JP2017223119A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both of suppression of torsional vibration and improvement of fuel consumption efficiency regarding an internal combustion engine capable of performing homogeneous lean operation.SOLUTION: A control device for an internal combustion engine comprises: an operation switching part for switching an operation mode between stoichiometric operation and homogeneous lean operation; a lean operation determination part for determining whether or not the homogeneous lean operation can be performed based on an operational state of the internal combustion engine; a vibration generation estimation part for estimating generation of torsional vibration in a drive system; and an ignition timing control part for controlling ignition timing in such a manner that the torsional vibration is suppressed, in the case where the generation of the torsional vibration is estimated. In the case where it is determined that the homogeneous lean operation can be performed and the generation of the torsional vibration is not estimated, the operation switching part sets the operation mode to the homogeneous lean operation. In the case where it is determined that the homogeneous lean operation can be performed and the generation of the torsional vibration is estimated, even under an operational state where the homogeneous lean operation can be performed, the operation switching part sets the operation mode to the stoichiometric operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine capable of homogeneous lean operation.

  When the vehicle accelerates, the engine torque may change suddenly and an acceleration shock may occur. At this time, “torsional vibration” may occur in the drive system that transmits the output of the internal combustion engine to the drive wheels. Since the generation of torsional vibrations leads to a decrease in drivability and running stability, it is desirable to suppress torsional vibrations.

  Patent Document 1 discloses an ignition timing control device for an internal combustion engine that suppresses torsional vibration. The ignition timing control device includes acceleration detection means, retard angle control means, phase control means, rotational speed change amount detection means, and switching means. The acceleration detection means detects that the internal combustion engine is in an acceleration state. When the acceleration state is detected, the retard angle control means performs retard angle control in order to reduce acceleration shock. Further, the phase control means performs ignition timing control for generating an engine torque having a phase opposite to that of the torsional vibration in order to reduce the torsional vibration. The rotation speed change amount detecting means detects a change amount of the rotation speed of the internal combustion engine. After the acceleration state is detected, when the amount of change in the rotation speed first becomes a positive predetermined value or more, the switching unit switches the ignition timing control from the retard control unit to the phase control unit.

  As other conventional techniques, Patent Literature 2, Patent Literature 3, and Patent Literature 4 are known.

JP-A-5-321803 JP-A-8-303282 JP 2004-197753 A JP 2002-349332 A

  As one of operation modes (combustion modes) of an internal combustion engine, homogeneous lean operation (homogeneous lean combustion) is known. Since the air-fuel ratio in the cylinder in the homogeneous lean operation is higher than that in the stoichiometric operation, the homogeneous lean operation is preferable from the viewpoint of improving fuel consumption. On the other hand, in the case of the homogeneous lean operation, the range of the ignition timing at which misfire does not easily occur is narrower than in the case of the stoichiometric operation. Therefore, if ignition timing control as disclosed in Patent Document 1 is performed in order to suppress torsional vibration during homogeneous lean operation, misfire may occur.

  One object of the present invention is to provide a technology capable of achieving both suppression of torsional vibration and improvement of fuel consumption for an internal combustion engine capable of homogeneous lean operation.

  In one aspect of the present invention, a control device for an internal combustion engine is provided. The control device includes an operation switching unit that switches an operation mode of the internal combustion engine between a stoichiometric operation and a homogeneous lean operation, a lean operation determination unit that determines whether or not the homogeneous lean operation is possible based on an operation state of the internal combustion engine, and a drive A vibration generation estimator that estimates the occurrence of torsional vibration of the system, and an ignition timing control unit that controls the ignition timing so that torsional vibration is suppressed when the occurrence of torsional vibration is estimated; Is provided. When it is determined that the homogeneous lean operation is possible and the occurrence of torsional vibration is not estimated, the operation switching unit sets the operation mode to the homogeneous lean operation. When it is determined that the homogeneous lean operation is possible and the occurrence of torsional vibration is estimated, the operation switching unit sets the operation mode to the stoichiometric operation even in an operation state in which the homogeneous lean operation is possible. .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to aim at coexistence of suppression of torsional vibration, and improvement of a fuel consumption about the internal combustion engine which can perform a homogeneous lean driving | operation.

It is a conceptual diagram for demonstrating the outline | summary of embodiment of this invention. It is a block diagram which shows the structural example of the control apparatus of the internal combustion engine which concerns on embodiment of this invention. It is a flowchart which shows the operation mode control by the control apparatus which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

1. Outline First, an outline of an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of the temporal change of the engine operating state in the present embodiment. As the engine operation state, an engine rotation speed, an engine torque, and an operation mode are shown. In the present embodiment, at least two types of operation modes of the engine (internal combustion engine) are possible: stoichiometric operation and homogeneous lean operation. That is, the operation mode can be switched at least between stoichiometric operation and homogeneous lean operation.

  In the example shown in FIG. 1, the driver first removes his / her foot from the accelerator pedal, and the engine is not driving the vehicle (driven state). Thereafter, the driver depresses the accelerator pedal (this operation is called “chip-in”), and at time t1, the engine changes to a state of driving the vehicle (driving state). Thereafter, the driver further depresses the accelerator, and the vehicle accelerates.

  During acceleration of the vehicle, “torsional vibration” may occur in a drive system such as a drive shaft that transmits engine output to drive wheels. Torsional vibration appears as vibration of engine rotation speed, for example. In the example of FIG. 1, both the case where torsional vibration occurs at time t2 and the case where no torsional vibration occurs are shown.

  First, the case where torsional vibration does not occur will be described. In order to perform the homogeneous lean operation, the engine operating state needs to be within an area where the homogeneous lean operation is possible. More specifically, it is necessary that the engine load (engine torque, intake pipe pressure, intake air amount, etc.) and the engine rotation speed are within the permitted ranges. In the example shown in FIG. 1, homogeneous lean operation is not yet possible when vehicle acceleration begins. Therefore, the operation mode is set to stoichiometric operation. Thereafter, the engine rotation speed and the engine torque increase, and at time t3, the engine operating state enters an area where homogeneous lean operation is possible. In response to this, the operation mode is immediately switched from the stoichiometric operation to the homogeneous lean operation. By performing homogeneous lean operation, fuel efficiency is improved.

  Next, consider the case where torsional vibration occurs at time t2. When torsional vibration is generated, it is preferable to suppress the torsional vibration at an early stage. For that purpose, for example, it is conceivable to perform ignition timing control as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 5-321803). However, in the case of homogeneous lean operation, the minimum torque that can be realized is larger (cannot be reduced) than in the case of stoichiometric operation, and it is difficult to perform retard control (light load torque control) for reducing acceleration shock. Further, in the homogeneous lean operation, compared to the stoichiometric operation, the torque sensitivity with respect to the change of the ignition timing is poor, and it is difficult to perform the ignition phase control for suppressing torsional vibration. That is, in the case of the homogeneous lean operation, the ignition timing control as disclosed in Patent Document 1 may not work effectively. In the homogeneous lean operation, the range of the ignition timing at which misfire is difficult to occur is narrower than in the stoichiometric operation. Accordingly, if the ignition timing control is forcibly performed in order to suppress torsional vibration during the homogeneous lean operation, misfire may occur.

  Therefore, according to the present embodiment, while the generation of torsional vibration is estimated, even if the homogeneous lean operation is possible, the homogeneous lean operation is prohibited. While the homogeneous lean operation is prohibited, the operation mode is not switched to the homogeneous lean operation even if the engine operation state enters the region where the homogeneous lean operation is possible. That is, when the occurrence of torsional vibration is estimated, the operation mode is set to the stoichiometric operation even under the engine operation state in which the homogeneous lean operation is possible. In the example shown in FIG. 1, the occurrence of torsional vibration is estimated at time t2, and the homogeneous lean operation is prohibited. At time t3, the engine operating state enters an area where homogeneous lean operation is possible, but since the homogeneous lean operation is prohibited, the operation mode is not switched and the stoichiometric operation is maintained.

  On the other hand, when the occurrence of torsional vibration is estimated, ignition timing control for suppressing torsional vibration is performed. In the example shown in FIG. 1, after the occurrence of torsional vibration is estimated at time t2, ignition timing control is performed so that torsional vibration is suppressed. As described above, after the time t2, the homogeneous lean operation is prohibited and the operation mode is set to the stoichiometric operation. In the stoichiometric operation, the ignition timing is less likely to cause misfire than in the homogeneous lean operation. By performing the ignition timing control during such stoichiometric operation, torsional vibration can be reliably suppressed without causing misfire.

  The ignition timing control is performed until the end condition is satisfied. As the end condition, for example, it is conceivable that a certain time elapses from the start of ignition timing control, or that the amplitude of torsional vibration falls below a threshold value. When the end condition is satisfied, the ignition timing control ends and the prohibition of the homogeneous lean operation is released. In the example of FIG. 1, the end condition is satisfied at time t4 after time t3, and the prohibition of the homogeneous lean operation is released. Since the engine operating state is in a region where homogeneous lean operation is possible, the operation mode is switched from stoichiometric operation to homogeneous lean operation. By performing homogeneous lean operation, fuel efficiency is improved.

  As described above, according to the present embodiment, when the occurrence of torsional vibration is estimated, the homogeneous lean operation is prohibited until the end condition is satisfied. While the homogeneous lean operation is prohibited, the operation mode is set to the stoichiometric operation even if the engine operating state is in the region where the homogeneous lean operation is possible. Then, ignition timing control for suppressing torsional vibration is performed in a state where the operation mode is set to stoichiometric operation. In the stoichiometric operation, the ignition timing is less likely to cause misfire than in the homogeneous lean operation. By performing the ignition timing control during such stoichiometric operation, torsional vibration can be reliably suppressed without causing misfire.

  Further, according to the present embodiment, when the engine operating state is in a region where homogeneous lean operation is possible and generation of torsional vibration is not estimated, homogeneous lean operation is permitted. If the homogeneous lean operation is permitted, the operation mode is immediately set to the homogeneous lean operation. By performing homogeneous lean operation, fuel efficiency is improved.

  That is, according to the present embodiment, the frequency of the homogeneous lean operation (lean frequency) can be increased as much as possible while reliably performing the ignition timing control for suppressing torsional vibration. Thereby, both suppression of torsional vibration and improvement of fuel consumption can be achieved.

2. Configuration Example Next, a configuration example for realizing the processing described in FIG. 1 will be described. FIG. 2 is a block diagram illustrating a configuration example of the control device 1 according to the present embodiment. The control device 1 is a microcomputer that controls the operation of the engine (internal combustion engine) ENG, and is also called an ECU (Electronic Control Unit). The control device 1 receives various state information from the engine ENG and sensors mounted on the vehicle, and controls the operating state of the engine ENG based on the received state information.

  In the present embodiment, at least two types of operation modes of the engine ENG are possible: stoichiometric operation and homogeneous lean operation. That is, the operation mode can be switched at least between stoichiometric operation and homogeneous lean operation. For example, the engine ENG is a supercharged lean burn engine equipped with a booster.

  As shown in FIG. 2, the control device 1 includes an operation switching unit 10, a drive driven determination unit 20, a lean operation determination unit 30, a vibration generation estimation unit 40, and an ignition timing control unit 50 as functional blocks. Yes. These functional blocks are realized by the control device 1 (microcomputer) executing a software program.

  The operation switching unit 10 switches the operation mode of the engine ENG between at least a stoichiometric operation and a homogeneous lean operation.

  The drive driven determination unit 20 determines whether the engine ENG is in a state of driving the vehicle (drive state) or not in a state of driving the vehicle (driven state). For example, when the engine load (torque, intake pipe pressure, intake air amount, etc.) is equal to or greater than a predetermined reference value, the drive driven determination unit 20 determines that the engine ENG is in a drive state. Alternatively, when the acceleration of the vehicle is equal to or greater than a predetermined reference value, drive driven determination unit 20 determines that engine ENG is in a drive state. Alternatively, when the clutch is in the engaged state, the drive driven determination unit 20 determines that the engine ENG is in the drive state.

  The lean operation determination unit 30 determines whether or not the homogeneous lean operation is possible based on the operation state of the engine ENG. In order to perform the homogeneous lean operation, the engine operating state needs to be within an area where the homogeneous lean operation is possible. More specifically, it is necessary that the engine load (engine torque, intake pipe pressure, intake air amount, etc.) and engine rotation speed are within the permitted ranges. When the engine load and the engine rotation speed are within the permitted ranges, the lean operation determination unit 30 determines that the homogeneous lean operation is possible.

  The vibration generation estimation unit 40 estimates the generation of torsional vibration of the drive system. For example, a technique disclosed in Patent Document 1 can be used to estimate the occurrence of torsional vibration. As shown in FIG. 1, the torsional vibration appears as engine rotational speed vibration. Therefore, the vibration generation estimation unit 40 can estimate the generation of torsional vibration by monitoring the amount of change in the engine speed after the start of acceleration. For example, when the change amount of the engine rotation speed becomes equal to or greater than the positive threshold value for the first time after starting acceleration, the vibration generation estimation unit 40 estimates that torsional vibration has started. This positive threshold depends on the size and structure of the engine. Moreover, you may change a positive threshold value for every gear.

  The duration of torsional vibration is finite. Therefore, when the end condition is satisfied after the start of torsional vibration is estimated, the vibration generation estimation unit 40 can estimate that the torsional vibration is no longer generated. The end condition is, for example, that a certain time has elapsed since the start of torsional vibration was estimated. Alternatively, the termination condition is that the amplitude of the torsional vibration (amount of change in engine rotation speed) falls below a threshold value for a certain period. When the termination condition is satisfied, the vibration generation estimation unit 40 estimates that no torsional vibration has occurred.

  When the occurrence of torsional vibration is estimated, the ignition timing control unit 50 controls the ignition timing of the engine ENG so that the torsional vibration is suppressed. For such ignition timing control, for example, a technique disclosed in Patent Document 1 can be used. In this case, the ignition timing control unit 50 includes an acceleration state detection unit 51, an ignition delay control unit 52, an ignition phase control unit 53, and an ignition control switching unit 54.

  The acceleration state detection unit 51 detects that the vehicle is in an acceleration state. Whether or not the vehicle is in an acceleration state can be determined based on the throttle opening, the intake pipe pressure, or the intake air amount. For example, when the amount of change in the throttle opening is equal to or greater than a predetermined value, the acceleration state detection unit 51 determines that the vehicle is in an acceleration state.

  The ignition retard control unit 52 performs retard control (light load torque control) in order to reduce acceleration shock. The retard control is a control that retards the ignition timing to reduce the engine torque and prevent a sudden increase in engine torque. The retard amount is calculated based on the throttle opening, the engine speed, the intake air amount, and the like. It is expected that the torsional vibration caused by the acceleration shock will be weakened by reducing the acceleration shock.

  The ignition phase control unit 53 performs ignition phase control in order to quickly suppress torsional vibration. The ignition phase control is control for changing the ignition timing so that the phase of the engine torque is opposite to the phase of torsional vibration. By performing the ignition phase control, it is possible to quickly suppress torsional vibration.

  The ignition control switching unit 54 switches the ignition timing control to be performed on the engine ENG between the retard angle control and the ignition phase control. For example, when the acceleration state detection unit 51 detects the acceleration state, the ignition control switching unit 54 first causes the ignition delay angle control unit 52 to perform the retard control in order to reduce acceleration shock. If the occurrence of torsional vibration is estimated by the vibration generation estimation unit 40 after the execution of the retard control, the ignition control switching unit 54 switches from the retard control to the ignition phase control. That is, the ignition control switching unit 54 causes the ignition retard control unit 52 to end the retard control, and causes the ignition phase control unit 53 to start the ignition phase control. Thereby, torsional vibration is quickly suppressed. Thereafter, when the termination condition is satisfied, the ignition control switching unit 54 causes the ignition phase control unit 53 to terminate the ignition phase control. As the end condition, for example, it is conceivable that a certain time elapses from the start of the retard control, or that the amplitude of torsional vibration falls below a threshold value.

3. Operation Mode Control FIG. 3 is a flowchart showing operation mode control by the control device 1 according to the present embodiment. This operation mode control is realized by the control device 1 performing a routine process.

Step S1:
The drive driven determination unit 20 determines whether the engine ENG is in a state of driving the vehicle (drive state) or not in a state of driving the vehicle (driven state). In the driving state (step S1; Yes), the processing flow proceeds to step S2. On the other hand, in the driven state (step S1; No), the process flow proceeds to step S4.

Step S2:
The lean operation determination unit 30 determines whether or not the homogeneous lean operation is possible based on the operation state of the engine ENG. That is, the lean operation determination unit 30 determines whether or not the engine operation state is within a region where homogeneous lean operation is possible. If the homogeneous lean operation is possible (step S2; Yes), the process flow proceeds to step S3. On the other hand, when the homogeneous lean operation is impossible (step S2; No), the process flow proceeds to step S4.

Step S3:
The vibration generation estimation unit 40 estimates generation of torsional vibration. This estimation process is executed, for example, within a predetermined period after the determination result in step S1 is changed from the driven state to the driving state. When the vibration generation estimation unit 40 estimates the generation of torsional vibration (step S3; Yes), the processing flow proceeds to step S4. On the other hand, when the vibration generation estimation unit 40 does not estimate the generation of torsional vibration (step S3; No), the process flow proceeds to step S5. After the start of torsional vibration is estimated, if the above-described end condition is satisfied, the vibration generation estimation unit 40 estimates that no torsional vibration has occurred. Also in this case, the processing flow proceeds to step S5.

Step S4:
The operation switching unit 10 prohibits homogeneous lean operation. In this case, the operation switching unit 10 sets the operation mode to stoichiometric operation even if the engine operation state is in a region where homogeneous lean operation is possible. During this stoichiometric operation, the ignition timing control unit 50 performs the above-described ignition timing control so that torsional vibration is suppressed. After step S4, the process flow returns to step S1.

Step S5:
The operation switching unit 10 permits homogeneous lean operation. In this case, the operation switching unit 10 sets the operation mode to the homogeneous lean operation. After step S5, the process flow returns to step S1.

  Next, an example of operation mode control will be described using the example shown in FIG.

  First, consider the case where torsional vibration does not occur. At time t1, the engine ENG is in a driving state (step S1; Yes). Between times t1 and t3, the engine operating state is not within the region where homogeneous lean operation is possible (step S2; No). Therefore, the operation switching unit 10 prohibits the homogeneous lean operation and sets the operation mode to stoichiometric operation (step S4). At time t3, the engine operating state enters a region where homogeneous lean operation is possible (step S2; Yes). At this time, the vibration generation estimation unit 40 does not estimate the generation of torsional vibration (step S3; No). Therefore, the operation switching unit 10 permits the homogeneous lean operation and sets the operation mode to the homogeneous lean operation (step S5).

  Next, consider the case where torsional vibration occurs. The operation mode between times t1 and t3 is stoichiometric operation as in the case where the torsional vibration described above does not occur. However, at time t2, the vibration generation estimation unit 40 estimates the generation of torsional vibration. When the generation of torsional vibration is estimated, the ignition timing control unit 50 starts ignition timing control in order to suppress the torsional vibration. At time t3, the engine operating state enters a region where homogeneous lean operation is possible (step S2; Yes). However, since the occurrence of torsional vibration is estimated (step S3; Yes), the operation switching unit 10 prohibits the homogeneous lean operation and maintains the operation mode as the stoichiometric operation (step S4). As a result, ignition timing control for suppressing torsional vibration is performed during the stoichiometric operation. Thereafter, the end condition is satisfied at time t4 (step S3; No). The operation switching unit 10 permits the homogeneous lean operation and sets the operation mode to the homogeneous lean operation (step S5).

4). Effect As described above, according to the present embodiment, when the occurrence of torsional vibration is estimated, the homogeneous lean operation is prohibited until the end condition is satisfied. While the homogeneous lean operation is prohibited, the operation mode is set to the stoichiometric operation even if the engine operating state is in the region where the homogeneous lean operation is possible. Then, ignition timing control for suppressing torsional vibration is performed in a state where the operation mode is set to stoichiometric operation. In the stoichiometric operation, the ignition timing is less likely to cause misfire than in the homogeneous lean operation. By performing the ignition timing control during such stoichiometric operation, torsional vibration can be reliably suppressed without causing misfire.

  Further, according to the present embodiment, when the engine operating state is in a region where homogeneous lean operation is possible and generation of torsional vibration is not estimated, homogeneous lean operation is permitted. If the homogeneous lean operation is permitted, the operation mode is immediately set to the homogeneous lean operation. By performing homogeneous lean operation, fuel efficiency is improved.

  That is, according to the present embodiment, the frequency of the homogeneous lean operation (lean frequency) can be increased as much as possible while reliably performing the ignition timing control for suppressing torsional vibration. Thereby, both suppression of torsional vibration and improvement of fuel consumption can be achieved.

5. Modified Example In the above description, the vibration generation estimation unit 40 estimates the generation of torsional vibration based on the amount of change in engine rotation speed after the start of acceleration. However, the method for estimating the occurrence of torsional vibration is not limited thereto.

  For example, there is a high probability that acceleration shock and torsional vibration will occur within a certain period (or within a predetermined number of cycles) after clutch engagement. Therefore, the vibration generation estimation unit 40 may estimate that torsional vibration is generated for a certain period (or within a predetermined cycle integration) after the clutch is engaged.

  Alternatively, after the accelerator pedal is turned on, there is a high probability that acceleration shock and torsional vibration will occur within a certain period (or within a predetermined cycle integration). Therefore, the vibration generation estimation unit 40 may estimate that torsional vibration has occurred for a certain period (or within a predetermined cycle integration) after the accelerator pedal is turned on.

DESCRIPTION OF SYMBOLS 1 Control apparatus 10 Operation switching part 20 Drive driven determination part 30 Lean driving | operation determination part 40 Vibration generation estimation part 50 Ignition timing control part 51 Acceleration state detection part 52 Ignition delay angle control part 53 Ignition phase control part 54 Ignition control switching part ENG Engine (internal combustion engine)

Claims (1)

An operation switching unit for switching the operation mode of the internal combustion engine between stoichiometric operation and homogeneous lean operation;
A lean operation determination unit that determines whether or not the homogeneous lean operation is possible based on an operation state of the internal combustion engine;
A vibration generation estimator for estimating the generation of torsional vibration of the drive train;
An ignition timing control unit for controlling an ignition timing so that the torsional vibration is suppressed when occurrence of the torsional vibration is estimated, and
When it is determined that the homogeneous lean operation is possible and the occurrence of the torsional vibration is not estimated, the operation switching unit sets the operation mode to the homogeneous lean operation,
When it is determined that the homogeneous lean operation is possible and the occurrence of the torsional vibration is estimated, the operation switching unit is configured to operate the operation mode even under the operation state in which the homogeneous lean operation is possible. A control device for an internal combustion engine that sets the stoichiometric operation.

Images