JP2009243371A - Method and device for controlling internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately adjust a cylinder air volume to reliably prevent abnormal combustion during transition in which an intake valve closing timing shifts between quick closure operation and slow closure operation. <P>SOLUTION: This control method has: a regular control step to control the intake valve closing timing depending on an operation mode, assuming quick closure operation mode when a desired cylinder air volume is smaller than a predetermined air volume or slow closure operation mode when the desired cylinder air volume is equal to or larger than the predetermined air volume; and a transition control step to control the transition from quick closure operation mode to slow closure operation mode as the desired cylinder air volume increases. The transition control step includes: a first step to retard the intake valve closing timing to a predetermined timing according to the increase of the desired cylinder air volume and to decrease an intake pressure to a predetermined pressure as well; and a second step to further retard the intake valve closing timing and increase the intake pressure after the intake valve closing timing becomes the predetermined timing and the intake pressure decreases to the predetermined pressure and to increase the intake pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control method and apparatus, generally relates to an internal combustion engine intake valve close timing setting method, and more specifically, an intake valve close suitable for an internal combustion engine having a relatively high compression ratio. The present invention relates to a timing setting method.

  It is known that the valve lift amount of the intake valve is changed in accordance with the engine operating conditions, as disclosed in, for example, Patent Document 1. The higher the engine speed, the greater the intake inertia force. Accordingly, if there is a valve lift amount greater than a predetermined value determined according to the air flow rate, the charging efficiency becomes maximum when the intake valve is closed at a predetermined timing delayed according to the engine speed. The charging efficiency decreases as the intake valve closing timing departs from the predetermined timing corresponding to the maximum charging efficiency, that is, the advance angle or the retard angle. In accordance with this principle, the cam-driven variable valve operating device described in Patent Document 1 increases the valve lift amount according to the increase in the target cylinder air amount, and the intake valve closing timing according to the increase in the valve lift amount. Is configured to retard. Therefore, in the configuration of Patent Document 1, the cylinder air amount can be controlled to the target amount while the intake pressure is kept high (the intake negative pressure is reduced). And by keeping intake pressure high in this way, pump loss can be reduced and engine operating efficiency can be improved.

  On the other hand, increasing the expansion ratio is known as another measure for increasing the engine operating efficiency. The expansion ratio is the ratio of the cylinder volume when the piston is at bottom dead center to the cylinder volume when the piston is at top dead center. Therefore, as the expansion ratio is increased, the energy of the air-fuel mixture is converted with higher efficiency by the work of the piston, and as a result, the engine operating efficiency can be improved. However, this also increases the compression ratio.

When increasing the compression ratio of a spark ignition internal combustion engine, there is a problem that the possibility of abnormal combustion such as self-ignition of the air-fuel mixture or knocking increases. In order to cope with this, for example, Patent Document 2 discloses a method for reducing the effective compression ratio, that is, the charging efficiency, by retarding or advancing the closing timing of the intake valve when an operation state in which self-ignition is likely to occur is detected. Is disclosed.
JP 2006-97647 A JP 2001-159348 A

  In the case of developing a technique for improving the engine operation efficiency by the high expansion ratio by combining the methods of Patent Document 1 and Patent Document 2, in the operation region where the target cylinder air amount is small, the intake valve closing timing is set to the charging efficiency at the engine speed. (The valve closing operation by such setting is also referred to as “early closing”) to suppress the mechanical loss in the low load operation region and the target cylinder air amount In an operation region where there is a large amount, the intake valve closing timing is set to the retarded angle side relative to the timing at which the charging efficiency becomes maximum at the engine speed (the valve closing operation by such setting is also referred to as “slow closing”). It is conceivable to secure a sufficient amount of air in the load operation region.

  However, while the intake valve closing timing is shifted between the early closing operation and the late closing operation, the air tends to become excessive, and in particular, in a high compression ratio engine, there is an increased concern about abnormal combustion such as pre-ignition.

  Therefore, it is conceivable to reduce the intake pressure when there is a tendency to excessive air, but the response of the change in the intake valve closing timing to the control signal does not necessarily match the response of the change in the intake pressure. It was difficult to properly adjust the cylinder air amount at the time of transition in which the intake valve closing timing changes.

  In view of the above circumstances, the present invention is an internal combustion engine capable of appropriately adjusting the cylinder air amount and reliably preventing abnormal combustion during the transition in which the intake valve closing timing shifts between the early closing operation and the late closing operation. It is an object of the present invention to provide an engine control method and apparatus.

  In order to solve the above problems, an internal combustion engine control method according to the present invention includes an intake valve that reciprocates in synchronization with rotation of a crankshaft of the internal combustion engine to open and close an intake passage from a cylinder. A method of controlling an internal combustion engine in which the closing timing can be changed, and when the target cylinder air amount, which is the target value of the air amount charged into the cylinder, is smaller than a predetermined air amount, the intake valve closing timing is filled. The fast closing operation mode is set within the first closing timing range on the advance side of the intake valve closing timing that maximizes the efficiency. When the target cylinder air amount is equal to or greater than the predetermined air amount, the intake valve closing timing is set to the charging efficiency. The intake valve closing timing is controlled according to the operation mode as the delayed closing operation mode that is set within the second closing timing range that is retarded from the intake valve closing timing at which A normal control step and a transition control step for performing control when shifting from the early closing operation mode to the slow closing operation mode due to an increase in the target cylinder air amount, and the transition control step increases the target cylinder air amount. Accordingly, the first step of delaying the intake valve closing timing to the predetermined timing and reducing the intake pressure to the predetermined pressure, the intake valve closing timing becomes the predetermined timing, and the intake pressure is decreased to the predetermined pressure. Then, the second step of further delaying the intake valve closing timing and increasing the intake pressure is included.

  According to this method, when the target cylinder air amount is smaller than the predetermined air amount, the intake valve is quickly closed, so that the cylinder air amount can be controlled to the target value while keeping the intake pressure high. The pump loss can be reduced, and the valve operation amount can be reduced to reduce the mechanical loss. On the other hand, when the target cylinder air amount is greater than or equal to the predetermined air amount, the intake valve is closed late, so that the necessary cylinder air amount can be ensured while avoiding abnormal combustion such as pre-ignition.

  In addition, when the target cylinder air amount increases to shift from the early closing operation mode to the late closing operation mode, the closing timing at which the charging efficiency is maximized is passed while the intake valve closing timing is shifted from early closing to late closing. However, the intake air pressure is reduced during the shift of the intake valve closing timing, thereby preventing the cylinder air amount from becoming excessive.

  In this case, there is a response delay in the change in the intake valve closing timing and the change in the intake pressure, and if there is a difference in each responsiveness, the timing when the intake valve closing timing passes the closing timing at which the charging efficiency becomes maximum, There is a possibility that a difference occurs between the time when the intake pressure decreases to a predetermined pressure and the effect of suppressing the increase in the cylinder air amount may be impaired.

  In order to deal with such a problem, the present invention proceeds to the second step after the intake valve closing timing reaches the predetermined timing by the first step and the intake pressure decreases to the predetermined pressure. Therefore, the time difference between the timing when the intake valve closing timing passes the predetermined timing and the timing when the intake pressure decreases to the predetermined pressure is eliminated, and the increase in the cylinder air amount is suppressed during the shift of the intake valve closing timing. It is possible to reliably achieve the function to prevent abnormal combustion.

  Another aspect of the method of the present invention includes an intake valve that reciprocates in synchronization with rotation of the crankshaft of the internal combustion engine to open and close the intake passage from the cylinder, and the closing timing of the intake valve can be changed. The method of controlling the internal combustion engine, wherein when the target cylinder air amount, which is the target value of the air amount charged into the cylinder, is smaller than a predetermined air amount, the intake valve closing timing is the intake valve that maximizes the charging efficiency When the target cylinder air amount is equal to or greater than the predetermined air amount, the intake valve closing timing is set so that the charging efficiency is maximized when the target cylinder air amount is equal to or greater than the predetermined air amount. A normal control step for controlling the intake valve closing timing in accordance with the operation mode as the delayed closing operation mode set in the second closing timing range on the retard angle side of the timing; A transition control step for performing control when transitioning from the same operation mode to the early closing operation mode due to a decrease in the target cylinder air amount, the transition control step corresponding to the decrease in the target cylinder air amount, the intake valve closing timing Is advanced to a predetermined timing and the intake valve is closed after the intake valve closing timing reaches the predetermined timing and the intake pressure decreases to the predetermined pressure. And a second step of further increasing the timing and increasing the intake pressure.

  According to this aspect, when shifting from the slow closing operation mode to the early closing operation mode due to a decrease in the target cylinder air amount, the cylinder air amount becomes excessive because the intake pressure decreases during the shift of the intake valve closing timing. In particular, the time difference between the timing when the intake valve closing timing passes the predetermined timing and the timing when the intake pressure decreases to the predetermined pressure is eliminated, and the cylinder air amount is changed during the shift of the intake valve closing timing. The action of suppressing the increase can be reliably achieved, and abnormal combustion can be reliably prevented.

  In the control method of the present invention, in the transition control step, when the intake pressure does not reach the predetermined pressure when the intake valve closing timing reaches the predetermined timing, the intake air pressure is increased until the intake pressure reaches the predetermined pressure. It is preferable to maintain the valve closing timing at the predetermined timing. Further, when the intake valve closing timing does not reach the predetermined timing when the intake pressure is reduced to the predetermined pressure, the intake pressure is maintained at the predetermined pressure until the intake valve closing timing reaches the predetermined timing. It is preferable.

  This corrects the time lag between the timing when the intake valve closing timing passes the predetermined timing and the timing when the intake pressure decreases to the predetermined pressure.

  Further, when the normal control step is in the early closing operation mode, the intake valve is closed while maintaining the intake pressure substantially constant according to the increase or decrease of the target cylinder air amount within a range smaller than the predetermined air amount. It is preferable to change the timing.

  Thus, in the early closing operation mode, the cylinder air amount is adjusted by changing the intake valve closing timing while reducing the pump loss by maintaining the intake pressure at a substantially constant high pressure.

  In the first step of the transition control step, it is preferable to perform a response control process on the change in the target cylinder air amount during the period during which the intake pressure is reduced.

  In this way, the controllability is improved by more appropriately limiting the change in the target cylinder air amount during the period when the response limit to the change in the target cylinder air amount is low, and the intake valve closing timing is more reliably achieved. An increase in the cylinder air amount during the shift can be suppressed.

  When the response control process is performed in this way, the response limiting process may be weakened after the intake valve closing timing reaches the predetermined timing and the intake pressure has decreased to the predetermined pressure.

  The predetermined timing may be an intake valve closing timing that maximizes the charging efficiency.

  The control device for an internal combustion engine according to the present invention includes an intake valve that reciprocates in synchronization with rotation of a crankshaft of the internal combustion engine to open and close the intake passage from the cylinder, and a displacement adjustment that adjusts a displacement characteristic of the intake valve. A mechanism, an intake pressure adjusting means for adjusting the intake pressure, and a controller for controlling the intake valve closing timing and the intake pressure by controlling the displacement adjusting mechanism and the intake pressure adjusting means. When the target cylinder air amount, which is the target value of the air amount charged into the engine, is smaller than the predetermined air amount, the intake valve closing timing is a first closing timing range on the advance side with respect to the intake valve closing timing at which the charging efficiency becomes maximum. When the target cylinder air amount is equal to or greater than the predetermined air amount, the intake valve closing timing is later than the intake valve closing timing at which the charging efficiency is maximized. As a late closing operation mode set within the second closing timing range on the side, means for controlling the intake valve closing timing according to the operation mode, and the late closing operation by increasing the target cylinder air amount from the early closing operation mode Transition control means for performing control when shifting to the mode, the transition control means retards the intake valve closing timing to a predetermined timing and increases the intake pressure to a predetermined pressure in accordance with an increase in the target cylinder air amount. And a control for lowering the intake valve closing timing and increasing the intake pressure after the intake valve closing timing reaches the predetermined timing and the intake pressure decreases to the predetermined pressure. It is configured.

  Another aspect of the device of the present invention is an intake valve that reciprocates in synchronization with rotation of a crankshaft of an internal combustion engine to open and close an intake passage from a cylinder, and a displacement adjustment that adjusts a displacement characteristic of the intake valve. A mechanism, an intake pressure adjusting means for adjusting the intake pressure, and a controller for controlling the intake valve closing timing and the intake pressure by controlling the displacement adjusting mechanism and the intake pressure adjusting means. When the target cylinder air amount, which is the target value of the air amount charged into the engine, is smaller than the predetermined air amount, the intake valve closing timing is a first closing timing range on the advance side with respect to the intake valve closing timing at which the charging efficiency becomes maximum. When the target cylinder air amount is equal to or higher than the predetermined air amount, the intake valve closing timing is retarded from the intake valve closing timing at which the charging efficiency is maximized. As the late closing operation mode set within the second closing timing range, the means for controlling the intake valve closing timing according to the operation mode, and the early closing operation mode by the reduction of the target cylinder air amount from the slow closing operation mode. Transition control means for performing control at the time of transition, and the transition control means advances the intake valve closing timing to a predetermined timing and decreases the intake pressure to a predetermined pressure in accordance with a decrease in the target cylinder air amount. And control for further advancing the intake valve closing timing and increasing the intake pressure after the intake valve closing timing reaches the predetermined timing and the intake pressure decreases to the predetermined pressure. It is what.

  According to such a control device, the above-described control method of the present invention can be effectively implemented by the displacement adjusting mechanism, the intake pressure adjusting means, and the controller.

  In this control device, the displacement adjusting mechanism includes a phase variable mechanism that can change the rotational phase of the camshaft relative to the crankshaft and a variable valve lift mechanism that can continuously change the lift amount of the intake valve. It is preferable.

  If it does in this way, a valve lift amount, a valve-opening period, etc. can be adjusted appropriately with adjustment of an intake valve closing timing by the above-mentioned displacement adjustment mechanism.

  As described above, the present invention first delays the intake valve closing timing to a predetermined timing when shifting from the early closing operation mode to the slow closing operation mode, or when shifting from the slow closing mode to the early closing operation mode. In addition to advancing, the intake pressure is reduced to a predetermined pressure, the intake valve closing timing reaches a predetermined timing, and after the intake pressure has decreased to the predetermined pressure, the intake valve closing timing is further retarded or advanced. In addition, since the intake pressure is increased, it is possible to reliably prevent the cylinder air amount from becoming excessive during the shift of the intake valve closing timing and to reliably prevent abnormal combustion.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of an internal combustion engine system including a control device according to an embodiment of the present invention.

  Referring to FIG. 1, the internal combustion engine system includes an engine 1, various actuators associated with the engine 1, various sensors, and an engine control unit 100 as a controller that controls the actuators based on signals from the sensors.

  The engine 1 is a spark ignition type internal combustion engine, and has the first to fourth four cylinders 11, 11,..., But may have any number of cylinders. The engine 1 is mounted on a vehicle such as an automobile, and its crankshaft 14 is connected to drive wheels via a transmission to propel the vehicle.

  The engine 1 according to the present embodiment has a geometric compression ratio of 13 or more, and the geometric compression ratio is preferably 14 or more and 16 or less.

  That is, a large geometric compression ratio means that the expansion ratio is large, so that the engine efficiency increases as the ratio increases. Therefore, in the present embodiment, the geometric compression ratio is set to 13 or more, and the high torque and the fuel consumption are significantly reduced while avoiding knocking by a method such as ignition retard.

  However, the higher the compression ratio, the more likely the occurrence of abnormal combustion. Therefore, it is necessary to reduce the effective compression ratio and reduce the charging efficiency. If so, the output obtained for the cylinder volume decreases, and the efficiency when viewed in terms of the weight ratio of the engine decreases. On the other hand, when the engine 1 is mounted on a vehicle such as an automobile, a problem arises in mountability in the engine room. Therefore, the upper limit of the geometric compression ratio is preferably 16 or less.

  The engine 1 includes a cylinder block 12 and a cylinder head 13 placed on the cylinder block 12, and cylinders 11, 11,. A crankshaft 14 is rotatably supported on the cylinder block 12, and the crankshaft 14 is connected to a piston 15 via a connecting rod 16.

  The piston 15 is slidably inserted into each cylinder 11 to define a combustion chamber 17. In the cylinder head 13, two intake ports 18 and two exhaust ports 19 are formed for each cylinder 11 (only one is shown in the drawing) and communicates with the combustion chamber 17. As shown in the figure, an intake valve 21 and an exhaust valve 22 are arranged for the intake port 18 and the exhaust port 19 so that they can be shut off (closed) from the combustion chamber 17. The intake valve 21 is driven by an intake valve drive mechanism 30 as a valve operating device, and the exhaust valve 22 is driven by an exhaust valve drive mechanism 40 to reciprocate at a predetermined timing to open and close the intake port 18 and the exhaust port 19. To do.

  The intake valve drive mechanism 30 has an intake camshaft 31, and the exhaust valve drive mechanism 40 has an exhaust camshaft 41. The camshafts 31 and 41 are connected by the crankshaft 14 via a power transmission mechanism such as a known chain / sprocket mechanism. As is well known, the power transmission mechanism is configured such that the camshafts 31 and 41 rotate once while the crankshaft 14 rotates twice.

The phase angle of the camshaft is detected by the cam phase sensor 35, and the detection signal θ _{VCT_A} is input to the engine control unit 100.

The spark plug 51 is attached to the cylinder head 13. Ignition system 52 receives a control signal SA _D from the engine control unit 100, so that the spark plug 51 generates a spark at a desired ignition timing, energizing it.

  The fuel injection valve 53 is attached to one side of the cylinder head 13 (in the illustrated example, the intake side). The tip of the fuel injection valve 53 faces the combustion chamber 17 below the two intake ports 18 in the vertical direction and in the middle of the two intake ports 18 in the horizontal direction.

Although not shown, the fuel supply system 54 is a high-pressure pump that boosts and supplies fuel to the fuel injection valve 53, a pipe and a hose that supply fuel from the fuel tank to the high-pressure pump, and the fuel injection valve 53. And an electric circuit for driving. This electric circuit receives the control signal FP _D from the engine control unit 100 and operates the solenoid of the fuel injection valve 53 to inject a desired amount of fuel at a predetermined timing.

The intake port 18 communicates with the surge tank 55 a through an intake path 55 b in the intake manifold 55. An intake air flow from an air cleaner (not shown) passes through the throttle body 56 and is supplied to the surge tank 55a. A throttle valve 57 is disposed on the throttle body 56, and the intake flow toward the surge tank 55a is throttled to adjust the flow rate as is well known. Throttle actuator 58 receives a control signal TVO _D from the engine control unit 100, adjusts the opening of the throttle valve 57.

  The exhaust port 19 communicates with a passage in the exhaust pipe as is well known by an exhaust path in the exhaust manifold 60. An exhaust gas purification system having one or more catalytic converters 61 is disposed in the exhaust passage downstream of the exhaust manifold 60. The catalytic converter 61 can be a well-known three-way catalyst, lean NOx catalyst, oxidation catalyst, or the like, and any other type that can meet the purpose of exhaust gas purification by a specific fuel control method. It may be a catalyst.

  The engine control unit 100 is a controller based on a well-known microcomputer, and includes a central calculation processing unit (CPU) that executes a program, a memory that is configured by, for example, a RAM or a ROM and stores a program and data, And an input / output (I / O) bus for inputting and outputting electrical signals.

The engine control unit 100 accepts various inputs such as an intake air flow rate AF from the air flow sensor 71, an intake manifold pressure MAP from the intake pressure sensor 72, and a crank angle pulse signal from the crank angle sensor 73. The engine control unit 100 calculates the engine speed N _ENG based on, for example, a crank angle pulse signal. The engine control unit 100 also accepts an input from the oxygen concentration sensor 74 regarding the oxygen concentration EGO of the exhaust gas. Furthermore, an accelerator control signal α from an accelerator opening sensor 75 that detects the depression amount of the accelerator pedal is received. The engine control unit 100 also receives a vehicle speed signal VSP from a vehicle speed sensor 76 that detects the rotational speed of the output shaft of the transmission.

More specifically, the engine control unit 100 calculates the following control parameters of the engine 1 based on the input as described above. For example, the desired throttle opening TVO, fuel injection amount FP, ignition timing SA, valve phase angle θ _VCT , valve lift amount θ _{VVL and the} like. Based on these control parameters, the corresponding control signals include throttle control signal TVO _D , fuel injection pulse signal FP _D , ignition pulse signal SA _D , valve phase angle signal θ _{VCT_D} , valve lift amount signal θ _{VVL_D,} etc. Output to the throttle actuator 58, the fuel supply system 54, the ignition system 52, the intake camshaft phase variable mechanism 32, and the like.

  Next, the details of the intake valve drive mechanism 30 according to the present embodiment will be described with reference to FIG. FIG. 2 is a perspective view showing a specific configuration of the intake valve drive mechanism 30 according to the embodiment of FIG. 1, and FIG. 3 is a cross-sectional view showing a main part of the intake valve drive mechanism 30 of FIG. 3, (A) shows when the valve lift amount is 0 in the large lift control state, (B) shows when the valve lift amount is maximum in the large lift control state, and (C) shows the small lift control state. In FIG. 2, the valve lift amount is 0, and (D) shows the maximum valve lift amount in the small lift control state.

  The intake valve drive mechanism 30 of this embodiment includes a displacement adjustment mechanism that adjusts the displacement characteristics of the intake valve 21. The displacement adjusting mechanism includes a phase variable mechanism (VCT mechanism) 32 that can change the rotational phase of the camshaft 31 with respect to the crankshaft 14 and a variable valve lift mechanism (VVL) that can continuously change the lift amount of the intake valve. Mechanism) 33.

  The VCT mechanism 32 is drivingly connected to the crankshaft 14 by a chain drive mechanism. In addition to the driven sprocket 104, the chain drive mechanism includes a drive sprocket of the crankshaft 14 and a chain wound around both the sprockets (not shown).

  The VCT mechanism 32 includes a case fixed to the driven sprocket 104 so as to rotate integrally, and a rotor housed therein and fixed to the inner shaft 105 so as to rotate integrally. A plurality of hydraulic chambers are formed between the case and the rotor around the central axis X (shown in FIG. 3) (in the circumferential direction). Then, the liquid pressurized by the pump (for example, engine oil) is selectively supplied to each hydraulic pressure chamber to form a pressure difference between the hydraulic pressure chambers facing each other.

The engine control unit 100 as a VCT control unit outputs a control signal (valve phase angle signal) θ _{VCT_D} to the electromagnetic valve 32 a of the VCT mechanism 32, and the electromagnetic valve 32 a receives the control signal θ _{VCT_D} and the hydraulic valve 32 a controls the hydraulic pressure. By adjusting the flow rate, the flow rate and pressure of the liquid supplied to the hydraulic pressure chamber are adjusted. This changes the actual phase difference between the sprocket 104 and the inner shaft 105, thereby achieving the desired rotational phase of the inner shaft 105 as is well known. Note that the VCT control unit may be configured by a unit having a configuration different from that of the engine control unit 100.

  As shown in FIGS. 3A to 3D, the VVL mechanism 33 has a disk-shaped cam 106 provided on the inner shaft 105 corresponding to each cylinder 11. The cam 106 is provided eccentric from the axis of the inner shaft 105 and rotates at a phase defined by the VCT mechanism 32. The inner periphery of the ring-shaped arm 107 is rotatably fitted to the outer periphery of the eccentric cam 106. When the inner shaft 105 rotates about its central axis X, the ring-shaped arm 107 rotates around the same central axis X. It rotates around the center of the eccentric cam 106 while revolving.

  The inner shaft 105 is provided with a rocker connector 110 for each cylinder 11. The rocker connector 110 has a cylindrical shape, and is externally attached to the inner shaft 105 and is coaxially supported. In other words, the rocker connector 110 is rotatably supported around the central axis X. Is a bearing journal, and is rotatably supported by a bearing cap (not shown) disposed on the cylinder head 13.

  The rocker connector 110 is integrally provided with first and second rocker cams 111 and 112. Since the configuration is the same, FIGS. 3A to 3D show the rocker cam 111. The rocker cam 111 has a cam surface 111a and a circumferential base surface 111b (FIG. D)), and they are all in sliding contact with the upper surface of the tappet 115. The rocker cam 111 presses the tappet 115 and opens the valve in the same manner as a cam of a general intake valve drive mechanism, except that it does not rotate continuously and swings. The tappet 115 is supported by a valve spring 116. The valve spring 116 is supported between the cages 117 and 118 as is well known.

  Referring again to FIG. 2, the control shaft 120 is disposed above the inner shaft 105 and the rocker cam parts 110 to 112 along with the assembly thereof. The control shaft 120 is rotatably supported by a bearing (not shown), and a coaxial worm gear 121 protruding from the outer peripheral surface is integrally provided near the center in the longitudinal direction.

The worm gear 121 meshes with the worm 122. The worm 122 is fixed to the output shaft of, for example, a stepping motor 123 that is an actuator of the VVL mechanism 33. Therefore, the control shaft 120 can be rotated to a desired position by the operation of the stepping motor 123 that receives the control signal (valve lift amount signal) θ _{VVL_D} from the engine control unit 100. A control arm 131 for each cylinder 11 is attached to the control shaft 120 thus rotated, and these control arms 131 are integrally rotated by the rotation of the control shaft 120.

  Further, the control arm 131 thus rotated is connected to the ring-shaped arm 107 by a control link 132. That is, one end of the control link 132 is rotatably connected to the tip of the control arm 131 by the control pivot 133, and the other end of the control link 132 is rotatably connected to the ring-shaped arm 107 by the common pivot 134. Yes.

  Here, the common pivot 134 connects the other end of the control link 132 to the ring-shaped arm 107 as described above, and penetrates the ring-shaped arm 107 so that it can also rotate to one end of the rocker link 135. It is linked to. The other end of the rocker link 135 is rotatably connected to the rocker cam 111 by a rocker pivot 136, whereby the rotation of the ring-shaped arm 107 is transmitted to the rocker cam 111.

  More specifically, when the inner shaft 105 rotates and the eccentric cam 106 rotates integrally therewith, if the eccentric cam 106 is positioned on the lower side as shown in FIGS. The arm 107 is also positioned on the lower side. On the other hand, as shown in FIGS. 3B and 3D, when the eccentric cam 106 is positioned on the upper side, the ring-shaped arm 107 is also positioned on the upper side.

  At this time, the position of the common pivot 134 that connects the ring-shaped arm 107 and the control link 132 is the three-way positional relationship between the position of the control pivot 133 and the common center position of the eccentric cam 106 and the ring-shaped arm 107. Therefore, if the position of the control pivot 133 does not change as shown in the figure (the control shaft 120 does not rotate), the common pivot 134 rotates around the common center of the eccentric cam 106 and the ring-shaped arm 107. In response to this, the reciprocation is generally made up and down.

  Such reciprocating motion of the common pivot 134 is transmitted to the first rocker cam 111 by the rocker link 135, and the first rocker cam 111 together with the second rocker cam 112 connected by the rocker connector 110 is the central axis X. Swing around. As shown in FIGS. 3B and 3C, the rocker cam 111 that swings in this manner resists the tappet 115 against the spring force of the valve spring 116 while the cam surface 111 a contacts the upper surface of the tappet 115. The tappet 115 pushes down the intake valve 21 to open the intake port 18.

  On the other hand, as shown in FIGS. 3A and 3C, when the base surface 111b of the rocker cam 111 contacts the upper surface of the tappet 115, the tappet 115 is not pushed down. This is because the radius of the base surface 111 b of the rocker cam 111 around the central axis X is set to be equal to or smaller than the distance between the central axis X and the upper surface of the tappet 115.

  If the position of the control pivot 133 changes in the mutual positional relationship between the control pivot 133, the common pivot 134, and the common center of the eccentric cam 106 and the ring-shaped arm 107 as described above, the three-way mutual positional relationship. Thus, the common pivot 134 reciprocates along a path different from that described above.

  Therefore, the swing range of the rocker cams 111 and 112 can be changed by rotating the control shaft 120 and the control arm 131 by the operation of the motor 123 and changing the position of the control pivot 133. For example, when the control arm 131 is rotated clockwise in FIG. 3 and the control pivot 133 is shifted from the position shown in FIG. 3A to the upper left side as shown in FIG. The swing range has a relatively strong tendency that the base surface 111b contacts the upper surface of the tappet 115.

  FIG. 4 is a diagram illustrating a setting example of the intake valve drive mechanism 30 according to the present embodiment.

As shown in this figure, in this embodiment, the components related to the intake valve drive mechanism 30 and which was described above, the valve lift theta _VVL is in the range up to theta _VVLmax from example theta _{VVL_min,} the target cylinder air amount The intake valve closing timing is _controlled from θ _{VCT_min} to θ _VCTmax according to an increase in the valve lift amount θ _VVL . Delay in range.

In the present embodiment, for example, when the intake valve 21 is opened and closed in the intake stroke when the engine speed (engine speed) N _ENG is 1500 rpm, the opening timing of the intake valve 21 is almost immediately before the exhaust top dead center in most operating regions. The valve opening is started and the closing timing is changed according to the required torque.

Here, in the present embodiment, as the closing timing of the intake valve 21, the first closing valve set to the advance side with respect to the intake valve closing timing at which the charging efficiency becomes maximum at the engine rotational speed (engine speed) N _ENG . A timing range IVC _1st and a second range that is set on the retard side with respect to the intake valve closing timing at which the charging efficiency becomes maximum at the engine rotational speed (engine speed) N _{ENG and} that is separated from the first valve closing timing range IVC _1st . The valve closing timing range IVC _2nd is set, and the early closing operation mode M _{EIVC in} which the intake valve 21 is operated to close in the first valve closing timing range IVC _1st , and the intake valve 21 is in the second valve closing timing range. A slow closing operation mode M _LIVC operated so as to be closed at IVC _2nd can be set.

The early closing operation mode M _EIVC is a mode selected at a low load when the cylinder air amount (the amount of air charged in the cylinder) is small. On the other hand, the slow closing operation mode M _LIVC is a mode selected at the time of high load with a large amount of cylinder air.

Here, in the present embodiment, the second valve closing timing range IVC _2nd in which the slow closing operation mode M _LIVC is set is retarded from the first valve closing timing range IVC _1st in which the early closing operation mode M _EIVC is set. And spaced apart. Therefore, between each valve closing timing range IVC _1st and IVC _2nd , there is an intermediate valve closing timing range (abnormal combustion concern range) IVC _IM in which the intake valve 21 does not close during steady operation. There is an intake valve closing timing at which the charging efficiency becomes maximum near the bottom dead center BDC in the valve timing range IVC _IM .

  Next, the reason why the operation mode as described above is set will be described.

  In order to increase the output of the engine 1 and reduce fuel consumption, the closing timing of the intake valve 21 is set as a method of increasing the expansion ratio by advancing or retarding the closing timing of the intake valve 21 from the intake bottom dead center. When the operation of the engine 1 is controlled by early closing that is advanced from the intake bottom dead center, as is apparent from FIGS. 3C and 3D, the rocking amount of the rocker cam 111 is reduced, and the valve spring 116 is moved. Is also preferable on the low load side. However, if the closing timing of the intake valve 21 is retarded to the vicinity of the intake bottom dead center in accordance with the increase in the required load, the engine 1 set to the high compression ratio as described above causes abnormal combustion such as pre-ignition. The possibility increases. Further, if the intake valve 21 is quickly closed while avoiding an operation region in which abnormal combustion is a concern, the cylinder air amount cannot be secured as the required load increases, and the required output cannot be obtained. .

On the other hand, when the intake valve closing timing IVC is set to be retarded from the timing at which the charging efficiency becomes maximum at the engine rotational speed N _ENG , air is introduced into the cylinder 11 until the piston 15 moves to the bottom dead center. Therefore, even if the intake valve 21 is closed when the effective compression ratio is reduced, a relatively sufficient amount of cylinder air can be ensured. On the other hand, as shown in FIGS. In an operating region where the target cylinder air amount is small at low load, it is necessary to set the valve lift amount and valve operating range of the intake valve 21 to be close to the maximum value, thereby avoiding problems such as increased mechanical loss. I can't.

Therefore, in the present embodiment, in a high compression ratio engine, while increasing the expansion ratio in the continuous operation region as much as possible, the knocking is avoided, the pump loss is reduced, and the machine in the operation region where the target cylinder air amount is small. The first valve closing timing range IVC _1st and the second valve closing timing range IVC _2nd are set as described above in order to reduce the power loss and ensure the output in the operation region where the target cylinder air amount is large.

Further, the _transition from the early closing operation mode M _EIVC in which the first valve closing timing range IVC _1st is _set to the slow closing operation mode M _LIVC in which the second valve closing timing range IVC _2nd is set, or the early _closing from the late closing operation mode M _{LIVC is made.} when the transition to the closed operating mode M _EIVC is performed, but the closing timing the intake valve passes through an intermediate closing timing range IVC _IM, by the intake pressure is low at this time, tendency to excess air can be suppressed.

  FIG. 5 is a characteristic diagram showing an example of an operation region for setting the operation mode.

As shown in this figure, in this embodiment, in the operation region R _LIVC that is a high load side that is higher than the high load side characteristic L1, the slow closing operation mode M _LIVC is on the low load side that is lower than the low load side characteristic L2. In a certain operation region R _EIVC , an early closing operation mode M _EIVC is set to be selected. In the illustrated example, the operation region R _TR between the characteristics L1 and the characteristics L2 is an area used for switching the operation mode by providing hysteresis. Even if the required load increases from the operation region R _EIVC , the characteristic L1 is _maintained. The operation mode is maintained in the early closing operation mode M _EIVC until the operating range is exceeded, and even if the required load decreases from the operation region R _LIVC , the operation mode is maintained in the operation region R _LIVC until the characteristic L2 is exceeded.

When the operation mode M_now is the early closing operation mode M _EIVC , for example, the intake valve closing timing IVC and the throttle opening TVO are controlled in the control example shown in FIGS.

That is, in the control of the intake valve closing timing IVC in the early closing operation mode M _EIVC , the engine speed N _ENG is high as shown in FIG. _6A within the first valve closing timing range IVC _1st . Indeed, the closing timing of the intake valve 21 is retarded. Further, the closing timing of the intake valve 21 is retarded as the target cylinder air amount increases. As a result, when the operation is performed in the first valve closing timing range IVC _1st , the closing timing of the intake valve 21 is retarded, so that the charging efficiency is increased and the torque corresponding to the required torque can be output. .

As the control of the throttle opening TVO in the early closing operation mode _MEIVC , as shown in FIG. 6B, a characteristic L3 proportional to the engine speed N _ENG is set on the low load side in parallel with the characteristic L1, In the operating region on the lower load side than this characteristic L3, the throttle opening TVO is fully open or equivalent to full open, and the cylinder air amount (the amount of air charged in the cylinder) is exclusively the closing timing of the intake valve 21. It is controlled by. For this reason, it is possible to control the cylinder air amount so that no pump loss occurs. On the other hand, between the characteristics L1 and the characteristics L3, the throttle opening degree TVO is controlled to decrease as the required load increases or as the engine speed N _ENG decreases. For this reason, the cylinder air amount can be reduced as the operation state approaches the low speed and high load operation region where the operation mode M needs to be set to the slow closing operation mode M _LIVC from the medium / high speed / low / medium load operation region. In the present embodiment employing a high compression ratio engine, the cylinder air amount can be adjusted while avoiding abnormal combustion such as pre-ignition even in an unstable operation region close to the switching point of the operation mode M. it can. The characteristic L3 may be on the lower load side than the characteristic L2 in FIG. 5, or may be equal to or higher than the characteristic L2.

Further, when the operation mode M_now is the slow closing operation mode M _LIVC , the intake valve closing timing IVC and the throttle opening TVO are controlled by the control example shown in FIGS. 7A and 7B, for example.

That is, as control of the intake valve closing timing IVC in the case of the slow closing operation mode M _LIVC , the engine speed N _ENG is high as shown in FIG. 7A within the second valve closing timing range IVC _2nd . The closer the intake valve 21 closes, the more the target cylinder air amount increases, and the more the intake valve 21 closes. On the other hand, as shown in FIG. 7B, the throttle opening TVO is controlled by making the throttle opening TVO constant with respect to the change in the target cylinder air amount, and as the engine speed N _ENG increases. TVO is getting bigger.

In this way, in the slow closing operation mode _MLIVC , the required cylinder air amount can be secured while suppressing knocking by the slow closing.

  FIG. 8 is a block diagram showing an algorithm of control by the engine control unit 100.

  As shown in this figure, the engine control unit includes a target torque (TQ) calculation unit 201, a target combustion torque (Pi_t) calculation unit 202, an operation region switching threshold value calculation unit 203, and a control amount calculation unit 204.

The target torque calculation unit 201 calculates a target torque TQ based on the accelerator control signal α from the accelerator opening sensor 75, the engine speed N _ENG based on the crank angle pulse signal, and the vehicle speed signal VSP from the vehicle speed sensor 76. To do. The target combustion torque calculator 202 adds a torque loss factor pf to the target torque TQ, and calculates a target combustion torque Pi_t that is a torque that should actually be generated by the engine. This target combustion torque Pi_t is specifically a target value of the indicated mean effective pressure Pi and corresponds to the target cylinder air amount.

The operation region switching threshold value calculation unit 203 is a threshold corresponding to the boundary of the operation regions R _LIVC , R _TR , and R _EIVC in the operation region map shown in FIG. 5, that is, the characteristic in this figure. A value corresponding to the engine speed N _ENG at that time is calculated on the line L1 and the characteristic line L2.

  Then, the control amount calculation unit 204 calculates the target operation region R_t from the threshold value obtained by the operation region switching threshold value calculation unit 203 and the target combustion torque Pi_t, and the target operation region R_t and Based on the target combustion torque Pi_t and the like, a target boost Bt_t and a target intake valve closing timing IVC_t are calculated.

  Further, the engine control unit includes an operation mode determination unit 205, an actual closing timing calculation unit 206, a transition control amount calculation unit 207, and a control signal output processing unit 208.

  The operation mode determination unit 205 determines the current operation mode and the target operation mode, and determines whether it is necessary to switch the operation mode.

When it is necessary to switch the operation mode, the control amount calculation unit 207 at the time of transition calculates the target combustion torque Pi_t, target boost Bt_t, target intake valve closing timing IVC_t, intake manifold pressure MAP, and actual closing timing calculation unit 206. Based on a signal such as the actual intake valve closing timing IVC_e, the control amount at the time of shifting to the operation mode is calculated. In this case, the target combustion torque Pi_t is subjected to a response limiting process as described later, and control amounts such as the target boost Bt_t and the target intake valve closing timing IVC_t are calculated according to the target combustion torque Pi_t after the response limiting process. . The actual closing timing calculation unit 206 calculates the actual intake valve closing timing IVC_e based on the valve phase angle θ _VCT and the valve lift amount θ _VVL .

  Then, control amounts such as the target boost Bt_t and the target intake valve closing timing IVC_t at the time of transition to the operation mode calculated by the transition control amount calculation unit 207 are given to the control signal output processing unit 208. Note that the control amount calculated in the control amount calculation 204 is given to the control signal output processing unit 208 except when the operation mode is shifted.

The control signal output processing unit 208 is a fuel injection amount or ignition timing determined based on the control amount calculated by the control amount calculating unit 204 or the transition control amount calculating unit 207, the engine speed N _ENG and the target combustion torque Pi_t. based on the control amount and the like, and outputs the control signal _{FP D, SA D, θ VVL} -D, θ VCT-D, the TVO _D to the actuator in response to each.

  The calculation process at the time of transition to the operation mode performed in the transition time control amount calculation unit 207 will be described with reference to FIG.

  FIG. 9A shows the processing at the time of shifting to the operation mode in the case of this embodiment. When the target torque changes and the operation mode is switched, the response delay of the boost change or the change of the intake valve closing timing is shown. Considering this, a response limiting process is performed on the target combustion torque Pi_t, and the boost change and the change in the intake valve closing timing are adjusted in terms of time. FIG. 9B is a comparative example, in which the target combustion torque Pi_t, the target boost Bt_t, the target intake valve closing timing IVC_t, etc. are simply changed as required without considering the response delay. Is shown. This figure shows a case where the target torque increases from the early closing operation mode and the operation shifts to the late closing operation mode.

In this figure, target torque TQ, area determination flag, target torque response limit, target torque change rate (tilt) dTQ, combustion torque Pi, throttle opening TVO, boost Bt, intake valve closing timing IVC, valve lift amount θ _VVL And the time change of valve _| bulb phase angle (theta) _VCT is shown. With respect to the combustion torque Pi, the one-dot chain line is the target value before the response limiting process, the broken line is the target value after the response process, and the solid line is the actual value. Further, regarding the throttle opening TVO, the boost Bt, the intake valve closing timing IVC, the valve lift amount θ _VCT , and the valve phase angle θ _VVL , the broken line is the target value, and the solid line is the actual value.

  As shown in this figure, in the early closing operation mode, the throttle opening is kept at a constant opening (opening that can secure an intake flow rate equivalent to full opening in the low speed range) to reduce pump loss, and the boost is 0. The intake valve closing timing IVC is adjusted in accordance with the target torque or the like within the range of the first timing (early closing).

  When the target torque TQ is increased by depressing the accelerator pedal from the operating region in the early closing operation mode, the target value of the combustion torque Pi increases correspondingly, and this target value reaches a predetermined threshold value Pi0. Then, processing (transition control step) that fulfills the function of the transition control means is started. As a first step of the transition control process, the target value of the intake valve closing timing IVC is gradually retarded and the target value of the boost Bt is once reduced to a predetermined pressure.

  In this case, the change in the combustion torque Pi has a response limit. In particular, when the boost Bt is lowered in the above-described transition control, the torque response limit is lowered and becomes lower than the target torque change rate dTQ. Even if the target value of the combustion torque Pi is changed in response to the change, the actual combustion torque Pi cannot follow the target value, and the response delay of the actual value with respect to the target value increases.

  Therefore, during the period in which the torque response limit is lower than the target torque change rate dTQ, the change in the target value of the combustion torque Pi is limited (broken line), that is, the target value of the combustion torque Pi corresponds to the target torque TQ. It is limited to change more slowly than (dashed line).

  When the transition control process is started, the throttle opening TVO is made small in order to reduce the boost Bt. In this embodiment, the target value of the throttle opening TVO is advanced and corrected in order to improve the response of the throttle control.

  Further, the target value of the boost Bt decreases to a predetermined pressure, and the target value of the intake valve closing timing IVC is retarded. In this case, in the comparative example in which the torque response limiting process is not performed, the boost Bt and the intake valve Although a large response delay occurs in each actual value with respect to each target value of the closing timing IVC, in this embodiment, the target value of the boost Bt and the intake valve closing correspond to the combustion torque Pi subjected to the response limiting process. Since the target value of the timing IVC changes, the followability of the actual value (solid line) with respect to these target values (broken line) is improved.

Since the intake valve closing timing IVC is determined by the valve lift amount θ _VVL and the valve phase angle θ _VCT , the target values of the valve lift amount θ _VVL and the valve phase angle θ _VVL correspond to the target values of the intake valve closing timing IVC. According to the present embodiment, the followability of the actual value (solid line) with respect to the target value (broken line) can also be improved with respect to the valve lift amount θ _VVL and the valve phase angle θ _VCT .

  When the transition control process proceeds, the restriction canceling condition is that the actual value of the intake valve closing timing IVC reaches a predetermined timing (the closing timing at which the charging efficiency is maximized) and the actual value of the boost Bt decreases to a predetermined pressure. When the restriction release condition is satisfied, the area determination flag is switched to the late closing, the response restriction is released, and the target value of the combustion torque Pi increases rapidly. In the second step, the target value of the throttle opening TVO is increased, the target value of the boost Bt is increased, and the intake valve closing timing IVC is further delayed from the predetermined timing. When the combustion torque Pi, the boost Bt, the intake valve closing timing IVC, etc. reach values corresponding to the target torque in the operation mode after the transition, the transition control process ends.

  The processing performed by the engine control unit 100 as described above is shown in a flowchart in FIGS. 10 and 11.

First, with reference to FIG. 10, the engine control unit 100 reads various signals (step S1). Next, a target torque TQ is calculated based on the accelerator control signal α, the vehicle speed signal VSP, and the engine rotational speed N _ENG (step S2). Further, the target combustion torque Pi_t is calculated based on the calculated target torque TQ and the torque loss factor pf assumed in advance (step S3). This torque loss factor pf is mechanical resistance and pump loss, and is a map of data obtained in advance through experiments or the like based on the operating state (engine speed N _ENG , in-cylinder temperature, etc.).

Next, the engine control unit 100 calculates operating region switching threshold values L1 and L2 based on the engine rotation speed N _ENG (step S4). Based on the operation region switching threshold values L1 and L2, the target combustion torque Pi_t and the like, the target operation region is calculated and the operation mode corresponding to the target operation region is determined (step S5). Further, the target boost Bt_t and the target intake valve closing timing IVC_t are calculated based on the operation mode, the target combustion torque Pi_t, the engine speed N _{ENG and the} like (step S6).

  Next, the engine control unit 100 determines whether or not it is necessary to switch the operation mode based on the calculated parameters (step S7). That is, when the current operation mode is the early closing mode and it is predicted that the operation region should be changed to the late closing mode due to an increase in the target torque TQ, or conversely, the current operation mode is the late closing mode. In the case where it is predicted that the operation range should be changed to the early closing mode due to the decrease in the target torque TQ, it is determined that the operation mode needs to be switched.

If switching of the operation mode is not required (NO in step S7), the engine control unit 100 performs control signals FP _D , SA _D , θ corresponding to the current operation mode M_now as processing corresponding to the normal control step. _{VVL-D, θ VCT-D} , by outputting the TVO _D, to control the actuators of the intake valve drive mechanism 30 and the throttle valve 57 (step S8). Thereafter, the process returns and the processing from step S1 is repeated.

  On the other hand, when it is determined in step 7 that the operation mode needs to be switched (YES in step S7), the engine control unit 100 determines whether or not the target combustion torque Pi_t has reached a predetermined threshold value Pi0. When the determination is made (step S9) and the predetermined threshold value Pi0 is reached, processing as a transition control step after step S10 is performed.

The process as the transition control step will be described in the case of shifting from the early closing operation mode to the late closing operation mode due to an increase in the target torque. In the engine control unit 100, the target combustion torque Pi_t reaches a predetermined threshold value Pi0. From this point, the increase in the target combustion torque Pi_t is limited (step S10), that is, the increase in the target combustion torque Pi_t is moderated as shown in FIG. In this way, while limiting the increase in the target combustion torque Pi_t, the target intake valve closing timing IVC_t is retarded according to the increase in the target combustion torque Pi_t (step S11), and the target according to the increase in the target combustion torque Pi_t. Boost Bt_t is reduced (step S12). Then, based on the target combustion torque Pi_t, the target intake valve closing timing IVC_t, the target boost Bt_t and the other control variables during the transition control obtained in steps S10 to S12, the control signals FP _D , SA _D , θ _VVL-D outputs theta _VCT-D, the TVO _D to each actuator (step S13).

Next, the engine control unit 100 calculates the actual intake valve closing timing IVC_e based on the valve phase angle θ _VCT and the valve lift amount θ _VVL , and actual boost Bt_e based on the intake manifold pressure MAP detected by the intake pressure sensor 72. Is calculated (step S14).

  Then, it is determined whether or not the actual intake valve closing timing IVC_e has reached a predetermined timing (the closing timing at which the charging efficiency is maximized) (step S15), and whether or not the actual boost Bt_e has decreased to a predetermined pressure ( Steps S16 and S17) are performed.

  Based on these determinations, the engine control unit 100 determines that the actual intake valve closing timing IVC_e has not reached the predetermined timing and the actual boost Bt_e has not decreased to the predetermined pressure (both steps S15 and S17 are NO). In the case of), the processing from step S10 is repeated. When the actual intake valve closing timing IVC_e has reached the predetermined timing but the actual boost Bt_e has not decreased to the predetermined pressure (when step S15 is YES and step S16 is NO), the target intake valve closing timing IVC_t is set to the predetermined timing. This is maintained and the actual intake valve closing timing IVC_e coincides (step S18), and only the boost is changed, and the processing from step S13 is repeated. Further, when the intake valve closing timing IVC_e has not reached the predetermined timing but the actual boost Bt_e has decreased to the predetermined pressure (when Step S15 is NO and Step S17 is YES), the target boost Bt_t is maintained at the predetermined pressure. This is in a state where the actual boost Bt_e matches (step S19), and only the intake valve closing timing is changed, and the processing from step S13 is repeated.

  When the actual intake valve closing timing IVC_e reaches a predetermined timing and the actual boost Bt_e has decreased to a predetermined pressure (when both step S15 and step S16 are YES), the engine control unit 100 determines the change in the target combustion torque Pi_t. The restriction is released (step S20), the target intake valve closing timing IVC_t is further retarded according to the increase in the target combustion torque Pi_t (step S21), and the target boost Bt_t is set according to the increase in the target combustion torque Pi_t. Increase (step S22).

  Next, the engine control unit 100 determines whether or not the mode transition has ended (step S23). If it has not ended, the process from step S21 is repeated, and if it has ended, the process returns.

  Note that the processing in steps S9 to S23 is also applied to the case where the slow closing operation mode is shifted to the early closing operation mode due to a decrease in the target torque. However, in this case, as shown in parentheses in the flowchart, the reduction of the target combustion torque Pi_t is restricted in step S10, and the target intake valve closing timing IVC_t is advanced in accordance with the reduction of the target combustion torque Pi_t in step S11. In step S12, the target boost Bt_t is decreased according to the decrease in the target combustion torque Pi_t. In step S21, the target intake valve closing timing IVC_t is advanced according to the decrease in the target combustion torque Pi_t, and in step S22, the target boost Bt_t is increased according to the decrease in the target combustion torque Pi_t.

According to the method and apparatus of the present embodiment as described above, when the target cylinder air amount is smaller than the predetermined air amount, the intake valve 21 is closed within the first valve closing timing range IVC _1st by the early closing operation, When the target cylinder air amount is equal to or greater than the predetermined air amount, the intake valve 21 is closed within the second valve closing timing range IVC _2nd that is retarded from the first valve closing timing range IVC _1st by the delayed closing operation and spaced apart. . Therefore, in the operation range where the target cylinder air amount is relatively small, the internal combustion engine is operated with a small valve opening amount corresponding to the required air amount by the early closing operation, and mechanical loss due to excessive valve operation is reduced. In addition, the throttle valve 57 is fully opened or an opening corresponding to full opening, and the intake pressure is increased to about atmospheric pressure, thereby reducing pump loss.

On the other hand, in an operation region where the target cylinder air amount is high, the necessary cylinder air amount can be secured and high engine output can be obtained while avoiding abnormal combustion such as pre-ignition by the slow closing operation. Further, in the high engine high load state of the target cylinder air amount, because the engine output is increased, then a possibility that the engine rotational speed N _ENG is increased high, the engine rotational speed N _ENG, the higher the intake valve to obtain a constant charging efficiency Since the closing timing IVC is delayed, it is advantageous to secure the cylinder air amount in the high speed range to make the closing slowly. In addition, the effective compression ratio can be lowered by slow closing to reduce the pump loss, and the problem of the high compression ratio can be prevented while the expansion ratio is increased to improve the engine operation efficiency. it can.

  Further, in the process (steps S10 to S22) as a transition control step performed at the time of transition from the early closing operation mode to the slow closing operation mode, or at the time of transition from the slow closing operation mode to the early closing operation mode, first, first In step, in response to an increase (or decrease) in target combustion torque, the intake valve closing timing is retarded (or advanced) to a predetermined timing, the intake pressure is decreased to a predetermined pressure, and then in a second step, In order to further retard (advance) the intake valve closing timing and increase the intake pressure, the cylinder air amount increases when the intake valve closing timing passes a predetermined timing (the intake valve closing timing at which the charging efficiency is maximized) This tendency can be canceled out by lowering the intake pressure, and abnormal combustion such as pre-ignition can be prevented.

  In particular, in the first step, when the intake valve closing timing has reached a predetermined timing but the boost has not decreased to the predetermined pressure, the process waits until the boost decreases to the predetermined pressure, and the boost has decreased to the predetermined pressure. However, when the intake valve closing timing has not reached the predetermined timing, it waits for the intake valve closing timing to reach the predetermined timing, and the condition that the intake valve closing timing reaches the predetermined timing and the boost is reduced to the predetermined pressure. The processing of the second step is performed after both conditions are satisfied. This eliminates the time lag between the timing when the intake valve closing timing passes the predetermined timing and the timing when the boost drops to the predetermined pressure, and cancels the tendency of the cylinder air amount to increase during the change of the intake valve closing timing. Can be reliably achieved, and abnormal combustion can be reliably prevented.

  Further, a response limiting process for limiting the rate of change of the target combustion torque is performed during the period in which the boost is reduced in the first step, and the target intake valve closing timing is determined according to the change in the target combustion torque subjected to the response limiting process. Since the target boost is changed, the followability of the actual value with respect to the intake valve closing timing and the target value of the boost can be improved, and the controllability can be improved. Therefore, the action of preventing abnormal combustion can be enhanced more reliably by eliminating the responsiveness difference between the change in intake valve closing timing and the change in boost.

  The above-described embodiments are merely examples of preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments. It goes without saying that various modifications are possible within the scope of the claims of the present invention.

1 is a schematic configuration diagram of an internal combustion engine according to an embodiment of the present invention. It is a perspective view which shows the specific structure of the intake valve drive mechanism which concerns on embodiment of FIG. FIGS. 3A and 3B are cross-sectional views showing the main part of the intake valve drive mechanism of FIG. 2, in which FIG. 3A shows a case where the valve lift amount is 0 in the large lift control state, and FIG. (C) shows when the valve lift amount is 0 in the small lift control state, and (D) shows when the valve lift amount is maximum in the small lift control state. It is a figure which shows the example of a setting of the intake valve drive mechanism which concerns on this embodiment. It is a characteristic view which shows the example of a setting of an operation area | region. It is a figure which shows the example of control in the early closing operation mode, (A) is a control example of intake valve closing timing, (B) is a control example of throttle opening. It is a figure which shows the example of control in a slow closing operation mode, (A) is a control example of intake valve closing timing, (B) is a control example of throttle opening. It is a block diagram which shows an example of the concrete algorithm of control by an engine control unit. It is a timing chart which shows an example at the time of performing a transition control step. It is a flowchart which shows an example of the arithmetic control process performed by an engine control unit. It is a flowchart which shows an example of the arithmetic control process performed by an engine control unit.

Explanation of symbols

1 engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 11 Cylinder 21 Intake valve 30 Intake valve drive mechanism 32 Phase variable mechanism 33 Variable valve lift mechanism 57 Throttle valve 100 Engine control unit (controller)
IVC _1st 1st valve closing timing range IVC _2nd 2nd valve closing timing range IVC _IM intermediate valve closing timing range M _EIVC early closing operation mode M _LIVC late closing operation mode R _EIVC early closing mode operation region R _LIVC late closing mode operation region

Claims (11)

This is a method for controlling an internal combustion engine that includes an intake valve that reciprocates in synchronization with the rotation of the crankshaft of the internal combustion engine to open and close the intake passage from the cylinder, and in which the closing timing of the intake valve can be changed. And
When the target cylinder air amount, which is the target value of the air amount charged into the cylinder, is smaller than the predetermined air amount, the intake valve closing timing is a first closing timing that is more advanced than the intake valve closing timing at which the charging efficiency becomes maximum. When the target cylinder air amount is equal to or greater than a predetermined air amount, the intake valve closing timing is set to the second closing timing range that is retarded from the intake valve closing timing at which the charging efficiency is maximized. A normal control step for controlling the intake valve closing timing according to the operation mode, as a slow closing operation mode set in
A transition control step for performing control when shifting from the early closing operation mode to the slow closing operation mode due to an increase in the target cylinder air amount;
The transition control step is a first step of delaying the intake valve closing timing to a predetermined timing and reducing the intake pressure to a predetermined pressure according to an increase in the target cylinder air amount, and the intake valve closing timing becomes the predetermined timing. And a second step of further delaying the intake valve closing timing and increasing the intake pressure after the intake pressure has decreased to the predetermined pressure. This is a method for controlling an internal combustion engine that includes an intake valve that reciprocates in synchronization with the rotation of the crankshaft of the internal combustion engine to open and close the intake passage from the cylinder, and in which the closing timing of the intake valve can be changed. And
When the target cylinder air amount, which is the target value of the air amount charged into the cylinder, is smaller than the predetermined air amount, the intake valve closing timing is a first closing timing that is more advanced than the intake valve closing timing at which the charging efficiency becomes maximum. When the target cylinder air amount is equal to or greater than a predetermined air amount, the intake valve closing timing is set to the second closing timing range that is retarded from the intake valve closing timing at which the charging efficiency is maximized. A normal control step for controlling the intake valve closing timing according to the operation mode, as a slow closing operation mode set in
A transition control step for performing control when shifting from the slow closing operation mode to the early closing operation mode due to a decrease in the target cylinder air amount;
In the transition control step, the intake valve closing timing is advanced to a predetermined timing in accordance with the decrease in the target cylinder air amount, and the intake valve closing timing is the predetermined timing. And a second step of further advancing the intake valve closing timing and increasing the intake pressure after the intake pressure has decreased to the predetermined pressure. In the control method of the internal combustion engine according to claim 1 or 2,
In the transition control step, if the intake pressure does not reach the predetermined pressure when the intake valve close timing reaches the predetermined timing, the intake valve close timing is set to the predetermined timing until the intake pressure reaches the predetermined pressure. A control method for an internal combustion engine, characterized in that: The internal combustion engine control method according to any one of claims 1 to 3,
In the transition control step, when the intake valve closing timing has not reached the predetermined timing when the intake pressure has decreased to the predetermined pressure, the intake pressure is set to the predetermined pressure until the intake valve closing timing reaches the predetermined timing. A control method for an internal combustion engine, characterized by maintaining the pressure. In the control method of the internal-combustion engine according to any one of claims 1 to 4,
In the normal control step, when in the early closing operation mode, the intake valve closing timing is set while maintaining the intake pressure substantially constant in accordance with the increase or decrease of the target cylinder air amount within a range smaller than the predetermined air amount. A control method of an internal combustion engine, characterized by changing. In the control method of the internal-combustion engine according to any one of claims 1 to 5,
In the first step of the transition control step, a response control process is applied to a change in the target cylinder air amount during a period in which the intake pressure is reduced. The method for controlling an internal combustion engine according to claim 6, wherein
The control method for an internal combustion engine, wherein the transition control step weakens the response limiting process after the intake valve closing timing reaches the predetermined timing and the intake pressure is reduced to the predetermined pressure. In the control method of the internal-combustion engine according to any one of claims 1 to 7,
The control method for an internal combustion engine, wherein the predetermined timing is an intake valve closing timing at which charging efficiency is maximized. An intake valve that reciprocates in synchronization with the rotation of the crankshaft of the internal combustion engine to open and close the intake passage from the cylinder, a displacement adjustment mechanism that adjusts the displacement characteristics of the intake valve, and an intake pressure adjustment means that adjusts the intake pressure And a controller for controlling the intake valve closing timing and the intake pressure by controlling the displacement adjusting mechanism and the intake pressure adjusting means,
The controller is
When the target cylinder air amount, which is the target value of the air amount charged into the cylinder, is smaller than the predetermined air amount, the intake valve closing timing is a first closing timing that is more advanced than the intake valve closing timing at which the charging efficiency becomes maximum. When the target cylinder air amount is equal to or greater than a predetermined air amount, the intake valve closing timing is set to the second closing timing range that is retarded from the intake valve closing timing at which the charging efficiency is maximized. Means for controlling the intake valve closing timing according to the operation mode, as a slow closing operation mode set in
Transition control means for performing control when transitioning from the early closing operation mode to the slow closing operation mode due to an increase in the target cylinder air amount;
The transition control means retards the intake valve closing timing to a predetermined timing in accordance with the increase in the target cylinder air amount, and controls to reduce the intake pressure to a predetermined pressure, and the intake valve closing timing becomes the predetermined timing, and A control apparatus for an internal combustion engine, wherein after the intake pressure is reduced to the predetermined pressure, the intake valve closing timing is further retarded and the intake pressure is increased. An intake valve that reciprocates in synchronization with the rotation of the crankshaft of the internal combustion engine to open and close the intake passage from the cylinder, a displacement adjustment mechanism that adjusts the displacement characteristics of the intake valve, and an intake pressure adjustment means that adjusts the intake pressure And a controller for controlling the intake valve closing timing and the intake pressure by controlling the displacement adjusting mechanism and the intake pressure adjusting means,
The controller is
When the target cylinder air amount, which is the target value of the air amount charged into the cylinder, is smaller than the predetermined air amount, the intake valve closing timing is a first closing timing that is more advanced than the intake valve closing timing at which the charging efficiency becomes maximum. When the target cylinder air amount is equal to or greater than a predetermined air amount, the intake valve closing timing is set to the second closing timing range that is retarded from the intake valve closing timing at which the charging efficiency is maximized. Means for controlling the intake valve closing timing according to the operation mode, as a slow closing operation mode set in
Transition control means for performing control when shifting from the slow closing operation mode to the early closing operation mode due to a decrease in the target cylinder air amount;
The transition control means advances the intake valve closing timing to a predetermined timing in accordance with a decrease in the target cylinder air amount, controls the intake pressure to a predetermined pressure, the intake valve closing timing becomes the predetermined timing, and A control apparatus for an internal combustion engine configured to perform control for further advancing the intake valve closing timing and increasing the intake pressure after the intake pressure has decreased to the predetermined pressure. 12. The control apparatus for an internal combustion engine according to claim 10, wherein the displacement adjustment mechanism is capable of continuously changing a lift amount of the intake valve and a phase variable mechanism that can change a rotation phase of the camshaft with respect to the crankshaft. And a variable valve lift mechanism.