Fuel cell module

Abstract

To provide a configuration that can reliably remove corrosion of a contact of a contact switch.SOLUTION: A fuel cell module includes a fuel cell, a contact switch, a capacitor, a discharge resistor, a current circuit, and a controller. The contact switch is provided on a path for supplying power from the fuel cell to an electrical device for consuming power generated by the fuel cell, and can cut off the supply of power from the fuel cell to the electrical device. The capacitor can store the power generated by the fuel cell. The discharge resistor consumes the power generated by the fuel cell. The current circuit uses the power stored in the capacitor to pass a current through the discharge resistor and the contact switch. The controller controls the contact switch and the current circuit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuel cell module.

Background Art

[0002] In many cases, a device or circuit for supplying power to an electrical device includes a switch for interrupting the power supply. For example, a vehicle such as an industrial vehicle includes a switch (such as a contactor or a relay) for interrupting the power supply between a power source such as a fuel cell and various devices.

[0003] A switch for supplying / interrupting power is realized, for example, by a contact switch. The contact switch is controlled to be in an ON state or an OFF state in response to an instruction from a controller. The ON state (or closed state) is a state where the contacts are in contact with each other, and current flows through the contact switch. The OFF state (or open state) is a state where the contacts are not in contact with each other, and the power supply is interrupted in the contact switch.

[0004] However, depending on the usage mode of the contact switch, the contact resistance of the contacts may increase. For example, when silicon oxide or the like adheres to the contacts, the contact resistance increases, and there is a risk that the voltage applied to the electrical device may decrease.

[0005] For this reason, a method for removing corrosion of the switch contacts has been proposed. For example, Patent Document 1 describes a method for removing corrosion of contacts by flowing a corrosion removal current larger than the current flowing during normal operation when corrosion is presumed to have occurred at the contacts of the switch.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, techniques for removing corrosion of contacts of a contact switch have been proposed. However, in the conventional technology, the procedure for removing contact corrosion is not always reliably executed. For example, in a configuration in which a corrosion removal current is passed when it is presumed that corrosion has occurred on the contacts of a switch, a voltage drop may occur when the presumption is incorrect.

[0008] An object according to one aspect of the present invention is to provide a configuration capable of reliably removing corrosion of contacts of a contact switch.

Means for Solving the Problems

[0009] A fuel cell module according to one aspect of the present invention includes a fuel cell, a contact switch provided on a path for supplying power from the fuel cell to an electrical device that consumes the power generated by the fuel cell, the contact switch being capable of interrupting the supply of power from the fuel cell to the electrical device, a capacitor capable of storing the power generated by the fuel cell, a discharge resistor that consumes the power generated by the fuel cell, a current circuit that passes a current through the discharge resistor and the contact switch using the power stored in the capacitor, and a controller that controls the contact switch and the current circuit.

[0010] According to this configuration, by passing a current through the contact switch using the power stored in the capacitor, oxides and the like adhering to the contacts can be removed. Therefore, the contacts of the switch can be cleaned when the fuel cell is not generating power. Further, since a current is passed through the contact switch via the discharge resistor used during the warm-up operation of the fuel cell, there is no need to add a dedicated component.

[0011] In the fuel cell module configured as described above, when the controller receives a stop instruction to stop the fuel cell, it opens and closes the contact switch a predetermined number of times while closing the current circuit. According to this configuration, when the fuel cell stops, the contacts of the switch are cleaned, so it is possible to reliably avoid a situation where oxides or the like adhere to the contacts and the output voltage decreases.

[0012] Also, in the fuel cell module configured as described above, when a start instruction to start the fuel cell is received during the operation of opening and closing the contact switch, the controller may stop the operation of opening and closing the contact switch and return the current circuit to the open state. In this case, after stopping the operation of opening and closing the contact switch, when the controller opens and closes the contact switch in response to the next stop instruction, the contact switch may be opened and closed by the number of times that have not been executed out of the predetermined number of times.

[0013] Furthermore, the fuel cell module configured as described above may further include a voltage sensor that detects a voltage drop in the contact switch when power is supplied to the electrical device via the contact switch. In this case, when the voltage drop or the resistance value of the contact switch calculated based on the voltage drop exceeds a predetermined threshold value, the controller opens and closes the contact switch while closing the current circuit in response to the stop instruction. According to this configuration, when it is expected that oxides or the like are not attached to the contacts of the switch, the operation of opening and closing the switch is not performed.

[0014] Note that the fuel cell module configured as described above is mounted on a vehicle, for example. In this case, the stop instruction is generated in response to a key-off operation for stopping the vehicle.

Advantages of the Invention

[0015] According to the above aspect, corrosion of the contacts of the contact switch can be reliably removed.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0017] FIG. 1 shows an example of the configuration of a fuel cell module according to an embodiment of the present invention. The fuel cell module 10 according to an embodiment of the present invention is mounted on and used in the vehicle 1 in this example. The vehicle 1 is, for example, an industrial vehicle such as a forklift. However, the vehicle 1 is not limited to an industrial vehicle and may be a passenger car or the like.

[0018] The fuel cell module 10 includes a fuel cell 11, a DC / DC converter 12, a capacitor 13, a discharge resistor 14, a contact switch 15, and a fuel cell controller 16. However, the fuel cell module 10 may include other devices, circuits, and elements not shown in FIG. 1.

[0019] In this example, the fuel cell 11 is composed of a cell stack in which a plurality of fuel cells are stacked. Therefore, the fuel cell may be called an "FC (Fuel Cell) stack". Each fuel cell generates electric power by electrochemically reacting hydrogen and oxygen through an electrolyte. For example, by adjusting the amount of hydrogen and / or air supplied to the fuel cell according to the demand from an external load, the electric power required by the external load is generated. In FIG. 1, the configuration for supplying hydrogen to the fuel cell 11, the configuration for supplying air to the fuel cell 11, the configuration for circulating hydrogen, etc. are omitted.

[0020] The DC / DC converter 12 converts the output voltage of the fuel cell 11 into a specified voltage. Note that the DC / DC converter 12 may be a step-down DC / DC converter or a step-up DC / DC converter.

[0021] The power generated by the fuel cell 11 is supplied to the load 21 via the DC / DC converter 12 and the power lines PL1a, PL1b. The load 21 is a device mounted on the vehicle 1 and operates using the power generated by the fuel cell 11. The load 21 may be a driving motor of the vehicle 1, or in the case where the vehicle 1 is a forklift, it may be a cargo handling motor.

[0022] The load 21 is controlled by the vehicle controller 22. The vehicle controller 22 is, for example, an ECU (Electronic Control Unit) including a processor and a memory, and operates using the power supplied from the capacitor 13 via the power lines PL2a, PL2b. Note that the power supplied to the vehicle controller 22 is smaller than the power supplied to the load 21. Therefore, the current flowing through the power lines PL2a, PL2b is smaller than the current flowing through the power lines PL1a, PL1b. Note that the load 21 and the vehicle controller 22 are an example of electrical devices that consume the power generated by the fuel cell 11.

[0023] The capacitor 13 can store the electric power generated by the fuel cell 11. The positive terminal of the capacitor 13 is connected to the power line PL1a by the power line PL3a, and the negative terminal of the capacitor 13 is connected to the power line PL1b by the power line PL3b. Here, a relay RL1 for electrically connecting / disconnecting the power line PL1a and the capacitor 13 is provided on the power line PL3a. Note that the fuel cell module 10 may supply electric power from the capacitor 13 to the load 21. Also, the fuel cell module 10 may store electric power in the capacitor 13 during the operation of the load 21. The capacitor 13 is an example of a capacitor that stores the electric power generated by the fuel cell 11. Therefore, the fuel cell module 10 may include, for example, a rechargeable battery as a capacitor instead of the capacitor 13.

[0024] The discharge resistor 14 is connected to the power lines PL3a and PL1b by the power lines PL4a and PL4b, respectively. That is, one terminal of the discharge resistor 14 is connected to the power line PL3a by the power line PL4a, and the other terminal of the discharge resistor 14 is connected to the power line PL1b by the power line PL4b. Here, a relay RL2 for electrically connecting / disconnecting the power line PL3a and the discharge resistor 14 is provided on the power line PL4a. A relay RL3 for electrically connecting / disconnecting the discharge resistor 14 and the power line PL1b is provided on the power line PL4b.

[0025] A contact switch 15 is provided on one of the power lines PL2a and PL2b for supplying electric power from the fuel cell module 10 to the vehicle controller 22. In this embodiment, the contact switch 15 is provided on the power line PL2a. The contact switch 15 can electrically connect / disconnect the capacitor 13 and the vehicle controller 22. That is, the contact switch 15 permits or blocks the supply of electric power from the fuel cell module 10 to the vehicle controller 22.

[0026] The fuel cell module 10 includes a voltage sensor V that measures the voltage drop across the contact switch 15 (or the voltage across both ends of the contact switch 15). One terminal of the contact switch 15 (here, the terminal on the fuel cell 11 side) is electrically connected to the power line PL4b via the power line PL5a, and the other terminal of the contact switch 15 (here, the terminal on the vehicle controller 22 side) is electrically connected to the power line PL3b via the power line PL5b. Further, the fuel cell module 10 includes relays RL4 and RL5 connected in series to the contact switch 15 on the power line PL2a. The relay RL4 can electrically connect / disconnect the capacitor 13 and the contact switch 15. The relay RL5 can electrically connect / disconnect the contact switch 15 and the vehicle controller 22.

[0027] The fuel cell module 10 further includes a current circuit that uses the power stored in the capacitor 13 to pass a current through the discharge resistor 14 and the contact switch 15. This current circuit includes power lines PL3a and PL4a that electrically connect the positive terminal of the capacitor 13 and one terminal of the discharge resistor 14, power lines PL4b and PL5a that electrically connect the other terminal of the discharge resistor 14 and one terminal of the contact switch 15, and power lines PL5b and PL3b that electrically connect the other terminal of the contact switch 15 and the negative terminal of the capacitor 13.

[0028] The fuel cell controller 16 is an ECU that includes a processor and a memory, and controls the operation of the fuel cell module 10 in response to an instruction from a higher-level system (not shown). For example, the fuel cell controller 16 activates the fuel cell module 10 in response to a key-on operation of the vehicle 1, generates power from the fuel cell 11 in response to a power request from the load 21 or the vehicle controller 22, and stops the fuel cell module 10 in response to a key-off operation of the vehicle 1. At this time, the fuel cell controller 16 controls the states of the contact switch 15 and the relays RL1 to RL5. Further, the fuel cell controller 16 may control the operation of the fuel cell module 10 based on the voltage drop across the contact switch 15 detected by the voltage sensor V.

[0029] In the fuel cell module 10 configured as described above, when the fuel cell controller 16 receives the key-on operation of the vehicle 1, it activates the fuel cell module 10. Here, a warm-up operation may be performed in the fuel cell module 10. For example, when starting the fuel cell module 10 in a low-temperature environment, a warm-up operation is performed to melt the ice around the fuel cell 11. Also, since the fuel cell 11 has a high power generation efficiency when operating around 70°C, a warm-up operation may be performed before supplying power to the load.

[0030] During the warm-up operation, the fuel cell controller 16 controls, for example, the relays RL1 to RL3 to be in the on state and the relays RL4 and RL5 to be in the off state. Then, the fuel cell controller 16 starts the power generation of the fuel cell 11. Then, the fuel cell 11 itself generates heat and the temperature rises. At this time, the power generated by the fuel cell 11 is not supplied to the load 21 and the vehicle controller 22 but is consumed in the discharge resistor 14. After the temperature of the fuel cell 11 rises to the target temperature, the fuel cell module 10 shifts to an operation mode of supplying power to the load 21 and the vehicle controller 22.

[0031] When operating the load 21, the fuel cell controller 16 controls the relays RL1, RL4, RL5, and the contact switch 15 to be in the on state and the relays RL2 and RL3 to be in the off state. Then, the power generated by the fuel cell 11 is supplied to the load 21 via the DC / DC converter 12, and power is supplied from the capacitor 13 to the vehicle controller 22. At this time, if the power required from the load 21 is small, power is stored in the capacitor 13.

[0032] Incidentally, generally, the contacts of a contact switch are formed of a predetermined metal material, and corrosion progresses according to the use environment. For example, an oxide film such as a silicon oxide film adheres to the surface of the metal material constituting the contact. Then, the electrical resistance at the contact of the switch increases, and the voltage drop in the switch increases, so the voltage applied to the load decreases. In the fuel cell module 10, if an oxide film adheres to the contacts of the contact switch 15, there is a risk that the voltage applied to the vehicle controller 22 will decrease.

[0033] Note that the oxide film adhering to the contacts of the switch is generally removed when a large current flows through the switch. However, in the fuel cell module 10, the power required by the vehicle controller 22 is small, and the current flowing through the contact switch 15 during normal operation is small. Also, if a large current flows through the contact switch 15 during normal operation, there is a risk that the vehicle controller 22 will malfunction.

[0034] Therefore, the fuel cell module 10 according to the embodiment of the present invention uses the discharge resistor 14 provided for performing a warm-up operation to remove the oxide film adhering to the contacts of the contact switch 15. In the following description, removing the oxide film adhering to the contacts may be referred to as "refreshing".

[0035] When refreshing the contacts, the fuel cell controller 16 forms a closed circuit that allows current to flow through the discharge resistor 14 and the make contact switch 15 using the power stored in the capacitor 13. Specifically, the fuel cell controller 16 controls the relay RL2 to the on state and controls the relays RL1, RL3 - RL5 to the off state. Thereby, a current circuit is formed from the positive electrode of the capacitor 13, through the power line PL3a, the relay RL2, the power line PL4a, the discharge resistor 14, the power line PL4b, the power line PL5a, the make contact switch 15, the power line PL5b, and the power line PL3b, to the negative electrode of the capacitor 13. Also, the relay RL5 cuts off the path between the fuel cell module 10 and the vehicle controller 22 so that a large current flowing through this current circuit does not flow into the vehicle controller 22.

[0036] Here, assume that the capacitor 13 stores a voltage between the positive and negative electrodes of about 40 - 50V. Also, assume that the resistance value of the discharge resistor 14 is about 10 ohms. Then, a current of 4 - 5 amperes flows through this current circuit.

[0037] With the above - described current circuit formed, the fuel cell controller 16 opens and closes the make contact switch 15. That is, the make contact switch 15 repeatedly alternates between the on state and the off state. At this time, the opening and closing operation of the make contact switch 15 is repeated a predetermined number of times at a predetermined period. Although not particularly limited, this opening and closing operation is performed 100 times, for example, at a period of 2 - 3 seconds. As a result, the oxide adhering to the contacts of the make contact switch 15 is removed.

[0038] Figure 2 is a flowchart showing an example of the refresh method according to an embodiment of the present invention. In this example, assume that the fuel cell module 10 is supplying power to a load (in the example shown in FIG. 1, the load 21 and the vehicle controller 22).

[0039] In S1, the fuel cell controller 16 measures the resistance value between the terminals of the make contact switch 15 using the voltage sensor V. When the current flowing through the make contact switch 15 (in the example shown in FIG. 1, the current flowing from the fuel cell module 10 to the vehicle controller 22) is substantially constant and known, the resistance value between the terminals of the make contact switch 15 can be obtained based on the voltage drop across the make contact switch 15. Further, when the current flowing through the make contact switch 15 is not constant, the current flowing from the fuel cell module 10 to the vehicle controller 22 is measured, and the resistance value between the terminals of the make contact switch 15 is obtained by dividing the measured current value by the voltage drop across the make contact switch 15. In this case, the fuel cell module 10 includes a current sensor that measures the current flowing from the fuel cell module 10 to the vehicle controller 22.

[0040] In S2, the fuel cell controller 16 waits for a stop instruction to stop the fuel cell module 10. This stop instruction is generated by the upper system, for example, when the vehicle 1 is turned off by the user of the vehicle 1. Then, when the stop instruction is received, the process of the fuel cell controller 16 proceeds to S3.

[0041] In S3, the fuel cell controller 16 stops the power generation of the fuel cell 11. At this time, the fuel cell controller 16 stops the supply of hydrogen and air to the fuel cell 11. It is assumed that the capacitor 13 has sufficiently stored power at this point.

[0042] In S4, the fuel cell controller 16 compares the resistance value between the terminals of the contact switch 15 with a predetermined threshold value. This threshold value is an index for determining whether the contacts of the contact switch 15 are corroded by an oxide film or the like, and is determined in advance based on experiments or the like. If the resistance value between the terminals of the contact switch 15 is smaller than the threshold value, the fuel cell controller 16 determines that the contacts of the contact switch 15 are not corroded. In this case, the processes of S5 to S6 are skipped. On the other hand, when the resistance value between the terminals of the contact switch 15 is larger than the threshold value, the fuel cell controller 16 determines that the contacts of the contact switch 15 are corroded and executes the processes of S5 to S6.

[0043] In S5, the fuel cell controller 16 forms a current circuit for flowing a current through the discharge resistor 14 and the contact switch 15 by using the electric power stored in the capacitor 13. At this time, the relay RL2 provided between one terminal (for example, the positive electrode) of the capacitor 13 and one terminal of the discharge resistor 14 is controlled to be in an on state. Also, the relays RL1, RL3 to RL5 are controlled to be in an off state. Thereby, the above-described current circuit becomes a closed circuit, and a state in which a current flows through the discharge resistor 14 and the contact switch 15 is configured.

[0044] In S6, the fuel cell controller 16 opens and closes the contact switch 15 a predetermined number of times at a predetermined cycle. Thereby, a state in which the contacts of the contact switch 15 come into contact with each other and a large current flows and a state in which the contacts are separated from each other and no current flows are alternately repeated, and oxides or the like adhering to the contacts are removed.

[0045] Thus, in the embodiment of the present invention, when the operation of the fuel cell module 10 ends, the contacts of the make contact switch 15 are refreshed. Therefore, the voltage applied to the load (in the example shown in FIG. 1, the vehicle controller 22) does not decrease. Also, when refreshing the contacts, a current is passed from the capacitor 13 to the make contact switch 15 through the discharge resistor 14. Here, the discharge resistor 14 used in the warm-up operation is provided in many fuel cell modules. Therefore, an appropriate level of current can be generated without adding new components to perform contact refreshing.

[0046] Note that in the above procedure, the fuel cell controller 16 does not necessarily need to measure or calculate the resistance value between the terminals of the make contact switch 15. That is, the fuel cell controller 16 may always refresh the contacts of the make contact switch 15 at the end of the operation of the fuel cell module 10 regardless of whether the resistance value between the terminals of the make contact switch 15 has increased. In this case, compared with the procedure shown in FIG. 2, since the frequency of refreshing the contacts increases, the number of times the make contact switch 15 is opened and closed in one refresh may be reduced. For example, when 100 open / close operations are performed in S6 shown in FIG. 2, in the case where the contacts of the make contact switch 15 are always refreshed at the end of the operation of the fuel cell module 10, 50 open / close operations may be sufficient. According to this procedure, the time required for one refresh is reduced.

[0047] FIG. 3 is a flowchart showing another example of the refreshing method according to the embodiment of the present invention. Note that S1 to S5 are substantially the same in FIGS. 2 and 3. That is, when the resistance value between the terminals of the make contact switch 15 is large, the fuel cell controller 16 forms a current circuit when receiving a stop instruction.

[0048] In S11, the fuel cell controller 16 determines whether an interruption flag is set. The interruption flag indicates whether the refresh operation has been executed to the end. In this embodiment, the state in which the interruption flag is set indicates that the previous refresh operation has not been executed to the end.

[0049] If the interruption flag is not set, the fuel cell controller 16 opens and closes the make-and-break switch 15 a predetermined number of times at a predetermined period in S6, in the same procedure as shown in FIG. 2. On the other hand, when the interruption flag is set, the fuel cell controller 16 opens and closes the make-and-break switch 15 by the number of unprocessed times in the previous refresh operation in S12. For example, assume that the make-and-break switch 15 is opened and closed 100 times in a normal refresh operation. Also, assume that the previous refresh operation ended when the make-and-break switch 15 was opened and closed 60 times. That is, in the previous refresh operation, 40 open / close operations are unprocessed. In this case, 40 open / close operations are performed in S12.

[0050] In S13, the fuel cell controller 16 waits for a start instruction to start the fuel cell module 10. This start instruction is generated by the upper system when the vehicle 1 is keyed on by the user of the vehicle 1. Also, the fuel cell controller 16 waits for this start instruction during the period when the make-and-break switch 15 is being opened and closed in S6 or S12. And if the processing in S6 or S12 ends before the start instruction is received, the processing of the fuel cell controller 16 ends.

[0051] When the start instruction is received before the processing in S6 or S12 ends, the fuel cell controller 16 aborts the refresh operation in S14. That is, the fuel cell controller 16 aborts the opening and closing of the make-and-break switch 15 and returns the current circuit for flowing a current through the discharge resistor 14 and the make-and-break switch 15 using the power stored in the capacitor 13 to an open state. At this time, at least the relay RL2 is controlled to an off state.

[0052] Subsequently, at S15, the fuel cell controller 16 records the number of unprocessed times in the refresh operation. For example, assume that the make-and-break switch 15 is opened and closed 100 times in a normal refresh operation. Also, assume that in the case where S6 is executed, a startup instruction is received when the make-and-break switch 15 is opened and closed 70 times. In this case, "30" is recorded as the number of unprocessed times. Further, the fuel cell controller 16 sets an interrupt flag. The number of unprocessed times and the interrupt flag are used when the procedure of the flowchart shown in FIG. 3 is executed next. Note that in other embodiments shown in FIG. 3, the procedure of determining whether to perform a refresh based on the resistance value between the terminals of the make-and-break switch 15 may be omitted.

Explanation of Reference Numerals

[0053] 1 Vehicle 10 Fuel cell module 11 Fuel cell 12 DC / DC converter 13 Capacitor (electric storage device) 14 Discharge resistor 15 Make-and-break switch 16 Fuel cell controller 21 Load 22 Vehicle controller

Claims

1. A fuel cell, a contact switch provided on a path for supplying power from the fuel cell to an electrical device that consumes the power generated by the fuel cell, and capable of interrupting the supply of power from the fuel cell to the electrical device, a capacitor capable of storing the power generated by the fuel cell, a discharge resistor that consumes the power generated by the fuel cell, a current circuit that uses the power stored in the capacitor to pass a current through the discharge resistor and the contact switch, a controller that controls the contact switch and the current circuit, A fuel cell module comprising the above.

2. When the controller receives a stop instruction to stop the fuel cell, the controller opens and closes the contact switch a predetermined number of times while keeping the current circuit in a closed state. The fuel cell module according to claim 1, characterized in that.

3. During the operation of opening and closing the contact switch, when the controller receives a start instruction to start the fuel cell, the controller stops the operation of opening and closing the contact switch and returns the current circuit to an open state. The fuel cell module according to claim 2, characterized in that.

4. After stopping the operation of opening and closing the contact switch, when the controller opens and closes the contact switch in response to the next stop instruction, the controller opens and closes the contact switch by the number of times that have not been executed among the predetermined number of times. The fuel cell module according to claim 3, characterized in that.

5. Further comprising a voltage sensor that detects a voltage drop across the contact switch when power is being supplied to the electrical device through the contact switch, When the voltage drop or the resistance value of the contact switch calculated based on the voltage drop exceeds a predetermined threshold value, the controller opens and closes the contact switch while keeping the current circuit in a closed state in response to the stop instruction. The fuel cell module according to claim 2, characterized in that.

6. The fuel cell module is mounted on a vehicle, The stop instruction is generated in response to a key-off operation for stopping the vehicle. The fuel cell module according to claim 2, characterized in that.

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