JP6647983B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a control device for a vehicle having an internal combustion engine as a prime mover, and more particularly to a device 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 a side leaner than a stoichiometric air-fuel ratio.

  Patent Document 1 discloses a control device for an internal combustion engine capable of lean operation. According to this control device, when switching the combustion mode of the engine from weak stratified combustion to homogeneous lean combustion during rich spike control, The opening degrees of the throttle valve and the exhaust gas recirculation valve are changed to the close side suitable for the homogeneous lean operation, and the fuel injection amount is increased and corrected. As a result, output torque fluctuation due to switching of the combustion mode is prevented.

  Patent Document 2 discloses a control method that suppresses output torque fluctuation 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 control for increasing the intake air amount is started, the ignition timing is retarded from the time when the increase in the actual intake air amount is started while the air-fuel ratio is maintained at the stoichiometric air-fuel ratio, and then the lean air-fuel ratio is reduced. Control for shifting to the fuel ratio and advancing the ignition timing is performed.

JP-A-2000-2142 Japanese Patent No. 3064782

  The increase correction of the fuel injection amount in the control device disclosed in Patent Literature 1 simply increases the fuel injection amount by a preset fixed amount. Appropriate correction cannot be performed, and output torque fluctuation is not sufficiently suppressed.

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

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

To achieve the above object, an invention according to claim 1 is a control device for a vehicle drivable by an internal combustion engine (1), wherein the engine theoretically determines an air-fuel ratio (AF) of an air-fuel mixture burned in the engine. In a vehicle control device configured to be able to execute a lean operation in which a lean air-fuel ratio (AFLN) is set to a leaner side than an air-fuel ratio (AFST), a required torque of the engine (based on a request of a driver of the vehicle) TRQCMD), target air-fuel ratio calculating means for calculating a target air-fuel ratio (AFCMD) of the air-fuel mixture based on the intake air amount (GAIRCYL) of the engine, and air-fuel ratio of the air-fuel mixture ( fuel quantity control means for controlling the AF) is the amount of fuel supplied to the combustion chamber of the engine so that the coincides with the target air-fuel ratio (AFCMD) (GFUEL), the combustion chamber of the gas A dilution degree parameter calculating means for calculating a dilution degree parameter (GFR) indicating a ratio between the amount and the fuel, wherein the dilution degree parameter calculating means includes a fresh air amount (GAIRCYL) in the combustion chamber and a recirculated exhaust gas amount (GEGR). ) And a parameter indicating a fuel amount (GFUEL), and the dilution degree parameter (GFR) is calculated. The fuel amount control means sets the air-fuel ratio (AF) of the air-fuel mixture to the lean air-fuel ratio (AFLN). In a transient state in which the engine is switched between the stoichiometric air-fuel ratio (AFST), the torque conversion coefficient (KGFTRQ) for converting the fuel amount (GFUEL) into the output torque of the engine is determined by the dilution degree parameter (GFR) and the engine. calculated in accordance with the rotational speed (NE), using the required torque (TRQCMD) and the torque conversion factor (KGFTRQ) And performing calculation of the fuel quantity (GFUEL).

According to this configuration, the required torque of the engine is set based on the request of the driver of the vehicle, and the target air-fuel ratio of the air-fuel mixture is calculated based on the intake air amount of the engine. The amount of fuel supplied to the combustion chamber is controlled so as to match the air-fuel ratio. Further, a dilution degree parameter indicating a ratio of a gas amount and a fuel in the combustion chamber is calculated based on parameters indicating a fresh air amount, a recirculation exhaust amount, and a fuel amount in the combustion chamber, and the air-fuel ratio of the air-fuel mixture is set to a lean air-fuel ratio. In the transient state of switching between and the stoichiometric air-fuel ratio, a torque conversion coefficient for converting the fuel amount to the engine output torque is calculated according to the dilution degree parameter and the engine speed, and the required torque and the torque conversion coefficient are calculated. To calculate the amount of fuel to be supplied to the combustion chamber. The output torque of the engine is basically proportional to the amount of fuel, but since the thermal efficiency changes depending on the engine speed, air-fuel ratio, and the amount of exhaust gas recirculated, it is necessary to accurately match the output torque with the required torque. Therefore, it is necessary to improve the calculation accuracy of the 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 one curve under the condition that the engine speed is constant . . Therefore, by calculating the torque conversion coefficient according to the dilution degree parameter and the engine speed, and calculating the fuel amount using the required torque and the torque conversion coefficient , the air-fuel ratio and the recirculated exhaust gas amount and the engine speed are calculated. Without using a plurality of maps, it is possible to accurately calculate the fuel amount that matches the engine output torque with the required torque. As a result, it is possible to execute the fuel supply control in the transient state with high accuracy 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. Correction means for correcting the target air-fuel ratio (AFCMD) to a value near the stoichiometric air-fuel ratio (AFST) when the target air-fuel ratio (AFCMD) is smaller than the switching air-fuel ratio (AFLMT); The means delays the ignition timing (IGCMD) from the optimum ignition timing (IGMAP) such that the output torque (TRQA) of the engine matches the required torque (TRQCMD) when the correction is performed by the correction means. When the target air-fuel ratio (AFCMD) is equal to or greater than the switching air-fuel ratio (AFLMT), the ignition timing (IGCMD) is set to the optimum ignition timing. (IGMAP), the optimal ignition timing (IGMAP) is the 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-state lean air-fuel ratio (AFLN) and larger than the stoichiometric 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 near the stoichiometric air-fuel ratio so that the engine output torque matches the required torque. Control is performed to retard the ignition timing from the optimum 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 optimum ignition timing is performed. The switching air-fuel ratio is set to a value smaller than the steady-state lean operation air-fuel ratio set in the steady state of the 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 near the stoichiometric air-fuel ratio, and the ignition timing is retarded to reduce the engine output torque. If the target air-fuel ratio is equal to or higher than the switching air-fuel ratio while the control to match the required torque is performed, 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, it is possible to prevent the target air-fuel ratio from being set in the air-fuel ratio range in which the NOx concentration in the exhaust increases, to suppress the increase in the NOx concentration, and to prevent torque fluctuation by retarding the ignition timing. Can be.

  According to a third aspect of the present invention, in the vehicle control device according to the second aspect, the switching air-fuel ratio (AFLMT) is an allowable limit of a NOx concentration (CNOx) contained in exhaust gas discharged from the combustion chamber. (CNOxLMT) or less.

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

  According to a fourth aspect of the present invention, in the control device for a vehicle according to the second or third aspect, the ignition timing control means reduces the output torque (TRQA) of the engine when the correction by the correction means is performed. When the ignition timing (IGCMD) that matches the required torque (TRQCMD) is on the retard side from the retard limit value (IGRTDLMT), the ignition timing (IGCMD) is set to the optimal ignition timing (IGMAP). The correction means does not correct the target air-fuel ratio (AFCMD).

  According to this configuration, when the 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 output torque of the engine coincide with the required torque is delayed from the retard limit value. When it is on the corner side, control is performed to set the ignition timing to the optimal 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 (misfire or unstable combustion is caused), in that case, the fuel supply control is executed by directly applying the calculated target air-fuel ratio. This prevents torque fluctuation. Since the increase in the amount of NOx emission is limited to 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 is drivable by the engine (1) and the electric motor (61), and controls the electric motor (61). Means for setting the target air-fuel ratio (AFCMD) to the switching air-fuel ratio (AFLMT) 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 motor control means, when the correction is performed by the correction means, adjusts 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) is changed to the switching air-fuel ratio ( When the engine speed is equal to or higher than FLMT, control is performed so that the engine output torque compensation is not performed. The switched air-fuel ratio (AFLMT) is smaller than the steady-state lean operation air-fuel ratio (AFLN) set in the steady state of the lean operation and is theoretically smaller. It is characterized by being 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 electric motor is increased by the difference between the engine output torque and the required torque. Is increased while the target air-fuel ratio is equal to or higher than the switching air-fuel ratio, a control not to execute the 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 increases, and to prevent the increase in the NOx emission and the torque fluctuation while maintaining the ignition timing at the optimum 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. FIG. 4 is a diagram for explaining setting of a target air-fuel ratio according to an engine operation region defined by an engine speed (NE) and a required torque (TRQCMD). FIG. 4 is a diagram showing a relationship between an air-fuel ratio (AF) of an air-fuel mixture burning in a combustion chamber and a NOx concentration (CNOx) in exhaust gas downstream of an exhaust purification catalyst. 5 is a time chart for explaining an outline of air-fuel ratio switching transient control executed when switching a target air-fuel ratio from a stoichiometric air-fuel ratio to a predetermined lean air-fuel ratio in a state where a required torque is constant. 5 is a time chart for explaining an 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. 6 is a time chart for explaining control when the ignition timing reaches a retard limit value while retarding the ignition timing. Relationship between the gas-fuel ratio (GFR) under a constant engine speed (NE) and the torque conversion coefficient (KGFTRQ) corresponding to the thermal efficiency of the engine, and the engine speed (NE) under a constant gas-fuel ratio condition FIG. 6 is a diagram showing a relationship between the torque conversion coefficient (KGFTRQ). 5 is a flowchart of an air-fuel ratio switching transient control process (first embodiment). 9 is a flowchart of an IGRTD calculation process executed in the process of FIG. FIG. 10 is a diagram showing a map referred to in the processing of FIG. 9. 9 is a flowchart illustrating a modification of the process illustrated in FIG. 8. It is a figure which shows typically the structure of the drive device of the vehicle provided with an internal combustion engine and an electric motor as a prime mover. 9 is a time chart for explaining an 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 (second embodiment). It is a flowchart of an air-fuel ratio switching transient control process (2nd Embodiment). 15 is a flowchart of a TRQMOT calculation process executed in the process of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of a direct injection type internal combustion engine for driving a vehicle according to an embodiment of the present invention and a control device thereof. The vehicle of the present embodiment has an internal combustion engine (hereinafter referred to as “motor”) shown in FIG. 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 a combustion chamber. The operation of the injector 6 is controlled by an electronic control unit (hereinafter referred to as “ECU”) 5. An ignition plug 8 is mounted on each cylinder of the engine 1, and the ignition timing of the ignition plug 8 is controlled by the ECU 5.

  The ECU 5 includes an intake air amount sensor 21 for detecting an intake air amount GAIR of the engine 1, an intake temperature sensor 22 for detecting an intake temperature TA, a throttle valve opening sensor 23 for detecting a throttle valve opening TH, and an intake pressure PBA. An intake pressure sensor 24 for detecting, a cooling water temperature sensor 25 for detecting an engine cooling water temperature TW, a crank angle position sensor 26 for detecting a rotation angle of a crankshaft (not shown) of the engine 1, an accelerator of a vehicle driven by the engine 1 An accelerator sensor 27 for detecting the pedal operation amount AP and other sensors (for example, a vehicle speed sensor, an atmospheric pressure sensor, and the like) not shown are connected, and detection signals of 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 this pulse signal is used for various timing controls such as fuel injection timing, ignition timing, and the like, and detection of the engine speed NE. You.

  An exhaust gas 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 exhaust manifold communicating with each cylinder, and the exhaust passage 10 detects the oxygen concentration in the exhaust gas. Thus, the air-fuel ratio AF of the air-fuel mixture burning in the combustion chamber is detected. Although not shown, the engine 1 includes a well-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 ECU 5 controls the fuel injection by the injector 6 and the ignition plug 8 according to the engine operating state (mainly, the engine speed NE and the required torque TRQCMD). And the intake air amount is controlled by the actuator 3a and the throttle valve 3. 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 such 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 a first region RST (stoichiometric operation region) corresponding to a low-speed low-medium load region and a medium-high speed low-load region, and a second region corresponding to a medium-speed medium load region. (Lean operation region) In RLEAN, a predetermined lean air-fuel ratio AFLN is set. In a third region RSTE corresponding to a high load side and a high rotation side region of the second region RLEAN, a stoichiometric air-fuel ratio AFST is set, and In a fourth region RRICH corresponding to a region on the higher load side than RSTE, the air-fuel ratio AFRC is set to be richer than the stoichiometric air-fuel ratio AFST. 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 exhaust gas (feed gas) discharged from the combustion chamber is lower than an allowable limit and which can realize stable combustion, for example, "30".

  In the present embodiment, as shown by arrows A and B, when the target air-fuel ratio AFCMD is switched between the first region RST and the second region RLEAN with the required torque TRQCMD being 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”) for suppressing an increase in NOx emission is executed.

  FIG. 3 is a diagram showing the relationship between the air-fuel ratio AF of the air-fuel mixture burning in the combustion chamber and the NOx concentration CNOx in the exhaust gas on the downstream side of the exhaust purification catalyst 11. In order to make the NOx concentration CNOx equal to or less than the allowable limit CNOxLMT, a first air-fuel ratio AFSTL (for example, “16”) slightly leaner than the stoichiometric air-fuel ratio AFST to a switching air-fuel ratio AFLMT (for example, about 25) is used. It is necessary to avoid setting the target air-fuel ratio AFCMD in the lean air-fuel ratio range RLN1. 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 above transient control. FIG. 4 shows a required torque TRQCMD, a lean operation request flag FLEAN, a cylinder intake air amount in the transient control when shifting from the stoichiometric operation to the lean operation. Changes in GAIRCYL and target intake air amount GAIRCMD (target value of cylinder intake air amount GAIRCYL), steady-state target air-fuel ratio AFCMDSS and target air-fuel ratio AFCMD, and ignition timing IGCMD (defined to increase as the angle advances). 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 lean operation request flag FLEAN is changed from “0” to “1” at time t0 while the required torque TRQCMD is fixed to the constant value TRQ0, the target intake air amount GAIRCMD becomes as shown in FIG. As indicated by the dashed line, the air amount GAST during the stoichiometric operation increases stepwise 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 dashed line shown in FIG. 4D indicates the steady-state 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 accordance with the increase in the cylinder intake air amount GAIRCYL. There is a need. When the target air-fuel ratio AFCMD is increased in response to the increase in the cylinder intake air amount GAIRCYL, as indicated by a dashed line in FIG. 4D, the target air-fuel ratio AFCMD is changed to the air of the first lean air-fuel ratio range RLN1 shown in FIG. Since the fuel ratio is set, in this embodiment, the stoichiometric air-fuel ratio AFST is maintained until time t1, as shown by the solid line in FIG. 4D. At time t1, the target air-fuel ratio AFCMD is set to the switching air-fuel ratio AFLMT, and thereafter, the air-fuel ratio gradually increasing control for increasing the target air-fuel ratio AFCMD in response to the increase in the cylinder intake air amount GAIRCYL is executed. 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 time t1, the cylinder intake air amount GAIRCYL increases while the target air-fuel ratio AFCMD is maintained at the stoichiometric air-fuel ratio AFST, so that the ignition timing IGCMD is reduced as indicated by the 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, the ignition timing IGCMD is gradually retarded from the optimum ignition timing IGST during the stoichiometric operation, as shown by the solid line in the figure, so that the actual output torque TRQA matches the required torque TRQCMD. Perform 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 stepwise as shown by a broken line in FIG. The intake air amount GAIRCYL gradually decreases as shown by the solid line. The dashed line shown in FIG. 5D indicates 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 decreases in response to the decrease in the cylinder intake air amount GAIRCYL. It needs to be reduced. When the target air-fuel ratio AFCMD is decreased in response to the decrease in the cylinder intake air amount GAIRCYL between the times t11 and t12, as indicated by the one-dot chain line in FIG. 5D, the target air-fuel ratio AFCMD becomes the first value shown in FIG. Since the air-fuel ratio in the lean air-fuel ratio range RLN1 is set, in this embodiment, as shown by the solid line in FIG. 5D, cylinder intake is performed until the target air-fuel ratio AFCMD reaches the switching air-fuel ratio AFLMT until time t11. The air-fuel ratio gradual decrease control for decreasing the target air-fuel ratio AFCMD is executed in response to the decrease in the air amount GAIRCYL, and after time t11, the target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST. 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-state target air-fuel ratio AFCMDSS, the transient control ends.

  Between time t11 and time t12, the cylinder intake air amount GAIRCYL decreases while the target air-fuel ratio AFCMD is maintained at the stoichiometric air-fuel ratio AFST, so that the ignition timing IGCMD is set to the cylinder intake air amount 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 the figure, the ignition timing IGCMD is retarded to perform the ignition timing retard control that matches the actual output torque TRQA with the required torque TRQCMD.

  In the transient control shown in FIG. 4, the ignition timing IGCMD is retarded during a period from time t0 to t1. However, if the ignition timing IGCMD is excessively retarded, combustion may become unstable or misfire may occur. Therefore, the ignition timing IGCMD is controlled so as not to be set on the retard side from the retard limit value IGRTDLMT calculated according to 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 control when the ignition timing IGCMD reaches the retard limit value IGRTDLMT when the ignition timing IGCMD is retarded (prior to time t1). The transition of the air-fuel ratio AFCMD and the ignition timing IGCMD are 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 for changing to the optimum ignition timing corresponding to the amount GAIRCYL is performed. In this transient control, the target air-fuel ratio AFCMD at which the NOx concentration CNOx becomes slightly higher is temporarily applied, but since it is an extremely short time, deterioration of the exhaust characteristics is negligible.

Next, a method of 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 equation (1).
TRQCMD = GFUEL × KGFTRQ (1)

  Here, KGFTRQ is a torque conversion coefficient for converting the fuel amount into torque. Equation (1) is based on the assumption that the ignition timing IGCMD is set to the optimum ignition timing IGMAP. The optimal ignition timing IGMAP is the maximum torque ignition timing at which the output torque of the engine 1 becomes maximum, and the most retarded value (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 the ignition timing 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 equation (2) is a mass, and the fuel injection amount GFUEL is converted into a valve opening time TOUT of the injector 6 according to the fuel pressure PF and the fuel density using a known method. The fuel amount 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 KGFTRQ according to these parameters. Although required, in the present 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 a dilution degree parameter defined by the following equation (3). It is calculated using a single map.
GFR = (GAIRCYL + GEGR) / GFUEL (3)
Here, GEGR is a recirculated exhaust gas amount (mass) that is an exhaust gas amount (including an internal exhaust gas recirculated amount) that is recirculated into the combustion chamber, and a known method for calculating the recirculated exhaust gas amount GEGR (for example, Japanese Patent No. 5270008). ) 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 constant engine speed NE. By setting a single KGFTRQ map in advance according to the gas-fuel ratio GFR and the engine speed NE, a plurality of maps corresponding to the air-fuel ratio AF, the exhaust gas recirculation rate REGR, and the engine speed NE are used. Without this, it is possible to accurately calculate the fuel injection amount GFUEL that matches the actual output torque TRQA with the required torque TRQCMD. The KGFTRQ map is set so that the torque conversion coefficient KGFTRQ increases as the gas-fuel ratio GFR increases. 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 the condition that the gas-fuel ratio GFR is constant. As shown in this figure, the torque conversion coefficient KGFTRQ becomes maximum when the engine rotational speed NE is at the mid-range rotational speed NEMX (for example, 3000 rpm), and decreases as the engine rotational speed NE decreases at a lower rotational speed than the mid-range rotational speed NEMX. The torque conversion coefficient KGFTRQ decreases because the time per revolution increases and the efficiency 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 that the torque conversion coefficient KGFTRQ decreases.

FIG. 8 is a flowchart of an 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, in a four-cylinder engine, every 180 degrees of crank angle). 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, a target intake air amount GAIRCMD is calculated according to the required torque TRQCMD and the lean operation request flag FLEAN. The throttle valve opening TH is controlled by an intake air amount control process (not shown) such that the cylinder intake air amount GAIRCYL matches the target intake air amount GAIRCMD.

In step S14, a cylinder intake air amount GAIRCYL is calculated using the detected intake air amount GAIR. To calculate the cylinder intake air amount GAIRCYL, a known method (for example, Japanese Patent No. 5118247) can be applied. In step S15, the recirculated exhaust gas amount GEGR is calculated using the detected intake air amount GAIR and the detected intake pressure PBA. 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 of Expression (3) with the previously 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 provisional fuel injection amount GFULTMP is calculated using the following equation (2a). calculate. Expression (2a) is obtained by replacing GFUEL in Expression (2) with GFULTMP.
GFULTMP = TRQCMD / KGFTRQ (2a)

In step S19, the provisional target air-fuel ratio AFCMDMTMP 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 provisional target air-fuel ratio AFCMDMTMP is smaller than the switching air-fuel ratio AFLMT, and 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 to t11, the target air-fuel ratio AFCMD is set to the provisional target air-fuel ratio AFCMDMTMP, the fuel injection amount GFUEL is set to the provisional fuel injection amount GFULTMP (step S25), and the ignition timing IGCMD is set to the optimal ignition timing IGMAP. (Step S26). The optimum 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, in the period from time t0 to t1 in FIG. 4 or the period from time t11 to t12 in FIG. 5, the target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST. (Step S21). Since the target air-fuel ratio AFCMD is set to the stoichiometric air-fuel ratio AFST instead of the tentative target air-fuel ratio AFCMDMTMP, in step S22, the tentative fuel injection amount GFULTMP is applied to the following equation (5) to calculate the fuel injection amount GFUEL.
GFUEL = (AFCMDMTMP / AFCMD) × GFUELTMP (5)

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

  In step S31 of FIG. 9, the gas fuel ratio GFR is calculated by applying the fuel injection amount GFUEL calculated in step S22 to the above equation (3). In step S32, similarly to 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)

When the ignition timing IGCMD is retarded from the optimal ignition timing IGMAP, and the torque reduction rate KIGTRQDN is used when the actual output torque TRQA matches the required torque TRQCMD, the required torque TRQCMD can be expressed by the following equation (7). By transforming equation (7), equation (6) is obtained. GAIRCYL / AFCMD in equation (7) is equal to the fuel injection amount GFUEL.
TRQCMD = GAIRCYL / AFCMD × KGFTRQ × KIGTRQDN
(7)

  In step S34, the KIGTRQDN map shown in FIG. 10 is inversely searched according to the torque reduction rate KIGTRQDN and the engine speed NE to calculate the retard amount IGRTD. In FIG. 10, curves L11 to L13 respectively correspond to predetermined engine speeds NE11, NE12, and NE13 (NE11 <NE12 <NE13). The KIGTRQDN map is set such that the torque reduction rate KIGTRQDN decreases as the retard amount IGRTD increases, and the torque reduction rate KIGTRQDN increases as the engine speed NE increases, and the torque reduction rate KIGTRQDN is “ 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. 8 and 9.

  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 driver of the vehicle, 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 injection valve coincides with the target air-fuel ratio AFCMD. A gas-fuel ratio GFR as a dilution degree parameter indicating a ratio of a gas amount and a fuel in the combustion chamber is calculated using a cylinder intake air amount GAIRCYL, a recirculation exhaust amount GEGR, and a fuel injection amount GFUEL indicating a new air amount in the combustion chamber. In the air-fuel ratio switching transient control for switching the air-fuel ratio AF 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. Although the actual output torque TRQA of the engine 1 is basically proportional to the fuel injection amount GFUEL, the thermal efficiency changes depending on the engine speed NE, the air-fuel ratio AF, and the recirculation exhaust gas GEGR (exhaust recirculation rate REGR). In order to make the actual output torque TRQA accurately coincide with the required torque TRQCMD, it is necessary to increase 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 represented by one curve as shown in FIG. 7A under the condition that the engine speed NE is constant. It has been 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 and the exhaust gas recirculation rate REGR, and the engine speed NE are obtained. , The calculation of the fuel injection amount GFUEL that matches the actual output torque TRQA with the required torque TRQCMD can be performed with high accuracy. As a result, it is possible to execute the fuel supply control in the transient state with high accuracy while greatly reducing the number of map setting steps in the design stage.

  When the provisional 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 stoichiometric air-fuel ratio AFST, and the actual output torque TRQA Is controlled such that the ignition timing IGCMD is retarded from the optimal ignition timing IGMAP such that the ignition timing IGCMD becomes equal to the required torque TRQCMD. On the other hand, when the provisional target air-fuel ratio AFCMDMTMP is equal to or higher than the switching air-fuel ratio AFLMT, the target air-fuel ratio AFCMD is set to the provisional target air-fuel ratio AFCMDMTMP, and control is performed to set the ignition timing IGCMD to the optimum 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 a steady state of the lean operation and larger than a stoichiometric air-fuel ratio AFST. That is, when the provisional target air-fuel ratio AFCMDMTMP 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. On the other hand, when the provisional target air-fuel ratio AFCMDMTMP is equal to or greater than the switching air-fuel ratio AFLMT while the control for matching the actual output torque TRQA to the required torque TRQCMD is performed, the provisional target air-fuel ratio AFCMD corresponding to the cylinder intake air amount GAIRLCYL remains unchanged. The ignition timing IGCMD is controlled to the optimum ignition timing IGMAP while being applied as the air-fuel ratio AFCMD. Therefore, it is possible to prevent the target air-fuel ratio AFCMD from being set to the air-fuel ratio in the first lean air-fuel ratio range RLN1 where the NOx concentration CNOx in the exhaust is increased, to suppress the increase in the NOx concentration CNOx, and to increase the ignition timing. It is possible to prevent torque fluctuation by retarding IGCMD.

  As shown in FIG. 3, the switching air-fuel ratio AFLMT is not more than the allowable limit CNOxLMT within a range in which the NOx concentration CNOx contained in the exhaust downstream of the exhaust purification catalyst 11 increases in response to the decrease in the air-fuel ratio. Since the target air-fuel ratio AFCMD is set to a value between the stoichiometric air-fuel ratio AFST and the switching air-fuel ratio AFLMT, that is, a value in a range where the NOx concentration CNOx increases, the NOx concentration CNOx is prevented. Can be suppressed to the allowable limit CNOxLMT or less. In a range where the NOx concentration CNOx increases in response to the decrease in the air-fuel ratio (a range leaner than the air-fuel ratio at which the maximum NOx concentration becomes the maximum shown in FIG. 3), the exhaust purification catalyst 11 has no purification ability. Since the CNOx is equal to the NOx concentration on the upstream side of the exhaust purification catalyst 11, that is, the NOx concentration in the exhaust gas discharged from the combustion chamber of the engine 1, the switching air-fuel ratio AFLMT is the same as that in the exhaust gas discharged from the combustion chamber. It can be defined as the minimum air-fuel ratio at which the NOx concentration falls below the allowable limit CNOxLMT.

[Modification]
FIG. 11 is a flowchart showing a modified example of the process shown in FIG. The processing in FIG. 11 is obtained by adding step S27 to the processing in FIG. Step S27 is a step for implementing the control described with reference to FIG. 6, and determines 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). No), and if the answer is affirmative (YES), the flow 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 AFCMDMTMP corresponding to the cylinder intake air amount GAIRCYL. In addition, transient control is performed to set the ignition timing IGCMD to the optimal ignition timing IGMAP corresponding to the current cylinder intake air amount GAIRCYL.

  In this modified example, when the temporary target air-fuel ratio AFCMDTMP is smaller than the switching air-fuel ratio AFLMT, when the ignition timing IGCMD for making the actual output torque TRQA coincide with the required torque TRQCMD is on the retard side from the retard limit value IGRTDLMT, Control is performed to set the air-fuel ratio AFCMD to the temporary target air-fuel ratio AFCMDTMP and set the ignition timing IGCMD to the optimum ignition timing IGMAP. Since the ignition timing IGCMD cannot be controlled to the retard side from the retard limit value IGRTDLMT (misfire or instability of combustion is caused), in this case, the fuel supply using the calculated tentative target air-fuel ratio AFCMDMTMP as it is. Executing the control prevents torque fluctuation.

  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 comprises target air-fuel ratio calculation means, dilution degree parameter calculation means, ignition timing control. Means and correction means.

[Second embodiment]
This embodiment is one in which the present invention is applied to a vehicle including an engine 1 and an electric motor as prime movers, and is the same as the first embodiment except for the points described below.

  FIG. 12 schematically shows the entire configuration of the vehicle drive device. This vehicle drive device includes the above-described engine 1, 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 a transmission 52, and is configured to drive a driving wheel 56 via an output shaft 53 of the transmission 52, a differential gear mechanism 54, and a driving shaft 55. I have. 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 including an odd-numbered stage clutch and an even-numbered stage clutch corresponding to each of the odd-numbered gear and the even-numbered gear. According to the vehicle drive device, it is possible to perform engine mode traveling in which only the engine 1 operates as a prime mover, and hybrid mode traveling in which both the engine 1 and the motor 61 operate as prime movers. By setting both clutches in the disengaged state, it is also possible to perform an electric mode traveling in which only the motor 61 operates as a prime mover.

  When the motor 62 is driven with a positive driving torque, that is, when the motor 61 is driven by the power output from the high-voltage battery 63, the 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 performs a regenerative operation, 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, controls the operation of the motor 61, and controls charging and discharging of the high-voltage battery 63. The ECU 30 controls the operation of the motor 61 in addition to the functions of the ECU 5 in the first embodiment. The ECU 30 is configured by, for example, connecting the ECU 5 of the first embodiment and a 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, similarly to FIG. I have. In FIG. 13A, a constant required torque TRQCMD is indicated by a broken line, and a solid line indicates a transition of the actual output torque TRQA. The transitions of the target intake air amount GAIRCMD and the cylinder intake air amount GAIRCYL shown in FIG. 13C are the same as those shown in FIG. FIG. 13F shows the transition of the motor required torque TRQMOT.

  In the present 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 stoichiometric air-fuel ratio AFST to the switching air-fuel ratio AFLMT. Therefore, 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, since the actual output torque TRQA increases in response to the increase in the cylinder intake air amount GAIRCYL, the required motor torque TRQMOT is reduced by the increase.

  The one-dot chain line shown in FIG. 13D indicates the provisional target air-fuel ratio AFCMDMTMP corresponding to the cylinder intake air amount GAIRCYL. When the provisional target air-fuel ratio AFCMDMTMP reaches the switching air-fuel ratio AFLMT at time t21, the actual output torque TRQA Becomes equal to the required torque TRQCMD, the motor required torque TRQMOT is set to “0”, and thereafter, the air-fuel ratio gradually increasing control for increasing the target air-fuel ratio AFCMD in response to the increase in the cylinder intake air amount GAIRCYL is executed. At time t22, when the cylinder intake air amount GAIRCYL reaches the target intake air amount GAIRCMD, the transient control ends. 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 according to the present embodiment. This processing is obtained by deleting steps S21, S23, and S24 of the processing shown in FIG. 8 and adding steps S41 to S43.

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 in step S22, the fuel injection corresponding to the target air-fuel ratio AFCMD (switching air-fuel ratio AFLMT). Calculate the quantity GFUEL. In step S42, a TRQMOT calculation process shown in FIG. 15 is executed to calculate the required motor torque TRQMOT.
If the answer to step S20 is negative (NO), the motor required 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. I 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 required motor torque TRQMOT is calculated by the following equation (9).
TRQMOT = TRQCMD-TRQENGEST (9)

  As described above, in the present embodiment, when the provisional target air-fuel ratio AFCMDMTMP 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 When engine output torque compensation is set to the difference between the estimated output torque TRQENGEST of the engine 1 and the required torque TRQCMD, the target air-fuel ratio AFCMD is set to the temporary target air-fuel ratio AFCMD when the temporary target air-fuel ratio AFCMDMTMP is equal to or greater than the switching air-fuel ratio AFLMT. Control is performed in which AFCMDMTP is set and the motor 61 does not execute engine output torque compensation. Therefore, it is possible to prevent the target air-fuel ratio AFCMD from being set within the first lean air-fuel ratio range RLN1 where the NOx emission increases, and to increase the NOx emission while maintaining the ignition timing IGCMD at the optimum ignition timing IGMAP. Torque fluctuation can be prevented.

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

  Note that the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above-described embodiment, when the temporary target air-fuel ratio AFCMDMTP 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. Instead of the AFST itself, a value near the stoichiometric air-fuel ratio AFST may be set. The range in the vicinity of the stoichiometric air-fuel ratio is, for example, from the stoichiometric air-fuel ratio AFST to the air-fuel ratio AFSTL shown in FIG. 3 (a range in which the NOx concentration CNOx becomes equal to or less than the allowable limit CNOxLMT).

  Further, in the above-described second embodiment, an example has been described in which the motor required torque TRQMOT at the start of the transient control is “0”. However, when the motor 61 is being 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 is shown in which the present invention is applied to a control device for a vehicle including, as a prime mover, an internal combustion engine having a direct injection injector that injects fuel into a combustion chamber. However, the present invention injects fuel into an intake port. The present invention is also applicable to a control device for a vehicle including, as a prime mover, an internal combustion engine having a port injection injector, or an internal combustion engine having 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 (requested torque setting means, target air-fuel ratio calculation means, fuel amount control means, dilution degree parameter calculation means, ignition timing control means, correction means, electric motor control means)
6. Injector (fuel amount control means)
Reference Signs List 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 motor 62 power drive unit (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 be capable of performing a lean operation of setting an air-fuel ratio of a mixture that burns in the engine to a lean air-fuel ratio leaner than a stoichiometric air-fuel ratio. In the control device of the vehicle
Request torque setting means for setting a request torque of the engine based on a request of a driver of the vehicle,
Target air-fuel ratio calculation 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 an amount of fuel supplied to a combustion chamber of the engine such that an air-fuel ratio of the air-fuel mixture matches the target air-fuel ratio;
Dilution degree parameter calculation means for calculating a dilution degree parameter indicating the ratio of the gas amount and the fuel in the combustion chamber,
The dilution degree parameter calculating means,
Calculating the dilution degree parameter using a parameter indicating the fresh air amount, the recirculated exhaust gas amount, and the fuel amount in the combustion chamber,
In a transient state in which the fuel amount control means switches the air-fuel ratio of the air-fuel mixture between the lean air-fuel ratio and the stoichiometric air-fuel ratio, a torque conversion coefficient for converting the fuel amount into the output torque of the engine is: A control device for a vehicle, wherein the control unit calculates the fuel amount using the required torque and the torque conversion coefficient, in accordance with the dilution degree parameter and the engine speed . Ignition timing control means for controlling the ignition timing of the engine;
Correction means for correcting the target air-fuel ratio to a value near the stoichiometric air-fuel ratio when the target air-fuel ratio calculated by the target air-fuel ratio calculation means is smaller than the switching air-fuel ratio in the transient state;
The ignition timing control means, when the correction by the correction means is performed, retards the ignition timing from the optimum ignition timing so that the output torque of the engine matches the required torque, and the target air-fuel ratio is When the switching air-fuel ratio is equal to or more than the set the ignition timing to the optimal ignition timing,
The optimal ignition timing is an ignition timing that maximizes the output torque of the engine,
2. The control device for a vehicle according to claim 1, wherein the switching air-fuel ratio is set to a value smaller than a steady-state lean operation air-fuel ratio set in a steady state of the lean operation and larger than a stoichiometric 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 exhaust gas discharged from the combustion chamber is equal to or less than an allowable limit. The ignition timing control means, when the correction by the correction means is performed, when the ignition timing for matching the output torque of the engine to the required torque is on the retard side from the retard limit value, the ignition timing is controlled. Setting the optimal ignition timing,
The control device according to claim 2, wherein the correction unit does not correct the target air-fuel ratio. The vehicle is drivable by the engine and the electric motor,
Motor control means for controlling the motor,
Correcting 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 executes engine output torque compensation to increase 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 increased. When the switching air-fuel ratio is equal to or more than the control that does not execute the engine output torque compensation,
2. The control device for a vehicle according to claim 1, wherein the switching air-fuel ratio is set to a value smaller than a steady-state lean operation air-fuel ratio set in a steady state of the lean operation and larger than a stoichiometric air-fuel ratio.

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