JP2004293429A - Control device of cylinder injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a cylinder injection internal combustion engine for maintaining a superior combustion state regardless of a change in cylinder air current strength caused by a change with the lapse of time of deposition of an intake air deposit. <P>SOLUTION: An electronic control device 20 estimates a change in the tumble ratio by a change with the lapse of time of the deposition of the intake air deposit on the basis of a change in the combustion gas temperature detected by an exhaust temperature sensor 21, and delayably corrects the fuel injection timing in stratified combustion operation when the estimated tumble ratio increases. Thus, fuel is injected in the sufficiently weakened timing of a residual air current regardless of a change in the residual air current in a compression stroke caused by an increase in the tumble ratio, and since excessive agitation of the fuel caused by an increase in the tumble ratio is restrained, a layer of a variable thick air-fuel mixture can be stably formed in the vicinity of a spark plug 17. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder, and more particularly to an improvement in a control structure corresponding to a change in in-cylinder airflow intensity caused by a change over time.
[0002]
[Prior art]
In the above-described in-cylinder injection type internal combustion engine, the state of the air-fuel mixture in the cylinder is appropriately controlled by using the in-cylinder airflow such as a tumble flow and a swirl flow formed by the inflow of intake air from an intake port. As a result, a good combustion state is ensured. For example, during homogeneous combustion operation, by injecting fuel during the intake stroke, mixing of the injected fuel and air is promoted by in-cylinder airflow formed according to the inflow of intake air from the intake port, and the fuel is injected into the cylinder. Combustion is performed in a state in which a homogeneous mixture is formed. In addition, during stratified combustion, fuel injected during the compression stroke collects the fuel injected from the injector near the spark plug by using the recess formed on the top surface of the piston, and combustible only near the spark plug. Combustion is performed in a state in which a rich air-fuel mixture is formed (see Patent Document 1 and the like).
[0003]
[Patent Document 1]
JP-A-2002-276421
[0004]
[Problems to be solved by the invention]
By the way, in such a direct injection internal combustion engine, deposits may gradually accumulate in intake ports, intake valves, and the like in accordance with long-term use. Such accumulation of the intake deposit changes the intensity of the in-cylinder airflow and affects the combustion state of the internal combustion engine.
[0005]
That is, as shown in FIG. 1, when the intake deposit D accumulates on the intake valve or the intake port, the flow passage area of the intake decreases accordingly. As a result, the flow of intake air is hindered and the amount of intake air decreases, but at the same time, the flow rate of intake air flowing into the cylinder from the intake port increases due to the narrowed intake flow path, and the in-cylinder air flow increases. It also becomes stronger.
[0006]
Such a change in the in-cylinder airflow intensity changes the state of the air-fuel mixture in the cylinder, and has a considerable effect on the combustion state. However, in the related art, measures against the change in the in-cylinder airflow intensity due to such a change with time have not been sufficiently provided, and the combustion state has been deteriorated.
[0007]
The present invention has been made in view of such circumstances, and an object thereof is to provide a cylinder capable of maintaining a good combustion state irrespective of a change in the in-cylinder airflow intensity due to a change with time such as accumulation of intake deposit. An object of the present invention is to provide a control device for an internal injection type internal combustion engine.
[0008]
[Means for Solving the Problems]
Hereinafter, means for achieving the above-described object and the effects thereof will be described.
The invention according to claim 1 is applied to an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder, and a state in which a part of the cylinder is richer in an air-fuel mixture than another part. In the control device for a direct injection internal combustion engine performing a stratified combustion operation in which combustion is performed in a cylinder, an estimating means for estimating a change in the in-cylinder airflow intensity due to a temporal change, and when the estimated in-cylinder airflow intensity increases In addition, the gist of the present invention is to provide a correction means for retarding the fuel injection timing during the stratified charge combustion operation.
[0009]
According to a second aspect of the present invention, in the control apparatus for a direct injection internal combustion engine according to the first aspect, the correction means determines that the intensity of the in-cylinder airflow remaining during fuel injection is equal to the in-cylinder airflow intensity. The gist of the present invention is to perform the retard correction so that the fuel injection is performed at the same time as before the change.
[0010]
When the strength of the in-cylinder airflow such as the tumble flow and swirl flow formed by the inflow of intake air from the intake port increases by a certain amount due to the secular change such as the accumulation of intake deposit, a relatively strong in-cylinder airflow is generated until the latter stage of the compression stroke. It will survive. Therefore, the injected fuel is agitated by the remaining in-cylinder airflow (remaining airflow), and it is not possible to appropriately form a rich portion of the air-fuel mixture, and the combustion state during the stratified combustion operation deteriorates. Would.
[0011]
In this regard, in each of the configurations according to the first and second aspects, a change in the strength of the in-cylinder airflow due to a change with time is estimated, and when the estimated strength of the in-cylinder airflow increases, the fuel injection during the stratified combustion operation is performed. The timing has been corrected to the retard side. As a result, the fuel is injected after the residual airflow becomes weaker, and the fuel is prevented from being over-stirred due to an increase in the strength of the in-cylinder airflow due to aging. Therefore, a good combustion state can be maintained irrespective of a change in the intensity of the in-cylinder airflow due to a change over time. In particular, if the retard correction of the fuel injection timing is performed as described in claim 2, the combustion state can be maintained more reliably.
[0012]
In the "stratified combustion operation" here, for example, by performing fuel injection in both the intake stroke and the compression stroke, a mixture having a lower stratification degree than in the normal stratified combustion operation is formed in the cylinder. It also includes a so-called "weak stratified combustion operation" in which combustion is performed in a decomposed state.
[0013]
The invention according to claim 3 is applied to a direct injection internal combustion engine that directly injects fuel into a cylinder, and performs a homogeneous combustion operation in which combustion is performed in a state where a homogeneous mixture is formed in the cylinder. An estimating means for estimating a change in the in-cylinder airflow intensity due to a temporal change in the control device of the internal injection internal combustion engine; and a fuel injection timing for the homogeneous combustion operation when the estimated in-cylinder airflow intensity increases. And a correcting means for correcting the angle of the light.
[0014]
According to a fourth aspect of the present invention, in the control apparatus for a direct injection internal combustion engine according to the third aspect, the correction means is configured to determine whether a degree of fuel agitation in the cylinder is a change in the in-cylinder airflow intensity. The gist of the present invention is to perform the retard correction so as to be approximately the same as before.
[0015]
As described above, during the homogeneous combustion operation, the mixing of the injected fuel and air is promoted by the in-cylinder airflow formed according to the inflow of the intake air from the intake port. However, if the in-cylinder air flow becomes too strong and the fuel is excessively agitated, the amount of fuel adhering to the cylinder wall surface, piston top surface, etc. increases, and the amount of fuel actually supplied to combustion is increased. , Which causes problems such as deterioration of fuel efficiency.
[0016]
In this regard, in each of the configurations according to the third and fourth aspects, a change in the strength of the in-cylinder airflow due to a change with time is estimated, and when the estimated strength of the in-cylinder airflow increases, the fuel injection during the homogeneous combustion operation is performed. The timing has been corrected to the retard side. Accordingly, the period during which the fuel is agitated in the cylinder is shortened in accordance with the increase in the strength of the in-cylinder airflow, and the increase in the amount of fuel adhering to the cylinder wall surface or the like is suppressed. Therefore, a good combustion state can be maintained irrespective of a change in the intensity of the in-cylinder airflow due to a change over time. In particular, if the retard correction of the fuel injection timing is performed as described in claim 4, the combustion state can be maintained more reliably.
[0017]
The invention according to claim 5 is applied to a direct injection internal combustion engine that directly injects fuel into a cylinder, and performs a homogeneous combustion operation in which combustion is performed in a state where a homogeneous mixture is formed in the cylinder. In the control device of the internal injection internal combustion engine, an estimating means for estimating a change in the in-cylinder airflow intensity due to a change over time, and when the estimated in-cylinder airflow intensity increases, the ignition timing during the homogeneous combustion operation is set. The gist of the invention is to provide a correction means for correcting the retardation.
[0018]
According to a sixth aspect of the present invention, in the control apparatus for a direct injection internal combustion engine according to the fifth aspect, the correction means is configured to reduce the combustion period in accordance with the increase in the in-cylinder airflow intensity. The gist of the invention is to perform the retard correction so as to retard the ignition timing.
[0019]
When the strength of the in-cylinder airflow increases, mixing of fuel and air is promoted, and the homogeneity of the air-fuel mixture in the cylinder increases, so that the combustion state during the homogeneous combustion operation is improved. The optimum ignition timing shifts to the retard side as the combustion speed increases due to the improvement of the combustion state. As a result, the ignition timing becomes over-advanced, which causes problems such as deterioration of fuel efficiency and increase in torque fluctuation.
[0020]
In this regard, in each of the configurations according to the fifth and sixth aspects, the ignition timing during the homogeneous combustion operation is retarded in accordance with the increase in the in-cylinder airflow. Over-advanced timing is preferably avoided. Therefore, a good combustion state can be maintained irrespective of a change in the intensity of the in-cylinder airflow due to a change over time. Particularly, if the ignition timing is corrected for retardation as described in claim 6, a favorable combustion state can be maintained more reliably.
[0021]
The invention according to claim 7 is applied to an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder, and a fuel mixture in which fuel concentration is unevenly distributed so that only a part of the injected fuel is burned. An estimating means for estimating a change in the in-cylinder airflow intensity over time in a control device of an in-cylinder injection type internal combustion engine which is formed in a cylinder and performs a catalyst heating injection for supplying unburned fuel to an exhaust catalyst; The gist of the invention is to provide a correction means for correcting the air-fuel ratio at the time of the catalyst temperature increase injection to a rich side when the estimated in-cylinder airflow intensity increases.
[0022]
In a direct injection internal combustion engine, at the time of a cold start or the like, combustion is performed in a state in which an air-fuel mixture in which the fuel concentration is unevenly distributed is formed so that only a part of the injected fuel is burned. In some cases, a fuel-fuel-injection is performed to supply the fuel and burn the fuel there to accelerate the temperature of the exhaust catalyst. Such a catalyst temperature-increasing injection is performed by, for example, forming a flammable rich air-fuel mixture only in the vicinity of the ignition plug, and forming a lean air-fuel mixture in other parts of the cylinder so that combustion is not established. Here, if the in-cylinder airflow at the time of increasing the temperature of the catalyst is increased due to the above-described temporal change, the injected fuel is agitated by the airflow, and a flammable rich air-fuel mixture cannot be formed near the ignition plug. Sometimes. As a result, a misfire may occur, or the amount of unburned fuel supplied to the exhaust catalyst may become excessive, resulting in an excessive rise in the catalyst bed temperature.
[0023]
In this regard, in the above-described configuration, the air-fuel ratio at the time of increasing the temperature of the catalyst is corrected to the rich side in accordance with the increase in the strength of the in-cylinder airflow. It can be formed to maintain stable combustion. Therefore, in the above configuration, a good combustion state can be maintained regardless of the change in the strength of the in-cylinder airflow due to the change over time.
[0024]
According to an eighth aspect of the present invention, in the control apparatus for a direct injection internal combustion engine according to any one of the first to seventh aspects, the estimating means changes the in-cylinder airflow intensity based on a combustion gas temperature. The gist is to estimate
[0025]
As described above, when the strength of the in-cylinder airflow changes due to a temporal change such as the accumulation of intake deposit, the combustion state changes. As a result, the combustion gas temperature also changes. For example, during homogeneous combustion operation, the in-cylinder airflow is strengthened to promote mixing of the injected fuel and air, and the mixture is further homogenized, so that the combustion state is improved according to the increase in the in-cylinder airflow intensity. As a result, the combustion gas temperature decreases. In addition, during stratified charge combustion operation, the fuel is over-stirred in response to the strengthening of the in-cylinder air flow, and it becomes difficult to form a sufficiently rich mixture near the spark plug. To rise. Therefore, based on the detection result of the combustion gas temperature as in the above configuration, it is possible to accurately estimate a change in the strength of the in-cylinder airflow due to a change with time such as the accumulation of intake deposit.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS.
[0027]
FIG. 2 shows a main part of a vehicle-mounted internal combustion engine 10 to which the present embodiment is applied, and a configuration of a control system thereof. The internal combustion engine 10 shown in FIG. 1 is an in-cylinder injection internal combustion engine that directly injects fuel into a cylinder, and includes an intake passage 11, a combustion chamber 12, an exhaust passage 13, and the like. . The intake passage 11 is connected to the combustion chamber 12 via an intake port 14 and an intake valve 15. The combustion chamber 12 is provided with an injector 16 for directly injecting fuel into the combustion chamber 12 and a spark plug 17 for spark-igniting the injected fuel. An exhaust passage 13 connected to the combustion chamber 12 via an exhaust valve 19 and an exhaust port 20 is provided with an exhaust temperature sensor 21 for detecting the temperature of combustion gas discharged as exhaust from the combustion chamber 12. I have.
[0028]
The control system of the internal combustion engine 10 mainly includes an electronic control unit 22 for controlling the engine. The electronic control unit 22 includes a CPU that executes various processes related to engine control, a ROM that stores programs and information for engine control, a RAM that stores information necessary during engine control, and various types of external control. It is provided with an input port and an output port for exchanging signals.
[0029]
In addition to the in-cylinder pressure sensor 18 and the exhaust gas temperature sensor 21, various sensors such as an NE sensor 23 for detecting an engine rotation speed and an accelerator sensor 24 for detecting an accelerator operation amount are connected to an input port of the electronic control unit 22. I have. In addition, the input port is also required for engine control, such as a water temperature sensor for detecting the temperature of the engine cooling water, an intake air temperature sensor for detecting the intake air temperature, and an intake pressure sensor for detecting the intake pressure. Various sensors for detecting information are connected. On the other hand, an output port of the electronic control unit 22 is connected to an injector 16 and a spark plug 17 provided in each cylinder. The electronic control unit 22 controls the fuel injection from the injector 16 and the ignition of the fuel by the spark plug 17 based on the detection signals of the sensors input through the input ports.
[0030]
Further, as a part of such engine control, the electronic control unit 22 performs control for switching the combustion method of the internal combustion engine 10 between homogeneous combustion and stratified combustion according to the engine operating state. During the homogeneous combustion operation, the fuel is injected during the intake stroke, and the injected fuel is homogeneously mixed into the air in the cylinder by utilizing the airflow formed in the cylinder by the inflow of intake air from the intake port 14. Combustion is performed in this state. Incidentally, in the internal combustion engine 10, an airflow that rotates in the vertical direction of the cylinder, that is, a tumble flow is formed in the cylinder in response to the inflow of the intake air. In the stratified charge combustion operation, the fuel is injected during the compression stroke, so that the fuel injected from the injector 16 is collected near the ignition plug 17 by using the concave portion formed on the piston top surface. Then, combustion is performed in a state in which a layer of combustible dense air-fuel mixture is formed only in the vicinity of the ignition plug 17.
[0031]
Further, the electronic control unit 22 of the present embodiment performs a process of estimating a change in the in-cylinder airflow intensity due to the accumulation of the intake deposit on the intake port 14 and the intake valve 15 during the operation of the engine. Here, “tumble ratio” is used as an index value indicating the in-cylinder airflow intensity. "Tumble ratio" is defined as the ratio of the rotation speed of the tumble flow to the engine rotation speed.
[0032]
Hereinafter, the manner of estimating the change in the in-cylinder airflow intensity in the present embodiment will be described in detail.
As described above, during the homogeneous combustion operation, the injected fuel is mixed with the air by stirring with the in-cylinder airflow (tumble flow) formed according to the inflow of the intake air. Therefore, if the in-cylinder airflow becomes strong, that is, if the tumble ratio becomes large, the mixing of air and fuel is promoted, and a more homogeneous air-fuel mixture is formed, so that the combustion state is improved. If the combustion state is improved in this way, the combustion speed is increased and the combustion period is shortened, so that the temperature of the combustion gas is reduced. Therefore, it can be estimated that the intensity of the in-cylinder airflow has increased due to the decrease in the combustion gas temperature during the homogeneous combustion operation.
[0033]
On the other hand, during the stratified charge combustion operation, combustion is performed in a state in which a flammable rich air-fuel mixture is formed only in the vicinity of the ignition plug 17. At this time, when the in-cylinder airflow is strengthened and the tumble ratio is increased, a strong tumble flow remains in the cylinder until the latter stage of the compression stroke, and the air-fuel mixture is easily diffused. As a result, it becomes difficult to form a sufficiently rich mixture in the vicinity of the ignition plug 17, and the combustion state deteriorates. At this time, the combustion speed decreases and the combustion period increases, so that the temperature of the combustion gas increases. Therefore, it can be estimated that the strength of the in-cylinder airflow has increased due to the increase in the combustion gas temperature during the stratified charge combustion operation.
[0034]
Therefore, the current tumble ratio, that is, the degree of change in the in-cylinder airflow intensity can be estimated based on the change in the combustion gas temperature. FIG. 3 shows a flowchart of the “tumble ratio estimation process” of the present embodiment. The process of FIG. 3 is periodically executed by the electronic control unit 22 during operation of the engine.
[0035]
When this process is started, first, in step S100, it is determined whether or not the internal combustion engine 10 is in an idling stable state. If the internal combustion engine 10 at that time is not in the idling stable state (NO), the present process is temporarily terminated. In the present embodiment, the comparison of the combustion gas temperature before and after the change in the tumble ratio can be appropriately performed based on the combustion gas temperature in the idle stable state.
[0036]
If the internal combustion engine 10 is in the idling stable state (YES), it is determined in step S110 whether the internal combustion engine 10 at that time is in the homogeneous combustion operation or the stratified combustion operation.
[0037]
At the time of the homogeneous combustion operation, in step S120, based on the combustion gas temperature detected by the exhaust gas temperature sensor 21, a tumble ratio estimation map for the homogeneous combustion operation as shown in FIG. An estimate is calculated. On the other hand, in the stratified combustion operation, in step S130, based on the detected combustion gas temperature, the tumble ratio estimated value is calculated using a tumble ratio estimated value calculation map for the stratified combustion operation as illustrated in FIG. Is calculated. In these calculation maps, the relationship between the combustion gas temperature and the tumble ratio during the homogeneous combustion operation and the stratified combustion operation is stored in advance. After calculating the tumble ratio estimated value, the processing of this routine is temporarily ended.
[0038]
When the change in the tumble ratio due to the temporal change such as the accumulation of the intake deposit is confirmed in this way, the appropriate value of the engine control amount changes according to the change in the combustion state accompanying the change. In the present embodiment, the adaptation process for adjusting the fuel injection timing during the stratified charge combustion operation to an optimum value (adaptation value) according to the change in the tumble ratio is performed.
[0039]
Here, first, a description will be given of a manner of changing the appropriate value of the fuel injection timing according to the change in the tumble ratio during the stratified charge combustion operation.
The tumble flow formed in the cylinder by the inflow of intake air from the intake port 14 during the intake stroke remains to some extent as a residual airflow during the compression stroke in which fuel is injected during the stratified charge combustion operation. A curve L1 in FIG. 6 shows a change in the strength of the remaining airflow during the compression stroke before the change in the tumble ratio, and a curve L2 shows a change in the strength of the remaining airflow after the increase in the tumble ratio. Further, time t0 in the same figure shows an appropriate value of the fuel injection timing before the change in the tumble ratio.
[0040]
When the intensity of the in-cylinder airflow, that is, the tumble ratio increases due to the above-described temporal change, a strong residual airflow remains until a later stage of the compression stroke, as shown by a curve L2 in FIG. In the example shown in the figure, the intensity of the residual airflow at the time t0 increases from the value AR0 before the tumble ratio change to the value AR1. Therefore, if the fuel is injected at this time t0, the injected fuel is agitated by the strong residual airflow, and it becomes difficult to form a sufficiently rich mixture near the ignition plug 17. As a result, the combustion state deteriorates, which causes problems such as an increase in torque fluctuation.
[0041]
At this time, if the fuel injection timing is retarded until the intensity of the remaining airflow decreases to the same level as before the change in the tumble ratio, the deterioration of the combustion state due to such an increase in the tumble ratio can be avoided. In the example shown in the figure, the intensity of the residual airflow after the increase in the tumble ratio has decreased to the above value AR0 at the time t1, and the fuel injection timing is corrected by the retard angle until the time t1, so that the change in the tumble ratio before the change is obtained. The same good combustion state as described above can be maintained.
[0042]
FIG. 7 shows a change in the relationship between the fuel injection timing and the torque fluctuation amount in the stratified combustion operation when the tumble ratio is changed in three stages of large, medium, and small. As shown in the drawing, the fuel injection timing at which the amount of torque fluctuation is minimized, that is, the combustion state becomes good, shifts to the retard side as the tumble ratio increases.
[0043]
Therefore, in the present embodiment, during the stratified charge combustion operation, the electronic control unit 22 sets the fuel injection timing as the estimated tumble ratio increases, based on the tumble ratio estimated value obtained in the tumble ratio estimation process, as the estimated tumble ratio increases. Correction is made to the retard side to make it suitable.
[0044]
FIG. 8 shows a flowchart of a process according to the present embodiment relating to the adaptation of the fuel injection timing during the stratified charge combustion operation according to the change in the tumble ratio. The process of FIG. 7 is periodically executed by the electronic control unit 22 during operation of the engine.
[0045]
When the present process is started, first, in step S200, it is determined whether or not a stratified combustion operation is being performed. If it is not during the stratified charge combustion operation (NO), the current process is terminated.
[0046]
At the time of stratified combustion operation (S200: YES), at step S210, a basic injection timing at the time of stratified combustion operation is calculated. The basic injection timing is an appropriate value of the fuel injection timing when there is no change in the tumble ratio due to a change over time, and is calculated based on, for example, the engine speed and the engine load.
[0047]
In the following step S220, based on the tumble ratio estimation value obtained in the above-described tumble ratio estimation process and the engine speed detected by the NE sensor 23, the fuel injection timing is delayed according to the increase in the tumble ratio due to aging. An angle correction amount is obtained. The calculation of the retard correction amount here is performed with reference to a calculation map stored in the ROM of the electronic control unit 22 in advance. Here, the retardation correction amount is set so that the fuel injection timing is retarded until the strength of the remaining airflow decreases to the same extent as before the tumble change.
[0048]
FIG. 9 shows an example of setting the above-mentioned retard correction amount according to the estimated tumble ratio value at a specific engine rotational speed in such a calculation map. As shown in the figure, the retard correction amount is set to “0” when the estimated value of the tumble ratio is the initial value, that is, the tumble ratio before the change with time occurs, and the tumble ratio is calculated from the initial value. The value is set so as to increase as the estimated value increases.
[0049]
After calculating the retardation correction amount, in step S230, the basic injection timing is retarded according to the retardation correction amount to calculate the final injection timing, and the current process is temporarily terminated. After that, the electronic control unit 22 controls the injector 16 so that the fuel is injected at the final injection timing calculated in this way.
[0050]
In the present embodiment described above, the processing of steps S110 to S130 of the tumble ratio estimation processing corresponds to the processing of the “estimating means” for estimating a change in the in-cylinder airflow intensity due to a temporal change. Further, the processing of steps S220 and S230 of the adaptation processing corresponds to the processing of the "correction means" for retarding the fuel injection timing during the stratified combustion operation when the estimated in-cylinder airflow intensity increases. .
[0051]
According to the embodiment described above, the following effects can be obtained.
(1) In the present embodiment, a change in the tumble ratio due to aging is estimated, and when the estimated tumble ratio increases, the fuel injection timing during stratified charge combustion operation is retarded. More specifically, the fuel injection timing at the time of stratified charge combustion operation is retarded so that the fuel injection is performed at a time when the strength of the residual airflow at the time of the fuel injection becomes substantially the same as before the change in the tumble ratio. ing. As a result, the fuel is injected after the residual airflow is sufficiently weakened, and excessive stirring of the fuel is suppressed. Therefore, a good combustion state can be maintained irrespective of a change in the intensity of the in-cylinder airflow due to a change over time.
[0052]
(2) In the present embodiment, the change in the tumble ratio due to the change over time is estimated based on the combustion gas temperature. The change in the tumble ratio due to the change over time changes the combustion state, and is conspicuously expressed as a change in the combustion gas temperature. Therefore, it is possible to accurately estimate a change in the tumble ratio due to a change with time.
[0053]
(2nd Embodiment)
Next, a second embodiment of the present invention will be described, focusing on differences from the first embodiment.
[0054]
The change in the in-cylinder airflow due to the temporal change such as the accumulation of the intake deposit as described above greatly affects the combustion state during the homogeneous combustion operation. Therefore, in the present embodiment, the above-described problems are avoided by performing an adaptation process for adjusting the fuel injection timing and the ignition timing during the homogeneous combustion operation to optimal values in accordance with the change in the tumble ratio due to aging. I am trying to do it.
[0055]
Hereinafter, an outline of a process of adapting the fuel injection timing and the ignition timing in the homogeneous combustion operation in the present embodiment in the present embodiment will be described.
FIG. 10 shows an example of the variation of the output torque of the internal combustion engine 10 according to the fuel injection timing during the homogeneous combustion operation, when the tumble ratio is small, by a solid line, and when the tumble ratio is large, by a broken line. In the example shown in the figure, when the tumble ratio is small, the maximum output torque is obtained by setting the fuel injection timing to time t2.
[0056]
During homogeneous combustion operation, the mixing of fuel into the air is promoted by strengthening the tumble flow.However, if the tumble flow becomes too strong and fuel is excessively agitated in the cylinder, the cylinder wall and More fuel will be deposited on the top surface. Then, as a result, the amount of fuel actually supplied to the combustion is reduced, so that the output torque of the internal combustion engine 10 is reduced, which causes problems such as deterioration of fuel efficiency.
[0057]
Therefore, when the tumble ratio is large, the time required for optimal fuel mixing is shorter than when the tumble flow is small, so that the optimal fuel / air mixing state is obtained, and the maximum output is obtained. The fuel injection timing at which the torque is obtained shifts to the retard side. In the example shown in the figure, when the tumble ratio is large, the fuel injection timing at which the maximum output torque is obtained shifts to time t3, which is later than time t2 when the tumble ratio is small.
[0058]
Therefore, in the present embodiment, based on the tumble ratio estimation value calculated in the tumble ratio estimation process, the more the estimated tumble flow increases, the more the fuel injection timing during the homogeneous combustion operation is retarded. I have. Here, the amount of retard correction of the fuel injection timing is set so that the time from fuel injection to ignition is reduced until the degree of stirring of the fuel in the cylinder becomes the same as before the change in the tumble ratio. I am trying to do it. The degree of agitation of the fuel in the cylinder can be represented by, for example, a multiplication value of a time from injection to ignition and a rotation speed (or a tumble ratio) of the tumble flow as an index value.
[0059]
On the other hand, as shown in FIG. 11, the optimal ignition timing also changes according to the change in the tumble ratio due to the change over time. In the same figure, an example of a change mode of the output torque of the internal combustion engine 10 according to the ignition timing at the time of the homogeneous combustion operation is shown by a solid line when the tumble ratio is small and by a broken line when the tumble ratio is large. . In the example shown in the figure, when the tumble ratio is small, the ignition timing at which the maximum output torque is obtained, that is, the MBT point of the ignition timing is time t4.
[0060]
As described above, during the homogeneous combustion operation, if the tumble flow is strong, the mixing of the injected fuel and air is promoted, and the mixture is homogenized, so that the combustion state is improved and the combustion speed is increased. Become. As a result, the ignition timing at which the maximum output torque is obtained, that is, the MBT point of the ignition timing shifts to the retard side in accordance with the strengthening of the tumble flow. In the example shown in the figure, the MBT point of the ignition timing when the tumble ratio is large shifts to time t5 later than the time t4 when the tumble ratio is small. Therefore, if the ignition timing is maintained as it is despite the change in the tumble ratio, the ignition timing will be over-advanced, causing problems such as deterioration of fuel efficiency and increase in torque fluctuation.
[0061]
Therefore, in the present embodiment, the ignition timing during the homogeneous combustion operation is also estimated based on the tumble ratio estimated value calculated in the tumble ratio estimation process and the engine speed detected by the NE sensor 23. The retard correction is performed as the tumble flow increases. Here, such an ignition timing retard correction amount is set such that the ignition timing is retarded by an amount corresponding to a reduction in the combustion period in accordance with an increase in the combustion speed due to the enhancement of the tumble flow due to the above-mentioned aging. ing.
[0062]
FIG. 12 shows a flowchart of a process for adapting the fuel injection timing and the ignition timing in the homogeneous combustion operation according to the change in the tumble ratio in the present embodiment. The process of FIG. 7 is periodically executed by the electronic control unit 22 during operation of the engine.
[0063]
When the present process is started, first, in step S200, it is determined whether or not a homogeneous combustion operation is being performed. If it is not during the homogeneous combustion operation (NO), the current process is temporarily terminated.
[0064]
During the homogeneous combustion operation (S300: YES), in step S310, the above-described tumble ratio estimation value calculated in the tumble ratio estimation process (FIG. 3) and the engine speed detected by the NE sensor 23 are used as described above. In this manner, the retard correction amount of the fuel injection timing and the retard correction amount of the ignition timing are calculated.
[0065]
Then, in step S320, the basic values of the fuel injection timing and the ignition timing during the homogeneous combustion operation, which are calculated by a separate process, are respectively retarded by the retardation correction amounts to obtain the final fuel injection timing and the final fuel injection timing. A command value for the ignition timing is calculated, and the current process is temporarily terminated. Thereafter, the electronic control unit 22 determines the timing of the fuel injection from the injector 16 and the timing of the ignition by the spark plug 17 during the homogeneous combustion operation based on the final fuel injection timing and ignition timing command values calculated here. Control.
[0066]
In the present embodiment described above, the processing of steps S310 and S320 of the above-described adaptation processing is performed when the estimated in-cylinder airflow intensity increases, the fuel injection timing and the ignition timing during the homogeneous combustion operation are retarded. This corresponds to the processing of the “correction unit” for correcting.
[0067]
According to the present embodiment described above, the following effect can be further obtained in addition to the effect described in the above (2).
(3) In the present embodiment, a change in the tumble ratio due to a change over time is estimated, and when the estimated tumble ratio increases, the fuel injection timing in the homogeneous combustion operation is retarded. More specifically, the fuel injection timing during the homogeneous combustion operation is delayed and corrected so that the fuel injection in the cylinder is performed at a timing when the degree of agitation of the fuel in the cylinder is substantially the same as before the change in the tumble ratio. I have. Accordingly, the period during which the fuel is agitated in the cylinder is shortened in accordance with the increase in the tumble ratio due to aging, and the adhesion of the fuel to the cylinder wall surface or the like is suppressed. Therefore, a good combustion state can be maintained irrespective of a change in the intensity of the in-cylinder airflow due to a change over time.
[0068]
(4) In the present embodiment, a change in the tumble ratio due to a change with time is estimated, and when the estimated tumble ratio increases, the ignition timing in the homogeneous combustion operation is retarded. More specifically, the ignition timing in the homogeneous combustion operation is corrected so as to retard the ignition timing by an amount corresponding to the reduction in the combustion period due to the increase in the combustion speed in accordance with the increase in the tumble ratio. ing. For this reason, an excessive advance of the ignition timing due to an increase in the combustion speed due to an increase in the tumble ratio due to aging is preferably avoided. Therefore, a good combustion state can be maintained irrespective of a change in the intensity of the in-cylinder airflow due to a change over time.
[0069]
(Third embodiment)
Next, a third embodiment of the invention will be described, focusing on the differences from the above embodiments.
[0070]
In the internal combustion engine 10 to which the present embodiment is applied, at the time of a cold start, a catalyst temperature increase injection for increasing the bed temperature of the exhaust catalyst provided in the exhaust passage 13 is performed. At the time of raising the temperature of the catalyst, fuel is injected late in the exhaust stroke to form a variable mixture layer only in the vicinity of the spark plug 17 as shown in FIG. To form a layer of a lean mixture. At this time, only a necessary minimum amount of fuel for achieving combustion exists in the vicinity of the ignition plug 17. Therefore, unlike the case of the stratified charge combustion operation, only a part of the injected fuel is burned and the remaining fuel is discharged to the exhaust passage 13 together with the exhaust without being burned, unlike the case of the stratified combustion operation. The discharged unburned fuel is burned by the exhaust catalyst and contributes to the temperature rise.
[0071]
If the tumble ratio increases due to the above-described aging during the catalyst temperature increase injection, the injected fuel is agitated, and a layer of a rich air-fuel mixture sufficient to achieve combustion is provided near the ignition plug 17. Is difficult to form. As a result, there is a possibility that a misfire may occur, or that the amount of unburned fuel supplied to the exhaust catalyst may become excessive, resulting in an excessive rise in the catalyst bed temperature.
[0072]
Therefore, in the present embodiment, based on the tumble ratio estimation value calculated in the tumble ratio estimation process, the more the estimated tumble flow increases, the more the fuel injection amount during the catalyst temperature increase injection is increased, and the empty amount is corrected. The fuel ratio is corrected to the rich side. Thus, a sufficiently flammable rich mixture layer is formed in the vicinity of the spark plug 17 irrespective of fuel diffusion due to an increase in the tumble ratio.
[0073]
FIG. 14 shows a flowchart of a process related to the adjustment of the air-fuel ratio at the time of increasing the temperature of the catalyst in the present embodiment. The process of FIG. 7 is periodically executed by the electronic control unit 22 during operation of the engine.
[0074]
When this process is started, first, in step S300, it is determined whether or not the catalyst temperature increasing injection is being performed. Here, if the catalyst temperature increase injection is not being performed (NO), the current process is temporarily terminated.
[0075]
If the catalyst temperature increase injection is being performed (S300: YES), in step S310, based on the tumble ratio estimation value calculated in the tumble ratio estimation process (FIG. 3), the fuel injection amount increase correction amount is determined. Is calculated. The calculation of the increase correction amount is performed with reference to a calculation map stored in the ROM of the electronic control device 22 in advance.
[0076]
FIG. 15 shows an example of setting the increase correction amount according to the tumble ratio estimated value at a specific engine rotation speed in such a calculation map. As shown in the figure, in this calculation map, the increase correction amount is set to “0” when the estimated value of the tumble ratio is the initial value, that is, the tumble ratio before the change with time occurs, Is set so that the larger the estimated value of the tumble ratio becomes, the larger the value becomes.
[0077]
Then, in subsequent step S320, the final fuel injection amount is calculated by increasing the basic fuel injection amount during the catalyst temperature increase injection calculated in a separate process according to the increase correction amount, thereby calculating the final fuel injection amount. Once terminated. Thereafter, the electronic control unit 22 controls the fuel injection amount from the injector 16 on the basis of the final fuel injection amount thus corrected to increase the air-fuel ratio at the time of the catalyst temperature increase injection before the change in the tumble ratio. Is corrected to the rich side.
[0078]
In the present embodiment described above, the processing of steps S410 and S420 of the above-mentioned adaptation processing corrects the air-fuel ratio at the time of increasing the temperature of the catalyst to the rich side when the estimated in-cylinder airflow intensity increases. This corresponds to the processing of the "correction means".
[0079]
According to the present embodiment described above, the following effect can be further obtained in addition to the effect described in the above (2).
(5) In the present embodiment, a change in the tumble ratio due to a change with time is estimated, and when the estimated tumble ratio increases, the fuel injection amount at the time of the catalyst temperature-increasing injection is increased and corrected to perform the same injection. Is corrected to the rich side. Therefore, regardless of the diffusion of the fuel due to the increase in the tumble ratio, a combustible air-fuel mixture layer is stably formed in the vicinity of the ignition plug 17, and stable combustion is maintained. Therefore, a good combustion state can be maintained irrespective of a change in the tumble ratio due to a change over time.
[0080]
The above embodiment can be modified and implemented as follows.
If the in-cylinder internal combustion engine performs both the homogeneous combustion operation and the stratified combustion operation, the process related to the adjustment of the fuel injection timing at the time of the stratified combustion operation shown in FIG. Both the processing related to the adjustment of the fuel injection timing and the ignition timing during the combustion operation may be performed together. In addition, in the case of a direct injection internal combustion engine that executes the stratified combustion operation or the homogeneous combustion operation and the above-described catalyst heating injection, any one of the processes in FIG. 8 or FIG. The process related to the adaptation of the air-fuel ratio at the time may be performed together. Of course, if the in-cylinder injection type internal combustion engine performs all of the homogeneous combustion operation, the stratified combustion operation, and the catalyst temperature-increasing injection, all of the processes in FIGS. 8, 12, and 14 may be performed together. good.
[0081]
In the adaptation process of FIG. 12, both the fuel injection timing and the ignition timing during the homogeneous combustion operation are retarded in accordance with the increase in the tumble ratio due to aging. Such a retard correction may be applied to only one of the fuel injection timing and the ignition timing during the homogeneous combustion operation. Even in that case, any of the effects (3) and (4) can be obtained.
[0082]
In the process related to the adjustment of the air-fuel ratio at the time of raising the temperature of the catalyst shown in FIG. 14, the air-fuel ratio at the time of raising the temperature of the catalyst at the time of increasing the estimated tumble ratio is increased by correcting the fuel injection amount by increasing the fuel injection amount. Although the air-fuel ratio is corrected to the rich side, the air-fuel ratio can be similarly corrected to the rich side by reducing the intake air amount. In this case, the same effect as the above (5) can be obtained.
[0083]
In the tumble ratio estimating process of FIG. 3, the change in the tumble ratio over time is estimated based on the combustion gas temperature. However, the estimation may be performed based on parameters other than the combustion gas temperature. . For example, a similar estimation can be made based on the in-cylinder pressure. That is, if the tumble ratio changes over time and the combustion state changes, the aspect of the in-cylinder pressure during combustion also changes. For example, if the combustion state is improved by a change in the tumble ratio, the combustion period is shortened, the peak value of the in-cylinder pressure during combustion is increased, and the timing at which the in-cylinder pressure reaches a peak during combustion is advanced. It can be grasped based on the detection result of the in-cylinder pressure.
[0084]
In the above embodiments, the case where the present invention is applied to the in-cylinder injection type internal combustion engine 10 that forms a tumble flow in the cylinder in response to the inflow of intake air from the intake port 14 has been described. The present invention can be applied to an in-cylinder injection type internal combustion engine in which a swirl flow is formed in a cylinder, in a similar or similar manner. In this case, it is possible to maintain a good combustion state with respect to a change in the intensity of the swirl flow due to a change with time.
[Brief description of the drawings]
FIG. 1 is a sectional view of an intake port and an intake valve to which an intake deposit is attached.
FIG. 2 is a schematic view showing the entire structure of the first embodiment of the present invention.
FIG. 3 is a flowchart of a tumble ratio estimation process of the embodiment.
FIG. 4 is a diagram showing an example of a calculation map of a tumble ratio estimated value during a homogeneous combustion operation.
FIG. 5 is a diagram illustrating an example of a calculation map of a tumble ratio estimated value during stratified charge combustion operation.
FIG. 6 is a time chart showing changes in the strength of the residual airflow.
FIG. 7 is a graph showing a change in a correlation between a fuel injection timing and a torque fluctuation amount during a stratified charge combustion operation according to a tumble ratio.
FIG. 8 is a flowchart of a fuel injection timing adjustment process in the first embodiment.
FIG. 9 is a diagram showing an example of a retard correction amount calculation map used in the matching process.
FIG. 10 is a graph showing a change according to a tumble ratio of a correlation between a fuel injection timing and an output torque during a homogeneous combustion operation.
FIG. 11 is a graph showing a change according to a tumble ratio of a correlation between an ignition timing and an output torque during a homogeneous combustion operation.
FIG. 12 is a flowchart of a process for adjusting a fuel injection timing and an ignition timing in a second embodiment.
FIG. 13 is a cross-sectional view showing an aspect in a cylinder at the time of catalyst temperature rising injection.
FIG. 14 is a flowchart of a fuel injection amount adaptation process according to the third embodiment.
FIG. 15 is a diagram showing an example of an increase correction amount calculation map used in the matching process.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 12 ... Combustion chamber, 13 ... Exhaust passage, 14 ... Intake port, 15 ... Intake valve, 16 ... Injector, 17 ... Spark plug, 19 ... Exhaust valve, 20 ... Exhaust port, 21 ... exhaust temperature sensor, 22 ... electronic control device, 23 ... NE sensor, 24 ... accelerator sensor.

Claims (8)

The present invention is applied to a direct injection internal combustion engine that directly injects fuel into a cylinder, and performs a stratified charge combustion operation in which combustion is performed in a state in which a part of the cylinder has a mixture richer than another part in the cylinder. In the control device of the in-cylinder injection type internal combustion engine,
Estimating means for estimating a change in the in-cylinder airflow intensity due to a change over time;
Correction means for retarding the fuel injection timing during the stratified combustion operation when the estimated in-cylinder airflow intensity increases,
A control device for a direct injection internal combustion engine, comprising: 2. The retardation correction device according to claim 1, wherein the correction unit performs the retard angle correction so that the fuel injection is performed at a time when the strength of the in-cylinder airflow remaining at the time of the fuel injection becomes substantially the same as before the change in the in-cylinder airflow strength. 4. The control device for a direct injection internal combustion engine according to claim 1. Applied to a direct injection internal combustion engine that directly injects fuel into a cylinder, a control device for a direct injection internal combustion engine that performs a homogeneous combustion operation in which combustion is performed in a state where a homogeneous mixture is formed in the cylinder. ,
Estimating means for estimating a change in the in-cylinder airflow intensity due to a change over time;
Correction means for retarding the fuel injection timing during the homogeneous combustion operation when the estimated in-cylinder airflow intensity increases,
A control device for a direct injection internal combustion engine, comprising: 4. The cylinder injection type internal combustion engine according to claim 3, wherein the correction unit performs the retard correction so that a degree of agitation of the fuel in the cylinder is substantially the same as before the change in the in-cylinder airflow intensity. 5. Control device. Applied to a direct injection internal combustion engine that directly injects fuel into a cylinder, a control device for a direct injection internal combustion engine that performs a homogeneous combustion operation in which combustion is performed in a state where a homogeneous mixture is formed in the cylinder. ,
Estimating means for estimating a change in the in-cylinder airflow intensity due to a change over time;
Correction means for retarding the ignition timing during the homogeneous combustion operation when the estimated in-cylinder airflow intensity increases,
A control device for a direct injection internal combustion engine, comprising: 6. The in-cylinder injection system according to claim 5, wherein the correction means performs the retard correction so as to retard the ignition timing by an amount corresponding to a reduction in a combustion period in accordance with an increase in the intensity of the in-cylinder airflow. Control device for internal combustion engine. The present invention is applied to an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder, and forms a mixture in which the fuel concentration is unevenly distributed in the cylinder so that only a part of the injected fuel is burned. In the control device of the in-cylinder injection type internal combustion engine that performs the catalyst temperature increasing injection for supplying the unburned fuel,
Estimating means for estimating a change in the in-cylinder airflow intensity due to a change over time;
Correction means for correcting the air-fuel ratio at the time of the catalyst temperature increase injection to the rich side when the estimated in-cylinder airflow intensity increases,
A control device for a direct injection internal combustion engine, comprising: The control device for a direct injection internal combustion engine according to any one of claims 1 to 7, wherein the estimating means estimates a change in the in-cylinder airflow intensity based on a combustion gas temperature.

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