector is an ejector having a nozzle diameter that varies according to the position of the needle, calculates a supply flow rate of the fuel gas required for the ejector, and positions the needle according to the calculated supply flow rate. And a control means for moving the needle using the calculated position of the needle as a needle target position.

  Thereby, since the ejector can be feedforward controlled, it is possible to cope with a sudden load fluctuation in the fuel cell system, and it is possible to prevent a shortage of fuel gas due to a sudden increase in output current.

  In the fuel cell system, the control means can correct the supply flow rate of the fuel gas required for the ejector based on the pressure value of the fuel gas on the outlet side of the ejector and the target pressure value of the fuel gas.

  As a result, the ejector can be feedforward-controlled and feedback-controlled, so that it is possible to cope with a sudden load fluctuation in the fuel cell system and to prevent a shortage of fuel gas due to a sudden increase in output current. Become.

  In the fuel cell system, the control means calculates an estimated position of the needle based on the current needle target position and the previous needle target position, and based on the calculated estimated needle position, the fuel gas from the ejector is calculated. The supply flow rate can be calculated, and the allowable output current of the fuel cell can be calculated based on the calculated supply flow rate.

  As a result, the output current of the fuel cell can be suppressed to an allowable output current or less according to the estimated position of the needle, so that it is possible to prevent a shortage of fuel gas due to a delay in the operation of the needle.

  According to the present invention, the pressure of the fuel gas supplied from the ejector to the fuel cell can be suppressed below the allowable pressure of the fuel cell with a simple configuration.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a fuel cell system according to the invention will be described with reference to the accompanying drawings. Each embodiment demonstrates the case where the fuel cell system concerning the present invention is used as an in-vehicle power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle). In the fuel cell system in the first embodiment, an ejector having a constant nozzle diameter is used as the ejector, and in the fuel cell system in the second embodiment, an ejector having a variable nozzle diameter is used as the ejector.
[First embodiment]

  First, the configuration of the fuel cell system in the first embodiment will be described. FIG. 1 is a configuration diagram schematically showing a fuel cell system.

  As shown in the figure, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction upon receiving supply of an oxidizing gas and a fuel gas as reaction gases, and air as an oxidizing gas to the fuel cell 2. It has the oxidizing gas piping system 3 to supply, the hydrogen gas piping system 4 which supplies the hydrogen gas as fuel gas to the fuel cell 2, and the control part 5 which performs overall control of the whole system.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The unit cell has a structure having a cathode electrode on one surface of an electrolyte made of an ion exchange membrane, an anode electrode on the other surface, and a pair of separators so as to sandwich the cathode electrode and the anode electrode from both sides. It has become. In this case, hydrogen gas is supplied to the hydrogen gas flow path of one separator, oxidizing gas is supplied to the oxidizing gas flow path of the other separator, and electric power is generated by the chemical reaction of these reaction gases.

  The oxidizing gas piping system 3 is discharged from the fuel cell 2, a compressor 30 that takes in and compresses the oxidizing gas in the atmosphere, sends it, an air supply channel 31 for supplying the oxidizing gas to the fuel cell 2, and And an air discharge passage 32 for discharging the oxidizing off gas. The air supply channel 31 and the air discharge channel 32 are provided with a humidifier 33 that humidifies the oxidizing gas pumped from the compressor 30 using the oxidizing off gas discharged from the fuel cell 2. The oxidizing off gas that has undergone moisture exchange or the like in the humidifier 33 is finally exhausted into the atmosphere outside the system as exhaust gas.

  The hydrogen gas piping system 4 includes a hydrogen tank 40 as a fuel supply source storing high-pressure hydrogen gas, and a hydrogen supply channel 41 as a fuel supply channel for supplying the hydrogen gas in the hydrogen tank 40 to the fuel cell 2. And a hydrogen circulation passage 42 as a fuel circulation passage for returning the hydrogen off-gas discharged from the fuel cell 2 to the hydrogen supply passage 41. The hydrogen supply channel 41 includes a regulator 43 that adjusts the pressure of the hydrogen gas to a preset secondary pressure, an ejector 45 that recirculates the hydrogen off-gas in the hydrogen circulation channel 42 to the hydrogen supply channel 41, and the ejector 45. And an adjustment valve 44 (valve) for adjusting the supply amount of hydrogen gas. The adjustment valve 44 does not necessarily have a function of adjusting the supply amount. For example, the adjustment valve 44 may have a function of blocking or allowing the supply of hydrogen gas to the ejector 45.

  The ejector 45 combines the hydrogen gas supplied from the hydrogen tank 40 and the hydrogen off-gas discharged from the fuel cell 2, and supplies the mixed gas to the fuel cell 2. The ejector 45 in the first embodiment is an ejector having a constant nozzle diameter. In this ejector 45, the hydrogen gas supplied from the hydrogen tank 40 is injected from the nozzle toward the diffuser, thereby generating a negative pressure in the diffuser. Then, the hydrogen off gas is sucked into the diffuser using this negative pressure, and the sucked hydrogen off gas and the hydrogen gas injected from the nozzle are mixed and discharged.

  In the hydrogen supply channel 41, pressure sensors P1 and P2 for detecting the pressure of the hydrogen gas are respectively provided on the inlet side and the outlet side of the ejector 45. The pressure sensor P <b> 1 detects the pressure of hydrogen gas in the hydrogen supply passage 41 between the adjustment valve 44 and the ejector 45. The pressure sensor P2 detects the pressure of hydrogen gas in the hydrogen supply channel 41 between the ejector 45 and the fuel cell 2.

  Hydrogen off-gas in the hydrogen circulation passage 42 is absorbed by the ejector 45 through the check valve 49. A discharge flow path 47 is connected to the hydrogen circulation flow path 42 via a gas-liquid separator 46. The gas-liquid separator 46 recovers moisture from the hydrogen off gas. The exhaust passage 47 is provided with an exhaust drain valve 48 (exhaust valve). The exhaust drain valve 48 is normally closed, but includes water collected by the gas-liquid separator 46 and impurities in the hydrogen circulation flow path 42 by opening as appropriate in accordance with a command from the control unit 5. The hydrogen off-gas is discharged (purged).

The hydrogen gas piping system 4 is designed so as to satisfy the following formula 1, for example.

P _{1 in the} above equation 1 is the pressure value of hydrogen gas in the hydrogen supply passage 41 between the regulating valve 44 and the ejector 45. P ₂ is the pressure value of hydrogen gas in the hydrogen supply channel 41 between the ejector 45 and the fuel cell 2. P _2max is the maximum pressure value allowed as P ₂ , and the allowable pressure value of the fuel cell 2 is set. V ₁ is the volume of the closed space formed between the regulating valve 44 and the ejector 45. V ₂ is the volume of the closed space formed between the ejector 45 and the fuel cell 2.

In the fuel cell system satisfying the above formula 1, when the operation of the system is stopped, the regulating valve 44 is closed. Then, hydrogen gas flows from the inlet side of the ejector 45 to the outlet side due to the differential pressure of the hydrogen gas generated on the inlet side and the outlet side of the ejector 45. Thereafter, when the pressure difference between the inlet side and the outlet side of the ejector 45 is eliminated, the inflow of hydrogen gas stops. That is, when the pressure P ₁ and the pressure P ₂ become equal, the inflow of hydrogen gas stops. In this description, for the sake of convenience, loss of hydrogen gas pressure in the ejector 45 is not considered.

When the pressure P ₁ is equal to the pressure P ₂ , the above formula 1 is expressed by the following formula 2.

That is, by setting the pressures P ₁ and P ₂ and the volumes V ₁ and V ₂ so as to satisfy the above formula 1, after the operation of the fuel cell system is stopped and the regulating valve 44 is closed, the ejector 45 Even if the maximum amount of hydrogen gas that can flow in due to the differential pressure flows from the inlet side to the outlet side, the hydrogen gas pressure P ₂ on the outlet side of the ejector 45 is equal to the fuel cell, as shown in the above formula 2. The allowable pressure value P _2max of 2 is not exceeded.

Here, when the above equation 1 is converted into an equation representing the pressure P ₁ of the hydrogen gas on the inlet side of the ejector 45, the following equation 3 is obtained.

上記式４に示すように、圧力Ｐ₁の上限値Ｐ_1maxは、燃料電池の許容圧力値Ｐ_2max、エゼクタ４５の出口側における水素ガスの圧力値Ｐ₂、調整弁４４とエゼクタ４５との間に形成される閉空間の容積Ｖ₁、およびエゼクタ４５と燃料電池２との間に形成される閉空間の容積Ｖ₂を用いて定められることになる。 Since the above equation 3 indicates that the pressure P ₁ of the hydrogen gas on the inlet side of the ejector 45 is equal to or less than the value on the right side, the right side of the above equation 3 represents the maximum pressure allowed as the pressure P _1. value P _1max, i.e. the upper limit value P _1max pressure of the hydrogen gas at the inlet side of the ejector 45 will represent (hereinafter, referred to. the upper limit value P _1max of the pressure P ₁₎ (see formula 4).

As shown in the above equation 4, the upper limit value P _1max of the pressure P ₁ is the allowable pressure value P _2max of the fuel cell, the pressure value P ₂ of hydrogen gas at the outlet side of the ejector 45, and between the regulating valve 44 and the ejector 45. volume V ₁ of the closed space formed in, and will be determined using a volume V ₂ of the closed space formed between the ejector 45 and the fuel cell 2.

In this way, by setting the upper limit value P _1max of the pressure P ₁ so as to satisfy the above expression 4, after the operation of the fuel cell system is stopped and the regulating valve 44 is closed, the inlet side of the ejector 45 Even if the maximum amount of hydrogen gas that can flow in due to the differential pressure flows from the outlet to the outlet side, the pressure P ₂ of the hydrogen gas on the outlet side of the ejector 45 is suppressed to the allowable pressure value P _2max or less of the fuel cell 2. It becomes possible to do.

By the way, since the ejector 45 in the first embodiment is an ejector having a constant nozzle diameter, the pressures P ₁ and P ₂ are variable according to the flow rate of the hydrogen gas, and the pressures P ₁ and P ₂ are uniquely determined. I can't. Thus, in the first embodiment, considering that the pressure P _1, P ₂ are variable, the following procedure determines the pressure P _1, P ₂ and volume V _1, V _2.
(1) A possible range of the pressure P ₂ is calculated, and the maximum value is adopted as the value of the pressure P ₂ .
(2) A possible range of the pressure P ₁ is calculated, and the maximum value is adopted as the value of the pressure P ₁ .
(3) The volume V ₂ is determined in consideration of the physique of the fuel cell 2 and the like.
(4) The volume V ₁ is calculated by substituting the pressure P ₂ , the pressure P ₁ , the volume V ₂ and the allowable pressure value P _2max of the fuel cell into the above equation 1, respectively.

It should be noted that there is a time lag after the valve closing command is sent to the adjusting valve 44 until the adjusting valve 44 is actually closed. That is, an operation delay of the adjusting valve 44 occurs. When the operation delay of the regulating valve 44 occurs, the pressures P ₁ and P ₂ may increase due to the hydrogen gas supplied from the regulating valve 44 to the ejector 45 during the operation delay. Therefore, when the operation delay of the regulating valve 44 occurs, it may be considered that an error occurs if the above equation 1 is used. Therefore, in order to eliminate the errors, it is also possible to correct the value of the above formula 1 and formula 3 with a supply amount Q _E of the hydrogen gas supplied from the regulator valve 44 during the operation delay.

In this case, Equation 1 and Equation 3 become Equation 5 and Equation 6 below.

The supply amount Q _E of the hydrogen gas supplied from the adjustment valve 44 during the operation delay can be calculated by the following equation 7, for example.

  ΔP in Expression 7 is a hydrogen gas pressure difference between the upstream side and the downstream side of the regulating valve 44. C is the ease of gas flow in the regulating valve 44. t is the time [min] from when the valve closing command is sent to the adjusting valve 44 until the adjusting valve 44 is actually closed. G is the specific gravity of hydrogen gas, and T is the temperature [k]. As the temperature T, a predetermined temperature may be used, or the temperature of a hydrogen tank or the temperature of hydrogen gas may be used.

The supply amount Q _E of the hydrogen gas is not limited to being calculated by the above equation 7. For example, a map may be created in advance through experiments or the like, and calculation may be performed using the map, or constants calculated in advance through experiments or the like may be used.

  The control unit 5 detects an operation amount of an acceleration operation member (for example, an accelerator) provided in the fuel cell vehicle, and controls information such as an acceleration request value (for example, a required power generation amount from a power consumption device such as a traction motor). In response, the operation of various devices in the system is controlled. In addition to the traction motor, the power consuming device includes, for example, an auxiliary device (for example, a motor of the compressor 30) necessary for operating the fuel cell 2, various devices (transmission, Wheel control device, steering device, suspension device, etc.), occupant space air conditioner (air conditioner), lighting, audio, etc. are included.

When the pressure P ₁ of the hydrogen gas on the inlet side of the ejector 45 exceeds the upper limit value P _1max of the pressure P ₁ , the control unit 5 (control means) in the first embodiment at least _{detects the} excess pressure (P _{1- P1max} ). This is a control executed in order to solve the problem described below.

For example, depending on the pressures P ₁ and P ₂ and the supply amount Q _{E of} hydrogen gas, there may be a restriction that the volume V ₁ must be reduced and the volume V ₂ must be increased. However, it is conceivable that the volume V ₁ cannot be reduced due to a physical problem, and as a result, the above expression 3 or 6 (expression 1 or 5) cannot be satisfied. That is, the pressure P ₁ may be larger than the upper limit value P _1max .

In order to solve such a problem, control for reducing at least the excess pressure (P ₁ -P _1max ) is executed. As a result, the requirements for the volumes V ₁ and V ₂ can be relaxed, so that the degree of freedom of the piping volume of the hydrogen supply passage 41 is increased and the degree of freedom of the mounting positions of the regulating valve 44 and the ejector 45 is increased. It becomes possible to raise. As a method for reducing the excess pressure, for example, there are the following two methods.

The first method is to reduce the excess pressure by causing the fuel cell 2 to consume extra hydrogen gas supplied to the ejector 45 when the pressure is exceeded. The amount Q _o of the hydrogen gas excess fed to the ejector 45 by the pressure exceeded (hereinafter, referred to as the excess amount of hydrogen gas Q _o.) Can be calculated by Equation 8 below.

Specifically, the fuel cell 2 is caused to generate power to increase the output current, thereby consuming hydrogen gas corresponding to the excess hydrogen gas amount _Qo .

The second method reduces the excess pressure by discharging the hydrogen off-gas corresponding to the excess hydrogen gas amount Q _o by opening the exhaust drain valve 48.

In the two methods described above, the pressure at which the differential pressure (P ₁ -P ₂ ) between the hydrogen gas on the inlet side and the outlet side of the ejector 45 decreases by passing through the ejector 45 (hereinafter referred to as pressure loss in the ejector). It may be executed when it is larger than. If the differential pressure of the hydrogen gas (P ₁ -P ₂₎ is below the pressure loss in the ejector, a phenomenon that the hydrogen gas flows from the inlet side to the outlet side of the ejector 45 is because is eliminated.

  Here, the control unit 5 physically includes, for example, a CPU, a ROM that stores a control program and control data processed by the CPU, a RAM that is mainly used as various work areas for control processing, And an input / output interface. These elements are connected to each other via a bus. Various sensors such as pressure sensors P1 and P2 are connected to the input / output interface, and various drivers for driving the compressor 30, the adjustment valve 44, the exhaust drainage valve 48, and the like are connected.

  The CPU receives the detection results of various sensors via the input / output interface according to the control program stored in the ROM, and processes them using various data in the RAM, thereby controlling overpressure reduction of the fuel cell system. Control processing. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface.

As described above, according to the fuel cell system in the first embodiment, the pressure of the hydrogen gas supplied from the ejector to the fuel cell can be suppressed to be equal to or lower than the allowable pressure of the fuel cell with a simple configuration.
[Second Embodiment]

  A second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in that the second embodiment uses an ejector having a variable nozzle diameter instead of the ejector having a constant nozzle diameter in the first embodiment. Since other configurations are the same as those in the first embodiment, the same reference numerals are given to the respective components and the description thereof will be omitted. In the following, differences from the first embodiment will be mainly described. The point will be described.

  When an ejector having a variable nozzle diameter is used as the ejector, the nozzle diameter is appropriately changed. Therefore, it is difficult to accurately grasp the supply amount of hydrogen gas supplied from the ejector. Although it is conceivable to add a flow meter or the like in order to grasp the supply amount of hydrogen gas, the addition of the flow meter or the like causes problems such as an increase in cost and a delay in measurement response. Similar to the fuel cell system of the first embodiment, the fuel cell system in the second embodiment is configured to suppress the pressure of the hydrogen gas supplied from the ejector to the fuel cell with a simple configuration below the allowable pressure of the fuel cell. In addition, the supply amount of hydrogen gas by the ejector is simply calculated, and the supply of hydrogen gas by the ejector is accurately controlled.

The point which designs the hydrogen gas piping system 4 so that the said Formula 1 or Formula 5 may be satisfy | filled is the same as that of 1st Embodiment mentioned above. By designing the pressures P ₁ and P ₂ and the volumes V ₁ and V ₂ so as to satisfy the above expression 1 or 5, the ejector 45 is operated after the operation of the fuel cell system is stopped and the regulating valve 44 is closed. Even if the maximum amount of hydrogen gas that can flow in due to the differential pressure flows from the inlet side to the outlet side, the hydrogen gas pressure P ₂ on the outlet side of the ejector 45 is set to the allowable pressure value P _2max of the fuel cell 2. It becomes possible to suppress to the following.

  The ejector 45 in the second embodiment is an ejector whose nozzle diameter varies depending on the position of the needle. The ejector 45 injects hydrogen gas toward the diffuser, generates a negative pressure in the diffuser for sucking off hydrogen off gas, a needle that changes the opening area of the nozzle, and a drive that moves the position of the needle. Part.

  Below, the control content peculiar to the control part 5 (control means) in 2nd Embodiment is demonstrated.

First, a method for estimating the supply flow rate Q _g of the hydrogen gas nozzle diameter is supplied from the ejector 45 to be variable. The control unit 5 calculates the supply flow rate Q _g [NL / min] of the hydrogen gas from the ejector 45 using the following formula 9.

C in Equation 9 is the ease of gas flow in the ejector, G is the specific gravity of the hydrogen gas, T is the temperature [k], and ΔP is the differential pressure of the hydrogen gas upstream and downstream of the ejector 45. it is a (P ₁ -P _2).

  The gas flowability C in the ejector can be calculated using, for example, a map shown in FIG. FIG. 2 is a map showing the relationship between the position of the needle and the ease of gas flow in the ejector. The horizontal axis indicates the position of the needle, and the vertical axis indicates the ease of gas flow in the ejector. As the position of the needle moves in a direction that increases the opening area of the nozzle, the gas flows more easily. This map can be obtained in advance by experiments or the like. The position of the needle may be a value detected by a position sensor or a predicted value. The temperature T may be a predetermined temperature, or may be the temperature of the hydrogen tank 40 or the temperature of hydrogen gas.

By calculating the supply flow rate Q _g of hydrogen gas from the ejector 45 using the above equation 9, it becomes possible to estimate accurately the supply amount of the hydrogen gas supplied from the ejector 45, the supply of hydrogen gas The amount can be easily adjusted. Hereinafter, a method for adjusting the supply amount of the hydrogen gas using the above-described equation 9 will be described.

  First, a procedure for calculating the position of the needle using the hydrogen gas supply flow rate required for the ejector 45 and the above equation 9 and performing feedforward control of the ejector 45 using the position of the needle will be described.

The control unit 5 calculates the flow rate Q _{F of} hydrogen gas required by the fuel cell (hereinafter referred to as the required flow rate Q _{F of} hydrogen gas) using the output current of the fuel cell, the pressure of hydrogen gas, and the like. Subsequently, the control unit 5 regards the calculated required flow rate Q _F of hydrogen gas as the supply flow rate Q _{g of the} hydrogen gas required for the ejector 45, and eases gas flow C in the ejector 45 using the above equation 9. Is calculated. Subsequently, the control unit 5 calculates the position of the needle using the calculated gas flowability C in the ejector 45 and the map of FIG. Subsequently, the control unit 5 outputs a movement command for moving the needle to the ejector 45 with the calculated needle position as the target position.

  By executing the feedforward control described above, it is possible to cope with a sudden load fluctuation in the fuel cell system, and to prevent a shortage of hydrogen gas due to a sudden increase in output current.

The hydrogen gas supply flow rate Q _g may be calculated using pressures P ₁ and P ₂ , volumes V ₁ and V ₂ , temperature T, and the like.

  Next, a procedure for calculating the position of the needle using the hydrogen gas supply flow rate required for the ejector 45 and the above equation 9 and performing feedforward control and feedback control of the ejector 45 using the position of the needle will be described.

The control unit 5 calculates the required flow rate Q _F of hydrogen gas using the output current of the fuel cell, the pressure of the hydrogen gas, and the like. Subsequently, the control unit 5, the calculated required flow rate Q _F of hydrogen gas regarded as a supply flow rate Q _g of the hydrogen gas required for the ejector 45, hydrogen in the correction value Q _gd obtained using Equation 10 below The gas supply flow rate _Qg is corrected. Subsequently, the control unit 5 calculates the gas flowability C in the ejector 45 by substituting the corrected hydrogen gas supply flow rate _Qg into the above equation 9. Subsequently, the control unit 5 calculates the position of the needle using the calculated gas flowability C in the ejector 45 and the map of FIG. Subsequently, the control unit 5 outputs a movement command for moving the needle to the ejector 45 with the calculated needle position as the target position. The hydrogen gas supply flow rate Q _g may be calculated using pressures P ₁ and P ₂ , volumes V ₁ and V ₂ , temperature T, and the like.

V _{2 in the} above equation 10 is the volume of the closed space formed between the ejector 45 and the fuel cell 2. P ₂ is the pressure value of hydrogen gas in the hydrogen supply channel 41 between the ejector 45 and the fuel cell 2. P _2S is a target pressure value of the pressure P ₂ , and A to F are correction coefficients.

  By executing the feedforward control and the feedback control described above, it is possible to cope with a sudden load fluctuation in the fuel cell system, and to prevent a shortage of hydrogen gas due to a sudden increase in output current.

  By the way, in the feedforward control and the feedback control based on the needle movement command described above, the operation delay of the needle is not considered. Actually, the supply amount of hydrogen gas gradually increases and decreases with the movement of the needle. For example, when the required flow rate of hydrogen gas suddenly increases, hydrogen gas is supplied according to the request. It takes a long time and may cause a shortage of hydrogen gas. Therefore, the present position of the needle is estimated, the supply flow rate of hydrogen gas corresponding to the estimated position is calculated, and the output current that can be output at this supply flow rate is controlled as the allowable output current, thereby preventing hydrogen gas shortage. It was decided.

  Hereinafter, a procedure for controlling the ejector 45 in consideration of the operation delay of the needle in addition to the feedforward control and the feedback control based on the needle movement command described above will be described.

The control unit 5 estimates the needle position by substituting the target position of the needle included in the movement command output by the above-described feedforward control or feedback control into the following Expression 11.

S _r of the equation 11 is the estimated position of the needle, S _m is the previous target position of the needle, S _s is the present target position of the needle. A is a correction coefficient corresponding to the moving speed of the needle (speed per dt time). The previous target position S _m of the needle is stored in the memory.

Subsequently, the control unit 5 calculates the C ease the flow of the gas in the ejector with the map of the estimated position S _r and 2 of the calculated needle. Subsequently, the control unit 5 calculates the supply flow rate Q _g of hydrogen gas from the ejector with ease flow of gas in the calculated ejector C and the formula 9. Subsequently, the control unit 5 calculates the allowable output current I of the fuel cell by substituting the calculated hydrogen gas supply flow rate _Qg into the following Expression 12.

In the above equation 12, Q _g is the supply flow rate of hydrogen gas, and N is the number of fuel cells. Subsequently, the control unit 5 outputs an output current command whose upper limit is the calculated allowable output current I to the fuel cell. Thereby, the output current of the fuel cell is suppressed to an allowable output current I or less.

  By considering the needle operation delay in this way, the output current of the fuel cell can be suppressed to an allowable output current or less according to the estimated position of the needle, thereby preventing a shortage of hydrogen gas due to the needle operation delay. Is possible.

  As described above, according to the fuel cell system of the second embodiment, the pressure of the hydrogen gas supplied from the ejector to the fuel cell can be suppressed to an allowable pressure of the fuel cell or less with a simple configuration. In addition, the amount of hydrogen gas supplied by the ejector can be easily calculated, and the supply of hydrogen gas by the ejector can be accurately controlled.

  In each of the above-described embodiments, the case where the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been described, but the present invention is also applied to various mobile bodies (robots, ships, aircrafts, etc.) other than the fuel cell vehicle. The fuel cell system according to the invention can be applied. Moreover, the fuel cell system according to the present invention can also be applied to a stationary power generation system used as a power generation facility for buildings (houses, buildings, etc.).

It is a lineblock diagram showing typically the fuel cell system in an embodiment. It is a map which shows the relationship between the position of a needle and the ease of gas flow in an ejector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Oxidation gas piping system, 4 ... Hydrogen gas piping system, 5 ... Control part, 40 ... Hydrogen tank, 41 ... Hydrogen supply flow path, 42 ... Hydrogen circulation flow path, 44 ... Adjustment valve, 45 ... Ejector, 47 ... Discharge passage, 48 ... Exhaust drain valve, P1, P2 ... Pressure sensor

Claims (9)

A fuel cell that receives supply of an oxidizing gas and a fuel gas, and generates electric power by an electrochemical reaction of the reactive gas;
A fuel supply flow path for supplying the fuel gas from a fuel supply source to the fuel cell;
An ejector that is provided in the fuel supply flow path and that combines the fuel gas supplied from the fuel supply source with the fuel off-gas discharged from the fuel cell and supplies the fuel gas to the fuel cell;
A valve that is provided upstream of the ejector in the fuel supply flow path, and that shuts off or allows the supply of the fuel gas to the ejector,
Even when the pressure value of the fuel gas at the inlet side of the ejector is equal to the pressure value of the fuel gas at the outlet side of the ejector, the pressure value of the fuel gas at the outlet side of the ejector is the same as that of the fuel cell. An upper limit value of the pressure of the fuel gas on the inlet side of the ejector is determined so as to be equal to or lower than an allowable pressure value.   The upper limit value of the pressure of the fuel gas on the inlet side of the ejector is an allowable pressure value of the fuel cell, a pressure value of the fuel gas on the outlet side of the ejector, and a closed state formed between the valve and the ejector. 2. The fuel cell system according to claim 1, wherein the fuel cell system is determined based on a volume of the space and a volume of a closed space formed between the ejector and the fuel cell.   The upper limit value of the pressure of the fuel gas on the inlet side of the ejector is the supply amount of the fuel gas supplied to the ejector after the valve closing command is sent to the valve until the valve is closed. 3. The fuel cell system according to claim 2, wherein the fuel cell system is determined by using as a correction value. The ejector is an ejector having a constant nozzle diameter,
When the pressure value of the fuel gas on the inlet side of the ejector exceeds the upper limit value of the pressure of the fuel gas on the inlet side of the ejector, it further comprises control means for reducing at least the excess pressure. The fuel cell system according to any one of claims 1 to 3.   The fuel cell system according to claim 4, wherein the control unit reduces the excess pressure by causing the fuel cell to generate electric power. A fuel circulation passage for returning the fuel off-gas to the fuel gas supply passage;
A discharge valve for discharging the fuel off-gas and moisture in the fuel circulation channel to the outside, and
The fuel cell system according to claim 4, wherein the control means reduces the excess pressure by opening the discharge valve. The ejector is an ejector whose nozzle diameter varies according to the position of the needle,
Control means for calculating a supply flow rate of the fuel gas required for the ejector, calculating a position of the needle according to the calculated supply flow rate, and moving the needle using the calculated needle position as a needle target position. The fuel cell system according to claim 1, further comprising:   The said control means correct | amends the supply flow volume of the fuel gas calculated | required by the said ejector based on the pressure value of the said fuel gas in the exit side of the said ejector, and the target pressure value of the said fuel gas, It is characterized by the above-mentioned. The fuel cell system described.   The control means calculates the estimated position of the needle based on the current needle target position and the previous needle target position, and determines the supply flow rate of fuel gas from the ejector based on the calculated estimated position of the needle. 9. The fuel cell system according to claim 7, wherein an allowable output current of the fuel cell is calculated based on the calculated supply flow rate.

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