JP2018178967A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of eliminating a difference in torque responsiveness between transition from a supercharging lean operation to a supercharging stoichiometric operation, and transition from a non-supercharging stoichiometric operation to the supercharging stoichiometric operation.SOLUTION: Target setting means sets a target opening and the like of a throttle valve so that a change of actual torque approaches a change of torque realized when the target torque changes during execution of a non-supercharging stoichiometric operation, when the target torque changes from first target torque in a supercharging lean operation region to second target torque in a supercharging stoichiometric operation region. The target setting means includes: target air-fuel ratio setting means for gradually changing a target air-fuel ratio from a lean air-fuel ratio to a stoichiometric air-fuel ratio according to the change of target torque; and target opening setting means estimating a change of an intake amount (estimated air intake amount during lean prohibition) realized when the target torque changes, and setting the target opening to a closing side so that the change of estimated intake amount is realized.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a control device of an internal combustion engine. More particularly, the present invention relates to a control device for an internal combustion engine that can change the boost pressure of intake air by a supercharger and can change the air-fuel ratio between stoichiometric and lean.

  There are various operation modes in an internal combustion engine that can change the supercharging pressure by the supercharger and can change the air-fuel ratio between stoichiometric and lean. Supercharged lean operation refers to an operation mode in which the air-fuel ratio is made lean while driving the turbocharger, and supercharged stoichiometric operation refers to an operation mode in which the air-fuel ratio is made stoichiometric while driving the turbocharger. The feed lean operation refers to an operation mode in which the air fuel ratio is made lean without driving the supercharger, and the non-supercharged stoichiometric operation refers to an operation mode in which the air fuel ratio is made stoichiometric without driving the supercharger.

  Here, for example, it is assumed that the driving mode is switched from the supercharging lean operation to the supercharging stoichiometric operation in response to the driver's request for acceleration while the supercharging lean operation is being performed. In this case, the air-fuel ratio switches from lean to stoichiometry in response to the request for acceleration. At this time, the supercharging pressure is maintained higher than the atmospheric pressure because the supercharger is already driven at the time of the acceleration request. For this reason, the actual torque of the internal combustion engine increases with a relatively small delay relative to the acceleration request.

  Next, for example, while the non-supercharged stoichiometric operation is being performed, the operation mode changes from the non-supercharged stoichiometric operation to the supercharged stoichiometric operation in response to an acceleration request similar to that in the previous example from the driver. Assume the case of switching to. In this case, since the supercharger is stopped when acceleration is requested, the supercharging pressure is about atmospheric pressure, which is lower than that in the above example. For this reason, the actual torque of the internal combustion engine is increased later than in the above example by the response delay of the turbocharger (so-called turbo lag). As shown in these two examples, if the driving mode at the time the driver performs the acceleration operation is different, the responsiveness of the torque is different even in the same acceleration operation, and the driver may feel discomfort.

  By the way, the technique which eliminates the discomfort of the driver resulting from the supercharging delay by a supercharger by patent document 1, 2 is shown. According to the technology of Patent Document 1, when the operation mode is switched from supercharged lean operation to supercharged stoichiometric operation in response to an acceleration request from the driver, the air-fuel ratio is immediately changed from lean to stoichiometric according to the request from the driver. The problem is that if this is changed, large torque fluctuations may occur. According to the technique of Patent Document 1, when the operation mode is switched from supercharged lean operation to supercharged stoichiometric operation, the target torque is increased immediately in response to the driver's request by multiplying the target torque by the rate limit. Instead of gradually rising under certain limits.

  Further, for example, Patent Document 2 shows a technique in which the problem of the supercharge delay larger in lean operation occurs in the stoichiometric operation. According to the technology of Patent Document 2, the acceleration characteristic in the stoichiometric operation and the acceleration characteristic in the lean operation are made equal by performing control of the throttle valve so that the rise of torque becomes quicker in the stoichiometric operation.

JP, 2015-117604, A JP, 2007-263127, A

  Here, in order to eliminate the difference in torque responsiveness between the transition from supercharged lean operation to supercharged stoichiometric operation and the transition from non-supercharged stoichiometric operation to supercharged stoichiometric operation, Patent Document 1, 1 It is conceivable to apply the two techniques.

  However, in the technique of Patent Document 1, since the torque is simply rate-limited, the driver's feeling of discomfort is somewhat reduced, but the difference in torque responsiveness between the two operation modes is eliminated. It does not come.

  Further, as described above, according to the technology of Patent Document 2, the throttle valve is controlled to accelerate the rise of torque in the stoichiometric operation on the premise that the supercharging delay larger in the stoichiometric operation occurs than in the lean operation. The rise of torque at the time of stoichiometric operation and at the time of lean operation is made equal. However, for example, when the throttle valve is already fully opened, the control of the throttle valve can not accelerate the rise of torque. Therefore, the technology of Patent Document 2 can not always be applied.

  The present invention is a control device for an internal combustion engine that can eliminate the difference in torque responsiveness between the transition from supercharged lean operation to supercharged stoichiometric operation and the transition from non-supercharged stoichiometric operation to supercharged stoichiometric operation. Intended to provide.

  (1) In an internal combustion engine (for example, an engine 1 described later), the supercharging pressure of intake air can be changed by a supercharger (for example, a supercharger 8 described later), and the air fuel ratio can be changed between lean and stoichiometric. It is. Further, a control device (for example, a control device 2 described later) of this internal combustion engine calculates target torque for the internal combustion engine according to a request, and target torque calculation means (for example, ECU 7 described later) When within the lean operation range, the supercharge lean operation is performed to make the air-fuel ratio lean while driving the supercharger, and the target torque is higher on the torque side than the supercharge lean operation region. Operation mode switching means (e.g., ECU 7 described later) which executes the supercharging stoichiometric operation to make the air-fuel ratio stoichiometric while driving the supercharger when in the stoichiometric operation region, and the lean operation prohibition condition is satisfied If not, even if the target torque is in the supercharging lean operating region, the non-supercharged stoichiometric operation is performed to make the air-fuel ratio stoichiometric without driving the supercharger. The lean operation prohibiting means (for example, the ECU 7 described later), and a transition period from the first target torque in the supercharge lean operation region to the second target torque in the supercharge stoichiometric operation region as the actual torque. If the target torque changes from the first target torque to the second target torque during execution of the supercharging lean operation, a change in actual torque during the transition period is the non-supercharged stoichiometric operation. Target setting means (e.g., an ECU 7 described later) for setting the target opening degree of the throttle valve and the target air-fuel ratio so as to approach the change in torque realized when the change in target torque occurs during execution of A torque control unit (e.g., an ECU 7 described later) for controlling the opening degree of the throttle valve and the air-fuel ratio so that the target opening degree and the target air-fuel ratio are realized; Target air-fuel ratio setting means (for example, an ECU 7 described later) which gradually changes the target air-fuel ratio from lean to stoichiometry in response to the change of the target torque from the first target torque to the second target torque. And the intake amount change realized when the target torque change occurs during execution of the non-supercharged stoichiometric operation in consideration of the supercharging delay, and the estimated intake amount change is realized Thus, a target opening setting means (for example, an ECU 7 described later) for setting the target opening on the closing side with respect to the reference opening is characterized.

  (2) A control device (for example, the control device 2 described later) of the internal combustion engine (for example, the engine 1 described later) calculates target torque for the internal combustion engine according to a request. And, if the target torque is in the supercharging lean operating range, the supercharging lean operation is performed to make the air-fuel ratio lean while driving the supercharger, and the target torque is the supercharging lean operation Operation mode switching means (for example, the ECU 7A described later) that executes a supercharged stoichiometric operation that makes the air-fuel ratio stoichiometric while driving the supercharger when within a supercharged stoichiometric operation region on the higher torque side than the region And when the lean operation prohibition condition is satisfied, the air / fuel ratio is made stoichiometric without driving the supercharger even if the target torque is within the supercharging lean operation range. Supercharged lean operation prohibiting means for executing non-supercharged stoichiometric operation and transition from actual target torque from the first target torque in the supercharged lean operation region to the second target torque in the supercharged stoichiometric operation region A period is defined, and when the target torque changes from the first target torque to the second target torque during execution of the supercharging lean operation, a change of the actual torque in the transition period is the non-supercharging. Target setting means (for example, ECU 7A described later) for setting a target ignition timing and a target air-fuel ratio of the internal combustion engine so as to approach a change in torque realized when a change in the target torque occurs during the stoichiometric operation. And torque control means (for example, an ECU 7A described later) for controlling the ignition timing and the air-fuel ratio such that the target ignition timing and the target air-fuel ratio are realized. The target setting means gradually changes the target air-fuel ratio from lean to stoichiometric in response to the change of the target torque from the first target torque to the second target torque. And the torque change realized when the change in the target torque occurs during execution of the non-supercharged stoichiometric operation, in consideration of the supercharging delay, the estimated torque change is realized. As described above, it is characterized by comprising target ignition timing setting means (for example, an ECU 7A described later) for setting the target ignition timing on the retarded side with respect to the reference ignition timing.

  (3) In this case, the target air-fuel ratio setting means sets the target air-fuel ratio to be lean before the target ignition timing setting means starts to set the target ignition timing on the retarded side of the reference ignition timing. It is preferable to start changing to stoichiometry.

  (1) A case where the target torque changes from the first target torque in the supercharge lean operation region to the second target torque in the supercharge stoichiometric operation region by performing the acceleration operation during execution of the supercharge lean operation Suppose. In this case, the operation mode shifts from supercharged lean operation to supercharged stoichiometric operation. On the other hand, when the lean operation prohibition condition is satisfied, the execution of the supercharged lean operation is prohibited, and instead, the non-supercharged stoichiometric operation is performed. Therefore, by performing the same acceleration operation, the operation mode may shift from the non-supercharged lean operation to the supercharged stoichiometric operation. For this reason, the actual torque is the first target torque from the first target torque depending on whether the supercharging lean operation was performed or the non-supercharged stoichiometric operation was performed at the time of performing the acceleration operation despite the same acceleration operation. The problem that the response characteristic of a torque will change may arise in the transient period until it reaches 2 target torque.

  With respect to such problems, in the present invention, when the target torque changes from the first target torque to the second target torque during execution of the supercharging lean operation, the change of the actual torque during the transition period is a non-supercharging stoichiometric condition. The target opening of the throttle valve and the target air-fuel ratio are set so as to approach the change in torque realized when the target torque changes as described above during operation, and the target opening and target air-fuel ratio are realized Control the throttle opening and the air-fuel ratio so that Here, in particular, the target air-fuel ratio setting means of the present invention gradually changes the target air-fuel ratio in the transition period from lean to stoichiometry in response to the target torque changing from the first target torque to the second target torque. The response from the air-fuel ratio operation to the actual torque is faster than the response from the throttle valve operation to the actual torque. Therefore, the response characteristic of the actual torque in the initial period of the transition period can be made close to the torque response characteristic at the time of acceleration from the non-supercharged stoichiometric operation. Further, the target opening setting means of the present invention estimates the intake amount change realized when the target torque changes as described above during execution of the non-supercharged stoichiometric operation, taking into consideration the presence of the supercharging delay. Further, the target opening is set on the closing side (that is, the torque reduction side) with respect to the reference opening so that the estimated intake amount change is realized. As a result, it is possible to make the response characteristic of the actual torque in the later period which can not be handled by the operation of the air-fuel ratio in the transition period close to the response characteristic at the time of acceleration from the non-supercharged stoichiometric operation. As described above, according to the present invention, the response characteristic of the actual torque during the transition period from the supercharging lean operation to the supercharging stoichiometric operation, the torque response at the transition from the non-supercharged stoichiometric operation to the supercharged stoichiometric operation Since the characteristics can be approximated, it is possible to eliminate the difference in torque response between the two transitions. In addition, since the driver can always obtain the same torque response regardless of the type of the operation mode being executed at the time of performing the acceleration operation, there is no sense of incongruity, and therefore, the productability can be improved.

  (2) The target air-fuel ratio setting means of the present invention gradually changes the target air-fuel ratio in the transition period from lean to stoichiometry in response to the target torque changing from the first target torque to the second target torque. The response from the air-fuel ratio operation to the actual torque is faster than the response from the throttle valve operation to the actual torque. Therefore, the response characteristic of the actual torque in the initial period of the transition period can be made close to the torque response characteristic at the time of acceleration from the non-supercharged stoichiometric operation. Further, the target ignition timing setting means of the present invention estimates a torque change realized when the target torque changes as described above during execution of the non-supercharged stoichiometric operation, in consideration of the presence of the supercharging delay, Further, the target ignition timing is set on the retarded side (that is, the torque reduction side) with respect to the reference ignition timing so that the estimated torque change is realized. As a result, it is possible to make the response characteristic of the actual torque in the later period which can not be handled by the operation of the air-fuel ratio in the transition period close to the response characteristic at the time of acceleration from the non-supercharged stoichiometric operation. As described above, according to the present invention, the response characteristic of the actual torque during the transition period from the supercharging lean operation to the supercharging stoichiometric operation, the torque response at the transition from the non-supercharged stoichiometric operation to the supercharged stoichiometric operation Since the characteristics can be approximated, it is possible to eliminate the difference in torque response between the two transitions. In addition, since the driver can always obtain the same torque response regardless of the type of the operation mode being executed at the time of performing the acceleration operation, there is no sense of incongruity, and therefore, the productability can be improved.

  (3) If the target ignition timing is retarded with respect to the reference ignition timing, although torque can be reduced compared to the case where the target ignition timing is set to the reference ignition timing, the fuel consumption may be deteriorated. The period of time is preferably as short as possible. The target air-fuel ratio setting means of the present invention starts changing the target air-fuel ratio from lean to stoichiometry before the target ignition timing setting means starts to set the target ignition timing on the retard side of the reference ignition timing. As a result, in the present invention, since the period in which the target ignition timing is retarded from the reference ignition timing can be shortened within the transition period, it is possible to suppress the deterioration of the fuel efficiency caused by the retardation of the ignition timing.

It is a figure showing composition of an engine concerning the 1st embodiment of the present invention, and its control device. It is a flow chart which shows a concrete procedure of intake control. It is a figure which shows an example of a normal time map. It is a figure which shows an example of the map at the time of lean driving | running | working prohibition. It is a figure for demonstrating the difference of the torque responsiveness which may generate | occur | produce in a supercharging lean / stoichiometric transition period. It is a functional block diagram which shows the specific procedure of presumed supercharging pressure arithmetic processing. It is a functional block diagram which shows the specific procedure which calculates a target air fuel ratio and the target opening degree of a throttle valve. It is a time chart which shows the example of control realized by ECU concerning the above-mentioned embodiment. It is a functional block diagram which shows the specific procedure which calculates the target air fuel ratio and target ignition timing which concern on 2nd Embodiment of this invention. It is a time chart which shows the example of control realized by ECU concerning the above-mentioned embodiment.

First Embodiment
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing the configuration of an internal combustion engine (hereinafter referred to as an “engine”) 1 according to the present embodiment and its control device 2.

  The engine 1 is a multi-cylinder engine including a plurality of cylinders 1a and a plurality of pistons 1b (only one is shown in FIG. 1). The engine 1 can change the air-fuel ratio in the combustion chamber formed in each cylinder between a stoichiometric air-fuel ratio (for example, A / F = 14.7) and a lean air-fuel ratio (for example, A / F = 30) is there. The engine 1 is provided with a fuel injection valve 1c and a spark plug 1d (only one is shown in FIG. 1) for each cylinder. The fuel injection valves 1 c are electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 7 which constitutes a part of the control device 2. The ECU 7 calculates a target air-fuel ratio which is a target for the air-fuel ratio in the combustion chamber in each cylinder according to the procedure described later with reference to FIG. 5 and the like, and these fuel injection valves 1c Control the fuel injection amount and injection timing from The spark plugs 1 d are also electrically connected to the ECU 7. The ECU 7 calculates a target ignition timing which is a target for the timing at which a spark is generated by the spark plug 1d by a process not shown, and controls the ignition timing by the spark plug 1d such that the target ignition timing is realized.

  The engine 1 is provided with an intake pipe 11 through which intake air flows, an exhaust pipe 12 through which exhaust gas flows, and a supercharger 8 that compresses the intake air using energy of the exhaust gas. The intake pipe 11 is connected to the intake port of each cylinder 1 a of the engine 1 via a plurality of branch portions of the intake manifold. The exhaust pipe 12 is connected to the exhaust port of each cylinder 1 a of the engine 1 via a plurality of branches of the exhaust manifold.

  The supercharger 8 includes a turbine wheel 81 provided in the exhaust pipe 12, a compressor wheel 82 provided in the intake pipe 11, and a turbine shaft 83 connecting the turbine wheel 81 and the compressor wheel 82. The turbine wheel 81 is rotationally driven by blowing the exhaust gas discharged from the engine 1. The compressor wheel 82 is rotationally driven by the turbine wheel 81, compresses the intake air of the engine 1 and pumps it to the engine 1.

  Further, the exhaust pipe 12 is provided with a bypass passage 86 connecting the upstream side and the downstream side of the turbine wheel 81. Further, the bypass passage 86 can be opened and closed, and the flow rate of the exhaust blown to the turbine wheel 81 is changed. A waste gate valve 85 is provided to make the When the waste gate valve 85 is opened, the exhaust gas is discharged through the bypass passage 86 without passing through the turbine wheel 81, and when the waste gate valve 85 is closed, the exhaust gas is passed through the turbine wheel 81 without passing through the bypass passage 86. Discharged. Therefore, when the engine 1 is operated under natural intake without driving the supercharger 8, the waste gate valve 85 is controlled to be fully open, and the supercharger 8 is driven to receive the supercharged intake. When the engine 1 is operated, the waste gate valve 85 is controlled between fully open and fully closed.

  The waste gate valve 85 is connected to the ECU 7 via an actuator 87. The degree of opening of the waste gate valve 85 is adjusted by the ECU 7 controlling the duty ratio of the drive current supplied from the battery (not shown) to the actuator 87. The ECU 7 sets a target for the opening degree of the waste gate valve 85 by an intake control process described later with reference to FIG. 2 and performs energization control of the actuator 87 so that the target is realized.

  An intercooler 14 for cooling air pressurized by the turbocharger 8 and a throttle valve 9 for controlling the intake air amount of the engine 1 are provided downstream of the turbocharger 8 in the intake pipe 11. ing. The throttle valve 9 is an electromagnetic valve provided in the intake pipe 11 so as to be openable and closable, and is connected to the ECU 7 through an actuator 91. The opening degree of the throttle valve 9 is adjusted by the ECU 7 controlling the duty ratio of the drive current supplied from the battery (not shown) to the actuator 91. The ECU 7 calculates the target opening degree corresponding to the target for the opening degree of the throttle valve 9 by the intake control process described later with reference to FIG. 2, and performs the energization control of the actuator 91 so that the target opening degree is realized. Do.

  On the downstream side of the turbocharger 8 in the exhaust pipe 12, a catalyst purification device 15 for purifying the exhaust gas under the action of a catalyst is provided. The catalyst purification device 15 reduces and purifies NOx in the exhaust under a lean air-fuel ratio exhaust, and a three-way catalyst that purifies HC, CO and NOx in the exhaust under a stoichiometric air-fuel ratio exhaust, and a lean air-fuel ratio exhaust Equipped with a lean NOx catalyst.

  The ECU 7 performs an A / D conversion of the detection signal of the sensor, an intake control process of FIG. 2, an estimated boost pressure calculation process of FIG. 4, and a target air fuel ratio of FIG. RAM and ROM storing various data such as various programs such as processing to be calculated and maps in Fig. 3A and Fig. 3B etc. CPU performing various arithmetic processing according to the above program, and various actuators according to the arithmetic processing result of CPU It is comprised by the drive circuit etc. which perform electricity supply control.

  Various sensors such as an air flow meter 61, a throttle opening degree sensor 62, a crank angle position sensor 63, an accelerator opening degree sensor 64, a catalyst temperature sensor 65, and an engine water temperature sensor 66 are used in the ECU 7 to grasp the operating state of the engine 1. Is connected.

  The air flow meter 61 is provided in the intake pipe 11, detects the amount of air flowing into the intake manifold of the engine 1 through the intake pipe 11 (hereinafter, also referred to as "intake amount"), and is a signal substantially proportional to the detected value Is sent to the ECU 7.

  The throttle opening degree sensor 62 detects the opening degree of the throttle valve 9 and transmits a signal substantially proportional to the detected value to the ECU 7. The ECU 7 calculates the actual opening degree of the throttle valve 9 based on the detection signal of the throttle opening degree sensor 62.

  The crank angle position sensor 63 transmits a pulse signal to the ECU 7 at each predetermined crank angle in accordance with the rotation of the pulsar fixed to the crankshaft of the engine 1. The ECU 7 calculates the engine speed based on the pulse signal from the crank angle position sensor 63.

  The accelerator opening sensor 64 detects the amount of depression of the accelerator pedal operated by the driver, and transmits a detection signal corresponding to the amount to the ECU 7. The target torque corresponding to the load required of the engine 1 by the driver is calculated by the ECU 7 based on the detection signal of the accelerator opening sensor 64 and the engine speed.

  The catalyst temperature sensor 65 detects the temperature of the catalyst of the catalyst purification device 15 and transmits a detection signal corresponding to this to the ECU 7. The catalyst temperature of the catalyst purification device 15 is calculated by the ECU 7 based on the detection signal of the catalyst temperature sensor 65.

  The engine water temperature sensor 66 detects the temperature of the cooling water (not shown) of the engine 1 and transmits a detection signal corresponding to the temperature to the ECU 7. The coolant temperature of the engine 1 is calculated by the ECU 7 based on the detection signal of the engine water temperature sensor 66.

  Next, a specific procedure of intake control by the ECU 7 will be described. This intake control is processing for controlling the intake amount introduced into the engine by controlling the supercharger and the throttle valve, and is repeatedly executed in the ECU 7 at predetermined intervals.

FIG. 2 is a flowchart showing a specific procedure of intake control.
In S1, the ECU 7 calculates the target torque corresponding to the target with respect to the actual torque of the engine by acquiring the engine rotational speed and the accelerator opening and searching a map not shown based on these two values.

  Next, in S2, the ECU 7 acquires the current catalyst temperature and engine water temperature, and determines based on these two values whether the lean operation prohibition condition is satisfied. Here, the lean operation prohibition condition is a condition for determining whether or not the lean operation is currently prohibited. For example, in the case where the catalyst temperature has not reached the predetermined activation temperature, it is preferable to prohibit the lean operation in order to activate the exhaust purification catalyst promptly. When the engine water temperature does not reach a predetermined warm-up temperature, it is preferable to prohibit lean operation in order to promote warm-up of the engine. Therefore, in S2, the ECU 7 determines that the lean operation prohibition condition is satisfied if the acquired catalyst temperature has not reached the activation temperature or if the acquired engine water temperature has not reached the warm-up temperature. The processing proceeds to S4, and in the other cases, it is determined that the lean operation prohibition condition is not satisfied, and the processing proceeds to S3.

  In S3, that is, when the lean operation prohibition condition is not satisfied, the ECU 7 selects the normal mode map shown in FIG. 3A as the operation mode determination map, and proceeds to S4. In S4, that is, when the lean operation prohibition condition is satisfied, the ECU 7 selects the lean operation prohibition time map shown in FIG. 3B as the operation mode determination map, and proceeds to S5.

FIG. 3A is a view showing an example of the normal time map, and FIG. 3B is a view showing an example of the lean operation prohibited time map.
As shown in FIG. 3A, when the normal mode map is selected as the operation mode determination map, in the engine operation region represented by the engine rotational speed as the horizontal axis and the target torque as the vertical axis, the medium rotation and medium torque region In this case, lean operation is performed to make the air-fuel ratio lean. In FIG. 3B, the boundary line of the lean operation area defined by the normal time map is indicated by an alternate long and short dash line for reference. Further, in the operating range other than the lean operating range, the stoichiometric operation is performed to make the air-fuel ratio stoichiometric. Further, as indicated by a thick broken line in FIG. 3A, a boundary line L1 separating the supercharged area and the non-supercharged area is determined to pass through the center of the lean operation area in the normal time map.

  Therefore, in the normal-time map of FIG. 3A, the region indicated by reference numeral R1 is a supercharging stoichiometric operation region where the supercharging stoichiometric operation is performed in which the air-fuel ratio is made stoichiometric while driving the supercharger. The region indicated by reference R2 is a non-supercharged stoichiometric operation region in which a non-supercharged stoichiometric operation is performed to make the air-fuel ratio stoichiometric without driving the supercharger. The region indicated by symbol R3 is a supercharging lean operating region in which a supercharging lean operation is performed to make the air-fuel ratio lean while driving the supercharger. Further, a region indicated by reference R4 is a non-supercharging lean operating region in which a non-supercharging lean operation is performed to make the air-fuel ratio lean without driving the supercharger.

  As shown in FIG. 3B, no lean operation area is defined in the lean operation prohibition time map. Therefore, when the lean operation prohibition time map is selected as the operation mode determination map, the stoichiometric operation is performed regardless of the engine speed and the target torque. In addition, the lean operation prohibition time map differs from the normal time map in the supercharged area and the non-supercharged area as well. More specifically, in the lean operation prohibition time map, the boundary line L2 separating the supercharged area and the non-supercharged area is set on the higher torque side than the boundary line L1 defined in the normal time map. That is, in the lean operation prohibition time map, the non-supercharging region is set wider than that in the normal time map. Further, the boundary line L2 is set to pass near the boundary line on the high torque side of the lean operation area in the normal time map.

  Returning to FIG. 2, in S5, the ECU 7 executes throttle valve control processing. More specifically, in the throttle valve control process, the ECU 7 sets the target opening degree of the throttle valve according to the procedure described later with reference to FIG. 5 and the like, and detects the throttle valve detected by the throttle opening degree sensor. The throttle valve actuator is driven so that the actual opening degree becomes the set target opening degree.

  In S6, the ECU 7 determines whether or not the current operating state is within the supercharging region by searching the operating mode determination map previously selected using the target torque and the engine speed calculated in S1. Do.

  If the determination in S6 is NO, the ECU 7 determines that the non-supercharging operation should be performed, proceeds to S7, controls the waste gate valve to a fully open state, and ends the processing of FIG. When the determination in S6 is YES, the ECU 7 determines that the supercharging operation should be performed, and proceeds to S8.

  In S8, the ECU 7 calculates a target intake pressure corresponding to a target for the pressure of the intake air in the intake manifold by searching a map (not shown) using the target torque and the engine rotational speed.

  In S9, the ECU 7 calculates a target boost pressure corresponding to the current target intake pressure according to the procedure described later with reference to FIG. 4 and estimates estimated boost pressure corresponding to the estimated value of the current boost pressure. calculate. Furthermore, in S10, the ECU 7 controls the opening degree of the waste gate valve between fully open and fully closed according to a known feedback control law so that the calculated estimated boost pressure becomes the target boost pressure, and the process of FIG. finish.

  FIG. 4 is a functional block diagram showing a specific procedure of estimated boost pressure calculation processing for calculating the target boost pressure and the estimated boost pressure from the target intake pressure in the ECU 7. The supercharger controls the supercharging pressure by controlling the degree of opening of the waste gate valve, but there are delays due to various factors until the supercharging pressure actually responds after operating the waste gate valve . The ECU 7 calculates the estimated supercharging pressure in consideration of the presence of such supercharging delay by performing computation according to the functional block shown in FIG. 4.

  The ECU 7 includes a steady state calculation unit 71 that calculates a steady arrival boost pressure, a turbine delay calculation unit 72 that calculates a temporary value of estimated boost pressure by performing delay processing on the steady arrival boost pressure, and a correction term. A correction term calculation unit 73 to be calculated, and a summing unit 74 to calculate an estimated boost pressure by summing the provisional value of the estimated boost pressure and the correction term. The ECU 7 repeatedly performs the calculations of the steady state calculation unit 71, the turbine delay calculation unit 72, the correction term calculation unit 73, and the summing unit 74 for each predetermined cycle to estimate the supercharging pressure for each cycle. Calculate

  Here, the steady state supercharging pressure corresponds to the maximum value of the supercharging pressure that can be achieved when the waste gate valve is controlled to the fully closed state in the current engine operating condition. The steady state calculation unit 71 includes a limit intake pressure calculation unit 731, an in-manifold delay calculation unit 732, an intake amount calculation unit 733, a valve closing steady arrival charge pressure calculation unit 734, and a target charge pressure calculation unit 735. Such steady arrival supercharging pressure is calculated by using the target arrival determination unit 736.

  The limit intake pressure calculation unit 731 calculates the limit intake pressure by comparing the current value of the target intake pressure calculated in the process of S8 of FIG. 2 with the previous value of the estimated boost pressure. More specifically, when the current value of the target intake pressure is equal to or less than the previous value of the estimated boost pressure, the limit intake pressure calculation unit 731 outputs the current value of the target intake pressure as the limit intake pressure. If the current value of the intake pressure is larger than the previous value of the estimated boost pressure, the previous value of the estimated boost pressure is output as the limit intake pressure. That is, the limit intake pressure corresponds to the target intake pressure subjected to limit processing with the previous value of the estimated boost pressure as the upper limit. This is based on the fact that it is considered that an intake pressure that exceeds the previous value of the estimated boost pressure can not be realized.

The in-manifold delay calculation unit 732 corresponds to the estimated value of the present intake pressure by performing delay processing that simulates response delay of the intake manifold and the throttle valve among the supercharge delay as shown below for the limit intake pressure. Calculate the estimated inspiratory pressure. More specifically, the intake manifold delay calculation unit 732 calculates an estimated intake pressure by performing first-order lag filtering calculation as shown in the following equation (1) on the limit intake pressure. In the following equation (1), the current value of the estimated intake pressure is expressed as "PBest (k)", the previous value of the estimated intake pressure is expressed as "PBest (k-1)", and the current value of the limit intake pressure is expressed as It is written as "PBlmt (k)". Further, in the following formula (1), “K1” is a weight coefficient set to a value larger than 0 and smaller than 1. The intake delay calculation unit 732 calculates the estimated intake pressure based on the following equation (1) to control the throttle valve so that the intake pressure becomes the limit intake pressure, the response delay of the throttle valve, and the intake It is possible to consider the time it takes for the fuel to flow from the throttle valve into the intake manifold.
PBest (k) = K1 · PBlmt (k)
+ (1-K1) · PBest (k-1) (1)

  The intake amount calculation unit 733 calculates an estimated intake amount corresponding to an estimated value of the flow rate of intake air flowing into the intake manifold in the current cycle by searching a map not shown according to the engine rotational speed and the estimated intake pressure. .

  The valve closing steady state supercharging pressure calculation unit 734 first calculates a flat equivalent value of the steady state supercharging pressure by searching a map not shown according to the engine speed and the estimated intake air amount. The flat equivalent value of the steady state supercharging pressure is set to a larger value as the engine speed is higher or as the estimated intake air amount is larger. This is based on the fact that the higher the engine speed or the larger the estimated intake air amount, the higher the maximum boost pressure that can be achieved by the turbocharger.

  The valve closing steady state supercharging pressure calculation unit 734 multiplies the flat ground equivalent value calculated as described above by the correction coefficient calculated using the atmospheric pressure at the present time detected using the atmospheric pressure sensor (not shown). By doing this, the closing time value of the steady-state reaching boost pressure is calculated. The valve closing value corresponds to a value obtained by converting the flat ground equivalent value into the equivalent value at the present atmospheric pressure.

  The target boost pressure calculation unit 735 calculates a target boost pressure that achieves the target intake pressure by searching a map (not shown) according to the target intake pressure.

  The target attainment determination unit 736 performs the following calculation using the target boost pressure, the closing time value of the steady arrival boost pressure, and the previous value of the estimated boost pressure to obtain the steady arrival boost pressure. Calculate

  The target attainment determination unit 736 first determines the absolute value of the difference between the estimated value of the estimated boost pressure and the target boost pressure to determine how much the current boost pressure has reached the target boost pressure. Calculate the value and let this be the pressure deviation. If the pressure deviation is equal to or less than the threshold set to a value slightly larger than 0, the target attainment determining unit 736 determines that the supercharging pressure has almost reached the target supercharging pressure, and the steady attainment supercharging pressure It is determined whether the valve closing time value of the valve is equal to or higher than the target boost pressure. The target attainment determination unit 736 determines that the target boost pressure can be realized by controlling the opening of the waste gate valve when the closing time value of the steady arrival boost pressure is equal to or higher than the target boost pressure. The target boost pressure is output as a steady state boost pressure.

  Further, the target arrival determination unit 736 achieves the target boost pressure even if the pressure deviation is larger than the threshold or the closing time value of the steady arrival boost pressure is lower than the target boost pressure and therefore the waste gate valve is controlled. If it is determined that it can not be performed, the valve closing time value of the steady state boost pressure is output as the steady state boost pressure.

The turbine delay calculation unit 72 performs delay processing that simulates, in particular, the delay of the turbine in the supercharge delay, as described below, to the steady arrival boost pressure calculated by the steady state calculation unit 71 as described above. The provisional value of the estimated boost pressure is calculated by More specifically, the turbine delay calculation unit 72 calculates a provisional value of the estimated boost pressure by performing first-order lag filtering computation as shown in the following equation (2) on the steady arrival boost pressure. In the following equation (2), the present value of the provisional value of the estimated boost pressure is written as "PTCtmp (k)", and the previous value of the provisional value of the estimated boost pressure is written as "PTCtmp (k-1)" The current value of the steady state supercharging pressure is denoted as "PTC sta (k)". Further, in the following formula (2), “K2” is a weighting coefficient set to a value larger than 0 and smaller than 1. The turbine delay calculation unit 72 calculates the temporary value of the estimated boost pressure based on the following equation (2) to control the supercharger so that the boost pressure becomes the steady arrival boost pressure. The response delay of the feed turbine can be taken into account.
PTC tmp (k) = K2 · PTC sta (k)
+ (1-K2) · PTC tmp (k-1) (2)

  The correction term calculation unit 73 performs the following calculation using the estimated intake pressure calculated by the in-manifold delay calculation unit 732 and the previous value of the estimated boost pressure to correct the correction term for the steady arrival boost pressure. calculate.

  First, the correction term calculation unit 73 calculates an estimated intake pressure change amount by subtracting the current value of the estimated intake pressure from the previous value of the estimated intake pressure calculated by the intake manifold delay calculation unit 732. Next, the correction term calculation unit 73 calculates the absolute value of the deviation between the previous value of the estimated boost pressure and the previous value of the estimated intake pressure, and sets this as the pressure deviation.

  Next, the correction term calculation unit 73 determines whether the calculated pressure deviation is larger than a threshold set to a value slightly larger than zero. Then, the correction term calculation unit 73 outputs the value 0 as a correction term when the pressure deviation is equal to or less than the threshold.

  Further, when the pressure deviation is larger than the threshold value, the correction term calculation unit 73 determines that the degree of deviation between the estimated boost pressure and the estimated intake pressure is large, and searches a map not shown according to the engine speed. , Correction term gain is calculated. The correction term gain is set to be a larger value as the engine speed is higher. This is because, as the engine speed is higher, the sensitivity of the boost pressure to the estimated intake pressure change increases, and this is reflected in the calculation result of the estimated boost pressure. Then, the correction term operation unit 73 outputs a value obtained by multiplying the correction term gain by the estimated intake pressure change amount as a correction term.

  The summing unit 74 estimates a value obtained by adding together the steady attainment boost pressure calculated by the turbine delay calculation unit 72 as described above and the correction term calculated by the correction term calculation unit 73 as an estimated charge pressure. Output.

  Next, problems that may occur when the operation mode is determined using the normal time map and the lean operation prohibition time map as described above will be described in detail. First, in the case where the normal time map of FIG. 3A is used as the driving mode determination map, the driver performs the acceleration operation from the state where the driving state is at the driving point P1 defined in the supercharging lean driving region. The case is considered where the target torque is increased due to and the operation point P2 is shifted to the operation point P2 defined in the supercharging stoichiometric operation region. When such an acceleration operation is performed with the normal time map selected, the target torque increases stepwise from the first target torque to the second target torque as shown by a thick broken line in FIG. 3C, and the operation mode is , Shift from supercharged lean operation to supercharged stoichiometric operation. Under the present circumstances, since a supercharger is already driven at the time of acceleration operation being performed, there is no response delay of a supercharger, Therefore The torque which generate | occur | produces with an engine is a target as shown by a dashed dotted line in FIG. 3C. It can be made to follow promptly according to the increase in torque.

  On the other hand, when the same acceleration operation is performed in a state where the lean operation prohibition time map of FIG. 3B is used as the operation mode determination map, as shown in FIG. 3B, the operation mode is from supercharged stoichiometric operation to supercharged operation. It will shift to stoichiometric operation. That is, when the lean operation prohibition time map is selected, the supercharger is not driven at the time when the acceleration operation is performed. For this reason, since the response delay of the supercharger occurs at the time of acceleration, the torque generated at the transition of the operation mode is gentle as compared with the case where the normal time map is selected as shown by the solid line in FIG. 3C. To rise. That is, in the case where the normal time map is selected and in the case where the lean operation prohibition time map is selected, the torque actually generated is the first target torque compared to the case where the acceleration operation as described above is performed. There may be a difference in torque responsiveness in the transition period between the time of reaching the second target torque and the time of reaching the second target torque. Hereinafter, a control method of a target air-fuel ratio and a throttle valve constructed in consideration of a problem that may occur when the above-described acceleration operation is performed will be described with reference to FIG. 5 and the like.

  FIG. 5 is a functional block diagram showing a specific procedure for calculating the target air fuel ratio and the target opening of the throttle valve in the ECU 7. As shown in FIG. The ECU 7 includes an operation area determination unit 751, a final target intake air amount calculation unit 752, an actual intake air amount supercharging delay operation unit 753, a lean prohibition target air intake amount calculation unit 754, and a lean prohibition air intake amount charging delay calculation. The unit 755 includes a target opening degree computing unit 756, an estimated actualized torque computing unit 761, and a target air fuel ratio computing unit 762. In the ECU 7, the operation area determination unit 751, the final target intake amount calculation unit 752, the actual intake amount supercharge delay calculation unit 753, the lean prohibited target intake amount calculation unit 754, and the lean prohibited intake amount supercharge delay By repeatedly performing calculations of calculation unit 755, target opening degree calculation unit 756, estimated realized torque calculation unit 761, and target air fuel ratio calculation unit 762 for each predetermined cycle, the target air fuel ratio and the target for each cycle are calculated. Calculate the opening degree.

  The driving range determination unit 751 searches the driving mode determination map selected in the process of S3 or S4 in FIG. 2 according to the target torque and the engine rotational speed, so that the current driving range is the supercharged stoichiometric driving range. It is determined which of the non-supercharged stoichiometric operating region, the supercharged lean operating region, and the non-supercharged lean operating region it belongs to.

  The final target intake air amount calculation unit 752 uses the determination result of the operation area determination unit 751 and the target supercharging pressure calculated in advance to generate the engine and the turbocharger under the currently executed operation mode. When driving is continued, a final target intake air amount corresponding to the target intake air amount to be finally achieved is calculated. More specifically, when the current target operating range is the lean operating range, the final target intake air amount computing unit 752 sets the air fuel ratio (for example, A / F = 30) to be finally realized during the lean operating. A final target intake air amount is calculated by searching a map (not shown) based on the current target boost pressure. Further, when the current operation range is the stoichiometric operation range, the final target intake air amount calculation unit 752 sets the air fuel ratio (for example, A / F = 14.7) to be finally realized at the stoichiometric operation and the current target A final target intake air amount is calculated by searching a map (not shown) based on the supercharging pressure. The final target intake air amount calculated in this manner changes in a step-like manner when the driving range is switched due to the driver's acceleration operation or deceleration operation (thick broken line in FIG. reference).

  If it is assumed that the actual intake amount supercharging delay calculation unit 753 keeps maintaining the opening degree of the throttle valve at the effective opening degree (for example, full opening) where air throttling does not occur in the final target intake amount, it actually occurs. The estimated actual supercharged intake amount is calculated by performing processing that simulates the estimated actual supercharge delay. That is, the estimated actual supercharged intake quantity corresponds to an estimated value of the intake quantity which is realized when the opening degree of the throttle valve is maintained at the effective opening degree.

  The actual intake amount supercharge delay calculation unit 753 performs processing that simulates such actual supercharge delay by performing calculation using the estimated boost pressure calculation processing of FIG. 4 on the final target intake amount. More specifically, the actual intake amount supercharging delay calculation unit 753 calculates the target intake pressure by unit converting the final target intake amount from flow rate to pressure, and calculates the target intake pressure calculated from the final target intake amount The estimated intake pressure is calculated by inputting to the limit intake pressure calculation unit 731 and the target boost pressure calculation unit 735 in FIG. 4. Further, the actual intake amount supercharge delay calculation unit 753 calculates the estimated actual supercharge intake amount by unit converting the estimated intake pressure obtained by the calculation using the estimated supercharge pressure calculation processing of FIG. 4 from pressure to flow rate. Do.

  Here, as described above, the actual intake amount supercharging delay calculation unit 753 calculates the supercharging delay that occurs when the opening degree of the throttle valve is maintained at the effective opening degree at which air throttling does not occur. Do. This means that in the estimated boost pressure calculation process of FIG. 4, the calculation in the in-manifold delay calculation unit 732 does not consider the response delay of the throttle valve. Therefore, when the actual intake amount supercharge delay calculation unit 753 uses the estimated supercharge pressure calculation processing of FIG. 4 for calculation, the weighting coefficient K1 in the in-manifold delay calculation unit 732 does not consider the response delay of the throttle valve. More preferably, it is set to a value closer to 1.

  The lean prohibited target intake air amount calculation unit 754 does not depend on the determination result of the operating area determining unit 751, and currently assumes that the lean operating prohibited map shown in FIG. 3B is selected as the operating mode determination map. The final target intake air amount during lean prohibition is calculated using the lean operation prohibition time map and the target boost pressure. The lean-nominated final target intake air amount corresponds to a target intake air amount to be finally achieved under the assumption, assuming that the lean operation is currently prohibited.

  More specifically, the lean prohibited time target intake air amount calculation unit 754 first searches the lean operating prohibited time map according to the current target torque and the engine rotational speed, so that the current driving point is lean operating. On the prohibition time map, it is determined to which operation region the supercharged stoichiometric operation region or the non-supercharged stoichiometric operation region belongs. Then, when the current operation range is the supercharging stoichiometric operation range, the lean-nominated target intake air amount computation unit 754 finally realizes an air-fuel ratio (for example, A / F = 14.14) to be realized at the supercharging stoichiometric operation. The final target intake air amount during lean prohibition is calculated by searching a map (not shown) based on 7) and the current target boost pressure. Further, when the current operation range is the non-supercharged stoichiometric operation range, the lean prohibited target intake air amount calculation unit 754 is an air-fuel ratio to be finally realized at the non-supercharged stoichiometric operation (for example, A / F = By searching a map (not shown) based on 14.7) and the current target boost pressure (i.e., atmospheric pressure), the final target intake air amount during lean inhibition is calculated.

  A lean-provision intake amount supercharge delay calculation unit 755 is assumed to occur when it is assumed that the operation of the engine and the supercharger is continued under the lean operation prohibition time map in the lean prohibition target air intake amount. The estimated lean intake amount is calculated by performing a typical supercharging delay process. That is, the lean prohibited estimated intake amount corresponds to a virtual estimated intake amount that is realized when it is assumed that the operation of the engine and the turbocharger is continued under the lean operation prohibited map.

  Such a virtual supercharging delay is simulated by performing calculations using the estimated supercharging pressure calculation processing of FIG. 4 in the lean prohibited target intake air amount in the lean prohibited air intake amount charging calculation unit 755. Apply processing More specifically, the lean prohibited intake amount supercharging delay calculation unit 755 calculates a target intake pressure by converting the lean prohibited target intake amount into a unit from flow rate to pressure, and calculates from the lean prohibited target intake amount. The estimated intake pressure is calculated by inputting the calculated target intake pressure to the limit intake pressure calculation unit 731 and the target boost pressure calculation unit 735 shown in FIG. Further, the lean prohibited intake air amount supercharge delay calculation unit 755 performs unit conversion from pressure to flow rate of the estimated intake pressure obtained by the calculation using the estimated supercharge pressure calculation processing of FIG. Calculate

  The target opening degree calculation unit 756 calculates the target opening degree of the throttle valve by using the determination result by the operation area determination unit 751, the estimated actual supercharged intake amount, and the estimated lean intake amount. As described with reference to FIG. 3C, with the normal time map selected as the operation mode determination map, the target torque from the first target torque in the supercharging lean operation region to the second in the supercharged stoichiometric operation region A transition period immediately after rising to the target torque and until the torque generated by the engine reaches the second target torque from the first target torque (hereinafter, this transition period is particularly referred to as “supercharged lean / stoichiometric transition period” The torque responsiveness realized in (4) is better than the torque responsiveness realized when the lean operation prohibition map is selected. Therefore, the target opening degree calculation unit 756 calculates the target opening degree by dividing into the supercharged lean / stoichiometric transition period and the other period.

  More specifically, the target opening degree calculation unit 756 determines that the torque responsiveness difference described with reference to FIG. 3C does not occur in the period other than the supercharging lean / stoichiometric transition period, By searching a map (not shown) based on the estimated actual supercharged intake amount, the effective opening degree of the throttle valve according to the estimated actual supercharged intake amount is calculated, and this is output as the target opening degree. Here, the effective opening degree of the throttle valve according to the estimated actual supercharged intake amount is the opening degree of the throttle valve which can realize the estimated actual supercharged intake amount without generating air throttling, basically It is fully open.

  Further, the target opening degree calculation unit 756 estimates estimated actual supercharged intake air during the supercharged lean / stoichiometric transition period, that is, when a large deviation occurs between the estimated actual supercharged intake air amount and the estimated lean intake time. By searching a map (not shown) based on the lean prohibited estimated intake amount smaller than the amount, the throttle valve opening that realizes the lean prohibited estimated intake amount is calculated by generating air throttling, and this is calculated Output as the target opening. Here, since the estimated supercharged intake amount during lean operation prohibition is always equal to or less than the estimated actual supercharged intake amount, the target opening degree determined based on the estimated supercharged intake amount during lean operation inhibition is the estimated actual supercharged intake amount It is always the closing side (ie, the torque down side) than the target opening determined based on the quantity. In other words, in the supercharging lean / stoichiometric transition period, the torque reduction control to lower the torque so as to approach the torque realized when the lean operation is prohibited, from the torque which can be realized by opening the throttle valve to the effective opening. Is done.

The estimated actualized torque computing unit 761 calculates estimated estimated torque by subjecting the target torque to a delay process that simulates the response delay of the fuel injection valve as described below. The estimated realized torque corresponds to the torque realized by adjusting the air-fuel ratio using the fuel injection valve. More specifically, the estimated realized torque computing unit 761 calculates estimated estimated torque by performing first-order lag filtering calculation as shown in the following equation (3) on the target torque. In the following equation (3), the current value of the estimated actual torque is denoted as "TRQest (k)", the previous value of the estimated actual torque is denoted as "TRQest (k-1)", and the current value of the target torque is " Write "TRQcmd (k)". Further, in the following equation (3), “K3” is a weight coefficient set to a value larger than 0 and smaller than 1. In the fuel injection valve when the fuel injection valve is controlled such that the actual torque quickly follows the target torque by calculating the estimated realized torque based on the following equation (3) in the estimated realized torque calculation unit 761: Response delay can be considered.
TRQest (k) = K3 · TRQ cmd (k)
+ (1-K3) · TRQest (k-1) (3)

  The target air-fuel ratio calculation unit 762 calculates an air-fuel ratio that realizes the estimated actualized torque under the current operating range by searching a map not shown according to the estimated actualized torque, and uses this as the target air-fuel ratio. Output.

  Next, an example of control realized by the ECU 7 as described above will be described with reference to the time chart of FIG. FIG. 6 shows temporal changes of an amount related to a torque such as a target torque, an amount related to an intake amount such as a final target intake amount, a target air-fuel ratio, and a target opening degree of a throttle valve.

  In FIG. 6, in the state where the normal mode map is selected as the operation mode determination map (that is, in the state where the lean operation is not prohibited), the target torque is supercharged from time t0 to time t1. The target torque is set to the first target torque (for example, driving point P1 in FIG. 3A) defined in the driving range, and the driver performs acceleration operation at time t1. The time chart realized when changing to the 2nd target torque (for example, driving point P2 in Drawing 3A) defined inside is shown.

  First, as indicated by a thick broken line in the uppermost stage of FIG. 6, the target torque changes stepwise from the first target torque to the second target torque as acceleration operation is performed at time t1. Therefore, in the operation mode, the supercharging lean operation is performed between time t0 and t1, and the supercharging stoichiometric operation is performed after time t1. Further, the torque actually realized by the ECU 7 is indicated by a solid line at the top of FIG. Therefore, the time period until the actual torque starts to increase from the first target torque at time t1 and reaches the second target torque at time t4 corresponds to the above-described supercharging lean / stoichiometric transition period.

  As the target torque increases from the first target torque to the second target torque, the final target intake air amount calculated by the final target intake air amount calculation unit 752 is as shown by a thick broken line in the second stage from the top of FIG. At time t1, it changes stepwise. Further, it is assumed that the actual intake amount supercharge delay calculation unit 753 keeps maintaining the opening degree of the throttle valve at the effective opening degree at which air throttling does not occur with respect to the final target intake amount changing in such a step shape. The estimated actual supercharged intake amount (the alternate long and short dash line in the second stage from the top of FIG. 6) is calculated by performing processing that simulates the actual supercharge delay that is estimated to occur actually. Therefore, as shown in FIG. 6, the estimated actual supercharged intake air amount gradually rises to follow the step-like change in the final target intake air amount as shown in FIG. 6, and approximately reaches the final target intake air amount at time t3. . In the example shown in FIG. 6, the supercharged lean operation is performed from time t0 to time t1, and the turbine of the supercharger is already rotating. The intake and intake amounts rise immediately without being affected by the supercharging delay.

  On the other hand, the lean prohibited intake amount supercharging delay calculation unit 755 is a virtual supercharged delay presumed to occur when it is assumed that the operation of the engine and the supercharger is always continued under the lean operation prohibited map. By performing the process, the estimated lean intake amount (the two-dot chain line in the second stage from the top of FIG. 6) is calculated. Therefore, during the period from time t0 to time t1, the lean prohibited estimated intake amount is always smaller than the estimated actual supercharged intake amount. Further, unlike the estimated actual supercharged intake amount, the estimated lean intake amount does not increase substantially after the target torque has increased to the second target torque at time t1, but gradually starts to increase at time t2. This is because, as shown in FIG. 3B, the operation point P1 specified by the first target torque is within the non-supercharged stoichiometric operation region on the lean operation prohibition map, and is charged between time t0 and t1. It is assumed that the turbine of the aircraft has stopped. That is, assuming that the operation is always continued under the lean operation prohibition map, the turbine starts to rotate at time t1 and therefore, the turbine starts to rotate and the boost pressure actually starts to increase. There is a delay in supercharging. Further, the lean-prohibited estimated intake amount gradually starts to rise at time t2, and approximately reaches the final target intake amount at time t4. As described above, during the time period t1 to t4, since the lean-prohibition estimated intake air amount is calculated by the lean-prohibition supercharge delay calculation unit 755 in consideration of the supercharge delay of the supercharger, the estimated It is always smaller than the supercharged air intake, and it takes a long time to reach the final target air intake.

  Next, the target opening degree calculation unit 756 calculates the target opening degree of the throttle valve as indicated by the solid line in the lowermost stage of FIG. 6 by dividing the cases into the supercharging lean / stoichiometric transition period and the other periods. . Here, between time t0 and t1, the target opening degree calculation unit 756 sets the opening degree of the throttle valve to realize the estimated actual supercharged intake amount (for example, the effective opening degree indicated by the broken line in the lowermost stage of FIG. Calculate (fully open) as the target opening degree. Further, as described above, after time t1, the target opening degree calculation unit 756 determines that the supercharged lean operation has shifted to the supercharged stoichiometric operation, that is, shifts to within the supercharged lean / stoichiometric transition period. The throttle valve opening degree is set as the target opening degree such that the lean prohibited estimated intake air amount smaller than the estimated actual supercharged intake air amount is realized by generating the air throttling. Therefore, as shown in FIG. 6, the target opening degree is changed from the effective opening degree indicated by the broken line to the closing side at time t1. For this reason, as shown by the solid line in the second stage from the top of FIG. 6, the intake quantity realized by such control of the throttle valve is lean prohibited from the estimated actual supercharged intake quantity (dashed dotted line) from time t1. It begins to decrease so as to approach the estimated hourly intake amount (two-dot chain line), and at time t2, the estimated lean intake amount is reached.

  Further, between time t2 and t3, the target opening degree calculation unit 756 maintains the target opening degree of the throttle valve substantially constant so that the estimated lean intake amount is realized. As a result, the amount of intake air to be realized changes from the time t2 to the time t3 so as to be in line with the lean-prohibition-time estimated intake air amount. Also, between times t3 and t4, as the difference between the lean prohibited estimated intake amount and the estimated actual supercharged intake amount gradually decreases, the target opening degree of the throttle valve realizes the estimated actual supercharged intake amount. It gradually changes to the open side toward the effective opening.

  At the top of FIG. 6, changes in torque that are realized when the target opening of the throttle valve is always maintained at the effective opening are indicated by alternate long and short dashed lines for reference.

  Next, the estimated actualized torque calculation unit 761 performs the delay process simulating the response delay of the fuel injection valve to the target torque to calculate an estimated actualized torque as shown by a two-dot chain line in the uppermost stage of FIG. Further, the target air-fuel ratio calculation unit 762 outputs an air-fuel ratio that realizes the estimated realized torque as a target air-fuel ratio. Therefore, as shown in the second stage from the bottom of FIG. 6, the target air-fuel ratio changes from the lean air-fuel ratio from time t1 to t2 in response to the change of the target torque from the first target torque to the second target torque. It is gradually changed to the stoichiometric air-fuel ratio.

  As described above, in the supercharging lean / stoichiometric transition period (time t1 to t4) generated when the target torque changes from the first target torque to the second target torque, the ECU 7 makes the target air-fuel ratio stoichiometric from the air-fuel ratio It is realized when the target opening degree of the throttle valve is always maintained at the effective opening degree by gradually changing to the air fuel ratio and setting the target opening degree of the throttle valve to the closing side with respect to the effective opening degree. The actually realized torque (solid line in the top row of FIG. 6) can be lower than torque (see the dashed-dotted line in the top row of FIG. 6). Further, in the supercharging lean / stoichiometric transition period, the ECU 7 sets the target opening degree of the throttle valve in accordance with the lean prohibited estimated intake air amount to realize the intake air amount from the non-supercharged stoichiometric operation to the supercharged stoichiometric operation. Therefore, the torque realized in the supercharged lean / stoichiometric transition period is also realized in the transition from the non-supercharged stoichiometric operation to the supercharged stoichiometric operation. It can approach torque. Therefore, the driver can always obtain the same torque response regardless of the type of operation mode being executed at the time of performing the acceleration operation, so there is no sense of incongruity, and therefore, the productability can be improved.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 7 is a functional block diagram showing a specific procedure for calculating the target air fuel ratio and the target ignition timing of the spark plug in the ECU 7A according to this embodiment. The ECU 7A according to the present embodiment differs from the ECU 7 according to the first embodiment in the specific procedure for calculating the target ignition timing. More specifically, the ECU 7 according to the first embodiment performs torque down control using the throttle valve during the supercharging lean / stoichiometric transition period. On the other hand, the ECU 7A according to the present embodiment differs from the ECU 7 according to the first embodiment in that the torque reduction control using the ignition plug is performed in the supercharging lean / stoichiometric transition period. In the following, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The ECU 7A calculates an operation area determination unit 751, a final target intake air amount calculation unit 752, an actual intake air amount supercharging delay operation unit 753, a lean prohibition target air intake amount calculation unit 754, and a lean prohibition air intake amount charging delay calculation. The unit 755 includes a lean prohibited torque estimation unit 771, a target ignition timing calculation unit 772, an estimated realized torque calculation unit 761, and a target air fuel ratio calculation unit 762.

  The lean prohibited torque estimation unit 771 searches the map not shown for the lean prohibited estimated intake amount by using the lean prohibited estimated intake amount calculated by the lean prohibited intake amount supercharging delay calculation unit 755. A torque that is realized when intake is introduced is calculated, and this is output as an estimated torque during lean operation inhibition.

  The target ignition timing calculation unit 772 calculates the target ignition timing of the spark plug by using the determination result by the operation range determination unit 751, the estimated actual supercharged intake amount, and the lean operation prohibition estimated torque. Similar to the target opening degree computing unit 756 according to the first embodiment, the target ignition timing computing unit 772 calculates the target ignition timing by dividing the case into the supercharging lean / stoichiometric transition period and the other period.

  More specifically, the target ignition timing calculation unit 772 determines that the torque responsiveness difference described with reference to FIG. 3C does not occur in the period other than the boost lean / stoichiometric transition period, By searching a map (not shown) based on the estimated actual supercharged intake amount, the ignition timing (so-called MBT) that maximizes the torque generated by the engine and provides the best fuel efficiency is calculated and calculated as the target ignition timing. Do.

  Further, the target ignition timing calculation unit 772 estimates that the lean operation is prohibited when the supercharged lean / stoichiometric transition period is under, that is, when a large deviation occurs between the estimated actual supercharged intake amount and the estimated lean amount at the time of lean prohibition. By searching a map (not shown) based on the torque, an ignition timing that achieves this lean operation prohibited estimated torque is calculated, and this is calculated as a target ignition timing. Here, when the ignition timing is changed to the retard side with respect to MBT which is the ignition timing at which the torque generated by the engine becomes maximum as described above, the torque generated by the engine according to the retardation amount from this MBT is also descend. Therefore, the target ignition timing is set to be more retarded than the MBT by the target ignition timing calculation unit 772 within the supercharging lean / stoichiometric transition period. In other words, in the supercharging lean / stoichiometric transition period, the torque reduction control is performed to reduce the torque from the torque that can be realized by setting the ignition timing to MBT so that it approaches the torque that is realized when the lean operation is prohibited. To be done.

  If the ignition timing is changed from MBT to the retard side in a short time, a misfire may occur. Therefore, the target ignition timing calculation unit 772 calculates the target ignition timing under the rate limit in order to prevent such a misfire from occurring in the supercharging lean / stoichiometric transition period. That is, within the supercharging lean / stoichiometric transition period, the target ignition timing calculation unit 772 gradually changes the target ignition timing at a speed which does not exceed this rate limit.

  In addition, when the ignition timing is changed from MBT to the retard side, torque may decrease and fuel efficiency may also deteriorate. Therefore, it is preferable that the period in which the target ignition timing be retarded from MBT be as short as possible. Therefore, when the target ignition timing calculation unit 772 shifts to the supercharging lean / stoichiometric transition period, it immediately shifts to the supercharging lean / stoichiometric transition period without delaying the target ignition timing from the MBT. Preferably, the retardation of the target ignition timing is started after a predetermined waiting time has elapsed.

  As described in the first embodiment, the target air-fuel ratio calculation unit 762 starts to gradually change the target air-fuel ratio from the lean air-fuel ratio to the stoichiometric air-fuel ratio when shifting into the supercharging lean / stoichiometric transition period. Therefore, after the target ignition timing calculation unit 772 shifts to within the supercharging lean / stoichiometric transition period, the target ignition timing is delayed after the target air fuel ratio falls below the threshold set to a value slightly larger than the stoichiometric air fuel ratio. Start.

  Although not shown in FIG. 7, in the ECU 7A, the target opening degree of the throttle valve corresponds to the throttle according to the estimated actual supercharged intake amount by searching a map not shown based on the estimated actual supercharged intake amount. The effective opening of the valve is calculated, and this is output as the target opening.

  Next, an example of control realized by the ECU 7A as described above will be described with reference to the time chart of FIG. In FIG. 8, from the upper stage, an amount related to the torque such as the target torque, an amount related to the intake amount such as the final target intake amount, a target air fuel ratio, a target opening degree of the throttle valve, and a target ignition timing of the spark plug Indicate.

  Similar to FIG. 6, FIG. 8 shows a time chart realized when the target torque is changed from the first target torque to the second target torque by the driver performing the acceleration operation at time t1.

  First, as shown by a thick broken line in the uppermost stage of FIG. 8, at time t1, the target torque changes stepwise from the first target torque to the second target torque. Therefore, in the operation mode, the supercharging lean operation is performed between time t0 and t1, and the supercharging stoichiometric operation is performed after time t1. Further, the torque actually realized is indicated by a solid line at the top of FIG. Therefore, the time period until the actual torque starts to increase from the first target torque at time t1 and reaches the second target torque at time t5 corresponds to the above-described supercharging lean / stoichiometric transition period.

  As the target torque increases from the first target torque to the second target torque, the final target intake air amount calculated by the final target intake air amount calculation unit 752 is shown by a thick broken line in the second stage from the top of FIG. At time t1, it changes stepwise. Therefore, as described with reference to FIG. 6, the estimated actual supercharged intake amount (thick dotted line in the second stage from the top of FIG. 6) follows the step-like change of the final target intake amount from time t1. Thus, the pressure gradually rises to reach the final target intake air amount approximately at time t4. As described with reference to FIG. 6, the estimated actual supercharged intake air amount rises rapidly without being affected by the supercharging delay between times t1 and t4.

  Further, as shown in the second stage from the bottom in FIG. 8, the target opening of the throttle valve is an effective opening (for example, full opening) such that the estimated actual supercharged intake amount is realized without generating air throttling. It is set. For this reason, as shown by the thin solid line in the second stage from the top of FIG. 8, the actually realized intake amount exhibits substantially the same change as the estimated actual supercharged intake amount.

  On the other hand, the lean prohibited intake amount supercharging delay calculation unit 755 is a virtual supercharged delay presumed to occur when it is assumed that the operation of the engine and the supercharger is always continued under the lean operation prohibited map. By performing the processing, the estimated lean intake amount (the alternate long and short dash line in the second stage from the top of FIG. 8) is calculated. Therefore, during the period from time t0 to time t1, the lean prohibited estimated intake amount is always smaller than the estimated actual supercharged intake amount. Also, even after the target torque changes from the first target torque to the second target torque at time t1, the lean prohibited estimated intake amount is smaller than the estimated actual supercharged intake amount, and until the final target intake amount is reached. The time (time t1 to t4) is also long. This is because the lean prohibited estimated intake amount is calculated on the assumption that the turbine of the supercharger is stopped between time t0 and t1. That is, assuming that the operation is always continued under the lean operation prohibition map, the turbine starts to rotate at time t1 and therefore, the turbine starts to rotate and the boost pressure actually starts to increase. This is because there is a delay in supercharging.

  Next, the lean prohibited torque estimation unit 771 uses the lean prohibited estimated intake amount thus calculated to introduce a torque that is realized when the lean prohibited estimated intake amount is introduced. Output as the estimated torque when prohibited. At the top of FIG. 8, changes in the estimated torque during lean operation inhibition are displayed by thick dotted lines.

  Next, the estimated actualized torque calculation unit 761 performs the delay process simulating the response delay of the fuel injection valve to the target torque to calculate an estimated actualized torque as shown by a two-dot chain line in the uppermost stage of FIG. Further, the target air-fuel ratio calculation unit 762 outputs an air-fuel ratio that realizes the estimated realized torque as a target air-fuel ratio. Therefore, as shown in the third stage from the bottom of FIG. 8, the target air-fuel ratio changes from the lean air-fuel ratio from time t1 to t3 in response to the change of the target torque from the first target torque to the second target torque. It is gradually changed to the stoichiometric air-fuel ratio.

  On the other hand, the target ignition timing calculation unit 772 calculates the target ignition timing of the spark plug as indicated by the solid line in the lowermost stage of FIG. 8 by dividing the cases into the supercharging lean / stoichiometric transition period and the other period. Here, between time t0 and t1, the target ignition timing calculation unit 772 calculates MBT (see, for example, a broken line in the lowermost stage in FIG. 8) calculated based on the estimated actual supercharged intake amount as the target ignition timing. Do.

  Further, after the target ignition timing calculation unit 772 shifts to within the supercharging lean / stoichiometric transition period at time t1, the target air-fuel ratio falls below a threshold set to a value slightly larger than the stoichiometric air-fuel ratio at time t2. In response, retardation of the target ignition timing is started. More specifically, the target ignition timing calculation unit 772 sets the target ignition timing on the retard side with respect to the MBT so that the above-described estimated lean operation prohibition torque is realized. Therefore, at time t2, the target ignition timing is changed from the MBT indicated by the broken line to the retard side. At this time, the target ignition timing calculation unit 772 changes the target ignition timing to the retard side under the rate limit in order to prevent a misfire. For this reason, the target ignition timing is gradually changed from the MBT to the retardation side over time t2 to t3.

  Further, between time t3 and time t4, the target ignition timing calculation unit 772 maintains the target ignition timing substantially at a timing delayed by a predetermined amount with respect to the MBT so that the lean operation prohibition estimated torque is realized. As a result, the torque to be realized changes from the time t3 to the time t4 in line with the lean operation prohibited estimated torque. Further, between times t4 and t5, the target ignition timing is changed to the advance side so as to gradually approach MBT as the difference between the lean operation prohibited estimated torque and the second target torque gradually decreases. Ru.

  As described above, in the supercharging lean / stoichiometric transition period (time t1 to t5) that occurs when the target torque changes from the first target torque to the second target torque, the ECU 7A makes the target air-fuel ratio stoichiometric from the air-fuel ratio The torque realized when the target ignition timing is always maintained at MBT by gradually changing the air fuel ratio and setting the target ignition timing to be retarded with respect to MBT (one point at the top of FIG. 8 The actually realized torque (see the thin solid line at the top of FIG. 8) can be reduced compared to the dashed line). Further, in the ECU 7A, in the supercharged lean / stoichiometric transition period, when the torque to be realized is shifted from the non-supercharged stoichiometric operation to the supercharged stoichiometric operation by setting the target ignition timing according to the lean prohibited estimated torque. (Ie, the torque achieved when there is a delay in supercharging (see the thick dotted line at the top of FIG. 6)). Therefore, the driver can always obtain the same torque response regardless of the type of operation mode being executed at the time of performing the acceleration operation, so there is no sense of incongruity, and therefore, the productability can be improved.

1 ... Engine (internal combustion engine)
1c: Fuel injection valve 1d: Ignition plug 2: Control device 7: ECU (target torque calculation means, operation mode switching means, supercharging lean operation prohibition means, target setting means, target air fuel ratio setting means, target opening degree setting means)
7A ... ECU (target torque calculation means, operation mode switching means, supercharging lean operation prohibition means, target setting means, target ignition timing setting means, target opening setting means)
751 ··· Operation area determination unit 752 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 時 · · · 吸 気 · 吸 気 · · · 目標 · · · target opening Degree calculation unit 761 ... Estimated realized torque calculation unit 762 ... Target air-fuel ratio calculation unit 771 ... Lean prohibited torque estimation unit 772 ... Target ignition timing calculation unit 8 ... Supercharger

Claims (3)

A control device for an internal combustion engine capable of changing the supercharging pressure of intake air by a supercharger and changing the air-fuel ratio between lean and stoichiometric,
Target torque calculation means for calculating a target torque for the internal combustion engine according to a request;
When the target torque is in the supercharging lean operating range, supercharging lean operating is performed to make the air-fuel ratio lean while driving the supercharger, and the target torque is higher than the supercharging lean operating range Operation mode switching means for executing a supercharged stoichiometric operation for making the air-fuel ratio stoichiometric while driving the supercharger in a high torque side supercharged stoichiometric operation region;
When the lean operation prohibition condition is satisfied, even if the target torque is in the supercharged lean operation region, the non-supercharged stoichiometric operation in which the air-fuel ratio is made stoichiometric without driving the supercharger. Means for prohibiting supercharging lean operation to be performed;
A period from when the actual torque reaches the first target torque in the supercharging lean operation region to the second target torque in the supercharging stoichiometric operation region is defined as a transient period, and the target during the supercharging lean operation is determined When the torque changes from the first target torque to the second target torque, a change in the actual torque during the transition period occurs when a change in the target torque occurs during execution of the non-supercharged stoichiometric operation. Target setting means for setting the target opening of the throttle valve and the target air-fuel ratio so as to approach a change in torque to be realized;
Torque control means for controlling the opening degree of the throttle valve and the air-fuel ratio so that the target opening degree and the target air-fuel ratio are realized;
The target setting means is
Target air-fuel ratio setting means for gradually changing the target air-fuel ratio from lean to stoichiometric according to the target torque changing from the first target torque to the second target torque;
The intake quantity change that is realized when the change in the target torque occurs during execution of the non-supercharged stoichiometric operation is estimated in consideration of the supercharging delay, so that the estimated intake quantity change is realized, A control device for an internal combustion engine, comprising: target opening setting means for setting the target opening on the closing side with respect to a reference opening. A control device for an internal combustion engine capable of changing the supercharging pressure of intake air by a supercharger and changing the air-fuel ratio between lean and stoichiometric,
Target torque calculation means for calculating a target torque for the internal combustion engine according to a request;
When the target torque is in the supercharging lean operating range, supercharging lean operating is performed to make the air-fuel ratio lean while driving the supercharger, and the target torque is higher than the supercharging lean operating range Operation mode switching means for executing a supercharged stoichiometric operation for making the air-fuel ratio stoichiometric while driving the supercharger in a high torque side supercharged stoichiometric operation region;
When the lean operation prohibition condition is satisfied, even if the target torque is in the supercharged lean operation region, the non-supercharged stoichiometric operation in which the air-fuel ratio is made stoichiometric without driving the supercharger. Means for prohibiting supercharging lean operation to be performed;
A period from when the actual torque reaches the first target torque in the supercharging lean operation region to the second target torque in the supercharging stoichiometric operation region is defined as a transient period, and the target during the supercharging lean operation is determined When the torque changes from the first target torque to the second target torque, a change in the actual torque during the transition period occurs when a change in the target torque occurs during execution of the non-supercharged stoichiometric operation. Target setting means for setting a target ignition timing and a target air-fuel ratio of the internal combustion engine so as to approach a change in torque to be realized;
Torque control means for controlling the ignition timing and the air-fuel ratio so that the target ignition timing and the target air-fuel ratio are realized;
The target setting means is
Target air-fuel ratio setting means for gradually changing the target air-fuel ratio from lean to stoichiometric according to the target torque changing from the first target torque to the second target torque;
The reference ignition timing is estimated such that a torque change realized when a change in the target torque occurs during execution of the non-supercharged stoichiometric operation in consideration of a supercharging delay, and the estimated torque change is realized. And a target ignition timing setting means for setting the target ignition timing on the retard side.   The target air-fuel ratio setting means may start changing the target air-fuel ratio from lean to stoichiometry before the target ignition timing setting means starts to set the target ignition timing on the retard side of the reference ignition timing. The control device of an internal combustion engine according to claim 2, characterized by

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