JP7435315B2 - Engine fuel reforming system - Google Patents

Description

The present invention relates to a fuel reforming system in which a fuel reforming catalyst is provided in an EGR passage connecting an intake passage and an exhaust passage of an engine.

As an engine to which the above-described fuel reforming system is applied, the engine disclosed in Patent Document 1 below is known. Specifically, the engine of Patent Document 1 includes an EGR passage that connects an intake passage and an exhaust passage, a fuel injection valve (reformed fuel fuel injection valve) that injects reforming fuel into the EGR passage, The fuel reforming catalyst is provided at a position downstream of the fuel injection valve in the EGR passage. The fuel reforming catalyst contains, for example, a rhodium-based catalytic metal, and has the function of reforming hydrocarbon fuel at high temperatures to generate hydrogen.

JP 2018-9492 Publication

In Patent Document 1, fuel injected into an EGR passage is introduced into a fuel reforming catalyst together with high-temperature EGR gas, whereby the fuel is reformed and hydrogen is generated. Hydrogen has a fast combustion speed, so by supplying reformed fuel containing hydrogen to the engine body (cylinder), even under conditions where the EGR rate (the proportion of EGR gas contained in the intake air) is high. It is said to achieve stable combustion. Therefore, Patent Document 1 is expected to be effective in improving fuel efficiency by increasing the EGR rate as much as possible while ensuring combustion stability.

However, in Patent Document 1, an EGR valve (exhaust gas recirculation control valve) that opens and closes an EGR passage is simply provided as a means for adjusting the EGR rate. For this reason, for example, under operating conditions where the pressure difference between the exhaust passage and the intake passage is small (for example, high load conditions), even if the EGR valve is opened to the fully open position, a sufficient amount of EGR gas cannot be secured, and the There was a possibility that the fuel efficiency improvement effect of the previous period would not be achieved.

The present invention has been made in view of the above circumstances, and provides an engine fuel reformer that can accurately adjust the amount of EGR gas introduced into a fuel reforming catalyst for fuel reforming. The purpose is to provide a quality system.

In order to solve the above problems, the present invention provides an engine including an engine body, an intake passage through which intake air introduced into the engine body flows, and an exhaust passage through which exhaust gas discharged from the engine body flows. A fuel reforming system applied to a fuel reforming system, comprising: an EGR passage connecting the intake passage and the exhaust passage; a reforming injector capable of injecting fuel into the EGR passage; and a reforming injector in the EGR passage. A fuel reforming catalyst is provided on the downstream side of the injector and is capable of reforming the fuel injected from the reforming injector, and a fuel reforming catalyst is provided in the exhaust passage and is capable of generating electricity from the energy of the exhaust gas flowing through the exhaust passage. A power generation turbine, an air supply compressor that is provided in the EGR passage and can be driven by the electric power generated by the power generation turbine, and a controller that controls the reforming injector, the power generation turbine, and the air supply compressor. , the controller controls an EGR system in which the flow rate of EGR gas, which is exhaust gas recirculated from the exhaust passage to the intake passage through the EGR passage, is insufficient during execution of reforming control for injecting fuel into the reforming injector. If the occurrence of a shortage is confirmed, EGR promotion control is executed to increase the rotational speed of the air supply compressor and increase the amount of power generated by the power generation turbine (Claim 1). .

According to the present invention, the EGR passage is provided with the fuel reforming catalyst and the air supply compressor, and the fuel injected from the reforming injector into the EGR passage can be introduced into the fuel reforming catalyst. The suction force of exhaust gas into the EGR passage can be adjusted by controlling the rotation, and the flow rate of EGR gas introduced into the fuel reforming catalyst together with fuel can be adjusted to an appropriate value depending on the operating conditions. Furthermore, since the power generating turbine is provided in the exhaust passage, at least a portion of the power consumed by the air supply compressor can be covered by the power generated using the energy of the exhaust gas. This, together with the fuel reforming effect (improving combustibility) due to the endothermic reaction in the fuel reforming catalyst, increases the efficiency of exhaust heat recovery that returns the exhaust heat from the engine to output. can sufficiently improve fuel efficiency.

In addition, if an EGR shortage occurs in which the flow rate of EGR gas is insufficient during the execution of the control (reforming control) for introducing fuel into the fuel reforming catalyst as described above, the rotation speed of the air supply compressor is increased. Since the EGR promotion control is executed to increase the amount of power generated by the power generation turbine, the EGR shortage can be promptly resolved and an appropriate amount of EGR gas for fuel reformation can be secured. In other words, an increase in the rotational speed of the air supply compressor increases the suction force of exhaust gas into the EGR passage, and an increase in the amount of power generated by the power generation turbine increases the flow resistance of exhaust gas in the exhaust passage. The action promotes the diversion of exhaust gas from the exhaust passage to the EGR passage, thereby quickly resolving the EGR shortage. As described above, in the present invention, even if an EGR shortage occurs, it can be quickly resolved, so the flow rate of EGR gas introduced into the fuel reforming catalyst can be adjusted with high precision, and good fuel consumption can be achieved based on the adjustment. It is possible to obtain the modification performance of

The target value of the EGR rate, which is the ratio of the EGR gas to the intake air introduced into the engine body, is the target EGR rate, the actual value of the EGR rate is the actual EGR rate, and the value obtained by subtracting the actual EGR rate from the target EGR rate is the insufficient EGR. The controller sequentially calculates the insufficient EGR rate during execution of the reforming control, and when it is confirmed that the calculated insufficient EGR rate is larger than a predetermined threshold value, the controller calculates the EGR It is preferable to perform accelerated control (Claim 2).

According to this configuration, it is possible to appropriately determine whether there is a shortage of EGR based on the comparison between the target EGR rate and the actual EGR rate.

In the configuration, more preferably, the controller adjusts the rotational speed of the air compressor to the insufficient EGR rate such that the larger the insufficient EGR rate is with respect to the threshold value, the larger the rotational speed of the air compressor increases. Based on the feedback control (Claim 3).

According to this configuration, the EGR shortage can be quickly resolved by appropriately controlling the rotation speed of the air supply compressor according to changes in the EGR shortage rate.

Preferably, the controller lowers the rotational speed of the air supply compressor and lowers the rotation speed of the power generation turbine, when occurrence of excess EGR in which the flow rate of the EGR gas becomes excessive is confirmed during execution of the reforming control. EGR suppression control is executed to reduce the amount of power generation (claim 4).

According to this configuration, when excess EGR occurs, in which the flow rate of EGR gas is excessive, both the rotational speed of the air compressor and the amount of power generated by the power generation turbine decrease, so the excess EGR can be promptly resolved and fuel reforming can be performed. An appropriate amount of EGR gas can be secured for this purpose. In other words, the reduction in the rotational speed of the air compressor reduces the suction force of exhaust gas into the EGR passage, and the reduction in the amount of power generated by the power generation turbine reduces the flow resistance of exhaust gas in the exhaust passage. The action suppresses the branching of exhaust gas from the exhaust passage to the EGR passage, thereby quickly eliminating excess EGR. In this way, with the above configuration, even if excessive EGR occurs, it can be quickly resolved, so the flow rate of EGR gas introduced into the fuel reforming catalyst can be adjusted with high precision, and good fuel consumption can be achieved based on the adjustment. It is possible to obtain the modification performance of

The target value of the EGR rate, which is the ratio of the EGR gas to the intake air introduced into the engine body, is the target EGR rate, the actual value of the EGR rate is the actual EGR rate, and the value obtained by subtracting the target EGR rate from the actual EGR rate is the excessive EGR. The controller sequentially calculates the excess EGR rate during execution of the reforming control, and when it is confirmed that the calculated excess EGR rate is larger than a predetermined threshold value, the controller calculates the excess EGR rate. It is preferable to execute inhibitory control (claim 5).

According to this configuration, it is possible to appropriately determine whether there is excessive EGR based on the comparison between the target EGR rate and the actual EGR rate.

In the configuration, more preferably, the controller feeds back the power generation amount of the power generation turbine based on the excess EGR rate so that the power generation amount of the power generation turbine decreases more as the excess EGR rate is larger than the threshold value. control (Claim 6).

According to this configuration, excess EGR can be promptly resolved by appropriate power generation control of the power generation turbine in accordance with changes in the excess EGR rate. Furthermore, in a situation where excessive EGR occurs, a large amount of exhaust gas must have flowed before that, and it is highly likely that sufficient power was being generated by the power generation turbine. On the other hand, in the above configuration, the amount of power generation is quickly reduced by feedback control according to the degree of excess EGR rate, so that excess EGR can be quickly resolved while avoiding unnecessary power generation.

As described above, according to the engine fuel reforming system of the present invention, the amount of EGR gas introduced into the fuel reforming catalyst for reforming fuel can be adjusted with high precision.

1 is a plan view schematically showing the overall configuration of an engine to which a fuel reforming system according to an embodiment of the present invention is applied. It is a block diagram showing a control system of the above-mentioned engine. It is a flowchart which shows an example of the control performed during operation of the said engine. This is a subroutine showing the first half of the reforming control performed in step S3 of FIG. 3. This is a subroutine showing the latter half of the above reforming control. 3 is a graph schematically showing the relationship between engine load and target EGR rate. These are graphs showing trends in maps for determining the amount of fuel injection for reforming, where graph (a) shows the relationship between the catalyst inlet temperature and the amount of fuel injection for reforming, and graph (b) shows the relationship between the EGR gas flow rate and the amount of reforming fuel. The relationship with the quality fuel injection amount is shown respectively. It is a graph showing the relationship between the fuel ratio (ratio of direct injection fuel amount and reforming fuel injection amount) and catalyst inlet temperature. It is a time chart which shows an example of the time change of various state quantities when the said reforming control is performed.

(1) Overall configuration of engine FIG. 1 is a plan view schematically showing the overall configuration of an engine to which a fuel reforming system according to an embodiment of the present invention is applied. The engine shown in this figure is a four-cycle gasoline engine mounted on a vehicle as a power source for driving, and includes an engine body 1, an intake passage 10 through which intake air introduced into the engine body 1 flows, and an engine body. The exhaust gas passage 20 includes an exhaust passage 20 through which exhaust gas (burnt gas) discharged from the exhaust passage 1 flows, and an EGR passage 30 that connects the intake passage 10 and the exhaust passage 20.

The engine body 1 is of an in-line multi-cylinder type including a plurality of (here, four) cylinders 2 arranged in a row. A piston (not shown) is accommodated in each cylinder 2 so as to be able to reciprocate.

Each cylinder 2 of the engine body 1 is provided with a direct injector 3, a spark plug 4, an intake valve 5, and an exhaust valve 6, respectively. The direct injector 3 is an injection valve that injects fuel containing gasoline into the cylinder 2. The spark plug 4 is a plug that ignites a mixture of fuel and air. The intake valve 5 is a valve that opens and closes an unillustrated intake port that communicates the intake passage 10 (each independent intake pipe 11 described later) and the cylinder 2 with each other. The exhaust valve 6 is a valve that opens and closes an unillustrated exhaust port that communicates the exhaust passage 20 (each independent exhaust pipe 21 described later) with the cylinder 2.

The fuel supplied from the direct injection injector 3 to the cylinder 2 is mixed with air in a combustion chamber defined above the piston inside the cylinder 2 to form an air-fuel mixture. The air-fuel mixture is ignited by the spark plug 4 and combusted, and the piston reciprocates in response to the expansion force caused by the combustion. The reciprocating motion of the piston is transmitted to the output shaft (crankshaft) of the engine main body 1 via a crank mechanism (not shown), causing the output shaft to rotate. The engine body 1 is provided with a crank angle sensor SN1 that detects a rotation angle (crank angle) and a rotation speed (engine rotation speed) of the output shaft. Note that in this embodiment, in addition to (or in place of) the fuel supplied from the direct injection injector 3, fuel supplied from a reforming injector 32, which will be described later, through the EGR passage 30 is combusted in the cylinder 2. It is also possible (details will be described later).

The intake passage 10 has a plurality of (four in this case) independent intake pipes 11 connected to one side of the engine body 1, and the upstream end (the side far from the engine body 1) of each independent intake pipe 11 is common. It has a surge tank 12 connected to the surge tank 12, and a single-tubular common intake pipe 13 extending upstream from the surge tank 12. Each independent intake pipe 11 is connected to the engine body 1 so as to communicate with each cylinder 2 via the intake port.

A throttle valve 15 for adjusting the intake flow rate is provided in the middle of the common intake pipe 13 so as to be openable and closable. Further, on the downstream side of the throttle valve 15 in the common intake pipe 13, an air flow sensor SN2 is provided to detect the intake air flow rate. The air flow sensor SN2 is provided at a position downstream of the throttle valve 15 and upstream of the outlet of the EGR passage 30 so as to be able to detect the flow rate of intake air (that is, fresh air) before being mixed with EGR gas. .

The exhaust passage 20 includes a plurality of (four in this case) independent exhaust pipes 21 connected to the other side of the engine body 1 and a downstream end (farthest from the engine body 1) of each independent exhaust pipe 21. The exhaust gas has a common exhaust pipe 23 in the form of a single pipe extending downstream from the collecting part 22. Each independent exhaust pipe 21 is connected to the engine body 1 so as to communicate with each cylinder 2 via the exhaust port.

The common exhaust pipe 23 is provided with a power generation turbine 25 that generates power using the energy of the exhaust gas flowing through the common exhaust pipe 23. The power generating turbine 25 includes a turbine case 26 interposed in the middle of the common exhaust pipe 23, a turbine impeller 27 disposed inside the turbine case 26, and a power generating turbine connected to the turbine impeller 27 via a connecting shaft 27a. It has a machine 28. The turbine impeller 27 is an impeller that rotates by receiving the energy of exhaust gas passing through the turbine case 26 . The generator 28 has a built-in rotor coil that rotates in conjunction with the turbine impeller 27, and generates power by electromagnetic induction caused by the rotation of the rotor coil.

Generator 28 is electrically connected to battery 40 . The battery 40 can store electric power generated by the generator 28 and can supply electric power to various electric devices (for example, a motor 38 described later) connected to the battery 40. The battery 40 is provided with a battery sensor SN4 that detects the terminal voltage and input/output current of the battery 40.

The EGR passage 30 is provided to connect a position in the common exhaust pipe 23 upstream of the turbine case 26 and a position in the common intake pipe 13 downstream of the throttle valve 15 to each other. In the EGR passage 30, an EGR valve 31, a reforming injector 32, a fuel reforming catalyst 33, and an air supply compressor 35 are arranged in this order from the upstream side (the side closer to the exhaust passage 20).

The EGR valve 31 is a valve that is openable and closable in order to adjust the flow rate of EGR gas, which is exhaust gas that is recirculated from the exhaust passage 20 to the intake passage 10 through the EGR passage 30.

The reforming injector 32 is an injection valve that injects the same fuel as that injected by the above-mentioned direct injection injector 3, that is, fuel containing gasoline. The fuel injected into the EGR passage 30 from the reforming injector 32 is introduced into the fuel reforming catalyst 33 together with the EGR gas.

The fuel reforming catalyst 33 includes, for example, a porous carrier (monolith carrier) having a honeycomb structure and a catalyst material coated on the surface of the carrier. The catalyst material includes, for example, a rhodium-based catalyst metal, and has the function of reforming the fuel at a high temperature exceeding a predetermined activation temperature (for example, about 500° C.). Specifically, the catalyst substance reforms the gasoline-containing fuel (hydrocarbon fuel) supplied together with the high-temperature EGR gas from the reforming injector 32 through an endothermic reaction, and converts it into carbon monoxide (CO) and hydrogen (H ₂ ). Generate ingredients containing. A reformed fuel containing these components (carbon monoxide and hydrogen) has a faster combustion rate and generates more heat per unit mass than the fuel before reformation (hydrocarbon fuel). This has the effect of reducing the total amount of fuel required to generate the same output torque. Moreover, since the reforming reaction that leads to these effects is achieved using the heat of EGR gas (exhaust gas), it is similar to exhaust heat recovery that returns exhaust heat from an engine to output. effect is obtained, and the fuel efficiency of the engine is improved.

A catalyst temperature sensor SN3 is attached to the fuel reforming catalyst 33 to detect the temperature at the inlet portion of the catalyst 33.

The air supply compressor 35 includes a compressor case 36 provided downstream of the fuel reforming catalyst 33 in the EGR passage 30, a compressor impeller 37 disposed inside the compressor case 36, and a connecting shaft 37a between the compressor impeller 37 and the compressor impeller 37. and a motor 38 connected to the motor 38. The motor 38 is electrically connected to a battery 40 and operates upon receiving power from the battery 40. The compressor impeller 37 is an impeller rotationally driven by the motor 38, and is capable of compressing the EGR gas flowing through the EGR passage 30 and sending it out to the downstream side (towards the intake passage 10).

(2) Control System FIG. 2 is a block diagram showing the control system of the engine of this embodiment. The ECU 50 shown in this figure is a microprocessor for controlling the engine in an integrated manner, and is composed of a well-known CPU, ROM, RAM, and the like. Note that the ECU 50 corresponds to a "controller" in the present invention.

Detection information from various sensors is input to the ECU 50. For example, the ECU 50 is electrically connected to the above-mentioned crank angle sensor SN1, air flow sensor SN2, catalyst temperature sensor SN3, and battery sensor SN4. , intake air flow rate, catalyst inlet temperature, battery voltage/current, etc.) are successively input to the ECU 50.

Furthermore, the vehicle is provided with an accelerator sensor SN5 that detects the opening degree of the accelerator pedal operated by the driver driving the vehicle (accelerator opening degree), and the detection signal from the accelerator sensor SN5 is also sequentially input to the ECU 50. be done.

The ECU 50 controls each part of the engine while executing various determinations, calculations, etc. based on input signals from the sensors SN1 to SN5. That is, the ECU 50 is electrically connected to the direct injection injector 3, the spark plug 4, the throttle valve 15, the generator 28 of the power generation turbine 25, the EGR valve 31, the reforming injector 32, the motor 38 of the air compressor 35, etc. Based on the results of the above calculations, control signals are output to each of these devices.

(3) Reforming control Next, the details of the control for injecting fuel from the reforming injector 32 and reforming the fuel in the fuel reforming catalyst 33 (hereinafter referred to as reforming control) are shown in FIGS. This will be explained with reference to the flowchart in FIG.

When the control shown in FIG. 3 starts, the ECU 50 determines the total amount of fuel, which is the total amount of fuel to be supplied to each cylinder 2 (step S1). Specifically, the ECU 50 adjusts the total fuel amount so that the air-fuel ratio (A/F) of the air-fuel mixture in each cylinder 2 matches the stoichiometric air-fuel ratio (14.7) or a target air-fuel ratio set close to the stoichiometric air-fuel ratio (14.7). decide. This total fuel amount can be determined based on the detected value of the air flow sensor SN2. That is, the ECU 50 calculates the intake air amount, which is the amount of fresh air introduced into each cylinder 2, from the detected value of the air flow sensor SN2, and also calculates the calculated intake air amount at the target air-fuel ratio (≒14.7). The divided value is determined as the total fuel amount.

Next, the ECU 50 determines whether the catalyst inlet temperature (temperature at the inlet of the fuel reforming catalyst 33) detected by the catalyst temperature sensor SN3 is greater than a predetermined threshold Tx (step S2). The threshold value Tx is set to a value slightly higher than the activation temperature of the fuel reforming catalyst 33 (for example, about 500° C.).

If the determination in step S2 is YES and it is confirmed that the catalyst inlet temperature exceeds the threshold Tx, the ECU 50 performs reforming control such that at least a portion of the total fuel amount supplied to each cylinder 2 is used for reforming. The reforming injector 32 and the direct injection injector 3 are controlled so that they are supplied with the fuel supplied from the injector 32 (in other words, the fuel reformed by the fuel reforming catalyst 33) (step S3). Details of this reforming control will be described later.

On the other hand, if the determination in step S2 is NO and it is confirmed that the catalyst inlet temperature is equal to or lower than the threshold value Tx, the ECU 50 performs non-reforming control so that all of the total fuel amount supplied to each cylinder 2 is directly injected. The reforming injector 32 and the direct injection injector 3 are controlled so that they are supplied with the fuel injected from the injector 3 (step S4). That is, the ECU 50 injects the same amount of fuel as the total amount of fuel supplied to each cylinder 2 from the direct injection injector 3 of each cylinder 2, and stops fuel injection by the reforming injector 32.

4 and 5 are subroutines showing details of the reforming control in step S3. When the control shown in FIG. 4 starts, the ECU 50 opens the EGR valve 31 to the fully open position (step S10). In other words, in the reforming control, the EGR valve 31 is basically not used as a means for adjusting the EGR rate, that is, the ratio of EGR gas to intake air (fresh air and EGR gas) introduced into each cylinder 2. The EGR rate is controlled based on a pressure difference (pressure difference between the intake passage 10 and the exhaust passage 20) caused by the operation of the air supply compressor 35 and the power generation turbine 25, which will be described later. Note that there is a possibility that the desired pressure difference cannot be generated only by operating the air supply compressor 35 and the power generation turbine 25, but in such a case, control to reduce the opening degree of the EGR valve 31 is executed as an exception. shall be taken as a thing.

Next, the ECU 50 obtains a target EGR rate R1 that is a target value of the EGR rate (the ratio of EGR gas to intake air) (step S11). The target EGR rate R1 is predetermined, for example, in a map format so as to take a different value depending on the operating conditions (load and rotation speed) of the engine. The ECU 50 determines a target EGR rate R1 that matches the current operating conditions based on the engine load specified from the detected value of the accelerator sensor SN5 and the engine rotation speed specified from the detected value of the crank angle sensor SN1. do.

FIG. 6 is a graph schematically showing the relationship between engine load and target EGR rate R1. As shown in this graph, the target EGR rate R1 is set to increase as the engine load increases. Such a tendency of the target EGR rate R1 is determined with the aim of efficient fuel reforming at the fuel reforming catalyst 33. That is, as a finding from the research of the present inventor, the fuel reforming rate, which is the proportion of fuel reformed by the fuel reforming catalyst 33 out of the total amount of injection injected from the reforming injector 32, varies depending on the EGR rate. It is also known that the EGR rate at which the maximum fuel reformation rate can be obtained increases as the engine load increases. Therefore, in this embodiment, the target EGR rate R1 is set to a larger value on the higher load side so that the highest possible fuel reformation rate can be obtained under each operating condition. Note that the target EGR rate R1 may vary depending on the engine speed, but a description of this tendency will be omitted here.

Next, the ECU 50 calculates the actual EGR rate, which is the actual value of the EGR rate (step S12). The actual EGR rate can be calculated in various ways, but as an example, the ECU 50 estimates the amount of intake air (fresh air and EGR gas) introduced into each cylinder 2 from the current engine operating conditions, and calculates the estimated amount. The actual EGR rate is calculated based on the intake air amount and the flow rate of fresh air detected by the air flow sensor SN2.

Next, the ECU 50 calculates the flow rate of EGR gas flowing through the EGR passage 30 (EGR gas flow rate) based on the actual EGR rate calculated in step S12 (step S13). The EGR gas flow rate is calculated as a larger value as the actual EGR rate is higher.

Next, the ECU 50 determines the reforming fuel injection amount, which is the amount of fuel to be injected from the reforming injector 32 (step S14). Note that the reforming fuel injection amount herein refers to the injection amount per injection of fuel that is intermittently injected from the reforming injector 32 for repeated combustion in each cylinder 2 of the engine body 1. It is. That is, the reforming injector 32 injects fuel at an appropriate timing linked to the intake stroke of each cylinder 2 so that the fuel injected from the injector 32 reaches each cylinder 2 during the intake stroke of each cylinder 2. Spray repeatedly. The reforming fuel injection amount in step S14 is the amount of fuel intermittently injected from the reforming injector 32 per injection.

In step S14, the reforming fuel injection amount is determined based on the catalyst inlet temperature (temperature at the inlet of the fuel reforming catalyst 33) detected by the catalyst temperature sensor SN3 and the EGR gas flow rate calculated in step S13. Determined based on the map used as a parameter. FIG. 7 is a graph schematically showing the trend of this map, with graph (a) showing the relationship between catalyst inlet temperature and reforming fuel injection amount, and graph (b) showing the relationship between EGR gas flow rate and reforming fuel injection amount. The relationship with the injection amount is shown respectively. As shown in the graph (a) of FIG. 7, the reforming fuel injection amount is set to increase as the catalyst inlet temperature increases with respect to the above-mentioned threshold value Tx. Further, as shown in the graph (b) of FIG. 7, the reforming fuel injection amount is set to increase as the EGR gas flow rate increases. In the graph (a) that defines the relationship between the catalyst inlet temperature and the injection amount, it is assumed that the EGR gas flow rate is constant at a value greater than 0, and in the graph (b) that defines the relationship between the EGR gas flow rate and the injection amount. ), the catalyst inlet temperature is assumed to be constant at a value higher than the threshold value Tx.

The reason why the reforming fuel injection amount is determined according to the above tendency is to prevent the catalyst outlet temperature (temperature at the outlet of the fuel reforming catalyst 33) from falling below the activation temperature. That is, since the reaction of reforming the fuel by the fuel reforming catalyst 33 is an endothermic reaction, the catalyst outlet temperature is lower than the catalyst inlet temperature. Therefore, if an unnecessarily large amount of fuel is introduced into the fuel reforming catalyst 33, the catalyst outlet temperature may fall below the activation temperature (for example, about 500° C.), and the fuel reforming rate at the catalyst 33 may decrease. Conversely, the higher the catalyst inlet temperature is compared to the activation temperature, the greater the amount of fuel that can be introduced into the fuel reforming catalyst 33 under the condition that the catalyst outlet temperature does not fall below the activation temperature. Further, since EGR gas has a high temperature, the larger the EGR gas flow rate, the more the fuel reforming catalyst 33 is kept warm, and the temperature drop thereof is suppressed. Therefore, as the EGR gas flow rate increases, the amount of fuel that can be introduced into the fuel reforming catalyst 33 increases under the condition that the catalyst outlet temperature does not fall below the activation temperature. The trends in the reforming fuel injection amount shown in graphs (a) and (b) of FIG. 7 are determined from this viewpoint. That is, in this embodiment, in order to introduce as much fuel as possible into the fuel reforming catalyst 33 and reform it within a range where the catalyst outlet temperature does not fall below the activation temperature, the reforming fuel injection amount is adjusted to the catalyst inlet temperature and the EGR gas. It is set variably (proportional to each parameter) depending on the flow rate.

When the reforming fuel injection amount is determined as described above, the ECU 50 determines the direct injection fuel amount, which is the amount of fuel to be injected from each direct injection injector 3 into each cylinder 2 of the engine main body 1 ( Step S15). Specifically, the direct injection fuel amount is the total fuel amount determined in step S1 according to the engine operating conditions (load and rotational speed), that is, the amount of direct injection fuel in each cylinder 2 in order to generate torque that matches the current operating conditions. It is calculated based on the amount of fuel to be injected (required fuel amount) and the reforming fuel injection amount determined in step S14 above. For example, when the direct injection fuel amount is F1, the reforming fuel injection amount is F2, and the total fuel amount of each cylinder 2 is F0, the direct injection fuel amount F1 is calculated from the total fuel amount F0 to the reforming fuel injection amount F2. It can be calculated as the value obtained by subtracting (F0 - F2).

Here, since the reforming fuel injection amount varies depending on the catalyst inlet temperature and the EGR gas flow rate as described above, the direct injection fuel amount also varies depending on the catalyst inlet temperature and the EGR gas flow rate. In other words, the ratio (fuel ratio) between the direct injection fuel amount and the reforming fuel injection amount changes depending on the catalyst inlet temperature and the EGR gas flow rate. FIG. 8 is a graph showing the relationship between fuel ratio and catalyst inlet temperature. In this graph, the "direct injector share" is the ratio of the fuel injected from the direct injector 3 to the total fuel amount, and the "reforming injector share" is the ratio of the fuel injected from the direct injection injector 3 to the total fuel amount. On the other hand, it refers to the proportion of fuel injected from the reforming injector 32. As shown in FIG. 8, when the catalyst inlet temperature is equal to or lower than the threshold value Tx, the total fuel amount (100%) is covered by the injected fuel (direct injection fuel amount) from the direct injection injector 3. On the other hand, when the catalyst inlet temperature exceeds the threshold value Tx, the ratio of the injected fuel from the reforming injector 32 (reforming fuel injection amount) increases as the amount exceeding the threshold value Tx increases, and up to 100% reach %. In this way, the ratio of the direct injection fuel amount to the reforming fuel injection amount is adjusted such that the higher the catalyst inlet temperature, the larger the ratio of the reforming fuel injection amount. Although not shown, the ratio also changes depending on the EGR gas flow rate, and is adjusted so that the higher the EGR gas flow rate, the larger the ratio of the reforming fuel injection amount. Note that, as a premise of steps S14 and S15, the catalyst inlet temperature exceeds the threshold Tx, so the ratio of the reforming fuel injection amount (reforming injector sharing ratio) is at least greater than 0%. value and can increase up to 100%.

Next, the ECU 50 causes the reforming injector 32 and the direct injection injector 3 to inject fuel according to each injection amount determined in steps S14 and S15 above (step S16). That is, the ECU 50 controls the reforming injector 32 so that the reforming injector 32 injects an amount of fuel corresponding to the reforming fuel injection amount determined in step S14, and also controls the reforming injector 32 to inject fuel corresponding to the reforming fuel injection amount determined in step S15. The direct injection injector 3 is controlled so that an amount of fuel corresponding to the direct injection fuel amount is injected from the direct injection injector 3.

Next, the ECU 50 moves to step S21 in FIG. 5, and changes the actual EGR rate R2 from the target EGR rate R1 based on the target EGR rate R1 and the actual EGR rate R2 calculated in steps S11 and S12 (FIG. 4). It is determined whether or not the insufficient EGR rate (R1-R2), which is the value obtained by subtracting , is larger than a predetermined threshold value X1. The threshold value X1 is a value greater than 0 (for example, a value corresponding to 5 to 10% of the target EGR rate R1), and the fact that the insufficient EGR rate is greater than this threshold value X1 means that the actual EGR rate R2 is higher than the target EGR rate R1. This is a relatively large drop, which means that there is a substantial EGR shortage. On the other hand, the insufficient EGR rate being less than or equal to the threshold value X1 means that the EGR rate matches the target or is within a value slightly lower than this, that is, there is no substantial EGR shortage.

If the determination in step S21 is NO and it is confirmed that there is no EGR shortage, the ECU 50 determines in advance that the excess EGR rate (R2-R1) is the value obtained by subtracting the target EGR rate R1 from the actual EGR rate R2. It is determined whether or not it is larger than a predetermined threshold value X2 (step S22). The threshold value X2 is a value greater than 0, and the fact that the excess EGR rate is greater than this threshold value X2 means that the actual EGR rate R2 exceeds the target EGR rate R1 by a relatively large amount, that is, a substantial EGR excess has occurred. means that On the other hand, the fact that the excess EGR rate is less than or equal to the threshold value X2 means that the EGR rate matches the target or is within a slightly higher value, that is, that no substantial excess EGR occurs. Note that the threshold value X2 used in this step S22 can be set to the same value as the threshold value X1 used in the above step S21 or a value close thereto.

If the determination in step S22 is NO and it is confirmed that excess EGR has not occurred, the ECU 50 changes the rotation speed of the air compressor 35 and the amount of power generation of the power generation turbine 25 to the current engine operating conditions (load and rotation speed). Execute normal control to set the basic value according to the number). This normal control includes the following steps S23 and S24.

First, in step S23, the ECU 50 controls the air compressor 35 so that the rotational speed of the air compressor 35 (compressor impeller 37) becomes a basic rotational speed determined according to the current operating conditions of the engine. That is, the rotation speed of the air compressor 35 for feeding EGR gas in an amount corresponding to the target EGR rate into the intake passage 10 is determined by numerical simulation, experiment, etc. for each engine operating condition (combination of load and rotation speed). It can be known in advance. In step S23, a predetermined map or model formula based on this known data is used to determine the transmission rate to achieve the target EGR rate (the target EGR rate R1 determined in step S11 above) under the current operating conditions. The rotational speed of the air compressor 35 is determined as a basic rotational speed, and the motor 38 of the air supply compressor 35 is controlled so that the compressor impeller 37 rotates at a rotational speed that matches the basic rotational speed.

In subsequent step S24, the ECU 50 controls the power generation turbine 25 so that the power generation amount of the power generation turbine 25 becomes the basic power generation amount determined according to the current operating conditions of the engine. The basic power generation amount is set to a value that slightly exceeds the power consumption consumed by the air sending compressor 35 when the air sending compressor 35 is rotating at the above-mentioned basic rotation speed. This is to reliably prevent the charge amount of the battery 40 from decreasing due to the drive of the air supply compressor 35. In step S24, the basic power generation amount based on such a request is determined using a map or a model formula, and the generator 28 of the power generation turbine 25 is controlled so that electric power matching this basic power generation amount is generated.

Next, a description will be given of control when the determination in step S22 is NO, that is, when excessive EGR occurs where the excessive EGR rate (R2-R1) exceeds the threshold value X2. In this case, the ECU 50 executes EGR suppression control that reduces both the rotational speed of the air supply compressor 35 and the amount of power generated by the power generation turbine 25. This EGR suppression control includes the following steps S25 and S26.

First, in step S25, the ECU 50 controls the air compressor 35 so that the rotational speed of the air compressor 35 (compressor impeller 37) becomes the basic rotational speed, as in step S23 described above. However, as described above, since the basic rotational speed is the rotational speed necessary to achieve the target EGR rate R1 under the current operating conditions, step S25 of matching the rotational speed of the air supply compressor 35 to the basic rotational speed By this control, the rotational speed of the air supply compressor 35 is reduced. That is, as a premise of step S25, since excess EGR has occurred in which the actual EGR rate R2 significantly exceeds the target EGR rate R1 (R2-R1>X2), the control in step S25 is executed in this state. As a result, the air supply compressor 35 is controlled in accordance with the basic rotation speed corresponding to the relatively low target EGR rate R1, and as a result, the rotation speed becomes lower than that immediately before excessive EGR occurs.

In subsequent step S26, the ECU 50 performs feedback control on the amount of power generated by the power generating turbine 25 so that the amount of power generated by the power generating turbine 25 becomes a value corresponding to the excess EGR rate (R2-R1). Specifically, the ECU 50 adjusts the power generation amount of the power generation turbine 25 by so-called PID control so that the larger the excess EGR rate is with respect to the threshold value X2, the more the power generation amount of the power generation turbine 25 decreases. As is well known, PID control is a type of feedback control that controls the input value based on the comparison between the output value and its target value, and is based on three elements: the deviation between the output value and the target value, its integral, and its derivative. This is a control that determines the input value based on the input value. Due to this PID control, in step S26, the amount of power generation decreases significantly immediately after excess EGR (R2-R1>X2) is confirmed, and thereafter the amount of decrease in the amount of power generation gradually decreases (the actual EGR rate R2 is set to the target The generator 28 of the power generation turbine 25 is controlled so as to reduce the EGR rate (as the EGR rate approaches R1).

As described above, when the EGR suppression control (S25, S26) is executed, the rotational speed of the air supply compressor 35 and the amount of power generation of the power generation turbine 25 are respectively reduced compared to before execution of the same control. This results in a decrease in the suction force of the exhaust gas into the EGR passage 30 by the air supply compressor 35 and a decrease in the flow resistance of the exhaust gas in the exhaust passage 20 by the power generation turbine 25, thereby reducing the EGR rate. .

Next, a description will be given of control when the determination is YES in step S21, that is, when an EGR shortage occurs where the insufficient EGR rate (R1-R2) exceeds the threshold value X1. In this case, the ECU 50 determines whether the current charge amount of the battery 40 is larger than a predetermined lower limit charge amount Y (step S27). The amount of charge of the battery 40 can be specified from the detected value of the battery sensor SN4. The lower limit charge amount is a value determined in consideration of ensuring the operation of electrical equipment including the air compressor 35 and deterioration of the battery 40, and is set to a value larger than 0% to some extent.

If the determination in step S27 is YES and it is confirmed that the charge amount of the battery 40 is larger than the lower limit charge amount Y, the ECU 50 increases both the rotation speed of the air compressor 35 and the power generation amount of the power generation turbine 25. Execute first EGR promotion control. This first EGR suppression control includes the following steps S28 and S29.

First, in step S28, the ECU 50 feedback-controls the rotation speed of the air supply compressor 35 so that the rotation speed of the air supply compressor 35 becomes a value corresponding to the insufficient EGR rate (R1-R2). Specifically, the ECU 50 adjusts the rotation speed of the air supply compressor 35 by PID control so that the rotation speed of the air supply compressor 35 increases as the insufficient EGR rate is larger than the threshold value X1. Due to this PID control, in step S28, the rotation speed increases significantly immediately after EGR shortage (R1-R2>X1) is confirmed, and thereafter, the increase in the rotation speed increases gradually (the actual EGR rate The motor 38 of the air supply compressor 35 is controlled to reduce the EGR rate (as the EGR rate approaches R1).

In the following step S29, the ECU 50 controls the power generation turbine 25 so that the amount of power generated by the power generation turbine 25 becomes the basic amount of power generation, as in step S24 described above. However, as mentioned above, the basic power generation amount is the power consumption when the air supply compressor 35 is rotating at the rotation speed (basic rotation speed) required to achieve the target EGR rate R1 under the current operating conditions. Since it is set to a value close to (slightly higher than) the basic power generation amount, the power generation amount of the power generation turbine 25 is increased by the control in step S29 that makes the power generation amount of the power generation turbine 25 match the basic power generation amount. That is, as a premise of step S29, an EGR shortage has occurred in which the target EGR rate R1 significantly exceeds the actual EGR rate R2 (R1-R2>X1), and the basic rotation speed of the air supply compressor 35 is equal to the current rotation speed. Since the value is set to a higher value than The generator 28 is controlled, and its power generation amount increases compared to immediately before the EGR shortage occurs.

As described above, when the first EGR promotion control (S28, S29) is executed, the rotational speed of the air supply compressor 35 and the amount of power generation of the power generating turbine 25 are respectively increased compared to before execution of the same control. This results in an increase in the suction force of the exhaust gas into the EGR passage 30 by the air supply compressor 35 and an increase in the flow resistance of the exhaust gas in the exhaust passage 20 by the power generation turbine 25, thereby increasing the EGR rate. .

Next, a description will be given of control when the determination in step S27 is NO, that is, when the amount of charge of the battery 40 is equal to or less than the lower limit amount of charge Y. In this case, the ECU 50 executes second EGR promotion control that increases both the rotational speed of the air supply compressor 35 and the amount of power generated by the power generation turbine 25. The second EGR promotion control is similar to the first EGR promotion control (S28, S29) described above in controlling the air supply compressor 35, but differs in controlling the power generation turbine 25. That is, the second EGR promotion control includes the following steps S30 and S31.

First, in step S30, the ECU 50 uses the same feedback control (PID control) as in step S28 described above to control the rotation speed of the air compressor 35 to a value corresponding to the insufficient EGR rate (R1-R2). The air supply compressor 35 is controlled so that the rotation speed of the air supply compressor 35 increases as the insufficient EGR rate increases.

In subsequent step S31, the ECU 50 controls the power generation turbine 25 so that the amount of power generated by the power generation turbine 25 matches the actual power consumption by the air compressor 35. Since the power consumption in the air compressor 35 is increased by the rotation speed feedback control (PID control) in step S30, the power generation amount of the power generation turbine 25 is increased by the control in step S31. .

FIG. 9 is a time chart showing an example of changes over time in various state quantities when the reforming control shown in FIGS. 4 and 5 is executed. Chart (a) shows changes in the EGR rate, chart (b) ) shows the change in the rotational speed of the air supply compressor 35, chart (c) shows the change in the amount of power generated by the power generation turbine 25, and chart (d) shows the change in the amount of charge of the battery 40.

As shown in chart (a) of FIG. 9, it is assumed that the target EGR rate R1 changes in the order of V1, V2, and V3 in response to changes in engine operating conditions. That is, it is assumed that the target EGR rate R1 is set to V1 at time t1, increases from V1 to V2 at subsequent time t2, and further decreases from V2 to V3 at subsequent time t5. In chart (a), the dashed lines above and below the dashed-dotted line corresponding to the target EGR rate R1 indicate the allowable range of deviation from the target EGR rate R1. When the actual EGR rate R2 (thick solid line waveform) is included, it means that normal control (steps S23 and S24 in FIG. 5) is executed. In other words, the upper limit of the above tolerance range (upper dashed line) corresponds to threshold X2, which is the limit of the excess EGR rate (R2-R1), and the lower limit of the above tolerance range (lower dashed line) corresponds to the threshold value X1 which is the limit of the insufficient EGR rate (R1-R2).

During the period from time t1 to t2, the actual EGR rate R2 is included in the allowable range of the target EGR rate R1 (=V1). Therefore, normal control is executed during the same period (t1 to t2). That is, the rotational speed of the air supply compressor 35 and the power generation amount of the power generation turbine 25 are set to the basic rotational speed N1 and the basic power generation amount G1 corresponding to the target EGR rate R1 (=V1) (charts (b) and (c)). )reference). The basic power generation amount G1 is set to a value that slightly exceeds the power consumed by the air supply compressor 35 that rotates at the basic rotation speed N1. Therefore, by this normal control, the charge amount of the battery 40 gradually increases in a range larger than the lower limit charge amount Y between time points t1 and t2 (see chart (d)).

When the target EGR rate R1 increases from V1 to V2 at time t2, an EGR shortage occurs in which the insufficient EGR rate (R1-R2) exceeds the threshold value X1. As a result, the control shifts to the first EGR promotion control after time t2. That is, the rotational speed of the air supply compressor 35 is set to the rotational speed N2a, which is a feedback control value according to the insufficient EGR rate (R1-R2) (see chart (b)), and the power generation amount of the power generation turbine 25 is The basic power generation amount G2 is set corresponding to the target EGR rate R1 (=V2) (see chart (c)). As shown in chart (b), if the basic rotational speed corresponding to the increased target EGR rate R1 (=V2) is N2, the rotational speed N2a of the air supply compressor 35 under feedback control is lower than the basic rotational speed N2. Set to a large value. However, since the insufficient EGR rate (R1-R2) decreases over time after time t2 (see chart (a)), the amount of increase in rotational speed N2a with respect to basic rotational speed N2 also gradually decreases accordingly (chart (see (b)). Further, as the air supply compressor 35 is driven at the rotation speed N2a higher than the basic rotation speed N2 as described above, the air supply compressor 35 consumes electric power that exceeds the basic power generation amount G2. As a result, the amount of charge of the battery 40 gradually decreases after time t2 (see chart (d)).

At time t3, which is delayed from time t2, the charge amount of the battery 40 decreases to the lower limit charge amount Y. As a result, control shifts to second EGR promotion control after time t3. That is, the rotational speed of the air supply compressor 35 is set to the rotational speed N2b, which is a feedback control value according to the insufficient EGR rate (R1-R2) (see chart (b)), and the power generation amount of the power generation turbine 25 is set to The power generation amount G2b is set to correspond to the actual power consumption in the air compressor 35 (see chart (c)). The rotational speed N2b of the air supply compressor 35 is made larger than the basic rotational speed N2 by feedback control, and is gradually decreased over time. In addition, in accordance with this, the power generation amount G2b of the power generation turbine 25 is also made larger than the basic power generation amount G2, and gradually decreases over time. The charge amount of the battery 40 is maintained at the lower limit charge amount Y (see chart (d)).

At time t4, which is delayed from time t3, the actual EGR rate R2 increases to a value included in the allowable range of the target EGR rate R1 (=V2). As a result, the control shifts to normal control at time t4. That is, the rotation speed of the air supply compressor 35 and the power generation amount of the power generation turbine 25 are set to the basic rotation speed N2 and the basic power generation amount G2, respectively, which correspond to the increased target EGR rate R1 (=V2) (see chart (b) )(c)). The basic power generation amount G2 slightly exceeds the power consumed by the air supply compressor 35 that rotates at the basic rotation speed N2. Therefore, by this normal control, the charge amount of the battery 40 gradually increases from the lower limit charge amount Y after time t4 (see chart (d)).

At time t5, which is later than time t4, the target EGR rate R1 decreases from V2 to V3, thereby causing excess EGR in which the excess EGR rate (R2-R1) exceeds the threshold value X2. As a result, control shifts to EGR suppression control after time t5. That is, the power generation amount of the power generation turbine 25 is set to the power generation amount G3a, which is a feedback control value according to the excess EGR rate (R2-R1) (see chart (c)), and the rotation speed of the air supply compressor 35 is decreased. The basic rotation speed N3 is set according to the subsequent target EGR rate R1 (=V3) (see chart (b)). If the basic power generation amount determined according to the reduced target EGR rate R1 (=V3) is G3, the power generation amount G3a of the power generation turbine 25 under feedback control is set to a value smaller than the basic power generation amount G3. Furthermore, since the excess EGR rate (R2-R1) decreases over time after time t5, the amount of decrease in the power generation amount G3a relative to the basic power generation amount G3 gradually decreases accordingly.

At time t6, which is delayed from time t5, the actual EGR rate R2 decreases to a value included in the allowable range of the target EGR rate R1 (=V3). As a result, the control shifts to normal control at time t6. That is, the rotation speed of the air compressor 35 and the power generation amount of the power generation turbine 25 are set to the basic rotation speed N3 and the basic power generation amount G3, respectively, which correspond to the target EGR rate R1 (=V3) after the decrease (see chart (b) )(c)).

(4) Effects, etc. As explained above, in this embodiment, the EGR passage 30 is provided with the fuel reforming catalyst 33 and the air supply compressor 35, and the fuel injected from the reforming injector 32 into the EGR passage 30 is Since it can be introduced into the reforming catalyst 33, the suction force of exhaust gas into the EGR passage 30 can be adjusted by controlling the rotation of the air supply compressor 35, and the EGR gas introduced into the fuel reforming catalyst 33 together with fuel can be adjusted. The flow rate can be adjusted to an appropriate value depending on the operating conditions. Further, since the power generation turbine 25 is provided in the exhaust passage 20, at least a portion of the power consumed by the air supply compressor 35 can be covered by the power generated using the energy of the exhaust gas. This, together with the fuel reforming effect (improvement of combustibility) due to the endothermic reaction in the fuel reforming catalyst 33, increases the efficiency of exhaust heat recovery that returns exhaust heat from the engine to output. can sufficiently improve fuel efficiency.

In addition, during the execution of the control (reforming control) for introducing fuel into the fuel reforming catalyst 33 as described above, it is possible to detect that the flow rate of EGR gas is insufficient, that is, the actual EGR rate R2 is subtracted from the target EGR rate R1. If it is confirmed that an EGR shortage is occurring where the insufficient EGR rate (R1-R2) exceeds a predetermined threshold value Since the EGR promotion control (the first EGR promotion control in steps S28 and S29 or the second EGR promotion control in steps S30 and S31) is executed, the EGR shortage can be quickly resolved and an appropriate amount of EGR gas for fuel reforming can be achieved. can be ensured. That is, an increase in the number of revolutions of the air supply compressor 35 increases the suction force of exhaust gas into the EGR passage 30, and an increase in the amount of power generated by the power generation turbine 25 (as a result of an increase in the rotational resistance of the turbine impeller 27), the exhaust passage Since the flow resistance of the exhaust gas in the exhaust gas passage 20 increases, these two effects promote the branching of the exhaust gas from the exhaust passage 20 to the EGR passage 30, thereby quickly resolving the EGR shortage. In this way, in this embodiment, even if EGR is insufficient, it can be quickly resolved, and therefore the flow rate of EGR gas introduced into the fuel reforming catalyst 33 can be adjusted with precision, and a good It is possible to obtain excellent fuel reforming performance.

Further, in the above embodiment, during execution of the reforming control, the flow rate of EGR gas is excessive, that is, the excess EGR rate (R2-R2) obtained by subtracting the target EGR rate R1 from the actual EGR rate R2 is When it is confirmed that excess EGR exceeding a predetermined threshold value X2 has occurred, EGR suppression control (steps S25, S26) is performed to reduce the rotation speed of the air supply compressor 35 and reduce the amount of power generated by the power generation turbine 25. Since this is executed, excess EGR can be promptly resolved and an appropriate amount of EGR gas for fuel reformation can be secured. That is, the reduction in the rotational speed of the air supply compressor 35 reduces the suction force of exhaust gas into the EGR passage 30, and the reduction in the amount of power generated by the power generation turbine 25 (thereby reducing the rotational resistance of the turbine impeller 27) causes the exhaust passage to Since the flow resistance of the exhaust gas in the exhaust gas passage 20 is reduced, these two effects suppress the branching of the exhaust gas from the exhaust passage 20 to the EGR passage 30, thereby quickly eliminating excess EGR. In this way, in this embodiment, even if there is excessive EGR, it can be quickly resolved, so the flow rate of EGR gas introduced into the fuel reforming catalyst 33 can be adjusted with precision, and the It is possible to obtain excellent fuel reforming performance.

In particular, in the above embodiment, during EGR promotion control (first or second EGR promotion control), the rotation speed of the air supply compressor 35 increases more as the insufficient EGR rate (R1-R2) is larger than the threshold value X1. Since the rotational speed is feedback-controlled, the EGR shortage can be quickly resolved by appropriately adjusting the rotational speed according to changes in the insufficient EGR rate.

Similarly, during EGR suppression control, the power generation amount of the power generation turbine 25 is feedback-controlled so that the larger the excess EGR rate (R2-R1) is with respect to the threshold value X2, the greater the power generation amount of the power generation turbine 25 is. Excessive EGR can be quickly resolved by appropriately adjusting the amount of power generation in response to changes in the rate. Furthermore, in a situation where excessive EGR occurs, a large amount of exhaust gas should have flowed before that, and it is highly likely that the power generation turbine 25 was generating sufficient power. On the other hand, in the embodiment described above, the amount of power generation is quickly reduced by feedback control according to the degree of excess EGR rate, so that excess EGR can be quickly resolved while avoiding unnecessary power generation.

In the above embodiment, as a method of calculating the actual EGR rate, the amount of intake air (fresh air and EGR gas) introduced into each cylinder 2 is estimated from the current engine operating conditions, and then the estimated intake air amount is calculated. The method of calculating the actual EGR rate based on the detected value of the fresh air flow rate by the air flow sensor SN2 has been exemplified. It is also possible to calculate the actual EGR rate based on this.

1: Engine body 10: Intake passage 20: Exhaust passage 25: Power generation turbine 30: EGR passage 32: Reforming injector 33: Fuel reforming catalyst 35: Air supply compressor 50: ECU (controller)
X1: Threshold (of insufficient EGR rate) X2: Threshold (of excess EGR rate)

Claims (6)

A fuel reforming system applied to an engine comprising an engine body, an intake passage through which intake air introduced into the engine body flows, and an exhaust passage through which exhaust gas discharged from the engine body flows,
an EGR passage connecting the intake passage and the exhaust passage;
a reforming injector capable of injecting fuel into the EGR passage;
a fuel reforming catalyst that is provided downstream of the reforming injector in the EGR passage and is capable of reforming the fuel injected from the reforming injector;
a power generation turbine installed in the exhaust passage and capable of generating electricity using the energy of exhaust gas flowing through the exhaust passage;
an air supply compressor that is provided in the EGR passage and can be driven by the electric power generated by the power generation turbine;
A controller that controls the reforming injector, the power generation turbine, and the air supply compressor,
During execution of reforming control for injecting fuel into the reforming injector, the controller detects EGR insufficiency in which the flow rate of EGR gas, which is exhaust gas that is recirculated from the exhaust passage to the intake passage through the EGR passage, is insufficient. 1. A fuel reforming system for an engine, characterized in that when occurrence of the above is confirmed, EGR promotion control is executed to increase the rotational speed of the air supply compressor and increase the amount of power generated by the power generation turbine. The engine fuel reforming system according to claim 1,
The target value of the EGR rate, which is the ratio of the EGR gas to the intake air introduced into the engine body, is the target EGR rate, the actual value of the EGR rate is the actual EGR rate, and the value obtained by subtracting the actual EGR rate from the target EGR rate is the insufficient EGR. The controller sequentially calculates the insufficient EGR rate during execution of the reforming control, and when it is confirmed that the calculated insufficient EGR rate is larger than a predetermined threshold value, the controller calculates the EGR A fuel reforming system for an engine, characterized in that the system performs acceleration control. The engine fuel reforming system according to claim 2,
The controller is characterized in that the controller performs feedback control of the rotational speed of the air supply compressor based on the insufficient EGR rate so that the rotational speed of the air supply compressor increases as the insufficient EGR rate is larger than the threshold value. Fuel reforming system for engines. In the engine fuel reforming system according to any one of claims 1 to 3,
The controller is configured to reduce the rotational speed of the air supply compressor and reduce the power generation amount of the power generation turbine, if occurrence of EGR excess in which the flow rate of the EGR gas is excessive is confirmed during execution of the reforming control. 1. A fuel reforming system for an engine, characterized in that the system executes EGR suppression control that reduces EGR. The engine fuel reforming system according to claim 4,
The target value of the EGR rate, which is the ratio of the EGR gas to the intake air introduced into the engine body, is the target EGR rate, the actual value of the EGR rate is the actual EGR rate, and the value obtained by subtracting the target EGR rate from the actual EGR rate is the excessive EGR. The controller sequentially calculates the excess EGR rate during execution of the reforming control, and when it is confirmed that the calculated excess EGR rate is larger than a predetermined threshold value, the controller calculates the excess EGR rate. A fuel reforming system for an engine, characterized in that it performs suppression control. The engine fuel reforming system according to claim 5,
The controller is characterized in that the controller performs feedback control on the power generation amount of the power generation turbine based on the excess EGR rate so that the power generation amount of the power generation turbine decreases more as the excess EGR rate is larger than the threshold value. Engine fuel reforming system.

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