JP2010174733A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine inhibiting increase of torque fluctuation all the more because of the control for torque fluctuation reduction while reducing torque fluctuation caused by exhaust gas recirculation. <P>SOLUTION: The control device for the internal combustion engine 10 includes a variable valve train 90 varying open close timing of an intake valve 22, and an exhaust gas recirculation device 80 recirculating exhaust gas in an exhaust passage 61 to an intake passage 41. Valve open timing of the intake valve 22 is advanced in a range where an valve overlap period does not exceeds a prescribed value when exhaust gas recirculation quantity is greater than a reference quantity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that includes a variable valve mechanism that varies the opening timing of an intake valve, and an exhaust gas recirculation device that recirculates exhaust gas in an exhaust passage to the intake passage.

  In order to improve engine output, reduce exhaust emissions, and the like, an internal combustion engine is provided with an exhaust gas recirculation device that introduces exhaust gas in an exhaust passage into a combustion chamber again. Here, in the internal combustion engine provided with the exhaust gas recirculation device, exhaust gas is returned to the combustion chamber, so that the following inconvenience is concerned.

  That is, for example, when the fuel injection pressure is low, such as during cold operation, fuel cannot be injected properly, and the particles of the injected fuel become larger, and vaporization is not promoted. Alternatively, even if the vaporization of the injected fuel is promoted, the ratio of the new amount (oxygen) necessary for combustion in the combustion chamber is reduced by introducing the exhaust gas into the combustion chamber. Combustion deterioration will be promoted. And when the said combustion deterioration arises, misfire and torque fluctuation will be unavoidable resulting from this.

  Therefore, in the control device of Patent Document 1, the amount of exhaust gas introduced into the combustion chamber is limited by changing the valve overlap period to suppress the deterioration of combustion.

Japanese Patent No. 4089641

  On the other hand, under a state in which the valve overlap period is set, a so-called internal EGR phenomenon occurs in which the exhaust gas sent from the combustion chamber to the exhaust passage again flows into the combustion chamber. The amount of exhaust (hereinafter referred to as “internal EGR gas”) returned from the exhaust passage to the combustion chamber by the internal EGR tends to increase as the valve overlap period increases.

  Here, in order to suppress the deterioration of combustion, it is performed by simultaneously increasing the intake valve and the exhaust valve of the variable valve mechanism, that is, by increasing the positive valve overlap period of the intake valve and the exhaust valve. However, when the positive valve overlap period is increased, the amount of increase in torque fluctuation due to the increase in the flow rate of the internal EGR is larger than the amount of decrease in torque fluctuation due to the improvement in combustion deterioration due to the increase during the same period. There was a case. As a result, when the positive valve overlap period is increased, torque fluctuation may be deteriorated.

  Therefore, the present invention has been made in view of the above circumstances, and its purpose is to reduce the amount of torque fluctuation caused by exhaust gas recirculation and to increase the amount of torque fluctuation by control for this purpose. An object of the present invention is to provide a control device for an internal combustion engine that can be suppressed.

In the following, means for achieving the above object and its effects are described.
(1) An invention according to claim 1 is a control device for an internal combustion engine comprising: a variable valve mechanism that makes the intake valve open / close timing variable; and an exhaust gas recirculation device that recirculates exhaust gas in the exhaust passage to the intake passage. Based on the fact that the exhaust gas recirculation amount is larger than the reference amount, the valve opening timing of the intake valve is advanced within a range in which the valve overlap period does not exceed a predetermined value.

  In an internal combustion engine in which the valve opening timing of the intake valve is variable, when the valve opening timing is advanced, the actual compression ratio increases as the amount of intake air supplied to the combustion chamber increases. On the other hand, when the valve opening timing of the intake valve is advanced in a state where the valve overlap period exists, the internal EGR gas amount increases. That is, when the valve opening timing is advanced in the state where the valve overlap period exists, the torque fluctuation amount is reduced by the increase of the actual compression ratio and the torque fluctuation amount due to the increase of the internal EGR gas amount. The increasing action is changed together. According to the inventor of the present application, when the valve overlap period is smaller than the predetermined value, the torque fluctuation amount reducing action due to the increase in the actual compression ratio is the torque fluctuation quantity increasing action due to the increase in the internal EGR gas amount. It has been confirmed that Therefore, when torque fluctuations occur due to exhaust gas recirculation by the exhaust gas recirculation device, the torque fluctuations are suppressed through advancement of the valve opening timing of the intake valve, and a valve overlap period is set in accordance with this. By not exceeding the value, it is possible to suppress an increase in the amount of torque fluctuation caused by the synchronization period exceeding a predetermined value.

  In view of the above, in the present invention, since the recirculation amount of the exhaust gas is larger than the reference amount, the valve opening timing of the intake valve is advanced. First, the actual compression ratio with the increase of the intake amount is increased. The amount of torque fluctuation due to the increase can be reduced. In addition, since the valve overlap period does not exceed a predetermined value when the valve opening timing is advanced, torque fluctuation is controlled by control for reducing the amount of torque fluctuation (advance angle of valve opening timing). It becomes possible to suppress the amount from increasing instead. As described above, according to the present invention, while the torque fluctuation amount due to the exhaust gas recirculation is reduced, it is possible to suppress the torque fluctuation amount from being increased by the control for this.

  The valve overlap period is smaller than the predetermined value when the valve overlap period is present and the synchronization period is set between the predetermined value and “0” and the valve overlap period is Both states that do not exist are shown. Further, the predetermined value for the valve overlap period is the valve overlap when the magnitude relationship between the torque fluctuation amount reducing action due to the increase in the actual compression ratio and the torque fluctuation quantity increasing action due to the increase in the internal EGR gas amount is switched. Indicates the period.

The schematic diagram which shows the structure of the engine about embodiment which actualized the control apparatus of the internal combustion engine of this invention. (A) About the internal combustion engine of the embodiment, the timing chart which shows the opening and closing timing of the initial setting state of an intake valve and an exhaust valve. (B) The timing chart which shows the change aspect of the opening / closing timing of an intake valve when it has a positive valve overlap period. The graph which shows transition of the torque fluctuation | variation with respect to the amount of external EGR gas about the internal combustion engine of the embodiment. The flowchart which shows the execution procedure of the advance angle control process of an intake valve about the internal combustion engine of the embodiment.

With reference to FIGS. 1-4, one Embodiment which actualized the control apparatus of the internal combustion engine concerning this invention is described.
As shown in FIG. 1, an engine 10 includes an engine body 20 that generates power through combustion of a mixture of air and fuel, an intake device 40 that takes external air into the engine body 20 through an intake passage 41, and an engine body The fuel injection valve 50 for supplying fuel to the combustion chamber 31 in the engine 20, the exhaust device 60 for discharging the air-fuel mixture combusted in the combustion chamber 31 to the outside through the exhaust passage 61, and these devices are comprehensively controlled. And an electronic control unit 70. Further, the engine 10 is provided with an exhaust gas recirculation device 80 including a communication passage 81 that allows the exhaust device 60 and the intake device 40 to communicate with each other.

  The engine body 20 is provided with a cylinder block 21 having a cylinder. A piston 24 is accommodated in the cylinder. A combustion chamber 31 is formed by a space surrounded by the intake valve 22, the exhaust valve 23, and the piston 24.

  The combustion chamber 31 is provided with a spark plug 26 for igniting the air-fuel mixture introduced therein. An igniter 27 is connected to the spark plug 26. The spark plug 26 operates when a high voltage output from the igniter 27 is applied. Through the operation control (ignition timing control) of the igniter 27, the air-fuel mixture is combusted at an appropriate timing. A crankshaft 25 is connected to the piston 24, and the crankshaft 25 rotates as the piston 24 reciprocates.

  The intake passage 41 and the combustion chamber 31 are communicated or blocked by the opening / closing operation of the intake valve 22. The intake valve 22 opens and closes with the rotation of the intake camshaft 28 to which the rotation of the crankshaft 25 is transmitted. On the other hand, the exhaust passage 61 and the combustion chamber 31 are communicated or blocked by the opening / closing operation of the exhaust valve 23. The exhaust valve 23 opens and closes with the rotation of the exhaust camshaft 29 to which the rotation of the crankshaft 25 is transmitted.

  Here, the intake camshaft 28 is provided with a variable valve mechanism 90. The variable valve mechanism 90 adjusts the rotation angle of the intake camshaft 28 with respect to the rotation angle (crank angle) of the crankshaft 25 to advance or close the opening / closing timing of the intake valve 22 (hereinafter “valve timing VT”). It is to retard. The variable valve mechanism 90 is operated through, for example, operation control (opening / closing timing control) of an actuator 91 such as a hydraulic control valve.

  The intake passage 41 of the intake device 40 is provided on the intake upstream side in the passage 41, and a throttle body 43 for adjusting the flow rate of fresh air through opening and closing of the throttle valve 42, and the intake downstream side of the throttle body 43 And an intake manifold 44 connecting the intake upstream side of the engine body 20. The intake manifold 44 is provided with a surge tank 45 for retaining fresh air that has passed through the throttle body 43 and a plurality of sub-pipes 46 for sending intake air in the surge tank 45 to each intake port of the engine body 20. It has been. Further, each intake port of the engine body 20 is provided with a fuel injection valve 50.

  The exhaust device 60 includes an exhaust passage 61 through which an air-fuel mixture combusted in the combustion chamber 31 (hereinafter referred to as “exhaust”) flows, and a catalyst device 62 that is provided in the exhaust passage 61 and purifies the exhaust gas. Has been.

  The communication passage 81 of the exhaust gas recirculation device 80 connects a portion of the exhaust passage 61 upstream of the catalyst device 62 and the intake manifold 44 of the intake passage 41. In addition, an EGR valve that controls the amount of exhaust (hereinafter referred to as “external EGR gas amount”) that recirculates from the exhaust passage 61 to the intake passage 41 by changing the size of the cross-sectional area of the communication passage 81. 82 is provided. The opening degree of the EGR valve 82 is controlled through the actuator 83 according to the engine operating state of the engine 10, thereby adjusting the amount of external EGR gas recirculated through the communication path 81.

  The electronic control unit 70 captures detection signals from various sensors and performs various calculations. Based on the calculation results, the electronic control unit 70 performs throttle control, fuel injection control, ignition timing control, intake valve opening / closing timing control, and external EGR amount. Various controls such as control are executed. Here, the various sensors include, for example, a crank sensor 71 that detects the rotational speed of the crankshaft 25, an intake air sensor 72 that detects the amount of intake air that passes through the intake passage 41, and the depression amount of the accelerator pedal AP. An accelerator sensor 73 is provided for detection. A throttle sensor 74 for detecting the throttle opening, a cam sensor 75 for detecting the rotation angle of the intake camshaft 28, and an opening sensor 76 for detecting the opening of the EGR valve 82 are provided.

  The relationship between the valve timing of the intake valve 22 and the valve overlap period will be described with reference to FIG. Hereinafter, a period in which both the intake valve 22 and the exhaust valve 23 are in the closed state is referred to as a “negative overlap period MOV”, and both the intake valve 22 and the exhaust valve 23 are in the open state for distinction from this. The valve overlap period at is indicated as “positive overlap period POV”.

  As shown in FIG. 2A, the valve timing VT of the intake valve 22 is set to the valve timing VTX (hereinafter, “initial timing VTX”) in the initial state. When a change request for the valve timing VT is set based on the engine operating state, the variable valve mechanism 90 changes the valve timing VT from the initial timing VTX to the advance side and the retard side, respectively. The valve timing VT is set to the valve timing VTZ (hereinafter, “advance timing VTZ”) when advanced to the maximum.

  When the valve timing VT is set to the initial timing VTX, the period MOVX is secured as the negative overlap period MOV. As the valve timing VT is advanced from this state, the negative overlap period MOV gradually decreases. When the valve timing VT reaches the valve timing VTY (hereinafter, “intermediate timing VTY”), the negative overlap period MOV is set to “0”. At this time, the positive overlap period POV is also set to “0”.

  Here, when the valve timing VT of the intake valve 22 is advanced, the actual compression ratio increases as the amount of intake air supplied to the combustion chamber 31 increases. On the other hand, when the valve timing VT is advanced in a state where the positive overlap period POV exists, the internal EGR gas amount increases. That is, when the valve timing VT is advanced in a state where the positive overlap period POV exists, the torque fluctuation amount is reduced by increasing the actual compression ratio, and the torque fluctuation amount is increasing by increasing the internal EGR gas amount. Will change together. When the positive overlap period POV is smaller than the predetermined period POVA (hereinafter referred to as “boundary period POVA”), the torque fluctuation reduction effect due to the increase in the actual compression ratio is the torque due to the increase in the internal EGR gas amount. It has been confirmed that it exceeds the effect of increasing the fluctuation amount.

  The state in which the positive overlap period POV is smaller than the boundary period POVA is a state in which the synchronization period is set between the boundary period POVA and “0” when the positive overlap period POV exists. And a state where there is no positive overlap period POV. The boundary period POVA indicates a valve overlap period when the magnitude relation between the torque fluctuation amount reducing action due to the increase in the actual compression ratio and the torque fluctuation quantity increasing action due to the increase in the internal EGR gas amount is switched. It can be grasped in advance through a test or the like.

  With reference to FIG. 2 (b), the torque fluctuation amount reducing action due to the increase in the actual compression ratio accompanying the change in the valve overlap period and the torque fluctuation quantity increasing action due to the increase in the internal EGR gas amount will be described below. (State 1) to (State 4) will be described as an example.

  (State 1) The actual compression ratio increases when the negative overlap period MOV is set to the period MOV1 because the valve timing VT is set to the first timing VT1 on the advance side of the initial timing VTX. The torque fluctuation amount reducing action by the engine exceeds the torque fluctuation quantity increasing action by the internal EGR gas amount increase. At this time, since the negative overlap period MOV is set, the internal EGR gas amount is substantially “0”, so that the effect of reducing the torque fluctuation amount by increasing the actual compression ratio is sufficiently high. It becomes.

  (State 2) The actual compression ratio increases when the positive overlap period POV is set to the period POV2 because the valve timing VT is set to the second timing VT2 on the more advanced side than the first timing VT1. The effect of reducing the torque fluctuation amount due to is greater than the action of increasing the torque fluctuation amount due to the increase of the internal EGR gas amount. At this time, since the positive overlap period POV is set, the internal EGR gas amount becomes larger than “0”, and therefore the effect of reducing the torque fluctuation amount due to the increase in the actual compression ratio (state 1) ).

  (State 3) Since the valve timing VT is set to the third timing VT3 on the more advanced side than the second timing VT2, the positive overlap period POV is smaller than the boundary period POVA and in the period POV3 immediately before it. When set, the torque fluctuation reducing action by increasing the actual compression ratio exceeds the torque fluctuation increasing action by increasing the internal EGR gas quantity. Further, at this time, since the positive overlap period POV is immediately before the boundary period POVA, although the effect of reducing the torque fluctuation amount due to the increase in the actual compression ratio is expected, the degree is within the range where the effect is expected. It will be the smallest.

  (State 4) Since the valve timing VT is set to the fourth timing VT4 that is more advanced than the third timing VT3, the positive overlap period POV is set to a period POV4 that is greater than the boundary period POVA. When the actual compression ratio is increased, the torque fluctuation amount reducing action is less than the torque fluctuation amount increasing action due to the internal EGR gas amount increasing.

  In the present embodiment, in view of the above, when there is a request to reduce the torque fluctuation caused by the exhaust gas recirculation, the torque fluctuation is suppressed through the advance of the valve timing VT of the intake valve 22, and in conjunction with this, By preventing the positive overlap period POV from exceeding the boundary period POVA, an increase in the amount of torque fluctuation caused by the synchronization POV exceeding the boundary period POVA is also suppressed.

  With reference to FIG. 3, an example of a control mode of the valve timing VT based on the relationship between the external EGR gas amount and the torque fluctuation amount will be described. FIG. 3 is a graph showing the relationship between the amount of external EGR gas and the amount of torque fluctuation obtained by experiments or the like. Further, in the figure, a straight line G1 shows the relationship between the external EGR gas amount and the torque fluctuation amount when the valve timing VT is set to the initial timing VTX. A straight line G2 indicates the relationship between the external EGR gas amount and the torque fluctuation amount when the valve timing VT is set to the advance side by the predetermined advance amount ΔVT from the initial timing VTX.

  As indicated by the straight lines G1 and G2, the torque fluctuation amount increases as the external EGR gas amount increases. When the valve timing VT is set to the initial timing VTX, when only the external EGR gas amount is changed among various engine operating conditions, the torque fluctuation occurs when the gas amount exceeds the first predetermined amount A1. The amount is larger than the allowable limit amount BX.

  In this embodiment, when it is estimated that the torque fluctuation amount exceeds the allowable limit amount BX, the torque fluctuation amount is reduced through the control of the valve timing VT described above. That is, the valve timing VT is advanced by a predetermined advance amount ΔVT to change the valve timing VT from the initial timing VTX to the intermediate timing VTY. Note that a predetermined fixed value is used as the predetermined advance amount ΔVT.

  As a result, the torque fluctuation amount is changed from the torque fluctuation amount B1 when the initial timing VTX and the external EGR gas amount A1 (hereinafter, “first predetermined amount A1”) to the intermediate timing VTY and the external EGR gas amount A1. To the torque fluctuation amount B2 at the time. Further, since a margin is secured between the torque fluctuation amount B2 and the allowable limit amount BX by a difference ΔB between the torque fluctuation amount B1 and the torque fluctuation amount B2, the external EGR gas amount is set to be greater than the first predetermined amount A1. Even if it is increased, the torque fluctuation amount does not immediately exceed the allowable limit amount BX.

  When the external EGR gas amount is increased after the advance of the valve timing VT, the torque fluctuation amount increases in accordance with the relationship indicated by the straight line G2. Then, when the external EGR gas amount exceeds the second predetermined amount A2 that is larger than the first predetermined amount A1, the torque fluctuation amount exceeds the allowable limit amount BX.

  As described above, according to the advance control of the valve timing VT of the present embodiment, the second amount of the external EGR gas larger than the first predetermined amount A1 while suppressing the torque fluctuation amount from exceeding the allowable limit amount BX. It can be increased up to a predetermined amount A2.

  Here, in a state where the negative overlap period MOV is set, the torque fluctuation amount is increased as the advance amount of the valve timing VT is increased, that is, as the negative overlap period MOV is decreased toward “0”. The reduction effect of is improved. Therefore, in the case of reducing the torque fluctuation amount by the advance angle of the valve timing VT, from the viewpoint of reducing the torque fluctuation amount, the predetermined advance angle amount ΔVT is set within a range where the positive overlap period POV is not set. It can be said that it is desirable to make it as large as possible. For this purpose, the valve timing is set such that even if the advance angle of the predetermined advance angle amount ΔVT of the valve timing VT is executed, an operating region where the positive overlap period POV is not set in the changed valve timing is secured. When the timing VT is at the initial timing VTX, it can be said that a sufficiently large negative valve overlap period MOVX is required.

  Therefore, in the present embodiment, in order to satisfy such a requirement, the negative valve overlap period MOVX when the valve timing VT is at the initial timing VTX is set. That is, when the advance angle of the predetermined advance amount ΔVT is performed during the negative overlap period MOV corresponding to the initial timing VTX, the changed valve timing VT is set to a timing that is retarded from the intermediate timing VTY. Is done.

  With reference to FIG. 4, the content of the advance angle control process that defines a specific process procedure for the control of the valve timing VT described above will be described. The control process is periodically executed through the electronic control unit 70, for example, with a time interrupt at predetermined time intervals.

  In this advance angle control process, first, in step S10, it is determined whether or not the external EGR gas amount is abnormal in the reference amount GX. Here, the reference amount GX is set in advance through a test or the like as a value for determining whether or not the external EGR gas amount has increased until the torque fluctuation amount exceeds the allowable limit amount BX. Further, since the reference amount GX shows different values depending on the valve timing VT, a plurality of values corresponding to each valve timing VT are set in advance.

  In the determination in step S10, the reference amount GX corresponding to the valve timing VT at that time is compared with the actual external EGR gas amount. For example, when the valve timing VT is set to the initial timing VTX, the reference amount GX corresponding to the timing VTX, that is, the first predetermined amount A1 shown in FIG. 3 is compared with the actual external EGR gas amount.

  Here, when it is determined that the external EGR gas amount is greater than or equal to the reference amount GX, that is, when it is estimated that the torque fluctuation amount exceeds the allowable limit amount BX, in the next step S11, the positive overlap period POV is set. It is determined whether or not it is smaller than the boundary period POVA. On the other hand, when it is determined that the external EGR gas amount is less than the reference amount GX, that is, when it is estimated that the torque fluctuation amount is smaller than the allowable limit amount BX, this processing is temporarily ended.

  When it is determined by the determination process in step S11 that the positive overlap period POV is smaller than the boundary period POVA, that is, it is confirmed that there is still room for reducing the torque fluctuation amount through the advance of the valve timing VT. Then, the process proceeds to the next step S12.

  In this step S12, the valve timing VT is changed to the advance side by a predetermined advance amount ΔVT. Further, when executing this process, when it is previously confirmed that the positive overlap period POV exceeds the boundary period POVA at the valve timing VT after the change according to the advance of the predetermined advance amount ΔVT, the predetermined advance amount ΔVT Instead of the advance angle, the valve timing VT is advanced to the intermediate timing VTY. That is, in the process of step S12, the valve timing VT is advanced in a range where the positive overlap period POV does not exceed the boundary period POVA.

  The advance of the valve timing VT, which is performed instead of the advance of the predetermined advance amount ΔVT, is not limited to the intermediate timing VTY, and is appropriately advanced in a range where the positive overlap period POV is smaller than the boundary period POVA. It is permissible to set the quantity. In addition to the advance angle of the valve timing VT, for example, the process of step S13 can be employed as the process performed instead of the advance angle of the predetermined advance amount ΔVT. Furthermore, when it is determined that the positive overlap period POV is longer than the boundary period POVA, it is possible to perform control for making the positive overlap period POV smaller than the boundary period POVA in conjunction with the above-described controls.

  On the other hand, when it is determined in step S11 that the positive overlap period POV is greater than the boundary period POVA, that is, when it is confirmed that the torque fluctuation amount cannot be reduced through the advance of the valve timing VT. Then, the process proceeds to the next step S13. In step S13, the ignition timing is corrected so as to make the torque fluctuation amount smaller than the allowable limit amount BX through the ignition timing control. In addition to the correction of the ignition timing, it is also possible to perform control so that the positive overlap period POV is smaller than the boundary period POVA.

According to the control device for an internal combustion engine of the present embodiment, the following effects can be obtained.
(1) In this embodiment, since the valve timing VT of the intake valve 22 is advanced based on the fact that the external EGR gas amount is larger than the reference amount GX, first, the actual compression ratio accompanying the increase in the intake amount As a result, the torque fluctuation amount can be reduced. Further, since the valve timing VT is advanced in such a range that the positive overlap period POV does not exceed the boundary period POVA having a predetermined value, control for reducing the torque fluctuation amount (valve timing) It is also possible to suppress the torque fluctuation amount from increasing due to (VT control). As described above, according to the present embodiment, it is possible to suppress an increase in the torque fluctuation amount by the control for this while reducing the torque fluctuation amount accompanying the increase in the actual compression ratio.

  As control for suppressing torque fluctuation accompanying supply of external EGR, one that performs only ignition timing control is known. However, according to the torque fluctuation suppression control that relies only on the ignition timing control, there is a possibility that the torque fluctuation cannot be appropriately suppressed when the ignition timing control malfunctions for some reason. Therefore, by reducing the amount of torque fluctuation caused by advancing the valve timing VT of the intake valve 22 under the above conditions, the amount of torque fluctuation can be appropriately reduced even when the ignition timing control malfunctions under the above conditions. It becomes possible to do.

(Other embodiments)
According to the control device for an internal combustion engine of the present invention, the following changes can be made without being limited to the above embodiment.

  In the above embodiment, the variable valve mechanism 90 includes the variable valve timing mechanism that changes the valve timing VT of the intake valve 22. However, if the valve opening timing of the intake valve 22 is changed, the variable valve mechanism 90 Other mechanisms may be employed as the valve mechanism. An example of such a variable valve mechanism is one that enlarges and reduces the valve opening timing (working angle) of the intake valve 22.

  In the above embodiment, based on the fact that the external EGR gas amount is larger than the reference amount GX, it is determined that the torque fluctuation amount exceeds the allowable limit amount BX, thereby increasing the actual compression ratio accompanying the increase in the intake air amount. Although the request for reducing the torque fluctuation amount is set, the setting mode of the request is not limited to this. For example, the torque fluctuation amount is estimated each time, and a request to reduce the torque fluctuation amount due to the increase in the actual compression ratio accompanying the increase in the intake air amount based on the estimated torque fluctuation amount exceeding the allowable limit amount BX. Can also be set. As a calculation method of the torque fluctuation amount, for example, there is a method of calculating based on a difference between the engine rotation speed at that time and the engine rotation speed before a predetermined period.

  In the above embodiment, a fixed value is used as the predetermined advance amount ΔVT of the valve timing VT in the advance angle control of the intake valve 22, but for example, this advance angle is based on at least one of the engine load and the engine speed. The amount can be variably set. In this case, the advance amount of the valve timing VT can be set larger as the engine operation state in which the torque fluctuation amount becomes larger. Further, as the negative valve overlap period MOVX corresponding to the initial timing VTX, the positive overlap period POV is set at the changed valve timing VT even if the advance of the maximum predetermined advance amount ΔVT is performed. Can be avoided.

  In the above embodiment, control for advancing the valve timing VT in a range where the positive overlap period POV does not exceed the boundary period POVA is adopted as control for reducing the amount of torque fluctuation associated with the supply of external EGR gas. However, the advance control of the valve timing VT is not limited to this. For example, the advance angle control can be changed to any one of the following (a) to (d).

  (A) When there is a request to reduce the torque fluctuation amount due to the external EGR, the valve timing VT is advanced within a range in which the negative overlap period MOV is set to be larger than “0”.

  (B) When there is a request to reduce the amount of torque fluctuation due to the external EGR, the valve timing VT is advanced on the condition that the valve timing VT is set to the initial timing VTX.

  (C) A request to preset an upper limit period that is smaller than the boundary period POVA and larger than “0” as the upper limit period of the positive overlap period POV instead of the boundary period POVA, and to reduce the torque fluctuation amount due to the external EGR When there is, the valve timing VT is advanced within a range where the positive overlap period POV does not exceed the upper limit period.

  (D) When there is a request to set the upper limit timing of the advance angle on the retard side of the boundary period POVA and reduce the amount of torque fluctuation due to the external EGR, the valve timing VT The valve timing VT is advanced within the range where it is not possible.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 20 ... Engine body, 21 ... Crankcase, 22 ... Intake valve, 23 ... Exhaust valve, 24 ... Piston, 25 ... Crankshaft, 26 ... Spark plug, 27 ... Igniter, 28 ... Intake cam Shaft 29 ... Exhaust camshaft 31 ... Combustion chamber 40 ... Intake device 41 ... Intake passage 42 ... Throttle body 43 ... Throttle valve 44 ... Intake manifold 45 ... Surge tank 46 ... Subpipe 50 ... Injector , 60 ... exhaust device, 61 ... exhaust passage, 62 ... catalyst device, 70 ... electronic control device (control device), 71 ... crank sensor, 72 ... intake air sensor, 73 ... accelerator sensor, 74 ... throttle sensor, 75 ... position Sensor 76 opening degree sensor 80 exhaust recirculation device 81 communication path 83 actuator 9 ... variable valve mechanism, 91 ... actuator.

Claims (1)

In a control device for an internal combustion engine, comprising: a variable valve mechanism that varies the opening and closing timing of the intake valve; and an exhaust gas recirculation device that recirculates exhaust gas in the exhaust passage to the intake passage.
The control apparatus for an internal combustion engine, wherein the valve opening timing of the intake valve is advanced within a range in which a valve overlap period does not exceed a predetermined value based on the recirculation amount of the exhaust gas being larger than a reference amount.

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