JP4673617B2 - Fuel cell system and control method thereof - Google Patents

Description

  The present invention relates to a fuel cell system that warms up a fuel cell using a hydrogen storage alloy and a control method thereof.

  In recent years, fuel cells that are clean and have high energy efficiency have attracted attention as power sources for fuel cell vehicles. In this fuel cell, air containing oxygen is supplied to the cathode side and hydrogen is supplied to the anode side, whereby electricity is generated by reacting these hydrogen and oxygen.

  By the way, the fuel cell as described above exhibits its power generation performance to a maximum at a certain temperature, and has a characteristic that the power generation performance is lowered at a low temperature. Therefore, when starting a fuel cell in winter or in a cold region, it is necessary to warm up the fuel cell (warm up to a predetermined temperature). As a technique for solving such a problem, conventionally, when a fuel cell is started, hydrogen gas to be supplied to the fuel cell is temporarily stored in the hydrogen storage alloy so that the hydrogen storage alloy generates heat and the fuel cell is heated. There is known a fuel cell system capable of reusing hydrogen gas by releasing the hydrogen gas from the hydrogen storage alloy and returning it to the fuel cell after the warm-up. Hereinafter, such a fuel cell system will be described with two examples.

  The first fuel cell system includes a fuel cell, a high-pressure hydrogen tank for supplying hydrogen gas to the fuel cell, a hydrogen supply path connecting the fuel cell and the high-pressure hydrogen tank, and high-pressure hydrogen in the high-pressure hydrogen tank. In order to supply gas to the fuel cell after depressurizing the gas stepwise, a primary regulator and a secondary regulator that are sequentially arranged in the hydrogen supply path from the upstream side, an MH tank containing a hydrogen storage alloy, and the hydrogen There has been known one provided with a portion of a supply path between a primary regulator and a secondary regulator and a single pipe connecting an MH tank (see Patent Documents 1 and 2). In the following description, for the sake of convenience, a portion between the high pressure hydrogen tank and the primary regulator is referred to as a “high pressure hydrogen line”, and a portion between the primary regulator and the secondary regulator is referred to as a “medium pressure hydrogen line”. The part between the next regulator and the fuel cell will be referred to as the “low pressure hydrogen line”. According to this fuel cell system, the introduction of hydrogen gas from the intermediate pressure hydrogen line to the MH tank and the return of hydrogen gas from the MH tank to the intermediate pressure hydrogen line can be performed by a single pipe. There is an advantage that it can be simplified.

  As a second fuel cell system, in addition to the structure described above, by providing another pipe connecting the low-pressure hydrogen line and the MH tank, when warming up, hydrogen gas is introduced from the intermediate-pressure hydrogen line into the MH tank, When returning the hydrogen gas occluded with the hydrogen occlusion alloy to the fuel cell, there is known one that returns the hydrogen gas from the MH tank to the low-pressure hydrogen line (see Patent Document 3). According to this fuel cell system, it is only necessary to return the hydrogen gas in the MH tank to the low-pressure hydrogen line having a pressure lower than that of the intermediate-pressure hydrogen line, so that the MH tank can be quickly emptied. .

JP 2004-22365 A JP 2003-86213 A JP 2002-222658 A

  However, the first fuel cell system described above has an advantage that the structure can be simplified, but when returning the hydrogen gas in the MH tank to the intermediate pressure hydrogen line, the MH tank is more than in the intermediate pressure hydrogen line. Since the pressure has to be high, there is a problem that it takes time to empty the MH tank. The second fuel cell system has an advantage that the MH tank can be quickly emptied. However, when the hydrogen gas in the MH tank is returned to the low-pressure hydrogen line, the low-pressure hydrogen is discharged from the MH tank. There is a problem that the structure is complicated because it is necessary to provide a throttle or the like so that the hydrogen gas introduced into the line is not disturbed.

  Therefore, an object of the present invention is to provide a fuel cell system and a control method thereof that can quickly return the hydrogen gas in the MH tank to the fuel cell without complicating the structure.

The invention according to claim 1 of the present invention that solves the above-mentioned problems includes a fuel cell that generates electric power by a reaction of hydrogen gas and oxidant gas, a hydrogen supply means that supplies hydrogen gas to the fuel cell, and the fuel A hydrogen gas supply path connecting the battery and the hydrogen supply means; a primary regulator for depressurizing the hydrogen gas released from the hydrogen supply means; and a secondary regulator for further depressurizing the hydrogen gas decompressed by the primary regulator A hydrogen storage alloy, an MH tank that generates heat by storing hydrogen gas in the hydrogen storage alloy, and warms up the fuel cell; the primary regulator of the hydrogen gas supply path; and the 2 and a portion between the next regulator, the MH and MH passage that connects the tank, and the connecting portion of the hydrogen gas supply channel and said MH passage, et provided between the primary regulator , And a medium pressure valve for switching the communicating state of the hydrogen gas supply channel, the medium-pressure valve, when releasing hydrogen gas from the hydrogen absorbing alloy, the consumption of hydrogen gas by the fuel cell that generates Accordingly, the fuel cell system is closed so that the pressure on the downstream side of the intermediate pressure valve decreases.

  According to the first aspect of the present invention, when the fuel cell is warmed up, by opening the intermediate pressure valve, hydrogen gas is supplied from the hydrogen supply means into the MH tank, and the hydrogen storage alloy inside thereof is Since the heat is generated, the fuel cell can be warmed up by applying this heat to the fuel cell via cooling water, for example. When returning the hydrogen gas stored in the MH tank to the fuel cell, the intermediate pressure valve is closed manually or automatically and, for example, the heat generated by the power generation of the fuel cell is given to the MH tank via the cooling water. Then, hydrogen gas is discharged from the hydrogen storage alloy in the MH tank to the medium pressure hydrogen line. At this time, by closing the intermediate pressure valve, the hydrogen gas downstream from the intermediate pressure valve is consumed in the fuel cell, and the downstream pressure gradually decreases. It is possible to easily release hydrogen gas to

  The invention according to claim 2 is the fuel cell system according to claim 1, further comprising a controller that closes the intermediate pressure valve when releasing hydrogen gas from the hydrogen storage alloy. To do.

  According to the second aspect of the invention, when the hydrogen gas is released from the hydrogen storage alloy, the control unit closes the intermediate pressure valve to promote the release of the hydrogen gas from the hydrogen storage alloy.

  A third aspect of the present invention is the control method for a fuel cell system according to the first aspect, wherein the intermediate pressure valve is closed when hydrogen gas is released from the hydrogen storage alloy.

  According to the third aspect of the present invention, when the hydrogen gas is released from the hydrogen storage alloy, the intermediate pressure valve is closed, which facilitates the release of the hydrogen gas from the MH tank to the intermediate pressure hydrogen line.

  According to the invention described in claim 1 or claim 3, by merely providing an intermediate pressure valve in the intermediate pressure hydrogen line, the pressure on the downstream side of the intermediate pressure valve is lowered, and the MH tank to the intermediate pressure hydrogen line is reduced. Since the hydrogen gas can be easily released, the hydrogen gas in the MH tank can be quickly returned to the fuel cell without complicating the structure.

  According to the second aspect of the present invention, when the hydrogen gas is released from the hydrogen storage alloy, the intermediate pressure valve is automatically closed by the control unit. Therefore, compared with the case where the intermediate pressure valve is manually closed, Release of hydrogen gas into the medium pressure hydrogen line can be easily performed.

  Next, an embodiment according to the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a configuration diagram showing a fuel cell system according to the present embodiment.

  As shown in FIG. 1, the fuel cell system S mainly includes an air supply system 1, a hydrogen supply system 2, an MH tank 3, a fuel cell 4, and an ECU (control unit) 5.

  The air supply system 1 includes a compressor 6 that compresses and supplies air, an air supply passage 61 that guides the air from the compressor 6 to the fuel cell 4, and an air exhaust that guides the air discharged from the fuel cell 4 to the outside. The flow path 62 is mainly provided. The air discharge channel 62 is provided with a back pressure valve (not shown) for controlling the pressure (back pressure) on the cathode electrode side.

  The hydrogen supply system 2 mainly includes a high-pressure hydrogen tank (hydrogen supply means) 7, a hydrogen gas supply path 8, and a circulation path 9.

  The high-pressure hydrogen tank 7 is filled with high-pressure hydrogen gas. This hydrogen gas is released by opening a shut-off valve (not shown) provided in the high-pressure hydrogen tank 7 or an intermediate-pressure valve 81 described later. The fuel gas is supplied to the fuel cell 4 through the hydrogen gas supply path 8. The hydrogen gas in the high-pressure hydrogen tank 7 is also supplied into the MH tank 3 by opening the MH shut-off valve 33 described later in addition to the shut-off valve and the intermediate pressure valve 81 described above. It has become.

  The hydrogen gas supply path 8 is a flow path that connects the high-pressure hydrogen tank 7 and the fuel cell 4, and a primary regulator R 1, an intermediate pressure valve 81, and a secondary regulator R 2 are arranged in that order from the high-pressure hydrogen tank 7 side. Is provided. The primary regulator R1 and the secondary regulator R2 are pressure reducing valves for reducing the pressure of the hydrogen gas supplied from the upstream side. Therefore, the pressure relationship from the high-pressure hydrogen tank 7 to the fuel cell 4 is highest from the high-pressure hydrogen tank 7 to the primary regulator R1, followed by the primary regulator R1 to the secondary regulator R2, and the secondary regulator R2. To fuel cell 4 is the lowest. In the following description, for the sake of convenience, the line between the high-pressure hydrogen tank 7 and the primary regulator R1 is the high-pressure hydrogen line 8a, and the line between the primary regulator R1 and the secondary regulator R2 is the medium-pressure hydrogen line 8b, 2 A line between the next regulator R2 and the fuel cell 4 is referred to as a low-pressure hydrogen line 8c.

  The intermediate pressure valve 81 is a valve for switching the communication state (shutoff / communication) of the hydrogen gas supply path 8, and is located at an appropriate position of the intermediate pressure hydrogen line 8 b (specifically, the hydrogen gas supply path 8 and a hydrogen introduction / discharge path described later) 32 and the primary regulator R1). When the intermediate pressure valve 81 is closed during operation of the fuel cell 4, hydrogen gas in the intermediate pressure hydrogen line 8 b and the low pressure hydrogen line 8 c on the downstream side of the intermediate pressure valve 81 is consumed by the fuel cell 4. Thus, the inside of the intermediate pressure hydrogen line 8b and the low pressure hydrogen line 8c is reduced in pressure.

  The circulation channel 9 is connected to the outlet 4b of the fuel cell 4 and the low-pressure hydrogen line 8c so that the unused hydrogen gas discharged from the fuel cell 4 can be returned to the fuel cell 4 again. Although not shown, the circulation channel 9 is appropriately provided with an ejector or a pump for circulating hydrogen gas. Further, in this circulation flow path 9, a purge hydrogen pipe for discharging hydrogen gas containing impurities contained in the hydrogen gas and water generated in the fuel cell 4 to a diluter (not shown). 91 is connected. The hydrogen gas in the circulation passage 9 is intermittently purged (discharged) from the fuel cell 4 to the diluter by appropriately opening and closing a purge valve 92 provided at an appropriate position of the purge hydrogen pipe 91 by the ECU 5. ).

  The MH tank 3 is a container in which the hydrogen storage alloy 31 is housed. The MH tank 3 generates heat by storing the hydrogen gas supplied from the high-pressure hydrogen tank 7 in the hydrogen storage alloy 31, and the heat is supplied to the fuel via the cooling water. It is transmitted to the battery 4. Further, the MH tank 3 is configured such that heat generated by the power generation of the fuel cell 4 is transmitted through the cooling water, and the internal hydrogen storage alloy 31 is heated by this heat, whereby hydrogen storage is performed. The hydrogen gas stored in the alloy 31 is returned to the intermediate pressure hydrogen line 8b. The introduction of hydrogen gas into the MH tank 3 and the discharge of hydrogen gas from the MH tank 3 into the intermediate pressure hydrogen line 8b are performed by a single hydrogen introduction / discharge passage (MH passage) 32. It has come to be.

  The hydrogen storage alloy 31 is capable of storing the surrounding hydrogen gas by being cooled to a predetermined temperature (first temperature), and to a predetermined temperature (second temperature) higher than the first temperature. It has the property of being able to release hydrogen stored as a hydrogen gas when heated. Further, under the same temperature condition, the hydrogen storage alloy 31 releases hydrogen gas to the surroundings when the surrounding pressure becomes a predetermined pressure (release pressure) or lower, and the surrounding pressure is higher than the release pressure. When the pressure exceeds a predetermined pressure (occlusion pressure), the surrounding hydrogen gas is occluded.

Further, the hydrogen storage alloy 31 has a property of generating heat when storing hydrogen gas and absorbing heat when releasing hydrogen gas. In addition, as such a hydrogen storage alloy 31, the following can be used, for example.
AB ₂ type alloy (Laves phase _{alloys); TiCr 2, (Zr,} Ti) (Ni, Mn, V, Fe) 2 ·· AB 5 type alloys; LaNi _5, MnNi ₅ ·· BCC alloys; Ti-V- Cr, Ti-V-Mn, etc .; Mg-based alloy

  The hydrogen introduction / discharge passage 32 is a flow passage that connects the intermediate pressure hydrogen line 8b (specifically, a portion between the intermediate pressure valve 81 and the secondary regulator R2) and the MH tank 3, and the hydrogen introduction / discharge passage 32 is disposed at an appropriate position. An MH cutoff valve 33 is provided for switching the communication state.

  The fuel cell 4 generates power by an electrochemical reaction between hydrogen gas serving as fuel stored in the high-pressure hydrogen tank 7 and air (oxidant gas) supplied from the compressor 6. On the anode side of the fuel cell 4, a hydrogen gas supply path 8 is connected to the inlet 4a, and a circulation path 9 is connected to the outlet 4b.

  The ECU 5 controls each device of the fuel cell system S, mainly the compressor 6, the back pressure valve and shutoff valve, the intermediate pressure valve 81, the MH shutoff valve 33, the purge valve 92, and the like. In particular, the ECU 5 appropriately heats the fuel cell 4 by the MH tank 3 (hereinafter also referred to as “warming up”) by appropriately controlling the intermediate pressure valve 81 and the MH cutoff valve 33 when the fuel cell 4 is started. ) And discharge of hydrogen gas from the MH tank 3 to the fuel cell 4 (hereinafter also referred to as “MH regeneration”).

  Specifically, the ECU 5 has a function of opening the shut-off valve, the intermediate pressure valve 81, and the MH shut-off valve 33 when a start command (for example, an ignition switch ON signal) of the fuel cell 4 is received. is doing. Thereby, when the fuel cell 4 is started, hydrogen gas is supplied from the high-pressure hydrogen tank 7 to the MH tank 3.

  In the present embodiment, when the start command for the fuel cell 4 is received, the above-described shutoff valve, intermediate pressure valve 81 and MH shutoff valve 33 are opened, but the present invention is limited to this. It is not a thing. For example, based on the start command of the fuel cell 4 and the current temperature of the fuel cell 4, it is determined whether or not the fuel cell 4 needs to be warmed up. If the shut-off valve, the intermediate pressure valve 81 and the MH shut-off valve 33 are opened and it is not necessary to warm up, only the shut-off valve and the intermediate pressure valve 81 described above may be opened. According to this, it is possible to prevent the fuel cell 4 from being warmed up unnecessarily, and to quickly start the fuel cell 4.

  Further, the ECU 5 determines whether or not the warm-up process of the fuel cell 4 as described above has been completed, and has a function of closing the intermediate pressure valve 81 when determining that it has been completed. As a result, when the MH regeneration is performed after the fuel cell 4 is warmed up, the downstream side thereof is decompressed by the closed intermediate pressure valve 81, so that the MH regeneration can be performed quickly.

  As a method for determining the end of the warm-up process as described above, for example, a method for determining whether or not the temperature of the fuel cell 4 has become a predetermined value or more based on a signal from a temperature sensor provided in the fuel cell 4. Alternatively, any method may be used, such as simply determining whether a predetermined time has elapsed since the start of the warm-up process.

  Next, the operation of the ECU 5 when the fuel cell system S according to this embodiment is started will be described with reference to FIGS. In the drawings to be referred to, FIG. 2 is a configuration diagram showing the operation of the ECU when the fuel cell is warmed up, and FIG.

  As shown in FIG. 2, when an ignition switch (not shown) is turned on to start the fuel cell 4, a start command for the fuel cell 4 is transmitted to the ECU 5. Then, the MH cutoff valve 33 is opened. Thereby, a part of the hydrogen gas in the high-pressure hydrogen tank 7 is supplied into the MH tank 3, and the rest is supplied to the fuel cell 4.

  When hydrogen gas is supplied into the MH tank 3 in this way, the hydrogen storage alloy 31 in the MH tank 3 stores the hydrogen gas and generates heat along with the storage, and the heat passes through the cooling water. Is transmitted to the fuel cell 4. Therefore, the fuel cell 4 is warmed up satisfactorily. Here, since the hydrogen gas supplied into the MH tank 3 is at a relatively high pressure (intermediate pressure) reduced only by the primary regulator R1, the storage by the hydrogen storage alloy 31 is also performed well. It is like that.

  When the warm-up of the fuel cell 4 is completed, the ECU 5 closes the intermediate pressure valve 81 as shown in FIG. As a result, the pressure downstream of the intermediate pressure valve 81 gradually decreases due to the consumption of the hydrogen gas by the fuel cell 4, and the hydrogen gas in the MH tank 3 (the hydrogen storage alloy 31 of the hydrogen storage alloy 31) is at an intermediate pressure. The surrounding hydrogen gas) flows out to the depressurized medium pressure hydrogen line 8b. In addition, since the power generation by the fuel cell 4 is started after the warm-up of the fuel cell 4 is completed, the heat generated by this power generation is transmitted to the MH tank 3 through the cooling water. Therefore, hydrogen gas is released from the hydrogen storage alloy 31 in the MH tank 3, and the released hydrogen gas also flows to the reduced-pressure intermediate pressure hydrogen line 8b.

  That is, in the conventional structure in which the intermediate pressure valve 81 is not provided, it is necessary to heat the MH tank 3 so that the pressure in the MH tank 3 becomes higher than the intermediate pressure hydrogen line 8b after the warm-up of the fuel cell 4 is finished. Although it takes time from the end of the machine to the MH regeneration, in this embodiment, the MH regeneration can be performed immediately after the warm-up is completed by closing the intermediate pressure valve 81 after the warm-up of the fuel cell 4 is completed. ing.

According to the above, the following effects can be obtained in the present embodiment.
Only by providing the intermediate pressure valve 81 in the intermediate pressure hydrogen line 8b, the pressure downstream of the intermediate pressure valve 81 can be lowered to facilitate the release of hydrogen gas from the MH tank 3 to the intermediate pressure hydrogen line 8b. Therefore, the hydrogen gas in the MH tank 3 can be quickly returned to the fuel cell 4 without complicating the structure.

In addition, this invention is implemented in various forms, without being limited to the said embodiment.
In the present embodiment, the cooling water is circulated between the fuel cell 4 and the MH tank 3, but the present invention is not limited to this, and the cooling water may be circulated also to the radiator. In this case, it is desirable to provide a bypass for bypassing these in the vicinity of the MH tank and the radiator. By configuring in this manner, for example, during normal operation, the fuel cell can be efficiently cooled by bypassing the MH tank and circulating the cooling water only between the fuel cell and the radiator, Further, at the time of warming up, the fuel cell can be warmed up efficiently by bypassing the radiator and circulating the cooling water only between the fuel cell and the MH tank.

  In the present embodiment, the intermediate pressure valve 81 is closed after the warm-up is completed. However, the present invention is not limited to this, and it is only necessary to close the intermediate pressure valve 81 when releasing hydrogen gas from the hydrogen storage alloy 31. . That is, for example, when hydrogen gas stored in the MH tank 3 is used when the fuel cell 4 is stopped, the intermediate pressure valve 81 may be closed at that time.

  In the present embodiment, one hydrogen introduction / discharge passage 32 corresponds to the “MH passage” in the claims, but the present invention is not limited to this. For example, two flow paths (an introduction flow path for introducing hydrogen gas into the MH tank 3 and the intermediate pressure hydrogen line 8b from the MH tank 3 between the MH tank 3 and the intermediate pressure hydrogen line 8b in the present embodiment. When a discharge channel for discharging hydrogen gas is provided, the discharge channel corresponds to the “MH channel” in the claims. That is, when two flow paths are provided in this way, if an intermediate pressure valve is provided between the discharge flow path and the primary regulator, the intermediate pressure valve is temporarily placed downstream of the introduction flow path. Even if it is disposed, the effect of the present invention can be obtained.

It is a block diagram which shows the fuel cell system which concerns on this embodiment. It is a block diagram which shows operation | movement of ECU at the time of warming up of a fuel cell. It is a block diagram which shows operation | movement of ECU at the time of MH reproduction | regeneration.

Explanation of symbols

S Fuel Cell System 1 Air Supply System 2 Hydrogen Supply System 3 MH Tank 31 Hydrogen Storage Alloy 32 Hydrogen Introduction / Discharge Channel (MH Channel)
33 MH shutoff valve 4 Fuel cell 5 ECU (control unit)
7 High-pressure hydrogen tank (hydrogen supply means)
8 Hydrogen gas supply path 8a High pressure hydrogen line 8b Medium pressure hydrogen line 8c Low pressure hydrogen line 81 Medium pressure valve R1 Primary regulator R2 Secondary regulator

Claims (3)

A fuel cell that generates electricity by reaction of hydrogen gas and oxidant gas;
Hydrogen supply means for supplying hydrogen gas to the fuel cell;
A hydrogen gas supply path connecting the fuel cell and the hydrogen supply means;
A primary regulator for depressurizing the hydrogen gas released from the hydrogen supply means;
A secondary regulator for further decompressing the hydrogen gas decompressed by the primary regulator;
An MH tank containing a hydrogen storage alloy, generating heat by storing hydrogen gas in the hydrogen storage alloy, and warming up the fuel cell ;
A flow path for MH connecting the portion of the hydrogen gas supply path between the primary regulator and the secondary regulator and the MH tank;
An intermediate pressure valve provided between a connecting portion between the hydrogen gas supply path and the MH flow path and the primary regulator, for switching a communication state of the hydrogen gas supply path ;
With
The intermediate pressure valve is closed such that when hydrogen gas is released from the hydrogen storage alloy, the pressure on the downstream side of the intermediate pressure valve decreases as the hydrogen gas is consumed by the fuel cell that generates power.
A fuel cell system. The fuel cell system according to claim 1,
A fuel cell system comprising a control unit that closes the intermediate pressure valve when releasing hydrogen gas from the hydrogen storage alloy. A control method for a fuel cell system according to claim 1,
A control method for a fuel cell system, wherein the intermediate pressure valve is closed when hydrogen gas is released from the hydrogen storage alloy.

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