JP4962580B2 - 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 an internal combustion engine, and the intake valve closing timing in a low load condition is set to a more advanced side than the bottom dead center, and the intake valve closing timing in a high load condition is set. Control of an internal combustion engine in which the timing is set to be delayed from the bottom dead center and the set intake valve closing timing is changed from the leading side from the bottom dead center to the delayed side from the bottom dead center when accelerating from the low load condition. In the device
The actual intake valve closing timing is sequentially obtained during the acceleration,
Avoiding the occurrence of knocking only while the actual intake valve closing timing is within 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. It is characterized by correcting the amount of fuel increase that can be performed.
In one aspect, a period in which the absolute value of the angle difference between the actual intake valve closing timing and the bottom dead center is smaller than the absolute value of the angular difference between the target intake valve closing timing and the bottom dead center. Then, the fuel increase correction is performed.

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. Thus, when the actual intake valve closing timing becomes the bottom dead center, the effective compression ratio becomes excessive and knocking is likely to occur. In the present invention, during the process of changing the actual intake valve closing timing at the time of acceleration, while the actual intake valve closing timing is in a predetermined range near the bottom dead center including the bottom dead center , the fuel increase correction is performed, thereby making a transient Knocking is avoided.

  Here, it is desirable to increase the fuel increase correction amount as the deviation amount between the actual value and the target set value increases.

  Further, the fuel increase correction amount may be corrected in accordance with the engine rotational speed so as to be small when the engine rotational speed is high. Since the combustion time is shortened as the engine speed is higher, knocking is less likely to occur.

  The lower the temperature of the internal combustion engine, the greater the margin until the occurrence of knocking. Therefore, the fuel increase correction amount can be reduced.

  Similarly, the set effective compression ratio or the set compression ratio may be corrected to the higher compression ratio side as the temperature of the internal combustion engine is lower.

  Further, the lower the intake air temperature, the greater the margin until knocking occurs, so that the fuel increase correction amount can be reduced.

  Similarly, the set effective compression ratio or the set compression ratio may be corrected to the higher compression ratio side as the intake air temperature is lower.

  Further, according to one aspect of the present invention, there is provided ignition timing control means for setting the ignition timing according to the rotational speed, load and actual compression ratio of the internal combustion engine, and when the fuel increase correction is performed, The ignition timing is corrected to the advance side. That is, since the margin until the occurrence of knocking increases due to the increase in fuel, the torque reduction can be avoided by correcting the ignition timing to advance.

According to the present invention, during the acceleration of the internal combustion engine, in the process of changing the actual intake valve closing timing , the fuel increase is performed while the actual intake valve closing timing is within the predetermined bottom dead center range including the bottom dead center. Therefore, it is possible to surely avoid the occurrence of knocking due to transiently approaching bottom dead center and excessive effective compression ratio, and to make ignition timing retard accompanied by torque reduction unnecessary or minimized. Can do. 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 1st Example of fuel increase correction. Explanatory drawing which shows 2nd Example of fuel increase correction. Explanatory drawing which shows 3rd Example of fuel increase correction. Explanatory drawing which shows the relationship between deviation | shift amount and fuel increase correction amount. Explanatory drawing of the Example which changes a fuel increase correction amount with an engine speed. Explanatory drawing which shows correction | amendment of ignition timing. Explanatory drawing of the Example which changes the fuel increase correction amount with the oil-water temperature of an engine. Explanatory drawing of the Example which changes the fuel increase correction amount with the intake air temperature of an engine.

  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.

  FIG. 3 is an explanatory view showing a first embodiment of fuel increase correction. The occurrence of knocking at high loads is caused by the fact that the unburned gas in the cylinder becomes high temperature and ignites before ignition. Therefore, in order to avoid knocking at acceleration, the cylinder is reduced by reducing the effective compression ratio. It is effective to reduce the compression temperature of the internal gas. Accordingly, when the acceleration is started from a state where the effective compression ratio is high in the low speed and low load state, that is, when the throttle opening increases rapidly and reaches a constant opening as shown in FIG. Therefore, in order to avoid knocking, the target effective compression ratio decreases as shown in (b), and the variable compression ratio mechanism and variable valve mechanism are controlled to achieve this. Is done. However, in order to reduce the effective compression ratio, it is necessary to reduce the mechanical compression ratio by a variable compression ratio mechanism or to delay the intake valve closing timing by a variable valve mechanism. It takes a long time. Therefore, in the process of decreasing the effective compression ratio, the actual effective compression ratio is temporarily deviated from the set effective compression ratio. As shown in (c), while the actual effective compression ratio is larger than the set effective compression ratio, that is, during the period T, the fuel increase set for the set effective compression ratio is corrected to the increasing side. The The actual effective compression ratio is obtained from the actual compression ratio by the variable compression ratio mechanism, the actual operating angle and the actual center angle by the variable valve mechanism.

  FIG. 4 is an explanatory view showing a second embodiment of fuel increase correction. In this embodiment, only the above-described variable compression ratio mechanism is provided, and thereby the mechanical compression ratio of the internal combustion engine, that is, the nominal compression ratio is variably controlled. When acceleration is started from a state where the mechanical compression ratio is high in a low speed and low load state, that is, when the throttle opening increases rapidly and reaches a constant opening as shown in FIG. 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. As shown in (c), while the actual compression ratio is larger than the set compression ratio, that is, during the period T, the fuel increase set for the set compression ratio is corrected to the increase side.

  FIG. 5 is an explanatory view showing a third embodiment of fuel increase correction. In this embodiment, only the above-described variable valve mechanism is provided, and the intake valve closing timing is variably controlled so as to change the effective compression ratio. When acceleration is started from a state where the effective compression ratio is high in the low speed and low load state, that is, when the throttle opening increases rapidly and reaches a certain opening as shown in FIG. 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 fuel increase correction as in each of the above embodiments, even if the effective compression ratio, mechanical compression ratio, or intake valve closing timing changes with a delay from the target set value during sudden acceleration, knocking can be reliably generated. Can be avoided. 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.

  FIG. 6 shows the relationship between the fuel increase correction amount and the divergence amount (difference between the set value and the actual value). As shown in (b), for example, the divergence between the set effective compression ratio and the actual effective compression ratio is However, as shown in (c), the larger the deviation, the larger the fuel increase correction amount is given. As a result, knocking can be reliably avoided while minimizing deterioration in fuel consumption due to fuel increase.

  FIG. 7 is an explanatory view showing an embodiment in which the fuel increase correction amount is changed according to the engine speed, and the deviation shown in FIG. 7B (eg, the deviation between the set effective compression ratio and the actual effective compression ratio). Accordingly, the fuel increase correction amount is given as in (c). At this time, when the engine speed is high, the fuel increase correction amount is given less than when the engine speed is low. That is, even under the same load and compression ratio conditions during acceleration, knocking is less likely to occur because the combustion time is shortened as the engine speed increases. That is, the amount of fuel increase necessary for avoiding knocking is reduced. Therefore, by reducing the fuel increase correction amount as the rotational speed is higher, it is possible to suppress deterioration in fuel consumption while avoiding knocking.

  FIG. 8 is an explanatory diagram of the ignition timing at the time of fuel increase correction. The ignition timing basically has a predetermined margin until the occurrence of knocking according to the engine speed, engine load, and actual compression ratio. Is set. Here, the ignition timing retard for avoiding knocking is not preferable because it significantly reduces the torque. However, when the fuel increase correction is performed in accordance with the deviation of the effective compression ratio or the like, the margin until the occurrence of knocking is increased by the fuel increase correction, so that the ignition timing can be further advanced. Therefore, in this embodiment, during the period T during which the fuel increase correction is performed as shown in (c), the ignition timing is corrected to the advance side according to the magnitude of the fuel increase correction as shown in (d). . Thereby, the torque fall by ignition timing retard can be avoided.

  FIG. 9 is an explanatory diagram for the increase / decrease correction of the fuel increase correction amount based on the temperature of the internal combustion engine (lubricating oil temperature, cooling water temperature, etc.). The lower the oil / water temperature of the internal combustion engine, the lower the heat received from the wall surface of the combustion chamber, so that the in-cylinder temperature tends to decrease and the margin until knocking increases. In this embodiment, the fuel increase correction amount is given as shown in (c) according to the deviation shown in (b) (for example, the deviation between the set effective compression ratio and the actual effective compression ratio). When the water temperature is low, the fuel increase correction amount is given less than when the oil water temperature is high.

  When the oil water temperature is low, for example, the set effective compression ratio may be corrected to the higher compression ratio side. As a result, the deviation amount is reduced, and the fuel increase correction amount is reduced.

  FIG. 10 is an explanatory diagram for the increase / decrease correction of the fuel increase correction amount based on the intake air temperature of the internal combustion engine. The lower the intake air temperature, the lower the compression temperature of the in-cylinder gas and the greater the margin until knocking occurs. In this embodiment, the fuel increase correction amount is given as shown in (c) according to the deviation amount shown in (b) (for example, the deviation amount between the set effective compression ratio and the actual effective compression ratio). When the air temperature is low, the fuel increase correction amount is smaller than when the intake air temperature is high.

  When the intake air temperature is low, for example, the set effective compression ratio may be corrected to the higher compression ratio side. As a result, the deviation amount is reduced, and the fuel increase correction amount is reduced.

DESCRIPTION OF SYMBOLS 12 ... Control shaft 15 ... Actuator 33 ... Lift / actuation angle control actuator 43 ... Phase control actuator 51 ... First variable valve mechanism 52 ... Second variable valve mechanism

Claims (3)

Equipped with a variable valve mechanism that changes the intake valve closing timing of the internal combustion engine, the intake valve closing timing in the low load condition is set to a more advanced side than the bottom dead center, and the intake valve closing timing in the high load condition is In the control apparatus for an internal combustion engine that is set on the delay side from the point, and the set intake valve closing timing changes from the advance side to the delay side from the bottom dead center when accelerating from the low load condition,
The actual intake valve closing timing is sequentially obtained during the acceleration,
Avoiding the occurrence of knocking only while the actual intake valve closing timing is within 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. A control device for an internal combustion engine, which performs a fuel increase correction that can be performed. The absolute value of the angular difference between the actual intake valve closing timing and the bottom dead center, a smaller period than the absolute value of the angular difference between the bottom dead center and set the intake valve closing timing to a target fuel increase correction The control device for an internal combustion engine according to claim 1, wherein: When the actual intake valve closing timing enters the above-mentioned range near the bottom dead center, a predetermined amount of fuel increase correction is started, and then the fuel increase is performed until the actual intake valve closing timing reaches the set intake valve closing timing. 3. The control device for an internal combustion engine according to claim 1 or 2, characterized in that the amount of the engine is gradually reduced.

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