Fuel cell system

In a fuel cell system, when fully closing an upstream-side valve, a controller performs controlled fully-closed opening-degree control that adjusts the opening degree of the upstream-side valve to a controlled fully-closing opening degree greater than zero by means of a drive mechanism. Upon determining that, during the controlled fully-closed opening-degree control, there is a leakage of oxidant gas in the upstream-side valve, the controller corrects the controlled fully-closed opening degree to the valve-closing side until reaching a zero-position opening degree at which the amount of leakage of the oxidant gas in the upstream-side valve becomes zero.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a US national phase application based on the PCT International Patent Application No. PCT/JP2018/016258 filed on Apr. 20, 2018, and claiming the priority of Japanese Patent Application No. 2017-103837 filed on May 25, 2017, the entire contents of which are herewith incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a fuel cell system provided with a fuel cell which generates electric power upon receipt of supply of fuel gas and oxidant gas and, more particularly, to a fuel cell system suitable to be mounted in fuel-cell vehicles.

BACKGROUND ART

As one of conventional arts, there is a fuel cell system disclosed in Patent Document 1. This fuel cell system is provided with a fuel cell stack (fuel cells), a gas supply passage for supplying oxidant gas to the fuel cell stack, an upstream-side valve for controlling supply of the oxidant gas to the fuel cell stack, a compressor provided in the gas supply passage, a gas exhaust passage for exhausting the oxidant gas from the fuel cell stack, a downstream-side valve for controlling the exhaust of the oxidant gas from the fuel cell stack, a bypass passage for exhausting the oxidant gas to the gas exhaust passage by detouring around the fuel cell stack, and a bypass valve provided in the bypass passage and configured to regulate a flow rate of the oxidant gas to be made to flow in the bypass passage.

Regarding such a fuel cell system, the present applicant has proposed a Japanese patent application No. 2017-041580, for example, to perform a controlled fully-closed opening-degree control that adjusts an opening degree of an upstream-side valve to a controlled fully-closed opening degree during deceleration of a fuel cell vehicle. Herein, the foregoing controlled fully-closed opening degree is an opening degree which is slightly larger than 0° and at which a valve element is in contact with a seal part provided in a valve seat, thereby keeping a valve-closed state.

RELATED ART DOCUMENTS

Patent Documents

SUMMARY OF INVENTION

Problems to be Solved by the Invention

In the above-mentioned fuel cell system, however, the controlled fully-closed opening-degree control is performed during deceleration in which the vehicle is operated with high frequency. This increases the number of times the opening degree of the upstream-side valve becomes the controlled fully-closed opening degree. Therefore, if the number of times the valve element contacts with the seal part provided in the valve seat increases, the seal part wears down. In such a situation, when the opening degree of the upstream-side valve is adjusted to the controlled fully-closed opening degree, oxidant gas may leak through the upstream-side valve. Thus, unnecessary oxidant gas may be supplied to a fuel cell. This oxidant gas reacts with the fuel gas already supplied to the fuel cell, generating electric power. Consequently, unnecessary electric power may be generated in the fuel cell.

The present disclosure has been made to solve the above problems and has a purpose to provide a fuel cell system capable of preventing unnecessary power generation in a fuel cell.

Means of Solving the Problems

To achieve the above purpose, one aspect of the invention provides a fuel cell system comprising: a fuel cell; an oxidant gas supply passage for supplying oxidant gas to the fuel cell; an upstream-side valve provided in the oxidant gas supply passage, and a controller configured to perform various controls, wherein the upstream-side valve comprises: a valve seat; a valve element; and a drive mechanism configured to drive the valve element to open and close a gap between the valve seat and the valve element, either one of the valve seat and the valve element is provided with a seal member including a seal part that contacts with an other of the valve element and the valve seat during valve-closing, wherein when the upstream-side valve is to be fully closed, the controller is configured to perform a controlled fully-closed opening-degree control that causes the drive mechanism to adjust an opening degree of the upstream-side valve to a controlled fully-closed opening degree that is larger than 0, and while the controlled fully-closed opening-degree control is being performed, when it is determined that leakage of the oxidant gas occurs in the upstream-side valve, the controller is configured to correct the controlled fully-closed opening degree to a valve-closing side until reaching a zero-position opening degree at which a leakage amount of the oxidant gas in the upstream-side valve becomes zero.

According to the above configuration, during execution of the controlled fully-closed opening-degree control, when leakage of oxidant gas occurs due to wear of the seal part in the upstream-side valve, this system can correct the controlled fully-closed opening degree to a valve-closing side according to a wear amount of the seal part to make zero the leakage amount of oxidant gas in the upstream-side valve. Thus, unnecessary supply of oxidant gas to a fuel cell can be reduced. This can prevent unnecessary generation of electric power in the fuel cell. Consequently, auxiliaries or auxiliary machines (AUXS) no longer need to consume electric power for electric discharge in order to consume unnecessary electric power generated in the fuel cell. This can prevent deterioration of fuel consumption and occurrence of noise vibration (NV).

In the foregoing configuration, the controller is configured to determine the leakage amount of the oxidant gas in the upstream-side valve based on a power generation amount of the fuel cell.

According to the above configuration, there is no need to further adopt a supplementary detection means, such as a sensor, for detecting a leakage amount of oxidant gas in the upstream-side valve. Cost reduction can thus be achieved.

In the foregoing configuration, preferably, the power generation amount of the fuel cell is an amount of electric power generated after the oxidant gas remaining in the fuel cell at start of the controlled fully-closed opening-degree control is consumed.

According to the above configuration, the amount of electric power generated in the fuel cell is a power generation amount corresponding to the amount of oxidant gas leaking through the upstream-side valve during execution of the controlled fully-closed opening-degree control. Thus, the system can accurately determine the leakage amount of oxidant gas in the upstream-side valve based on the power generation amount in the fuel cell.

Another aspect of the present disclosure made to solve the aforementioned problems provides a fuel cell system comprising: a fuel cell; an oxidant gas exhaust passage for exhausting oxidant gas supplied to the fuel cell; a downstream-side valve provided in the oxidant gas exhaust passage, and a controller configured to perform various controls, wherein the downstream-side valve comprises: a valve seat; a valve element; and a drive mechanism configured to drive the valve element to open and close a gap between the valve seat and the valve element, either one of the valve seat and the valve element is provided with a seal member including a seal part that contacts with an other of the valve element and the valve seat during valve-closing, wherein when an auxiliaries (AUXS) power-generation request to cause the fuel cell to generate electric power to drive auxiliaries is present, the controller is configured to perform an AUXS power-generation opening-degree control that causes the drive mechanism to adjust an opening degree of the downstream-side valve to an AUXS power-generation opening degree corresponding to a request AUXS power-generation amount, and while the AUXS power-generation opening-degree control is being performed, when it is determined that a flow rate of the oxidant gas in the downstream-side valve is larger than a first predetermined flow rate, the controller is configured to correct the AUXS power-generation opening degree to a valve-closing side until reaching a first target position opening degree at which the flow rate of the oxidant gas in the downstream-side valve becomes the first predetermined flow rate.

According to the foregoing configuration, during execution of the AUXS power-generation opening-degree control, when a flow rate of oxidant gas increases due to wear of the seal part in the downstream-side valve, the system can correct the AUXS power-generation opening degree to a valve-closing side according to the wear amount of the seal part and adjust the flow rate of oxidant gas in the downstream-side valve to a target flow rate. Accordingly, supply of unnecessary (excess) oxidant gas to the fuel cell is reduced, thus preventing generation of unnecessary (excess) electric power in the fuel cell. Consequently, the system can prevent excessive increase of the power generation amount in the fuel cell and hence prevent deterioration of fuel consumption and further eliminate the need to unnecessarily drive the auxiliaries.

In the foregoing configuration, while the AUXS power-generation opening-degree control is being performed, when it is determined that the flow rate of the oxidant gas in the downstream-side valve is lower than a second predetermined flow rate that is lower than the first flow rate, the controller is configured to correct the AUXS power-generation opening degree to a valve-opening side until reaching a second target position opening degree at which the flow rate of the oxidant gas in the downstream-side valve becomes the second predetermined flow rate.

According to the above configuration, when the control for correcting the AUXS power-generation opening degree is to be performed, the the system can reduce the occurrence of hunting of the downstream-side valve and regulate the flow rate of oxidant gas in the downstream-side valve within a target range. Since the required electric power can be generated by the fuel cell, the auxiliaries can be driven according to the AUXS power-generation request.

In the foregoing configuration, the controller is configured to determine the flow rate of the oxidant gas in the downstream-side valve based on a power generation amount of the fuel cell.

According to the above configuration, there is no need to further adopt a supplementary detection means, such as a sensor, for detecting a flow rate of oxidant gas in the downstream-side valve. Thus, cost reduction can be achieved.

Effects of the Invention

According to a fuel cell system of the present disclosure, unnecessary power generation in the fuel cell can be reduced.

MODE FOR CARRYING OUT THE INVENTION

A detailed description of an embodiment of a fuel cell system which is one of typical embodiments of this disclosure will now be given referring to the accompanying drawings. In the present embodiment described below, the fuel cell system of the present disclosure is applied to a fuel cell system to be mounted in a fuel cell vehicle to supply electric power to a drive motor (not shown).

As shown inFIG. 1, a fuel cell system101in the present embodiment includes a fuel cell stack (fuel cells)111, a hydrogen system112, and an air system113.

The fuel cell stack111generates electricity upon receipt of supply of fuel gas and supply of oxidant gas. In the present embodiment, the fuel gas is hydrogen gas and the oxidant gas is air. Specifically, the fuel cell stack111is configured to produce electric power upon receipt of the hydrogen gas supplied from the hydrogen system112and the air supplied from the air system113. The electric power generated in the fuel cell stack111will be supplied to a drive motor (not shown) through an inverter (not shown).

The hydrogen system112is provided on an anode side of the fuel cell stack111. This hydrogen system112is provided with a hydrogen supply passage121, a hydrogen exhaust passage122, and a filling passage123. The hydrogen supply passage121is a flow passage to supply hydrogen gas from a hydrogen tank131to the fuel cell stack111. The hydrogen exhaust passage122is a flow passage to exhaust hydrogen gas to be discharged out of the fuel cell stack111(hereinafter, appropriately referred to as “hydrogen offgas”). The filling passage123is a flow passage to fill hydrogen gas into the hydrogen tank131through a fill port151.

The hydrogen system112includes, on the hydrogen supply passage121, a main stop valve132, a high-pressure regulator133, a medium-pressure relief valve134, a pressure sensor135, an injector part136, a low-pressure relief valve137, and a pressure sensor138, which are arranged from a side close to the hydrogen tank131. The main stop valve132is a valve for switching supply and shutoff of hydrogen gas from the hydrogen tank131to the hydrogen supply passage121. The high-pressure regulator133is a pressure regulating valve to reduce the pressure of hydrogen gas. The medium-pressure relief valve134is a valve configured to open when the pressure between the high-pressure regulator133and the injector part136becomes a predetermined pressure or higher in order to regulate the pressure to below the predetermined pressure. The pressure sensor135is a sensor to detect the pressure in the hydrogen supply passage121between the high-pressure regulator133and the injector part136. The injector part136is a mechanism for regulating a flow rate of hydrogen gas. The low-pressure relief valve137is a valve configured to open when the pressure in the hydrogen supply passage121between the injector part136and the fuel cell stack111becomes a predetermined pressure or higher in order to regulate the pressure to below the predetermined pressure. The pressure sensor138is a sensor to detect the pressure in the hydrogen supply passage121between the injector part136and the fuel cell stack111.

The hydrogen system112further includes, on the hydrogen exhaust passage122, a gas-liquid separator141and an exhaust-drain valve142arranged in this order from a side close to the fuel cell stack111. The gas-liquid separator141is a device to separate moisture from the hydrogen offgas. The exhaust-drain valve142is a valve to switch exhaust and shutoff of hydrogen offgas and moisture from the gas-liquid separator141to a diluter182of the air system113.

The air system113is provided on a cathode side of the fuel cell stack111. This air system113is provided with an air supply passage161(an oxide gas supply passage), an air exhaust passage162, and a bypass passage163. The air supply passage161is a flow passage to supply air from the outside of the fuel cell system101into the fuel cell stack111. The air exhaust passage162is a flow passage to exhaust air discharged out of the fuel cell stack111(hereinafter, appropriately referred to as “air offgas”). The bypass passage163is a flow passage to allow air to flow from the air supply passage161to the air exhaust passage162without passing through the fuel cell stack111.

The air system113further includes an air cleaner171, a compressor172, an intercooler173, and an inlet sealing valve (an upstream-side valve)174, which are arranged in this order. The air cleaner171is a device to clean up air externally taken in the fuel cell system101. The compressor172is a device to supply air to the fuel cell stack111. The intercooler173is a device to cool air. The inlet sealing valve174is a sealing valve to switch supply and shutoff of air flow to the fuel cell stack111. As this inlet sealing valve174, an eccentric valve is adopted in which a seal surface of a valve element is placed eccentrically from a rotary shaft. The details of the inlet sealing valve174will be described later.

The air system113further includes, on the air exhaust passage162, an outlet integration valve (a downstream-side valve)181and a diluter182arranged in this order from a side close to the fuel cell stack111.

The outlet integration valve181is a valve (a valve having a function of pressure regulation (flow control)) to regulate the back pressure of the fuel cell stack111to thereby control an exhaust amount of air offgas from the fuel cell stack111. The outlet integration valve181in the present embodiment is an eccentric valve basically identical in structure to the inlet sealing valve174(a rubber seat21can be different in structure). The details of this outlet integration valve181will be described later.

The diluter182is a device to dilute hydrogen offgas exhausted from the hydrogen exhaust passage122by the air offgas and the air flowing through the bypass passage163.

The air system113further includes a bypass valve191on the bypass passage163. The bypass valve191is a valve to control a flow rate of air in the bypass passage163. As this bypass valve191, an eccentric valve is adopted, which is substantially identical in structure (excepting the absence of the rubber seat21) to the inlet sealing valve174and the outlet integration valve181. The details of the bypass valve191will be described later.

The fuel cell system101is further provided with a controller (a controller)201to control the system. Specifically, the controller201is configured to control each part or device of the fuel cell system101and perform various determinations. In addition, the fuel cell system101also includes a cooling system (not shown) to cool the fuel cell stack111.

In the fuel cell system101configured as above, the hydrogen gas supplied from the hydrogen supply passage121to the fuel cell stack111is consumed in the fuel cell stack111to generate electric power and thereafter is exhausted as hydrogen offgas from the fuel cell stack111to the outside of the fuel cell system101through the hydrogen exhaust passage122and the diluter182. The air supplied from the air supply passage161to the fuel cell stack111is consumed in the fuel cell stack111to generate electric power and then is exhausted as air offgas from the fuel cell stack111to the outside of the fuel cell system101through the air exhaust passage162and the diluter182.

Herein, the inlet sealing valve174, the outlet integration valve181, and the bypass valve191will be described below with reference toFIGS. 2 to 21. Those valves are basically identical in structure excepting that the inlet sealing valve174and the outlet integration valve181may be different in structure of a rubber seat and that the bypass valve191includes no rubber seat. Thus, the following explanation will be given with a focus on the inlet sealing valve174, and explanations of the outlet integration valve181and the bypass valve191are appropriately added.

As shown inFIGS. 2 and 3, the inlet sealing valve174is provided with a valve section2and a drive mechanism section3. The valve section2includes a pipe part12(seeFIG. 8) having a passage11for allowing air (atmospheric air) to flow. In this passage11, there are placed a valve seat13, a valve element14, and a rotary shaft15. The rotary shaft15receives a driving force (torque) transmitted from the drive mechanism section3. This drive mechanism section3includes a motor32and a speed-reducing mechanism33(seeFIGS. 8 and 9).

As shown inFIGS. 4 and 5, the passage11is formed with a recessed shoulder10in which the valve seat13is fitted. The valve seat13has a circular ring shape formed with a valve hole16at the center. The valve hole16is formed, at its circumferential edge, with an annular seat surface17. The valve element14includes a circular disc-shaped portion whose outer periphery has an annular seal surface18which corresponds to, i.e., which will be brought in contact with, the seat surface17. The valve element14is integrally provided with the rotary shaft15and rotatable together with the rotary shaft15.

In the present embodiment, the valve seat13is provided with a rubber seat (a seal member)21(seeFIG. 21). The seat surface17is formed in this rubber seat21. The details of the rubber seat21will be described later. In the bypass valve191that is not provided with the rubber seat21, the seat surface17is formed in the valve seat13.

In the present embodiment, referring toFIGS. 4 and 5, the inlet sealing valve174is configured such that the passage11formed on an opposite side (i.e., an upper side in the figures) to the valve element14and the rotary shaft15with respect to the valve seat13is located on a side close to the fuel cell stack111(on a downstream side of air flow), while the passage11formed on a side (i.e., a lower side in the figures) close to the valve element14and the rotary shaft15with respect to the valve seat13is located on a side close to a compressor (on an upstream side of air flow). In other words, in the present embodiment, the air will flow in the passage11from the valve element14(the rotary shaft15) side toward the valve seat13side.

In the outlet integration valve181, reversely from the inlet sealing valve174, the passage11formed on the opposite side to the valve element14and the rotary shaft15with respect to the valve seat13is located on the side close to the fuel cell stack11(on an upstream side of air flow), while the passage11formed on the side close to the valve element14and the rotary shaft15with respect to the valve seat13is located on a side close to the diluter182(on a downstream side of air flow). In other words, in the outlet integration valve181, the air will flow in the passage11from the valve seat13side toward the valve element14(the rotary shaft15) side.

In the bypass valve191, furthermore, the passage11formed on the side close to the valve element14and the rotary shaft15with respect to the valve seat13is located on a side close to the air supply passage161(on an upstream side of air flow), while the passage11formed on the side opposite to the valve element14and the rotary shaft15with respect to the valve seat13is located on a side close to the air exhaust passage162(on a downstream side of air flow). In other words, in the bypass valve191, the air will flow in the passage11from the valve element14(the rotary shaft15) side toward the valve seat13side.

As shown inFIGS. 6 and 7, the central axis Ls of the rotary shaft15extends in parallel to the diameter of the valve element14(more concretely, the diameter of the disc-shaped portion of the valve element14) and is positioned eccentrically from the central axis P1of the valve hole16to one side in a radial direction of the valve hole16. The seal surface18of the valve element14is positioned eccentrically from the central axis Ls of the rotary shaft15to an extending direction of the central axis Lv of the valve element14.

By rotation of the valve element14about the central axis Ls of the rotary shaft15, the valve element14is movable between a valve-closing position in which the seal surface18of the valve element14is in surface contact with the seat surface17(seeFIG. 4) and a fully-opened position in which the seal surface18is most away from the seat surface17(seeFIG. 5).

As shown inFIGS. 8 and 9, a valve housing35made of either metal or synthetic resin is provided with the passage11and the pipe part12. An end frame36made of either metal or synthetic resin closes an open end of the valve housing35. The valve element14and the rotary shaft15are placed in the valve housing35. The rotary shaft15includes a pin15ain its distal end portion. The pin15aspecifically is provided at one end of the rotary shaft15in a direction of the central axis Ls (on the side close to the valve element14). The pin15ahas a diameter smaller than a diameter of a part of the rotary shaft15other than the pin15a. At the other end of the rotary shaft15(on the side close to the main gear41) in the direction of the central axis Ls, there is provided with a proximal end portion15b.

The distal end portion of the rotary shaft15formed with the pin15ais a free distal end which is inserted and placed in the passage11of the pipe part12. The rotary shaft15is supported in a cantilever configuration through two bearings arranged apart from each other, that is, a first bearing37and a second bearing38, so that the rotary shaft15is rotatable with respect to the valve housing35. The first bearing37and the second bearing38are each constituted of a ball bearing. Those first and second bearings37and38are placed between the valve element14and the main gear41in the direction of the central axis Ls of the rotary shaft15to rotatably support the rotary shaft15. In the present embodiment, the first bearing37is located at a position on a side close to the main gear41relative to the second bearing38. The valve element14is fixed by welding to the pin15ain the distal end portion of the rotary shaft15and is placed in the passage11.

The end frame36is secured to the valve housing35with a plurality of clips39(seeFIGS. 2 and 3). As shown inFIGS. 8 and 9, to the proximal end portion15bof the rotary shaft15, the main gear41provided with a fan-shaped gear is fixed. A return spring40is provided between the valve housing35and the main gear41to produce a return spring force Fs1. This return spring force Fs1is the force that rotates the rotary shaft15in a valve closing direction and that urges the valve element14in a valve closing direction.

The return spring40is an elastic member made of wire wound in a coil shape and is provided, at both ends, with a far-side hook40aand a near-side hook40bas shown inFIG. 11. The far-side hook40aand the near-side hook40bare spaced at an interval of about 180° in a circumferential direction of the return spring40. The far-side hook40ais located on a side close to the valve housing35(on a far-side of a drawing sheet ofFIG. 11) so that it contacts a spring hook part35c(seeFIG. 19) of the valve housing35. In contrast, the near-side hook40bis located on a side close to the main gear41(on a near-side of the drawing sheet ofFIG. 11) so that it contacts a spring hook part41cof the main gear41.

As shown inFIGS. 8 to 11, the main gear41includes a full-close stopper part41a, a gear part41b, a spring hook part41c, a spring guide part41d, and others. In the circumferential direction (a counterclockwise direction inFIG. 11) of the main gear41, the full-close stopper part41a, the gear part41b, and the spring hook part41care arranged in this order. The main gear41is integrally provided with the rotary shaft15and is configured to receive driving force generated by the motor32. The full-close stopper part41ais a part that abuts on the full-close stopper part35bof the valve housing35when an opening degree θ is 0.

As shown inFIG. 8, the motor32is accommodated and fixed in a holding cavity35aof the valve housing35. The motor32is operative to generate driving force to rotate the rotary shaft15in a valve opening direction and a valve closing direction. The motor32is coupled to the rotary shaft15to transmit the driving force through the speed reducing mechanism33in order to open and close the valve element14. Specifically, a motor gear43is fixed to an output shaft32a(seeFIG. 10) of the motor32. This motor gear43is connected to the main gear41to transmit the driving force thereto through an intermediate gear42.

The intermediate gear42is a double gear having a large-diameter gear42aand a small-diameter gear42band is rotatably supported by the valve housing35through a pin shaft44. The diameter of the large-diameter gear42ais larger than the diameter of the small-diameter gear42b. The large-diameter gear42ais drivingly engaged with the motor gear43, while the small-diameter gear42bis drivingly engaged with the main gear41. In the present embodiment, the main gear41, the intermediate gear42, and the motor gear43, constituting the speed reducing mechanism33, are each made of resin.

The motor32is one example of a “drive mechanism” in the present disclosure. The intermediate gear42(a drive transmission part) transmits the driving force of the motor32to the rotary shaft15.

In the inlet sealing valve174configured as above, when the motor32is energized from a state that the valve element14is held in a valve-closed state (in which the entire circumference of the seal surface18of the valve element14is in contact with the entire circumference of the seat surface17of the valve seat13(the rubber seat21)) as shown inFIG. 4, even though the details will be described later, the force (the motor driving force Fm1(seeFIG. 14)) that pushes the gear teeth is exerted on the main gear41, thereby moving the valve element14in a direction toward the valve seat13by the principle of leverage (seeFIG. 15). After that, when the drive voltage (current) applied to the motor32is gradually raised, the output shaft32aand the motor gear43are rotated in a forward direction (i.e., a direction to open the valve element14) and this rotation is reduced in speed through the intermediate gear42and then transmitted to the main gear41. Accordingly, the valve element14is opened against the return spring force Fs1that is generated by the return spring40and that urges the valve element14in the valve closing direction, and thus the passage11is opened (seeFIGS. 16 and 18). Subsequently, when the drive voltage applied to the motor32is maintained at a constant level in the process of opening the valve element14, the motor driving force Fm1and the return spring force Fs1become balanced with each other at the opening degree of the valve element14at that time, so that the valve element14is held at a predetermined opening degree.

The details of the operations of the inlet sealing valve174in the present embodiment will be described below. During non-operation of the motor32that is not energized (i.e., during stop of the motor32), the valve opening degree θ is 0, that is, the inlet sealing valve174is fully closed (at a mechanical fully-closed opening degree). At that time, as shown inFIG. 11, the full-close stopper part41aof the main gear41contacts with the full-close stopper part35bof the valve housing35.

In the above state, considering the relationship of forces in terms of a circumferential direction of, or around, the rotary shaft15, the spring hook part41cof the main gear41receives the return spring force Fs1from the near-side hook40bof the return spring40as shown inFIG. 12. As shown inFIG. 12, in a rectangular or Cartesian coordinate system consisting of an origin represented by the central axis Ls of the rotary shaft15, an x-axis represented by a horizontal line, and a y-axis represented by a vertical line, a first quadrant is a part defined by a +x axis and a +y axis, a second quadrant is a part defined by a −x axis and the +y axis, a third quadrant is a part defined by the −x axis and a −y axis, and a fourth quadrant is a part defined by the +x axis and the −y axis. At that time, the far-side hook40aand the full-close stopper part41aare placed in a position corresponding to the first quadrant, and the near-side hook40band the spring hook part41care placed in a position corresponding to the third quadrant.

Herein, based on the principle of leverage, a fulcrum, or pivot point, is set at the full-close stopper part41a, a point of effort is set at the spring hook part41c, and a point of load is set at a middle part between the full-close stopper part41aand the spring hook part41c. Thus, the return spring force Fs1applied to the spring hook part41ccauses a force Fs2to act on the middle part between the full-close stopper part41aand the spring hook part41c. This is expressed by: “Force Fs2”=2×“Return spring force Fs1”. InFIG. 12, the distance between the full-close stopper part41aand the spring hook part41cis set to “2R”.

At that time, considering the relationship of forces in terms of a cross section of the rotary shaft15taken along the central axis Ls, a +y direction component of the force Fs2is a component force Fs3as shown inFIG. 13. The +y direction is a direction perpendicular to the central axis Lj direction of the first bearing37and the second bearing38(the x direction) and is a direction in which the valve seat13is placed relative to the valve element14(an upward direction in the drawing sheets ofFIGS. 12 and 13). This is expressed by: “Component force Fs3”=“Force Fs2”×“sin θ1”. The angle θ1 is an angle of the arrangement direction in which the full-close stopper part41aand the spring hook part41care arranged with respect to the x direction as shown inFIG. 12.

This component force Fs3causes a force Fs4(a separating-direction urging force) to act in the +y direction on the spring guide part41d. This is expressed by: “Force Fs4”=“Component force Fs3”×Lb/La. In this way, the force Fs4is a force that is caused by the return spring force Fs1and acts in a direction perpendicular to the central axis Lj of the first bearing37and the second bearing38. The distance La is a distance in the x direction from a position in which the first bearing37is placed to a position on which the force Fs4acts. The distance Lb is a distance in the x direction from the position where the first bearing37is placed to a position on which the force Fs3acts.

When the force Fs4acts in the +y direction in the position of the spring guide part41d, the rotary shaft15integral with the spring guide part41dis caused to turn and incline clockwise inFIG. 13about the first bearing37serving as the fulcrum. Accordingly, by the principle of leverage, the main gear41provided in the proximal end15bof the rotary shaft15is moved in the +y direction, while the valve element14provided in the pin15aof the rotary shaft15is moved in the −y direction. Therefore, the valve element14is moved in a direction away from the valve seat13(a separating direction). While the inlet sealing valve174is in a valve-closed state during non-operation of the motor32, the valve element14is moved in the direction away from the valve seat13by the force Fs4in the above manner. At that time, the rotary shaft15is restrained by the second bearing38from further inclining.

At that time, in the present embodiment, the valve element14is in contact with the rubber seat21(the seal member) provided in the valve seat13as shown inFIG. 13. Specifically, as shown inFIG. 21, the valve element14is in contact with the seal part21aprovided in the rubber seat21. More concretely, the valve element14is in contact with the entire circumference of the seat surface17of the seal part21a. The seal part21ais configured to be deformable when pressed by the valve element14. The seal part21ahas such a shape as to increase the surface pressure of a portion in contact with the seal surface18of the valve element14as the upstream-side pressure of the inlet sealing valve174becomes higher than the downstream-side pressure (that is, a front-rear differential pressure becomes larger). For instance, the seal part21amay be a bead seal, a lip seal, or another type of seals. In this way, the rubber seat21closes (seals) between the valve seat13and the valve element14. Thus, the inlet sealing valve174enhances the sealing performance with a simple structure.

Accordingly, during deceleration of a vehicle in which the fuel cell system101is mounted, when supply of air to the fuel cell stack111is to be stopped, the inlet sealing valve174is fully closed to increase the pressure in the air supply passage161or the stack pressure in the fuel cell stack111is decreased, thereby enabling sealing of the air on an inlet side of the fuel cell stack111. Thus, when the supply of air to the fuel cell stack111is stopped, surplus (unnecessary) air is less supplied to the fuel cell stack111. This can minimize unnecessary power generation in the fuel cell stack111during deceleration.

At that time, the opening degree θ and the open area S establish the relationship as indicated by a point P1ainFIG. 20. Herein, the definition “when the inlet sealing valve174is in a fully-closed state (a mechanical fully-closed state)” means that the opening degree θ (the opening degree of the valve element14) is 0, that is, the rotation angle of the rotary shaft15is an angle for full closure (a smallest angle within a rotation range of the rotary shaft15).

Subsequently, while the motor32is driven by energization, the small-diameter gear42b(seeFIG. 11) of the intermediate gear42exerts the motor driving force Fm1to the gear teeth part41b(seeFIG. 11) of the main gear41to cause rotation of the main gear41. When seen from the force relationship in terms of the circumferential direction of the rotary shaft15at that time, the motor driving force Fm1acts in the −y direction as shown inFIG. 14. This −y direction is a perpendicular direction to the central axis Lj direction (the x direction) of the first bearing37and the second bearing38and a direction in which the valve element14is placed relative to the valve seat13(a downward direction in the drawing sheets ofFIGS. 12 and 13).

The motor driving force Fm1causes the force Fm2to act in the −y direction at the position of the central axis Ls of the rotary shaft15. Further, when seen from the force relationship in terms of the cross section of the rotary shaft15taken along the central axis Ls, a force Fm3(a seating-direction urging force) acts in the −y direction at the position of the spring guide part41das shown inFIG. 15. This is expressed by: “Force Fm3”=“Force Fm2”×Lb/La. During operation of the motor32, in the above manner, the force Fm3is generated. This force Fm3is a force that is caused by the motor driving force Fm1and that acts in a direction perpendicular to the central axis Lj of the first bearing37and the second bearing38. The force Fm3causes the rotary shaft15to turn and incline about the first bearing37serving as the fulcrum, thereby urging the valve element14in a direction toward the valve seat13.

As shown inFIG. 15, when the force Fm3becomes larger than the force Fs4, the rotary shaft15integral with the spring guide part41dof the main gear41is caused to turn and incline counterclockwise inFIG. 15about the first bearing37serving as the fulcrum. Accordingly, by the principle of leverage, the main gear41is moved in the −y direction, while the valve element14moves in the +y direction. Therefore, the valve element14is moved in a direction toward the valve seat13(the seating direction) by the force Fm3.

In the present embodiment, at that time, the seal part21aof the rubber seat21is pressed and deformed by the valve element14. However, this seal part21ais deformed within an elastic deformation region and is not plastically deformed. At that time, the relationship between the opening degree θ and the open area S is as indicated by a point P1binFIG. 20.

Subsequently, when the drive voltage applied to the motor32rises and thus the motor driving force Fm1become large, the rotary shaft15is caused to further turn and incline counterclockwise inFIG. 16about the first bearing37serving as the fulcrum. Accordingly, the main gear41is further moved in the −y direction, while the valve element14is further moved in the +y direction. At that time, the rotary shaft15is rotated about the central axis Ls, so that the opening degree θ (the rotation angle of the rotary shaft15) becomes an opening degree “α” (seeFIG. 17) corresponding to a position slightly open from the opening degree 0°. In this state, the full-close stopper part41aof the main gear41separates from the full-close stopper part35bof the valve housing35as shown inFIG. 17. This state is a controlled fully-closed state which will be described later, in which the opening degree α is a controlled fully-closed opening degree. The details of the controlled fully-closed opening degree will be described later. As shown inFIG. 16, the rotary shaft15is stopped by the second bearing38. At that time, the relationship between the opening degree θ and the open area S is changed as a point P1cinFIG. 20. The open area S is nearly zero.

Thereafter, as the motor driving force Fm1becomes larger, the rotary shaft15is further rotated about the central axis Ls, thereby causing the valve element14to separate from the valve seat13as shown inFIG. 18to increase the open area S for valve-opening. At that time, the valve opening degree θ becomes “β” (seeFIG. 19). Further, the relationship between the opening degree θ and the open area S at that time is established as indicated by a point P1dinFIG. 20. In the above manner, the valve opening operation of the inlet sealing valve174is performed by the motor driving force Fm1.

The outlet integration valve181is also configured as above except for the following configuration. Specifically, in the outlet integration valve181, the seal part of the rubber seat is configured to decrease the surface pressure of a portion in contact with the seal surface of the valve element as the upstream-side pressure of the outlet integration valve181becomes larger than the downstream-side pressure. The bypass valve191is also configured as above except for the absence of the rubber seat21. In the air system113, as described above, the eccentric valves basically identical in structure are used for the inlet sealing valve174, the outlet integration valve181, and the bypass valve191as shown inFIG. 22to allow commonality of valves in the air system113, except that the inlet sealing valve174and the outlet integration valve181are different in structure of the rubber seat and the bypass valve191includes no rubber seat. Further, since the inlet sealing valve174, the outlet integration valve181, and the bypass valve191are common in structure except for the rubber seats, the opening and closing control (operation) itself is common and thus those valves can be controlled in cooperation. From the above-mentioned configuration, the fuel cell system101can be reduced in cost and the controller201can be simplified in control of opening and closing the valves.

In the present embodiment, when the inlet sealing valve174is to be fully closed during system stop or deceleration, the valve element14is seated on the valve seat13by making the seal surface18of the valve element14slide on the seal part21aof the rubber seat21. As wear of the seal part21adue to sliding contact of the seal surface18develops, accordingly, the inlet sealing valve174cannot provide high sealing performance. During system stop, if the sealing performance of the inlet sealing valve174cannot be ensured, the seal-off degree of the fuel cell stack111during system stop may be decreased, causing a reaction in the fuel cell stack111and deterioration by oxidation in the fuel cell stack111.

In the fuel cell system101, therefore, when supply of air to the fuel cell stack111is stopped during deceleration or system stop, the following control on the basis of the aforementioned control is preferably executed to suppress wear of the seal part21ato enhance the sealing performance of the inlet sealing valve174during system stop in order to prevent degradation of the fuel cell stack111.

To be concrete, the controller201has only to execute the control based on control flowcharts inFIGS. 23 to 25. The controller201firstly determines whether or not an operation request to the fuel cell stack111is continued (step S50). When this operation request to the fuel cell stack111is continued (step S50: YES), the controller201then determines whether or not the vehicle changes from the acceleration/steady state to the deceleration state (step S51).

When the vehicle changes from the acceleration/steady state to the deceleration state (step S51: YES), the controller201determines whether or not a discharge release flag is 0 (step S52). This discharge release flag being “0” indicates the presence of the request, while the discharge release flag being “1” indicates the absence of the request. The discharge request is generated when the electric power generated in the fuel cell stack111during deceleration cannot be charged to the battery.

When the discharge release flag is 0 (step S52: YES), the controller201performs the full-opening control to fully open the bypass valve191from the fully-closed state (step S53). Accordingly, the compressor pressure of the compressor172no longer acts on the inlet sealing valve174, resulting in a decrease in the front-rear differential pressure of the inlet sealing valve174. When the discharge release flag is 1 (step S52: NO), the controller201carries out the processings in steps S90to S93mentioned later.

Further, controlled fully-closed opening-degree control is executed to close the outlet integration valve181from the opening degree meeting the output (acceleration/steady) request before deceleration to a controlled fully-closed opening degree α (step S54). It is to be noted that the processing in this step S54may be omitted. However, when the processing in step S54is performed in addition to the processing step S53, the front-rear differential pressure of the inlet sealing valve174can be reduced even if either valve, that is, the bypass valve or the outlet integration valve, is broken down (bypass valve closing failure or outlet integration valve opening failure).

Furthermore, the controller201performs the valve-closing control that closes the inlet sealing valve174from the fully-opened state to a predetermined opening degree γ (step S55). This predetermined opening degree γ may be set to an opening degree (e.g., in the order of 5 to 15°) corresponding to a position slightly before the valve element14contacts with the seal part21a. In the present embodiment, the predetermined opening degree γ is set to 10°.

The controller201then takes the compressor pressure (Pin) of the compressor172and the stack pressure pstack (step S56) and calculates a front-rear differential pressure ΔPIN (=Pin−pstack) of the inlet sealing valve174(step S57). When this front-rear differential pressure ΔPIN is smaller than a predetermined pressure P (step S58: YES), the controller201performs the controlled fully-closed opening-degree control that adjusts the opening degree of the inlet sealing valve174to a controlled fully-closed opening degree (step S59). Concretely, the controller201controls the motor32to close the inlet sealing valve174to the controlled fully-closed opening degree α. Thus, the opening degree of the inlet sealing valve174is changed from the predetermined opening degree γ to the controlled fully-closed opening degree α.

The controlled fully-closed opening degree α is an opening degree which is slightly larger than the mechanical fully-closed opening degree (Opening degree=) 0° and at which the valve element14is maintained in the valve-closed state in contact with the seal part21a; for example, the opening degree α may be set to several degrees. In the present embodiment, the controlled fully-closed opening degree α is set to 3°. The predetermined pressure P may be set to a pressure value (about several kPa) under which the seal part21aof the rubber seat21is never deformed.

At that time, since the bypass valve191has been fully opened, the front-rear differential pressure ΔPIN of the inlet sealing valve174is basically small. However, for a bypass valve191having a small valve hole, for example, it takes time from when the bypass valve191is opened until the front-rear differential pressure ΔPIN of the inlet sealing valve174becomes small. This may cause the inlet sealing valve174to be adjusted to the controlled fully-closed opening degree α before the front-rear differential pressure ΔPIN of the inlet sealing valve174decreases. Thus, the inlet sealing valve174may be brought into the controlled fully-closed state while the seal part21aremains deformed.

Therefore, when the inlet sealing valve174is to be brought into the controlled fully-closed state, the inlet sealing valve174is firstly closed to the predetermined opening degree γ, as mentioned above and, after the front-rear differential pressure ΔPIN of the inlet sealing valve174becomes smaller than the predetermined pressure P, the controlled fully-closed opening-degree control is performed. This can reliably avoid the inlet sealing valve174from being brought into the controlled fully-closed state while the seal part21aremains deformed.

Thereafter, the controller201determines whether or not the opening degree of the inlet sealing valve174having been subjected to the controlled fully-closed opening-degree control executed in step S59has reached the controlled fully-closed opening degree α (step S60). When it is confirmed that the opening degree of the inlet sealing valve174has reached the controlled fully-closed opening degree α (step S60: YES), the controller201sets a controlled fully-closed flag of the inlet sealing valve174to 1 (step S61) and performs the full-closing control to fully close the bypass valve191from the fully-opened state (step S62). Thus, the compressor pressure of the compressor172acts on the seal part21aof the inlet sealing valve174, thereby pressing the seal part21aagainst the valve element14. Therefore, the inlet sealing valve174can enhance the sealing performance even when the opening degree is controlled to the controlled fully-closed opening degree α. Accordingly, at the time of stopping supply of air to the fuel cell stack111during deceleration, even when the inlet sealing valve174is brought into the controlled fully-closed state without being mechanically fully closed, the inlet sealing valve174can seal out the air.

In the inlet sealing valve174, as described above, the fully-closed opening degree (controlled fully-closed opening degree) during deceleration is different from the fully-closed opening degree (mechanical fully-closed opening degree) during system stop. Therefore, as shown inFIG. 26, the position of a contact point CP1between the valve element14and the seal part21ain the mechanical fully-closed opening degree state during system stop and the position of a contact point CP2between the valve element14and the seal part21ain the controlled fully-closed opening degree state during deceleration are different from each other. During deceleration in which the inlet sealing valve174is operated to be fully closed with high frequency, the seal part21amay wear away at the fully-closed opening degree position (the controlled fully-closed opening degree position: Opening degree θ=α). In contrast, during system stop in which the inlet sealing valve174is less operated as compared with during deceleration, wear of the seal part21aat the fully-closed opening degree position (the mechanical fully-closed opening degree position: Opening degree θ=0) can be greatly reduced. Accordingly, the inlet sealing valve174can enhance the sealing performance during system stop. In the inlet sealing valve174, even when the seal part21ahas worn away at the controlled fully-closed opening degree position, the seal part21ais pressed against the valve element14by the compressor pressure of the compressor172during deceleration. Thus, high sealing performance can be achieved.

When the discharge request is present (step S80: YES), as shown inFIG. 24, the controller201takes the compressor pressure (Pin) and the number of compressor revolutions (cprpm) of the compressor172(step S81). The controller201then determines whether or not the compressor pressure (Pin) is smaller than a discharge target pressure A (Pin<A) (step S82). When the compressor pressure (Pin) is smaller than the discharge target pressure A (step S82: YES), the controller201controls the bypass valve191to close to increase the compressor pressure (Pin) (step S83). When the compressor pressure (Pin) is equal to or larger than the discharge target pressure A (step S82: NO), the controller201controls the bypass valve191to open to decrease the compressor pressure (Pin) (step S84).

The controller201then determines whether or not the compressor revolution number (cprpm) is smaller than the discharge target revolution number B (cprpm<B) (step S85). When the compressor revolution number (cprpm) is smaller than the discharge target revolution number B (step S85: YES), the controller201increases the number of revolutions of the compressor172(step S86). When the compressor revolution number (cprpm) is equal to or larger than the discharge target revolution number B (step S85: NO), the controller201decreases the number of revolutions of the compressor172(step S87).

By the aforementioned discharge control, it is possible to control the compressor pressure and the compressor revolution number respectively to around the discharge target pressure A and around the discharge target revolution number B to thereby cause the compressor172to efficiently discharge surplus electric power generated in the fuel cell stack111.

In contrast, when the discharge request is absent, that is, when charging of the battery is enabled (step S80: NO), the controller201sets the discharge release flag to 1 (step S88). The controller201then determines whether an auxiliaries (AUXS) power-generation request is absent (step S90). When the AUXS power-generation request is absent (step S90: YES), the controller201performs the regenerative brake control, and opens the bypass valve191and controls the number of revolutions of the compressor172according to the regenerative brake request in order to charge the electric power generated in the fuel cell stack111to the battery. Since the bypass valve191is open, even when the compressor172is maintained at the constant revolution number, the load (power consumption) of the compressor172is low.

When the AUXS power-generation request is present (step S90: NO), the controller201determines whether or not the controlled fully-closed flag is 0 (step S92). When the controlled fully-closed flag of the inlet sealing valve174is 0 (step S92: YES), the controller201controls the opening degree of the outlet integration valve181and the opening degree of the bypass valve191individually and also controls the number of revolutions of the compressor172according to the AUXS power-generation request (step S93). When the controlled fully-closed flag of the inlet sealing valve174is 1 (step S92: NO), the processings in step S70and subsequent steps which will be described later are performed.

Returning toFIG. 23, when the acceleration/steady state is maintained or when deceleration is terminated (step S51: NO), as shown inFIG. 25, the controller201determines whether or not the controlled fully-closed flag of the inlet sealing valve174is 1 (step S70). When the controlled fully-closed flag is 1 (step S70: YES), return control from the deceleration control is performed. Specifically, the controller201executes the full-opening control to fully open the bypass valve191from the fully-closed state (step S71). At that time, the outlet integration valve181continuously undergoes the controlled fully-closed opening-degree control (step S72). If the processing in step S54is omitted, the processing in step S72is unnecessary.

At that time, when the front-rear differential pressure ΔPIN of the inlet sealing valve174is high, the seal part21aof the rubber seat21may be bent back and deformed by the differential pressure. If the seal part21aof the rubber seat21is bent or curled back in the course of opening the inlet sealing valve174as shown inFIG. 27, the seal part21amay abnormally wear away. If the seal part21ahas abnormally worn away, the inlet sealing valve174cannot ensure the sealing performance during full-closing.

Therefore, the controller201takes the compressor pressure (Pin) of the compressor172and the stack pressure (pstack) (step S73) and calculates the front-rear differential pressure ΔPIN (=Pin−pstack) of the inlet sealing valve174(step S74). When the front-rear differential pressure ΔPIN is smaller than a predetermined pressure P (step S75: YES), the controller201performs the full-opening control that adjusts the opening degree of the inlet sealing valve174from the controlled fully-closed opening degree to a fully-opened opening degree (step S76). Thereafter, the controller201sets the controlled fully-closed flag of the inlet sealing valve174to 0 (step S77) and sets the discharge release flag to 0 (step S78).

Accordingly, the inlet sealing valve174is opened after the front-rear differential pressure ΔPIN of the inlet sealing valve174becomes small as above. This can reliably prevent the seal part21aof the rubber seat21from being bent back and deformed during valve-opening of the inlet sealing valve174. Therefore, when the inlet sealing valve174is to be opened after completion of deceleration, the inlet sealing valve174can prevent abnormal wear of the seal part21aof the rubber seat21and thus can enhance the sealing performance of the inlet sealing valve174.

When the controlled fully-closed flag is 0, that is, when the acceleration/steady state is maintained (step S70: NO), the inlet sealing valve174is kept in the fully-opened position. The controller201individually controls the opening degree of the outlet integration valve181and the opening degree of the bypass valve191according to the output (acceleration/steady) request at that time and also controls the number of revolutions of the compressor172(step S79).

Returning toFIG. 23, when the operation request of the fuel cell stack111is not continued, that is, when a system stop request is present (step S50: NO), the controller201executes the processings in step S100and subsequent steps to stop the fuel cell system101.

Herein, when the controlled fully-closed opening-degree control is performed during deceleration, the number of times the valve element14slides on the seal part21ais greatly increased at a controlled fully-closed opening degree position during deceleration shown inFIG. 28than at a mechanical fully-closed opening degree position during system stop. Therefore, as shown inFIG. 29, a portion (hatched portion) of the seal part21athat contacts and slides with respect to the valve element14at the controlled fully-closed opening degree position gets worn, which may cause a wear step or ridge D to be formed in the seal part21aas shown inFIG. 30. When the wear step D is formed in the seal part21a, during system stop, the inlet sealing valve174could not be closed to the mechanical fully-closed opening degree (Opening degree=0°) only by the urging force (the return spring force Fs1) of the return spring40.

Therefore, when the system is to be stopped, the controller201performs the zero-opening control described below on the inlet sealing valve174to reliably bring the inlet sealing valve174to a fully-closed state (a mechanical fully-closed opening degree) during system stop.

Specifically, the controller201executes the full-opening control to fully open the bypass valve191from the fully-closed state (step S100). The controller201further performs the zero-opening control that controls the motor32to forcibly adjust the opening degree of the inlet sealing valve174to 0° to thereby bring the inlet sealing valve174to a fully-closed (a mechanical fully-closed) state (step S101). Similarly, the outlet integration valve181is subjected to the zero-opening control to be fully closed (step S102).

Subsequently, the controller201stops the compressor172. When the revolution number becomes 0 (zero) (step S103: YES), the controller201performs the full-closing control that operates the bypass valve191from full open to full close (step S104) and stops the fuel cell system101(step S105).

Since the fuel cell system101is stopped as above, even when a wear step D occurs in the seal part21a, the inlet sealing valve174can be reliably closed to the mechanical fully-closed opening degree by the motor32. Further, the seal part21acan be greatly suppressed from wearing away at the mechanical fully-closed position as described above. Accordingly, the inlet sealing valve174can enhance the sealing performance during system stop. In the present embodiment, furthermore, the outlet integration valve181is also configured to perform the zero-opening control as with the inlet sealing valve174. Thus, the outlet integration valve181can also enhance the sealing performance during system stop. The seal-off degree of the fuel cell stack111during system stop can be enhanced. Thus, the reaction in the fuel cell stack111is less likely to occur and the deterioration due to oxidation in the fuel cell stack111can be suppressed.

Next, learning of controlled fully-closed position of the inlet sealing valve174will be described. When the inlet sealing valve174is to be fully closed during deceleration, as described above, the controller201performs the controlled fully-closed opening-degree control that adjusts the opening degree of the inlet sealing valve174to the controlled fully-closed opening degree α (see step S59inFIG. 23). Herein, the controlled fully-closed opening-degree control is executed during deceleration in which the vehicle is operated with high frequency, so that the opening degree of the inlet sealing valve174becomes the controlled fully-closed opening degree α with high frequency. This increases the number of times the valve element14comes into contact with the seal part21aof the rubber seat21provided in the valve seat13, which may cause much wear of the seal part21a. Accordingly, there is a demand to control the controlled fully-closed opening degree α in order to reduce wear of the seal part21a.

In case the seal part21amuch wears away, causing air leakage to occur in the inlet sealing valve174when the opening degree of the inlet sealing valve174is adjusted to the controlled fully-closed opening degree α, unnecessary air is supplied to the fuel cell stack111. In this case, the supplied unnecessary air reacts with hydrogen gas already supplied to the fuel cell stack111, causing power generation, so that unnecessary electric power is generated in the fuel cell stack111. If unnecessary electric power is much generated in the fuel cell, such an electric power could not be completely discharged only by power consumption of auxiliaries. As the power consumption of the compressor172needs to be increased, for example, the number of revolutions of the compressor172may increase or the pressure at an outlet of the compressor172may rise. These situations may deteriorate fuel consumption or generate noise vibration (NV).

Thus, the controlled fully-closed opening degree α is controlled according to the amount of wear of the seal part21a, so that the amount of air leaking through the inlet sealing valve174can be kept zero during the controlled fully-closed opening-degree control. In the present embodiment, therefore, the air leakage amount in the inlet sealing valve174is determined based on the amount of electric power generated (“power generation amount”) in the fuel cell stack111and thus the controlled fully-closed opening degree α is changed (learnt) to a valve-closing side (toward 0°). In the following description, the controlled fully-closed opening degree α is expressed as a controlled fully-closed opening degree Kα+for convenience.

To be concrete, the controller201performs the control shown inFIG. 31. As shown inFIG. 31, while the controlled fully-closed opening-degree control is being performed (step S201: YES), after electric power by stack remaining power generation is completely consumed (step S202: YES), the controller201takes a controlled fully-closed opening degree Kα+(an opening degree α+(i)) (step S203). The controlled fully-closed opening degree Kα+taken in step S203is assumed as an opening degree α+(i).

Herein, the condition “while the controlled fully-closed opening-degree control is being performed” is conceived as for example a situation that the inlet sealing valve174is fully closed during deceleration (step S59inFIG. 23) as described above. However, not limited thereto, this condition may also include another situation that the inlet sealing valve174is fully closed during any operations except for during deceleration.

Further, the condition “electric power by stack remaining power generation” indicates the electric power generated in the fuel cell stack111with the air that remains in the fuel cell stack111when the controlled fully-closed opening-degree control is performed, starting stop of air supply to the fuel cell stack111.

The controlled fully-closed opening degree Kα+(the opening degree α+(i)) is an opening degree that is slightly larger than the mechanical fully-closed opening degree (the opening degree 0°) at which the valve element14is in contact with the seal part21aand maintained in a valve-closed state. For example, this opening degree is set to several degrees. In the present embodiment, the controlled fully-closed opening degree Kα+(the opening degree α+(i)) is set to 3° or smaller, in which the alphabet i is a positive integer.

The controller201successively takes a stack power generation amount sekw which is a power generation amount of the fuel cell stack111(step S204) and determines whether this stack power generation amount sekw is less than a predetermined power generation amount Akw (step S205). The predetermined power generation amount Akw is a power generation amount at which the power generation in the fuel cell stack111can be judged or regarded as being stopped; for example, 0 kW to several (e.g., 3) kW.

Herein, the fuel cell stack111is maintained in a rich (much) state with hydrogen gas. Thus, depending on whether or not air is supplied to the fuel cell stack111, the fuel cell stack111performs or stops power generation. During execution of the controlled fully-closed opening-degree control, therefore, if no air leakage occurs in the inlet sealing valve174, air supply to the fuel cell stack111is stopped and the power generation in the fuel cell stack111is thus stopped. If the power generation in the fuel cell stack111continues, it indicates that air is being supplied to the fuel cell stack111. It is thus conceived that air leakage occurs in the inlet sealing valve174.

In the present embodiment, therefore, the controller201is configured to determine the amount of air leaking through the inlet sealing valve174based on the stack power generation amount sekw. Herein, the stack power generation amount sekw is the amount of electric power generated in the fuel cell stack111after the air remaining in the fuel cell stack111at the start of the controlled fully-closed opening-degree control is consumed. The amount of air remaining in the fuel cell stack111at the start of the controlled fully-closed opening-degree control is obtained based on the flow rate of air flowing in the air supply passage161just before the start of the controlled fully-closed opening-degree control, for example, based on the number of revolutions of the compressor172.

Accordingly, when the stack power generation amount sekw is determined to be the predetermined power generation amount Akw or larger (step S205: NO), it is conceived that air leakage occurs in the inlet sealing valve174. Thus, the controller201performs a controlled fully-closed opening-degree valve-closing control, i.e., updates the controlled fully-closed opening degree (step S206). Herein, the “controlled fully-closed opening-degree valve-closing control” is a control that corrects, or updates, the opening degree α+(i) (the controlled fully-closed opening degree) to the valve-closing side (toward 0°). To be concrete, the controller201makes a calculation using the following expression:
α+(i)=α+(i−1)−a%  (Exp. 1)
wherein a %=0.01 to 0.1%.

After completion of the controlled fully-closed opening-degree valve-closing control in step S206and further after a lapse of a fixed time t (e.g., several seconds (1 to 2 seconds)) (step S207: YES), the controller201takes a stack power generation amount sekw again (step S204).

When the stack power generation amount sekw is less than the predetermined power generation amount Akw (step S205: YES), it is conceived that no air leakage occurs in the inlet sealing valve174, i.e., that the leakage amount is zero, the controller201performs the controlled fully-closed position learning, i.e., storage of the controlled fully-closed opening degree (step S208). In step S208, specifically, the controller201learns, i.e., corrects the controlled fully-closed opening degree Kα+to the opening degree α+(i).

In the present embodiment as described above, during execution of the controlled fully-closed opening-degree control, after the electric power by the stack remaining power generation has been consumed, the controller201determines the air leakage amount in the inlet sealing valve174based on the stack power generation amount sekw. When it is determined that air leakage has occurred in the inlet sealing valve174since the stack power generation amount sekw is the predetermined power generation amount Akw or larger, the controller201further corrects the controlled fully-closed opening degree Kα+to the valve-closing side until reaching a zero-position opening degree at which the air leakage amount in the inlet sealing valve174becomes zero. In contrast, when the controller201determines that no air leakage has occurred in the inlet sealing valve174, i.e., that the leakage amount is zero, because the stack power generation amount sekw is less than the predetermined power generation amount Akw, the controller201maintains the controlled fully-closed opening degree Kα+.

According to the present embodiment described above, while the controlled fully-closed opening-degree control is in execution, when it is determined that air leakage has occurred in the inlet sealing valve174, the controller201corrects the controlled fully-closed opening degree Kα+to the valve-closing side until reaching the zero-position opening degree at which the air leakage amount in the inlet sealing valve174becomes zero.

Accordingly, during execution of the controlled fully-closed opening-degree control, when air leakage occurs because of wear of the seal part21ain the inlet sealing valve174, the controller201corrects the controlled fully-closed opening degree Kα+to the valve-closing side according to the wear amount of the seal part21a, so that the air leakage amount in the inlet sealing valve174can be reduced to zero. Thus, unnecessary air supply to the fuel cell stack111is reduced and thus unnecessary power generation in the fuel cell stack111can be prevented. Consequently, discharge by power consumption of auxiliaries is no longer necessary to consume the electric power generated by unnecessary power generation in the fuel cell stack111. This can prevent deterioration of fuel consumption and occurrence of NV.

Herein, if the controlled fully-closed opening degree Kα+is set in advance to such an opening degree as to cause the surface pressure of the seal part21aacting on the seal surface18of the valve element14to decrease, air leakage is likely to occur due to slight wear of the seal part21a. In the present embodiment, however, the controlled fully-closed opening degree Kα+is controlled according to the wear amount of the seal part21a, so that the surface pressure of the seal part21ais decreased to reduce wear of the seal part21a, that is, to enhance durability, and also the air leakage amount can be maintained at zero during the controlled fully-closed opening-degree control.

Furthermore, the controller201is configured to determine the air leakage amount in the inlet sealing valve174based on the stack power generation amount sekw. Thus, there is no need to further adopt a supplementary detection means, such as a sensor, for detecting the air leakage amount in the inlet sealing valve174. Cost reduction can thus be achieved.

The stack power generation amount sekw is the amount of electric power generated after the air remaining in the fuel cell stack111at the start of the controlled fully-closed opening-degree control has been consumed. Thus, the stack power generation amount sekw becomes the power generation amount corresponding to the air leakage amount in the inlet sealing valve174generated while the controlled fully-closed opening-degree control is executed. The air leakage amount in the inlet sealing valve174can accordingly be determined based on the stack power generation amount sekw.

Next, learning of a controlled position of the outlet integration valve181for driving of auxiliaries (“AUXS-control position learning”) will be described. At the time of an AUXS power-generation request, for example, when an AUXS power-generation request is present (step S90: NO) inFIG. 24, the controller201performs an AUXS power-generation opening-degree control that adjusts the opening degree of the outlet integration valve181to an AUXS power-generation opening degree corresponding to a request AUXS power-generation amount. The condition “at the time of an AUXS power-generation request” indicates the time when power generation in the fuel cell stack111is requested in order to drive auxiliaries, such as the compressor172.

At that time, the AUXS power-generation opening degree is adjusted to a very small opening degree and thus the contact area between the valve element14and the seal part21ais large. This state may cause wear of the seal part21aand result in an increase in the flow rate (the leakage amount) of air in the outlet integration valve181. Accordingly, the amount of air supplied to the fuel cell stack111increases, resulting in excessive power generation amount in the fuel cell stack111. For consumption of this unnecessary electric power, fuel consumption deteriorates and the auxiliaries need to be driven unnecessarily.

In the present embodiment, therefore, based on the stack power generation amount sekw obtained while the control of the outlet integration valve181for auxiliaries (“AUXS control”) is being executed, the controller201determines that the air flow rate increases due to wear of the seal part21ain the outlet integration valve181, as with the inlet sealing valve174, and changes, i.e., learns, the AUXS power-generation controlled opening degree to the valve-closing side (toward 0°).

To be concrete, the controller201performs the control shown inFIG. 32. As shown inFIG. 32, during execution of the AUXS control that controls the opening degree of the outlet integration valve181according to the AUXS power generation request (step S301: YES), the controller201obtains a request AUXS power-generation amount Bkw (step S302). Herein, the “request AUXS power-generation amount Bkw” is the amount of electric power generated in the fuel cell stack111requested to perform the AUXS control.

Successively, the controller201obtains an AUXS power-generation controlled opening degree β, i.e., a target outlet-valve controlled opening degree, based on the obtained request AUXS power generation amount Bkw by referring to a relationship graph shown inFIG. 33.

The controller201then takes a correction controlled opening degree kβ(i) (step S304) and obtains an AUXS power-generation outlet-valve controlled opening degree tβ (step S305). Specifically, the controller201corrects the AUXS power-generation controlled opening degree β with the correction controlled opening degree kβ(i) to calculate the AUXS power-generation outlet-valve controlled opening degree tβ by the following expression:
tβ=β+kβ(i)  (Exp. 2).

The controller201further adjusts the opening degree of the outlet integration valve181to the AUXS power-generation outlet-valve controlled opening degree tβ (step S306). Subsequently, after a lapse of a fixed time (e.g., several seconds (1 of 2 seconds)) (step S307: YES), the controller201takes the stack power generation amount sekw (step S308) and determines whether or not this stack power generation amount sekw is equal to or smaller than the request AUXS power generation amount Bkw (step S309).

In the present embodiment, as described above, after a lapse of the fixed time from when the outlet integration valve181is controlled to the AUXS power-generation outlet-valve controlled opening degree tβ, the air flow rate in the outlet integration valve181is evaluated based on the stack power generation amount sekw.

When the stack power generation amount sekw is determined to be larger than the request AUXS power generation amount Bkw (step S309: NO), it is considered that the flow rate of air flowing through the outlet integration valve181is excessive, that is, the air flow rate is higher than a first predetermined flow rate, the controller201obtains the correction controlled opening degree kβ(i) (step S310). Herein, in step S310, the controller201updates the correction controlled opening degree kβ(i) to the valve-closing side (toward 0°). In step S310, therefore, the controller201makes a calculation using the following expression:
kβ(i)=kβ(i−1)−b%  (Exp. 3)
wherein b % is for example 0.1% to 1% and larger than the foregoing a %.

Subsequently, the controller201takes the correction controlled opening degree kβ(i) (step S304). After performing the processings in steps S305to S308, when the controller201determines that the stack power generation amount sekw is equal to or smaller than the request AUXS power generation amount Bkw (step S309: YES), the controller201further determines whether or not the stack power generation amount sekw is equal to or larger than a predetermined power generation amount (Bkw-Ckw) (step S311). This Ckw is a value for example as large as 10% to 20% of Bkw.

When the stack power generation amount sekw is determined to be equal to or larger than the predetermined power generation amount (Bkw-Ckw) (step S311: YES), the controller201performs the AUXS-control position learning (storage) (step S312). The controller201corrects the AUXS power-generation opening degree to the valve-closing side (toward 0°) until reaching a first target position opening degree at which the air flow rate in the outlet integration valve181becomes the first predetermined flow rate.

In contrast, when the stack power generation amount sekw is determined to be smaller than the predetermined power generation amount (Bkw-Ckw) (step S311: NO), it is conceived that the air flow rate in the outlet integration valve181is too low, that is, the air flow rate is lower than a second predetermined flow rate that is lower than the first predetermined flow rate, the controller201obtains the correction controlled opening degree kβ(i) (step S313) and further performs the processings in step S304and subsequent steps. Herein, in step S313, the controller201updates the correction controlled opening degree kβ(i) to a valve-opening side. In step S313, therefore, the controller201makes a calculation using the following expression:
kβ(i)=kβ(i−1)+b%  (Exp. 4).

In the above way, the controller201corrects the AUXS power-generation opening degree to the valve-opening side until reaching a second target position opening degree at which the air flow rate in the outlet integration valve181becomes the second predetermined flow rate.

In the present embodiment as described above, the AUXS control is the control to be performed with a very small opening degree. This opening degree is anticipated to slightly deviate according to a power generation request (an opening degree). Thus, feedback control using the stack power generation amount sekw is performed.

According to the foregoing present embodiment, while the AUXS power-generation opening-degree control is being executed, when the air flow rate in the outlet integration valve181is determined to be higher than the first predetermined flow rate, the controller201corrects the AUXS power-generation opening degree to the valve-closing side until reaching the first target position opening degree at which the air flow rate in the outlet integration valve181becomes the first predetermined flow rate.

Accordingly, during execution of the AUXS power-generation opening-degree control, when the air flow rate in the outlet integration valve181increases due to wear of the seal part21a, the controller201corrects the AUXS power-generation opening degree to the valve-closing side according to the wear amount of the seal part21a, so that the air flow rate in the outlet integration valve181can be adjusted to the target flow rate. Thus, unnecessary (excess) air supply to the fuel cell stack111is reduced and thus unnecessary (excess) power generation in the fuel cell stack111can be prevented. Consequently, the system can prevent the electric power from being excessively generated in the fuel cell stack111and thus prevent deterioration of fuel consumption, and also can eliminate the need to unnecessarily drive the auxiliaries.

When the controller201determines that the air flow rate in the outlet integration valve181is lower than the second predetermined flow rate that is lower than the first predetermined flow rate while performing the AUXS power-generation opening-degree control, the controller201corrects the AUXS power-generation opening degree to the valve-opening side until reaching the second target position opening degree at which the air flow rate in the outlet integration valve181becomes the second predetermined flow rate.

Accordingly, when the control that corrects the AUXS power-generation opening degree is performed, it is possible to prevent the occurrence of hunching of the outlet integration valve181and regulate the air flow rate in the outlet integration valve181within a target range. Therefore, the fuel cell stack111can generate the electric power as requested and thus enables the auxiliaries to be driven in response to the AUXS power generation request.

The controller201further determines the air flow rate in the outlet integration valve181based on the stack power generation amount sekw. Accordingly, there is no need to further adopt a supplementary detecting means, such as a sensor, for detecting the air flow rate in the outlet integration valve181. Cost reduction can thus be achieved.

The foregoing embodiments are mere example and give no limitations to the present disclosure. The present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof. For instance, in the foregoing embodiment, the rubber seat21is provided in the valve seat13. As an alternative, this rubber seat21may be provided in the valve element14. Furthermore, the rotary shaft15may be configured in a both-end supported structure that its both ends are supported by the first bearing37and another bearing separately provided on an opposite side of the valve element14. The inlet sealing valve174, the outlet integration valve181, and the bypass valve191are not limited to the valves configured in the foregoing embodiment and may be other types of valves, such as a poppet valve in which a valve element that is movable in a direction perpendicular to a seat surface of a valve seat.

REFERENCE SIGNS LIST