JP6815960B2 - In-cylinder injection type internal combustion engine control device - Google Patents

Description

The present invention relates to a control device for an in-cylinder injection type internal combustion engine, and more particularly to control of multi-stage injection in which fuel is injected in a plurality of times in one combustion cycle.

According to Patent Document 1, when the engine temperature is equal to or lower than a predetermined temperature, the total injection amount to be injected in one combustion cycle increases, or the total injection pulse width required in one combustion cycle increases. As a result, a fuel injection control device for an in-cylinder injection engine, characterized in that the number of split injections in one combustion cycle is increased, is disclosed.

Japanese Unexamined Patent Publication No. 2014-020211

By the way, in an in-cylinder injection type internal combustion engine, when performing multi-stage injection in which the total fuel injection amount in one combustion cycle is divided into a plurality of times, the number of injections in the multi-stage injection (the number of divisions of the total fuel injection amount) is determined. It is adapted to the number of times that the number of emitted particles PN (Particulate Number) of particulate matter (particulate matter) and the amount of fuel dissolved in engine oil (oil dilution amount) can be sufficiently suppressed.
However, depending on the change in friction in the internal combustion engine and the operating state of accessories, if the optimum number of injections is set, the injection pulse width per multi-stage injection will be the minimum injection pulse width that can maintain the fuel measurement accuracy. Could be less than.
Here, if the number of injections in the multi-stage injection is reduced from the optimum number in order to secure the injection pulse width equal to or larger than the minimum injection pulse width, there arises a problem that the PN and the oil dilution amount deteriorate.

The present invention has been made in view of the conventional circumstances, and an object of the present invention is to allow the number of injections in the multi-stage injection while suppressing the injection pulse width per injection of the multi-stage injection from being less than the minimum injection pulse width. An object of the present invention is to provide a control device for an in-cylinder injection type internal combustion engine that can maintain an optimum value.

According to the present invention, in one aspect thereof, when the fuel pressure is the base fuel pressure and the injection pulse width per injection in the multi-stage injection is less than the minimum injection pulse width, the fuel pressure is higher than the base fuel pressure. The multi-stage injection control unit has a multi-stage injection control unit that reduces the injection pulse width per injection so that the injection pulse width exceeds the minimum injection pulse width, and the multi- stage injection control unit sets the number of injections to Ntg and the minimum injection pulse width. When the total fuel injection pulse width corresponding to the total fuel injection amount is set to TI when the fuel pressure is TImin and the fuel pressure is the base fuel pressure, TImin × Ntg / TI is a condition that becomes the first determination value (<1.0) or less. In this case, when multi-stage injection is performed at the base fuel pressure and the condition is that TImin × Ntg / TI becomes larger than the first determination value, the fuel pressure is adjusted so that TI / Ntg is the minimum injection pulse width TImin or more from the base fuel pressure. Reduce the fuel pressure to.

According to the above invention, the number of injections in the multi-stage injection can be maintained at the optimum value as much as possible while suppressing the injection pulse width per injection in the multi-stage injection from being smaller than the minimum injection pulse width.

It is a figure which shows the fuel injection system of the in-cylinder injection type internal combustion engine. It is a block diagram which shows the fuel injection control function of a control device. It is a time chart exemplifying the behavior such as fuel pressure FP, target injection count Ntg, pulse ratio PR, etc. when the process of reducing the number of injections in multi-stage injection is performed. It is a diagram which shows the change of PN with respect to the fuel pressure for each injection number of multi-stage injection. It is a time chart which exemplifies the behavior such as a fuel pressure FP, a target number of injections Ntg, a pulse ratio PR, and the like when the process of lowering a fuel pressure is performed. It is a time chart exemplifying the behavior such as fuel pressure FP, target injection count Ntg, pulse ratio PR, etc. when the process of lowering the fuel pressure and the process of reducing the number of injections in multi-stage injection are performed. It is a time chart which exemplifies the behavior such as a fuel pressure FP, a target number of injections Ntg, and a pulse ratio PR when a process of reducing the number of injections in a multi-stage injection is performed after warming up.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram showing a fuel injection system of an in-cylinder injection type internal combustion engine for a vehicle.
The fuel injection system of FIG. 1 includes an internal combustion engine 101, a fuel injection valve 105, and an ECU (Engine Control Unit) 109 which is a computer that controls overall control of the internal combustion engine 101 including fuel injection by the fuel injection valve 105. Have.

In FIG. 1, the intake air of the internal combustion engine 101 passes through the air flow meter 120, the electronically controlled throttle valve 119, and the collector 115 in this order, and then sucks into the combustion chamber 121 via the intake pipe 110 and the intake valve 103 provided in each cylinder. Will be done.
On the other hand, the electric low-pressure fuel pump 124 sends the fuel in the fuel tank 123 to the engine-driven high-pressure fuel pump 125.

The high-pressure fuel pump 125 boosts the fuel supplied from the low-pressure fuel pump 124 and sends it to the fuel injection valve 105 via the high-pressure fuel pipe 128, and the ECU 109 adjusts the discharge amount of the high-pressure fuel pump 125. The pressure of the fuel sent to the fuel injection valve 105 (hereinafter referred to as fuel pressure) is controlled to the target fuel pressure.
The fuel tank 123, the low-pressure fuel pump 124, the high-pressure fuel pump 125, the high-pressure fuel pipe 128, and the like constitute a fuel supply device 129 that changes the fuel pressure supplied to the fuel injection valve 105.

The fuel injection valve 105 is an electromagnetic fuel injection valve that directly injects fuel into the combustion chamber 121 (inside the cylinder) of the internal combustion engine 101, receives a command (injection pulse signal) from the ECU 109, and is designated by the command. By opening the valve only for the required time, an amount of fuel proportional to the valve opening time is injected into the combustion chamber 121.
The ECU 109 sets the total amount of fuel (total fuel injection amount) to be injected from the fuel injection valve 105 during one combustion cycle (during one cylinder and one cycle) based on the engine operating state, and also sets the total fuel injection based on the engine operating state. The number of injections (the number of divisions of the total fuel injection amount) in the multi-stage injection in which the amount is injected in a plurality of times in one combustion cycle is set, and the multi-stage injection by the fuel injection valve 105 is controlled.
That is, the ECU 109 functions as a total injection amount setting unit for setting the total fuel injection amount, a number setting unit for setting the number of injections in the multi-stage injection, and a multi-stage injection control unit for performing multi-stage injection by the fuel injection valve 105. Prepare as software.

The fuel pressure sensor 126 detects the fuel pressure FP in the high-pressure fuel pipe 128, that is, the fuel pressure FP supplied to the fuel injection valve 105.
Then, the ECU 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 adjusts the discharge amount of the high-pressure fuel pump 125. The so-called feedback control in which the operation amount is set by the proportional operation based on the deviation ΔFP, the integration operation, or the like is performed, and the fuel pressure FP is brought closer to the target fuel pressure FPtg.

Further, the internal combustion engine 101 includes an ignition device having an ignition coil 107 and a spark plug 106.
The ECU 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 burned by the spark generated by the spark plug 106, and the exhaust gas generated by the combustion is discharged from the inside of the combustion chamber 121 to the exhaust pipe 111 via the exhaust valve 104.
The exhaust pipe 111 is provided with a catalyst converter 112 containing a three-way catalyst for purifying the exhaust gas.

The ECU 109 includes a water temperature sensor 108 that measures the water temperature TW, which is the temperature of the cooling water of the internal combustion engine 101, a crank angle sensor 116 that measures the angle of the crankshaft (not shown) of the internal combustion engine 101, and an intake air flow rate QA of the internal combustion engine 101. 120, an air-fuel ratio sensor 113 that detects the air-fuel ratio of the air-fuel mixture based on the oxygen concentration in the exhaust gas of the internal combustion engine 101, and an accelerator opening sensor 122 that indicates the opening ACC of the accelerator operated by the driver. , And the detection signal from the fuel pressure sensor 126 or the like described above is input.

Then, the ECU 109 calculates the required torque of the internal combustion engine 101 from the signal of the accelerator opening sensor 122, and determines whether or not the internal combustion engine 101 is in the idle operation state.
Further, the ECU 109 calculates the engine rotation speed NE based on the detection signal of the crank angle sensor 116, and determines whether or not the internal combustion engine 101 is warming up based on the detection signal of the water temperature sensor 108.

Further, the ECU 109 calculates the target intake air amount from the above-mentioned required torque and the like, outputs an opening signal corresponding to the target intake air amount to the electronically controlled throttle valve 119, and injects the total fuel in one combustion cycle. The amount is calculated based on the intake air amount, engine rotation speed, etc., and multi-stage injection is performed by the fuel injection valve 105. Furthermore, the ignition timing is calculated according to the engine load, engine rotation speed, etc., and the ignition signal is sent to the ignition coil 107. Is output.

FIG. 2 is a functional block diagram showing a multi-stage injection control function included in the ECU 109.
The basic injection pulse width calculation unit 200 mixes the theoretical air-fuel ratio when the fuel pressure FP is the reference fuel pressure FPs based on the intake air flow rate QA detected by the air flow meter 120 and the engine rotation speed NE (engine rotation speed rpm). Calculate the basic fuel injection pulse width TP [ms] for generating qi.

The fuel injection pulse width calculation unit 201 (total injection amount setting unit) sets the basic fuel injection pulse width TP based on various fuel correction terms based on operating conditions such as water temperature TW and the fuel pressure FP detected by the fuel pressure sensor 126. The total fuel injection pulse width TI in one combustion cycle is calculated by correcting according to the fuel pressure correction term and the like.
The total fuel injection pulse width TI corresponds to the total fuel injection amount injected from the fuel injection valve 105 during one combustion cycle.

The target fuel pressure map unit 202 includes, for example, a map storing the target fuel pressure FPtgm according to operating conditions such as the basic fuel injection pulse width TP (engine load), engine rotation speed NE, and water temperature TW for each of a plurality of combustion modes.
The plurality of combustion modes include, for example, a stratified combustion mode, a homogeneous combustion mode, and a retard mode of ignition timing during catalyst warm-up.

The multi-stage injection number map unit 203 (number setting unit) has a target injection number Ntgm (total fuel) in multi-stage injection according to operating conditions such as basic fuel injection pulse width TP (engine load), engine rotation speed NE, and water temperature TW. A map that stores the number of divisions of the injection pulse width TI) is provided for each of a plurality of combustion modes.
The multi-stage injection division ratio map unit 204 stores a plurality of maps storing the target division ratio SRtgm of multi-stage injection according to operating conditions such as basic fuel injection pulse width TP (engine load), engine rotation speed NE, and water temperature TW. It is provided for each combustion mode and each injection count N.

Here, the target division ratio SRtgm specifies what percentage of the total fuel injection pulse width TI is to be distributed to each injection of the multi-stage injection, and the total division ratio (%) of each injection of the multi-stage injection is 100. %become.
For example, in multi-stage injection (target number of injections Ntgm = 2 times) in which the total fuel injection pulse width TI is injected in two times, when the division ratio SR of the first injection is specified to 25%, the total fuel injection is performed in the first injection. 25% of the pulse width TI is injected, and 75% of the total fuel injection pulse width TI is injected in the second injection. However, in multi-stage injection, the total fuel injection pulse width TI can be evenly allocated to each injection.

The injection timing map unit 205 stores a plurality of maps storing the injection timing IT of each injection of multi-stage injection according to operating conditions such as basic fuel injection pulse width TP (engine load), engine rotation speed NE, and water temperature TW. It is prepared for each combustion mode and each injection count Ntg.
The multi-stage injection control unit 206 receives information on the total fuel injection pulse width TI, the minimum injection pulse width TImin capable of maintaining the fuel measurement accuracy by the fuel injection valve 105, and the combustion mode, and receives information on the combustion mode from the target fuel pressure map unit 202, and the operating conditions at that time. The target fuel pressure FPtgm corresponding to the above is searched, and the target injection number Ntgm corresponding to the operating condition at that time is searched from the multi-stage injection number map unit 203.

Then, the multi-stage injection control unit 206 is based on the total fuel injection pulse width TI, the minimum injection pulse width TImin, and the target injection count Ntgm, and under the conditions of the current target fuel pressure FPtgm (base fuel pressure), the multi-stage injection control unit 206 has the target injection count Ntgm. Determine if injection is possible.
The multi-stage injection control unit 206 sets the injection pulse width TIsn (TIsn = TI / Ntgm) in each injection of the multi-stage injection, assuming that the total fuel injection pulse width TI is evenly divided into the target injection times Ntgm for multi-stage injection. When the minimum injection pulse width is TImin or more, it is determined that multi-stage injection is possible with the target injection count Ntgm and the target fuel pressure FPtgm as prerequisites.

At this time, the multi-stage injection control unit 206 sets the target injection count Ntgm as it is to the final target injection count Ntg, and sets the target injection count Ntg to the multi-stage injection division ratio control unit 207 and the multi-stage injection timing control unit 208, which will be described later. The target fuel pressure FPtgm is set to the final target fuel pressure FPtg as it is, and is output to the fuel pressure control unit 209.
The fuel pressure control unit 209 performs feedback control for adjusting the discharge amount of the high-pressure fuel pump 125 based on the target fuel pressure FPtg and the fuel pressure FP detected by the fuel pressure sensor 126.

On the other hand, assuming that the multi-stage injection control unit 206 uniformly divides the total fuel injection pulse width TI into the target number of injections Ntgm and performs multi-stage injection, the injection pulse width TIsn in each injection of the multi-stage injection is the minimum injection pulse width TImin. If it is less than, it is judged that multi-stage injection at the target injection frequency Ntgm and the target fuel pressure FPtgm, which are the preconditions, is impossible.
That is, when multi-stage injection is performed with an injection pulse width TIsn smaller than the minimum injection pulse width TImin, the fuel weighing accuracy by the fuel injection valve 105 is lowered, and an amount of fuel corresponding to the total fuel injection pulse width TI is injected accurately. This makes it impossible to control the air-fuel ratio, which reduces the accuracy.

Therefore, the multi-stage injection control unit 206 determines that the condition in which multi-stage injection is performed with an injection pulse width TIsn lower than the minimum injection pulse width TImin is a state in which multi-stage injection is impossible, and multi-stage injection with an injection pulse width TIsn equal to or larger than the minimum injection pulse width TImin. The conditions of multi-stage injection are changed so that the injection is performed.
Specifically, the multi-stage injection control unit 206 obtained the target fuel pressure FPtg from the map according to the operating conditions at that time when the multi-stage injection is performed under the condition that the injection pulse width TIsn is smaller than the minimum injection pulse width TImin. By lowering the target fuel pressure than FPtgm (base fuel pressure), the injection pulse width (valve opening time) required to inject the same amount of fuel is lengthened, and in each injection of multi-stage injection without changing the target injection number Ntgm. Set the injection pulse width TIsn to be equal to or greater than the minimum injection pulse width TImin.
By the control function of the multi-stage injection control unit 206, multi-stage injection with an injection pulse width TIsn lower than the minimum injection pulse width TImin while maintaining the optimum target injection frequency Ntgm, that is, fuel measurement accuracy by the fuel injection valve 105 The decrease is suppressed.

Further, the multi-stage injection control unit 206 sets the target fuel pressure when the injection pulse width TIsn in each injection of the multi-stage injection does not exceed the minimum injection pulse width TImin even if the target fuel pressure FPtg is lowered to a predetermined lower limit value (limiter FPmin). By returning FPtg to the base fuel pressure and reducing the target injection count Ntg from the target injection count Ntgm (base injection count) obtained from the map according to the operating conditions at that time, the injection pulse width TIsn in each injection of multi-stage injection. Is set to the minimum injection pulse width TImin or more.
The control function of the multi-stage injection control unit 206 can prevent the target fuel pressure FPtg from being lowered excessively, and multi-stage injection with an injection pulse width TIsn lower than the minimum injection pulse width TImin, that is, fuel by the fuel injection valve 105. The decrease in measurement accuracy is suppressed.

The multi-stage injection division ratio control unit 207 receives information such as the target injection number Ntg, total fuel injection pulse width TI, minimum injection pulse width TImin, and combustion mode set by the multi-stage injection control unit 206, and the multi-stage injection division ratio map unit. From 204, the target division ratio SRtgm corresponding to the operating conditions and the target number of injections Ntg at that time is searched.
Then, the multi-stage injection division ratio control unit 207 determines whether or not multi-stage injection at the target division ratio SRtgm is possible from the total fuel injection pulse width TI, the minimum injection pulse width TImin, the target injection number Ntg, and the target division ratio SRtgm. To judge.

That is, when it is assumed that the multi-stage injection division ratio control unit 207 injects the total fuel injection pulse width TI by dividing it into the target injection count Ntg, and sets the injection pulse width TIsn of each injection according to the target division ratio SRtgm. In addition, if the injection pulse width TIsn of each injection is all equal to or more than the minimum injection pulse width TImin, it is determined that multi-stage injection by allocating the pulse width according to the target division ratio SRtgm is possible.
On the other hand, when it is assumed that the multi-stage injection division ratio control unit 207 injects the total fuel injection pulse width TI by dividing it into the target injection number Ntg, and sets the injection pulse width TIsn of each injection according to the target division ratio SRtgm. If any of the injection pulse width TIsn of each injection is less than the minimum injection pulse width TImin, it is determined that multi-stage injection by allocating the pulse width according to the target division ratio SRtgm is impossible.

When the multi-stage injection division ratio control unit 207 determines that multi-stage injection at the target division ratio SRtgm is possible, the target division ratio SRtgm searched from the map is set as it is to the final target division ratio SRtg and output.
Further, when the multi-stage injection division ratio control unit 207 determines that multi-stage injection at the target division ratio SRtgm is impossible, the division ratio SR of the injection times set to the injection pulse width TIsn smaller than the minimum injection pulse width TImin is increased. Then, the injection pulse width TIsn of the minimum injection pulse width TImin or more is corrected so as to be allocated, and the division ratio of the injection times set to the injection pulse width TIsn of the minimum injection pulse width TImin or more is set to the injection pulse width TIsn. Is reduced within the range not less than the minimum injection pulse width TImin.

That is, the multi-stage injection division ratio control unit 207 adjusts the allocation of the total fuel injection pulse width TI to each injection time so that the injection pulse widths at each injection time do not fall below the minimum injection pulse width TImin. ..
Then, the multi-stage injection division ratio control unit 207 outputs the target division ratio SRtgm corrected as described above as the final target division ratio SRtg.
When the multi-stage injection division ratio control unit 207 determines that multi-stage injection by allocating the pulse width according to the target division ratio SRtgm is impossible, the total fuel injection pulse width TI is set to each injection time of the multi-stage injection. It is possible to output the target division ratio SRtg to be evenly distributed.

The multi-stage injection timing control unit 208 receives information on the target injection number Ntg and the combustion mode, and searches the injection timing map unit 205 for the injection timing IT corresponding to the operating conditions and the target injection number Ntg at that time.
The fuel injection valve drive control unit 210 receives information on the target number of injections Ntg, the target division ratio SRtg, the total fuel injection pulse width TI, and the injection timing IT, and sets the injection pulse width TIsn of each injection of the multi-stage injection according to the command. It is determined, and the injection pulse signal of the injection pulse width TIsn is output to the fuel injection valve 105 at the timing corresponding to the command of the injection timing IT.

FIG. 3 shows a target without changing the target fuel pressure FPtg as a control for the ECU 109 to set the injection pulse width TIsn to the minimum injection pulse width TImin or more in the fast idle state of the internal combustion engine 101 in the cold state. It is a time chart which exemplifies the behavior such as the target injection number Ntg and the pulse ratio PR when performing the injection number control which reduces the injection number Ntg.

In the first idle, the idle rotation speed after the start is set higher than that after the warm-up in order to maintain the rotation of the internal combustion engine 101 after the cold start (during warm-up), and to secure the warm-up and running performance. It is an operating condition in which the target injection number Ntgm is set to a relatively large number of times, the total fuel injection pulse width TI is short, and the injection pulse width TIsn tends to be less than the minimum injection pulse width TImin.
The pulse ratio PR is a value calculated as RP = Timin × Ntg / TI based on the target injection number Ntg of multi-stage injection, the minimum injection pulse width TImin, and the total fuel injection pulse width TI.

Therefore, when the injection pulse width TIsn when the total fuel injection pulse width TI is evenly divided into the target number of injections Ntg matches the minimum injection pulse width TImin, the pulse ratio PR = 1.0, and the pulse ratio PR is the total fuel injection pulse. As the injection pulse width TIsn when the width TI is evenly divided into the target injection count Ntg becomes larger than the minimum injection pulse width TImin, the value becomes smaller than 1.0.
When the pulse ratio PR exceeds 1.0, it indicates that the injection pulse width TIsn when evenly allocated is less than the minimum injection pulse width TImin, and when the pulse ratio PR is 1.0 or less, it indicates that the injection pulse width when evenly allocated. It is shown that the TIsn becomes equal to or more than the minimum injection pulse width TImin, and multi-stage injection is possible at the target injection number Ntg.

In the cold first idle state, which is the operating condition of the internal combustion engine 101 in FIG. 3, in other words, in the warm-up state of the internal combustion engine 101, the target idle rotation speed is set higher than after warm-up, and the ignition timing is warmed up. By retarding the catalyst converter 112 more than after, the catalyst warm-up of the catalytic converter 112 may be promoted.
When the catalyst warm-up acceleration treatment is carried out, the intake air amount of the internal combustion engine 101 is large in the idle state, and the fuel pressure FP is set to a high fuel pressure of, for example, 20 MPa or more in order to reduce PN. Yes, in the example of FIG. 3, the target injection count Ntgm is set to 3 times.
Here, in the case of the internal combustion engine 101 in which the required air amount in the fast idle state is relatively small due to individual differences, the total fuel injection pulse width TI decreases as the engine rotation speed approaches the target idle rotation speed after starting, and the pulse The ratio PR gradually increases.

The determination value X shown in FIG. 3 is a threshold value of the pulse ratio PR for determining whether or not multi-stage injection at the target injection number Ntg is impossible, and is set to, for example, a determination value X = 1.0. The determination value X can be set to X <1.0 in consideration of variations in the valve opening characteristics of the fuel injection valve 105 and the like.
When the pulse ratio PR exceeds the determination value X at time t1, the ECU 109 determines that multi-stage injection at the target injection count Ntgm (map value) is impossible, and reduces the target injection count Ntg from 3 times to 2 times. ..

When the target number of injections Ntg is 3 to 2 times, the pulse ratio PR rapidly decreases. For example, under the conditions of TImin = 0.5ms, TI = 1.45ms, Ntg = 3 times, PR = 1.034, whereas under the conditions of TImin = 0.5ms, TI = 1.45ms, Ntg = 2 times, PR = 0.689. By reducing the target number of injections Ntg from 3 to 2 times, multi-stage injection (double injection, 2-split injection) can be performed with an injection pulse width of TIsn of the minimum injection pulse width TImin or more.
However, by reducing the target injection speed Ntg from the optimum map value (target injection speed Ntgm) of 3 to 2, the amount of fuel adhered to the cylinder wall surface, the homogeneity of the air-fuel mixture, etc. changed. Combustion may deteriorate, exhaust properties may deteriorate, including deterioration of PN, and the engine speed may decrease.

The determination value Y shown in FIG. 3 is the target injection count Ntg from the map value (target injection count Ntgm) when the total fuel injection pulse width TI starts to increase due to a change in the operating region or an auxiliary load. This is the threshold value of the pulse ratio PR for determining the timing for returning to the map value (target injection count Ntgm) from the reduced state.
This determination value Y (Y <X ≦ 1.0) is a target in consideration of the pulse ratio PR in which the target injection count Ntgm of the map value can be set and the fluctuation of the pulse ratio PR when the target injection count Ntg is reduced. The number of injections is set to a value that can suppress hunting of Ntg.

At time t2 in FIG. 3, the ECU 109 determines that the pulse ratio PR has fallen below the determination value Y, and changes the target injection count Ntg from 2 to 3 times, which is the map value (target injection count Ntgm), that is, at that time. Perform the process of returning to the optimum value under the operating conditions of.
When the target number of injections Ntg is returned to the original three times, the amount of fuel adhering to the cylinder wall surface, the homogeneity of the air-fuel mixture, and the like are improved, and the torque increases due to the improvement in combustion, so that the engine rotation speed increases.
Then, when the engine speed increases, the total fuel injection pulse width TI decreases, and when the total fuel injection pulse width TI decreases, the pulse ratio PR starts to increase again and exceeds the determination value X, and the ECU 109 sets the time t3. When it is determined that the pulse ratio PR exceeds the determination value X, the process of reducing the target injection number Ntg from the map value of 3 times to 2 times is performed again.

As described above, if the target number of injections Ntg is reduced from the optimum value, multi-stage injection can be performed with an injection pulse width TIsn of the minimum injection pulse width TImin or more, but deterioration of exhaust properties including deterioration of PN may occur. There is sex.
Therefore, the ECU 109 is configured to perform reduction control of the target fuel pressure FPtg as a control for performing multi-stage injection with an injection pulse width TIsn of the minimum injection pulse width TImin or more. In the following, the target fuel pressure FPtg is reduced. Explain that the control can suppress the deterioration of PN as compared with the case of reducing the target injection frequency Ntg.

FIG. 4 is a graph showing the change in PN with respect to the fuel pressure FP for each target injection count Ntg (Ntg = 1, 2, 3) of multi-stage injection. The horizontal axis represents the fuel pressure FP and the vertical axis represents the PN. ..
When the fuel pressure FP is increased, atomization of the fuel spray is promoted, so that PN is reduced in any of the first injection (Ntg = 1), the second injection (Ntg = 2), and the third injection (Ntg = 3). Although there is a tendency, when the fuel pressure is increased, the penetration force of the fuel spray becomes stronger and the reach becomes longer, so that the PN, which tends to decrease as the fuel pressure rises, starts to rise when the fuel pressure exceeds a certain level.

Here, even if the fuel pressure FP is the same, the larger the target number of injections Ntg for multi-stage injection, in other words, the shorter the injection pulse width TIsn per injection, the weaker the penetration force of the fuel spray and the shorter the reach. Therefore, the PN tends to decrease as the target number of injections Ntg increases.
Further, from the relationship between the promotion of vaporization by atomizing the fuel spray and the penetration force (reaching distance) of the spray, the fuel pressure region in which the PN reduction effect can be maximized differs depending on the target number of injections Ntg.

In consideration of such characteristics, the map values (FPtgm, Ntgm) of the target fuel pressure FPtg and the target injection frequency Ntg are set to the optimum values for each operating region.
For example, in the characteristics shown in FIG. 4, when the target fuel pressure FPtg = FP1 and the target injection count Ntg = 3 times are the operating conditions set as the optimum values (FPtgm, Ntgm), the injection is less than the minimum injection pulse width TImin. It is assumed that the target injection count Ntg is reduced from 3 to 2 under the condition that the pulse width TIsn is set.

In this case, the amount of increase in PN due to the reduction of the target injection count Ntg from 3 to 2 is ΔPN, but the fuel pressure FP is changed from FP1 to FP2 (FP2 <FP1) while maintaining 3 injections. The amount of increase in PN when lowered is the same ΔPN.
That is, if the fuel pressure FP can be adjusted between FP1 and less than FP2 and set to the injection pulse width TIsn of the minimum injection pulse width TImin or more while maintaining the target injection count Ntg of 3, the target injection count Ntg can be set to 3 times. It is possible to perform multi-stage injection with an injection pulse width of TIsn of the minimum injection pulse width of TImin or more while suppressing deterioration of PN, as compared with the case of reducing from 2 times.

Therefore, when the condition is such that the injection pulse width TIsn lower than the minimum injection pulse width TImin is set, the ECU 109 lowers the target fuel pressure FPtg while maintaining the target injection count Ntg to exceed the minimum injection pulse width TImin. The injection pulse width TIsn is set.
However, when it is necessary to set the fuel pressure lower than the fuel pressure FP2 shown in FIG. 4 in order to set the injection pulse width TIsn of the minimum injection pulse width TImin or more, the target injection count Ntg is reduced from 3 times to 2 times. It will be worse than ΔPN, which is the amount of increase in PN in the case.

Therefore, when the ECU 109 needs to reduce the fuel pressure FP to the fuel pressure FP2 in order to set the injection pulse width TIsn equal to or larger than the minimum injection pulse width TImin, the ECU 109 lowers the fuel pressure FP to reduce the injection pulse width TIsn to the minimum injection pulse width TImin. Instead of doing the above, the fuel pressure FP is returned to the optimum value FP1 (target fuel pressure FPtgm which is the map value), the target injection count Ntg is subtracted from the target injection count Ntgm (map value), and the injection pulse having the minimum injection pulse width TImin or more Allows the width TIsn to be set.
Further, since the ECU 109 performs multi-stage injection with an injection pulse width TIsn equal to or larger than the minimum injection pulse width TImin, when the fuel pressure FP is lowered while maintaining the target injection count Ntg at the target injection count Ntgm which is a map value, If the PN change with respect to the required fuel pressure fluctuation near the required fuel pressure FP is sudden, the fuel pressure FP is set to the optimum value FP1 (target fuel pressure FPtgm) instead of lowering the target fuel pressure FPtg from the map value target fuel pressure FPtgm. Return and subtract the target injection count Ntg from the target injection count Ntgm to set the injection pulse width TIsn equal to or greater than the minimum injection pulse width TImin.

This is in the region where the PN changes significantly due to the fuel pressure fluctuation (for example, the fuel pressure FP2 in the three injections in FIG. 4) in order to set the injection pulse width TIsn of the minimum injection pulse width TImin or more in consideration of the fuel pressure controllability. Rather than controlling the fuel pressure, the target injection count Ntg is reduced from the map value of the target injection count Ntgm, and the fuel pressure FP is in a region where the PN change due to the fuel pressure fluctuation is gradual (for example, the fuel pressure FP1 in the two injections in FIG. 4). This is because it is desirable to control the exhaust performance.
Therefore, the ECU 109 stores the limiter FPmin (lower limit target fuel pressure), which is the lower limit of the target fuel pressure FPtg set in consideration of the PN deterioration allowance and the PN change characteristic, and is required to reduce the fuel pressure below the limiter FPmin. Occasionally, the fuel pressure lowering process for performing multi-stage injection with an injection pulse width TIsn of the minimum injection pulse width TImin or more is canceled, the target fuel pressure FPtg is returned to the optimum value (target fuel pressure FPtgm which is a map value), and the target injection count is performed. Ntg is subtracted from the target injection count Ntgm, which is the map value.

FIG. 5 is a diagram for explaining a fuel pressure lowering process for performing multi-stage injection with an injection pulse width TIsn of the minimum injection pulse width TImin or more, and is a cold first idle state of the internal combustion engine 101 (idle operation during warm-up). ) Shows an example of behavior such as target fuel pressure FPtg.
The pulse ratio PR, the determination value X, and the determination value Y shown in FIG. 5 are the same as those described in FIG. 3, and detailed description thereof will be omitted.

The determination value A (first determination value) is a threshold value of the pulse ratio PR for determining the timing for starting the control for lowering the target fuel pressure FPtg, and is a determination for determining whether or not to reduce the target injection count Ntg. It is a value lower than the value X (second judgment value) (judgment value A <judgment value X ≦ 1.0).
This considers the response delay until the actual fuel pressure FP changes due to the fuel pressure control, starts the process of lowering the fuel pressure FP before the pulse ratio PR reaches the determination value X, and during the transient response of the fuel pressure FP decrease. This is to prevent injection with an injection pulse width of TIsn smaller than the minimum injection pulse width of TImin.

Further, the determination value B is a threshold value of the pulse ratio PR for determining the timing for starting the control for increasing the target fuel pressure FPtg so as to return to the map value, the target fuel pressure FPtgm (base fuel pressure), and is the same as the determination value A. In addition, a value higher than the judgment value Y (third judgment value) is set in consideration of the response delay of the fuel pressure FPn (judgment value Y <judgment value B <judgment value A <judgment value X ≦ 1.0).

The time t1 in FIG. 5 is the start timing of the internal combustion engine 101, and the target fuel pressure FPtg is held at the target fuel pressure FPtgm which is a map value from the time t1 to the time t2 when the pulse ratio PR reaches the determination value A. The target injection count Ntg is held at the map value of 3 times.
The period from time t2 to time t3 in FIG. 5 is a period in which the ECU 109 reduces and changes the fuel pressure FP because the pulse ratio PR exceeds the determination value A.

When the pulse ratio PR exceeds the determination value A, the ECU 109 lowers the target fuel pressure FPtg by a predetermined pressure at regular intervals with the target fuel pressure FPtgm (base fuel pressure) as the map value as the initial value, and gradually lowers the fuel pressure FP. Let me. The ECU 109 can variably set the amount of decrease (decrease rate) of the target fuel pressure FPtg according to the deviation between the pulse ratio PR and the determination value A.
Further, a limiter FPmin is provided for the process of lowering the target fuel pressure FPtg, and the ECU 109 sets the target fuel pressure FPtg until the pulse ratio PR falls below the determination value A or until the target fuel pressure FPtg reaches the limiter FPmin. Gradually decrease.

The limiter FPmin is set between the fuel pressures FP1 and FP2 in FIG. 4 (FP2 <FPmin <FP1). Further, the ECU 109 can calculate the limiter FPmin by a function of the target fuel pressure FPtgm (base fuel pressure).
When the target fuel pressure FPtg (actual fuel pressure FP) is lowered, the injection pulse width for injecting the same amount of fuel increases, so that the pulse ratio PR decreases, and the pulse ratio PR becomes the judgment value A at time t3. The process of lowering the target fuel pressure FPtg is stopped.

The period from time t3 to time t4 in FIG. 5 is a period in which the pulse ratio PR is a value between the judgment value A and the judgment value B, and the target fuel pressure FPtg is the target when the pulse ratio PR reaches the judgment value A. It is held at the fuel pressure FPtg, and the target injection count Ntg is held at the map value of 3 times.
During the period from time t4 to time t5 in FIG. 5, the pulse ratio PR drops to the determination value B, and the ECU 109 executes a process of returning the target fuel pressure FPtg to the map value target fuel pressure FPtgm (base fuel pressure). Is.

When the pulse ratio PR reaches the determination value B, the ECU 109 increases the target fuel pressure FPtg toward the map value target fuel pressure FPtgm (base fuel pressure) by a predetermined pressure at regular intervals, and the target fuel pressure FPtg becomes the target fuel pressure FPtgm. At the time of returning (time t5 in FIG. 5), the gradual increase processing of the target fuel pressure FPtg is stopped.
The ECU 109 can variably set the amount of increase (increasing speed) of the target fuel pressure FPtg according to the deviation between the pulse ratio PR and the determination value B.

FIG. 6 shows a pulse ratio PR exceeding the determination value X even if the ECU 109 lowers the target fuel pressure FPtg to the limiter FPmin in the cold first idle state (during warm-up) of the internal combustion engine 101, and the ECU 109 maps the target injection count Ntg. It shows an example of behavior such as pulse ratio PR, target fuel pressure FPtg, and target injection count Ntg in a situation where the processing of reducing the value from 3 times to 2 times is performed.
The pulse ratio PR, the determination value X, the determination value A, the determination value B, and the determination value Y shown in FIG. 6 are the same as those in FIGS. 3 and 5, and detailed description thereof will be omitted.

Since the pulse ratio PR exceeded the determination value A at time t1 in FIG. 6, the ECU 109 started a process of gradually reducing the target fuel pressure FPtg from the map value target fuel pressure FPtgm (base fuel pressure), and at time t2, the target fuel pressure FPtg Stops the process of gradually reducing the target fuel pressure FPtg because the limiter FPtg is reached, and the target fuel pressure FPtg is held in the limiter FPmin.
Even after the target fuel pressure FPtg reached the limiter FPmin, the pulse ratio PR increased, and the pulse ratio PR exceeded the judgment value X at time t3. Therefore, the ECU 109 changed the target injection count Ntg from the map value of 3 times to 2 times. Along with the reduction, the process of returning the target fuel pressure FPtg from the limiter FPmin to the map value target fuel pressure FPtgm is started.

Since the target injection count Ntg was reduced from the map value of 3 times to 2 times, the pulse ratio PR started to decrease after time t3, and the pulse ratio PR fell below the judgment value Y at time t4, so that the ECU109 Determined that the condition (total fuel injection pulse width TI) was reached in which the injection pulse width TIsn of the minimum injection pulse width TImin or more could be set even if the target injection count Ntg was returned to the map value (target injection count Ntgm). The number of injections Ntg is returned from 2 to 3 which is the map value.
In this way, the ECU 109 basically controls the target fuel pressure FPtg so that the pulse ratio PR does not exceed the determination value X, but even if the target fuel pressure FPtg is lowered to the limiter FPmin, the pulse ratio PR remains the determination value X. If it exceeds, the target fuel pressure FPtg is returned to the map value, and then the target injection count Ntg is subtracted from the target injection count Ntgm, which is the map value, to eliminate the state in which the pulse ratio PR exceeds the determination value X.

The ECU 109 targets the target fuel pressure FPtg so that when the target fuel pressure FPtg is returned to the map value, the target fuel pressure FPtgm, it is possible to prevent the measurement accuracy of the fuel injection valve 105 from deteriorating due to sudden fluctuations in the fuel pressure FP. Gradually increase toward the fuel pressure FPtgm.
Further, the ECU 109 returns the target fuel pressure FPtg to the map value when the target injection count Ntg is reduced at the target fuel pressure FPtg in the region where the change in PN with respect to the fuel pressure FP fluctuation is small, as shown in FIG. This is to enable the PN to be stably controlled to a small state even if there is a variation in the control of the fuel pressure FP.
The ECU 109 controls the target fuel pressure FPtg based on the pulse ratio PR described with reference to FIGS. 5 and 6 described above, and controls the exhaust gas and the PN when the target injection frequency Ntg is reduced. It can be carried out only during the warm-up of the catalyst, that is, during the warm-up of the internal combustion engine 101.

FIG. 7 shows the behavior of the target injection count Ntg in the idle state after the catalyst warm-up is completed in the configuration in which the control of the target fuel pressure FPtg based on the pulse ratio PR described above is performed on the condition that the catalyst warm-up is in progress. This is just one example.
The pulse ratio PR, the determination value X, the determination value A, the determination value B, and the determination value Y shown in FIG. 7 are the same as those in FIGS. 3, 5, and 6, and detailed description thereof will be omitted.

When the ECU 109 determines that the catalyst warm-up is completed at time t1 in FIG. 7, that is, the catalyst temperature has reached the active temperature, the ECU 109 is controlled to retard the ignition timing for the catalyst warm-up by switching the combustion mode to normal ignition. The control shifts to the timing, and the target idle rotation speed is lowered from the high rotation speed for catalyst warm-up to the target idle rotation speed according to the water temperature TW. By such control, the internal combustion engine 101 shifts to the operating region where the required air amount is small.
Further, the target injection count Ntg is set to 3 to 2 times by switching the map in which the ECU 109 searches for the target injection count Ntgm in accordance with the catalyst warm-up completion determination (combustion mode switching determination) at time t1 in FIG. Is changed to.

At the subsequent time t2, the pulse ratio PR exceeds the determination value A, but the pulse ratio PR is set by the ECU 109 because it is after the completion of the catalyst warm-up, which is a condition in which the control of the target fuel pressure FPtg based on the pulse ratio PR is not performed. Even if the judgment value A is exceeded, the control for lowering the target fuel pressure FPtg is not performed.
When the friction of the internal combustion engine 101 is relatively small and the total fuel injection pulse width TI is calculated to be shorter than the standard, the pulse ratio PR further increases after the time t2.

Then, when the pulse ratio PR exceeds the determination value X at time t3, the ECU 109 reduces the target injection count Ntg from the map value of 2 to 1 and sets the injection pulse width TIsn of the minimum injection pulse width TImin or more. Yes, in other words, the pulse ratio PR is adjusted to the target number of injections Ntg that can be equal to or less than the judgment value X.
After the target number of injections Ntg has been reduced from 2 to 1, the total fuel injection pulse width TI has increased to a value that can reduce the target number of injections Ntg to 2 due to changes in the operating range and the operating conditions of accessories. By doing so, the pulse ratio PR becomes lower than the determination value Y at time t4.

However, when the target injection count Ntg is reduced based on the pulse ratio PR in the idle state after the catalyst warm-up is completed, the ECU 109 continues until the idle condition is not satisfied (until the internal combustion engine 101 is accelerated and exits the idle state). ), It is configured to maintain the target injection count Ntg reduced from the map value (target injection count Ntgm).
When the target number of injections Ntg decreases or increases (returns), the combustion state changes due to changes in the amount of fuel adhering to the cylinder wall surface and the homogeneity of the air-fuel mixture, so rotation speed fluctuations are likely to occur, especially. In the idle region where the engine speed is low, the rotation speed fluctuation due to the combustion change is likely to appear remarkably.

Therefore, the ECU 109 is in an operating state in which the influence of exhaust gas and PN by reducing the target injection count Ntg from the map value (target injection count Ntgm) is relatively small, after the catalyst warm-up determination or the water temperature, oil temperature, etc. Only in the idle region above the predetermined temperature, even if the pulse ratio PR falls below the judgment value Y, the target injection count Ntg reduced from the map value is maintained, and the rotation fluctuation occurs due to the return of the target injection count Ntg. Deter.
Then, when the idle state in which the target injection count Ntg is reduced from the map value is released (in other words, the ECU 109 shifts from the idle state in which the target injection count Ntg is reduced from the map value to the non-idle state). ), Increase the target injection count Ntg so as to return to the map value.

Although the embodiment of the present invention has been described in detail above, the parameters for controlling the fuel pressure and the number of injections of the multi-stage injection are the above-mentioned minimum injection pulse width TImin and the total fuel injection pulse width TI per combustion cycle. Needless to say, the same operation can be performed by using a new parameter capable of estimating the injection pulse width and the injection pulse width in addition to the ratio of.
The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

In the control function of the ECU 109 shown in FIG. 2, the ECU 109 searches the map for a standard target fuel pressure FPtgm according to the operating conditions of the internal combustion engine 101, a standard target injection count Ntgm according to the operating conditions of the internal combustion engine 101, and the like. However, the ECU 109 can calculate the target fuel pressure FPtgm (base fuel pressure) and the target injection count Ntgm (base injection count) based on a function with the operating conditions as variables.

Further, the ECU 109 is replaced with a configuration for determining whether or not multi-stage injection can be performed with an injection pulse width TIsn of the minimum injection pulse width TImin or more based on the pulse ratio PR (RP = TImin × Ntg / TI). , Total fuel injection pulse width TI, target number of injections Ntgm, target division ratio SRtgm The shortest injection pulse width of the injection pulse width TIsn specified based on SRtgm and the minimum injection pulse width TImin are compared and minimized. It is possible to determine whether or not the condition is such that multi-stage injection can be performed with an injection pulse width of TIsn of the injection pulse width of TImin or more.

Further, when the ECU 109 determines that the shortest injection pulse width of the injection pulse width TIsn in each injection according to the target division ratio SRtgm is less than the minimum injection pulse width TImin, the target division ratio SRtgm is within a predetermined range. If the injection pulse width TIsn at each injection time can be set to the minimum injection pulse width TImin or more by changing with, the target division ratio SRtgm may be changed and the target division ratio SRtgm may be changed within a predetermined range. When the injection pulse width TIsn at each injection time cannot be made equal to or more than the minimum injection pulse width TImin, the target fuel pressure FPtg can be lowered.
Further, when the ECU 109 determines that the shortest injection pulse width of the injection pulse width TIsn in each injection according to the target division ratio SRtgm is less than the minimum injection pulse width TImin, the ECU 109 does not change the target division ratio SRtgm. In addition, the injection pulse width TIsn at each injection time can be set to the minimum injection pulse width TImin or more by lowering the target fuel pressure FPtg.

Further, even after the internal combustion engine 101 is warmed up, the ECU 109 performs a process of lowering the target fuel pressure FPtg from the base fuel pressure in order to set all the injection pulse width TIsn at each injection time to the minimum injection pulse width TImin or more. be able to.
Further, the ECU 109 can change the level of the determination value A according to the increase speed of the pulse ratio PR, and the faster the increase speed of the pulse ratio PR is, the lower the level of the determination value A is to reduce the fuel pressure FP. By accelerating the start of the fuel pressure control, it is possible to prevent the injection pulse width TIsn from becoming less than the minimum injection pulse width TImin due to the response delay of the fuel pressure control, and to prevent excessive control for lowering the fuel pressure FP.

101 ... Internal combustion engine, 105 ... Fuel injection valve, 109 ... ECU (control device), 129 ... Fuel supply device, 201 ... Fuel injection pulse width calculation unit (total injection amount setting unit), 203 ... Multi-stage injection count map unit (number of times) Setting unit), 206 ... Multi-stage injection control unit

Claims (10)

In-cylinder injection type applied to an in- cylinder injection type internal combustion engine equipped with a fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine and a fuel supply device that changes the fuel pressure supplied to the fuel injection valve. It is a control device for an internal combustion engine .
A total injection amount setting unit that sets the total fuel injection amount to be injected from the fuel injection valve during one combustion cycle, and
A number setting unit for setting the number of injections in multi-stage injection in which the total fuel injection amount is injected in a plurality of times in one combustion cycle.
When the injection pulse width in the multi-stage injection when the fuel pressure is the base fuel pressure is less than the minimum injection pulse width, the fuel pressure is lowered to be lower than the base fuel pressure and the injection per injection is performed. A multi-stage injection control unit that performs multi-stage injection so that the pulse width exceeds the minimum injection pulse width.
Have a,
The multi-stage injection control unit
When the number of injections is Ntg, the minimum injection pulse width is TImin, and the total fuel injection pulse width corresponding to the total fuel injection amount is TI when the fuel pressure is the base fuel pressure, TImin × Ntg / TI If the condition is equal to or less than the first determination value (<1.0), multi-stage injection is performed at the base fuel pressure.
In-cylinder injection type internal combustion engine control device. In-cylinder injection type applied to an in- cylinder injection type internal combustion engine equipped with a fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine and a fuel supply device that changes the fuel pressure supplied to the fuel injection valve. It is a control device for an internal combustion engine .
A total injection amount setting unit that sets the total fuel injection amount to be injected from the fuel injection valve during one combustion cycle, and
A number setting unit for setting the number of injections in multi-stage injection in which the total fuel injection amount is injected in a plurality of times in one combustion cycle.
When the injection pulse width in the multi-stage injection when the fuel pressure is the base fuel pressure is less than the minimum injection pulse width, the fuel pressure is lowered to be lower than the base fuel pressure and the injection per injection is performed. A multi-stage injection control unit that performs multi-stage injection so that the pulse width exceeds the minimum injection pulse width.
Have a,
The multi-stage injection control unit
When the number of injections is Ntg, the minimum injection pulse width is TImin, and the total fuel injection pulse width corresponding to the total fuel injection amount is TI when the fuel pressure is the base fuel pressure, TImin × Ntg / TI When the condition is larger than the first determination value (<1.0), the fuel pressure is reduced from the base fuel pressure to a fuel pressure at which TI / Ntg becomes the minimum injection pulse width TImin or more.
In-cylinder injection type internal combustion engine control device. In-cylinder injection type applied to an in- cylinder injection type internal combustion engine equipped with a fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine and a fuel supply device that changes the fuel pressure supplied to the fuel injection valve. It is a control device for an internal combustion engine .
A total injection amount setting unit that sets the total fuel injection amount to be injected from the fuel injection valve during one combustion cycle, and a total injection amount setting unit.
A number setting unit for setting the number of injections in multi-stage injection in which the total fuel injection amount is injected in a plurality of times in one combustion cycle.
When the injection pulse width in the multi-stage injection when the fuel pressure is the base fuel pressure is less than the minimum injection pulse width, the fuel pressure is lowered to be lower than the base fuel pressure and the injection per injection is performed. A multi-stage injection control unit that performs multi-stage injection so that the pulse width exceeds the minimum injection pulse width.
Have a,
The multi-stage injection control unit
When the number of injections is Ntg, the minimum injection pulse width is TImin, and the total fuel injection pulse width corresponding to the total fuel injection amount is TI when the fuel pressure is the base fuel pressure, TImin × Ntg / TI If the condition is equal to or less than the first judgment value (<1.0), multi-stage injection is performed at the base fuel pressure.
When the condition is such that TImin × Ntg / TI becomes larger than the first determination value, the fuel pressure is reduced from the base fuel pressure to a fuel pressure at which TI / Ntg becomes the minimum injection pulse width TImin or more.
In-cylinder injection type internal combustion engine control device. The multi-stage injection control unit
When the TImin × Ntg / TI becomes smaller than the first determination value in a state where the fuel pressure is lower than the base fuel pressure, the fuel pressure is increased toward the base fuel pressure.
The control device for an in- cylinder injection type internal combustion engine according to claim 2 or 3. The multi-stage injection control unit
The fuel pressure is changed within a predetermined range.
The control device for an in-cylinder injection type internal combustion engine according to any one of claims 2 to 4 . In-cylinder injection type applied to an in- cylinder injection type internal combustion engine equipped with a fuel injection valve that directly injects fuel into the cylinder of the internal combustion engine and a fuel supply device that changes the fuel pressure supplied to the fuel injection valve. It is a control device for an internal combustion engine .
A total injection amount setting unit that sets the total fuel injection amount to be injected from the fuel injection valve during one combustion cycle, and
A number setting unit for setting the number of injections in multi-stage injection in which the total fuel injection amount is injected in a plurality of times in one combustion cycle.
When the injection pulse width in the multi-stage injection when the fuel pressure is the base fuel pressure is less than the minimum injection pulse width, the fuel pressure is lowered to be lower than the base fuel pressure and the injection per injection is performed. A multi-stage injection control unit that performs multi-stage injection so that the pulse width exceeds the minimum injection pulse width.
Have a,
The multi-stage injection control unit
Even if the fuel pressure is lowered to a predetermined fuel pressure lower than the base fuel pressure, when the injection pulse width per injection is less than the minimum injection pulse width, the number of injections is reduced to reduce the number of injections per injection. Fuel injection is performed so that the injection pulse width exceeds the minimum injection pulse width.
In-cylinder injection type internal combustion engine control device. The multi-stage injection control unit
When the TImin × Ntg / TI when the fuel pressure is the base fuel pressure exceeds the second determination value larger than the first determination value, the number of injections is reduced to increase the injection pulse width per injection. Multi-stage injection is performed so as to exceed the minimum injection pulse width.
The control device for an in-cylinder injection type internal combustion engine according to claim 2 or 3 . The multi-stage injection control unit
When the TImin × Ntg / TI in the state where the number of injections is reduced exceeds the third determination value which is smaller than the first determination value, the state in which the number of injections is reduced is maintained and the TImin × Ntg / TI becomes When the value falls below the third determination value, the number of injections is increased.
The control device for an in- cylinder injection type internal combustion engine according to claim 7. The multi-stage injection control unit
Increasing the fuel pressure when reducing the number of injections,
The control device for an in- cylinder injection type internal combustion engine according to claim 6 or 7. The multi-stage injection control unit
When the number of injections is reduced in the idle state after the internal combustion engine is warmed up, the number of injections is increased when the idle state is released.
The control device for an in- cylinder injection type internal combustion engine according to claim 6 or 7.