JP5012565B2 - Internal combustion engine control method and internal combustion engine system - Google Patents

Description

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

  It is known that the maximum valve lift amount of the intake valve is changed according to the engine operating condition, as disclosed in, for example, Patent Document 1. The higher the engine speed, the greater the intake inertia force. Therefore, if there is a valve lift amount that exceeds a predetermined value determined according to the air flow rate, the cylinder air charge amount becomes maximum when the intake valve is closed at a predetermined timing that is retarded according to the engine speed. As the intake valve closing timing departs from the predetermined timing corresponding to the maximum filling amount, that is, as the advance angle or the retard angle increases, the cylinder air filling amount decreases. In accordance with this principle, the cam-driven variable valve operating device described in Patent Document 1 is controlled so as to increase the valve lift amount in accordance with an increase in the target air filling amount in each cylinder, and the valve lift amount The intake valve closing timing is retarded in accordance with the increase of. Therefore, the cylinder air charge amount can be controlled to the target amount while the intake pipe pressure is kept high.

  Here, when the piston descends during the intake stroke, the cylinder internal pressure and the crankcase internal pressure act on the upper and lower sides of the piston, respectively. The cylinder internal pressure is substantially equal to the intake pipe pressure, and the crankcase internal pressure is substantially equal to the atmospheric pressure. Therefore, if the intake pipe pressure is lower than the atmospheric pressure, the pressure acting on the lower surface of the lowering piston exceeds the pressure acting on the upper surface, creating a resistance against the piston lowering motion, and so-called pump loss occurs. Therefore, by keeping the intake pipe pressure as high as possible, the pump loss can be reduced and the engine operating efficiency can be improved.

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

When the compression ratio of a spark ignition internal combustion engine is increased, there is a possibility of occurrence of abnormal combustion such as self-ignition of the air-fuel mixture or knocking. In order to cope with this, for example, in Patent Document 2, when an operating state in which self-ignition is likely to occur is detected, the closing timing of the electromagnetically driven intake valve is retarded or advanced to obtain an effective compression ratio, that is, target air filling A method for reducing the amount is disclosed.
JP 2006-97647 A JP 2001-159348 A

  With the method of Patent Document 2, it is possible to improve the engine operating efficiency due to the high expansion ratio while eliminating the problems associated with the high compression ratio.

  However, in a case where an engine with a high geometric compression ratio is employed, a configuration in which the rotational movement of the crankshaft is mechanically converted into the reciprocating movement of the intake valve as exemplified in the variable valve operating apparatus disclosed in Patent Document 1 is adopted. Therefore, it is not always easy to achieve both improvement in output utilizing the high compression ratio and prevention of abnormal combustion such as pre-ignition.

  That is, in the variable valve operating apparatus as disclosed in Patent Document 1, the intake valve is increased in accordance with the increase in the target air filling amount while keeping the change amount of the intake valve opening timing relatively small with respect to the rotational phase of the crankshaft. The closing timing is retarded. The intake valve closing timing is set to an advance side with respect to the timing at which the air filling amount becomes maximum at the engine speed, and the cylinder air filling amount is increased by being retarded. In the operating range where the engine combustion speed is low and the required output is high, where there is a high possibility that abnormal combustion such as self-ignition of the air-fuel mixture will occur. When restricted to the following, the following problems occur.

  That is, if the engine output is high, the engine speed increases. Along with this, the intake valve closing timing at which the cylinder air filling amount becomes maximum 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, the target intake valve closing timing is retarded at a high speed as the engine speed increases. However, as disclosed in Patent Document 1, when mechanically retarding with respect to the phase of the crankshaft, the response is limited. This places the actual intake valve closing timing on the more advanced side than the target intake valve closing timing, which may lead to a decrease in the cylinder air charge amount. Due to the shortage of cylinder air charge, there is not enough mixture in the cylinder, and even if the mixture burns, the target output cannot be obtained.

In order to solve the above problems, the present invention provides 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 blocked from the combustion chamber. A control method for an internal combustion engine having an intake valve, wherein a target air charge amount in the cylinder in each cylinder cycle is equal to or greater than a predetermined air charge amount that may cause abnormal combustion , and the engine speed is low during operation in the retarded-closing region set in the load operation zone in each cylinder cycle, the inside second closing timing range is set to lag the intake valve closing timing air filling amount is maximum step of closing the intake valve, and the late closing during operation in the early closing region and the target air charge amount is low region and the engine speed is set to a higher area than in each cylinder cycle, air Hamaryou is set to the advance side than the intake valve closing timing having the maximum and the closes the intake valve in the first valve closing timing range spaced from the second valve closing timing range, the intake valve closing timing Is a step of retarding the engine as the target air charge amount increases and the engine speed increases .

In this aspect, when the target air filling amount is smaller than the predetermined air filling amount, the intake valve is closed within the first valve closing timing range (for example, before the bottom dead center) (hereinafter, this operation is “early closed”). On the other hand, when the target air filling amount is equal to or larger than the predetermined air filling amount, the second valve closing timing range is retarded and separated from the first valve closing timing range (for example, after the intake bottom dead center). The intake valve is then closed (this operation is also referred to as “slow closing”). Therefore, for example, when a variable valve device is used in which the intake valve closing timing is retarded in accordance with the increase in the target air filling amount while maintaining the amount of change in the intake valve opening timing relatively small, the target air filling amount is In a relatively small operating range, the early closing operation allows the internal combustion engine to be operated with a small valve opening amount corresponding to the required air filling amount, reducing mechanical loss due to excessive valve operation and reducing the target air In the operation region where the filling amount is high, the abnormal closing such as pre-ignition can be avoided while the necessary air filling amount is sufficiently secured by the slow closing operation. Further, in the engine high load state where the target air filling amount is high, the engine output increases, so that the engine speed is likely to increase thereafter. Due to the influence of the intake inertia force, the higher the engine speed, the slower the intake valve closing timing for obtaining a constant air charge amount. Therefore, during operation in the low-speed and high-load operation region (slow closing region), the intake valve closing timing is set in the second valve closing timing range, so that the subsequent increase in engine speed ( increase in engine speed from the slow closing region). The amount of change in the intake valve closing timing at the time of shifting to the early closing region) can be minimized, so that the responsiveness of the operation of changing the intake valve closing timing as the engine speed increases can be improved .

In a preferred aspect, in the low speed operation region of the internal combustion engine, the first valve closing timing range is before the intake bottom dead center of each cylinder cycle, and the second valve closing timing range is the intake bottom dead center of each cylinder cycle. Later. In this aspect, it is possible to reduce mechanical loss while reliably avoiding abnormal combustion such as pre-ignition, particularly in a low-speed operation region where pre-ignition is a problem.

In a preferred aspect, the method further includes a step of reducing the pressure of the air flowing into the combustion chamber in accordance with the increase in the target air filling amount during the operation in the slow closing region . In this aspect, immediately after the target air filling amount becomes equal to or greater than the predetermined air filling amount, the pressure of the air flowing into the combustion chamber, that is, the intake pipe pressure is set to be relatively low. Therefore, the intake valve closing timing at that time is set to a relatively advanced angle side of the second valve closing timing range, that is, a side closer to the first valve closing timing range. Therefore, the amount of change in the intake valve closing timing when the target air filling amount exceeds the predetermined air filling amount can be minimized, and a switching operation is required when switching from the early closing operation to the late closing operation. It is simplified to the minimum, and the switching of the driving operation can be completed in a short time.

In a preferred aspect, the method further includes a step of reducing the pressure of the air flowing into the combustion chamber in accordance with an increase in the target air filling amount during the operation in the early closing region . In this aspect, the intake pipe pressure is reduced immediately before the target air filling amount becomes equal to or greater than the predetermined air filling amount. Therefore, even if the intake valve closes in the intermediate valve closing timing range located between the first valve closing timing range and the second valve closing timing range in the process of switching the early closing operation to the late closing operation, Since the intake pipe pressure is reduced, abnormal combustion such as pre-ignition can be avoided.

In a preferred aspect, the method further includes a step of advancing the intake valve closing timing in each cylinder cycle in accordance with an increase in the target air filling amount during operation in the slow closing region . In this aspect, since the intake valve closing timing approaches the timing at which the maximum air filling amount is obtained in accordance with the increase in the target air filling amount, the target air filling amount can be obtained over a wide operating region without accompanying pump loss. .

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 valve that can block the intake passage from the combustion chamber. An internal combustion engine having a variable valve system that opens and closes the intake valve at a variable timing, and a target air charge amount in each cylinder cycle in the cylinder is greater than or equal to a predetermined air charge amount that may cause abnormal combustion and during operation in the retarded-closing region set the engine speed is lower low-speed, high-load operation region, in each cylinder cycle, a second of air filling amount is set to lag the intake valve closing timing having the maximum while closing the intake valve in the closing timing range, during operation in the early closing region and the retarded-closing region and the engine speed is low the target air charge amount than the region is set to a high area, each cylinder cycle Oite, air filling amount is set to the advance side of the intake valve closing timing having the maximum and closes the intake valve in the first valve closing timing range spaced from said second closing timing range, An internal combustion engine system comprising: a controller that controls the variable valve gear so that the intake valve closing timing is retarded as the target air filling amount increases and the engine speed increases .

  In a preferred internal combustion engine system, the internal combustion engine has a geometric compression ratio of 13 or more.

As described above, the present invention operates the internal combustion engine with a small valve opening amount corresponding to the required air filling amount by an early closing operation in an operation region where the target air filling amount is relatively small, Mechanical loss due to valve operation can be reduced, and in the operation range where the target air filling amount is high, the necessary air filling amount can be secured sufficiently by the slow closing operation, and abnormal combustion such as pre-ignition can be avoided. Can do . In addition, for example, when a variable valve system is used in which the intake valve closing timing is retarded in response to an increase in the target air charge while maintaining the intake valve opening timing constant, the intake valve closing timing is increased as the engine speed increases. There is a remarkable effect that the responsiveness of the operation of changing can be improved .

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

  FIG. 1 is a schematic configuration diagram of an internal combustion engine system 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 Se engine control unit as a control unit for controlling the actuator based on a signal from the capacitors 100.

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

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

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

  The engine 1 includes a cylinder block 12 and a cylinder head 13 placed on the cylinder block 12, and cylinders 11, 11,. 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. Although only one is shown in the figure, in the cylinder head 13, two intake ports 18 are formed in the cylinder head 13 for each cylinder 11 and communicate with the combustion chamber 17. Similarly, in the cylinder head 13, two exhaust ports 19 are formed in the cylinder head 13 for each cylinder 11 and communicate with the combustion chamber 17. As shown in the figure, the intake valve 21 and the 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 to open and close the intake port 18 and the exhaust port 19. To do.

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

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

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

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

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

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

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

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 (referred to as EGR gas) and mixes with fresh air drawn from the intake manifold 55 into the combustion chamber 17. become. The EGR pipe 62 is provided with an EGR valve 63 for adjusting the flow rate of the EGR gas. The EGR valve actuator 64 receives the control signal EGR _OPEN from the engine control unit 100 and adjusts the opening degree of the EGR valve 63.

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

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

More specifically, the engine control unit 100 calculates the following control parameters of the engine 1 based on the input as described above. For example, the desired throttle opening TVO, fuel injection amount FP, ignition timing SA, valve phase angle θ _VCT , EGR amount (EGR valve opening) Q _{EGR, and the} like. Then, based on these control parameters, as corresponding control signals, throttle opening signal TVO _D , fuel injection pulse signal FP _D , ignition pulse signal SA _D , valve phase angle signal θ _{VCT_D} , EGR opening signal EGR _OPEN , Output to the throttle actuator 58, the fuel supply system 54, the ignition system 52, the intake camshaft phase varying mechanism 32, the EGR actuator 64, and the like.

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

  The intake valve drive mechanism 30 of this embodiment includes a variable cam timing mechanism (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 housed therein and fixed to the inner shaft 105 so as to rotate integrally. A plurality of hydraulic chambers are formed between the case and the rotor around the central axis X (shown in FIG. 3) (in the circumferential direction). Then, the liquid pressurized by the pump (for example, engine oil) is selectively supplied to each hydraulic pressure chamber to form a pressure difference between the hydraulic pressure chambers facing each other.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

With reference to FIG. 4, in the present embodiment, the valve lift amount θ _VVL is _applied to each cylinder 11 in the range from θ _{VVL_min} to θ _{VVL_max} , for example, by the above-described intake valve drive mechanism 30 and related components. The intake valve closing timing is retarded in the range of θ _{VCT_min} to θ _{VCT_max} according to the increase of the valve lift amount θ _VVL . Any combination of the opening operation timing and the closing operation timing of the intake valve 21 is possible as required. For example, a so-called lost motion operation in which the valve lift amount is zero is also possible.

In this embodiment, for example, when the intake valve 21 is opened and closed in the intake stroke when the engine speed (engine speed) N _ENG is 1500 rpm, in this embodiment, the opening timing of the intake valve 21 is almost in the operating range. The valve opening is started immediately before exhaust top dead center (crank angle is, for example, 20 ° CA), and the closing timing is changed according to the required torque.

Here, in the present embodiment, as the closing timing of the intake valve 21, the first closing is set to the advance side with respect to the intake valve closing timing at which the air filling amount becomes maximum at the engine rotation speed (engine speed) N _ENG . The valve timing range IVC _1st is set on the retard side with respect to the intake valve closing timing at which the air filling amount becomes maximum at the engine rotational speed (engine speed) N _ENG and is separated from the first valve closing timing range IVC _1st . The second valve closing timing range IVC _2nd 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 , and the intake valve 21 is the second valve closing timing. and later closing mode M _LIVC is operated to close in the range IVC _2nd, and the advance transition mode M _TR-a for switching to the earlier closing mode M _EIVC from later closing mode M _LIVC operating mode And it is configured to be set a retard transition mode M _TR-R to switch the operation mode to the later closing mode M _LIVC from earlier closing mode M _EIVC. Note that the first and second valve closing timing ranges are both set with respect to the intake valve closing timing at which the air filling amount becomes maximum at the engine rotational speed N _ENG , as will be described in detail later. It is not necessarily set based on the intake bottom dead center (see FIG. 14 described later).

The early closing mode M _EIVC is a mode selected when the load is low, and the valve lift amount θ _VVL of the intake valve 21 is reduced, and the intake valve closing timing is set according to the valve lift amount θ _VVL , for example, intake bottom dead center. More advanced.

On the other hand, the slow closing mode M _LIVC is a mode selected at a high load, and the valve lift amount θ _VVL of the intake valve 21 is increased, and the intake valve closing timing is set to, for example, the intake valve closing timing corresponding to the valve lift amount θ _VVL. Delayed from dead center.

Here, in the present embodiment, the second valve closing timing range IVC _2nd in which the slow closing mode M _LIVC is set is delayed from the first valve closing timing range IVC _1st in which the early closing mode M _EIVC is set and It is separated. Therefore, the closing timing range IVC _1st, between IVC _2nd, intermediate closing timing range IVC _IM without the intake valve 21 is closed is to be set.

  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. As a method for lowering the effective compression ratio, when the operation of the engine 1 is controlled so that the closing timing of the intake valve 21 is advanced earlier than the intake bottom dead center, it is apparent from FIGS. 3 (A) and 3 (B). As described above, the rocking amount of the rocker cam 111 is reduced, and the resistance of the valve spring 116 is also reduced, 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 closing timing of the intake valve 21 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 intake valve closing timing with the actual intake valve closing timing as a target. There is a risk of lowering the cylinder air charge amount by placing it on the more advanced side.

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 values (see FIG. 4), which may increase mechanical loss.

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 about 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, it is set so that the flowchart of FIG.

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

First, referring to FIG. 5, engine control unit 100 first executes initialization of various settings (step S1). In this initialization, the engine control unit 100 sets the current operation mode M to the early closing mode M _EIVC .

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

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

  FIG. 7 is a characteristic diagram showing an example of the operation region determined in the flowchart of FIG.

As shown in FIG. 7, in the present embodiment, characteristics L1 and L2 (an example of a predetermined air charge amount) proportional to the engine speed N _ENG are set, which are equal to or higher than the characteristic L1 on the high load side and abnormal combustion occurs . there is a possibility of occurrence later closing mode M _LIVC the operating range R _LIVC of low-speed high-load, low-load side of the characteristic L2 following operating region R _EIVC (i.e. the low-speed high-load operation region than the R _LIVC low load side In the area and the area on the high speed side) , the early closing mode M _EIVC is set to be selected. In the illustrated example, the transition region R _TR between characteristics L1 and the characteristic L2 is an area used for switching the operation mode by providing a hysteresis, even if high load demand from the driver region R _EIVC, the characteristics L1 The operation mode is maintained in the early closing mode M _EIVC until it exceeds, and even if the required load decreases from the operation region R _LIVC , the operation mode is maintained in the late closing mode M _LIVC until the characteristic L2 is exceeded. Hereinafter, the operation region R _{LIVC is referred} to as a slow closing region, and the operation region R _EIVC is _referred to as an early closing region.

Referring to FIG. 5, engine 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 engine control unit 100 further determines the operation region R based on the current target air filling amount CE and the engine rotational speed N _ENG , and the current operation region R is delayed. closed Ji or is other than realm R _LIVC, i.e. closing timing range IVC of the intake valve 21 based on the required load is equal to or other than the second closing timing range IVC _2nd (step S6). If the current of the current operating range R is other than Oso閉Ji realm R _LIVC, the engine control unit 100 sets the operation mode M to the earlier closing mode M _EIVC (step S7). Next, the engine 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 based on the target air filling amount CE and the engine speed N _ENG in the early closing mode M _EIVC . The throttle opening TVO is calculated (step S8), the calculated valve lift amount θ _VVL , the valve opening period θ _VCT , the throttle opening TVO, the fuel injection amount FP calculated in step S3, the EGR amount Q _EGR , and the ignition timing SA. control signal corresponding to _{FP D, EGR OPEN, SA D} , θ VVL-D, θ VCT-D, by outputting the TVO _D, to control the actuators of the intake valve drive mechanism 30 and the throttle valve 57. Then, it transfers to step S2 and repeats the control mentioned above.

FIG. 8 is a diagram showing a control example of the intake valve closing timing in the early closing mode _MEIVC set by the flowchart of FIG.

Referring to FIG. 8, in the control example shown in FIG. 8, when the operation region R is other than the late closing region R _LIVC (early closing region R _EIVC ) , that is, the closing timing of the intake valve 12 is the first closing timing. When the engine is operated in the range IVC _1st , the closing timing of the intake valve 21 is retarded as the engine speed N _ENG increases. Further, the 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 closing timing of the intake valve 21 is retarded, thereby increasing the air filling amount CE and outputting a torque commensurate with the required torque. ing.

FIG. 9 is a diagram illustrating a control example of the throttle opening degree in the early closing mode _MEIVC set by the flowchart of FIG.

Referring to FIG. 9, in the control example shown in FIG. 9, a characteristic L3 proportional to the engine speed N _ENG is set on the low load side in parallel with the characteristic L1. The characteristic L3 may be on the lower load side than the characteristic L2 in FIG. 8, or may be equal to or higher than the characteristic L2. In the operating region on the lower load side than the characteristic L3, the throttle opening TVO is fully open, and the target air filling amount CE is controlled exclusively at the closing timing of the intake valve 21. 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 characteristics L1 and the characteristics L3, the throttle opening degree TVO is controlled to decrease as the required load increases or as the engine speed N _ENG decreases. For this reason, as the operation state approaches the low speed and high load operation region (delay close region R _LIVC ) in which the operation mode M needs to be set to the slow close mode M _LIVC from the medium / high speed / low / medium load operation region, the throttle valve 57 downstream. The pressure in the intake pipe including the intake port 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. 5, when the current operation region R is the late closing region R _LIVC in step S6 (NO in step S6), the engine control unit 100 changes the operation mode M to the retarded angle. Mode M _TR-R is set (step S10). Next, the engine control unit 100 sets a predetermined count time C _TR-R as the count value C _TR (step S11), the target air charge amount CE and the engine speed N in this retard transition mode M _TR-R. Based on the _ENG , 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 S12). The predetermined count time C _TR-R is provided until the closing timing setting of the intake valve 21 by the intake valve drive mechanism 30 is switched, so that the filling amount CE is temporarily reduced and an abnormality such as pre-ignition is performed. 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 , the throttle opening TVO, calculated in the retard transition mode M _TR-R , and fuel injection amount FP calculated in step S3, and the control signal FP _D corresponding to the ignition timing _{SA, EGR OPEN, SA D,} θ VVL-D, by outputting the θ _VCT-D, TVO D, the intake valve driving 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. 10 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. 10, 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. 6), and ends at the timing t2. . The intake valve drive mechanism 30 starts retarding in order to move the closing timing of the intake valve 21 to the second valve closing timing range IVC _2nd from the timing t0 when the counting is started. At this time, the throttle opening TVO is reduced in proportion to the delay of the closing timing of the intake valve 21, and the intake pipe pressure is reduced. 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 a concern in the cylinder 11, abnormal combustion is prevented due to a decrease in the intake pipe pressure. . Similarly, the opening degree (EGR amount) Q _EGR of the EGR valve 63 also increases in proportion to the delay of the closing timing of the intake valve 21. As a result, the external EGR having a temperature lower than that of the internal EGR that 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 closing timing of the intake valve 21 ends at a timing t1 earlier than the counting end timing t2. Then, when this timing t1 has elapsed, Q _EGR and TVO set in step S12 are switched in the same manner as in the slow closing mode _MLIVC, and the transition of the operation mode is completed.

Next, in step S5 of the flowchart shown in FIG. 5, when the operation mode M set in the engine control unit 100 is not the early closing mode M _EIVC (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 engine 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 engine 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 faster. closed Ji or is other than realm R _EIVC, i.e. closing timing range IVC of the intake valve 21 based on the required load is equal to or other than the first closing timing range IVC _1st (step S21). If the current operating range R is other than Haya閉Ji realm R _EIVC, the engine control unit 100 sets the later closing mode M _LIVC the operation mode M (step S22). Next, the engine 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, based on the target air filling amount CE and engine speed N _ENG in the slow closing mode M _LIVC . The throttle opening TVO is calculated (step S23), the calculated valve lift amount θ _VVL , valve opening period θ _VCT , throttle opening TVO, fuel injection amount FP, EGR amount Q _EGR calculated in step S3, and ignition timing SA. control signal corresponding to _{FP D, EGR OPEN, SA D} , θ VVL-D, θ VCT-D, by outputting the TVO _D, to control the actuators of the intake valve drive mechanism 30 and the throttle valve 57. Then, it transfers to step S2 and repeats the control mentioned above.

Figure 11 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. 6, FIG. 12 is a later closing mode M _LIVC set by the flowchart of FIG. 6 It is a figure which shows the example of control of the throttle opening. In each figure, (A) shows a case where the throttle opening is controlled in parallel according to the target air filling amount CE, and (B) shows a case where the throttle opening is kept constant.

Referring to FIGS. 11A and 12A, 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. Regardless of the increase or decrease of the target air filling amount CE, the cylinder air filling amount changes by making the closing timing of the intake valve 21 constant and controlling the pressure in the intake passage including the intake port 18 downstream of the throttle valve 57. To do.

On the other hand, as shown in FIG. 11 (B) and FIG. 12 (B), as the target air charge amount CE increases while the throttle opening TVO is kept constant under the condition that the engine speed is constant, the intake valve When the closing timing is advanced, as the intake valve closing timing advances within the second valve closing timing IVC _2nd , it approaches the valve closing timing at which the maximum cylinder air filling amount at that time is obtained. The 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.

11A and 11B, the closing timing of the intake valve 21 is retarded as the engine speed N _ENG increases. In any case of FIGS. 12A and 12B, the throttle opening TVO is controlled to be larger as the engine speed N _ENG is higher. This corresponds to the fact that the intake inertia force increases as the engine rotational speed N _ENG increases, and the intake valve closing timing at which the air charge amount becomes maximum at the engine rotational speed (engine speed) N _ENG is retarded. The required target air filling amount CE can be ensured by this control.

Next, referring to FIG. 6, in step S21, when the valve closing timing range IVC of intake valve 21 based on the current required load is first valve closing timing range IVC _1st (in the case of NO in step S21). The engine control unit 100 sets the operation mode M to the advance transition mode M _TR-A (step S24). Next, the engine control unit 100 sets a predetermined count time C _TR-A as the count value C _TR (step S25), the target air charge amount CE and the engine speed N in this advance transition mode M _TR-A. Based on the _ENG , 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, so that the valve lift amount θ _VVL , the valve opening period θ _VCT , the EGR amount Q _EGR , the throttle opening TVO, calculated in the advance angle transition mode M _TR-A , and fuel injection amount FP calculated in step S3, and the control signal FP _D corresponding to the ignition timing _{SA, EGR OPEN, SA D,} θ VVL-D, by outputting the θ _VCT-D, TVO D, the intake valve driving 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. 13 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. 13, 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. 6), and ends at the timing t2. . The intake valve drive mechanism 30 starts to advance in order to move the closing timing of the intake valve 21 to the first valve closing timing range IVC _1st from the timing t0 when the counting is started. At this time, the throttle opening TVO is reduced in proportion to the advance timing of the closing timing of the intake valve 21, and the intake pipe pressure is reduced. 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 a concern in the cylinder 11, abnormal combustion is prevented due to a decrease in the intake pipe pressure. . Similarly, the opening degree (EGR amount) Q _EGR of the EGR valve 63 also increases in proportion to the advance timing of the closing timing of the intake valve 21. Thereby, since the relatively low temperature external EGR is introduced into the cylinder, it is possible to more reliably avoid abnormal combustion.

The specification is set so that the transition of the closing timing of the intake valve 21 ends at a timing t1 earlier than the counting end timing t2. When the timing t1 has elapsed, Q _EGR and TVO set in step S26 are switched in the same manner as in the early closing mode M _EIVC, and the operation mode transition ends.

Next, in the flowchart of FIG. 6, when the operation mode M set in the engine control unit 100 is not the slow closing mode M _LIVC (NO in step S20), the operation mode M is the retard transition mode M. Either _TR-R or advance transition mode M _TR-A .

Therefore, in the present embodiment, first, the engine 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 engine 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 engine 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 completed. Therefore, the process proceeds to step S7 and subsequent steps, and the operation mode M is changed. _Switch to the early closing mode _MEIVC and repeat the operation control in the early closing mode described above.

In step S28, when the operation mode M is the retard transition mode M _TR-R , the engine control unit 100 determines whether or not the count value C _TR is greater than 0 (step S30). If the count value _CTR is larger than 0, the engine 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, if the count value _CTR is 0 or less in step S30, the operation mode switching of the intake valve 21 by the intake valve drive mechanism 30 has already been completed. M is switched to the slow closing mode _MLIVC , and the above-described operation control in the early closing mode is repeated.

FIG. 14 is a graph of intake valve closing timing showing a control example in which the flowcharts of FIGS. 5 and 6 are executed. In FIG. 14, (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. _14A , when controlling the throttle opening 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. 3) when switching from the early closing mode M _EIVC to the slow closing mode M _LIVC is minimized, and the early closing mode The time required for switching from M _EIVC can be shortened as much as possible.

On the other hand, referring to FIG. 14B, in the control of the intake valve closing timing in the slow closing mode M _LIVC , when the throttle opening is kept constant, 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. 3) becomes maximum, but the intake pipe pressure can be maintained high, so that the pump loss can be minimized and high output can be maintained. .

In any case, as the engine speed N _ENG increases, the intake valve closing timing is retarded. Therefore, as the engine speed N _ENG increases, the first valve closing timing range IVC _1st and the second valve closing timing range are increased. The intermediate valve closing timing range IVC _IM between IVC _2nd and the intake valve 21 is closed only within the second valve closing timing range IVC _2nd at a certain rotational speed (for example, 2500 rpm) or higher. Switching is not necessary.

  As described above, in the present embodiment, the cylinder 11 that defines the combustion chamber 17 together with the reciprocating piston 15, the intake port 18 through which air introduced into the combustion chamber 17 passes, and the intake port 18 are combusted. The engine 1 having the intake valve 21 that can be shut off from the chamber 17 and the closing timing of the intake valve 21 are delayed according to the increase in the target air filling amount CE to each cylinder 11 while maintaining the intake valve opening timing constant. This is an engine system including an intake valve drive mechanism 30 as a variable valve operating device configured to be square and an engine control unit 100 as a controller.

When the target air filling amount CE into the cylinder 11 in each cylinder cycle is smaller than the predetermined air filling amount by the engine control unit 100, the air filling amount becomes maximum at the engine rotational speed N _ENG in each cylinder cycle. The step of closing the intake valve 21 within the first valve closing timing range IVC _1st set to the advance side with respect to the intake valve closing timing (steps S5 to S9 in FIG. 5), and the target air filling amount CE is the predetermined air filling When the amount is equal to or greater than the amount, in each cylinder cycle, the second closed position is set on the retard side with respect to the intake valve closing timing at which the air filling amount becomes maximum at the engine rotational speed N _ENG and is separated from the first valve closing timing range. A step of closing the intake valve 21 within the valve timing range IVC _2nd (steps S20 to S23 in FIG. 6 and step S9 in FIG. 5). I have.

Therefore, in the present embodiment, when the target air filling amount CE is smaller than the predetermined air filling amount, the intake valve 21 is closed within the first valve closing timing range IVC _1st (for example, before the intake bottom dead center), When the target air filling amount CE is equal to or larger than the predetermined air filling amount, the intake valve 21 is closed within the second valve closing timing range IVC _2nd (for example, after the bottom dead center). Therefore, as in the above-described example, for example, the intake valve drive mechanism 30 is used in which the intake valve closing timing is retarded in accordance with the increase in the target air filling amount CE while keeping the change amount of the intake valve opening timing relatively small. In this case, in the operation region where the target air filling amount CE is relatively small, the engine 1 is operated by a small valve opening amount corresponding to the required air filling amount CE by the early closing operation, and the machine is caused by excessive valve operation. Loss can be reduced, and in the operation region where the target air filling amount CE is high, the required air filling amount CE can be sufficiently secured by the slow closing operation, and abnormal combustion such as pre-ignition can be avoided. . Further, in an engine high load state in which the target air filling amount CE is high, the engine output increases, so that the engine speed N _ENG is likely to increase thereafter. Due to the effect of the intake inertia force, the higher the engine speed, the later the intake valve closing timing for obtaining a constant air charge amount CE. Therefore, during operation at low speed and high load operation region (later closing region R _LIVC), by setting the closing timing of the intake valve 21 in the second closing timing range IVC _2nd, then in rotation increase (slow Since the amount of change in the intake valve closing timing in the transition from the closing region R _LIVC to the early closing region R _{EIVC due} to the increase in engine speed can be minimized , the intake valve closing timing is changed as the engine speed increases. The responsiveness of the operation can be improved .

In the present embodiment, in the low speed operation region of the engine 1, the first valve closing timing range IVC _1st is before the intake bottom dead center of each cylinder cycle, and the second valve closing timing range IVC _2nd is the intake air of each cylinder cycle. After the bottom dead center. Therefore, in the present embodiment, it is possible to reduce the mechanical loss while reliably avoiding abnormal combustion such as pre-ignition, particularly in a low-speed operation region where pre-ignition is a problem.

In the present embodiment, the step of reducing the pressure of the air flowing into the combustion chamber 17 in accordance with the increase in the target air filling amount CE during operation in the slow closing region R _LIVC (FIG. 11A, FIG. A), the control shown in FIGS. 13A and 14A). For this reason, in this embodiment, immediately after the target air filling amount CE becomes equal to or greater than the predetermined air filling amount, the pressure of the air flowing into the combustion chamber 17, that is, the intake pipe pressure is set to be relatively low. Therefore, the intake valve closing timing at this time is set to a relatively advanced angle side of the second valve closing timing range IVC _2nd , that is, a side closer to the first valve closing timing range IVC _1st . Accordingly, the amount of change in the intake valve closing timing when the target air filling amount CE is equal to or greater than the predetermined air filling amount can be minimized, so that the switching operation when switching from the early closing operation to the late closing operation is performed. It is simplified to the minimum necessary, and the switching of the driving operation can be completed in a short time.

Further, in the present embodiment, a step of reducing the pressure of the air flowing into the combustion chamber 17 in accordance with the increase of the target air filling amount CE during the operation in the early closing region R _EIVC (control in FIG. 9) is further provided. Yes. Therefore, in the present embodiment, the intake pipe pressure is reduced immediately before the target air filling amount CE becomes equal to or greater than the predetermined air filling amount. Thus, in the process of switching to early closing operation of the late closing operation, the intake valve 21 closes at an intermediate closing timing range IVC _IM located between the first closing timing range IVC _1st and second closing timing range IVC _2nd Even so, abnormal combustion such as pre-ignition can be avoided because the intake pipe pressure is reduced at that time.

In the present embodiment, the target air filling amount CE is set during operation in the slow closing region R _LIVC , that is, in the slow closing mode M _LIVC in which the intake valve 21 is controlled to close in the second valve closing timing range IVC _2nd . A step of advancing the closing timing of the intake valve 21 in each cylinder cycle in accordance with the increase (control in FIGS. 11B, 12B, 13B, and 14B) is further provided. Yes. For this reason, in this embodiment, the target air filling amount CE can be obtained over a wide operation region without accompanying pump loss.

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

1 is a schematic configuration diagram of an internal combustion engine system according to an embodiment of the present invention. It is a perspective view which shows the specific structure of the intake valve drive mechanism which concerns on embodiment of FIG. 2A and 2B are cross-sectional views showing the main part of the intake valve drive mechanism of FIG. 1, in which FIG. 1A shows when the valve lift amount is 0 in the large lift control state, and FIG. (C) shows when the valve lift amount is 0 in the small lift control state, and (D) shows when the valve lift amount is maximum in the small lift control state. It is a figure which shows the example of a setting of the intake valve drive mechanism which concerns on this embodiment. It is a flowchart which shows the example of control of the engine which concerns on embodiment of this invention. It is a flowchart which shows the example of control of the engine which concerns on embodiment of this invention. FIG. 6 is a characteristic diagram illustrating an example of an operation region determined in the flowchart of FIG. 5. It is a figure which shows the example of control of the intake valve closing timing 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. 6 is a timing chart showing an example of control in the retarded angle transition mode according to the flowchart of FIG. 5. FIG. 7 is a diagram showing an example of control of intake valve closing timing in the slow closing mode set by the flowchart of FIG. 6, where (A) controls the throttle opening in parallel, and (B) keeps the throttle opening constant. It is a case to maintain. FIG. 7 is a diagram illustrating an example of throttle opening control in the slow closing mode set by the flowchart of FIG. 6, where (A) controls the throttle opening in parallel, and (B) keeps the throttle opening constant. It is a case of maintaining. It is a timing chart which shows the example of control in the advance angle transition mode by the flowchart of FIG. FIG. 7 is a graph of intake valve closing timing showing a control example in which the flowcharts of FIG. 5 and FIG. 6 are executed, and (A) is a case where the throttle opening is controlled in parallel in the control of the intake valve closing timing in the slow closing mode. (B) is a case where the throttle opening is kept constant in the control of the intake valve closing timing in the slow closing mode.

1 Engine (an example of an internal combustion engine)
DESCRIPTION OF SYMBOLS 11 Cylinder 15 Piston 17 Combustion chamber 18 Intake port 19 Exhaust port 21 Intake valve 22 Exhaust valve 30 Intake valve drive mechanism 32 Intake camshaft phase variable mechanism 100 Engine control unit (an example of controller)
CE target air charge amount M _EIVC earlier closing mode M _LIVC retarded-closing mode M _TR-A advance transition mode M _TR-R retard transition mode R operating region R _EIVC Haya閉Ji realm R _LIVC Oso閉Ji realm R _TR Transition area IVC valve closing timing range IVC _1st 1st valve closing timing range IVC _2nd 2nd valve closing timing range IVC _IM intermediate valve closing timing range θ _VCT valve opening period θ _VVL valve lift amount

Claims (7)

A control method for an internal combustion engine, comprising: a cylinder defining a combustion chamber together with a reciprocating piston; an intake passage through which air introduced into the combustion chamber passes; and an intake valve capable of shutting off the intake passage from the combustion chamber There,
During operation in the slow closing region set in the low-speed high-load operation region where the target air filling amount in the cylinder in each cylinder cycle is equal to or higher than a predetermined air filling amount that may cause abnormal combustion and the engine speed is low in each cylinder cycle, the step of closing the intake valve in the second valve closing timing range air filling amount is set to lag the intake valve closing timing having the maximum and
During operation in the retarded-closing than in the region close the early target air charge amount is low region and the engine speed is set to a high area region, in each cylinder cycle, the intake valve closing timing of the air filling amount is maximum The intake valve is closed within a first valve closing timing range that is set to an advanced angle side and is separated from the second valve closing timing range, and the intake valve closing timing is set to a value with a high target air charge amount and an engine. A control method for an internal combustion engine comprising a step of retarding as the speed increases . The method for controlling an internal combustion engine according to claim 1,
In the low speed operation region of the internal combustion engine, the first valve closing timing range is before the intake bottom dead center of each cylinder cycle, and the second valve closing timing range is after the intake bottom dead center of each cylinder cycle. A control method of an internal combustion engine characterized by the above. In the control method of the internal combustion engine according to claim 1 or 2,
A control method for an internal combustion engine, further comprising a step of reducing the pressure of air flowing into the combustion chamber in accordance with an increase in the target air filling amount during operation in the slow closing region . The method for controlling an internal combustion engine according to any one of claims 1 to 3,
The method of controlling an internal combustion engine, further comprising a step of reducing a pressure of air flowing into the combustion chamber in accordance with an increase in the target air filling amount during operation in the early closing region . In the control method of the internal combustion engine according to claim 1, 2 , 4 ,
A control method for an internal combustion engine, further comprising a step of advancing the intake valve closing timing in each cylinder cycle in accordance with an increase in the target air filling amount during operation in the slow closing region . A cylinder that defines a combustion chamber with a reciprocating piston, an intake passage through which air introduced into the combustion chamber passes, an intake valve that can block the intake passage from the combustion chamber, and the intake valve at variable timing An internal combustion engine having a variable valve system that opens and closes, and a low-speed and high-load with a target air charge amount in each cylinder cycle that exceeds the predetermined air charge amount that may cause abnormal combustion and a low engine speed during operation in the retarded-closing region set in the operating region, in each cylinder cycle, the intake in the second closing timing range is set to lag the intake valve closing timing air filling amount is maximum while closing the valve, the late closing during operation in the early target air charge amount is low region and the engine speed is set to a higher area closed area than in each cylinder cycle, air loading The intake valve closing timing is set within the first valve closing timing range that is set on the advance side with respect to the intake valve closing timing at which is maximized and is separated from the second valve closing timing range, and the intake valve closing timing is An internal combustion engine system comprising: a controller that controls the variable valve gear so that the target air filling amount is increased and the angle is retarded as the engine speed is increased . The internal combustion engine system according to claim 6 , wherein
An internal combustion engine system, wherein the internal combustion engine has a geometric compression ratio of 13 or more.

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