JP2007052947A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of finishing warming-up in a short time by shortening temperature rising time of a cooling water. <P>SOLUTION: The fuel cell system 1 has a fuel cell 2, a circulation passage 5 which is a flow passage of a cooling liquid to cool the fuel cell 2 and in which the cooing liquid is circulated between a radiator 4 to cool the cooling liquid and the fuel cell 3, a detour route 6 which is the flow passage of the cooling liquid to detour the radiator 4 and in which both ends are connected to the circulation passage 5, and a thermovalve 7 to switch the flow passage of the cooling liquid to either of the flow passage passing through the radiator 4 or the flow passage passing through the detour route 6. Moreover, a weir 8 to adjust a circulation amount by damming a part of the cooling liquid when it is circulated by passing through the detour route 6 is installed at the flow passage of the cooling liquid. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system having a detour that is a flow path of a coolant and bypasses a radiator.

  The fuel cell has a structure in which an anode and a cathode are arranged with an electrolyte membrane interposed therebetween. Then, when hydrogen (fuel gas) comes into contact with the anode and oxygen (oxidant gas) comes into contact with the cathode, an electrochemical reaction occurs between the two electrodes to generate an electromotive force.

  Generally, in a fuel cell, heat is also generated when an electromotive force is generated. For this reason, in the fuel cell system, heat is released into the atmosphere by the radiator. However, if the amount of heat generated exceeds the cooling capacity of the radiator due to an increase in the electromotive force in the fuel cell, the fuel cell overheats, leading to problems such as a drop in output voltage and destruction of the fuel cell. For this reason, conventionally, a method for preventing overheating of the fuel cell has been proposed.

  Patent Document 1 discloses a fuel cell system that protects a fuel cell from overheating by adjusting the power generation amount of the fuel cell so that the amount of heat generated by the fuel cell does not exceed the cooling capacity of the radiator. Yes.

JP 2002-83622 A JP 2004-178826 A JP 2004-158279 A JP 2003-331886 A JP 2004-14324 A JP 2004-220850 A

  In the fuel cell system described in Patent Literature 1, cooling water bypasses the radiator as necessary. That is, the temperature of the cooling water sent to the fuel cell is kept constant by adjusting the flow rate of the cooling water passing through the radiator and the flow rate of the cooling water passing through the bypass.

  On the other hand, the power generation amount of the fuel cell is small at low temperatures, but the desired power generation efficiency can be obtained by warming up. Here, the warm-up time is preferably as short as possible. However, when a detour is provided, there is a problem that it takes time to warm up because all the cooling water in the detour must also be heated.

  The flow rate of the cooling water in the detour can be reduced by reducing the pipe diameter of the detour. However, since the flow rate of the cooling water passing through the radiator is relatively increased, there has been a problem that the temperature change of the cooling water sent to the fuel cell becomes large. In addition, since the pressure loss increases as the pipe diameter decreases, there is a problem in that the efficiency of the pump for circulating the cooling water decreases.

  The present invention has been made in view of these problems. That is, an object of the present invention is to provide a fuel cell system capable of shortening the temperature rising time of cooling water and finishing warming up in a short time.

  Other objects and advantages of the present invention will become apparent from the following description.

  The fuel cell system of the present invention includes a fuel cell, a flow path for a coolant that cools the fuel cell, and a circulation path through which the coolant circulates between the heat exchanger that cools the coolant and the fuel cell. A flow path of the coolant that bypasses the heat exchanger, and the coolant flows in one of the bypass path that connects both ends to the circulation path, the flow path that passes through the heat exchanger, and the flow path that passes through the bypass path. A switching valve for switching a path, and a flow path for the cooling liquid is provided with a weir for blocking a part of the cooling liquid and adjusting a circulation amount when the cooling liquid circulates through the detour It is characterized by this. In the present invention, the heat exchanger can be a radiator.

  The weir is preferably provided on the detour.

  A plurality of weirs can be provided.

  It can be assumed that the flow below the coolant in the direction of gravity is blocked by the weir.

  The weir can be a butterfly valve.

  According to the present invention, since the weir for adjusting the circulating amount of the cooling water is provided in the cooling water flow path, the heating time of the circulating cooling water can be shortened and the warming of the fuel cell system can be completed in a short time. It becomes possible.

  FIG. 1 is a partial configuration diagram of a fuel cell system according to the present embodiment. In the figure, gas is supplied to the cathode and anode of the fuel cell, for example, a compressor that supplies compressed air to the cathode, and moisture contained in the cathode off-gas discharged from the fuel cell is recovered and supplied to the fuel cell. A humidifier that humidifies the air to be performed, a pressure regulating valve that adjusts the pressure of the air sent from the compressor, a fuel gas supply system that supplies gas to the anode, and the like are omitted. Further, this fuel cell system can be applied to various uses such as in-vehicle use and stationary type.

  As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2 that is supplied with fuel gas and oxidizing gas to generate an electromotive force, a circulation pump 3 that circulates cooling water inside the fuel cell system 1, A radiator 4 that cools water, a circulation path 5 through which cooling water circulates between the fuel cell 2 and the radiator 4, a flow path that bypasses the radiator 4, and a detour 6 that has both ends connected to the circulation path 5. And a thermo valve 7 that switches the flow path of the cooling water to one of a flow path that passes through the radiator 4 and a flow path that passes through the detour 6 at a predetermined temperature. Here, the thermo valve 7 corresponds to the switching valve in the present invention. Further, in the present embodiment, the fuel cell 2 may be cooled using a coolant other than the cooling water. Furthermore, a heat exchanger other than the radiator 4 can be used.

  During warm air, the cooling water is circulated through the fuel cell system 1 through the bypass 6. That is, in order to shorten the warm-up time, it is necessary to quickly raise the temperature of the cooling water. Therefore, it is effective to circulate the cooling water without passing through the radiator 4. The cooling water flow path is provided with a weir 8 that dams a part of the cooling water and adjusts the circulation amount when the cooling water circulates through the bypass 6. As the weir 8, for example, a butterfly valve, a solenoid or a rotary valve can be used. In particular, a butterfly valve is suitable because of its small pressure loss.

  FIG. 2A is a plan view of the butterfly valve. As shown in the figure, the butterfly valve 81 has a circular valve element 82 that rotates around the valve shaft 83, and the outer peripheral edge of the valve element 82 contacts the ring packing 85 that is fitted to the inner peripheral surface of the valve casing 84. When in contact, the valve is closed.

  FIG. 3 is a schematic sectional view of the detour 6, and shows a case where the butterfly valve 81 of FIG. 2A is used as the weir 8. In addition, the arrow of FIG. 3 has shown the direction through which cooling water flows.

  In FIG. 2, a step 12 is provided at the bottom of a pipe 11 constituting the detour 6. When the valve element 82 rotates around the valve shaft 83, the valve element 82 moves along the step 12 between the points A and B in the figure. When the valve body 82 stops at point A, the butterfly valve 81 is in a closed state. On the other hand, when the valve body 82 moves in the direction of the point B, the butterfly valve 81 is opened, and when the valve body 82 stops at the point B, the valve is most greatly opened.

  The warm air is started in a state where the butterfly valve 81 is opened to such an extent that a predetermined amount of cooling water is circulated. For example, it is assumed that warming is started in a state where the valve body 82 is stopped at the point C. At this time, the cooling water flowing from the right direction in the figure is blocked by the butterfly valve 81. Specifically, the downward flow with respect to the direction of gravity of the cooling water is hindered and stays. On the other hand, the upward flow with respect to the gravity direction proceeds to the left through the butterfly valve 81. Therefore, by providing the butterfly valve 81, the amount of cooling water circulating through the fuel cell system 1 through the bypass 6 can be reduced. In general, the cooling water has a temperature distribution, and the upper water temperature tends to be higher than the lower water temperature. Therefore, by providing the butterfly valve 81 and hindering the flow of the lower cooling water, only the warm upper cooling water can be circulated.

  As described above, according to the present embodiment, the amount of cooling water flowing out from the detour is reduced, and the cold cooling water is retained so that the warm cooling water circulates. It becomes possible to finish warming in a short time by shortening the temperature rising time.

  Since the temperature of the circulating cooling water gradually increases, after the water temperature reaches a predetermined temperature, the butterfly valve 81 is opened so that the remaining cooling water having a low water temperature is also circulated. To do. At this time, it is preferable that the butterfly valve 81 has a valve opening continuously (or intermittently). Specifically, the valve opening is gradually increased by gradually moving the valve body 82 from the point C to the point B.

  When the butterfly valve 81 is opened all at once, a large amount of cold cooling water is mixed with the warm cooling water, and the temperature of the circulating cooling water may rapidly decrease. On the other hand, if the butterfly valve 81 is opened so that the valve opening increases continuously (or intermittently), the cold cooling water is gradually mixed with the warm cooling water. Can be prevented from rapidly decreasing.

  FIG. 4A is an example of a flowchart showing control of the cooling water circulation rate. FIG. 4B is a diagram showing the relationship between the rotational speed of the circulation pump and the temperature of the cooling water, and the valve opening of the butterfly valve.

  As shown in FIG. 4A, the temperature of the cooling water is low when the fuel cell is started, and warming is started in this state (step 1). First, the number of revolutions of the circulation pump that circulates the cooling water is set to a value corresponding to the amount of power generated by the fuel cell (step 2). In addition, it is good also as a rotation speed according to water temperature instead of electric power generation amount. In this case, the temperature sensor is preferably provided in the vicinity of the coolant outlet 2b of the fuel cell 2 shown in FIG.

  Next, the valve opening degree of the butterfly valve 81 is determined from the rotation speed of the circulation pump and the water temperature with reference to the iso-opening degree map (FIG. 4B) obtained in advance (step 3). Then, the rotational speed of the circulation pump is set again according to the power generation amount or the water temperature (step 1).

  After the above steps 1 to 3 are repeated, the butterfly valve 81 is slowly opened until the valve opening reaches a value exceeding the upper limit of the equal opening degree map (step 4). Then, with the butterfly valve 81 fully opened, the activation of the butterfly valve 81 is finished (step 5).

  The above describes the opening of the butterfly valve 81. On the other hand, by closing the butterfly valve 81 completely, the following effects can be obtained.

  For example, when the power generation amount of the fuel cell 2 increases rapidly, it is necessary to circulate a large amount of low-temperature cooling water in order to suppress overheating of the fuel cell 2. At this time, it takes a certain amount of time for the thermovalve 7 to operate and the flow path of the cooling water to switch from the flow path passing through the detour 6 to the flow path passing through the radiator 4. For this reason, only control by the thermovalve 7 has a limit in the response | compatibility to the sudden increase in the electric power generation amount of the fuel cell 2, and can respond only to a certain width. On the other hand, if the butterfly valve 81 is completely closed, the cooling water always passes through the radiator 4. Here, the butterfly valve 81 can be opened and closed in a short time. Therefore, if the butterfly valve 81 is closed instead of switching the flow path by the thermo valve 7, it is possible to quickly cope with a sudden increase in the amount of power generated by the fuel cell 2.

  The fluctuation of the power generation amount of the fuel cell 2 can be observed by, for example, a current value. Specifically, when the change in current value per unit time exceeds a predetermined range, the butterfly valve 81 is moved and stopped at point A. Thereby, the butterfly valve 81 can be quickly closed. Note that the fluctuation of the water temperature may be observed instead of the current value, and the butterfly valve 81 may be closed when the water temperature exceeds a predetermined value. Then, after the current value or the water temperature becomes a stable value, the butterfly valve 81 is opened again. And the flow path of the cooling water after this may be controlled by the thermo valve 7.

  In the present embodiment, the weir 8 may be provided in the flow path from the junctions 9 and 10 of the bypass 6 and the circulation path 5 to the fuel cell 2 instead of the bypass 6. (In FIG. 1, the thermo valve 7 is provided at the junction 9). In this case, the same effect as described above can be obtained. However, the cooling water circulates through the bypass 6 during warm air, but circulates through the radiator 4 during normal operation. Therefore, the weir 8 effective for raising the temperature of the cooling water during the warm air circulates. It is preferable to be provided in the detour 6 rather than in the path 5. Further, during normal operation, it may be necessary to circulate a large amount of cooling water due to a sudden increase in the amount of power generated by the fuel cell 2, and therefore there is a member that causes pressure loss in the flow path through which the cooling water circulates. Preferably as little as possible. If the weir 8 is provided in the detour 6, the pressure loss during normal operation can be reduced as compared with the case where it is provided in the circulation path 5.

  In the present embodiment, a plurality of weirs may be provided.

  FIG. 5 is an example in which two butterfly valves are provided in the bypass 6 along the direction in which the cooling water flows. By doing so, the lower cooling water whose flow is blocked stays on the upstream side of each of the first butterfly valve 81a and the second butterfly valve 81b. In this case, since the second butterfly valve 81b is provided on the upstream side of the first butterfly valve 81a, the cooling water whose flow is blocked by the first butterfly valve 81a stays between them. Therefore, compared with the case where there is only one butterfly valve, the lower cooling water can be retained more effectively, so that the lower cooling water flows out beyond the first butterfly valve 81a. Can be suppressed.

  Moreover, when providing a weir in two places, it is preferable to arrange | position so that the distance between these may become large. In this way, since the area where the lower temperature cooling water is retained becomes larger, the warm cooling water can be circulated more preferentially and more effectively. Accordingly, it is possible to further shorten the heating time of the circulating cooling water and finish the warming up in a shorter time.

  Further, in the above case, when two weirs are provided in the flow path from the junctions 9 and 10 of the detour 6 and the circulation path 5 to the fuel cell 2, as shown in FIG. The circulation pump 3 is arranged in the vicinity of the cooling water inlet 2a, one is provided between the junction 9 and the circulation pump 3, and the other is provided between the junction 10 and the cooling water outlet 2b of the fuel cell 2. Is preferred. The reason for not providing the weir on the downstream side of the circulation pump 3 is to prevent the circulation of the cooling water from being disturbed by the circulation pump 3.

  Further, when two weirs are provided, it is preferable that the upstream weir opens before the downstream weir. In this way, first, the low-temperature cooling water that has been blocked by the upstream weir gradually starts to flow downstream. At this time, the low-temperature cooling water flows together with the high-temperature cooling water. And the flow is prevented again by the downstream weir, and the cooling water below stays. Next, when the downstream weir is opened, the remaining cooling water gradually circulates. In this way, by shifting the valve opening timing, the cooling water having a low water temperature can gradually flow out, so that the temperature of the circulating cooling water can be prevented from changing suddenly.

  Further, as the weir, another thermo valve that opens at a lower temperature than the thermo valve 7 may be used.

  For example, at the water temperature of 10 ° C. or less, the bypass 6 is provided with a first thermo valve that is opened only to the extent that a predetermined amount of cooling water circulates. Further, a second thermo valve that operates at 60 ° C. and switches the flow path of the cooling water is provided as the thermo valve 7. When the water temperature is 10 ° C. or lower, the flow of the cooling water in the bypass 6 is blocked by the first thermo valve, and the upper cooling water having a relatively high temperature circulates in the fuel cell system 1. When the water temperature exceeds 10 ° C., the first thermo valve is further opened. At this time, in order to prevent the temperature of the cooling water from changing suddenly, it is preferable to open the valve gradually (or intermittently) as the water temperature increases. Furthermore, when the water temperature reaches 60 ° C., the second thermo valve operates, and the cooling water circulates in the fuel cell system 1 not through the bypass 6 but through the radiator 4.

  The warm-up described above may be performed when the fuel cell is started, or may be performed after the fuel cell is stopped. When performing at the time of starting, the time for which the output of the fuel cell is limited can be shortened by providing the weir. On the other hand, when the operation is performed after the operation is stopped, the time for removing the water remaining in the fuel cell system can be shortened.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above embodiment, the valve body of the butterfly valve need not necessarily be circular. For example, as shown in FIG. 3B, an opening 86 is always provided between the upper portion of the valve body 82 'and the ring packing 85' with respect to the valve shaft 83 'regardless of the movement of the valve body 82'. It may be a butterfly valve 81 '. This is due to the following reason.

  As described above, the cooling water circulates through the detour 6 when warming up. For example, it is assumed that the temperature at which the thermo valve 7 is operated to switch the flow path of the cooling water is 60 ° C. At the start of warming up, the temperature is low, and the thermovalve 7 is configured so that cooling water circulates through the detour 6. At this time, the weir 8 is opened to such an extent that a predetermined amount of cooling water is circulated. Next, the weir 8 is further opened as the temperature of the cooling water rises. When the water temperature reaches 60 ° C., the thermo valve 7 is activated, and the cooling water circulates through the radiator 4 instead of the bypass 6.

  Thus, since the switching of the flow path of the cooling water is performed by the thermovalve 7, it is not always necessary that the weir 8 has a structure that can completely stop the flow of the cooling water. Rather, as long as the butterfly valve 81 ′ having the structure shown in FIG. 3B is opened to the extent that the required amount of cooling water is circulated from the beginning, the time required for opening the valve is not required. This is further beneficial for shortening the warm-up time. However, in this case, the situation where the power generation amount of the fuel cell 2 rapidly increases must be dealt with by switching the flow path by the thermovalve 7. Therefore, the butterfly valve (81, 81 ') of any structure is selected. Whether or not to do so must be determined by comparing the advantages and disadvantages of each.

  Further, in the above-described embodiment, the lower flow with respect to the gravity direction of the cooling water is retained, while the upper flow with respect to the gravity direction is circulated in the fuel cell system. However, the present invention is not limited to this, and the upper flow with respect to the direction of gravity may be retained so that the lower flow circulates with respect to the direction of gravity. Also by this, since the flow rate of the circulating cooling water can be reduced, the temperature of the cooling water can be raised quickly, and warming can be completed in a short time.

  Specifically, a first butterfly valve and a second butterfly valve are provided in the upper part of the pipe along the direction of the flow of the cooling water, and the flow of the cooling water flowing upward is prevented by these butterfly valves. do it. In this case, since the downward flow is not hindered, the flow rate of the circulating cooling water can be reduced.

It is a partial block diagram of the fuel cell system in this Embodiment. (A) And (b) is a top view of the butterfly valve applicable to this Embodiment. It is an example of the cross-sectional schematic diagram of the detour of the fuel cell system in this Embodiment. In the present embodiment, (a) is a flowchart showing control of the circulating amount of the cooling water, and (b) shows the relationship between the rotational speed of the circulating pump and the temperature of the cooling water, and the valve opening of the butterfly valve. FIG. It is another example of the cross-sectional schematic diagram of the detour of the fuel cell system in this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell 3 Circulation pump 4 Radiator 5 Circulation path 6 Detour 7 Thermo valve 8 Weir 9, 10 Junction point 11 Piping 12 Level | step difference 81 Butterfly valve 82 Valve body 83 Valve shaft 84 Valve casing 85 Ring packing 86 Opening part

Claims (6)

A fuel cell;
A coolant flow path for cooling the fuel cell, a heat exchanger for cooling the coolant, and a circulation path for circulating the coolant between the fuel cell;
A flow path for the coolant that bypasses the heat exchanger, with both ends connected to the circulation path;
A switching valve that switches the flow path of the coolant to either one of the flow path that passes through the heat exchanger and the flow path that passes through the bypass.
The fuel flow path is provided with a weir for blocking a part of the cooling liquid and adjusting a circulation amount when the cooling liquid circulates through the bypass. Battery system.   The fuel cell system according to claim 1, wherein the heat exchanger is a radiator.   The fuel cell system according to claim 1, wherein the weir is provided in the bypass.   The fuel cell system according to claim 1, comprising a plurality of the weirs.   The fuel cell system according to any one of claims 1 to 4, wherein a downward flow with respect to a gravity direction of the coolant is blocked by the weir.   The fuel cell system according to claim 1, wherein the weir is a butterfly valve.

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