JP2006274904A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of preventing fluctuations in output torque with excellent responsiveness when switching an air-fuel ratio by changing an intake air volume and fuel injection quantity. <P>SOLUTION: The device is equipped with torque index calculation means 50, 52, 82, 84 for calculating torque indices in cylinders in which the pressure in a combustion chamber is detected on the basis of pressure in a combustion chamber, and with a switching control means 28 for controlling a fuel quantity injected in the combustion chamber through a fuel injection valve 8 so as to make torque indices calculated by the torque index calculation means 50, 52, 82, 84 equal to torque indices calculated by the torque index calculation means 50, 52, 82, 84 before switching while controlling intake air volume adjusting means 12, 20 so as to obtain an intake air volume in response to an operating state after switching when switching from one to the other of operating states by lean air-fuel ratio and rich air-fuel ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device suitable for an internal combustion engine that can switch an air-fuel ratio between lean and rich.

In recent years, it has been known that the air-fuel ratio of an internal combustion engine is switched in accordance with the operating state because of the requirement for exhaust gas regulations and fuel efficiency improvement.
For example, when a NOx storage catalyst is used as the exhaust purification device, the NOx storage catalyst stores NOx in the exhaust when the exhaust air-fuel ratio is lean, and releases the stored NOx when the exhaust air-fuel ratio is rich. Therefore, during normal operation, the average air-fuel ratio in the combustion chamber is made lean so that NOx in the exhaust gas is stored in the NOx storage catalyst, and the average air-fuel ratio in the combustion chamber is appropriately rich so that the storage capacity of the NOx storage catalyst is not saturated. The NOx occluded in the NOx occlusion catalyst is released and reduced.

  At this time, in order to switch the average air-fuel ratio in the combustion chamber from one of rich and lean to the other, the amount of air sucked into the combustion chamber is changed and the supply amount of fuel injected into the combustion chamber is changed. For example, when switching from a lean air-fuel ratio to a rich air-fuel ratio, the intake air amount is decreased and the fuel injection amount is increased. At this time, the torque reduction accompanying the decrease in the intake air amount and the increase in the fuel injection amount are increased. Therefore, the output torque is not balanced with the increase in torque caused by the change in output torque.

In order to eliminate such problems, the amount of additional fuel required to increase the output torque by the amount corresponding to the decrease in torque due to the decrease in the intake air amount is stored in advance in the map, and the intake air decreases when the air-fuel ratio is switched. There has been proposed one that prevents the occurrence of torque fluctuation at the time of air-fuel ratio switching by increasing the fuel injection amount by an additional fuel amount read from this map corresponding to the amount (Patent Document 1).
Japanese Patent Laid-Open No. 7-279718

However, in the control device of Patent Document 1, only the intake air amount and the fuel injection amount after switching are instructed when the air-fuel ratio is switched, and the operating state, the intake air amount and the fuel injection amount during the air-fuel ratio switching are indicated. Not monitoring.
However, since there is a response delay in the actual change of the intake air amount and the fuel injection amount with respect to the instruction to change the intake air amount and the fuel injection amount, the intake after the switching is simply performed as in the control device of Patent Document 1. If only the air amount and the fuel injection amount are instructed, there is a mismatch between the change in the intake air amount and the change in the fuel injection amount during the air-fuel ratio switching, which may lead to torque fluctuation and increase in combustion noise. .

For example, when the air-fuel ratio is switched from lean to rich, the response of the intake air amount is slower than the fuel injection amount. Therefore, in the control device of Patent Document 1, the fuel injection amount is not reduced so much. As a result, the output torque increases.
The present invention has been made in view of such problems, and the object of the present invention is to change the output torque in a responsive manner when switching the air-fuel ratio by changing the intake air amount and the fuel injection amount. An object of the present invention is to provide a control device for an internal combustion engine that can prevent the above-described problem.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention changes the amount of air sucked into a combustion chamber of a cylinder and the amount of fuel injected into the combustion chamber to thereby achieve a lean air condition. In an internal combustion engine control apparatus capable of switching between a first operating state based on a fuel ratio and a second operating state based on a rich air-fuel ratio, intake air amount adjusting means for adjusting the amount of air sucked into the combustion chamber; A fuel injection valve for injecting fuel into the combustion chamber, an in-cylinder pressure detecting means for detecting the pressure in the combustion chamber, and a pressure in the combustion chamber is detected based on the pressure in the combustion chamber detected by the in-cylinder pressure detecting means. A torque index calculating means for calculating a torque index in the cylinder, and when switching from one of the first operating state and the second operating state to the other, The intake air amount adjusting means is controlled so as to obtain a corresponding intake air amount, and the torque index calculated by the torque index calculating means is a torque index calculated by the torque index calculating means before the switching. And switching control means for controlling the amount of fuel injected from the fuel injection valve into the combustion chamber so as to be equal to each other (Claim 1).

Specifically, the torque index calculation unit integrates the pressure in the combustion chamber detected by the in-cylinder pressure detection unit over a predetermined stroke period in one cycle in the cylinder in which the pressure in the combustion chamber is detected. The torque index is calculated by (Claim 2).
Or a crank angle detecting means for detecting a crank angle, wherein the torque index calculating means obtains the volume of the operating combustion chamber based on the crank angle detected by the crank angle detecting means, and the in-cylinder pressure detecting means Based on the pressure in the combustion chamber detected by the above and the volume of the combustion chamber, the pressure in the combustion chamber represented by the volume of the combustion chamber as a variable is set to one cycle in the cylinder in which the pressure in the combustion chamber is detected. The torque index is calculated by integrating with the volume of the combustion chamber over a period of (3).

According to the control apparatus for an internal combustion engine according to claims 1 to 3, when the air-fuel ratio is switched, the intake air amount adjusting means is controlled so that the intake air amount becomes a value corresponding to the operating state after the switching. The fuel injection amount is controlled so that the torque index being switched is equal to the torque index before switching.
4. The control apparatus for an internal combustion engine according to claim 1, wherein the in-cylinder pressure detecting means detects pressures in combustion chambers of a plurality of cylinders, and the torque index calculating means is configured to detect the in-cylinder pressure. The torque index is calculated for each cylinder in which the pressure in the combustion chamber is detected by the means, and the switching control means determines that the torque index for each cylinder calculated by the torque index calculation means is The amount of fuel injected from the fuel injection valve into the combustion chamber is controlled so as to be equal to the torque index calculated by the torque index calculating means (claim 4).

According to the control apparatus for an internal combustion engine of the fourth aspect, the torque index is calculated for a plurality of cylinders, and the fuel injection amount is controlled so that the torque index during switching in each cylinder is equal to the torque index before switching. .
5. The control apparatus for an internal combustion engine according to claim 1, wherein the switching control means is configured to change the fuel when the rate of change of the pressure in the combustion chamber detected by the in-cylinder pressure detecting means exceeds a predetermined value. The fuel injection timing from the injection valve is delayed (Claim 5).

According to the control apparatus for an internal combustion engine of claim 5, when the pressure change in the combustion chamber is steep, the fuel injection timing from the fuel injection valve is delayed, and the pressure change in the combustion chamber is mitigated.
Further, in the control device for an internal combustion engine according to any one of claims 1 to 5, the switching control means is configured such that the combustion period estimated based on the pressure in the combustion chamber detected by the in-cylinder pressure detecting means becomes a predetermined period or longer. The pressure of the fuel supplied to the fuel injection valve is increased, and the fuel injection timing of the fuel injection valve is shortened (Claim 6).

  According to the control device for an internal combustion engine of claim 6, when the combustion period becomes equal to or longer than the predetermined period, the pressure of the fuel supplied to the fuel injection valve is increased and the fuel injection timing of the fuel injection valve is shortened. Thus, the necessary fuel amount is secured and the combustion period is shortened.

  According to the control apparatus for an internal combustion engine of claims 1 to 3, the intake air amount adjusting means is controlled so that the intake air amount having relatively poor responsiveness becomes a value corresponding to the operating state after switching, and compared. The fuel injection amount with good responsiveness is controlled so that the torque index during switching is equal to the torque index before switching, so that the occurrence of output torque fluctuation can be prevented with good response even during air-fuel ratio switching. it can.

According to the control apparatus for an internal combustion engine of claim 4, since the fuel injection amount is controlled so that the torque index during switching in each cylinder is equal to the torque index before switching, the output torque can be more accurately controlled. Variations can be prevented.
Furthermore, according to the control apparatus for an internal combustion engine of claim 5, an increase in combustion noise can be prevented by relaxing the pressure change in the combustion chamber.

  Further, according to the control device for an internal combustion engine of the sixth aspect, it is possible to suppress an increase in smoke and a deterioration in fuel consumption by shortening the combustion period.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which a control device according to an embodiment of the present invention is applied.
The engine 1 includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder, and pressurizes fuel light oil supplied from a fuel tank (not shown) by a high-pressure fuel injection pump 4. It is supplied to the common rail 2 through the pipe 6. The high-pressure light oil stored in the common rail 2 is supplied to the injectors 8 provided in the respective cylinders, and is injected from the injectors 8 into the respective cylinders.

Each cylinder of the engine 1 is provided with an in-cylinder pressure sensor (in-cylinder pressure detecting means) 10 for detecting the pressure in the combustion chamber.
The intake passage 6 is provided with an intake control valve 12 that operates as one of the intake air amount adjusting means. The intake air drawn from an air cleaner (not shown) is adjusted in flow rate by the intake control valve 12, and then the intake manifold 14.

The intake control valve 12 is opened and closed by an actuator such as a step motor.
On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe 18 via an exhaust manifold 16.
An EGR passage 22 between the exhaust manifold 16 and the intake manifold 14 is communicated with the exhaust manifold 16 and the intake manifold 14 via an EGR control valve 20 that operates as an intake air amount adjusting means together with the intake control valve 12. Is provided. The EGR control valve 20 is driven to open and close by an actuator such as a step motor.

The exhaust pipe 18 is connected to a casing 26 in which the NOx storage catalyst 24 is accommodated, and the exhaust discharged from the engine 1 is introduced into the NOx storage catalyst 24 in the casing 26 through the exhaust manifold 16 and the exhaust pipe 18. The
The NOx occlusion catalyst 24 itself is known and has a function of occluded NOx in the exhaust when the exhaust air-fuel ratio is lean, and releases and reduces the occluded NOx when the exhaust air-fuel ratio is rich. Yes.

The ECU 28 not only functions as the switching control means of the present invention but also performs overall control of the engine 1 and is composed of a CPU, a memory, a timer counter, etc., and calculates various control amounts, Various devices are controlled based on the control amount.
On the input side of the ECU 28, in-cylinder pressure sensor 14, an accelerator opening sensor 30 for detecting the depression amount of the accelerator pedal, and a crank angle sensor (for detecting the rotation phase of the crankshaft) to collect information necessary for various controls. Various sensors such as a crank angle detecting means) 32 are connected, and on the output side, the high pressure fuel injection pump 4 that is controlled based on the calculated control amount, the injector 8, the actuator of the intake control valve 12, the EGR control valve Various devices such as 20 actuators are connected.

  The ECU 28 performs calculation of the fuel supply amount to each cylinder of the engine 1 and control of fuel supply from the injector 4 based on the calculated fuel supply amount. The calculation of the fuel supply amount (main injection amount) necessary for the operation of the engine 1 is stored in advance based on the engine speed detected by the crank angle sensor 32 and the accelerator opening detected by the accelerator opening sensor. It is determined by reading from the map. The amount of fuel supplied to each cylinder is adjusted by the valve opening time of the injector 8, and each injector 8 is driven to open in a driving time corresponding to the determined fuel amount.

  The above is the configuration of the control device according to the embodiment of the present invention. However, since the NOx storage amount by the NOx storage catalyst 24 is limited, the NOx stored in the NOx storage catalyst 24 is appropriately released to release the NOx. It is necessary to regenerate the storage catalyst 24. Therefore, when regeneration of the NOx storage catalyst 24 becomes necessary, the exhaust air-fuel ratio is switched from lean to rich by switching the average air-fuel ratio in the combustion chamber, which has been lean until now, to rich, thereby the NOx storage catalyst. NOx is released from 24 and reduced.

In order to switch the average air-fuel ratio in the combustion chamber from lean to rich at the time of regeneration of the NOx storage catalyst 24, the intake control valve 12 is closed and the opening degree of the EGR control valve is increased to increase the EGR amount. In order to reduce the amount of air sucked in, the fuel injection amount is increased in order to suppress a drop in output torque accompanying a decrease in the amount of intake air.
Details of such air-fuel ratio switching control will be described below.

  FIG. 2 is a block diagram showing a flow of air-fuel ratio switching control performed by the ECU 28. When regeneration of the NOx storage catalyst 24 is required and an air-fuel ratio switching command is issued by an air-fuel ratio switching signal, the opening degree of the intake control valve 12 after the air-fuel ratio switching is stored in advance in block 36. From the map 34, the opening of the intake control valve 12 corresponding to the accelerator opening detected by the accelerator opening sensor 30 and the engine speed based on the crank angle detected by the crank angle sensor is read. This intake control valve opening map 34 shows the degree of opening of the intake control valve 12 required to make the air-fuel ratio rich when the NOx storage catalyst 24 is regenerated, by experiments or the like in advance using the accelerator opening and the engine speed as parameters. It has been sought and memorized.

  At the same time, in block 40, the accelerator opening detected by the accelerator opening sensor 30 from the EGR control valve opening map 38 in which the opening of the EGR control valve 20 after the air-fuel ratio switching is stored in advance. The opening degree of the EGR control valve 20 corresponding to the engine speed based on the crank angle detected by the crank angle sensor is read out. This EGR control valve opening map 38 indicates that the opening degree of the EGR control valve 20 required to make the air-fuel ratio rich when the NOx storage catalyst 24 is regenerated is previously determined by experiments or the like using the accelerator opening and the engine speed as parameters. It has been sought and memorized.

The intake control valve 12 is controlled by the block 42 and the EGR control valve is controlled by the block 44 so that the intake control valve opening and the EGR control valve opening set in this way are obtained. Note that the intake air amount and the EGR amount are changed by the intake control valve 12 and the EGR control valve 20 immediately in consideration of poor response.
On the other hand, in block 48, from the fuel injection amount map 46 in which the reference injection amount of the fuel after the air-fuel ratio switching is stored in advance, the accelerator opening detected by the accelerator opening sensor 30 and the crank angle sensor are detected. A reference injection amount corresponding to the engine speed based on the crank angle is read. In this fuel injection amount map 46, the reference value of the fuel injection amount necessary to compensate for the decrease in output torque caused by the decrease in the intake air amount by the control of the intake control valve 12 and the EGR control valve 20 is the accelerator opening degree. It is obtained and memorized in advance by experiments or the like using the engine speed as a parameter.

  When the fuel of the reference injection amount set in this way is supplied to the engine 1 as it is, the change of the intake air amount by the intake control valve 12 and the EGR control valve 20 is not very responsive, whereas the change of the fuel injection amount is Since the responsiveness is good, during the switching of the air-fuel ratio, the consistency between the intake air amount and the fuel injection amount is not achieved, and the output torque fluctuates. Therefore, by correcting the reference injection amount, occurrence of fluctuations in output torque during air-fuel ratio switching is prevented, and the details thereof will be described in detail below.

In block 50, before the air-fuel ratio switching command is issued, the pressure value in the combustion chamber detected by the in-cylinder pressure sensor 10 is expanded from the predetermined crank angle CA _{1 at the} initial stage of the compression stroke in the cylinder in which the pressure is detected. Accumulated over a predetermined period up to a predetermined crank angle CA ₂ at the end of the stroke, and calculated as a torque index. Such calculation of the torque index is updated every predetermined period only until the air-fuel ratio switching command is issued. The in-cylinder pressure sensor 10 is provided in each cylinder, and the calculation and update of the torque index is performed for each cylinder based on the detection value of the corresponding in-cylinder pressure sensor 10.

On the other hand, when the air-fuel ratio switching command is issued, similarly to the calculation of the torque index by the block 50, the block 52 performs the predetermined crank angle CA ₁ from the initial compression stroke to the predetermined crank angle CA ₂ at the end of the expansion stroke. The pressure values in the combustion chamber detected by the in-cylinder pressure sensor 10 are integrated over a period, and a torque index after starting the air-fuel ratio switching control is calculated. This torque index is also updated every predetermined period in the corresponding cylinder.

Therefore, these block 50 and block 52 correspond to the torque index calculation means in the present invention.
The torque index before and after the start of air-fuel ratio control calculated in this way represents the magnitude of torque generated in each cylinder before and during air-fuel ratio switching. Therefore, the greater the deviation between the torque index before air-fuel ratio switching and the torque index during air-fuel ratio switching, the greater the torque fluctuation that occurs during air-fuel ratio switching.

  Therefore, in block 54, based on the deviation of the torque index obtained by subtracting the torque index during the air-fuel ratio switching from the torque index before the air-fuel ratio switching, the PID correction amount corresponding to the proportional value, differential value and integral value of this deviation is calculated. To do. The PID correction amount calculated in this way is to correct the deviation of the torque index during the air-fuel ratio switching from the torque index before the air-fuel ratio switching. In block 56, the reference injection amount of fuel set in block 48 The fuel injection valve of the cylinder for which the current torque index is to be calculated is controlled so that the fuel of the injection amount obtained by adding the PID correction amount to is injected. Such fuel injection control is performed for each cylinder in each cycle after the start of air-fuel ratio switching control.

The movement of each part at this time is shown in FIG. In FIG. 3, from the upper stage, changes in the air-fuel ratio switching signal, the opening degree of the EGR control valve, the opening degree of the intake control valve, the intake air amount, the fuel injection amount, and the output torque are shown as time passes. .
When regeneration of the NOx storage catalyst 24 is necessary and the air-fuel ratio switching signal becomes rich from lean to rich, the EGR control valve 20 and the intake control valve 12 are controlled so as to have the openings set in the blocks 40 and 36, respectively. The opening gradually changes as the actuator is driven. At this time, the intake air amount is decreased by the increase of the EGR amount due to the opening of the EGR control valve, in addition to the decrease by the close operation of the intake control valve 12. Then, after the EGR control valve reaches the opening set by the block 40, the EGR amount does not increase, so the intake air amount decreases more gradually than before.

  On the other hand, the fuel injection amount is controlled to increase in accordance with the reference injection amount set in block 48, but the fuel injection amount changes when the reference injection amount of fuel is supplied without correction based on the torque index. And the change of the output torque at this time is shown with a dashed-dotted line in a figure. As shown in FIG. 3, when the fuel of the reference injection amount is supplied as it is, the fuel injection amount is more responsive than the intake air amount. Immediately increases to the reference injection amount. As a result, the output torque temporarily increases from before the start of the air-fuel ratio switching control, and protrudes as shown by a one-dot chain line in the figure.

However, in practice, as described above, the reference injection amount is corrected according to the deviation between the torque index before the start of the air-fuel ratio switching control and the torque index during the air-fuel ratio switching control. As shown by the solid line, the output torque gradually increases, and the output torque maintains the magnitude before the start of the air-fuel ratio switching control.
FIG. 4 shows the change in the in-cylinder pressure during a predetermined period from the predetermined crank angle CA _{1 at the} beginning of the compression stroke to the predetermined crank angle CA ₂ at the end of the expansion stroke at the timings ta, tb and tc shown in FIG. The torque index at the timing ta before the air-fuel ratio switching control is started corresponds to the area Sa.

When there is no correction of the reference injection amount according to the deviation between the torque index before the start of the air-fuel ratio switching control and the torque index during the air-fuel ratio switching control, the area corresponding to the torque index at the timing tb is due to the increase in the fuel injection amount. It becomes Sb ′ and increases from Sa, and the output torque protrudes as shown in FIG.
On the other hand, when the reference injection amount is corrected, the area corresponding to the torque index at the timing tb does not increase and the area Sb is equal to Sa, so that the output torque does not protrude.

At timing tc, the change of the intake air amount is completed, and the area Sc corresponding to the torque index becomes equal to Sa without correction of the reference injection amount, so that the correction to the reference injection amount is not performed.
Thus, by correcting the fuel injection amount based on the deviation between the torque index before the air-fuel ratio switching and the torque index during the air-fuel ratio switching, the torque index during the air-fuel ratio switching becomes equal to the torque index before the air-fuel ratio switching. Thus, the occurrence of torque fluctuation during air-fuel ratio switching is satisfactorily suppressed.

In the air-fuel ratio switching control described above, when the air-fuel ratio is switched, both the intake control valve 12 and the EGR control valve 20 are controlled to change the intake air amount. The intake air amount may be changed by controlling only one of them according to the above.
In parallel with the air-fuel ratio switching control as described above, the combustion noise prevention control is performed by the ECU 28 in order to prevent the combustion noise generated when the air-fuel ratio is switched. FIG. 5 is a block diagram showing the flow of combustion noise prevention control.

  In block 58, the engine based on the accelerator opening detected by the accelerator opening sensor 30 and the crank angle detected by the crank angle sensor from a fuel injection timing map (not shown) in which the target fuel injection timing is stored in advance. A target injection timing corresponding to the rotational speed is read out. In this fuel injection timing map, the target value of the optimal fuel injection timing that does not cause combustion noise is obtained and stored in advance through experiments or the like using the accelerator opening and the engine speed as parameters.

In block 60, an upper limit value of the in-cylinder pressure change rate at which combustion noise does not occur is set as the in-cylinder pressure reference change rate.
On the other hand, in block 62, the actual change rate of the pressure in the combustion chamber detected by the in-cylinder pressure sensor 10 is calculated. Based on the deviation between the in-cylinder pressure reference change rate set in block 60 and the actual pressure change rate calculated in block 62, the PID correction amount corresponding to the proportional value, differential value, and integral value of this deviation is calculated. The operation is performed in block 64. The PID correction amount calculated in this way is used to correct the target fuel injection timing in the delay direction when the in-cylinder pressure change rate during air-fuel ratio switching exceeds the in-cylinder pressure reference change rate and combustion noise may occur. In block 66, the cylinder for which the in-cylinder pressure change rate is to be calculated is injected so that the fuel is injected at the injection timing obtained by adding the PID correction amount to the target fuel injection timing set in block 58. The fuel injection valve 8 is controlled.

In this way, by correcting the fuel injection timing according to the deviation between the cylinder pressure reference change rate and the actual pressure change rate in the combustion chamber, the generation of combustion noise during air-fuel ratio switching control can be satisfactorily prevented.
In the control shown in FIG. 5, the fuel injection timing is advanced when the actual pressure change rate in the combustion chamber is less than the in-cylinder pressure reference change rate. Alternatively, it may be performed only when delaying.

Further, if the combustion period is too long during the air-fuel ratio switching control, smoke may be generated. Therefore, the smoke prevention control is performed by the ECU 28 in parallel with the air-fuel ratio switching control. FIG. 6 is a block diagram showing the flow of smoke prevention control.
In block 68, the engine speed based on the accelerator opening detected by the accelerator opening sensor 30 and the crank angle detected by the crank angle sensor from a fuel pressure map (not shown) in which the target fuel pressure is stored in advance. Are read out. In this fuel pressure map, the target value of the fuel pressure that is an optimal combustion period without causing smoke is obtained and stored in advance by experiments or the like using the accelerator opening and the engine speed as parameters. .

In block 70, the in-cylinder pressure at a predetermined crank angle corresponding to the combustion end timing at which smoke does not occur is set as the reference in-cylinder pressure.
On the other hand, in the block 72, the pressure in the combustion chamber detected at the predetermined crank angle is inputted by the in-cylinder pressure sensor 10. Then, based on the deviation between the reference in-cylinder pressure set in block 70 and the actual combustion chamber pressure inputted in block 72, the PID correction amount corresponding to the proportional value, differential value and integral value of this deviation is shown in block 74. Calculate with. The PID correction amount calculated in this way corrects the fuel pressure in the upward direction when the in-cylinder pressure at the predetermined crank angle during air-fuel ratio switching exceeds the reference in-cylinder pressure and there is a possibility that smoke may be generated due to prolonged combustion. In block 76, the high-pressure fuel injection pump 4 is controlled so that the fuel pressure is obtained by adding the PID correction amount to the target fuel pressure set in block 68. Further, since the fuel injection amount from the fuel injection valve 8 also changes due to the increase in fuel pressure, the required fuel injection amount after the fuel pressure change is determined in block 78 based on the target fuel pressure corrected with the PID correction amount. The fuel injection period is corrected so as to be obtained, and the fuel injection valve is controlled so that the fuel is injected in the corrected fuel injection period.

In this way, during the air-fuel ratio switching control, the fuel injection period is corrected by increasing the fuel pressure in accordance with the deviation between the reference cylinder pressure at the predetermined crank angle corresponding to the combustion end timing and the actual pressure in the combustion chamber. The occurrence of smoke in is prevented satisfactorily.
In the control shown in FIG. 6, the fuel pressure is decreased when the actual pressure in the combustion chamber at the predetermined crank angle is less than the reference in-cylinder pressure. However, the correction of the fuel pressure is increased more than the target fuel pressure. You may make it carry out only when doing.

Although the description of the control device for an internal combustion engine according to one embodiment of the present invention has been completed above, the present invention is not limited to the above-described embodiment.
For example, the torque index is calculated by integrating the pressure in the combustion chamber detected by the in-cylinder pressure sensor 10, but the calculation method of the torque index is not limited to this, and a modified example will be described below. .

FIG. 7 is a PV diagram showing a change in in-cylinder pressure with the in-cylinder volume of one cylinder in the engine 1 as a variable. In FIG. 7, the shaded area corresponds to the magnitude of torque generated in the cylinder, and the area of this area can be used as a torque index.
That is, as indicated by an arrow in the figure, when the in-cylinder volume decreases from V ₁ through V ₂ to V ₃ , the change until the in-cylinder pressure increases from P ₁ to P ₂ (from point a) (change to point b) integrated with the in-cylinder volume and when the in-cylinder volume increases from V ₃ to V ₁ through V ₂ until the in-cylinder pressure decreases from P ₃ to P ₁ By adding the value obtained by integrating (change from point c to point e through point d) with the in-cylinder volume, the area of the hatched portion is calculated.

  FIG. 8 is a block diagram showing the flow of control when applied to the air-fuel ratio switching control using the torque index based on the PV diagram based on such an idea. Since this modification is different from the above-described embodiment only in the fuel injection amount correction portion, the fuel injection amount correction portion in the block diagram of FIG. In the figure, the same reference numerals are used for parts common to the block diagram of FIG.

Note that the control of the intake control valve 12 and the EGR control valve 20 at the time of air-fuel ratio switching is the same as in the above-described embodiment, and thus the description thereof is omitted.
In FIG. 8, in the block 48, as in the above-described embodiment, the accelerator opening detected by the accelerator opening sensor 30 from the fuel injection amount map 46 in which the reference injection amount of the fuel after the air-fuel ratio switching is stored in advance is stored. The reference injection amount corresponding to the degree and the engine speed based on the crank angle detected by the crank angle sensor is read out.

  In block 82, the volume of the combustion chamber is determined based on the pressure in the combustion chamber detected by the cylinder pressure sensor 10 and the crank angle detected by the crank angle sensor 32 in a state before the air-fuel ratio switching command is issued. 7 is obtained from the in-cylinder volume and the in-cylinder pressure that changes corresponding to the change in the in-cylinder volume, and the above integration is performed to obtain the PV diagram in FIG. Is calculated as a torque index before air-fuel ratio switching control.

Thus, the calculation of the torque index performed by the block 82 is performed only until the air-fuel ratio switching command is issued, and the torque index is updated every cycle. The in-cylinder pressure sensor 10 is provided in each cylinder, and the calculation and update of the torque index is performed for each cylinder based on the detection value of the corresponding in-cylinder pressure sensor 10.
On the other hand, when the air-fuel ratio switching command is issued, the block 84 calculates the torque index after the start of the air-fuel ratio switching control in the same manner as the calculation of the torque index by the block 82. This torque index is also updated for each cycle in the corresponding cylinder.

Therefore, these block 82 and block 84 also correspond to the torque index calculating means in the present invention.
Based on the deviation between the torque index before the air-fuel ratio switching control and the torque index after the start of the air-fuel ratio switching control thus determined, the proportional value, differential value and integral value of this deviation are the same as in the above-described embodiment. The PID correction amount corresponding to is calculated. The PID correction amount calculated in this way is to correct the deviation of the torque index during the air-fuel ratio switching from the torque index before the air-fuel ratio switching. In block 56, the reference injection amount of fuel set in block 48 The fuel injection valve of the cylinder that is the target of the current torque index calculation is controlled so as to inject the fuel of the injection amount obtained by adding the PID correction amount to. Such fuel injection control is performed for each cylinder in each cycle after the start of air-fuel ratio switching control.

In this way, the fuel injection amount is corrected so that the torque index during the air-fuel ratio switching becomes equal to the torque index before the air-fuel ratio switching, so that the output torque during the air-fuel ratio switching is the same as in the above-described embodiment. Fluctuations are well suppressed.
In the above-described embodiment and the above-described modification, the in-cylinder pressure sensor 10 is provided in all the cylinders, and the air-fuel ratio switching control based on the torque index is individually performed, but the in-cylinder pressure is only applied to some of the plurality of cylinders. For a cylinder that is provided with a sensor and does not have an in-cylinder pressure sensor, air-fuel ratio switching control for the cylinder having the in-cylinder pressure sensor may be shared as appropriate. Alternatively, the in-cylinder pressure sensor 10 may be provided in only one of the cylinders, and the air-fuel ratio switching control may be performed in common for all the cylinders based on the detection result of the in-cylinder pressure sensor 10.

The same applies to the combustion noise prevention control and smoke prevention control, and it is not always necessary to provide in-cylinder pressure sensors for all cylinders.
In the above-described embodiment and the above-described modification, air-fuel ratio switching control when the air-fuel ratio is switched from lean to rich in order to regenerate the NOx storage catalyst 24, and combustion noise prevention control and smoke prevention control associated therewith are shown. However, the present invention is not limited to this, and can be applied not only to return from rich to lean, but also to satisfactorily prevent fluctuations in output torque when switching various air-fuel ratios. Further, it is possible to satisfactorily prevent generation of combustion noise and smoke.

  Finally, the type of engine is not limited to a diesel engine, but can also be applied to a gasoline engine.

1 is an overall configuration diagram of a control device for an internal combustion engine according to an embodiment of the present invention. It is a block diagram which shows the flow of the air fuel ratio switching control by the control apparatus of FIG. 2 is a time chart showing changes in control amount and output torque during air-fuel ratio switching control by the control device of FIG. 1. It is a figure which shows the change of the cylinder pressure in the case of the air fuel ratio switching control by the control apparatus of FIG. It is a block diagram which shows the flow of the combustion noise prevention control by the control apparatus of FIG. It is a block diagram which shows the flow of the smoke noise prevention control by the control apparatus of FIG. It is a PV diagram of an engine. It is a block diagram which shows the modification of the air fuel ratio switching control by the control apparatus of FIG.

Explanation of symbols

1 Engine 8 Fuel Injection Valve 10 Cylinder Pressure Sensor (Cylinder Pressure Detection Means)
12 Intake control valve (intake air amount adjusting means)
20 EGR control valve (intake air amount adjusting means)
28 ECU (switching control means)
32 Crank angle sensor (Crank angle detection means)
50, 52, 82, 84 Torque index calculation means

Claims (6)

By changing the amount of air sucked into the combustion chamber of the cylinder and the amount of fuel injected into the combustion chamber, the first operating state with a lean air-fuel ratio and the second operating state with a rich air-fuel ratio In an internal combustion engine control device capable of switching between
Intake air amount adjusting means for adjusting the amount of air sucked into the combustion chamber;
A fuel injection valve for injecting fuel into the combustion chamber;
In-cylinder pressure detecting means for detecting the pressure in the combustion chamber;
Torque index calculation means for calculating a torque index in the cylinder in which the pressure in the combustion chamber is detected based on the pressure in the combustion chamber detected by the in-cylinder pressure detection means;
When switching from one of the first operation state and the second operation state to the other, the intake air amount adjusting means is controlled so that the intake air amount corresponds to the operation state after the switching. At the same time, the torque index calculated by the torque index calculation means is injected from the fuel injection valve into the combustion chamber so as to be equal to the torque index calculated by the torque index calculation means before the switching. A control device for an internal combustion engine, comprising: switching control means for controlling the amount of fuel.   The torque index calculation means integrates the pressure in the combustion chamber detected by the in-cylinder pressure detection means over a predetermined stroke period in one cycle in a cylinder in which the pressure in the combustion chamber is detected. 2. The control device for an internal combustion engine according to claim 1, wherein the control device calculates the internal combustion engine. It further comprises crank angle detection means for detecting the crank angle,
The torque index calculation means obtains the volume of the combustion chamber in operation based on the crank angle detected by the crank angle detection means, and the pressure in the combustion chamber detected by the in-cylinder pressure detection means and the volume of the combustion chamber. And integrating the pressure in the combustion chamber represented by the volume of the combustion chamber as a variable with the volume of the combustion chamber over a period of one cycle in the cylinder in which the pressure in the combustion chamber is detected. The control device for an internal combustion engine according to claim 1, wherein an index is calculated. The in-cylinder pressure detecting means detects pressures in combustion chambers of a plurality of cylinders,
The torque index calculation means calculates the torque index for each cylinder in which the pressure in the combustion chamber is detected by the in-cylinder pressure detection means,
The switching control means controls the fuel injection valve so that the torque index for each cylinder calculated by the torque index calculating means is equal to the torque index calculated by the torque index calculating means before the switching. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein an amount of fuel injected into the combustion chamber is controlled.   The switching control means delays the fuel injection timing from the fuel injection valve when the rate of change of the pressure in the combustion chamber detected by the in-cylinder pressure detecting means becomes a predetermined value or more. The control device for an internal combustion engine according to any one of claims 1 to 4.   The switching control means increases the pressure of the fuel supplied to the fuel injection valve when a combustion period estimated based on the pressure in the combustion chamber detected by the in-cylinder pressure detecting means becomes a predetermined period or longer. The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the fuel injection timing of the fuel injection valve is shortened.

Images