JP5446579B2 - Internal combustion engine system control method and internal combustion engine system - Google Patents

Description

  The present invention belongs to a technical field related to an internal combustion engine, a control method for an internal combustion engine system including a throttle valve, and an intake valve closing timing variable mechanism, and the internal combustion engine system.

  Conventionally, for example, as disclosed in Patent Document 1, the lift amount of the intake valve is increased in accordance with the increase in the target air filling amount, and the valve closing timing of the intake valve (also referred to as intake valve closing timing) accompanying this increase. It is known that the cylinder air amount is controlled by delaying the). As a result, the pump loss caused by the air amount control by the throttle valve can be suppressed and the engine operation efficiency can be improved.

  On the other hand, it is known to increase the expansion ratio in order to increase the engine operating efficiency. Increasing the expansion ratio inevitably increases the compression ratio. Therefore, abnormal combustion is likely to occur in a high load low speed region. In order to prevent this abnormal combustion, it is effective to reduce the cylinder air filling amount. Therefore, for example, as shown in Patent Document 2, if the effective compression ratio is decreased, the air filling amount can be decreased without increasing the pump loss. The effective compression ratio can be reduced by separating the intake valve closing timing toward the advance side or the retard side with respect to the timing when the air filling amount becomes maximum at the engine speed.

JP 2005-264804 A JP 2001-159348 A

  By the way, the high load low speed region usually shifts to a high load medium speed region in a short time. Accordingly, the intake valve closing timing at which the air filling amount becomes maximum is retarded at high speed. Correspondingly, the acceleration performance of the engine can be kept high by delaying the intake valve closing timing in advance at the time of shifting to the high load low speed region.

  Therefore, in order to reduce the effective compression ratio, in the low speed range from low load to medium load, the target intake air amount is within the early closing range set on the advance side of the intake valve closing timing at which the air charge amount is maximum. While the intake valve is closed at a timing retarded in response to an increase in the engine speed, in a high load low speed region, a delay that is set on the retard side of the intake valve closing timing at which the air filling amount is maximum and is separated from the early closing range. It is desirable to close the intake valve within the closed range. As a result, when the required air amount changes greatly, the intake valve closing timing shifts between the early closing range and the late closing range that are separated from each other.

  Here, the intake valve is generally driven by a crankshaft to open and close. That is, the opening / closing drive of the intake valve is performed via a shaft such as a camshaft that rotates in synchronization with the crankshaft. In such a valve operating mechanism, in order to change the intake valve closing timing, it is inevitable to change it continuously. For this reason, in order to shift the intake valve closing timing between the early closing range and the late closing range, it is necessary to shift between both ranges continuously, and as a result, at the time of the transition, There will be a moment when the maximum air charge is reached. At this time, since the air filling amount becomes excessive, in order to prevent this, it is conceivable to reduce the intake pressure by reducing the throttle valve.

  However, for example, a problem occurs when the traction control is activated due to slipping of the wheels (drive wheels) and the required torque is reduced, and the intake valve closing timing is shifted from the late closing range to the early closing range. In other words, during the transition from the slow closing range to the early closing range, the wheel slip amount may decrease sharply due to the recovery of the wheel grip force, and the engine speed may drop rapidly. Since the intake throttle effect of the throttle valve is reduced, the intake pressure may not be sufficiently reduced. For this reason, at the time of transition from the late closing range to the early closing range, in order to reliably prevent the occurrence of abnormal combustion due to excessive cylinder air charge, the throttle valve is made to be more throttled, and the throttle valve with that throttle It is necessary to set control parameters on the assumption of the opening. As a result, there is a possibility that the pump loss increases and the engine operation efficiency is lowered.

  The present invention has been made in view of such points, and an object of the present invention is to set the closing timing of the intake valve to an early closing range and a late closing range, and to delay the closing timing of the valve closing timing. When the throttle valve is throttled during the transition from the first to the early closing range, it is intended to reduce the pump loss as much as possible by setting the throttle valve opening degree to be open.

To achieve the above object, according to the present invention, a cylinder that defines a combustion chamber together with a reciprocating piston, an intake passage through which air introduced into the combustion chamber passes, and the intake passage can be shut off from the combustion chamber. An intake valve driven by a crankshaft, a throttle valve disposed in the intake passage, and an intake valve closing timing for controlling the closing timing of the intake valve driven by the crankshaft When the required torque of the internal combustion engine is equal to or higher than a first predetermined torque determined for each engine speed, the air speed at the engine speed is determined in each cylinder cycle. The step of closing the intake valve within a delay closing range set on the retard side with respect to the timing when the filling amount becomes maximum, and the required torque is equal to the first predetermined torque. And closing the intake valve within an early closing range that is set to an advance side of the timing at which the air charge amount becomes maximum at the engine speed and is separated from the slow closing range in each cylinder cycle. The engine speed may decrease by a predetermined amount or more when the required torque decreases from the first predetermined torque or more to a second predetermined torque set to be equal to or less than the first predetermined torque. And determining the intake valve closing timing variable mechanism so that the closing timing of the intake valve shifts from the late closing range to the early closing range when it is determined that the possibility is lower than a predetermined level. controls so as to suppress abnormal combustion in an intermediate closing timing range between the retarded-closing range and the early closing range, the step of driving the throttle valve temporarily closing direction, the accessibility When sex is determined to the a predetermined level or more, the closing timing of the intake valve is so and a step of controlling the intake valve closing timing varying mechanism to remain later closing range above.

  As a result, when the required torque of the internal combustion engine decreases from the state where it is equal to or higher than the first predetermined torque to exceed the second predetermined torque, it is determined that the engine speed may decrease by a predetermined amount or more. When it is determined that the level is equal to or higher than the level, the intake valve closing timing (intake valve closing timing) remains in the late closing range, and the intake valve closing timing is determined only when it is determined that the possibility is lower than the predetermined level. Shifts from the late closing range to the early closing range, and at this transition, the throttle valve temporarily operates in the closing direction. As a result, the possibility that the engine speed decreases by a predetermined amount or more during the temporary closing operation control of the throttle valve is reduced, and the possibility that the cylinder air filling amount becomes excessive due to the reduction of the intake throttle effect by the throttle valve is eliminated. Can do. Therefore, the control parameters (throttle valve opening, intake valve closing timing, etc.) are premised on the assumption that the throttle valve opening is open when the intake valve closing timing shifts from the slow closing range to the early closing range due to a decrease in the required torque. Can be set. Therefore, the pump loss can be reduced and the engine operation efficiency can be kept high.

  The step of determining the possibility determines that the possibility is higher as the amount of decrease when the required torque is lower than the second predetermined torque from a state where the required torque is equal to or higher than the first predetermined torque is larger. It is preferable that it is a process.

  As a result, the greater the amount of decrease in the required torque, the higher the possibility that the engine speed will decrease by a predetermined amount or more, and the transition from the late closing range to the early closing range of the intake valve closing timing is limited. Particularly in the case of traction control, the larger the amount of decrease in the required torque, the larger the amount of decrease in the engine speed. Therefore, it is possible to appropriately suppress an excessive amount of cylinder air filling due to a decrease in the intake throttle effect by the throttle valve. be able to.

  It is preferable that the predetermined level is set higher as the engine speed is higher when the required torque is lower than the second predetermined torque from a state where the required torque is equal to or higher than the first predetermined torque.

  This makes it possible to appropriately cope with an increase in the cylinder air charge amount due to a reduction in the throttle effect proportional to the intake air flow rate.

  The method may further include a step of reducing a required torque of the internal combustion engine when a slip amount of a wheel to which power from the internal combustion engine is transmitted is a predetermined value or more.

  When the required torque decreases due to such traction control operation, it is predicted that the engine speed decreases due to the decrease. The reduction amount of the engine speed can be easily predicted from the wheel slip amount or the like, and the possibility that the engine speed is reduced by a predetermined amount or more can be easily determined.

Another aspect of the present invention includes a cylinder that defines a combustion chamber together with a reciprocating piston, an intake passage through which air introduced into the combustion chamber passes, and an intake passage that can be shut off from the combustion chamber and by a crankshaft. An internal combustion engine having a driven intake valve; a throttle valve disposed in the intake passage; a throttle actuator that drives the throttle valve; and a closing timing of the intake valve that is driven by the crankshaft. An intake valve closing timing variable mechanism, and a controller for controlling the throttle actuator and the intake valve closing timing variable mechanism, wherein the controller is configured so that the required torque of the internal combustion engine is an engine When the torque is equal to or higher than the first predetermined torque determined for each speed, the air charge amount is maximum at the engine speed in each cylinder cycle. When the intake valve closing timing variable mechanism is controlled so that the intake valve is closed within a delay closing range set on the retard side of the predetermined timing, and the required torque is smaller than the first predetermined torque. In each cylinder cycle, the intake valve closing is performed so that the intake valve is closed within an early closing range that is set to an advance side with respect to the time when the air filling amount becomes maximum at the engine speed and that is separated from the slow closing range. The engine speed is controlled when the timing variable mechanism is controlled and the required torque decreases from the first predetermined torque or higher to a second predetermined torque set to be lower than the first predetermined torque. It determines the possibility of reduced more than a predetermined amount, and, when the possibility is determined to be lower than the predetermined level, so that the closing timing of the intake valve is shifted to the early closing range of the late closing range Operation controls the intake valve closing timing varying mechanism, so as to suppress abnormal combustion in an intermediate closing timing range between the retarded-closing range and the early closing range, the throttle valve is temporarily closing direction controls by the Hare before Symbol throttle actuator, and, when the possibility is determined to the a predetermined level or more, the intake valve closing timing varying as the valve closing timing of the intake valve remains in late closing range the It is assumed that the mechanism is controlled.

  With this configuration, the same operational effects as those of the control method of the internal combustion engine system can be obtained.

As described above, according to the control method and the internal combustion engine system of the present invention, the required torque of the internal combustion engine is set to be equal to or lower than the first predetermined torque from the state where the required torque is equal to or higher than the first predetermined torque. 2 When it is determined that the engine speed decreases beyond a predetermined level, the possibility that the engine speed will decrease by a predetermined amount or more is determined, and when it is determined that the possibility is lower than a predetermined level, the closing timing of the intake valve The throttle valve is temporarily operated in the closing direction so as to suppress the abnormal combustion in the intermediate valve closing timing range between the late closing range and the early closing range. When it is determined that the possibility is equal to or higher than the predetermined level, the closing speed of the intake valve remains in the late closing range, so that the engine speed may be reduced during the temporary closing operation control of the throttle valve. The control parameter can be set on the premise of the open throttle valve opening when the intake valve closing timing shifts from the late closing range to the early closing range, thus reducing pump loss. And maintain high engine operating efficiency.

1 is a schematic configuration diagram of an internal combustion engine system according to an embodiment of the present invention. It is a top view which shows roughly the power transmission device from the engine to a wheel in the said internal combustion engine system. It is a perspective view which shows the specific structure of the intake valve drive mechanism which concerns on embodiment of FIG. 4A and 4B are cross-sectional views showing the main part of the intake valve drive mechanism, where FIG. 5A shows when the valve lift amount is 0 in the large lift control state, and FIG. 4B shows when the valve lift amount is maximum in the large lift control state. (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 said intake valve drive mechanism. It is a flowchart which shows the example of control of the engine by a control unit. It is a flowchart which shows the example of control of the engine by a control unit. FIG. 7 is a characteristic diagram illustrating an example of a control map for determining an operation region in the flowchart of FIG. 6. It is a figure which shows the example of control of the intake valve closing timing (valve closing timing of an intake valve) in the early closing mode set by the flowchart of FIG. It is a figure which shows the example of control of the throttle opening in the early closing mode set by the flowchart of FIG. It is a timing chart which shows the example of control in the retard transition mode by the flowchart of FIG. FIG. 8 is a diagram showing a control example of intake valve closing timing (intake valve closing timing) in the slow closing mode set by the flowchart of FIG. 7, and (A) shows a case where the throttle opening is controlled in parallel. , (B) shows a case where the throttle opening is kept constant. FIG. 8 is a diagram illustrating an example of throttle opening control in the slow closing mode set by the flowchart of FIG. 7, where (A) illustrates a case where the throttle opening is controlled in parallel, and (B) illustrates the throttle opening. The case where it is kept constant is shown. It is a timing chart which shows the example of control in the advance angle transition mode by the flowchart of FIG. FIG. 8 is a graph of the relationship between the intake valve closing timing (intake valve closing timing) and the target air charge amount, showing a control example in which the flowcharts of FIGS. 6 and 7 are executed, and (A) is the intake valve in the delayed closing mode. In the closing timing control, a case where the throttle opening is controlled in parallel is shown, and (B) shows a case where the throttle opening is kept constant in the intake valve closing timing control in the slow closing mode. It is a graph showing the variation of the predetermined engine speed decrease amount .DELTA.N _ENG 1 relative to the engine rotational speed (engine speed). It is a flowchart which shows the processing operation of the traction control of a control unit. It is a flowchart which shows the processing operation at the time of the request | requirement torque fall by a traction control operation | movement of a control unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its use.

  FIG. 1 is a schematic configuration diagram of an internal combustion engine system 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 a 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, which has four cylinders 11 (see FIG. 2), but may have any number of cylinders 11. The engine 1 is mounted on a vehicle such as an automobile, and its crankshaft 14 is connected to the left and right front wheels 7 of the vehicle via a power transmission device 2 mounted on the vehicle, as shown in FIG. The power of the engine 1 is transmitted to the front wheels 7 by the power transmission device 2 to propel the vehicle.

  The power transmission device 2 includes an automatic transmission 5 including a torque converter 3 and a transmission mechanism 4, and a differential mechanism 6. Although not shown, the torque converter 3 includes a pump impeller that is connected to the crankshaft 14 of the engine 1 and receives the output of the engine 1, and a turbine that faces the pump impeller. It is output to the speed change mechanism 4.

  Although not shown, the speed change mechanism 4 is provided between an input shaft to which the rotation of the turbine is input, an output shaft connected to the front wheel 7 through the differential mechanism 6, and these input / output shafts. It has a transmission gear mechanism such as a planetary gear mechanism and a plurality of clutches for changing the gear ratio of the transmission gear mechanism. The transmission mechanism 4 is configured to be capable of shifting from, for example, the first forward speed to the fifth speed by engaging and releasing the clutch.

  The left and right front wheels 7 are each provided with a wheel speed sensor 7a for detecting the wheel speed of the front wheel 7, and the left and right rear wheels 8 in the vehicle are wheels for detecting the wheel speed of the rear wheel 8. A speed sensor 8a is provided.

  The engine 1 has a geometric compression ratio of 13 or more, and the geometric compression ratio is preferably 14 or more and 16 or less. A large geometric compression ratio means that the expansion ratio is large, so that the operating efficiency of the engine 1 increases as the geometric compression ratio increases. Therefore, in this embodiment, the geometric compression ratio is set to 13 or more, and a high torque and a significant reduction in fuel consumption are achieved while avoiding knocking by a method such as ignition retard.

  However, the higher the compression ratio, the higher the possibility of abnormal combustion. Therefore, it is necessary to reduce the effective compression ratio, that is, to reduce the cylinder air charge amount. As a result, the output obtained for the cylinder volume is reduced, so that the efficiency when viewed in terms of the weight ratio of the engine 1 is reduced, and there is a problem in the mountability of the engine 1 in the engine room of the vehicle. . 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 mounted thereon, and four cylinders 11 that define a combustion chamber 17 together with a piston 15 described later are formed therein. . As is well known, a crankshaft 14 is rotatably supported on the cylinder block 12 by a journal, a bearing or the like, and this 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 (only one is shown in FIG. 1) are formed for each cylinder 11, and each communicates with the combustion chamber 17. Similarly, in the cylinder head 13, two exhaust ports 19 (only one is shown in FIG. 1) are formed for each cylinder 11, and each communicates with the combustion chamber 17. In the cylinder head 13, an intake valve 21 and an exhaust valve 22 are arranged so that the intake port 18 and the exhaust port 19 can be shut off (closed) from the combustion chamber 17, respectively. 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, thereby causing the intake port 18 and the exhaust port 19 to move. Each opens and closes.

  The intake valve drive mechanism 30 has an inner shaft 105 described later, and the exhaust valve drive mechanism 40 has an exhaust camshaft 41. The inner shaft 105 and the exhaust camshaft 41 are driven by the crankshaft 14 in synchronism with the crankshaft 14 via a known power transmission mechanism such as a chain / sprocket mechanism. As is well known, this power transmission mechanism is configured such that the inner shaft 105 and the exhaust camshaft 41 rotate once while the crankshaft 14 rotates twice. The intake valve 21 and the exhaust valve 22 are driven by the inner shaft 105 and the exhaust camshaft 41, that is, are driven by the crankshaft 14 in synchronization with the crankshaft 14. The intake valve drive mechanism 30 will be described in detail later.

The phase angle of the inner shaft 105 is detected by the phase sensor 35, and a detection signal θ _{VCT_A from the} phase sensor 35 is input to the control unit 100.

A spark plug 51 is disposed on the central axis of each cylinder 11 in the cylinder head 13. The spark plug 51 is attached to the cylinder head 13 by a known structure such as a screw. Ignition system 52 to perform an ignition by the spark plug 51 receives a control signal SA _D from the control unit 100, so that the spark plug 51 generates a spark at a desired ignition timing, energizing it.

  A fuel injection valve 53 is attached to one side of the cylinder head 13 (intake side in the illustrated example) with a known structure such as using a bracket. The tip of the fuel injection valve 53 faces the combustion chamber 17 so as to be positioned below the two intake ports 18 in the vertical direction and in the middle of the two intake ports 18 in the horizontal direction.

A fuel supply system 54 that supplies fuel to the fuel injection valve 53 is not shown, but a high-pressure pump that boosts the fuel to the fuel injection valve 53 and supplies the fuel to the high-pressure pump from a fuel tank. And an electric circuit for driving the fuel injection valve 53. This electric circuit receives the control signal FP _D from the control unit 100 and operates the solenoid of the fuel injection valve 53 to inject a desired amount of fuel into the combustion chamber 17 at a predetermined timing.

The intake port 18 communicates with the surge tank 55a by an intake path 55b in the intake manifold 55 (which together with the intake port 18 constitutes an intake passage through which air introduced into the combustion chamber 17 passes). 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. Then, the throttle actuator 58 receives a control signal TVO _D from the control unit 100, the opening degree (hereinafter, referred to as throttle opening) drives the throttle valve 57 to adjust the.

  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.

Further, in order to circulate a part of the exhaust gas to the intake system (hereinafter also referred to as EGR), the intake manifold 55 (downstream of the throttle valve 57) and the exhaust manifold 60 are connected by an EGR pipe 62. Yes. Since the pressure on the exhaust side is higher than that on the intake side, a part of the exhaust gas flows into the intake manifold 55 via the EGR pipe 62 (this flowing gas is called EGR gas). 17 will be mixed with fresh air inhaled. The EGR pipe 62 is provided with an EGR valve 63 for adjusting the flow rate of the EGR gas. Then, the EGR valve actuator 64 receives the control signal EGR _OPEN from the control unit 100 and drives the EGR valve 63 to adjust its opening.

  The 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 electrical signal And an input / output (I / O) bus.

The control unit 100 receives 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 control unit 100 calculates an engine rotation speed (hereinafter also referred to as engine speed) N _ENG based on, for example, a crank angle pulse signal. The control unit 100 also receives an input from the oxygen concentration sensor 74 regarding the oxygen concentration EGO of the exhaust gas. Further, an accelerator opening signal α from an accelerator opening sensor 75 that detects the depression amount of the accelerator pedal is received. The 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 mechanism 4 of the automatic transmission 5.

More specifically, the 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 , EGR amount Q _EGR (EGR gas flow rate), and the like. Based on these control parameters, the throttle opening signal TVO _D , fuel injection pulse signal FP _D , ignition pulse signal SA _D , valve phase angle signal θ _{VCT_D} , and EGR opening signal EGR _OPEN are provided as corresponding control signals. , The throttle actuator 58, the fuel supply system 54, the ignition system 52, the intake camshaft phase variable mechanism 32, which will be described later, and the EGR valve actuator 64, respectively.

  Next, details of the intake valve drive mechanism 30 according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a perspective view showing a specific configuration of the intake valve drive mechanism 30 according to the embodiment of FIG. 1, and FIG. 4 is a cross-sectional view showing a main part of the intake valve drive mechanism 30 of FIG. 4, (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 an intake camshaft phase variable mechanism (variable cam timing mechanism; hereinafter referred to as VCT mechanism) 32, which 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 accommodated 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. 4) of the inner shaft 105 (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 control unit 100 that functions as a VCT control unit that controls the VCT mechanism 32 outputs a control signal θ _{VCT_D} to the electromagnetic valve 32a of the VCT mechanism 32, and receives the control signal θ _{VCT_D} , so that the electromagnetic valve 32a has a hydraulic pressure duty. By controlling, 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 control unit having a configuration different from that of the control unit 100.

  As shown in FIGS. 4A to 4D, the inner shaft 105 has a disc-shaped eccentric cam 106 provided integrally with each cylinder 11. The eccentric cam 106 is provided eccentric from the axis (center axis X) 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.

  First and second rocker cams 111 and 112 are integrally provided at both ends of the rocker connector 110, respectively. Since both the configurations are the same, FIGS. 4A to 4D 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. 3, the control shaft 120 is arranged 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 an output shaft of, for example, a stepping motor 123 that is an actuator of a variable valve lift mechanism (VVL). 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 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 portion of the control link 132 is rotatably connected to the tip end portion of the control arm 131 by the control pivot 133, and the other end portion of the control link 132 is rotatably connected to the ring-shaped arm 107 by the common pivot 134. Has been.

  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, as shown in FIGS. 4A and 4C, if the eccentric cam 106 is positioned on the lower side, the ring On the other hand, when the eccentric cam 106 is positioned on the upper side as shown in FIGS. 4B and 4D, 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 is connected to the central shaft along with the second rocker cam 112 connected by the rocker connector 110. Swing around X. As shown in FIGS. 4B and 4C, the rocker cam 111 swinging in this way resists the spring force of the valve spring 116 while the cam surface 111a 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. 4A and 4D, 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 rocking 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 stepping motor 123 and changing the position of the control pivot 133. For example, when the control arm 131 is rotated clockwise in FIG. 4 and the control pivot 133 is shifted from the position shown in FIG. 4A to the upper left side as shown in FIG. The rocking range is relatively strong in that the base surface 111b tends to come into contact with the upper surface of the tappet 115.

  FIG. 5 is a diagram illustrating a setting example of the intake valve driving mechanism 30 according to the present embodiment.

Referring to FIG. 5, in the present embodiment, the valve lift amount θ _VVL is, for example, from θ _{VVL_min} by the intake valve driving mechanism 30 and the related components (particularly, the VCT mechanism 32 and the variable valve lift mechanism). In the range up to θ _{VVL_max} , control is performed so as to increase as the target air filling amount CE in each cylinder 11 increases, and the valve closing timing of the intake valve 21 (also referred to as intake valve closing timing) is the valve lift. The angle is continuously _{retarded in} the range of θ _{VCT_min} to θ _{VCT_max as} the amount θ _VVL increases. The valve opening timing and the valve closing timing of the intake valve 21 can be any combination as required. For example, a so-called lost motion operation in which the valve lift amount is zero is also possible. Thus, the intake valve drive mechanism 30 (particularly the VCT mechanism 32 and the variable valve lift mechanism) constitutes an intake valve closing timing variable mechanism that controls the valve closing timing of the intake valve 21.

In the present embodiment, for example, when the intake valve 21 is opened and closed in the intake stroke when the engine speed N _ENG is 1500 rpm, the valve opening timing of the intake valve 21 is almost immediately before the exhaust top dead center (crank angle). Thus, the valve opening is started from, for example, 20 ° CA, and the valve closing timing is changed in accordance with the required torque (target torque TQ) of the engine 1.

Here, in the present embodiment, as the closing timing of the intake valve 21, the first valve closing set to the advance side with respect to the intake valve closing timing at which the target air filling amount CE becomes maximum at the engine rotational speed N _ENG . The timing range IVC _1st (corresponding to the early closing range) and the first valve closing timing range IVC which is set on the retard side with respect to the intake valve closing timing at which the target air charge amount CE becomes maximum at the engine speed N _ENG The second valve closing timing range IVC _2nd (corresponding to the late closing range) separated from _1st is set, and the early closing mode M _EIVC in which the intake valve 21 is operated to close in the first valve closing timing range IVC _1st. When the later closing mode M _LIVC intake valve 21 is operated to close the second valve closing timing range IVC _2nd, the earlier closing mode M _EIVC from later closing mode M _LIVC operating mode Advance the transition mode M _TR-A changing Ri is capable of setting a retard transition mode M _TR-R switch to the later closing mode M _LIVC the operation mode from the earlier closing mode M _EIVC. The first and second valve closing timing ranges IVC _1st and IVC _2nd are respectively advanced and retarded with respect to the intake valve closing timing at which the target air filling amount CE becomes maximum at the engine speed N _ENG . As will be described later in detail, it is not necessarily set based on the intake bottom dead center (see FIG. 15 described later).

In the slow closing mode _MLIVC , the engine operating state consisting of the required torque in the engine 1 (in other words, the target torque TQ, that is, the target air filling amount CE) and the engine speed (engine rotational speed N _ENG ) is high load and low speed. When the required torque of the engine 1 is equal to or greater than a predetermined torque (see characteristic line L1 or L2 in FIG. 8) determined for each engine speed (the target air filling amount CE is equal to or larger than the predetermined air filling amount). In this slow closing mode M _LIVC , the valve lift amount θ _VVL of the intake valve 21 is increased, and the intake valve closing timing corresponding to the valve lift amount θ _VVL is, for example, the intake valve Delayed from bottom dead center. Hereinafter, the operation region on the high load low speed side is referred to as a slow closing operation region.

On the other hand, in the early closing mode M _EIVC , when the engine operating state is in a lower load or higher speed operating region than the delayed closing operating region, that is, when the required torque of the engine 1 is smaller than the predetermined torque ( This mode is selected when the target air filling amount CE is smaller than the predetermined air filling amount. In this early closing mode M _EIVC , the valve lift amount θ _VVL of the intake valve 21 is reduced, and this valve lift amount θ _VVL In response to this, the intake valve closing timing is advanced from, for example, the intake bottom dead center. Hereinafter, an operation region at a lower load or higher speed than the slow closing operation region is referred to as an early closing operation region.

  In this embodiment, since hysteresis is provided for switching the operation mode as will be described later, when switching from the slow-close operation region to the early-close operation region, and from the early-close operation region to the late-close operation region. Both operation regions (the predetermined torque) change at the time of switching (see FIG. 8).

As described above, the first valve closing timing range IVC _1st in which the early closing mode M _EIVC is set is advanced and separated from the second valve closing timing range IVC _2nd in which the late closing mode M _LIVC is set. . Between these valve closing timing ranges IVC _1st and IVC _2nd, an intermediate valve closing timing range IVC _{IM in} which the intake valve 21 does not close in the late closing mode M _LIVC and the early closing mode M _EIVC is set. As described later, in the retard transition mode M _TR-R and the advance transition mode M _TR-A , the intake valve closing timing becomes the intermediate valve closing 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 increase the expansion ratio in order to reduce fuel consumption, in order to suppress the occurrence of abnormal combustion, the closing timing of the intake valve 21 is advanced or retarded from the intake bottom dead center. Thus, as a method of reducing the effective compression ratio, when the engine 1 is operated and controlled by early closing in which the closing timing of the intake valve 21 is advanced from the intake bottom dead center, FIGS. 4 (A) and 4 (B). As is apparent from the above, the rocking amount of the rocker cam 111 is small, and the resistance of the valve spring 116 is small, which is preferable on the low load side. However, as the engine speed increases as the required load increases, the closing timing of the intake valve 21 for obtaining a predetermined cylinder air charge amount is retarded. In addition, as the engine speed increases, the possibility of abnormal combustion decreases due to the increased fluidity of the air-fuel mixture in the cylinder, so the amount of restriction on the advance side of the target intake valve closing timing decreases. . Therefore, it is necessary to retard the intake valve closing timing IVC at a high speed as the engine speed increases. However, since it is difficult to retard the closing timing of the intake valve 21 at a high speed according to the target due to a response delay of the intake valve drive mechanism 30, the actual intake valve closing timing is determined as the target intake valve. There is a possibility that the cylinder side air charge amount may be reduced due to the advance side of the closing timing.

On the other hand, when the intake valve closing timing IVC is set to be retarded from the timing at which the cylinder air filling amount becomes maximum at the engine rotational speed N _ENG , air _remains in the cylinder 11 until the piston 15 moves to the bottom dead center. Is introduced. Furthermore, the effective compression ratio is reduced by returning the air in the cylinder into the intake passage while the piston 15 is rising beyond the bottom dead center. In order to realize this, it is necessary to set the valve lift amount and the valve operating range of the intake valve 21 to be close to the maximum value (see FIG. 5), and there is a concern that mechanical loss increases.

Therefore, in the present embodiment, the first valve closing timing range IVC _1st and the second valve closing timing range IVC _2nd are set, and in the high compression ratio engine, the expansion ratio is increased in the continuous operation region as much as possible. In the intermediate valve closing timing range IVC _{IM where there} is a high concern for abnormal combustion, measures for knocking are taken to improve output and reduce fuel consumption while avoiding abnormal combustion such as pre-ignition.

  In order to realize such a configuration, in the present embodiment, the flowcharts of FIGS. 6 and 7 are set to be executed.

  6 and 7 are flowcharts showing an example of control of the engine 1 according to the embodiment of the present invention.

First, referring to FIG. 6, the control unit 100 first initializes various settings (step S1). In this initialization, the control unit 100 sets the current operation mode M to the early closing mode M _EIVC .

Next, the control unit 100 reads or calculates the accelerator opening signal α from the accelerator opening sensor 75, the engine rotation speed N _ENG based on the crank angle pulse signal, and the vehicle speed signal VSP from the vehicle speed sensor 76, and uses these information as information. Based on this, a target torque TQ is calculated (step S2).

Next, the control unit 100 calculates the fuel injection amount FP (or air-fuel ratio), the target air filling amount CE, the EGR amount Q _EGR , and the ignition timing SA based on the target torque TQ and the engine speed N _ENG (step S3). ).

Next, the control unit 100 reads the data of the control map M1 stored in advance in the memory, and based on this control map M1, the current operating region that matches the target air charge amount CE and the engine rotational speed N _ENG value. R is determined (step S4). As a result, the control unit 100 determines the operation region R as shown in FIG.

  FIG. 8 is a characteristic diagram showing an example of the operation region determined in the flowchart of FIG.

As shown in FIG. 8, in this embodiment, characteristic lines L1 and L2 (the predetermined torque) proportional to the engine rotational speed N _ENG are set, and the slow closing operation region on the high load low speed side with respect to the characteristic line L1. R _LIVC (including upper characteristic line L1), i.e. the required torque of the engine 1 is equal to or greater than the predetermined torque (target air charge amount is the predetermined air charge amount or more) retarded-closing operating range R _LIVC the later closing mode M _LIVC is , The early closing operation region R _EIVC on the low load or high speed side with respect to the characteristic line L2, that is, the required torque of the engine 1 is smaller than the predetermined torque (the target air filling amount is smaller than the predetermined air filling amount). In _REEIVC , the early closing mode M _EIVC is set to be selected. In the illustrated example, the transition region R _TR between the characteristic line L1 and the characteristic line L2 is a region used for switching the operation mode by providing hysteresis, and the required load is increased from the early closing operation region R _EIVC. However, until the characteristic line L1 is reached or the characteristic line L1 is exceeded, the early closing mode M _EIVC is maintained until the characteristic line L1 is exceeded, even if the required load decreases from the late closing operation region R _LIVC. The operation mode is maintained in the slow closing mode M _LIVC . Although it is not always necessary to provide hysteresis, it is necessary to provide hysteresis in order to minimize the chances of occurrence of the transient and unstable advance transition mode M _TR-A and retard transition mode M _TR-R. Is preferred.

Referring to FIG. 6, control unit 100 determines whether or not current operation mode M is early closing mode M _EIVC (step S5). If the operation mode M is the early closing mode M _EIVC , the control unit 100 further determines the current operation region R based on the current target air charge amount CE and the engine rotational speed N _ENG , and the current operation region R is It is determined whether it is outside the slow closing operation region R _LIVC , that is, whether the intake valve closing timing IVC based on the required load is outside the second valve closing timing range IVC _2nd (step S6). When the current operation region R is other than the slow closing operation region R _LIVC , the control unit 100 sets the operation mode M to the early closing mode M _EIVC (step S7). Next, the control unit 100 determines the valve lift amount θ _{VVL of} the intake valve 21, the valve opening period θ _VCT of the intake valve 21, the throttle based on the target air filling amount CE and engine speed N _ENG in the early closing mode M _EIVC. The opening degree TVO is calculated (step S8), the calculated valve lift amount θ _VVL , the valve opening period θ _VCT and the throttle opening degree TVO, the fuel injection amount FP, the EGR amount Q _EGR and the ignition timing SA calculated in step S3. corresponding control signal _{θ VVL-D, θ VCT-} D, TVO D, FP D, by outputting the EGR _OPEN and SA _D, to control the actuators of the intake valve drive mechanism 30 and the throttle valve 57 (step S9). Then, it transfers to step S2 and repeats the control mentioned above.

FIG. 9 is a diagram illustrating a control example of the intake valve closing timing in the early closing mode _MEIVC set by the flowchart of FIG.

Referring to FIG. 9, in the control example shown in FIG. 9, the operation region R is other than the slow closing operation region R _LIVC , that is, when the closing timing of the intake valve 12 is operated in the first valve closing timing range IVC _1st. As the engine speed N _ENG increases, the closing timing of the intake valve 21 is retarded. Further, the valve closing timing of the intake valve 21 is retarded as the target air filling amount CE increases. As a result, when the operation is performed in the first valve closing timing range IVC _1st , the air closing amount CE is increased by delaying the valve closing timing of the intake valve 21 so that torque corresponding to the required torque can be output. It has become.

FIG. 10 is a diagram showing a control example of the throttle opening in the early closing mode _MEIVC set by the flowchart of FIG.

Referring to FIG. 10, in the control example shown in FIG. 10, a characteristic line L3 proportional to the engine speed N _ENG is set on the low load side in parallel with the characteristic line L1. The characteristic line L3 may be on the lower load or higher speed side than the characteristic line L2 shown in FIG. 8, and may be the same as the characteristic line L2 or on the higher load or lower speed side than the characteristic line L2. In an operating region on the low load or high speed side with respect to this characteristic line L3, the throttle opening TVO is fully open, and the target air filling amount CE is controlled exclusively by the closing timing of the intake valve 21. It has become. For this reason, it is possible to secure a sufficient air filling amount CE and control so that no pump loss occurs. On the other hand, between the characteristic line L1 and the characteristic line 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, as the engine operating state approaches the high load low speed operation region where the operation mode M needs to be set to the slow closing mode M _LIVC from the low medium load high speed operation region, the intake port downstream of the throttle valve 57 The pressure in the intake passage including 18 is reduced. As a result, in the present embodiment employing a high compression ratio engine, even in a transient and unstable operation region in which the operation mode M is switched, the cylinder air charge amount is temporarily excessively increased with a change in the intake valve closing timing. Therefore, abnormal combustion such as pre-ignition can be avoided.

Next, referring to FIG. 6, when the current operation region R is the late closing region R _LIVC (NO in step S6), the control unit 100 changes the operation mode M to the retard transition mode in step S6. Set to M _TR-R (step S10). Next, the control unit 100 sets a predetermined count time C _TR-R as the count value C _TR (step S11), the target air filling amount CE and the engine speed N _{ENG in the} retard transition mode M _TR-R. Based on the above, the valve lift amount θ _{VVL of} the intake valve 21, the valve opening period θ _VCT of the intake valve 21, the EGR amount Q _EGR , and the throttle opening TVO are calculated (step S 12). The predetermined count time C _TR-R is provided until the intake valve closing timing setting by the intake valve drive mechanism 30 is switched, so that the target air filling amount CE is temporarily reduced to cause abnormalities such as pre-ignition. This is to avoid combustion.

After step S12 is executed, the process proceeds to step S9, whereby the valve lift amount θ _VVL , the valve opening period θ _VCT , the EGR amount Q _EGR and the throttle opening TVO calculated in the retarded angle transition mode M _TR-R , In addition, by outputting the control signals θ _VVL-D , θ _VCT-D , EGR _OPEN , TVO _D , FP _D and SA _D corresponding to the fuel injection amount FP and ignition timing SA calculated in step S3, the intake valve is driven. The actuators of the mechanism 30 and the throttle valve 57 are controlled. Then, it transfers to step S2 and repeats the control mentioned above.

FIG. 11 is a timing chart showing an example of control in the retard transition mode M _TR-R according to the flowchart of FIG.

As shown in FIG. 11, when the control in the retarded angle transition mode M _TR-R is executed, the count value C _TR is decremented from the start timing t0 (see step S27 in FIG. 7), and ends at the timing t2. . The intake valve drive mechanism 30 starts retarding in order to move the intake valve closing timing to the second valve closing timing range IVC _2nd from the timing t0 when the counting is started. In this retard transition mode M _TR-R , the throttle actuator 58 temporarily drives the throttle valve 57 in the closing direction to reduce the pressure in the intake passage. That is, when the intake valve 21 is closed on the advance side with respect to the intake valve closing timing at which the target air filling amount CE is maximized at the engine rotational speed N _ENG , the throttle opening TVO is the closing timing of the intake valve 21. Is reduced (for example, in proportion to the retarded angle), and the intake valve 21 is set on the retarded side with respect to the intake valve closing timing at which the target air charge amount CE becomes maximum at the engine speed N _ENG . When closing, the throttle opening TVO increases as the closing timing of the intake valve 21 is retarded. As a result, even if the intake valve 21 enters the intermediate valve closing timing range IVC _{IM in} which abnormal combustion such as pre-ignition is concerned in the cylinder 11, the pressure in the intake passage due to the temporary closing operation of the throttle valve 57 is reduced. Abnormal combustion is prevented by the decrease.

Further, in the retard transition mode M _TR-R , the EGR valve actuator 64 temporarily drives the EGR valve 63 in the opening direction to increase the opening degree (EGR amount Q _EGR ) of the EGR valve 63. That is, when the intake valve 21 is closed on the advance side of the intake valve closing timing at which the target air filling amount CE becomes maximum at the engine speed N _ENG , the EGR amount Q _EGR is the valve closing timing of the intake valve 21. Is increased (for example, in proportion to the retarded angle), and the intake valve 21 is set on the retarded side with respect to the intake valve closing timing at which the target air charge amount CE becomes maximum at the engine rotational speed N _ENG . In the case of closing, the EGR amount Q _EGR decreases as the closing timing of the intake valve 21 is retarded. Due to the temporary opening operation of the EGR valve 63, the external EGR having a temperature lower than the internal EGR, which is the in-cylinder residual gas, is introduced into the cylinder, so that abnormal combustion can be avoided more reliably.

The specification is set so that the transition of the intake valve closing timing ends at timing t1 earlier than the count end timing t2. That is, when this timing t1 has elapsed, the EGR amount Q _EGR and the throttle opening TVO set in step S12 are switched to the same values as in the slow closing mode M _LIVC . For this reason, when the timing t1 has elapsed, the transition to the operation mode is actually completed although it is still in the retard transition mode _MTR-R .

Next, in step S5 of the flowchart shown in FIG. 6, a control example when the operation mode M set in the control unit 100 is not the early closing mode M _EIVC (in the case of NO in step S5) This will be described with reference to the flowchart shown in FIG.

When the operation mode M is not the early closing mode M _EIVC , the control unit 100 further determines whether or not the operation mode M is the late closing mode M _LIVC (step S20). If the operation mode M is the slow closing mode M _LIVC , the control unit 100 further determines the operation region R based on the current target air filling amount CE and the engine speed N _ENG , and the current operation region R is quickly closed. It is determined whether it is outside the operating range R _EIVC , that is, whether the intake valve closing timing IVC based on the required load is outside the first valve closing timing range IVC _1st (step S21). When the current operation region R is other than the early close operation region _REEIVC , the control unit 100 sets the operation mode M to the late close mode M _LIVC (step S22). Next, the control unit 100 determines the valve lift amount θ _{VVL of} the intake valve 21, the valve opening period θ _VCT of the intake valve 21, the throttle based on the target air filling amount CE and the engine speed N _ENG in the slow closing mode M _LIVC. The opening degree TVO is calculated (step S23), the calculated valve lift amount θ _VVL , the valve opening period θ _VCT and the throttle opening degree TVO, the fuel injection amount FP, the EGR amount Q _EGR and the ignition timing SA calculated in step S3. corresponding control signal _{θ VVL-D, θ VCT-} D, TVO D, FP D, by outputting the EGR _OPEN and SA _D, to control the actuators of the intake valve drive mechanism 30 and the throttle valve 57 (step S9). Then, it transfers to step S2 and repeats the control mentioned above.

Figure 12 is a diagram showing an example of control of intake valve closing timing in the later closing mode M _LIVC set by the flowchart of FIG. 7, FIG. 13 is a later closing mode M _LIVC set by the flowchart of FIG. 7 It is a figure which shows the example of control of the throttle opening. In each figure, (A) is a case where the throttle opening is controlled in parallel according to the target air filling amount CE, and (B) is a case where the throttle opening is kept constant.

Referring to FIGS. 12A and 13A, when the intake valve 21 is closed in the second valve closing timing range IVC _2nd , the target air filling amount CE is controlled while changing the throttle opening TVO. The cylinder air charge amount is changed by controlling the pressure in the intake passage including the intake port 18 downstream of the throttle valve 57 by keeping the intake valve closing timing constant regardless of the increase or decrease in the target air charge amount CE. To do.

On the other hand, as shown in FIG. 12 (B) and FIG. 13 (B), the throttle opening TVO is kept constant under the condition where the engine speed is constant, and the intake air is increased as the target air charge amount CE increases. When the valve closing timing is advanced, as the intake valve closing timing advances within the second valve closing timing IVC _2nd , it approaches the intake valve closing timing at which the maximum cylinder air filling amount can be obtained. The cylinder air charge amount is controlled. At that time, the throttle opening TVO is kept constant at a relatively large value, and the pressure in the intake passage is kept high, so that the pump loss is kept low.

12A and 12B, the valve closing timing of the intake valve 21 is retarded as the engine speed N _ENG increases. Further, in any case of FIGS. 13A and 13B, the throttle opening TVO is controlled to be larger as the engine speed N _ENG becomes higher. This is because as the engine speed N _ENG is high, the intake inertial force is increased, since the target air charge amount CE is compatible with that retarded the intake valve closing timing having the maximum in the engine rotational speed N _ENG With this control, the required target air filling amount CE can be ensured.

Next, referring to FIG. 7, in step S21, when the intake valve closing timing IVC based on the current required load is in the first valve closing timing range IVC _1st (NO in step S21), the control unit 100 Sets the operation mode M to the advance transition mode M _TR-A (step S24). Next, the control unit 100 sets a predetermined count time C _TR-A as the count value C _TR (step S25), and the target air filling amount CE and the engine speed N _{ENG in the} advance transition mode M _TR-A. Based on the above, the valve lift amount θ _{VVL of} the intake valve 21, the valve opening period θ _VCT of the intake valve 21, the EGR amount Q _EGR and the throttle opening TVO are calculated (step S 26).

After step S26 is executed, the process proceeds to step S9, whereby the valve lift amount θ _VVL , the valve opening period θ _VCT , the EGR amount Q _EGR and the throttle opening TVO calculated in the advance angle transition mode M _TR-A , In addition, by outputting the control signals θ _VVL-D , θ _VCT-D , EGR _OPEN , TVO _D , FP _D and SA _D corresponding to the fuel injection amount FP and ignition timing SA calculated in step S3, the intake valve is driven. The actuators of the mechanism 30 and the throttle valve 57 are controlled. Then, it transfers to step S2 and repeats the control mentioned above.

FIG. 14 is a timing chart showing an example of control in the advance angle transition mode M _TR-A according to the flowchart of FIG.

As shown in FIG. 14, when the control in the advance angle transition mode M _TR-A is executed, the count value C _TR is decremented from the start timing t0 (see step S27 in FIG. 7), and ends at the timing t2. . The intake valve drive mechanism 30 starts to advance in order to move the intake valve closing timing to the first valve closing timing range IVC _1st from the timing t0 when the counting is started. In the advance angle transition mode M _TR-A , the throttle actuator 58 temporarily drives the throttle valve 57 in the closing direction to reduce the pressure in the intake passage. That is, when the intake valve 21 is closed on the retard side with respect to the intake valve closing timing at which the target air filling amount CE becomes maximum at the engine rotational speed N _ENG , the throttle opening TVO is set to the closing timing of the intake valve 21. Is reduced (for example, in proportion to the advance angle), and the intake valve 21 is set on the advance side of the intake valve closing timing at which the target air charge amount CE becomes maximum at the engine speed N _ENG . In the case of closing, the throttle opening TVO increases as the closing timing of the intake valve 21 advances. As a result, even if the intake valve 21 enters the intermediate valve closing timing range IVC _{IM in} which abnormal combustion such as pre-ignition is concerned in the cylinder 11, the pressure in the intake passage due to the temporary closing operation of the throttle valve 57 is reduced. Abnormal combustion is prevented by the decrease.

Further, in the advance angle transition mode M _TR-A , the EGR valve actuator 64 temporarily drives the EGR valve 63 in the opening direction to increase the opening degree (EGR amount Q _EGR ) of the EGR valve 63. That is, when the intake valve 21 is closed on the retard side with respect to the intake valve closing timing at which the target air filling amount CE becomes maximum at the engine rotational speed N _ENG , the EGR amount Q _EGR is the valve closing timing of the intake valve 21. Is increased (for example, in proportion to the advance angle), and the intake valve 21 is set on the advance side with respect to the intake valve closing timing at which the target air charge amount CE becomes maximum at the engine rotation speed N _ENG . In the case of closing, the EGR amount Q _EGR decreases as the closing timing of the intake valve 21 advances. Due to the temporary opening operation of the EGR valve 63, the external EGR having a temperature lower than the internal EGR, which is the in-cylinder residual gas, is introduced into the cylinder, so that abnormal combustion can be avoided more reliably.

The specification is set so that the transition of the intake valve closing timing ends at timing t1 earlier than the count end timing t2. That is, when this timing t1 has elapsed, the EGR amount Q _EGR and the throttle opening TVO set in step S26 are switched to the same values as in the early closing mode M _EIVC . For this reason, when the timing t1 has elapsed, the transition to the operation mode has actually ended although it is still in the advance transition mode _MTR-A .

Next, in the flowchart of FIG. 7, when the operation mode M set in the control unit 100 is not the slow closing mode M _LIVC (NO in step S20), the operation mode M is the retarded transition mode M. _{One of TR-R} and advance angle transition mode M _TR-A .

Therefore, in the present embodiment, first, the control unit 100 decrements the count value C _TR (step S27), and determines whether or not the operation mode M is the advance transition mode M _TR-A (step S28).

If the operation mode M is the advance transition mode M _TR-A , the control unit 100 determines whether or not the count value C _TR is greater than 0 (step S29). If the count value _CTR is larger than 0, the control unit 100 executes the control after step S26. Thereby, the operation control in the advance angle transition mode M _TR-A is continued.

In step S29, when the count value _CTR is 0 or less, the operation mode switching of the intake valve 21 by the intake valve drive mechanism 30 has already been completely completed. M is switched to the early closing mode _MEIVC , and the above-described operation control in the early closing mode is repeated.

In step S28, when the operation mode M is the retard transition mode M _TR-R , the control unit 100 determines whether or not the count value C _TR is larger than 0 (step S30). If the count value _CTR is larger than 0, the control unit 100 executes the control after step S12. Thereby, the operation control in the retarded angle transition mode M _TR-R is continued. On the other hand, when the count value _CTR is 0 or less in step S30, since the operation mode switching of the intake valve 21 by the intake valve drive mechanism 30 has already been completed, the process proceeds to step S22 and subsequent steps. The operation mode M is switched to the slow closing mode _MLIVC , and the above-described operation control in the slow closing mode is repeated.

FIG. 15 is a graph of the relationship between the intake valve closing timing and the target air charge amount CE, illustrating a control example in which the flowcharts of FIGS. 6 and 7 are executed. In FIG. 15, (A) is the control of the intake valve closing timing in the slow closing mode M _LIVC , and when the throttle opening is controlled in parallel, (B) is the intake valve closing timing in the slow closing mode M _LIVC . In the control, the throttle opening is maintained constant.

Referring to FIG. 15A, when the throttle opening is controlled in parallel in the control of the intake valve closing timing in the slow closing mode _MLIVC , the closing timing of the intake valve 21 is fixed to the most advanced side. Since the target air filling amount CE can be controlled, the displacement amount (the rotation angle of the control shaft 120 in FIG. 4) when switching from the early closing mode M _EIVC to the slow closing mode M _LIVC is minimized, and the early closing mode is _achieved . The time required for switching from mode M _EIVC can be shortened as much as possible.

On the other hand, referring to FIG. 15B, in the control of the intake valve closing timing in the slow closing mode M _LIVC , when the throttle opening is kept constant, the switching from the early closing mode M _EIVC to the slow closing mode M _LIVC is performed. The amount of displacement at the time (the rotation angle of the control shaft 120 in FIG. 4) is maximum, but the pressure in the intake passage can be maintained high, so that the pump loss is minimized and high output is maintained. Can do.

In either case, as the engine rotational speed N _ENG is increased, since the closing timing the intake valve is retarded, the engine rotational speed N _ENG, the higher the first closing timing range IVC _1st and second closing timing range IVC intermediate closing timing range IVC _IM between _2nd decreases, there rotational speed (e.g., 2500 rpm) or more exclusively intake valve becomes 21 be closed at the second closing timing range IVC _2nd, switching of the operation mode M Is no longer necessary.

  In the present embodiment, the control unit 100 is also configured to execute traction control. The traction control may be performed by a control unit different from the control unit 100.

Specifically, signals from wheel speed sensors 7 a and 7 b provided on the front wheel 7 and the rear wheel 8 are input to the control unit 100. Based on these input signals, the wheel speed V _{F of the} front wheel 7 (drive wheel) (the average value of the wheel speeds of the left and right front wheels) and the wheel speed V _R of the rear wheel 8 (the average value of the wheel speeds of the left and right rear wheels) are obtained. Ask. Then, when the slip amount V _SLIP of the front wheel 7, which is a value obtained by subtracting the wheel speed V _R of the rear wheel 8 from the wheel speed V _F of the front wheel 7, is equal to or greater than the predetermined value V _SLIP 1, the traction control is activated. That is, the torque reduction amount dTQ of the engine 1 is calculated based on the slip amount V _SLIP . This torque decrease amount dTQ increases as the slip amount V _SLIP increases. The required torque of the engine 1 is reduced by this torque reduction amount dTQ.

In the _case of the slow closing mode M _LIVC , the control unit 100 determines that when the current operation region R becomes the early closing operation region R _EIVC due to a decrease in the required torque due to the operation of the traction control, that is, the required torque. However, when the torque is lower than the predetermined torque from the state where the torque is higher than the predetermined torque, it is determined that the engine speed may be decreased by a predetermined amount or more due to the decrease in the required torque, and this possibility is lower than the predetermined level. When the determination is made, the advance angle transition mode M _TR-A is set, and finally the early closing mode M _EIVC is set. On the other hand, when it is determined that the possibility is equal to or higher than the predetermined level, the advanced angle transition mode M _TR-A is not set so as to remain in the late closing mode M _LIVC . In the present embodiment, the predetermined torque corresponds to the first predetermined torque of the present invention, and also corresponds to the second predetermined torque set to the same value at the same engine speed with respect to the first predetermined torque.

The possibility that the engine speed is reduced by a predetermined amount or more is higher as the reduction amount (the torque reduction amount dTQ) when the required torque is lower than the predetermined torque from the state where the required torque is exceeded is larger. judge. Torque decrease amount dTQ becomes larger the larger the slip amount V _SLIP, the larger the slip amount V _SLIP, slip amount V _SLIP and predictable engine speed decrease amount .DELTA.N _ENG and a reduction ratio GR of the transmission mechanism 4 is increased Therefore, in this embodiment, the possibility is determined based on the predicted engine speed decrease amount ΔN _ENG . In this case, the predetermined level is a predetermined engine speed decrease amount ΔN _ENG 1, and the value of the predetermined engine speed decrease amount ΔN _ENG 1 is equal to or greater than the predetermined torque as shown in FIG. It is preferable to set the engine speed N _ENG higher when the engine torque N _ENG decreases from the state of exceeding the predetermined torque (for example, set higher in proportion to the engine speed N _ENG ). Therefore, when the engine speed decrease amount .DELTA.N _ENG is determined less than the predetermined engine speed decrease amount .DELTA.N _ENG 1 is the advance transition mode M to _TR-A, the engine speed decrease amount .DELTA.N _ENG predetermined engine speed decrease amount .DELTA.N _{When ENG is} 1 or more, it will stay in the slow closing mode _MLIVC .

  Here, the processing operation of the traction control of the control unit 100 will be described based on the flowchart of FIG.

In the first step S51, various signals are read. In the next step S52, the slip amount V _SLIP (= V _F − of the front wheel 7 is determined based on signals from the read wheel speed sensors 7a and 7b. V _R ) is obtained.

In the next step S53, it is determined whether or not the slip amount V _SLIP is equal to or greater than a predetermined value V _SLIP 1. When the determination in step S53 is NO, the process returns as it is, while when the determination in step S53 is YES, the process proceeds to step S54.

In step S54, the traction control is activated, and in the next step S55, the torque reduction amount dTQ is calculated based on the slip amount V _SLIP of the front wheel 7. In the next step S56, the required torque of the engine 1 is reduced by the torque reduction amount dTQ, and then the process returns.

  Accordingly, when the front wheel 7 slips and the slip amount is equal to or greater than a predetermined value, the output torque of the engine 1 is reduced, whereby the grip force of the front wheel 7 is recovered and the slip amount is reduced. When the slip amount becomes smaller than the predetermined value, the operation of the traction control is stopped.

  Next, the processing operation of the control unit 100 when the required torque is reduced by the traction control operation will be described based on the flowchart of FIG.

  In the first step S61, various signals are read, and in the next step S62, it is determined whether or not the traction control is operating. When the determination in step S62 is NO, the process returns as it is, while when the determination in step S62 is YES, the process proceeds to step S63.

In step S63, it is determined whether or not the current operation region R is the early closing operation region R _EIVC . When the determination in step S63 is NO, the process returns as it is, while when the determination in step S63 is YES, the process proceeds to step S64.

In step S64, it is determined whether or not the current operation mode M is the early closing mode M _EIVC . When the determination in step S64 is YES, the process returns as it is. On the other hand, when the determination in step S63 is NO, the process proceeds to step S65.

In step S65, the engine speed decrease amount ΔN _ENG is predicted from the slip amount V _SLIP and the reduction gear ratio GR of the transmission mechanism 4.

In the next step S66, (as shown in FIG. 16, a value corresponding to the engine speed N _ENG) engine speed decrease amount .DELTA.N _ENG predetermined engine speed decrease amount .DELTA.N _ENG 1 equal to or larger than. When the determination in step S66 is YES (when the possibility that the engine speed is reduced by a predetermined amount or more is a predetermined level or more), the process returns as it is, while when the determination in step S66 is NO (the engine speed is If the possibility of a decrease by a predetermined amount or less is lower than a predetermined level), the process proceeds to step S67.

In step S67, it is determined whether or not the current operation mode M is the advance angle transition mode M _TR-A . When the determination in step S67 is YES, the process returns as it is, while when the determination in step S67 is NO, the process proceeds to step S68.

In step S68, the current operation mode M is set to the advance transition mode M _TR-A , and then the process returns.

In this way, when the traction control is activated, the required torque of the engine 1 is reduced, and when the operation mode is switched from the slow closing mode M _LIVC to the early closing mode M _EIVC , the engine speed exceeds a predetermined amount due to the reduction in the required torque. When it is determined that the possibility of decrease is lower than the predetermined level (the engine speed decrease amount ΔN _ENG is smaller than the predetermined engine speed decrease amount ΔN _ENG 1), When the advance angle transition mode M _{TR-A is selected} and it is determined that the possibility is greater than or equal to the predetermined level (the engine speed decrease amount ΔN _ENG is greater than or equal to the predetermined engine speed decrease amount ΔN _ENG 1) Mode M is left as _LIVC .

Therefore, in the present embodiment, in the advance angle transition mode M _TR-A , the throttle actuator 58 temporarily drives the throttle valve 57 in the closing direction to reduce the pressure in the intake passage, so that the air filling amount is excessive. Thus, abnormal combustion can be prevented (the same applies to the retarded angle transition mode _MTR-R ).

Here, when the traction control operation reduces the required torque of the engine 1 and switches the operation mode from the slow closing mode M _LIVC to the early closing mode M _EIVC , it is not determined whether the engine speed may decrease by a predetermined amount or more. When the operation mode is switched in (1), during the switching (in the advance transition mode M _TR-A ), there is a possibility that the slip amount will be sharply reduced due to the restoration of the grip force of the front wheel 7 and the engine speed will be suddenly lowered. When the engine speed is reduced in this way, the intake throttle effect by the throttle valve 57 is reduced, and the intake pressure may not be sufficiently reduced. For this reason, in the advance angle transition mode M _TR-A , in order to reliably prevent the occurrence of abnormal combustion due to excessive cylinder air charge, the throttle valve 57 is made to be more throttled and the throttle opening of the throttle throttle is set to be smaller. It is necessary to set control parameters on the premise, and as a result, the pump loss may increase and the operating efficiency of the engine 1 may be reduced.

However, in the present embodiment, only when it is determined that the engine speed is reduced by a predetermined amount (an amount that affects the intake throttle effect) and the possibility is lower than a predetermined level, Since the operation mode is switched from the slow closing mode M _LIVC to the early closing mode M _EIVC , the possibility that the engine speed decreases by a predetermined amount or less during the temporary closing operation control of the throttle valve 57 is reduced. It is possible to eliminate the possibility that the cylinder air filling amount becomes excessive due to the decrease in the above. Therefore, in the advance angle transition mode M _TR-A , the control parameter (throttle valve opening degree) is premised on the throttle valve opening degree that is open (substantially the same throttle valve opening degree as when throttled in the retard angle transition mode M _TR-R ). And intake valve closing timing, etc.) can be set. Therefore, pump loss can be reduced and the operating efficiency of the engine 1 can be kept high.

  In the above embodiment, when the required torque of the engine 1 is greater than or equal to the predetermined torque, it is determined whether or not the engine speed may decrease by a predetermined amount or more when the engine 1 decreases beyond the predetermined torque. However, from the state where the required torque of the engine 1 is equal to or higher than the predetermined torque (this is referred to as the first predetermined torque), the second predetermined torque (see FIG. 8) set smaller than the first predetermined torque at the same engine speed. At the lower side of the characteristic line L2, for example, a characteristic line parallel to the characteristic line L2), the engine speed is more likely to decrease by a predetermined amount or more. The possibility may be determined. In this case, if the required torque of the engine 1 does not decrease beyond the second predetermined torque even when the required torque is equal to or lower than the first predetermined torque, the operation mode is switched without determining the possibility that the engine speed will decrease by a predetermined amount or more. Become.

  Here, when the required torque of the engine 1 is lower than the predetermined torque from the state where the required torque is higher than the predetermined torque, the phenomenon that the engine speed decreases by a predetermined amount or more may occur when the traction control is operated. Not limited. For example, in the case of a manual transmission, when a shift-up operation is performed, the engine speed may decrease by a predetermined amount or more due to the shift-up operation. Therefore, the determination of the possibility that the engine speed will decrease by a predetermined amount or more is performed not only when the required torque of the engine 1 decreases due to the operation of the traction control, but in any case where a phenomenon that the engine speed decreases by a predetermined amount or more can occur. It is good.

  INDUSTRIAL APPLICABILITY The present invention is useful for an internal combustion engine, a control method for an internal combustion engine system provided with a throttle valve, and an intake valve closing timing variable mechanism, and the internal combustion engine system thereof. This is useful when the throttle valve is temporarily throttled when shifting to the range.

1 Engine (spark ignition internal combustion engine)
11 cylinder 14 crankshaft 15 piston 17 combustion chamber 18 intake port (intake passage)
21 Intake valve 30 Intake valve drive mechanism (Intake valve closing timing variable mechanism)
55b Intake manifold intake passage (intake passage)
57 Throttle valve 58 Throttle actuator 100 Control unit (controller)

Claims (5)

A cylinder that defines a combustion chamber together with a reciprocating piston; an intake passage through which air introduced into the combustion chamber passes; and an intake valve that can be shut off from the combustion chamber and driven by a crankshaft A control method for an internal combustion engine system, comprising: an internal combustion engine; a throttle valve disposed in the intake passage; and an intake valve closing timing variable mechanism that controls a valve closing timing of the intake valve driven by the crankshaft. Because
When the required torque of the internal combustion engine is equal to or greater than a first predetermined torque determined for each engine speed, a delay set on the retard side from the timing at which the air charge amount becomes maximum at the engine speed in each cylinder cycle. Closing the intake valve within a closing range;
When the required torque is smaller than the first predetermined torque, in each cylinder cycle, it is set to an advance side with respect to the time when the air charge amount becomes maximum at the engine speed, and is quickly separated from the slow closing range. Closing the intake valve within a closing range;
When the required torque is lower than the first predetermined torque and exceeds the second predetermined torque set to be equal to or lower than the first predetermined torque, it is determined that the engine speed may decrease by a predetermined amount or more. And a process of
When the possibility is determined to be lower than the predetermined level, the closing timing of the intake valve to control the intake valve closing timing varying mechanism to transition to the early closing range of the retarded-closing range, wherein Temporarily driving the throttle valve in the closing direction so as to suppress abnormal combustion in an intermediate valve closing timing range between the late closing range and the early closing range ;
Controlling the intake valve closing timing variable mechanism so that the closing timing of the intake valve remains in the delayed closing range when it is determined that the possibility is equal to or higher than the predetermined level. A control method for an internal combustion engine system. The method for controlling an internal combustion engine system according to claim 1,
The step of determining the possibility determines that the possibility is higher as the amount of decrease when the required torque is lower than the second predetermined torque from a state where the required torque is equal to or higher than the first predetermined torque is larger. A control method for an internal combustion engine system, characterized in that the method is a process. In the control method of the internal combustion engine system according to claim 1 or 2,
The internal combustion engine characterized in that the predetermined level is set to be higher as the engine speed is higher when the required torque is lower than the second predetermined torque from a state where the required torque is equal to or higher than the first predetermined torque. How to control the system. In the control method of the internal-combustion engine system according to any one of claims 1 to 3,
A control method for an internal combustion engine system, further comprising a step of reducing a required torque of the internal combustion engine when a slip amount of a wheel to which power from the internal combustion engine is transmitted is a predetermined value or more. A cylinder that defines a combustion chamber together with a reciprocating piston; an intake passage through which air introduced into the combustion chamber passes; and an intake valve that can be shut off from the combustion chamber and driven by a crankshaft An internal combustion engine; a throttle valve disposed in the intake passage; a throttle actuator that drives the throttle valve; and an intake valve closing timing variable mechanism that controls a valve closing timing of the intake valve driven by the crankshaft; A controller for controlling the throttle actuator and the intake valve closing timing variable mechanism, and an internal combustion engine system comprising:
The controller is
When the required torque of the internal combustion engine is equal to or greater than a first predetermined torque determined for each engine speed, in each cylinder cycle, the delayed closing that is set on the retard side from the timing at which the air charge amount becomes maximum at the engine speed. Controlling the intake valve closing timing variable mechanism so that the intake valve is closed within a range; and
When the required torque is smaller than the first predetermined torque, in each cylinder cycle, the early closing that is set to an advance side of the time when the air filling amount becomes the maximum at the engine speed and separated from the slow closing range is performed. Controlling the intake valve closing timing variable mechanism so that the intake valve is closed within a range; and
When the required torque is lower than the first predetermined torque and exceeds the second predetermined torque set to be equal to or lower than the first predetermined torque, it is determined that the engine speed may decrease by a predetermined amount or more. And
When it is determined that the possibility is lower than a predetermined level, the intake valve closing timing variable mechanism is controlled so that the closing timing of the intake valve shifts from the late closing range to the early closing range, and the delay is controlled. wherein a closed range to suppress abnormal combustion in an intermediate closing timing range between the early closing range, the throttle valve is temporarily controlled by the Hare before Symbol throttle actuator operates in the closing direction, and,
When it is determined that the possibility is equal to or higher than the predetermined level, the intake valve closing timing variable mechanism is controlled so that the closing timing of the intake valve remains in the delayed closing range.
An internal combustion engine system.

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