JP4267303B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine (hereinafter referred to as an engine), and more specifically, includes a variable valve mechanism that can change the overlap amount of intake and exhaust valves, and an exhaust flow rate adjustment mechanism that limits the exhaust flow rate. The present invention relates to a control device for an internal combustion engine.
[0002]
[Related background]
In recent years, various approaches have been taken to reduce engine emissions and reduce fuel consumption.For example, with regard to the valve mechanism of an engine, the exhaust valve closing timing and intake valve opening timing can be changed to change to the operating state. A variable valve mechanism that realizes an appropriate amount of overlap of the intake and exhaust valves according to the requirements has been put into practical use, or, regarding the exhaust system of the engine, exhaust flow rate adjustment that quickly raises the catalyst temperature by limiting the exhaust flow rate The mechanism has been put into practical use.
[0003]
Although the exhaust flow rate restriction by the exhaust flow rate adjustment mechanism is performed at the time of cold start or the like, if the exhaust flow rate is restricted, the internal EGR of the engine increases and the combustion becomes unstable. A mechanism may be used (see, for example, Patent Document 1). In the technique described in Patent Document 1, when the exhaust flow rate is limited by the exhaust flow rate adjustment mechanism, the overlap amount of the intake and exhaust valves is simultaneously reduced by the variable valve mechanism to stabilize the combustion.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-271515
[Problems to be solved by the invention]
However, the technique described in Patent Document 1 is based on the premise that the desired overlap amount is achieved by the control by the variable valve mechanism. For example, when the overlap amount is large, the exhaust gas is exhausted. When the exhaust flow rate is limited by the flow rate adjustment mechanism, even if the variable valve mechanism is adjusted to suppress the internal EGR and the overlap amount is reduced, the response of the variable valve mechanism is delayed. Due to a temporary follow-up delay of the actual overlap amount with respect to the target overlap amount, the internal EGR increases due to an excessive overlap amount with respect to the target overlap amount, and the internal EGR can be controlled appropriately. In addition, there is a risk that the combustion state of the engine may be worsened in combination with the restriction of the exhaust flow rate by the exhaust flow rate adjusting mechanism. This problem becomes more prominent as the overlap amount is larger.
[0006]
In addition, for example, when the variable valve mechanism is stuck with a large overlap amount or becomes inoperable due to insufficient hydraulic pressure, the overlap amount cannot be reduced appropriately. As the internal EGR increases, the combustion state of the engine may be worsened.
It is an object of the present invention to accurately control a variable valve mechanism and an exhaust flow rate adjustment mechanism, thereby avoiding an increase in internal EGR due to sticking of the variable valve mechanism and a follow-up delay. An object of the present invention is to provide a control device for an internal combustion engine capable of realizing a combustion state.
[0007]
[Means for Solving the Problems]
To achieve the above object, a first aspect of the invention, capable of changing the overlap amount of the intake and exhaust valves by changing at least one of the closing valve timing of the exhaust valve and the opening timing of the intake valve of an internal combustion engine A variable valve mechanism that adjusts the overlap amount so as to follow the target overlap amount obtained from the operating region of the internal combustion engine, and an exhaust flow rate that is provided in the exhaust passage of the internal combustion engine and adjusts the opening to the closed side In an internal combustion engine control device having an exhaust flow rate adjustment mechanism that limits exhaust gas and raises exhaust pressure, an overlap amount detection means that detects an actual overlap amount of the intake and exhaust valves, and an overlap amount detection means And an exhaust restriction suppressing means for controlling the exhaust flow rate adjusting mechanism to open when the actual overlap amount is greater than or equal to the first set value .
[0008]
Therefore, while the overlap amount of the intake and exhaust valves is changed by the variable valve mechanism so as to follow the target overlap amount obtained from the operating region of the internal combustion engine, when a predetermined start condition is satisfied, for example, Adjust exhaust flow rate when rapid catalyst temperature rise is required, such as during start-up, or when the catalyst temperature decreases as the engine heat generation decreases, such as during lean operation or vehicle deceleration By adjusting the opening of the mechanism to the closed side, the exhaust flow rate of the internal combustion engine is limited, the exhaust pressure rises , and the temperature of the catalyst is increased and the temperature is maintained.
[0009]
If the actual overlap amount detected by the overlap amount detection means is greater than or equal to the first set value and a delay in the response of the variable valve mechanism occurs, the exhaust flow rate adjustment mechanism is opened. Be controlled . Therefore, the exhaust flow rate is limited by the exhaust flow rate adjusting mechanism according to the overlap amount by the variable valve mechanism, and the situation in which the internal EGR of the internal combustion engine further increases due to the delay in the operation response is avoided in advance. Is done.
[0013]
The invention of claim 2, Oite to claim 1, when the difference between the actual overlap amount and the target overlap amount is equal to or greater than the second set value, the exhaust restriction suppressing means exhaust flow rate adjusting mechanism to the open side It is something to control .
For example, due to the responsiveness of the variable valve mechanism, when the actual overlap amount in the follow-up delay with respect to the target overlap amount changes reduction direction occurs, the difference between the actual overlap amount and the target overlap amount is Although transiently exceeding the second set value, at this time, the exhaust flow rate adjusting mechanism is controlled to open, so that an increase in internal EGR due to this follow-up delay can be avoided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an engine control apparatus embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing an engine control apparatus according to the present embodiment. The engine 1 is configured as an in-cylinder injection type engine that injects fuel into a cylinder, and a DOHC 4-valve type is adopted as the valve operating mechanism. Timing pulleys 5a and 5b are connected to the front ends of the intake cam shaft 3a and the exhaust cam shaft 3b on the cylinder head 2, respectively. The timing pulleys 5a and 5b are connected to the crankshaft 7 via the timing belt 6. When the timing pulleys 5a and 5b are driven to rotate as the crankshaft 7 rotates, the camshafts 3a and 3b rotate to intake air. The valve 8a and the exhaust valve 8b are driven to open and close.
[0015]
A variable valve actuator 4 is provided between the exhaust camshaft 3b and the timing pulley 5b. The configuration of the variable valve actuator 4 is well known in, for example, Japanese Patent Laid-Open No. 2000-27609, and will not be described in detail. However, a vane rotor is rotatably provided in a housing provided in the timing pulley 5b, and an exhaust cam is provided on the vane rotor The shaft 3b is connected. Lubricating oil for the engine 1 is supplied to the variable valve actuator 4 as an operating oil via an oil control valve (hereinafter referred to as OCV) 4a, and hydraulic pressure is applied to the vane rotor in accordance with the switching of the OCV 4a, and the timing pulley 5b. The phase of the exhaust camshaft 3b with respect to the valve, that is, the opening timing and closing timing of the exhaust valve 8b are adjusted. In the present embodiment, a variable valve mechanism is constituted by the variable valve actuator 4 and OCV 4a.
[0016]
The cylinder head 2 is provided with a fuel injection valve 10 together with an ignition plug 9 for each cylinder, and high-pressure fuel supplied from a fuel pump (not shown) is directly injected into the combustion chamber 11 from the fuel injection valve 10. The combustion chamber 11 of each cylinder is connected to a common intake passage 13 via an intake port 12. The intake air introduced into the intake passage 13 via an air cleaner 14 is adjusted in flow rate by a throttle valve 15 and then is taken into the intake air. It is introduced from the port 12 into the combustion chamber 11 of each cylinder. The combustion chamber 11 of each cylinder is connected to a common exhaust passage 17 via an exhaust port 16, and exhaust gas after combustion in the combustion chamber 11 is discharged from the exhaust port 16 to the exhaust passage 17, and the catalyst 18 and the muffler are silenced. It is discharged outside through the container 19.
[0017]
A butterfly exhaust throttle valve 20 is provided between the catalyst 18 interposed in the exhaust passage 17 and the silencer 19, and the exhaust throttle valve 20 is positioned at two positions, a fully closed position and a fully open position, by an exhaust throttle actuator 21. It is driven to open and close. A bypass passage 22 is connected to the exhaust passage 17 so as to bypass the exhaust throttle valve 20, and a pressure adjusting valve 23 is provided in the bypass passage 22. The pressure regulating valve 23 is normally closed, and opens when the exhaust pressure on the upstream side of the exhaust passage 17 rises due to the exhaust throttle valve 20 being fully closed or the like, thereby allowing the exhaust gas to flow therethrough. The exhaust pressure in 17 is maintained at its own set pressure. In the present embodiment, the exhaust throttle valve 20, the exhaust throttle actuator 21, the bypass passage 22, and the pressure adjustment valve 23 constitute an exhaust flow rate adjustment mechanism.
[0018]
In the vehicle compartment, an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.) used for storing control programs and control maps, an ECU (engine) equipped with a central processing unit (CPU), a timer counter, etc. A control unit 31 is installed and performs overall control of the engine 1. On the input side of the ECU 31, there are a rotation speed sensor 32 for detecting the engine rotation speed Ne, a throttle sensor 33 for detecting the opening degree θth of the throttle valve 14, and a cam angle sensor 34 for detecting the phase of the exhaust camshaft 3b (overlap amount). Various sensors such as detection means) are connected. Further, the OCV 4a, the spark plug 9, the fuel injection valve 10, the exhaust throttle actuator 21 and the like are connected to the output side of the ECU 31.
[0019]
The ECU 31 executes various controls such as fuel injection control and ignition timing control based on detection information from each sensor. In addition, the ECU 31 operates in accordance with a decrease in the amount of heat generated by the engine, such as when the engine 1 is required to be quickly heated, such as when the engine 1 is cold-started, or when the engine heat generation is reduced, such as during lean operation or vehicle deceleration. In an operating state in which the temperature decreases, exhaust throttle control is performed by switching the exhaust throttle valve 20 to the fully closed position by the exhaust throttle actuator 21 to increase the exhaust pressure, thereby limiting the exhaust flow rate and increasing the temperature of the catalyst 18. Keep warm.
[0020]
Further, the ECU 31 controls the phase of the exhaust camshaft 3b by driving the OCV 4a based on the detection information from each sensor, and the phase of the exhaust camshaft 3b at this time makes the combustion of the engine 1 unstable. When in the state, the exhaust throttle control is prohibited.
Therefore, the prohibition determination of the exhaust throttle control will be described. Prior to this, phase control of the exhaust camshaft 3b will be described. The ECU 31 executes the cam phase control routine shown in FIG. 2 at a predetermined control interval, and first determines whether or not the exhaust throttle control start condition is satisfied in step S2. As the exhaust throttle control start condition, the cold start of the engine 1, the lean operation, the vehicle deceleration, etc. are set, and the exhaust throttle control start condition is satisfied when any of the conditions is satisfied. Considered.
[0021]
When the determination in step S2 is NO (No), the process proceeds to step S4, and the phase of the exhaust camshaft 3b, that is, the target values of the valve opening timing and valve closing timing of the exhaust valve 8b are calculated. For example, the target value of the phase is expressed as a target advance amount tgtθ from the most retarded position of the exhaust camshaft 3b, and the target average effective pressure Pe and volumetric efficiency Ev (correlated with the engine load) of the engine 1 and the engine speed. It is calculated from a map (not shown) based on Ne. In step S6, the ECU 31 obtains the actual advance angle amount θ of the exhaust camshaft 3b based on the detection information from the cam angle sensor 34, and drives and controls the OCV 4a so that the actual advance angle amount θ becomes the target advance angle amount tgtθ. Then, the routine ends.
[0022]
On the other hand, if YES is determined in step S2 because the exhaust throttle control start condition is satisfied, the process proceeds to step S8. The processing content of step S8 is the same as that of step S4, but the map characteristics to be applied are different, and a larger target advance amount tgtθe is calculated compared to the target advance amount tgtθ of step S4 in the same operation region. After the OCV 4a is driven and controlled in the subsequent step S6 based on the target advance amount tgtθe, the routine is terminated.
[0023]
By the phase control of the exhaust camshaft 3b described above, the exhaust throttle control in which the valve opening timing of the exhaust valve 8b is appropriately controlled according to the operation region of the engine 1 and the internal EGR of the engine 1 is increased by limiting the exhaust flow rate. In some cases, the exhaust camshaft 3b is controlled to the advance side based on the larger target advance amount tgtθe, and the overlap amount OL of the intake and exhaust valves 8a, 8b is reduced to stabilize the combustion (overload). Wrap amount reduction control means).
[0024]
In particular, when phase control is performed on the exhaust side in this way, the return amount of exhaust gas to the combustion chamber 11 decreases with the advance angle of the exhaust camshaft 3b, and a direct internal EGR suppression effect is achieved. As compared with the case where the intake side is retarded and controlled to the same overlap amount OL, the stabilization of combustion becomes more reliable.
Further, as described in steps S4 and S8 in FIG. 2, the air-fuel ratio A / F, the fuel injection timing IT, the ignition timing applied in the fuel injection control are the same as the target advance amount tgtθ of the exhaust camshaft 3b. The target value of the ignition timing SA applied in the control is also switched according to the exhaust throttle control start condition (operation control parameter switching means).
[0025]
On the other hand, the prohibition determination of the exhaust throttle control is performed based on an exhaust throttle prohibition determination routine shown in FIG. The ECU 31 executes the routine at a predetermined control interval. First, in step S12, it is determined whether or not the exhaust throttle control start condition is satisfied as in step S2. When the determination is NO, the routine is terminated. .
[0026]
On the other hand, when the determination in step S12 is YES, the process proceeds to step S14 to determine whether or not the actual overlap amount OL of the intake and exhaust valves 8a and 8b is less than the first set value OL0 (OL <OL0). Since the phase of the intake camshaft 3a is fixed, the actual overlap amount OL is uniquely derived based on the phase of the exhaust camshaft 3b detected by the cam angle sensor 34.
[0027]
When the phase of the exhaust camshaft 3b is controlled to, for example, the most advanced position in order to reduce the overlap amount in the normal phase control range of the exhaust camshaft 3b, the first set value OL0 is It is set corresponding to the phase position of the exhaust camshaft 3b that causes an operation response delay and generates an excessive overlap amount with respect to the target overlap amount. When the phase of the exhaust camshaft 3b is in the normal control range and the actual overlap amount OL is smaller than the first set value OL0, the variable movement is performed so as to decrease the overlap amount with the exhaust throttle. Even if the valve mechanism is adjusted, it can be estimated that there is little delay in actuation response and an excessive amount of overlap does not occur, and the ECU 31 makes a YES determination in step S14 and proceeds to step S16.
[0028]
In step S16, it is determined whether or not the difference ΔOL obtained by subtracting the target overlap amount tgtOL from the actual overlap amount OL is less than the second set value ΔOL0 (OL−tgtOL = ΔOL <ΔOL0). Similar to the actual overlap amount OL, the target overlap amount tgtOL is uniquely derived from the target advance amount tgtθ.
As a result of the phase control of the exhaust camshaft 3b described above, the target overlap amount tgtOL changes in accordance with a change in the operating region of the engine 1 or switching between steps S4 and S8 in FIG. 2, and follows the target overlap amount tgtOL. Thus, the actual overlap amount OL is controlled. When the target overlap amount tgtOL changes in the expansion direction, the difference ΔOL is negative because the actual overlap amount OL that follows is smaller than the target overlap amount tgtOL, and the target overlap amount tgtOL is If there is no large follow-up delay in the phase control by the variable valve actuator 4 even when changing in the reduction direction, the difference ΔOL is positive, but less than the second set value ΔOL0. That is, in these cases, it can be estimated that the phase control is normally performed in a transitional sense, and the ECU 31 makes a determination of YES in step S16 and proceeds to step S18.
[0029]
In step S18, in response to the establishment of the exhaust throttle control start condition in step S12, the routine is terminated after the execution of the exhaust throttle control is permitted. Based on this permission command, in the exhaust throttle control, the exhaust throttle valve 20 is switched to the fully closed position by the exhaust throttle actuator 21, and the exhaust flow rate is limited by the exhaust pressure increase thereby, and the catalyst 18 is heated and kept warm.
[0030]
On the other hand, when the determination in step S14 is NO (OL ≧ OL0), an excessive overlap amount is generated due to the delay in the response of the variable valve mechanism, and the internal EGR cannot be properly suppressed, or the OCV 4a It can be inferred that the variable valve actuator 4 is inoperable when the actual overlap amount OL is large due to the vane rotor sticking to the variable valve actuator 4 or due to insufficient hydraulic pressure. In this case, the ECU 31 proceeds to step S20 and terminates the routine after prohibiting execution of the exhaust throttle control.
[0031]
When the determination in step S16 is NO (ΔOL ≧ ΔOL0), the actual overlap amount OL is smaller than the first set value OL0, but the target overlap amount tgtOL changes to the reduction side. It can be inferred that there is a possibility that the internal EGR cannot be properly suppressed because the actual overlap amount OL temporarily causes a follow-up delay due to the responsiveness of the variable valve actuator 4. Also in this case, the ECU 31 proceeds to step S20 and terminates the routine after prohibiting the execution of the exhaust throttle control.
[0032]
While step S14 estimates the occurrence of an excessive overlap amount, step S16 differs in that the occurrence of an excessive overlap amount is actually detected, but the internal EGR of the engine 1 increases. The point is common. When the exhaust throttle control is started in this state, the internal EGR further increases due to the restriction of the exhaust flow rate, but the exhaust throttle valve 20 is held fully open on the exhaust throttle control side in response to the prohibition command in step S20. Therefore, this increase in internal EGR is avoided in advance.
[0033]
Therefore, according to the control device for the engine 1 of the present embodiment, the phase control by the variable valve actuator 4 and the exhaust throttle control by the exhaust throttle valve 20 are accurately coordinated, and there is an operation response delay or trouble on the phase control side. Even if it occurs, an increase in internal EGR can be avoided and a good combustion state of the engine 1 can be realized.
Note that if the determination in step S14 is NO, the exhaust throttle control continues to be prohibited. However, if the determination in step S16 is NO, the point in time when the temporary overlap OL is eliminated (follow-up delay). Since the exhaust throttling control is permitted at the time when is eliminated, thereafter, the advantage of the exhaust throttling control such as the temperature rise and the heat retention of the catalyst 18 can be obtained.
[0034]
On the other hand, when the exhaust throttle control start condition is satisfied, not only the overlap amount OL of the intake / exhaust valves 8a and 8b is reduced in advance in step S8 on the phase control side to stabilize combustion but also fuel injection control. The target values of the air-fuel ratio A / F, the fuel injection timing IT, and the ignition timing SA applied in the ignition timing control are simultaneously switched. Therefore, optimal fuel injection control and ignition timing control can be realized with respect to the overlap amount OL after reduction, and there is also an advantage that adverse effects on the operation of the engine 1 due to the overlap reduction can be suppressed.
[0035]
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the control device for the direct injection engine 1 is embodied. However, a variable valve mechanism for changing the overlap amount OL of the intake / exhaust valves 8a and 8b and an exhaust flow rate adjusting mechanism for limiting the exhaust flow rate are provided. As long as the engine is equipped, the type of the engine is not limited to this. For example, the engine may be applied to an intake pipe injection type engine or a diesel engine.
[0036]
In the above embodiment, the variable valve actuator 4 controls the phase of the exhaust camshaft 3b (the valve closing timing of the exhaust valve 8b). Instead, the phase of the intake camshaft 3a (the valve opening of the intake valve 8a). Timing) or the phases of the intake and exhaust camshafts 3a and 3b may be controlled together.
Further, in the above embodiment, the exhaust throttle valve 20 is fully closed and kept at a predetermined exhaust pressure by the pressure adjustment valve 23 provided in the bypass passage 22. However, the exhaust throttle is not provided without providing the bypass passage 22 and the pressure adjustment valve 23. A predetermined exhaust pressure may be realized by controlling the valve 20 to a minute opening near the fully closed position.
[0037]
On the other hand, in the above-described embodiment, the exhaust throttle valve 20 is held fully open by the prohibition process in step S20. However, if the overlap amount OL is not so excessive, the exhaust throttle control may not be completely prohibited. For example, when the pressure adjusting valve 23 is not used as described above, the exhaust pressure can be arbitrarily adjusted according to the opening of the exhaust throttle valve 20, so that as the overlap amount OL increases as the processing of step S20, The opening degree of the exhaust throttle valve 20 may be adjusted to the open side so as to suppress the restriction of the exhaust flow rate. With this configuration, even when the overlap amount OL becomes excessive due to a trouble on the phase control side, it is possible to obtain as much as possible a temperature increase and a heat retaining action of the catalyst 18 by the exhaust throttle control.
[0038]
【The invention's effect】
As described above, according to the control apparatus for an internal combustion engine of the first aspect of the present invention, when the actual overlap amount of the intake and exhaust valves by the variable valve mechanism is greater than or equal to the first set value, the exhaust flow rate adjustment mechanism is opened. to control the, avoiding to precisely coordinated control of the variable valve mechanism and the exhaust flow rate adjusting mechanism, has been an increase in the internal EGR of the engine due to the operation response delay of the variable valve mechanism in advance, good A good combustion state can be realized.
[0040]
According to the control apparatus for an internal combustion engine of the invention 請 Motomeko 2, in addition to claim 1, the difference between the actual overlap amount and the target overlap amount is an exhaust flow rate adjusting mechanism when the more than the second set value Since the control is performed on the open side, it is possible to reliably avoid an increase in internal EGR due to a delay in the response of the variable valve mechanism and realize a good combustion state.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram illustrating an engine control apparatus according to an embodiment.
FIG. 2 is a flowchart showing a cam phase control routine executed by the ECU.
FIG. 3 is a flowchart showing an exhaust throttling prohibition determination routine executed by an ECU.
[Explanation of symbols]
1 engine (internal combustion engine)
4 Variable valve actuator (Variable valve mechanism)
4a OCV (Variable valve mechanism)
8a Intake valve 8b Exhaust valve 20 Exhaust throttle valve (Exhaust flow rate adjusting mechanism)
21 Exhaust throttle actuator (exhaust flow rate adjustment mechanism)
22 Bypass passage (exhaust flow rate adjustment mechanism)
23 Pressure adjustment valve (exhaust flow rate adjustment mechanism)
31 ECU (exhaust restriction suppression means, overlap reduction control means, operation control parameter switching means)
34 Cam angle sensor (overlap amount detection means)

Claims (2)

Is capable of changing the overlap amount of the intake and exhaust valves by changing at least one of the closing valve timing of the exhaust valve and the opening timing of the intake valve of an internal combustion engine, the target overlap obtained from the operation region of the internal combustion engine A variable valve mechanism for adjusting the overlap amount so as to follow the amount ;
An exhaust flow rate adjustment mechanism that is provided in the exhaust passage of the internal combustion engine and that increases exhaust pressure by limiting the exhaust flow rate by adjusting the opening to the closed side ;
An overlap amount detecting means for detecting an actual overlap amount of the intake and exhaust valves;
And an exhaust restriction suppressing means for controlling the exhaust flow rate adjusting mechanism to open when the actual overlap amount detected by the overlap amount detecting means is equal to or greater than a first set value. Engine control device. The exhaust restriction suppressing means controls the exhaust flow rate adjusting mechanism to an open side when a difference between the actual overlap amount and the target overlap amount is a second set value or more. control device 1 Symbol placement of an internal combustion engine.

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