JP2009245802A - Fuel battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery system capable of suppressing temperature irregularity inside a fuel battery. <P>SOLUTION: The fuel battery system includes a cooling system that circulates a cooling medium (heat-exchanging medium), such as a coolant. A coolant channel inside the fuel battery 10 is connected to a pipeline 20, which in turn includes a radiator 22 and a pump 24 disposed in the middle of the pipeline 20. The pump 24 is rotated clockwise, counterclockwise, and clockwise in order by rotation switchover to operate the system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 10-340734, a fuel cell system that adjusts the temperature inside a fuel cell to a desired temperature by circulating a refrigerant in a cooling system is known. . In such a fuel cell system, a radiator is usually included in the cooling system. As the circulation amount of the refrigerant in the cooling system is increased, more heat is released from the refrigerant through the radiator, and as a result, the fuel cell is actively cooled.

  The circulation of the refrigerant in the fuel cell plays a role of cooling the fuel cell and suppressing temperature unevenness in the fuel cell. When the flow rate of the refrigerant is changed, the effect of alleviating temperature unevenness inside the fuel cell also changes accordingly. In the conventional fuel cell system, taking advantage of this point, when the temperature distribution inside the fuel cell is large, that is, when the temperature variation inside the fuel cell is recognized to be large, the refrigerant flow rate per unit time is reduced. It is getting bigger.

JP 10-340734 A JP 2007-87779 A JP 2003-223915 A JP 2002-313386 A

  However, when there are various requirements for the cooling system, there may be a situation where the conventional technology cannot sufficiently meet the demand.

  For example, when there is a request to refrain from active heat release such as when the fuel cell is at a low temperature, the cooling system of the conventional fuel cell system described above suppresses the circulation flow rate of the refrigerant and reduces the amount of heat released through the radiator. It is possible to reduce it. However, in association with this, the function of reducing the temperature unevenness inside the fuel cell is reduced, and the temperature unevenness reducing effect is unnecessarily reduced.

  Therefore, the present inventor conducted intensive research and found another method capable of suppressing temperature unevenness inside the fuel cell.

  An object of this invention is to provide the fuel cell system which can suppress the temperature nonuniformity inside a fuel cell.

In order to achieve the above object, a first invention is a fuel cell system,
A fuel cell having a refrigerant flow path for circulating the refrigerant;
A refrigerant flow mechanism for causing a flow in the refrigerant in the refrigerant flow path;
Switching means capable of switching the flow direction of the refrigerant in the refrigerant flow path between a first direction and a second direction opposite to the first direction;
Control means for switching the flow direction of the refrigerant in the refrigerant flow path in the order of the first direction, the second direction, and the first direction;
It is characterized by providing.

The second invention is the first invention, wherein
When the control means causes the refrigerant to flow in the first direction and / or causes the refrigerant to flow in the second direction, an amount of refrigerant equal to or greater than the total volume of the refrigerant passage in the fuel cell is supplied. It is characterized by flowing.

The third invention is the first or second invention, wherein
The control means reduces the amount of flowing the refrigerant in one direction out of the first direction and the second direction less than the amount of flowing the refrigerant in the other direction, An operation mode for switching in the second direction is provided.

According to a fourth invention, in any one of the first to third inventions,
Detecting means for detecting the temperature of the fuel cell;
When the fuel cell is started, when the temperature of the fuel cell is lower than a predetermined temperature, the fuel cell is provided with starting means for executing switching of the refrigerant flow direction by the control means.

  According to the first aspect of the present invention, it is possible to reduce the temperature unevenness inside the fuel cell by causing the refrigerant to flow back and forth via the refrigerant flow path of the fuel cell.

  According to the second invention, the refrigerant can be once taken out of the fuel cell, and the refrigerant can be sufficiently mixed in the process. Thereby, the temperature of the refrigerant repeatedly poured into the fuel cell can be made more uniform. As a result, temperature unevenness inside the fuel cell can be further alleviated.

  According to the third invention, the overall position of the refrigerant with respect to the fuel cell can be shifted while flowing the refrigerant so as to reciprocate with respect to the fuel cell. By doing in this way, it can avoid that the temperature of the refrigerant | coolant which flows in into a fuel cell changes rapidly.

  According to the fourth invention, the temperature of the fuel cell can be raised in a short time when the fuel cell is started at a low temperature.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 shows the configuration of a fuel cell system according to Embodiment 1 of the present invention. The fuel cell system of Embodiment 1 includes a fuel cell 10. The fuel cell 10 is a unit in which a plurality of unit cells 12 are stacked in the left-right direction on the paper (so-called fuel cell stack). In the first embodiment, it is assumed that unit cells 12 are stacked in units of several hundreds of fuel cells 10 such as 200.

  The unit cell 12 is a plate-like structure having a spread in the depth direction of the paper surface of FIG. Each unit cell 12 includes a membrane electrode assembly therein. The membrane electrode assembly is a power generator in which an anode and a cathode are formed with an electrolyte membrane interposed therebetween. On the anode side, there is formed a gas flow path for allowing a fuel gas containing hydrogen (in this embodiment, hydrogen gas) to flow in the plane. In addition, a gas flow path for allowing an oxidizing gas containing oxygen (in this embodiment, air) to flow in the plane is formed on the cathode side. By receiving the supply of the fuel gas and the oxidizing gas, a power generation reaction occurs in the unit cell 12. The unit cell 12 generates heat along with the power generation reaction.

  A passage (hereinafter also referred to as “cooling liquid flow path”) for circulating a refrigerant (in the first embodiment, a cooling liquid also referred to as LLC: Long life Coolant) is used at the boundary of each unit cell 12. Is provided. Specifically, the coolant flow path branches and extends in the plane of each unit cell 12 so as to cover almost the entire area in the plane of the unit cell 12.

  Although not shown, the fuel cell 10 of Embodiment 1 includes first and second coolant manifolds. One end of the coolant flow path of each unit cell 12 is bundled by the first coolant manifold. The other ends of the coolant flow paths of the individual unit cells 12 are bundled by a second coolant manifold. Via the first and second coolant manifolds, the coolant flow paths of the individual unit cells 12 can be connected to the outside of the fuel cell 10. In addition, since the structure of such a unit cell and the structure of the fuel cell which laminated | stacked the said unit cell are well-known, further description is abbreviate | omitted here.

  The fuel cell system of Embodiment 1 has a pipe line 20. One end of the conduit 20 is connected to the first coolant manifold, and the other end of the conduit 20 is connected to the second coolant manifold. As a result, the coolant can be circulated via the conduit 20 and the coolant channels of the individual unit cells 12.

  The pipe line 20 includes a radiator 22 in the middle thereof. The radiator 22 can release the heat of the coolant flowing through the pipe line 20 to the outside of the system.

  The pipe line 20 includes a pump 24 in the middle thereof. In the first embodiment, a pump 24 that can reverse its rotation direction (that is, the coolant flow direction) is selected. Thereby, inside the circulation system including the fuel cell 10, the pipe line 20, and the radiator 22, the cooling water can flow in the forward direction or the reverse direction. However, on the paper surface of FIG. 1, as shown with an arrow in the drawing, the clockwise flow is referred to as “forward direction”, and the opposite counterclockwise flow is referred to as “reverse direction”.

  The pump 24 is connected to the controller 26. By operating the controller 26, the rotation direction and flow rate of the pump 24 can be appropriately changed.

The fuel cell system of the first embodiment includes temperature sensors 30 and 32 at a position in the vicinity of the fuel cell 10 in the pipe line 20. The temperature sensor 30 can measure the temperature of the coolant before flowing into the fuel cell 10 when the coolant is flowing in the forward direction (hereinafter, this temperature is also referred to as “coolant temperature t ₁ ”). . The temperature sensor 32 can measure the temperature of the coolant that has flowed out of the fuel cell 10 when the coolant is flowing in the forward direction (hereinafter, this temperature is also referred to as “coolant temperature t ₂ ”).

  The fuel cell system of Embodiment 1 includes an ECU (Electronic Control Unit) 40. The ECU 40 is connected to the controller 26 and the temperature sensors 30 and 32. By sending a control signal from the ECU 40 to the controller 26, the rotation direction of the pump 24 can be switched. Further, the ECU 40 can acquire information on the temperature environment of the fuel cell 10 by referring to the outputs of the temperature sensors 30 and 32.

  In the first embodiment, the total volume of the coolant flow path of the system (specifically, the total volume of the coolant flow path inside the fuel cell 10, the volume of the pipe line 20, the volume in the radiator 22, etc.) The volume of the coolant flow path in the fuel cell 10 is sufficiently large (at least twice or more, for example, about 3 to 4 times).

  In the following description, the configuration for cooling the fuel cell 10 in Embodiment 1 (the coolant flow path, the pipe line 20, the radiator 22, and the pump 24 inside the fuel cell 10) is comprehensively described as “cooling system”. May be called. Further, in the first embodiment, a coolant circulation path is constructed by connecting the coolant flow path of the fuel cell 10 and the pipe line 20.

[Operation of Embodiment 1]
(Basic operation of the first embodiment)
Strictly speaking, the calorific value of the unit cells 12 due to the power generation reaction varies among the individual unit cells 12. Further, even within the surface of one unit cell 12, heat is not generated completely uniformly. Due to such a variation in the heat generation amount, a variation in temperature (temperature unevenness) occurs in the fuel cell 10. In particular, when a plurality of unit cells 12 are stacked in units of several hundreds, it is considered that such temperature variations are likely to increase.

  In the fuel cell system of the first embodiment, the rotation direction of the pump 24 can be fixed in the forward direction or the reverse direction, and the coolant can be circulated in the system. By circulating the coolant, the fuel cell 10 can be cooled and temperature unevenness in the fuel cell 10 can be suppressed.

(Characteristic operation of the first embodiment)
In the first embodiment, in addition to the operation of circulating the coolant, the system is further operated while flowing the coolant in the following two modes (referred to as “first operation” and “second operation”, respectively). You can drive.

(I) First Operation Hereinafter, the first operation of the first embodiment will be described with reference to FIG. FIG. 2 is a diagram showing the time change of the behavior of the pump 24 with the vertical axis representing the number of rotations per unit time of the pump 24 and the horizontal axis representing time. In FIG. 2, the number of rotations above the page with zero as the boundary is the number of rotations in the state where the pump 24 is rotating in the forward direction, and the number of rotations below the sheet with respect to zero is the rotation of the pump 24 in the reverse direction. The number of rotations in the state of The maximum value of the number of rotations in the forward direction and the reverse direction is the same value and is denoted by A (for the sake of convenience, a minus sign is attached to the reverse direction). Since there is a correlation between the number of rotations of the pump and the flow rate of the coolant, the vertical axis in FIG. 2 can be read as a flow rate (liter / second) per unit time.

  In FIG. 2, the area of the hatched region (hereinafter also simply referred to as “region 50”) is the curve of one cycle (W in FIG. 2) of the rotation direction of the pump 24 in the forward direction. It is the value integrated by. As described above, since the vertical axis in FIG. 2 can be read as a flow rate per unit time, the area 50 has an area that is the flow rate that the pump 24 flows in one cycle of the forward rotation side (that is, the flow rate in the period W). Means the volume of the coolant: liter).

  As shown in FIG. 2, in the first operation of the first embodiment, the period in which the pump 24 rotates in the forward direction and the period in which the pump 24 rotates in the reverse direction are alternately generated. Here, the rotation direction of the pump 24 is considered to mean the direction of the flow of the coolant flowing through the pipe line 20 and the like as it is. Therefore, according to the first operation, the coolant flows while reversing the flow direction alternately between the forward direction and the reverse direction.

  According to such an operation, the coolant reciprocates repeatedly inside the fuel cell 10, and the temperature inside the fuel cell 10 (more specifically, in the plane of each unit cell 12) as the coolant flows. The gradient is smoothed. Therefore, the temperature unevenness generated in the fuel cell 10 can be alleviated and the entire fuel cell 10 can be brought closer to a more uniform temperature.

Further, in the first embodiment, the area of the region 50 is just “the total volume of the coolant channel in the fuel cell 10” and “the portion of the conduit 20 from the fuel cell 10 to the temperature sensors 30, 32. It is determined so as to be equal to the total volume V _{FC including} The volume V _FC is a volume of the coolant flow path at a site surrounded by a broken line in FIG.

  By doing in this way, first, at least “cooling liquid flow volume in the fuel cell 10” or more of the volume of cooling liquid can be flowed in the forward direction and the reverse direction. That is, the operation of once discharging all the coolant in the fuel cell 10 to the pipe line 20 and then returning the same amount of coolant to the fuel cell 10 is repeated. By doing in this way, the cooling liquid heated in each unit cell 12 from which temperature differs can be once gathered to the pipe line 20, and can be mixed so that it may become average temperature. Further, by adding the “volume of the portion of the pipe line 20 from the fuel cell 10 to the temperature sensors 30 and 32”, the temperature sensors 30 and 32 accurately measure the temperature environment in the fuel cell 10. be able to.

  For example, under the following circumstances, the first operation can exhibit the following effects.

  When the fuel cell 10 is at a low temperature, it may be desired to refrain from aggressive release of heat from the system until the fuel cell 10 is warmed to some extent. More specifically, at a low temperature, a cold start, in particular, a sub-freezing start. In such a case, it is desirable to warm up rapidly in order to prevent freezing inside the fuel cell 10 and start the system early.

  The more the coolant is circulated, the more heat is dissipated by the radiator 22 and the system is cooled. At low temperatures as described above, it is desirable to refrain from actively releasing heat from the system to the outside. Therefore, it is conceivable to reduce the heat radiation through the radiator 22 by circulating the cooling liquid while suppressing the flow rate of the cooling liquid, or stopping the pump 24 to eliminate the flow of the cooling liquid itself. However, when the flow rate of the coolant is reduced, the effect of alleviating temperature unevenness inside the fuel cell 10 realized by the flow of the coolant is also reduced.

  According to the first operation, such a difficulty can be solved. As described above, in the first embodiment, the flow of the cooling liquid in the cooling system is reversed between the forward direction and the reverse direction. The coolant can be reciprocated in the vicinity of the fuel cell 10 by setting the rotation time in the forward direction and the rotation time in the reverse direction to the same value and appropriately determining these times.

  According to such an operation, the coolant that has been heated by receiving heat from the fuel cell 10 does not reach the radiator 22 side (without going around the cooling system), and reciprocates around the fuel cell 10. And keep flowing. Therefore, the heat generated by the fuel cell 10 is concentrated and accumulated in the coolant near the fuel cell 10, and it is possible to refrain from releasing heat from the radiator 22 to the outside of the system. As a result, the temperature of the fuel cell 10 can be quickly raised. If the flow rate of the coolant (specifically, the amplitude of the waveform of the pump rotation number in FIG. 2) is appropriately determined, the flow of the coolant can be sufficiently ensured. Therefore, the effect of alleviating temperature unevenness inside the fuel cell 10 can be sufficiently ensured.

  As described above, according to the first operation, it is possible to achieve both suppression of heat dissipation from the fuel cell 10 and securing of an effect of reducing temperature unevenness of the fuel cell 10. Note that, according to the above-described operation, the low-temperature coolant flows back and forth near the radiator 22. Therefore, in the fuel cell system of Embodiment 1, there is substantially no temperature difference before and after the radiator 22 during the first operation.

Further, according to the first operation, the heat capacity (the total amount of heat necessary for warming up) when warming up the fuel cell 10 can be reduced. If the warm-up is performed while circulating the coolant, it is required that the temperature of all the coolants in the cooling system rise. On the other hand, according to the first operation, if the temperature of the coolant that is about twice the volume V _FC increases, a favorable temperature environment is secured at least around the fuel cell 10. Comparing these, it can be seen that the first operation can warm up the fuel cell 10 with a smaller heat capacity. Moreover, the fact that the heat capacity is small is nothing but the fact that the temperature of the fuel cell 10 can be raised in a short time.

(Ii) Second Operation Hereinafter, the second operation of the first embodiment will be described with reference to FIG. As shown in FIG. 3, in the second operation, the reciprocating operation of the coolant described in the first operation is performed, and the center of the reciprocation (if the curve of the time variation of the pump rotation speed is regarded as vibration is considered as vibration). Shift the center) to the positive side. Along with this, the maximum value (in other words, the width of vibration) on the forward direction side and the reverse direction side as viewed from the center of reciprocation is reduced. Finally, as shown in FIG. 3, the pump speed is converged to a fixed value A _0. In other words, if the fluctuation of the pump rotation speed due to the first operation is regarded as an AC component, the second operation is an operation in which a DC component on the positive direction side is added to the AC component and finally converges to a fixed value. Can be expressed.

  If the total amount of coolant flowing in the forward direction is larger than the total amount of coolant flowing in the reverse direction, the reciprocating flow of the coolant is maintained, but the coolant moves as a whole in the forward direction. . According to the second operation, the coolant can be shifted in the forward direction in the cooling system while repeating the reciprocation of the coolant in the cooling system.

In the first embodiment, the pump 24 is controlled so that the area of the region 60 shown in FIG. 3 coincides with the volume V _FC described in the first operation. That is, the length of one cycle in the forward direction side or the reverse direction side is increased as the range of fluctuation of the pump rotation speed becomes smaller.

In the first embodiment, as shown in FIG. 3, it is increasing gradually with the DC component of the positive side to the fixed value A _0. Here, in FIG. 3, the area 70 drawn by the added value of the DC component on the positive direction side is the steady operation (the state where the rotation speed is set to the fixed value A ₀ ) after the start of the second operation. It means the total amount of the coolant that moves in the cooling system by the direct current component in the time until the start. In the first embodiment, the size of the area 70 is matched with the total volume of the cooling system of the fuel cell system. As a result, it is possible to complete the circulation of the coolant in the cooling system and then immediately switch the operation of the pump 24 to the steady operation.

  For example, under the following circumstances, the second operation can exhibit the following effects.

  When the first operation described above is performed in a low temperature environment, the temperature of the coolant in the vicinity of the fuel cell 10 rises, but at other positions (particularly the position farthest from the fuel cell 10 in the cooling system). The coolant is still maintained at a low temperature. In such a case, if the coolant is circulated immediately after the warm-up around the fuel cell 10 is completed by the first operation, the low-temperature coolant suddenly flows into the fuel cell 10.

  In this respect, according to the second operation, the coolant can be shifted while repeating the reciprocating operation in the cooling system, so that the coolant can be sequentially heated in the process. As a result, it is possible to avoid a sudden change in the temperature of the refrigerant flowing into the fuel cell.

  Note that the fuel cell system of Embodiment 1 also has the following advantages. There may be a case where a bypass channel (pipe, etc.) is provided in the cooling system of the fuel cell system so that the coolant flows around the radiator in the cooling system. By selectively using such a bypass flow path, it is possible to switch between a case in which the coolant flows through the radiator and a case in which the coolant flows without passing through the radiator. However, the bypass channel complicates the system configuration. Also, if the volume of the bypass flow path is large, the heat capacity is still large because it does not change in that much coolant must be heated.

In this regard, the fuel cell system of Embodiment 1 does not have the bypass flow path as an essential configuration, and a simple configuration can be employed. Further, since the volume of the coolant flowing back and forth near the fuel cell 10 when warming up can be sufficiently reduced (in Embodiment 1, it is twice the volume V _FC , but may be smaller than this). The effect of reducing the heat capacity can be sufficiently obtained.

[Specific Processing in First Embodiment]
Hereinafter, specific processing performed by the fuel cell system of Embodiment 1 will be described with reference to FIG. FIG. 4 is a flowchart of a routine executed by ECU 40 in the first embodiment. In the first embodiment, it is assumed that this routine is executed during power generation of the fuel cell 10 when the fuel cell system is started.

In the routine shown in FIG. 4, first, determination of the first temperature environment of the fuel cell 10 is performed (step S100). In this step, it is determined whether or not the temperature of the coolant in the cooling system is sufficiently high. Specifically, it is determined whether or not the average value (t ₁ + t ₂ ) / 2 of the temperatures t ₁ and t ₂ indicated by the temperature sensors 30 and 32 is below a predetermined temperature T ₁ . The predetermined temperature T ₁ of, for example, by circulating a cooling fluid in advance specified from such specifications and experiments the minimum temperature of the cooling fluid can permitted to flow, may be determined based on this. For example, the predetermined temperatures T ₁ can be determined in the order of several tens of ° C..

If the condition in step S100 is negative, it is determined that the temperature of the coolant is high enough to be acceptable. As a result, the constant rotation operation is performed as it is (step S110). The low rotational speed operating, in the first embodiment, a driving rotating at a constant rotation speed A ₀ the pump 24 in the forward direction.

When the condition of step S100 is satisfied, the determination of the second temperature environment of the fuel cell 10 is performed (step S102). In this step, it is determined whether or not the temperature environment of the fuel cell 10 is below freezing. Specifically, the average value of the temperature _{t 1} and _{t 2 (t 1 + t 2} ) / 2 is, whether less than the predetermined temperature _{T 2} is determined. Predetermined temperature _{T 2} is zero ° C..

  When the condition of step S102 is satisfied, it is determined that the fuel cell system is in a low temperature environment, and the fuel cell 10 is warmed up (step S104). In this step, the first operation described above is executed, and the fuel cell 10 is quickly warmed up. As a result, various adverse effects such as the possibility of freezing can be surely avoided, and the fuel cell system can be stably started.

After the execution of step S104 is started, the process returns to step S102 again, and the average value (t ₁ + t ₂ ) / 2 and the predetermined temperature T ₂ are compared again. As a result, the temperature environment of the fuel cell 10 is continuously monitored, and the warm-up operation of the fuel cell 10 is maintained until the value of (t ₁ + t ₂ ) / 2 becomes zero ° C. or higher. Thereafter, when the condition of step S102 is denied, the process exits the loop of steps S102 and S104 and shifts to the coolant warm-up operation (step S106). Note that the value of T ₂ + ΔT ₂ obtained by adding ΔT ₂ (for example, about 1.5 ° C.) to the predetermined temperature T ₂ may be used as the determination value in the second and subsequent steps S102 after entering the loop.

  In the coolant warm-up operation in step S106, the second operation described above is executed. That is, the rotational speed of the pump 24 is controlled according to the curve shown in FIG. As a result, the coolant can be shifted while repeating the reciprocating operation in the cooling system, so that the coolant can be sequentially heated in the process. As a result, the temperature of the coolant in the cooling system can be entirely increased while avoiding a sudden change in the temperature of the refrigerant flowing into the fuel cell 10.

After the execution of step S106 is started, it is determined whether or not at least one of a sufficient rise in the coolant temperature and a cycle of the coolant in the cooling system has been established (step S108). In this step, first, it is determined whether or not the average value (t ₁ + t ₂ ) / 2 of the coolant temperature is equal to or higher than a predetermined temperature T ₁ . Thereby, it can be determined whether or not the temperature of the coolant has risen to some extent.

In addition, as described in the second operation, it is also determined whether or not the cooling liquid having a volume corresponding to the area of the region 70 has flowed and the cooling system has made a round in the cooling system. This determination may, for example, time or from the start of the step S106, whether or not the rotational speed of the current of the pump 24 matches the fixed value A ₀ is a convergence value, or the like in the forward direction using a flow meter This can be realized from various viewpoints such as actually measuring the total amount of the coolant that has flowed. It should be noted that only one of the temperature condition and the coolant circulation cycle condition determination may be performed.

  In step S108, while both the temperature condition and the coolant circulation cycle condition are denied, the coolant warm-up operation in step S106 is maintained. In step S108, when at least one of the temperature condition and the coolant circulation cycle condition is satisfied, the routine proceeds to constant rotation operation (step S110).

  According to the above processing, when starting the fuel cell system, the fuel cell 10 and the coolant can be quickly warmed up while avoiding a sudden temperature change in accordance with the temperature environment. it can.

  In the first embodiment, the fuel cell 10 is the “fuel cell” in the first invention, the pump 24 is the “refrigerant distribution mechanism” in the first invention, and the controller 26 is the first invention. Corresponds to “switching means” in FIG. In the first embodiment described above, the “control means” in the first aspect of the present invention is realized by executing step S104 of the routine of FIG.

  In the first embodiment described above, the second operation realized in step S106 of the routine of FIG. 4 corresponds to the “operation mode” in the third aspect of the invention.

  In the first embodiment described above, the temperature sensors 30 and 32 correspond to the “detecting means” in the fourth invention, and the “starting” in the fourth invention is performed by steps S100 and S102 of the routine of FIG. Means "are realized.

[Modification of Embodiment 1]
(First modification)
FIG. 5 is a diagram illustrating a first modification of the first embodiment. In the first modified example, as compared with the first embodiment, the period in which the rotation direction of the pump 24 is maintained in the forward direction / reverse direction is shortened, and the maximum value of the rotation speed is increased. Execute the operation. That is, as FIG. 2 showing a first operation of the first embodiment, in comparison with FIG. 5, the relationship A <A ₂ KatsuW> _{W 2} is established. In the first modification, the area of the hatched region 80 in FIG. 5 is the same as the area 50 of FIG.

  The larger the value of the current during power generation of the fuel cell 10, the greater the amount of heat generated by the fuel cell 10. Therefore, it is conceivable that when the fuel cell 10 is warmed up, the fuel cell 10 generates more current. On the other hand, in order to realize the operation of the pump as shown in FIG. 5, the pump 24 requires more electric power than in the case of the first embodiment. Therefore, in the first modification, the current generated by the fuel cell 10 is consumed by the pump 24. As a result, the fuel cell 10 can be warmed up more quickly.

  It should be noted that both the first operation of the first embodiment (FIG. 2) and the first operation of the first modification (FIG. 5) are set as operation modes for the first operation of the pump 24. Alternatively, they may be selectively switched as necessary.

(Second modification)
In the first embodiment, in the first operation and the second operation, the amount of the coolant flowing in the forward direction or the reverse direction is set to the volume V _FC . However, the present invention is not limited to this. The amount of cooling fluid to flow in the forward direction or reverse direction, such as setting less more set or volume V _FC than the volume V _FC, may be changed amount of coolant flowing in the forward direction or reverse direction as required . Further, the cooling system to be the subject of the present invention is not limited to the one in which the volume of the pipe line 20 is sufficiently large as compared with the volume of the coolant channel in the fuel cell 10 as in the first embodiment. The present invention can be applied to various cooling systems.

(Third Modification)
In the first embodiment, the flow direction of the coolant is switched by reversing the rotation direction of the pump 24. However, the present invention is not limited to this. For example, as disclosed in Japanese Patent Application Laid-Open No. 2007-87779, the flow of the coolant to the fuel cell 10 can be performed by selectively switching a pipe line using a valve or the like without changing the rotation direction of the pump itself. There is a mechanism for switching the direction of the. Such a switching mechanism may be used.

(Fourth modification)
The second operation of the first embodiment can be expressed as an operation in which a DC component on the positive direction side is placed on this AC component when the fluctuation in the pump speed is regarded as an AC component. In the first embodiment, as shown in FIG. 3, the direct current component is gradually increased. However, the present invention is not limited to this. A certain direct current component may be placed. This is because if the amount of the coolant flowing in the forward direction is set larger than the amount of the coolant flowing in the reverse direction, the overall position of the coolant can be gradually moved in the forward direction.

  In the first operation of the first embodiment, switching between the forward direction and the reverse direction is periodically repeated many times. However, the present invention is not limited to this. The reversal of the coolant flow may be performed (repeated) a plurality of times. By switching the forward direction → reverse direction → forward direction and the rotation direction of the pump 24, the coolant flow is reversed twice in total (reversal of the coolant flow from the forward direction to the reverse direction and the reverse direction to the forward direction). Reversal of the coolant flow in the direction). Further, the number of reversals of the flow can be increased by an arbitrary number of times by continuing in the reverse direction and the forward direction. Further, after switching from the forward direction to the reverse direction to the forward direction, the stationary rotation may be performed in the state where the reverse direction is finally set. In the first embodiment, for the sake of convenience, the positive direction is defined as the clockwise direction in FIG. 1, but the left direction in FIG. Which direction is the positive direction with respect to the cooling system may be arbitrarily determined.

  In the first embodiment, it is assumed that both the first operation and the second operation are executed. However, the present invention is not limited to this, and only the first operation can be used, or only the second operation can be used. Although the circulation type cooling system is used in the first embodiment, the present invention may be realized by a non-circulation type system as long as the reversal of the flow can be repeated.

  In the first embodiment described above, the advantages of the first and second operations at the time of low temperature or cold start of the fuel cell system have been mainly described. However, the first and second operations may be used as necessary regardless of the temperature environment and the operating state, that is, under conditions other than low temperature or other than startup. Thereby, the temperature unevenness inside the fuel cell can be reduced or eliminated.

It is a figure which shows the structure of the fuel cell system of Embodiment 1 of this invention. FIG. 3 is a diagram for explaining the operation of the fuel cell system according to the first embodiment. FIG. 3 is a diagram for explaining the operation of the fuel cell system according to the first embodiment. 4 is a flowchart of a routine executed in the first embodiment. 6 is a diagram showing a modification of the first embodiment. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 12 Unit cell 20 Pipe line 22 Radiator 24 Pump 26 Controller 30 Temperature sensor 32 Temperature sensor

Claims (4)

A fuel cell having a refrigerant flow path for circulating the refrigerant;
A refrigerant flow mechanism for causing a flow in the refrigerant in the refrigerant flow path;
Switching means capable of switching the flow direction of the refrigerant in the refrigerant flow path between a first direction and a second direction opposite to the first direction;
Control means for switching the flow direction of the refrigerant in the refrigerant flow path in the order of the first direction, the second direction, and the first direction;
A fuel cell system comprising:   When the control means flows at least one of the refrigerant in the first direction and the refrigerant in the second direction, an amount of refrigerant equal to or larger than the total volume of the refrigerant passage in the fuel cell is supplied. The fuel cell system according to claim 1, wherein the fuel cell system is flowed.   The control means reduces the amount of flowing the refrigerant in one direction out of the first direction and the second direction less than the amount of flowing the refrigerant in the other direction, The fuel cell system according to claim 1, wherein the fuel cell system has an operation mode in which switching in the second direction is performed. Detecting means for detecting the temperature of the fuel cell;
The starter for switching the flow direction of the refrigerant by the controller when the temperature of the fuel cell is lower than a predetermined temperature when the fuel cell is started. 4. The fuel cell system according to any one of 3.

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