JP2019082112A - Internal combustion engine control apparatus - Google Patents

Abstract

To provide an internal combustion engine control apparatus capable of effectively suppressing a spike of NOx when returning from a fuel cut.SOLUTION: In an internal combustion engine 10 that has an external EGR device 26 and an exhaust gas variable valve device 24, a control apparatus performs: controlling a VVT advance angle of an exhaust valve 20 so as to increase an internal EGR gas volume when returning from a fuel cut; controlling the VVT advance angle in accordance with a target VVT advance angle so as to increase the VVT advance angle of the exhaust valve 20 while the fuel cut is performed; and selecting, as the target VVT advance angle, a smaller of a first maximum VVT advance angle with which a misfire does not occur even if returning from a fuel cut and a second VVT advance angle with which a permissible maximum deceleration while a fuel cut is performed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for controlling an internal combustion engine provided with an external EGR device and a variable valve device capable of adjusting the amount of internal EGR gas.

  For example, Patent Document 1 discloses a control device of an internal combustion engine provided with an external EGR device and a variable valve device capable of adjusting the amount of internal EGR gas. In this control device, the amount of exhaust gas (internal EGR gas amount) remaining in the cylinder is temporarily increased by extending the valve overlap period when returning from the fuel cut. As a result, it is possible to suppress a spike-like increase (so-called NOx spike) in the amount of emission of NOx that occurs due to the response delay of the external EGR gas immediately after the recovery from the fuel cut.

JP 2012-002100 A JP, 2016-130486, A

  In the technology described in Patent Document 1, the operation delay of the variable valve device for adjusting the internal EGR gas amount is not taken into consideration. For this reason, at the time of recovery from the fuel cut, the increase in the amount of the internal EGR gas may be delayed due to the operation delay of the variable valve device, and the NOx spike may not be sufficiently suppressed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device of an internal combustion engine that can suppress NOx spikes more effectively when returning from a fuel cut.

The control device for an internal combustion engine according to the present invention comprises an external EGR device having an EGR passage connecting an exhaust passage and an intake passage, and an EGR valve for opening and closing the EGR passage, closing timing of the exhaust valve and opening of the intake valve. A variable valve system capable of adjusting the amount of internal EGR gas is controlled by making at least one of the timings variable.
The controller is
A control amount corresponding to at least one of an advancing amount or a retarding amount of the closing timing and an advancing amount of the opening timing is controlled so that the internal EGR gas amount increases when returning from the fuel cut. The first process to
A second process of controlling the control amount according to a target control amount so that the same control amount as that controlled by the first process is increased during execution of the fuel cut;
Selection of selecting the smaller of the first maximum control amount that does not cause a fire even if the fuel cut returns and the second maximum control amount that satisfies the allowable maximum deceleration during the fuel cut as the target control amount Processing and
Run.

  According to the present invention, in addition to the first process for controlling the control amount to increase the amount of internal EGR gas at the time of recovery from the fuel cut, the same as that controlled by the first process during the execution of the fuel cut A second process of controlling the control amount according to the target control amount is performed so that the control amount increases. As described above, by increasing the control amount during execution of the fuel cut, it is possible to reduce the control amount necessary for increasing the internal EGR gas amount at the time of return. As a result, it is possible to suppress the delay of the inflow of the internal EGR gas amount caused by the operation delay of the variable valve device at the time of recovery, and thus it is possible to suppress the NOx spike more effectively. And according to the present invention, the target control is the smaller one of the first maximum control amount that does not cause a fire even if it returns from the fuel cut and the second maximum control amount that satisfies the allowable maximum deceleration during execution of the fuel cut. Selected as a quantity. This enables effective suppression of NOx spikes while meeting requirements for misfires and vehicle deceleration.

It is a figure for demonstrating the example of a structure of the system which concerns on Embodiment 1 of this invention. It is a time chart for explaining a subject about control of NOx spike at the time of return from a fuel cut. It is a time chart for explaining an outline of control of an exhaust variable valve device according to Embodiment 1 of the present invention. It is a flow chart which shows a routine of processing of ECU about control of an exhaust variable valve device concerning a 1st embodiment of the present invention. It is a figure for demonstrating the determination method of the basic time used for determination of step S106. It is a diagram showing the oxygen (O ₂₎ properties of the map used to calculate the concentration in the EGR passage. It is a figure showing the relationship between the oxygen concentration in EGR passage, and a VVT advance amount correction amount.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. When the number of the number, the number, the quantity, the range, etc. of each element is mentioned in the embodiment shown below, the number mentioned except when clearly indicated or the number is clearly specified in principle. Thus, the present invention is not limited. In addition, the structures, steps, and the like described in the embodiments below are not necessarily essential to the present invention, unless otherwise specified or clearly specified in principle.

Embodiment 1
1. Configuration Example of System FIG. 1 is a diagram for describing a configuration example of a system according to the first embodiment of the present invention. The system shown in FIG. 1 comprises an internal combustion engine 10. The internal combustion engine 10 is, for example, a diesel engine and is used as a power source of a vehicle.

  An intake passage 14 and an exhaust passage 16 communicate with a cylinder 12 of the internal combustion engine 10. An intake valve 18 is provided at an end of the intake passage 14 on the cylinder 12 side, and an exhaust valve 20 is provided at an end of the exhaust passage 16 on the cylinder 12 side.

  The internal combustion engine 10 includes an intake variable valve operating device 22 that drives an intake valve 18 and an exhaust variable valve operating device 24 that drives an exhaust valve 20. The intake variable valve system 22 and the exhaust variable valve system 24 are configured to be capable of changing the rotational phase of the camshaft with respect to the rotational phase of the crankshaft, as one example. According to such a configuration, the open / close timing can be advanced or retarded within a predetermined range while the valve opening period of the intake valve 18 or the exhaust valve 20 is fixed.

  In addition, the internal combustion engine 10 is provided with an external EGR device 26. The external EGR device 26 includes an EGR passage 28 and an EGR valve 30. The EGR passage 28 connects the exhaust passage 16 and the intake passage 14. The EGR valve 30 is configured to open and close the EGR passage 28. According to such an external EGR device 26, by controlling the opening degree of the EGR valve 30, the exhaust gas (i.e., the external EGR gas) recirculated into the cylinder 12 through the EGR passage 28 and the intake passage 14 The amount can be adjusted.

  Furthermore, the internal combustion engine 10 is provided with a variable nozzle turbocharger. A turbine 32 of a variable nozzle type turbocharger and a variable nozzle mechanism 34 are disposed in the exhaust passage 16 on the downstream side of the connection position of the EGR passage 28. An exhaust gas purification device (post-treatment device) 36 is disposed downstream of the turbine 32 to purify the exhaust gas. In addition, the internal combustion engine 10 is provided with a fuel injection valve 38 for injecting fuel into the cylinder 12.

  As shown in FIG. 1, the system of the present embodiment further includes an electronic control unit (ECU) 40. The ECU 40 includes the internal combustion engine 10 and various sensors mounted on a vehicle equipped with the internal combustion engine 10, and the internal combustion engine 10 including the variable valve devices 22 and 24, the EGR valve 30, the variable nozzle mechanism 34, and the fuel injection valve 38 described above. The various actuators for controlling the operation are electrically connected. The various sensors described above include a crank angle sensor 42 and an accelerator opening degree sensor 44 that output signals in accordance with the crank angle. The ECU 40 can acquire the engine rotational speed using the crank angle sensor 42.

  The ECU 40 comprises a processor, a memory and an input / output interface. The input / output interface takes in sensor signals from the various sensors described above and outputs operation signals to the various actuators described above. The memory stores various control programs and maps for controlling various actuators. The processor reads the control program from the memory and executes it. Thereby, the function of the "control device for an internal combustion engine" according to the present embodiment is realized.

2. Control of the exhaust variable valve device during execution of fuel cut and return from fuel cut In the internal combustion engine 10 of the present embodiment, fuel injection is performed when predetermined fuel cut execution conditions such as deceleration or shift of the vehicle are satisfied. A "fuel cut" is performed to stop the fuel supply by the valve 38.

2-1. Problems related to the suppression of NOx spikes when returning from a fuel cut When a fuel cut is performed in an internal combustion engine provided with an external EGR device like the internal combustion engine 10, only intake air flows into the cylinder and the exhaust passage, Air also flows into the EGR passage. Therefore, immediately after the return from the fuel cut, the air in the EGR passage is discharged to the intake passage, and then the exhaust gas (burned gas) generated by the combustion after the return is introduced from the EGR passage to the intake passage It will be. Due to such a delay in the return of the external EGR gas, at the time of recovery from the fuel cut, a phenomenon (so-called NOx spike) in which the amount of NOx discharged from the cylinder increases in a spike shape occurs.

  FIG. 2 is a time chart for describing a problem regarding suppression of NOx spikes at the time of recovery from a fuel cut. In the example of the fuel cut performed at the time of deceleration as in the example of FIG. 2, the fuel cut (F / C) is started with the establishment of the predetermined execution condition including the OFF of the accelerator pedal. When ON (depression) is made, return from fuel cut is performed.

  The waveform shown by a thick line in FIG. 2 corresponds to an example in which no measures have been taken to suppress NOx spikes. On the other hand, the waveform shown by a thin line in FIG. 2 is a comparative example in which the amount of internal EGR gas is temporarily increased over a predetermined period immediately after recovery for compensating for the response delay of the external EGR gas at the time of recovery from fuel cut. It corresponds to More specifically, the adjustment of the internal EGR gas amount is performed using a variable valve device. In this comparative example, the increase of the target EGR gas amount (instruction value) for the temporary increase of the internal EGR gas amount is started at the time of return from the fuel cut.

  According to the comparative example indicated by a thin line, the internal EGR gas amount is introduced into the cylinder immediately after the recovery from the fuel cut, instead of the external EGR gas whose introduction is delayed. For this reason, as shown in FIG. 2, it is possible to suppress the NOx spike as compared with the example shown by the thick line. However, as with the variable valve devices 22 and 24 of the present embodiment, if there is a delay in the operation of the variable valve device used to adjust the amount of internal EGR gas, temporary return of the amount of internal EGR gas at the time of recovery There is a possibility that the NOx spike can not be sufficiently suppressed because a delay also occurs in the increase. And this subject becomes more remarkable, so that the operation delay of the variable valve apparatus used is large.

2-2. Outline of Control of Exhaust Variable Control Valve Device of First Embodiment FIG. 3 is a time chart for explaining an outline of control of the exhaust variable valve control device 24 according to the first embodiment of the present invention. Although FIG. 3 exemplifies a fuel cut to be executed at the time of deceleration, the fuel cut to be subjected to the present control includes, for example, at the time of a shift (this may be said to be an instantaneous deceleration).

  In the present embodiment, the adjustment of the internal EGR gas amount is performed using the advance angle of the closing timing EVC of the exhaust valve 20 by the exhaust variable valve device 24 as an example. More specifically, according to the exhaust variable valve device 24, the advancing or retarding of the opening phase (opening period) of the exhaust valve 20 advances or retards the closing timing EVC together with the opening timing EVO. Then, the amount of exhaust gas (that is, internal EGR gas) remaining in the cylinder can be increased by advancing the closing timing EVC based on the exhaust top dead center. The amount of internal EGR gas increases as the amount of advance of the closing timing EVC with respect to the exhaust top dead center (also referred to as “VVT advance amount of the exhaust valve 20” in the example shown in FIG. 3) increases. In FIG. 3, for the sake of convenience of the description, the advance angle of the closing timing EVC is also used to increase the amount of internal EGR gas in the comparative example (same as the comparative example in FIG. 2) shown by thin lines. Do.

  In the control example of the present embodiment shown by a thick line in FIG. 3, unlike the comparative example shown by a thin line, the advance timing of the closing time EVC is performed not only at the time of recovery (immediately after recovery) but also during fuel cut execution. . That is, during the fuel cut, the closing timing EVC is operated (advanced) in the same direction as the closing timing EVC for increasing the amount of internal EGR gas at the time of return.

  By advancing the closing timing EVC during the fuel cut as described above, as shown in FIG. 3, the target VVT advance angle for increasing the amount of internal EGR gas at the time of return The control amount of the exhaust variable valve device 24 (that is, the VVT advance angle amount of the exhaust valve 20) required to realize the amount can be reduced as compared with the comparative example. Therefore, the actual VVT advance amount can be made closer to the target VVT advance amount at an earlier timing than the comparative example. That is, at the time of return, the operation delay of the exhaust variable valve device 24 can be guaranteed. The waveform of the internal EGR gas amount can be considered to change in the same manner as the waveform of the VVT advance amount of the exhaust valve 20 in FIG. According to such control of the present embodiment, as shown in FIG. 3, the NOx spike can be more effectively suppressed as compared with the comparative example.

  Further, the target VVT advance angle amount used during execution of the fuel cut in the control of the present embodiment is determined as follows. That is, among the first maximum VVT advance amount that does not cause a fire even if it returns from a fuel cut, and the second maximum VVT advance amount that satisfies the allowable maximum deceleration of the vehicle during fuel cut execution and return from a fuel cut. The smaller one is selected as the target VVT advance amount.

2-3. FIG. 4 is a flow chart showing a routine of processing of the ECU 40 relating to control of the exhaust variable valve device 24 according to the first embodiment of the present invention. The present routine is started when predetermined fuel cut execution conditions including the OFF of the accelerator pedal are satisfied during the operation of the internal combustion engine 10.

  In the routine shown in FIG. 4, the ECU 40 first obtains an instruction value of the engine rotation number (NE) and the fuel injection amount (Q) based on the crank angle sensor 42 (step S100).

  Next, the ECU 40 performs the process of steps S102 and S106 to S110 for calculating the first maximum VVT advance amount (which may be accompanied by a correction taking into consideration the presence of the residual burned gas in the EGR passage). 2) The process of step S104 for calculating the maximum VVT advance angle amount is executed in parallel.

  In step S102, calculation of a first maximum VVT advance amount according to the engine rotational speed and the fuel injection amount acquired in step S100 is performed. More specifically, the first maximum VVT advance amount is the maximum possible while securing a fresh air amount capable of preventing a misfire even if the fuel cut returns under the conditions of the current engine speed and fuel injection amount. VVT advance amount. For this calculation, a map (not shown) that defines a first maximum VVT advance angle amount according to the engine speed and the fuel injection amount is used.

  More specifically, the value of the first maximum VVT advance amount at each point of the above map is, for example, a steady state test, and the maximum value of HC and CO can be suppressed by considering the increase of HC and CO as misfire. It can be determined as the VVT advance amount of. Further, in this determination, a transient phenomenon in which the engine rotational speed and the fuel injection amount change may be taken into consideration, and a margin for reliably preventing a misfire may be provided for the map value. The first maximum VVT advance angle amount may be calculated as a value corresponding to only the engine speed, instead of the above-described engine speed and fuel injection amount.

  In step S104, calculation of a second maximum VVT advance amount according to the engine speed and the fuel injection amount acquired in step S100 is performed. The second maximum VVT advance angle amount is used to suppress the deterioration of drivability (too small or excessive deceleration) due to the change of the engine torque caused by the advance angle of the closing timing EVC.

  More specifically, when the VVT advance angle amount of the exhaust valve 20 is increased, the crank angle period in which both the intake valve 18 and the exhaust valve 20 are closed in the exhaust stroke is extended, so that the pump loss is increased. The presence of this pump loss acts as a decelerating action of the vehicle. The second maximum VVT advance amount is the maximum VVT advance amount which satisfies the allowable maximum deceleration while suppressing the deterioration of the drivability described above. For this calculation, a map (not shown) that defines a second maximum VVT advance amount according to the engine speed and the fuel injection amount is used. The value of the second maximum VVT advance amount at each point of this map can be determined, for example, by a step test. In this step test, for each point, the lead angle is executed stepwise from the reference point (lead angle zero) of the closing timing EVC, and the maximum VVT lead angle amount satisfying the allowable maximum deceleration is obtained.

  Similarly to the first maximum VVT advance angle, the second maximum VVT advance angle may be calculated as a value corresponding to only the engine rotation speed, instead of the above-described engine rotation speed and fuel injection amount. However, the deceleration action due to the advance timing of the closing timing EVC affects the vehicle not only during execution of the fuel cut where combustion is not being performed, but also when returning from the fuel cut (when fuel injection is restarted). Exert. In the example of the process of step S120 described later, calculation of the second maximum VVT advance amount is performed also at the time of return. For this reason, it is preferable to consider the fuel injection amount together with the engine speed in order to calculate the second maximum VVT advance angle amount as in the above example.

  Further, the processing of steps S106 to S110 is executed to determine the first maximum VVT advance amount including the presence or absence of the correction taking into consideration the presence of the residual burned gas in the EGR passage 28.

  In step S106, it is determined whether or not there is any burnt gas in the EGR passage 28. This determination can be performed, for example, as follows. That is, while the elapsed time U from the start of the fuel cut has not yet reached the predetermined time, it is determined that there is burned gas, and when the elapsed time U has reached the predetermined time, it is determined that there is no burned gas. The predetermined time can be determined, for example, as the time from the start of fuel cut to the time when the burnt gas does not reach the cylinder. Also, this predetermined time is the time from the start of fuel cut to the time when the burnt gas in the EGR passage 28 disappears, and a predetermined offset amount (a value dependent on the intake manifold volume, but in practice it is approximately zero It may be determined as a value that can be considered.

Furthermore, the predetermined time may be determined as follows. FIG. 5 is a diagram for describing a method of determining the basic time used in the determination of step S106. As shown in FIG. 5, the oxygen (O ₂ ) concentration in the EGR passage 28 increases with the elapsed time U of the fuel cut, and the increase causes the inside of the EGR passage 28 to be filled with fresh air. I will fit when. The time from the fuel cut start time to this convergence time corresponds to the above basic time. The ECU 40 stores a map (not shown) indicating the relationship between the basic time and the engine speed and the fuel injection amount. According to such a map, it is possible to calculate the basic time according to the current engine rotational speed and fuel injection amount acquired in step S100.

  The predetermined time is preferably calculated as a value in which the following correction time is sequentially considered with respect to the basic time. Specifically, the VVT advance angle amount of the exhaust valve 20 determined by the processing of the present routine is changed according to the changes in the engine speed and the fuel injection amount during execution of the fuel cut. If the VVT advance angle amount becomes large after the basic time is calculated during execution of the fuel cut, it becomes difficult to intake air. This leads to an increase in the predetermined time. Therefore, this correction time is determined as a time according to the amount of change of the VVT advance angle amount from the value at the time of calculation of the basic time. The predetermined time can be calculated more accurately by sequentially reflecting such a correction time on the basic time.

When it is determined in step S106 that there is burned gas in the EGR passage 28, the ECU 40 proceeds to step S108, and calculates the VVT advance amount correction amount by the burned gas. FIG. 6 is a graph showing the characteristics of the map used to calculate the oxygen (O ₂ ) concentration in the EGR passage 28. As shown in FIG. FIG. 7 is a diagram showing the relationship between the oxygen concentration in the EGR passage 28 and the VVT advance amount correction amount. The ECU 40 stores a map that defines the relationships represented by FIGS.

  In the map shown in FIG. 6, the relationship between the fuel cut elapsed time U and the oxygen concentration in the EGR passage 28 is specified. This map is created to be different according to the engine speed and the fuel injection amount. According to such a map, it is possible to calculate the oxygen concentration corresponding to the current engine speed and fuel injection amount acquired in step S100 and the current elapsed time U. Note that, instead of the above example, this oxygen concentration may be determined to be different according to only one of the engine speed and the fuel injection amount together with the elapsed time U.

  When burnt gas remains in the EGR passage 28 at the time of recovery from the fuel cut, the amount of internal EGR gas to be realized by the VVT advance angle may be small, or the fresh air amount is only the remaining burnt gas Less. Therefore, it can be said that the VVT advance angle amount should be smaller as the amount of burned gas remaining at the time of return is larger. According to the map shown in FIG. 7, the VVT advance amount correction amount decreases as the oxygen concentration in the EGR passage 28 increases, and the oxygen concentration becomes equal to the oxygen concentration (23.2%) in the air. It is set to be zero when. Therefore, according to this map, the VVT advance amount correction amount can be appropriately set in accordance with the oxygen concentration calculated by the map shown in FIG. 6 (that is, the amount of remaining burned gas in the EGR passage 28). it can.

  When the ECU 40 executes the process of step S108 or when it is determined in step S106 that there is no burnt gas in the EGR passage 28, the process proceeds to step S110. When the process directly proceeds from step S106 to step S110, the first maximum VVT advance amount calculated in step S102 is determined as the first maximum VVT advance amount to be finally used. On the other hand, when the process proceeds to step S110 via step S108, a value obtained by subtracting the VVT advance amount correction amount from the first maximum VVT advance amount calculated in step S102 is finally used. Calculated (fixed) as the first maximum VVT advance amount.

  Next, the ECU 40 executes processing for selecting the smaller one of the first maximum VVT advance amount determined in step S110 and the second maximum VVT advance amount calculated in step S104 (step S112). According to such processing, it is possible to select a safe value out of the two maximum VVT advance amounts.

  Next, the ECU 40 calculates (determines) the value selected in step S112 as the final VVT advance amount (target VVT advance amount) during execution of the fuel cut, and this final VVT advance amount is obtained. As described above, the variable exhaust valve device 24 is controlled (step S114).

  Next, the ECU 40 determines whether a condition for returning from the fuel cut such as turning on of the accelerator pedal is satisfied (step S116). If the determination result is negative, that is, if the fuel cut is being performed, the ECU 40 repeatedly executes the process after step S100.

  On the other hand, when the condition for returning from the fuel cut is satisfied in step S116, the ECU 40 executes a process to reduce the nozzle opening degree of the variable nozzle mechanism 34 (control to the closing side) (step S118). When the variable nozzle mechanism 34 is provided, by performing such processing, the exhaust pressure can be increased when returning from the fuel cut, and the amount of internal EGR gas can be efficiently increased.

  Next, the ECU 40 calculates a target VVT advance amount for increasing the amount of internal EGR gas at the time of recovery from a fuel cut, and increases the amount of internal EGR gas (that is, VVT advance at this target VVT advance amount) The variable exhaust valve device 24 is controlled so that the angular movement is performed (step S120). Specifically, the calculation of the target VVT advance angle amount in step S120 is performed, for example, by performing the same process as the process of steps S100 to S14 described above.

  Next, the ECU 40 determines whether or not a response delay time (a time at which a return delay of the external EGR gas occurs) t (see FIG. 3) from the fuel cut return time has elapsed (step S122). The calculation of the response delay time t can be calculated, for example, using the method described in Japanese Patent Application Laid-Open No. 2012-002100.

  While the response delay time t has not elapsed, the decrease of the nozzle opening (step S118) and the increase of the internal EGR gas amount (step S120) are continued. On the other hand, when the response delay time t has elapsed, it is considered that the burned gas (exhaust gas) generated by the combustion after the return from the fuel cut has arrived in the cylinder. In this case, the ECU 40 ends the decrease in the nozzle opening and the increase in the amount of internal EGR gas (step S124).

3. Effect of control of the exhaust variable valve device during fuel cut execution and return from fuel cut According to the control of the present embodiment described above, exhaust is caused by an increase in the amount of internal EGR gas upon return from fuel cut. In addition to advancing the closing timing EVC of the valve 20, during the fuel cut, operation (advancement) of the closing timing EVC in the same direction as the operation direction of the closing timing EVC at return is performed. Thus, by increasing the VVT advance amount of the exhaust valve 20 during the fuel cut, the exhaust valve necessary to realize the target VVT advance amount for increasing the amount of internal EGR gas at the time of return The VVT advance amount of 20 can be reduced. As a result, it is possible to suppress the delay of the inflow of the internal EGR gas amount caused by the operation delay of the exhaust variable valve device 24 at the time of recovery, and it is possible to suppress the NOx spike more effectively.

  Then, according to the present embodiment, among the first maximum VVT advance amount that does not cause a fire even if it returns from the fuel cut, and the second maximum VVT advance amount that satisfies the allowable maximum deceleration of the vehicle during the fuel cut. The smaller of is selected as the target VVT advance amount. This enables effective suppression of NOx spikes while meeting requirements for misfires and vehicle deceleration.

  In the first embodiment described above, the process of step S120 corresponds to the "first process" according to the present invention, the process of steps S100 to S110 corresponds to the "second process" according to the present invention, and The processes of steps S112 and S11 correspond to the "selection process" according to the present invention. Further, the amount of advance of the closing timing EVC, the target VVT advance amount, the first maximum VVT advance amount, and the second maximum VVT advance amount correspond to the “control amount”, the “target control amount”, and the “first control amount” according to the present invention. The maximum control amount and the second maximum control amount correspond to each other.

Other embodiments.
In the first embodiment described above, the closing timing EVC is advanced to temporarily increase the internal EGR gas amount at the time of return from the fuel cut. However, adjustment of the internal EGR gas amount by using the variable valve device can also be performed by controlling the amount of retardation of the closing timing EVC with respect to the exhaust top dead center, instead of advancing the closing timing EVC, Alternatively, it can also be performed by adjusting the amount of advance of the opening timing IVO of the intake valve 18 with respect to the exhaust top dead center. Therefore, the “control amount” to be controlled by the variable valve system according to the present invention is an advance amount or a retard amount of the closing timing EVC of the exhaust valve 20 and an advancing angle of the opening timing IVO of the intake valve 18 The invention is not limited to the example of the first embodiment (the amount of advance of the closing time EVC) as long as it corresponds to at least one of the amounts.

  Further, the control of the advancing amount or the retarding amount of the closing timing EVC of the exhaust valve 20 is controlled in conjunction with the exhaust variable valve device 24 (that is, interlocked with the closing timing EVC) that changes the phase (opening period) of the exhaust valve 20. Instead of changing the opening timing EVO), it may be performed using a working angle changing device that changes only the closing timing EVC without changing the opening timing EVO. The same applies to the control of the advance amount of the opening timing IVO of the intake valve 18.

10 internal combustion engine 12 cylinder 14 intake passage 16 exhaust passage 18 intake valve 20 exhaust valve 22 intake variable valve device 24 exhaust variable valve device 26 external EGR device 28 EGR passage 34 variable nozzle mechanism 38 fuel injection valve 40 electronic control unit (ECU )
42 crank angle sensor 44 accelerator opening sensor

Claims (1)

An external EGR device having an EGR passage that connects an exhaust passage and an intake passage, and an EGR valve that opens and closes the EGR passage;
A variable valve device capable of adjusting the amount of internal EGR gas by varying at least one of the closing timing of the exhaust valve and the opening timing of the intake valve;
A control device for controlling an internal combustion engine comprising:
The controller is
A control amount corresponding to at least one of an advancing amount or a retarding amount of the closing timing and an advancing amount of the opening timing is controlled so that the internal EGR gas amount increases when returning from the fuel cut. The first process to
A second process of controlling the control amount according to a target control amount so that the same control amount as that controlled by the first process is increased during execution of the fuel cut;
Selection of selecting the smaller of the first maximum control amount that does not cause a fire even if the fuel cut returns and the second maximum control amount that satisfies the allowable maximum deceleration during the fuel cut as the target control amount Processing and
A control device for an internal combustion engine, characterized in that:

Images