JP2004197630A - Controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of an internal combustion engine for restraining degradation of operability of the engine which is caused by deposits on the intake system. <P>SOLUTION: Even when the intake system of the engine 1 is coated with deposits, a maximum lift of an intake valve 9 is increased to a prescribed value on the increase side so as to increase the intake air flow. Consequently, shortage in the intake air flow, which is attendant on the deposit on the exhaust system, is restrained, and a mean air-fuel ratio of all cylinders #1-#4 is restrained from shifting in consequence of the insufficient intake to a rich side from the theoretical air-fuel ratio of an aimed value in a combustion at the theoretical air-fuel ratio of a homogeneous mixture. Further, degradation of operability of the engine 1, which is caused by rotational variation in the engine 1 resulting from the shifting of the means air-fuel ratio, is restricted. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an internal combustion engine.
[0002]
[Prior art]
In an internal combustion engine such as an automobile engine, fuel or oil present in the intake system contacts the high-temperature wall surface and carbonizes and deposits as deposits, thereby reducing the air circulation area of the intake system. In the intake system of the engine, the temperature that is high enough to carbonize when fuel or oil comes into contact is the back surface of the intake valve head or the vicinity of the combustion chamber of the intake port, which is susceptible to heat during fuel combustion in the combustion chamber. Due to the inner surface, deposits are deposited at these locations.
[0003]
In a so-called port injection type internal combustion engine that injects fuel into the intake system of an internal combustion engine in order to remove deposits from the back surface of the intake valve head, the fuel is directed toward the back surface of the intake valve head or the inner surface of the intake port near the combustion chamber. There is one in which fuel is injected and supplied, and deposits attached to those locations are washed away by the injected fuel.
[0004]
Also, in a so-called in-cylinder injection type internal combustion engine that directly injects fuel into a combustion chamber of the internal combustion engine, fuel is injected near the intake bottom dead center before the intake valve closes in order to flush the deposit of the intake system. It has also been proposed (see Patent Document 1). In this case, the fuel injected and supplied into the combustion chamber flows toward the inside of the intake port by moving to the top dead center side of the piston, and the deposit attached to the back surface of the umbrella portion of the intake valve is washed away.
[0005]
[Patent Document 1]
JP 2001-289097 A
[0006]
[Problems to be solved by the invention]
As described above, the deposits can be removed to some extent by washing away the deposits adhered to the back surface of the umbrella portion of the intake valve and the inner surface of the intake port near the combustion chamber with the fuel. However, even if the back surface of the intake valve umbrella and the inner surface of the intake port near the combustion chamber are cleaned with the fuel, the deposit cannot always be completely removed from these locations, and this causes some inconvenience. It could be the cause.
[0007]
For example, an internal combustion engine having a maximum lift variable mechanism for varying the maximum lift of the intake valve, a multi-cylinder internal combustion engine having a plurality of cylinders, and a variable valve timing mechanism for varying the valve timing of the intake valve are provided. In the internal combustion engine, the following problem may occur due to the adhesion of the deposit.
[0008]
[Internal combustion engine with variable maximum lift mechanism]
In the internal combustion engine, the maximum lift variable mechanism is controlled so that the maximum lift of the intake valve becomes a value suitable for the operating state of the engine. That is, since the required intake air intake amount decreases as the engine light load becomes smaller, the maximum lift amount of the intake valve is reduced and the intake air amount is reduced. By reducing the intake air amount by reducing the maximum lift amount of the intake valve in this way, it is not necessary to control the throttle valve to the closed side to reduce the intake air amount. It is possible to hold each time. For this reason, it is possible to suppress that the pump loss of the internal combustion engine increases due to the control of the throttle valve to the closing side as described above, and the improvement of the fuel efficiency of the engine is hindered.
[0009]
If deposits adhere to the back surface of the intake valve umbrella or the inner surface near the combustion chamber of the intake port, the deposits will become inflow resistance and the amount of intake air will be insufficient for the required amount. The fuel ratio deviates from the appropriate value to the rich side. In particular, when the maximum lift amount of the intake valve is small and the intake air amount is small, the proportion of the shortage of the intake air amount due to the deposit to the total required intake air amount is large. In addition, the influence of the shortage of the intake air amount due to the deposit becomes large. For this reason, the deviation amount of the air-fuel ratio from the appropriate value to the rich side due to the shortage of the intake air amount also becomes large, and it is inevitable that the operation of the internal combustion engine becomes unstable due to rotation fluctuation of the internal combustion engine.
[0010]
When the engine is lightly loaded, in addition to holding the throttle valve on the open side to reduce the maximum lift amount of the intake valve to secure the required intake air amount as described above, In some cases, a necessary intake air amount is secured by controlling the opening of the throttle valve. Also in this case, the same problem as described above occurs because the amount of intake air is insufficient for the required amount due to the adhesion of the deposit.
[0011]
[Multi-cylinder internal combustion engine]
In the internal combustion engine, an intake valve is provided for each intake port of each cylinder, and the back surface of the umbrella portion of these intake valves and the inner surface of the intake port near the combustion chamber are washed with fuel. However, the back surface of the umbrella portion of the intake valve of each cylinder and the inner surface near the combustion chamber of the intake port are not always washed uniformly between the cylinders, and the amount of deposit that cannot be removed by washing with fuel is There is a high possibility that the value will be different every time. Therefore, there are a cylinder with a large amount of deposit and a cylinder with a small amount, or a cylinder with a deposit and a cylinder without a deposit, and the amount of intake air due to the deposit is increased. The shortage also differs for each cylinder. For this reason, the deviation amount of the air-fuel ratio from the appropriate value to the rich side also differs for each cylinder, and the fluctuation of the air-fuel ratio among the cylinders causes a rotation fluctuation in the internal combustion engine, thereby stably operating the engine. It becomes difficult.
[0012]
[Internal combustion engine with variable valve timing mechanism]
In the internal combustion engine, the variable valve timing mechanism is controlled such that the valve timing of the intake valve is suitable for the operating state of the engine. That is, in the same engine, since air is pulsated into the combustion chamber during the intake stroke, the intake valve is closed when the pressure in the intake port reaches the peak value, thereby reducing the intake air amount as much as possible. In many cases, the engine output can be improved. For this reason, the valve timing of the intake valve is controlled such that the valve closing timing of the intake valve becomes a timing at which the pressure in the intake port reaches a peak value.
[0013]
However, if the deposit adheres to the back surface of the intake valve umbrella or the inner surface near the combustion chamber of the intake port, the air circulation area of the intake port becomes smaller by that amount, and the pulsation mode such as the wavelength of the pulsation of the intake air changes. As a result, the timing at which the pressure in the intake port reaches a peak shifts to the advance side or the retard side. For this reason, the timing at which the pressure in the intake port reaches the peak value is deviated from the timing at which the intake valve closes, and there is a possibility that the amount of intake air is reduced and the required value is insufficient. If the air-fuel ratio deviates from the appropriate value to the rich side due to the shortage of the intake air amount, the operation of the internal combustion engine becomes unstable due to fluctuations in the rotation of the internal combustion engine.
[0014]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine capable of suppressing a decrease in operability of an internal combustion engine due to a deposit attached to an intake system of the engine. An object of the present invention is to provide an engine control device.
[0015]
[Means for Solving the Problems]
Hereinafter, the means for achieving the above object and the effects thereof will be described.
In order to achieve the above object, the invention according to claim 1 is applied to an internal combustion engine having a maximum lift variable mechanism for varying a maximum lift of an intake valve, and the maximum lift is suitable for an engine operating state. In the control device for the internal combustion engine that controls the maximum lift variable mechanism, the detection device detects the adhesion of the deposit to the intake system of the internal combustion engine, and the detection device detects the adhesion of the deposit to the intake system. Control means for controlling the maximum lift variable mechanism such that when detected, the maximum lift of the intake valve is increased.
[0016]
Even when deposits adhere to the intake system, the maximum lift of the intake valve is increased at that time, and the amount of intake air of the internal combustion engine is increased. Therefore, the shortage of the intake air amount due to the adhesion of the deposit to the intake system is suppressed, and the air-fuel ratio deviates from the appropriate value to the rich side due to the shortage, causing the rotation fluctuation of the internal combustion engine, etc. The decrease can be suppressed.
[0017]
According to a second aspect of the present invention, in the first aspect of the present invention, the control means detects that deposit has adhered to the intake system at least when the engine is in an engine operating region where the maximum lift is small. Based on this, the maximum lift variable mechanism is controlled to increase the maximum lift.
[0018]
When the maximum lift amount of the intake valve is small, the shortage of the intake air amount due to the adhesion of the deposit to the intake system accounts for a large proportion of the total required intake air amount. The inconvenience due to the shortage of the intake air amount due to this is also great. However, since such a shortage of the intake air amount is suppressed by increasing the maximum lift amount of the intake valve, the air-fuel ratio deviates from an appropriate value to the rich side due to the shortage of the intake air amount, and the accompanying Problems such as rotation fluctuations can be suppressed, and a decrease in operability of the internal combustion engine can be suppressed.
[0019]
According to a third aspect of the present invention, in the first or second aspect of the invention, the control means controls the maximum lift amount variable mechanism such that the larger the amount of deposit attached to the intake system, the larger the maximum lift amount. It was controlled.
[0020]
The greater the amount of deposit attached to the intake system, the greater the deficiency in the amount of intake air due to the attachment. For this reason, by increasing the maximum lift amount of the intake valve as the deposit amount increases as described above, it is possible to accurately suppress the shortage of the intake air amount due to the deposit adhesion. In addition, it is possible to suppress a deviation of the air-fuel ratio from the appropriate value to the rich side due to the shortage of the intake air amount and the fluctuation of the rotation of the internal combustion engine, and the like, thereby suppressing a decrease in the operability of the internal combustion engine.
[0021]
According to a fourth aspect of the present invention, in the first or second aspect of the present invention, in the engine operating region where the required intake air amount is small, the throttle valve of the engine has a predetermined opening degree on the opening side. And the maximum lift amount of the intake valve is made variable so that the intake air amount is adjusted to a required value. The required intake air amount is controlled by controlling the maximum lift amount variable mechanism so as to fix the maximum lift amount to a predetermined increasing value based on the adhesion of the deposit and controlling the opening of the throttle valve. Is to be secured.
[0022]
Insufficient intake air due to deposits adhering to the intake system is larger as the maximum lift of the intake valve is smaller than the required intake air. By fixing to the value of, it is suppressed exactly. The excess of the intake air amount when the maximum lift amount is fixed as described above is absorbed by adjusting the intake air amount by controlling the opening degree of the throttle valve. Therefore, it is possible to suppress the occurrence of an excessive intake air amount and adjust the intake air amount to a required value.
[0023]
The invention according to claim 5 is applied to a multi-cylinder internal combustion engine having a plurality of cylinders, and has an internal lift variable mechanism capable of changing the maximum lift of an intake valve of the engine for each cylinder. In the control device of the engine, detecting means for detecting adhesion of deposits to the intake system for each cylinder of the internal combustion engine, and according to the amount of deposits to the intake system for each cylinder detected by the detecting means, Control means for controlling the maximum lift variable mechanism so that the maximum lift of the intake valve is increased for each cylinder.
[0024]
Even if the presence or absence of deposits on the intake system and the amount of deposited deposits differ for each cylinder, the maximum lift of the intake valve is increased for each cylinder in accordance with the amount of deposits for each cylinder, The intake air amount is increased for each cylinder. Therefore, the shortage of the intake air amount differs for each cylinder due to the difference in the amount of deposit attached to the intake system of each cylinder, and the deviation amount from the appropriate value of the air-fuel ratio to the rich side differs for each cylinder. Can be suppressed. In addition, it is possible to suppress a decrease in the operability of the internal combustion engine caused by the variation in the air-fuel ratio among the cylinders due to the variation in the air-fuel ratio.
[0025]
In the invention described in claim 6, in the invention described in claim 5, the control means, when increasing the maximum lift amount, increases the maximum lift amount as the amount of deposit attached increases. The maximum lift variable mechanism is controlled.
[0026]
The greater the amount of deposit attached to the intake system, the greater the deficiency in the amount of intake air due to the attachment. For this reason, by increasing the maximum lift amount of the intake valve as the deposit amount increases as described above, it is possible to accurately suppress the shortage of the intake air amount due to the deposit adhesion. Therefore, it is possible to prevent the shortage of the intake air amount from being different for each cylinder, and it is possible to appropriately suppress the occurrence of a variation in the air-fuel ratio between the cylinders.
[0027]
According to a seventh aspect of the present invention, in the invention of the fifth or sixth aspect, the control unit is configured to control the amount of deposit attached to the intake system of each cylinder at least when the engine is in an engine operating region where the maximum lift amount is small. The maximum lift amount variable mechanism is controlled so that the maximum lift amount is increased for each cylinder in accordance with.
[0028]
When the maximum lift amount of the intake valve is reduced, the ratio of the shortage of the intake air amount due to the adhesion of the deposit to the intake system to the total required intake air amount becomes large. For this reason, when the amount of deposits on the intake system differs for each cylinder, the shortage of the intake air amount for each cylinder also greatly deviates from each other, and the air-fuel ratio between the cylinders decreases. The variation may be large. However, by increasing the maximum lift amount of the intake valve for each cylinder based on the amount of deposit of each cylinder, the shortage of the intake air amount for each cylinder is suppressed from being largely deviated, and the Large variations in the air-fuel ratio at the same time can also be suppressed.
[0029]
In a control apparatus for an internal combustion engine which is applied to a multi-cylinder internal combustion engine having a plurality of cylinders and controls a fuel injection amount of the engine to a value suitable for an engine operation state, each cylinder of the internal combustion engine Detecting means for detecting the adhesion of the deposit to the intake system for each cylinder; and decreasing the fuel injection amount for each cylinder in accordance with the amount of the deposit attached to the intake system for each cylinder detected by the detecting means. And control means for performing control.
[0030]
Even if the presence or absence of deposits on the intake system and the amount of deposits are different for each cylinder, the fuel injection amount is controlled to the decreasing side for each cylinder according to the amount of deposits for each cylinder. The deviation of the air-fuel ratio of each cylinder to the rich side is suppressed. Therefore, it is possible to prevent the deviation amount of the air-fuel ratio from the appropriate value to the rich side from being different for each cylinder due to the difference in the amount of deposit attached to the intake system of each cylinder. In addition, it is possible to suppress a decrease in the operability of the internal combustion engine due to a fluctuation in the rotation of the internal combustion engine due to the variation in the air-fuel ratio between the cylinders.
[0031]
According to a ninth aspect of the present invention, in the invention of the eighth aspect, when the fuel injection amount is reduced, the control means controls the fuel injection amount such that the larger the deposit amount, the larger the fuel injection amount. Control was performed.
[0032]
As the amount of deposit attached to the intake system increases, the amount of intake air shortage due to the attachment increases, and the amount of deviation of the air-fuel ratio from the appropriate value to the rich side also increases. For this reason, as described above, the larger the amount of deposit attached, the greater the decrease in fuel injection amount, so that it is possible to accurately suppress the deviation of the air-fuel ratio from the appropriate value due to the attachment of deposit to the rich side. it can. Therefore, it is possible to exactly suppress the occurrence of the variation in the air-fuel ratio between the cylinders.
[0033]
According to a tenth aspect of the present invention, in the invention of the eighth or ninth aspect, the control means uniformly increases or decreases the fuel injection amount of all the cylinders so that the average air-fuel ratio of all the cylinders becomes a target value. The fuel injection amount is controlled to be reduced for cylinders that are rich with respect to the air-fuel ratio, and the fuel injection amount is controlled to be increased for cylinders that are lean with respect to the average air-fuel ratio.
[0034]
According to the above configuration, when deposits are attached to the intake system of each cylinder, the fuel injection amount is increased or decreased for each cylinder so that the air-fuel ratio of each cylinder approaches the average air-fuel ratio (target value) of all cylinders, Variations in the air-fuel ratio among the cylinders can be more accurately suppressed.
[0035]
According to an eleventh aspect of the present invention, in the invention of the tenth aspect, the control means increases or decreases the fuel injection amount for each cylinder as the deviation of the air-fuel ratio of each cylinder from the average air-fuel ratio increases. To do.
[0036]
According to the above configuration, when deposits are attached to the intake system of each cylinder, the larger the deviation of the air-fuel ratio of each cylinder from the average air-fuel ratio is, the larger the increase / decrease of the fuel injection amount of each cylinder is. Therefore, the air-fuel ratio of each cylinder can be accurately approximated to the average air-fuel ratio of all cylinders.
[0037]
According to a twelfth aspect of the present invention, in the invention according to any one of the eighth to eleventh aspects, when the fuel injection amount changes for each cylinder based on the adhesion of the deposit, the control means controls the fuel injection in each cylinder. Parameters related to the output torque other than the amount are controlled so that the variation in the output torque among the cylinders is suppressed.
[0038]
If the fuel injection amount is changed for each cylinder based on the adhesion of the deposit, the output torque of each cylinder will be different.However, such a variation in the output torque among the cylinders is a parameter other than the fuel injection amount in each cylinder. Is controlled through the control of. Therefore, it is possible to suppress the occurrence of rotational fluctuation in the internal combustion engine due to the variation in the output torque among the cylinders.
[0039]
According to a thirteenth aspect of the present invention, in the twelfth aspect of the present invention, the control means controls the parameter such that the output torque of the cylinder having a high output torque among the cylinders is reduced based on the operation of the cylinder. It was taken.
[0040]
After changing the fuel injection amount for each cylinder based on the adhesion of the deposit, since the output torque is reduced for the cylinders with high output torque among the cylinders, the variation in the output torque among the cylinders can be accurately determined. Can be suppressed.
[0041]
According to a fourteenth aspect of the present invention, in the twelfth aspect of the present invention, the control means controls the parameter such that an output torque based on the operation of the cylinder increases for a cylinder having a low output torque among the cylinders. It was taken.
[0042]
After changing the fuel injection amount for each cylinder based on the adhesion of the deposit, the output torque of each of the cylinders having a low output torque is increased, so that the variation in the output torque among the cylinders can be accurately determined. Can be suppressed.
[0043]
In the invention according to claim 15, in the invention according to any one of claims 8 to 14, in the multi-cylinder internal combustion engine, a maximum lift amount of an intake valve is variable according to an engine operation state, The control means controls the fuel injection amount for each cylinder according to the amount of deposit attached to the intake system for each cylinder at least in the engine operating region where the maximum lift amount is small.
[0044]
When the maximum lift of the intake valve is reduced, the ratio of the shortage of the intake air due to the deposit on the intake system to the total required intake air becomes large, and the appropriate value of the air-fuel ratio The deviation from this will also be large. For this reason, when the amount of deposits on the intake system differs for each cylinder, the shortage of the intake air amount for each cylinder also greatly deviates from each other, and the air-fuel ratio between the cylinders decreases. The variation may be large. However, by controlling the fuel injection amount for each cylinder in accordance with the amount of deposit on each cylinder, it is possible to suppress a large variation in the air-fuel ratio between the cylinders.
[0045]
The invention according to claim 16 is applied to an internal combustion engine provided with a variable valve timing mechanism for making the valve timing of the intake valve variable, and the valve timing variable so that the valve timing becomes a value suitable for the engine operating state. In a control device for an internal combustion engine that controls a mechanism, detecting means for detecting adhesion of a deposit to an intake system of the internal combustion engine, and closing the intake valve when the detection means detects adhesion of the deposit to the intake system. Control means for controlling the variable valve timing mechanism such that the timing approaches the timing at which the pressure in the intake port of the internal combustion engine reaches a peak value with the pulsation of air in the intake system.
[0046]
In an internal combustion engine, air flowing while pulsating through an intake system is sucked into a combustion chamber via an intake port of the engine. Normally, when the pressure in the intake port of the internal combustion engine reaches a peak value, the valve timing of the intake valve is set to a value suitable for the engine operating state so that the intake valve closes. Is secured as much as possible to improve the engine output. However, if deposits are attached to the intake system and the air circulation area of the intake system is small, the pulsation mode such as the pulsation wavelength of air sucked from the intake system into the combustion chamber changes, and the air in the intake port is changed. The timing at which the pressure reaches a peak is shifted from the closing timing of the intake valve. According to the above configuration, when deposits are attached to the intake system, the closing timing of the intake valve is brought close to the timing at which the pressure in the intake port reaches the peak value. Shortage is suppressed. In addition, it is possible to prevent the air-fuel ratio from deviating from an appropriate value to the rich side due to the shortage of the intake air amount, thereby causing the rotation fluctuation of the internal combustion engine and the like, and reducing the operability of the engine.
[0047]
According to a seventeenth aspect, in the invention according to the sixteenth aspect, the control means sets the timing as the timing at which the pressure in the intake port reaches a peak value and the closing timing of the intake valve become more distant from each other. The control amount at the time of controlling the variable valve timing mechanism so as to approach is increased.
[0048]
The timing at which the pressure in the intake port reaches the peak value changes according to the amount of deposit attached to the intake system. However, as the valve closing timing of the intake valve departs from the above timing, the control amount when controlling the variable valve timing mechanism is increased so that those timings become closer, so that the valve closing timing of the intake valve is reduced by the pressure in the intake port. Can accurately approach the timing at which the peak value is reached. Therefore, it is possible to prevent the intake air amount from becoming insufficient and the air-fuel ratio from being shifted from the appropriate value to the rich side due to the shift of the timing, thereby suppressing a decrease in the operability of the internal combustion engine due to a rotation fluctuation of the engine. it can.
[0049]
According to an eighteenth aspect of the present invention, in the invention according to the sixteenth or seventeenth aspect, the internal combustion engine is a multi-cylinder internal combustion engine having a plurality of cylinders, and the variable valve timing mechanism includes a valve of an intake valve of each cylinder. The timing can be individually changed, and the control unit sets the valve closing timing of the intake valve to a timing that is more than a predetermined period apart from the timing at which the pressure in the intake port reaches a peak value. The variable valve timing mechanism is controlled so as to approach.
[0050]
If the presence or absence of deposits on the intake system and the amount of deposits are different for each cylinder, the amount by which the closing timing of the intake valve departs from the timing at which the pressure in the intake port reaches the peak value also differs for each cylinder. Will be different. However, according to the above configuration, with respect to the cylinders whose timings are separated by a predetermined amount or more, the valve timing variable mechanism is controlled so that the timings are close to each other, and the cylinder timing is changed according to the change in the pulsation mode of the intake air due to the adhesion of the deposit. The shortage of the intake air amount is suppressed. Therefore, the shortage of the intake air amount is different for each cylinder, and the air-fuel ratio among the cylinders is varied, thereby causing the rotation of the internal combustion engine to fluctuate and the operability of the engine to be reduced. it can.
[0051]
According to a nineteenth aspect, in the invention according to any one of the first to eighteenth aspects, the gist is that the internal combustion engine is a direct injection internal combustion engine that directly injects fuel into a combustion chamber.
[0052]
In a direct injection type internal combustion engine that directly injects fuel into the combustion chamber, deposits tend to adhere to the back surface of the back of the intake valve and the inner surface of the intake port near the combustion chamber. However, these problems can be properly dealt with.
[0053]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
An embodiment in which the present invention is applied to an in-cylinder injection spark ignition type four-cylinder engine mounted on an automobile will be described below with reference to FIGS.
[0054]
In the engine 1 shown in FIG. 1, air is sucked into the combustion chambers 2 of the first to fourth cylinders # 1 to # 4 (only the first cylinder # 1 is shown) through the intake passage 3 and the fuel is injected. Fuel is injected and supplied directly from the valve 4. When the mixture of air and fuel is ignited by the ignition plug 5, the mixture is burned, the piston 6 reciprocates, and the crankshaft 7, which is the output shaft of the engine 1, rotates. Then, the air-fuel mixture after combustion is sent out from each combustion chamber 2 to the exhaust passage 8 as exhaust gas.
[0055]
The output of the engine 1 is adjusted by adjusting the opening of the throttle valve 19 (throttle opening) provided in the intake passage 3 when a homogeneous air-fuel mixture in which air and fuel are uniformly mixed is burned at a stoichiometric air-fuel ratio. This is achieved by: That is, when the throttle opening is adjusted, the intake air amount of the engine 1 changes, the fuel injection amount is controlled in accordance with the change, the amount of air-fuel mixture charged into the combustion chamber 2 changes, and the output of the engine 1 changes. Will be adjusted. The throttle opening is adjusted based on the amount of depression of the accelerator pedal 16 operated by the driver (the amount of accelerator depression).
[0056]
In the engine 1, communication between the combustion chamber 2 and the intake passage 3 is opened / closed by opening / closing an intake valve 9, and communication between the combustion chamber 2 and the exhaust passage 8 is opened / closed by an exhaust valve 10. . The intake valve 9 and the exhaust valve 10 open and close with the rotation of the intake camshaft 11 and the exhaust camshaft 12 to which the rotation of the crankshaft 7 is transmitted.
[0057]
The intake camshaft 11 is provided with a variable valve timing mechanism 13 that adjusts the relative rotation phase of the intake camshaft 11 with respect to the crankshaft 7 to advance or retard the valve timing (valve opening period) of the intake valve 9. I have. Further, between the intake camshaft 11 and the intake valve 9, there is provided a maximum lift variable mechanism 14 for continuously varying the maximum lift of the valve 9. The adjustment of the valve timing of the intake valve 9 by the variable valve timing mechanism 13 and the adjustment of the maximum lift of the intake valve 9 by the maximum lift variable mechanism 14 are uniformly performed on the intake valves 9 of the cylinders # 1 to # 4. Is done.
[0058]
The vehicle is equipped with an electronic control unit 15 that controls the operation of the engine 1. Through the electronic control unit 15, fuel injection control, ignition timing control, throttle opening control, valve timing control of the intake valve 9, and maximum lift control of the engine 1 are performed. Further, detection signals from the following various sensors are input to the electronic control unit 15.
[0059]
A crank position sensor 25 that outputs a signal corresponding to the rotation of the crankshaft 7;
A cam position sensor 26 that outputs a signal corresponding to the rotational position of the intake camshaft 11;
[0060]
An accelerator position sensor 17 for detecting a depression amount (acceleration depression amount) of an accelerator pedal 16 which is depressed by a driver.
A throttle position sensor 20 for detecting a throttle opening;
[0061]
An air flow meter 18 for detecting a flow rate of air passing through the intake passage 3;
A pressure sensor 22 that can detect, for each cylinder, a pressure in an intake port 21 which is a portion connected to each of the combustion chambers 2 of the first to fourth cylinders # 1 to # 4 in the intake passage 3.
[0062]
An air-fuel ratio sensor 23 that detects the oxygen concentration of the exhaust gas discharged from the combustion chambers 2 of the first to fourth cylinders # 1 to # 4 for each cylinder and outputs a signal corresponding to the oxygen concentration.
An oxygen sensor that outputs a rich signal or a lean signal based on the oxygen concentration in the exhaust gas after the exhaust gas discharged from the combustion chambers 2 of the first to fourth cylinders # 1 to # 4 joins in the exhaust passage 8. 24.
[0063]
Next, the fuel injection amount control of the engine 1 when the homogeneous air-fuel mixture is burned at the stoichiometric air-fuel ratio will be described.
In such fuel injection amount control, an injection amount command value is calculated based on an engine operating state such as an engine rotation speed and an engine load, and the fuel injection valve 4 is controlled through the electronic control unit 15 so that an amount of fuel corresponding to the command value is injected. Is realized by performing the drive control of.
[0064]
The engine speed is determined based on a detection signal from the crank position sensor 25, and the engine load is determined based on a parameter related to the intake air amount of the engine 1 and the engine speed. The parameters related to the intake air amount of the engine 1 include the intake air amount obtained from the detection signal of the air flow meter 18, the accelerator depression amount obtained from the detection signal of the accelerator position sensor 17, and the detection signal of the throttle position sensor 20. The required throttle opening and the like are used.
[0065]
When the engine 1 is in a stable operation state after completion of warm-up, air-fuel ratio feedback for accurately adjusting the average air-fuel ratio of the first to fourth cylinders # 1 to # 4 to the target value, that is, the stoichiometric air-fuel ratio. Control is performed. This air-fuel ratio feedback control is to increase or decrease the fuel injection amount command value depending on whether the average air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.
[0066]
When the average air-fuel ratio is richer than the stoichiometric air-fuel ratio and a rich signal is output from the oxygen sensor 24, the feedback correction value FAF used for correcting the fuel injection amount command value is reduced. Then, based on the fuel injection amount command value corrected by the correction value FAF, the drive control of each of the fuel injection valves 4 of the first to fourth cylinders # 1 to # 4 is performed, so that each of the cylinders # 1 to # 4 is controlled. The fuel injection amount is reduced and the average air-fuel ratio is adjusted to the lean side.
[0067]
When the average air-fuel ratio is leaner than the stoichiometric air-fuel ratio and a lean signal is being output from the oxygen sensor 24, the feedback correction value FAF is increased. Then, based on the fuel injection amount command value corrected by the correction value FAF, the drive control of each of the fuel injection valves 4 of the first to fourth cylinders # 1 to # 4 is performed, so that each of the cylinders # 1 to # 4 is controlled. The fuel injection amount is increased and the average air-fuel ratio is adjusted to the rich side.
[0068]
As described above, by performing the air-fuel ratio feedback control, even if the average air-fuel ratio of all cylinders # 1 to # 4 deviates from the stoichiometric air-fuel ratio for some reason, the deviation is corrected and the average air-fuel ratio is changed to the stoichiometric air-fuel ratio. Can be adjusted to exactly. One of the causes of the deviation of the average air-fuel ratio from the stoichiometric air-fuel ratio is that deposits adhere to the intake system of the engine 1, particularly to the back surface of the umbrella portion of the intake valve 9, or to the inner surface of the intake port 21 near the combustion chamber 2. Is conceivable.
[0069]
Next, the control of the maximum lift of the intake valve 9 and the control of the opening of the throttle valve 19 will be described.
The maximum lift amount of the intake valve 9 is controlled to a value suitable for the engine operating state by controlling the drive of the maximum lift amount variable mechanism 14 through the electronic control unit 15 based on the engine speed, the engine load, and the like. For example, under the condition that the engine rotation speed is constant, the maximum lift of the intake valve 9 is increased as the engine load increases to make it easier to secure the intake air amount of the engine 1. This is because the larger the engine load, the higher the engine output is required, and the larger the amount of intake air required to obtain the output.
[0070]
On the other hand, the throttle valve 19 is controlled to be opened through the electronic control unit 15 as the accelerator depression amount representing the driver's output request for the engine 1 increases. When the homogeneous air-fuel mixture is burned at the stoichiometric air-fuel ratio, the larger the throttle opening, the larger the intake air amount of the engine 1 and the larger the fuel injection amount accordingly. The amount of the air-fuel mixture to be increased increases, and the engine output increases. Thus, an engine output corresponding to the driver's output request for the engine 1 can be obtained.
[0071]
By the way, in an engine operation region where the required intake air amount is small, for example, in an engine low load region such as during idling operation, the throttle valve 19 is controlled to close to adjust the intake air amount to a required value. Is done. As a result, the intake resistance of the engine 1 increases, resulting in a pump loss, which adversely affects the fuel efficiency of the engine 1. Therefore, in recent years, it has been proposed that the throttle valve 19 is fixed on the open side when the engine load is low, and the adjustment of the intake air amount is realized by making the maximum lift amount of the intake valve 9 variable in a low lift region. In this case, the increase in the intake resistance of the engine 1 due to the control of the throttle valve 19 to the closed side is suppressed, so that the fuel efficiency of the engine 1 is improved.
[0072]
When the intake air amount is adjusted by varying the maximum lift amount of the intake valve 9 when the engine is under a low load as described above, the maximum lift amount of the intake valve 9 is set to an extremely small value because the required intake air amount is small. You. However, in such a state, if deposits adhere to the intake system of the engine 1 and the air circulation area of the intake system becomes small, a shortage of the intake air amount due to the adhesion of the deposits is required. It is larger than the intake air volume. Therefore, the deviation of the average air-fuel ratio of all the cylinders # 1 to # 4 toward the rich side due to the shortage of the intake air amount also increases.
[0073]
The deviation of the average air-fuel ratio toward the rich side is suppressed by reducing the fuel injection amount by the feedback correction value FAF during the air-fuel ratio feedback control. However, even if the deviation of the average air-fuel ratio to the rich side can be suppressed by the air-fuel ratio feedback control, it is inevitable that the amount of the air-fuel mixture to be burned will be smaller than appropriate at this time. Insufficient air volume causes engine 1 to fluctuate in rotation and the like. Therefore, when the average air-fuel ratio shifts to the rich side, the rotation of the engine 1 fluctuates due to this, and the engine operation becomes unstable.
[0074]
Note that the above-mentioned problem with the deposit is limited to the engine 1 that secures a necessary intake air amount by varying the maximum lift amount of the intake valve 9 while individualizing the throttle valve 19 on the opening side in an engine low load region. Not something. For example, a similar problem occurs in an engine that secures a necessary intake air amount by controlling the opening degree of the throttle valve 19 while fixing the maximum lift amount of the intake valve 9 when the engine is under a low load.
[0075]
Here, a procedure for suppressing the engine operation from becoming unstable due to the adhesion of the deposit to the intake system will be described with reference to FIGS. 2 and 3.
FIG. 2 is a flowchart showing an intake control routine for controlling the maximum lift of the intake valve 9 and controlling the opening of the throttle valve 19 when deposits adhere to the intake system. FIG. 3 is used to explain how the control modes of the maximum lift amount control and the throttle opening degree control change depending on the presence or absence of deposit on the intake system when the engine is under a low load. It is a time chart.
[0076]
The intake control routine shown in FIG. 2 is executed by the electronic control unit 15 at, for example, a time interruption every predetermined time. In this routine, first, it is determined whether or not deposits have adhered to the intake system (S101).
[0077]
Such a determination is made, for example, that one or more of the air-fuel ratios of the cylinders # 1 to # 4 obtained from the detection signal of the air-fuel ratio sensor 23 during the air-fuel ratio feedback control is shifted from the stoichiometric air-fuel ratio by a predetermined amount to the rich side. This is performed based on whether or not the user is away. That is, when one or more of the air-fuel ratios of the cylinders # 1 to # 4 is shifted to the rich side by a predetermined amount or more due to the adhesion of the deposit to the intake system, the amount of the deposit attached to the intake system is reduced to the engine 1 Is estimated to have reached a predetermined value or more that has an adverse effect on the intake air amount, and an affirmative determination is made in step S101.
[0078]
Further, the determination as to whether or not the deposit has occurred on the intake system may be made based on the rotation fluctuation of the crankshaft 7. This rotational fluctuation is obtained, for example, by calculating the angular velocity when the crankshaft 7 passes a predetermined crank angle in the combustion stroke for each of the cylinders # 1 to # 4, and calculating the angular velocity of the cylinder in the previous combustion stroke and the angular velocity of the cylinder in the current combustion stroke. It can be obtained by calculating the difference from the angular velocity. When deposits adhere to the intake system, since the amount of deposits differs for each of the cylinders # 1 to # 4, the angular velocity also takes a different value for each of the cylinders # 1 to # 4. Accordingly, the angular velocity of each of the cylinders # 1 to # 4 causes a difference due to the adhesion of the deposit, which leads to the fluctuation of the rotation of the crankshaft 7. Therefore, it is determined whether the adhesion of the deposit to the intake system based on the rotation fluctuation. Can be determined.
[0079]
If a negative determination is made in step S101, it means that the deposit has not adhered to the intake system enough to cause a problem. In this state, in order to improve the fuel efficiency of the engine 1, the throttle opening is fixed to the open value as shown in FIG. 3C when the engine is under a low load, and the maximum lift amount of the intake valve 9 is increased. Is controlled so that the required intake air amount is obtained in the low lift region as shown in FIG. As described above, the throttle opening control and the maximum lift amount control suppress the increase in the intake resistance of the engine 1 and improve the fuel efficiency.
[0080]
On the other hand, if an affirmative determination is made in step S101 (FIG. 2), the maximum lift amount of the intake valve 9 is fixed to a predetermined increasing value (S102), and further, the intake air amount is adjusted to a required value. The throttle opening control is executed (S103).
[0081]
For example, when it is determined that the deposit has adhered to the intake system as shown in FIG. 3A when the engine is under a low load, the maximum lift amount of the intake valve 9 is reduced after the timing t in FIG. As shown in FIG. 3B, the value is raised to a predetermined value on the increasing side, and then fixed. By fixing the maximum lift amount to a predetermined increase value in this manner, the shortage of the intake air amount with respect to the required amount due to the adhesion of the deposit to the intake system is suppressed. For this reason, the deviation of the average air-fuel ratio of all the cylinders # 1 to # 4 to the rich side due to the shortage of the intake air amount is suppressed, and the deviation causes rotation fluctuation of the engine 1 and unstable engine operation. Is suppressed.
[0082]
By fixing the maximum lift amount to a predetermined value on the increasing side, shortage of the intake air amount is suppressed. Further, the excess amount of intake air caused by fixing the maximum lift amount to a predetermined increase value as described above is absorbed by adjusting the intake air amount by controlling the throttle opening. Therefore, after the timing t, the throttle opening changes to the closed side as shown in FIG. 3C, and the intake air amount is adjusted to a required value in the closed side opening region. Be controlled.
[0083]
According to the embodiment described above, the following effects can be obtained.
(1) Even if deposits adhere to the intake system of the engine 1, at that time, the maximum lift amount of the intake valve 9 is increased to a predetermined increase value, and the intake air amount is increased. Therefore, the shortage of the intake air amount due to the adhesion of the deposit to the intake system is suppressed, and the shortage of the intake air amount is suppressed. Deviation from a certain stoichiometric air-fuel ratio to the rich side is suppressed. In addition, it is possible to suppress a decrease in the operability of the engine 1 due to the rotation fluctuation of the engine 1 caused by the deviation of the average air-fuel ratio.
[0084]
(2) The increase in the maximum lift amount as described above is also performed at a low engine load, such as during idling operation when the required intake air amount decreases. At such a low engine load, the required amount of intake air is small, so the maximum lift amount of the intake valve 9 is set to an extremely small value. In this state, if deposits are attached to the intake system, the shortage of the intake air amount will make up a large proportion of the total required intake air amount, and the average air-fuel ratio accompanying the shortage will be large. Is also a big problem. However, since the shortage of the intake air amount is suppressed by the increase in the maximum lift amount described above, it is possible to suppress the above-described problem due to the shortage of the intake air amount.
[0085]
(3) When the maximum lift amount is fixed to a predetermined increasing value when deposits adhere to the intake system, the excess intake air amount is absorbed by adjusting the intake air amount by controlling the throttle opening. Therefore, it is possible to suppress the occurrence of an excessive intake air amount and adjust the intake air amount to a required value.
[0086]
[Second embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a flowchart illustrating an intake control routine according to the present embodiment. In this embodiment, when it is determined that deposits are attached to the intake system of the engine 1 (S201: YES), the maximum lift amount of the intake valve 9 is controlled to increase by an amount corresponding to the attached amount of the deposits. (S202). The deposit amount can be estimated, for example, from the amount of the air-fuel ratio of the cylinders # 1 to # 4, which is the richest side with respect to the stoichiometric air-fuel ratio, shifted to the rich side. Therefore, as the air-fuel ratio shifts toward the rich side, it is estimated that the amount of deposit attached to the intake system increases, and the maximum lift of the intake valve 9 is controlled to increase.
[0087]
Here, the control mode of the maximum lift amount control of the intake valve 9 and the control of the opening degree of the throttle valve 19 when it is determined that the deposit is attached when the engine is under a low load will be described with reference to a time chart of FIG. I do.
[0088]
When it is determined that deposits have been attached to the intake system as shown in FIG. 5A at a low engine load (timing t2), the maximum lift amount of the intake valve 9 is reduced as shown in FIG. 5B. As shown in (2), the amount is increased by an amount corresponding to the amount of deposit, and in this state, control is performed so that a required intake air amount is obtained. Since the required intake air amount is secured even when deposits are deposited by such maximum lift amount control, the throttle opening is maintained at a fixed value on the opening side as shown in FIG. 5C. Therefore, the throttle valve 19 is controlled to the closed side in accordance with the adhesion of the deposit when the engine load is low as in the first embodiment, and the improvement of the fuel efficiency of the engine 1 is not hindered.
[0089]
According to the present embodiment, the following effects can be obtained.
(4) Even if deposits adhere to the intake system of the engine 1, at that time, the maximum lift amount of the intake valve 9 is controlled to increase by an amount corresponding to the amount of deposits. The larger the amount of deposit, the greater the shortage of intake air.However, by controlling the maximum lift as described above to increase the amount of intake air, the shortage of intake air due to deposit adhesion can be reduced. It can be suppressed exactly. Accordingly, due to the shortage of the intake air amount due to the adhesion of the deposit to the intake system, the average air-fuel ratio of all the cylinders # 1 to # 4 at the time of combustion at the stoichiometric air-fuel ratio of the homogeneous mixture is reduced from the stoichiometric air-fuel ratio which is the target value The shift to the rich side is suppressed. Then, it is possible to suppress a decrease in the operability of the engine 1 due to the rotation fluctuation of the engine 1 caused by the difference in the average air-fuel ratio.
[0090]
(5) At the time of engine low-load operation when deposits are adhered, the required intake air amount can be secured by the maximum lift amount control, so that the throttle opening is fixed to the value on the opening side. Can be stored. For this reason, it is not necessary to control the throttle valve 19 to the closed side when the deposit is attached, and it is possible to suppress the improvement of the fuel efficiency of the engine 1 from being hindered by the control to the closed side.
[0091]
[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
In this embodiment, when the amount of deposit on the intake system differs for each of the cylinders # 1 to # 4, the air-fuel ratio of each of the cylinders # 1 to # 4 approaches the average air-fuel ratio of all the cylinders # 1 to # 4. In this manner, the fuel injection amount is corrected for each cylinder so as to suppress variations in the air-fuel ratio among the cylinders # 1 to # 4. In this way, by suppressing the variation in the air-fuel ratio among the cylinders # 1 to # 4, it is possible to suppress the occurrence of rotational fluctuations in the engine 1 due to the variation and the unstable engine operation. Can be.
[0092]
FIG. 6 is a flowchart showing a fuel injection amount correction routine for executing the above-described fuel injection amount correction. The fuel injection amount correction routine is executed by the electronic control unit 15 at, for example, an angle interruption every predetermined crank angle.
[0093]
In the fuel injection amount correction routine, first, it is determined whether the air-fuel ratio feedback control is being executed (S301). During the air-fuel ratio feedback control, the fuel injection amounts of the cylinders # 1 to # 4 are uniformly increased and decreased based on the feedback correction value FAF so that the average air-fuel ratio of all the cylinders # 1 to # 4 becomes the stoichiometric air-fuel ratio. Is done. In this state, as shown in FIG. 7, the average air-fuel ratio of all the cylinders # 1 to # 4 becomes the stoichiometric air-fuel ratio while the fuel injection amounts of the cylinders # 1 to # 4 become uniform.
[0094]
However, at this time, if the amount of the deposit attached to the intake system differs for each of the cylinders # 1 to # 4 and the intake air amount differs for each of the cylinders # 1 to # 4, as shown in FIG. The air-fuel ratio varies among the cylinders # 1 to # 4. In order to suppress such variations in the air-fuel ratio, the processes of steps S302 and S303 in the fuel injection amount correction routine (FIG. 6) are executed. In step S302, the deviation amounts of the air-fuel ratios of the cylinders # 1 to # 4 with respect to the average air-fuel ratio (stoichiometric air-fuel ratio) are calculated. Subsequently, in step S303, the fuel injection amount is corrected for each of the cylinders # 1 to # 4 based on the deviation calculated as described above so that the air-fuel ratio of each of the cylinders # 1 to # 4 approaches the average air-fuel ratio. Is done.
[0095]
That is, in a cylinder leaner than the average air-fuel ratio, the fuel injection amount is increased and corrected in accordance with the shift amount of the air-fuel ratio to the lean side with respect to the average air-fuel ratio. The increase correction amount of the fuel injection amount at this time is set to increase as the deviation amount of the air-fuel ratio toward the lean side increases. Further, in a cylinder richer than the average air-fuel ratio, the fuel injection amount is corrected to decrease in accordance with the amount of deviation of the air-fuel ratio from the average air-fuel ratio to the rich side. At this time, the fuel injection reduction correction amount is set to increase as the deviation amount of the air-fuel ratio toward the rich side increases. By correcting the fuel injection amount for each of the cylinders # 1 to # 4, the air-fuel ratio of each of the cylinders # 1 to # 4 approaches the average air-fuel ratio (the stoichiometric air-fuel ratio) of all the cylinders # 1 to # 4. Can be
[0096]
In addition, as the fuel injection amount correction for each of the cylinders # 1 to # 4, in addition to the fuel injection amount correction for each cylinder in S303, the fuel injection amount correction based on the feedback correction value FAF is also performed. . By these two fuel injection amount corrections, the greater the amount of deposits in each of the cylinders # 1 to # 4, the more the fuel injection amount of each of the cylinders # 1 to # 4 is corrected to a larger amount.
[0097]
When the fuel injection amount correction for each cylinder in S303 described above is completed for all cylinders # 1 to # 4, the fuel injection amount differs for each cylinder # 1 to # 4 as shown in FIG. Although the air-fuel ratio becomes uniform among the cylinders # 1 to # 4, the amount of air-fuel mixture charged into the combustion chamber 2 varies among the cylinders. For this reason, the output torque among the cylinders # 1 to # 4 varies, and the variation may cause the engine 1 to vary in rotation. In order to suppress such variations in the output torque, the processes of steps S304 to S306 in the fuel injection amount correction routine (FIG. 6) are executed.
[0098]
That is, when it is determined in step S304 that the above-described fuel injection amount correction has been completed for all cylinders # 1 to # 4, the output torque of each cylinder based on the operation of each cylinder # 1 to # 4 is calculated (S305). ). Such an output torque can be calculated, for example, from the rotation fluctuation of the crankshaft 7 based on the operation of each of the cylinders # 1 to # 4, and as shown in FIG. It will be the corresponding value. Then, in the processing of the subsequent step S306 (FIG. 6), the torque is reduced in the cylinder having the higher output torque among the cylinders # 1 to # 4.
[0099]
For example, a deviation amount of the output torque of each of the other cylinders from the output torque of the cylinder having the smallest output torque is obtained, and a parameter other than the fuel injection amount is controlled in the other cylinder based on the deviation amount, thereby reducing the output torque. Is achieved. Such parameters include an ignition timing and a fuel injection timing. As the deviation increases, at least one of the ignition timing and the fuel injection timing is controlled to be more retarded, so that a cylinder having a high output torque has the same output. The torque can be reduced.
[0100]
Here, the output torque, the ignition timing retard amount, and the fuel injection for each of the cylinders # 1 to # 4 when the variation of the output torque among the cylinders is suppressed by both the ignition timing retard and the fuel injection timing retard FIG. 9 shows the timing delay amount.
[0101]
As shown in the figure, the larger the deviation of the output torque of each of the other cylinders from the output torque of the cylinder with the smallest output torque, the larger the ignition timing retard amount and the fuel injection timing retard amount. Is done. As a result, the output torque of the other cylinder is reduced in accordance with the output torque of the cylinder with the smallest output torque, and the output torque of each of the cylinders # 1 to # 4 is made uniform. Therefore, when the fuel injection amount is corrected for each cylinder so that the air-fuel ratio of each of the cylinders # 1 to # 4 approaches the average air-fuel ratio, variations in the output torque among the cylinders may cause rotational fluctuations in the engine 1. Is suppressed.
[0102]
In order to make the output torques of the cylinders # 1 to # 4 uniform, the output torque of each cylinder was adjusted to that of the cylinder with the smallest output torque. Instead, the output torque of each cylinder was adjusted to the cylinder with the largest output torque. The output torque of another cylinder may be increased. In this case, as an increase in the output torque of each cylinder, for example, the ignition timing or the fuel injection timing is advanced.
[0103]
According to the embodiment described above, the following effects can be obtained.
(6) Even if the amount of deposit on the intake system differs for each of the cylinders # 1 to # 4, it is based on the fuel injection amount correction and the feedback correction value FAF for each of the cylinders # 1 to # 4 in S303 described above. With the uniform fuel injection amount correction for all cylinders # 1 to # 4, the fuel injection amount is reduced for each cylinder based on the deposit amount. In such a correction of the fuel injection amount for each cylinder, the larger the amount of deposit, the larger the correction amount. For this reason, it is possible to suppress the difference in the air-fuel ratio from the initial state toward the rich side from being different for each of the cylinders # 1 to # 4 due to the difference in the amount of deposit of the cylinders # 1 to # 4. Can be. In addition, it is possible to suppress a decrease in the operability of the engine 1 due to the rotation fluctuation of the engine 1 caused by the variation in the air-fuel ratio between the cylinders.
[0104]
(7) The fuel injection amount correction for each of the cylinders # 1 to # 4 in S303 described above is performed by changing the average air-fuel ratio to the stoichiometric air-fuel ratio by the uniform fuel injection amount correction for all cylinders # 1 to # 4 in the air-fuel ratio feedback control. And then executed. The correction of the fuel injection amount for each of the cylinders # 1 to # 4 in S303 causes the fuel injection amount to be increased for the cylinders leaner than the average air-fuel ratio (the stoichiometric air-fuel ratio) of all the cylinders # 1 to # 4. Is performed, and for cylinders that are richer than the average air-fuel ratio, the fuel injection amount is reduced. Further, the correction amount of the increase / decrease of the fuel injection amount becomes larger as the deviation amount of the air-fuel ratio of each of the cylinders # 1 to # 4 from the average air-fuel ratio becomes larger. Therefore, it is possible to accurately bring the air-fuel ratio of each of the cylinders # 1 to # 4 closer to the stoichiometric air-fuel ratio, which is the target value of the average air-fuel ratio, and accurately suppress the variation in the air-fuel ratio among the cylinders # 1 to # 4. it can.
[0105]
(8) The fuel injection amount correction for each cylinder # 1 to # 4 in S303 and the uniform fuel injection amount correction for all cylinders # 1 to # 4 based on the feedback correction value FAF are performed when the required intake air amount is small. It is also executed when the engine is under a low load, such as during idling operation when the load decreases. At such a low engine load, the required intake air amount is small, so the actual intake air amount is adjusted to an extremely small value. In this state, if deposits are attached to the intake system, the shortage of the intake air amount will make up a large proportion of the required intake air amount, and the air-fuel ratio will deviate from the appropriate value. Will also be large. For this reason, when the amount of deposit attached to each of the cylinders # 1 to # 4 is different, the shortage of the intake air amount for each of the cylinders # 1 to # 4 is also largely different from each other. The variation in the air-fuel ratio among # 1 to # 4 may be large. However, the fuel injection amount correction can suppress the variation in the air-fuel ratio among the cylinders # 1 to # 4.
[0106]
[Fourth embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
In the engine 1, valve timing control of the intake valve 9 is performed so that the intake air amount is as large as possible to improve the engine output. That is, in the intake stroke, air is sucked into the combustion chamber 2 while pulsating. Therefore, when the pressure in the intake port 21 reaches a peak value, the valve timing is variable through the electronic control device 15 so that the intake valve 9 closes. The mechanism 13 is driven, so that the maximum amount of intake air is ensured.
[0107]
However, when the air circulation area of the intake port 21 becomes small due to the adhesion of the deposit to the intake system, the pulsation mode such as the pulsation wavelength of the intake air changes, and the timing at which the pressure in the intake port 21 reaches the peak value is advanced. Side or retard side. In this embodiment, when the timing at which the pressure in the intake port 21 reaches the peak value is shifted due to the adhesion of the deposit, the valve timing is corrected so that the closing timing of the intake valve 9 approaches the same timing. is there. By performing such valve timing correction, the timing at which the pressure in the intake port 21 reaches a peak value is shifted from the timing at which the intake valve 9 closes, resulting in a shortage of the intake air amount, and the air-fuel ratio becomes richer than the appropriate value. It is possible to prevent the engine 1 from rotating and fluctuating, thereby causing unstable operation of the engine.
[0108]
FIG. 10 is a flowchart showing a valve timing correction routine for performing the valve timing correction. This valve timing correction routine is executed by the electronic control unit 15 at, for example, an angle interruption every predetermined crank angle.
[0109]
In the valve timing correction routine, when it is determined that the deposit has adhered to the intake system (S401: YES), the actual timing at which the pressure in the intake port 21 reaches the peak value (actual peak timing maxR) is determined by the pressure sensor. It is obtained for each of the cylinders # 1 to # 4 based on the detection signal of S22 (S402).
[0110]
Here, the transition tendency of the pressure in the intake port 21 of the predetermined cylinder during the intake stroke is shown in FIGS. In these figures, the solid line shows the transition of the pressure in the intake port 21 in a state where there is no deposit, and the timing when the valve closing timing Lc of the intake valve 9 reaches the peak value of the pressure (theoretical peak timing) maxtV). That is, normally, the valve timing control of the intake valve 9 is executed through the electronic control device 15 so that the valve closing timing Lc becomes the theoretical peak timing maxtV.
[0111]
On the other hand, when deposits occur in the cylinder, the pulsation mode of the pressure in the intake port 21 changes, and the pressure changes as indicated by broken lines in FIGS. 11 and 12, for example. The timing at which the peak value is reached is shifted toward the retard side (FIG. 11) or shifted toward the advance side (FIG. 12). The actual peak timing maxR in step S402 is determined as the timing at which the pressure becomes highest in a predetermined range (Lc-TC to Lc + TC) including the valve closing timing Lc of the intake valve 9. As the predetermined range (Lc−TC to Lc + TC), for example, a maximum range in which the timing at which the pressure reaches the peak value due to the deposition of the deposit can be adopted.
[0112]
In step S403 of the valve timing correction routine (FIG. 10), valve timing correction for correcting the valve timing of the intake valve 9 based on the theoretical peak timing maxtV and the actual peak timing maxtR for each of the cylinders # 1 to # 4. The value tH is calculated. That is, by subtracting the actual peak timing maxtR from the theoretical peak timing maxtV for each of the cylinders # 1 to # 4, the valve timing correction value tH is calculated for each of the cylinders # 1 to # 4. When the valve timing correction value tH becomes a positive value, the valve timing of the intake valve 9 is advanced in the valve timing correction, and when the valve timing correction value tH becomes a negative value, the valve timing of the intake valve 9 is corrected in the correction. This is for retarding the valve timing.
[0113]
When the actual peak timing maxtR shifts to the retard side from the theoretical peak timing maxtV as shown in FIG. 11 due to the adhesion of the deposit, the valve timing correction value tH becomes a negative value, that is, the valve timing of the intake valve 9 is retarded. This is the value to be corrected. When the actual peak timing maxtR deviates from the theoretical peak timing maxtV toward the advance side as shown in FIG. 12 due to the adhesion of the deposit, the valve timing correction value tH becomes a positive value, that is, the valve timing of the intake valve 9 is changed. This is the value to be advanced.
[0114]
In the following step S404, an average correction value tHav which is an average value of the valve timing correction values tH for each of the cylinders # 1 to # 4 is calculated. The absolute value of the average correction value tHav increases as the actual peak timing maxtR of each of the cylinders # 1 to # 4 departs from the theoretical peak timing maxtV (the normal closing timing Lc of the intake valve 9). When the average correction value tHav is out of the allowable range (-DP to DP) (S405: NO), the valve timing of the intake valve 9 is uniformly corrected for all the cylinders # 1 to # 4 by the average correction value tHav. Is done. By this valve timing correction, the closing timing of the intake valve 9 is made closer to the timing (actual peak timing maxtR) at which the pressure in the intake port 21 reaches the peak value in each of the cylinders # 1 to # 4.
[0115]
According to the embodiment described above, the following effects can be obtained.
(9) When deposits adhere to the intake system, the valve timing of the intake valve 9 is advanced and retarded so that the closing timing of the intake valve 9 approaches the actual peak timing maxR. Excessive shortage of the intake air amount due to the deviation is suppressed. Due to the shortage of the intake air amount, the air-fuel ratio of each of the cylinders # 1 to # 4 and the average air-fuel ratio of all the cylinders # 1 to # 4 deviate from an appropriate value to the rich side, causing rotation fluctuation of the engine 1 and causing engine rotation. A decrease in drivability can be suppressed.
[0116]
(10) The actual peak timing maxR changes in accordance with the amount of deposit attached to the intake system. However, as the actual peak timing maxtR departs from the closing timing Lc (theoretical peak timing maxtV) of the intake valve 9, the absolute value of the average correction value tHav increases, and the advance and retard correction of the valve timing increases. Is done. Therefore, the valve closing timing of the intake valve 9 can be accurately brought close to the actual peak timing maxtR by the advance / retard correction of the valve timing.
[0117]
[Other embodiments]
Each of the above embodiments can be modified, for example, as follows.
In the first to fourth embodiments, the present invention is applied to the direct injection type engine 1. However, the present invention may be applied to, for example, a port injection type engine that injects fuel into the intake port 21. . It should be noted that in the direct injection type engine 1, deposits tend to adhere to the intake system, and various problems are likely to occur due to a shortage of intake air due to the deposits. Will be performed.
[0118]
In the first embodiment, the present invention is applied to the engine 1 that secures a necessary intake air amount by adjusting the maximum lift amount of the intake valve 9 while fixing the throttle valve 19 to the open side when the engine is under a low load. The present invention may be applied to the engine 1 that secures a necessary intake air amount by another method. For example, the present invention may be applied to an engine that secures a required intake air amount by controlling the opening degree of the throttle valve 19 while fixing the maximum lift amount of the intake valve 9 when the engine is under a low load.
[0119]
In the second embodiment, the maximum lift control when deposits adhere to the intake system is uniformly performed for each of the cylinders # 1 to # 4, but is individually performed for each of the cylinders # 1 to # 4. May be. In this case, as the maximum lift variable mechanism that controls the maximum lift of the intake valve 9 for each of the cylinders # 1 to # 4, the intake valve 9 may be, for example, a so-called electromagnetically driven valve that is opened and closed by an electromagnetic force. Can be The electromagnetic drive valve (intake valve 9) is individually driven through the electronic control unit 15 for each of the cylinders # 1 to # 4 so that the maximum lift amount is controlled to increase for each of the cylinders # 1 to # 4. Controlled. In the maximum lift control for each of the cylinders # 1 to # 4, it is preferable that the larger the deposit amount of each of the cylinders # 1 to # 4, the larger the maximum lift. Note that the deposit amount of each of the cylinders # 1 to # 4 can be estimated based on the air-fuel ratio of each of the cylinders # 1 to # 4 and the rotation fluctuation of the crankshaft based on the operation of each of the cylinders # 1 to # 4. it can.
[0120]
In the third embodiment, in order to suppress the variation in the air-fuel ratio among the cylinders # 1 to # 4, each of the cylinders # 1 to # 4 approaches the average air-fuel ratio of all the cylinders # 1 to # 4. Although the fuel injection amount is corrected for every # 4, the present invention is not limited to this. For example, the intake valve 9 is made to be the above-described electromagnetically driven valve or the like so that the maximum lift amount can be individually changed for each of the cylinders # 1 to # 4, and the air-fuel ratio of each cylinder # 1 to # 4 approaches the average air-fuel ratio. Thus, the maximum lift amount may be controlled for each cylinder. In this case, as in the above case, it is preferable that the larger the deposit amount of each of the cylinders # 1 to # 4, the larger the maximum lift amount. Thus, it is possible to prevent the amount of deposit from being different for each of the cylinders # 1 to # 4 and the shortage of the intake air amount from being different for each of the cylinders. Thus, it is possible to accurately suppress the occurrence of variations in the air-fuel ratio. Since the maximum lift amount control for each of the cylinders # 1 to # 4 at the time of deposit attachment is performed even at the time of a low engine load where the required intake air amount is small, at that time, the control between the cylinders # 1 to # 4 is performed. A large variation in the air-fuel ratio can be suppressed.
[0121]
In the third embodiment, the ignition timing is retarded or the fuel injection timing is retarded for a cylinder having a high output torque to reduce the output torque, but other parameters such as the internal EGR amount are used as parameters for decreasing the output torque. May be used. When the internal EGR amount is used, for example, the intake valve 9 is configured by the above-described electromagnetically driven valve so that the valve timing of the intake valve 9 can be made variable for each of the cylinders # 1 to # 4. For a cylinder having a high output torque, the valve timing of the intake valve 9 is advanced to increase the valve overlap, and the output torque is reduced by increasing the internal EGR amount.
[0122]
In the fourth embodiment, as the valve timing control mechanism for controlling the valve timing of the intake valve 9 for each of the cylinders # 1 to # 4, the intake valve 9 is, for example, the above-described electromagnetically driven valve, and for each of the cylinders # 1 to # 4. The valve timing may be corrected so that the valve closing timing of the intake valve 9 approaches the actual peak timing maxtR. In this case, the valve timing correction of the intake valve 9 is performed for each of the cylinders # 1 to # 4 using the valve timing correction value tH for each of the cylinders # 1 to # 4.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an entire in-cylinder injection spark ignition type four-cylinder engine to which a control device according to a first embodiment is applied;
FIG. 2 is a flowchart showing a procedure of executing a maximum lift control of an intake valve and a control of an opening degree of a throttle valve when deposits adhere to an intake system in the first embodiment;
FIGS. 3 (a) to 3 (c) show control modes of a maximum lift amount control and a throttle opening degree control in the first embodiment in accordance with the presence / absence of deposits on an intake system at a low engine load. Time chart used to explain how it changes.
FIG. 4 is a time chart showing an execution procedure of maximum lift control of an intake valve when deposits adhere to an intake system in a second embodiment.
FIGS. 5A to 5C show control modes of a maximum lift amount control and a throttle opening degree control in the second embodiment in accordance with the presence or absence of a deposit on an intake system at a low engine load. Time chart used to explain how it changes.
FIG. 6 is a flowchart showing a fuel injection amount correction procedure when deposits adhere to the intake system in the third embodiment.
FIG. 7 is a graph showing a fuel injection amount and an air-fuel ratio of each cylinder during an air-fuel ratio feedback control, and an average air-fuel ratio of all cylinders.
FIG. 8 is a graph showing a fuel injection amount and an air-fuel ratio of each cylinder and an average air-fuel ratio of all cylinders when the above-described fuel injection amount correction is performed in accordance with deposits on an intake system.
FIG. 9 shows the fuel injection amount, output torque, and ignition timing delay for each cylinder when suppressing the variation in the output torque of each cylinder when the above-described fuel injection amount correction is performed due to the adhesion of the deposit to the intake system. 5 is a graph showing an angle amount and a fuel injection timing retard amount.
FIG. 10 is a flowchart showing a procedure for correcting a valve timing of an intake valve when a deposit adheres to an intake system in a fourth embodiment.
FIG. 11 is a time chart showing a transition tendency of a pressure in an intake port of a predetermined cylinder in an intake stroke.
FIG. 12 is a time chart showing a transition tendency of a pressure in an intake port of a predetermined cylinder in an intake stroke.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, # 1-# 4 ... First to fourth cylinder, 2 ... Combustion chamber, 3 ... Intake passage, 4 ... Fuel injection valve, 5 ... Spark plug, 6 ... Piston, 7 ... Crankshaft, 8 ... Exhaust Passageway 9 Intake valve 10 Exhaust valve 11 Intake camshaft 12 Exhaust camshaft 13 Valve timing variable mechanism 14 Maximum lift amount variable mechanism 15 Electronic control device (detection means, control means ), 16: accelerator pedal, 17: accelerator position sensor, 18: air flow meter, 19: throttle valve, 20: throttle position sensor, 21: intake port, 22: pressure sensor, 23: air-fuel ratio sensor (detection means), 24 ... oxygen sensor, 25 ... crank position sensor (detection means), 26 ... cam position sensor (detection means).

Claims (19)

The present invention is applied to an internal combustion engine having a maximum lift amount variable mechanism for making the maximum lift amount of the intake valve variable, and controls the maximum lift amount variable mechanism so that the maximum lift amount becomes a value suitable for the engine operating state. In the control device of the internal combustion engine,
Detecting means for detecting adhesion of deposits to an intake system of the internal combustion engine;
Control means for controlling the maximum lift variable mechanism such that the maximum lift of the intake valve is increased when deposit is detected on the intake system by the detection means;
A control device for an internal combustion engine, comprising: The control unit is configured to control the maximum lift amount variable mechanism to increase the maximum lift amount based on detection of deposit adhesion to the intake system at least in an engine operating region where the maximum lift amount is small. 2. The control device for an internal combustion engine according to claim 1, wherein the control device controls: 3. The control device for an internal combustion engine according to claim 1, wherein the control unit controls the maximum lift amount variable mechanism so that the maximum lift amount increases as the amount of deposit attached to the intake system increases. 4. In the internal combustion engine, in the engine operating region where the required intake air amount is small, the throttle valve of the engine is fixed at a predetermined opening on the open side, and the maximum lift amount of the intake valve is variable. In this way, the intake air amount is adjusted to a required value,
The control means controls the maximum lift variable mechanism such that the maximum lift is fixed to a predetermined increase side value based on the adhesion of the deposit to the intake system of the internal combustion engine, and opens the throttle valve. 3. The control device for an internal combustion engine according to claim 1, wherein the degree of intake is controlled to secure a required intake air amount. Applied to a multi-cylinder internal combustion engine having a plurality of cylinders, a control device for an internal combustion engine including a maximum lift variable mechanism capable of changing a maximum lift of an intake valve of the engine for each cylinder,
Detecting means for detecting adhesion of a deposit to an intake system for each cylinder of the internal combustion engine;
Control means for controlling the maximum lift variable mechanism such that the maximum lift of the intake valve is increased for each cylinder in accordance with the amount of deposits on the intake system for each cylinder detected by the detection means. When,
A control device for an internal combustion engine comprising: 6. The internal combustion engine according to claim 5, wherein, when increasing the maximum lift amount, the control unit controls the maximum lift amount variable mechanism so that the increase amount of the maximum lift amount increases as the amount of deposit attached increases. Control device. The control unit is configured to increase the maximum lift amount for each cylinder in accordance with an amount of deposit attached to an intake system for each cylinder at least in an engine operation region where the maximum lift amount is small. The control device for an internal combustion engine according to claim 5 or 6, which controls the variable amount mechanism. Applied to a multi-cylinder internal combustion engine having a plurality of cylinders, a control device for an internal combustion engine that controls the fuel injection amount of the engine to a value suitable for the engine operating state
Detecting means for detecting adhesion of a deposit to an intake system for each cylinder of the internal combustion engine;
Control means for controlling the fuel injection amount to a decreasing side for each cylinder in accordance with the amount of deposit attached to the intake system for each cylinder detected by the detection means;
A control device for an internal combustion engine comprising: 9. The control device for an internal combustion engine according to claim 8, wherein the control unit performs the fuel injection amount control such that, when the fuel injection amount is reduced, the decrease in the fuel injection amount is increased as the deposit amount increases. 10. The control means uniformly increases and decreases the fuel injection amount of all cylinders so that the average air-fuel ratio of all cylinders becomes a target value, and controls the fuel injection amount to a decreasing side for cylinders that are rich with respect to the average air-fuel ratio. 10. The control device for an internal combustion engine according to claim 8, wherein the fuel injection amount is controlled to be increased for a cylinder that is lean with respect to the average air-fuel ratio. 11. The control device for an internal combustion engine according to claim 10, wherein the control unit increases or decreases the amount of fuel injection for each cylinder as the deviation of the air-fuel ratio of each cylinder from the average air-fuel ratio increases. When the fuel injection amount changes for each cylinder based on the adhesion of the deposit, the control means controls parameters related to output torque other than the fuel injection amount in each cylinder to suppress variations in output torque among the cylinders. The control device for an internal combustion engine according to any one of claims 8 to 11, wherein the control is performed such that the control is performed. 13. The control device for an internal combustion engine according to claim 12, wherein the control means controls the parameter such that an output torque based on the operation of the cylinder with a high output torque among the cylinders decreases. 13. The control device for an internal combustion engine according to claim 12, wherein the control unit controls the parameter so that an output torque based on the operation of the cylinder with a low output torque among the cylinders increases. The multi-cylinder internal combustion engine, the maximum lift amount of the intake valve is variable according to the engine operating state,
The control means controls the fuel injection amount for each cylinder in accordance with the amount of deposit attached to the intake system for each cylinder, at least when the maximum lift amount is in an engine operation region where the maximum lift amount is small. 15. The control device for an internal combustion engine according to any one of 14. Control of the internal combustion engine, which is applied to an internal combustion engine having a variable valve timing mechanism for varying the valve timing of an intake valve, and controls the variable valve timing mechanism so that the valve timing is suitable for an engine operating state. In the device,
Detecting means for detecting adhesion of deposits to an intake system of the internal combustion engine;
When deposits are detected on the intake system by the detection means, the closing timing of the intake valve approaches the timing at which the pressure in the intake port of the internal combustion engine reaches a peak value due to pulsation of air in the intake system. A control means for controlling the variable valve timing mechanism,
A control device for an internal combustion engine, comprising: The control means increases the control amount when controlling the variable valve timing mechanism such that the timing at which the pressure in the intake port reaches a peak value and the closing timing of the intake valve are closer to each other. 17. The control device for an internal combustion engine according to claim 16, wherein: The internal combustion engine is a multi-cylinder internal combustion engine having a plurality of cylinders,
The valve timing variable mechanism is capable of individually changing the valve timing of the intake valve of each cylinder,
The control means controls the valve timing variable mechanism such that the valve closing timing of the intake valve approaches the timing of a cylinder which is apart from the timing at which the pressure in the intake port reaches a peak value by a predetermined period or more from the timing at which the pressure in the intake port reaches a peak value. Item 18. The control device for an internal combustion engine according to Item 16 or 17. 19. The control device for an internal combustion engine according to claim 1, wherein the internal combustion engine is a direct injection internal combustion engine that injects fuel directly into a combustion chamber.

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