Fuel cell system

Abstract

To provide a highly durable fuel cell system.SOLUTION: A fuel cell system includes a fuel cell stack. The fuel cell system includes an inlet-side sealing valve that is installed at a supply passage where oxidant gas is supplied to the fuel cell stack and that closes when the fuel cell stack is shut down. The fuel cell system includes a pressure regulating valve that is installed at an exhaust passage where used oxidant gas is exhausted from the fuel cell stack and that can control a pressure in the inside of the stack of the oxidant gas by adjusting the opening thereof. The fuel cell system includes a control unit that controls the opening and closing of the inlet-side sealing valve and that also controls the opening of the pressure regulating valve. The control unit calculates the opening of the pressure regulating valve depending on a power generation demand for the fuel cell stack. During a period when the calculated opening is equal to or less than a predetermined opening, the control unit closes the inlet-side sealing valve and maintains the opening of the pressure regulating valve at the predetermined opening or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a fuel cell system. [Background technology]

[0002] Patent Document 1 discloses a fuel cell system in which a pressure regulator is disposed in the exhaust path of the oxidant gas of the fuel cell stack. The pressure of the oxidant gas in the fuel cell stack can be controlled by adjusting the opening of the pressure regulator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-207292 A Summary of the Invention [Problem to be solved by the invention]

[0004] The more the pressure regulating valve operates at a small opening, the more the various components such as the seals wear out. In particular, under heavy use conditions such as commercial use, the fuel cell stack tends to operate and stop repeatedly, resulting in a very large number of operations at a small opening. This can lead to a deterioration in the sealing performance of the pressure regulating valve due to wear. [Means for solving the problem]

[0005] In the fuel cell system described in claim 1, the opening of the pressure regulating valve can be maintained at or above the predetermined opening by closing the inlet side sealing valve during the period when the calculated opening is equal to or less than the predetermined opening. Since the number of operations at a small opening equal to or less than the predetermined opening can be reduced, wear of various members such as seal members can be suppressed. [Brief description of the drawings]

[0006] [Figure 1]1 is a schematic configuration diagram of a fuel cell system 1. FIG. [Diagram 2] 2 is an operation flowchart of the fuel cell system 1 in the first embodiment. [Diagram 3] 10 is an operation flowchart of the fuel cell system 1 in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0007] <Configuration of fuel cell system 1> A fuel cell system 1 will be described with reference to Fig. 1. The fuel cell system 1 is mounted on, for example, a fuel cell vehicle. The fuel cell system 1 mainly comprises a fuel cell stack 10, an air supply path 20a, an air discharge path 20b, a hydrogen supply path 30a, a hydrogen discharge path 30b, and a control unit 40. Note that signal lines are indicated by dotted lines in Fig. 1.

[0008] The fuel cell stack 10 is a device that generates electricity through a chemical reaction between hydrogen and oxygen. Water is produced by the chemical reaction between hydrogen and oxygen. The fuel cell stack 10 includes a plurality of unit cells (not shown). Each unit cell includes a fuel electrode and an air electrode. Electricity is generated by supplying a fuel gas (hydrogen gas) to the fuel electrode and an oxidant gas (air containing oxygen) to the air electrode. The electricity generated by the fuel cell stack 10 is supplied to, for example, a motor that drives a fuel cell vehicle.

[0009] The control unit 40 is a control means for controlling various devices of the fuel cell system 1. The control unit 40 includes a CPU, a memory, and peripheral circuits. The control unit 40 controls the air pump 21, the inlet side sealing valve 22, the pressure adjusting valve 23, the outlet side sealing valve 24, etc., which will be described later, in response to detection signals and the like of each sensor (not shown).

[0010] The air supply passage 20a is connected to an air inlet portion (oxidant gas inlet portion) 11a of the fuel cell stack 10. An air pump 21 and an inlet-side sealing valve 22 are provided in the air supply passage 20a. The air pump 21 is a device for pressurizing and sending air drawn in from the atmosphere to the fuel cell stack 10. The air pump 21 varies its rotation speed in response to a control signal output from a control unit 40, which will be described later, to adjust the amount of air supplied to the fuel cell stack 10. The open / close state of the inlet-side sealing valve 22 is controlled by an open / close command Sa input from the control unit 40.

[0011] The air discharge path 20b is connected to an air outlet portion (oxidant gas outlet portion) 11b of the fuel cell stack 10. The air discharge path 20b is a path for discharging unreacted air present inside the fuel cell stack 10 and water generated by electrochemical reactions to the outside. The air discharge path 20b is provided with an outlet side sealing valve 24 and a pressure regulating valve 23. The open / close state of the outlet side sealing valve 24 is controlled by an open / close command Sb input from the control unit 40.

[0012] The pressure regulating valve 23 is a valve that controls the pressure of the oxidant gas (air) inside the stack based on the opening instruction Sθ input from the control unit 40. Valves of various structures can be used for the pressure regulating valve 23. In this embodiment, the pressure regulating valve 23 is a double eccentric butterfly valve. The pressure regulating valve 23 mainly includes a valve body, a valve element, and a seal material. Inside the cylindrical valve body, a disk-shaped valve element rotates 90 degrees around the valve stem as an axis. The pressure and flow rate of the air can be adjusted by changing the angle (opening) of the valve element relative to the flow direction. In addition, a ring-shaped seal material is disposed in the valve body. When the opening of the valve element becomes equal to or less than a predetermined opening θc, the seal material and the valve element start to come into contact with each other. When the valve body is fully closed, the valve element and the seal material come into close contact with each other, thereby obtaining high sealing performance.

[0013] A hydrogen supply path 30a, which introduces hydrogen as a fuel gas into the fuel cell stack 10, is connected to a hydrogen inlet portion (fuel gas inlet portion) 12a of the fuel cell stack 10. A hydrogen discharge path 30b, which discharges unreacted hydrogen and generated water discharged from the fuel cell stack 10, is connected to a hydrogen outlet portion (fuel gas outlet portion) 12b of the fuel cell stack 10. A detailed description of the hydrogen supply path 30a and the hydrogen discharge path 30b will be omitted.

[0014] <Operation of fuel cell system 1> The process executed by the control unit 40 of the fuel cell system 1 will be described with reference to the flowchart of Fig. 2. The control unit 40 starts the process of Fig. 2 when an operation for starting the operation of the fuel cell system 1 is received from a user.

[0015] In S10, the control unit 40 starts up the fuel cell stack 10. Specifically, it opens the inlet-side sealing valve 22 and the outlet-side sealing valve 24. It also operates the air pump 21 to supply air to the air supply path 20a.

[0016] In S20, the control unit 40 calculates a calculated opening θv of the pressure regulating valve 23 in response to a power generation request for the fuel cell stack 10. For example, a target air flow rate corresponding to a command current value for the fuel cell stack 10 may be calculated, and the calculated opening θv may be obtained based on the target air flow rate.

[0017] In S30, the control unit 40 determines whether the calculated opening θv is equal to or smaller than the predetermined opening θc. If the calculated opening θv is greater than the predetermined opening θc (S30: NO), the process proceeds to S40.

[0018] In S40, the control unit 40 transmits the calculated opening θv as an opening command Sθ to the pressure regulating valve 23. As a result, the opening of the pressure regulating valve 23 is controlled based on the calculated opening θv. Then, the process proceeds to S60.

[0019] On the other hand, if the calculated opening θv is equal to or less than the predetermined opening θc (S30: YES), the process proceeds to S50. In S50, the control unit 40 transmits an opening / closing instruction Sa to the inlet-side sealing valve 22 to instruct it to close. Also, it transmits an opening instruction Sθ to the pressure regulating valve 23 to instruct it to maintain the opening at or above the predetermined opening θc. By closing the inlet-side sealing valve 22 to reduce the air flow rate, it is possible to realize the target air flow rate at a small opening equal to or less than the predetermined opening θc, even when the opening of the pressure regulating valve 23 is maintained at or above the predetermined opening θc. Then, the process proceeds to S60.

[0020] In S60, the control unit 40 judges whether or not to stop the operation of the fuel cell stack 10. One example of a case where operation is stopped is when a stop command is input by the user. If operation is to be continued (S60: NO), the process returns to S20 and the loop process continues. It is preferable that the cycle of the loop process is short enough to obtain a predetermined response speed of the fuel cell system 1. On the other hand, if operation is to be stopped (S60: YES), the process proceeds to S70.

[0021] At S70, the control unit 40 executes a process for stopping the fuel cell stack 10. Specifically, it stops the air pump 21. It also transmits opening / closing instructions Sa and Sb to the inlet side sealing valve 22 and the outlet side sealing valve 24 to close the valves. This makes it possible to seal the area from the inlet side sealing valve 22 through the fuel cell stack 10 to the outlet side sealing valve 24 from the atmosphere. By sealing it from the atmosphere, it is possible to prevent the fuel cell stack 10 from being exposed to the atmosphere during shutdown and from deteriorating.

[0022] <Challenges and Effects> The problem will be explained. When the pressure regulating valve 23 is opened at a small opening equal to or less than the predetermined opening θc, the valve body comes into contact with the sealing material. As a result, the more the pressure regulating valve 23 operates at a small opening equal to or less than the predetermined opening θc, the more the sealing material wears. As a result, there is a risk that the sealing performance of the pressure regulating valve 23 will deteriorate. In particular, under heavy use conditions such as commercial use, the fuel cell stack 10 is repeatedly started and stopped, and as a result, there is a tendency for the number of operations at a small opening equal to or less than the predetermined opening θc to become very frequent. Therefore, wear of the sealing material becomes a problem.

[0023] Therefore, in the technology of this specification, during the period when the calculated opening θv is equal to or less than the predetermined opening θc (S30: YES), the inlet-side seal valve 22 is closed, so that the opening of the pressure regulating valve 23 can be maintained at or above the predetermined opening θc (S50). That is, in the past, the pressure inside the stack was adjusted only by the pressure regulating valve 23, but in the technology of this specification, the pressure inside the stack can be adjusted by using the inlet-side seal valve 22 in addition to the pressure regulating valve 23. As a result, even when the opening of the pressure regulating valve 23 is set to equal to or more than the predetermined opening θc, the target air flow rate at a small opening equal to or less than the predetermined opening θc can be realized. Since the number of operations at a small opening equal to or less than the predetermined opening θc can be reduced, wear of the seal material of the pressure regulating valve 23 can be suppressed. EXAMPLES

[0024] The control process of the fuel cell system 1 according to the second embodiment will be described with reference to the flowchart of Fig. 3. Steps identical to those in the control process of the first embodiment (Fig. 2) are given the same reference numerals and will not be described. Steps unique to the second embodiment are distinguished by adding "a" to the end of the reference numerals.

[0025] If it is determined in S30 that the calculated opening θv is equal to or smaller than the predetermined opening θc (S30: YES), the process proceeds to S32a. In S32a, the control unit 40 determines whether the opening count value Cθc is smaller than the count upper limit value Clim. The opening count value Cθc and the count upper limit value Clim are stored in a memory (not shown) of the control unit 40. The opening count value Cθc is the number of times that the opening of the pressure regulating valve 23 is set to the predetermined opening θc or less. In other words, the opening count value Cθc is the number of times that the pressure regulating valve 23 operates at a small opening equal to or smaller than the predetermined opening θc, and is the number of times that the valve body of the pressure regulating valve 23 comes into contact with the sealing material. The opening count value Cθc may be the accumulated number of times since the fuel cell system 1 was new.

[0026] The count upper limit Clim is the upper limit of the opening count value Cθc at which the pressure regulating valve 23 can maintain a predetermined sealing performance. In other words, when the number of operations at a small opening equal to or less than the predetermined opening θc is smaller than the count upper limit Clim, the wear of the sealing material is within an allowable range. The count upper limit Clim can be determined in advance by a durability test or a simulation.

[0027] If the opening count value Cθc is smaller than the count upper limit Clim (S32a: YES), the process proceeds to S34a. In S34a, the control unit 40 increments the opening count value Cθc stored in the memory by 1. Then, the process proceeds to S40, where the control unit 40 controls the opening of the pressure regulating valve 23 based on the calculated opening θv.

[0028] On the other hand, if the opening count value Cθc is equal to or greater than the count upper limit Clim (S32a: NO), the process proceeds to S50. In S50, the control unit 40 closes the inlet side cutoff valve 22 and maintains the opening of the pressure regulating valve 23 at or greater than the predetermined opening θc.

[0029] <Effects> During the period when the opening count value Cθc is smaller than the count upper limit Clim (S32a: YES), the wear of the seal material of the pressure regulating valve 23 is within the allowable range. Therefore, the air flow rate at the small opening degree equal to or less than the predetermined opening degree θc is controlled only by the pressure regulating valve 23 (S40). On the other hand, when the opening count value Cθc becomes equal to or more than the count upper limit Clim (S32a: NO), the wear of the seal material of the pressure regulating valve 23 may exceed the allowable range. Therefore, the air flow rate at the small opening degree equal to or less than the predetermined opening degree θc is controlled by using the pressure regulating valve 23 and the inlet side seal valve 22 (S50). Since the number of operations at the small opening degree equal to or less than the predetermined opening degree θc can be reduced, further wear of the seal material can be suppressed. The life of the seal material of the pressure regulating valve 23 can be extended. [Explanation of symbols]

[0030] 1: fuel cell system 10: fuel cell stack 20a: air supply path 20b: air exhaust path 21: air pump 22: inlet side sealing valve 23: pressure adjusting valve 24: outlet side sealing valve 40: control unit θc: predetermined opening θv: calculated opening

Claims

[Claim 1] A fuel cell stack; an inlet side sealing valve provided in a supply passage for supplying an oxidant gas to the fuel cell stack, the inlet side sealing valve being closed when the fuel cell stack is stopped; a pressure regulating valve that is provided in a discharge passage through which the used oxidant gas is discharged from the fuel cell stack and that is capable of controlling the pressure of the oxidant gas inside the stack by adjusting an opening degree of the pressure regulating valve; a control unit that controls opening and closing of the inlet side sealing valve and controls an opening degree of the pressure regulating valve; Equipped with The control unit is calculating the opening degree of the pressure regulating valve in response to a power generation request for the fuel cell stack; during a period in which the calculated opening degree is equal to or smaller than a predetermined opening degree, the inlet-side stop valve is closed and the opening degree of the pressure regulating valve is maintained at or larger than the predetermined opening degree; Fuel cell system.

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