JP5333199B2 - Operation control system for direct injection engine - Google Patents

Description

  The present invention relates to an apparatus for controlling the operation of a direct injection engine.

  The operation control device for a direct injection engine disclosed in Patent Document 1 divides and injects fuel into a plurality of times in one cycle when, for example, it is necessary to warm up the exhaust gas purification catalyst. When the divided fuel injection amount is too small and may fall below the allowable lower limit injection amount, the operation control device increases the fuel injection amount and corrects the ignition timing so as to offset the increase in torque due to the increase correction. Correct the angle. The related document known invention is also described in Patent Document 2.

JP 2001-323834 A Japanese Patent Laid-Open No. 10-212987

  However, when the ignition timing is retarded (for example, after compression top dead center) in order to warm up the exhaust gas purification catalyst early, the ignition timing is changed when switching from the split injection operation to the batch injection operation. However, if the fuel injection amount falls below the allowable lower limit injection amount in such a case, even if the fuel injection amount is corrected to increase as in the conventional direct injection engine operation control device described above, Since the ignition timing cannot be retarded, torque fluctuations are likely to occur and it is difficult to switch smoothly.

  The present invention has been made paying attention to such a conventional problem, and is an operation of a direct injection engine capable of smoothly switching from a divided injection operation to a batch injection operation while suppressing the occurrence of torque fluctuation. An object is to provide a control device.

  The present invention solves the above problems by the following means.

  The present invention relates to an apparatus for controlling the operation of a direct injection engine in which fuel is directly injected into a cylinder. When a request for split injection operation is received, a split injection operation unit that divides the fuel into a plurality of times in one cycle and retards the ignition timing as compared with the batch injection operation, and a request for transition to the batch injection operation are received. A transition operation unit that makes the air-fuel ratio richer than the air-fuel ratio of the divided injection operation and increases the ratio of the injection that minimizes the injection amount among the plurality of divided injections to advance the ignition timing. It is characterized by having.

  According to the present invention, when the shift from the split injection operation to the collective injection operation is performed, the occurrence of torque fluctuation is suppressed and a smooth transition can be made.

It is a figure explaining one Embodiment of the operation control apparatus of the direct injection engine by this invention. It is a flowchart which shows an example of the control logic of the operation control apparatus of the direct injection engine by this invention. It is a flowchart which shows an example of the control logic of division | segmentation injection driving | operation. It is a flowchart which shows an example of the control logic of a transfer driving | operation start. It is a timing chart explaining the operation | movement when a control logic is performed.

  Hereinafter, embodiments for carrying out the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a diagram for explaining an embodiment of an operation control apparatus for a direct injection engine according to the present invention.

  First, the direct injection engine 2 to which the engine operation control device 1 is applied will be described.

  The direct injection engine 2 is an engine in which fuel is directly injected into the cylinder 20a. A fuel injection valve 21, a spark plug 22, and a water temperature sensor 23 are attached to the main body 20 of the direct injection engine 2. The operation of the direct injection engine 2 is controlled by the engine operation control device 1. The fuel injection valve 21 faces the cylinder 20a. The fuel injection valve 21 directly injects fuel into the cylinder 20a. The fuel injection valve 21 is an electromagnetically operated injection valve. The spark plug 22 faces the cylinder 20a. The spark plug 22 ignites the air-fuel mixture in the cylinder 20a. The water temperature sensor 23 detects the cooling water temperature of the engine.

  An air flow sensor 241 and a throttle valve 242 are disposed in the intake passage 24 of the direct injection engine 2. The air flow sensor 241 detects the amount of air taken into the direct injection engine 2. The detection signal is transmitted to the engine operation control device 1. The throttle valve 242 adjusts the opening according to the signal from the engine operation control device 1 and controls the amount of air taken into the direct injection engine 2. The actual opening of the throttle valve 242 is detected by an opening sensor 243. The detection signal is transmitted to the engine operation control device 1.

  An exhaust gas purification catalyst 251 is disposed in the exhaust passage 25 of the direct injection engine 2. The exhaust gas purification catalyst 251 is, for example, a three-way catalyst. The exhaust gas purification catalyst 251 is warmed up and exhibits exhaust gas purification performance. The exhaust gas purification catalyst 251 can purify the exhaust gas with high efficiency, particularly when the temperature becomes equal to or higher than a predetermined activation temperature.

  The engine operation control device 1 is a device that controls the operation of the direct injection engine 2. The engine operation control device 1 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The engine operation control apparatus 1 may be composed of a plurality of microcomputers. The engine operation control device 1 detects the operation state of the engine based on signals transmitted from the water temperature sensor 23, the airflow sensor 241, the opening degree sensor 243, and the like. Then, the fuel injection timing and fuel injection amount by the fuel injection valve 21 and the ignition timing by the spark plug 22 are controlled.

  As described above, the exhaust gas purification catalyst 251 is warmed up and can exhibit exhaust gas purification performance. In particular, exhaust gas can be purified with high efficiency at a temperature equal to or higher than a predetermined activation temperature. Therefore, it is desirable that the exhaust gas purifying catalyst 251 quickly reaches the activation temperature. Therefore, the engine operation control apparatus 1 controls the fuel injection valve 21 so that the ignition timing is retarded from the compression top dead center, and fuel is divided and injected into a plurality of times in one cycle. As a result, the thermal efficiency decreases and the exhaust gas temperature rises, so that the exhaust gas purification catalyst 251 quickly reaches the activation temperature. Further, if the ignition timing is retarded until after the compression top dead center, the engine torque decreases. Therefore, the intake air amount is increased more than after the catalyst is warmed up to increase the fuel injection amount.

Here, when switching from split injection operation to batch injection operation, the ignition timing is advanced from after compression top dead center to before compression top dead center, and in accordance with the reduction of intake air amount for engine torque adjustment If the fuel injection amount is reduced, the fuel injection amount of the fuel injection valve 21 becomes too small, and the fuel injection amount may fall below the allowable lower limit injection amount. In view of this, it is conceivable to increase the ratio of the split injections that minimizes the fuel injection amount. On the other hand, the present inventors have conducted intensive research and found that, for example, when the fuel is injected in two divided portions, the second injection amount particularly contributes to the engine torque. Therefore, when the fuel is injected by dividing into the first injection with a smaller injection amount and the second injection with a larger injection amount, and switching from the divided injection operation to the batch injection operation, the fuel injection amount becomes the allowable lower limit injection amount. If the ratio of the injection quantity of the first injection to the injection quantity of the second injection is increased so that it does not fall below, the ratio of the injection quantity of the second injection becomes smaller and torque fluctuations occur.
Therefore, when the transition from the split injection operation to the batch injection operation is started, the injection amount of the second injection is kept constant by making the air-fuel ratio richer than the air-fuel ratio of the split injection operation.

  Further, during the transition operation, the injection amount of the first injection is made the same as the injection amount of the second injection so that the transition operation can be performed as long as possible. If there is some amount instead of the same amount, the divided injection operation must be terminated when one of the smaller injection amounts reaches the allowable lower limit injection amount. By making the injection amount of the first injection the same as the injection amount of the second injection, it is possible to lengthen the time until the injection amount reaches the allowable lower limit injection amount, and in this respect also, torque fluctuation is less likely to occur.

  Specific contents will be described below.

  FIG. 2 is a flowchart showing an example of the control logic of the operation control apparatus for a direct injection engine according to the present invention.

  For example, when the exhaust gas purifying catalyst is in a cold state, the engine operation control device 1 repeatedly executes this processing in a cycle of several milliseconds.

  In step S1, the engine operation control device 1 determines whether or not the transition operation from the split injection operation to the collective injection operation has started. The engine operation control apparatus 1 proceeds to step S2 before starting the transition operation, and proceeds to step S5 after starting the transition operation.

  In step S2, the engine operation control apparatus 1 determines whether or not it is requested to end the split injection operation and shift to the batch injection operation. For example, when the exhaust gas purification catalyst does not need to be warmed up (warm-up), it is required to end the split injection operation and shift to the batch injection operation. Whether or not the exhaust gas purification catalyst needs to be warmed up may be estimated based on the engine cooling water temperature detected by the water temperature sensor 23. Further, a temperature sensor may be provided in the exhaust gas purification catalyst 251 and the determination may be made based on the temperature directly detected by the temperature sensor. If there is no shift request, the engine operation control apparatus 1 proceeds to step S3, and if there is a shift request, proceeds to step S4.

  In step S3, the engine operation control apparatus 1 performs a split injection operation (fuel injection in the intake stroke and the compression stroke). Specific contents will be described later.

  In step S4, the engine operation control apparatus 1 starts a transition operation. Specific contents will be described later.

  In step S5, the engine operation control apparatus 1 gradually advances the ignition timing.

  In step S6, the engine operation control apparatus 1 maintains the air-fuel ratio by decreasing the fuel injection amount in accordance with the decrease in the intake air amount while maintaining the fuel injection amount split ratio.

  In step S7, the engine operation control apparatus 1 determines whether or not the fuel injection amount is larger than the allowable lower limit injection amount. If it is larger, the engine operation control apparatus 1 once exits the process, and if not larger, the process proceeds to step S8.

  In step S8, the engine operation control apparatus 1 ends the split injection operation and starts a collective injection operation (for example, a homogeneous combustion operation in which fuel is injected collectively in the intake stroke).

  FIG. 3 is a flowchart showing an example of the control logic of the split injection operation.

  In step S31, the engine operation control apparatus 1 sets the fuel injection amount so as to achieve the target air-fuel ratio. The target air-fuel ratio is, for example, an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. By doing in this way, unburned hydrocarbon HC can be reduced.

  In step S32, the engine operation control apparatus 1 divides the fuel injection amount set in step S31 by 1 so that the split ratio of the injection amount of the first injection and the injection amount of the second injection becomes 4: 6. An injection amount for the second injection and an injection amount for the second injection are set.

  In step S33, the engine operation control apparatus 1 sets the ignition timing after compression top dead center, and controls the ignition timing of the spark plug 22. Further, in order to prevent a decrease in engine torque due to a delay of the ignition timing after compression top dead center, the opening of the throttle valve is made larger than the opening during the batch injection operation.

  FIG. 4 is a flowchart illustrating an example of the control logic for starting the transition operation.

  In step S41, the engine operation control apparatus 1 sets the opening of the throttle valve to the opening of the batch injection operation.

  In step S42, the engine operation control device 1 starts the advance control of the ignition timing toward the ignition timing of the collective injection operation.

  In step S43, the engine operation control apparatus 1 sets the split ratio between the injection amount of the first injection and the injection amount of the second injection to 5: 5 and makes the target air-fuel ratio richer than that in the split injection operation. Maintain the injection quantity of the second injection.

  FIG. 5 is a timing chart for explaining the operation when the control logic is executed.

  The above control logic is executed and operates as follows.

  The engine operation control device 1 starts this control during the split injection operation. Until it is required to end the split injection operation and shift to the collective injection operation, the engine operation control device 1 repeatedly performs steps S1 → S2 → S3 (S31 → S32 → S33).

  Then, a target air-fuel ratio (15.5 in the present embodiment) that is leaner than the stoichiometric air-fuel ratio is set in advance (FIG. 5D), and the fuel injection amount is set so as to be the target air-fuel ratio. Then, the injection quantity of the first injection and the injection quantity of the second injection are set so that the ratio of the injection quantity of the first injection and the injection quantity of the second injection is 4: 6 (FIG. 5E) ( FIG. 5 (F)). Further, the ignition timing is set after compression top dead center (ATDC) (FIG. 5C). As the ignition timing is retarded after compression top dead center, the throttle is opened more than in the batch injection operation (FIG. 5A).

  When it is requested to end the split injection operation at time t1 and shift to the collective injection operation, the engine operation control device 1 advances the process in steps S1 → S2 → S4 (S41 → S42 → S43).

  Then, the throttle valve is closed (FIG. 5A), and the intake air amount is reduced (FIG. 5B). In addition, the ignition timing starts to advance toward the ignition timing of the collective injection operation (FIG. 5C). Then, the division ratio between the injection amount of the first injection and the injection amount of the second injection is set to 5: 5 (FIG. 5E), and the air-fuel ratio richer than the theoretical air-fuel ratio (14 in this embodiment). (FIG. 5D), the injection amount of the second injection is maintained, and the injection amount of the first injection is increased so as to be the same as the injection amount of the second injection (FIG. 5 ( F)).

  Since the transition operation is started at time t1, the engine operation control device 1 repeats steps S1 → S5 → S6 → S7 after the next cycle.

  Then, the ignition timing is gradually advanced (FIG. 5C). Since the throttle is closed at time t1 (FIG. 5A), the intake air amount is reduced after time t1 (FIG. 5B), and the fuel injection amount is reduced (FIG. 5F).

  At time t2, the fuel injection amount reaches the allowable lower limit injection amount. The engine operation control apparatus 1 advances the process in steps S1 → S5 → S6 → S7 → S8.

  Then, the split injection operation is completed, and the collective injection operation (for example, the homogeneous combustion operation in which fuel is injected collectively in the intake stroke) is started.

  The engine operation control device of the present embodiment makes the air-fuel ratio leaner than the stoichiometric air-fuel ratio during the split injection operation and retards the ignition timing after compression top dead center. Since it did in this way, an exhaust gas purification catalyst reaches | attains activation temperature rapidly, and unburned hydrocarbon HC is reduced.

The engine operation control device of the present embodiment sets the division ratio between the injection amount of the first injection and the injection amount of the second injection to 5: 5 when starting the transition operation from the divided injection operation to the collective injection operation. To do. When switching from split injection operation to batch injection operation, the fuel injection amount is adjusted to reduce the intake air amount to adjust the engine torque while advancing the ignition timing from after compression top dead center to before compression top dead center If the amount is reduced, the fuel injection amount becomes too small and the fuel injection amount may fall below the allowable lower limit injection amount. Therefore, by increasing the ratio of the injection amount of the first injection to the injection amount of the second injection, the fuel injection amount does not fall below the allowable lower limit injection amount.
On the other hand, when the ratio of the injection quantity of the first injection to the injection quantity of the second injection is increased, the ratio of the injection quantity of the second injection is reduced, that is, the second injection quantity contributing to the engine torque varies. As a result, torque fluctuation occurs. Therefore, the engine operation control device of the present embodiment maintains the injection amount of the second injection by making the air-fuel ratio richer than that in the split injection operation when starting the transition operation from the split injection operation to the collective injection operation. To do. Since the second injection has a higher contribution to the engine torque than the first injection, according to the present embodiment, the occurrence of torque fluctuation is suppressed.

  Furthermore, the engine operation control apparatus of this embodiment makes the injection amount of the first injection the same as the injection amount of the second injection during the transition operation. If there is some amount instead of the same amount, the divided injection operation must be terminated when one of the smaller injection amounts reaches the allowable lower limit injection amount. By doing like this embodiment, the period until a division | segmentation injection driving | operation is complete | finished becomes long, and a division | segmentation injection driving | operation can be complete | finished after the amount of intake air decreases sufficiently. Also in this respect, the occurrence of torque fluctuation is suppressed.

  Furthermore, the engine operation control device of the present embodiment operates at a lean air-fuel ratio rather than the stoichiometric air-fuel ratio during the split injection operation, but when starting the transition operation from the split injection operation to the collective injection operation, Is made richer than the theoretical air-fuel ratio. Therefore, it can also serve as a rich spike.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the above description, the number of divisions in the divided injection operation is two, but may be three or more.

  In addition, specific numerical values such as a division ratio and an air-fuel ratio are only examples. What is necessary is just to determine suitably according to the specification etc. of an engine.

  Furthermore, although the case where it is necessary to warm up the catalyst in the case of the split injection operation is illustrated, it is not limited thereto.

  The engine operation control device of the above embodiment changes the split ratio of the first injection and the second injection and changes the air-fuel ratio to rich when starting the transition operation from the split injection operation to the collective injection operation. These may be changed during the transition from the split injection operation to the collective injection operation, and when the fuel injection amount reaches the allowable lower limit injection amount during the transition from the split injection operation to the collective injection operation. You can change it.

  The engine operation control device of the above embodiment performs the first injection in the intake stroke and the second injection in the compression stroke, but the first injection may be performed in the compression stroke, and the second injection may be performed in the expansion stroke. Good.

DESCRIPTION OF SYMBOLS 1 Engine operation control apparatus 2 Direct injection engine 20a Cylinder 21 Fuel injection valve 22 Spark plug 251 Exhaust gas purification catalyst Step S3 Split injection operation part Step S4 Transition operation part

Claims (7)

A device for controlling the operation of a direct injection engine in which fuel is directly injected into a cylinder,
Upon receiving a request for split injection operation, a split injection operation unit that injects fuel into a plurality of times in one cycle and retards the ignition timing than the collective injection operation;
Upon receiving the request for transition to the batch injection operation, the air-fuel ratio is made richer than the air-fuel ratio in the split injection operation, and the ratio of the injection that minimizes the injection amount among the plurality of split injections is increased, and the ignition timing is set. A transition driving part that advances,
A direct-injection engine operation control device. In the direct injection engine operation control device according to claim 1,
The divided injection operation unit injects fuel in one cycle, divided into a first injection with a smaller injection amount and a second injection with a larger injection amount,
The transition operation unit increases a ratio of an injection amount of the first injection to an injection amount of the second injection;
An operation control apparatus for a direct injection engine. A device for controlling the operation of a direct injection engine in which fuel is directly injected into a cylinder,
Upon receiving a request for split injection operation, a split injection operation unit that injects fuel into a plurality of times in one cycle and retards the ignition timing than the collective injection operation;
When a request for transition to the batch injection operation is received, the fuel injection amount is made while making the air-fuel ratio richer than the air-fuel ratio of the divided injection operation and maintaining the injection amount of the latest injection timing among the plurality of divided injections A transition operation part that increases the injection amount of the injection that minimizes and advances the ignition timing;
A direct-injection engine operation control device. In the direct injection engine operation control device according to claim 3,
The divided injection operation unit injects fuel in one cycle, divided into a first injection with a smaller injection amount and a second injection with a larger injection amount,
The transition operation unit increases the injection amount of the first injection while maintaining the injection amount of the second injection.
An operation control apparatus for a direct injection engine. In the direct-injection engine operation control device according to any one of claims 1 to 4,
The split injection operation unit receives a request for split injection operation when it is necessary to warm up the exhaust gas purification catalyst,
The transition operation unit receives a transition request to a batch injection operation when it is not necessary to warm up the exhaust gas purification catalyst.
An operation control apparatus for a direct injection engine. In the direct injection engine operation control device according to any one of claims 1 to 5,
The split injection operation unit operates at an air / fuel ratio leaner than the stoichiometric air / fuel ratio, and the transition operation unit operates at an air / fuel ratio richer than the stoichiometric air / fuel ratio,
An operation control apparatus for a direct injection engine. The operation control apparatus for a direct injection engine according to any one of claims 1 to 6,
The transition operation unit makes the injection amount of the first injection the same as the injection amount of the second injection.
An operation control apparatus for a direct injection engine.

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