JP2007120469A - Operation control device for internal combustion engine - Google Patents

Abstract

An operation control device for an internal combustion engine that eliminates or suppresses an air-fuel ratio shift of an air-fuel mixture when a failure occurs in any of the cylinder groups in an engine having a plurality of cylinder groups.
Each bank 2L, 2R is provided with a common air flow meter 78, and each bank 2L, 2R is provided with each bank 2L, 2R with respect to a V-type engine E provided with an intake system that utilizes an inertial supercharging effect. When one of the variable intake control valves 74L, 74R provided in 2L, 2R fails and the air-fuel ratio feedback control is stopped, the bank 2L on the side where the variable intake control valve 74L fails Is corrected to decrease the fuel injection amount, and the fuel injection amount is corrected to be increased for the bank 2R on the side where the variable intake control valve 74R has not failed.
[Selection] Figure 2

Description

  The present invention relates to an operation control device for an internal combustion engine represented by an automobile engine or the like. In particular, the present invention relates to a countermeasure for improving an air-fuel ratio deviation of an air-fuel mixture when a failure occurs in any cylinder group in an internal combustion engine having a plurality of cylinder groups such as a V-type internal combustion engine.

  Conventionally, an internal combustion engine provided with an intake system using an inertial supercharging effect (which increases the volumetric efficiency of the engine by using the intake air pulsation effect of the air column in the intake pipe) as disclosed in, for example, Patent Document 1 below An engine is known. In other words, a low-speed passage having a relatively long passage length and a high-speed passage having a relatively short passage length are provided as intake passages, and the intake air used for intake by opening and closing the variable intake control valve provided in the intake passage. The passage is switched according to the operating state of the engine (rotation speed, etc.). As a result, it is possible to increase the efficiency of charging air into the cylinder by the inertia supercharging effect at both the high speed rotation and the low speed rotation of the engine and increase the engine output.

  The variable intake control valve is provided, for example, in the high-speed passage. When the engine is running at a low speed and high load, the variable intake control valve is closed to allow air to flow through the low-speed passage. In a region (so-called partial load region or the like), the variable intake control valve is opened so that air flows through the high-speed passage. FIG. 8 shows a valve opening / closing control map for performing opening / closing control of the variable intake control valve according to the engine speed and the engine load. In the following description, the case where the low-speed passage is used is described as when the variable intake control valve is closed, and the case where the high-speed passage is used is described as when the variable intake control valve is opened.

  As one of the engine forms, for example, a V-type engine as disclosed in Patent Document 2 below is known. As a general configuration of the intake system of the V-type engine, each bank has a common air flow meter and a surge tank, and an intake passage is branched for each bank on the downstream side of the surge tank so that air is supplied to each cylinder. It has been introduced.

  When the intake system using the inertial supercharging effect is applied to the V-type engine, the low speed passage and the high speed passage are provided for each bank, and the variable intake control valve is provided for each bank. Each will be prepared. Then, the variable intake control valves are opened and closed in synchronization with the engine operating state. In other words, when the engine is running at low speed and high load, both the variable intake control valves are closed to allow air to flow through the low-speed passages of the banks, while in other operating areas, the variable intake control valves are both open. Allow air to flow through the high-speed passages in each bank.

In this type of V-type engine, as the air-fuel ratio control of the air-fuel mixture in each cylinder, feedback control of the air-fuel ratio is performed for each bank. Specifically, as an exhaust system of a V-type engine, each bank is provided with an independent exhaust passage, and an oxygen concentration sensor (hereinafter referred to as an O ₂ sensor) or an air-fuel ratio sensor (hereinafter referred to as an “O ₂ sensor”) is provided in each exhaust passage. (Referred to as A / F sensor). The sensor detects the oxygen concentration or the air-fuel ratio (A / F) in the exhaust gas, and controls (feedback control) the fuel injection amount for each bank so as to achieve a predetermined target air-fuel ratio based on the detected oxygen concentration. ing.

More specifically, the intake air amount to each cylinder is calculated assuming that ½ of the intake air amount (total amount of intake air amount into the engine) detected by the air flow meter is introduced into each bank. The air-fuel ratio in the cylinder is controlled by injecting fuel at a predetermined fuel injection amount with respect to the intake air amount of each cylinder. Then, the fuel injection amount is increased and corrected for the cylinders in the bank whose air-fuel ratio is detected to be lean with respect to the target air-fuel ratio by the O ₂ sensor or A / F sensor, while the O ₂ sensor or A / F is corrected. The fuel injection amount is corrected to decrease for the cylinders in the bank in which the sensor detects that the air-fuel ratio is rich with respect to the target air-fuel ratio.

In such air-fuel ratio feedback control, the air-fuel ratio feedback control is performed when the target air-fuel ratio is stoichiometric (theoretical air-fuel ratio: about 14.5), but the target air-fuel ratio is out of stoichiometry. In this case, for example, when the air-fuel ratio is richer than the stoichiometric air-fuel ratio (when a high torque is required, such as at low rotation and high load), the air-fuel ratio feedback control is stopped, and the target air-fuel ratio ( For example, a fuel injection amount of 12.5) is obtained from the injector. This is because, when the target air-fuel ratio is out of stoichiometry, the target air-fuel ratio detection accuracy may not be sufficiently obtained by the O ₂ sensor or the A / F sensor. This is because the fuel injection amount is set so that the target air-fuel ratio can be obtained and the control performance of the air-fuel ratio is improved.
JP-A-6-50153 JP 2005-61270 A

  In a V-type engine that is capable of air-fuel ratio feedback control as described above and that has an intake system that uses the inertial supercharging effect, the situation described below occurs when the variable intake control valve of one bank fails. become. Here, a case where the variable intake control valve in the left bank has failed will be described as an example.

  In this case, since the inertial supercharging effect cannot be obtained in the left bank, the intake air amount of each cylinder in the left bank is reduced compared to before the occurrence of the failure. On the other hand, since the inertial supercharging effect is obtained in the right bank, the intake air amount of each cylinder in the right bank is maintained regardless of the failure of the variable intake control valve in the left bank. Further, the intake air amount of the engine as a whole is reduced by the reduction amount of the left bank.

  FIG. 9A shows the actual intake air amount of each bank, the total intake air amount to the engine, and the intake air amount of each bank recognized in the control when each variable intake control valve is operating normally. Show. Thus, when each variable intake control valve is operating normally, the intake air amount of each bank recognized in the control substantially matches the actual intake air amount in each bank. On the other hand, FIG. 9B shows the actual intake air amount of each bank, the total intake air amount to the engine, and the intake air amount of each bank recognized in the control when the variable intake control valve of the left bank fails. Show. As described above, when the variable intake control valve of the left bank fails, a deviation occurs between the intake air amount of each bank recognized in the control and the actual intake air amount of each bank. For this reason, in each cylinder of the left bank, the air-fuel ratio shifts to the rich side by the amount of the reduced intake air amount. On the other hand, in each cylinder in the right bank, it is mistakenly recognized that the intake air amount in each cylinder in the right bank has decreased as the intake air amount as a whole of the engine has decreased. As a result, the air-fuel ratio shifts to the lean side. At this time, if the operating state of the engine is in an operation region where the air-fuel ratio feedback control is performed, the air-fuel ratio deviation is eliminated by the air-fuel ratio feedback control. In the above case, the fuel injection amount is corrected to decrease in the left bank where the air-fuel ratio has shifted to the rich side, while the fuel injection amount is corrected to increase in the right bank where the air-fuel ratio has shifted to the lean side. As described above, in the engine operating region where the air-fuel ratio feedback control is performed, even if the variable intake control valve fails, the air-fuel ratio is appropriately controlled to the target air-fuel ratio (stoichiometric).

  However, when the variable intake control valve in the left bank fails in the engine operating state where the air-fuel ratio feedback control is stopped (during low rotation and high load, etc.), 1/2 of the intake air amount detected by the air flow meter. Are assumed to be introduced equally to each bank (incorrect recognition), and the operation of determining the fuel injection amount to each cylinder is continued. That is, as described above, the situation in which the air-fuel ratio in each cylinder in the left bank shifts to the rich side and the air-fuel ratio in each cylinder in the right bank shifts to the lean side is maintained. This is continued until the operating state is an operating region in which air-fuel ratio feedback control is started. As a result, the temperature of the catalytic converter provided in the exhaust system cannot be maintained at an appropriate temperature, so that its performance cannot be obtained sufficiently or its durability is lowered, or the spark plug is wet with liquid phase fuel. There is a risk that the ignitability of the air-fuel mixture will deteriorate or abnormal combustion will occur in the combustion chamber.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a deviation of the air-fuel ratio of an air-fuel mixture when a failure occurs in any of the cylinder groups in an engine having a plurality of cylinder groups. An object of the present invention is to provide an operation control device for an internal combustion engine that eliminates or improves the above.

-Principle of solving the problem-
The solution of the present invention taken to achieve the above object is a case where a failure (for example, a failure of the variable intake control valve) occurs in any cylinder group in an internal combustion engine having a plurality of cylinder groups. Therefore, when the air-fuel ratio feedback control is not performed, the actual air-fuel ratio is prevented from greatly deviating from the target air-fuel ratio by switching to the fuel injection control corresponding to the occurrence of the failure. . Alternatively, if the feedback control is not performed because the target air-fuel ratio (for example, 12.5) is set to a value with low detection accuracy of the air-fuel ratio sensor, The control is switched to feedback control using an air-fuel ratio sensor.

-Solution-
Specifically, the present invention includes a plurality of cylinder groups and a variable valve for each cylinder group that varies the flow of intake air in an intake passage provided for each of these cylinder groups. An operation control device for an internal combustion engine that enables feedback control of the air-fuel ratio is assumed. When at least one variable valve of each cylinder group fails when the air-fuel ratio feedback control is not executed, the fuel supply amount is individually corrected for each cylinder group. Fail-time air-fuel ratio correcting means is provided.

  When the air-fuel ratio feedback control is not executed (for example, at low engine speed and high load), the intake air amount of each cylinder is obtained assuming that the air introduced into the internal combustion engine is evenly distributed to each cylinder group. Based on this, the fuel injection amount is controlled so as to obtain a predetermined target air-fuel ratio. However, when one of the variable valves fails, the air introduced into the internal combustion engine is not evenly distributed to each cylinder group, and a difference occurs in the intake air amount for each cylinder group. For this reason, a predetermined target air-fuel ratio cannot be obtained by fuel injection amount control assuming that air is evenly distributed to the cylinder groups. In the present solution, when at least one variable valve fails when the air-fuel ratio feedback control is not executed, a fuel supply amount set in advance for each cylinder group is obtained instead of the fuel injection amount control performed so far. Therefore, it is switched to the fuel correction control for correcting individually. For example, correction for decreasing the fuel injection amount is performed for the cylinder group in which the variable valve has failed, and correction for increasing the fuel injection amount is performed for the other cylinder groups. In the cylinder group in which the variable valve has failed, the intake air amount may be reduced due to this failure, and the fuel injection amount is reduced accordingly. In addition, in the cylinder group in which the variable valve has not failed, the intake air amount in the cylinder group in which this failure has not occurred is also reduced due to the decrease in the intake air amount as a whole internal combustion engine due to the above failure. In this case, the fuel injection amount is controlled to decrease, and the fuel injection amount is increased on the assumption that the air-fuel ratio may be shifted to the lean side.

  More specifically, the configuration for individually correcting the fuel supply amount for each cylinder group when the at least one variable valve fails is as follows.

  First, a plurality of cylinder groups, intake air amount detection means for detecting the total amount of intake air of the internal combustion engine, and variable valves for each cylinder group for varying the flow of intake air in the intake passage provided for each cylinder group, And an oxygen concentration sensor that is provided in an exhaust passage provided for each cylinder group and detects the oxygen concentration in the exhaust gas, and for each cylinder group based on the oxygen concentration in the exhaust gas detected by the oxygen concentration sensor. An operation control device for an internal combustion engine that enables feedback control of the air-fuel ratio of the air-fuel mixture is assumed. The operation control device for the internal combustion engine is capable of receiving a failure detection means capable of detecting a failure of at least one variable valve in each of the cylinder groups, and an output of the failure detection means. When at least one variable valve in each cylinder group fails during non-execution of the feedback control, the fuel supply amount is individually corrected for each cylinder group, and the air-fuel ratio becomes rich with the failure of the variable valve. In the cylinder, the fuel supply amount is corrected to decrease, while the cylinder in which the air-fuel ratio has become lean due to the failure of the variable valve is provided with a fail-time air-fuel ratio correction means for increasing the fuel supply amount. I am letting. Note that the cylinder in which the air-fuel ratio becomes rich due to the failure of the variable valve here is that the actual air-fuel ratio after the failure of the variable valve becomes richer than the actual air-fuel ratio before the failure of the variable valve. For example, the cylinder group on the side where the variable valve has failed. A cylinder whose air-fuel ratio has become lean due to the failure of the variable valve is a cylinder whose actual air-fuel ratio has become lean after the variable valve has failed compared to the actual air-fuel ratio before the variable valve has failed. That is, for example, a cylinder group on the side where the variable valve is not broken (operating normally).

  Other configurations include the following. A plurality of cylinder groups, intake air amount detection means for detecting the total amount of intake air of the internal combustion engine, variable valves for each cylinder group for varying the flow of intake air in the intake passage provided for each cylinder group, and cylinders An air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gas provided in an exhaust passage provided for each group, and based on the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor, the air-fuel ratio of each cylinder group An operation control device for an internal combustion engine that enables feedback control of the fuel ratio is assumed. The operation control device for the internal combustion engine is capable of receiving a failure detection means capable of detecting a failure of at least one variable valve in each of the cylinder groups, and an output of the failure detection means. When at least one variable valve of each cylinder group fails during non-execution of the feedback control, if the target air-fuel ratio is within the air-fuel ratio detectable range of the air-fuel ratio sensor, it is detected by this air-fuel ratio sensor. If the target air-fuel ratio is not within the air-fuel ratio detectable range of the air-fuel ratio sensor while the feedback control is performed on the air-fuel ratio of the air-fuel mixture for each cylinder group based on the air-fuel ratio of the exhaust gas, The fuel supply amount is individually corrected, and in the cylinder in which the air-fuel ratio becomes rich due to the failure of the variable valve, the fuel supply amount is corrected to decrease, and the fuel supply amount is reduced due to the failure of the variable valve. There In the cylinder becomes lean and let a fail time air-fuel ratio correcting means for increasing correction of fuel supply amount.

  In particular, the air-fuel ratio sensor can perform feedback control of the air-fuel ratio of the air-fuel mixture even when the target air-fuel ratio is a value deviating from stoichiometry. As long as the reliability of detection accuracy is ensured to some extent, it is possible to prevent the actual air-fuel ratio from deviating significantly from the target air-fuel ratio by performing feedback control using this air-fuel ratio sensor.

  Specific examples of the configuration of the internal combustion engine to which the above-described solving means are applied include the following. In other words, the internal combustion engine is a V-type engine, and each bank is provided with a low-speed passage having a relatively long intake passage length and a high-speed passage having a relatively short intake passage length. In contrast to the configuration in which the inertial supercharging effect is obtained according to the operating state of the internal combustion engine by switching, the fail-time air-fuel ratio correcting means is provided for each cylinder group when the variable valve of the bank on one side fails. The fuel supply amount is individually corrected.

  In the present invention, when a variable valve fails in any cylinder group in an internal combustion engine having a plurality of cylinder groups and the air-fuel ratio feedback control is not performed, a response is made according to the failure occurrence state. By switching to control for correcting the fuel supply amount, the actual air-fuel ratio is prevented from deviating significantly from the target air-fuel ratio. For this reason, it becomes possible to eliminate the deviation of the air-fuel ratio of each cylinder group due to the failure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each embodiment described below, a case where the present invention is applied to a V-type six-cylinder engine (internal combustion engine) for an automobile will be described.

<First Embodiment>
-Description of overall engine configuration-
FIG. 1 is a diagram showing a schematic configuration inside an engine when a V-type engine E according to the present embodiment is viewed from a direction along the axis of a crankshaft C. FIG. 2 is a system configuration diagram showing an outline of the engine E and the intake / exhaust system.

  As shown in these drawings, the V-type engine E has a pair of banks (cylinder groups) 2L and 2R protruding in a V-shape at the top of the cylinder block 1. Each bank 2L, 2R includes a cylinder head 3L, 3R installed at the upper end of the cylinder block 1 and a head cover 4L, 4R attached to the upper end thereof. The cylinder block 1 is provided with a plurality of cylinders 5L, 5R,... (For example, three in each bank 2L, 2R) with a predetermined sandwich angle (for example, 90 °). The pistons 51L, 51R,... The pistons 51L, 51R,... Are connected to the crankshaft C through connecting rods 52L, 52R,. Further, a crankcase 6 is attached to the lower side of the cylinder block 1, and a space extending from the lower part in the cylinder block 1 to the inside of the crankcase 6 is a crank chamber 61. An oil pan 11 serving as an oil reservoir is disposed further below the crankcase 6.

  The cylinder heads 3L and 3R are respectively assembled with intake valves 32L and 32R for opening and closing the intake ports 31L and 31R and exhaust valves 34L and 34R for opening and closing the exhaust ports 33L and 33R. The valves 32L, 32R, 34L, and 34R are opened and closed by the rotation of the cam shafts 35L, 35R, 36L, and 36R disposed in the cam chambers 41L and 41R formed between the head covers 4L and 4R. To be done.

  On the other hand, intake manifolds 7L and 7R corresponding to the banks 2L and 2R are disposed on the inner side (between banks) of the banks 2L and 2R. The upstream ends of the intake manifolds 7L, 7R are connected to a (single) surge tank 71 common to the banks 2L, 2R, while the downstream ends are branched for each cylinder to provide intake ports 31L, 31R,. Communicating with

  Further, the intake system of the engine E according to the present embodiment employs an intake system that uses the inertia supercharging effect. Specifically, as shown in FIG. 2, the intake manifolds 7L and 7R include low-speed intake passages 72L and 72R having a relatively long passage length and high-speed intake passages 73L and 73R having a relatively short passage length. These intake passages 72L, 72R, 73L, and 73R are provided for the cylinders of the banks 2L and 2R, respectively. As described above, each of the intake manifolds 7L, 7R has an upstream end communicating with the surge tank 71 and a downstream end communicating with each intake port 31L, 31R,. The passages 73L and 73R also communicate with the surge tank 71 at their respective upstream ends and the intake ports 31L, 31R,... Of the corresponding cylinders at their respective downstream ends.

  In addition, variable intake control valves (variable valves) 74L and 74R are provided at positions immediately upstream of the junctions with the low speed intake passages 72L and 72R in the downstream portions of the high speed intake passages 73L and 73R. The variable intake control valves 74L and 74R are constituted by butterfly valves that open and close the high-speed intake passages 73L and 73R by opening and closing in accordance with driving of an actuator (valve motor or the like) attached to the rotating shaft. Thus, the intake passage used for intake is switched between the high-speed intake passages 73L and 73R and the low-speed intake passages 72L and 72R. That is, when the variable intake control valves 74L and 74R are opened (the state shown in FIGS. 1 and 2), intake air flows through the high-speed intake passages 73L and 73R, while the variable intake control valves 74L and 74R are closed. In this case, intake air flows through the low-speed intake passages 72L and 72R. Then, depending on the operating state of the engine E (rotation speed, etc.), the variable intake control valves 74L and 74R are opened and closed to change the intake passage length, so that the inertia supercharging is performed at both high speed and low speed. It is possible to increase the efficiency of air filling into the cylinder due to the effect and increase the output of the engine.

  The upstream side of the surge tank 71 communicates with an intake pipe 76 having a (one) throttle valve 75 common to the banks 2L and 2R, and an air cleaner 77 is provided upstream of the intake pipe 76. It has been. A common (one) air flow meter (intake air amount detection means) 78 is provided in the banks 2L and 2R at the downstream side of the air cleaner 77 in the intake pipe 76. The total amount of intake air is detected. That is, when there is no failure in the intake system of the engine E, 1/2 of the intake air amount detected by the air flow meter 78 is distributed to each bank 2L, 2R, and each bank 2L, 2R is distributed. 1/3 of the intake air amount at is distributed to each cylinder. That is, 1/6 of the intake air amount detected by the air flow meter 78 is introduced into each cylinder.

  The intake manifolds 7L and 7R are provided with injectors (fuel injection valves) 81L and 81R, respectively. Air introduced into the intake manifolds 7L and 7R enters the manifolds 7L and 7R from the injectors 81L and 81R. The fuel is mixed with the injected fuel to become an air-fuel mixture, which is introduced into the combustion chambers 82L and 82R when the intake valves 32L and 32R are opened. In addition, spark plugs 83L and 83R are disposed at the tops of the combustion chambers 82L and 82R.

  In the combustion chambers 82L and 82R, the combustion gas generated by the combustion of the air-fuel mixture accompanying the ignition of the ignition plugs 83L and 83R is discharged to the exhaust manifolds 9L and 9R as the exhaust gas when the exhaust valves 34L and 34R are opened. . Exhaust pipes 91L and 91R are connected to the exhaust manifolds 9L and 9R, respectively, and further, catalytic converters 92L and 92R each incorporating a three-way catalyst are provided in the exhaust pipes 91L and 91R, respectively. The exhaust gas discharged to the exhaust manifolds 9L and 9R passes through the exhaust pipes 91L and 91R and is discharged to the outside. At this time, the exhaust gas passes through the catalytic converters 92L and 92R, so that hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide component (NOx) contained in the gas are purified. ing.

In addition, O ₂ sensors 93L and 93R are disposed upstream of the catalytic converters 92L and 92R in the exhaust pipes 91L and 91R, respectively. The O ₂ sensors 93L and 93R output detection signals corresponding to the oxygen concentration in the exhaust gas flowing in the exhaust pipes 91L and 91R, so that whether the air-fuel ratio of the exhaust gas is the stoichiometric air-fuel ratio. Alternatively, it is possible to recognize whether it is deviated from this stoichiometric air-fuel ratio (in the direction of rich side or lean side).

-ECU-
The operation of the engine E configured as described above is controlled by an ECU (electronic control unit) 100. As shown in FIG. 3, the ECU 100 includes a CPU 101, a ROM 102, a RAM 103, a backup RAM 104, and a counter 105 that counts the number of times of fuel injection.

  The ROM 102 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 101 executes arithmetic processing based on various control programs and maps stored in the ROM 102. The RAM 103 is a memory that temporarily stores calculation results in the CPU 101, data input from each sensor, and the like. The backup RAM 104 is a non-volatile memory that stores data to be saved when the engine E is stopped. It is. The ROM 102, CPU 101, RAM 103, backup RAM 104, and counter 105 are connected to each other via a bus 108, and are connected to an external input circuit 106 and an external output circuit 107.

The external input circuit 106 includes an air flow meter 78, O ₂ sensors 93 L and 93 R, a water temperature sensor 110 that detects the temperature of cooling water circulating through the water jacket of the engine E (cooling water temperature), and a downstream side of the throttle valve 75. A vacuum sensor 111 for detecting the intake pressure, an accelerator position sensor 112 for detecting the accelerator opening, a throttle position sensor 113 for detecting the opening of the throttle valve 75, and a crank position for transmitting a pulse signal corresponding to the rotational speed of the crankshaft C Sensor 114, cam position sensor 115 for transmitting a pulse signal corresponding to the number of rotations of camshafts 35L, 35R, ignition switch 116, and rotation position of variable intake control valve 74L provided in intake manifold 7L of left bank 2L are detected. Left side And the right bank valve opening sensor 120R (failure detecting means) for detecting the rotational position of the variable intake control valve 74R provided in the intake manifold 7R of the right bank 2R. ing.

  The external output circuit 107 includes injectors 81L and 81R, an igniter 117 for operating the spark plugs 83L and 83R, a throttle motor 118 for operating the throttle valve 75, a starter motor 119 for performing a cranking operation when starting the engine, A valve motor 121 and the like for operating the variable intake control valves 74L and 74R in synchronization are connected.

  The ECU 100 opens and closes the injectors 81L and 81R based on outputs from various sensors such as the water temperature sensor 110, the vacuum sensor 111, the accelerator position sensor 112, the throttle position sensor 113, the crank position sensor 114, and the cam position sensor 115. Various controls (including air-fuel ratio feedback control described later) of the engine E including control (control of fuel injection start timing and injection end timing) are executed. The ECU 100 also controls the opening and closing of the injectors 81L and 81R (fuel injection amount) when a failure of one of the variable intake control valves 74L (74R) is detected by the output signals from the valve opening sensors 120L and 120R. Control) (control by the fail-time air-fuel ratio correcting means in the present invention, which will be described in detail later).

  Next, opening / closing control of the variable intake control valves 74L and 74R for realizing the inertia supercharging effect of the intake system and air-fuel ratio feedback control for bringing the actual air-fuel ratio closer to the target air-fuel ratio will be described.

-Opening / closing control of variable intake control valves 74L, 74R-
FIG. 4 shows a valve opening / closing control map for performing opening / closing control of the variable intake control valves 74L, 74R according to the engine speed and the engine load. In FIG. 4, a region where the variable intake control valves 74L and 74R are opened and a region where the variable intake control valves 74R are closed are indicated by a solid line. Further, in this valve opening / closing control map, the execution region of the air-fuel ratio feedback control and the stop region thereof are also shown, and these regions are indicated by broken lines.

  As can be seen from this valve opening / closing control map, in the engine E according to this embodiment, the variable intake control valves 74L and 74R are closed in the low-rotation and high-load operation region of the engine E, and the low-speed intake passages 72L and 72R Inhalation is performed. On the other hand, in other operating regions, the variable intake control valves 74L and 74R are opened, and intake from the high-speed intake passages 73L and 73R is performed. In this way, by changing the intake pipe length in accordance with the engine speed or the like, the efficiency of air filling into the cylinder due to the inertia supercharging effect is increased at both the high speed rotation and the low speed rotation of the engine E, thereby increasing the engine E The output can be achieved.

  The variable intake control valves 74L and 74R in this embodiment are given an urging force to the open side by an urging force of a spring or the like, and the valve motor 121 is driven only in the low rotation and high load operation region. The variable intake control valves 74L and 74R are synchronously closed against the urging force of the spring. In the other operation region, the valve motor 121 is stopped, and the variable intake control valves 74L and 74R are opened by the biasing force of the spring. For this reason, as an example of a failure occurrence mode of the variable intake control valves 74L and 74R, the variable intake control valves 74L and 74R in an open state are fixed to the inner surfaces of the intake manifolds 7L and 7R by the urging force of the spring, and the valve motor 121 is attached. There is a case in which the closed state does not occur even when driven (the control operation in this case will be described later).

-Air-fuel ratio feedback control-
On the other hand, as shown in the valve opening / closing control map, the target air-fuel ratio is set to stoichiometric (theoretical air-fuel ratio: about 14.5) when the operation region is relatively low load. In this case, each bank 2L , Feedback control of the air-fuel ratio is performed every 2R. That is, by detecting the oxygen concentration in the exhaust gas flowing through the exhaust pipes 91L and 91R by the O ₂ sensors 93L and 93R, respectively, the air-fuel ratio of the exhaust gas is at the stoichiometric air-fuel ratio, or this theoretical It recognizes whether it is deviated from the air-fuel ratio (in the direction of rich side or lean side). Then, the fuel injection amount (fuel supply amount) is increased and corrected for the cylinders in the bank in which the actual air-fuel ratio is detected to be lean with respect to the target air-fuel ratio, while the actual air-fuel ratio is compared with the target air-fuel ratio. The fuel injection amount is corrected to decrease for the cylinders in the bank detected as being rich.

On the other hand, the target air-fuel ratio is set to rich (for example, 12.5) when the operation range is relatively high (when high torque is required), and in this case, the air-fuel ratio feedback control is stopped. Thus, a fuel injection amount that provides a target air-fuel ratio (12.5) with respect to the intake air amount detected by the air flow meter 78 is injected from each injector 81L, 81R. This is because, if the target air-fuel ratio is out of stoichiometry, the target air-fuel ratio detection accuracy may not be sufficiently obtained by the O ₂ sensors 93L, 93R, so the intake air amount detected by the air flow meter 78 This is because the fuel injection amount is set according to the above so as to obtain the target air-fuel ratio, and the control performance of the air-fuel ratio is improved.

  The opening / closing control operation and the air-fuel ratio feedback control operation of the variable intake control valves 74L and 74R as described above are executed in the engine E according to the present embodiment.

-Control action at the time of failure of variable intake control valves 74L, 74R-
Next, the control operation at the time of failure of the variable intake control valves 74L and 74R, which is an operation characteristic of the present embodiment, will be described. Here, the variable intake control valve 74L of the left bank 2L fails, and as described above, the variable intake control valve 74L cannot be closed (the open state is maintained) at the timing at which the variable intake control valve 74L should be closed (the engine E low-rotation high-load operation region). ) A case will be described as an example.

  In this case, as described with reference to FIG. 9 above, since the inertial supercharging effect cannot be obtained in the left bank 2L, the intake air amount of each cylinder in the left bank 2L is reduced compared to before the occurrence of the failure. Become. On the other hand, in the right bank 2R, the variable intake control valve 74R closes normally and an inertia boost effect is obtained. Therefore, the intake air amount of each cylinder in the right bank 2R is maintained regardless of the failure of the variable intake control valve 74L. Is done. Further, the intake air amount of the engine E as a whole is reduced by the amount of reduction of the left bank 2L. That is, the air flow meter 78 detects the reduced intake air amount.

  Since the air-fuel ratio feedback control is stopped at the timing when the variable intake control valve 74L should be closed (see the valve opening / closing control map in FIG. 4), the intake air amount detected by the air flow meter 78 is reduced. Assuming that 1/2 was introduced equally to each bank 2L and 2R (incorrect recognition), the fuel injection amount to each cylinder was determined, and the air-fuel ratio in each cylinder in the left bank 2L shifted to the rich side And the situation where the air-fuel ratio in each cylinder of the right bank 2R is shifted to the lean side will be maintained. In this embodiment, by switching the fuel injection amount control for the banks 2L and 2R in such a situation, the air-fuel ratio deviation can be eliminated.

  Hereinafter, the procedure of the control operation when the variable intake control valve 74L fails will be described with reference to the flowchart of FIG. This operation is executed every predetermined time, for example, every several milliseconds. Alternatively, it is executed every predetermined crank angle rotation.

  First, in step ST1, the current operation state of the engine E is the operation region of the variable intake control valves 74L and 74R, that is, the operation region in which the valve motor 121 is driven and the variable intake control valves 74L and 74R are synchronously closed. It is determined whether or not it is in the (low rotation high load operation region). If this determination is NO, it is determined that the variable intake control valves 74L and 74R are not in operation, that is, the variable intake control valves 74L and 74R are open, and the routine proceeds to step ST5 where the variable intake control valves are opened. This routine is ended because it is not necessary to perform correction control of the fuel injection amount when 74L, 74R fails.

  On the other hand, if YES is determined in step ST1, the process proceeds to step ST2 where the outputs of the left bank valve opening sensor 120L and the right bank valve opening sensor 120R are received and the variable intake control valves 74L and 74R are output. It is determined whether or not the rotational positions are different, that is, whether or not the variable intake control valve 74L (74R) on one side is not closed and has failed. When this determination is NO, it is determined that the variable intake control valves 74L and 74R are both closed and operating normally, and after moving to step ST5, this routine is terminated.

  If the determination in step ST2 is YES, it is determined that one variable intake control valve 74L (74R) is not in a closed state and has failed. Determination of which variable intake control valve 74L (74R) has failed can be made based on the outputs of the respective valve opening sensors 120L and 120R. That is, it is determined that the variable intake control valve 74L (74R) that is not in the closed position despite the output of the valve closing signal from the ECU 100 to the valve motor 121 has failed.

  Thereafter, the process proceeds to step ST3, in which whether or not the current operating state of the engine E is in the air-fuel ratio feedback control stop region, that is, the region where the target air-fuel ratio is richer than the stoichiometric range. Is determined. If this determination is NO, the process proceeds to step ST5, and the routine is terminated because the correction control of the fuel injection amount is not necessary. If NO is determined in step ST3, the current operating state of the engine E is in the execution range of the air-fuel ratio feedback control, and the air-fuel ratio deviation can be eliminated by this air-fuel ratio feedback control. Therefore, the routine is terminated assuming that the fuel injection amount correction control is not necessary when the variable intake control valves 74L and 74R fail.

  On the other hand, if YES is determined in step ST3, the process proceeds to step ST4, and fuel injection amount correction control according to the failure state of the variable intake control valve 74L (74R) is executed. Specifically, as described above, if the variable intake control valve 74L in the left bank 2L is out of order, the air-fuel ratio in each cylinder in the left bank 2L is shifted to the rich side, and the air-fuel ratio in each cylinder in the right bank 2R is In step ST4, the fuel injection amount is corrected to be reduced for each cylinder in the left bank 2L in which the air-fuel ratio is rich with respect to the target air-fuel ratio (for example, the fuel injection amount is set to 20). On the other hand, for each cylinder of the right bank 2R in which the air-fuel ratio is lean with respect to the target air-fuel ratio, the fuel injection amount is increased (for example, the fuel injection amount is corrected by 20%). become. Conversely, if the variable intake control valve 74R in the right bank 2R is out of order, the fuel injection amount is corrected to decrease for each cylinder in the right bank 2R, while the fuel injection is performed in each cylinder in the left bank 2L. The amount is corrected to increase. Here, the increase value and the decrease value of the fuel injection amount are set to 20%, but this value is not limited to this and can be arbitrarily set. Further, the increase value and the decrease value may be set to different values.

  As described above, in this embodiment, when a failure of one of the variable intake control valves 74L (74R) is detected, by switching to the fuel injection amount control corresponding to the failure, the banks 2L and 2R are empty. The deviation of the fuel ratio can be eliminated or reduced. For this reason, the temperature of the catalytic converters 92L and 92R provided in the exhaust pipes 91L and 91R can be maintained at an appropriate temperature, the performance can be sufficiently exhibited, and the durability can be improved. Further, the fogging state of the spark plugs 83L and 83R is not caused, and the ignitability of the air-fuel mixture can be maintained well, and abnormal combustion in the combustion chambers 82L and 82R can be avoided.

Second Embodiment
Next, a second embodiment of the present invention will be described. In the engine E of the first embodiment described above, the O ₂ sensors 93L and 93R are disposed in the exhaust pipes 91L and 91R, respectively. On the other hand, in the engine E according to the second embodiment, the exhaust pipes 91L and 91R are provided with A / F sensors. Since the other configuration of the engine E is the same as that of the first embodiment described above, description thereof is omitted here.

  As is well known, the A / F sensor can detect the A / F even when the A / F of the exhaust gas is a value (for example, 12.5) deviated from the stoichiometric (about 14.5). Feedback control of the air-fuel ratio of the air-fuel mixture with this value as the target air-fuel ratio is possible.

  In this embodiment, air-fuel ratio feedback control is performed using different control maps for normal operation and failure of the variable intake control valves 74L and 74R. Specifically, what is shown in FIG. 6A is a control map (normal control map) for performing air-fuel ratio feedback control during normal operation of the variable intake control valves 74L and 74R, and FIG. What is shown is a control map (control map for failure) for performing air-fuel ratio feedback control when the variable intake control valves 74L and 74R fail. In these drawings, the execution range of the air-fuel ratio feedback control and its stop region are indicated by a broken line. Note that these control maps also show the areas where the variable intake control valves 74L and 74R are opened and closed, and these areas are indicated by a solid line.

  Accordingly, during normal operation of the variable intake control valves 74L and 74R, as can be seen from the control map shown in FIG. 6A, the target air-fuel ratio is stoichiometric (theoretical air-fuel ratio) in the relatively low load operation region. : About 14.5). In this case, feedback control of the air-fuel ratio is performed for each bank 2L, 2R. That is, by detecting the A / F (air-fuel ratio) in the exhaust gas flowing through the exhaust pipes 91L and 91R by the A / F sensors, the air-fuel ratio of the exhaust gas is at the stoichiometric air-fuel ratio, or The amount of fuel injection is corrected by recognizing how much the theoretical air-fuel ratio deviates from this, so that the actual air-fuel ratio approaches the target air-fuel ratio. On the other hand, the target air-fuel ratio is set to a rich value (for example, 12.5 or 11.0) when the operation range is a relatively high load. In this case, the air-fuel ratio feedback control is stopped and the air flow meter 78 is set. Thus, a fuel injection amount that can obtain the target air-fuel ratio with respect to the intake air amount detected by the above is injected from each of the injectors 81L and 81R.

  On the other hand, at the time of failure of the variable intake control valves 74L and 74R, as can be seen from the control map shown in FIG. 6 (b), the execution range of the air-fuel ratio feedback control is expanded (the hatched area in FIG. 6 (b)). Region), the air-fuel ratio feedback control based on the detection signal of each A / F sensor is executed even in the region where the air-fuel ratio feedback control is stopped during the normal operation of the variable intake control valves 74L and 74R. ing. The execution range of the air-fuel ratio feedback control that is expanded in this case is expanded only in the region where the target air-fuel ratio is within the air-fuel ratio detectable range (for example, 12.0 or more) of the A / F sensor. Specifically, this range is an operation region of relatively low rotation and high load. In the case shown in FIG. 6B, the target air-fuel ratio in the range where the execution range of the air-fuel ratio feedback control is not expanded (the feedback control stop region and not shaded) is, for example, 11.0. Is set to

-Control action at the time of failure of variable intake control valves 74L, 74R-
Next, the procedure of the control operation at the time of failure of the variable intake control valves 74L and 74R, which is the characteristic operation of the second embodiment, will be described with reference to the flowchart of FIG. This operation is executed every predetermined time, for example, every several milliseconds. Alternatively, it is executed every predetermined crank angle rotation.

  First, in step ST11, it is determined whether or not the current operating state of the engine E is in the operation region of the variable intake control valves 74L and 74R, that is, the operation region in which the variable intake control valves 74L and 74R are synchronously closed. The If this determination is NO, it is determined that the variable intake control valves 74L and 74R are not in operation, that is, the variable intake control valves 74L and 74R are opened, and the routine proceeds to step ST16, where the variable intake control valves are controlled. This routine is ended because it is not necessary to perform correction control of the fuel injection amount when 74L, 74R fails.

  On the other hand, if YES is determined in step ST11, the process proceeds to step ST12, where the outputs of the left bank valve opening sensor 120L and the right bank valve opening sensor 120R are received and the variable intake control valves 74L and 74R are output. It is determined whether or not the rotational positions are different, that is, whether or not the variable intake control valve 74L (74R) on one side is not closed and has failed. If this determination is NO, it is determined that the variable intake control valves 74L and 74R are both closed and operating normally, and after moving to step ST16, the present routine is terminated.

  If the determination in step ST12 is YES, it is determined that one variable intake control valve 74L (74R) is not in a closed state and has failed. The determination of which variable intake control valve 74L (74R) has failed is made based on the outputs of the respective valve opening sensors 120L and 120R. In accordance with the YES determination in step ST12, the process proceeds to an operation of determining the execution region of the air-fuel ratio feedback control and the stop region thereof based on the failure time control map (see FIG. 6B). That is, the execution range of the air-fuel ratio feedback control is expanded to a region where the target air-fuel ratio is within the air / fuel ratio detectable range of the A / F sensor. Therefore, in step ST13, it is determined whether or not the current target air-fuel ratio is within the A / F sensor air-fuel ratio detectable range (for example, 12.0 or more). If this determination is YES, In step ST14, the air-fuel ratio feedback control in the expanded region is executed. On the other hand, if the determination in step ST13 is NO, the process moves to step ST15 and the air-fuel ratio feedback control is not executed. In addition, correction control of the fuel injection amount according to the failure state of the variable intake control valve 74L (74R) is executed. Specifically, as in the case of the first embodiment described above, the fuel injection amount is corrected to be reduced (for example, the fuel injection amount) for each cylinder in the bank where the air-fuel ratio is richer than the target air-fuel ratio. On the other hand, for each cylinder in the bank where the air-fuel ratio is leaner than the target air-fuel ratio, the fuel injection amount is increased (for example, the fuel injection amount is corrected by 20%). . Also in the second embodiment, these values can be arbitrarily set. Other control operations are the same as those in the first embodiment described above.

  As described above, in this embodiment, when the variable intake control valve 74L (74R) fails, air-fuel ratio feedback control by the A / F sensor is performed within a range in which the reliability of the detection accuracy of the A / F sensor is ensured to some extent. By performing this, it is possible to prevent the actual air-fuel ratio from significantly deviating from the target air-fuel ratio. In the case of the second embodiment, highly accurate air-fuel ratio feedback control by the A / F sensor is possible, so that the fully closed state is maintained as a failure mode of the variable intake control valve 74L (74R). In addition to this, it is possible to cope with a situation where the vehicle stops in a half-open state.

-Other embodiments-
In each embodiment described above, the case where the present invention is applied to the V-type engine E for automobiles has been described. The present invention is not limited to this, and can also be applied to a horizontally opposed engine for automobiles. Moreover, it is applicable not only to a gasoline engine but also to a diesel engine. Furthermore, the present invention can be applied not only to automobiles but also to other engines. Further, the number of cylinders, the fuel injection method, and other specifications of the engine E are not particularly limited.

  Further, in each of the above-described embodiments, the case where the variable intake control valves 74L and 74R cannot be closed at the timing when the variable intake control valves 74L and 74R cannot be closed is described as an example of the failure of the variable intake control valves 74L and 74R. A similar control operation may be executed even when 74L and 74R cannot be opened at the timing to be opened.

  In the above-described embodiments, the case where the variable intake control valves 74L and 74R have failed has been described. The present invention is not limited to this. For each cylinder group provided with a valve that varies the flow of intake air in the intake passage, such as a tumble control valve, the present invention can be similarly applied to a case where the valve fails. is there.

  Further, in each of the above-described embodiments, whether or not the variable intake control valves 74L and 74R have failed is determined based on the valve rotation positions detected by the valve opening sensors 120L and 120R. The present invention is not limited to this, and the presence or absence of the failure may be determined by detecting the intake negative pressure for each of the banks 2L and 2R, or the presence or absence of the failure may be determined based on the combustion temperature in the cylinder. . That is, the determination may be made using a sensing value that is influenced by whether or not the variable intake control valves 74L and 74R are defective.

It is a figure which shows schematic structure inside the engine which looked at the V-type engine which concerns on embodiment from the direction along the axial center of a crankshaft. It is a system configuration diagram showing an outline of an engine and intake and exhaust systems. It is a block diagram which shows the structure of control systems, such as ECU. It is a figure which shows the valve opening / closing control map in 1st Embodiment. It is a flowchart figure which shows the procedure of control operation at the time of the variable intake control valve failure in 1st Embodiment. It is a figure which shows the control map in 2nd Embodiment. It is a flowchart figure which shows the procedure of the control action at the time of the variable intake control valve failure in 2nd Embodiment. It is a figure which shows the conventional valve opening / closing control map. (A) is a diagram showing the actual intake air amount of each bank, the total intake air amount to the engine, and the intake air amount of each bank recognized in the control when each variable intake control valve is operating normally. (B) shows the actual intake air amount of each bank, the total intake air amount to the engine, and the intake air amount of each bank recognized in the control when the variable intake control valve of the left bank fails. FIG.

Explanation of symbols

2L, 2R banks (cylinder group)
74L, 74R Variable intake control valve (variable valve)
78 Air flow meter (intake air volume detection means)
93L, 93R O ₂ sensor (oxygen concentration sensor)
120L, 120R Valve opening sensor (Failure detection means)
E engine (internal combustion engine)

Claims (4)

Provided with a plurality of cylinder groups and a variable valve for each cylinder group that varies the flow of intake air in the intake passage provided for each cylinder group, and enables feedback control of the air-fuel ratio of the air-fuel mixture in each cylinder group In an operation control device for an internal combustion engine,
A fail-time air-fuel ratio correcting means for individually correcting the fuel supply amount for each cylinder group when at least one variable valve of each cylinder group fails when the air-fuel ratio feedback control is not executed; An internal combustion engine operation control device. A plurality of cylinder groups, intake air amount detection means for detecting the total amount of intake air of the internal combustion engine, variable valves for each cylinder group for varying the flow of intake air in the intake passage provided for each cylinder group, and cylinders An oxygen concentration sensor that is provided in an exhaust passage provided for each group and detects the oxygen concentration in the exhaust gas, and based on the oxygen concentration in the exhaust gas detected by the oxygen concentration sensor, the air-fuel mixture in each cylinder group In the internal combustion engine operation control device that enables feedback control of the air-fuel ratio of
Failure detection means capable of detecting that at least one variable valve in each of the cylinder groups has failed;
The output of the failure detection means can be received, and when at least one variable valve of each cylinder group fails when the air-fuel ratio feedback control is not executed, the fuel supply amount is individually set for each cylinder group In the cylinder with the air / fuel ratio becoming rich due to the failure of the variable valve, the fuel supply amount is corrected to decrease, while the cylinder having the air / fuel ratio lean due to the failure of the variable valve is corrected. An operation control device for an internal combustion engine, comprising: a fail-time air-fuel ratio correction means for correcting an increase in fuel supply amount. A plurality of cylinder groups, intake air amount detection means for detecting the total amount of intake air of the internal combustion engine, variable valves for each cylinder group for varying the flow of intake air in the intake passage provided for each cylinder group, and cylinders An air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gas provided in an exhaust passage provided for each group, and based on the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor, the air-fuel ratio of each cylinder group In an internal combustion engine operation control device that enables feedback control of the fuel ratio,
Failure detection means capable of detecting that at least one variable valve in each of the cylinder groups has failed;
The output of the failure detection means can be received, and when at least one variable valve of each cylinder group fails when the air-fuel ratio feedback control is not executed, the target air-fuel ratio is detected by the air-fuel ratio sensor. If within the possible range, the air-fuel ratio of the air-fuel mixture in each cylinder group is feedback controlled based on the air-fuel ratio of the exhaust detected by the air-fuel ratio sensor, while the target air-fuel ratio is the air-fuel ratio of the air-fuel ratio sensor. If it is not within the detectable range, the fuel supply amount is individually corrected for each cylinder group, and the fuel supply amount is corrected to decrease for cylinders whose air-fuel ratio has become rich due to the failure of the variable valve. In addition, the cylinder in which the air-fuel ratio becomes lean due to the failure of the variable valve is provided with a fail-time air-fuel ratio correcting means for increasing the fuel supply amount. The control device. In the internal combustion engine operation control device according to claim 1, 2, or 3,
The internal combustion engine is a V-type engine, and each bank is provided with a low speed passage having a relatively long intake passage length and a high speed passage having a relatively short intake passage length to switch opening and closing of the variable valve. Thus, the inertial supercharging effect can be obtained according to the operating state of the internal combustion engine. An operation control device for an internal combustion engine, characterized in that the correction is made individually.

Images