JP4742585B2 - Hybrid system - Google Patents

Description

The present invention relates to a hybrid system of an internal combustion engine and a fuel cell, and more particularly to operation temperature control of the fuel cell.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. This fuel cell has been developed widely as a future energy supply system because it is environmentally friendly and can achieve high energy efficiency. In general, fuel cells are roughly classified into five types, that is, solid polymer type, alkali type, phosphoric acid type, molten carbonate type, and solid oxide type, depending on the electrolyte to be used, and each has a different operating temperature.

In recent years, a technique for thermally connecting an internal combustion engine to such a fuel cell has been disclosed (see, for example, Patent Document 1). According to this technique, the waste heat of the internal combustion engine released to the surrounding environment can be used to maintain the operating temperature of the fuel cell, and high thermal efficiency can be obtained.
JP 2003-129836 A

  However, the means for thermally connecting the internal combustion engine to the fuel cell is configured such that the waste heat of the internal combustion engine is always transmitted to the fuel cell. Therefore, the fuel cell is overheated and power generation efficiency is reduced.

  The present invention has been made in view of the above problems, and provides a hybrid system capable of optimally controlling waste heat transmission by preventing a fuel cell from being overheated by waste heat of an internal combustion engine and reducing power generation efficiency. For the purpose.

The present invention relates to an internal combustion engine, a fuel cell, heat transfer means for transferring waste heat of the internal combustion engine to the fuel cell, and transmission of the waste heat by the heat transfer means in accordance with an operating state of the fuel cell. A transmission control means for controlling the waste transfer by the heat transfer means when only the fuel cell is stopped from a state where both the internal combustion engine and the fuel cell are operating. A hybrid system characterized in that heat transfer is performed . Since the transfer of waste heat is controlled according to the operating state of the fuel cell, the transfer of waste heat from the internal combustion engine to the fuel cell can be optimized. Further, since the waste heat of the internal combustion engine is transferred when the operation of the fuel cell is stopped, the temperature decrease of the fuel cell due to the stop of the operation of the fuel cell can be suppressed. As a result, the restartability of the fuel cell is improved. Can be improved.

  The transfer control means causes the heat transfer means to perform the transfer of the waste heat when the fuel cell is required to warm up, and the heat transfer means performs the heat transfer when the fuel cell is warmed up. It can be set as the structure which stops transmission of waste heat. With this configuration, unnecessary fuel cell warm-up caused by the transfer of waste heat of the internal combustion engine can be suppressed even after the completion of warm-up of the fuel cell, so that overheating of the fuel cell can be suppressed.

The heat transfer means includes an exhaust gas passage that is an exhaust gas passage of the internal combustion engine, a gas passage in the fuel cell, and a fuel cell case that is formed around the fuel cell. An exhaust gas supply passage that communicates with at least one of the exhaust gas supply passage, the transmission control means for shutting off the inflow of the exhaust gas to the exhaust gas supply passage, and operating the shutoff means for the fuel cell. It can be set as the structure which has the interruption | blocking control means controlled according to a driving | running state.

The exhaust gas passage further includes exhaust purification means for purifying the exhaust gas upstream of a branching portion to the exhaust gas supply passage, and the gas passage includes anode gas passages and cathode gas passages of the fuel cell. It can be set as the structure which is either. With this configuration, the exhaust gas with reduced HC and CO content is supplied to the anode gas passage or the cathode gas passage, so that the exhaust gas of the internal combustion engine flows into the anode gas passage or the cathode gas passage to warm the fuel cell. In this case, poisoning of the noble metal catalyst at the anode or cathode due to HC and CO contained in the exhaust gas of the internal combustion engine can be suppressed.

  According to the present invention, the fuel cell is overheated due to the waste heat of the internal combustion engine, and the power generation efficiency is prevented from decreasing, and further, the waste heat is transmitted from the internal combustion engine to the fuel cell as necessary. Waste heat transfer can be optimized. Even when the exhaust gas is supplied to the anode gas passage or the cathode gas passage, poisoning of the noble metal catalyst can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic diagram showing a configuration of a hybrid system having both a fuel cell and an internal combustion engine. As shown in FIG. 1, the hybrid system 100 includes an internal combustion engine 1, a fuel cell 2, an exhaust purification catalyst 3, a flow switching valve 4, a reformer 5, an exhaust gas passage 6, an exhaust gas supply passage 7, and a gas passage 8. A fuel cell case 9, a control unit 11, a sensor 12, and an external exhaust pipe 13. The reformer 5, the gas passage 8, and the fuel cell 2 constitute a fuel cell system 10. The fuel cell system 10 includes a device such as a heat exchanger, a shift reaction unit, a selective CO oxidation unit, and a hydrogen separation membrane (not shown) between the reformer 5 and the fuel cell 2 as necessary. It may be. A secondary battery (not shown) may be included in the hybrid system.

  The internal combustion engine 1 is, for example, a gasoline engine, and burns a mixture of combustion raw materials and air. The exhaust purification catalyst 3 purifies exhaust gas discharged from the internal combustion engine 1. The purified exhaust gas is selectively discharged to the outside through the flow path switching valve 4 provided in the exhaust gas passage 6 or exhausted to the exhaust gas supply passage 7. The flow path switching valve 4 is controlled by the control unit 11 as described later.

  The reformer 5 reforms the reforming raw material and supplies hydrogen to the fuel cell 2 through the gas passage 8. The fuel cell 2 includes an anode, a cathode, and an electrolyte. The fuel cell 2 generates water and electricity from hydrogen in the reformed gas supplied to the anode and air (oxygen) supplied to the cathode. The anode off gas discharged from the fuel cell 2 is purified as necessary and discharged to the outside. The cathode off gas discharged from the fuel cell 2 is supplied to the reformer 5 as a reforming raw material.

  The fuel cell system 10 includes devices such as a heat exchanger, a shift reaction unit, a selective CO oxidation unit, and a hydrogen separation membrane (not shown) between the reformer 5 and the fuel cell 2 as necessary. It may be the composition which includes. The heat exchanger converts the temperature of the reformed gas into the operating temperature of the fuel cell 2. The shift reaction unit reacts carbon monoxide in the reformed gas with water to generate hydrogen and carbon dioxide. The selective CO oxidation unit reacts carbon monoxide with hydrogen to generate carbon dioxide. The hydrogen separation membrane separates hydrogen gas from the reformed gas. A secondary battery (not shown) may be included in the hybrid system.

  In the traveling state of the hybrid system having such a configuration, the internal combustion engine 1 and the fuel cell system 10 move simultaneously or only one of them. If only the internal combustion engine 1 moves and the fuel cell system 10 is stopped, the temperature of the fuel cell 2 decreases due to heat dissipation. Further, when the hybrid system is activated, the temperature of the fuel cell 2 is low. Therefore, the present invention includes a configuration for controlling the transfer of waste heat from the internal combustion engine 1 to the fuel cell 2 in accordance with the operating state of the fuel cell 2 to prevent the temperature of the fuel cell 2 from decreasing, and the fuel cell 2. Even after the completion of the warming-up, unnecessary fuel cell warm-up due to the transfer of waste heat of the internal combustion engine is suppressed, and the fuel cell 2 is prevented from being reduced in power generation efficiency due to overheating.

  Specifically, the hybrid system shown in FIG. 1 has heat transfer means for transferring waste heat of the internal combustion engine 1 to the fuel cell 2 and the transfer of waste heat by the heat transfer means in accordance with the operating state of the fuel cell 2. Transmission control means for controlling.

  The heat transfer means branches from the exhaust gas passage 6 and the exhaust gas communicating with at least one of the gas passage 8 in the fuel cell 2 and the fuel cell case 9 formed around the fuel cell 2. And a gas supply passage 7. In FIG. 1, exhaust gas is supplied to both the gas passage 8 and the fuel cell case 9 (portion indicated by an arrow), but either one may be used. The specific exhaust gas introduction passage on the fuel cell 2 side includes an anode gas passage, a cathode gas passage, a refrigerant passage (however, in the case of an air-cooled fuel cell, not shown here), or a plurality of cells stacked. Any flow path capable of transferring heat to the fuel cell 2 such as the inside of the fuel cell case 9 formed around the fuel cell 2 to be configured may be used. In this case, even when exhaust gas flows through the anode gas passage and the cathode gas passage of the fuel cell 2, the exhaust gas downstream of the exhaust purification catalyst 3 is introduced, so that poisoning of the catalyst of the fuel cell 2 is prevented. can do.

The transmission control means includes a flow path switching valve 4 that functions as a shut-off means for shutting off the inflow of exhaust gas to the exhaust gas supply passage 7, and a shut-off control that controls this operation according to the operating state of the fuel cell 2. And a control unit 11 functioning as means. For example, when the warming-up of the fuel cell 2 is requested, the control unit 11 controls the flow path switching valve 4 to transmit the waste heat of the internal combustion engine 1 and the warming-up of the fuel cell 2 is completed. Then, the flow path switching valve 4 is controlled to stop the transmission of waste heat. With this configuration, it is possible to suppress unnecessary warm-up of the fuel cell 2 due to the transfer of waste heat of the internal combustion engine 1 even after the warm-up of the fuel cell 2 is completed, so that overheating of the fuel cell 2 is suppressed. Can do.
For example, when only the fuel cell 2 is stopped from a state where both the internal combustion engine 1 and the fuel cell 2 are operating, the control unit 11 controls the flow path switching valve 4 to transmit waste heat. Let With this configuration, the waste heat of the internal combustion engine 1 is transferred when the operation of the fuel cell 2 is stopped, so that the temperature drop of the fuel cell 2 due to the stop of the operation of the fuel cell 2 can be suppressed. The restartability of the battery 2 can be improved.

  In this way, the exhaust gas of the internal combustion engine 1 is introduced into the fuel cell 2 as necessary, that is, according to the operating state of the fuel cell 2, so that the fuel cell 2 is not required to be newly charged. The temperature can be maintained, and as a result, a highly efficient and highly responsive system can be realized.

  Next, the control performed by the control unit 11 to enable the temperature of the fuel cell 2 to be maintained when the internal combustion engine 1 is operated will be described. FIG. 2 is a flowchart illustrating the control performed by the control unit 11.

  As shown in FIG. 2, the control unit 11 determines whether or not the temperature is equal to or lower than the setting from the output signal of the sensor 12 that detects the temperature of the fuel cell 2 (step S1). If it is determined in step S1 that the temperature of the sensor 12 is equal to or lower than the setting (warming of the fuel cell 2 is required), the control unit 11 determines the switching state of the flow path switching valve 4 (step S1). S2). When it is determined in step S2 that the exhaust gas supply passage 7 that is a flow path toward the fuel cell 2 is blocked, the control unit 11 controls the flow path switching valve 4 and the external exhaust pipe 13. And the exhaust gas is caused to flow into the gas passage 8 and / or the fuel cell case 9 through the exhaust gas supply passage 7 (step S3). At this time, in the air-cooled fuel cell, exhaust gas may be supplied to the refrigerant passage. Hereinafter, the control unit 11 repeats the operation from step S1.

  On the other hand, when it is determined in step S1 that the temperature of the sensor 12 is not lower than the set value (warming of the fuel cell 2 has been completed), the control unit 11 determines the switching state of the flow path switching valve 4 ( Step S4). In step S4, when it is determined that the flow path to the external exhaust pipe 13 is blocked, the control unit 11 controls the flow path switching valve 4 to cause the exhaust gas to flow into the external exhaust pipe 13, The flow path to the gas passage 8 or the fuel cell case 9 is shut off (step S5). Hereinafter, the control unit 11 repeats the operation from step S1. If it is determined in step S2 that the flow path to the fuel cell 2 side is not blocked, the operation from step S1 is repeated. If it is determined in step S4 that the flow path to the external exhaust pipe is not blocked, the operation from step S1 is repeated.

  As described above, when the fuel cell 2 has not reached the operating temperature, the exhaust gas is caused to flow into the fuel cell 2 side by the flow path switching valve 4, and when the operating temperature is reached, the exhaust gas to the fuel cell 2 side is Since the supply is shut off, the temperature of the fuel cell 2 can always be maintained, and a highly efficient and highly responsive hybrid system can be realized.

  In general, the temperature of the fuel cell 2 when the hybrid system is started is lower than the temperature when the fuel cell 2 is at rest. Accordingly, when the hybrid system is started, the exhaust gas of the internal combustion engine 1 is supplied to both the gas passage 8 and the fuel cell case 9 (and the refrigerant passage in the case of an air-cooled fuel cell) in order to warm up the fuel cell 2 as efficiently as possible. However, the fuel cell 2 may be supplied to either one when the fuel cell 2 is stopped. In this case, a valve is provided between the exhaust gas supply passage 7 and the fuel cell case 9 and is controlled by the control unit 11. The exhaust gas of the internal combustion engine 1 may be supplied to either the anode gas passage or the cathode gas passage of the fuel cell 2, but is preferably supplied to the cathode passage when the fuel cell 2 is stopped. This is because when supplied to the anode gas passage, hydrogen supplied from the reformer 5 reacts with oxygen in the exhaust gas.

It is a figure which shows the structure of the hybrid system which concerns on one Example of this invention. It is an operation | movement flowchart of the control part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Fuel cell 3 Exhaust purification catalyst 4 Flow path switching valve 5 Reformer 6 Exhaust gas passage 7 Exhaust gas supply passage 8 Gas passage 9 Fuel cell case 10 Fuel cell system 11 Control part 12 Sensor 13 External exhaust pipe 100 Hybrid system

Claims (4)

An internal combustion engine;
A fuel cell;
Heat transfer means for transferring waste heat of the internal combustion engine to the fuel cell;
Transmission control means for controlling the transfer of the waste heat by the heat transfer means according to the operating state of the fuel cell ,
The transfer control means causes the waste heat to be transferred by the heat transfer means when only the fuel cell is stopped from a state where both the internal combustion engine and the fuel cell are operating. Hybrid system to do.   The transfer control means causes the heat transfer means to perform the transfer of the waste heat when the fuel cell is required to warm up, and the heat transfer means performs the heat transfer when the fuel cell is warmed up. The hybrid system according to claim 1, wherein transmission of waste heat is stopped. The heat transfer means includes an exhaust gas passage that is an exhaust gas passage of the internal combustion engine, a gas passage in the fuel cell, and a fuel cell case that is formed around the fuel cell. And an exhaust gas supply passage communicating with at least one of
The transmission control means includes a shut-off means for shutting off the inflow of the exhaust gas to the exhaust gas supply passage, and a shut-off control means for controlling the operation of the shut-off means according to the operating state of the fuel cell. The hybrid system according to claim 1, wherein the hybrid system is characterized. The exhaust gas passage further includes an exhaust gas purification means for purifying the exhaust gas upstream of a branch portion to the exhaust gas supply passage, and the gas passage is one of an anode gas passage and a cathode gas passage of the fuel cell. hybrid system according to claim 3, characterized in that.

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