JP2008280887A - Device and method for internal combustion engine control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately control combustion of an internal combustion engine according to combustion states by detecting a change in flame propagation speed indicating the combustion state based on the generation pattern of ion current. <P>SOLUTION: Appropriateness of a first peak generation period PT1 of the ion current and a second peak generation period PT2 thereof is determined (S102, S105). If it is considered reasonable, a crank angle difference or a time difference between the first peak generation period PT1 and the second peak generation period PT2 is detected (S104), and ignition timing, the amount of fuel injected and fuel injection timing are corrected (S108) so that the detected crank angle difference or the detected time difference becomes substantially equal (S107) to a previously set crank angle difference or a previously set time difference (S106). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device and a control method for an internal combustion engine that correct an ignition timing, a fuel injection timing, and a fuel injection amount of the internal combustion engine based on a change in an ionic current flowing in a combustion flame of the internal combustion engine.

Various internal electronic devices and control devices for these electronic devices have been introduced into conventional internal combustion engines in order to improve economic efficiency and reduce the influence on the global environment.
In particular, combustion control of an internal combustion engine is highly important in terms of improving and stabilizing output and purifying exhaust gas, and fuel injection control and ignition timing control are strictly performed.
In a normal internal combustion engine mounted on a vehicle, the combustion characteristics are not directly measured from the viewpoint of cost, reliability, etc., but based on a preset control value based on a combination of the shaft rotational speed of the internal combustion engine and the intake air amount. Thus, fuel injection control and ignition timing control are performed.

For various controls based on preset control values, correction control is performed to keep the air-fuel ratio (that is, the mixing ratio of fuel and air) obtained from the exhaust gas component at an appropriate value. In an internal combustion engine having a plurality of cylinders, individual correction control corresponding to the combustion state of each cylinder is hardly performed.
As a method for detecting the combustion state of each cylinder in detail in order to perform correction control for each cylinder, it is known to measure the pressure change in the combustion chamber, but to realize this, expensive detection means are required. It is.

In Japanese Patent Laid-Open No. 9-324690 (Patent Document 1), in which the combustion state is indirectly detected by a cheaper means and correction control is performed, an intermediate product of combustion generated in the combustion flame of each cylinder is disclosed. A correction control method based on the peak value of the ion current detected by the action of various ions or the time when the peak of the ion current occurs is shown.
Ion currents are weak, such as microamperes, mainly caused by intermediate products with radicals (radicals) in the flame when hydrocarbon fuels such as gasoline burn. It is the flow of electricity.
Specifically, when a combustion flame is present in a space to which a potential is applied in some electrical circuit, radicals generated in the flame by the action of the potential are collected by the negative electrode, and the flow of electrons in the electrical circuit (i.e., Current) occurs.

FIG. 1 shows an example of a change pattern of ion current detected in a combustion process (combustion cycle) in an internal combustion engine, where the horizontal axis represents the crank angle and the vertical axis represents the magnitude of the ion current.
As shown in the figure, the ionic current is detected immediately after the start of combustion, and "peak P0 due to discharge at the time of ignition" which is detected by ionizing part of the fuel or air due to spark of the spark plug. It has a “first peak P1 due to combustion” and a “second peak P2” detected when the combustion flame propagates in the cylinder and the combustion is most active.

Non-Patent Document 1, “The Society of Automotive Engineers of Japan Academic Lecture Preprint 962-1996-5”, FIG. 1 shows that the first peak occurs when the pressure in the combustion chamber (CylinderPressure) starts to rise rapidly, and the second peak occurs when the pressure in the combustion chamber becomes almost maximum.
That is, it is shown that the detection pattern of the ionic current in the combustion process (that is, the change pattern) includes a part of the characteristic of the pressure change in the combustion chamber.
JP-A-9-324690 Automobile Engineers Association Academic Lecture Preprint 962-1996-5 Document No. 9633144

However, since the ionic current is a weak current generated due to radicals generated inside the combustion flame, the contamination of the electrodes that collect radicals and the influence of the electrical circuit that detects the ionic current (especially the resistance of the electrical circuit) It has been confirmed that the value of the ion current changes due to the influence of the element, such as temperature drift, that does not depend on combustion characteristics.
In the conventional control device for an internal combustion engine disclosed in Japanese Patent Laid-Open No. 9-324690, correction control of ignition timing and fuel injection amount is performed based on the peak value of ion current. There is a problem that the correction control is executed even when the combustion characteristic does not actually change because the value changes due to the influence not depending on the characteristic).

In addition, a technique for performing correction control of the ignition timing and the fuel injection amount based on the peak generation timing of the ion current is shown, but the first peak is obtained only by comparing the peak generation timing of the ion current with the reference peak position. It is difficult to distinguish between “change in the combustion start time” indicated by the generation time and “change in the time when the combustion flame is propagated into the cylinder and combustion is most active” indicated by the second peak generation time. Since only one feature of the pressure change in the combustion chamber is detected, the amount of information related to the pressure change is small and accurate correction control cannot be performed.
The “reference peak position” is an average value of peak occurrence times for a predetermined number of cycles.

  The present invention solves the above-described problems, can accurately determine the combustion state of the internal combustion engine, and optimally corrects the ignition timing, the fuel injection timing, and the fuel injection amount according to the determined combustion state. An object of the present invention is to provide a control device and a control method for an internal combustion engine.

  An internal combustion engine control apparatus according to the present invention comprises: an ion current detection means for continuously detecting the value of an ion current flowing in a combustion chamber by the action of ions generated in the combustion process of the internal combustion engine; and the detection by the ion current detection means. The first peak generation time PT1 at which the ion current value peaks first after the start of combustion based on the value of the ion current, and the second at which the ion current value peaks after the first peak generation time PT1. An ion current peak generation timing detection means for detecting a peak generation timing PT2, and the first peak generation timing PT1 and / or the second peak generation timing PT2 detected by the ion current peak generation timing detection means are determined by the internal combustion engine. A peak generation time determination means for determining whether or not it depends on combustion characteristics; and the ion current peak generation time detection. Based on the first peak generation time PT1 and the second peak generation time PT2 detected by the means, the combustion state determination means for determining the combustion state of the internal combustion engine, the determination result of the peak generation time determination means and the combustion And a correction unit that corrects at least one set value of a preset ignition timing, fuel injection timing, and fuel injection amount in accordance with a determination result of the state determination unit.

The control method for an internal combustion engine according to the present invention includes an ion current detection step for continuously detecting the value of an ion current flowing in the combustion chamber by the action of ions generated in the combustion process of the internal combustion engine, and the ion current detection step. First ion generation time PT1 at which the ion current value peaks first after the start of combustion, and the ion current value peaks after the first peak generation time PT1 based on the value of the ion current detected at An ion current peak generation timing detection step for detecting a second peak generation timing PT2, and the first peak generation timing PT1 and / or the second peak generation timing PT2 detected in the ion current peak generation timing detection step are the internal combustion engine. A peak generation time determination step for determining whether or not the combustion characteristic depends on the engine combustion characteristics; A combustion state determination step for determining a combustion state of the internal combustion engine based on the first peak generation time PT1 and the second peak generation time PT2 detected in the ion current peak generation time detection step, According to the determination result in the generation timing determination step and the determination result in the combustion state determination step, at least one set value of the preset ignition timing, fuel injection timing, and fuel injection amount is corrected. is there.

  According to the present invention, when it is determined that the peak position of the ionic current is detected by an influence other than the combustion characteristics by determining the validity of the first peak generation time PT1 and the second peak generation time PT2 of the ionic current. Therefore, it is possible to exclude the correction value from the calculation and correct the ignition timing, the fuel injection timing, and the fuel injection amount accurately according to the determined combustion state of the internal combustion engine.

First, the basic principle and configuration related to the present invention will be described.
The present invention performs truly accurate correction control by detecting a change in flame propagation velocity indicating a combustion state based on a change in ion current generated in an internal combustion engine.
As described above, the ionic current is mainly generated by a charged intermediate product called a radical (radical) in the flame in the course of combustion of hydrocarbon fuel such as gasoline. It is a weak current of amperage.
Specifically, when a combustion flame is present in a space to which a potential is applied in some electrical circuit, radicals generated in the flame by the action of the potential are collected by the negative electrode, and the flow of electrons in the electrical circuit (i.e., Current) occurs.
FIG. 1 is a diagram showing a change example of an ionic current detected in a combustion process in an internal combustion engine. As described above, an ionic current is detected by ionizing a part of fuel or air by an ignition spark. ”Peak P0 due to discharge at ignition”, “First peak P1 due to combustion” detected immediately after the start of combustion, and detection when the combustion flame is most actively activated by propagating into the cylinder “Second peak P2”.
In FIG. 1, PT0 is a time (crank angle or time) when the peak P0 occurs, PT1 is a time when the peak P1 occurs (crank angle or time), and PT2 is a time when the peak P2 occurs (crank angle or time). It is.

In addition, the above-mentioned Japan Society for Automotive Engineers Academic Lecture Preprint 962 is included in FIG. As shown in FIG. 1, the “first peak generation time” of the ion current indicates a time when the pressure in the combustion chamber starts to rapidly increase, and the “second peak generation time” indicates that the pressure in the combustion chamber is almost equal. The maximum time is shown, and the ion current detection pattern in the combustion process includes a part of the characteristic of the pressure change in the combustion chamber.
Further, since the pressure change in the combustion chamber has information on the combustion state such as the flame propagation speed, the change in the flame propagation speed is detected by detecting the change in the first peak P1 generation time PT1 and the second peak P2 generation time PT2. It is possible to detect.
That is, by detecting changes in the first peak P1 generation time PT1 and the second peak P2 generation time PT2 indicating the pressure change in the combustion chamber, the combustion state of the internal combustion engine is indirectly detected, and the combustion state becomes good. Thus, it is possible to execute truly accurate correction control.

First, the configuration of the control device for an internal combustion engine according to the present invention is applied to a “lean combustion type internal combustion engine” in which the air-fuel ratio is diluted to improve fuel efficiency and the combustion state is more likely to change than the stoichiometric air-fuel ratio combustion. Based on
FIG. 2 is a diagram showing a schematic configuration of an entire automobile internal combustion engine to which the control apparatus for an internal combustion engine according to the present invention is applied.
As shown in FIG. 2, the intake pipe 5 is connected to the intake port of the engine body 6 via the surge tank 4, and the exhaust pipe 9 is connected to the exhaust port.
The surge tank 4 is a part for preventing intake pulsation.
The air cleaner 1 has a filter that removes dust contained in the air sucked into the engine body 6, and the air flow sensor 2 is, for example, a hot-wire air flow sensor that corresponds to the mass flow rate of the intake air. Generate a voltage signal.

The throttle valve 3 adjusts the intake air amount in conjunction with an accelerator pedal (not shown). Further, the throttle valve 3 includes a potentiometer, for example, and is provided with a throttle valve opening sensor 13 for detecting the throttle valve opening.
The crank angle sensor 11 outputs a pulse signal every time the crankshaft of the engine body 6 rotates a certain amount.
The cam angle sensor 12 outputs a pulse signal every time the camshaft of the engine body 6 rotates a certain amount. For example, the crank angle sensor 11 outputs a rotation angle detection pulse every 10 ° of the crank rotation angle.
Since the cam angle sensor 12 outputs a different signal for each cylinder, the cylinder can be specified in combination with the signal of the crank angle sensor 11.

The fuel injection valve 7 is provided for each cylinder, opens in response to a signal from an ECU (engine control unit) 21, and injects pressurized fuel into the combustion chamber 24 of each cylinder.
An air-fuel mixture is formed in the combustion chamber 24 by the injected fuel and air flowing in from the intake pipe 5 and ignited by the spark plug 23.
The combusted air-fuel mixture (exhaust gas) is guided to the exhaust pipe 9, and the catalyst 8 disposed in the exhaust pipe 9 simultaneously purifies the three components of HC, NOx, and CO in the exhaust gas.
Further, an air-fuel ratio sensor 10 is provided upstream of the catalyst 8, and the air-fuel ratio can be detected linearly (that is, proportionally) from the oxygen concentration contained in the exhaust gas.

On the other hand, the ECU 21 provided in the passenger compartment is a microcomputer system that performs fuel injection control, ignition timing control, and the like, and includes an input / output interface 19, a central processing unit 16, a ROM 17, a RAM 18, a drive circuit 20, and the like. Has been.
Various sensors and switches are connected to the input side of the ECU 21, and various sensor outputs are A / D converted via the interface and taken into the ECU 21.
The ECU 21 executes arithmetic processing based on the input signal.
Based on the calculation result, various actuator control signals can be output to control the actuators such as the injection valve 7 and the spark plug 23.

FIG. 3 is a block diagram for explaining the fuel injection amount control.
The fuel injection amount control in the internal combustion engine will be described with reference to FIG.
The ECU 21 performs A / D conversion on the output of the air flow sensor 2 and reads it, and integrates the intake air amount in the signal section of the crank angle sensor 11 to calculate the intake air amount per intake stroke.
In order to simulate the response delay in the surge tank 4, the intake air amount entering the combustion chamber is calculated by applying a primary filter to the intake air amount.
The basic fuel injection amount TB is calculated so that the theoretical air-fuel ratio is obtained with respect to the intake air amount thus obtained.
In addition, the operation of the internal combustion engine determined by the engine speed and the intake air amount is used to switch between basic lean combustion for the purpose of improving fuel economy and stoichiometric air-fuel ratio combustion when torque is required for acceleration, etc. A (Air) / F (Fuel) correction caf according to the point is performed.

The combustion state correction (fuel injection amount correction) cdf corrects the basic fuel injection amount TB according to the combustion state of the internal combustion engine detected by the ionic current (correction amount: cdf).
Further, various other fuel correction amounts cetc corresponding to the operating environment of the internal combustion engine such as engine coolant temperature and intake air temperature are calculated.
In addition, during the stoichiometric air-fuel ratio combustion, since disturbance has occurred in the engine, the actual air-fuel ratio detected by the air-fuel ratio sensor 10: AFO is corrected when the A / F ratio deviates from the stoichiometric air-fuel ratio AFtgt: cfb Has been added.
Using the correction amount thus obtained, the basic fuel injection amount TB is corrected, and the effective fuel injection amount Ta is calculated.
Further, after adding the invalid fuel injection amount TD for correcting the valve opening delay time of the fuel injection valve 7 and calculating the actual fuel injection amount TI, the fuel injection valve 7 is driven via the drive circuit 20.

FIG. 4 is a block diagram for explaining fuel injection timing control.
The fuel injection timing control in the internal combustion engine will be described with reference to FIG.
In the following description, it is assumed that “timing” such as fuel injection timing and ignition timing is represented by a crank angle “θ”.
A basic fuel injection timing θfb corresponding to the operating point of the internal combustion engine determined by the engine speed and the intake air amount is calculated.
Various fuel injection timing corrections θfetc such as high temperature correction and knock countermeasures by signals from other sensors are calculated, and combustion state correction (fuel injection timing) θfd is basically based on the combustion state detected by the ion current The fuel injection timing θfb is corrected.
The state of the internal combustion engine is comprehensively determined, an optimal fuel injection timing is determined, and the fuel injection valve 7 is driven via the drive circuit 20.

Further, the ignition timing control will be described with reference to FIG.
FIG. 5 is a block diagram for explaining ignition timing control in the internal combustion engine.
A basic ignition timing θeb corresponding to the operating point of the internal combustion engine determined by the engine speed and the intake air amount is calculated.
Various ignition timing corrections θeetc are calculated from signals from other sensors, and the combustion state correction (ignition timing) θed corrects the basic ignition timing θeb according to the combustion state detected by the ion current.
The state of the internal combustion engine is comprehensively determined, an optimal ignition timing is determined, and the ignition plug 23 is controlled and driven by an ignition signal (not shown) via the drive circuit 20.

Further, the internal combustion engine is provided with an ion current detection circuit 22 (see FIG. 2) for detecting a combustion state based on ions generated during combustion in the combustion chamber 24.
Ions are generated when the air-fuel mixture burns, and ions generated in the combustion chamber 24 flow by applying a bias voltage to the ignition plug 23 from a bias circuit (not shown) provided in the ion current detection circuit 22, The current detection circuit 22 detects the ion current.

  In the control apparatus for an internal combustion engine configured as described above, the “first peak generation time PT1” of the ion current, which is a time when the pressure in the combustion chamber starts to suddenly increase, and the ion current, which is the time when the pressure in the combustion chamber becomes substantially maximum If the "second peak generation time PT2" is detected, the change in the combustion state is detected based on the detected change in the ionic current (that is, the change in the first peak generation time PT1 and the second peak generation time PT2). The ignition timing, the fuel injection timing, or the fuel injection amount can be appropriately corrected and controlled according to the combustion state.

Embodiment 1 FIG.
As described above, the ionic current generated during combustion occurs during the main flame propagation period in the combustion flame of the internal combustion engine, and immediately after the start of combustion, that is, immediately after the flame is generated in the vicinity of the spark plug, The generated radicals are collected by the negative electrode and show a first peak, and the second peak is characterized in that the combustion flame propagates in the combustion chamber and occurs when combustion is most active.
That is, the difference between the first peak occurrence time PT1 and the second peak occurrence time PT2 represents the spread of the combustion flame and indirectly indicates the flame propagation speed.
In the present invention, accurate correction control is executed based on the change in the flame propagation speed.

Hereinafter, specific contents of the first embodiment of the present invention will be described.
If the fuel injection amount, fuel injection timing, and ignition timing are not appropriate, the combustion state is slow or ends early, the combustion state is poor, and good thermal efficiency cannot be obtained.
When the combustion state is slow, the time when the pressure in the combustion chamber becomes maximum from the start of combustion becomes longer, and the difference between the first peak generation time PT1 and the second peak generation time PT2 of the ionic current correlated with the pressure in the combustion chamber becomes longer. Become.
On the other hand, when it ends early, the time when the pressure in the combustion chamber becomes maximum from the start of combustion becomes shorter, and the first peak generation time PT1 and the second peak generation time PT2 of the ionic current correlated with the pressure in the combustion chamber. The difference is also shortened.
Therefore, the fuel injection amount, the fuel injection timing, and the ignition timing are appropriately controlled in accordance with the change in the flame propagation speed so that the best thermal efficiency can be maintained.

Specifically, a crank angle difference or a time difference between the first peak generation time PT1 and the second peak generation time PT2 is detected as the flame propagation speed indicating the combustion state from the ion current at each ignition, and the combustion state is the best. The ignition timing, the fuel injection amount, and the fuel injection timing are corrected so as to be substantially equal to the target value.
As described above, the value changes due to the influence of the electric circuit (that is, the ion current detection circuit 22) for detecting the ionic current (in particular, the influence not depending on the combustion characteristics such as the temperature drift of the resistance element). May be difficult to detect the first peak or the second peak of the ion current.
Therefore, the validity of the generation time of the first peak and the second peak of the ion current is also determined.
The detection of the peak time of the ionic current is performed by, for example, detecting a difference for each predetermined sample of the ionic current value continuously detected for each ignition by the ionic current detection circuit 22, and the difference is decreased from an increase. The crank angle or time when turning is the peak time.

FIG. 6 is a flowchart showing a control routine (control program) in the control apparatus for an internal combustion engine according to the first embodiment, and shows a control routine executed for each ignition of the internal combustion engine.
First, in step S101, the first peak occurrence time PT1 indicating the combustion start time is detected by the crank angle or time.
For example, the first peak is very small and difficult to detect, and the second peak becomes the second peak due to the influence of the temperature drift of the resistance element of the electric circuit that detects the ionic current and the like. Since it may be erroneously recognized as one peak, in step S102, the validity of the first peak occurrence time PT1 is determined by comparing the first peak occurrence time PT1 with the predetermined period 1.
If the first peak generation time PT1 deviates from the predetermined period 1, it may have been affected by the combustion characteristics, so any correction values for the ignition timing, fuel injection timing, and fuel injection amount are changed. Without this, the present routine is terminated to prevent erroneous correction.

On the other hand, when it is determined that the first peak occurrence time PT1 is appropriate (when the first peak occurrence time PT1 is within a predetermined period 1 set in advance), the first time indicating the time when combustion is most active in step S103. The two-peak occurrence time PT2 is detected by the crank angle or time.
Next, in step S104, a difference (ΔPT = PT2−PT1) between the first peak generation time PT1 and the second peak generation time PT2 indicating the flame propagation speed is calculated, and the process proceeds to step S105, where the first peak generation time PT1 and Similarly, the validity of the second peak occurrence time PT2 is determined.
Second within a predetermined period 2 indicated by the crank angle or time from the first peak occurrence time PT1.
If the peak occurrence time PT2 cannot be detected, there is a possibility that it has been influenced not by combustion, so this routine is terminated to prevent erroneous correction of the ignition timing, the fuel injection timing, and the fuel injection amount.

On the other hand, when it is determined that the second peak occurrence time PT2 is appropriate, in step S106, the target value BPT at which the combustion state is good is read from the memory, and the combustion state is determined in step S107.
When the difference (ΔPT) between the first peak generation time PT1 and the second peak generation time PT2 indicating the flame propagation speed is substantially equal to the target value (BPT), it is determined that the combustion state is good and the correction value is changed. However, if the difference from the target value BPT is larger than the predetermined determination value 1, the combustion state has deteriorated. Therefore, in step S108, the ignition timing, fuel injection timing, and fuel injection amount are determined. Is corrected according to the change in the flame propagation speed so that the combustion state becomes good.

As described above, in the present embodiment, the flame propagation speed indicating the combustion state is detected based on the difference between the first peak generation time PT1 and the second peak generation time PT2, so that it can be accurately detected according to the change in the combustion state. Correction control can be executed.
As a specific correction method, for example, first, advance correction is performed for the ignition timing and fuel injection timing, and increase correction is performed for the fuel injection amount. If the combustion state deteriorates, retard correction or decrease correction is conversely performed. If the state is changed to a good state, the advance angle correction or the increase amount correction is performed as it is, and the correction control is performed so that the combustion state is the best (that is, the flame propagation speed becomes substantially equal to the target value). Correction control).

  As described above, the control apparatus for an internal combustion engine according to the present embodiment has an ion current detection means (ion ion) that continuously detects the value of the ion current flowing in the combustion chamber by the action of ions generated in the combustion process of the internal combustion engine. Based on the value of the ion current detected by the current detection circuit 22) and the ion current detection means, after the first peak generation time PT1 and the first peak generation time PT1 at which the ion current value first peaks after the start of combustion. An ion current peak generation time detection means for detecting a second peak generation time PT2 at which the ion current value reaches a peak, and a first peak generation time PT1 and / or a second peak generation detected by the ion current peak generation time detection means. A peak generation timing determination means for determining whether the timing PT2 depends on the combustion characteristics of the internal combustion engine; Based on the first peak generation time PT1 and the second peak generation time PT2 detected by the generation time detection means, the combustion state determination means for determining the combustion state of the internal combustion engine, the determination result of the peak generation time determination means and the combustion state determination According to the determination result of the means, there is provided correction means for correcting at least one set value of preset ignition timing, fuel injection timing and fuel injection amount.

  The internal combustion engine control method according to the present embodiment includes an ion current detection step for continuously detecting the value of an ion current flowing in the combustion chamber by the action of ions generated in the combustion process of the internal combustion engine, and an ion current detection step. The first peak generation time PT1 at which the ion current value peaks first after the start of combustion and the second peak generation at which the ion current value peaks after the first peak generation time PT1 based on the value of the ion current detected in The ion current peak generation time detection step for detecting the time PT2 and the first peak generation time PT1 and / or the second peak generation time PT2 detected in the ion current peak generation time detection step depend on the combustion characteristics of the internal combustion engine. A peak generation time determination step for determining whether or not there is an ion current peak generation time detection step. And a combustion state determination step for determining the combustion state of the internal combustion engine based on the first peak generation time PT1 and the second peak generation time PT2 detected in step 1, the determination result in the peak generation time determination step and the combustion state In accordance with the determination result in the determination step, at least one set value among the preset ignition timing, fuel injection timing, and fuel injection amount is corrected.

  Therefore, according to the present embodiment, the combustion state of the internal combustion engine is accurately determined by detecting the first peak generation time PT1 and the second peak generation time PT2 of the ion current, and according to the determined combustion state. The ignition timing, fuel injection timing and fuel injection amount can be optimally corrected.

Further, the peak generation timing determination means of the control device for an internal combustion engine according to the present embodiment is such that the ion current peak generation timing detection means does not detect the first peak within the first predetermined timing (predetermined period 1) from the start of combustion. The first peak generation timing PT1 is determined not to depend on the combustion characteristics of the internal combustion engine, and the correction means changes any correction value for the preset ignition timing, fuel injection timing, and fuel injection amount. do not do.
Therefore, according to the present embodiment, when it is determined that the peak position of the ionic current is detected by the influence other than the combustion characteristics by the determination of the validity of the first peak generation time PT1, the correction value is calculated. This eliminates erroneous correction of the ignition timing, the fuel injection timing, and the fuel injection amount.

Further, the peak generation timing determining means of the control device for an internal combustion engine according to the present embodiment is such that the ion current peak generation timing detection means is within the second predetermined period (predetermined period 2) from the first peak generation timing PT1. Is not detected, it is determined that the second peak occurrence timing PT2 does not depend on the combustion characteristics of the internal combustion engine, and the correcting means is configured to perform the preset ignition timing, fuel injection timing, and fuel injection amount. Neither correction value is changed.
Therefore, according to the present embodiment, when it is determined that the peak position of the ionic current is detected by an influence other than the combustion characteristics by determining the validity of the second peak generation time PT2, the correction value is calculated. This eliminates erroneous correction of the ignition timing, the fuel injection timing, and the fuel injection amount.

Further, according to the control apparatus for an internal combustion engine according to the present embodiment, the combustion state determination means determines in advance the difference between the first peak generation time PT1 and the second peak generation time PT2 detected by the ion current peak generation time detection means. When it is determined that the difference from the set target value is larger than the predetermined value, the correcting means makes the difference between the first peak occurrence time PT1 and the second peak occurrence time PT2 substantially equal to the preset target value. In addition, at least one set value of the ignition timing, the fuel injection timing, and the fuel injection amount is corrected.
Therefore, according to the present embodiment, the ignition timing, the fuel injection amount, and the fuel injection timing can be corrected so that the combustion is in an appropriate state.

Embodiment 2. FIG.
FIG. 7 is a flowchart showing a control routine (control program) in the control apparatus for an internal combustion engine according to the second embodiment, and shows a control routine executed for each ignition of the internal combustion engine.
The internal combustion engine control apparatus according to Embodiment 2 will be described below.
When the ignition timing, the fuel injection timing, and the fuel injection amount are not appropriate and the combustion state deteriorates, the combustion fluctuation increases. That is, the pressure fluctuation in the combustion chamber for each combustion cycle increases.
Therefore, the flame propagation speed (that is, the difference between the first peak generation time PT1 and the second peak generation time PT2) showing a part of the characteristic of the pressure change in the combustion chamber also appears as a fluctuation.
Therefore, the fuel injection amount, the fuel injection timing, and the ignition timing are appropriately corrected in accordance with the fluctuation of the flame propagation speed, which is an index of the combustion fluctuation, so that the combustion fluctuation becomes small, and the combustion state is kept good.
Specifically, the fluctuation rate of the flame propagation speed indicating the combustion fluctuation is detected from the change of the ion current in a predetermined period such as a predetermined number of cycles or a predetermined operation time, and the ignition timing, the fuel injection amount are set so that the fluctuation ratio becomes small. And correct the fuel injection timing.

Based on FIG. 7, the control apparatus for an internal combustion engine in the present embodiment will be described.
In FIG. 7, the operations from step S201 to step S205 are basically the same as those in the first embodiment, and while determining the validity of the first peak occurrence time PT1 and the second peak occurrence time PT2, ΔPT (k), which is the difference between the first peak occurrence time PT1 and the second peak occurrence time PT2 indicating the flame propagation speed, is calculated.
“K” indicates the number of times of calculation of the difference between the first peak occurrence time PT1 and the second peak occurrence time PT2.
First, the operation from step S201 to step S205 will be described.
As in the case of the first embodiment, in step S201, the first peak occurrence time PT1 indicating the combustion start time is detected by the crank angle or time.

In step S202, the validity of the first peak occurrence time PT1 is determined by comparing the first peak occurrence time PT1 with the predetermined period 1.
If the first peak occurrence time PT1 deviates from the predetermined period 1, it may have been influenced by the combustion characteristics, so that any correction values for the ignition timing, the fuel injection timing, and the fuel injection amount can be changed. First, by terminating this routine, erroneous correction is prevented.
On the other hand, when it is determined that the first peak occurrence time PT1 is appropriate (when the first peak occurrence time PT1 is within a predetermined period 1 set in advance), the second time indicating the time when the combustion is most active in step S203. The peak occurrence time PT2 is detected by the crank angle or time.
Next, in step S204, the difference (ΔPT (k) = PT2−PT1) between the first peak generation time PT1 and the second peak generation time PT2 indicating the flame propagation speed is calculated, and the process proceeds to step S205, where the first peak is generated. The validity of the second peak occurrence time PT2 is determined in the same manner as the occurrence time PT1.
If the second peak generation time PT2 cannot be detected within the predetermined period 2 indicated by the crank angle or time from the first peak generation time PT1, this routine may be terminated because it may have been influenced by the combustion characteristics. Then, erroneous correction is prevented for the ignition timing, the fuel injection timing, and the fuel injection amount.

Next, in step S206, as a variation rate of the flame propagation speed, for example, based on the following formulas (1) and (2), a variation rate of the flame propagation speed (ΔPT) in a predetermined number of cycles or a predetermined operation time: C12 is calculated.
First, from the flame propagation speed detected this time (ΔPT (k)) and the flame propagation speed at the predetermined number of cycles or the number of detections (n) within a predetermined operation time detected before, as shown in the equation (1): The moving average (ΔPTadv) is calculated.
ΔPTadv = (ΔPT (k) + ΔPT (k-1) +... + ΔPT (k-n + 1)) / n (1)
Further, the standard deviation is divided by the moving average (ΔPTadv), and the variation rate (C12) is calculated as shown in equation (2).

Next, in step S207, if the fluctuation rate of the flame propagation speed is equal to or less than the predetermined determination value 2, the combustion state is stable, so that correction is made for the control parameters of the ignition timing, the fuel injection amount, and the fuel injection timing. This routine ends without changing the value.
On the other hand, when the fluctuation rate is larger than the predetermined determination value 2, it indicates that the combustion fluctuation is large and the combustion state is deteriorated, so that the combustion state is stabilized in step S208 (that is, the fluctuation of the flame propagation speed). The control parameters of the ignition timing, the fuel injection timing, and the fuel injection amount are corrected so that the rate C12 becomes smaller.

As described above, in the control apparatus for an internal combustion engine according to the present embodiment, the first peak generation time PT1 and the second peak generation detected by the ion current peak generation time detection means within the predetermined period by the combustion state determination means. When it is determined that the variation rate of the difference between the timings PT2 is larger than the predetermined value, the correction unit performs ignition so that the variation rate of the difference between the first peak generation timing PT1 and the second peak generation timing PT2 is small within the predetermined period. At least one set value of the timing, the fuel injection timing, and the fuel injection amount is corrected.
Therefore, according to the present embodiment, by detecting the combustion fluctuation detected from the difference between the first peak generation time PT1 and the second peak generation time PT2 of the ion current, an accurate ignition timing according to the combustion fluctuation is obtained. The fuel injection amount and the fuel injection timing can be corrected.

Embodiment 3 FIG.
FIG. 8 is a flowchart showing a control routine (control program) in the control apparatus for an internal combustion engine according to the third embodiment, and shows a control routine executed for each ignition of the internal combustion engine.
The internal combustion engine control apparatus according to Embodiment 3 will be described below.
The basic contents are the same as in the first embodiment, and the first peak occurrence time PT1 and the first peak generation time PT1 within a predetermined period (predetermined cycle number or predetermined operation time) are used as flame propagation speed indicating the combustion state from the ion current for each ignition. The average value of the differences between the two peak generation times PT2 is calculated, and the ignition timing, the fuel injection amount, and the fuel injection timing are corrected so as to be approximately equal to the target value at which the combustion state is in the best state.

Based on FIG. 8, the control apparatus of the internal combustion engine in the present embodiment will be described.
In FIG. 8, steps S301 to S306 are the same as in the first embodiment, and the first and the second indicating the flame propagation speed while judging the validity of the first peak occurrence time PT1 and the second peak occurrence time PT2. A difference (ΔPT (k)) between the second peak generation times is calculated, and a target value (BPT) at which the combustion state is good is read out.
Next, in step S307, in order to remove the influence of the combustion fluctuation that occurs to some extent even in a good combustion state, as in the case of the second embodiment, the flame propagation at the predetermined number of cycles or the number of detections (n) within the predetermined operation time. The average value of speed (ΔPTadv) is calculated by equation (3).
ΔPTadv = (ΔPT (k) + ΔPT (k-1) + ... + ΔPT (k-n + 1)) / n (3)
Next, in step S308 and step S309, as in the first embodiment, control parameters for the ignition timing, the fuel injection timing, and the fuel injection amount are set so that the average value (ΔPTadv) of the flame propagation speed approaches the target value (BPT). Make corrections.

As described above, in the control apparatus for an internal combustion engine according to the present embodiment, the first peak generation time PT1 and the second peak generation detected by the ion current peak generation time detection means within the predetermined period by the combustion state determination means. When it is determined that the difference between the average value of the differences in the timing PT2 and the preset target value is larger than the predetermined value, the correction means determines the difference between the first peak occurrence timing PT1 and the second peak occurrence timing PT2 within the predetermined period. The at least one set value of the ignition timing, the fuel injection timing, and the fuel injection amount is corrected so that the average value of is substantially equal to a preset target value.
Therefore, according to the present embodiment, the change in the flame propagation speed is detected from the average value of the difference between the first peak generation time PT1 and the second peak generation time PT2 of the ion current. By absorbing the fluctuation, it is possible to detect stably, and it is possible to correct the ignition timing, the fuel injection amount and the fuel injection timing accurately according to the change of the combustion state without erroneous detection.

Embodiment 4 FIG.
FIG. 9 is a flowchart showing a control routine (control program) in the control apparatus for an internal combustion engine according to the fourth embodiment, and shows a control routine executed for each ignition of the internal combustion engine.
Hereinafter, an internal combustion engine control apparatus according to Embodiment 4 will be described.
In the present embodiment, the fluctuation rate of the first peak generation time PT1 and the second peak generation time PT2 is calculated from the ion current for each combustion cycle, and the ignition timing, the fuel injection amount, and the fuel injection are reduced so that the fluctuation rate becomes small. Perform time correction.
Based on FIG. 9, the control apparatus of the internal combustion engine in the present embodiment will be described.
In FIG. 9, the operations from step S401 to step S405 are basically the same as those in the first embodiment, and the validity of the first peak occurrence time PT1 and the second peak occurrence time PT2 is determined.

Next, in step S406 and step S407, as a change in flame propagation speed, for example, based on the following formulas (4) and (5), the first peak occurs in a predetermined period such as a predetermined number of cycles and a predetermined operation time: A fluctuation rate (C1) of the time PT1 and a fluctuation rate (C2) of the second peak occurrence time PT2 are calculated.
First, the moving average (PT1adv) is calculated from the first peak occurrence time detected at this time (PT1 (k)) and the first peak occurrence time at the predetermined number of cycles or the number of detections (n) within the predetermined operation time detected before that. And
PT1adv = (PT1 (k) + PT1 (k-1) + ... + PT1 (k-n + 1)) / n (4)
Further, the standard deviation is divided by the moving average (PT1adv) to calculate the variation rate (C1).

The calculation method of the variation rate (C2) of the second peak occurrence time PT2 is also the same.
Next, in step S408, the magnitude of the fluctuation rate at each peak occurrence time is compared using predetermined determination value 3 and determination value 4, and if larger, the combustion state is stabilized in step S409 so that the combustion state is stabilized. As in the case of, correction is performed for the control parameters of the ignition timing, the fuel injection amount, and the fuel injection timing.

As described above, in the control apparatus for an internal combustion engine according to the present embodiment, the combustion state determining means detects the first peak occurrence time PT1 detected by the ion current peak occurrence time detection means within the predetermined period and / or the description. If it is determined that the fluctuation rate of the two-peak occurrence time PT2 is greater than a predetermined value, the correction means detects the first peak occurrence time PT1 and / or the second peak occurrence detected by the ion current peak occurrence time detection means within the predetermined period. At least one set value of the ignition timing, the fuel injection timing, and the fuel injection amount is corrected so that the variation rate of the timing PT2 becomes small.
Therefore, according to the present embodiment, the fluctuation of the flame propagation speed is detected from the fluctuation rate of the first peak generation time PT1 and / or the second peak generation time PT2 of the ionic current. It is possible to correct the ignition timing, the fuel injection amount, and the fuel injection timing.

Although the present embodiment has been described in detail based on the configuration of the lean combustion internal combustion engine, it is possible to detect the fluctuation of the flame propagation speed by the ionic current even in the internal combustion engine configuration of the stoichiometric air fuel ratio combustion, This technique can be used.

  The present invention is useful for realizing a control device for an internal combustion engine that can accurately determine the combustion state of the internal combustion engine and optimally correct the ignition timing, the fuel injection timing, and the fuel injection amount in accordance with the combustion state.

It is a figure which shows the example of a change of the ionic current detected in the combustion process in an internal combustion engine. 1 is a diagram showing a schematic configuration of an entire internal combustion engine for an automobile to which a control device for an internal combustion engine according to the present invention is applied. It is a block diagram for demonstrating fuel injection amount control. It is a block diagram for demonstrating fuel injection timing control. It is a block diagram for demonstrating the ignition timing control in an internal combustion engine. 3 is a flowchart showing a control routine in the control apparatus for an internal combustion engine according to the first embodiment. 6 is a flowchart showing a control routine in the control apparatus for an internal combustion engine according to the second embodiment. 6 is a flowchart showing a control routine in a control device for an internal combustion engine according to a third embodiment. 6 is a flowchart showing a control routine in a control device for an internal combustion engine according to a fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air cleaner 2 Air flow sensor 3 Throttle valve 4 Surge tank 5 Intake pipe 6 Engine main body 7 Fuel injection valve 8 Catalyst 9 Exhaust pipe 10 Air-fuel ratio sensor 11 Crank angle sensor 12 Cam angle sensor 13 Throttle valve opening sensor 14 Idle switch 15 Water temperature sensor 16 Central processing unit 17 ROM 18 RAM
19 I / O interface 20 Drive circuit 21 Engine control unit 22 Ion current detection circuit 23 Spark plug 24 Combustion chamber.

Claims (8)

Ion current detection means for continuously detecting the value of ion current flowing in the combustion chamber by the action of ions generated in the combustion process of the internal combustion engine;
Based on the value of the ion current detected by the ion current detection means, the first peak generation time when the ion current value peaks after the start of combustion, and the ion current value after the first peak generation time. An ion current peak generation timing detection means for detecting a second peak generation timing that becomes a peak;
Peak generation timing determination means for determining whether the first peak generation timing and / or the second peak generation timing detected by the ion current peak generation timing detection means depends on the combustion characteristics of the internal combustion engine. When,
Combustion state determination means for determining the combustion state of the internal combustion engine based on the first peak generation time and the second peak generation time detected by the ion current peak generation time detection means;
Correction means for correcting at least one set value of preset ignition timing, fuel injection timing, and fuel injection amount in accordance with the determination result of the peak occurrence timing determination means and the determination result of the combustion state determination means And a control device for an internal combustion engine. The peak generation time determining means determines that the first peak generation time is in accordance with the combustion characteristics of the internal combustion engine when the ion current peak generation time detection means does not detect the first peak within a first predetermined period from the start of combustion. Judge that it doesn't depend,
2. The control device for an internal combustion engine according to claim 1, wherein the correction unit does not change the correction for any of preset values of the ignition timing, the fuel injection timing, and the fuel injection amount. . The peak generation time determination means is configured to determine that the second peak generation time is the internal combustion engine when the ion current peak generation time detection means does not detect the second peak within a second predetermined period from the first peak generation time. Judged not to depend on the combustion characteristics of the engine,
2. The control device for an internal combustion engine according to claim 1, wherein the correction unit does not change the correction for any of preset values of the ignition timing, the fuel injection timing, and the fuel injection amount. .   When the difference between the first peak generation time and the second peak generation time detected by the ion current peak generation time detection means and a preset target value is greater than a predetermined value, the combustion state determination means When the determination is made, the correction means adjusts the ignition timing, the fuel injection timing, and the fuel injection amount so that the difference between the first peak generation timing and the second peak generation timing is substantially equal to a preset target value. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein at least one set value is corrected.   When the combustion state determination means determines that the variation rate of the difference between the first peak generation time and the second peak generation time detected by the ion current peak generation time detection means within a predetermined period is greater than a predetermined value The correction means sets at least one of the ignition timing, the fuel injection timing, and the fuel injection amount so that a variation rate of a difference between the first peak generation timing and the second peak generation timing is reduced within a predetermined period. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the value is corrected. The combustion state determination means is configured to obtain an average value of a difference between the first peak generation time and the second peak generation time detected by the ion current peak generation time detection means within a predetermined period, and a preset target value. When it is determined that the difference is greater than a predetermined value, the correction means causes the average value of the difference between the first peak occurrence time and the second peak occurrence time to be substantially equal to a preset target value within a predetermined period. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein at least one set value of the ignition timing, the fuel injection timing, and the fuel injection amount is corrected.   When the combustion state determination means determines that the fluctuation rate of the first peak generation time and / or the second peak generation time detected by the ion current peak generation time detection means within a predetermined period is greater than a predetermined value The correction means is arranged so that the fluctuation rate of the first peak generation time and / or the second peak generation time detected by the ion current peak generation time detection means within a predetermined period is reduced. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein at least one set value of the fuel injection timing and the fuel injection amount is corrected. An ion current detection step for continuously detecting the value of the ion current flowing in the combustion chamber by the action of ions generated in the combustion process of the internal combustion engine;
Based on the value of the ion current detected in the ion current detection step, the first peak generation time when the ion current value peaks after the start of combustion, and the ion current value after the first peak generation time. An ion current peak generation timing detection step for detecting a second peak generation timing that becomes a peak;
Peak generation timing determination step for determining whether the first peak generation timing and / or the second peak generation timing detected in the ion current peak generation timing detection step depends on the combustion characteristics of the internal combustion engine. When,
A combustion state determination step of determining a combustion state of the internal combustion engine based on the first peak generation time and the second peak generation time detected in the ion current peak generation time detection step;
According to the determination result in the peak generation timing determination step and the determination result in the combustion state determination step, at least one set value of a preset ignition timing, fuel injection timing, and fuel injection amount is corrected. A control method of an internal combustion engine characterized by the above.

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