JP7449148B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to a control device for an internal combustion engine that controls split injection in which fuel injection by a fuel injection valve is performed in multiple parts.

The diesel engine control device of Patent Document 1 performs split injection in an idling operating state, and when a stable idling operating state is obtained, the energization time of the first stage injection corresponds to the injection amount for each stage. Updated and stored as a learned value of energization time.

Japanese Patent Application Publication No. 2003-027995

By the way, in split injection in which the fuel injection by the fuel injection valve is performed in multiple steps, in order to suppress variations in the injection amount, the number of splits is set so that the pulse width of one injection does not fall below the minimum pulse width. While it is necessary to limit the number of divisions, there is also a demand for increasing the number of divisions as much as possible in order to improve exhaust properties.
Here, if variations in the internal combustion engine (machine difference variations) are considered to a minimum, it is possible to set a large number of target divisions for each engine operating region, but in the operating region near the boundary where the target number of divisions is changed, Internal combustion engines that cannot inject may occur.
On the other hand, if the target number of divisions for each engine operating range is set to a relatively small number in consideration of variations in internal combustion engines, it is possible to prevent an internal combustion engine from being unable to perform split injection at the target number of divisions. As a result, there is a problem in that the effect of improving exhaust properties through split injection is diminished.

The present invention has been made in view of the conventional situation, and its purpose is to set the target number of split injections as large as possible, while preventing the occurrence of internal combustion engines in which split injection cannot be performed at the target number of split injections. An object of the present invention is to provide a control device for an internal combustion engine that can suppress the above.

Therefore, as one aspect of the control device for an internal combustion engine according to the present invention, there is provided a split injection control unit that controls split injection that causes a fuel injection valve included in the internal combustion engine to perform fuel injection in multiple steps ; A division number setting unit that sets the number of divisions in divided injection by the control unit, and when the fuel injection pulse width of one injection is less than the minimum pulse width when the number of divisions is set as the target number of divisions, fuel injection of one injection is performed. When the split injection control section performs split injection after reducing the number of divisions below the target number of divisions so that the pulse width does not fall below the minimum pulse width, and the number of divisions is set to the target number of divisions. the division number setting unit, which causes the division injection control unit to perform division injection after setting the division number to the target division number when the fuel injection pulse width of one injection is equal to or greater than the minimum pulse width; and a minimum pulse width changing unit that changes the minimum pulse width to a shorter pulse width when the frequency at which the number setting unit reduces the number of divisions below the target number of divisions exceeds a determination value .
Further, as one aspect of the control device for an internal combustion engine according to the present invention, there is provided a split injection control unit that controls split injection that causes a fuel injection valve included in the internal combustion engine to perform fuel injection in multiple times; a division number setting section that sets the number of divisions in the split injection so that the fuel injection pulse width of one injection does not become less than the minimum pulse width; and a division number setting section that sets the number of divisions in the division number setting section and the target division number. a minimum pulse width changing section that changes the minimum pulse width based on the frequency at which deviation occurs, and the division number setting section sets the minimum pulse width for each fuel pressure, and changes the minimum pulse width. When changing the minimum pulse width based on the frequency, the unit uniformly changes the minimum pulse width for each fuel pressure based on the degree of change of the minimum pulse width in the changing process.
Further, as one aspect of the control device for an internal combustion engine according to the present invention, there is provided a split injection control unit that controls split injection that causes a fuel injection valve included in the internal combustion engine to perform fuel injection in multiple times; A division number setting unit that sets the number of divisions in divided injection by the control unit, and when the fuel injection pulse width of one injection is less than the minimum pulse width when the number of divisions is set as the target number of divisions, fuel injection of one injection is performed. When the split injection control section performs split injection after reducing the number of divisions below the target number of divisions so that the pulse width does not fall below the minimum pulse width, and the number of divisions is set to the target number of divisions. When the fuel injection pulse width of one injection is equal to or greater than the minimum pulse width, the division number setting unit sets the division number to the target division number and then causes the division injection control unit to perform division injection, and the internal combustion When the combustion state detection unit detects the combustion state of the engine and the division number setting unit reduce the division number from the target division number, the combustion state is set to the minimum value within a range in which the combustion state does not deteriorate beyond a predetermined level. and a minimum pulse width changing section that changes the pulse width to be shorter.

According to the above invention, it is possible to set the target number of divided injections as large as possible, and to prevent an internal combustion engine from being unable to perform split injection at the target number of divided injections.

FIG. 1 is a system configuration diagram of an internal combustion engine. 3 is a flowchart illustrating a procedure for setting the number of divisions. 3 is a flowchart illustrating a procedure for setting the number of divisions. It is a figure which shows the table which stores the initial pulse width TImin for every fuel pressure. It is a diagram showing a map of the target number of divisions Mtg. 3 is a flowchart illustrating a procedure for setting the number of divisions. 3 is a flowchart illustrating a procedure for setting the number of divisions.

Embodiments of the present invention will be described below.
FIG. 1 is a configuration diagram showing one aspect of an internal combustion engine for a vehicle.

The internal combustion engine 101 includes a fuel injection valve 105 , and the control device 109 controls the operation of the internal combustion engine 101 by controlling fuel injection by the fuel injection valve 105 .
The control device 109 is an electronic control device equipped with a microcomputer 109a including a microprocessor, rewritable nonvolatile memory, and the like.

Intake air from the internal combustion engine 101 passes through an air flow meter 120, an electronically controlled throttle valve 119, and a collector 115 in this order, and is then sucked into a combustion chamber 121 via an intake port 110 and an intake valve 103 provided in each cylinder.
The internal combustion engine 101 also includes a variable fuel pressure device 129 that adjusts the pressure of fuel supplied to the fuel injection valve 105 to a target pressure depending on engine operating conditions. 124 and an engine-driven high-pressure fuel pump 125.

Low pressure fuel pump 124 sends fuel in fuel tank 123 to high pressure fuel pump 125 .
On the other hand, the high-pressure fuel pump 125 boosts the pressure of the fuel supplied from the low-pressure fuel pump 124 and sends the boosted fuel to the fuel injection valve 105 via the high-pressure fuel pipe 128.
The control device 109 adjusts the discharge amount of the high-pressure fuel pump 125 to control the pressure of the fuel supplied to the fuel injection valve 105 to a target fuel pressure (target value) according to engine operating conditions.

The fuel pressure sensor 126 detects the fuel pressure FP within the high-pressure fuel pipe 128, that is, the fuel pressure FP supplied to the fuel injection valve 105.
Then, the control device 109 calculates the deviation ΔFP between the fuel pressure FP detected by the fuel pressure sensor 126 and the target fuel pressure FPtg set according to the engine operating conditions, and controls the electromagnetic metering valve that adjusts the discharge amount of the high-pressure fuel pump 125. By setting the manipulated variable based on the deviation ΔFP, the fuel pressure FP detected by the fuel pressure sensor 126 is brought closer to the target fuel pressure FPtg.

The fuel injection valve 105 is an electromagnetic fuel injection valve that directly injects fuel into the combustion chamber 121 of the internal combustion engine 101, and the internal combustion engine 101 is a direct injection type internal combustion engine.
The fuel injection valve 105 receives the injection pulse signal output from the control device 109 and injects fuel into the combustion chamber 121 in an amount proportional to the pulse width (fuel injection pulse width) of the injection pulse signal.

The control device 109 sets a standard injection pulse width corresponding to the total amount of fuel to be injected from the fuel injection valve 105 during one combustion cycle based on engine operating conditions such as intake air flow rate, engine rotation speed, and cooling water temperature. The injection pulse width is calculated as the injection pulse width when the pressure is the standard pressure, and the standard injection pulse width is further corrected according to the fuel pressure at that time to set the corrected injection pulse width.
In addition, the control device 109 sets the number of divisions (number of divisions ≧1) in split injection in which injection with the corrected injection pulse width is divided into multiple times during one combustion cycle, and controls the split injection by the fuel injection valve 105. Control.
That is, the control device 109 has a function as a split injection control unit that controls split injection in which fuel injection by the fuel injection valve 105 is performed in multiple steps.

Further, the internal combustion engine 101 includes an ignition device having an ignition coil 107 and a spark plug 106.
The control device 109 controls the generation of sparks by the spark plug 106 by controlling the energization of the ignition coil 107 .

Then, the air-fuel mixture in the combustion chamber 121 is ignited and combusted by the spark generated by the ignition plug 106, and the exhaust gas generated by the combustion is discharged from the combustion chamber 121 to the exhaust pipe 111 via the exhaust valve 104.
The exhaust pipe 111 is equipped with a catalytic converter 112 containing a three-way catalyst for purifying exhaust gas.

The control device 109 acquires detection signals output from various sensors that detect the operating state of the internal combustion engine 101.
In addition to the aforementioned fuel pressure sensor 126, the various sensors mentioned above include a water temperature sensor 108 that detects the cooling water temperature TW of the internal combustion engine 101, a crank angle sensor 116 that measures the rotation angle of the crankshaft of the internal combustion engine 101, and a crank angle sensor 116 that measures the rotation angle of the crankshaft of the internal combustion engine 101. An air flow meter 120 that measures the intake air flow rate QA, an air-fuel ratio sensor 113 that detects the air-fuel ratio based on the oxygen concentration of exhaust gas upstream of the catalytic converter 112, and an air-fuel ratio sensor 113 that detects the opening degree ACC of the accelerator operated by the vehicle driver. An accelerator opening sensor 122 and the like are provided.

Then, the control device 109 calculates the required torque of the internal combustion engine 101 based on the accelerator opening degree ACC detected by the accelerator opening degree sensor 122, and also determines whether or not the internal combustion engine 101 is in an idling operating state. .
The control device 109 also calculates the engine rotation speed NE based on the rotation angle of the crankshaft detected by the crank angle sensor 116, and determines whether the internal combustion engine 101 is warming up based on the cooling water temperature TW detected by the water temperature sensor 108. It is determined whether or not.

Further, the control device 109 calculates a target intake air amount from the required torque set based on the accelerator opening degree ACC, and outputs an opening degree control signal based on this target intake air amount to the electronically controlled throttle valve 119.
Further, the control device 109 calculates the ignition timing based on engine operating conditions such as the engine load and the engine rotational speed NE, and outputs an ignition control signal to the ignition coil 107 based on the calculated ignition timing, thereby controlling the spark plug 106. Controls ignition timing.

Furthermore, the control device 109 determines the standard injection pulse width TI at the standard fuel pressure, which corresponds to the total fuel injection amount in one combustion cycle, based on the intake air flow rate QA, engine rotational speed NE, cooling water temperature TW, air-fuel ratio, etc. Then, the standard injection pulse width TI is corrected based on the fuel pressure at that time to obtain the corrected injection pulse width TIA.
Further, the control device 109 sets the number of divisions M in divisional injection (multi-stage injection) in which injection with the corrected injection pulse width TIA is performed in a plurality of divisions, and controls the divisional injection based on the number of divisions M.

Below, the process of setting the number of divisions M of split injection performed by the control device 109, in other words, the functions of the number of divisions setting unit and the minimum pulse width changing unit included in the control device 109 will be described in detail.
2 and 3 are flowcharts showing the procedure for setting the number of divisions M.

The control device 109 acquires the corrected injection pulse width TIA in step S501.
Next, in step S502, the control device 109 selects the minimum pulse width stored corresponding to the current target fuel pressure FPtg (or actual fuel pressure FP) from a table that stores the minimum pulse width TImin in an updatable manner for each fuel pressure level. Search for width TImin.
The minimum pulse width TImin is the lower limit value of the injection pulse width that can limit the injection amount variation within an allowable range, and the control device 109 includes a table of the minimum pulse width TImin on the built-in rewritable nonvolatile memory.

FIG. 4 shows one aspect of a table that stores the minimum pulse width TImin depending on the fuel pressure.
The minimum pulse width TImin table divides the variable range of the target fuel pressure FPtg into a plurality of regions, and stores an initial value of the minimum pulse width TImin in advance for each fuel pressure region.
As will be described later, the control device 109 has a function (functioning as a minimum pulse width updating section) of updating the minimum pulse width TImin for each fuel pressure region in the minimum pulse width TImin table.

Next, in step S503, the control device 109 selects a map corresponding to the current engine load and engine rotation speed NE from a map storing the target number of divisions Mtg for each region divided into a plurality of regions based on the engine load and engine rotation speed NE. The target number of divisions Mtg is searched for, and the target number of divisions Mtg retrieved from the map is set as the initial value of the number of divisions M.

FIG. 5 shows one aspect of a map of the target number of divisions Mtg.
The target number of divisions Mtg is set to a larger number as the engine load becomes higher, and is set to a larger number as the engine rotational speed NE becomes higher.
The engine load can be represented by the standard injection pulse width TI, and the control device 109 has a map of the target number of divisions Mtg on its built-in nonvolatile memory.

Then, in step S504, the control device 109 calculates the division ratio DR according to the following equation (1) based on the corrected injection pulse width TIA, the minimum pulse width TImin, and the number of divisions M.
Division ratio DR=(TImin×M)/TIA...(1)

The division ratio DR is an index value indicating the correlation between the fuel injection pulse width of one injection when the injection of the corrected injection pulse width TIA is divided into the number of divisions M and the minimum pulse width TImin.
If the fuel injection pulse width of one injection in split injection is greater than or equal to the minimum pulse width TImin, the split ratio DR will be 1.0 or less, and if the fuel injection pulse width of one injection in split injection is less than the minimum pulse width TImin, split The ratio DR will exceed 1.0.

Next, the control device 109 proceeds to step S505 and determines whether the division ratio DR is less than or equal to the determination value THdr.
The determination value THdr is set to, for example, 1.0, and when the determination value THdr=1.0, the control device 109 determines the injection pulse per injection when the corrected injection pulse width TIA is divided into the number of divisions M in step S505. It is determined whether the width is equal to or greater than the minimum pulse width TImin.

That is, in step S505, the control device 109 determines whether the fuel injection pulse width of one injection falls within the limit by the minimum pulse width TImin when the corrected injection pulse width TIA is divided into the number of divisions M. .
Note that the control device 109 can also limit the fuel injection pulse width of one injection to be longer than the minimum pulse width TImin by setting the determination value THdr to a value less than 1.0.

When the division ratio DR is less than or equal to the determination value THdr, the control device 109 enables divided injection according to the number of divisions M. In other words, the fuel injection pulse width of one injection is within the limit by the minimum pulse width TImin. It is determined that this is the case, and the process advances to step S507.
On the other hand, when the split ratio DR exceeds the determination value THdr, the control device 109 determines that if split injection is performed according to the split number M, the setting of the split number M when calculating the split ratio DR means that the amount of fuel per injection is It is determined that the injection pulse width is less than the minimum pulse width TImin, and the process proceeds to step S506.

In step S506, the control device 109 performs an update process to reduce the number of divisions M by 1, thereby increasing the fuel injection pulse width per injection in the divided injection.
Then, the control device 109 returns to step S504 from step S506, calculates the division ratio DR again based on the number of divisions M reduced in step S506, and determines whether the division ratio DR is equal to or less than the determination value THdr in the next step S505. Decide whether or not.

That is, if the control device 109 determines that the split ratio DR exceeds the determination value THdr and that split injection cannot be performed at the target number of splits Mtg (initial value of the number of splits M), the control device 109 changes the number of splits M to be less than the target number of splits Mtg. In other words, the number of divisions M at which the fuel injection pulse width per injection exceeds the minimum pulse width TImin or the minimum pulse width TImin is determined.
When the number of divisions M for which the division ratio DR is equal to or less than the determination value THdr is determined, the control device 109 proceeds to step S507 (divided injection control section) and performs divided injection by the fuel injection valve 105.

In the split injection, the control device 109 calculates the fuel injection pulse width per injection by equally dividing the corrected injection pulse width TIA according to the number of splits M, and divides the fuel injection based on the calculated fuel injection pulse width into the number M of splits. Just repeat.
As a result, the same total amount of fuel as when injected with the corrected injection pulse width TIA is injected from the fuel injection valve 105 during one combustion cycle.

The processing content of the control device 109 in steps S501 to S507 described above is a division number setting unit that sets the number of divisions M in the divided injection so that the fuel injection pulse width of one injection in the divided injection does not become less than the minimum pulse width TImin. It shows the function as
Further, the control device 109 has a function as a minimum pulse width changing unit that changes the minimum pulse width TImin based on the frequency at which a deviation occurs between the number of divisions M set by the division number setting unit and the target number of divisions Mtg, Such functionality will be explained in detail below.
Note that step S508 and step S509 are part of the function of the minimum pulse width changing unit of the control device 109, and will therefore be described in detail later.

In step S601, the control device 109 acquires information on the fuel pressure FP detected by the fuel pressure sensor 126 and the target fuel pressure FPtg according to the engine operating conditions.
Next, in step S602, the control device 109 determines whether or not the fuel pressure FP is near the target fuel pressure FPtg, thereby establishing the steady operating state of the internal combustion engine 101, which is the execution condition for the minimum pulse width TImin update process. Determine whether or not.

Note that when the internal combustion engine 101 is equipped with an evaporated fuel processing device, the control device 109 determines that the amount of evaporated fuel introduced into the intake system of the internal combustion engine 101 is less than a predetermined amount (in other words, the amount of evaporated fuel introduced into the intake system of the internal combustion engine 101 is (that the disturbance is sufficiently small) can be used as a condition for updating the minimum pulse width TImin instead of or together with the condition for the fuel pressure FP.
The evaporated fuel processing device described above adsorbs and collects evaporated fuel generated in the fuel tank 123 in a charcoal canister, purges the evaporated fuel from the charcoal canister during operation of the internal combustion engine 101, and enters the intake passage of the internal combustion engine 101. This device introduces the fuel into the combustion chamber 121 and performs combustion processing within the combustion chamber 121.

If the control device 109 determines in step S602 that the conditions for executing the minimum pulse width TImin update process, including that the fuel pressure FP is near the target fuel pressure FPtg, are satisfied, the process proceeds to step S603.
On the other hand, if the control device 109 determines in step S602 that the conditions for executing the process of updating the minimum pulse width TImin are not satisfied, the process returns to step S601 and updates information such as the fuel pressure FP and the target fuel pressure FPtg.

When the control device 109 proceeds to step S603, the control device 109 determines the number of times NS (cumulative number) set to reduce the number of divisions M from the target number of divisions Mtg in step S506, in other words, the number of divisions M that is less than the target number of divisions Mtg. Find the set frequency.
That is, in step S603, the control device 109 determines the frequency at which a deviation occurs between the number of divisions M set based on the division ratio DR and the target number of divisions Mtg.

The control device 109 includes a map on a rewritable nonvolatile memory that stores the number of times NS in an updatable manner for each region divided into a plurality of regions based on the engine load and the engine rotational speed NE.
Then, when the control device 109 executes the process of reducing the number of divisions M from the target number of divisions Mtg in step S506, in step S603, the control device 109 stores the number of divisions in an area on the map corresponding to the conditions of the engine load and engine rotational speed NE at that time. The number of times NS that has been read out is read out, the number of times NS that has been read out is counted up by one, and the result is overwritten on the corresponding area of the map, and the number of times NS that has set the number of divisions M that is less than the target number of divisions Mtg is counted for each area.

Next, the control device 109 proceeds to step S604 and compares the number of times NS counted up in step S603 with the determination value THn, and determines whether or not the number of times NS is equal to or greater than the determination value THn. It is determined whether the frequency at which the number of times M is set to be reduced from the target number of divisions Mtg is greater than a predetermined value.
The control device 109 has a map in a non-volatile memory that stores the judgment value THn according to engine operating conditions such as engine load and engine rotational speed NE, and searches from the map based on the engine operating conditions at that time. The determined determination value THn is used in step S604.

Then, if the number of times NS is not equal to or greater than the determination value, that is, if split injection has been substantially performed at the target number of splits Mtg, the control device 109 determines that it is unnecessary to change the minimum pulse width TImin and steps Return to S601.
On the other hand, if the number of times NS is equal to or greater than the determination value, that is, if the divided injection at the target number of divisions Mtg cannot be performed, the control device 109 proceeds to step S605.

In step S605, the control device 109 calculates the minimum pulse width TImin-new as an updated value of the minimum pulse width TImin based on the following equation (2).
TImin-new=TImin×1/DR…(2)
Note that the division ratio DR in equation (2) is a value calculated based on the number of divisions M before the subtraction process in step S506, that is, the division ratio DR determined to exceed the determination value THdr.

The control device 109 performs processing to reduce the number of divisions M when the division ratio DR exceeds the determination value THdr (for example, THdr=1.0), and the division ratio DR becomes a smaller value as the minimum pulse width TImin becomes shorter.
Therefore, the control device 109 makes it difficult to reduce the number of divisions M by changing the minimum pulse width TImin to a shorter value.

The minimum pulse width TImin-new obtained according to the above equation (2) becomes the injection pulse width per injection when the corrected injection pulse width TIA is divided into injections by the target number of divisions Mtg.
Therefore, if this minimum pulse width TImin-new is applied, the division ratio DR at the target number of divisions Mtg will be 1.0, which will be less than or equal to the judgment value THdr (THdr = 1.0), and the process to reduce the target number of divisions Mtg will not be performed. It turns out.

However, if the control device 109 excessively shortens the fuel injection pulse width of one injection in order to perform split injections at the target number of splits Mtg, the amount of fuel actually injected from the fuel injection valves 105 will vary greatly. As a result, the combustion state of the internal combustion engine 101 deteriorates.
Therefore, from step S606 onward, the control device 109 verifies whether the minimum pulse width TImin-new obtained in step S605 can be applied as is.

In step S606, the control device 109 performs processing to temporarily set the minimum pulse width TImin-new obtained in step S605 to the minimum pulse width TImin determined in step S502.
As a result, the control device 109 executes split injection at the target number of splits Mtg in step S507.

In step S508, the control device 109 determines whether the current divided injection is a divided injection with the number of divisions M set provisionally using the minimum pulse width TImin-new.
Then, if the split injection is not based on the minimum pulse width TImin-new but the split injection based on the established minimum pulse width TImin, the control device 109 proceeds to step S509 and splits the injection without detecting the combustion state. Perform injection.

On the other hand, in the case of split injection based on the minimum pulse width TImin-new, the control device 109 proceeds to step S607 (combustion state detection unit) and detects the combustion state of the internal combustion engine 101.
In other words, if the minimum pulse width TImin-new is too small, in other words, if the fuel injection pulse width of one injection in split injection is set too short, the injection amount dispersion of the fuel injection valve 105 becomes large and the combustion condition will deteriorate beyond a predetermined level.

Therefore, by detecting the combustion state, the control device 109 determines whether the minimum pulse width TImin-new is so short as to deteriorate the combustion state beyond a predetermined value.
In step S607, the control device 109 detects physical quantities that change depending on the combustion state, such as a change in crank angular velocity, an integrated value of cylinder pressure, and a peak value of cylinder pressure, as a combustion state detection process.

If the minimum pulse width TImin-new is too small and the fuel injection pulse width for one injection is set too short, the amount of fuel injected by the fuel injection valve 105 will vary, and the control accuracy of the air-fuel ratio will deteriorate.
As a result, the change in the crank angular velocity increases, and the integrated value of the cylinder pressure and the peak value of the cylinder pressure decrease, resulting in deterioration of the combustion state.
Note that the control device 109 can detect changes in the crank angular velocity based on the output of the crank angle sensor 116, and when the internal combustion engine 101 includes a sensor that detects the cylinder pressure, the integrated value of the cylinder pressure and/or The peak value of cylinder pressure can be detected.

In step S608, the control device 109 determines whether the combustion state has deteriorated beyond a predetermined level by comparing the physical quantity representing the combustion state detected in step S607 with the determination value.
The control device 109 has a map stored in a non-volatile memory in which judgment values of physical quantities representing the combustion state are stored according to engine operating conditions such as engine load and engine speed NE, and determines the engine operation at that time from the map. The determination value searched based on the conditions is used in step S608.

For example, if the change in crank angular velocity exceeds the determination value and deterioration of the combustion state is recognized, the control device 109 determines that the minimum pulse width TImin-new is too small and the fuel injection pulse width for one injection has become excessively short. It can be estimated that the amount of fuel injected by the injection valve 105 varies and the accuracy of controlling the air-fuel ratio deteriorates.
In this case, by increasing the minimum pulse width TImin-new, it is possible to suppress deterioration of the combustion state.

On the other hand, if the combustion condition does not deteriorate when the minimum pulse width TImin-new is applied, the minimum pulse width TImin-new is within the allowable range, and the control device 109 sets the subsequent number of divisions M. This means that it can be used for
That is, when the number of divisions M is set to be less than the target number of divisions Mtg, the control device 109 changes the minimum pulse width TImin to be shorter within a range in which the combustion state does not deteriorate beyond a predetermined level.

If the control device 109 determines that the combustion state has deteriorated beyond a predetermined level as a result of applying the minimum pulse width TImin-new, the process proceeds from step S608 to step S609, and the minimum pulse width TImin-new is recalculated (increasing direction). modification) is carried out based on the following equation (3).
TImin-new=TImin×1/DR×K…(3)

In the above equation (3), the coefficient K is a value satisfying K>1.0.
The minimum pulse width TImin-new calculated by the above equation (3) is the result of multiplying the minimum pulse width TImin-new calculated by the above equation (2) by a coefficient K, and the minimum pulse width TImin-new calculated by the above equation (2) is multiplied by the coefficient K. The calculated minimum pulse width TImin-new is a longer time than the minimum pulse width TImin-new calculated using equation (2).

After updating the minimum pulse width TImin-new in step S609, the control device 109 returns to step S606 and temporarily sets the minimum pulse width TImin used in the process of setting the number of divisions M to the minimum pulse width TImin-new obtained in step S609. Execute the replacement process.
Thereafter, the control device 109 performs the processes of steps S606 to S608 again to determine whether the combustion state will deteriorate when the number of divisions M is set based on the minimum pulse width TImin-new updated in step S609. Verify whether

If the control device 109 determines in step S608 that, for example, the change in crank angular velocity is below the determination value and that the combustion state is within a good range, the control device 109 proceeds to step S610 and divides the minimum pulse width TImin-new into the number of times M By updating and storing the minimum pulse width TImin used for setting, the adoption of the minimum pulse width TImin-new is confirmed.
In step S610, the control device 109 rewrites only the minimum pulse width TImin corresponding to the fuel pressure at that time to the minimum pulse width TImin-new in the table storing the minimum pulse width TImin in an updatable manner for each fuel pressure level, and sets the minimum pulse width TImin to the minimum pulse width TImin-new. The pulse width TImin can be updated individually for each fuel pressure level.

Further, in step S610, the control device 109 rewrites the minimum pulse width TImin corresponding to the fuel pressure at that time to the minimum pulse width TImin-new, and at the same ratio (degree) as the change ratio (degree of change) due to the rewriting, The stored minimum pulse width TImin can be uniformly rewritten according to other fuel pressures.
In the following, a process for uniformly changing the minimum pulse width TImin for each fuel pressure will be described with reference to the minimum pulse width TImin table in FIG. 4.

FIG. 4 shows that when the minimum pulse width TImin when the fuel pressure is 12 MPa is rewritten, the minimum pulse width TImin stored according to other fuel pressures is changed to the minimum pulse width TImin when the fuel pressure is 12 MPa. Shows how to uniformly change the same ratio as the ratio.
FIG. 4 shows that when the fuel pressure is 12 MPa, the initial value of the minimum pulse width TImin is 500 μs, and when the control device 109 executes the processing shown in the flowcharts of FIGS. 2 and 3, the fuel pressure is 12 MPa. The case where the minimum pulse width TImin is rewritten from 500 μs to 470 μs is shown.

At this time, the change ratio (change degree, change ratio), which is the ratio of the minimum pulse width TImin before and after the change when the fuel pressure is 12 MPa, is 470/500 = 94%, and the minimum pulse width TImin is 94% of the initial value. This means that it has been rewritten to %.
Here, the control device 109 uniformly rewrites the minimum pulse width TImin stored corresponding to fuel pressures other than 12 MPa (fuel pressure = 0.3-10, 14-24 [MPa]) to 94% of the initial value. Perform processing.

In the example of FIG. 4, the initial value of the minimum pulse width TImin when the fuel pressure is in the range of 0.3 MPa to 14 MPa is all 500 μs, which is the same as when the fuel pressure is 12 MPa. Similarly to the minimum pulse width TImin, the minimum pulse width TImin within the range of fuel pressure from 0.3 MPa to 14 MPa is uniformly rewritten to 470 μs.
Further, in the example of FIG. 4, the initial value of the minimum pulse width TImin when the fuel pressure is in the range of 16 MPa to 24 MPa is all 540 μs, and the control device 109 controls the change ratio of the minimum pulse width TImin when the fuel pressure is 12 MPa. The minimum pulse width TImin within the range of fuel pressure from 16 MPa to 24 MPa is uniformly rewritten to 507 μs (0.94≈507/540) so that the same change ratio is obtained.

As described above, when updating the minimum pulse width TImin based on the number of times NS (frequency) obtained by reducing the number of divisions M, the control device 109 updates the minimum pulse width TImin corresponding to a fuel pressure other than the fuel pressure condition under which the update is performed. The minimum pulse width TImin can be uniformly updated at the same rate (change ratio) whenever the pulse width is changed.
With such a configuration, the minimum pulse width TImin corresponding to the fuel pressure that is rarely used can be updated appropriately at an early stage, and even if the fuel pressure conditions change, the minimum pulse width TImin can be updated as quickly as possible while preventing deterioration of the combustion state. Therefore, it is possible to perform split injection with a large number of splits M.

According to the process of setting the number of divisions by the control device 109 shown in the flowcharts of FIGS. 2 and 3, the target number of divisions Mtg is set as large as possible, and the internal combustion engine 101 becomes unable to perform split injection at the target number of divisions Mtg. can be prevented from occurring.
If the target number of divisions Mtg for each engine operating region is set to a relatively small value by taking into account the variations in the internal combustion engine 101 (machine difference variations), it is possible to prevent the internal combustion engine 101 from being unable to perform split injection at the target number of divisions Mtg. Although this can be suppressed, since the target number of divisions Mtg is small, the effect of improving the exhaust properties by the divisional injection is diminished.

On the other hand, in setting the target number of divisions Mtg, if the variation of the internal combustion engine 101 is minimized, the target number of divisions Mtg can be set to a large number for each engine operating region. There is a possibility that the internal combustion engine 101 may not be able to inject at the target number of divisions Mtg.
On the other hand, the control device 109 reduces the minimum pulse width TImin when the frequency (number NS) of reducing the number of divisions M from the target number of divisions Mtg exceeds a predetermined value, so that the target number of divisions Mtg can be reduced as much as possible. While setting a large number of times Mtg, it is possible to prevent the internal combustion engine 101 from being unable to perform split injection at the target number of splits Mtg.
Furthermore, since the control device 109 reduces the minimum pulse width TImin within a range that can suppress deterioration of the combustion state, it is possible to set the number of divisions M as large as possible within a range that does not deteriorate the combustion state.

By the way, the control device 109 can verify whether or not the combustion state deteriorates with the minimum pulse width TImin set to decrease from the initial value while the internal combustion engine 101 is in an idling state.
When the internal combustion engine 101 is idling, the combustion state is likely to deteriorate due to variations in the injection amount, and if the combustion state does not deteriorate when the minimum pulse width TImin is applied while the internal combustion engine 101 is idling, the control device 109 It can be estimated that deterioration of the combustion state does not occur even in operating ranges where the engine load and engine speed are higher than in the idling state.

FIGS. 6 and 7 are flowcharts illustrating a process for setting the number of divisions, which determines whether or not the combustion state will deteriorate by applying the minimum pulse width TImin-new in the idling state of the internal combustion engine 101.
Since the control device 109 performs the same processing as steps S501 to S507 in the flowchart of FIG. 2 in steps S701 to S707, a detailed explanation of the processing contents in each step of steps S701 to S707 will be omitted.
Furthermore, since the control device 109 performs the same processing as steps S601 to S605 in the flowchart of FIG. 3 in steps S801 to S805, a detailed explanation of the processing contents in each step of steps S801 to S805 will be omitted. .

After calculating the minimum pulse width TImin-new in step S805, the control device 109 proceeds to step S806 and determines whether the internal combustion engine 101 is in an idling state.
Note that the low load and low rotational speed region including the idling state is an operating condition in which the target number of divisions Mtg is set to one and divisional injection is not substantially performed.

If the internal combustion engine 101 is not in an idling state, the control device 109 repeats the determination process in step S806, and if the internal combustion engine 101 is in an idling state, the process proceeds from step S806 to step S807.
In step S807, the control device 109 sets the injection pulse width when the internal combustion engine 101 is idling to the minimum pulse width TImin-new.
Next, the control device 109 gradually increases the target fuel pressure in the idling state and controls the injection pulse width in the idling state to be close to the minimum pulse width TImin-new.

Next, in step S808, the control device 109 detects the combustion state (physical quantity such as a change in crank angular velocity) of the internal combustion engine 101, similarly to step S607.
Then, in the next step S809, the control device 109 determines whether the combustion state has deteriorated beyond a predetermined level by comparing the physical quantity correlated with the combustion state detected in step S808 with the determination value. to judge.

If the control device 109 determines in step S809 that the combustion state has deteriorated beyond the predetermined level, the control device 109 proceeds from step S809 to step S810, and similarly to step S609, recalculates the minimum pulse width TImin-new as described above. The minimum pulse width TImin-new is increased and modified based on equation (3).
After updating the minimum pulse width TImin-new in step S810, the control device 109 returns to step S806.

Then, if the internal combustion engine 101 is in the idling state, the control device 109 re-executes the processes from step S807 to step S809 to set the minimum pulse width TImin-new updated in step S810 to the injection pulse width in the idling state. Verify whether the combustion condition deteriorates when the setting is set to .
Here, if the control device 109 determines in step S809 that the change in crank angular velocity is less than or equal to the determination value and that the combustion state is within a good range, the control device 109 proceeds to step S811, and similarly to step S610, the minimum pulse width is By updating and storing TImin-new as the minimum pulse width TImin used for setting the number of divisions M, the adoption of the minimum pulse width TImin-new is confirmed.
If the idling state of the internal combustion engine 101 is used to determine whether or not the combustion condition will deteriorate by applying the minimum pulse width TImin-new, it will be possible to determine whether or not the minimum pulse width TImin-new can be finally adopted. It is possible to ensure the frequency of arithmetic processing for making decisions.

The technical ideas described in the above embodiments can be used in combination as appropriate, as long as there is no contradiction.
Further, although the content of the present invention has been specifically explained with reference to preferred embodiments, it is obvious that those skilled in the art can make various modifications based on the basic technical idea and teachings of the present invention. It is.

For example, the internal combustion engine 101 is not limited to a direct injection type internal combustion engine, but may be an intake port injection type internal combustion engine in which the fuel injection valve 105 injects fuel into the intake port 110.
Further, when the control device 109 sets the number of divisions M that is less than the target number of divisions Mtg, the control device 109 sets the minimum pulse width TImin-new that can realize the target number of divisions Mtg, and when this minimum pulse width TImin-new is adopted. If the combustion condition worsens, the minimum pulse width TImin-new is increased, but instead of such processing, the minimum pulse width TImin-new is gradually shortened from the initial value, and the combustion condition deteriorates. The minimum pulse width TImin can be updated based on the minimum pulse width TImin-new at the time.

In addition, the control device 109 executes the process of changing the minimum pulse width TImin after the frequency of setting the number of divisions M that is lower than the target number of divisions Mtg becomes high. Each time the minimum pulse width TImin is changed, the minimum pulse width TImin is changed shorter, and if the combustion condition deteriorates with the changed minimum pulse width TImin, the minimum pulse width TImin can be corrected in the direction of increasing it.

101... Internal combustion engine, 105... Fuel injection valve, 109... Control device

Claims (6)

A control device for an internal combustion engine,
a split injection control unit that controls split injection that causes a fuel injection valve included in the internal combustion engine to perform fuel injection in multiple parts;
A division number setting unit that sets the number of divisions in the divisional injection by the divisional injection control unit,
When the fuel injection pulse width of one injection is less than the minimum pulse width when the number of divisions is the target number of divisions, the number of divisions is set to the target division so that the fuel injection pulse width of one injection does not become less than the minimum pulse width. causing the split injection control unit to perform split injection after reducing the number of times,
When the fuel injection pulse width of one injection is equal to or greater than the minimum pulse width when the number of divisions is set to the target number of divisions, the division number is set to the target number of divisions, and the divided injection is performed by the divided injection control unit. make it happen,
the division number setting section;
a minimum pulse width changing unit that changes the minimum pulse width to a shorter pulse width when the frequency at which the division number setting unit reduces the number of divisions below the target number of divisions becomes a determination value or more;
An internal combustion engine control device having: The control device for an internal combustion engine according to claim 1 ,
The minimum pulse width changing section is
comprising a combustion state detection section that detects a combustion state of the internal combustion engine,
changing the minimum pulse width to a shorter pulse width within a range where the combustion state does not deteriorate beyond a predetermined level;
Internal combustion engine control device. The control device for an internal combustion engine according to claim 2 ,
The minimum pulse width changing section is
In the idling state of the internal combustion engine, the changed minimum pulse width is set as the fuel injection pulse width to perform fuel injection, and if the combustion state deteriorates beyond a predetermined level at this time, the minimum pulse width increase,
Internal combustion engine control device. The control device for an internal combustion engine according to claim 1,
further comprising a target division number setting unit that sets the target division number based on an engine load and an engine rotation speed;
Internal combustion engine control device. A control device for an internal combustion engine that is applied to an internal combustion engine that includes a fuel injection valve and a variable fuel pressure device that variably controls fuel pressure that is the pressure of fuel supplied to the fuel injection valve,
a split injection control unit that controls split injection that causes a fuel injection valve included in the internal combustion engine to perform fuel injection in multiple parts;
a division number setting unit that sets the number of divisions in the divided injection so that the fuel injection pulse width of one injection in the divided injection does not fall below a minimum pulse width;
a minimum pulse width changing unit that changes the minimum pulse width based on the frequency at which a deviation occurs between the number of divisions set by the number of divisions setting unit and the target number of divisions;
has
The division number setting unit sets the minimum pulse width for each fuel pressure,
The minimum pulse width changing section is
When changing the minimum pulse width based on the frequency, uniformly changing the minimum pulse width for each fuel pressure based on the degree of change of the minimum pulse width in the changing process,
Internal combustion engine control device. A control device for an internal combustion engine,
a split injection control unit that controls split injection that causes a fuel injection valve included in the internal combustion engine to perform fuel injection in multiple parts;
A division number setting unit that sets the number of divisions in the divisional injection by the divisional injection control unit,
When the fuel injection pulse width of one injection is less than the minimum pulse width when the number of divisions is the target number of divisions, the number of divisions is set to the target division so that the fuel injection pulse width of one injection does not become less than the minimum pulse width. causing the split injection control unit to perform split injection after reducing the number of times,
When the fuel injection pulse width of one injection is equal to or greater than the minimum pulse width when the number of divisions is set to the target number of divisions, the division number is set to the target number of divisions, and the divided injection is performed by the divided injection control unit. make it happen,
the division number setting section;
a combustion state detection section that detects a combustion state of the internal combustion engine;
a minimum pulse width changing unit that changes the minimum pulse width to a shorter value within a range in which the combustion condition does not deteriorate beyond a predetermined level when the division number setting unit reduces the division number to be less than the target division number; ,
An internal combustion engine control device having: