WO2013114170A1

WO2013114170A1 - Internal combustion engine system

Info

Publication number: WO2013114170A1
Application number: PCT/IB2013/000074
Authority: WO
Inventors: Hiroyuki Suganuma; Kohsuke Yamamoto; Hidefumi Nakao
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2012-02-03
Filing date: 2013-01-23
Publication date: 2013-08-08
Also published as: JP2013161616A

Abstract

An internal combustion engine system (10) includes: an internal combustion engine (14); a fuel cell system (50) having a gas discharge passage (60) that is connected to an exhaust passage (18) of the internal combustion engine (14); and a gas flow control device (D) configured to control flow of exhaust gas of the fuel cell system (50) so that the exhaust gas of the fuel cell system (50) flows to the exhaust passage (18) of the internal combustion engine (14).

Description

INTERNAL COMBUSTION ENGINE SYSTEM

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to an internal combustion engine system that is configured such that exhaust gas of a power generation device flows into an exhaust passage of an internal combustion engine.

2. Description of Related Art

[0002] Various combinations of an internal combustion engine and a fuel cell have been proposed. For instance, Japanese Patent Application Publication No. 2007-16641 (JP 2007- 16641 A) discloses a hybrid system provided with a fuel cell and an internal combustion engine that is equipped with a supercharger. In this system, one or both of hydrogen-containing gas that is supplied to the fuel cell and anode-off gas from the fuel cell is/are supplied to a turbine housing of the supercharger when it is determined that the load in the internal combustion engine will increase.

[0003] Also, Japanese Patent Application Publication No. 2004- 169696 (JP 2004-169696 A) discloses a composite power generation facility, in which air that is compressed by a compressor is supplied to a fuel cell, and exhaust gas of the fuel cell is supplied to a turbine inlet side. In this facility, exhaust gas from a diesel engine or a gasoline engine, as a reciprocating engine, is likewise supplied to the turbine inlet side.

[0004] In the cases where the exhaust gas of the fuel cell is supplied to the exhaust passage of an internal combustion engine, a concern arises as regards limitations that constrain the inflow of exhaust gas of the fuel cell into the exhaust passage, depending on the pressure in the exhaust passage. During high-load operations, for instance, the pressure in the exhaust passage of the internal combustion engine is relatively high, so that, if the pressure of the exhaust gas of the fuel cell is significantly lower than that pressure, not only may the exhaust gas of the fuel cell fail to flow into the exhaust passage, but the exhaust gas of the internal combustion engine may flow back towards the fuel cell.

SUMMARY OF THE INVENTION

[0005] The invention provides an internal combustion engine system that has a fuel cell system and with which it is possible to more appropriately make exhaust gas of the fuel cell system flow to the exhaust passage of the internal combustion engine.

[0006] An aspect of the invention is an internal combustion engine system including an internal combustion engine, a fuel cell system having a gas discharge passage connected to an exhaust passage of the internal 'combustion engine; and a gas flow control device configured to control the flow of exhaust gas of the fuel cell system in such a manner that exhaust gas of the fuel cell system flows to the exhaust passage of the internal combustion engine. In the above configuration, there is- provided a gas flow control device configured to control the flow of exhaust gas of the fuel cell system so that exhaust gas of the fuel cell system flows to the exhaust passage of the internal combustion engine. Therefore, the exhaust gas of the fuel cell system can flow appropriately to the exhaust passage of the internal combustion engine.

[0007] The gas flow control device may include a one-way valve provided in the gas discharge passage. Herein, the one-way valve allows the exhaust gas of the fuel cell system to flow to the exhaust passage of the internal combustion engine, while preventing flow of exhaust gas of the internal combustion engine in the opposite direction.

[0008] The gas flow control device may include a supply amount control unit configured to control at least one of an air supply amount and a fuel supply amount in the fuel cell system. The supply amount control unit may be configured to control at least one of the air supply amount and the fuel supply amount in the fuel cell system, in accordance with the pressure of exhaust gas of the internal combustion engine. When the supply amount control unit controls at least one of the air supply amount and fuel supply amount in accordance with the pressure of the exhaust gas of the internal combustion engine, the pressure of the exhaust gas of the fuel cell system can be adjusted to a preferable height with respect to the pressure of the exhaust gas of the internal combustion engine. The supply amount control unit may be configured to control at least one of the air supply amount and the fuel supply amount so as to render the pressure of the exhaust gas of the fuel cell system equal to or higher than a predetermined pressure. When the supply amount control unit controls at least one of the air supply amount and the fuel supply amount so as to render the pressure of the exhaust gas of the fuel cell system equal to or higher than a predetermined pressure, the exhaust gas of the fuel cell system can be made to flow more appropriately to the exhaust passage by increasing the pressure of the exhaust gas of the fuel cell system. In particular, the supply amount control unit may be configured to execute control of increasing the air supply amount in the fuel cell system in preference to the fuel supply amount in the fuel cell system. This configuration makes it possible to improve fuel economy by executing control that involves increasing the air supply amount in the fuel cell system in preference to the fuel supply amount in the fuel cell system.

[0009] The gas flow control device may further include: a second discharge passage having one end connected to the gas discharge passage of the fuel cell system and having the other end connected to the exhaust passage on a downstream side of a connection section, at which the gas discharge passage and the exhaust passage are connected; at least one valve for adjusting a gas flow rate in the gas discharge passage and the gas flow rate in the second discharge passage; and a valve control unit that is configured to control the abovementioned at least one valve. Such a configuration makes it possible to adjust the gas flow rate of the gas discharge passage and the gas flow rate of the second discharge passage. For instance, when the exhaust pressure of the internal combustion engine is high, the exhaust gas of the fuel cell system can flow, via the second discharge passage, to the downstream portion of the exhaust passage where pressure is lower than on the upstream side. The valve control unit may be configured to control the abovementioned at least one valve on the basis of at least one of an engine load and an engine rotational speed of the internal combustion engine. In this case, since there is a relationship between at least one of the engine load and engine rotational speed of the internal combustion engine and the pressure of the exhaust gas of the internal combustion engine, it is possible to make the exhaust gas of the fuel cell system appropriate flow into the exhaust passage.

[0010] The internal combustion engine system according to the above aspect may further include a small catalyst device that is provided upstream of an exhaust control device, in the exhaust passage of the internal combustion engine, and a warm-up determination unit that is configured to determine a warm-up state of the exhaust control device, wherein the gas discharge passage is connected to the exhaust passage upstream of the small catalyst device, the second discharge passage is connected to the exhaust passage between the small catalyst device and the exhaust control device, and the valve control unit is configured to control the abovementioned at least one valve so that exhaust gas of the fuel cell system flows to the small catalyst device when the warm-up determination unit determines that warm-up of the exhaust control device is not completed. This makes it possible to more appropriately warm up the exhaust control device.

[0011] The internal combustion engine system according to the above aspect may further include a turbocharger that has a turbine disposed in the exhaust passage, wherein the gas discharge passage is connected to the exhaust passage upstream of the turbine, and the second discharge passage is connected to the exhaust passage downstream of the turbine. In this case, since the pressure of the exhaust passage downstream of the turbine is lower than the pressure in the exhaust passage upstream of the turbine, it is possible to make the exhaust gas of the fuel cell system flow appropriately to the exhaust passage by exploiting the difference in these pressures.

[0012] The internal combustion engine system according to the above aspect may further include a turbocharger that has a turbine that is disposed in the exhaust passage of the internal combustion engine and that has a waste gate valve, wherein the gas discharge passage is connected to the exhaust passage upstream of the turbine, the second discharge passage is connected to the exhaust passage downstream of the turbine, the valve control unit is configured to control the abovementioned at least one valve so that exhaust gas of the fuel cell system flows to the turbine when the waste gate valve is closed, and the valve control unit is configured to control the abovementioned at least one valve so that exhaust gas of the fuel cell system flows to the exhaust passage downstream of the turbine when the waste gate valve is open. In this case, the energy of the exhaust gas of the fuel cell system can be used in the turbine when the waste gate valve is closed, and the exhaust gas of the fuel cell system can be discharged appropriately to the exhaust passage when the waste gate valve is open.

[0013] In the internal combustion engine system according to the above aspect, the valve control unit may be configured to control the at least one valve so that exhaust gas of the fuel cell system flows to the gas discharge passage when the internal combustion engine is stopped. With this configuration, the turbocharger is brought to a driving state through supply of the exhaust gas of the fuel cell system to the turbine. Therefore, quick operation response upon engine restart is achieved.

[0014] With the internal combustion engine of the invention, it is possible to make exhaust gas of a fuel cell system flow to an exhaust passage of the internal combustion engine in a preferable manner.

BRIEF DESCRIPTION OF THE DRAWINGS [0015] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a conceptual diagram of an internal combustion engine system according to a first embodiment of the invention, and of a vehicle in which the internal combustion engine system is installed;

FIG. 2 is a flowchart relating to a stop-restart control of an internal combustion engine in the first embodiment;

FIG. 3 is a schematic diagram illustrating the flow of electricity, gas, fuel, cooling water and oil as a result of an operation of a power generation device in a state where the internal combustion engine of FIG. 1 is stopped;

FIG. 4 is a schematic diagram illustrating a relationship between exhaust gas pressure of the internal combustion engine of FIG. 1 and the pressure of exhaust gas of a power generation device that is a fuel cell system;

FIG. 5 is a conceptual diagram of an internal combustion engine system according to a second embodiment of the invention, and of a vehicle in which the internal combustion engine system is installed;

FIG. 6 is a flowchart in an internal combustion engine system of a .third embodiment;

FIG. 7 is mapped data that represents an operating region, relating to the third embodiment;

FIG. 8 is an explanatory diagram, relating to the third embodiment, in the form of a schematic diagram that illustrates an example of the relationship between exhaust gas pressure of an internal combustion engine and pressure of exhaust gas in a power generation device;

FIG. 9 is a conceptual diagram of an internal combustion engine system according to a fourth embodiment of the invention, and of a vehicle in which the internal combustion engine system is installed;

FIG. 10 is a flowchart in the internal combustion engine system of the fourth embodiment;

FIG. 11 is a flowchart of an internal combustion engine system in a fifth embodiment; FIG. 12 is mapped data that represents an operating region, relating to the fifth embodiment;

FIG. 13 is a flowchart of an internal combustion engine system in a sixth embodiment;

FIG. 14 is a conceptual diagram of an internal combustion engine system according to a seventh embodiment of the invention, and of a vehicle in which the internal combustion engine system is installed; and

FIG. 15 is a flowchart of the internal combustion engine system in the seventh embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0016] A first embodiment according to the invention will be described in detail below.

[0017] An internal combustion engine system (hereafter also referred to simply as engine) 10 according to the first embodiment of the invention is installed in a vehicle 12. The engine 10 is herein a gasoline engine. However, engines in which the invention is used may be internal combustion engines of any type, for instance spark-ignition internal combustion engines or compression ignition internal combustion engines.

[0018] The engine 10 includes an engine main body (internal combustion engine) 14, an intake passage 16 and an exhaust passage 18 that are connected to the engine main body 14, and a fuel injection device 22 that supplies fuel from a fuel tank (not shown), through the operation of a fuel pump 20. The fuel, which is injected through a fuel injection valve (not shown) of the fuel injection device 22, is burned in cylinders of the engine main body 14, and the resulting exhaust is discharged via the exhaust passage 18. An air cleaner (not shown) is provided in the upstream end side of the intake passage 16 of the engine 10. [0019] The engine 10 is further provided with a turbocharger 24. A turbine 26 of the turbocharger 24 is disposed in the exhaust passage 18. A compressor 28 of the turbocharger 24, which accommodates a compressor wheel that is coaxially coupled to the turbine wheel of the turbine 26, is disposed in the intake passage 16. Therefore, the turbine wheel of the turbine 26 is rotated by the exhaust that is led via the exhaust passage 18, which causes the compressor wheel of the compressor 28 to rotate, so that supercharging is performed. An intercooler 30, as a cooling device for cooling air the temperature of which rises on account of compression by the compressor 28, is provided in the intake passage, downstream of the compressor 28.

[0020] There is also provided an exhaust valve mechanism 31 for regulating the inflow amount of exhaust to the turbine 26 of the turbocharger 24. The exhaust valve mechanism 31 has a valve 32 that is provided in a detour 34 that is formed so as to bypass the turbine 26. The exhaust valve mechanism 31 and the valve 32 may be referred to as a waste gate valve. The valve 32 or the exhaust valve mechanism 31 of the embodiment has a mechanical configuration such that the valve 32 or the exhaust valve mechanism 31 opens through compression of a spring that is pressed on account of exhaust pressure when the latter becomes equal to or higher than a predetermined pressure. The valve 32 or the exhaust valve mechanism 31 is normally closed when the engine is stopped. However, the valve 32 or the exhaust valve mechanism 31 may have various mechanical configurations, such as a configuration in which the valve 32 or the exhaust valve mechanism 31 opens as a result of a diaphragm of an actuator being pressed by supercharging pressure when the supercharging pressure becomes equal to or higher than a predetermined pressure, or, alternatively, may be configured in the form of an electromagnetically driven valve.

[0021] An intake valve mechanism 36 for controlling supercharging pressure is provided in the compressor 28 of the turbocharger 24. The intake valve mechanism 36 has a valve 38 provided in a detour 40 that is formed so as to bypass the compressor 28. The intake valve mechanism 36 and the valve 38 may be referred to as an air bypass valve (ABV). The valve 38 or intake valve mechanism 36 in the embodiment is configured in the form of an electromagnetically driven valve. However, the valve 38 or intake valve mechanism 36 may have a mechanical configuration, such as the one of the above-described valve 32 or exhaust valve mechanism 31.

[0022] An exhaust control device 42 is provided in the exhaust passage 18, in such a manner that exhaust that passes through the turbine 26 and the valve 32 is led to the exhaust control device 42. The exhaust control device 42 may adopt various configurations. For instance, the exhaust control device 42 may be provided with an oxidation catalyst that prompts unbumed components, such as HC and CO, to react with O? to yield CO, C0₂, H₂0 and the like. Alternatively, the exhaust control device 42 may be configured in the form of what is called a three-way catalyst. The exhaust control device 42 may have a filtering structure, such as that of a diesel particulate filter (DPF), so as to trap microparticles (particulate matter (PM)), for instance soot or the like, in exhaust gas. An oxidation catalyst may be further provided in that case. Catalytic substances that can be used in the oxidation catalyst include, for instance, Pt/Ce0₂, Mn/CeO?, Fe/Ce0₂. Ni/Ce0₂, Cu/Ce0₂ or the like. The exhaust control device 42 may have a NOx catalyst in order to purify NOx (nitrogen oxides) in the exhaust gas. In FIG. 1 just one exhaust control device 42 is depicted, but two or more exhaust control devices may be provided, in series or in parallel. In a case where a plurality of exhaust control devices are provided, the configurations of the exhaust control devices may be identical or dissimilar to each other.

[0023] The engine 10 is provided with a power generation device 50. The power generation device 50 is configured in the form of a fuel cell system, so as to generate power by electrochemical reactions between air and fuel. In the embodiment, in particular, the power generation device 50 is configured in the form of a solid oxide fuel cell (SOFC). The power generation device 50 can operate when the engine 10 is in an active state, but, as described in detail later, the power generation device 50 is configured so as to be capable of operating also when the engine 10 is in an inactive state. Part of a below-described electronic control unit (ECU) functions herein as a control device or a control means of the power generation device 50.

[0024] The power generation device 50 has a power generator main body 52. The power generator main body 52 is configured herein in the form of a fuel cell main body. An air introduction passage (intake passage of the power generation device) 54 is connected to the power generator main body 52. The air introduction passage 54 is connected to the power generator main body 52 in such a manner that air is introduced to the power generator main body 52. A fuel supply passage 56 is connected to the power generator main body 52. The fuel supply passage 56 is included in the fuel supply device 58, which is provided for the purpose of supplying fuel to the power generator main body 52. A gas discharge passage (exhaust passage of the power generation device) 60 is connected to the power generator main body 52. The gas discharge passage 60 is connected to the power generator main body 52 in order for gas to be discharged from the power generator main body 52.

[0025] The power generator main body 52 has a structure, sometimes referred to as cell stack, resulting from connecting unit cells each of which is made up of a fuel electrode, as an anode, an air electrode, as a cathode, and an electrolyte. As the electrolyte there can be used an oxide ionic conductor, which is a ceramic. The invention does not exclude a configuration, in which the power generator main body 52 has only a unit cell, instead of a plurality thereof.

[0026] The fuel supply device 58 includes the above-mentioned pump 20 for supplying fuel from inside the fuel tank (not shown). In the embodiment, the fuel supply device 58 is integrated with the fuel injection device 22 and also includes the fuel tank and the fuel pump 20 of the fuel injection device 22. Therefore, gasoline as the fuel is supplied herein to the power generator main body 52.

[0027] The fuel supply device 58 may be configured to be completely separate from the fuel injection device 22. In such a case, the fuel for the engine and the fuel for the power generation device may be identical or dissimilar to each other. Examples of the fuel for the power generation device that can be used herein include, for instance, a fuel other than a fuel such as gasoline or diesel, although natural gas or propane gas may also be used. The power generation device 50 may be configured in the form of an SOFC and may operate at a relatively high temperature (for instance, 800 to 1000°C), so that it is possible to reform fuel with the use of the resulting high temperature. Accordingly, the power generation device 50 is not provided with a fuel reformer. However, the fuel supply device 58 of the power generation device 50 may be provided with a fuel reformer. The power generation device 50 may be manufactured to have a configuration of, for instance, a solid polymer fuel cell (PEFC), a molten carbonate fuel cell (MCFC), or a phosphoric acid fuel cell (PAFC). The fuel supply device 58 may be provided, as needed, with a fuel reformer of the necessary type.

[0028] The air introduction passage 54 in the power generation device 50 is connected to the intake passage 16 of the engine 10 so as to enable introduction of air that has passed through the compressor 28. In the embodiment, the air introduction passage 54 is connected to the intake passage downstream of the compressor 28. A valve 62 is provided in the air introduction passage 54. A valve, i.e. a throttle valve 64 is provided in the intake passage downstream of the connection section of the air introduction passage 54 and the intake passage 16. In the embodiment, the valves 62. 64 are configured in the form of electromagnetically driven valves. The valves 62, 64 can be integrated in the form of a one three-way valve. The air introduction passage 54 may be directly connected to the compressor 28. In that case, the air introduction passage 54 may be connected to a position of the compressor 28 that enables flow, into the air introduction passage 54. of the air that has passed through the compressor wheel of the compressor 28. Herein, the intercooler 30 is disposed at the intake passage downstream of the connection section of the air introduction passage 54 and the intake passage 16. Therefore, air can be supplied, at a relatively high temperature, to the power generator main body 52. Meanwhile, air at a relatively low temperature having passed through the intercooler 30 can be supplied to the engine main body 14. The invention does not exclude a configuration in which the intercooler 30 is disposed in the intake passage upstream of the connection section of the air introduction passage 54 and the intake passage 16, but, preferably, the intercooler 30 is disposed in the intake passage downstream of this connection section, because it is preferable that warm or hot air be led to the power generator main body 52.

[0029] The gas discharge passage 60 in the power generation device 50 is connected to the exhaust passage 18 of the engine 10 in such a manner that the exhaust gas of the power generation device 50 can be supplied to the turbine 26. In the embodiment, the gas discharge passage 60 is connected to the exhaust passage upstream of the turbine 26. A reed valve 66, which is a one-way valve, is provided in the gas discharge passage 60. The reed valve 66 is a gas flow control device D that is configured to control the flow of the exhaust gas of the power generation device 50 in such a manner that the exhaust gas of the power generation device 50 flows to the exhaust passage 18 of the engine 10. The reed valve 66 is provided in such a manner that the exhaust gas of the power generation device 50 flows to the exhaust passage 18 of the engine 10 but the exhaust gas of the engine 10 does not flow through the gas discharge passage 60 towards the power generator main body 52. Another form of a one-way valve, for instance a check valve, can be provided instead of the reed valve 66.

[0030] The connection section of the gas discharge passage 60 and the exhaust passage 18 is positioned in the exhaust passage upstream_. of the detour 34 and the valve 32. Accordingly, the exhaust gas of the power generation device 50 that reaches the exhaust passage 18 from the gas discharge passage 60 can pass .through the turbine 26, and can pass through the valve 32 upon opening of this valve 32. The exhaust gas of the power generation device 50 flows thus into the exhaust control device 42. A reformer 68 is provided in the gas discharge passage 60, in order to adjust components of the gas. Specifically, the reformer 68, which is configured to decompose hydrocarbon components, is provided with an oxidation catalyst, as in the case of the exhaust control device 42. However, the reformer 68 may be configured differently, and may be for instance configured for electrolysis. The reformer 68, however, may be omitted.

[0031] The electricity generated in the power generation device 50 having the above configuration is stored (charged) in the battery 70 (not shown in FIG. 1 but depicted in the FIG. 3). Therefore, the power generation device 50 operates basically in accordance with the remaining charge of the battery 70. The engine 10, unlike a conventional engine, is not provided with a power generation device, specifically an alternator, that is used to convert mechanical kinetic energy, transmitted from the engine, to electric energy. Accordingly, the power generation device in the engine 10 of the vehicle 12 is the power generation device 50 alone, and the electricity stored in the battery 70 depends only on the power generation device 50. In the invention, a power generation device, for instance an alternator that is widely used in conventional engines, may be provided in the engine 10, in addition to the power generation device 50, and may also be provided in conjunction with a power generation device (regenerative power generation device) such as those provided in what are called hybrid vehicles.

[0032] In the engine 10, the stator motor (not shown) of the engine 10, the valves 38, 62, 64 and the fuel pump 20 are all operated using electricity stored in the battery 70. Electricity of the battery 70 is used also for the operation of a water pump 72 of a coolant supply device that is configured so as to cool the engine 10 that has the turbocharger 24. The electricity of the battery 70 is used also for the operation of the oil pump 74 of the oil supply device that is configured so as to supply oil, i.e. lubricating oil, to the turbocharger 24. In the embodiment, the power generation device 50 is configured in the form of an SOFC, and the temperature of the stack of the power generator main body 52 is controlled, in a manner that will not be described, using process air, and hence the cooling device or the cooling water system is not necessary. However, a cooling water system may be provided in the power generation device 50. In that case, the pump for supplying cooling water may be driven using electricity of the battery 70.

[0033] The operation of the stator motor, the valves 38, 62, 64, the fuel pump 20, the water pump 72, the oil pump 74 and so forth are controlled by an electronic control unit (ECU) 80 that actually provides the function of a control device or control means (or a control unit) of the engine 10 and the vehicle 12. The ECU 80 is configured in the form of a computer, or having a computer as a main constituent thereof, and is provided with, for instance, a central processing unit (CPU), storage devices such as a read only memory (ROM) and a random access memory (RAM), an analog-to-digital (A/D) converter, an input interface and an output interface. The storage device stores various control programs and data. Various sensors including the below-described sensors are electrically connected to the input interface. The ECU 80 electrically outputs an operation signal (driving signal) from the output interface, so as to enable smooth running and operation of the engine 10, i.e. of the vehicle 12, according to a program (including data) that is set beforehand, on the basis of the outputs (detection signals) of the abovementioned various sensors.

[0034] The engine 10 and the vehicle 12 are provided with sensors that electrically output, to the ECU 80, signals for detecting (and/or estimating) various values. Several such sensors will be described in detail below. An air flow meter 82 for detecting the amount of intake air is provided in the intake passage 16. There is also provided an accelerator depression amount sensor 84 for detecting a position corresponding to a depression amount of an accelerator pedal (not shown) that is operated by the driver i.e. for detecting an accelerator depression amount. A crank position sensor 86 for detecting a crank rotation signal of the crankshaft of the engine 10 is also mounted. Herein, the crank position sensor 86 may be used as an engine rotational speed sensor for detecting the engine rotational speed. Also provided is a vehicle speed sensor 88 for detecting the speed of the vehicle 12 (vehicle speed) having the engine 10 installed therein. There is also provided a stop lamp switch 90, as a brake request detection sensor, that outputs a signal in accordance with the operation state of a brake pedal (not shown). The stop lamp switch 90 is switched on when the brake pedal is depressed. A capacity detection sensor 92 for detecting the capacity or remaining charge of the battery 70 is further provided. The capacity detection sensor 92 is, for instance, a current sensor.

10035] The engine 10 is provided with a stop-restart system 94 that automatically stops the engine 10 when a predetermined stop condition is met, and that automatically restarts the engine 10 when a restart condition (predetermined release condition) holds after the predetermined stop condition is met. Part of the ECU 80 provides the function of control unit or control means of the system 94. For instance, the ECU 80 performs idle reduction control (referred to as idle stop control in Japan) that involves stopping temporarily the engine 10 automatically, at a predetermined timing, when, during travel of the vehicle 12, the vehicle 12 temporarily stops and the engine 10 is brought to an idling state according to, for instance, a stop indication by traffic lights, and, thereafter, the engine 10 is restarted at a predetermined timing. In idle reduction control, thus, a stop condition meeting determination means '(a stop condition meeting determination unit) for determining whether the predetermined stop condition is met, includes part of the ECU 80. A restart condition meeting determination means (restart condition meeting determination unit) for determining whether a predetermined restart condition is met, includes part of the ECU 80. An engine stop control means (engine stop control unit) for executing control for stopping the engine 10, for instance through prohibition of fuel injection from the fuel injection valve, includes part of the ECU 80. An engine restart control means (engine restart control unit) for executing control of restarting the engine 10 includes part of the ECU 80. The foregoing means may be associated, directly or indirectly, with each other.

[0036] Specifically, temporary stop of the engine 10 in idle reduction control is executed by the ECU 80 when a predetermined stop condition is satisfied. A predetermined stop condition herein is that the vehicle is stopped and a braking operation is being performed. Whether or not the vehicle is stopped is determined on the basis of the output from the vehicle speed sensor 88. This determination corresponds to determining whether the vehicle speed is zero or not. Whether a braking operation is being performed or not is determined on the basis of the output from the stop lamp switch 90, as a braking operation detection device or means; specifically, this determination corresponds to whether the stop lamp switch 90 is on or not. Also, a braking operation is determined to be being performed when the ECU 80 determines that the accelerator pedal is not being depressed on the basis of the output from the accelerator depression amount sensor 84, as an acceleration request detection means.

[0037] Restart of the engine 10, i.e. start of the engine 10 after stop of the engine 10 as described above, is executed by the ECU 80 when the predetermined restart condition is satisfied. The predetermined restart condition is that at least one condition from among the abovetnentioned stop conditions is not satisfied. For instance, the predetemiined restart condition is determined to be met when the brake operation is lifted, i.e. when the stop lamp switch 90 switches from on to off. For instance, the predetermined restart condition is determined to be met when the accelerator pedal is depressed when the engine 10 stops according to idle reduction control.

[0038] At the time of restart of the engine 10 after temporary stop thereof according to idle reduction control such as the above, quick operation response of the engine 10 is desirable. For instance, in a case where the engine 10 is restarted through depression of the accelerator pedal, by the driver, the fact that the engine 10 was stopped until then gives rise to a time lag from depression of the accelerator pedal, until such engine output is obtained as corresponds to the depression of the accelerator pedal. In addition, some time is required in order to revert the engine 10 to the state that held immediately prior to stop of the engine in cases where the driver simply lifts the foot off the brake pedal and the vehicle starts off gradually, in particular when the vehicle 12 is equipped with an automatic transmission. This time lag is preferably as short as possible, from the viewpoint of the operation feeling of the vehicle 12 that the driver experiences.

[0039] Herein, therefore, the power generation device 50 operates during the lapse of time from temporary stop of the engine 10 according to idle reduction control until the engine 10 is restarted. The operation of the power generation device 50 relating to idle reduction control will be described based on the flowchart of FIG. 2.

[0040] As can be understood from the connection layout of the passages 54 and 60, the turbocharger 24 is driven tlirough operation of the power generation device 50 when the engine 10 stops according to idle reduction control. Therefore, the water pump 72 and the oil pump 74 are electric pumps, as described above. To promote appropriate driving of the turbocharger 24, specifically, the water pump 72 and the oil pump 74 are both operated over a period of time since an engine operation initiation request is issued by the driver (for instance, after the engine ignition switch is switched on) until the driver issues an engine stop request (for instance, until the engine ignition switch is switched oft), regardless of the operating state of the engine 10. In FIG. 1 , arrows denote schematically the flow of gas (such as air), fuel, cooling water and oil at a time where the engine 10 and the power generation device 50 are both in an active state.

[0041] In step S201 of FIG. 2, it is determined whether the predetermined stop condition in idle reduction control is met or not. The predetermined stop condition is as described above. When the predetermined stop condition is not satisfied (negative determination in step S201 ), the engine 10 is kept in an operation state, i.e. an active state.

[0042] When in step S201 it is determined that the predetermined stop condition is met, the engine 10 is stopped in step S203, and the power generation device 50 is brought to an active state. If the power generation device 50 was hitherto in an active state, that active state is maintained, while if the power generation device 50 was in a stopped state at that point of time, the power generation device 50 is brought to an active state.

[0043] The power generation device 50 is thus brought to an active state when the engine 10 is temporarily stopped by the system 94. When the engine 10 is stopped, the valves (intake-system valves) 62, 64 are controlled in such a manner that the valve bodies of the valves 62, 64 are positioned at a power generation dedicated position, so as to cause all air that passes through the compressor 28 to be introduced into the air introduction passage 54 when the engine 10 is stopped by the system 94. Specifically, the valve 62 is opened and the valve 64 is closed. As a result, air that has passed through the compressor 28 of the intake passage 16 is led to the power generator main body 52, as indicated by the arrow in FIG. 3, when the engine 10 is stopped according to the idle reduction control. Herein, it is sufficient that at least one of the pump 20 and the valve 62 be controlled in such a manner that the air supply amount and fuel supply amount in the power generation device 50 are balanced, or in such a manner that the fuel supply amount becomes smaller with respect to the air supply amount.

[0044] Fuel is supplied to the power generator main body 52, through operation of the pump 20 of the fuel supply device 58, when the engine 10 is stopped according to idle reduction control. As a result, power is generated in the power generator main body 52, and gas is discharged via the gas discharge passage 60. At this time, the valve 32 is basically closed, and hence gas- is led to the turbine 26, as indicated by the arrow in FIG. 3, where the turbine wheel is rotated by the gas. Thus, while the engine 10 is stopped, the turbocharger 24 is brought into a driven state through operation of the power generation device 50.

[0045] The lines A and arrows in FIG. 3 schematically depict the flow of electricity, gas, fuel, cooling water and oil as a result of the operation of the power generation device 50 in a state where the engine 10 is stopped. As can be grasped from FIG. 3 and the description above, electricity is generated, and also consumed, as a result of the operation of the power generation device 50, when the engine 10 is stopped according to idle reduction control. The generation amount and usage amount of electricity is regulated by the ECU 80, because the capacity of the battery 70 is limited, overcharge of the battery 70 must be prevented, and the battery remaining charge must be kept at or above a predetermined level. In the embodiment, the portion of the ECU 80 that provides the function of control unit of the oil supply device, and the portion of the ECU 80 that provides the function of control unit of the coolant supply device, control the operation of both the water pump 72 and the oil pump 74 (operation amount regulation control), on the basis of the output of the sensor 92, so as to control the amount of electric power, i.e. the battery charge amount, in accordance with the remaining charge of the battery 70. To that end, there may be controlled the operation of the at least one of the water pump 72 and the oil pump 74.

[0046] In step S205, subsequent to step S203, it is determined whether the predetermined restart condition in idle reduction control is met or not. The predetermined restart condition is as described above. When the predetermined restart condition is not satisfied (negative determination in step S205), the engine 10 is maintained in a stopped state and the power generation device 50 is kept in an active state.

[0047] When in step S205 it is determined that the predetermined restart condition is met. the engine 10 is restarted in step S207. At this time, in order to make the engine 10 operate appropriately, the valves 62, 64 are controlled in such a manner that air flows to the engine main body 14 and that at least the valve body of the valve 64 is at a position that enables engine operation. Specifically, the throttle valve 64 is opened. The active state of the power generation device 50 is maintained for at least a given period of time upon restart of the engine 10. However, the power generation device 50 may be brought immediately to a stopped state upon restart of the engine 10.

[0048] In step S205, the turbocharger 24 is being driven, as described above, when the driving engine 10 is started. In this state, the valve 64 is switched to a position that enables engine operation; thereby, air having had the pressure thereof raised by the compressor 28 is supplied, at high speed, to the engine main body 14. Therefore, the rise upon restart of the engine 10 can be speeded up, and the quick operation response of the engine 10 is achieved.

[0049] Upon stop of the engine 10 according to idle reduction control, air that has passed through the engine compressor 28 is supplied to the power generator main body 52, fuel is likewise supplied to the power generator main body 52, and the exhaust gas from the power generator main body 52 is supplied to the turbine 26, so that the compressor wheel is rotated. Accordingly, the turbocharger 24 does not stop when the engine 10 is stopped by the system 94.

[0050] The exhaust gas of the power generation device 50 flows into the exhaust control device 42, through operation of the power generation device 50, when the engine 10 is stopped according to idle reduction control. Therefore, catalyst warm-up in the exhaust control device 42 becomes possible also during engine stop according to idle reduction control. In consequence, engine stop according to idle reduction control is allowable also when the engine is cold.

[0051] When the engine 10 is in an active state, the exhaust from the engine main body 14 of the engine 10 flows through the exhaust passage 18. When the power generation device 50 is in an active state at a time where the engine 10 is in an active state, by contrast, the exhaust gas from the power generator main body 52 of the power generation device 50 flows through the gas discharge passage 60.

[0052] FIG. 4 schematically illustrates, in the form of a line LI , the fluctuation of pressure of the exhaust gas of the engine 10 in the exhaust passage 18 of the engine 10, in particular the exhaust passage upstream of the turbine 26. In FIG. 4, a line L2 schematically denotes the fluctuation of pressure of exhaust gas of the power generation device 50 at the inlet of the gas discharge passage 60 or at the outlet of the power generator main body 52.

[0053] As illustrated in FIG. 4, the exhaust gas of the engine 10 exhibits a fluctuation of pressure that is equal to or greater than a given degree. The exhaust pressure from the engine 10 has moments of low pressure (troughs) and moments of high pressure (peaks). By contrast, the exhaust gas of the power generation device 50 exhibits no prominent fluctuation of pressure, as compared with that of the exhaust gas of the engine 10, and can be regarded as being substantially constant.

[0054] The engine 10 of the embodiment and the power generation device 50 are designed in such a manner that the pressure of the exhaust gas of the engine and the pressure of the exhaust gas of the power generation device 50 exhibit a relationship, substantially such as the one of FIG. 4, at the connection section between the exhaust passage 18 and the gas discharge passage 60, or in the vicinity of that connection section (for instance, in the vicinity of the reed valve 66), during engine operation in an ordinary operation state (for instance, urban driving mode) when the engine 10 and the power generation device 50 are operating simultaneously. That is, the engine 10 and the power generation device 50 are designed in such a manner that the exhaust gas of the power generation device 50 has a pressure that is intermediate between a pressure value of a peak of pressure of exhaust gas of the engine 10 at that time, and a pressure value of a trough of that pressure; preferably the exhaust gas of the power generation device 50 has a pressure equal to or higher than the middle pressure of the foregoing pressure values. The reed valve 66 of the gas discharge passage 60 is configured so as to open when the pressure of the exhaust gas of the power generation device 50 is higher than the pressure of exhaust gas of the engine in the exhaust passage 18.

[0055] Therefore, the reed valve 66 opens, and the exhaust gas of the power generation device 50 is discharged to the exhaust passage 18. when the relationship between exhaust gas of the engine 10 and the exhaust gas of the power generation device 50 corresponds to a region S I illustrated in FIG. 4, i.e. when the pressure of the exhaust gas of the power generation device 50 is higher than the pressure of exhaust gas of the engine in the exhaust passage 18. Conversely, the reed valve 66 closes when the relationship between exhaust gas of the engine 10 and the exhaust gas of the power generation device 50 corresponds to a region S2 illustrated in FIG. 4, i.e. when the pressure of the exhaust gas of the power generation device 50 is lower than the pressure of exhaust gas of the engine 10. In this way, it becomes possible to prevent the exhaust gas of the engine 10 from flowing into the gas discharge passage 60, i.e. to prevent backflow of the exhaust gas.

[0056] In the engine of the first embodiment, as described above, circulation of exhaust gas of the power generation device in the exhaust passage of the engine is secured by providing the valve 66 in the gas discharge passage 60. In addition, backflow of the exhaust gas of the engine towards the power generator main body is prevented likewise by providing the valve 66 in the gas discharge passage 60.

[0057] The turbocharger of the first embodiment may be provided with a variable nozzle mechanism for controlling the inflow of gas into the turbine. The abovementioned waste gate valve may be omitted if a variable nozzle mechanism is provided in the turbocharger.

[0058] A second embodiment according to the invention will be described in detail below. The description of the second embodiment below will deal mainly with differences with respect to the first embodiment, and constituent elements identical or corresponding to already-described constituent elements will be denoted by identical or corresponding reference numerals, and a description thereof will be omitted.

[0059] FIG. 5 is a schematic diagram of an engine 1 10 according to the second embodiment of the invention, and of a vehicle 112 provided with the engine 110. The engine 1 10 is configured in the fonn of a naturally-aspirated engine, and is provided with no turbocharger. In the engine 1 10, a compressor or blower 196 is provided, as an air supply device, in order to supply air to a power generator main body 52 of a power generation device 150 that is configured in the fonn of a fuel cell system. A switching valve 154a is provided in the air introduction passage 54 so as to make it possible to selectively supply, to the power generator main body 52, air from the blower 196 and air from the intake passage 16. The switching valve 154a is configured in the fonn of a three-way valve. The blower 196 and the switching valve 154a are provided in order to operate the power generation device 150 when the engine 1 10 is brought to a stopped state by the stop-restart system 94. The switching valve 154a is controlled so as to bring the intake passage 16 to a communicating state with the power generator main body 52, via the air introduction passage 54, and to bring the blower 196-side passage 196a to a non-communicating state with the air introduction passage 54, during engine operation. On the other hand, when the engine 1 10 is kept in a stopped state by the system 94, the switching valve 154a is controlled so as to bring the intake passage 16 to a non-communicating state with the power generator main body 52, and to bring the blower 196-side passage 196a to a communicating state with the air introduction passage 54. The blower 196 and the valve 154a are controlled by an ECU 180 that substantially has the configuration and functions of the above-described ECU 80, more specifically, by a portion, in the ECU 180, that provides the function of air supply control unit of the system 94. When the engine 110 is in an active state, the air supply amount to the power generation device 150 is controlled by the valve 62 that is provided in the air introduction passage 54.

[0060] In the engine 110, the reed valve 66 is provided in the gas discharge passage 60, as in the case of the engine 10. Therefore, the exhaust gas of the power generation device can flow to the exhaust passage 18, as described above on the basis of FIG. 4, when the power generation device 150 is in an active state while the engine 1 10 is in operation. In addition, it is also possible to prevent inflow or backflow of engine exhaust from the exhaust passage 18 into the gas discharge passage 60 when the power generation device 150 is in a stopped state and the engine 1 10 is in an active state, or when both the engine 1 10 and the power generation device 150 are in an active state.

[0061] In the engine 110, a starter catalytic converter 142u is provided in the exhaust passage upstream of the exhaust control device 42. The starter catalytic converter 142u is provided downstream of the connection section of the gas discharge passage 60 and the exhaust passage 18. The starter catalytic converter 142u, which is provided for warm-up of the exhaust control device 42, is a small oxidation catalyst device that has an oxidation catalyst. Examples of oxidation catalytic substances that can be used in the oxidation catalyst include Pt/Ce0₂. Mn/CeC , Fe/CeCb, Ni/Ce0₂, and Cu/CeOi. The exhaust control device 42 may be referred to herein as a downstream device relative to the starter catalytic converter 142u.

[0062] The power generation device 150 operates as described above when the engine 1 10 is brought to a stopped state by the stop-restart system 94. At this time, the blower 196 operates using electricity of a battery, not shown in FIG. 5, and the switching valve 154a is switched so as to bring the intake passage 16 to a non-communicating state with the power generator main body 52, so that air from the blower 196 is led to the power generator main body 52. Therefore, the power generation device 150 is brought to an active state, and the exhaust gas of the power generation device 150 is supplied to the starter catalytic converter 142u, even while the engine 1 10 is stopped. Accordingly, it is possible to reliably prevent cooling of the exhaust control device 42 while the engine 110 is stopped, and to enable warm-up of the exhaust control device 42 by exploiting the heating action of the starter catalytic converter 142u, also in cases where warm-up of the exhaust control device is not completed.

[0063] In the first and second embodiments, a one-way valve is provided in the gas discharge passage 60, so that, as a result, the exhaust gas of the power generation devices 50, 150 flows into the exhaust passage 18. In the above embodiments, however, it may become difficult for the exhaust gas of the power generation device to flow into the exhaust passage 18 when, for instance, the engine is in a operation state in which pressure is high at the exhaust passage upstream of the turbine, or when a variable nozzle mechanism for controlling inflow of gas to the turbine is provided in the turbocharger and a variable nozzle vane is controlled to be closed. A concern arises also as regards the problem of insufficient power generation in the power generation device when the exhaust gas of the power generation device, which is a fuel cell system, flows with difficulty, and becomes stuck. Accordingly, the operation of the power generation device 50 may be prohibited in such a case. However, prohibiting the operation of the power generation device 50 is hardly the best approach in order to reliably secure a predetermined or higher level of battery remaining charge. A more preferred embodiment as regards this feature will be described next.

[0064] A third embodiment according to the invention will be described in detail below. The description of the third embodiment below will deal mainly with differences with respect to the first embodiment. An engine according to the third embodiment has substantially the same configuration as that of the engine 10 of the first embodiment, and differs from the engine 10 substantially only in control of the engine. Therefore, constituent elements identical or corresponding to constituent elements already described will be denoted by the same reference numerals, and drawings of the engine according to the third embodiment, as well as a description of the features in the drawings, will be omitted.

[0065] In the third embodiment as well, the power generation device 50 operates in accordance with the remaining charge of the battery 70, during operation of the engine 10, or when the engine 10 is brought to a stopped state by the stop-restart system 94.

[0066] In the third embodiment, the power generation device 50 operates in such a manner that the exhaust gas of the engine 10 and the exhaust gas of the power generation device 50 exhibit a relationship such as the above-described relationship described on the basis of FIG. 4, regardless of the operating region the engine operation state may be in. The detailed description below will be based on the flow of FIG. 6 and the mapped data in FIG. 7. The control described hereafter is executed by the portion, in the ECU 80, that provides the function of supply amount control unit of the gas flow control device D. The flow control device D in the third embodiment has the reed valve 66 and a supply amount control unit (corresponding to the ECU 80).

[0067] The ECU 80 determines firstly, in step S601 , whether power generation is in progress or not. In this determination, specifically, it is determined whether the power generation device 50 is in operation or not. When an affirmative determination is made in step S601 , the process proceeds to step S603.

[0068] In step S603, the ECU 80 determines whether the engine operation state is in a first operating region or not. Specifically, the ECU 80 determines whether the engine operation state is in a first operating region or not on the basis of the output of the accelerator depression amount sensor 84 and the output of the crank position sensor 86. A first operating region Rl will be described on the basis of FIG. 7. FIG. 7 illustrates an engine region, in which the abscissa axis represents an engine rotational speed Ne and the ordinate axis represents an engine load TQ. The engine load is in a substantially proportional relationship with the accelerator depression amount. The first operating region Rl is a region such that the engine rotational speed exceeds a first rotational speed Nl and the engine load exceeds a first load Kl , and is established as a region at or below full load — wide open throttle (WOT). The first operating region is determined experimentally on the basis of the pressure in the exhaust passage upstream of the turbine 26, in particular on the basis of the pressure at the turbine inlet. Therefore, the determination in step S603 is equivalent to a determination of whether or not the engine exhaust pressure, i.e. the pressure in the exhaust passage upstream of the turbine, lies within a first pressure range that corresponds to the first operating region. Therefore, an exhaust pressure sensor may be provided in the exhaust passage and the determination in step S603 may be performed on the basis of the output of that exhaust pressure sensor. The valve 32, as a waste gate valve, is designed in such a manner that the valve 32 opens when the engine operation state is in the first operating region. That is, the first operating region corresponds to a waste gate valve open region.

[0069] When step S601 or step S603 yields a negative determination, it is likely that a relationship, such as that illustrated in FIG. 4, holds between the pressure of the exhaust gas of the engine 10 and the pressure of the exhaust gas of the power generation device 50. Therefore, a basic exhaust gas amount control mode, which is basically set as the control mode of the power generation device 50, is set in step S605, and the routine ends. On the other hand, when step S603 yields an affirmative determination, the process proceeds to step S607.

[0070] In step S607, it is determined whether or not the operation state of the engine is in a second operating region. Specifically, the ECU 80 determines whether the engine operation state is in a second operating region or not on the basis of the output of the accelerator depression amount sensor 84 and the output of the crank position sensor 86. The second operating region R2 is a region, illustrated in FIG. 7, in which the engine rotational speed exceeds a second rotational speed N2 and the engine load exceeds a second load K2, and is established as a region at or below full load (WOT). The second operating region R2 is determined experimentally on the basis of the pressure in the exhaust passage upstream of the turbine 26, in particular on the basis of the pressure at the turbine inlet. Therefore, the determination in step S607 is equivalent to a determination of whether or not the engine exhaust pressure, i.e. the pressure in the exhaust passage upstream of the turbine, lies within a second pressure range that corresponds to the second operating region. Therefore, an exhaust pressure sensor may be provided in the exhaust passage and the determination in step S607 may be performed on the basis of the output of that exhaust pressure sensor. The second operating region is part of the first operating region.

[0071] When the engine operation state is not in the second operating region and S607 therefore yields a negative determination, a first exhaust gas amount increment control mode is set, in step S609, as a control mode of the power generation device 50, and the routine ends. On the other hand, when the engine operation state is in the second operating region and step S607 therefore yields an affirmative determination, a second exhaust gas amount increment control mode is set, in step S611, as the control mode of the power generation device 50, and the routine ends.

[0072] In a basic setting, the power generation device 50 operates in such a manner that the pressure of the exhaust gas of the power generation device 50 exhibits the above-described relationship of FIG. 4 with respect to the pressure of the exhaust gas of the engine 10 at a time where the vehicle 12, in which the engine 10 is installed, is traveling in an ordinary urban area, for instance at a time where the engine operation state is in a low-load, low-rotational speed operating region (outside the first operating region). That is, the supply amount control unit of the ECU 80 executes basic exhaust gas amount control at this time.

[0073] FIG. 8 schematically illustrates, in the form of a line LI ', the fluctuation of the pressure of the exhaust gas of the engine 10 when the engine operation state is in the first operating region or the second operating region. FIG. 8 also schematically illustrates, in the form of a line L2 (corresponding to the line L2 of FIG. 4), the fluctuation of the pressure of the exhaust gas of the power generation device 50 that is operating in the basic exhaust gas amount control mode. As FIG. 8 shows, the pressure of the exhaust gas of the engine 10 rises as a whole when the engine operation state is in the first operating region or the second operating region, and hence the pressure of the exhaust gas of the power generation device 50 relatively drops with respect to the pressure of the exhaust gas of the engine 10. It becomes thus difficult for the exhaust gas of the power generation device 50 to flow out appropriately to the exhaust passage 18. Herein, therefore, the air supply amount and the fuel supply amount in the power generation device are controlled in such a manner that the pressure of the exhaust gas of the power generation, device 50 is raised (arrow in FIG. 8) so that the pressure of the exhaust gas of the power generation device 50 exhibits a relationship with the engine exhaust pressure such as the one illustrated in FIG. 4.

[0074] When the first exhaust gas amount increment control mode is set in step S609, the ECU 80, which provides the function of the supply amount control unit, controls the air supply amount and fuel supply amount in the power generation device 50 in such a manner that the pressure of the exhaust gas of the power generation device 50 is raised to or above a predetermined pressure. Herein, first exhaust gas amount increment control involves increasing the exhaust gas amount of the power generation device 50 to a first exhaust gas amount, and changing the flow of gas in the gas discharge passage. The increment in exhaust gas is achieved through an increase of the air supply amount and the fuel supply amount to the power generation device 50. In terms of fuel economy, in particular, the exhaust gas amount of the power generation device 50 is increased by increasing predominantly (actively) the air supply amount. Specifically, the degree of opening of the valve 62 is increased so as to increase the air supply amount, and the pump 20 is controlled so as to increase the fuel supply amount.

[0075] In basic exhaust gas amount control, the supply amounts are controlled in such a manner that the fuel amount and the air amount are balanced in the power generation device 50. In the first exhaust gas amount increment control, however, the air supply amount is firstly increased to be greater, by a predetermined fraction, than the air supply amount set in the case of the basic exhaust gas amount control, and power generation is executed in the power generation device 50 in a state of excess air. As a result, the exhaust gas amount increases at least by an amount corresponding to the air increment fraction. Therefore, it becomes possible to increase the pressure of the exhaust gas of the power generation device 50, for instance the pressure at the outlet section of the power generator main body 52. When the pressure of the exhaust gas of the power generation device 50 is to be increased, the fuel supply amount to the power generator main body 52 of the power generation device 50 is increased by a predetermined fraction to be greater than the fuel supply amount set in the case of the basic exhaust gas amount control. Data relating to the increment of the fuel supply amount and the increment of the air supply amount set in the first exhaust gas amount increment control are experimentally determined beforehand in accordance with the engine operation state. Accordingly, the foregoing are set to be variable depending on the engine operation state.

[0076] On the other hand, the second exhaust gas amount increment control mode is set in step S611, the ECU 80, which provides the function of supply amount control unit, likewise controls the air supply amount and the fuel supply amount in the power generation device 50 so as to raise the pressure of the exhaust gas of the power generation device 50 to or above a predetermined pressure. Herein, the second exhaust gas amount increment control involves increasing the exhaust gas amount of the power generation device 50 to a second exhaust gas amount, and changing the flow of gas of the gas discharge passage. The second exhaust gas amount is greater than the first exhaust gas amount. . The second exhaust gas amount increment control is control to increase the exhaust gas amount of the power generation device 50 by increasing the fuel supply amount. In the second exhaust gas amount increment control, the air supply amount in the power generation device 50 is set at a maximum supply amount of the first exhaust gas amount control. In the second exhaust gas amount increment control, the fuel supply amount is increased by a predetermined amount with respect to the fuel supply amount set in the basic exhaust gas amount control and with respect to the fuel supply amount set in the first exhaust gas amount increment control, on the basis of data relating to the increment of fuel supply amount determined experimentally beforehand in accordance with the engine operation state. Even when fuel leaks from the power generation device 50 due to a fuel excess, for example, the fuel is burned in the reformer 68. Accordingly, that fuel effectively contributes to increasing the exhaust gas amount and the pressure of the exhaust gas of the power generation device 50.

[0077] The exhaust gas amount from the power generation device 50 is increased, as described above, through setting the of the exhaust gas amount increment control mode in step S609 or step S611. Therefore, it is possible to make the pressure of the exhaust gas of the engine 10 and the pressure of the exhaust gas of the power generation device 50 have a relationship such as the one illustrated in FIG. 4, and hence the exhaust gas of the power generation device 50 can appropriately flow to the exhaust passage 18.

[0078] The amount of increment of the exhaust gas amount from the power generation device 50, as a result of exhaust gas amount increment control, i.e. the amount of increment of the air supply amount and the amount of increment of the fuel supply amount, are set in such a manner that the pressure of the exhaust gas of the power generation device 50 becomes equal to or greater than a predetermined pressure, i.e. target pressure determined experimentally beforehand in accordance with the engine operation state, i.e. in accordance with the engine exhaust pressure. Specifically, a target pressure of the exhaust gas of the power generation device 50, i.e. the predetermined pressure, is set to a pressure that between a minimum value and a maximum value of the exhaust pressure of the engine at any given time, and is preferably set to a pressure equal to or higher than the average pressure of the exhaust pressure of the engine. [0079] The increasing method of the exhaust gas amount of the power generation device 50 through exhaust gas amount increment control is not limited to the method in the third embodiment. The invention allows for any control scheme in which at least one of the air supply amount and the fuel supply amount to the power generator main body 52 of the power generation device 50 is controlled in such a manner that the pressure of the exhaust gas of the power generation device 50 becomes a predetermined pressure or higher.

[0080] The operation state of the engine 10 is substantially not influenced, even if the exhaust gas amount of the power generation device 50 is intentionally increased when, as described above, the engine operation state is in the first predetermined region or the second predetermined region. This is because, when the engine operation state is in the first predetermined region or the second predetermined region, the engine operation state is in a waste gate valve open region and therefore, the rotational speed of the turbine wheel does not significantly change and the intake amount to the engine 10 is controlled by the valve 64.

[0081] In the third embodiment described above, the above-described control by the supply amount control unit of the gas flow control device D of the third embodiment (specifically, control described on the basis of the FIG. 6) can be likewise used in the engine of the second embodiment. An embodiment in which control using the supply amount control unit of the third embodiment is used in the engine of the second embodiment will not be described herein.

[0082] A fourth embodiment according to the invention will be described in detail below. The description of the fourth embodiment below will deal mainly with differences with respect to the first embodiment, and constituent elements identical or corresponding to already-described constituent elements will be denoted by identical or corresponding reference numerals, and a description thereof will be omitted.

[0083] FIG. 9 illustrates an engine 210 according to the fourth embodiment, and a vehicle 212 in which the engine 210 is installed. The engine 210, which differs from the engine 10 of the first embodiment, is provided with a gas flow control device D that is configured in such a manner that the exhaust gas from the power generator main body 52 flows selectively to the exhaust passage upstream of the turbine 26 of the turbocharger 24, or to the exhaust passage downstream of the turbine 26.

[0084] A second discharge passage 298 is provided that is connected to the gas discharge passage 60 of a power generation device 250. One end of the second discharge passage 298 is connected to a portion (portion on the power generator main body side) of the gas discharge passage 60 upstream of the reed valve 66. The other end of the second discharge passage 298 is connected to the exhaust passage downstream of the turbine 26 and upstream of the exhaust control device 42. A flow channel switching valve 298a is provided in a connection section between the gas discharge passage 60 and the second discharge passage 298. The flow channel switching valve 298a is controlled by an ECU 280 having substantially the configuration and the function of the above-described ECU 80. Part of the ECU 280 provides the function of valve control unit that controls the flow channel switching valve 298a. The gas flow control device D in the fourth embodiment includes the reed valve 66, the second discharge passage 298, the flow channel switching valve 298a and the valve control unit (corresponding to the ECU 280).

[0085] The power generation device 250 in the fourth embodiment operates in accordance with the remaining charge of a battery (not illustrated in FIG. 9) during operation of the engine 210, or when the engine 210 is brought to a stopped state by the stop-restart system 94. The flow channel switching valve 298a is controlled in accordance with the state of the engine 210 in such a manner that the exhaust gas of the power generation device 250 flows appropriately to the exhaust passage 18. Control of the flow channel switching valve 298a will be described next on the basis of the flowchart of FIG. 10.

[0086] In step SI 001 , the ECU 280 determines whether the engine 210 is stopped or not by the stop-restart system 94. When step SI 001 yields an affirmative determination, the flow channel switching valve 298a is switched in step S I 003 so as to supply the gas from the power generation device 250 to the turbine 26. The flow channel switching valve 298a is switched in such a manner that the second discharge passage 298 is shut off from the gas discharge passage 60. As a result, the turbocharger 24 is brought to a driving state through supply of the exhaust gas of the power generation device 250 to the turbine 26. Therefore, quick operation response upon engine restart is achieved. The exhaust gas of the power generation device 250 is supplied to the exhaust control device 42. Therefore, it becomes possible to prevent cooling of the exhaust control device 42 that is caused by engine stop.

[0087] When the engine is operating and step 1001 therefore yields a negative determination, the flow channel switching valve 298a is switched in step S 1005 so as to supply gas from the power generation device 250 to the exhaust passage downstream of the turbine 26. During engine operation, the pressure in the exhaust passage upstream of the turbine 26 is high, whereas the pressure in the exhaust passage downstream of the turbine 26 is relatively low. Therefore, the gas from the power generation device 250 can appropriately flow to the exhaust passage 18, even if the engine exhaust pressure is higher than the pressure of the exhaust gas of the power generation device as a whole.

[0088] The reed valve 66 can be omitted in the fourth embodiment described above. This is because, even if the reed valve 66 is absent, the exhaust gas of the power generation device 250 can flow to the exhaust passage 18 while inflow or backflow of exhaust gas from the exhaust passage 18 to gas discharge passage 60 is prevented, through switching control of the flow channel switching valve 298a in the above-described manner. A one-way valve such as a reed valve or a check valve may be provided in the second discharge passage 298. The purpose of doing so is to reliably prevent backflow, i.e. flow of the engine exhaust towards the power generator main body 52 via the second discharge passage 298.

[0089] A fifth embodiment according to the invention will be described in detail below. The description of the fifth embodiment will deal mainly with differences with respect to the fourth embodiment. An engine according to the fifth embodiment has substantially the same configuration as the engine 210 according to the fourth embodiment, and differs from the engine 210 only in control of the engine. Therefore, constituent elements identical or corresponding to constituent elements already described will be denoted by the same reference numerals, and drawings of the engine according to the fifth embodiment, as well as a description of the features in the drawings, will be omitted.

[0090] The power generation device 250 in the engine 210 of the fifth embodiment operates in accordance with the remaining charge of the battery during operation of the engine 210, or when the engine 210 is brought to a stopped state by the stop-restart system 94. The flow channel switching valve 298a is controlled in accordance with the operation state of the engine 210 in such a manner that the exhaust gas of the power generation device 250 flows appropriately to the exhaust passage 18. Control of the flow channel switching valve 298a will be described next on the basis of the flowchart of FIG. 1 1.

[0091] In step SI 101, the ECU 280 determines whether or not the operation state of the engine 210 is in a predetermined operating region. A predetermined operating region R is represented by mapped data of FIG. 12, in which the abscissa axis represents an engine rotational speed Ne and the ordinate axis represents an engine load TQ. The predetermined operating region R is established as a region at or below full load (WOT). The predetermined operating region includes a high-load, high-rotational speed region, but may be another region. The determination as to whether or not the engine operation state is in a predetermined operating region is executed on the basis of the output of the accelerator depression amount sensor 84 and the output of the crank position sensor 86.

[0092] When the operation state of the engine 210 is not in a predetermined operating region and step SI 101 therefore yields a negative determination, the flow channel switching valve 298a is switched in step S I 103 in such a manner that the exhaust gas of the power generation device 250 is supplied to the turbine 26. The flow channel switching valve 298a is switched in such a manner that the second discharge passage 298 is shut off from the gas discharge passage 60. In the embodiment, the power generation device 250 operates in such a manner that, when the engine operation state is not in a predetermined operating region and the power generation device 250 is operating, at least a condition is satisfied that the pressure of the exhaust gas of the power generation device 250 and the pressure of the exhaust gas of the engine 210 exhibit a relationship described on the basis of FIG. 4. Therefore, the exhaust gas of the power generation device 250 can flow appropriately to the exhaust passage 18 through control of the flow channel switching valve 298a as described above. Note that the situation, in which the operation state of the engine 210 is not in a predetermined operating region, includes a situation, in which the engine 210 is kept in a stopped state by the stop-restart system 94.

[0093] When the engine operation state of the engine 210 is in a predetermined operating region and step 1101 yields an affirmative determination, the flow channel switching valve 298a is switched in step S I 105 in such a manner that the exhaust gas of the power generation device 250 is supplied to the exhaust passage downstream of the turbine 26. The pressure of the exhaust passage upstream of the turbine 26 is high when the engine operation state is in a predetermined operating region. Upon operation of the power generation device 250 in this situation, the pressure of the exhaust gas of the engine 210 (exhaust pressure upstream of the turbine) tends to be higher than the pressure of the exhaust gas of the power generation device 250 as a whole. Herein, however, the gas discharge passage 60 is connected, via the second discharge passage, to the exhaust passage downstream of the turbine 26, where pressure is low. Therefore, it becomes possible for the exhaust gas of the power generation device 250 to flow appropriately to the exhaust passage 18.

[0094] In this embodiment, the flow channel switching valve 298a is controlled on the basis of both engine load and engine rotational speed. However, the flow channel switching valve 298a may be controlled on the basis of at least one of engine load and engine rotational speed. A valve for adjusting the gas flow rate of the gas discharge passage 60, and a valve for adjusting the gas flow rate of the second discharge passage 298, may be provided instead of the flow channel switching valve 298a that is a three-way valve. Also, at least one valve may be provided in order to adjust the gas flow rate of the gas discharge passage 60 and the gas flow rate of the second discharge passage 298.

[0095] A sixth embodiment according to the invention will be described in detail below. The description of the sixth embodiment will deal mainly with differences with respect to the fifth embodiment. An engine according to the sixth embodiment has substantially the same configuration as the engines 210 according to the fourth and fifth embodiments, but differs from the foregoing in control of the flow channel switching valve. Therefore, constituent elements identical or corresponding to constituent elements already described will be denoted by the same reference numerals, and drawings of the engine according to the sixth embodiment, as well as a description of the features in the drawings, will be omitted.

[0096] In the engine 210 according to the sixth embodiment, the power generation device 250 operates in accordance with the remaining charge of the battery during operation of the engine 210, or when the engine 210 is brought to a stopped state by the stop-restart system 94. The flow channel switching valve 298a is controlled in accordance with the operation state of the engine 210 in such a manner that the exhaust gas of the power generation device 250 flows appropriately to the exhaust passage 18. The flow channel switching valve 298a is controlled in accordance with the degree of opening of the valve 32 as the waste gate valve of the turbocharger 24. Control of the flow channel switching valve 298a in the sixth embodiment will be described next on the basis of the flowchart of FIG. 13.

[0097] In step SI 301 , it is determined whether or not the engine operation state is in a predetermined operating region. Herein, step SI 301 corresponds to step S I 101 , and the predetermined operating region is identical to the predetermined operating region R of step Sl lOl .

[0098] Upon negative determination in step S I 301 , a basic exhaust gas amount control mode is set in step S I 303. The basic exhaust gas amount control mode is identical to the mode in step S605 described above.

[0099] After the process proceeds to step 1303, the flow channel switching valve 298a is switched in step SI 305 in such a manner that gas from the power generation device 250 is supplied to the turbine 26, in the same way as in step S I 103 described above. Then routine ends.

[0100] When the engine operation state is in a predetermined operating region and step SI 301 yields an affirmative determination, it is determined in step SI 307 whether the valve 32, as a waste gate valve, is closed or not. The valve 32, as described above, is configured so as to open when the exhaust pressure is equal to or greater than a predetermined pressure. Therefore, determining whether or not the waste gate valve is closed is equivalent to determining whether or not the exhaust pressure is smaller than a predetermined pressure. Whether the valve 32, as a waste gate valve, is closed or not, i.e. whether the exhaust pressure is smaller than a predetermined pressure or not, is determined herein in accordance with the engine operation state. That is, the determination is performed on the basis of the output of the accelerator depression amount sensor 84 and the output of the crank position sensor 86. However, a sensor may be provided in the valve 32 or the vicinity thereof and the above determination may be performed in accordance with the output of that sensor. The operating region at which the valve 32, as a waste gate valve, is open, lies within the predetermined operating region in step SI 301 , and is smaller than the predetermined operating region.

[0101] Upon affirmative determination in step SI 307, the exhaust gas amount increment control mode is set, in step S I 309, in such a manner that the exhaust gas of the power generation device 250 is supplied to the exhaust passage 18, in particular to the turbine 26. This corresponds to the setting of the first exhaust gas amount increment control mode in the step S609 and setting of the second exhaust gas amount increment control mode in step S611. As a result, the pressure of the exhaust gas of the power generation device 250 is increased aboye the pressure of the exhaust gas of the power generation device 250 that occurs during operation in the basic exhaust gas amount control mode. The pressure of the exhaust gas of the power generation device 250 is increased through control of at least one of the air supply amount and the fuel supply amount to the power generator main body in the power generation device. Herein, control of at least one of the air supply amount and fuel supply amount to the power generator main body may be performed on the basis of at least one of engine load and engine rotational speed.

[0102] Therefore, it becomes possible to supply the gas from the power generation device 250 to the turbine 26 through control, as described above, of the flow channel switching valve 298a in the subsequent step S I 305. After the process proceeds to step S I 305, the routine ends.

[0103] When the valve 32, as a waste gate valve, is open and step 1307 therefore yields a negative determination, the basic exhaust gas amount control mode is set in step S 1311 , as in the case of step S 1303. In step S 1313 , in the same way as in step SI 105 above, the flow channel switching valve 298a is switched in such a manner that the exhaust gas of the power generation device 250 is supplied to the exhaust passage downstream of the turbine 26. Therefore, it becomes possible for the exhaust gas to be released appropriately to the exhaust passage 18, without wasteful increase in the exhaust gas amount from the power generation device 250.

[0104] In the sixth embodiment, as described above, the portion of the ECU that provides the function of valve control unit controls the flow channel switching valve in such a manner that when the waste gate valve is closed, the exhaust gas of the power generation device flows to the turbine (or upstream of the turbine), and, when the waste gate valve is open, the exhaust gas of the power generation device flows to the exhaust passage downstream of the turbine. The portion of the ECU that provides the function of the supply amount control unit executes exhaust gas amount increment control when the flow channel switching valve is controlled so that the exhaust gas of the power generation device flows to the turbine when the waste gate valve is closed.

(0105) A seventh embodiment according to the invention will be described in detail below. In the description of the seventh embodiment, constituent elements identical or corresponding to constituent elements already described will be denoted by the same reference numerals, and recurrent description thereof will be omitted.

[0106] FIG. 14 illustrates an engine 310 according to the seventh embodiment, and a vehicle 312 in which the engine 310 is installed. The engine 310 is a naturally-aspirated engine, and is configured in the form of a combination of the engine 110 of the second embodiment and the engine 210 of the fourth embodiment. In the engine 310, the starter catalytic converter 142u is provided in the exhaust passage 18, upstream of the exhaust control device 42. The second discharge passage 298, one end whereof is connected to the gas discharge passage 60, is connected to the exhaust passage downstream of the starter converter 142u and upstream of the exhaust control device 42. Control of the flow channel switching valve 298a at the connection section of the gas discharge passage 60 and the second discharge passage 298 will be described next with reference to the flowchart of FIG. 15.

[0107] In step S I 501 it is determined whether the exhaust control device 42 is warming up, i.e. whether or not warm-up of the exhaust control device 42 is completed. The above determination is executed by a portion, of the ECU 380, that provides the function of a warm-up determination unit that determines the warm-up state of the exhaust control device 42. The determination is performed on the basis of the engine operation state, specifically, on the basis of the output of the accelerator depression amount sensor 84 and the output of the crank position sensor 86. The determination of step SI 501 may be performed by estimating the temperature of the exhaust control device 42, on the basis of the output of the accelerator depression amount sensor 84 and the output of the crank position sensor 86, or alternatively by directly detecting the temperature of the exhaust control device 42 with a temperature sensor provided in the exhaust passage 18 or in the exhaust control device 42.

[0108] When warming up is in progress and step S I 501 therefore yields an affirmative determination, it is determined in step S I 503 whether or not the engine operation state is in a predetermined operating region. Herein, the determination in step SI 503 corresponds to the determination in step SI 101 , and the predetermined operating region is identical to the predetermined operating region R of step SI 101.

[0109] When the engine operation state is not in a predetermined operating region and step 1503 therefore yields a negative determination, the flow channel switching valve 298a is controlled, in step S I 505, so as to supply the exhaust gas of the power generation device 350 to the starter catalytic converter (referred to as "sta-con" in FIG. 15) 142u. As a result, the exhaust gas of the power generation device 350 is supplied to the starter converter 142u via the reed valve 66, which promotes heating of the exhaust control device 42. When the engine operation state is not in a predetermined operating region, the engine exhaust temperature is not vey high. Thus, it is possible to avoid overheating of the starter catalytic converter 142u and the exhaust control device 42 even if exhaust gas of the power generation device 350 is supplied to the starter catalytic converter 142u.

[0110] On the other hand, when warm-up is completed and step S I 501 therefore yields a negative determination, or when the engine operation state is in a predetermined operating region and step S I 503 yields an affirmative determination, the flow channel switching valve 298a is controlled in step SI 507 in such a manner that the exhaust gas of the power generation device 350 is supplied to the exhaust passage downstream of the starter catalytic converter 142u. The pressure in the exhaust passage downstream of the starter converter 142u is lower than the pressure in the exhaust passage upstream of the starter converter 142u. Accordingly, it is possible to supply appropriately, to the exhaust passage 18, the exhaust gas of the power generation device 350. Also, gas of the power generation device is supplied to the exhaust passage downstream of the starter converter when the exhaust control device 42 requires no heating, or when the engine operation state is in a predetermined operating region, so that overheating of the starter converter 142u and the exhaust control device 42 can be prevented.

[0111] In the seventh embodiment, the exhaust gas amount increment control mode may be set as in step SI 309, when the process reaches step S I 505 and/or step S I 507, so as to enable the exhaust gas of the power generation device to flow appropriately to the exhaust passage. In the engine of the seventh embodiment, at least one of the air supply amount and fuel supply amount in the power generation device may be controlled, in accordance with the pressure of the exhaust gas of the engine, in such a manner that the pressure of the exhaust gas of the power generation device is increased to a predetermined pressure or above.

[0112] The invention has been described above on the basis of embodiments and modifications thereof. However the invention is not limited to the embodiments or the modifications, and allows for other embodiments. For instance, the invention allows for other embodiments that result from partial or total combinations of any of the above-described seven embodiments and modifications thereof. The invention is intended to include all modifications, applications and equivalents encompassed by the invention as defined by the appended claims.

Claims

CLAIMS:

1. An internal combustion engine system, comprising:

an internal combustion engine;

a fuel cell system having a gas discharge passage that is connected to an exhaust passage of the internal combustion engine; and

a gas flow control device configured to control flow of exhaust gas of the fuel cell system so that the exhaust gas of the fuel cell system flows to the exhaust passage of the internal combustion engine.

2. The internal combustion engine system according to claim 1 , wherein

the gas flow control device comprises a one-way valve that is provided in the gas discharge passage.

3. The internal combustion engine system according to claim 1 or 2, wherein the gas flow control device comprises a supply amount control unit that is configured to control at least one of an air supply amount and a fuel supply amount in the fuel cell system,

4. The internal combustion engine system according to claim 3, wherein

the supply amount control unit is configured to control at least one of the air supply amount and the fuel supply amount in accordance with a pressure of exhaust gas of the internal combustion engine.

5. The internal combustion engine system according to claim 3 or 4, wherein the supply amount control unit is configured to control at least one of the air supply amount and the fuel supply amount so as to render the pressure of the exhaust gas of the fuel cell system equal to or higher than a predetermined pressure.

6. The internal combustion engine system according to any one of claims 3 to 5, wherein

the supply amount control unit is configured to execute control of increasing the air supply amount in the fuel cell system in preference to the fuel supply amount in the fuel cell system.

7. The internal combustion engine system according to any one of claims 1 to 6, wherein

the gas flow control device includes:

a second discharge passage having one end connected to the gas discharge passage of the fuel cell system and having the other end connected to the exhaust passage on a downstream side of a connection section, at which the gas discharge passage and the exhaust passage are connected;

at least one valve for adjusting a gas flow rate in the gas discharge passage and a gas flow rate in the second discharge passage; and

a valve control unit that is configured to control the at least one valve.

8. The internal combustion engine system according to claim 7, wherein

the valve control unit is configured to control the at least one valve on the basis of at least one of an engine load and an engine rotational speed of the internal combustion engine.

9. The internal combustion engine system according to claim 7 or 8, further comprising:

a small catalyst device that is provided upstream of an exhaust control device, in the exhaust passage of the internal combustion engine; and

a warm-up determination unit that is configured to determine a warm-up state of the exhaust control device, wherein:

the gas discharge passage is connected to the exhaust passage upstream of the small catalyst device;

the second discharge passage is connected to the exhaust passage between the small catalyst device and the exhaust control device; and

the valve control unit is configured to control the at least one valve so that exhaust gas of the fuel cell system flows to the small catalyst device when the warm-up determination unit determines that warm-up of the exhaust control device is not completed.

10. The internal combustion engine system according to claim 7 or 8, further comprising

a turbocharger that includes a turbine disposed in the exhaust passage, wherein the gas discharge passage is connected to the exhaust passage upstream of the turbine, and

the second discharge passage is connected to the exhaust passage downstream of the turbine.

11. The internal combustion engine system according to claim 7 or 8, further comprising

a turbocharger including a turbine that is disposed in the exhaust passage of the internal combustion engine and that has a waste gate valve, wherein:

the gas discharge passage is connected to the exhaust passage upstream of the turbine;

the second discharge passage is connected to the exhaust passage downstream of the turbine;

the valve control unit is configured to control the at least one valve so that exhaust gas of the fuel cell system flows to the turbine when the waste gate valve is closed; and the valve control unit is configured to control the at least one valve so that exhaust gas of the fuel cell system flows to the exhaust passage downstream of the turbine when the waste gate valve is open.

12. The internal combustion engine system according to claim 10 or 1 1 , wherein the valve control unit is configured to control the at least one valve so that exhaust gas of the fuel cell system flows to the gas discharge passage when the internal combustion engine is stopped.