JP2004027971A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the efficient and stable operation of an internal combustion engine by solving problems in accompany with the introduction of various controls to improve the practical fuel consumption and the exhaust gas performance in an internal combustion engine. <P>SOLUTION: This controller for the internal combustion engine can switch a multicylinder engine 1 between full cylinder operation and partial cylinder operation, and the torque shock is prevented by retarding an ignition period in a transition period of the switching. The exhaust gas performance can be improved by introducing EGR into the engine 1, and the introduction of EGR is forbidden by closing an EGR valve 26 in switching the operation. Whereby the instable combustion can be surely prevented in switching the operation, even when the EGR is applied in the engine 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that can appropriately perform operation switching with a change in the number of operating cylinders.
[0002]
[Prior art]
2. Description of the Related Art Techniques for efficiently operating an internal combustion engine by variously controlling it to reduce fuel consumption and improve exhaust gas performance have been conventionally employed. For example, in a multi-cylinder internal combustion engine, variable displacement control is performed to increase or decrease the number of operating cylinders, that is, the number of cylinders that actually perform combustion, according to the operating state. This control stops the operation of some cylinders (reduced cylinder operation) in low-load operation states such as low-speed operation and idle operation to reduce fuel consumption, while performing full-cylinder operation in high-load operation states. In this way, the required output can be obtained.
[0003]
Further, in various types of internal combustion engines, EGR control is performed to reduce the combustion temperature by recirculating (refluxing) a part of the exhaust gas to the intake system to prevent deterioration of the exhaust gas. Such EGR control is widely recognized as a technique particularly effective in reducing NOx contained in exhaust gas.
[0004]
[Problems to be solved by the invention]
Although the above-described variable displacement control is suitable for efficiently operating the internal combustion engine when viewed comprehensively, the output fluctuation of the internal combustion engine is temporarily changed during the transition between the full cylinder operation and the reduced cylinder operation. May be accompanied. Further, since the EGR control has a function of slowing down the combustion, there is a possibility that the combustion may be destabilized in the above-described transitional period, particularly in combination with the variable displacement control.
[0005]
Therefore, an object of the present invention is to solve the problems associated with the introduction of various controls and to realize efficient and stable operation of the internal combustion engine.
[0006]
[Means for Solving the Problems]
A control device for an internal combustion engine according to the present invention includes an ignition timing control unit and an EGR control unit. In particular, when the operation of the internal combustion engine is switched between the full cylinder operation and the reduced cylinder operation, The ignition timing is retarded over a period, and the recirculation of exhaust gas is prohibited during this period. As a result, the ignition timing is retarded during the transitional period of the switching accompanied by the change in the number of operating cylinders, thereby suppressing the extreme torque fluctuation, and during this period, the recirculation of the exhaust gas is prohibited, so that the deterioration of the combustion is also reduced. Is prevented.
[0007]
Further, the control device according to the present invention relates to the EGR control, and after the operation of the internal combustion engine is switched, the recirculation amount of the exhaust gas is made different between the full cylinder operation and the reduced cylinder operation (claim 2). More preferably, the exhaust gas recirculation amount is reduced in the reduced-cylinder operation as compared with the all-cylinder operation, so that the EGR control according to the number of operating cylinders is effected.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described as a control device of an internal combustion engine mounted on a vehicle. However, the present invention is not applied only to an internal combustion engine for a vehicle.
FIG. 1 shows an embodiment in which a control device is applied to an engine 1 which is a multi-cylinder internal combustion engine. The engine 1 has, for example, an in-line four-cylinder type cylinder layout, and fuel is supplied to each cylinder by a multipoint injection system. For this reason, the intake manifold 2 of the intake system is provided with four fuel injection valves 4 corresponding to the intake ports connected to the respective cylinders, but FIG. 1 shows only one of them.
[0009]
A surge tank 6 is provided upstream of the intake manifold 2, and an electric throttle valve 8 is attached to an inlet of the surge tank 6. The electric throttle valve 8 is opened and closed by a throttle actuator 10 and is maintained at a desired opening.
The engine 1 includes a cam profile switching mechanism 16 in a valve train of an intake valve 12 and an exhaust valve 14. The switching mechanism 16 has, for example, a plurality of types of cams having different cam shapes, and achieves variable valve timing and variable valve lift by switching the cam that lifts the intake and exhaust valves 12 and 14 according to the operation state. are doing.
[0010]
The switching mechanism 16 can stop the operation of the intake and exhaust valves 12 and 14 by releasing the connection between the rocker arm and the rocker shaft connected to each valve. When the operation of the intake / exhaust valves 12 and 14 is stopped for a specific cylinder by the switching mechanism 16, the cylinder enters a stop (cylinder closed) state without performing combustion. The fuel injection into the stopped cylinder is stopped.
[0011]
The switching mechanism 16 has a hydraulic actuator, and the specific operation of the switching mechanism 16 can be performed by the hydraulic actuator. For this purpose, the switching mechanism 16 is provided with a hydraulic supply / discharge system (not shown). The hydraulic supply / discharge system opens and closes an oil passage connecting the hydraulic actuator and a hydraulic source with a solenoid valve, for example, to the hydraulic actuator. Supply and discharge of the working hydraulic pressure.
[0012]
The engine 1 is provided with an ignition plug 18 for each cylinder, and the ignition plug 18 is connected to an ignition coil 20 for supplying a high voltage. An EGR passage 24 is connected to the exhaust manifold 22 of the exhaust system, and the EGR passage 24 is connected to the intake manifold 2 via an EGR valve 26. The control device of the present embodiment is equipped with an electronic control unit (hereinafter abbreviated as “ECU”) 28 for controlling various electronic devices. The output of the engine 1 and the operation of the switching mechanism 16 described above can be controlled by the ECU 28.
[0013]
For example, an accelerator position sensor 30 is provided in the vehicle, and the accelerator position sensor 30 detects an accelerator opening and outputs it to the ECU 28. The intake manifold 2 is provided with a pressure sensor 40, and the ECU 28 can detect the intake air amount of the engine 1 based on a sensor signal from the pressure sensor 40.
[0014]
In addition, a vehicle speed sensor 36 is provided in the vehicle, and a vehicle speed signal is input to the ECU 28 from the vehicle speed sensor. The engine 1 is provided with a crank angle sensor 38. The crank angle sensor 38 is connected to the ECU 28 and outputs a crank angle signal to the ECU 28.
The ECU 28 adjusts the opening of the electric throttle valve 8 based on the accelerator opening, receives a sensor signal from the pressure sensor 40, detects the amount of intake air of the engine 1, and adjusts the fuel so as to obtain a predetermined air-fuel ratio. The injection valve 4 is operated. Further, the ECU 28 controls the operation of the above-described switching mechanism 16, and appropriately switches the valve timing and the lift amount between, for example, a low vehicle speed region and a high vehicle speed region. Since the output control and the operation control of the switching mechanism 16 are all publicly known, a detailed description of each control is omitted.
[0015]
The above is the basic content of various control functions by the ECU 28. In the present embodiment, the ECU 28 further has a function of appropriately controlling the engine 1 by comprehensively performing various controls.
Hereinafter, the control function of the ECU 28 will be described with a specific example. Further, other configurations of the control device will be clear from the following description.
[0016]
FIG. 2 shows a control example in the case where the operation of the engine 1 is switched from the all-cylinder operation to the reduced-cylinder operation by the ECU 28. Switching of the operation involving such a change in the number of operating cylinders (in this case, reduced from four cylinders to two cylinders) is performed based on the operating state of the engine 1. For example, the ECU 28 detects an operation state of the engine 1 from various variables such as a vehicle speed, an accelerator opening, an engine rotation speed, and a boost pressure (operation state detection means). Here, as an index that specifically represents the driving state, for example, a vehicle speed and a rotation speed of the engine 1 are given.
[0017]
For example, when the actual vehicle speed shifts to a low speed range while the engine 1 is performing all-cylinder operation, or when the vehicle stops and the engine 1 shifts from load operation to idling operation, the ECU 28 determines the number of operating cylinders. It can be determined that the vehicle is in the operating state to be changed (in this case, reduced).
When such a determination is made, the ECU 28 activates the switching mechanism 16 to suspend operation of a specific cylinder (for example, two cylinders). At this time, the ECU 28 switches the operation of the engine 1 according to the following procedure in order to prevent the occurrence of a shock due to a sudden change in torque with the transition from the full cylinder operation to the reduced cylinder operation.
[0018]
As shown in FIG. 2, when the above determination is made (time t ₀ ), the control of the ECU 28 is switched from the full cylinder operation mode A to the reduced cylinder operation mode R. At this time, the ECU 28 controls the operation of the ignition coil 20 to start the ignition timing retard (time t _{0 to} t ₁ ), closes the EGR valve 26, and immediately stops the recirculation of exhaust gas.
[0019]
During this time (time t _{0 to} t ₁ ), the ECU 28 temporarily increases the throttle opening, holds the opening, then reduces the throttle opening, and holds the throttle opening until the ignition timing retard ends.
Note ECU28 stops the operation of the fuel injection valve 4 for one particular cylinder at a timing immediately before terminating the ignition timing retard (before time t _1). As a result, the fuel injection to the specific one cylinder is stopped at the same time as the termination of the ignition timing retard.
[0020]
Then ECU28 causes retarding the ignition timing comprises the cylinder deactivation of the second cylinder (time _t 1 _~t 2). During this time, the ECU 28 once again sets the throttle opening to a larger value than before and then reduces the throttle opening, and holds this until the retard of the ignition timing ends. During this time (time _t 1 _~t 2), likewise boost pressure rises further.
[0021]
Similarly, ECU 28 stops the operation of the fuel injection valve 4 for the second cylinders at a timing immediately before terminating the retarded ignition timing (before time t _2). After a lapse of a short time (1 IG), the switching mechanism 16 (operating cylinder number switching valve) is operated to stop the driving of the intake and exhaust valves 12 and 14, whereby the two cylinders are brought into a completely stopped state. Become.
[0022]
After two specific cylinder becomes dormant, until a certain time has elapsed (time t ₂ ~t _3), ECU 28 maintains the ignition timing constant. Thereafter, ECU 28 is to shift to the ignition timing control using the ignition timing map for the reduced-cylinder operation, thereby gradually change the ignition timing while the tailing process (time t ₃ ~t _4). The ECU28 when starting the tailing process, to reduce the throttle opening degree at the time of the immediately (after time t _3). At this time, since the throttle opening corresponds to the reduced cylinder operation, the throttle opening is smaller than the opening in the full cylinder operation.
[0023]
Then, when the ignition timing retard is finally ended, the ECU 28 opens the EGR valve 26 at this time (time t ₄ ). Thus, the exhaust gas recirculation is restarted in the reduced cylinder operation.
Here, at least three positions are set in the EGR valve 26, and the EGR valve 26 is in the full cylinder position Pa during full cylinder operation, the closed position Po during operation switching, and in the reduced cylinder operation. The respective positions are controlled to the cylinder rest positions Pr. In particular, the opening degree is smaller at the closed cylinder position Pr than at the full cylinder position Pa, and the recirculation amount of the exhaust gas is reduced accordingly. As a result, an exhaust gas recirculation amount suitable for the reduced cylinder operation is obtained, so that the EGR control is effectively performed.
[0024]
As described above, switching to the reduced-cylinder operation from the all-cylinder operation is performed by the ECU 28 (operation cylinder number changing means), the ignition timing is retarded by the ECU 28 over this time a predetermined period (time t ₀ ~t ₄₎ (Ignition timing control means). Also the predetermined time period (time _t 0 ~t ₄₎ is, EGR valve 26 is prohibited refluxing the exhaust gas by being controlled to the closed position Po by ECU 28 (EGR control means).
[0025]
As a result, by executing the ignition timing retard control, a sudden change in torque due to a change in the number of operating cylinders is suppressed, and during this period, combustion instability (misfire, etc.) due to the introduction of EGR is reliably prevented. During this time (time t _{0 to} t ₄ ), the boost pressure gradually increases with a decrease in the intake air amount, and the load on the engine 1 decreases after switching to the reduced cylinder operation.
[0026]
Next, FIG. 3 shows a control example when the ECU 28 switches the engine 1 from the reduced cylinder operation to the all-cylinder operation.
For example, when the required output increases while the engine 1 is performing the reduced-cylinder operation, or when the operation shifts from the idling operation to the load operation, the ECU 28 determines the operating state in which the number of operating cylinders should be changed (in this case, increased). Can be determined.
[0027]
Similarly, when such a determination is made, the ECU 28 activates the switching mechanism 16 to restart the operation of the cylinders (for example, two cylinders) that have been in the idle state until then. Further, at this time, the ECU 28 switches the operation of the engine 1 according to the following procedure in order to prevent the occurrence of torque shock accompanying the transition from the reduced cylinder operation to the all-cylinder operation.
[0028]
In this case, as shown in FIG. 3, when it is determined that the operating state is such that the number of operating cylinders should be changed, the control of the ECU 28 at that time (time t ₁₀ ) starts from the reduced cylinder operation mode R from all cylinders. The mode is switched to the operation mode A. At this time, the ECU 28 closes the EGR valve 26 to immediately stop the recirculation of the exhaust gas (time t ₁₀ ).
The ECU 28 operates the switching mechanism 16 (operating cylinder number switching valve) one IG after the mode switching to restart the driving of the intake and exhaust valves 12 and 14. Next, after a lapse of a predetermined time (time t ₁₁ ), the ECU 28 restarts the operation of the fuel injection valve 2 for one cylinder in the idle state. Thus, after a short time (time t ₁₂ ), the torque rises, and from this point on, the ECU 28 performs the ignition timing retard control. In this case, the ECU 28 retards the ignition timing once, and then gradually returns to the advance side. Also during this time (time _t 10 _{~t 13),} the throttle opening is held in a state during the reduced-cylinder operation.
[0029]
Upon completion of the first ignition timing retard control by operation resumption of the cylinder, after the elapse of a predetermined time (time t _13), ECU 28 similarly for the second resting cylinder remaining resuming the operation of the fuel injection valve 2 . Further in accordance with this, ECU 28 from timing after at a slight time (time t ₁₄₎ is carrying out the ignition timing retard control. Also in this case, the ECU 28 once retards the ignition timing and then gradually returns to the advance side. Further ECU28, in order to shift to the ignition timing control using the ignition timing map for driving all cylinders, thereby gradually change the ignition timing while the tailing process (time _{t 14 ~t 15).}
[0030]
When the tailing process is started, the ECU 28 increases the throttle opening immediately after the tailing process. As a result, the intake air amount is increased in accordance with the all-cylinder operation, and the engine 1 enters the state of the all-cylinder operation.
When the ECU 28 finally ends the ignition timing retard control, the ECU 28 opens the EGR valve 26 (all cylinder positions Pa) at this time (time t ₁₅ ). Thus, the recirculation of exhaust gas is restarted in all-cylinder operation, and an exhaust gas recirculation amount corresponding to all-cylinder operation is obtained.
[0031]
As described above, all the cylinders is switched to the operation is performed (operation cylinder number changing means) from the reduced-cylinder operation by ECU 28, the ignition timing retard rows by ECU 28 over this time a predetermined period (time _t 10 _{~t 15)} (Ignition timing control means). Also the predetermined time period (time _t 10 _{~t 15)} is, EGR valve 26 is prohibited refluxing the exhaust gas by being controlled to the closed position Po by ECU 28 (EGR control means).
[0032]
As a result, by performing the ignition timing retard, a sudden change in torque due to a change in the number of operating cylinders is suppressed, and during this period, combustion instability (misfire, etc.) due to the introduction of EGR is reliably prevented.
In the above control example, the two cylinders are closed during the reduced cylinder operation, but only one cylinder may be closed. The number of cylinders to be closed and their positions can be changed as appropriate. For example, the number of cylinders to be closed can be determined according to the total number of cylinders and the cylinder layout.
[0033]
Further, in one embodiment, the specific cylinder is deactivated by deactivating the intake and exhaust valves 12, 14, but may be realized by other means.
The cylinder layout of the engine 1 to which the present invention is applied is not limited to the in-line type, and may be, for example, a V-type or opposed type. The fuel injection system of the engine 1 may employ, for example, an in-cylinder injection system.
[0034]
【The invention's effect】
The control device for an internal combustion engine according to the present invention (Claim 1) can switch the operation in which the number of operating cylinders is changed without generating torque shock while improving exhaust gas performance by introducing EGR.
Further, since the exhaust gas introduction amount can be changed according to the number of operating cylinders (claim 2), the EGR control can be effectively functioned in any of the full cylinder operation and the reduced cylinder operation.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an embodiment of a control device.
FIG. 2 is a timing chart showing a control example at the time of switching from all-cylinder operation to reduced-cylinder operation.
FIG. 3 is a timing chart showing a control example when switching from reduced cylinder operation to all cylinder operation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 Intake manifold 4 Fuel injection valve 16 Switching mechanism (operating cylinder number switching means)
18 spark plug 24 EGR passage 26 EGR valve 28 ECU (various control means)

Claims (2)

Operating state detecting means for detecting an operating state of the internal combustion engine,
The number of operating cylinders that switches the operation of the internal combustion engine between full-cylinder operation and reduced-cylinder operation when it is determined that the operating state should be changed based on the operating state detected by the operating state detecting means. Switching means;
When switching of the operation of the internal combustion engine is performed by the operating cylinder number switching means, ignition timing control means for retarding the ignition timing of the internal combustion engine over a predetermined period,
EGR control for recirculating a part of the exhaust gas to the intake system during the operation of the internal combustion engine, while prohibiting the recirculation during the period in which the ignition timing is retarded by the switching of the operation of the internal combustion engine by the operating cylinder number switching means. And a control device for an internal combustion engine. 2. The control device for an internal combustion engine according to claim 1, wherein the EGR control unit changes the recirculation amount of the exhaust gas between the full cylinder operation and the reduced cylinder operation after the switching by the operating cylinder number switching unit. 3.

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