Fuel circuit of the fuel cell system

FIELD OF THE INVENTION

[0001] The present invention relates to a fuel circuit of the fuel cell system which circulates and supplies fuel to a fuel cell. More particularly, the present invention relates to a fuel circuit of the fuel cell system wherein fuel circuit of the system of a fuel cell system is equipped with a fuel pump and ejector.

BACKGROUND OF THE INVENTION

[0002] In recent years, polymer electrolyte fuel cell attracts attention as a source of power of an electric vehicle etc. The solid polymer electrolyte fuel cell (PEFC) can generate electricity at normal temperature also, and is being put in practical use by various uses.

[0003] Generally, a fuel cell system divides a cathode pole to one side, and anode pole to the other side, having polymer electrolyte membrane interposed therebetween. It is a system which drives external load with an electric power generated by the chemical reaction of oxygen in the air supplied to the cathode pole, and hydrogen supplied to the anode pole.

[0004] In a fuel cell system with above arrangement, hydrogen and air must be supplied fully more than a fuel cell consumes to discharge condensation water from the fuel cell which is generated within the fuel cell or to obviate damage of the fuel cell due to a fuel shortage.

[0005] By the way, hydrogen is supplied to a fuel cell from a high-pressure hydrogen storage tank such as a cylinder. If the hydrogen which is not consumed is emitted into the atmosphere, this becomes a causative factor of worsening hydrogen fuel consumption remarkably. Therefore, a fuel circuit of the fuel cell system adapted to circulate through hydrogen by ejector which is a kind of a hydrogen pump (fuel pump) which performs inhalation and sending by movable portions, such as a rotation mechanism and a rocking part, as shown in FIG. 19 and FIG. 20, or a jet pump is devised.

[0006] A fuel circuit of the fuel system is arranged in a below-mentioned manner.

[0007] Fuel circuit of the fuel cell system 100 which circulates through fuel only with a hydrogen pump decompresses the pressure of the hydrogen discharged from high-pressure hydrogen storage tank 104 by regulator 103, as shown in FIG. 19. The decompressed hydrogen is supplied to fuel cell 101 through fuel supply stream passage 105. The hydrogen supplied to the fuel cell 101 reacts with oxygen in the air which is supplied to a cathode pole side to cause electricity to be generated in the fuel cell 101. The hydrogen remaining unreacted and existing in the fuel cell 101 is discharged from the fuel cell 101, and is taken in by hydrogen pump 102 provided in fuel circuit stream passage 106. The unreacted hydrogen which was taken in by the hydrogen pump 102 and sent out is made to be merged with the hydrogen which flows through the hydrogen supply stream passage 105 on a downstream of the hydrogen pump 102, and recirculated to be supplied to the fuel cell 101.

[0008] On the other hand, a fuel circuit of the fuel cell system is also arranged in a below-mentioned manner.

[0009] The fuel circuit of the system 200 which circulates through fuel only by ejector decompresses the pressure of the hydrogen discharged from high-pressure hydrogen storage tank 204 with regulator 203 as shown in FIG. 20. Then, the decompressed hydrogen is supplied to ejector 202. The hydrogen thus supplied to ejector 202 generates negative pressure before being supplied to fuel cell 201. The hydrogen supplied to fuel cell 201 reacts with oxygen in an ambient-air which is supplied to a cathode pole side to cause electricity to be generated in the fuel cell 201. The existing unreacted hydrogen is discharged from the fuel cell 201, and merged with inhalation mouth 202a which has negative pressure of ejector 202. The existing unreacted hydrogen which has been merged is mixed and compressed with the hydrogen supplied from regulator 203 within ejector 202, and recirculated to fuel cell 201.

[0010] However, since fuel circuit of the fuel cell system 100 with hydrogen pump 102 only circulates through hydrogen by hydrogen pump 102 independently, broad flow rate range is needed to be covered by one set of the hydrogen pump 102 only. This poses a problem of scaling up of the hydrogen pump 102 per se to operate where efficiency is bad. Then, a problem of increasing of power consumption is also involved therein.

[0011] Also, in a fuel circuit of the fuel cell system 200 with ejector 202 only, negative pressure is generated by use of a pressure energy in high-pressure hydrogen storage tank 204, and this negative pressure is used in such a manner that the hydrogen remaining unreacted discharged from fuel cell 201 is made to be merged with the hydrogen supplied from regulator 203, then subjected to be mixed and compressed therein, and recirculated. Whereas, a problem of wasting pressure energy is involved in the fuel circuit of the fuel cell system 100 with only hydrogen pump 102.

[0012] On the other hand, fuel circuit of the fuel cell system 200 with ejector 202 only also poses a problem. Since a nozzle for transforming pressure energy into speed energy is inserted into ejector 202, if output of fuel cell 201 increases rapidly in the time of acceleration of vehicles, response delay as shown in FIG. 21A arises incurring the problem in which circulation amount does not reach a target value immediately.

[0013] On the contrary, when output of fuel cell 201 is narrowed down in the time of a slowdown of vehicles, since hydrogen is not consumed by the fuel cell 201 as shown in FIG. 21B, negative pressure stops being generated in ejector 202. Therefore, circulation is no longer performed, incurring the problem that circulation amount of ejector 202 falls immediately.

SUMMARY OF THE INVENTION

[0014] In order to overcome the above described problems the present invention is provided. Namely, a fuel circuit of the fuel cell system which can secure the required amount of fuel circulation in the time of the output change in a fuel cell, as well as scaling down a fuel pump per se wherein power consumption is controlled is achieved.

[0015] A fuel circuit of the fuel cell system as set forth in claim 1 to overcome above problems comprises:

[0016] a fuel cell which generates electricity by being supplied with fuel and oxidant; a fuel supply stream passage for supplying the fuel to the fuel cell; a fuel circuit stream passage for making the unreacted fuel discharged from the fuel cell merged with the fuel supply stream passage by which the fuel is made to be circulated; a fuel pump which takes in and sends out the unreacted fuel; and an ejector which inhales the unreacted fuel using negative pressure generated when the fuel flows so as to be made to be merged with said fuel supplied to a fuel cell from.

[0017] According to the invention as set forth in a claim 1, the below-mentioned action and effects are obtained.

[0018] (1) When supplying fuel to a fuel cell while circulating, pressure energies of a fuel source of supply can be collected by ejector. This contributes to suppressing the increase in power consumption of a fuel pump which has posed a problem when circulating through fuel by the fuel pump independently.

[0019] (2) Also, by having a fuel pump, load can be arbitrarily changed. Whereby response delay at the time of the output change (for example when acceleration/deceleration of vehicles is executed) in a fuel cell and the amount fall of circulation of ejector which has posed a problem can be compensated with operating a fuel pump temporarily.

[0020] (3) Namely, by having both ejector and a fuel pump, while either is not functioning among ejector and a fuel pump, the equipment of another side can obviate the performance fall of one equipment.

[0021] The fuel circuit of the fuel cell system according to claim 2 is a fuel circuit of the fuel cell system as set forth in claim 1, wherein a fuel pump is provided in the fuel circuit stream passage which is merged with inhalation mouth belonging to the ejector provided in the fuel supply stream passage.

[0022] According to the arrangement described in claim 2, a compression process is formed into two steps to thereby divide the compressive ability required of each of ejector and a fuel pump, thereby achieving the synergistic effect such as improvement in air flow rate performance for ejector and reduction in power consumption for a fuel pump.

[0023] A fuel circuit of the fuel cell system according to claim 3 is a fuel circuit of the fuel cell system as set forth in claim 1, wherein stream passage which branches from the fuel circuit stream passage and merges with a downstream of the ejector provided in the fuel supply stream passage is provided, and by having the fuel pump in this stream passage, two fuel circuit stream passages are obtained.

[0024] According to the invention as set forth in claim 3, flow rate which a fuel pump and ejector take charge of respectively is shared. Accordingly, since the flow rate which a fuel pump takes charge of becomes small, scaling down of a fuel pump per se is possible.

[0025] A fuel circuit of the fuel cell system according to claim 4 is a fuel circuit of the fuel cell system as set forth in claim 1, wherein the fuel pump is formed in a downstream of the ejector provided in the fuel supply stream passage.

[0026] According to the invention as set forth in claim 4, since fuel (dry gas) supplied to a fuel cell and the unreacted fuel (saturated steam) discharged from the fuel cell come to be mixed through ejector. This surely causes unsaturated steam gas to be generated at the outlet of ejector and this gas is subjected to be compressed with a fuel pump in downstream. Whereby, generation of the condensation water accompanying compression can be overwhelmingly lessened as compared with another process.

[0027] A fuel circuit of the fuel cell system according to claim 5 is a fuel circuit of the fuel cell system as set forth in claim 2, wherein a purge valve is provided in purge conduit which is branched from the fuel circuit stream passage and/or check valve is provided in the fuel circuit stream passage.

[0028] According to the invention as set forth in claim 5, below-mentioned action and effects are obtained.

[0029] (1) By having a purge valve, nitrogen which migrates through a fuel cell stack via fuel cell 1 and superfluous moisture discharged from the fuel cell can be separated and discharged from the system.

[0030] (2) Also, by having check valve, a fuel currently supplied to the fuel cell is prevented from flowing backwards to a fuel circuit stream passage without passing the fuel cell when the unreacted fuel discharged from the fuel cell is purged with a purge valve.

[0031] A fuel circuit of the fuel cell system according to claim 6 is a fuel circuit of the fuel cell system as set forth in claim 5, wherein the check valve is an electro magnetic check valve, and is driven based on the state amount of the fuel circuit of the fuel cell system.

[0032] According to the invention as set forth in claim 6, by employing an electro magnetic check valve instead of a mechanical check valve as a check valve according to this invention, pressure loss of the check valve can be made small. Whereby circulation amount of a fuel improves.

[0033] A fuel circuit of the fuel cell system according to claim 7 is a fuel circuit of the fuel cell system as set forth in claim 2, wherein a bypass stream passage which bypasses the fuel pump and/or the ejector, and a valve in this bypass stream passage are provided.

[0034] The invention as set forth in claim 7 has the below-mentioned action and effects.

[0035] (1) In an operation domain where a fuel pump is hardly functioning or stopped, unnecessary pressure loss which is generated through unreacted fuel (or mixed gas of unreacted fuel and fuel supplied to a fuel cell) passing the fuel pump is obviated.

[0036] (2) In an operation domain in which ejector can hardly collect pressure energies, unnecessary pressure loss which is generated through unreacted fuel (or mixed gas of the unreacted fuel and fuel supplied to a fuel cell) passing ejector is obviated.

[0037] A fuel circuit of the fuel cell system according to claim 8 is a fuel circuit of the fuel cell system as set forth in claim 2, wherein a bypass stream passage in which the valve for bypassing the ejector is formed in the fuel supply stream passage is provided.

[0038] According to the invention as set forth in claim 8, even when a lot of fuel to a fuel cell is needed to be supplied for a short period of time in the time of acceleration of vehicles etc. supply can be satisfied with a good response.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]
FIG. 1A is a general block diagram of a first embodiment of a fuel circuit of the fuel cell system according to this invention.

[0040]
FIG. 1B is an explanatory view showing the feature of the first embodiment of a fuel circuit of the fuel cell system according to this invention.

[0041]
FIG. 1C is a view showing a relation between differential pressure of ejector and the circulation amount.

[0042]
FIG. 2 is a general block diagram showing the whole arrangement of a second embodiment of a fuel circuit of the fuel cell system according to this invention.

[0043]
FIG. 3 is a general block diagram showing the whole arrangement of a third embodiment of a fuel circuit of the fuel cell system according to this invention.

[0044]
FIG. 4 is a general block diagram showing the whole arrangement of a fourth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0045]
FIG. 5A is a general block diagram of a fifth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0046]
FIG. 5B is a general block diagram showing a more preferable exemplary modification of the fifth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0047]
FIG. 6A is a general block diagram of a sixth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0048]
FIG. 6B is an explanatory view showing the feature of the sixth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0049]
FIG. 7A is a general block diagram showing a seventh embodiment of a fuel circuit of the fuel cell system according to this invention.

[0050]
FIG. 7B is an explanatory view showing the installation point of a check valve according to this invention.

[0051]
FIG. 8A is a general block diagram showing an eighth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0052]
FIG. 8B is an explanatory view showing the feature of the eighth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0053]
FIG. 9 is a general block diagram showing a ninth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0054]
FIG. 10 is a general block diagram showing a tenth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0055]
FIG. 11 is a general block diagram showing an eleventh embodiment of a fuel circuit of the fuel cell system according to this invention.

[0056]
FIG. 12 is a general block diagram showing a twelfth embodiment of a fuel circuit of the fuel cell system according to this invention.

[0057]
FIG. 13 is a view (however, hydrogen flow rate supplied to a fuel cell 1 is substantially fixed) showing the each flow rate ratio to an output current of a fuel cell when operating ejector mainly in a high load domain, and operating a hydrogen pump in a low load domain.

[0058]
FIG. 14 is a view (however, hydrogen flow rate to be supplied to a fuel cell is substantially fixed) showing each flow rate ratio to the output current of the fuel cell when operating ejector mainly in a low load domain, and operating a hydrogen pump in a high load domain.

[0059]
FIG. 15 is an explanatory view showing the assistant function of a hydrogen pump at the time of acceleration of vehicles.

[0060]
FIG. 16 is an explanatory view showing the assistant function of a hydrogen pump at the time of a slowdown of vehicles.

[0061]
FIG. 17 is a view showing the relation of pressure loss to the flow rate of mechanical check valve and electro magnetic check valve.

[0062]
FIG. 18 is a view showing the various methods for detecting whether the counter flow occurs in a fuel circuit of the fuel cell system.

[0063]
FIG. 18A is a view showing the system which detects an adverse current by pressure.

[0064]
FIG. 18B is a view showing the system which detects an adverse current by temperature.

[0065]
FIG. 18C is a view showing the system which detects an adverse current by a dew point and humidity.

[0066]
FIG. 18D is a view showing the system which detects an adverse current by the flow rate of a circuit stream passage.

[0067]
FIG. 19 is a general block diagram showing the whole arrangement of a fuel circuit of the fuel cell system which circulates through fuel only with a conventional hydrogen pump.

[0068]
FIG. 20 is a general block diagram showing the whole arrangement of a fuel circuit of the fuel cell system which circulates through fuel only with a conventional ejector.

[0069]
FIG. 21 is an explanatory view showing the problem of a fuel circuit of the fuel cell system which circulates through fuel only by the conventional ejector.

[0070]
FIG. 21A is an explanatory view showing problems at the time of acceleration of vehicles in a fuel circuit of the fuel cell system which circulates through fuel only by ejector etc.

[0071]
FIG. 21B is an explanatory view showing problems at the time of a slowdown of vehicles in a fuel circuit of the fuel cell system which circulates through fuel only by ejector etc.

DESCRIPTION OF THE PREFFERED EMBODIMENT

[0072] Exemplary embodiment of the fuel circuit of the fuel cell system carried in vehicles according to this invention will now be explained with reference to FIG. 1 to FIG. 18.

[0073] First, the fuel circuit of the fuel cell system (series hybrid type) according to first embodiment to fifth embodiment of this invention will be explained with reference to FIG. 1 to FIG. 5.

[0074] Incidentally, a series hybrid type is a fuel circuit of the fuel cell system which includes ejector in the fuel supply stream passage, and the fuel pump in the fuel circuit stream passage, having a fuel cell interposed therebetween.

[0075] First, a fuel circuit of the fuel cell system of the first embodiment will be explained with reference to FIG. 1. Incidentally, FIG. 1A is a general block diagram of the first embodiment of the fuel circuit of the fuel cell system according to this invention, FIG. 1B is an explanatory view showing the feature of the first embodiment of the fuel circuit of the fuel cell system according to this invention, and FIG. 1C is a diagram showing the relation between the differential pressure of ejector and the circulation amount.

[0076] In a fuel circuit of the fuel cell system of the first embodiment, main part comprises:

[0077] fuel cell 1 which generates electricity by being supplied with hydrogen which is a fuel, and oxygen-containing air which is an oxidant;

[0078] fuel supply stream passage 7 for supplying hydrogen to the fuel cell 1 from high-pressure hydrogen storage tank 4;

[0079] regulator 3 provided in the fuel supply stream passage 7 to adjust the pressure of the hydrogen which is supplied to fuel cell 1;

[0080] ejector 2 having inhalation mouth 2a which makes unreacted anode-exhaust gas which is discharged from fuel cell 1 merge with hydrogen which is supplied to fuel cell 1 from the high-pressure hydrogen storage tank 4 using the negative pressure generated when the hydrogen flows therein;

[0081] fuel circuit stream passage 6 wherein unreacted anode-exhaust gas discharged from the fuel cell 1 is caused to be merged with the ejector 2 to circulate hydrogen; and

[0082] hydrogen pump 5 which is a fuel pump provided in the fuel circuit stream passage 6, and takes in and sends out the anode-exhaust gas.

[0083] An action of a fuel circuit of the fuel cell system of the first embodiment with above arrangement will be explained with reference to FIG. 1A.

[0084] Incidentally, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles (for example, the filling pressure 20-50 MPaG).

[0085] (1) Ignition switch of vehicles is ON.

[0086] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. At this time, supply pressure of the hydrogen to the fuel cell 1 is adjusted by regulator 3.

[0087] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the ambient air which is an oxidant supplied to the fuel cell 1, and generates electricity in the fuel cell 1.

[0088] (4) The unreacted hydrogen existing in fuel cell 1 is discharged from the fuel cell 1 as anode-exhaust gas; is taken in hydrogen pump 5 which is a fuel pump and sent out; and is made to be returned to inhalation mouth 2a of ejector 2.

[0089] (5) Anode-exhaust gas returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, and recirculated to the fuel cell 1.

[0090] According to a fuel circuit of the fuel cell system of the first embodiment having above-described arrangement and action,

[0091] (1) When supplying hydrogen while performing a circulation thereof to fuel cell 1, by having ejector 2 since the pressure energies from high-pressure hydrogen storage tank 4 can be collected by ejector 2, increase in power consumption may be controlled which has posed a problem when circulating through hydrogen by hydrogen pump 5 independently.

[0092] (2) Moreover, by having hydrogen pump 5, load can be arbitrarily changed. This contributes to overcome such a problem as response delay of ejector 2 at the time of the output change in fuel cell 1 (for example, at the time of acceleration/deceleration of vehicles), or amount fall of circulation of ejector 2 which have posed a problem when circulating through fuel by ejector 2 independently.

[0093] (3) Namely, while either ejector 2 or hydrogen pump 5 is not functioning, it can be operated so that the equipment of another side may obviate the performance fall of one equipment.

[0094] (4) by having ejector 2 and hydrogen pump 5 in a fuel supply stream passage 7, and in fuel circuit stream passage 6, respectively boosting of hydrogen supply pressure ΔP for supplying to fuel cell 1 by not one step but two steps is carried out using each equipment. Accordingly air flow rate performance can be improved for ejector 2 (since pressure loss ΔPe before and behind ejector 2 is reduced, circulation amount is increased due to the relation that pressure loss ΔPe and the circulation amount Qe of ejector 2 in FIG. 1C are in inverse proportion). For the hydrogen pump 5, since compression work is reduced, power consumption can be reduced. Synergistic effect is thus obtained.

[0095] A fuel circuit of the fuel cell system of the second embodiment according to this invention will next be explained with reference to FIG. 2. Incidentally, FIG. 2 is a general view showing the whole arrangement of the fuel circuit of the fuel cell system of a second embodiment.

[0096] Difference in arrangement between the fuel circulation type fuel-cell system of the second embodiment and the fuel circuit of the fuel-cell system of the first embodiment is as shown in FIG. 2, resides in having purge conduit 9 which is branched from fuel circuit stream passage 6 and used for drainage of the fluid outside of the system; purge valve 10 which is arbitrarily opened and closed in this purge conduit 10; and check valve 8 which allows a flow from hydrogen pump 5 to ejector 2 and bars a flow from ejector 2 to the hydrogen pump 5 on a downstream of the hydrogen pump 5 which is a fuel pump formed in the fuel circuit stream passage 6 in the fuel circuit of the fuel cell system of the second embodiment.

[0097] Accordingly, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the first embodiment used for the explanation so far are designated the same numerals and signs.

[0098] Referring to the action of a fuel circuit of the fuel cell system of the second embodiment with above-described arrangement will be explained with reference to FIG. 2. Incidentally, high-pressure hydrogen is supplied beforehand from the hydrogen filling mouth (not shown) in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0099] (1) Ignition switch of vehicles is ON.

[0100] (2) Hydrogen is supplied to a fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. At this time, supply pressure of the hydrogen to fuel cell 1 is adjusted by regulator 3.

[0101] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to fuel cell 1, and generates electricity in the fuel cell 1.

[0102] (4) Unreacted hydrogen existing in fuel cell 1 is discharged from the fuel cell 1 as anode-exhaust gas, is taken in hydrogen pump 5 which is a fuel pump and sent out, and is made to be returned to inhalation mouth 2a of ejector 2.

[0103] (5) Anode-exhaust gas returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, so as to be recirculated to fuel cell 1.

[0104] (6) in order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1 or superfluous moisture discharged from the fuel cell 1 out of the system, purge valve 10 provided in purge conduit 9 which is branched from fuel circuit stream passage 6 is periodically opened and a hydrogen purge is performed.

[0105] (7) Also, when hydrogen purge is performed, since check valve 8 is installed in a downstream of hydrogen pump 5, hydrogen from high-pressure hydrogen storage tank 4 does not flow backwards. Hence, there is no fuel shortage in fuel cell 1. Consequently, fuel cell 1 is stably operated. In addition, check valve 8 may be provided in an upstream of the hydrogen pump 5.

[0106] According to a fuel circuit of the fuel cell system of the second embodiment with above-described arrangement and an action,

[0107] (1) By having purge valve 10 in purge conduit 9 which is branched from fuel circuit stream passage 6, and check valve 8 in fuel circuit stream passage 6, a flooding which is caused to be generated when condensation water is accumulated in fuel cell 1, or fuel shortage (hesitation) in the fuel cell 1 is obviated and the fuel cell 1 can be stably operated.

[0108] A fuel circuit of the fuel cell system of a third embodiment according to this invention will next be explained with reference to FIG. 3. Incidentally, FIG. 3 is a general view showing the whole arrangement of the fuel circuit of the fuel cell system of the third embodiment.

[0109] Difference in arrangement between a fuel circuit of the fuel-cell system of the third embodiment and a fuel circuit of the fuel-cell system of the second embodiment resides in having bypass stream passage 11 which bypasses hydrogen pump 5 which is a fuel pump of the fuel circuit of the fuel-cell system of the second embodiment, and a valve 12 which can be opened and closed arbitrarily in this bypass stream passage 11 as shown in FIG. 3 in the fuel circuit of the fuel-cell system of the third embodiment.

[0110] Incidentally, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the second embodiment used for the explanation so far are designated the same numerals and signs.

[0111] An action of the fuel circuit of the fuel cell system of the third embodiment thus arranged will be explained with reference to FIG. 3. Incidentally, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0112] (1) Ignition switch of vehicles is ON.

[0113] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed.

[0114] (3) Hydrogen which is the fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to fuel cell 1, and generate electricity in the fuel cell 1.

[0115] (4) Unreacted hydrogen existing in fuel cell 1 is discharged as anode-exhaust gas from the fuel cell 1, is taken in hydrogen pump 5 which is a fuel pump and sent out, and is made to be returned to inhalation mouth 2a of ejector 2.

[0116] (5) Anode-exhaust gas returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, so as to be recirculated to the fuel cell 1.

[0117] (6) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1 and superfluous moisture discharged from the fuel cell 1 out of the system, purge valve 10 provided in purge conduit 9 which is branched from fuel circuit stream passage 6, is opened periodically and a hydrogen purge is performed.

[0118] (7) Also, since check valve 8 is installed in a downstream of hydrogen pump 5 and hydrogen does not flow backwards when performing a hydrogen purge, a fuel cell can be stably operated. Incidentally, a check valve may be formed in an upstream of the hydrogen pump 5.

[0119] (8) Further, in operation domain in which hydrogen pump 5 is hardly functioning or stopped, by opening valve 12 provided in bypass stream passage 11 which is branched from purge conduit 9 and is connected to a downstream of the hydrogen pump 5, anode-exhaust gas discharged from fuel cell 1 can be passed the bypass stream passage 11 side. This permits unnecessary pressure loss generated by passing anode-exhaust gas in the hydrogen pump 5 to be obviated.

[0120] According to a fuel circuit of the fuel cell system of the third embodiment with above-described arrangement and an action;

[0121] In an operation domain where hydrogen pump 5 is hardly functioning or stopped, by employment of bypass stream passage 11 which bypasses the hydrogen pump 5, and valve 12 in this bypass stream passage 11, unnecessary pressure loss which is caused to be generated by anode-exhaust gas discharged from fuel cell 1 passing the hydrogen pump 5 is obviated. Accordingly, since pressure loss is reduced as compared with the case when anode-exhaust gas is made to pass in the hydrogen pump 5, circulation amount of ejector 2 improves.

[0122] A fuel circuit of the fuel cell system of the fourth embodiment according to this invention will next be explained with reference to FIG. 4. Incidentally, FIG. 4 is a general view showing the whole arrangement of the fuel circuit of the fuel cell system of the fourth embodiment. Difference between the fourth embodiment of a fuel circuit of the fuel cell system and the second embodiment of a fuel circuit of the fuel cell system resides in having bypass stream passage 13 which is branched from a downstream of hydrogen pump 5 which is a fuel pump and merges with a downstream of ejector 2, and valve 14 which can be opened and closed arbitrarily in this bypass stream passage 13 provided in the fourth embodiment of a fuel circuit of the cell system.

[0123] An action of the fuel circuit of the fuel cell system of the fourth embodiment thus arranged will next be explained with reference to FIG. 4. In addition, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0124] (1) Ignition switch of vehicles is ON.

[0125] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. Supply pressure of the hydrogen supplied to fuel cell 1 at this time is adjusted by regulator 3.

[0126] (3) Hydrogen which is the fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to fuel cell 1, and generates electricity in the fuel cell 1.

[0127] (4) The unreacted hydrogen existing in fuel cell 1 is discharged from the fuel cell 1 as anode-exhaust gas, is taken in hydrogen pump 5 which is a fuel pump and sent out, and is made to be returned to inhalation mouth 2a of ejector 2.

[0128] (5) Further, anode-exhaust gas returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, and recirculated to the fuel cell 1.

[0129] (6) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1, or superfluous moisture discharged from the fuel cell 1 out of the system, purge valve 10 provided in purge conduit 9 which is branched from the fuel circuit stream passage 6 is opened periodically and a hydrogen purge is performed.

[0130] (7) Also, when a hydrogen purge is performed, since check valve 8 is installed in the lower stream of hydrogen pump 5, hydrogen does not flow backwards. Hence, fuel cell 1 is stably operated. In addition, the check valve 8 may be formed in an upstream of the hydrogen pump 5.

[0131] (8) Also, in an operation domain where ejector 2 can hardly collect pressure energies, by opening valve 14 provided in bypass stream passage 13 which connects a downstream of a hydrogen pump 5 and a downstream of ejector 2, anode-exhaust gas discharged from fuel cell 1 is made to pass the bypass stream passage 13 side. Accordingly, unnecessary pressure loss generated by making anode-exhaust gas pass in ejector 2 is obviated.

[0132] According to a fuel circuit of the fuel cell system of the fourth embodiment having above-described arrangement and an action,

[0133] In an operation domain where ejector 2 can hardly collect pressure energies, by employment bypass stream passage 13 which bypasses ejector 2 and valve 14 in this bypass stream passage 13 unnecessary pressure loss generated by anode-exhaust gas discharged from fuel cell 1 passing ejector 2 with a state of being mixed with hydrogen to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4 is obviated.

[0134] Therefore, since pressure loss on the suction side of hydrogen pump 5 is reduced as compared with when making anode-exhaust gas pass ejector 2, circulation amount improves. Accordingly, increase in power consumption of the hydrogen pump 5 can be controlled.

[0135] A fuel circuit of the fuel cell system of the fifth embodiment according to this invention will next be explained with reference to FIG. 5A. In addition, FIG. 5A is a general view showing the whole arrangement of the fuel circuit of the fuel cell system of the fifth embodiment. The fuel circuit of the fuel cell system of the fifth embodiment is arranged in a manner of incorporating the fuel circuit of the fuel cell system of the third embodiment into the fuel circuit of the fuel cell system of the fourth embodiment. That is, it is the fuel circuit of the fuel cell system wherein bypass 13 and 11 are provided in both of the ejector 2 provided in the fuel gas supply stream passage 7 and hydrogen pump 5 which is a fuel pump provided in the fuel circuit stream passage 6 respectively, and valves 14 and 12 are formed in the bypass stream passages 13 and 11 respectively.

[0136] An action of the fuel circuit of the fuel cell system of the fifth embodiment thus arranged will be explained with reference to FIG. 5A. Incidentally, high-pressure hydrogen is supplied from hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0137] (1) Ignition switch of vehicles is ON.

[0138] (2) Hydrogen is supplied to fuel cell 1 via fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. Supply pressure of the hydrogen supplied to fuel cell 1 at this time is adjusted by regulator 3.

[0139] (3) Hydrogen which is the fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to fuel cell 1, and generates electricity in the fuel cell 1.

[0140] (4) Unreacted hydrogen existing in fuel cell 1 is discharged from the fuel cell 1 as anode-exhaust gas, is taken in a hydrogen pump 5 which is a fuel pump to be sent out, and is made to be returned to inhalation mouth 2a of ejector 2.

[0141] (5) Anode-exhaust gas returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, and recirculated to fuel cell 1.

[0142] (6) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1, and moisture discharged from the fuel cell out of the system, purge valve 10 provided in purge conduit 11 which is branched from the fuel circuit stream passage 6 is opened periodically and a hydrogen purge is performed.

[0143] (7) Also, when a hydrogen purge is performed, since check valve 8 is installed in a downstream of hydrogen pump 5, hydrogen does not flow backwards.

[0144] (8) Further, in an operation domain where hydrogen pump 5 is hardly functioning or stopped, by opening valve 12 provided in bypass stream passage 11 which is branched from purge conduit 9 and is connected to a downstream of the hydrogen pump 5, anode-exhaust gas discharged from fuel cell 1 is made to be passed the bypass stream passage 11 side. Then, unnecessary pressure loss generated by the anode-exhaust gas which is made to pass the hydrogen pump 5 is avoidable.

[0145] (9) Further, in an operation domain where ejector 2 can hardly collect pressure energies, by opening valve 14 provided in bypass stream passage 13 which connects a downstream of the hydrogen pump 5 and a downstream of ejector 2, and by making anode-exhaust gas discharged from fuel cell 1 pass bypass stream passage 13 side, unnecessary pressure loss generated by the anode-exhaust gas which is made to pass ejector 2 is obviated.

[0146] According to a hydrogen supply equipment for the fuel cells of the fifth embodiment with above-described arrangement and an action,

[0147] (1) In an operation domain where hydrogen pump 5 is hardly functioning or stopped, by employment of bypass stream passage 11 which bypasses the hydrogen pump 5, and valve 12 in this bypass stream passage 11, unnecessary pressure loss generated by anode-exhaust gas discharged from fuel cell 1 which passes the hydrogen pump 5 is avoidable. Therefore, since pressure loss is reduced as compared with when making the anode-exhaust gas pass the hydrogen pump 5, circulation amount of ejector 2 improves.

[0148] (2) In an operation domain where ejector 2 can hardly collect pressure energies, unnecessary pressure loss generated by anode-exhaust gas discharged from fuel cell 1 passing the ejector 2 with a state of being mixed with hydrogen to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4 is obviated by employment of bypass stream passage 13 which bypasses ejector 2, and valve 14 in this bypass stream passage 13.

[0149] Accordingly, since the pressure loss on the suction side of hydrogen pump 5 is reduced as compared with when making anode-exhaust gas pass ejector 2, circulation amount improves. Consequently, increase in the power consumption of the hydrogen pump 5 can be controlled.

[0150] (3) By these synergistic effects, a fuel circuit of the fuel cell system wherein scaling down of hydrogen pump 5 is achieved and power consumption of the hydrogen pump 5 can be controlled is obtained.

[0151] Incidentally, more preferable modification of a fuel circuit of the fuel cell system of the fifth embodiment will be shown in FIG. 5B. In addition, difference in arrangement from a fuel circuit of the fuel cell system of the fifth embodiment resides in having bypass stream passage 25a which bypasses an upstream and a downstream of ejector 2 provided in fuel supply stream passage 7, and valve 26a which can be opened and closed arbitrarily in this bypass stream passage 25a in the modified example. In addition, FIG. 5B is a more preferable general block diagram of a modified example. Components and portions of the same designation as those in the fuel circuit of the fuel cell system of the first embodiment used for the explanation so far are designated the same numerals and signs.

[0152] Action of more preferable modification of a fuel circuit of the fuel cell system of the fifth embodiment thus arranged will be explained with reference to FIG. 5B, omitting and simplifying the overlapping explanation of the same actions of the above-described fifth embodiment as those described in (1) to (9) used for the explanation so far.

[0153] (10) By having bypass stream passage 25a which connects an upstream and a downstream of ejector 2 provided in fuel supply stream passage 7, and valve 26a in this bypass stream passage 25a, even when a lot of hydrogen is needed to be supplied to fuel cell 1, there is no response delay by passing ejector 2, and demand can be preferably followed.

[0154] The sixth embodiment of a fuel circuit of the fuel cell system according to this invention and the seventh embodiment of a fuel circuit of the fuel cell system (parallel hybrid type) will next be explained with reference to FIG. 6 and FIG. 7.

[0155] Incidentally, a parallel hybrid type corresponds to a fuel circuit of the fuel cell system, wherein stream passage 15 is formed so as to be branched from fuel circuit stream passage 6 and merged with a downstream of ejector 2 to be adapted to have two fuel circuit stream passages including fuel pumps in this stream passage 15 in the above-described series hybrid type fuel circuit of the fuel cell system.

[0156] A fuel circuit of the fuel cell system of the sixth embodiment will be first explained with reference to FIG. 6. FIG. 6A is a general block diagram of the sixth embodiment of a fuel circuit of the fuel cell system and FIG. 6B is an explanatory view showing the feature of the fuel circuit of the fuel cell system of the sixth embodiment. Incidentally, difference in arrangement between the sixth embodiment of the fuel circuit of the fuel cell system and the second embodiment of the fuel circuit of the fuel cell system resides in having hydrogen pump 5 which is a fuel pump of the fuel circuit of the fuel cell system of the second embodiment, in such a manner that it is branched from fuel circuit stream passage 6 and transferred to stream passage 15 which is merged with a downstream of ejector 2 provided in fuel supply stream passage 7.

[0157] Incidentally, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the second embodiment used for the explanation so far are designated the same numerals and signs.

[0158] In a fuel circuit of the fuel cell system of the sixth embodiment as shown in FIG. 6A, main portion thereof comprises:

[0159] fuel cell 1 which generates electricity by being supplied with hydrogen which is a fuel, and oxygen containing air which is an oxidant; fuel supply stream passage 7 for supplying hydrogen to the fuel cell 1 from high-pressure hydrogen storage tank 4; regulator 3 provided in the fuel supply stream passage 7 and adapted to adjust the pressure of the hydrogen which is supplied to the fuel cell 1; ejector 2 provided in the lower stream of the regulator 3, including inhalation mouth 2a in which anode-exhaust gas discharged from the fuel cell 1 is taken in by use of a negative pressure generated when hydrogen flows therein to be merged with hydrogen which is supplied to the fuel cell 1 from the high-pressure hydrogen storage tank 4; fuel circuit stream passage 6 equipped with check valve 8 which makes anode-exhaust gas containing air ingredient discharged from the fuel cell 1 to be merged with inhalation mouth 2a of the ejector 2, and recirculated; stream passage 15 which branches from the fuel circuit stream passage 6, and merges with a downstream of ejector 2; hydrogen pump 5 which is a fuel pump formed in the stream passage 15, takes in the anode-exhaust gas, and send it out to hydrogen supply stream passage 7; purge conduit 9 which is branched from the fuel circuit stream passage 6; and valve 10 which is provided in this purge conduit 9 and adapted to be opened and closed arbitrary.

[0160] An action of the fuel circuit of the fuel cell system of the sixth embodiment thus arranged will be explained with reference to FIG. 6A.

[0161] Incidentally, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in a high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0162] (1) Ignition switch of vehicles is ON.

[0163] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. Supply pressure of the hydrogen supplied to fuel cell 1 at this time is adjusted by regulator 3.

[0164] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to the fuel cell 1, and generate electricity within the fuel cell 1.

[0165] (4) Unreacted hydrogen existing in fuel cell 1 is discharged as anode-exhaust gas from the fuel cell 1, taken in partially by hydrogen pump 5 which is a fuel pump formed in stream passage 15, sent out to fuel supply stream passage 7, and recirculated to the fuel cell 1.

[0166] (5) On the other hand, residual anode-exhaust gas is made to be returned to inhalation mouth 2a of ejector 2, is mixed and compressed with hydrogen supplied to fuel cell 1 from the high-pressure hydrogen storage tank 4, and recirculated to fuel cell 1.

[0167] (6) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1, or superfluous moisture discharged from the fuel cell 1 out of the system, purge valve 10 provided in purge conduit 9 which is branched from the fuel circuit stream passage 6 is made to be opened periodically to perform a hydrogen purge.

[0168] (7) Also, when a hydrogen purge is performed, check valve 8 installed in an upstream (fuel circuit stream passage 6 side) of ejector 2 allows fuel cell 1 to be operated stably without making hydrogen flow backwards.

[0169] According to a fuel circuit of the fuel cell system of the sixth embodiment with above-described arrangement and action, fuel circuit stream passage 6 equipped with check valve 8 wherein anode-exhaust gas discharged from fuel cell 1 is made to be merged with inhalation mouth 2a of ejector 2 and recirculated as shown in FIG. 6B, and stream passage 15 which branches from the fuel circuit stream passage 6 and is connected to a downstream of ejector 2 are provided, and this stream passage 15 includes hydrogen pump 5. By including the hydrogen pump 5 in this stream passage 15, the flow rate which the hydrogen pump 5 and each of ejector 2 take charge of is shared. That is, circulation flow rate Qb turns into totaled value of ejector flow rate Qe and hydrogen pump flow rate Qp. Accordingly, as compared with a fuel circuit of the fuel cell system with a hydrogen pump only, the hydrogen pump 5 can reduce flow rate. This contributes to scaling down the hydrogen pump 5.

[0170] Also, this sixth embodiment is effective to make pressure loss small especially in stream passage 15 as compared with the later seventh embodiment.

[0171] A fuel circuit of the fuel cell system of the seventh embodiment will next be explained with reference to FIG. 7. Incidentally, FIG. 7A is a general block diagram of the seventh embodiment of the fuel circuit of the fuel cell system and FIG. 7B is a diagram showing the installation point of a check valve according to this invention.

[0172] Difference in arrangement between the seventh embodiment of a fuel circuit of the fuel cell system and the sixth embodiment of a fuel circuit of the fuel cell system resides in having check valve 16 in either an upstream or a downstream of both sides of the hydrogen pump 5 in stream passage 15 (with this embodiment, provided in an upstream of the hydrogen pump 5), in the fuel circuit of the fuel cell system of the seventh embodiment. This is a preferable modified example of the sixth embodiment of a fuel circuit of the fuel cell system.

[0173] Accordingly, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the sixth embodiment used for the explanation so far are designated the same numerals and signs.

[0174] An action of a fuel circuit of the fuel cell system of the seventh embodiment with above-described arrangement will be explained with reference to FIG. 7, omitting and simplifying the overlapping explanation of the same actions of the above-described sixth embodiment as those described in (1) to (6) used for the explanation so far.

[0175] (7) When a hydrogen purge is performed, check valve 8 is installed in an upstream of ejector 2 to thereby prevent hydrogen from flowing backwards towards a fuel circuit stream passage 6 from inhalation mouth 2a. Furthermore, since check valve 16 is installed also in an upstream (or downstream of a flow) of hydrogen pump 5, counter flow prevention of more than fluid resistance within the hydrogen pump 5 is performed, to thereby control appropriately hydrogen flowing in towards fuel circuit stream passage 6 from a downstream of ejector 2. Hence, more stable operation of a fuel cell is achieved.

[0176] According to a fuel circuit of the fuel cell system of the seventh embodiment with above-described arrangement and action, as shown in FIG. 7, check valve 8 is equipped in a fuel circuit stream passage 6 in which anode-exhaust gas discharged from fuel cell 1 is made to join inhalation mouth 2a of ejector 2, so that hydrogen may be circulated. Along with this, check valve 16 is also equipped in an upstream of hydrogen pump 5 provided in stream passage 15. Accordingly, in the domain where one of the two of ejector 2 or the hydrogen pumps 5 has stopped operation, it can be prevented more preferably than the fuel circuit of the fuel cell system of the sixth embodiment that hydrogen causes a counter flow with the result that hydrogen is supplied to fuel cell 1 from the outlet side of the fuel cell 1.

[0177] In addition, if the attachment position of check valve 8 and 16 in this case are provided in an upstream side of the turning point of fuel circuit stream passage 6, as shown in FIG. 7B, an internal circuit way is formed in a downstream side of a turning point. The result shows that it is impossible to attract anode-exhaust gas. Therefore, attachment position is preferably determined in a downstream side of the turning point of the fuel circuit stream passage 6.

[0178] Because of the arrangement in the sixth embodiment of a fuel circuit of the fuel cell system or the seventh embodiment of the fuel circuit of the fuel cell system described thus far, by having check valve 8 and/or check valve 16 equipped in a downstream side of the turning point of the fuel circuit stream passage 6 of fuel cell 1, it can be prevented that hydrogen causes a counter flow resulting in recirculating to the fuel cell 1 from the outlet side of the fuel cell 1 in a domain where either one of ejector 2 or hydrogen pump 5 has stopped operation at the time other than purging.

[0179] In addition, although not represented in the drawing, as a more preferable modified example of a fuel circuit of the fuel cell system of the seventh embodiment which is similar to the fifth embodiment of the fuel circuit of the fuel cell system, a bypass stream passage which bypasses an upstream and a downstream of ejector 2 provided in fuel supply stream passage 7, and a valve adapted to be opened and closed arbitrarily in this bypass stream passage may be provided.

[0180] With a fuel circuit of the fuel cell system arranged in the above manner, by having a bypass stream passage which bypasses an upstream and a downstream of ejector 2 in fuel supply stream passage 7 and a valve adapted to be opened and closed arbitrarily in this bypass stream passage, even when a big amount of hydrogen is needed to be supplied to fuel cell 1 for a short period of time, by opening the valve provided in the bypass stream passage, there is no response delay by passing ejector 2, to thereby preferably follow a demand.

[0181] A fuel circuit of the fuel cell system from the eighth embodiment of the fuel circuit of the fuel cell system according to this invention to the twelfth embodiment of the fuel circuit of the fuel cell system (boost hybrid type) will next be explained with reference to FIG. 8 to FIG. 12.

[0182] Incidentally, a boost hybrid type is a fuel circuit of the fuel cell system which formed hydrogen pump 5 in a downstream of ejector 2 provided in fuel supply stream passage 7. The eighth embodiment of a fuel circuit of the fuel cell system will be explained first with reference to FIG. 8. Here, FIG. 8A is a general block diagram of the eighth embodiment of the fuel circuit of the fuel cell system and FIG. 8B is an explanatory view of the feature of the eighth embodiment of the fuel circuit of the fuel cell system. Difference in arrangement between a fuel circuit of the fuel cell system of the eighth embodiment and a fuel circuit of the fuel cell system of the second embodiment which is similar to the eighth embodiment resides in having a hydrogen pump 5 which is a fuel pump of the fuel circuit of the fuel cell system of the second embodiment transferred to a downstream of ejector 2 provided in fuel supply stream passage 7 in the eighth embodiment of the fuel circuit of the fuel cell system. Incidentally, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the second embodiment used for the explanation so far are designated the same numerals and signs.

[0183] In a fuel circuit of the fuel cell system of the eighth embodiment as shown in FIG. 8, the main part thereof comprises:

[0184] Fuel cell 1 which generates electricity by being supplied with hydrogen which is a fuel, and oxygen containing air which is an oxidant; fuel supply stream passage 7 for supplying hydrogen to the fuel cell 1 from high-pressure hydrogen storage tank 4; regulator 3 provided in the fuel supply stream passage 7 which adjusts the pressure of the hydrogen to be supplied to the fuel cell 1 from the high-pressure hydrogen storage tank 4; ejector 2 having inhalation mouth 2a provided in a downstream of the regulator 3 which makes the unreacted anode-exhaust gas discharged from the fuel cell 1 merge with hydrogen which is supplied to the fuel cell 1 from the high-pressure hydrogen storage tank 4 using the negative pressure generated when hydrogen flows; hydrogen pump 5 which is a fuel pump formed in a downstream of the ejector 2, takes in the mixed gas of hydrogen and anode-exhaust gas discharged from ejector 2, and send it out to the fuel cell 1; fuel circuit stream passage 6 which has check valve 8 which makes the unreacted anode-exhaust gas discharged from the fuel cell 1 merge with inhalation mouth 2a of ejector 2 to be recirculated; purge conduit 9 which is branched from the fuel circuit stream passage 6; and valve 10 adapted to be opened and closed arbitrarily provided in this purge conduit 9.

[0185] An action of a fuel circuit of the fuel cell system of the eighth embodiment thus arranged will be explained with reference to FIG. 8.

[0186] Incidentally, high-pressure hydrogen is supplied beforehand from a hydrogen filling mouth (not shown) in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in a high-pressure hydrogen storage tank 4 carried in fuel cell vehicles

[0187] (1) Ignition switch of vehicles is ON.

[0188] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. Supply pressure of the hydrogen supplied to the fuel cell 1 at this time is adjusted by regulator 3.

[0189] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to the fuel cell 1, and generates electricity in the fuel cell 1.

[0190] (4) Unreacted hydrogen existing in fuel cell 1 is discharged as anode-exhaust gas from the fuel cell 1, and is made to be returned to inhalation mouth 2a of ejector 2 via check valve 8.

[0191] (5) Anode-exhaust gas which is made to return to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, and is recirculated to the fuel cell 1.

[0192] By employment of above-described arrangement, as shown in FIG. 8B, since anode-exhaust gas, which is saturated steam is mixed and compressed with the hydrogen (dry hydrogen which hardly contains moisture) supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, it always becomes a gas with a high dew point (unsaturated steam hydrogen containing gas), and is supplied to hydrogen pump 5 which is a fuel pump.

[0193] (6) Unsaturated steam hydrogen containing gas supplied to hydrogen pump 5 is supplied to fuel cell 1 without generating condensation water, even when compressed within hydrogen pump 5.

[0194] (7) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1, or superfluous moisture discharged from the fuel cell 1 out of the system, purge valve 10 provided in the purge conduit 9 which is branched from the fuel circuit stream passage 6 is made to be periodically opened and a hydrogen purge is performed.

[0195] (8) Also, when a hydrogen purge is performed, since check valve 8 is installed in an upstream (fuel circuit stream passage 6 side) of ejector 2 and hydrogen does not flow backwards, to thereby allow fuel cell 1 to be operated stably.

[0196] According to the eighth embodiment of a fuel circuit of the fuel cell system with above-described arrangement and action,

[0197] (1) Generally, anode-exhaust gas emitted from the outlet of fuel cell 1 is emitted with a state of saturated steam. Compression of gas of such saturated steam is known to give rise condensation water generated when steam condenses. However, if saturated steam is inhaled through ejector 2 as described in this embodiment and dry hydrogen is introduced, these will be mixed and compressed within ejector 2 resulting in unsaturated steam hydrogen containing gas. Accordingly, condensation water will not arise even when gas is compressed. Consequently, even when unsaturated steam hydrogen containing gas is compressed with hydrogen pump 5, generation of condensation water is rarely checked as compared with another process.

[0198] A fuel circuit of the fuel cell system of the ninth embodiment according to this invention will next be explained with reference to FIG. 9. Incidentally, FIG. 9 is a general block diagram showing the whole arrangement of the ninth embodiment of a fuel circuit of the fuel cell system. Difference in arrangement between the fuel circuit of the fuel-cell system of the ninth embodiment and the fuel circuit of the fuel-cell system of the eighth embodiment resides in having bypass stream passage 17 which bypasses hydrogen pump 5 which is a fuel pump of the fuel circuit of the fuel-cell system of the eighth embodiment and valve 18 adapted to be opened and closed arbitrarily in this bypass stream passage 17 in the ninth embodiment of a fuel circuit of the fuel-cell system.

[0199] Components and portions of the same designation as those in the fuel circuit of the fuel cell system of the eighth embodiment used for the explanation so far are designated the same numerals and signs.

[0200] An action of a fuel circuit of the fuel cell system of the ninth embodiment thus arranged will be explained with reference to FIG. 9. In addition, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in a fuel cell vehicles.

[0201] (1) Ignition switch of vehicles is ON.

[0202] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. Supply pressure of the hydrogen supplied to the fuel cell 1 at this time is adjusted by regulator 3.

[0203] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to the fuel cell 1, and generates electricity in the fuel cell 1.

[0204] (4) Unreacted hydrogen existing in fuel cell 1 is discharged as anode-exhaust gas from the fuel cell 1, and is made to be returned to inhalation mouth 2a of ejector 2 via check valve.

[0205] (5) Anode-exhaust gas which is made to be returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4 and recirculated to fuel cell 1.

[0206] Because of the arrangement described thus far, since anode-exhaust gas, which is saturated steam is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, it always turns into gas (unsaturated steam hydrogen containing gas) with high dew point, and is supplied to hydrogen pump 5.

[0207] (6) Unsaturated steam hydrogen containing gas supplied to hydrogen pump 5 is supplied to fuel cell 1 without generating condensation water even if compressed within the hydrogen pump 5.

[0208] (7) In an operation domain where hydrogen pump 5 is hardly functioning or stopped during operation, unnecessary pressure loss generated by making hydrogen containing gas pass the hydrogen pump 5 side is obviated by opening valve 18 provided in the bypass stream passage of the hydrogen pump 5 to make hydrogen containing gas pass the bypass stream passage 17 side, to thereby allow the circulation capability of ejector 2 to be maintained in high state.

[0209] (8) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1 or superfluous moisture discharged from the fuel cell 1 out of the system, a purge valve 10 provided in purge conduit 9 which is branched from the fuel circuit stream passage 6 is periodically opened and a hydrogen purge is performed.

[0210] (9) Also, when a hydrogen purge is performed, since check valve 8 is installed in an upstream side (fuel circuit stream passage 6 side) of ejector 2 and hydrogen does not flow backwards. Hence, a stable operation of fuel cell 1 is achieved.

[0211] According to the fuel circuit of the fuel cell system of the ninth embodiment with above-described arrangement and action, in an operation domain where hydrogen pump 5 is hardly functioning or stopped during operation, unnecessary pressure loss generated by making hydrogen containing gas pass the hydrogen pump 5 side is obviated by making hydrogen containing gas pass the bypass stream passage 17 side, to thereby allow the circulation capability of ejector 2 to be maintained in high state.

[0212] A fuel circuit of the fuel cell system of the tenth embodiment will next be explained with reference to FIG. 10. Incidentally, FIG. 10 is a general block diagram of the tenth embodiment of a fuel circuit of the fuel cell system.

[0213] Difference in arrangement of a fuel circuit of the fuel cell system of the tenth embodiment and the fuel circuit of the fuel cell system of the eighth embodiment is resides in having bypass stream passage 19 which bypasses ejector 2, and valve 20 which can be arbitrarily opened and closed in this bypass stream passage 19.

[0214] Incidentally, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the eighth embodiment used for the explanation so far are designated the same numerals and signs.

[0215] Action of a fuel circuit of the fuel cell system of the tenth embodiment thus arranged will be explained with reference to FIG. 10. Incidentally, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0216] (1) Ignition switch of vehicles is ON.

[0217] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. Supply pressure of the hydrogen supplied to a fuel cell 1 at this time is adjusted by regulator 3.

[0218] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant supplied to fuel cell 1, and generates electricity in the fuel cell 1.

[0219] (4) Hydrogen remaining unreacted existing in fuel cell 1 is discharged as anode-exhaust gas from the fuel cell 1, and is made to be returned to inhalation mouth 2a of ejector 2 via check valve 8.

[0220] (5) Anode-exhaust gas which is made to be returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, recirculated to fuel cell 1.

[0221] By employment of above-described arrangement, since anode-exhaust gas which is saturated steam is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, it always turns into gas with high dew point (unsaturated steam hydrogen containing gas), and is supplied to hydrogen pump 5.

[0222] (6) Unsaturated steam hydrogen containing gas supplied to hydrogen pump 5 is supplied to fuel cell 1 without generating condensation water, even when compressed within the hydrogen pump 5.

[0223] (7) In an operation domain where the circuit capability of ejector 2 is scarce, by opening valve 20 provided on bypass stream passage 19 of ejector 2 during operation to make anode-exhaust gas bypass the bypass stream passage 19 side, pressure loss of the suction side of the hydrogen pump 5 can be made small as much as possible. Then, increase in power consumption can be controlled.

[0224] (8) Also, in order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1 or superfluous moisture discharged from fuel cell 1 out of the system, purge valve 10 provided in purge conduit 9 which is branched from the fuel circuit stream passage 6 is periodically opened and a hydrogen purge is performed.

[0225] (9) Also, when hydrogen purge is performed, since check valve 8 is installed in an upstream side of ejector 2 and hydrogen does not flow backwards, stable operation of fuel cell 1 is achived.

[0226] According to a fuel circuit of the fuel cell system of the tenth embodiment with above described arrangement and action, in an operation domain where the circuit capability of ejector 2 is scarce, unnecessary pressure loss generated by anode-exhaust gas passing ejector 2 side is avoidable by opening valve 20 provided in bypass stream passage 19 of ejector 2. Accordingly, since pressure loss on the suction side of hydrogen pump 5 can be made small as much as possible, increase in power consumption can be controlled.

[0227] A fuel circuit of the fuel cell system of the eleventh embodiment will next be explained with reference to FIG. 11. Incidentally, a fuel circuit of the fuel cell system of the eleventh embodiment is arranged in such a manner as incorporating the fuel circuit of the fuel cell system of the ninth embodiment into the fuel circuit of the fuel cell system of the tenth embodiment. That is, the fuel circuit of the fuel cell system includes, bypass stream passage 19 which bypasses ejector 2 and valve 20 which can be arbitrarily opened and closed in this bypass stream passage 19. Furthermore, it is a fuel circuit of the fuel cell system which includes bypass stream passage 21 provided in such a manner as being branched from bypass stream passage 19 to bypass hydrogen pump 5, and a similar valve 22 with valve 20 in this bypass stream passage 21.

[0228] Also, in this fuel circuit of the fuel cell system, bypass stream passage 23 which connects an upstream of ejector 2 provided in fuel supply stream passage 7 and a downstream of hydrogen pump 5, and valve 24 which can be arbitrarily opened and closed in this bypass stream passage 23 are provided.

[0229] In addition, FIG. 11 is a block diagram showing the whole arrangement of a fuel circuit of the fuel cell system of the eleventh embodiment.

[0230] Accordingly, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the tenth embodiment used for the explanation so far are designated the same numerals and signs.

[0231] Action of a fuel circuit of the fuel cell system of the eleventh embodiment thus arranged will be explained with reference to FIG. 11. Incidentally, high-pressure hydrogen is supplied from the hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0232] (1) Ignition switch of vehicles is ON.

[0233] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed. At this time, supply pressure of the hydrogen supplied to fuel cell 1 is adjusted by regulator 3.

[0234] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant to be supplied to fuel cell 1, and electricity is generated in the fuel cell 1.

[0235] (4) Unreacted hydrogen existing in fuel cell 1 is discharged as anode-exhaust gas from the fuel cell 1, and is made to be returned to inhalation mouth 2a of ejector 2 via check valve 8.

[0236] (5) Anode-exhaust gas which is made to be returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) to be supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, and recirculated to fuel cell 1.

[0237] By employment of this arrangement, since anode-exhaust gas, which is saturated steam is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, it always turns into a gas having high dew point (unsaturated steam hydrogen containing gas), and is supplied to hydrogen pump 5.

[0238] (6) Unsaturated steam hydrogen containing gas supplied to hydrogen pump 5 is supplied to fuel cell 1 without generating condensation water, even when compressed within the hydrogen pump 5.

[0239] (7) In an operation domain where the circuit capability of ejector 2 is scarce during operation, by opening valve 20 provided in bypass stream passage 19 of ejector 2, and making anode-exhaust gas bypass the bypass stream passage 19 side, pressure loss in the suction side of the hydrogen pump 5 can be made small as much as possible, and increase in power consumption can be controlled.

[0240] (8) On the other hand in an operation domain where hydrogen pump 5 is hardly functioning or stopped, since unnecessary pressure loss generated by passing the hydrogen pump 5 side is avoidable by opening valve 22 provided in bypass stream passage 21 side of the hydrogen pump 5, circuit capability of ejector 2 is maintainable in high state.

[0241] (9) Also, flow rate of hydrogen containing gas supplied to fuel cell 1 which is intended to pass ejector 2 side or hydrogen pump 5 side can be finely adjusted by shared conduit which can be obtained by uniting two bypass ways 19 and 21.

[0242] (10) Moreover, bypass stream passage 23 which connects between upstream of ejector 2 provided on fuel supply stream passage 7 and a downstream of hydrogen pump 5, and valve 24 in this bypass stream passage 23 are provided. This preferably allows a demand to be followed with no response delay caused by passing ejector 2, by opening valve 24 provided in the bypass stream passage 23 in case where it is necessary to supply a lot of hydrogen to fuel cell 1 for a short period of time.

[0243] (11) In addition, in order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1 and condensation water in fuel cell 1, etc. out of the system, purge valve 10 provided in purge conduit 9 which is branched from fuel circuit stream passage 6 is periodically opened, and a hydrogen purge is performed.

[0244] (12) Also, when a hydrogen purge is performed, since check valve 8 is installed in an upstream side (fuel circuit stream passage 6 side) of ejector 2, hydrogen does not flow backwards. Whereby a stable operation of fuel cell 1 is achieved.

[0245] According to a fuel circuit of the fuel cell system of the eleventh embodiment with thus described arrangement and action,

[0246] (1) By employment of the arrangement in such a manner as having bypass stream passage 19 which bypasses ejector 2, valve 20 in this bypass stream passage 19, bypass stream passage 21 provided so as to be branched from the bypass stream passage 19 to bypass hydrogen pump 5, and valve 22 in this bypass stream passage 22, when supplying hydrogen containing gas to a fuel cell, flow rate to be passed to the ejector 2 or hydrogen pump 5 side can be finely adjusted.

[0247] (2) Also, by having bypass stream passage 23 which connects an upstream of ejector 2 provided in fuel supply stream passage 7 to a downstream of hydrogen pump 5, and valve 24 in this bypass stream passage 23, even when a big amount of hydrogen is needed to be supplied to fuel cell 1 for a short period of time, there is no response delay by passing ejector 2, to thereby preferably follow a demand.

[0248] (3) Moreover, when controlling polar differential pressure of fuel cell 1, since apparatus is not provided in stream passage which supplies hydrogen to the fuel cell 1 via bypass stream passage 23 from regulator 3, response when supplying hydrogen to fuel cell 1 improves.

[0249] Incidentally, difference in arrangement between a fuel circuit of the fuel cell system of the twelfth embodiment and a fuel circuit of the fuel-cell system of the eleventh embodiment resides in having bypass stream passage 25b which connects an upstream of ejector 2 provided in fuel supply stream passage 7 to an upstream of a hydrogen pump, and valve 26b which can be arbitrarily opened and closed in this bypass stream passage 25b.

[0250] Moreover, FIG. 12 is a general block diagram of a twelfth embodiment of a fuel circuit of the fuel cell system. Accordingly, the components and portions of the same designation as those in the fuel circuit of the fuel cell system of the eleventh embodiment used for the explanation so far are designated the same numerals and signs.

[0251] Action of a fuel circuit of the fuel cell system of the twelfth embodiment thus arranged will be explained with reference to FIG. 12. Incidentally, high-pressure hydrogen is supplied from a hydrogen filling mouth (not shown) beforehand in a high-pressure hydrogen supply type filling place (for example, the filling pressure 20-50 MPaG) and stored in high-pressure hydrogen storage tank 4 carried in fuel cell vehicles.

[0252] (1) Ignition switch of vehicles is ON.

[0253] (2) Hydrogen is supplied to fuel cell 1 through fuel supply stream passage 7 from high-pressure hydrogen storage tank 4 as needed.

[0254] (3) Hydrogen which is a fuel supplied to fuel cell 1 reacts with oxygen in the oxygen containing air which is an oxidant to be supplied to fuel cell 1, and electricity is generated in fuel cell 1.

[0255] (4) Unreacted hydrogen existing in fuel cell 1 is discharged as anode-exhaust gas from fuel cell 1, and is made to be returned to inhalation mouth 2a of ejector 2 via check valve 8.

[0256] (5) Anode-exhaust gas made to be returned to inhalation mouth 2a of ejector 2 is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, and recirculated to fuel cell 1.

[0257] Because of the arrangement described thus far, since anode-exhaust gas which is saturated steam is mixed and compressed with hydrogen (dry hydrogen which hardly contains moisture) supplied to fuel cell 1 from high-pressure hydrogen storage tank 4, it always turns into gas (unsaturated steam hydrogen containing gas) with high dew point, and is supplied to hydrogen pump 5.

[0258] (6) Unsaturated steam hydrogen containing gas supplied to hydrogen pump 5 is supplied to fuel cell 1 without generating condensation water, even if compressed within the hydrogen pump 5.

[0259] (7) In an operation domain where circulation capability of ejector 2 is scarce, by opening valve 20 provided in bypass stream passage 19 of ejector 2 during operation to make anode-exhaust gas bypass the bypass stream passage 19 side, pressure loss in the suction side of the hydrogen pump 5 can be made small as much as possible. Then, increase in power consumption can be controlled.

[0260] (8) On the other hand in operation domain where hydrogen pump 5 is hardly functioning or stopped, since unnecessary pressure loss generated by passing the hydrogen pump 5 side is avoidable by opening valve 22 provided in bypass stream passage 21 side of the hydrogen pump 5, circulation capability of ejector 2 is maintainable in high state.

[0261] (9) Also, flow rate of hydrogen containing gas to be supplied to fuel cell 1 which is intended to pass ejector 2 side or hydrogen pump 5 side can be finely adjusted by shared conduit which can be obtained by uniting two bypass ways 19 and 21.

[0262] (10) In a fuel circuit of the fuel cell system arranged in above-described manner, by having bypass stream passage 25b which bypasses an upstream of ejector 2 and a downstream of hydrogen pump 5 provided in fuel supply stream passage 7 and valve 26b adapted to be arbitrarily opened and closed in this bypass stream passage 25b, even when a big amount of hydrogen is needed to be supplied to fuel cell 1 for a short period of time, by opening the valve 26b provided in the bypass stream passage 25b, there is no response delay by passing ejector 2, to thereby preferably follow a demand.

[0263] (11) In order to separate and remove nitrogen which migrates through fuel circuit stream passage 6 via fuel cell 1 or superfluous moisture discharged from the fuel cell 1 out of the system, purge valve 10 provided in purge conduit 9 which is branched from the fuel circuit stream passage 6 is periodically opened and a hydrogen purge is performed.

[0264] (12) Also, when a hydrogen purge is performed, since check valve 8 is installed in an upstream side (fuel circuit stream passage 6 side) of ejector 2 and hydrogen does not flow backwards. Hence, a stable operation of a fuel cell 1 is achieved.

[0265] According to a fuel circuit of the fuel cell system of the twelfth embodiment with above-described arrangement and action,

[0266] (1) By employment of the arrangement in such a manner as having bypass stream passage 19 which bypasses ejector 2, valve 20 in this bypass stream passage 19, bypass stream passage 21 provided so as to be branched from the bypass stream passage 19 to bypass hydrogen pump 5, and valve 22 in this bypass stream passage 22 when supplying hydrogen containing gas to fuel cell 1, flow rate to be passed the ejector 2 or hydrogen pump 5 side can be finely adjusted.

[0267] (2) Moreover, bypass stream passage 25b which connects upstream of ejector 2 provided on fuel supply stream passage 7 to an upstream of hydrogen pump 5, and valve 26b in this bypass stream passage 25b are provided. This preferably allows a demand to be followed with little response delay, when fuel cell 1 needs a big amount of hydrogen to be supplied for a short period of time.

[0268] (3) Furthermore, by having bypass stream passage 25b which connects an upstream of ejector 2 provided in fuel supply stream passage 7, and an upstream of hydrogen pump 5, and valve 26b in this bypass stream passage 25b, compression of the moisture containing gas in ejector 2 can be avoided, and the effect of condensation water generating prevention within the hydrogen pump 5 can be heightened.

[0269] As described in the foregoing, arrangement etc. from the first embodiment to twelfth embodiment of fuel circuit of the fuel cell systems were explained. By having both of a hydrogen pump which is actually a fuel pump and an ejector built into the fuel circuit system of a fuel cell, why power-saving and the whole energy efficiency are heightened will be explained with reference to FIG. 13 to FIG. 16 as in the following.

[0270] In a fuel circuit of the fuel cell system according to this invention, ratio of circulation amount/the total gas supply amount supplied to a fuel cell, in relation to output current of the fuel cell when operating ejector mainly in a high load domain and operating hydrogen pump in a low load domain is shown in FIG. 13, (however, hydrogen flow rate supplied to fuel cell 1 is substantially fixed). In FIG. 13, axis of ordinate denotes a circulation amount of gas ratio to the total supply amount of gas, while axis of abscissa denotes output current of a fuel cell.

[0271] Flow rate characteristic of an ejector itself independently will be explained as hereunder. Namely, as shown in FIG. 1C, if differential pressure ΔPe before and behind ejector is decreased, circulation amount Qe will be increased, whereas if differential pressure ΔPe before and behind ejector is increased, circulation amount Qe will be decreased. Moreover, if there is little supply amount of hydrogen to a fuel cell, since negative pressure is hard to come to be generated, it is becoming hard to circulate the anode-exhaust gas which is discharged from the fuel cell.

[0272] Hereupon, if the system is arranged in such a manner that ejector is operated in a high load side where output current of fuel cell 1 is large, (there is much hydrogen supply amount), and if hydrogen pump is operated in a low load side where output current of fuel cell 1 is small, since flow rate can be made to be shared with each other based on the output current value of a fuel cell, hydrogen pump capacity can be made small and the power consumption of a hydrogen pump can be decreased.

[0273] On the other hand, ratio of the circulation amount/total gas supply amount supplied to a fuel cell, in relation to the output current of the fuel cell when operating ejector mainly in a low load domain, and operating a hydrogen pump in a high load domain in the fuel circuit of the fuel cell system according to this invention will be shown in FIG. 14. (However, hydrogen flow rate supplied to fuel cell 1 is substantially fixed). In FIG. 14, axis of ordinate denotes the gas circulation amount ratio to the gas supply amount, whereas axis of abscissa denotes output current of the fuel cell.

[0274] As a flow rate characteristic of hydrogen pump itself independently, there is an aspect in which efficiency becomes low in a low flow rate region.

[0275] Hereupon, in the system as shown in FIG. 14, contrary to the system as shown in FIG. 13, ejector is operated in a low load side where output current of a fuel cell is small, whereas hydrogen pomp is operated in a high load side where output current of a fuel cell is large. By employing above-described arrangement, since a hydrogen pump had an aspect in which efficiency is low in a low flow rate region, the operation domain is assisted by ejector to allow energy efficiency to be raised as a whole.

[0276] In addition, not only ejector but the flow rate characteristic of a pump generally has mountain-shaped characteristics. In order to bring it close to a target value as shown in FIG. 14, and to secure a large operation domain, it is necessary to make the peak of a mountain exceed a target value once.

[0277] Next, when a fuel circuit of the fuel cell system is used at the time of acceleration/deceleration of vehicles, how the problem posed by the system using ejector only is overcome will be explained with reference to FIG. 15 and FIG. 16.

[0278] Incidentally, FIG. 15 is an explanatory view showing hydrogen pump assistance at the time of acceleration, and FIG. 16 is an explanatory view showing the hydrogen pump assistance at the time of a slowdown.

[0279] First, with reference to FIG. 15, hydrogen pump assistance at the time of vehicles acceleration will be explained. Incidentally, in FIG. 15, axis of ordinate denotes output and flow rate, and axis of abscissa denotes time.

[0280] This method is performed, when a lot of hydrogen is needed at the acceleration time of vehicles. As shown in FIG. 15, it is a method by which the flow rate insufficiency to be supplied to a fuel cell is compensated in the hydrogen pump side by raising the output of a hydrogen pump temporarily by control means (not shown) in response to the response delay of time generated in ejector.

[0281] By operating as is described so far, a remarkable damage to a fuel cell ascribed to a hydrogen lack state within a fuel cell caused by an excessive load is avoidable.

[0282] Next, with reference to FIG. 16, hydrogen pump assistance at the time of a vehicles slowdown will be explained.

[0283] Incidentally, axis of ordinate denotes output and flow rate, and axis of abscissa denotes time.

[0284] This method is a method which raises an output of a hydrogen pump temporarily by control means (not shown) in order to compensate the shortage of circuit capability generated in ejector at the time of a slowdown, and secure the circulation amount compulsorily.

[0285] By operating in this manner, a remarkable damage to a fuel cell ascribed to a hydrogen lack state within the fuel cell caused by excessive load is avoidable.

[0286] Next, a check valve used in a fuel circuit of the fuel cell system according to this invention, and a counter flow detection method of the gas in a fuel circuit of the fuel cell system according to this invention will be explained with reference to FIG. 17 and 18.

[0287]
FIG. 17 is a view showing a relation of a pressure loss and the flow rate of mechanical check valve and electro magnetic check valve, and FIG. 18A to FIG. 18D are views showing various methods for detecting whether the counter flow occurred in a fuel circuit of the fuel cell system according to this invention.

[0288] Generally as check valves, there are mechanical check valves, such as a lead valve and a pop-off valve, and electro magnetic check valve which realizes suitable opening and closing of a stream passage with magnetic absorption etc. by solenoid

[0289] Mechanical check valve has a high pressure loss over flow rate compared with electro magnetic check valve, as shown in FIG. 17. If pressure loss of check valve is high, since differential pressure ΔPe of ejector is increased as shown in FIG. 1C, circulation amount is decreased. Therefore, it is advantageous to use electro magnetic check valve with little pressure loss for making circulation capability of ejector high. Accordingly, as check valve used with each embodiment, if electric electro magnetic check valve is used as a whole, it is more preferable.

[0290] However, electric electro magnetic check valve needs to get an electric signal by a certain means to detect an counter flow to be operated.

[0291] (1) FIG. 18A is a view showing how to detect a counter flow with a pressure difference of the inlet-outlet of a fuel cell. A pressure gauge P1 is formed in the inlet of a fuel cell 1, and the pressure gauge P2 is formed in the outlet. Each data measured with the pressure gauge P1 and the pressure gauge P2 is taken in to the electronic control unit ECU. Then, a pressure difference is determined. When a counter flow of fuel cell 1 occurs, usually detected value of the pressure difference of fuel cell 1 is decreased. Whether or not the counter flow occurs is thus detected.

[0292] (2) FIG. 18B is a view showing how to detect a counter flow by the difference of temperature of the inlet-outlet of a fuel cell. A thermometer T1 is provided in the inlet of a fuel cell 1, and a thermometer T2 is provided in the outlet. Each data measured with the thermometer T1 and the thermometer T2 is taken in to the electronic control unit ECU, and a difference of temperature is determined. Since gas is supplied to the outlet of a fuel cell 1 with temperature of new gas if as counter flow is caused, usually detected value of the difference in temperature of the inlet-outlet of the fuel cell 1 is decreased. Whether or not the counter flow occurs is thus detected.

[0293] (3) FIG. 18C is a view showing how to detect a counter flow with the difference (or humidity difference) of the dew point of the inlet-outlet of a fuel cell. A dew point meter Td1 is provided in the inlet of a fuel cell 1, and a dew point meter Td2 is provided in the outlet. Data measured with the dew point meter Td1 and the dew point plan Td2 is taken in to the electronic control unit ECU, and difference (or humidity difference) of the dew point is determined. When a counter flow occurs, since gas is supplied to the outlet of a fuel cell 1 with the temperature of new gas, usually detected value of the difference of the dew point of the inlet-outlet of the fuel cell 1 is decreased. Whether or not the counter flow occurs is thus detected.

[0294] (4) FIG. 18D is a view showing how to detect a counter flow by the flow rate of the anode-exhaust gas discharged from a fuel cell. A flow meter Q is provided in the outlet of a fuel cell 1. Since the flow rate value of the flow meter Q is decreased when a counter flow occurs to cause usually detected direction of the flow to be reversed, the counter flow is detectable.

[0295] Thus, not mechanical check valve but electric electro magnetic check valve is used for check valve used by a fuel circuit of the fuel cell system according to this invention. Pressure loss by check valve can be made smaller than the case when mechanical check valve is used. Therefore, by operating the electro magnetic check valve based on the electric signal when measuring the pressure etc. which is the state amount of a fuel circuit of fuel cell system, pressure loss caused by the check valve can be made smaller than when using a mechanical check valve. This allows circulation amount of ejector to be improved.

Fuel circuit of the fuel cell system

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