JP2005166539A - Internal combustion engine having fuel cell in gas discharge system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology that raises temperature of a fuel cell to an operating temperature without deteriorating operation state of an internal combustion engine in the internal combustion engine having the fuel cell in a gas discharge system and that can supply a fuel to the fuel cell without deteriorating the operation state of the internal combustion engine. <P>SOLUTION: The fuel cell 3 is warmed up by the heat generated in a first catalyst 7 by supplying discharge gas in which HC or CO concentration is enhanced by a fuel injection of which timing is different from the main injection. After completion of the warming-up of the fuel cell 3, the discharge gas of which HC or CO concentration is high is supplied to the fuel cell 3 as the power generating fuel by detouring the first catalyst 7 via a first detour 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine having a fuel cell in an exhaust system.

A technology in which a fuel cell is provided in an exhaust system, and an unburned component discharged by operating an internal combustion engine in an excessive fuel state is supplied to the fuel electrode side of the fuel cell as a fuel for power generation (see, for example, Patent Document 1). It has been known. Furthermore, a technique for supplying oxygen into an exhaust passage upstream of a fuel cell provided in an exhaust system of an internal combustion engine is known (see, for example, Patent Document 2).
JP 2002-175824 A JP 2002-151119 A

  However, depending on the operating conditions of the internal combustion engine, it may be difficult to operate in an excessive fuel state. In such a case, fuel cannot be supplied to the fuel cell. In such a case, if the internal combustion engine is operated in a fuel-rich state with priority on power generation by the fuel cell, the operation state of the internal combustion engine deteriorates, causing torque fluctuations and emission deterioration. Further, since the fuel cell operates at a high temperature, it is necessary to raise the temperature of the fuel cell to the operating temperature. However, if this temperature rise takes time, there is a possibility that required power cannot be secured.

  When a catalyst is provided upstream of the fuel cell, the fuel reacts with the catalyst before the fuel is supplied to the fuel cell, and the fuel cannot be stably supplied to the fuel cell. Furthermore, there is a concern that the catalyst may overheat due to the reaction of the fuel with the catalyst.

  The present invention has been made in view of the above problems, and in an internal combustion engine having a fuel cell in an exhaust system, the temperature of the fuel cell is rapidly raised to the operating temperature without deteriorating the operating state of the internal combustion engine. A further object is to provide a technique capable of supplying fuel to the fuel cell without deteriorating the operating state of the internal combustion engine.

In order to achieve the above object, an internal combustion engine having a fuel cell in the exhaust system of the present invention employs the following means. That is,
Fuel injection means for injecting fuel into a cylinder of the internal combustion engine;
A fuel injection means for power generation that performs main injection by the fuel injection means and increases the concentration of HC or CO in the exhaust by fuel injection at a time different from the main injection;
A fuel cell having a fuel electrode side connected to an exhaust passage of the internal combustion engine;
A first catalyst provided in an exhaust passage downstream of the internal combustion engine and upstream of the fuel cell;
A first bypass that connects an exhaust passage upstream of the first catalyst and an exhaust passage downstream of the first catalyst and upstream of the fuel cell;
First temperature detection means for detecting the temperature of the exhaust gas downstream of the first catalyst and upstream of the fuel cell;
When the HC or CO concentration in the exhaust gas is increased by the power generation fuel injection means and when the temperature of the fuel cell is raised, the exhaust gas is mainly circulated through the first catalyst,
When the temperature detected by the first temperature detection means becomes a temperature required for power generation of the fuel cell, first flow path switching means for mainly circulating exhaust gas to the first bypass route;
It is provided with.

  The greatest feature of the present invention is that fuel is injected into the cylinder of the internal combustion engine at a time different from the main injection, thereby increasing the amount of HC or CO emission, thereby generating heat in the first catalyst and fuel. The temperature of the battery is raised, and after the temperature of the fuel cell rises, the exhaust gas is mainly circulated through the first bypass and HC or CO is supplied to the fuel cell as power generation fuel.

  In the internal combustion engine having the fuel cell in the exhaust system configured as described above, the internal combustion engine is operated by the main injection from the fuel injection means. On the other hand, the power generation fuel injection means performs the fuel injection to the internal combustion engine by the fuel injection means in addition to the main injection. For example, a large amount of CO can be discharged from the internal combustion engine by performing fuel injection when the piston from the end of the exhaust stroke to the early stage of the intake stroke is near top dead center. A large amount of HC can be discharged by injecting fuel in the expansion stroke or exhaust stroke after the main injection.

  The HC and CO discharged in this manner react with the first catalyst and raise the temperature of the exhaust. That is, it is desirable that the first catalyst is a catalyst having an oxidation ability that can raise the temperature of exhaust gas by supplying HC or CO. Thus, the temperature of the fuel cell is raised to a temperature at which the fuel cell can generate power (hereinafter referred to as the operating temperature) by raising the temperature of the exhaust gas and causing the exhaust gas having a high temperature to flow into the fuel cell. be able to.

  However, even if the fuel cell can generate power, if HC and CO are reacted in the first catalyst, HC and CO as power generation fuel supplied to the fuel cell are reduced. The amount of power generation is reduced. Further, if HC or CO is continuously supplied to the first catalyst, the first catalyst may be overheated.

  In that regard, after the temperature of the fuel cell rises to the operating temperature, if the exhaust gas is mainly circulated through the first bypass by the first flow path switching means, HC and CO flowing into the fuel cell can be increased, The amount of power generation can be increased. In addition, since the amount of HC and CO supplied to the first catalyst is reduced, the heat generated in the first catalyst can be reduced, and overheating of the first catalyst can be suppressed.

  The first temperature detecting means may detect the temperature of the first catalyst. Further, when the HC or CO concentration in the exhaust gas is increased by the power generation fuel injection means and the temperature of the fuel cell is increased, the exhaust gas is circulated only through the first catalyst, and the first temperature is increased. When the temperature detected by the detection means becomes a temperature required for power generation of the fuel cell, it is more preferable that the exhaust gas is circulated only through the first bypass.

In the present invention, further comprising a second temperature detection means for detecting the temperature of the exhaust downstream of the fuel cell,
Even after the temperature detected by the first temperature detecting means reaches the temperature required for power generation of the fuel cell, the temperature detected by the second temperature detecting means is equal to or lower than the operating temperature of the fuel cell. In this case, the first flow path switching unit can mainly distribute the exhaust gas to the first catalyst.

When exhaust gas is mainly circulated through the first bypass, HC and CO in the exhaust gas do not react with the first catalyst, so that more fuel for power generation can be supplied to the fuel cell. However, the exhaust gas that does not pass through the first catalyst has a low temperature, which may lower the temperature of the fuel cell. And if a fuel cell becomes below operating temperature, electric power generation will no longer be performed. In that respect, when the temperature detected by the second temperature detecting means is equal to or lower than the operating temperature of the fuel cell, it is possible to raise the temperature of the fuel cell again by mainly circulating the exhaust gas through the first catalyst. Become.

  In addition, it is more preferable that the exhaust gas be circulated only through the first catalyst when the temperature detected by the second temperature detecting means is equal to or lower than the operating temperature of the fuel cell. Further, the second temperature detection means may detect the temperature of the fuel cell. Further, the first flow path switching means is not limited to the case where the temperature detected by the second temperature detection means is lower than the operating temperature of the fuel cell, but is mainly used when there is a possibility that the temperature will be lower than the operating temperature. Exhaust gas may be circulated through the catalyst.

In the present invention, a battery for storing electrical energy generated in the fuel cell;
A storage amount calculating means for integrating the amount of electrical energy stored in the battery;
A discharge amount calculating means for integrating the amount of electric energy discharged from the battery;
A remaining charge amount calculating means for calculating an amount of electrical energy stored in the battery based on a calculation result by the charge amount calculating means and the discharge amount calculating means;
Further comprising
The power generation fuel injection means can adjust the HC or CO concentration in the exhaust based on the calculation result of the remaining power storage amount calculation means.

  By storing the electric energy generated in the fuel cell in a battery and supplying the electric energy from the battery to each member that requires the electric energy, the electric energy can be supplied stably. However, if the amount of electrical energy consumed by each member is greater than the amount of electrical energy generated by the fuel cell, the electrical energy stored in the battery decreases, making it difficult to stably supply electrical energy to each member. There is a risk of becoming. In that respect, if the amount of electrical energy stored in the battery (hereinafter referred to as the amount of charge of the battery) decreases, increasing the concentration of HC or CO in the exhaust increases the amount of power generated by the fuel cell, and the battery The amount of charge can be increased. Further, when the charge amount of the battery is sufficient, it is possible to suppress the deterioration of fuel consumption by reducing the HC or CO concentration in the exhaust.

  In the present invention, when the temperature detected by the first temperature detection means is equal to or higher than the activation temperature of the first catalyst, the power generation fuel injection means stops the increase of the HC or CO concentration in the exhaust. Alternatively, the rising amount can be reduced, and the first flow path switching means can reduce the amount of exhaust gas flowing through the first bypass.

  If the fuel for power generation is continuously supplied, the first catalyst may be overheated. Therefore, when the temperature of the fuel cell rises to the operating temperature, the exhaust gas is circulated through the first bypass to suppress the temperature rise of the first catalyst. However, when the first catalyst is already overheated, it is necessary to quickly reduce the temperature of the first catalyst. At that time, if an exhaust gas that does not contain much HC and CO is passed through the first catalyst, the heat of the first catalyst is taken away by the exhaust gas, so that the temperature of the first catalyst can be lowered.

  The first flow path switching means is not limited to the case where the temperature detected by the first temperature detection means is equal to or higher than the activation temperature, but flows through the first bypass when there is a possibility that the temperature will be equal to or higher than the activation temperature. The amount of exhaust may be reduced.

In the present invention, a turbocharger provided upstream of the first catalyst;
A second detour connecting the exhaust passage upstream of the turbocharger and the exhaust passage downstream of the first catalyst and upstream of the fuel cell;
Second flow path switching means for mainly circulating exhaust gas to the second bypass when increasing the power generation amount of the fuel cell;
Can be provided.

  When the turbocharger is provided in the exhaust passage in this way, the turbocharger becomes an exhaust resistance, and an exhaust pressure difference between the upstream side and the downstream side becomes larger than the turbocharger. That is, the exhaust pressure difference between the upstream side and the downstream side of the second bypass route becomes large, so that when the exhaust gas is circulated through the second bypass route, the flow velocity is faster than when the exhaust gas is circulated through the first bypass route. Become. Therefore, by circulating the exhaust gas through the second bypass, it is possible to quickly supply CO and HC to the fuel cell, and to quickly increase the amount of power generation.

  In the present invention, the turbocharger is a variable capacity turbocharger, and the nozzle vane of the variable capacity turbocharger can be controlled to the closed side when the power generation amount of the fuel cell is increased.

  By controlling the nozzle vanes of the variable displacement turbocharger to the closed side, it becomes possible to increase the pressure difference between the upstream side and the downstream side of the turbocharger, and more quickly generate fuel for power generation into the fuel cell. It becomes possible to supply.

In the present invention, a second catalyst provided in an exhaust passage downstream of the fuel cell;
A heat exchanger that is provided in an exhaust passage downstream of the fuel cell and upstream of the second catalyst, and performs heat exchange between the exhaust and the heat medium;
A third detour connecting the exhaust passage upstream of the heat exchanger and the exhaust passage downstream of the heat exchanger and upstream of the second catalyst;
Third temperature detecting means for detecting the temperature of the exhaust downstream of the second catalyst;
When the temperature detected by the third temperature detecting means is equal to or lower than the activation temperature of the second catalyst, the temperature mainly detected by the third temperature detecting means by allowing exhaust gas to flow through the third bypass. Is higher than the activation temperature of the second catalyst, second flow path switching means for mainly circulating the exhaust gas to the heat exchanger;
Can be provided.

  Here, the temperature of the gas discharged from the fuel cell operating at a high temperature is high, and this heat can be recovered by providing a heat exchanger downstream of the fuel cell. For example, the temperature of the exhaust passage can be increased by supplying the air whose temperature has been increased by the heat exchanger to the upstream side of the fuel cell. Thereby, it becomes possible to suppress adhesion of unburned fuel components to the exhaust passage, and efficient power generation becomes possible.

  By the way, harmful components that have not been purified by the first catalyst and power generation fuel that has not reacted by the fuel cell are purified by the second catalyst. Here, when the temperature of the exhaust gas is lowered by the heat exchanger, the low temperature exhaust gas flows into the second catalyst, so that the temperature of the second catalyst is lowered. And if the temperature of a 2nd catalyst becomes below activation temperature, the purification rate of a harmful | toxic component will fall.

  Therefore, when the temperature detected by the third temperature detecting means is equal to or lower than the activation temperature of the second catalyst, the exhaust gas is mainly circulated through the third bypass. As a result, it is possible to suppress a decrease in the temperature of the exhaust, and thus suppress a decrease in the temperature of the second catalyst.

  In addition, when the temperature detected by the 3rd temperature detection means becomes below the activation temperature of a 2nd catalyst, it is more preferable to distribute | circulate exhaust_gas | exhaustion only to a 3rd detour. Further, the third temperature detection means may detect the temperature of the second catalyst. Furthermore, the second flow path switching means is not limited to the case where the temperature detected by the third temperature detection means is lower than the activation temperature, but is mainly used for the third bypass when there is a possibility that the temperature is lower than the activation temperature. You may make it distribute | circulate exhaust_gas | exhaustion.

  In an internal combustion engine having a fuel cell in an exhaust system according to the present invention, the temperature of the fuel cell can be raised to the operating temperature without deteriorating the operating state of the internal combustion engine, and further, fuel for power generation can be supplied to the fuel cell. it can.

  Hereinafter, specific embodiments of an internal combustion engine having a fuel cell in an exhaust system according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an engine 1 and its exhaust system according to this embodiment. The engine 1 shown in FIG. 1 is a diesel engine.
An exhaust passage 2 for releasing burned gas from the engine 1 into the atmosphere is connected to the engine 1. A fuel cell 3 is provided in the middle of the exhaust passage 2. The fuel cell 3 is electrically connected to the auxiliary machinery 4 via the battery 5 and supplies electric power to the auxiliary machinery 4. In this embodiment, a solid oxide fuel cell (hereinafter referred to as Solid Oxide Fuel Cell), which has a simple structure and control, does not require a fuel cell catalyst, and can reform the fuel inside the fuel cell. Adopted SOFC).

The SOFC 3 includes three types of oxide electrolytes, that is, a fuel electrode 3a, an electrolyte 3b, and an air electrode 3c.
The exhaust passage 2 between the engine 1 and the SOFC 3 is provided with a turbocharger 6, a first catalyst 7, and a first flow path switching valve 8 in order from the engine 1 side. One end of a first bypass 9 that bypasses the first catalyst 7 is connected to the exhaust passage 2 between the turbocharger 6 and the first catalyst 7, and the other end of the first bypass 9 is the first. It is connected to the flow path switching valve 8. The first flow path switching valve 8 is a valve that operates in response to a signal from the ECU 10 to be described later and adjusts the amount of exhaust gas flowing through the first catalyst 7 and the first bypass circuit 9.

A first exhaust temperature sensor 11 for detecting the exhaust temperature is attached to the exhaust passage 2 between the first catalyst 7 and the first flow path switching valve 8.
The exhaust passage 2 downstream of the SOFC 3 is provided with a heat exchanger 12 and a second catalyst 13 in order from the SOFC 3 side. In the heat exchanger 12, heat exchange is performed between the exhaust flowing through the exhaust passage 2 and the air sent from the air pump 14. The air sent from the air pump 14 is supplied to the exhaust passage 2 between the engine 1 and the turbocharger 6 via the air supply passage 15.

  A second exhaust temperature sensor 16 for detecting the exhaust temperature is attached to the exhaust passage 2 between the SOFC 3 and the heat exchanger 12, and the exhaust passage 2 downstream of the second catalyst 13 is connected to the exhaust passage 2. A third exhaust temperature sensor 17 for detecting temperature is attached.

The first catalyst 7 and the second catalyst 13 can be an oxidation catalyst, a three-way catalyst, or an NOx storage reduction catalyst, respectively.
Here, the power generation fuel introduced into the SOFC 3 reacts with the water vapor on the fuel electrode 3a to be reformed into hydrogen (H ₂ ) and carbon monoxide (CO). Thus, in SOFC3, it is possible to reform the fuel in the battery. On the other hand, air is supplied to the air electrode 3 c via the pump 18. In the air electrode 3c, oxygen in the air dissociates at the interface with the electrolyte 3b to become oxygen ions (O ²⁻ ), and moves in the electrolyte 3b toward the fuel electrode 3a. Oxygen ions (O ²⁻ ) reaching the interface between the electrolyte 3b and the fuel electrode 3a react with hydrogen (H ₂ ) and carbon monoxide (CO) to form water (H ₂ O) and carbon dioxide (CO ₂ ). ) Is generated. Power generation by the SOFC 3 is performed by taking out the electrons emitted at this time.

  In this way, the chemical energy of the fuel is directly converted into electric energy, so that loss due to energy conversion is small and highly efficient power generation is possible. Such power generation is performed at a temperature of 700 to 1000 ° C., for example.

  Thus, since the operating temperature of the SOFC 3 is high, high temperature gas is discharged from the fuel electrode 3a side. Therefore, while the SOFC 3 is generating power, even if the temperature of the exhaust gas discharged from the engine 1 is low, the temperature of the exhaust gas in the SOFC 3 rises, so the temperature of the exhaust gas downstream of the SOFC 3 is Get higher. In the present embodiment, heat exchange is performed between the exhaust gas having a high temperature and the air, and thereby the air whose temperature has been increased is supplied to the exhaust passage 2 upstream of the turbocharger 6.

  As a result, the wall temperature of the exhaust passage 2 and the temperature of the exhaust can be increased. And it can suppress that the fuel for electric power generation adheres to the wall surface of the exhaust passage 2 by raising the wall temperature of this exhaust passage 2, and the temperature of exhaust_gas | exhaustion.

  Such an engine 1 is provided with an ECU 10 that is an electronic control unit for controlling the engine 1. The ECU 10 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and the driver's request.

  Various sensors are connected to the ECU 10 through electrical wiring, and output signals from these sensors are input to the ECU 10. The ECU 10 is connected to an FC ECU 19 for controlling the SOFC 3.

  The SOFC 3 is operated by a signal from the FC ECU 19. A part of the electric power obtained by the power generation is temporarily stored in the battery 5. Auxiliary machinery 4 such as an electric water pump, an electric compressor for an air conditioner, an electric oil pump, and an electric pump for power steering is electrically connected to the battery 5, and electric power is supplied to these devices.

  The ECU 10 is electrically connected to a fuel injection valve 20 that injects fuel into the cylinder of the engine 1. Since the fuel injection valve 20 is opened and closed by a signal from the ECU 10, the ECU 10 can adjust the fuel injection timing and the fuel injection amount.

  By the way, in an internal combustion engine having a fuel cell in a conventional exhaust system, the engine is operated in a state of excessive fuel, and unburned components discharged at that time are supplied to the fuel electrode side of the fuel cell as power generation fuel. It was. Therefore, when the fuel cell requires a large amount of power generation fuel, it has been necessary to operate the engine at a rich air-fuel ratio to discharge a large amount of unburned fuel.

  However, since the diesel engine is normally operated at a lean air-fuel ratio, the oxygen concentration in the exhaust gas is high, and it is difficult to obtain the necessary power. On the other hand, if the engine is operated at a richer air-fuel ratio with more fuel than the air-fuel ratio during normal operation in an attempt to supply fuel for power generation to the fuel cell, torque fluctuations and emission deterioration may be induced. It was. Furthermore, depending on the operating state of the engine, it may be difficult to operate at a richer air-fuel ratio, and in such a case, necessary electric power could not be secured.

  Further, as described above, since the operating temperature of the SOFC 3 is high, power generation is performed unless the temperature is increased to the operating temperature (hereinafter referred to as “warming up”). I can't. In a diesel engine, the temperature of the normal exhaust gas is low, and it is difficult to quickly complete the warm-up of the fuel cell.

  In this regard, in this embodiment, fuel is injected into the cylinder when the piston from the end of the exhaust stroke to the early stage of the intake stroke is in the vicinity of the top dead center. Hereinafter, such fuel injection is referred to as VIGOM injection. According to this VIGOM injection, the amount of carbon monoxide (CO) emitted from the engine 1 can be increased.

  Further, fuel may be injected from the fuel injection valve 20 as a secondary during the expansion stroke or the exhaust stroke. Hereinafter, such fuel injection is referred to as post injection. By this post injection, the amount of unburned fuel component (HC) discharged from the engine 1 can be increased.

Further, according to the VIGOM injection or the post injection, it is possible to suppress the deterioration of the operation state due to the increase of the engine output as compared with the case where the main injection amount is increased.
The high-concentration CO or HC discharged in this way reacts with the first catalyst 7 and raises the temperature of the exhaust. By supplying the exhaust gas whose temperature has increased to the SOFC 3, the temperature of the SOFC 3 can be quickly increased.

  However, if a high concentration of CO or HC is continuously supplied to the first catalyst 7, the temperature of the first catalyst 7 will rise too much and induce thermal degradation. Therefore, in this embodiment, after the temperature of the SOFC 3 rises to the SOFC fuel reaction temperature, the first flow path switching valve 8 is operated to cause the exhaust gas to flow through the first bypass circuit 9. Here, the SOFC fuel reaction temperature is a temperature at which the fuel can react in the SOFC 3. When SOFC3 becomes higher than this temperature, CO and HC can be reacted in SOFC3, and power generation becomes possible. Further, by circulating the exhaust gas through the first bypass 9, it becomes possible to supply high concentration CO or HC to the SOFC 3 as a power generation fuel.

Next, power generation control of the SOFC 3 according to the present embodiment will be described.
FIG. 2 is a flowchart showing a flow of power generation control of the SOFC 3 according to this embodiment.

  In step S101, an ignition switch (hereinafter referred to as an IG switch) is turned on. This flow may be started when the IG switch is turned on. Thereafter, the engine 1 is started.

In step S102, it is determined whether or not the engine speed Ne is higher than 0, that is, whether or not the engine 1 has been started.
If an affirmative determination is made in step S102, the process proceeds to step S103. On the other hand, if a negative determination is made, the process of step S102 is repeated.

  In step S <b> 103, a signal is sent to the first flow path switching valve 8 so that the exhaust gas flows through the first catalyst 7 and the exhaust gas does not flow through the first bypass 9. As a result, high-concentration CO or HC is supplied to the first catalyst 7.

  In step S104, the amount of fuel injected in the VIGOM injection or the post injection is adjusted. The fuel injection amount at this time is a fuel injection amount suitable for increasing the temperature of the exhaust gas by the first catalyst 7.

  In step S105, it is determined whether or not the exhaust temperature obtained from the first exhaust temperature sensor 11 is higher than the SOFC fuel reaction temperature. Until the exhaust temperature obtained from the first exhaust temperature sensor 11 becomes higher than the SOFC fuel reaction temperature, the temperature of the SOFC 3 is increased by supplying high-concentration CO or HC to the first catalyst 7.

If an affirmative determination is made in step S105, the process proceeds to step S106, whereas if a negative determination is made, the process returns to step S103.
In step S <b> 106, a signal is sent to the first flow path switching valve 8, exhaust gas is circulated through the first bypass circuit 9, and exhaust gas is not circulated through the first catalyst 7. Thereby, it can suppress that the 1st catalyst 7 overheats.

  In step S107, the amount of fuel injected in the VIGOM injection or the post injection is adjusted. The fuel injection amount at this time is a fuel injection amount that can obtain the power generation amount required for the SOFC 3.

  In step S108, it is determined whether or not the exhaust temperature obtained from the second exhaust temperature sensor 16 is within the working gas temperature range. The working gas temperature range is a temperature range of exhaust gas exhausted from the SOFC 3 when power generation is performed inside the SOFC 3. That is, based on the exhaust temperature obtained from the second exhaust temperature sensor 16, it is determined whether or not power generation is being performed in the SOFC 3.

If an affirmative determination is made in step S108, the process proceeds to step S109. On the other hand, if a negative determination is made, the process returns to step S103.
In step S109, it is determined whether or not the charge amount of the battery 5 is equal to or greater than the discharge amount of the battery 5. If the discharge amount of the battery 5 is larger, the power supplied from the battery 5 to the auxiliary machinery 4 may be insufficient. Therefore, in such a case, in order to increase the power generation amount in the SOFC 3, the fuel injection amount in the VIPOM injection or the post injection is increased.

If an affirmative determination is made in step S109, this routine is terminated. On the other hand, if a negative determination is made, the routine returns to step S107.
In this way, rapid warm-up of the SOFC 3 and power generation after warming-up can be realized by VIGOM injection, post injection, and further switching of the exhaust flow path.

  As described above, according to the present embodiment, it is possible to supply power generation fuel to the SOFC 3 without deteriorating the operating state of the engine 1. Further, the warm-up of the SOFC 3 can be quickly completed by the reaction heat of CO or HC in the first catalyst 7.

  In Example 1, the SOFC 3 was warmed up by the first catalyst 7. However, when the temperature of the SOFC 3 is set as the SOFC fuel reaction temperature, the temperature of the first catalyst 7 may be overheated to the activation temperature or higher. Further, when the exhaust passage 2 is closed in step S106, the exhaust does not flow through the first catalyst 7, so that the heat generated in the first catalyst 7 is not lost to the exhaust, and the temperature of the first catalyst 7 is increased. May rise excessively.

  Therefore, in this embodiment, when the temperature of the first catalyst 7 is equal to or higher than the activation temperature, a part of the exhaust gas is circulated through the first bypass 9. That is, the exhaust gas is circulated through the first bypass 9 and the first catalyst 7.

Next, power generation control of the SOFC 3 according to the present embodiment will be described.
FIG. 3 is a flowchart showing a flow of power generation control of the SOFC 3 according to this embodiment.

Up to step S108 is the same as the flowchart shown in FIG.
In step S209, it is determined whether or not the charge amount of the battery 5 is equal to or greater than a value obtained by multiplying the discharge amount of the battery 5 by a coefficient K. Here, the coefficient K is a value smaller than 1, for example, 0.9. The coefficient K is a value obtained from conditions for suppressing overheating of the first catalyst 7, and is set in advance.

If an affirmative determination is made in step S209, the process proceeds to step S210. On the other hand, if a negative determination is made, the process returns to step S107.
In step S210, it is determined whether or not the exhaust temperature obtained from the first exhaust temperature sensor 11 is higher than the activation temperature of the first catalyst 7 (for example, 700 ° C.). Until the exhaust temperature obtained from the first exhaust temperature sensor 11 becomes higher than the activation temperature of the first catalyst 7, the temperature of the SOFC 3 is increased by supplying high-concentration CO or HC to the first catalyst 7. .

If an affirmative determination is made in step S210, the process proceeds to step S211. On the other hand, if a negative determination is made, the process returns to step S107.
In step S211, the amount of fuel injected in the VIGOM injection or the post injection is adjusted. At this time, the fuel injection amount is set so that overheating of the first catalyst 7 can be suppressed. Specifically, the concentration of CO and HC in the exhaust is reduced. Moreover, you may make it not perform VIOM injection and post injection.

  In step S <b> 212, a signal is sent to the first flow path switching valve 8, and the exhaust gas is circulated through the first bypass 9 and the first catalyst 7. Thereby, it can suppress that the 1st catalyst 7 overheats. That is, when the exhaust gas having a low concentration of CO or HC is circulated through the first catalyst 7, the heat of the first catalyst 7 is taken away by the exhaust gas, so that the temperature of the first catalyst 7 can be lowered.

When step S212 ends, the process returns to step S210.
In this way, the SOFC 3 can be warmed up while suppressing overheating of the first catalyst 7.

  This embodiment differs from the above embodiment in the following points. In other words, the second detour 21 that bypasses the turbocharger 6 and the first catalyst 7 is provided, and when the charge amount of the battery 5 is insufficient, the exhaust gas is circulated through the second detour 21 to quickly reach the SOFC 3. Supply fuel for power generation.

  FIG. 4 is a diagram showing a schematic configuration of the engine 1 and its exhaust system according to the present embodiment. The second bypass 21 has one end connected between the engine 1 and the turbocharger 6 and the other end connected to the first flow path switching valve 8.

  Here, when CO or HC is supplied to the first catalyst 7, the power generation fuel of the SOFC 3 is consumed by the first catalyst 7, so that the power generation amount of the SOFC 3 decreases. Thereby, there exists a possibility that the charge amount of the battery 5 may run short. In such a case, it is necessary to rapidly increase the power generation amount of SOFC3.

  In that respect, according to the present embodiment, when the power generation amount is desired to be increased rapidly by the SOFC 3, the flow path switching valve 8 is operated to circulate the exhaust gas to the second bypass route 21, and the first bypass route 9, Exhaust gas is not circulated through the turbocharger 6 and the first catalyst 7. As a result, exhaust having high pressure upstream from the turbocharger 6 flows into the SOFC 3 at once, and a large amount of fuel for power generation can be quickly supplied to the SOFC 3.

The turbocharger 6 is more preferably a variable capacity turbocharger. When exhaust is circulated through the second bypass 21, the pressure in the exhaust passage 2 upstream of the turbocharger 6 can be increased by controlling the nozzle vanes of the variable displacement turbocharger to the closed side. As a result, the pressure difference between the upstream side and the downstream side of the second bypass 21 becomes large, the flow rate of the exhaust gas flowing through the second bypass 21 can be increased, and the fuel for power generation is supplied to the SOFC 3 more quickly. can do.

Next, power generation control of the SOFC 3 according to the present embodiment will be described.
FIG. 5 is a flowchart showing a flow of power generation control of the SOFC 3 according to this embodiment.

Except for the processing after the negative determination is made in step S210, the processing is the same as the flowchart shown in FIG.
If a negative determination is made in step S210, the process proceeds to step S313.

  In step S313, it is determined whether or not the charge amount of the battery 5 is equal to or greater than a value obtained by multiplying the discharge amount of the battery 5 by a coefficient K ′. Here, the coefficient K ′ is a value smaller than the coefficient K described in step S209, and is set to 0.6, for example. The coefficient K ′ is a value obtained from conditions that require rapid power generation of the SOFC 3 and is set in advance.

If an affirmative determination is made in step S313, the process proceeds to step S314. On the other hand, if a negative determination is made, the process returns to step S107.
In step S <b> 314, a signal is sent to the first flow path switching valve 8 and the exhaust gas is circulated through the second bypass 21. Further, when a variable displacement turbocharger is provided, the nozzle vane is controlled to the closed side (VNT is closed in FIG. 5). Thereby, the fuel for power generation can be quickly supplied to the SOFC 3.

Note that the amount of exhaust gas flowing through each of the first bypass route 9, the second bypass route 21, and the first catalyst 7 may be adjusted based on the charge amount of the battery 5.
When step S314 ends, the process returns to step S313.

  In this way, it is possible to increase the power generation amount of the SOFC 3 and suppress the shortage of the charge amount of the battery 5.

  This embodiment differs from the above embodiment in the following points. That is, when the temperature of the exhaust gas flowing out from the second catalyst 13 is lower than the activation temperature of the second catalyst 13, the third bypass 22 is provided. By causing the exhaust gas to flow, a decrease in the exhaust gas temperature is suppressed, and thus the temperature of the second catalyst 13 is kept at the activation temperature.

  FIG. 6 is a diagram showing a schematic configuration of the engine 1 and its exhaust system according to the present embodiment. One end of the third bypass 22 is connected between the second exhaust temperature sensor 16 and the heat exchanger 12, and the other end is provided downstream of the heat exchanger 12 and upstream of the second catalyst 13. It is connected to the two flow path switching valve 23. The second flow path switching valve 23 is a valve that operates in response to a signal from the ECU 10 and adjusts the amount of exhaust flowing through the heat exchanger 12.

  Here, since the first catalyst 7 is mainly used to raise the temperature of the SOFC 3, it is desirable that the capacity of the first catalyst 7 is reduced and the temperature of the first catalyst 7 itself rises quickly. Therefore, it becomes difficult to purify all harmful substances in the exhaust gas in the first catalyst 7. In addition, CO and HC may flow out downstream of the SOFC 3 without reacting in the SOFC 3. These harmful substances are purified by the second catalyst 13.

However, even if the exhaust gas having a high temperature is discharged from the SOFC 3, the exhaust gas passes through the heat exchanger 12, so that the temperature of the exhaust gas is lowered. For this reason, exhaust gas having a low temperature flows through the second catalyst 13, and the temperature of the second catalyst 13 may be lowered to an activation temperature or lower (for example, 200 to 250 ° C.).

  In this regard, in this embodiment, when the temperature of the exhaust gas obtained by the third exhaust temperature sensor 17 becomes equal to or lower than the activation temperature of the second catalyst 13, the exhaust gas is circulated through the third bypass 22, that is, the heat The exhaust gas is prevented from passing through the exchanger 12 to suppress a decrease in the exhaust gas temperature, thereby suppressing the temperature of the second catalyst 13 from decreasing.

Next, switching control of the second flow path switching valve 23 according to the present embodiment will be described.
FIG. 7 is a flowchart showing a flow of switching control of the second flow path switching valve 23 according to the present embodiment.

This routine is executed every specified time.
In step S401, it is determined whether or not the exhaust temperature obtained from the third exhaust temperature sensor 17 is equal to or lower than the activation temperature of the second catalyst 13 (for example, 200 to 250 ° C.). When the exhaust temperature obtained from the third exhaust temperature sensor 17 is within the activation temperature range of the second catalyst 13, the exhaust gas is caused to flow through the heat exchanger 12.

If an affirmative determination is made in step S401, the process proceeds to step S402. On the other hand, if a negative determination is made, the process proceeds to step S403.
In step S <b> 402, a signal is sent to the second flow path switching valve 23, and the exhaust gas is circulated through the third bypass 22. Thereby, the fall of the temperature of exhaust_gas | exhaustion is suppressed.

In step S <b> 403, it is determined whether the exhaust temperature obtained from the third exhaust temperature sensor 17 is higher than the activation temperature of the second catalyst 13.
If an affirmative determination is made in step S403, the process proceeds to step S404. On the other hand, if a negative determination is made, this routine is terminated.

  In step S <b> 404, a signal is sent to the second flow path switching valve 23, and the exhaust gas is circulated through the heat exchanger 12. As a result, the temperature of the exhaust gas is lowered, and the temperature of the air flowing through the air supply passage 15 can be increased.

  In this way, it is possible to suppress the temperature of the second catalyst 13 from dropping below the activation temperature and to purify harmful substances in the exhaust.

It is a figure which shows schematic structure of the engine by Example 1 and 2, and its exhaust system. FIG. 3 is a flowchart illustrating a flow of SOFC power generation control according to the first embodiment. 6 is a flowchart showing a flow of SOFC power generation control according to Embodiment 2. FIG. It is a figure which shows schematic structure of the engine by Example 3, and its exhaust system. FIG. 6 is a flowchart showing a flow of SOFC power generation control according to a third embodiment. It is a figure which shows schematic structure of the engine by Example 4, and its exhaust system. It is the flowchart figure which showed the flow of switching control of the 2nd flow-path switching valve by Example 4. FIG.

Explanation of symbols

1 Engine 2 Exhaust passage 3 Fuel cell (SOFC)
3a Fuel electrode 3b Electrolyte 3c Air electrode 4 Auxiliary machinery 5 Battery 6 Turbocharger 7 First catalyst 8 First flow path switching valve 9 First bypass 10 ECU
11 First exhaust temperature sensor 12 Heat exchanger 13 Second catalyst 14 Air pump 15 Air supply passage 16 Second exhaust temperature sensor 17 Third exhaust temperature sensor 18 Pump 19 ECU for FC
20 Fuel injection valve 21 Second bypass 22 Third bypass 23 Second flow path switching valve

Claims (7)

Fuel injection means for injecting fuel into a cylinder of the internal combustion engine;
A fuel injection means for power generation that performs main injection by the fuel injection means and increases the concentration of HC or CO in the exhaust by fuel injection at a time different from the main injection;
A fuel cell having a fuel electrode side connected to an exhaust passage of the internal combustion engine;
A first catalyst provided in an exhaust passage downstream of the internal combustion engine and upstream of the fuel cell;
A first bypass that connects an exhaust passage upstream of the first catalyst and an exhaust passage downstream of the first catalyst and upstream of the fuel cell;
First temperature detection means for detecting the temperature of the exhaust gas downstream of the first catalyst and upstream of the fuel cell;
When the HC or CO concentration in the exhaust gas is increased by the power generation fuel injection means and the temperature of the fuel cell is raised, the exhaust gas is mainly circulated through the first catalyst, and the first temperature detection is performed. When the temperature detected by the means becomes a temperature required for power generation of the fuel cell, first flow path switching means for mainly circulating the exhaust gas to the first bypass route;
An internal combustion engine having a fuel cell in an exhaust system. A second temperature detecting means for detecting the temperature of the exhaust gas downstream from the fuel cell;
Even after the temperature detected by the first temperature detecting means reaches the temperature required for power generation of the fuel cell, the temperature detected by the second temperature detecting means is equal to or lower than the operating temperature of the fuel cell. 2. The internal combustion engine having a fuel cell in an exhaust system according to claim 1, wherein the first flow path switching unit mainly causes exhaust gas to flow through the first catalyst. A battery for storing electrical energy generated in the fuel cell;
A storage amount calculating means for integrating the amount of electrical energy stored in the battery;
A discharge amount calculating means for integrating the amount of electric energy discharged from the battery;
A remaining charge amount calculating means for calculating an amount of electrical energy stored in the battery based on a calculation result by the charge amount calculating means and the discharge amount calculating means;
Further comprising
3. The fuel cell in the exhaust system according to claim 1, wherein the power generation fuel injection unit adjusts the HC or CO concentration in the exhaust based on a calculation result of the remaining storage amount calculation unit. Internal combustion engine having.   When the temperature detected by the first temperature detection means is equal to or higher than the activation temperature of the first catalyst, the power generation fuel injection means stops the increase of the HC or CO concentration in the exhaust or reduces the increase amount. An internal combustion engine having a fuel cell in an exhaust system according to any one of claims 1 to 3, wherein the first flow path switching means reduces the amount of exhaust gas flowing through the first bypass. organ. A turbocharger provided upstream of the first catalyst;
A second detour connecting the exhaust passage upstream of the turbocharger and the exhaust passage downstream of the first catalyst and upstream of the fuel cell;
Second flow path switching means for mainly circulating exhaust gas to the second bypass when increasing the power generation amount of the fuel cell;
The internal combustion engine which has a fuel cell in the exhaust system in any one of Claim 1 to 4 characterized by the above-mentioned. 6. The exhaust system according to claim 5, wherein the turbocharger is a variable capacity turbocharger, and the nozzle vane of the variable capacity turbocharger is controlled to a closed side when the power generation amount of the fuel cell is increased. An internal combustion engine having a fuel cell. A second catalyst provided in an exhaust passage downstream of the fuel cell;
A heat exchanger that is provided in an exhaust passage downstream of the fuel cell and upstream of the second catalyst, and performs heat exchange between the exhaust and the heat medium;
A third detour connecting the exhaust passage upstream of the heat exchanger and the exhaust passage downstream of the heat exchanger and upstream of the second catalyst;
Third temperature detecting means for detecting the temperature of the exhaust downstream of the second catalyst;
When the temperature detected by the third temperature detecting means is equal to or lower than the activation temperature of the second catalyst, the temperature mainly detected by the third temperature detecting means by allowing exhaust gas to flow through the third bypass. Is higher than the activation temperature of the second catalyst, second flow path switching means for mainly circulating the exhaust gas to the heat exchanger;
The internal combustion engine which has a fuel cell in the exhaust system in any one of Claim 1 to 6 characterized by the above-mentioned.

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