JP2004071228A - Fuel cell system for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve following characteristics of the feed control of oxygen to the feed of hydrogen in a fuel cell system for a vehicle. <P>SOLUTION: This fuel cell system for the vehicle is provided with a fuel cell 1 reacting the hydrogen with the oxygen and generating an electric energy, a hydrogen tank 3 feeding the hydrogen to the fuel cell 1, a flow control valve 5 controlling the flow rate of the hydrogen to be fed to the fuel cell 1, a compressor 9 feeding air including the oxygen to the fuel cell 1, a motor 13 driving the compressor 9, and a control part 17 controlling the opening of the flow control valve 5 according to a load demand to be input from an operation device such as an accelerator pedal, adjusting the rotation speed of the motor 13 related to the opening of the flow control valve 5, driving the compressor 9, and controlling the flow rate of the air to be fed to the fuel cell 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system for a vehicle, and more particularly to a fuel cell system mounted on a vehicle and used for powering the vehicle.
[0002]
[Prior art]
2. Description of the Related Art A fuel cell is a device that generates electric power by utilizing a chemical reaction between hydrogen and oxygen. Research and development for practical use have been widely pursued from the viewpoints of high efficiency and low pollution. As the hydrogen supplied to the fuel cell, hydrogen stored in a cylinder or the like, or a reformed fuel is used, and oxygen generally contained in air is used.
[0003]
Such power generation control of the fuel cell is performed by controlling the amounts of hydrogen and oxygen supplied to the fuel cell according to the required power generation. For example, according to the control method described in Japanese Patent Application Laid-Open No. 7-14599, the supply amount of hydrogen is controlled in accordance with the required power generation amount, and the supply amount of oxygen is controlled based on the output current of the fuel cell. I am trying to do it.
[0004]
[Problems to be solved by the invention]
However, when the supply amount of air is controlled based on the output current of the fuel cell as in the above-described conventional technique, the response of the air supply amount control to the change in the supply amount of hydrogen due to the delay of the reaction time in the fuel cell is reduced. Gets worse. If such a control method is applied to a fuel cell system used for powering a vehicle, the increase or decrease in the amount of power generated by the fuel cell is delayed in the case of a vehicle having a large load fluctuation range such as sudden acceleration or sudden deceleration. As a result, there is a problem that a sense of discomfort occurs between the operation amount of an operating device such as an accelerator pedal and the actual acceleration / deceleration.
[0005]
An object of the present invention is to improve the followability of oxygen supply control with respect to hydrogen supply in a fuel cell system.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a fuel cell system according to the present invention has a fuel cell that generates electric energy by reacting hydrogen and oxygen, a hydrogen supply source that supplies hydrogen to the fuel cell, and a fuel cell that is supplied to the fuel cell. A flow control valve that controls the flow rate of hydrogen, an oxygen supply source that supplies oxygen to the fuel cell, and an opening of the flow control valve that is controlled in accordance with a load request, and correlated with the opening of the flow control valve. And control means for controlling the flow rate of oxygen.
[0007]
In other words, considering that there is a certain relationship between the valve opening of the flow control valve and the flow rate, the supply amount of oxygen is adjusted according to the hydrogen supply amount corresponding to the opening degree of the flow control valve that controls the flow rate of hydrogen. Was controlled. The relationship between the opening degree of the valve and the hydrogen supply amount is obtained in advance by measurement or the like, and the correlation is stored in the control means, or the oxygen supply amount is directly associated with the opening degree of the flow control valve. May be stored. Therefore, according to the present invention, the flow rate of oxygen can be quickly controlled in correlation with the amount of hydrogen controlled according to the load request. As a result, even when the load fluctuation range of the vehicle is large, the amounts of hydrogen and oxygen supplied to the fuel cell are quickly increased or decreased according to the load request. It is possible to reduce a sense of discomfort that occurs during deceleration.
[0008]
On the other hand, instead of controlling the supply amount of oxygen according to the opening degree of the flow control valve, a flow meter for detecting the amount of hydrogen supplied to the fuel cell is provided, and the flow rate is measured based on the detected flow rate of hydrogen. Alternatively, the flow rate of oxygen may be controlled.
[0009]
In view of the fact that the relationship between the valve opening degree and the hydrogen supply amount determined in advance changes due to various factors such as aging, the oxygen flow rate is controlled based on the actually measured hydrogen supply amount. It was done. According to this, an appropriate amount of oxygen can be supplied even if the relationship between the opening degree of the flow control valve and the flow rate changes due to a change over time or the like.
[0010]
By the way, when the temperature or pressure of oxygen changes, the density of oxygen changes. If the density of oxygen changes, the mass flow rate of oxygen supplied to the fuel cell changes even if the volume flow rate is constant. Therefore, it is necessary to control the oxygen volume flow rate accordingly. Therefore, it is preferable to detect the density of oxygen supplied to the fuel cell and correct the volume flow rate of oxygen based on the detected density of oxygen. The density detecting means can be constituted by at least one of a temperature detecting means for detecting the temperature of oxygen and a pressure detecting means for detecting the pressure of oxygen.
[0011]
In addition, when the compressor includes a compressor that compresses air and a motor that drives the compressor as an oxygen supply source, the amount of air supplied to the fuel cell is controlled by controlling the number of revolutions of the motor. can do.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, an embodiment of a vehicle fuel cell system to which the present invention is applied will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a main part of the present embodiment. FIG. 2 is a diagram for explaining the operation of the present embodiment.
[0013]
As shown in FIG. 1, the fuel cell system according to the present embodiment includes a fuel cell 1, a hydrogen tank 3, a flow control valve 5, a compressor 9, a cooler 11, a motor 13, an inverter 15, a control unit 17, and a condenser. 19. The fuel cell 1 is configured such that a hydrogen electrode 1a and an oxygen electrode 1b are opposed to each other with a hydrogen ion permeable membrane 1c interposed therebetween. The hydrogen electrode 1a is provided in contact with a hydrogen chamber through which hydrogen or a gas containing a large amount of hydrogen passes, and the oxygen electrode 1b is provided in contact with an air chamber into which air is compressed and sent. The hydrogen electrode 1a and the oxygen electrode 1b are connected to an electric motor (not shown), which is a power unit of the vehicle, and the electric power generated by the fuel cell 1 is supplied to the electric motor.
[0014]
Hydrogen is supplied from a hydrogen tank 3 to a hydrogen chamber of the fuel cell 1 via a flow control valve 5. The hydrogen tank 3 is provided with a regulator (not shown) for controlling the supply pressure of hydrogen to a predetermined value. The flow control valve 5 is controlled by the control unit 17, and controls the amount of hydrogen supplied to the fuel cell 1 according to a load request input from an operating device such as an accelerator pedal.
[0015]
On the other hand, air is supplied from the compressor 9 to the air chamber of the fuel cell 1 via the cooler 11. As the compressor 9, a screw air compressor that controls the amount of air supplied by changing the rotation speed of the motor 13 is applied. The rotation speed of the motor 13 is controlled by the control unit 17 via the inverter 15. The control unit 17 controls the number of rotations of the motor 13 via the inverter 15 in correlation with the valve opening of the flow control valve 5, and controls the amount of air supplied from the compressor 9. As described above, in the present embodiment, by increasing the pressure of the air above the atmospheric pressure and supplying it to the fuel cell 1, the bonding reaction between hydrogen and oxygen is promoted, and the output of the fuel cell 1 is improved or the size of the fuel cell 1 is reduced. .
[0016]
The cooler 11 cools air taken in from the outside and compressed by the compressor 9. The condenser 19 collects water generated in the fuel cell 1. The gas discharged to the condenser 19 together with the water is returned to the fuel cell 1 via the compressor 9.
[0017]
Here, the configuration of the characteristic portion of the present embodiment will be described together with the operation. In the fuel cell system of the present embodiment, a data diagram (c) showing the relationship between the valve opening of the flow control valve 5 and the inverter frequency is stored in the control unit 17 in advance. FIG. 2A is data showing the relationship between the valve opening degree of the flow control valve 5 and the hydrogen supply amount obtained in advance by measurement or the like. FIG. 2B is data showing the relationship between the inverter frequency and the air supply amount. Here, since the amount of air to be supplied is determined with respect to the amount of supplied hydrogen, the valve shown in FIG. 2C is determined based on the relationship between the amount of air supplied and the amount of hydrogen supplied in FIGS. 2A and 2B. The correspondence between the opening and the inverter frequency is derived.
[0018]
The control unit 17 obtains the supply amount of hydrogen according to a predetermined relationship according to the load request, and controls the opening of the flow control valve 5 according to the relationship shown in FIG. Next, the control unit 17 gives a command of the inverter frequency corresponding to the opening degree of the flow control valve 5 to the inverter 15 based on FIG. Thus, the rotation speed of the motor 13 is controlled via the inverter 15, and the amount of air supplied from the compressor 9 to the fuel cell 1 is controlled to a value corresponding to the amount of hydrogen supplied.
[0019]
As described above, according to the present embodiment, the followability of the oxygen supply amount control to the hydrogen supply amount is improved by controlling the air supply amount by associating the opening degree of the flow control valve 5 with the inverter frequency. can do. Therefore, even when the load fluctuation range of the vehicle is large, the supply amounts of hydrogen and air are rapidly increased or decreased in response to a load request input from an operation device such as an accelerator pedal, so that the operation amount of the operation device and the actual addition amount are controlled. It is possible to reduce a sense of discomfort that occurs during deceleration.
[0020]
Further, since it is possible to suppress a delay in controlling the air with respect to the amount of hydrogen, it is possible to reduce an increase in unreacted hydrogen discharged from the fuel cell 1 and an insufficient output of the fuel cell 1. Similarly, an increase in the supply amount of air, an increase in power for compressing air unnecessary for the reaction can be suppressed, and the efficiency of the fuel cell system can be improved.
[0021]
In addition, it is known that the energy of compressed air discharged from a fuel cell using an expander is recovered and used for compressing air, thereby reducing compression power and improving the efficiency of the fuel cell system. However, according to the present embodiment, the supply of excess air can be suppressed, so that the efficiency of the fuel cell system can be improved.
[0022]
Further, the relationship between the valve opening degree of the flow control valve 5 and the inverter frequency controls the amount of air supplied to the fuel cell 1 based on FIG. 2 (c). Alternatively, it may be stored in the control unit 17 as a data table. Further, the opening degree of the flow control valve 5 is detected, a hydrogen supply amount is obtained from the detected opening degree based on the relationship of FIG. 2 (a), and a necessary air amount for this is calculated. The inverter frequency may be obtained based on the relationship.
[0023]
(Second embodiment)
A second embodiment of a vehicle fuel cell system to which the present invention is applied will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration of a main part of the present embodiment. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.
[0024]
This embodiment is different from the first embodiment in that a flow sensor 25 is provided between the flow control valve 5 and the fuel cell 1. As the flow sensor 25, an instantaneous flow meter such as a float type or an impeller type having no time delay is preferable.
[0025]
The flow rate sensor 25 outputs the detected flow rate of hydrogen to the control unit 27. The control unit 27 provides a control signal to the inverter 15 based on the detected hydrogen amount. Thus, the rotation speed of the motor 13 is controlled via the inverter 15 and the amount of air supplied from the compressor 9 to the fuel cell 1 is controlled. For this reason, even if the relationship between the valve opening and the hydrogen supply amount changes due to aging or disturbance, an appropriate amount of air can be supplied to the hydrogen supplied to the fuel cell 1 and the accuracy can be improved. High control can be performed.
[0026]
Further, in the present embodiment, since the supply amount of air is controlled based on the hydrogen amount detected by the flow rate sensor 25, it is not necessary to previously measure the relationship between the valve opening degree and the hydrogen supply amount by measurement or the like. Become.
[0027]
In the present embodiment, when controlling the air supply amount, data indicating the relationship between the flow rate of hydrogen and the inverter frequency is stored in the control unit in advance, and the air supply amount is controlled based on this data. . Alternatively, a relational expression for obtaining the number of rotations of the compressor corresponding to the flow rate of hydrogen, a data table, or the like may be stored in the control unit in advance, and the air supply amount may be controlled based on these. .
[0028]
(Third embodiment)
A third embodiment of a fuel cell system for a vehicle to which the present invention is applied will be described with reference to FIGS. FIG. 4 is a block diagram illustrating a configuration of a main part of the present embodiment. FIG. 5 is a diagram for explaining the concept of correction according to the present embodiment. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.
[0029]
The present embodiment is different from the first embodiment in that a thermometer 29 for measuring the temperature of the air sucked into the compressor 9 is provided, and a control value of an inverter frequency command value is controlled by a control unit 30 based on the detected temperature. It is to correct. The control unit 30 stores data for correction based on temperature in advance. The present embodiment has been made in view of the fact that the mass flow rate changes with temperature even when the volume flow rate of air is the same. For example, when the temperature is low, the volume of air containing the same mass, that is, the same number of oxygen molecules, is reduced as compared with the case where the temperature is high. It is necessary to reduce the amount of intake air compared to when it is high. Specifically, when the temperature is low, the operating frequency of the compressor 9 is reduced by lowering the inverter frequency.
[0030]
Data as shown in FIG. 5 is stored in the control unit 30 of the present embodiment. The horizontal axis in FIG. 5 indicates the inverter frequency, and the vertical axis indicates the air (oxygen) supply mass. As shown in the figure, for example, lines 31, 32, and 33 are set using the temperature as a parameter, and the relationship between the inverter frequency and the air (oxygen) supply mass when the temperature is low, normal, and when the temperature is high is stored. .
[0031]
As described above, by detecting the air temperature with the thermometer 29 and correcting the supplied air amount based on the detected value, even when the air temperature changes, the hydrogen supplied to the fuel cell 1 can be reduced. An appropriate amount of air can be supplied, and a decrease in efficiency due to loss of compression power and an increase in discharge of unreacted hydrogen can be suppressed.
[0032]
Further, in the present embodiment, instead of the data of FIG. 5, a relational expression or a data table for making the relationship between the inverter frequency and the air (oxygen) supply mass correspond to the temperature is stored in the control unit 30 in advance. The supply amount of air may be corrected based on these.
[0033]
Further, in the first to third embodiments, the air supply source includes the compressor 9 for compressing the air and the motor 13 for driving the compressor 9, but the present invention relates to the first embodiment. Not only the air supply source of the third embodiment but also a known air supply source or oxygen supply source can be applied. The point is that any amount of oxygen that reacts with the hydrogen supplied to the fuel cell without excess or shortage can be supplied.
[0034]
Further, the compressor is defined as “a machine having a pressure ratio of 2 or more or a discharge pressure of about 0.1 MPa or more” in JIS B0132 “Blower / Compressor Terminology”. Describes the compressor as including the range of the blower lower than this pressure.
[0035]
Although the fuel cell systems of the first to third embodiments use the hydrogen tank 3 as a hydrogen supply source, the fuel cell system of the present invention uses a known hydrogen supply source such as a hydrogen cylinder or a reformer. Can be applied.
[0036]
Further, the fuel cell system of the present invention can be provided with at least one of a pressure gauge for detecting the pressure of hydrogen supplied to the fuel cell and a thermometer for detecting the temperature. In this case, the control unit stores a data table and a relational expression for correction based on pressure and temperature. Further, a pressure control valve may be provided in the hydrogen supply source instead of the pressure gauge. In this case, the set pressure of the pressure control valve can be used. This makes it possible to correct the amount of air to be supplied based on the output from the pressure gauge or the thermometer, or the set pressure of the pressure control valve, so that the hydrogen is supplied to the fuel cell even when the pressure or temperature changes. An appropriate amount of oxygen can be supplied with respect to the amount of hydrogen.
[0037]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the followability of the supply control of oxygen with respect to the supply of hydrogen in a fuel cell system can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of a first embodiment of a vehicle fuel cell system to which the present invention is applied.
FIG. 2 is a diagram for explaining the operation of the first embodiment of the vehicle fuel cell system to which the present invention is applied.
FIG. 3 is a block diagram showing a configuration of a main part of a second embodiment of a vehicle fuel cell system to which the present invention is applied.
FIG. 4 is a block diagram showing a configuration of a main part of a third embodiment of a vehicle fuel cell system to which the present invention is applied.
FIG. 5 is a diagram for explaining a concept of correction in a third embodiment of a vehicle fuel cell system to which the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel cell 3 Hydrogen tank 5 Flow control valve 9 Compressor 11 Cooler 13 Motor 15 Inverter 17, 27, 30 Control part 19 Condenser 25 Flow sensor 29 Thermometer

Claims (4)

A fuel cell that generates electrical energy by reacting hydrogen and oxygen;
A hydrogen supply source for supplying hydrogen to the fuel cell;
A flow control valve for controlling the flow rate of hydrogen supplied to the fuel cell,
An oxygen supply source for supplying oxygen to the fuel cell;
A fuel cell system for a vehicle, comprising: control means for controlling an opening degree of the flow control valve in accordance with a load request, and controlling an oxygen flow rate in correlation with the opening degree of the flow control valve. Providing a flow meter between the flow control valve and the fuel cell,
The fuel cell system for a vehicle according to claim 1, wherein the control unit controls the flow rate of oxygen based on the flow rate of hydrogen detected by the flow meter. A density detection unit for detecting a density of oxygen supplied to the fuel cell,
The vehicle fuel cell system according to claim 1, wherein the control unit corrects the flow rate of oxygen based on the density detected by the density detection unit. The oxygen supply source is an air supply source, the air supply source is configured to include a compressor that compresses air, and a motor that drives the compressor,
The vehicle fuel according to any one of claims 1 to 3, wherein the control unit controls a flow rate of oxygen supplied to the fuel cell by controlling a rotation speed of the motor. Battery system.

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