JPH1137027A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the discharge of a noxious exhaust gas component such as NOx or HC. SOLUTION: The controller for an engine 1 has a variable valve timing mechanism 25 for variably controlling opening timing for at least either of an intake air valve 8 and an exhaust valve 9. The controller for the engine 1 detects the abnormality of the variable valve timing mechanism 25 on the quantity of a valve overlap between the intake air valve 8 and the exhaust valve 9, and in a case where the abnormality of the variable valve timing mechanism 25 has been detected, the ignition timing of the engine 1 is regulated according to the number of revolutions and load of the engine 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control apparatus for an internal combustion engine having a variable valve timing mechanism, and more particularly to a control apparatus for an internal combustion engine that reduces the amount of exhaust gas when the variable valve timing mechanism fails.

[0002]

2. Description of the Related Art A variable valve timing mechanism disclosed in, for example, Japanese Patent Application Laid-Open No. 7-77073 is known as this kind of technology.

The variable valve timing mechanism described in the above publication purifies exhaust gas by controlling the valve overlap between an intake valve and an exhaust valve.
By increasing the valve overlap, the internal EGR
Works effectively. As a result, the emission amount of NOx is reduced. Further, by expanding the valve overlap, HC discharged to the exhaust system is re-inhaled into the combustion chamber.
As a result, the emission amount of HC is reduced.

[0004]

However, if the intake valve or the exhaust valve is stuck on the retard side (that is, the side where the valve overlap is reduced) due to the failure of the variable valve timing mechanism, the above-described exhaust gas is exhausted. Since the gas purification function does not work, a large amount of harmful exhaust gas components such as NOx and HC are discharged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and provides a control device for an internal combustion engine capable of reducing the amount of exhaust gas emitted even when a variable valve timing mechanism fails. The purpose is to:

[0006]

A control device for an internal combustion engine according to the present invention is a control device for an internal combustion engine having a variable valve timing mechanism for variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve. Means for detecting an abnormality in the variable valve timing mechanism based on a magnitude of a valve overlap between the intake valve and the exhaust valve; and detecting an abnormality in the variable valve timing mechanism when the abnormality in the variable valve timing mechanism is detected. Means for adjusting the ignition timing of the internal combustion engine according to the number of revolutions and the load is provided, whereby the object is achieved.

Another control device for an internal combustion engine according to the present invention is a control device for an internal combustion engine having a variable valve timing mechanism for variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve. Means for detecting an abnormality in the variable valve timing mechanism based on the magnitude of the valve overlap with the exhaust valve, and when an abnormality in the variable valve timing mechanism is detected,
Means for adjusting the air-fuel ratio of the internal combustion engine according to the number of revolutions and the load of the internal combustion engine, whereby the object is achieved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a control device for an internal combustion engine according to an embodiment of the present invention. In the present embodiment, the internal combustion engine is 4
It is assumed that the engine is a four-cylinder cylinder engine. FIG. 1 shows a structural cross section of an arbitrary cylinder of the engine.

The engine 1 has a piston 3 that can move up and down in a cylinder 2 of each cylinder. The upper side of the piston 3 is a combustion chamber 4. An ignition plug 5 is provided in the combustion chamber 4. The combustion chamber 4 has an intake passage 6 through an intake port 6a and an exhaust port 7a.
And the exhaust passage 7 are connected to each other. An intake valve 8 and an exhaust valve 9 are provided at the intake port 6a and the exhaust port 7a, respectively.

The intake valve 8 and the exhaust valve 9 are driven by the rotation of an intake camshaft 10 and an exhaust camshaft 11. An intake-side timing pulley 12 and an exhaust-side timing pulley 13 are provided at one end of the intake-side camshaft 10 and the exhaust-side camshaft 11, respectively. The intake-side timing pulley 12 and the exhaust-side timing pulley 13 are connected to a crankshaft (not shown) via a timing belt 14.

When the engine 1 is operating, the timing belt 14 and the timing pulley 1
The engine 1 is connected to the camshafts 10 and 11 via
Is transmitted. The intake valve 8 and the exhaust valve 9 are opened and closed according to the rotation of the camshafts 10 and 11.

As described above, the intake valve 8 and the exhaust valve 9 are driven at a predetermined timing in synchronization with the rotation of the crankshaft. That is, the intake valve 8 and the exhaust valve 9 are opened and closed at a predetermined timing in synchronization with four cycles of an intake cycle, a compression cycle, an explosion / expansion cycle, and an exhaust cycle.

At the inlet side of the intake passage 6, an air cleaner 1 is provided.
5 are provided. An air cleaner 15 is provided in the intake passage 6.
Outside air is taken in through. An intake air temperature sensor 71 for detecting the intake air temperature THA is provided near the air cleaner 15. An injector 16 for fuel injection is provided near the intake port 6a.

Fuel is injected from the injector 16 into the outside air taken into the intake passage 6. The mixture of the outside air and the fuel is sucked into the combustion chamber 4 in synchronization with the opening of the intake valve 8 in the suction cycle. The air-fuel mixture sucked into the combustion chamber 4 is exploded and burned by the operation of the ignition plug 5. Thereby, the crankshaft rotates, and the driving force of the engine 1 is obtained. Exhaust gas generated by the explosion and combustion in the combustion chamber 4 is discharged from the combustion chamber 4 through the exhaust port 7a and further through the exhaust passage 7 to the outside in synchronization with the opening of the exhaust valve 9 in the exhaust cycle. You.

A throttle valve 17 which opens and closes in response to operation of an accelerator pedal (not shown) is provided in the intake passage 6.
Is provided. By opening and closing the throttle valve 17, the amount of outside air taken into the intake passage 6 (that is, the amount of intake air) is adjusted. A throttle sensor 72 for detecting the throttle opening TA is provided near the throttle valve 17. A surge tank 18 for smoothing intake pulsation is provided downstream of the throttle valve 17. The surge tank 18 is provided with an intake pressure sensor 73 for detecting the intake pressure PM.

The exhaust passage 7 is provided with a catalytic converter 20 having a three-way catalyst 19 for purifying exhaust gas, and an oxygen sensor 74 for detecting oxygen concentration in exhaust gas. Further, the temperature of the cooling water of the engine 1 (cooling water temperature) T
A water temperature sensor 75 for detecting HW is provided.

The ignition plug 5 includes a distributor 2
The ignition signal distributed by 1 is applied. The distributor 21 applies the high voltage output from the igniter 22 to the rotation of the crankshaft (that is, the crank angle).
Is distributed to the ignition plug 5 in synchronization with. The ignition timing of the ignition plug 5 is determined by the timing at which the igniter 22 outputs a high voltage.

The distributor 21 has a rotor (not shown) that rotates in synchronization with the rotation of the crankshaft. The distributor 21 has a rotation speed (engine rotation speed) N of the engine 1 according to the rotation of the rotor.
A rotation speed sensor 76 for detecting E is attached.
The distributor 21 is provided with a cylinder discrimination sensor 77 that detects a crank angle reference position GP of the engine 1 at a predetermined rate in accordance with the rotation of the rotor.

The crankshaft rotates twice for four cycles of the engine 1. The rotation speed sensor 76 detects the crank angle at a rate of 30 ° CA per pulse. The cylinder discriminating sensor 77 detects the crank angle at a rate of 360 ° CA per pulse.

Electronic control unit (hereinafter referred to as "ECU")
80 controls each part of the engine 1. The ECU 80 is connected to an intake air temperature sensor 71, a throttle sensor 72, an intake pressure sensor 73, an oxygen sensor 74, a water temperature sensor 75, a rotation speed sensor 76, and a cylinder discrimination sensor 77, respectively. The ECU 80 controls the injector 16 and the igniter 22 based on the output signals of these sensors 71 to 77.
Control.

The ECU 80 controls a variable valve timing mechanism (hereinafter, simply referred to as "VVT") 25 to make the opening / closing timing of the intake valve 8 variable. VVT2
Reference numeral 5 is provided on the intake-side timing pulley 12.

The VVT pulley 92 is provided at the front end of the intake cam. The VVT pulley 92 continuously changes the intake valve timing by making the phases of the intake cam and the crankshaft variable according to the control oil pressure from the OCV 94. The OCV 94 controls the oil pressure according to a command from the ECU 80. The cam angle sensor 96 detects the cam angle of the intake cam, and outputs a cam timing signal indicating the cam angle to the ECU 80.

The ECU 80 sequentially calculates the valve timing based on the crank angle signal output from the crank angle sensor and the cam timing signal output from the cam angle sensor 96, and calculates the optimal valve timing according to the operating state of the engine 1. Calculate the control amount for the timing.

FIG. 2 shows a sectional structure of the VVT pulley 92. The piston 110 has a helical spline with a reverse twist inside and outside. The internal teeth of the piston 110 are fixed to the camshaft 10 via the inner gear 112. The external teeth of the piston 110 are fixed to the VVT pulley 92 via the outer gear 116. Piston 11
Hydraulic chambers (advance side hydraulic chamber 120a and retard side hydraulic chamber 120b) are arranged before and after zero. By supplying the hydraulic pressure controlled by the OCV 94 to the advance hydraulic chamber 120a and the retard hydraulic chamber 120b, the piston 11
0 can be moved to any position in the direction along the camshaft 10. This makes it possible to continuously change the phase of the camshaft 10 with respect to the VVT pulley 92.

FIG. 3 shows a sectional structure of the OCV 94. O
The CV 94 uses a spool valve 130 to continuously control the oil pressure for engine lubrication in two directions, an advance side and a retard side. The hydraulic pressure controlled by the OCV 94 is supplied to the VVT pulley 92.

When the duty ratio of the signal supplied from the ECU 80 to the OCV 94 is small, the OCV 94
The hydraulic pressure is introduced into the retard hydraulic chamber 120b of the VT pulley 92, and the hydraulic pressure is discharged from the advance hydraulic chamber 120a of the VVT pulley 92. Thereby, the piston 110 of the VVT pulley 92 moves rightward in FIG. Piston 11
The camshaft 10 rotates to the retard side with respect to the VVT pulley 92 due to the helical spline torsion cut to zero. As a result, the valve timing shifts to the retard side.

When the duty ratio of the signal supplied from the ECU 80 to the OCV 94 is large, the OCV 94
The hydraulic pressure is introduced into the advance hydraulic chamber 120a of the VT pulley 92, and the hydraulic pressure is discharged from the retard hydraulic chamber 120b of the VVT pulley 92. Thereby, the piston 110 of the VVT pulley 92 moves to the left in FIG. Piston 11
The camshaft 10 rotates to the advance side with respect to the VVT pulley 92 due to the helical spline torsion cut to zero. As a result, the valve timing shifts to the advance side.

As described above, by continuously controlling the waveform of the signal output from the OCV 94, the valve timing can be continuously changed.

FIGS. 4A and 4B show the relationship between the crank angle and the opening / closing timing of the intake valve 8 and the exhaust valve 9. FIG. 4A and 4B, the TDC
Indicates the position where the piston 3 rises most in the cylinder 2 (that is, top dead center), and BDC indicates the position where the piston 3 descends most in the cylinder 2 (that is, bottom dead center).

The opening / closing timing of the intake valve 8 is shown in FIG.
The state continuously changes between the state shown in FIG. 4A and the state shown in FIG. Thereby, the valve overlap changes continuously. Here, the valve overlap refers to a period during which the intake valve 8 is open and the exhaust valve 9 is open. Such a change in the valve overlap is achieved by retarding or advancing the opening / closing timing of the intake valve 8 with respect to the opening / closing timing of the exhaust valve 9.

The opening / closing timing of the intake valve 8 is controlled as follows.
This is performed by feedback control that causes the actual displacement angle to follow the target displacement angle. The target displacement angle is the engine 1
Of the engine 1 and the load of the engine 1 (for example, the intake pressure P
M) is calculated by the ECU 80 based on The actual displacement angle is detected by a crank angle sensor (for example, a rotation speed sensor 76) and a cam angle sensor 96,
80. The ECU 80 controls the VVT 25 so that the target displacement angle matches the actual displacement angle.

If the actual displacement angle does not follow the target displacement angle due to the failure of the VVT 25, the valve overlap may become smaller than in the normal operation. For example, when the opening / closing timing of the intake valve 8 is stuck on the retard side, the valve overlap is fixed to the size shown in FIG. If such a state is left, a large amount of harmful exhaust gas components such as NOx and HC will be discharged. In order to prevent this, the ECU 80 executes a VVT retarded fail determination routine and an ignition timing calculation routine.

FIG. 5 shows a processing procedure of a VVT retarded fail determination routine. This processing procedure is stored in, for example, a ROM (not shown) in the ECU 80 in the form of a program code. The VVT retard fail determination routine is performed by the EC
Performed by U80.

In step S11, it is determined whether or not VVT 25 is under feedback control. Such a determination is achieved by determining whether a feedback condition is satisfied. The feedback condition may be, for example, a condition relating to the temperature THW of the cooling water or a condition relating to the rotational speed NE of the engine 1.

In step S12, the target displacement angle (VT
It is determined whether the deviation between T) and the actual displacement angle (VT) is equal to or greater than a predetermined value α. Here, VTT and VT are represented by advance amounts with respect to a predetermined reference angle (for example, the most retarded angle reference). The target displacement angle (VTT) and the actual displacement angle (V
When the deviation of T) is equal to or larger than the predetermined value α, it means that the valve overlap is smaller than that during normal operation.

In step S13, the target displacement angle (VT
It is determined whether or not the state in which the deviation between T) and the actual displacement angle (VT) is equal to or greater than a predetermined value α has continued for a predetermined time β.

If the determinations in steps S11 to S13 are all "Yes", the value of the retard fail flag XVTFR is set to "1" (step S1).
4). Otherwise, the retard fail flag XVT
The value of FR is set to "0" (step S15). The value of the retard fail flag XVTFR is determined by R
AM (not shown).

FIG. 6 shows a processing procedure of an ignition timing calculation routine. This processing procedure is stored in, for example, a ROM (not shown) in the ECU 80 in the form of a program code. The ignition timing calculation routine is executed by the ECU 80.

In step S21, it is determined whether the value of the retard fail flag XVTFR is "1".

"Yes" in the determination of step S21
If so, the process proceeds to step S22; otherwise, the process proceeds to step S23.

In step S22, the final output ignition timing A
OP is calculated according to (Equation 1).

[0043]

## EQU1 ## where ASE represents the basic ignition timing calculated based on the rotational speed NE of the engine 1 and the load of the engine 1 (for example, the intake pressure PM). ARET represents the ignition timing retard amount at the time of the VVT retard failure.

In step S23, the final output ignition timing A
OP is calculated according to (Equation 2).

[0045]

AOP = ABSE The final output ignition timing AOP calculated by the ECU 80 according to (Equation 1) or (Equation 2) is supplied to the igniter 22. Thus, the ignition plug 5 fires at a predetermined timing.

As described above, in the present embodiment, the ignition timing of the engine 1 is delayed at the time of the VVT retarded fail.
This makes it possible to reduce the emission amount of NOx and HC.

The same NOx can also be obtained by shifting the center of the air-fuel ratio of the engine 1 to the rich side at the time of the VVT retarded fail, instead of controlling the ignition timing of the engine 1.
A reduction effect is obtained. Such adjustment of the air-fuel ratio of the engine 1 can be achieved, for example, by replacing the integration constant of the air-fuel ratio feedback of the catalytic converter 20.

In the above-described embodiment, the valve overlap is adjusted by changing only the opening / closing timing of the intake valve 8 by the VVT 25 provided on the camshaft 10 on the intake side. In contrast,
A VVT is provided on the camshaft 11 on the exhaust side, and the VVT is provided.
By changing only the opening / closing timing of the exhaust valve 9, the valve overlap may be adjusted. Alternatively, a VVT may be provided for each of the camshafts 10 and 11, and the valve overlap may be adjusted by changing the opening / closing timing of the intake valve 8 and the exhaust valve 9 with each VVT.

[0049]

According to the control apparatus for an internal combustion engine according to the present invention, the abnormality of the variable valve timing mechanism is detected based on the magnitude of the valve overlap between the intake valve and the exhaust valve. When the abnormality of the variable valve timing mechanism is detected, the ignition timing of the internal combustion engine is adjusted according to the rotation speed and the load of the internal combustion engine. Alternatively, when the abnormality of the variable valve timing mechanism is detected, the air-fuel ratio of the internal combustion engine is adjusted according to the rotation speed and the load of the internal combustion engine. Thereby, the emission amount of harmful exhaust gas components such as NOx and HC is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of a VVT pulley 92.

FIG. 3 is a diagram showing a cross-sectional structure of the OCV 94.

FIGS. 4A and 4B are diagrams showing the relationship between the crank angle and the opening / closing timing of an intake valve 8 and an exhaust valve 9;

FIG. 5 is a flowchart illustrating a processing procedure of a VVT retard failure determination routine;

FIG. 6 is a flowchart showing a processing procedure of an ignition timing calculation routine.

[Explanation of symbols]

 Reference Signs List 1 engine 4 combustion chamber 6 intake passage 7 exhaust passage 8 intake valve 9 exhaust valve 25 variable valve timing mechanism (VVT) 72 throttle sensor 73 intake pressure sensor 76 rotation speed sensor 77 cylinder discrimination sensor 80 ECU

Claims (2)

[Claims] 1. A control device for an internal combustion engine having a variable valve timing mechanism for variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve, wherein a valve overlap between the intake valve and the exhaust valve is large. Means for detecting an abnormality of the variable valve timing mechanism based on the ignition timing, and, when an abnormality of the variable valve timing mechanism is detected, an ignition timing of the internal combustion engine according to a rotation speed and a load of the internal combustion engine. A control device for an internal combustion engine, comprising: means for adjusting pressure. 2. A control device for an internal combustion engine having a variable valve timing mechanism for variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve, wherein a valve overlap between the intake valve and the exhaust valve is large. Means for detecting an abnormality of the variable valve timing mechanism based on the detected value, and, when an abnormality of the variable valve timing mechanism is detected, an air-fuel ratio of the internal combustion engine according to a rotation speed and a load of the internal combustion engine. A control device for an internal combustion engine, comprising: means for adjusting pressure.