JP2000195533A - Warming-up system of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exert sufficient warming performance in a warming-up system of a fuel cell. SOLUTION: This warming-up system is provided with an air pump 5 that compresses the air from an intake passage 41 into which an new air is sucked and feeds it to a fuel cell 1, a circulating passage 65 that branches from an exhaust passage 42 for releasing the air exhausted from the fuel cell 1 to join to the intake passage 41, and thus circulates the air from the fuel cell 1 to the air pump 5, and a switching valve 6 for switching the opening of. the circulating passage 65; and is so structured that the circulating passage 65 is opened by controlling the switch valve 6 with a control means 9 before feeding the fuel and the air, the air pump 5 is set to work and thereby, the fuel cell 1 is warmed by the circulated air that is compressed and heated when flowing through the circulating passage 65 and passing the air pump 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell warm-up system.

[0002]

2. Description of the Related Art In recent years, attention has been paid to electric vehicles in the field of automobiles in consideration of the environment, particularly the atmosphere,
Electric vehicles equipped with storage batteries as power sources are already in the stage of practical use. However, the storage battery type electric vehicle has a problem that it is difficult to solve such as a relatively short traveling distance and a long charging time in relation to the power storage capacity. Instead, a fuel cell electric vehicle equipped with a fuel cell that generates power by an electrochemical oxidation-reduction reaction between a fuel such as hydrogen and an oxidizing gas such as oxygen is expected to be put to practical use.

[0003] In a fuel cell, when the temperature is low, the electrochemical oxidation-reduction reaction is not performed efficiently and the power is not sufficiently generated.
Since the energy conversion efficiency, that is, the power generation efficiency is high, the heat generation due to the power generation loss is small, and the ability to warm up by itself is small. Due to such characteristics, when the fuel cell is started, particularly in a cold state, the reaction between the fuel and oxygen is not actively performed due to the low temperature of the fuel cell, and unburned hydrogen is discharged, or immediately after the start. There was a problem that it was difficult to obtain sufficient vehicle power.

Japanese Patent Application Laid-Open No. Hei 7-94202 discloses that an electric heater is provided in a water storage tank of a fuel cell cooling system for storing cooling water, and the cooling water is supplied to the electric heater from the storage battery or the fuel cell. There has been proposed a fuel cell warm-up system for heating a fuel cell to warm up the fuel cell.

[0005]

However, in the warming-up system described in Japanese Patent Application Laid-Open No. 7-94202, cooling water is used as a working fluid for transporting heat. In other words, the cooling water circulating through the cooling system needs a large heat capacity to secure the required cooling capacity,
Also, a large amount of cooling water is stored in the water storage tank.
This consumes enormous amount of heater power,
If a heater having a large heater capacity is not used, it takes a long time to warm up or cannot sufficiently warm up when the outside air temperature is low.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to propose a fuel cell warm-up system that exhibits sufficient warm-up performance and consumes less power.

[0007]

According to the first aspect of the present invention, there is provided a warm-up system comprising: an air pump for compressing air from an intake passage through which fresh air is sucked and supplying the compressed air to a fuel cell; A return path that branches from an exhaust flow path that discharges air to the outside, merges with the intake flow path, and returns exhaust air from the fuel cell to an air pump, and a return path opening degree switching unit that switches the degree of opening of the return path. , Control means for controlling the supply of fuel and air. The control means controls the recirculation path opening degree switching means to open the recirculation path and operate the air pump prior to the supply of fuel to the fuel cell. Warm up the fuel cell with circulating air.

[0008] The total heat capacity of the air flowing through the circulation path formed by the return path is much smaller than the cooling water of the fuel cell. Thus, in the present invention, the air used for warming up the fuel cell quickly rises without inputting an enormous amount of electric power to the electric heater and the like, and heat exchange is efficiently performed in the fuel cell, and the fuel cell is sufficiently cooled. Warm up can be performed.

According to the second aspect of the present invention, an intake passage opening degree switching means for switching the opening degree of the intake passage is provided upstream of the branch of the intake passage with the recirculation passage. An exhaust flow path opening degree switching means for switching the degree of opening of the exhaust flow path is provided downstream of the branch from the recirculation path, and the control means opens the intake flow path before supplying fuel to the fuel cell. The degree switching means and the exhaust path opening degree switching means are controlled so that the intake path and the exhaust path are closed.

By closing the intake passage and the exhaust passage during warm-up before the power generation operation, only the circulating air is supplied to the fuel cell for warming-up, and the fuel cell can be warmed up more efficiently.

According to a third aspect of the present invention, a temperature sensor for detecting the temperature of the fuel cell is provided, and the control means supplies the fuel to the fuel cell when the detected temperature exceeds a preset power generation start reference temperature. Set to start.

[0012] It can be determined from the detected temperature whether the fuel cell has been sufficiently warmed up, and as soon as the fuel cell has been sufficiently warmed up, it is possible to immediately shift to the power generation operation.

[0013] In the invention described in claim 4, the control means is set so as to switch the opening degree of the return path so that the detected temperature becomes a preset steady state reference temperature during the power generation operation.

By switching the recirculation path opening degree, the recirculation amount of the exhaust air from the fuel cell having a higher temperature than the fresh air to the fuel cell is adjusted, so that the outside air temperature is low and the fuel cell temperature is lowered during the power generation operation. In such a case, the fuel cell temperature can be maintained, and a decrease in power generation efficiency can be prevented.

[0015]

(First Embodiment) FIG. 1 shows a first embodiment of a fuel cell warm-up system according to the present invention. The cell 1 a of the fuel cell 1 has a fuel electrode 12 on one surface of an electrolyte plate 11.
The air electrode 13 is brought into close contact with the other surface, and the cell 1a is formed into a plate-like separator 14 made of carbon or the like.
15 are pinched. Fuel electrode 1 of separators 14 and 15
The fuel chamber 101 is formed with the separator 14 on the fuel electrode 12 side and the fuel electrode 12 as a chamber wall surface by the concave portion formed on the surface on the side of the cathode 2 or the air electrode 13. An air chamber 102 serving as a wall surface is formed.

Hydrogen as fuel is introduced into the fuel chamber 101 via the switching valve 3, and air is introduced from the air pump 5 into the air chamber 102. The air from the intake passage 41 into which fresh air is sucked is introduced into the air pump 5. As the air pump 5, a general non-lubricated electric pump for supplying air to the fuel cell is used. The air pump 5 compresses and discharges the taken-in air to keep the inside of the fuel cell 1 clean and free from oil and other foreign matter. To supply. And fuel electrode 1
2. A voltage is generated between the fuel electrode 12 and the air electrode 13 by an electrochemical oxidation-reduction reaction of hydrogen in the air electrode 13 and oxygen in the air to supply power to the load 2. An exhaust passage 42 is connected to the air chamber 102 so as to discharge a gas generated by the electrochemical oxidation-reduction reaction to the outside.

The warm-up system includes the basic components of the fuel cell 1 such as the air pump 5 and the intake passage 41. The switching valve 6 is provided in the intake passage 41 and the exhaust passage 42. The air switching valve 6 communicates with two intake passage ports 61 and 62 communicating with the upstream and downstream portions of the intake passage 41, and with the upstream and downstream portions of the exhaust passage 42, respectively. And two exhaust passage ports 63 and 64 for switching between a warm-up state and a normal state. The switching state of the switching valve 6 will be described. In both states, the upstream part and the downstream part of the intake passage 41 communicate with each other, and the upstream part and the downstream part of the exhaust passage 42 communicate with each other. ing. In the warmed-up state (the state shown in the figure), the intake passage 41 and the exhaust passage 42 communicate with each other through the return passage 65 formed inside the switching valve 6, and in the normal state, the intake passage 41 and the exhaust passage 42 communicate with each other. Shuts off. That is, the switching valve 6 opens and closes the recirculation passage 65 that connects the intake passage 41 and the exhaust passage 42.

A switching valve 6 for air is provided in the intake passage 41.
A throttle valve 71 is provided upstream of the intake passage 41 so that the opening degree of the intake passage 41 can be adjusted. A throttle valve 72 is provided in the exhaust passage 42 downstream of the switching valve 6.
2 is adjustable.

A control device 9 for controlling the air pump 5, the switching valves 3 and 6, and the throttle valves 71 and 72 is provided to start and stop the fuel cell 1 and warm up the fuel cell 1. The control device 9 is configured by a microcomputer or the like.

A temperature sensor 8 is provided near the entrance of the air chamber 102 of the fuel cell 1, which is the most downstream part of the intake passage 41, and detects the temperature of the air flowing into the air chamber 102, and outputs a detection signal. Is input to the control device 9. The temperature detected by the temperature sensor 8 is the temperature near the entrance of the air chamber 102 of the fuel cell 1. The electrolyte plate 11, the fuel electrode 12, and the air electrode 13 are compared with the separators 14, 15 that mechanically sandwich them. Since it is much thinner, the heat capacity is small and the heat conduction of the air electrode 13 is good, and the detected temperature follows the temperature of the cell 1a with a higher responsiveness than when the temperature sensors are provided on the separators 14 and 15. As described above, the temperature of the cell 1a can be substantially detected by the temperature sensor 8 provided at the most downstream portion of the intake passage 41. A humidifier 73 for humidifying the air discharged from the pump 5 is arranged between the air pump 5 and the temperature sensor 8. The humidifier 73 is controlled by the control device 9, and is controlled by a signal from the control device 9 when the temperature of the air discharged from the pump 5 reaches a predetermined value (when the temperature has stopped at the time of low-temperature startup). Is supplied from the humidifier 73 to the air. Thereby, the air discharged from the pump 5 is humidified. The reason for humidifying the air is that the cell 1a of the fuel cell 1 is made of, for example, an ionic conductive polymer film, and if the polymer film does not contain water, the polymer film becomes an ionic conductor. It does not function as When the temperature of the air discharged from the pump 5 falls below a predetermined value, the humidifier 7
The reason for not supplying the water from 3 is to suppress a decrease in the temperature of the air and a decrease in the warm-up promoting effect.

FIG. 2 is a time chart showing the operation of each part of the system from the start of the warm-up system to the generation of electricity.
(A) is the temperature detected by the temperature sensor 8, (B) is the opening degree of the throttle valves 71 and 72, (C) is the amount of air discharged from the air pump 5 and supplied to the fuel cell 1, D)
Is the amount of hydrogen supplied to the fuel cell 1. The operation of the warm-up system will be described with reference to FIG. 1 and the control procedure executed in the control device 9. The control device 9
When the fuel cell 1 is started, before the fuel switching valve 3 is opened, that is, before the supply of hydrogen to the fuel cell 1 is started, the fuel cell 1 is closed (the state shown in FIG. 1). The fuel cell 1 is warmed up as follows. First, both the throttle valves 71 and 72 are fully closed, and the air switching valve 6 is
The state shown in FIG. 1 in which the intake passage 41 and the exhaust passage 42 are connected via the recirculation passage 65 is set. Then, the air pump 5 is started in this state. The air discharged from the air pump 5 flows from the fuel cell 1 to the upstream part of the exhaust passage 42 to the switching valve 6.
Circulate a circulation path that reaches the downstream of the intake passage 41 and returns to the air pump 5. The driving voltage to the air pump 5 is set so as to operate in the rotation range where the theoretical efficiency is the highest, so that the maximum amount of air flows through the air chamber 102 of the fuel cell 1.

The air pump 5 generates heat during operation due to compression loss and mechanical loss. Particularly, a non-lubricated type generates a considerable amount of heat. When the air passes through the air pump 5, the temperature of the air rises, and then the air is radiated to the cell 1a of the fuel cell 1 by the air electrode 13. Here, since the maximum amount of air flows through the air chamber 102 as described above, the flow velocity of the air in the air chamber 102 is extremely high, and the heat exchange between the air and the cell 1a is efficiently performed. Since the circulation path through which the air flows forms a closed loop, there is no exchange of air, and there is no portion in the circulation path such as a tank that increases the heat capacity. In addition, air as a working fluid has a lower specific heat than water. As described above, since the heat capacity of the air existing in the circulation path is small, the temperature of the circulation air instantaneously rises to nearly 100 ° C.

When the detected temperature becomes close to a preset power generation start reference temperature of 100.degree. C., the throttle valves 71 and 72 are gradually opened to open the fuel cell 1 for intake of fresh air and exhaust air.
By gradually discharging the air to the outside, the ratio of the amount of circulating air is reduced, and finally, the throttle valves 71 and 72 are fully opened. Then, the drive voltage of the air pump 5 is reduced to reduce the amount of air and prepare for a power generation operation. The control of the air pump 5 and the like is performed so that the detected temperature increases toward the power generation start reference temperature.

When the detected temperature reaches the power generation start reference temperature, the fuel switching valve 3 is opened to supply hydrogen to the fuel chamber 101 of the fuel cell 1 to start power generation.

When the temperature of the air discharged from the air pump 5 rises and the detected temperature reaches the steady-state reference temperature after the start of the power generation operation, the air switching valve 6 is switched to the normal state to change the intake passage. 41 and the exhaust flow path 42 are shut off, and all air supplied from the air pump 5 to the fuel cell 1 is supplied to the intake flow path 41.
It is assumed that fresh air is inhaled from the uppermost stream of the.

When the outside air temperature is extremely low in a cold region or the like and the detected temperature does not reach the steady-state reference temperature, the air switching valve 6 is kept warm, that is, the recirculation path 65 is kept open, and the fuel The high-temperature air flowing back from the exhaust passage 42 is mixed with the supply air to the battery 1 so that the temperature of the air flowing into the fuel cell 1 becomes the reference temperature in the steady state. As a result, it is possible to prevent a decrease in the power generation efficiency due to a decrease in the temperature of the cell 1a, and it is possible to secure power supply to the load 2.

(Second Embodiment) FIG. 3 shows a second embodiment of the warming-up system according to the present invention. In the configuration of FIG. 1, the configuration for recirculating air from the exhaust flow path 42 to the intake flow path 41 is replaced with another configuration. In the figure, portions denoted by the same reference numerals as those in FIG. Since the operation is the same as that of the warm-up system shown in FIG. The throttle valve 6A has one end connected to the intake passage 41 at a downstream portion of the intake throttle valve 71, the other end connected to the exhaust passage 42,
It is connected at the upstream of the exhaust throttle valve 72. This recirculation throttle valve 6A is configured so that the opening can be adjusted.
The opening is adjusted by the control device 9.

By opening the throttle valve 6A fully, the control device 9 transfers the exhaust air from the fuel cell 1 to the intake passage as in the case where the switching valve 6 (FIG. 1) is warmed up in the first embodiment. By causing the air to return to the air pump 5 via 41 and fully closing the throttle valve 6A, the intake flow path 41 and the exhaust flow path 42 can be shut off as in the case where the switching valve 6 is in the normal state. Further, since the opening degree of the throttle valve 6A can be continuously changed from the fully closed state to the fully opened state, after the intake throttle valve 71 and the exhaust throttle valve 72 are fully opened, the opening degree of the throttle valve 6A which is the recirculation path is changed. Is controlled so that the temperature is gradually reduced, so that the temperature detected by the temperature sensor 8 can be smoothly set to the steady-state temperature.

The configuration of the warming-up system is not limited to the above embodiments, and may be any configuration as long as it does not contradict the spirit of the present invention. Alternatively, a simple on-off valve that closes during warm-up before starting fuel supply can be used. In addition, these throttle valves and on-off valves may be omitted depending on the demand for startup of warm-up, and fresh air and return air for warm-up may be mixed and flow into the fuel cell.

If the correspondence between the detected temperature of the temperature sensor provided in the intake passage and the cell temperature is not sufficient, for example, when the capacity of the fuel cell is large and the number of cells is large, it is necessary to conduct an experiment in advance to determine the intake passage. The relationship between the air temperature and the cell temperature at the most downstream portion may be determined, and the result may be input to the control device as a map. If it is not necessary to know whether the warm-up is sufficient or not, the temperature sensor may be omitted, and the warm-up period may be simply set by a timer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell warm-up system of the present invention.

FIG. 2 is a time chart for explaining the operation of the fuel cell warm-up system of the present invention.

FIG. 3 is a configuration diagram of another fuel cell warm-up system of the present invention.

[Explanation of symbols]

 Reference Signs List 1 fuel cell 1a cell 11 electrolyte plate 12 fuel electrode 13 air electrode 14, 15 separator 2 load 3 switching valve 41 intake flow path 42 exhaust flow path 5 air pump 6 switching valve (return path opening degree switching means) 65 return path 6A throttle valve (Reflux path, recirculation path opening degree switching means) 71 Throttle valve (intake path opening degree switching means) 72 Throttle valve (exhaust path opening degree switching means) 8 Temperature sensor 9 Control device (control means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuo Inagaki 14 Iwatani, Shimowakaku-cho, Nishio-shi, Aichi Prefecture Inside Japan Automotive Parts Research Institute Co., Ltd. F term in reference (reference) 5H027 AA06 BC19 KK46 MM03 MM04 5H115 PA11 PG04 PI18

Claims (4)

[Claims] 1. An air pump for compressing air from an intake passage through which fresh air is sucked and supplying the compressed air to a fuel cell, and an exhaust passage branching from an exhaust passage for discharging air discharged from the fuel cell to the outside. A recirculation path that merges with the path and recirculates exhaust air from the fuel cell to the air pump; recirculation path opening degree switching means for switching the degree of opening of the recirculation path; and control means for controlling the supply of fuel and air. The control means controls the return path opening degree switching means to open the return path and operate the air pump prior to the supply of fuel to the fuel cell, and sets the circulating air to flow through the return path and raise the temperature when passing through the air pump. A warm-up system for a fuel cell, comprising: 2. A fuel cell warm-up system according to claim 1, wherein the opening of the intake passage is switched to an opening of the intake passage upstream of a branch from the return passage of the intake passage. Means, and an exhaust flow path opening degree switching means for switching the degree of opening of the exhaust flow path is provided downstream of the branch of the exhaust flow path from the return path. A fuel cell warm-up system in which the intake passage opening degree switching unit and the exhaust passage opening degree switching unit are controlled prior to the supply of the fuel cell to close the intake passage and the exhaust passage. 3. The fuel cell warm-up system according to claim 1, further comprising a temperature sensor for detecting a temperature of the fuel cell, wherein the control means sets the detected temperature to a power generation start reference set in advance. A fuel cell warm-up system set to start supplying fuel when the temperature is exceeded. 4. The fuel cell warm-up system according to claim 3, wherein the control means switches the degree of opening of the return passage so that the detected temperature becomes a preset steady state reference temperature during the power generation operation. Fuel cell warm-up system set to.