JP2018017154A - Vehicular control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device capable of executing the control of a fuel supply amount in a transient state, in which the changeover from a stoichiometric operation to a lean operation or vice versa is performed, highly precisely by using a relatively few maps.SOLUTION: A request torque TRQCMD is set in accordance with an accelerator pedal operation amount AP indicating the request of the driver of a vehicle. A target air/fuel ratio AFCMD is calculated on the basis of a cylinder suction air quantity GAIRCYL. A fuel injection amount GFUEL is controlled by using the target air/fuel ratio AFCMD. A gas/fuel ratio GFR indicating the proportion of the gas quantity and the fuel in a combustion chamber is calculated by using a cylinder suction air quantity GAIRCYL indicating a fresh air amount in the combustion chamber, a recirculation exhaust amount GEGR, and a fuel injection amount GFUEL. In the air-fuel ratio switching control, in which the air/fuel ratio AF is switched between a predetermined lean air/fuel ratio AFLN and a stoichiometric air/fuel ratio AFST, the calculation of the fuel injection amount GFUEL is performed by using the gas/fuel ratio GFR.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a control apparatus for a vehicle including an internal combustion engine as a prime mover, and more particularly to an apparatus for controlling an internal combustion engine that performs a lean operation in which an air-fuel ratio of an air-fuel mixture is set to be leaner than a theoretical air-fuel ratio.

  Patent Document 1 shows a control device for an internal combustion engine capable of lean operation. According to this control device, when the engine combustion system is switched from weak stratified combustion to homogeneous lean combustion during rich spike control, The opening degree of the throttle valve and the exhaust gas recirculation valve is changed to the closed side suitable for the homogeneous lean operation, and the fuel injection amount is corrected to increase. Thereby, the output torque fluctuation | variation accompanying switching of a combustion system is prevented.

  Patent Document 2 discloses a control method for suppressing fluctuations in output torque when switching from stoichiometric operation in which the air-fuel ratio of the air-fuel mixture is set to the stoichiometric air-fuel ratio to lean operation. According to this control method, the intake air amount increase control is started, the ignition timing is retarded from the start timing of the actual intake air amount while maintaining the air-fuel ratio at the theoretical air-fuel ratio, and then the air-fuel ratio is set to the lean air-fuel ratio. Control is performed to shift to the fuel ratio and advance the ignition timing.

JP 2000-2142 A Japanese Patent No. 3064782

  The increase correction of the fuel injection amount in the control device disclosed in Patent Document 1 simply increases the fuel injection amount by a preset constant amount. When there is a change in engine characteristics over time or characteristic variation, Appropriate correction cannot be performed and output torque fluctuations are not sufficiently suppressed.

  Further, in the control method disclosed in Patent Document 2, the retard start timing, the advance start timing, and the time to advance the ignition timing are searched for a map corresponding to the throttle valve opening and the engine speed. Therefore, there is a problem that it takes a lot of man-hours to set the map.

  The present invention has been made paying attention to the above points, and accurately controls the fuel supply amount in a transient state in which switching from stoichiometric operation to lean operation or vice versa is performed using a relatively small map. It is an object of the present invention to provide a control device that can do the above.

  In order to achieve the above object, an invention according to claim 1 is a vehicle control apparatus that can be driven by an internal combustion engine (1), wherein the engine theoretically calculates an air-fuel ratio (AF) of an air-fuel mixture combusted in the engine. In a control apparatus for a vehicle configured to be able to execute a lean operation that is set to a lean air-fuel ratio (AFLN) that is leaner than an air-fuel ratio (AFT), a required torque of the engine (based on a request from the driver of the vehicle) Required torque setting means for setting TRQCMD), target air-fuel ratio calculation means for calculating the target air-fuel ratio (AFCMD) of the air-fuel mixture based on the intake air amount (GAIRCYL) of the engine, and air-fuel ratio ( A fuel amount control means for controlling a fuel amount (GFUEL) supplied to the combustion chamber so that AF) matches the target air-fuel ratio (AFCMD), and a gas amount in the combustion chamber, A dilution degree parameter calculating means for calculating a dilution degree parameter (GFR) indicating a ratio to the charge, the dilution degree parameter calculating means comprising a fresh air amount (GAIRCYL), a recirculation exhaust amount (GEGR) in the combustion chamber, And the dilution degree parameter (GFR) is calculated using a parameter indicating the fuel amount (GFUEL), and the fuel amount control means converts the air-fuel ratio (AF) of the mixture into the lean air-fuel ratio (AFLN) and the theoretical air-fuel ratio. In a transient state in which the fuel ratio (AFST) is switched, the fuel amount (GFUEL) is calculated using the dilution degree parameter (GFR).

  According to this configuration, the required torque of the engine is set based on the request of the vehicle driver, the target air-fuel ratio of the air-fuel mixture is calculated based on the intake air amount of the engine, and the air-fuel ratio of the air-fuel mixture is set to the target The amount of fuel supplied to the combustion chamber is controlled so as to coincide with the air-fuel ratio. Further, a dilution degree parameter indicating the ratio between the gas amount in the combustion chamber and the fuel is calculated based on the parameters indicating the fresh air amount, the recirculated exhaust amount, and the fuel amount in the combustion chamber, and the air-fuel ratio of the air-fuel mixture is determined as the lean air-fuel ratio. In a transient state where the engine is switched between the stoichiometric air-fuel ratio and the stoichiometric air-fuel ratio, the amount of fuel supplied to the combustion chamber is calculated using the dilution degree parameter. The engine output torque is basically proportional to the amount of fuel, but the thermal efficiency changes depending on the engine speed, air-fuel ratio, and recirculation exhaust volume. In order to make the output torque exactly the required torque, It is necessary to improve the calculation accuracy of thermal efficiency. According to the study of the inventor of the present invention, it has been confirmed that the relationship between the dilution degree parameter and the torque conversion coefficient corresponding to the thermal efficiency can be approximated by a single curve under a condition where the engine speed is constant. By calculating the fuel amount using the dilution degree parameter, the fuel amount that matches the engine output torque to the required torque without using a plurality of maps according to the air-fuel ratio, the recirculated exhaust amount, and the engine rotational speed can be obtained. Calculation can be performed with high accuracy. As a result, it is possible to accurately execute fuel supply control in a transient state while greatly reducing the number of map setting steps in the design stage.

  According to a second aspect of the present invention, in the vehicle control device according to the first aspect, the ignition timing control means for controlling the ignition timing (IGCMD) of the engine and the target air-fuel ratio calculation means in the transient state are calculated. Correction means for correcting the target air-fuel ratio (AFCMD) to a value close to the theoretical air-fuel ratio (AFST) when the target air-fuel ratio (AFCMD) to be performed is smaller than the switching air-fuel ratio (AFLMT), and the ignition timing control The means retards the ignition timing (IGCMD) from the optimal ignition timing (IGMAP) so that the output torque (TRQA) of the engine matches the required torque (TRQCMD) when the correction by the correction means is performed. When the target air-fuel ratio (AFCMD) is equal to or higher than the switching air-fuel ratio (AFLMT), the ignition timing (IGCMD) is set to the optimum ignition. The optimal ignition timing (IGMAP) is an ignition timing that maximizes the output torque (TRQA) of the engine, and the switching air-fuel ratio (AFLMT) is set in the steady state of the lean operation. It is characterized by being set to a value smaller than the set steady lean operation air-fuel ratio (AFLN) and larger than the theoretical air-fuel ratio (AFST).

  According to this configuration, when the target air-fuel ratio calculated in the transient state is smaller than the switching air-fuel ratio, the target air-fuel ratio is corrected to a value close to the theoretical air-fuel ratio so that the engine output torque matches the required torque. Control is performed to retard the ignition timing from the optimal ignition timing. On the other hand, when the target air-fuel ratio is equal to or higher than the switching air-fuel ratio, the calculated target air-fuel ratio is not corrected, and control for setting the ignition timing to the optimal ignition timing is performed. The switching air-fuel ratio is set to a value smaller than the steady lean operation air-fuel ratio set in the steady state of lean operation and larger than the stoichiometric air-fuel ratio. That is, when the target air-fuel ratio calculated based on the intake air amount is smaller than the switching air-fuel ratio, the target air-fuel ratio is corrected to a value close to the theoretical air-fuel ratio, and the engine output torque is reduced by retarding the ignition timing. While the control to match the required torque is performed, when the target air-fuel ratio is equal to or higher than the switching air-fuel ratio, the target air-fuel ratio corresponding to the intake air amount is applied as it is, and the ignition timing is controlled to the optimal ignition timing. . Therefore, the target air-fuel ratio can be prevented from being set in the air-fuel ratio range in which the NOx concentration in the exhaust increases, the increase in the NOx concentration can be suppressed, and torque fluctuations can be prevented by retarding the ignition timing. Can do.

  According to a third aspect of the present invention, in the vehicle control device according to the second aspect of the present invention, the switching air-fuel ratio (AFLMT) is an allowable limit of a NOx concentration (CNOx) contained in exhaust discharged from the combustion chamber. It is characterized by being set to a minimum value which is equal to or less than (CNOxLMT).

  According to this configuration, the switching air-fuel ratio is set to the minimum value at which the NOx concentration contained in the exhaust gas discharged from the combustion chamber is below the allowable limit, so that the target air-fuel ratio increases the NOx concentration in the exhaust gas. Setting to a value in the range is avoided, and the NOx concentration in the exhaust can be suppressed to an allowable limit or less.

  According to a fourth aspect of the present invention, in the vehicle control device according to the second or third aspect, the ignition timing control means is configured to change the output torque (TRQA) of the engine when the correction by the correction means is performed. When the ignition timing (IGCMD) matched with the required torque (TRQCMD) is retarded from the retard limit value (IGRTDLMT), the ignition timing (IGCMD) is set to the optimum ignition timing (IGMAP), The correcting means does not correct the target air-fuel ratio (AFCMD).

  According to this configuration, when correction by the correction means is performed, that is, when the calculated target air-fuel ratio is smaller than the switching air-fuel ratio, the ignition timing for making the engine output torque coincide with the required torque is later than the retard limit value. When the angle is on the corner side, control is performed to set the ignition timing to the optimum ignition timing without correcting the target air-fuel ratio. Since the ignition timing cannot be controlled to the retard side from the retard limit value (causing misfire or instability of combustion), in this case, the fuel supply control is performed by directly applying the calculated target air-fuel ratio. Thus, torque fluctuation is prevented. Since the increase in the NOx emission amount is limited within an extremely short time, the deterioration of the exhaust characteristics is negligible.

  According to a fifth aspect of the present invention, in the vehicle control apparatus according to the first aspect, the vehicle can be driven by the engine (1) and the electric motor (61), and the electric motor control for controlling the electric motor (61). And when the target air-fuel ratio (AFCMD) calculated by the target air-fuel ratio calculating means in the transient state is smaller than the switching air-fuel ratio (AFLMT), the target air-fuel ratio (AFCMD) is changed to the switching air-fuel ratio (AFLMT). When the correction by the correction means is performed, the motor control means is configured to correct the motor (61) by the difference between the output torque (TRQENGEST) of the engine and the required torque (TRQCMD). The engine output torque compensation for increasing the output torque (TRQMOT) is executed, and the target air-fuel ratio (AFCMD) becomes the switching air-fuel ratio (AFCMD). When the engine output torque is equal to or greater than (FLMT), the engine output torque compensation is not executed, and the switching air-fuel ratio (AFLMT) is smaller than the steady lean operation air-fuel ratio (AFLN) set in the steady state of the lean operation. It is set to a value larger than the air-fuel ratio (AFST).

  According to this configuration, when the target air-fuel ratio calculated in the transient state is smaller than the switching air-fuel ratio, the target air-fuel ratio is corrected to the switching air-fuel ratio, and the output torque of the motor is equal to the difference between the engine output torque and the required torque. On the other hand, when the target air-fuel ratio is equal to or higher than the switching air-fuel ratio, control for not executing engine output torque compensation is performed. Therefore, it is possible to prevent the target air-fuel ratio from being set within the air-fuel ratio range in which the NOx emission amount increases, and to prevent the increase in NOx emission amount and torque fluctuation while maintaining the ignition timing at the optimal ignition timing. it can.

1 is a diagram illustrating a configuration of a direct injection internal combustion engine that drives a vehicle and a control device thereof according to an embodiment of the present invention. It is a figure for demonstrating the setting of the target air fuel ratio according to the engine operating area | region defined by an engine speed (NE) and a request torque (TRQCMD). It is a figure which shows the relationship between the air fuel ratio (AF) of the air-fuel mixture which burns in a combustion chamber, and the NOx density | concentration (CNOx) in exhaust_gas | exhaustion in the downstream of an exhaust purification catalyst. 6 is a time chart for explaining the outline of air-fuel ratio switching transient control executed when the target air-fuel ratio is switched from the stoichiometric air-fuel ratio to a predetermined lean air-fuel ratio in a state where the required torque is constant. 6 is a time chart for explaining the outline of air-fuel ratio switching transient control executed when the target air-fuel ratio is switched from a predetermined lean air-fuel ratio to a stoichiometric air-fuel ratio in a state where the required torque is constant. 7 is a time chart for explaining control when the ignition timing reaches a retardation limit value while retarding the ignition timing. The relationship between the gas fuel ratio (GFR) under a condition where the engine speed (NE) is constant and the torque conversion coefficient (KGFTRQ) corresponding to the thermal efficiency of the engine, and the engine speed (NE) under a condition where the gas fuel ratio is constant And a torque conversion coefficient (KGFTRQ). 3 is a flowchart of air-fuel ratio switching transient control processing (first embodiment). It is a flowchart of the IGRTD calculation process performed by the process of FIG. It is a figure which shows the map referred by the process of FIG. It is a flowchart which shows the modification of the process shown in FIG. It is a figure which shows typically the structure of the drive device of a vehicle provided with an internal combustion engine and an electric motor as a motor. 12 is a time chart for explaining an overview of air-fuel ratio switching transient control executed when the target air-fuel ratio is switched from the stoichiometric air-fuel ratio to a predetermined lean air-fuel ratio in a state where the required torque is constant (second embodiment). It is a flowchart of the air-fuel ratio switching transient control process (second embodiment). It is a flowchart of the TRQMOT calculation process performed by the process of FIG.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of a direct injection internal combustion engine that drives a vehicle according to an embodiment of the present invention and a control device thereof. The vehicle according to the present embodiment is an internal combustion engine (hereinafter referred to as “hereinafter referred to as“ motor ”) shown in FIG. Only engine). A throttle valve 3 is arranged in the intake passage 2 of the engine 1. The engine 1 has, for example, four cylinders, and each cylinder is provided with an injector 6 that injects fuel directly into the combustion chamber. The operation of the injector 6 is controlled by an electronic control unit (hereinafter referred to as “ECU”) 5. A spark plug 8 is attached to each cylinder of the engine 1, and the ignition timing by the spark plug 8 is controlled by the ECU 5.

  The ECU 5 includes an intake air amount sensor 21 that detects the intake air amount GAIR of the engine 1, an intake air temperature sensor 22 that detects the intake air temperature TA, a throttle valve opening sensor 23 that detects the throttle valve opening TH, and an intake pressure PBA. An intake pressure sensor 24 for detecting, a coolant temperature sensor 25 for detecting engine coolant temperature TW, a crank angle position sensor 26 for detecting a rotation angle of a crankshaft (not shown) of the engine 1, and a vehicle accelerator driven by the engine 1 An accelerator sensor 27 that detects the pedal operation amount AP and other sensors (not shown) (for example, a vehicle speed sensor, an atmospheric pressure sensor, etc.) are connected, and detection signals from these sensors are supplied to the ECU 5. The crank angle position sensor 26 outputs a plurality of pulse signals indicating the crank angle position, and these pulse signals are used for various timing control such as fuel injection timing and ignition timing, and detection of the engine speed NE. The

  An exhaust purification catalyst (for example, a three-way catalyst) 11 is provided in the exhaust passage 10. An air-fuel ratio sensor 28 is mounted on the upstream side of the exhaust purification catalyst 11 and on the downstream side of the collection portion of the exhaust manifold communicating with each cylinder, and the exhaust passage 10 detects the oxygen concentration in the exhaust. Thus, the air-fuel ratio AF of the air-fuel mixture combusted in the combustion chamber is detected. Although not shown, the engine 1 includes a known exhaust gas recirculation mechanism that recirculates exhaust gas to the intake passage 2.

  The ECU 5 has a well-known configuration including a CPU, a memory, an input / output circuit, and the like. The fuel injection control by the injector 6 and the spark plug 8 are performed according to the engine operating state (mainly the engine speed NE and the required torque TRQCMD). Ignition control by the actuator 3 and intake air amount control by the actuator 3a and the throttle valve 3 are performed. The required torque TRQCMD is calculated mainly according to the accelerator pedal operation amount AP, and is calculated so as to increase as the accelerator pedal operation amount AP increases. The target intake air amount GAIRCMD is calculated according to the target air-fuel ratio AFCMD and the required torque TRQCMD, and is calculated so as to be substantially proportional to the target air-fuel ratio AFCMD and the required torque TRQCMD. The intake air amount control for driving the throttle valve 3 by the actuator 3a is performed so that the cylinder intake air amount GAIRCYL calculated using the detected intake air amount GAIR matches the target intake air amount GAIRCMD.

  FIG. 2 is a diagram for explaining the setting of the target air-fuel ratio AFCMD according to the operating range of the engine 1 defined by the engine speed NE and the required torque TRQCMD. The target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST in the first region RST (stoichiometric operation region) corresponding to the low rotation / low / medium load region and the medium / high rotation / low load region, and the second region corresponding to the medium rotation / medium load region. (Lean operation region) In RLEAN, the predetermined lean air-fuel ratio AFLN is set, and in the third region RSTE corresponding to the high load side and high rotation side regions of the second region RLEAN, the stoichiometric air-fuel ratio AFST is set. In the fourth region RRICH, which corresponds to a region on the higher load side than RSTE, the air-fuel ratio AFRC on the richer side than the theoretical air-fuel ratio AFST is set. In the first region RST, exhaust gas recirculation is not performed by the exhaust gas recirculation mechanism, and in the third region RSTE, exhaust gas recirculation is performed by the exhaust gas recirculation mechanism. The predetermined lean air-fuel ratio AFLN is set to a value at which the NOx concentration in the exhaust gas (feed gas) discharged from the combustion chamber is lower than the allowable limit and stable combustion can be realized, for example, “30”.

  In the present embodiment, as indicated by arrows A and B, when the target air-fuel ratio AFCMD is switched between the first region RST and the second region RLEAN while the required torque TRQCMD is constant, the engine 1 While maintaining the actual output torque TRQA at the required torque TRQCMD, air-fuel ratio switching transient control (hereinafter simply referred to as “transient control”) that suppresses an increase in the NOx emission amount is executed.

  FIG. 3 is a diagram showing the relationship between the air-fuel ratio AF of the air-fuel mixture combusting in the combustion chamber and the NOx concentration CNOx in the exhaust gas downstream of the exhaust purification catalyst 11. In order to set the NOx concentration CNOx below the allowable limit CNOxLMT, the first air-fuel ratio AFSMT (for example, “16”) slightly leaner than the theoretical air-fuel ratio AFST to the first switch air-fuel ratio AFLMT (for example, about “25”). It is necessary to avoid setting the target air-fuel ratio AFCMD in the lean air-fuel ratio range RLN1, and in the transient control described below, the actual output torque is set without setting the target air-fuel ratio AFCMD in the first lean air-fuel ratio range RLN1. Control is performed to maintain TRQA at a constant required torque TRQCMD.

  FIG. 4 is a time chart for explaining the outline of the transient control. In this figure, the required torque TRQCMD, the lean operation request flag FLEAN, and the cylinder intake air amount in the transient control when shifting from the stoichiometric operation to the lean operation are shown. Changes in GAIRCYL and target intake air amount GAIRCMD (target value of cylinder intake air amount GAIRCYL), steady target air-fuel ratio AFCMDSS and target air-fuel ratio AFCMD, and ignition timing IGCMD (defined to increase with advance). It is shown. The cylinder intake air amount GAIRCYL is the amount of air taken into the combustion chamber of one cylinder per cycle.

  When the required torque TRQCMD is fixed to the constant value TRQ0 and the lean operation request flag FLEAN is changed from “0” to “1” at time t0, the target intake air amount GAIRCMD is as shown in FIG. As indicated by the broken line, the air amount GAST during the stoichiometric operation increases in a stepped manner from the air amount GALN during the lean operation, but the actual cylinder intake air amount GAIRCYL gradually increases as indicated by the solid line. The broken line shown in FIG. 4D shows the steady target air-fuel ratio AFCMDSS corresponding to the target intake air amount GAIRCMD, and the actual target air-fuel ratio AFCMD is gradually increased in response to the increase in the cylinder intake air amount GAIRCYL. There is a need. When the target air-fuel ratio AFCMD is increased in correspondence with the increase in the cylinder intake air amount GAIRCYL as indicated by the one-dot chain line in FIG. 4D, the target air-fuel ratio AFCMD becomes the empty range of the first lean air-fuel ratio range RLN1 shown in FIG. In this embodiment, the stoichiometric air-fuel ratio AFST is maintained until time t1, as indicated by the solid line in FIG. 4 (d). At time t1, the target air-fuel ratio AFCMD is set to the switching air-fuel ratio AFLMT, and thereafter, air-fuel ratio gradual increase control is executed to increase the target air-fuel ratio AFCMD in response to the increase in the cylinder intake air amount GAIRCYL. At time t2, when the cylinder intake air amount GAIRCYL reaches the target intake air amount GAIRCMD and the target air-fuel ratio AFCMD reaches a predetermined lean air-fuel ratio AFLN that is the steady target air-fuel ratio AFCMDSS, the transient control ends.

  Between time t0 and t1, the cylinder intake air amount GAIRCYL increases while maintaining the target air / fuel ratio AFCMD at the theoretical air / fuel ratio AFST, so that the ignition timing IGCMD is changed to the cylinder intake air as shown by a broken line in FIG. When the optimum ignition timing corresponding to the amount GAIRCYL is set, the actual output torque TRQA increases. Therefore, in the present embodiment, as shown by the solid line in the figure, by gradually retarding the ignition timing IGCMD from the optimal ignition timing IGST during the stoichiometric operation, the ignition timing retardation that makes the actual output torque TRQA coincide with the required torque TRQCMD. Take control. After time t1, the ignition timing IGCMD is set to the optimal ignition timing corresponding to the cylinder intake air amount GAIRCYL, and reaches the optimal ignition timing IGLN for lean operation at time t2.

FIG. 5 is a time chart for explaining the transient control when shifting from the lean operation to the stoichiometric operation contrary to FIG.
When the lean operation request flag FLEAN is changed from “1” to “0” at time t10, the target intake air amount GAIRCMD decreases in a step shape as indicated by a broken line in FIG. The intake air amount GAIRCYL gradually decreases as shown by the solid line. The broken line shown in FIG. 5 (d) shows the setting of the steady target air-fuel ratio AFCMDSS corresponding to the target intake air amount GAIRCMD, and the actual target air-fuel ratio AFCMD gradually increases corresponding to the decrease in the cylinder intake air amount GAIRCYL. It needs to be reduced. When the target air-fuel ratio AFCMD is decreased corresponding to the decrease in the cylinder intake air amount GAIRCYL between the times t11 and t12 as indicated by a one-dot chain line in FIG. 5D, the target air-fuel ratio AFCMD becomes the first air-fuel ratio AFCMD shown in FIG. Since the air-fuel ratio in the lean air-fuel ratio range RLN1 is set, in this embodiment, as shown by a solid line in FIG. 5D, cylinder suction is performed until time t11 when the target air-fuel ratio AFCMD reaches the switching air-fuel ratio AFLMT. Air-fuel ratio gradually decreasing control for decreasing the target air-fuel ratio AFCMD corresponding to the decrease in the air amount GAIRCYL is executed, and the target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST after time t11. At time t12, when the cylinder intake air amount GAIRCYL reaches the target intake air amount GAIRCMD, and the target air-fuel ratio AFCMD reaches the stoichiometric air-fuel ratio AFST which is the steady target air-fuel ratio AFCMDSS, the transient control ends.

  Between time t11 and t12, the cylinder intake air amount GAIRCYL decreases while the target air-fuel ratio AFCMD is maintained at the stoichiometric air-fuel ratio AFST. Therefore, the ignition timing IGCMD is determined as the cylinder intake air as shown by the broken line in FIG. When the optimal ignition timing corresponding to the amount GAIRCYL is maintained, the actual output torque TRQA increases. Therefore, in the present embodiment, as shown by the solid line in FIG. 2, ignition timing retard control is performed to retard the ignition timing IGCMD so that the actual output torque TRQA matches the required torque TRQCMD.

  In the transient control shown in FIG. 4, the ignition timing IGCMD is retarded in the period from time t0 to t1, but if the retardation amount of the ignition timing IGCMD is excessive, combustion instability or misfire may occur. Therefore, the ignition timing IGCMD is controlled so as not to be set to the retard side with respect to the retard limit value IGRTDLMT calculated in accordance with the engine speed NE and the intake air amount GAIR. FIG. 4 shows an example in which the ignition timing IGCMD does not reach the retard limit value IGRTDLMT.

  FIG. 6 is a time chart for explaining the control when the ignition timing IGCMD reaches the retardation limit value IGRTDLMT when the ignition timing IGCMD is retarded (before time t1). The transition of the air-fuel ratio AFCMD and the ignition timing IGCMD is shown.

  In such a case, when the ignition timing IGCMD reaches the retard limit value IGRTDLMT at time t1a, the target air-fuel ratio AFCMD is changed to a value corresponding to the cylinder intake air amount GAIRCYL, and the ignition timing IGCMD is changed to the cylinder intake air. Transient control is performed to change to the optimal ignition timing corresponding to the amount GAIRCYL. In this transient control, the target air-fuel ratio AFCMD in which the NOx concentration CNOx is slightly increased is temporarily applied. However, since it is an extremely short time, the deterioration of the exhaust characteristics is negligible.

Next, a method for calculating the fuel injection amount (mass / cycle) GFUEL injected into the combustion chamber by the injector 6 in the present embodiment will be described.
The relationship between the required torque TRQCMD and the fuel injection amount GFUEL can be expressed by Expression (1).
TRQCMD = GFUEL × KGFTRQ (1)

  Here, KGFTRQ is a torque conversion coefficient for converting the fuel amount into torque. Equation (1) assumes that the ignition timing IGCMD is set to the optimal ignition timing IGMAP. The optimum ignition timing IGMAP is the maximum torque ignition timing at which the output torque of the engine 1 is maximized, but the most retarded value (the knock limit ignition timing) of the ignition timing at which knocking is likely to occur in a high load operation state is the torque. When it is retarded from the maximum ignition timing, the knock limit ignition timing is set.

By modifying the above equation (1), the following equation (2) is obtained, and the fuel injection amount GFUEL can be calculated using the equation (2).
GFUEL = TRQCMD / KGFTRQ (2)
The fuel injection amount calculated by the equation (2) is mass, and the fuel injection amount GFUEL is converted into the valve opening time TOUT of the injector 6 according to the fuel pressure PF, the fuel density, and the like using a known method. The amount of fuel supplied in the combustion chamber per cycle is controlled to be the fuel injection amount GFUEL.

Since the torque conversion coefficient KGFTRQ changes depending on the engine speed NE, the air-fuel ratio AF, and the exhaust gas recirculation rate REGR, conventionally, a plurality of maps are used to calculate the torque conversion coefficient KGFRQ according to these parameters. Although necessary, in this embodiment, the torque conversion coefficient KGFTRQ is set according to the gas fuel ratio GFR and the engine speed NE by using the gas fuel ratio GFR as the dilution degree parameter defined by the following equation (3). The calculation is made with a single map.
GFR = (GAIRCYL + GEGR) / GFUEL (3)
Here, GEGR is a recirculation exhaust amount (mass) that is an exhaust amount recirculated into the combustion chamber (including the internal exhaust recirculation amount), and a known method (for example, Japanese Patent No. 5270008) is used to calculate the recirculation exhaust amount GEGR. ) Is applicable.

  The inventor of the present invention has confirmed that the relationship between the gas fuel ratio GFR and the torque conversion coefficient KGFTRQ can be approximated by a single curve as shown in FIG. 7A under a condition where the engine speed NE is constant. By setting a single KGFTRQ map in advance according to the gas fuel ratio GFR and the engine speed NE, a plurality of maps according to the air-fuel ratio AF, the exhaust gas recirculation rate REGR, and the engine speed NE are used. Therefore, the fuel injection amount GFUEL that causes the actual output torque TRQA to coincide with the required torque TRQCMD can be accurately calculated. The KGFTRQ map is set so that the torque conversion coefficient KGFTRQ increases as the gas fuel ratio GFR increases. Note that the change range of the torque conversion coefficient KGFTRQ corresponding to the change range (14 to 28) of the gas fuel ratio GFR shown in FIG. 7A is about 0.35 to 0.4.

  FIG. 7B shows the relationship between the engine speed NE and the torque conversion coefficient KGFTRQ under a condition where the gas fuel ratio GFR is constant. As shown in this figure, the torque conversion coefficient KGFTRQ is maximized when the engine speed NE is at the mid-range speed NEMX (for example, 3000 rpm), and decreases as the engine speed NE decreases at a lower speed than the mid-range speed NEMX. Since the time per rotation becomes longer and the efficiency decreases, the torque conversion coefficient KGFTRQ decreases. On the high speed side, as the engine speed NE increases, the time TCYL per cycle becomes shorter and the ratio of the combustion time to the time TCYL increases, so the torque conversion coefficient KGFTRQ decreases.

FIG. 8 is a flowchart of the air-fuel ratio switching transient control process for executing the above-described transient control. This process is executed by the ECU 5 in synchronization with the rotation of the engine 1 (for example, every four crank angles in a four-cylinder engine). Is done.
In step S11, the required torque TRQCMD is calculated according to the accelerator pedal operation amount AP, and in step S12, the lean operation request flag FLEAN is set according to the engine speed NE and the required torque TRQCMD.

  In step S13, the target intake air amount GAIRCMD is calculated according to the required torque TRQCMD and the lean operation request flag FLEAN. By the intake air amount control process (not shown), the throttle valve opening TH is controlled so that the cylinder intake air amount GAIRCYL matches the target intake air amount GAIRCMD.

In step S14, the cylinder intake air amount GAIRCYL is calculated using the detected intake air amount GAIR. For calculating the cylinder intake air amount GAIRCYL, a known method (for example, Japanese Patent No. 5118247) can be applied. In step S15, the recirculation exhaust amount GEGR is calculated using the detected intake air amount GAIR and the intake pressure PBA, and in step S16, the gas fuel ratio GFR is calculated by the following equation (3a). Expression (3a) is obtained by replacing the fuel injection amount GFUEL in Expression (3) with the previous calculated value GFUELZ.
GFR = (GAIRCYL + GEGR) / GFUELZ (3a)

In step S17, a map search (see FIG. 7) is performed according to the engine speed NE and the gas fuel ratio GFR to calculate a torque conversion coefficient KGFTRQ. In step S18, the temporary fuel injection amount GFUELTMP is calculated using the following equation (2a). calculate. Formula (2a) is obtained by replacing GFUEL in Formula (2) with GFUELTMP.
GFUELTMP = TRQCMD / KGFTRQ (2a)

In step S19, the temporary target air-fuel ratio AFCMDTMP is calculated by applying the cylinder intake air amount GAIRCYL, the target intake air amount GAIRCMD, and the steady target air-fuel ratio AFCMDSS to the following equation (4).
AFCMDTMP = (GAIRCYL / GAIRCMD) × AFCMDSS (4)

  In step S20, it is determined whether or not the temporary target air-fuel ratio AFCMDTMP is smaller than the switching air-fuel ratio AFLMT. If the answer is negative (NO), that is, the period from time t1 to t2 in FIG. 4 or time t10 in FIG. In the period from t11 to t11, the target air-fuel ratio AFCMD is set to the temporary target air-fuel ratio AFCMDTMP, the fuel injection amount GFUEL is set to the temporary fuel injection amount GFUELTMP (step S25), and the ignition timing IGCMD is set to the optimal ignition timing IGMAP. (Step S26). The optimal ignition timing IGMAP is calculated by a known method in an ignition timing calculation process (not shown).

If the answer to step S20 is affirmative (YES), that is, during the period from time t0 to t1 in FIG. 4 or from time t11 to t12 in FIG. 5, the target air-fuel ratio AFCMD is set to the theoretical air-fuel ratio AFST. (Step S21). Since the target air-fuel ratio AFCMD is set not to the temporary target air-fuel ratio AFCMDTMP but to the stoichiometric air-fuel ratio AFST, in step S22, the temporary fuel injection amount GFUELTMP is applied to the following equation (5) to calculate the fuel injection amount GFUEL.
GFUEL = (AFCMDTMP / AFCMD) × GFUELTMP (5)

  In step S23, the IGRTD calculation process shown in FIG. 9 is executed to calculate the retard amount IGRTD, and in step S24, the ignition timing IGCMD is set to a value obtained by subtracting the retard amount IGRTD from the optimal ignition timing IGMAP.

  In step S31 of FIG. 9, the fuel ratio GFR is calculated by applying the fuel injection amount GFUEL calculated in step S22 to the above equation (3). In step S32, as in step S17, a torque conversion coefficient KGFTRQ is calculated according to the gas fuel ratio GFR and the engine speed NE.

In step S33, a torque reduction rate KIGTRQDN by retarding the ignition timing IGCMD is calculated using the following equation (6).
KIGTRQDN = TRQCMD × AFCMD / (GAIRCYL × KGFTRQ)
(6)

If the torque reduction rate KIGTRRQDN in the case where the ignition timing IGCMD is retarded from the optimum ignition timing IGMAP and the actual output torque TRQA is matched with the required torque TRQCMD is used, the required torque TRQCMD can be expressed by the following equation (7). The above formula (6) is obtained by modifying the formula (7). GAIRCYL / AFCMD of Expression (7) is equal to the fuel injection amount GFUEL.
TRQCMD = GAIRCYL / AFCMD × KGFTRQ × KIGTRRQDN
(7)

  In step S34, a retard amount IGRTD is calculated by reversely searching the KIGTRQDN map shown in FIG. 10 according to the torque reduction rate KIGTRQDN and the engine speed NE. In FIG. 10, curves L11 to L13 correspond to predetermined engine speeds NE11, NE12, and NE13, respectively (NE11 <NE12 <NE13). The KIGTRQDN map is set so that the torque reduction rate KIGTRQDN decreases as the retard amount IGRTD increases, and the torque reduction rate KIGTRRQDN increases as the engine speed NE increases. It takes a value between “0” and “1”.

  The control of the target air-fuel ratio AFCMD and the control of the ignition timing IGCMD shown in FIGS. 4 and 5 are executed by the control processing shown in FIGS.

  As described above, in the present embodiment, the required torque TRQCMD is set according to the accelerator pedal operation amount AP indicating the request of the vehicle driver, and the target air-fuel ratio AFCMD is calculated based on the cylinder air amount GAIRCYL. The fuel injection amount GFUEL by the injector 6 is controlled so that the air-fuel ratio AF of the fuel cell coincides with the target air-fuel ratio AFCMD. The gas fuel ratio GFR as a dilution degree parameter indicating the ratio between the gas amount in the combustion chamber and the fuel is calculated using the cylinder intake air amount GAIRCYL, the recirculation exhaust amount GEGR, and the fuel injection amount GFUEL indicating the fresh air amount in the combustion chamber. In the air-fuel ratio switching transient control in which the air-fuel ratio AF is switched between the predetermined lean air-fuel ratio AFLN and the stoichiometric air-fuel ratio AFST, the fuel injection amount GFUEL is calculated using the gas fuel ratio GFR. The actual output torque TRQA of the engine 1 is basically proportional to the fuel injection amount GFUEL, but the thermal efficiency changes depending on the engine speed NE, the air-fuel ratio AF, and the recirculation exhaust amount GEGR (exhaust recirculation rate REGR). In order to make the actual output torque TRQA exactly coincide with the required torque TRQCMD, it is necessary to improve the calculation accuracy of the thermal efficiency. According to the study of the inventor of the present invention, the relationship between the gas fuel ratio GFR and the torque conversion coefficient KGFTRQ corresponding to the thermal efficiency is one curve as shown in FIG. 7 (a) under the condition that the engine speed NE is constant. It is confirmed that the fuel injection amount GFUEL is calculated using the gas fuel ratio GFR, and a plurality of maps corresponding to the target air-fuel ratio AFCMD, the exhaust gas recirculation rate REGR, and the engine speed NE are calculated. The fuel injection amount GFUEL that matches the actual output torque TRQA with the required torque TRQCMD can be accurately calculated. As a result, it is possible to accurately execute fuel supply control in a transient state while greatly reducing the number of map setting steps in the design stage.

  When the temporary target air-fuel ratio AFCMDTMP calculated based on the cylinder intake air amount GAIRCYL in the air-fuel ratio switching transient control is smaller than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the theoretical air-fuel ratio AFST, and the actual output torque TRQA Is controlled so as to retard the ignition timing IGCMD from the optimal ignition timing IGMAP so as to match the required torque TRQCMD. On the other hand, when the temporary target air-fuel ratio AFCMDTMP is equal to or higher than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the temporary target air-fuel ratio AFCMDTMP, and control is performed to set the ignition timing IGCMD to the optimal ignition timing IGMAP. The switching air-fuel ratio AFLMT is set to a value smaller than a predetermined lean air-fuel ratio AFLN set in the steady state of lean operation and larger than the theoretical air-fuel ratio AFST. That is, when the temporary target air-fuel ratio AFCMDTMP calculated based on the cylinder intake air amount GAIRCYL is smaller than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST, and the ignition timing IGCMD is retarded. When the temporary target air-fuel ratio AFCMDTMP is equal to or higher than the switching air-fuel ratio AFLMT, control is performed to make the actual output torque TRQA coincide with the required torque TRQCMD. While being applied as an air-fuel ratio AFCMD, the ignition timing IGCMD is controlled to the optimal ignition timing IGMAP. Therefore, the target air-fuel ratio AFCMD can be prevented from being set to the air-fuel ratio in the first lean air-fuel ratio range RLN1 in which the NOx concentration CNOx in the exhaust increases, and the increase in the NOx concentration CNOx can be suppressed and the ignition timing can be suppressed. Torque fluctuations can be prevented by retarding the IGCMD.

  Further, as shown in FIG. 3, the switching air-fuel ratio AFLMT is less than or equal to the allowable limit CNOxLMT within a range in which the NOx concentration CNOx contained in the exhaust increases on the downstream side of the exhaust purification catalyst 11 in accordance with the decrease in the air-fuel ratio. Therefore, it is avoided that the target air-fuel ratio AFCMD is set to a value between the theoretical air-fuel ratio AFST and the switching air-fuel ratio AFLMT, that is, a value in a range where the NOx concentration CNOx increases, and the NOx concentration CNOx. Can be suppressed below the allowable limit CNOxLMT. Note that in the range where the NOx concentration CNOx increases in response to the decrease in the air-fuel ratio (range leaner than the air-fuel ratio at which the maximum NOx concentration shown in FIG. 3), the exhaust purification catalyst 11 does not have the purification capability, so the NOx concentration Since CNOx is the same as the NOx concentration upstream of the exhaust purification catalyst 11, that is, the NOx concentration in the exhaust discharged from the combustion chamber of the engine 1, the switching air-fuel ratio AFLMT is the same as that in the exhaust discharged from the combustion chamber. It can be defined as the minimum air-fuel ratio at which the NOx concentration is below the allowable limit CNOxLMT.

[Modification]
FIG. 11 is a flowchart showing a modification of the process shown in FIG. The process of FIG. 11 is obtained by adding step S27 to the process of FIG. Step S27 is a step for realizing the control described with reference to FIG. 6, and whether or not the ignition timing IGCMD retarded in step S24 is smaller than the retard limit value IGRTDLMT (whether it is on the retard side). If the answer is affirmative (YES), the process proceeds to step S25.

  Therefore, when the ignition timing IGCMD becomes smaller than the retard limit value IGRTDLMT during the ignition timing retard control, the retard control is terminated and the target air-fuel ratio AFCMD is changed to the temporary target air-fuel ratio AFCMDTMP corresponding to the cylinder intake air amount GAIRCYL. In addition to the setting, transient control is performed in which the ignition timing IGCMD is set to the optimum ignition timing IGMAP corresponding to the cylinder intake air amount GAIRCYL at that time.

  In this modification, when the temporary target air-fuel ratio AFCMDTMP is smaller than the switching air-fuel ratio AFLMT, when the ignition timing IGCMD for matching the actual output torque TRQA with the required torque TRQCMD is on the retard side with respect to the retard limit value IGRTDLMT, Control is performed such that the air-fuel ratio AFCMD is set to the temporary target air-fuel ratio AFCMDTMP, and the ignition timing IGCMD is set to the optimum ignition timing IGMAP. Since the ignition timing IGCMD cannot be controlled to be retarded from the retard limit value IGRTDLMT (causes misfire or instability of combustion), in this case, the fuel supply to which the calculated temporary target air-fuel ratio AFCMDTMP is applied as it is The torque fluctuation is prevented by executing the control.

  In the present embodiment, the accelerator sensor 27 and the ECU 5 constitute required torque setting means, the injector 6 and the ECU 5 constitute fuel amount control means, and the ECU 5 includes target air-fuel ratio calculation means, dilution degree parameter calculation means, ignition timing control. Means and correction means.

[Second Embodiment]
This embodiment applies this invention to the vehicle provided with the engine 1 and an electric motor as a motor | power_engine, and is the same as 1st Embodiment except the point demonstrated below.

  FIG. 12 schematically shows the overall configuration of the vehicle drive device. This vehicle drive device includes an engine 1 described above, an electric motor (hereinafter referred to as “motor”) 61 having functions as a prime mover and a generator, and a transmission 52 for transmitting the driving force of the engine 1 and / or the motor 61. The crankshaft 51 of the engine 1 is connected to the transmission 52, and is configured to drive the drive wheels 56 via the output shaft 53, the differential gear mechanism 54, and the drive shaft 55 of the transmission 52. Yes. The motor 61 is connected to a power drive unit (hereinafter referred to as “PDU”) 62, and the PDU 62 is connected to a high voltage battery 63. The transmission 52 is a twin clutch transmission that includes an odd-numbered clutch and an even-numbered clutch corresponding to an odd-numbered gear and an even-numbered gear, respectively. According to the vehicle drive device, it is possible to perform engine mode travel in which only the engine 1 is operated as a prime mover, and hybrid mode travel in which both the engine 1 and the motor 61 are actuated as prime movers. By setting both clutches in the disengaged state, it is possible to perform electric mode running in which only the motor 61 is operated as a prime mover.

  When driving the motor 62 with a positive driving torque, that is, when driving the motor 61 with electric power output from the high voltage battery 63, the electric power output from the high voltage battery 63 is supplied to the motor 61 via the PDU 62. . When the motor 61 is driven with a negative driving torque, that is, when the motor 61 is regeneratively operated, the electric power generated by the motor 61 is supplied to the high voltage battery 63 via the PDU 62 and the high voltage battery 63 is charged. The PDU 62 is connected to the ECU 30 to control the operation of the motor 61 and to control charging and discharging of the high voltage battery 63. The ECU 30 controls the operation of the motor 61 in addition to the function of the ECU 5 in the first embodiment. The ECU 30 is configured, for example, by connecting the ECU 5 of the first embodiment and the motor control ECU via a communication bus.

  FIG. 13 is a time chart for explaining the transient control in the present embodiment, and shows an operation example when the target air-fuel ratio AFCMD is switched from the stoichiometric air-fuel ratio AFST to the predetermined lean air-fuel ratio AFLN as in FIG. Yes. In FIG. 13A, the constant required torque TRQCMD is indicated by a broken line, and the solid line indicates the transition of the actual output torque TRQA. The transition of the target intake air amount GAIRCMD and the cylinder intake air amount GAIRCYL shown in FIG. 13C is the same as the transition shown in FIG. FIG. 13F shows the transition of the motor required torque TRQMOT.

  In this embodiment, the difference between the actual output torque TRQA and the required torque TRQCMD in the period from time t20 to t21 shown in FIG.

  When the lean operation request flag FLEAN is changed from “0” to “1” at time t20, the target air-fuel ratio AFCMD is changed from the theoretical air-fuel ratio AFST to the switching air-fuel ratio AFLMT. As a result, the fuel injection amount GFUEL decreases and the actual output torque TRQA decreases to the torque value TRQ1. In response to this, the motor required torque TRQMOT is set to the torque difference DTRQE (= TRQ0−TRQ1) (FIG. 13 (f)). Thereafter, the actual output torque TRQA increases corresponding to the increase in the cylinder intake air amount GAIRCYL, and therefore the motor required torque TRQMOT is decreased by the increase.

  The dash-dot line in FIG. 13 (d) indicates the temporary target air-fuel ratio AFCMDTMP corresponding to the cylinder intake air amount GAIRCYL. When the temporary target air-fuel ratio AFCMDTMP reaches the switching air-fuel ratio AFLMT at time t21, the actual output torque TRQA Is equal to the required torque TRQCMD, the motor required torque TRQMOT is set to “0”, and thereafter, the air-fuel ratio gradual increase control for increasing the target air-fuel ratio AFCMD corresponding to the increase in the cylinder intake air amount GAIRCYL is executed. When the cylinder intake air amount GAIRCYL reaches the target intake air amount GAIRCMD at time t22, the transient control is terminated. The ignition timing IGCMD is set to the optimum ignition timing IGMAP corresponding to the increase in the cylinder intake air amount GAIRCYL as shown in FIG.

  FIG. 14 is a flowchart of the air-fuel ratio switching transient control process in the present embodiment. In this process, steps S21, S23, and S24 in the process shown in FIG. 8 are deleted, and steps S41 to S43 are added.

If the answer to step S20 is affirmative (YES), the target air-fuel ratio AFCMD is set to the switching air-fuel ratio AFLMT (step S41), and fuel injection corresponding to the target air-fuel ratio AFCMD (switching air-fuel ratio AFLMT) is performed in step S22. The quantity GFUEL is calculated. In step S42, the TRQMOT calculation process shown in FIG. 15 is executed to calculate the motor required torque TRQMOT.
If the answer to step S20 is negative (NO), the motor request torque TRQMOT is set to “0” after executing step S25 (step S43).

In step S51 of FIG. 15, the fuel injection amount GFUEL calculated in step S22 is applied to the above equation (3) to calculate the gas fuel ratio GFR. In step S52, the torque conversion coefficient KGFTRQ is calculated as in step S17. To do. In step S53, the estimated output torque TRQENGEST of the engine 1 is calculated by the following equation (8).
TRQENGEST = GAIRCYL / AFCMD × KGFTRQ (8)

In step S54, the motor required torque TRQMOT is calculated by the following equation (9).
TRQMOT = TRQCMD-TRQENGEST (9)

  As described above, in the present embodiment, when the temporary target air-fuel ratio AFCMDTMP calculated in the transient control is smaller than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the switching air-fuel ratio AFLMT, and the motor required torque TRQMOT is set as follows. While the engine output torque compensation set to the difference between the estimated output torque TRQENGEST of the engine 1 and the required torque TRQCMD is executed, when the temporary target air-fuel ratio AFCMDTMP is equal to or higher than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the temporary target air-fuel ratio. Control that does not execute engine output torque compensation by the motor 61 is set to AFCMDTMP. Therefore, setting of the target air-fuel ratio AFCMD within the first lean air-fuel ratio range RLN1 in which the NOx emission amount increases is avoided, and the ignition timing IGCMD is maintained at the optimal ignition timing IGMAP, while the NOx emission amount increases and Torque fluctuation can be prevented.

  In the present embodiment, the accelerator sensor 27 and the ECU 30 constitute a required torque setting means, the injector 6 and the ECU 30 constitute a fuel amount control means, and the ECU 30 includes a target air-fuel ratio calculation means, a dilution degree parameter calculation means, and a correction means. The ECU 30 and the PDU 62 constitute an electric motor control means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, when the temporary target air-fuel ratio AFCMDTMP calculated during the transient control is smaller than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST. It may be set to a value close to the theoretical air-fuel ratio AFST instead of AFST itself. The range in the vicinity of the stoichiometric air-fuel ratio is, for example, the stoichiometric air-fuel ratio AFST to the air-fuel ratio AFSTL shown in FIG. 3 (the range in which the NOx concentration CNOx is equal to or less than the allowable limit CNOxLMT).

  In the second embodiment described above, the example in which the motor required torque TRQMOT at the start of the transient control is “0” is shown. However, when the motor 61 is driven at that time, the torque difference (TRQCMD−TRQENGEST ), The engine output torque compensation for increasing the motor required torque TRQMOT is executed. Thus, the decrease in the actual output torque TRQA of the engine 1 during the transient control can be compensated for by the increase in the output torque of the motor 61.

  In the above-described embodiment, an example in which the present invention is applied to a vehicle control device including an internal combustion engine having a direct injection injector that injects fuel into a combustion chamber as a prime mover is shown. However, the present invention injects fuel into an intake port. The present invention can also be applied to an internal combustion engine that includes a port injection injector, or a vehicle control device that includes, as a prime mover, an internal combustion engine that includes both a direct injection injector and a port injection injector.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Throttle valve 5,30 Electronic control unit (Request torque setting means, target air-fuel ratio calculation means, fuel amount control means, dilution degree parameter calculation means, ignition timing control means, correction means, motor control means)
6 Injector (fuel amount control means)
8 Spark plug 10 Exhaust passage 11 Exhaust purification catalyst 21 Intake air amount sensor 24 Intake pressure sensor 26 Accelerator sensor (required torque setting means)
61 Electric motor 62 Power drive unit (electric motor control means)

Claims (5)

A control device for a vehicle that can be driven by an internal combustion engine, wherein the engine is configured to perform a lean operation in which an air-fuel ratio of an air-fuel mixture combusted in the engine is set to a lean air-fuel ratio that is leaner than a stoichiometric air-fuel ratio. In a vehicle control device,
Requested torque setting means for setting a requested torque of the engine based on a request of a driver of the vehicle;
Target air-fuel ratio calculating means for calculating a target air-fuel ratio of the air-fuel mixture based on the intake air amount of the engine;
Fuel amount control means for controlling the amount of fuel supplied to the combustion chamber so that the air-fuel ratio of the air-fuel mixture matches the target air-fuel ratio;
A dilution degree parameter calculating means for calculating a dilution degree parameter indicating the ratio of the amount of gas and fuel in the combustion chamber;
The dilution degree parameter calculation means includes:
Calculate the dilution degree parameter using parameters indicating the amount of fresh air in the combustion chamber, the amount of recirculated exhaust gas, and the amount of fuel,
The fuel amount control means calculates the fuel amount using the dilution degree parameter in a transient state in which the air-fuel ratio of the air-fuel mixture is switched between the lean air-fuel ratio and the stoichiometric air-fuel ratio. Control device. Ignition timing control means for controlling the ignition timing of the engine;
Correction means for correcting the target air-fuel ratio to a value close to the theoretical air-fuel ratio when the target air-fuel ratio calculated by the target air-fuel ratio calculating means is smaller than the switching air-fuel ratio in the transient state;
When the correction by the correction means is performed, the ignition timing control means retards the ignition timing from an optimal ignition timing so that the output torque of the engine matches the required torque, and the target air-fuel ratio is When it is equal to or higher than the switching air-fuel ratio, the ignition timing is set to the optimum ignition timing,
The optimal ignition timing is an ignition timing that maximizes the output torque of the engine,
The vehicle control device according to claim 1, wherein the switching air-fuel ratio is set to a value smaller than a steady lean operation air-fuel ratio set in a steady state of the lean operation and larger than a theoretical air-fuel ratio.   3. The vehicle control device according to claim 2, wherein the switching air-fuel ratio is set to a minimum value at which a NOx concentration contained in the exhaust gas discharged from the combustion chamber is equal to or less than an allowable limit. In the case where the correction by the correction means is performed, the ignition timing control means sets the ignition timing when the ignition timing for making the output torque of the engine coincide with the required torque is more retarded than the retard limit value. Set to the optimal ignition timing,
The vehicle control device according to claim 2 or 3, wherein the correction means does not correct the target air-fuel ratio. The vehicle can be driven by the engine and an electric motor,
Motor control means for controlling the motor;
Correction means for correcting the target air-fuel ratio to the switching air-fuel ratio when the target air-fuel ratio calculated by the target air-fuel ratio calculating means is smaller than the switching air-fuel ratio in the transient state;
When the correction by the correction unit is performed, the motor control unit performs engine output torque compensation for increasing the output torque of the motor by a difference between the output torque of the engine and the required torque, and the target air-fuel ratio is When it is equal to or higher than the switching air-fuel ratio, the engine output torque compensation is not performed,
The vehicle control device according to claim 1, wherein the switching air-fuel ratio is set to a value smaller than a steady lean operation air-fuel ratio set in a steady state of the lean operation and larger than a theoretical air-fuel ratio.

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