JP5206856B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine in which an effective compression ratio is changed using a variable compression ratio mechanism or a variable valve mechanism.

  Various variable compression ratio mechanisms that can change the mechanical compression ratio of the engine, that is, the nominal compression ratio, in order to improve the thermal efficiency of the internal combustion engine in the low and medium load ranges and at the same time avoid knocking in the high load range Proposed. Since the effective compression ratio of the internal combustion engine depends on the intake valve closing timing in addition to the mechanical compression ratio, the effective compression ratio is appropriately set by various variable valve mechanisms that can variably control the intake valve closing timing. It is possible to control. In Patent Document 1 previously proposed by the present applicant, the effective compression ratio is appropriately set by combining the variable control of the mechanical compression ratio by the variable compression ratio mechanism and the variable control of the intake valve closing timing by the variable valve mechanism. A technique for controlling is disclosed.

  Further, in Patent Document 2, in an internal combustion engine having a variable compression ratio mechanism, when knocking occurs, in addition to the ignition timing retardation and the compression ratio decrease, the fuel supply amount is corrected to increase, thereby adjusting the temperature in the combustion chamber. Techniques for reducing and suppressing knocking are disclosed.

JP 2002-285876 A JP-A 63-16137

  As described above, in an internal combustion engine equipped with means for variably controlling the effective compression ratio according to the mechanical compression ratio or the intake valve closing timing, control is performed so that the effective compression ratio is lowered to avoid knocking when the internal combustion engine is accelerated. However, in general, the variable compression ratio mechanism and variable valve mechanism with a mechanical mechanism are less responsive than electrical ignition timing control, and therefore, in the process where the effective compression ratio decreases during acceleration. There arises a problem that knocking occurs transiently or that the ignition timing is significantly retarded to avoid knocking and the torque is reduced.

  Further, if the fuel increase is uniformly performed during acceleration, the fuel increase may become excessive, which causes a deterioration in fuel consumption.

The present invention includes a variable valve mechanism that changes the intake valve closing timing of the internal combustion engine, and a variable compression ratio mechanism that changes the mechanical compression ratio of the internal combustion engine, the variable valve mechanism being in a low load condition. The intake valve closing timing is set to an advance side from the bottom dead center, and the intake valve closing timing at a high load condition is set to a delay side from the bottom dead center. The compression ratio is set to be relatively higher than the mechanical compression ratio under the high load condition , and when accelerating from the low load condition , the intake valve closing timing is advanced from the bottom dead center and delayed from the bottom dead center. In the control device for an internal combustion engine in which the mechanical compression ratio changes to a relatively low compression ratio ,
The actual intake valve closing timing is sequentially obtained during the acceleration,
The fuel increase correction avoid knock during the acceleration, while the actual intake valve closing timing is in a predetermined bottom dead center neighborhood range including the bottom dead center, is characterized by performing.

That is, in the above arrangement, since the intake valve closing timing in accordance with the acceleration is changed to the side delayed even leading side than the bottom dead center, in the middle of the course of the change, when the actual intake valve closing timing is bottom dead center There must be. At the same time, the mechanical compression ratio is changed from a high compression ratio to a low compression ratio by the variable compression ratio mechanism. However, before the final target low compression ratio is reached, the actual intake valve closing timing generally dies. Approach the point. Therefore, the actual intake valve closing timing is near the bottom dead center while the mechanical compression ratio is relatively high, the effective compression ratio becomes excessive, and knocking is likely to occur. In the present invention, the actual intake valve closing timing is sequentially obtained during acceleration, and while the actual intake valve closing timing is within a predetermined bottom dead center range including the bottom dead center , the fuel increase correction is performed, thereby minimizing the necessary amount. Transient knocking is reliably avoided with increased fuel .

In one specific aspect, the absolute value of the angle difference between the actual intake valve closing timing and bottom dead center is greater than the absolute value of the angle difference between the target set intake valve closing timing and bottom dead center. The fuel increase correction is performed in a small period.

Further, in one aspect, when the actual intake valve closing timing enters the predetermined bottom dead center range, a predetermined amount of fuel increase correction is started, and then the actual intake valve closing timing is set to the set intake valve closing timing. The fuel increase is gradually reduced until reaching

According to the present invention, during the acceleration of the internal combustion engine , the actual intake valve closing timing is sequentially obtained, and the fuel increase is performed while the actual intake valve closing timing is within a predetermined bottom dead center range including the bottom dead center . While the mechanical compression ratio by the variable compression ratio mechanism is relatively high, it is possible to reliably avoid the occurrence of knocking due to transiently approaching bottom dead center and excessive effective compression ratio, and to reduce torque. The accompanying ignition timing retard can be made unnecessary or minimal. Further, since the fuel increase is performed only while the actual intake valve closing timing is in the vicinity of the bottom dead center, it is possible to suppress the deterioration of the fuel consumption accompanying the fuel increase.

Structure explanatory drawing which shows an example of a variable compression ratio mechanism. Structure explanatory drawing which shows an example of a variable valve mechanism. Explanatory drawing which shows operation | movement of the variable compression ratio mechanism at the time of acceleration . Explanatory drawing which shows one Example of fuel increase correction.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an embodiment of a variable compression ratio mechanism capable of variably controlling a mechanical compression ratio (nominal compression ratio) of an internal combustion engine as one of effective compression ratio variable means in the present invention. The variable compression ratio mechanism itself is known from the above-described Patent Document 1 and the like.

  This variable compression ratio mechanism uses a multi-link type piston-crank mechanism, and an upper link 5 having one end connected to a piston 3 sliding in a cylinder 2 of a cylinder block 1 via a piston pin 4; The lower link 9 is connected to the other end of the upper link 5 via a connecting pin 6 and is rotatably connected to the crankpin 8 of the crankshaft 7. In order to limit the degree of freedom of the lower link 9 A control link 11 having one end connected to the lower link 9 via a connecting pin 10 and the other end swingably supported by the internal combustion engine body. The position is variably controlled by the eccentric cam portion 13 of the control shaft 12.

  The control shaft 12 is disposed in parallel with the crankshaft 7 and is rotatably supported by the cylinder block 1. The control shaft 12 is driven in the rotational direction by an actuator 15 made of an electric motor via a gear mechanism 14 and its rotational position is controlled.

  In the variable compression ratio mechanism configured as described above, the swing support position of the lower end of the control link 11 changes depending on the rotational position of the control shaft 12, that is, the position of the eccentric cam portion 13, and the initial posture of the lower link 9 changes. Along with this, the top dead center position of the piston 3, and thus the compression ratio changes.

  FIG. 2 shows an embodiment of a variable valve mechanism that can variably control the opening / closing timing of the intake valve together with the operating angle as one of the effective compression ratio variable means. This is because the first variable valve mechanism 51 capable of continuously expanding and reducing the lift / operating angle of the intake valve and the second variable valve capable of continuously delaying the central angle of the operating angle. The variable valve mechanism 52 is combined. The mechanical structure of the first variable valve mechanism 51 and the second variable valve mechanism 52 is known, and for example, has the same structure as the device described in Patent Document 1 described above. Therefore, only the outline will be described.

  The first variable valve mechanism 51 that variably controls the lift / operating angle is rotatably supported by a drive shaft 22 driven by a crankshaft of an internal combustion engine, an eccentric cam 23 fixed to the drive shaft 22. The eccentric cam 23 includes a control shaft 32, a rocker arm 26 that is swingably supported by the eccentric cam portion 38 of the control shaft 32, and a swing cam 29 that contacts the tappet 30 of the intake valve 53. The rocker arm 26 is linked by a link arm 24, and the rocker arm 26 and the swing cam 29 are linked by a link member 28.

  The rocker arm 26 is supported at its substantially central portion by the eccentric cam portion 38 so as to be swingable, and the arm portion of the link arm 24 is linked to one end portion thereof via a connecting pin 25. The upper end portion of the link member 28 is linked to the end portion via a connecting pin 27. The eccentric cam portion 38 is eccentric from the axis of the control shaft 32, and accordingly, the rocking center of the rocker arm 26 changes according to the angular position of the control shaft 32.

  The swing cam 29 is rotatably supported by being fitted to the outer periphery of the drive shaft 22, and a lower end portion of the link member 28 is linked to an end portion extending laterally via a connecting pin 37. ing. On the lower surface of the swing cam 29, a base circle surface concentric with the drive shaft 22 and a cam surface extending in a predetermined curve from the base circle surface are continuously formed. These base circle surface and cam surface come into contact with the upper surface of the tappet 30 according to the swing position of the swing cam 29.

  The control shaft 32 is configured to rotate within a predetermined angle range by a lift / operating angle control actuator 33 provided at one end. The lift / operating angle control actuator 33 is composed of, for example, an electric motor that drives the control shaft 32 via the worm gear 35, and is controlled by a control signal from the control unit 54. The rotation angle of the control shaft 32 is detected by a control shaft sensor 34.

  According to the first variable valve mechanism 51, the lift and the operating angle of the intake valve 53 are continuously expanded and reduced simultaneously according to the rotational angle position of the control shaft 32, With the change in size, the opening timing and closing timing of the intake valve 53 change substantially symmetrically. Since the magnitude of the lift / operating angle is uniquely determined by the rotation angle of the control shaft 32, the actual lift / operating angle at that time is indicated by the detected value of the control shaft sensor 34.

  On the other hand, the second variable valve mechanism 52 that variably controls the center angle is configured such that the sprocket 42 provided at the front end portion of the drive shaft 22 is relative to the sprocket 42 and the drive shaft 22 within a predetermined angle range. And a phase control actuator 43 that is rotated in an automatic manner. The sprocket 42 is linked to the crankshaft via a timing chain or timing belt (not shown). The phase control actuator 43 is a hydraulic rotary actuator in this embodiment, and is controlled by a control signal from the control unit 54 via a hydraulic control valve (not shown). The action of the phase control actuator 43 causes the sprocket 42 and the drive shaft 22 to rotate relative to each other, thereby delaying the lift center angle in the valve lift. That is, the lift characteristic curve itself does not change, and the whole advances or retards. This change can also be obtained continuously. The control state of the second variable valve mechanism 52 is detected by a drive shaft sensor 36 that responds to the rotational position of the drive shaft 22.

  In the internal combustion engine provided with the variable compression ratio mechanism and the variable valve mechanism as described above, since both the mechanical compression ratio and the intake valve closing timing can be changed, the effective compression ratio is determined by both.

Figure 3 shows the operation at the time of acceleration of the variable compression ratio mechanism that is above mentioned, the mechanical compression ratio, i.e. the nominal compression ratio of the internal combustion engine is variably controlled by the variable compression ratio mechanism. When the mechanical compression ratio in the low speed low load conditions starts to accelerate from a high state, i.e. when the throttle opening as shown in FIG. 3 (a) reaches the increased and constant opening abruptly rapidly load of the engine Therefore, in order to avoid knocking, the target set compression ratio decreases as shown in (b), and the variable compression ratio mechanism is controlled to realize this. However, while the throttle opening change time is about 0.1 seconds at the time of maximum acceleration, the mechanical compression ratio reduction requires a long time of about 0.4 seconds, for example, in the above-described variable compression ratio mechanism. Therefore, in the process in which the mechanical compression ratio decreases, the actual compression ratio temporarily increases with respect to the set compression ratio .

FIG. 4 is an explanatory diagram showing an example of fuel increase correction . To vary the effective compression ratio by the variable valve mechanism described above mentioned the intake valve closing timing is variably controlled. When the effective compression ratio in the low speed low load conditions starts to accelerate from a high state, i.e. when the throttle opening as shown in FIGS. 4 (a) reaches the increased and constant opening abruptly rapidly load of the engine Therefore, in order to avoid knocking, the target intake valve closing timing is given to a position that is significantly retarded from the bottom dead center (BDC) as shown in FIG. The variable valve mechanism is controlled. However, while the throttle opening change time is about 0.1 seconds at the maximum acceleration, the retarding operation of the intake valve closing timing generally requires a longer time. Therefore, in the process in which the intake valve closing timing is retarded, the effective compression ratio temporarily becomes larger than the desired effective compression ratio. In particular, if the intake valve closing timing is set before the bottom dead center in the low-speed and low-load conditions before acceleration, the intake valve closing timing is set before the bottom dead center. The closing time approaches the bottom dead center, passes through the bottom dead center, and is delayed more than this. Therefore, when the intake valve closing timing approaches the bottom dead center, the effective compression ratio temporarily increases. Therefore, in this embodiment, as shown in (c), the angle difference (absolute value) between the bottom dead center and the actual intake valve closing timing is the angle difference (absolute value) between the bottom dead center and the set intake valve closing timing. Is smaller, that is, during the period T, the fuel increase is corrected to the increasing side.

By performing good urchin fuel increase correction of the above, even if the rapid acceleration machine械的compression ratio or intake valve closing timing at the time changes with a delay from the set value as a target, it is possible to reliably avoid occurrence of knocking . As a result, the actuator 15 of the variable compression ratio mechanism and the actuators 33 and 43 of the variable valve mechanism do not require high responsiveness for avoiding knocking, and these actuators can be miniaturized.

DESCRIPTION OF SYMBOLS 12 ... Control shaft 15 ... Actuator 33 ... Actuator for lift / operation angle control 43 ... Actuator for phase control 51 ... First variable valve mechanism 52 ... Second variable valve mechanism

Claims (2)

A variable valve mechanism for changing the intake valve closing timing of the internal combustion engine, and a variable compression ratio mechanism for changing the mechanical compression ratio of the internal combustion engine, wherein the variable valve mechanism has an intake valve closing timing under a low load condition. Is set to an advance side from the bottom dead center, and the intake valve closing timing in a high load condition is set to a delay side from the bottom dead center, and the variable compression ratio mechanism has a mechanical compression ratio in a low load condition. It is set relatively higher than the mechanical compression ratio in the high load condition, and when accelerating from the low load condition, the intake valve closing timing changes from the leading side from the bottom dead center to the delay side from the bottom dead center. In addition, in the control device for an internal combustion engine in which the mechanical compression ratio changes to a relatively low compression ratio,
The actual intake valve closing timing is sequentially obtained during the acceleration,
Avoiding the occurrence of knocking when the actual intake valve closing timing enters a predetermined range near the bottom dead center including the bottom dead center in the delaying process of the actual intake valve closing timing during the acceleration. The fuel increase correction of a predetermined amount that can be started is started, and then the fuel increase is gradually decreased until the actual intake valve closing timing reaches the set intake valve closing timing that is behind the bottom dead center. A control device for an internal combustion engine characterized by the above.   Fuel increase correction in a period where the absolute value of the angle difference between the actual intake valve closing timing and bottom dead center is smaller than the absolute value of the angle difference between the target intake valve closing timing and bottom dead center The control device for an internal combustion engine according to claim 1, wherein:

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