JP2006161576A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress decline in acceleration feeling when forced return is performed for a relatively short time after a fuel cut start condition is achieved, in an internal combustion engine recirculating exhaust gas during execution of the fuel cut at the time of deceleration, in regard to a control device for the internal combustion engine. <P>SOLUTION: In the control device for the internal combustion engine, when it is recognized that the fuel cut start condition is achieved (time t0), to extend a valve overlap period, intake valve timing VVT is advanced (E) and an EGR valve is closed (F). When the intake valve timing VVT reaches a timing advance rated value (t1), a throttle opening TA is controlled to be fully closed (C). After that, when predetermined time A passes (t2), fuel cut is executed (D). When predetermined time B passes after full closing of the throttle opening TA (t3), the opening of the EGR valve is opened to an opening corresponding to the number of steps at the time of deceleration (F). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable as an apparatus for controlling an internal combustion engine that recirculates exhaust gas during execution of fuel cut during deceleration.

  Conventionally, for example, Patent Document 1 discloses that in an engine of a hybrid vehicle in which an engine and a driving motor are combined, a valve timing variable mechanism that changes the valve timing of the engine and a return valve (EGR valve) are controlled to exhaust A technique is disclosed that includes an exhaust gas recirculation device that recirculates exhaust gas flowing through a pipe to the intake pipe side. In a hybrid vehicle, since it is possible to run only with a running motor, fuel cut control for temporarily cutting fuel to the engine may be performed frequently and over a long period of time. In the above conventional technique, when the operation by the engine is stopped due to the execution of the fuel cut control, the exhaust gas recirculation device exhausts the fuel during the fuel cut in order to suppress excessive cooling of the catalyst. The gas is to be refluxed.

  More specifically, in the above-described conventional technology, during the fuel cut that is performed when the vehicle travels using only the travel motor, the valve overlap period is lengthened and then the reflux valve is opened to perform the fuel cut. After that, the valve overlap period is restored after the reflux valve is closed. In the above technique, by executing such control, it is possible to suppress pressure fluctuations in the combustion chamber and prevent shock pressure from being applied to the exhaust gas recirculation device.

JP-A-9-329060 JP-A-8-170552

  By the way, in the internal combustion engine, when the fuel cut is executed at the time of deceleration, when the accelerator request (acceleration request) from the driver is detected, a process of returning from the fuel cut (forced return) is executed. The timing of the accelerator request from the driver cannot be predicted in advance. Therefore, in the above-described conventional technique, the accelerator pedal is depressed to forcibly return from the fuel cut under the condition that the exhaust gas is recirculated by opening the recirculation valve during the fuel cut during deceleration. In this case, since the exhaust gas scavenging is started after the condition for forced return is satisfied, a predetermined time is required until the exhaust gas remaining at a high concentration in the combustion chamber is scavenged. Become.

  As a result, after the forced return condition is satisfied, until the exhaust gas is sufficiently scavenged, the combustion is performed in a situation where the residual exhaust gas concentration in the combustion chamber is high, that is, in a high EGR rate situation. This causes the problem of reduced acceleration. In addition, if frequent operation is performed in a relatively short period of time after the fuel cut start condition is satisfied during deceleration, the exhaust gas recirculation and forced exhaustion will again occur before scavenging is fully completed. The exhaust gas scavenging due to the return is repeated in a short time, and the exhaust gas scavenging does not proceed satisfactorily, so the above problem becomes more prominent.

  The present invention has been made to solve the above-described problems, and in an internal combustion engine that recirculates exhaust gas during execution of fuel cut during deceleration, it is compulsory in a relatively short time after the fuel cut start condition is satisfied. It is an object of the present invention to provide a control device for an internal combustion engine that can suppress a decrease in acceleration feeling when the engine is restored.

In order to achieve the above object, the first invention communicates a variable valve mechanism that varies a valve overlap period in which an intake valve opening period and an exhaust valve opening period overlap, and an intake passage and an exhaust passage. An EGR valve disposed in the middle of an exhaust gas recirculation passage, and a control device for an internal combustion engine that recirculates exhaust gas while cutting fuel while decelerating,
Variable valve timing control means for driving the variable valve mechanism to increase the valve overlap period to a predetermined value when a fuel cut start condition is satisfied;
EGR valve control means for opening the EGR valve when a predetermined time has elapsed after the valve overlap period is increased,
It is characterized by providing.

According to a second aspect of the present invention, in order to achieve the above object, a variable valve mechanism for varying a valve overlap period in which an intake valve opening period and an exhaust valve opening period overlap, an intake passage, an exhaust passage, An EGR valve disposed in the middle of an exhaust gas recirculation passage that communicates with the engine, and a control device for an internal combustion engine that recirculates exhaust gas while cutting fuel during deceleration,
Variable valve timing control means for driving the variable valve mechanism to increase the valve overlap period to a predetermined value when a fuel cut start condition is satisfied;
Fuel cut execution means for executing fuel cut when a predetermined time elapses after the valve overlap period is increased;
EGR valve control means for opening the EGR valve after the fuel cut is performed,
It is characterized by providing.

  According to a third invention, in the first or second invention, when the valve overlap is increased, the throttle valve is made smaller than the opening before the fuel cut start condition is satisfied, Throttle control means for controlling the throttle valve to be fully closed when the valve overlap reaches the predetermined value is provided.

In a fourth aspect based on the third aspect, the fuel cut execution means executes the fuel cut when a first predetermined time elapses after the throttle valve is fully closed by the throttle control means. ,
The EGR valve control means opens the EGR valve when a second predetermined time elapses from the fuel cut execution time after the first predetermined time elapses.

  According to the first invention, in the initial stage when the fuel cut start condition is satisfied, only the exhaust gas recirculation is performed by increasing the valve overlap, so that the exhaust gas return introduced into the combustion chamber is performed. The flow rate is relatively small. Therefore, according to the present invention, when forced recovery is performed in a relatively short time after the fuel cut start condition is satisfied, the time required to replace the exhaust gas recirculation gas with fresh air is set to the time when the fuel cut start condition is satisfied. Compared to when exhaust gas recirculation based on control of the EGR valve is executed from the beginning, it is possible to reduce the acceleration feeling at the time of forced return.

  According to the second aspect, when the fuel cut start condition is satisfied, the fuel cut is executed after a predetermined time has elapsed after the valve overlap is increased. For this reason, according to the present invention, when forced return is performed in a relatively short time after the fuel cut start condition is satisfied, the time required for replacing the exhaust gas recirculation gas with fresh air is reduced. The decrease in acceleration feeling can be suppressed. Further, according to the present invention, the period from when the start condition is satisfied to when the fuel cut is started can be reliably ensured as the period during which the reduction in acceleration feeling can be reduced.

  According to the third invention, the throttle valve is fully closed after waiting for the valve overlap to reach a predetermined value. If the throttle opening is fully closed during the fuel cut, fresh air can be more reliably prevented from flowing into the combustion chamber during the fuel cut. According to the present invention, the fully closed timing of the throttle opening for that purpose is not the time when the fuel cut start condition is satisfied, but the time when the valve overlap becomes a predetermined value as described above. Even in the case where the forced return is frequently performed in a relatively short time after the establishment, the time required to replace the exhaust gas recirculation gas with fresh air can be further reduced. In contrast, a reduction in acceleration feeling can be more reliably mitigated.

  According to the fourth aspect, by appropriately setting the first predetermined time and the second predetermined time, it is possible to adjust the period during which the decrease in acceleration feeling after the forced return can be reduced.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. A combustion chamber 12 is formed in the cylinder of the internal combustion engine 10. An intake passage 14 and an exhaust passage 16 communicate with the combustion chamber 12.

  A throttle valve 18 is disposed in the intake passage 14. The throttle valve 18 is an electronically controlled valve that is driven by a throttle motor based on the accelerator opening. A throttle position sensor 20 for detecting the throttle opening degree TA is disposed in the vicinity of the throttle valve 18. According to such a configuration, the engine speed NE of the internal combustion engine 10 can be controlled to a predetermined idling rotation by setting the opening degree TA of the throttle valve 18 to the idle opening degree TA0. Note that the present invention is not limited to such a configuration, and a bypass passage that bypasses the throttle valve 18 is provided in the intake passage 14, an ISC valve is arranged in the middle of the bypass passage, and the opening of the ISC valve is adjusted to idle. A configuration in which the rotational speed is controlled to a predetermined value may be employed.

  The internal combustion engine 10 is a multi-cylinder engine having a plurality of cylinders, and FIG. 1 shows a cross section of one of the cylinders. Each cylinder included in the internal combustion engine 10 is provided with an intake port that communicates with the intake passage 14 and an exhaust port that communicates with the exhaust passage 16. A fuel injection valve 22 for injecting fuel into the intake port is disposed in the intake port. The intake port and the exhaust port are provided with an intake valve 24 and an exhaust valve 26 for bringing the combustion chamber 12 and the intake passage 14 or the combustion chamber 12 and the exhaust passage 16 into a conductive state or a cut-off state, respectively. .

  The intake valve 24 and the exhaust valve 26 are driven by an intake variable valve operating (VVT) mechanism 28 and an exhaust variable valve operating (VVT) mechanism 30, respectively. The variable valve mechanisms 28 and 30 respectively open and close the intake valve 24 and the exhaust valve 26 in synchronization with the rotation of the crankshaft, and change their valve opening characteristics (valve opening timing, operating angle, lift amount, etc.). can do.

  The internal combustion engine 10 includes a crank angle sensor 32 in the vicinity of the crankshaft. The crank angle sensor 32 is a sensor that reverses the Hi output and the Lo output each time the crankshaft rotates by a predetermined rotation angle. According to the output of the crank angle sensor 32, it is possible to detect the rotational position and rotational speed of the crankshaft, and the engine rotational speed NE. The internal combustion engine 10 also includes a cam angle sensor 34 in the vicinity of the intake camshaft. The cam angle sensor 34 is a sensor having the same configuration as the crank angle sensor 32. According to the output of the cam angle sensor 34, the rotational position (advance value) of the intake camshaft can be detected.

  An upstream catalyst (SC) 36 and a downstream catalyst (UF) 38 for purifying exhaust gas are arranged in series in the exhaust passage 16 of the internal combustion engine 10. An air-fuel ratio sensor 40 for detecting the exhaust air-fuel ratio at that position is disposed upstream of the upstream catalyst 36. Further, an oxygen sensor 42 that generates a signal corresponding to whether the air-fuel ratio at that position is rich or lean is disposed between the upstream catalyst 36 and the downstream catalyst 38.

  The system shown in FIG. 1 includes an exhaust gas recirculation passage 44 that connects the intake passage 14 and the exhaust passage 16. An EGR valve 46 is provided in the middle of the exhaust gas recirculation passage 44. Further, the exhaust gas recirculation passage 44 is provided with an exhaust gas cooler (EGR cooler) 48 for cooling the exhaust gas recirculated to the intake passage 14.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. In addition to the various sensors described above, the ECU 50 is connected to an accelerator position sensor 52 for detecting the accelerator pedal opening PA and the various actuators described above. The ECU 50 can control the operating state of the internal combustion engine 10 based on those sensor outputs.

[Outline of catalyst deterioration suppression control by exhaust gas circulation]
The system of the present embodiment configured as described above is a process for stopping fuel injection when the throttle opening TA is set to the idle opening TA0 during operation of the internal combustion engine 10, that is, fuel cut (F / C). F / C is started when the throttle opening TA is suddenly closed during the operation of the internal combustion engine 10. For this reason, after the start of F / C, a state is formed in which the intake pipe pressure PM is large and easily becomes negative. At this time, if the intake pipe pressure PM becomes excessively negative, an increase in oil occurs in the internal combustion engine 10 and the amount of oil consumption increases.

  Incidentally, the negative pressure of the intake pipe pressure PM can be avoided by increasing the throttle opening degree TA. Therefore, if the throttle opening TA is maintained at an opening larger than the basic idle opening TA0 after the start of F / C, it is possible to prevent the intake pipe pressure PM from becoming excessively negative, that is, It is possible to prevent the oil from rising. However, since fuel injection is not performed during execution of F / C, the gas flowing into the catalyst (upstream catalyst 36 and downstream catalyst 38) is extremely lean. When a lean gas flows into the high-temperature catalyst, the catalyst tends to deteriorate. For this reason, if the throttle opening TA is opened after the start of F / C to increase the amount of lean gas flow, the increase in oil consumption can be prevented, but the deterioration of the upstream catalyst 36 and the downstream catalyst 38 is promoted.

  According to the system shown in FIG. 1, the exhaust gas can be recirculated to the combustion chamber 12 through the intake passage 14 by adjusting the opening of the EGR valve 46 appropriately (external EGR control). Further, according to the system shown in FIG. 1, the valve opening phase of the intake valve 24 is advanced (more specifically, the valve opening timing is advanced) by the intake variable valve mechanism 28, so that the valve overlap period, That is, the period during which both the intake valve 24 and the exhaust valve 26 are open can be extended. If the valve overlap period is extended during execution of F / C during deceleration when the intake pipe pressure PM is in a negative pressure state, the amount of burned gas that flows back to the intake passage 14 after the intake valve 24 is opened, That is, the internal EGR amount increases (internal EGR control).

  The intake pipe pressure PM approaches the atmospheric pressure as the amount of gas downstream of the throttle valve 18 increases. The amount of gas is the sum of the amount of fresh gas that has passed through the throttle valve 18 and the amount of EGR gas generated by external EGR control and / or internal EGR control. For this reason, if the EGR amount is sufficiently large, the intake pipe pressure PM does not become excessively negative no matter how small the throttle opening TA is.

  As described above, according to the system shown in FIG. 1, the throttle opening TA is sufficiently reduced in a state where the EGR valve opening is set to a sufficient value or a sufficient valve overlap is generated. As a result, a sufficient amount of EGR can be generated, and the deterioration of the upstream catalyst 36 and the downstream catalyst 38 can be effectively suppressed while preventing the oil from rising. Hereinafter, such control, that is, control for suppressing deterioration of the catalysts 36 and 38 by introducing EGR gas into the combustion chamber 12 during execution of F / C during deceleration is referred to as “catalyst deterioration suppression control by exhaust gas circulation”. Or simply referred to as “catalyst deterioration suppression control”.

[Characteristics of Embodiment 1]
There are two conditions for returning from the F / C during deceleration. That is, when the engine speed NE is close to idling (natural recovery) and when an accelerator request (acceleration request) is issued from the driver (forced return). In the former case, it is possible to detect in advance the timing at which the return is started, but in the latter case, since it is a command from the driver, it cannot be reliably predicted. In this specification, if the operation to return to steady running after the F / C start condition is satisfied is a return operation based on the accelerator request, the fuel cut operation is not yet performed after the start condition is satisfied. Even if the return operation is not performed, it is referred to as “forced return”.

  Here, the characteristics of the external EGR control and the internal EGR control are compared. In the external EGR control, since the exhaust gas is recirculated to the intake passage 14 via the exhaust gas recirculation passage 44, it is easy to ensure a relatively large amount of circulation. On the other hand, however, the external EGR control takes a long time until the introduced exhaust gas recirculation amount is replaced with fresh air by the capacity of the passage from the EGR valve 46 to the combustion chamber 12 at the time of forced recovery from the F / C. Cost. On the other hand, in the internal EGR control, since EGR gas moves back and forth between the combustion chamber 12 and the intake passage 14 in the vicinity of the intake valve 24, the circulation amount is smaller than that in the external EGR control, and the exhaust air is exhausted for a long time. It is difficult to keep the fuel ratio stoichiometric. However, on the other hand, the internal EGR control can shorten the time required to switch to fresh air when forcibly returning from F / C.

  From the above, using external EGR control can increase the exhaust gas recirculation amount as compared with the case of internal EGR control, which is advantageous in executing the catalyst deterioration suppression control. Since it takes a lot of time to switch to, the response is not as good as in the case of internal EGR control. Further, as described above, the timing of forced recovery from the F / C cannot be detected in advance. For this reason, until the EGR gas is sufficiently scavenged after the forced recovery from the F / C, combustion occurs under a high EGR rate condition, which causes a problem of a reduction in acceleration feeling.

  In addition, if frequent operation is performed in a relatively short time from when the F / C start condition at the time of deceleration is satisfied, the EGR gas is recirculated by the F / C again before scavenging is sufficiently completed. The EGR gas scavenging due to the forced return is repeated in a short time, and the EGR gas scavenging does not proceed satisfactorily, so the above problem becomes more prominent. Therefore, in the system of the present embodiment, the following control is executed when the deceleration F / C start condition is satisfied in order to suppress a decrease in acceleration feeling at the time of forced return from F / C.

Next, with reference to FIG. 2 and FIG. 3, the specific process in Embodiment 1 of this invention is demonstrated.
FIG. 2 is a flowchart of a routine executed by the ECU 50 in the present embodiment. Note that this routine is periodically executed at predetermined time intervals.
FIG. 3 is a timing chart for explaining operations realized by the processing of the routine shown in FIG. More specifically, FIG. 3A shows a waveform representing a change in the accelerator pedal opening PA. FIG. 3B shows a waveform representing a change in the throttle opening degree TA. A waveform indicated by “ISC” in FIG. 3C is a waveform representing a change in required flow rate (intake air amount) control during idling. FIG. 3D shows a waveform representing success / failure of F / C execution. FIG. 3E shows a waveform representing a change in the advance amount of the intake valve timing VVT controlled by the intake variable valve mechanism 28. FIG. 3F shows a waveform representing a change in the number of steps (opening degree) of the EGR valve 46.

  In the routine shown in FIG. 2, it is first determined whether or not the accelerator pedal opening PA is fully closed (step 100). As a result, when it is determined that the accelerator pedal opening PA is in the fully closed position, the throttle opening TA is set to the idle opening TA0 (step 102). Next, it is determined whether or not a deceleration F / C start condition is satisfied (step 104). A time t0 shown in FIG. 3 indicates the time when the F / C start condition is satisfied. That is, F / C is determined when the accelerator pedal is fully closed (FIG. 3 (A)) and the throttle opening TA is set to the idle opening TA0 (FIG. 3 (B)). Is determined to have been established.

  If it is determined in step 104 that the deceleration F / C start condition is satisfied, then, the intake valve timing VVT is advanced from the advance amount during steady running to the advance angle specified value corresponding to the driving state ( Step 106). That is, processing for increasing the valve overlap period to a predetermined value is executed. More specifically, the advance amount of the intake valve timing VVT controlled in this step 106 is related to the engine speed NE in order to set the intake pipe pressure PM during the deceleration F / C to a target value. Based on this, the engine speed NE is set to be smaller as the engine speed NE is lower.

  Further, if it is determined in step 104 that the deceleration F / C start condition is satisfied, the EGR step number is set to zero from the step number during steady running in order to stop the supply of EGR gas by the external EGR control. That is, the EGR valve 46 is fully closed (step 108).

  Next, it is determined whether or not the advance value of the intake valve timing VVT has reached the prescribed advance value (step 110). The advance speed of the intake valve timing VVT can be grasped in advance based on the specifications of the intake variable valve mechanism 28. Therefore, based on the advance amount to the advance angle specified value set in step 106, the time (t1−t0) until the advance angle specified value is reached (see FIG. 3) can be calculated. In step 110, it is determined whether or not the intake valve timing VVT has reached the advance angle regulation value based on the arrival time to the advance angle regulation value.

  Next, when it is determined in step 110 that the advance value of the intake valve timing VVT has reached the advance value, the throttle opening degree TA is controlled to be fully closed (step 112). The response speed of the throttle valve 18 is extremely faster than the response speed of control of the intake valve timing VVT by the intake variable valve mechanism 28. For this reason, if the throttle opening degree TA is fully closed before the intake valve timing VVT reaches the advance angle regulation value, the intake pipe pressure PM will become negative more than the target value. Therefore, in this step 112, the throttle opening TA is fully closed when the intake valve timing VVT reaches the advance angle prescribed value t1 (FIG. 3C). Further, by fully closing the throttle opening degree TA, the inflow of fresh air can be more reliably suppressed during the F / C period after the time point t1. If the configuration includes an ISC valve, in this step 112, in addition to the throttle valve 18 being fully closed, the ISC valve is also fully closed.

  Next, after the throttle opening degree TA is fully closed, it is determined whether or not the predetermined time A has elapsed (step 114). At the time t2 when the predetermined time A has been recognized, the fuel injection is stopped. It is executed (step 116). According to such processing, after the throttle opening degree TA is fully closed, oxygen remaining in the combustion chamber 12 is burned as much as possible, so that the EGR concentration in the combustion chamber 12 can be sufficiently increased. . The predetermined time A is a value set in advance to ensure such a combustion time.

  Next, after the throttle opening degree TA is fully closed, it is determined whether or not the predetermined time B has elapsed (step 118), and at the time t3 when the predetermined time B has elapsed, the EGR valve 46 is opened. The degree is set to an opening corresponding to the number of steps during deceleration (step 120). More specifically, the number of EGR steps (the opening degree of the EGR valve 46) controlled in this step 120 is set to the engine speed NE in order to set the intake pipe pressure PM during the deceleration F / C as a target value. Based on this relationship, the engine speed NE is set to increase as the engine speed NE increases. Note that the timing chart shown in FIG. 3 shows an example in which the advance angle of the intake valve timing VVT is maintained after the EGR valve 46 is opened at time t3. After the gas is introduced, the advance amount of the intake valve timing VVT may be returned to the value during steady running.

  When the EGR gas is introduced into the combustion chamber 12 by the external EGR control after the F / C start condition is satisfied, the acceleration feeling is reduced after the forced return from the F / C as described above. There's a problem. As described above, the internal EGR control based on the change of the intake valve timing VVT is more responsive than the external EGR control based on the change of the opening degree of the EGR valve 46. Therefore, the predetermined time B in step 120 is an acceleration feeling after forced recovery from the F / C based on the actual F / C execution frequency obtained by investigating the usage mode of the vehicle and the execution time. It is set to an appropriate time so as to suppress the decrease in the amount. In other words, according to the process of step 120, the predetermined time B from when the throttle opening degree TA is fully closed to when the EGR valve 46 is opened can be appropriately set, and forced recovery from F / C is performed. It is possible to adjust the period during which the later decrease in acceleration feeling can be reduced.

  As described above, according to the routine shown in FIG. 2, when it is determined that the F / C start condition is satisfied, the EGR valve 46 is fully closed at the initial stage after the start condition is satisfied. Only the advance angle of the intake valve timing VVT with good engine speed is executed, that is, only the internal EGR control is executed without executing the external EGR control. When only the internal EGR control is performed, the amount of EGR gas introduced into the combustion chamber 12 is relatively small. For this reason, according to the system of the present embodiment, when a forced return from the F / C is performed in a relatively short time after the F / C start condition is satisfied, the external EGR control is executed from the beginning of the start condition being satisfied. Compared with the case where it is, the time required to replace the EGR gas with fresh air can be shortened, and the deterioration of the acceleration feeling can be suppressed. Further, according to the above routine, the advance angle of the intake valve timing VVT is executed before the start of the fuel cut, the fuel cut is performed after the intake valve VVT reaches the specified advance angle and a predetermined time A has elapsed. Is executed. For this reason, according to the system of the present embodiment, it is possible to reliably ensure a period in which a decrease in acceleration feeling can be suppressed when a forced return occurs in a relatively short time after the F / C start condition is satisfied.

  If the throttle opening degree TA is fully closed during execution of F / C, it is possible to more reliably suppress the flow of fresh air into the combustion chamber 12 during execution of F / C. According to the routine shown in FIG. 2, the fully closed timing of the throttle opening TA is not set to the intake valve timing VVT at the advance start time t0, but the advance amount of the intake valve timing VVT is set to the advance angle regulation. After reaching the value, that is, when the predetermined time has elapsed from the start of the advancement of the intake valve timing VVT, the time t1 is set. Therefore, according to the system of the present embodiment, the throttle opening TA is not fully closed until the time t1 from the start of the advancement of the intake valve timing VVT, so after the F / C start condition is satisfied Even when forced recovery is frequently performed in a relatively short period of time, the time required to replace the EGR gas with fresh air can be further shortened. Thereby, it can reduce more reliably that the fall of an acceleration feeling arises.

  In the first embodiment described above, the valve overlap period is changed by changing the state of the intake variable valve mechanism 28, and as a result, the internal EGR amount is changed. However, the internal EGR amount is changed. The technique to make is not limited to such a technique. For example, the valve overlap period may be changed by changing the state of the exhaust variable valve mechanism 30 and, as a result, the internal EGR amount may be changed.

  Further, the method of changing the internal EGR amount is not limited to the method of increasing or decreasing the valve overlap period. For example, when the closing timing of the exhaust valve 26 is set in the crank angle region before the exhaust top dead center, the amount of residual gas trapped in the combustion chamber 12 in the exhaust stroke is increased or decreased by moving the closing timing back and forth. To do. For this reason, the internal EGR amount may be increased or decreased by adjusting the closing timing of the exhaust valve 26 in the crank angle region before the exhaust top dead center.

In the first embodiment, the ECU 50 executes the process of step 106, so that the “variable valve timing control means” in the first or second invention executes the process of step 120. Thus, the “EGR valve control means” in the first aspect of the invention is realized.
In the first embodiment described above, the ECU 50 executes the process of step 116 after the determination of step 110 is established, whereby the “fuel cut execution means” in the second aspect of the invention is the step 116. By executing the processing of step 120 after the above processing is executed, the “EGR valve control means” in the second invention is realized.
In the first embodiment described above, the “throttle control means” according to the third aspect of the present invention is realized by the ECU 50 executing the processing of steps 102, 110, and 112 described above.
In the first embodiment described above, the predetermined time A corresponds to the “first predetermined time” in the fourth invention, and the predetermined time B corresponds to the “second predetermined time” in the fourth invention. ing.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. FIG. 3 is a timing chart for explaining operations realized by processing of the routine shown in FIG. 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Intake passage 16 Exhaust passage 18 Electronically controlled throttle valve 20 Throttle position sensor 28 Intake variable valve mechanism (VVT) mechanism 30 Exhaust variable valve mechanism (VVT) mechanism 32 Crank angle sensor 34 Cam angle sensor 44 Exhaust gas recirculation passage 46 EGR valve 50 ECU (Electronic Control Unit)
52 Accelerator position sensor

Claims (4)

A variable valve mechanism for varying a valve overlap period in which an intake valve opening period and an exhaust valve opening period overlap; an EGR valve disposed in the middle of an exhaust gas recirculation path that connects the intake passage and the exhaust passage; A control device for an internal combustion engine that recirculates exhaust gas while cutting fuel while decelerating,
Variable valve timing control means for driving the variable valve mechanism to increase the valve overlap period to a predetermined value when a fuel cut start condition is satisfied;
EGR valve control means for opening the EGR valve when a predetermined time has elapsed after the valve overlap period is increased,
A control device for an internal combustion engine, comprising: A variable valve mechanism for varying a valve overlap period in which an intake valve opening period and an exhaust valve opening period overlap; an EGR valve disposed in the middle of an exhaust gas recirculation path that connects the intake passage and the exhaust passage; A control device for an internal combustion engine that recirculates exhaust gas while cutting fuel while decelerating,
Variable valve timing control means for driving the variable valve mechanism to increase the valve overlap period to a predetermined value when a fuel cut start condition is satisfied;
Fuel cut execution means for executing fuel cut when a predetermined time elapses after the valve overlap period is increased;
EGR valve control means for opening the EGR valve after the fuel cut is performed,
A control device for an internal combustion engine, comprising:   When the valve overlap is increased, the throttle valve is made smaller than the opening before the fuel cut start condition is satisfied, and when the valve overlap reaches the predetermined value, the throttle valve is The control apparatus for an internal combustion engine according to claim 1 or 2, further comprising throttle control means for controlling the valve fully closed. The fuel cut execution means executes a fuel cut when a first predetermined time elapses after the throttle valve is fully closed by the throttle control means,
4. The internal combustion engine according to claim 3, wherein the EGR valve control means opens the EGR valve when a second predetermined time elapses from the fuel cut execution time after the first predetermined time elapses. 5. Control device.

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