JP4343954B2 - Engine control device - Google Patents

Description

【Technical field】
[0001]
  The present invention relates to an internal combustion engine (engine).To the control unitIn particular, an engine equipped with a variable valve mechanism that variably sets the valve opening amount and opening / closing timing of the intake valve.To the control unitRelated.
[Background]
[0002]
  In recent years, a variable valve mechanism that can variably set the opening / closing timing of an intake valve is becoming widespread for the purpose of improving fuel economy performance, output performance, and exhaust gas performance of an automobile engine. In an engine provided with a variable valve mechanism, an intake valve opening amount (valve lift amount) and an opening / closing timing are variably set in accordance with an operating state (load).
[0003]
  If the valve opening amount and the opening / closing timing of the intake valve are changed during acceleration, the air filling amount of the engine combustion chamber changes with an overshoot phenomenon (see FIG. 3 (h), FIG. 8 (h)). A step, that is, a torque shock occurs in the engine output torque. Hereinafter, the change in the valve opening amount and the opening / closing timing of the intake valve may be simply referred to as an opening / closing characteristic change.
[0004]
  For the purpose of avoiding the occurrence of torque shock, for example, the Japanese Patent Office Patent Publication No. JP-A-8-14073 discloses the closing timing of the intake valve as the current timing and the changing timing when the opening / closing characteristics are changed. A control device is shown in which it is temporarily held at a timing intermediate between (control target timing) and then changed to the control target timing.
[0005]
  However, this control device is effective when the amount of change in the valve closing timing is small, but if the amount of change in the valve closing timing is large, there is a possibility that torque shock will occur in two stages.
[0006]
  Japanese Patent Office Patent Publications and Japanese Patent Application Laid-Open No. 2001-221071 disclose that the actual negative pressure in the intake passage is detected and the variable valve mechanism is switched when the actual negative pressure matches the target negative pressure. A control device for performing the control is shown.
[0007]
  However, this control device is effective in avoiding the generation of a torque step in an engine having a variable valve mechanism that can arbitrarily control the opening / closing operation, but it accelerates the engine having a variable valve device that cannot arbitrarily control the opening / closing operation. It is not possible to avoid the occurrence of torque steps.
[0008]
  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an engine equipped with a variable valve mechanism capable of variably setting the opening / closing characteristics of an intake valve, particularly during acceleration. It is an object to provide an engine control device and a control method for performing control for accurately avoiding the occurrence of a torque step due to a change in opening / closing characteristics in the engine.
DISCLOSURE OF THE INVENTION
[0009]
  The present invention is a control device for an internal combustion engine comprising a throttle valve that controls the intake air amount, and a variable valve mechanism that can variably set the opening / closing characteristics of the intake valve. When the acceleration state is entered, the variable valve mechanism is controlled to increase the lift amount of the intake valve, and the stationary timing after acceleration of the intake valve closing timing is increased.CloseThe throttle valve is retarded until a timing after intake bottom dead center that is later than the valve timing, and the throttle valve is controlled in the valve closing direction.
[0010]
  Therefore, in an engine equipped with a variable valve mechanism, immediately after acceleration, the period during which the intake valve is open after intake bottom dead center is increased, and a part of the air taken into the combustion chamber is taken in during the intake stroke. Backflow outflows into the port, and this backflow outflow prevents the intake air amount in the combustion chamber from increasing suddenly immediately after acceleration, that is, the occurrence of an overshoot phenomenon. Thus, even when the opening / closing characteristics of the intake valve are switched by the variable valve mechanism during acceleration, a large torque step does not occur, and the occurrence of torque shock is well avoided.
[0011]
  Further, in a specific aspect of the present invention, a steady target after accelerating the closing timing of the intake valve a predetermined time after the internal combustion engine enters an acceleration state.CloseControl to shift to valve timing.
[0012]
  In yet another specific aspect of the present invention,The predetermined time is variably set based on at least one of an operation state immediately before acceleration of the internal combustion engine and a target operation state at the time of acceleration..
[0013]
  Furthermore, in another specific aspect of the present invention, when the pressure in the intake passage downstream of the throttle valve becomes equal to or lower than a predetermined value, a steady target after accelerating the closing timing of the intake valve.CloseControl to shift to valve timing.
[0014]
  Furthermore, in another specific embodiment of the present invention,The predetermined value is variably set based on at least one of an operation state immediately before acceleration of the internal combustion engine and a target operation state at the time of acceleration.
BEST MODE FOR CARRYING OUT THE INVENTION
[0015]
  Preferred embodiments according to the present invention will be described with reference to the accompanying drawings.
[0016]
  [Embodiment 1]
  FIG. 1 is a configuration diagram of an engine according to the first embodiment. The engine 1 has a piston 3 in a cylinder 2, and the cylinder 2, the piston 3 and the cylinder head 4 define a combustion chamber 5. The piston 3 is drivingly connected to a crank mechanism (not shown) by a connecting rod 6, and the reciprocating motion of the piston 3 is converted into rotational motion by the crank mechanism.
[0017]
  An intake port 7 and an exhaust port 8 are formed in the cylinder head 4. An intake valve 9 that opens and closes an intake port 7, an exhaust valve 10 that opens and closes an exhaust port 8, and a spark plug 11 are attached to the cylinder head 4. The intake valve 9 is provided with a variable valve mechanism 12 that variably sets an opening / closing characteristic, that is, a valve opening amount (valve lift amount) and a valve opening timing and a valve closing timing with respect to a crank angle.
[0018]
  The engine 1 sucks air into the combustion chamber 5 that becomes negative pressure by the reciprocating motion of the piston 3. An electric throttle valve 14 is installed in the intake passage 13 communicating with the intake port 7, and the electric throttle valve 14 controls the amount of intake air taken into the combustion chamber 5. A fuel injection valve 15 is attached to the cylinder head 4. The engine 1 sucks the fuel injected from the fuel injection valve 15 into the intake port 7 into the combustion chamber 5 together with the air sucked into the combustion chamber 5.
[0019]
  The air-fuel mixture sucked into the combustion chamber 5 is ignited by the spark plug 11 and burned. Exhaust gas generated by this combustion is discharged out of the combustion chamber 5 from the exhaust port 8 by the reciprocating motion of the piston 3.
[0020]
  In the engine 1, the fuel system, the ignition system, and the valve system are collectively controlled by the control unit 20. The control unit 20 is of an electronic control type including a microcomputer, detects an operating state of the engine 1 from output signals of various sensors, and a variable valve mechanism that is mounted on the engine 1 according to the detection result. 12, the operation of the fuel injection valve 15, the electric throttle valve 14 and the spark plug 11 is controlled.
[0021]
  Signals input from the various sensors to the control unit 20 are shown below. In the present embodiment, the crank angle, cylinder discrimination signal, throttle opening, accelerator pedal depression amount, brake pedal depression amount, intake air temperature, intake air amount, water temperature, exhaust temperature, and exhaust oxygen concentration are transferred from the various sensors to the control unit 20. Entered. Only the intake air amount sensor 16 and the throttle valve opening sensor 17 are shown in the figure.
[0022]
  The control unit 20 includes an engine control unit 21, a variable valve control unit 22, an injector drive circuit 23, a transmission control unit 24, an acceleration state detection unit 25, and the like.
[0023]
  The control unit 20 calculates the engine speed from the crank angle signal, and calculates the acceleration of the accelerator pedal when the accelerator pedal is depressed from the accelerator pedal depression amount. Using these calculated values and output signals from other various sensors, the target engine speed and target engine torque of the engine are calculated.
[0024]
  The fuel injection and ignition timing for each cylinder are controlled by the control unit 20, and the injection pulse signal and the ignition signal are processed in the control unit 20 to control the injection and ignition timing.
[0025]
  In the engine 1, the opening / closing characteristics of the intake valve 9 are variably set by a variable valve mechanism 12 provided in the intake valve 9, and the valve opening timing, the valve closing timing, and the valve lift amount (effective opening area of the intake port 7). Can be changed.
[0026]
  Specifically, as shown in FIG. 2, the variable valve mechanism 12 is configured so that the opening / closing characteristics of the intake valve 9 are set to a maximum operation pattern Pmax with a large valve lift amount and a large operating angle (long valve opening period), The lift amount and the minimum operation angle (short valve opening period) are given as two minimum operation patterns Pmin, and the operation pattern can be switched stepwise between the maximum operation pattern Pmax and the minimum operation pattern Pmin. Yes. That is, the variable valve mechanism 12 is configured to switch in a stepwise manner by providing opening / closing characteristics having different opening areas, valve opening times, and timings.
[0027]
  In the present embodiment, in the low torque region, the opening / closing characteristics of the intake valve 9 are those having a small opening area, and the intake air amount control is performed by the intake valve 9 and the electric throttle valve 14. Thereby, the pump loss in the low torque region is reduced, and the fuel efficiency can be improved.
[0028]
  In the middle torque to high torque region, the opening / closing characteristics of the intake valve 9 are those having a large opening area so that a large intake air amount can be secured and the required torque can be accommodated.
[0029]
  Therefore, in the middle torque region, it is necessary to lower the intake pipe pressure downstream from the electric throttle valve 14 compared to the low torque region. This is because, in the middle torque region, an opening / closing characteristic of the intake valve 9 having a large opening area is used, so that torque control needs to be performed by the electric throttle valve 14.
[0030]
  During acceleration, the opening / closing characteristics of the intake valve 9 are switched to an operation pattern (maximum operation pattern Pmax) having an opening area larger than an operation pattern having a small opening area (minimum operation pattern Pmin).
[0031]
  In the present embodiment, the opening / closing characteristics of the intake valve 9 are two patterns, but may be more than that.
[0032]
  The acceleration state detection unit 25 detects that the engine 1 is in an acceleration state from the engine speed obtained from the crank angle and the accelerator pedal depression amount.
[0033]
  When the acceleration state of the engine 1 is detected by the acceleration state detection unit 25, the variable valve control unit 22 performs control to increase the valve lift amount of the intake valve 9 immediately after the detection, and closes the intake valve 9. Delay angle control for delaying the valve timing after intake bottom dead center more than the steady target valve closing timing after acceleration is performed for a predetermined time (this predetermined time is referred to as a retard control time Tret). Thereafter, control is performed to shift the closing timing of the intake valve 9 to the steady target closing timing after acceleration.
[0034]
  As illustrated in FIG. 2, the control for delaying the closing timing of the intake valve 9 immediately after detection of the acceleration state is performed by setting the maximum operation pattern Pmax in the same pattern to the retard side by a predetermined amount Ret and phase. This can be performed according to the shifted retard angle operation pattern Pret.
[0035]
  In this case, the valve opening timing immediately after the acceleration state is detected also deviates on the retard side with respect to the steady target valve opening period after acceleration.
[0036]
  Therefore, in this case, when the acceleration state of the engine 1 is detected by the acceleration state detection unit 25, the variable valve control unit 22 performs control to increase the valve lift amount of the intake valve 9 immediately after the detection. At the same time, the opening timing of the intake valve 9 is delayed from the steady target valve opening period after acceleration, and the closing timing is greater than the steady target valve closing timing after acceleration after the intake bottom dead center. The retard control for retarding is performed over the retard control time Tret, and then the opening timing and closing timing of the intake valve 9 are respectively set to the steady target opening timing and the target closing timing after acceleration. Control to be transferred.
[0037]
  Next, details of the control of the variable valve mechanism 12 according to the present embodiment will be described with reference to FIG. This control is performed by the control unit 20.
[0038]
  When the acceleration state detection unit 25 detects the start of acceleration from the low torque region to the middle torque region at time point (acceleration state detection time point) t1, the target engine of the engine 1 to be reached using output signals from various sensors. Calculation of the rotational speed and the target engine torque is performed. Based on these calculation results, the control target opening degree (throttle valve opening command value) of the electric throttle valve 14 and the control target valve lift amount (intake valve target opening area) of the intake valve 9 are determined. (See FIGS. 3A and 3B).
[0039]
  As shown in FIG. 3A, the target opening degree of the electric throttle valve 14 decreases at the acceleration state detection time t1.
[0040]
  Accordingly, as shown in FIG. 3D, the actual opening of the electric throttle valve 14 gradually decreases starting from the acceleration state detection time t1. The reduction in the actual opening of the electric throttle valve 14 is because, as described above, it is necessary to lower the intake pipe pressure downstream of the electric throttle valve 14 in the middle torque region than in the low torque region.
[0041]
  Further, as shown in FIG. 3B, at the acceleration state detection time t1, the opening / closing characteristics of the intake valve 9 are switched step by step from a small opening area to a large opening area. As a result, as shown in FIG. 3E, the actual opening area of the intake valve 9 increases stepwise at the acceleration state detection time t1.
[0042]
  At the acceleration state detection time t1, as shown in FIG. 3C, the target valve closing timing of the intake valve 9 is set to the steady target valve closing timing Vcaf after acceleration after the intake bottom dead center. Delay angle control for delaying more by a predetermined amount Ret is immediately started. Time measurement of the retard control time Tret is started at the acceleration state detection time t1, and this retard control is performed from the acceleration state detection time t1 to a time t2 when a predetermined retardation control time Tret elapses.
[0043]
  As a result, as shown in FIG. 3F, the actual closing timing of the intake valve 9 is larger than the steady target closing timing Vcaf after acceleration by a predetermined amount Ret at the acceleration state detection time t1. The state is retarded and this state is maintained until time t2.
[0044]
  When a predetermined retardation control time Tret has elapsed from the acceleration state detection time t1 (time t2), the target valve closing timing of the intake valve 9 is a steady target after acceleration as shown in FIG. The valve closing timing is changed to Vcaf. Thereby, as shown in FIG. 3F, the actual closing timing of the intake valve 9 is set to the steady target closing timing Vcaf after acceleration.
[0045]
  Due to the retard control over the retard control time Tret described above, the period during which the intake valve 9 is open after the intake bottom dead center is increased. As a result, part of the air sucked into the combustion chamber 5 flows back into the intake port 7 during the intake stroke, and this intake backflow outflow immediately after acceleration as shown in FIG. In addition, a sudden increase in the amount of intake air in the combustion chamber 5 is avoided.
[0046]
  As described above, since the delay control time Tret is provided immediately after acceleration and before the stationary target valve closing timing Vcaf after acceleration is set, the retard control time Tret is provided. During the time Tret, as shown in FIG. 3G, it can be expected that the intake pipe pressure downstream of the electric throttle valve 14 is sufficiently reduced.
[0047]
  Thus, even if the valve closing timing of the intake valve 9 is subsequently advanced to the steady target valve closing timing Vcaf after acceleration, the amount of air taken into the combustion chamber 6 does not increase rapidly.
[0048]
  Therefore, even when the opening / closing characteristics of the intake valve 9 are switched by the variable valve mechanism 12 during acceleration, a large torque step does not occur and the occurrence of a torque shock is avoided.
[0049]
  The variable valve control unit 22 variably sets the retard control time Tret to an appropriate value based on the operation state immediately before acceleration of the engine 1 or the target operation state at the time of acceleration. The setting of the retard control time Tret will be described with reference to FIG.
[0050]
  When the opening / closing characteristic of the intake valve 9 immediately before the acceleration state detection unit 25 detects the start of acceleration from the low torque region to the middle torque region is used, the opening / closing characteristic having a small opening area is used, and the engine torque Te is relatively large. It is necessary to increase the retard control time Tret. This is due to the following reason.
[0051]
  When an opening / closing characteristic having a small opening area is used and the engine torque Te is relatively large, the intake pipe pressure downstream of the electric throttle valve 14 becomes relatively large. On the other hand, when an opening / closing characteristic having a large opening area is used in the middle torque region, the throttle is provided by the electric throttle valve 14, so that the intake pipe pressure downstream of the electric throttle valve 14 becomes relatively small.
[0052]
  For this reason, since it takes a lot of time to lower the intake pipe pressure downstream of the electric throttle valve 14, it is necessary to increase the retard control time Tret.
[0053]
  Further, when the engine speed Ne immediately before the acceleration state detection unit 25 detects the start of acceleration from the low torque region to the middle torque region is low, it is necessary to increase the retard control time Tret. This is because when the engine speed Ne is low, a long time is required until the intake pipe pressure downstream of the electric throttle valve 14 is reduced.
[0054]
  When the opening and closing characteristics of the intake valve 9 immediately before the acceleration state detection unit 25 detects the start of acceleration from the low torque region to the middle torque region is used, and when the engine torque Te is relatively small When the engine speed Ne is large, the retard control time Tret may be shortened, contrary to the method of giving the retard control time Tret described above.
[0055]
  As shown in FIG. 5, the retard control time Tret is the difference ΔNe between the engine speed immediately before the start of acceleration and the target engine speed, and the difference between the engine torque immediately before the start of acceleration and the target engine torque. It can also be set according to ΔTe.
[0056]
  The retardation amount Ret may also be variably set based on the same idea as the setting characteristic of the retardation control time Tret described above.
[0057]
  The acceleration control procedure according to this embodiment will be described with reference to the flowchart shown in FIG.
  First, acceleration determination is performed (step S1). This acceleration determination is to determine whether or not the acceleration is started from the normal driving state (steady driving state), and is performed by detecting the acceleration state based on the detected value of the accelerator pedal depression amount, for example. . If no acceleration is detected, this control routine is terminated and normal steady state control is executed.
[0058]
  When acceleration is detected, the engine speed and acceleration when the accelerator pedal is depressed are calculated from the crank angle signal and the accelerator pedal stroke, and using these calculated values and output signals from various other sensors, A target engine speed and a target engine torque are calculated. From these calculation results, the target opening of the electric throttle valve 14 and the target opening / closing characteristics of the intake valve 9 are calculated and determined (step S2).
[0059]
  Next, the retard control time Tret is determined in accordance with the characteristics shown in FIG. 4 or FIG. 5 from the respective engine speeds and engine torques in the steady operation and the target operation region before detecting acceleration (step). S3).
[0060]
  Then, after detecting the acceleration state, it is determined whether or not the retard control time Tret has elapsed (step S4). When the retard control time Tret elapses after the acceleration state is detected, the change to the target opening / closing characteristic of the intake valve 9 is started (step S5).
[0061]
  [Embodiment 2]
  FIG. 7 is a configuration diagram of an engine according to the second embodiment. 1, parts corresponding to those in FIG. 7 are denoted by the same reference numerals as those in FIG. 7, and the description thereof is omitted.
[0062]
  A pressure sensor 18 that measures the intake pipe pressure downstream of the electric throttle valve 14 is installed downstream of the electric throttle valve 14. The output from the pressure sensor 18 is input to the control unit 20. Except for this point, the mechanical configuration of the present embodiment is the same as that of the first embodiment.
[0063]
  Therefore, also in this embodiment, as shown in FIG. 2, the variable valve mechanism 12 has the opening / closing characteristics of the intake valve 9 with the maximum operation pattern Pmax depending on the large valve lift amount and the large operating angle (long valve opening period), A configuration in which a small valve lift amount and a small operation angle (short valve opening period) are given as two patterns, that is, a minimum operation pattern Pmin, and the operation pattern can be switched stepwise between the maximum operation pattern Pmax and the minimum operation pattern Pmin. It has become.
[0064]
  Also in the present embodiment, in the low torque region, the opening / closing characteristics of the intake valve 9 are those having a small opening area, and the intake air amount control is performed with low pump loss by the intake valve 9 and the electric throttle valve 14. In the middle torque to high torque region, a large opening area is used as the opening / closing characteristics of the intake valve 9 to ensure a large intake air amount.
[0065]
  Therefore, at the time of acceleration, the opening / closing characteristics of the intake valve 9 are switched to an operation pattern (maximum operation pattern Pmax) having a larger opening area than an operation pattern having a smaller opening area (minimum operation pattern Pmin). In the middle torque to high torque range, torque control is performed by the electric throttle valve 14.
[0066]
  When the acceleration state of the engine 1 is detected by the acceleration state detection unit 25, the variable valve control unit 22 performs control to increase the valve lift amount of the intake valve 9 immediately after the detection, and closes the intake valve 9. The intake pipe pressure downstream of the electric throttle valve 14 detected by the pressure sensor 18 is used to perform a retard control that retards the valve timing after the intake bottom dead center by a larger amount than the steady target valve closing timing after acceleration. Control is performed until the valve timing is lowered to a predetermined threshold value, and thereafter, the valve closing timing of the intake valve 9 is shifted to a steady target valve closing timing after acceleration.
[0067]
  Next, details of the control of the variable valve mechanism 12 according to the present embodiment will be described with reference to FIG.
  When the acceleration state detection unit 25 detects the start of acceleration from the low torque region to the middle torque region at time point (acceleration state detection time point) t1, the target engine of the engine 1 to be reached using output signals from various sensors. Calculation of the rotational speed and the target engine torque is performed. Based on these calculation results, the control target opening degree (throttle valve opening command value) of the electric throttle valve 14 and the control target valve lift amount (intake valve target opening area) of the intake valve 9 are determined. (See FIGS. 8A and 8B).
[0068]
  As shown in FIG. 8A, the opening command value of the electric throttle valve 14 decreases at the acceleration state detection time t1. Along with this, as shown in FIG. 8D, the actual opening of the electric throttle valve 14 gradually decreases starting from the acceleration state detection time t1.
[0069]
  Further, as shown in FIG. 8B, at the acceleration state detection time t1, the target opening area of the intake valve 9 is switched step by step from a small one to a large one. As a result, as shown in FIG. 8E, the actual opening area of the intake valve 9 increases stepwise at the acceleration state detection time t1.
[0070]
  Further, at the acceleration state detection time t1, as shown in FIG. 8C, the target closing timing of the intake valve target opening area air valve 9 is set to a steady state after acceleration after the intake bottom dead center. The retard control for retarding the target valve closing timing Vcaf by a predetermined amount Ret is immediately started. This retarding control is performed after the acceleration state detection time t1 until the intake pipe pressure downstream of the electric throttle valve 14 detected by the pressure sensor 18 decreases to a predetermined threshold value Pis.
[0071]
  As a result, as shown in FIG. 8 (f), the actual valve closing timing of the intake valve 9 is larger by a predetermined amount Ret than the steady target valve closing timing Vcaf after acceleration at the acceleration state detection time t1. The state is retarded and this state is maintained until the intake pipe pressure downstream from the electric throttle valve 14 decreases to a predetermined threshold value Pis as shown in FIG.
[0072]
  As shown in FIG. 8F, after the acceleration, when the intake pipe pressure downstream of the electric throttle valve 14 detected by the pressure sensor 18 falls to a predetermined threshold value Pis (time point t3), FIG. As shown in (c), the target valve closing timing of the intake valve 9 is changed to a steady target valve closing timing Vcaf after acceleration. Thereby, as shown in FIG. 8F, the actual closing timing of the intake valve 9 is set to the steady target closing timing Vcaf after acceleration.
[0073]
  As described above, the delay angle control is performed until the intake pipe pressure downstream of the electric throttle valve 14 reaches the predetermined threshold Pis, and the period during which the intake valve 9 is opened after the intake bottom dead center by the delay angle control is a period. Rather than becoming larger, part of the air sucked into the combustion chamber 5 flows out back into the intake port 7 during the intake stroke. Thereby, as shown in FIG. 8 (h), it is avoided that the intake air amount in the combustion chamber 5 increases rapidly immediately after acceleration.
[0074]
  Thus, even if the valve closing timing of the intake valve 9 is subsequently advanced to the steady target valve closing timing Vcaf after acceleration, the amount of air taken into the combustion chamber 6 does not increase rapidly.
[0075]
  Therefore, even when the opening / closing characteristics of the intake valve 9 are switched by the variable valve mechanism 12 during acceleration, a large torque step does not occur and the occurrence of a torque shock is avoided.
[0076]
  As shown in FIG. 9, the intake pipe pressure threshold value Pis is variably set to an appropriate value in accordance with the engine torque in the target operation region. If the target operation region is a high torque region, the threshold value Pis is large, and if the target operation region is a medium torque region, the threshold value Pis is small compared to the high torque region. In this way, by setting the threshold value Pis of the intake pipe pressure according to the engine torque in the target operation region, it is possible to effectively generate a torque step corresponding to the time change until the predetermined intake pipe pressure is reached. Can be reduced.
[0077]
  The acceleration control procedure according to the present embodiment will be described with reference to the flowchart shown in FIG.
  First, acceleration determination is performed (step S11). This acceleration determination is to determine whether or not the acceleration is started from the normal driving state (steady driving state), and is performed by detecting the acceleration state based on the detected value of the accelerator pedal depression amount, for example. . If no acceleration is detected, this control routine is terminated and normal steady state control is executed.
[0078]
  When acceleration is detected, the engine speed and acceleration when the accelerator pedal is depressed are calculated from the crank angle signal and the accelerator pedal stroke, and using these calculated values and output signals from various other sensors, A target engine speed and a target engine torque are calculated. From these calculation results, the target opening degree of the electric throttle valve 14 and the target opening / closing characteristic of the intake valve 9 are calculated and determined (step S12).
[0079]
  Next, the threshold value Pis of the intake pipe pressure is determined from the engine torque in the target operation region according to the characteristic shown in FIG. 9 (step S13).
[0084]
  Then, it is determined whether or not the intake pipe pressure downstream of the electric throttle valve 14 detected by the pressure sensor 18 has decreased to a predetermined threshold value Pis (step S14). When the tracheal pressure decreases to the predetermined threshold value Pis, the variable to the target opening / closing characteristic of the intake valve 9 is started (step S15).
[0080]
  [Other Embodiments]
  In any of the above-described embodiments, immediately after the acceleration state is detected, the target valve closing timing of the intake valve 9 is delayed by a predetermined amount Ret after the intake bottom dead center and after the steady target valve closing timing Vcaf after acceleration. If the steady target valve closing timing Vcaf after acceleration is after the intake bottom dead center, as shown by the broken line in FIG. Immediately after the acceleration state is detected, the target opening area of the intake valve 9 may be increased and the target valve closing timing may be set to the steady target valve closing timing Vcaf after acceleration.
[0081]
  In this case as well, since there is a period during which the intake valve is open after intake bottom dead center, part of the air sucked into the combustion chamber flows back into the intake port during the intake stroke, and this backflow outflow causes Immediately after acceleration, it is possible to reduce the sudden increase in the amount of intake air in the combustion chamber. Even when the opening / closing characteristics of the intake valve are switched by the variable valve mechanism during acceleration, a large torque step does not occur, and torque shock Generation can be reduced.
[Brief description of the drawings]
[0082]
FIG. 1 is a system diagram showing Embodiment 1 of an engine to which an engine control apparatus according to the present invention is applied;
FIG. 2 is a graph showing operating characteristics of an engine variable valve mechanism to which an engine control apparatus according to the present invention is applied;
FIG. 3 is a time chart showing the operation of the engine control apparatus according to the first embodiment.
FIG. 4 is a graph showing an example of retard angle control time setting characteristics of the engine control apparatus according to the first embodiment.
FIG. 5 is a graph showing another example of retard angle control time setting characteristics of the engine control apparatus according to the first embodiment;
FIG. 6 is a flowchart illustrating a procedure of acceleration control of the engine control apparatus according to the first embodiment.
FIG. 7 is a system diagram showing Embodiment 2 of an engine to which the engine control apparatus according to the present invention is applied.
FIG. 8 is a time chart showing the operation of the engine control apparatus according to the second embodiment.
FIG. 9 is a graph showing an example of a threshold setting characteristic of the intake pipe pressure of the engine control apparatus according to the second embodiment.
FIG. 10 is a flowchart illustrating a control procedure during acceleration of the engine control apparatus according to the embodiment.

Claims (1)

A control device for an internal combustion engine, comprising: a throttle valve that controls an intake amount; and a variable valve mechanism that can variably set an opening / closing characteristic of the intake valve,
When the internal combustion engine enters an acceleration state, the control device controls the variable valve mechanism to increase the lift amount of the intake valve and to stabilize the intake valve closing timing after acceleration. together it is retarded to timing after goal closing valve timing slower intake bottom dead center, and controls the throttle valve in the closing direction,
After a predetermined time after the internal combustion engine enters an acceleration state, a control is performed to shift the closing timing of the intake valve to a steady target closing timing after acceleration,
The predetermined time is based on the engine torque and engine speed immediately before acceleration of the internal combustion engine, or the difference between the engine torque immediately before acceleration and the target engine torque, and the difference between the engine speed immediately before acceleration and the target engine speed. The control device for an internal combustion engine , which is variably set based on the above .

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