JP2008151059A - Controller for internal combustion engine having variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine having a variable valve train for properly controlling an operation condition of the internal combustion engine while satisfactorily preventing occurrence of knocking in the internal combustion engine having the variable valve train varying at least closing timing of an intake valve. <P>SOLUTION: An intake variable valve train 34 varying closing timing of an intake valve 30 is installed. The intake variable valve train 34 is provided with a first control mode, in which closing timing IVC of the intake valve 30 is controlled on an advance side beyond a predetermined range including an intake bottom dead center BDC, and a second control mode, in which the closing timing IVC of the intake valve 30 is controlled on a retard side beyond the predetermined range. In a comparatively low load side area, the IVC variable control (the first control mode) for varying the intake valve 30 closing timing IVC according to a load is selected. On a comparatively high load side, the intake retarded closing control (the second control mode) for controlling the intake valve 30 by sufficiently retarded closing timing IVC is selected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device including a variable valve mechanism.

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine that includes a variable valve mechanism that makes the intake valve open / close timing and lift amount variable. In this conventional control device, when knock is detected, control for knock suppression and torque fluctuation suppression is executed. More specifically, as an example, the conventional control device advances the closing timing of the intake valve and increases the opening area of the intake valve when a knock is detected.

JP 2002-180857 A JP 2004-116315 A JP-A-4-246249

  As in the conventional internal combustion engine described above, in an internal combustion engine equipped with a variable valve mechanism that makes the intake valve open / close timing, lift amount, etc. variable, in order to improve fuel efficiency by reducing pump loss, the following The intake air amount may be controlled. That is, there is a case where the intake air amount is controlled such that the throttle opening is increased by that amount while restricting the valve passing air amount by reducing the operating angle of the intake valve to advance the closing timing.

  In the control of the intake air amount as described above, when shifting from the low load region to the high load region, the pump loss can be reduced by gradually increasing the operating angle according to the load required for the internal combustion engine. Figured. As a result, in the middle load range, an operating angle that is the timing at which the intake valve closes near the bottom dead center is used. When the intake valve is closed near the bottom dead center, the actual compression ratio in the cylinder increases and the possibility of knocking increases.

  The present invention has been made in order to solve the above-described problems. In an internal combustion engine having a variable valve mechanism that makes at least the closing timing of an intake valve variable, an internal combustion engine can be avoided while satisfactorily avoiding the occurrence of knocking. An object of the present invention is to provide a control device that can appropriately control the operating state of an engine.

A first invention is a control device for an internal combustion engine comprising a variable valve mechanism that makes at least the closing timing of an intake valve variable.
A first control mode for controlling the closing timing of the intake valve on the advance side from a predetermined range including the intake bottom dead center, and a second control mode for controlling the closing timing of the intake valve on the retard side from the predetermined range; An intake valve control means for controlling the closing timing of the intake valve in either the first control mode or the second control mode;
Control mode selection means for selecting the first control mode in a relatively low load side region and selecting the second control mode in a relatively high load side region;
It is characterized by providing.

  According to a second aspect of the present invention, in the first aspect, at least the first control mode of the first control mode and the second control mode determines the closing timing of the intake valve according to the load of the internal combustion engine. It is the control to perform.

  In a third aspect based on the first aspect, the closing timing of the intake valve is determined so that the second control mode is a closing timing that occurs even when the return of intake air to the intake passage is in a steady state. This is characterized in that the intake air late closing control is performed.

  In a fourth aspect based on the third aspect, the first control mode is control for determining the closing timing of the intake valve in accordance with the load of the internal combustion engine.

  Further, a fifth invention is characterized in that, in the third or fourth invention, the intake slow closing control is used in an operating region where the engine speed is equal to or lower than a predetermined value and the load is equal to or higher than a predetermined value. To do.

  According to a sixth aspect, in the fourth aspect, the control mode selection means selects the first control mode until the load becomes higher as the engine speed increases.

A seventh aspect of the invention relates to any one of the first to sixth aspects of the invention, torque control means for controlling the torque of the internal combustion engine in addition to control of the intake valve closing timing by the intake valve control means,
Torque control switching means for switching from torque control by the intake valve control means to torque control by the torque control means when the second control mode is selected by the control mode selection means;
Is further provided.

  According to an eighth aspect based on the seventh aspect, the torque control means is a throttle valve for controlling an intake air amount, and is switched from the first control mode to the second control mode. The opening degree of the throttle valve is adjusted according to at least the closing timing of the intake valve among the closing timing of the intake valve and the operating angle of the intake valve.

  According to a ninth invention, in any one of the first to eighth inventions, the ignition timing of the internal combustion engine is synchronized with the switching of the control mode between the first control mode and the second control mode. It further has an ignition timing changing means for changing.

  In a tenth aspect based on the ninth aspect, the ignition timing changing means has a valve overlap when the control mode is switched between the first control mode and the second control mode. The advance amount of the ignition timing is determined according to the period.

  According to the first invention, since the control mode is switched between the first control mode and the second control mode in accordance with the load state of the internal combustion engine, the intake valve is closed near the intake bottom dead center. It can be avoided. Therefore, according to the present invention, it is possible to appropriately control the operation state of the internal combustion engine while favorably avoiding the occurrence of knocking.

  According to the second aspect of the invention, it is possible to achieve an improvement in fuel consumption by reducing pump loss while avoiding knocking well.

  According to the third aspect of the present invention, it is possible to achieve appropriate intake valve control in order to improve fuel efficiency in a high load range while avoiding knocking well.

  According to the fourth aspect of the invention, it is possible to select appropriate intake valve control in accordance with the load state of the internal combustion engine in order to improve fuel efficiency while favorably avoiding knocking.

  According to the fifth aspect of the present invention, in the low-rotation and high-load region where the possibility of knocking is most concerned, appropriate intake valve control is realized in order to improve fuel efficiency while favorably avoiding knocking. be able to.

  According to the sixth aspect, the control mode can be suitably selected so that the optimum control of the intake valve in terms of fuel consumption can be used more reliably in accordance with the current engine speed.

  According to the seventh aspect, in the high load range where the second control mode is selected, for example, the intake valve closing timing is sufficiently retarded using the intake slow closing control, and the predetermined torque is set. An operation of controlling the intake air amount by the control means is possible.

  According to the eighth aspect, when the throttle valve is used as the torque control means in the second control mode, the opening degree of the throttle valve can be set appropriately.

  According to the ninth aspect of the invention, it is possible to suitably suppress a torque step accompanying switching of the control mode between the first control mode and the second control mode.

  According to the tenth aspect, it is possible to suitably suppress the occurrence of a torque step due to deterioration in combustion when the control mode is switched.

Embodiment 1 FIG.
[System configuration]
FIG. 1 is a diagram for explaining a configuration of an internal combustion engine 10 according to a first embodiment of the present invention. The system of this embodiment includes an internal combustion engine 10. Here, it is assumed that the internal combustion engine 10 is an in-line four-cylinder engine. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed in the cylinder of the internal combustion engine 10 on the top side of the piston 12. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. A throttle valve 22 is provided downstream of the air flow meter 20. The throttle valve 22 is an electronically controlled throttle valve that can control the throttle opening TA independently of the accelerator opening. In the vicinity of the throttle valve 22, a throttle sensor 24 for detecting the throttle opening degree TA is disposed.

  A fuel injection valve 26 for injecting fuel into the intake port of the internal combustion engine 10 is disposed downstream of the throttle valve 22. A spark plug 28 is attached to the cylinder head of the internal combustion engine 10 so as to protrude from the top of the combustion chamber 14 into the combustion chamber 14. The intake port and the exhaust port are respectively provided with an intake valve 30 and an exhaust valve 32 for bringing the combustion chamber 14 and the intake passage 16 or the combustion chamber 14 and the exhaust passage 18 into a conductive state or a cut-off state.

  The intake valve 30 and the exhaust valve 32 are driven by an intake variable valve mechanism 34 and an exhaust variable valve mechanism 36, respectively. The detailed configuration of these variable valve mechanisms 34 and 36 will be described later with reference to FIGS.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 is connected to a crank angle sensor 42 that detects the engine speed and an accelerator opening sensor 44 that detects the accelerator opening PA. In addition, the various actuators described above are connected to the ECU 40. The ECU 40 can control the operating state of the internal combustion engine 10 based on those sensor outputs.

[Configuration of Variable Valve Mechanism of this Embodiment]
FIG. 2 is a diagram showing the configuration of the intake variable valve mechanism 34 provided in the system shown in FIG. Hereinafter, the intake variable valve mechanism 34 will be further described with reference to FIG. The exhaust variable valve mechanism 36 has substantially the same configuration as the intake variable valve mechanism 34, and therefore detailed illustration and description thereof will be omitted.

  As shown in FIG. 2, the internal combustion engine 10 includes two intake valves 30 per cylinder. The internal combustion engine 10 includes the four cylinders (# 1 to # 4) as described above, and the explosion stroke is performed in the order of # 1 → # 3 → # 4 → # 2. The intake variable valve mechanism 34 includes two devices, that is, an intake variable valve mechanism 34A and an intake variable valve mechanism 34B. The intake variable valve mechanism 34A drives the intake valves 30 provided in the # 2 and # 3 cylinders, and the intake variable valve mechanism 34B drives the intake valves 30 provided in the # 1 and # 4 cylinders.

  The intake variable valve mechanism 34A includes an electric motor (hereinafter referred to as a motor) 50A as a drive source, a gear train 52A as a transmission mechanism that transmits the rotational motion of the motor 50A, and the rotational motion transmitted from the gear train. A camshaft 54A that converts the valve 30 into a linear opening / closing motion. Similarly, the intake variable valve mechanism 34B includes a motor 50B, a gear train 52B, and a camshaft 54B.

  The motors 50A and 50B are servo motors capable of controlling the rotation speed and the rotation amount. For example, a DC brushless motor or the like is preferably used as the motors 50A and 50B. The motors 50A and 50B incorporate rotation angle detection sensors such as a resolver and a rotary encoder for detecting the rotation position (rotation angle). The rotational speed and amount of rotation of the motors 50A and 50B are controlled by the ECU 40.

  A cam drive gear 56 that rotates integrally with the camshafts 54A and 54B and a cam 58 that also rotates integrally with the camshafts 54A and 54B are provided on the outer periphery of the camshafts 54A and 54B, respectively.

  The gear train 52A may be configured such that the rotation of the motor gear 62A attached to the output shaft 60 of the motor 50A causes the camshaft 54A to rotate at an equal speed via the intermediate gear 64A, with respect to the motor gear 62A. The cam drive gear 56 may be configured to increase or decrease speed. Similarly, the gear train 52B transmits the rotation of the motor gear 62B attached to the output shaft of the motor 50B to the cam drive gear 56 of the camshaft 54B via the intermediate gear 64B (not shown in FIG. 2).

  As shown in FIG. 2, the camshaft 54A is disposed above the intake valves 30 of the # 2 and # 3 cylinders, and the cams 58 provided on the camshaft 54A make the intake valves 30 of the # 2 and # 3 cylinders. It is opened and closed. The camshaft 54B is divided into two parts and is disposed on the upper part of the intake valves 30 of the # 1 and # 4 cylinders. The cam 58 provided on the camshaft 54B is used to intake the # 1 and # 4 cylinders. The valve 30 is driven to open and close. The camshaft 54B divided into two is connected via a connecting member inserted into the hollow camshaft 54A and is configured to rotate integrally.

  FIG. 3 is a schematic diagram showing how the intake valve 30 is driven by the cam 58. The cam 58 is formed as a kind of plate cam in which a nose 58a is formed by inflating a part of an arc-shaped base circle 58b coaxial with the camshafts 54A and 54B outward in the radial direction. The profile of the cam 58 is set so that a negative curvature does not occur over the entire circumference, that is, a convex curved surface is drawn outward in the radial direction. In the present embodiment, the direct drive type valve system in which the cam 58 directly drives the intake valve 30 is illustrated, but the intake valve 30 may be driven via a rocker arm. In the case of a valve train that drives the intake valve 30 via a rocker arm, the profile of the cam 58 may be set to draw a concave curved surface toward the outside in the radial direction.

  As shown in FIG. 2, each intake valve 30 includes a valve shaft 30a. Each cam 58 faces a valve lifter 66 provided at one end of the valve shaft 30 a of the intake valve 30. Each intake valve 30 is biased toward the cam 58 by a compression reaction force of a valve spring (not shown). When the base circle 58b of the cam 58 faces the valve lifter 66, the intake valve 30 is brought into close contact with the valve seat (not shown) of the intake port by the urging force of the valve spring, and the intake port is closed.

  When the rotational motion of the motors 50A and 50B is transmitted to the camshafts 54A and 54B via the gear trains 52A and 52B, the cam 58 rotates integrally with the camshafts 54A and 54B, and the nose 58a passes over the valve lifter 66. The valve lifter 66 is pushed down, and the intake valve 30 lifts (opens) against the urging force of the valve spring.

  3A and 3B show two drive modes of the cam 58. FIG. In the drive mode of the cam 58, the motors 50A and 50B are continuously rotated in one direction so that the cam 58 is at the maximum lift position as shown in FIG. Is a normal rotation drive mode in which the valve lifter 66) is continuously rotated beyond the position in contact with the valve lifter 66) in the normal rotation direction (the arrow direction in FIG. 3A), and the motor 50A before reaching the maximum lift position in the normal rotation drive mode. , And a swing drive mode in which the cam 58 is reciprocated as shown in FIG.

  In the normal rotation drive mode, the operating angle of the intake valve 30 is controlled by controlling the rotational speed of the cam 58. In the swing drive mode, the operating angle and lift amount of the intake valve 30 can be controlled by controlling the rotational speed of the cam 58 and the angle range in which the cam 58 swings. Thus, according to the intake variable valve operating mechanism 34, it is possible to drive the intake valve 30 with the optimum operating angle and lift amount (valve opening characteristic) according to the operating state.

  FIG. 4 is a schematic diagram showing the relationship between the engine speed and torque (load) of the internal combustion engine 10 and the drive mode of the cam 58. As shown in FIG. 4, the drive mode of the cam 58 is selectively used in association with the engine speed and torque (load). Basically, the swing drive mode is selected in the low rotation range, and the normal rotation drive mode is selected in the high rotation range. As a result, control is performed to reduce the operating angle and lift amount of the intake valve 30 in the low rotation range, and to increase the operating angle and lift amount of the intake valve 30 in the high rotation range, which is optimal according to the engine speed and torque. It is possible to send a large amount of air into the cylinder.

  FIG. 5 is a schematic diagram showing in detail two cams 58 provided on the camshaft 54A. As shown in FIG. 5, on the camshaft 54A, the cam 58 for driving the intake valve 30 for the # 2 cylinder and the cam 58 for driving the intake valve 30 for the # 3 cylinder are at an angular position of 180 °. Are spaced apart. In the four-cylinder internal combustion engine, the explosion strokes are performed in the order of # 1, # 3, # 4, and # 2 during the crank angle of 720 °. Therefore, the intake stroke of the # 2 cylinder and the # 3 cylinder is 360 ° of the crank angle. Done every time. In the intake variable valve mechanism 34A, the # 2 cylinder cam 58 and the # 3 cylinder cam 58 alternately drive the # 2 cylinder intake valve 30 and the # 3 cylinder intake valve 30 at every 360 ° crank angle. Then, the camshaft 54A is rotated or swung. Similarly, the camshaft 54B is provided with a cam 58 for driving the intake valves 30 of the # 1 cylinder and # 4 cylinder, and the intake variable valve mechanism 34B rotates or swings the camshaft 54B. Thus, the intake valve 30 of the # 1 cylinder and the intake valve 30 of the # 4 cylinder are driven.

  According to the system of the present embodiment configured as described above, in the normal rotation drive mode, the rotation speed of the cam 58 is changed during one rotation of the cam 58, and the cam 58 lifts the intake valve 30. The operating angle of the intake valve 30 can be changed by changing the rotational speeds of the motors 50A and 50B so that. In the normal rotation drive mode, the target operating angle of the intake valve 30 is set in the ECU 40 according to the operating state of the internal combustion engine 10. The ECU 40 controls the operation of the motors 50A and 50B so that the rotational speeds of the motors 50A and 50B corresponding to the target operating angles can be realized.

  In the swing drive mode, the operation of the intake valve 30 is performed by changing the rotation speed and rotation amount of the motors 50A and 50B so that the rotation speed of the cam 58 and the angle range in which the cam 58 swings are changed. The angle and maximum lift can be changed. In the swing drive mode, the target operating angle and the target maximum lift amount of the intake valve 30 are set in the ECU 40 according to the operating state of the internal combustion engine 10. The ECU 40 controls the operation of the motors 50A and 50B so that the rotation amounts and rotation speeds of the motors 50A and 50B corresponding to the target operating angle and the target maximum lift amount can be realized.

[Characteristics of Embodiment 1]
FIG. 6 is a diagram for explaining a control method of the closing timing IVC of the intake valve 30 used in the first embodiment of the present invention. The waveform shown in FIG. 6 shows an equi-action angle line. 6 will be described later together with the description of the routine shown in FIG.

  The system of the present embodiment can use the intake variable valve mechanism 34 and the throttle valve 22 described above as intake air amount control means. In the present embodiment, the intake air amount is controlled mainly using the control of the valve opening characteristics of the intake valve 30 by the intake variable valve mechanism 34.

  More specifically, in the system of the present embodiment, the following intake air amount control is performed for the purpose of improving fuel consumption by reducing pump loss. That is, the intake air amount is controlled such that the throttle opening TA is increased by that amount while the valve passing air amount is limited by reducing the operating angle of the intake valve 30 and advancing the closing timing IVC. .

For this purpose, the target operating angle of the intake valve 30 is determined in accordance with the required load factor of the internal combustion engine 10 and the engine speed, and the opening / closing timing of the intake valve 30 to realize the target operating angle at an appropriate valve opening phase. Is determined. According to such control, the operating angle is made variable according to the load (load factor) of the internal combustion engine 10 and the engine speed, and the closing timing IVC of the intake valve 30 is controlled. More specifically, as shown in FIG. 6, as the load factor and engine speed increase, the operating angle is gradually increased, and the closing timing IVC of the intake valve 30 is gradually retarded.
In the following description of the present specification, the control for adjusting the intake air amount by making the closing timing IVC of the intake valve 30 variable according to the load in this way is referred to as “IVC variable control”.

  FIG. 7 is a diagram showing an example of opening / closing timing of the intake valve 30 used in the IVC variable control. FIG. 7A shows the opening / closing timing of the intake valve 30 in a low load range where a small operating angle is selected. In this case, after the intake valve 30 is opened near the intake top dead center TDC, the intake valve 30 is closed at a relatively earlier stage than the intake bottom dead center BDC. FIG. 7B shows the valve timing of the intake valve 30 in a high load range where a large operating angle is selected. In this case, after the intake valve 30 is opened at a crank position advanced with respect to the intake top dead center TDC than the case shown in FIG. 7A in order to obtain a desired valve overlap period. The valve is closed at a timing later than the intake bottom dead center BDC so that a sufficient amount of air is taken into the cylinder.

  According to the IVC variable control described above, for example, when shifting from a low load range to a high load range, the throttle opening TA is basically maintained at a relatively large opening while the load required for the internal combustion engine 10 is required. Accordingly, the pump loss can be reduced by a method of delaying the closing timing IVC of the intake valve 30 (for example, from FIG. 7A to FIG. 7B) so that the operating angle gradually increases. It is possible to control the intake air amount while favorably.

  FIG. 8 is a diagram showing the opening / closing timing of the intake valve in which the occurrence of knocking is a concern in the IVC variable control. When the above IVC variable control is executed without any consideration for the intake valve closing timing IVC, in the middle load range where the load factor is about 60 to 70%, as shown in FIG. The working angle that is the timing to close near the dead center BDC will be used. In such a medium load range, if the intake valve is closed within a predetermined range near the intake bottom dead center BDC, the throttle opening is controlled to be relatively large. The compression ratio increases and the possibility of knocking increases.

  Therefore, in this embodiment, basically, the intake air amount is controlled by controlling the closing timing IVC of the intake valve 30 according to the load using the above IVC variable control, and then the intake air amount is reduced. A first control mode for controlling the closing timing IVC of the intake valve 30 on the advance side from the predetermined range including the dead center BDC, and a second control mode for controlling the closing timing IVC of the intake valve 30 on the retard side of the predetermined range. And a control mode. Then, the first control mode is selected in the region on the relatively low load side, and the second control mode is selected in the region on the relatively high load side.

  FIG. 9 is a flowchart of a routine executed by the ECU 40 in the first embodiment to realize the above function. In the routine shown in FIG. 9, first, the current load factor of the internal combustion engine 10 is calculated (step 100). The load factor is calculated based on sensor values such as the accelerator opening, the engine speed, the intake air amount by the air flow meter 20, and the intake pipe negative pressure.

  Next, a control mode corresponding to the current operating state is selected from the first control mode and the second control mode based on the current load factor and the engine speed (step 102). Next, it is determined whether or not the selected current control mode is the first control mode (step 104).

  If it is determined in step 104 that the current control mode is the first control mode, then a load increase request to the higher load side (based on the accelerator opening, the accelerator opening change rate, etc.) It is determined whether or not there is an acceleration request (step 106). As a result, when it is determined that there is such a load increase request, it is determined whether or not the load increase request is a load increase request from the knock concern valve timing region (step 108).

  The knock of the internal combustion engine tends to occur in a load region where the load factor exceeds about 60%, particularly in a low engine speed region. Therefore, in this step 108, in order to avoid that the closing timing IVC of the intake valve 30 is controlled within the predetermined range near the intake bottom dead center BDC when the IVC variable control is applied, the occurrence of knocking is avoided. A region having a load factor of about 50 to 80% (see FIG. 6) including a load region having a highest possibility of a load factor of about 60 to 70% is defined as a “knock concern valve timing region”. In FIG. 6, the knock concern valve timing region is constant regardless of the engine speed, but is not limited to such a setting, and may be made variable according to the engine speed and the compression end temperature.

  If it is determined in step 108 that the current load increase request is not a load increase request from the knock concern valve timing region, the first control mode, which is the current control mode, is continuously used as it is ( Step 110). Therefore, in this case, the closing timing IVC of the intake valve 30 is controlled according to the load so that the intake air amount according to the load can be obtained.

  On the other hand, if it is determined in step 108 that the current load increase request is a load increase request from the knock concern valve timing region, the current control mode, which is the first control mode, is instantaneously changed to the second control mode. (Step 112). More specifically, for example, the intake variable valve mechanism 34 instantly changes from the first control mode in which the operating angle is about 150 ° CA to the second control mode in which the operating angle is about 210 ° CA. Be changed. In this case, torque adjustment is then performed by adjusting the throttle opening TA and the ignition timing so that no torque step is caused by changing the control mode (step 114).

  In the routine shown in FIG. 9, if it is determined in step 104 that the current control mode is not the first control mode, that is, the second control mode, then the accelerator opening degree and the accelerator opening are determined. Based on the degree of change rate or the like, it is determined whether or not there is a load reduction request (deceleration request) to the lower load side (step 116). As a result, when it is determined that there is such a load reduction request, it is determined whether or not the load reduction request is a load reduction request from the knock concern valve timing region (step 118).

  If it is determined in step 118 that the current load reduction request is not a load reduction request from the knock concern valve timing region, the second control mode, which is the current control mode, is continuously used as it is ( Step 120). Therefore, in this case, the closing timing IVC of the intake valve 30 is controlled according to the load so that the intake air amount according to the load can be obtained.

  On the other hand, if it is determined in step 118 that the current load reduction request is a load reduction request from the knocking concern valve timing region, the current control mode is immediately switched from the second control mode to the first control mode. (Step 122). More specifically, for example, the intake variable valve mechanism 34 instantaneously changes from the second control mode in which the operating angle is about 210 ° CA to the first control mode in which the operating angle is about 150 ° CA. Be changed. In this case, torque adjustment is then performed by adjusting the throttle opening degree TA and the ignition timing so that a torque step does not occur due to the change in the control mode (step 124).

  According to the routine shown in FIG. 9 described above, if there is a load change request when the current load region of the internal combustion engine 10 enters the knock concern valve timing region, avoid the vicinity of the intake bottom dead center BDC. Thus, the closing timing IVC of the intake valve 30 is controlled. And according to the intake variable valve mechanism 34 of the present embodiment, it is possible to instantly switch between the first control mode and the second control mode for each cycle of the internal combustion engine 10. Therefore, according to the processing of the above routine, the closing timing IVC of the intake valve 30 is prevented from passing in the vicinity of the intake bottom dead center BDC during the switching of the control mode in the load region where the occurrence of knocking is a concern. It becomes possible. As described above, according to the system of the present embodiment, the operation state of the internal combustion engine 10 is controlled by the intake air amount control using the IVC variable control that can obtain good fuel efficiency while avoiding knocking. It can be controlled appropriately.

  In the first embodiment described above, the ECU 40 executes the processing of step 110, 112, 120, or 122, so that the “intake valve control means” in the first aspect of the invention is the steps 102, 108. , Or 118, the “control mode selection means” in the first aspect of the present invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 12 described later instead of the routine shown in FIG. 9 using the hardware configuration shown in FIG.

[Characteristics of Embodiment 2]
FIG. 10 is a diagram for explaining the opening / closing timing of the intake valve 30 used as the second control mode in the second embodiment of the present invention. FIG. 10 shows the closing timing at which the intake valve 30 is opened at a position relatively advanced from the intake top dead center and the intake air is blown back into the intake passage in order to lower the actual compression ratio. An example is shown in which the closing timing IVC of the intake valve 30 is sufficiently retarded to IVC.

  The closing timing IVC at which the intake air blowback is intentionally generated here means that the intake air blowback occurs in a steady state after reaching the target operating state in a state controlled by the closing timing IVC. It means the closing time IVC. More specifically, the closing timing IVC is more delayed than the closing timing IVC (for example, ABDC 30 to 40 ° CA) employed at high speed and high load for securing output in a general internal combustion engine. This refers to IVC. For example, the closing timing IVC such as ABDC80 to 100 ° CA including the case of ABDC 90 ° CA after the intake bottom dead center shown in FIG.

  In the following description, the second control mode used in the present embodiment, that is, the control of the closing timing IVC of the intake valve 30 aiming at the Atkinson cycle by the late closing of the intake valve 30 will be described in the following description. It is also referred to as “intake slow closing control”. More specifically, at the time of execution of this intake slow closing control, the closing timing IVC of the intake valve 30 is controlled to the predetermined closing timing IVC that is sufficiently retarded as described above, and then suctioned by the throttle valve 22. The amount of air is controlled. Further, the closing timing IVC of the intake valve 30 at the time of execution of the intake slow closing control is not a constant value, and may be variable according to the operating state such as the load and the engine speed, for example.

  At this stage, the difference between the intake air intake closing control and the IVC variable control in the first embodiment is clarified. In the IVC variable control, the intake air amount is controlled by closing the intake valve 30 when it can be determined that a predetermined intake air amount can be obtained according to the load and the engine speed while the throttle opening TA is sufficiently large. It is a technique to do. Therefore, in the first embodiment in which this IVC variable control is used as the first control mode and the second control mode, the transient immediately after the instantaneous changeover from the first control mode to the second control mode at the time of a load increase request is made. Sometimes, even if IVC variable control is used, the intake air blows back temporarily. However, the IVC variable control is different from the intake slow closing control which is intended to cause the intake air to blow back in a steady state.

  FIG. 11 is a diagram for explaining an operation region in which the use of the intake air closing control described above is effective in improving fuel efficiency. The low-rotation and high-load region indicated by hatching in FIG. 11 indicates a region in which the intake air intake closing control is superior to the IVC variable control in terms of fuel consumption. The reason why the intake slow closing control is superior in the low rotation and high load range is that the pump loss is the same in both controls, but the intake slow closing control is due to the increase of the valve overlap period near the intake top dead center TDC EGR (Exhaust Gas Recirculation) Reduction of cooling loss (combustion temperature) due to increased gas volume, improvement of in-cylinder mixture distribution due to long intake flow, and improvement of combustion due to increase of intake turbulence This is because it is superior to IVC variable control in that it can be achieved.

  On the other hand, in a region other than the hatched region in FIG. 11, the IVC variable control is superior in terms of fuel consumption to the intake air late closing control. In particular, the reason why the IVC variable control is superior in terms of fuel consumption in the low rotation and low load range is as follows. That is, when the intake slow closing control is used, the intake air warmed by heat exchange with the intake valve 30 and the wall surface of the combustion chamber 14 or the like during intake into the cylinder is blown back to the intake passage, and the intake compression period Is short (the actual compression ratio is small due to the slow closing), so that the compression end temperature cannot be sufficiently increased. The low rotation and low load region is originally a severe region in terms of ensuring good combustion. Due to these factors, the use of IVC variable control improves combustion in the low-rotation and low-load region, and thus is superior in terms of fuel consumption.

  In addition, as shown in FIG. 11, in the engine speed range where the engine speed is about 2500 rpm or less (an example), the intake late closing control is performed in terms of fuel efficiency to the lower load side than the area where knocking is a concern. The area to win is reaching. Therefore, in the present embodiment, when there is a load increase request at the stage where IVC variable control is being performed, a fuel efficiency improvement request is made if it is within a predetermined engine speed (about 2500 rpm in the example of FIG. 11). Based on the above, we switched from IVC variable control to intake slow closing control as needed. Specifically, for example, when the operating angle is 280 ° CA from a state controlled at the closing timing IVC (about BBDC 40 ° before intake bottom dead center) of the intake valve 30 such that the operating angle becomes 140 ° CA. The closing timing IVC (and the opening timing IVO) of the intake valve 30 is instantaneously switched so that the closing timing IVC (about ABDC 80 ° after intake bottom dead center) is obtained.

  In this embodiment, the middle engine speed range that is higher than the predetermined engine speed, that is, the knock concern area extends to the lower load side than the area where the intake slow closing control is superior in terms of fuel efficiency. In this case, based on the knock avoidance request, the IVC variable control is switched to the intake slow closing control as necessary. Specifically, for example, when the operating angle is 280 ° CA from a state controlled at the closing timing IVC (about BBDC 20 ° before intake bottom dead center) of the intake valve 30 such that the operating angle becomes 160 ° CA. The closing timing IVC (and the opening timing IVO) of the intake valve 30 is instantaneously switched so that the closing timing IVC (about ABDC 80 ° after intake bottom dead center) is obtained.

  FIG. 12 is a flowchart of a routine executed by the ECU 40 in the second embodiment in order to realize the above function. This routine assumes control in a region below a predetermined engine speed (3000 rpm in the example shown in FIG. 11). This routine may be similarly applied to other high engine speeds, or in the high engine speed region, the second control mode is set to IVC variable control, and the above-described FIG. The same routine may be executed. In FIG. 12, the same steps as those shown in FIG. 9 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 12, after the current load factor of the internal combustion engine 10 is calculated in step 100, the current control factor is selected from the first control mode and the second control mode based on the current load factor and the engine speed. A control mode corresponding to the operating state is selected (step 200). In this routine, the IVC variable control is used in the first control mode, and the intake air late closing control is used in the second control mode.

  In the routine shown in FIG. 12, when it is determined that the current control mode is the first control mode (step 104) and it is determined that there is a load increase request (step 106), Next, it is determined whether or not the current load increase request is a load increase request to an area where intake late closing control is superior in terms of fuel efficiency (step 202). The ECU 40 stores a relationship as shown in FIG. 11 above, that is, a relationship that represents a region in which the intake slow-closing control is superior in terms of fuel consumption in the operation region represented by the load factor and the engine speed. The process of this step 202 is executed by comparing such a relationship with the current load increase request.

  If it is determined in step 202 that the intake slow-closing control is not a load increase request to an area where fuel consumption is superior, then the current load increase request is a load increase request from the knock concern valve timing area. Is determined (step 108). As a result, if the determination in step 108 is not established, the first control mode, which is the current control mode, is continuously used as it is (step 110).

  On the other hand, if the determination in step 108 is satisfied, the current control mode is instantly changed from the first control mode to the second control mode (step 204). More specifically, for example, the intake variable valve mechanism 34 instantaneously changes from the first control mode in which the operating angle is about 160 ° CA to the second control mode in which the operating angle is about 280 ° CA. Changed to In this case, the torque control by the throttle valve 22 is then switched, and the ignition timing is changed in synchronization with the control mode switching. Then, torque adjustment is performed by adjusting the throttle opening TA and the ignition timing so that a torque step does not occur due to the change of the control mode (step 206).

  Further, when it is determined in step 202 that the intake slow-close control is a load increase request to an area where fuel consumption is superior, the current control mode, which is the first control mode, is instantaneously changed to the second control mode. It is changed (step 208). More specifically, for example, the intake variable valve mechanism 34 instantaneously changes from the first control mode in which the operating angle is about 140 ° CA to the second control mode in which the operating angle is about 280 ° CA. Changed to In this case, the torque control by the throttle valve 22 is then switched, and the ignition timing is changed in synchronization with the control mode switching. Then, torque adjustment is performed by adjusting the throttle opening TA and the ignition timing so that a torque step does not occur due to the change of the control mode (step 210).

  In the routine shown in FIG. 12, when it is determined that the current control mode is the second control mode (step 104) and it is determined that there is a load reduction request (step 116), Next, it is determined whether or not the current load increase request is a load decrease request to an area where the intake slow closing control is superior in terms of fuel efficiency (step 212).

  If it is determined in step 212 that the intake slow-closing control is a load reduction request to an area where fuel consumption is superior, the second control mode, which is the current control mode, is continuously used (step 214). .

  On the other hand, if it is determined in step 212 that the intake slow-closing control is not a load reduction request to an area where fuel consumption is superior, that is, it is determined that the IVC variable control is a load reduction request to an area where fuel consumption is superior. If so, the current control mode is instantaneously changed from the second control mode to the first control mode (step 216). More specifically, for example, from the second control mode in which the operating angle is set to about 280 ° CA, the first control mode in which the operating angle is set to about 140 to 160 ° CA according to the engine speed is set. The intake variable valve mechanism 34 is instantly changed. In this case, the torque control by the throttle valve 22 is then switched, and the ignition timing is changed in synchronization with the control mode switching. Then, torque adjustment is performed by adjusting the throttle opening TA and the ignition timing so that a torque step does not occur due to the change of the control mode (step 218).

  According to the routine shown in FIG. 12, the IVC variable control is used when there is a load change request straddling the region where the IVC variable control is superior in terms of fuel consumption and the region where the intake air intake closing control is superior in terms of fuel efficiency. The control mode is instantaneously switched using the intake variable valve mechanism 34 between the first control mode and the second control mode using the intake slow closing control. According to such control, the closing timing IVC of the intake valve 30 is prevented from passing near the intake bottom dead center BDC during the switching of the control mode even when the load range where the occurrence of knocking is concerned is reached. Is possible. In the present embodiment, as the second control mode utilized on the high load side, intake late closing control is used in which the closing timing IVC of the intake valve 30 is further delayed more than the IVC variable control. For this reason, according to the system of the present embodiment, it is possible to realize intake air amount control that can avoid the occurrence of knocking well and obtain higher fuel efficiency than the system of the first embodiment. Can do.

  Further, as shown in FIG. 11, the boundary line between the region where the intake slow closing control is superior in terms of fuel consumption and the region where the IVC variable control is superior in terms of fuel consumption shifts to the high load side as the engine speed increases. In the routine shown in FIG. 12, in consideration of the relationship shown in FIG. 11, it is determined whether or not the current load change request needs to change the control mode (see steps 202 and 212). . According to such control, in a predetermined low engine speed region, as the engine speed becomes higher, the load is not changed from the IVC variable control to the intake air late closing control unless the load becomes higher. Unless the load becomes low, the intake air slow closing control is not changed to the IVC variable control. As a result, the control mode can be suitably selected so that optimal control in terms of fuel consumption is more reliably used according to the current engine speed.

In the second embodiment described above, the throttle valve 22 corresponds to the “torque control means” in the seventh aspect of the invention, and the ECU 40 executes the processing of step 206, 210, or 218 described above. The “torque control switching means” according to the seventh aspect of the present invention is realized.
Further, the “ignition timing changing means” according to the ninth aspect of the present invention is realized by the ECU 40 executing the processing of step 206, 210, or 218.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 13 described later instead of the routine shown in FIG. 12 using the hardware configuration shown in FIG.

[Characteristics of Embodiment 3]
The system of the present embodiment is characterized by a method of torque adjustment (see step 300 and the like) when the control mode is instantaneously switched between IVC variable control and intake air intake closing control. More specifically, the present embodiment is characterized in that the change range of the throttle opening degree TA is adjusted based on the closing timing IVC and the operating angle of the intake valve 30 after switching of the control mode. .

  Further, when the intake slow closing control using the opening / closing timing of the intake valve 30 as shown in FIG. 10 is executed, the valve overlap period is increased by the advance angle of the opening timing IVO of the intake valve 30, The amount of internal EGR gas increases. An increase in the amount of internal EGR gas at an appropriate amount will bring about an improvement in fuel efficiency, but combustion will be slightly worsened. Therefore, in the present embodiment, the ignition timing is changed in synchronization with the switching of the control mode. Then, the advance amount of the ignition timing after switching the control mode is adjusted based on the valve overlap period (the intake timing IVO of the intake valve 30). More specifically, the advance amount of the ignition timing is increased as the valve overlap period becomes longer.

  FIG. 13 is a flowchart of a routine executed by the ECU 40 in the third embodiment to realize the above function. The routine shown in FIG. 13 is the same as the routine shown in FIG. 12 except that steps 206, 210, and 218 are replaced with steps 300, 302, and 304, respectively. For this reason, in FIG. 13, the same steps as those shown in FIG. 12 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. Further, this routine is a combination of the torque adjustment of this embodiment with the routine shown in FIG. 12 in the above-described second embodiment, but instead of this, the routine shown in FIG. 9 in the above-described first embodiment is used. You may make it combine the torque adjustment of this embodiment.

  In the routine shown in FIG. 13, it is determined that the current load increase request is a load increase request from the knock concern valve timing region (step 108, instantaneously from the first control mode, which is the current control mode), to the second control mode. If it has been changed (step 204), torque adjustment by adjusting the throttle opening TA and ignition timing is then executed (step 300) so as not to cause a torque step due to the change of the control mode.

The ECU 40 stores a map (not shown) in which the amount of change in the throttle opening TA is determined in advance in relation to the closing timing IVC of the intake valve 30 and the operating angle after the control mode is switched. Then, the throttle opening degree TA after the control mode is switched is adjusted. Further, the ECU 40 stores a map (not shown) in which the advance amount of the ignition timing is predetermined in relation to the valve overlap period (opening timing IVO of the intake valve 30) after switching the control mode. With reference to the map, the advance amount of the ignition timing after switching the control mode is adjusted.
In the routine shown in FIG. 13, steps 302 and 304 similar to step 300 are executed, but the processes executed in steps 302 and 304 are the same as those in step 300. Therefore, the detailed description is omitted here.

  According to the routine shown in FIG. 13 described above, the throttle opening after the control mode is switched is appropriately adjusted based on the relationship between the closing timing IVC of the intake valve 30 and the operating angle after the control mode is switched. Can do. Further, according to the above routine, the advance amount of the ignition timing after switching the control mode is appropriately adjusted based on the relationship with the valve overlap period after switching the control mode so that combustion is improved. be able to. For this reason, according to the system of this embodiment, the torque level difference of the internal combustion engine 10 accompanying the switching of the control mode can be suitably suppressed.

  In the first to third embodiments described above, the camshafts 54A and 54B are driven by the motors 50A and 50B provided in the intake variable valve mechanism 34 so that the intake valves 30 of the respective cylinders are driven to open and close. However, in the present invention, the variable valve mechanism that makes at least the closing timing IVC of the intake valve variable is not limited to such a configuration, for example, an electromagnetic drive that drives the intake valve with electromagnetic force. Also good. Furthermore, it has a function to continuously change the closing timing IVC of the intake valve at least in the first control mode, and instantly switches between the first control mode and the second control mode, for example, by adjusting the coupling and release of pins. If possible, a mechanical variable valve mechanism may be used.

It is a figure for demonstrating the structure of the internal combustion engine of Embodiment 1 of this invention. It is a figure which shows the structure of the intake variable valve mechanism with which the system shown in FIG. 1 is provided. It is a schematic diagram which shows a mode that an intake valve is driven with a cam. It is a schematic diagram which shows the relationship between the engine speed of an internal combustion engine, torque (load), and the drive mode of a cam. It is a schematic diagram which shows in detail the two cams provided in the cam shaft. It is a figure for demonstrating the control method of the closing timing IVC of the intake valve used in Embodiment 1 of this invention. It is a figure which shows the example of the opening / closing timing of the intake valve used by IVC variable control. It is a figure which shows the opening-and-closing timing of the intake valve in which generation | occurrence | production of a knock is anxious about IVC variable control. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the opening / closing timing of the intake valve 30 used as 2nd control mode in Embodiment 2 of this invention. It is a figure for demonstrating the driving | operation area | region where utilization of intake late closing control is effective in aiming at a fuel consumption improvement. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Combustion chamber 16 Intake passage 18 Exhaust passage 22 Throttle valve 28 Spark plug 30 Intake valve 34 Intake variable valve mechanism 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Accelerator opening sensor 50A, 50B Motor 54A, 54B Camshaft 58 Cam

Claims (10)

A control device for an internal combustion engine comprising a variable valve mechanism that makes at least the closing timing of the intake valve variable,
A first control mode for controlling the closing timing of the intake valve on the advance side from a predetermined range including the intake bottom dead center, and a second control mode for controlling the closing timing of the intake valve on the retard side from the predetermined range; An intake valve control means for controlling the closing timing of the intake valve in either the first control mode or the second control mode;
Control mode selection means for selecting the first control mode in a relatively low load side region and selecting the second control mode in a relatively high load side region;
A control device for an internal combustion engine comprising a variable valve mechanism.   2. The control according to claim 1, wherein at least the first control mode of the first control mode and the second control mode is control for determining a closing timing of the intake valve in accordance with a load of the internal combustion engine. A control device for an internal combustion engine comprising a variable valve mechanism.   The second control mode is characterized in that the intake valve closing timing is determined so that the closing timing of the intake valve is determined so that the closing timing occurs even when the return of the intake air to the intake passage is in a steady state. An internal combustion engine control device comprising the variable valve mechanism according to claim 1.   4. The control apparatus for an internal combustion engine having a variable valve mechanism according to claim 3, wherein the first control mode is control for determining a closing timing of the intake valve according to a load of the internal combustion engine.   5. The internal combustion engine having a variable valve mechanism according to claim 3, wherein the intake slow closing control is used in an operation region where the engine speed is equal to or lower than a predetermined value and the load is equal to or higher than a predetermined value. Control device.   5. The control device for an internal combustion engine having a variable valve mechanism according to claim 4, wherein the control mode selection means selects the first control mode until the load becomes higher as the engine speed increases. . Torque control means for controlling the torque of the internal combustion engine in addition to control of the intake valve closing timing by the intake valve control means;
Torque control switching means for switching from torque control by the intake valve control means to torque control by the torque control means when the second control mode is selected by the control mode selection means;
The control apparatus for an internal combustion engine comprising the variable valve mechanism according to any one of claims 1 to 6.   The torque control means is a throttle valve that controls the amount of intake air, and is selected from the closing timing of the intake valve and the operating angle of the intake valve when the first control mode is switched to the second control mode. 8. The control apparatus for an internal combustion engine having a variable valve mechanism according to claim 7, wherein the opening degree of the throttle valve is adjusted at least according to the closing timing of the intake valve.   9. An ignition timing changing means for changing an ignition timing of the internal combustion engine in synchronization with switching of the control mode between the first control mode and the second control mode. An internal combustion engine control device comprising the variable valve mechanism according to any one of the above.   The ignition timing changing means determines an advance amount of the ignition timing according to a valve overlap period when the control mode is switched between the first control mode and the second control mode. A control device for an internal combustion engine comprising the variable valve mechanism according to claim 9.

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