JP5098133B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system suitable for mounting in a vehicle.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-47149, a fuel cell system is known. The fuel cell included in the conventional system has an electrode layer, a diffusion layer, and a plurality of current-carrying portions on the anode side and the cathode side, respectively. An electrolyte layer is provided between the anode-side electrode layer and the cathode-side electrode layer.

On the anode side, hydrogen H ₂ is supplied to the electrode layer through the diffusion layer. In the electrode layer, hydrogen is ionized to generate electrons e ⁻ . The generated electron e ⁻ passes through the diffusion layer to reach the current-carrying portion, and is then transmitted to the outside of the fuel cell. Further, the hydrogen ions H ⁺ reach the electrode layer on the cathode side through the electrolyte layer.

On the cathode side, air is supplied to the electrode layer through the diffusion layer. Further, the electron e ⁻ transmitted from the outside of the fuel cell is supplied to the electrode layer on the cathode side. As a result, in the cathode electrode layer, oxygen O ₂ in the air, hydrogen ions H ⁺ , and electrons e ⁻ react to generate water H ₂ O.

  The fuel cell generates electrical energy by causing the above-described chemical reaction between the electrode layer on the anode side and the electrode layer on the cathode side. Since this chemical reaction is an exothermic reaction, the temperature of the fuel cell gradually increases after startup. On the other hand, the energy generation efficiency of the fuel cell is better as the temperature is higher. For this reason, the startability of the fuel cell becomes better as the temperature rise after startup becomes faster.

In the conventional system described above, a part of the plurality of energization parts is separated from the diffusion layer when the fuel cell is started. In this case, on the anode side, all the electrons e ⁻ generated in the electrode layer move intensively toward a part of the current-carrying part that maintains contact with the diffusion layer. As a result, some of the electrons e ⁻ follow a detour path as compared with the case where all of the energization units are in contact with the diffusion layer. In this system, at the time of starting the fuel cell, a part of the current-carrying part is made from the diffusion layer even on the cathode side. For this reason, a phenomenon occurs in which the electron e ⁻ moves along a detour path also on the cathode side.

The heat generation effect accompanying the movement of the electron e ⁻ increases as the movement distance increases. For this reason, when the electron e ⁻ moves along a detour path, the diffusion layer is heated more efficiently than when the movement is performed at the shortest distance, that is, the temperature rise of the fuel cell is accelerated. be able to. Therefore, according to the conventional system, it is possible to give a good startability to the fuel cell.

JP 2004-47149 A

  A fuel cell usually has a structure in which a plurality of cells are stacked. In addition, current collecting plates are disposed on both sides of the plurality of cells. Each of the plurality of cells has the above-described structure on the anode side and the cathode side, and is stacked so as to be connected in series with each other. Conductive wires are connected to the anode-side current collector plate and the cathode-side current collector plate, respectively, and the electric energy generated by the fuel cell is extracted to the outside through the conductive wires.

  The current collector plate and the conductive wire are required to have excellent conductivity. For this reason, they are usually formed of a highly conductive material such as copper. However, highly conductive materials such as copper generally exhibit high thermal conductivity. For this reason, a conductive wire functions as a kind of heat sink. And the heat radiation amount by a conductive wire becomes so large that the contact area of a conductive wire and a current collecting plate is large.

  In order to quickly increase the temperature when the fuel cell is started up, it is desirable that the amount of heat released by the conductive wire is small. Therefore, in order to obtain good starting characteristics, it is preferable that the contact area between the current collector plate and the conductive wire is small. However, the contact area between the current collector plate and the conductive wire needs to be sufficiently secured in order to reduce the power loss accompanying power transmission. For this reason, in the conventional structure, it was difficult to suppress the heat radiation from the conductive wire. In this regard, the above-described conventional fuel cell system leaves room for further improvement in increasing the temperature rising rate of the fuel cell at the time of startup.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell system that can sufficiently suppress the amount of heat released from a conductive wire without increasing transmission loss. And

In order to achieve the above object, a first invention is a fuel cell system,
A fuel cell comprising a current collector plate at the end of a plurality of stacked cells;
A conductive wire disposed outside the fuel cell and electrically connected to the current collector;
A conductive area variable mechanism that is disposed between the current collector plate and the conductive wire so as to be in contact with the current collector plate, and that can change the contact area between the two through a conductive material ;
The conductive area variable mechanism is
A plurality of movable conductive parts that are made of the conductive material and selectively realize an ON state that contacts both the current collector plate and the conductive wire, and an OFF state that is separated from at least one of the two,
Characterized Rukoto and an actuator for driving the movable conductive portion.

A second invention is a fuel cell system for achieving the above object,
A fuel cell comprising a current collector plate at the end of a plurality of stacked cells;
A conductive wire disposed outside the fuel cell and electrically connected to the current collector;
A conductive area variable mechanism that is disposed between the current collector plate and the conductive wire so as to be in contact with the current collector plate, and that can change the contact area between the two through a conductive material;
The conductive area variable mechanism is
A slide member disposed between the current collector plate and the conductive wire;
An actuator for driving the slide member,
The slide member includes a slide conductive portion formed of the conductive material, and a slide low heat conductive portion formed to mold the slide conductive portion with a material having a lower thermal conductivity than the slide conductive portion. Prepared,
The actuator drives the slide member so that a contact area of the slide conductive portion with respect to both the current collector plate and the conductive wire changes.

According to a third aspect of the present invention, in the first or second aspect of the present invention , the fuel cell includes a temperature detection unit that detects a temperature of the fuel cell, and the conductive area variable mechanism reduces the contact area as the temperature of the fuel cell decreases. It is characterized by being made small.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the apparatus includes a start-up temperature detecting unit that detects a start-up temperature of the fuel cell. The increase in the contact area is delayed.

Further, a fifth aspect of the present invention is the method of the third or fourth aspect , further comprising an atmospheric temperature detecting unit that detects an atmospheric temperature surrounding the fuel cell, and the conductive area variable mechanism increases in temperature as the atmospheric temperature decreases. The increase of the contact area with respect to is delayed.

According to a sixth invention, in any one of the third to fifth inventions,
Water amount detection means for detecting the amount of water produced by the operation of the fuel cell;
A stop water amount storage means for storing the water generation amount when the fuel cell is stopped as a stop water amount;
The conductive area variable mechanism delays the increase of the contact area with respect to a temperature rise as the amount of water at the stop is larger.

  According to the first invention, the contact area between the current collector plate and the conductive wire can be changed by changing the state of the conductive area variable mechanism. For this reason, according to the present invention, by ensuring a large contact area, it is possible to create a state in which transmission loss can be sufficiently suppressed even when large power is generated. Further, by reducing the contact area, it is possible to create a state in which the amount of heat released from the conductive wire can be sufficiently suppressed.

Further, according to this invention, the movable conductive portion by the ON state by the actuator, it is possible to secure a large contact area between the current collector plate and the conductive line. Further, the contact area can be reduced by turning the movable conductive portion OFF by the actuator.

According to the second invention, by driving the slide member by the actuator, the contact area between the current collector plate and the conductive wire can be continuously increased or decreased steplessly. Furthermore, according to the present invention, the slide conductive portion is molded by the slide low heat conductive portion. According to such a structure, sufficient reliability can be given to the slide conductive portion.

According to the third invention, the contact area between the current collector plate and the conductive portion can be reduced as the temperature of the fuel cell is lower. The fuel cell does not generate a large amount of power at low temperatures. For this reason, if the contact area is reduced at low temperatures and the contact area is increased at high temperatures, the transmission loss can always be kept small. Furthermore, if the contact area is reduced at low temperatures, the amount of heat released from the conductive wire can be reduced at low temperatures, and the startability of the fuel cell can be improved.

According to the fourth aspect of the invention, the lower the startup temperature of the fuel cell, the slower the contact area increase with respect to the temperature rise. The amount of water generated before the temperature of the fuel cell rises to a specific temperature increases as the starting temperature decreases. In addition, from the viewpoint of preventing freezing of water in the fuel cell, the necessity of suppressing heat dissipation from the conductive wire at the time of startup increases as the amount of water in the fuel cell increases. According to the present invention, the necessity can be met by changing the increasing tendency of the contact area according to the temperature at start-up.

According to the fifth aspect of the invention, the lower the ambient temperature surrounding the fuel cell, the slower the increase in the contact area with respect to the temperature rise. The temperature of the fuel cell at the start-up is less likely to increase as the atmospheric temperature is lower. For this reason, the necessity to suppress the heat radiation from the conductive wire at the start-up becomes greater as the atmospheric temperature is lower. According to the present invention, the necessity can be met by changing the increasing tendency of the contact area according to the atmospheric temperature.

According to the sixth aspect of the invention, the larger the amount of water at the time of stoppage, that is, the greater the amount of water already present in the fuel cell at the time of startup, the more the increase in contact area with respect to the temperature rise can be delayed. The necessity of suppressing heat dissipation from the conductive wire at the time of starting the fuel cell increases as the amount of water in the fuel cell increases. According to the present invention, the necessity can be met by changing the increasing tendency of the contact area according to the amount of water at the time of stoppage.

Embodiment 1 FIG.
[Overall Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining an outline of a fuel cell system according to Embodiment 1 of the present invention. More specifically, FIG. 1A is a diagram for explaining a state after the fuel cell is warmed up. On the other hand, FIG. 1 (B) is a diagram for explaining a state immediately after the start of the fuel cell.

  As shown in FIG. 1B, the system of this embodiment includes a fuel cell 10. The fuel cell 10 has a structure in which a plurality of cells 12 are stacked. A current collecting plate 14 is laminated on the uppermost cell 12. Similarly, a current collector plate 14 is laminated under the lowermost cell 12. The current collector plate 14 is made of a highly conductive material such as copper.

  The current collecting plate 14 has a conductive area variable mechanism 16 incorporated therein. The conductive area variable mechanism 16 includes a plurality of movable conductive portions 18. Each movable conductive portion 18 is a columnar member made of a highly conductive material such as copper, like the current collector plate 14. The current collector plate 14 is provided with a storage space (not shown) in which the movable conductive portion 18 can be stored for a predetermined length. On the other hand, the movable conductive portion 18 is configured to be displaced in the axial direction using the storage space. Furthermore, the conductive area variable mechanism 16 includes an actuator (not shown) for causing the movable conductive portion 18 to move as described above. For this reason, each movable conductive part 18 can expand and contract the protruding part from the current collector plate 14 by being driven by an actuator.

  Conductive wires 20 are arranged in the vicinity of the conductive area variable mechanism 16. The conductive wire 20 is a power line for connecting the anode and the cathode of the fuel cell 10 to an external device, and is made of a highly conductive material such as copper, like the current collector plate 14. All the movable conductive portions 18 included in the conductive area variable mechanism 16 can be in contact with the end face of the conductive wire 20 by being displaced in the extending direction. Hereinafter, this state is referred to as an “ON state” of the movable conductive portion 18. Further, the movable conductive portion 18 can be separated from the end face of the conductive wire 20 by being displaced in the reduction direction. Hereinafter, this state is referred to as an “OFF state” of the working conductive portion 18.

  FIG. 1B shows a state in which the upper conductive area variable mechanism 16 has one movable conductive portion 18 turned on and all other movable conductive portions 18 are turned off. On the other hand, FIG. 1A shows a state in which the conductive area mechanism 16 has turned all the movable conductive parts 18 to the ON state. As will be described later, the system of the present embodiment realizes the state shown in FIG. 1B when the fuel cell 10 is started at a low temperature, and when the fuel cell 10 has sufficiently warmed up, FIG. A state shown in A) is realized.

  The substantial contact area between the current collector plate 14 and the conductive wire 20 is determined by the number of movable conductive portions 18 in the ON state. Therefore, according to the system of this embodiment, when the fuel cell 10 is started at a low temperature, the contact area can be reduced, and the contact area can be increased when the fuel cell 10 is warmed up.

[Cell structure and operation]
FIG. 2 is a cross-sectional view for explaining the structure of one cell 12 included in the fuel cell 10. As shown in FIG. 2, the cell 12 has an electrolyte layer 22. On both sides of the electrolyte layer 22, an anode side electrode layer 24 and a cathode side electrode layer 26 are provided, respectively. The surface of the anode electrode layer 24 is covered with a diffusion layer 28. Similarly, the surface of the cathode side electrode layer 26 is covered with a diffusion layer 30.

The surfaces of the diffusion layers 28 and 30 are covered with current-carrying portions 32 and 34, respectively. Part of the diffusion layers 28 and 30 are in contact with the gas flow paths 36 and 38, respectively. Hydrogen H ₂ circulates in the gas flow path 36 on the anode side. On the other hand, air, that is, a gas containing oxygen O ₂ circulates in the gas flow path 38 on the cathode side.

The diffusion layers 28 and 30 are porous conductive materials, permitting gas flow and charge transfer. Hydrogen H ₂ flowing through the anode-side gas flow path 36 reaches the anode-side electrode layer 24 via the diffusion layer 28. As a result, in the anode side electrode layer 24, hydrogen ions H ⁺ and electrons e ⁻ are generated by the following reaction.
^{H2 → 2H + + 2e - ···} (1)

Electrons e ⁻ generated by the above reaction reach the current-carrying portion 32 through the diffusion layer 28 and propagate from there to the outside of the cell 12. Further, the hydrogen ions H ⁺ generated together with the electrons e ⁻ pass through the electrolyte 22 and reach the cathode side electrode layer 26. Furthermore, electrons e ⁻ supplied from the outside of the cell 12 and oxygen O ₂ supplied from the gas flow path 38 reach the cathode side electrode layer 26. As a result, the following reaction occurs in the cathode side electrode layer 26.
_{^{4H + + 4e - + O 2}} → 2H 2 O ··· (2)

  Each cell 12 of the fuel cell 10 generates electric energy while generating water by causing the reactions (1) and (2) above. Since this reaction is an exothermic reaction, as long as the reaction continues, the temperature of the fuel cell 10 gradually increases after startup. However, when the starting temperature of the fuel cell 10 is below the freezing point, the water generated in the cathode side electrode layer 26 may freeze and cover the surface.

Under the condition where the surface of the cathode side electrode layer 26 is covered with ice, the oxygen O ₂ supplied from the gas flow path 38 cannot reach the cathode side electrode layer 26, and thus the reaction (2) occurs. I don't get it. In this case, the melting of ice does not proceed because no heat is generated. As a result, the operation of the fuel cell is stopped. For this reason, in order to continuously operate the fuel cell 10 in an extremely low temperature environment, it is necessary to reliably avoid freezing of water inside the cell 12. For this purpose, it is effective to reduce the amount of heat released from the fuel cell 10 as much as possible.

[Operation of variable conductive area mechanism]
FIG. 3 is a diagram for explaining the electrical configuration of the system of the present embodiment. As shown in FIG. 3, the system of this embodiment includes an ECU (Electronic Control Unit) 40. An ECU 40 is connected to an intake air temperature sensor 42 that detects the outside air temperature THA and an actuator 44 that drives the movable conductive portion 18 described above.

  FIG. 4 is a flowchart for explaining the contents of processing executed by the ECU 40 shown in FIG. 3 in the present embodiment. As shown in FIG. 4, in this routine, it is first determined whether or not the activation of the fuel cell 10 is requested (step 100).

  Until the start of the fuel cell 10 is requested, the process of step 100 is repeatedly executed. When the start-up is requested, the start-up temperature Tint of the fuel cell 10 is detected (step 102).

  The temperature of the fuel cell 10 converges to the outside temperature THA when a sufficient stop time has elapsed. For this reason, in the present embodiment, the outside temperature THA at the time of startup of the fuel cell 10 is handled as the startup temperature Tint. Therefore, in step 102, specifically, the outside air temperature THA detected by the intake air temperature sensor 42 is detected as the starting temperature Tint of the fuel cell 10.

  Next, it is determined whether the startup temperature Tint is 0 ° C. or less (step 104). As a result, if it is determined that the startup temperature Tint is not 0 ° C. or less, the actuators 44 are driven so that all the movable conductive portions 18 are turned on (step 106).

  When all the movable conductive portions 18 are turned on, a large contact area is secured between the current collector plate 14 and the conductive wires 20. The highly conductive material that constitutes the movable conductive portion 18 and the conductive wire 20 exhibits a high thermal conductivity as well as a high conductivity. For this reason, the larger the contact area between the current collector plate 14 and the conductive wire 20, the more difficult it is to generate a loss when current is exchanged between the two, while the heat generated in the fuel cell 10 is transmitted through the conductive wire 20. Easily released to the outside.

  When the starting temperature Tint of the fuel cell 10 exceeds 0 ° C., it can be determined that there is no possibility that water will freeze in the fuel cell 10 at that time. Further, since the reaction occurring inside the fuel cell 10 is an exothermic reaction, if the starting temperature Tint exceeds 0 ° C, the temperature T of the fuel cell 10 does not fall below 0 ° C thereafter. Therefore, in this case, it is not always necessary to reduce the heat radiation amount from the fuel cell 10 to the conductive wire 20.

  On the other hand, under a temperature environment in which the temperature T exceeds 0 ° C., the fuel cell 10 exhibits a certain amount of power generation capability. For this reason, it is desirable to ensure a sufficiently large contact area between the current collector plate 14 and the conductive wire 20 in order to suppress loss due to current transmission.

  As described above, according to the routine shown in FIG. 4, when the starting temperature Tint exceeds 0 ° C., all the movable conductive parts 18 are immediately turned ON, and the current collecting plate 14 is electrically connected. A maximum contact area is ensured between the lines 20. For this reason, according to the system of this embodiment, under such a temperature environment, the fuel cell 10 can be favorably started up while ensuring high energy efficiency.

  In the routine shown in FIG. 4, when it is determined in step 104 that the startup temperature Tint is 0 ° C. or less, the actuator 44 is turned off so that the state of FIG. 1B is formed. (Step 108). Specifically, the actuator 44 is driven so that all other variable conductive portions 18 are turned off except for one variable conductive portion 18. As a result, the contact area between the current collector plate 14 and the conductive wire 20 is minimized.

  If the contact area between the current collector plate 14 and the conductive wire 20 is minimized, the amount of heat transferred from the fuel cell 10 to the conductive wire 20 can be minimized, and a state advantageous for heating the fuel cell 10 can be created. In addition, the fuel cell 10 cannot generate large electric energy in a low temperature environment where the temperature T is 0 ° C. or less. For this reason, under such a temperature environment, even if the contact area between the current collector plate 14 and the conductive wire 20 is minimized, an unreasonably large loss does not occur with power transmission.

  Therefore, in an environment where Tint ≦ 0 ° C. is established, the amount of heat transferred from the fuel cell 10 to the conductive wire 20 is minimized without increasing the loss associated with power transmission by executing the processing of step 108. Can be stopped. As a result, freezing of water inside the fuel cell 10 can be effectively prevented, and the startability of the fuel cell 10 at low temperatures can be improved.

  In the routine shown in FIG. 4, following the process of step 108, it is determined whether or not the temperature raising condition of the fuel cell 10 is satisfied (step 109). The temperature rise condition is determined to be established when the temperature T of the fuel cell 10 is estimated to have risen to 0 ° C. or higher. The ECU 40 counts the elapsed time after the start of the fuel cell 10. The time required for the fuel cell 10 to reach 0 ° C. can be determined as a function of the startup temperature Tint. In step 109, specifically, it is determined that the temperature raising condition is satisfied when the elapsed time after the start reaches the required time.

  If the establishment of the temperature raising condition is denied in step 109, the process of step 108 is executed again. As a result, the state where the contact area is minimized is maintained. On the other hand, if it is confirmed in step 109 that the temperature raising condition is established, all the movable conductive portions 18 are turned on by the processing in step 106. As a result, the contact area is maximized, and a state suitable for a large current flow is realized.

  As described above, according to the routine shown in FIG. 4, when the temperature of the fuel cell 10 is low and there is a possibility that water freezes inside, the contact area between the current collector plate 14 and the conductive wire 20 is increased. As a minimum, it is possible to create a state suitable for preventing freezing. Further, when the fuel cell 10 has been warmed up and the possibility of freezing has been eliminated, the contact area can be increased to create a state suitable for a large current flow. For this reason, according to the system of the present embodiment, the startability of the fuel cell 10 can be effectively improved without causing a large power transmission loss.

  By the way, in Embodiment 1 mentioned above, it is supposed that the conductive area variable mechanism 16 includes the three movable conductive portions 18 and changes the states of the two movable conductive portions 18 (see FIG. 1). It is not limited to this. That is, in Embodiment 1, the ratio between the maximum contact area and the minimum contact area is 3: 1, but the ratio is not limited to this. That is, the ratio between the maximum contact area and the minimum contact area may be a larger value, for example, about 10: 1.

  Moreover, in Embodiment 1 mentioned above, although all the electroconductive parts with which the electroconductive area variable mechanism 16 is provided shall be the variable electroconductive parts 18, this invention is not limited to this. That is, the conductive part that maintains the ON state when realizing the minimum contact area may be a fixed conductive part instead of the movable conductive part.

  In the first embodiment described above, the OFF state is realized by separating the movable conductive portion 18 from the conductive wire 20, but the present invention is not limited to this. That is, the movable conductive portion 18 may be separated from the current collector plate 14 to realize the OFF state.

  In the first embodiment described above, only the upper contact area variable mechanism 16 shown in FIG. 1B is turned ON / OFF, but the present invention is not limited to this. That is, the contact area variable mechanism 16 may be turned ON / OFF on both the anode side and the cathode side.

In the first embodiment described above, the success or failure of the temperature raising condition is determined based on the elapsed time after startup, but the determination method is not limited to this. For example, the temperature T of the fuel cell 10 may be measured and the success or failure of the temperature raising condition may be determined based on the measured temperature T. Further, the temperature T is estimated by a known method based on the current I _FC and voltage V _FC information generated by the fuel cell 10 and the startup temperature Tint of the fuel cell 10, and the temperature is increased based on the estimated temperature T. The success or failure of the condition may be determined.

In the first embodiment described above, the contact area is reduced only when the temperature is low, but the reference for switching the contact area is not limited to the temperature T. For example, the smaller the current I _FC generated by the fuel cell 10, the smaller the contact area.

  In the first embodiment described above, the state of the variable conductive portion 18 is switched from the OFF state to the ON state when the temperature T of the fuel cell 10 is estimated to have reached 0 ° C. However, the temperature T is not limited to this. That is, the switching temperature T may be any temperature that can prevent freezing inside the fuel cell 10 and may be set as appropriate according to the system specifications.

In the first embodiment described above, the “temperature detecting means” according to claim 3 is realized by the ECU 40 detecting the temperature Tint at the time of activation and counting the elapsed time after the activation. By executing the processing of steps 104 to 109, the “conductive area variable mechanism” according to claim 3 is realized.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. 5 and FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 6 described later in place of the routine shown in FIG. 4 in the system of the first embodiment.

  In the first embodiment described above, the contact area between the current collector plate 14 and the conductive wire 20 is changed in two stages. On the other hand, the system of the present embodiment is characterized in that the contact area is switched in multiple stages as the temperature T increases. FIG. 5 is a timing chart for explaining the operation of the movable conductive portion 18 in the system of the present embodiment.

  In the system of the present embodiment, as in the case of the first embodiment, the current collecting plate 14 and the conductive wire 20 are turned on by turning on / off two of the three movable conductive portions 18 included in the conductive area variable mechanism 16. The contact area is switched. In FIG. 5, the waveforms indicated by the symbols “CH1” and “CH2” indicate how the two movable conductive portions 18 are switched according to the temperature T of the fuel cell 10.

  As shown in FIG. 5, in the region where the temperature T is −20 ° C. or lower, both the CH1 movable conductive portion 18 and the CH2 movable conductive portion 18 are turned off. In this case, the contact area between the current collector plate 14 and the conductive wire 20 is minimized. When the temperature T exceeds −20 ° C., only the movable conductive portion 18 of CH1 is turned on. When the temperature T exceeds 0 ° C., all the movable conductive parts 18 are turned on, and the contact area is maximized.

  According to the above operation, after the fuel cell 10 is started, the contact area between the current collector plate 14 and the conductive wire 20 can be gradually increased in the process in which the temperature T gradually increases. The necessity to suppress the heat radiation from the conductive wire 20 gradually decreases as the temperature T increases. On the other hand, the necessity of reducing the power transmission loss between the current collector plate 14 and the conductive wire 20 gradually increases as the temperature T increases. According to the control described above, by turning on the variable conductive portion 18 step by step, it is possible to meet these requirements.

[Specific Processing in Second Embodiment]
FIG. 6 is a flowchart of a routine executed by the ECU 40 in the present embodiment in order to realize the above function. In FIG. 6, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

That is, in the routine shown in FIG. 6, after the start-up temperature Tint is detected by the process of step 102, information on the current I _FC and the voltage V _FC of the fuel cell 10 is acquired (step 110). Next, the temperature T of the fuel cell 10 is calculated (step 112). The current I _FC and the voltage V _FC have a correlation with the heat generation amount of the fuel cell 10. Therefore, when the current I _FC and the voltage V _FC are known together with the startup temperature Tint, the temperature T of the fuel cell 10 can be estimated by a known method.

  Next, it is determined whether or not the temperature T of the fuel cell 10 is −20 ° C. or lower (step 114). As a result, when the establishment of T ≦ −20 ° C. is recognized, it can be determined that the necessity of suppressing the heat radiation from the conductive wire 20 is extremely high. In this case, the movable conductive portions 18 of CH1 and CH2 are both turned off, and the contact area is minimized (step 116). Thereafter, the processing after step 110 is executed again.

  If it is denied in step 114 that T ≦ −20 ° C., it is next determined whether or not the temperature T is 0 ° C. or less (step 118). As a result, when it is determined that T ≦ 0 ° C. is established, it can be determined that it is still necessary to avoid heat dissipation from the conductive wire 20. In this case, only the movable conductive portion 18 of CH1 is turned on, and the contact area is set to an intermediate value (step 120). Thereafter, the processing after step 110 is executed again.

  If it is determined in step 118 that T ≦ 0 ° C. is not established, it can be determined that the possibility of freezing of water inside the fuel cell 10 is low. In this case, in addition to the movable conductive portion 18 of CH1, the movable conductive portion 18 of CH2 is also turned on, and the contact area is maximized (step 122).

  As described above, according to the routine shown in FIG. 6, the contact area between the current collector plate 14 and the conductive wire 20 can be gradually changed in three stages according to the temperature T of the fuel cell 10. For this reason, according to the system of the present embodiment, the effect of improving the startability of the fuel cell 10 while suppressing power transmission loss can be realized more satisfactorily than the system of the first embodiment. it can.

  In the second embodiment described above, the temperature T of the fuel cell 10 is estimated and printed based on the current IFC and the voltage VFC, but the present invention is not limited to this. That is, the estimation of the temperature T of the fuel cell 10 may be performed based on the elapsed time after activation.

  In the second embodiment described above, the contact area between the current collector plate 14 and the conductive wire 20 is switched in three stages, but the present invention is not limited to this. That is, it is possible to switch the contact area in more stages after incorporating more variable conductive portions 18 into the conductive area variable mechanism 16.

In the second embodiment described above, the ECU 40 executes the processing of steps 102, 110, and 112, thereby realizing the “temperature detection means” according to claim 3 and the step 114. The “conductive area variable mechanism” according to claim 3 is realized by executing the processes of .about.122.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 7 is a perspective view for explaining the configuration and operation of the conductive area variable mechanism 50 used in the present embodiment. More specifically, FIG. 7A shows a state of the conductive area variable mechanism 50 when the contact area between the current collector plate 14 and the conductive wire 20 is maximized. FIG. 7B shows the state of the conductive area variable mechanism 50 when the contact area is reduced.

  The system of the present embodiment is realized by arranging the conductive area variable mechanism 50 in place of the conductive area variable mechanism 16 in the system shown in FIG. 1 and causing the ECU 40 to execute a routine shown in FIG. be able to. As shown in FIG. 7, the conductive area variable mechanism 16 used in this embodiment includes two fixing members 52 and 54 and a slide member 56 sandwiched between them.

  The fixing member 52 includes a fixed conductive portion 58 and a fixed low heat conductive portion 60. The fixed conductive portion 58 is made of a highly conductive material such as copper, like the current collector plate 14 and the like. On the other hand, the fixed low thermal conductive portion 60 is a member for molding the fixed conductive portion 58 and is made of a resin having a sufficiently low thermal conductivity compared to copper or the like. The fixing member 54 has the same configuration as that of the fixing member 52, and includes a fixed conductive portion 62 and a fixed low thermal conductivity portion 64.

  The slide member 56 has the same configuration as the fixed members 52 and 54 except that the slide member 56 can slide between the fixed members 52 and 54. That is, the slide member 56 includes a slide conductive portion 66 made of a highly conductive material and a slide low heat conductive portion 68 that molds the slide conductive portion 66.

  The fixing member 52 is disposed so that the end surface of the fixed conductive portion 58 is in contact with the current collector plate 14. The fixing member 54 is disposed so that the end surface of the fixed conductive portion 62 is in contact with the conductive wire 20. The conductive area variable mechanism 50 includes an actuator 44 (not shown), and can slide the slide member 56 in response to a command from the ECU 40.

  FIG. 7A shows a state in which the slide member 56 is controlled to a position where it overlaps with the fixing members 52 and 54 (hereinafter referred to as “reference position”). The contact area between the current collector plate 14 and the conductive wire 20 is maximized when the conductive area variable mechanism 50 takes this state. The contact area is continuously reduced by sliding the slide member 56 from the reference position. For this reason, in the system of this embodiment, by controlling the position of the slide member 56, the contact area between the current collector plate 14 and the conductive wire 20 can be continuously expanded or reduced.

[Specific Processing in Embodiment 3]
FIG. 8 is a flowchart of a routine executed by the ECU 40 in the present embodiment. In FIG. 8, the same steps as those shown in FIG. 4 or FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 8, after the fuel cell 10 is activated, the temperature T of the fuel cell 10 is calculated in the same manner as in the second embodiment (steps 100 to 112). Subsequent to step 112, the slide amount S to be given to the slide member 56 is calculated (step 130).

FIG. 9 is a map stored in the ECU 40 in order to calculate the slide amount S. In this map, the slide amount S is such that the minimum value is “zero” in the region where the temperature T exceeds 0 ° C., and the slide amount S increases as the temperature T decreases in the region where −30 <T ≦ 0 ° C. In the region of T ≦ −30 ° C., the maximum value S _MAX is set. In step 130, a slide amount S corresponding to the temperature T of the fuel cell 10 is set according to this map.

Next, the actuator 44 is driven so that the set slide amount S is realized. The slide member 56 is controlled to the reference position shown in FIG. 7A when the slide amount S is zero, and the slide member 56 is controlled to a position farther from the reference position as the slide amount S is larger. The maximum slide amount S _MAX is a value that ensures a minimum contact area between the current collector plate 14 and the conductive wire 20. Therefore, the contact area between the current collector plate 14 and the conductive wire 20 decreases toward the minimum value as the temperature T of the fuel cell 10 decreases, and is maximized in a region where the temperature T exceeds 0 ° C.

  In the routine shown in FIG. 8, it is next determined whether or not the temperature T exceeds 0 ° C. (step 134). As a result, when it is recognized that T> 0 ° C. is not established, the process of step 110 is executed again. On the other hand, when establishment of T> 0 ° C. is recognized, it is determined that the contact area has reached the maximum value, and the current process is completed.

  As described above, according to the routine shown in FIG. 8, when the fuel cell 10 is started, the contact area between the current collector plate 14 and the conductive wire 20 can be increased steplessly as the temperature T rises. it can. For this reason, according to the system of the present embodiment, the effect of improving the startability of the fuel cell 10 while suppressing power transmission loss can be realized more satisfactorily than the system of the second embodiment. it can.

  Further, in the system of the present embodiment, the conductive portions that ensure the contact between the current collector plate 14 and the conductive wires 20, that is, the fixed conductive portions 58 and 62 and the slide conductive portion 66 are fixed to the fixed low heat traditional portions 60 and 64 and the slide. Each of them is molded by the low heat conduction part 68. According to such a structure, the impact resistance and corrosion resistance of those conductive portions can be increased, and the reliability of the contact area variable mechanism 50 can be increased. For this reason, according to the system of the present embodiment, superior reliability can be realized as compared with the case of the first or second embodiment.

  In the above-described third embodiment, the slide amount S is set based on the temperature T of the fuel cell 10, but the present invention is not limited to this. That is, the slide amount S may be set based on the starting temperature Tint of the fuel cell 10 and the elapsed time after starting.

Embodiment 4 FIG.
[Features of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 10 described later in place of the routine shown in FIG. 4 in the system of the first embodiment.

  In the systems of the first to third embodiments described above, when the fuel cell 10 is started, the contact area between the current collector plate 14 and the conductive wire 20 is changed according to an increase in the temperature T of the fuel cell 10. More specifically, in these systems, a contact area according to the temperature T of the fuel cell 10 is secured between the current collector plate 14 and the conductive wire 20.

  By the way, the amount of water generated inside the fuel cell 10 does not necessarily correspond to the temperature T itself of the fuel cell 10. For example, the amount of water generated when the temperature of the fuel cell 10 rises to −5 ° C. is when the startup temperature Tint is −20 ° C. or when it is −10 ° C. And not the same. That is, comparing these cases, more exothermic reaction is required when the temperature T is raised from −20 ° C. to −5 ° C. As a result, more water is generated inside the fuel cell 10. Can be guessed.

  The purpose of reducing the amount of heat released from the fuel cell 10 is mainly to prevent freezing of water. In the fuel cell 10, freezing is more likely to occur as the amount of water generated increases. For this reason, even if the temperature T of the fuel cell 10 is the same, the necessity for suppressing the amount of heat release increases as the amount of water generated increases. For this reason, in the system of the present embodiment, the contact area between the current collector plate 14 and the conductive wire 20 is increased as the temperature T of the fuel cell 10 increases, and at the same time, the amount of water is predicted to be large. As the starting temperature Tint is lower, the increase in the contact area with respect to the increase in the temperature T is delayed.

[Specific Processing in Embodiment 4]
FIG. 10 is a flowchart of a routine executed by the ECU 40 in the present embodiment. The routine shown in FIG. 10 is the same as the routine shown in FIG. 6 except that the processing following step 112 is changed to steps 140 to 146 instead of steps 114 to 122. In FIG. 10, the same steps as those shown in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 10, when the fuel cell 10 is started, following the calculation of the temperature T (steps 100 to 112), the correction temperature F (T, Tint) is calculated according to the following equation (step 140).
F (T, Tint) = T + 0.2 * (Tint + 20) (3)

  In the above equation (3), 0.2 * (Tint + 20) is a correction value for reflecting the amount of water generated at the time of startup to the correction temperature F (T, Tint). This correction value is zero when the starting temperature Tint is −20 ° C., negative when Tint is lower than −20 ° C., and positive when Tint is higher than −20 ° C. Become. That is, the correction temperature F (T, Tint) is set to a value lower than the actual temperature T when the startup temperature Tint is lower than −20 ° C., whereas the startup temperature Tint is higher than −20 ° C. In this case, the temperature is higher than T.

  In the routine shown in FIG. 10, it is next determined whether the correction temperature F (T, Tint) is equal to or lower than the determination temperature, or specifically equal to or lower than −10 ° C. (step 142). As a result, when the establishment of F (T, Tint) ≦ −10 ° C. is recognized, it is determined that there is a strong demand for suppressing the heat radiation to the conductive wire 20, and the variable conductive portion 18 is turned off. The actuator 44 is driven (step 144). In this case, the processing after step 110 is executed again thereafter.

  On the other hand, in the above-described step 142, when F (T, Tint) ≦ −10 ° C. is not established, it is determined that the necessity to suppress the heat radiation to the conductive wire 20 is reduced, and the variable conductive portion 18 is The actuator 44 is driven so as to be in the ON state (step 146). As a result, the contact area between the current collector plate 14 and the conductive wire 20 is maximized, and a state in which power transmission loss is minimized is realized.

  As described above, in the routine shown in FIG. 10, the contact area is expanded based on whether or not the correction temperature F (T, Tint) has reached the determination temperature (−10 ° C.). If the temperature T is the same, the corrected temperature F (T, Tint) is calculated as a lower value as the startup temperature Tint is lower. Therefore, according to the routine shown in FIG. 10, the lower the startup temperature Tint, the higher the temperature T at which the contact area is expanded. For this reason, according to the system of this embodiment, the state where importance is placed on prevention of heat dissipation can be maintained for a long period of time as the amount of water present in the fuel cell 10 increases. As a result, according to the system of the present embodiment, the effect of improving the startability of the fuel cell 10 is always realized satisfactorily while suppressing power transmission loss regardless of the difference in the amount of water inside the fuel cell 10. be able to.

  By the way, in Embodiment 4 mentioned above, it is supposed that the contact area of the current collecting plate 14 and the conductive wire 20 will be changed in two steps, However, This invention is not limited to this. That is, as in the case of the second embodiment, the contact area may be switched in more stages. Further, as in the case of the third embodiment, the contact area may be continuously changed steplessly.

  In the fourth embodiment described above, the influence of the startup temperature Tint is reflected on the correction temperature F (T, Tint) to change the tendency of the contact area to increase with respect to the increase in temperature T. However, the present invention is not limited to this. That is, a similar function may be realized by reflecting the startup temperature Tint on the judgment temperature (here, −10 ° C.) side.

In the fourth embodiment described above, the ECU 40 executes step 102 shown in FIG. 10 so that the “starting temperature detection means” in the fourth invention executes the processing of steps 140 to 146. Thus, the “conductive area variable mechanism” in the fourth invention is realized.

Embodiment 5 FIG.
[Features of Embodiment 5]
Next, Embodiment 5 of the present invention will be described with reference to FIG. 11 and FIG. The system of the present embodiment is realized by causing the ECU 40 to execute a routine shown in FIG. 11 and a routine shown in FIG. 12 described later instead of the routine shown in FIG. 4 in the system of the first embodiment. Can do.

  As described in the description of the fourth embodiment, the necessity of suppressing the heat radiation from the conductive wire 20 increases as the amount of water generated in the fuel cell 10 increases. This amount of water is determined by the amount of water generated after starting up the fuel cell 10 and the amount of water already present when the fuel cell 10 is started up. Further, the amount of water present at the time of startup can be regarded as the amount of water that was present when the fuel cell 10 was stopped. For this reason, in the present embodiment, the amount of water that was present when the fuel cell 10 was stopped was reflected in the control of the contact area variable mechanism 16 during the subsequent activation.

[Specific Processing in Embodiment 5]
(Detection of water amount Aw0 when stopped)
FIG. 11 is a flowchart of a routine that is executed by the ECU 40 in the present embodiment to detect the amount of water present in the fuel cell 10 when stopped. This routine is a routine that is repeatedly activated at predetermined time intervals while the fuel cell 10 is operating.

In this routine, first, information regarding the resistance R _FC of the fuel cell 10 is acquired (step 150). Next, the outside air temperature THA is detected based on the output of the intake air temperature sensor 42 (step 152). Further, information regarding the current I _FC generated by the fuel cell 10 is acquired (step 154).

The amount of water generated by the fuel cell 10 has a correlation with the current I _FC . Further, the amount of water present inside the fuel cell 10 can be obtained as a function of the resistance R _FC of the fuel cell 10 and the outside temperature THA. Therefore, if the resistance R _FC , the outside air temperature THA, and the current IFC are known, it is possible to estimate and print the total amount of water present in the fuel cell 10 at each moment. Following the processing of step 154, the ECU 40 calculates the amount of water Aw in the fuel cell 10 based on the detected values by a known method (step 156).

  Next, it is determined whether or not the stop of the fuel cell 10 is requested (step 158). As a result, if it is determined that a stop request has not occurred, the current process is completed. On the other hand, when the stop request is accepted, the water amount Aw calculated at that time is stored as the stop water amount Aw0 (step 160).

(Control of contact area at startup)
FIG. 12 is a flowchart of a routine executed by the ECU 40 in order to control the contact area between the current collector plate 14 and the conductive wire 20 when the fuel cell 10 is started. The routine shown in FIG. 12 is the same as the routine shown in FIG. 10 except that steps 170 and 172 are inserted after step 102 and steps 174 and 176 are inserted instead of step 140. is there. In FIG. 12, the same steps as those shown in FIG. 10 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  That is, in the routine shown in FIG. 12, when the fuel cell 10 is started, the reading process of the stop time water amount Aw0 is executed (step 170) following the reading process of the starting temperature Tint (step 102). Subsequently, a water amount correction value K = f (Aw0) is calculated based on the stopped water amount Aw0 (step 172). Here, the water amount correction value K becomes the minimum value zero when the stop time water amount Aw0 is zero, and is set to a larger value as the amount of Aw0 increases.

  In the routine shown in FIG. 12, after the correction temperature F (T, Tint) is calculated in step 140, the final correction temperature F ′ is calculated according to the following equation (step 174). As a result, the final correction temperature F ′ is calculated to be lower than the correction temperature F (T, Tint) by the water amount correction value K. F '= F (T, Tint) -K (4)

  In the routine shown in FIG. 12, next, it is determined whether the final correction temperature F ′ is equal to or lower than the determination temperature, or specifically equal to or lower than −10 ° C. (step 176). As a result, if F ′ ≦ −10 ° C. is established, the variable conductive portion 18 is turned off (step 144). On the other hand, if F ′ ≦ −10 ° C. does not hold, the variable conductive portion 18 is turned on (step 146).

  As described above, in the routine shown in FIG. 12, the contact area is expanded based on whether or not the final correction temperature F ′ has reached the determination temperature (−10 ° C.). If the temperature T and the startup temperature Tint are the same, the final correction temperature F ′ is calculated as a lower value as the water amount correction value K is larger. That is, the final corrected temperature F ′ is calculated to be lower as the stop water amount Aw0 is larger. Therefore, according to the routine shown in FIG. 12, the temperature T at which the contact area is expanded at the time of start-up shifts to the higher temperature side as the stop water amount Aw0 increases. For this reason, according to the system of this embodiment, the state where importance is placed on prevention of heat dissipation can be maintained for a long period of time as the amount of water present in the fuel cell 10 increases. As a result, according to the system of the present embodiment, the effect of improving the startability of the fuel cell 10 can be realized satisfactorily while suppressing power transmission loss regardless of the amount of water at the time of stoppage. .

  By the way, in the systems of the first to fifth embodiments described above, it is assumed that the startup temperature Tint of the fuel cell 10 is equal to the atmospheric temperature THA. However, when a sufficient stop time is not secured, the startup temperature Tint of the fuel cell 10 may be higher than the atmospheric temperature THA. In order to cope with such a situation, a temperature sensor that measures the temperature T of the fuel cell 10 may be provided, and the stop-time temperature Tint may be detected from the output value of the sensor.

  In such a case, even if the stop-time temperature Tint is the same, if the atmospheric temperature THA is different, a difference occurs in the temperature rise characteristics when the fuel cell 10 is started. In other words, even when the stop-time temperature Tint is the same, the amount of water that is generated when the fuel cell 10 causes a desired temperature rise increases as the atmospheric temperature THA decreases. When the fuel cell 10 is started up, the more water is generated, the more necessity for preventing heat dissipation. For this reason, when the starting temperature Tint and the atmospheric temperature THA are different, the temperature T at which the contact area is expanded when the fuel cell 10 is started may be shifted to a higher temperature as the atmospheric temperature THA is lower. .

In the above-described fifth embodiment, the ECU 40 can realize the “atmospheric temperature detecting means” in the fifth invention by detecting the atmospheric temperature THA. Further, the ECU 40 shifts the expansion temperature T of the contact area to the higher temperature side as the atmospheric temperature THA is lower, thereby realizing the “conductive area variable mechanism” in the fifth aspect of the invention.

Further, here, the ECU 40 executes the processing of the above steps 150 to 156, so that the “water amount detecting means” in the sixth invention executes the processing of the above steps 158 and 160, thereby the sixth invention. The “stopped water amount storage means” in FIG. 6 executes the processes of steps 170, 172, 174, and 176, thereby realizing the “conductive area variable mechanism” in the sixth aspect of the invention.

It is a figure for demonstrating the whole structure of Embodiment 1 of this invention. It is sectional drawing for demonstrating the cell structure of the fuel battery | cell shown in FIG. It is a figure for demonstrating the electrical structure of the system of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a timing chart for demonstrating operation | movement of Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the structure and operation | movement of a contact area variable mechanism used in Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. FIG. 9 is a map of a slide amount S referred to during execution of the routine shown in FIG. 8. It is a flowchart of the routine performed in Embodiment 4 of this invention. In Embodiment 5 of this invention, it is a flowchart of the routine performed in order to detect the water quantity at the time of a stop. In Embodiment 5 of this invention, it is a flowchart of the routine performed in order to control a contact area.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 12 Cell 14 Current collecting plate 16, 50 Contact area variable mechanism 18 Movable conductive part 20 Conductive line 40 ECU (Electronic Control Unit)
56 Slide member 66 Slide conductive part 68 Slide low heat conductive part

Claims (6)

A fuel cell comprising a current collector plate at the end of a plurality of stacked cells;
A conductive wire disposed outside the fuel cell and electrically connected to the current collector;
A conductive area variable mechanism that is disposed between the current collector plate and the conductive wire so as to be in contact with the current collector plate, and that can change the contact area between the two through a conductive material ;
The conductive area variable mechanism is
A plurality of movable conductive parts that are made of the conductive material and selectively realize an ON state that contacts both the current collector plate and the conductive wire, and an OFF state that is separated from at least one of the two,
The fuel cell system according to claim Rukoto and an actuator for driving the movable conductive portion. A fuel cell comprising a current collector plate at the end of a plurality of stacked cells;
A conductive wire disposed outside the fuel cell and electrically connected to the current collector;
A conductive area variable mechanism that is disposed between the current collector plate and the conductive wire so as to be in contact with the current collector plate, and that can change the contact area between the two through a conductive material;
The conductive area variable mechanism is
A slide member disposed between the current collector plate and the conductive wire;
An actuator for driving the slide member,
The slide member includes a slide conductive portion formed of the conductive material, and a slide low heat conductive portion formed to mold the slide conductive portion with a material having a lower thermal conductivity than the slide conductive portion. Prepared,
The actuator fuel cell system that is characterized in that for driving the slide member so that the contact area of the sliding conductor part for both of the collector plate and the conductive line is changed. Comprising temperature detecting means for detecting the temperature of the fuel cell;
The conductive area varying mechanism, a fuel cell system according to claim 1 or 2, wherein said fuel cell is characterized in that to reduce the contact area as is at a low temperature. A startup temperature detection means for detecting the startup temperature of the fuel cell;
4. The fuel cell system according to claim 3, wherein the conductive area variable mechanism delays an increase in the contact area with respect to a temperature rise as the startup temperature is lower. An atmospheric temperature detecting means for detecting an atmospheric temperature surrounding the fuel cell;
5. The fuel cell system according to claim 3, wherein the conductive area variable mechanism delays an increase in the contact area with respect to a temperature rise as the atmospheric temperature is lower. Water amount detection means for detecting the amount of water produced by the operation of the fuel cell;
A stop water amount storage means for storing the water generation amount when the fuel cell is stopped as a stop water amount;
6. The fuel cell system according to claim 3, wherein the conductive area variable mechanism delays an increase in the contact area with respect to a temperature rise as the amount of water at the stop is larger.

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