JP6303884B2 - Engine and control method thereof - Google Patents

Description

  The present invention relates to a technique for improving the combustion state of an engine during EGR by adding hydrogen to exhaust gas to be recirculated.

  In order to reduce NOx discharged from the engine, it is effective to perform exhaust gas recirculation (EGR) in which a part of the exhaust gas is recirculated to the intake side and supplied to the engine together with fresh air. When EGR is performed, the maximum temperature during combustion is lowered, so that generation of NOx during combustion can be suppressed. Further, the pumping loss of the engine is reduced, and the fuel efficiency of the engine can be improved.

  However, on the other hand, there is a problem that if the EGR rate is high, combustion slows down and the generation rate of unburned components increases.

  In order to suppress such slowing of combustion, as disclosed in Patent Document 1, it is effective to reform the fuel to produce hydrogen and supply it to the engine together with the exhaust gas that recirculates it. Since hydrogen has high combustibility, if it is added to the exhaust gas to be recirculated, the combustion speed can be increased and the slowing of combustion can be suppressed.

JP 2004-293971 A

  When hydrogen is added to the exhaust gas to be refluxed, it is necessary to adjust the amount of hydrogen to be added according to the EGR rate. This is because if an amount of hydrogen commensurate with the EGR rate is not supplied, engine misfire, knock, and vibration may be caused.

  However, when the reforming catalyst is arranged in the EGR passage for recirculating exhaust gas and hydrogen is generated by supplying fuel to the reforming catalyst, the exhaust gas that has been recirculated until fuel is supplied to the reforming catalyst is used. The reforming catalyst is at a high temperature, and the hydrogen generation efficiency of the reforming catalyst is high. For this reason, immediately after the fuel supply to the reforming catalyst is started, hydrogen is excessively generated, and there is a possibility that the amount of hydrogen added temporarily becomes excessive.

  The present invention has been made in view of such technical problems, and in an engine in which hydrogen is added to exhaust gas to be recirculated during EGR, the amount of hydrogen supplied to the engine is leveled, and engine misfire, knock, The purpose is to prevent vibration.

  An engine according to an aspect of the present invention includes an EGR passage that recirculates a part of exhaust gas to an intake passage, and an exhaust gas that is disposed in the EGR passage and reforms the fuel to generate hydrogen, and the generated hydrogen is recirculated. And a fuel supply device for supplying fuel to the reforming catalyst according to the EGR rate.

When the fuel is supplied from the fuel supply device, the engine passes the first supply amount, which is the fuel supply amount per unit time from the start of fuel supply until the predetermined reduction period elapses. The second supply amount that is the fuel supply amount per unit time after the time point is reduced. Here, in the engine, the fuel reduction value is equal to the target hydrogen concentration determined by the EGR rate, with the maximum value of the hydrogen concentration obtained by supplying the first supply amount of fuel to the reforming catalyst. Set as follows.

According to the above aspect, since the amount of fuel supplied from the fuel supply device to the reforming catalyst at the beginning of fuel supply decreases, the temperature of the reforming catalyst at the beginning of fuel supply is high and hydrogen generation efficiency is high. Even if it exists, generation | occurrence | production of excess hydrogen is suppressed. Since the amount of hydrogen supplied to the engine is leveled, it is possible to prevent engine misfire, knocking, and vibration due to excessive hydrogen being supplied to the engine. Furthermore, by setting the weight loss value, it is possible to suppress the hydrogen concentration from exceeding the target hydrogen concentration corresponding to the EGR rate, and to further suppress the generation of excessive hydrogen.

1 is a schematic configuration diagram of an engine according to an embodiment of the present invention. It is the flowchart which showed the content of the main routine of hydrogenation control. It is the flowchart which showed the content of the subroutine (weight reduction process) of hydrogenation control. It is the flowchart which showed the content of the subroutine (learning process) of hydrogenation control. It is the time chart which showed the catalyst temperature change and hydrogen concentration change when a weight reduction process is not performed (comparative example). It is the time chart which showed the catalyst temperature change and hydrogen concentration change when a weight reduction process is performed (this embodiment). It is a time chart which showed the catalyst temperature change and hydrogen concentration change when a weight reduction process is performed (part modification of this embodiment).

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a schematic configuration of an engine 1 according to an embodiment of the present invention.

  The engine 1 is a so-called port injection type internal combustion engine, and a fuel injection valve 3 for injecting gasoline supplied from a fuel tank 2 into an intake port is provided at an intake port of each cylinder.

  The exhaust from the engine 1 passes through the exhaust passage 4 and is purified by the three-way catalyst 5 and then released to the atmosphere. An EGR passage 6 is branched from the position of the exhaust passage 4 between the engine 1 and the three-way catalyst 5, and a part of the exhaust gas is recirculated to the intake passage 7 through the EGR passage 6 during execution of EGR. .

  In the EGR passage 6, a fuel supply device 8, a reforming catalyst 9, an EGR cooler 10, and an EGR valve 11 are arranged in this order from the exhaust passage 4 side.

  The fuel supply device 8 is a device that supplies fuel for generating hydrogen to the reforming catalyst 9. The fuel supply device 8 is an injection valve in this example, but may be a fuel atomization device using a venturi or a gasoline vaporization device that heats and vaporizes the fuel. Arbitrary liquid hydrocarbons can be used as the fuel for generating hydrogen. In this example, gasoline that is the fuel of the engine 1 is used as the fuel for generating hydrogen.

The reforming catalyst 9 converts the hydrocarbon added in the exhaust gas into the following endothermic reaction:
HC + H ₂ O → CO ₂ + H ₂
It is a catalyst that is reformed to obtain hydrogen. A catalyst temperature sensor 21 for detecting the catalyst temperature T is attached to the reforming catalyst 9. A hydrogen concentration sensor 22 for detecting the hydrogen concentration in the recirculated exhaust gas is attached to the outlet side of the reforming catalyst 9.

  The EGR cooler 10 is a heat exchanger that cools the exhaust gas flowing through the EGR passage 6 with the cooling water of the engine 1.

  The EGR valve 11 is a valve whose opening degree can be adjusted by an actuator, and by changing the opening degree of the EGR valve 11, execution / stop of EGR and an EGR rate during execution of EGR can be adjusted.

  The controller 30 includes a CPU, a storage device such as a ROM and a RAM, an input / output interface, and a bus for connecting them. The controller 30 receives signals from the catalyst temperature sensor 21, the hydrogen concentration sensor 22, the accelerator opening sensor 23, the crank angle sensor 24, the air flow meter 25, and the like, performs predetermined arithmetic processing based on the received signals, and performs fuel calculation. The injection amount, ignition timing, intake air amount, EGR rate, etc. are controlled.

  In addition, the controller 30 performs hydrogen addition control for adding hydrogen to the exhaust gas that is recirculated in order to suppress the slowing of combustion in the engine 1 when executing EGR, particularly when executing EGR at a high EGR rate. In the hydrogen addition control, the controller 30 determines a target value (target hydrogen concentration Ct) of the hydrogen concentration C in the exhaust gas recirculated based on the EGR rate, and can achieve the target hydrogen concentration Ct in the equilibrium state per unit time. The fuel supply amount is set as the basic supply amount Qt. Then, the controller 30 supplies the basic supply amount Qt of fuel from the fuel supply device 8 to the reforming catalyst 9, and adds the hydrogen generated by the reforming catalyst 9 to the exhaust gas to be recirculated.

  Further, when the catalyst temperature T at the start of the hydrogen addition control is high due to the exhaust gas recirculated so far, the hydrogen generation efficiency by the reforming catalyst 9 is high, and the basic supply amount Qt of fuel is supplied to hydrogen. If supplied from the beginning of the addition control, hydrogen will be generated excessively. For this reason, the controller 30 performs a reduction process for reducing the amount of fuel to be supplied from the basic supply quantity Qt by a predetermined reduction value dQ until the predetermined reduction period TL has elapsed from the start of the hydrogen addition control, and the exhaust gas that is recirculated. Level the hydrogen concentration inside.

  2 to 4 are flowcharts showing the contents of the hydrogenation control executed by the controller 30. FIG. The specific contents of the hydrogenation control will be described with reference to these.

  FIG. 2 shows the contents of the main routine of hydrogenation control.

  According to this, in step S11, the controller 30 determines whether or not hydrogen addition is necessary based on whether or not the EGR rate exceeds a predetermined value. The predetermined value is a predetermined high EGR rate at which deterioration of the combustion state starts to become obvious due to slowing of combustion by EGR.

  If the EGR rate does not exceed the predetermined value, the combustion is sufficiently stable without adding hydrogen to the recirculated exhaust gas. Therefore, the controller 30 determines that hydrogen addition is unnecessary, and the fuel supply device 8 The process ends without supplying fuel. On the other hand, when the EGR rate exceeds the predetermined value, the controller 30 determines that hydrogen addition is necessary, and advances the process to step S12 and subsequent steps to perform hydrogen addition for suppressing combustion slowdown due to EGR.

  In step S12, the controller 30 determines whether or not the catalyst temperature T detected by the catalyst temperature sensor 21 exceeds a predetermined high temperature TRi. The predetermined high temperature TRi is a temperature at which an overshoot in which the hydrogen concentration C in the recirculated exhaust gas rises beyond the target hydrogen concentration Ct starts to occur when the basic supply amount Qt is supplied from the start of the hydrogen addition control. Is set.

  If it is determined that the catalyst temperature T exceeds the predetermined high temperature TRi, the controller 30 advances the process to step S13.

  In step S13, the controller 30 executes a reduction process (FIG. 3) described later, and the fuel supply amount per unit time is determined from the basic supply amount Qt until a predetermined reduction period TL elapses from the start of hydrogenation control. Fuel is supplied to the reforming catalyst 9 as an amount reduced by a predetermined reduction value dQ (first supply amount), and the fuel supply amount per unit time is changed to the basic supply amount Qt (second supply) after a predetermined reduction period TL has elapsed. (Return to amount).

  On the other hand, if it is determined in step S12 that the catalyst temperature T does not exceed the predetermined high temperature TRi, even if the basic supply amount Qt of fuel is supplied to the reforming catalyst 9 from the start of the hydrogen addition control, Since the overshoot of the concentration C does not occur, the controller 30 executes normal control for supplying fuel with the fuel supply amount per unit time as the basic supply amount Qt from the start of the hydrogen addition control.

  FIG. 3 shows the content of the weight reduction process executed in step S13 of FIG.

  According to this, in step S21, the controller 30 sets a basic supply amount Qt, a decrease value dQ (a decrease amount from the basic supply amount Qt), and a decrease period TL.

  The basic supply amount Qt is calculated based on a value obtained by obtaining the target hydrogen concentration Ct by referring to the map based on the EGR rate and multiplying this by the rotational speed of the engine 1. The target hydrogen concentration Ct and the basic supply amount Qt tend to be 0 when the EGR rate is lower than the predetermined high EGR rate, and when the EGR rate is higher than the predetermined high EGR rate, the higher the EGR rate, the larger the tendency is. .

  The larger the load of the engine 1, the stronger the flow in the cylinder and the better the combustion, and the smaller the amount of hydrogen necessary to suppress the slowing down of the combustion of the engine 1, so the larger the load of the engine 1, the more the basic supply amount Qt becomes. The target hydrogen concentration Ct or the basic supply amount Qt may be corrected according to the load of the engine 1 so as to decrease.

  The decrease value dQ is set so that the maximum hydrogen concentration Cmax, which is the maximum value of the hydrogen concentration C, becomes the target hydrogen concentration Ct when the amount of fuel obtained by subtracting the decrease value dQ from the basic supply amount Qt is supplied from the fuel supply device 8. Is set. Specifically, the reduction value dQ is learned to a value obtained by referring to the map based on the catalyst temperature T (or the temperature of generated hydrogen), the EGR rate (or the amount of exhaust gas recirculated), and the basic supply amount Qt. A value obtained by multiplying the correction coefficient iq is set. The learning correction coefficient iq is a coefficient for correcting manufacturing variation, deterioration with time, and the like.

  The reduction value dQ is set to a larger value as the catalyst temperature T at the start of hydrogenation control is higher. This is because the higher the catalyst temperature T, the higher the hydrogen generation efficiency. In order to suppress the overshoot of the hydrogen concentration C, it is necessary to reduce the amount of fuel supplied to the reforming catalyst 9 as the catalyst temperature T increases. Because there is.

  In order to set the reduction period TL, first, based on the basic supply amount Qt, the EGR rate (or the amount of exhaust gas that is recirculated), and the temperature of the exhaust gas that is recirculated, fuel of the basic supply amount Qt is supplied to the reforming catalyst 9. Thus, the equilibrium temperature Tbal of the reforming catalyst 9 realized is obtained. Then, based on the difference between the equilibrium temperature Tbal and the current catalyst temperature T and the heat capacities of the reforming catalyst 9 and the case, an endothermic amount required to lower the current catalyst temperature T to the equilibrium temperature Tbal is obtained. Then, the reduction period TL obtains the time until the total amount of heat absorption by supplying the amount of fuel obtained by subtracting the reduction value dQ from the basic supply amount Qt to the reforming catalyst 9 reaches the required heat absorption amount. It is set to a value multiplied by the learning correction coefficient it. The learning correction coefficient it is a coefficient for correcting manufacturing variation, deterioration with time, and the like. As the equilibrium temperature Tbal is lower, the necessary endothermic amount is larger, so the reduction period TL is set longer as the equilibrium temperature Tbal is lower.

  In step S22, the controller 30 starts a timer t. The timer t is a timer for measuring an elapsed time from the time when fuel supply to the reforming catalyst 9 is started.

  In step S23, the controller 30 starts monitoring the hydrogen concentration C and the catalyst temperature T, and stores the hydrogen concentration C and the catalyst temperature T in the storage device in time series order.

  In step S24, the controller 30 determines whether the timer t is smaller than the weight reduction period TL. If the timer t is smaller than the reduction period TL, that is, if the reduction period TL has not yet elapsed since the start of fuel supply to the reforming catalyst 9, the controller 30 advances the process to step S25, and the basic supply amount. An amount of fuel (first supply amount) obtained by subtracting the reduction value dQ from Qt is supplied from the fuel supply device 8.

  On the other hand, if the timer t is longer than the reduction period TL in step S24, that is, if the reduction period TL has elapsed since the start of fuel supply to the reforming catalyst 9, the controller 30 performs the process in step S26. The amount of fuel supplied from the fuel supply device 8 is returned to the basic supply amount Qt (second supply amount). The supply of the basic supply amount Qt is continued until it is determined in step S11 of the main routine shown in FIG.

  In step S27, the controller 30 reaches the reached temperature Tf, which is the catalyst temperature T realized by supplying the reforming catalyst 9 with an amount of fuel obtained by subtracting the reduction value dQ from the basic supply amount Qt, and the catalyst temperature T has reached. The maximum hydrogen concentration Cmax, which is the maximum value of the hydrogen concentration C in the period until reaching the temperature Tf, is searched from the time series data of the catalyst temperature T and the hydrogen concentration C stored in the storage device.

  The ultimate temperature Tf is the catalyst temperature T immediately before the influence of returning the amount of fuel supplied to the reforming catalyst 9 to the basic supply amount Qt appears in the catalyst temperature T. The reached temperature Tf is a catalyst stored in the storage device based on the delay time until the fuel supplied from the fuel supply device 8 reaches the reforming catalyst 9 and the delay time resulting from the reaction rate of the reforming reaction. It is obtained by searching the value of the corresponding time from the time series data of the temperature T. If there is no manufacturing variation or deterioration of the reforming catalyst 9 over time, the ultimate temperature Tf becomes equal to the equilibrium temperature Tbal of the reforming catalyst 9 when the basic supply amount Qt of fuel is supplied to the reforming catalyst 9.

  In step S28, the controller 30 corrects the decrease value dQ and the decrease period TL by a learning process described later based on the reached temperature Tf searched in step S27 and the maximum hydrogen concentration Cmax.

  FIG. 4 shows the contents of the learning process executed in step S28 of FIG.

  According to this, in step S31, the controller 30 compares the deviation between the maximum hydrogen concentration Cmax and the target hydrogen concentration Ct with predetermined values d1 and d2. If the deviation exceeds the predetermined value d1 or d2, the controller 30 executes the correction process in step S32.

  Specifically, when the value obtained by subtracting the target hydrogen concentration Ct from the maximum hydrogen concentration Cmax is larger than the predetermined value d1, the reduction value dQ is not sufficient and an overshoot of the hydrogen concentration C occurs, so the controller 30 Increases and corrects the learning correction coefficient iq so that the decrease value dQ after the next time becomes larger than that before correction under the same conditions. Further, the controller 30 increases and corrects the learning correction coefficient iq so that the decrease period TL becomes longer by the amount that the decrease value dQ is increased, so that the total amount of fuel supplied to the reforming catalyst 9 does not change.

  When the value obtained by subtracting the maximum hydrogen concentration Cmax from the target hydrogen concentration Ct is larger than the predetermined value d2, the decrease value dQ is excessive and the hydrogen concentration C is too low. Under the same conditions, the learning correction coefficient iq is corrected so as to be smaller than before correction. Further, the learning correction coefficient it is corrected to decrease so that the decrease period TL is shortened as much as the decrease value dQ is reduced, so that the total amount of fuel supplied to the reforming catalyst 9 does not change.

  As a result, the maximum hydrogen concentration Cmax is brought close to the target hydrogen concentration Ct so that excess or deficiency of hydrogen does not occur.

  In step S33, the controller 30 compares the deviation between the reached temperature Tf and the equilibrium temperature Tbal with the predetermined values d3 and d4. If the deviation exceeds the predetermined value d3 or d4, the correction process in step S34 is performed. Execute.

  Specifically, when the value obtained by subtracting the equilibrium temperature Tbal from the ultimate temperature Tf is larger than the predetermined value d3, the endotherm due to the reforming reaction in the weight reduction period TL is not sufficient, and the catalyst temperature T has decreased to the equilibrium temperature Tbal. Therefore, the controller 30 increases and corrects the learning correction coefficient it so that the subsequent weight loss period TL is longer than that before correction under the same conditions.

  When the value obtained by subtracting the reached temperature Tf from the equilibrium temperature Tbal is larger than the predetermined value d4, the endotherm due to the reforming reaction in the weight reduction period TL is excessive, and the reached temperature Tf is lower than the equilibrium temperature Tbal. The increase correction of the learning correction coefficient it is performed so that the subsequent reduction period TL is shorter than that before the correction under the same conditions.

  As a result, the ultimate temperature Tf can be brought close to the equilibrium temperature Tbal, the change in the hydrogen concentration when the influence of the return of the fuel supply amount to the basic supply amount Qt starts to be suppressed, and the excess or deficiency of hydrogen does not occur. To.

  FIG. 5 is a time chart showing a change in catalyst temperature and a change in hydrogen concentration when the hydrogenation control is performed at the time of a high EGR rate but the weight reduction process is not performed (comparative example).

  In this example, the fuel supply is started from the fuel supply device 8 at the basic supply amount Qt at time t11, the generation of hydrogen in the reforming catalyst 9 is started, and the hydrogen concentration C in the recirculated exhaust gas rises with a delay. . The reason why the hydrogen concentration C increases after the time t11 is delayed until the fuel supplied from the fuel supply device 8 reaches the reforming catalyst 9, and there is a delay due to the reaction rate of the reforming reaction. Because there is. Further, since the reforming reaction is an endothermic reaction, the catalyst temperature T decreases.

  At time t11, the catalyst temperature T is high due to the heat of the exhaust gas that has flown through the reforming catalyst 9, and the hydrogen generation efficiency is high. For this reason, when the basic supply amount Qt is supplied from the start of fuel supply as in this example, an overshoot occurs in which the hydrogen concentration C rises above the equilibrium hydrogen concentration Cbal.

  On the other hand, FIG. 6 is a time chart showing changes in catalyst temperature and hydrogen concentration when hydrogen addition control is performed at a high EGR rate and the above-described weight reduction process is performed.

  Fuel supply from the fuel supply device 8 is started at time t21, but from the start of fuel supply until time t22 when the reduction period TL elapses, an amount of fuel reduced from the basic supply quantity Qt by the reduction value dQ is supplied. Is done.

  By reducing the amount of fuel supplied in the reduction period TL by the reduction value dQ, the maximum hydrogen concentration Cmax is substantially equal to the target hydrogen concentration Ct, and thereafter the hydrogen concentration C substantially maintains the target hydrogen concentration Ct.

  Therefore, according to the weight reduction process, excess hydrogen is not supplied to the engine 1, and misfire, knocking, and vibration can be prevented from being caused by the excess hydrogen.

  Continuously, the effect of this embodiment is demonstrated.

  The engine 1 according to the present embodiment is disposed in an EGR passage 6 that recirculates part of exhaust gas to an intake passage, and the EGR passage 6, reforms the fuel to generate hydrogen, and recirculates the generated hydrogen. A reforming catalyst 9 to be added to the exhaust gas and a fuel supply device 8 for supplying fuel to the reforming catalyst 9 are provided. When the controller 30 supplies fuel from the fuel supply device 8 to the reforming catalyst 9, the fuel supply amount from the fuel supply start time until the decrease period TL elapses is less than the basic supply amount tQ. In this way, the amount of fuel supplied from the fuel supply device 8 to the reforming catalyst 9 is controlled.

  When the basic supply amount tQ is supplied from the start of fuel supply, the catalyst temperature T is increased by the heat of the exhaust gas that has flown through the reforming catalyst 9 until then, and the generation efficiency of hydrogen is increased. Hydrogen temporarily becomes excessive. However, in this embodiment, since the fuel supply amount from the start of fuel supply until the reduction period TL has elapsed is set to be smaller than the basic supply amount tQ, it is possible to suppress excessive generation of hydrogen, Can be prevented from being misfired, knocked, or vibrated by being supplied to the engine 1 excessively.

  In the present embodiment, the maximum hydrogen concentration Cmax obtained by supplying the amount of fuel that is smaller than the basic supply amount tQ by the amount of decrease dQ in the decrease amount dQ in the decrease processing is determined according to the EGR rate. It was set to be equal to the hydrogen concentration Ct. If the reduction value dQ is set in this way, the hydrogen concentration C does not increase beyond the target hydrogen concentration Ct during the hydrogenation control, and excessive hydrogen generation can be further suppressed.

  In this embodiment, the reduction value dQ is set to be larger as the catalyst temperature T at the start of fuel supply is higher. Since the generation efficiency of hydrogen is higher as the catalyst temperature T is higher, the generation of excess hydrogen can be further suppressed by setting the weight loss value dQ according to the catalyst temperature T in this way.

  In the present embodiment, the reduction period TL is set longer as the equilibrium temperature Tbal of the reforming catalyst 9 when the basic supply amount Qt is supplied is lower. This corresponds to the fact that the lower the equilibrium temperature Tbal, the greater the difference between the catalyst temperature T at the start of fuel supply and the equilibrium temperature Tbal, and the greater the amount of heat that needs to be absorbed from the reforming catalyst 9 during the reduction period TL. Is.

  As a result, the reached temperature Tf, which is the temperature of the reforming catalyst 9 reached by supplying the amount of fuel obtained by subtracting the reduction value dQ from the basic supply amount Qt (by returning the fuel supply amount to the basic supply amount Qt). The temperature immediately before the influence is brought close to the equilibrium temperature Tbal, the change in the hydrogen concentration when the influence of the return of the fuel supply amount to the basic supply amount Qt starts to be suppressed, and the excess or deficiency of hydrogen does not occur. be able to.

  In the present embodiment, the reduction value dQ for the next and subsequent times is based on the deviation between the maximum hydrogen concentration Cmax and the equilibrium hydrogen concentration Cbal obtained by supplying the amount of fuel obtained by subtracting the reduction value dQ from the basic supply amount Qt. Was corrected. As a result, even if the amount of hydrogen generated deviates from the design value due to manufacturing variations or deterioration with time, the reduction value dQ can be corrected and the amount of generated hydrogen can be eliminated.

  In the correction of the weight loss value dQ, when the weight loss value dQ after the next time is corrected to decrease, the weight loss period TL after the next time is corrected to decrease, and when the weight loss value dQ after the next time is corrected to increase, the weight loss period after the next time. TL was increased and corrected. Thereby, it can suppress that the total amount of produced | generated hydrogen changes, and it can prevent that excess and deficiency arises in the amount of hydrogen supplied to the engine 1. FIG.

  Further, in the present embodiment, the next time based on the deviation between the reached temperature Tf that is the temperature reached by the reforming catalyst 9 by supplying the amount of fuel obtained by subtracting the reduction value dQ from the basic supply amount Qt and the equilibrium temperature Tbal. The subsequent weight loss period TL was corrected. This makes it possible to suppress the hydrogen concentration change when the effect of returning the fuel supply amount to the basic supply amount Qt is brought close to the ultimate temperature Tf close to the equilibrium temperature Tbal, and to prevent excessive or insufficient hydrogen. Can do.

  Further, in the present embodiment, when the catalyst temperature T is lower than the predetermined high temperature TRi, the above reduction process is not performed. When the temperature of the reforming catalyst 9 is lower than the predetermined high temperature TRi, the amount of hydrogen produced is not excessive in the first place. Therefore, in such a situation, the fuel supply amount should not be reduced. Thus, it is possible to prevent a shortage of the hydrogen amount due to unnecessary reduction of the fuel supply amount.

  The embodiment of the present invention has been described above, but the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. is not.

  For example, in the above embodiment, the decrease value dQ from the start of fuel supply to the reforming catalyst 9 until the decrease period TL elapses maintains the initially set value, but until the decrease period TL elapses. The method of setting the decrease value dQ during the period is not limited to this. For example, as shown in FIG. 7, after the start of the supply of fuel to the reforming catalyst 9, the decrease value dQ is decreased stepwise as time elapses. You may do it. Or although illustration is abbreviate | omitted, you may make it reduce the weight reduction value dQ continuously as time passes. If the reduction value dQ is changed in this way, the change in the hydrogen concentration C at the beginning of fuel supply can be moderated, and the overshoot of the hydrogen concentration C can be easily suppressed.

  In the above embodiment, the hydrogen concentration downstream of the reforming catalyst 9 is detected by the hydrogen concentration sensor 22 and used for the reduction process. However, the amount of fuel supplied from the fuel supply device 8, the EGR rate (or The amount of hydrogen produced may be estimated from the amount of exhaust gas recirculated) and the like, and the hydrogen concentration estimated based on this may be used for the reduction process.

1 Engine 6 EGR passage 8 Fuel supply device 9 Reforming catalyst 30 Controller (weight reduction processing means)

Claims (9)

An EGR passage that recirculates part of the exhaust to the intake passage;
A reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust;
A fuel supply device for supplying fuel to the reforming catalyst according to an EGR rate;
When fuel is supplied from the fuel supply device, a first supply amount that is a fuel supply amount per unit time from the start of fuel supply until a predetermined reduction period elapses is determined from the start of fuel supply. A weight reduction processing means for performing a weight reduction process for reducing the fuel supply amount per unit time after the predetermined weight loss period has elapsed, which is less than the second supply amount;
Equipped with a,
The reduction processing means performs the reduction processing so that the maximum value of the hydrogen concentration obtained by supplying the first supply amount of fuel to the reforming catalyst becomes equal to the target hydrogen concentration determined according to the EGR rate. Set the fuel loss value,
An engine characterized by that. An EGR passage that recirculates part of the exhaust to the intake passage;
A reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust;
A fuel supply device for supplying fuel to the reforming catalyst according to an EGR rate;
When fuel is supplied from the fuel supply device, a first supply amount that is a fuel supply amount per unit time from the start of fuel supply until a predetermined reduction period elapses is determined from the start of fuel supply. A weight reduction processing means for performing a weight reduction process for reducing the fuel supply amount per unit time after the predetermined weight loss period has elapsed, which is less than the second supply amount;
With
The weight reduction processing means sets the fuel reduction value by the weight reduction processing to be larger as the temperature of the reforming catalyst at the start of the fuel supply is higher.
An engine characterized by that. An EGR passage that recirculates part of the exhaust to the intake passage;
A reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust;
A fuel supply device for supplying fuel to the reforming catalyst according to an EGR rate;
When fuel is supplied from the fuel supply device, a first supply amount that is a fuel supply amount per unit time from the start of fuel supply until a predetermined reduction period elapses is determined from the start of fuel supply. A weight reduction processing means for performing a weight reduction process for reducing the fuel supply amount per unit time after the predetermined weight loss period has elapsed, which is less than the second supply amount;
With
The reduction processing means sets the predetermined reduction period longer as the equilibrium temperature of the reforming catalyst when the second supply amount of fuel is supplied is lower.
An engine characterized by that. An EGR passage that recirculates part of the exhaust to the intake passage;
A reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust;
A fuel supply device for supplying fuel to the reforming catalyst according to an EGR rate;
When fuel is supplied from the fuel supply device, a first supply amount that is a fuel supply amount per unit time from the start of fuel supply until a predetermined reduction period elapses is determined from the start of fuel supply. A weight reduction processing means for performing a weight reduction process for reducing the fuel supply amount per unit time after the predetermined weight loss period has elapsed, which is less than the second supply amount;
With
The weight reduction processing means is based on the deviation between the maximum value of the hydrogen concentration obtained by supplying the first supply amount and the target hydrogen concentration determined according to the EGR rate, and the fuel in the fuel reduction by the subsequent weight reduction processing. Correct the weight loss value,
An engine characterized by that. The engine according to claim 4 ,
The reduction processing means corrects the fuel reduction value by the reduction processing after the next time to decrease, corrects the predetermined reduction period after the next time, and increases the fuel reduction value by the reduction processing from the next time. If so, increase the predetermined weight loss period after the next time,
An engine characterized by that. An EGR passage that recirculates part of the exhaust to the intake passage;
A reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust;
A fuel supply device for supplying fuel to the reforming catalyst according to an EGR rate;
When fuel is supplied from the fuel supply device, a first supply amount that is a fuel supply amount per unit time from the start of fuel supply until a predetermined reduction period elapses is determined from the start of fuel supply. A weight reduction processing means for performing a weight reduction process for reducing the fuel supply amount per unit time after the predetermined weight loss period has elapsed, which is less than the second supply amount;
With
The reduction processing means supplies a deviation between a temperature reached by the reforming catalyst by supplying the first supply amount of fuel and an equilibrium temperature of the reforming catalyst when the second supply amount of fuel is supplied. To correct the predetermined weight loss period after the next time,
An engine characterized by that. An EGR passage that recirculates part of the exhaust to the intake passage;
A reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust;
A fuel supply device for supplying fuel to the reforming catalyst according to an EGR rate;
When fuel is supplied from the fuel supply device, a first supply amount that is a fuel supply amount per unit time from the start of fuel supply until a predetermined reduction period elapses is determined from the start of fuel supply. A weight reduction processing means for performing a weight reduction process for reducing the fuel supply amount per unit time after the predetermined weight loss period has elapsed, which is less than the second supply amount;
With
The weight reduction processing means does not perform the weight reduction processing when the temperature of the reforming catalyst is lower than a predetermined high temperature.
An engine characterized by that. The engine according to any one of claims 1 to 7 ,
The weight reduction processing means decreases the fuel reduction value by the weight reduction processing as the elapsed time from the fuel supply start time becomes longer.
An engine characterized by that. An EGR passage that recirculates part of the exhaust to the intake passage; a reforming catalyst that is disposed in the EGR passage, reforms the fuel to generate hydrogen, and adds the generated hydrogen to the recirculated exhaust; and EGR An engine control method comprising a fuel supply device that supplies fuel to the reforming catalyst according to a rate,
When supplying the fuel from the fuel supply device, the first supply amount from the start a fuel supply amount per unit time to a predetermined reduction period elapses fuel supply, wherein from the start of the fuel supply There rows reduction process to less than the second feed amount is a fuel supply amount per unit of time after the point of a predetermined reduction period has elapsed,
In the reduction process, the fuel by the reduction process is such that the maximum value of the hydrogen concentration obtained by supplying the first supply amount of fuel to the reforming catalyst becomes equal to the target hydrogen concentration determined according to the EGR rate. Set weight loss value for
An engine control method characterized by the above.

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